bluuebunny/crossref_metadata_2025 huggingface dataset:
What is the role of architects and urban planners in crime prevention?
Authors: Ceccato Vania , Brantingham Patricia
Published: August 2024

In this article, we discuss the role of urban planning professionals in situational crime prevention. We begin by examining their role as city “shapers” and the reasons behind their frequent neglect of crime-related factors in their decision-making process. We also explore why criminology tends to underestimate the influence of urban planning professionals on the urban environment, a factor crucial for effective crime prevention. To highlight the disconnection between urban planning and crime prevention, we present findings from a survey conducted with urban planners and safety experts in 290 Swedish municipalities. The article concludes with future research and practice recommendations, stressing the urgent need for improved communication and collaboration between urban shapers and environmental criminologists and a more comprehensive understanding from all parties involved.
GaN-based tunnel junction with negative differential resistance by metalorganic chemical vapor deposition
Authors: Hagar B. G. , Routh E. L. , Abdelhamid M. , Colter P. C. , Muth J. , Bedair S. M.
Published: August 2024

We present metalorganic chemical vapor deposition-grown III-nitride tunnel junction (TJ) devices showing negative differential resistance (NDR) under forward bias with a peak to valley ratio of 1.3 at room temperature. Previously, NDR in GaN material systems has only been achievable utilizing molecular beam epitaxy or polarization enhanced AlGaN interlayers. The TJ devices presented here utilize structures based on p+InGaN/n+InGaN materials with the n-side of the junction doped with both Si and Mg and with electron and hole concentrations roughly in the 1019 cm−3 range. The Mg precursor flow is maintained at a constant rate during the whole TJ growth. This co-doped technique can eliminate several Mg-related issues such as delayed incorporation, the memory effect, and Mg solid-state diffusion. Structures grown on relaxed InGaN semibulk templates show enhanced hole concentrations and improved TJ performance.
Numerical analysis of the effect of zeta potential on the performance of micro-electrohydrodynamic conduction pump
Authors: Wang Junxiu , Peng Yuxing , Vázquez Pedro A. , Wu Jian
Published: August 2024

As an advanced flow-drive technology, micro-electrohydrodynamic (EHD) conduction pumping has become a new prospect in many micro-scale industrial applications, including lab-on-chip devices and microfluidic cooling systems. Under micro-scale conditions, the effect of the electric double layer (EDL) has to be considered. Zeta potential is an adjustable and measurable experimental value and has been proposed to estimate the strength of EDL in simulations. In this work, the effect of zeta potential on the performance of micro-EHD conduction pumping has been numerically investigated. A method to estimate the surface charge density without the Debye–Hückel approximation was introduced. A two-dimensional flush electrode configuration with a typical size of 50 μm was considered. The coupled series of governing equations was implemented in the finite-volume framework of OpenFOAM® and solved based on the PIMPLE algorithm. The results show that zeta potential can enhance the asymmetry of the electric field and change the distribution of the Coulomb force. For the construction considered in this work, negative zeta potential can reduce the size and strength of the vortex in the flow field and improve the pump's net flow rate and static pressure. In contrast, positive zeta potential has the opposite effect. Maximum performance enhancement up to 94.8%–115.1% has been observed for different electrode length ratios within the parameters studied in this paper. The results guide the zeta potential optimization of micro-EHD conduction pumping. By matching the pairs of solid and liquid materials, researchers can adjust zeta potential to an optimal value, thereby improving the pump performance.
Kinetic model of anisotropic force-free current sheets
Authors: Wu Ya-Ze , Yang Fan , Zhou Xu-Zhi , Artemyev Anton V. , An Xin , Liu Zhi-Yang , Wang Shan , Zong Qiu-Gang
Published: August 2024

Force-free current sheets, characterized by field-aligned electric currents and approximately uniform plasma pressures, have been widely observed in the planetary magnetosphere and throughout the heliosphere. Recent observations of force-free current sheets have clearly shown the presence of anisotropic electron distributions with different temperatures perpendicular and parallel to the local magnetic field. In most of the kinetic models for one-dimensional, force-free current sheets, however, the electron distributions are nearly isotropic, which necessitates the construction of new models accounting for the electron temperature anisotropy. In this paper, we develop a model for anisotropic force-free current sheets, by incorporating the magnetic moment as an additional invariant of motion into the nearly isotropic electron distribution function of a previous model. Despite the different electron distributions, the electromagnetic profiles of the new model are often close to those in the nearly isotropic model. The applicability of our model is then validated via a comparison to a typical force-free current sheet in the Jovian magnetodisk, which shows good agreement between the model and the observations.
Surface dependence of electronic growth of Cu(111) on MoS2
Authors: Harms Haley A. , Cunningham Connor J. , Kidd Timothy E. , Stollenwerk Andrew J.
Published: August 2024

Scanning tunneling microscopy shows that copper deposited at room temperature onto a freshly exfoliated MoS2 surface forms Cu(111) clusters with periodic preferred heights of 5, 8, and 11 atomic layers. These height intervals correlate with Fermi nesting regions along the necks of the bulk Cu Fermi surface, indicating a connection between physical and electronic structures. Density functional theory calculations of freestanding Cu(111) films support this as well, predicting a lower density of states at the Fermi level for these preferred heights. This is consistent with other noble metals deposited on MoS2 that exhibit electronic growth, in which the metal films self-assemble as nanostructures minimizing quantum electronic energies. Here, we have discovered that it is critical for the metal deposition to begin on a clean MoS2 surface. If copper is deposited onto an already Cu coated surface, even if the original film displays electronic growth, the resulting Cu film lacks quantization. Instead, the preferred heights of the Cu clusters simply increase linearly with the amount of Cu deposited upon the surface. We believe this is due to different bonding conditions during the initial stages of growth. Newly deposited copper would bond strongly to the already present copper clusters, rather than the weak bonding, which exists to the van der Waals terminated surface of MoS2. The stronger bonding with previously deposited clusters hinders additional Cu atoms from reaching their lowest quantum energy state. The interface characteristics of the van der Waals surface enable surface engineering of self-assembled structures to achieve different applications.
A new natural fracture width prediction method based on fluid dynamics constrained neural network
Authors: Liang Junqiao , Yang Hu , Xiong Shilong , Zhang Donghua , Xian Xinlong , Zhou Penggao
Published: August 2024

The width of natural fractures is an important parameter in the leak prevention and plugging operations for oil and gas drilling. To accurately predict the fracture width of the leaking formation when well leakage occurs during oilfield drilling, based on the mud logging data of adjacent oil wells during the loss process, the Spearman correlation analysis and data normalization methods were used to preprocess the data. A new method was then established to predict the natural fracture width based on FDCNN (Fluid Dynamics Constrained Neural Network), which is a neural network algorithm constrained by the prior knowledge of fluid dynamics. In this method, first, based on the fluid dynamics prior knowledge that there is a strict positive partial derivative relationship between the natural fracture width and the leakage volume and pressure difference in the fluid dynamics model, the constraint conditions of the neural network were optimized. Second, the augmented Lagrange multiplier method was used to establish the performance index of the neural network through a multiplier and a penalty factor. Finally, the model was trained using the backpropagation learning rule and gradient descent training methods. The results indicate that this method, utilizing FDCNN, can train the model with a small sample training set, demonstrating superior generalization ability and prediction accuracy compared to traditional fluid dynamics models and Data-Driven Neural Network (which refers to an algorithm training a neural network solely on data samples without using fluid dynamics prior knowledge). This approach can effectively reduce the prediction error of fracture width, providing valuable reference for the development of field plugging programs.
Evaluation of performance for day-ahead solar irradiance forecast using numerical weather prediction
Authors: Dou Weijing , Wang Kai , Shan Shuo , Li Chenxi , Wen Jiahao , Zhang Kanjian , Wei Haikun , Sreeram Victor
Published: August 2024

Numerical weather prediction (NWP) is widely used for day-ahead solar irradiance forecast, which is essential for applications in day-ahead energy market and energy management of different scales ranging from public level to civil level. In the literature, many NWP correction methods have been proposed to obtain more accurate solar irradiance forecast. However, when facing different real-world scenarios, it is crucial to efficiently design corresponding correction schemes, which require a detailed and reliable error evaluation foundation. To solve this problem, the performance for day-ahead NWP Global Horizontal Irradiance (GHI) forecast is evaluated under different weather conditions and seasons. The statistical analysis was conducted at each time of day and each NWP GHI forecast level with both publicly available datasets and actual field dataset, aiming to explore the detailed error characteristics of NWP GHI forecasts. The results demonstrate variations in NWP GHI error across diverse weather conditions and seasons, which indicates that future NWP GHI corrections should be developed under different weather conditions and seasons. For weather conditions, NWP GHI forecasts have the lowest accuracy during overcast conditions, followed by cloudy conditions, while the highest accuracy is observed during sunny conditions. Moreover, overestimations are more likely to occur during overcast and cloudy conditions. For seasons, the accuracy of NWP GHI forecasts is generally highest during winter. Additionally, we have summarized some common error characteristics under different weather conditions and seasons. This study provides useful information for improving the accuracy and efficiency of NWP correction works and for the stable operation of power systems.
Mechanical response of double-stranded DNA: Bend, twist, and overwind
Authors: Mou Xuankang , Liu Kai , He Linli , Li Shiben
Published: August 2024

We employed all-atom molecular dynamics simulations to explore the mechanical response of bending, twisting, and overwinding for double-stranded DNA (dsDNA). We analyzed the bending and twisting deformations, as well as their stiffnesses, using the tilt, roll, and twist modes under stretching force. Findings indicate that the roll and twist angles vary linearly with the stretching force but show opposite trends. The tilt, roll, and twist elastic moduli are considered constants, while the coupling between roll and twist modes slightly decreases under stretching force. The effect of the stretching force on the roll and twist modes, including both their deformations and elasticities, exhibits sequence-dependence, with symmetry around the base pair step. Furthermore, we examined the overwinding path and mechanism of dsDNA from the perspective of the stiffness matrix, based on the tilt, roll, and twist modes. The correlations among tilt, roll, and twist angles imply an alternative overwinding pathway via twist–roll coupling when dsDNA is stretched, wherein entropic contribution prevails.
Relativistic calculations of neutron and gamma-ray spectra from beam–target reactions in magnetized plasmas
Authors: Valentini A. , Reman B. C. G. , Nocente M. , Eriksson J. , Järleblad H. , Moseev D. , Rud M. , Snicker A. , Salewski M.
Published: August 2024

We present a fully relativistic analytical model for calculating synthetic spectra from beam–target fusion reactions. When the target particle is assumed at rest, Monte Carlo sampling of reactant velocities can be avoided, and spectrum computations are considerably faster. A fully analytical treatment additionally gives more insight into the spectrum formation. The fully relativistic formulation now makes it possible to handle massless particles in the model, for example from one-step gamma-ray reactions, and the results are corroborated by simulations from established codes.
Effects of wave damping and finite perpendicular scale on three-dimensional Alfvén wave parametric decay in low-beta plasmas
Authors: Li Feiyu , Fu Xiangrong , Dorfman Seth
Published: August 2024

Shear Alfvén wave parametric decay instability (PDI) provides a potential path toward significant wave dissipation and plasma heating. However, fundamental questions regarding how PDI is excited in a realistic three-dimensional (3D) open system and how the finite perpendicular wave scale—as found in both laboratory and space plasmas—affects the excitation remain poorly understood. Here, we present the first 3D, open-boundary, hybrid kinetic-fluid simulations of kinetic Alfvén wave PDI in low-beta plasmas. Key findings are that the PDI excitation is strongly limited by the wave damping present, including electron–ion collisional damping (represented by a constant resistivity) and geometrical attenuation associated with the finite-scale Alfvén wave, and ion Landau damping of the child acoustic wave. The perpendicular wave scale alone, however, plays no discernible role: waves of different perpendicular scales exhibit similar instability excitation as long as the magnitude of the parallel ponderomotive force remains unchanged. These findings are corroborated by theoretical analysis and estimates. This new understanding of 3D kinetic Alfvén wave PDI physics is essential for laboratory study of the basic plasma process and may also aid future evaluation of the relevance/role of PDI in low-beta space plasma.
Statistical evaluation of electric field distributions in 3D composites with a random spatial distribution of dielectric inclusions
Authors: Weber Tobias , Dyczij-Edlinger Romanus , Pelster Rolf
Published: August 2024

Electromagnetic applications of composites often impose constraints on the internal electric fields, such as an upper limit on the field strength to prevent local heating or dielectric breakthrough. However, owing to heterogeneity, the local fields in a composite differ from those in a homogeneous material. Moreover, they are accessible neither by experiment nor by effective medium theories, at least for arbitrary microstructures. In this work, we use numerical simulations to evaluate the electric field distribution and the effective permittivity for 3D systems of monodisperse impenetrable spheres dispersed in a continuous matrix phase. We restrict ourselves to loss-free dielectric materials and to a random spatial distribution of particles. Samples are placed in a parallel plate waveguide and exposed to a transverse electromagnetic wave. The local field amplitudes are calculated via the finite element method and are normalized to those of a homogeneous sample exhibiting the same effective permittivity and geometry. We analyze the distribution of the local electric field strength in both constituents, namely, particles and matrix. Thus, we evaluate mean values and standard deviations as well as the field strengths characterizing the highest and lowest percentiles. Increasing particle concentration or permittivity enhances heterogeneity, and so the local electric field strength in some domains can become much higher than its average value. The methods we apply here can also be used in further investigations of more complex systems, including lossy materials and agglomerating particles.
Robustness of higher-order interdependent networks with reinforced nodes
Authors: Zhang Junjie , Liu Caixia , Liu Shuxin , Wang Yahui , Li Jie , Zang Weifei
Published: August 2024

In reality, pairwise interactions are no longer sufficient to describe the higher-order interactions between nodes, such as brain networks, social networks, etc., which often contain groups of three or more nodes. Since the failure of one node in a high-order network can lead to the failure of all simplices in which it is located and quickly propagates to the whole system through the interdependencies between networks, multilayered high-order interdependent networks are challenged with high vulnerability risks. To increase the robustness of higher-order networks, in this paper, we proposed a theoretical model of a two-layer partial high-order interdependent network, where a proportion of reinforced nodes are introduced that can function and support their simplices and components, even losing connection with the giant component. We study the order parameter of the proposed model, including the giant component and functional components containing at least one reinforced node, via theoretical analysis and simulations. Rich phase transition phenomena can be observed by varying the density of 2-simplices and the proportion of the network’s reinforced nodes. Increasing the density of 2-simplices makes a double transition appear in the network. The proportion of reinforced nodes can alter the type of second transition of the network from discontinuous to continuous or transition-free, which is verified on the double random simplicial complex, double scale-free simplicial complex, and real-world datasets, indicating that reinforced nodes can significantly enhance the robustness of the network and can prevent networks from abrupt collapse. Therefore, the proposed model provides insights for designing robust interdependent infrastructure networks.
A hydrodynamic approach to reproduce multiple spinning vortices in horizontally rotating three-dimensional liquid helium-4
Authors: Tsuzuki Satori
Published: August 2024

This paper reports a three-dimensional (3D) simulation of a rotating liquid helium-4, using a two-fluid model with spin-angular momentum conservation. Our model was derived from the particle approximation of an inviscid fluid with residual viscosity. Despite the fully classical mechanical picture, the resulting system equations were consistent with those of the conventional two-fluid model. We consider bulk liquid helium-4 to be an inviscid fluid, assuming that the viscous fluid component remains at finite temperatures. As the temperature decreased, the amount of the viscous fluid component decreased, ultimately becoming a fully inviscid fluid at absolute zero. Weak compressibility is assumed to express the volume change because some helium atoms do not render fluid owing to Bose–Einstein condensations or change states because of local thermal excitation. One can solve the governing equations for an incompressible fluid using explicit smoothed-particle hydrodynamics, simultaneously reproducing density fluctuations and describing the fluid in a many-particle system. We assume the following fluid–particle duality: a hydrodynamic interfacial tension between the inviscid and viscous components or a local interaction force between two types of fluid particles. The former can be induced in the horizontal direction when non-negligible non-uniformity of the particles occurs during forced two-dimensional rotation, and the latter is non-negligible when the former is negligible. We performed a large-scale simulation of 3D liquid helium forced to rotate horizontally using 32 graphics processing units. Compared with the low-resolution calculation using 2.4 × 106 particles, the high-resolution calculation using 19.6 × 106 particles showed spinning vortices close to those of the theoretical solution. We obtained a promising venue to establish a practical simulation method for bulk liquid helium-4.
Laser induced fluorescence using frequency modulated light
Authors: Scime E. E. , Freeze J. , Gilbert T. J. , Steinberger T. E.
Published: August 2024

The small signal-to-noise ratio (SNR) of conventional laser induced fluorescence (LIF) measurements using a continuous wave laser, either diode or dye, is typically overcome by amplitude modulating the laser at a specific frequency and then using lock-in amplification to extract the signal from measurement noise. Here, we present LIF measurements of the neutral helium velocity distribution function in an rf plasma using frequency modulated (FM) laser injection. A pulse train of 100% amplitude modulation is generated synthetically with a random sequence of pulse lengths. The FM signal then drives an acoustic optic modulator placed in the path of the injection beam in an LIF measurement. The signal from a fast photomultiplier tube is digitized and cross-correlated with the known modulation signal. The resultant FM-based LIF signal outperforms a conventional lock-in-based LIF measurement on the same plasma in terms of SNR and precision.
The next-generation magnetic recoil spectrometer (MRSnext) on OMEGA and NIF for diagnosing ion temperature, yield, areal density, and alpha heating
Authors: Wink C. W. , Gatu Johnson M. , Mackie S. , Kunimune J. H. , Dannhoff S. G. , Lawrence Y. , Berg G. P. A. , Casey D. T. , Schlossberg D. J. , Gopalaswamy V. , Katz J. , Regan S. P. , Stoeckl C. , Burgett T. , Ivancic S. , McClow H. , Scott M. , Frelier J. , Frenje J. A.
Published: August 2024

The next-generation magnetic recoil spectrometer (MRSnext) is being designed to replace the current MRS at the National Ignition Facility and OMEGA for measurements of the neutron spectrum from an inertial confinement fusion implosion. The MRSnext will provide a far-superior performance and faster data turnaround than the current MRS systems, i.e., a 2× and 6× improvement in energy resolution at the NIF and OMEGA, respectively, and 20× improvement in data turnaround time. The substantially improved performance of the MRSnext is enabled by using electromagnets that provide a short focal plane (12–16 cm) and unprecedented flexibility for a wide range of applications. In addition to being able to measure neutron yield, apparent ion temperature, areal density, and plasma-flow velocity over a wide range of yields, the NIF MRSnext will be able to directly, uniquely assess the alpha heating of the fuel ions through measurements of the alpha knock-on tail in the neutron spectrum. The goal is to implement a radiation-hard electronic detection system capable of providing rapid data acquisition and analysis. The development of the MRSnext will also set the foundation for the more advanced, time-resolving MRSt and serve as a testbed for its implementation on the NIF.
Microscopic mechanism of squeeze expulsion in granular size segregation
Authors: Shi Shanshan , Wu Ping , Li Li , Zuo Zhongqi , Fu Heping , Zhang Shiping , Dong Chunyang , Wang Li
Published: August 2024

In the gravity-driven free-surface flow of grains, the mechanism of the segregation phenomenon in binary granular flow is mainly attributed to kinetic sieving and squeeze expulsion. Although much literature has delved into the penetration of small grains through random fluctuation sieving, independent research on the microscopic mechanism of squeeze expulsion remains insufficient. Our previous research found that squeeze expulsion is particularly prominent in quasi-two-dimensional binary disk grain flow. Based on this result, we used the discrete element method (DEM) and experiments to explore the mechanism of squeeze expulsion. The results show that the anisotropy of the contact force chain network and the velocity difference of the grains in different positions play a key role in the expulsion behavior of the grains. This expulsion behavior is influenced by the dynamics and instability of the force chains, manifesting itself as a probabilistic phenomenon. Through DEM simulations, we quantified the probabilities of large grains being expelled at different positions and under various slope angles. It was found that as the slope angle increases, the probability of large grains being expelled to the upper layer also increases, intensifying granular segregation. The probability of large grains being expelled is highest in the granular flow substrate layer. The revealed mechanism of squeeze expulsion in this study is crucial for understanding grain mixing and separation.
Water entry of a seaplane section considering the wave effect
Authors: Sun Jia-Yu , Sun Shi-Li , Zhang Zi-Lin , Ren Hui-Long
Published: August 2024

The landing of a seaplane on the wave is a crucial issue with practical engineering applications in the fields of aeronautical and ocean engineering. The safe landing of seaplanes on wave surfaces prompts an urgent investigation on further understanding the mechanism by which the wings affect loads. This study examines the slamming force characteristics, pressure distributions, and free surface profiles of a two-dimensional seaplane section with varied heel angles into waves, considering different entry velocities, entry locations, and wave steepnesses. The overset mesh technique has been integrated into the waves2Foam toolbox to achieve a numerical wave tank based on the overset mesh. Numerical results for the vertical slamming force, slamming pressure coefficient distribution, and free surface profile were validated against published semi-analytical solutions and laboratory tests. The slamming force during the water entry of the seaplane section under the wave effect shows similar but more complex characteristics than those of the wedge section, manifesting as a phenomenon of multiple peaks. In addition to the bottom slamming of the airframe, localized high-pressure regions appear beneath the wing due to the combined squeezing effect on the air layer by the wing and water particle, which is similar to the wing-in-ground (WIG) effect. Slight sawtooth fluctuations of the wavefront were observed as a consequence of the disturbance of the air layer by the wings.
Polarization-insensitive terahertz third-harmonic generation from degenerate pairs of mirror-coupled super-BICs
Authors: Sun Guangcheng , Wang Yue , Xie Rongbo , Zhao Xiaoguang
Published: August 2024

Resonant nanostructures have emerged as versatile photonic platforms for boosting optical nonlinear responses on a subwavelength scale for their ability to confine intense electromagnetic fields while relaxing the phase-matching requirements. Recent significant advances in this field are associated with the utilization of non-radiative eigenmodes above the light cone, termed bound states in the continuum (BICs), which provide a unique mechanism for light trapping to realize excitation of ultrahigh quality (Q) factor resonances. Nevertheless, the current studies on BICs predominantly focus on symmetry-protected BICs (SP-BICs), whose excitation requires symmetry breaking, and Q factors are limited by fabrication imperfections. Here, we demonstrate a simple and feasible scheme for creating degenerate pairs of mirror-coupled super-BICs by harnessing magnetic dipole resonances coupled to their mirror images in adjacent metal films. Unlike trivial SP-BICs, mirror-coupled BICs showcases the huge enhancement of Q factors and are resilient against fabrication imperfections. By combining mirror-coupled resonance with the engineered radiative loss, we obtain a perfect absorber with near-unity absorption and ultra-narrow bandwidth at a critical coupling condition. Finally, we numerically demonstrate the terahertz (THz) regime, polarization-insensitive highly efficient third-harmonic generation benefiting from the maximum field enhancement localized within the perfect absorber. Our work not only paves the way toward unlocking the full potential of BIC resonance but also promise valuable insights for developing efficient THz optoelectronic devices and metadevices across a wide range of fields.
Implementation and verification of an OpenFOAM solver for gas-droplet two-phase detonation combustion
Authors: Chen Huangwei , Zhao MingHao , Qiu Hua , Zhu Yuejin
Published: August 2024

Due to the complexity and short timescale of detonation, it is usually difficult to capture its transient characteristics experimentally. Advanced numerical methods are essential for enhancing the understanding of the flow field structure and combustion mechanism of detonation. In this study, a density-based compressible reactive flow solver called CDSFoam is developed for simulating gas-droplet two-phase detonation combustion based on OpenFOAM. The primary feature of this solver is its implementation of two-way coupling between gas and liquid phases, utilizing the Eulerian–Lagrangian method. The key enhancement is an improved approximate Riemann solver used to solve the convective flux, reducing dissipation while ensuring robustness. Time integration is achieved through the third-order strong stability preserving Runge–Kutta method. Additionally, CDSFoam incorporates dynamic load balancing and adaptive mesh refinement techniques to mitigate computational costs while achieving high-resolution flow fields dynamically. To validate the reliability and accuracy of the solver, a series of benchmark cases are examined, including the multi-component inert and reactive shock tube, the stable diffusion process, the Riemann problem, the one-dimensional detonation, the two-dimensional detonation and oblique detonation, the droplet phase model, the two-dimensional gas–liquid two-phase detonation, and the two-phase rotating detonation. The results show that CDSFoam can well predict the shock wave discontinuity, shock wave induced ignition, molecular diffusion, detonation key parameters, detonation cell size, and the main characteristics of gas–liquid two-phase detonation.
A novel micro-continuum lattice Boltzmann approach for multiscale modeling immiscible two-phase flow in porous media
Authors: Liu Yang , Min Jingchun , Zhang Xuan
Published: August 2024

Immiscible two-phase flow in porous media is crucial in various industrial processes, necessitating a robust numerical tool to capture this complex multiscale behavior. This paper aims to introduce a novel micro-continuum multiphase solver, abbreviated as DBS-CG, which integrates lattice Boltzmann method with the Darcy–Brinkman–Stokes approach via embedding a volume-averaging scheme into the color-gradient model. The fluid–solid interactions in free and porous regions are effectively reproduced by the continuum surface force and micro-capillary force incorporated in DBS-CG. Validations against analytical solutions and numerical experiments confirm that DBS-CG is capable of monolithic modeling the trans-scale immiscible flow in spatially fluctuated porosity fields. Additionally, the water–oil displacement processes in mix-wetted and fractured–vuggy porous systems are tentatively investigated by DBS-CG, where various fingering patterns and preferential flow paths under different structural conditions and fluid properties are discussed. Non-monotonic trends of the recovery efficiency indicate that this multiphase process is competitively manipulated by the capillary or Darcy drag forces in microporous regions and inertial or viscous forces in solid-free regions, and thus, the moderate wettability and sedimentation are more beneficial for oil extraction.
Propagation of nonclassical shock waves in Hall-magnetohydrodynamics model of non-ideal fluids
Authors: Yadav Neelam , Shukla Triveni P.
Published: August 2024

We investigate the behavior of nonlinear waves in the Hall-magnetohydrodynamics model of non-ideal fluids with the van der Waals equation of state. It is shown that the Hall effect leads to the formation of a nonclassical shock wave that does not follow Oleinik's entropy condition and propagates as an undercompressive shock. The evolution of a rectangular pulse is discussed by solving a Riemann problem with initial data containing a pair of discontinuities. In particular, we provide a thorough discussion of interaction of various waves emerging from the discontinuities. It is observed that during this interaction, a nonclassical shock may transform into a classical sonic shock depending on the critical value of the Hall parameter. Furthermore, we analyze the effects of van der Waals parameters and the Hall parameter on various aspects of wave propagation, such as shock speed, shock strength, width of wave fan, and interaction time.
Experimental study on hydraulic performance optimization of ultra-low specific speed centrifugal pump
Authors: Wang Jiaqiong , Dang Jianing , Yang Tao , Zhang Ruijie
Published: August 2024

To improve the head and efficiency performance of an ultra-low specific speed centrifugal pump, this paper takes a marine magnetic-driven ultra-low specific speed centrifugal pump with a specific speed of 27 as the object of study. On the basis of the original model impeller with three blades, impeller A and impeller B with four blades of the same outer diameter and outlet widths of 4 and 2.5 mm were optimized and designed. Taking methanol as the medium, the impacts of factors such as the structure of the impeller, the aperture diameter of the throttling ring, and the cutting impeller outer diameter on the hydraulic performance of the ultra-low specific speed centrifugal pump are investigated. The influence of impeller structure, throttle ring aperture, cutting impeller outer diameter, and other factors on the hydraulic performance of an ultra-low specific speed centrifugal pump was explored. The study shows that the flow condition range of the original model impeller pump is very small, and the head decreases very fast, which cannot meet the design requirements; the head and efficiency of impeller A and impeller B are generally improved, but the flow or head deviates from the design condition, so it is necessary to set up a throttling ring or cut the outer diameter of the impeller to regulate the pump's operating parameters. The pump outlets were set up for the 12 and 15 mm inner diameter of the throttle ring and no throttle ring, respectively. Comparative experiments show that impeller A in the design head point using three kinds of throttle ring structure and the pump flow is greater than the design value of impeller B in the throttle ring bore diameter of 15 mm and that the pump flow and head can be achieved at the same time as the design value.
The investigation on vortex breakdown prior to stall in a compressor rotor with non-uniform tip clearance
Authors: Yang Fan , Wu Yanhui , Spence Stephen , Li Bo , Chen Zhiyang
Published: August 2024

Pre-stall disturbances and rotating instability (RI) are two typical phenomena observed in axial compressors prior to stall. In this study, experimental measurements and numerical simulations were employed to investigate the relationship between pre-stall disturbances and RI and their physical mechanisms in an axial compressor rotor with a non-uniform tip clearance gap. A post phase-locking technique was used in analyses of pressure fluctuations in the blade tip region. The resulting power spectrum estimation indicated that pre-stall disturbances shared the same frequency characteristics as RI, but differed in their spatial distribution. Pre-stall disturbances were the result of the upstream migration of RI. Numerical simulation results, validated by experimental measured distribution of pressure fluctuations, showed that the tip leakage vortex originating from the large blade tip clearance underwent a spiral-type breakdown, which was the originating mechanism of RI. When the back flow vortex generated by breakdown encountered the blade leading edge due to throttling, pre-stall disturbances were detected at the blade leading edge.
Stability mechanism of crystalline CO2 and Xe
Authors: Tanaka Hideki , Matsumoto Masakazu , Yagasaki Takuma , Takeuchi Munetaka , Mori Yoshihito , Kono Takumi
Published: August 2024

We explore the phase behaviors of simple molecular crystals in order to investigate the molecular basis of the stability mechanism relative to their liquid counterparts. The free energies of the face centered cubic crystals of Xe and CO2 are calculated as a collection of oscillators, and those of the liquids are from an equation of state via molecular dynamics simulations. The vibrational free energy in the solid is separated into the harmonic and anharmonic terms. The harmonic free energies decrease harshly with the expansion of the volume manifested as the large positive Grüneisen parameters, but the anharmonic free energies are positive and increase with volume, both of which originate from the deviation of the potential surface from the parabolic curve. The anharmonic free energies, though less significant in magnitude and destabilize the solids thermodynamically, serve to enhance their mechanical stability. The solid–liquid phase boundaries cannot be settled correctly without the exquisite balance between the two opposing contributions. A sharp contrast regarding the solid free energy is found in low-pressure ice, where the harmonic free energy does not decrease monotonically with volume and its anharmonic free energy is negative.
Wavelet analysis of intermittent dynamics in nocturnal electrocardiography and electroencephalography data
Authors: Zhuravlev M. , Egorov E. , Moskalenko O. , Zhuravleva Yu. , Akimova N. , Kiselev A. , Drapkina O. , Runnova A.
Published: August 2024

This paper presents the results of a study of the characteristics of phase synchronization between electrocardiography(ECG) and electroencephalography (EEG) signals during night sleep. Polysomnographic recordings of eight generally healthy subjects and eight patients with obstructive sleep apnea syndrome were selected as experimental data. A feature of this study was the introduction of an instantaneous phase for EEG and ECG signals using a continuous wavelet transform at the heart rate frequency using the concept of time scale synchronization, which eliminated the emergence of asynchronous areas of behavior associated with the “leaving” of the fundamental frequency of the cardiovascular system. Instantaneous phase differences were examined for various pairs of EEG and ECG signals during night sleep, and it was shown that in all cases the phase difference exhibited intermittency. Laminar areas of behavior are intervals of phase synchronization, i.e., phase capture. Turbulent intervals are phase jumps of 2π. Statistical studies of the observed intermittent behavior were carried out, namely, distributions of the duration of laminar sections of behavior were estimated. For all pairs of channels, the duration of laminar phases obeyed an exponential law. Based on the analysis of the movement of the phase trajectory on a rotating plane at the moment of detection of the turbulent phase, it was established that in this case the eyelet intermittency was observed. There was no connection between the statistical characteristics of laminar phase distributions for intermittent behavior and the characteristics of night breathing disorders (apnea syndrome). It was found that changes in statistical characteristics in the phase synchronization of EEG and ECG signals were correlated with blood pressure at the time of signal recording in the subjects, which is an interesting effect that requires further research.
Phosphatidylinositol-3-phosphate mediates Arc capsid secretion through the multivesicular body pathway
Authors: Mehta Kritika , Yentsch Henry , Lee Jungbin , Yook Yeeun , Lee Kwan Young , Gao Tianyu Terry , Tsai Nien-Pei , Zhang Kai
Published: August 2024

Activity-regulated cytoskeleton-associated protein (Arc/Arg3.1) is an immediate early gene that plays a vital role in learning and memory. Arc protein has structural and functional properties similar to viral Group-specific antigen (Gag) protein and mediates the intercellular RNA transfer through virus-like capsids. However, the regulators and secretion pathway through which Arc capsids maneuver cargos are unclear. Here, we identified that phosphatidylinositol-3-phosphate (PI3P) mediates Arc capsid assembly and secretion through the endosomal–multivesicular body (MVB) pathway. Indeed, reconstituted Arc protein preferably binds to PI3P. In HEK293T cells, Arc forms puncta that colocalize with FYVE, an endosomal PI3P marker, as well as Rab5 and CD63, early endosomal and MVB markers, respectively. Superresolution imaging resolves Arc accumulates within the intraluminal vesicles of MVB. CRISPR double knockout of RalA and RalB, crucial GTPases for MVB biogenesis and exocytosis, severely reduces the Arc-mediated RNA transfer efficiency. RalA/B double knockdown in cultured rat cortical neurons increases the percentage of mature dendritic spines. Intake of extracellular vesicles purified from Arc-expressing wild-type, but not RalA/B double knockdown, cells in mouse cortical neurons reduces their surface GlutA1 levels. These results suggest that unlike the HIV Gag, whose membrane targeting requires interaction with plasma-membrane-specific phosphatidyl inositol (4,5) bisphosphate (PI(4,5)P2), the assembly of Arc capsids is mediated by PI3P at endocytic membranes. Understanding Arc’s secretion pathway helps gain insights into its role in intercellular cargo transfer and highlights the commonality and distinction of trafficking mechanisms between structurally resembled capsid proteins.
Embryonic exposure to environmental factors drives transmitter switching in the neonatal mouse cortex causing autistic-like adult behavior
Authors: Godavarthi Swetha K. , Li Hui-quan , Pratelli Marta , Spitzer Nicholas C.
Published: August 2024

Autism spectrum disorders (ASD) can be caused by environmental factors. These factors act early in the development of the nervous system and induce stereotyped repetitive behaviors and diminished social interactions, among other outcomes. Little is known about how these behaviors are produced. In pregnant women, delivery of valproic acid (VPA) (to control seizure activity or stabilize mood) or immune activation by a virus increases the incidence of ASD in offspring. We found that either VPA or Poly Inosine:Cytosine (which mimics a viral infection), administered at mouse embryonic day 12.5, induced a neurotransmitter switch from GABA to glutamate in PV- and CCK-expressing interneurons in the medial prefrontal cortex by postnatal day 10. The switch was present for only a brief period during early postnatal development, observed in male and female mice at postnatal day 21 and reversed in both males and females by postnatal day 30. At postnatal day 90, male mice exhibited stereotyped repetitive behaviors and diminished social interaction while female mice exhibited only stereotyped repetitive behavior. Transfecting GAD1 in PV- and CCK-expressing interneurons at postnatal day 10, to reintroduce GABA expression, overrode the switch and prevented expression of autistic-like behavior. These findings point to an important role of neurotransmitter switching in mediating the environmental causes of autism.
3.8 × 3.8 mm2 compact piezoelectric resonant MEMS scanner using fork-shaped and ring-shaped actuators
Authors: Okamoto Yuki , Nakashima Rihachiro , Oda Ryo , Gorwadkar Sucheta , Takei Yusuke , Okada Hironao
Published: August 2024

This study presents a compact 3.8 × 3.8 mm2 resonant piezoelectric micro-electro-mechanical systems scanner featuring a 1.0 mm mirror and double-coupling frames. It employs a novel mechanical coupling of two Pb(Zr,Ti)O3 piezoelectric actuators–fork-shaped and ring-shaped. This dual-actuator configuration enhances the efficiency of actuator area usage per die and significantly improves the resonant frequency through their mechanical coupling. Additionally, the design strategy effectively reduces mechanical stress by operating the scanning frequency above those of other modes. The resonant frequency achieved by the proposed scanner is 27.09 kHz, with an optical scan angle of 40∘, utilizing a unipolar driving voltage of 25.2 V.
Neutron–antineutron oscillation accompanied by CP-violation in magnetic fields
Authors: Hao Yongliang , Nyirenda Kamphamba Sokalao , Chen Zhenwei
Published: August 2024

In this work, we explore the possibility of the n–

n

¯

oscillation accompanied by CP-violation in the presence of magnetic fields. The n–

n

¯

oscillation, which violates the baryon number (

B

) by two units (

∣
Δ
B
∣
=
2

), can originate from the mixing between the neutron (n) and the neutral elementary particle (η) and may give rise to non-trivial physical consequences that can be testable in future experiments. We show that the probability of the n–

n

¯

oscillation can be greatly enhanced by properly adjusting the magnetic field. In particular, the peak values of the oscillation probability in the presence of resonance magnetic fields can be 8–10 orders of magnitude higher than that in the absence of magnetic fields. We point out that there might not be sizable CP-violating effects in the n–

n

¯

oscillation unless the mass of η is close to the mass of the neutron. We also analyze the interplay among various parameters associated with both

B

-violation and CP-violation and attempt to disentangle the effects of such parameters. The n–

n

¯

oscillation process accompanied by CP-violation may open a promising avenue for exploring new physics beyond the Standard Model (SM).
Comprehensive investigation of structural, magnetic, electronic, optical, mechanical, and piezoelectric properties of ATiO3 (A = Mn, Fe, Ni) compounds for sustainable energy materials
Authors: Lalhumhima  , Lalroliana Bernard , Lalmuanchhana  , Zosiamliana R , Rai D P , Tiwari R C , Lalhriatzuala
Published: August 2024

This work employs density functional theory (DFT) to investigate the characteristics of ATiO3 (A = Mn, Fe, Ni) by utilizing generalized gradient approximation (GGA) and DFT + U formalisms. Our results reveal that the investigated compounds exhibit a ground-state magnetic arrangement in the G-type antiferromagnetic configuration. Substitution of the A-site atoms along the row leads to a decrease in volume due to poor electronic shielding effects with transition metals. All systems investigated are stable under dynamical conditions, with no imaginary phonon. From the formation energy calculations, NiTiO3 was identified as the most formable and stable compound. DFT + U was most effective for FeTiO3, resulting in significantly wider bandgaps compared to the GGA-level bandgaps. Optical properties such as static dielectric constants, refractive index, and reflectivity were overestimated by the GGA when compared to DFT + U results. The absorption edges of FeTiO3, MnTiO3, and NiTiO3 were analyzed, with DFT + U showing delayed onset compared to GGA. FeTiO3 was found to be the most effective absorber within the visible spectrum according to DFT + U, while NiTiO3 was predicted to be the best absorber by GGA. Each compound’s mechanical stability was tested and verified based on the Born criteria, with FeTiO3 exhibiting the highest elastic moduli under DFT + U, while NiTiO3 had the highest shear and Young’s modulus according to GGA. Among the studied compounds, FeTiO3 is the best-performing and most efficient piezoelectric compound with

e

16

= 5.418

C 

m

−
2

under DFT + U. Overall, the studied compounds demonstrate promising capabilities for a wide range of applications in the field of photovoltaic devices, and piezoelectric materials, due to their remarkable optical, and piezoelectric properties.