• 한국유체기계학회 논문집
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• 제2권1호
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• pp.15-21
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• 1999

Some sized centrifugal compressors were designed and their performance measured to investigate the effects of exit blade thickness, width and back swept angle. The impeller of larger blade thickness shows low pressure ratio compared with that of smaller ones. Backswept angle also have a large effect on the efficiency. Measured values of slip factor are quite different from the estimated values of the Wiesner-Busemann model and an increase in the flow late.

• International Journal of Air-Conditioning and Refrigeration
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• 제14권2호
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• pp.76-83
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• 2006

An efficiency of a refrigeration cycle and a reliability of a compressor can be reduced if a refrigerant including excessive lubricating oil is exhausted from the compressor. Thus, the analysis of the oil behavior inside the compressor is required to prevent the problem. A tested rotary compressor with visualization windows has been manufactured. in this study to investigate the oil behavior using developed visualization techniques. The oil behaviors at various operating conditions have been quantified to obtain the relationship with the outlet pressure inside the compressor. Also, the effect of the operating conditions on the quantity of the exhausted oil from the rotary compressor has been investigated using a manufactured test model.

• 천문학회지
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• 제23권1호
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• pp.71-82
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• 1990

Theoretical calculations of the combined radiative transfer and statistical equilibrium equation including the charge-particle conservations have been earned out for a multilevel hydrogen atom in quiescent prominences. Cool and dense models show the steep changes of population and radiation field in the vicinity of the surface, while these physical quantities remain unchanged for models with temperature of 7,300K, regardless of total densities. Ionization rate of hydrogen atom related with metallic line formation varies in considerable amounts from the surface to the center of model prominences cooler than 6,300K. However, such cool models cannot release enough hydrogen line emissions to explain observed intensities. Prominence models with a temperature higher than 8,000K can yield the centrally reversed Lyman line profiles confirmed by satellite EUV observations. We find that queiscent prominence with a density between $2{\times}10^{11}$ and $10^{12}cm^{-3}$ should be in temperature range between 6,300K and 8,300K, in order to explain consistently observed H alpha, beta line emissions and $n_p/n_l$ ratio.

• 천문학회지
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• 제23권1호
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• pp.31-42
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• 1990

Fine structures of a quiescent prominence are studied by analyzing high resolution H alpha filtergrams and H alpha line spectra observed at the Hida Observatory of Kyoto University. We have found two kinds of downward motions in the prominence. One of them is a movement with a constant acceleration below the solar gravity(${\simeq}1/4g_s$) and the other with an uniform velocity(${\simeq}16Km/s$). The average life time and the size of prominence knots are estimated to be about 7 minutes and 4000Km, respectively. Spatial and brightness distribution of knots are also presented in this paper. With the analytical solutions derived from magnetostatic equilibrium in the prominence, we have examined the filamentary structure based on the Kippenhahn-Schluter model. Sag angles of the magnetic fields supporting the prominence matter are predicted from the observed density profile.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.308-311
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• 1998

Experiments and design efforts have been made to develope a hybrid-type magnet for magnetically levitated(MAGLEV) vehicle using NdFeB permanent magnet. The permanent magnet, which embedded in both poles of the magnet, has been designed, analyzed using FEM program. The model is manufactured and tested to verify its performance.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.98-100
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• 1998

This paper presents the fluid characteristics simulation and design guide line of the fluid path inside the rotor, which has an high-Tc superconducting field winding using Ag sheathed BSCCO-2223. The analysis was conducted with an equivalent model of the high-Tc superconducting synchronous motor under transition condition that occurs during the load varying from 250watt to 500watt. The results show that the designed fluid circulation system performs adequately in maintaining the superconducting state in the winding.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.340-342
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• 1998

This paper presents the ac losses simulation in the rotor having an high-Tc superconducting field winding using Ag sheathed Bi-2223. The analysis was conducted with an equivalent model of the high-Tc superconducting motor under transition condition during the load that varies from 250watt to 500watt. The simulation results show that the transient state lasts for about 2 seconds, and the ac losses decreased exponentially from the initial value above 2 watts.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1999년도 유체기계 연구개발 발표회 논문집
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• pp.125-133
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• 1999

This paper reports the impeller performance of centrifugal pump, modified HES65-250. Developed CFD code uses SIMPLE algorithm, power-law scheme, standard k-$\epsilon$ turbulence model in curvilinear coordinate system. The calculations are conducted for 5 cases, from 0.6 to 1.4 of flow rate ratio with 0.2 increment. The flow characteristics inside of impeller are analysed. The results show that reversal flows exist at the inlet of impeller which have small rotary stagnation pressure. The obtained results are compared with the experimental data at impeller exit and shows good qualitative agreement.

• 전기학회논문지
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• 제60권3호
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• pp.492-499
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• 2011

This paper describes that the evaluation on operation practicality of Al conductor cable will be used instead of Cu conductor cable. Analysis is divided into two kinds of cases as transmission and distribution. To evaluate that Al conductor line has the insulation strength indeed safely, various analysis and calculation such as single line-to-ground fault current, lightning surge and allowance current were carried. Model was established based on real combined transmission and distribution is being used in utility with EMTP. The analysis results on Al and Cu conductor line were compared each other. It was proved that Al conductor line can be operated instead of Cu conductor line without special insulation problem in transmission and distribution, in electrical view point such as overvoltage and allowance current.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 A
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• pp.137-139
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• 1993

This paper details methods used to verify the adquacy of a dc traction power supply for design in Seoul matropolitain subway Line-6 system. Examples of the approach are given for a major subway presently under construction. The performance of trains operating at maximum system design capacity is modelled using a train simulation program. Using a dc network analyser program, the maximum train operating timetable, and a model of the ac and dc electrical suppy system, the electrical performance of the entire system can be modelled over a 24-hour period. The results of this analysis are used to determime: train voltage at a level sufficient to ensure train schedules: adequacy of traction transformers, rectifier, and switchgear ratings; sizes of the overhead contact systern conductors, and ac and de feeder cables: and power and energy demands at the utility company's supply points for inital and final timetable operations.