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Statistics of Superluminal Motion in Active Galactic Nuclei

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Chinese Journal of Astronomy and Astrophysics 2008年第4期8卷 385-394页

作者： Yong-wei zhang jun-Hui Fan Center for Astrophysics Guangzhou University Guangzhou 510006 China

We have collected an up-to-date sample of 123 superluminal sources （84 quasars, 27 BL Lac objects and 12 galaxies） and calculated the apparent velocities （βapp） for 224 components in the sources with the A-CDM model. We checked the relationships between their proper motions, redshifts,βapp and 5 GHz flux densities. Our analysis shows that the radio emission is strongly boosted by the Doppler effect. The superluminal motion and the relativistic beaming boosting effect are, to some extent, the same in active galactic nuclei.

关键词： galaxies jets - galaxies general - BL Lacertae objects active - quasars data analysis

Vibration analysis of hydropower house based on fluid-structure coupling numerical method

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Water Science and Engineering 2010年第1期3卷 75-84页

作者： Shu-he wei Liao-jun zhang College of Water Conservancy and Hydropower Engineering Hohai University Nanjing 210098 P. R. China

By using the shear stress transport （SST） model to predict the effect ot random now motion in a fluid zone, and using the Newmark method to solve the oscillation equations in a solid zone, a coupling model of the .powerhouse and its tube water was developed. The effects of fluid-structure interaction are considered through the kinematic and dynamic conditions applied to the fluid-structure interfaces （FSI）. Numerical simulation of turbulent flow through the whole flow passage of the powerhouse and concrete structure vibration analysis in the time domain were carried out with the model. Considering the effect of coupling the turbulence and the powerhouse structure, the time history response of both turbulent flows through the whole flow passage and powerhouse structure vibration were generated. Concrete structure vibration analysis shows that the displacement, velocity, and acceleration of the dynamo floor respond dramatically to pressure fluctuations in the flow passage. Furthermore, the spectrum analysis suggests that pressure fluctuation originating from the static and dynamic disturbances of hydraulic turbine blades in the flow passage is one of the most important vibration sources.

关键词： hydropower house fluid-structure interaction Navier-Stokes equations structuralvibration, numerical simulation

A New Simplified Zonal Method for Furnace Thermal Radiation Calculation Based on Imaginary Planes

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Journal of Iron and Steel Research International 2014年第4期21卷 419-426页

作者： wei-jun zhang Zhi YI Hai-geng CHEN College of Materials and Metallurgy Northeastern University

When solving the complex radiative heat transfer problems in reheating furnaces, there are a number of difficulties with the traditional zonal methods. To circumvent these difficulties, a new simplified method was pro- posed, which employed imaginary planes, referred to as the imaginary plane model. With the new model, crown wall reduction process was simplified. Therefore, every model zone could be treated as a closed square cavity. It could also solve the problem of radiative blocking in industrial furnaces more effectively. Besides, the new imaginary plane based model may lead to a problem that the denominator was zero. This problem was solved by transforming the ex- pressions of reflex heat flux in the model. The model was capable of dealing with the systems that included black sur- faces. The model was validated by considering the heat transfer in a reheating furnace where the temperature fields in the furnace chamber （including the steel, wall and gas） were obtained. A detailed comparison was made between the simulation and the black box experiment. The results show that the new model developed was valid and accurate.

关键词： imaginary plane zonal method crown wall reduction total radiative exchange area

FeNi doped porous carbon as an efficient catalyst for oxygen evolution reaction

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Frontiers of Chemical Science and Engineering 2021年第2期15卷 279-287页

作者： jun-wei zhang Hang zhang Tie-Zhen Ren Zhong-Yong Yuan Teresa JBandosz Hebei Provincial Key Laboratory of Green Chemical Technology&High Efficient Energy Saving School of Chemical Engineering and TechnologyHebei University of TechnologyTianjin 300130China Key Laboratory of Advanced Energy Materials Chemistry(Ministry of Education) School of Materials Science and EngineeringNankai UniversityTianjin 300350China Department of Chemistry and Biochemistry The City College of New YorkNew YorkNY 10031USA

Polymer-derived porous carbon was used as a support of iron and nickel species with an objective to obtain an efficient oxygen reduction reaction(OER)*** surface features were extensively characterized using X-ray diffraction,X-ray photoelectron spectroscopy and high-resolution transmission electron *** FeNi-modified carbon the overpotential for OER was very low(280 mV)and comparable to that on noble metal catalyst IrO_(2).The electrochemical properties have been investigated to reveal the difference between the binary alloy-and single metal-doped *** work demonstrates a significant step for the development of low-cost,environmentally-friendly and highly-efficient OER catalysts.

关键词： OER polystyrene salt porous carbon FeNi alloy p/n junction

Deriving Energy-Level Gap of a System in Presence of a Kerr-like Medium by Virtue of Invariant Eigen-operator Method

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Communications in Theoretical Physics 2006年第4期45卷 614-616页

作者： GUI wei-jun GUI Jia-zhang TANG Gang Department of Machinery and Electronic Engineering Nanchang institute of Technology Nanchang 330099 China

In this paper, we find the invariant eigen-operators （IEOs） and the energy-level gap of a system with a two-level atom interacting with single mode cavity field through multi-photon transition in the presence of a Kerr-like medium. From this work, one can see that the IEO method in many eases is simpler and easier on obtaining the energy-level gap formula than the usual way.

关键词： energy-level gap Kerr-like medium invariant eigen-operator

The Substitution Secant/Finite Difference Method for Large Scale Sparse Unconstrained Optimization

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Acta Mathematicae Applicatae Sinica 2005年第4期21卷 581-596页

作者： Hong-wei zhang jun-xiang Li Department of Applied Mathematics Dalian University of Technology Dalian 116024 China

This paper studies a substitution secant/finite difference （SSFD） method for solving large scale sparse unconstrained optimization problems. This method is a combination of a secant method and a finite difference method, which depends on a consistent partition of the columns of the lower triangular part of the Hessian matrix. A q-superlinear convergence result and an r-convergence rate estimate show that this method has good local convergence properties. The numerical results show that this method may be competitive with some currently used algorithms.

关键词： Unconstrained optimization substitution Hessian sparsity secant method

Space-frequency-polarization-division multiplexed wireless communication system using anisotropic space-time-coding digital metasurface

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National Science Review 2022年第11期9卷 149-160页

作者： jun Chen Ke Xiangyu Chen Wankai Tang Ming Zheng Chen Lei zhang Li Wang jun Yan Dai Jin Yang jun wei zhang Lijie Wu Qiang Cheng Shi Jin Tie jun Cui State Key Laboratory of Millimeter Waves Southeast University Institute of Electromagnetic Space Southeast University Frontiers Science Center for Mobile Information Communication and Security Southeast University National Mobile Communications Research Laboratory Southeast University Southeast University Wuxi Campus

In the past few years, wireless communications based on digital coding metasurfaces have gained research interest owing to their simplified architectures and low cost. However, in most of the metasurface-based wireless systems, a single-polarization scenario is used, limiting the channel capacities. To solve the problem, multiplexing methods have been adopted, but the system complexity is inevitably increased. Here,a space-frequency-polarization-division multiplexed wireless communication system is proposed using an anisotropic space-time-coding digital metasurface. By separately designing time-varying control voltage sequences for differently oriented varactor diodes integrated on the metasurface, we achieve frequency-polarization-division multiplexed modulations. By further introducing different time-delay gradients to the control voltage sequences in two polarization directions, we successfully obtain space-frequency-polarization-division multiplexed modulations to realize a wireless communication system with a new architecture. The new communication system is designed with compact dual-polarized meta-elements, and can improve channel capacity and space utilization. Experimental results demonstrate the high-performance and real-time transmission capability of the proposed communication system,confirming its potential application in multiple-user collaborative wireless communications.

关键词： polarization-division multiplexing frequency-division multiplexing space-division multiplexing space-time coding wireless communication

Engineering heterostructured Ni@Ni(OH)_(2) core-shell nanomaterials for synergistically enhanced water electrolysis

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Green Energy & Environment 2022年第5期7卷 1024-1032页

作者： jun-wei zhang Xian-wei Lv Tie-Zhen Ren Zheng Wang Teresa J.Bandosz Zhong-Yong Yuan Hebei Provincial Key Laboratory of Green Chemical Technology&High Efficient Energy Saving School of Chemical Engineering and TechnologyHebei University of TechnologyTianjin300130China Key Laboratory of Advanced Energy Materials Chemistry(Ministry of Education) School of Materials Science and EngineeringNankai UniversityTianjin300350China State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering Ningxia UniversityYinchuan750021NingxiaChina Department of Chemistry and Biochemistry The City College of New YorkNY10031USA

Heterostructure engineering of electrocatalysts provides a fascinating platform to reasonably manipulate the physicochemical properties of nanomaterials and further improve their catalytic efficiency for water ***,it still remains a huge challenge to construct welldesigned core-shell heterostructured catalysts and identify the key role of components for synergistic ***,a melted polymeric salt tactics was innovatively developed to synthesize heterostructured Ni@Ni(OH)_(2) core-shell nanomaterials supported on porous carbon(named Ni@Ni(OH)_(2)/PC),wherein well-defined Ni(OH)_(2)-Ni heterostructure plays a pivotal role in improving electrocatalytic activity for water reduction and ***,the stable porous carbon support functions as a highway for continuous electron transfer between Ni and Ni(OH)_(2),and simultaneously enables the full exposure of accessible active *** fabricated Ni@Ni(OH)_(2)/PC exhibits outstanding bifunctional electrocatalytic performance for overall water splitting(η_(10)=1.55 V) with a good long-time *** work sheds new light on the design of engineering heterostructure of active bifunctional electrocatalysts for efficient energy conversion system.

关键词： stability synergistic splitting

Frequency-modulated continuous waves controlled by space-time-coding metasurface with nonlinearly periodic phases

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Light(Science & Applications) 2022年第10期11卷 2424-2434页

作者： jun Chen Ke jun Yan Dai jun wei zhang Zhanye Chen Ming Zheng Chen Yunfeng Lu Lei zhang Li Wang Qun Yan Zhou Long Li Jin Shan Ding Qiang Cheng Tie jun Cui Institute of Electromagnetic Space Southeast University210096 NanjingChina State Key Laboratory of Millimeter Waves Southeast University210096 NanjingChina School of Electronic Engineering Xidian University710071 Xi'anChina

The rapid development of space-time-coding metasurfaces(STCMs)offers a new avenue to manipulate spatial electromagnetic beams,waveforms,and frequency spectra simultaneously with high *** date,most studies are primarily focused on harmonic generations and independent controls of finite-order harmonics and their spatial waves,but the manipulations of continuously temporal waveforms that include much rich frequency spectral components are still limited in both theory and experiment based on ***,we propose a theoretical framework and method to generate frequency-modulated continuous waves(FMCWs)and control their spatial propagation behaviors simultaneously via a novel STCM with nonlinearly periodic *** the carrier frequency of FMCW changes with time rapidly,we can produce customized time-varying reflection phases at will by the required FMCW under the illumination of a monochromatic *** importantly,the propagation directions of the time-varying beams can be controlled by encoding the metasurface with different initial phase gradients.A programmable STCM prototype with a full-phase range is designed and fabricated to realize reprogrammable FMCW functions,and experimental results show good agreement with the theoretical analyses.

关键词： nonlinear continuous periodic