• 멤브레인
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• 제30권2호
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• pp.97-110
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• 2020

이산화탄소 포집 및 저장기술(CCS)은 인류발생적 요인에 의한 이산화탄소 배출 증가와 그로 인한 기후변화를 완화시킬 수 있는 기술 중 하나이다. 그 중, 매체 순환식 연소(chemical looping combustion, CLC)와 칼슘루핑(calcium looping) 기술은 현재 아민 스크러빙(amine scrubbing)을 대체할 수 있는 유망한 기술로 주목받고 있다. 두 방법 모두 금속 산화물을 이용한 연속적인 순환 사이클 반응에 의한 것이다. 전체적인 이산화탄소 포집 및 저장 성능의 향상을 위해서는 사이클을 거듭하며 발생하는 소결(sintering)로 인한 안정성 저하 문제를 해결하고 금속 산화물의 구조 또한 최적화해야 한다. 금속 산화물 표면에 얇은 박막을 형성하는 것은 소결로 인한 손상을 막을 수 있는 방법이다. 이러한 박막 제조 기술로 잘 알려진 기술에는 화학기상증착법(chemical vapor deposition)과 원자층증착기술(atomic layer deposition)이 있다. 본 총설에서는 CVD, ALD 기술을 비롯하여 효과적인 반응 안정성 향상을 위한 안정제 첨가 방법, 금속 산화물 구조 개선에 대한 다양한 최근 기술들을 다루었다.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 2004년도 춘계 학술발표회 논문집
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• pp.347-352
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• 2004

• 한국수소및신에너지학회논문집
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• 제28권4호
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• pp.384-391
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• 2017

Effects of operating variables on solid circulation rate were measured and discussed using two-interconnected circulating fluidized bed system at ambient temperature and pressure. OCN 706-1100 particles were used as oxygen carrier. The measured solid circulation rates increased as the lower loop seal gas flow rates and the solid height in the fuel reactor increased. Suitable operating conditions to avoid choking of the air reactor were confirmed. Continuous long-term operations of steady-state solid circulation were also demonstrated at two different conditions based on the operating window.

• 정보처리학회논문지A
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• 제9A권2호
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• pp.163-170
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• 2002

연속미디어 파일을 위한 버퍼 캐시 기법들은 연속 미디어의 순차적 접근만을 고려하고 반복참조는 고려하지 않았다. 그러나, 외국어 영상 학습의 경우 사용자가 어떤 장면을 반복 구간으로 설정하면 자동으로 수회 반복 상영하는 기능이 있을 수 있다. 본 논문에서는 순차 참조와 반복 참조가 혼재하는 연속미디어 파일 시스템을 위한 새로운 버퍼 캐시 기법을 제안한다. 제안한 기법은 파일의 참조 유형을 탐지하고 파일 별로 적절한 교체 정책을 적용하여 버퍼 캐시 적중률을 높인다.

• 한국수소및신에너지학회논문집
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• 제29권1호
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• pp.90-96
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• 2018

Reaction characteristics and kinetics of a oxygen carrier (OCN717-R1SU) for chemical looping combustion (CLC) have been investigated using TGA by changing gas concentration (10-30 vol.% $CH_4$) and reaction temperature ($825-900^{\circ}C$). Reaction rate of OCN717-R1SU increased as temperature increased and it was found that reaction is delayed at the initial reaction regime. Johnson-Mehl-Avrami (JMA) model was adopted to explain the reaction phenomenon. The activation energy (E) determined by JMA model in reduction reaction of OCN717-R1SU is $151.7{\pm}2.03kJ/mol$ and pre-exponential factor and JMA exponent were also obtained. The parameters calculated in this study will be applied in design of the reactor and operation conditions for CLC process.

• 한국수소및신에너지학회논문집
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• 제27권4호
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• pp.404-411
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• 2016

To select appropriate oxygen carrier candidates for chemical looping combustion, reduction characteristics of seven oxygen carriers were measured and discussed using three different reduction gases, such as $H_2$, CO, and $CH_4$. Moreover, attrition losses of those oxygen carriers also measured and compared. Among seven oxygen carrier particles, OCN703-1100 and NiO/bentonite particles showed higher oxygen transfer capacity than other particles, but these particles showed more attrition loss than other particles. C14 and C28 particles which used as cheap oxygen carriers in European country showed lower oxygen transfer capacity and less attrition loss. Based on the experimental results, we could select OCN717-R1SU, NC001, and N002 particles as candidates for future works because these oxygen carriers showed enough oxygen transfer capacity and good attrition resistance.

• 한국수소및신에너지학회논문집
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• 제20권1호
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• pp.45-54
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• 2009

Reduction reactivity and carbon deposition characteristics of three oxygen carrier particles(OCN01, OCN02, OCN03) have been investigated by using hydrogen, methane, syngas, and natural gas as fuels. For all particles, the maximum conversion, the oxygen transfer capacity, and the degree of carbon deposition increased as the reactive carbon contents increased. The reduction rate and the oxygen transfer rate increased as the moles of required oxygen per input gas increased. The change of maximum conversion, reduction rate, oxygen transfer capacity, oxygen transfer rate and degree of carbon deposition for different fuels can be explained consistently by using parameters such as the reactive carbon contents and the moles of require oxygen per input gas.

• 한국수소및신에너지학회논문집
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• 제19권4호
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• pp.348-358
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• 2008

Reduction reactivity and carbon deposition characteristics of mass produced oxygen carrier particle(OCN-650) have been investigated by using hydrogen, methane, syngas, and natural gas as fuels. For all fuels, the maximum conversion and oxygen transfer capacity increased as the temperature increase. The reduction rate and the oxygen transfer rate increased as the temperature increase for methane. However, those values showed maximum at 900$^{\circ}C$ for hydrogen, syngas, and natural gas. To explain consistently the change of maximum conversion, reduction rate, oxygen transfer capacity, oxygen transfer rate and degree of carbon deposition for different fuels, new parameters such as reactive carbon contents and require oxygen per input gas were adopted.

• 한국멀티미디어학회논문지
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• 제5권1호
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• pp.47-56
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• 2002

멀티미디어 저장 시스템을 위한 기존의 버퍼 캐시 기법들은 멀티미디어 파일의 순차적 접근만을 고려하고 반복 참조는 고려하지 않고 있다. 그러나, 외국어 영상 학습의 경우 사용자가 어떤 장면을 반복 구간으로 설정하면 자동으로 수회 반복 상영하는 기능이 있을 수 있다. 본 논문에서는 순차 참조와 반복 참조가 혼재하는 멀티미디어 저장 시스템을 위한 새로운 버퍼 교체 기법인 HBM(Hybrid Buffer Management)을 제안한다. 제안한 기법은 응용 수준에서 파일의 참조 유형을 파일 시스템에게 알려주고 HBM이 각 파일에 적절한 버퍼교체 정책을 적용한다. 실험 결과, HBM은 DISTANCE나 LRU와 같은 이전 버퍼 교체 기법보다 캐시 적중률을 높일 수 있음을 알 수 있었다.

• Clinical Endoscopy
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• 제57권4호
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• pp.501-507
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• 2024

Background/Aims: Polyps greater than 30 mm are classified as "giants". Their endoscopic removal represents a technical challenge. The choice of the endoscopic removal technique is important because it provides a resection sample for precise histopathological staging. This is pivotal for diagnostic, prognostic, and management purposes. Methods: From a retrospective analysis, we obtained a sample of 38 giant polyps. Eighteen polypectomies were performed using the epinephrine volume reduction (EVR) method, nine polypectomies utilized endo-looping or clipping methods, and 11 patients underwent surgery. Results: We obtained en bloc resection with the EVR method in all cases; histology confirmed the correct indication for endoscopic resection in all cases. Moreover, no early or delayed complications were observed, and no patient required hospitalization. Using endo-looping or clipping methods, we observed advanced histology in 1/9 (11.1%) cases, while another patient (1/9, 11.1%) had delayed bleeding. Among patients who underwent surgery, 5/11 (45.5%) were deemed overtreated and three had post-surgical complications. Conclusions: We propose EVR as an alternative technique for giant polyp resection due to its safety, effectiveness, cost-efficiency, and the advantage of avoiding the need to postpone polypectomy to a later time. Further prospective studies might help improve this experience and enhance the technique.