bluuebunny/crossref_metadata_2025 huggingface dataset:
Initial Outcomes following Fresh Meniscus Allograft Transplantation in the Knee
Authors: Cook James L. , Stannard James P. , Rucinski Kylee J. , Nuelle Clayton W. , Crecelius Cory R. , Cook Cristi R. , Ma Richard
Published: August 2024

Based on recent evidence-based advances in meniscus allograft transplantation (MAT), fresh (viable) meniscus allografts have potential for mitigating key risk factors associated with MAT failure, and preclinical and clinical data have verified the safety of fresh meniscus allografts as well as possible efficacy advantages compared with fresh-frozen meniscus allografts. The objective of this study was to prospectively assess clinical outcomes for the initial cohort of patients undergoing MAT using fresh meniscus allografts at our center. Patients who were prospectively enrolled in a dedicated registry were included for analyses when they had undergone primary MAT using a fresh meniscus allograft for treatment of medial and/or lateral meniscus deficiency with at least 1-year follow-up data recorded. Forty-five patients with a mean final follow-up of 47.8 months (range = 12–90 months) were analyzed. The mean patient age was 30.7 years (range = 15–60 years), mean body mass index (BMI) was 29.7 kg/m2 (range = 19–48 kg/m2), and 14 patients (31%) were females. In total, 28 medial, 13 lateral, and 4 combined medial and lateral MATs with 23 concurrent ligament reconstructions and 2 concurrent osteotomies were included. No local or systemic adverse events or complications related to MAT were reported for any patient in the study. Treatment success rate for all patients combined was 91.1% with three patients requiring MAT revision and one patient requiring arthroplasty. Treatment failures occurred 8 to 34 months after MAT and all involved the medial meniscus. None of the variables assessed were significantly different between treatment success and treatment failure cohorts. Taken together, the data suggest that the use of fresh (viable) meniscus allografts can be considered a safe and effective option for medial and lateral MAT. When transplanted using double bone plug suspensory fixation with meniscotibial ligament reconstruction, fresh MATs were associated with a 91% success rate, absence of local or systemic adverse events or complications, and statistically significant and clinically meaningful improvements in patient-reported measures of pain and function at a mean of 4 years postoperatively.
Comparison between two approaches to classify topological insulators using K-theory
Authors: Scaglione Lorenzo
Published: August 2024

We compare two approaches which use K-theory for C*-algebras to classify symmetry protected topological phases of quantum systems described in the one particle approximation. In the approach by Kellendonk, which is more abstract and more general, the algebra remains unspecified and the symmetries are defined using gradings and real structures. In the approach by Alldridge et al., the algebra is physically motivated and the symmetries implemented by generators which commute with the Hamiltonian. Both approaches use van Daele’s version of K-theory. We show that the second approach is a special case of the first one. We highlight the role played by two of the symmetries: charge conservation and spin rotation symmetry.
Wattmeter based on tunnel-effect magnetoresistance sensor
Authors: Soriano-Díaz S. , Ramírez-Muñoz D. , García-Gil R. , Cardoso S. , Freitas P. P.
Published: August 2024

This work shows how the tunnel-effect based magnetoresistance (TMR) technology can be used as a competitive sensing method in electrical current and power processors. The sensor is arranged in a Wheatstone bridge topology, and each magnetoresistance was composed of a series connection of 360 magnetic tunnel junction elements with the following structure (thickness in nm): 100 SiO2/5 Ta/15 Ru/5 Ta/15 Ru/5 Ta/5 Ru/20 IrMn/2 CoFe30/0.85 Ru/2.6 CoFe40B20/1.2 MgO/2 CoFe40B20/0.21 Ta/4 NiFe/0.20 Ru/6 IrMn/2 Ru/5 Ta/10 Ru. First, the electrical and thermal characteristics of the sensor were evaluated by analyzing its response to DC current sweeps at various temperatures, controlled using a climatic chamber. Nominal values of current sensitivity S (0.324 mV/A), bridge output offset voltage Vo,s,o (−37.1 mV), bridge input resistance Rinp,bridge (0.958 kΩ), and their thermal behavior were obtained (0.0036 mV/A°C, 0.079 mV/°C, and −0.31 Ω/°C). Second, an instrumentation system is introduced to characterize the sensor, measuring its sensitivity to AC line currents from the mains up to 10 Arms. Finally, an electronic wattmeter was developed showing the relevant quantities of its design. The circuit is able to interface a TMR Wheatstone bridge to an analog processor. Power and current measurements were obtained from a 150 Vrms AC mains 1.5 kW load with resistive and capacitive components, achieving less than 1% deviation over the expected values. The circuit shown can be used to interface these signals to more complex smart digital engines with active or reactive energy processing capabilities, while providing inherent high voltage isolation, thanks to its TMR measurement technology.
Effect of viscous dissipation on thermal convection in bidispersive porous media with vertical throughflow: Global stability analysis
Authors: S. M. Bhavyashree , Ragoju Ravi , Reddy G. Shiva Kumar
Published: August 2024

This article investigates the onset of convection in a bidispersive porous medium, considering the impact of viscous dissipation and throughflow using both linear and nonlinear theories. The flow is modeled using the Oberbeck–Boussinesq approximation and Darcy's law, with local thermal equilibrium between the fluid and solid phases. The temperature field depends solely on the vertical coordinate in the basic solution. The study employs a two-pronged approach to analyze the system's stability, utilizing the normal mode technique for linear analysis and the energy method for nonlinear analysis. The article confirms the validity of the principle of exchange of stabilities. The numerical solution of the eigenvalue problem for both linear and nonlinear theories is obtained using the bvp4c routine. The research explores the influence of various physical parameters on the system's stability. Viscous dissipation's effect on convection onset is noticeable only with significant throughflow. In the absence of viscous dissipation, the throughflow direction does not affect the system's stability. The effective permeability ratio stabilizes the system with upward throughflow and exhibits opposite behavior with downward throughflow. The sub-critical region remains unchanged for the Gebhart number range but increases with higher moment transfer coefficient and effective permeability ratio. Additionally, an analytical expression is derived for the small Peclet number regime of the Rayleigh number using asymptotic analysis.
Investigating the impact of supply voltage fluctuations on phase noise in quartz crystal oscillators
Authors: Xu Lin , Ye Peng , Liao Shuang , Chen Cheng , Zhu Guibing , Tan Feng
Published: August 2024

The impact of power supply voltage fluctuations on the phase noise of quartz crystal oscillators (XOs) remains an open issue. Currently, there is a lack of comprehensive analysis on this matter. This work presents a novel phase-noise drive sensitivity (PNDS) model for the XO to reveal its mechanism. This model based on five noise modulation processes demonstrates the distribution of the PNDS in the frequency domain clearly, and there exists a PNDS bandwidth fS that limits the supply voltage fluctuation, which is similar to the effect of the noise bandwidth of the classical Leeson model. Using the PNDS, we successfully predict the phase noise of a 10 MHz oscillator under different supply voltage noises. In addition, experimental results show that the PNDS floor is determined by the phase modulation of the sustaining amplifier, while the amplitude-frequency effect of the resonator and the tuning of the diode often play crucial roles in the near-carrier PNDS.
Nonreciprocal transmission enabled by time modulation of penetrable metasurface assisted by surface waves
Authors: Yılmaz H. Önder , Yaman Fatih
Published: August 2024

This study introduces a novel approach to achieving nonreciprocal transmission by implementing time modulation to the bianisotropic metasurface. For the first time, we present the analytical solution of the excitation of anti-symmetric surface waves on penetrable metasurfaces depending on the excitation direction. Exploiting this finding, we numerically demonstrate asymmetric control of the transmission coefficient under a fast-time scale by employing solely time modulation. This approach lowers the complexity of the modulation scheme and implementation encountered in the space-time modulation technique. We develop and simulate a 3D unit cell model in the microwave domain, which forms a surface cavity that incorporates time-varying capacitors. The impedance transfer matrix method and harmonic balance numerical solutions are applied to the retrieved equivalent circuit for the numerical simulations. The results reveal optimized phase-coherent and incoherent nonreciprocal transmission at the significant isolation level (≥40 dB) for forward and backward transmissions. We discuss the consistency and discrepancies between numerical methods and consider the impact of the losses and nonlinearity on the metastructure performance.
Direct numerical simulations of compressible turbulence in a periodic box: Effect of isothermal assumptions on turbulence statistics
Authors: Sakurai Yoshiki , Ishihara Takashi
Published: August 2024

Direct numerical simulations of compressible nonisothermal turbulence in a periodic box with up to 40963 grid points were conducted by varying Reynolds numbers and resolution levels. The results were compared with those of compressible isothermal turbulence by Sakurai and Ishihara [“Direct numerical simulations of compressible isothermal turbulence in a periodic box: Reynolds number and resolution-level dependence,” Phys. Rev. Fluids 8, 084606 (2023)] to study the effect of isothermal assumption on turbulence statistics. The turbulent Mach number and ratio of the dilatational to solenoidal root mean square velocities were fixed at approximately 0.3 and 0.4, respectively. A comparison under approximately equal flow conditions showed that the dilatational component of the energy spectra for the nonisothermal case exhibited approximately equal k−3 scaling at kη>1 as observed for the isothermal case and was consistently smaller in the wavenumber range 0.05<kη<0.6 than that for the isothermal case, where η is the Kolmogorov length. The dilatational energy is mainly dissipated around kη≈0.3, the same wavenumbers as the solenoidal energy dissipation irrespective of the isothermal assumption. As the Reynolds number increased, the dilatational energy dissipation caused by shocklets around kη≈2 became larger, especially in the nonisothermal case. It was found that the isothermal assumption weakened the intermittency of the velocity divergence. No significant differences were observed in the normalized mean energy dissipation rates and pressure statistics. The local flow topology was also marginally affected by the isothermal assumption; however, the difference was significantly less than the changes owing to the different values of parameters such as the Reynolds number and Mach number.
Calibration techniques for Thomson scattering diagnostics on large fusion experiments
Authors: Fuchert G. , Wagner J. , Henschke L. V. , Pasch E. , Beurskens M. N. A. , Bozhenkov S. A. , Brunner K. J. , Chen S. , Frank J. M. , Hirsch M. , Knauer J. , Wolf R. C. ,   W7-X Team
Published: August 2024

Larger fusion experiments require long beam paths for laser diagnostics, which requires mechanical stability and measures to deal with remaining alignment variations. At the same time, due to technical and organizational boundary conditions, calibrations become challenging. The current mid-sized experiments face the same issues, yet on a smaller scale, which makes them ideal testing environments for novel calibration methods, since a comparison with the established best practices is still possible. At the stellarator Wendelstein 7-X, the calibration and operation of the Thomson scattering diagnostic is hampered by beam displacements, coating of windows during operation, and access restrictions while the superconducting coils are active. New calibration techniques were developed to improve the profile quality and reduce calibration time. While positional variations of the laser beam have to be minimized, the remaining displacements can be accounted for during the absolute calibration. An in situ spectral calibration has been developed based on Rayleigh scattering, which calibrates the whole diagnostic, including observation windows. In addition, a less accurate but faster method has been developed, which utilizes stray-light of a tunable OPO to perform spectral calibration within minutes and does not require torus hall access. Finally, a workflow has been established to consider finite linewidths of the calibration source in the spectral calibration. While these methods will be used at W7-X to complement existing calibration techniques, they may also solve some of the aforementioned issues expected for even larger and nuclear experiments, where access restrictions are stringent and calibration becomes even more demanding.
Heat and mass transfer performance of fluid flow behind an L-shaped flexible beam connected to a cylinder within a microchannel at various Reynolds numbers
Authors: Hu Enkai , Li Yan , Jing Dalei
Published: August 2024

To analyze and compare the influence of an asymmetric flexible beam connected to a bluff body on the heat and mass transfer performance of microchannel flow at different Reynolds number, this study numerically investigated the effects of an L-shaped flexible beam with varying sizes connected to a cylinder on pressure loss, Nusselt number, and outlet mixing efficiency of the microchannel flow at three Reynolds numbers based on the cylinder diameter Red of 25, 50, and 100. The results revealed that adjusting the dimensions of the L-shaped flexible beam enhances the thermal and mixing performance of the microchannel flow compared to the fluid flow within the microchannel with only a single cylinder under the same inlet flow condition. This enhancement is particularly significant at Red = 25, where the L-shaped flexible beam facilitates the transition of flow pattern to vortex flow from the laminar flow observed within the channel with only a single cylinder. Compared to the single cylinder configuration, the Nusselt number and the outlet mixing efficiency increased by 29.42%, 27.68%, 25.51% and 434.75%, 29.67%, 16.54% when Red are 25, 50, and 100, respectively. This research provides valuable insights into enhancing the heat and mass transfer efficiency of low-Reynolds-number microchannel flow through the utilization of advanced asymmetric flexible vortex generators, with potential applications in high-efficiency microfluidic mixing enhancement and thermal management.
A 44-cm3 physics package for the high-performance pulsed optically pumped atomic clock
Authors: Hao Qiang , Yang Shaojie , Zheng Shuguang , Yun Peter , Ruan Jun , Zhang Shougang
Published: August 2024

The pulsed optically pumped (POP) atomic clock has demonstrated unexpected performance in terms of frequency stability and drift. However, it remains a huge challenge to make this type of atomic clock more compact. Herein, we report the design of a miniaturized physics package, which is equipped with a magnetron microwave cavity holding a vapor cell of 1.3 cm internal diameter. The Zeeman transition spectrum reveals that the microwave cavity resonates in TE011-like mode. Based on a low-noise testbed, we also quantitatively analyze the relaxation time, linewidth, and noise sources of the resulting POP atomic clock. The population and coherence relaxation time are measured to be 3.16(0.16) and 2.97(0.03) ms under the temperature of 333 K, which are compatible well with the theoretical calculation. The Ramsey signal shows a contrast of 35% and a linewidth of 192 Hz. The total volume of the physics package is about 44 cm3, including a layer of magnetic shielding. The short-term frequency stability is measured to be 4.8 × 10−13τ−1/2 (where τ is the averaging time), which is mainly limited by the relative intensity noise of the laser system.
Numerical investigations on compressible thermal flows in high-speed water entry
Authors: Yang Liu , Xiang Junbang , Kang Huifeng , Wang Xiaoguang , Wen Chuang , Rao Zhonghao
Published: August 2024

The high-speed entry of a projectile into water involves numerous physical phenomena, with temperature playing a significant role in these. In this study, numerical simulations are used to study projectile water entry at 700 m/s under non-isothermal conditions, with the accuracy of the simulation method first being verified with experimental data. The entry process is divided into three stages: initial, intermediate, and complete. Initially, impact kinetic energy causes a sudden temperature increase, with the temperature distribution and shock waves exhibiting similarities. In the intermediate stage, thermal wake development and phase changes in the cavity formed by impact cause temperature variations. In the complete stage, the projectile becomes fully submerged, the thermal wake diminishes, and cavity expansion consumes energy, reducing both temperature and pressure. The air cushion phenomenon has a significant effect on pressure, but a relatively weak influence on temperature. Vortex monitoring reveals a decrease in tail temperature due to double-vortex cancellation, and relative flow within the cavity affects temperature changes. Velocity and temperature monitoring indicate a sharp increase, oscillation, and eventual stabilization in temperature. Cavitation-induced phase changes primarily drive temperature variations, while condensation of water vapor reduces temperature. This paper addresses the lack of considerations of thermal effects in previous studies of high-speed water entry, thereby providing a new perspective on this topic.
Reciprocity quad-band electromagnetically induced transparency-like metamaterials
Authors: Ning Renxia , Zheng Xueyan , Zhu Jiale , Zhang Yanfei , Liu Shaobin
Published: August 2024

In this paper, a sandwich structure metamaterial was designed, in which the substrate is radio frequency (RF) F4B, and the metal pattern of copper is prepared by the substrate on both sides. Analyzed the transmission of the structure, and the quad-band and reciprocal electromagnetically induced transparency (EIT)-like phenomena of the structure were obtained. The physical mechanism of the EIT-like phenomenon was explained by the electric field distribution. Discussing the size of the structure, the influence of structure parameters on EIT-like phenomena was further illustrated. By comparing the measured results with the calculated results in a microwave anechoic chamber, the results are in good agreement. This structure has potential applications in multi-band filtering, sensing, and other fields.
Characterization of field emission from random nano-structured surface in using fractional field emission models
Authors: Kanwal Samra , Raheem Noreen , Mehmood M. Q. , Zubair M. , Ang L. K.
Published: August 2024

It is known that field emission from random nano-structured surfaces cannot be well characterized with the original field emission model known as the Fowler–Nordheim (FN) law or the Murphy–Good (MG) law. To account for the roughness effects, the traditional approach was to introduce the arbitrary field enhancement factor β in the FN and MG laws. In this paper, by treating the random roughness of field emitters as a fractional dimension object with 0<α<1, fractional models of the FN and MG law, which were formulated recently may serve as alternate characterization tools. At α=1, the models will recover the traditional FN and MG laws valid for a perfect flat planar surface. These generalized fractional FN law (FNα) and the fractional MG law (MGα) will be used to characterize various field emission experiments by finding the best 0<α<1 values to account for the degree of the random roughness. The findings will be compared among the traditional and fractional emission models, where the best-fitting results will be shown for each case. It is found that the fractional field emission models provide more physical and appropriate field emission parameters, i.e., field enhancement factor and field emission area, in comparison with traditional field emission models.
Optimization design on blade with bionic protuberances of horizontal axis wind turbine
Authors: Wei Xuntong , Li Deyou , Chang Hong , Zhang Ruiyi , Wang Hongjie
Published: August 2024

The operating conditions of wind turbines are changeable, and the flow separation limits the power generation capacity. In order to improve the output power of wind turbines, based on the principle of bionics, the leading-edge protuberance (LEP) of the humpback whale flipper is introduced to the blade. The optimization of LEP parameters and distribution on the blade performance is studied. The shape and distribution of nonlinear, non-uniform LEPs are controlled by three design variables: amplitude, attenuation, and number. The optimization system consists of modules such as model generation, computational fluid dynamics, and genetic algorithm. The results show that the optimized bionic wind turbine can increase the output power by 3.95% under the rated condition. The optimized LEP structure can improve the performance of the trough sections without sacrificing part of the performance of peak sections, with a maximum increase of 20%. The theory of entropy production is used to analyze the location of energy loss and its impact on the wake. The distribution of the local entropy production rate of the wind turbine wake after optimization is improved. The power spectral density analysis shows that the LEPs cause different variation laws in the wake from the original wind turbine.
Application of the FlowNet model for history matching and production optimization in water alternating gas enhanced oil recovery
Authors: Xu Yunfeng , Liu Wei , Zhao Hui , Rao Xiang , Liu Botao
Published: August 2024

Enhanced oil recovery (EOR) strategies, particularly CO2 flooding, play a crucial role in optimizing oil reservoir exploitation while addressing carbon sequestration. Despite their effectiveness, the application of these techniques is often hindered by complex reservoir dynamics and the computational intensity of traditional simulation models. This study introduces a novel approach utilizing the FlowNet model, which combines data-driven analytics and physics-based modeling, aimed at expediting history matching and production optimization processes. The FlowNet model simplifies the representation of reservoirs by using virtual well points along flow paths and employs a non-linear solver for quick resolution of flow equations. Our method significantly enhances the efficiency of history matching by reducing computational overheads and leveraging streamlined network structures, thereby facilitating faster and more accurate production forecasts. We implement the model in several case studies involving CO2 and water alternating gas flooding, which demonstrate an 11% increase in the economic net present value compared to traditional methods. These findings highlight the potential of integrating data-driven techniques with physical modeling to improve EOR performance predictions and optimize production strategies, ultimately promoting more sustainable and economically viable oil recovery practices.
Photo-induced dynamics with continuous and discrete quantum baths
Authors: Xie Zhaoxuan , Moroder Mattia , Schollwöck Ulrich , Paeckel Sebastian
Published: August 2024

The ultrafast quantum dynamics of photophysical processes in complex molecules is an extremely challenging computational problem with a broad variety of fascinating applications in quantum chemistry and biology. Inspired by recent developments in open quantum systems, we introduce a pure-state unraveled hybrid-bath method that describes a continuous environment via a set of discrete, effective bosonic degrees of freedom using a Markovian embedding. Our method is capable of describing both, a continuous spectral density and sharp peaks embedded into it. Thereby, we overcome the limitations of previous methods, which either capture long-time memory effects using the unitary dynamics of a set of discrete vibrational modes or use memoryless Markovian environments employing a Lindblad or Redfield master equation. We benchmark our method against two paradigmatic problems from quantum chemistry and biology. We demonstrate that compared to unitary descriptions, a significantly smaller number of bosonic modes suffices to describe the excitonic dynamics accurately, yielding a computational speed-up of nearly an order of magnitude. Furthermore, we take into account explicitly the effect of a δ-peak in the spectral density of a light-harvesting complex, demonstrating the strong impact of the long-time memory of the environment on the dynamics.
An experimental study of supersonic conical cooling films subjected to different ratios of static pressure
Authors: Lin Juncan , Wang Qiancheng , Zhao Yuxin , Lu Xiaoge
Published: August 2024

Research into the flow mechanisms and heat transfer characteristics of two-dimensional supersonic cooling films has been extensive, yet studies on supersonic conical cooling films remain scarce. This study examined the flow characteristics and mechanisms of supersonic conical cooling film under varying ratios of static pressure (RSPs) using nanoparticle planar laser scattering and particle image velocimetry techniques. The mainstream Mach number was Ma∞=3.8, and the supersonic conical cooling film was tangentially injected through a precisely calibrated annular nozzle of Maj=2.8. Analysis of the instantaneous flow structure characteristics along and normal to the flow direction segmented the flow downstream of the slot into three distinct zones: the potential core region, the large-scale coherent structure region, and the turbulent boundary layer region. The reattachment location was assessed both qualitatively and quantitatively based on time-averaged and statistical velocity field data. The results indicated that the reattachment location extended with higher RSP. Moreover, the reattachment point of the supersonic conical cooling film was further forward than that of a two-dimensional supersonic cooling film. It was found that the supersonic conical cooling film was more significantly affected by the compression effect of the conical stream tube compared to the impact of RSP.
Unveiling the bi-stable character of stealthy hydrogen–air flames
Authors: Palomeque-Santiago Rubén , Domínguez-González Alba , Martínez-Ruiz Daniel , Rubio-Rubio Mariano , Fernández Tarrazo Eduardo , Sánchez-Sanz Mario
Published: August 2024

Ultra-lean hydrogen–air flames propagating in narrow gaps, under the influence of cold walls and high preferential diffusion, can form two distinct isolated structures. They exhibit either circular or double-cell shapes and propagate at different speeds, with the latter roughly doubling in size and traveling speed to the former. Hydrogen mass diffusivity, convective effects, and conductive heat losses are the physical mechanisms that explain the alterations in morphology and propagation speed. In previous experiments, Veiga-López et al. [Phys. Rev. Lett. 124, 174501 (2020)] found these clearly distinguished flame structures for different combinations of equivalence ratio, channel gap, and the effect of gravity on the dynamics of upward and downward propagating flames in a vertical chamber. Present observations in horizontal channels show the simultaneous appearance of these two stable structures, which arise under identical experimental conditions and conform the first evidence that multiplicity of stable solutions coexists in real devices. To explain the observations, we performed numerical simulations using the simplified model, which shows that symmetry-breaking details during the ignition transient explain the concurrent emergence of the two stable configurations. This discovery urges the need to implement additional engineering tools to account for the possibility of the formation and propagation of isolated flame kernels at different speeds in hydrogen-fueled systems.
Experimental study on influences of steps on hypersonic boundary layer transition at different angles-of-attack
Authors: Xu Xiwang , Ye Zihao , Yi Shihe , Xue Yifei , Chen Zhi
Published: August 2024

The influences of the forward-facing step (FFS) and backward-facing step (BFS) on the 7° half-angle conical boundary layer instability and transition are investigated at different angles-of-attack (AoAs) in a hypersonic quiet wind tunnel using the Nano-tracer-based Planar Laser Scattering techniques, Temperature-Sensitive Paints, and high-frequency pressure sensors. The results show that the FFS stabilizes the second mode instability but strongly destabilizes the crossflow instability. Conversely, the BFS destabilizes both the second mode and crossflow instabilities, yet its impact on crossflow instability is weaker compared to that of an FFS with an identical height. At a small AoA (AoA < 3° in this paper), the boundary layer transition is dominated by the second mode instability. For sharp cones, the transition is delayed on the windward side but promoted on the leeward side, resulting in a monotonically inclined transition front. In contrast, blunt cones exhibit localized depressions in the transition front on the leeward side. At large AoA, the transition process is dominated by the crossflow instability, resulting in heat flux stripes on the leeward side, making the transition front distribution more complex. Therefore, at small AoAs, the promotion effect of the BFS on the conical boundary layer transition is stronger than that of the FFS with the same height. Moreover, the FFS with a small height even exhibits a suppressive effect on the transition. However, as the AoA increases, low-frequency instability modes, such as crossflow instability, gradually become dominant. Consequently, the promoting effect of the FFS surpasses that of the BFS.
Miniature magneto-oscillatory wireless sensor for magnetic field and gradient measurements
Authors: Fischer F. , Jeong M. , Qiu T.
Published: August 2024

Magneto-oscillatory devices have been recently developed as very potent wireless miniature position trackers and sensors with an exceptional accuracy and sensing distance for surgical and robotic applications. However, it is still unclear to which extend a mechanically resonating sub-millimeter magnet interacts with external magnetic fields or gradients, which induce frequency shifts of sub-mHz to several Hz and, therefore, affect the sensing accuracy. Here, we investigate this effect experimentally on a cantilever-based magneto-oscillatory wireless sensor (MOWS) and build an analytical model concerning magnetic and mechanical interactions. The millimeter-scale MOWS is capable to detect magnetic fields with sub-µT resolution to at least ±5 mT and simultaneously detects magnetic field gradients with a resolution of 65 µT/m to at least ±50 mT/m. The magnetic field sensitivity allows direct calculation of mechanical device properties, and by rotation, individual contributions of the magnetic field and gradient can be analyzed. The derived model is general and can be applied to other magneto-oscillatory systems interacting with magnetic environments.
Electron scattering at interfaces in epitaxial W(001)–Mo(001) multilayers
Authors: Shen Poyen , Gall Daniel
Published: August 2024

Epitaxial W–Mo multilayers are employed as a model system to demonstrate how resistivity measurements parallel to metal–metal interfaces can be used to quantify the specific interface resistance without sub-10-nm patterning that would be required for direct transport measurements across the interface. 50-nm-thick epitaxial multilayer stacks containing 2–60 individual W(001) and Mo(001) layers are deposited on MgO(001) substrates and their resistivity ρ measured as a function of superlattice period Λ at 293 and 77 K. The measured room temperature ρ increases from 7.10 to 8.62 μΩ cm with decreasing Λ = 50–1.7 nm, which is attributed to the increasing electron-interface scattering. The semiclassical Fuchs–Sondheimer model for surface scattering dramatically overestimates the resistivity, which is attributed to coherent electron transmission across multiple interfaces. A new Boltzmann transport model treats each interface as a boundary condition where electrons either scatter diffusely or traverse without momentum loss with a probability T for the first encountered interface and with 100% transmission at subsequent interfaces until they are relaxed by a bulk scattering event. This model has a single unknown parameter T, which becomes the fitting parameter for experimental data analysis, yielding a temperature-independent T = 0.8 ± 0.1 and a corresponding contact resistance at the W(001)–Mo(001) interface of 2.6 × 10−16 Ω m2.
Cavitated Ag paste for cost-effective solar cells
Authors: Intal Donald , Ebong Abasifreke , Hankey Dana , Tibbetts Marshall
Published: August 2024

This paper reports on the investigation of cavitated silver paste produced by cavitation technology as a cost-effective alternative to traditional three-roll milling. Cavitation, utilizing high-frequency sound waves, enhances metal paste dispersion, reduces oxidation, extends shelf life, and minimizes waste. Passivated emitter and rear cell solar cells made with cavitated silver paste achieved 21% energy conversion efficiency, slightly lower than the 22% efficiency of a conventional paste. A cavitated paste produced finer gridlines, reducing silver usage and costs but increasing contact resistance, leading to a lower fill factor. Despite this, cavitation technology shows promise for more efficient and cost-effective solar cell production. Further research is needed to optimize efficiency and resistance, highlighting the potential for cavitation technology in commercial applications.
A data-driven phase change model for injection flow modeling
Authors: Li Yanfei , Zhao Chenxiang , Cheng Song , Guo Hengjie
Published: August 2024

A deep learning approach is developed to swiftly evaluate phase change in computational fluid dynamics (CFD) simulations of a multi-component, liquid–gas two-phase injection flow. This method significantly improves computational efficiency by using a deep feedforward neural network (DFNN) to replace the complex iterative solution of multi-species vapor–liquid equilibrium (VLE). The DFNN takes instantaneous pressure, temperature, and system composition as input and predicts the corresponding phase equilibrium state. A parametric study was conducted to optimize the neural network's hyperparameters, including the activation function, number of hidden layers, and neurons per hidden layer. The rate of phase change is then calculated as a linear relaxation toward phase equilibrium, guiding subsequent computational steps in the CFD solver. A case study was performed to test the proposed methodology, involving the injection of a superheated liquid ethanol–water mixture into a gaseous nitrogen environment. The simulation results and computational cost were examined. It is found that the DFNN model, while accurately representing the non-ideal non-equilibrium phase change of a multi-component injection flow, speeds up the VLE solution by four orders of magnitude, leading to a 30%–40% reduction in overall flow simulation time. This model shows promise for injection flow simulations, especially for systems with a large number of compositions, such as sustainable aviation fuels.
External static electric field assisted THz radiation generation via optical rectification of secant hyperbolic laser pulse in a plasma
Authors: Shukla Vivek Kumar , Singh Monika , Hussain Saba , Singh Ram Kishor
Published: August 2024

In collisionless plasma, the function of an externally imposed static electric field has been investigated for facilitating the generation of high-power terahertz (THz) radiation. A nonlinear transient current density occurs at THz radiation frequency due to the optical rectification of high-power laser pulse having secant hyperbolic temporal intensity profile. This transient current driving a THz radiation is found to be strongly depended on the pulse width of laser, electron plasma frequency, and externally applied electric field. The effect of mismatched phase between the generated THz wave and laser has also been studied. Numerical simulations show that the strength of THz amplitude initially increases with propagation distance and then decreases.
A tensegrity-based mechanochemical model for capturing cell oscillation and reorientation
Authors: Zhou Wei-Hua , Yin Xu , Xie She-Juan , Ji Fan-pu , Chang Zhuo , Xu Guang-Kui
Published: August 2024

The cytoskeleton, a dynamic network of structural proteins within cells, is essential for cellular deformation and responds to external mechanical cues. Here, based on the structure of the cytoskeleton, combined with the biochemical reactions of the activator RhoA and the inhibitor F-actin, we develop a novel mechanochemical cytoskeleton model to investigate the mechanical behavior of cells. Interestingly, we find that active stress fibers exhibit diverse dynamical modes at specific inhibitor concentration thresholds. The existence of concentration differences and sustained mechanochemical feedback in activators and inhibitors trigger a global oscillation of isolated cells. In addition, under uniaxial and biaxial stretches, activators and inhibitors preferentially diffuse toward the more significantly deformed cytoskeletal elements, and their dynamic interactions regulate the cell to align with the main stretching direction. Our findings, consistent with many experimental results, provide fundamental insights into cytoskeletal remodeling and cellular mechanosensing mechanisms.
A PIKfyve modulator combined with an integrated stress response inhibitor to treat lysosomal storage diseases
Authors: Hou William C. , Massey Lynée A. , Rhoades Derek , Wu Yin , Ren Wen , Frank Chiara , Overkleeft Herman S. , Kelly Jeffrey W.
Published: August 2024

Lysosomal degradation pathways coordinate the clearance of superfluous and damaged cellular components. Compromised lysosomal degradation is a hallmark of many degenerative diseases, including lysosomal storage diseases (LSDs), which are caused by loss-of-function mutations within both alleles of a lysosomal hydrolase, leading to lysosomal substrate accumulation. Gaucher’s disease, characterized by <15% of normal glucocerebrosidase function, is the most common LSD and is a prominent risk factor for developing Parkinson’s disease. Here, we show that either of two structurally distinct small molecules that modulate PIKfyve activity, identified in a high-throughput cellular lipid droplet clearance screen, can improve glucocerebrosidase function in Gaucher patient–derived fibroblasts through an MiT/TFE transcription factor that promotes lysosomal gene translation. An integrated stress response (ISR) antagonist used in combination with a PIKfyve modulator further improves cellular glucocerebrosidase activity, likely because ISR signaling appears to also be slightly activated by treatment by either small molecule at the higher doses employed. This strategy of combining a PIKfyve modulator with an ISR inhibitor improves mutant lysosomal hydrolase function in cellular models of additional LSD.
ACLY and ACSS2 link nutrient-dependent chromatin accessibility to CD8 T cell effector responses
Authors: Kaymak Irem , Watson McLane J. , Oswald Brandon M. , Ma Shixin , Johnson Benjamin K. , DeCamp Lisa M. , Mabvakure Batsirai M. , Luda Katarzyna M. , Ma Eric H. , Lau Kin , Fu Zhen , Muhire Brejnev , Kitchen-Goosen Susan M. , Vander Ark Alexandra , Dahabieh Michael S. , Samborska Bozena , Vos Matthew , Shen Hui , Fan Zi Peng , Roddy Thomas P. , Kingsbury Gillian A. , Sousa Cristovão M. , Krawczyk Connie M. , Williams Kelsey S. , Sheldon Ryan D. , Kaech Susan M. , Roy Dominic G. , Jones Russell G.
Published: August 2024

Coordination of cellular metabolism is essential for optimal T cell responses. Here, we identify cytosolic acetyl-CoA production as an essential metabolic node for CD8 T cell function in vivo. We show that CD8 T cell responses to infection depend on acetyl-CoA derived from citrate via the enzyme ATP citrate lyase (ACLY). However, ablation of ACLY triggers an alternative, acetate-dependent pathway for acetyl-CoA production mediated by acyl-CoA synthetase short-chain family member 2 (ACSS2). Mechanistically, acetate fuels both the TCA cycle and cytosolic acetyl-CoA production, impacting T cell effector responses, acetate-dependent histone acetylation, and chromatin accessibility at effector gene loci. When ACLY is functional, ACSS2 is not required, suggesting acetate is not an obligate metabolic substrate for CD8 T cell function. However, loss of ACLY renders CD8 T cells dependent on acetate (via ACSS2) to maintain acetyl-CoA production and effector function. Together, ACLY and ACSS2 coordinate cytosolic acetyl-CoA production in CD8 T cells to maintain chromatin accessibility and T cell effector function.
Increasing stability of the acoustic and elastic inverse source problems in multi-layered media
Authors: Wang Tianjiao , Xu Xiang , Zhao Yue
Published: August 2024

This paper investigates inverse source problems for the Helmholtz and Navier equations in multi-layered media, considering both two and three-dimensional cases respectively. The study reveals a consistent increase in stability for each scenario, characterized by two main terms: a Hölder-type term associated with data discrepancy, and a logarithmic-type term that diminishes as more frequencies are considered. In the two-dimensional case, measurements on interfaces and far-field data are essential. By employing the fundamental solution in free-space as the test function and utilizing the asymptotic behavior of the solution and continuation principle, stability results are obtained. In the three-dimensional case, measurements on interfaces and artificial boundaries are taken, and the stability result can be derived by applying the arguments for inverse source problems in homogeneous media.
Pseudo-differential integral autoencoder network for inverse PDE operators
Authors: Chen Ke , Lai Jasen , Wang Chunmei
Published: August 2024

Partial differential equations (PDEs) play a foundational role in modeling physical phenomena. This study addresses the challenging task of determining variable coefficients within PDEs from measurement data. We introduce a novel neural network, ‘pseudo-differential IAEnet’ (pd-IAEnet), which draws inspiration from pseudo-differential operators. pd-IAEnet achieves significantly enhanced computational speed and accuracy with fewer parameters compared to conventional models. Extensive benchmark evaluations are conducted across a range of inverse problems, including electrical impedance tomography, optical tomography, and seismic imaging, consistently demonstrating pd-IAEnet’s superior accuracy. Notably, pd-IAEnet exhibits robustness in the presence of measurement noise, a critical characteristic for real-world applications. An exceptional feature is its discretization invariance, enabling effective training on data from diverse discretization schemes while maintaining accuracy on different meshes. In summary, pd-IAEnet offers a potent and efficient solution for addressing inverse PDE problems, contributing to improved computational efficiency, robustness, and adaptability to a wide array of data sources.
Silicon-based perovskite plasmonic diode with highly polarized emission
Authors: Mao Xin-Rui , Chu Zihao , Yi Xiaogen , Cong Riyu , Li Yanping , Xu Wanjin , Ran Guangzhao
Published: August 2024

Here, we propose and develop a silicon (Si)-based perovskite plasmon-emitting diode (PED) with controlled linear polarization in this study. Such polarization originates from the efficient excitation of surface plasmons by excitons in the active layer of the device and the efficient outcoupling by a wedged boundary of a metal electrode. Furthermore, a p-type Si substrate serves as an anode of the diode, and a hole blocking layer of SiO2 is introduced in the PEDOT:PSS/Si heterojunction for carrier injection balance. Pure green emission light has been achieved from devices with varied thicknesses of the emitting layer, and the maximum degree of polarization is measured to be 0.79. The field distribution and polarization of the PED were simulated and measured. Such a low-cost Si-based plasmonic diode provides a promising way to realize simpler and more compact multiple-functional light sources, which are extensively demanded for optoelectronic integration.
On adhesive contact between spheres with rolling adhesion
Authors: Ma Zhao-Yang , He Jin-Shan , Huang Gan-Yun , Ke Liao-Liang
Published: August 2024

The tendency of relative motion via rolling between contacting objects exists in various aspects of industry and nature because, in many practical situations, forces and moments may be simultaneously induced at the contacting interfaces. Due to the presence of adhesion, which may be prominent on small scales, research on contacts with the tendency to roll, termed herein as rolling adhesion, is very limited. In the present work, a novel double-Hertz model is developed for adhesive contact between spherical objects subjected to the combined action of normal forces and moments. The results from the new model agree well with available numerical simulations and experimental results. It has been demonstrated that the contact behavior with the effect of rolling adhesion seemingly resembles that of conventional adhesive contact, but the applied moment may impact the pull-off force and may even induce novel contact instability if large enough. The resistance moment at the interface has also been obtained analytically, which is proportional to adhesion hysteresis and contact area. Given the applicability to the full range of the Tabor parameter and nonsingular stresses involved, these results might shed light on adhesive contacts with rolling adhesion and help to characterize them better than existent models.
Investigation and modeling of the role of interface defects in the optical degradation of InGaN/GaN LEDs
Authors: Roccato Nicola , Piva Francesco , Buffolo Matteo , Santi Carlo De , Trivellin Nicola , Haller Camille , Carlin Jean-François , Grandjean Nicolas , Meneghesso Gaudenzio , Zanoni Enrico , Meneghini Matteo
Published: August 2024

We investigate the degradation mechanisms of In0.2Ga0.8N/GaN light emitting diodes through combined experimental analysis and simulations. The devices were submitted to constant current stress at 100 mA. Depending on the measuring current level, two degradation trends were observed: at high test currents (e.g. 200 mA), a monotonic decrease in optical power was observed; at low test currents (e.g. 5 mA), an initial degradation was observed, followed by an improvement in device efficiency (positive ageing). For the first time, such recovery effect was analyzed and modeled, as due to the generation of charged defects at the InGaN/GaN interface, resulting in the increase in the injection efficiency at low bias levels. The role of interface defects was validated by means of numerical simulations, with good agreement with the experimental data.