• Applied Biological Chemistry
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• 제12권
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• pp.43-51
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• 1969

우리나라 주요 식품들의 단백질 아미노산 함량을 최근에 와서 크게 실용화되고 있는 GLC 방법에 의해 분석함에 있어서 GLC의 기술적 재평가를 하고자 시험 하였든바 1. 우선 여러식품들의 단백질 질소함량을 조사하여 GLC 분석에 필요한 시료량을 정하였으며 2. GLC에 주입한 17종 아미노산들이 대하여 조사한 결과 Arginine, Cystine, Histidine, Tyrosine을 제외한 13종만이 주입한 량에 비례하여 detector response 를 얻었다. 3. 13종 아미노산에 대한 RMR 치(値)를 얻었다. 4. 아미노산에 대한 recovery 검정(檢定)을 하였든바 거의 100% 가까이 recover되었으며, 가수분해가 recovery에 미치는 영향을 조사하였든바 별 영향이 없었음을 알았다. 5. GLC와 ion-exchange chromatography 분석법을 비교시험하였든바 백어포 시료에 있어서는 Threonine과 Asparagine만이 두 방법에서 거의 같게 나왔고 다른 아미노산들은 GLC에서 보다 많은량이 나타났다. 6. 각식품들에 대한 단백질 아미노산함량을 측정하였든바 식품종류에 따라 그리고 보리 및 대두에 있어서는 품종에 따라서도 아미노산 함량이 다르게 나타났다.

• 공업화학
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• 제32권2호
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• pp.149-156
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• 2021

크래프트 회수보일러(kraft recovery boiler)는 펄프 공정에서 생성된 흑액을 연소하여 발전용 스팀을 생산하는 장치이다. 특히 연소로 상단부에 존재하는 과열기(superheater)는 포화 증기가 연소가스와 열교환을 통해 과열 증기로 전환되는 구간으로, 연소가스와 포화 증기 사이의 열교환 효율 향상은 발전용 과열 증기 생산량 증가 및 발전 효율이 증가하므로 매우 중요하다. 과열기 하단부에 위치한 노즈 아치는 과열기의 부식의 원인이 되는 연소로에서 발생한 복사열을 막는 중요한 역할을 하지만, 연소가스 유동을 방해하여 포화증기와 열교환이 끝난 저온의 연소가스가 과열기를 나가지 못하고 재순환되어 열교환 효율을 저하시키는 직접적인 원인이 된다. 따라서 본 연구에서는 CFD를 활용하여 노즈아치 구조에 따른 재순환 영역의 크기와 연소가스 출구 온도를 비교하였다. 결과적으로 노즈 아치 하단부 각도를 106.5°에서 150°로 변경할 경우 연소가스의 재순환 영역이 감소하여 연소가스와 과열기 사이의 열교환 효율이 10.3% 향상되는 것을 확인하였다.

• Journal of the korean society of oceanography
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• 제38권3호
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• pp.135-142
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• 2003

Gas flux across the air-sea interface is often determined by the product of gas transfer velocity k) and the difference of concentrations in water and air. k is primarily controlled by wind stress on the air-sea interface, thus all parameterizations ofk involve wind speed, a rough indicator of wind stress, as one of the independent variables. We attempted to explore the spatial and temporal variations of k in the East (Japan) Sea using a database from Naet al. (1992). Three different parameterizations were employed: those of Liss and Merlivat (1986), Wanninkhof(1992), and Wanninkhofand McGillis (1999). The strong non-linear dependence of k on wind speed in all parameterizations leads us to examine the effect of time resolution, in which the binned wind speeds are averaged, on the estimation ofk. Two time resolutions of 12 hours (short-term) and one month (long-term) were chosen. The mean wind speeds were fed into the given parameterizations, resulting in six different transfer velocities of $CO_2$ ranging from 12 to 32 cm/h. In addition to the threefold difference depending on the choice of parameterization, the long-term average of wind speed results in a value ofk up to 20% higher than the short-term (12 hours) average of wind speed due to the non-Rayleigh wind distribution in the East (Japan) Sea. While it is not known which parameterization is more reliable, this study proposes that the time-averaged wind speed should not be used in areas where non-Ralyleigh wind distribution prevails such as the East (Japan) Sea. The net annual $CO_2$ flux was estimated using the value of k described above and the monthly ${\Delta}fCO_2$ of Oh et al. (1999); this ranges from 0.034 to 0.11 Gt-C/yr.

• 한국수소및신에너지학회논문집
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• 제35권3호
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• pp.290-299
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• 2024

In this study, a theoretical study was conducted on the pre-cooling temperature of hydrogen gas and the heat exchanger area in a small-scale liquefied hydrogen system. The small-scale liquefaction system was built and liquid hydrogen production experiments were performed. In this process, the temperature of precooled hydrogen gas was measure to be about 120 K, and then the possibility of a cause was analyzed through pressure analysis of hydrogen gas and container, and analysis of the amount of liquid hydrogen produced. It was found that some reasonable results were obtained from the theoretical approaches. Based on this theoretical approach, we aim to improve the production of liquid hydrogen by optimizing the heat exchange area according to flow rate.

• 대한기계학회논문집B
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• 제26권3호
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• pp.491-497
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• 2002

In the present study, a new wood boiler was developed through the performance test. The efficiency of the boiler was obtained up to about 63.7%, which is 67% higher than that of conventional wood boiler, about 38.2%. The structure of the new boiler is more complicated than the conventional boiler. The passage of combustion gas is sufficiently long to exchange heat well with heating water. Therefore, the obtained efficiency is so high, and the temperature of exhaust gas was lower than 200$^{\circ}C$, which is as low as that of light oil boiler. The composition of exhaust gas was measured, and the CO gas concentration was obtained more than 3000 ppm. So, it seems that more study is needed to lower the concentration of CO gas.

• 한국가스학회지
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• 제11권3호
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• pp.40-43
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• 2007

스택의 디자인과 운전조건을 최적화하여 PEMFC stack의 성능을 상당히 증진시킬수 있다. 그러한 결과로, 500시간의 DSS(Daily Start-up & Shutdown) 누적 운전후에 일별 운전성능은 조금의 편차가 있었지만 (0.02-0.9%), 스택의 성능은 거의 변화가 없음을 알 수 있었다. 따라서 PEMFC 시스템의 상용화를 위해서는 스택의 수명 및 운전의 신뢰성을 향상시켜야 한다.

• 한국자동차공학회논문집
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• 제14권6호
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• pp.50-56
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• 2006

Residual gas fraction in a combustion process is very crucial to improve combustion and cyclic variations. Especially, the residual gas fraction is strongly affected by backflow of the residual gas during the valve overlap period in an idle operation. Therefore, it is one of the most interesting that valve timings can affect flow characteristics of gas exchange process, especially during idle operation. This analysis investigates residual gas fraction with respect to valve timing changes which is critical for combustion efficiency and engine performance. Flow characteristics of residual gas by changing intake and exhaust valve timing are calculated by CFD methodology during an idle operation in an SI engine. It is analyzed that retarded EVO and advanced IVO results in the increase of valve overlap period and consequently, residual gas fraction. Futhermore, changes in IVO have stronger effects on variation of residual gas fraction.

• 한국자동차공학회논문집
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• 제23권6호
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• pp.608-614
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• 2015

Nitrogen oxide(NOx) emission reductions are required to meet the strict emission regulations for environmental protection. Most of the Exhaust Gas Recirculation(EGR) system applied to a diesel engine can relatively decrease the NOx at a low cost, but it has a disadvantage in that the PM generation is promoted due to the hot intake air temperature. Thus, high heat exchange efficiency of the EGR cooler is required for an effective removal of NOx. In this study, heat exchange efficiency for various types of heat exchangers used in EGR cooler was measured under same conditions, and determined best heat exchange performance shape depending on type of heat exchanger.

• The Journal of Asian Finance, Economics and Business
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• 제9권5호
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• pp.285-294
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• 2022

Using the ARDL approach, this study examined the impact of macro factors on Vietnam's stock market in the short and long run from 2010 to 2021. The State Bank of Vietnam and the International Monetary Fund provided time series data for this study. Research results show that in the long run, money supply and exchange rate respectively affect the stock market. The money supply had a positive effect on the VN-Index, while the exchange rate showed the opposite effect. However, the study did not find a relationship between world oil price and interest rates on VN-Index in the long run. On the other hand, in the short term, there are relationships between variables; specifically, interest rates and exchange rates have a negative impact on the VN-Index, while the world oil price and the fluctuation of money supply M2 of the previous one and two months showed an impact in the same direction on this index. The differences in the regression results on the impact of exchange rate and oil price on the VN-Index compared to previous studies come from the characteristics of Vietnam's stock market, with the large capitalization of companies in the oil and gas sector, and the structure of Vietnam's economy with export heavily depends on FDI sector.

• 한국가스학회지
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• 제21권4호
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• pp.42-46
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• 2017

화석연료의 무분별한 사용으로 인한 이산화탄소의 대기 중 방출은 지구의 연평균 기온을 상승시키는 원인으로 작용하고 있다. 이를 해결하기 위한 대체에너지로써 지열은 연중 일정한 온도를 갖는 무한자원이다. 지열에너지를 널리 보급하기 위해서는 히트펌프의 성능과 지중열교환기의 열교환 효율이 매우 중요하다. 이에 본 연구는 히트펌프의 성능을 증가시키기 위해 팽창변을 이중으로 구성하고 지중열교환기의 열교환 효율을 높이기 위해 입출관과 유입관 사이에 간격유지부재를 사용하여 실험하였다. 실험한 결과 팽창변을 이중으로 구성하였을 때 냉난방 능력이 최대 11.4%가 증가됨을 얻을 수 있었고, 간격유지부재를 사용 시 열교환 효율이 17.5% 향상되었다. 이러한 결과를 토대로 지열시스템의 설치 시 히트펌프의 성능과 지중열교환기의 열교환 효율의 상승으로 인해 설치비용이 많이 절감될 것으로 판단된다.