检索结果-内蒙古大学图书馆

Synergetic effects of multiple junction and surface hydroxyl in Cu/CuO/Cu2O/TiO2 heterostructures towards highly efficient photocatalysts for hydrogen generation

学校读者我要写书评

暂无评论

Materials Science for Energy Technologies 2025年 8卷 131-142页

作者： Subagyo, Riki Anindika, Garcelina Rizky Aufkani, Afif Akmal Zhang, Lei Ardhyananta, Hosta Burhan, R.Y. Perry Nugraheni, Zjahra Vianita Akhlus, Syafsir Bahruji, Hasliza Prasetyoko, Didik Wellia, Diana Vanda Ivansyah, Atthar Luqman Arramel Kusumawati, Yuly Department of Chemistry Faculty of Science and Analytic Data Institut Teknologi Sepuluh Nopember Surabaya60111 Indonesia Center of Excellence Applied Physics and Chemistry Nano Center Indonesia Jl PUSPIPTEK South Tangerang Banten15314 Indonesia Department of Physics National University of Singapore Singapore117551 Singapore Department of Materials and Metallurgical Engineering Faculty of Industrial Technology and Systems Engineering Institut Teknologi Sepuluh Nopember Surabaya60111 Indonesia Centre of Advanced Material and Energy Science Universiti Brunei Darussalam Jalan Tungku Link BE 1410 Brunei Department of Chemistry Faculty of Mathematics and Natural Sciences Universitas Andalas Padang25163 Indonesia Master Program in Computational Science Faculty of Mathematics and Natural Science Institut Teknologi Bandung Jalan Ganesha No. 10 Bandung40132 Indonesia Instrumentation and Computational Physics Research Group Department of Physics Faculty of Mathematics and Natural Sciences Institut Teknologi Bandung Jalan Ganesha No.10 West Java Bandung40132 Indonesia

The implementation of titanium dioxide (TiO2) as a photocatalyst material in hydrogen (H2) evolution reaction (HER) has embarked renewed interest in the past decade. Rapid electron-hole pairs recombination and wide band gap of a photo-sensitive material of TiO2 are detrimental toward the targeted catalytical reaction. In this study, we present the rational design, fabrication, photocatalytic performance of TiO2-Cu/CuO/Cu2O heterostructures (CuTi) using viable chemical reduction method. The Z-scheme and S-scheme are succesfully generated across the TiO2/CuO/Cu2O interfaces, while the Schottky junction arises on the Cu perimeters. This is evidenced from the blue shifted about 0.3 eV of Cu 2p core level determined by using X-ray photoemission spectroscopy (XPS), in combination with the formation of inverse V-shape of the Mott-Schottky plots. In addition, we find that Cu/CuO/Cu2O facilitates photon absorption range up to the visible region. The multiple heterojunction and the large number of OHsurface enhanced charge carrier transfer are associated to the suppression of photoluminescence (PL) intensity, high surface hydroxyl (OHsurface) density in CuTi probed by XPS, and fast electron transfer based on the electrochemical measurements. The presence of OHsurface inhibits the recombination of electron. A significant H2 photogeneration rate enhancement is achieved when an optimized 5 wt% Cu/CuO/Cu2O concentration is used on TiO2 to achieve 7,157.19 μmol·g−1 (1,789.30 μmol·g−1·h−1). Based on this finding, zero emission energy innitiative could be materialized under multiple heterojunctions in photocatalytic process is beneficial for enhancing the H2 production. © 2025 The Authors

关键词： Titanium dioxide

Adiabatic elimination and Wigner function approach in microscopic derivation of open quantum Brownian motion

学校读者我要写书评

暂无评论

arXiv 2025年

作者： Zungu, Ayanda Sinayskiy, Ilya Petruccione, Francesco School of Chemistry and Physics University of KwaZulu-Natal Durban4001 South Africa Centre for Space Research North-West University Mahikeng2745 South Africa Stellenbosch South Africa School of Data Science and Computational Thinking Department of Physics Stellenbosch University Stellenbosch7604 South Africa

Open quantum Brownian motion (OQBM) represents a new class of quantum Brownian motion where the dynamics of the Brownian particle depend not only on the interactions with a thermal environment but also on the state of the internal degrees of freedom. For an Ohmic bath spectral density with a Lorentz-Drude cutoff frequency at a high-temperature limit, we derive the Born-Markov master equation for the reduced density matrix of an open Brownian particle in a harmonic potential. The resulting master equation is written in phase-space representation using the Wigner function, and due to the separation of associated timescales in the high-damping limit, we perform adiabatic elimination of the momentum variable to obtain OQBM. We numerically solve the derived master equation for the reduced density matrix of the OQBM for Gaussian and non-Gaussian initial distributions. In each case, the OQBM dynamics converge to several Gaussian distributions. To gain physical insight into the studied system, we also plotted the dynamics of the off-diagonal element of the open quantum Brownian particle and found damped coherent oscillations. Finally, we investigated the time-dependent variance in the position of the OQBM walker and observed a transition between ballistic and diffusive behavior. Copyright © 2025, The Authors. All rights reserved.

关键词： Brownian movement

ULX collimation by outflows in moderately magnetized neutron stars

学校读者我要写书评

暂无评论

arXiv 2025年

作者： Kayanikhoo, Fatemeh Kluźniak, Wlodek Čemeljić, Miljenko Nicolaus Copernicus Astronomical Center the Polish Academy of Sciences Bartycka 18 Warsaw00-716 Poland Research Centre for Computational Physics and Data Processing Institute of Physics Silesian University in Opava Bezručovo nám. 13 OpavaCZ-74601 Czech Republic Nicolaus Copernicus Superior School College of Astronomy and Natural Sciences Gregorkiewicza 3 Toruń87-100 Poland Academia Sinica Institute of Astronomy and Astrophysics P.O. Box 23-141 Taipei106 Taiwan

We perform radiative magnetohydrodynamics simulations in general relativity (GRRMHD) of super-Eddington disk accretion onto neutron stars endowed with a magnetic dipole corresponding to surface strengths not exceeding 100 GigaGauss. Accretion is found to power strong outflows which collimate the emergent radiation of the accretion columns, leading to apparent radiative luminosities of ∼ 100 Eddington, when the true luminosity is a few Eddington units. Surprisingly, the collimation cone/angle widens with increasing magnetic field. Thus, in our simulations the apparent luminosity of the neutron star is substantially larger for the weaker magnetic fields (1010 G) than for the stronger ones (1011 G). We conclude that a super-Eddington accreting neutron star with the dipole magnetic field 1010 G is the most likely source of ultraluminous X-rays. © 2025, CC BY.

关键词： Neutrons

Launching of asymmetric outflows from the star-disk magnetosphere

学校读者我要写书评

暂无评论

arXiv 2025年

作者： Čemeljić, Miljenko Kotek, Aleksandra Kluźniak, Wlodek Nicolaus Copernicus Astronomical Center The Polish Academy of Sciences Bartycka 18 Warsaw00-716 Poland Nicolaus Copernicus Superior School College of Astronomy and Natural Sciences Gregorkiewicza 3 Toruń87-100 Poland Research Centre for Computational Physics and Data Processing Institute of Physics Silesian University in Opava Bezručovo nám. 13 OpavaCZ-746 01 Czech Republic Academia Sinica Institute of Astronomy and Astrophysics P.O. Box 23-141 Taipei106 Taiwan

In resistive and viscous magnetohydrodynamical simulations, we obtain axial outflows launched from the innermost magnetosphere of a star-disk system. The launched outflows are found to be asymmetric. We find the part of the parameter space corresponding to quasi-stationary axial outflows and compute the mass load and angular momentum flux in such outflows. We display the obtained geometry of the solutions and measure the speed of propagation and rotation of the obtained axial outflows. © 2025, CC BY.

关键词： Stars

Eigenvalue-Based Randomness Test for Residual Diagnostics in Panel data Models

学校读者我要写书评

暂无评论

arXiv 2025年

作者： Kurbucz, Marcell T. Garrido, Betsabé Pérez Jakovác, Antal Institute for Global Prosperity The Bartlett University College London 149 Tottenham Court Road LondonW1T 7NF United Kingdom Department of Computer Science Institute of Data Analytics and Information Systems Corvinus University of Budapest 8 Fővám Square Budapest1093 Hungary Department of Computational Sciences Institute for Particle and Nuclear Physics HUN-REN Wigner Research Centre for Physics 29-33 Konkoly-Thege Miklós Street Budapest1121 Hungary Department of Statistics Institute of Data Analytics and Information Systems Corvinus University of Budapest 8 Fővám Square Budapest1093 Hungary

This paper introduces the Eigenvalue-Based Randomness (EBR) test—a novel approach rooted in the Tracy-Widom law from random matrix theory—and applies it to the context of residual analysis in panel data models. Unlike traditional methods, which target specific issues like cross-sectional dependence or autocorrelation, the EBR test simultaneously examines multiple assumptions by analyzing the largest eigenvalue of a symmetrized residual matrix. Monte Carlo simulations demonstrate that the EBR test is particularly robust in detecting not only standard violations such as autocorrelation and linear cross-sectional dependence (CSD) but also more intricate non-linear and non-monotonic dependencies, making it a comprehensive and highly flexible tool for enhancing the reliability of panel data *** Codes 62H25, 15B52, 62M10 © 2025, CC BY.

关键词： Eigenvalues and eigenfunctions

Modulation of X-ray flux by obscuration of neutron star boundary layer

学校读者我要写书评

暂无评论

arXiv 2025年

作者： Török, Gabriel Klimovičová, Kateřina Lančová, Debora Matuszková, Monika Šrámková, Eva Urbanec, Martin Čemeljić, Miljenko Šprňa, René Karas, Vladimír Research Center for Computational Physics and Data Processing Institute of Physics Silesian University in Opava Bezručovo nám. 13 OpavaCZ-746-01 Czech Republic Nicolaus Copernicus Astronomical Center Polish Academy of Sciences Bartycka 18 Warsaw00-716 Poland College of Astronomy and Natural Sciences SGMK Nicolaus Copernicus Superior School Nowogrodzka 47A Warsaw00-695 Poland Academia Sinica Institute of Astronomy and Astrophysics P.O. Box 23-141 Taipei106 Taiwan Astronomical Institute of the Czech Academy of Sciences Boční II 1401 PragueCZ-14100 Czech Republic

The quasi-periodic oscillations (QPOs) observed in the X-ray variability of both black hole (BH) and neutron star (NS) systems provide a tool for probing strong gravity and dense matter equations of state. Nevertheless, the mechanism of QPO modulation in NS systems, where the amplitudes of QPOs with frequencies approaching kHz range are very high in comparison to BH high-frequency QPOs, remains an unsolved puzzle. Relativistic ray tracing of photons emitted from the immediate vicinity of compact objects has, to date, been used to investigate various mechanisms that explain the observed weak BH QPOs. However, it has not been applied to model the NS QPO signal, which requires incorporating the NS surface and a bright boundary layer (BL) on it. Here, we explore the QPO modulation mechanisms based on the BL obscuration. Using simplified models of axisymmetric oscillations of thick accretion discs (tori), we demonstrate that the disc oscillations drive the high NS QPO amplitudes through BL obscuration, which is relevant especially for vertical oscillations. We also demonstrate that obscuration effects enable the observability of the Keplerian frequency in the case of discs that decay due to instabilities. © 2025, CC BY.

关键词： Neutrons

Pseudo-Newtonian simulation of a thin accretion disk around a Reissner-Nordström naked singularity

学校读者我要写书评

暂无评论

arXiv 2025年

作者： Čemeljić, Miljenko Kluzniak, Wlodek Mishra, Ruchi Wielgus, Maciek College of Astronomy and Natural Sciences SGMK Nicolaus Copernicus Superior School Nowogrodzka 47A Warsaw00-695 Poland Nicolaus Copernicus Astronomical Center The Polish Academy of Sciences Bartycka 18 Warsaw00-716 Poland Research Center for Computational Physics and Data Processing Institute of Physics Silesian University in Opava Bezručovo nám. 13 OpavaCZ-746-01 Czech Republic Academia Sinica Institute of Astronomy and Astrophysics P.O. Box 23-141 Taipei106 Taiwan Instituto de Astrofísica de Andalucía-CSIC Glorieta de la Astronomía s/n GranadaE-18008 Spain

We present the first numerical simulations of a thin accretion disk around a Reissner-Nordström (RN) naked singularity (a charged point mass). The gravity of the RN naked singularity is modeled with a pseudo-Newtonian potential that reproduces exactly the radial dependence of the RN Keplerian orbital frequency;in particular, orbital angular velocity vanishes at the zero gravity radius and has a maximum at 4/3 of that radius. Angular momentum is transported outwards by viscous stresses only outside the location of this maximum. Nonetheless, even at that radius, accretion proceeds at higher latitudes, the disk having thickened there owing to excess pressure. The accretion stops at a certain distance away from the singularity, with the material accumulating in a toroidal structure close to the zero-gravity sphere. The shape of the structure obtained in our simulations is reminiscent of fluid figures of equilibrium analytically derived in full general relativity for the RN singularity. The presence of a rotating ring, such as the one found in our simulations, could be an observational signature of a naked singularity. For charge to mass ratios close to but larger than unity, the inner edge of the quasi-toroidal inner accretion structure would be located well within the Schwarzschild marginally stable orbit (ISCO), and the maximum orbital frequency in thin accretion disks would be much higher than the Schwarzschild ISCO frequency. © 2025, CC BY.

关键词： Relativity

Populating Large N-body Simulations with LRGs Using Neural Networks

学校读者我要写书评

暂无评论

arXiv 2025年

作者： Icaza-Lizaola, M. Sirks, E.L. Song, Yong-Seon Norberg, Peder Shi, Feng Korea Astronomy and Space Science Institute 776 Daedeok-daero Yuseong-gu Daejeon34055 Korea Republic of Departamento de Física Teórica Facultad de Ciencias M-8 Universidad Autónoma de Madrid Madrid28049 Spain Facultad de Ciencias Universidad Autónoma de Madrid Madrid28049 Spain School of Physics The University of Sydney SydneyNSW2006 Australia The Australian Research Council Centre of Excellence for Dark Matter Particle Physics Australia Institute for Computational Cosmology Department of Physics Durham University South Road DurhamDH1 3LE United Kingdom Institute for Data Science Department of Physics Durham University South Road DurhamDH1 3LE United Kingdom Centre for Extragalactic Astronomy Department of Physics Durham University South Road DurhamDH1 3LE United Kingdom School of Aerospace Science and Technology Xidian University Xi’an710126 China

The analysis of state-of-the-art cosmological surveys like the Dark Energy Spectroscopic Instrument (DESI) survey requires high-resolution, large-volume simulations. However, the computational cost of hydrodynamical simulations at these scales is prohibitive. Instead, dark matter (DM)-only simulations are used, with galaxies populated a posteriori, typically via halo occupation distribution (HOD) models. While effective, HOD models are statistical in nature and lack full physical motivation. In this work, we explore using neural networks (NNs) to learn the complex, physically motivated relationships between DM haloes and galaxy properties. Trained on small-volume, high-resolution hydrodynamical simulations, our NN predicts galaxy properties in a larger DM-only simulation and determines which galaxies should be classified as luminous red galaxies (LRGs). Comparing the original LRG sample to the one generated by our NN, we find that, while the subhalo mass distributions are similar, our NN selects fewer low-mass subhaloes as LRG hosts, possibly due to the absence of baryonic feedback effects in DM-only simulations. This feedback could brighten or redden galaxies, altering their classification. Finally, we generate a new LRG sample by fitting an HOD model to the NN-generated LRG sample. We verify that both the HOD- and NN-generated samples preserve a set of bias parameter relations, which assume that the higher-order parameters, ｂｓ2 and ｂ3nl, are determined by the linear bias parameter ｂ1. These relations are commonly used to simplify clustering analyses. © 2025, CC BY.

关键词： Dark Matter

Probing globular cluster with MeerKAT and FAST: A pulsar polarization census

学校读者我要写书评

暂无评论

Science Bulletin 2025年

作者： Zhang, Lei Abbate, Federico Li, Di Possenti, Andrea Bailes, Matthew Ridolfi, Alessandro Freire, Paulo C.C. Ransom, Scott M. Zhang, Yong-Kun Guo, Meng Ni, Meng-Meng Hu, Jia-Le Feng, Yi Wang, Pei Zhang, Jie Zhi, Qi-Jun National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China Centre for Astrophysics and Supercomputing Swinburne University of Technology VIC3122 Australia INAF – Osservatorio Astronomico di Cagliari Via della Scienza 5 SelargiusI-09047 Italy Max-Planck-Institut für Radioastronomie Auf dem Hügel 69 BonnD-53121 Germany Department of Astronomy Tsinghua University Beijing100190 China Swinburne University of Technology VIC3122 Australia Faculty of Physics University of Bielefeld Bielefeld33501 Germany National Radio Astronomy Observatory Charlottesville22903 United States National Supercomputing Center in Jinan Qilu University of Technology Jinan250103 China Jinan Institute of Supercomputing Technology Jinan250103 China Research Center for Intelligent Computing Platforms Zhejiang Laboratory Hangzhou311100 China Institute for Astronomy School of Physics Zhejiang University Hangzhou310027 China College of Physics and Electronic Engineering Qilu Normal University Jinan250200 China Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processing Guizhou Normal University Guiyang550001 China