• Bulletin of the Korean Chemical Society
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• 제28권11호
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• pp.2025-2028
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• 2007

Homogeneous zinc tetrahalide complexes, highly active catalysts for the coupling reactions of alkylene oxide and CO2 produce alkylene carbonates, were heterogenized due to their tendency to decompose produced alkylene carbonates during the distillation process. Heterogenization of homogeneous zinc tetrahalide complexes was achieved by polymerizing 1-alkyl-3-vinylimidazolium zinc tetrahalides. These polymerized zinc tetrahalide catalysts displayed similar activities to their corresponding monomeric analogues for the coupling reactions of carbon dioxide with ethylene oxide (EO) or propylene oxide (PO) to produce ethylene carbonate (EC) or propylene carbonate (PC). TGA studies showed that the polymer-supported zinc tetrahalide catalysts are thermally stable up to 320 oC. The catalyst recycle test showed that the supported catalysts could be reused over six times. After removal of the polymer-supported catalyst through a simple filtration, EC was able to be isolated without decomposition.

• Korean Chemical Engineering Research
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• 제43권3호
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• pp.344-351
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• 2005

수소에너지는 기존의 석유화학공업의 원료로서 뿐만 아니라 연료전지와 연계하여 소요량이 급속히 증가할 것으로 예측된다. 장기적으로는 재생에너지를 사용한 물 전기분해, 원자력을 이용한 수소 제조가 주목받고 있지만, 안정된 기술이 확보되기까지는 화석연료를 사용한 수소 제조법이 대용량 수소 제조법 중 가장 경제적인 것으로 분석되고 있다. 현재 화석 연료 중 천연가스를 이용한 수증기 개질 수소 제조법이 상업적인 공정으로 채택되고 있으나 $CO_2$ 분리 처리 비용이 경제성 평가에 중요한 항목으로 부각되고 있다. 따라서 천연가스를 이용한 수소 제조에도 다양한 공정이 제안되고 있으므로 천연가스를 원료로 한 수소 제조 기술의 개발 현황을 살펴보았다.

• Molecules and Cells
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• 제43권9호
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• pp.831-840
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• 2020

The β-class of carbonic anhydrases (β-CAs) are zinc metalloenzymes widely distributed in the fungal kingdom that play essential roles in growth, survival, differentiation, and virulence by catalyzing the reversible interconversion of carbon dioxide (CO₂) and bicarbonate (HCO₃^-). Herein, we report the biochemical and crystallographic characterization of the β-CA CafA from the fungal pathogen Aspergillus fumigatus, the main causative agent of invasive aspergillosis. CafA exhibited apparent in vitro CO₂ hydration activity in neutral to weak alkaline conditions, but little activity at acidic pH. The high-resolution crystal structure of CafA revealed a tetramer comprising a dimer of dimers, in which the catalytic zinc ion is tetrahedrally coordinated by three conserved residues (C119, H175, C178) and an acetate anion presumably acquired from the crystallization solution, indicating a freely accessible "open" conformation. Furthermore, knowledge of the structure of CafA in complex with the potent inhibitor acetazolamide, together with its functional intolerance of nitrate (NO₃^-) ions, could be exploited to develop new antifungal agents for the treatment of invasive aspergillosis.

• 한국염색가공학회지
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• 제31권3호
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• pp.147-154
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• 2019

In this study, poly(ethylene terephthalate)(PET) fibres dyed with Disperse Red 167 using supercritical $CO_2$ technology. The purpose of this study was to investigate relationship between PET fibers and supercritical $CO_2$ during dyeing. The effects of temperature, pressure, dyeing time and mass ratio between the dye and PET in the dyeing chamber were considered. Thermal and mechanical properties of the fibers were investigated. Tensile strength of dyed PET fibers decreased at higher temperature and pressure conditions. DSC and DMA results indicated that the Tg and Tm values decreased significantly when compared to the pure PET fibers. However, uniformly dyed PET fibers were typically observed.

• International Journal of Air-Conditioning and Refrigeration
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• 제17권3호
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• pp.88-93
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• 2009

Lubricant oil is needed in air conditioning and refrigeration system because the compressor requires oil to prevent surface to surface contact between its moving parts, to remove heat, to provide sealing, to keep out contaminants, to prevent corrosion, and to dispose of debris created by wear. Thus, the oil separation in an oil separator is one of the most important characteristics for proper compressor operation. In this study, a gravity type of oil separator is used. Oil separation characteristics have been investigated for $CO_2$/PAG mixture in the range of oil concentration 0 to 5 weight-percent and the mixture temperature range of $0^{\circ}C$ to $15^{\circ}C$ at 50 bar and $70^{\circ}C$ to $90^{\circ}C$ at 80 bar. The results obtained indicate that the oil separation is increased with an increase in the oil concentration. It is also found that the oil separation in liquid state is increased with an increase in the mixture temperature while the oil separation in gas state is decreased.

• 한국가스학회지
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• 제23권1호
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• pp.19-26
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• 2019

본 연구에서는 친환경적 냉매로 주목받고 있는 이산화탄소 자연 냉매를 이용하여 1톤 크기의 냉동 탑차에 들어가는 냉방 시스템을 개발하고, COP를 올리기 위해 열교환기 및 Unit cooler를 설계하였다. 또한 LNG의 기존 CNG 5톤 냉동탑차를 LNG 차량으로 개조하여 냉방시스템의 효율을 높임과 동시에 CNG 대비 안전성을 확보하였다. 결과적으로 1톤 및 5톤 크기에서 자연 냉매를 사용한 친환경적인 냉동탑차를 개발하였다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 봄 학술논문 발표대회
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• pp.77-78
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• 2020

In Korea, more than 30,000 tons of waste Styrofoam are produced every year. Styrofoam is spent more than 500 years decomposing during the reclamation process, so it needs to be recycled. The recycling rate of waste styrofoam continues to be the third highest in the world, but it is lower than that of Germany and Japan. Therefore, measures are needed to increase the recycling rate of waste Styropol. Another problem is that cement is mainly used in existing lightweight foam concrete. However, large amounts of CO2 from cement-producing processes cause environmental pollution. Currently, Korea is increasing its greenhouse gas reduction targets to cope with energy depletion and climate change, and accelerating efforts to identify and implement reduction measures for each sector. In 2013 alone, about 600 million tons of carbon dioxide was generated in the cement industry. Therefore, this study replaces CO2 generation cement with furnace slag fine powder, uses crude steel cement for initial strength development of bubble concrete, and manufactures hardening materials to study its properties using waste styrofoam. As a result of the experiment, the hardening agent replaced by micro powder of furnace slag was less intense and more prone to absorption than cement using ordinary cement. Further experiments on the segmentation and strength replenishment of furnace slag are believed to contribute to the manufacture of environmentally friendly lightweight foam concrete.

• Journal of Yeungnam Medical Science
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• 제40권4호
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• pp.423-425
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• 2023

Porokeratosis ptychotropica is an uncommon form of porokeratosis, which was initially described in 1995. It is clinically characterized by symmetrical reddish to brown-colored hyperkeratotic, verrucous, or psoriasiform plaques on the perianal and gluteal regions. The lesions tend to integrate and expand centrally, with small peripheral satellite lesions. Early skin biopsy and appropriate diagnosis are essential because malignant change occurs in 7.5% of porokeratotic lesions. Conventional treatment options include topical steroid, retinoid, imiquimod, 5-fluorouracil, isotretinoin, excimer laser, photodynamic therapy, intralesional steroid or bleomycin injection, cryotherapy, carbon dioxide (CO₂) laser, and dermatome and excision, but none seem to achieve complete clearance. A 68-year-old woman presented with diffuse hyperkeratotic scaly lichenoid plaques on the buttocks that had persisted for several years. A skin biopsy of the buttocks revealed multiple cornoid lamellae and intense hyperkeratosis. There were some dyskeratotic cells beneath the cornoid lamellae and the granular layer was absent. Porokeratosis ptychotropica was diagnosed based on the characteristic clinical appearance and typical histopathological manifestations. She was treated with a CO₂ laser in one session and topical application of urea and imiquimod cream for 1 month. The lesions slightly improved at the 1-month follow-up. We herein present a rare case of porokeratosis ptychotropica.

• 한국환경과학회지
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• 제22권2호
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• pp.139-149
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• 2013

Anthropogenic increases in greenhouse gas concentrations, primarily through radiative forcing from carbon dioxide, continue to challenge earth's climate. This study quantified $CO_2$ storage and uptake by dominant forest types and age classes in the middle region of Korea. In addition, the role of forest landscapes in reducing atmospheric $CO_2$ against $CO_2$ emissions based on energy consumption was evaluated. Mean $CO_2$ storage and uptake per unit area by woody plants for three forest types and four age classes were estimated applying regression equations derived to quantify $CO_2$ storage and uptake per tree; and computations per soil unit area were also performed. Total $CO_2$ storage and uptake by forest landscapes were estimated by extrapolating $CO_2$ storage and uptake per unit area. Results indicated mean $CO_2$ storage per unit area by woody plants and soils was higher in older age classes for the same forest types, and higher in broadleaved than coniferous forests for the same age classes, with the exception of age class II (11-20 years). $CO_2$ storage by broadleaved forests of age class V (41-50 years) averaged 662.0 t/ha (US$331.0 hundred/ha), highest for all forest types and age classes evaluated. Overall, an increased mean $CO_2$ uptake per unit area by woody plants was evident for older age classes for the same forest types. However, decreased $CO_2$ uptake by broadleaved forests at age class V was observed, compared to classes III and IV with an average of 27.9 t/ha/yr (US$14.0 hundred/ha/yr). Total $CO_2$ storage by woody plants and soils in the study area was equivalent to 3.4 times the annual $CO_2$ emissions, and woody plants annually offset the $CO_2$ emissions by 17.7%. The important roles of plants and soils were associated with 39.1% of total forest area in South Korea, and $CO_2$ emissions comprised 62.2% of the total population. Therefore, development of forest lands may change $CO_2$ sinks into sources. Forest landscape management strategies were explored to maintain or improve forest roles in reducing atmospheric $CO_2$ levels.

• 한국해양환경ㆍ에너지학회지
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• 제8권3호
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• pp.111-115
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• 2005

화석연료소비로 인하여 대기 중의 온실가스농도가 계속해서 증가하고 있는 추세이며, 이에 따른 기상이변, 생물다양성감소와 해수면 상승등 예상치 못한 기후 변동이 계속 발생하고 있다. 본 기술논문에서는 온실가스의 대부분을 차지하는 $CO_2$를 심해양(2,000 m이상)에 친환경적으로 처리하는 기술(심해분사법, 해저저류법, 해저지중처리법)에 대해 비교연구를 수행하였다. 뿐만아니라 $CO_2$ 처리기술의 유효성 평가, $CO_2$ 처리기술의 환경영향 평가기술, $CO_2$ 해양처리에 관한 국제법적, 사회적 수용여부와 국내 연구방향 및 기대효과등에 관하여 논하였다.