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Bandgap formation and low-frequency structural vibration suppression for stiffened plate-type metastructure with general boundary conditions

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Chinese Journal of Aeronautics 2023年第10期36卷 210-228页

作者： tian ZHAO Zhichun YANG Yanlong XU Wei tian School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China

Metastructures with unique mechanical properties have shown attractive potential application in vibration and noise ***,most of the metastructures deal with the vibration bandgap properties of infinite structures without considering specific boundary condition and dynamic behaviors,which cannot be directly applied to the engineering *** this research,we design a Stiffened Plate-type Metastructure(SPM)composed of a plate with periodic stiffeners and cantilever beam-type resonators subjected to general boundary conditions for low-frequency vibration *** effects of boundary conditions and the number and orientation of the stiffeners on Locally Resonant(LR)type bandgap properties in SPM are further *** analytical modeling framework is developed to predict the bandgap formations and vibration behaviors of SPMs in finite-size *** governing equations of the SPM reinforced by various arrangements of stiffeners are derived based on the first-order shear deformation theory and Hamilton’s principle,and a Fourier series combined with auxiliary functions is employed to satisfy the arbitrary boundary *** element analysis and experimental investigations of vibration behaviors for the SPM are carried out to validate the accuracy and reliability of the present analytical *** practical designs of the SPMs with specific boundary conditions,it is found that there exist optimal numbers of stiffeners and resonators which can produce the significant LR-type bandgap ***,various arrangements of stiffeners and resonators are explored for different boundary conditions by breaking the requirement of spatially *** is shown that for the designed SPM,the vibration modes of its host structure should be considered to widen the frequency range in which the resonators transfer and store energy,and hence improve the performance of low-frequency vibration *** present work can pro

关键词： Bandgap Locally resonant Metastructure Stiffened plate Vibration suppression

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Science China Materials 2018年第1期61卷 127-128页

作者： Yongjun tian State Key Laboratory of Metastable Materials Science and Technology Yanshan University

When a metal is subject to cyclic loading with cyclic stress values much lower than its tensile strength,fatigue occurs due to accumulative and irreversible damages developed in the microstructure,causing service failure of the metal workpiece or even fatal disaster in the worst *** develop materials with higher fatigue limit and longer fatigue life relies on reducing or suppressing

关键词： Rise of correlated dislocations in nanotwinned metals against fatigue

Link Prediction in Brain Networks Based on a Hierarchical Random Graph Model

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Tsinghua Science and Technology 2015年第3期20卷 306-315页

作者： Yanli Yang Hao Guo tian tian Haifang Li School of Computer Science and Technology Taiyuan University of Technology

Link prediction attempts to estimate the likelihood of the existence of links between nodes based on available brain network information, such as node attributes and observed links. In response to the problem of the poor efficiency of general link prediction methods applied to brain networks, this paper proposes a hierarchical random graph model based on maximum likelihood estimation. This algorithm uses brain network data to create a hierarchical random graph model. Then, it samples the space of all possible dendrograms using a Markov-chain Monte Carlo algorithm. Finally, it calculates the average connection probability. It also employs an evaluation index. Comparing link prediction in a brain network with link prediction in three different networks （Treponemapallidum metabolic network, terrorist networks, and grassland species food webs） using the hierarchical random graph model, experimental results show that the algorithm applied to the brain network has the highest prediction accuracy in terms of AUC scores. With the increase of network scale, AUC scores of the brain network reach 0.8 before gradually leveling off. In addition, the results show AUC scores of various algorithms computed in networks of eight different scales in 28 normal people. They show that the HRG algorithm is far better than random prediction and the ACT global index, and slightly inferior to local indexes CN and LP. Although the HRG algorithm does not produce the best results, its forecast effect is obvious, and shows good time complexity.

关键词： brain network link prediction hierarchical random graph maximum likelihood estimation method

Higher-order Optimality Conditions and Duality for Approximate Solutions in Non-convex Set-valued Optimization

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Acta Mathematicae Applicatae Sinica 2019年第3期35卷 620-628页

作者： Guo-lin YU tian-tian GONG North Minzu University

This paper deals with higher-order optimality conditions and duality theory for approximate solutions in vector optimization involving non-convex set-valued ***,under the assumption of near cone-subconvexlikeness for set-valued maps,the higher necessary and sufficient optimality conditions in terms of Studniarski derivatives are derived for local weak approximate minimizers of a set-valued optimization ***,applications to Mond-Weir type dual problem are presented.

关键词： studniarski derivatives optimality conditions set-valued optimization problem efficiency duality

Accelerated life-time test of MEA durability under vehicle operating conditions in PEM fuel cell

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Frontiers in Energy 2017年第3期11卷 326-333页

作者： tian tian Jianjun TANG Wei GUO Mu PAN State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Hubei Provincical Key Laboratory of Fuel Cell Wuhan University of Technology Wuhan 430070 China

In this paper, a novel accelerated test method was proposed to analyze the durability of MEA, considering the actual operation of the fuel cell vehicle. The proposed method includes 7 working conditions： open circuit voltage （OCV）, idling, rated output, overload, idling-rated cycle, idling-overload cycle, and OCV-idling cycle. The experimental results indicate that the proposed method can effectively destroy the MEA in a short time （165 h）. Moreover, the degradation mechanism of MEA was analyzed by measuring the polarization curve, CV, SEM and TEM. This paper may provide a new research direction for improving the durability of fuel cell.

关键词： polymer electrolyte membrane fuel cell accelerated life-time test load cycling test durability

A Coding Scheme for Noisy Image Based on Layer Segmentation

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Chinese Journal of Electronics 2016年第4期25卷 700-705页

作者： LI Tao tian Xin XIONG Chengyi tian Jinwen Nanjing Research Institute of Electronics Technology Wuhan University South–Central University for Nationalities Huazhong University of Science and Technology

Heavy noises distribute in the images when imaging in a poor *** randomness of noises makes pixels distributing singularly,which weakens the1-D piecewise smooth property of original ***,wavelets-based compression method no longer works *** this paper,a layer segmentation based compression scheme is proposed for gray *** textures and some high frequency noises are described in a high frequency layer while the coarse part of the image is described in the low frequency *** high frequency layer is represented by a joint dictionary,and the low frequency layer is coded with the traditional *** proposed scheme is tested on nature images and synthetic *** results show that the proposed scheme achieves better rate-distortion performance compared with several competing compression ***,further degradation of edges is avoided by the proposed compression scheme.

关键词： Image coding Noisy image model Sparse representation Edge detection

Improving differential evolution with a new selection method of parents for mutation

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Frontiers of Computer Science 2016年第2期10卷 246-269页

作者： Yiqiao CAI Yonghong CHEN tian WANG Hui tian College of Computer Science and Technology Huaqiao University Xiamen 361021 China

In differential evolution （DE）, the salient feature lies in its mutation mechanism that distinguishes it from other evolutionary algorithms. Generally, for most of the DE algorithms, the parents for mutation are randomly chosen from the current population. Hence, all vectors of population have the equal chance to be selected as parents without selective pressure at all. In this way, the information of population cannot be fully exploited to guide the search. To alleviate this drawback and improve the performance of DE, we present a new selection method of parents that attempts to choose individuals for mutation by utilizing the population information effectively. The proposed method is referred as fitnessand-position based selection （FPS）, which combines the fitness and position information of population simultaneously for selecting parents in mutation of DE. In order to evaluate the effectiveness of FPS, FPS is applied to the original DE algorithms, as well as several DE variants, for numerical optimization. Experimental results on a suite of benchmark functions indicate that FPS is able to enhance the performance of most DE algorithms studied. Compared with other selection methods, FPS is also shown to be more effective to utilize information of population for guiding the search of DE.

关键词： differential evolution mutation operator parents selection population information numerical optimization

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高速飞行器气动光学效应

中山大学学报（自然科学版）（中英文） 2025年第1期64卷 257-264页

作者：田立丰杨东霖黄开诱中山大学航空航天学院广东深圳518107 深圳市智能微小卫星星座技术与应用重点实验室广东深圳518107

采用数值模拟、计算光学方法和理论,对超声速飞行器流场进行数值模拟研究,获取不同飞行高度和攻角下光学窗口上方流场的密度分布,根据Gladstone-Dale关系得到光学窗口上方的折射率场,利用光线追迹法计算流场光程差分布情况。对流场光程... 详细信息

采用数值模拟、计算光学方法和理论,对超声速飞行器流场进行数值模拟研究,获取不同飞行高度和攻角下光学窗口上方流场的密度分布,根据Gladstone-Dale关系得到光学窗口上方的折射率场,利用光线追迹法计算流场光程差分布情况。对流场光程差的分布情况进行分析,可以得出结论:随着飞行高度的增加,气动光学效应逐渐减弱;随着攻角的增大,气动光学效应逐渐增强。

关键词：气动光学飞行高度攻角光程差

A novel subsidence monitoring technique based on space-surface bistatic differential interferometry using GNSS as transmitters

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Science China(Information Sciences) 2015年第6期58卷 68-83页

作者： ZENG Tao ZHANG tian tian WeiMing HU Cheng Beijing Key Laboratory of Embedded Real-time Information Processing Technology Radar Research Laboratory School of Information and ElectronicsBeijing Institute of Technology

Synthetic Aperture Radar Differential Interferometry(DIn SAR) technique is an effective tool with large coverage and high spatial accuracy for subsidence monitoring. Nevertheless, the temporal resolution is usually poor so that rapid deformation cannot be measured due to the long revisit time of radar *** SAR Differential Interferometry technique using Global Navigation Satellite System(GNSS) as illuminator has a shorter revisit time, whereas the measurement accuracy is constrained by low signal power, narrow bandwidth and atmospheric delay error. To cope with these problems, in this paper, we propose a novel subsidence monitoring technique based on Space-Surface bistatic Differential Interferometry(SS-DI) with GNSS transmitters, where two stations consist of a reference one and a measurement one that are deployed on the ground. First, we applied a space differential processing between two stations to cancel identical errors such as tropospheric and ionospheric errors etc. Then we used a long time coherent integration to improve the signal noise ratio. Subsequently, we also utilized a time differential processing to construct double differential equations with respect to unknown deformation variables. Finally, we solved the equations to obtain a highly accurate estimation of three dimension deformation. Furthermore, an SS-DI experiment using Beidou-2 as transmitters was carried out to validate the proposed method, where a high accuracy(0.01 mm) device was utilized to simulate subsidence deformation. The experimental results reveal that the proposed method has better performance of spatial measurement accuracy of 0.53 mm compared with differential GPS method.

关键词： differential interferometry subsidence monitoring Beidou-2/Compass-2 space-surface bistatic radar differential GPS