bluuebunny/crossref_metadata_2025 huggingface dataset:
On thermal performance of spine fin in magnetized hybrid fluid rooted with Cu and MoS4 nanoparticles
Authors: Tanuja T. N. , L Kavitha , Rehman Khalil Ur , Kumar G. V. , Shatanawi Wasfi , Varma S. V. K. , Asghar Zeeshan
Published: January 2024

This study examines the thermal performance of diverse profiles of spine fins with variable thermal conductivity. A hybrid nanofluid comprising Cu, and MoS4 with water as the base fluid, is modeled mathematically. Both the cylindrical and concave parabolic profiles are taken into account. The comparative outcomes are inferred from numerical and semi-analytical methods. The non-dimensional temperature profiles are analyzed graphically while considering the fin tip to be insulated, and the effects of various thermal parameters are also investigated. We have observed that the heat transfer rate shows an opposite trend toward convective-conduction and porosity parameter. The study also revealed that the concave parabolic profile emits more heat in comparison with the cylindrical profile.
Oblique wave trapping by sinusoidal rippled barrier of finite thickness placed on closely spaced semi-circular seabed
Authors: Venkateswarlu V. , Vijay K. G. , Nishad C. S. , Behera H.
Published: January 2024

The oblique wave trapping by a sinusoidal rippled barrier (SRB) of finite thickness placed far away from a partially reflecting seawall is examined under the assumption of linear potential flow theory. The sinusoidal ripples are identical, and the barrier is installed in the presence of a semi-circular bottom (SCB). As a special case, the wave trapping by a thick non-rippled barrier (NRB) is also studied to show the significance of the ripples on the wave trapping. The multi-domain boundary element method is employed to tackle the wave-trapping performance of the SRB satisfying Darcy's law. Various types of structural configurations, such as (a) SRB alone, (b) SRB placed on SCB with trapping chamber, (c) without trapping chamber, (d) NRB alone, and (e) NRB placed on SCB with trapping chamber, are proposed and evaluated under oblique wave incidence. The correctness of the study results is verified with the available results for specific structural configurations. The effect of wall reflection, chamber length, plate porosity, and plate submergence depth on wave-trapping coefficients (wave reflection and wave run-up) and force coefficients (horizontal force on the wall and vertical force on the barrier) are presented against relative wavelength. The enhanced wave trapping is obtained after installing a SRB when compared with the NRB of finite thickness. The chamber spacing minimizes the trapping coefficients when compared with the non-chamber rippled barrier. The study recommends the SRB with SCB of thickness 0.10≤D/h≤0.15, porosity 20%, width B/h=2, and chamber spacing 1≤L/h≤2 to replace the gravity-type breakwaters to be installed against intermediate and deep-water waves.
Investigating lipid bilayer self-assembly and formation of ripple phase: Insights from a coarse-grained implicit solvent model
Authors: Bawali Biplab , Datta Alokmay , Saha Jayashree
Published: January 2024

In this study, we present a comprehensive exploration of the formation of different phases in lipid molecules using a coarse-grained implicit solvent model, where each lipid molecule is presented as a rigid, three-bead, rod-like structure. Our study not only successfully replicates the spontaneous self-assembly of lipid bilayers but also elucidates the intricate phase transitions between the gel phase, the liquid phase, and the elusive ripple phase (Pβ). Specifically, we uncover the pivotal role of molecular rigidity in promoting the formation of the ripple phase. The significance of our findings lies in their potential to reshape our understanding of lipid bilayer dynamics and phase transitions. By shedding light on the ripple phase, a phase previously difficult to simulate convincingly, the insights gained from this study have the potential to guide future investigations into the behavior of biological membranes and their role in cellular processes.
Second quantization-based symmetry-adapted perturbation theory: Generalizing exchange beyond single electron pair approximation
Authors: Tyrcha Bartosz , Brzęk Filip , Żuchowski Piotr S.
Published: January 2024

This paper presents a general second-quantized form of a permutation operator interchanging n pairs of electrons between interacting subsystems in the framework of the symmetry-adapted perturbation theory (SAPT). We detail the procedure for constructing this operator through the consecutive multiplication of single-pair permutation operators. This generalized form of the permutation operator has enabled the derivation of universal formulas for S2n approximations of the exchange energies in the first and second order of the interaction operator. We present expressions for corrections of S4 approximations and assess its efficacy on a selection of systems anticipated to exhibit a slowly converging overlap expansion. Additionally, we outline a method to sum the overlap expansion series to infinity in second-quantization, up to the second order in V. This new approach offers an alternative to the existing formalism based on density-matrix formulations. When combined with a symbolic algebra program for automated derivations, it paves the way for advancements in SAPT theory, particularly for intricate wavefunction theories.
Experimental simulation study on influencing factors of liquid production capacity in heterogeneous water drive reservoirs
Authors: Fu Dekui , Fu Yu , Zhang YunJun , Wang Mingwei
Published: January 2024

Oilfield development involves a complex, dynamic flow process of oil and water, with reservoir characteristics and environmental conditions continually evolving as the field evolves. Particularly when a waterflooding reservoir reaches a stage of ultra-high water cut, prolonged waterflooding intensifies challenges in reservoir development: the exacerbation of reservoir heterogeneity and development behaviors disrupts the initial understanding of the reservoir's liquid production capacity from current development conditions. Thus, it becomes imperative to adjust the productivity prediction methods for oil wells in heterogeneous waterflooding reservoirs. Leveraging the flow simulation of reservoir micro channel networks, and integrating features such as the geometric characteristics of the reservoir percolation field, micro channel characteristics, interlayer differences of mixed layers, degree of plane heterogeneity, production pressure differentials, and fluid properties, a visual sand filling experimental model is established that adheres to specific similarity criteria. Using this sand filling experimental model, we simulate the percolation characteristics of oil–water two-phase flow during the waterflooding process, and uncover the diverse influencing factors and their varying degrees of impact on the oil-phase flow during this waterflooding phase. Qualitative and semi-quantitative percolation simulation experiments are employed to intuitively demonstrate the interlayer interference, degree of plane heterogeneity, and oil–water distribution in heterogeneous reservoirs, which influence the change in oil well productivity during waterflooding. This lays bare the microscopic percolation mechanisms behind the productivity changes in heterogeneous waterflooding reservoirs. The simulation experiment results show that the higher the permeability, the stronger the micro-heterogeneity, and the smaller the overall mobility increase after flooding, the smaller the JLDmax obtained by testing or calculation. At the same permeability, the greater the driving pressure difference, the greater the microscopic sweep coefficient within the pore network, and the greater the mobility increase after flooding, the greater the JLDmax. There is interlayer interference in commingled mining, and the higher the permeability of the high-permeability layer (the greater the interlayer difference), the higher the initial productivity of the commingled well. However, due to the high permeability layer being prone to flooding, resulting in ineffective water circulation, the low-permeability tube is difficult to completely flood, resulting in a small increase in overall mobility, and therefore, JLDmax is small. Water drive preferentially breaks through the high permeability zone on the plane, and the shape of the water drive sweep zone is controlled by the planar permeability gradient, the width of the high permeability zone, and the displacement pressure difference.
Measurement of high water-cut heavy oil flow based on differential pressure of swirling flow
Authors: Wang Zhi-Hui , Zhang Xing-Kai , Liao Rui-Quan , Ma Zhi-Xiong , Wang Dong , Yang Wei-Xia
Published: January 2024

Real-time measurement of heavy oil production is critical to ensure stable production. Due to the complex kinematic characteristics of heavy oil, existing methods cannot accurately measure its flow rate and water cut. In this paper, a novel method is proposed to measure the high water-cut heavy oil flow by using the differential pressure of the two-phase swirling flow in the pipe. For the swirling flow in the pipe, the radial differential pressure and the axial differential pressure exist simultaneously, which are very sensitive to the flow rate and water cut. The formation mechanism of the two kinds of differential pressure is analyzed theoretically, and their relationship with flow rate and water cut is studied by experiment and numerical simulation. The measurement model of heavy oil–water two-phase flow on the above relations is validated by field experiments. The radial differential pressure is only related to the two-phase flow rate, varying exponentially with the flow rate when the oil viscosity is greater than 10 000 mPa s. This characteristic is very useful for the heavy oil–water two-phase flow measurement. The axial differential pressure decreases with the increase in water cut in cases of water cut <85%, while it increases with the water cut in cases of water cut >85%. With the increase in water cut, the ratio of axial differential pressure to radial differential pressure first decreases and then increases. The relative errors of the established measurement model for flow rate and water cut are 0.19%–17.92% and 0.21%–15.5%, respectively, and more than 70% of the measurements with a relative error of less than 10%. The study of the heavy oil–water two-phase flow measurement method can optimize the measurement cost and accelerate the process of intelligent oilfield construction.
Improved dynamic characteristics of oxide electrolyte-gated transistor for time-delayed reservoir computing
Authors: Fang Renrui , Li Xufan , Ren Kuan , Zhang Woyu , Xu Han , Wang Lingfei , Shang Dashan
Published: January 2024

Time-delayed reservoir computing (RC) equipped with prominent superiorities such as easy training and friendly hardware implementation is identified as a high-efficient answer to complex temporal tasks, and thereby draws increasing attention. Oxygen ion-based oxide electrolyte-gated transistor (Ox-EGT) with rich ion dynamic characteristics is deemed as a promising candidate for RC. However, it is still a challenge to produce the required dynamic characteristics for RC implementation. Herein, we develop an Ox-EGT with an oxygen vacancy-electron-coupled electric-double-layer at the electrolyte/channel interface to implement time-delayed RC. Effects of oxygen vacancy concentration on the short-term plasticity are investigated, revealing the optimal concentration range of oxygen vacancies for the dynamic characteristics improvement. The underlying physical mechanism is demonstrated by TCAD simulations. Simulations using the waveform classification and handwritten-digit recognition tasks validate the good information processing ability of the Ox-EGT RC system. These results provide a promising approach to exploit Ox-EGT dynamics for large-scale and energy-efficient neuromorphic computing hardware.
On low-frequency unsteadiness of single-incident and dual-incident shock waves/turbulent boundary layer interactions with large-scale separations
Authors: Li Xin , Wang Zi-Yun , Tan Hui-Jun , Yu Hang , Zhang Hao , Zhang Yue
Published: January 2024

Interactions between turbulent boundary layer and single-incident or dual-incident shock waves are commonly observed in supersonic inlets. To provide novel insights into the unsteadiness of these interactions, six incident shock wave/turbulent boundary layer interactions (ISWTBLIs), including both single-ISWTBLIs and dual-ISWTBLIs, are experimentally investigated using dynamic wall-pressure measurements at Mach 2.73 flow conditions. Through spectral analysis and correlation analysis, the unsteadiness characteristics of single-ISWTBLIs and dual-ISWTBLIs are comparatively examined, revealing significant influences of shock-wave strength and shock-wave distance on low-frequency unsteadiness. Specifically, both regions near the separation and reattachment points exhibit distinct low-frequency unsteadiness in single-ISWTBLIs and dual-ISWTBLIs with relatively strong separations. An increase in the deflection angle from 10° to 12° in single-ISWTBLIs extends the streamwise separation length, while causing a dramatic decrease in both characteristic frequency and normalized characteristic frequency (Strouhal number) of low-frequency unsteadiness. However, for dual-ISWTBLIs, as the shock-wave distance increases, there is an initial increase followed by a subsequent decrease in the separation length accompanied by a continuously increasing characteristic frequency, thus indicating a different relationship between separation length and characteristic frequency of unsteadiness in dual-ISWTBLIs in comparison with that observed in single-ISWTBLIs. Moreover, correlation analysis revealed that the pressure signals in the reattachment region are of strong negative correlation with those near the separation-shock foot, and the correlation increases with increasing shock-wave strength in single-ISWTBLIs and decreasing shock-wave distance in dual-ISWTBLIs.
Fast crystal growth in deeply undercooled ZrTi melts
Authors: Yan Zhihuang , Huang Feiqi , Wu Yanxue , Liu Huashan , Peng Hailong
Published: January 2024

We investigate the growth of crystals in Zr50Ti50 melts by classical molecular-dynamics simulations with an embedded atom method and a Stillinger–Weber potential model. Both models display fast solidification rates that can be captured by the transition state theory or the Ginzburg–Landau theory at small undercoolings. Fast crystal-growth rates are found to be affected by the pre-existing ordering in liquids, such as the body-centered cubic-like and icosahedral-like structures. The interface-induced ordering unveiled by the crystal-freezing method can explain the rate difference between these two models. However, these orderings fail to rationalize the temperature evolution of the growth rate at deep undercoolings. We correlate the growth kinetics with the detailed dynamical processes in liquids, finding the decoupling of hierarchic relaxation processes when collective motion emerges in supercooled liquids. We find that the growth kinetics is nondiffusive, but with a lower activation barrier corresponding to the structural relaxation or the cage-relative motion in ZrTi melts. These results explore a new relaxation mechanism for the fast growth rate in deeply undercooled liquids.
Quantitative characterization of the pseudo-boiling contribution to supercritical heat transfer
Authors: He Xiaotian , Xu Jinliang , Xie Jian
Published: January 2024

This paper explores the supercritical heat transfer mechanism by characterizing the boiling contribution ratio qb/q, where qb is the boiling heat flux and q is the applied heat flux. Experiments are performed using nickel–chromium wire in 15 °C liquid carbon dioxide at 5.2, 7.6, 9.0, and 11.0 MPa. The evaporation heat flux qe is the amount of heat used for vapor generation, while qb is the heat transfer in the bulk liquid due to the disturbance of the flow/temperature field by vapor–liquid interface motion. A data processing procedure is developed to measure qb/q from the captured images. Similar trends appear for both supercritical pseudo-boiling and subcritical boiling. The evaporation-like regime at supercritical pressures reaches qb/q = 0.21–0.43, while the film boiling (evaporation) regime achieves qb/q = 0.08. In the supercritical-boiling-like regime, qb/q increases sharply from 0.19 to 0.65, whereas in the subcritical-nucleate-boiling regime, qb/q maintains a value of 0.30 followed by a rapid rise to 0.68 under a vigorous bubble merging and departing mechanism. At both subcritical and supercritical pressures, the heat transfer deteriorates in the evaporation regime, but is significantly enhanced by phase-change-induced flow/temperature field perturbations. The boiling curves differ in the two pressure domains. At supercritical pressures, natural convection transitions smoothly to the evaporation-like regime, then to the boiling-like regime. At subcritical pressures, a steep transition from natural convection to nucleate boiling occurs, and then, film boiling is induced through the action of surface tension. The above findings complete the inverse boiling curves in the two pressure domains.
Experimental study on laser cutting process of titanium–zirconium amorphous alloy
Authors: Yao YanSheng , Xu XinPeng , Zhang Chenglin , Ma Xiaoqiang
Published: January 2024

This paper aims to assess the effects of various laser cutting parameters on the surface roughness of 2 mm thick titanium–zirconium amorphous alloy sheets. With multiple linear regression, a mathematical model was proposed to predict the maximum height of surface Sz as a function of two laser cutting parameters: cutting speed and assist gas pressure. The adequacy of the proposed model was evaluated using the analysis of variance method. Scanning electron microscopy was then used to observe the surface topography of the material following laser cutting under different conditions. It was found that for a fixed laser power, cutting speed dominates the parameter that determines the maximum height of surface roughness.
The mobilization mechanism of low oil saturation reservoirs
Authors: Bai Hao , Zhou Fujian , Wu Junlin , Zhang Kun , Ding Zhiyuan , Xu Hang , Dong Yuepeng , Zhang Mengchuan , Yao Erdong
Published: January 2024

After fracturing with a guar fluid system in Chang 8 oil reservoir, some wells have high oil production, and some have low production and even only produce water. Therefore, a comparative study is carried out in oil-producing and water-producing wells. The results show that: ① Organic wax adsorbed in oil-producing and water-producing well core pores accounts for 95.39% and 56.67%, respectively, making wells strong oil-wet. A certain proportion of inorganic salts and some other oil-wet organic compounds exist in water-producing wells. ② Under the reservoir conditions, the oil wettability of the water-producing well core is strong, and its original formation wettability is also oil-wet. The original wettability of the oil-producing well formation is water-wet, with oil production capacity. ③ The core residual oil saturation using the guar fluid is 24.7%–29.87%. This results in no oil phase permeability or difficulty to mobilize oil in most oil reservoirs. ④ Forced displacement can mobilize oil in large pores and has a significant effect in producing well, with mobilization efficiency of 53.49%. This article elucidates the wettability formation and crude oil mobilization mechanism of two types of wells, providing direction for the development of this type of reservoir.
Enhancement of coercivity in polybenzoxazine/CoxMg1−xFe2O4 nanoferrite composites: Synthesis and characterization
Authors: Ghosh Ashesh , Zaheen Muntaka , Islam Ariful , Rahman Md. Sohanur , Sharif Ahmed , Hoque Sheikh Manjura
Published: January 2024

In this research, we synthesize composites of CoxMg1−xFe2O4 (0 ≤ x ≤ 1) spinel nano-ferrites and polybenzoxazine (PBZ) and characterize their structural, optical, and magnetic properties. The magnetic nanoparticles are fabricated using the chemical co-precipitation method. The benzoxazine (BZ) monomer is synthesized by Mannich condensation reaction using aniline, paraformaldehyde, and phenol. Specific weights of the ferrite particles and BZ monomer are then mixed and thermally treated to produce the composites. X-ray diffraction (XRD) ensures that the desired spinel phase is formed. Moreover, the average crystallite size calculated from the XRD data ranges from 5.3 to 15.5 nm, which shows a fair degree of agreement with the transmission electron microscope images. Energy dispersive x-ray spectroscopy has confirmed the chemical composition of the samples. Fourier transform infrared characterization has been used to confirm the formation of BZ and PBZ. The magnetic properties at room temperature are evaluated using a vibrating sample magnetometer. Increasing the cobalt content has increased the saturation magnetization (Ms) significantly in the ferrite samples while creating composites with PBZ decreased the Ms values. We find that the coercivity (Hc) of the composites has increased more than that of the bare ferrite particles. The optical properties are evaluated by ultraviolet–visible spectrophotometry (UV–Vis) analysis, where it is found that the optical bandgap increases with an increase in the Mg component. Higher retention of the magnetic properties in the composite, especially coercivity (Hc), shows potential for applications that require high magnetic properties in combination with structural flexibility.
Fluorescence in the estimation of chlorophyll-a in public water reservoirs in the Brazilian cerrado
Authors: Souza de Barros Lucélia , de Almeida Tati , Moraes Soares Raquel , Dias Batista Bruno , Dantas Borges Henrique , Ennes Cicerelli Rejane
Published: January 2024

Context The usual strategy for monitoring of eutrophication process is the use of traditional limnological methods, based on laboratory analysis. These procedures involve costly and time-consuming analyses, usually with in vitro methodologies, which can still have limitations in terms of sensitivity and reliability, if poorly managed. Phytoplankton pigments, such as chlorophyll-a (Chl-a), are highly fluorescent and can provide the environmental status of water bodies. Aims This study aims to analyse, compare and evaluate an estimation of Chl-a through fluorescence in public water sources in the Brazilian cerrado. Exploratory statistical analyses were conducted by using absolute fluorescence units (AFU) and relative fluorescence units (RFU) compared with traditional laboratory data (standard procedure for the determination of Chl-a by spectroscopic methods) to evaluate the significance of differences in estimating Chl-a concentration. Subsequently, empirical models, based on spectral band combinations, were generated to convert fluorescence measurement in Chl-a concentration, by linear regression. Key results The generated model found a strong correlation and coefficient of determination (r = 0.88; R2 = 0.78). The efficiency of the model was also confirmed by statistical indicators (RMSE = 1.27, MAPE = 26.72 and BIAS = −6.32). Conclusions We concluded that the estimate of Chl-a through RFU was better than through AFU. Implications Therefore, based on the results of this study, it is recommended that RFU be used to obtain more precise and accurate estimates of Chl-a concentration through empirical models based on linear regression.
Family ideals in an era of low fertility
Authors: Aassve Arnstein , Adserà Alícia , Chang Paul Y. , Mencarini Letizia , Park Hyunjoon , Peng Chen , Plach Samuel , Raymo James M. , Wang Senhu , Jean Yeung Wei-Jun
Published: January 2024

Taking stock of individuals’ perceived family ideals is particularly important in the current moment given unprecedented fertility declines and the diversification of households in advanced industrial societies. Study participants in urban China, Japan, South Korea, Singapore, the United States, Italy, Spain, and Norway were asked to evaluate vignettes describing families whose characteristics vary on ten dimensions. In contrast to previous studies that focused on a single dimension, such as fertility ideals or gender roles, this holistic vignette approach identifies the relative importance of each dimension. Multilevel regression analysis reveals both expected and unexpected findings. Parenthood remains a positive ideal, but the number of children does not matter once other family dimensions are considered, a potentially important finding in light of conventional wisdom regarding the two-children ideal. When evaluating families with at least one child, respondents tend to positively evaluate more traditional arrangements, including valuing marriage relative to cohabitation and, particularly, divorce. Also, in addition to financial resources, good communication between immediate and extended family members, as well as maintaining respect in the larger community, are highly salient attributes of an ideal family. Notwithstanding some important cross-national differences, egalitarian gender roles and avoiding work–family conflict are also valued positively. Overall, even as the study reveals some notable variations between societies, respondents across countries identify similar components of an ideal family.
Bioorthogonal chemical labeling of endogenous neurotransmitter receptors in living mouse brains
Authors: Nonaka Hiroshi , Sakamoto Seiji , Shiraiwa Kazuki , Ishikawa Mamoru , Tamura Tomonori , Okuno Kyohei , Kondo Takumi , Kiyonaka Shigeki , Susaki Etsuo A. , Shimizu Chika , Ueda Hiroki R. , Kakegawa Wataru , Arai Itaru , Yuzaki Michisuke , Hamachi Itaru
Published: January 2024

Neurotransmitter receptors are essential components of synapses for communication between neurons in the brain. Because the spatiotemporal expression profiles and dynamics of neurotransmitter receptors involved in many functions are delicately governed in the brain, in vivo research tools with high spatiotemporal resolution for receptors in intact brains are highly desirable. Covalent labeling by chemical reaction (chemical labeling) of proteins without genetic manipulation is now a powerful method for analyzing receptors in vitro. However, selective target receptor labeling in the brain has not yet been achieved. This study shows that ligand-directed alkoxyacylimidazole (LDAI) chemistry can be used to selectively tether synthetic probes to target endogenous receptors in living mouse brains. The reactive LDAI reagents with negative charges were found to diffuse well over the whole brain and could selectively label target endogenous receptors, including AMPAR, NMDAR, mGlu1, and GABA
A
R. This simple and robust labeling protocol was then used for various applications: three-dimensional spatial mapping of endogenous receptors in the brains of healthy and disease-model mice; multi-color receptor imaging; and pulse–chase analysis of the receptor dynamics in postnatal mouse brains. Here, results demonstrated that bioorthogonal receptor modification in living animal brains may provide innovative molecular tools that contribute to the in-depth understanding of complicated brain functions.
Evaluating sequential and allosteric activation models in IKs channels with mutated voltage sensors
Authors: Fedida David , Sastre Daniel , Dou Ying , Westhoff Maartje , Eldstrom Jodene
Published: January 2024

The ion-conducting IKs channel complex, important in cardiac repolarization and arrhythmias, comprises tetramers of KCNQ1 α-subunits along with 1–4 KCNE1 accessory subunits and calmodulin regulatory molecules. The E160R mutation in individual KCNQ1 subunits was used to prevent activation of voltage sensors and allow direct determination of transition rate data from complexes opening with a fixed number of 1, 2, or 4 activatable voltage sensors. Markov models were used to test the suitability of sequential versus allosteric models of IKs activation by comparing simulations with experimental steady-state and transient activation kinetics, voltage-sensor fluorescence from channels with two or four activatable domains, and limiting slope currents at negative potentials. Sequential Hodgkin–Huxley-type models approximately describe IKs currents but cannot explain an activation delay in channels with only one activatable subunit or the hyperpolarizing shift in the conductance–voltage relationship with more activatable voltage sensors. Incorporating two voltage sensor activation steps in sequential models and a concerted step in opening via rates derived from fluorescence measurements improves models but does not resolve fundamental differences with experimental data. Limiting slope current data that show the opening of channels at negative potentials and very low open probability are better simulated using allosteric models of activation with one transition per voltage sensor, which implies that movement of all four sensors is not required for IKs conductance. Tiered allosteric models with two activating transitions per voltage sensor can fully account for IKs current and fluorescence activation kinetics in constructs with different numbers of activatable voltage sensors.
Implication of nano-Hertz stochastic gravitational wave on dynamical dark matter through a dark first-order phase transition
Authors: Jiang Siyu , Yang Aidi , Ma Jiucheng , Huang Fa Peng
Published: January 2024

For the first time, the expected stochastic gravitational wave background is probably discovered after observing the Hellings Downs correlation curve by several pulsar timing array (PTA) collaborations around the globe including NANOGrav, European PTA, Parkes PTA, and Chinese PTA. These new observations can help to explore or constrain the dark matter (DM) formation mechanisms in the early Universe. We study the implication of those results on the dynamical DM formation mechanisms through a dark first-order phase transition in the early Universe. Both the Q-ball DM and super-cool DM are investigated in the strong super-cooling dark phase transition scenario which may give an interpretation of the observed stochastic gravitational wave background.
Study on fracture characteristics and mechanisms of red sandstone under high-voltage pulse discharge
Authors: Hao Qiqi , Zhang Fengpeng , Peng Jianyu , Yan Guangliang , Du Chuan
Published: January 2024

To investigate the influences of geometrical size and discharge voltage of the pulse discharge equipment on the fracture characteristics and mechanisms of sandstone under high-voltage pulses, a series of experiments was conducted using a high-voltage pulse discharge device on sandstone circular disc specimens of sandstone with a thickness of 10 mm. These experiments covered a range of disc diameters ranging from 50 mm to 142 mm and discharge voltages from 15 kV to 40 kV. Through these experiments, the fracture characteristics of sandstone at both macroscopic and microscopic levels were investigated. In the experiments, a quantitative analysis of surface fracture was undertaken based on fracture density and fractal damage. Additionally, using the principle of energy equivalence, numerical simulation methods were used to study the damage evolution process in sandstone. The research results indicate that the formation and distribution of fractures in the sandstone specimens are significantly affected by geometrical size and discharge voltage. By analyzing the interaction between stress waves and fracture propagation, combined with indoor experimental results, the fracture mechanism was revealed. The high temperature and shock wave generated by the plasma channel leads to the crushing zone near the electrode, while the circumferential tensile component of the stress wave can result in radial fractures, and the reflected tensile wave leads to circumferential and radial fractures near the boundary.
Re-emerging magnetic order in correlated van der Waals antiferromagnet NiPS3
Authors: Zhou Xueli , Xu Haihong , Zhang Jiang , Tang Lingyun , Chen Xi , Mao Zhongquan
Published: January 2024

Van der Waals (vdW) gap is a significant feature that distinguishes vdW magnets from traditional magnets. Manipulating the magnetic properties by changing the vdW gap has been hot topic in condensed matter research. Here we report a re-emerging magnetic order induced by pressure in a correlated vdW antiferromagnetic insulator NiPS3. It is found that the interlayer magnetoresistance (MR) nearly vanishes at the critical pressure where the crystal structure transforms from C2/m phase to the sliding C2/m phase. On further compression within the sliding C2/m phase, a substantially enhanced MR emerges from low temperature associated with an insulator-to-metal transition, indicating a metallic antiferromagnetic phase. The enhanced re-emerging MR in sliding C2/m phase can be ascribed to the increasing magnetic interaction between neighboring layers due to the vdW gap narrowing. Our results provide important experimental clues for understanding the pressure effects on magnetism in correlated layered materials.
Fault prediction of unmanned aerial vehicles based on entropy weight fusion and temporal graph convolutional network with non-Euclidian structure
Authors: Zhang Shaohui , Yao Yongjie , Jiang Fei , Mo Jinhua , Wu Zhaoqian , Liang Jinglun
Published: January 2024

Predicting weak and hidden faults in unmanned aerial vehicles (UAVs) is challenging due to their variable operation conditions and complex mechanisms. Conventional neural network models process the multisensory data in the form of Euclidean structure, the intrinsic connections among the individual data points are easy to be disregarded. Additionally, multisensory data are always directly fed into the model without adequately considering the importance or contribution of each sensor. Hence, an UAV fault prediction method is proposed by combining entropy weight fusion with a temporal graph convolutional network (GCN) to address the above problems. Firstly, the importance of multisensory data of UAVs are evaluated by each entropy value, and the multisensory data fusion is further realized by multiplying corresponding signal and entropy weight. Secondly, the multisensory data combined with fusion data are transferred together into graph-structure by adjacent matrix based on the node connection between different sensor data. Finally, the graph-structure data with non-Euclidian distance properties are input into temporal GCN to both capture the spatial and temporal relationship of the data, achieving better fault prediction results of UAVs. It is demonstrated that the proposed method is both applicable and superior in characterizing and predicting fault time series information of UAVs through parameter analysis and comparison studies with various existing algorithms.
Preparation of a high-performance H2S gas sensor based on CuO/Co3O4 composite derived from bimetallic MOF
Authors: Li Zhanhong , Wang Xu , Yao Yu , Xin Jiangang , Xie Lili , Han Yutong , Zhu Zhigang
Published: January 2024

The bimetallic metal–organic frameworks (MOFs), Cu/Co-MOF, was synthesized through a solvothermal method and calcined to obtain CuO/Co3O4 composites. By adjusting the molar ratio between Cu and Co ions, a composite material of CuO/Co3O4 (Cu:Co = 1:1) was developed and showed excellent sensing capabilities, and the response reached as high as 196.3 for 10 ppm H2S detection. Furthermore, the optimal operating temperature as low as 40 °C was found. In comparison with the sensors prepared by pristine CuO and pristine Co3O4, the sensor based on CuO/Co3O4 composite exhibited a significant response. Additionally, the sensor can detect H2S gas down to 300 ppb. The gas sensing mechanism is discussed in depth from the perspective of p–p heterojunction formation between the p-type CuO and p-type Co3O4. The as-prepared CuO/Co3O4 composite-based sensor is expected to find practical application in the low-power monitoring of H2S.
Plasma kinetic simulation in Eulerian approach fully respecting f≥0 requirement and total particle number conservation
Authors: Lin H , Liu C P
Published: January 2024

Plasma kinetic simulation in Eulerian approach (PKSiEA) can yield a dynamic description on plasmas and hence is a popular method in theoretical plasmas physics. Its mathematical model consists of 8 members: 5 partial differential equations (PDEs), a phase space boundary condition and an initial condition of the distribution function (PDF) f, and a mandatory non-negativity requirement on f. Because Vlasov equation (VE) is a PDE with variable coefficients and the non-negativity requirement is mandatory, when 5 PDEs (4 Maxwell equations and the VE) are treated as an initial-value problem, the temporal evolution of f is difficult to be attacked by existing popular computational mathematics techniques, such as Fourier analysis technique and finite-difference technique, and hence these techniques do not yield efficient and reliable schemes of the PKSiEA. In a universal scheme of the PKSiEA presented here, because the phase space boundary condition f∣
r=∞,∣υ∣=c
= 0 causes the VE to yield a conservation of total particle number ∫fd
3
rd
3
υ, we propose an efficient and strict expression of the f-profile in terms of two classes of functions of phase space coordinates

r
,
υ

, and the VE displays a universal relation between two classes. By this new expression, we express the initial-value problem of 5 PDEs in terms of allowed deformation modes from an initial f-profile, and ensure the PKSiEA fully respecting the non-negativity requirement on f.
Degradable and biocompatible nanofibrous scaffold incorporating a natural cell culture medium for skin tissue engineering
Authors: Afrashi Mehran , Semnani Dariush , Hashemibeni Batool , Shokrgozar Mohammad Ali
Published: January 2024

The use of green materials in biomedical and bioengineering applications has significantly expanded in recent years. In this study, we utilized egg white (EW) as an abundant and cost-effective green material, blended with polycaprolactone/gelatin (PCL/Gel), to fabricate an electrospun scaffold. The fabricated samples underwent comprehensive physicochemical characterization, including SEM, FT-IR spectroscopy, tensile assay, and contact angle measurement. These optimized samples were subsequently employed for cell culture experiments. The average diameter of the prepared nanofibers ranged from 215.9 to 434.1 nm. FT-IR and DSC assays confirmed the physical blending of EW, PCL, and Gel without any occurrence of new chemical reactions. The contact angle test demonstrated a decrease in scaffold hydrophilicity from 26.25° to 116.5° with an increase in EW content within the PCL/Gel blend (0%-15%). Notably, the electrospun PCL/Gel nanofibrous mat containing 10% EW exhibited enhanced bioactivity compared to other samples with varying amounts of EW. Consequently, incorporating 10% EW into PCL/Gel nanofibers can significantly improve the efficiency of fibroblast culture. This research introduces a novel nanofibrous scaffold for skin tissue engineering, incorporating Gel and EW as low-cost and readily available materials, with great potential for various biological applications.
Pulsar kicks in ultralight dark matter background induced by neutrino oscillation
Authors: Lambiase Gaetano , Poddar Tanmay Kumar
Published: January 2024

The interaction of neutrinos with ultralight scalar and vector dark matter backgrounds induce a modification of the neutrino dispersion relation. The effects of this modification are reviewed in the framework of asymmetric emission of neutrinos from the supernova core, and, in turn, of pulsar kicks. We consider the neutrino oscillations, focusing in particular to active-sterile conversion. The ultralight dark matter induced neutrino dispersion relation contains a term of the form δ
Ω · p̂, where δ
Ω is related to the ultralight dark matter field and p̂ is the unit vector along the direction of neutrino momentum. The relative orientation of p with respect to δ
Ω affects the mechanism for the generation of the observed pulsar velocities. We obtain the resonance condition for the active-sterile neutrino oscillation in ultralight dark matter background and calculate the star parameters in the resonance surface so that both ultralight scalar and vector dark matter backgrounds can explain the observed pulsar kicks. The asymmetric emission of neutrinos in presence of ultralight dark matter background results gravitational memory signal which can be probed from the future gravitational wave detectors such as adLIGO (advanced LIGO), adVIRGO (advanced VIRGO), DECIGO (DECi-hertz Interferometer Gravitational wave Observatory), BBO (Big Bang Observer), and ET (Einstein Telescope). We also establish a relation between the ultralight dark matter parameters and the Lorentz and CPT invariance violation parameters.
Strong decays of the P
c(4312) and its isospin cousin via the QCD sum rules*
Authors: Wang Xiu-Wu , Wang 王 Zhi-Gang 志刚
Published: January 2024

In this study, considering the conservation of isospin in the strong decays, we investigate the strong decays of the pentaquark molecule candidate

and its possible higher isospin cousin

in the framework of the QCD sum rules. Further, the pole residue of the Δ baryon with isospin eigenstate

is obtained. If the possible pentaquark molecule candidate

could be determined, it would shed light on the interpretations of the

states in future experiments.
Prediction of cognitive conflict during unexpected robot behavior under different mental workload conditions in a physical human–robot collaboration
Authors: John Alka Rachel , Singh Avinash K , Gramann Klaus , Liu Dikai , Lin Chin-Teng
Published: January 2024

Objective. Brain–computer interface (BCI) technology is poised to play a prominent role in modern work environments, especially a collaborative environment where humans and machines work in close proximity, often with physical contact. In a physical human robot collaboration (pHRC), the robot performs complex motion sequences. Any unexpected robot behavior or faulty interaction might raise safety concerns. Error-related potentials, naturally generated by the brain when a human partner perceives an error, have been extensively employed in BCI as implicit human feedback to adapt robot behavior to facilitate a safe and intuitive interaction. However, the integration of BCI technology with error-related potential for robot control demands failure-free integration of highly uncertain electroencephalography (EEG) signals, particularly influenced by the physical and cognitive state of the user. As a higher workload on the user compromises their access to cognitive resources needed for error awareness, it is crucial to study how mental workload variations impact the error awareness as it might raise safety concerns in pHRC. In this study, we aim to study how cognitive workload affects the error awareness of a human user engaged in a pHRC. Approach. We designed a blasting task with an abrasive industrial robot and manipulated the mental workload with a secondary arithmetic task of varying difficulty. EEG data, perceived workload, task and physical performance were recorded from 24 participants moving the robot arm. The error condition was achieved by the unexpected stopping of the robot in 33% of trials. Main results. We observed a diminished amplitude for the prediction error negativity (PEN) and error positivity (Pe), indicating reduced error awareness with increasing mental workload. We further observed an increased frontal theta power and increasing trend in the central alpha and central beta power after the unexpected robot stopping compared to when the robot stopped correctly at the target. We also demonstrate that a popular convolution neural network model, EEGNet, could predict the amplitudes of PEN and Pe from the EEG data prior to the error. Significance. This prediction model could be instrumental in developing an online prediction model that could forewarn the system and operators of the diminished error awareness of the user, alluding to a potential safety breach in error-related potential-based BCI system for pHRC. Therefore, our work paves the way for embracing BCI technology in pHRC to optimally adapt the robot behavior for personalized user experience using real-time brain activity, enriching the quality of the interaction.
Improving the performance of P300-based BCIs by mitigating the effects of stimuli-related evoked potentials through regularized spatial filtering
Authors: Mobaien Ali , Boostani Reza , Sanei Saeid
Published: January 2024

Objective. the P300-based brain–computer interface (BCI) establishes a communication channel between the mind and a computer by translating brain signals into commands. These systems typically employ a visual oddball paradigm, where different objects (linked to specific commands) are randomly and frequently intensified. Upon observing the target object, users experience an elicitation of a P300 event-related potential in their electroencephalography (EEG). However, detecting the P300 signal can be challenging due to its very low signal-to-noise ratio (SNR), often compromised by the sequence of visual evoked potentials (VEPs) generated in the occipital regions of the brain in response to periodic visual stimuli. While various approaches have been explored to enhance the SNR of P300 signals, the impact of VEPs has been largely overlooked. The main objective of this study is to investigate how VEPs impact P300-based BCIs. Subsequently, the study aims to propose a method for EEG spatial filtering to alleviate the effect of VEPs and enhance the overall performance of these BCIs. Approach. our approach entails analyzing recorded EEG signals from visual P300-based BCIs through temporal, spectral, and spatial analysis techniques to identify the impact of VEPs. Subsequently, we introduce a regularized version of the xDAWN algorithm, a well-established spatial filter known for enhancing single-trial P300s. This aims to simultaneously enhance P300 signals and suppress VEPs, contributing to an improved overall signal quality. Main results. analyzing EEG signals shows that VEPs can significantly contaminate P300 signals, resulting in a decrease in the overall performance of P300-based BCIs. However, our proposed method for simultaneous enhancement of P300 and suppression of VEPs demonstrates improved performance in P300-based BCIs. This improvement is verified through several experiments conducted with real P300 data. Significance. this study focuses on the effects of VEPs on the performance of P300-based BCIs, a problem that has not been adequately addressed in previous studies. It opens up a new path for investigating these BCIs. Moreover, the proposed spatial filtering technique has the potential to further enhance the performance of these systems.
Ultrahigh neutral pressures in the sub-divertor of the Large Helical Device
Authors: Wenzel U. , Motojima G. , Kobayashi M. , Goto M. , Hayashi Y. , Masuzaki S. , Kawamura G. , Jagielski B. , Haak V.
Published: January 2024

In the Large Helical Device (LHD) a low temperature mode (LTM) of the helical divertor was discovered. It combines particle detachment and very large sub-divertor pressures up to 1.4 Pa. During the LTM, the electron temperature in the divertor was in the range from 0.25 to 0.42 eV so that volume recombination occurred. This result is remarkable because in the stellarators LHD and Wendelstein 7-X only low sub-divertor pressures (0.03–0.3 Pa) were expected and measured up to now due the loss of pressure conservation along flux tubes by an enhanced cross-field transport. It demonstrates that the more complex, three-dimensional divertors of stellarators can achieve a similar performance with respect to particle exhaust and detachment like the geometrically simpler poloidal divertors in tokamaks even if the favorable effect of flux amplification is absent. The LTM of the helical divertor depends, however, on the magnetic configuration, i.e. on geometry. It was only observed in the inward shifted configuration with

R

a
x

=
3.55

 m, but not in the more frequently studied configuration with

R

a
x

=
3.6

 m. A nuclear fusion reactor based on the heliotron concept (DEMO) would benefit from the LTM by the very compact divertor configuration and the excellent performance.