• Structural Engineering and Mechanics
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• v.82 no.2
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• pp.191-204
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• 2022

A three-mass vehicle model including one rigid mass and two unsprung masses is adopted to predict the vehicle-bridge interaction (VBI) and to establish the nonlinear coupled governing equations. To overcome the numerical instability and large computation problems concerning the vehicle-bridge system, the perturbation method is used to convert the nonlinear coupled governing equations into a set of linear uncoupled equations. Formulas for bridge's natural frequencies considering both the VBI and the dynamic responses of bridge and vehicle are proposed. Compared with the numerical results obtained by the Newmark-β method, the theoretical solutions for natural frequencies and dynamic responses are validated. The effects of the important factors of unsprung mass, vehicle damping, surface irregularity on the natural frequencies and dynamic responses of bridge and vehicle are discussed, based on the theoretical solutions.

• Journal of The Korean Association For Science Education
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• v.27 no.6
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• pp.477-487
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• 2007

Previous studies show that students have difficulties in understanding and using molecular visualization tools. This study focuses on the ways in which first year chemistry undergraduates use ball-and-stick molecular models to explain the concept of addition reaction and the difficulties that they face using the models. Video recordings of interviews with undergraduates manipulating ball-and-stick models to solve problems related to reaction mechanisms are analysed to determine if they are able to elucidate their understanding with use of models. The results showed that students have difficulties with viewing the ball-and-stick models from the proper perspective and understanding the relationship between the various structures that they have created using the models. They also find the use of ball-and-stick models tedious and prefer drawing molecular structures on paper to explain their ideas. Implications for the teaching using ball-and-stick molecular models are discussed.

• Journal of the Korean Professional Engineers Association
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• v.44 no.3
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• pp.20-24
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• 2011

According to Natural disasters due to extreme weather, In particular earthquake, It has become important to avoid by aseismic design. Do not entrust with it to non-specialists. By all means, It has to be Structural Professional Engineers. Therefore, foresee and Prevent problems in the near future.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.4 no.1
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• pp.79-92
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• 2000

We investigate numerical properties of Newton's algorithm for improving an eigenpair of a real matrix A using only fixed precision arithmetic. We show that under natural assumptions it produces an eigenpair of a componentwise small relative perturbation of the data matrix A.

• 한국가스학회:학술대회논문집
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• 2005.10a
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• pp.17-22
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• 2005

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.125-132
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• 2000

This study presents the application of genetic algorithms(GA) to the back analysis of tunnels. GA based on the theory of natural evolution, and have been evaluated very effective for their robust performances, particularly for optimizing structure problems. In the back analysis method, the selection of initial value and uncertainty of field measurements influence significantly on the analysis result. GA can improve this problems through a probabilistic approach. Besides, this technique have two other advantages over the back analysis. One is that it is not significantly affected by the form of problems. Another one is that it can consider two known parameter simultaneously. The propriety of this study is verified as the comparison in the same condition of the back analysis(Gens et al, 1987). In this study, it was performed to estimated the geotechnical parameters in the case of weak rock mass at the Kyung Bu Express railway tunnel. GA have been shown for effective application to a geotechnical engineering.

• Journal of agricultural medicine and community health
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• v.35 no.1
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• pp.21-35
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• 2010

There are many work-related injuries and diseases of fisheries in Korea. Fishermen have exposed to harmful environment, such as natural disasters, ultraviolet, noise, vibration, organic solvents, ergonomic risk factors, loss of fresh water and food, and psychologic stress. They have suffered from numerous work-related health problems, including musculoskeletal disorders, cardiovascular diseases, infectious diseases, pyschological diseases, decompression sickness, and so on. Sea accidents can cause deaths of fishermen and if sea pollution is occurred, fishermen have a great economic damage. However, the concern of these injuries and diseases has been little because they are small in number and have decreased. Fisheries are important core industries, so the problems of fisheries have to be solved by a government. But work-related injuries and diseases are not investigated properly and accurate diagnoses are not made due to loss of concern. We hope that this article will be a cornerstone to solving the work-related problems of fisheries.

• Journal of Korean Institute of Industrial Engineers
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• v.31 no.1
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• pp.10-19
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• 2005

The minimum spanning tree (MST) problem is one of the traditional optimization problems. Unlike the MST, the degree constrained minimum spanning tree (DCMST) of a graph cannot, in general, be found using a polynomial time algorithm. So, finding the DCMST of a graph is a well-known NP-hard problem of importance in communications network design, road network design and other network-related problems. So, it seems to be natural to use evolutionary algorithms for solving DCMST. Especially, when applying an evolutionary algorithm to spanning tree problems, a representation and search operators should be considered simultaneously. This paper introduces a new tree representation scheme and a genetic operator for solving combinatorial tree problem using evolutionary algorithms. We performed empirical comparisons with other tree representations on several test instances and could confirm that the proposed method is superior to other tree representations. Even it is superior to edge set representation which is known as the best algorithm.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.11
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• pp.2922-2931
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• 1994

We propose a modified 6-node element, where the sampling point of Gauss quadrature moved in the thickness direction. The modified 6-node element has been applied to static problems and forced motion analyses. In this study, this method is extended to the finite element analysis of the natural frequencies of two dimensional problems. We also propose a modified 16-node element for three dimensional problems, which behaves much like a 20-node element with smaller degree of freedom. The modified 6-node and 16-node elements have been applied to the modal analyses of beams and plates, respectively. The results agree well with the results of the 8-node or 20-node element models.

• Journal of the Korea Furniture Society
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• v.27 no.4
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• pp.362-374
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• 2016

The ability of 'creative thinking' is one of the most important fact for designers to complete their design process. It is not only the overall concept of the process but also all details related to each steps of the process such as planning product strategies, research, finding ways to solve problems image development, broadening ideas, etc. It is, however, not easy to creative as designers by natural learning through experiences unless they have geniuses for creative designing. Many experienced designers in the field are even in dilemmas being not be able to differentiate from copying other designs. This study is focused on the researches on the works of famous designers, architects and artists who have shown great creativities throw their works or processes. It is aimed to define their ways of thinking which could be fundamental motives for the creativeness, various behavioral methods to solve problems in creative ways, technical approaches to improve creativities, and overall intuition in the design working processes.