Density Distribution Research Articles

The Seismic Station and Site Amplification Service: Continuously Updated Information on Italian Seismic Stations

Abstract We present STATION (Seismic sTATion and sIte amplificatiON—see Data and Resources), the prototype of an innovative service aimed at providing updated information on specific seismological characteristics of more than 2500 Italian and European seismic stations, belonging to both permanent and temporary networks. The stations are characterized by exploiting recordings from about 120,000 earthquakes that have occurred in Italy and neighboring regions in the period from 2005 to 2024. This extensive database includes local magnitude residuals, horizontal-to-vertical spectral ratios (HVSRs), and mean noise spectra, enabling detailed site-specific seismic assessments as well as supporting postevent analyses. Not only is STATION equipped with a user-friendly web interface, but its seismological products can also be accessed directly through specific station queries (see Data and Resources), enabling quick retrieval of scientific results (e.g., HVSR) and associated metadata, which in turn increases the efficiency of the service itself and its interoperability with other web services. The STATION database is designed to be continually updated and expanded as new data become available from the scientific community (e.g., from the installation of new seismic stations and the recording of new earthquakes). Possible future developments and improvements to the service may include the dynamic updating of the database; the introduction of directional HVSRs and summary maps showing the amplification distribution; the dissemination of individual HVSR curves and spectra for specific requests; the calculation and dissemination of probabilistic distributions of noise power spectral densities; the integration of additional parameters describing site amplification effects; its potential extension to other European and possibly non-European regions.

Trap Density Estimation for TDDB Testing in SiC Power MOSFETs

Abstract The trap density estimation of SiC power MOSFET in time-dependent dielectric breakdown (TDDB) was investigated by using experiment and TCAD simulation. The gate leakage current (IGSS) under negative voltage was measured and a current spike was found which was linearly shifted with TDDB stress. Based on four-state nonradiative multi phonon (NMP) defect capture model, the mechanism and modeling of IGSS current spike was studied. Based on TCAD simulation, the characteristics of gate oxygen donor traps including trap energy level, trap density, and position distribution were estimated, and the trap density model in TDDB experiment was proposed and verified. This study may contribute to the estimation of trap density in SiC MOSFET.

Dynamically Switchable Multifunctional Device for Terahertz Application using Vanadium Dioxide and Graphene-Based Metasurface

Abstract In this article, a dynamically switchable and multifunctional metasurface is realized using a combination of vanadium dioxide (VO2) and graphene-based structures. The device can be tuned using the temperature transition property of vanadium dioxide from a wideband linear-to-circular polarization converter (LTCPC) to a wideband linear-to-linear cross polarization converter (LTLPC) and a dual-band absorber. The unit cell is designed with a gold-backed lossy-silicon dioxide (SiO2) substrate with a permittivity of 3.9, and the top metasurface layer is designed with a graphene-based dual triangle loaded split ring (DTLSR) and two stripes of vanadium oxide to cover the split partially. The proposed device can be used as a wideband LTCPC at normal temperature (298 K) from 1.43 THz to 2.85 THz, i.e., 66.35% fractional bandwidth (FBW). At temperatures greater than 341 K, VO2 exhibits metallic properties, and the structure functions as LTLPC from 1.82 THz to 3.31 THz (PCR ≥ 80%), i.e., 58.08 % FBW and maximum polarization conversion ratio (PCR) reported as high as 99.65 %. Furthermore, at this metallic condition, two absorption peaks are obtained at 1.22 THz and 3.30 THz with absorptivity of 93.5% and 100%, respectively. The device offers incident angle invariability up to 40° for LTCPC and up to 50° for LTLPC operation. Further insight into the mechanism of operation is developed using the surface current density and electric field distribution analysis. The advantage of the proposed metasurface over other similar structures is assessed with respect to multifunctional behavior, bandwidth, and stability under oblique incidence.

Investigation of kaonic atom optical potential by the high precision data of kaonic 3He and 4He atoms

Abstract We investigate kaonic atom optical potentials of 3He and 4He phenomenologically based on the latest high precision data of the 2p states of the kaonic atoms in helium (J-PARC E62). We consider a simple phenomenological form for the optical potential proportional to the nuclear density distributions and clarify the meanings and implications of the data by determining the potential parameters by the latest data. We find two sets of potential parameters for each of K− − 3He and K− − 4He that reproduce the data. We then extract the potential parameters consistent with the data of 3He and 4He atoms simultaneously. We report the possible strong isospin dependence of the potential, and the different strength of the data of K− − 3He and K− − 4He in the restrictions on the potential parameters. We mention that the study of the 1s states of the kaonic helium atom is very interesting as a next step. Observing these states could provide valuable information on potential parameters and kaonic nuclear s states because of the mutual influence between the atomic and the nuclear states of kaon with the same orbital angular momentum.

Optimizing Electrode Combinations to Improve Welding Current Density Distribution and Intermetallic Layer Morphology Growth for Resistance Spot Welding of Aluminum Alloys to Steels

Optimizing Electrode Combinations to Improve Welding Current Density Distribution and Intermetallic Layer Morphology Growth for Resistance Spot Welding of Aluminum Alloys to Steels

ON THE SIMULTANEOUS DETERMINATION OF THE DENSITY DISTRIBUTION OF EQUIVALENT SOURCES UNDER AN EXTERNAL FIELD AND THE SPECTRUM OF USEFUL SIGNAL

The article investigates the possibility of simultaneously recovering equivalent sources under an external field and the spectral characteristics of a useful signal. Examples of variational formulations for different versions of the method of linear integral representations are presented, and the problem of finding the density distribution of gravitating or magnetic masses on several horizontal planes is formulated. Additionally, the Fourier transform of the anomalous field element based on the known signal values at certain observation points, complicated by noise, is discussed.

Adsorption and Diffusion of CH4, N2, and Their Mixture in MIL-101(Cr): A Molecular Simulation Study.

A comprehensive quantitative grasp of methane (CH4), nitrogen (N2), and their mixture's adsorption and diffusion in MIL-101(Cr) is crucial for wide and important applications, e.g., natural gas upgrading and coal-mine methane capturing. Previous studies often overlook the impact of gas molecular configuration and MIL-101 topology structure on adsorption, lacking quantitative assessment of primary and secondary adsorption sites. Additionally, understanding gas mixture adsorption mechanisms remains a research gap. To bridge this gap and to provide new knowledge, we utilized Monte Carlo and molecular dynamics simulations for computing essential MIL-101 properties, encompassing adsorption isotherms, density profiles, self-diffusion coefficients, radial distribution function (RDF), and CH4/N2 selectivity. Several novel and distinctive findings are revealed by the atomic-level analysis, including (1) the significance of C=C double bond of the benzene ring within MIL-101 for CH4 and N2 adsorption, with Cr and O atoms also exerting notable effects. (2) Density distribution analysis reveals CH4's preference for large and medium cages, while N2 is evenly distributed along pentagonal and triangular window edges and small tetrahedral cages. (3) Calculations of self-diffusion and diffusion activation energies suggest N2's higher mobility within MIL-101 compared to CH4. (4) In the binary mixture, the existence of CH4 can decrease the diffusion coefficient of N2. In summary, this investigation provides valuable microscopic insights into the adsorption and diffusion phenomena occurring in MIL-101, thereby contributing to a comprehensive understanding of its potential for applications, e.g., natural gas upgrading and selective capture of coal-mine methane.

Analysis of Tidal Cycle Wave Breaking Distribution Characteristics on a Low-Tide Terrace Beach Using Video Imagery Segmentation

Wave breaking is a fundamental process in ocean energy dissipation and plays a crucial role in the exchange between ocean and nearshore sediments. Foam, the primary visible feature of wave breaking areas, serves as a direct indicator of wave breaking processes. Monitoring the distribution of foam via remote sensing can reveal the spatiotemporal patterns of nearshore wave breaking. Existing studies on wave breaking processes primarily focus on individual wave events or short timescales, limiting their effectiveness for nearshore regions where hydrodynamic processes are often represented at tidal cycles. In this study, video imagery from a typical low-tide terrace (LTT) beach was segmented into four categories, including the wave breaking foam, using the DeepLabv3+ architecture, a convolutional neural networks (CNNs)-based model suitable for semantic segmentation in complex visual scenes. After training and testing on a manually labelled dataset, which was divided into training, validation, and testing sets based on different time periods, the overall classification accuracy of the model was 96.4%, with an accuracy of 96.2% for detecting wave breaking foam. Subsequently, a heatmap of the wave breaking foam distribution over a tidal cycle on the LTT beach was generated. During the tidal cycle, the foam distribution density exhibited both alongshore variability, and a pronounced bimodal structure in the cross-shore direction. Analysis of morphodynamical data collected in the field indicated that the bimodal structure is primarily driven by tidal variations. The wave breaking process is a key factor in shaping the profile morphology of LTT beaches. High-frequency video monitoring further showed the wave breaking patterns vary significantly with tidal levels, leading to diverse geomorphological features at various cross-shore locations.

B─C Bonding Configuration Manipulation Strategy Toward Synergistic Optimization of Polarization Loss and Conductive Loss for Highly Efficient Electromagnetic Wave Absorption

AbstractIn non‐metallic atom‐doped carbonaceous materials, the disparity in electronegativity between the doped constituents and carbon atoms predetermines the bonding topology of covalent bonds and the distribution of electron density. This, consequently, influences the polarization and electron transport behavior within the doped domain and the electromagnetic wave attenuation attributes of the carbonaceous material. However, the influence of covalent bonds formed by doping with weakly electronegative atoms on electron density distribution, polarization effects, and electromagnetic wave attenuation remains uncharted. To address this deficiency, this study fabricates a porous carbonaceous material (NCP) and incorporates boron‐doped atoms to form a material with tunable B─C bonding configurations (B‐NCP). By modulating the B─C bonding configuration and proportion, it is feasible to achieve the synergistic optimization of conductive loss and polarization loss of the B‐NCP specimen. The optimized prototype B‐NCP‐1200 sample displays exceptionally efficient electromagnetic wave absorption capabilities with a minimum reflection loss (RLmin) of −52.03 dB and an effective absorption bandwidth (EAB) of 5.36 GHz. This study presents a conscientious model for comprehending the electromagnetic attenuation mechanisms associated with weakly electronegative atom doping in carbon‐based electromagnetic wave‐absorbing materials.

EMC3-EIRENE simulations of edge plasma and impurity transport by toroidally localized argon seeding on CFETR X-divertor

Abstract Three-dimensional (3D) Edge Monte Carlo transport code EMC3-EIRENE has been employed to study edge plasma and impurity transport with toroidally localized argon seeding on Chinese fusion engineering testing reactor (CFETR) X-divertor configuration. The argon impurity seeded at different poloidal locations has been investigated to evaluate the varied profile of the main plasma in the scrape-off layer (SOL) and on the divertor targets, which shows a strong dependence on the poloidal position of argon gas puffing. The argon impurity seeded at the upstream SOL regions can result in a toroidally asymmetric distribution of electron density and temperature, while a toroidally symmetric distribution is obtained for argon seeded at the strike point regions. The deposition pattern of electron density and temperature shows the several lobe-like and island-like structures on the 3D divertor targets of CFETR with upstream argon injections, whereas the perturbed profile is achieved for argon seeding at the strike point regions. In order to verify the toroidal asymmetry of heat loads distribution, the argon impurity seeded at different poloidal locations has been investigated to estimate its influence on toroidal heat loads on divertor plates. The argon injected at the strike point regions gives rise to a toroidal asymmetry of heat loads distribution on divertor targets, while a toroidal symmetry of heat loads distribution is gained for argon injected at the upstream SOL locations.

High temperature condensation and many body localization of blended ferrons in antiferromagnetic clusters

Abstract This paper presents a multiferron system and analyzes the conditions under which it forms a localized many-body state. We determined the self-trapping potential of this system and showed that the ferrons pair up to form bound biferron states, which interact through their relative spin cloud and settle into two different configurations mimicking the Bose-Einstein Condensate (BEC) and Bardeen-Cooper-Schrieffer (BCS) states. The external B-field strengthens the magnetic coupling, which favors the pairing of the ferrons. It also creates a vortex, providing good confinement of the particles and favoring condensation. The system's state functions are well described by the nonlinear Schr"{o}dinger equation, whose solution is a bell-shaped soliton representing the density of particle distribution in the condensate. The system's critical temperature is obtained as a function of the biferron energy shift and thus strongly depends on the applied field.

An endogenous aryl hydrocarbon receptor ligand induces preeclampsia-like phenotypes in rats.

Preeclampsia (PE) is a hypertensive disorder during human pregnancy. Aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor. Exogenous and endogenous AhR ligands can induce hypertension in male rats and mice. Herein, using rats as a model, we tested the hypothesis that over-regulation of endogenous AhR ligands during pregnancy impairs vascular functions by disrupting the transcriptome in the placenta, contributing to the development of PE. Pregnant rats were injected daily with an endogenous AhR ligand, 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE), from gestational day (GD) 10 to 19. Maternal mean blood pressure was measured on GD16-20. Proteinuria and uteroplacental blood flow were monitored on GD20. Placentas collected on GD20 were used to determine changes in vascular density and transcriptome. Compared with the vehicle control, ITE elevated maternal mean blood pressure by 22% and 16% on GD16 and 17, respectively. ITE increased proteinuria by 50% and decreased uteroplacental blood flow by 26%. ITE reduced the placental vascular density by 18%. RNA sequencing analysis revealed that ITE induced 1316 and 2020 differentially expressed genes (DEGs) in female and male placentas, respectively. These DEGs were enriched in pathways relevant to heart diseases, vascular functions and inflammation. Bioinformatics analysis also predicted that ITE altered immune cell infiltration in placentas depending on fetal sex. These data suggest that over-regulation of endogenous AhR ligands may lead to PE with impaired vascular functions and disrupted fetal sex-specific transcriptomes and immune cell infiltration in placentas. These AhR ligand-induced DEGs and pathways may represent promising therapeutic targets for PE-induced cardiovascular dysfunctions. KEY POINTS: An endogenous AhR ligand (ITE) elevated maternal blood pressure and proteinuria in pregnant rats, and decreased uteroplacental blood flow and fetal and placental growth, all of which are hallmarks of preeclampsia. ITE reduced vascular density and altered immune cell distribution in rat placentas. ITE dysregulated transcriptomes in rat placentas in a fetal sex-specific manner. These ITE-dysregulated genes and pathways are highly relevant to diseases of heart, vascular functions and inflammatory responses.

The influence of density models on wormhole formation in Finsler–Barthel–Randers geometry

This paper investigates the structure and stability of wormholes within the framework of Finsler–Barthel–Randers geometry, focusing on the influence of different density models. Finsler geometry, as a generalization of Riemannian geometry, allows for the incorporation of anisotropic characteristics, making it a valuable tool in exploring cosmological phenomena. By employing osculating Riemannian space approaches, we develop wormhole models under non-commutative geometry and power-law energy density distributions. We analyze the role of the Finsler parameter η while evaluating the energy conditions in each model. The specific models developed here with Finsler geometry offer insights into the physical viability of wormholes in this context, potentially resolving some of the longstanding issues in wormhole theory. These findings suggest that Finsler geometry, combined with osculating Barthel–Randers geometry, provides a promising avenue for the construction of stable and physically plausible wormhole structures, The results are validated through analytical solutions and 3-D visualizations, thus contributing to our broader understanding of gravitational physics and spacetime geometry.

Features and prospects for kilonova remnant detection with current and future surveys

We study the observable spectral and temporal properties of kilonova remnants (KNRs) analytically, and point out quantitative differences with respect to supernova remnants. We provide detection prospects of KNRs in the context of ongoing radio surveys. We find that there is a good chance to expect tens of these objects in future surveys with a flux threshold of $ 0.1$ mJy. Kilonova remnants from a postulated population of long-lived supermassive neutron star remnants of neutron star mergers are even more likely to be detected, as they are extremely bright and peak earlier. For an ongoing survey with a threshold of sim 1 mJy, we expect to find tens to hundreds of such objects if they are a significant fraction of the total kilonova (KN) population. Considering that there are no such promising KN candidates in presently ongoing surveys, we constrain the fraction of these extreme KN to be no more than 30 percent of the overall KN population. This constraint depends sensitively on the details of ejecta mass and external density distribution.

A Study on the Influence of Natural Fractures in Tight Sandstone Reservoirs on Hydraulic Fracture Propagation Behavior and Post-Fracture Productivity

Tight sandstone gas reservoirs are rich in reserves and are an important part of unconventional oil and gas resources. However, natural fractures’ impact on hydraulic fracture propagation behavior and network formation mechanisms remain unclear. Exploring how to optimize fracturing parameters to maximize post-fracturing productivity requires further investigation. Therefore, this study focused on the characteristics of tight sandstone gas reservoirs and established a three-dimensional numerical simulation model for hydraulic fracture propagation and post-fracturing productivity using production history matching to validate the reliability of the model. Based on this model, this study investigated the influence mechanisms of natural fracture angles, density, and lengths on hydraulic fracture propagation behavior and network formation. The spatial distribution of hydraulic fracture widths in three dimensions is also explored. When natural fracture angles are lower, a greater number of natural fractures are activated, leading to more developed secondary hydraulic fractures and the formation of complex fracture networks. Hydraulic fractures tend to penetrate directly through high-angle natural fractures. Single-well cumulative gas production increases initially with increasing natural fracture angles, then decreases, but increases with higher natural fracture density and length. Optimal fracturing in areas with longer natural fractures, lower angles, and higher density distribution enhances single-well productivity effectively.

Novel Artificial Neural Network Aided Structural Topology Optimization

In this paper, novel artificial neural networks are adopted for the topology optimization of full structures at both coarse and fine scales. The novelty of the surrogate-based method is to use neural networks to optimize the relationship from boundary and mesh conditions to structure density distribution. The objective of this study is to explore the feasibility and effectiveness of deep learning techniques for structural topology optimization. The newly developed neural networks are used for optimizing various types of structures with different meshes, partition numbers, and parameters. The finite element computation takes more than 90% of the total operation time of the SIMP method, but it decreases to 40%. It is indicated that the computational cost for the whole structural design process is relatively low, while the accuracy is acceptable. The proposed artificial neural network method is used to perform topology optimization for some numerical examples such as the cantilever beam, the MBB beam, the L-shape beam, the column, and the rod-supported bridge. It is demonstrated that computational efficiency is considerably improved while the proposed neural network method is adopted.

Aspects of Modeling Coal Enrichment Processes by Gravity Methods

This study examines the challenges associated with processing hard coal, with a specific focus on gravitational enrichment methods and the utilization of jigs for coal separation. The research involves the simulation and modeling of physical property distributions and the analysis of both the feed density distribution and the characteristics of the enrichment products. Findings indicate that the resultant density distributions are influenced not only by the gravitational enrichment process but also by the preceding procedures and the inherent properties of the coal, such as particle size, sulfur content, and ash content, all of which significantly affect the quality of the outcomes. In modeling and optimization efforts, the study emphasizes approximating grain density using selected statistical distributions—specifically, the Weibull, logistic, and Gaudin–Schuhmann–Andreyev (GSA) distributions—before and after the enrichment process. Statistical analyses demonstrate that the GSA distribution most accurately fits the grain density distribution in the feed, while the Weibull distribution provides the best approximation for the separation products. The quality of these approximations was assessed using the coefficient of determination (R2) and the Mean Squared Error (MSE). The best quality of approximation for feed was obtained by means of the GSA distribution function, and the MSE was approximately 3.1 for two analyzed values of feed flow rates. In the case of concentrates and tailings, the results are not unequivocal.

3D simulations of the RF wave propagation and power coupling in cold magnetized plasma near an ICRF antenna

Abstract The electromagnetic wave propagations and their coupling characteristics in magnetized plasma near the antenna of Ion Cyclotron Range of Frequencies (ICRF) is studied based on self-developed 3DFEM-IA code. This code effectively resolves the three-dimensional (3D) geometry and the electromagnetic field using the finite element method. Our findings reveal that the distributions of electromagnetic fields and energy flow density significantly depend on the antenna phases, surface current density on the antenna straps, and background plasma density. Notably, the non-uniform surface current density on the antenna straps, resulting from the presence of induced currents, contributes to a reduction in coupling power within the edge plasma. Furthermore, the calculated coupling impedance increases with plasma density, corroborating well with experimental measurements.

Urban sprawl and firm green total factor productivity: Evidence from China

Based on corrected nighttime light data and firm-level data from 1998 to 2010, we use an urban sprawl index that properly captures the subtle differences in density distribution within cities, extend a hyperbolic distance specification within a parametric stochastic framework to the analysis of firm green total factor productivity (GTFP), and examine the impact of urban sprawl on firm GTFP. The empirical results show that urban sprawl has a significant negative impact on GTFP. Our results are robust after considering several potential problems. We also examine the possible mechanisms by which urban sprawl affects firm GTFP based on the agglomeration economy perspective. Our findings show that urban sprawl negatively impacts the urban agglomeration economies and hinders the formation of labor pools, intermediate input sharing, and knowledge spillovers, consequently diminishing firm GTFP. Heterogeneity analysis shows that urban sprawl has a more significant impact on small and medium-sized urban firms, firms in low-technology industries, and small and medium-sized firms. The moderating effects reveal that the institutional environment and infrastructure, including transportation infrastructure and information infrastructure, can significantly mitigate the impact of urban sprawl on the firm GTFP.

Unsymmetric Protonation Driven Highly Efficient H2O2 Photosynthesis in Supramolecular Photocatalysts via One‐Step Two‐Electron Oxygen Reduction

AbstractPhotocatalytic hydrogen peroxide (H2O2) production has emerged as an attractive alternative to the traditional anthraquinone process. However, its performance is often hindered by low selectivity and sluggish kinetics of oxygen reduction reaction (ORR). Herein, we report an anthrazoline‐based supramolecular photocatalyst, SA‐SADF‐H+, featuring an unsymmetric protonation structure for H2O2 photosynthesis from water and air. The introduction of unsymmetric protonation disrupts the initial mirror symmetry of SADF, significantly enhancing the molecular dipole and facilitating efficient charge separation and electron transfer. Additionally, this modification increases the hydrophilicity of SA‐SADF‐H+, enabling the interaction of water and dissolved oxygen with the catalytic sites. The altered electron density distribution creates numerous dual active sites for Yeager‐type O2 adsorption, facilitating an efficient ORR towards H2O2 via a direct one‐step two‐electron pathway. Notably, SA‐SADF‐H+ achieves an outstanding photocatalytic H2O2 production at a rate of 4666.7 μmol L−1 h−1, with a remarkable solar‐to‐chemical conversion (SCC) of 1.35 %, surpassing most organic photocatalytic systems. Furthermore, SA‐SADF‐H+ demonstrates remarkable photocatalytic antibacterial activity, achieving 100 % antibacterial efficiency against Staphylococcus aureus within 60 min.