• 충청수학회지
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• 제29권2호
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• pp.375-383
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• 2016

This paper investigates an optimal consumption, portfolio, and life insurance strategies of a family when there is a borrowing constraint and risk aversion change at the time of death of the breadwinner. A CRRA utility is employed and by using the dynamic programming method, we obtain analytic expressions for the optimal strategies.

• 대한산업공학회지
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• 제27권2호
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• pp.140-149
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• 2001

The paper discusses the problem of finding the Origin-Destination(O-D) shortest paths in internodal transportation networks with time-schedule constraints. The shortest path problem on the internodal transportation network is concerned with finding a path with minimum distance, time, or cost from an origin to a destination using all possible transportation modalities. The time-schedule constraint requires that the departure time to travel from a transfer station to another node takes place only at one of pre-specified departure times. The scheduled departure times at the transfer station are the times when the passengers are allowed to leave the station to another node using the relative transportation modality. Therefore, the total time of a path in an internodal transportation network subject to time-schedule constraints includes traveling time and transfer waiting time. In this paper, a genetic algorithm (GA) approach is developed to deal with this problem. The effectiveness of the GA approach is evaluated using several test problems.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.1805-1810
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• 1991

This paper derives the upper and the lower bound of the mean cycle time and the mean service time of the class 6 and the class 4, within which the minimum utilization constrain of the class 4 is guaranteed. Also, derived are conditions under which the token bus network is stable or unstable. These bounds and stable conditions are represented in terms of the high priority token hold time, the token rotation time and the arrival rate and the total station number etc. This paper suggest a parameter tuning algorithm in a partially symmetric token bus network with two classes, which maximizes the token rotation time for a suitable high priority token hold time and at the same time meets the stability condition of the network, the real time constraint and the minimum utilization constraint of the class 4.

• 한국통신학회논문지
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• 제32권1A호
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• pp.13-23
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• 2007

본 논문에서는 OFDMA(Orthogonal Frequency Division Multiple Access) 시스템에서 실시간 트래픽 전송을 위한 효율적 패킷 스케줄링 기법을 제안한다. 본 방식은 패킷의 시간 지연 구속을 우선 만족시키면서 데이터 전송률도 향상시키는 기법으로 TEDC(Throughput Enhancement Under Delay-Constraint)라 불리운다. 사용자별 트래픽 특성에 따른 허용 지연 시간(Tolerable Delay Time TDT)을 정의하여 다양한 시간 지연 요구 조건을 차별화 하여 관리함으로써 무선 자원의 사용 효율을 향상시킨다. 논문에서 제안하는 TEDC 방식은 두 단계로 이루어진다. 첫 번째 단계에서는, 실시간 서비스를 위해 요구되는 시간 지연 구속을 만족하기 위해 잔여 허용 시간이 남지 않은 긴급한 사용자들에게 우선적으로 무선자원을 할당한다. 두 번째 단계에서는 첫 번째 단계에서 할당하고 남은 잉여 무선 자원에 대해서 자원의 활용도를 최대화하여 전체 데이터 전송률(Throughput)을 향상시킨다. 제안된 TEDC 방식의 성능은 기존의 자원할당 방식인 Round robin, M-LWDF, EXP 방식과 패킷 손실률, 데이터 전송률, 채널 활용도 측면에서 비교, 분석된다. 시뮬레이션 결과, TEDC 방식이 패킷 손실률, 데이터 전송률, 채널 활용도 측면에서 다른 자원 할당 방식보다 모두 우수한 성능을 보였다.

• 제어로봇시스템학회논문지
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• 제19권1호
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• pp.56-64
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• 2013

We propose an efficient minimum-time cornering motion planning algorithms for differential-driven wheeled mobile robots with motor control input constraint, under piecewise constant control input sections. First, we established mobile robot's kinematics and dynamics including motors, divided the cornering trajectory for collision-free into one translational section, followed by one rotational section with angular acceleration, and finally the other rotational section with angular deceleration. We constructed an efficient motion planning algorithm satisfying the bang-bang principle. Various simulations and experiments reveal the performance of the proposed algorithm.

• 한국경영과학회지
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• 제24권4호
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• pp.111-122
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• 1999

In this paper, we consider a queueing network model. where the population constraint within each subnetwork is controlled by a semaphore queue. The total number of customers that may be present in the subnetwork can not exceed a given value. Each node has a constant service time and the arrival process to the queueing network is an arbitrary distribution. A major characteristics of this model is that the lower layer flow is halted by the state of higher layer. We present some properties that the inter-change of nodes does not make any difference to customer's waiting time in the queueing network under a certain condition. The queueing network can be transformed into a simplified queueing network. A dramatic simplification of the queueing network is shown. It is interesting to see how the simplification developed for sliding window flow control, can be applied to multi-layered queueing network.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1995년도 Proceedings of the Korea Automation Control Conference, 10th (KACC); Seoul, Korea; 23-25 Oct. 1995
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• pp.534-537
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• 1995

In this paper, we propose a control strategy for a class of nonholonomic systems. A system with nonholonomic constraint is called a nonholonomic system, and as Brockett showed, the equilibrium of such systems can not be stabilized with any continuous static state feedbacks even though the system is controllable in the sense of nonlinear. A control strategy we propose is transforming this system into time-state control form by coordinate transformation and input transformation. We will apply this control strategy to the motion control of a rigid ball that is held between two parallel plates.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2000년도 춘계학술대회논문집
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• pp.21-25
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• 2000

An inverse finite element approach is employed for more capability to design the optimum blank shape from the desired final shape with small amount of expense and computation time For multi-stage sheet metal forming processes numerical analysis is expense difficult to carry out the to its complexities and convergence problem. It also requires lots of computation time. For the analysis of elliptic cup with large aspect ratio intermediate sliding constraint surfaces are difficult to describe. in this paper multi-stage finite element inverse analysis is applied to multi-stage elliptic cup drawing processes to calculate intermediate blank shapes and strain distributions in each stages. To describe intermediate sliding constraint surfaces an analytic scheme is introduced to deal with merged-arc type sliding surfaces.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제23권1호
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• pp.1-18
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• 2019

In contrast to the well-developed convex splitting schemes for gradient flows of two-component system, there were few efforts on applying the convex splitting idea to gradient flows of multi-component system, such as the vector-valued Cahn-Hilliard (vCH) equation. In the case of the vCH equation, one need to consider not only the convex splitting idea but also a specific method to manage the partition of unity constraint to design an unconditionally energy stable scheme. In this paper, we propose a constrained Convex Splitting (cCS) scheme for the vCH equation, which is based on a convex splitting of the energy functional for the vCH equation under the constraint. We show analytically that the cCS scheme is mass conserving and unconditionally uniquely solvable. And it satisfies the constraint at the next time level for any time step thus is unconditionally energy stable. Numerical experiments are presented demonstrating the accuracy, energy stability, and efficiency of the proposed cCS scheme.

• 산업경영시스템학회지
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• 제25권2호
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• pp.92-101
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• 2002

The Job Shop Scheduling Problem(JSSP) is concerned with schedule of m different machines and n jobs where each job consists of a chain of operations, each of which needs to be processed during an uninterrupted time period of a given length on a given machine. The purpose of this paper is to develop the efficient heuristic method for solving the minimum makespan problem of the large scale job shop scheduling. The proposed heuristic method is based on a Tabu Search(TS) and on a Constraint Satisfaction Technique(CST). In this paper, ILOG libraries is used to embody the job shop model, and a CST is developed for this model to generate the increased solution. Then, TS is employed to overcome the increased search time of CST on the increased problem size md to refine the next-current solution. Also, this paper presents the new way of finding neighbourhood solution using TS. On applying TS, a new way of finding neighbourhood solution is presented. Computational experiments on well known sets of MT and LA problem instances show that, in several cases, our approach yields better results than the other heuristic procedures discussed In literature.