• Journal of the military operations research society of Korea
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• v.17 no.2
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• pp.90-99
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• 1991

In this paper a dispatching rule, $D^{*}$, for AGV operations in automated manufacturing system is proposed to improve the performance measures. And the algorithm is compared with existing heuristic rules via simulation to evaluate its capabilities. It is shown that the proposed rule enhances mean flow time, makespan and throughput, and avoids the locking phenominon which can be fatal to the operation of automated manufacturing systems.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1995.04a
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• pp.939-954
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• 1995

We propose a policy for controlling the release of raw wafers into the semiconductor wafer fabrication lines. The proposed policy exploits up-to-date factory floor information gathered by tracking systems used to calculate the time and amount of a new release to minimize mean flow times and mean tardiness while maintaining the maximum output rates of the system. Extensive computer experiments show that the proposed policy results in significant improvements for the same output rates compared to existing release rules.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.04a
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• pp.13-16
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• 2000

In this paper the authors proposed a new anisotropic yield criterion for porous ductile materials. By using the proposed yield criterion and its flow rules a damage evolution of anisotropic sheet under biaxial tensile loading is investigated. A comparison of yield locus and damage evolution between the proposed yield criterion and experiments are carried out. the results are in good agreement.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.837-841
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• 2010

농업용 저수지는 주로 관개용수를 공급하는 역할을 해 왔으나 4대강 살리기 사업의 저수지 둑 높이기로 확보한 저수량을 이용하여 하류하천의 유지유량 공급과 홍수조절용량으로 이용하기 위한 저수지의 운영률 설정을 요구하고 있다. 관개용수를 공급하면서 하천유지유량을 상시공급, 유량부족시 공급, 30일, 60일, 90일 집중 공급 등 시나리오별 공급효과와 홍수기 홍수조절용량을 단계별로 설정하여 각 운영효과를 분석해 저수지 운영률을 합리적으로 설정할 수 있는 방법을 검토하였으며, 탑정저수지와 미호저수지에 대해 적용한 사례를 제시하였다.

• Journal of Korean Society of Transportation
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• v.14 no.3
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• pp.127-141
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• 1996

This paper presents a unique approach to urban traffic network signal control. This paper begins with an introduction to traffic control in general, and then goes on to describe the approach of fuzzy control, where the signal timing parameters at a given intersection are adjusted as functions of the local traffic network condition and adjacent intersection. The signal timing parameters evolve dynamically using only local information to improve traffic signal flow. The signal timing at an intersection is defined by three parameters : cycle time, phase split, off set. Fuzzy decision rules are used to adjust three parameters based only on local information. The amount of change in the timing parameters during each cycle is limited to a small fraction of the current parameters to ensure smooth transition. In this paper the effectiveness of this method is showed through simulation of the traffic signal flow in a network of controlled intersection.

• Journal of the Korean Operations Research and Management Science Society
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• v.24 no.2
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• pp.1-15
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• 1999

This research involves the development and evaluation of a work flow control model for a type of flexible manufacturing system(FMS) called a flexible flow line(FFL). The control model can be considered as a kind of hybrid intelligent model in that it utilizes both computer simulation and neural network technique. Training data sets were obtained using computer simulation of typical FFL states. And these data sets were used to train the neural network model. The model can easily incorporate particular aspects of a specific FFL such as limited buffer capacity and dispatching rules used. It also dynamically adapts to system uncertainty caused by such factors as machine breakdowns. Performance of the control model is shown to be superior to the random releasing method and the Minimal Part Set(MPS) heuristic in terms of machine utilization and work-in-process inventory level.

• IE interfaces
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• v.10 no.2
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• pp.57-67
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• 1997

This paper is a report of a simulation study that investigates a dynamic approach to scheduling jobs in a conventional shop floor, especially in an assemoly-type welding process. We consider both JIT arrival and JIT delivery. Various dispatching rules are tested for the following performance measures; mean flow time, rate of tardy jobs, mean tardiness, sum of mean tardiness and mean earliness. The results indicate that SPT rule is the best for the mean flow time. MSLACK that we suggest in this paper, is the best for the mean tardiness and the sum of mean tardiness and mean earliness. However, it is not clear that which rule is the best for the rate of tardy jobs.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.11
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• pp.1426-1433
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• 1999

Topological and kinematical studies of the singular points found in flows around a surface-mounted cube in a channel are presented. Numerical simulation was carried out using high-resolution grid systems. Singular points(saddles and nodes) were found around the cube, which satisfy the topological rules suggested by Hunt et al. As the Reynolds number increases, the structure of vortices around the cube becomes complex and the number of singular points increases. Nevertheless, the rule governing the numbers of singular points is still valid. This confirms that our simulation is correct from topological and kinematical point of view, and enables one to infer complex flow patterns in our simulation.

• IE interfaces
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• v.11 no.3
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• pp.1-13
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• 1998

This paper addresses a scheduling scheme for Flexible Flow Shop(FFS) in the case that a factory is a sub-plant of an electronic device manufacturing plant. Under this environment, job orders for the sub-plants in the production route are generated together with job processing time bucket when the customer places orders for final product. The processing time bucket for each job is a duration from possible release date to permissible due date. A sub-plant modeled FFS should schedule these jobs orders within time bucket. Viewing a Printed Circuit Board(PCB) assembly line as a FFS, the developed scheme schedules an incoming order along with the orders already placed on the scheduled. The scheme consists of the four steps, 1)assigning operation release date and due date to each work cells in the FFS, 2)job grouping, 3)dispatching and 4)machine allocation. Since the FFS scheduling problem is NP-complete, the logics used are heuristic. Using a real case, we tested the scheme and compared it with the John's algorithm and other dispatching rules.

• Journal of the Korea Society for Simulation
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• v.4 no.1
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• pp.75-86
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• 1995

There has been a great deal of interest in the area of group technology recently. They suggest that group technology's formation of cells of machines which are dedicated to production of families of parts will bring many of the advantages of cellular layout of job shops. In this context, Yoon [2] designed and suggested 3 types of the layout structure for a small firm, by introducing the cellular layout into the traditional flow line of an existing factory. Also he found that P5C, i.e. process layout /5 cells layout, outperformed the rest types. However, he performed the experiments in the standpoint of the existing factory operation and did not consider other operating methods including changing the dispatching and sequencing rules. Therefore, in this paper, we compared the performance of 3 different layout by the simulation technique using the real data from the existing factory, considering a newly suggested dispatching and machine selection rule.