• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.62.1-62.1
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• 2018

Galaxies in the cluster environment interact with the intracluster medium (ICM), losing the interstellar medium (ISM) and alternating their evolution. Observational evidences of the extraplanar ISM stripped by the ICM's ram pressure are prevalent in HI imaging studies of cluster galaxies. However, current theoretical understanding of the ram pressure stripping (or ICM-ISM interaction in general) is still limited mainly due to the lack of numerical resolution at ISM scales in large-scale simulations. Especially, self-consistent modeling of the turbulent, multiphase ISM is critical to understand star formation in galaxies interacting with the ICM. To achieve this goal, we utilize the TIGRESS simulation suite, simulating a local patch of galactic disks with high resolution to resolve key physical processes in the ISM, including cooling/heating, self-gravity, MHD, star formation, and supernova feedback. We then expose the ISM disk to ICM flows and investigate the evolution of star formation rate and the properties of the ISM. By exploring ICM parameter space, we discuss an implication of the simple ram pressure stripping condition (so called the Gunn-Gott condition) to the realistic ISM.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.11
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• pp.1659-1666
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• 2001

The objective of this study was to investigate the characteristics of air flow and heat transfer caused by trapezoid rods array in impinging air jet system. Trapezoid rods have been set up on front of flat plate to act as a turbulence promoter. Local Nusselt numbers were determined as a function of three parameters : (a) the space from re(Is to heating surface(C=1, 2, 4mm), (b) the pitch between each rods(P=30, 40, 50mm), (c) the distance from nozzle exit to flat plate(H/B=2, 6, 10). The measurements were compared with those of the experiment without trapezoid rods. As a result, when rods are installed in front of the impinging palate, the acceleration of the flow and the eddies due to the rods seem to contribute to the heat transfer enhancement. Heat transfer performance was best under the condition of C=1mm and as the pitch is 30mm. The maximum rate of heat transfer augmentation is about 1.9 times greater compared to that without trapezoid rods.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.10
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• pp.823-831
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• 2007

This paper presents the experimental and simulation study of a loop heat pipe (LHP) that can be applied to present electronics, space missions and thermal control systems. The present experimental study was carried out employing sintered alumina ceramic wick ($d=2.96\;{\mu}m$, ${\phi}=0.61$). High purity R-134a, R-22 and water were also used as alternative working fluids in addition to ammonia. The experimental study showed that the maximum heat transfer performance for the test LHP in the vertical top heating mode was over 100 Watts when ammonia was used as the working fluid. The simulation results have been compared with the experimental results to validate a simulation model based on the thermal resistance network that was developed to evaluate the performance of LHPs, focusing on their prospective applications in electronics. The simulation model is based on the loop overall energy, mass, and momentum balance. The simulation program can predict the effects of various parameters which affect the performance of LHP within 5% compared with the experimental results.

• Korean Journal of Human Ecology
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• v.18 no.2
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• pp.509-522
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• 2009

This is a basic study to improve air quality of school classrooms in winter time. The purposes are to check indoor thermal and air environment in school classrooms during winter and to analyze influencing factors on indoor environment. The measurements of students' physical elements with questionnaire surveys were carried out in a total of 6 classrooms. As a result, this research shows that the temperature of one classroom was below indoor thermal standard level, three classrooms had lack of heat, and two classrooms are heated much, which induce relatively low humidity. All of 6 classrooms had lack of ventilation, being high level of $CO_2$ concentration and 2 classrooms are in condition of high PM10 concentration. The majority of students(76%) answered that the cause of their 'heated space syndrome' is because of the lack of ventilation. Students' opening windows for ventilations is hardly carried out at normal times, except that indoor temperature is over standard. That is, we can suggest one of solutions, which is to enable students to operate heating and ventilating system by themselves according to students' physical condition.

• KIEAE Journal
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• v.12 no.1
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• pp.55-63
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• 2012

Ever since China declared its economic reform and opening up policies in the late 1970s, it has been under rapid change. The modernization process of China's history and society was in progress at a pace far too fast in the middle of the 20th century, and housing sector was no exception. This study is based on the houses showing enough changes of modernization process in the rural area, and with a comparative analysis based on the field survey data conducted respectively in the present decade, considered the architectural elements and changing aspects of housing lifestyle. This paper will explore (1) The changes and the status of the members of the village, (2) The changes and the status of the structures, (3) The changes and the status of the main areas of housing, (4) The changes and the status of the heating system and the kitchen that crucially affects the space size among the housing facilities, and (5) The changes and the status of the bathroom. Through this analysis, this paper will firstly look at how traditional rural houses has been changed under the modernization process, and will objectively evaluate the modernization process of the traditional rural houses so that it will help find a way of improving China's rural houses in the future.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.142.2-142.2
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• 2011

Hydrodynamic simulations of gas clouds in the central hundred parsecs region of the Milky Way that is modeled with a three-dimensional bar potential are presented. Our simulations consider realistic gas cooling and heating, star formation, and supernova feedback. A ring of dense gas clouds forms as a result of $X_1-X_2$ orbit transfer, and our potential model results in a ring radius of ~200 pc, which coincides with the extraordinary reservoir of dense molecular clouds in the inner bulge, the Central Molecular Zone (CMZ). The gas clouds accumulated in the CMZ can reach high enough densities to form stars, and with an appropriate choice of simulation parameters, we successfully reproduce the observed gas mass and the star formation rate (SFR) in the CMZ, ${\sim}2{\times}10^7\;M_{\odot}$ and ${\sim}0.1\;M_{\odot}/yr$. Star formation in our simulations takes place mostly in the outermost $X_2$ orbits, and the SFR per unit surface area outside the CMZ is much lower. These facts suggest that the inner Galactic bulge may harbor a mild version of the nuclear star-forming rings seen in some external disk galaxies. We also find that the stellar population resulting from sustained star formation in the CMZ would be enlogated perpendicularly to the main bar, and this "inner bar" can migrate the gas in the CMZ further down to the central parsecs region.

• KIEAE Journal
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• v.4 no.4
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• pp.61-68
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• 2004

Daylight is a critical factor in architecture, as it helps enhance the working efficiency and pleasantness of the people working inside, in addition to reduce the power consumption in heating and cooling and make the interior space brighter. There are many kinds of glazing and daylighting systems. At present, research and efforts for their development are carried out, alongside quantitative evaluation. This study aims to present basic materials to be used to design proper glazing and daylighting systems in architecture based on a quantitative evaluation by scale models of existing office buildings. The result of the study can be summarized as follows. 1)As a result of the experiment, it appeared that the ratio of the interior illumination (i.e. at the working table, ceiling and wall) against the outdoor illumination increases at a constant rate, as the transmittance of the glazing goes up. 2) It was found that the SIR(Sunlight Illuminance Ratio) of a separated window system goes up by 20-50% at the rear part than in the case of an ordinary window system.

• Nuclear Engineering and Technology
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• v.38 no.4
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• pp.343-352
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• 2006

Convenient analytical tools for evaluation of the aperiodic and the fluctuating instabilities of the passive residual heat removal system (PRHRS) of an integral reactor are developed and results are discussed from the viewpoint of the system design. First, a static model for the aperiodic instability using the system hydraulic loss relation and the downcomer feedwater heating equations is developed. The calculated hydraulic relation between the pressure drop and the feedwater flow rate shows that several static states can exist with various numbers of water-mode feedwater module pipes. It is shown that the most probable state can exist by basic physical reasoning, that there is no flow rate through the steam-mode feedwater module pipes. Second, a dynamic model for the fluctuating instability due to steam generation retardation in the steam generator and the dynamic interaction of two compressible volumes, that is, the steam volume of the main steam pipe lines and the gas volume of the compensating tank is formulated and the D-decomposition method is applied after linearization of the governing equations. The results show that the PRHRS becomes stabilized with a smaller volume compensating tank, a larger volume steam space and higher hydraulic resistance of the path $a_{ct}$. Increasing the operating steam pressure has a stabilizing effect. The analytical model and the results obtained from this study will be utilized for PRHRS performance improvement.

• Journal of the Korean Solar Energy Society
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• v.25 no.2
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• pp.63-69
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• 2005

This study is the survey of a transition procedure of building services systems(heat source, HVAC, water supply) through the survey of existing office buildings, building design documents. The preference & major consideration of system selection is the engineer's opinions. The results of this survey can be used in selection of building services system design. In this survey, "Hot & cold water generator system" and "single duct CAV+FCU system", "Elevated water tank system" are selected. The most important consideration in system selection is the energy saving in heat source system, and comfort in HVAC system, and water pressure in water supply system. They prefer "steam boiler+absorption chiller system" for heat source system, "steam boiler+ice thermal storage system", "hot & cold water generator system", "district heating+absorption chiller system" : "single duct CAV+FCU system" and "single duct VAV+convector system" for HVAC system: and "booster pump system" for water supply system.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.2109-2113
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• 2008

As the standard of living is higher, the passengers using public transportations desire better qualities of environment as well as more comfortable indoor environment. In case of train, the passengers' comfort in passenger cabin is one of the most important elements to be competitive with other transport systems. The indoor air quality of the cabin should be managed properly, because many passengers travel for a long time in the small space of $144\;m^3$. For proper management of the air quality, the heating, ventilation and air conditioning (HVAC) system is required for the ventilation of the compartment. To maintain comfortable environment in the compartment, the automatic ventilation system is needed to exchange the indoor air with fresh air or clean indoor air. In this study, we investigated the indoor air quality (PM-10, $CO_2$, and VOCs) in the compartment of train. In addition, type and pattern of PM-10 has been analyzed through the clustering analysis. Based on the analysis, we could found that the fine particulate matters in the compartment can be a serious hazard to human. To control the concentration of PM-10 and $CO_2$ air cleaners were developed. Through this study, it is expected that people who take a train will be in a more comfortable environment.