• Carbon letters
• /
• 제14권3호
• /
• pp.186-189
• /
• 2013

We report a highly sensitive $NO_2$ gas sensor based on multi-layer graphene (MLG) films synthesized by a chemical vapor deposition method on a microheater-embedded flexible substrate. The MLG could detect low-concentration $NO_2$ even at sub-ppm (<200 ppb) levels. It also exhibited a high resistance change of ~6% when it was exposed to 1 ppm $NO_2$ gas at room temperature for 1 min. The exceptionally high sensitivity could be attributed to the large number of $NO_2$ molecule adsorption sites on the MLG due to its a large surface area and various defect-sites, and to the high mobility of carriers transferred between the MLG films and the adsorbed gas molecules. Although desorption of the $NO_2$ molecules was slow, it could be enhanced by an additional annealing process using an embedded Au microheater. The outstanding mechanical flexibility of the graphene film ensures the stable sensing response of the device under extreme bending stress. Our large-scale and easily reproducible MLG films can provide a proof-of-concept for future flexible $NO_2$ gas sensor devices.

• 한국작물학회지
• /
• 제31권3호
• /
• pp.356-360
• /
• 1986

엽녹소형광측정에 의한 수도 내냉성검정의 가능성을 검토하기 위하여 내냉성이 다양한 11개 품종을 1 /5000a pot에 원형직파하여 육성된 재료들을 수잉기에 1$0^{\circ}C$의 저온에 8 일간 처리하여 저온처리전후의 가변형광량( $F_{VAR}$)과 형광증가속도(F/sun R/)의 변화를 비교하였다. 내냉성이 약한 품종들에서 저온처리에 의한 형광특성들의 감소가 커서 각 품종들의 저온장해정도와 가변형광량 및 형광증가속도의 저온처리전후의 대비지수는 부의 유의상관을 나타내어 이들 형광특성들은 도체형양기관에 나타나는 저온장해의 정도를 판단하는데 유용하게 이용될 수 있을 것으로 판단되었다. 엽록소형광을 이용한 내냉성검정방법은 다량의 육종재료 검정에 정밀성, 경제성, 신속성과 함께 검정에 공시된 개체를 계속 육종에 이용할 수 있어 이의 활용이 기대된다.다.

• 한국환경과학회지
• /
• 제7권1호
• /
• pp.27-35
• /
• 1998

The present study intends to investigate the transient response of an atmosphere /ocean general circulation model to a gradual Increase of atmospheric carbon dioxide. To detect the climatic change of the for 1% $CO_2$ run with increasing $CO_2$ and the control run with fried $CO_2$ are compared. From response of the surface air temperature due to the gradual increase of atmospheric carbon dioxide is slowly increased with latitudes and is clearly larger over continents than oceans. The annual goffal mean temperature is continuously increased with 0.03552 per one year with strong SIN ratio and distinguished from the natural variability The time dependent response of the gradual increasing $CO_2$ has the strong seasonal variability with small change In summer and large change in winter, and the strong regional In the Asian and the American continents. It has been suggested that the direct and the feedback processes in the climate systems should be investigated by the detailed sensitivity runs to get the meaninguul estimate of the $CO_2$ forced variability.

• 한국농공학회논문집
• /
• 제48권6호
• /
• pp.31-41
• /
• 2006

The analysis used in this work was cost-benefit analysis method. All future costs and returns of a given mushroom house were discounted to the time of initial investment (present) by means of 3.5% discount rate. Then the cost of ownership was compared to the return from the system. This analysis method has been developed and coded into a balance sheet for use on a EXCEL program. Using this programmed analysis,a large number of the case studies were examined using different combinations of economic conditions. These results will be very useful to individuals considering investment in a mushroom house, or any similar production system. By the way of the sensitivity analysis for each important parameter, the change of the marginal cost-benefit period could be finally determined. These parameters were typically construction cost of mushroom house, cost of cooling system, required cooling and heating energy amounts, unit price of mushroom media bottle, growing number of media bottles, production weight per unit bottle, sale price of mushroom, and annual number of growing period, etc.

• 한국해안해양공학회지
• /
• 제8권2호
• /
• pp.174-184
• /
• 1996

본 연구에서는 완전개방 직사각형 항만을 대상으로 항만 부진동 해석에 많이 사용되는 복합요소 수치모형의 실제 적용시에 관계되는 주요인자에 대한 민감도 해석을 수행하였다. 그 결과 유한요소 영역은 수심 변화가 크지 않은 곳까지 확장하는 것이 바람직한 것으로 나타났으며, 해석해 영역의 수심은 두 영역의 경계면을 따른 평균수심을 사용하는 것이 적절한 것으로 나타났다. 해석해의 Fourier 성분수는 일정수심의 단순한 항만에서는 큰 의미가 없으나 복잡한 형상의 변동수심의 항만에서는 그 중요성이 증가할 것으로 예상된다. 입사파향은 제1 공진 모드에는 큰 영향을 주지 않으나 수심 경사가 커질수록 그 영향이 증대되며, 특히 고차 모드는 큰 영향을 받게 되는 것으로 나타났다.

• 한국지형학회지
• /
• 제28권2호
• /
• pp.59-70
• /
• 2021

This study aims to determine the sunlight exposure according to depositional environment to improve the accuracy of optically simulated luminescence (OSL) dating. Sufficient sunlight exposure during transportation of sediment is a basic assumption of the OSL dating, and if the process does not occur enough, the results may be overestimated compared to the actual depositional age. Therefore, the main purpose of this study is to establish a correction method by determining residual or unbleachable dose after sunlight exposure in the actual deposition process, not in the laboratory measurement. Four samples from two sites were collected according to the depositional environment from rivers and coasts, and various OSL signals, including the size of residual dose, degree of dispersion between grains, and OSL signal sensitivity, were measured. As a result, it was confirmed that sediments formed under temporarily high energy environments, such as floods and surges, had relatively high residual dose or large dispersion of residual dose between particles. In further studies, the OSL signal characteristics of river sediments by flow velocity will be identified and the relationship between energy and OSL signal characteristics will be identified in more detail. Moreover, a method of reconstructing the paleo-environment at the time of deposition for existing sediments will be devised. It is expected to provide important information for the frequency of disaster recurrence and prediction of future climate change.

• 한국기후변화학회지
• /
• 제1권1호
• /
• pp.21-30
• /
• 2010

본 연구에서는 홍수, 가뭄, 물관리 등 수자원 분야 취약성을 규준(criteria) 및 지표(indicators)를 활용하여 평가하는 방법을 제시하였다. 제시된 방법을 통해 전국 및 지역 단위의 취약성 평가를 실시하였다. 또한, 평가 규모별 적정 유역 크기에 대한 방안도 아울러 제시하였다. 수자원 취약성 평가에 이용한 규준은 크게 평가 대상지의 민감도, 기후에의 노출, 기후변화에 대한 적응력으로 분류할 수 있으며, 각 규준을 지표로 계량화 및 표준화하여 취약성 평가에 반영한다. 기후변화에 대한 수자원 분야의 취약성은 일반적으로 시간이 갈수록 증가하는 것으로 평가되었다. 평가 대상지의 유역 규모는 국가 차원의 취약성 평가는 대유역을 기준으로 설정하는 것이 유의하며, 지역 차원의 평가는 소유역을 기준이 적절함을 알 수 있었다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
• /
• pp.195-195
• /
• 2012

Recently, graphene based solution-gated field-effect transistors (SGFETs) have been received a great attention in biochemical sensing applications. Graphene and reduced graphene oxide (RGO) possess various advantages such as high sensitivity, low detection limit, label-free electrical detection, and ease of fabrication due to their 2D nature and large sensing area compared to 1D nanomaterials- based nanobiosensors. Therefore, graphene or RGO -based SGFET is a good potential candidate for sensitive detection of protons (H+ ions) which can be applied as the transducer in various enzymatic or cell-based biosensing applications. However, reports on detection of H+ ions using graphene or RGO based SGFETs have been still limited. According to recent reports, clean graphene grown by CVD or exfoliation is electrochemically insensitive to changes of H+ concentration in solution because its surface does not have terminal functional groups that can sense the chemical potential change induced by varying surface charges of H+ on CVD graphene surface. In this work, we used RGO -SGFETs having oxygen-containing functional groups such as hydroxyl (OH) groups that effectively interact with H+ ions for expectation of increasing pH sensitivity. Additionally, we also investigate RGO based SGFETs for bio-sensing applications. Hydroloytic enzymes were introduced for sensing of biomolecular interaction on the surface of RGO -SGFET in which enzyme and substrate are acetylcholinesterase (AchE) and acetylcholine (Ach), respectively. The increase in H+ generated through enzymatic reaction of hydrolysis of Ach by AchE immobilized on RGO channel in SGFET could be monitored by the change in the drain-source current (Ids).

• Nuclear Engineering and Technology
• /
• 제55권8호
• /
• pp.3017-3029
• /
• 2023

In the late in-vessel phase of a nuclear reactor severe accident, the internal heat transfer and crust evolution during the debris bed melting process have important effects on the thermal load distribution along the vessel wall, and further affect the reactor pressure vessel (RPV) failure mode and the state of melt during leakage. This study coupled the phase change model and large eddy simulation to investigate the variations of the temperature, melt liquid fraction, crust and heat flux distributions during the debris bed melting process in the hypothetical severe accident of HPR1000. The results indicated that the heat flow towards the vessel wall and upper surface were similar at the beginning stage of debris melting, but the upward heat flow increased significantly as the development of the molten pool. The maximum heat flux towards the vessel wall reached 0.4 MW/m². The thickness of lower crust decreased as the debris melting. It was much thicker at the bottom region with the azimuthal angle below 20° and decreased rapidly at the azimuthal angle around 20-50°. The maximum and minimum thicknesses were 2 and 90 mm, respectively. By contrast, the distribution of upper crust was uniform and reached stable state much earlier than the lower crust, with the thickness of about 10 mm. Moreover, the sensitivity analysis of initial condition indicated that as the decrease of time interval from reactor scram to debris bed dried-out, the maximum debris temperature and melt fraction became larger, the lower crust thickness became thinner, but the upper crust had no significant change. The sensitivity analysis of in-vessel retention (IVR) strategies indicated that the passive and active external reactor vessel cooling (ERVC) had little effect on the internal heat transfer and crust evolution. In the case not considering the internal reactor vessel cooling (IRVC), the upper crust was not obvious.

• 한국방재학회 논문집
• /
• 제10권2호
• /
• pp.123-133
• /
• 2010

강변저류지와 같은 소규모 수공구조물에 의한 홍수저감방안의 필요성이 증가하고 있으며, 대상 유역내에 다수의 후보지역이 존재하는 강변저류지 계획에 있어서, 네트워크로 간주된 전체 저류지군의 실질적인 홍수조절효과의 산정이 필수적이다. 본 연구에서는 저류용량, 월류고, 월류폭 등과 같은 강변저류지 제원에 대한 민감도 분석을 통한 강변저류지군의 홍수저감효과 개선기법을 제안하였다. 제안된 기법은 설계빈도 홍수사상에 대하여 강변저류지 제원 변화에 따른 직하류부 및 유역출구 홍수저감량 민감도 분석을 실시하고, 민감도분석 결과를 이용하여 직하류부와 유역출구에서의 홍수저감량이 최대가 되게 하는 강변저류지 제원을 결정한다. 제안된 기법을 안성천 유역에 적용하여 적용성을 검토하였으며, 기존의 연구결과와 본 연구에서 제안한 기법의 결과를 비교분석하였다.