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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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The Korea Society for Simulation
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Volume & Issues
Volume 7, Issue 2 - Dec 1998
Volume 7, Issue 1 - Jun 1998
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Automated Methodology for Campus Network Design and Performance Analysis
Journal of the Korea Society for Simulation, volume 7, issue 2, 1998, Pages 1~16
This paper presents an automated methodology for campus network design and performance analysis using the rule-based SES and DEVS modeling & simulation techniques. Proposed methodology for structural design and performance analysis can be utilized not only in the early stage of network design for selecting configurable candidate from all possible design alternatives, but also in simulation verification for generating performance data. Our approach supercedes conventional methodologies in that, first, it can support the configuration automation by utilizing the knowledge of design expert ; second, it can provide the simulation-based performance evaluation ; third, it is established on the basis of the well-formalized framework so that it can support a hierarchical and modular system design. Several simulation tests performed on a campus network example will illustrate our technique.
A Simulation on the Two-Phase Flow Characteristics in Gas Bubble Driven Circulation Systems
Journal of the Korea Society for Simulation, volume 7, issue 2, 1998, Pages 17~32
The flow fields in Gas Bubble Driven Circulation Systems were numerically analyzed. In various gas flow rate and bubble size, the flow characteristics were predicted. Eulerian-Eulerian approach was used for the formulation of both the continuous and dispersed phases. The modification of the general purpose computer program PHOENICS code was employed to predict the mean flow fields, turbulent characteristics, gas dispersion, volume fraction. The predicted shows very satisfactory agreement with experimental results for all regions of ladle. The results are of interest in the design and operation of wide variety of material processing.
A Performance Evaluation of Multimedia-on-demand Server Using Simulation Method
Journal of the Korea Society for Simulation, volume 7, issue 2, 1998, Pages 33~43
To evaluate the server performance and forecast capacity requirements, we carry out simulation of Multimedia-on-demand(MOD) server. In multimedia service environment, especially for on-demand service, one of the key problems is capacity planning, which requires ensuring that adequate computer resources will be available to meet the future workload demands in a cost-effective manner. In this paper, we design and implement a simulation model for MOD server with failures of components (e.g., processors, disks and networks). By acquisition of utilization and queue length parameters, we can estimate desirable capacity of server components with various arrival rates of customers and failure rates of components. For a given failure probability, we also compute packet delay probability and reliability of the server. It is possible to derive some important design information of the MOD server by using the above parameters.
Virtual System Buffer Model in Flexible Manufacturing Systems with an AGV System
Kyung Sup Kim ;
Journal of the Korea Society for Simulation, volume 7, issue 2, 1998, Pages 45~62
This research is concerned with buffer management in a multi-cell FMS with an AGVS. Buffers in manufacturing systems are required to reduce blocking and starving caused by breakdowns, variability in process times, and diversity of part routing. Due to the high per unit buffer cost, which primarily consists of floor space and equipment costs, the total capacity of buffers in and FMS is very limited. Proper buffer management can provide a high system efficiency. This paper presents a buffer management model for a multi-cell FMS with an AGVS and a simulation study to compare the proposed model to a conventional buffer management model in a job shop FMS.
A Queueing Model for Mobile Communication Systems with Hierarchical Cell Structure
Journal of the Korea Society for Simulation, volume 7, issue 2, 1998, Pages 63~78
The hierarchical cell structure consists of the macrocell and microcells to increase the system capacity and to achieve broad coverage. The hierarchical cell structure provides services for users in different mobility. In this paper, an analytical queueing model in mobile networks is proposed for the performance evaluation of the hierarchical cell structure. The model for networks with the multiple levels can simplify multi-dimensional ones into one-dimensional queueing model. The computational advantage will be growing as the layers are constructed in multiple levels. The computer simulation is provided for validating the proposed analytical model.
Web-Based Simulation under Distributed Environment
Journal of the Korea Society for Simulation, volume 7, issue 2, 1998, Pages 79~90
This paper introduces the concept of web-based simulation and suggests the structure of web-based simulation which reduces the simulation run time and performs simulations in efficient way under distributed environments. Since its introducing in 1996, web-based simulation has been studied only with a tool of applet, but in this paper a method of server applications for client applets will be used. In server application, server transfers objects requested by clients such as simulation engines, reports, files. After each client connects to web-server, and then server allocates simulation modules to connected clients. These work magnify the transferring applets from server and simulation models which were made by clients. This paper also processes a structure for managing efficiently web-based simulation under distributed environment and steps in which clients connect, model, simulate with distributed structure, and programs of proposed structure.
An Evaluation of the Operation Plans for Port Container Terminal Using Simulation
Journal of the Korea Society for Simulation, volume 7, issue 2, 1998, Pages 91~104
This paper describes the simulation study which evaluates operation plans of container terminal. The operation plans of container terminal consist of berth plan, load plan, unload plan, yard plan, and equipment plan. It is discussed how to apply the simulation method to evaluate those plans that are interrelated with each other. This paper also deals with the assignment and coordination problems of container-handing equipment such as container cranes, transfer cranes, yard tractors, and trailers used in the transportation of containers. Simulation analysis is bases on data about plans from the operation planning system through an interface program. It is discussed what we should got the statistics about container-handing equipment in the simulation.
A Simulation for the Free Vibration of Pipe Systems Considering Initial Tension
Journal of the Korea Society for Simulation, volume 7, issue 2, 1998, Pages 105~114
Using finite elements, a simulation is prformed for the pipe systems to investigate free vibrational characteristics, that is natural frequencies, considering the intial tension due to the velocity and the pressure of the inside fluid flow. To confirm the program developed in this study, the results are compared with the results of commercial software ANSYS. When the initial tension is neglected in curved pipes, the natural frequencies are reduced as flow velocity increases, and the rapid decreases of the natural frequencies took place. However, when the initial tension is taken into account, the natural frequencies are not changed with the change of the flow velocity. In free vibrational simulation of pipe systems, it is necessary to calculate the initial state force due to the velocity and the pressure of the fluid flow from the equilibrium first, then the force should be included in the equation of motion of the systems to get more accurate natural frequencies.
A Simulation for the Natural Frequencies of Curved Pipes Containing Fluid Flow with Various Support Locations
Journal of the Korea Society for Simulation, volume 7, issue 2, 1998, Pages 115~123
A simulation is performed to investigate the effect of the pipe supports on the change of the natural frequencies of curved pipe systems containing fluid flow, for different elbow angles and geometry of the pipe systems. Based upon the Hamilton's principle, the equations of motions are derived, and the finite element equation is constructed to solve the corresponding eigenvalue problem. The angles of elbows do not affect the change of the fundamental natural frequency, but affect the change of the third or higher natural frequencies. Without any support, the change of the fundamental natural frequency due to the geometric change is smaller than the change of the second or higher natural frequencies. The more curve parts exist in the pipe system, the less change of lower frequency range, compared with the change of higher frequency range, is observed. Spring supports can be used to reduce the fundamental natural frequency, without change of the second or higher natural frequencies. To avoid resonance, which is critically dangerous from the view point of structural dynamics, the mechanical properties such as stiffness or the location of pipe supports are need to be changed to isolate the natural frequencies from the frequency range of dominant vibration modes.
A Simulation of the Railway Signal System Using Pattern Control Technique to Upgrade the Railway Efficiency
Journal of the Korea Society for Simulation, volume 7, issue 2, 1998, Pages 125~136
To upgrade railway traffic density without any change of signal block length between stations on existing railway lines, a new signalling system of train control "the pattern control technique" is suggested. It needs very little change to computerize the cab signal using transponders. A computer simulation system is developed to experiment the new control method. The new signalling system shows much increase of the railway traffic efficiency. The train head-way time by the fixed signalling system and the new pattern control system is analyzed. The pattern control technique shows 35% increasement of trair operation under same condition of railway and trains.nd trains.
Discrete Event Simulation with Embedded Distributed Expert System: Application to Manufacturing Process Monitoring and Diagnosis
Journal of the Korea Society for Simulation, volume 7, issue 2, 1998, Pages 137~152
One of the components that constitute the simulation models is the state variables whose values are determined by the time related simulation process. Embedding rule-based expert systems into the simulation models should provide a systematic way of handling these time-dependent variables without distracting the essential problem solving capabilities of the expert systems which are well suited for expressing the decision making function of complex cases. The expert system, however, is inefficient in dealing with the time elapsing characteristics of target system compare to the simulation models. To solve the problem, this paper provides an interruptible inference engine whose inferencing process can be interrupted when the variables' value, which are used as the parameters of the rules, are not yet determined due to the time dependent nature of the state variables. The process is resumed when the variables are ready. The elapse of time is calculated by time-advance function of the simulation model to which the expert system has been embedded. The example modeling shown exploits the embedded interruptible inferencing capability for the controlling and monitoring of metal grating process.
Performance Analysis of a Novel CDMA Soft Handoff Algorithm Using Mobile Terminal Profiles
Journal of the Korea Society for Simulation, volume 7, issue 2, 1998, Pages 153~165
In the Is-95 soft handoff scheme of CDMA, there occurs a tradeoff between improving quality due to the space diversity and additional resource management like updates of the active set during soft handoffs. In addition, if a mobile terminal is alternating two adjacent cells, a well-known phenomenon called ping-ping causes the resource management to be seriously degraded. By noting that in general the probability that a user initiates additional handoffs is exponentially decreased as the user has already handed over one or more times, we present a soft handoff algorithm making use of handoff profiles of mobile terminals to improve resource utilization. In the proposed algorithm the number of handoffs made so far during the call is recorded in the mobile profile and the profile data is used for adjusting handoff parameters such as the value of add or drop threshold (T_ADD or T_DROP). Through simulations, the result of the proposed algorithm is shown to improve the handoff performance by lowering the number of handoffs while simultaneously reducing resource waste.