Subjects -> MATHEMATICS (Total: 1074 journals)     - APPLIED MATHEMATICS (86 journals)    - GEOMETRY AND TOPOLOGY (23 journals)    - MATHEMATICS (793 journals)    - MATHEMATICS (GENERAL) (43 journals)    - NUMERICAL ANALYSIS (23 journals)    - PROBABILITIES AND MATH STATISTICS (106 journals) MATHEMATICS (793 journals)            First | 1 2 3 4
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Similar Journals
 Journal of Theoretical and Applied PhysicsJournal Prestige (SJR): 0.207 Citation Impact (citeScore): 1Number of Followers: 8     Open Access journal ISSN (Print) 1735-9325 - ISSN (Online) 2251-7235 Published by SpringerOpen  [259 journals]
• Influence of the inlet gas velocity components on the survival of the
vertex of gas in the plasma torch

• Abstract: The vortex gas injection into plasma torch is considered as a method for reducing electrodes erosion. In order to investigate the effects of vortex gas injection on plasma structure, as well as the effect of gas viscosity on the rate of rotation, a three-dimensional nonequilibrium and time-dependent non-transferred DC plasma torch model has been simulated. Viewing the general characteristics of the plasma shows that the model works well. The results have shown that if the components of the inlet gas velocity are not properly selected, it is possible that the rotary effects of the gas are greatly depleted even before the gas reaches the cathode tip and plasma formation. In this case, only the change in the axial component of the gas causes changes in the structure of the plasma. Vortex reduction is also observed during the movement of cold gases. It is observed that the change in viscosity of gas has significant effects on the rate of the vortex.
PubDate: 2020-03-01

• A study of the corrosion of stainless steel 304L coated with a
190 nm-thick manganese layer and annealed with nitrogen flux in a
0.4-mole solution of H 2 SO 4  at different temperatures

• Abstract: A method for enhancing the resistance against corrosion of stainless steel 304L coated with 190 nm-thick manganese film and annealed with nitrogen flux at constant temperature (723 K) is reported. The variable quantity in this work is the temperature of the corroding solution (293 K and 333 K). X-ray diffraction analysis was employed to investigate the crystallographical changes of the annealed samples; atomic force microscope and scanning electron microscope were used for the morphology and studying the roughness of their surfaces; polarization analysis, electrochemical impedance spectroscopy, and phase and Bode diagrams, as well as the Kramers–Kronig transformation, were employed to study the susceptibility of the samples to corrosion, at temperatures 293 K and 333 K in 0.4 M H2SO4 solutions. Our results, from all the above analyses, unanimously point to the fact that in the process of enhancing resistance to corrosion, the annealing stage is the most crucial for improving the coating and the crystal structure of the samples and that the adsorption of Mn is not sufficient for the enhancement of the surface layer. Moreover, it was observed that increasing the temperature of the solution decreases the resistance of the samples owing to an increase in the rate of corrosion.
PubDate: 2020-03-01

• Behaviour of sheath in electronegative warm plasma

• Abstract: Behaviour of sheath formed on two types of probes, namely cylindrical and spherical probes, has been investigated in terms of its thickness, in front of the conducting probes immersed in an electronegative plasma for different negative to positive ion mass ratios, by considering three electronegative gases, i.e. CF4, O2 and C60. Contrary to others’ work, complete fluid equations are written for negative ions also in addition to those of positive ions considering their different masses. Increasing negative to positive ion mass ratio is found to result in an increment of the sheath thickness. The magnitude of the sheath thickness is enhanced with an increment in the positive ions’ temperature, whereas the magnitude of the sheath thickness is reduced with increased negative ions’ temperature and background density of the negative ions. The analysis of the case of a large probe radius, used in the surface-nitriding process, for both the geometries is attended. Additionally, the comparison between the results for electropositive plasma and electronegative plasma and for behaviour of negative ions with their Boltzmann distribution and fluid approach has also been attempted herewith and a noteworthy difference is realized. The case of doubly charged ions is also entertained herewith.
PubDate: 2020-02-17

• Higher-curvature corrections to holographic mutual information

• Abstract: In this paper, we study some non-local measurements of quantum correlations in extended gravities with higher-order curvature terms, including conformal gravity. Precisely, we consider higher-curvature correction on holographic mutual information in conformal gravity. There is in fact one deformation in the states because of the higher-curvature corrections. Here by making use of the holographic methods, we study the deformation in the holographic mutual information due to the higher-curvature terms. We also address the change in the quantum phase transition due to these deformations.
PubDate: 2020-02-15

• Fabrication and characterization of PSi/nanometal hybrid structures by
laser for CO gas sensor

• Abstract: Mesoporous silicon (mesoPSi) layers fabricated by the photoelectrochemical etching (PECE) method in hydrofluoric acid (HF) are active as carbon monoxide gas sensors. The modified porous silicon (PSi) can be used with noble metals to manufacture an effective gas sensor. Embedded gold, platinum, and palladium nanoparticles Au, Pt, and Pd-NPs could modify the surface morphology of mesoPSi and form mesoPSi/AuPtPd-NPs hybrid structures through a simple and dipping process in fixed salt concentrations. The morphology of the hybrid structures has been studied using scanning electron microscopy and X-ray diffraction. The prepared gas sensor has measured the electrical characteristics at room temperature. Shape, nanoparticle size, and specific surface area strongly influenced the current–voltage characteristics. The results show that Au, Pd, and Pt-NPs sizes prepared by the dipping process for mesopore-like structures were in the range from 0.64 to 7.53 nm. Besides, considerable improvements in the response, recovery times and sensitivity of gas sensor were noticed when decreasing the incorporated Au, Pd, and Pt-NPs to the mesoPSi matrix.
PubDate: 2020-02-11

• Design and fabrication of runaway probe for studying the behavior of
runaway electrons in IR-T1 Tokamak

• Abstract: Several theoretical and experiential studies of runaway electrons in the well-known Tokamaks of the world have been made over the past few decades. In the present study, the measurements of runaway electrons energy were carried out by a new runaway probe in the IR-T1 Tokamak. In the IR-T1 Tokamak, the hard X-ray diagnostic system is used as a diagnostic global measurement system at the vessel wall of Tokamak. Runaway probe was first designed and fabricated for local measurement near the plasma edge in IR-T1 Tokamak. The new diagnostic has the advantage that the local interaction of runaways with materials can be evaluated, along with the direct measurement of the runaway electrons. The runaway probe consists of 2 LYSO (Lu 1.8Y.2SiO5:Ce) crystals covered by a graphite housing which is shielded by tungsten filter placed in the direction of runaway electrons. The main elements of the runaway probe are LYSO crystals which convert the energy of runaway electrons into visible light which is instructed to silicon photomultipliers. The present study aimed to evaluate a new runaway probe in the IR-T1 Tokamak to detect beta and gamma rays. The results indicated that electron spectrum is between 500 keV and 2 MeV at the plasma edge in the IR-T1 Tokamak.
PubDate: 2020-01-28

• Full structure of the thermal plasma including the ion isothermal drag

• Abstract: In order to study the ion temperature effect on the space-charge structure and the plasma variables on the wall, the ion thermal force has been added to the ion motion equation in the plasma fluidal model. In the eigenvalue problem of plasma, the plasma equations are numerically solved in a whole area from the plasma center to the wall and it is displayed that the ion temperature has significant effects on the plasma structure and floating variables. However, the fluidal theory of plasmas introduces a singular point among the space charge of plasma boundary layer if the static pressure and the inertial mass of the thermal ions are taken into account at the same time. Finding a full numerical solution for the thermal plasma equations needs to cross the singular point. The singular point and how crossing the point will be depicted too.
PubDate: 2020-01-07

• Comparative study of dust acoustic solitons in two-temperature ion
homogeneous and inhomogeneous plasmas

• Abstract: The dust acoustic solitary waves are theoretically investigated in dusty plasmas for different cases of with and without density gradients. These low-frequency solitary waves are studied using appropriate Korteweg–de Vries equations obtained using relevant stretched coordinates. The soliton solutions in homogeneous plasma, weakly inhomogeneous plasma and strongly inhomogeneous plasma, are thoroughly investigated for studying the effect of different parameters like dust charge and density of all the plasma species on the soliton profiles. The combination of the dust charge with its number density changes the dynamics of the solitons and that is further affected by the number density of the hot ion with respect to the cold ions.
PubDate: 2020-01-07

• Simulation study to find suitable dopants of CdS buffer layer for CZTS
solar cell

• Abstract: The performance of CZTS solar cell, a promising candidate in the field of energy production from sunlight, can be improved by optimizing the parameters of most widely used CdS buffer layer. In this work, numerical study have been done on the typical CZTS solar cell structures containing Mo thin film as back contact on glass substrate using SCAPS-1D solar cell simulation software. Then, the CZTS has been used as the absorber layer followed by CdS buffer later. Following, ZnO and transparent conducting oxide n-ITO layers have been considered as window layer and front contact, respectively. In the simulations, the CdS buffer layer has been doped with three different materials such as Silver (Ag), Copper (Cu) and Chlorine (Cl) for a wide acceptable range of carrier concentration. After obtaining the suitable carrier concentration, the thickness of the doped buffer layer has been varied keeping other layer parameters constant to see the variation of performance parameters open circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF) and efficiency (η) of the CZTS solar cell.
PubDate: 2019-12-27

• Inactivation by helium cold atmospheric pressure plasma for Escherichia
coli and Staphylococcus aureus

• Abstract: A helium cold atmospheric pressure plasma jet (HCAPPJ) driven by a commercial neon power supply was designed and utilized for inactivation bacteria. The generated reactive spices by HCAPPJ were investigated by optical emission spectroscopy. The reactive species of OH, OI, OI, N21+, N21+ and He were identified in the UV–Vis wavelength region. The reactive species was not detected between 200 nm and 300 nm, as the flow rate of helium gas increased that led to the plasma temperature reducing to a value near to the room temperature. In this work, we studied the impact of HCAPPJ on Gram-positive and Gram-negative bacteria. The survival amounts of the two types of bacteria were decreased vastly when the rate flow rate was equal to 10 L/min.
PubDate: 2019-12-17

• Investigation of carbon monoxide gas adsorption on the Al 2 O 3 /Pd(NO 3 )
2 /zeolite composite film

PubDate: 2019-12-17

• Effect of rapid thermal annealing on structural and optical properties of
ZnS thin films fabricated by RF magnetron sputtering technique

• Abstract: The ZnS thin films have been deposited by radio frequency magnetron sputtering at room temperature. Post-deposition rapid thermal annealing treatment was done for the films deposited at different powers ranging from 70 to 100 W. One peak is observed for as-deposited and annealed thin films at around 28.48° corresponding to the (111) reflection plane indicating a zincblende structure. The overall intensity of the peaks and the FWHM values of as-deposited films increased after annealing corresponding to the increase in crystallinity. The optical energy bandgap is found in the range of 3.24–3.32 eV. With increasing annealing temperature, the decrease in the Urbach energy values indicating a decrease in localized states which is in good agreement with the XRD results where the crystallinity increased. The surface morphology of the films seems to be composed of Nano-granules with a compact arrangement. Apparently, the grain size increases in the deposited films as annealing temperature increases. The compositional ratio attained close to the stoichiometric ratio of 1:1 after annealing. From the Hall effect measurement, the carrier concentration and mobility are found to increase after annealing. The high carrier concentration and mobility also comply with structural and optical analysis. Best results are found for the film annealed at 400 °C deposited at 90 W.
PubDate: 2019-12-02

• Density functional theory study on the effect of Cu- and Na-substituted
layers on spin-dependent transport and TMR in the Fe/ZnO/Fe MTJ

• Abstract: Using density functional theory, effects of Na- and Cu-substituted layers on the spin-dependent electronic transport properties of Fe/ZnO/Fe magnetic tunnel junction based on zinc oxide barrier tunnel, with rock-salt crystalline structure, have been studied. In zero-bias voltage, conductance and tunneling magneto-resistance (TMR) ratio of structures are calculated. It is showed that substituted layers in the pristine junction greatly affect conductance and TMR ratio of this junction. The results indicated that Cu-substituted layer with reducing conductance of pristine structure in the antiparallel alignment configuration, and increasing its conductance in the parallel alignment, leads to a large TMR ratio, up to 1800%. Due to the large conductance of pristine and Cu-substituted devices in the parallel alignment, these structures would be very beneficial for experimental applications that require the spin-polarized current.
PubDate: 2019-12-01

• Ripple transport and neoclassical diffusion in IR-T1 tokamak

• Abstract: In tokamaks, small variations in the magnetic field create ripple. The discontinuous nature of the magnetic field coils in an axisymmetric torus conduces to additional particle trapping, and it is responsible for an additional neoclassical diffusion. Ripples also reduce the particle removal efficiency and disturb plasma confinement and cause constraints in the design of magnet of fusion reactor. Therefore, it is quite important to include the ripple for the design of plasma edge components. Herein, several considerations are taken into account to calculate and evaluate the diffusion coefficient and ion heat conductivity in ripple transport and also to compare it with neoclassical mode.
PubDate: 2019-11-26

• The texture ordering in L1 0 -FePt–Ag nanocomposites

• Abstract: L10-FePt nanoparticles with different Ag percentages were prepared. The presence of 6% Ag in co-sputtering process with deposition rate of 1 $${\dot{A}}/\text{s}$$ at 500 °C led to the formation of FePt nanoparticles with 5–7 nm size in L10-fct phase. Moreover, Ag atoms laying in boundaries of these nanoparticles in these circumstances caused c axis to orient and (001) peak intensity in XRD spectrum to increase. This is the result of the indirect exchange interactions of Fe magnetic atoms through Ag atoms in these boundaries. Therefore, where L10-FePt grains have the most boundaries with each other, the order index would be maximum.
PubDate: 2019-11-12

• Effect of BN nanodots on the electronic properties of α- and β-graphyne
sheets: a density functional theory study

• Abstract: The effect of BN nanodots with hexagonal shape on the electronic properties of α- and β-graphyne sheets is investigated. The structural and electronic properties of α- and β-graphyne sheets doped with BN nanodots are studied by using density functional theory. The cohesive energies of the systems indicate all considered structures are thermally stable. It is found that hexagonal BN nanodots can effectively open the band gap in α- and β-graphyne sheets. It means BN nanodots change α- and β-graphyne sheets from semimetal to semiconductor. The BN nanodots with different sizes are considered. It is found that band gaps of the studied α- and β-graphyne sheets doped with BN nanodots increase with the increase in the size of BN nanodots. Hence, α- and β-graphyne sheets doped with BN nanodots are promising materials for use in nanoelectronic devices based on semiconductors.
PubDate: 2019-10-08

• Memory effect in silicon nitride deposition using ICPCVD technique

• Abstract: In this study, a plasma-based low-temperature, low-pressure SiN film deposition is investigated for device applications. Ammonia, nitrogen and silane are being used for optimization of the quality of SiN film for device passivation by ICPCVD. Characterization of SiN film is done using elastic recoil detection analysis, AFM, FTIR and ellipsometry. The effect of previous process parameters on subsequent process is called memory effect, which has been investigated by all the characterization techniques. During deposition, this effect has been observed for the same parameters that are used to maintain the stoichiometry of the film. It has been observed that some of the residues of gases used for SiN deposition remain present even after the deposition in the chamber and are carried over for the next deposition process and alter the film property, though parameters such as flow rate, temperature, pressure and time remain fixed. This memory effect alters the film surface roughness and stoichiometry thus affecting device characteristics after passivation.
PubDate: 2019-10-05

• Investigation of dopant centres dominating the conduction process in the
bulk of un-doped GaSb

• Abstract: In this paper, first, the theoretical description of the effects of the dopant densities and the activation energies on the ionization densities, the chemical potentials corresponding to each dopant levels, the majority carrier densities and the Fermi-energy levels in one-acceptor-level system, highly compensated system and two-acceptor-level system are described in detail. Upon fitting the theoretical to the experimental results obtained by the temperature-dependent Hall effect measurements for three samples of un-doped GaSb, the dopant densities and the activation energies for a system with different dopants are investigated. The obtained results revealed that the dopant activation energy has less (no) effect on the Fermi-energy level and the majority carrier density in the highest temperature regimes. The doping density has also less (no) effect on the Fermi-energy level in the lowest temperature regimes. Finally, fitting of the theoretical to the experimental Hall effect measurements results confirmed the presence of three acceptor and one donor levels dominating the majority carrier densities at different temperature regions in all the samples of un-doped GaSb semiconductor.
PubDate: 2019-10-04

• Effect of plasma oxidation parameters on physical properties of
nanocrystalline nickel oxide thin films grown by two-step method: DC
sputtering and plasma oxidation

• Abstract: Nanocrystalline nickel oxide (NiO) thin films were successfully grown on quartz substrates by two-step method. In the first step, nickel films were deposited on quartz substrates by DC magnetron sputtering technique. Then, the plasma oxidation of nickel films was used for preparation of nickel oxide. The effect of DC plasma power and treatment time on the structural, morphological and optical properties of the NiO films were investigated by different analyses. XRD results indicated that the plasma powers effectively influenced the structure of films, and the best crystallinity was obtained for plasma power of 15 w and treatment time of 20 min. The XPS, RBS and EDS analysis confirmed the presence of Ni and O elements. The FESEM and AFM images showed a granular structure with spherical shapes of grains. The optical band gap of the films synthesized under different plasma oxidation conditions was also discussed.
PubDate: 2019-09-19

• Detection of overtone and combined peaks using Mn/Cu helical star-shaped
(pine-tree-like) sculptured thin films in surface-enhanced Raman
spectroscopy

• Abstract: Mn helical star-shaped (pine-tree-like) nano-sculptured thin films with three-, four-and fivefold symmetry on copper substrates were produced using oblique angle deposition method in conjunction with rotation of sample holder at certain angles. Raman spectroscopy of the samples which were subjected to impregnation by 4,4′-bipyridine (C10H8N2) solution was carried out by 632.8 nm wavelength laser. The analysis of the Raman spectra showed enhancement for the 4,4′-bipyridine main bands (1592 and 1297 cm−1) belonging to the C=C stretching mode, aromatic ring stretching ring and in-plane ring mode of 4,4′-bipyridine, same as results obtained for Ag nano-structures. In addition, overtone and combined peaks are detected that may be related to the particular sculptured structure of the thin films fabricated in this work and the laser wavelength used for Raman spectroscopy. UV–Vis (absorption mode) spectra showed consistent observations with the SERS results leading to important role of surface electromagnetic selection rule in intensification of SERS, in addition pointing out the importance of the effect of the size of hot spots on the frequency of the localized surface plasmonic oscillations.
PubDate: 2019-09-09

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