• 대한기계학회논문집A
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• 제29권3호
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• pp.369-386
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• 2005

Various aspects of structural optimization techniques under transient loads are extensively reviewed. The main themes of the paper are treatment of time dependent constraints, calculation of design sensitivity, and approximation. Each subject is reviewed with the corresponding papers that have been published since 1970s. The treatment of time dependent constraints in both the direct method and the transformation method is discussed. Two ways of calculating design sensitivity of a structure under transient loads are discussed - direct differentiation method and adjoint variable method. The approximation concept mainly focuses on re- sponse surface method in crashworthiness and local approximation with the intermediate variable Especially, as an approximated optimization technique, Equivalent Static Load method which takes advantage of the well-established static response optimization technique is introduced. And as an application area of dynamic response optimization technique, the structural optimization in flexible multibody dynamic systems is re- viewed in the viewpoint of the above three themes

• 한국자동차공학회논문집
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• 제13권1호
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• pp.119-125
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• 2005

The current automotive is seeking the improvement of performance, the prevention of environmental pollution and the saving of energy resources according to miniaturization and lightweight of the components. And the variance analysis on the basis of structure analysis and DOE is applied to the lower control am. We have proposed a statistical design model to evaluate the effect of structural modification by performing the practical multi-objective optimization considering weight, stress and fatigue lift. The lower control arm is performed the fatigue analysis using the load history of real road test. The design model is determined using the optimization of acquired load history with the fatigue characteristic. The characteristic function is made use of the optimization according to fatigue characteristics to consider constrained function in the optimization of DOE. The structure optimization of a lower control arm according to fatigue characteristics is performed. And the optimized design variable is D=47 m, T=36mm, W=12 mm. In the real engineering problem of considering many objective functions, the multi-objective optimization process using the mathematical programming and the characteristic function is derived an useful design solution.

• Journal of Electrical Engineering and Technology
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• 제13권5호
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• pp.1821-1830
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• 2018

With the wide application of intelligent household appliances, the optimization of electricity behavior has become an important component of home-based intelligent electricity. In this study, a multi-objective optimization model in an intelligent electricity environment is proposed based on economy and comfort. Firstly, the domestic consumer's load characteristics are analyzed, and the operating constraints of interruptible and transferable electrical appliances are defined. Then, constraints such as household electrical load, electricity habits, the correlation minimization electricity expenditure model of household appliances, and the comfort model of electricity use are integrated into multi-objective optimization. Finally, a continuous search multi-objective particle swarm algorithm is proposed to solve the optimization problem. The analysis of the corresponding example shows that the multi-objective optimization model can effectively reduce electricity costs and improve electricity use comfort.

• 한국해양공학회지
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• 제35권2호
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• pp.131-140
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• 2021

The paper deals with comparative study of various surrogate models based approximate optimization in the structural design of the passive type deck support frame under design load conditions. The passive type deck support frame was devised to facilitate both transportation and installation of 20,000 ton class topside. Structural analysis was performed using the finite element method to evaluate the strength performance of the passive type deck support frame in its initial design stage. In the structural analysis, the strength performances were evaluated for various design load conditions. The optimum design problem based on surrogate model was formulated such that thickness sizing variables of main structure members were determined by minimizing the weight of the passive type deck support frame subject to the strength performance constraints. The surrogate models used in the approximate optimization were response surface method, Kriging model, and Chebyshev orthogonal polynomials. In the context of numerical performances, the solution results from approximate optimization were compared to actual non-approximate optimization. The response surface method among the surrogate models used in the approximate optimization showed the most appropriate optimum design results for the structure design of the passive type deck support frame.

• 한국항공우주학회지
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• 제48권12호
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• pp.953-960
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• 2020

본 논문은 회전익기용 엔진 감속기 주 기어열의 기어 웹 형상 최적화에 대해 기술하였다. 최적화 목표는 총중량, 전달 오차, 정렬 오차, 치면 하중 분포 계수 값의 최소화로 설정하였으며, 기어의 웹 두께, 웹과 축의 연결 위치, 웹과 림의 연결 위치를 설계변수로 선정하였다. 최적화 과정에서 기어의 웹, 축, 림은 3D 캐드 모델로부터 유한요소 모델로 변환되었으며, 기어 해석 프로그램 MASTA에 입력되었다. 최적화 알고리즘은 NSGA-II를 사용하였다. 최적화 결과 주 기어열의 총중량, 전달 오차, 정렬 오차, 치면 하중 분포 계수 값은 모두 감소하였으며, 최대 응력도 안전한 수준으로 나타나서 전반적으로 기어 성능이 개선되었음을 확인하였다.

• 한국산학기술학회논문지
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• 제13권4호
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• pp.1480-1487
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• 2012

최근, 국내 탄광의 안전성이 향상되고 있으나 사고는 꾸준히 발생하고 있다. 대부분의 터널 지보는 I빔과 I빔을 연결하는 이음판 부분에서 지압을 견디지 못하고 파손이 발생한다. XX 탄광의 경우, 터널지보의 아치부가 일반적인 굽힘 거동이 아닌, 위쪽 방향으로 굽힘이 발생하고 있다. 이러한 경우는 터널지보에 수직하중 이외에 수평하중이 과대하게 작용하는 경우로 볼 수 있으며 이러한 수평하중은 지하암반의 급격한 변화에 의한 암반의 이완범위의 증가나 지하수의 누출 등으로 인한 수리학적인 요인 등의 복합적인 문제가 작용하여 나타난다. 따라서 본 연구에서는 위쪽 방향으로 굽힘을 일으키는 수평하중의 크기를 추정하기 위하여 실험계획법과 최적화 알고리듬을 적용하여 터널지보의 굽힘거동을 규명하였다.

• 한국습지학회지
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• 제18권3호
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• pp.226-231
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• 2016

토지이용에 따른 수질에 미치는 영향을 파악하기 위해서는 토지피복기반의 토지계 발생부하 원단위가 필요하다. 실측자료를 기반으로 토지피복기반 원단위를 도출하기에는 많은 인력과 시간을 필요로 한다. 이에 본 연구에서는 최적화를 통해 토지피복기반의 원단위 도출 방법을 제안하였다. 최적화란 주어진 조건 안에서 가장 좋은 최적해를 구하는 과정이며, 본 연구에서는 상용 프로그램인 Microsoft Excel에서 제공하고 있는 Excel Solver를 이용하여 최적화를 수행하였다. 공주시와 서천군의 2010년 위성영상 기반으로 작성된 2012년 환경부 중분류 토지피복도를 활용하여, BOD, T-N, T-P에 대한 토지피복기반 원단위를 도출하였다. 본 연구에서 수행한 토지피복기반 원단위 산정 연구는 국토 이용에 따른 오염원 발생변화를 보다 명확히 판별할 수 있을 것으로 판단된다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권5호
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• pp.1569-1586
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• 2015

This paper considers the optimal cell association and resource allocation for load balancing in a heterogeneous cellular network subject to user's quality-of-service (QoS) constraints. We adopt the proportional fairness (PF) utility maximization formulation which also accommodates the QoS constraints in terms of minimum rate requirements. With equal resource allocation this joint optimization problem is either infeasible or requires relaxation that yields a solution which is difficult to implement. Nevertheless, we show that this joint optimization problem can be effectively solved without any priori assumption on resource allocation and yields a cell association scheme which enforces single BS association for each user. We re-formulated the joint optimization problem as a network-wide resource allocation problem with cardinality constraints. A reweighted heuristic l₁-norm regularization method is used to obtain a sparse solution to the re-formulated problem. The cell association scheme is then derived from the sparsity pattern of the solution, which guarantees a single BS association for each user. Compared with the previously proposed method based on equal resource allocation, the proposed framework results in a feasible cell association scheme and yields a robust solution on resource allocation that satisfies the QoS constraints. Our simulations illustrate the impact of user's minimum rate requirements on cell association and demonstrate that the proposed approach achieves load balancing and enforces single BS association for users.

• Steel and Composite Structures
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• 제25권1호
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• pp.105-116
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• 2017

This paper presents the dynamic stability study of laminated composite plates with different force combinations and aspect ratios. Optimum non-diverging stacking is obtained for certain loading combination and aspect ratio. In addition, the stability force is maximized for a definite operating frequency. A dynamic version of the principle of virtual work for laminated composites is used to obtain force-frequency relation. Since dynamic stiffness governs the divergence or flutter, an efficient optimization method is necessary for the response functional and the relevant constraints. In this way, a model based on the ant colony optimization (ACO) algorithm is proposed to search for the proper stacking. The ACO algorithm is used since it treats with large number of dynamic stability parameters. Governing equations are formulated using classic laminate theory (CLT) and von-Karman plate technique. Load-frequency relations are explicitly obtained for fundamental and secondary flutter modes of simply supported composite plate with arbitrary aspect ratio, stacking and boundary load, which are used in optimization process. Obtained results are compared with the finite element method results for validity and accuracy convince. Results revealed that the optimum stacking with stable dynamic response and maximum critical load is in angle-ply mode with almost near-unidirectional fiber orientations for fundamental flutter mode. In addition, short plates behave better than long plates in combined axial-shear load case regarding stable oscillation. The interaction of uniaxial and shear forces intensifies the instability in long plates than short ones which needs low-angle layup orientations to provide required dynamic stiffness. However, a combination of angle-ply and cross-ply stacking with a near-square aspect ratio is appropriate for the composite plate regarding secondary flutter mode.

• Advances in Computational Design
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• 제1권1호
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• pp.1-25
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• 2016

Domes are architectural and elegant structures which cover a vast area with no interrupting columns in the middle, and with suitable shapes can be also economical. Domes are built in a wide variety of forms and specialized terms are available to describe them. According to their form, domes are given special names such as network, lamella, Schwedler, ribbed, and geodesic domes. In this paper, an optimum topology design algorithm is performed using the enhanced colliding bodies optimization (ECBO) method. The network, lamella, ribbed and Schwedler domes are studied to determine the optimum number of rings, the optimum height of crown and tubular sections of these domes. The minimum volume of each dome is taken as the objective function. A simple procedure is defined to determine the dome structures configurations. This procedure includes calculating the joint coordinates and element constructions. The design constraints are implemented according to the provision of LRFD-AISC (Load and Resistance Factor Design-American Institute of Steel Constitution). The wind loading act on domes according to ASCE 7-05 (American Society of Civil Engineers). This paper will explore the efficiency of various type of domes and compare them at the first stage to investigate the performance of these domes under different kind of loading. At the second stage the wind load on optimum design of domes are investigated for Schwedler dome. Optimization process is performed via ECBO algorithm to demonstrate the effectiveness and robustness of the ECBO in creating optimal design for domes.