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Revised regional importance measures in the presence of epistemic and aleatory uncertainties

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Science China(Physics,Mechanics & Astronomy) 2015年第1期58卷 84-94页

作者： cheng lei LU ZhenZhou WU DanQing School of Aeronautics Northwestern Polytechnical University

Two revised regional importance measures(RIMs),that is,revised contribution to variance of sample mean(RCVSM)and revised contribution to variance of sample variance(RCVSV),are defined herein by using the revised means of sample mean and sample variance,which vary with the reduced range of the epistemic *** RCVSM and RCVSV can be computed by the same set of samples,thus no extra computational cost is introduced with respect to the computations of CVSM and *** the plots of RCVSM and RCVSV,accurate quantitative information on variance reductions of sample mean and sample variance can be read because of reduced upper bound of the range of the epistemic *** general form of quadratic polynomial output,the analytical solutions of the original and the revised RIMs are *** example is employed and results demonstrate that the analytical results are consistent and *** engineering example is applied to testify the validity and rationality of the revised RIMs,which can give instructions to the engineers about how to reduce variance of sample mean and sample variance by reducing the range of epistemic parameters.

关键词： revised rims sample mean sample variance variance reduction analytical solution

Treatment of desizing wastewater from the textile industry by wet air oxidation

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Journal of Environmental Sciences 2000年第3期12卷 290-295页

作者： lei Le-cheng SUN Yuan Department of Environmental Science and Engineering College of Chemical EngineeringZhejiang UniversityHangzhou 310027China.

This paper describes the application of wet air oxidation to the treatment of desizing wastewater from two textile companies. A two\|liter high temperature, high pressure autoclave reactor was used in the study. The range of operating temperatures examined was between 150 and 290℃, and the partial pressure of oxygen ranged from 0.375 to 2.25 MPa. Variations in pH, COD Cr and TOD content were monitored during each experiment and used to assess the extent of conversion of the process. The effects of temperature, pressure and reaction time were explored extensively. More than 90% COD Cr reduction and 80% TOC removal have been obtained. The results have also been demonstrated that WAO is a suitable pre\|treatment methods due to improvement of the BOD\-5/COD\-\{Cr\} ratio of desizing wastewater. The reaction kinetics of wet air oxidation of desizing wastewater has been proved to be two steps, a fast reaction followed by a slow reaction stage.

关键词： wet air oxidation wastewater treatment textile wastewater

Science Letters:Development of supported boron-doping TiO_2 catalysts by chemical vapor deposition

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第1期9卷 109-112页

作者： Xing-wang ZHANG Le-cheng lei nstitute of Environmental Pollution Controlling Technologies Zhejiang University Hangzhou 310028 China

In this study, supported nonmetal (boron) doping TiO2 coating photocatalysts were prepared by chemical vapor deposition (CVD) to enhance the activity under visible light irradiation and avoid the recovering of TiO2. Boron atoms were successfully doped into the lattice of TiO2 through CVD, as evidenced from XPS analysis. B-doped TiO2 coating catalysts showed drastic and strong absorption in the visible light range with a red shift in the band gap transition. This novel B-TiO2 coating photocatalyst showed higher photocatalytic activity in methyl orange degradation under visible light irradiation than that of the pure TiO2 photocatalyst.

关键词： Chemical vapor deposition (CVD) TiO2 Boron Visible light Photocatalysis

CPA-VoD： Cloud and Peer-Assisted Video on Demand System for Mobile Devices

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Journal of Computer Science & Technology 2016年第6期31卷 1087-1095页

作者： lei-Gen cheng Laizhong Cui Yong Jiang Graduate School at Shenzhen Tsinghua University Shenzhen 518055 China College of Computer Science and Software Engineering Shenzhen University Shenzhen 518060 China

With the rapid development of WiFi and 3G/4G, people tend to view videos on mobile devices. These devices are ubiquitous but have small memory to cache videos. As a result, in contrast to traditional computers, these devices aggravate the network pressure of content providers. Previous studies use CDN to solve this problem. But its static leasing mechanism in which the rental space cannot be dynamically adjusted makes the operational cost soar and incompatible with the dynamically video delivery. In our study, based on a thorough analysis of user behavior from Tencent Video, a popular Chinese on-line video share platform, we identify two key user behaviors. Firstly, lots of users in the same region tend to watch the same video. Secondly, the popularity distribution of videos conforms with the Pareto principle, i.e., the top 20% popular videos own 80% of all video traffic. To turn these observations into silver bullet, we propose and implement a novel cloud- and peer-assisted video on demand system （CPA-VoD）. In the system, we group users in the same region as a peer swarm, and in the same peer swarm, users can provide videos to other users by sharing their cached videos. Besides, we cache the 10% most popular videos in cloud servers to further alleviate the network pressure. We choose cloud servers to cache videos because the rental space can be dynamically adjusted. According to the evaluation on a real dataset from Tencent Video, CPA-VoD alleviates the network pressure and the operation cost excellently, while only 20.9% traffic is serviced by the content provider.

关键词： cloud peer-to-peer (P2P) video on demand (VoD) mobile application

Environmental Behaviors and Biological Effects of Engineered Nanomaterials:Important Roles of Interfacial Interactions and Dissolved Organic Matter

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Chinese Journal of Chemistry 2021年第2期39卷 232-242页

作者： Yanlong Wang cheng lei Daohui Lin Department of Environmental Science Zhejiang UniversityHangzhouZhejiang310058 China Zhejiang Provincial Key Laboratory of Organic Pollution Process and Control Zhejiang UniversityHangzhouZhejiang310058 China

With the fast development of nanotechnology,reactive engineered nanomaterials(ENMs)are increasingly discharged into the environment,where they interact with environmental components and organisms and thus pose potential *** interactions-derived formation of nano-environmental and nano-bio interfaces determines environmental behaviors and biological effects of ENMs,and ubiquitous dissolved organic matter(DOM)is bound to impact the interfacial interactions and the resulted environmental ***,we systematically investigated adsorptive interactions between ENMs and various DOM representatives,and thereby demonstrated the effects of DOM on the aqueous suspension/aggregation,mobility in porous media,adsorption of contaminants,transformation,and biological accumulation and toxicity of ***,we conclude that natural DOM can in general expand environmental distribution of ENMs while limit their toxicity to organisms.

关键词： Nanoparticles Natural organic matter Colloidal behavior Adsorption Nanotoxicity

Optimization of mixing time in a ladle with dual plugs

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International Journal of Minerals,Metallurgy and Materials 2010年第6期17卷 709-714页

作者： Dian-qiao Geng Hong lei Ji-cheng He Key Laboratory of Electromagnetic Processing of Materials （Ministry of Education of China） Northeastern University Shenyang 110819 China

Based on the two-phase fluid （Eulerian-Eulerian） model, a mathematical model about the gas-liquid flow and mixing behavior was developed to investigate the effect of the offset of dual plugs, the included angle of dual plugs with a center point, and gas flow rate on the mixing time in a ladle with dual plugs. Numerical results indicate that two types of recirculation zones exist in the ladle. One is the middle recirculation between gas and liquid plumes, and the other is the sidewall recirculation between plumes and the ladle sidewall. The correction shows that the mixing time is in proportion to -0.2676 power of gas flow rate. There is a unique optimum offset of dual plugs with a particular included angle, in turn, a unique optimum included angle of dual plugs exits with a particular offset.

关键词： ladles refining mixing time optimization numerical simulation

Position tracking and attitude control for quadrotors via active disturbance rejection control method

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Science China(Information Sciences) 2019年第1期62卷 5-14页

作者： Yuan YUAN lei cheng Zidong WANG Chong SUN Department of Computer Science Brunel University London School of Astronautics Northwestern Polytechnical University

In this paper, a trigonometric-saturation-function-based position controller is designed for the quadrotor system with internal and external disturbances. Furthermore, in the attitude control problem, a dual closed-loop structure is put forward. Specifically, a nonlinear extended-state-observer(ESO) is employed to provide an estimate for the so-called total disturbance. Then, based on the estimate provided by the ESO,a nonlinear composite control strategy is designed for the purpose of angular tracking. Some sufficient conditions are established to guarantee that the position and attitude subsystems are stable. The contributions are mainly as follows.(1) A trigonometric-saturation-function is used in the position control which could guarantee that the studied system is fully-actuated.(2) The nonlinear ESO is implemented in the attitude control-loop which could enhance the anti-disturbance property. Finally, some numerical simulations and practical experiments are provided to verify the applicability of the proposed methodology.

关键词： position control quadrotor system extended-state-observer attitude control

A Cost-Efficient Approach to Storing Users'Data for Online Social Networks

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Journal of Computer Science & Technology 2019年第1期34卷 234-252页

作者： Jing-Ya Zhou Jian-Xi Fan cheng-Kuan Lin Bao-lei cheng School of Computer Science and Technology Soochow UniversitySuzhou 215006China Provzncial Key Laboratory for Computer Information Processing Technology Soochow UniversitySuzhou 215006China Collaborative Innovation Center of Novel Software Technology and Industrialization Nanjing University Nanjing 210023China

As users increasingly befriend others and interact online via their social media accounts,online social networks (OSNs)are expanding *** with the big data generated by users,it is imperative that data storage be distributed,scalable,and *** one of the most significant challenges about this topic is determining how to minimize the cost without deteriorating system *** many storage systems use the distributed key value store,it cannot be directly applied to OSN storage *** because users'data are highly correlated,hash storage leads to frequent inter-server communications,and the high inter-server traffic costs decrease the OSN storage system's scalability. Previous studies proposed conducting network partitioning and data replication based on social ***,data replication increases storage costs and impacts traffic ***,we consider how to minimize costs from the perspective of data storage,by combining partitioning and *** cost-efficient data storage approach supports scalable OSN storage *** proposed approach co-locates frequently interactive users together by conducting partitioning and replication simultaneously while meeting load-balancing *** experiments are undertaken on two real- world traces,and the results show that our approach achieves lower cost compared with state-of-the-art *** we conclude that our approach enables economic and scalable OSN data storage.

关键词： online social network inter-server traffic cost storage cost network partitioning data replication

Effect of high-temperature reduction pretreatment on internal quality of 42CrMo casting billet

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Journal of Iron and Steel Research International 2021年第6期28卷 693-702页

作者： Hong-qiang Liu Zhi-cheng cheng Wei Yu Zhao-yuan Zhou lei cheng Qing-wu Cai Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing 100083China Institute of Engineering Technology University of Science and Technology BeijingBeijing 100083China

Comparative analysis was conducted to illustrate the effect of high-temperature reduction pretreatment on the internal quality of 42CrMo casting *** of macrostructure clarifies that reduction pretreatment could reduce the size of central cavities and equiaxed crystals and improve the segregation degree and porosity on *** bainite matrix and granular structure on segregation bands mainly dominate the microstructure of original billet,while pro-eutectoid ferrite and its accompanying troostite are added due to the application of reduction ***,C,Mn,and Mo are suggested to be enriched in segregation bands where pores and inclusions tend to be *** clarifying the microstructure evolution during cooling process,physical compression and multiplication of prior austenite grain boundaries caused by recrystallization are regarded as the main reasons in improving the internal quality of 42CrMo billet.

关键词： 42CrMo billet Reduction pretreatment Continuous casting Recrystallization