bluuebunny/crossref_metadata_2025 huggingface dataset:
Shear-induced polydomain structures of nematic lyotropic chromonic liquid crystal disodium cromoglycate
Authors: Baza Hend , Turiv Taras , Li Bing-Xiang , Li Ruipeng , Yavitt Benjamin M. , Fukuto Masafumi , Lavrentovich Oleg D.
Published: August 2020

Shear causes a lyotropic chromonic liquid crystal to tumble and to form a cascade of textural instabilities with polydomain director structures, disclinations and periodic stripes.
Rapid Syllable Transition Treatment—A Treatment for Childhood Apraxia of Speech and Other Pediatric Motor Speech Disorders
Authors: McCabe Patricia , Thomas Donna Claire , Murray Elizabeth
Published: August 2020

Purpose

Childhood apraxia of speech (CAS) is a speech disorder that many generalist speech-language pathologists feel underqualified to treat. For children with CAS, this may result in ad hoc interventions resulting in slower progress. Research evidence for various CAS treatments is primarily limited to single-case experimental design studies; however, two treatments (Rapid Syllable Transition Treatment [ReST] and the Nuffield Dyspraxia Programme, Third Edition) have been compared in a single randomized controlled trial.

Conclusion

This tutorial describes one of those treatments: ReST which was designed to address the three consensus core features of CAS simultaneously: consistency and accuracy of sounds, sequencing, and prosody. The treatment uses nonwords to help children build and store accurate motor plans and programs using principles of motor learning. Treatment data are described, and commonly reported clinical issues are discussed. Recommendations for which children may be suitable for ReST and for evidence-based practice are described.
Dual cost‐sensitivity factors‐based power system transient stability assessment
Authors: Li Nan , Li Baoluo , Han Yongqiang , Gao Lei
Published: August 2020

In actual power system operation, there is a significant imbalance between the number of stable and unstable samples, and the misclassification costs of the two classes of samples are different. In addition to the class imbalance, there is another imbalance of regional samples in the feature space. In order to reduce the impact of class imbalance and regional imbalance on the performance of the model, a method of dual cost‐sensitivity factors for transient stability assessment is proposed. The method sets the balance factor and modulating factor in the loss function of light gradient boosting machine. The former corrects the classification bias caused by class imbalance, and the latter focuses on improving the classification accuracy of overlapping area samples. Combining the two factors, the model not only improves the accuracy of unstable samples, but also reduces the misjudgement of stable samples. In online application, a fast update scheme with memory function is proposed. In this scheme, incremental learning is used to update the model with fewer samples and less computational time, so as to achieve better evaluation performance. Case studies on three power systems demonstrate the generalisation performance of the proposed model and the effectiveness of the update scheme.
LSTM auto‐encoder based representative scenario generation method for hybrid hydro‐PV power system
Authors: Yang Jingxian , Zhang Shuai , Xiang Yue , Liu Jichun , Liu Junyong , Han Xiaoyan , Teng Fei
Published: August 2020

The increasing penetration of renewable energy sources causes complex uncertainties of the power system. To capture such uncertainties in power system planning, an important step is to generate representative scenarios. In this work, a long short term memory (LSTM) auto‐encoder based approach is proposed to generate representative scenarios in an integrated hydro‐photovoltaic (PV) power generation system, which consists of feature extraction by LSTM Encoder, scenario clustering in feature domain by combining gap statistics method and K‐means++, and representative scenario reconstruction by using LSTM Decoder. Compared with traditional scenario selection and generation methods, the proposed method can better capture the patterns of multivariate time‐series data in both temporal and spatial dimensions. A case study in southwest China is used to demonstrate the effectiveness of the proposed method, which outperforms other existing methods by achieving the lowest SSE and DBI indices of 0.89 and 0.12, respectively, and obtaining the best SIL and CHI scores of 0.93 and 2.30, respectively, In addition, the case study shows the proposed model setup works more stable for scenario generation.
Molecular gas in the central region of NGC 7213
Authors: Salvestrini F. , Gruppioni C. , Pozzi F. , Vignali C. , Giannetti A. , Paladino R. , Hatziminaoglou E.
Published: August 2020

We present a multi-wavelength study (from X-ray to mm) of the nearby low-luminosity active galactic nucleus NGC 7213. We combine the information from the different bands to characterise the source in terms of contribution from the AGN and the host-galaxy interstellar medium. This approach allows us to provide a coherent picture of the role of the AGN and its impact, if any, on the star formation and molecular gas properties of the host galaxy. We focused our study on archival ALMA Cycle 1 observations, where the CO(2–1) emission line has been used as a tracer of the molecular gas. Using the 3DBAROLO code on ALMA data, we performed the modelling of the molecular gas kinematics traced by the CO(2–1) emission, finding a rotationally dominated pattern. The molecular gas mass of the host galaxy was estimated from the integrated CO(2–1) emission line obtained with APEX data, assuming an αCO conversion factor. Had we used the ALMA data, we would have underestimated the gas masses by a factor ∼3, given the filtering out of the large-scale emission in interferometric observations. We also performed a complete X-ray spectral analysis on archival observations, revealing a relatively faint and unobscured AGN. The AGN proved to be too faint to significantly affect the properties of the host galaxy, such as star formation activity and molecular gas kinematics and distribution.
Fly-by-Wire Actuation System Modeling and Force Fight Equalization Research
Authors: Tian Liang , Zhang Yanshan , Wang Haiwei
Published: August 2020

Aiming at the actuation system force fight problem resulted from active-active operational mode of fly-by-wire aircraft, and considering the technical maturity and reliability from safety aspect, the inertial integration algorithm and PI control law are established. After tradeoff study on these two methods, the PI control law is selected lastly.By physical model equivalent transformation, mechanical kinetics analysis, position closed-loop servo control modeling and AMEsim modeling and simulation analysis of the actuation system, the results show that using PI control can make the static force fight almost decrease to zero, make the dynamic force fight decrease to 1.288 9×106 Pa, 62.58% lower than requirement.It demonstrates the feasibility of the designed PI control law, and can be taken as the theoretic evidence of the forthcoming force fight equalization test on test rig.
SOM-Based High-Dimensional Design Spaces Mapping for Multi-Objective Optimization
Authors: Zhang Zebin , Zhang Pengfei , Li Ruizhen
Published: August 2020

Multi-objective optimization can reveal the complex parameter-objective relationships in the high-dimensional design problems. However, the data-extraction and data-presentation of the high-dimensional complex nonlinear system suffers from the increasing dimensionality. Key features and data-distribution of high-dimensional design spaces:parameter and objective spaces could be obtained by using Self-Organizing Maps (SOM) method, which re-clusters the high-dimensional multi-attribute data existing on the Pareto front into several low-dimensional maps. Correlations among all the design variables can be drawn according the colorized topological structure of the maps. Under the constraints including geometric structure and operating parameters, a low-cost and high accurate Kriging surrogate model was established to optimize a hybrid sliding bearing based on the sequential design method. Correlations between 3 objectives:"friction-to-load" ratio, temperature rise, instability threshold speed and 4 design parameters were extracted by SOM. Optimal feature regions were captured and analyzed. Results show that, within the specific feasible design space, supply pressure, axial bearing land width have important impact on the selected objectives, whereas the other parameters such as deep pocket depth and shallow pocket angle have relatively limited impact. A series of corresponding design decisions and optimization results help to understand the mechanism of the hybrid sliding bearing system in a much more intuitive way.
Preliminary investigations on extrusion of high viscosity slurry using direct writing technique
Authors: Tesfaye Kebede Ali , Balasubramanian Esakki , Praveen AS , Rohit Lade , Arvind Kumar
Published: August 2020

Traditionally solid propellants are manufactured using casting and molding techniques. The effective burning rate of solid propellants is strongly depended on its cross section and geometry. The preparation of mold and mandrel for the manufacturability of various geometric profiles are tedious, time consuming, increases the cost and more human efforts are needed. In order to mitigate these issues, a disruptive technology called additive manufacturing (AM) is in the verge of development. Although the method is effective, additional study must be conducted to improve the flow characteristics of slurries for the high solid loading and there is a huge necessity to reduce the prolonged curing time. The present study focuses on preliminary investigations of extrusion of high viscosity slurry using a pneumatically driven extrusion system. The slurry was prepared with a 80 wt.% solid loading of NaCl having particle sizes of 45 µm and 150 µm, 15.6 wt.% HTPB, 2.2 wt.% TDI, 2.2 wt.% DOA and 0.03 wt.% of ferric acrylacetonate. The slurry was extruded with an aid of pneumatically controlled extruder and each layer was formed. Formed by extruding the slurry using 1.65 mm internal diameter nozzle. Infrared (IR) heater was utilized to transfer the radiational energy for partial curing of each layer and thereby adhesion of other layer was guaranteed. Simulation is performed to determine the temperature distribution using ANSYS platform for comparing the curing temperature of the printed part top surface. Preliminary experiments confirm that extrusion of slurry and heating of each layer can be effectively achieved with the proposed 3D printing technique. Three tensile specimens were produced in accordance with ASTMD 412-C and their corresponding mechanical properties are evaluated. The printed parts have the tensile strength of 0.7 MPa, elongation of 4.85 % and modulus of elasticity of 18.5 MPa which are comparable with the properties of conventional casted part.
Preparation, analysis, and application of coated glass targets for the Wendelstein 7-X laser blow-off system
Authors: Wegner Th. , Geiger B. , Foest R. , Jansen van Vuuren A. , Winters V. R. , Biedermann C. , Burhenn R. , Buttenschön B. , Cseh G. , Joda I. , Kocsis G. , Kunkel F. , Quade A. , Schäfer J. , Schmitz O. , Szepesi T. ,   W7-X Team
Published: August 2020

Coated glass targets are a key component of the Wendelstein 7-X laser blow-off system that is used for impurity transport studies. The preparation and analysis of these glass targets as well as their performance is examined in this paper. The glass targets have a high laser damage threshold and are coated via physical vapor deposition with µm thick films. In addition, nm-thin layers of Ti are used as an interface layer for improved ablation efficiency and reduced coating stress. Hence, the metallic or ceramic coating has a lateral homogeneity within 2% and contaminants less than 5%, being optimal for laser ablation processing. With this method, a short (few ms) and well defined pulse of impurities with about 1017 particles can be injected close to the last closed flux surface of Wendelstein 7-X. In particular, a significant amount of atoms with a velocity of about 1 km/s enters the plasma within 1 ms. The atoms are followed by a negligible concentration of slower clusters and macro-particles. This qualifies the use of the targets and applied laser settings for impurity transport studies with the laser blow-off system in Wendelstein 7-X.
Second-shocked Hugoniot state of warm dense 6LiD: Quantum molecular dynamics simulations
Authors: Li Wei-Jie , Li Zi , Shi Yan-Bo , He Xian-Tu , Wang Cong , Zhang Ping
Published: August 2020

We use quantum molecular dynamics to systematically study the equation of state of 6LiD in the density range 1.76 to 3.68 g/cm3. The calculations involve the self-consistent determination of (a) the equation of state, (b) the principal and second-shocked Hugoniot curves, (c) the conductivity and reflectivity of the warm dense states, and (d) the electronic structure. Upon comparing our results with experiments, we find that the all-electron Li pseudopotential gives a better description of the second-shocked Hugoniot states than the Li pseudopotential with only 2s valence electrons. The optical conductivity increases with pressure along the principal Hugoniot curves. The atomic pair correlation functions reveal the order-to-disorder transition of 6LiD.
Maximum Markovian order detection for collective behavior
Authors: Zhang Yifan , Wu Ge , Liu Xiaolu , Yu Wenwu , Chen Duxin
Published: August 2020

Many advances have been achieved in the study of collective behavior of animal groups and human beings. Markovian order is a significant property in collective behavior, which reveals the inter-agent interaction strategy of the system. In this study, we propose a method using the time-series data of collective behavior to determine the optimal maximum Markov order of time-series motion data so as to reflect the maximum memory capacity of the interacting network. Our method combines a time-delayed causal inference algorithm and a multi-order graphical model. We apply the method to the data of pigeon flocks, dogs, and a group of midges to determine their optimal maximum order for validation and construct high-order De Bruijn graphs as a stochastic model to describe their interacting relationships. Most temporal network data of animal movements can be effectively analyzed by our method, which may provide a practical and promising solution to detection of the optimal maximum Markovian order of collective behavior.
Eradication of non-capacitive effects with potassium incorporation in perovskite solar cells
Authors: Raj Vidya , Sarkar Shaibal K.
Published: August 2020

The presence of redox reactions due to slow-moving ions at perovskite/contact interfaces is a major concern for the long-term stability of perovskite solar cells. In this work, we have evidently demonstrated the contribution of K+ ions on the removal of these non-capacitive effects that primarily accelerate the degradation mechanism in the devices. The intermittent current–voltage characteristics at the short-circuit conditions elucidate the role of K+ ions on reducing the rapid degradation at the interfaces due to the chemical reactivity of the accumulated ions by eliminating the burn-in decay in the photocurrent. Dark current–voltage measurements, time-resolved staircase voltammetry, and electrochemical impedance spectroscopy verified that both capacitive and non-capacitive currents, consequence of slow ion migration, are reduced by the incorporation of K+. Thus, this work signifies how K+ incorporation diminishes the internal degradation and enhances intrinsic stability of perovskite solar cells.
The singular limits of solutions to the Riemann problem for the liquid–gas two-phase isentropic flow model
Authors: Shen Chun
Published: August 2020

All the possible Riemann solutions are constructed in fully explicit forms for the one-dimensional inviscid liquid–gas two-phase isentropic flow model of drift-flux type. The concentration and cavitation phenomena are observed and investigated in the Riemann solutions when the pressure in the mixture momentum equation tends to zero. It is proved rigorously that the Riemann solution consisting of a 1-shock wave, 2-contact discontinuity, and 3-shock wave converges to a delta shock wave solution. By comparison, the Riemann solution consisting of a 1-rarefaction wave, 2-contact discontinuity, and 3-rarefaction wave converges to a solution consisting of 1-contact discontinuity, the vacuum state, and 3-contact discontinuity.
The effect of inter-pulse delay on the spectral emission and expansion dynamics of plasma in dual-pulse fiber-optic laser-induced breakdown spectroscopy
Authors: Qiu Yan , Wang Aosong , Liu Yanzhang , Huang Dapeng , Wu Jian , Li Jilong , Zhang Zhi , Li Xingwen , Wu Qingchao
Published: August 2020

The role of inter-pulse delay on plasma dynamics and spectral emission in dual-pulse fiber-delivery plasma has been investigated using fast imaging, optical emission spectroscopy, and laser shadowgraphy. The detection on the return spectrum in dual-pulse fiber-optic laser-induced breakdown spectroscopy showed that the self-reversal and self-absorption were reduced as the inter-pulse delay increased from 50 to 1000 ns. Using scanning electron microscopy, the ablation depth showed a changing trend of increasing first and then decreasing, and a maximum of ∼2.8 μm was achieved at 250-ns inter-pulse delay. Experimental results confirmed that the improvement was due to the reduction of the plasma thickness from 1.161 mm to 0.964 mm, and the calculation of electronic excitation temperature along the photon collection path showed that the excited atom densities became more spread, which both contributed to the self-absorption reduction. At a long inter-pulse delay, the plasma trailing edge would gradually separate from the target surface with a little further expansion distance of the leading edge, resulting in the reduction of plasma thickness after a time delay of several hundred nanoseconds. The heating of the peripheral cold particles by the second-generation plasma in the later expansion led to the rapid reduction of the peak temperature. Also, the early expansion trajectory of the second-generation plasma was tracked by laser shadowgraphy, which started to appear at an inter-pulse delay of 100 ns, and the average expansion velocity reached its maximum of ∼3.8 km/s.
Laser-plasma instabilities in long scale-length plasmas relevant to shock-ignition
Authors: Seaton A. G. , Arber T. D.
Published: August 2020

We present 2D particle-in-cell simulations of laser-plasma instabilities (LPI) performed using conditions relevant to experiments on the OMEGA and NIF laser facilities. The laser intensity used is 2×1015 W cm−2, which allows comparison with previous experiments and simulations investigating shock ignition, though this is a relatively low intensity for the scheme. We find that the large convective gain of the instabilities leads to dynamics that are largely controlled by pump depletion and to scattering or absorption by LPIs predominantly occurring away from the quarter-critical density. The two-plasmon decay (TPD) instability is dominant for OMEGA-type conditions and remains important at the NIF-scale. In both cases, most absorption from TPD occurs near its Landau cutoff density, and we examine its nonlinear dynamics in this region, focusing on the ion-acoustic waves responsible for saturation. For NIF-type conditions, stimulated Raman scattering (SRS) and stimulated Brillouin scattering divert significant fractions of laser energy, and we find that SRS backscatter can occur with high gain at low densities due to kinetic effects. An in-depth analysis of hot-electron production is performed to identify the main sources and their characteristic electron temperature. For both simulations presented, the overall hot-electron temperature lies between 30 and 35 keV. This is relatively low and will likely increase shock pressure; however, the distributions also contain a significant number of high-energy (Ek>100 keV) electrons that would likely cause unacceptable preheat. We, therefore, suggest some strategies that may be utilized to minimize this high-energy component.
Tuning field-emission characteristics of ZnO nanorods through defect engineering via O+ ion irradiation
Authors: Singh Avanendra , Senapati Kartik , Singh Ranveer , Rajput Parasmani , Som Tapobrata , Sahoo Pratap K.
Published: August 2020

Vertically aligned ZnO nanorods grown by a wet chemical method were implanted with O+ ions with three different ion fluences: (Φ)=5×1014, 5×1015, and 5×1016 ions/cm2. It is observed that the concentration of Oxygen vacancies (OV) introduced by implantation first increases from 25.94% to 54.76% with increasing Φ and decreases beyond Φ=5×1015 ions/cm2. We attribute this to the knocking out of oxygen atoms from the host matrix, which gets saturated due to the presence of an ample amount of O+ ions inside the host matrix beyond Φ=5×1015 ions/cm2 and further confirmed by extended x-ray absorption fine structure measurements. Therefore, the abundant OV becomes more delocalized followed by overlapping with the maxima of valence bands resulting in the narrowing of the bandgap of ∼0.4 eV. The appearance of an additional Raman peak at ∼575cm−1 in Raman spectra further confirmed the presence of impurity states. It is evident that at a fixed J=100 μA/cm2, the turn-on field increases from 3.61 V/μm to 6.61 V/μm with increasing Φ, and as a result of this, the field-enhancement factor (β) decreases. We attribute this increase in turn-on field as a consequence of charge trapping in deep-level states created by OV.
The motional Stark effect diagnostic reliably measures significant deviations in safety factor profile during DIII-D sawteeth
Authors: Heidbrink W. W. , Victor B. S.
Published: August 2020

Motional Stark effect data acquired during large fast-ion stabilized sawteeth are critically reexamined. The safety factor at the sawtooth crash changes by Δq≃0.15, much more than any likely errors.
On the problem of steady bifurcation of a falling sphere in a Navier–Stokes liquid
Authors: Galdi Giovanni P.
Published: August 2020

We study steady bifurcation for the coupled system body-liquid consisting of a sphere freely falling in a Navier–Stokes liquid under the action of gravity. In particular, we show that, under the assumption that for the bifurcating solution, the translational velocity of the sphere is parallel to the gravity, bifurcation takes place, provided that 1 is a simple eigenvalue of a suitable linear operator and the transversality property holds. Moreover, we also give sufficient conditions for symmetry breaking.
Size-dependent anomalous Hall effect in noncollinear antiferromagnetic Mn3Sn films
Authors: Bai Hua , Zhu Wenxuan , You Yunfeng , Chen Xianzhe , Zhou Xiaofeng , Pan Feng , Song Cheng
Published: August 2020

The coercive field of ferromagnets generally increases with decreasing the sample size to hundreds of nanometers mainly because of the (edge) defect pinning. We investigate size-dependent anomalous Hall effect (AHE) in (112¯0)-oriented noncollinear antiferromagnetic Mn3Sn films. The switching field (coercive field) of the AHE decreases abruptly when the width of the Hall bar decreases to hundreds of nanometers, giving rise to the reduced coercive field from 445 to 30 mT for Hall bar with width from 2 μm to 100 nm. This observation is in contrast to the ferromagnetic counterpart. The transition from a multidomain to single domain-like mode and the reduction of Néel temperature are proposed to explain the coercivity variation. Our finding provides a promising candidate for the device miniaturization and adds a different dimension to antiferromagnetic spintronics.
Improved evaluation of spin-polarization energy contributions using broken-symmetry calculations
Authors: David Grégoire , Ferré Nicolas , Trinquier Georges , Malrieu Jean-Paul
Published: August 2020

Spin-polarization effects may play an important role in free radicals and in the magnetic coupling between radical centers. Starting from restricted open-shell calculations, i.e., a closed-shell description of the non-magnetic core electrons, a low-order perturbation expansion identifies the spin-polarization contribution to the energy of mono-radicals and to singlet–triplet energy differences in diradicals. Broken-symmetry (BS) single-determinant calculations introduce only a fraction of spin-polarization effects, and in a biased manner, since BS determinants are not spin eigenfunctions. We propose a simple technique to correctly evaluate spin-polarization energies by taking into account the effect of spin-flip components on one-hole one-particle excited configurations. Spin-decontamination corrections are shown to play a non-negligible role in the BS evaluation of bond energies. The importance of spin decontamination is illustrated in cases for which spin polarization is the leading contribution to the singlet–triplet gap, which characterizes twisted conjugated double bonds and disjoint diradicals.
Multiphysics modeling of metal surface cleaning using atmospheric pressure plasma
Authors: Samaei Arash , Chaudhuri Santanu
Published: August 2020

An atmospheric pressure plasma (APP) system offers advanced, cost-effective processing routes for surface cleaning without a vacuum chamber. The appeal of APP systems in surface cleaning, however, is reduced by lack of a predictive link among the processing parameters, surface-plasma reactions, and plasma chemistry responsible for efficient removal. Here, we present a comprehensive multiphysics model of surface cleaning using a microwave assisted atmospheric plasma system as an alternative to chemical cleaning of surfaces. This model can quantitatively predict the processing time for the removal of the contaminant species from the surface. The presented model investigates the dependencies of removal rates and the nature of the contaminant species on the processing parameters. We demonstrate these dependencies by using polypropylene as a model hydrocarbon impurity. The complex and cooperative effects of microwave power, gas flow rate, torch-substrate distance, and tilt angle have been explored for understanding factors behind efficient cleaning. Our results show that the rate of hydrocarbon degradation is highly dependent on gas temperatures over the surface, flow pattern, and torch-substrate distance and depends less on the angle of attack. This study helps to optimize the values for operational parameters of atmospheric plasma processing that speeds up the experiments toward achieving a higher surface cleaning rate.
Brillouin zone center phonon modes in ZnGa2O4
Authors: Stokey Megan , Korlacki Rafał , Knight Sean , Hilfiker Matthew , Galazka Zbigniew , Irmscher Klaus , Darakchieva Vanya , Schubert Mathias
Published: August 2020

Infrared-active lattice mode properties of melt-grown high-quality single bulk crystals of ZnGa2O4 are investigated by combined spectroscopic ellipsometry and density functional theory computation analysis. The normal spinel structure crystals are measured by spectroscopic ellipsometry at room temperature in the range of 100 cm–1–1200 cm–1. The complex-valued dielectric function is determined from a wavenumber-by-wavenumber approach, which is then analyzed by the four-parameter semi-quantum model dielectric function approach augmented by impurity mode contributions. We determine four infrared-active transverse and longitudinal optical mode pairs, five localized impurity mode pairs, and the high frequency dielectric constant. All four infrared-active transverse and longitudinal optical mode pairs are in excellent agreement with results from our density functional theory computations. With the Lyddane–Sachs–Teller relationship, we determine the static dielectric constant, which agrees well with electrical capacitance measurements performed on similarly grown samples. We also provide calculated parameters for all Raman-active and for all silent modes and, thereby, provide a complete set of all symmetry predicted Brillouin zone center modes.
Hydroplastic response of a square plate due to impact on calm water
Authors: Abrahamsen B. C. , Alsos H. S. , Aune V. , Fagerholt E. , Faltinsen O. M. , Hellan Ø.
Published: August 2020

This paper investigates large, plastic deflections of a square plate due to impact on calm water. Most research in the area has examined linear elastic structural responses to such impact, but hydrodynamic responses during large, plastic deformations of engineering structures remain under-explored. A setup for an experimental drop test was designed for this purpose with equal emphasis on the hydrodynamical and structural mechanical aspects. Dual cameras were used to monitor the deforming plate from above during impact, and its deformation was tracked using a three-dimensional digital image correlation technique. The complex hydrodynamics of the impact were captured using a high-speed camera from below. The experimental results for flat impact showed a large air pocket under the deforming plate. The material properties of the plate were documented through separate tests. Hydroelastic theories were offered to account for large deformations and validated against the experimental results. Analytical hydroplastic theory shows that the maximum deflection is approximately equal to the velocity of impact times the square root of the ratio of the added mass to the plastic membrane capacity of the plate. An important source of error between the theory and the experiments was the effect of deceleration of the drop rig on deflection of the plate. This error was estimated using direct force integration and Wagner’s theory.
Progress and perspective on CsPbX3 nanocrystals for light emitting diodes and solar cells
Authors: Wu Yangqing , Wei Haoming , Xu Leimeng , Cao Bingqiang , Zeng Haibo
Published: August 2020

All-inorganic perovskite CsPbX3 nanocrystals (NCs) have made remarkable achievements in optoelectronic applications due to their enhanced stability, low-cost, easy-to-perform synthetic routes, broad emission spectra tunability, and high photoluminescence quantum yields, especially for light emitting diodes (LEDs) and solar cells (SCs). In this perspective, the structure and optoelectronic properties of CsPbX3 NCs are reviewed, and the recent research progresses in LEDs and SCs are presented. Finally, a brief outlook of this field is proposed to point out some important challenges and possible solutions.
More about hot electrons between cold walls
Authors: Kiramov Dmitrii I. , Breizman Boris N.
Published: August 2020

This paper adds new findings to the recently described hampering of electron cooling by electron trapping in a developing electrostatic potential well between the two cold walls [D. I. Kiramov and B. N. Breizman, Phys. Plasmas 27, 022302 (2020)]. We show that the self-consistent process of the potential well formation and electron trapping is tractable analytically when the end walls reflect most of the incoming electrons. For immobile ions, this process creates a steady-state that retains a significant fraction of the initial electron kinetic energy. We also describe the subsequent slow decay of the system due to ion motion.
Neural network potential from bispectrum components: A case study on crystalline silicon
Authors: Yanxon Howard , Zagaceta David , Wood Brandon C. , Zhu Qiang
Published: August 2020

In this article, we present a systematic study on developing machine learning force fields (MLFFs) for crystalline silicon. While the main-stream approach of fitting a MLFF is to use a small and localized training set from molecular dynamics simulations, it is unlikely to cover the global features of the potential energy surface. To remedy this issue, we used randomly generated symmetrical crystal structures to train a more general Si-MLFF. Furthermore, we performed substantial benchmarks among different choices of material descriptors and regression techniques on two different sets of silicon data. Our results show that neural network potential fitting with bispectrum coefficients as descriptors is a feasible method for obtaining accurate and transferable MLFFs.
Phase transformation and magnetocaloric effect of Co-doped Mn–Ni–In melt-spun ribbons
Authors: Yang Yiqiao , Li Zongbin , Sánchez-Valdés César Fidel , Sánchez Llamazares José Luis , Yang Bo , Zhang Yudong , Esling Claude , Zhao Xiang , Zuo Liang
Published: August 2020

Ribbon-shaped magnetocaloric materials are favorable to achieve high heat-transfer efficiencies due to their large specific surface area. In this work, Mn50Ni41−xIn9Cox (0 ≤ x ≤ 4) ribbons were prepared using a melt-spinning technique, and the corresponding phase transformation and magnetocaloric properties were studied. The large temperature gradient during melt-spinning caused the initial austenite in the ribbons to form typical columnar-shaped grains with a strong ⟨001⟩A preferred orientation perpendicular to the ribbon plane. After cooling, the ribbons undergo martensitic transformation from cubic austenite to monoclinic eight-layered modulated (8 M) martensite. High angle annular dark field-scanning transmission electron microscopy observations indicate that martensite lattice modulation is inhomogeneous at atomic scales. Co substitution for Ni not only strongly influences the phase transformation temperatures but also greatly enhances ferromagnetic coupling. As a result, an enlarged magnetization difference across the martensitic transformation under a field change of 5 T in the Mn50Ni38In9Co3 ribbon induces a large magnetic entropy change up to 12.1 J kg−1 K–1 and a refrigeration capacity of 197 J kg–1 around room temperature. In addition, a wide operational temperature region up to 31 K is obtained in the Mn50Ni37In9Co4 ribbon due to the enhanced sensitivity of the transformation temperature shift under a magnetic field.
Electrokinetic membrane pumping flow model in a microchannel
Authors: Tripathi Dharmendra , Narla V. K. , Aboelkassem Yasser
Published: August 2020

A microfluidic pumping flow model driven by electro-osmosis mechanisms is developed to analyze the flow characteristics of aqueous electrolytes. The pumping model is designed based on a single propagative rhythmic membrane contraction applied on the upper wall of a microchannel. The flow lubrication theory coupled with a nonlinear Poisson–Boltzmann equation is used to model the microchannel unsteady creeping flow and to describe the distribution of the electric potential across the electric double layer. A generic solution is obtained for the Poisson–Boltzmann equation without the Debye–Hückel linearization. The effects of zeta potential, Debye length, and electric field on the potential distribution, pressure distribution, velocity profiles, shear stress, and net flow rate are computed and interpreted in detail. The results have shown that this electrokinetic membrane pumping model can be used to understand microlevel transport phenomena in various physiological systems. The proposed model can also be integrated with other microfluidic devices for moving microvolume of liquids in artificial capillaries used in modern biomedical applications.
Quantum imaging for the semiconductor industry
Authors: Paterova Anna V. , Yang Hongzhi , Toa Zi S. D. , Krivitsky Leonid A.
Published: August 2020

Infrared (IR) imaging is one of the significant tools for the quality control measurements of fabricated samples. Standard IR imaging techniques use direct measurements, where light sources and detectors operate in the IR range. Due to the limited choices of IR light sources or detectors, challenges in reaching specific IR wavelengths may arise. In our work, we perform indirect IR microscopy based on the quantum imaging technique. This method allows us to probe the sample with IR light, while the detection is shifted into the visible or near-IR range. Thus, we demonstrate IR quantum imaging of the silicon chips at different magnifications, wherein a sample is probed at a 1550 nm wavelength, but the detection is performed at 810 nm. We also analyze the possible measurement conditions of the technique and estimate the time needed to perform quality control checks of samples.
Experimental and analytical investigation of meso-scale slug bubble dynamics in a square capillary channel
Authors: Azadi Reza , Wong Jaime , Nobes David. S.
Published: August 2020

The flow of dispersed gas bubbles in a viscous liquid can create a bubbly, slug bubble, or elongated bubble flow regime. A slug bubble flow, characterized by bubble sizes equal to the hydraulic diameter of the channel, is a transition regime with a complex local flow field that has received little attention in the past. In this study, dynamics of this flow regime in a square capillary with a cross-sectional area of 3 × 3 mm2 was studied analytically and experimentally. The main geometric parameters of the flow field, such as film and corner thicknesses and volume fraction, were calculated for different flow conditions based on a semi-empirical approach. Using velocity fields from particle image velocimetry (PIV), combined with the analytical equations derived, local mean variations of the film and corner flow thicknesses and velocity were analyzed in detail. Analysis of the results reveals a linear relation between the bubble speed and the liquid slug velocity that was obtained using sum-of-correlation PIV. Local backflow, where the liquid locally flows in the reverse direction, was demonstrated to occur in the slug bubble flow, and the theoretical analysis showed that it can be characterized based on the bubble cross-sectional area and ratio of the liquid slug and bubble speed. The backflow phenomenon is only contributed to the channel corners, where the speed of liquid can increase to the bubble speed. However, there is no evidence of reverse flow in the liquid film for the flow conditions analyzed in this study.
A coaxial-type pulsed arc plasma doping process for the lithium-ion thin-film electrolyte application
Authors: Wang Min-Chuan , Tsai Ding-Guey , Yeh Yu-Lin , Li Yu-Chen
Published: August 2020

A combinatorial lithium-ion thin-film electrolyte deposition process that uses different types of arc plasma sources has been developed for thin-film inorganic complementary electrochromic devices (ECDs). With the coaxial-type pulsed arc plasma doping process, the lithium doping tantalum pentoxide (Ta2O5:Li) thin-film electrolyte doped with two different frequencies has been investigated. Although a lower ion conductivity of 9.30 × 10−9 S/cm has been obtained with the Ta2O5:Li doped with the arc discharge frequency of 1 Hz than the arc discharge frequency of 4 Hz, the ECD has demonstrated a better optical modulation (ΔT) of 58.25%. To analyze the detailed material characteristic, the ion mobility and concentration have also been extracted from the Li drift current by the current–voltage (I–V) measurement with the isothermal transient ionic current method. The optimal Ta2O5:Li doped with the arc discharge frequency of 1 Hz has demonstrated a higher ion mobility of 8.22 × 10−10 cm2/V s and a lower concentration of 7.07 × 1019 cm−3. As a result, the electrolyte with higher ion mobility and lower concentration is more important than the higher ion conductivity for ECD applications.
Width-induced metal–insulator transition in SrVO3 lateral nanowires spontaneously formed on the ultrathin film
Authors: Oka Hirofumi , Okada Yoshinori , Kaminaga Kenichi , Oka Daichi , Hitosugi Taro , Fukumura Tomoteru
Published: August 2020

We investigated lateral nanowires at the topmost layer of SrVO3 (001) ultrathin films using in situ low-temperature scanning tunneling microscopy and spectroscopy. The nanowires were spontaneously formed in the topmost layer of SrVO3 with a (√2 × √2)-R45° reconstruction on the terrace of a (√5 × √5)-R26.6° reconstruction. The electronic states of nanowires were significantly influenced by the nanowire width. With reducing the nanowire width from 5.5 nm to 1.7 nm, the zero-bias conductance of nanowires steeply decreased toward zero, exhibiting a metal–insulator transition possibly driven by dimensional crossover, previously observed in thickness-reduced SrVO3 ultrathin films.
A matrix completion algorithm to recover modes orthogonal to the minimum energy path in chemical reactions
Authors: Quiton Stephen Jon , Mitra Urbashi , Mallikarjun Sharada Shaama
Published: August 2020

Structured statistical methods are promising for recovering or completing information from noisy and incomplete data with high fidelity. In particular, matrix completion exploits underlying structural properties such as rank or sparsity. Our objective is to employ matrix completion to reduce computational effort associated with the calculation of multiple quantum chemical Hessians, which are necessary for identification of temperature-dependent free energy maxima under canonical variational transition state theory (VTST). We demonstrate proof-of-principle of an algebraic variety-based matrix completion method for recovering missing elements in a matrix of transverse Hessian eigenvalues constituting the minimum energy path (MEP) of a reaction. The algorithm, named harmonic variety-based matrix completion (HVMC), utilizes the fact that the points lying on the MEP of a reaction step constitute an algebraic variety in the reaction path Hamiltonian representation. We demonstrate that, with as low as 30% random sampling of matrix elements for the largest system in our test set (46 atoms), the complete matrix of eigenvalues can be recovered. We further establish algorithm performance for VTST rate calculations by quantifying errors in zero-point energies and vibrational free energies. Motivated by this success, we outline next steps toward developing a practical HVMC algorithm, which utilizes a gradient-based sampling protocol for low-cost VTST rate computations.
Chimera-like behavior in a heterogeneous Kuramoto model: The interplay between attractive and repulsive coupling
Authors: Frolov Nikita , Maksimenko Vladimir , Majhi Soumen , Rakshit Sarbendu , Ghosh Dibakar , Hramov Alexander
Published: August 2020

Interaction within an ensemble of coupled nonlinear oscillators induces a variety of collective behaviors. One of the most fascinating is a chimera state that manifests the coexistence of spatially distinct populations of coherent and incoherent elements. Understanding of the emergent chimera behavior in controlled experiments or real systems requires a focus on the consideration of heterogeneous network models. In this study, we explore the transitions in a heterogeneous Kuramoto model under the monotonical increase of the coupling strength and specifically find that this system exhibits a frequency-modulated chimera-like pattern during the explosive transition to synchronization. We demonstrate that this specific dynamical regime originates from the interplay between (the evolved) attractively and repulsively coupled subpopulations. We also show that the above-mentioned chimera-like state is induced under weakly non-local, small-world, and sparse scale-free coupling and suppressed in globally coupled, strongly rewired, and dense scale-free networks due to the emergence of the large-scale connections.
Microbial communities of upland peat swamps were no different 1 year after a hazard reduction burn
Authors: Christiansen Nicole A. , Fryirs Kirstie A. , Green Timothy J. , Hose Grant C.
Published: August 2020

Fire in wetlands is poorly understood, yet hazard reduction burns are a common management practice and bushfires are becoming increasingly prevalent because of climate change. Fire may have long-lasting implications for the microbial component of these wetland ecosystems that regulate carbon and nutrient cycling. The extremely fire-prone Blue Mountains World Heritage Area in south-eastern Australia contains hundreds of endangered peat-forming upland swamps that regularly experience both bushfires and hazard reduction burns. In a before–after control–­impact study, we surveyed the sediment microbial community of these swamps to test the impact of a low-intensity hazard reduction burn. Along with sediment pH, moisture and organic content, we measured gene abundances including those relating to carbon cycling (quantitative PCR (qPCR) of pmoA, mcrA, bacterial 16S rRNA and archaeal 16S rRNA), and bacteria community fingerprint (terminal restriction fragment length polymorphism (T-RFLP)). One year after the hazard reduction burn, there were no significant differences in the gene abundances or microbial community fingerprint that could be attributed to the fire, suggesting that the hazard reduction burn did not have a long-term impact on these microbial communities.
Brain circuits signaling the absence of emotion in body language
Authors: Sokolov Arseny A. , Zeidman Peter , Erb Michael , Pollick Frank E. , Fallgatter Andreas J. , Ryvlin Philippe , Friston Karl J. , Pavlova Marina A.
Published: August 2020

Significance

How do we infer absence of emotion? As opposed to the brain mechanisms for recognizing emotions, this issue has remained underinvestigated. Present findings bond communication between the amygdala and insula with the ability to infer the absence of emotion in body language. Previously, both the amygdala and insula have been associated with emotion perception. The outcome of this study extends the conceptualization of these brain regions and their interplay to the processing of social signals without emotional content. This may have wide-ranging implications for better understanding neuropsychiatric conditions characterized by misinterpretation of neutral for emotional signals, such as depression or schizophrenia. The findings call for interdisciplinary research on how the brain infers the lack of emotional valence in social signals.
Neological cancer metaphors in the Chinese cyberspace
Authors: Lang Jun
Published: August 2020

This study examines emerging cancer metaphors that are encoded as a neological construction [X-ái‘cancer’] using corpus data retrieved from Chinese social media. The quantitative findings show that [X-ái] is a highly productive construction where the open slot X attracts a wide variety of lexical items. The qualitative findings are twofold. First, the central meaning of this construction is to express subjective feelings such as self-mockery (e.g., laziness cancer) and contempt for other people’s behaviors in gender discourse (e.g.. straight man cancer). Second, the development of this construction is caused by the exemplar-based cognitive mechanism through social labeling practices. I argue that this neological language use is employed to convey collective emotions in gender discourse and that it indexes a group style, either playful and humorous or contemptuous and disparaging, both of which construct language user identity and sociocultural ideology in the Chinese cyberspace. This study has implications for research on neological metaphors and for language use in digital culture in general.
Morphologically Derived Adjectives in Spanish
Authors: Fábregas Antonio
Published: August 2020

This is the first book that presents a complete empirical description and theoretical analysis of all major classes of derived adjectives in Spanish, both deverbal and denominal. The reader will find here both a detailed empirical description of the syntactic, morphological and semantic properties of derived adjectives in contemporary Spanish and a cohesive Neo-Constructionist analysis of the syntactic and semantic tools that contemporary Spanish has available to build adjectives from other grammatical categories within a Nanosyntactic-oriented framework. In doing so, this book sheds light on the nature of adjectives as a grammatical category and argues that adjectives are syntactically built by recycling functional heads belonging to other categories. The book will be useful both to researchers in Spanish linguistics or theoretical morphology and to advanced students of Spanish interested in the main ways of building new adjectives through suffixation in this language.