• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.33.1-33.1
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• 2020

Ram pressure stripping (RPS) which is known to be one of the key effects that can remove the interstellar gas in the dense environment, can be described as a simple momentum transfer relation (Gunn & Gott 1972). However, it has been suggested that the actual gas stripping process is likely more complicated than Gunn & Gott's prescription due to the complexity of gas physics such as compression, cooling and heating. By comparing the gas truncation radius predicted by theory with the stripping radius measured from the HI observation of Virgo cluster galaxies, we attempt to verify how well the RPS process can be understood by momentum transfer alone. Among the sample of galaxies undergoing active RPS, we generally find a good agreement between what is predicted and what is observed within the measurement uncertainties. However, those galaxies with the signs of other environmental effects than RPS such as tidal interaction, and/or the ones likely at relatively early or later stages of RPS show some offsets between the theory and the observation. These results imply that Gunn & Gott's formula works reasonably well in a broad sense when the RPS is a dominant process and the surrounding environment at the current location of the sample can be well defined. Otherwise, the impact of the second mechanism, as well as the (current and past) environment of the sample, should be more carefully reviewed to assess the impact of RPS on galaxy evolution.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.10
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• pp.515-529
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• 2017

EnergyPlus, which is widely used in various fields, provides Simple Window Model, a window model that can be used practically. However, the results of building load using the model are different from those of the standard model. The main cause of the deviation by Simple Window Model was analyzed to be due to the assumption that all windows were considered as single layer. The purpose of this study is to propose a window model that improves the cause of deviation by Simple Window Model and can be easily calculated from the algebraic relations. The proposed window model solved the heat balance equation algebraically by using seven window characteristic coefficients. The coefficient relationships consisted of the heat transmission coefficient and solar heat gain coefficient as input parameters make practical use and calculation possible. As a result of comparing the deviation between each window model by implementing the dynamic analysis method, the proposed window model showed that the deviation of the total heating/cooling energy consumption was reduced to 1/3 compared to Simple Window Model for one year. Although the maximum energy consumption did not show any significant improvement, the indoor temperature evaluation showed significantly reduced deviation.

• Journal of Welding and Joining
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• v.27 no.5
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• pp.62-67
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• 2009

Welding deformation during the assembly process is affected by not only local shrinkage due to rapid heating and cooling, but also root gap and misalignment between parts to be welded. Therefore, the prediction and control of welding deformation have become of critical importance. In this study, it was focused on the development of the 3-axis apparatus for real-time measurement of the welded deformation. To achieve the objective, a D-H algorithm has been carried out to check the behavioral and performance evaluation for the developed robot. The sequence experiments were taken the base materials of $400{\times}200{\times}4.5mm$ plate for butt welding. The real-time experimental measurements are in good agreement with the measured results.

• Journal of Korea Society of Industrial Information Systems
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• v.20 no.1
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• pp.37-42
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• 2015

This paper highlights the home concentrate device(HCD) that integrates the data reading and display of the six types of meters (water, hot water, heating, cooling, gas and electricity) used in Korean residential areas. Unlike the conventional system which utilizes single MCU, the developed system uses two MCUs for one MCU to gather the meter readings and for the other MCU to communicate to the server computer. Hard ware design, communication protocols, LCD design and program structures are discussed and the test results are shown in this paper. With the implementation of integrated meter reading, the developed system can increase the popularity of automatic meter reading(AMR) with its better scalability, pricing, installation fee, maintenance and faster response.

• Solar Energy
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• v.12 no.1
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• pp.72-80
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• 1992

This paper is concerned with the accurate estimation of the thermal mass effect on the variation of indoor temperature for residential buildings. To carry out the analysis here, the method called "PSTAR(Primary and Secondary Terms Analysis and Renormalization)" has been extensively used. This method was originally developed by the National Renewable Energy Laboratory(NREL) in the United States. The test results reported here represent two extreme cases of the interior thermal mass, which demonstrate its effect on the interior thermal environment as well as on the overall thermal behavior of the building structure. The monthly heating and cooling loads are also extrapolated by using the renormalized model, which are crucial in designing and refurbishing HVAC systems for the building.

• Solar Energy
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• v.17 no.2
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• pp.3-11
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• 1997

In conventional heat and vent dryer, both sensible and latent heat could not be recovered from the exhaust air, but this problem could be solved by introducing a heat pump to a conventional dryer, having a connection with cooling, dehumidifying and heating of heat pump. In this work, HFC134a as a substitute refrigerant of CFC12 adopted in heat pump and a batch type is also introduced. The variables affected on the system performance are holding temperature of a drying chamber, bypass air ratio, degree of superheat and refrigerant flowrate, etc. The moisture contents were decreased curvilinearly in the range of $86{\sim}75%$ on the wet basis. Under the constant drying temperature, the face velocity plays an important role to the drying performance. The COPs are increased in accordance with the air velocity, on the other hand the SMERs are gradually decreased.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.4
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• pp.177-181
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• 2017

Auxiliary power supply for railway vehicle is a equipment that focuses on the service of passengers in a vehicle. It supplies power to controllers used in heating and cooling devices, fluorescent lamps, batteries and many other electrical equipments. Most of the auxiliary power supply for railway vehicle are mainly used for the round trips and circulation routes within the metropolitan area and have a capacity of 170~200 kVA. In this study, we developed the auxiliary power supply capacity to 240kVA for 200km/h class. As such, the auxiliary power supply is an important device for securing the reliability and safety of the railway vehicle and improving the passenger convenience, so the performance verification of the performance must be ensured. In this paper, 240kVA auxiliary power supply is developed. Also, performance of the auxiliary power supply manufactured through the analysis of various characteristics related to the auxiliary power supply was confirmed while operating the actual line.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.12
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• pp.2358-2367
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• 1992

This paper deals with preliminary design conditions for a thermally actuated Vuilleumier refrigerator/heat pump. The previously reported approximate adiabatic analysis which is based on the 8-volume model makes it possible to evaluate exchanged heats per cycle as well as cyclic pressure, temperature and mass variation of each working volume. Calculated results reveal not only there exists an optimum value for the phase angle and the swept volume ratio maximizing a specific thermal output, but also design parameters can be determined independently of each other. Under a given combination of operating temperature levels, the optimum conditions for refrigeration are different from those for heat pumping and the differences between two operating modes become larger with decreasing the dead volume ratio. Both the optimum phase angle and the optimum swept volume ratio are increased asymptotically toward 0.5 pi and 1.0 respectively, as the dead volume ratio approaches to unity. When a VM machine is used for cooling and heating simultaneously, the design parameters should be carefully determined to reach the best performance.

• Journal of Korean Ophthalmic Optics Society
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• v.6 no.2
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• pp.111-114
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• 2001

This paper presents the influence of the additive composition on flexural strength and hardness of SiC-TiC composites materials for spectacle lens cutting materials. The materials were hot-pressed at $1800^{\circ}C$ and subsequently annealed at $1910^{\circ}C$ for 3h. The heating rate was $15^{\circ}C/min$ and the cooling rate about $25^{\circ}C/min$ in from the sintering temperature to $1300^{\circ}C$. The growth of particles of spectacle lens cutting materials was analysed by SEM and crystalline phases were discussed by x-ray diffractometry. Typical fracture toughness and hardness of materials for spectacle lens cutting were $6.1MPa{\cdot}m^{1/2}$ and 14.9 GPa, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.176-177
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• 2006

Two kinds of alumina nanofluids are prepared by dispersing $Al_2O_3$ nanoparticles m transformer oil. The thermal conductivity of the nanoparticle-oil mixtures increases with particle volume fraction and thermal conductivity of the solid particle itself. The $Al_2O_3$ nanoparticles at a volume of 0.5% can increase the thermal conductivity of the transformer oil by 5.7%, and the overall heat transfer coefficient by 20%. From the natural convection test using a prototype transformer, the cooling effect of $Al_2O_3$-oil nanofluids on the heating element and oil itself is confirmed. However, excessive quantities of the surfactant have a harmful effect on viscosity, and thus it is strongly recommended to control the addition of the surfactant with great care.