• Bulletin of the Korean Mathematical Society
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• v.56 no.6
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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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• v.1 no.1
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• pp.23-31
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• 1969

Whole cure shrimp, eviscerated common squid and little squid meats were irradiated with gamma radiation from 60Co using varying dose up to one Mrad. Changes in quality were assessed by organoleptic, chemical (VRS and TMA-N), biochemical (hypoxanthine) and microbiological tests； and the effect of radiation on prolonging of the storage life at 2-4 C was studied. With the cure shrimp, 0.12-0.20 Mrad appears to be optimal with 8 days of storage life, whereas the unirradiated control samples had a storage life of 3 days. With the common squid meat, 0.20-0.30 Mrad appears to be optimal with 14-21 days of storage life, where-as the unirradiated control samples had a storage life of 8 days. And for the little squid meat, 0.12-0.20 Mrad appears to be optimal with 10 days of storage, where-as the unirradiated control samples had a storage life of 5 to 6 days.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.1
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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.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.1
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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.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.6
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• pp.687-693
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• 2012

In this paper, we propose a optimal deployment method for cooperative exploration of swarm robots. The proposed method consists of two parts such as optimal deployment and path planning. The optimal area deployment is proposed by the K-mean Algorithm and Voronoi tessellation. The path planning is proposed by the potential field method and A* Algorithm. Finally, the numerical experiments demonstrate the effectiveness and feasibility of the proposed method.

• Aerospace Engineering and Technology
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• v.4 no.1
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• pp.186-195
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• 2005

This paper deals with attitude control design for a thruster system which is mainly used as a control system of space vehicles. Attitude controllers are designed based on a simple blowing-down thruster system structure. In order to consider severe time-delay effects of the thruster system during controller design, the control design problem is defined based on the corresponding limit cycle analysis. Optimal roll controllers and optimal pitch/yaw controllers are resulted from co-evolutionary optimum design processes for each flight phase. The control performances are verified by computer simulations.

• Journal of Korean Institute of Industrial Engineers
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• v.36 no.4
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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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• v.3 no.4
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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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• 2005.06a
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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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• v.52 no.3
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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.