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Aeroelastic effect on aerothermoacoustic response of metallic panels in supersonic flow

Chinese Journal of Aeronautics 2016年第6期29卷 1635-1648页

作者： Wang Xiaochen Yang Zhichun Zhou Jian Hu wei School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China Xi’an Aerospace Propulsion Institute Xi’an 710100China

A finite element formulation is presented for the analysis of the aeroelastic effect on the aerothermoacoustic response of metallic panels in supersonic flow. The first-order shear deformation theory(FSDT) and the von Karman nonlinear strain-displacement relationships are employed to consider the geometric nonlinearity induced by large deflections. The piston theory and the Gaussian white noise are used to simulate the mean flow aerodynamics and the turbulence from the boundary layer. The thermal loading is assumed to be steady and uniformly distributed, and the material properties are assumed to be temperature independent. The governing equations of motion are firstly formulated in structural node degrees of freedom by using the principle of virtual work,and then transformed and reduced to a set of coupled nonlinear Duffing oscillators in modal coordinates. The dynamic response of a panel is obtained by the Runge-Kutta integration method. The results indicate that the increasing aeroelastic effect can lead the panel vibration from a random motion to a highly ordered motion in the fashion of diffused limit cycle oscillations(LCOs), and remarkably alter the stochastic bifurcation and the spectrum of the aerothermoacoustic *** the other hand there exists a counterbalance mechanism between the external random loading and the aeroelastic effect, which mainly functions through the nonlinear frequency-amplitude response. It is surmised that the aeroelastic effect must be considered in sonic fatigue analysis for panel structures in supersonic flow.

关键词： Aeroelastic effect Aerothermoacoustic response Metallic panels Nonlinear frequencyamplitude response Sonic fatigue

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Design of Time-constrained Guidance Laws via Virtual Leader Approach

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Chinese Journal of Aeronautics 2010年第1期23卷 103-108页

作者： Zhao Shiyu Zhou Rui wei Chen Ding Quanxin School of Automation Science and Electrical Engineering Beijing University of Aeronautics and Astronautics Beijing 100191 China National Defense Key Lab of Fire Control Technique Luoyang Institute of Electro-optical Equipment of A VIC Luoyang 471009 China

Guidance problems with flight time constraints are considered in this article. A new virtual leader scheme is used for design of guidance laws with time constraints. The core idea of this scheme is to adopt a virtual leader for real missiles to convert a guidance problem with time constraints to a nonlinear tracking problem,thereby making it possible to settle the problem with a variety of control methods. A novel time-constrained guidance （TCG） law, which can control the flight time of missiles to a prescribed time,is designed by using the virtual leader scheme and stability method. The TCG law is a combination of the well-known proportional navigation guidance（PNG） law and the feedback of flight time error. What＇ s more, this law is free of singularities and hence yields better performances in comparison with optimal guidance laws with time constraints. Nonlinear simulations demonstrate the effectiveness of the proposed law.

关键词： guidance missiles salvo attack time constraint virtual leader

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Spatial patterns of leaf nitrogen and phosphorus stoichiometry across southeast to central Tibet

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Journal of Mountain Science 2022年第9期19卷 2651-2663页

作者： WANG wei ZHAO Jia-min XING Zhen College of Resources and Environmental Sciences Tibet Agriculture&Animal Husbandry UniversityNyingchi 860000China Research institute of Tibet Plateau Ecology Tibet Agriculture&Animal Husbandry UniversityNyingchi 860000China

Leaf N and P stoichiometry in terrestrial ecosystems has been widely investigated in recent years owing to the importance of these elements in improving the predicted vegetation responses to global *** vertical distribution of leaf N and P stoichiometry has attracted increasing attention because of the dramatic changes in environmental factors at regional ***,the characteristics of leaf N and P stoichiometry in the southeast Qinghai–Tibet plateau(SET)are not clear,although this area is sensitive to global ***,we analyzed the leaf N and P concentrations in dominant plant species on natural altitudinal gradients on the Duoxiongla(DXL),Sejila(SJL),Mila(ML),and Gangbala(GBL)mountains across the SET all the way to central *** results showed that the leaf N concentrations were comparable among the regions,whereas the leaf P concentrations dramatically decreased from SET to central Tibet(CT).The leaf N concentrations were 23.6,21.3,20.8,and 22.4 g kg^(-1),and the leaf P concentrations were 2.40,2.49,1.94,and 1.59 g kg^(-1) on the SJL,DXL,ML and GBL mountains,*** leaf N/P ratios on the DXL,SJL,ML,and GBL mountains were 8.81,10.3,11.2,and 14.2,*** the increasing trend of the leaf N/P ratio from southeast Qinghai–Tibet plateau to central Tibet,N limitation might widely exist in well vegetated ecosystems in the Qinghai–Tibet plateau.

关键词： Leaf N and P concentration Southeast Tibet Stoichiometry Spatial variations

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Robust Object Tracking via Information Theoretic Measures

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International Journal of Automation and computing 2020年第5期17卷 652-666页

作者： wei-Ning Wang Qi Li Liang Wang Center for Research on Intelligent Perception and Computing National Laboratory of Pattern RecognitionInstitute of AutomationChinese Academy of SciencesBeijing 100190China School of Artificial Intelligence University of Chinese Academy of SciencesBeijing 100190China Artificial Intelligence Research Chinese Academy of SciencesQingdao 266300China

Object tracking is a very important topic in the field of computer *** sophisticated appearance models have been *** them,the trackers based on holistic appearance information provide a compact notion of the tracked object and thus are robust to appearance variations under a small amount of ***,in practice,the tracked objects are often corrupted by complex noises(e.g.,partial occlusions,illumination variations)so that the original appearance-based trackers become less *** paper presents a correntropy-based robust holistic tracking algorithm to deal with various ***,a half-quadratic algorithm is carefully employed to minimize the correntropy-based objective *** on the proposed information theoretic algorithm,we design a simple and effective template update scheme for object *** results on publicly available videos demonstrate that the proposed tracker outperforms other popular tracking algorithms.

关键词： Object tracking information theoretic measures correntropy template update robust to complex noises

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A novel RHT-TBD approach for weak targets in HPRF radar

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Science China Earth Sciences 2016年第12期59卷 59-72页

作者： Hongbo YU Guohong WANG wei WU Shuncheng TAN Institute of Information Fusion Naval Aeronautical and Astronautical University

A novel approach, which can handle ambiguous data from weak targets, is proposed within the randomized Hough transform track-before-detect(RHT-TBD) framework. The main idea is that, without the pre-detection and ambiguity resolution step at each time step, the ambiguous measurements are mapped by the multiple hypothesis ranging(MHR) procedure. In this way, all the information, based on the relativity in time and pulse repetition frequency(PRF) domains, can be gathered among different PRFs and integrated over time via a batch procedure. The final step is to perform the RHT with all the extended measurements, and the ambiguous data is unfolded while the detection decision is confirmed at the end of the processing *** classic methods, the new approach resolves the problem of range ambiguity and detects the true track for targets. Finally, its application is illustrated to analyze and compare the performance between the proposed approach and the existing approach. Simulation results exhibit the effectiveness of this approach.

关键词： high pulse repetition frequency weak targets track-before-detect randomized Hough transform multiple hypothesis ranging range ambiguity resolution

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Experimental long-distance quantum secure direct communication

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Science Bulletin 2017年第22期62卷 1519-1524页

作者： Feng Zhu wei Zhang Yubo Sheng Yidong Huang Tsinghua National Laboratory for Information Science and Technology Department of Electronic Engineering Tsinghua University Beijing 100084 China College of Telecommunications and Information Engineering Nanjing University of Posts and Telecommunication Nanjing 210003 China

Quantum secure direct communication(QSDC) is an important quantum communication branch, which realizes the secure information transmission directly without encryption and decryption ***, two table-top experiments have demonstrated the principle of QSDC. Here, we report the first long-distance QSDC experiment, including the security test, information encoding, fiber transmission and decoding. After the fiber transmission of 0.5 km, quantum state fidelities of the two polarization entangled Bell states are 91% and 88%, respectively, which are used for information coding. We theoretically analyze the performance of the QSDC system based on current optical communication technologies,showing that QSDC over fiber links of several tens kilometers could be expected. It demonstrates the potential of long-distance QSDC and supports its future applications on quantum communication networks.

关键词： Quantum secure direct communication Polarization entangled Bell state Optical fibers Bell’s inequality test Bell state measurement

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Motion compensation algorithm in narrowband imaging for mid-course targets

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Journal of Systems Engineering and Electronics 2017年第1期28卷 40-50页

作者： Xizhang wei Zhen Liu Xiaofeng Ding Bo Peng School of Electronic Science and Engineering National University of Defense TechnologyChangsha 410073China Unit 31006 of the PLA Beijing 100086China

Imaging precession targets based on the narrowband radar to distinguish the real warhead from mid-course targets is a new technique in missile defense systems. Aiming at the typical mid-course flying scene, this paper describes the principle of the narrowband imaging method, and analyzes the influence on the narrowband imaging by the target translational motion. Then the precision qualification is deduced for both the distance compensation and the velocity compensation, and the conclusion that the velocity compensation is more appropriate for the motion compensation in the narrowband imaging is given. Furthermore, this paper proposes a motion compensation algorithm for the narrowband radar which reduces the interference of the signal phase chaos caused by the rebuilt real signal phase, thus realizing the precise translational motion compensation of the narrowband signal. Finally, the effectiveness of this method is proved by both theoretic analysis and experiment results. © 1990-2011 Beijing Institute of Aerospace Information.

关键词： Radar Radar imaging

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Photo-Crosslinking Induced Geometric Restriction Controls the Self-Assembly of Diphenylalanine Based Peptides

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Chinese Physics Letters 2011年第2期28卷 235-238页

作者： TIE Zuo-Xiu QIN Meng ZOU Da-wei CAO Yi WANG wei National Laboratory of Solid State Microstructure and Department of Physics Nanjing UniversityNanjing 210093

The diphenylalanine(FF)motif has been widely used in the design of peptides that are capable of forming various ordered structures,such as nanotubes,nanospheres and *** these assemblies,FF based peptides adopt an antiparallel structure and are stabilized by n-TT stacking among the phenyl *** we show that assembly of FF-based peptides can be controlled by their geometric *** tripeptide FFY(L-Phe-L-Phe-L-Tyr)as an example,we demonstrate that photo-crosslinking of C-terminal tyrosine can impose a geometric restriction to the formation of an antiparallel structure,leading to a structural change of the assemblies from nanosphere to amorphous.

关键词： amorphous spheres crosslinking

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Calculation method of ship collision force on bridge using artificial neural network

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第5期9卷 614-623页

作者： wei FAN Wan-cheng YUAN Qi-wu FAN State Key Laboratory for Disaster Reduction in Civil Engineering Tongji University Shanghai 200092 China Department of Civil Engineering Southwest Jiaotong University Chengdu 610031 China

Ship collision on bridge is a dynamic process featured by high nonlinearity and instantaneity. Calculating ship-bridge collision force typically involves either the use of design-specification-stipulated equivalent static load, or the use of finite element method (FEM) which is more time-consuming and requires supercomputing resources. In this paper, we proposed an alternative approach that combines FEM with artificial neural network (ANN). The radial basis function neural network (RBFNN) employed for calculating the impact force in consideration of ship-bridge collision mechanics. With ship velocity and mass as the input vectors and ship collision force as the output vector, the neural networks for different network parameters are trained by the learning samples obtained from finite element simulation results. The error analyses of the learning and testing samples show that the proposed RBFNN is accurate enough to calculate ship-bridge collision force. The input-output relationship obtained by the RBFNN is essentially consistent with the typical empirical formulae. Finally, a special toolbox is developed for calculation efficiency in application using MATLAB software.

关键词： Ship-bridge collision force Finite element method (FEM) Artificial neural network (ANN) Radial basis function neural network (RBFNN)

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Ionic thermal up-diffusion in nanofluidic salinity-gradient energy harvesting

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National Science Review 2019年第6期6卷 1266-1273页

作者： Rui Long Zhengfei Kuang Zhichun Liu wei Liu School of Energy and Power Engineering Huazhong University of Science and Technology

Advances in nanofabrication and materials science give a boost to the research in nanofluidic energy harvesting. Contrary to previous efforts on isothermal conditions, here a study on asymmetric temperature dependence in nanofluidic power generation is conducted. Results are somewhat counterintuitive. A negative temperature difference can significantly improve the membrane potential due to the impact of ionic thermal up-diffusion that promotes the selectivity and suppresses the ion-concentration polarization,especially at the low-concentration side, which results in dramatically enhanced electric power. A positive temperature difference lowers the membrane potential due to the impact of ionic thermal down-diffusion,although it promotes the diffusion current induced by decreased electrical resistance. Originating from the compromise of the temperature-impacted membrane potential and diffusion current, a positive temperature difference enhances the power at low transmembrane-concentration intensities and hinders the power for high transmembrane-concentration intensities. Based on the system's temperature response, we have proposed a simple and efficient way to fabricate tunable ionic voltage sources and enhance salinity-gradient energy conversion based on small nanoscale biochannels and mimetic nanochannels. These findings reveal the importance of a long-overlooked element—temperature—in nanofluidic energy harvesting and provide insights for the optimization and fabrication of high-performance nanofluidic power devices.

关键词： energy harvesting ionic thermal up-diffusion ionic voltage source nanofluidics

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