• Journal of the Korean Operations Research and Management Science Society
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• v.22 no.2
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• pp.125-137
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• 1997

We are concerned with the packing policy determines the optimal packing of products with variable sizes to minimize the penalty costs for idle space and product spliting. Optimal packing problem is closely related to the optimal packet/record sizing problem in that randomly generated data stream with variable bytes are divided into a unit of packet/record for transmitting or storing. Assuming the product size and the production period are independently determined by renewal process, we can approximate the renewal process and formulate the optimization problem that minimize the expected packing cost for a production period. The problem is divided into two cases according to whether a product is allowed to split or not. Computational results for various distributions will be given to verify the approximation procedure and the resulting optimization problem.

• Archives of Plastic Surgery
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• v.32 no.3
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• pp.319-326
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• 2005

This study was designed to investigate the optimal period of pedicles implantation in the prefabricated periosteofascial flap using a vascular tissue transfer. Flap prefabrication was prepared with a transposition of the central pedicles of right auricle on the calvarium of the New Zealand white rabbit. Thirty flaps were divided into five groups of six flaps, including control group (group I) of the conventional periosteofascial flap based on the right lateral border of parietal bone. The prefabricated flap was elevated as a $2{\times}2cm$ sized island flap and reposed in place in 1, 2, 3, and 4 weeks after the pedicles transfer in groups II, III, IV, and V, respectively. Five days after flap repositioning, the flap viability and vascularity were evaluated with microangiography and histological study quantitatively. The flap survival was increased in accordance with the implanted period of the pedicle. New vessels developed around the implanted pedicle in the 2nd week, and overall vascularization of the flap was accomplished in the 3rd week. The flap with 4 weeks of implantation period, however, showed the same survival rate as the control group. In conclusion, prefabricated periosteo- fascial flap can be created with a vascular tissue transfer, and the optimal duration of the pedicle implantation is more than 4 weeks to obtain adequate flap survival.

• Journal of the Korea Society of Computer and Information
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• v.8 no.4
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• pp.111-116
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• 2003

We proposed a optimal clock period selection algorithm for low power Register Transfer Level design. The proposed algorithm use the way of maintaining the throughput by reducing supply voltage after improve the system performance in order to minimize the power consumption. In this paper, it select the low power to use pipeline in the transformation of architecture. Also, the proposed algorithm is important the clock period selection in order to maximize the resource sharing. however, it execute the optimal clock period selection algorithm. The experiment result is to set the same result AR and HAL filter on the high level benchmark and to reduce in the case of two pipe stage 10.5% and three pipe stage as many as 33.4%.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.844-847
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• 1997

In this paper, scheduling problem is dealt for the minimization of due date penalty for the customer order. Multiproduct batch processes have been dealt with for their suitability for high value added low volume products. Their scheduling problems take minimization of process operation for objective function, which is not enough to meet the customer satisfaction and the process efficiency simultaneously because of increasing requirement of fast adaptation for rapid changing market condition. So new target function has been suggested by other researches to meet two goals. Penalty function minimization is one of them. To present more precisely production scheduling, we develop new scheduling model with penalty function of earliness and tardiness We can find many real cases that penalty parameters are divergent by the difference between the completion time of operation and due date. That is to say, the penalty parameter values for the product change by the customer demand condition. If the order charges different value for due date, we can solve it with the due date period. The period means the time scope where penalty parameter value is 0. If we make use of the due date period, the optimal sequence of our model is not always same with that of fixed due date point. And if every product have due date period, due date of them are overlapped which needs optimization for the maximum profit and minimum penalty. Due date period extension can be enlarged to makespan minimization if every product has the same abundant due date period and same penalty parameter. We solve this new scheduling model by simulated annealing method. We also develop the program, which can calculate the optimal sequence and display the Gantt chart showing the unit progress and time allocation only with processing data.

• Journal of The Korean Society of Agricultural Engineers
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• v.49 no.3
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• pp.11-20
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• 2007

Estimation of crop consumptive use is a key term of agricultural water resource systems design and operation. The 10-year return period drought has special aspects as a reference period in design process of irrigation systems in terms of agricultural water demand analysis so that crop evapotranspiration (ETc) about the return period also has to be analyzed to assist understanding of crop water requirement of paddy rice. In this study, The ETc of 10-year return period drought was computed using frequency analysis by 54 meteorological stations. To find an optimal probability distribution, 8 types of probability distribution function were tested by three the goodness of fit tests including ${\chi}^2$(Chi-Square), K-S (Kolmogorov-Smirnov) and PPCC (Probability Plot Correlation Coefficient). Optimal probability distribution function was selected the 2-parameter Log-Normal (LN2) distribution function among 8 distribution functions. Using the two selected distribution functions, the ETc of 10-year return period drought was estimated for 54 meteorological stations and compared with prior study results suggested by other researchers.

• Journal of Korean Institute of Industrial Engineers
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• v.35 no.3
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• pp.185-193
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• 2009

We consider a two-fare, two-period airline seat capacity allocation problem where consumers may choose different options in purchasing an airline ticket. A consumer may decide to wait for reopening of the same fare class ticket which is originally intended to buy, or may buy a different fare class ticket within the same period, if the originally requested fare is unavailable. We investigate the impact of the consumer buying behavior on the optimal solutions and the expected revenue.

• Journal of Korean Society of Transportation
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• v.34 no.5
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• pp.421-436
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• 2016

Public-Private-Partnerships tend to be committed high project development cost and recover the cost through future revenue during the operation period. In general, long-term concession can bring on more revenue to private investors, but short-term concession less revenue due to the short recovering opportunities. The concession period is usually determined by government in advance or by the private sectors's proposal although it is a very crucial factor for the PPPs. Accurate traffic forecasting should be most important in planing and evaluating the operation period in that the forecasted traffic determines the project revenue with user fees in PPPs. In this regards, governments and the private investors are required to consider the traffic forecast risk when determining concession period. This study proposed a model for the optimal concession period in the PPPs transportation projects. Monte Carlo simulation was performed to find out the optimal concession period while traffic forecast uncertainty is considered as a project risk under the expected return of the private sector. The simulation results showed that the optimal concession periods are 17 years and 21 years at 5.5% and 7% discount level, respectively. This study result can be applied for the private investors and/or any other concerned decision makers for PPPs projects to set up a more resonable concession period.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.11
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• pp.944-954
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• 2013

Cognitive radio technology gives secondary users chances that they can use specific spectrum of the primary user when the primary user doesn't use it. This paper proposes the algorithm that maximizes the benefit of the primary user considering spectrum price and auction period by using the auction game theory. According to the ratio of spectrum that secondary users bid, primary user allocates spectrum to secondary users. In the process of repeated auction, the primary user gets to find the optimal price of spectrum. Using the price and the proposed utility function of primary user, we derive the optimal auction period. At the same time, the primary user finally determines the price of spectrum appropriate for the optimal period.

• Journal of the Korean Data and Information Science Society
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• v.17 no.2
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• pp.367-377
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• 2006

This paper develops a periodic preventive maintenance(PM) policy following the expiration of warranty. Two types of warranty are considered: renewing warranty and non-renewing warranty. Also, we consider the situation where each PM cost is an increasing function of the PM effect. We determine the optimal number of PM's before replacing the system by a new one and the optimal length of period for the periodic PM following the expiration of warranty. Explicit solutions to determine the optimal periodic PM are presented for the Weibull distribution case.

• Journal of Korean Society for Quality Management
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• v.31 no.3
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• pp.193-204
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• 2003

In this paper, we consider a periodic preventive maintenance(PM) policy in which each PM reduces the hazard rate but remains the pattern of hazard rate unchanged. And the system undergoes only minimal repairs at failures between PM's. The expected cost rate per unit time is obtained. The optimal number N of PM and the optimal period x, which minimize the expected cost rate per unit time are discussed. Explicit solutions for the optimal periodic PM are given for the Weibull distribution case.