检索结果-南通市图书馆

Revisiting rolling and sliding in two-dimensional discrete element models

在线全文

学校读者我要写书评

暂无评论

Particuology 2015年第1期13卷 35-41页

作者： Yucang Wang Fernando Alonso-Marroquin Sheng xue Jun xie School of Engineering and Technology.Central Queensland University Earth Science and Resource Engineering The Commonwealth Scientific and Industrial Research Organisation(CSIRO) School of Civil Engineering The University of Sydney

It has long been recognized that the rotation of single particles plays a very important role in simulations of granular flow using the discrete element method （DEM）. Many researchers have also pointed out that the effect of rolling resistance at the contact points should be taken into account in DEM simulations. However, even for the simplest case involving two-dimensional circular particles, there is no agreement on the best way to define roiling and sliding, and different definitions and calculations of rolling and sliding have been proposed. It has even been suggested that a unique rolling and sliding definition is not possible. In this paper we assess results from previous studies on rolling and sliding in discrete element models and find that some researchers have overlooked the effect of particles of different sizes. After considering the particle radius in the derivation of rolling velocity, all results reach the same outcome： a unique solution. We also present a clear and simple derivation and validate our result using cases of rolling. Such a decomposition of relative motion is objective, or independent of the reference frame in which the relative motion is measured.

关键词： Discrete element method Rolling Sliding

Generalized Empirical Likelihood Inference in Semiparametric Regression Model for Longitudinal Data

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2008年第12期24卷 2029-2040页

作者： Gao rong LI Ping TIAN Liu Gen xue College of Applied Sciences Beijing University of Technology Beijing 100022 P. R. China School of Finance and Statistics East China Normal University Shanghai 200241 P. R. China Department of Mathematics Xuchang University Xuchang 461000 P. R. China

In this paper, we consider the semiparametric regression model for longitudinal data. Due to the correlation within groups, a generalized empirical log-likelihood ratio statistic for the unknown parameters in the model is suggested by introducing the working covariance matrix. It is proved that the proposed statistic is asymptotically standard chi-squared under some suitable conditions, and hence it can be used to construct the confidence regions of the parameters. A simulation study is conducted to compare the proposed method with the generalized least squares method in terms of coverage accuracy and average lengths of the confidence intervals.

关键词： longitudinal data semiparametric regression model empirical likelihood confidence region

Integrated electrocatalysts derived from metal organic frameworks for gas-involved reactions

在线全文

学校读者我要写书评

暂无评论

Nano Materials Science 2023年第2期5卷 161-176页

作者： Yuke Song Wenfu xie Mingfei Shao xue Duan State Key Laboratory of Chemical Resource Engineering Beijing University of Chemical TechnologyBeijing100029China

Integrated electrocatalysts(IECs)containing well-defined functional materials directly grown on the current collector have sparked increasing interest in the fields of electrocatalysis owing to efficient activity,high stability and the fact that they are easily assembled into ***,metal organic frameworks(MOFs)provide a promising platform for constructing advanced IECs because of their properties of low cost,large surface area and efficient structural *** this review,the design principles of state-of-the-art IECs based on MOFs are presented,including by hydrothermal/solvothermal,template-directed,electrospinning,electrodeposition and other *** high performance of MOF-derived IECs has also been demonstrated in electrocatalytic gasinvolved *** is promising for green energy storage and *** structure-activity relationship and performance improvement mechanism of IECs are uncovered by discussing some in situ technologies for ***,we provide an outlook on the challenges and prospects in this booming field.

关键词： Integrated electrocatalyst Metal organic framework Structure-activity relationship Gas-involved reaction

A practical synthesis of bis(indolyl)methanes catalyzed by BF_3·Et_2O

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2014年第3期25卷 406-410页

作者： Xia-Fei Xu Yan Xiong xue-Ge Ling Xi-Mi xie Jie Yuan Shu-Ting Zhang Zhong-rong Song School of Chemistry and Chemical Engineering Chongqing University State Key Laboratory of Elemento-organic Chemistry Nankai University School of Materials and Chemical Engineering Chongqing University of Arts and Science

Practical ***20 catalyzed reactions between indoles and a series of carbonyl compounds at room temperature are described, which afford bis（indolyl）methanes with isolated yields up to 96%,

关键词： Bis(indolyl)methanes BF3.Et2O lndoles Aldehydes Ketones

Discussion on dynamic reliability tolerance design technology of electromagnetic relay

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第3期8卷 439-443页

作者： YE xue-rong LIANG Hui-min ZHAI Guo-fu School of Electrical Engineering and Automation Harbin Institute of Technology Harbin 150001 China

Reliability tolerance design of electromagnetic relay during its design period plays an essential role in guaranteeing the consistencies of reliability and output characteristic. The reliability tolerance design can ensure that the products would work well under the influence of disturbing factors (including internal interference, external interference, and machining dispersion). Com- pared with static characteristic, dynamic characteristic of electromagnetic relay can describe its operating process better. This article researches influence of the three kinds of disturbing factors on the dynamic characteristic of electromagnetic relay based on calculating dynamic characteristic. Then, the dynamic reliability tolerance design method of electromagnetic relay is discussed considering three kinds of disturbing factors. Conclusions reached can help to assure the reliability of electromagnetic relay from the beginning of design.

关键词： Electromagnetic relay Tolerance design Reliability Dynamic characteristic

Dithienocarbazole- and benzothiadiazole-based donor-acceptor conjugated polymers for bulk heterojunction polymer solar cells

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2015年第2期58卷 294-300页

作者： Ziqing rong Yunfeng Deng Zhiyuan xie Yanhou Geng Fosong Wang State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of Sciences University of Chinese Academy of Sciences

Donor-acceptor （D-A）-conjugated polymers P（BT-C1） and P（BT-C2）, with dithieno[2,3-b;7,6-b]carbazole （C1） or dithi- eno[3,2-b;6,7-b]carbazole （C2） as D-unit and benzothiadiazole （BT） as A-unit, were synthesized. The optical bandgaps of the polymers are similar （1.84 and 1.88 eV, respectively）. The structures of donor units noticeably influence the energy levels and backbone curvature of the polymers. P（BT-C1） shows a large backbone curvature; its highest occupied molecular orbital （HOMO） energy level is -5.18 eV, whereas P（BT-C2） displays a pseudo-straight backbone and has a HOMO energy level of -5.37 eV. The hole mobilities of the polymers without thermal annealing are 1.9×10^-3 and 2.7×10^-3 cm^2 V-1 s^-1 for P（BT-C1） and P（BT-C2）, respectively, as measured by organic thin-film transistors （OTFTs）. Polymer solar cells using P（BT-C1） and P（BT-C2） as the donor and phenyl-Cyl-butyric acid methyl ester （PCyLBM） as the acceptor were fabricated. Power conversion efficiencies （PCEs） of 4.9% and 5.0% were achieved for P（BT-C1） and P（BT-C2）, respectively. The devices based on P（BT-C2） exhibited a higher Voc due to the deeper HOMO level of the polymer, which led to a slightly higher PCE.

关键词： conjugated polymer dithienocarbazole benzothiadiazole polymer solar cells power conversion efficiency

Accelerating sample preparation of graded thermoelectric materials using an automatic powder feeding system

在线全文

学校读者我要写书评

暂无评论

Advances in Manufacturing 2019年第3期7卷 278-287页

作者： Hua-Yan Pu rong-Qing xie Yan Peng Yang Yang Shi-Yang He Jun Luo Yi Sun Shao-rong xie Jun Luo School of Mechatronic Engineering and Automation Shanghai UniversityShanghai 200444People's Republic of China School of Materials Science and Engineering Shanghai UniversityShanghai 200444People's Republic of China Materials Genome Institute Shanghai UniversityShanghai 200444People's Republic of China

In recent years,the development of techniques for the controlled preparation of functional graded materials(FGMs)has become a vigorous research *** this study,to improve the efficiency and accuracy of sample preparations,an automated feeding system based on gravimetric principles for dry powder with three dosing feeders is designed and *** feeding rate and accuracy can be regulated by coordinating the protruded length L(mm)and rotational speed V(r/min)of the feeder *** demonstrate this automatic sample preparation system,the well-known thermoelectric material BixSb2-x-Te3(x=0.3,0.4,0.5,0.6,0.7 and 0.8)is selected and prepared by the developed system,and the composition distribution of the functional graded material is *** results show that the BixSb2_xTe3(x=0.3-0.8)functionally graded material crystalizes in the rhombohedral phase after hot-pressing sintering and annealing and the prepared sample has a good gradient composition *** verifies the reliability and accuracy of the feeding *** concept of samples with a gradient component and application of the automatic powder feeding system could considerably accelerate the research and development of new materials.

关键词： Powder feeding Automatic system Functional graded material Thermoelectric

Efficient video downscaling transcoder from MPEG-2 to H.264

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第4期9卷 457-463页

作者： Xiang-wen WANG Jun SUN rong xie Song-yu YU Shanghai Key Lab. of Digital Media Processing ＆ Transmissions Institute of lmage Communication ＆ Information Processing Shanghai Jiao Tong University Shanghai 200240 China

The new H.264 video coding standard achieves significantly higher compression performance than MPEG-2. As the MPEG-2 is popular in digital TV, DVD, etc., bandwidth or memory space can be saved by transcoding those streams into H.264 in these applications. Unfortunately, the huge complexity keeps transcoding from being widely used in practical applications. This paper proposes an efficient transcoding architecture with a smart downscaling decoder and a fast mode decision algorithm. Using the proposed architecture, huge buffering memory space is saved and the transcoding complexity is reduced. Performance of the proposed fast mode decision algorithm is validated by experiments.

关键词： Video transcoding Mode decision Edge direction analysis

Studies of surface plasmon resonance sensor using bi-beam differential measurement approach

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第12期8卷 2027-2031页

作者： ZENG Han-rong WANG Xiao-ping ZHANG xue-jiao Department of Optical Engineering Zhejiang University Hangzhou 310027 China

In this paper, a low-cost measurement approach with bi-beam was presented, which can be used for real-time detection and online analysis of solution refractive index, based on systematical analysis and experiments of conventional detection methods on surface plasmon resonance sensor. This novel method was analyzed theoretically and based on it a sensor system set was established. The factors that affect the sensor's sensitivity and working range were discussed. The angular adjustment setup was simplified, errors produced by movable components were avoided and the maneuverability was enhanced with this new method. The noiseproof feature and stability of the sensor system were greatly improved as well.

关键词： Kretschmann prism structure Light intensity Bi-beam measurement Light differential Surface plasmon resonance