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Movable-Antenna-Assisted Covert Communications With Reconfigurable Intelligent Surfaces

IEEE Internet of Things Journal 2025年第9期12卷 12369-12382页

作者： Xie, Wenwu Li, Zilong Yu, Chao Xu, Hongbo Wang, Ji Wu, Weimin Li, Xingwang Yang, Liang Hunan Institute of Science and Technology School of Information Science and Engineering Yueyang414006 China Central China Normal University College of Physical Science and Technology Department of Electronics and Information Engineering Wuhan430079 China Huazhong University of Science and Technology School of Electronic Information and Communications Wuhan430074 China Henan Polytechnic University School of Physics and Electronic Information Engineering Jiaozuo454003 China Hunan University College of Computer Science and Electronic Engineering Changsha410082 China

This article proposes a novel covert communication framework utilizing movable antennas (MAs) to enable covert communications in which the evading detection eavesdropper aided by a reconfigurable intelligent surface (RIS). The trajectories of the MAs over the entire time slot, transmit beamforming, and the phase shift of the RIS in each time slot are jointly optimized to improve the covert rate. Specifically, the movement trajectories of the MAs are modeled as a Markov decision process (MDP), optimized by developing a novel deep reinforcement learning (DRL) approach. Furthermore, an alternating optimization (AO) algorithm is designed to jointly optimize the beamforming and phase. In particular, penalty-based two-layer iterative algorithm is proposed to guarantee that the solution satisfies the rank-one constraints. Numerical results show that the proposed MA-assisted covert communications system significantly outperforms conventional fixed-position antenna (FPA) schemes in terms of covert rate. © 2014 IEEE.

关键词： Markov processes

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High-Quality Single Crystal of Kitaev Spin Liquid Candidate Material RuBr_(3) Synthesized under High Pressure

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Chinese physics Letters 2025年第2期42卷 249-254页

作者： Bowen Zhang Xiangjun Li Limin Yan Wenbo Li Nana Li Jianfa Zhao Xiaobing Liu Shun-Li Yu Zhiwei Hu Wenge Yang Runze Yu Center for High-Pressure Science and Technology Advanced Research Beijing 100093China Laboratory of High-Pressure Physics and Material Science School of Physics and Physical EngineeringQufu Normal UniversityQufu 273165China Institute of Physics Chinese Academy of SciencesBeijing 100190China National Laboratory of Solid-State Microstructures and Department of Physics Nanjing UniversityNanjing 210093China Max-Planck Institute for Chemical Physics of Solids Dresden 01187Germany

Kitaev quantum spin liquids have attracted significant attention in condensed matter physics over the past *** understand their emergent quantum phenomena,high-quality single crystals of substantial size are ***,we report the synthesis of single crystals of the Kitaev quantum spin liquid candidate RuBr_(3),achieving millimeter-sized crystals through a self-flux method under high pressure and high temperature *** crystals exhibit well-defined cleavage planes with a lustrous *** characterizations exhibit a narrow band-gap semiconducting behavior with 0.13 eV and 0.11 eV band-gap in ab plane and along𝑐axis,*** measurement shows a transition to antiferromagnetic(AFM)state at approximately 29K both in ab plane and along the c ***,the N′eel temperature increases to 34K with an applied magnetic field of up to 7T in the ab plane,but without any change along𝑐*** large size and high quality of RuBr3 single crystals provide a valuable platform for investigating various interactions,particularly the Kitaev interaction,and for elucidating the intrinsic physical properties of Kitaev quantum spin liquids.

关键词： quantum narrow sized

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Molecular dynamics evaluation of self-diffusion coefficients in two-dimensional dusty plasmas

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Chinese physics B 2025年第4期34卷 457-466页

作者： Muhammad Asif Shakoori Misbah Khan Haipeng Li Aamir Shahzad Maogang He Syed Ali Raza School of Materials Science and Physics China University of Mining and TechnologyXuzhou 221116China Department of Refrigeration and Cryogenic Engineering School of Energy and Power EngineeringXi’an Jiaotong UniversityXi’an 710049China Department of Physics Government College University Faisalabad(GCUF)Allama Iqbal RoadFaisalabad 38000Pakistan Key Laboratory of Thermo-Fluid Science and Engineering of Ministry of Education(MOE) Xi’an Jiaotong UniversityXi’an 710049China School of Electrical Engineering Xi’an Jiaotong UniversityXi’an 710049China

We employ the Green–Kubo(G-K)and Einstein relations to estimate the self-diffusion coefficients(denoted as D_(G)and D_(E),respectively)in two-dimensional(2D)strongly coupled dusty plasmas(SC-DPs)via equilibrium molecular dynamics(EMD)simulations.D_(G)and D_(E)are computed for a broad domain of screening length(κ)and coupling parameters(Г)along with different system *** is observed that both D_(G)and D_(E)decrease linearly with increasing G in warm liquid states and increase with increasingκ.In cold liquid states,the Einstein relation accurately predicts D_(E)in 2D SC-DPs because diffusion motion is close to normal diffusion,but the G-K relation provides overestimations of D_(G),because VACF indicates anomalous diffusion;thus,D_(G)is not *** new simulation outcomes reveal that D_(G)and D_(E)remain independent of system ***,our investigations demonstrate that at higher temperatures,D_(G)and D_(E)converge,suggesting diffusion motion close to normal diffusion,while at lower temperatures,these two values *** find reasonable agreement by comparing current and existing numerical,theoretical and experimental ***,when normalizing diffusion coefficients by the Einstein frequency and testing against the universal temperature scaling law,D_(G)deviates from theoretical curves at low temperatures and k,whereas D_(E)only disagrees with theory at very smallκ(■0.10).These findings provide valuable insight into diagnosing dust component parameters within 2D DP systems and contribute to the broader understanding of diffusion processes in DP environments.

关键词： dusty(complex)plasmas self-diffusion coefficients molecular dynamics simulation Green-Kubo and Einstein relations

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Annual Energy Analysis of a Building-Integrated Semitransparent Photovoltaic Thermal Façade

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Journal of Solar Energy engineering 2025年第3期147卷 034501页

作者： Hazarika, Puja Shyam Kalita, Pankaj Gaur, Ankita School of Energy Science and Engineering Indian Institute of Technology Assam Guwahati781039 India Department of Physics Kirori Mal College University of Delhi Delhi110007 India

This study numerically examines the performance of a building-integrated semitransparent photovoltaic thermal (BiSPVT) façade in Srinagar, India's weather conditions. The primary objective is to explore the façade's potential to reduce building energy consumption while enhancing the electrical efficiency of photovoltaic (PV) modules by effectively cooling their surfaces through adjacent air circulation. A 1-D thermal model, implemented in matlab, analyzes the façade's performance under distinct weather conditions: clear day, hazy day, hazy and cloudy day, and fully cloudy day. The assessment of climatic conditions considers their impact on both building-integrated photovoltaic (BIPV) cell temperature and the annual energy output in a steady-state, considering the fluctuations in thermal losses. Results reveal the highest electrical efficiency of 18.9% and an overall thermal efficiency of 57.58% in January. Annually, the BiSPVT façade system generated 121.22 kWh/m2 of electrical energy, 61.06 kWh/m2 of thermal energy, 366.23 kWh/m2 of overall thermal energy, and 122.36 kWh/m2 of useful exergy. These findings offer insight into the reduction in the utilization of conventional sources of energy due to sustainable building design and renewable energy utilization. Copyright © 2025 by ASME.

关键词： Green buildings

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Fast and accurate poisson solver algorithm in 3D simply and double connected domains with a smooth complex geometry with applications in optics

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Optical and Quantum Electronics 2025年第2期57卷 1-26页

作者： El-Gamel, Mohamed Nassar, Nader R. El-Shenawy, Atallah Department of mathematics and engineering physics faculty of engineering Mansoura university Mansoura Egypt Higher Institute of Engineering and Technology New Damietta Egypt Department of Mathematics Faculty of science New Mansoura University New Mansoura Egypt

This paper introduces an innovative approach for addressing the Poisson equation in simply and doubly connected 3D domains with irregular surfaces, which has significant implications in various scientific and engineering fields, such as irregular cross-section optical waveguides and electromagnetic wave propagation. The Poisson equation is extensively utilized across disciplines like physics, engineering, and mathematics, and its solution offers insight into diverse physical phenomena. The solution to the Poisson equation is helpful in constructing potentials crucial for the comprehension and design of optical and electromagnetic systems. The application of Radial Basis Functions (RBFs) collocation method with changeable form parameters presents novel opportunities for precise and efficient resolutions of this significant equation. Our methodology is relevant to both simply and doubly connected three-dimensional domains with irregular surfaces, frequently seen in various practical applications, such as complex waveguide geometries. Seven instances are presented for various complex simply and doubly connected 3D domains, illustrating the efficacy of the suggested Poisson solver in generating potentials to improve the precision and efficiency of the method. The proposed method can be considered as a benchmark solver for such type of problems appearing in optics and electromagnetic wave engineering. keyword: Radial Basis Functions, Simply Connected Domains, Double Connected Domains, Variable shape parameter, Three dimensional Laplace equation, Three dimensional Poisson Equation. © The Author(s) 2025.

关键词： Poisson equation

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Shaping attosecond pulses via high-order harmonic generation driven by two mixed Laguerre-Gaussian vortex beams

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Optics Express 2025年第8期33卷 18540-18555页

作者： Wang, Beiyu Yin, Zhiming Wu, Shengfei Li, Baochang Han, Jiaxin Yang, Zengqiang Jin, Cheng Department of Applied Physics Nanjing University of Science and Technology Jiangsu Nanjing210094 China School of Physics and Information Science Shaanxi University of Science and Technology Shaanxi Xi’An710021 China MIIT Key Laboratory of Semiconductor Microstructure and Quantum Sensing Engineering Research Center of Semiconductor Device Optoelectronic Hybrid Integration in Jiangsu Province Nanjing University of Science and Technology Jiangsu Nanjing210094 China

Shaping the waveform of attosecond pulses is crucial for controlling electron dynamics and is typically achieved using a high-order harmonic generation (HHG) spectrum containing a minimum. Here, we propose a novel method for shaping attosecond pulses via HHG without carrying orbital angular momentum (OAM), driven by two mixed Laguerre-Gaussian vortex beams with oppositely signed OAMs. We show that the waveform of an attosecond pulse train synthesized using low-divergent, non-vortical high harmonics in the far field can be significantly regulated;specifically, the number of emission bursts within half an optical cycle of the driving laser increases to five compared to one or two bursts in the previous studies. We also show that the spectral structure of on-axis high harmonics in the far field, as well as the waveform of the resulting attosecond pulses, can be modified by varying the position or thickness of the gas medium. Additionally, we analyze the phase-matching mechanism of near-field harmonics, which generate on-axis harmonics in the far field after propagation. Transverse and longitudinal phase-matching mechanisms are identified for thin and thick gas media, respectively. We anticipate that this work will provide new insights into expanding the applications of employing vortex beams to drive the HHG process in gas media. © 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.

关键词： Vortex flow

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Innovative Approaches to Task Scheduling in Cloud Computing Environments Using an Advanced Willow Catkin Optimization Algorithm

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Computers, Materials & Continua 2025年第2期82卷 2495-2520页

作者： Jeng-Shyang Pan Na Yu Shu-Chuan Chu An-Ning Zhang Bin Yan Junzo Watada College of Computer Science and Engineering Shandong University of Science and TechnologyQingdao266590China Department of Information Management Chaoyang University of TechnologyTaichung41349Taiwan College of Electronics Communication and PhysicsShandong University of Science and TechnologyQingdao266590China Graduate School of Information Production and SystemsWaseda UniversityKitakyushu808-0135Japan

The widespread adoption of cloud computing has underscored the critical importance of efficient resource allocation and management, particularly in task scheduling, which involves assigning tasks to computing resources for optimized resource utilization. Several meta-heuristic algorithms have shown effectiveness in task scheduling, among which the relatively recent Willow Catkin Optimization (WCO) algorithm has demonstrated potential, albeit with apparent needs for enhanced global search capability and convergence speed. To address these limitations of WCO in cloud computing task scheduling, this paper introduces an improved version termed the Advanced Willow Catkin Optimization (AWCO) algorithm. AWCO enhances the algorithm’s performance by augmenting its global search capability through a quasi-opposition-based learning strategy and accelerating its convergence speed via sinusoidal mapping. A comprehensive evaluation utilizing the CEC2014 benchmark suite, comprising 30 test functions, demonstrates that AWCO achieves superior optimization outcomes, surpassing conventional WCO and a range of established meta-heuristics. The proposed algorithm also considers trade-offs among the cost, makespan, and load balancing objectives. Experimental results of AWCO are compared with those obtained using the other meta-heuristics, illustrating that the proposed algorithm provides superior performance in task scheduling. The method offers a robust foundation for enhancing the utilization of cloud computing resources in the domain of task scheduling within a cloud computing environment.

关键词： Willow catkin optimization algorithm cloud computing task scheduling opposition-based learning strategy

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Fabrication of dye-sensitised solar cell using dry Ixora extract as sensitiser

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Materials Research Innovations 2025年第3期29卷 135-142页

作者： Osolobri, Blessing Uyoyou O. E. Enaroseha, Omamoke Anho, Lawrence Oghenerivwe Department of Science Laboratory Technology Delta State Polytechnic Ogwashi–Uku Nigeria Department of Physics Delta State University Abraka Nigeria Department of Chemical Engineering Federal University of Petroleum Resources Effurun Nigeria

A dye-sensitised solar cell was fabricated using dry Ixora flower extract. The sensitiser was obtained by physical extraction using a mixture of ethanol and distilled water as solvent in the ratio of 7:3. The optical study of the sample was done within wavelength range of 230 nm to 1100 nm using spectrophotometer (UV- 750 series). The outcome shows an optimum absorption in the visible region of the EM spectrum, which shifted to the UV region when adsorbed onto a nano-porous TiO2 surface. An alternative peak of 0.95a.u in the visible region was observed with enhanced optical absorption across the infrared region of the spectrum. The absorption coefficient values suggest the extract absorbs light in the visible region, which was also confirmed with the relatively high extinction coefficient observed in the visible region of the EM spectrum. The extract exhibits a low transmittance in the visible range, which increases to over 99% in the red wavelengths. The extract has low reflectance of about 20% in the visible range, which falls lower as wavelength increases into the infrared region. The energy band gap (for direct transition) of 2.13 eV was obtained for dry Ixora dye extract. The fabricated solar cell performed a fill factor of 0.27, Jsc of 0.1273 mA/cm2, Voc of 0.7001 V, and conversion efficiency of about 0.02%. with these results, the dye extract of dry ixora flower can serve as a good photo-sensitiser for the fabrication of dye-sensitised solar cell. © 2024 Informa UK Limited, trading as Taylor & Francis Group.

关键词： Optical properties

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Twofold symmetric superconductivity in NbSe2 monolayers with vacancy defects

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Physical Review B 2025年第6期111卷 L060503-L060503页

作者： Jizheng Wu Wenyu He Yong Xu Chen Si School of Materials Science and Engineering Beihang University Beijing 100191 China School of Physical Science and Technology ShanghaiTech University Shanghai 201210 China State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics Tsinghua University Beijing 100084 China Frontier Science Center for Quantum Information Beijing 100084 China

Monolayer NbSe2, as an Ising superconductor, has attracted considerable attention. Experimentally, its samples inevitably contain defects, yet the effects of these defects on superconductivity remain largely unexplored. Here, we demonstrate that selenium (Se) monovacancies, the most common defects in monolayer NbSe2, critically affect superconductivity. Specifically, Se monovacancies disrupt both the out-of-plane mirror symmetry and the C3z rotational symmetry in pristine monolayer NbSe2, resulting in an asymmetric spin-orbit coupling (SOC). While pristine monolayer NbSe2, which possesses Ising SOC, exhibits an isotropic in-plane upper critical field (Bc2), the asymmetric SOC induced by Se monovacancies leads the in-plane Bc2 to display an anisotropic twofold symmetry in response to the direction of the in-plane magnetic field. Furthermore, Se monovacancies significantly reduce the in-plane spin susceptibility of the superconducting state, causing Bc2 to exceed the Pauli limit only moderately, consistent with experimental observations. These findings provide valuable insights into the role of defects in tuning superconductivity of two-dimensional materials.

关键词： Spin orbit coupling

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Spin Hall effect driven photocurrent in nonmagnetic single metals

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Physical Review B 2025年第14期111卷 L140406-L140406页

作者： Taiki Nishijima Ryo Ohshima Youichi Yanase Ryota Ishii Masashi Shiraishi Yuichiro Ando Department of Electronic Science and Engineering Kyoto University Kyoto Kyoto 615-8510 Japan Department of Physics Graduate School of Science Kyoto University Kyoto Kyoto 606-8502 Japan PRESTO Japan Science and Technology Agency Honcho Kawaguchi Saitama 332-0012 Japan Department of Physics and Electronics Osaka Metropolitan University 1-1 Gakuencho Sakai Osaka 599-8531 Japan

Nonlinear phenomena in condensed matter physics have been explored extensively in exotic materials, including materials with broken inversion symmetry, topological materials, metamaterials, and quantum wells. However, conventional nonmagnetic transition metals have largely been overlooked in this context because of their perceived relative simplicity. Here, we reveal the unexplored potential of nonmagnetic single-element metals by focusing on one type of nonlinear phenomenon: photocurrent generation induced by spin accumulation due to the spin Hall effect at the material edges. Distinctive behavior at the material edges, where the spatial symmetry is intrinsically broken, leads to observation of the nonlinear phenomenon. The resulting photocurrent is identified as a linear injection current and is associated with both time-reversal symmetry breaking and space-inversion symmetry breaking. This observation challenges the prevailing notion that nonlinear phenomena are exclusively observed in more exotic materials. We perform scanning photovoltage microscopy on Pt, W, Cu, and perpendicular magnetic anisotropy films to verify and characterize the observed linear injection current experimentally, thus confirming the crucial roles of spin accumulation and edge asymmetry in photocurrent generation. This finding provides a comprehensive understanding of linear injection currents realized during symmetry violation and is promising for development of spin- and symmetry-based techniques.

关键词： Magnetic anisotropy

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