• 한국통신학회논문지
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• 제33권12B호
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• pp.1097-1102
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• 2008

An effective method for calculating delay bounds of flows through flow aggregations and deaggregations is given. Based on this calculation, it is suggested a simple criteria for flow aggregation whether the aggregation will induce an increased delay bound. The criteria is evaluated in a few realistic scenarios.

• Industrial Engineering and Management Systems
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• 제14권1호
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• pp.22-31
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• 2015

In this paper, a two-stage hybrid flow shop problem is considered. Specifically, there exist identical parallel machines at stage 1 and two dedicated machines at stage 2, and the objective of the problem is to minimize makespan. After being processed by any machine at stage 1, a job must be processed by a specific machine at stage 2 depending on the job type, and one type of jobs can have different processing times on each machine. First, we introduce the problem and establish complexity of several variations of the problem. For some special cases, we develop optimal polynomial time solution procedures. Then, we establish some simple lower bounds for the problem. In order to solve this NP-hard problem, three heuristics based on simple rules such as the Johnson's rule and the LPT (Longest Processing Time first) rule are developed. For each of the heuristics, we provide some theoretical analysis and find some worst case bound on relative error. Finally, we empirically evaluate the heuristics.

• 한국통신학회:학술대회논문집
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• 한국통신학회 1991년도 추계종합학술발표회논문집
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• pp.145-149
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• 1991

In this paper, an algorithm is proposed to analyze the approximating reliability of the capacity considered communication networks. In the case ofthe former methods to evaluate the source-to-termianl node reliability, it is very difficult to contract and delete the jointed terms in the simple path group. Therefore, the reliability bounds are used and compared to the exact reliability by TURBO PROLOG, the natural lanquage of artficial intelligence. In the reliability bounds, the upper bound used the valid cutset that isthe group of simple path and the lower bound used the minimal cutset by complement operation and the esact reiability is compared to this reliability bounds.

• 대한수학회보
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• 제36권4호
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• pp.661-669
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• 1999

L. Degui introduced an upper bound of Reidemeister number. In this paper we give a simple proof of Degui's Theorem.

• 한국전자파학회논문지
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• 제11권3호
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• pp.352-357
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• 2000

이 논문에서는 동기 MPSK 신호에 대하여 새로운 간단한 심볼 오류 확률 하한식을 유도하고 분석한다. 보통 심볼 오류 확률 유도는 먼저 덧셉꼴 백색 정규잡음(AWGN) 환경에서 유도하고 이에 대한 결과를 바탕으로 여러 페이딩 환경에서의 심볼 오류 확률을 구하는 것이 일반적인 방법이다. 그러나 동기 MPSK의 경우는 여러 페 이딩 환경에서의 오류 확률 식이 구해져 있으나 가장 기본이 되는 덧셈팔 백색 정규 잡음 환경에서는 정확히 closed-form으로 유도하지 못하는 것으로 알려져 있다. 여기서는 먼저 나카가미 페이딩 환경에서 동기 MPSK 신호의 심볼 오류 확률식을 이용하여 나카가미 페이딩 지수가 무한대로 감에 따라 페이딩이 없는 덧셈꼴 백색 정규 잡음 채널로 돌아가는 성질을 이용하여 새로운 근사식을 유도하고 분석한다.

• International Journal of Control, Automation, and Systems
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• 제6권6호
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• pp.960-967
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• 2008

This paper shows that design of a robustly stable repetitive control system is equivalent to that of a feedback control system for an uncertain linear time-invariant system satisfying the well-known robust performance condition. Once a feedback controller is designed to satisfy the robust performance condition, the feedback controller and the repetitive controller using the performance weighting function robustly stabilizes the repetitive control system. It is also shown that we can obtain a steady-state tracking error described in a simple form without time-delay element if the robust stability condition is satisfied for the repetitive control system. Moreover, using this result, a sufficient condition is provided, which ensures that the least upper bound of the steady-state tracking error generated by the repetitive control system is less than or equal to the least upper bound of the steady-state tracking error only by the feedback system.

• ETRI Journal
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• 제31권5호
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• pp.518-524
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• 2009

Single parity check (SPC) product codes are simple yet powerful codes that are used to correct errors and/or recover erasures. The focus of this paper is to evaluate the performance of such codes under erasure scenarios and to develop a closed-form tight upper bound for the post-decoding erasure rate. Closed-form exact expressions are derived for up to seven erasures. Previously published closed-form bounds assumed that all unrecoverable patterns should contain four erasures in a square. Additional non-square patterns are accounted for in the proposed expressions. The derived expressions are verified using exhaustive search. Eight or more erasures are accounted for by using a bound. The developed expressions improve the evaluation of the recoverability of SPC product codes without the need for simulation or search algorithms, whether exhaustive or novel.

• 대한산업공학회지
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• 제23권4호
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• pp.661-667
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• 1997

We consider a generalized problem of the continuous multiple choice knapsack problem and study on the LP relaxation of the candidate problems which are generated in the branch and bound algorithm for solving the generalized problem. The LP relaxed candidate problem is called the generalized continuous multiple choice linear knapsack problem and characterized by some variables which are partitioned into continuous multiple choice constraints and the others which only belong to simple upper bound constraints. An efficient algorithm of order O($n^2logn$) is developed by exploiting some structural properties and applying binary search to ordered solution sets, where n is the total number of variables. A numerical example is presented.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2006년도 추계학술대회
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• pp.138-141
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• 2006

This paper considers a two-machine flow-shop scheduling problem for minimizing mean flow time. Each job has three non-preemptive operations, where the first and third operations must be Processed on the first and second machines, respectively, but the second operation can be processed on either machine. A lower bound based on SPT rule is derived, which is then used to develop a branch-and-bound algorithm. Also, an efficient simple heuristic algorithm is developed to generate a near-optimal schedule. Numerical experiments are performed to evaluate the performances of the proposed branch-and-bound and the heuristic algorithm

• 산업경영시스템학회지
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• 제32권1호
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• pp.79-84
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• 2009

In this paper, a best-first branch and bound algorithm based upon the bottom-up approach for the unweighted unconstrained two-dimensional cutting problem is proposed to find the optimal solution to the problem. The algorithm uses simple and effective methods to prevent constructing duplicated patterns and reduces the searching space by dividing the branched node set. It also uses a efficient bounding strategy to fathom the set of patterns. Computational results are compared with veil-known exact algorithms and demonstrate the efficiency of the proposed algorithm.