bluuebunny/crossref_metadata_2025 huggingface dataset:
Excellent piezoelectric and ferroelectric properties of ScxGa1−xN alloy with high Sc concentration
Authors: Uehara Masato , Hirata Kenji , Nakamura Yoshiko , Anggraini Sri Ayu , Okamoto Kazuki , Yamada Hiroshi , Funakubo Hiroshi , Akiyama Morito
Published: December 2024

Alloying wurtzite aluminum nitride and gallium nitride (GaN) with scandium (Sc) enhances the piezoelectric and ferroelectric properties, but increasing the Sc concentration while maintaining the wurtzite phase is a major challenge. We meticulously optimized the sputtering conditions to successfully obtain a high-Sc-concentration GaN alloy (ScxGa1−xN, 0.44 < x ≤ 0.53), which has not yet been achieved. The prepared ScxGa1−xN films exhibit excellent piezoelectricity and ferroelectricity. The maximum piezoelectric constant d33 of 33 pC/N exceeds the values of ScxAl1−xN used in radio frequency filters. The minimum coercive field of ferroelectricity Ec of 1.49 MV/cm is the lowest of any ferroelectric wurtzite to date and is comparable to those of state-of-the-art ferroelectric HfO2-based materials used in compute-in-memory for artificial intelligence. Structural analysis showed that the ScxGa1−xN films have a c-axis-oriented wurtzite texture without a rock salt phase. The lattice constant ratio c/a varies greatly depending on the sputtering conditions. Decreasing c/a causes d33 to increase almost linearly, and minimizing Ec requires a small c/a and high Sc concentration.
Enhancing optical absorbance and accelerating rotational speed in molecular motors through oriented external electric fields
Authors: Wu Liang-Ting , Nachimuthu Santhanamoorthi , Kaleta Jiří , Jiang Jyh-Chiang
Published: December 2024

Accelerating the rotational speed of light-driven molecular motors is among the foremost concerns in molecular machine research, as this speed directly influences the performance of a motor. Controlling the motor’s rotation is crucial for practical applications, and using an oriented external electric field (OEEF) represents a feasible method to achieve this objective. We have investigated the impact of an OEEF on the optical and kinetic properties of a novel π-donor/acceptor di-substituted molecular motor, R2,3-(NH2, CHO). We employed density functional theory (DFT) and time-dependent DFT methods to analyze the electronic excitation and thermal isomerization behavior. Our results demonstrate that the absorption wavelength, absorption efficiency of the motor, and rate constant of the thermal isomerization reaction can be adjusted by applying OEEFs, which are predictable based on the dipole moment and polarizability of the molecules under consideration. In particular, we observed a shift in the absorption wavelength toward longer ranges, an enhancement in light absorption intensity, and an acceleration in the rotation rate when applying a weak positive directional external electric field to the R2,3-(NH2, CHO) motor. In summary, this theoretical study highlights the potential of OEEFs for improving the performance of molecular motors.
Acoustic effects on aerodynamic characteristics of a surface-mounted square cylinder
Authors: Zhao Lixuan , Li Qiusheng
Published: December 2024

The coupling between sound and flow likely influences the aerodynamics of bluff bodies, which deserves in-depth investigations. This paper presents a comprehensive experimental study of the effects of sound on the near wake flow and aerodynamic forces of a finite three-dimensional (3D) square cylinder in smooth flow and grid-generated turbulent flows. The study centers on the respective influences of a wider range of sound frequencies (1–2000 Hz) and sound pressure levels (60–100 dB) compared to previous studies. Employing a combination of particle image velocimetry and pressure measurements, the effects of sound on the aerodynamic characteristics, specifically, the near wake flow field, vortex shedding dynamics and pressure distributions are investigated. The spectral analysis and proper orthogonal decomposition analysis are conducted to gain deeper insights into the effects of sound on the coherent structures of the aerodynamic forces around the square cylinder. The results demonstrate that the influences of sound in modulating the wind pressure distributions on the cylinder are dependent on both the sound frequency and sound pressure level. The findings also highlight the occurrence of acoustic resonance and its impact on vortex-shedding behaviors and flow fields, demonstrating the sensitivity of these phenomena to specific sound frequencies and sound pressure levels. Furthermore, these sound-induced change phenomena can be weakened when turbulence is added to the approaching flows. The degree of this attenuation is found to vary depending on specific characteristics of a turbulent flow, such as turbulence intensities and integral length scales.
Rational design of static wetting on roughness-engineered heterogeneous surfaces
Authors: Martí Balaguer Gerard , Serra-Peralta Marc , Rius Gemma
Published: December 2024

Surface roughness and chemical composition are crucial in controlling the static wetting properties of surfaces. Here, conventional surface structuring methods used in Si microfabrication are used as a reference to analyze the impact of precisely engineered surface roughness. The static wettability of rough chemically heterogeneous surfaces is experimentally studied through contact angle measurements and compared against computational simulations to categorize the wetting behavior of water droplets. Heterogeneous samples are observed to already show significant dependence on the surface fraction covered by each material. Furthermore, owing to the presence of a resist layer on top of the Si pillars, intermediate states between the Wenzel (W) and Cassie–Baxter (CB) models are observed. Consistent with these models, we find that local chemical modifications of microstructured surfaces are crucial for controlling their surface wettability properties. Additionally, a comparison of equivalent microstructures made of Si or polydimethylsiloxane (PDMS) reveals the quantitative impact of the hydrophilic/hydrophobic nature of the material on the evolution of the wetting properties with increasing roughness factors. While Si surfaces behave according to the W model, PDMS surfaces show intermediate wetting states at significantly lower roughness levels. Bubbles trapped beneath water droplets demonstrate the existence of intermediate states that cannot be defined by either the W or CB models. By combining experimental results with finite element simulations, we not only demonstrate wettability control through specific roughness and chemical modifications but also provide insight into how these parameters interact to accurately predict and adjust static wetting properties.
Analysis of electromagnetic force characteristics and wheelbase design of Maglev car based on double permanent magnet electrodynamic wheels
Authors: Yang Yiying , Ke Zhihao , Bi Jingguo , Li Zhengyan , Zheng Jun , Deng Zigang
Published: December 2024

With the advantage of “suspension-drive” integration, the Maglev car has broad application prospects in fields, such as Maglev highways. Currently, a laboratory-scale Maglev car prototype has been built by one of the groups of Southwest Jiaotong University equipped with four permanent magnet electrodynamic wheels. A full-scale Maglev car is planned for design. The distance between the front and rear electrodynamic wheels (EDWs) of a Maglev car will directly affect the safety of the entire car system operation; therefore, it is necessary to explore the wheelbase design. This paper first analyzes the relationship between the electromagnetic force of double EDWs (DEDWs) and the wheelbase under the size of a scaled prototype through 3D simulation and verifies the effectiveness of the simulation model through experiments. Furthermore, the electromagnetic force characteristics of full-scale DEDWs were explored through finite element simulation methods. Finally, we provide the wheelbase design standards for the Maglev car of any size. The findings indicate that the electromagnetic force of DEDWs first rapidly decreases and then stabilizes with increasing wheelbase. The ratio of the inner and outer radius of the DEDWs, and the material and thickness of the conductor plate do not affect the critical value of the wheelbase, while the rotation speed and air gap of DEDWs are the parameters affecting the design of the wheelbase. This article provides a new idea for the wheelbase design of the Maglev car, which is expected to provide some reference for the structural design and parameter optimization of multi-EDW devices.
Boundary element simulations of dynamic wetting with a mesoscale contact line model
Authors: Zhang Zheming , Gao Peng
Published: December 2024

It is known that numerical simulations of moving contact lines are challenging owing to the fact that multiple scales are inherently involved. In this paper, we propose an efficient boundary element method for numerical simulations of dynamic wetting/dewetting. The flow domain is truncated in a mesoscopic scale, where boundary conditions resulted from a wedge flow and the asymptotic theory of the intermediate region are imposed. This procedure avoids the high resolution near the contact line in full-scale simulations and hence significantly reduces the computational cost. Numerical tests for dip coating problem show that the meniscus profiles and slopes produced by the proposed method agree well with high-resolution full-scale simulations as well as the local asymptotic theory.
Investigation of the flow characteristics and NOx formation mechanism of hydrogen micromix diffusion combustion with vortex generator
Authors: Mo Da , Lin Yuzhen , Liu Yixiong , Han Xiao , Wang Yuchen
Published: December 2024

It is well established that hydrogen has become one of the most promising fuels for achieving zero-carbon emissions. However, hydrogen combustion still faces many challenges, particularly the flashback issue and high NOx emissions, which necessitate the exploration of hydrogen combustion technologies and pollution control measures. This paper proposes a micromix diffusion combustion scheme with a disturbance vortex generator (DVG). The flow characteristics of the micromix element were analyzed, including the velocity distribution, penetration depth, jet vortex length, and vortex structure. It was found that DVG would create an air streamwise vortex within the main airflow, thus accelerating the axial velocity decay and facilitating the penetration of hydrogen. The hydrogen jet vortex rolls up the mainstream air, forming a coupled vortex system, which further enhances mixing. Sensitivity analysis was carried out to study the influences of the key parameters of the micromix element. The hydrogen injection hole diameter and the DVG height were found to be the most influential factors. The interactions between vortex, flame, and NOx were investigated to obtain the mechanism of NOx formation. By conducting a comparative analysis of the effects of the hydrogen orifice diameter and the vortex generator height, it has been observed that augmenting the length of the jet vortex can significantly promote the mixing of hydrogen with the mainstream air, playing an essential role in reducing emissions. This study establishes a solid foundation for future research endeavors in the development of micromix diffusion combustors.
Deep learning-based predictive modeling of transonic flow over an airfoil
Authors: Chen Liwei , Thuerey Nils
Published: December 2024

Effectively predicting transonic unsteady flow over an airfoil presents significant challenges due to its complex dynamics. In this study, we utilize a deep neural network architecture designed to capture intricate flow behavior. Through comprehensive training, our models successfully represent the complexities of transonic and unsteady flow, even under previously unseen conditions. By leveraging the differentiable nature of neural network representations, we develop a framework for evaluating fundamental physical properties using linear stability analysis. This approach bridges neural network modeling with traditional modal analysis, providing critical insights into transonic flow dynamics while improving the interpretability of neural network-based flow diagnostics.
Molecular dynamics simulation on the density distribution and multilayer adsorption of methane in nanopores
Authors: Zhang Rui , Tang Yao
Published: December 2024

The adsorption behavior of methane (CH4) in nanopores affects its spatial density distribution, which is essential for the shale gas extraction. While the average density of CH4 in nanopores has been commonly utilized in practice, the density distribution and the mechanisms of multilayer adsorption remain unclear. In this study, molecular dynamics simulations were conducted to investigate the formation of adsorption layers in nanopores. The effects of pressure, pressure gradient, pore width, and temperature on adsorption were examined. As CH4 pressure increases from 1 to 80 MPa, the adsorption layer transitions from one layer to three, resulting in multilayer adsorption. Although the increased pressure enhances the interactions between CH4 molecules, the force exerted by the pore walls on the CH4 molecules remains unchanged. When the repulsive force from the preceding adsorption layer exceeds the attractive force from the pore walls, a minimum methane density is reached, leading to the formation of a new adsorption layer. Following the application of the methane pressure gradient, it was observed that the carbon (C) atoms are displaced from their adsorption sites to regions of higher potential energy, reducing the peak density value. Additionally, the pore width has a minimal effect on the density distribution, as it does not alter the force exerted on the C atoms. Furthermore, temperature can increase the thermal motion of CH4 molecules, resulting in a more uniform spatial density distribution. Finally, a model was proposed to predict the spatial density distribution of CH4 in nanopores, accounting for multilayer adsorption.
Optimization study on fluid flow and heat transfer in a rectangular channel with cross-scale ribs for turbine blade internal cooling
Authors: Wang Yi-Bo , Yan Ke-Chuan , Wang Chen-Xi , Wang Shao-Yu , Zhang Ben-Xi , Yang Yan-Ru , Wang Xiao-Dong
Published: December 2024

In turbine engines, ribbed channels are a common internal cooling structure that can significantly enhance heat transfer but often lead to a noticeable reduction in flow performance. Although many optimization methods have been proposed to address the issue, it is challenging to improve both flow and heat transfer performance. In the present study, a cross-scale design concept that combines both micro-ribs and macro-ribs is proposed to optimize both flow and heat transfer performance simultaneously. Using the v2f turbulence model, the feasibility of this new design is evaluated through comprehensive three-dimensional numerical simulations across a wide range of Reynolds numbers from 20 000 to 80 000. For the macro-ribs, the linearly decreasing height (LDH) rib arrangement with the best heat transfer performance in existing studies is used. For the micro-ribs, different designs are tested, including blade ribs, triangular ribs (sawtooth ribs), and trapezoidal grooves (interval triangular ribs). The simulation results demonstrate that the combination of micro-ribs and macro-ribs can not only enhance heat transfer performance but also significantly reduce pressure loss. The improvement is attributed to the micro-ribs increasing the gas flow velocity near the wall. This not only reduces flow resistance but also enhances heat exchange between the main gas stream and the wall. Among the three kinds of micro-ribs, blade micro-ribs with the highest shear stress reduction rate have the greatest improvement on the overall thermal performance of LDH rib channels. Specifically, the factor (Nu/Nu0)/(f/f0) increased by 8.06%, and the factor (Nu/Nu0)/(f/f0)1/3 increased by 3.24%.
Probe-type optical fiber sensors for electric field distribution measurement
Authors: Chen Chen , Liang Xinyu , Li Yang , Peng Zongren , Song Ping , Sun Zheng
Published: December 2024

This paper reports a compact fiber optical electric field (E-field) sensor aiming for the precise detection of transient E-field distributions. Here, a reflective polarization-reciprocal optical path is proposed, which inherently mitigates the temperature-induced birefringence interference of the electro-optical crystal without the need for additional optical elements, thereby facilitating a reduced-size sensing probe. Furthermore, an adaptive particle swarm optimization (A-PSO) algorithm has been utilized for the first time to optimize the insulation structure of the optical E-field sensor, which significantly suppresses field distortion within the sensing region by 50%. This method addresses the technical gap in optical E-field sensor structure optimization, providing an effective means to improve its spatial resolution. The experimental results demonstrate that the proposed sensor exhibits a broad response frequency range from 50 Hz to 15 MHz, with a sensitivity of 0.675 V/kV cm−1. The proposed sensor successfully monitors the spatial distribution of electric fields in the lightning interception region of a lightning rod, thereby validating its effectiveness.
Suppression and excitation by collisions of two-stream and bump-on-tail instabilities
Authors: Hou Y. W. , Yu M. Y. , Wang J. F. , Liu C. Y. , Chen M. X. , Wu B.
Published: December 2024

Two-stream (TS) and bump-on-tail (BOT) electron distributions in plasma can lead to electrostatic instabilities and turbulence, and they have been extensively studied. Collisions usually mitigate these instabilities since they tend to hinder the motion of the participating electrons. Here, we numerically solve the full Vlasov–Poisson equations with Krook collisions to reconsider the evolution of the TS and BOT instabilities. It is found that even in the stable parameter regime predicted by linear theory, during the initial evolution (i.e., damping) stage, collisions can excite the TS instability. The reason is that during the evolution, efficient Krook collisions cause rapid thermalization of the TS electrons, leading to broadening of the initial velocity distributions of the two beams and appearance of regimes with unstable velocity gradients and trapped electrons. On the contrary, such a behavior does not occur for the BOT instability.
Structural and electrical characterization of self-assembled Sb4 molecules on metal surfaces
Authors: Li Shicheng , Li Qingyan , Duan Ruiping , Zhang Yong , Niu Gefei , Yang Yuhang , Sun Li , Gao Lei , Lu Jianchen , Cai Jinming
Published: December 2024

Antimonene is a promising two-dimensional material that is calculated to have a significant fundamental bandgap usable for advanced applications such as field-effect transistors, photoelectric devices, and the quantum-spin Hall state. Herein, we conducted a comprehensive investigation of self-assembled Sb4 islands on Au and Ag surfaces by scanning tunneling microscopy. The Sb4 molecules form α-phase and β-phase structures on Au and Ag surfaces, respectively, each exhibiting distinct island patterns. We simulated these structures using density functional theory calculations. Finally, we demonstrated the metallic band structure of Sb4 islands and observed the spatial and energy-dependent contributions of Sb4 molecules to the electronic states. This research enhances the understanding of the synthesis process of antimonene on metal surfaces and provides valuable insights for the industrial production of antimonene.
Cooperation resonance based on link strategy reinforcement learning and conformity
Authors: Gao Bo , Zuo Pengfei , Dai Xiangfeng , Fu Rongrong , Bai Zhiyan , Lan Zhongzhou
Published: December 2024

We propose a game model that integrates reinforcement learning (RL) with link strategies and conformity behavior to investigate the emergence and maintenance of cooperation. The model operates on a lattice network with periodic boundaries and includes two types of nodes: RL nodes with link strategies and conformist nodes. Simulation results reveal a range of critical mass. Within this range, the interaction between these two types of nodes exhibits a nonlinear response between the cooperation rate and the temptation to betray, resulting in the phenomena of resonance-like cooperation and resonance-like defection, showing a nonlinear response between the cooperation rate and the temptation to betray. This study reveals the complex interactions between the two strategies as well as their influence on system behavior through numerical simulations and analysis. Our results provide fresh insights into understanding and promoting cooperative behavior between artificial intelligence and humans.
Silicon-based light-emitting transistor with Ge(Si) nanoislands embedded in a photonic crystal: Control of the spectrum and spatial distribution of the emission
Authors: Yablonskiy A. N. , Shmagin V. B. , Zakharov V. E. , Yurasov D. V. , Shaleev M. V. , Demidov E. V. , Mikhaylov A. N. , Tetelbaum D. I. , Rodyakina E. E. , Morozova E. E. , Shengurov D. V. , Kraev S. A. , Novikov A. V.
Published: December 2024

Light-emitting transistors (LETs) represent the next step in the development of light-emitting diodes (LEDs), offering additional control over emission. In this work, the transport properties and spatial distribution of electroluminescence (EL) in the spectral range of 1.2–1.7 μm were studied for lateral p+-i-n+ LEDs based on silicon-on-insulator structures with self-assembled Ge(Si) islands embedded in photonic crystals. It is shown that due to the low mobility of holes and their effective trapping in the islands, the maximum EL yield is observed at the i/p+ junction of the LED. It is demonstrated that the sign and magnitude of the bias voltage applied to the substrate (to the gate) have a significant influence on the transport and emission properties of the LEDs with Ge(Si) islands, turning them into LETs. In particular, applying a negative gate voltage shifts the position of the maximum emission region from the i/p+ to the i/n+ junction of the LET, which is related to the formation of a hole conductivity channel near the buried oxide layer. The embedding of a specially designed photonic crystal in the i-region of the LET makes it possible to manage the spectral properties of the near-IR emission by changing the sign of the gate voltage. The results obtained may be useful for the future development of optoelectronic devices.
Tailoring nondiffracting structured lights along arbitrary three-dimensional trajectories via an inversed design
Authors: Wang Yishu , Hu Juntao , Wei Wenjun , Ye Wenni , Ying Zhihao , Li Xinzhong , Qian Yixian
Published: December 2024

We develop an inverse-designed caustic approach to tailor nondiffracting structured lights that exhibit arbitrary intensity structures. Simultaneously, these lights can propagate in an accelerated manner along an arbitrary three-dimensional trajectory. The scheme inherently gives rise to caustics, which are intensity singularities in geometric optics. These types of structured lights possess sharp intensity shapes and exhibit a significant intensity gradient. Moreover, these types of structured nondiffracting lights exhibit structured orbital angular momentum. The proposed approach breaks the restriction of conventional nondiffracting light beams, which preserve fixed propagation trajectories and structures. We experimentally validate our theory prediction. These diverse accelerating nondiffracting light beams will pave the way for optically trapping and moving particles along arbitrary three-dimensional trajectories and are likely to result in applications in wavefront control, optical micromachining, and depth imaging.
Variations of physical and mechanical properties of granite with different cooling treatments: An experimental study
Authors: Long Kun , Wu Yeqiu , Zhang Ruijie , Chen Ziqi , Yang Hongyun , Cheng Yugang , Wu Yang
Published: December 2024

The temperature gradient plays a critical role in the evolution of pore structure and mechanical properties of rock, but the underlying mechanisms remain unclear. This study conducts experiments on granite to investigate the effects of temperature gradients on pore structure and rupture propagation under different media, specifically liquid nitrogen and air. The pore structures and granite's transverse relaxation time (T2) are quantified using nuclear magnetic resonance (NMR). Then, Brazilian disk experiments are performed to explore the mechanical properties of granite following heating-holding treatments. Under the same temperature gradient, cooling with liquid nitrogen significantly influences the pore structures and mechanical properties of granite compared to air cooling. As the heat treatment temperature gradient increases, the mass loss rate, volume expansion ratio, and NMR porosity of granite increase, while the density, longitudinal wave velocity, and peak stress decrease. Splitting failure is caused by the constant propagation of the prominent cracks generated from the loading end to the load-bearing end. With increasing temperature in the thermal treatment, the secondary cracks increase and propagate toward the direction of the main cracks under the loading effect. These research results can provide a reference for developing high-temperature reservoirs and the technology for fracture initiation in such reservoirs.
Focused deposition of levitated nanoscale Au droplets
Authors: Coppock Joyce E. , Kane B. E.
Published: December 2024

We describe a method for depositing nanoscale liquid Au droplets, initially levitated in an ion trap in high vacuum, onto a remote substrate. A levitated Au nanosphere is melted, expelled from the trap, and maintained in the molten state, with a laser directed along the droplet trajectory, until it reaches the substrate and rapidly solidifies. During transit, the charged droplets are focused to a small region of the substrate with an electrostatic lens. After deposition, the substrate is removed from the vacuum chamber and imaged and analyzed by techniques such as electron microscopy and energy dispersive spectroscopy. Over 90% of launched particles are deposited on the substrate, and when the lens is focused, particles land in a region of diameter 120 μm after traversing a distance of 236 mm. Our technique is of value for analysis of materials prepared or processed while levitated that can be melted. Also, Au droplets may be useful as tracers for future experiments involving smaller projectiles or oriented solids.
Combustion dynamic stability analysis in stratified-rotation ethanol/air flame
Authors: Ren Shoujun , Lou Yue , Gao Jianbing , Jones William P.
Published: December 2024

The flame-dynamic stability and internal mechanism in a stratified-rotation ethanol/air flame are investigated through the utilization of a stratified vortex-tube combustor based on an advanced numerical calculation method. The performance of flame-dynamic and combustion stability is examined by evaluating the stability limit, pressure fluctuation, and flame topology. Results demonstrate that the stratified vortex-tube combustor exhibits excellent combustion and flame-dynamic stabilities, with the lean stability limit consistently below 0.2 and pressure fluctuations within 2000 Pa, accompanied by a uniform flame topology without significant temporal variations over time. The burning velocity displays good adaptability to flow field disturbances, aligning well with the normal flow velocity on the flamelet throughout time. Slight variations in flame topology result in weak heat release fluctuations, effectively suppressing fluid disturbances in the post-flame zone. Decreased momentum flux and its alterations in the post-flame zone play a crucial role in achieving flame-dynamic stability due to intense momentum exchange within this highly rotating reactive flow environment. The Rayleigh parameter and flame transfer function are employed to quantify flame-dynamic stability, revealing that both weak thermo-acoustic coupling degree and limited response level of heat release rate fluctuations to fluid fluctuations significantly contribute to maintaining stable flames. These findings systematically elucidate underlying mechanisms responsible for achieving robust flame-dynamic stability observed within this highly rotating reactive environment.
Neural deflection field for sparse-view tomographic background oriented Schlieren
Authors: Li Jiawei , Meng Xuhui , Xiong Yuan , Jia Tong , Pan Chong , Wang Jinjun
Published: December 2024

Three-dimensional (3D) density-varying turbulent flows are widely encountered in high-speed aerodynamics, combustion, and heterogeneous mixing processes. Multicamera-based tomographic background-oriented Schlieren (TBOS) has emerged as a powerful technique for revealing 3D flow density structures. However, dozens of cameras are typically required to obtain high-quality reconstructed density fields. Limited by the number of available optical windows and confined space in the harsh experimental environments, TBOS with only sparse views and limited viewing angles often becomes the necessary choice practically, rendering the inverse problem for TBOS reconstruction severely ill-posed and resulting in degraded tomography quality. In this study, we propose a novel TBOS reconstruction method, neural deflection field, utilizing an extremely light-weight deep neural networks to represent the density gradient fields without using any pretrained neural network models. Particularly, state-of-the-art positional encoding techniques and hierarchical sampling strategies are incorporated to capture the density structures of high spatial frequencies. Required background images for TBOS reconstructions are synthesized based on a high-fidelity nonlinear ray-tracing method with the ground truth flows from conducting large eddy simulations on premixed turbulent flames. Owing to these synthesized BOS images, the superiority of the proposed method is quantitatively verified compared to the classical TBOS reconstruction methods, and the specific contributions from the position encoding and the hierarchical sampling strategy are also elucidated.
A multi-resolution weighted compact nonlinear scheme with unconditionally optimal high order
Authors: Hao Tianchu , Chen Yaming , Wang Shenghao , Tang Lingyan , Song Songhe
Published: December 2024

In a recent work [J. Comput. Phys. 477 (2023) 111877], an efficient multi-resolution weighted compact nonlinear scheme (WCNS) is proposed for solving compressible flows. This paper mainly focuses on improving the nonlinear interpolation scheme therein in terms of shock-capturing capability. Additionally, to address the issue of the effect of the small parameter employed to avoid division by zero, the nonlinear weights are designed to be of the exponential-type, as proposed in a recent study [J. Comput. Phys. 478 (2023) 111978], such that the order of the scheme is irrelevant to the order of the critical points. To simplify the computation of smoothness indicators, we also propose to only use the ones for traditional Jiang-Shu-type nonlinear weights. Numerical examples are conducted to show the improvement of the proposed scheme in terms of shock-capturing capability.
Polarization-induced two-dimensional hole gases in N-polar AlGaN/GaN heterostructures
Authors: Yu Changkai , Zhang Zexuan , Jena Debdeep , Xing Huili Grace , Cho YongJin
Published: December 2024

We report the observation of two-dimensional hole gases (2DHGs) in N-polar AlGaN/GaN heterostructures grown on single-crystal GaN substrates by plasma-assisted molecular beam epitaxy. A systematic study varying AlGaN barrier thickness is performed. The presence of 2DHGs is confirmed by persistent p-type conductivity and high hole mobility observed in temperature-dependent Hall-effect measurements down to 10 K, and the dependence of 2DHG density on the AlGaN barrier thickness indicates its polarization induced origin. 2DHG with a sheet density of 7.5×1012 cm−2 shows a relatively high hole mobility of 273 cm2 V−1 s−1 at 10 K. Mobility model fit suggests that acoustic phonon scattering is the dominant scattering mechanism in the sub-room temperature region. This work indicates that the quality of N-polar 2DHGs is comparable to that of state-of-the-art metal-polar 2DHGs, contributing to a building block for potential high-quality N-polar p-channel devices.
Generalized and high-efficiency arbitrary-positioned buffer for smoothed particle hydrodynamics
Authors: Zhang Shuoguo , Fan Yu , Ren Yaru , Qian Bin , Hu Xiangyu
Published: December 2024

This paper develops a generalized, high-efficiency buffer for particle generation and deletion at arbitrary-positioned in-/outlets in the smoothed particle hydrodynamics method. To achieve generality, we standardize the position comparison of particles with an arbitrary-positioned in-/outlet bound by introducing coordinate transformation. To enhance efficiency, particle candidates subjected to position comparison at a specific in-/outlet are restricted to those within the local cell-linked lists near the defined buffer region, thereby avoiding the inefficiency in the straightforward approach of sequentially checking all fluid particle positions across the computational domain. We validate the effectiveness and versatility of the developed buffer through two-dimensional and three-dimensional non-orthogonal and orthogonal, uni- and bidirectional flows with arbitrary-positioned in- and outlets, driven by pressure or velocity boundary conditions.
Combined Raman spectroscopy and electrical transport measurements in ultra-high vacuum down to 3.7 K
Authors: Shchukin K. P. , Hell M. , Grüneis A.
Published: December 2024

An instrument for the simultaneous characterization of thin films by Raman spectroscopy and electronic transport down to 3.7 K has been designed and built. This setup allows for the in situ preparation of air-sensitive samples, their spectroscopic characterization by Raman spectroscopy with different laser lines and five-probe electronic transport measurements using sample plates with prefabricated contacts. The lowest temperatures that can be achieved on the sample are directly proven by measuring the superconducting transition of a niobium film. The temperature-dependent Raman shift and narrowing of the silicon F2g Raman line are shown. This experimental system is specially designed for in situ functionalization and optical spectroscopic and electron transport investigation of thin films. It allows for easy on-the-fly change of samples without the need to warm up the cryomanipulator.
Input signal accumulation capability of the FitzHugh–Nagumo neuron
Authors: Bukh A. V. , Shepelev I. A. , Vadivasova T. E.
Published: December 2024

We present numerical results on the effects of two presynaptic FitzHugh–Nagumo neurons on a postsynaptic neuron under unidirectional electrical coupling. The presynaptic neurons affect the postsynaptic neuron not simultaneously but with a certain time shift. We consider cases where the amplitudes of the presynaptic spikes can be both higher and lower than the excitation threshold level. The latter case receives the main attention in our work. We carefully examine the conditions under which the postsynaptic neuron is excited by the two asynchronous external spikes. With arbitrarily chosen parameters, the FitzHugh–Nagumo neuron is almost incapable of accumulating the energy of external signals, unlike, for example, the leaky integrate-and-fire neuron. In this case, the postsynaptic neuron only excites with a very short time delay between external impulses. However, we have discovered, for the first time, a parameter region where neuron excitation is possible even with significant time delays between presynaptic impulses with subthreshold amplitudes. We explain this effect in detail and describe the mechanism behind its occurrence. We identify the boundaries of this region in the parameter plane of time delay and coupling coefficient by varying the control parameter values of the neurons. The FitzHugh–Nagumo neuron has not previously been used as a node in spiking neural networks for training via spike-timing-dependent plasticity due to the lack of an integrate-and-fire effect. However, the detection of a certain range of parameters makes the potential application of this neuron for STDP training possible.
Quantitative neuromuscular monitoring with train-of-four ratio using sonomechanomyography (SMMG): Toward more sensitive evaluation of neuromuscular blockade
Authors: Zhu Pancheng , Song Zhen , Wong Stanley Sau-ching , Zheng Yongping
Published: December 2024

In the post-anesthesia care unit, there is a high occurrence of residual neuromuscular blockade, which puts patients at risk of negative consequences such as hypoxia. Assessment based on the train-of-four ratio (TOFR) has been used to avoid residual neuromuscular blockade when the TOFR is greater than 0.9, measured at the adductor pollicis muscle (APM). The most commonly used quantitative neuromuscular monitoring (QNM) modalities include acceleromyography (AMG) and electromyography (EMG). However, the poor user-friendliness of current QNM methods hinders their widespread adoption. To overcome this, we developed a new monitoring method using ultra-fast ultrasound imaging to generate a two-dimensional map of muscle transient motion, i.e., sonomechanomyography (SMMG). SMMG of the APM and AMG of the thumb were used to get the TOFR of 20 normal adults. The results showed no significant difference between the left and right hands for both AMG and SMMG TOFR, with p-values larger than 0.05. In addition, the mean accuracy of SMMG TOFR (0.6% relative error) was higher than AMG (1.4% relative error). Moreover, the Bland–Altman plot showed that all the difference values were within the limits of agreement and the mean bias was 0.02, indicating that the two methods had a very good agreement. In particular, using SMMG did not require additional calibration before testing. Overall, the results demonstrated that the method has the potential as a new QNM approach for further clinical studies to benefit patients in need. To demonstrate its clinical potential, further studies are required to evaluate this method in patients during and post-anesthesia.
Investigation on evolution law of water flow deterioration caused by sedimentation in sewer pipelines: An approach based on fluid–structure coupling
Authors: Chen Zhuo , Di Danyang , Yang Wen , Fang Hongyuan , Sun Bin , Wang Niannian , Li Bin
Published: December 2024

With the increase in the length and age of urban sewer pipeline construction, black smelly water pollution caused by siltation and deposition has increased in sewer pipelines, affecting their flow capacity and increasing the risk of flooding. This presents a significant challenge to the water environment, urban environment, and human life and health. Hence, to investigate potential approaches for controlling pipeline siltation and deposition, governing equations and dynamic simulation model of fluid–structure coupling for silted pipeline are constructed by combining theory of fluid dynamics analysis, method of unit volume analysis, computational fluid dynamics (CFD), and discrete element method (DEM). Then, to predict sedimentation law of pipeline siltation particles with high accuracy, an adaptive punishment mechanism (APM) for intelligent prediction of particle settlement of pipeline sediment and hyperparameter optimization is adopted based on probability settlement function (PSF), non-dominated sorting genetic algorithm (NSGA) and multiscale bidirectional long short-term memory neural network (MBLSTM). By combining self-punishment mechanism based on PSF-NSGA-MBLSTM intelligent prediction of pipeline siltation particle settlement with CFD-DEM, a high-resolution numerical simulation method CFD-DEM-APM for hydraulic transport of siltation particles in sewer pipelines is proposed to describe the particle-phase and fluid-phase state transfer process. Experimental results show that the accuracy of CFD-DEM-APM is maintained within the 5%–11% range, which is far better than that of other algorithms. This study provides guidance on critical conditions for desilting and pipe inlet velocity/flow control to scour siltation and deposition of sewer pipelines for urban environment improvement and water pollution restriction.
A numerical simulation research on fish adaption behavior based on deep reinforcement learning and fluid–structure coupling: The refuge–predation behaviors of intelligent fish under varying environmental pressure
Authors: Li Tao , Zhang Chunze , Zhang Guibin , Zhou Qin , Hou Ji , Diao Wei , Meng Wanwan , Zhang Xujin , Wang Xiaoyi
Published: December 2024

The study of fish swimming behavior and locomotion mechanisms holds substantial scientific and engineering significance. With the rapid progression of artificial intelligence, the integration of artificial intelligence with high-precision numerical simulation methods presents a novel and highly efficient tool for investigating fish behavior. In this paper, we proposed a fish perception model that more closely reflects natural logic. By introducing the individual vision and partially visibility model, a physics-based visual system that mirrored the sensory capabilities of live fish was developed. Furthermore, through the construction of a flow vision using conventional neural networks, we enhanced the intelligent fish's ability to detect unsteady hydrodynamic parameters via numerical lateral line. The validity of the new model was demonstrated through experiments, which the intelligent fish hunts complex moving targets in unsteady flow. Finally, we applied the model to study the refuge/predation behaviors of coral reef fish under varying unsteady flow pressures. The results indicated that swimming capabilities significantly impact fish survival strategies in high flow velocity, highly unsteady hydrodynamic environments, shaping distinct evolutionary decision-making traits. These insights may help to understand the niche competition mechanisms of fish in different flow conditions.
Regime switching in coupled nonlinear systems: Sources, prediction, and control—Minireview and perspective on the Focus Issue
Authors: Franović Igor , Eydam Sebastian , Eroglu Deniz
Published: December 2024

Regime switching, the process where complex systems undergo transitions between qualitatively different dynamical states due to changes in their conditions, is a widespread phenomenon, from climate and ocean circulation, to ecosystems, power grids, and the brain. Capturing the mechanisms that give rise to isolated or sequential switching dynamics, as well as developing generic and robust methods for forecasting, detecting, and controlling them is essential for maintaining optimal performance and preventing dysfunctions or even collapses in complex systems. This Focus Issue provides new insights into regime switching, covering the recent advances in theoretical analysis harnessing the reduction approaches, as well as data-driven detection methods and non-feedback control strategies. Some of the key challenges addressed include the development of reduction techniques for coupled stochastic and adaptive systems, the influence of multiple timescale dynamics on chaotic structures and cyclic patterns in forced systems, and the role of chaotic saddles and heteroclinic cycles in pattern switching in coupled oscillators. The contributions further highlight deep learning applications for predicting power grid failures, the use of blinking networks to enhance synchronization, creating adaptive strategies to control epidemic spreading, and non-feedback control strategies to suppress epileptic seizures. These developments are intended to catalyze further dialog between the different branches of complexity.
Behavioral interventions to motivate plant-based food selection in an online shopping environment
Authors: Katare Bhagyashree , Zhao Shuoli
Published: December 2024

Encouraging consumption of plant-based food products can help mitigate the impact of dietary choices on climate change. Research suggests that modifying environments in which people make purchasing decisions has the potential to achieve behavioral changes toward sustainable consumption. We examine the impact of two behavioral interventions, carbon footprint labeling, and product categorization, to promote sustainable food selection in an online grocery shopping environment. Online grocery shopping data collected from 2,359 US participants show that carbon footprint labels increased the selection of plant-based food products by 37% and categorization increased it by 25%. A combination of both nudges increased plant-based food selection by 32%. Participants underestimated the environmental impact of different types of foods despite exposure to carbon footprint information. As the global market for online grocery shopping continues to grow, this study presents a potential for simple and scalable interventions in online shopping environments to encourage sustainable choices.
Opportunities and challenges of plant proteins as functional ingredients for food production
Authors: Etzbach Lara , Gola Susanne , Küllmer Fabian , Acir Ismail-Hakki , Wohlt Daria , Ignatzy Laura Melanie , Bader-Mittermaier Stephanie , Schweiggert-Weisz Ute
Published: December 2024

Consumer interest in meat and dairy alternatives drives demand for plant-based protein ingredients. While soy and gluten dominate the market, there is a trend to explore alternative crops for functional ingredient production. The multitude of ingredients poses challenges for food manufacturers in selecting the right protein. We investigated 61 commercially available protein ingredients from various sources, categorizing them based on their protein content into protein-rich flours (protein content less than 50%), protein concentrates (protein content between 50% and 80%), and protein isolates (protein content higher than 80%). Methionine, cysteine, and lysine were decisive for the amino acid score, which even varied between ingredients produced from the same raw material. Such differences were also observed in the protein solubility profiles, characterized by their raw material–specific protein pattern. By focusing on soy, pea, and fava bean ingredients, the broad spectra of emulsifying and foaming properties were illustrated. These ranged from non–emulsifying and non–foaming to high emulsifying capacities of 737 mL/g ingredient and foaming activities of 2,278%, accompanied by a foam stability of 100%. Additionally, we demonstrated that the functionality of ingredients obtained from different batches could vary by up to 24% relative SD. Protein solubility, powder wettability, color, and particle size were determined as key properties for the differentiation of soy, pea, and fava bean protein ingredients by principal component analysis. In our study conclusion, we propose essential measures for overcoming challenges in protein ingredient production and utilization to realize their full potential in fostering sustainable and innovative plant-based food production.
RAD51 plays critical roles in DNMT1-mediated maintenance methylation of genomic DNA by dually regulating the ubiquitin ligase UHRF1
Authors: Liu Guangxue , Huang Kaiyan , Liu Shiyao , Xie Yali , Huang Jinyan , Liang Tingbo , Zhang Pumin
Published: December 2024

RAD51
is related to the bacterial RecA protein and is best known for its role in homologous recombination-mediated repair of DNA damage. Here, we report an unexpected function of
RAD51
in the maintenance methylation of genomic DNA, a function that is separable from its role in homologous recombination. First, it acts as an inhibitor of the E3 ubiquitin ligase UHRF1. Deficiency in
RAD51
causes excessive ubiquitination and degradation of the DNA methyltransferase DNMT1, leading to the loss of global DNA methylation. Second, RAD51 helps UHRF1 to monoubiquitinate histone H3 to generate DNMT1 recruiting signal. It binds H3 directly, enabling UHRF1 to bind and ubiquitinate H3 more readily. Disrupting the interaction between RAD51 and H3 diminishes DNMT1 recruitment and the failure of maintenance methylation of genomic DNA. Thus, RAD51 dually regulates UHRF1. These results establish RAD51 as a guardian of the integrity of both the genome and the epigenome.