• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.5
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• pp.459-467
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• 2014

ILM(Incremental Launching Method) bridges pass both the middle of spans and supports during launching. The launching noses are used to minimize the maximum positive moments and negative moments of the superstructure occurring during launching for ILM bridges. In this study, the simplified analysis formula considering diaphragm to calculate the bending moment that occurs during launching is induced and analyzes the optimum design conditions considering diaphragm. The accuracy of the proposed simplified analysis formular compared to the MIDAS Civil has an error of less than 5%. There is a difference up to 13% in the moment between the cases when the diaphragm is considered and is not. In addition, the criteria for deciding the unit weight of equivalent cross section and average stiffness value of equivalent cross section that can be applied to the simplified analysis formula is proposed. In this study, an effective way to optimize the launching nose is proposed that the optimum design is taken in the condition of minimizing the negative moment because of the mechanic characteristic of ILM bridges.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.7
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• pp.821-826
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• 2011

CAE-based structural optimization techniques are applied for the design of a lightweight crane. The boom of the crane is designed by shape optimization with the shape of the cross section of the boom as the design variable. The design objective is mass minimization, and the static strength and dynamic stiffness of the system are set as the design constraints. Hyperworks, a commercial analysis and optimization software, is used for shape and topology optimization. In order to consistently change the shape of the elements of the boom with respect to the change in the shape of its cross section, the morphing function in Hyperworks is used. The support of the boom of the original model is simplified to model the design domain for topology optimization, which is discretized by using three-dimensional solid elements. The final result after shape and topology optimization is 19% and 17% reduction in the masses of the boom and support, respectively, without a deterioration in the system stiffness.

• Journal of Biosystems Engineering
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• v.10 no.2
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• pp.55-62
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• 1985

박(朴)(1982, 1983, 1984 및 1985)이 개발(開發)한 배합사료공장(配合飼料工場)의 투자비용(投資費用) 및 운전비용(運轉費用)의 수학적모형(數學的模型)을 이용(利用)하여, 배합사료공장(配合飼料工場)의 적정(適正) 시스템의 설계(設計)를 예(例)를 들어 소개하였다. 적정(適正)시스템의 설계(設計)를 위(爲)하여 비선형(非線型) 프로그램의 "Single Objective Programming Problem(단일목적함수(單一目的函數))"와 "'Multiple Objective Decision Making Method(다목적함수(多目的函數))"의 2가지 방법(方法)을 적용(適用)하였다. Single Objective Programming Problem에서는 "Generalized Reduced Gradient(GRG) Method"를 이용(利用)하였고, Multiple Objective Decision Making Method(MODM)에서는 "Interactive Nonlinear Goal Program(INGP)"를 이용(利用)하였으며 그 결과(結果)는 다음의 몇가지로 요약(要約)할 수 있다. 1. 박(朴)이 개발(閒發)한 수학적(數學的) 모형(模型)들은 2 가지 방법(方法) 모두 사료공장(飼料工場)의 최적화(最適化) 설계(設計)에 효과적으로 이용(利用)할 수가 있었다. 2. MODM방법(方法)에 의(依)하여 얻어진 최적(最適)시스템은 Single Objective Program Problem에서 구(求)한 결과(結果)보다 균형(均衡)이 있는 시스템이었으며 장래(將來)의 사료원료(飼料原料), 사료구매시장(飼料購買市場), 기타 다른 조건(條件)들의 변화)에 대(對)해서 보다 탄력(彈力)이 있는 시스템으로 나타났다. 3. 엄밀한 의미(意味)에서 절대적(絶對的)인 최적사료공장(最適飼料工場)이란 있을 수 없으며, 주위의 조건(條件), 원료가격(原料價格), 사료가격(飼料價格), 공장주(工場主)의 취향 및 설계조건등(設計條件等)에 따라 최적(最適) 시스템은 각각(各各) 다르게 나타난다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.4
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• pp.153-163
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• 2004

The main objective of this study is to develop a multi-objective fuzzy optimum design program of steel structures and to verify that the multi-objective fuzzy optimum design is more reasonable than the single objective optimum design in real structural design. In the optimization formulation, the objective functions are both total weight and deflection. The design constraints are derived from the ultimate strength of service ability requirement of AISC-LRFD specification. The structural analysis was performed by the finite element method and also considered geometric non-linearity. The different importance of optimum criteria were reflected with two weighting methods ; membership weighting method and objective weighting method. Thus, designers could choose rational optimum solution of structures with application of two weighting methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.4
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• pp.387-397
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• 1992

The spatial domain design of 2-dimensional separable denominator digital filters(SDDF) based on the reduced dimensional decomposition can be realized when the given 2-D impulse response specifications are decomposed into a pair of 1-D specifications via singular value decompositions(SVD). Because of use of the balaned approximation and equivalent transform as 1-D design algorithm, 2-D design algorithm retains the advantage that is numerically stable and can minimize quantization errors. In this paper in order to analyze and reduce these errors, minimum comfficient quantization realization is directly derived from impulse response specification. And using the equivalent trans form relation between mininum coefficient quantization error and minimum roundoff error realizations, we optimally realize a SDDF. This algorithm is analyzed by the simulation, which shows that it is superior to direct or balanced realization in quantization errors.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.135-140
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• 2007

An analysis has been conducted of the optimal condition to maximize the specific impulse for a liquid rocket engine with film cooling. The present engine performance has been compared with the published conceptual design to be verified satisfactorily accurate. The optimal combination of film coolant flow rate and the regenerative cooling capacity has been found for maximum specific impulse. The optimal fuel pump pressure increases and the optimal film coolant flow decreases for a larger thrust engine. Higher turbine inlet temperature increases both the fuel pump pressure and the film coolant flow rate as the optimal condition. The coking temperature has the same qualitative effect as the turbine inlet temperature.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.6
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• pp.37-46
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• 2001

In this research, a controller design method based on optimization is proposed that can satisfy constraints on maximum responses of building structures subject to around excitation modeled by partially stochastic process. The class of controllers to be optimized is restricted to LQR. Weighting matrix on controlled outputs is used as design variable. Objective function, constraint functions and their gradients are computed by the parameterization of control gain with Riccati matrix. Full state feedback controllers designed by proposed optimization method satisfy various design objectives and their necessary maximum control forces are computed for the production of actuator. LQG controllers composed of Kalman filter and LQR designed by proposed method perform well with little deterioration. So it is possible to design output feedback controllers satisfying constraints on various maximum responses of structures.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.5
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• pp.91-96
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• 2004

An optimal design of the gas generator for Liquid Rocket Engine (LRE) was conducted. A fuel-rich gas generator in open cycle turbopump system was designed for 10ton in thrust with RP-1/LOx propellant. The optimal design was done for maximizing specific impulse of thrust chamber with constraints of combustion temperature and for matching the power requirement of turbopump system. Design variables are total mass flow rate to gas generator, O/F ratio in gas generator, turbine injection angle, partial admission ratio, and turbine rotational speed. Results of optimal design provide length, diameter, and contraction ratio of gas generator. And the operational condition predicted by design code with resulting configuration was found to maximize the objective function and to meet the design constraints. The results of optimal design will be tested and verified with combustion experiments.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.7
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• pp.13-18
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• 2004

This paper describes an efficient and robust optimization method for helicopter rotor airfoil design in forward flight. Navier-Stokes analysis was employed to compute the dynamic response of an airfoil, which simulates the unsteady rotor flow-field in forward flight. The optimization system consists of two categories; Response Surface Method to construct the response surface model based on D-optimal 3-level factorial design, and Genetic Algorithm to obtain the optimum solution of a defined objective function including penalty terms of constraints. The influence of design variables and their interactions on the aerodynamic performance was examined through the optimization process.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.1
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• pp.1-8
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• 2014

Using the level set and the meshfree methods, we develop a topological shape optimization method applied to linear elasticity problems. Design gradients are computed using an efficient adjoint design sensitivity analysis(DSA) method. The boundaries are represented by an implicit moving boundary(IMB) embedded in the level set function obtainable from the "Hamilton-Jacobi type" equation with the "Up-wind scheme". Then, using the implicit function, explicit boundaries are generated to obtain the response and sensitivity of the structures. Global nodal shape function derived on a basis of the reproducing kernel(RK) method is employed to discretize the displacement field in the governing continuum equation. Thus, the material points can be located everywhere in the continuum domain, which enables to generate the explicit boundaries and leads to a precise design result. The developed method defines a Lagrangian functional for the constrained optimization. It minimizes the compliance, satisfying the constraint of allowable volume through the variations of boundary. During the optimization, the velocity to integrate the Hamilton-Jacobi equation is obtained from the optimality condition for the Lagrangian functional. Compared with the conventional shape optimization method, the developed one can easily represent the topological shape variations.