Subjects -> MATHEMATICS (Total: 1119 journals)
    - APPLIED MATHEMATICS (92 journals)
    - GEOMETRY AND TOPOLOGY (23 journals)
    - MATHEMATICS (822 journals)
    - MATHEMATICS (GENERAL) (45 journals)
    - NUMERICAL ANALYSIS (25 journals)
    - PROBABILITIES AND MATH STATISTICS (112 journals)

MATHEMATICS (822 journals)            First | 1 2 3 4 5     

Showing 401 - 538 of 538 Journals sorted alphabetically
Journal of Computer Engineering, System and Science (CESS)     Open Access  
Journal of Contemporary Mathematical Analysis     Hybrid Journal  
Journal of Cryptology     Hybrid Journal   (Followers: 5)
Journal of Difference Equations and Applications     Hybrid Journal  
Journal of Differential Equations     Full-text available via subscription   (Followers: 1)
Journal of Discrete Algorithms     Hybrid Journal   (Followers: 4)
Journal of Discrete Mathematics     Open Access   (Followers: 1)
Journal of Dynamics and Differential Equations     Hybrid Journal  
Journal of Engineering Mathematics     Hybrid Journal   (Followers: 2)
Journal of Evolution Equations     Hybrid Journal  
Journal of Experimental Algorithmics     Full-text available via subscription   (Followers: 1)
Journal of Flood Risk Management     Hybrid Journal   (Followers: 14)
Journal of Formalized Reasoning     Open Access   (Followers: 2)
Journal of Function Spaces     Open Access  
Journal of Functional Analysis     Full-text available via subscription   (Followers: 2)
Journal of Geochemical Exploration     Hybrid Journal   (Followers: 1)
Journal of Geological Research     Open Access   (Followers: 1)
Journal of Geovisualization and Spatial Analysis     Hybrid Journal  
Journal of Global Optimization     Hybrid Journal   (Followers: 7)
Journal of Global Research in Mathematical Archives     Open Access   (Followers: 1)
Journal of Group Theory     Hybrid Journal   (Followers: 2)
Journal of Homotopy and Related Structures     Hybrid Journal  
Journal of Honai Math     Open Access  
Journal of Humanistic Mathematics     Open Access   (Followers: 1)
Journal of Hyperbolic Differential Equations     Hybrid Journal  
Journal of Indian Council of Philosophical Research     Hybrid Journal  
Journal of Industrial Mathematics     Open Access   (Followers: 2)
Journal of Inequalities and Applications     Open Access  
Journal of Infrared, Millimeter and Terahertz Waves     Hybrid Journal   (Followers: 3)
Journal of Integrable Systems     Open Access   (Followers: 1)
Journal of K-Theory     Full-text available via subscription  
Journal of Knot Theory and Its Ramifications     Hybrid Journal   (Followers: 1)
Journal of Kufa for Mathematics and Computer     Open Access   (Followers: 1)
Journal of Liquid Chromatography & Related Technologies     Hybrid Journal   (Followers: 7)
Journal of Logical and Algebraic Methods in Programming     Hybrid Journal  
Journal of Manufacturing Systems     Full-text available via subscription   (Followers: 4)
Journal of Mathematical Analysis and Applications     Full-text available via subscription   (Followers: 5)
Journal of mathematical and computational science     Open Access   (Followers: 7)
Journal of Mathematical and Fundamental Sciences     Open Access  
Journal of Mathematical Behavior     Hybrid Journal   (Followers: 3)
Journal of Mathematical Chemistry     Hybrid Journal   (Followers: 3)
Journal of Mathematical Cryptology     Hybrid Journal   (Followers: 1)
Journal of Mathematical Extension     Open Access   (Followers: 3)
Journal of Mathematical Finance     Open Access   (Followers: 9)
Journal of Mathematical Imaging and Vision     Hybrid Journal   (Followers: 6)
Journal of Mathematical Logic     Hybrid Journal   (Followers: 3)
Journal of Mathematical Modelling and Algorithms     Hybrid Journal   (Followers: 1)
Journal of Mathematical Neuroscience     Open Access   (Followers: 10)
Journal of Mathematical Sciences     Hybrid Journal  
Journal of Mathematical Sciences and Applications     Open Access   (Followers: 2)
Journal of Mathematical Sociology     Hybrid Journal   (Followers: 3)
Journal of Mathematics     Open Access  
Journal of Mathematics and Statistics     Open Access   (Followers: 8)
Journal of Mathematics and Statistics Studies     Open Access   (Followers: 3)
Journal of Mathematics and the Arts     Hybrid Journal   (Followers: 2)
Journal of Mathematics Education at Teachers College     Open Access   (Followers: 3)
Journal of Mathematics in Industry     Open Access  
Journal of Mathematics Research     Open Access   (Followers: 6)
Journal of Metallurgy     Open Access   (Followers: 8)
Journal of Modern Mathematics Frontier     Open Access  
Journal of Multidisciplinary Modeling and Optimization     Open Access  
Journal of Multivariate Analysis     Hybrid Journal   (Followers: 13)
Journal of Natural Sciences and Mathematics Research     Open Access  
Journal of Nonlinear Analysis and Optimization : Theory & Applications     Open Access   (Followers: 4)
Journal of Nonlinear Mathematical Physics     Hybrid Journal   (Followers: 1)
Journal of Nonlinear Science     Hybrid Journal   (Followers: 1)
Journal of Numerical Cognition     Open Access   (Followers: 1)
Journal of Numerical Mathematics     Hybrid Journal   (Followers: 2)
Journal of Optimization     Open Access   (Followers: 5)
Journal of Peridynamics and Nonlocal Modeling     Hybrid Journal  
Journal of Problem Solving     Open Access   (Followers: 2)
Journal of Progressive Research in Mathematics     Open Access   (Followers: 5)
Journal of Pseudo-Differential Operators and Applications     Hybrid Journal  
Journal of Pure and Applied Algebra     Full-text available via subscription   (Followers: 4)
Journal of Quantitative Analysis in Sports     Hybrid Journal   (Followers: 9)
Journal of Quantitative Linguistics     Hybrid Journal   (Followers: 6)
Journal of Scientific Computing     Hybrid Journal   (Followers: 18)
Journal of Scientific Research     Open Access  
Journal of Symbolic Computation     Hybrid Journal   (Followers: 1)
Journal of the Australian Mathematical Society     Full-text available via subscription  
Journal of the Egyptian Mathematical Society     Open Access  
Journal of the European Mathematical Society     Full-text available via subscription   (Followers: 1)
Journal of the Indian Mathematical Society     Hybrid Journal   (Followers: 1)
Journal of the Institute of Mathematics of Jussieu     Hybrid Journal  
Journal of the London Mathematical Society     Hybrid Journal   (Followers: 2)
Journal of the Nigerian Mathematical Society     Open Access   (Followers: 1)
Journal of Theoretical and Applied Physics     Open Access   (Followers: 8)
Journal of Topology and Analysis     Hybrid Journal  
Journal of Transport and Supply Chain Management     Open Access   (Followers: 16)
Journal of Turbulence     Hybrid Journal   (Followers: 9)
Journal of Uncertainty Analysis and Applications     Open Access   (Followers: 1)
Journal of Universal Mathematics     Open Access  
Journal of Urban Regeneration & Renewal     Full-text available via subscription   (Followers: 11)
JRAMathEdu : Journal of Research and Advances in Mathematics Education     Open Access   (Followers: 6)
JUMLAHKU : Jurnal Matematika Ilmiah STKIP Muhammadiyah Kuningan     Open Access   (Followers: 2)
JURING (Journal for Research in Mathematics Learning)     Open Access   (Followers: 1)
Jurnal Ilmiah AdMathEdu     Open Access  
Jurnal Matematika     Open Access   (Followers: 1)
Jurnal Matematika Integratif     Open Access  
Jurnal Matematika, Sains, Dan Teknologi     Open Access  
Jurnal Natural     Open Access  
Jurnal Pendidikan Matematika Raflesia     Open Access  
Jurnal Penelitian Pembelajaran Matematika Sekolah     Open Access  
Jurnal Penelitian Sains (JPS)     Open Access  
Jurnal Riset Pendidikan Matematika     Open Access  
Jurnal Sains Matematika dan Statistika     Open Access  
Jurnal Tadris Matematika     Open Access  
Jurnal Teknologi dan Sistem Komputer     Open Access  
Kontinu : Jurnal Penelitian Didaktik Matematika     Open Access   (Followers: 3)
Kreano, Jurnal Matematika Kreatif-Inovatif     Open Access   (Followers: 6)
Le Matematiche     Open Access  
Learning and Teaching Mathematics     Full-text available via subscription   (Followers: 7)
Lettera Matematica     Hybrid Journal  
Lietuvos Matematikos Rinkinys     Open Access   (Followers: 3)
Limits : Journal of Mathematics and Its Applications     Open Access   (Followers: 1)
Linear Algebra and its Applications     Full-text available via subscription   (Followers: 23)
Linear and Multilinear Algebra     Hybrid Journal   (Followers: 8)
Lithuanian Mathematical Journal     Hybrid Journal  
LMS Journal of Computation and Mathematics     Free  
Lobachevskii Journal of Mathematics     Open Access  
Logic and Analysis     Hybrid Journal   (Followers: 1)
Logic Journal of the IGPL     Hybrid Journal   (Followers: 1)
Logica Universalis     Hybrid Journal  
manuscripta mathematica     Hybrid Journal  
MaPan : Jurnal Matematika dan Pembelajaran     Open Access  
Marine Genomics     Hybrid Journal   (Followers: 2)
Matemáticas, Educación y Sociedad     Open Access  
Matematicheskie Zametki     Full-text available via subscription  
Matematychni Studii     Open Access  
Mathematica Eterna     Open Access  
Mathematica Scandinavica     Full-text available via subscription   (Followers: 1)
Mathematica Slovaca     Hybrid Journal   (Followers: 1)
Mathematical and Computational Forestry & Natural-Resource Sciences     Free  
Mathematical Communications     Open Access  
Mathematical Computation     Open Access   (Followers: 1)
Mathematical Geosciences     Hybrid Journal   (Followers: 3)
Mathematical Journal of Interdisciplinary Sciences     Open Access   (Followers: 1)
Mathematical Medicine and Biology: A Journal of the IMA     Hybrid Journal   (Followers: 1)
Mathematical Methods in the Applied Sciences     Hybrid Journal   (Followers: 4)
Mathematical Methods of Statistics     Hybrid Journal   (Followers: 4)
Mathematical Modelling and Analysis     Open Access   (Followers: 1)
Mathematical Modelling in Civil Engineering     Open Access   (Followers: 5)
Mathematical Modelling of Natural Phenomena     Full-text available via subscription   (Followers: 1)
Mathematical Models and Methods in Applied Sciences     Hybrid Journal   (Followers: 2)
Mathematical Models in Engineering     Open Access   (Followers: 1)
Mathematical Notes     Hybrid Journal  
Mathematical Proceedings of the Cambridge Philosophical Society     Full-text available via subscription   (Followers: 2)
Mathematical Programming Computation     Hybrid Journal   (Followers: 3)
Mathematical Sciences     Open Access  
Mathematical Social Sciences     Hybrid Journal   (Followers: 1)
Mathematical Theory and Modeling     Open Access   (Followers: 13)
Mathematical Thinking and Learning     Hybrid Journal   (Followers: 4)
Mathematics and Statistics     Open Access   (Followers: 5)
Mathematics Education Forum Chitwan     Open Access   (Followers: 2)
Mathematics Education Journal     Open Access   (Followers: 3)
Mathematics Education Research Journal     Partially Free   (Followers: 20)
Mathematics in Science and Engineering     Full-text available via subscription  
Mathematics of Control, Signals, and Systems (MCSS)     Hybrid Journal   (Followers: 5)
Mathematics of Quantum and Nano Technologies     Open Access  
Mathématiques et sciences humaines     Open Access   (Followers: 6)
Mathematische Annalen     Hybrid Journal   (Followers: 1)
Mathematische Nachrichten     Hybrid Journal   (Followers: 1)
Mathematische Semesterberichte     Hybrid Journal  
Mathematische Zeitschrift     Hybrid Journal   (Followers: 1)
MathLAB Journal     Open Access   (Followers: 5)
MATICS     Open Access   (Followers: 2)
Matrix Science Mathematic     Open Access   (Followers: 1)
Measurement Science Review     Open Access   (Followers: 3)
Mediterranean Journal of Mathematics     Hybrid Journal  
Memetic Computing     Hybrid Journal  
Mendel : Soft Computing Journal     Open Access  
Metaheuristics     Hybrid Journal  
Metals and Materials International     Hybrid Journal  
Metascience     Hybrid Journal   (Followers: 1)
Metrology and Instruments / Метрологія та прилади     Open Access  
Milan Journal of Mathematics     Hybrid Journal  
Mitteilungen der DMV     Hybrid Journal  
MLQ- Mathematical Logic Quarterly     Hybrid Journal   (Followers: 1)
MONA : Matematik- og Naturfagsdidaktik     Hybrid Journal   (Followers: 5)
Monatshefte fur Mathematik     Hybrid Journal  
Moroccan Journal of Pure and Applied Analysis     Open Access   (Followers: 4)
Moscow University Mathematics Bulletin     Hybrid Journal  
MSOR Connections     Open Access   (Followers: 1)
Multiscale Modeling and Simulation     Hybrid Journal   (Followers: 3)
MUST : Journal of Mathematics Education, Science and Technology     Open Access   (Followers: 2)
Nagoya Mathematical Journal     Hybrid Journal  
Nano Research     Hybrid Journal   (Followers: 4)
Nanotechnologies in Russia     Hybrid Journal   (Followers: 1)
Natural Resource Modeling     Hybrid Journal   (Followers: 1)
New Mathematics and Natural Computation     Hybrid Journal  
Nonlinear Analysis : Modelling and Control     Open Access   (Followers: 1)
Nonlinear Analysis : Theory, Methods & Applications     Hybrid Journal   (Followers: 1)
Nonlinear Analysis: Hybrid Systems     Hybrid Journal  
Nonlinear Analysis: Real World Applications     Hybrid Journal   (Followers: 2)
Nonlinear Differential Equations and Applications NoDEA     Hybrid Journal  
Nonlinear Engineering     Open Access  
Nonlinear Oscillations     Hybrid Journal   (Followers: 1)
North Carolina Journal of Mathematics and Statistics     Open Access  
North-Holland Mathematical Library     Full-text available via subscription   (Followers: 1)
North-Holland Mathematics Studies     Full-text available via subscription  

  First | 1 2 3 4 5     

Similar Journals
Journal Cover
Journal of Infrared, Millimeter and Terahertz Waves
Journal Prestige (SJR): 0.803
Citation Impact (citeScore): 2
Number of Followers: 3  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1866-6892 - ISSN (Online) 1866-6906
Published by Springer-Verlag Homepage  [2656 journals]
  • A Model of Terahertz Parametric Process Including Spontaneous Parametric
           Down-conversion
    • Abstract: A new numerical model of terahertz parametric process is demonstrated, which takes the spontaneous parametric down-conversion into consideration by adding tens of frequency components in the coupled-wave equations. To set the values of some parameters in this model, the residual pump energy and idler spectra during spontaneous parametric down-conversion are measured experimentally for different pump energy and crystal lengths. Compared with previous models which only involve three waves, the new model is more accurate, especially when the seed power is low or the generated terahertz-wave is in the low frequency region.
      PubDate: 2021-05-11
       
  • Terahertz Generation by Optical Rectification in Sugar Crystal
    • Abstract: We report on THz pulse generation through optical rectification of femtosecond laser pulses in sugar crystals. The sugar crystals were grown from an aqueous solution of caster cane sugar bought in a local grocery. Sugar exhibits rather good nonlinear coefficients ( \(d_{23}\simeq 56\) pm/V), but the optical-THz conversion efficiency remains quite weak because of the lack of phase-matching, when pumped by a laser beam of 0.8-μm central wavelength. Nevertheless, sugar availability at a low price makes it a relevant material for trial experiments.
      PubDate: 2021-05-07
       
  • High–Bias–Field Operation of GaAs Photoconductive Terahertz
           Emitters
    • Abstract: We demonstrate experimentally the increase of optical-to-terahertz conversion efficiency for GaAs-based photoconductive terahertz emitters. This increase is achieved by preventing device breakdown through series resistors, which act as a current limiter. Pulsed photoexcitation and potential current fluctuations result in heat dissipation leading to local heating, which further increases the current and may lead to device breakdown. We manage to increase the maximum bias field before device breakdown by a factor of 3 under illuminated conditions. For a laser system with 250-kHz repetition rate, the terahertz emission amplitude increases linearly with applied bias field up to 120 kV/cm bias field, which results in 3 times higher signal as compared to the standard device. Furthermore, we have also achieved this expanded breakdown prevention at 78-MHz repetition rate, where an integrated on-chip resistance leads to an enhancement of the terahertz field amplitude by 70%. This simple technique can increase the performance of almost all photoconductive terahertz emitters by using appropriate resistances according to the emitter capacitance and laser repetition rate.
      PubDate: 2021-05-05
       
  • Calculations on Mode Eigenvalues in a Corrugated Waveguide with Varying
           Diameter and Corrugation Depth
    • Abstract: The present paper addresses numerical calculations on the eigenvalues of hybrid modes in corrugated circular waveguides with varying diameter and corrugation depth. Such calculations are essential for the numerical optimization of advanced mode converters and diameter tapers for future low-loss high-power microwave applications, like broadband high-power radar sensors for space debris observation in low earth orbit (LEO). Corresponding mode converters and diameter tapers may be synthesized based on coupled mode theory. Of particular importance here is the ability to consider varying mode eigenvalues along the perturbed waveguide. The procedure presented here is able to consider arbitrary variations of the corrugation depth as well as the waveguide diameter and therefore is highly flexible. The required computational effort is low. Limitations of the method are discussed.
      PubDate: 2021-04-23
       
  • Impedance-Matching Technique for an Infrared Folded Dipole Antenna
    • Abstract: Modifications of the geometry of a folded dipole antenna operating in the infrared were studied with the objective to increase the antenna input impedance. These modified folded dipoles were designed and optimized using numerical simulations. Candidate antennas were fabricated, and input impedance was measured experimentally using scattering-scanning near-field optical microscopy. Numerical and experimental results confirm that the choice of an appropriate antenna geometry leads to an input impedance of 1 kΩ or above. With this impedance, the modified folded dipole antenna could be implemented as a solution for the impedance mismatch challenge that arises in antenna-coupled infrared detectors.
      PubDate: 2021-04-20
       
  • Wideband Phase-Compensated VGA with PMOS Switch in 40-nm CMOS for 120-GHz
           Band
    • Abstract: This paper presents a 120-GHz wideband phase-compensated variable gain amplifier (VGA) with a p-type metal–oxide–semiconductor (PMOS) switch using a 40-nm CMOS process. By applying a PMOS switch to the common source (CS) amplifier, the gain of the CS amplifier can be controlled by as much as 6.1 dB with 2° phase variations in 15.1-GHz bandwidth ranging from 100.9 to 115 GHz. The measured gain and 3-dB bandwidth of the VGA are 19.1 dB and 33.8 GHz for high-gain state, and 13 dB and 44.2 GHz for low gain state, respectively. Meanwhile, the DC power consumption in the high-gain state is 45 mW, and the OP1dB is −2.7 dBm.
      PubDate: 2021-04-17
       
  • Correction to: Study of the Effect of Reflections on High-Power, 110-GHz
           Pulsed Gyrotron Operation
    • Abstract: A Correction to this paper has been published: https://doi.org/10.1007/s10762-021-00783-w
      PubDate: 2021-04-12
       
  • Fast Quantitative Analysis of Hidden Dangerous Substances in Mail Based on
           Specific Interval PLS
    • Abstract: Terahertz radiation has many unique characteristics that make it useful for noninvasive mail inspection. While qualitative analysis of mail for suspicious objects is a relatively instantaneous process, quantitative analysis methods may be time-consuming. Multivariate analysis methods, including principal component analysis (PCA), partial least squares (PLS), and interval partial least squares (iPLS), were used for quantitative model building and to predict the content of substances in mail. The optimal spectral interval was selected by analyzing the influence of different spectral regions on the predicted results. A specific interval partial least squares (SiPLS) model was established to improve prediction accuracy and reduce the root mean square error (RMSE) by an order of magnitude. The content of dangerous substances was calculated using SiPLS, established by referencing spectral data of pure substances. Our methods demonstrated that establishing a multiple regression model based on spectral data of pure substances could predict the content of dangerous substances in mail.
      PubDate: 2021-04-10
       
  • Epoxy Resin (DGEBA/TETA) Exposed to Water: a Spectroscopic Investigation
           to Determine Water-Epoxy Interactions
    • Abstract: Epoxy resin, diglycidyl ether of bisphenol A (DGEBA) and triethylenetetramine (TETA), is known to be hygroscopic in nature, which eventually leads to mechanical performance degradation of the material. The long-standing debate on the nature of water-epoxy interaction has been investigated in this study with the help of terahertz spectroscopy, which is able to probe sub 100 cm− 1 wavenumbers in which hydrogen bonds of water are active as well as infrared spectroscopy, which is able to probe 600–1000 cm− 1 in which the libration motions of the water molecules are dominant. Based on observations, it can be demonstrated that both hydrogen-bonded water (with epoxy) and free interstitial water (hydrogen-bonded with itself) is present when the epoxy resin is exposed to normal or saline water. A schematic diagram is presented to demonstrate epoxy-water interactions.
      PubDate: 2021-04-07
       
  • Analysis of Subcycle Electro-Optic Sampling Without Background
    • Abstract: We explore background-free options to detect mid-infrared (MIR) electric transients. The MIR field and a near-infrared probe interact via sum- (SFG) and difference-frequency generation (DFG) in an electro-optic crystal. An intuitive picture based on a phasor representation and rigorous numerical calculations are used for analysis. It turns out that separating photons generated either by SFG or DFG from the local oscillator via spectral filtering leads to a signal purely proportional the MIR intensity envelope. Background-free phase information may be extracted in a spectral window containing both SFG and DFG components and blocking the local oscillator background based on its orthogonal polarization. This variant leads to signal proportional to the square of the MIR field amplitude. It is limited by the finite efficiency of polarization filtering. The Hilbert transform as a conjugate variable to the electric field in the time domain turns out to play a fundamental role for the context discussed in this paper.
      PubDate: 2021-04-07
       
  • Submillimeter-Wave Multiphase Oscillation Using Traveling Pulses in a
           Resonant-Tunneling Diode-Oscillator Lattice
    • Abstract: We recently proposed a multiphase oscillator utilizing a periodic pulse train generated and propagated in a closed one-dimensional lattice of resonant-tunneling diode (RTD) oscillators, each of which establishes the neighbor-to-neighbor coupling through lossy inductors. In this work, we develop the design criteria for the bias dependence of oscillation frequency through the bifurcation analysis based on the quasi-continuous model of the lattice. We then model the lattice in the full-wave scheme using the finite-difference time-domain method and validate the multiphase oscillation in submillimeter-wave frequencies. Finally, several experimental observations conducted in MHz frequencies using tunnel diodes in place of RTDs are presented to validate several synchronization properties of the pulse train in the lattice including the direction-specified transmission of pulse train and its application to the multiphase oscillator.
      PubDate: 2021-04-01
       
  • Propagation Channel Measurements in the mm- and Sub-mm Wave Range for
           Different Indoor Communication Scenarios
    • Abstract: Increasing data rates in wireless communications are accompanied with the need for new unoccupied and unregulated bandwidth in the electromagnetic spectrum. Higher carrier frequencies in the lower THz frequency range might offer the solution for future indoor wireless communication systems with data rates of 100 Gbit/s and beyond that cannot be located elsewhere. In this review, we discuss propagation channel measurements in an extremely broad frequency range from 50 to 325 GHz in selected indoor communication scenarios including kiosk downloading, office room communication, living rooms, and typical industrial environments.
      PubDate: 2021-04-01
       
  • A FFT-Based Millimeter-Wave Imaging Algorithm with Range Compensation for
           Near-Field MIMO-SAR
    • Abstract: In this article, an improved fast Fourier transform (FFT)–based millimeter-wave imaging algorithm with range compensation is presented, which can be used to reconstruct 3D images for near-field multiple-input multiple-output synthetic aperture radar (MIMO-SAR). The frequency-domain interpolation is avoided and only one-step spherical-wave decomposition is employed in this algorithm. During the image reconstruction process, the amplitude factor is considered for the compensation of signal propagation loss, and the final target image can be obtained by FFT/IFFT and coherent accumulation steps. As demonstrated with numerical theoretical analysis and experimental results, the proposed method greatly reduces the computational load but ensures the quality of image reconstruction compared to the back-projection (BP) algorithm. Moreover, it is superior to the MIMO-range migration algorithm (MIMO-RMA) in compensating propagation loss and other performance indexes in the image reconstruction results.
      PubDate: 2021-04-01
       
  • Theoretical Analysis of Frequency Stabilization and Pulling Effects in a
           Gyrotron with Delayed Reflection
    • Abstract: The effect of delayed reflection on frequency stabilization and pulling in a gyrotron oscillator is studied. Simple theoretical formulas for start-oscillation current, oscillation frequency, and frequency stabilization rate are derived in the framework of the linear (or small-signal) theory and verified by numerical simulation for the gyrotron with fixed axial profile of the RF field. Capabilities of increasing frequency stability are analyzed. A possibility of expanding frequency tunability range owing to excitation of high-order axial modes is demonstrated.
      PubDate: 2021-04-01
       
  • Uncooled Antenna-Coupled Microbolometer for Detection of Terahertz
           Radiation
    • Abstract: In this contribution, we describe the design, technology, and physical parameters of antenna-coupled microbolometer, used for broadband detection of terahertz electromagnetic spectrum. This microbolometer features an application of La0.67Sr0.33MnO3 layer grown on multilayered material stack ensuring lattice matching of the sensing LSMO layer to silicon. By virtue of bulk micromachining of silicon-on-insulator substrates, the sensing structure is built on thin suspended membrane to provide weak thermal link, increasing thermal response, thus sensitivity. Additionally, it helps suppressing excitation of in-plane guided surface modes that will otherwise deteriorate the antenna radiation diagram and affect the spectral responsivity of the sensor. Finally, the operation of sensor is demonstrated using a molecular laser setup at 762 GHz (and also 1.4 THz) emission line. The parameters of the said microbolometers are analyzed in terms of response and time constant. Optimal working temperature of the detectors is about 65 °C.
      PubDate: 2021-03-10
      DOI: 10.1007/s10762-021-00781-y
       
  • Design Procedure for a Broadband TE 11 /HE 11 Mode Converter for
           High-Power Radar Applications
    • Abstract: The HE11 hybrid mode, propagating in an overmoded corrugated circular waveguide, is widely used for low loss transmission of high-power microwaves. Due to the inherent broadband frequency behaviour, this will be also essential for future broadband high-power radar applications, like space debris observation in low earth orbit (LEO). A promising amplifier concept for such radar sensors is a helical gyro-TWT. However, since the HE11 hybrid mode is not suitable for electron-beam-wave interaction in this kind of vacuum electron device, an additional mode converter is required. The present paper addresses the design procedure of a broadband high-power mode converter, designed for a helical gyro-TWT intended for future broadband high-power radar applications in the W-band. The interaction mode of the helical gyro-TWT under consideration can be easily transferred to the circular waveguide TE11 mode. Therefore, a TE11 ↦ HE11 mode converter is addressed here. The design procedure is based on a scattering matrix formalism and leads to a high HE11 mode content of ≥98.6% within the considered frequency range from 92 GHz to 100 GHz. Inside this frequency band, the mode content is even better and reaches ≈ 99.7% at ≈95 GHz. This allows broadband frequency operation of a helical gyro-TWT and is suitable for broadband high-power radar applications.
      PubDate: 2021-03-09
      DOI: 10.1007/s10762-021-00773-y
       
  • Electromagnetic-Induced Transparency Resonance with Ultrahigh Figure of
           Merit Using Terahertz Metasurfaces
    • Abstract: In this paper, a terahertz metasurface supercell consists of two ring resonators with slightly different radii is proposed. Electromagnetic-induced transparency (EIT)–like resonance is excited with an ultrahigh figure of merit. Furthermore, the impact of the coupling between the two rings is investigated on the transmission amplitude response, the quality factor, and the EIT peak amplitude by varying the radius of the top resonator. The achieved figure of merit of the EIT peak reaches 88.65 and almost 20,000 when gold and a perfect electric conductor are used for the metallic layer, respectively. The simplicity and unique properties of the proposed design could render it to be a desirable candidate for filtering, slow light applications, and sensing.
      PubDate: 2021-02-26
      DOI: 10.1007/s10762-021-00775-w
       
  • Sensitive Near-Field Slit Probe with High  Spatial Resolution for Passive
           Millimeter-Wave Microscopy
    • Abstract: A novel type of near-field slit probe with high sensitivity and high spatial resolution is proposed. We tested the implementation of this in passive millimeter-wave microscopy at frequencies around 50 GHz. The slit probe comprises a standard rectangular waveguide incorporating a triple-screw tuner penetrating into the waveguide, followed by a four-section quarter-wave transformer, and a metal-coated silicon chip with a micro-slit aperture fabricated at the probe tip using a bulk micromachining technique. The probe allows the transmission of the thermal radiation collected at the probe aperture to the radiometric receiver used in passive millimeter-wave microscopy to be maximized, resulting in highly sensitive measurements. The system noise temperature of the radiometric receiver including the slit probe used in the passive measurements was found to be 1800 K, meaning that a temperature resolution of 0.18 K with the integration time set to 1 s was achieved. This system noise temperature is four times better than that when a tapered slit probe with no tuning circuit was used. Image acquisition with a spatial resolution of better than 100 μm was demonstrated over the temperature range from 210 to 310 K.
      PubDate: 2021-02-26
      DOI: 10.1007/s10762-021-00777-8
       
  • Contribution of Microwave to the Formation of Octacalcium Phosphate
           Intercalating Succinate Ions
    • Abstract: We applied microwave light with frequencies 10, 212, and 419 GHz to form octacalcium phosphate (OCP) intercalated with succinate ions (SCI). The composition of starting reagents (i.e., α-type tricalcium phosphate (TCP), calcium hydrogenphosphate dihydrate (DCPD), and SCI in pure water) did not enable us to form OCP intercalated with SCI in a thermostatic water bath. Although microwave irradiation typically acts as a heat source in water, it has brought a valuable contribution to OPC formation. This paper reports the following interesting result; microwave irradiation of power less than 0.1 W enabled us to synthesize OCP intercalated with SCI which was not possible to form with power values exceeding 0.1 W.
      PubDate: 2021-02-17
      DOI: 10.1007/s10762-021-00774-x
       
  • A 61.2-dBΩ, 100 Gb/s Ultra-Low Noise Graphene TIA over D-Band Performance
           for 5G Optical Front-End Receiver
    • Abstract: This work reports in first time a 100-Gb/s, ultra-low noise, variable gain multi-stagger tuned transimpedance amplifier (VGMST-TIA) over the D-band performance. The whole work is binding into two phases. The first phase involves the modeling and characterization of graphene field-effect transistor (GFET) with an optimized transition frequency of operation. While in the second phase, a TIA design employs a T-shaped symmetrical L-R network at the input, which mitigates the effect of photo diode capacitance and achieves a D-band of operation. The proposed work uses a VGMST to establish TIA, which realizes optimum noise performance. The high gain 3-stage VGMST-TIA effectively minimizes the white noise and illustrates a sharp out-of-band roll-off to achieve considerable noise reduction at high frequencies. The active feedback mechanism controls the transimpedance gain by tuning the control voltage which results better group delay. Besides, an L-C circuit is employed at the output to enhance bandwidth. The full TIA is implemented and fabricated using a commercial nano-manufacturing 9-nm graphene film FET on a silicon wafer using 0.065-μm process. The TIA achieves a flat transimpedance gain of 61.2 dBΩ with ± 9 ps group delay variation over the entire bandwidth. The proposed TIA measured an impedance bandwidth of 0.2 THz with ultra-low input-referred noise current density of 2.03 pA/√Hz. The TIA supports a 100-Gb/s data transmission due to large bandwidth; therefore, a bit-error-rate (BER) less than 10−12 is achieved. The chip occupies an area of 0.92 * 1.34 mm2 while consuming power of 21 mW under supply of 1.8 V.
      PubDate: 2021-01-14
      DOI: 10.1007/s10762-021-00771-0
       
 
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