• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.35.2-35.2
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• 2015

We present the results of simultaneous observations of the H2O and SiO masers emitted from the circumstellar envelopes (CSEs) of the late-type stars. These observations have been carried out at the four frequency bands (K, Q, W and D bands) using KVN to apply the source frequency phase referencing (SFPR) analysis to the maser lines. We obtain the relative positions between the H2O and the SiO maser spots by using the SFPR method, which are very important to study the physical links between the inner and the outer parts of the CSEs of the late-type stars. The relative positions between the SiO maser spots of the different transitions are also obtained very accurately, which are very crucial to investigate the pumping mechanism of the SiO maser lines. From our results, the capability of the simultaneous multi-band observation of KVN is proved to be powerful to study the complicated physical environments of the CSEs and the stellar evolution of the late-type stars.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.992-996
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• 2004

Small electric motors in an automobile perform various tasks such as engine cooling, pumping, and in heating, ventilating, and air-conditioning (HVAC) system. At present, most of dc motors are supplied by 12V or 24V batteries. However, DC motors surfer from lack of efficiency, low life cycles and unreliability. Therefore, there is a growing interest in substituting DC motors for advanced AC motors including switched reluctance motors. Although there are several other forms SRM converters, they are either unsatisfactory to the control performance or unsuitable for the 12V-battery powered 3-phase SRM drives. Taking into account the requirement for effective operation and simplicity structure of converter in the limited internal environment of automobiles, the author inclines toward selecting the modified C-dump converter as well as the energy efficient C-dump converter. This is so that more economical and efficient converter topology in automobile industries can be utilized. This paper describes the foundation for the design and development of a 12V-250W-3000rpm SRM drives for automobiles. Furthermore, complete circuit, computer simulation and experiment results are presented to verify the performance of the C-dump converters.

• Korean Chemical Engineering Research
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• v.50 no.6
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• pp.988-993
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• 2012

Energy and cost analysis of the preprocessing for carbon capture and storage transportation such as supercritical compression and liquefaction is done using chemical simulation model. Direct compression to supercritical phase (process 1-1), liquefaction and pumping (process 1-2), carbon dioxide compression and expansion as a refrigerant itself (process 2), usage of other refrigerant with compression and expansion (process 3-1), with absorption chiller (process 3-2), cascade refrigeration (process 3-2) have been simulated and evaluated. The specific cost is about 4 to 7 $/ton.

• Korean Journal of Optics and Photonics
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• v.5 no.1
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• pp.84-89
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• 1994

A tunable pulsed dye laser was operated in a single longitudinal mode by injection locking with a cw ring dye laser. A doubled Nd:YAG laser was used as the pumping source. Phase sensitive detection technique was applied to maintain the required match between the master laser frequency and the slave resonator cavity length. The fluctuation of the center frequency of the pulsed laser was < 10 MHz, and the pulse duration (FWHM) was 6 ns. The linewidth measured by scanning confocal interferometer was 130 MHz. When pumped by 50 mJ of the doubled Nd:YAG laser, the output energy of the pulsed dye laser was 2 mJ and the peak power was 330 kW. 30 kW.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.489-492
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• 2007

Understanding the thermohydraulic processes in the aquifer is necessary for a proper design of the aquifer thermal energy utilization system under given conditions. Experimental and numerical test were accomplished to evaluate the relationship between the geothermal heat exchanger operation and hydrogeological conditions in the open-loop geothermal system. Sand tank experiments were designed to investigate the open-loop geothermal system. Water injection and extract ion system as open-loop borehole heat exchanger was applied to observe the temperature changes in time at injection well, extraction well and ambient groundwater. The thermohydraulic transfer for heat storage was simulated using FEFLOW for two cases of extraction and injection phase operation in sand tank model. As one case, the movement of the thermal plume was simulated with variable locations of injection and extraction well. As another case, the simulation was performed with fixed location of injection and extraction well. The simulation and experimental results showed that the temperature distribution depends highly on the injected water temperature and the length of injection time and the groundwater flow and pumping rate sensitively affect the heat transfer.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.114-116
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• 2005

Natural attenuation has been actively studied and often selected as final clean-up process in remediation of contaminated ground-water and soil for the last decade. Accordingly, understanding of natural processes affecting the fate and transport of contaminants in the subsurface becomes important for a success of implementation of the natural remediation strategy, Contaminant advection and diffusion processes in the unsaturated zone are naturally related to environmental changes in the atmosphere. The atmospheric pressure changes affecting the transport of contaminants in the subsurface are investigated in this study. Moisture content, trichloroethylene (TCE) concentration, temperature, and pressure variations in the subsurface were measured for the July, August, November, and December 2001 at Picatinny Arsenal, New Jersey. These data were used for a one-phase flow and one-component transport model in simulating the soil-gas flow and accordingly the TCE transport in the subsurface in accordance with the atmosphere pressure variations at the surface. The soil-gas velocities during the sampling periods varied with a magnitude of $10^{-6}\;to\;10^{-7}\;m\;s^{-1}$ at land surface. The TCE advection fluxes at land surface were several orders of magnitude smaller than the TCE diffusion fluxes. A sensitivy analysis indicated that advection fluxes were more sensitive to changes in geo-environmental conditions compared to diffusion fluxes. Of all the parameters investigated in this study, moisture content has the most significant effect on TCE advection and diffusion fluxes.

• Korean Journal of Hydrosciences
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• v.8
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• pp.31-40
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• 1997

Flow carrying capacity of water distribution systems is getting reduced by deterioration of pipes in the systems. The objective of this paper is to present a managerial decision-making model for the rehabilitation of water distribution systems with a mininum cost. The decisions made by the model also satisfy the requirements for discharge and pressure at demanding nodes in the systems. Replacement cost, pipe break repair cost, and pumping cost are considered in the economic evaluation of the decision along with the break rate and the interest rate to determine the optimal replacement time for each pipe. Then, the hydraulic integrity of the water distribution system is checked for the decision by a pipe network simulator, KYPIPE, if discharge and pressure requirements are satisfied. In case the system does not satisfy the hydraulic requirements, the decision made for the optimal replacement time is revised until the requirments are satisfied. The model is well applied to an existing water distribution system, the Seoul Metropolitan Water Supply System (1st Phase). The results show that the decisions for the replacement time determined by the economic analysis are accepted as optimal and hydraulic integrity of the system is in good condition.

• Journal of Biosystems Engineering
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• v.27 no.4
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• pp.327-334
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• 2002

In this study, energy conversion from thermal energy to mechanical power by using n-pentane was tested and exergy variation, cycle number, water quantity pumped and thermal efficiency were analyzed. The energy conversion was done and the water head could be ten meters on the experimental conditions. The operating temperature range of cycle was recommended to be around the liquid-vapour saturation temperature of the working fluid on the viewpoint of the maximum work. The cycle diagram was analyzed by the exergy analysis. For the constant water head, the cycle number was decreased and the water quantity per day was increased and thermal efficiency become higher when the water quantity per cycle become increasing. For the constant pumping water quantity per cycle, cycle number and the water quantity per day was decreased and the thermal efficiency become higher because the saturation temperature become higher when the water head become higher.

• Applied Science and Convergence Technology
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• v.25 no.6
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• pp.120-123
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• 2016

The rotor of a turbomolecular drag pump is generally made of an aluminum alloy. Its surface finish is affected by various processes that the rotor itself undergoes during the manufacturing phase. The impact of different surface finishes on the pumping performances of a turbomolecular pump has been mainly investigated by Sawada et al [1]. The present work aims to broaden the previous bibliographic study to the drag stages of a turbomolecular pump by testing the impact of different surface finishes on the compression ratio of the pump. Experimental tests have been made focusing on two processes: the corundum sandblasting and the glass microspheres shot-peening. Both the processes flatten and/or physically remove EDM melted spheres; in particular, blasted surfaces obtained by glass shot-peening are generally smoother than surfaces obtained by corundum sandblasting. In order to characterize the surface texture left by such processes, preliminary surface roughness measurements have been made on the drag rotor disks of several pumps. The experimental tests conducted on both sandblasted and shot-peened rotors confirms previous results obtained on the turbo stages by Sawada et al. [1], showing that the average roughness of the surface has an impact on the compression ratio of the pump; in particular, an increment in the surface roughness causes a corresponding increment in the compression ratio of the pump and vice versa. For the tested pumps, the higher surface roughness gives a factor of increment of about 2 on the measured hydrogen maximum compression ratio of the pump.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.416-422
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• 2007

The application analysis of bubble pump on the domestic solar water heater system is presented. The system investigated in this study is a passive device, self pumping and self regulating. It was test to use the bubble pump on solar water heater system. The test experiment has been taken on the existed vacuum tube about the efficiency, working fluid temperature and pressure and circulated power. In order to check the working temperature and working pressure effectively, the bubble pump was test separated from the solar water heater. The equipment consists of the bubble pump, heater and heat exchanger. The main structure of bubble pump was design depend on the character of two phase flow. The complete system was instrumented to measure pressures, temperatures and their relationship with the solar radiation intensity. The theory analysis of design bubble pump has been given and the experiment result analysis has been included in the paper.