bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensing depths in frequency domain thermoreflectance
Authors: Hodges Wyatt , Jarzembski Amun , McDonald Anthony , Ziade Elbara , Pickrell Greg W.
Published: June 2022

A method is developed to calculate the length into a sample to which a Frequency Domain Thermoreflectance (FDTR) measurement is sensitive. Sensing depth and sensing radius are defined as limiting cases for the spherically spreading FDTR measurement. A finite element model for FDTR measurements is developed in COMSOL multiphysics and used to calculate sensing depth and sensing radius for silicon and silicon dioxide samples for a variety of frequencies and laser spot sizes. The model is compared to experimental FDTR measurements. Design recommendations for sample thickness are made for experiments where semi-infinite sample depth is desirable. For measurements using a metal transducer layer, the recommended sample thickness is three thermal penetration depths, as calculated from the lowest measurement frequency.
Properties of AgBiI4 using high through-put DFT and machine learning methods
Authors: Barone Victor T. , Tuttle Blair R. , Khare Sanjay V.
Published: June 2022

Silver iodo-bismuthates show promise for optoelectronic and other applications. Within this family of materials, AgBiI4 is a prominent model compound. The complexity of AgBiI4 has prevented a conclusive determination of specific atomic arrangements of metal atoms in the bulk material. Here, we employ high through-put density functional and novel machine learning methods to determine physically relevant unit cell configurations. We also calculate the fundamental properties of the bulk material using newly discovered configurations. Our results for the lattice constant (12.7 Å) and bandgap (1.8 eV) agree with the previous theory and experiment. We report new predictions for the bulk modulus (7.5 GPa) and the temperature-dependent conductivity mass for electrons (m0 at T = 300 K) and holes (7m0 at T = 300 K); these masses will be useful in AgBiI4-based device simulations.
Comparison between sonic jets with one jet orifice and two opposite orifices into a Ma-3.0 supersonic crossflow through circular ducts
Authors: Liang Chang-Hai , Sun Ming-Bo , Xiong Da-Peng
Published: June 2022

Large-eddy simulations and nanoparticle-based planar laser scattering experiments are conducted to investigate various physical aspects of transverse sonic jets injected into a Ma-3.0 supersonic crossflow through a circular pipe. Configurations with one jet and two opposite jets are compared. For the single jet, a separation shock is generated by the recirculation zone on the opposite wall, and this intersects with the jet shear layer to push several jet plumes into the near-wall region. For the two jets, the bow shocks interact with each other, forming an oblique shock train. All of the shocks promote vortex breakage in jet wakes. A counter-rotating vortex pair is generated in the jet near-field region, enhancing the local mixing. A near-wall region in the jet lee between the counter-rotating vortex pair branches exhibits a low fuel mass fraction. The jet fluid in the downstream near-wall region is entrained by the crossflow upstream of the jet. The interaction between the bow shocks and shear layers of the two jets induces recirculation zones in the lee of the jet, which enhance the fuel mixing. This explains the phenomenon whereby the total pressure recovery coefficient and mixing efficiency of two jets are higher than those of the single jet.
High-frequency conductivity and temperature dependence of electron effective mass in AlGaN/GaN heterostructures
Authors: Korotyeyev Vadym V. , Kochelap Vyacheslav A. , Kaliuzhnyi Vladyslav V. , Belyaev Alexander E.
Published: June 2022

We present calculations of frequency and wavevector dispersion of conductivity of two-dimensional electrons confined in AlGaN/GaN heterostructures at the arbitrary level of the degeneracy and the presence of strongly inelastic scattering mechanism by the optical phonons. We found that the high-frequency conductivity deviates from that of the standard Drude–Lorentz model and changes significantly at elevated temperature. The results were applied for simulation of the spectral characteristics of the grating-based plasmonic structure for wide temperature range. We found that thermal activation of the inelastic scattering leads to significant red-shift of the plasmon resonances. This facilitates refinement of interpretation of experimental results published in series of recent papers. We concluded that for AlGaN/GaN heterostructures, the electron effective mass changes in narrower diapason of 0.22me,…,0.26me, when temperature varies from 77 to 300 K. We suggest that found peculiarities of the high-frequency conductivity and its spatial dispersion are of a general character and can be important for high-frequency and high power devices based on AlGaN/GaN heterostructures.
Post-annealing treatment in improving high dielectric constant MgO-based metal-oxide-semiconductor diodes
Authors: Hwang J. D. , Chang Chin-Yang
Published: June 2022

Metal-oxide-semiconductor (MOS) diodes with a high dielectric constant magnesium-oxide (MgO) insulating layer were fabricated using a magnetron radio frequency sputtering system. MgO has a high dielectric constant of approximately 11.2, which is three times higher than the dielectric constant (3.9) of silicon dioxide (SiO2), thereby ensuring a three times thicker gate oxide and reducing gate leakage current while maintaining the same capacitance density. Post-annealing treatment was employed on the MgO film to study how annealing treatment affects the electrical characteristics of MOS diodes. It was observed that the post-annealing treatment of MgO effectively diminished the gate leakage current by approximately one order, thereby increasing the rectification ratio from 8.5 × 103 to 6.8 × 104 for the MOS diodes with as-deposited and post-annealed MgO. In contrast to the MOS diodes with as-deposited MgO, the post-annealing treatment of MgO significantly decreased the flatband voltage shift from 7.8 to 1.3 V and reduced the fixed oxide charge density from 1.3 × 1012 to 2.3 × 1011 cm−2; also, the interface trap charge density was suppressed from 1.8 × 1013 to 3.2 × 1012 cm−2 eV−1. Large quantities of fixed oxide charge attracted more electrons accumulated at the Si surface, which decreased the barrier height from 0.85 to 0.81 eV for the MOS diodes with post-annealed and as-deposited MgO. Moreover, x-ray photoelectron spectroscopy showed that the oxide charges were caused by the defects inside MgO, particularly oxygen vacancies. The oxygen vacancies were compensated by the oxygen atoms introduced from the air during the post-annealing treatment.
Synaptic transistors with a memory time tunability over seven orders of magnitude
Authors: Fu Yang Ming , Wei Tianye , Brownless Joseph , Huang Long , Song Aimin
Published: June 2022

The human brain is capable of short- and long-term memory with retention times ranging from a few seconds to several years. Electrolyte-gated transistors have drawn attention for their potential to mimic synaptic behaviors in neuromorphic applications, but they generally operate at low voltages to avoid instability and, hence, offer limited tunability. Sputtered silicon dioxide electrolytes are utilized in this work to gate indium-gallium-zinc-oxide thin-film transistors, which offer robust operation at much higher voltages. The synaptic memory behavior is studied under single and multiple pulses and under mild (1 V) and strong stimuli (up to 8 V). The devices are found to be capable of providing an extremely wide range of memory retention time from ∼2 ms to ∼20 000 s, over seven orders of magnitude. Furthermore, based on the experimental data on individual transistors, pattern learning and memorizing functionalities are conceptually demonstrated.
Lid-driven cavity flow-induced dynamics of a neutrally buoyant solid: Effect of Reynolds number, flexibility, and size
Authors: Prasad Vinay , Sharma Atul , Kulkarni Salil S.
Published: June 2022

The present work is on Fluid flexible–Solid Interaction (FfSI), involving a recirculating flow-induced motion of a neutrally buoyant and deformable circular solid. For a Newtonian fluid flow and neo-Hookean flexible-solid deformation, a single FfSI solver—based on fully Eulerian and monolithic approaches—is used. The effect of Reynolds Number Re (20–500), volume fraction Φ (1%–12%) of the solid, and its non-dimensional shear modulus G*(0.02–1) on transient/periodic flow-induced solid-motion and the associated FfSI analysis is presented. The solid undergoes a transient spiraling motion before attaining a periodic orbit-based limit cycle. The flow also attains the periodic state after the initial transients. Time-averaged flow velocity-magnitude ⟨v*⟩ surrounding the limit cycle increases with increasing Re, increasing G*, and decreasing Φ. Equivalent radius req* of the limit cycle and time-averaged velocity-magnitude ⟨vc*⟩ of the centroid of the solid increase with increasing Re and decrease with decreasing G* (or increasing flexibility) and increasing volume fraction Φ (or size) of the solid. Also, frequency f* of the limit cycle decreases with increasing Re and remains almost constant with G* and Φ. With increasing Φ, the limit cycle undergoes a transition from the single loop to double loop beyond a critical volume fraction Φc=2%. A critical Reynolds number Rec, below which the periodic limit cycle collapses to a point, decreases with decreasing Φ. Our findings will help in the prediction and control of the motion of the solid in a bounded fluid flow involving solids of varying flexibility, which is relevant to a wide range of industrial and biological applications.
Modal analysis of propeller wakes under different loading conditions
Authors: Wang Lianzhou , Liu Xinyu , Wang Nian , Li Mijian
Published: June 2022

Propeller wakes under different loading conditions obtained by the improved delayed detached eddy simulation method were studied based on the flow decomposition technique. The sparsity-promoting dynamic mode decomposition was used to study the flow physics in the wake of a propeller, with particular emphasis placed on identifying the underlying temporal and spatial scales that play important roles in the onset of propeller wake instabilities. The morphology of flow structures of different modes selected by the sparsity-promoting algorithm at different frequencies characterizes the instability process of the wake system. It shows that the circumferential diffusion of tip vortex structures promotes the approaching of adjacent tip vortices, enhancing the interaction of the vortex pairs, which plays an important role in the instability triggering mechanism of the propeller wake, especially the mutual inductance between neighboring tip vortices. The present study further extends knowledge of propeller wake instability inception mechanisms under different loading conditions.
Numerical study on the surface signature of internal solitary waves
Authors: Wen Zehua , Zou Li , Hu Yingjie , Sun Tiezhi , Wang Xueyu
Published: June 2022

The propagation of internal solitary waves (ISWs) underwater and their interactions with surface waves can affect the sea surface state and generate distinct surface signatures of bright–dark striped patterns in remote sensing imagery. These patterns have been one of the most important methods for wide coverage detection and observation of ISWs. This study establishes a fully nonlinear numerical model for ISW–surface wave interaction simulation based on the multi-domain boundary element method. By numerical simulation, the formation mechanism, characteristics, and influencing factors of ISW surface signatures are revealed. The physical essence of the ISW surface signature is the spatially inhomogeneous wavelength and roughness changes in the surface waves due to the convergence and divergence effects of the ISW. Based on the surface wave wavelength changes, the surface area affected by an ISW is divided into three regions from front to back—the converging, diverging, and restoring regions—corresponding to the regions where the surface waves are compressed, stretched, and recover, respectively. By comparing different cases, it is found that the ISW amplitude, surface wave amplitude, and surface wave wavelength are the main factors influencing the ISW surface signature. ISWs with larger amplitudes have stronger convergence and divergence effects on surface waves, making the overall scale of the ISW surface signature larger. Larger surface wave amplitudes provide stronger resistance to the ISW divergence effect and lead to smaller diverging regions, and larger surface wave wavelengths make the converging region larger and the diverging and restoring regions smaller.
Linear modal global instabilities of hypersonic flow over an inclined cone
Authors: Liu Shuyi , Wan Bingbing , Yuan Xianxu , Zhang Ligeng , Chen Jianqiang , Chen Xi
Published: June 2022

A systematic parametric study is presented on the modal global linear instability of Mach 6 boundary-layer flow over an inclined cone at a 6° angle of attack under typical wind tunnel conditions. The analysis is performed using the spatial BiGlobal theory. Results reveal two classes of global instabilities in the outboard region away from the leeward plane: high-frequency (hundreds of kHz) second mode instabilities and low-frequency (tens of kHz) crossflow instabilities. In the global eigenvalue spectra of the second mode instability, two distinct branches of significantly unstable modes are identified, namely, an approximately continuous spectrum (branch S) and a few discrete points (branch D). The branch D modes peak at the windward centerline, while branch S modes lie at a certain distance away from the windward meridian. The global stability characteristics of the crossflow instability over a conical configuration are uncovered for the first time. In the global eigenvalue spectra of the crossflow instability, many unstable modes emerge and form a complex pattern, with the most amplified frequency of around 30 kHz. The unstable crossflow modes are mainly distributed on the leeward side and wave angles obviously increase toward the leeward centerline. The peak growth rates are slightly smaller than those of second modes, and yet the most amplified frequency varies rather mildly along the streamwise direction so that they may achieve larger integrated growth rates than second modes do.
Broadband acoustic absorbing metamaterial via deep learning approach
Authors: Liu Le , Xie Long-Xiang , Huang Weichun , Zhang Xiu Juan , Lu Ming-Hui , Chen Yan-Feng
Published: June 2022

Sound absorption is important for room acoustics and remediation of noise. Acoustic metamaterials have recently emerged as one of the most promising platforms for sound absorption. However, the working bandwidth is severely limited because of the strong dispersion in the spectrum caused by local resonance. Utilizing the coupling effect among resonators can improve the absorbers' performance, but the requirement of collecting coupling effects among all resonators, not only the nearest-neighbor coupling, makes the system too complex to explore analytically. This Letter describes deep learning based acoustic metamaterials for achieving broadband sound absorption with no visible oscillation in a targeted frequency band. We numerically and experimentally achieve an average absorption coefficient larger than 97% within the ultra-broadband extending from 860 to 8000 Hz, proving the validity of the deep learning based acoustic metamaterials. The excellent ultra-broadband and near-perfect absorption performance allows the absorber for versatile applications in noise-control engineering and room acoustics. Our work also reveals the significance of modulating coupling effects among resonators, and the deep learning approach may blaze a trail in the design strategy of acoustic functional devices.
Stress inversion in waveguides with arbitrary cross sections with acoustoelastic guided waves
Authors: Zhao Chunyu , Chen Xin , Li Jian , Liu Yang
Published: June 2022

Acoustoelasticity or the change in elastic wave speeds with stress is promising for prestress measurements in waveguides. The theory of guided wave propagation in initially isotropic materials with arbitrary cross sections and under homogeneous biaxial stresses is developed using Semi-Analytical Finite Element (SAFE) modeling in this article. Based on the anisotropic effect induced by the applied biaxial load, an inversion method for biaxial force was developed. The acoustoelastic response for a particular mode and frequency is described by only two constants, which can be determined from known uniaxial loading experiments. The magnitude and direction of the biaxial force can be obtained by further coefficient fitting. Stress inversion can be obtained without considering the shape of the cross section and applies to multiple guided wave modes. The inversion has been verified by the results of SAFE and 3D Sweeping Frequency Finite Element Modeling (SFFEM) method, and the Mean Absolute Errors of stresses obtained by different methods are all within 1%. The 3D SFFEM was combined with the Matrix Pencil Method using the time domain information to extract the dispersion curve. Unlike previous finite element modeling, here the inheritance of the solution between the two solvers was set instead of approximating static load conditions by shortening the guided wave travel time. It guarantees the steady state of the force in the time-variant study, ensuring the high precision required for the study of the acoustoelastic effect.
Diffusiophoresis of a highly charged conducting fluid droplet
Authors: Fan Leia , Lee Eric
Published: June 2022

Diffusiophoresis of a perfectly conducting droplet-like liquid metal in electrolyte solutions is investigated theoretically, focusing on the chemiphoresis component, the very heart of diffusiophoresis, where the droplet motion is induced solely by the chemical gradient. The resulting electrokinetic equations are solved with a pseudo-spectral method based on Chebyshev polynomials. For the isothermal electrokinetic system of a perfectly conducting droplet considered here, there is no Marangoni effect, which is a motion-inducing effect due to the variation of interfacial tension along the droplet surface. No Maxwell traction is present as well. The droplet motion is full of hydrodynamic nature. It is found, among other things, that contrary to a dielectric droplet, a conducting droplet always moves up the chemical gradient toward the region with a higher concentration of ions in chemiphoresis. This implies that a perfectly conducting droplet like a gallium or its alloy droplet is superior to the commonly utilized dielectric droplet like a liposome in drug delivery in terms of self-guarding itself toward the desired destination of injured or infected area in the human body, as specific ionic chemicals are often released there. Optimum droplet size yielding the fastest migration rate is predicted.
Automated workflow for computation of redox potentials, acidity constants, and solvation free energies accelerated by machine learning
Authors: Wang Feng , Cheng Jun
Published: June 2022

Fast evolution of modern society stimulates intense development of new materials with novel functionalities in energy and environmental applications. Due to rapid progress of computer science, computational design of materials with target properties has recently attracted a lot of interest. Accurate and efficient calculation of fundamental thermodynamic properties, including redox potentials, acidity constants, and solvation free energies, is of great importance for selection and design of desirable materials. Free energy calculation based on ab initio molecular dynamics (AIMD) can predict these properties with high accuracy at complex environments, however, they are being impeded by high computational costs. To address this issue, this work develops an automated scheme that combines iterative training of machine learning potentials (MLPs) and free energy calculation and demonstrates that these thermodynamic properties can be computed by ML accelerated MD with ab initio accuracy and a much longer time scale at cheaper costs, improving poor statistics and convergence of numerical integration by AIMD. Our automated scheme lays the foundation for computational chemistry-assisted materials design.
Evolutionary optimization of the Verlet closure relation for the hard-sphere and square-well fluids
Authors: Bedolla Edwin , Padierna Luis Carlos , Castañeda-Priego Ramón
Published: June 2022

The Ornstein–Zernike equation is solved for the hard-sphere and square-well fluids using a diverse selection of closure relations; the attraction range of the square-well is chosen to be λ=1.5. In particular, for both fluids, we mainly focus on the solution based on a three-parameter version of the Verlet closure relation [Verlet, “Integral equations for classical fluids. II. Hard spheres again,” Mol. Phys. 42, 1291–1302 (1981)]. To find the free parameters of the latter, an unconstrained optimization problem is defined as a condition of thermodynamic consistency based on the compressibility and solved using Evolutionary Algorithms. For the hard-sphere fluid, the results show good agreement when compared with mean-field equations of state and accurate computer simulation results; at high densities, i.e., close to the freezing transition, expected (small) deviations are seen. In the case of the square-well fluid, good agreement is observed at low and high densities when compared with event-driven molecular dynamics computer simulations. For intermediate densities, the explored closure relations vary in terms of accuracy. Our findings suggest that a modification of the optimization problem to include, for example, additional thermodynamic consistency criteria could improve the results for the type of fluid here explored.
Historical retention, progressive nation, or the eye of the beholder?
Authors: Anderwald Lieselotte
Published: June 2022

This article investigates the time-depth of three groups of present-day morphological Americanisms: past participle gotten, new strong verbs (dove, snuck), and regularized verbs (burned, learned, dreamed). Relating corpus-linguistic evidence to metalinguistic comments shows that even if the divergence from British English started in the nineteenth century, this was often not noticed or commented on; besides, the dominant discourse in nineteenth-century America was one of legitimizing American forms by referring to British parallels. In all cases, myth building (of American English as more innovative, or American English as more conservative) only happened after the fact, and is largely a twentieth-century development; prescriptive sources were thus not instrumental in actively dissociating American English from British English in the 1800s.
Grammar, text type, and diachrony as factors influencing complement choice in historical American English1
Authors: Tyrkkö Jukka , Rudanko Juhani
Published: June 2022

A key task in the study of the system of English predicate complementation is to account for the variation between to infinitive and gerundial complements of verbs and adjectives in recent English. This chapter examines to infinitive and to ‑ing complements of the adjective accustomed, with data from the Corpus of Historical American English (COHA), in order to assess the impact of factors of different types on the variation in question. The grammatical factors are the Extraction and Choice Principles, and attention is also paid to the possible role of insertions. Following a discussion of the key theoretical concepts and a description of the primary data, a logistic regression model is used to analyse the role of independent variables on complement selection of the adjective accustomed.
“Gems of elocution and humour”
Authors: Dossena Marina
Published: June 2022

Recommended usage of linguistic forms has often been based on ideological tenets, such as in the case of early American English, when attention was paid to its patriotic value. Ideology is found in grammars, dictionaries, and in other more popular genres, the relatively low cost of which made them accessible also to minimally-schooled audiences.

The aim of this study is to highlight some significant features of the latter group of materials, in order to see how American distinctiveness was emphasized and placed in a specific historical context; examples taken from literary sources may prove of particular interest, in order to assess the indebtedness of those books to European and/or American traditions and to outline some of the connections existing between cultural attitudes and normativity.
Dialects as a mirror of historical trajectories
Authors: Tagliamonte Sali A.
Published: June 2022

A multi-year project on dialects in Ontario, Canada demonstrates how synchronic variation mirrors historical trajectories of change. Three linguistic features are examined, come vs. came, adjectives of smallness and 3rd person male referents. Using quantitative methods and a comparative sociolinguistic approach, I demonstrate how these features vary by geographical location, date of birth and social and linguistic factors. Some features are stable, providing a foundation of constancy. Other features are changing but are distinguished by locale. Changes are advancing most vigorously in the urban centre, while conservative variants persist in peripheral locations. The results highlight how synchronic dialect data can expose diachronic trends in contemporary English and provide a window on earlier varieties.
Erratum: Photonic Thermal Rectification with Composite Metamaterials [Chin. Phys. Lett. 38, 016801 (2021)]
Authors: Ogundare Rasheed Toyin , Ge Wenxuan , Gao Lei
Published: June 2022

In this paper, the name of the first author was written as Ogundare Rasheed Toyin. To comply with the style of journal publication, the order of given name, Rasheed Toyin, and family name, Ogundare, should be exchanged. The name should be written as Rasheed Toyin Ogundare.
Uniqueness of a spherically symmetric refractive index from modified transmission eigenvalues
Authors: Gintides Drossos , Pallikarakis Nikolaos , Stratouras Kyriakos
Published: June 2022

In the present work we study the modified transmission eigenvalue problem for the case of the spherically symmetric refractive index. This problem occurs as a modification of the classic transmission eigenvalue problem for a fixed wavenumber, by introducing a new spectral parameter. We prove the existence of infinite and discrete eigenvalues using asymptotic expressions and monotonicity properties of the characteristic functions. Next, we define the inverse spectral problem of determining the refractive index from the knowledge of modified transmission eigenvalues. We show that one eigenvalue corresponding to each characteristic function is sufficient to uniquely determine the fraction of the boundary Cauchy data. The knowledge of these data, in combination with a Dirichlet-to-Neumann mapping property allows us to establish uniqueness for the inverse problem.
The impacts of sidewall passivation via atomic layer deposition on GaN-based flip-chip blue mini-LEDs
Authors: Lai Shouqiang , Lin Wansheng , Chen Jinlan , Lu Tingwei , Liu Shibiao , Lin Yi , Lu Yijun , Lin Yue , Chen Zhong , Kuo Hao-Chung , Guo Weijie , Wu Tingzhu
Published: June 2022

In order to investigate the photoelectric characteristics of 80 × 120 µm2 mini-light-emitting-diodes (mini-LEDs) with sidewall passivation by atomic layer deposition (ALD), this paper uses the techniques of spectrometer-based spectroradiometer and microscopic hyperspectral imaging (µ-HSI). The temperature-dependent electroluminescence is measured using a spectrometer-based spectroradiometer. By analyzing the rising parts of external quantum efficiency at room temperature with a two-level model, the difference of physical mechanisms between mini-LEDs with ALD and without ALD are determined. In addition, the thermal quenching indicates that the ALD sidewall passivation can enhance the temperature stability of the mini-LEDs. The ALD sidewall passivation also enhances the light extraction efficiency according to the theoretical calculation of transmittance. Moreover, the µ-HSI technique is used to evaluate different local areas of mini-LEDs. The obtained results reveal the optimization on lateral distribution of current density within the chip after sidewall passivation.
Systematic 1D electric field induced second harmonic measurement on primary-to-secondary transition phase of positive streamer discharge in atmospheric-pressure air
Authors: Inada Yuki , Shioda Tatsutoshi , Nakamura Ryosuke , Maeyama Mitsuaki , Kumada Akiko , Nakamura Shin , Ono Ryo
Published: June 2022

The electric field induced second harmonic generation (E-FISH) technique has been widely utilized for the electric field measurement of atmospheric-pressure nonthermal plasmas. However, the measurement accuracy has not been quantified. Further, the E-FISH signal generation that is necessary to the evaluation of the measurement accuracy has been formulated only for the probe laser beam focused by a spherical lens and not for the cylindrical lens. Here, the E-FISH method utilizing the focusing cylindrical lens was studied for accurate one-dimensional (1D) electric field measurement of the primary-to-secondary transition phase of a single-filament positive streamer discharge generated in atmospheric-pressure air. A combination of numerical analysis and the E-FISH signal measurement was used to establish the radial distribution of the electric field vectors and the accompanying measurement accuracy. The E-FISH methodology captured a distinct evolution in the 1D electric field varying over timescales of

∼

1

 ns and length scales of 100 µm. At the instant when the primary streamer arrived at the cathode, the electric field at 3 mm above the cathode surface was found to be as high as 225 Td, while the field at 10 mm above the cathode surface was as low as 5 Td. At the final stage of the primary-to-secondary transition phase completed in 3 ns from the primary streamer arrival at the cathode, the electric field at 3 mm above the cathode was found to be lower than that observed at 10 mm from the cathode; this finding is consistent with predictions made based on a previous model describing the initiation of the secondary streamer discharge and previously published electron density measurement.
A phenomenological model for interfacial water near hydrophilic polymers
Authors: Earls A , Calderer M-C , Desroches M , Zarnescu A , Rodrigues S
Published: June 2022

We propose a minimalist phenomenological model for the ‘interfacial water’ phenomenon that occurs near hydrophilic polymeric surfaces. We achieve this by combining a Ginzburg–Landau approach with Maxwell’s equations which leads us to a well-posed model providing a macroscopic interpretation of experimental observations. From the derived governing equations, we estimate the unknown parameters using experimental measurements from the literature. The resulting profiles of the polarization and electric potential show exponential decay near the surface, in qualitative agreement with experiments. Furthermore, the model’s quantitative prediction of the electric potential at the hydrophilic surface is in excellent agreement with experiments. The proposed model is a first step towards a more complete parsimonious macroscopic model that will, for example, help to elucidate the effects of interfacial water on cells (e.g. neuronal excitability), the effects of infrared neural stimulation or the effects of drugs mediated by interfacial water.
A denoising and multiscale residual deep network for soft sensor modeling of industrial processes
Authors: Gao Renzhi , Zhu Hegong , Wang Gang , Wu Zhangjun
Published: June 2022

Deep learning plays an important role in soft sensors of industrial processes for the timely measurement of key quality variables. However, since sensors are often operated under noisy and nonstationary industrial conditions, the collected industrial process data exhibit extreme complexity, which severely restricts the learning capacity and measurement accuracy of deep learning methods. In this paper, a novel denoising and multiscale residual deep network (DMRDN) is proposed for soft sensor modeling. Firstly, a stacked denoising autoencoder with level-aware attention is developed to denoise the process data, in which denoised features on different levels are learned and fused. Secondly, the denoised features are fed into multiscale residual convolutional neural network with scale-aware attention, which is designed to capture and fuse deep dynamic features from different scales. Finally, experiments were conducted on an industrial debutanizer column. The experimental results demonstrate that the proposed DMRDN greatly strengthens the learning ability and achieves better prediction performance compared with other methods.
Porous polyvinyl alcohol/graphene oxide composite film for strain sensing and energy-storage applications
Authors: Cui Xu , Guo Jia , Araby Sherif , Abbassi Fethi , Zhang Chunyan , Diaby Abdullatif Lacina , Meng Qingshi
Published: June 2022

In this study, a flexible porous polyvinyl alcohol (PVA)/graphene oxide (GO) composite film was developed and tested for flexible strain sensing and energy-storage applications. Morphology and mechanical properties were studied; tensile strength and Young’s modulus increased by 225% and 86.88%, respectively, at 0.5 wt% GO. The PVA/GO film possesses exceptional sensing ability to various mechanical strains, such as tension, compression, bending, and torsion. For example, the gauge factor of the PVA/GO film as a tensile-strain sensor was measured as 2.46 (246%). Under compression loads, the PVA/GO composite film showed piezoresistive and capacitive strain-sensing characteristics. Under 5 kPa of compression load, the relative resistance increased by 81% with a 100 msec response time; the relative capacitance increased by 160% with a 120 msec response time. The PVA/GO strain sensor exhibited high durability and reliability over 20 × 103 cycles of tensile strain and bending at 3.33 Hz. Moreover, the PVA/GO composite film showed good electrochemical properties due to its porous structure; the maximum capacitance was 124.7 F g−1 at 0.5 wt% GO. After 20 × 103 charging–discharging cycles, the capacitance retention rate was 94.45%, representing high stable capacitance performance. The results show that electrically conductive porous PVA nanocomposite films are promising candidates for strain sensing and energy-storage devices.
Anomalous self-similar solutions of exponential type for the subcritical fast diffusion equation with weighted reaction
Authors: Iagar Razvan Gabriel , Sánchez Ariel
Published: June 2022

We prove existence and uniqueness of the branch of the so-called anomalous eternal solutions in exponential self-similar form for the subcritical fast-diffusion equation with a weighted reaction term

∂

t

u

=

Δ

u

m

+
|
x

|

σ

u

p

,

posed in

R

N

with N ⩾ 3, where

0
<
m
<

m

c

=

N
−
2

N

,
p
>
1
,

and the critical value for the weight

σ
=

2

(

p
−
1

)

1
−
m

.

The branch of exponential self-similar solutions behaves similarly as the well-established anomalous solutions to the pure fast diffusion equation, but without a finite time extinction or a finite time blow-up, and presenting instead a change of sign of both self-similar exponents at m = m
s = (N − 2)/(N + 2), leading to surprising qualitative differences. In this sense, the reaction term we consider realizes a perfect equilibrium in the competition between the fast diffusion and the reaction effects.
Integrable semi-discretisation of the Drinfel’d–Sokolov hierarchies
Authors: Yin Yue , Fu Wei
Published: June 2022

We propose a novel semi-discrete Kadomtsev–Petviashvili equation with two discrete and one continuous independent variables, which is integrable in the sense of having the standard and adjoint Lax pairs, from the direct linearisation framework. By performing reductions on the semi-discrete Kadomtsev–Petviashvili equation, new semi-discrete versions of the Drinfel’d–Sokolov hierarchies associated with Kac–Moody Lie algebras

A

r

(

1

)

,

A

2
r

(

2

)

,

C

r

(

1

)

and

D

r
+
1

(

2

)

are successfully constructed. A Lax pair involving the fraction of

Z

N

graded matrices is also found for each of the semi-discrete Drinfel’d–Sokolov equations. Furthermore, the direct linearisation construction guarantees the existence of exact solutions of all the semi-discrete equations discussed in the paper, providing another insight into their integrability in addition to the analysis of Lax pairs.
Comparing two- and three-dimensional models of scrape-off layer turbulent transport
Authors: Nicholas T E G , Omotani J , Riva F , Militello F , Dudson B
Published: June 2022

There exists a large body of previous work using reduced two-dimensional models of the scrape-off layer (SOL), which model fluctuations in the drift-plane but approximate parallel transport with effective loss terms. Full size three-dimensional simulations of SOL turbulence in experimental geometries are now possible, but are far more computationally expensive than 2D models. We therefore use a flux-tube geometry model of the SOL to compare the results of 2D simulations to 3D simulations with a similar setup, looking for systematic differences. Our setup mimics the outer SOL of a double-null plasma, with no neutrals and no shear, and is therefore likely more favourable to agreement. Overall, we do find good agreement in the basic radial profiles, probability distribution functions, and power spectra of fluctuations. However, the average temperature is over-predicted in 2D relative to 3D, and we explain the difference in terms of the effect of geometrical simplifications of devices at low power. Varying geometric parameters, we find that supersonic flow in the divertor leg, which occurs because our simulations do not include neutrals and so represent low-recycling conditions, means that the divertor leg length only has a weak effect on the output. Finally, we examine the effect of altering the magnitude of source and sink terms in 2D, concluding that they cannot easily be used to recreate both the density and temperature profiles observed in 3D simultaneously.
Thermonuclearizing the plasma focus—converting plasma focus fusion mechanism from beam-gas target to thermonuclear
Authors: Lee S
Published: June 2022

It has been reported that over a range of 3–280 kJ, neutron-optimized deuterium plasma focus machines operate with a near constant speed factor S = 89 ± 8 kA cm−1 per (torr)0.5. This near-constant value of S is consistent with a narrow range of peak axial speeds approximately 10 cm μs−1 and peak radial speeds 20–30 cm μs−1, resulting in focus pinch temperatures less than 0.5 keV and inductively generated high voltages, producing deuteron beams with energies from high tens to hundreds keV. The low pinch temperatures and high beam-deuteron energies result in fusion neutrons predominantly from a beam-target mechanism. A converging taper ending in radius a
e, is added to the end of the standard cylindrical anode of radius ‘a’. This taper converts the pinch from one with starting radius ‘a’ to one with a reduced starting radius a
e. This increases the value of S and consequently the pinch temperature. This study examines the scaling of the end taper and finds that a taper ending in a radius, which is 1/20 that of the before-taper section increases the pinch temperature by a factor approximately 200, to above 20 keV. This increases the thermonuclear cross-sections by up to 14 orders of magnitude. Numerical experiments using the Lee code confirm that the thermonuclear component of the fusion yield becomes predominant. Such a taper may be considered as a thermonuclear converter.
Dependence of latch-up and threshold voltages on channel length in single-gated feedback field-effect transistor
Authors: Woo Sola , Kim Sangsig
Published: June 2022

This study demonstrates an optimal design method for the channel length in a p
+–i–p–n
+ structure of feedback field-effect transistors (FBFETs) for next-generation memory devices. We demonstrate the dependence of latch-up and threshold voltages on the channel length in single-gated FBFETs with silicon channels consisting of gated and non-gated regions. The operation principle of the latch-up phenomena related to the channel length using an equivalent circuit in an FBFET has been described. The abrupt increase in the drain current of the single-gated FBFETs at the latch-up (threshold) voltage in the sweep of the drain (gate) voltage was analyzed with current gains in an equivalent circuit. The current gain depends on the gated and non-gated channel lengths; thereby, the latch-up and threshold voltages too depend on the gated and non-gated channel lengths. The dependences of the latch-up and threshold voltages on the non-gated channel length were found to be 3.62 times and 1.68 times higher than that on the gated channel length, respectively.
Piezoelectric transducer design for simultaneous ultrasonic power transfer and backscatter communication
Authors: Allam Ahmed , Sabra Karim , Erturk Alper
Published: June 2022

Ultrasonic waves can transfer power and data to sensors and devices deployed to traditionally inaccessible locations, such as inside the human body or deep in the ocean, eliminating the need for battery replacement. In ultrasonic power and data transfer systems, a piezoelectric transducer converts incident ultrasonic waves to useful electric power while transmitting data by modulating its reflected signal through backscatter communication. Existing approaches rely on reflecting a portion of the incident power to communicate, reducing the harvested power. This work realizes uninterrupted power harvesting with simultaneous backscatter communication through frequency multiplexing. A piezoelectric transducer is first designed and tested experimentally for high sensitivity and high bandwidth operation through low-loss broadband acoustic and electrical impedance matching. The transducer achieved 70% bandwidth at 1 MHz with a 10 dB difference between reflecting and absorbing incident ultrasonic waves. A frequency multiplexing technique is then developed to separate power and data into different frequency bands achieving simultaneous operation. The technique extends the range and bandwidth of ultrasonically powered devices such as biomedical implants and ocean monitoring sensors.
Multi-physical modeling and fabrication of high-performance IPMC actuators with serrated interface
Authors: Rao Manting , Tang Fei , Li Yan , Chang Longfei , Zhu Zicai , Aabloo Alvo
Published: June 2022

Ionic Polymer–Metal Composite (IPMC) has been widely recognized as a promising and representative candidate of soft intelligent materials actuated under low voltage. In the last few years, the importance of the electrode/substrate interface has received growing attention for research on both the modeling of ion-based mass transport and practical performance of the manipulation of ionic electro-active actuators. In this paper, based on a macroscopic serrated interface morphology, the influences of the interface were revealed comprehensively by distinguishing the bending direction as well as the variation of interfacial area, excisional volume and moment of inertia. The offsetting interaction from different aspects were analyzed in detail. On this basis, an interesting result showed that, contrary to current understanding, an enlarged interface area did not necessarily lead to better deformation, which was primarily ascribed to the trade-off of influences from the increasing excisional volume and decreasing bending inertia moment. In addition, a corresponding fabrication process was established, which verified experimentally that IPMC with a super simple macroscopic serrated interface can present a high electro-active performance, providing a minimalist design strategy for ionic electroactive polymer structures.
Microstructure, pinning properties, and aging of CSD-grown SmBa2Cu3O7−δ
films with and without BaHfO3 nanoparticles
Authors: Hänisch Jens , Iida Kazumasa , Cayado Pablo , Erbe Manuela , Grünewald Lukas , Hatano Takafumi , Okada Tatsunori , Gerthsen Dagmar , Awaji Satoshi , Holzapfel Bernhard
Published: June 2022

In order to improve the electrical transport properties of REBa2Cu3O7−δ
nanocomposite films, SmBa2Cu3O7−δ
films with and without BaHfO3 nanoparticles were grown by chemical solution deposition, and their microstructural and transport properties were investigated in a detailed study using transmission electron microscopy and transport measurements in magnetic fields up to 24 T. The optimization process of the crystallization step (temperature and oxygen partial pressure) as well as an aging effect, which is due to the release of trapped fluorine, are described. Critical temperature and critical current densities surprisingly improve initially during the aging. Due to the complex microstructure, the additional BaHfO3 nanoparticles have only a positive effect at low magnetic fields for our samples.
Absence of stationary states and non-Boltzmann distributions of fractional Brownian motion in shallow external potentials
Authors: Guggenberger Tobias , Chechkin Aleksei , Metzler Ralf
Published: June 2022

We study the diffusive motion of a particle in a subharmonic potential of the form U(x) = |x|
c
(0 < c < 2) driven by long-range correlated, stationary fractional Gaussian noise ξ

α
(t) with 0 < α ⩽ 2. In the absence of the potential the particle exhibits free fractional Brownian motion with anomalous diffusion exponent α. While for an harmonic external potential the dynamics converges to a Gaussian stationary state, from extensive numerical analysis we here demonstrate that stationary states for shallower than harmonic potentials exist only as long as the relation c > 2(1 − 1/α) holds. We analyse the motion in terms of the mean squared displacement and (when it exists) the stationary probability density function. Moreover we discuss analogies of non-stationarity of Lévy flights in shallow external potentials.
Study of radiation effect and bismuth content on the physical properties of some chalcogenides based on selenium
Authors: Abd El-Raheem M M , Solieman A H M , Wakkad M M , Ali H M , Mohammed S K , Mohamed H F
Published: June 2022

A series of Ge18BixSe82−x (x = 0.5, 2, 4, 6 & 8) thin films were prepared using thermal evaporation on glass substrates. The structural, optical and electrical properties of the prepared samples were investigated. The samples were exposed to γ-ray of 60Co source with gradually increased doses up to (150 kGy). The changes of the properties of the irradiated samples have been studied. Single oscillator and Drude models were used to describe the dispersion region. The changes of the optical parameters such as optical energy gap (Eop), Urbach energy (Eu), and the plasma frequency

(

ω

p

)

due to gamma irradiation were studied. The results obtained were explained in terms of the interaction of radiation with matter. The electrical conductivity was studied for both the as-prepared and irradiated films revealing negative differential conductance behavior.
Vacuum energy density measured from cosmological data
Authors: Prat J. , Hogan C. , Chang C. , Frieman J.
Published: June 2022

Within the ΛCDM cosmological model, the absolute value of Einstein's cosmological constant Λ, sometimes expressed as the gravitating mass-energy densityρΛof the physical vacuum, is a fundamental constant of nature, whose accurate measurement plays a central role in testing some proposed theories of quantum gravity. Several combinations of currently public cosmological data and an assumed flat ΛCDM cosmological model are used here to make a joint Bayesian inference on the combination of conventional parameters ΩΛh2that corresponds to the absolute physical densityρΛ. In physical units, we obtainρΛ= (60.3 ± 1.3)× 10-31g/cm3, the most accurate constraint to date, with an absolute calibration of cosmological measurements based on CMB temperature. Significantly different values are obtained with calibrations that use a local distance scale, mainly connected to systematic differences in the value of the Hubble constant. It is suggested that future comprehensive cosmological parameter studies assuming the ΛCDM model include constraints on the vacuum density.