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Numerical simulation of sand load applied on high-speed train in sand environment

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Journal of Central South university 2017年第2期24卷 442-447页

作者：王田天蒋崇文高振勋李椿萱 National Laboratory for Computational Fluid Dynamics School of Aeronautic Science and Engineering Beihang University Beijing 100191 China

High-speed train running in the sand environment is different from the general environment. In the former situation, there will be sand load applied on high-speed train(SLAHT) caused by sand particles hitting train surface. This will have a great impact on the train stability, running drag and surface corrosion. Numerical simulation method of SLAHT in sand environment is studied. The velocity and mass flow rate models of saltation and suspension sand particles and the calculation model of SLAHT caused by sand particles hitting train surface are established. The discrete phase method is adopted for numerical simulating the process of saltation and suspension sand particles moving to train surface and generating sand load. By comparison with the field tests, the numerical simulation reliability is analysed. The theoretical formula of SLAHT changing with cross-wind and train speed is proposed. SLAHT changing law is analyzed. Research results indicate that SLAHT changing with cross-wind and train speed is a quadratic relationship. When train speed is constant, SLAHT increases quadratically with cross-wind speed improvement. When cross-wind speed is constant, SLAHT increases quadratically with train speed improvement.

关键词： sand environment train saltation suspension sand load numerical simulation

Lightweight and Manageable Digital Evidence Preservation System on Bitcoin

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Journal of Computer Science & Technology 2018年第3期33卷 568-586页

作者： Mingming Wang Qianhong Wu Bo Qin Qin Wang Jianwei Liu Zhenyu Guan School of Electronic and Information Engineering Beihang University Beijing 100191 China School of Information Renmin University of China Beijing 100872 China

An effective and secure system used for evidence preservation is essential to possess the properties of anti- loss, anti-forgery, anti-tamper and perfect verifiability. Traditional architecture which relies on centralized cloud storage is depressingly beset by the security problems such as incomplete confidence and unreliable regulation. Moreover, an expensive, inefficient and incompatible design impedes the effort of evidence preservation. In contrast, the decentralized blockchain network is qualified as a perfect replacement for its secure anonymity, irrevocable commitment, and transparent traceability. Combining with subliminal channels in blockchain, we have weaved the transaction network with newly designed evidence audit network. In this paper, we have presented and implemented a lightweight digital evidence-preservation architecture which possesses the features of privacy-anonymity, audit-transparency, function-scalability and operation-lightweight. The anonymity is naturally formed from the cryptographic design, since the cipher evidence under encrypted cryptosystem and hash-based functions leakages nothing to the public. Covert channels are efficiently excavated to optimize the cost, connectivity and security of the framework, transforming the great computation power of Bitcoin network to the value of credit. The transparency used for audit, which relates to the proof of existence, comes from instant timestamps and irreversible hash functions in mature blockchain network. The scalability is represented by the evidence chain interacted with the original blockchain, and the extended chains on top of mainchain will cover the most of auditors in different institutions. And the lightweight, which is equal to low-cost, is derived from our fine-grained hierarchical services. At last, analyses of efficiency, security, and availability have shown the complete accomplishment of our system.

关键词： blockchain covert channel data auditing digital evidence

Facile strategy for carbon foam fabrication with lignin as sole feedstock and its applications

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Frontiers of Chemical Science and Engineering 2023年第8期17卷 1051-1064页

作者： Linghong Yin Zizhu Zhao Meng Han Wangda Qu Laboratory of Lignin-Based Materials College of Life SciencesQingdao Agricultural UniversityQingdao 266109China shenzhen Institute of Advanced Electronic Materials Shenzhen Institute of Advanced TechnologyChinese Academy of SciencesShenzhen 518055China

This research is a follow-up to our recent discovery of a facile strategy for directly converting lignin powder into carbon *** this work,we report that the thermal pretreatment parameters in air can remarkably influence the formation and properties of the derived carbon *** pretreatment parameters(heating rate,temperature,and residence time)were systematically investigated and a conversion mechanism into carbon foam was *** the thermal pretreatment,relatively low temperatures,low heating rates,and short residence time hindered the formation of smooth and well-connected structures in the carbon *** overall product yields were similar regardless of the thermal pretreatment *** densities of the different carbon foams ranged 0.27–0.83 g∙cm^(−3).The carbon foams with the highest compressive strengths(>10 MPa)were KLPC280-2-5,KLPC300-0-5,and ***280-2-5 exhibited a high iodine sorption value(182 mg∙g^(−1)).KLPC300-2-5 exhibited a specific capacitance of 158 F∙g^(−1) at a current density of 0.05 A∙g^(−1).The maximum evaporation rates in the solar vapor generation experiments were 1.05 and 1.38 kg∙m^(−2)∙h^(−1) under 100 and 150 mW∙cm^(−2) irradiation,*** good performances are attributed to the robust,porous,and continuous structure.

关键词： lignin carbon foam thermal pretreatment solar vapor generation

Current progress in developing metal oxide nanoarrays-based photoanodes for photoelectrochemical water splitting

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Science Bulletin 2019年第18期64卷 1348-1380页

作者： Yongcai Qiu Zhenghui Pan Haining Chen Daiqi Ye Lin Guo Zhiyong Fan Shihe Yang Guangdong Provincial Key Laboratory of Atmospheric Environment and Pollution Control School of Environment and EnergySouth China University of TechnologyGuangzhou 510006China State Key Laboratory of Luminescent Materials and Devices South China University of TechnologyGuangzhou 510640China Department of Materials Science and Engineering National University of SingaporeSingapore 117574Singapore School of Materials Science and Engineering Beihang UniversityBeijing 100191China School of Chemistry and Environment Beihang UniversityBeijing 100191China Department of Electronic and Computer Engineering The Hong Kong University of Science and TechnologyHong KongChina Department of Chemistry The Hong Kong University of Science and TechnologyHong KongChina Guangdong Key Lab of Nano-Micro Material Research School of Chemical Biology and Biotechnology Shenzhen Graduate SchoolPeking UniversityShenzhen 518055China

Solar energy driven photoelectrochemical(PEC) water splitting is a clean and powerful approach for renewable hydrogen production. The design and construction of metal oxide based nanoarray photoanodes is one of the promising strategies to make the continuous breakthroughs in solar to hydrogen conversion efficiency of PEC cells owing to their owned several advantages including enhanced reactive surface at the electrode/electrolyte interface, improved light absorption capability, increased charge separation efficiency and direct electron transport pathways. In this Review, we first introduce the structure,work principle and their relevant efficiency calculations of a PEC cell. We then give a summary of the state-of the-art research in the preparation strategies and growth mechanism for the metal oxide based nanoarrays, and some details about the performances of metal oxide based nanoarray photoanodes for PEC water splitting. Finally, we discuss key aspects which should be addressed in continued work on realizing high-efficiency metal oxide based nanoarray photoanodes for PEC solar water splitting systems.

关键词： Photoelectrochemical water splitting Metal oxide based nanoarray photoanodes Preparation strategies and growth mechanism

Optimal Placement of Phasor Measurement Unit in Smart Grids Considering Multiple Constraints

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Journal of Modern Power Systems and Clean Energy 2023年第2期11卷 479-488页

作者： Tengpeng Chen He Ren Yuhao Sun Markus Kraft Gehan A.J.Amaratunga Department of Instrumental and Electrical Engineering Xiamen UniversityXiamenChina shenzhen Research Institute of Xiamen university ShenzhenChina CTC Intelligence(shenzhen)Technology Co. Ltd.ShenzhenChina Department of Chemical Engineering and Biotechnology University of CambridgeCambridgeUK Cambridge Centre for Advanced Research and Education in Singapore CREATE TowerSingapore School of Chemical and Biomedical Engineering Nanyang Technological UniversitySingapore Department of Engineering University of CambridgeUK

The distribution of measurement noise is usually assumed to be Gaussian in the optimal phasor measurement unit(PMU)placement(OPP)***,this is not always accurate in *** paper proposes a new OPP method for smart grids in which the effects of conventional measurements,limited channels of PMUs,zero-injection buses(ZIBs),single PMU loss contingency,state estimation error(SEE),and the maximum SEE variance(MSEEV)are *** SEE and MSEEV are both obtained using a robust t-distribution maximum likelihood estimator(MLE)because t-distribution is more flexible for modeling both Gaussian and non-Gaussian *** A-and G-optimal experimental criteria are utilized to form the SEE and MSEEV *** allows the optimization problem to be converted into a linear objective function subject to linear matrix inequality observability *** performance of the proposed OPP method is verified by the simulations of the IEEE 14-bus,30-bus,and 118-bus systems as well as the 211-bus practical distribution system in China.

关键词： Phasor measurement unit(PMU) smart grids optimal placement state estimation(SE).

Mining Typical Treatment Duration Patterns for Rational Drug Use from Electronic Medical Records

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Journal of Systems Science and Systems Engineering 2019年第5期28卷 602-620页

作者： Jingfeng Chen Chonghui Guo Leilei Sun Menglin Lu Institute of Systems Engineering Dalian University of Technology Dalian 116024 China SKLSDE and BDBC Lab Beihang University Beijing 100083 China

Rational drug use requires that patients receive medications for an adequate period of *** adequate duration time of medications not only improve the therapeutic effect of medicines,but also reduce the side effects and adverse reactions of *** paper proposes a data-driven method to mine typical treatment duration patterns for rational drug use from electronic medical records (EMRs).Firstly,a quintuple is defined to describe drug use duration statistics (DUDS) for each drug and treatment record is further represented with DUDS vector (DUDSV).Next a similarity measure method is adopted to compute the similarity between treatment ***,a clustering algorithm is used to cluster all patient treatment records to extract typical treatment duration patterns including typical drug sets,effective drug use day sets,and the DUDSs of each typical *** the extracted typical treatment duration patterns are evaluated and annotated based on patients' demographic information,disease severity scores,treatment outcome and diagnostic ***,a real-world EMR dataset is performed to indicate that the approach we proposed can effectively mine typical treatment duration patterns from EMRs and recommend the appropriate treatment regimens for patients based on their admission information.

关键词： EMR data mining rational drug use typical treatment duration pattern similarity measure clustering

EScope:Effective Event Validation for IoT Systems Based on State Correlation

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Big Data Mining and Analytics 2023年第2期6卷 218-233页

作者： Jian Mao Xiaohe Xu Qixiao Lin Liran Ma Jianwei Liu School of Cyber Science and Technology Beihang UniversityBeijing 100191China beihang Hangzhou Innovation Institute Yuhang Hangzhou 310023China Department of Computer Science Texas Christian UniversityFort WorthTX 76129USA

Typical Internet of Things(IoT)systems are event-driven platforms,in which smart sensing devices sense or subscribe to events(device state changes),and react according to the preconfigured trigger-action logic,as known as,automation rules.“Events”are essential elements to perform automatic control in an IoT ***,events are not always *** fake event notifications injected by attackers(called event spoofing attack)can trigger sensitive actions through automation rules without involving authorized *** solutions verify events via“event fingerprints”extracted by surrounding ***,if a system has homogeneous sensors that have strong correlations among them,traditional threshold-based methods may cause information redundancy and noise amplification,consequently,decreasing the checking *** at this,in this paper,we propose“EScope”,an effective event validation approach to check the authenticity of system events based on device state *** selects informative and representative sensors using an Neural-Network-based(NN-based)sensor selection component and extracts a verification sensor set for event *** evaluate our approach using an existing dataset provided by *** experiment results demonstrate that EScope achieves an average 67%sensor amount reduction on 22 events compared with the existing work,and increases the event spoofing detection accuracy.

关键词： Internet of Things(IoT) event spoofing event fingerprint correlation analysis

Complex conforming Delaunay triangulation

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Science China(Information Sciences) 2010年第6期53卷 1130-1140页

作者： MENG XianHai 1, LI JiGang 1, YANG Qin 1, CAI Qiang 2 & CHEN QiMing 3 1 NLSDE, School of Computer Science and Engineering, beihang university, Beijing 100083, China 2 School of Computer Sciences, Beijing Technology and Business university, Beijing 100037, China 3 School of Mechanical Engineering and Automation, beihang university, Beijing 100083, China NLSDE School of Computer Science and Engineering BeiHang University Beijing China School of Computer Sciences Beijing Technology and Business University Beijing China School of Mechanical Engineering and Automation BeiHang University Beijing China

A novel algorithm of conforming Delaunay triangulation for curved geometry is presented in the paper.A progress has been made for the problem puzzled Delaunay refinement where curved constraints cannot be accepted as input *** algorithm is based on a new sufficient condition for the existence of constraints in *** requires computing only the intersection between constraints and Voronoi edges or faces instead of the circum-sphere of curved *** the termination of the algorithm when small input angles exist in constraints, a weighted method is applied to ensure that the algorithm can terminate under any *** two-dimensional and three-dimensional results are also *** is shown that the algorithm has the capability of dealing with both linear and nonlinear constraints in a consistent way, without the need of maintaining triangular meshes on face constraints.

关键词： mesh generation Delaunay triangulation conforming curved constraints tetrahedralization weight

Cluster-Delay Consensus for Second-Order Nonlinear Multi-agent Systems

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Journal of Systems Science & Complexity 2020年第2期33卷 333-344页

作者： HUANG Jun WEN Guoguang PENG Zhaoxia ZHANG Yunlong Department of Mathematics Beijing Jiaotong UniversityBeijing 100044China School of Transportation Science and Engineering Beihang UniversityBeijing 100191China

This paper investigates the second-order nonlinear multi-agent systems subject to the cluster-delay *** multi-agent systems consist of leader and agents,whose dynamics are second-order *** objective is that the agents track the leader asymptotically with different time delays,i.e.,the agents in different groups reach delay consensus,while the agents in the same group reach identical *** guarantee the cluster-delay consensus for the second-order multi-agent systems,a new control protocol is *** some corresponding conditions for cluster-delay consensus are derived by using Lyapunov directed method and matrix ***,the effectiveness of the theoretical analysis results are verified by some numerical simulations.

关键词： Cluster consensus multi-agent systems second-order nonlinear dynamics time delay