• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.2
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• pp.249-255
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• 2013

A large-sized refrigerator has a complicated inner structure such as a shelf and a rack for product loading. Therefore, when the refrigerator door is opened and closed, the temperature inside the refrigerator varies and vibrations occur due to the physical force applied for opening and closing the door. Owing to these factors, an abnormal sound is generated by the relative distortion between the inner structures. In this study, we aimed to clarify the mechanism that generates this abnormal noise inside the refrigerator using experimental approaches, and we also investigated ways by which to reduce this noise. Toward this end, we developed an experimental setup for measuring the noise, temperature, inner pressure, as well as amount of vibration, and we analyzed the main factors causing the noise based on the experimental results. Furthermore, we suggested a way by which to reduce the noise; this method can be applied in the design stage itself.

• Tribology and Lubricants
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• v.36 no.3
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• pp.139-146
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• 2020

Global warming has led to an increase in demand of eco-friendly vehicles, such as electric cars, for reducing greenhouse gas emissions, and especially, regulating carbon dioxide generation. In addition, electric vehicles are equipped with an electric drive-type hermetic scroll compressor and a refrigerant, which exhibit current and future trends of using environmentally friendly refrigerants, including R-1234yf. In this study, polyol ester-based refrigeration oils are prepared via condensation esterification of polyol and fatty acids. The oils can be combined with R-1234yf refrigerant for applications in air conditioning and cooling systems of electric vehicles. The structure of synthetic polyol esters is confirmed via ¹H-NMR and FT-IR spectrum analysis, and the composition of the polyol ester is analyzed via gas chromatogram analysis. Furthermore, kinematic viscosity, viscosity index, total acid value, pour point, and color are analyzed as fundamental physical properties of the synthetic polyol esters. The compatibility and chemical stability of the synthetic polyol ester combined with the R-1234yf refrigerant are obtained via high temperature and high pressure oil-resistant refrigerant tests. The changes in the oil color and catalyst activity are observed before and after the experiment to determine whether it is suitable as a refrigerator oil.

• Korean Journal of Materials Research
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• v.24 no.6
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• pp.293-300
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• 2014

Coal-tar pitch, a feedstock which can be heat-treated to create graphite, is composed of very complex molecules. Coal-tar pitch is a precursor of many useful carbon materials (e.g., graphite, carbon fibers, electrodes and matrices of carbon/carbon composites). Modified coal-tar pitch (MCTP) was prepared using two different heat-treatment methods and their properties were characterized and compared. One was prepared using heat treatment in nitrogen gas; the other was prepared under a pressure of 350 mmHg in air. The MCTPs were investigated to determine several properties, including softening point, C/H ratio, coke yield, formation of anisotropic mesophase and viscosity. The MCTPs were subject to considerable changes in chemical composition due to condensation and polymerization in the used-as-received coal-tar pitch after heat-treatment under different conditions. The MCTPs showed considerable increases in softening point, C/H ratio, and coke yield, compared to those of as-received coal-tar pitch. The MCTP formed by heat-treatment in nitrogen showed isotropic phases below $350^{\circ}C$ for 1 h of soaking time. However, MCTP heat-treated under high pressure (350 mmHg) showed isotropic phases below $300^{\circ}C$, and showed anisotropic phases above $350^{\circ}C$, for 1 h of soaking time. The viscosity of the MCTPs increased with increase in their softening points.

• Atmosphere
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• v.21 no.4
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• pp.391-404
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• 2011

This study investigates the impact of cumulus parameterization scheme (CPS) with different horizontal grid sizes on the simulation of the local heavy rainfall case over the Korean Peninsula. The Weather Research and Forecasting (WRF)-based real-time forecast system of the Joint Center for High-impact Weather and Climate Research (JHWC) is used. Three CPSs are used for sensitivity experiments: the BMJ (Betts-Miller-Janjic), GD (Grell-Devenyi ensemble), and KF (Kain-Fritsch) CPSs. The heavy rainfall case selected in this study is characterized by low-level jet and low-level transport of warm and moist air. In 27-km simulations (DM1), simulated precipitation is overestimated in the experiment with BMJ scheme, and it is underestimated with GD scheme. The experiment with KF scheme shows well-developed precipitation cells in the southern and the central region of the Korean Peninsula, which are similar to the observations. All schemes show wet bias and cold bias in the lower troposphere. The simulated rainfall in 27-km horizontal resolution has influence on rainfall forecast in 9-km horizontal resolution, so the statements on 27-km horizontal resolution can be applied to 9-km horizontal resolution. In the sensitivity experiments of CPS for DM3 (3-km resolution), the experiment with BMJ scheme shows better heavy rainfall forecast than the other experiments. The experiments with CPS in 3-km horizontal resolution improve rainfall forecasts compared to the experiments without CPS, especially in rainfall distribution. The experiments with CPS show lower LCL(Lifted Condensation Level) than those without CPS at the maximum rainfall point, and weaker vertical velocity is simulated in the experiments with CPS compared to the experiments without CPS. It means that CPS suppresses convective instability and influences mainly convective rainfall. Consequently, heavy rainfall simulation with BMJ CPS is better than the other CPSs, and even in 3-km horizontal resolution, CPS should be applied to control convective instability. This conclusion can be generalized by conducting more experiments for a variety of cases over the Korean Peninsula.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.3
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• pp.213-221
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• 2002

The emission characteristics of particulate matter (PMs) and heavy metals from hazardous industrial wast incinerators were investigated. The particle size distribution (PSD) of PM-10 showed different patterns for two tripes of incinerators; stoker and rotary kiln. However both types showed bimodal form at inlet of air pollution control devices (APCD) and each peak (mode) is located at smaller than 1 ${\mu}{\textrm}{m}$ and near 10 ${\mu}{\textrm}{m}$. It could explain the growth of fine PM by nucleation/coagulation/condensation of metal vapors for fine mode. The PSD of PM-10 after APCD was also influenced by APCD types that had different collection mechanism, and both electrostatic precipitator and bag filter showed less collection efficiency for particles ranged from 0.2 to 0.4 ${\mu}{\textrm}{m}$ and led to a mode in the range of 0.2 to 0.8 ${\mu}{\textrm}{m}$. However the hag filter showed two modes of PSD, while the electrostatic precipitator had one peak. The PMs and heavy metals emission factors, the representative value of emission quantity for sources, for tested facilities were developed. The emission factor of uncontrolled total PM and PM-10 were 14.7 and 7.05 kg/ton waste, respectively. The emission factors from this study were a little bit different with those from US EPA AP-42. It may thus be appropriate to use these results in the course of developing national emission factors.

• Environmental Engineering Research
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• v.25 no.2
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• pp.222-229
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• 2020

Membrane assisted condenser is an innovative membrane operation that exploits the hydrophobic nature of microporous membranes to promote water vapor condensation and recovery. It can be used for water and chemicals recovery from waste gaseous streams. In this work, the testing of membrane condenser for water and ammonia recovery from synthetic streams (i.e., a saturated air stream with ammonia) simulating the plume of cooling tower is illustrated. The modeling of the process was carried out for predicting the membrane-based process performance and for identifying the minimum operating conditions for effectively recovering liquid water. The experimental data were compared with the results achieved through the simulations showing good agreement and confirming the validity of the model. It was found that the recovery of water can be increased growing the temperature difference between the plume and the membrane module (DT), the relative humidity of the plume (RH^plume) and the feed flow rate on membrane area ratio. Moreover, the concentration of NH₃ in the recovered liquid water increased with the growing DT, at increasing NH₃ concentration in the fed gaseous stream and at growing relative humidity of the feed.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.26 no.4
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• pp.399-406
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• 2000

With the increase of industrialization, leisures, sports activities and traffic, the risk of trauma has increased markedly. Midfacial bones are relatively common sites of trauma, and are difficult sites of correct reduction and reconstruction, because midface is composed of mostly thin cortical bone surrounding cavities filled with either air or fat with discrete areas of bony condensation. A clinical study on 208 patients with midfacial bone fracture who visited Sanggye Paik Hospital during 5 years($1990{\sim}1995$) was done by analyzing sex, age, cause, fracture site, treatment method, complication and involvement of other body part, etc. The results obtained were as follows : 1. The occurrence was more frequent in male than in female with ratio of 2.7 : 1 and most frequently in twenties. 2. Traffic accident was the most common cause of midface fractures. 3. Zygoma was the most frequently occurred site(50%) of midface fractures. 4. Simple fracture(75%) was more frequently occurred than compound fracture(25%). 5. As treatment method, open reduction(76.4%) was used more frequently than closed reduction(23.6%) 6. Generally, operations are done in 5 days after admission(59.1%), and intermaxillary fixation was done in 78.4% of cases. 7. Teeth and alveolar bone damages were occurred in 32.2% of cases. 8. Other injuries that were related to midface fracture occurred in 63.3% of cases. 9. Post-operative complications occurred in 9% of cases.

• KIEAE Journal
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• v.14 no.6
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• pp.75-80
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• 2014

Development of temporary housing for victims whose house damaged is required. In this study is to plan temporary house space 'Mobile Energy Shelter House ; MeSH' that can be inhabited for a long time. And measure the indoor Environmental performance. 'Mobile Energy Shelter House : MeSH' was made by reflecting Passive Design, Universal Design. Also, thermal insulation that meets the 'Korea standard insulation' for use low energy. Winter season, measuring temperature, humidity, air velocity and radiation temperature when floor heating that temperature controllers ware installed is used. Confirmed the data for the 8:00pm to 8:00am because evening hours are expected as residents live. Average outdoor temperature was $-11.3^{\circ}C$ and Indoor temperature was from $16.09^{\circ}C$ to $20.63^{\circ}C$. Calculated the TDRi of the window surface for checked condensation risk. TDRi value was 0.185. Furthermore, PMV value was -0.08 to -0.85. It was satisfied to ISO comfort criterion ranged.

• Architectural research
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• v.16 no.4
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• pp.203-210
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• 2014

The packaged terminal air conditioner, the typical cooling system for the residential buildings, consumes a large amount of electricity in a short period time during peak hours. In order to reduce the peak load and conserve the electricity, the thermally activated building system can be used as a secondary system to handle the partial cooling load. However, the thermally activated building system may cause condensation and under-cooling. Thus, design of both systems should be performed with careful investigation in characteristics of both systems to amplify the advantages. Since the thermally activated building system has the time-delay effect which may cause under-cooling, the system is designed to handle the base load of the building. Hence, simple simulation with EnergyPlus was performed to observe the characteristics of cooling load in residential buildings. Once the possible range of the load handling ratio of the thermally activated building system was decided, characteristics of system was analyzed in terms of hardware component and operation parameters. The hardware components were analyzed in plant and system aspects and the operation parameter was evaluated in the thermal comfort aspect. As the load handling ratio increased, the thermal comfort increased due to the lower radiant mean temperatures. Within the range of thermal comfort, the several adjustments were made in setpoint temperature and electricity consumptions of difference cases were observed to decide which components and parameters were important for designing the systems.

• Korean Journal of Animal Reproduction
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• v.26 no.4
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• pp.353-360
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• 2002

Although successful pronuclear formation and apposition were seen in porcine oocytes following mouse sperm injection, little is known on the morphology of male and female pronuclei following sperm injection. The objective of this study is to describe the ultrastructure of porcine zygote following murine sperm injection in relation to the chronology of pronuclear S phase. At 40h ~ 44h following in vitro maturation, Cumulus cells were removed in TCM-HEPES with 0.1% hyaluronidase. Then, spermatozoa was injected into the cytoplasm of oocytes. After. injection, all oocytes were transferred to NCSU23 medium and cultured at 39$^{\circ}C$ under 5% $CO_2$ in air. Oocytes were fixed in 2% glutaraldehyde in Dulbeccos phosphate-buffered saline and observed by Transmission Electron Microscopy. Nuclear precursor bodies were observed in each pronucleus. A cluster of large and small granules was attached in the nucleolus precursor body. After the apposition of male and female chromatin, chromatin condensation was observed throughout the nucleoplasm and nucleolus precursor bodies and condensed chromatin in contact with clusters of small and large granules and the nuclear envelope were found in apposed pronuclear regions. These results suggest that non-species specific nuclear cytoplasmic interactions take place during pronuclear formation and apposition following sperm injection.