• 대한수학회보
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• 제56권6호
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• pp.1467-1483
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• 2019

This paper analyzes a robust optimal reinsurance and investment strategy for an Ambiguity-Averse Insurer (AAI), who worries about model misspecification and insists on seeking robust optimal strategies. The AAI's surplus process is assumed to follow a jump-diffusion model, and he is allowed to purchase proportional reinsurance or acquire new business, meanwhile invest his surplus in a risk-free asset and a risky-asset, whose price is described by an Ornstein-Uhlenbeck process. Under the criterion for maximizing the expected exponential utility of terminal wealth, robust optimal strategy and value function are derived by applying the stochastic dynamic programming approach. Serval numerical examples are given to illustrate the impact of model parameters on the robust optimal strategies and the loss utility function from ignoring the model uncertainty.

• Nuclear Engineering and Technology
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• 제1권1호
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• pp.23-31
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• 1969

젓새우(Acetes chinensis), 피둥어꼴뚜기 (Todarodes Pacifcus, 속칭 동해안산의 오징어), 젓꼴뚜기 (Loligo beka)를 1 Mrad까지의 각 성량의 ${\gamma}$선을 조사하여 이것들을 2~4$^{\circ}C$에서 저장하여 방사선에 의한 저장효과를 시험하였다. 원료와 저장중의 어체선도는 관능검사, 화학적 검사 (VRS, TMA-N량), 생화학적검사 (Hypo-xanthine 량) 및 세균학적검사 (생균수)에 의거하여 판정하였다. VRS 값은 3어종에 있어서 모두 관능검사치와 잘 부합되지는 않으나 TMA-N, Hypoxanthine 식 및 생균수는 관능검사치와 잘 부합되며, 각 어종의 선도판정치로서 이용할수 있다. 비조사 젓새우는 3일간의 저장이 가능하나 최적선량 0.12-0.20 Mrad에서 8일간까지 저장할 수 있고, 피둥어꼴뚜기는 8일간의 저장을 최적선량 0.20-0.30 Mrad 에서 14-21일간의 저장이 가능하였으며, 젓꼴뚜기는 5-6일의 저장기간이 최적선량 0.12-0.20 Mrad에서 약 10일간의 저장이 가능하였다.

• 한국생산제조학회지
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• 제20권1호
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• pp.34-39
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• 2011

Temperature control of a rubber injection mold is important for the dimensional accuracy of product. The main objective of this paper is to optimize the arrangement of heaters by FEM and optimal design method. Firstly, 3-dimensional transient heat transfer analysis was carried out for a square specimen mold. Results of FE analysis are a good agreement with the experimental results, showing about 1.22~7.22% error in temperature distribution. Secondly, we suggested the optimal method about an arrangement of heaters of rubber injection mold by using the optimal design technique. Distances between heater's center and the contact surface of mold, distances between heater's center and symmetric surface were considered as design variables. And the variances between the temperatures of cavity surfaces and their average temperature were used as the objective functions. Applying the optimal solution, the temperature variation was improved about 52.9~88.1 % compared to the existing mold. As a result of sensitivity analysis for design variables, design variables parallel to the direction of the split plane in mold affect the largest on the surface temperature variation in mold cavity.

• 한국생산제조학회지
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• 제8권1호
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• pp.100-111
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• 1999

This paper resents a discrete-time model of an edge-following with accommodation force control. Since an irregular workpiece shape causes disturbances to the system while following an edge, the use of preview control is proposed to improve the system performance. The preview control employs future information of the workpiece contour shape, and it can be developed by LQ-optimal control principles. This study provides a general method how to utilize the local future information obtained by the finite preview to minimize an optimality criterion evaluated over a problem duration. The force controller is designed based on the preview control scheme, and then implemented on a VME-based computer. Experimental results using an industrial robot show that the preview control system achieves faster tracking speed and better force regulation than the conventional nonpreview control system.

• 한국지능시스템학회논문지
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• 제22권6호
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• pp.687-693
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• 2012

본 논문에서는 군집로봇의 효과적인 협조탐색을 위한 탐색영역에 대한 군집로봇의 최적배치을 제안한다. 먼저, 탐색영역에 대한 최적의 배치를 위해 보로노이 테셀레이션과 K-mean 알고리즘을 이용하여 탐색영역을 분할한다. 분할된 영역을 안전한 주행을 위해 전역경로계획과 지역경로계획을 한다. 전역경로계획은 A*알고리즘을 이용하여 전역경로계획을 하여 최적의 전역경로를 찾고, 지역경로계획은 포텐셜 필드방법을 이용하여 장애물 회피 통해 안전하게 목표점에 이르게 한다. 마지막으로 제안한 알고리즘은 시물레이션을 통해 그 응용가능성을 검토한다.

• 항공우주기술
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• 제4권1호
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• pp.186-195
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• 2005

본 논문에서는 우주비행체 자세제어용으로 추력기 시스템이 사용될 경우의 3축 자세제어설계 문제를 다룬다. 블로우다운 방식의 추력기 시스템이 사용되는 경우를 가정한다. 추력기 시스템의 심각한 시간 지연 효과를 제어설계 시에 적절히 고려하기 위한 방안으로 리미트 사이클 분석 결과를 토대로 최적제어설계 문제를 정의한다. 공진화 기법을 적용해서 주어진 요구조건을 만족하는 최적 롤 제어기 및 최적 피치/요 제어기 설계가 가능함을 보인다. 설계된 제어기에 대한 성능 분석은 비선형 시뮬레이션을 통해 이루어지게 된다.

• 대한산업공학회지
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• 제36권4호
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• pp.243-247
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• 2010

Every products, which made by mass production, is not identical in their size but have variations in some intervals specified by tolerance dimensions. Tolerances play major role in standardization of part and its quality, and also make a huge impact on manufacturing cost. The optimal condition for tolerances is giving the values as loose as possible for low production cost while satisfying quality specification, which usually demand tight control of tolerances. Tolerance analysis is necessary to get an optimal solution for this conflict situation. This paper have studied tolerance analysis for universal joint assembly of vehicle steering system and tried to find useful results of the study for product design and quality control.

• International Journal of Precision Engineering and Manufacturing
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• 제3권4호
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• pp.43-53
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• 2002

Polishing a die that has free-form surfaces is a time-consuming and tedious job, and requires a considerable amount of high-precision skill. In order to reduce the polishing time and cope with the shortage of skilled workers, a user-friendly automatic polishing system was developed. The polishing system is composed of two subsystems, a three-axis machining center and a two-axis polishing robot. The system has five degrees of freedom and is able to keep the polishing tool in a position normal to the die surface during operation. A sliding mode control algorithm with velocity compensation was proposed to reduce tracking errors. Trajectory tracking experiments showed that the tracking error can be reduced prominently by the proposed sliding mode control compared to a PD (proportional derivative) control. To evaluate the polishing performance of the polishing system and to and the optimal polishing conditions, the polishing experiments were conducted.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1716-1722
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• 2005

Fuzzy logic, neural network, fuzzy-neural network play an important as the key technology of linguistic modeling for intelligent control and decision in complex systems. The fuzzy-neural network (FNN) learning represents one of the most effective algorithms to build such linguistic models. This paper proposes bacteria foraging algorithm based optimal learning fuzzy-neural network (BA-FNN). The proposed learning scheme is the fuzzy-neural network structure which can handle linguistic knowledge as tuning membership function of fuzzy logic by bacteria foraging algorithm. The learning algorithm of the BA-FNN is composed of two phases. The first phase is to find the initial membership functions of the fuzzy neural network model. In the second phase, bacteria foraging algorithm is used for tuning of membership functions of the proposed model.

• Nuclear Engineering and Technology
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• 제52권3호
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• pp.544-551
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• 2020

Reactor control is a standout amongst the most vital issues in the nuclear power plant. In this paper, the optimal design of variable structure controller (VSC) based on the lightning search algorithm (LSA) is proposed for a nuclear reactor power system. The LSA is a new optimization algorithm. It is used to find the optimal parameters of the VSC instead of the trial and error method or experts of the designer. The proposed algorithm is used for the tuning of the feedback gains and the sliding equation gains of the VSC to prove a good performance. Furthermore, the parameters of the VSC are tuned by the genetic algorithm (GA). Simulation tests are carried out to verify the performance and robustness of the proposed LSA-based VSC compared with GA-based VSC. The results prove the high performance and the superiority of VSC based on LSA compared with VSC based on GA.