bluuebunny/crossref_metadata_2025 huggingface dataset:
Analyzing the influence of dimensions of the body behind the cavitator on ventilated cavitation
Authors: Kamali Hossein Ali , Pasandidehfard Mahmoud , Kadivar Ebrahim
Published: June 2024

Investigating the impact of various parameters on the characteristics of supercavitation is an essential and continuously evolving matter. In the current study, the influence of the geometry behind the cavitator on the characteristics of ventilation supercavitation at different Froude numbers and at a constant ventilation coefficient has been investigated. For this purpose, at first, by using the experimental method on a model with a disk cavitator at different Froude numbers, the ventilation cavitation has been investigated and the appropriate numerical method has been validated based on the experimental results. Next, using the numerical method, the effect of filling the cavity volume by geometry with different dimensions and confined inside the cavity on the characteristics of the ventilated supercavity was investigated. Also, the geometry with unlimited length and variable diameter was investigated in order to determine the effect of increasing the diameter on the characteristics of the cavity. The results indicate that increasing the volume of the aft body confined within the supercavity does not have a significant effect on its characteristics. However, increasing the diameter of the aft body caused a significant reduction in the length of the supercavity for the geometry with an infinite body length.
A global rho-axis method for fitting asymmetric tops with one methyl internal rotor and two 14N nuclei: Application of BELGI-2N to the microwave spectra of four methylimidazole isomers
Authors: Antonelli Eléonore , Gougoula Eva , Walker Nicholas R. , Schwell Martin , Nguyen Ha Vinh Lam , Kleiner Isabelle
Published: June 2024

A number of internal rotation codes can deal with the combination of one or two internal rotors with one 14N quadrupole nucleus, but once it comes to two 14N nuclei, no such code is available even for the case of one internal rotor. We present here the extension of our internal rotor program called BELGI-2N using the rho-axis method global approach to deal with compounds containing one methyl rotor and two weakly coupling 14N nuclei. To test our new code, we applied it to the microwave data recorded for N-methylimidazole, 2-methylimidazole, 4-methylimidazole, and 5-methylimidazole using a chirped-pulse Fourier transform microwave spectrometer in the 7.0–18.5 GHz frequency range. Compared to the previously published study, BELGI-2N was able to (i) significantly increase the number of assigned and fitted lines, (ii) fit the complete datasets considering both the internal rotation and the 14N nuclear quadrupole coupling effects simultaneously, and (iii) achieve standard deviations within the measurement accuracy for all methylimidazole isomers.
Zeolitic-imidazolate framework (ZIF-67) based bipolar memristor for nonvolatile ReRAM application
Authors: Kaushik Divya , Sharma Harshit , Saini Nitish , Suman C. K. , Srivastava Ritu
Published: June 2024

In the realm of next-generation nonvolatile memories, there is a strong demand for resistive random access memory (ReRAM) devices that are affordable, stable, and simple to produce. Metal–organic frameworks (MOFs) have garnered extensive research attention across diverse fields due to their remarkable chemical adaptability, stability, and exceptional structural variability. In this work, a ReRAM device has been fabricated that incorporates a solution-processed thin film of zeolitic imidazolate framework (ZIF-67), a material of MOFs class, as the resistive switching (RS) layer. This Al/ZIF-67/ITO structured device possesses a consistent RS behavior with a high on/off resistance ratio of ∼104. The retention of low resistance state and high resistance state have been shown up to 104 s. Furthermore, the device also shows a consistent switching for 500 cycles of pulse switching signals of +6 V/−1.8 V (set/reset). Based on the impedance spectroscopy analysis, a filamentary switching mechanism has been established for the RS behavior of the device. The robust and enduring performance, coupled with the substantial on/off resistance ratio and high retention of the states, makes this device a promising candidate for nonvolatile ReRAM applications.
Threshold pressure gradient in fractured reservoirs: Experimental simulation and mathematical modeling
Authors: Zong Peng , Xu Hao , Tang Dazhen , Huo Feiyu
Published: June 2024

Aiming to solve the problems of unclear fluid flow laws and controlling factors in fractured reservoirs, as well as the lack of a mathematical model of threshold pressure gradient (TPG) considering fracture structural parameters, research on the structural characterization of fractured reservoirs, physical simulation of fluid flow, and TPG prediction models has been carried out. Physical simulations demonstrate that fluid flow in fractured reservoirs under stress is nonlinear and exhibits TPG. The TPG displays a significant positive exponential relationship with confining pressure and water saturation. As the confining pressure or water saturation increases, the effective opening of fractures decreases. The TPG will increase dramatically when the fracture opening decreases to the critical thickness for the rapid increase in TPG. On the basis of the fluid flow law study, the TPG fractal prediction model is further developed based on fractal dimension of fracture length distribution (Df), fractal dimension of tortuosity (DT), water saturation (Sw), maximum fracture width (wmax), limit shear stress (η0), and sample characteristic length (L0). The results predicted by the model show good agreement with physical simulations (with average relative error of 7.56%). Experimental simulation and mathematical modeling of TPG in fractured reservoirs can reveal the fluid flow mechanism and improve the accurate evaluation of production capacity during different development processes.
Influence of the barrier layer on the electrical properties of the V/Al-based Ohmic contact on n-type high-Al-fraction AlGaN
Authors: Guo X. Q. , Xu F. J. , Lang J. , Wang J. M. , Zhang L. S. , Zhang Z. Y. , Ji C. , Tan F. Y. , Ji C. Z. , Wu Y. , Kang X. N. , Tang N. , Wang X. Q. , Qin Z. X. , Ge W. K. , Shen B.
Published: June 2024

Influence of the barrier layer on the electrical properties of V/Al-based Ohmic contact is investigated by comparing the surface morphology and alloying results of V/Al/Ni/Au (with barrier Ni) and V/Al/Cr/Au (with barrier Cr) contacts on n-AlGaN (Al molar fraction>60%) after 850 °C annealing. Due to the clustering of Ni during annealing, a thin Al layer (AlOx) and a number of Al-Au alloy clusters are formed at the contact interface of n-AlGaN, which increases the contact resistance of the V/Al/Ni/Au Ohmic contacts. In contrast, the annealed V/Al/Cr/Au electrodes cover the surface uniformly, which not only contributes to the increased contact area, but also suppresses the formation of high resistance products. Thanks to the Cr barrier layer, the specific contact resistivity of V/Al-based Ohmic contact is reduced by 26%.
In-cylinder flow evolution in the horizontal plane of a motoring compression ignition engine
Authors: Jena Ashutosh , Agarwal Avinash Kumar
Published: June 2024

This study used the two-dimensional particle image velocimetry technique to quantify the in-cylinder horizontal plane velocity field evolution in a swirl-supported light-duty single-cylinder diesel engine. The data were acquired at a constant engine speed of 1600 revolutions per minute. For each case, the distance of the laser sheet from the fire deck was varied (z = 5, 10, and 20 mm) to investigate the axial variations in the flow field during the flow evolution in the compression stroke. A vortex identification algorithm was used to detect the swirl center and its deviation from the rigid body rotation. A Bessel fit was obtained using the experimental data. The result revealed that the in-cylinder flow was not axisymmetric. The swirl center approached the geometrical center as the piston approached the top dead center. The flow evolved at the farthest plane from the fire deck. The axial diffusion of angular momentum resulted in the formation of the swirl flow structure in the plane closer to the fire deck. Angular momentum analysis of a simplified geometry has been presented to explain the swirl amplification. The estimated results were compared with the experimental results to show the momentum stratification in the engine cylinder later in the compression stroke.
Formation of ferromagnetic Fe5Se8 via phase transition and enhanced hydrogen evolution reaction with alternating magnetic fields
Authors: Chen Mingyue , Zhou Wenda , Luo Xingfang , Xu Weiyang , Ye Daojian , Yuan Cailei , Wang Shouguo
Published: June 2024

Leveraging alternating magnetic fields (AMFs) to induce localized heating in catalysts has emerged as a powerful approach to boost electrocatalytic reactions. However, the rational design and synthesis of ferromagnetic catalysts that can be stably coupled with an AMF to improve the hydrogen evolution reaction (HER) performance are still urgent and challenging. Herein, the ferromagnetic triclinic Fe5Se8 has been realized through the phase transition from nonmagnetic orthorhombic FeSe2 synergistically triggered by the selenium vacancies and the strain engineering, making it a good candidate for AMFs-assisted HER. Experimental results and theoretical calculation demonstrate that the phase transition-prepared ferromagnetic Fe5Se8 exhibits much better HER performance than nonmagnetic FeSe2. More importantly, under high-frequency AMF stimulation, the HER performance of ferromagnetic Fe5Se8 is greatly enhanced (the overpotential decreased by 63 mV), which is mainly attributed to the localized magnetic heating effect. This study realizes the controlled phase transition synthesis of ferromagnetic catalysts, indicating that AMF is an effective approach to manipulate the performance of ferromagnetic catalysts.
A new turbulent viscosity modification method based on multiphase compressibility for cavitating flows
Authors: Liu Dong , Xu Chenxi , Liu Benqing , Zhou Lingjiu , Liu Zhuqing , Yang Wei
Published: June 2024

The alteration of physical properties in cavitating flows due to phase transition presents challenges for accurately expressing turbulent viscosity in Reynolds-Averaged Navier–Stokes models. Addressing this issue is crucial for capturing cavitating flow characteristics effectively. This study introduces a modification to turbulent viscosity by considering the compressibility of the vapor–liquid mixture, applied within the k-omega Shear-Stress Transport (SST k−ω) model framework. Simulations of cavitating flow around the Clark-Y hydrofoil, National Advisory Committee for Aeronautics 66 hydrofoil, and wedge are conducted to validate the proposed method. Results indicate that the modified model can reproduce the cavity inception, development, cutoff, and shedding processes observed in the experiment. Notably, the modification model accurately reproduces distinct cavitating flow features such as U-shaped cavities, secondary shedding, and high-pressure phenomena resulting from collapse. Moreover, the predicted time-averaged velocity, time-averaged Reynolds stress component, and dominant frequencies of pressure and phase volume fraction surpass those of the original SST k−ω model, demonstrating improved performance. These findings highlight the enhanced accuracy and reliability of the proposed SST-multiphase compressibility modification k−ω model for simulating cavitating flows, thus contributing to improved understanding and prediction capabilities in relevant engineering applications.
Impact of rotor–stator axial spacing on the gas–liquid–solid flow characteristics of a multiphase rotodynamic pump based on the Euler multi-fluid model
Authors: Hu Liwei , Liang Ao , Li Huichuang , Zhang Wenwu , Zhu Baoshan
Published: June 2024

Multiphase rotodynamic pumps are used by the oil and gas industry to transport mixed media in pipelines. The characteristics of gas–liquid–solid flow in such pumps are significantly affected by the rotor–stator axial spacing so that further investigation is required. Based on the Euler multi-fluid model, the Computational Fluid Dynamics simulations were conducted in this study on the gas–liquid–solid multiphase rotodynamic pump at the rotor–stator axial spacings of 8, 10, 12, 14, and 16 mm, respectively. Changes in the pump's characteristics of external, multiphase flow, and pressure fluctuation were systematically analyzed by using ANSYS-CFX. The results showed that, an overall decreasing trend for the efficiency and head of the multiphase rotodynamic pump were demonstrated with increases in the rotor–stator axial spacing from 8 to 16 mm, which can be categorized into plummets I, moderation, and plummets II. As the rotor–stator axial spacing increased, the pressurization decreased from the inlet to outlet of guide vane while the aggregation of gas and solid increased. Additionally, vorticity increased and vortex structure was found to be more significant. As a result, the overall performance of the multiphase rotodynamic pump deteriorated. The pressure fluctuation in the multiphase rotodynamic pump was determined by the rotor–stator interaction and multiphase flow under gas–liquid–solid flow conditions, resulting in a non-positive correlation between the pressure fluctuation and the pump's external and internal flow characteristics. The location of maximum pressure fluctuation in the multiphase rotodynamic pump was changed from the impeller outlet to the guide vane inlet with increases in rotor–stator axial spacing.
A theoretical method for oblique and curved detonation waves
Authors: Yan Hao , Xiong Haochen , Han Xin , Shi Chongguang , You Yancheng
Published: June 2024

In this paper, a theoretical solution method for the post-wave parameters of detonation is proposed and developed with a series of analyses and applications. Based on Newton's method, the objective function for shock-coupled chemical reactions is constructed along with its derivative. Two verification examples demonstrate that the method can calculate accurate post-wave parameters quickly and is suitable for single-step and detailed mechanistic chemical reactions. In addition, the method provides sensitivities between various aerodynamic parameters to offer a fresh perspective for detonation, polar analysis with sensitivity is built as a result. Moreover, the method can predict the transition pattern of the detonation, and the validity is supported by the comparison of different examples. Rather than being limited to oblique detonation, the post-wave parameters of the curved detonation can also be calculated correctly, which indicates the excellent applicability of the method. This method can also be applied to the thermodynamic efficiency of detonation combustion and its sensitivity, which demonstrates the unique advantages of this method. Furthermore, the method can be rewritten as a solution for wedge angle under the given wave angle by changing the independent variable. This solution is validated by the simulation results, which implies that the method can be used as a simple inverse design method in oblique detonation engines. In general, the proposed method is an effective theoretical solution, analytical tool, and inverse design method for detonation.
Thermal-flow-force-electrical coupling characteristics of microchannel cooling systems in high heat flux chips
Authors: Yang Ruixue , Deng Zilong , Li Bo , Chen Yongping
Published: June 2024

To address the challenges faced by designers of multi-field coupled cooling systems for high heat flux chips, this paper proposes a “near-source” microchannel cooling strategy and establishes a thermal–flow-force electrically coupled model for chips. The effects of chip Joule heat and cooling water flow rate on the cooling performance with respect to multi-field coupling effects were studied. The impact of multi-field coupling effects was revealed, and a method for enhancing microchannel cooling performance in light of multi-field coupling effects is proposed. The results indicated that considering multi-field coupling effects in the microchannel cooling process leads to a deterioration in the thermal performance of chips, accompanied by a significant increase in electrical fluctuations and thermal deformation amplitude. Compared to chips upstream of the cooling water, chips downstream subjected to thermal cascade effects were more sensitive to multi-field coupling effects. Moreover, the temperature variance index, output current, and strain energy density of high heat flux chips were positively correlated with Joule heat but inversely proportional to the Reynolds number of the cooling water for cases in respect of multi-field coupling effects. Additionally, serpentine microchannels maximized the operational performance of high heat flux chips by reducing temperature of chip by up to 55.1%, decreasing strain energy density by 96.7%, and increasing input potential by 120%.
Consideration of the dielectric response for radiation chemistry simulations
Authors: Toigawa Tomohiro , Kai Takeshi , Kumagai Yuta , Yokoya Akinari
Published: June 2024

The spur reaction, a spatially nonhomogeneous chemical reaction following ionization, is crucial in radiolysis or photolysis in liquids, but the spur expansion process has yet to be elucidated. One reason is the need to understand the role of the dielectric response of the solvating molecules surrounding the charged species generated by ionization. The dielectric response corresponds to the time evolution of the permittivity and might affect the chemical reaction–diffusion of the species in a spur expansion process. This study examined the competitive relationship between reaction–diffusion kinetics and the dielectric response by solving the Debye–Smoluchowski equation while considering the dielectric response. The Coulomb force between the charged species gradually decreases with the dielectric response. Our calculation results found a condition where fast recombination occurs before the dielectric response is complete. Although it has been reported that the primary G-values of free electrons depend on the static dielectric constant under low-linear-energy transfer radiation-induced ionization, we propose that considering the dielectric response can provide a deeper insight into fast recombination reactions under high-linear-energy transfer radiation- or photo-induced ionization. Our simulation method enables the understanding of fast radiation-induced phenomena in liquids.
Ga2O3/NiO junction barrier Schottky diodes with ultra-low barrier TiN contact
Authors: Gong Hehe , Sun Na , Hu Tiancheng , Yu Xinxin , Porter Matthew , Yang Zineng , Ren Fangfang , Gu Shulin , Zheng Youdou , Zhang Rong , Zhang Yuhao , Ye Jiandong
Published: June 2024

Power Schottky barrier diodes (SBDs) face an inherent trade-off between forward conduction loss and reverse blocking capability. This limitation becomes more severe for ultra-wide bandgap (UWBG) SBDs due to the large junction field. A high Schottky barrier is usually required to suppress the reverse leakage current at the price of an increased forward voltage drop (VF). This work demonstrates a Ga2O3 junction barrier Schottky (JBS) diode that employs the embedded p-type NiO grids to move the peak electric field away from the Schottky junction, thereby allowing for the use of an ultra-low barrier TiN Schottky contact. This JBS diode concurrently realizes a low VF of 0.91 V (at forward current of 100 A/cm2) and a high breakdown voltage over 1 kV, with the VF being the lowest in all the reported vertical UWBG power diodes. Based on the device characteristics measured up to 200 °C, we further analyze the power loss of this JBS diode across a wide range of operational duty cycles and temperatures, which is found to outperform the TiN/Ga2O3 SBDs or NiO/Ga2O3 PN diodes. These findings underscore the potential of low-barrier UWBG JBS diodes for high-frequency, high-temperature power electronics applications.
Fluid identification with Graph Transformer using well logging data
Authors: Sun Youzhuang , Pang Shanchen , Zhang Yongan
Published: June 2024

The prediction of fluid through well logging is a cornerstone in guiding exploratory efforts in the energy sector. Comprehending the fluid composition beneath the surface empowers exploration teams to effectively gauge the extent, reserves, and caliber of oil and gas resources. This leads to enhanced strategies in exploration and the judicious use of resources. We introduce an innovative machine learning framework named “Graph Transformer” for predicting fluid. This model melds graph convolutional layers with a Transformer module. It excels in decoding spatial and temporal patterns within well logging data, thus unraveling complex geological dependencies by factoring in the interconnectedness of various data points. Additionally, it features a Positional Encoding module to enhance understanding of sequential data points in terms of depth, thereby overcoming the limitations of sequence independence. The Transformer's Multi-Head Self-Attention mechanism is pivotal in discerning and integrating spatial and temporal interconnections across various depths, elevating its capability to represent geological structures. Initially, the model harnesses key well log data like Density, Acoustic, Gamma-ray, and Compensated Neutron Logs for extracting geological features. These insights are then processed through the Graph Transformer to establish relationship between fluid characteristics and logging parameters. Furthermore, we compare this model with other leading models using precision, recall, and accuracy metrics. Experimental findings affirm the model's high accuracy in predicting fluid within intricate geological settings. Its exceptional adaptability makes it apt for various geological conditions and logging tools. Thus, our Graph Transformer model stands out as a sophisticated, efficient machine learning solution in the realm of well logging fluid prediction, offering geologists and engineers precise tools for exploration and development.
Fully solution-driven charge trapping synaptic transistor with low energy consumption for neuromorphic computing
Authors: Xie Hongfu , Miao Guangtan , Liu Guoxia , Shan Fukai
Published: June 2024

Brain-inspired neuromorphic computing has garnered significant attention for going beyond the constraint of von Neumann architecture. To emulate the human brain functions, various artificial synaptic devices have been proposed. Due to the high reliability and the CMOS compatibility, the synaptic transistors based on charge trapping (CT) mechanism have been considered to be one of the most promising candidates. However, most of the synaptic transistors based on CT mechanism were fabricated by costly vacuum-based techniques. In this report, based on a fully solution-driven strategy, the InZnO synaptic transistors, with Nd2O3 as the CT layer and ZrO2 as the dielectric layer, were integrated. The typical synaptic behaviors, including excitatory postsynaptic current, inhibitory postsynaptic current, memory enhancement, potentiation, and depression characteristics, were simulated by modulating presynaptic spikes. It is confirmed that the fabricated synaptic transistor shows low channel conductance and low energy consumption of 0.13 pJ per synaptic event. A recognition accuracy of 93.0% was achieved for the MNIST handwritten digital image dataset by an artificial neural network simulation. This study demonstrates the feasibility of solution-processed synaptic transistors, which exhibit significant potential for the neuromorphic applications.
Enhancing dynamic mixing and heat transfer of polymer by inducing ductile flow applying field synergy principle
Authors: Jian Ranran , Pan Wei , Huang Shizheng , Yang Weimin , Li Shujiang
Published: June 2024

An innovative and effective approach for screw design and optimization has been proposed, derived from multi-field synergy to address a growing challenge affected by the inadequate mixing and thermal management in plasticizing process of extrusion or injection. Dimensionless field synergy equations for incompressible non-Newtonian viscous polymers were established, and subsequently, two new types of screw structures—field synergy torsion element (FST) and field synergy elongation element (FSE)—were designed, fabricated, and validated through both simulation and experiment. Spiral and elongational flows were established in the newly designed screws owing to their unique structures of torsion channel and convergent channel, promoting the shear and stretch ductile deformations of polymer melt, documented to be a meaningful progress on flow patterns generated by conventional screw. A comparative investigation in this work of the newly designed screw with a conventional one showed that the newly proposed screws equipped with FSTs or FSEs performed better mixing and improved heat transfer and thermal uniformity. Multi-field synergy analysis revealed that the spiral and elongational flow enhanced the radial convection, improved the dependence of velocity and velocity gradient fields to facilitate melt stretching deformation as well as the dependence of velocity and temperature gradient fields to achieve heat transfer enhancement.
Stabilizing perpendicular magnetic anisotropy with strong exchange bias in PtMn/Co by magneto-ionics
Authors: Bednarz Beatrice , Syskaki Maria-Andromachi , Pachat Rohit , Prädel Leon , Wortmann Martin , Kuschel Timo , Ono Shimpei , Kläui Mathias , Herrera Diez Liza , Jakob Gerhard
Published: June 2024

Electric field control of magnetic properties offers a broad and promising toolbox for enabling ultra-low power electronics. A key challenge with high technological relevance is to master the interplay between the magnetic anisotropy of a ferromagnet and the exchange coupling to an adjacent antiferromagnet. Here, we demonstrate that magneto-ionic gating can be used to achieve a very stable out-of-plane (OOP) oriented magnetization with strong exchange bias in samples with as-deposited preferred in-plane (IP) magnetization. We show that the perpendicular interfacial anisotropy can be increased by more than a factor 2 in the stack Ta/Pt/PtMn/Co/HfO2 by applying −2.5 V gate voltage over 3 nm HfO2, causing a reorientation of the magnetization from IP to OOP with a strong OOP exchange bias of more than 50 mT. Comparing two thicknesses of PtMn, we identify a notable trade-off: while thicker PtMn yields a significantly larger exchange bias, it also results in a slower response to ionic liquid gating within the accessible gate voltage window. These results pave the way for post-deposition electrical tailoring of magnetic anisotropy and exchange bias in samples requiring significant exchange bias.
Using a pruned basis and a sparse collocation grid with more points than basis functions to do efficient and accurate MCTDH calculations with general potential energy surfaces
Authors: Wodraszka Robert , Carrington Tucker
Published: June 2024

We propose a new collocation multi-configuration time-dependent Hartree (MCTDH) method. It reduces point-set error by using more points than basis functions. Collocation makes it possible to use MCTDH with a general potential energy surface without computing any integrals. The collocation points are associated with a basis larger than the basis used to represent wavefunctions. Both bases are obtained from a direct product basis built from single-particle functions by imposing a pruning condition. The collocation points are those on a sparse grid. Heretofore, collocation MCTDH calculations with more points than basis functions have only been possible if both the collocation grid and the basis set are direct products. In this paper, we exploit a new pseudo-inverse to use both more points than basis functions and a pruned basis and grid. We demonstrate that, for a calculation of the lowest 50 vibrational states (energy levels and wavefunctions) of CH2NH, errors can be reduced by two orders of magnitude by increasing the number of points, without increasing the basis size. This is true also when unrefined time-independent points are used.
A driven Kerr oscillator with two-fold degeneracies for qubit protection
Authors: Venkatraman Jayameenakshi , Cortiñas Rodrigo G. , Frattini Nicholas E. , Xiao Xu , Devoret Michel H.
Published: June 2024

We present the experimental finding of multiple simultaneous two-fold degeneracies in the spectrum of a Kerr oscillator subjected to a squeezing drive. This squeezing drive resulting from a three-wave mixing process, in combination with the Kerr interaction, creates an effective static two-well potential in the phase space rotating at half the frequency of the sinusoidal drive generating the squeezing. Remarkably, these degeneracies can be turned on-and-off on demand, as well as their number by simply adjusting the frequency of the squeezing drive. We find that when the detuning Δ between the frequency of the oscillator and the second subharmonic of the drive equals an even multiple of the Kerr coefficient
K
,

Δ
/
K
=
2
m

, the oscillator displays

m
+
1

exact, parity-protected, spectral degeneracies, insensitive to the drive amplitude. These degeneracies can be explained by the unusual destructive interference of tunnel paths in the classically forbidden region of the double well static effective potential that models our experiment. Exploiting this interference, we measure a peaked enhancement of the incoherent well-switching lifetime, thus creating a protected cat qubit in the ground state manifold of our oscillator. Our results illustrate the relationship between degeneracies and noise protection in a driven quantum system.
High-frequency solutions to the Einstein equations
Authors: Huneau Cécile , Luk Jonathan
Published: June 2024

We review recent mathematical results concerning the high-frequency solutions to the Einstein vacuum equations and the limits of these solutions. In particular, we focus on two conjectures of Burnett, which attempt to give an exact characterization of high-frequency limits of vacuum spacetimes as solutions to the Einstein–massless Vlasov system. Some open problems and future directions are discussed.
First-principles study of carrier mobility and strain effect in MX (M=Sn, Pb; X=P, As) monolayers
Authors: Zhang Bo , Wan Wenhui , Liu Yong , Ge Yanfeng
Published: June 2024

The pursuit of two-dimensional semiconductor materials that feature tunable electronic structures and high mobility is crucial for advancing nanoelectronic and optoelectronic devices. In this study, the MX monolayers (M = Sn, Pb; N = P, As) are investigated with first-principles calculations based on Boltzmann transport theory. The results show that SnP, SnAs, and PbAs all exhibit indirect band gaps, whereas PbP is the only semiconductor with a direct band gap. One important finding is that intravalley scattering has a significant impact on electron–phonon coupling. Interestingly, changes in carrier concentration do not affect the electron mobility within these MX monolayers, with SnP exhibiting the highest electron mobility among them. Subsequently, the SnP under a 6% biaxial strain is further explored and the results demonstrated a considerable increase in electron mobility to 2,511.9 cm

2

V

−
1

s

−
1

, which is attributable to decreased scattering. This suggests that MX monolayers, especially SnP, are promising options for 2D semiconductor materials in the future.
Rolling element bearing fault diagnosis based on multi-objective optimized deep auto-encoder
Authors: Chang Xiaoxin , Yang Shaopu , Li Shaohua , Gu Xiaohui
Published: June 2024

Bearing fault diagnosis holds significant importance, with widespread attention focused on enhancing its accuracy and efficiency. Existing diagnostic methods based on deep learning and transfer learning typically tackle this issue by introducing new function modules and diagnostic strategies, such as attention mechanism, adversarial domain adaptation, etc. However, most studies do not consider the structure and hyperparameters optimization of the network to improve the diagnostic performance of the network itself. To address this limitation, a novel multi-objective optimized deep auto-encoder is proposed in this paper. The optimal network structure and hyperparameters is determined by a multi-objective particle swarm optimization algorithm. Crucially, the method is based on a data-driven approaches to automatically search for network structures with stronger generalization and feature extraction capabilities to address engineering problems in different scenarios. Finally, this method is examined in both multi-fault classification diagnosis and transfer diagnosis scenarios, demonstrating strong self-adaptability through experimental results. In comparison with typical deep learning fault diagnosis methods, the proposed method demonstrates higher diagnostic accuracy and superior generalization ability.
Accurate detection of subsurface microcavity by bimodal atomic force microscopy
Authors: Lou Pengtao , Bi Zhuanfang , Shang Guangyi
Published: June 2024

Subsurface detection capability of bimodal atomic force microscopy (AFM) was investigated using the buried microcavity as a reference sample, prepared by partially covering a piece of highly oriented pyrolytic graphite (HOPG) flake with different thickness on a piece of a cleaned CD-R disk substrate. This capability can be manifested as the image contrast between the locations with and without the buried microcavities. The theoretical and experimental results demonstrated that the image contrast is significantly affected by the critical parameters, including the second eigenmode amplitude and frequency as well as local structural and mechanical properties of the sample itself. Specifically, improper parameter settings generally lead to incorrect identification of the buried microcavity due to the contrast reduction, contrast reversal and even disappearance. For accurate detection, the second eigenmode amplitude should be as small as possible on the premise of satisfying the signal-to-noise ratio and second eigenmode frequency should be close to the resonance frequency of the cantilever. In addition, the detectable depth is closely related to microcavity dimension (thickness and width) of the HOPG flake and local stiffness of the sample. These results would be helpful for further understanding of the detection mechanism of bimodal AFM and facilitating its application in nano-characterization of subsurface structures, such as the micro-/nano- channels to direct the flow of liquids in lab-on-a-chip devices.
Paired conditional generative adversarial network for highly accelerated liver 4D MRI
Authors: Xu Di , Miao Xin , Liu Hengjie , Scholey Jessica E , Yang Wensha , Feng Mary , Ohliger Michael , Lin Hui , Lao Yi , Yang Yang , Sheng Ke
Published: June 2024

Purpose. 4D MRI with high spatiotemporal resolution is desired for image-guided liver radiotherapy. Acquiring densely sampling k-space data is time-consuming. Accelerated acquisition with sparse samples is desirable but often causes degraded image quality or long reconstruction time. We propose the Reconstruct Paired Conditional Generative Adversarial Network (Re-Con-GAN) to shorten the 4D MRI reconstruction time while maintaining the reconstruction quality. Methods. Patients who underwent free-breathing liver 4D MRI were included in the study. Fully- and retrospectively under-sampled data at 3, 6 and 10 times (3×, 6× and 10×) were first reconstructed using the nuFFT algorithm. Re-Con-GAN then trained input and output in pairs. Three types of networks, ResNet9, UNet and reconstruction swin transformer (RST), were explored as generators. PatchGAN was selected as the discriminator. Re-Con-GAN processed the data (3D + t) as temporal slices (2D + t). A total of 48 patients with 12 332 temporal slices were split into training (37 patients with 10 721 slices) and test (11 patients with 1611 slices). Compressed sensing (CS) reconstruction with spatiotemporal sparsity constraint was used as a benchmark. Reconstructed image quality was further evaluated with a liver gross tumor volume (GTV) localization task using Mask-RCNN trained from a separate 3D static liver MRI dataset (70 patients; 103 GTV contours). Results. Re-Con-GAN consistently achieved comparable/better PSNR, SSIM, and RMSE scores compared to CS/UNet models. The inference time of Re-Con-GAN, UNet and CS are 0.15, 0.16, and 120 s. The GTV detection task showed that Re-Con-GAN and CS, compared to UNet, better improved the dice score (3× Re-Con-GAN 80.98%; 3× CS 80.74%; 3× UNet 79.88%) of unprocessed under-sampled images (3× 69.61%). Conclusion. A generative network with adversarial training is proposed with promising and efficient reconstruction results demonstrated on an in-house dataset. The rapid and qualitative reconstruction of 4D liver MR has the potential to facilitate online adaptive MR-guided radiotherapy for liver cancer.
Enhanced classification of left ventricular hypertrophy in cardiac patients using extended Siamese CNN
Authors: Farhad Moomal , Masud Mohammad Mehedy , Beg Azam , Ahmad Amir , Memon Sehar
Published: June 2024

Objective. Left ventricular hypertrophy (LVH) is the thickening of the left ventricle wall of the heart. The objective of this study is to develop a novel approach for the accurate assessment of LVH) severity, addressing the limitations of traditional manual grading systems. Approach. We propose the Multi-purpose Siamese Weighted Euclidean Distance Model (MSWED), which utilizes convolutional Siamese neural networks and zero-shot/few-shot learning techniques. Unlike traditional methods, our model introduces a cutoff distance-based approach for zero-shot learning, enhancing accuracy. We also incorporate a weighted Euclidean distance targeting informative regions within echocardiograms. Main results. We collected comprehensive datasets labeled by experienced echocardiographers, including Normal heart and various levels of LVH severity. Our model outperforms existing techniques, demonstrating significant precision enhancement, with improvements of up to 13% for zero-shot and few-shot learning approaches. Significance. Accurate assessment of LVH severity is crucial for clinical prognosis and treatment decisions. Our proposed MSWED model offers a more reliable and efficient solution compared to traditional grading systems, reducing subjectivity and errors while providing enhanced precision in severity classification.
An examination of acute physiological and perceptual responses following blood flow restriction exercise using a traditional research device or novel, automated system
Authors: Moreno Enrique N , Figueroa Elias C , Heath Andrew W , Buckner Samuel L
Published: June 2024

Objective. To compare the acute physiological and perceptual responses to blood flow restriction (BFR) exercise using a traditional research device or novel, automated system. Methods. Forty-four resistance trained individuals performed four sets of unilateral elbow flexion exercise (30% one-repetition maximum) to volitional failure using two distinct restrictive devices [SmartCuffs PRO BFR Model (SMARTCUFF), Hokanson E20 Rapid Inflation device (HOKANSON)] and with two levels of BFR [40% limb occlusion pressure (LOP), 80% LOP]. Blood pressure (BP), muscle thickness (MT), and isometric strength (ISO) were assessed prior to and following exercise. Perceptual responses [ratings of perceived exertion (RPE), discomfort] were assessed prior to exercise and following each exercise set. Main results. Data are displayed as means (SD). Immediately following exercise with 40% LOP, there were no statistical differences between devices for BP, MT, and ISO. However, only following Set 1 of exercise, RPE was greater with SMARTCUFF compared to HOKANSON (p < 0.05). In addition, only following Set 2 of exercise, discomfort was greater with HOKANSON compared to SMARTCUFF (p < 0.001). Immediately following exercise with 80% LOP, there were no statistical differences between devices for BP, MT, and ISO. However, only following Set 4 of exercise, RPE was greater with HOKANSON compared to SMARTCUFF (p < 0.05). In addition, following all exercise sets, discomfort was greater with HOKANSON compared to SMARTCUFF (p < 0.001). For repetitions completed with 40% LOP there were no statistical differences between SMARTCUFF and HOKANSON across any exercise sets. For repetitions completed with 80% LOP there were no statistical differences between SMARTCUFF and HOKANSON across Set 1 of exercise (p = 0.34), however, for Sets 2–4 of exercise, significantly greater number of repetitions were completed during SMARTCUFF than HOKANSON. Significance. The present study provides valuable insight into the efficacy of a novel, automated BFR system (SMARTCUFF) eliciting comparable acute physiological responses to BFR exercise and in some cases favorable perceptual responses when compared to a traditional research device (HOKANSON).
Interface trap-induced radiofrequency and low-frequency noise analysis under temperature variation of a heterostacked source L-gate tunnel field effect transistor
Authors: Das Debika , Chakraborty Ujjal , Borah Pranjal
Published: June 2024

This work offers a comprehensive analysis of the adverse impact of interface trap charge (ITC) under the influence of temperature variation on a heterostacked (HS) source L-gate tunnel field effect transistor (TFET) having a SiGe pocket. An investigation of both static and radiofrequency (RF) characteristics has been carried out. It appears that ITCs situated at the Si–oxide interface fluctuate the flat-band voltage to alter the various analog/RF parameter characteristics. Uniform ITCs are seen to be less susceptible to degradation in device characteristics. Low-frequency noise (LFN) analysis has also been carried out considering the impact of different trap distributions (uniform and Gaussian) and densities, which are compared. The temperature dependence of LFN has been studied under the influence of different distributed ITCs, and this has rarely been explored. Moreover, a comparative analysis has been made of the device behavior and LFN characteristics of HS L-gate TFET structures with and without a SiGe pocket. Structures with SiGe pockets were found not to be susceptible to noise effects.
High strength induced wide band gap formations in additively manufactured cubic metamaterial
Authors: Guo J C , Li J R , Wang H Y , Dong Z Y , Zhang Z
Published: June 2024

Strength and band gap are the two basic physical features of the cubic metamaterial. How to design band gap characteristics with high strength of structure is the key for the further industrial application in vibration control of the cubic metamaterial. Here a cubic metamaterial is designed by optimal selection of crystal orientation angle to obtain wide band gaps with high strength. The prototype samples were fabricated using advanced additive manufacturing technology to tensile-pressure experiments and sine frequency sweep experiment, thereby demonstrating the validity of the obtained results. Results indicated that the normalized bandwidth of simple cubic (SC) metamaterials is 0.47 and the ultimate strength is 25.99 MPa. The normalized bandwidth is increased by 3.1 times and 47 times higher than that of the metamaterials of face-centered cubic (FCC) and body-centered cubic (BCC). Its ultimate strength is increased by 3.5 times and 6.7 times. The static simulation results revealed that the maximum mises stress values of SC, FCC, and BCC metamaterials were 1.71, 10.49, and 31.40 MPa respectively. The attenuation amplitude of the elastic wave measured by experiment is 80 dB, which is consistent with the simulation results. The bandwidths of cubic metamaterials exhibit a positive correlation with their strength. The variation in crystal orientation angles plays a crucial role in elucidating the underlying mechanism behind the positive correlation between the strength and the band gap. The further buckling analysis of SC metamaterial with high strength and wide bandgap characteristics reveals that the negative Poisson’s ratio structure experiences a reduction in bandwidth and strength as buckling deformation intensifies.
Improving the performance of magnetorheological elastomer-based adaptive isolator through integrated compression-torsion structure
Authors: Gao Wei , Lu Junyan , Han Wenheng , Chen Guolong , Wang Xingzhe
Published: June 2024

In this paper, a novel magnetorheological elastomer (MRE) isolator with a compression-torsion structure was developed to address existing challenges related to stiffness variation, damping force, and magnetic control range. Through performance testing of the vibration isolator prototype and theoretical analysis based on traditional magnetic dipole model of the MRE, the effects of applied magnetic field and compression displacement on the performance of the designed MRE isolator were systematically evaluated. The results showed that integrating the compression-torsion structure not only enhances the magneto-induced mechanical performance of the MRE but also improves the overall performance of the entire MRE isolator. The output force of the MRE isolator with a compression-torsion structure generally surpasses than that of the MRE isolator lacking this feature. The isolator’s stiffness can vary by up to 119% compared to its initial stiffness when a 2 A current is applied at a compression displacement of 0.5 mm. The proposed design, combining the compression-torsion structure and the MRE isolator, offers new insights for future research and applications in the realm of MRE isolators.
Vector dark matter, inflation, and non-minimal couplings with gravity
Authors: Özsoy Ogan , Tasinato Gianmassimo
Published: June 2024

We propose a cosmological dark matter production mechanism in the form of a longitudinal
massive vector boson. We build upon the work [1] including non-minimal couplings
of the massive vector with gravity, developing a well motivated set-up from an effective field
theory perspective. We carefully track the dynamics of vector field in passing from inflation to
radiation dominated universe to show that the late time abundance of longitudinal modes —
excited initially by the quantum fluctuations during inflation — can provide the observed dark
matter abundance for sufficiently weak non-minimal coupling and wide range of vector masses 5
× 10-7 ≲ m [eV] ≲ 5 × 103. The final abundance of dark
matter depends on two parameter, the vector mass and its non-minimal coupling with gravity. We
discuss experimental venues to probe this framework, including the production of a stochastic
gravitational wave background. The latter is especially interesting, as the same mechanism that
generates dark matter can potentially lead to the production of gravitational waves in the LISA
frequency band, through the second-order effects of large dark matter iso-curvature perturbations
at small scales. We take a first step in this direction, identifying the potential information
that gravitational wave experiments can provide on the parameter space of dark matter within
this scenario.