bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Resistance Training Overload Progression Protocols on
Strength and Muscle Mass
Authors: Chaves Talisson Santos , Scarpelli Maíra Camargo , Bergamasco João Guilherme Almeida , Silva Deivid Gomes da , Medalha Junior Ricardo Alessandro , Dias Nathalia Fernanda , Bittencourt Diego , Carello Filho Paulo Cesar , Angleri Vitor , Nóbrega Sanmy Rocha , Roberts Michael D. , Ugrinowitsch Carlos , Libardi Cleiton Augusto
Published: January 2024

The aim of this study was to compare the effects of progressive overload in
resistance training on muscle strength and cross-sectional area (CSA) by
specifically comparing the impact of increasing load (LOADprog) versus an
increase in repetitions (REPSprog). We used a within-subject experimental design
in which 39 previously untrained young persons (20 men and 19 women) had their
legs randomized to LOADprog and REPSprog. Outcomes were assessed before and
after 10 weeks of training. Muscle strength was assessed using the one
repetition maximum (1RM) test on the leg extension exercise, and the CSA of the
vastus lateralis was assessed by ultrasonography. Both protocols increased 1RM
values from pre (LOADprog: 52.90±16.32 kg; REPSprog: 51.67±15.84 kg) to post
(LOADprog: 69.05±18.55 kg, REPSprog: 66.82±17.95 kg), with no difference between
them (P+>+0.05). Similarly, both protocols also increased in CSA
values from pre (LOADprog: 21.34±4.71 cm²; REPSprog: 21.08±4.62 cm²) to post
(LOADprog: 23.53±5.41 cm², REPSprog: 23.39±5.19 cm²), with no difference between
them (P+>+0.05). In conclusion, our findings indicate that the
progression of overload through load or repetitions can be used to promote gains
in strength and muscle hypertrophy in young men and women in the early stages of
training.
Stereodivergent Carbon–Carbon Bond-Forming Reactions
Authors: Healy Alan R.
Published: January 2024

Stereodivergent catalysis has emerged as a compelling strategy for achieving stereochemical diversity in small-molecule library design and natural product synthesis. In this short review, key examples of pioneering catalytic carbon–carbon bond-forming transformations that provide access to all stereoisomers of a given product are presented. Current trends and future directions in the field are discussed, highlighting ongoing initiatives to enhance the efficiency and broaden the scope of stereodivergent methodologies.

1 Introduction

2 Mono-catalysis

2.1 Change of Reaction Conditions

2.2 Change of Catalyst

3 Multi-catalysis

3.1 Bifunctional Catalysis

3.2 Sequential/Cascade Catalysis

3.3 Synergistic/Cooperative Catalysis

4 Conclusions and Outlook
HRI London 2023: The Homeopathy Research Community Reunites after a 4-Year Hiatus, Sparking Fresh Collaborations between Researchers ‘Old and New’
Authors: Roberts E. Rachel , Mosley Angelina J. , van der Werf Esther T. , Tournier Alexander L.
Published: January 2024

The Homeopathy Research Institute's (HRI) 5th international research conference took place in the heart of London, from 16th to 18th June 2023. With 230 attendees from 27 countries, HRI's conferences remain truly international. HRI London 2023 will be remembered for its inspiring blend of ‘old and new’, with a programme notable for the maturity of the evidence presented by experienced names drawing on decades of work, as well as the enthusiasm and skill of up-and-coming researchers who took the floor to present their new findings. In this report, we present scientific highlights from the event.
Meta-analysis: Bilateral and Unilateral Cerebral Perfusion in Type A Dissection
Authors: Naito Noritsugu , Takagi Hisato
Published: January 2024

Background This meta-analysis compared the outcomes of bilateral cerebral perfusion (BCP) and unilateral cerebral perfusion (UCP) in aortic surgery for acute type A aortic dissection.

Methods A systematic literature search identified 12 studies involving 4,547 patients. Pooled odds ratios (OR) with 95% confidence intervals (CI) were calculated to analyze perioperative characteristics, short-term mortality rates, and postoperative neurological complications.

Results No significant differences were found between the BCP and UCP groups in terms of cardiopulmonary bypass time, aortic cross clamp time, lowest body temperature, and lower body circulatory arrest time. Short-term mortality rates (OR [95% CI] = 0.87 [0.64–1.19], p = 0.40) and permanent neurological deficits (OR [95% CI] = 1.01 [0.69–1.47], p = 0.96) were comparable between the groups. However, subgroup analysis of studies exclusively involving total arch replacement showed a lower short-term mortality rate (OR [95% CI] = 0.42 [0.28–0.63], p < 0.01) and permanent neurological deficits (OR [95% CI] = 0.53 [0.30–0.92], p = 0.03) in the BCP group. The BCP group also had a lower rate of temporary neurological deficits (OR [95% CI] = 0.70 [0.53–0.93], p = 0.01), particularly in studies exclusively involving total arch replacement (OR [95% CI] = 0.58 [0.40–0.85], p < 0.01).

Conclusion This meta-analysis suggests that BCP and UCP yield comparable outcomes. However, BCP may be associated with lower short-term mortality rates and reduced incidence of neurological complications, particularly in cases requiring total arch replacement. BCP should be considered as a preferred cerebral perfusion in specific patient populations.
Atomic layer self-transducing MoS2 vibrating channel transistors with 0.5 pm/Hz1/2 displacement sensitivity at room temperature
Authors: Yousuf S M Enamul Hoque , Feng Philip X.-L.
Published: January 2024

We report on the experimental demonstration of high-performance suspended channel transistors with single- and bilayer (1L and 2L) molybdenum disulfide (MoS2), and on operating them as vibrating channel transistors (VCTs) and exploiting their built-in dynamic electromechanical coupling to read out picoampere (pA) transconduction current directly at the vibrating tones, without frequency conversion or down-mixing, for picometer (pm)-scale motion detection at room temperature. The 1L- and 2L-MoS2 VCTs exhibit excellent n-type transistor behavior with high mobility [150 cm2/(V·s)] and small subthreshold swing (98 mV/dec). Their resonance motions are probed by directly measuring the small-signal drain-source currents (iD). Electromechanical characteristics of the devices are extracted from the measured iD, yielding resonances at f0 = 31.83 MHz with quality factor Q = 117 and f0 = 21.43 MHz with Q = 110 for 1L- and 2L-MoS2 VCTs, respectively. The 2L-MoS2 VCT demonstrates excellent current and displacement sensitivity (Si1/2 = 2 pA/Hz1/2 and Sx1/2 = 0.5 pm/Hz1/2). We demonstrate f0 tuning by controlling gate voltage VG and achieve frequency tunability Δf0/f0 ≈ 8% and resonance frequency change Δf0/ΔVG ≈ 0.53 kHz/mV. This study helps pave the way to realizing ultrasensitive self-transducing 2D nanoelectromechanical systems at room temperature, in all-electronic configurations, for on-chip applications.
Interplay between metastable magnetic domains and superconducting vortices in a ferromagnet–superconductor hybrid
Authors: Yun Jinyoung , Haberkorn N. , Han Yoonseok , Baumbach R. , Bauer E. D. , Ronning F. , Movshovich R. , Park Tuson , Choi Jae-Hyuk , Kim Jeehoon
Published: January 2024

The interplay between superconductivity and magnetism has been a subject of significant interest for decades. While extensive research has focused on modifying the superconducting state through a magnetic domain as an independent variable, the manipulation of magnetic domains by the superconducting state has been relatively unexplored, primarily due to their higher stiffness compared to the energy associated with superconducting vortices. In this Letter, we demonstrate the manipulation of magnetic domains by thermally activated superconducting vortices in a ferromagnet/superconductor hybrid. We observe a reversible domain transition between metastable magnetic stripes and bubbles in a Nb/CeRu2Ga2B hybrid induced by vortex motion and the trapped field within the Nb superconducting film. The comparable Curie and superconducting critical temperatures and the presence of magnetic metastable states enable the magnetic domain changes driven by superconducting vortices in this hybrid system.
Grain boundaries in polycrystalline materials for energy applications: First principles modeling and electron microscopy
Authors: Quirk J. , Rothmann M. , Li W. , Abou-Ras D. , McKenna K. P.
Published: January 2024

Polycrystalline materials are ubiquitous in technology, and grain boundaries have long been known to affect materials properties and performance. First principles materials modeling and electron microscopy methods are powerful and highly complementary for investigating the atomic scale structure and properties of grain boundaries. In this review, we provide an introduction to key concepts and approaches for investigating grain boundaries using these methods. We also provide a number of case studies providing examples of their application to understand the impact of grain boundaries for a range of energy materials. Most of the materials presented are of interest for photovoltaic and photoelectrochemical applications and so we include a more in depth discussion of how modeling and electron microscopy can be employed to understand the impact of grain boundaries on the behavior of photoexcited electrons and holes (including carrier transport and recombination). However, we also include discussion of materials relevant to rechargeable batteries as another important class of materials for energy applications. We conclude the review with a discussion of outstanding challenges in the field and the exciting prospects for progress in the coming years.
Recent developments in low-dimensional heterostructures of halide perovskites and metal chalcogenides as emergent materials: Fundamental, implementation, and outlook
Authors: Maulida Pramitha Yuniar Diah , Hartati Sri , Firdaus Yuliar , Hidayat Anjar Taufik , Diguna Lina Jaya , Kowal Dominik , Bruno Annalisa , Cortecchia Daniele , Arramel Arramel , Birowosuto Muhammad Danang
Published: January 2024

In the past decades, halide perovskites and chalcogenide materials have provided significant contributions to the vast development for optoelectronic applications. Halide perovskites are known for their tunable properties, while chalcogenides are known for their high efficiency. The combination of these types of materials as heterostructures is thought to have been able to produce a superior device/photophysical performance. A peculiar aspect to consider is an inherent weak interaction between these layers via the stacking of different materials, promoting the realization of van der Waals heterostructures with novel functional properties. In this review, we summarize the progress and foresee the prospectives of material systems obtained by combining low-dimensional (0D, 1D, and 2D) halide perovskite and chalcogenide systems. Both emergent materials share their promise in terms of energy and charge transfer consideration. In addition, several aspects that are mutually important in this context will be outlined, namely, interlayer excitons, interfacial engineering, quantum confinement effect, and light–matter interactions. Based on these fundamental approaches, we translate the current understanding by highlighting several representative heterostructures with prominent performance such as light-emitting diodes, x-ray detectors, photodetectors, and solar cells. In this review, we focus on the rich chemistry and photophysics of these heterostructures, emphasizing the open questions related to their structure–property relationship. Finally, potential research directions and outlooks based on the implementation of halide perovskite–chalcogenide heterostructures are also proposed.
Direct pore-level simulation of hydrogen flame anchoring mechanisms in an inert porous media
Authors: Muller F. , Dounia O. , Selle L.
Published: January 2024

This work addresses the stabilization of hydrogen flames inside porous media. Hydrogen is a peculiar fuel with a large molecular diffusivity, triggering preferential diffusion and other effects related to non-unity Lewis numbers. Consequently, the macro-scale behavior of hydrogen flames is highly influenced by the flame-wall interactions at the pore-scale. In this study, direct pore-level simulations are used for the investigation of anchoring mechanisms and burning-rate enhancement for lean hydrogen flames embedded in inert porous media. It is observed that preferential diffusion greatly enhances flame anchoring, in the wake of the struts, leading to a high increase in flame surface. Also, the local heat release rate is enhanced not only by the higher gas temperature resulting from the heat recirculation but also by the higher local equivalence ratio resulting from preferential diffusion. Furthermore, most of the heat produced by a hydrogen flame is released by the hydroperoxyl reactions, effective at low temperatures but necessitating radicals, mostly H. These radicals are produced by the shuffle reactions, effective at higher gas temperatures. The coupling between those two reaction groups is very dependent on the transport of radicals, which can be impacted by the pore scale velocity gradient, leading to hydrodynamic dispersion and flame wrinkling. Consequently, it is shown that the burning-rate enhancement observed within porous burners fueled with hydrogen is not only due to heat recirculation but also to increased transports of radicals and preferential diffusion effects, which should be accounted for in macroscopic models.
Investigation of deep learning-based filtered density function for large eddy simulation of turbulent scalar mixing
Authors: Bansude Shubhangi , Sheikhi Reza
Published: January 2024

A filtered density function (FDF) model based on deep neural network (DNN), termed DNN-FDF, is introduced for large eddy simulation (LES) of turbulent flows involving conserved scalar transport. The primary objectives of this study are to develop the DNN-FDF models and evaluate their predictive capability in accounting for various filtered moments, including that of non-linear source terms. A systematic approach is proposed to select the DNN training sample size and architecture via learning curves to minimize bias and variance. Two DNN-FDF models are developed, one utilizing FDF data from direct numerical simulations (DNS) of constant-density temporal mixing layer and the other from zero-dimensional pairwise mixing stirred reactor simulations. The latter is particularly intended for cases where generating DNS data is computationally infeasible. DNN-FDF models are applied for LES of a variable-density temporal mixing layer. The accuracy and consistency of both DNN-FDF models are established by comparing their predicted filtered scalar moments with those of conventional LES, where moment transport equations are directly solved. The DNN-FDF models are shown to outperform a widely used presumed-FDF model, especially for multi-modal FDFs and higher variance values. Results are further assessed against DNS and the transported FDF method. The latter couples LES with Monte Carlo for mixture fraction FDF computation. Most importantly, the study shows that DNN-FDF models can accurately filter highly non-linear functions within variable-density flows, highlighting their potential for turbulent reacting flow simulations. Overall, the DNN-FDF approach is shown to offer an accurate yet computationally economical approach for describing turbulent scalar transport.
Epitaxial Hf0.5Zr0.5O2 films: A temperature dependence study
Authors: Xiong Ke , Huang Xinning , Zhou Yong , Xiao Yongguang , Liao Lei , Yan Haoran , Lin Tie , Shen Hong , Chen Pan , Wang Lifen , Bai Xuedong , Meng Xiangjian , Wang Xudong , Chu Junhao , Wang Jianlu
Published: January 2024

Hafnia-based films are gaining prominence in the advancement of next-generation memory and logic devices. Their significance arises from their pronounced ferroelectricity at the nanoscale and their synergy with silicon processes. However, there are questions surrounding how their polarization stability responds to changes in temperature. In our study, we synthesized (111)-oriented Hf0.5Zr0.5O2 (HZO) ferroelectric thin films through pulsed laser deposition. This process corroborated the domain-matching epitaxy growth mechanism. We observed that HZO films possess distinct temperature-dependent ferroelectric traits. Specifically, a decrease in temperature triggers a fall in remanent polarization. Notably, the coercive field diminishes initially, only to rebound around the 200 K mark. Utilizing low-temperature in situ x-ray diffraction techniques, we have identified that lattice strain, induced by the differing thermal expansion of the films due to temperature changes, alters the migration rate of oxygen vacancies, resulting in the observed variations in remanent polarization and coercive field as reported in the article. Our findings deepen the understanding of ferroelectric mechanisms inherent in hafnia-based oxide thin films.
Shock tube experiments on the three-layer Richtmyer–Meshkov instability
Authors: Schalles M. , Louie C. , Peabody K. , Sadler J. , Zhou Y. , Jacobs J.
Published: January 2024

A vertical shock tube is used for experiments on the three-layer Richtmyer–Meshkov instability. Two closely spaced membrane-less interfaces are formed by the flow of two different sects of three gases: one with air above CO2 above SF6 and the other with helium above air above SF6. The lightest of the three gases enters the shock tube at the top of the driven section and flows downward. Conversely, the heaviest gas enters at the bottom of the shock tube and flows upward while the intermediate density gas enters at the middle through porous plates. All three gases are allowed to escape through holes at the layer location, leaving an approximately 30-mm layer of intermediate-density gas suspended between the lightest gas from above and the heaviest gas from below. A single-mode, two-dimensional initial perturbation is then imposed on the lower interface by oscillating the shock tube in the horizontal direction. The flow is visualized by seeding the intermediate gas with particles and illuminating it with a pulsed laser. Image sequences are then captured using high-speed video cameras. Perturbation amplitude measurements are made from the three-layer system and compared with measurements from 2, two-layer systems. It is observed that the presence of the upper, initially flat interface produces a decrease in growth of instability amplitude in the nonlinear phase over an equivalent single-interface configuration.
A method for examining ensemble averaging forms during the transition to turbulence in HED systems for application to RANS models
Authors: Pellone S. , Rasmus A. M. , Di Stefano C. A. , Merritt E. C. , Doss F. W.
Published: January 2024

This paper discusses a strategy to initialize a two-dimensional (2D) Reynolds-averaged Navier–Stokes model [LANL's Besnard–Harlow–Rauenzahn (BHR) model] in order to describe an unsteady transitional Richtmyer–Meshkov (RM)-induced flow observed in on-going high-energy-density ensemble experiments performed on the OMEGA-EP facility. The experiments consist of a nominal single-mode perturbation (initial amplitude a0≈10 and wavelength λ=100 μm) with target-to-target variations in the surface roughness subjected to the RM instability with delayed Rayleigh–Taylor in a heavy-to-light configuration. Our strategy leverages high-resolution three-dimensional (3D) implicit large eddy simulations (ILES) simulations to initialize BHR-relevant parameters and subsequently validate the 2D BHR results against the 3D ILES simulations. A suite of five 3D ILES simulations corresponding to five experimental target profiles is undertaken to generate an ensemble dataset. Using ensemble averages from the 3D simulations to initialize the turbulent kinetic energy in the BHR model (K0) demonstrates the ability of the model to predict the time evolution of the interface as well as the density-specific-volume covariance, b. To quantify the sensitivity of the BHR results to the choice of K0 and the initial turbulent length scale, S0, we execute a parameter sweep spanning four orders of magnitude for both S0 and K0, generating a parameter space consisting of 26 simulations. The Pearson's correlation coefficient is used as a measure of discrepancy between the 2D BHR and 3D ILES simulations and reveals that the ranges 8≲S0≲20 μm and 109≲K0≲1010 cm2/s2 produce predictions that agree best with the 3D ILES results.
Symmetry and asymptotic solutions for a magnetohydrodynamics Darcy–Forchheimer flow with a p-Laplacian operator
Authors: Rahman S. , Díaz Palencia José Luis , Reyes Enrique G.
Published: January 2024

Fluid flows under a p-Laplacian operator formulation have been considered recently in connection with the modeling of non-Newtonian fluid processes. To a certain extent, the main reason behind the interest in p-Laplacian operators is the possibility of determining experimental values for the constant p appearing in them. The goal of the present study is to introduce the analysis of solutions of a one-dimensional porous media flow arising in magnetohydrodynamics with generalized initial data under a Lebesgue integrability condition. We present a weak formulation of this problem, and we consider boundedness and uniqueness properties of solutions and also its asymptotic relation with the standard parabolic p-Laplacian equation. Then, we explore solutions arising from classical symmetries (including an explicit kink solution in the p = 3 case) along with asymptotic stationary and non-stationary solutions. The search for stationary solutions is based on a Hamiltonian approach. Finally, non-stationary solutions are obtained by using an exponential scaling resulting in a Hamilton–Jacobi type of equation.
Advancing the temporal direct deconvolution method with spatial regularization
Authors: Oberle Daniel , Pruett C. David , Jenny Patrick
Published: January 2024

This study continues the exploration of temporal large-eddy simulation, particularly the extension of the temporal direct deconvolution method (TDDM) with a regularization term based on spatial dissipation. Furthermore, we aim to put insight stemming from previous work to test. Specifically, the hypothesis is that the temporal residual-stress leads to a reduction of the required artificial dissipation in under-resolved simulations. Moreover, this work seeks corroborate earlier discoveries with a posteriori results. We perform a numerical examination of two different spatial regularization terms in conjunction with TDDM: a spatial variant of selective frequency damping, functioning as a relaxation term that gradually drifts the velocity toward the filtered velocity, and the dynamic Smagorinsky model incorporating a prefactor. We test various cases, including the Taylor–Green vortex flow with a Reynolds number of Re = 3000, forced homogeneous isotropic turbulence with Reλ=200, turbulent channel flow at Reτ=590, and the flow over a periodic hill with Re = 10 935. Additionally, we also analyze the various dissipation contributions in TDDM as well as their interrelations. We also discuss grid artifacts and energy budget errors using these to compare the different models. Our results confirm the hypothesis that residual-stress dissipation reduces the necessary artificial dissipation. Because of the numerical ill-conditioning of deconvolution, whether temporal or spatial, there are practical limitations in the size of the filter width. Due to these limitations, the impact remains relatively minor. The a posteriori results of the new spatial regularization term show it to be effective in eliminating energy from the high wavenumber range.
Superior optical transparency of nano-grain magnesium aluminate spinel at high shock pressure
Authors: Cao Xiuxia , Wu Qiang , Sokol Maxim , Qi Jianqi , Yu Yin , Meng Chuanmin , He Hongliang , Zhang Chongyu , Hu Jianbo
Published: January 2024

Optical transparency is of paramount importance for visual armor and certain optical devices when subjected to severe impact conditions. Shock wave loading not only generates high pressure during hypervelocity impacts but also diminishes optical transmittance. To investigate optical transparency of transparent polycrystalline ceramic under harsh shock wave compression, this study performed experimental measurements considering the grain size effect. The findings, which pertain to polycrystalline magnesium aluminate spinel (PMAS), indicate that PMAS with nano-sized grains within the 900–1500 nm wavelength range demonstrates superior optical transparency compared to conventional PMAS with micrometer-sized grains. This result highlights the excellent optical properties of nano-grain transparent ceramics and raises hopes for their widespread application at high shock pressures.
Hydrodynamic drag reduction in ribbed microchannel with infused non-Newtonian lubricants
Authors: R. Nair Adarsh , Chandran K. Nandakumar , Ranjith S. Kumar
Published: January 2024

Liquid-infused surfaces have recently gained prominence in engineering applications owing to their versatile characteristics such as self-cleaning, anti-fogging, drag reduction, and enhanced heat transfer. In this article, a numerical analysis of pressure-driven flow past a periodic array of rectangular transverse grooves infused with non-Newtonian immiscible lubricants is performed. The volume of fluid method is employed to capture the interface between primary and secondary fluids, and the power-law model is deployed to mimic the non-Newtonian lubricant. The drag reduction capability of the microchannel is examined for various parameters such as Reynolds number, liquid fraction, viscosity ratio, viscosity index, and contact angle. It is observed that the introduction of a non-Newtonian fluid (shear-thickening or shear-thinning) drastically modifies the interface velocity and hydrodynamic resistance. In particular, a shear-thinning lubricant enhances the slip length as the viscosity index (n) is reduced owing to the reduced viscosity at the interface. Note that, for a lubricant having n = 0.7, the percentage improvement in the slip length is 382% in comparison with a Newtonian counterpart having the same viscosity ratio, N = 0.1. Importantly, the introduction of a shear-thinning lubricant with a viscosity ratio N = 5, a liquid fraction of 0.8, and a behavior index n = 0.7 yielded a pressure drag reduction of 63.6% with respect to a classical no-slip channel and of 23% with reference to a microchannel with the Newtonian lubricant. Moreover, at high Reynolds numbers, Re→50, the drag mitigation is slightly lowered due to the primary vortex shift in the cavity. Furthermore, the effect of the interface contact angle (θc) is investigated, as θc drops from 90° (flat) to 45° (convex); the meniscus curvature is enhanced, and the effective slip length is reduced. These observations suggest that a shear-thinning lubricant-infused microchannel is a promising candidate for drag reduction in lab-on-chip applications.
Terahertz ring beam independent on
ω
–2ω phase offset in the course of two-color femtosecond filamentation
Authors: Nikolaeva I. A. , Vrublevskaya N. R. , Rizaev G. E. , Pushkarev D. V. , Mokrousova D. V. , Shipilo D. E. , Panov N. A. , Seleznev L. V. , Ionin A. A. , Kosareva O. G. , Savel'ev A. B.
Published: January 2024

We measured and simulated the spectrally resolved angular distributions of 0.3–1-THz emission from the two-color filament with its plasma length (∼40 mm) exceeding the dephasing length (∼25 mm) between the fundamental (740 nm) and the second harmonic (370 nm) pulses in air. We show that only the forwardly propagating on-axis terahertz (THz) radiation is sensitive to the variation of the phase offset φ between fundamental and second harmonics, while the ring-like THz beam carrying ≳80% of the overall THz yield is independent of φ. Utilization of the THz ring allows one to omit the tedious adjustment of the frequency-doubling crystal position in the experiment.
Energy transport mechanisms and characteristic vibration energy regimes for thermal conduction in bulk metallic glass
Authors: Yang Shuhang , Bu Hengtong , Shao Yang , Liang Xin
Published: January 2024

Bulk metallic glass (BMG) exhibits intriguing physical transport behavior due to its amorphous nature. In this work, by taking a classical BMG material Zr41.2Ti13.8Ni10Cu12.5Be22.5 (Vit1) as the model system, we reveal the impact of structural transition, from a fully amorphous state to a partial and then a completely crystalline state, on the heat and charge transport processes in the temperature range of 4–300 K. We identify the dominant types of energy carriers, which we find change considerably with temperature and structural details. We resolve the contribution of three types of vibrons, namely, propagons, diffusons, and locons, to thermal conduction in the amorphous state and determine their characteristic vibration energy regimes. The present work provides a further understanding of transport behavior of BMG, with important implications for engineering practice at elevated temperatures.
Numerical simulation of a thixotropic-viscoelastic model in contraction geometries
Authors: Castillo-Sánchez Hugo A. , de Araújo Manoel S. B. , Bertoco Juliana , Fernandes C. , Ferrás L. L. , Castelo Antonio
Published: January 2024

This work presents a comprehensive numerical implementation of a viscoelastic thixotropic model known as the modified-Bautista–Manero (MBM) model (a model widely used to characterize the rheological behavior of wormlike micellar solutions). This implementation is integrated into the OpenFOAM computational fluid dynamics software, specifically using the rheoTool library. In contrast to previous studies, our approach includes simulations of inertial flows and we account for convective terms within all the governing equations. Moreover, we use two numerical techniques that have been proven to be efficient methods in computational simulations of viscoelastic fluids through a planar contraction: (1) the high-resolution scheme called convergent and universally bounded interpolation scheme for the treatment of advection to discretize the convective terms of the momentum, viscoelastic, and thixotropic equations; and (2) the logarithm-conformation reformulation to tackle the high-Weissenberg number problem. This expansion of the model's scope results in a more realistic representation of the fluid's behavior and, consequently, more accurate computational results. To validate the implementation of the MBM model, we performed numerical simulations in two different industrial-relevant geometries: the planar 4:1 contraction and the 4:1:4 contraction–expansion configurations. Two fluids with different structural responses are studied: one with quick structural recovery and the other with mildly slow recovery. The numerical method developed in this work allowed us to run stable simulations of these fluids up to Reynolds and Deborah number values of Re = 1.11 and De = 14.0, respectively, and the influence of inertial, viscoelastic, and thixotropic effects on various flow field variables is investigated. These variables include velocity, viscosity, normal stresses, and corner vortex size. Transient and steady solutions of corner vortexes across a range of Deborah and Reynolds numbers are also presented. In addition, the results obtained in this work are also directly compared with numerical simulations obtained using the non-thixotropic rubber network-based exponential Phan-Thien–Tanner model. For the planar 4:1 contraction simulations, the analysis of the results is based on three dimensionless numbers (the viscoelastic Mach, the elasticity, and the thixoelastic numbers), which allows to conclude that vortex enhancement is mainly seen when high elasticity is coupled with quick structural reformation and very low inertial effects. We further report from the planar 4:1:4 contraction–expansion results that an increase in inertia leads both to vortex inhibition in the upstream channel and to slight vortex enhancement in the downstream channel. Finally, we demonstrate the strong influence of fluid convection on fluidity profiles and on the size of the upstream/downstream corner vortex.
Temperature-resilient random number generation with stochastic actuated magnetic tunnel junction devices
Authors: Rehm Laura , Morshed Md Golam , Misra Shashank , Shukla Ankit , Rakheja Shaloo , Pinarbasi Mustafa , Ghosh Avik W. , Kent Andrew D.
Published: January 2024

Nanoscale magnetic tunnel junction (MTJ) devices can efficiently convert thermal energy in the environment into random bitstreams for computational modeling and cryptography. We recently showed that perpendicular MTJs actuated by nanosecond pulses can generate true random numbers at high data rates. Here, we explore the dependence of probability bias—the deviations from equal probability (50/50) 0/1 bit outcomes—of such devices on temperature, pulse amplitude, and duration. Our experimental results and device model demonstrate that operation with nanosecond pulses in the ballistic limit minimizes variation of probability bias with temperature to be far lower than that of devices operated with longer-duration pulses. Furthermore, operation in the short-pulse limit reduces the bias variation with pulse amplitude while rendering the device more sensitive to pulse duration. These results are significant for designing true random number generator MTJ circuits and establishing operating conditions.
Simulation and analytical modeling of high-speed droplet impact onto a surface
Authors: Liu Yanchao , Chu Xu , Yang Guang , Weigand Bernhard
Published: January 2024

The fluid dynamics of liquid droplet impact on surfaces hold significant relevance to various industrial applications. However, high impact velocities introduce compressible effects, leading to material erosion. A gap in understanding and modeling these effects has motivated this study. We simulated droplet impacts on solid surfaces and proposed a new analytical model for impact pressure and droplet turning line, targeting at predictions for enhanced cavitation. The highly compressed liquid behind the droplet expands sideways, causing lateral jetting. As the droplet encounters a shock wave, it reflects as a rarefaction wave, leading to low-pressure zones within the droplet. These zones converge at the droplet's center, causing cavitation, which, upon collapse, induces another shock wave, contributing to erosion. Using the well-established model for the low-velocity impact shows a significant discrepancy. Hence, an analytical model for the turning line radius is introduced, incorporating the lateral jetting's characteristic length scale. Comparing our model with existing ones, our new model exhibits superior predictive accuracy.
Effect of dolphin-inspired transverse wave microgrooves on drag reduction in turbulence
Authors: Zheng Tengfei , Liu Jianbo , Qin Liguo , Lu Shan , Mawignon Fagla Jules , Ma Zeyu , Hao Luxin , Wu Yuhao , An Dou , Dong Guangneng
Published: January 2024

The transverse skin of dolphins exhibits a remarkable drag reduction effect. Although previous studies have identified the drag reduction effect of transverse grooves, no clear guidelines exist regarding the impact of groove parameters on turbulent drag reduction. Hence, this paper suggests a novel numerical study using the Reynolds-averaged Navier–Stokes method to investigate the influence of half-sine wave structure parameters on turbulent drag. The results showed that the aspect ratio of shape parameters significantly affected the drag reduction rate by altering the flow velocity and drag distribution near the wall and increasing the viscous sublayer thickness. Moreover, a novel index friction pressure ratio FPr was introduced to evaluate the drag reduction. It was revealed that the ratio FPr was stable at optimal drag reduction effect regardless of the velocity. By optimizing the FPr, a maximum drag reduction of 29.3% was achieved. These findings provide insight for optimizing transverse groove in drag-reducing surface applications.
Exciton dynamics in two-dimensional metal halide perovskite: The impact of film processing
Authors: Bhandari Sahil , Kundar Milon , Chakraborty Manjari , Pal Suman Kalyan
Published: January 2024

We investigate the hot carrier and exciton dynamics in two-dimensional (2D) metal halide perovskites using time-resolved spectroscopy. 2D perovskite films were prepared with and without dimethyl sulfoxide treatment to elucidate the effect of film processing techniques on optoelectronic properties. Femtosecond transient absorption measurements reveal that the charge carrier dynamics are different in the two samples, and excitons survive for a longer time in the treated sample than the untreated one. While the early-time carrier dynamics in the untreated sample are dominated by charges trapped by defect states, the hot free carriers govern the dynamics in the treated sample due to fewer defects in it. Morphological and other spectroscopic studies, including time-resolved photoluminescence, further suggest the formation of more defects in the untreated sample. These results can guide the future development of efficient 2D perovskite-based optoelectronic devices.
Time-multiplexing single-photon imaging lidar with single-pixel detector
Authors: Shangguan Mingjia , Liang Yayun , Li Ye , Mo Yican
Published: January 2024

A time-multiplexing technique is proposed and demonstrated for single-photon imaging lidar, utilizing a large-area single-pixel single-photon detector to simultaneously detect the multi-pixel echoes. In this time-division multiplexing lidar, the echo signals from different pixels of the fiber array are delayed through fibers of varying lengths, merged into a fiber bundle, and then sequentially detected by the large-area single-pixel detector. In the experimental demonstration, a two-detector system capable of imaging 122 pixels using single-photon imaging lidar was showcased in three-dimensional imaging. Furthermore, the spectral broadening caused by multimode fiber dispersion was analyzed. Imaging of four different targets at a distance of 80 m was experimentally validated. This time-multiplexing technique can greatly reduce the number of single-photon detectors required in imaging lidar systems, making it suitable for low-cost lidar applications.
Capillary waves and dendritic instability on radial Hele–Shaw displacements
Authors: Abedi Behbood , Oliveira Rafael M. , Berghe Lara S. , de Souza Mendes Paulo R.
Published: January 2024

The displacement of a fluid by another less viscous one in isotropic quasi-two-dimensional Hele–Shaw cells typically leads to viscous fingering patterns characterized by repeated tip-splitting and side-branching. When anisotropy is present, the viscous fingering patterns are replaced by dendritic instability. In isotropic cells, Couder et al. [“Dendritic growth in the Saffman-Taylor experiment,” Europhys. Lett. 2, 437 (1986)] induced the growth of a dendritic finger by placing a small isolated bubble in contact with the tip of a finger. Moreover, in rectangular displacements, Kopf-Sill and Homsy [“Narrow fingers in a Hele–Shaw cell,” Phys. Fluids 30, 2607–2609 (1987)] observed for specific ranges of modified capillary numbers, Ca, that narrow fingers develop into dendritic patterns after carefully cleaning the Hele–Shaw cell with a soap solution. In the current work, by injecting air to radially displace a lubricant oil with strong adsorption properties, we observe for the first time the growth of dendritic instability in displacements confined in isotropic Hele–Shaw cells in the absence of air bubbles driving the fingertip. These structures are driven by the formation of capillary waves inside the finger adjacent to the Hele–Shaw surfaces. Furthermore, we compare displacements of different materials at similar high Ca values and obtain significantly different morphological results, indicating the pattern formation may not scale with this parameter in this range. Discrepancies are explained based on both wetting and inertia effects.
Modeling of the unsteady aerodynamic force of turbine blades considering nonuniform vane pitch
Authors: Zhang Weihao , Liao Xiangli , Fan Wenyi , Wang Yufan , Mu Yumo , Xin Jianqiang
Published: January 2024

The nonuniform vane spacing of a turbine is a crucial technique for reducing the unsteady aerodynamic excitation force of the downstream blades, but it still lacks a quick and accurate forecast approach for its suppression effect. Employing the rectangular wave, we propose a modeling strategy for the unsteady aerodynamic force of turbine blades and construct a fast prediction model (FPM) for the excitation force. The model takes into account the physical mechanism of wake and potential field variations induced by vane nonuniformity and has reliable accuracy and robustness. The results demonstrate that FPM can rapidly predict the suppression benefit of the aerodynamic force on blades under a wide design range, and most of the errors in the forecast results of the maximum amplitude change rate are less than 10% compared with the numerical simulation. In addition, to guide the nonuniform configuration design, the suppression characteristic diagram is formed based on FPM and the nonuniform vane spacing law, through which the excitation suppression effect of the nonuniform scheme can be evaluated. The characteristic diagram shows that the scheme with a larger nonuniform pitch variation range and a smaller period ratio can achieve a more significant excitation reduction.
Poloidal magnetic field in the dense plasma focus
Authors: Auluck S. K. H.
Published: January 2024

Existence of an axial (poloidal) component of magnetic field in the dense plasma focus has been inferred using multiple diagnostics in many laboratories since 1979. It has not received much attention because its origin as well as role in plasma focus physics was unclear till recently. Recent discovery of long-lasting neutron emission perpendicular to the axis in PF-1000 and neutron fluence ratio (end/side) less than unity in Gemini shows that azimuthally accelerated and radially confined deuterons play an observable role in fusion reactions. A spontaneously generated poloidal magnetic field can provide both the azimuthal electric field necessary for acceleration and radial confinement of the ions being accelerated in the acceleration zone. A comprehensive survey of plasma focus research also confirms the role of spontaneously self-organized plasma objects in the fusion reaction process where their three-dimensional magnetic field structure provides a mechanism for accelerating and trapping ions making them repeatedly pass through a dense plasma target. With emerging appreciation of the likely role of the axial magnetic field in plasma focus neutron emission, it becomes imperative to consider models for its origin. This Letter proposes a partial theory of growth of the axial (poloidal) magnetic field via a simple dynamo, with the geomagnetic field as the seed, which converts the kinetic energy of the plasma into energy of the poloidal magnetic field. This theory leads to an experimentally testable proposition.
A consistent generalized model-based lattice Boltzmann flux solver for incompressible porous flows
Authors: Yang Liuming , Li Xuhang , Yang Yunfei , Qin Shenglei , Hou Guoxiang , Qin Jiangtao
Published: January 2024

The recently developed lattice Boltzmann flux solver (PLBFS) for the incompressible porous flow is free from the limitations of coupled streaming time step and the mesh spacing, and the uniform meshes and the complex distribution function treatment at the boundary. However, the local flux reconstruction is inconsistent with the global governing equations in PLBFS. To overcome the drawback, a consistent generalized lattice Boltzmann flux solver for the incompressible porous flow is proposed based on the generalized lattice Boltzmann method (GLBM). The recovered macroscopic governing equations given by the Chapman–Enskog analysis of GLBM are globally resolved by the finite volume method. Specifically, the macroscopic variables are updated at cell centers using the three-step Runge–Kutta method, while the solution of the GLBM is locally applied for the fluxes reconstruction at cell interfaces. Unlike the PLBFS, the forcing term can be naturally incorporated into the interface fluxes reconstruction, which gives the present method a stronger physical basis and ensures global consistency. Moreover, different from the PLBFS, the streaming time step used at the cell interface is decoupled from the updating time step at the cell center in the present solver. Furthermore, a simplified flux reconstruction strategy is proposed to avoid complex calculations and save computing resources. Several numerical examples have been adopted to test the proposed method. The simulations of the nonlinear lid-driven cavity flow show that our method is more accurate than the original PLBFS. Results also demonstrate that the simplified method can reduce the computational time by 43%.
A novel model of nonlocal photoacoustic and plasmaelastic heated by laser pulsed excitation of nanoscale semiconductor medium
Authors: Lotfy Kh. , El-Bary A. , Daoud S. , Ahmed M. H. , Allan M.
Published: January 2024

The study takes into account the diffusion of photo-excited carriers in the presence of a laser pulse and theoretically investigates photoacoustic wave propagation in the thermoelastic domain. In a nonlocality medium, the phenomena of thermomechanical and acoustic wave interaction are considered. Thermoelasticity, photothermal, and photoacoustic theories provide the controlling formulas. Photoacoustic waves are not dependent on electron–phonon or electron–hole thermalization processes; rather, they are produced by thermoelastic stress resulting from the temperature increase induced by the laser. The optical, elastic, and thermoelastic characteristics of nanoscale semiconductor materials are taken into account and photoacoustic signals are predicted by solving a thermal diffusion issue and a thermoelastic problem in combination. The mathematical model can be solved using the harmonic wave approach. By obtaining numerical solutions, all the physical fields of the physical domain, such as thermal, acoustic, mechanical, and carrier density diffusion, as well as displacements and temperatures, can be derived. The influences of nonlocal parameters, thermal delay, and laser pulse effect are investigated and compared using two- and three-dimensional visual representations, corresponding to two-dimensions and three-dimensions domains, respectively.
General soliton solutions for the complex reverse space-time nonlocal mKdV equation on a finite background
Authors: Wang Xin , Wang Lei , Du Zhong , He Jinman , Zhao Jie
Published: January 2024

Three kinds of Darboux transformations are constructed by means of the loop group method for the complex reverse space-time (RST) nonlocal modified Korteweg–de Vries equation, which are different from that for the PT symmetric (reverse space) and reverse time nonlocal models. The N-periodic, the N-soliton, and the N-breather-like solutions, which are, respectively, associated with real, pure imaginary, and general complex eigenvalues on a finite background are presented in compact determinant forms. Some typical localized wave patterns such as the doubly periodic lattice-like wave, the asymmetric double-peak breather-like wave, and the solitons on singly or doubly periodic waves are graphically shown. The essential differences and links between the complex RST nonlocal equations and their local or PT symmetric nonlocal counterparts are revealed through these explicit solutions and the solving process.