http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
( Zi Yan ),( Bonnie G. Berger ),( David A. Tobar ),( Bradley J. Cardinal ) 한국스포츠정책과학원(구 한국스포츠개발원) 2015 International Journal of Applied Sports Sciences Vol.27 No.1
Background. People exercise for different reasons. Reasons for exercise may influence exercise behavior via influencing important psychological factors of habitual exercisers, exercise enjoyment, and self-efficacy. The aim of this study was to explore how different reasons for exercise are associated with exercise enjoyment and self-efficacy by males and females from differing cultural backgrounds. Method. Undergraduate students from a midwest university in the United States (males = 42, females = 171, age M = 21.68 years) and a national university in China (males = 64, and females = 149, age M = 21.47 years) participated in the study. Reasons for exercise, exercise enjoyment, and exercise self-efficacy were measured by questionnaire. Results. Individuals who exercised for non-appearance based reasons reported higher levels of exercise enjoyment compared to students who exercised for appearance based reasons, and this finding was irrespective of cultural background or gender. Women who exercised for mood alteration reasons reported higher self-efficacy compared to women who exercised for other reasons. In addition, gender and cultural differences were related to reasons for exercise and self-efficacy. Conclusion. Understanding exercise participants`` reasons for exercise and how these relate to their exercise enjoyment and self-efficacy may help to foster greater rates of physical activity participation.
Ziyan Ren,Hyunjin Cho,Junmo Yeon,Chang-Seop Koh IEEE 2015 IEEE transactions on magnetics Vol.51 No.3
<P>Due to the existence of randomness and fuzziness in engineering problems, the reliable performance prediction is very complex. In addition, in the early design stage of a new product, the insufficient information on uncertainty further aggravates the difficulty of performance prediction and robustness evaluation. This paper suggests a new reliability analysis method using possibility theory to evaluate constraint feasibility even with insufficient uncertainty data in design variables. In order to save the computing time, two strategies of approximating performance constraints are proposed: 1) design sensitivity-based method and 2) dynamic Kriging-based method. Through applications to analytic example and engineering problem, the proposed methods are investigated and discussed.</P>
Numerically Efficient Algorithm for Reliability-Based Robust Optimal Design of TEAM Problem 22
Ziyan Ren,Chanhyuk Park,Chang-Seop Koh IEEE 2014 IEEE transactions on magnetics Vol.50 No.2
<P>The robust optimization and reliability-based optimization have been proven effective to deal with uncertainties in design variables. However, there are scarcely any publications about comparison of robust and reliable designs, not to mention the combination of robustness and reliability in the electrical engineering. In this paper, the optimal design of superconducting magnetic energy storage system is taken as an example to comparatively investigate robust and reliable designs. Furthermore, the performance robustness and constraint feasibility are integrated into a single optimization model - reliability-based robust design optimization (RBRDO). The proposed RBRDO formulation yields results that provide new alternatives to the designer.</P>
Ziyan Ren,Doojong Um,Chang-Seop Koh 한국자기학회 2014 Journal of Magnetics Vol.19 No.3
In this paper, we suggest reliability as a metric to evaluate the robustness of a design for the optimal design of electromagnetic devices, with respect to constraints under the uncertainties in design variables. For fast numerical efficiency, we applied the sensitivity-assisted Monte Carlo simulation (S-MCS) method to perform reliability calculation. Furthermore, we incorporated the S-MCS with single-objective and multi-objective particle swarm optimization algorithms to achieve reliability-based optimal designs, undertaking probabilistic constraint and multi-objective optimization approaches, respectively. We validated the performance of the developed optimization algorithms through application to the optimal design of a superconducting magnetic energy storage system.
Ziyan Ren,Minh-Trien Pham,Minho Song,Dong-Hun Kim,Chang Seop Koh IEEE 2011 IEEE transactions on magnetics Vol.47 No.5
<P>An effective methodology for a robust global optimization of electromagnetic devices is developed based on the gradient index and multi-objective optimization method. The method transforms a given optimization problem into a multi-objective optimization one by adding another optimization target for minimizing the gradient index. The performance and robustness of the obtained optimal designs from the proposed algorithm are investigated through a numerical experiment with the TEAM Workshop Problem 22.</P>
Ziyan Ren,Minh-Trien Pham,Chang Seop Koh IEEE 2013 IEEE transactions on magnetics Vol.49 No.2
<P>The uncertainties in design variables are unavoidable in the optimal design of electromagnetic devices, and there is an imperative demand to find a robust design, which is insensitive to the uncertainties and remains within the feasible region of constraints even perturbed by the uncertainties. In this paper, a gradient-based worst case optimization (G-WCO) algorithm is proposed in a limited uncertainty set to increase the numerical efficiency based on the worst case optimization (WCO) algorithm. Through applications to the robust optimal design of TEAM 22, the performances of the proposed G-WCO, conventional WCO, and multiobjective optimization approach using gradient index (GI) are compared.</P>
Ziyan Ren,Chang-Seop Koh 대한전기학회 2013 Journal of Electrical Engineering & Technology Vol.8 No.4
In the reliability-based design optimization of electromagnetic devices, the accurate and efficient reliability assessment method is very essential. The first-order sensitivity-assisted Monte Carlo Simulation is proposed in the former research. In order to improve its accuracy for wide application, in this paper, the second-order sensitivity analysis is presented by using the hybrid direct differentiation-adjoint variable method incorporated with the finite element method. By combining the second-order sensitivity with the Monte Carlo Simulation method, the second-order sensitivity-assisted Monte Carlo Simulation algorithm is proposed to implement reliability calculation. Through application to one superconductor magnetic energy storage system, its accuracy is validated by comparing calculation results with other methods.
Ziyan Ren,Dianhai Zhang,Chang Seop Koh 대한전기학회 2013 Journal of Electrical Engineering & Technology Vol.8 No.2
A new reliability calculation method is proposed based on design sensitivity analysis by the finite element method for nonlinear performance constraints in the optimal design of electromagnetic devices. In the proposed method, the reliability of a given design is calculated by using the Monte Carlo simulation (MCS) method after approximating a constraint function to a linear one in the confidence interval with the help of its sensitivity information. The validity and numerical efficiency of the proposed sensitivity-assisted MCS method are investigated by comparing its numerical results with those obtained by using the conventional MCS method and the first-order reliability method for analytic functions and the TEAM Workshop Problem 22.
Ziyan Ren(렌지얀),Dianhai Zhang(장전해),Chanhyuk Park(박찬혁),Chang Seop Koh(고창섭) 대한전기학회 2013 전기학회논문지 Vol.62 No.1
In this paper, for constrained optimization problem, one multi-objective optimization algorithm that ensures both performance robustness and constraint feasibility is proposed when uncertainties are involved in design variables. In the proposed algorithm, the gradient index of objective function assisted by design sensitivity with the help of finite element method is applied to evaluate robustness; the reliability calculated by the sensitivity-assisted Monte Carlo simulation method is used to assess the feasibility of constraint function. As a demonstration, the performance and numerical efficiency of the proposed method is investigated through application to the optimal design of TEAM problem 22--a superconducting magnetic energy storage system.