bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical analysis of the powder mixed electrical discharge machining (PMEDM) process for TZM-molybdenum superalloy using finite element method
Authors: Surani Kapil , Patel Shailesh , Mounagurusamy Mathan Kumar , Abdul Zahra Musaddak Maher , Panchal Hitesh , Haque Siddiqui Md Irfanul , Shah Mohd Asif , L Natrayan , Kumar Abhinav
Published: February 2024

The powder mixed electrical discharge machining (PMEDM) process was simulated via finite element analysis in the current study to assess heat behavior and material removal rate. The goal of this paper is to conduct a thorough experimental and thermal examination of electrical discharge machining (EDM) in order to forecast its cutting characteristics and subsequently optimize the output variables using a response surface methodology for simulations and choosing the most suitable set of process variables related to the PMEDM process. This study’s objective is to design a 2D axisymmetrical transient thermal model that might also describe the physics of material removal in a single spark PMEDM operation on a Titanium Zirconium Molybdenum (TZM) superalloy. ANSYS (version 9.1) software is used to perform transient heat transfer simulations to determine the temperature profile with the amount of material removal at different current, pulse on and off times, gap voltages, and fraction of heat that enters the specimen. The PMEDM process produced craters with a lower diameter and depth, which increased the material removal rate and enhanced the surfacing quality. Compared to the conventional EDM process, the inclusion of powder raised the heat flux given to the work material by 10%–12%. It has been determined that with the single spark modeling technique, the temperature significantly dropped in both the radial and depth directions. The computational results are compared with experimental observations for similar machining conditions, and both results agree satisfactorily.
Quantum integrability and chaos in a periodic Toda lattice with balanced loss–gain
Authors: Ghosh Supriyo , Ghosh Pijush K.
Published: February 2024

We consider an equal-mass quantum Toda lattice with balanced loss–gain for two and three particles. The two-particle Toda lattice is integrable, and two integrals of motion that are in involution have been found. The bound-state energy and the corresponding eigenfunctions have been obtained numerically for a few low-lying states. The three-particle quantum Toda lattice with balanced loss–gain and velocity-mediated coupling admits mixed phases of integrability and chaos depending on the value of the loss–gain parameter. We have obtained analytic expressions for two integrals of motion that are in involution. Although an analytic expression for the third integral has not been found, the numerical investigation suggests integrability below a critical value of the loss–gain strength and chaos above this critical value. The level spacing distribution changes from the Wigner–Dyson to the Poisson distribution as the loss–gain parameter passes through this critical value and approaches zero. An identical behavior is seen in terms of the gap-ratio distribution of the energy levels. The existence of mixed phases of quantum integrability and chaos in the specified ranges of the loss–gain parameter has also been confirmed independently via the study of level repulsion and complexity in higher order excited states.
Some new lump molecules and hybrid molecular states of a (3 + 1)-dimensional generalized variable coefficient Kadomtsev–Petviashvili equation
Authors: Yue Juan , Zhao Zhonglong
Published: February 2024

In this paper, a (3 + 1)-dimensional generalized variable coefficient Kadomtsev–Petviashvili equation is investigated systematically, which can characterize evolution of the long water waves and small amplitude surface waves with the weak nonlinearity, weak dispersion, and weak perturbation in fluid mechanics. We investigate one lump and lump molecules obtained from one breather and breather molecules by a new degenerating breather method, respectively. In addition, the bound state of lump molecules and other localized waves is derived theoretically by velocity resonance. Considering the condition of variable coefficient, the several sets of interesting solutions having a complex structure are obtained, which include the type of parabolic, S-shaped, and periodic. The analysis method can also help us to study lump molecules existing in other integrable systems from a new perspective.
Impact of external magnetic field on temperature anisotropy driven Weibel instability in a magnetized plasma
Authors: Pahuja Twinkle , Kumar Amit , Sagar Himank , Gupta Ruby , Sharma Jyotsna
Published: February 2024

In this paper, we investigate the impact of an external magnetic field on the Weibel instability driven by temperature anisotropy in a magnetized plasma. The study provides the influence of electron temperature anisotropy, considering both cold as well as warm ions. We derive expressions for the growth rate Γ (s−1) in each case to quantify the effect of some specific parameters on the instability. For example, the growth rate is plotted against the magnetic field for three distinct cases: considering only electrons, including cold ions, and incorporating warm ions. It is observed that the growth rate decreases as the applied magnetic field increases. Furthermore, the addition of both cold and warm ions to the plasma significantly influences the observed effects. It can be explained as follows: in the presence of cold ions, the growth rate is decreased with an increase in the wave number kz (cm−1). In addition, a decrease in the growth rate is observed with an increasing wave number in the case of warm ions. Therefore, it can be seen that the Weibel instability, propelled by thermal anisotropy, holds significant implications owing to its prevalence in both astrophysical and laboratory plasmas. The findings presented here are expected to contribute to the advancements in magnetic field generation and particle acceleration in various astrophysical phenomena, including gamma-ray bursts, relativistic collisionless shock fronts, radio supernovae, and pulsar winds.
Positivity preserving density matrix minimization at finite temperatures via square root
Authors: Leamer Jacob M. , Dawson William , Bondar Denys I.
Published: February 2024

We present a Wave Operator Minimization (WOM) method for calculating the Fermi–Dirac density matrix for electronic structure problems at finite temperature while preserving physicality by construction using the wave operator, i.e., the square root of the density matrix. WOM models cooling a state initially at infinite temperature down to the desired finite temperature. We consider both the grand canonical (constant chemical potential) and canonical (constant number of electrons) ensembles. Additionally, we show that the number of steps required for convergence is independent of the number of atoms in the system. We hope that the discussion and results presented in this article reinvigorate interest in density matrix minimization methods.
Multifunctional HfAlO thin film: Ferroelectric tunnel junction and resistive random access memory
Authors: Park Yongjin , Lee Jong-Ho , Lee Jung-Kyu , Kim Sungjun
Published: February 2024

This study presents findings indicating that the ferroelectric tunnel junction (FTJ) or resistive random-access memory (RRAM) in one cell can be intentionally selected depending on the application. The HfAlO film annealed at 700 °C shows stable FTJ characteristics and can be converted into RRAM by forming a conductive filament inside the same cell, that is, the process of intentionally forming a conductive filament is the result of defect generation and redistribution, and applying compliance current prior to a hard breakdown event of the dielectric film enables subsequent RRAM operation. The converted RRAM demonstrated good memory performance. Through current–voltage fitting, it was confirmed that the two resistance states of the FTJ and RRAM had different transport mechanisms. In the RRAM, the 1/f noise power of the high-resistance state (HRS) was about ten times higher than that of the low-resistance state (LRS). This is because the noise components increase due to the additional current paths in the HRS. The 1/f noise power according to resistance states in the FTJ was exactly the opposite result from the case of the RRAM. This is because the noise component due to the Poole–Frenkel emission is added to the noise component due to the tunneling current in the LRS. In addition, we confirmed the potentiation and depression characteristics of the two devices and further evaluated the accuracy of pattern recognition through a simulation by considering a dataset from the Modified National Institute of Standards and Technology.
Experimental study on spray characteristics of aviation kerosene from a pressure-swirl nozzle in high-speed airflow with elevated temperatures
Authors: Zheng Ke , Gan Zhiwen , Wang Xinyao , Han Xuesong , Zheng Tianqi , Wang Jianchen
Published: February 2024

Spray characteristics of aviation kerosene are critical to the performance of gas turbine combustors. Actual gas turbine combustors are mainly operated at high temperatures and high-speed airflow environments, whereas almost all research on spray characteristics in high-speed airflow is limited to room temperature in the literature. In this paper, the spray characteristics of aviation kerosene from a pressure-swirl nozzle are investigated experimentally in the airflow temperature range of 313–500 K and the airflow speed range of 108–136 m/s. The information on spray characteristics such as droplet flux, velocity, and diameter was obtained by phase Doppler anemometry. Planar Mie scatter was performed to obtain the information on the concentration distribution of spray. The results show that the droplet flux, velocity, concentration, and Sauter mean diameter (D32) change significantly with airflow temperatures. In special, D32 in the center recirculation zone shows an increasing trend with increasing airflow temperature. The difference in the change of D32 along the propagation direction at elevated airflow temperatures is mainly due to the difference in evaporation processes. It was found that the evaporation models of a droplet that existed in literature do not predict well the D32 variation of spray in this experiment. A new spray evaporation model considering turbulence and fuel vapor fraction is proposed, which significantly reduces the prediction errors of variation in D32 in this experiment. This paper can provide experimental data and preliminary theoretical references for subsequent investigation of spray characteristics in high-speed airflow with elevated temperatures.
Robust mode analysis of three-bluff-body combustion flow
Authors: Gunaratne Gemunu H. , Fugger Christopher A. , Caswell Andrew W.
Published: February 2024

Studies of combustion flows behind bluff-body configurations help optimize stability and efficacy of propulsion engines. However, theoretical and computational analyses of these systems are difficult in realistic configurations, especially for strongly driven flows. The advent of high-resolution, high-frequency imaging opens a new avenue to study these systems through data-analytic approaches. We use a recently introduced methodology, robust mode analysis (RMA), to study a series of combustion flows behind a three-bluff-body configuration. RMA identifies periodically evolving spatial structures in a flow common between multiple, nominally identical realizations of a flow and, hence, can be used to discard noise and other irregular flow facets. Our experiment records the flow in two spatial perspectives and through a set of time-series pressure measurements. Periods of robust modes, computed through the three recordings, are shown to be consistent for the entire set of experiments. A method to quantify the proximity of spatial structures of modes from different imaging viewpoints is introduced. It is used to compare robust modes in the two imaging views, to identify quasi-periodically evolving flow constituents, and to construct bifurcation diagrams for each constituent.
Magnetic properties and cryogenic magnetocaloric effect of pyrochlore structure RE2Ti2O7 (RE = Gd, Tb, and Ho) compounds
Authors: Xu Bo , Xie Huicai , Mo Zhaojun , Gao Xinqiang , Wang Junfeng , Li Zhenxing , Shen Jun
Published: February 2024

Magnetic refrigeration technology is regarded as one of the ideal solutions for cryogenic refrigeration, while magnetocaloric materials are the crucial ones. A series of polycrystalline RE2Ti2O7 (RE = Gd, Tb, and Ho) compounds were prepared by a simple one-step solid-phase reaction method in the atmosphere. The crystal structure, magnetic properties, and magnetocaloric effect (MCE) of these compounds were systematically investigated. Crystallographic research indicates that these compounds crystallized in a pyrochlore structure. Meanwhile, magnetic measurements illustrate that this class of pyrochlore oxides is highly frustrated magnetic materials and exhibits complex magnetic behavior. In addition, under the field change of 0–1 T, the values of the maximum magnetic entropy change (−ΔSMmax) and the refrigeration capacity are calculated to be 0.9 and 5.8 J/kg for Gd2Ti2O7, 9.0 and 32.9 J/kg for Tb2Ti2O7, 9.9 and 29.9 J/kg for Ho2Ti2O7, respectively. Therefore, RE2Ti2O7 (RE = Tb and Ho) pyrochlores exhibit excellent MCEs under low magnetic fields, providing candidate materials for the application of cryogenic magnetic refrigeration technology.
Numerical analysis of discharge gap related fluctuations in a cylindrical positive discharge corona
Authors: Talib Kamran Abu , Naz Muhammad Yasin , Ibrahim Ahmed Ahmed , Kamran Kashif , Ayyaz Muhammad , Shoaib Muhammad
Published: February 2024

An efficient technique was used to model corona discharges without incorporating flux corrections. A position-state separation (POSS) technique was employed to solve the convection-dominated continuity equations prevalent in designing efficient corona discharges. The suggested approach utilizes an Eulerian scheme to solve the convective acceleration, diffusion, and response subproblems. The exceptional performance of POSS in terms of computing cost, resilience, and resolution is demonstrated by a series of numerical tests in various dimensions and coordinate systems. MATLAB was used to run four tests, namely, the square test, Davies test, general advection-diffusion test, and corona test. The average error in POSS was calculated as 0.06, which is much lower than the error in FEM-FCT (0.2677) and FVM-MUSCL (0.2650) algorithms. A 1 mm thick peak of space charge was formed around the anode after 1.2 ns. For an outer radius of 2 cm, ripples in ionizing waves were seen at t = 5000 ns. All the ionizing peaks were produced at around 0.5 cm away from the anode.
Supermirrors and spin wave amplifications
Authors: Wang X. R. , Gong X. , Jing K. Y.
Published: February 2024

Superradiance, a phenomenon of multiple facets, normally occurs in classical/quantum physics under extreme conditions. Here, we present its manifestation in spin waves under a practical condition. We show that an interface between a current-free ferromagnetic region and a current-flow ferromagnetic region can be a spin wave supermirror whose reflection coefficient is larger than 1. The super-reflection is the consequence of current-induced spectrum inversion where phase and group velocities of spin waves are in the opposite directions. An incident spin wave activates a backward propagating refractive wave inside the current-flow region. The refractive spin wave re-enters the current-free region to constructively interfere with the reflective wave. It appears that the current-flow region coherently emits reflective waves, leading to a super-reflection. The process resembles superradiance of a spinning black hole through the Hawking radiation process or Dicke superradiance of cavity photons inside population inverted media.
He Aroka Urutā. Rural health provider perspectives of the COVID-19 vaccination rollout in rural Aotearoa New Zealand with a focus on Māori and Pasifika communities: a qualitative study
Authors: Blattner Katharina , Clay Lynne , Keenan Rawiri , Taafaki Jane , Crengle Sue , Nixon Garry , Fortune Kiri , Stokes Tim
Published: February 2024

Introduction From a coronavirus disease (COVID-19) pandemic perspective, Aotearoa New Zealand (NZ) rural residents formed an at-risk population, and disparities between rural and urban COVID-19 vaccination coverage have been found. Aim To gain insight into factors contributing to the urban–rural COVID-19 vaccination disparity by exploring NZ rural health providers’ experiences of the vaccine rollout and pandemic response in rural Māori and Pasifika communities. Methods Rural health providers at four sites participated in individual or focus group semi-structured interviews exploring their views of the COVID-19 vaccine rollout. Thematic analysis was undertaken using a framework-guided rapid analysis method. Results Twenty interviews with 42 participants were conducted. Five themes were identified: Pre COVID-19 rural situation, fragile yet resilient; Centrally imposed structures, policies and solutions – urban-centric and Pakehā focused; Multiple logistical challenges – poor/no consideration of rural context in planning stages resulting in wasted resource and time; Taking ownership – rural providers found geographically tailored, culturally anchored and locally driven solutions; Future directions – sustained investment in rural health services, including funding long-term integrated (rather than ‘by activity’) health services, would ensure success in future vaccine rollouts and other health initiatives for rural communities. Discussion In providing rural health provider perspectives from rural areas serving Māori and Pasifika communities during the NZ COVID-19 vaccine rollout, the importance of the rural context is highlighted. Findings provide a platform on which to build further research regarding models of rural health care to ensure services are designed for rural NZ contexts and capable of meeting the needs of diverse rural communities.
Variations in life-history traits in exploited and unexploited populations of Perth herring (Nematalosa vlaminghi): evidence for density-dependent growth?
Authors: Smith Kimberley A. , Hesp Sybrand Alexander , Coulson Peter G.
Published: February 2024

Context Fishing can reduce population biomass, allowing remaining individuals to grow faster and mature earlier because of greater resource availability, which potentially compensates for lost reproductive output over a shortened lifespan resulting from fishing mortality. Aims To compare life-history traits of Nematalosa vlaminghi, a long-lived (20 years), semi-anadromous fish endemic to south-western Australia, in exploited and unexploited populations living in similar environments. Methods Populations were sampled in 2016–2018. Total mortality (Z) was estimated using catch-curve analyses, allowing for annual recruitment variability. Maturation age and length was estimated by logistic regression analysis. Growth curves were fitted to length-at-age data. Key results Compared to the unexploited population, Z was 2.6 times greater, juvenile growth was more than twice as fast, and maturity was attained at least 3 years earlier in the unexploited population. Conclusions Results supported the hypothesis of faster growth in exploited populations because of density-dependent processes. Environmental factors may also have contributed to trait differences between populations. Implications Faster growth and earlier maturation may partly compensate for lost reproductive output in exploited populations, although severe age truncation owing to fishing is still likely to decrease population resilience in this species, irrespective of any compensatory density-dependent processes.
Deportation threat predicts Latino US citizens and noncitizens’ psychological distress, 2011 to 2018
Authors: Johnson Amy L. , Levesque Christopher , Lewis Neil A. , Asad Asad L.
Published: February 2024

The national context of deportation threat, defined as the federal government’s approach to deportation and/or deportation’s salience to the US public, fluctuated between 2011 and 2018. US Latinos across citizenship statuses may have experienced growing psychological distress associated with these changes, given their disproportionate personal or proximal vulnerabilities to deportation. Drawing on 8 y of public- and restricted-access data from the National Health Interview Survey (2011 to 2018), this article examines trends in psychological distress among Latinos who are US-born citizens, naturalized citizens, and noncitizens. It then seeks to explain these trends by considering two theoretical pathways through which the national context of deportation threat could distress Latinos: 1) through discrete dramatic societal events that independently signal a change to the country’s approach to deportation and/or that render deportation temporarily more salient to the public or 2) through more gradual changes to the country’s everyday institutional (i.e., quotidian efforts to detain and deport noncitizens) and social (i.e., deportation’s ongoing salience to a concerned public) environment of deportation threat. We find that, though both pathways matter to some degree, there is more consistent evidence that the gradual changes are associated with Latino US citizens and noncitizens’ overall experiences of psychological distress. The article highlights how, even absent observable spillover effects of dramatic societal events bearing on deportation threat, the institutional and social environment in which they occur implicates Latinos’ well-being.
Deep learning models reveal replicable, generalizable, and behaviorally relevant sex differences in human functional brain organization
Authors: Ryali Srikanth , Zhang Yuan , de los Angeles Carlo , Supekar Kaustubh , Menon Vinod
Published: February 2024

Sex plays a crucial role in human brain development, aging, and the manifestation of psychiatric and neurological disorders. However, our understanding of sex differences in human functional brain organization and their behavioral consequences has been hindered by inconsistent findings and a lack of replication. Here, we address these challenges using a spatiotemporal deep neural network (stDNN) model to uncover latent functional brain dynamics that distinguish male and female brains. Our stDNN model accurately differentiated male and female brains, demonstrating consistently high cross-validation accuracy (>90%), replicability, and generalizability across multisession data from the same individuals and three independent cohorts (N ~ 1,500 young adults aged 20 to 35). Explainable AI (XAI) analysis revealed that brain features associated with the default mode network, striatum, and limbic network consistently exhibited significant sex differences (effect sizes > 1.5) across sessions and independent cohorts. Furthermore, XAI-derived brain features accurately predicted sex-specific cognitive profiles, a finding that was also independently replicated. Our results demonstrate that sex differences in functional brain dynamics are not only highly replicable and generalizable but also behaviorally relevant, challenging the notion of a continuum in male-female brain organization. Our findings underscore the crucial role of sex as a biological determinant in human brain organization, have significant implications for developing personalized sex-specific biomarkers in psychiatric and neurological disorders, and provide innovative AI-based computational tools for future research.
Diverse cytomegalovirus US11 antagonism and MHC-A evasion strategies reveal a tit-for-tat coevolutionary arms race in hominids
Authors: Zimmermann Cosima , Watson Gabrielle M. , Bauersfeld Liane , Berry Richard , Ciblis Barbara , Lan Huan , Gerke Carolin , Oberhardt Valerie , Fuchs Jonas , Hofmann Maike , Freund Christian , Rossjohn Jamie , Momburg Frank , Hengel Hartmut , Halenius Anne
Published: February 2024

Recurrent, ancient arms races between viruses and hosts have shaped both host immunological defense strategies as well as viral countermeasures. One such battle is waged by the glycoprotein US11 encoded by the persisting human cytomegalovirus. US11 mediates degradation of major histocompatibility class I (MHC-I) molecules to prevent CD8+ T-cell activation. Here, we studied the consequences of the arms race between US11 and primate MHC-A proteins, leading us to uncover a tit-for-tat coevolution and its impact on MHC-A diversification. We found that US11 spurred MHC-A adaptation to evade viral antagonism: In an ancestor of great apes, the MHC-A A2 lineage acquired a Pro184Ala mutation, which confers resistance against the ancestral US11 targeting strategy. In response, US11 deployed a unique low-complexity region (LCR), which exploits the MHC-I peptide loading complex to target the MHC-A2 peptide-binding groove. In addition, the global spread of the human HLA-A*02 allelic family prompted US11 to employ a superior LCR strategy with an optimally fitting peptide mimetic that specifically antagonizes HLA-A*02. Thus, despite cytomegaloviruses low pathogenic potential, the increasing commitment of US11 to MHC-A has significantly promoted diversification of MHC-A in hominids.
The global RNA–RNA interactome ofKlebsiella pneumoniaeunveils a small RNA regulator of cell division
Authors: Ruhland Eric , Siemers Malte , Gerst Ruman , Späth Felix , Vogt Laura Nicole , Figge Marc Thilo , Papenfort Kai , Fröhlich Kathrin Sophie
Published: February 2024

The ubiquitous RNA chaperone Hfq is involved in the regulation of key biological processes in many species across the bacterial kingdom. In the opportunistic human pathogenKlebsiella pneumoniae, deletion of thehfqgene affects the global transcriptome, virulence, and stress resistance; however, the ligands of the major RNA-binding protein in this species have remained elusive. In this study, we have combined transcriptomic, co-immunoprecipitation, and global RNA interactome analyses to compile an inventory of conserved and species-specific RNAs bound by Hfq and to monitor Hfq-mediated RNA–RNA interactions. In addition to dozens of RNA–RNA pairs, our study revealed an Hfq-dependent small regulatory RNA (sRNA), DinR, which is processed from the 3′ terminal portion ofdinImRNA. Transcription ofdinIis controlled by the master regulator of the SOS response, LexA. As DinR accumulates inK. pneumoniaein response to DNA damage, the sRNA represses translation of theftsZtranscript by occupation of the ribosome binding site. Ectopic overexpression of DinR causes depletion offtsZmRNA and inhibition of cell division, while deletion ofdinRantagonizes cell elongation in the presence of DNA damage. Collectively, our work highlights the important role of RNA-based gene regulation inK. pneumoniaeand uncovers the central role of DinR in LexA-controlled division inhibition during the SOS response.
Purely elastic turbulence in pressure-driven channel flows
Authors: Lellep Martin , Linkmann Moritz , Morozov Alexander
Published: February 2024

Solutions of long, flexible polymer molecules are complex fluids that simultaneously exhibit fluid-like and solid-like behavior. When subjected to an external flow, dilute polymer solutions exhibit elastic turbulence—a unique, chaotic flow state absent in Newtonian fluids, like water. Unlike its Newtonian counterpart, elastic turbulence is caused by polymer molecules stretching and aligning in the flow, and can occur at vanishing inertia. While experimental realizations of elastic turbulence are well-documented, there is currently no understanding of its mechanism. Here, we present large-scale direct numerical simulations of elastic turbulence in pressure-driven flows through straight channels. We demonstrate that the transition to elastic turbulence is sub-critical, giving rise to spot-like flow structures that, further away from the transition, eventually spread throughout the domain. We provide evidence that elastic turbulence is organized around unstable coherent states that are localized close to the channel midplane.
Conditional Subsidies for Domestic Tourists: The Case ofPreViajein Argentina
Authors: Garcia Carolina I. , Porto Natalia , Ciaschi Matías O.
Published: February 2024

This case study exploresPreViaje(in English, PreTrip), an unprecedented tourism demand program launched in 2020 in Argentina as a response to the COVID-19 outbreak.

PreViajeis a public policy at the national level that subsidises the selling of tourism services to residents travelling within the country. Itssui generisnature primarily lies in two characteristics: (i) the selling of tourism services takes place before travelling and (ii) the government subsidises (up to) half of the tourist spending. The program features conditionalities that determine eligibility for the subsidy.

To study the emergence and evolution of the program, we use the three policy strategies suggested by the UNWTO to deal with the negative effects of COVID-19: (i) managing the crisis and mitigating the impact, (ii) providing stimulus and accelerating recovery and (iii) preparing for tomorrow.

Information

© The Authors 2024
Wafer-scale silicon microfabrication technology toward realization of low-cost sub-THz waveguide devices
Authors: Zhao Xinghai , Wu Peng , Liu Fei
Published: February 2024

This paper presents a wafer-scale silicon microfabrication technology for the sub-terahertz (sub-THz) waveguide device mass production. Based on the effective scheme, a WR-5 (140–220 GHz) straight rectangular waveguide and a WR-2.8 (260–400 GHz) rectangular waveguide bandpass filter are implemented as demonstrated examples. The silicon deep reactive ion etching (DRIE) process is employed to etch through the total thickness of the silicon wafer and form the main waveguide channels. Then, a low-temperature thermal compression process is used to bond the trough-etched wafer with the top and bottom metallised silicon wafers to form the closed waveguide structures without any precise alignment process. The fabricated waveguide has the benefit of low transmission loss (0.03–0.05 dB mm−1) at the whole G band. Besides, to measure the fabricated WR-2.8 waveguide filter and solve the measuring equipment standard waveguide difference, silicon micromachined waveguide transitions are explored and fabricated to match two different frequency-band modules for measuring the waveguide filters in the desired full frequency band, which also has a potential application for the different size waveguide conversion. The measured results agree well with the simulated ones. The measured 3 dB bandwidth is 9.3%, with a central frequency of 343 GHz; the average insertion loss (IL) is about 1.6 dB in the pass band, including two extra straight waveguides of 8 mm length on input/output ends and two external waveguide-to-waveguide transitions. The proposed method provides a feasible and cost-effective solution for the mass production of high-performance waveguide devices and integrated systems in sub-THz frequency bands and beyond.
Extraction of contact resistivity for a partial contact solar cell
Authors: Kailasam Shanmugam , Vijayan Ramachandran Ammapet , Varadharajaperumal Muthubalan
Published: February 2024

Partial contacts are used in solar cells and other electronic devices. The contact resistivity and contact resistance of these partial contacts play a significant role in the performance optimization of these devices. In this work, we propose a strategy for accurate extraction of the partial contact resistivity

(

ρ

PC

)

of a solar cell with Ohmic (or linear) and Schottky (or non-linear) contacts. We demonstrate how the Cox–Strack method can accurately estimate the

ρ

PC

of a solar cell using Sentaurus TCAD-based simulations. Our simulation predicts that for linear contact solar cells,

ρ

PC

is approximately constant when the contact fraction is varied, whereas for non-linear contact,

ρ

PC

decreases with contact fraction as opposed to the previously reported works. The experimentally reported data is also shown to support the claim for the linear contacts further. Despite the larger full-contact resistivity of non-linear contacts, the contact resistivity and fill factor (FF) of both linear and non-linear partial contact solar cell is almost similar to

∼

3.5
−
5

m

Ω

c

m

−
2

and

∼

75% respectively at a 0.3% contact fraction. This is attributed to the reduction in contact resistivity for non-linear contacts with contact fraction. We finally show the generality of this study for any contact material system. This work can be applied to any device with partial contacts.
Characterization of a hyperbolic vortex plasma reactor for the removal of aqueous phase micropollutants
Authors: Klymenko Roman , de Kroon Esther , Agostinho Luewton L F , Fuchs Elmar C , Woisetschläger Jakob , Hoeben Wilfred F L M
Published: February 2024

The present study focuses on the characterization of a hyperbolic vortex plasma reactor through the comparison of various plasma-atmospheric regimes for the production efficiency of reactive nitrogen (RNS) and reactive oxygen (ROS) species. The research also explores effectiveness in the removal of micropollutants, including pharmaceuticals and per- and polyfluoroalkyl substances (PFAS). The technology includes several degradation mechanisms, such as advanced oxidation, ultraviolet photolysis, ozonation, electrolysis, and shockwave water purification, without the need for additional chemicals. Our results indicate that the plasma of bipolar or ‘flashover’ mode is notably more effective and efficient than both positive or negative polarity. Through the testing of various energy levels, it has been demonstrated that higher energy plasma yields lower efficiency but necessitates shorter treatment times compared to lower energy treatment. When plasma is produced under ambient atmosphere, water chemical properties change significantly in comparison to treatment under argon (Ar) or nitrogen (N2) due to the presence of both oxygen and N2 molecules. In a N2 atmosphere, the predominant formation is of RNS due to the chemical reactivity of N2 exited states, whereas under Ar atmosphere, predominantly ROS are generated. Notable advantages of this technology are its scalability and its low energy requirements. The scalability of the technology involves increasing the size of the reactor, the power and electrode count.
Friction of a driven chain: role of momentum conservation, Goldstone and radiation modes
Authors: Das Debankur , Vink Richard , Krüger Matthias
Published: February 2024

We analytically study friction and dissipation of a driven bead in a 1D harmonic chain, and analyze the role of internal damping mechanism as well as chain length. Specifically, we investigate Dissipative Particle Dynamics and Langevin Dynamics, as paradigmatic examples that do and do not display translational symmetry, with distinct results: For identical parameters, the friction forces can differ by many orders of magnitude. For slow driving, a Goldstone mode traverses the entire system, resulting in friction of the driven bead that grows arbitrarily large (Langevin) or gets arbitrarily small (Dissipative Particle Dynamics) with system size. For a long chain, the friction for DPD is shown to be bound, while it shows a singularity (i.e. can be arbitrarily large) for Langevin damping. For long underdamped chains, a radiation mode is recovered in either case, with friction independent of damping mechanism. For medium length chains, the chain shows the expected resonant behavior. At the resonance, friction is non-analytic in damping parameter γ, depending on it as γ
−1. Generally, no zero frequency bulk friction coefficient can be determined, as the limits of small frequency and infinite chain length do not commute, and we discuss the regimes where ‘simple’ macroscopic friction occurs.
Indexes for evaluation of dynamic characteristics of pressure-sensitive paint based on pressure sensitivity and frequency response
Authors: Kasai Miku , Nagata Takayuki , Nonomura Taku
Published: February 2024

Two evaluation indexes were proposed to select the optimal PSP for unsteady pressure measurement from various PSPs with different pressure sensitivity and frequency response. An effective sensitivity coefficient calculated by pressure sensitivity and gain attenuation due to the response delay was proposed. Furthermore, an effective amount of intensity change was recommended, which takes into account the emission intensity and the effective sensitivity coefficient, because the magnitude of the intensity of a PSP is also important for unsteady-pressure measurement with high-speed sampling. A total of five types of PC-PSPs developed in previous studies were compared: two types of fast-response PC-PSPs using Pt(II) meso-tetra (pentafluorophenyl) porphine (PtTFPP) with poly(isobutyl methacrylate) (poly(IBM)) and ruthenium complex with RTV silicone, respectively, and three types of PC-PSPs using PtTFPP with poly[1-trimethylsilyl)-1-propyne] (poly(TMSP)). A comparison was made using the proposed evaluation indexes under various pressure ranges. The results shows that poly(TMSP)-based PC-PSP has a high effective sensitivity coefficient at pressures less than 20 kPa. On the other hand, poly(IBM)-based PC-PSP has the highest effective sensitivity coefficient at a pressure of 100 kPa. The effective amount of intensity change of poly(TMSP)-based PC-PSP is the highest at 2 kPa, but that of poly(IBM)-based PC-PSP is the highest at a pressure higher than 5 kPa among the evaluated PC-PSPs due to its high luminescence intensity. A PSP with high emission intensity will provide high performance in terms of fluctuation of emission intensity detected by the photodetector when the excitation intensity and the exposure time are limited due to limitations of optical equipment or high-speed sampling.
A robust pairing method for two-pulse particle tracking velocimetry based on coherent point drift
Authors: Mercier Bertrand , Thomas Lionel , Tremblais Benoit , David Laurent
Published: February 2024

Particle tracking velocity has reached a high level of maturity in time-resolved measurements since the introduction and development of the Shake-The-Box algorithm. The effectiveness of this approach lies, in part, in its ability to exploit the temporal coherence of particle trajectories to reject the ghost particles while increasing the density of true particles. However, certain situations may prevent time-resolved measurements. In those cases, a Two-Pulse configuration is often the only option. This raises a challenge with regard to the capacity in separating the ghost from the true particles due to the lack of long-term trajectories. This article proposes a new approach to solve this problem using the coherent point drift (CPD) method. This method identifies a spatially coherent deformation field that models the transformation between two correlated sets of points. In the context of particle tracking velocimetry, the imposed spatial coherence of this calculation is believed to act in the same way as the temporal coherence that made Shake-The-Box successful. The CPD is governed by three parameters whose optimal values have been evaluated in the present contribution. These values were found to be weakly sensitive to the characteristics of the flow under study, ensuring that this method is robust without further tuning of the parameters. The method is then compared with the Two-Pulse implementation of Shake-The-Box (2P-STB) available in Davis 10.2. For this purpose, sets of realistic images were generated at two successive times for different configurations based of synthetically generated turbulent flows. The Iterative-Particle-Reconstruction in Davis 10.2 was then used to extract the list of particles to be processed by CPD. The comparison shows a better recall with 2P-STB than CPD, especially for large time intervals between frames, but an overall better rejection of ghost particles by CPD than 2P-STB, which was the expected benefit of this method.
Investigation of spatial resolution of electrical capacitance tomography based on the electromagnetic momentum (ECT-EMM)
Authors: Yang Yidan , Liu Guoqiang , Liu Jing
Published: February 2024

Electrical capacitance tomography (ECT) is a permittivity imaging method widely used in industrial inspection. The equations described by the ECT technique are nonlinear and ill-posed, which results in low image resolution. ECT can be considered an imaging method based on the Green’s reciprocity theorem, an energetic reciprocity theorem. ECT detects scalars, i.e. capacitances. Electromagnetic fields have both ‘energy’ and ‘momentum.’ In recent years, the electromagnetic momentum reciprocity theorem has enriched the electromagnetic reciprocity theorem. The electromagnetic momentum reciprocity theorem is an imaging method that detects vectors, i.e. capacitance gradients. Vectors contain richer information than scalars; thus, electrical capacitance tomography based on electromagnetic momentum (ECT-EMM) methods is expected to improve the resolution of permittivity imaging. This paper briefly describes the principle of the ECT-EMM technique for image reconstruction using sensitivity matrix gradient and capacitance gradient. Tikhonov regularisation algorithm is applied. The two methods, with and without capacitance measurements, are used to evaluate imaging resolution. Under different numbers of pixels and electrodes, typical permittivity distributions are used for reconstruction, and correlation coefficients are calculated. Simulations and experiments show that the ECT-EMM technique recognises object boundaries more clearly with high noise immunity. Five quality measures are used to evaluate the performance of the point spread function without capacitance measurements. Compared to ECT, the ECT-EMM technique is more sensitive to the central region away from the electrodes, recognises smaller minimum objects, and has smaller shape deformation.
Planar nanoscale vacuum channel transistors based on resistive switching
Authors: Zhang Yan , Zhang Gengmin , Zhan Fangyuan , He Yidan
Published: February 2024

Resistance switching (RS) offers promising applications in a variety of areas. In particular, silicon oxide (SiO
x
) under RS can serve as electron sources in new types of miniature vacuum electron tubes. In this work, planar nanoscale vacuum channel transistors (NVCTs) with graphene electrodes and RS SiO
x
electron sources were developed. In each RS-NVCT, the resistance between the ground and the gate underwent high–low–high transitions, which resulted from formation and subsequent rupture of Si conducting filaments. Electrons were emitted from the post-reset Si filaments and the current received by the collector (I
C) was well controlled by the gate voltage (V
G). The transfer characteristics reveal that I
C was quite sensitive to V
G when RS occurred. With V
G sweeping from 0 to −20 V, the obtained subthreshold swing (SS) of 76 mV dec−1 was quite close to the theoretical limit of the SS of a field effect transistor at room temperature (60 mV dec−1). The largest ON/OFF ratio was of the order of 106. The output characteristics of the devices indicate that the dependence of I
C on the collector voltage (V
C) weakened at high V
C values. These results demonstrate the application potential of RS-NVCTs as either switching devices or amplifiers.
Monotonic convergence of positive radial solutions for general quasilinear elliptic systems
Authors: Devine Daniel , Karageorgis Paschalis
Published: February 2024

We study the asymptotic behavior of positive radial solutions for quasilinear elliptic systems that have the form

Δ
p

u

=

c
1

|

x

|

m
1

⋅

g
1

v

⋅

|

∇
u

|

α

in 

R

n

,

Δ
p

v

=

c
2

|

x

|

m
2

⋅

g
2

v

⋅

g
3

|

∇
u

|

in 

R

n

,

where

Δ
p

denotes the p-Laplace operator, p > 1,

n
⩾
2

,

c
1

,

c
2

>
0

and

m
1

,

m
2

,
α
⩾
0

. For a general class of functions gj
which grow polynomially, we show that every non-constant positive radial solution (u, v) asymptotically approaches

(

u
0

,

v
0

)
=
(

C
λ

|

x

|

λ

,

C
μ

|

x

|

μ

)

for some parameters

λ
,
μ
,

C
λ

,

C
μ

>
0

. In fact, the convergence is monotonic in the sense that both

u

/

u
0

and

v

/

v
0

are decreasing. We also obtain similar results for more general systems.
The impacts of SiO2 atomic-layer-deposited passivation layer thickness on GaN-based green micro-LEDs
Authors: Deng Youcai , Chen Jinlan , Li Saijun , Huang He , Liu Zhong , Yan Zijun , Lai Shouqiang , Zheng Lijie , Yang Tianzhi , Chen Zhong , Wu Tingzhu
Published: February 2024

In this study, we fabricated 76 × 127 µm2 green GaN-based micro-light-emitting-diodes (micro-LEDs) with atomic-layer-deposited (ALD) SiO2 passivation layers whose thicknesses were 0, 15, and 100 nm. The optoelectrical and communication performances of these devices were measured and analysed. The current-voltage results showed that ALD technology reduced the leakage current and enhanced the forward current of micro-LEDs. Compared with those of micro-LEDs without the passivation layer, the external quantum efficiency of micro-LEDs with 15 and 100 nm-thick SiO2 passivation layers increased by 23.64% and 19.47%, respectively. Furthermore, analysis of the EQE of the samples at room temperature using the ABC + f(n) model revealed the differences in the physical mechanisms of green micro-LEDs. Moreover, the communication performance indicated that ALD sidewall passivation reduced the carrier lifetime and improved the communication performance of green micro-LEDs.
Sawtooth suppression by flux pumping on HBT-EP
Authors: Li Boting , Levesque J.P. , Navratil G.A. , Mauel M.E.
Published: February 2024

This study examines the mechanisms underlying sawtooth suppression in the High Beta Tokamak-Extended Pulse (HBT-EP) device. It is observed that strong-intensity sawtooth activities correlate with reduced-amplitude magnetohydrodynamics (MHD) edge modes which are identified as

m

/

n
=
3

/

1

external kink modes, while sawtooth suppression correlates with larger and saturated edge mode amplitudes. To further investigate these correlations, the plasma–wall coupling was manipulated by adjusting the positions of the conducting walls in HBT-EP. It was found that strong sawtooth events occur when the normalized wall radius

b

/

a

is within a critical value. This implies that the plasma–wall distance must be sufficiently small to ensure effective stabilization of the edge mode. Even slight differences in major radius result in significantly different discharge styles, categorized as ‘sawtoothing discharges’ and ‘sawtooth-suppressed discharges’ respectively. Through a series of mode structure analyses, we confirm the coexistence and coupling of the

m

/

n
=
1

/

1

helical core,

m

/

n
=
2

/

1

tearing mode, and

m

/

n
=
3

/

1

external kink mode during sawtooth-suppression, and that this coupling induces anomalous current broadening. Based on these findings, we conclude that sawtooth suppression in the HBT-EP tokamak is consistent with the process of magnetic flux pumping.