• 산업경영시스템학회지
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• 제43권2호
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• pp.79-86
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• 2020

To make a satisfactory decision regarding project scheduling, a trade-off between the resource-related cost and project duration must be considered. A beneficial method for decision makers is to provide a number of alternative schedules of diverse project duration with minimum resource cost. In view of optimization, the alternative schedules are Pareto sets under multi-objective of project duration and resource cost. Assuming that resource cost is closely related to resource leveling, a heuristic algorithm for resource capacity reduction (HRCR) is developed in this study in order to generate the Pareto sets efficiently. The heuristic is based on the fact that resource leveling can be improved by systematically reducing the resource capacity. Once the reduced resource capacity is given, a schedule with minimum project duration can be obtained by solving a resource-constrained project scheduling problem. In HRCR, VNS (Variable Neighborhood Search) is implemented to solve the resource-constrained project scheduling problem. Extensive experiments to evaluate the HRCR performance are accomplished with standard benchmarking data sets, PSPLIB. Considering 5 resource leveling objective functions, it is shown that HRCR outperforms well-known multi-objective optimization algorithm, SPEA2 (Strength Pareto Evolutionary Algorithm-2), in generating dominant Pareto sets. The number of approximate Pareto optimal also can be extended by modifying weight parameter to reduce resource capacity in HRCR.

• 콘크리트학회논문집
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• 제14권3호
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• pp.373-381
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• 2002

프리캐스트 프리스트레스트 콘크리트 보의 크기와 자중은 그 운송과 조립에 드는 비용을 결정한다. 본 연구에서는 단면 최적화에 의하여 휨 응력의 구속을 받는 단면의 크기와 초기 긴장력의 크기 등을 결정하여 부재의 자중을 최소화하여 운송 및 시공의 편리성을 극대화하려한다. 프리캐스트 부재는 각 시공단계별 강도, 처짐, 그리고 부재 상, 하단에서 응력검토가 필요하다. 각 단계별 응력 제한치를 만족하는 최소자중 프리캐스트 U형보를 최적설계에 의하여 제안하였다. 최적설계에 의해 제안된 U형보는 기존의 직사각형 단면보다 39~50%까지의 자중감축이 가능할 것으로 예상된다. 본 연구에서 두 개의 대표적인 실물크기 U형보를 실험하였다. 이 실험에서 U형보는 설계하중과 공칭강도를 상회하는 휨강도에서 종국 파괴되었다.

• 대한전자공학회논문지SD
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• 제39권9호
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• pp.37-44
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• 2002

학습된 신경망(Pre-trained neural network)은 고정된 가중치(weight)를 갖는다. 이 논문에서는 이러한 특성을 이용하여 신경망의 효과적인 디지털 하드웨어의 설계방법을 제안한다. 이를 위해 신경망의 PEs(Processing Elements)연산은 행렬-벡터 곱셈으로 표하고 고정된 가중치와 입력 데이터의 관계를 비트-레벨 어레이(array) 구조로 표현하여, 노드 소거와 가중치 비트 패턴에 따른 공유 노드 설정을 통한 최적화로 연산에 필요한 노드를 최소화한다. FPGA 시뮬레이션 결과, 완전한 정확성에 기반한 하드웨어를 설계하는 경우, 하드웨어 비용을 상당부분 줄였고 동작 주파수가 높다는 것을 확인하였다. 또한, 제안한 설계방법은 한정된 공간 내에서 많은 수의 PEs 구현이 가능함으로, 큰 신경망 모델에 대한 온-칩(on-chip) 구현이 가능하다.

• 한국기계가공학회지
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• 제20권6호
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• pp.33-43
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• 2021

A60 class bulkhead penetration piece is a fire resistance system installed on a bulkhead compartment to protect lives and to prevent flame diffusion in a fire accident on a ship and offshore plant. This study focuses on the approximate optimization of the fire resistance design of the A60 class bulkhead penetration piece using a multi-island genetic algorithm. Transient heat transfer analysis was performed to evaluate the fire resistance design of the A60 class bulkhead penetration piece. For approximate optimization, the bulkhead penetration piece length, diameter, material type, and insulation density were considered discrete design variables; moreover, temperature, cost, and productivity were considered constraint functions. The approximate optimum design problem based on the meta-model was formulated by determining the discrete design variables by minimizing the weight of the A60 class bulkhead penetration piece subject to the constraint functions. The meta-models used for the approximate optimization were the Kriging model, response surface method, and radial basis function-based neural network. The results from the approximate optimization were compared to the actual results of the analysis to determine approximate accuracy. We conclude that the radial basis function-based neural network among the meta-models used in the approximate optimization generates the most accurate optimum design results for the fire resistance design of the A60 class bulkhead penetration piece.

• 한국정밀공학회지
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• 제26권3호
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• pp.81-87
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• 2009

Lightweight board has been used for manufacturing various fields of automotive interior trims for years. The GMPU board was constructed with glass fiber mat, honeycomb and polyurethane foamed using polyol and isocyanate materials which were sprayed by robot that is interlocked foaming machine. For more lightweight and cost reduction this paper shows how to optimize GMPU process parameters that related to foaming condition, robot position and robot velocity for polyurethane weight. The results show that flexural strength and modulus of board's specimens were evaluated by robot velocity and moving pattern. Based on that, a innovative process was developed for more lightweight and cost reduction.

• 한국정밀공학회지
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• 제17권6호
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• pp.111-118
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• 2000

The design of reference trajectory with respect to drag acceleration is necessary to decelerate from hypersonic speed safely after atmosphere re-entry of space vehicle. The re-entry guidance design involves trajectory optimization, generation of a reference drag acceleration profile with the satisfaction of 6 trajectory constraints during the re-entry flight. This reference drag acceleration profile can be considered as the reference trajectory. The cost function is composed of the accumulated total heating on vehicle due to the reduction of weight. And a regularization is needed to prevent optimal drag profile from varying too fast and achieve realized trajectory. This paper shows the relations between velocity, drag acceleration and altitude in drag acceleration profile, and how to determine the reference trajectory.

• 한국산업융합학회 논문집
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• 제21권3호
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• pp.125-131
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• 2018

In this paper, we propose a homogeneous multisensor-based navigation algorithm for a mobile robot, which is intelligently searching the goal location in unknown dynamic environments with moving obstacles using multi-ultrasonic sensor. Instead of using "sensor fusion" method which generates the trajectory of a robot based upon the environment model and sensory data, "command fusion" method by fuzzy inference is used to govern the robot motions. The major factors for robot navigation are represented as a cost function. Using the data of the robot states and the environment, the weight value of each factor using fuzzy inference is determined for an optimal trajectory in dynamic environments. For the evaluation of the proposed algorithm, we performed simulations in PC as well as real experiments with mobile robot, AmigoBot. The results show that the proposed algorithm is apt to identify obstacles in unknown environments to guide the robot to the goal location safely.

• 한국자동차공학회논문집
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• 제13권2호
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• pp.108-113
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• 2005

The damageability and repairability of similar platform type vehicles could be very concerned with design optimization. In all the vehicles crash tested, small size passenger vehicles were weakness in aspect of damageability and repairability. The most critical area appears to be repair cost considering that parts cost is the largest portion of total repair cost segments. Besides repair cost, attaching method of front sidemember and subframe are placed special importance for impact energy absorption and damageability and repairability. So in order to improve damageability and repairability of vehicle structure and body component of the monocoque type passenger vehicles, the end of front side member and front back beam should be designed with optimum level and to supply the end of front side member as a partial condition approx 300mm. The effectiveness of design concept on the 40% offset frontal impact characteristics of the passenger vehicle structure is investigated and summarized.

• 한국항공우주학회지
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• 제39권1호
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• pp.50-55
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• 2011

본 연구에서는 고고도 장기 체공 항공기 날개의 스팬과 주날개보의 형상을 설계변수로 동시에 고려하는 공력-구조 동시 설계를 수행하였다. 이 때 공기역학적 성능 최대화와 중량 최소화를 한 번에 수행하기 위해 다목적 최적화를 이용하였다. 설계 대상이 된 날개는 구조적 대변형이 발생되므로 전산유체역학과 유한요소법을 이용하여 비선형 정적 공탄성 해석을 수행하였다. 설계를 위한 해석에 요구되는 계산 비용을 감소시키기 위해 반응면을 구성하였으며 이를 위해 실험계획법이 이용되었다. 또한 본 연구에서는 대변형이 발생되지 않은 형상과 대변형이 발생한 형상의 공력 성능을 비교하여 대변형이 발생하는 경우 설계를 위해 반드시 변형이 고려되어야 함을 검증하였다.

• 대한기계학회논문집A
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• 제29권3호
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• pp.503-510
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• 2005

In this paper, the topology optimization of inner-wall stiffener of cylindrical containers for the use as a rocket fuel tank is presented. Such structures for space mission should have high stiffness against the buck]ins while their weight should be maintained low from the viewpoint of cost and performance. Therefore, in the present work the reciprocal of critical buckling load is adopted as an objective function and the total mass of stiffener is constrained to a prescribed value. Due to the restriction of computational resources a section of cylindrical container is topologically optimized and this result is repeated to obtain the full design. Also, for manufacturability the concept of periodic topology pattern in design domain is newly introduced. In the numerical examples, the results by the proposed approach are investigated and compared with those of isogrid design.