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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korea Society for Simulation
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Journal DOI :
The Korea Society for Simulation
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Volume & Issues
Volume 8, Issue 4 - Sep 1999
Volume 8, Issue 3 - Sep 1999
Volume 8, Issue 2 - Jun 1999
Volume 8, Issue 1 - Mar 1999
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A Method for Design of Discrete Variable Stochastic Systems using Simulation
Journal of the Korea Society for Simulation, volume 8, issue 3, 1999, Pages 1~16
This paper deals with a discrete simulation optimization method for designing a complex probabilistic discrete event system. The proposed algorithm in this paper searches the effective and reliable alternatives satisfying the target values of the system to be designed through a single run in a relatively short time period. It tries to estimate an autoregressive model, and construct mean and confidence interval for evaluating correctly the objective function obtained by small amount of output data. The experimental results using the proposed method are also shown.
Performance Analysis of Pattern/Path Hybrid Branch Prediction Strategy
Journal of the Korea Society for Simulation, volume 8, issue 3, 1999, Pages 17~28
Recently studies have shown that conditional branches can be accurately predicted by recording the path leading up to the branch. But path predictors are more complex and uncompatible with existing pattern branch predictors. In order to solve these problems, we propose a simple path branch predictor(SPBP) that hashes together two most recent branch instruction addresses. In addition, we propose a pattern/path hybrid branch predictor composed of the SPBP and existing pattern branch predictors. Through the trace-driven simulation of six benchmark programs, the performance improvement by the proposed pattern/path hybrid branch prediction is analysed and validated. The proposed predictor can improve the prediction accuracy from 94.21% to 95.03%.
Development of an Escalator Simulation Program for a Designer
Journal of the Korea Society for Simulation, volume 8, issue 3, 1999, Pages 29~37
When an escalator is developed or modified to improve its performance, estimation of dynamic characteristics of the escalator is required. But modeling of the escalator for a design purpose is very difficult and time consuming. Especially, it is very difficult for a designer to use the simulation model during design process because preparing a proper model takes time and also the designer needs to know how to use the simulation program. In order to solver these problems, a graphic user interface program that can predict dynamic characteristics of an escalator is developed for the designer. Since this program makes the necessary escalator model for simulation for itself, the designer does not need to know how to use the simulation program while design is in progress. In this paper, a designer oriented interface program is developed and an example is presented to show the effectiveness of the developed program.
A Simulation for the Critical Speeds of a Geared Rotor System with Time Varying Mesh Stiffnesses and Bearing Flexibilities.
Journal of the Korea Society for Simulation, volume 8, issue 3, 1999, Pages 39~48
A finite element model of geared rotor system with flexible bearings were used to simulate the critical speeds and to investigate the effects of bearing coefficients on the dynamic behaviors of the systems. The finite element model includes the effects of tooth mesh stiffness, gyroscopic moment, rotary inertia, shear, and torque of the shaft. The gear mesh was modelled as a pair of rigid disks connected by a spring of time varying stiffness. The time varying mesh stiffness results in the abrupt change of the critical speeds of spur geared systems. As the bearing stiffness increases, critical speeds increase rapidly in case of stiff shafts, compared with flexible shafts.
Performance Analysis of Scheduling Rules in Semiconductor Wafer Fabrication
Journal of the Korea Society for Simulation, volume 8, issue 3, 1999, Pages 49~66
Semiconductor wafer fabrication is known to be one of the most complex manufacturing processes due to process intricacy, random yields, product diversity, and rapid changing technologies. In this study we are concerned with the impact of lot release and dispatching policies on the performance of semiconductor wafer fabrication facilities. We consider several semiconductor wafer fabrication environments according to the machine failure types such as no failure, normal MTBF, bottleneck with low MTBF, high randomness, and high MTBF cases. Lot release rules to be considered are Deterministic, Poisson process, WR(Workload Regulation), SA(Starvation Avoidance), and Multi-SA. These rules are combined with several dispatching rules such as FIFO (First In First Out), SRPT (Shortest Remaining Processing Time), and NING/M(smallest Number In Next Queue per Machine). We applied the combined policies to each of semiconductor wafer fabrication environments. These policies are assessed in terms of throughput and flow time. Basically Weins fabrication setup was used to make the simulation models. The simulation parameters were obtained through the preliminary simulation experiments. The key results throughout the simulation experiments is that Multi-SA and SA are the most robust rules, which give mostly good performance for any wafer fabrication environments when used with any dispatching rules. The more important result is that for each of wafer fabrication environments there exist the best and worst choices of lot release and dispatching policies. For example, the Poisson release rule results in the least throughput and largest flow time without regard to failure types and dispatching rules.
Dynamic Routing and Scheduling of Multiple AGV System
Journal of the Korea Society for Simulation, volume 8, issue 3, 1999, Pages 67~76
The study of the optimization of operating policy of AGV system, which is used in many factory automation environments has been proceeded by many researchers. The major operating policy of AGV system consists of routing and scheduling policy. AGV routing is composed with collision avoidance and minimal cost path find algorithm. To allocate jobs to the AGV system, AGV scheduling has to include AGV selection rules, parking rules, and recharging rules. Also in these rules, the key time parameters such as processing time of the device, loading/unloading time and charging time should be considered. In this research, we compare and analyze several operating policies of multiple loop-multiple AGV system by making a computer model and simulating it to present an appropriate operating policy.
Non-parametric Adaptive Importance Sampling for Fast Simulation Technique
Journal of the Korea Society for Simulation, volume 8, issue 3, 1999, Pages 77~89
Simulating rare events, such as probability of cell loss in ATM networks, machine failure in highly reliable systems, requires huge simulation efforts due to the low chance of occurrence. Importance Sampling (IS) has been applied to accelerate the occurrence of rare events. However, it has a drawback of effective biasing scheme to make the estimator of IS unbiased. Adaptive Importance Sampling (AIS) employs an estimated sampling distribution of IS to the system of interest during the course of simulation. We propose Nonparametric Adaptive Importance Sampling (NAIS) technique which is nonparametrical version of AIS. We test NAIS to estimate a probability of rare event in M/M/1 queueing model. Comparing with classical Monte Carlo simulation, the computational efficiency and variance reductions gained via NAIS are substantial. A possible extension of NAIS regarding with random number generation is also discussed.
Development and Performance Evaluation of a Car Assignment and Routing Algorithm for Reducing Transportation Cost in a Logistics System
Journal of the Korea Society for Simulation, volume 8, issue 3, 1999, Pages 91~103
This paper proposes an algorithm which reduces transportation cost while goods are delivered in time in a logistics system. The logistics system assumed in this paper is the system in which multiple cars moves various goods from spatially distributed warehouses to stores. For reducing transportation cost, the car assignment algorithm which allocates goods to minimal cars employs the BF method; routing of each car is modelled as the TSP and is solved by using the genetic algorithm. For evaluating the proposed algorithm, the logistics system is modelled and simulated by using the DEVS formalism. The DEVS formalism specifies discrete event systems in a hierarchical, modular manner. During simulation, each car is modelled as a message and traverses warehouse and stores. When a car arrives at a warehouse or a store, predetermined amount of goods are loaded or unloaded. The arrival time and departure time of cars are analyzed and eventually whether goods are delivered in the desired time bound is verified.
Performance Evaluation and Design of Intrusion Detection System Based on Immune System Model
Journal of the Korea Society for Simulation, volume 8, issue 3, 1999, Pages 105~121
Computer security is considered important due to the side effect generated from the expansion of computer network and rapid increase of the use of computers. Intrusion Detection System(IDS) has been an active research area to reduce the risk from intruders. We propose a new IDS model, which consists of several computers with IDS, based on the immune system model and describe the design of the IDS model and the prototype implementation of it for feasibility testing and evaluate the performance of the IDS in the aspect of detection time, detection accuracy, diversity which is feature of immune system, and system overhead. The IDSs are distributed and if any of distributed IDSs detect anomaly system call among system call sequences generated by a privilege process, the anomaly system call can be dynamically shared with other IDSs. This makes the IDSs improve the ability of immunity for new intruders.