• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.04a
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• pp.451-457
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• 2000

In many dynamic problems such as foundation vibrations ultrasonic nondestructive evaluation and blasting analysts are confronted with the problem of wave propagation in an infinite or semi-infinite media. In order to simulate this situation by a finite analytical model provisions must be made to absorb the stress waves arriving at the boundary. Absorbing boundaries are mathematical artifacts used to prevent wave reflections at the boundaries of discrete models for infinite media under dynamic loads. An analytical study is carried out to examine the effectiveness of Lysmer-Kuhlemeyer model one of the most widely used absorbing boundaries. Validity of the absorbing boundary conditions suggested by Lymer-Kuhlemeyer is examined by adopting the solution of Ewing et al. to the problem of plane waves from a harmonic normal force on the surface of an elastic half-space. The Ewing's problem is than numerically simulated using the finite element method on a semi-circular mesh with and without absorbing boundaries which are represented by viscous dashpots. The absorption ratios are calculated by comparing the displacements at the absorbing boundaries to those at the free field without absorbing boudaries.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2009.11a
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• pp.72-76
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• 2009

Along with the heightening development of modern medical technology in the world, the economy and quality of lifestyle has contributed to the increase in the average lifespan. Therefore the issue to deal with the aging population is becoming an important social issue. As aging population becomes a serious social problem, the issue of supporting the senior citizens is confronted with a more difficult situation. From the perspective of senior citizen's physical and social and economic situations, there are great difficulties to deal with, like lowered physical ability compared to the rest of population. Therefore the supply of senior welfare facility that is based on senior citizen's physical characteristics yet provides the opportunity to be independent needs to provided rather than just planning a simple facility that provides living accommodations. This research examines thereinto welfare center's usage of residential circulation system from the senior welfare facilities' type classification to understand the actual usage problem and presents a circulation plan that will resolve the problem.

• Journal of the Korean School Mathematics Society
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• v.1 no.1
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• pp.111-119
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• 1998

So far the studies on mathematical problem-solving education have failed to realize the anticipated result from students. The purpose of this study is to examine the reasons from the metacognitional viewpoint, and to think of making meta-items which enables learners to study through making effective use of the meaning of problem-solving and through establishing a general, well-organized theory on metacognition related to mathematic teaching guiedance. Metacognition means the understanding of knowledge of one's own and significance in the situation that can be reflection so as to express one's own knowledge and use it effectively when was questioned. Mathematics teacher can help students to learn how to control their behaviors by showing the strategy clearly, the decision and the behavior which are used in his own planning, supervising and estimating the solution process himself. If mathematics teachers want their students to be learners not simply knowing mathematical facts and processes, but being an active and positive, they should develop effective teaching methods. In fact, mathematics learning activities are accomplished under the complex condition arising from the factors of various cognition activities. therefore, mathematical education should consider various factors of feelings as well as a factor as fragmentary mathematical knowledge.

• Journal of Distribution Research
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• v.2 no.1
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• pp.215-230
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• 1997

Today, The biggest problem in the structure of high cost and low efficient economic situation in Korea is found due to problem of cost circulation field, so the government officials and enterprises trying to solve it. In fact, The high cost, low efficient structure is not good to poor circulation of goods among businesses, especially in Dae-gus local industries. also, we face there is a shortage of indirect social capital which caused by a lack of connectoin among businesses in the circulation field. Recently, in order to solve the problem of circulation, it is above all necessary that government and local authorities pay attention to it and effort of positive and drastical investment. As the economy of Dae-gu would be activiate and local firms competion should be strengthen, it is request that the policy for efficiency in the circulation of goods need to effort as follows; 1. The highest class of local firms try to convert of knowledge in order to reduce the cost of goods. 2. To efficient of firms goods, it is essential that standardize the goods and spread for automation, so in the long run, There will be thrust forward establishment of total goods information network.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.270-277
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• 2004

In this paper, path-independent values of the J-integral in the fininte element context for arbitrary two-dimensional and three-dimensional crack configurations in welds are presented. For the fracture mechanics analysis of cracks in welds, residual stress analysis and fracture analysis must be performed simultaneously. In the analysis of cracked bodies containing residual stress, the usual domain integral formulation results in path-dependent values of the J-integral. This paper discusses modifications of the conventional J-integral that yield path independence in the presence of residual stress generated by welding. The residual stress problem is treated as an initial strain problem and the J-integral modified for this class of problem is used. And a finite element program which can evaluate the J-integral for cracks in two-dimensional and three-dimensional residual stress bearing bodies is developed using the modified J-integral definition. The situation when residual stress only is present is examed as is the case when mechanical stresses are applied in conjunction with a residual stress field.

• Structural Engineering and Mechanics
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• v.4 no.2
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• pp.191-202
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• 1996

This paper presents a construction of adaptive boundary element for the problem with mixed boundary conditions such as heat transfer between heated body surface and surrounding medium. The scheme is based on the sample point error analysis and on the extended error indicator, proposed earlier by the authors for the potential and elastostatic problems, and extended successfully to multidomain and thermoelastic analyses. Since the field variable is connected with its derivative on the boundary, their errors are also interconnected by the specified condition. The extended error indicator on each boundary element is modified to meet with the situation. Two numerical examples are shown to indicate the differences due to the prescribed boundary conditions.

• Education of Primary School Mathematics
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• v.8 no.1
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• pp.33-50
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• 2004

This study is intended to investigate the effect on the development of multiplicative thinking and multiplicative ability by teaching repeated addition, rate, comparison, area-array, and combination problems. Two research questions are established: first, is there any difference of multiplicative thinking between the experimental group(the modeling of problem situation learning group) and the control group(the traditional learning group)\ulcorner Second, is there any difference of multiplicative ability between the experimental group and the control group\ulcorner The treatment process for the experimental group is based on modeling problem situations for nine lesson periods. In order to answer the research questions the chi-square analysis was used for the first research question and the t-test was used for the second one. The findings are summarized as follows: there is no significant difference of multiplicative thinking be1ween the experimental and the control group but there is significant difference of multiplicative ability.

• Korean Journal of Computational Design and Engineering
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• v.5 no.4
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• pp.319-326
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• 2000

Expert systems using uncertain and ambiguous knowledge are not of the recent interests about uncertainty problem for performing inference similar to the decision making of a human expert. Human factors on rule-based systems often involve uncertain information. Expert systems had been used the methods of conflict resolution in a rule conflict situation, but this methods not properly solved the rule conflict. If a human expert appends a new rule to an original rule base, the rule base rightly causes a rule conflict. In this paper, the problem of rule conflict is regarded as one in which uncertainty of information is fundamentally involved. In the reduction of problem with uncertainty, we propose an enhanced rule ordering method, which improve the rule ordering method using Dempster-Shafer theory. We also propose a combinative index, which involve human factors of experts decision making.

• Journal of the Korean Operations Research and Management Science Society
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• v.37 no.4
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• pp.197-209
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• 2012

This paper studies an emergency service vehicle location problem, where minimum reliability level pre-specified at each demand point is assured. Several models are suggested depending on the busy fraction, which is the time proportion of unavailability for the ambulances. In this paper a new model on computing the busy fraction is suggested, where it varies depending on the distance between the demand point and ambulances, hence it may respond the more realistic situation. The busy fraction for the ambulance location determined by the optimization model is computed by the simulation, and updated through the iterative procedure. It has been shown that the performances of the solutions obtained by the algorithm suggested for the instances appeared in the literature.

• Solar Energy
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• v.8 no.1
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• pp.82-94
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• 1988

The hydrodynamic stability equations for natural convection flows adjacent to a vertical isothermal surface in cold or warm water (Boussinesq or non-Boussinesq situation for density relation), constitute a two-point-boundary-value (eigenvalue) problem, which was solved numerically using the simple shooting and the orthogonal collocation method. This is the first instance in which these stability equations have been solved using a computer code COLSYS, that is based on the orthogonal collocation method, designed to solve accurately two-point-boundary-value problem. Use of the orthogonal collocation method significantly reduces the error propagation which occurs in solving the initial value problem and avoids the inaccuracy of superposition of asymptotic solutions using the conventional technique of simple shooting.