• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.102-106
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• 1999

One of the main causes of unwanted dimensional changes in precision metal mold casting parts is excessive and irregular residual stresses induced by temperature gradients and plastic deformation in the solidifying shell. Residual stresses can also cause stress cracking and lower the fatigue life and fracture strength of the casting parts,. In the present study aluminum alloy casting system with metal mold equipped with electrical heating elements and water cooling units was designed and the casting specimens were produced to quantify the effects of different cooling conditions on the development of residual stresses. the layer removal method was used to measure the biaxial residual stresses in casting specimens produced from the experiments. The experimental results agreed with Tien-Richmond's theoretical model for thermal stress development for the solidifying metal plate

• Journal of the Korean Home Economics Association
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• v.35 no.3
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• pp.171-179
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• 1997

The purpose of this research was to grasp the space funtions, the preferred image in bathroom and to find out the plan of bathroom. The subjects of investigation included university students in third decades of which data were obtained by the questionnaire survey method. The major findings were as follows: 1) The space funtions of bathroom were the hygienic activities and the supplementary funtions as resting and health-care. 2) Total and facility image in bathroom take a serious view of a sanitary, a function and following to a mood , a sense of space. 3) The preferred type of bathrooms were identified as the 2-space type. Furthermore, the demands were needed in radiator & pannel heating system, storing furniture and funtional lighting & mirror. According to those results, three types of space plan for bathroom can be suggested and color & forms of design elements can be proposed.

• Journal of Biosystems Engineering
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• v.17 no.4
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• pp.336-343
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• 1992

In this study, to obtain basic information for the design of a latent heat storage system, (1) the cylindrical type and the rectangular type of latent heat storage elements were designed, (2) the finite element method was adopted for the prediction of temperature profile of phase change material in heating and cooling process, and (3) experiments were performed to verify the numerical solutions, and then (4) the optimum size of latent heat storage units was predicted by the computer simulation. The results could be summarized as follows : (1) In cooling process, the predicted temperatures of latent heat storage units by computer simulation were in good agreement with measured. (2) The effective diameter of cylindrical element was observed to be 28 mm and the effective thickness of rectangular element was observed to be 21 mm.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.11a
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• pp.179-183
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• 1999

Rubbing occurs when a rotating element comes in contact with a stationary element. In the steam turbines, the rotating element is the rotor while the stationary elements are usually the oil deflectors and packing seals. Rubbing phenomenon may be often obseued on a new or rebuilt machine rather than on a machine that has been operating for several months or years. Rubbing in the turbine has been classified into two modes by the operating conditions: 1) start up or shut down, 2) steady state. At start up or shut down operation, rubbing produces synchronous whirl vibration, which are caused by thermal bow of the shaft due to localized heating on the shaft surface. While subsynchronous whirl vibration is caused by partial rubbing during the steady state operation. In this paper, the two case studies of troubleshooting for excessive vibration caused by rubbing in the actual steam turbines are investigated.

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.126-128
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• 2005

This paper presents a 3-D finite element analysis of a magneto-thermal coupled problem with moving conductor. In the magnetic and thermal analyses, temperature-dependent magnetic and thermal material properties were considered. Transient finite element method for analysis of moving conductor needs many number of elements and much time to make calculation. Therefore, in this paper, finite element formulation derived from quasi-state is adopted. Finite element results were compared with the experimental results. The results demonstrate that this approach is suitable to solve the magneto-thermal coupled problem.

• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.282-285
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• 2008

In this paper, the numerical analysis of the model without air-guide was carried out in wind power generator. From numerical results, the temperature rise was not satisfied for the class F insulation and the non-uniformity of temperature distribution was a wide difference in heating elements. To improve these problems, the air-guide was installed in front of the coil head of non-drive end(NDE). The short distance between coil head and air-guide was more effective than long distance in cooling performance. Compared to that of the preliminary design, it was found that the cooling performance of the modification design was improved about 12%.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.1
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• pp.101-108
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• 2009

This paper presents dynamic analysis of HVAC(heating ventilation & air conditioning) heater case which consists of heater and evaporator unit for passenger car. To analyze the dynamic characteristics of HVAC heater case, finite element model which consists of shell elements is constructed for modal analysis and experimental modal analysis has been conducted. Finite element analysis results are compared with experimental results to evaluate of validity of finite element model. After identifying mode shape and natural frequency of HVAC heater case, local stiffness of HVAC case is evaluated through point mobility using finite element analysis and experiment.

• Journal of the Semiconductor & Display Technology
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• v.3 no.2
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• pp.17-21
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• 2004

Aluminum nitride(AlN) thin films were deposited on silicon substrate by reactive RF magnetron sputtering without substrate heating. We investigated the dependence of some properties for AlN thin film on sputtering conditions such as working pressure, $N_2$ concentration and RF power. XRD, Ellipsometer and AES has been measured to find out structural properties and preferred orientation of AlN thin films. Deposition rate of AlN thin film was increased with an increase of RF power and decreased with an increase of $N_2$ concentration. AES in-depth measurements showed that stoichiometry of Aluminium and Nitrogen elements were not affected by $N_2$ concentration. It has shown that low working pressure, low $N_2$ concentration and high RF power should be maintained to deposit AlN thin film with a high degree of (0002) preferred orientation.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.6
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• pp.588-593
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• 1997

This paper shows a design and implementation of throttle valve controller for engine dynamometer system using fuzzy logic. Recently, we demanded the excellent measuring equipment so as to improve engine performance. The throttle valve control for engine dynamometer system is a very particular part in the engine control. Since the structure of engine dynamometer system is very complicated and has nonlinear elements which are influenced by disturbance of vibration, heating, cooling, and energy loss so on. In this paper, fuzzy logic control application have been successful in throttle valve control problem for engine dynamometer system in which the conventional control had difficulties dealing with the system. In this study, we propose a method that the control strategy uses Fuzzy Look-up table and normalization and obtained the satisfying result from realized throttle valve controller for engine dynamometer system.

• Analytical Science and Technology
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• v.17 no.4
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• pp.363-367
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• 2004

A simple and convenient digestion method was developed for the determination of heavy metal in polyurethane sample using only nitric acid in open system without heating. This digestion method had prevented loss of volatile elements of Hg and As and reduced the pretreatment time for the sample digestion. The detection limit is lowered over 10 times than that of microwave digestion method. Recoveries in polyurethane material were 108% for As, 96 ~ 99% for Hg, 102 ~ 103% for Cr, 98 ~ 102% for Pb, 86 ~ 90% for Cd, and 90 ~ 93% for Cu.