• 한국항해항만학회지
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• 제36권5호
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• pp.349-355
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• 2012

본 논문에서는 선박에서 배출되는 $CO_2$ 배출을 최소화하기 위한 노력의 일환으로 선박에서 배출되는 열에너지를 회수하고 재활용하여 극대화 시킬 수 있는 방안들을 조사하고 버려지는 열에너지를 이용하여 ORC(Organic Rankine Cycle) 발전장치를 구동함으로써 선박의 에너지 효율을 높이고 온실가스 배출을 최소화할 수 있는 방안들을 연구하였다. 선박에서 배출되는 배기가스의 폐열을 열원으로 하는 유기냉매 랭킨사이클을 구성하는 방안과 열에너지 비중은 높지만 상대적으로 낮은 온도인 해수냉각 시스템으로 배출되는 열에너지를 재활용하여 터빈 발전기를 구동하는 ORC 발전시스템을 설계하고 시뮬레이션 하였다. 시스템 해석 결과 배기가스에서는 1,000kW급, 해수 냉각 시스템에서는 650kW급 발전 출력을 얻을 수 있었고, 다양한 친환경 유기냉매를 이용하여 온도와 유량 조건에 따른 열 해석을 실시하여 시스템의 효율과 출력을 비교하였다.

• Asian-Australasian Journal of Animal Sciences
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• 제32권11호
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• pp.1789-1800
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• 2019

Objective: Although alveolar macrophages play a key role in the respiratory immunity of livestock, studies on the mechanism of differentiation and survival of alveolar macrophages are lacking. Therefore, we undertook to investigate changes in the lipid metabolism and survival rate, using 3D4/31 macrophages and Dudleya brittonii which has been used as a traditional asthma treatment. Methods: 3D4/31 macrophages were used as the in vitro porcine alveolar macrophages model. The cells were activated by exposure to phorbol 12-myristate 13-acetate (PMA). Dudleya brittonii extraction was performed with distilled water. For evaluating the cell survival rate, we performed the water-soluble tetrazolium salt cell viability assay and growth curve analysis. To confirm cell death, cell cycle and intracellular reactive oxygen species (ROS) levels were measured using flow cytometric analysis by applying fluorescence dye dichlorofluorescein diacetate and propidium iodide. Furthermore, we also evaluated cellular lipid accumulation with oil red O staining, and fatty acid synthesis related genes expression levels using quantitative polymerase chain reaction (qPCR) with SYBR green dye. Glycolysis, fatty acid oxidation, and tricarboxylic acid (TCA) cycle related gene expression levels were measured using qPCR after exposure to Dudleya brittonii extract (DB) for 12 h. Results: The ROS production and cell death were induced by PMA treatment, and exposure to DB reduced the PMA induced downregulation of cell survival. The PMA and DB treatments upregulated the lipid accumulation, with corresponding increase in the acetyl-CoA carboxylase alpha, fatty acid synthase mRNA expressions. DB-PMA co-treatment reduced the glycolysis genes expression, but increased the expressions of fatty acid oxidation and TCA cycle genes. Conclusion: This study provides new insights and directions for further research relating to the immunity of porcine respiratory system, by employing a model based on alveolar macrophages and natural materials.

• Journal of Electrochemical Science and Technology
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• 제10권2호
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• pp.223-230
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• 2019

A facile method for surface coating with $Li_2TiF_6$ which has a high lithium-ion conductivity, on $LiMn_2O_4$ spinel cathode material for high performance lithium ion batteries. The surface coating is performed by using a co-precipitation method with $Li_2CO_3$ powder and $H_2TiF_6$ solution under room temperature and atmospheric pressure without special equipment. Total coating amount of $Li_2TiF_6$ is carefully controlled from 0 to 10 wt.% based on the active material of $LiMn_2O_4$. They are evaluated by a systematic combination of analyses comprising with XRD, SEM, TEM and ICP. It is found that the surface modification of $Li_2TiF_6$ is very beneficial to high cycle life and excellent rate capability by reducing surface failure and supporting lithium ions transportation on the surface. The best coating condition is found to have a high cycle life of $103mAh\;g^{-1}$ at the 100th cycle and a rate capability of $102.9mAh\;g^{-1}$ under 20 C. The detail electrochemical behaviors are investigated by AC impedance and galvanostatic charge and discharge test.

• The Plant Pathology Journal
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• 제32권3호
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• pp.260-265
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• 2016

We observed the changes in aggressiveness and fecundity of the anthracnose pathogen Colletotrichum acutatum on hot pepper, under the ambient and the twice-ambient treatments. Artificial infection was repeated over 100 cycles for ambient ($25^{\circ}C/400ppm$ $CO_2$) and twice-ambient ($30^{\circ}C/700ppm$ $CO_2$) growth chamber conditions, over 3 years. During repeated infection cycles (ICs) on green-pepper fruits, the aggressiveness (incidence [% of diseased fruits among 20 inoculated fruits] and severity [lesion length in mm] of infection) and fecundity (the average number of spores per five lesions) of the pathogen were measured in each cycle and compared between the ambient and twice-ambient treatments, and also between the early (ICs 31-50) and late (ICs 81-100) generations. In summary, the pathogen's aggressiveness and fecundity were significantly lower in the late generation. It is likely that aggressiveness and fecundity of C. acutatum may be reduced as global $CO_2$ and temperatures increase.

• 한국자동차공학회논문집
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• 제15권4호
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• pp.67-75
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• 2007

This paper deals with the research for the effects of the operating parameters that could be used for a transcritical $CO_2$ mobile air-conditioning system on the cooling performance. The experimental conditions of the performance tests for a system and components such as a gas cooler and an evaporator were suggested to compare the performance of each with the standardized test conditions. And this research presents experimental results for the performance characteristics of a $CO_2$ mobile air conditioning system with various operating conditions such as different gas cooler inlet pressures and frontal air velocities/temperatures passing through an evaporator and a gas cooler. Experimental results show that the cooling capacity was more than 5kW and coefficient of performance (COP) was more than 2.1, also. Therefore, we checked that the mobile air-conditioning system using $CO_2$ has good performance compared to that using HFC-134a.

• 설비공학논문집
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• 제20권4호
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• pp.230-237
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• 2008

The objective of this paper is to investigate the performance characteristics of a $CO_2$ cooling and water heating system using a twin-rotary compressor with the compression volume ratio of 0.6. The cooling performances of the $CO_2$ heat pump were measured and analyzed with the variations of charge amount, EEV opening, and compressor frequency. In addition, the performance of the combined system including cooling and water heating was also measured and analyzed by varying inlet temperature of the EEV. As a result, the optimal normalized charge and cooling COP in the cooling mode were 0.307 and 2.06, respectively. The application of the water heating into the $CO_2$ heat pump improved the cooling performance over 78% and decreased the EEV inlet temperature by $8^{\circ}C$, which can increase system reliability.

• Korean Chemical Engineering Research
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• 제43권3호
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• pp.432-437
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• 2005

혼합가스로부터 $CO_2$를 분리, 회수하기 위하여 활성탄소섬유를 흡착제로 사용한 전기변동흡착(electric swing adsorption, ESA) 공정의 타당성을 검토하였다. 활성탄소 섬유는 상압에서도 $CO_2$에 대해 빠른 흡착 속도를 보였으며, 비교적 짧은 흡착대와 긴 파과시간, 흡착제의 단위무게당 높은 흡착량을 나타내었다. 포화흡착된 흡착탑의 재생에서 비표면적이 큰 활성탄소섬유일수록 일정한 모양의 파과곡선을 유지하여 흡착-탈착의 재생사이클에 유리하였다. 진공탈착에 의한 흡착탑의 재생률은 64 cmHg의 압력에서도 64％ 이상이었고, 전기탈착을 병행한 hybrid 재생단계에서는 17％의 추가적인 재생률을 보이며 7-8 Wh의 낮은 재생에너지에서도 높은 재생률을 보였다.

• 설비공학논문집
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• 제16권12호
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• pp.1134-1139
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• 2004

The evaporative heat transfer coefficient of $CO_2$ (R-744) in a horizontal tube was investigated experimentally. The experiments were conducted without oil in a closed refrigerant loop which was driven by a magnetic gear pump. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and evaporator (test section). The test section consists of a smooth, horizontal stainless steel tube of inner diameter of 7.75 mm. The experiments were conducted at mass flux of 200 to 500 kg/m$^2$s, saturation temperature of -5 to 5$^{\circ}C$, and heat flux of 10 to 40kW/m$^2$. The test results showed the heat transfer of $CO_2$ has a greater effect on nucleate boiling more than convective boiling. Mass flux of $CO_2$ does not affect nucleate boiling too much, and the effect of mass flux on evaporative heat transfer of $CO_2$ is much smaller than that of refrigerant R-22 and R-134a. In comparison with test results and existing correlations, correlations failed to predict the evaporative heat transfer coefficient of $CO_2$, therefore, it is necessary to develope reliable and accurate predictions determining the evaporative heat transfer coefficient of $CO_2$ in a horizontal tube.

• Journal of Animal Science and Technology
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• 제65권2호
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• pp.427-440
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• 2023

The current study evaluated carbon dioxide (CO₂) emissions from beef and pork production and distribution chains in the South Korean meat industry. Data from industrial example farms and slaughterhouses were assessed on the basis of both the guidelines from the United Kingdom's Publicly Available Specification (PAS) 2050:2011 and the Korea Environmental Industry & Technology Institute carbon footprint calculation. The main factors for our estimations were animal feeds, manure waste, transportation, energy and water, refrigerants, and package data. Our analyses show that 16.55 kg CO₂ equivalent (eq) was emitted during the production of 1 kg of live cattle. When retail yields and packing processes were considered, the CO₂-eq of 1 kg of packaged Hanwoo beef was 27.86 kg. As for pigs, emissions from 1 kg of live pigs and packaged pork meat were 2.62 and 12.75 kg CO₂-eq, respectively. While we gathered data from only two farms and slaughterhouses and our findings can therefore not be extrapolated to all meats produced in the South Korean meat industry, they indicate that manure waste is the greatest factor affecting ultimate CO₂ emissions of packaged meats.

• 열처리공학회지
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• 제37권3호
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• pp.128-137
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• 2024

In this study, the carburizing heat treatment process used in aircraft gear manufacturing was compared with the general carburizing heat treatment process using AISI 9310 steel. The process of carburizing followed by slow cooling, and then quenching after austenitizing(Process A) showed less compressive residual stress and less retained austenite in the surface layer compared to the process of quenching directly after carburizing(Process B). In prpcess B, there was a large amount of retained austenite when quenched immediately after carburization, and when treated with subzero, martensite rapidly increased and the compressive residual stress increased significantly, but at the same time, there is a risk of cracking due to severe expansion in volume. Therefore, in the case of aviation parts, it is believed that a step-by-step heat treatment cycle was adopted to ensure stability against heat treatment cracks. As a result of the final tempering after sub-zero treatment, the A process specimen showed a deeper effective case depth and HV700 depth and a higher hardness value above HV700 than the B process specimen.