bluuebunny/crossref_metadata_2025 huggingface dataset:
Additively manufactured plastic plasma spectrometer
Authors: Larrick Quetzal , Pollock Craig , Hampton Donald , Avanov Levon , Gershman Daniel , Thorsen Denise , Shipman Greg , Atencio Jesse , Melkomukov Anthony
Published: November 2024

We report results in the development and testing of a low resource tophat electrostatic analyzer (ESA) for space plasma measurements. This device has been additively manufactured (3D-printed) using fused deposition modeling. The classic tophat design is composed of four plastic pieces, without any surface coatings. The three conducting electrodes are printed from carbon nanotube infused polyether ether ketone (CNT-PEEK). The fourth piece, an insulating electrode support, uses pure PEEK. This ESA is designed to detect electrons in space from 10 eV up to 30 keV. We demonstrate that the printed CNT-PEEK is sufficiently electrically conductive to support the fast high voltage slewing often required for high time resolution measurements. The plastic ESA has been successfully vibrated beyond standard pre-flight levels, tested under keV electron beam illumination over a wide range of temperatures, and tested under UV illumination, simulating the solar Ly-α flux. In comparison with an identical machined aluminum ESA, our CNT-PEEK ESA provides nominal energy/angle bandpasses, closely matching simulation. These bandpasses imply minimal impact from surface charging at beam energies of 2–3 keV, although more investigation is needed. We also find that the CNT-PEEK ESA provides far superior out-of-band electron rejection and UV photon rejection compared to the machined aluminum ESA. We do not detect any problems with trapped gases or outgassing. This development offers the potential for significant mass savings, implementation of otherwise unattainable geometric configurations, and dramatic simplification in manufacturing and assembly processes required for the development of space plasma instruments.
Research of neural network-based model for nonlinear temperature drift compensation of MEMS accelerometers
Authors: Wei Minghui , Liu Zhenhao
Published: November 2024

Downhole instrumentation requires more and more accuracy of MEMS inertial sensors. However, in measurement while drilling, temperature drift phenomenon of the sensor will have a cumulative impact on the drill pipe attitude solution. After experimental testing, the output response of the accelerometer had strong local linear and global nonlinear characteristics. In this paper, we proposed a temperature compensation model based on tent chaotic mapping and sparrow search algorithm optimized back propagation (BP) neural network (Tent-SSA-BPNN). Sparrow search algorithm (SSA) was optimized by tent chaotic mapping, which was utilized to improve the uniformity and search ability of SSA populations. Then, the improved SSA was used to optimize the weight and bias parameters of the BP neural network for constructing the temperature compensation model. Finally, the trained compensation model is integrated into the microprogram control unit for real-time compensation testing. The experimental results show that after sacrificing a small amount of sampling frequency, the compensation model proposed in this article has good global compensation performance, and the mean absolute percentage error is reduced from 2% to 0.2% compared to the original output. The mean absolute error and root mean square error of the improved compensation model are all reduced compared to the pre-improved BP compensation model. This temperature-compensated modeling method has a reference value for low-cost and high-precision modeling in high temperature environments, while greatly saving time cost and measurement costs.
2D-IR spectroscopy of azide-labeled carbohydrates in H2O
Authors: Gasse P. , Stensitzki T. , Müller-Werkmeister H. M.
Published: November 2024

Carbohydrates constitute one of the key classes of biomacromolecules, yet vibrational spectroscopic studies involving carbohydrates remain scarce as spectra are highly congested and lack significant marker vibrations. Recently, we introduced and characterized a thiocyanate-labeled glucose [Gasse et al., J. Chem. Phys. 158, 145101 (2023)] demonstrating 2D-IR spectroscopy of carbohydrates using vibrational probes. Here, we build on that work and test azide groups as alternative for studies of carbohydrates to expand the available set of local probes. Many common carbohydrates with different azide labeling positions, such as galactose, glucose, or lactose, are readily available due to their application in click chemistry and hence do not require additional complex synthesis strategies. In this work, we have characterized azide-labeled glucose,, galactose, acetylglucosamine and lactose in water using IR and 2D-IR spectroscopy to test their potential for future applications in studies of carbohydrate–protein interactions. Our findings indicate that their absorption profiles and vibrational dynamics are primarily determined by the labeling position on the ring. However, we also observe additional variations between samples with the same labeling position. Furthermore, we demonstrate that their usage remains feasible at biologically relevant concentrations, highlighting their potential to probe more complex biological processes, i.e., enzymatic catalysis.
Unveiling the origin of multiple peak emission in derivative perovskite single crystals, CH3NH3Pb(Br1−xClx)3 (x = 0–1)
Authors: Dutt Shankar , Urkude Rajashri , Singh S. D. , Sagdeo Archna
Published: November 2024

Despite the overwhelming success of organic–inorganic metal halide perovskites in the field of energy harvesting, many of the aspects of these materials are not well understood even now. Specifically, the origin of multiple peaks emergence in photoluminescence (PL) spectra is widely debated. In the present work, emission spectra of mix halide perovskites, MAPb(Br1−xClx)3 (x = 0–1) on single crystal samples, have been investigated in detail. In addition to the band-to-band transition peak, two other peaks were observed. The amplitude of these two additional peaks appears to be strongly dependent on halide composition. Observed extra peaks in PL spectra were seen to be less pronounced in the pure end compositions (x = 0 and 1) and intense for intermediate compositions. It has been observed that multiple peaks seen in the bulk emission spectra are closely related to the coordination chemistry of a halide anion. X-ray absorption near edge spectroscopy indicated the existence of a different environment for the bromine anion, which might be responsible for the modification in the electronic structure with the change in halide composition. This modification in the electronic structure is suggested to be responsible for the appearance of debated multiple peak emissions in the PL spectra. These results are anticipated to pave the way for further research to enhance the understanding of the optoelectronic properties of mixed halide perovskites.
Unveiling the interactions between preexisting dislocations and displacement cascades in the refractory high-entropy alloy WTaCrV
Authors: Li Jie , Zhu Yaxin , Zhao Lv , Liang Shuang , Huang Minsheng , Li Zhenhuan
Published: November 2024

Refractory high-entropy alloys (RHEAs) represented by WTaCrV are excellent candidates for future nuclear reactor structures. Both the preexisting edge dislocations (EDs) and screw dislocations (SDs) can significantly impact the irradiation performance of RHEAs. To explore the influence of preexisting dislocations on the generation and evolution of irradiation point defects in the RHEA WTaCrV, the interactions between preexisting dislocations (including EDs and SDs) and displacement cascades are studied by molecular dynamics simulations in this work. In addition, the results of the RHEA WTaCrV without preexisting dislocations and of pure W with preexisting dislocations are included for comparison. It is found that the presence of preexisting dislocations leads to a significant increase in the number of remained point defects after the cascades. However, the absorption of vacancies by dislocation cores in the RHEA WTaCrV is more significant than that in the pure W. Therefore, preexisting dislocations can reduce the possibility of void formation and act as sites for recombination of vacancies and interstitials in the subsequent long-term evolution. For the preexisting EDs in the RHEA WTaCrV, the local pinning of EDs, the attraction of vacancies, and the severe lattice distortion jointly cause the bowing out of EDs, which is conductive to accommodate vacancies. For the preexisting SDs, the abundant cross kinks tend to bind vacancies or interstitials, promoting the motion of SDs as well as the annihilation of point defects. In this sense, the preexisting dislocations in the RHEA WTaCrV can significantly enhance the irradiation resistance. The results of this research can provide design guidance for regulating the anti-irradiation performance of RHEAs.
Strong coupling of metamaterial quadrupolar mode with molecular vibration
Authors: Wulan Qiqige , Liu Lu , Xing Li , Yu Jiachen , Wang Jingyu , Liu Zhijun
Published: November 2024

Metamaterial multipolar mode presents a compelling scheme for exploring fundamental properties and technological applications of light-matter interactions due to its strong near field and high quality factor. In this work, we demonstrate strong coupling and mode hybridization between metamaterial quadrupolar mode and molecular vibration in the mid-infrared. In our fabricated cross-shaped metasurfaces spin-coated with a polydimethylsiloxane (PDMS) film, a quadrupolar resonance with a quality factor of 33 is excited at oblique incidence, whose electric dipolar component efficiently couples to the Si-CH3 vibration with pronounced spectral splitting and anti-crossing behaviors. The coupling strength increases with the PDMS film thickness and reaches the strong coupling regime for thickness above 27 nm. A Rabi splitting of 0.79–1.13 THz is measured in the strong coupling regime. Our results indicate that the use of quadrupolar mode in plasmonic nanostructures provides an effective and convenient approach for the realization of vibrational polaritons, which hold promise for applications in ultrasensitive infrared sensing and photochemistry.
Lower hybrid drift instability in nonthermal plasmas
Authors: Arya Neetasha , Kakad Amar , Yoon Peter H.
Published: November 2024

Lower hybrid drift instability (LHDI) is driven by the cross-field current and operates in the vicinity of the lower-hybrid frequency, between the ion- and electron-gyro frequencies, and with wavelengths between the electron and ion thermal gyro radii. The free energy source that drives this instability resides in the density gradient associated with an inhomogeneous plasma. The existing literature on LHDI assumes that the charged particle distribution function is given by a Maxwellian form, but the space plasma is pervasively observed to feature nonthermal characteristics. This paper extends the theory of LHDI to nonthermal plasmas. The generalized theory of LHDI is, thus, applicable to various space plasma environments characterized by nonthermal plasma velocity distribution functions.
Polarization-insensitive bifocal metalenses by combining nanoimprint lithography and atomic layer deposition in the visible spectrum
Authors: Mao Xu , Yu Gang , Yang Fuhua , Wang Xiaodong
Published: November 2024

Multifocal lenses are essential components for microscopy, spectroscopic detection, and optical trapping. Benefiting from the unprecedented capability of metasurfaces in light control, metalenses are able to provide multi-foci functionality with a more compact footprint, making them attractive alternatives to traditional bulky lenses. However, current manufacturing techniques encounter some challenges, including low throughput, high cost, and limited patterning areas. Here, we demonstrate the wafer-scale, low-cost, and high-throughput production of polarization-insensitive bifocal metalenses at a wavelength of 450 nm by combining nanoimprint lithography and atomic layer deposition. The nanoimprint process is simplified by using the imprinted resin itself as meta-atoms, which exhibit high aspect ratios (∼10:1) and small critical dimensions (∼90 nm). The effective refractive index of the meta-atoms is increased through atomic layer deposition of the high-index TiO2 film, providing 0–1.5π sufficient phase coverage. Metalenses with diameters of 480 μm are fabricated on the silica substrate, exhibiting two diffraction-limited focal spots along the optical axis. Moreover, the fabricated metalenses demonstrate the polarization-insensitive feature under various polarization states. The fabrication process presented in this Letter paves the way for large-scale and low-cost production of versatile metasurfaces operating in the visible or shorter spectrum.
Structural and bonding properties of Ta2Cn−/0 (n = 1–7) clusters: Size-selected anion photoelectron spectroscopy and theoretical calculations
Authors: Zhang Chao-Jiang , Xu Hong-Guang , Xu Xi-Ling , Zheng Wei-Jun
Published: November 2024

The structures and chemical bond evolution of ditantalum doped carbon clusters Ta2Cn−/0 (n = 1–7) were studied via size-selected anion photoelectron spectroscopy and theoretical calculations. It is found that Ta2C−/0 has a triangular structure and Ta2C2−/0 has a quasi-rhombus structure with C2v symmetry. Ta2C3− has a quasi-planar structure with a carbon atom and a C2 unit interacting with two tantalum atoms, and the lowest-energy isomer of neutral Ta2C3 has a triangular bipyramid structure with three carbon atoms around the Ta2 unit. Ta2C4−/0 has two C2 units connected with the Ta2 unit in parallel. Two isomers of Ta2C5− are observed, where both isomers have one carbon atom and two C2 units bound to the Ta2 unit in different ways. The most stable structure of neutral Ta2C5 has one carbon atom added on top of the Ta2C4 cluster. The most stable structures of Ta2C6-7−/0 can be viewed as a C2 unit and a C3 unit capping a butterfly like Ta2C4 structure, respectively. Molecular orbital analysis shows that neutral Ta2C3 has a large gap between its highest occupied molecular orbital and lowest unoccupied molecular orbital. Chemical bonding analysis reveals that the Ta–Ta interactions in Ta2Cn−/0 (n = 1–7) clusters are slightly weaker than the Ta–Ta interaction in bare Ta2 due to the participation in forming multicenter bonds.
Optical constants of magnetron sputtered aluminum in the range 17–1300 eV with improved accuracy and ultrahigh resolution in the L absorption edge region
Authors: Burcklen Catherine , Delmotte Franck , Alameda Jennifer , Salmassi Farhad , Gullikson Eric , Soufli Regina
Published: November 2024

This work determines a new set of EUV/x-ray optical constants for aluminum (Al), one of the most important materials in science and technology. Absolute photoabsorption (transmittance) measurements in the 17–1300 eV spectral range were performed on freestanding Al films protected by carbon (C) layers, to prevent oxidation. The dispersive portion of the refractive index was obtained via the Kramers–Kronig transformation. Our data provide significant improvements in accuracy compared to previously tabulated values and reveal fine structure in the Al L1 and L2,3 regions, with photon energy step sizes as small as 0.02 eV. The implications of this work in the successful realization of EUV/x-ray instruments and in the validation of atomic and molecular physics models are also discussed.
High electromechanical coupling factor Lamb wave resonator
Authors: Cao Tengbo , Ding Rui , Gao Feng , Xuan Weipeng , Wan Qing , Luo Jack , Luo Yuxuan , Khelif Abdelkrim , Bermak Amine , Dong Shurong
Published: November 2024

Lamb wave resonators (LWRs) based on lithium niobate on insulator (LNOI) substrates operating in an A1 mode at frequencies above 5 GHz typically exhibit high electromechanical coupling coefficients (K2) ranging from 20% to 30%. This makes them promising candidates to replace current bulk acoustic wave technology in next-generation broadband RF filters. However, the K2 of conventional LWRs still struggles to meet application requirements for bandwidths exceeding 1 GHz, such as WiFi-6E. This paper presents an analytical optimization approach for rapid and comprehensive scanning of the full 3D Euler space to find the maximum effective K2 of LWR devices. Such a full scan is difficult to achieve by the conventional time-consuming finite element method (FEM). The K2 results for a selected subset of Euler angles obtained through this analytical approach align with FEM simulation results. The optimized results show that LWRs on LNOI can achieve the highest K2 of 59.92% at Euler angles of (0, −151°, −60°), providing bandwidths exceeding 1 GHz at 5 GHz. To validate this optimization approach, LWRs with various orientations were fabricated on both 41° YX-cut and Z-cut LNOI wafers, with measured K2 values at different Euler angles agreeing well with both analytical and FEM results. The proposed K2 optimization method serves as a valuable guideline for selecting substrate cuts and device orientations in the design of ultra-broadband filters for next-generation telecommunications.
Comprehensive assessment of terahertz quantum-cascade lasers performance characteristics
Authors: Pistore Valentino , Lü Xiang , Biermann Klaus , Schrottke Lutz
Published: November 2024

Terahertz (THz) quantum-cascade lasers (QCLs) are attracting an ever-increasing interest for both scientific and industrial applications in key areas, such as high-resolution spectroscopy of atomic and molecular absorption lines. Advancements in the active-region and resonator designs, hence, play a pivotal role in determining the future of this technology, especially regarding the wall-plug efficiency and the operating temperature, which are still the main factors limiting their widespread adoption. A sound characterization approach is, therefore, the foundation of the coming improvements to these semiconductor lasers. To overcome the overreliance on simulation tools for the determination of fundamental device characteristics, we report a comprehensive characterization approach to measure all relevant electrical, optical, and thermal parameters of THz QCLs in a consistent manner. Based on the lattice temperature dependence of the QCL output power, the thermal conductivity of the QCLs is extracted. We then retrieve light–current density–lattice temperature maps to decouple the influence of the bias and lattice temperature on the device performance. Applying this method to two sets of QCLs with different active-region designs allowed us to determine the internal quantum efficiency (∼12%), waveguide losses (8–20 cm−1), and transparency current density. A transparency current density greater than 60% of the threshold current density is observed for the two active regions, which demonstrates leakage currents to be the dominant factor limiting THz QCLs efficiency even at low temperatures and for optimized designs employing tall barriers of nominally pure AlAs.
A novel discrete memristive hyperchaotic map with multi-layer differentiation, multi-amplitude modulation, and multi-offset boosting
Authors: Wang Xinyan , Wei Yuqi , Sun Xu , Fan Zhenyi , Du Baoxiang
Published: November 2024

In recent years, the introduction of memristors in discrete chaotic map has attracted much attention due to its enhancement of the complexity and controllability of chaotic maps, especially in the fields of secure communication and random number generation, which have shown promising applications. In this work, a three-dimensional discrete memristive hyperchaotic map (3D-DMCHM) based on cosine memristor is constructed. First, we analyze the fixed points of the map and their stability, showing that the map can either have a linear fixed point or none at all, and the stability depends on the parameters and initial state of the map. Then, phase diagrams, bifurcation diagrams, Lyapunov exponents, timing diagrams, and attractor basins are used to analyze the complex dynamical behaviors of the 3D-DMCHM, revealing that the 3D-DMCHM enters into a chaotic state through a period-doubling bifurcation path, and some special dynamical phenomena such as multi-layer differentiation, multi-amplitude control, and offset boosting behaviors are also observed. In particular, with the change of memristor initial conditions, there exists an offset that only homogeneous hidden chaotic attractors or a mixed state offset with coexistence of point attractors and chaotic attractors. Finally, we confirmed the high complexity of 3D-DMCHM through complexity tests and successfully implemented it using a digital signal processing circuit, demonstrating its hardware feasibility.
Large-eddy simulation-based fluid–structure interaction framework for predicting coupled aero-vibro-acoustic instabilities in turbopumps
Authors: Noun Mark , Mohanamuraly Pavanakumar , Gicquel Laurent Y. M.
Published: November 2024

The design and operation of rocket engines are challenging due to the intricate dynamics and complexity of the interactions between components. One such critical component is the turbopump, a turbomachinery device responsible for delivering the propellants to the combustion chamber at an optimized pressure. During operations, the turbopump is prone to the “pressure band” vibration problem, a self-sustained oscillatory motion of the fluid capable of coupling with adjoining components. It poses an enormous risk to the structural integrity of the device. The compressible fluid–structure interaction exposes a three-way aero-vibro-acoustic coupling between the fluid, the structure, and the turbopump cavity acoustic modes. High-fidelity numerical simulations equipped with recent experimental and theoretical efforts hold significant potential to advance the state of the art in predicting and understanding this phenomenon. To address this problem, we propose a large eddy simulation (LES)-based fluid–structure interaction (FSI) framework using the partitioned coupling scheme that combines an existing LES compressible flow solver and a modal analysis and elastodynamics solver for the structure. The solvers within the framework target turbomachinery applications where the density ratio between the solid and fluid is typically quite large. The validation of the structural solver and the coupled FSI solver is first carried out using two dimensional (2D) and three dimensional (3D) test cases from the literature. Then, the proposed FSI framework is used to simulate the instabilities occurring due to the interactions between the flow, the disk, and the cavity of a 3D experimental reduced-scale turbopump. The simulation results show excellent agreement with the experiments, demonstrating the capability of the FSI framework in capturing such complex aero-vibro-acoustic interactions and instabilities.
Validation of galvanomagnetic and thermomagnetic transport measurements using Standard Reference Material 3451
Authors: Beekman Matt , Benedetti Matteo , Dominguez Deja , Hewett-Abbott Hayden , Jarymowycz Andrew , Leibowitz Matthew , Nichols Travis , Dorris Roger , Thomson Kyle , Watzman Sarah J. , Gibson Thu , Schlaak Katherine A.
Published: November 2024

In the “method of four coefficients,” electrical resistivity (ρ), Seebeck coefficient (S), Hall coefficient (RH), and Nernst coefficient (Q) of a material are measured and typically fit or modeled with theoretical expressions based on Boltzmann transport theory to glean experimental insights into features of electronic structure and/or charge carrier scattering mechanisms in materials. Although well-defined and readily available reference materials exist for validating measurements of ρ and S, none currently exists for RH or Q. We show that measurements of all four transport coefficients—ρ, S, RH, and Q—can be validated using a single reference sample, namely, the low-temperature Seebeck coefficient Standard Reference Material® (SRM) 3451 (composition Bi2Te3+x) available from the National Institute for Standards and Technology (NIST) without the need for inter-laboratory sample exchange. RH and Q data for NIST SRM 3451 reported here for the temperature range 80–400 K complement the data already available for ρ and S and will therefore be of interest to researchers desiring to validate new or existing galvanomagnetic and thermomagnetic transport properties measurement systems.
Data-driven models for microfluidics: A short review
Authors: Chang Yu , Shang Qichen , Yan Zifei , Deng Jian , Luo Guangsheng
Published: November 2024

Microfluidic devices have many unique practical applications across a wide range of fields, making it important to develop accurate models of these devices, and many different models have been developed. Existing modeling methods mainly include mechanism derivation and semi-empirical correlations, but both are not universally applicable. In order to achieve a more accurate and general modeling process, the use of data-driven modeling has been studied recently. This review highlights recent advances in the application of data-driven modeling techniques for simulating and designing microfluidic devices. First, it introduces the application of traditional modeling approaches in microfluidics; subsequently, through different database sources, it reviews studies on data-driven modeling in three categories; and finally, it raises some open issues that require further investigation.
Ultra-flatbands in twisted penta-hexa-CB bilayer with large twist angles
Authors: Chen Rongrong , Gao Jin , Yang Lei , Shi Xiaowen , Xue Desheng , Jia Chenglong , Tao Kun
Published: November 2024

We report the discovery of ultra-flatbands in twisted penta-hexa-carbon boron (PH-CB) bilayers, a finding with profound implications for condensed matter physics. Using first-principles calculations, we show that PH-CB bilayers exhibit an exceptionally narrow bandwidth of 0.13 meV at a distortion angle of 9.6°, indicating the robust electron correlation effects. This observation contrasts with the need for tiny twist angles in graphene to achieve similar effects. The PH-CB system, with its indirect bandgap of 2.11 eV, represents a versatile platform for exploring novel electronic phenomena that may lead to advances in quantum materials. Our results highlight the inverse relationship between wave function localization and bandwidth and provide a new perspective for the design of two-dimensional materials with tailored electronic properties.
Electric and thermal coupled light fields regulating photoelectric sensing performance in photoferroelectrics
Authors: Liu Yaping , Zhang Jiayi , Qin Tian , Du Hongyu , Yang Bo , Zhao Shifeng
Published: November 2024

Traditional photoelectric semiconductors with single-source energy sensing or hybrid energy sensing integrated with other materials constrain their effectiveness in achieving power stability and device miniaturization. In contrast, photoferroelectrics offer multiple energy responses to electric, thermal, and light fields within a single material, thereby regulating the photoelectric sensing performances. This work proposes a multi-field coupling effect involving electrical, thermal, and light fields to enhance photoelectric sensing performances in electroneutral ion group doped BiFeO3 photoferroelectrics with synergistic improvement in polarization, bandgap, and leakage properties. Notably, the photocurrent output is significantly engineered by applying dual-field modes of pre-poling or thermal coupled light fields compared with the light field sensing solely. More importantly, the responsivity of the optimized photoelectric sensors is increased by nearly five times when pre-poling and thermal fields are applied simultaneously, providing convincible evidence of the sensing enhancement derived from the multi-field coupling effect. This work provides a feasible strategy to improve the photoelectric sensors through multi-field coupling, promoting the application of multifunctional photoelectric devices.
Multi-channel nonreciprocal radiation of transverse electric wave with photonic crystal heterostructure
Authors: Liang Guoyu , Wang Bo
Published: November 2024

An apparatus that accomplishes productive energy conversion by breaking conventional Kirchhoff's law is the nonreciprocal thermal emitter. Previous research universally focused on the nonreciprocal thermal emitter operated under transverse magnetic wave. The nonreciprocal thermal radiation proposed is operated under transverse electric (TE) wave, filling the gap in previous research. Meanwhile, the emitter, utilizing a photonic crystal (PC) heterostructure scheme composed of two one-dimensional PCs and an Al basement, accomplishes multi-channel nonreciprocal thermal radiation. With the external magnetic field of 3T, the emitter displays nonreciprocity behavior at bands of 15.933, 16.248, and 16.527 μm. Furthermore, under alternative sets of structural parameters, the structure can achieve four-port nonreciprocal radiation at bands of 16.437, 16.804, 17.139, and 17.478 μm. Both operating states indicate that the heterostructure under the magnetic field of 3 T exhibits nonreciprocal radiation performance for the TE wave. In addition, the exploration of the flat plate structure (IG)n(GI)mM shows that this scheme has multi-band nonreciprocity in TE wave.
Non-inertia wave model approximation with stage-discharge relationship imposed at the downstream end and a space- and time-dependent lateral inflow
Authors: Kandpal Shiva , Bora Swaroop Nandan
Published: November 2024

An analytical solution for the non-inertia wave model is presented for a lateral inflow that is uniformly distributed between any two locations. The model is solved by using the Laplace transform. A stage-discharge relation is taken at downstream boundary, and the upstream boundary is either water-depth based or flow rate based. The flow rate responses for the positions between the lateral inflow boundaries are found to be dependent on the location of observation, which is not the case for the positions downstream and upstream of the lateral inflow boundaries. The backwater effect induced by the lateral inflow is observed in the flow rate as well as the water depth, irrespective of the type of upstream boundary. For a flow rate hydrograph imposed at the upstream section, the flow rate and water-depth responses for the locations downstream to the location of lateral inflow are independent to the location of lateral inflow in contrast to the case of a water-depth hydrograph at the upstream section.
Effect of three-dimensional surface roughness on CH4 adsorption and diffusion in coal nanopores
Authors: Wang Xiaolei , Du Xidong , Guang Wenfeng , Zhou Junping , Wang Guangjin , Zhang Dengfeng , Abbas Naeem , Jia Yunzhong , Cheng Yugang , Wang Hui , Zeng Mengru
Published: November 2024

Coalbed methane has garnered increased attention from researchers due to its potential for efficient development and utilization. In this study, the roughness data of coalbed pore surfaces were first obtained using atomic force microscopy tests. A novel method for constructing three-dimensional rough surfaces was proposed by combining these data with molecular simulation technology. Consequently, a more realistic three-dimensional coalbed surface roughness model was built, and the influence of surface roughness on CH4 adsorption and diffusion was explored. The results show that the CH4 adsorption configuration on coalbed nanopore surfaces is closely related to surface roughness. The grooves formed by the rough surface provide more adsorption space for CH4 storage. CH4 preferentially adsorbs in these grooves, forming intermittent adsorption layers. The adsorption capacity of the coal matrix slit nanopore system with rough surface is as follows: the groove part of the groove space > the surface part of the groove space > the convex surface part of the coal matrix > the convex part of the groove space > the middle part of the slit nanopore. CH4 average adsorption density increases with greater surface roughness and smaller pore size. Pore size is the main factor controlling CH4 diffusion; larger pores promote diffusion, while increased surface roughness hinders diffusion. Differences in CH4 diffusion coefficients due to surface roughness tend to equalize under high pressure. The analysis of the potential energy and average heat of adsorption indicates that CH4 adsorption is more stable under conditions of rough surfaces, small pore sizes, and high pressure.
Influence of gap size and cavity depth on the performance of a squealer tip with rail crown holes in turbine blades
Authors: Zhou Haimeng , Luo Lei , Guo Hailong , Yan Han , Du Wei , Wang Songtao
Published: November 2024

In modern gas turbines, turbine blade tips often face severe thermal erosion and aerodynamic losses. Squealer cavity structures have demonstrated significant advantages in improving tip harsh working conditions, making them a widely researched and applied solution. Among them, the squealer tip with rail crown holes has been proved a novel and more effective structure for controlling tip leakage flow and enhancing tip cooling. In this paper, for the novel structure, the effects of tip gaps and cavity depths on its performance are investigated. The results show that, as the gap size increases, more gap leakage flow impinges on the leading-edge floor, and the swirling strength of the cavity vortex is enhanced, which causes the increasing heat transfer coefficient (h) and decreasing film cooling efficiency (η) on the cavity floor. The coolant is distributed over a larger radial space up the rail with the increasing gap size, thereby the cooling intensity on the rail crown is diminished. In the case with a smaller gap, the impact of coolant on the leakage flow rate is more pronounced, and the leakage flow exhibits a distinct stripe-like morphology. When the cavity depth alters, the η distribution on the rail crown surface remains unchanged, thereby it primarily correlates with the gap size. In the small cavity depth scheme, the pass-over coolant is subjected to axial shear by the cavity flow within the cavity. Consequently, the lower part of the coolant flow is scraped along the axial direction by the cavity flow, resulting in the coolant jets having a significantly dispersed flow state but with strong swirling characteristics. As the cavity depth increases, the scraping effect on the coolant is reduced, thereby the coolant can maintain its original form as it flows to the suction side, thereby forming localized high-h regions in a spotted pattern on the suction-side rail crown.
A numerical study on the in-nozzle flow and near-field spray dynamics of spirally grooved hole nozzles: Effects of injection pressure and length/diameter ratio
Authors: Leng Xianyin , Xing Mochen , Deng Yicheng , Jin Yu , He Zhixia
Published: November 2024

The nozzle geometry in internal combustion engines plays a critical role in determining cavitating flow characteristics, which affect in-cylinder atomization, combustion, and engine performance. In this study, the multi-phase flow inside and outside spirally grooved hole nozzles were simulated using the Volume of Fluid model coupled with the Discrete Phase Model. This approach allowed for detailed examination of how injection pressure and length-to-diameter (L/D) ratio influence cavitation and atomization. The results showed that the nozzles with spiral grooves structure can increase the near-field spreading angle of the jet, but cavitation can negatively affect the distribution of droplets by decreasing the radial velocity. Moreover, when the L/D ratio is decreased from 5 to 2.5, the radial momentum intensity of the internal flow increased by 80%, leading to enhanced atomization. Notably, increasing the injection pressure from 150 to 250 MPa and reducing the L/D ratio from 5 to 2.5 both achieved similar improvements in fuel atomization, resulting in a 10% reduction in the Sauter mean diameter of droplets. A lower L/D ratio enhances atomization by shortening the flow path and increasing the radial momentum ratio, whereas higher injection pressure improves atomization by increasing jet kinetic energy and enhancing fluid–air interaction.
Modeling on shock wave collision between asymmetric clouds driven by powerful laser
Authors: Ren Can , Sun Wei , Yuan Wenqiang , Zhang Yapeng , Tian Baoxian , Wang Yuanhang , Feng Li , Lv Chong , Wang Zhao
Published: November 2024

The cloud–cloud collision is one of the primary mechanisms proposed for forming massive stars. In addition to astronomical observations, plenty of numerical simulations have been conducted. However, relevant laboratory astrophysical studies remain relatively lacking. Using a magnetohydrodynamic simulation code, we simulate the collision of asymmetric plasma shock waves driven by a laser to model the cloud–cloud collision. We investigate the evolution of the collision region with external magnetic fields in different directions. The results indicate that when a strong magnetic field is perpendicular to the collision velocity (referred to as the collision plane), the development of turbulence within the collision region is effectively suppressed, and the magnetic field component in this direction is significantly amplified, the magnetic field in the collision region exhibits a coherent structure. Such coherent magnetic structures may contribute to the formation of coherent interstellar magnetic fields. Additionally, the probability density function of mass density shifts toward high-density regions. This shift could result in the formation of more massive cores from cloud–cloud collisions in the presence of strong magnetic fields.
Strain engineering of ferroelectric polarization and domain in the two-dimensional multiferroic semiconductor
Authors: Gao Lijing , Chen Xiaofang , Qi Jingshan
Published: November 2024

Two-dimensional (2D) ferroelectricity has attracted great interest for its potential to develop various flexible and stretchable ultra-thin smart devices. The ultra-thin nature of 2D materials makes domain control very challenging, as an external electric field inevitably leads to leakage currents and even material breakdown. Therefore, it is highly desirable to explore more practical and feasible methods to control ferroelectric (FE) domains. In this work, based on the coupling between the ferroelasticity and ferroelectricity in 2D multiferroic materials, we propose a strategy to control the FE polarization direction and domain through the strain engineering. Taking β′-In2Se3 as an example, we revealed the regulation mechanism of the uniaxial strain and shear strain on the ferroelasticity and ferroelectricity. We found that the polarization direction of FE β′-In2Se3 is tunable by manipulating the strain, which demonstrates the feasibility to tailor the FE single domain as well as domain wall (DW) patterns. In addition, we also found that the angle between the stretching direction and the DW plays a crucial role in regulating the DW type, which provides an important reference for controlling DW. Therefore, the strain engineering not only provides an alternative solution for forming large-sized single domain FE materials, but also enable customized FE domain structures for DW electronics by ingeniously designing strain patterns.
Efficient smoothed particle hydrodynamics modeling of airtanker water dropping: From basic validations to practical applications
Authors: Guan Xiang-Shan , Sun Peng-Nan , Huang Ling-Cai , Huang Xiao-Ting
Published: November 2024

The water-dropping (by water-dropping, we mean the phenomenon of water flow dispersing into droplets under the influence of airflows) of airtankers (by airtankers, we mean the aircraft carrying out firefighting missions) has always been a challenge in computational fluid dynamics simulation due to its complex mechanism and vast splashing space. Although the smoothed particle hydrodynamics (SPH) method has advantages in dealing with splashing problems, the multiphase flow SPH model faces the challenge of low computational efficiency in simulating splashing problems in the vast space. An efficient SPH model considering airflow resistance based on the single-phase coupling algorithm between fluid particles and airflows is proposed in this paper. The SPH model can calculate the airflow resistance of fluid particles based on their windward surface and surface normal and then simulate the splashing trajectory and pattern of SPH particles under the influence of high-speed airflows. In this article, two benchmark cases, including water jet and dropped water in the wind, are simulated based the SPH model. The simulation results are consistent with experimental results, verifying the computational accuracy and efficiency of the proposed SPH model. After that, the entire pattern of water-dropping about an airtanker is simulated, proving the feasibility of the algorithm for simulating large-scale water-dropping engineering problems.
Thermoacoustic CBE imaging for monitoring microwave ablation of the liver: A feasibility study
Authors: Feng Lian , Song Ling , Yang Zeqi , Song Jieni , Peng Wanting , Wu Zhenru , Huang Lin , Luo Yan
Published: November 2024

Microwave ablation is the most commonly used minimally invasive technique for thermal ablation of liver tumors, and accurate monitoring of the ablation area is crucial for evaluating treatment efficacy. While traditional imaging techniques play an important role in clinical monitoring, they still face several insurmountable challenges. Microwave-induced thermoacoustic imaging (TAI) has emerged as a promising modality for ablation detection due to its high resolution and deep imaging capabilities. To further enhance the effectiveness of TAI in ablation monitoring, we propose a technique based on thermoacoustic changes in backscattered energy (CBE) imaging. This method accurately delineates the liver ablation area by monitoring temperature variations before and after ablation. Experimental results show that thermoacoustic CBE imaging offers significant advantages over traditional TAI, achieving accuracies of 97.12% in ex vivo and 93.46% in in vivo experiments. Its superior resolution makes it an ideal choice for monitoring tissue damage during microwave ablation.
Nonlinear chiroptical response in lithium niobate metasurface driven by quasi-bound states in the continuum
Authors: Duan Hong , He Haoxuan , Yi Yingfei , Wang Lulu , Zhang Ying , Yan Xia , Huang Jing , Zhou Chaobiao
Published: November 2024

Quasi-bound states in the continuum (QBIC) can significantly localize the light field and enhance light–matter interactions at the nanoscale, providing a platform for high-Q chiral light response and promoting nonlinear effects of materials. In this work, we numerically study the chiral linear and nonlinear light responses of the QBIC lithium niobate (LN) metasurface and achieve chirality modulation. The designed metasurface consists of LN nanobar dimers, and the chiral QBIC mode is excited by breaking the in-plane and out-of-plane symmetries of the structure, with the circular dichroism (CD) value and Q-factor reaching 0.92 and 1.24×104, respectively. Then, we investigate the second harmonic generation (SHG) of this device. The conversion efficiency of SHG under right circularly polarized pumping reaches 7.3×10−3, which is more than three orders of magnitude higher than that under the left circularly polarized pumping. The corresponding CD value of SHG reaches 0.99. In addition, by introducing phase change materials, we study the active modulation of the chiroptical response. Our results provide a crucial route for high-quality chiral light sources.
Enhancing thermal dissipation ability and electrical performance in GaN-on-GaN HEMTs through stepped-carbon buffer design
Authors: Li Shiming , Meng Biwei , Wu Mei , Sun Haolun , Yang Bowen , Yang Ling , Zou Xu , Zhang Meng , Lu Hao , Hou Bin , Yuan Chao , Ma Xiaohua , Hao Yue
Published: November 2024

This study investigates the thermal dissipation ability and electrical performance of GaN-on-GaN HEMTs through a stepped-C buffer design. We analyzed the relationship between impurity (C and Fe) concentrations and the thermal conductivity of the GaN material by fitting Debye–Callaway model. A stepped-C buffer design is proposed to avoid the Fe impurity and its tailing effect on thermal conduction in GaN epitaxial layers. In addition, the high concentration of C doping is designed to suppress the epitaxial interface leakage in GaN-on-GaN structures. The transducer-less transient thermoreflectance (TL-TTR) technique revealed that the stepped-C structure significantly improves thermal conductivity of epitaxial layers compared with that of Fe/C co-doped structure. Due to the optimization of heat dissipation ability, the peak temperature of the stepped-C sample decreased by ∼30 °C compared to the Fe/C co-doped sample at PDC = 10.4 W/mm. Consequently, the GaN-on-GaN HEMTs with the stepped-C buffer achieved a record output power density (Pout) of 14.8 W/mm and a power-added efficiency (PAE) of 48.2% at 3.6 GHz, underscoring the critical role of thermal management in advancing GaN-on-GaN HEMT RF performance.
Spin wave linear response of three-dimensional structures calculated in the frequency domain
Authors: Giovannini L.
Published: November 2024

A theory is presented for calculating the spin wave response of a three-dimensional damped magnetic system to an external excitation, in the frequency domain. The equation of motion, written in the Hamiltonian formalism, is discretized within a finite-element method, and the corresponding large system of equations is first linearized and then solved with well-established techniques of linear algebra, leading directly to the spectral response. This approach is therefore particularly suitable for interpreting the results of all-electric microwave measurements of magnonic crystals. The response of a three-dimensional structure, composed of a portion of a square array of circular dots placed in close proximity of a magnetic substrate, is then investigated. A prominent, narrow feature with a large rejection ratio is observed in the spin wave transmission spectrum, making this structure useful as a narrowband notch filter.
Time-resolved magneto-optical effects in the altermagnet candidate MnTe
Authors: Gray Isaiah , Deng Qinwen , Tian Qi , Chilcote Michael , Dodge J. Steven , Brahlek Matthew , Wu Liang
Published: November 2024

α -MnTe is an antiferromagnetic semiconductor with above room temperature TN = 310 K, which is promising for spintronic applications. Recently, it was reported to be an altermagnet, containing bands with momentum-dependent spin splitting; time-resolved experimental probes of MnTe are, therefore, important both for understanding novel magnetic properties and potential device applications. We investigate ultrafast spin dynamics in epitaxial MnTe(001)/InP(111) thin films using pump-probe magneto-optical measurements in the Kerr configuration. At room temperature, we observe an oscillation mode at 55 GHz that does not appear at zero magnetic field. Combining field and polarization dependence, we identify this mode as a magnon, likely originating from inverse stimulated Raman scattering. Magnetic field-dependent oscillations persist up to at least 335 K, which could reflect coupling to known short-range magnetic order in MnTe above TN. Additionally, we observe two optical phonons at 3.6 and 4.2 THz, which broaden and redshift with increasing temperature.