bluuebunny/crossref_metadata_2025 huggingface dataset:
Increased accuracy and signal-to-noise ratio through recent improvements in infra-red video bolometer fabrication and calibration
Authors: Federici Fabio , Lovell Jack J. , Wurden G. A. , Peterson Byron J. , Mukai Kiyofumi
Published: October 2024

The infra-red video bolometer (IRVB) is a diagnostic equipped with an infra-red camera that measures the total radiated power in thousands of lines of sight within a large field of view. Recently validated in MAST-U [Fderici et al., Rev. Sci. Instrum. 94, 033502 (2023)], it offers a high spatial resolution map of the radiated power in the divertor region, where large gradients are expected. The IRVB’s sensing element comprises a thin layer of high Z absorbing material, typically platinum, usually coated with carbon to reduce reflections [Peterson et al., Rev. Sci. Instrum. 79, 10E301 (2008)].Here, the possibility of using a relatively inert material such as titanium, is explored that can be produced in layers up to 1 μm compared to 2.5 μm for Pt and then coat it with Pt of the desired thickness (0.3 μm per side here) and carbon. This leads to a higher temperature signal (about 3 times) and better spatial resolution (about 4 times), resulting in higher accuracy in the measured power [Peterson et al., Rev. Sci. Instrum. 79, 10E301 (2008)]. This assembly is also expected to improve foil uniformity, as the Pt layer is obtained via deposition rather than mechanical processes [Mukai et al., Rev. Sci. Instrum. 87, 2014 (2016)].Given its multi-material composition, measuring the thermal properties of the foil assembly is vital. Various methods using a calibrated laser as a heat source have been developed, analyzing the temperature profile shape [Sano et al., Plasma and Fusion Res. 7, 2405039 (2012)] and [Mukai et al., Rev. Sci. Instrum. 89, 10E114 (2018)] or fitting the calculated laser power for different intensities and frequencies [Fderici et al., Rev. Sci. Instrum. 94, 033502 (2023)]. Here, a simpler approach is presented, which relies on analyzing the separate components of the foil heat equation for a single laser exposure in a given area. This can then be iterated over the entire foil to capture local deviations.
Plasmon-enhanced two photon excited emission from edges of one-dimensional plasmonic hotspots with continuous-wave laser excitation
Authors: Itoh Tamitake , Yamamoto Yuko S.
Published: October 2024

One-dimensional junctions between parallelly and closely arranged multiple silver nanowires (NWs) exhibit a large electromagnetic (EM) enhancement factor (FR) owing to both localized and surface plasmon resonances. Such junctions are referred to as one-dimensional (1D) hotspots (HSs). This study found that two-photon excited emissions, such as hyper-Rayleigh, hyper-Raman, and two-photon fluorescence of dye molecules, are generated at the edge of 1D HSs of NW dimers with continuous-wave near-infrared (NIR) laser excitation and propagated through 1D HSs; however, they were not generated from the centers of 1D HSs. Numerical EM calculations showed that FR of the NIR region for the edges of 1D HSs was larger than that for the centers by ∼102 times, resulting in the observation of two-photon excited emissions only from the edge of 1D HSs. The analysis of the NW dimer gap distance dependence of FR revealed that the lowest surface plasmon (SP) mode, compressed and localized at the edges of 1D HSs, was the origin of the large FR in the NIR region. The propagation of two-photon-excited emissions was supported by the higher-order coupled SP mode.
Enhanced thermoelectric performance of silicon powder arrays by remotely doping
Authors: Guo Yahui , He Xuting , Liang S.
Published: October 2024

We report improved thermoelectric (TE) properties of mesostructured silicon powder arrays simply prepared by die-pressing without sintering. In contrast to bromoethane's modest effect, the symmetric dibromoethane molecule coupling could significantly increase the conductivity of Si powder array TE device, from 12.7 S cm−1 of a silicon powder array to 62.3 S cm−1, which is possibly caused by the high electronic transmission probability of symmetric organic molecule–Si crystal coupling, and additionally enhanced by Si bandgap narrowing and defect states of an organic–inorganic interface identified by UV–vis absorption spectra and photoluminescence spectroscopy. Boosted by the very low thermal conductivity (0.58 W m−1 K−1), the dimensionless figure of merit, the ZT value of an Si powder array remotely doped by dibromoethane, ∼0.173, was obtained at 385 K, which is about 17 times higher than that of the bulk Si. An Si–organic hybrid TE device shows potentials to approach the threshold of practical applications with moderate ZT performance and low cost.
FPGA-based measurements of the relative arrival time of a high-repetition rate, quasi-cw fourth generation light source
Authors: Ponomaryov A. N. , Deinert J.-C. , de Oliveira T. V. A. G. , Ilyakov I. , Prajapati G. L. , Arshad A. , Kuntzsch M. , Gensch M. , Kovalev S.
Published: October 2024

In this paper, we demonstrate the successful implementation of reconfigurable field-programmable gate array technology into a pulse-resolved data acquisition system to achieve a femtosecond temporal resolution in ultrafast pump–probe experiments in real-time at large scale facilities. As proof of concept, electro-optic sampling of terahertz waveforms radiated by a superradiant emitter of a quasi-cw accelerator operating at a 50 kHz repetition rate and probed by an external laser system is performed. Options for up-scaling the developed technique to a MHz range of repetition rates are discussed.
Effect of peptide hydrophilicity on membrane curvature and permeation
Authors: Mathath Anjana V. , Chakraborty Debashree
Published: October 2024

Using a well-developed reaction coordinate in umbrella sampling, we studied the single peptide permeation through a model cancerous cell membrane, varying the hydrophilicity and the charge of the peptides. Two peptides, melittin and pHD108, were studied. The permeation mechanism differs from a barrel-stave-like mechanism to toroidal pore and vesicle formation based on the number and the placement of the hydrophilic amino acids in the peptide. Membrane curvature changes dynamically as the permeation process occurs. In the case of vesicles, the peptide traverses along a smooth, homogenous pathway, whereas a rugged, steep pathway was found when lipid molecules did not line up along the wall of the membrane (barrel-stave-like mechanism). A mechanism similar to a toroidal pore consists of multiple minima. Higher free energy was found for the permeating terminal containing charged amino acid residues. Vesicle formation was found for pHD108 peptide N-terminal with a maximum membrane thinning effect of 54.4% with free energy cost of 8.20 ± 0.10 kcal mol−1 and pore radius of 2.33 ± 0.07 nm. Insights gained from this study can help to build synthetic peptides for drug delivery.
Spiking activities in small neural networks induced by external forcing
Authors: Rybalova E. , Semenova N.
Published: October 2024

Neurons in an excitable mode do not show spiking activity and, therefore, do not contribute to information transfer transmission and its processing. However, some external influences, coupling, or time delay can lead to the appearance of oscillations in individual systems or networks. The main goal of this paper is to uncover the connection parameters and parameters of external influences that lead to the arising of spiking behavior in a small network of locally coupled FitzHugh–Nagumo oscillators. In this study, we analyze the dynamics of a small network in the absence and presence of several types of external influences. First, we consider the impact of periodic-pulse exposure generated as a periodic sequence of Gaussian pulses. Second, we show what behavior can be induced by far less regular pulsed influence (Lévy noise) and its special case called white Gaussian noise. For all types of influences, we have identified the appropriate parameters (local coupling strength, intensity, and frequency) that induce spiking activity in the small network.
Contrasting behavior of urea in strengthening and weakening confinement effects on polymer collapse
Authors: James Alen , Nayar Divya
Published: October 2024

Biomolecules inhabit a crowded living cell that is packed with high concentrations of cosolutes and macromolecules that result in restricted, confined volumes for biomolecular dynamics. To understand the impact of crowding on the biomolecular structure, the combined effects of the cosolutes (such as urea) and confinement need to be accounted for. This study involves examining these effects on the collapse equilibria of three model 32-mer polymers, which are simplified models of hydrophobic, charge-neutral, and uncharged hydrophilic polymers, using molecular dynamics simulations. The introduction of confinement promotes the collapse of all three polymers. Interestingly, addition of urea weakens the collapse of the confined hydrophobic polymer, leading to non-additive effects, whereas for the hydrophilic polymers, urea enhances the confinement effects by enhancing polymer collapse (or decreasing the polymer unfolding), thereby exhibiting an additive effect. The unfavorable dehydration energy opposes collapse in the confined hydrophobic and charge-neutral polymers under the influence of urea. However, the collapse is driven mainly by the favorable change in polymer–solvent entropy. The confined hydrophilic polymer, which tends to unfold in bulk water, is seen to have reduced unfolding in the presence of urea due to the stabilizing of the collapsed state by urea via cohesive bridging interactions. Therefore, there is a complex balance of competing factors, such as polymer chemistry and polymer–water and polymer–cosolute interactions, beyond volume exclusion effects, which determine the collapse equilibria under confinement. The results have implications to understand the altering of the free energy landscape of proteins in the confined living cell environment.
Dual efficacy of potassium-doping in perovskite solar cells: Reducing hysteresis and boosting open-circuit voltage
Authors: Li Weijie , Liu Ting , Chen Guanwen , Li Ning , Wang Xia , Liu Zongming , Cao Bingqiang
Published: October 2024

The incorporation of potassium into perovskite solar cells (PSCs) has been empirically validated to mitigate hysteresis phenomena and boost the power conversion efficiency (PCE). However, the doping mechanism of potassium ions in the perovskite film and their effect on photocarrier recombination remains a topic of debate. Here, we grew doped MAPbI3: K single crystals by inverse temperature crystallization using KI as a dopant, and then perovskite thin films were spin-coated with dissolved MAPbI3: K crystals as a precursor. The doped MAPbI3: K perovskite films exhibit better crystal quality with large columnar grains and lower defect density. Employing Hall effect, ultraviolet photoelectron spectroscopy, and Kelvin probe force microscopy measurements, we definitively demonstrate that K-doping transforms the conductivity type of the perovskite film from a marginally N-type to a distinct P-type semiconductor. Furthermore, this doping strategy induces a concurrent downward shift in both the conduction band minimum and valence band maximum. As a result, the PCE of the PSCs increases from 15.15% to an impressive 20.66%, and the J–V curve hysteresis almost disappears. Additionally, theoretical simulations using SCAPS-1D software reveal a profound modification in the device's energy band diagram after K+-doping. Specifically, the energy level offset between the perovskite layer and the electron transport layer diminishes from 0.24 to 0.14 eV, with a result of bigger quasi-Fermi energy level splitting. This, in turn, elevates the open-circuit voltage (Voc) of the doped perovskite solar cell, underscoring the profound impact of potassium doping on enhancing PSC performance.
Optical frequency filtering for Raman beams
Authors: Ramírez-Meléndez Gustavo , López-Vázquez Alejandra , Ochoa Haydee Guadalupe , Jiménez Luis , Hernandez Raul Josue , Gomez Eduardo
Published: October 2024

We present an optical filter that is appropriate for use with Raman beams in atomic interferometry. This is a filter that lets the light of the two frequencies of the Raman pair go through and rejects spurious frequencies that may be close to the atomic resonance and cause decoherence. We characterized the filter’s performance optically and also by shining the light into atoms in a Ramsey sequence, to look for decoherence effects from photon scattering. We found that it is safe to use tapered amplifiers in single and double pass for light amplification in the Raman beams since the pedestal of emission has a negligible effect, which can be further reduced by the use of the filter we present.
A multilayered homogeneous hydrodynamic cloak realized in a free fluid flow
Authors: Chen Mengyao , Shen Xiangying , Xu Lei
Published: October 2024

In recent years, hydrodynamic invisibility cloaks have attracted significant attention from the scientific and engineering communities due to their potential in applications such as fluid flow manipulation, drag reduction, submarine stealth, and biomedical engineering. However, cloaks based on transformation mapping theory typically require porous medium flow, limiting practical implementation. To address this, we draw inspiration from Hele-Shaw flow and develop a homogeneous hydrodynamic cloak composed of multiple layers in free fluid flow at low Reynolds numbers (Re≪1). Through structural optimization, we construct a cloaking shell with ten concentric layers of alternating heights, achieving near-perfect cloaking as demonstrated by simulations and experiments. This non-porous cloak design offers valuable insights into the rapidly advancing field of hydrodynamic metamaterials and enables methods for controlling fluid flow at the microscale, with promising applications in microfluidics.
A multi-modal high pressure and high temperature reaction cell for combined x-ray spectroscopy, scattering, and imaging
Authors: Kathyola Thokozile A. , Keylock Stephen J. , Ignatyev Konstantin , Filik Jacob , Drnec Jakub , Webb Paul B. , Kroner Anna B. , Diaz-Moreno Sofia
Published: October 2024

A free-standing and compact reaction cell for combined in situ/operando x-ray spectroscopy, scattering, and imaging measurements at high pressures and high temperatures is described. The cell permits measurements under realistic operating conditions (up to 50 bar and 1000 °C), under static and flow conditions (up to 100 ml/min), over a wide range of hard x-ray energies, variable detection modes (transmission, fluorescence, and scattering), and at all angles of rotation. An operando XAS, x-ray fluorescence, x-ray computed tomography, and x-ray diffraction computed tomography case study on the reduction of a heterogeneous catalyst is presented to illustrate the performance of the reaction cell.
The influence of serrated trailing edge on pulsating pressure and noise performance of pump-jet propulsor under submarine self-propulsion condition
Authors: Yang Chun , Sun Cong , Wang Chao , Guo Chunyu , Yue Qihui
Published: October 2024

Owls make almost no noise when gliding, thanks to the unique feather structure at the tail of their wings. Drawing on the tail structure of the owl wings, the trailing edge of the duct in the pump-jet propulsor (PJP) system is improved. Based on the detached eddy simulation method, the influence of serrated trailing edge on the pulsating pressure and noise performance of a PJP under submarine self-propulsion conditions is numerically analyzed. The results show that the influence of the serrated trailing edge on the self-propulsion performance is negligible. The serrated trailing edge destroys the large-scale duct-induced vortices in the spanwise direction, and additional secondary vortices are formed in the wakefield, increasing the pulsating pressure of the downstream flow field. The pulsation amplitude of each order at the downstream monitoring point of the serrated duct PJP (SD-PJP) model is significantly greater than that of the benchmark PJP (BM-PJP) model. The serrated trailing edge can effectively reduce the noise of PJP. The maximum noise reduction in the axial and radial planes is 1.23 and 0.91 dB.
Evolution of topological extended state in multidimensional non-Hermitian topolectrical circuits
Authors: Lin Wei , Ruan Banxian , Liu Chao , Dai Xiaoyu , Xiang Yuanjiang
Published: October 2024

The extended state pertains to the dispersion of the system's eigenfunctions across the whole lattice. Recent studies have shown that the non-Hermitian skin effect (NHSE) can reshape the wavefunction of topological modes. The localized states of topological modes within the bandgap gradually delocalized into extended states through the manipulation of NHSE. Here, we clarify the NHSE direction using the Bloch spectral winding numbers and reestablish the bulk-boundary correspondence through the non-Bloch winding numbers in the generalized Brillouin zone. We elucidate the formation of extended state by employing the localized decay length. Then, we have designed non-Hermitian topological circuits for experimental verification based on the voltage follower. The corner states, edge states, and extended states in 1D, 2D, and 3D circuits were observed through the measurement of node voltage. Our work can achieve the sustainable extended mode and provides significant cases for the analysis of topolectrical circuits.
A new higher-order super compact finite difference scheme to study three-dimensional non-Newtonian flows
Authors: Punia Ashwani , Ray Rajendra K.
Published: October 2024

This work introduces a new higher-order accurate super compact (HOSC) finite difference scheme for solving complex unsteady three-dimensional (3D) non-Newtonian fluid flow problems. As per the author's knowledge, the proposed scheme is the first ever developed higher-order compact finite difference scheme to solve 3D non-Newtonian flow problems. The proposed scheme is fourth-order accurate in space and second-order accurate in time, utilizing only seven adjacent grid points at the (n+1)th time level for the finite difference discretization. A time-marching methodology is employed with pressure calculated via a pressure-correction strategy based on the modified artificial compressibility method. Using the power-law viscosity model, we tackle the benchmark problem of a 3D lid-driven cavity, systematically analyzing the varied rheological behavior of shear-thinning (n = 0.5), shear-thickening (n = 1.5), and Newtonian (n = 1.0) fluids across different Reynolds numbers (Re=1,50,100,200). Both Newtonian and non-Newtonian results are carefully investigated in terms of streamlines, velocity variation, pressure distributions, and viscosity contours, and the computed results are validated with the existing benchmark results. The findings demonstrate excellent agreement with the existing results. It is found that for shear-thinning fluid (n = 0.5), u velocity is higher near the top moving wall than the case of Newtonian (n = 1.0) and shear-thickening fluid (n = 1.5) for all Re values. This extensive analysis, using the new HOSC scheme, not only increases our understanding of non-Newtonian fluid behavior but also provides a robust foundation for future research and practical applications.
Conversion mechanisms and transformed waves for the (3 + 1)-dimensional nonlinear equation
Authors: Zhang Xueqing , Ren Bo
Published: October 2024

In this paper, we focus on investigating the (3 + 1)-dimensional nonlinear equation which is used to describe the propagation of waves in the shallow water. The study begins with the application of the Hirota bilinear method to obtain N-soliton solution. Building on this foundation, the research delves into the construction of first-order breather wave by imposing complex conjugate constraints on the parameters of two solitons. Further analysis of the characteristic lines of breathers leads to the derivation of conversion conditions. Under this specific condition, a series of nonlinear transformed waves are presented, including quasi-kink solitons, W-shaped kink solitons, oscillation W-shaped kink solitons, multipeaks solitons, quasi-periodic waves, and line rogue waves. Each of these transformed waves exhibits unique structural and dynamic properties, enriching the understanding of wave behavior in higher-dimensional nonlinear systems. The study also explores the nonlinear superposition mechanism between solitary wave and periodic wave. This mechanism elucidates the formation process of nonlinear waves, explaining how their locality and oscillatory characteristics emerge from the superposition of different wave components. Moreover, the geometric properties of the two characteristic lines of the waves are analyzed to understand the time-varying nature of the transformed waves. This temporal analysis is crucial for predicting the evolution and interaction of these waves over time. Finally, the research extends to the higher-order breather wave and explores the interactions among various waves. These interactions reveal the complex dynamics that may arise in the (3 + 1)-dimensional nonlinear systems and provide deeper insights into the interactions among different wave structures.
Nucleation and phase transition of decagonal quasicrystals
Authors: Zhou Tiejun , Zhang Lei , Zhang Pingwen , Shi An-Chang , Jiang Kai
Published: October 2024

In this work, we study the nucleation of quasicrystals from liquid or periodic crystals by developing an efficient order–order phase transition algorithm, namely, the nullspace-preserving saddle search method. In particular, we focus on nucleation and phase transitions of the decagonal quasicrystal (DQC) based on the Lifshitz–Petrich model. We present the nucleation path of DQC from the liquid and demonstrate one- and two-stage transition paths between DQC and periodic crystals. We provide a perspective of the group–subgroup phase transition and nucleation rates to understand the nucleation and phase transition mechanisms involving DQC. These results reveal the one-step and multi-step modes of symmetry breaking or recovery in the phase transition from DQC, where the multi-step modes are more probable.
Predicting kinetics of spin-dependent reactions in an external magnetic field with nonadiabatic statistical theory
Authors: Rooein Mitra , Varganov Sergey A.
Published: October 2024

We introduce a theoretical framework to study the kinetics of the chemical reactions involving transitions between electronic states with different spin quantum numbers in an external magnetic field. The new equations for calculating transition probabilities and rate constants are used to generalize the nonadiabatic statistical theory, which now accounts for both the spin–orbit and Zeeman couplings between electronic states. Focusing on the singlet–triplet transitions, we define two dimensionless parameters to characterize (1) the magnetic field strength relative to the strength of spin–orbit coupling and (2) the relative magnitudes of the spin–orbit coupling matrix elements that couple the singlet state to different components of the triplet state. Based on the values of these dimensionless parameters, we define distinct coupling regimes and propose specific approaches to calculating the transition probabilities and rate constants in these regimes. We apply the introduced theoretical framework to study the effect of an external magnetic field on the kinetics of spin-forbidden isomerization of the Ni(dpp)Cl2 [dpp = 1,3-bis(diphenylphosphino)propane] complex in the strong and weak field regimes. Our calculations predict that in a magnetic field of 50 T, the isomerization rate constant increases by about 10%. We hope this work will facilitate renewed efforts in controlling spin-dependent chemical reactions with an external magnetic field.
The role of biomarkers on hemodynamics in atherosclerotic artery
Authors: Ray Ruchira , Dey Bibaswan
Published: October 2024

Atherosclerosis, a chronic inflammatory cardiovascular disease, leads to arterial constriction caused by the accumulation of lipids, cholesterol, and various substances within artery walls. Such plaque can rupture, resulting in a blood clot that obstructs major arteries and may initiate myocardial infarction, ischemic stroke, etc. Atherosclerotic plaque formation begins with the accumulation of foam cells and macrophages within the intima layer of the arterial wall. At the latter stage, the smooth muscle cells migrated from deeper artery wall layers, contributing to the fibrous cap formation and plaque stabilizing. A developed plaque gradually enters the lumen and narrows down the lumen to impede blood flow. We introduce a two-phase and macroscopic model to investigate the progression of plaque growth in its advanced stage and analyze the minimum gap (Lumen Clearance) within an atherosclerotic artery so that blood cells can pass through. Cardiac troponin, a high specificity and sensitivity biomarker, facilitates early detection of elevated myocardial infarction, ischemic stroke risks, etc. This study aims at establishing a relationship between the troponin concentration in atherosclerotic arteries and their internal clearance, which could significantly improve our understanding of disease progression. Our observations show that the plaque undergoes rapid evolution in its initial stages, gradually slowing down over time to reach a stable state. A positive correlation exists between the maximum plaque depth and cardiac troponin concentration in the blood. However, the lumen clearance exhibits the opposite behavior. The speed of blood cells slows down at an enhanced plaque depth within atherosclerotic arteries.
Molecular dynamics study of N,N′-di-n-alkyl-3,4,9,10-perylenetetracarboxylic diimide (PTCDI)/rubrene interface: Why the charge transfer at the interface is optimized depending on the alkyl chain length of PTCDI
Authors: Ishiyama Tatsuya , Morimoto Masahiro , Naka Shigeki
Published: October 2024

Molecular dynamics simulations were performed to investigate the interfacial structure of the N,N′-di-n-alkyl-3,4,9,10-perylenetetracarboxylic diimide (PTCDI)/rubrene interface, which represents the donor/acceptor interface in new types of organic light-emission diodes. In particular, the interfacial structure was examined for different alkyl chain lengths of PTCDI (Cn-PTCDI) at n = 4, 8, and 13, in order to elucidate the observed maximum charge transfer efficiency at the C8-PTCDI/rubrene interface in a recent experiment. The results revealed that the molecular conformation of the acceptor (Cn-PTCDI) molecules at the interface undergoes changes depending on the alkyl chain length when interacting with the rubrene molecule. It was found that the closest complex between Cn-PTCDI and rubrene is formed at n = 8, consistent with the experimental observation. In addition, the interfacial structures of Cn-PTCDI/air and rubrene/air were examined and compared to gain insights into the inherent stability associated with the intermolecular interactions at the interface.
Analysis of differential scanning calorimetry data for aged plutonium
Authors: Chiravalle Vincent P.
Published: October 2024

Differential scanning calorimetry data for samples of a 52 year old plutonium alloy with 3.3 at. % Ga that were heated beyond the melting point is analyzed using transition state theory to find activation energies for the δ to ɛ and ɛ to liquid phase transitions. A Bayesian statistical method involving a Gaussian process model is used to find mean values and confidence intervals for the activation energies. The activation energy for the δ to ɛ phase transition increases by 3.3 ± 3.8% per decade, relative to the case when all age related plutonium lattice point defects have been removed through annealing. The corresponding increase in activation energy for the ɛ to liquid transition is shown to be 7.1 ± 1.8% per decade. It is postulated that the change in activation energy with age for both phase transitions is caused, in part, by the accumulation of the same type of lattice point defects associated with the observed increase in elastic bulk modulus over time.
Prediction of interface morphology formed by the oblique gas jet impinging on a liquid surface
Authors: Fu Weijie , Li Daqi , Zhang Xinming
Published: October 2024

This study presents a theoretical analysis of the oblique gas jet impingement process on a liquid surface, elucidating the evolution of the flow field distribution and the influence of jet parameters on cavity shape dynamics. By integrating surface tension effects, the existing Blanks and Chandrasekhara model was refined to develop an advanced predictive model for cavity morphology. The theoretical framework was substantiated through numerical simulations and corroborated with experimental measurements of cavity dimensions, captured using state-of-the-art machine vision technology. The findings reveal a consistent trend in cavity dimension variations: an increase in the cavity surface width with the elevation of the impinging angle from the vertical and an escalation in gas jet velocity. Conversely, a reduction in the impinging angle coupled with an increase in jet velocity leads to a deeper cavity. To enhance the predictive accuracy, the model underwent iterative optimization, incorporating experimental data and accounting for jet parameters. The refined model demonstrated achieved a maximum error of 0.135 mm and a minimum error of 0.03 mm, providing reliable forecasts of cavity depth, which is pivotal for applications in fluid dynamics and related engineering fields.
Targeting attack activity-driven networks
Authors: Zhao Dandan , Wang Li , Zhang Bo , Qian Cheng , Zhong Ming , Li Shenghong , Han Jianmin , Peng Hao , Wang Wei
Published: October 2024

Real-world complex systems demonstrated temporal features, i.e., the network topology varies with time and should be described as temporal networks since the traditional static networks cannot accurately characterize. To describe the deliberate attack events in the temporal networks, we propose an activity-based targeted attack on the activity-driven network to investigate temporal networks’ temporal percolation properties and resilience. Based on the node activity and network mapping framework, the giant component and temporal percolation threshold are solved according to percolation theory and generating function. The theoretical results coincide with the simulation results near the thresholds. We find that targeted attacks can affect the temporal network, while random attacks cannot. As the probability of a highly active node being deleted increases, the temporal percolation threshold increases, and the giant component increases, thus enhancing robustness. When the network’s activity distribution is extremely heterogeneous, network robustness decreases consequently. These findings help us to analyze and understand real-world temporal networks.
Epitaxial (AlxGa1−x−yIny)2O3 alloys lattice matched to monoclinic Ga2O3 substrates
Authors: Schaefer Stephen , Smeaton Michelle , Egbo Kingsley , Hasan Syed , Callahan William , Teeter Glenn , Zakutayev Andriy , Tellekamp M. Brooks
Published: October 2024

We have epitaxially stabilized a series of monoclinic (AlxGa1−x−yIny)2O3 alloys by careful choice of molecular beam epitaxy growth conditions, which balance alloy growth with suboxide desorption. The films are pseudomorphic to (010) β-Ga2O3 substrates at thicknesses up to 150 nm with compositions ranging from (Al0.01Ga0.83In0.16)2O3 to (Al0.24Ga0.75In0.03)2O3. The absorption edge shifts from approximately 4.62–5.14 eV with coincidently increasing Al and decreasing In mole fractions. J–V measurements reveal an increase in resistivity over four orders of magnitude with a maximum value of 4.2 × 105 Ω-cm for (Al0.17Ga0.76In0.07)2O3, which has nearly identical lattice parameters (both in-plane and out-of-plane) to the underlying β-Ga2O3. Scanning transmission electron microscopy of this sample reveals a mostly uniform and single crystalline film, though we identify areas of non-uniform In incorporation and some γ-phase inclusions. This work demonstrates the feasibility of thick layers lattice-matched to β-Ga2O3 with increased bandgap compared to phase-separation limited (Al,Ga)2O3. These alloys can enable higher bandgap epitaxial dielectrics and high sheet charge density transistors by increasing the conduction band offset with respect to β-Ga2O3.
Systematic Uncertainties from Gribov Copies in Lattice Calculation of Parton Distributions in the Coulomb Gauge
Authors: Gao Xiang , He Jinchen , Zhang Rui , Zhao Yong
Published: October 2024

Recently, a new method has been proposed to compute parton distributions using boosted correlators fixed in the Coulomb gauge (CG) within the framework of large-momentum effective theory. This approach, which does not involve Wilson lines, could greatly improve the efficiency and precision of lattice quantum chromodynamics calculations. However, concerns remain regarding whether systematic uncertainties from Gribov copies, which correspond to ambiguities in lattice gauge-fixing, are adequately controlled. This work assesses the effects of Gribov copies on Coulomb-gauge-fixed quark correlators. We utilize different strategies for Coulomb-gauge fixing, selecting two different groups of Gribov copies based on lattice gauge configurations. We examine the differences in the resulting spatial quark correlators in both vacuum and pion states. Our findings indicate that the statistical errors of the matrix elements from both Gribov copies, regardless of the correlation range, decrease proportionally to the square root of the number of gauge configurations. The difference between the strategies does not show statistical significance compared to the gauge noise, demonstrating that the effect of the Gribov copies can be neglected in practical lattice calculations of quark parton distributions.
On the convergence of cosmographic expansions in Lemaître–Tolman–Bondi models
Authors: Modan Asha B , Koksbang S M
Published: October 2024

We study cosmographic expansions of the luminosity distance for a variety of Lemaître–Tolman–Bondi (LTB) models which we specify inspired by local large-scale structures of the Universe. We consider cosmographic expansions valid for general spacetimes and compare to the Friedmann–Lemaître–Robertson–Walker (FLRW) limit of the expansions as well as to its naive isotropic extrapolation to an inhomogeneous Universe. The FLRW expansions are often poor near the observer but become better at higher redshifts, where the light rays have reached the FLRW background. In line with this we find that the effective Hubble, deceleration and jerk parameters of the general cosmographic expansion are often very different from the global ΛCDM values, with deviations up to several orders of magnitude. By comparing with the naive isotropic extrapolation of the FLRW expansion, we assess that these large deviations are mainly due to gradients of the shear. Very close to the observer, the general cosmographic expansion is always best and becomes more precise when more expansion terms are included. However, we find that the convergence radius of the general cosmographic expansion is small for all studied models and observers and the general cosmographic expansion becomes poor for most of the studied observers already before a single LTB structure has been traversed. The small radius of convergence of the general cosmographic expansion has also been indicated by earlier work and may need careful attention before we can safely apply the general cosmographic expansion to real data.
Back-decay of the muonic molecular ion

(
α
μ
t

)

01

2
+

resonantly formed in

(
t
μ
)

1
s

+
4

HeH

+

collision
Authors: Czapliński Wilhelm
Published: October 2024

Resonant formation of the muonic molecular ion

(
α
μ
t

)

01

2
+

in the collision of the muonic tritium atom with the helium hydride ion,

(
t
μ
)

1
s

+
4

HeH

+

→

[

(
α
μ
t
)

01

2
+

, 
p
,
e
e
]

+

, is proposed. The

(
α
μ
t
)

01

2
+

ion is formed in the rotational-vibrational state (0,1) as one of the two nuclei of the final complex. Back-decay process

[

(
α
μ
t
)

01

2
+

,
 
p
,
e
e
]

K
n

+

→

(
t
μ
)

1
s

+
4

HeH

K
′

n
′

+

, where K and n (

K
′

and

n
′

) is the rotational and vibrational quantum number, respectively, is considered in detail and the corresponding decay widths for all possible rotational-vibrational

(
K
,
n
)
→
(

K
′

,

n
′

)

transitions are calculated. Numerous inelastic decay channels of

(
α
μ
t

)

01

2
+

are also presented and discussed. The possible fast resonant formation of the

(
α
μ
t
)

01

2
+

ion may provide an interesting tool for experimental studies of

t

(
α
,
γ
)

7

Li

nuclear fusion, which is one of the most important reactions in Big-Bang nucleosynthesis models. Studying this reaction may prove important for solving the lithium problem.
Geometry, anomaly, topology, and transport in Weyl fermions
Authors: Ahmad Azaz , K Gautham Varma , Sharma Gargee
Published: October 2024

Weyl fermions are one of the simplest objects that link ideas in geometry and topology to high-energy physics and condensed matter physics. Although the existence of Weyl fermions as elementary particles remains dubious, there is mounting evidence of their existence as quasiparticles in certain condensed matter systems. Such systems are termed Weyl semimetals (WSMs). Needless to say, WSMs have emerged as a fascinating class of materials with unique electronic properties, offering a rich playground for both fundamental research and potential technological applications. This review examines recent advancements in understanding electron transport in WSMs. We begin with a pedagogical introduction to the geometric and topological concepts critical to understanding quantum transport in Weyl fermions. We then explore chiral anomaly, a defining feature of WSMs, and its impact on transport phenomena such as longitudinal magnetoconductance and planar Hall effect. The Maxwell-Boltzmann transport theory extended beyond the standard relaxation-time approximation is then discussed in the context of Weyl fermions, which is used to evaluate various transport properties. Attention is also given to the effects of strain-induced gauge fields and external magnetic fields in both time-reversal broken and inversion asymmetric inhomogeneous WSMs. The review synthesizes theoretical insights, experimental observations, and numerical simulations to provide a comprehensive understanding of the complex transport behaviors in WSMs, aiming to bridge the gap between theoretical predictions and experimental verification.
Online classroom student engagement analysis based on facial expression recognition using enhanced YOLOv5 for mitigating cyberbullying
Authors: Wang Shuai , Chen Miaoxia , Ratnavelu K , Bin Shibghatullah Abdul Samad , Keoy Kay Hooi
Published: October 2024

The rapid expansion of online education has heightened concerns about cyberbullying in virtual classrooms. This paper presents a comprehensive approach for detecting cyberbullying by analyzing students’ engagement and emotional responses in online classrooms. Due to the influence of camera resolution and surrounding light in online classrooms, students’ facial expressions are often blurry, and the changes in facial features may not be significant. Moreover, most current recognition algorithms utilize larger models, which may not be suitable for real-time detection in online environments. To address these challenges, this study introduces a student facial expression recognition (SFER) method based on an enhanced YOLOv5 (you only look once version 5) model, termed SFER-YOLOv5. Firstly, the improved soft-non-maximum suppression (NMS) is employed to replace the original NMS, effectively enhancing training efficiency. Then, the coordinate attention module is incorporated into the backbone network to improve detection accuracy, particularly in classroom settings with multiple students or when students are at a considerable distance from the camera. Next, the efficient intersection over union (EIoU) loss function is utilized. EIoU calculates width and height losses separately based on complete-IoU, replacing the aspect ratio. Finally, focal loss is introduced to address sample imbalance issues. The comparative results show that SFER-YOLOv5 achieves an mAP@0.5 of 78.4% on the facial expression recognition-2013 dataset, 98.1% on the CK+ dataset, and 88.9% on our self-constructed dataset student facial expressions in classroom (SFEC). These results underscore the effectiveness of SFER-YOLOv5 in enhancing the accuracy of SFER. The proposed method detects reduced engagement, offering a preventive strategy for mitigating cyberbullying in virtual learning environments.
Elucidating a proper framework for the determination of threading dislocation densities in semiconductor films: a comprehensive study based on Ge/Si(001)
Authors: Xu Chi , Wu Zhengjie , Li Yue , Wang Xiaoyu , Chang Xiyan , Xie Changjiang , Wang Caile , Chen Chen , Wang Yixin , Cong Hui , Xue Chunlai
Published: October 2024

Methods of deducing threading dislocation densities (TDDs) from x-ray diffraction (XRD) peak widths have been reevaluated based on crystallography theories. Moreover, Ge/Si heteroepitaxial structures were taken as model materials for investigation. The procedure is tailored in accordance with the specific designs of modern XRD systems to minimize instrumental interference, whereas practical characteristics of heteroepitaxial films are also considered to avoid intrinsic errors. TDDs of samples grown with different epitaxy methods were investigated using the newly implemented XRD method and etch pit density (EPD) method, and satisfactory agreement has been achieved among three independently calculated sets of TDD results: two from XRD and one from EPD. These values were further corroborated by cross-sectional transmission electron microscopy analysis. Key considerations that are of scientific and technical importance in TDD studies are also discussed in detail. The present work provides not only the most up-to-date elucidation on obtaining TDD values in semiconductor epitaxial films, but also insights into the long-existing ambiguity in TDD calculation methods, which will be helpful for the future studies of defect density characterizations in various material systems.
Enhanced photocatalytic degradation of organic pollutants by randomly oriented 2D SnS2 nanostructures
Authors: Kumari Ritu , Kumar Rakesh
Published: October 2024

In this study, we present a bottom-up solvothermal technique using tin tetrachloride pentahydrate (SnCl4.5H2O) and thioacetamide as precursors to synthesize SnS2 nanostructures. Different solvents including isopropyl alcohol, ethanol (EN), and ethylene glycol were used in the reaction to enhance the photodegradation efficiency of organic pollutants, Methylene Blue (MB), and Tetracycline (TC) in an aqueous medium under simulated solar light irradiation. The SnS2 nanostructures synthesized with these solvents were characterized using various structural, morphological, and optical techniques, including x-ray diffraction, RAMAN, field emission scanning electron microscope, x-ray photoelectron spectroscopy, UV–Vis, and Brunauer–Emmett–Teller analysis. The choice of solvent was found to significantly affect the structural, morphological, and optical properties of the SnS2 nanostructures. Notably, the sample synthesized with EN as the solvent displayed a unique morphology, enhanced light-harvesting ability, efficient charge carrier separation, and a larger specific surface area, all of which contributed to its superior photocatalytic activity. This sample achieved 99.9% degradation of MB and 95% degradation of TC within 20 and 40 min, respectively. The kinetic analysis revealed maximum rate constant (k) values of 0.15242 min−1 for MB and 0.060 95 min−1 for TC, as determined by the pseudo-first-order kinetic model. We also discuss the plausible mechanism involving visible light-induced electron–hole pairs that generate reactive species, leading to the mineralization of dyes into H2O, CO2, and other gaseous products. The synthesized SnS2 nanostructures demonstrate significant potential for enhanced photocatalytic activity in organic pollutant degradation, underscoring their promise in addressing water pollution challenges.
Self-similarity of multilayer networks
Authors: Wang 王 Bing 冰 , Yu 于 Huizhi 蕙芷 , Wei 魏 Daijun 代俊
Published: October 2024

Research on the self-similarity of multilayer networks is scarce, when compared to the extensive research conducted on the dynamics of these networks. In this paper, we use entropy to determine the edge weights in each sub-network, and apply the degree–degree distance to unify the weight values of connecting edges between different sub-networks, and unify the edges with different meanings in the multilayer network numerically. At this time, the multilayer network is compressed into a single-layer network, also known as the aggregated network. Furthermore, the self-similarity of the multilayer network is represented by analyzing the self-similarity of the aggregate network. The study of self-similarity was conducted on two classical fractal networks and a real-world multilayer network. The results show that multilayer networks exhibit more pronounced self-similarity, and the intensity of self-similarity in multilayer networks can vary with the connection mode of sub-networks.
Exact quantum dynamics for two-level systems with time-dependent driving
Authors: He 贺 Zhi-Cheng 郅程 , Wu 吴 Yi-Xuan 奕璇 , Xue 薛 Zheng-Yuan 正远
Published: October 2024

It is well known that the time-dependent Schrrödinger equation can only be solved exactly in very rare cases, even for two-level quantum systems. Thus, finding the exact quantum dynamics under a time-dependent Hamiltonian is not only fundamentally important in quantum physics but also facilitates active quantum manipulations for quantum information processing. In this work, we present a method for generating nearly infinite analytically assisted solutions to the Schrödinger equation for a qubit under time-dependent driving. These analytically assisted solutions feature free parameters with only boundary restrictions, making them applicable in a variety of precise quantum manipulations. Due to the general form of the time-dependent Hamiltonian in our approach, it can be readily implemented in various experimental setups involving qubits. Consequently, our scheme offers new solutions to the Schrödinger equation, providing an alternative analytical framework for precise control over qubits.
Experimental test of an extension of the Rosenzweig–Porter model to mixed integrable-chaotic systems experiencing time-reversal invariance violation
Authors: Zhang 张 Xiaodong 晓东 , Che 车 Jiongning 炯宁 , Dietz Barbara
Published: October 2024

We report on the theoretical and experimental investigations of the transition of a typical quantum system with mixed regular-integrable classical dynamics to one with violated time-reversal (

T

) invariance. The measurements are performed with a flat superconducting microwave resonator with circular shape in which chaoticity is induced by using either long antennas or inserting two circular disks into the cavity, and by magnetizing a ferrite disk placed at its center, which leads to violation of

T

invariance. We propose an extension of the Rosenzweig–Porter (RP) model, which interpolates between mixed regular-chaotic instead of integrable dynamics and fully chaotic dynamics with violated

T

-invariance, and derive a Wigner-surmise like analytical expression for the corresponding nearest-neighbor spacing distribution. We propose a procedure involving this result and those for the RP model to determine the size of

T

-invariance violation and chaoticity and validate it employing the experimental eigenfrequency spectra.