• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.247-254
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• 2008

The primary objective of this research is to develop an efficient design and optimization methodology for SRM Wagon Wheel Grain and to develop of software for practical designing and optimization of Wagon Wheel grains. This work will provide a design process reference guide for engineers in the field of Solid Rocket Propulsion. Using these proposed design methods, SRM Wagon Wheel grains can be designed for various geometries, their optimal solutions can be found and best possible configuration be attained thereby ensuring finest design in least possible iterations & time. The main focus is to improve computational efficiency at various levels of the design work. These have been achieved by the following way. a. Evaluation of system requirements and design objectives. b. Development of Geometric Model of Wagon Wheel grain configuration. c. Internal ballistic performance predictions. d. Preliminary designing of the Wagon Wheel grain configuration involving various independent geometric variables. e. Optimization of the grain configuration using Sequential Quadratic Programming f. In depth analysis of the optimal results considering affects of various geometric variables on ballistic parameters and analysis of performance prediction outputs have been performed g. Development of software for design and optimization of Wagon Wheel Grain. By using these proposed design methods, SRM Wagon Wheel grains can be designed by using geometric model, their optimal solutions can be found and best possible configuration be attained thereby ensuring finest design.

• 한국기계가공학회지
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• 제17권5호
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• pp.123-130
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• 2018

In this study, the optimum design of mold feed systems is determined for plug cover housing (PCH), which is a cover-assembly product that protects the wiring of automobile connectors. The design goal is to achieve the filling balance of the resin in the left and right covers while avoiding the occurrence of weld lines in the hinge as much as possible. For the optimization, an orthogonal array experiment and a main effect analysis of the design factors are performed, and the factors that cause the interactions with the two design characteristics are selected as the design variables. We present some design alternatives, i.e., some combinations of the design variables, and analyze the filling-simulation results, expected molding risk, and cost economics to select an optimum design solution among the design alternatives. In the optimal solution, the weld line is generated at a position outside the hinge, and the filling balance is also acceptable, showing that both design goals can be satisfied simultaneously despite conflicting with each other.

• 한국환경복원기술학회지
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• 제17권2호
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• pp.109-123
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• 2014

Kaloula borealis is the species of Amphibia which belongs to Kaloula genus and it is the only species inhabiting in Korea. The population size and habitat of Kaloula borealis have been significantly decreased on a national scale due to the diversified developments and the uses of agricultural pesticides. Accordingly, the Ministry of Environment has designated and managed them as the class II of endangered species, in accordance with "Endangered Species Protection and Management Act"; however, a particular study focused on the ecological restoration of Kaloula borealis is desperately needed to prevent their extinction. This study was conducted to propose the HSI (Habit Suitability Index) of Kaloula borealis based on literature survey on ecology and habitats of Kaloula borealis, as well as their HSI. Factors to be investigated in HSI include: space, feed, cover, water(breeding) and threatening factors and the variables of each factor were also proposed. The distance from wetland, grassland, farm, stream and rice paddy, as well as the altitude of spawning pond were proposed as the variables of space, whereas the bed structure of forest and low-rise grassland were proposed as the variables of feeding. The variables of water (breeding) include the area of permanent and temporary wetlands, coverage of emerged pants (ratio of open water), water depth, water temperature, water quality, pH level, etc., whereas the presence of predator, distance from street and pollutants were proposed as the variables of threatening factor. The sub-standards by HSI factor of Kaloula borealis have been drawn from in-depth consultation with experts and based on this, the final HSI of Kaloula borealis was developed.

• 응용통계연구
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• 제25권1호
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• pp.215-223
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• 2012

반응표면 방법론은 어떤 공정을 개선하거나 최적화하는데 이용되는 아주 유용한 통계적방법이다. 이러한 최적조건을 추정하기 위하여 최적조건이 있으리라 예상되는 실험구역을 탐색하여 실험을 실시한다. 그런데 이 실험구역은 실험의 환경의 제약 그리고 연구자의 선택 등으로 그 모습이 다양하게 달라질 수 있다. 반응표면 설계는 실험구역의 모양에 따라 보통 둥그런 모양의 "구형설계"와 육면체 모양의 "입방형설계"로 구분한다. 구형설계는 회전성을 만족하거나 회전성에 상당히 근접하는 "유사회전성"을 갖는 특징이 있다. 반응표면 설계에서 가장 많이 사용되는 중심합성설계는 실험구역이 구형인 5수준 실험설계이다. 이 때, 축점의 ${\alpha}$값을 ${\alpha}=\sqrt{k}$ 대신 ${\alpha}=1$로 조정하면 5-수준이 아닌 3-수준 입방형 중심합성설계를 얻을 수 있다. 그러나 입방형 중심합성설계는 실험구역이 구형이 아니므로 회전성을 만족하지 못하는 문제가 있다. 이러한 이유로, 변수들의 수준 수를 3으로 제한하면서 실험구역은 구형인 실험설계가 필요할 때가 많다. 이에 대한 대표적 실험설계가 바로 박스-벤켄 실험설계이다. 이 실험설계는 구형의 실험구역으로 회전성을 만족하나 실험구역의 크기가 변수의 개수가 증가해도 제자리 수준으로 좁은 특징이 있다. 현실적으로 실험구역의 가상 자리 부분에 대한 예측에 관심이 있을 경우 변수의 개수가 많아지면 이에 비례하여 실험구역이 커지는 실험설계가 바람직하다. 본 논문은 3-수준 입방형설계에 비하여 실험구역이 유달리 좁은 박스-벤켄 실험설계를 보완하여 구형설계를 만족하면서도 다른 한편으로는 변수 수에 따라 실험반경이 커지는 3-수준 구형 반응표면 설계를 소개하고자 한다. 이 방법을 기존의 실험설계들과 비교한 결과 변수수가 비교적 작을 경우 실험횟수 등을 고려하여 응용가치가 있음을 확인하였다.

• 대한간호학회지
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• 제27권1호
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• pp.189-201
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• 1997

This study was designed to test the relationship between effectiveness of nursing organizations and structural and managerial variables of nursing organizations that are described in the Robbins Organizational theory model. The data were collected through self reported questionnaires from 605 nurses working in, and 782 patients hospitalized in, five tertiary hospitals in Seoul. Results showed that according to MANOVA there was a significant difference in nurses job satisfaction and patient satisfaction among the five hospitals. According to cluster analysis of the structural and managerial variables of nursing organizations, the five hospitals were divided into two clusters and there was no significant difference in nurses job satisfaction or patient satisfaction between the two clusters. According to canonical correlation analysis the formalization and centralization of structural variables were shown to be predicting variables for nurses job satisfaction, and the managing job design and managing Change of managerial variables were shown to be predicting variables for nurses job satisfaction.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.152-155
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• 2008

In this paper, the effect of modification of geometric variables on the performance of a centrifugal compressor blade has been studied numerically. The compressor contains six main blades and six splitter blades. Reynolds averaged Navier-Stokes (RANS) equations with shear stress turbulence (SST) model are discretized by finite volume approximations and solved on hexahedral grids for flow analysis. The design variables from blade lean angle at tip and middle of the blade have been modified. The isentropic blade efficiency and pressure have been predicted with the variation of the variables. Frozen rotor simulation is performed and adiabatic wall condition has been used. One of the six blades of compressor has been used for simulation to reduce the computational load. Optimum number of meshes has been selected by grid-dependency test, and this is used for all the simulations with changing geometric variables. The detailed flow analysis results have been reported as well as the effects of the variables.

• 대한기계학회논문집A
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• 제30권11호
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• pp.1472-1478
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• 2006

Double-deck train has been attracted growing attention as next generation transportation around metropolis because of high passenger carrying capacity. To develop high-speed double-deck train with low operational costs, the carbody must be designed as light as possible. In addition, the carbody must be strong enough to ensure the safety of passengers. To meet these design requirements, we perform systematically weight minimization that determines thickness of aluminum extruded panels of the carbody. First, to reduce the design variables, we carry out the screening process that select sensitive or/and important design variables through design exploration. Then, weight minimization is accomplished under multi-loading condition such as vertical, compressive and torsional loads, while satisfying strength constraints of the design regulations. Finally, the result of design optimization is discussed by comparison with its initial design.

• 산업공학
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• 제21권1호
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• pp.43-50
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• 2008

Understanding consumers' latent desires for product form has now become a critical issue in product design. Accordingly, product development processes is rapidly changing from product-oriented development to user-centered development. Driver visibility is considered as an important element of driving posture packaging in automobile interior design. This study presents a systematic process for driver visibility analysis approached from affective engineering method that provides design variable selection and screening with respect to the image/impression element of the human visibility. Also, the analysis of front visibility, often called the feeling of "openness", in motor vehicle interior design, is selected and practiced a case study using the systematic process proposed in this study. Twenty six participants evaluated the feeling of openness for thirty motor vehicles following the perceived scale of affective design factors. The results showed that variables such as the height of head lining, the height of cluster housing, the gradient of windshield and the volume of A-pillar were the critical design variables which affect the feeling of openness in a motor vehicle.

• Structural Engineering and Mechanics
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• 제15권1호
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• pp.39-52
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• 2003

A computer program has been developed for the optimum design of prestressed concrete beams under flexure. Optimum values of prestressing force, tendon configuration, and cross-sectional dimensions are determined subject to constraints on the design variables and stresses. 28 constraints have been used including flexural stresses, cover requirement, the aspect ratios for top and bottom flanges and web part of a beam and ultimate moment. The objective function contains cost of concrete, prestressing force and formwork. Using this function, it is possible to obtain minimum cost design, minimum weight or cross-sectional area of concrete design and minimum prestressing force design. Besides the idealized I-shaped cross-section, which is widely used in literature, a general I-shaped cross-section with eight geometrical design variables are used here. Four examples, one of which is available in the literature and the others are modified form of it, have been solved for minimum cost and minimum cross-sectional area designs and the results are compared. The computer program, which employs modified grid search optimization method, can assist a designer in producing efficient designs rapidly and easily. Considerable savings in computational work are thus made possible.

• Corrosion Science and Technology
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• 제20권2호
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• pp.52-61
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• 2021

This study using experimental design and linear regression technique was implemented in order to predict the pitting potential of stainless steel in marine environments, with the target materials being AL-6XN and STS 316L. The various variables (inputs) which affect stainless steel's pitting potential included the pitting resistance equivalent number (PRNE), temperature, pH, Cl^- concentration, sulfate levels, and nitrate levels. Among them, significant factors affecting pitting potential were chosen through an experimental design method (screening design, full factor design, analysis of variance). The potentiodynamic polarization test was performed based on the experimental design, including significant factor levels. From these testing methods, a total 32 polarization curves were obtained, which were used as training data for the linear regression model. As a result of the model's validation, it showed an acceptable prediction performance, which was statistically significant within the 95% confidence level. The linear regression model based on the full factorial design and ANOVA also showed a high confidence level in the prediction of pitting potential. This study confirmed the possibility to predict the pitting potential of stainless steel according to various variables used with experimental linear regression design.