• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.489-491
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• 1993

Many optimization problem or multiple attribute, multiple alternative decision making problem may have fuzzy evaluation factors. In this case, fuzzy number operation technique is needed to evaluate and compare object functions which become fuzzy sets. Generally, fuzzy number operations can be defined by extension principle of fuzzy set theory, but it is tedious to do fuzzy number operations by using extension principle when the membership functions are defined by complex functions. Many fast methods which approximate the membership functions such as triangle, trapezoidal, or L-R type functions are proposed. In this paper, a fast fuzzy number operation method is proposed which do not simplify the membership functions of fuzzy numbers.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.05a
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• pp.762-763
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• 2016

In realizing a homomorphic encryption system, the operations of encrypt, decypt, and recrypt constitute major portions. The most important common operation for each back-bone operations include a polynomial modulo multiplication for over million-bit integers, which can be obtained by performing integer Fourier transform, also known as number theoretic transform. In this paper, we adopt and modify an algorithm for calculating big integer multiplications introduced by Schonhage-Strassen to propose an efficient algorithm which can save memory. The proposed architecture of number theoretic transform has been implemented on an FPGA and evaluated.

• Journal of the military operations research society of Korea
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• v.16 no.2
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• pp.83-95
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• 1990

This paper addresses the problem of determining the optimal number of spares for a system consisting of multi-item parts. In commercial sector, the cost minimization is mainly considered as an objective functions in most inventory models. However, in the military inventory systems, it is more stressed on maximizing the system availability than minimizing the system cost because the field commander always wants the system to be in perfect working condition to prepare against an emergence case. In this point of view, this paper develops an inventory model which decides the optimal number of spares by minimizing units short and simultaneously achieving a certain level of system availability. Solution algorithms are derived using the generalized Lagrange multiplier approach and marginal analysis approach. Sample data and output results are provided and sensitivity analysis is performed as the level of system availability changes in order to decide the optimal number of spares and availability in terms of economic sense.

• Journal of the military operations research society of Korea
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• v.7 no.2
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• pp.43-62
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• 1981

Computational expressions for point availability and average availability of a system of components each of which is subject to random failures and has random restoration times are determined. Each component is assumed to have a fixed number of spares such that where all spares are exhausted no restoration can take place. These expressions are useful in deciding PL and ASL in the military logistic applications. Given a fixed length of mission duration and finite number of spares, a system may not be available at the end of a mission due to lack of spares. The probability distribution of system down time due to lack of spares is determined as a function of number of spares and mission duration.

• Journal of the Korean Operations Research and Management Science Society
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• v.14 no.1
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• pp.27-35
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• 1989

An algorithm that searches the general AND-OR graph is proposed. The convergence and the efficiency of the algorithm is examined and compared with an existing algorithm for the AND-OR graph. It is proved that the proposed algorithm is superior to the existing method both in the quality of the solution and the number of node expansions.

• Journal of the Korean Operations Research and Management Science Society
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• v.34 no.4
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• pp.43-56
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• 2009

In korean peninsular, aircraft defense with SAM (Surface-to-Air Missile) is very important because of short range of combat space in depth. Effective and successful defense operation largely depends on two factors, SAM's location and the number of SAM for each target based on missile's availability in each SAM's location. However, most previous papers have handled only the former. In this paper, we developed Set covering model which can handle both factors simultaneously and Multi-heuristic algorithm for solving allocation problem of the batteries and missile assignment problem in each battery. Genetic algorithm is used to decide optimal location of the batteries. To determine the number of SAM, a heuristic algorithm is applied for solving missile assignment problem. If the proposed model is applied to allocation of SAM, it will improve the effectiveness of air defense operations.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1998.10a
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• pp.182-185
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• 1998

In the two-tier CDMA cellular system with microcells and overlaying macrocells, slow-moving mobile user are assigned to microcells and those who move fast are assigned to overlaying macrocells in order to minimize the total number of handoffs. With this consideration the problem is how to find the thresholds by which the system distinguishes fast-moving user from those who move slowly based on the estimated speed of users. In this paper, two methods for the mobile speed estimation are proposed and two operations schemes for micro-macro cellular CDMA system are suggested. Based on these, Optimization models to find the optimal thresholds for micro-macrocell selection, which are subject to the constrains of QoS, are developed in view of minimizing the weighted total number of handoffs. And then algorithms to find optimal solutions of the models are devised.

• Journal of the Korea Society for Simulation
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• v.8 no.4
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• pp.61-72
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• 1999

This paper presents an estimation method of container handling capacity and selection of resource allocation strategies of container terminals using the computer simulation models. Simulation models are developed to model container terminal consisting of 4 berths considering the berth allocation strategies, crane allocation strategies and the total number of container cranes using Arena simulation package. The proposed models do not consider the yard operations and gate operations. All the input parameters for the models are estimated on the basis of the existing container terminal operation data and the planning data for the automated container terminal planned by Korean government. Four berth allocation strategies and three crane allocation strategies are considered. The total number of container cranes considered ranges from 12 to 15. Non-terminating simulation techniques are utilized for the performance comparison among alternatives. The performance measures such as average ship turnaround time, average ship waiting time, average ship service time, the number of containers handled per year, and the number of ships processed per year are used. The result shows that the berth allocation strategy minimizing the sum of the number of ships waiting, the number of busy container cranes and number of ships handled performs better than any other berth allocation strategies. In addition, the crane allocation strategy allocating up to 5 container cranes per berth performs better than any other crane allocation strategies. Finally there are no significant performance differences among the alternatives consisting of different total number of container cranes allocated.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.11a
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• pp.284-287
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• 2006

We consider the transportation problem of optimizing the use of trailers and tractors. Several variants with fixed loading and unloading time are discussed. We show that the variant requiring on-time delivery can be solved in polynomial time, whereas the other variant requiring time-window delivery is NP-hard. We also discuss that if the number of loading and unloading operations assigned to each trailer or tractor is limited, even the variant requiring on-time delivery becomes NP-hard.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12B
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• pp.1418-1425
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• 2009

This paper proposes a novel FTL (Flash Translation Layer) algorithm based on sector-level mapping to reduce the number of total erase operations in flash memory accesses. The proposed algorithm can reduce the number of erase operations by utilizing the sector-level mapping table when writing data at flash memory. Sector-level mapping technique reduces flash memory access time and extendsthe life time of the flash memory. In the algorithm, wear-leveling is implemented by selecting victim blocks having the minimal number of erase operations, when empty spaces for write are not available. To evaluate the performance of the proposed FTL algorithm, experiments were performed on several applications, such as MP3 players, MPEG players, web browsers and document editors. The proposed algorithm reduces the number of erase operations by 72.4% and 61.9%, when compared with well-known BAST and FAST algorithms, respectively.