• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.6
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• pp.886-893
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• 2000

The Characteristics of dividing the dispersed bubble, plug, and slug steam-water flow in the horizontal junctions with horizontal branches have been experimentally investigated. The experimental investigation of the separation phenomena in a $45^{\circ}$ horizontal wye with equal pipe inner diameter of 25 mm is presented to provide a data base for the development and verification of the analytical models. The phase separation and pressure distribution in the three legs of each test section are obtained through the set of measurements made in the present work. And the dependence of phase separation on different parameters, such as inlet quality and mass flux, is discussed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.12
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• pp.1255-1265
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• 2001

A numerical study has been conducted to characterize the transient flow in a utility gas turbine burning natural gas. The solution domain encompasses the supply gas pressure regulator to the combustor of the gas turbine that employs multi-nozzle fuel injectors. Some results produced for verification in the present study agree suite well with the experimental ones. It is found that the total gas flow may decrease noticeably during its combustion mode change, which would be the reason of momentary combustion upset, when a reference case of opening ratios of control valves in the system is applied. Several parameters are then varied in order to make the total gas flow stable over that period of time. Results of this study may be useful to understand the unsteady behavior of combustion system burning natural gas.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.6
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• pp.538-544
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• 2012

Analysis of thermal performance is required for the economic operation of turbine cycle of power plant. We developed corrective model of main feed water flow which is the most important parameter for the precise analysis of turbine cycle performance. Classification model for the identification of feed water flow measurement status was applied to increase the suitability of the corrective model. We used neural network and support vector machine to develop estimation model of main feed water flow with more generalization capability. The estimation model can be used practically to evaluate corrective performance of turbine cycle plant.

• KIEE International Transactions on Power Engineering
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• v.12A no.1
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• pp.31-35
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• 2002

This paper presents a new operation scheme of UPFC to minimize both generation costs and active power losses in a normal operation state of power system. In a normal operation, cost minimization is a matter of primary concern among operating objectives. This paper considers two kinds of costs, generation costs and transmission losses. The total generation cost of active powers can be minimized by optimal power flow, and active power losses in the transmission system can be also minimized by power flow control of UPFC incorporated with minimization of generation costs. In order to determine amounts of active power reference of each UPFC required for the cost minimization, an iterative optimization algorithm based on the power flow calculation using the decoupled UPFC model is proposed. For verification of the proposed method, intensive studies have been performed on a 3-unit 6-bus system equipped with a UPFC.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.446-450
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• 2008

Urban transits of metropolises have been used by many citizens due to the merits of environment friendly traffic, mass transportation, safety and scheduled operation. It is very important to keep safety for the increased passengers. When the accidents as like fire occur, rapid evacuation from fire site is one of the most effective methods to decrease casualties. Furthermore, overseas buyers sometimes request the verification results of the passenger evacuation from rolling stock. In this study, algorithm for passenger flow analysis based on DEM(Discrete Element Method) is newly developed and made simulation program package. And, we applied it to the evacuation problem for urban transits. By using the developed program, we compared the simulation results of the effects of the location and size of door and elapsed time qualitatively and quantitatively.

• Water for future
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• v.28 no.6
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• pp.193-202
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• 1995

The subjective research attempts to apply a rainfall-runoff model capable of considering time-variation of soil water contents which are highly correlated to the river flows on the qpqyungchang river basin and to evaluate its performance for flow forecasting. The model used in this study is a physically-based conceptual time-continuous model, which is composed of the Sacramento soil moisture accounting model and the nonlinear multiple conceptual reservoirs model. The daily precipitation and evaporation data for 7 years and for 3 years were used for the parameter estimation and the model verification, respectively. As a result, the flows including a significant flood event were well simulated, and the cross-correlation coefficient between observed flows and computed flows for the verification periods was 0.87, but in general computed flows were underestimated for the low-flow periods. Also, the effects of precipitation and soil water content to the river flows were analysed for the flood and the drought.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.2
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• pp.270-278
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• 2017

This paper describes development procedure and verification test results of a bi-propellant thruster using hydrogen peroxide and kerosene. The design thrust of the thruster is about 500 N and six swirl type coaxial injectors were used. The passage type manifolds were employed for the injector head to reduce the response time. The passage was designed to minimize stagnation points and recirculation region to ensure uniform flow distribution and sufficient cooling performance through flow analysis using Fluent. A catalytic igniter using hydrogen peroxide was installed at the center of the injector head. The propellant feeding and spray characteristics were confirmed by hydraulic tests. Combustion tests were performed on design and off-design points to analyze combustion characteristics under various mixture ratio conditions. The combustion test results show that combustion efficiency was over 95 % and chamber pressure fluctuation were less than 1.5 % under all test conditions.

• The KIPS Transactions:PartD
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• v.10D no.7
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• pp.1189-1196
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• 2003

Owing to the developed If industry, many people are more and more interested in Workflow which is an automated business processing system. In this paper, we present basic structures and various parallel processing structures of a workflow using EMFG (Extended Mark Flow Graph) that makes conceptional design available. And then, We design a workflow with EMFG. We propose the commitability verification method to check whether a workflow can complete or not and the logical bug verification method to find whether invalid components exist or not by using simulation result of it. The proposed EMFG modeling and analysis method for a workflow make it possible to become a visual and formal design. Also, it makes intuitional and mathematical analysis possible.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.9
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• pp.899-905
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• 2009

Most supersonic-flow test facility has axisymmetric nozzles or two-dimensional symmetric nozzles. Compared to these nozzles, a two-dimensional asymmetric nozzle has advantages of reducing low cost for various Mach number testing and undesirable flow structure such as shock wave reflection because the nozzle part can be directly connected to the test section part in this type of nozzle. The two-dimensional asymmetric nozzle, which was Mach number 2, was designed for supersonic combustion experiment. And it was verified with the numerical analysis and visualization of Mach wave. This study suggested the practical method for design and verification of supersonic two dimensional asymmetric nozzles.

• Structural Engineering and Mechanics
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• v.57 no.5
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• pp.877-895
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• 2016

This paper is concerned with the analytical derivation of natural sloshing frequencies of liquid in annular cylindrical tank and its verification by experiment. The whole liquid domain is divided into three simple sub-regions, and the region-wise linearized velocity potentials are derived by the separation of variables. Two sets of matrix equations for solving the natural sloshing frequencies are derived by enforcing the boundary conditions and the continuity conditions at the interfaces between sub-regions. In addition, the natural sloshing frequencies are measured by experiment and the numerical accuracy of the proposed analytical method is verified through the comparison between the analytical and experimental results. It is confirmed that the present analytical method provides the fundamental sloshing frequencies which are in an excellent agreement with the experiment. As well, the effects of the tank radial gap, the bottom flow gap and the liquid fill height on the fundamental sloshing frequency are parametrically investigated.