• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.3
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• pp.311-318
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• 2015

A nonlinear dynamic response structural optimization process is proposed for the television (TV) packing system that protects the damage from a drop situation using the equivalent static loads (ESLs). Topology optimization using ESLs is carried out for conceptual design, and shape optimization using stress ESLs for a virtual model is performed for detailed design. Stress ESLs are static loads that generate the same displacement as well as the stress fields of linear static analysis as those of nonlinear dynamic analysis. Thus, the response of nonlinear dynamic analysis can be utilized as a constraint in the linear static structural optimization. An actual example is solved to validate the process. The drop test of a television packaging system is analyzed by LS-DYNA, and NASTRAN is used for optimization.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.659-675
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• 2006

Recently, significant progress has been made in performance-based engineering methods that rely mainly on nonlinear static seismic analysis procedures. The Capacity Spectrum Method (CSM) and the Displacement Coefficient Method (DCM) are the representative nonlinear static seismic analysis procedures. In order to evaluate the applicability of the procedures to the seismic evaluation and design process of new and existing structures, the accuracy of both CSM and DCM should be evaluated in advance. The accuracy of seismic responses by the nonlinear static procedures is evaluated in comparison with the shaking table test results for the structural wall specimen subjected to the far field and near field earthquakes. Also conducted are comparative studies where the shaking table test results are compared with those from nonlinear dynamic analysis procedures, i.e., Single-Degree-of-Freedom (SDOF), equivalent SDOF and Multi-Degree-of-Freedom (MDOF) systems.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.2
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• pp.9-17
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• 2004

The seismic performance evaluation and retrofit process are very important in old existing bridges. If the result is not appropriate. then a retrofit process are required. Among various retrofit methods, the seismic isolation is a very useful method. because it can be applied by replacing old bridge bearings. In this study, the effectiveness of seismic isolation is rationally verified. For this purpose, two seismic isolations used widely are selected and non-linear static and dynamic analyses are performed. The responses of existing bridges are compared with those of retrofited bridges by seismic isolation bridge for earthquake of target level. and seismic performances are evaluated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.1
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• pp.1-10
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• 2011

An optimization method is proposed for preform and billet shape designs in the forging process by using the Equivalent Static Loads (ESLs). The preform shape is an important factor in the forging process because the quality of the final forging is significantly influenced by it. The ESLSO is used to determine the shape of the preform. In the ESLSO, nonlinear dynamic loads are transformed to the ESLs and linear response optimization is performed using the ESLs. The design is updated in linear response optimization and nonlinear analysis is performed with the updated design. The examples in this paper show that optimization using the ESLs is useful and the design results are satisfactory. Consequently, the optimal preform and billet shapes which produce the desired final shape have been obtained. Nonlinear analysis and linear response optimization of the forging process are performed using the commercial software LS-DYNA and NASTRAN, respectively.

• Computational Structural Engineering
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• v.11 no.1
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• pp.27-37
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• 1998

본 고에서는 지진해석과 관련하여 가장 중요한 원칙과 해석법에 대한 개략을 제시하여 철근콘크리트 구조물의 지진해석과 관련된 용어 및 특수과제를 언급하고자 한다. 이 해석의 위력이나 매력적인 점에도 불구하고 지진응답에 대한 해석은 항상 많은 불확실성에 부닥칠 수 있다는 것을 강조하고자 한다. 해석은 설계과정의 한 단계에 불과하여 수많은 컴퓨터 출력 페이지가 빈틈없는(sound) 기술적 판단을 대신하여서는 안된다. 구조물에 있어서의 지진력은 외부에서 가해진 하중으로부터 발생하는 것이 아니다. 구조물에 압력 및 흡입력으로 작용하는 풍하중과는 달리, 구조물의 기저(base)에서의 주기적 운동에 의한 응답으로서 상부구조물은 가속도를 받게 되고 따라서 관성력으로서 지진력이 얻어지게 된다. 지진응답은 기본적으로 동적인 성질을 가지며 고유주기와 감쇠와 같은 동적 특성은 이 응답을 결정하는데 결정적인 역할을 한다. 만약 지진해석이 실제적인 것이 되자면, 단순화된 방식으로라도 이러한 동적 특성을 고려할 수 있는 것이어야 한다. 이러한 동적 성질이 복잡성의 한 요인이며, 다른 요인으로서 해석적 장애가 존재한다. 대부분의 구조물은 최대지진에 대하여 상당한 항복현상을 나타냄으로써 저항하도록 설계하고 있다. 따라서 설계자는 최대지진에 대한 구조물의 비선형 동적 거동에 대하여 어느 정도 이해를 하고 있어야 한다. 원칙적으로 이것은 매우 복잡하고 어려운 해석적 문제를 제기하게 된다. 실제로는 매우 단순화된 해석법, 적절한 설계 및 상세의 조합만으로도 만족스러운 거동을 얻는 것에 부족함이 없다. 어쨌든 이러한 해석기법의 바탕과 한계를 이해하는 것은 필수적이다.tidyl ethanolamine$(20.9{\sim}29.7%)$, phosphatidyl inositol$(18.4{\sim}26.1%)$ 순으로 많았다. 각 구성지질의 지방산조성은 4종의 버섯 공히 linoleic acid와 palmitic acid가 주요 지방산이었으나 싸리버섯은 중성지질에서 oleic acid의 함량이 높았다.n the part of special landscape management area, it is necessary to introduce landscape impact assessment system to more effective landscape management.ch served as supporting organizations. The control of the construction and management of the royal garden and landscape was held by decision makers, executors of works and management. 2) The general process of the construction and management of the royal garden and landscape included Sangji and Kyuho다 as the first step; In case of buildings and facilities, according to former examples and drawings, the most of the planning and design was already fixed.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1991.11a
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• pp.22-28
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• 1991

최근 전자 및 광학분야에 있어서의 눈부신 발전은 비구면 가공기나 초정밀 연삭기와 같은 초정밀 가공기계의 개발과 실용화에 힘입은 바 크다. 이러한 초정밀 가공기의 성능을 좌우하는 핵심요소로서 주축계를 들 수 있으며, 비교적 소형 경량의 공작물을 가공하는 기계의 주축용 베어링으로는 오일 베어링을 대신하여 공기베어링이 점차 널리 사용되고 있다. 본 논문에서는 점급기원의 가정하에 직접수치해법을 사용하는 해석 프로그램을 작성하여, 무차원화된 설게 변수들에 대한 외부가압 공기베어링의 정$\cdot$동특성수들을 구하고, 여기서 구해진 베어링의 정$\cdot$동특성수를 사용하여 베어리으이 공기막 반력을 계산한 후, 축중심 궤적의 비선형 해석을 수행함으로써 주축 회전 정도를 예측하고자 한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.8
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• pp.823-830
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• 2015

Structural optimization pursues improved performance of structures. Nowadays, structural optimization is applied to the design of huge and complex structures such as an airplane. As the number of the finite elements is increased, the analysis solution becomes more accurate. However, the design cost using the finite element model is significantly increased. The component mode synthesis method that is using the substructure synthesis method is frequently employed in order to keep the accuracy and reduce the cost. A new design method for structural optimization is proposed to reduce the design cost and to consider the dynamic effect of the structure. The proposed method reduces the design cost by applying the equivalent static loads on the design domain. An example of linear dynamic response optimization is solved and the efficiency of the proposed method is demonstrated.

• Journal of Industrial Technology
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• v.25 no.A
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• pp.31-38
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• 2005

Recent earthquakes have shown that near-field earthquakes can produce spectral demands significantly larger than those considered in current design code. International Atomic Energy Agency (IAEA) has recently initiated a coordinated research program on safety significance of near-field earthquakes. The purpose of this program is to focus on the assessment of vulnerability of nuclear facility structures by using and adapting the best available engineering practices appropriate to evaluate the effects of near-field earthquakes. The objective of this paper is to evaluate of seismic responses of a shear building test specimen subjected to near-filed earthquakes. To achieve the objective, the seismic responses of the test specimen, evaluated by the Displacement Coefficient Method (DCM) and Nonlinear Dynamic Analysis (NDA), are compared with those by the experimental tests.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.9
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• pp.3119-3124
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• 2010

The purpose of this paper is to analyze dynamic behaviors of the oil film thickness and engine bearings in both aligned and misaligned operation conditions of a crankshaft using computer simulation techniques. A crankshaft as an elastic body is modeled for a misaligned crankshaft which is very important design parameter of the film thickness and engine bearings. In this analysis, a dynamic characteristic of a minimum oil film is analyzed based on the elastohydrodynamic lubrication theory. The boundary conditions for analyzing the film behaviors include non-linear constraint forces and bending moments in engine bearings. The more expedient model of an engine bearing is extended to consider the effect of crankshaft misalignment. The computed results indicate that the minimum oil film thickness that causes a major influence on the performance of engine bearings has showed a decrease of 16% to 24% for the misaligned crankshaft compared with an aligned crankshaft. The computed results show that the misalignment of a crankshaft inevitably brings the reduction of minimum oil film thickness and this may increase the failure of a bearing. These results as design parameters are very useful for a bearing designer as a firm reference data of an automotive engine.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.11
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• pp.1361-1370
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• 2012

A shape optimization is proposed to obtain the desired final shape of forming and forging products in the manufacturing process. The final shape of a forming product depends on the shape parameters of the initial blank shape. The final shape of a forging product depends on the shape parameters of the billet shape. Shape optimization can be used to determine the shape of the blank and billet to obtain the appropriate final forming and forging products. The equivalent static loads method for non linear static response structural optimization (ESLSO) is used to perform metal forming and forging optimization since nonlinear dynamic analysis is required. Stress equivalent static loads (stress ESLs) are newly defined using a virtual model by redefining the value of the material properties. The examples in this paper show that optimization using the stress ESLs is quite useful and the final shapes of a forming and forging products are identical to the desired shapes.