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Evaluation and classification of e-learning systems from design perspectives

ICIC Express Letters, Part B: Applications 2011年第4期2卷 873-877页

作者： Kao, Han-Ying Liu, Ming-Chou Huang, Chiao-Ling Chang, Yi-Cheng Department of Computer Science and Information Engineering National Dong Hwa University No. 1 Da Hsueh Rd. Shou-Feng Hualien 974 Taiwan Department of Curriculum Design and Human Potentials Development National Dong Hwa University No. 1 Da Hsueh Rd. Shou-Feng Hualien 974 Taiwan

The e-learning systems have emerged as popular platforms in training and education. Subsequently, evaluation has become a key issue in this domain. Most investigations have focused on the outcomes of various systems from technological perspectives. However, users with varied backgrounds may show different levels of appreciation of the system design. This study intends to analyze e-learning system efficiency from design and implementation perspectives, and by conducting group oriented comparisons. First, the design efficiency of the e-learning system is assessed by using data envelopment analysis (DEA). In this model, each user is regarded as a decision making unit who determines the values of the factors in DEA. Second, the efficiency scores from the DEA are analyzed according to the user groups associated with their backgrounds. The results show that users in various groups have different preferences in terms of system design. Furthermore, we construct a Bayesian network classifier for predicting the relative efficiency and provide decision-making support for designing and implementing future e-learning systems. © 2011 ISSN 2185-2766.

关键词： Efficiency

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Erratum to “Optimization-based prediction of asymmetric human gait” [J. Biomech. 44 (4) (2011) 683–693]

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Journal of Biomechanics 2011年第6期44卷 1217-1217页

作者： Yujiang Xiang Jasbir S. Arora Karim Abdel-Malek Virtual Soldier Research (VSR) Program Center for Computer-Aided Design (CCAD) College of Engineering The University of Iowa Iowa City IA 52242 USA

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Interval analysis method of a powertrain mounting system with uncertain parameters

Interval analysis method of a powertrain mounting system wit...

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SAE 2010 World Congress and Exhibition

作者： Chen, Pengfei Zhang, Yunqing Qin, Gang Wu, Jinglai Center for Computer-Aided Design School of Mechanical Science and Engineering Huazhong University of Science and Technology Wuhan Hubei 430074 China

One of the most important vibration isolators in vehicles is the powertrain mounting system (PMS). It transmits the powertrain vibrations to the body, and the chassis vibrations excited by road to the powertrain. The design of a PMS is an essential part in vehicle safety and in improving the vehicle noise, vibration and harshness (NVH) performances. Many organizations are increasingly relying on design simulation rather than trail-and-error based experiments which are expensive and time-consuming for PMS evaluation. However, design parameters for PMS are always uncertain in actual cases due to tolerances in manufacturing and assembly processes. In this paper, based on a front wheel drive vehicle with a transversely four-cylinder engine, the uncertain characteristics of PMS are studied by interval analysis method. Considering the design parameters including locations, orientations and stiffness of the mounts as interval variables, the lower bounds, upper bounds of natural frequencies and the mode kinetic energy distributions of a PMS are estimated by means of interval analysis. Moreover, the first order analytical design sensitivities are derived to choose the more effective parameters. The response surface methodology (RSM) based on design of experiment (DOE) is investigated to obtain the exact expressions of natural frequencies and kinetic energy distributions. For comparison, a Monte Carlo simulation with normal distribution is used to illustrate the confidence and validity of the proposed method. Copyright © 2010 SAE International.

关键词： Natural frequencies

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Preface

2011 Proceedings of 7th International Conference on Perspect...

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2011 Proceedings of 7th International Conference on Perspective Technologies and Methods in MEMS design, MEMSTECH 2011 2011年 VII-VIII页

作者： Lobur, Mykhaylo Jakubiak, Andrzej Head of Computer Aided Design Department Lviv Polytechnic National University Ukraine Faculty of Electronics and Information Technology Warsaw University of Technology Poland

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design of Global Power Systems Stabilizer to Damp Interarea Oscillations Based on Wide-Area Collocated Control Technique

Design of Global Power Systems Stabilizer to Damp Interarea ...

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IEEE Power and Energy Society General Meeting

作者： Jing Ma Tong Wang Zengping Wang Jie Wu James S. Thorp School of Electrical and Electronic Engineering North China Electric Power University and also with the Bradley Department of Electrical and Computer Engineering Virginia Polytechnic Institute and State University Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University State Nuclear Electric Power Planning Design and Research Institute Bradley Department of Electrical and Computer Engineering Virginia Polytechnic Institute and State University

ISBN: (纸本)9781457710001

This paper develops a systematic procedure of designing global power system stabilizers (GPSSs) based on collocated control to enhance the damping during interarea oscillations. The availability of remote signals from phasor measurement units (PMUs) enables the wide-area control in large scale systems. The closed loop eigenvalues are excluded from a region of the complex plane by the collocated control algorithm guaranteeing that low frequency modes must be damped. The optimum locations for GPSSs were selected using controllability. The damping performance of a 16-machine, 68-bus study system reinforced with GPSSs is examined in the frequency and time domains. The simulation results show that the control scheme is able to damp out interarea oscillations following possible disturbances.

关键词： PMUs Interarea oscillations Collocated control Global power system stabilizers Phasor measurement units absorption of shock dinitrophenyl-aminopropyl-methylamine Oscillations Control technology Complex Plane Power system stability computer algorithms

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Numerical solution of stochastic differential equations with application to vehicle handling

Numerical solution of stochastic differential equations with...

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SAE 2010 World Congress and Exhibition

作者： Wu, Jinglai Zhang, Yunqing Chen, Pengfei Chen, Liping Center for Computer-Aided Design School of Mechanical Science and Engineering Huazhong University of Science and Technology Wuhan Hubei 430074 China

To solve the dynamic response problem that contains uncertain parameters needs, the stochastic differential equations needs to be calculated. Interval analysis has been widely used to solve engineering problems which contain many uncertain parameters usually. But the numerical solution method for stochastic differential equations based on the interval analysis method was seldom investigated. In this study a new numerical interval method for the stochastic differential equations based on the Euler's method is presented, which can be used to solve the linear system effectively and efficiently. The probabilistic and interval dynamics analysis of a two-degree-of-freedom bike car model with uncertain parameters are presented. Considering the automotive parameters which include the length from the front and rear axles to center of gravity of vehicle, front and rear tire cornering stiffness as interval variables, the lower and upper bound of the vehicle handling random responses are obtained by the proposed numerical interval method. The probabilistic dynamic responses of the vehicle handling are also obtained by using the Monte Carlo simulation method. The comparison between the numerical interval method and the Monte Carlo simulation method indicates the proposed numerical interval method is effective. Copyright © 2010 SAE International.

关键词： Dynamic response

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Multi-domain modeling and simulation of hydraulic power steering system based on Modelica

Multi-domain modeling and simulation of hydraulic power stee...

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SAE 2010 World Congress and Exhibition

作者： Sun, Ying Chen, Wei Zhang, Yunqing Chen, Liping Center for Computer-Aided Design School of Mechanical Science and Engineering Huazhong University of Science and Technology Wuhan Hubei 430074 China

Hydraulic power steering system, which can reduce the steering hand force by applying the output from a hydraulic actuator, has been widely used in vehicles. In this paper, a detailed steer model including steering column, steering trapezium, and detailed hydraulic power steering system which is consisting of steering cylinder, relief valve, rotary valve, pump and hydraulic lines were established, and a multi-body model of a heavy truck was established to connect with the hydraulic power steering system. Modelica simulation language, which can be efficiently used to investigate multi-domain problems, was used to in the modeling and simulation of the power steering system and the vehicle. The simulation was carried out to identify the effects of design variables on the lateral stability of the vehicle. The application of Modelica for investigating multi-domain problems is also demonstrated. Copyright © 2010 SAE International.

关键词： Automobile steering equipment

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Modeling and simulation of hydraulic system with fuzzy uncertain parameters

Modeling and simulation of hydraulic system with fuzzy uncer...

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SAE 2010 World Congress and Exhibition

作者： Jiang, Xuefeng He, Ping Zhang, Yunqing Chen, Wei Chen, Liping Center for Computer-Aided Design School of Mechanical Science and Engineering Huazhong University of Science and Technology Wuhan Hubei 430074 China

Hydraulic systems are popular on vehicles, such as power steering, shock absorbers, brakes, etc. Many previously works have been done on the modeling and simulation of the hydraulic systems. However, these models and parameters are usually established on the basis of plans, drawings, measurements, observations, experiences, expert knowledge and standards, and so on. In general, certain information and precise values do not exist. Uncertainty may result, e.g., from human mistakes and errors in the manufacture, from the use and maintenance of constructions, from expert evaluations, and from a lack of information. Actually, many uncertain factors will lead to great errors, and may have great effect on the hydraulic system, so the research on the hydraulic system under uncertainties is very necessary. In this paper, fuzzy algorithm is introduced to analysis the response of the hydraulic system with uncertain parameters. By using fuzzy set theory, uncertain input parameters such as the source pressure, the stiffness of the return spring, the friction between the piston and the chamber, etc., are described mathematically as fuzzy variables or fuzzy random variables and integrated into hydraulic system analysis. The simulations are carried out to analysis the system performance under fuzzy uncertain parameters. Results are presented showing the effectiveness of the method for modeling systems with uncertain parameters. Copyright © 2010 SAE International.

关键词： Fuzzy set theory

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An analytical framework for quadrilateral surface mesh improvement with an underlying triangulated surface definition

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19th International Meshing Roundtable, IMR 2010

作者： Shivanna, Kiran Grosland, Nicole Magnotta, Vincent Center for Computer Aided Design University of Iowa United States Department of Biomedical Engineering University of Iowa United States Department of Radiology University of Iowa United States

ISBN: (纸本)9783642154133

Surface mesh quality plays a very important role in the solution accuracy and in the quality of the ensuing volumetric mesh. Amongst the techniques available, optimization based methods are commonly used for mesh quality improvement. Optimization methods for volumetric and planar surface mesh quality improvement are very well researched. However, this is not true for non-planar meshes. In this manuscript, we focus on quadrilateral non-planar surface meshes obtained during hexahedral mesh generation of anatomic structures. A modified untangling function based on node normals for quadrilateral elements is proposed. A parameterization-based method available is enhanced by giving it an analytical framework. A new projection-based method is proposed and its performance is comparable to the parametric method. The results of the enhanced/proposed methods are superior to the results obtained from Laplacian smoothing. © 2010 Springer-Verlag Berlin Heidelberg.

关键词： Finite element method

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Materials design Workbench: An open-access database for materials and molecular design

Materials Design Workbench: An open-access database for mate...

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Computational Molecular Science and engineering Forum - Core Programming Topic at the 2011 AIChE Annual Meeting

作者： Ferguson, Glen Allen Greeley, Jeff Zapol, Peter Curtiss, Larry A. Nestorov, Svetlozar Evtimov Foster, Ian T. Landis, David Hummelshj, Jens Strabo Jacobsen, Karsten W. Bligaard, Thomas Nrskov, Jens Material Science Department Argonne National Laboratory ArgonneIL United States Center for Nanoscale Materials ArgonneIL United States Materials Science Division Argonne National Laboratory ArgonneIL United States Computer Science University of Chicago ChicagoIL United States Mathematics and Computer Science Department of Computer Science Argonne National Laboratory University of Chicago ArgonneIL United States Department of Physics CAMD Technical University of Denmark Kongens Lyngby Denmark SLAC National Accelerator Laboratory SUNCAT Menlo ParkCA United States Center for Atomic-scale Materials Physics Dept. of Physics Technical University of Denmark Lyngby Denmark Center for Atomic-scale Materials Design Technical University of Denmark Kgs. Lyngby Denmark Chemical Engineering Stanford University and SUNCAT StanfordCA United States

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