• Journal of Environmental Science International
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• v.29 no.7
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• pp.761-772
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• 2020

This research investigated the meteorologically relevant characteristics of high PM_2.5 episodes in Busan. The number of days when daily mean PM₁₀ concentration exceeded 100 ㎍/㎥ and the PM_2.5 concentration exceeded 50 ㎍/㎥ over the last four years in Busan were 24 and 58, respectively. Haze occurrence frequency was 37.6% in winter, 27.4% in spring, 18.6% in fall, and 16.4% in summer. Asian dust occurrence frequency was 81.8% in spring, 9.1% in fall and winter, and 0% in summer. During summer in Busan, high PM_2.5 episode occurred under the following meteorological conditions. 1) Daytime sea breeze. 2) Mist and haze present throuout the day. 3) Anti-cyclone located around the Korean peninsula. 4) Stable layer formed in the lower atmosphere. 5) Air parcel reached Busan by local transport rather than by long-range transport. These results indicate that understanding the meteorological relevance of high PM_2.5 episodes could provide insight for establishing a strategy to control urban air quality.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.12
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• pp.1033-1038
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• 2006

We carried out the experiments on particle deposition onto the cleanroom wall panels. And then we investigated the particle deposition characteristic coefficients for electrostatic voltages and particle size. It was found that there is little difference in characteristics of the particle deposition between the steel panel and the anti-static coating panel. In case of that the particle size is under $1.0{\mu}m$, the particle deposition characteristic coefficient becomes larger as the electrostatic voltage induced to the cleanroom wall panel is increasing. Where in case of that the particle size is over $3.0{\mu}m$, the particle deposition characteristic coefficients do not show any differences with the electrostatic voltages. It is due to that the electrostatic force is the major particle transport mechanism for submicron particles, while the gravitational settling is the major particle transport mechanism for overmicron particles when the electro-static voltages are induced to the cleanroom wall panel.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.5
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• pp.213-219
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• 2017

This study investigated the thermal conductivity of $CO_2$ gas mixtures in order to ascertain the effects of particular impurities in $CO_2$ in pipeline transportation. We predicted the thermal conductivity of three $CO_2$ gas mixtures ($CO_2+N_2$, $CO_2+H_2S$, and $CO_2+CH_4$) by utilizing three different methods : Chung et al., TRAPP, and the REFPROP model. We validated predictions by comparing the estimated results with 216 experimental data for $CO_2+CH_4$, $CO_2+N_2$, and $CO_2+C_2H_6$. Following $CO_2$ transportation conditions, we observed that the model developed by Chung et al. showed the lowest mean deviation of 3.07%. Further investigations were carried out on the thermal conductivity of $CO_2$ gas mixtures based on the Chung et al. model including the effects of the operation parameters of pressure, temperature, and mole fraction of impurities.

• International Journal of Air-Conditioning and Refrigeration
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• v.8 no.1
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• pp.50-61
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• 2000

The effects of an inserted coil on flow . patterns and heat transfer performance for a horizontal rotating heat pipe have been studied experimentally. Especially, the present study is to see an internally inserted helical coil inside a RHP would lead to the same kind of results as internal fins. Visualization test conducted for an acryl tube, charged water with at a volumetric rate of 20%. When the flow kept pool regime at a low rpm(less than 1,000rpm), the movement of coil forced the water to flow in axial direction. But this pumping effect of coil disappeared, when the pool regime changed to annular one which could be created by increasing rpm. The pumping effects for RHP with an inserted coil resulted in the enhancement in both condensation heat transfer coefficient and heat transport limitation, as obtained in case of using internal fins. But all these effects became negligible in the range of higher rpm(above 1,000-1,200) with the transition of flow regime to annular flow.

• International Journal of Air-Conditioning and Refrigeration
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• v.12 no.2
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• pp.79-86
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• 2004

An analytical and experimental study has been conducted to determine the optimal charging mass of working fluid for the maximum heat transport capacity of heat pipe with axially grooved wick. When the heat pipe is operated in a steady state, the liquid-vapor meniscus recession of working fluid to the bottom of groove is occurred in the evaporator region. In this work, the optimal charging mass of working fluid was obtained by considering the meniscus recession from the axial variation of capillary pressure, the radius of curvature and wetting angle of meniscus of liquid-vapor interface. Experimental results were also obtained by varying the charging mass of working fluid within a heat pipe, and presented for the trend of maximum heat transport capacity corresponding to the operating temperature and the elevation of heat pipe. Finally, the analytical results of the optimal charging mass of working fluid were compared with those from the experiment, both of which were in good agreement with each other.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.12
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• pp.1139-1144
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• 2005

This study has been performed to investigate the thermal performance of variable conductance heat pipe (VCHP) with meshed wick. The length of condenser portion in a VCHP is varied by the expansion of inert gas with the operation temperature, and the heat transport capacity is thus varied with the operating temperature. In this study, numerical evaluation of the VCHP is made for the thermal performance of VCHP, based on the diffusion model of inert gas. Water is used as a working fluid and nitrogen as a control inert gas in the copper tube. As a result, the thermal performance of VCHP has been compared with that of constant conductance heat pipe (CCHP) according to the variation of operation temperature. Maximum heat transport capacity of VCHP is mainly presented for operation temperature and the variation of operation temperature is also presented for heat transfer rate of VCHP.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.27 no.1
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• pp.57-68
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• 2019

The emission trading system implemented in Korea is a system in which the government allocates or sells emission rights by setting the emission allowable amount to economic players subject to the emission trading system, allowing companies to freely trade shortfall or extra money through the emission trading market. Korea also had implemented its first emission trading system scheme period of time from 2015 to 2017. As a result of the first planning period in which total of seven Korean airlines were targeted, the emission amount was about 5.51 million KAU, while the quota amount was only about 4.85 million KAU, about 116% of the actual quota was emitted and Domestic airlines have incurred additional costs of about 10.7 billion won. Due to ICAO's implementation of CORSIA, the airlines are expected to have to shoulder additional costs because purchasing exceed quota will be increased in order to offset excess emissions not only on domestic but also on international routes. Thus, this paper had analyzed the characteristics of the carbon trading system of air transport industry and suggested a mix of regulatory policies as an improvement method.

• International journal of advanced smart convergence
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• v.10 no.2
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• pp.158-167
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• 2021

Fishery industry is an important part of agricultural industry in coastal countries. The purpose of this study is to use the theory of industrial competitiveness for reference, use Analytic Hierarchy Process (AHP) and Delphi method to establish the evaluation index system, and analyze the fishery industry competitiveness of 11 coastal provinces in China. This study data came from China Fishery Statistical Yearbook 2020. The results show that Shandong Province is the most competitive province in fishery industry among the coastal provinces. The inter-provincial differences are great. Not only the resource endowment is the factor that affects the fishery industry competitiveness, but also the long-term profitability is too. The proportion of recreational fishery in the fishery economic output value has become one of the main indicators to measure the competitiveness of the fishery industry. The findings of this study suggest that all regions should adopt measures in accordance with local conditions, promote the integrated development of the fishery industry, enhance the added value of fishery products and enhance the competitiveness of fishery industry. The disadvantage of this study is that the fishery industry competitiveness of China's coastal provinces is only compared and analyzed. The future direction is to carry out a comparative study on the international competitiveness of fishery with other east Asian countries.

• The Journal of Economics, Marketing and Management
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• v.9 no.3
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• pp.11-21
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• 2021

Purpose: The purpose of this study is to understand the status quo of production efficiency in private industrial enterprises above designated scale in China's 31 provinces (including municipalities directly under the central government, autonomous regions) (hereinafter referred to as China's 31 provinces). Research design, data and methodology: Find out the factors affecting the development of production efficiency in private industrial enterprises, using DEA, Data Envelopment Analysis and Malmquist index analysis, build the evaluation model of production efficiency in private industrial enterprises, and analyze the data of China's 31 provinces private industrial enterprises in 2015-2019. Results: The research results show that the production efficiency of private industrial enterprises in China is improving on the whole. Although the total factor productivity has decreased slightly, the overall efficiency and pure technical efficiency have increased significantly. Conclusions: The conclusion of this study can provide reference for Chinese private industrial enterprises to improve production efficiency and make development plan. The limitation of this paper lies in the fact that the private industrial enterprises in inefficient provinces have not been given specific improvement plans.

• International journal of advanced smart convergence
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• v.11 no.2
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• pp.153-162
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• 2022

The impact of the information technology industry on economic development is becoming increasingly important. In this study, we take China's provincial-level regions from 2015 to 2020 as the research object, comprehensively evaluates the level of their information technology systems by the entropy weight method, and then measures the coupling coordination relationship between the information technology system and the economic development system by the coupling coordination degree model. As a result, we found that the income of the information technology industry, the investment of talents and science research have the most important influence on the level of the information technology system. During the research period, with increasing values, the coupling degree of the two systems was at a high level. Affected by development strategies, diffusion effects and industrial relocation, the coupling degree in the central and western regions has shown a rapid growth trend. The coordination degree of the two systems is relatively low, and 83.9% of the provinces are in the medium-low coordination stage. The information technology industry has obviously promoted economic development. Besides, relevant policies should be introduced to effectively support and guide the high-quality development of the information technology industry and promote the high-level coordinated development of the two systems.