Publisher: AIP   (Total: 27 journals)   [Sort alphabetically]

Showing 1 - 27 of 27 Journals sorted by number of followers
Physics Today     Hybrid Journal   (Followers: 78, SJR: 0.66, CiteScore: 1)
J. of Applied Physics     Hybrid Journal   (Followers: 69, SJR: 0.739, CiteScore: 2)
American J. of Physics     Full-text available via subscription   (Followers: 58, SJR: 0.456, CiteScore: 1)
Physics of Fluids     Hybrid Journal   (Followers: 46, SJR: 1.19, CiteScore: 3)
Applied Physics Letters     Hybrid Journal   (Followers: 44, SJR: 1.382, CiteScore: 3)
J. of Chemical Physics     Hybrid Journal   (Followers: 36, SJR: 1.252, CiteScore: 2)
J. of Mathematical Physics     Hybrid Journal   (Followers: 25, SJR: 0.644, CiteScore: 1)
Review of Scientific Instruments     Hybrid Journal   (Followers: 20, SJR: 0.585, CiteScore: 1)
J. of Laser Applications     Full-text available via subscription   (Followers: 14, SJR: 0.741, CiteScore: 2)
APL Materials     Open Access   (Followers: 12, SJR: 1.63, CiteScore: 4)
J. of Renewable and Sustainable Energy     Hybrid Journal   (Followers: 11, SJR: 0.44, CiteScore: 1)
Applied Physics Reviews     Hybrid Journal   (Followers: 11, SJR: 4.156, CiteScore: 12)
Physics of Plasmas     Hybrid Journal   (Followers: 10, SJR: 0.576, CiteScore: 1)
Acoustics Today     Hybrid Journal   (Followers: 9)
Biomicrofluidics     Open Access   (Followers: 7, SJR: 0.592, CiteScore: 2)
AIP Advances     Open Access   (Followers: 7, SJR: 0.472, CiteScore: 1)
Low Temperature Physics     Hybrid Journal   (Followers: 6, SJR: 0.264, CiteScore: 1)
Structural Dynamics     Open Access   (Followers: 6, SJR: 1.625, CiteScore: 4)
J. of Physical and Chemical Reference Data     Hybrid Journal   (Followers: 4, SJR: 1.046, CiteScore: 3)
Chaos : An Interdisciplinary J. of Nonlinear Science     Hybrid Journal   (Followers: 3, SJR: 0.716, CiteScore: 2)
AIP Conference Proceedings     Full-text available via subscription   (Followers: 2)
Biointerphases     Open Access   (Followers: 1, SJR: 0.558, CiteScore: 2)
Chinese J. of Chemical Physics     Hybrid Journal   (Followers: 1, SJR: 0.24, CiteScore: 1)
Surface Science Spectra     Hybrid Journal   (Followers: 1, SJR: 0.416, CiteScore: 1)
Scilight     Full-text available via subscription  
APL Bioengineering     Open Access  
APL Photonics     Open Access  
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AIP Advances
Journal Prestige (SJR): 0.472
Citation Impact (citeScore): 1
Number of Followers: 7  

  This is an Open Access Journal Open Access journal
ISSN (Online) 2158-3226
Published by AIP Homepage  [27 journals]
  • Coupled surface and bulk diffusion in crystals

    • Authors: S. S. Kosolobov
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      We analyze point defect bulk and surface diffusion near the crystal–vacuum interface and show that bulk diffusion is coupled with surface diffusion via the atomic processes in the intermediate subsurface layer. A set of self-contained differential equations describing the interaction of self-interstitials and bulk vacancies with the surface of crystal is proposed. The results show the existence of the fundamental relation between the equilibrium concentrations of the point defects in bulk and at the surface of the crystal. For the case of silicon, the energy barrier differences that restrict the point defect fluxes between the bulk and surface of the crystal are estimated.
      Citation: AIP Advances
      PubDate: 2022-05-19T03:48:19Z
      DOI: 10.1063/5.0091072
  • Enhancement of high-frequency performances by Al2O3 interlayer in
           FeCoHf/Al2O3/FeCoHf trilayers

    • Authors: Zhao-Xuan Jing, Shou-Heng Zhang, Shandong Li
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      In this study, Hf-doped FeCo alloy films with a high ferromagnetic resonance (FMR) frequency at zero external fields were prepared by a composition gradient sputtering method. In order to further enhance the high-frequency performances, Al2O3 spacers of various thicknesses were inserted in the middle of the FeCoHf film. It is revealed that the Al2O3 interlayer improves the magnetic anisotropy of trilayers, enhances the resistivity, and refines the grain size. As a result, the FMR frequency of the trilayer was enhanced to over 3 GHz, and the permeability was also evidently improved from 41 (single layer) to 86 (trilayer with Al2O3 thickness of 40 Å).
      Citation: AIP Advances
      PubDate: 2022-05-19T03:48:16Z
      DOI: 10.1063/5.0089503
  • Investigation of novel quaternary Heusler alloys XRuCrZ (X = Co, Ni, Rh,
           and Pd; Z = Si and Ge) via first-principles calculation for spintronics
           and thermoelectric applications

    • Authors: Roshme Prakash, G. Suganya, G. Kalpana
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The structural, electronic, magnetic, and transport properties of LiMgPdSb-type novel quaternary Heusler alloys XRuCrZ (X = Co, Ni, Rh, and Pd; Z = Si and Ge) have been studied employing the first-principles calculation derived from density functional theory. From the total energy calculations, it is found that all these alloys are stable in the cubic α phase, and spin-polarized calculations show that all the alloys favor a ferromagnetic state. In addition, it is ascertained that XRuCrZ (X = Co and Rh; Z = Si and Ge) exhibits half-metallic ferromagnetic property. In addition, the temperature-dependent transport properties have been studied. The calculated dimensionless figure of merit for CoRuCrSi is 0.43. Our results show that these alloys will be suitable for data storage and energy conversion applications.
      Citation: AIP Advances
      PubDate: 2022-05-19T03:48:13Z
      DOI: 10.1063/5.0088553
  • Predicting pressure coefficients of wing surface based on the transfer of
           spatial dependency

    • Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Multi-conditional holographic pressure coefficients over a wing are crucial for wing design, and a wind tunnel test is an indispensable means to obtain this profile. However, it is resource-consuming to obtain wind tunnel data under different conditions and only a limited number of sensors can be placed on the wing model during one test, which results in sparse pressure coefficient data with distribution inconsistency across cross sections and conditions. Thus, how to obtain pressure coefficients of more cross sections or even the whole wing surface with multiple conditions from the distribution-inconsistent sensor data becomes a challenging problem. Therefore, a deep learning framework based on transfer learning is proposed in this paper, in which the spatial dependency captured by a long short-term memory model between the obtained multi-conditional sensor data is transferred to other cross sections with few-condition data on the wing. The results demonstrate that the proposed framework achieves high accuracy on the pressure coefficients prediction of distribution-inconsistent cross sections on wind tunnel test data, and thus improves data utilization and cuts costs by reducing wind tunnel tests under different design conditions. Our work proves the possibility of reconstructing the holographic flow field from sparse sensor data of wind tunnel tests and puts forward recommendations on the placement of sensors for achieving this goal.
      Citation: AIP Advances
      PubDate: 2022-05-19T03:48:12Z
      DOI: 10.1063/5.0093144
  • Multi-field coupling mechanical failure of Pb(Zr0.95Ti0.05)O3
           ferroelectric ceramics under shock compression

    • Authors: Fu-Ping Zhang, Jin-Mei Du, Yu-Sheng Liu, Hong-Liang He
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      PZT 95/5 ferroelectric ceramics have been used in shock-driven pulsed-power supplies for many years; their mechanical failure under shock compression plays an important role in their applications. Multi-field coupling shock experiments have been conducted to understand such failure by measuring the interface particle velocity of the quartz buffer/window interface, and the wave evolution was analyzed with or without the existence of failure zone inner PZT 95/5. Results confirm that the delay time of the failure wave decreased with increasing the electric field, and when the electric field reaches the dielectric strength, the electrical breakdown happens, which makes the threshold stress of mechanical failure shift to the low stress (2.0 GPa) and the delay time of the failure wave decreases dramatically at high stress. The phenomena that the delay time decreases with increasing shock stress are also observed. At the same time, ferroelectric → antiferroelectric phase transformation makes it so that the delay time of the poled state is longer than that of the unpoled state, so it has the effect of phase transformation toughening.
      Citation: AIP Advances
      PubDate: 2022-05-19T03:48:10Z
      DOI: 10.1063/5.0086000
  • Dispersive propagation of trans-ionospheric pulse pairs in ionosphere

    • Authors: Y. Zhang, H.-C. Wu
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      As the most powerful natural radio waves on earth, trans-ionospheric pulse pairs (TIPPs) are emitted by lightning and have been recorded by several satellites. TIPPs commonly consist of two radio pulses with a clear ionospheric dispersion. Here, we calculate the propagation of TIPPs across the ionosphere by use of a method accurate for sub-cycle radio pulses. One can directly obtain dispersed waveforms in the time domain and then reproduce satellite-recorded frequency spectra. Our work affords a simple and robust tool to directly compare with observation data, which should be helpful to deduce original undispersed waveforms of TIPPs and characteristics of high-energy electrons produced by lightning.
      Citation: AIP Advances
      PubDate: 2022-05-18T01:48:12Z
      DOI: 10.1063/5.0087725
  • Tunable ultra-high quality factor graphene absorber based on
           semicylindrical silica array and distributed Bragg reflector structure

    • Authors: Jinlai Liu, Shuai Tang, Bin Ren, Jie Song, Yongyuan Jiang
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      We propose a tunable narrowband absorber by utilizing a graphene monolayer placed between a dielectric semicylindrical array and a multilayer silica/silicon distributed Bragg reflector (DBR) structure. The multi-band perfect absorption can be achieved due to the excitation of multiple resonant modes in the absorber, including the guided mode resonance of the dielectric silica array and BR-based guided mode resonance in the DBR structure. The ultra-high quality factor (Q) is mainly attributed to the low external leakage loss of the resonator and the low intrinsic loss of the graphene monolayer. Moreover, the Q-factor of absorption peaks can be tuned by electrically controlling the Fermi energy of graphene. The sensitivity of a spectral wavelength shift for the refractive index change of the resonator is up to 730 nm/RIU, and the figure of merit is 1043. The proposed graphene-based metamaterial offers potential applications for photodetectors, optical modulators, and sensors in the near infrared frequency regime.
      Citation: AIP Advances
      PubDate: 2022-05-18T01:48:10Z
      DOI: 10.1063/5.0089686
  • Effects of the excited states on electron kinetics and power absorption
           and dissipation in inductively coupled Ar plasmas

    • Authors: Wei Yang, Fei Gao, You-Nian Wang
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The effects of the excited states on electron kinetics as well as plasma power absorption and dissipation are numerically studied in radio frequency low-pressure inductively coupled Ar plasmas. The model used in this work is based on the coupling of the kinetic module, the electromagnetic field module, and the global model module. The existence of excited states caused by the electron-impact excitations of the ground state of Ar decreases the electron temperature due to the significant depletion of the electron energy probability function in the inelastic energy range. The reduction in electron temperature decreases the power dissipation of an electron per unit volume and, therefore, increases the electron density for the fixed total power. The profile and maximum variations of the absorption power density indicate that the increased electron density suppresses the power deposition deeper into the plasma with inclusion of the electron-impact excitations of the ground state to excited states of Ar. However, the collision processes involving the excited states as reactants hardly affect the electron kinetics and electromagnetic field properties due to far lower densities of the excited states than that of the ground state of Ar.
      Citation: AIP Advances
      PubDate: 2022-05-18T01:48:10Z
      DOI: 10.1063/5.0092556
  • Research on power penetration cable line fault location based on
           distributed traveling wave location technology

    • Authors: Xiaopo Mao, Bin Xiang, Suge Tu
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The power penetration line of high-speed railway adopts all-cable lines, and its failure will seriously affect the safety and reliability of railway transportation. The accurate location of the fault will greatly reduce the range of finding the cable fault point and the workload of cable fault repair, shorten the maintenance time, and improve the reliability of high-speed railway power supply. This paper introduces the current situation of power line fault location, analyzes various traveling wave location principles and the traveling wave transmission and attenuation characteristics of all-cable penetration lines, and analyzes the adaptability of the traditional traveling wave location technology in all-cable penetration line fault location. It is proposed that the distributed traveling wave location method can greatly reduce the transmission distance of fault traveling waves and can effectively reduce the influence of attenuation and distortion in the traveling wave transmission process. For different types of fault traveling waves, different fault transition resistances, and different positions of fault points, the method can achieve the accurate location. The practical application case shows that the technology has high location accuracy and meets the requirements of a precise location.
      Citation: AIP Advances
      PubDate: 2022-05-18T01:48:09Z
      DOI: 10.1063/5.0093049
  • Research on the effects of corrosion resistant zinc injection in primary
           circuit of large-scale PWR plants on core crud amount

    • Authors: Weiqiang Sun, Hu Xu, Shuran Mo, Chao Wang, Guang Hu, Huasi Hu
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      In recent years, the number of nuclear plants injecting zinc is increasing worldwide because zinc injection can reduce the corrosion rate of structural materials in the primary coolant circuit. However, at the initial stage of zinc injection, zinc can introduce a large amount of corrosion products entering into the coolant circuit by displacing other divalent species in oxide. These corrosion products will be carried into the core by the coolant and cause unevenness of the crud on fuel cladding surfaces, which can increase the probability of crud induced power shift (CIPS) and damage to fuel claddings. In this paper, the structural material corrosion model with or without zinc injection is built based on a mixed conduction model. The migration model of corrosion products in the primary circuit is established, and the relationship of crud amount with the time is obtained. The mechanism of interactions between zinc and formed oxide layers is analyzed. The extra amount of corrosion products due to zinc injection is calculated according to the different starting times. It is used to revise the crud mass. The influences of zinc injection on the crud amount are achieved, which can be the foundation of further research on the relationship between zinc injection and CIPS.
      Citation: AIP Advances
      PubDate: 2022-05-18T01:48:08Z
      DOI: 10.1063/5.0087998
  • Effects of ion extraction on discharges in gridded ion source

    • Authors: Y. R. Yang, S. H. Fu, Z. F. Ding
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Effects of ion extraction on gridded ion source discharge or the coupling between ion extraction and gridded ion source discharge are investigated for the first time by correlating the ratio of the ion impingement current (Ia) to ion beam current (Ib) with the total gray values extracted from images of discharge glows with and without ion extraction. The results indicate that, under equal power and gas pressure, discharges with high and low Ia/Ib values in the presence of ion extraction are, respectively, more intensive and weaker than those without ion extraction. The competing factors behind the coupling between ion extraction and ion source discharge are ion loss and energetic secondary γ-electron injection from the accelerator grid, which weakens and enhances ion source discharge, respectively.
      Citation: AIP Advances
      PubDate: 2022-05-18T01:48:08Z
      DOI: 10.1063/5.0082813
  • The influence of thermal parameters on the temperature distribution and
           output parameters of c-Si solar cell under actual test conditions

    • Authors: Xiaodong Lu, Sheng Gao, Chao Lu, Di Lu, Shuxian Lun
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The accurate measurement of the output parameters of photovoltaic (PV) cells is a key step in building a PV system. The output parameters of a PV cell under actual test conditions will appear different degrees of the deviation from those under the standard test conditions. In this work, we are primarily concerned with the deviations of the temperature distributions and output parameters of a testing c-Si solar cell caused by the heat transfer process under actual test conditions. The results show that the temperature distributions of c-Si solar cells under actual test conditions will be uneven and obviously deviate from those under the standard test conditions; the heat transfer coefficients at the interfaces between the front surface and environmental air and between the back surface and mental holder have important consequences for the temperature distributions of c-Si solar cells; under the actual test conditions of PV enterprises, the possible deviation range of short-circuit current density, open-circuit voltage, filling factor, and efficiency may be from −17 to 9 µA/cm2, from −11 to 17 mV, from −0.4% to 0.7%, and from −0.4% to 0.7%, respectively.
      Citation: AIP Advances
      PubDate: 2022-05-18T01:48:07Z
      DOI: 10.1063/5.0085215
  • Epitaxial growth of β-Ga2O3 by hot-wall MOCVD

    • Authors: Daniela Gogova, Misagh Ghezellou, Dat Q. Tran, Steffen Richter, Alexis Papamichail, Jawad ul Hassan, Axel R. Persson, Per O. Å. Persson, Olof Kordina, Bo Monemar, Matthew Hilfiker, Mathias Schubert, Plamen P. Paskov, Vanya Darakchieva
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The hot-wall metalorganic chemical vapor deposition (MOCVD) concept, previously shown to enable superior material quality and high performance devices based on wide bandgap semiconductors, such as Ga(Al)N and SiC, has been applied to the epitaxial growth of β-Ga2O3. Epitaxial β-Ga2O3 layers at high growth rates (above 1 μm/h), at low reagent flows, and at reduced growth temperatures (740 °C) are demonstrated. A high crystalline quality epitaxial material on a c-plane sapphire substrate is attained as corroborated by a combination of x-ray diffraction, high-resolution scanning transmission electron microscopy, and spectroscopic ellipsometry measurements. The hot-wall MOCVD process is transferred to homoepitaxy, and single-crystalline homoepitaxial β-Ga2O3 layers are demonstrated with a [math]01 rocking curve width of 118 arc sec, which is comparable to those of the edge-defined film-fed grown ([math]01) β-Ga2O3 substrates, indicative of similar dislocation densities for epilayers and substrates. Hence, hot-wall MOCVD is proposed as a prospective growth method to be further explored for the fabrication of β-Ga2O3.
      Citation: AIP Advances
      PubDate: 2022-05-18T01:48:04Z
      DOI: 10.1063/5.0087571
  • Heat transfer in a dense gas between two parallel plates

    • Authors: Masanari Hattori, Soichi Tanaka, Shigeru Takata
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Time-dependent heat transfer in a dense gas between two parallel plates, which is initiated by an abrupt change in temperature of one plate, is numerically investigated on the basis of the Enskog equation under the diffuse reflection boundary condition. Numerical computation is carried out by a finite-difference scheme combined with the Fourier spectral method for the efficient computation of the collision term of the Enskog equation. As a result, macroscopic quantities of the gas, such as heat flux and temperature, are obtained for various Knudsen numbers and ratios of the molecular diameter to the distance between plates. Compared to the case of an ideal gas, the heat flux in the stationary state is enhanced due to an effect of the finite size of molecules for not only small but also intermediate Knudsen numbers. The results imply that the finite-size effect also affects the propagation of disturbances in the initial stage, particularly for small Knudsen numbers.
      Citation: AIP Advances
      PubDate: 2022-05-17T02:51:05Z
      DOI: 10.1063/5.0091390
  • Effect of initial temperature on impact-induced spalling behavior in
           single-crystal aluminum studied by molecular dynamics simulations

    • Authors: Guoqiang Luo, Shanglin Huang, Jianian Hu, Youlin Zhu, Junjie Wang, Gang Yang, Ruizhi Zhang, Yi Sun, Jian Zhang, Qiang Shen
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Spallation is a typical dynamic fracture mode under shock loading and has attracted the attention of most researchers. However, due to the difficulty in measuring temperature in dynamic experiments, the effect of initial temperature on spalling response has been rarely investigated. Molecular dynamics simulation perfectly corresponds to the short duration and high strain rate of the spalling process. Therefore, in this work, molecular dynamics simulations are used to study the spalling reaction of single-crystal aluminum at different initial temperatures. The research has shown that the evolution of spallation is related to dislocation and hole nucleation. First, the spall strength of the material decreases as initial temperature increases, while the dislocation density gradually increases. However, when the initial temperature increases to 750 K, the dislocation density decreases. Then, the number of holes and the degree of damage change as initial temperature increases. However, at the low impact strength (v < 2.0 km/s), the changes in the number of holes and the degree of damage are highly dependent on the initial temperature. In the case of high impact strength, the opposite is true. Finally, the thermodynamic path of the material during impact compression is studied. It is found that melting may occur during compression, release or tension, and damage stages, depending on the initial temperature and impact strength. The discovery and research of these systems have laid a solid foundation for subsequent studies.
      Citation: AIP Advances
      PubDate: 2022-05-17T02:51:03Z
      DOI: 10.1063/5.0088039
  • Construction and characterization of conductive collagen/multiwalled
           carbon nanotube composite films for nerve tissue engineering

    • Authors: Qian Li, Chengfei Yue, Tao Chen, Changkun Ding, Hongtian Zhang
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Currently, a growing number of biomaterials have been evaluated to be beneficial to the application of neural tissue engineering. However, their deficient mechanical and electrical properties limit their further application, especially for nerve regeneration. Therefore, the combination of biological matrix and conductive materials has been applied to meet the requirements for nerve tissue engineering. In this work, conductive collagen (COL)/multiwalled carbon nanotube (MWNT) composite films with different MWNT concentrations were developed by the solvent–evaporation method. The effects of rigid MWNT on the structure, mechanical, thermal, and electrical properties of the flexible COL-based film were evaluated. The evaluation of mechanical properties revealed that the tensile strength of the COL/MWNT composite films was almost eight times as high as that of the pure COL film. The electrical property assessment demonstrated that the electrical conductivity of COL/MWNT-0.25% reached 0.45 S/cm, meeting the electrical stimulation conditions required for nerve growth. Furthermore, the cell viability assays revealed that the COL/MWNT composite films were non-cytotoxic and appropriate for cell growth. Our work proved that the conductive COL/MWNT composite films exhibited great potential for nerve tissue engineering application, which provided a novel self-electrical stimulated platform for the treatment of neural injuries.
      Citation: AIP Advances
      PubDate: 2022-05-17T02:51:01Z
      DOI: 10.1063/5.0090006
  • Effects of periodic suction-blowing excitation on the aerodynamic sound
           generated by a laminar flow past a square cylinder using the direct
           numerical simulation approach

    • Authors: Shashi Kumar, Naveen Ganta, Yogesh G. Bhumkar
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      This paper analyzes the effects of a periodic suction-blowing excitation on the aerodynamic sound generated by a laminar flow past a square cylinder using the direct numerical simulation approach. The periodic suction-blowing excitation has been prescribed on the top and bottom surfaces of the square cylinder. The proper orthogonal mode decomposition (POD) technique has been used to find information about important modes associated with disturbance pressure fields. The POD technique separated the contribution of the dominant lift dipole equivalent sources and the drag dipole equivalent sources to the disturbance pressure field for the no-excitation case. The POD technique also revealed that the periodic suction-blowing excitation introduced an additional monopole equivalent sound source and a drag dipole equivalent sound source due to periodic enhancement and reduction of the body’s effective cross-sectional area. Modifications in the sound field due to changes in excitation amplitude, forcing frequency, and the phase delay between the excitation and vortex shedding process have been studied in detail. Although no significant changes in the flow field were noticed due to a small amplitude of excitation, the directivity of the sound field was significantly altered. The sound fields have been classified into five distinct zones for different periodic suction-blowing excitation frequencies. The beats of sounds were noted when the forcing frequency of excitation and the Strouhal frequency associated with vortex shedding were sufficiently close. It is observed that the in-phase excitation in which either blowing or suction is applied on both surfaces of a cylinder at a particular instant introduces a significant bias in the sound field directivity. The interaction between the lift dipole equivalent sources due to vortex shedding and the monopole and the drag dipole equivalent sources due to excitation introduces a bias in the sound field directivity. As a result, a dominant sound field is observed either in the top-left or in the bottom-left parts of the domain.
      Citation: AIP Advances
      PubDate: 2022-05-17T02:51:01Z
      DOI: 10.1063/5.0096914
  • Blocking effect of desktop air curtain on aerosols in exhaled breath

    • Authors: Kotaro Takamure, Yasuaki Sakamoto, Tetsuya Yagi, Yasumasa Iwatani, Hiroshi Amano, Tomomi Uchiyama
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      A desktop-type air curtain system (DACS) capable of being installed on a desk to protect healthcare workers from infectious diseases was developed. Pseudo-exhaled air containing aerosol particles emitted from a mannequin was blown toward the air curtain generated by the DACS. The aerosol blocking effect of the DACS was investigated using particle image velocimetry measurements. A scenario in which the arm of a patient in the blood collection room is placed on the gate of the DACS was also investigated. Air curtain flow was maintained inside the gate of the DACS. The aerosol particles approaching the DACS were observed to bend abruptly toward the suction port without passing through the gate, signifying that the aerosol particles were blocked by the air curtain flow. When the arm of the patient was placed on the gate of the DACS during blood collection, the airflow above the arm was disrupted. However, the aerosol blocking performance remained unaffected. We envisage that this system will be useful as an indirect barrier not only in the medical field but also in situations where sufficient physical distance cannot be maintained, such as at the reception counter.
      Citation: AIP Advances
      PubDate: 2022-05-17T02:45:05Z
      DOI: 10.1063/5.0086659
  • Biogas fixed-bed upgrading through catalytic shift–methanation: A
           numerical investigation and experimental validation

    • Authors: Xinxin Dong, Xiang Pan, Jianwei Luo, Yaji Huang, Baosheng Jin
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The numerical investigation of simultaneous methanation and water gas shift reactions (shift–methanation) for biogas upgrading in a fixed-bed reactor is conducted in this work. The catalyst bed was represented as a porous media model, and the reaction kinetics were coupled with heat and mass transfer in the whole simulation process in order to visualize the composition change and temperature profile in the reactor. The effect of reaction temperature, H2/CO ratio of feed gas, and initial CH4 content on the process was separately investigated. It was found that the biogas upgrading with highest CO conversion and CH4 mole fraction could be realized under a reaction temperature of 630 K. Larger H2/CO and initial CH4 content was beneficial to the biogas upgrading process but, in the meantime, lead to a higher temperature rise in the catalyst bed zone. The mass fraction of each component showed uniformity in the radial direction but presented an axial gradient due to the isotropy of porous media, while the temperature profile displayed both radial and axial gradients, which were caused by the temperature difference between the catalyst bed and the reactor wall. The results of experimental validation were in good accordance with the expected ones via numerical simulation.
      Citation: AIP Advances
      PubDate: 2022-05-16T02:31:57Z
      DOI: 10.1063/5.0085415
  • Single charge transport in a fully superconducting SQUISET locally tuned
           by self-inductance effects

    • Authors: E. Enrico, L. Croin, E. Strambini, F. Giazotto
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      We present a single-electron device for the manipulation of charge states via quantum interference in nanostructured electrodes. Via self-inductance effects, we induce two independent magnetic fluxes in the electrodes and we demonstrate sensitivity to single charge states and magnetic field at variable temperature. Moreover, our approach allows us to demonstrate local and independent control of the single-particle conductance between nano-engineered tunnel junctions in a fully superconducting quantum interference single-electron transistor, thereby increasing the flexibility of our single-electron transistors. Our devices show a robust modulation of the current-to-flux transfer function via control currents while exploiting the single-electron filling of a mesoscopic superconducting island. Further applications of the device concept to single charge manipulation and magnetic-flux sensing are also discussed.
      Citation: AIP Advances
      PubDate: 2022-05-16T02:31:57Z
      DOI: 10.1063/5.0084168
  • Flow boiling heat transfer characteristics of two-phase flow in

    • Authors: Lei Guo, Shusheng Zhang, Jing Hu
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      A set of experimental platforms with widths of 0.5, 1.0, 1.5, and 2.0 mm was established to explore the mechanism of flow boiling bubble dynamics in microchannels, focusing on heat transfer characteristics, pressure loss, and two-phase flow pattern identification. Bubble flow, restricted bubble flow, and dry area were observed in all four channels. The appearance of flow pattern was related to flow rate and channel width. Under the condition of the same channel width, the initial heat flux of subcooled boiling gradually increased with increase in flow rate, and this change trend was close to the linear trend. Under the same flow rate, the initial heat flux of subcooled boiling increased with decrease in channel width. This condition was due to the faster flow rate of the working medium in the narrow channel, resulting in decrease of heating time. The increase in bubble generation frequency directly led to the increase in the wall heat transfer coefficient and the decrease in the bubble separation diameter. Mathematical analysis showed that under the condition of small flow, reduction of channel size led to reduction of the total wall heat transfer coefficient. In this condition, reduction of channel size cannot enhance heat transfer. With increasing volume flow rate, the range of hydrodynamic control area increased and the index decreased. When the flow rate was large, the total heat transfer coefficient increased greatly with the decrease in channel size. The theoretical values were in good agreement with the experimental data.
      Citation: AIP Advances
      PubDate: 2022-05-16T02:31:57Z
      DOI: 10.1063/5.0095786
  • Precisely controlled microdroplet merging by
           giant-electrorheological-fluid-based microvalve

    • Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      A microfluidic device with a microvalve incorporated with intelligent giant electrorheological fluid (GERF) was proposed to actively and accurately control micro-droplet merging in various droplet scales. The GERF is a suspension without an additional electric field, and its viscosity can be increased with the increase in the voltage. A chamber composed of an expanded channel with thin membranes on both sides and several pillars is used to realize droplet merging. The chamber can restrict droplet flow to ensure droplet contact. When the pressure is applied by the microvalve, the membranes would pump up to the merging chamber. Thus, the pressure difference between the merging chamber and GERF channel could be controlled by the membranes’ deformation and influence the merging of the droplets. Therefore, the number of merged droplets from zero to five can be controlled when the flow rate of both the continuous phase and the discrete phase was 0.5 µl/min or from four to zero when the flow rate of the continuous phase was 0.8 µl/min and the discrete phase was 0.2 µl/min. The micro-chip can be easily fabricated without complex equipment, and only a pair of electrodes are required to control the microvalve. Thus, the proposed device has excellent application prospects in chemical synthesis and single-cell analysis.
      Citation: AIP Advances
      PubDate: 2022-05-16T02:23:37Z
      DOI: 10.1063/5.0088269
  • Anisotropic electron and lattice dynamics in excitonic insulator Ta2NiSe5

    • Authors: Lingqiao Chu, Kai Zhang, Jin Yang, Huachao Jiang, Zhenyou Wang, Fuhai Su
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      We employ polarization-resolved femtosecond optical pump–probe spectroscopy to investigate the nonequilibrium photocarrier dynamics in excitonic insulator Ta2NiSe5. The electronic dynamics, including hot carrier cooling, exciton formation, and recombination in the timescale ranging from subpicoseconds to a few tens of picoseconds, have been established from the transient reflectivity spectra, showing strong in-plane anisotropy with respect to the probe polarization. Such anisotropic photocarrier dynamics possibly arise from the crystalline orientation dependence of the excitonic polarizability. Furthermore, we find that the amplitude of coherent phonons with a frequency of 1 THz is subject to the probe polarization, whereas it is not sensitive to the pump polarization. This substantiates that the displacive excitation of coherent phonons plays a decisive role in lattice dynamics. In addition, we find that the photo-induced dielectric screening tends to suppress the amplitude of coherent phonons with increasing pump fluence, manifesting a remarkable polarization dependence. Our work provides valuable insights into the excitonic dynamics and the origin of coherent phonon generation and also may contribute to the development of polarization-sensitive photoelectric devices based on Ta2NiSe5.
      Citation: AIP Advances
      PubDate: 2022-05-16T02:22:37Z
      DOI: 10.1063/5.0086701
  • Contribution of both bulk and surface states on photothermoelectric
           transport in epitaxial Bi2Se3 thin films

    • Authors: Mohan Kumar Ghimire, Donguk Kim, Yun Daniel Park
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Probing the surface states in Bi2Se3 via electronic transport measurements is difficult due to the significantly larger numbers of bulk carriers. Herein, we report the contribution of both bulk and surface states on the measured photocurrent at room temperature and the electrical transport measurements at low temperatures in an epitaxial thin film of intrinsic Bi2Se3 capped with a high K dielectric, Al2O3. The measured photocurrent continuously increases when the gate voltage is swept toward the negative side from 10 to −10 V, indicating the movement of the Fermi level below the conduction band edge. Moreover, the contribution of the surface state conduction increases when the Fermi level moves inside the bandgap toward the Dirac point. Furthermore, the measured Seebeck coefficient (S) continuously increases with sweeping gate voltage from 10 to −10 V. Similar correlations of the photocurrent and S value with the gate voltage illustrate the contribution of the photothermoelectric effect due to the conduction of both bulk and surface states. Additionally, the ambipolar charge transport was observed in the electrical measurement at 32 K for the four-probe configuration. The ambipolar charge transport is possibly indicative of surface state transport.
      Citation: AIP Advances
      PubDate: 2022-05-16T02:21:17Z
      DOI: 10.1063/5.0091706
  • Computational analysis of copper electrodeposition into a porous preform

    • Authors: Md Emran Hossain Bhuiyan, Majid Minary-Jolandan
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Electroplating of metals into a porous preform with conductive walls is relevant in the fabrication of structural composites, fuel cells and batteries, and microelectronics. Electrodeposition process parameters, such as direct current or pulsed current, electric potential, and electrolyte concentration, as well as preform geometry, have important implications in the process outcomes including the filling process and the percentage of the infiltrated volume. Although electroplating into a vertical interconnect access (with nonconductive walls) for microelectronic applications has been extensively studied, the "flow-through" electroplating into a channel geometry with conducive walls has not been previously investigated. Here, copper infiltration into a such channel has been investigated using computational analysis for the first time. The effects of the inlet flow velocity, potential, electrolyte concentration, and microchannel geometry are systematically studied to quantify their influence on the electrodeposition rate, uniformity of the deposition front, and the infiltrated area within the channel. Computational results revealed that the unfilled area can be reduced to lower than 1% with a low applied potential, a high electrolyte concentration, and no inflow velocity. The results can be used to guide experiments involving electroplating metals into porous preforms toward reliable and reproducible manufacturing processes.
      Citation: AIP Advances
      PubDate: 2022-05-16T02:19:37Z
      DOI: 10.1063/5.0086665
  • High-pressure polycrystalline thin-film synthesis and semiconducting
           property of platinum pernitride

    • Authors: Ken Niwa, Tomoki Iizuka, Masashi Kurosawa, Yuto Nakamura, Hubert Okadome Valencia, Hideo Kishida, Osamu Nakatsuka, Takuya Sasaki, Nico Alexander Gaida, Masashi Hasegawa
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      A polycrystalline platinum pernitride (PtN2) thin-film was successfully synthesized via nitridation of a platinum thin-film deposited on α-Al2O3 substrate at the pressure of ∼50 GPa by using the laser-heated diamond anvil cell. The current–voltage characteristic and optical reflectance of the synthesized PtN2 thin-film were measured under ambient conditions. Combined with first-principles calculations, these experimental results have revealed that PtN2 exhibits semiconducting property with a bandgap of ∼2 eV. This high-pressure thin-film synthesis technique could also be applied for revealing the physical properties of other novel pernitrides synthesized under ultra-high pressure, which can offer new insights into the physical properties and functionality of the pernitrides and related nitrides.
      Citation: AIP Advances
      PubDate: 2022-05-13T02:10:34Z
      DOI: 10.1063/5.0090089
  • Leading-to-trailing edge theoretical design of a generic scramjet

    • Authors: R. Carneiro, P. P. B. Araújo, G. S. Marinho, J. F. A. Martos, A. Passaro, P. G. P. Toro
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The aerospace vehicle flying at hypersonic speed, using an airbreathing propulsion system based on supersonic combustion (scramjet) technology, requires a highly integrated system without moving parts, making the propulsion system and vehicle shape indistinguishable. A scramjet uses shock waves, generated by its inlet during the hypersonic flight to provide the temperature and velocity of atmospheric air to burn the hydrogen, at the combustor at supersonic speed. The divergent exhaust nozzle accelerates the combustion products providing the thrust. A two-dimensional hydrogen-powered generic scramjet has been designed to demonstrate supersonic combustion in atmospheric flight at a Mach number of 6.8 and an altitude of 30 km. Temperature and velocity at the combustion chamber are the most important key parameters for a preliminary design. The inlet configuration must provide a temperature higher than the ignition temperature of the fuel to guarantee spontaneous combustion and the velocity must remain supersonics. The nozzle exit velocity should be higher than the vehicle flight velocity to obtain sustained flight and produce enough thrust. For this theoretical analysis, the air is considered a calorically perfect gas without viscous effects. The compressible flow is analyzed based on oblique shock waves and one-dimensional compressible flow with friction and heat addition and Prandtl–Meyer coupled to the area ratio to describe each key component of the scramjet, such as compression, combustor, and nozzle sections, respectively. The inlet mass flow and hydrogen mass flow are also critical for the scramjet design to ensure stoichiometrically combustion at the combustion chamber, generating the high flow velocity at the nozzle to produce thrust.
      Citation: AIP Advances
      PubDate: 2022-05-13T02:10:34Z
      DOI: 10.1063/5.0050786
  • Tuning the resonance frequency of piezoelectric energy harvesters by
           applying direct current electric field on piezoelectric elements

    • Authors: Guan Duan, Yingwei Li, Chi Tan
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Different from previous strategies utilized to improve the energy conservation efficiency of piezoelectric energy harvesters (PEHs) from the environment, by broadening the frequency-bandwidth of energy harvesters using a specifically designed structure or tuning their resonance frequency (RF) through changing the geometrical/dynamical constraints, we report a method—by applying a direct current (DC) electric field on piezoelectric elements—to tune the RF of PEH based on the phenomenon that the elastic parameters of piezoelectric material are related to its electric field boundary condition. The results of a confirmatory experiment revealed that with a pre-loading DC electric field of −0.5 to 0.75 kV/mm, the RF of a piezoelectric cantilever energy harvester can be tuned from 144 to 156 Hz. The effectiveness of this strategy was further verified by comparing the energy conservation output of the PEH at a frequency that deviates from its RF, and at the same frequency, with pre-loading DC electric field adjustment.
      Citation: AIP Advances
      PubDate: 2022-05-13T02:10:32Z
      DOI: 10.1063/5.0086657
  • Stability and contrast in bimodal amplitude modulation atomic force
           microscopy for different mode combinations in ambient air

    • Authors: Xilong Zhou, Rongshu Zhuo
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Bimodal amplitude modulation atomic force microscopy (AM-AFM) is widely used in nanoscale topography and mechanical property imaging for a variety of materials. In this paper, the stability of the amplitude/phase spectroscopy curves and the imaging contrast in bimodal AM-AFM for different mode combinations are investigated computationally in ambient air. The results show that with the second mode amplitude used for topography feedback on a stiff material, the amplitude/phase spectroscopy would probably undergo volatile fluctuation, leading to unstable imaging. With the third mode amplitude set for topography imaging, it would be difficult for the feedback to maintain the prescribed amplitude since a large cantilever position variation is required for different sample moduli. With the first mode amplitude set for topography feedback, the amplitude and the phase of the second mode vary monotonically with sample modulus or viscosity in comparison with the third or the fourth mode, which is suitable for compositional contrast imaging. These results would provide useful guidelines for optimum imaging in bimodal AFM measurements.
      Citation: AIP Advances
      PubDate: 2022-05-13T02:10:31Z
      DOI: 10.1063/5.0085325
  • First principles study on structure and mechanical properties of Cr2AlC

    • Authors: JianRong Zhang, KeWei Tao, LiDong Ma, YangYang Yang, Lei Yang, WenShan Duan
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The first principles method is used to study the intrinsic vacancy of Cr, Al, and C in Cr2AlC materials with formation energies of 1.89, 1.95, and 1.07 eV, respectively. It has been proven in previous research that Al layers could be easily removed from Cr2AlC, and the formation energies of Cr2AlC are, therefore, calculated in this study after removing two layers of Al atoms to form Cr2C. The formation energies of the H, He, and O atoms that replace the Al atoms are also calculated to be −2.83, 90.73, and −47.81 eV, respectively. It shows that under irradiation or a high temperature environment, Cr2AlC is easily oxidized to form Cr2C materials. Furthermore, the density of states of Cr2AlC with an Al layer substituted by H, He, and O atoms, as well as the phonon properties of Cr2AlC and Cr2C, are calculated. The results show that the Cr–C metal bond is dominant in Cr2AlC materials to maintain the stability of the structure. The calculation results of mechanical properties show that the presence of Al atoms enhances the plasticity of Cr2AlC.
      Citation: AIP Advances
      PubDate: 2022-05-13T02:10:30Z
      DOI: 10.1063/5.0091402
  • An estimation method of the spatial resolution for magnifying fast neutron

    • Authors: J. J. Li, Y. S. Dong, B. Yu, Z. J. Chen, J. H. Zheng, L. Yao, J. M. Yang
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Fast neutron radiography (FNR) using divergent neutron beams has the characteristic to magnify small cracks in low-Z materials. For such magnifying FNR systems, a simple method was developed using Monte Carlo simulations to estimate the spatial resolution. The resolution degrading factors, including neutron source size, object thickness, and crosstalk in the detector, have been investigated in this method. The calculated results of this method compare favorably to independent estimations of various designs for the same FNR system. For a magnifying FNR system, a better spatial resolution can be expected with larger magnifications and smaller sources.
      Citation: AIP Advances
      PubDate: 2022-05-13T02:10:28Z
      DOI: 10.1063/5.0088796
  • Critical behavior of quantum Fisher information in finite-size open Dicke

    • Authors: Meng Yu, Yang Yang, Hengna Xiong, Xianqin Lin
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      We explore the steady-state critical behavior of the finite-size open Dicke model—a model that incorporates spontaneous emission decay of the collective atomic spin states and decay of the cavity field. From the perspective of quantum information theory, we can often better characterize the quantum phase transition. In this paper, we characterize the super-radiant phase transition of the steady state of the open Dicke model by numerically calculating the quantum Fisher information (QFI). We calculate the QFI for the atomic state and the cavity field state, as well as their derivatives. We find that the QFI of the cavity field state is more sensitive to atomic decay, and is suppressed more severely in the presence of atomic decay. In contrast, the QFI of the atomic state is less sensitive to the photon loss of the cavity field.
      Citation: AIP Advances
      PubDate: 2022-05-13T02:10:28Z
      DOI: 10.1063/5.0091100
  • Heat transfer model and cooling performance of converter oxygen lance
           affected by slag sticking

    • Authors: Guangqiang Liu, Junnan Li, Kun Liu, Peng Han, Yingshi Xu
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The heat transfer mechanism and water-cooling effect during oxygen lance blowing changes by slag sticking at the nozzle. In order to effectively overcome this problem, in this study, the equivalent heat transfer method was applied to modify the heat transfer coefficient of the oxygen lance nozzle under different slag thicknesses and steel slag thermal conductivities. In addition, the gas–liquid two-phase heat transfer model was established by computational fluid dynamics numerical simulation, and the cooling effects for different types of oxygen lance nozzles were calculated by the improved model. The results show that the error rate between the calculated value of the modified model and the field measured value was reduced to 3.3%–4.6%. The nozzle with double angle and double flow design was found to be conducive to the improvement of the cooling system. In this study, the best cooling effect was obtained when the flow ratio of large nozzles and small nozzles is 60%/40% and the angle is 12°/17°.
      Citation: AIP Advances
      PubDate: 2022-05-13T02:10:28Z
      DOI: 10.1063/5.0090193
  • Potential soluble substrates for transient electronics applications: A

    • Authors: Sheetikanta Mohanty, Avi Arya, Dipun Jena, Shrabani Guhathakurata, Nabin Baran Manik, Gufran Ahmad, Sandipan Mallik
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The excessive usage and demand of consumer electronics have caused an elevation of electronic waste. Typically, consumer electronics are produced with non-biodegradable, non-biostable, and sometimes fatal materials, resulting in global alarming biological summons. Thence, to mend the drawbacks, an emerging field—named transient electronics—takes effect where the biomaterial, device, substrate, and total systems disappear untraceably after steady-state operation. Conspicuously, transient electronics have induced immense curiosity in researchers to perform interesting investigations due to the feature of disintegration after stable operation. The idea of transient electronics has been implemented in biomedical, military, and nanotechnology fields. Although rapid development is evident in transient technology in a short period, it is believed that the technology will deliver the utmost prospects in advanced electronic applications. Essentially, in transient technology, the vital challenge is to determine the platform materials that offer stability, resistance, biocompatibility, and mainly, the solubility to accommodate the transient devices. In this Review, a detailed overview of different soluble substrates, such as organic, polymer, and solid-state substrates, is described, along with the feasibility of the fabricated devices on the respective substrates to support transient electronics. Second, the dissolving mechanism of the corresponding substrates is analyzed.
      Citation: AIP Advances
      PubDate: 2022-05-13T02:10:26Z
      DOI: 10.1063/5.0066174
  • Suppress the vibration of tool system in milling process

    • Authors: Binbin Peng, Xianguo Yan, Juan Du
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      A nonlinear energy sink (NES) is used to suppress the vibration of the tool system in milling operations. The corresponding theoretical analysis is done on the nonlinear vibration absorption characteristics of NES. First, the dynamic model of the milling tool system and the milling force are analyzed. The dynamic model and equation of the tool-NES system are then deduced. The approximate analytical solution is solved by the harmonic balance method, and the correctness of the analytical solution is verified by the numerical solution. The numerical simulation reveals the suppression effect of NES on the transient vibration and steady vibration of the tool system.
      Citation: AIP Advances
      PubDate: 2022-05-13T02:10:26Z
      DOI: 10.1063/5.0091935
  • A garnet-structured (Y, Ca)3(Al, Mg)2(Al, Si)3O12:Ce3+ phosphor-in-glass
           engineering for use in high color rendering white LEDs

    • Authors: Huan Tu, Guoying Zhao, Jingshan Hou, Yufeng Liu, Yan Zhou, Ganghua Zhang, Hong-Tao Sun, Ji-Guang Li, Yongzheng Fang
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      White light emitting diodes (LEDs) suffer from two most common drawbacks: the deficiency of the red component and the poor thermal stability of silicone. Ce3+-doped garnet phosphors with tailor-made luminescence properties can be achieved by variations in {A}, {B}, and {C} cation sites. Herein, a simultaneous ion co-substitution design strategy has been adopted to synthesize a series of (Y, Ca)3(Al, Mg)2(Al, Si)3O12 garnet phosphors and corresponding phosphor-in-glass (PiG) films. The co-substitution is finely restricted to the assigned sites. The emission peak is shifted from 529 to 565 nm, which is beneficial to obtain low color temperatures and high color rendering using a single phosphor for white LEDs. By employing the as-synthesized phosphor, the corresponding PiG films were fabricated by the low temperature co-sintering technology using the SiO2–B2O3–ZnO–Na2O glass system characterized with excellent thermal stability and moisture resistance. The morphological and elemental analyses demonstrated that the as-made phosphor powders were uniformly distributed in the glass host without any interfacial reactions. Finally, modular white LEDs with a high color rendering (Ra = 82.7) is achieved through the as-synthesized PiG film on an InGaN blue chip. This study may open up a facile approach to obtain high quality luminescence based on the mono-luminescence center, avoiding excitation energy wastage and low quantum efficiency aroused by multi-luminescence centers or color compensation phosphors in glass.
      Citation: AIP Advances
      PubDate: 2022-05-12T01:50:51Z
      DOI: 10.1063/5.0084578
  • Real-space observation of non-collinear spin structure in centrosymmetric
           TbGa rare-earth magnet

    • Authors: Yang Gao, Xinqi Zheng, Zhuolin Li, Jiawang Xu, Jie Qi, Yaqin Guo, Chaoqun Hu, Weidu Qin, Congli He, Shipeng Shen, Hongxiang Wei, Ying Zhang, Shouguo Wang
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The exploration of non-collinear spin texture in the f-electron-based rare-earth magnets has attracted fascinating interest for its fundamental physics and potential spintronic applications. Here, the real-space observation of nanometric helical spin order with the period down to 20 nm in centrosymmetric TbGa magnets was presented by Lorentz transmission electron microscopy. It was found that the helical period and the initial temperature for the appearance of the periodic helix can be tuned by the thickness of single-crystal TbGa plates (71–169 nm). Furthermore, the domain evolution under the perpendicular magnetic fields and with the shape constriction reveals the high stability of the stripe domains.
      Citation: AIP Advances
      PubDate: 2022-05-12T01:50:51Z
      DOI: 10.1063/5.0077085
  • Influence of metachronal ciliary wave motion on peristaltic flow of
           nanofluid model of synovitis problem

    • Authors: Asha S. Kotnurkar, Namrata Kallolikar
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      In this article, we have considered the effect of metachronal ciliary wave motion on the peristaltic flow of the Buongiorno nanofluid model for the synovitis problem. This study is additionally limited by the assumption of a low Reynolds number and lubrication theory approximations. An internal energy generation is also taken into account. Shear-thinning (model I) and shear-thickening (model II) for the concentration fluids are considered. The obtained dimensionless rheological equation is solved by using the homotopy perturbation Sumudu transformation method. The influence of various physical parameters on the dimensionless velocity, pressure rise, temperature, volume fraction, multi-sinusoidal waves, triangular waves, and streamlines has been analyzed. A trapping phenomenon is thoroughly examined. It is observed from the investigation that the shear-thinning (model I) and shear-thickening (model II) have completely distinct characteristics. The synovial fluid parameter shows opposite behavior on velocity and pressure rise profiles for models I and II, whereas the multi-sinusoidal wave and triangular wave forms retain the same shape of the waves as in the pressure gradient. These models can be used to treat rheumatoid arthritis as synovial fluids are present in joints. Fluid transfer in biological organs is improved by metachronal ciliary motion. Patients with rheumatoid arthritis can be treated with nanoparticles and ciliary motion. It is primarily due to their biocompatibility, low toxicity, and controlled release as well as their capacity to boost bioavailability and bioactivity of treatments and enable targeting the injured joints through the use of nanoparticles. In the limited scenario, the current work is in good accord with the earlier research, and it is analyzed through a graph.
      Citation: AIP Advances
      PubDate: 2022-05-12T01:50:49Z
      DOI: 10.1063/5.0093107
  • Using numerical analysis of ordinary differential equation systems to
           predict the chemical concentration after plasma irradiation

    • Authors: T. Kladphet, V. P. Thai, W. T. L. S. Fernando, K. Takahashi, T. Kikuchi, T. Sasaki
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      In this study, a zero-dimensional numerical simulation of the atmospheric pressure plasma (APP) interface with a liquid solution was performed. By assuming that the solution reaction is dependent on the injection of radicals and electrons, we were able to obtain a single short APP discharge with the liquid solution. This study can predict excitation temperature, electron temperature, and population densities of species and result in optimum conditions for a chemical reaction for the synthesis of nanoparticles or other applications of the reaction between APP and liquid surface. This work aims to explain the effect of pH values on the synthesis of gold nanoparticles compared with experimental results. We found that the effect of pH value is expected to impact the generation of gold nanoparticles. Therefore, a high pH value is suitable for generating gold atoms for nano-synthesis. The fundamental plasma properties, such as population density, electron temperature, excitation temperature, and gas temperature, and chemical reaction process were studied. The simulation results were consistent with the experimental observations.
      Citation: AIP Advances
      PubDate: 2022-05-12T01:50:47Z
      DOI: 10.1063/5.0091403
  • Demonstration and modeling of time-bin entangled photons from a quantum
           dot in a nanowire

    • Authors: Philipp Aumann, Maximilian Prilmüller, Florian Kappe, Laurin Ostermann, Dan Dalacu, Philip J. Poole, Helmut Ritsch, Wolfgang Lechner, Gregor Weihs
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Resonant excitation of the biexciton state in an InAsP quantum dot by a phase-coherent pair of picosecond pulses allows preparing time-bin entangled pairs of photons via the biexciton–exciton cascade. We show that this scheme can be implemented for a dot embedded in an InP nanowire. The underlying physical mechanisms can be represented and quantitatively analyzed by an effective three-level open system master equation. Simulation parameters including decay and intensity dependent dephasing rates are extracted from experimental data, which in turn let us predict the resulting entanglement and optimal operating conditions.
      Citation: AIP Advances
      PubDate: 2022-05-12T01:50:46Z
      DOI: 10.1063/5.0081874
  • Flow in fuel nozzles under cavitation and flash-boiling conditions

    • Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Cavitation plays a crucial role in various fuel systems and spray applications. Due to the limitation in experimentally measuring the cavitation flow in fuel nozzles, numerical simulations can be used as an alternative in exploring the underlying physics. Most of the previous simulations of cavitation flow in nozzles were carried out under isothermal conditions, which become invalid when the thermal effect is strong. In this study, we use OpenFOAM and a modified cavitation model to investigate the influence of thermal effect on fuel nozzle flow characteristics under cavitation and flash boiling conditions. The comparison with experimental data shows that the modified cavitation model can predict well the cavitation flow in nozzles. Vaporization caused by cavitation at the nozzle throat and vaporization caused by the flash boiling near the outlet are simulated under different conditions. Phenomena such as mass flow reduction, outlet velocity blockage, and the transition from cavitation flow to flash boiling flow are well predicted. Further results show that with the increase in the inlet fuel temperature, the cavitation at the throat and flash boiling at the outlet occur gradually and then mix under high-temperature conditions. With the decrease in the ambient pressure, the flow in the nozzle gradually transits from single-phase flow to cavitation flow and then to flash-boiling flow. Increasing the injection pressure can inhibit the generation and the growth of superheated vapor near the nozzle outlet.
      Citation: AIP Advances
      PubDate: 2022-05-12T01:50:46Z
      DOI: 10.1063/5.0089755
  • An ultrahigh sensitivity three-dimensional electric-field sensor with
           barium titanate crystal waveguides

    • Authors: Mengxi Luo, DeGui Sun, Guangyong Jin
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The high-speed development and applications of modern automation production, high-capacity high-speed telecommunications, and aerospace are promoting the detection and sensing of various electric fields. In this article, we investigate a three-dimensional high-frequency electric-field sensor with a barium titanate (BaTiO3) crystal film waveguide due to an extremely high electrooptic (EO) coefficient, r51 = r42. First, the dependences of the lowest electric field, namely, the sensitivity of the sensor to the electric field and the most sensitive direction, are modeled through the nonlinear EO modulation equation of the EO coefficient, r51, and birefringence, beo, with an embedded waveguide/electrode regime. Then, for the given r51/beo values, broad dependences of device sensitivities are numerically simulated with a broad design of electrodes. Thus, as a result, for a given BaTiO3 crystal thin-film having an EO coefficient value of r51 = ≥500 pm/V and an absolute beo value of ≤0.01, the lowest electric field of tens of kilovolt/m level and the electric-field direction could also be detected with a sensing length of millimeters. Meanwhile, the frequency dependence of a scattering parameter of the microwave sensor antenna, S11, is simulated and the frequency point of 2.15 GHz for the highest gain antenna is found.
      Citation: AIP Advances
      PubDate: 2022-05-12T01:50:44Z
      DOI: 10.1063/5.0084369
  • Tunable nucleation process of nano-sized NaZn13-type and α-(Fe,Si) phases
           by doping boron in La–Fe–Si alloys during rapid solidification

    • Authors: Yuhu Hu, Huihui Song, Jinyu Fang, Jiale Zhang, Kai Xu, Shuiming Huang, Xueling Hou
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The effect of a small dose of boron-doping on the nucleation process of nano-sized 1:13 phase (NaZn13-type phase) and α-(Fe,Si) phase of the La–Fe–Si alloys during the rapid solidification was investigated. The simulation of classical nucleation theory indicates a competitive nucleation relationship between 1:13 and α-(Fe,Si) phases during the rapid solidification. Compared to the La–Fe–Si alloys undoped with boron atom, the undercooled temperature change (ΔT) for the same nucleation rate conditions of the 1:13 and α-Fe phases was significantly decreased from 673 K (x = 0) to 639 K (x = 0.3) during the rapid solidification of La–Fe–Si–B alloys. The analysis of the microstructure and phase structure of the La–Fe–Si alloys ribbons by scanning electron microscope , x-ray diffraction, and transmission electron microscope also concludes that the doping of boron promoted the formation of the 1:13 phase. The results of this study have considerable meaning for the engineering application of magnetic refrigeration materials (La–Fe–Si) in the future.
      Citation: AIP Advances
      PubDate: 2022-05-12T01:50:43Z
      DOI: 10.1063/5.0088184
  • Temperature dependence of tunnel magnetoresistance in serial magnetic
           tunnel junctions

    • Authors: Dongyan Zhao, Yubo Wang, Jin Shao, Yanning Chen, Zhen Fu, Qingtao Xia, Shuaipeng Wang, Xiuwei Li, Guangzhi Dong, Min Zhou, Dapeng Zhu
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Magnetic tunnel junctions have been widely used in various applications, such as magnetic sensors and magnetic random-access memories. In the practical application of MTJs, they are usually used in series toward high sensitivity and high stability, especially for sensor applications. In this paper, serial MTJs devices on 8 in. wafers were fabricated. The temperature dependence of the tunnel magnetoresistance ratio, resistances in parallel and antiparallel configurations, and dynamic conductance were systematically investigated. The results of serial MTJs devices are consistent with a single MTJ device. This research suggests that serial MTJs can be directly used to investigate the magnetic tunneling properties of MTJ stacks.
      Citation: AIP Advances
      PubDate: 2022-05-12T01:50:41Z
      DOI: 10.1063/5.0088020
  • Broad-frequency range of a 250 GHz medium-power gyrotron traveling-wave
           amplifier with a distributed-loss structure

    • Authors: Yi Sheng Yeh, Chien-Lun Hung, Tsun-Hsu Chang
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      A gyrotron traveling-wave amplifier (gyro-TWA) with a distributed-loss structure can achieve high gain over a broad bandwidth. In this study, a low-voltage, low-current subterahertz gyro-TWA with medium power (∼10 W) over a broad-frequency range (∼10 GHz) is designed. The excessive length of the copper section in this gyro-TWA leads to reflective oscillations and absolute instabilities. Reflective oscillations can be suppressed for a gyro-TWA with a high lossy-section resistivity and a short copper section. Absolute instabilities, conversely, can be suppressed for a gyro-TWA with a long lossy section and high lossy-section resistivity. The proposed gyro-TWA has a high lossy-section resistivity, a long lossy section, and a short copper section, which not only avoids mode competition but also achieves the desired characteristics of a high gain and broad-frequency range. For a 12 kV, 0.3 A electron beam, the frequency range of the 250 GHz 10 W level gyro-TWA with a distributed-loss structure, is ∼10 GHz when the input power is between 1 and 10 mW.
      Citation: AIP Advances
      PubDate: 2022-05-12T01:50:40Z
      DOI: 10.1063/5.0093711
  • Frequency splitting suppression in wireless power transfer using
           hemispherical spiral coils

    • Authors: Wangqiang Niu, Jiateng Jiang, Chen Ye, Wei Gu
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      In wireless power transfer (WPT) systems, frequency splitting phenomena always occur when the transfer distance is too small to obtain the maximum output efficiency in the working frequency. In this paper, a hemispherical spiral coil structure is proposed to suppress frequency splitting phenomena by containing the coupling the system without changing the original system size and transfer distance. Meanwhile, compared with the planar system, the hemispherical system can maintain high power and transfer efficiency and has better angular misalignment tolerance. A WPT system consisting of a hemispherical spiral coil and a planar spiral coil resonating at 110 kHz called the single hemispherical spiral coil WPT (SHWPT) system and another with two hemispherical spiral coils called the double hemispheric spiral coils WPT (DHWPT) system are suggested. Analytic models of these two structures are established to analyze the influence of the coil height on the frequency splitting. The critical coil height is closely related to the critical coupling that provides a reference for the design of the coil. Finally, the experimental results show that the hemispherical coil structure can suppress the frequency splitting to ensure the transmission stability of the WPT system. In the SHWPT system with a 1 cm inner diameter and a 13 cm outer diameter, the critical height of the coil is 5.2 cm, which can suppress frequency splitting when the transmission distance is 0 cm. In the DHWPT system, the critical height of the coil is 4.3 cm.
      Citation: AIP Advances
      PubDate: 2022-05-11T12:57:24Z
      DOI: 10.1063/5.0078744
  • Chemical bonds and weak interactions of methoxysalicylic acid isomers
           investigated by terahertz spectroscopy and density functional theory

    • Authors: Yuan Tang, Zhi Li, Huo Zhang, Shan Tu, Yulai She
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The characteristic absorption spectra of isomers (3-, 4-, and 6-methoxysalicylic acid) were investigated by terahertz time-domain spectroscopy (THz-TDS) in the range of 0.4–3.0 THz. In parallel with the experimental study, the unit cells of the three isomers were calculated by density functional theory, and we found that the theoretical spectral absorption peaks were basically consistent with the experimental results. To better comprehensively interpret the origin of the characteristic absorption peaks, the potential energy distribution (PED) method was used to assign the vibrational modes of absorption peaks. The interaction of the system was analyzed qualitatively and quantitatively by using the interaction region indicator (IRI) and energy decomposition analysis based on forcefield (EDA-FF). The analysis indicated the weak interaction types of 3-, 4-, and 6-methoxysalicylic acid were dominated by van der Waals interaction. There are slight differences in intra- and inter-molecular weak hydrogen bonds among the three substances. The weak interaction is mainly contributed by dispersion. The results show that THz-TDS can accurately identify isomers. It provides a novel idea for studying molecular vibration characteristics, chemical bonds, and weak interactions combined with PED, IRI, and EDA-FF analysis methods.
      Citation: AIP Advances
      PubDate: 2022-05-11T12:56:44Z
      DOI: 10.1063/5.0082819
  • A method for improving the betavoltaic cell’s conversion efficiency:
           Using the alloy as Schottky metal

    • Authors: Yu Wang, Jingbin Lu, Renzhou Zheng, Xiaoyi Li, Yumin Liu, Xue Zhang, Yuehui Zhang, Ziyi Chen
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Under the irradiation of a 63Ni source, the Al/diamond Schottky barrier diode and 2198 Al–Li alloy/diamond Schottky barrier diode can convert decay energy into electrical energy. Through the Monte Carlo method, the energy depositions of the 63Ni source in the energy converters are simulated separately. And then the electrical output properties of two betavoltaic batteries are calculated and compared. The short-circuit current density, open-circuit voltage, fill factor and maximum output power density of the Al/diamond and 2198 Al–Li alloy/diamond Schottky barrier batteries are 0.086 μA/cm2, 2.14 V, 0.93, 0.17 μW/cm2 and 0.089 μA/cm2, 2.66 V, 0.95, 0.22 μW/cm2, respectively. The maximum output power increased by about 29%, which indicates that using alloy as Schottky metal can significantly improve the output performance of a betavoltaic battery.
      Citation: AIP Advances
      PubDate: 2022-05-10T12:01:23Z
      DOI: 10.1063/5.0081680
  • The measurement of carbon density profile using charge exchange
           spectroscopy in KSTAR

    • Authors: J. K. Lee, H. H. Lee, W. H. Ko, B. Na, J. Ko, M. W. Lee, S. G. Lee
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The first measurement of the impurity density profile via charge exchange spectroscopy (CES) has been successfully achieved in KSTAR. Since the neutral beam density profile is essential for the measurement, the neutral beam penetration code that was originally developed for the Alcator C-mod tokamak has been optimized for the KSTAR experimental environment. The method of the impurity density measurement by the KSTAR CES system is introduced and the sensitivity analysis of various physical parameters, such as the effective charge in the estimation of the impurity density, is performed to examine the validation of the method. This method has been applied to measure the C6+ density profile affected by the resonant magnetic perturbations (RMPs), which is mainly used to suppress the edge localized modes (ELMs) in KSTAR. The dynamics of the C6+ density profile represent that the C6+ density decreases immediately after the application of RMPs but recovers soon during the ELM-suppressed phase.
      Citation: AIP Advances
      PubDate: 2022-05-10T12:01:22Z
      DOI: 10.1063/5.0080075
  • Spin–orbit torque driven nano-oscillators based on synthetic Néel-like
           skyrmion in magnetic tunnel junction

    • Authors: Byoung Choi, Mukesh Aryal, Minyeong Choi, Yang-Ki Hong
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      A synthetic skyrmion-based magnetic tunnel junction spintronic nano-oscillator is proposed. The oscillator consists of a Pt/Co/AlOx/Co heterostructure. It exploits the high-frequency eigenoscillations of a synthetic chiral nanomagnet, which is imprinted in the Pt/Co layer by the local manipulation of the magnetic anisotropy and interfacial Dzyaloshinskii–Moriya interaction. This synthetic nanomagnet has the spin texture equivalent to the Néel skyrmion, and its topological stabilization remains resilient with respect to the thermal fluctuations at finite temperatures. The oscillator is activated by spin Hall effect-induced spin–orbit torques, and an eigenoscillation with a frequency of ∼2.5 GHz is achieved. When the drive current exceeds a threshold value, the eigenfrequency shifts toward lower frequencies. This redshift is associated with the transition of skyrmion dynamics, in which its eigenmode evolves from the counter-clockwise rotation mode to a complex hybrid mode. Our result verifies the working performance of the proposed synthetic skyrmion-based oscillator and suggests promising prospects for using such artificial nanomagnets in future spintronic applications. It is also found that the synthetic skyrmions are topologically protected from annihilation under high drive currents and finite temperatures, and this resilience, thus, offers new opportunities to better design next generation skyrmion-based spintronic devices.
      Citation: AIP Advances
      PubDate: 2022-05-10T12:01:21Z
      DOI: 10.1063/5.0088199
  • Design considerations for diode-based nonlinear transmission lines

    • Authors: Nicholas Gardner, Kalyan Durbhakula, Anthony Caruso
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Diode-based nonlinear transmission lines (D-NLTL) are a class of pulse shaping networks capable of increasing the discrete spectral content of a pulse at high volumetric power density. However, a systematic design procedure for D-NLTLs is lacking, limiting their prototyping, evaluation, production, and adoption. To produce a D-NLTL design approach, parameters for UHF band (0.3–1 GHz) frequency generation are presented as a function of the input excitation pulse, network topology, and sub-components’ reactive value. Excitation pulse amplitude is found to have a strong effect on center frequency (fc), max frequency (fBragg), peak power (Ppeak), and RF power conversion efficiency (ηRF). In general, when cell inductance is decreased, both fc and signal propagation velocity are increased. The results are then presented as an example to design, build, test, and compare a 40-cell D-NLTL whose measured fc and fBragg are 256 and 446 MHz, respectively. Finally, we used the parameter space study results and empirical validation to present controllable waveform design rules-of-thumb.
      Citation: AIP Advances
      PubDate: 2022-05-10T12:01:19Z
      DOI: 10.1063/5.0091940
  • Electronic band structure and chemical bonding in trigonal Se and Te

    • Authors: V. G. Orlov, G. S. Sergeev
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Herein, the electronic band structure and charge density distribution are theoretically studied in trigonal Se and Te to clarify the uncertainty stemming from the different views on the types of chemical bonding in their crystals and to reconsider the role of valence s- and p-electrons in bonding. The lack of overlapping of the lower and upper bands of valence p-electrons in trigonal Se and the large band separation of valence s- and p-electrons present an opportunity to estimate the contributions of valence s- and p-electrons to the charge densities of two types of bond critical points (BCPs) in trigonal Se. Valence s-electrons and lower p-electrons significantly contribute to the charge density of BCPs of the first type, covalently connecting the nearest neighboring atoms within helical chains. In contrast, the lower and upper valence p-electrons are mainly responsible for the BCPs of the second type linking the neighboring chains in the Se and Te trigonal crystal structures. The nonlocal long-range van der Waals (vdW) correlation functional vdW-DF2, which is important for determining lattice constants, has a minimal effect on BCP parameters, which define the chemical bonding types. The exchange potential of Becke and Johnson modified by Tran and Blaha and the short-range electron–electron correlations considered in the local density approximation correctly reproduce not only the energy bandgap values but also various peculiarities in the electronic band structure of trigonal Se and Te, such as band crossings (Weyl nodes) of the valence p-electrons recently found in trigonal Te via angle-resolved photoemission spectroscopy experiments.
      Citation: AIP Advances
      PubDate: 2022-05-10T12:01:19Z
      DOI: 10.1063/5.0087880
  • Optimization of optical spin readout of the nitrogen-vacancy center in
           diamond based on spin relaxation model

    • Authors: Yuki Nakamura, Hideyuki Watanabe, Hitoshi Sumiya, Kohei M. Itoh, Kento Sasaki, Junko Ishi-Hayase, Kensuke Kobayashi
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      For quantum sensing, it is vital to develop an efficient technique for determining the quantum state of the sensor. We optimize the weighting of the photoluminescence intensity for readout of the spin state of the nitrogen-vacancy (NV) center in diamond. We find that adopting a physical model that considers the optical transitions and relaxations of the NV center allows for an efficient readout. Our method improves the signal-to-noise ratio of the readout by 5.4% in a short time of 3 s, while the existing methods typically require 1 min of integration time. We also show that our technique enhances the readout of the nuclear spin memory. The demonstrated way is helpful for a wide range of measurements, from a few minutes to several days.
      Citation: AIP Advances
      PubDate: 2022-05-10T12:01:18Z
      DOI: 10.1063/5.0090450
  • Accurate equation of state of rhenium as pressure scale up to 130 GPa
           and 3200 K

    • Authors: Yunting Xian, Shikai Xiang, Lei Liu, Junxiang Chen, Yin Luo
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The equations of states (EOSs) of inert metals are generally used as pressure scales in a high-pressure experiment. However, the thermodynamic model and the method used to constrain the parameters of the EOSs of these metals may cause pressure deviations of up to 7% at 100 GPa and room temperature, and even higher at higher pressures and higher temperatures. In this study, we provide a new approach for obtaining accurate EOS of inert metals. First, we use a set of thermodynamic models, within the quasi-Debye framework, to describe the thermodynamics. Second, both the volume vs pressure data from the shock compression experiment and the volume vs sound velocity data from the static compression experiment are used to constrain the parameters in the EOS formula. In the fitting process, a weighted least-square method based on the uncertainty of these data is used. The calculated Grüneisen parameter shows a strong dependence not only on volume but also on temperature. The variation of the Grüneisen parameter of Re can increase by up to 7% per 103 K under the same volume, which means the previous temperature-independent approximation of the Grüneisen parameter may cause an underestimate of the pressure at high temperature. The pressure–volume–temperature EOS of Re up to 140 GPa and 3200 K is established, which can be used as a high-pressure and high-temperature pressure gauge in the future.
      Citation: AIP Advances
      PubDate: 2022-05-10T12:01:17Z
      DOI: 10.1063/5.0089292
  • Photon excitation effect on formation of graphene nanocrystallites during
           carbon film growth process

    • Authors: Cheng Chen, Zhixin Zhang, Zhiquan Huang, Nan Jian, Dongfeng Diao
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      In this article, we propose a method to deposit nanocrystallite embedded carbon films by electron cyclotron resonance plasma sputtering with photon irradiation cooperated with electron or Ar+ ion irradiation. We found photon irradiation can enhance the growth of graphene nanocrystallites during carbon film deposition. The energy transfer from the photon to the metastable carbon structure excites the growth of sp2 hybridized graphene nanocrystallites, and photon-excited electrons can be accelerated by the bias and further promote the graphene nanocrystallite growth. Photons are the second quantum medium we found that can be used to deposit nanocrystallite embedded carbon films, and their quantum properties with electric neutrality can help us to further understand the formation of the carbon nanocrystallite structure and may shed light on the quantum fabrication of desired materials.
      Citation: AIP Advances
      PubDate: 2022-05-10T12:01:16Z
      DOI: 10.1063/5.0094173
  • Newly designed ignition circuit to improve the ignition reliability of
           Hall thruster

    • Authors: Jingjing Li, Wenbo Li, Liqiu Wei, Liwei Zhou, Tianyuan Ji, Wenjia Jiang, Tingwan Li, Hong Li, Jingfeng Tang, Yongfeng He, Yongjie Ding
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      This study proposes a newly designed ignition circuit that does not change the ignition starting parameters of a Hall thruster, reduces the critical ignition voltage, and improves ignition reliability. The complexity and weight of the Hall thruster power supply system are reduced by multiplexing the ignition and discharge power supplies. Under the condition that the design parameters are satisfied, that is, [math] is much larger than RCC1, the residual energy in the circuit after the cathode breakdown can be fed into the thruster discharge channel to improve the ignition energy supply. The experimental results show that when the anode voltage is 98 V, only nine of the 100 ignition tests are successful using the traditional ignition circuit, whereas the number of successes using the newly designed ignition circuit is as high as 99, which provides a simple solution method for improving the ignition reliability.
      Citation: AIP Advances
      PubDate: 2022-05-10T12:01:14Z
      DOI: 10.1063/5.0086662
  • Thin-film temperature sensors based on LPD-fabricated β-Ga2O3
           Schottky diodes

    • Authors: Sanjoy Paul, Tai-Siang Chen, Mau-Phon Houng, Jian V. Li
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      We report the synthesis of wide-bandgap β-Ga2O3 nanocrystalline thin films via the low-cost and non-vacuum-based liquid phase deposition (LPD) method. The morphological evolution of the nanocrystalline β-Ga2O3 grains was investigated as a function of the growth temperature, processing time, and pH value of the precursor solution. We successfully calcined gallium oxide hydroxide GaO(OH) through a 3-h annealing process at 800 °C to convert it into β-Ga2O3. We fabricated horizontal-structured Ni/β-Ga2O3 Schottky diodes and investigated the electrical characteristics pertinent to sensing temperature in the range of 100−800 K. The temperature sensitivity of the Ni/β-Ga2O3 Schottky-junction temperature sensors, defined as the temperature dependence of junction voltage at a fixed bias current of 10 µA, peaked at −2.924 mV/K in the range between 300 and 500 K. At room temperature, we measured a barrier height of 0.915 eV and a Richardson constant of 43.04 ± 0.01 A/cm2 K2 from the Ni/β-Ga2O3 Schottky junctions. These results indicate that the LPD-synthesized β-Ga2O3 material and devices hold promising potential for sensing applications especially at high temperatures.
      Citation: AIP Advances
      PubDate: 2022-05-10T12:01:14Z
      DOI: 10.1063/5.0090723
  • Nonlinear multiphoton modification of glass substrates for fabrication of
           high aspect ratio through-glass vias

    • Authors: Min-Kai Lee, Jyun-Zong Yu, Hsin-Yu Chang, Chia-Yuan Chang, Chien-Sheng Liu, Pai-Chen Lin
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      To meet the demands of high-frequency wireless communications and Internet of Things (IoT) applications, modern integrated circuit (IC) packages should support operating frequencies in the GHz range and be implemented on fine substrate structures. Glass has many advantages as an interposer material for three-dimensional IC (3D-IC) designs, including tunable electrical and mechanical properties, amenability to large-scale processing, and high optical transparency in the visible range. Moreover, glass is easily processed to produce the through-glass vias (TGVs) required to realize high-frequency circuit designs and microelectromechanical systems devices. The present study proposes a method for patterning TGVs on glass substrates via a nonlinear multiphoton-assisted modification process performed using single-pulse irradiation by a 1030-nm picosecond laser. A theoretical model is additionally proposed to describe the glass substrate modification mechanism induced by the nonlinear multiphoton excitation effect. The feasibility of the proposed method is demonstrated by patterning a TGV array with a high aspect ratio of 1:10 and a taper angle of ∼2° on a Corning SGW3 glass substrate.
      Citation: AIP Advances
      PubDate: 2022-05-09T01:40:08Z
      DOI: 10.1063/5.0086879
  • Suppression of non-axisymmetric field-induced α-particle loss channels in
           a quasi-axisymmetric stellarator

    • Authors: Yichao Zhang, Haifeng Liu, Jie Huang, Yuhong Xu, Jian Zhang, Akihiro Shimizu, Shinsuke Satake, Mitsutaka Isobe, Xianqu Wang, Jun Cheng, Hai Liu, Xin Zhang, Changjian Tang
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      In future fusion reactors, the confinement of α-particles is a crucial issue. The perfect omnigenity may be difficult to achieve in the quasi-isodynamic and quasi-symmetric stellarators when a multi-objective optimization is considered. Non-axisymmetric field can result in collisionless particles’ transport via localized trapping by ripples. Specific loss channels have been revealed to essentially exist in quasi-axisymmetric stellarators [Yang et al., Europhys. Lett. 129, 35001 (2020)] and W7-X [J. M. Faustin et al., Nucl. Fusion 56, 092006 (2016)]. It indicates a drastic loss of collisionless ions through these channels. This paper is devoted to investigate the effects of axisymmetry-breaking magnetic fields on collisionless α-particle transport in the CFQS (Chinese First Quasi-axisymmetric Stellarator) -like reactor configuration. A semi-analytic representation of radial and poloidal drifts in Boozer coordinates is given, by which we found an effective route to mitigate α-particle losses, i.e., adjusting the location of the quasi-axisymmetric radial position. Such a route enables the enhancement of the poloidal drift and decrease of radial drift in peripheral regions of the identified loss channels. The particles launched inside the quasi-axisymmetric radial surface can be well confined because localized particles that may fall in loss channels can transit into blocked particles near the quasi-axisymmetric surface, escaping from loss channels, which is beneficial for the improvement of the particle confinement. Moreover, this paper may provide a set of proxy functions for suppression of energetic particle losses to optimize stellarator configurations.
      Citation: AIP Advances
      PubDate: 2022-05-09T01:40:08Z
      DOI: 10.1063/5.0079827
  • Drag reduction due to nonionic-type surfactants in turbulent pipe flow of
           ethylene glycol aqueous solution

    • Authors: Shinji Tamano, Keijiro Taga, Taku Watanabe, Yuki Matsui, Yohei Morinishi, Toru Yamada
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The drag-reducing effects of two nonionic-type surfactants, oleyl-N, N-dimethylamine N-oxide (ODMAO) and octadecyl-N, N-bis(2-hydroxyethyl)amine N-oxide (C18BAO), in ethylene glycol (EG) aqueous solution were comprehensively investigated at various surfactant concentrations of up to 2000 ppm by weight at various solution temperatures ranging from −5 to 80 °C in turbulent pipe flows. In EG aqueous solution (30% by weight), the mixture of ODMAO with salicylic acid with a molar ratio of 0.2 could effectively reduce the turbulent drag in the low-temperature range (up to 40 °C), whereas the effect of C18BAO was more notable at a temperature higher than 40  °C. Furthermore, the mixture of ODMAO and C18BAO in EG aqueous solution exhibited a high drag reduction ratio of more than 60% in a considerably wider range of solution temperatures (from 20 to 60 °C), while the drag reduction performance deteriorated below 0 °C and beyond 60 °C.
      Citation: AIP Advances
      PubDate: 2022-05-09T01:40:06Z
      DOI: 10.1063/5.0088652
  • Influence of sublimation surface on mass transport in AlN crystal growth
           by physical vapor transport process

    • Authors: Danyang Fu, Qikun Wang, Gang Zhang, Zhe Li, Jiali Huang, Jiang Wang, Liang Wu
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      A series of numerical experiments were performed to investigate the influence of the sublimation surface on mass transport during the aluminum nitride (AlN) growth process. The distribution of Al partial pressure is strongly affected by the cover of the sublimation interface. The morphology of the growth interface can be controlled by the cover of the sublimation interface to achieve the growth of a specific crystal shape. Based on the same temperature field, the influence of sublimation interface cover on the growth rate indicates that temperature and temperature gradient are not the main limiting factors of the growth rate and further verifies that Al partial pressure gradient is the rate-limiting step. Under the growth system and specific growth conditions, a smooth growth interface can be obtained by using [0, 2/6] sublimation interface cover, so as to realize the rapid growth of high quality AlN crystals.
      Citation: AIP Advances
      PubDate: 2022-05-09T01:40:06Z
      DOI: 10.1063/5.0090077
  • A method to fabricate nanoscale gaps in graphene nano-constrictions by
           electrical breakdown

    • Authors: Oliver Schmuck, Davide Beretta, Roman Furrer, Jacopo Oswald, Michel Calame
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      This work reports on a method to open nanoscale gaps in h-shaped graphene nano-constrictions by electrical breakdown at room temperature and pressure below 10−5 mbar. The method was validated on 275 devices, fabricated on eight different chips, using Chemical Vapor Deposition (CVD)-grown graphene from in-house production and from two commercial sources. The gap width was estimated by fitting the I–V traces after electrical breakdown with the Simmons model for the intermediate-voltage range. The statistics on the collected data demonstrates that the method results in normally distributed nanoscale gaps in h-shaped graphene nano-constrictions, with an estimated average width centered around 1 nm and a gap fabrication yield of 95%.
      Citation: AIP Advances
      PubDate: 2022-05-09T01:40:06Z
      DOI: 10.1063/5.0087564
  • An unconventional optical sparse aperture metalens

    • Authors: Yangeng Dong, Yu Lin, Ti Sun, Chong Zhang, Jingpei Hu, Chinhua Wang, Aijun Zeng, Huijie Huang
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Metalens consisting of arrays of subwavelength nanostructures with ultrathin, lightweight, and tailorable characteristics have been in the spotlight to develop next-generation optical elements beyond existing refractive or diffractive optics. However, billions of subwavelength nanostructures of the metalens pose a serious challenge for fabrication, especially for the large-area ones. Herein, we designed and fabricated an unconventional optical sparse aperture (UOSA) metalens that consists of four identical and concentric annular sectors sub-aperture metalens, and it has the larger nonzero domain of modulation transfer function compared with the OSA metalens. The numerical simulation and experiments jointly show that the UOSA metalens has a limited diffraction resolution (0.91 µm) as the conventional full aperture metalens. The UOSA method can not only enlarge the effective aperture of the metalens with lower cost and less processing time but also extend a new degree of freedom for the design of the OSA metalens.
      Citation: AIP Advances
      PubDate: 2022-05-06T12:25:29Z
      DOI: 10.1063/5.0088358
  • Ab initio calculation of silicon monovacancy defect in amorphous-SiO2/Si

    • Authors: Pei Yao, Yu Song, Pei Li, Xu Zuo
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Defects significantly influence the electrical properties of semiconductors and their interfaces. The migration barriers and electrical properties of silicon monovacancy defect in an amorphous-SiO2/Si (a-SiO2/Si) interface are studied in this work. The minimum energy path and kinetics of monovacancy defect in the a-SiO2/Si interface are calculated by the climbing image nudged elastic band method. It is indicated that the a-SiO2/Si interface may be an effective sink for the monovacancies from the Si sublayers due to the unevenly distributed strain; the vacancy defect migrated into a-SiO2/Si interface can trigger structural changes by local distortion. The partial charge density of a monovacancy in the a-SiO2/Si interface shows that the induced defect level is localized around the unpaired Si dangling bonds and extends along the [110] zigzag chains of Si atoms. In addition, the formation energies of a silicon vacancy defect in the a-SiO2/Si interface are calculated with sophisticated corrections applicable to the interface system by combining the density functional theory calculation and finite element simulation. It is suggested that a Si monovacancy can appear in V0, V−, and V2−, and the (−/2−) and (0/−) transition levels lie at 0.15 and 0.2 eV below the CBMSi, respectively. The vacancies generated by displacement damage result in anisotropic migration and charge build-up in the a-SiO2/Si interface; for further dynamics, the ionization radiation can induce cascade reactions of displacement defects by synergistic effect between ionization and displacement radiation damages, and consequently excess base current and gain degradation in transistors.
      Citation: AIP Advances
      PubDate: 2022-05-06T12:25:27Z
      DOI: 10.1063/5.0088197
  • Erratum: “Identifying intrinsic ferroelectricity of thin film with
           piezoresponse force microscopy” [AIP Adv. 7, 095116 (2017)]

    • Authors: Zhao Guan, Zhen-Zheng Jiang, Bo-Bo Tian, Yi-Ping Zhu, Ping-Hua Xiang, Ni Zhong, Chun-Gang Duan, Jun-Hao Chu
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.

      Citation: AIP Advances
      PubDate: 2022-05-06T12:25:25Z
      DOI: 10.1063/5.0070460
  • Molecular dynamics simulation of kinetic boundary conditions and
           evaporation/condensation coefficients of direct-contact condensation in
           two-phase jet

    • Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Using non-equilibrium molecular dynamics simulations, the kinetic boundary condition (KBC) for direct-contact condensation in two-phase jet and its evaporation and condensation coefficients were studied to solve the Boltzmann equation. The evaporating and reflecting molecular behaviors were studied in detail. The normalized velocity distributions of reflecting molecules in the z-direction before and after reflection fit the Maxwell velocity distribution shifted by two large macroscopic velocities toward and away from the liquid surface owing to the strong net condensation rate. A singular definition of the evaporation coefficient has not been obtained in previous studies. We used a two-boundary method to count the evaporation coefficient and define a parameter to connect our result and the spontaneous evaporation coefficient. The condensation coefficient was studied using the condensation probability and showed larger than the evaporation coefficient in direct-contact condensation states. Both the evaporation and condensation coefficients were not independent of the incoming mass flux. When the incoming mass flux was small, the values of these two coefficients were close to the values under equilibrium states. Based on these results, we constructed the KBC of direct-contact condensation.
      Citation: AIP Advances
      PubDate: 2022-05-06T12:25:24Z
      DOI: 10.1063/5.0092010
  • Comparative study on laser cleaning SiO2 particle on SrTiO3 and Si

    • Authors: Lingyan Wu, Aini Yang, Chi Ma, Jun He, Lejun Yu, Bo Sun, Tianxing Ma, Ruifen Dou, Jiacai Nie, Changmin Xiong
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      In this paper, we perform a comparative study, both experimentally and theoretically, on the dry laser cleaning SiO2 particles on the surface of SrTiO3 (STO) and Si single crystal substrates. Firstly, the dependences of the cleaning efficiency on the laser energy density, the pulse number, and the size of SiO2 particles was investigated experimentally. It is found that the laser cleaning threshold decreases with the increase of SiO2 particle size. Furthermore, for the same size of SiO2 particles, the laser cleaning threshold of the STO surface is larger than that of Si. Then, based on the analysis of the interactions among the light field, the particles, and the substrate material, a corrected thermal expansion model with a quantified field enhancement effect was proposed, which provides a good simulation of the dependence of the laser cleaning threshold on the particle size and the substrate. These results further deepen our understanding of the laser dry cleaning, particularly the cleaning process on the oxide surface.
      Citation: AIP Advances
      PubDate: 2022-05-06T12:25:23Z
      DOI: 10.1063/5.0080911
  • Specific heat of metals and standard electrode potentials

    • Authors: Robert Schiller, Ákos Horváth
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Traditional thermodynamic considerations show that the standard electrode potentials, E0, of metal/metal ion electrodes are linearly related to the Fermi energies of the metal electrons, μ. Expressing E0 in volts, μ in volts/ion, and accounting for the dielectric screening of the solution, the expected slope of the straight line equals 1. Having evaluated μ from the electronic contributions of the specific heats of 11 sp metals in terms of Sommerfeld’s theory, we found a linear relationship between μ and E0. The slope of that line depends on the relative permittivity of water at the metal surface, ɛin. Taking ɛin = 6, in accordance with the general practice in electrochemistry, the expected slope was obtained without any parameter fitting. The intercept of the straight line can be interpreted as the absolute standard potential of the hydrogen electrode finding [math]. The calculations being based on equilibrium thermodynamics are independent of any actual mechanism.
      Citation: AIP Advances
      PubDate: 2022-05-06T12:25:23Z
      DOI: 10.1063/5.0082443
  • Possible Ferro-electro-magnetic performance of “reduced graphene
           oxide” deposited on “ZnO-nanorod (NR) decorated with nanocrystalline
           (nc) Au particles”

    • Authors: Sekhar C. Ray, W. F. Pong
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Possible ferro-electromagnetic performance of “reduced graphene oxide (r-GO)” deposited on the surface of “ZnO-nanorod (NR) decorated with nanocrystalline (nc) Au particles” is studied using different spectroscopies and magnetic measurements. The presence of carbon/zinc-interstitials (Zni), nc-Au, and oxygen vacancies are established through electronic property studies using different spectroscopic measurements. The magnetic moment (M) applied magnetic field (H) curve and electrical measurement current (I)–voltage (V) loops show that nc-Au/ZnO-NRs:r-GO is ferromagnetic and partial ferroelectric, respectively. The work functions are obtained from the lower kinetic energy of ultraviolet photoelectron spectroscopy, which is correlated with the enhancement of ferro-electro-magnetic performance. Both ferroelectric and ferromagnetic performance of nc-Au/ZnO-NRs:r-GO nanocomposite material could be useful for ferro-electro-magnetic technological applications.
      Citation: AIP Advances
      PubDate: 2022-05-06T12:25:22Z
      DOI: 10.1063/5.0091852
  • Numerical simulation of coaxial–coplanar dielectric-barrier
           discharge in atmospheric helium

    • Authors: Shuang Ran, Jing Wang, Bingying Lei, Simeng Liu, Jing Li, Yishan Wang, Wei Zhao, Yixiang Duan, Jie Tang
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      A self-consistent two-dimensional fluid model is employed to investigate the coaxial–coplanar dielectric-barrier discharge (DBD) excited by the sinusoidal voltage in atmospheric helium. Simulation results show that there are two current pulses in the positive half cycle, but only one in the negative half cycle. The discharge is transformed from the Townsend-like mode, through the glow-like mode, and back to the Townsend-like mode in both the positive and negative half cycles, during which the electric field line exhibits an arc-shape profile due to the configuration of coaxial–coplanar electrodes. In the glow-like mode, the cathode fall is located near the inner edge of the ground electrode at the first positive current peak, but close to the outer edge of the ground electrode at the second positive current peak. At the negative current peak, the cathode fall is distributed near the outer edge of the high voltage electrode. Since the instantaneous anode and the instantaneous cathode are on the same side of the discharge space, the dielectric layer is simultaneously covered by positive and negative surface charges due to the movement of charged particles. It is also found that the surface charge density changes significantly on the dielectric layer facing the electrodes. A further study reveals that a stronger discharge always occurs in the central circular area and an alternately complementary discharge takes place in the periphery ring area in the positive half cycle due to the activator–inhibitor effect. This feature is helpful for producing uniform plasma in a whole cycle of DBD.
      Citation: AIP Advances
      PubDate: 2022-05-05T09:36:06Z
      DOI: 10.1063/5.0089080
  • Hexagonal and rhombohedral polytypes in indium selenide films grown on
           c-plane sapphire

    • Authors: L. de Brucker, M. Moret, B. Gil, W. Desrat
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      We report on the growth of 2D layered indium selenide films on (0001)-oriented sapphire substrates by coevaporation. The θ − 2θ x-ray diffractograms reveal that the (00l) planes are preferentially oriented parallel to the substrate with a tendency to deviate from the 2D stacking as a function of the growth time. The ϕ-scans performed for the (107) and (10 10) orientations of the hexagonal (h) and rhombohedral (r) phases, respectively, reveal that both polytypes coexist in the epitaxial films. We show that the merging of the h-(100), r-(101), h-(101), and r-(102) lines results in different spectral shapes in the θ − 2θ scans according to samples, which gives qualitative information about the contribution of each polytype.
      Citation: AIP Advances
      PubDate: 2022-05-05T09:36:05Z
      DOI: 10.1063/5.0091675
  • Dependence of hysteresis loss of immobilized magnetic nanoparticles on the
           easy-axis angle: Effect of easy-axis alignment

    • Authors: Keiji Enpuku, Takashi Yoshida
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Magnetic nanoparticles (MNPs) have been widely studied for hyperthermia applications. We studied the hysteresis loss of immobilized MNPs with partially aligned easy axes. For this purpose, we investigated how the AC magnetization (M–H) curve of MNP depended on the easy-axis angle of magnetization, β, via numerical simulations of the Fokker–Planck equation. We clarified the dependences of the coercive field, Hc, and the hysteresis loss, A, on β. We, thus, obtained analytical expressions for Hc(β) and A(β) that explain simulation results for a wide range of MNP parameters and excitation conditions. The angle dependences were also discussed on the basis of magnetic moment reversal over the anisotropy energy barrier. We then examined the hysteresis loss of an MNP sample with partial alignment of the easy axes and obtained an expression for the loss by combining A(β) and a distribution function for β. We quantitatively clarified the relationship between the loss and the degree of easy-axis alignment. The loss of immobilized MNPs can be increased by a factor of 2.2 by using easy-axis alignment relative to the case of randomly oriented easy axes. Finally, we examined the alignment of easy axes induced by an AC field in suspended MNPs and showed that the loss of immobilized MNPs with partially aligned easy axes can be used to estimate the loss for suspended MNPs.
      Citation: AIP Advances
      PubDate: 2022-05-05T09:36:04Z
      DOI: 10.1063/5.0090915
  • Dielectric spectroscopy of poly(ethylene oxide)–carbon nanotube

    • Authors: Nuwansiri Nirosh Getangama, John R. de Bruyn, Jeffrey L. Hutter
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The dielectric properties of poly(ethylene oxide)–multiwalled carbon nanotube (MWCNT) nanocomposites have been studied over a wide range of frequency (0.1–106 Hz) and temperature (180–300 K). Nanocomposites were prepared by both melt mixing and twin-screw extrusion, and the concentration of MWCNTs was varied from 0 to 5 wt. %. Both the real and imaginary parts of the complex permittivity increase with the increasing MWCNT concentration. We observe a percolation transition in the DC conductivity of the composites above a critical MWCNT concentration pc. The data from the twin-screw extruded samples give a very well-defined value of pc and a percolation exponent of 1.9 ± 0.2, in good agreement with theoretical predictions. In contrast, both the percolation threshold and the critical exponent were more poorly defined for the melt-mixed nanocomposites. This indicates that the conductive properties of these materials can strongly depend on the details of sample preparation. Our data suggest that the dc conductivity of the nanocomposites is due to the conduction along the nanotubes, coupled with thermally activated transport of electrons across thin polymer bridges, which separate the nanotubes. The frequency dependence of the dielectric spectrum was studied as a function of temperature and composition. The primary dielectric relaxation process is due to the motions of electric dipoles on the polymer backbone. At low MWCNT concentrations, the relaxation involves the entire polymer chains and is slowed substantially when a low concentration of MWCNT is added. At higher MWCNT concentrations, the relaxation becomes much faster. We attribute this to binding of the polymer chains to the nanotubes, which reduces the length of the chain segments contributing to the dielectric relaxation.
      Citation: AIP Advances
      PubDate: 2022-05-05T09:36:02Z
      DOI: 10.1063/5.0064740
  • Thermoelectric model to study the cardiac action potential and arrhythmias

    • Authors: R. T. Djoumessi, Dan-Viorel Rafiroiu, F. B. Pelap
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      This paper proposes a new thermoelectric model to examine the behavior of the heart in cooling situations. A modified Karma model with temperature-dependence is exploited to describe the ion exchange dynamics at the mesoscopic scale while the propagation of the action potential is governed by a mono-domain equation at the macroscopic scale. In addition to perfusion and heat metabolism, we call the Penne equation coupled to the mono-domain equation by using the Joule effect to depict the temperature behavior in the system. Galerkin’s finite element method is utilized to start solving the partial differential equations governing the action potential and temperature propagations. The incomplete lower–upper decomposition and generalized minimal residual methods are solicited to solve the resulting nonlinear system. The cases of zero temperature and potential gradients are integrated through the scheme of Runge–Kutta, and the results obtained corroborate well with those of the literature. We analyze the contributions of the nonlinear coupling tensor and arterial temperature on the thermal and electrical responses of the system. The established results reveal that when the temperature in the medium augments, the duration of the action potential decreases and the Joule coupling tensor plays a crucial role in the propagation of the potential. Moreover, we show that temperature and action potential are in phase and that propagation of this potential generates thermal energy. Furthermore, we establish the existence of spiral waves in heart cells and show that the effect of global cooling helps to modulate or dampen these spiral waves, leading to control of the cardiac arrhythmia. This work also develops a technique to resolve conduction disorders and cancel them completely. It exhibits an increased added value to the use of hypothermia as therapy during cardiac arrest and makes it possible to anticipate and perhaps avoid this pathology.
      Citation: AIP Advances
      PubDate: 2022-05-05T09:36:01Z
      DOI: 10.1063/5.0076726
  • Research on the electric life evaluation technology of the arc
           extinguishing chamber of the 550 kV circuit breaker

    • Authors: Xiaopo Mao, Yaodong Zhang, Suge Tu, Bin Xiang
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      When the circuit breaker is switched on and off, the phenomenon of arc ablation will occur. Under the action of the electric arc, the surface of the contact is constantly damaged, resulting in deformation and material evaporation. With the increase in the electric arc temperature, the material loss on the contact surface of the circuit breaker increases. In this paper, according to the three major factors affecting the electrical life of the circuit breaker arc extinguishing chamber—the state of the arc contact, the nozzle, and the SF6 gas—the corresponding test detection methods and evaluation methods are proposed. With the continuous accumulation of the breaking current, the effective contact displacement between the arc contacts decreases and the average contact resistance increases. The effective contact displacement decreases exponentially with the increase in the cumulative breaking energy. The content of CF4 can be used not only to characterize the discharge ablation on the surface of the nozzle insulating material but also to characterize the discharge decomposition degree of SF6 in the system by adding carbonaceous compounds. Through the experiment, it is suggested that CF4 should reach 600 µl/l as the threshold for judging whether the arc extinguishing chamber needs maintenance. This method can be extended to the working condition evaluation of the arc extinguishing chamber of other types of the SF6 circuit breaker.
      Citation: AIP Advances
      PubDate: 2022-05-05T09:36:01Z
      DOI: 10.1063/5.0084883
  • Tunable skyrmion–edge interaction in magnetic multilayers by
           interlayer exchange coupling

    • Authors: Kai Wu, Sheng Yang, Yuelei Zhao, Xue Liang, Xiangjun Xing, Yan Zhou
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Magnetic skyrmions are appealing for applications in emerging topological spintronic devices. However, when magnetic skyrmions in a nanowire are driven by an in-plane current, a transverse Magnus force deflects their trajectories from the current direction, which tends to push the skyrmion toward the edge. If the current density is exceedingly large, the skyrmion will be annihilated around the edge, leading to a greatly reduced propagation distance and a maximum speed of the skyrmion, which is detrimental to skyrmion-based spintronic applications. Here, we prepare a magnetic multilayer Ta/[Pt/Co]3/Ru/[Co/Pt]3 and tailor the interlayer exchange coupling strength by varying the thickness of the Ru layer. Based on the magneto-optic Kerr effect microscope, we find that the skyrmion–edge interaction is tunable by the interlayer exchange coupling strength, namely, the strength of the repulsive potential from the film edge is tailored by the interlayer exchange coupling strength. Our results unveil the significant role of the interlayer exchange coupling in skyrmion dynamics.
      Citation: AIP Advances
      PubDate: 2022-05-05T09:36:00Z
      DOI: 10.1063/5.0084546
  • Basic understanding of perovskite solar cells and passivation mechanism

    • Authors: Yixin Yu, Jingxuan Xia, Yiwen Liang
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Although perovskite solar cells (PSCs) have made great achievements during the past few years, the efficiency of PSCs is only up to 25.5%, which is comparable to silicon-based solar cells. However, long-term stability is still an important problem for future commercialization. Enormous efforts have been made to prolong the lifetime of PSCs. The novel passivation strategy and advanced encapsulation are investigated, and great achievements are acquired. However, research on the basic understanding of the perovskite structure and the fabrication process of PSCs is rare, which stints the initial research for the abecedarian. At the same time, the defects among the perovskite film caused by the uncontrollable crystallization process and the fragile ionic nature also deteriorate the efficiency and stability of the perovskite devices. Herein, we summarized the investigations of the mechanism for perovskite materials and the manufacturing process of PSCs. The composition of perovskite materials, the orientation of perovskite grain, and various fabrication processes are explained. Simultaneously, the novel passivation strategy and technology are also discussed. We believe that a deeper understanding of the perovskite mechanism is beneficial to render more facilities for further development of perovskite application.
      Citation: AIP Advances
      PubDate: 2022-05-04T02:22:49Z
      DOI: 10.1063/5.0058441
  • Experimental analysis of fluid–structure interaction between a blast
           wave and a sandwich add-on armor

    • Authors: L. Blanc, D. Lebaillif, A. Bufalo
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      In various situations, targets with different characteristic dimensions are being exposed to blast waves generated by high explosive detonation. One of the existing mitigation methods consists of protecting the target from the explosion with a sandwiched crushable core between a front plate and the target. The pressure generated by the explosion is converted into the planar displacement of the front plate, which compresses the crushable core, delaying the transmission of the load to the target. The influence of the crushable core on the transmitted load in the form of a plateau stress is well described in the literature contrary to its influence on the transferred momentum. In this paper, momentum transmission during the crushing of the core has been experimentally investigated, taking into account the fluid–structure interaction effect, the mechanical behavior of the core, and the pneumatic effects generated by the air trapped into its cells. It is shown that the beneficial effects of fluid–structure interactions are often counterbalanced by the mechanical behavior of the core and that analytical models from the literature are sufficient to describe the order of magnitude of the uniaxial crushing process.
      Citation: AIP Advances
      PubDate: 2022-05-04T02:22:48Z
      DOI: 10.1063/5.0082336
  • Bubble generation and growth mechanism in PMMA microfluidic chip

    • Authors: Lianchao Jia, Zhiyong Li, Qingquan Wei
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Bubbles often impede microfluidic chip functionality, especially in areas where heating is required. In this article, the mechanism of bubble generation and growth in polymethyl methacrylate microchannels was analyzed. The sources of bubbles were taken into consideration: (i) dissolved gas in the liquid, (ii) insoluble gas in cavities of the channel, and (iii) the gas produced by the phase change of the liquid. The factors that affect bubbles in microchannels were analyzed, including the liquid flow rate, surface modification of channels, and pressure on the fluid in the microchannel. Three sets of experiments were designed and carried out, and the results demonstrated that the bubbles in the microchannel can be shrunk and even eliminated by improving the flow rate, modifying channel surface properties, and increasing the liquid pressure.
      Citation: AIP Advances
      PubDate: 2022-05-04T02:22:48Z
      DOI: 10.1063/5.0084308
  • Orbital projection technique to explore the materials genomes of optical

    • Authors: ZhenHua Li, Shuiquan Deng, Myung-Hwan Whangbo, Hong-Gang Luo
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The development in materials science and pharmaceutics shows that there exist some key materials genomes, i.e., certain groups of atoms with specific constituents and structures, which govern the property of a series of materials based on them. To pinpoint such materials, genomes are helpful to assemble functional units and synthesize new materials and, thus, have a profound meaning. In this work, we develop an innovative method based on the idea of projecting atomic orbitals’ wavefunction, which enables us to project every physical quantity into their orbital contribution and, thus, can be widely used to identify the materials genomes of various properties. Within this framework, we derive the expressions of the projected optical susceptibilities and exhibit a paradigm of studying the corresponding materials genomes of optical properties, especially the desired nonlinear optical materials.
      Citation: AIP Advances
      PubDate: 2022-05-04T02:22:47Z
      DOI: 10.1063/5.0067891
  • Design and mechanical characteristics research of rock burst prevention
           combined components of the double laminated springs

    • Authors: Dongming Guo, Guichuan Ye, Zhifeng Zhao, Fange Lan, Baoyin Liu, Haotian Zhang
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      In order to solve the engineering problem that the bolt tail is often broken under the impact of rock pressure, mining stress and the damage to the support structure contribute to great hidden danger to the safety of mining and tunneling. A new anti-impact bolt support structure is designed that can absorb energy under pressure. The double laminated springs and the inner spring deform under the impact load to achieve the purpose of absorbing most of the impact energy. The composition and working principle of the energy-absorbing structure is introduced. The static axial compression tests of the single laminated springs with cone angles of 30°, 45°, and 60° are carried out. The mechanical characteristics of the laminated springs in the three stages of energy absorption are investigated. It is found that the 45° laminated spring has the best energy absorption effect. The simulation method was used to analyze and optimize the energy absorption effect of anti-scour composite components. Double laminated spring anti-shock composite components absorb the impact energy and avoid the damage to the bolt support structure, which reduces the roadway support cost and has important engineering application value for ensuring the safety of deep tunneling and mining.
      Citation: AIP Advances
      PubDate: 2022-05-04T02:22:47Z
      DOI: 10.1063/5.0089491
  • On the flow characteristics of a four square-cylinder array at a 45°
           incidence angle and low Re

    • Authors: Yunji Zhu, Shouxu Zhang
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The four-cylinder model is widely applied in many engineering projects immersed in unsteady flow. However, its flow hydrodynamic characteristics are not fully understood. In the present work, the finite volume method is adopted in spatial discretization, while the SIMPLE algorithm in association with the non-iterative fractional step method is utilized to address the governing Navier–Stokes equation. Four equilaterally arranged cylinders at a flow incidence angle of 45° (α = 45°) are numerically simulated, and the corresponding Reynolds number ranges from 40 to 160. The accuracy and applicability of the numerical method employed in this investigation are verified by flow over a single cylinder. In the current work, the hydrodynamic characteristics, flow field characteristics, and structural vibration characteristics of cylinders are systematically investigated by changing the spacing ratio L/D (L/D = 1.2–4.0) and the Reynolds number. Numerical results show that the four cylinders have respective features and interaction effects. There are approximately eight wake flow patterns influenced by the spacing ratio. In addition, the numerical results also indicate that fluid dynamics are determined by flow patterns. These results can be a reference in engineering design, such as for ocean platforms with four cylindrical columns.
      Citation: AIP Advances
      PubDate: 2022-05-04T02:22:46Z
      DOI: 10.1063/5.0091440
  • Simultaneous measurement of a droplet’s curvature and contact angle
           using asymmetric deformation of its reflected laser beam

    • Authors: Yang Miao, Jun Chen, Qiliang Li, Yinfei Chen, Haibin Liu
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The asymmetric deformation of a laser beam reflected from the surface of a droplet on a slide was observed. The degree of deformation of the beam profile in the incident plane is related to the droplet contact angle, and the degree of deformation perpendicular to the incident plane is related to the droplet curvature. A simple, non-contact, real-time technique to measure droplet wetting parameters was established. The contact angle and radius of curvature for different liquid droplets were measured, and measurement errors were in the sub-degree and sub-millimeter orders of magnitude, respectively. The values obtained for the contact angle using the reported measurement technique compared with those obtained using a traditional measurement technique with an imaging contact angle meter showed the reported technique to be reliable. The contact angle and radius of curvature for four blood samples were measured and compared with those obtained from blood samples using a routine test. For samples with white blood cells, hemoglobin, and hematocrit exceeding the standard, their wetting parameters regularly deviated from those of normal samples.
      Citation: AIP Advances
      PubDate: 2022-05-04T02:22:46Z
      DOI: 10.1063/5.0082622
  • A vasculogenesis model based on flow-induced stresses on endothelial cells

    • Authors: Pooya Abdi, Bahman Vahidi
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Vascular network formation and sustenance in both normal and pathological froms of angiogenesis has been a focus of research in developmental biology. The assembly and remodeling of vascular structures play major roles in numerous pathologies, including the angiogenesis of tumors. Endothelial morphogenesis is dependent on a number of chemical and mechanical stimuli and cell–cell signaling. To understand the nature of angiogenesis and vasculogenesis, many models have been developed to simulate these phenomena based on the defined responses of endothelial cells to these stimuli. Among the mechanical signals affecting these cells, flow-related stresses, including shear stress, play a major role in migration, elongation, attachment to the matrix and neighboring cells, and eventually the morphogenesis of vascular networks. Here, we proposed a model to describe the cellular responses to shear and tensile stress induced by fluid flow, which can describe some of the morphological behaviors observed in in vitro and in vivo studies. The lattice Boltzmann method was utilized to model the flow, and the cellular Potts model was used to simulate the cellular responses to the flow. This model is based on the hypothesis that endothelial cell binding energy to the matrix is regulated by shear stress and tensile stress acting on the attachment site and is increased by shear stress and decreased by tensile stress. It was demonstrated that these rules can predict the development of vascular networks and the sustenance of lumens and regression in the low flow regions. The results of this study can be further improved to investigate endothelial dysfunctions, such as atherosclerosis, as well as tumor angiogenesis and vascular permeability, which are directly related to the flow rate and endothelial responses to shear stresses.
      Citation: AIP Advances
      PubDate: 2022-05-03T12:23:59Z
      DOI: 10.1063/5.0087884
  • Experimental analysis and prediction for the bonding strength of steel
           cord of conveyor belt under the temperature influence

    • Authors: Hongyue Chen, Hongyan Chen, Pengfei Li, Sizhe Liu
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      To research the effect of temperature on the interfacial bonding strength of the steel cord rubber conveyor belt, an electronic universal material testing machine and a temperature control box were used as the test equipment. The withdrawal force of the steel cord skeleton of the rubber conveyor belt was tested in the temperature range of −30 °C to +40 °C. Concurrently, the interfacial morphology between the steel cord and rubber at different temperatures was observed by using an ultra deep field electron microscope. Finally, different bonding strength prediction models were established. The results show that the variation trend of the steel cord withdrawal force with displacement is the same at different temperatures. With the increase in temperature, the interfacial bonding strength between the steel cord and the rubber matrix decreases gradually; the second-order polynomial bonding strength prediction model can meet the prediction requirements of the steel cord bonding strength at different temperatures, and the errors are controlled within 5%.
      Citation: AIP Advances
      PubDate: 2022-05-03T12:21:31Z
      DOI: 10.1063/5.0090434
  • A multi-feature predicting model of crown evolution involving material

    • Authors: Tianyu Ma, Yanchuang Cao, Jun Liu, Aiguo Xu, Jie Chen, Yingqi Jia, Dawei Chen
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      We propose a new model for the crown evolution after a single drop impacts on a thin film. In contrast with the existing models that mainly focus on the status of well-developed crown or the bottom radius evolution, multiple features are provided in our model, including the temporal evolution of the crown radius, height, velocity, and the characteristic time when the crown reaches its maximum height. Both the fluid viscosity and surface tension are considered in this work rather than ignoring one or both of them as in previous studies, resulting in improved accuracy for crown development prediction. The new model can be applied for droplets of various fluids impinging on relatively thin films (0.1 < δ < 0.67). The reliability of the model is validated via comparing results with five cases of droplet impact experiments.
      Citation: AIP Advances
      PubDate: 2022-05-03T12:20:20Z
      DOI: 10.1063/5.0086420
  • Simultaneous solar rejection and infrared emission switching using an
           integrated dielectrics-on-VO2 metasurface

    • Authors: Ken Araki, Richard Z. Zhang
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Passive infrared emittance switching can be achieved with a metal-to-insulating phase transition material vanadium dioxide (VO2), but its non-transitioning bandgap results in high absorptance in the visible wavelength range. To achieve a half-order reduction of absorptance in the visible to near-infrared region, we design integrated dielectric photonic metasurface structures on monolithic VO2 coatings. This combination of nano/micro-patterned dielectric diffractive and resonant gratings with a multilayer VO2 structure preserves the terrestrial thermal wavelength emission switching capabilities. We demonstrate a periodic microscale diffractive prism array, comparing the reflectance provided by either infrared-transparent germanium (Ge) or silicon (Si). Despite the advantage of total internal reflection in the broad near-infrared region, some bandgap absorption limits the performance in the visible wavelengths. A better theoretical means to reflect broadband light via waveguide-like Fabry–Pérot resonance are near-wavelength 1D and 2D High Contrast Grating (HCG) high-index metasurface structures surrounded by a low-index host medium. This HCG metasurface allows broadband high-quality reflection within the dual-mode (or tri-mode) region from 1.0 to 2.2 µm wavelengths for HCG with a refractive index of 4.0, which corresponds to Ge. This study investigates the advantages and disadvantages along with the thermal performance of these metasurface augments aimed to enable thermally switchable passive radiative cooling—thermal emission exceeding solar absorption—of solar cells, terrestrial buildings, and energy storage devices.
      Citation: AIP Advances
      PubDate: 2022-05-03T12:20:20Z
      DOI: 10.1063/5.0085111
  • Strain-rate correlation of biaxial tension and compression mechanical
           properties of HTPB and NEPE propellants

    • Authors: Qizhou Wang, Guang Wang, Zhejun Wang, Hongfu Qiang, Xueren Wang, Shudi Pei
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      An effective biaxial tension and compression test method is proposed based on the shortcomings of current research for the mechanical properties of solid propellants under complex stress states. The equal proportion biaxial tension and compression test of HTPB (Hydroxyl-terminated polybutadiene) and NEPE (NitrateEster Plasticized Polyether) solid propellants is performed at different rates while at room temperature, and the damage morphology of the tension–compression zone is analyzed using micro-CT. The results show that the failure mode of the solid propellant under biaxial tension and compression loading is similar to that under uniaxial tension. Meanwhile, the compressive strength is much greater than the tensile strength, which will eventually cause tensile failure. With an increased loading rate, the growth trend of the initial modulus, ultimate strength, and maximum elongation of the propellant is gradually flattened, and the damage degree is gradually reduced. Additionally, damage that forms in the HTPB propellant is from dewetting and particle fracture while that for the NEPE propellant is from matrix tearing. The porosity can be used as the meso-damage parameter of the propellant.
      Citation: AIP Advances
      PubDate: 2022-05-03T11:08:48Z
      DOI: 10.1063/5.0083205
  • Numerical simulation of fragment impacting solid rocket motors

    • Authors: Zhejun Wang, Hongfu Qiang, Biao Geng, Tingjing Geng
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      For the initiation characteristics of solid rocket motors (SRMs) filled with high-energy solid propellant under fragment impact, the related theoretical critical criterion for shock initiation was established based on the critical energy criterion and equivalent analysis method. Afterward, numerical simulation of fragment impacting SRM was carried out by using the ANSYS/LS-DYNA software and the nonlinear finite element method. Based on the calculated pressure and reactivity in the high-energy solid propellant grain, the shock critical initiation velocity of SRM and its variation with different forms of fragments and impact conditions were determined. It is found that the numerical simulation results under typical conditions are in good agreement with the data calculated with the developed theoretical critical criterion for shock initiation of SRM. However, the shock initiation mechanism becomes more complex when the case thickness of SRM increases to more than 5 mm; thus, the applicability of the developed theoretical critical criterion reduces. Moreover, it is found that all the case thickness, fragment shape, material properties of the fragment, and impact attitude can significantly affect the shock critical initiation velocity of SRM, even the initiation position and time. First, the critical velocity increases linearly with the increase in case thickness, and the increment rate is faster beyond the thickness of 6 mm. Second, the shock critical initiation velocity induced by fragments with different shapes is as follows: spherical fragment> cubic fragment> cylindrical fragment, while the initiation capacity of different fragment materials is ranked as follows: tungsten alloy> 45 steel> 2024 aluminum. Third, the effects of impact attitude on the shock critical initiation velocity, position and time are complex, and these effects are also influenced by fragment shape. When the impact angle is less than 60°, there is a higher shock critical initiation velocity of SRM under inclined impact than that under positive impact. In addition, the critical velocity induced by cubic fragment is the highest under the combination of vertex impact and positive impact. The variation of the critical velocity under this condition is approximately consistent with that by impacting with cylindrical fragment. Furthermore, when the impact angle is greater than 60°, the shock critical initiation velocity of SRM is less obviously influenced by impact attitude and fragment shape. Meanwhile, the critical velocity decreases sharply under this condition, which indicates that it is easier for SRM to detonate.
      Citation: AIP Advances
      PubDate: 2022-05-03T11:08:48Z
      DOI: 10.1063/5.0088412
  • Low energy dissipation superconducting flywheel based on structural design

    • Authors: Yanbin Ma, Baoqiang Zhang, Hongwei Zhao, Xingyi Zhang
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Superconducting flywheels have potential application value in aerospace field, and its suspension time is a key factor. Alternating Current (AC) loss associated with rotation is an important parameter that affects the suspension time, so it is very important to study how to reduce the AC loss. Recently, a method of preparing YBa2Cu3O7−x (YBCO) high-temperature superconducting flywheels by Direct-Ink-Writing (DIW) 3D printing was developed. In this paper, the circular hole superconducting flywheel prepared by this method is optimized by the idea of structural optimization. Based on the finite element method, the AC loss before and after optimization is calculated and analyzed. It is found that the elliptical holes make the superconducting flywheel have lower AC loss than circular holes, with a reduction of 58.49%. Then, the YBCO superconducting flywheel with an optimized elliptical structure was prepared by the DIW 3D printing method. The magnetic levitation experiment found that the levitation time of the optimized superconducting flywheel was increased to 162 s compared with the previous 120 s under the same conditions, and the optimized structure had a higher levitation mass ratio. It provides theoretical and experimental support for reducing the AC loss of superconductors by applying the idea of structural optimization design in engineering practice.
      Citation: AIP Advances
      PubDate: 2022-05-03T11:08:48Z
      DOI: 10.1063/5.0088076
  • Spectra dependent photonic structure design for energy harvesting by
           indoor photovoltaic devices

    • Authors: Ajanta Saha, Eymana Maria, Md Zunaid Baten
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      In this work, we report spectra-dependent energy harvesting by optimizing the photon management of an indoor photovoltaic device while taking into consideration the degradation of electrical transport characteristics caused by the nano-photonic structures. For the test case of a CdTe-based photovoltaic device, it has been shown that although the incorporation of dielectric-filled nanoholes in the absorber layer can enhance light absorption by about 40%, the optical-to-electrical conversion efficiency of the device is significantly diminished because of the degradation of the electrical transport characteristics. Instead, the best performance metrics are obtained when the nanostructures are incorporated in the window layer of the device alone. A finite difference time domain based numerical analysis, coupled with Poisson’s equation and continuity equation, shows that by controlling the areal density of the optimized structure in direct correlation with spectral characteristics of the illuminating light source, it is possible to maximize the overall power conversion efficiency of the indoor photovoltaic device. In the case of commercial white light-emitting diodes (LEDs), large arealdensities of holes are found to be more conducive for harvesting energy from cool-white LEDs, whereas smaller areal densities of holes provide better performances for illumination under warm-glow white LEDs.
      Citation: AIP Advances
      PubDate: 2022-05-03T11:08:47Z
      DOI: 10.1063/5.0084488
  • High extinction ratio thermo-optic based reconfigurable optical logic
           gates for programmable PICs

    • Authors: S. Hassan, D. Chack, L. Pavesi
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      In this paper, a new scheme is proposed to realize reconfigurable and multifunction optical logic gates (XOR, XNOR, NAND, and OR) using a Mach–Zehnder interferometer with a tunable thermo-optic phase shifter (TOPS). The reconfigurable optical logic gates are realized by tuning the phase of an optical signal using TOPS without changing the physical device structure. The logical input “0” or “1” is considered corresponding to the phase of the optical signal at TOPS. The logical output of the proposed device depends on the light intensity at output ports. The device is designed on silicon on insulator (SOI) platform and the simulation result shows that the on–off extinction ratio is greater than 37 dB at 1550 nm and>25 dB for the C-band. Moreover, it has a low insertion loss of 0.09 dB at a wavelength of 1550 nm and
      Citation: AIP Advances
      PubDate: 2022-05-03T11:08:46Z
      DOI: 10.1063/5.0086185
  • Local droplet etching on InAlAs/InP surfaces with InAl droplets

    • Authors: Xin Cao, Yiteng Zhang, Chenxi Ma, Yinan Wang, Benedikt Brechtken, Rolf J. Haug, Eddy P. Rugeramigabo, Michael Zopf, Fei Ding
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      GaAs quantum dots (QDs) grown by local droplet etching (LDE) have been studied extensively in recent years. The LDE method allows for high crystallinity, as well as precise control of the density, morphology, and size of QDs. These properties make GaAs QDs an ideal candidate as single photon and entangled photon sources at short wavelengths (
      Citation: AIP Advances
      PubDate: 2022-05-02T03:09:43Z
      DOI: 10.1063/5.0088012
  • Synthesis and electrochemical performance of V2O5 nanosheets for

    • Authors: Miao Li, Taotao Ai, Lingjiang Kou, Jiajia Song, Weiwei Bao, Yong Wang, Xueling Wei, Wenhu Li, Zhifeng Deng, Xiangyu Zou, Huhu Wang
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Electrode materials are the key to the electrochemical performance of supercapacitors. This study reports the electrochemical properties of V2O5 supercapacitors. V2O5 nanosheets with different morphologies were prepared by controlling the solvent under a facile hydrothermal method. The phase and the morphology of the samples were characterized by x-ray diffraction and scanning electron microscopy. The electrochemical properties of V2O5 nanosheets with different morphologies were studied by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. The charge transfers resistance decreases from 3.2 Ω of V2O5 particles to 2.0 Ω of V2O5 nanosheets. V2O5 nanosheets exhibit higher specific capacity (375 F g−1) than V2O5 particles (318 F g−1) in K2SO4 solution. The cycling capacity retention keeps 96.8% for 1000 cycles at 0.5 A g−1 in K2SO4 solution, indicating better cycling stability.
      Citation: AIP Advances
      PubDate: 2022-05-02T03:07:43Z
      DOI: 10.1063/5.0086344
  • Analysis and experimental study of patch tube mechanical properties based
           on screen pipe hydroforming patch technology

    • Authors: Shu-feng Liu, Han-xiang Wang, Yan-xin Liu, Xin Zhang, Jia-qi Che, Shao-hua Ma
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Hydroforming patch technology for damaged screen pipes is designed based on tube hydroforming technology, and the methods for determining the forming pressure range and forming defects are selected according to the forming process. The hydroforming patch model for screen pipes is established according to the technical demand parameters for screen pipe repair. From the mechanical properties of the material and digital–analog comparison analysis of the material formability, it is found that the determiners for formability (such as forming pressure, thinning rate, and springback) of 321 stainless steel (SS321) are better than those of 304L stainless steel (SS304L), and the patch tube materials meeting the technical requirements were selected. A test bench for the formability of patch tubes was built to verify the forming pressure of patch tubes with different thicknesses and the distribution of wall thickness after forming. The results show that the hydroforming patch technology is feasible and can realize the firm and close fit between the patch tube and screen pipe; moreover, SS321 can meet the material requirements of the patch tube.
      Citation: AIP Advances
      PubDate: 2022-05-02T03:07:43Z
      DOI: 10.1063/5.0087533
  • Thermoelastic coupling vibration analysis of precision coated TPU film

    • Authors: Yao Feng, Jimei Wu, Yan Wang, Mingyue Shao, Xuxia Guo
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      TPU (thermoplastic polyurethane) films are subjected to heating in production. As the temperature rises, thermal stress will be generated inside the TPU film. It causes defects, such as wrinkles and cracks, in the moving TPU film; therefore, it is of great significance to study the thermoelastic coupling effect of the moving TPU film in the printing process. To study the thermoelastic coupling vibration characteristics of the moving TPU film under the opposite edge tension, it includes combining the thermal conduction equation with temperature coupling term and the vibration differential equation with variable temperature effect to get the coupling equation. The differential quadrature method is used to discretize the vibration differential equation. The influence of the thermoelastic coupling coefficient, aspect ratio, and tension ratio on the vibration characteristics of the TPU film is studied.
      Citation: AIP Advances
      PubDate: 2022-05-02T03:04:44Z
      DOI: 10.1063/5.0088038
  • Vortex shedding, flow separation, and drag coefficient in the flow past an
           ellipsoid of different aspect ratios at moderate Reynolds number

    • Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Incompressible viscous flow past an ellipsoid of different aspect ratios (ARs, the ratio of the vertical to the horizontal axis of the ellipsoid, is ranged from 0.5 to 2) at a Reynolds number of 300 is investigated numerically by a finite volume method with adaptive mesh refinement, and the effects of different aspect ratios on vortex shedding, flow separation, and drag coefficient are analyzed in detail. The accuracy of the present results is ascertained by comparing the present drag coefficient and Strouhal number with other literature studies. The results show that the Strouhal frequency of vortex shedding decreases and the magnitude of vortex shedding becomes weaker with an increase in the aspect ratio. In particular, a secondary frequency will occur within a certain interval of 0.8 ≤ AR ≤ 1.2. The vortex shedding appears as a hairpin vortex at AR ∈ [0.5, 1.6], whereas it becomes a double-line vortex at AR ≥ 1.8. Both the upper flow separation angle and the length of the separation bubble increase with an increase in the aspect ratio. The flow separation is symmetrical about the (x, z)-plane only at 0.5 ≤ AR ≤ 0.7 and AR ≥ 1.8. Furthermore, the total drag coefficient and the pressure drag coefficient both increase gradually with an increase in the aspect ratio. Due to the trend of the contact area between the fluid and the surface of the ellipsoid, the friction drag coefficient decreases first (AR ≤ 1) and then increases (AR ≥1). The pressure drag coefficient reinforces the contribution to the total drag coefficient, and the contribution of the pressure drag coefficient grows with an increase in the aspect ratio.
      Citation: AIP Advances
      PubDate: 2022-05-02T03:04:43Z
      DOI: 10.1063/5.0090735
  • Multifunctional cellulose wood with effective acoustic absorption

    • Authors: Ju-Qi Ruan, Zhaoxi Li, Kai-Yue Xie, Wei Guo, Chunlong Fei, Ming-Hui Lu, Hai Yang
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      Wood is a sustainable material with big sound absorption potential based on its natural porous characteristics. However, the acoustic absorption performance of wood is greatly limited by the low permeability of wood structures. In this study, we prepared a new type of cellulose wood (CW) using a two-step delignification process on a natural basswood matrix followed by supercritical CO2 drying. The as-prepared CW exhibited a high air permeability of 33.78 Darcys (increase of 496.82%) and superior porous characteristics compared to the natural basswood, resulting in a significant improvement in the acoustic absorption performance with an increased average absorption of 106.25% and maximum absorption of 126.32%. The dissipation of sound energy in the structure of CW is well predicted by a designed porous media model. Moreover, a high specific stiffness of 2.14 × 105 m2 s−2 and a diffuse reflectance of 97.02% across the visible light were demonstrated for the CW as well. Such a fascinating multifunctional wood-derived material may provide new insights into the development of efficient and sustainable acoustic absorbers for various applications.
      Citation: AIP Advances
      PubDate: 2022-05-02T03:01:24Z
      DOI: 10.1063/5.0078482
  • Epitaxial growth and polarized Raman scattering of niobium dioxide films

    • Authors: Keisuke Shibuya, Akihito Sawa
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      We report the structural, electrical, and optical characterization of epitaxial niobium dioxide (NbO2) films fabricated on MgF2(001) substrates. The films were almost stoichiometric, had an indirect bandgap of 0.7 eV, and exhibited a phase transition at ∼1080 K. A polarized Raman scattering study of the films was conducted to investigate the Raman symmetry in the low-temperature phase. Based on the angular-dependent polarized Raman spectra, we assigned 13 modes to Ag symmetry and 14 to Bg symmetry. We also evaluated the Raman tensor elements of the Bg modes and found that the off-diagonal elements were nearly zero in most of the Bg modes, except for a phonon mode at 267 cm−1. This study aids understanding of the lattice dynamics of NbO2, which plays a critical role in the phase transition.
      Citation: AIP Advances
      PubDate: 2022-05-02T03:01:23Z
      DOI: 10.1063/5.0087610
  • 3.8-octave broadband nearfield generation with high stability and high
           tolerance using a gradually varying thickness thin-film waveguide

    • Authors: Takehiro Tachizaki
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The generation of an optical near-field spot through a gradually varying thickness waveguide composed of metallic and dielectric thin films was comprehensively analyzed by the finite element method. The incident angle of the excitation beam, excitation wavelength, and material dependent strength of the near-field hotspot were evaluated using three different material combinations. The analysis showed that the waveguide can generate a near-field spot with an electric field stronger than that of the excitation beam in the wide spectral range, reaching from visible 488 nm to mid-infrared 7000 nm (3.8-octave). From the wedge angle and excitation position dependency, the thin-film waveguide with varying thickness indicated the high stability, high freedom of design, and high tolerance to process precision. These manifold advantages progress optoelectronics, plasmonics, and nanotechnologies, including nanometric spectroscopy.
      Citation: AIP Advances
      PubDate: 2022-05-02T02:41:02Z
      DOI: 10.1063/5.0087917
  • A continuous underwater bubble localization method using passive acoustic
           array beamforming

    • Authors: Yu Zhang, Bingpu Wang, Xiaobo Rui, Jin Zhang, Hao Feng, Jian Li
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      The bubble is an effective carrier of underwater gas leakage detection, and its rapid localization is of great significance. In this paper, a continuous underwater bubble localization method using passive acoustic array beamforming is proposed. A specific array of hydrophones was constructed to capture the bubble acoustic signal. The signal of finite length is obtained by introducing the time window. Then, the time delay compensation is carried out according to the positions of the hydrophones in the array to estimate the direction of arrival. The influence of shape, number, and aperture of the hydrophone array on the algorithm performance is studied by simulation. Moreover, the experiment was carried out in a cuboid transparent tempered glass water tank in the laboratory, and a field programmable gate array is used as the core control unit of the data processing system to complete the signal acquisition and the algorithm execution. The localization results show that the passive acoustic cross array beamforming algorithm can accurately and stably estimate the leakage direction at different positions.
      Citation: AIP Advances
      PubDate: 2022-05-02T02:39:41Z
      DOI: 10.1063/5.0083892
  • Correlation of fast electron ejections, terahertz waves, and harmonics
           emitted from plasma mirrors driven by sub-relativistic ultrashort laser

    • Authors: Xiang-bing Wang, Guang-yue Hu, Bai-fei Shen, Hui-bo Tang, Zhi-meng Zhang, Yu-qiu Gu
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      When an ultrashort laser pulse incidents onto a plasma mirror, there exist fast electron ejections, terahertz (THz) radiation, and harmonic generation simultaneously. We investigated the correlation of these three emission phenomena at a preplasma density gradient scale length of (0.05–1)λ and sub-relativistic laser intensity (a0 = 0.4) via particle-in-cell simulation. It is shown that THz radiation is positively correlated with fast electron ejections. As the gradient scale length increases, both enhance first, reach a maximum at 0.4λ, and then degrade at a longer scale length. Harmonic generation, on the other hand, presents the strongest radiation at a sharp surface of 0.05λ and then decays continuously at a softer gradient, indicating that it has an anti-correlation with the fast electron ejections at first (
      Citation: AIP Advances
      PubDate: 2022-05-02T02:37:42Z
      DOI: 10.1063/5.0077354
  • Propagation characteristics of relativistic ultrashort laser pulse in
           inhomogeneous plasma

    • Authors: Xiao-Bo Zhang, Mao Huang, Rong-An Tang, Ai-Xia Zhang, Ju-Kui Xue
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      We study the propagation of a relativistic ultrashort laser pulse in two-dimensional inhomogeneous plasma with a density ripple based on the theoretical analysis and the particle-in-cell simulation. An analytical solution of the laser pulse propagating in the homogeneous plasma is completely obtained. It is found that the stable propagation of the relativistic ultrashort laser pulse in homogeneous plasma can be realized, and the propagation distance and intensity of the laser pulse and the spatial distribution of electron density can be effectively modulated by adjusting the pulsewidth of the incident laser and the plasma frequency. More interestingly, in the inhomogeneous plasma with a density ripple, when the wave amplitude of the density ripple is less than a critical value, the intensity of the ultrashort laser pulse is almost unchanged and the propagation characteristics of the laser in the inhomogeneous plasma are basically consistent with those in the homogeneous plasma. However, when the wave amplitude of the density ripple is larger than the critical value, the inhomogeneity of the plasma has an obvious effect on the laser characteristics, and the intensity and the spatial distribution of the laser pulse will be modulated by the plasma density ripple. The influence of the laser pulsewidth, plasma density, and plasma density ripple on the laser characteristics is discussed in detail.
      Citation: AIP Advances
      PubDate: 2022-05-02T02:37:41Z
      DOI: 10.1063/5.0085893
  • Analysis of the high-efficiency and low-damage abrasive processing
           mechanism for SiC based on the SPH simulation of single-grain indentation
           and scratching

    • Authors: Dong Shi, Qingming Hou, Tengfei Ma, Tianchen Zhao, Jinping Pan
      Abstract: AIP Advances, Volume 12, Issue 5, May 2022.
      During the wafer fabrication procedure, abrasive machining occupies a large proportion in time and economic cost, mainly including grinding, lapping, and polishing. The third-generation semiconductor materials, represented by SiC, have the properties of high hardness, large brittleness, and strong chemical inertness, which make abrasive machining more challenging. To improve the machining efficiency and quality, this paper applied the smoothed particle hydrodynamics (SPH) method to simulate the machining behavior of single abrasive grain for SiC wafer. The micro-mechanical mechanisms of the main influencing parameters, such as velocity, depth, and angle, were studied in abrasive machining for SiC wafer. First, it is proved that using SPH coupled with a finite element to study the mechanical effects of abrasive machining for SiC wafer is a feasible and useful method. Then, the explanations for the beneficial effects of ultrasonic vibration-assisted machining, high-speed machining, and other abrasive machining are provided through the analysis of the simulated results. In addition, the optimization basis for parameters such as scratching velocity, scratching depth, and ultrasonic vibration frequency is obtained. This research provides a good insight into implying the micro-mechanical mechanisms of abrasive machining and achieving the optimization for the abrasive machining of hard-brittle wafer materials, which help avoid the shortcomings of experimental research and produce economic benefits.
      Citation: AIP Advances
      PubDate: 2022-05-02T02:31:21Z
      DOI: 10.1063/5.0076269
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