• Korean Chemical Engineering Research
• /
• 제50권1호
• /
• pp.76-82
• /
• 2012

볏짚 톱밥과 같은 바이오매스는 석탄과 함께 사용할 수 있는 잠재력이 큰 에너지원으로 이들을 가스화공정에 적용하면 수송용 연료같은 bio-oil을 생산할 수 있다. 본 연구에서는 상압의 열천칭 반응기(thermobalance)에서 톱밥, 볏짚, 갈탄, 역청탄, 무연탄의 수증기 가스화 반응특성을 수행하였으며, 가스화 온도 $600{\sim}850^{\circ}C$, 수증기 분압 30~90 kPa의 범위에서 조업변수들이 가스화반응속도에 미치는 영향을 조사하였다. 세 가지의 기체-고체 화학반응모델이 가스화반응의 거동을 예측하는 능력을 비교하였으며, modified volumetric reaction model을 사용하여 공정설계에 필수적인 kinetic 정보를 도출하였다. 두 가지 바이오매스와 세 가지 석탄 촤의 가스화반응성을 비교하였다. Arrhenius plot으로부터 얻어진 바이오매스와 석탄의 활성화에너지는 모두 문헌상의 범위에 속하였다. 각 연료에 대하여 수증기분압에 대한 반응차수를 결정하였으며, 가스화공정 설계의 기초데이타로서 겉보기 반응속도식을 제시하였다.

• 해양환경안전학회지
• /
• 제13권1호
• /
• pp.29-37
• /
• 2007

1971년부터 2001년까지 해양 및 기상관측 자료를 활용하여 한국 서해에서 기상인자(기온, 바람, 강수량)가 수온과 염분 변화에 미치는 영향을 분석 하였다. 그 결과 수온-기온, 수온-강수량, 염분-풍속은 정상관(+)을, 수온-풍속, 염분-기온, 염분-강수량은 역상관(-)의 관계를 보였다. 기상인자와 해양인자간의 시간지연(time lag)은 표층에서 $0{\sim}4$개월, 저층까지 기상의 영향이 도달하는 데에는 표층보다 $0{\sim}4$개월의 시간지연이 더 있었다. 수온은 같은 해의 기온 변화의 영향을 크게 받는 반면, 염분은 그 직전해의 강수량의 영향을 크게 받았다. 풍속의 강약에 따라 수온, 염분의 변동 폭 또한 함께 변하였다.

• 태양에너지
• /
• 제16권2호
• /
• pp.49-63
• /
• 1996

측정지의 고도는 일사량 측정에 영향을 주는 중요한 요소이다. 대기중에 내포되어 있는 영속성개스 즉, 오존과 수증기 등은 대기의 순수한 혼합물 성분은 그 농도가 고도와 밀접한 함수관계를 갖기 때문에 해당 측정지 고도는 그 지역의 대기를 구성 하고 있는 성분에 상대적으로 비례하여 일사에 영향을 준다. 이에따라 소백산과 그인접 저지대인 풍기를 대상으로 일사강도를 측정하여 지역별 일사량자원의 특성과 향후 에너지자원으로서의 가능성을 목표로 두고 고지대와 저지대사이의 상호 비교가 가능하도록 하였다. 현지 측정사업의 내용을 중심으로 지금까지 나타난 결과를 살펴보면, 1) 소백산의 연평균 수평면 전일사량 조건은 청명한 날을 기준으로 하루에 4,093 $kcal/m^2$로 나타났다. 2) 소백산에서의 일사강도는 인접 저지대인 풍기보다 $6{\sim}7%$ 정도 높게 나타났다. 3) 대기청명도는 동일한 위도상인 소백산과 풍기지역간의 격차가 현저하게 존재 하였다. 는 점으로 요약된다.

• 대한화학회지
• /
• 제60권3호
• /
• pp.169-176
• /
• 2016

Borate 완충용액에서 Al의 부식과 부동화에 관하여 변전위법, 대 시간 전류법 그리고 다중 주파수 전기화학적 임피던스 측정법으로 조사하였다. 공기 또는 산소의 영향은 환원과정에 영향을 주었지만 산화반응에는 영향을 미치지 못 하는 것으로 보인다. 부동화 영역에서 생성되는 피막의 전기적 성질은 Mott-Schottky 식이 적용되는 n-type 반도체 성질을 보였다. 낮은 전극전위에서 생성되는 Al의 산화피막은 Al(OH)₃로 충분한 부동화 효과를 보이지 못하나, 전극전위가 증가하면서 Al₂O₃로 변하였다. Al₂O₃ 피막은 “전기장에 의한-이온의 이동” 과정에 의하여 성장하는 것으로 보인다.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2009년도 춘계학술대회 논문집
• /
• pp.1680-1686
• /
• 2009

삼각 분리 막대형 차압 유량계 압력 탭의 가공 조건에 따른 유량 특성을 연구하였다. 삼각 분리 막대탭 차압 유량계에 가공한 압력 탭의 크기는 1.0 mm 또는 1.5 mm로 하였다. 압력 탭의 개수는 5개 또는 17개로 가공하였다. 삼각 분리 막대탭 차압 유량계와 층류유량계를 직결한 후 유량 특성을 검정하였다. 삼각 분리 막대탭 차압 유량계의 질량 유량을 무차원 파라미터 H를 사용하여 나타내었다. H는 TSB 유량계에서의 배압, 기체 온도, 유량계 상류압과 하류압 간의 차압을 포함하는 무차원 파라미터이다. TSB 유량계의 질량 유량과 H 간에는 선형적 관계를 보였다. 압력 탭의 개수 보다는 압력 탭의 직경이 TSB 차압유량계의 유량 특성에 더 큰 영향을 미쳤다.

• Nuclear Engineering and Technology
• /
• 제48권4호
• /
• pp.932-940
• /
• 2016

Pool boiling heat transfer of water saturated at atmospheric pressure was investigated experimentally on Cu surfaces with high-temperature, thermally-conductive, microporous coatings (HTCMC). The coatings were created by sintering Cu powders on Cu surfaces in a nitrogen gas environment. A parametric study of the effects of particle size and coating thickness was conducted using three average particle sizes (APSs) of $10{\mu}m$, $25{\mu}m$, and $67{\mu}m$ and various coating thicknesses. It was found that nucleate boiling heat transfer (NBHT) and critical heat flux (CHF) were enhanced significantly for sintered microporous coatings. This is believed to have resulted from the random porous structures that appear to include reentrant type cavities. The maximum NBHT coefficient was measured to be approximately $400kW/m^2k$ with APS $67{\mu}m$ and $296{\mu}m$ coating thicknesses. This value is approximately eight times higher than that of a plain Cu surface. The maximum CHF observed was $2.1MW/m^2$ at APS $67{\mu}m$ and $428{\mu}m$ coating thicknesses, which is approximately double the CHF of a plain Cu surface. The enhancement of NBHT and CHF appeared to increase as the particle size increased in the tested range. However, two larger particle sizes ($25{\mu}m$ and $67{\mu}m$) showed a similar level of enhancement.

• 대기
• /
• 제27권2호
• /
• pp.163-175
• /
• 2017

The global terrestrial ecosystems have shown a large spatial variability in recent decades and represented a carbon sink pattern at mid-to-high latitude in Northern Hemisphere. However, there are many uncertainties in magnitude and spatial distribution of terrestrial carbon fluxes due to the effect of climate factors. So, it needs to accurately understand the spatio-temporal variations on carbon exchange flux with climate. This study focused on the effects of climate factors, .i.e. temperature, precipitation, and solar radiation, to terrestrial biosphere carbon flux. We used the terrestrial carbon flux that is simulated by a CarbonTracker, which performs data assimilation of global atmospheric $CO_2$ mole fraction measurements. We demonstrated significant interactions between Net Ecosystem Production (NEP) and climate factors by using the partial correlation analysis. NEP showed positive correlation with temperature at mid-to-high latitude in Northern Hemisphere but showed negative correlation pattern at $0-30^{\circ}N$. Also, NEP represented mostly negative correlation with precipitation at $60^{\circ}S-30^{\circ}N$. Solar radiation affected NEP positively at all latitudes and percentage of positive correlation at tropical regions was relatively lower than other latitudes. Spring and summer warming had potentially positive effect on NEP in Northern Hemisphere. On the other hand as increasing the temperature in autumn, NEP was largely reduced in most northern terrestrial ecosystems. The NEP variability that depends on climate factors also differently represented with the type of vegetation. Especially in crop regions, land carbon sinks had positive correlation with temperature but showed negative correlation with precipitation.

• 대기
• /
• 제29권5호
• /
• pp.689-698
• /
• 2019

Air pollution in urban areas has become a serious problem in the recent years. Especially, high concentrations of particulate matter (PM) cause negative effects on human health. Several studies suggest urban forest as a tool for improving air quality because of the capability of forests in reducing PM concentrations through deposition and adsorption using leaf area. For this reason, the National Institute of Forest Science plans to install in-situ observation stations for PM and biogenic volatile organic compounds (BVOCs) on a national scale to verify the net effect of forests on urban air pollution. To measure the quantitative change of PM concentrations due to the urban forest, stations should be located within and outside the forest area with respect to atmospheric circulation. In this study, we analyze the wind direction at the potential measurement sites to assess suitable locations for detecting the effect of urban forests on air quality in five cities (i.e. Gwangju, Daegu, Busan, Incheon, and Ilsan). This technical note suggests effective locations of in-situ measurements by considering main wind direction in the five cities of this study. A measurement station network created in the future based on the selected locations will allow quantitative measurements of PM concentration and BVOCs emitted from the urban forest and help provide a comprehensive understanding of the forest capabilities of reducing air pollution.

• Journal of Microbiology and Biotechnology
• /
• 제23권4호
• /
• pp.451-458
• /
• 2013

The human gastric pathogen Helicobacter pylori (Hp) has been considered a microaerophile. However, we recently reported that, when supplied with 10% $CO_2$, Hp growth is stimulated by an atmospheric level of $O_2$, suggesting that Hp is a capnophilic aerobe. In this study, we investigated the effects of aerobic $O_2$ tension on Hp cells by comparing gene expression profiles of cultures grown under microaerobic and aerobic conditions in the presence of 10% $CO_2$. The results showed that overall differences in gene expression in Hp cells grown under the two $O_2$ conditions were predominantly growth-phase-dependent. At 6 h, numerous genes were down-regulated under the aerobic condition, accounting for our previous observation that Hp growth was retarded under this condition. At 36 h, however, diverse groups of genes involved in energy metabolism, cellular processes, transport, and cell envelope synthesis were highly up- or down-regulated under the aerobic condition, indicating a progression of the cultures from the log phase to the stationary phase. The expression of several oxidative stress-associated genes including tagD, katA, and rocF was induced in response to aerobic $O_2$ level, whereas trxA, trxB, and ahpC remained unchanged. Altogether, these data demonstrate that aerobic $O_2$ tension is not detrimental to Hp cells but stimulates Hp growth, supporting our previous finding that Hp may be an aerobic bacterium that requires a high $CO_2$ level for its growth.

• 천문학논총
• /
• 제32권3호
• /
• pp.381-405
• /
• 2017

We give a detailed description of the installation and operation of a double-station meteor detection system which formed part of a research & education project between Korea Astronomy Space Science Institute (KASI) and Daejeon Science Highschool. A similar system is currently not existing in South Korea. A total of six light-sensitive CCD cameras were installed with three cameras at SOAO and three cameras at BOAO observatory. A double-station observation of a meteor event enables the determination of the three-dimensional heliocentric orbit in space. This project was initiated in response to the Jinju fireball event in March 2014. The cameras were installed in October/November 2014. The two stations are identical in hardware as well as software. Each station employes sensitive "Watec-902H2" cameras in combination with relatively fast f/1.2 lenses. Various fields of views were used for measuring differences in detection rates of meteor events. We employed the SonotaCo UFO software suite for meteor detection and their subsequent analysis. The system setup as well as installation/operation experience is described and first results are presented. We also give a brief overview of historic as well as recent meteor (fall) detections in South Korea. For more information please consult http://meteor.kasi.re.kr.