bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of surface impurities on photoelectric currents driven by intense soft x rays
Authors: Roberds N. A.
Published: March 2022

In an x-ray driven cavity experiment, an intense flux of soft x rays on the emitting surface produces significant emission of photoelectrons having several kiloelectronvolts of kinetic energy. At the same time, rapid heating of the emitting surface occurs, resulting in the release of adsorbed surface impurities and subsequent formation of an impurity plasma. This numerical study explores a simple model for the photoelectric currents and the impurity plasma. Attention is given to the effect of varying the composition of the impurity plasma. The presence of protons or hydrogen molecular ions leads to a substantially enhanced cavity current, while heavier plasma ions are seen to have a limited effect on the cavity current due to their lower mobility. Additionally, it is demonstrated that an additional peak in the current waveform can appear due to the impurity plasma. A correlation between the impurity plasma composition and the timing of this peak is elucidated.
Data-driven technique for disruption prediction in GOLEM tokamak using stacked ensembles with active learning
Authors: Chandrasekaran Jayakumar , Jayaraman Sangeetha
Published: March 2022

In a tokamak, disruption is defined as losing control over a confined plasma resulting in sudden extinction of the plasma current. Machine learning offers potent solutions to classify plasma discharges into disruptive and non-disruptive classes. Evolving experimental programs reduce the performance of machine learning models, and also, the need for labeling the huge volume of data incurs more labor cost and time. This paper proposes a data-driven based machine learning technique that employs an active learning approach for labeling and classification of plasma discharges. The designed model uses 117 normally terminated shots and 70 disruptive shots with 14 labeled diagnostic signals. The stacking classifier is built over three base learners: logistic regression, reduced error pruning tree, and categorial boost algorithm, and the logistic regression technique is used at the meta-learner. An active learning approach is proposed for labeling the unlabeled dataset using a modified uncertainty sampling technique with minimal queries. The proposed model queries the unlabeled data to an oracle based on a selection strategy with uncertainty sampling using entropy metrics. The new labeled data and the class probabilities of the base classifiers are channeled to the final predictor for classifying the plasma discharge. The proposed model achieves an accuracy of 98.75% in classifying the disruptive vs non-disruptive discharges, with a minimally trained dataset, and also, it is free from aging of predictors.
Fractional operators and multi-integral representations for associated Legendre functions
Authors: Durand Loyal
Published: March 2022

In a recent paper, Cohl and Costas-Santos derived a number of interesting multi-derivative and multi-integral relations for the associated Legendre and Ferrers functions in which the orders of those functions are changed in integral steps. These are of potential use in a number of physical problems. We show here how their results can be derived simply from more general relations involving non-integer changes in the order obtained using the fractional group operator methods developed earlier for SO(2,1), E(2,1) and its conformal extension, and SO(3). We also present general integral relations for fractional changes of the degrees of the functions and related multi-derivative and multi-integral representations.
Spectral preprocessing to improve accuracy of quantitative detection of elemental Cr in austenitic stainless steel by laser-induced breakdown spectroscopy
Authors: Yang Lei , Zhang Yanhui , Liu Jiaming , Zhang Zi , Xu Mengjie , Ji Feng , Chen Jingjing , Zhang Tengda , Lu Rongsheng
Published: March 2022

The production and consumption of austenitic stainless steel account for about 70% of stainless steel worldwide. The content of chromium (Cr) must be accurately detected and controlled to form a stable austenite structure and obtain strong properties in production. Laser-induced breakdown spectroscopy (LIBS) can be used to detect the Cr content of austenitic stainless steel in a complex production process. However, LIBS signals may be weak and unstable because the experimental signals are seriously affected by noise, self-absorption, the matrix effect, and the instability of the shot-to-shot signal, rendering the quantitative detection results inaccurate and unstable. The spectral-preprocessing methods of baseline correction and denoising can improve the accuracy of quantitative detection of LIBS. An improved segmented Hermite cubic-interpolation method is proposed herein to correct the baseline offset and produce baseline signals that are smooth and convergent (to overcome the Runge phenomenon). Empirical mode decomposition (EMD) based on the wavelet method is proposed to remove LIBS noise; this is done by exploiting the adaptivity of EMD to refine the wavelet-scaling coefficients. Compared with other denoising methods, the proposed method has good denoising evaluation indices and stability and, thus, effectively removes the noise. To verify detection accuracy, the internal standard quantitative method is used to detect the Cr content, and a cyclic-inversion prediction method is designed to verify detection stability. The results show that the correlation coefficient of the calibration curve is improved, the root-mean-square error is reduced, and the average relative error of the predicted Cr content decreases from 10.46% to 3.858%.
Nonlinear excitation of geodesic acoustic mode by drift waves in anisotropic tokamak plasmas with toroidal rotation
Authors: Huang Handi , Ren Haijun , Ming Zhengyang , Zhang Debing
Published: March 2022

Nonlinear excitation of geodesic acoustic mode (GAM) by ions drift waves is investigated in anisotropic toroidally rotating tokamak plasmas by using an ideal magnetohydrodynamic model and standard double adiabatic equations. It is found that the radial wave number kx of the effectively excited GAM and the GAM frequency increase with the ratio of the perpendicular pressure to the parallel pressure χ as well as the toroidal rotation Mach number. The equilibrium anisotropy and the ratio of the radial scale length of the equilibrium density to the tokamak major radius are shown to play a significant role in the growth rate and frequency shift of GAM. The growth rate increases with the normalized GAM frequency first and then decreases to zero as the GAM frequency increases. When the GAM frequency increases again, the growth rate continues to increase but with a relatively smaller magnitude.
High power vacuum ultraviolet source based on gasdynamic ECR plasma
Authors: Lapin R. L. , Skalyga V. A. , Golubev S. V. , Izotov I. V. , Razin S. V. , Tarvainen O.
Published: March 2022

We report experimental results of vacuum ultraviolet (VUV) emission from the plasma of an electron cyclotron resonance (ECR) discharge in hydrogen, sustained by millimeter-wavelength radiation of a gyrotron. The considered discharge is characterized with the high plasma density (1013 cm−3 order of magnitude) and, at the same time, the high electron average energy (10–300 eV), which makes it possible to significantly increase the efficiency of VUV re-emission of the energy deposited into the plasma by the microwave radiation. Experiments were performed with the plasma confined in a simple mirror trap and heated by pulsed gyrotron radiation of 37.5 GHz/100 kW under the ECR condition. The measured volumetric VUV emission power of Lyman-alpha line (122 10 nm) overlapping with the Werner band, Lyman band (160 10 nm), and molecular continuum (180 20 nm) reached 45, 25, and 55 W/cm3, respectively. The total absolute radiation power in these three ranges integrated over the plasma volume is estimated to be 22 kW, i.e., 22% of the incident microwave power, which matches theoretical predictions. The development of effective technological VUV sources of a kilowatt power level is expected to be the next step following the optimization of the conditions of the ECR hydrogen discharge sustained by powerful gyrotron radiation.
Digital micro-photogrammetry in analysis and modeling habit and sectoral structure of real high-pressure high-temperature single-crystal diamonds
Authors: Lytvyn Petro M. , Strelchuk Viktor V. , Nikolenko Andrii S. , Danylenko Ihor M. , Ivakhnenko Serii O. , Kovalenko Tetiana V. , Gontar Oleksandr G. , Malyuta Serhii V.
Published: March 2022

We demonstrate the potential of using digital stereo micro-photogrammetry for the analysis and modeling of the habit and sectoral structure of real high-pressure high-temperature single-crystal diamonds. A prototype scanning system with a resolution of 5 μm has been implemented based on a digital single-lens reflex camera, making it possible to create highly accurate reproductions of crystal shapes with a minimum size of 4 mm. This method makes it possible to monitor the effect of actual conditions on the physical processes of crystal growth, which is a useful advance for the development of active device elements based on semiconductor diamonds.
Theoretical simulation of the closed currents near non-uniformly strongly heated surface of tungsten due to thermo-emf
Authors: Popov V. A. , Arakcheev A. S. , Kandaurov I. V. , Kasatov A. A. , Kurkuchekov V. V. , Trunev Yu. A. , Vasilyev A. A. , Vyacheslavov L. N.
Published: March 2022

A problem of surface melting under the impact of plasmas is one of the most important in the development of future magnetic confinement fusion reactors. The expected high heat loads can lead to melting of tungsten chosen as the material of a divertor and the first wall of ITER. The tungsten melt can move under the action of forces and quickly deform a surface. This article shows that at high temperatures, a tungsten vapor can be considered as a conductive material with conductivity high enough to be taken into account during simulation of current through a sample. We describe the mechanism of current generation by the thermo-emf due to non-uniform heating of the vapor/condensed substance interface without external sources of charges. Even without direct contact with the external plasma, the density of this current is high enough to cause noticeable movement of the melt in an external magnetic field. Simulation shows that the melt moving observed at BETA may be caused not by a current of an electron beam but by non-uniformity of heating and can be reproduced by any other similar heat source in the external magnetic field.
Work function of van der Waals topological semimetals: Experiment and theory
Authors: Biswal Bubunu , Mishra Shashi B. , Yadav Renu , Poudyal Saroj , Rajarapu Ramesh , Barman Prahalad Kanti , Pandurang Khade Ramdas , Mandal Manasi , Singh Ravi Prakash , Nanda B. R. K. , Misra Abhishek
Published: March 2022

The work function (WF) of a material governs the back and forth movement of the charge carriers across the hetero-interface of two materials. Therefore, for optimum device performance, precise knowledge of the WF is prerequisite while employing any new material in electronic devices. In this work, using metal oxide semiconductor capacitors, we experimentally determine the WF of layered van der Waals topological semimetals (TSMs) 1T′-MoTe2, 1T-PtSe2, and Td-WTe2 as 4.87, 5.05, and 4.82 eV, respectively. The experimentally obtained results are corroborated with density functional theory calculations. Furthermore, by analyzing the vertical current transport across the metal oxide semiconductor stack using Fowler–Nordheim tunneling formalism, the barrier height between the TSMs and the gate insulator (SiO2) is experimentally calculated. The obtained barrier heights are also following the same trend as that of WF for three TSMs. These TSMs host unique topological nontrivial phases potentially useful for the development of emerging quantum technologies, and therefore, the findings of this study are significant for designing the future quantum devices.
On the p-Laplacian Kirchhoff–Schrödinger equation with potentials vanishing or unbounded at infinity in R3
Authors: Shi Zhiheng , Liang Sihua
Published: March 2022

This paper mainly deals with a class of the p-Laplacian Kirchhoff–Schrödinger equation with potentials vanishing or unbounded at infinity. We prove the existence and concentration behavior of positive solutions for the problem by the variational methods and concentration-compactness principle. The main feature of this paper is that the potential decays to zero at infinity like |x|−α with 0 < α ≤ 2, and the function K(x) is allowed to be unbounded, which is different from some previous papers.
On validity of quasi-linear theory for non-resonant pitch-angle diffusion by finite amplitude parallel propagating Alfvén waves
Authors: Nariyuki Y. , Sasaki M. , Hada T.
Published: March 2022

Pitch-angle diffusion of charged particles via non-resonant interaction with low-frequency magnetohydrodynamic waves is discussed. Even in the presence of finite amplitude waves, a quasi-linear theory in which the normalization using wave energy is carried out agrees well with numerical results of test particle simulations. The quasi-linear theory for non-resonant diffusion is also in good agreement with the numerical results, even if the spectra of the waves are not broad.
In situ transient Laue x-ray diffraction during high strain-rate tension
Authors: Zhang Dongsheng , Yu Can , Wang Ming , Chen Sen , Huang Chengpeng , Sun Darui , Yue Shuaipeng , Tao Ye , Zhang Bingbing
Published: March 2022

In situ transient synchrotron Laue x-ray diffraction based on high-energy and broadband x rays under high strain-rate tensile loading was developed at a superconducting wiggler beamline at the Beijing Synchrotron Radiation Facility. A split-Hopkinson tensile bar is utilized to realize this dynamic loading condition, while the transient Laue x-ray diffraction captures the transient internal structure of monocrystalline materials. Plastic deformation of a monocrystalline nickel specimen was investigated to prove the ability of this instrumentation in the characterization of a dynamic response of monocrystalline materials during a high strain-rate impact process with 5 µs time resolution.
A local orientational order parameter for systems of interacting particles
Authors: Çamkıran John , Parsch Fabian , Hibbard Glenn D.
Published: March 2022

Many physical systems are well modeled as collections of interacting particles. Nevertheless, a general approach to quantifying the absolute degree of order immediately surrounding a particle has yet to be described. Motivated thus, we introduce a quantity E that captures the amount of pairwise informational redundancy among the bonds formed by a particle. Particles with larger E have less diversity in bond angles and thus simpler neighborhoods. We show that E possesses a number of intuitive mathematical properties, such as increasing monotonicity in the coordination number of Platonic polyhedral geometries. We demonstrate analytically that E is, in principle, able to distinguish a wide range of structures and conjecture that it is maximized by the icosahedral geometry under the constraint of equal sphere packing. An algorithm for computing E is described and is applied to the structural characterization of crystals and glasses. The findings of this study are generally consistent with existing knowledge on the structure of such systems. We compare E to the Steinhardt order parameter Q6 and polyhedral template matching (PTM). We observe that E has resolution comparable to Q6 and robustness similar to PTM despite being much simpler than the former and far more informative than the latter.
Super modified KP hierarchy in Kac–van de Leur construction
Authors: Chen Huizhan , Cheng Jipeng , Wu Zhiwei
Published: March 2022

In this paper, the modified KP hierarchy in the Kupershmidt–Kiso version is extended to the super case by Kac–van de Leur construction, that is, using highest weight representations of the even part in the tensor product of the infinite-dimensional Lie superalgebra gl∞|∞ with Grassmann algebra G. First, the super modified KP (SmKP) hierarchy is constructed in terms of superfermionic bilinear equations. Then, the superbosonic form of the SmKP hierarchy is given by super boson–fermion correspondence. With the help of super Hirota bilinear operators, the corresponding super Hirota bilinear equations of the SmKP hierarchy are obtained. Next, the Darboux transformations of this new SmKP hierarchy are expressed in the form of free superfermions and various solutions are derived. Finally, the super bilinear equations in the form of super wave functions are also constructed from the superbosonic ones, which is hoped to be helpful to obtain the corresponding Lax structures.
Control strategies for tip leakage vortex using inclined squealer rim in axial turbines
Authors: Wang Yufan , Zhang Weihao , Huang Dongming , Jiang Shoumin , Chen Yun , Ma Guangjian
Published: March 2022

In a typical gas turbine, due to its complicated blade geometry, complex vortex structures appear and cause significant aerodynamic loss. Vortex systems dominated by a tip leakage vortex near the tip region are the primary source of this loss. In this paper, to improve the aerodynamic performance of the turbine, two novel control strategies for tip leakage vortex and the tip leakage flow of the cavity tip are proposed, and their coupling control effects are numerically investigated. The first control strategy is intended to control the loss caused by the breakdown of tip leakage vortex. By inclining the external wall of the suction side rim toward the passage, the emergence of a trailing edge pressure spike is delayed. This significantly reduces the adverse pressure gradient, suppressing the breakdown of tip leakage vortex and reducing tip leakage loss. The second control strategy controls tip leakage flow using the inclined inner wall of the suction side rim, which enhances the separation bubble on the top of the rim of the suction side and reduces the leakage rate by 7.7%. In this way, the formation and development of tip leakage vortex are indirectly manipulated, inhibiting the tip leakage loss. The coupling of the two strategies reduces the blocking effect on tip leakage flow slightly compared to the second strategy. However, the stage efficiency of the turbine is still improved by 0.24% because of the effective suppression of tip leakage vortex breakdown.
Aerodynamic performance of a self-propelled airfoil with a non-zero angle of attack
Authors: Wang Dou , Lin Qinfeng , Zhou Chao , Wu Jianghao
Published: March 2022

In the natural world, numerous flying creatures generate both thrust and lift by flapping their wings. Aerodynamic mechanisms of forward flight with flapping wings have received much attention from researchers. However, the majority of previous studies have simplified the forward-flight motion of flapping wings to be uniform, and there has been no detailed evaluation of the validity of this simplification. Motivated by this, aerodynamic characteristics of a self-propelled flapping wing with a non-zero angle of attack were investigated. The results showed that the asymmetric leading-edge vortex produced in the wing's upstroke and downstroke leads to transient thrust, driving the self-propelled wing to move with variable forward velocities. Compared to the uniform forward-flight cases, significant losses in lift and severe changes in the flow field were observed in self-propelled flapping wings. In addition, the changes in the aerodynamic performance—including the forward propulsion speed, lift, and power efficiency—of the self-propelled flapping wing with changes in various dimensionless parameters were also investigated. The heaving amplitude was shown to have significant effects on lift and propulsion speed of the self-propelled flapping wing, while the effects of ratio between the airfoil density and fluid density as well as the Reynolds number, were relatively small. In most conditions, when the Strouhal number was in the range 0.2–0.4, the self-propelled flapping wing performed well in terms of both lift generation and propulsive efficiency. These research results suggest that it is necessary to consider the fluctuating forward speed in aerodynamic modeling of propulsive flapping wings.
Influence of aspect ratio on the wake dynamics of a pitching wing
Authors: Vineeth V. K. , Patel Devendra Kumar
Published: March 2022

The three-dimensional flow around a custom wing performing pitching oscillation is analyzed numerically using large-eddy simulation with the wall adapting local eddy-viscosity subgrid-scale model. The wake characteristics behind the pitching wing with three different aspect ratios, AR=2/3, 1, 4/3, is investigated in an upstream flow with Reynolds number, Re=2640. The Q−function is employed to identify the swirling structures in the flow field, and four primary vortices, namely, primary leading edge vortex (PLEV), secondary leading edge vortex, wing tip vortices, and trailing edge vortex, are identified. The evolution of vortices over the wing surface is presented in detail, and the arrangement of vortex rings in the wake is compared for three different aspect ratios. The PLEV develops into an arch vortex using the self-induction phenomenon, and the interlinking between the subsequent vortex rings depends on the arch vortex leaving the trailing edge. The force coefficient computed over the wing shows a positive thrust for AR=4/3. The mean velocity field contours indicate a spanwise loading on the wing, which is unaccountable in two-dimensional studies. The Reynolds stresses generated due to large-scale periodic velocity fluctuations in the wake are presented. The vorticity field in the midplane of the wing appears to be diffusive at higher aspect ratios. The comparison of vorticity from the three-dimensional and two-dimensional models suggests that a two-dimensional model will over predict the vorticity distribution and force coefficients in the wake.
Unveiling the electrical and photo-physical properties of intrinsic n-type 2D WSe2 for high performance field-effect transistors
Authors: Rai Suyash , Singh Vijay K. , Pendurthi Rahul , Nasr Joseph R. , Das Saptarshi , Srivastava Anchal
Published: March 2022

Atomically thin semiconducting 2D transition metal dichalcogenides have garnered remarkable attention from the scientific community due to their prodigious contributions in the field of next-generation electronic and optoelectronic devices. In this continuation, we report a facile synthesis protocol of monolayer WSe2 films via the atmospheric-pressure chemical vapor deposition (APCVD) technique using hydrothermally synthesized hexagonal-phase tungsten oxide (h-WO3) nanorods. The as synthesized WSe2 crystal is a monolayer of ∼0.9 nm thickness as confirmed by atomic force microscopy. The confocal Raman and photoluminescence (PL) mapping suggests that the grown monolayer WSe2 triangles have lattice defects at edge sites, with a slight red-shift of ∼2 nm in PL, a blue-shift of ∼2 cm−1 in Raman peak and reduction in both the intensities. Confocal time-resolved PL mapping at edges reveals a fast-decay component of ∼582 ps and a slow-decay component of ∼2.18 ns that also signifies the presence of lattice defects, which serves as localized-states for photon-generated charge excitons. Furthermore, we have also investigated its electrical property by devising field-effect transistors (FETs). The fabricated WSe2 based FET shows intrinsic n-type behavior. WSe2 FET offers an electron mobility (μ) of ∼13.2 cm2 V−1 s−1, current ON/OFF ratio of ∼107 with a subthreshold slope (SS) of ∼397 mV/decade, which is relatable to the other reported works on WSe2 based FETs. In addition, the device exhibits very high on-current of order of ∼150 μA/μm. These results indicate that h-WO3 nanorod assisted APCVD synthesized WSe2 has prospective of being a competitor for next-generation optoelectronic, and valley-tronic devices.
Contribution of the dipole–dipole interaction to targeting efficiency of magnetite nanoparticles inside the blood vessel: A computational modeling analysis with different magnet geometries
Authors: Mohammadi Simah , Rafii-Tabar Hashem , Sasanpour Pezhman
Published: March 2022

The widespread use of magnetite nanoparticles inside the bloodstream for diagnostic and therapeutic purposes has made the influence of the interaction forces between these nanoparticles an important issue for predicting their behavior for improving the effectiveness of the protocols. Magnets with various geometries have been used in different biomedical applications, such as targeted drug delivery, to guide drugs carrying magnetite nanoparticles to specific areas. In this regard, using computational modeling, we have employed a multiphysics modeling approach using the particle tracing module in the COMSOL software environment to investigate the behavior of magnetite nanoparticles considering not only the magnetophoretic force, but also the dipole–dipole interaction forces between the nanoparticles. The effects of different geometries of magnets on the induced magnetic flux density and the laminar flow velocity inside the bloodstream were studied as well. The results of our study show that each geometry of the magnet induces different magnetic flux density profile and laminar velocity inside the blood flow. The behavior of ferrofluid flow is dependent on the geometry of the magnet and its remanent flux density. By increasing the size of magnetic nanoparticles, the magnetophoretic force enhances the particle velocity in the direction perpendicular to the vessel's walls, which could result in pull out. The results also reveal that the magnetic dipole–dipole interactions between nanoparticles could lead to the induction of higher dipole–dipole interaction forces in regions close to the magnet, especially on the upper wall of the blood vessel.
Comprehensive quantum transport analysis of M-superlattice structures for barrier infrared detectors
Authors: Singh Anuja , Mukherjee Swarnadip , Muralidharan Bhaskaran
Published: March 2022

In pursuit of designing superior type-II superlattice barrier infrared detectors, this study encompasses an exhaustive analysis of utilizing M-structured superlattices for both the absorber and barrier layers through proper band engineering and discusses its potential benefits over other candidates. The electronic band properties of ideally infinite M-structures are calculated using the eight band k.p method that takes into account the effects of both strain and microscopic interface asymmetry to primarily estimate the bandgap and density-of-states effective mass and their variation with respect to the thicknesses of the constituent material layers. In contrast, for practical finite-period structures, the local density-of-states and spectral tunneling transmission and current calculated using the Keldysh non-equilibrium Green’s function approach with the inclusion of non-coherent scattering processes offer deep insights into the qualitative aspects of miniband and localization engineering via structural variation. Our key results demonstrate how to achieve a wide infrared spectral range, reduce tunneling dark currents, induce strong interband wavefunction overlaps at the interfaces for adequate absorption, and excellent band-tunability to facilitate unipolar or bipolar current blocking barriers. This study, therefore, perfectly exemplifies the utilization of 6.1 Å material library to its full potential through the demonstration of band engineering in M-structured superlattices and sets up the right platform to possibly replace other complex superlattice systems for targeted applications.
Buoyancy-driven bubbles in a constricted vertical capillary
Authors: Zhu Zhi-Cheng , Liu Hao-Ran , Ding Hang
Published: March 2022

We numerically study the dynamics of buoyancy-driven bubbles in a constricted vertical capillary in which a throat with an arc shape is present. To investigate at what conditions and how the bubble would be entrapped at the capillary throat, a diffuse-interface immersed-boundary method is used in numerical simulations. Axisymmetric simulations are performed for various bubble and throat sizes, represented by the diameter ratio of the throat to the bubble, η (0.55≤η≤1.35), the Bond number (0.1≤Bo≤15), and the Reynolds number (78.5≤Re≤3367). We find that small bubbles have insignificant deformation and, thus, cannot pass through a throat with η<1, while relatively large bubbles encounter noticeable interface oscillations at their lower part when approaching the throat. In particular, the interface oscillations are composed of a standing wave arising from buoyancy and a capillary wave propagating radially. A phase diagram is presented regarding the eventual bubble morphology: pass-through and entrapment. For the critical diameter ratio ηc at the onset of bubble entrapment, we proposed two scaling laws based on the analysis of the deformability and oscillation of the bubble, i.e., ηc≈1.1 for Bo < 1 and ηc∼Bo−1/4 for Bo > 1. These theoretical predictions are in good agreement with our numerical results.
Electrochemical control and protonation of the strontium iron oxide SrFeOy by using proton-conducting electrolyte
Authors: Isoda Yosuke , Kan Daisuke , Ogura Yumie , Majima Takuya , Tsuchiya Takashi , Shimakawa Yuichi
Published: March 2022

To electrochemically control structural and transport properties of oxygen-deficient perovskite SrFeOy (2.5 ≦ y ≦ 3) (SFO) epitaxial films, we employed electric-field-effect transistor structures in which the proton-conducting solid electrolyte Nafion is used as a gate insulator. When a positive gate voltage (VGS) is applied and protons are injected toward the film channel layer, the SFO films are electrochemically reduced, leading to increases in the channel resistance. On the other hand, when a negative VGS is applied and protons are removed, the SFO films are oxidized, and as a result, the channel resistances decrease. In addition, we found that the electrochemically reduced SFO films accommodate protons, forming the proton-containing oxide HxSrFeO2.5 whose proton concentration is determined by elastic recoil detection analysis to be x ∼ 0.11. Our results indicate the usefulness of the proton-conducting solid electrolyte for electrochemically controlling transition metal oxides and for exploring proton-containing oxides.
Floor motion's influence on wake asymmetry of a notchback bluff body
Authors: He Kan , Minelli Guglielmo , Su Xinchao , Wang Jiabin , Gao Guangjun , Krajnović Siniša
Published: March 2022

Large eddy simulations are used to explore the influence of floor motions on asymmetric flows around a notchback bluff body. The focus of this study is on the aerodynamic forces and the extent of natural wake asymmetry presented under moving and stationary ground conditions. The different ground condition has a notable influence on the aerodynamic force and the surrounding pressure distribution of the body. On the other hand, the wake asymmetry, known to be a sensitive phenomenon, is not evidently affected by the floor motion. However, quantitative analysis of the averaged and the statistic flow still suggests slight differences in the degree of wake asymmetry between the two ground conditions. Modal analysis applying proper orthogonal decomposition confirms that the asymmetric wake dynamics and the wake shedding frequency are not sensitive to the floor motion. The accuracy of the numerical simulation is established by a grid-independence study.
Thermoplastic embossing device to probe rheological changes of supercooled metallic liquids during rapid heating
Authors: Kosiba Konrad
Published: March 2022

The setup and working principle of a device designed for thermoplastic embossing and investigating rheological changes during fast-resistive heating of bulk metallic glasses (BMGs) is presented. The device was developed and custom-built at the Leibniz Institute for Solid State and Materials Research Dresden (Leibniz IFW Dresden) and is integrated into a universal testing machine. By varying the electrical-current pulse signal, the rate at which BMGs are resistively heated is controlled. Next to temperature and electrical resistance, the displacement of the punch, which penetrates the sample during rapid heating, is monitored. Additional pre-heating controlled by thermocouples allows for stable heating conditions to minimize heat extraction from the resistively heated specimen, which could eventually lead to damage of the device. The main focus of this device is to study fundamental phenomena under kinetic constraints evoked by fast heating conditions and to structure the surface of BMGs by thermoplastic embossing. A case study, which is carried out with Zr52.5Cu17.9Ni14.6Al10Ti5 BMG, demonstrates the device’s performance covering heating rate ranges of three magnitudes and the access to rheological changes during the devitrification and subsequent crystallization of the BMG during rapid heating. Furthermore, the present device was successfully used to nanostructure the surface of the BMG at elevated heating rates.
Krypton isotopes tell the early story of Earth’s life-giving elements
Authors: Miller Johanna L.
Published: March 2022

Since its infancy, our planet has accumulated volatiles from more than one source.
Laser pulses probe quantum beats
Authors: Middleton Christine
Published: March 2022

States of nearly equal energy underlie physiological processes, but studying them directly has been a challenge.
A deterministic source of single photons
Authors: Lodahl Peter , Ludwig Arne , Warburton Richard J.
Published: March 2022

New quantum computing applications are now possible because of advances in atomic and solid-state physics.
Behaviour of a large ungulate reflects temporal patterns of predation risk
Authors: Wiskirchen Kevyn H. , Jacobsen Todd C. , Ditchkoff Stephen S. , Demarais Steve , Gitzen Robert A.
Published: March 2022

Context Many prey species exhibit antipredator behaviours when threatened, yet prey response to temporal variation in predation risk is not well-understood, despite being foundational to predator–prey dynamics and an important consideration among game population managers and recreationalists. Aims To examine white-tailed deer (Odocoileus virginianus) behaviour in response to temporal variation in predation risk imposed by recreational hunters and to assess the effect of deer sex and age on antipredator response. Methods Global positioning system (GPS) collars were used to monitor behaviour of female and male deer in response to diel and weekly patterns of recreational hunting in Alabama, USA. Key results Deer behaviour on weekends (i.e. Friday–Sunday), corresponding to periods of elevated risk, was similar to behaviour on weekdays (i.e. Monday–Thursday). However, when behaviour was examined by individual day of the week, movement rate decreased by 17%, net displacement decreased by 31%, and the probability of activity decreased by 24% during daylight hours on Sundays compared with Fridays. Behavioural changes among days were not detected at night. Daytime behavioural shifts persisted until Wednesdays, despite lower weekday hunting activity. Behavioural variation by deer sex and age was also observed. Conclusions Deer perceive temporal variation in predation risk and modify their behaviour to reduce the likelihood of predation. Variation in response across sex and age classes may be driven by previous experience with hunters and/or survival- and fitness-related trade-offs that affect prey decisions at the individual level. Antipredator response was not initially detectable when examined at a broad temporal scale (i.e. weekend vs weekday); however, a behavioural response was shown with a finer-scale analysis (i.e. individual day of the week), which more closely reflected the pattern of risk fluctuation. Implications Our findings demonstrated the acute awareness of a large ungulate to temporal changes in predation risk and provided insight into ways in which these prey behaviourally respond to reduce the likelihood of predatory encounters. Future studies should consider the temporal scale of risk fluctuation when examining antipredator response to avoid false conclusions. Ungulate hunters and managers can use this information to more efficiently achieve their goals.
Home language and literacy environments at the age of four: determinants and their relation to reading comprehension up to age nine (Ambientes de lenguaje y alfabetización inicial en el hogar a los cuatro años: determinantes y relación con comprensión lectora hasta los nueve años)
Authors: Mendive Susana , Aldoney Daniela , Mascareño Mayra , Pezoa José , Hoff Erika
Published: March 2022

This study determines (a) which factors of the parenting context, the child and their mothers are associated with environments that differ in their home literacy environment in a Chilean low-SES sample of 53-month-old children, and (b) whether reading comprehension at second and fourth grade is predicted by the socialization in the literacy environment. First, it found that the factors of maternal educational level and cognitions and the child’s task orientation and prosocial behaviour are related to the type of home literacy environment. Likewise, it found that the type of literacy environment predicts reading comprehension at age seven, with a major difference of one standard deviation between the two types of literacy environments. A similar distribution was found at age nine. This article discusses the implications of these results in informing early interventions in disadvantaged socioeconomic levels.
Axion as a fuzzy dark matter candidate: proofs in different gauges
Authors: Hwang Jai-chan , Noh Hyerim
Published: March 2022

Axion as a coherently oscillating massive scalar field is known to behave as a zero-pressure irrotational fluid with characteristic quantum stress on a small scale. In relativistic perturbation theory, the case was proved in the axion-comoving gauge up to fully nonlinear and exact order. Our basic assumption is that the field is oscillating with Compton frequency and the Compton wavelength is smaller than the horizon scale. Here, we revisit the relativistic proof to the linear order in the other gauge conditions. We show that the same equation for density perturbation known in the non-relativistic treatment can be derived in two additional gauge conditions: the zero-shear gauge and the uniform-curvature gauge. The uniform-expansion gauge fails to get the aimed equation, and the quantum stress term is missing in the synchronous gauge. For comparison, we present the relativistic density perturbation equations in the zero-pressure fluid in these gauge conditions. Except for the comoving and the synchronous gauge, the equations strikingly differ from the axion case. We clarify that the relativistic analysis based on time averaging is valid for scales larger than the Compton wavelength. Below the Compton wavelength, the field is not oscillating, and our oscillatory ansatz does not apply. We suggest an equation valid in all scales in the comoving gauge. For comparison, we review the non-relativistic quantum hydrodynamics and present the Schrödinger equation to first-order post-Newtonian expansion in the cosmological context.
Scale invariant FIMP miracle
Authors: Barman Basabendu , Ghoshal Anish
Published: March 2022

We study the freeze-in production of vector dark matter (DM) in a classically scale invariant theory, where the Standard Model (SM) is augmented with an abelian U(1)
X
gauge symmetry that is spontaneously broken due to the non-zero vacuum expectation value (VEV) of a scalar charged under the U(1)
X
. Generating the SM Higgs mass at 1-loop level, it leaves only two parameters in the dark sector, namely, the DM mass mX
and the gauge coupling gX
as independent, and supplement with a naturally light dark scalar particle. We show, for gX
~ 𝒪(10-5), it is possible to produce the DM X out-of-equilibrium in the early Universe, satisfying the observed relic abundance for mX
~ 𝒪(TeV), which in turn also determines the scalar mixing angle sinθ ~ 𝒪(10-5). The presence of such naturally light scalar mediator with tiny mixing with the SM,
opens up the possibility for the model to be explored in direct search experiment, which otherwise is insensitive to standard freeze-in scenarios. Moreover we show that even with such feeble couplings, necessary for the DM freeze-in, the scenario is testable in several light dark sector searches (e.g., in DUNE and in FASER-II),
satisfying constraints from the observed relic abundance as well as big bang nucleosynthesis (BBN). Particularly, we find, regions in the parameter space with mX
≳ 1.8 TeV becomes insensitive to direct detection probe but still can be accessible in lifetime frontier searches, again courtesy to the underlying scale invariance of the theory.
Measurements of energy spectra of relativistic electrons and gamma-rays from avalanches developed in the thunderous atmosphere with Aragats Solar Neutron Telescope
Authors: Chilingarian A. , Hovsepyan G. , Karapetyan T. , Sargsyan B. , Chilingaryan S.
Published: March 2022

Aragats solar neutron telescope (ASNT) is a unique
instrument allowing to measure the energy spectra of electrons
accelerated and multiplied in the strong electric fields of the
atmosphere.

We describe the instrument setup, its operation condition, software,
and hardware triggers. We present energy spectra of a very large
thunderstorm ground enhancement (TGE) event observed on 6 October
2021. The detector response function, algorithm to recover energy
spectra from the energy release histograms also are presented. The
spectra recovery procedure is verified by simulation of the response
function of the SEVAN detector, operating nearby ASNT. SEVAN is a
stacked 3 layered detector, interlayered by lead filters registering
both charged and neutral species of cosmic rays. The simulated and
measured count rates of all 3 layers of the SEVAN detector show good
agreement within 20%.
Simulation of a helicon plasma source in a magnetoplasma rocket engine
Authors: YANG Zhenyu , FAN Wei , WEI Jianguo , HAN Xianwei
Published: March 2022

The helicon plasma source, which generates high thrust and high impulse, is of vital importance for magnetoplasma rocket engines. In this work, a multi-component, two-dimensional, axisymmetric fluid model coupled with an electromagnetic field was developed to model the helicon discharge. The simulation results demonstrate that: (i) the discharge mode changes twice—each conversion is accompanied by a plasma density jump and an electron temperature peak in the discharge; (ii) when the input current increases, the plasma density increases, and ionization occurs faster; (iii) the background magnetic field clearly enhances the discharge; (iv) the plasma density may be smaller if the discharge has not entered the wave mode.
Plasma propagation in single-particle packed dielectric barrier discharges: joint effects of particle shape and discharge gap
Authors: ZHU Min , HU Shengyu , ZHANG Yinghao , WU Shuqun , ZHANG Chaohai
Published: March 2022

In this work, a single Al2O3 particle packed dielectric barrier discharge (DBD) reactor with adjustable discharge gap is built, and the influences of the particle shape (ball and column) and the residual gap between the top electrode and particle on the electrical and optical characteristics of plasma are studied. Our research confirms that streamer discharge and surface discharge are the two main discharge patterns in the single-particle packed DBD reactor. The strong electric field distortion at the top of the ball or column caused by the dielectric polarization effect is an important reason for the formation of streamer discharge. The length of streamer discharge is proportional to the size of the residual gap, but the number of discharge times of a single voltage cycle shows an opposite trend. Compared to the column, a smooth spherical surface is more conducive to the formation of large and uniform surface discharges. The surface discharge area and the discharge intensity reach a maximum when the gap is equal to the diameter of the ball. All in all, the results of this study will provide important theoretical support for the establishment of the synergistic characteristics of discharge and catalysis in plasma catalysis.
Isoperimetric inequalities in unbounded convex bodies
Authors: Leonardi Gian , Ritoré Manuel , Vernadakis Efstratios
Published: March 2022

We consider the problem of minimizing the relative perimeter under a volume constraint in an unbounded convex body

C
⊂

R

n

C\subset \mathbb {R}^{n}

, without assuming any further regularity on the boundary of

C
C

. Motivated by an example of an unbounded convex body with null isoperimetric profile, we introduce the concept of unbounded convex body with uniform geometry. We then provide a handy characterization of the uniform geometry property and, by exploiting the notion of asymptotic cylinder of

C
C

, we prove existence of isoperimetric regions in a generalized sense. By an approximation argument we show the strict concavity of the isoperimetric profile and, consequently, the connectedness of generalized isoperimetric regions. We also focus on the cases of small as well as of large volumes; in particular we show existence of isoperimetric regions with sufficiently large volumes, for special classes of unbounded convex bodies. We finally address some questions about isoperimetric rigidity and analyze the asymptotic behavior of the isoperimetric profile in connection with the notion of isoperimetric dimension.
Harvester ant nest architecture is more strongly affected by intrinsic than extrinsic factors
Authors: O’Fallon Sean , Lowell Eva Sofia Horna , Daniels Doug , Pinter-Wollman Noa
Published: March 2022

Behavior is shaped by genes, environment, and evolutionary history in different ways. Nest architecture is an extended phenotype that results from the interaction between the behavior of animals and their environment. Nests built by ants are extended phenotypes that differ in structure among species and among colonies within a species, but the source of these differences remains an open question. To investigate the impact of colony identity (genetics), evolutionary history (species), and the environment on nest architecture, we compared how two species of harvester ants, Pogonomyrmex californicus and Veromessor andrei, construct their nests under different environmental conditions. For each species, we allowed workers from four colonies to excavate nests in environments that differed in temperature and humidity for seven days. We then created casts of each nest to compare nest structures among colonies, between species, and across environmental conditions. We found differences in nest structure among colonies of the same species and between species. Interestingly, however, environmental conditions did not have a strong influence on nest structure in either species. Our results suggest that extended phenotypes are shaped more strongly by internal factors, such as genes and evolutionary history, and are less plastic in response to the abiotic environment, like many physical and physiological phenotypes.