bluuebunny/crossref_metadata_2025 huggingface dataset:
New anomalies in copper-based spin-glass Cu+Fe and Cu+Mn alloys: Hall Effect and EPR
Authors: Tsapin A. I. , Cherenkov V. A. , Burbaev D. Sh. , Khangulov S. V.
Published: December 2024

Measurements have been made of the resistance, Hall effect, magnetic susceptibility and EPR spectrum of spin glasses based on copper with iron and manganese impurities at temperatures of 4.2−60 °K in magnetic fields up to 13 T. Maxima have been seen in the Hall effect, the magnetic susceptibility, and the anisotropy of the EPR. The anomalies are explained within the framework of the BMW theory.
Temperature dependence of the electrical resistivity of metals in the intermediate temperature range
Authors: Merisov B. A. , Ermolaev A. M. , Krasnokutskii A. V. , Khotkevich V. I.
Published: December 2024

It is shown that the nonlinearity of the temperature dependence of the electrical resistivity of nonferromagnetic metals in the 70−300 °K range is not an anomaly but is determined by the presence of an inflection on the ρ (T) curve for Tp ∼ 0.36 Θ, which is already contained in the simplest Bloch–Gruneisen formula.
The effect of mechanical twinning on the T
c of vanadium
Authors: Gindin I. A. , Sokolenko V. I. , Starodubov Ya. D. , Lazareva M. B.
Published: December 2024

The effects of unidirectional and sign-alternating torsional deformation at 4.2 °K on the superconducting transition temperature of vanadium have been studied. A nonmonotonic variation of Tc with the degree of deformation was found: The initial sharp growth was replaced by a gradual decrease but Tc remained above the initial value up to destruction of the sample. The maximum growth of Tc was 0.43 °K. The structure of the sample surface was studied and it was shown that the deformation of vanadium during its initial stages occurs largely by mechanical twinning. It is concluded that the reason for the increase of Tc for vanadium is the appearance of twin layers with a high compressive stress in the neighborhood of their boundaries during the process of low-temperature deformation.
Symmetry and spin-flip transitions in antiferromagnetic crystals
Authors: L’vov V. A. , Yablonskiĭ D. A.
Published: December 2024

A symmetry analysis of spin-flip transitions (collapse of magnetic moments of sublattices in an external magnetic field) in antiferromagnetic crystals is performed. The directions of the magnetic field in which a spin-flip transition (SFT) can be observed are found for all crystallographic classes. It appears that depending on the specific crystallomagnetic structure of the antiferromagnet, three groups can be separated. In the first group, SFT can occur with any orientation of the external magnetic field H, in the second the SFT must be observed only for certain orientations of H, and in the third the SFT is absent for any orientation of H. The relativistic interactions that destroy the spin-flip phase are indicated for each specific case. It is also shown that in a certain group of antiferromagnets belonging to the trigonal, hexagonal, and cubic syngonies SFT occurs as a first-order phase transition. In antiferromagnetic crystals belonging to the crystalline classes Cn, Dn (n = 3, 4, 6), T, and O, the phase diagram contains a line of phase transitions that separates the spin-flip phase and the spatially nonuniform, noncollinear phase.
Analyzing adjustment and verification errors in electric metering devices for smart power systems considering multiple environmental factors
Authors: He Chuanliang , Xia Xin , Zhang Bo , Kang Wei , Zhang Jinxia , Chen Haipeng
Published: December 2024

Environmental conditions can greatly influence the precision of electric metering devices, resulting in heightened measurement errors. This paper presents a correction model for electric metering equipment, considering a range of environmental influences. Initially, the potential impacts of various environmental elements on electric metering devices are analyzed. Subsequently, mutual information methods are employed to screen out the environmental factors with significant influence on the electric metering devices. Then, an error adjustment model based on gated recurrent unit-attention is constructed, and the particle swarm optimization algorithm is adopted for the purpose of optimizing hyperparameters. Ultimately, various evaluation metrics are selected, followed by experimental validation to confirm the suggested method’s efficacy. Case studies demonstrate the proposed method performs well across different seasons, with the lowest RMSE reaching 1.24.
Using the Metropolis algorithm to explore the loss surface of a recurrent neural network
Authors: Casert Corneel , Whitelam Stephen
Published: December 2024

In the limit of small trial moves the Metropolis Monte Carlo algorithm is equivalent to gradient descent on the energy function in the presence of Gaussian white noise. This observation was originally used to demonstrate a correspondence between Metropolis Monte Carlo moves of model molecules and overdamped Langevin dynamics, but it also applies in the context of training a neural network: making small random changes to the weights of a neural network, accepted with the Metropolis probability, with the loss function playing the role of energy, has the same effect as training by explicit gradient descent in the presence of Gaussian white noise. We explore this correspondence in the context of a simple recurrent neural network. We also explore regimes in which this correspondence breaks down, where the gradient of the loss function becomes very large or small. In these regimes the Metropolis algorithm can still effect training, and so can be used as a probe of the loss function of a neural network in regimes in which gradient descent struggles. We also show that training can be accelerated by making purposely-designed Monte Carlo trial moves of neural-network weights.
Reevaluating erosion of wind turbine blades in wind-blown sand environments: Insights into particle collision areas and density
Authors: Huang Haojie , Bian Ye , Tong Guosong , Liu Hongyou , Wang Yan
Published: December 2024

Severe sand and dust storms are prevalent in western China, causing erosion of wind turbine blades and reducing their aerodynamic efficiency. Existing studies mostly use outcome-based approaches to analyze the power loss in wind turbines due to modifications in blade aerodynamic profiles, lacking in-depth research into the underlying mechanisms of these aerodynamic profile changes. This study explores the coupling between continuous and discrete phases and investigates the energy dissipation following particle-blade collisions. Collision areas and particle-blade density are analyzed under varying particle sizes and attack angles employing unsteady methods and stochastic trajectory models. Results indicate that collisions primarily occur at the blade's leading edge, yet a band-shaped area with minimal collision concentration forms at the intersection of the leading edge's suction and pressure sides due to leading edge separation, elucidating why the leading-edge tip is not the most heavily worn area initially. As particle size increases, this low-collision band widens, and the collision area shifts from the pressure side to the suction side, with fewer multiple collisions. Different attack angles reveal the blade tip endures the most collisions, followed by the pressure side, providing a theoretical framework for aerodynamic profile adjustments and offers insights for blade profile protection and restoration.
Monomer size effect in inelastic collisional dynamics of non-equilibrium soot nucleation
Authors: Morozov Alexander N. , Mebel Alexander M. , Frenklach Michael
Published: December 2024

Molecular dynamics (MD) simulations of the collisional dynamics of the coronene–acepyrene and coronene radical–acepyrene pairs have been carried out to investigate the size effect of monomers of polycyclic aromatic hydrocarbons (PAH) on their non-equilibrium dimerization. The results compared to the previous MD simulations of the smaller pyrene–acepyrene and pyrenyl–acepyrene systems corroborate the non-equilibrium hypothesis of crosslinking PAH dimerization enhanced by physical interaction between the monomers. The phenomenon of inelastic collisional dynamics responsible for non-equilibrium van der Waals dimerization, which fosters a covalent bond formation between the monomers, amplifies with increasing PAH size. The increase in the size of the colliding monomers enhances the non-equilibrium effects as the growing pool of low-frequency modes provides a larger sink for the energy of the colliding PAH monomers. Based on the direct count of the crosslinking reaction events observed in the MD simulations, the forward rate constant for the coronene radical–acepyrene association is estimated at ∼10−11 cm3 molecule−1 s−1, showing a 15-fold increase with respect to the value from the statistical Rice–Ramsperger–Kassel–Marcus calculations. A comparison with the eightfold increase reported previously for the pyrenyl–acepyrene system shows that the statistical (equilibrium-based) calculations increasingly underestimate the reaction rate with the increasing size of the interacting PAHs from pyrene to coronene. The total increase of the MD-assessed rate constant for the coronene radical–acepyrene dimerization reaction as compared to pyrenyl–acepyrene is a factor of 2.4, with the overall collision efficiency to produce dimerized products growing by 30%.
Probing electron trapping by current collapse in GaN/AlGaN FETs utilizing quantum transport characteristics
Authors: Abe Takaya , Shinozaki Motoya , Matsumura Kazuma , Aizawa Takumi , Kumasaka Takeshi , Ito Norikazu , Tanaka Taketoshi , Nakahara Ken , Otsuka Tomohiro
Published: December 2024

GaN is expected to be a key material for next-generation electronics due to its interesting properties. However, current collapse poses a challenge to the application of GaN FETs to electronic devices. In this study, we investigate the formation of quantum dots in GaN FETs under current collapse. By comparing the Coulomb diamond between standard measurements and those under current collapse, we find that the gate capacitance is significantly decreased under current collapse. This suggests that the current collapse changes the distribution of trapped electrons at the device surface, as reported in the previous study by operando x-ray spectroscopy. In addition, we show external control of quantum dot formation, previously challenging in an FET structure, by using current collapse.
Monolithic β-Ga2O3 bidirectional dual-gate MOSFET
Authors: Sharma Pooja , Chakrabarty Poulomi , Prajapati Prabhat , Sen Sera , Lodha Saurabh
Published: December 2024

We report a monolithic bidirectional dual-gate metal–oxide–semiconductor field-effect transistor fabricated on epitaxially grown β-Ga2O3, demonstrating efficient two-way conduction and blocking. It features two independently controlled gates and operates in four distinct modes, offering flexibility in managing current and voltage in the first and third quadrants. This versatility makes it ideal for various power conversion system applications. The device operates at a low negative threshold voltage (∼−2.4 V for both gates), with a zero turn-on drain voltage and an on-resistance of approximately 500 Ω· mm. It exhibits a high on/off current ratio of 107 in all three conducting modes. In the blocking mode, the device breakdown was measured to be higher than ± 400 V. The estimated breakdown field and power figure of merit for the device are 0.4 MV/cm and 2.1 MW/cm2, respectively.
Predicting solvation free energies with an implicit solvent machine learning potential
Authors: Röcken Sebastien , Burnet Anton F. , Zavadlav Julija
Published: December 2024

Machine learning (ML) potentials are a powerful tool in molecular modeling, enabling ab initio accuracy for comparably small computational costs. Nevertheless, all-atom simulations employing best-performing graph neural network architectures are still too expensive for applications requiring extensive sampling, such as free energy computations. Implicit solvent models could provide the necessary speed-up due to reduced degrees of freedom and faster dynamics. Here, we introduce a Solvation Free Energy Path Reweighting (ReSolv) framework to parameterize an implicit solvent ML potential for small organic molecules that accurately predicts the hydration free energy, an essential parameter in drug design and pollutant modeling. Learning on a combination of experimental hydration free energy data and ab initio data of molecules in vacuum, ReSolv bypasses the need for intractable ab initio data of molecules in an explicit bulk solvent and does not have to resort to less accurate data-generating models. On the FreeSolv dataset, ReSolv achieves a mean absolute error close to average experimental uncertainty, significantly outperforming standard explicit solvent force fields. Compared to the explicit solvent ML potential, ReSolv offers a computational speedup of four orders of magnitude and attains closer agreement with experiments. The presented framework paves the way for deep molecular models that are more accurate yet computationally more cost-effective than classical atomistic models.
A platform for non-local thermodynamic equilibrium atomic physics research using the buried layer target approach at a kJ level laser facility
Authors: Fraenkel M. , Marley E. V. , Ehrlich Y. , Henis Z. , Emig J. , Meir A. , Ferber Y. , Guttman D. , Strum G. , Kartoon D.
Published: December 2024

We present a design and first use of a kJ level laser facility for research of non-local thermodynamic equilibrium atomic physics using the buried layer target method. The target design included a metal layer buried inside a plastic tamper with thicknesses tailored to the expected laser intensities. The target was illuminated from each side by two laser beams with intensities of 0.5–5 × 1014 W/cm2. The advanced diagnostic suite included static and time-resolved imagers and spectrometers with various spectral resolutions. A 3D printed dual elliptically curved spectrometer is presented, and its results are compared to a traditional crystal spectrometer. Experimental results and radiation hydrodynamic simulations demonstrate that the target achieved the desired thermodynamic conditions of ne ≈ 1021–1022 cm−3 and Te ≈ 1–2 keV.
ZrTe3/PdSe2 vis-NIR detectors with Schottky barrier enhanced photovoltaic performance
Authors: Ding Guanchu , Zhang Yating , Feng Chunmeng , Li Mengyao , Zheng Aosheng , Yang Fan , Zhao Zhengyi , Tan Qi , Ren Huanyu , Liu Yanyan , Xu Hang , Yao Jianquan
Published: December 2024

Infrared photodetectors (PDs), particularly the near-infrared (NIR) PDs, are essential for applications in remote sensing, night vision, imaging, and so on. ZrTe3, a semimetallic transition metal trichalcogenide with zero bandgap, strong anisotropy, and enhanced conductivity, is emerging as a promising material for NIR PDs, provided that the noise can be effectively suppressed. The solution lies in constructing an appropriate barrier. PdSe2, a typical two-dimensional material with a layer-dependent bandgap is an excellent choice. By constructing a VdW heterostructure with ZrTe3 and six-layer PdSe2, a Schottky barrier is introduced to block photogenerated holes in ZrTe3, resulting in a five-order-of-magnitude reduction in dark current and an enhanced photovoltaic response. The ZrTe3/PbSe2 PD exhibits a self-powered photovoltaic response from 405 nm to 1.55 μm with a peak responsivity of 1.16 × 106 V/W, a rise/fall time of 58/66 μs, a 3 dB frequency of 4.6 kHz, and a linear polarization ratio of 3.15 at 808 nm. The strategy of introducing a Schottky barrier to semimetal-based PDs addresses the issues of high noise and biased working conditions, paving the way for high-performance semimetallic PDs in the NIR range.
Anisotropic magnetocapacitance of antiferromagnetic cycloids in BiFeO3
Authors: Winkler M. , Geirhos K. , Tyborowski T. , Tóth B. , Farkas D. G. , White J. S. , Ito T. , Krohns S. , Lunkenheimer P. , Bordács S. , Kézsmárki I.
Published: December 2024

Distinguishing different antiferromagnetic domains by electrical probes is a challenging task, which in itinerant compounds can be achieved, e.g., via the anisotropic magnetoresistance. Here, we demonstrate that in insulators, the anisotropic magnetocapacitance can be exploited for the same purpose. We studied the magnetic field dependence of the dielectric response in BiFeO3, one of the few room-temperature multiferroics. We observed a sizeable dielectric anisotropy upon the rotation of the modulation vector of the antiferromagnetic cycloid in the plane normal to the rhombohedral axis. Importantly, this anisotropy is characteristic of the cycloidal mono-domain state even in zero magnetic field, thus facilitating the determination of the antiferromagnetic domain population. This approach can be utilized to electrically distinguish between antiferromagnetic domains even in complex magnets, such as modulated spin structures, via the magnetodielectric coupling.
p-orbital-dependent ferrovalley characteristic in MXene Lu3N2O2
Authors: Zhang Wentao , Zhang Jianping , Ji Weixiao , Ren Miaojuan , Wang Yaping , Li Shengshi , Yan Shishen
Published: December 2024

Two-dimensional ferrovalley materials, which simultaneously exhibit ferromagnetism and valley polarization, have garnered substantial interest in recent years due to their fascinating physical properties and potential applications. However, the ferrovalley materials currently discovered are predominantly based on d orbitals. In this work, using first-principles calculations, we predict an exceptionally rare p-orbital-dependent ferrovalley characteristic in the MXene Lu3N2O2 monolayer. The monolayer shows intrinsic ferromagnetism contributed by the N-2p orbital with a magnetic moment of 1μB/u.c. Such 2p magnetism can be interpreted by the double exchange coupling between N anions mediated by the middle Lu cation. Owing to the simultaneous breaking of spatial inversion symmetry and time-reversal symmetry, the out-of-plane magnetization and spin–orbit coupling result in a sizable valley polarization of 80.93 meV in the conduction band for the monolayer. Notably, the energy dispersions that exhibit valley polarization are chiefly governed by the N-2p orbital, accompanied by a high Fermi velocity and a small effective electron mass. The demonstrated valley contrasting Berry curvature ensures that the monolayer can give rise to the anomalous valley Hall effect (AVHE) through electron doping, with the doping concentration evaluated in the range of 0.02–0.08 e/u.c. In addition to effectively modulating the magnitude of valley polarization, biaxial strain can also trigger the self-doping phenomenon, thereby enabling the monolayer to generate the AVHE independently of external electron doping. Our findings provide a more promising platform for valleytronic applications and significantly enrich the ferrovalley material family.
Nuclear quantum effects on glassy water under pressure: Vitrification and pressure-induced transformations
Authors: Eltareb Ali , Khan Bibi A. , Lopez Gustavo E. , Giovambattista Nicolas
Published: December 2024

We perform classical molecular dynamics (MD) and path-integral MD (PIMD) simulations of H2O and D2O using the q-TIP4P/F model over a wide range of temperatures and pressures to study the nuclear quantum effects (NQEs) on (i) the vitrification of liquid water upon isobaric cooling at different pressures and (ii) pressure-induced transformations at constant temperature between low-density amorphous and high-density amorphous ice (LDA and HDA) and hexagonal ice Ih and HDA. Upon isobaric cooling, classical and quantum H2O and D2O vitrify into a continuum of intermediate amorphous ices (IA), with densities in-between those of LDA and HDA (depending on pressure). Importantly, the density of the IA varies considerably if NQEs are included (similar conclusions hold for ice Ih at all pressures studied). While the structure of the IA is not very sensitive to NQE, the geometry of the hydrogen-bond (HB) is. NQE leads to longer and less linear HB in LDA, HDA, and ice Ih than found in the classical case. Interestingly, the delocalization of the H/D atoms is non-negligible and identical in LDA, HDA, and ice Ih at all pressures studied. Our isothermal compression/decompression MD/PIMD simulations show that classical and quantum H2O and D2O all exhibit LDA–HDA and ice Ih-HDA transformations, consistent with experiments. The inclusion of NQE leads to a softer HB-network, which lowers slightly the LDA/ice Ih-to-HDA transformation pressures. Interestingly, the HB in HDA is longer and less linear than in LDA, which is counterintuitive given that HDA is ≈25% denser than LDA. Overall, our results show that, while classical computer simulations provide the correct qualitative phenomenology of ice and glassy water, NQEs are necessary for a quantitative description.
Liquid, liquid crystal, and crystal states of different shaped colloids in nonuniform fields via osmotic force balance
Authors: Zhang Lechuan , Pellicciotti Alec J. , Sandag Michelle , Bevan Michael A.
Published: December 2024

We report a model to predict equilibrium density profiles for different shaped colloids in two-dimensional liquid, nematic, and crystal states in nonuniform external fields. The model predictions are validated against Monte Carlo simulations and optical microscopy experiments for circular, square, elliptical, and rectangular colloidal particles in AC electric fields between parallel electrodes. The model to predict the densities of all states of different shaped particles is based on a balance of the local quasi-2D osmotic pressure against a compressive force due to induced dipole-field interactions. The osmotic force balance employs equations of state for hard ellipse liquid, nematic, and crystal state osmotic pressures, which are extended to additional particle shapes. The resulting simple analytical model is shown to accurately predict particle densities within liquid, liquid crystal, and crystal states for a broad range of particle shapes, system sizes, and field conditions. These findings provide a basis for quantitative design and control of fields to assemble and reconfigure colloidal particles in interfacial materials and devices.
DensToolKit2: A comprehensive open-source package for analyzing the electron density and its derivative scalar and vector fields
Authors: Solano-Altamirano J. M. , Hernández-Pérez Julio M. , Sandoval-Lira J. , Barroso-Flores J.
Published: December 2024

In this article, we provide details of the suite DensToolKit-v2, which consists of a set of cross-platform, optionally parallelized programs for analyzing the molecular electron density (ρ), as well as different fields and chemical indices derived from it. Notably, with this version, the user can compute the Non-Covalent Interaction index, the Density Overlap Regions Index, and fields related to single-spin-type molecular orbitals, such as the spin density. In addition, DensToolKit-v2 includes several programs for analyzing other less-known fields, such as the Density Matrix of order 1, the two-electron pair density function, and the Fourier transforms of these fields, that is, functionals in momentum space. A new sub-program to compute integrated properties of each of the fields released in the suite is included. A simple graphical user interface is released, which eases the visualization of ρ critical points topology. Most interestingly, this version includes a program that renders estimations of pKa’s of carboxylic acids and pKb’s of amines (primary, secondary, and tertiary) through refined relations between experimental data and the molecular electrostatic potential computed at isosurfaces of ρ. Details related to the speed of the programs and a few examples of how to use the program in workflows are discussed, and the source code is released through a git repository under the GPLv3 terms.
Ferroelectric properties of HfAlOx-based ferroelectric memristor devices for neuromorphic applications: Influence of top electrode deposition method
Authors: Park Woohyun , Park Yongjin , Kim Sungjun
Published: December 2024

In this study, we compare the performance of ferroelectric memristor devices based on the fabrication method for the top electrode, focusing on atomic layer deposition (ALD) and physical vapor deposition techniques. We investigate the effects of these methods on the formation of the orthorhombic phase (o-phase) in HfAlOx (HAO) ferroelectric films, which is crucial for ferroelectric properties. The devices were fabricated with HAO films doped with 3.4% aluminum, followed by rapid thermal annealing at 700 °C. Our results demonstrate that the atomic layer deposition process forms a TiOxNy capping layer at the interface between the HAO film and the TiN top electrode, which promotes the o-phase formation. This capping layer effect leads to enhanced polarization characteristics, as evidenced by higher remnant polarization and tunneling electroresistance (TER) in the ALD-fabricated devices. The ALD method also results in a better interfacial layer condition, confirmed by a lower interfacial non-ferroelectric capacitance (Ci). Characterization techniques, including transmission electron microscopy, energy dispersive x-ray spectroscopy, and x-ray diffraction. These structural advantages contribute to enhanced electrical performance, demonstrating neuromorphic applications. Here, our study highlights the significant impact of the ALD deposition method on enhancing the ferroelectric properties and overall performance of ferroelectric memristor devices, making it a promising approach for advanced memory and neuromorphic computing applications.
A new rigid non-polarizable model for semi-heavy water: TIP4P/2005-SHW
Authors: Takayama Tetsuyuki , Otosu Takuhiro , Yamaguchi Shoichi
Published: December 2024

In molecular dynamics (MD) simulations of water, rigid non-polarizable models are still valuable and widely used because of their low computational cost and excellent performance. Most of such models have been for light water (H2O) for a long time, and a few have recently been reported for heavy water (D2O). The specific models of D2O are needed because of its notably slower dynamics and stronger hydrogen bond than H2O. To our knowledge, no models of semi-heavy water (HOD) were made, although HOD is the most abundant and, therefore, most important chemical species in isotopically diluted water (IDW) prepared by mixing equal amounts of H2O and D2O. For precise MD simulations of IDW, a specific model of HOD is definitely needed. Here, we report the development of a new rigid non-polarizable model of HOD, TIP4P/2005-SHW, on the basis of the most popular H2O model, TIP4P/2005, and its D2O counterpart, TIP4P/2005-HW. We show the details of the development and demonstrate the high reproducibility of TIP4P/2005-SHW in terms of the density, the temperature of maximum density, the viscosity, and the diffusion coefficient.
Manufacturing of sintered aluminum powder wicks by the liquid phase enhance sintering method for aluminum heat pipes
Authors: Liu Xiaolong , Li Xin , Meng Xin , Liu Yucheng , Tang Yong , Zhang Shiwei
Published: December 2024

The aluminum heat pipes have the advantages of lightweight and low-cost, which are widely applied to space satellites. The wick is the critical component of the heat pipe which provides the capillary pressure. Unfortunately, the performance of the aluminum heat pipes is limited by the wicks, which are difficult to manufacture due to the barriers of Al2O3 thin film during the aluminum powder wicks' sintering process. To overcome this problem, a novel sintered aluminum powder wick manufactured by the liquid phase enhance sintering (LPES) technology based on element doping and vacuum sintering was proposed in this work. Considering the material compatibility between the aluminum and working fluid, the brazing powder rich in Si was chosen to be doped to promote the formation of sintered necks. The mechanism of the LPES promoted by the Si was analyzed by thermodynamic and element distribution analysis. The wick is lightweight whose density is only 22.60% and 74.26% of the densities of copper and aluminum. The wettability and capillary performance of the wicks were also studied. The results show that all the samples are superhydrophilic with the working fluids of ethanol and acetone. The sample of CS15 (coarse pure aluminum powder with 15 wt. % brazing powder) has the best wettability and capillary performance in acetone, whose infiltration time, capillary rise height, and wicking coefficient are about 69.50 ms, 106.39 mm, and 12.35 mm/s0.5, respectively. The work provides a feasible approach to manufacturing lightweight and low-cost sintered powder wicks for aluminum heat pipes.
Direct visualization of quasiparticle concentration around superconducting vortices
Authors: Ge Jian-Feng , Bastiaans Koen M. , Niu Jiasen , Benschop Tjerk , Ortego Larrazabal Maialen , Allan Milan P.
Published: December 2024

Bogoliubov quasiparticles play a crucial role in understanding the behavior of a superconductor and in achieving reliable operations of superconducting quantum circuits. Diagnosis of quasiparticle poisoning at the nanoscale provides invaluable benefits in designing superconducting qubits. Here, we use scanning tunneling noise microscopy to locally quantify quasiparticles by measuring the effective charge. Using the vortex lattice as a model system, we directly visualize the spatial variation of the quasiparticle concentration around superconducting vortices, which can be described within the Ginzburg–Landau framework. This shows a direct, noninvasive approach for the atomic-scale detection of relative quasiparticle concentration as small as 10−4 in various superconducting qubit systems. Our results alert of a quick increase in quasiparticle concentration with decreasing intervortex distance in vortex-based Majorana qubits.
Numerical simulation of high-concentration droplet flow in an idealized mouth–throat airway model in the influence of environmental temperature and humidity
Authors: Liu Yu , Chen Xiaole , Xie Jun , Xie Xiaojian , Zhang Yi , Tao Feng
Published: December 2024

The exchange of water vapor between high-concentration droplets and air significantly influences droplet deposition in the upper airway model during nebulizer use. This study employed a two-way coupled Eulerian–Lagrange method to quantify nebulized droplet evaporation and relative humidity (RH) variations within an idealized mouth–throat (MT) airway model, utilizing validated numerical models. The water vapor interaction between high-concentration droplets and inhaled air was computed using a multiplier based on the particle parcel method. Simulations of normal saline droplet flow inhalation in the MT airway were conducted under two environmental conditions: indoor (26.5 °C, RH = 50%) and warm and wet (30 °C, RH = 75%), with various inhalation flow rates mirroring previous experiments. Droplet deposition fractions (DFs) and deposition patterns were recorded. The results indicated that DF initially decreased and then increased with rising inhalation flow rates. The largest discrepancy between predicted and measured DFs was 10.86%. These findings support the theory that the balance between droplet evaporation and elevated air RH dictates the deposition of nebulized droplets in the airway. Additionally, simulations revealed that environmental conditions significantly affect droplet DF, with variations up to 20.78%. The deposition hotspot shifted from the anterior to the posterior pharynx.
Novel artificial photosynthesis based carbon emission reduction technology with feasibility analysis of clean electricity generation
Authors: Das Uttara , Nandi Champa
Published: December 2024

Electricity generation leads to one third of greenhouse gas emissions in the world. Standing at the age of direct effect of global warming on global ecosystem, it is required to control global greenhouse gases within limit to avoid global climate alteration. For that, a new concept is proposed in this study for converting CO2 into glucose as well as generating power. Artificial photosynthesis concept is utilized here to design the glucose reactor. Artificial photosynthesis converts CO2 to glucose, integrating principles of carbon fixation, renewable energy, and electrochemistry for sustainable carbon utilization. Furthermore, the synthesized glucose is converted into power in an electrochemical way. A case study has been done based on wind power plant. Therefore, to execute the process, the system is powered by a wind power plant for cleaning the water molecules, CO2 molecule capture, which is synthesized into glucose. Then, the sensitivity analysis is carried out to find how the wind speed is affecting the production of glucose and power-regeneration. The result highlights that the designed system is capable of capturing total emitted CO2 from considered case study within few days. A single unit analysis of glucose reactor is given here. Moreover, the electrochemical system can produce power with that CO2-derived glucose. This concept will be surely benefited for carbon emission reduction, clean power generation, and sustainable development.
Unveiling the impact of biaxial strain on phonon transport in Janus γ-Ge2SSe monolayer for thermoelectric applications
Authors: Ramirez Rivera Victor José , Mamani Gonzalo Fredy , Nina Mendoza Henry Edgardo , Jeomar Piotrowski Maurício , Chacaltana Garcia Jesus Alfredo , Rodriguez Delgado Eduardo , Mamani Flores Efracio
Published: December 2024

Thermoelectricity offers an efficient means of converting heat directly into electricity without greenhouse gas emissions. Recently, the hexagonal γ-GeSe phase and a new class of monolayers called Janus have been synthesized, exhibiting exceptional thermoelectric properties. In this study, we investigate the phonon thermal transport in γ-Ge2SSe Janus monolayers under biaxial strain using density functional theory and Boltzmann transport theory. Our analysis reveals that acoustic phonon modes, particularly the transverse acoustic and longitudinal acoustic modes, dominate the thermal transport. The lattice thermal conductivity (κl) shows a strong dependence on biaxial strain, with a decrease observed under tensile biaxial strain, and the Grüneisen parameter reveals considerable anharmonicity, which promotes phonon scattering and reduces thermal conductivity. At room temperature and at 0% strain, κl of Janus γ-Ge2SSe is measured at 4.41 W/mK, demonstrating moderate thermal transport, while under 2% tensile strain, κl decreases to 3.13 Wm−1 K−1, highlighting the material’s strain sensitivity. These results suggest that strain engineering can be effectively used to optimize the thermoelectric performance of Janus γ-Ge2SSe monolayers, providing valuable insights for energy conversion applications.
Robust single-photon generation for quantum information enabled by stimulated adiabatic rapid passage
Authors: Karli Yusuf , Schwarz René , Kappe Florian , Vajner Daniel A. , Krämer Ria G. , Bracht Thomas K. , Covre da Silva Saimon F. , Richter Daniel , Nolte Stefan , Rastelli Armando , Reiter Doris E. , Weihs Gregor , Heindel Tobias , Remesh Vikas
Published: December 2024

The generation of single photons using solid-state quantum emitters is pivotal for advancing photonic quantum technologies, particularly in quantum communication. As the field continuously advances toward practical use cases and beyond shielded laboratory environments, specific demands are placed on the robustness of quantum light sources during operation. In this context, the robustness of the quantum light generation process against intrinsic and extrinsic effects is a major challenge. Here, we present a robust scheme for the coherent generation of indistinguishable single-photon states with very low photon number coherence using a three-level system in a semiconductor quantum dot. Our approach combines the advantages of adiabatic rapid passage and stimulated two-photon excitation. We demonstrate robust quantum light generation while maintaining the prime quantum-optical quality of the emitted light state. Moreover, we highlight the immediate advantages of the implementation of various quantum cryptographic protocols.
Short-time accuracy and intra-electron correlation for nonadiabatic quantum–classical mapping approaches
Authors: Lang Haifeng , Hauke Philipp
Published: December 2024

Nonadiabatic quantum–classical mapping approaches have significantly gained in popularity over the past several decades because they have acceptable accuracy while remaining numerically tractable even for large system sizes. In the recent few years, several novel mapping approaches have been developed that display higher accuracy than the traditional Ehrenfest method, linearized semiclassical initial value representation (LSC-IVR), and Poisson bracket mapping equation (PBME) approaches. While various benchmarks have already demonstrated the advantages and limitations of those methods, unified theoretical justifications of their short-time accuracy are still demanded. In this article, we systematically examine the intra-electron correlation, as a statistical measure of electronic phase space, which has been first formally proposed for mapping approaches in the context of the generalized discrete truncated Wigner approximation and which is a key ingredient for the improvement in short-time accuracy of such mapping approaches. We rigorously establish the connection between short-time accuracy and intra-electron correlation for various widely used models. We find that LSC-IVR, PBME, and Ehrenfest methods fail to correctly reproduce the intra-electron correlation. While some of the traceless Meyer–Miller–Stock–Thoss (MMST) approaches, partially linearized density matrix (PLDM) approach, and spin partially linearized density matrix (spin-PLDM) approach are able to sample the intra-electron correlation correctly, the spin linearized semiclassical (spin-LSC) approach, which is a specific example of the classical mapping model, and the other traceless MMST approaches sample the intra-correlation faithfully only for two-level systems. Our theoretical analysis provides insights into the short-time accuracy of semiclassical methods and presents mathematical justifications for previous numerical benchmarks.
Modeling of vibrational nonequilibrium effects on pressure Hessian tensor using physics-assisted deep neural networks
Authors: Shikha Deep , Srivastava Shishir , Sinha Sawan S.
Published: December 2024

This study focuses on modeling the effect of vibrational nonequilibrium on the pressure Hessian tensor. The pressure Hessian tensor is one of the unclosed processes involved in the velocity gradient evolution equation. Accessing the velocity gradient tensor following a fluid particle is needed to understand the physics of various nonlinear turbulent processes. Our modeling strategy employs a combination of two different deep neural networks (DNNs) to model the magnitude and the directional aspects of the vibrational nonequilibrium tensor separately. Both the DNNs are optimized using two appropriate physics-assisted custom loss functions, comparing the desired features of the DNN predictions against the exact behavior observed in the direct numerical simulation (DNS) database. A detailed investigation of four different DNS databases of vibrationally excited decaying compressible turbulence with different initial Reynolds numbers, Mach numbers, and vibrational Damköhler numbers is performed to identify the appropriate normalized forms of input and output quantities for the two neural networks. The training of both the DNNs is done using the DNS data of merely one simulation. The trained models are then subjected to extensive evaluation against different DNS databases. Indeed, the new model captures many DNS features quite well. Such an extensive evaluation of the new model proves the generalizability of the model, at least in the range of parameters involved in our study.
Mitigation of energy dissipation of graphene resonators by introduction of boron-nitride
Authors: Ben-Shimon Yahav , Jahn Yarden Mazal , Pradhan Anway , Ya'akobovitz Assaf
Published: December 2024

Uncovering the material dissipation mechanisms of two-dimensional materials is essential for their implementation in advanced devices. While graphene resonators are highly attractive due to their high operational frequency and excellent durability, they dissipate a considerable amount of energy due to significant material dissipation associated with atomic friction manifested by the relative slipping of atomic layers. We mitigate the atomic friction by changing the atomic composition of the devices through the insertion of boron and nitride atoms that create polar interlayer bonds and, therefore, also reduce the energy dissipation. As a case study, we built boron carbonitride (BCN) foam cantilever devices and studied their frequency responses compared to those of their graphene counterparts. Indeed, we show that inserting boron and nitride atoms into the lattice improves the interlayer interactions and, thus, reduces the interlayer atomic friction. In addition, the air dissipation of BCN is also lower than that of graphene. Therefore, we pave the path for the development of BCN devices with tunable dissipation.
Principle design and power generation research of magnetically coupled piezoelectric energy harvester
Authors: Li Biao , Shao Jiaru , Zheng Zijun , Yang Yu
Published: December 2024

This study systematically investigates the mechanism of magnetic coupling energy collection and designs an efficient energy collector. The experimental results demonstrate that the strategic installation of permanent magnets can effectively optimize the stress state of piezoelectric plates, significantly enhancing power generation efficiency. Under identical conditions, the peak voltage of the newly developed magnetically coupled energy collector reaches 168.3 V, surpassing the 67.19 V peak voltage reported in the reference. Optimizing the operational speed from 550 to 180 rpm improves the energy collector’s compatibility with low-frequency external excitation. The study also compares and analyzes the power generation performance of various piezoelectric plates, revealing that the maximum power outputs of series and parallel circuits are 22.4 and 3.98 mW, respectively. This research introduces novel concepts and methodologies for optimizing the design of energy collector structures.
Prediction of shut-off head for centrifugal pumps based on grey theory and GA-BP neural network
Authors: Yu Dehui , Zhang Jinfeng , Yuan Shouqi , Ma Wensheng , Bai Xiaobang , Chen Yan , Wang Chao
Published: December 2024

Calculating the shut-off head for centrifugal pumps poses significant challenges due to inaccuracies in existing empirical methods. This paper presents a predictive model based on extensive experimental data, employing a back propagation (BP) neural network optimized via grey theory and genetic algorithms (GAs). Data were collected from 141 single-stage volute centrifugal pumps, and grey theory was used to analyze nine critical parameters of the impeller and volute, yielding five optimal input schemes with correlation coefficients exceeding 0.6. The GA was utilized to optimize the weights and thresholds of the BP model. The training involved 121 samples, while 20 additional samples were used to evaluate the models against three established methods (throne, modified throne, and regression fitting). The results indicate that the optimal input scheme consists of four parameters (impeller diameter, blade wrap angle, inlet diameter, and rotational speed) with correlation coefficients greater than 0.7. Both the BP and GA-BP models achieved training regression coefficients approaching 0.999. Within the specific speed range of 22–215, the GA-BP model demonstrated superior performance to the BP model and the three established methods, with maximum testing errors of 10.0%, 20.6%, 20.7%, 19.9%, and 23.3%, and average relative errors of 3.9%, 5.0%, 8.4%, 8.1%, and 5.8%, respectively. This paper introduces a novel prediction model for the shut-off head with an accuracy of 96%, providing a valuable reference for hydraulic design and performance prediction in centrifugal pumps.
Gate stress-induced mobility degradation in NO-nitrided SiC(0001) MOSFETs
Authors: Kobayashi Takuma , Koyanagi Kaho , Hirai Hirohisa , Sometani Mitsuru , Okamoto Mitsuo , Watanabe Heiji
Published: December 2024

The impacts of gate voltage stress on the on-state characteristics of nitrided SiC(0001) metal-oxide-semiconductor field-effect transistors (MOSFETs) were examined. A strong negative voltage stress at 300 °C induced a decrease in the channel mobility of the MOSFETs. This mobility decrease occurred along with an increase in the interface state density. Through MOS Hall effect measurements, we proposed a model in which the stress-induced interface states are located on the SiC side of the interface, close to where free electrons in the MOS channel are confined, thereby acting as a strong source of Coulomb scattering.
Experimental investigation of the formation and distribution of remaining oil from pore scale to core scale during supercritical CO2 flooding
Authors: Li Lian , Kang Yong , Hu Yi , Pan Haizeng , Huang Yong , Yuan Quan
Published: December 2024

Research on the formation and distribution characteristics of remaining oil has primarily focused on individual scales, with studies at both the pore scale and core scale often lacking effective integration, particularly under supercritical conditions. In this study, a high-temperature and high-pressure microfluidic experimental system (temperature: 75 °C, pressure: 22 MPa) and micro-computed tomography (CT) scanning technology were employed to systematically investigate the formation mechanisms and distribution characteristics of five different types of remaining oil after CO2 injection. The experimental results indicate that after CO2 injection, the remaining oil mainly appears in columnar and droplet patterns, predominantly distributed in pores ranging from 4 to 13 μm, and is significantly influenced by the Marangoni effect and Jamin effect. Additionally, at the pore scale, the oil recovery increased by approximately 8.7% under high flow rates (0.5 ml/min) compared to low flow rates (0.1 ml/min); In contrast, at the core scale, the oil recovery decreased by 15.9%. This contrasting behavior can be attributed to flow non-uniformity caused by the fingering effect, which leads to uneven fluid distribution within the porous media. The comparison between pore scale and core scale provides new insights into understanding the distribution patterns of remaining oil.