bluuebunny/crossref_metadata_2025_split huggingface dataset:
Extracting optical absorption characteristics from semiconductor nanowire arrays
Authors: Kohandani Reza , Saini Simarjeet S 
Published: May 2022

Abstract
A method based on extraction of the effective absorption coefficient using Beer–Lambert’s law on simulated transmissions is used to understand the optical absorption characteristics of semiconductor nanowire arrays. Three different semiconductor nanowire arrays, viz. silicon (Si), gallium arsenide (GaAs) and amorphous silicon (a-Si), are evaluated using the method. These semiconductors were chosen since two of them have similar real parts of the refractive index in the visible range, while the other two have comparable imaginary parts of the refractive index in the visible range. We examine the roles of the real and imaginary parts of the refractive index in enhancing the absorption characteristics in the nanowire arrays due to the excitation of radial and photonic Bloch modes. We observe that high absorption peaks at modal resonances correspond to the resonance peaks in reflections from the nanowire–air interface. Further, the wavelengths of these two peak resonances are slightly detuned according to the Kramers–Kronig relation for an oscillator system. The study confirms that the resonance wavelengths of radial HE modes are diameter and refractive index dependent. The study extends the understanding to the absorption characteristics due to the excitation of the photonic Bloch modes caused by near-field coupling. Excitation of Bloch modes leads to increased absorption and quality factor as compared to only radial mode excitation. We also conclude that the imaginary part of the refractive index of the semiconductor, influence the diameters at which Bloch modes are excited for a given lattice spacing. We observe that semiconductors with a higher bulk value of absorption coefficient need to be ordered more densely in the nanowire array to be able to excite the photonic crystal modes within the array. Interestingly, we see that for Si, GaAs and a-Si arrays with an equal diameter of 80 nm and lattice spacing of 400 nm, the peak absorption is almost the same, even though GaAs and a-Si are highly absorptive materials compared to Si. Thus, both radial and Bloch mode excitations can be used to design absorption profiles in a semiconductor nanowire array.
Portable, desktop high-field magnet systems using bulk, single-grain RE–Ba–Cu–O high-temperature superconductors
Authors: Tsui Y , Moseley D A , Dennis A R , Shi Y-H , Beck M R , Cientanni V , Cardwell D A , Durrell J H , Ainslie M D 
Published: May 2022

Abstract
Bulk high-temperature superconducting materials can trap magnetic fields up to an order of magnitude larger than conventional permanent magnets. Recent advances in pulsed field magnetization (PFM) techniques now provide a fast and cost-effective method to magnetize bulk superconductors to fields of up to 5 T. We have developed a portable, desktop bulk high-temperature superconducting magnet system by combining advanced PFM techniques with state-of-the-art cryocooler technology and single-grain, RE–Ba–Cu–O [(RE)BCO, where RE is a rare-earth element or yttrium] bulk superconducting materials. The base temperature of the system is 41 K and it takes about 1 h for the system to cool down to 50 K from room temperature. A capacitor bank, combined with easily-interchangeable, solenoid- or split-type copper magnetizing coils and an insulated bipolar gate transistor acting as a high-speed switch, allows magnetic pulses to be generated with different pulse profiles. The system is capable of trapping magnetic fields of up to ∼3 T. In this work, we report the results of the magnetization of a range of single-grain Y–Ba–Cu–O, Eu–Ba–Cu–O and Gd–Ba–Cu–O (GdBCO), bulk superconducting discs using this system. A higher trapped field was recorded using a split coil incorporating iron yokes at temperatures of 65 K and above, whereas at lower temperatures, a higher trapped field was obtained using the solenoid coil. The GdBCO sample achieved the highest trapped field for both single-pulse (SP) and two-stage-multi-pulse (TSMP) methods using the solenoid coil. Maximum trapped fields of 2.26 T at 55 K and 2.85 T at 49 K were recorded at the centre of the top surface of the GdBCO sample for the SP and TSMP methods, respectively. The PFM process is substantially an adiabatic process so, therefore, the thermal contact between the sample and sample holder is of critical importance for cooling the bulk sample during application of the pulse. The design of the sample holder can be modified easily to enhance the thermal stability of the sample in order to achieve a higher trapped field.
Steady states of Λ-type three-level systems excited by quantum light with various photon statistics in lossy cavities
Authors: Rose H , Tikhonova O V , Meier T , Sharapova P R 
Published: May 2022

Abstract
The interaction between quantum light and matter is being intensively studied for systems that are enclosed in high-Q cavities which strongly enhance the light–matter coupling. Cavities with low Q-factors are generally given less attention due to their high losses that quickly destroy quantum systems. However, bad cavities can be utilized for several applications, where lower Q-factors are required, e.g., to increase the spectral width of the cavity mode. In this work, we demonstrate that low-Q cavities can be beneficial for preparing specific electronic steady states when certain quantum states of light are applied. We investigate the interaction between quantum light with various statistics and matter represented by a Λ-type three-level system in lossy cavities, assuming that cavity losses are the dominant loss mechanism. We show that cavity losses lead to non-trivial electronic steady states that can be controlled by the loss rate and the initial statistics of the quantum fields. We discuss the mechanism of the formation of such steady states on the basis of the equations of motion and present both analytical expressions and numerical simulations for such steady states.
Nonequlibrium magnetic features in a mixed spin (2, 5/2) Ising system driven by the external oscillating magnetic field by path probability method
Authors: Gençaslan Mustafa , Keskin Mustafa 
Published: May 2022

Abstract
Utilizing the path probability method, we investigated nonequilibrium magnetic features in a mixed spin (2, 5/2) Ising model Hamiltonian composed of bilinear and crystal-field interactions in the presence of an external oscillating magnetic field. We numerically solved the time dependence of average magnetizations to find the phases in the system. We examined the dynamic magnetizations to obtain dynamic phase transition (DPT) temperatures, the nature of the DPTs, and phases in the system. The dynamic phase diagrams (DPDs) were constructed in reduced temperature and the amplitude of oscillating magnetic field plane for various interaction parameters. We observed that the system gives very rich and interesting topological behaviors of DPDs, such as up to two dynamic tricritical points, six critical end points, a double critical end points, a zero-temperature critical point, one inverse critical end point and a quadruple point depending on interaction parameters. The system also exhibits paramagnetic, six distinct ferrimagnetic and three different nonmagnetic phases as well as up to eleven different mixed or hybrid phases. In addition, the system exhibits the reentrant behavior.
NANOGrav signal and LIGO-Virgo primordial black holes from the Higgs field
Authors: Yi Zhu , Zhu Zong-Hong 
Published: May 2022

Abstract
We show that the NANOGrav signal can come from the Higgs
field with a noncanonical kinetic term in terms of the scalar
induced gravitational waves. The scalar induced gravitational waves
generated in our model are also detectable by space-based
gravitational wave observatories. Primordial black holes with
stellar masses that can explain LIGO-Virgo events are also produced.
Therefore, the NANOGrav signal and the BHs in LIGO-Virgo events may
both originate from the Higgs field.
Hybrid fiber laser integrating fast and slow active media for accurate synthesis of high-energy arbitrary optical waveforms by cavity dumping
Authors: Nyushkov Boris , Ivanenko Aleksey , Smirnov Sergey 
Published: May 2022

Abstract
We demonstrate the possibility of the accurate direct laser synthesis of high-energy arbitrary optical waveforms by the programmable driving of partial cavity dumping in a specific continuous-wave fiber laser. To this effect we have developed an original hybrid laser configuration which integrates two different active media. The first medium, a semiconductor optical amplifier (SOA), acts as a saturated lumped preamplifier. It features a relatively fast (sub-nanosecond) gain recovery, and thus effectively suppresses the intracavity power fluctuations induced by cavity dumping. The second active medium, an erbium-doped fiber amplifier (EDFA), acts mainly as a booster amplifier. This distributed inertial amplifying medium effectively accumulates pump energy, thereby providing an enhancement of output energy upon cavity dumping. Our simple proof-of-concept laser setup has allowed the synthesis of nanosecond arbitrary optical waveforms with an energy up to 40 nJ and arbitrarily tunable repetition rate. The proposed combination of a slow (EDFA) and fast (SOA) amplifying stages prevents the laser from strong relaxation oscillations and power flux fluctuations which essentially restrict cavity dumping in conventional rare-earth-doped fiber lasers. The applied two-stage intracavity spectral filtering ensures spectral purity of a rather narrowband (⩽0.1 nm) laser output. For the purpose considered, the integrated SOA-EDFA laser configuration is preferable to a conventional architecture ‘master oscillator—power amplifier’ whose nonlinear gain can obstruct the accurate synthesis of high-energy optical waveforms.
Agile femtosecond synchronizable laser source from a gated CW laser
Authors: Renard William , Chan Clément , Dubrouil Antoine , Lhermite Jérôme , Santarelli Giorgio , Royon Romain 
Published: May 2022

Abstract
In this letter we demonstrate agile femtosecond pulse generation with a widely tunable repetition rate (10–100 MHz) from a continuous wave laser diode optically gated by a Mach–Zehnder electro-optic intensity modulator. Initial sub-50 ps pulses are strongly spectral broadened (>5 nm) by self-phase modulation in a polarization maintaining single-mode fiber. A tunable optical pulse train with pulse durations of a few hundred femtoseconds is obtained using a simple fixed grating compressor, thanks to spectral broadening saturation phenomena. The source is easily synchronized with low timing jitter using an external clock signal.
Two-dimensional Modeling of the Tearing-mode-governed Magnetic Reconnection in the Large-scale Current Sheet above the Two-ribbon Flare
Authors: Zhang Yining , Ye Jing , Mei Zhixing , Li Yan , Lin Jun 
Published: May 2022

Abstract
We attempt to model magnetic reconnection during the two-ribbon flare in a gravitationally stratified solar atmosphere with the Lundquist number of S = 106 using 2D simulations. We found that the tearing mode instability leads to inhomogeneous turbulence inside the reconnecting current sheet (CS) and invokes the fast phase of reconnection. Fast reconnection brings an extra dissipation of magnetic field which enhances the reconnection rate in an apparent way. The energy spectrum in the CS shows a power law pattern and the dynamics of plasmoids govern the associated spectral index. We noticed that the energy dissipation occurs at a scale l
ko of 100–200 km, and the associated CS thickness ranges from 1500 to 2500 km, which follows the Taylor scale l

T
= l
ko
S
1/6. The termination shock (TS) appears in the turbulent region above flare loops, which is an important contributor to heating flare loops. Substantial magnetic energy is converted into both kinetic and thermal energies via TS, and the cumulative heating rate is greater than the rate of the kinetic energy transfer. In addition, the turbulence is somehow amplified by TS, in which the amplitude is related to the local geometry of the TS.
How to successfully classify EEG in motor imagery BCI: a metrological analysis of the state of the art
Authors: Arpaia Pasquale , Esposito Antonio , Natalizio Angela , Parvis Marco 
Published: May 2022

Abstract

Objective. Processing strategies are analyzed with respect to the classification of electroencephalographic signals related to brain-computer interfaces (BCIs) based on motor imagery (MI). A review of literature is carried out to understand the achievements in MI classification, the most promising trends, and the challenges in replicating these results. Main focus is placed on performance by means of a rigorous metrological analysis carried out in compliance with the international vocabulary of metrology. Hence, classification accuracy and its uncertainty are considered, as well as repeatability and reproducibility. Approach. The paper works included in the review concern the classification of electroencephalographic signals in motor-imagery-based BCIs. Article search was carried out in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses standard and 89 studies were included. Main results. Statistically-based analyses show that brain-inspired approaches are increasingly proposed, and that these are particularly successful in discriminating against multiple classes. Notably, many proposals involve convolutional neural networks. Instead, classical machine learning approaches are still effective for binary classifications. Many proposals combine common spatial pattern, least absolute shrinkage and selection operator, and support vector machines. Regarding reported classification accuracies, performance above the upper quartile is in the 85%–100% range for the binary case and in the 83%–93% range for multi-class one. Associated uncertainties are up to 6% while repeatability for a predetermined dataset is up to 8%. Reproducibility assessment was instead prevented by lack of standardization in experiments. Significance. By relying on the analyzed studies, the reader is guided towards the development of a successful processing strategy as a crucial part of a BCI. Moreover, it is suggested that future studies should extend these approaches on data from more subjects and with custom experiments, even by investigating online operation. This would also enable the quantification of the results reproducibility.
Pareto-optimal trade-off for phenotypic switching of populations in a stochastic environment
Authors: Dinis L , Unterberger J , Lacoste D 
Published: May 2022

AbstractFinding optimal survival strategies of living systems embedded in fluctuating environments generally involves a balance between phenotypic diversification and sensing. If we neglect sensing mechanisms, it is known that slow, resp. fast, environmental transitions favor a regime of heterogeneous, resp. homogeneous, phenotypic response. We focus here on the simplest non-trivial case, i.e. two randomly switching phenotypes subjected to two stochastically switching environments. The optimal asymptotic (long term) growth rate of this model was studied elsewhere; we further expand these results by discussing finite time growth rate fluctuations. An exact asymptotic expression for the variance, alongside with approximations valid in different regimes, are tested numerically in details. Our simulations of the dynamics suggest a close connection between this variance and the extinction probability, understood as risk for the population. Motivated by an earlier trade-off analysis between average capital growth rate and risk in Kelly’s gambling model, we study the trade-off between the average growth rate and the variance in the present model. Despite considerable differences between the two models, we find similar optimal trade-off curves (Pareto fronts), suggesting that our conclusions are robust, and broadly applicable in various fields ranging from biology/ecology to economics.
Spectral studies of inductively coupled plasma characteristics of low pressure discharges for two configurations of vacuum chambers
Authors: Shemakhin Yu A , Samsonova E S , Voznesenskiy E F , Zhelonkin Y O , Yu Shemakhin E , Fadeev S A , Terentev T N , Maksimov R A , Tyurin V A 
Published: May 2022

Abstract
In this work, we carried out comparative studies of the electron temperature in Inductive coupled radio frequency (ICRF) for two configurations of discharge chambers – cylindrical and flat, considered as prototypes of ICP technological modules of the installation in the argon pressure range from 10 to 50 Pa. The study used optical emission spectrometry of the plasma. As a result, the dependences of the electron temperature on pressure and power were obtained. It is shown that with increasing pressure, different dynamics of the electron temperature is observed for the cylindrical and plane geometry of the inductor.
Nanodiamonds from Fuel
Authors: Timerkaev B A , Shakirov R B , Zalyalieva A A , Gevorgyan R K , Shaikhattarov R R 
Published: May 2022

Abstract
In this paper, we present the results of the synthesis of nanodiamonds from carbon nanostructures and diamondoids in an arc discharge. The electrodes used in the experiments were a molybdenum cathode and a copper anode coated with carbon nanostructures such as carbon nanotubes and diamondoids. The formation of carbon nanostructures on the surface of a copper electrode was carried out in an electric arc sunk into fuel oil. At the next stage, these carbon nanostructures served as a source of atomic carbon and diamondoids from the surface of the arc discharge anode. The use of fuel oil as a feedstock for creating the electrode material probably led to the retention of diamondoids contained in fuel oil during two vaporizations. It was found that, in addition to carbon nanotubes, nanodiamonds also formed on the cathode surface.
The Effect of Jet Electric Discharge on the Strength Characteristics of the Surface
Authors: Akhatov M F , Kayumov R R , Mardanov R R , Loginova I M 
Published: May 2022

Abstract
In this paper, the results of measuring the density of the skin of metallic tissues using an installation for assessing the strength of damaged layers (sclerometer) MV-11m, a study of the treatment of tissues with an electrolytic discharge, are revealed.
Hysteresis Phenomena and the Effect of Reorientation in a Polymer-Liquid Crystal System Under the Influence of Laser Radiation and Uniaxial Deformation
Authors: Makhsudov B I , Fayzulloev I K , Egamov M K 
Published: May 2022

Abstract
The orientational structure in a polymer-liquid crystal thin film induced by uniaxial mechanical deformation has been studied. It is shown that the dependence of the deflection angle of the director of a nematic liquid crystal on the direction of the tensile force has a hysteresis region in which the orientation structure spontaneously changes from a state with positive torsion of the director to a state with negative torsion. It is established that the effect of modification of the hysteresis loop leads to an expansion of the hysteresis region and a decrease in the field at which orientation bistability appears.
Application of the Harrington function in substantiating the choice of the best equipment for plasma processing of materials
Authors: Tazmeev B K , Tsybulevsky V V , Tazmeeva R N , Tazmeev G K 
Published: May 2022

Abstract
The possibility of using the Harrington desirability function in choosing the most suitable equipment for plasma processing of materials is confirmed. The search for the optimal variant was carried out by calculating the maximum value of the generalized index of desirability. Four types of equipment for plasma cutting of metal are considered. A comparative analysis was carried out on the following indicators: the cost of equipment and technological cutting speeds for low carbon steel, stainless steel, and aluminum. An example of choosing the best equipment from an alternative series is considered. A system of four scales of partial evaluation indicators was used. Graphical and analytical evaluation methods are presented. The value of the generalized desirability index equal to 0.65 corresponds to the optimal variant of equipment for plasma cutting of metal.
Creation of plasma flow from a liquid electrolyte cathode with an arbitrary orientation in space
Authors: Tazmeev G K , Tazmeev K K , Tazmeev B K 
Published: May 2022

Abstract
The gas discharge between a metal electrode and a liquid electrolyte supplied through a porous refractory material has been experimentally studied. The studies were carried out in the current range of 5–15 A. Aqueous solutions of sodium chloride were used as a liquid electrolyte. The specific electrical conductivity of the solutions was in the range of 6–18 mS/cm. The conditions necessary for the formation of a plasma flow are revealed. Plasma flows oriented in different directions in space have been created. The energy and spectral properties of the gas discharge are investigated.
INVESTIGATION OF VOLT-FARAD CHARACTERISTICS OF THIN MULTIFERRROIC FILMS
Authors: Saidzoda Q B , Semenov A A , Safarov M M 
Published: May 2022

Abstract
In this work, the influence of the concentration of manganese ions in BST films on the capacitance-voltage characteristics (CV characteristics, I–V characteristics, tgδ) of the Cu-Cr/BST/α-Al2O3 and Cu-Cr/BST/GGG structures was studied. To measure the electrophysical characteristics, multiferroic thin-film the samples were made in the form of planar capacitors. Measurements of the electrical properties of the formed planar structures were carried out at a frequency of 1 MHz.
Features of a burning electric arc superimposed on gas discharge with liquid electrolyte cathode
Authors: Tazmeev K K , Tazmeev A K 
Published: May 2022

Abstract
The conditions for burning an electric arc in a discharge plasma with a solution cathode have been studied. Both discharges were connected to the same metal anode. The electric arc burned in the current range of 5–10 A. The discharge current with a solution cathode varied within 8-15 A. In the experiments, aqueous solutions of common salt were used. The specific electrical conductivity of the solutions was 10–15 mS/cm. Spectral investigations of arc plasma radiation and discharge with a solution cathode have been carried out. Calculations of the parameters of the electron gas in the plasma column have been performed.
Studies of a monatomic Lennard-Jones system at slow cooling by molecular dynamics simulations and regression analysis
Authors: Farkhutdinov A R 
Published: May 2022

AbstractThe procedure of radial distribution function calculation at low cooling rates without a substantial increase in the computational cost is proposed in this paper. Results of its application to monatomic Lennard-Jones system at cooling rates γ =4×10-4...2×10-2ε/kBτ, density ρ ≈0.75σ-3and temperature rangeT= 0.3. 1.0ε/kBτusing various regression models are given. It is shown that k-nearest neighbors regression yields the minimum deviation from the results of molecular dynamics simulations in comparison with other models.
A STABLE NUMERICAL ALGORITHM FOR INVESTIGATING THE PROPERTIES OF TWO-DIMENSIONAL LASER WAVEGUIDES IN MULTILAYER QUANTUM-DIMENSIONAL SEMICONDUCTOR HETEROSTRUCTURES
Authors: Sh. Juraev H. , Mamatkulova N.O. , Makhsudov B.I. 
Published: May 2022

Abstract
The transfer of heat through nanostructures differs significantly from the corresponding processes inside macroscopic bodies. Various research methods, both theoretical and experimental, are applied to such objects. This approach to nanostructures gives great advantages. The hyperbolic equations we have obtained describe the wave process of the thermal signal flow and the properties of heat transfer in nanostructures across a thin layer, in which the simplest task is to determine the thermal conductivity.