• Journal of Welding and Joining
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• v.28 no.4
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• pp.26-32
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• 2010

The purpose of this study is to evaluate the residual stresses at the multi-pass FCA weldment using the finite element analysis (FEA). In order to do it, an H-type specimen was selected as a test specimen. The variable used was in-plane restraint intensity. The temperature distribution at the multi-pass FCA butt weldment was evaluated in accordance with the relevant guidance recommended by the KWJS. The effective conductivity for the weld metal corresponding to each welding pass was introduced to control the maximum temperature below the vaporization temperature of weld metal. The heat flux caused by welding arc was assumed to be applied to the weld metal corresponding to welding pass. With heat transfer analysis results, the distribution of transverse residual stresses was evaluated using the thermo-mechanical analysis and compared with the measured results by XRD and uniaxial strain gage. In thermo-mechanical analysis, the plastic strain resetting at the temperature above melting temperature of $1450^{\circ}C$ was considered and the weld metal and base metal was assumed to be bilinear kinematics hardening continuum. According to the comparison between FEA and experiment, transverse residual stresses at the multi-pass FCA butt weldment obtained by FEA had a good agreement with the measured results, regardless of in-plane rigidity. Based on the results, it was concluded that thermo-mechanical FE analysis based on temperature distribution calculated in accordance with the KWJS’s guidance could be used as a tool to predict the distribution of residual stress of the multi-pass FCA butt weldment.

• Journal of Energy Engineering
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• v.25 no.2
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• pp.21-28
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• 2016

This research was conducted for the optimal design of large commercial gas oven system. Equivalent ratio was determined through a numerical analysis and experiments on the combustion condition of the combustor. After reviewing the supply capacity of burner(20,000 kcal) and control method of convection fan, two types of heat exchangers designed. In order to maintain a uniform temperature inside the oven is required convection fan braking system. The center temperature in the oven rises more rapidly when the convectional fan is rotated in the counterclockwise direction than the counter-clockwise direction. And The efficiency of the system by installing a large heat transfer area was higher.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.4
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• pp.306-315
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• 1992

This paper addresses performance analysis of a reciprocating compressor. A computer simulation model has been developed to predict and estimate the compressor performance. Instead of using ideal gas equations, real gas equations are used in describing the state of gas. The compressor simulation model consists of a cylinder control volume, suction system and discharge system. Conservation laws of mass and energy are applied to the cylinder section only, The suction and discharge system are described by the Helmholtz resonator modeling. Some of input data required for the simulation have been obtained from experiments. These experimentally obtained input data are effective flow area, effective force area and dynamic characteristics of valves. Simulation results of real gas equations have been compared with those of ideal gas equations. It has been found that the simulation with real gas equations yields lower cylinder temperature and heat transfer compared with those of ideal gas equations. Differences in pressure, mass flowrates, valve motions and gas pulsations are found quite small.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.393-394
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• 2008

Carbon nanotubes are attractive nano-structured materials because of their remarkable electronic, physical, chemical properties. Due to these reasons, application researches of CNTs are actively processed on the display, the electronic element, the nano-diode fields and the semiconductor element. Today, The major issue of semiconductor technique are via and interconnects. CNTs are used to make via and interconnects because of high electric currents density and high heat transfer. Control of the orientation of grown CNTs is very important thing for making via and interconnects. Via are horizontal growth of CNTs and interconnects are vertical growth of CNTs. This research is based on the experiment using control of gas flow directions and DC bias. Scanning Electron Microscope (SEM) was used to check this experiment.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.1
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• pp.73-80
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• 2016

The preliminary test for the dual mode plasma torch system was carried out to explore the operation properties in advance. The dual mode plasma torch system that is able to operate in transferred, non-transferred, or dual mode is very adequate for melting the mixed wastes including nonconductive materials such as concrete, asbestos, etc. since it exploits both the high efficiency of heat transfer to the melt in transferred mode and stable operation in non-transferred mode. Also, system operation including restarting is reliable and very easy. A stationary melter with a refractory structure was designed and manufactured considering the melting behavior of slags to minimize the refractory erosion. The power supply for the dual mode plasma torch system built with high power insulated gate bipolar transistor (IGBT) modules has functions for both current control and voltage control and is sufficient to suppress the harmonics during the operation of the plasma torch. The power supply provides two different voltages for transferred operation and non-transferred. It is confirmed that the operation voltage in transferred is always higher than non-transferred. The dual mode plasma torch system was successfully developed and is under operation for a melting experiment to optimize operation data.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.8
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• pp.831-838
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• 2013

This paper focused on the design of an efficient temperature controller for a plant with a wide range of operating temperatures. The greater the temperature difference a plant has, the larger the nonlinearity it is exposed to in terms of heat transfer. For this reason, we divided the temperature range into five sections, and each was modeled using ARMAX(auto regressive moving average exogenous). The movement of the dominant poles of the sliced system was analyzed and, based on the variation in the system parameters with temperature, optimal control parameters were obtained through simulation and experiments. From the configurations for each section of the temperature range, a temperature-based gain-scheduled controller (TBGSC) was designed for parameter variation of the plant. Experiments showed that the TBGSC resulted in improved performance compared with an existing proportional integral derivative (PID) controller.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.6
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• pp.515-518
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• 2008

Organic light emitting diode(OLED) is one of the most promising type of future flat panel display. A linear source is used to deposite organic vapor to a large size OLED substrate. An electric heater which is attached on the side of linear source heats the organic powder for the sublimation. The nozzle of heater, which is attached at the top of the linear source has an optimal temperature. An numerical analysis has been performed to find optimal heater position for the optimal nozzle temperature. A commercial CFD program, FLUENT, is used on the analysis. Two-dimensional and three-dimensional analysis have been performed. The analysis showed that the heater should be attached at the outer side of crucible wall rather than inner side of housing, which was original design. Eighteen milimeter from the top of the linear source was suggested as the optimal position of heater. Improving thermal performance of linear source not only helps the uniformity of organic vapor deposition on the substrate but also increase productibity of vapor deposition process.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.6
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• pp.142-153
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• 2005

The brake judder is a phenomenon that the steering wheel is abnormally vibrating when the car is braked at a high speed. It is classified by the cold and the hot judder. The former is generated due to the initial uneven disk surface and the latter is resulted from the uneven heat spots on disc surface by repeatedly braking. There are two ways to reduce the judder. One is to control vibration by modification of the disk shapes and pad ingredients. The other is to improve modal characteristics of the suspension system. The latter approach is used in this research. In this paper, the real vehicle test and computer simulation are considered to systematically understand the judder phenomenon of the vehicle. The Macpherson strut suspension is employed. Especially, the judder sensitivity is calculated based on design sensitivity analysis. A bush stiffness was reworked and braking test was done to verify the sensitivity result. The judder reduction by the mode control was verified.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.830-833
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• 2004

An indoor package air-conditioner (PAC) has complex noise sources such as motor noise and fluid noise caused by the fan motor, heat transfer and shroud. Sound intensity techniques and ODS(Operational deflection shape) techniques are applied to identify the noise characteristics of an indoor air-conditioner's cabinet. The sound intensity is used to visualize the noise source locations. and the ODS to visualize the vibration pattern and to obtain the dynamic characteristics of the noise source. Acoustic intensity and operational deflection distribution are obtained in space domains as well as frequency domains. Using the visual information of source locations and its dynamic characteristics, the damping patch is applied to reduce structure borne noise in the cabinet. As a result, the noise emitted by the cabinet is reduced by 5dB.

• Journal of the Korean Institute of Gas
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• v.5 no.2 s.14
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• pp.22-29
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• 2001

The number of gas containers and the period of exchanging gas containers are vsy important in designing liquefied petroleum gas(LPG) supply system for small capacity domain. And also the evaluation of remaining LPG in containers to be exchanged is very useful information in commerce. However seldon has been studied on calculating method about those with respect to gas consumption pattern. In this study, a simulation method was developed to estimate the evaporation capacity of LPG container, the mass gas flow rate from LPG container, the temperature and vapor pressure of LPG, and the remained LPG at containers to be exchange by using LPG property equations, mass balance equation, and heat balance equation. The simulation results were correlated well with experimental data. The overall heat transfer coefficient from air to LPG is approximately $9{\~}13 kcal/m^2{\cdot}hr{\cdot}^{\circ}C$ and does not strongly affect on the evaporation capacity of LPG container. The mass gas flow rate from LPG container is constant when the vapor pressure of LPG is within pressure regulator's control range. While, out of range, it suddenly reduce to a evaporation rate which is balanced with heat transfer from air. The evaporation capacity of LPG container increased with surrounding temperature and the composition of propane, and decreased drastically with continuous gas consumption. The number of gas containers divided the number of houses using gas supply system was reduced by using automatic gas feeding device.