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Effect of dislocation structure evolution on low-angle grain boundary formation in 7050 aluminum alloy during aging

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International Journal of Minerals,Metallurgy and Materials 2015年第7期22卷 721-728页

作者： Wei Gu Jing-yuan Li yi-de Wang School of Materials Science and Engineering University of Science and Technology Beijing

The effect of dislocation structure evolution on low-angle grain boundary formation in 7050 aluminum alloy during aging was studied by using optical microscopy, transmission electron microscopy, and electron backscatter diffraction analysis of misorientation angle distribution, cumulative misorientation and geometrically necessary dislocation （GND） density. Experimental results indicate that coarse spindle-shaped grains with the dimension of 200 μm- 80 μm separate into fine equiaxed grains of 20μm in size as a result of newborn low-angle grain boundaries formed during the aging process. More specifically, the dislocation arrays, which are rearranged and formed due to scattered dislocations during earlier quenching, transform into low-angle grain boundaries with aging time. The relative frequency of 3°-5° low-angle grain boundaries increases to over 30%. The GND density, which describes low-angle grain boundaries with the misorientation angle under 3°, tends to decrease during initial aging. The inhomogeneous distribution of GNDs is affected by grain orientation. A decrease in GND density mainly occurs from 1.83 × 10^13 to 4.40 × 10^11 m^-2 in grains with 〈111〉 fiber texture. This is consistent with a decrease of unit cumulative misorientation. Precipitation on grain boundaries and the formation of a precipitation free zone （PFZ） are facilitated due to the eroding activity of the Graft etchant. Consequently, low-angle grain boundaries could be readily viewed by optical microscopy due to an increase in their electric potential difference.

关键词： aluminum alloys low-angle grain boundaries dislocation structure aging dislocation density

Minimizing Resource Cost for Camera Stream Scheduling in Video Data Center

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Journal of Computer Science & Technology 2017年第3期32卷 555-570页

作者： yi-Hong Gao Hua-Dong Ma Wu Liu Beijing Key Laboratory of Intelligent Telecommunications Software and Multimedia Beijing University of Posts and Telecommunications Beijing 100876 China

Video surveillance service, which receives live streams from IP cameras and forwards the streams to end users, has become one of the most popular services of video data center. The video data center focuses on minimizing the resource cost during resource provisioning for the service. However, little of the previous work comprehensively considers the bandwidth cost optimization of both upload and forwarding streams, and the capacity of the media server. In this paper, we propose an efficient resource scheduling approach for online multi-camera video forwarding, which tries to optimize the resource sharing of media servers and the networks together. Firstly, we not only provide a fine-grained resource usage model for media servers, but also evaluate the bandwidth cost of both upload and forwarding streams. Without loss of generality, we utilize two resource pricing models with different resource cost functions to evaluate the resource cost： the linear cost function and the non-linear cost functions. Then, we formulate the cost minimization problem as a constrained integer programming problem. For the linear resource cost function, the drift-plus-penalty optimization method is exploited in our approach. For non-linear resource cost functions, the approach employs a heuristic method to reduce both media server cost and bandwidth cost. The experimental results demonstrate that our approach obviously reduces the total resource costs on both media servers and networks simultaneously.

关键词： video data center resource scheduling video surveillance as a service multi-camera networking

Adaptive Two-stage Unscented Kalman Filter for Dynamic State Estimation of Synchronous Generator Under Cyber Attacks Against Measurements

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Journal of Modern Power Systems and Clean Energy 2024年第5期12卷 1408-1418页

作者： Dongchen Hou Yonghui Sun Venkata Dinavahi yi Wang the School of Electrical and Power Engineering Hohai UniversityNanjing 210098China the Department of Electrical and Computer Engineering University of AlbertaEdmontonAB T6G 2V4Canada the School of Electrical and Information Engineering Zhengzhou UniversityZhengzhou 450001China the Henan Engineering Research Center of Power Electronics and Energy Systems Zhengzhou 450001China

This paper develops an adaptive two-stage unscented Kalman filter(ATSUKF)to accurately track operation states of the synchronous generator(SG)under cyber *** achieve high fidelity,considering the excitation system of SGs,a detailed 9~(th)-order SG model for dynamic state estimation is ***,for several common cyber attacks against measurements,a two-stage unscented Kalman filter is proposed to estimate the model state and the bias in ***,to solve the deterioration problem of state estimation performance caused by the mismatch between noise statistical characteristics and model assumptions,a multi-dimensional adaptive factor matrix is derived to modify the noise covariance ***,a large number of simulation experiments are carried out on the IEEE 39-bus system,which shows that the proposed filter can accurately track the SG state under different abnormal test conditions.

关键词： Cyber attack dynamic state estimation Kalman filtering synchronous generator(SG) unscented transformation

Nonlinear Sampled-Data Systems with a Generalized Hold Polynomial-Function for Fast Sampling Rates

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Journal of Systems Science & Complexity 2019年第6期32卷 1572-1596页

作者： ZENG Cheng XIANG Shuwen HE yi DING Qianqian College of Computer Science&Technology Guizhou UniversityGuiyang 550025China School of Science Guizhou Institute of TechnologyGuiyang 550003China School of Mathematics and Statistics Guizhou UniversityGuiyang 550025China College of Mathematics and Information Science Guiyang UniversityGuiyang 550005China

It is well-known that such non-conventional digital control schemes,such as generalized sampled-data hold functions,have clear advantages over the conventional single-rate digital control ***,they have theoretical negative aspects that deviation of the input can lead to intersample oscillations or intersample *** paper investigates the zero dynamics of sampleddata models,as the sampling period tends to zero,composed of a new generalized hold polynomial function,a nonlinear continuous-time plant and a sampler in *** a new design of generalized hold circuit,the authors give the approximate expression of the resulting sampled-data systems as power series with respect to a sampling period up to the some order term on the basis of the normal form representation for the nonlinear continuous-time systems,and remarkable improvements in the stability properties of discrete system zero dynamics may be achieved by using proper adj us *** particular interest are the stability conditions of sampling zero dynamics in the case of a new hold ***,an insightful interpretation of the obtained sampled-data models can be made in terms of minimal intersample ripple by design,where the ordinary multirate sampled systems have a poor intersample *** has shown that the intersample behavior arising from the multirate input polynomial function can be localised by appropriately selecting the design parameters based on the stability condition of the sampling zero *** results presen ted here generalize the well-known notion of sampling zero dynamics from the linear case to nonlinear systems.

关键词： Generalized hold polynomial function nonlinear sampled-data models stability Taylor approach zero dynamics

A Hybrid Learning Method for the Data-Driven Design of Linguistic Dynamic Systems

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IEEE/CAA Journal of Automatica Sinica 2019年第6期6卷 1487-1498页

作者： Chengdong Li Jianqiang yi yisheng Lv Peiyong Duan School of Information and Electrical Engineering Shandong Jianzhu UniversityJinan 250101China Institute of Automation Chinese Academy of SciencesBeijing 100190China Institute of Automation Chinese Academy of SciencesBeijing 100190and also with Qingdao Academy of Intelligent IndustriesQingdao 266109China School of Information Science and Engineering Shandong Normal UniversityJinan 250014China

In lots of data based prediction or modeling applications,uncertainties and/or noises in the observed data cannot be *** such cases,it is more preferable and reasonable to provide linguistic(fuzzy)predicted results described by fuzzy memberships or fuzzy sets instead of the crisp estimates depicted by *** dynamic system(LDS)provides a powerful tool for yielding linguistic(fuzzy)***,it is still difficult to construct LDS models from observed *** solve this issue,this paper first presents a simplified LDS whose inputoutput mapping can be determined by closed-form ***,a hybrid learning method is proposed to construct the data-driven LDS *** proposed hybrid learning method firstly generates fuzzy rules by the subtractive clustering method,then carries out further optimization of centers of the consequent triangular fuzzy sets in the fuzzy rules,and finally adopts multiobjective optimization algorithm to determine the left and right end-points of the consequent triangular fuzzy *** proposed approach is successfully applied to three real-world prediction applications which are:prediction of energy consumption of a building,forecasting of the traffic flow,and prediction of the wind *** results show that the uncertainties in the data can be effectively captured by the linguistic(fuzzy)*** can also be extended to some other prediction or modeling problems,in which observed data have high levels of uncertainties.

关键词： Fuzzy set least square method linguistic dynamic system(LDS) multi-objective optimization

Parameterizing an agricultural production model for simulating nitrous oxide emissions in a wheat–maize system in the North China Plain

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Atmospheric and Oceanic Science Letters 2016年第6期9卷 403-410页

作者： LI ting-ting ZHANG Wei WANG Jun ZHANG Wen WANG Guo-Cheng XU Jing-Jing ZHANG Qing State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry Institute of Atmospheric PhysicsChinese Academy of Sciences Nansen-Zhu International Research Centre Institute of Atmospheric PhysicsChinese Academy of Sciences

Concentrations of atmospheric nitrous oxide （N2O）, a potent greenhouse gas, have been continuously increasing, and cropland soils are one of the largest sources of N2O. Variations in environmental and anthropogenic factors have substantial impacts on both the frequency and magnitude of N2O emissions. Based on measurements from a wheat-maize system in the North China Plain, the authors parameterized the Agricultural Production Systems Simulator （APSIM） model, which was initially developed in Australia, for simulating N2O emissions under different agricultural management practices. After calibrating one of the key parameters -- the fraction of N2O lost in nitrification （k2） -- the results showed that the model successfully captured the daily N2O fluxes under different nitrogen fertilization treatments, but underestimated some large peak fluxes. By pooling all data together, the calibrated APSIM model also performed well in representing cumulative N2O emissions under various treatments at annual and finer （monthly and daily） time scales.

关键词： Agricultural productionmodeling nitrous oxide wheat-maize system North China Plain

Application-Oriented Performance Comparison of 802.11p and LTE-V in a V2V Communication System

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Tsinghua Science and Technology 2019年第2期24卷 123-133页

作者： Mengkai Shi yi Zhang Danya Yao Chang Lu Department of Automation Tsinghua University National Laboratory for Information Science and Technology (TNList) Tsinghua University Jiangsu Province Collaborative Innovation Center of Modern Urban Traffic Technologies Tsinghua-Berkeley Shenzhen Institute(TBSI)

In recent years, the Vehicle-to-Vehicle(V2V) communication system has been considered one of the most promising technologies to build a much safer and more efficient transportation system. Both simulation and field test have been extensively performed to evaluate the performance of the V2V communication system. However,most of the evaluation methods are communication-based, and although in a transportation environment, lack a V2V application-oriented analysis. In this study, we conducted real-world tests and built an application-oriented evaluation model. The experiments were classified into four scenarios: static, following, face 2 face, and crossing vertically, which almost covered all the V2V communication patterns on the road. Under these scenarios, we conducted experiments and built a probability model to evaluate the performance of 802.11p and LTE-V in safetyrelated applications. Consequently, we found out that improvements are still needed in Non-Line-of-Sight scenarios.

关键词： Vehicle-to-Vehicle (V2V)communication connected vehicles performance evaluation intelligent transportation system application-oriented field test

Texture Repairing by Unified Low Rank Optimization

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Journal of Computer Science & Technology 2016年第3期31卷 525-546页

作者： Xiao Liang Xiang Ren Zhengdong Zhang yi Ma Institute for Advanced Study Tsinghua University Beijing 100086 China Department of Computer Science University of Illinois at Urbana-Champaign Urbana IL 61801 U.S.A. Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA 02139 U.S.A. School of Information Science and Technology ShanghaiTech University Shanghai 200031 China

In this paper, we show how to harness both low-rank and sparse structures in regular or near-regular textures for image completion. Our method is based on a unified formulation for both random and contiguous corruption. In addition to the low rank property of texture, the algorithm also uses the sparse assumption of the natural image： because the natural image is pieeewise smooth, it is sparse in certain transformed domain （such as Fourier or wavelet transform）. We combine low-rank and sparsity properties of the texture image together in the proposed algorithm. Our algorithm based on convex optimization can automatically and correctly repair the global structure of a corrupted texture, even without precise information about the regions to be completed. This algorithm integrates texture rectification and repairing into one optimization problem. Through extensive simulations, we show our method can complete and repair textures corrupted by errors with both random and contiguous supports better than existing low-rank matrix recovery methods. Our method demonstrates significant advantage over local patch based texture synthesis techniques in dealing with large corruption, non-uniform texture, and large perspective deformation.

关键词： low-rank texture convex optimization sparse error correction image repairing

Exploring the bioactive compounds of Feiduqing formula for the prevention and management of COVID-19 through network pharmacology and molecular docking

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Medical Data Mining 2024年第1期7卷 16-23页

作者： Shuang-Lin Qin Hui Yao ting Huang Hong-Fei Yang ting-ting Ge Jie-Qiong Wang Wei-Wu Wang Qing Min School of Pharmacy Xianning Medical CollegeHubei University of Science and TechnologyXianning 437100China Hubei Engineering Research Center of Traditional Chinese Medicine of South Hubei Province Xianning Medical CollegeHubei University of Science and TechnologyXianning 437100China Research&Development Center Hunan Ruitongtang Medical&Pharmaceutical Co.Ltd.Changsha 410205China

Background:To explore the effective chemical constituents of Feiduqing formula for prevention and treatment of coronavirus disease 2019(COVID-19).Methods:The compounds and action targets of twelve herbal medicines in Feiduqing formula were collected via Traditional Chinese Medicine Systems Pharmacology Database and Analytic *** genes corresponding to the targets were queried through the UniProt ***“herbal medicine-ingredient-target”network was established by Cytoscape *** Gene Ontology function enrichment analysis and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis were performed by Database for Annotation,Visualization and Integrated *** docking was used to analyze the binding force of core active compounds of Feiduqing formula with PTGS2,HSP90AA1,SARS-CoV-23CL hydrolase and angiotensin converting enzyme II(ACE2).Results:The“herbal medicine-ingredient-target”network included 434 nodes and 1948 edges,including 222 components such as quercetin,kaempferol,luteolin,*** key targets are PTGS2,HSP90AA1,PTGS1,ESR1,AR,NOS2,*** Ontology function enrichment analysis revealed 2530 items,including RNA polymerase II-specific,response to oxidative stress,transcription factor activity,*** Encyclopedia of Genes and Genomes pathway enrichment screened 169 signal pathways,including Human cytomegalovirus infection,Kaposi sarcoma-associated herpesvirus infection,Hepatitis B,Hepatitis C,IL-17,TNF,*** results of molecular docking showed that quercetin,luteolin,β-sitosterol,stigmasterol and other core active compounds have a certain degree of affinity with PTGS2,HSP90AA1,SARS-CoV-23CL hydrolase and ***:The active compounds of Feiduqing formula may have a therapeutic effect on COVID-19 pneumonia through the action on PTGS2,HSP90AA1,SARS-CoV-23CL hydrolase and ACE2,and regulating many signaling pathways.

关键词： Feiduqing formula COVID-19 network pharmacology molecular docking SARS-CoV-23CL hydrolase