• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.4
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• pp.369-376
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• 2016

In this study, a numerical analysis framework for investigating the nonlinear behavior of structures under fire conditions is presented. In particular, analysis procedure combining fire-driven flow simulation and thermo-mechanical analysis is discussed to investigate the mechanical behavior of fire-exposed representative volume structures made of steel and concrete, respectively. First of all, fire-driven flow analysis is conducted using Fire Dynamics Simulator(FDS) in a rectangular parallelepiped domain containing the structure. The FDS simulation yields the time history of temperature on the surface of the structure under fire conditions. Second, mechanical responses of the fire-exposed structure with respect to prescribed uniformly distributed loads are calculated by a coupled thermo-mechanical analysis using the time-varying surface temperature as boundary conditions. Material nonlinearities of steel and concrete have been considered in the thermo-mechanical analysis. A series of numerical results are presented to demonstrate the feasibility of the multiphysics structural fire analysis for investigating the structural behavior under fire conditions.

• Journal of the Korean Society of Safety
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• v.27 no.5
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• pp.35-41
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• 2012

The Numerical simulation was performed on the flow field around the two-dimensional rectangular bluff body in order to complement the previous experimental results of the bluff body stabilized flames [1]. For both fuel ejection configurations against an oxidizer stream, the flame stability was affected mainly by vortex structure and mixing field near bluff body. FDS(Fire Dynamic Simulator) based on the LES(Large Eddy Simulation) was employed to clarify the isothermal mixing characteristic and wake flow pattern around bluff body. The air used atmosphere and the fuel used methane. The result of counter flow configuration shows that the flow field depends on air velocity but the mixing field is influenced on the fuel velocity. At low fuel velocity the fuel mole fraction is below the flammable limit and hence the mixing is insufficient to react. Therefore, as the result, the flame formed at low fuel velocity is characterized by non-premixed flames. For the flow field of co-flow configuration, flame stability was affected by fuel velocity as well as air velocity. the vortex generated by fuel stream has counter rotating direction against the air stream. Therefore, the momentum ratio between air and fuel stream was important to decide the flame blow out limit, which is result in the characteristic of the partially premixed reacting wake near extinction.

• Transactions of Materials Processing
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• v.14 no.9 s.81
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• pp.798-803
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• 2005

In this paper, the six sigma scheme together with the rigid-viscoplastic finite element method is employed to obtain the optimal metal flow lines of a hot forging according to the six sigma processes, i.e., five steps such as define, measure, analyze, improve and control. Each step is investigated in detail to meet customer's requirements through improvement of product quality. A forging simulator is used for analysis of the metal flow lines of the hot forging, manufactured by a hot press forging machine, under various conditions of major factors determined at each step. The analyzed results are examined in order to reveal the effects of major factors on the metal flow lines and the formed shapes. The effects are then used to find an optimal process and the optimal process with die is devised and tested. The comparison between the required metal flow lines and the experiments shows that the approach is effective for optimal process design in hot forging considering metal flow lines.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.199-202
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• 2005

In this paper, the six sigma scheme is employed together with the rigid-viscoplastic finite element method to obtain the optimal metal flow lines in hot press forging. In general, the six sigma process is consisted of following five steps : define, measure, analyze, improve and control. Each step Is investigated in detail to meet customer's requirements through improvement of product quality. A forging simulator, AFDEX-2D, is used for analysis of the metal flow lines of a multi-stage hot forging process under various conditions of major factors, determined at each step of the six sigma process. The analyzed results are examined in order to reveal the effects of major factors on the metal flow lines and the formed shapes. The effects are used to find an optimal process and the optimal process with die is devised and tested. The comparison between required metal flow lines and experiments shows that the approach is effective for optimal process in hot forging design considering metal flow lines.

• Journal of Korean Society of Forest Science
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• v.95 no.3
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• pp.350-357
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• 2006

For the purpose of this study, the characteristics of surface flow through the survey of rainfall intensity and degree of slope on fire sites by using rainfall simulator was examined and analysed. And also the relationship between the amount of surface flow and rainfall intensity, degree of slope and elapsed year after forest fire occurrence influencing on the surface flow were analysed. The results obtained were as follows: 1. The amount of surface flow by year of occurrence of forest fire was increased 2,2 to 3,2 times as rainfall intensity was increased by 30 mm/hr, and 1.5 to 1.9 times as degree of slope was increased by $10^{\circ}$, 2, Even though ground vegetation in forest fire sites was recovered more than 80%, the amount of surface flow in initial rainfall was relatively much and it seemed that vegetation didn't play substantial roles in reducing runoff. 3, The amount of surface flow by rainfall intensity and degree of slope in accordance with elapsed years after forest fire was reduced 22,3% to 41,8% in three years after fire as compared to the first year of fire occurrence. The amount of surface flow were significantly differentiated by rainfall intensity and degree of slope in the first year of fire occurrence and the difference were gradually reduced afterwards. 4. In the analysis on influences of each factors on the amount of surface flow on forest fire sites, the amount of surface flow was significant differences in major impacts of each rainfall intensity, degree of slope and elapsed year after fire and interaction of rainfall intensity ${\times}$ degree of slope and rainfall intensity ${\times}$ elapsed year after fire, but no differences were observed in interaction of degree of slope ${\times}$ elapsed year after tire and rainfall intensity ${\times}$ degree of slope ${\times}$ elapsed year after tire. Rainfall intensity was the most affecting factor on the amount of surface flow and followed by degree of slope and elapsed year after fire.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.05a
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• pp.398-401
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• 2005

This paper presents a user-friendly application for voltage sag analysis and effective visualization for analysis date. This developed tool provides basic functions for voltage sag analysis such as load flow analysis, short circuit analysis and determination of vulnerability of sensitive equipments. Particularly it has the ability to visualize analysis results effectively using computer graphic and animation. In order to give the real sense, analysis results are displayed with geographical information in an intuitive and rapid manner. The developed voltage sag simulator is applied to the Jeju-Island power system in order to show its capabilities.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.11B
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• pp.1031-1037
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• 2003

A new scheduling scheme, which uses channel quality information of each flow in Bluetooth system of ad-hoc network for effective bandwidth assignment, has been proposed in this paper. By an effective bandwidth assignment, QoS (Quality of Service) could have been ensured in case of asymmetric data traffic, mixed data transmission, and congested data transmission in a specific channel. The scheduling algorithm determines channel weights using partial channel information of flows. Case studies conducted by NS-2 (Network Simulator 2) and Bluehoc simulator has been presented to show the effectiveness of the proposed scheduling scheme.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.11 s.254
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• pp.1117-1122
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• 2006

The PEM type regenerative fuel cell(RFC) for the ground simulator of the regeneration electric power system has been designed, manufactured, and tested. In this paper, the designing and manufacturing procedures of the RFC were presented. Also, the performance test results were showed briefly. The RFC consists of PEM type stack, humidifier, pressure and flow control valve, storage tanks, pump and controller. The performance tests were carried out with stack and system performance tests. The performance targets are more than 50% stack efficiency, 1.5kW stack power, less 400W parasitic power in design condition. Most of the performances required are satisfied.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.10
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• pp.956-960
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• 2004

The Vehicle Dynamic Simulator(VDS) is a key equipment of the performance verification of attitude control subsystem and it simulates the real dynamic environment that spacecraft undergoes during mission operation. All the software models and hardware interfaces necessary for the closed-loop simulation of the spacecraft dynamics are implemented. Using VDS, KOMPAT-2 attitude control logic functions and performance was verified. In this paper, the hardware and software configurations of KOMPSAT-2 VDS was described briefly and the information flow and exchanges between software models and actual hardwares during close loop simulation was described in the systematic point of view.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.12
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• pp.2385-2390
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• 2009

Based on the detailed analysis of output characteristics of PV array and residential load usage pattern, a design method to calculate optimal battery capacity for stand-alone PV generation systems is proposed. And also, according to power flow Actual irradiation and temperature data are analyzed to compose a PV array simulator and also six representative home appliances are electrically modeled for load simulator, along with 24hours usage pattern. The surplus and insufficient power can be calculated from the proposed simulation platform, so that selection of an optimal battery capacity can be possible. The theoretical analysis and design process will be explained, along with informative simulation results.