• Proceedings of the Korean Vacuum Society Conference
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• 2007.08a
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• pp.188-188
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• 2007

• Journal of Navigation and Port Research
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• v.31 no.10
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• pp.879-884
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• 2007

This study is to observe the change of temperature and relative humidity for various vegetables in vacuum precooling system. The materials for experiments were the lettuce, chinese cabbage, pak choi and cabbage. The experimental apparatus was constructed of vacuum chamber, vapor/water separator, water tank, pumps ejecting and cooling water circulation, refrigerator unit, cooling coil for water cooling, Hygrometer and Data logger measuring of the temperature change. The experiments were operated in 20torr and recorded every 3 minutes. It was found that the cooling temperature and speed of vegetables are depending on the percentage of its water content. The more water contains, the faster cooling speed and the lower cooling temperature.

• Journal of the Korean Vacuum Society
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• v.15 no.5
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• pp.458-464
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• 2006

The construction and the performance test of an ultra high vacuum (UHV) molecular beam epitaxy (MBE) system has been completed successfully. We have done domestic development and tried performance test for ultra high vacuum molecular beam epitaxy system. This system has reached pressure $2X10-^{10}$ Torr and the substrate has reached temperature $1,100^{\circ}C$. We have investigated into the characteristic of ZnSe/GaAs(001) by using scanning electron microscope (SEM), atomic force microscope (AFM), x-ray diffraction (XRD) and photolumi-nescence (PL).

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.10
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• pp.833-839
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• 2013

Thermal vacuum test should be performed prior to launch to verify satellites' functionality in a harsh space environment which is represented by extremely cold temperatures and vacuum conditions. A thermal vacuum chamber which consists of a vacuum vessel, a pumping system, and a thermal control system are used to perform thermal vacuum tests of a satellite system and its components. A cryogenic blower is a core component of the closed loop thermal control system for thermal vacuum chambers. This paper describes the fan design of the cryogenic blower, the design of the thermal protection interface between the driving part and the fluid part, which were verified by thermal and structural analyses. The performance of the cryogenic blower is confirmed by similarity test on the test bench.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.421-422
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• 2011

The first part is about development of a liquid target for a neutron source, which is designed to overcome many of the limitations of traditional beam-target neutron generators by utilizing a liquid target neutron source. One of the most critical aspects of the beam-target neutron generator is the target integrity under the beam exposure. A liquid target can be a good solution to overcome damage to the target such as target erosion and depletion of hydrogen isotopes in the active layer, especially for the one operating at high neutron fluxes with no need for water cooling. There is no inherent target lifetime for the liquid target neutron generator when used with continuous refreshment of the target surface exposed to the energetic beam. In this work, liquid target containing hydrogen has been developed and tested in vacuum environment. Potentially, liquid targets could allow a point neutron source whose spatial extension is on the order of 1 to $10{\mu}m$. And the second is about the vacuum ultraviolet (VUV) spectrometer which is designed as a five-channel spectral system for ITER main plasma measurement. To develop and verify the design, a two-channel prototype system was fabricated with No. 3 (14.4 nm~31.8 nm) and No. 4 (29.0 nm~60.0 nm) among the five channels. For test of the prototype system, a hollow cathode lamp is used as a light source. The system is composed of a collimating mirror to collect the light from source to slit, and two holographic diffraction gratings with toroidal geometry to diffract and also to collimate the light from the common slit to detectors. The two gratings are positioned at different optical distances and heights as designed. To study the appropriate detector for ITER VUV system, two different electronic detectors of the back-illuminated charge coupled device and the micro-channel plate electron multiplier were installed and the performance has been investigated and compared in the same experimental conditions. The overall system performance was verified by measuring the spectrums.

• Journal of Korea Foundry Society
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• v.27 no.4
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• pp.153-158
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• 2007

Molten metal flow in vacuum die casting was characterized by a numerical analysis. The VOF method was used to simulate the filling behaviors of molten metal during filling process. The various vacuum degrees of no vacuum(760 mmHg), 650, 500, 250 and 60mmHg were artificially applied in cavity. And the filling behaviors of molten metal with the applied vacuum conditions were simulated and compared with those of experiment. The results showed that molten metal was partially filled into cavity when vacuum was applied and the filling length of molten metal in cavity was increased with increasing applied reduced pressure in cavity. Also, the simulated filling behaviors of molten metal were apparently similar to those of experiment, indicating the numerical analysis developed in this study was highly effective. Through the result of fluid flow simulation, both relation equations of filling length and filling velocity with the variation of pressure conditions in cavity were calculated respectively and the internal gas contents of casting was significantly reduced by the modification of vacuum gate system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.5
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• pp.73-80
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• 2008

The recent trend in home network system includes intelligent home environments that remote monitoring and control service is achieved without restrictions by device types, time, and place. Also the use of a vacuum robot in homes is gradually generalized on account of the convenience of the use. In this paper, we proposed and realized new home-monitoring system with the employment of an self-movement robot as one trial for realizing an intelligent home under home network environment. The proposed system can freely monitor every where in home, because the system effectively overcame the surveillance limitations of the existing monitoring system by attaching a Wireless Router and WebCam to a commercial vacuum robot. The outdoor users of this system can readily monitor any place which they want to supervise by controlling a vacuum robot with mobile telecommunication devices such as PDA. The wireless router installed with Linux operation system "OpenWrt" made it possible for the system users to transmit images and to control a vacuum robot with RS-232 communication.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2064-2071
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• 2011

We are developing an innovative super-speed land transportation system running in a partial vacuum in tunnels with small inside diameter to reduce the aerodynamic drag forces. This paper presents the experimental results obtained on a small scale model when a super-speed train model passing through a tunnel with small inside diameter and a partial vacuum to reduce the aerodynamic drag forces. The experiments were performed on a 1/52-scale moving model rig in which a train model with a diameter of 58 mm and a length of 603 mm was accelerated in a launching tube with 12.27 m length by means of the compressed air launcher and then passed through a tunnel model with 17.149 m length. The partial vacuum was maintained in the tunnel in order to reduce the energy consumption of the propulsion system of the super-speed tube train at super-speed of 700 km/h. In this study, the blockage ratio of train to tunnel model is 0.336. Experimental results show the nonlinear effects of the vacuum on the speed-up of the train model in the tunnel model under the partial vacuum up to 0.21 atm and at the velocity up to 684 km/h. This paper is first study for experiments on the speed-up of a super-speed train model in the partial vacuum tunnels.

• Journal of the Korean Vacuum Society
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• v.16 no.4
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• pp.235-243
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• 2007

Nowadays, in our country, large vacuum chambers for huge experimental facilities such as the tokamak fusion device, high power neural beam test stand, and space simulator have been constructed. In such a vacuum chamber of very large size, it is quite complicate to check on leakage quantitatively, while the probability of a leak is relatively high. To investigate the feasibility of applying reliably a helium leak detection to the huge vacuum chambers, and to find a reasonable methodology of choosing an optimum set-up for leak detection, several virtual constructions of the leak detection system have been analyzed by calculating the pressure distribution in the system and the helium level in the sensor part.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.162.1-162.1
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• 2010

Cavitation phenomenon has long been a difficult problem that regarded as negative event to fluid machines or industrial facilities. In the latest, however, some engineers became to understand the power of cavitation and use it to cleaning wall after developing cavitation nozzle. In this paper, we introduce new concept for power-generation system using cavitation jet flow maid by nozzle and impulse turbine in vacuum condition. The vacuum needed to make cavitation is generated naturally by Torricelli's vacuum, 10.23m effective head drop without additional power. We analyzed water's boiling and the steam's mean free path according to vacuum purity levels for nozzles and turbine blades. The nozzles make water accelerate in the neck and boil in expansion section of the nozzles. The shape of the impulse turbine is designed for absorption of the molecule's kinetic energy of the steam.