• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 추계 학술대회논문집
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• pp.187-191
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• 2004

The conventional reliability based design optimization(RBDO) methods require high computational cost compared with the deterministic design optimization(DO) methods. To overcome the computational inefficiency of RBDO, single loop methods have been proposed. These need less function calls than that of RBDO but much more than that of DO. In this study, the approximate reliability method is proposed that the computational requirement is nearly the same as DO and the reliability accuracy is good compared with that of RBDO. Using this method, the 3-D viscous aerodynamic shape design optimization with uncertainty is performed very efficiently.

• 한국생산제조학회지
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• 제19권2호
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• pp.224-229
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• 2010

This paper presents a reliability-based topology optimization (RBTO) using bi-directional evolutionary structural optimization (BESO). An actual design involves uncertain conditions such as material property, operational load and dimensional variation. Deterministic topology optimization (DTO) is obtained without considering of uncertainties related to the uncertainty parameters. However, the RBTO can consider the uncertainty variables because it has the probabilistic constraints. In this paper, the reliability index approach (RIA) is adopted to evaluate the probabilistic constraint. RBTO based on BESO starting from various design domains produces a similar optimal topology each other. Numerical examples are presented to compare the DTO with the RBTO.

• 정보저장시스템학회논문집
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• 제4권1호
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• pp.6-12
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• 2008

The paper deals with the numerical analysis and design optimization of polysilicon micro thermal flexure actuator. The deflection of a thermal actuator is implicitly related to the actuation time so that such deflection is to be maximized under the consideration of structural performances such as maximum stress and natural frequencies. At first, the structural formulation of a thermal actuator is reviewed, and its CAE based simulation is performed to verify the numerical model. A parametric study is then conducted to identify the mainly effective design variables. Finally, the design of a micro thermal actuator is explored in the context of deterministic optimization and reliability based design optimization in the present study.

• 한국항공운항학회지
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• 제26권2호
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• pp.54-60
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• 2018

This paper contains the multi-mission scheduling optimization of UAV within a given operating time. Mission scheduling optimization problem is one of combinatorial optimization, and it has been shown to be NP-hard(non-deterministic polynomial-time hardness). In this problem, as the size of the problem increases, the computation time increases dramatically. So, we applied the genetic algorithm to this problem. For the application, we set the mission scenario, objective function, and constraints, and then, performed simulation with MATLAB. After 1000 case simulation, we evaluate the optimality and computing time in comparison with global optimum from MILP(Mixed Integer Linear Programming).

• 대한기계학회논문집A
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• 제27권6호
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• pp.905-913
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• 2003

Generally, most of optimization have been performed with fixed sizes and variables. But, the optimum value considering tolerance of design variables and material properties, might be useless owing to exist in infeasible region. It is needed that the tolerance of design variables and material properties is considered for a real design problem. A deterministic optimal solution can be in the feasible region by performing robust optimization considering tolerance. In the paper, robust design is suggested to gain an optimum insensitive to variation of design variables and it is applied for optimization problem of caliper disc brakes for vehicles.

• 한국공작기계학회논문집
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• 제13권6호
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• pp.107-113
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• 2004

This paper presents the pillar section optimization technique considering the reliability of the vehicle body structure consisted of complicated thin-walled panels. The response surface method is utilized to obtain the response surface models that describe the approximate performance functions representing the system characteristics on the section properties of the pillar and on the mass and the natural frequencies of the vehicle B.I.W. The reliability-based design optimization on the pillar sections Is performed and compared with the conventional deterministic optimization. The FORM is applied for the reliability analysis of the vehicle body structure. The developed optimization system is applied to the pillar section design considering the fundamental natural frequencies of passenger car body structure. By applying the proposed RBDO technique, it can be possible to optimize the pillar sections considering the reliability that engineers require.

• 대한수학회지
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• 제47권1호
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• pp.17-28
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• 2010

In this paper we deal with linear chance-constrained optimization problems, a class of problems which naturally arise in practical applications in finance, engineering, transportation and scheduling, where decisions are made in presence of uncertainty. After giving the deterministic equivalent formulation of a linear chance-constrained optimization problem we construct a conjugate dual problem to it. Then we provide for this primal-dual pair weak sufficient conditions which ensure strong duality. In this way we generalize some results recently given in the literature. We also apply the general duality scheme to a portfolio optimization problem, a fact that allows us to derive necessary and sufficient optimality conditions for it.

• 전자공학회논문지C
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• 제34C권12호
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• pp.61-69
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• 1997

This paper proposes a new method for improving the performances of the neural network for optimization using a hyubrid of gradient descent method and dynamic tunneling system. The update rule of gradient descent method, which has the fast convergence characteristic, is applied for high-speed optimization. The update rule of dynamic tunneling system, which is the deterministic method with a tunneling phenomenon, is applied for global optimization. Having converged to the for escaping the local minima by applying the dynamic tunneling system. The proposed method has been applied to the travelling salesman problems and the optimal task partition problems to evaluate to that of hopfield model using the update rule of gradient descent method.

• Computers and Concrete
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• 제13권4호
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• pp.457-482
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• 2014

This paper summarizes available literature on the optimization of reinforced concrete (RC) beams. The objective of optimization (e.g. minimum cost or weight), the design variables and the constraints considered by different studies vary widely and therefore, different optimization methods have been employed to provide the optimal design of RC beams, whether as isolated structural components or as part of a structural frame. The review of literature suggests that nonlinear deterministic approaches can be efficiently employed to provide optimal design of RC beams, given the small number of variables. This paper also presents spreadsheet implementation of cost optimization of RC beams in the familiar MS Excel environment to illustrate the efficiency of the exhaustive enumeration method for such small discrete search spaces and to promote its use by engineers and researchers. Furthermore, a sensitivity analysis is performed on the contribution of various design parameters to the variability of the overall cost of RC beams.

• 한국지반공학회논문집
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• 제35권4호
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• pp.27-35
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• 2019

역해석 수행 시 상대적으로 복잡한 공간 및 목표 설계 변수가 많은 경우, 지반공학 분야에 적용하기 위한 연구를 수행하였다. 지반공학 다변수 문제에 대한 모델로 터널 분야 및 흙막이벽체에 대해서 Sharan 공식 및 Blum 방법을 사용하였다. 최적화 방법은 크게 결정론적인 방법 및 확률론적인 방법으로 구분된다. 본 연구에서는 전자 중 모의강화법(SA), 후자 중 차분진화 알고리즘(DEA), 입자 군집 최적화 알고리즘(PSO)을 선택하여 다변수 모델을 적용해서 비교하였다. 지반공학 다변수 역해석 문제에서 결정론적인 방법은 문제가 있음을 확인하였고, 차분진화 알고리즘의 우수성을 확인하였다. DEA는 Sharan의 이론 해에 대한 문제에서 평균 3.12%, Blum 문제에 대해서 평균 2.23% 오차율을 보였고, 반복 탐색 회수도 가장 작은 것으로 파악되었다. DEA 대비해서 SA는 117.39~167.13배, PSO는 2.43~6.91배의 탐색시간이 소요되었다. 지반공학 문제의 다변수 역해석에 차분진화 알고리즘을 적용하면, 계산속도 및 정확도가 향상될 것으로 기대된다.