• Journal of Environmental Impact Assessment
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• v.22 no.4
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• pp.329-343
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• 2013

According to previous studies, the increased air temperature can lead to change of thermal stratification structure of lakes and reservoirs. The changed thermal stratification may result in alteration of materials and energy flow. The objective of this study was to predict the effect of climate change on the water temperature and stratification structure of Daecheong Reservoir, located in Geum River basin of Korea, using a three-dimensional(3D) hydrodynamic model(ELCOM). A long-term(100 years) weather data set provided by the National Institute of Meteorological Research(NIMR) was used for forcing the 3D model. The model was applied to two different hydrological conditions, dry year(2001) and normal year(2004). It means that the effect of air temperature increase was only considered. Simulation results showed that the surface water temperature of the reservoir tend to increase in the future, and the establishment of thermal stratification can occur earlier and prolonged longer. As a result of heat flux analysis, the evaporative heat loss can increase in the future than now and before. However, the convective heat loss and net long wave radiation from water surface decreased due to increased air temperature.

• Atmosphere
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• v.33 no.5
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• pp.505-517
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• 2023

This study investigates the impacts of carbon neutrality and air quality control policies on near-term climate change in East Asia, by examining three Shared Socioeconomic Pathways (SSPs) scenarios from five climate models. Specifically, low carbon and strong air quality control scenario (SSP1-1.9), high carbon and weak air quality control scenario (SSP3-7.0), and high carbon and strong air quality control scenario (SSP3-7.0-lowNTCF) are compared. For these scenarios, the near-term climate (2045-2054 average) changes are evaluated for surface air temperature (SAT), hot temperature extreme intensity (TXx), and hot temperature extreme frequency (TX90p). In all three scenarios, SAT, TXx, and TX90p are projected to increase in East Asia, while carbon neutrality reduces the increasing rate of SAT and hot temperature extremes. Air quality control strengthens the warming rate. These opposed mitigation effects are robustly forced in all model simulations. Nonetheless, the impact of carbon neutrality overcomes the impact of air quality control. These results suggest that fast carbon neutrality, more effective than an air quality control policy, is necessary to slowdown future warming trend in East Asia.

• Journal of the Korean Ceramic Society
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• v.55 no.6
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• pp.618-624
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• 2018

We developed a mass production method that simultaneously controls the phase transformation and crystal size of $TiO_2$ coatings on multiwalled carbon nanotubes (MWCNTs). Initially, MWCNTs were successfully coated with amorphous 15-20-nm-thick $TiO_2$ by an in-situ sol-gel method. As the calcination temperature increased in both air and argon atmospheres, the amorphous $TiO_2$ was gradually transformed into the fully anatase phase at approximately $600^{\circ}C$, a mixture of the anatase and rutile phases at approximately $700^{\circ}C$, and the fully rutile phase above approximately $800^{\circ}C$. The crystal size increased with increasing calcination temperature. Moreover, above $600^{\circ}C$, the size of crystals formed in air was approximately twice that of crystals formed in argon. The reason is thought to be that MWCNTs, which continuously supported the stresses associated with the reconstructive phase transformation, disappeared owing to complete oxidation in air at these high temperatures.

• Journal of Korean Society for Atmospheric Environment
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• v.28 no.6
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• pp.615-631
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• 2012

This study provides an evaluation for capability of Integrated Climate and Air quality Modeling System (ICAMS) on future regional scale climate projection. Temperature and precipitation are compared between ground-level observation data and results of regional models (MM5) for the past 30 years over the Korean peninsula. The ICAMS successfully simulates the local-scale spatial/seasonal variation of the temperature and precipitation. The probability distribution of simulated daily mean and minimum temperature agree well with the observed patterns and trends, although mean temperature shows a little cold bias about $1^{\circ}C$ compared to observations. It seems that a systematic cold bias is mostly due to an underestimation of maximum temperature. In the case of precipitation, the rainfall in winter and light rainfall are remarkably simulated well, but summer precipitation is underestimated in the heavy rainfall phenomena of exceeding 20 mm/day. The ICAMS shows a tendency to overestimate the number of washout days about 7%. Those results of this study indicate that the performance of ICAMS is reasonable regarding to air quality predication over the Korean peninsula.

• International Journal of Air-Conditioning and Refrigeration
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• v.15 no.4
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• pp.182-190
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• 2007

Refrigeration and air-conditioning equipments are indispensable products in this civilized society. However, discharged refrigerants used in the equipments and exhausted carbon dioxide to drive the refrigeration and air-conditioning equipments are related to serious environmental problems and energy problems. Especially, the destroyed ozonosphere by the discharged refrigerants and the increased normal temperature by carbon dioxide and fluorocarbon refrigerants (green house gases) are sounded as serious global problems. For alleviating these problems, environmental-friendly refrigeration and air-conditioning equipments must be developed and will spread soon. To develop new equipment, a suitable refrigerant for each usage must be presented. In this paper, the current state of refrigerants was introduced. And, thermophysical properties of the refrigerants were introduced briefly. From the properties, the refrigerants and refrigeration cycles are promising to be used in the future, were proposed

• Journal of the Korean Society of Safety
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• v.37 no.6
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• pp.18-24
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• 2022

Hydrogen is a clean fuel and is used in many applications in power systems such as fuel cells. It has unique properties such as wide flammability, high burning velocity, and difficulty to liquefy, which lead to critical safety issues. Fire and explosion are the most frequently occurring accidents and one of the major reasons is autoignition. In the ignition process, the chemistry of hydrogen combustion depends mainly on radical pools, and the temperature at which chain-branching and terminating rates are equal is called the crossover temperature. This study addresses the homogeneous autoignition of diluted hydrogen-air mixtures to investigate the effects of dilution on the crossover temperature to prevent explosions in the future. The new criterion for crossover temperature is introduced by only hydrogen radicals to adjust more simply. The detailed calculations indicate that the crossover temperatures are low at high dilutions of carbon dioxide and nitrogen because the concentrations of active radicals are reduced when an inert gas is added. This result is expected to contribute to hydrogen safety and realize a hydrogen society in the future.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.23-28
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• 2007

In most existing research, it is difficult to evaluate thermal comfort exactly because of reflecting individual ideal or psychological response by subjective questions. Physiological variable was selected in this study to evaluate objectively thermal comfort. MST was appeared very sensitively in indoor temperature and can express correctly thermal comfort of human body. The results of CSV are different each individual feeling sensation, so is difficult to evaluate detailedly thermal comfort unlike TSV. But the results of PP, AIx, ED, SEVR are greatly related to temperature change. So thermal comfort is evaluated more objectively by using PP, AIx, ED, SEVR on behalf of TSV, CSV. Human body was presented physiological feedback by temperature impetus and specially, tendency of heart rate agree with temperature change. Physiological reaction was showed sufficient possibility availing evaluation index of thermal comfort. In the future another one needs to review beside the selected physiological variable.

• Journal of Korean Society on Water Environment
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• v.36 no.1
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• pp.14-28
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• 2020

Future climate change may affect the hydro-thermal and biogeochemical characteristics of dam reservoirs, the most important water resources in Korea. Thus, scientific projection of the impact of climate change on the reservoir environment, factoring uncertainties, is crucial for sustainable water use. The purpose of this study was to predict the future water temperature and stratification structure of the Soyanggang Reservoir in response to a total of 42 scenarios, combining two climate scenarios, seven GCM models, one surface runoff model, and three wind scenarios of hydrodynamic model, and to quantify the uncertainty of each modeling step and scenario. Although there are differences depending on the scenarios, the annual reservoir water temperature tended to rise steadily. In the RCP 4.5 and 8.5 scenarios, the upper water temperature is expected to rise by 0.029 ℃ (±0.012)/year and 0.048 ℃ (±0.014)/year, respectively. These rise rates are correspond to 88.1 % and 85.7 % of the air temperature rise rate. Meanwhile, the lower water temperature is expected to rise by 0.016 ℃ (±0.009)/year and 0.027 ℃ (±0.010)/year, respectively, which is approximately 48.6 % and 46.3 % of the air temperature rise rate. Additionally, as the water temperatures rises, the stratification strength of the reservoir is expected to be stronger, and the number of days when the temperature difference between the upper and lower layers exceeds 5 ℃ increases in the future. As a result of uncertainty quantification, the uncertainty of the GCM models showed the highest contribution with 55.8 %, followed by 30.8 % RCP scenario, and 12.8 % W2 model.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.12
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• pp.54-64
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• 2021

Electric vehicles use lithium-ion battery packs as the power supply, where the batteries are connected in series or parallel. The temperature control of each battery is essential to ensure a consistent overall temperature. This study focused on reducing ohmic heating caused by batteries to realize a uniform battery temperature. The battery spacing was optimized to improve air cooling, and the tilt angle between the batteries was varied to optimize the internal structure of the batterypack. Simulations were performed to evaluate the effects of these parameters, and the results showed that the optimal scheme effectively achieved a uniform battery temperature under a constant power discharge. These findings can contribute to future research on cooling methods for battery packs.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.4
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• pp.115-121
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• 2007

This paper describes experiments of the breakdown characteristics by temperature change of $SF_6$ gas and Imitation Air(I-Air) in model GIS(Gas Insulated Switchgear). From the results of the experiments, the breakdown characteristics classify the vapor stage of $SF_6$ according to Paschen's law, in which the stage of coexistence for gas & liquid of the voltage value increases. This results in large deviation and the breakdown of the voltage(VB) low stage as the interior of the chamber is filled with a mixture of $SF_6$ that is not liquefacted and remaining air that can not be ventilated. The ability of $SF_6$ liquid($LSF_6$) insulation is higher than high-pressurize $SF_6$ gas. The VB of the I-Air decreases as the temperature drops and the VB also drops. It is considered that the results of this paper are fundamental data for the electric insulation design of superconductor and cryogenic equipment that will be studied and developed in the future.