bluuebunny/crossref_metadata_2025 huggingface dataset:
Design of magnetic flux concentrator composed of nanospheres for high-sensitivity magnetometers
Authors: Li Huiyu , Zhao Lin , Hu Guoqing , Zhou Zhehai , Chen Guangwei
Published: November 2024

Magnetometers have received considerable attention in recent years. Magnetic components offer an alternative methodology to improve the sensitivity. Due to their exceedingly small structural dimensions, metasurfaces exhibit significant competitiveness in field modulation. A magnetic field concentration phenomenon of spheres at the nanoscale is presented in this paper. The sensitivity of a magnetometer is, therefore, improved through the enhanced static or quasistatic magnetic field by the nanosphere concentrator. Magnetic field redistribution due to the assistance of nanospheres is discussed in this paper using the finite element method. The numerical method is verified with classical analytical equations with a single sphere. The simulation results show that the magnetic field concentrates in the near field behind the nanosphere along the direction of the magnetic flux density. The radius, material or permeability exactly, and distribution are critical parameters to the concentration strength. The magnetic gain of a single nanosphere with typical positive permeability of the typical soft magnetic material reaches 3, and thus, the field along the magnetic flux direction concentrates. Furthermore, the amplification factor is more prominent with the nanosphere arrays compared to a single sphere with the same scale of size, and amplification improves with the sphere numbers and distributions in the array arrangement, which provides a novel approach for the designing of the magnetic flux concentrator being monolithically integrated with the magnetometer probe. Our simulation results provide a new degree of freedom by using nanoscale structures to manipulate magnetic fields.
Reconfigurable logic gates driven by spatially designed excitation: Spectra manipulation the coupled random laser system
Authors: Shi Xiaoyu , Liu Zhe , Zhao Jinjiang , Shen Kaiyue , Zhai Tianrui
Published: November 2024

All-optical logic gates offer ultra-fast speed information processing and lower power consumption that still misses the reconfigurability, remaining beset for high power consumption and large space requirements. Considering random lasers with pump-reconstructed spectra without changing the structure, an optical platform for reconfigurable logic gate operations is developed based on random laser systems. By engineering the energy distribution of two pump regions, the interaction between the two equivalent random laser systems is changed from strongly correlated to weakly correlated, thereby realizing the transition from nonresonant laser with continuous frequency distribution to resonant random laser with discrete frequency distribution. By converting input pump signals into output random laser signals, the operation and facile reconfiguration of four 2-input logic gates (OR, NOR, NAND, and AND) in a single disordered gain film is demonstrated by simply managing the correlation of the two random laser regions through manipulating the energy distribution of the input pump. The proof-of-concept of the random laser-based optical logic gates features reconfigurability and ease of operation, providing a promising method for designing arithmetic logic units for optical network signal processing and optical computing.
Modified Debye–Hückel–Onsager theory for electrical conductivity in aqueous electrolyte solutions: Account of ionic charge nonlocality
Authors: Kalikin Nikolai N. , Budkov Yury A.
Published: November 2024

This paper presents a mean field theory of electrolyte solutions, extending the classical Debye–Hückel–Onsager theory to provide a detailed description of the electrical conductivity in strong electrolyte solutions. The theory systematically incorporates the effects of ion specificity, such as steric interactions, hydration of ions, and their spatial charge distributions, into the mean-field framework. This allows for the calculation of ion mobility and electrical conductivity, while accounting for relaxation and hydrodynamic phenomena. At low concentrations, the model reproduces the well-known Kohlrausch’s limiting law. Using the exponential (Slater-type) charge distribution function for solvated ions, we demonstrate that experimental data on the electrical conductivity of aqueous 1:1, 2:1, and 3:1 electrolyte solutions can be approximated over a broad concentration range by adjusting a single free parameter representing the spatial scale of the nonlocal ion charge distribution. Using the fitted value of this parameter at 298.15 K, we obtain good agreement with the available experimental data when calculating electrical conductivity across different temperatures. We also analyze the effects of temperature and electrolyte concentration on the relaxation and electrophoretic contributions to total electrical conductivity, explaining the underlying physical mechanisms responsible for the observed behavior.
Tunable kHz distributed feedback fiber laser fabricated in 3D-printed glass
Authors: Maniewski Pawel , Flint Alex I. , Bannerman Rex H. S. , Lee Timothy , Beresna Martynas
Published: November 2024

For short sections of fiber tailored to a specific application, fast laser-based manufacturing techniques can be considered as an attractive alternative to the often-cumbersome traditional manufacturing routes. With the use of high-power lasers, localized hot zones that are necessary for glass making can be obtained rapidly. For instance, laser-powder-deposition enables rapid fabrication of short, high gain fibers used in, e.g., distributed feedback fiber lasers (DFFLs). DFFLs offer sought after performance suitable for a broad range of applications in modern photonics, i.e., superior stability and narrower, single-frequency linewidth compared to conventional fiber lasers. Tunable, narrow laser sources with output in an eye-safe spectrum are desired for sensing, signal multiplexing, LIDAR systems, quantum applications, etc. In this work, we present DFFL obtained using laser-powder-deposition made Er-doped silica fiber. Milliwatt level, narrow line lasing (<704 kHz, equipment limited) was obtained using a phase-shifted grating written in 16 mm long fiber. The backward slope efficiency was as high as 24% when pumping at 976 nm. The results presented in this work showcase new possibilities in fiber fabrication that were unlocked through laser-assisted additive manufacturing. This fiber laser sets the stage for the future of rapid fabrication of advanced fiber devices through unconventional manufacturing routes.
On the interplay between fluid flow characteristics and small particle deposition in turbulent wall bounded flows
Authors: Abbasi Sanaz , Mehdizadeh Amirfarhang
Published: November 2024

This study investigates the transport and deposition of small particles (500 nm≤dp≤10 μm) in a fully developed turbulent channel flow, focusing on two fluid friction Reynolds numbers: Reτ=180 and Reτ=1000. Using the point particle–direct numerical simulation method under the assumption of one-way coupling, we study how fluid flow (carrier phase) characteristics influence particle deposition. Our findings suggest that changes in flow conditions can significantly alter the deposition behavior of particles with the same size and properties. Furthermore, we show for the first time that gravity has minimal impact on deposition dynamics only at high Reynolds numbers. This research enhances our understanding of small particle deposition and transport in turbulent flows at high Reynolds numbers, which is crucial for various industrial applications.
Exciton dynamics in CsPbBr3 single crystal: LT splitting energy, exciton–polariton dispersion, and biexciton binding energy
Authors: Shimosako Naoki , Kumamoto Mizuki , Muroga Yui , Liu Zihao , Sotome Masato , Kondo Takashi , Kunugita Hideyuki , Ema Kazuhiro
Published: November 2024

Metal halide perovskite materials (MHPs) are promising for several applications due to their exceptional properties. Understanding excitonic properties is essential for exploiting these materials. For this purpose, we focus on CsPbBr3 single crystals, which have higher crystal quality, are more stable, and have no Rashba effect at low temperatures compared to other 3D MHPs. We have estimated exciton energy positions, longitudinal-transverse splitting energy, and damping energy using low-temperature reflection spectra. Under high excitation intensity, two biexciton emissions (M-emission) and exciton–exciton scattering emission (P-emission) were observed. We assign the two M-emissions to the emission to the states of longitudinal and transverse excitons, i.e., ML and MT emissions. From the energy position of the MT emission, the biexciton binding energy has been estimated to be ∼2 meV. By analyzing P-emission obtained from the back side of the sample, we have estimated the exciton binding energy to be 17.8–23.7 meV. This estimation minimizes the influence of the wavenumber distribution in the scattering process. In addition, time-resolved transmittance measurements using pulsed white light have revealed the group velocity dispersion. Comparing experimental results with theoretical calculations using the Lorentz model clarifies that exciton dynamics in CsPbBr3 can be described with a simple Lorentz model. These insights enhance the understanding of exciton behavior and support the development of exciton-based devices using MHPs.
Electric field and rotational temperature measurements based on electric field-induced coherent anti-Stokes Raman scattering in visible region (E-CARSv) in hydrogen discharge plasmas
Authors: Koike Takeru , Muneoka Hitoshi , Terashima Kazuo , Ito Tsuyohito
Published: November 2024

Electric field measurements with a time resolution of a few nanoseconds using an electric field-induced coherent anti-Stokes Raman scattering in the visible region (E-CARSv) scheme were performed in a repetitively pulsed nanosecond discharge plasma in a 0.3-atm hydrogen environment. The rotational temperature was estimated using the E-CARSv scheme, which enables us to extract electric fields even at elevated gas temperatures. The estimated rotational temperature was 390 K, which reduced the E-CARSv signal intensity by approximately 50% when the rotational temperature was equal to the gas temperature. Considering the reduction, the peak electric field was estimated to be −1.4 kV/mm, which is 40% higher than −1.0 kV/mm, assuming no elevated temperatures.
Impact of chlorine substitution on valence orbitals and ionization dynamics in 3-chloropyridine: Insights from high-resolution vacuum ultraviolet mass-analyzed threshold ionization study
Authors: Park Sung Man , Kim Hyojung , Kwon Chan Ho
Published: November 2024

In this study, the effects of chlorine substitution on the valence orbitals and electronic states of 3-chloropyridine (3-CP) were investigated utilizing high-resolution vacuum ultraviolet mass-analyzed threshold ionization (VUV-MATI) spectroscopy and computational methods. High-quality vibrational spectra were obtained from the VUV-MATI spectra of 3-CP isotopomers (35Cl and 37Cl), revealing high-quality vibrational spectra for the lowest cationic states. The adiabatic ionization energies (AIEs) of these isotopomers were accurately determined, providing detailed information about the electronic structure and ionization dynamics. Intense spectra peaks were linked with the D1 excited state of the 3-CP cation, with vibronic transitions in this state closely matching those predicted by Franck–Condon simulations. This provided insights into the cationic structure and the roles of the highest occupied molecular orbital (HOMO) and the HOMO-1. The HOMO was primarily a π orbital of the pyridine ring, while the HOMO-1 consisted of nonbonding orbitals. The AIEs suggested that meta-chlorine substitution stabilizes nonbonding orbitals less effectively than ortho substitution, indicating closely spaced electronic states in the 3-CP cation. Minor discrepancies in vibrational frequencies and intensities, particularly above 800 cm−1, suggested the presence of vibronic coupling, warranting further investigation. Overall, this study provided a comprehensive understanding of the vibronic and ionization properties of 3-CP, emphasizing the influence of the position of the chlorine substitution on molecular orbitals and the value of advanced theoretical and experimental approaches for analyzing the vibrational spectra of complex molecules.
Landau-level terahertz emission from electrically biased graphene
Authors: Inamura Fumiyuki , Ueda Gen , Kim Sunmi , Patrashin Mikhail , Hosako Iwao , Komiyama Susumu , Ikushima Kenji
Published: November 2024

Terahertz (THz) emission from electrically biased graphene is studied under high magnetic fields. A quantum well (QW)-based charge-sensitive infrared phototransistor (CSIP) is used to detect weak THz emission from a graphene Hall bar. THz emission is clearly observed at around 5 T when the Hall voltage exceeds the corresponding Landau-level (LL) energy spacing between the zero-energy (N = 0) and first excited (N = +1 or N = −1) LLs, suggesting that the emission occurs primarily at the carrier entry and exit corners of the current contacts in the Hall bar. We also investigate the emission spectra through measurements of the QW spectrum of the CSIP. The emission spectra are well explained by the N = +1 → 0 (or N = −1 → 0) inter-LL radiative transition in monolayer graphene. The linewidth of the emission spectra is estimated to be on the order of 10 meV, even though no explicit LL splitting is observed in the magnetotransport at 5 T.
Experimental study of non-stationary aerodynamic effects on the wind turbine nacelles under extreme wind events
Authors: Yan Bowen , Yuan Yangjin , Zhou Xuhong , Li Yanan , Yang Qingshan , Liu Qingkuan , Yang Wei , Han Jia
Published: November 2024

The wind pressure coefficients on the nacelle model of a typical wind turbine are experimentally examined in nonstationary wind flows adopting an active-controlled multi-blade system installed in an atmospheric boundary layer wind tunnel. Various nonstationary winds, characterized by flow parameters of acceleration and initial velocity, are grouped as ramp-up and ramp-down flows. Particular attention is devoted to the influence of nonstationary attributes of incoming flow on the wind pressures acting on the nacelle envelope. The experimental results indicate that the wind pressures on the nacelle surfaces are significantly modified by the incoming nonstationary wind conditions. The overshoot ratios of wind pressure on the nacelle's top surface is increased with the increasing acceleration in the ramp-up flows, while the maximum overshoot ratio occurs at a middle-level acceleration magnitude. Moreover, the overshoot ratios increase with the reduction in the initial velocity of nonstationary winds. Additionally, the extreme pressure coefficients of the nacelle in the ramp-down flow are much increased compared with those in ramp-up winds with equivalent acceleration magnitude. The findings from this study are expected to be instrumental in improving the understanding of the unique characteristics of nonstationary wind pressures and their effect on the nacelle envelope.
Numerical study of noise attenuation by air-sheet barriers in water
Authors: Petris Giovanni , Hamid Naira , Cianferra Marta , Armenio Vincenzo
Published: November 2024

This paper discusses the acoustic mitigation properties of an air–water mixture excited by a monopole source. The numerical study reproduces a flat plate immersed in water and covered by an air film, acting as a sound barrier. This configuration mimics a mitigation device potentially in use for ship noise reduction, considering the flat plate as archetypal of a portion of the ship hull that works as a non-negligible scattering surface. The film, in this case, may also be used as an isolator with respect to the noise produced by the engines operating within the hull and propagating in the water. The study uses a homogeneous mixture model to reproduce the fluid dynamic field of air injected into the water. Once the air–water mixture is fully developed, the density and speed of sound distributions are extrapolated and used as input parameters for the acoustic propagation model. The monopole source exits the mixture layer, and the attenuation properties are assessed by recording the time signal on a probe positioned on the reflecting wall. The results show the difference in the transmission of acoustic pressure considering different frequencies and distributions of the mixture. These findings have significant practical implications, as they demonstrate how the air film can effectively attenuate the signal, with the mitigation effectiveness varying with the source's frequency and the distribution of the mixture of air and water in space.
Research on the flow behavior of bio-ink inside the extrusion nozzle during printing
Authors: Wei Qinghua , An Yalong , Li Mingyang , Zhao Xudong
Published: November 2024

Nozzle shape greatly affects the activity of cells and growth factors inside bio-ink, which is easy to be ignored. In this research, the finite element simulation software based on fluid dynamics theory was used to simulate the extrusion flow behavior of the bio-ink inside the printing needle. By establishing the flow models of two commonly used needles (cylindrical and conical needles), taking sodium alginate solution as bio-ink, the extrusion flow behavior of bio-ink inside the printing needle was simulated. Following, taking steady pressure, flow rate, and fluid shear stress as the research objectives, the response effects of nozzle geometry parameters, including shape, size, and feeding pressure, on the flow behavior of bio-ink were analyzed. Finally, a method based on the idea of integration for evaluating the cumulative damage to the active substances inside bio-ink has been proposed. Results show that the wall shear stress is the main stress suffered by bio-ink in the bio-printing process. Smaller inlet pressure and larger nozzle outlet diameter are beneficial for reducing wall shear stress. Compared with the cylindrical nozzle, although the maximum wall shear stress of the conical nozzle is higher than that of the cylindrical nozzle under the same inlet pressure and outlet nozzle diameter, the time of bio-ink subjected to the wall shear stress is shorter. The cumulative damage of the cylindrical nozzle is 29.65 Pa·s, and that of the conical nozzle is 18.25 Pa·s, which indicates that the conical nozzle has better biofriendliness and less damage to the active substance inside the bio-ink.
TM and P dual sites on polymeric carbon nitride enable highly selective CO reduction to C2 products with low potentials: A theoretical perspective
Authors: Ji Shuang , Lin Wei
Published: November 2024

The CO reduction reaction (CORR) for the production of high-value-added multi-carbon (C2+) products is currently being actively investigated, where searching for high-efficiency catalysts with moderate CO intermediate binding strength and low kinetic barrier for C–C coupling poses a significant challenge. In this study, we employed density functional theory computations to design four synergistic coupling dual sites catalysts for CORR to C2 products, namely, TM-P@melon, by co-doping transition metals (TM = Mn, Fe, Co, and Ni) and phosphorus (P) into the polymeric carbon nitride (i.e., melon-CN). Mn–P@melon and Ni–P@melon exhibit higher selectivity toward C2H5OH and C2H6, respectively, with limiting potentials (C–C coupling kinetic energy barriers) of −0.43 V (0.52 eV) and −0.17 V (0.26 eV), respectively. The introduction of TM and P atoms not only narrows the band gap of melon-CN but also favors the coupling of CO and *CHO, providing an active site for C–C coupling, thus facilitating the catalytic reaction. Our work provides rational insights for the design of stable, low-cost, and efficient CORR dual sites catalysts that facilitate the sustainable production of high-value C2 chemicals and fuels.
Revealing the vortex phases and second magnetization peaks in SmBCO superconductors
Authors: Shit Subhasis , Namburi Devendra K. , Das S. D. , Nath T. K.
Published: November 2024

Rare earth substitution in cuprate superconductors has sparked intense interest, driving progress in both fundamental research and advanced technology. In this investigation, we focus on SmBa2Cu3O7−δ (SmBCO), synthesized via the top-seeded melt growth method, with an aim to understand the corresponding vortex phases. Despite the minimal impact on transition temperature (Tc) when yttrium in YBa2Cu3O7−δ is replaced by Sm, the critical current density (Jc) remains exceptionally high under intense magnetic fields. Introducing Sm2Ba1Cu1O5 (Sm-211) phase as point defects significantly boosts the pinning potential (U) and pinning force (Fp) and enhances their stability against external magnetic fields. Contrary to other superconductors, the SmBCO sample displays a notable peak effect in the magnetic field-dependent Jc, driven by point defects introduced by the Sm-211 phase, which prompts vortex lattice softening and initiates a transition from an ordered to a disordered vortex glass phase, leading to the emergence of a second magnetization peak. Analysis suggests that the primary pinning mechanism in SmBCO involves a combination of normal point and Δκ pinning. Additionally, investigations of the vortex glass phase beneath the thermally activated flux flow regime indicate that vortices in SmBCO may freeze into a state akin to a 2D vortex glass state. This study leads to a detailed phase diagram that clarifies the evolution of vortex phases in SmBCO.
Numerical prediction on single-mode perturbation growth of Richtmyer–Meshkov instability in a cylindrical geometry
Authors: Zhou Ziming , Wang Zhanming , Huang Shenghong , Xiao Zuoli
Published: November 2024

The Richtmyer–Meshkov (RM) instability induced flows in a converging cylindrical geometry at high Mach numbers are numerically investigated using an improved smoothed particle hydrodynamics method. This newly enhanced smoothed particle hydrodynamics approach is based on Roe's Riemann solver, complemented with the Double-Sides-with-Shock solver, which is derived from the analytical solution of the Riemann problem specifically for locally strong shock processes, and augmented with a modified interfacial repulsive force. The new algorithm proves to effectively preserve the original periodic symmetry of the interfacial structure, prevent skewing of the spike/bubble structures, and achieve more accurate prediction of interfacial perturbation amplitudes. The numerical simulation results are in good agreement with existing experimental data. It is confirmed that there exists a unique scaling law for each development stage of the interfacial perturbation amplitude in all high-shock Mach number cases, even for the final growth stage after phase reversal. It is further found that there is a trend for the curves of perturbation amplitude to collapse onto each other as the Mach number increases, especially when the time is rescaled by a correction factor. It is also suggested that the significant Rayleigh–Taylor effect leads to the inapplicability of aforementioned scaling laws to the evolution of RM instability at low Mach numbers.
Interface effects of polycrystalline Fe2O3 thin films on Pt
Authors: Kostriukov Vladimir , Geri Lidor , Sharoni Amos
Published: November 2024

The magnetic state of an antiferromagnetic (AFM) insulator can be read and manipulated in spintronics devices using bilayers of an AFM and a conducting layer, making it useful for spintronics devices. To date, research has focused on single crystals of AFMs, which enables the study of properties related to different crystallographic surfaces. However, combining single-crystal AFMs in spintronics devices may be problematic due to substrate selectivity and deposition conditions. In this work, we study the properties of polycrystalline Fe2O3 coupled with Pt as the conducting layer, asking how the magnetoresistive behavior differs in polycrystalline AFMs. We report on the angle dependent magnetoresistance and transverse magnetoresistance properties as a function of temperature and magnetic fields, comparing Fe2O3/Pt and Fe2O3/Cu/Pt thin films, in addition to magnetometry and structural characterization. The magnetoresistance signals do not depend on the thickness or volume behavior of the Fe2O3 layer, but rather the Fe2O3/Pt interface. Angle dependent magnetoresistance measurements show ferromagnetic-like behavior but with a non-standard effect of field, while transverse measurements show a sign change with temperature. This differs from effects reported for single-crystal Fe2O3 based bilayers. Interestingly, using transverse field measurements, we find that at low temperatures, the Fe2O3/Pt interface spins develop a glass-like relaxation of the magnetic signal, which undergoes freezing as the sample is further cooled.
Pipeline leak detection and localization based on the flow balance and negative pressure wave methods
Authors: Li Wei , Fu Qing , Gao Hang
Published: November 2024

The traditional water supply pipeline leak detection and location method has problems of false alarms, low positioning accuracy, and low stability. This paper focuses on the pipeline leak detection and location experimental platform to investigate water supply pipeline leaks, followed by simulation and experimental validation. This study integrates the mass flow balance method and pressure change inflection points to determine pipeline leaks and introduces an improved negative pressure wave method for locating leakage points. The results demonstrate that the system accurately detects pipeline leaks. The average positioning error of the improved negative pressure wave method for the leakage point is 4.76%, which has good stability and high positioning accuracy.
A mutual information statistic for assessing state space partitions of dynamical systems
Authors: Lu Jason , Small Michael
Published: November 2024

We propose a mutual information statistic to quantify the information encoded by a partition of the state space of a dynamical system. We measure the mutual information between each point’s symbolic trajectory history under a coarse partition (one with few unique symbols) and its partition assignment under a fine partition (one with many unique symbols). When applied to a set of test cases, this statistic demonstrates predictable and consistent behavior. Empirical results and the statistic’s formulation suggest that partitions based on trajectory history, such as the ordinal partition, perform best. As an application, we introduce the weighted ordinal partition, an extension of the popular ordinal partition with parameters that can be optimized using the mutual information statistic, and demonstrate improvements over the ordinal partition in time series analysis. We also demonstrate the weighted ordinal partition’s applicability to real experimental datasets.
Probing photochemical dynamics using electronic vs vibrational sum-frequency spectroscopy: The case of the hydrated electron at the water/air interface
Authors: Pritchard Faith G. , Jordan Caleb J. C. , Verlet Jan R. R.
Published: November 2024

Photo-dynamics can proceed differently at the water/air interface compared to in the respective bulk phases. Second-order non-linear spectroscopy is capable of selectively probing the dynamics of species in such an environment. However, certain conclusions drawn from vibrational and electronic sum-frequency generation spectroscopies do not agree as is the case for the formation and structure of hydrated electrons at the interface. This Perspective aims to highlight these apparent discrepancies, how they can be reconciled, suggests how the two techniques complement one another, and outline the value of performing both techniques on the same system.
Electron beam induced multi-wavelength lasing in CdSe quantum dot lasers
Authors: Akimoto Ryoichi
Published: November 2024

This study investigates the effects of electron beam irradiation on the lasing characteristics of optically pumped CdSe quantum dot (QD) lasers grown on GaAs substrates using molecular beam epitaxy. The experimental setup allows the creation of two types of CdSe QDs with distinct size differences, with and without electron beam irradiation during the epitaxy. Lasing wavelengths were observed at 534 nm in the non-irradiated region and between 548 and 557 nm in the irradiated regions, depending on the electron beam irradiation conditions, achieving multi-wavelength lasing in the green-yellow ranges on a single chip. Internal laser parameters were evaluated for both irradiated and non-irradiated regions across different cavity lengths. Photoluminescence (PL) spectra revealed significantly higher integrated PL intensity in the irradiated regions compared to the non-irradiated regions, attributed to reduced point defects. However, at the lasing threshold, the impact of these defects is negligible. Lasing spectra exhibited a notable blue shift in the irradiated regions with an increase in threshold intensity due to the state-filling effect, which also causes a decrease in internal quantum efficiency. The modal gain and transparent intensity were evaluated, showing lower gain values in the irradiated regions, consistent with the observed broadening of the PL spectrum. These findings highlight the dynamic nature of the state-filling effect and its impact on lasing performance, providing insights into the mechanisms affecting CdSe QD lasers under electron beam irradiation in green-yellow spectrum range.
Couple-stress nanofluid flow comprised of titanium alloy subject to Hall current and Joule heating effects: Numerical investigation
Authors: Jubair Sidra , Ali Bilal , Rafique Khadija , Ahmad Ansari Mushtaq , Mahmood Zafar , Kumar Abhinav , Mukalazi Herbert , Alqahtani Haifa
Published: November 2024

Nanofluid flow over a rotating disk has several applications in engineering and industrial sectors, such as in cooling systems, heat exchangers, aerospace systems, and renewable energy systems. In the current analysis, the couple stress nanofluid flow over a rotating disk is reported. The nanofluid consists of ethylene glycol and titanium aluminum vanadium (Ti6Al4V) nanoparticles (NPs). The unique properties of Ti6Al4V-NPs, such as biocompatibility, high strength, high boiling point (1604–1660 °C), and high corrosion resistance, make them more suitable for automobile industries. For the heat and mass transfer, the Cattaneo–Christov concept is introduced. In addition, the fluid flow is subjected to magnetic field, Hall current, thermal radiation, and Joule heating. The modeled equations are restructured into the dimensionless system of ordinary differential equations (ODEs) by using the similarity approach. The system of ODEs is further numerically solved through a MATLAB package based on the finite difference method (BVP4c). The results are presented in figures. It has been observed that the energy and curves of the nanofluid decline with the influence of thermal and solutal time relaxation parameters, respectively.
Prediction model and risk assessment of dynamic gas emission during drilling in faulted coal seams
Authors: Yuan Xiuquan , Fan Jinyang , Li Zongze , Wang Weihao , Chen Jie , Wang Liang , Jiang Deyi
Published: November 2024

Influenced by multiple coupling physical fields, the disparities in gas migration characteristics between coal seams and faults may be the crucial factor triggering outbursts. This study established the initial permeability distribution of faulted coal seams using Caine's model and employed a transverse isotropic permeability model to characterize the directional of gas flow within the fault. A thermo-hydro-mechanical coupled mathematical model is proposed for simulating gas emission during drilling of faulted coal seams and validated using field data. Additionally, variations in fault azimuth, dip, width, and core width were analyzed to investigate their effects on gas emission volume during drilling. Moreover, the magnitude of the interaction of the factors was analyzed using response surface methodology to identify the fault morphology with the largest gas emission volume during drilling. Finally, a multivariate nonlinear regression model was established to describe the relationship between gas emission volume and fault core width. The results showed that the gas emission rate gradually rises as the borehole length grows but surges abruptly by approximately 95% as the borehole intersects the fault zone. Increases in fault azimuth and width enhance gas emission from the borehole, while increases in fault dip and core width inhibit it. With the fault azimuth, dip, width, and core width of 40°, 80°, 15 m, and 1 m, respectively, the gas emission volume during drilling peaked at 105.462 m3.This study is helpful for better predict and evaluate the outburst risk of faulted coal seams using dynamic gas emission during drilling.
Combining graph deep learning and London dispersion interatomic potentials: A case study on pnictogen chalcohalides
Authors: Kılıç Çetin , Güler-Kılıç Sümeyra
Published: November 2024

Machine-learning interatomic potential models based on graph neural network architectures have the potential to make atomistic materials modeling widely accessible due to their computational efficiency, scalability, and broad applicability. The training datasets for many such models are derived from density-functional theory calculations, typically using a semilocal exchange-correlation functional. As a result, long-range interactions such as London dispersion are often missing in these models. We investigate whether this missing component can be addressed by combining a graph deep learning potential with semiempirical dispersion models. We assess this combination by deriving the equations of state for layered pnictogen chalcohalides BiTeBr and BiTeI and performing crystal structure optimizations for a broader set of V–VI–VII compounds with various stoichiometries, many of which possess van der Waals gaps. We characterize the optimized crystal structures by calculating their x-ray diffraction patterns and radial distribution function histograms, which are also used to compute Earth mover’s distances to quantify the dissimilarity between the optimized and corresponding experimental structures. We find that dispersion-corrected graph deep learning potentials generally (though not universally) provide a more realistic description of these compounds due to the inclusion of van der Waals attractions. In particular, their use results in systematic improvements in predicting not only the van der Waals gap but also the layer thickness in layered V–VI–VII compounds. Our results demonstrate that the combined potentials studied here, derived from a straightforward approach that neither requires fine-tuning the training nor refitting the potential parameters, can significantly improve the description of layered polar crystals.
Optimization of fluid control laws through deep reinforcement learning using dynamic mode decomposition as the environment
Authors: Sakamoto T. , Okabayashi K.
Published: November 2024

The optimization of fluid control laws through deep reinforcement learning (DRL) presents a challenge owing to the considerable computational costs associated with trial-and-error processes. In this study, we examine the feasibility of deriving an effective control law using a reduced-order model constructed by dynamic mode decomposition with control (DMDc). DMDc is a method of modal analysis of a flow field that incorporates external inputs, and we utilize it to represent the time development of flow in the DRL environment. We also examine the amount of computation time saved by this method. We adopt the optimization problem of the control law for managing lift fluctuations caused by the Kármán vortex shedding in the flow around a cylinder. The deep deterministic policy gradient is used as the DRL algorithm. The external input for the DMDc model consists of a superposition of the chirp signal, containing various amplitudes and frequencies, and random noise. This combination is used to express random actions during the exploration phase. With DRL in a DMDc environment, a control law that exceeds the performance of conventional mathematical control is derived, although the learning is unstable (not converged). This lack of convergence is also observed with DRL in a computational fluid dynamics (CFD) environment. However, when the number of learning epochs is the same, a superior control law is obtained with DRL in a DMDc environment. This outcome could be attributed to the DMDc representation of the flow field, which tends to smooth out high-frequency fluctuations even when subjected to signals of larger amplitude. In addition, using DMDc results in a computation time savings of up to a factor of 3 compared to using CFD.
An extended variational method for the resistive wall mode in toroidal plasma confinement devices
Authors: Fitzpatrick R.
Published: November 2024

The external-kink stability of a toroidal plasma surrounded by a rigid resistive wall is investigated. The well-known analysis of Haney and Freidberg is rigorously extended to allow for a wall that is sufficiently thick that the thin-shell approximation does not necessarily hold. A generalized Haney–Freidberg formula for the growth-rate of the resistive wall mode is obtained. Thick-wall effects do not change the marginal stability point of the mode but introduce an interesting asymmetry between growing and decaying modes. Growing modes have growth-rates that exceed those predicted by the original Haney–Freidberg formula. On the other hand, decaying modes have decay-rates that are less than those predicted by the original formula. The well-known Hu–Betti formula for the rotational stabilization of the resistive wall mode is also generalized to take thick-wall effects into account. Increasing wall thickness facilitates the rotational stabilization of the mode, because it decreases the critical toroidal electromagnetic torque that the wall must exert on the plasma. On the other hand, the real frequency of the mode at the marginal stability point increases with increasing wall thickness.
Experimental study of gain characteristics in relation to quantum-well width of deep-ultraviolet laser diodes
Authors: Zhang Ziyi , Kushimoto Maki , Yoshikawa Akira , Aoto Koji , Sasaoka Chiaki , Amano Hiroshi
Published: November 2024

The gain characteristics of electrically injected AlGaN-based deep-ultraviolet laser diodes were studied with respect to their quantum-well (QW) width dependence by the analysis of the threshold currents and gains for various cavity lengths. Among the fabricated QWs with widths of d = 9, 4.5, and 3 nm, the QW with the smallest width of 3 nm was found to have the highest material gain and lowest transparency carrier density. In contrast to recent arguments in favor of wider QWs for deep-ultraviolet laser diodes, the strategy of narrowing QWs is still found to be effective in practical terms of reducing the threshold current density.
Classical characters of spinor fields in torsion gravity
Authors: Fabbri Luca
Published: October 2024

We consider the problem of having relativistic quantum mechanics re-formulated with hydrodynamic variables, and specifically the problem of deriving the Mathisson–Papapetrou–Dixon equations (describing the motion of a massive spinning body moving in a gravitational field) from the Dirac equation. The problem will be answered on a general manifold with torsion and gravity. We will demonstrate that when plane waves are considered the MPD equations describe the general relativistic wave-particle duality with torsion (Guedes and Popławski 2024 Class. Quantum Grav.
41 065011), but we will also see that in such a form the MPD equations become trivial.
The linearization of the boundary rigidity problem for MP-systems and generic local boundary rigidity
Authors: Muñoz-Thon Sebastián
Published: October 2024

We consider an

MP

-system, that is, a compact Riemannian manifold with boundary, endowed with a magnetic field and a potential. On simple

MP

-systems, we study the

MP

-ray transform in order to obtain new boundary rigidity results for

MP

-systems. We show that there is an explicit relation between the

MP

-ray transform and the magnetic one, which allows us to apply results from Dairbekov et al (2007 Adv. Math.
216 535–609) to our case. Regarding rigidity, we show that there exists a generic set

G

m

of simple

MP

-systems, which is open and dense, such that any two

MP

-systems close to an element in it and having the same boundary action function, must be k-gauge equivalent.
Nanosecond resolved vibrational kinetics of

CO
2

in

CO
2

/

N
2

mixtures measured in a pulsed discharge jet
Authors: Busch Christian A , Lepikhin Nikita D , Orel Inna , Kuhfeld Jan , Luggenhölscher Dirk , Czarnetzki Uwe
Published: November 2024

This work studies the vibrational kinetics of CO2/N2 mixtures in a nanosecond pulsed near atmospheric pressure plasma jet. Quantum-cascade laser absorption spectroscopy is used to measure the populations of rovibrationally excited states of CO2 without any assumption on a particular vibrational distribution function and with a variable time resolution of as high as 8 ns. These studies are complemented by measurements using electric field induced second harmonic generation and electrical measurements to characterize the discharge. The nanosecond pulsing, combined with fast diagnostics, allows for a temporal separation of processes on different timescales, namely, electron impact excitation (e-V) during the discharge and vibrational-vibrational (V-V) and vibrational-translational (V-T) transfer in the afterglow. During the discharge, the Fermi resonant

10
0

01

state is excited at a higher rate than the energetically close

02
2

01

state of the bending mode, leading to different effective vibrational temperatures. In the afterglow, the two vibrational temperatures converge to a combined vibrational temperature T
12 within

200

ns

. This equilibration process is observed here for the first time. In the afterglow, the populations of all vibrational states increase for several 10

μ
s

. This can be attributed to the V-V transfer from N2 to the asymmetric stretch mode of CO2 and from the latter to the other vibrational modes of CO2. An increase of the N2 admixture, which acts as an energy reservoir for the CO2, enhances the increase of the vibrational populations of CO2 in the afterglow and slows down the decay of the asymmetric mode in the late afterglow through continuous replenishment via V-V transfer. The combined data of all diagnostics allow for a detailed comparison with kinetic models.
Sulfur hexafluoride multiple breath washin and washout outcomes in infants are not interchangeable
Authors: Kentgens Anne-Christianne , Wyler Florian , Oestreich Marc-Alexander , Latzin Philipp , Yammine Sophie
Published: October 2024

Objective. Sulfur hexafluoride (SF6) multiple-breath washout (MBW) assesses ventilation inhomogeneity, as an early marker of obstructive respiratory diseases. Primary outcomes are customarily washout-derived, and it is unclear whether the preceding SF6-washin can provide similar estimates. We aimed to assess comparability of primary SF6-MBW outcomes between washin and washout phases of infant SF6-MBW data measured with the WBreath (ndd Medizintechnik AG, Zurich, Switzerland) and Spiroware (Eco Medics AG, Duernten, Switzerland) MBW-setups, respectively. Approach. We assessed mean relative differences in lung clearance index (LCI) and functional residual capacity (FRC) between the washin and washout of existing SF6-MBW data from healthy infants and infants with cystic fibrosis (CF). We assessed whether these differences exceeded the mean relative within-test between-trial differences of washout-derived outcomes, which can be attributed to natural variability. We also explored non-physiological factors using a pediatric lung simulator. Main results. LCI and FRC from washin and washout were not comparable, for both setups. The mean difference (SD) in LCI between washin and washout was 2.3(10.8)% for WBreath and −9.7(8.0)% for Spiroware, while in FRC it was −4.7(8.4)% for WBreath and −2.3(9.7)% for Spiroware. These differences exceeded the within-test between-trial differences in washout-derived outcomes. Outcomes from washin and washout were also not comparable in a pediatric lung simulator. Significance. Outcomes of the washin and washout were not comparable due to an interplay of physiological and non-physiological factors, and cannot be used interchangeably.
Sensitivity study of heat transfer in a Jeffrey ferro-hybrid nanofluid bioconvective squeezing flow with inclined MHD and higher-order chemical reaction: entropy analysis
Authors: Samal Seetalsmita , Ontela Surender
Published: November 2024

The present investigation concentrates on analyzing heat transfer and entropy formation in a time-reliant bioconvective flow of a blood-based Jeffrey hybrid nanofluid via a squeezing channel that is suctioned or injected at the lower plate. Cu nanoparticles and Fe
3
O
4 ferro-nanoparticles are suspended in base-fluid blood. Adding ferro-nanoparticles to a flow process allows for better control of the external magnetic field and improved heat transmission. Noble integration of an aligned magnetic field, Joule’s heating, thermal radiation, and higher-order chemical reactions is taken into account in the flow in a porous media. An appropriate choice of similarity variables leads to the non-dimensionalization of the governing equations, that are subsequently solved by the homotopy analysis method (HAM), yielding a semi-analytical solution. An innovative feature of this research is the optimization of heat transfer by the application of the response surface methodology (RSM) technique. Additionally, sensitivity analysis was carried out to identify the most influential parameter. The study’s findings indicate that increased suction reduces both velocity and temperature distributions in both the nanofluid and hybrid nanofluid models. In terms of thermal performance, the Blood/Fe
3
O
4 − Cu hybrid nanofluid surpasses the Blood/Fe
3
O
4 nanofluid. The rate of thermal energy transfer is highly sensitive to variations in the Eckert number, while thermal radiation has a relatively lesser impact. Moreover, elevated levels of the magnetic parameter, Eckert number, and nanoparticle concentration lead to augmented entropy formation. This mathematical model is effective for analyzing drug transport mechanisms throughout the human body and presents extensive potential applications in the fields of biology and healthcare.
High-efficiency wide-angle anomalous refraction with acoustic metagrating
Authors: Sun 孙 Kangyao 康瑶 , Fan 樊 Yuancheng 元成 , Ye 叶 Zhehao 哲浩 , Li 李 Jiahui 嘉荟 , Fu 付 Quanhong 全红 , Zeng 曾 Yali 雅丽 , Zhang 张 Fuli 富利
Published: November 2024

The emergent metagrating, with its unique and flexible beam shaping capabilities, offers new paths to efficient modulation of acoustic waves. In this work, an acoustic metagrating is demonstrated for high-efficiency and wide-angle anomalous refraction. It is shown that the normal reflection and transmission can be totally suppressed by properly modulating the amplitude and phase characteristics of the metagrating supercells for high-efficiency anomalous refraction. The anomalous refraction behavior is achieved in the wide range of incident angles from 28° to 78°, and the efficiency of −1st order diffraction is higher than 90% by finely designing the metagrating structure. The anomalous refraction behaviors are verified experimentally at incidence angle of 28°, 45°, and 78°, respectively. The demonstrated metagrating is anticipated to possess efficient wide-angle composite wavefront engineering applications in such fields as communications.