• Economic and Environmental Geology
• /
• v.52 no.1
• /
• pp.37-48
• /
• 2019

In geological $CO_2$ sequestration, the behavior of $CO_2$ within a reservoir can be characterized as two-phase flow in a porous media. For two phase flow, these processes include drainage, when a wetting fluid is displaced by a non-wetting fluid and imbibition, when a non-wetting fluid is displaced by a wetting fluid. In $CO_2$ sequestration, an understanding of drainage and imbibition processes and the resulting NW phase residual trapping are of critical importance to evaluate the impacts and efficiencies of these displacement process. This study aimed to observe migration and residual trapping of immiscible fluids in porous media via cyclic injection of drainage-imbibition. For this purpose, cyclic injection experiments by applying n-hexane and deionized water used as proxy fluid of $scCO_2$ and pore water were conducted in the two dimensional micromodel. The images from experiment were used to estimate the saturation and observed distribution of n-hexane and deionized water over the course drainage-imbibition cycles. Experimental results showed that n-hexane and deionized water are trapped by wettability, capillarity, dead end zone, entrapment and bypassing during $1^{st}$ drainage-imbibition cycle. Also, as cyclic injection proceeds, the flow path is simplified around the main flow path in the micromodel, and the saturation of injection fluid converges to remain constant. Experimental observation results can be used to predict the migration and distribution of $CO_2$ and pore water by reservoir environmental conditions and drainage-imbibition cycles.

• Economic and Environmental Geology
• /
• v.54 no.1
• /
• pp.105-115
• /
• 2021

The geological CO2 sequestration in underground geological formation such as deep saline aquifers and depleted hydrocarbon reservoirs is one of the most promising options for reducing the atmospheric CO2 emissions. The process in geological CO2 sequestration involves injection of supercritical CO2 (scCO2) into porous media saturated with pore water and initiates CO2 flooding with immiscible displacement. The CO2 migration and distribution, and, consequently, the displacement efficiency is governed by the interaction of fluids. Especially, the viscous force and capillary force are controlled by geological formation conditions and injection conditions. This study aimed to estimate the effects of surfactant on interfacial tension between the immiscible fluids, scCO2 and porewater, under high pressure and high temperature conditions by using a pair of proxy fluids under standard conditions through pendant drop method. It also aimed to observe migration and distribution patterns of the immiscible fluids and estimate the effects of surfactant concentrations on the displacement efficiency of scCO2. Micromodel experiments were conducted by applying n-hexane and deionized water as proxy fluids for scCO2 and porewater. In order to quantitatively analyze the immiscible displacement phenomena by n-hexane injection in pore network, the images of migration and distribution pattern of the two fluids are acquired through a imaging system. The experimental results revealed that the addition of surfactants sharply reduces the interfacial tension between hexane and deionized water at low concentrations and approaches a constant value as the concentration increases. Also it was found that, by directly affecting the flow path of the flooding fluid at the pore scale in the porous medium, the surfactant showed the identical effect on the displacement efficiency of n-hexane at equilibrium state. The experimental observation results could provide important fundamental information on immiscible displacement of fluids in porous media and suggest the potential to improve the displacement efficiency of scCO2 by using surfactants.

• Proceedings of the KIEE Conference
• /
• 2001.07b
• /
• pp.1325-1327
• /
• 2001

우리나라는 장기전력수급계획 및 10개년 에너지기본계획, 그리고 최근에 수립된 대체에너지보급 3개년 기본계획의 달성 및 보급확대를 위한 보급시나리오 구성에 따른 보급목표를 설정하였다. 대체에너지 지원규모를 산정하기 위한 방법으로는 대체에너지수요전망에서 산출된 대체에너지원별 전망치를 이용, 지원비율을 책정하여 지원규모를 시산하는 방법이 있으며 또 다른 방법으로는 전망된 수요량을 공급하기 위한 시설 및 장비에 드는 투자비를 산출하여 일정비율을 지원한다고 가정한 다음, 지원규모를 시산하는 방법도 있다. 본 연구에서는 후자의 방법을 통하여 재생전원의 보급목표의 설정과 현재의 설치단가를 기준으로 보급에 필요한 설치비용에 대한 지원규모를 개략적으로 분석하고자 하며, 아울러 정부의 대체에너지 보급목표를 달성하기 위한 지원금액을 추정 하고자 한다.

• Korean Journal of Childcare and Education
• /
• v.9 no.3
• /
• pp.209-228
• /
• 2013

The purpose of this study was to analyze the recognition of the substitute teacher system between public funds support and local province funds support and to search for a policy guideline. The participants were 49 substitute teachers supported by public funds and 53 substitute teachers supported by local province funds. Results were as follows: Firstly, substitute teachers supported by public funds participated through an internet site but substitute teachers supported by local province funds participated through printed materials from the Childcare Information Center and ambient solicitors. The participating motive for substitute teachers were to work together in different roles. Secondly, Substitute teachers thought the most important characteristics of substitute teachers was the flexibility to cope with various situations in childcare centers. Finally, substitute teachers by public funds support were satisfied with no overtime work but substitute teachers by local province funds were satisfied with experiences in various childcare centers.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2021.06a
• /
• pp.96-96
• /
• 2021

수문기상인자 중 하나인 증발산량은 수자원 계획 및 관리 시 고려되며, 특히 물수지 모형 등의 입력자료로 활용된다. 우리나라를 포함한 각국 기상청 및 국제기구에서는 직접 관측이 아닌 FAO56 Penman-Monteith(PM)을 통해 증발산량을 산출하고 있다. FAO56 PM 방법은 복사(radiation), 대기온도(air temperature), 습도(humidity), 풍속(wind speed) 등의 기상인자로부터 기준증발산량(reference evapotransipiration)을 추정하며, 상대적으로 높은 정확성을 보여준다. 그러나 FAO56 PM 방법은 많은 기상인자를 요구하므로 미계측 유역을 포함한 일부지역에 대한 증발산량 자료 구축이 어려운 실정이다. 또한, 기준증발산량의 특성이 시간에 따라 변화하므로 비정상성(nonstationary)을 고려한 분석이 요구된다. 본 연구에서는 온도인자 기반의 대체모형(surrogate model)을 개발하여 기준증발산량의 비정상성을 고려하고자 한다. 한강유역에 위치한 관측소를 대상으로 모형을 개발하였으며, 시간에 따라 변동하는 기준증발산량의 특성을 고려하기 위해 Bayesian 추론기법을 통해 매개변수를 시간에 따라 추정하였다. 또한, 본 연구에서는 대체모형으로 산정된 증발산량을 활용해 가뭄지수인 EDDI(evaporative demand drought index)를 제시하였다. 가뭄 모니터링 및 조기 경보 안내를 위해 개발된 EDDI를 활용하여 기존 가뭄보다 빠르게 진행되는 초단기 가뭄(flash drought)를 평가하였다. 본 연구에서 개발된 모형은 미계측 지역에서도 적용이 가능하므로 수자원분야에서 활용성이 높을 것으로 사료된다.

• Proceedings of the Korean Society for Bio-Environment Control Conference
• /
• 1999.04a
• /
• pp.15-19
• /
• 1999

IMF 이후 시설원예분야에 있어 생에너지, 에너지 절약형, 대체에너지 개발 등의 용어들이 자주 등장하고 하고 있다. 이는 시설원예 난방에너지원의 대부분을 수입에 의존함에 따라 지난 2년간에 걸친 유가의 상승으로 인한 온실경영의 어려움을 단적으로 보여주고 있는 것이라 하겠다. 따라서, 난방연료비의 상승에 대응하여 시설원예의 안정적인 유지 발전과 장기적으로 환경보존이라는 측면에서 난방에너지를 줄이고 대체에너지의 개발 등을 통한 난방비 부담의 감소와 안정된 생산기술을 확립하여야 한다. (중략)

• Review of KIISC
• /
• v.32 no.1
• /
• pp.19-29
• /
• 2022

2011 Jao와 De Feo에 의해 제안된 SIDH가 기존 타원곡선 사이의 isogeny를 이용한 암호보다 효율적인 성능을 제공하고, 그 후 2016년 Costello 등의 효율적인 연산 방법으로 SIDH 속도가 3배 이상 향상되면서, 타원곡선 사이의 isogeny를 이용한 암호가 양자 컴퓨팅 환경에서 RSA와 ECC를 대체할 암호로 주목을 받기 시작했다. 특히 isogeny 기반 암호는 다른 PQC 암호에 비해 작은 키 사이즈를 제공한다는 장점으로 현재까지 활발히 연구가 진행되고 있으며, SIDH를 기반으로 둔 SIKE는 NIST PQC 표준화 공모전 Round 3의 대체 후보이다. 다른 PQC 암호에 비해 속도가 느리다는 점이 isogeny 기반 암호의 단점인 만큼, isogeny 기반 암호는 처음 제안된 후 10년 동안 최적화를 중심으로 큰 발전을 이뤄왔다. 본 논문에서는 isogeny 기반 암호의 최신 연구 동향을 소개한다.

• The Journal of the Korea Contents Association
• /
• v.19 no.5
• /
• pp.104-114
• /
• 2019

In the global market competition, countries and businesses are actively engaged in technology prediction activities to maximize their profits by attempting to enter and preempting the core technology of the future. In this paper, we propose a growth model based on patent application trends to predict the time to replace a product with a promising new technology to dominate the market. Although the Fisher-Pry model that Bhargava generalized to predict the emergence of promising alternative technologies was relatively satisfactory compared to the original Fisher-Pry model, it was difficult to predict the replacement rate behavior properly due to a parameter problem. The application of the Fisher-Pry Modification Model in the form of a quadratic equation through the patent trend analysis of the optical storage system for the purpose of verifying the time alternative to the light storage technology has resulted in satisfactory verification results. It is expected that small and medium-sized companies and individual researchers will apply this model and use it more easily to predict the time to replace the market for promising replacement technologies.

• Environmental and Resource Economics Review
• /
• v.23 no.1
• /
• pp.91-132
• /
• 2014

We investigate the effect of ICT capital on the demands for labor and energy in manufacturing and electricity gas water industries of Korea, US, and UK. Assuming ICT capital, non-ICT capital, labor, electricity, fuel, and material as input factors for manufacturing and ICT capital, non-ICT capital, labor and energy material as input factors for electricity gas water industry, we estimate the Morishima elasticities of substitution. Considering the relative price changes of input factors, ICT capital has substituted labor in manufacturing and electricity water gas industries of the three countries. ICT capital has substituted both electricity and fuel in US and UK manufacturing. Although ICT capital has substituted electricity and fuel each other in Korean manufacturing, ICT capital is unlikely to decrease the demands for electricity and fuel when considering their relative price changes. ICT capital has substituted energy material in electricity gas water industries of the three countries.

• Journal of Animal Science and Technology
• /
• v.46 no.4
• /
• pp.603-612
• /
• 2004

This study was carried out to investigate the replacing fish meal or soybean meal effect of with feather meal or Bacillus sp. inoculated feather meal in broiler diets on the performances and nutrient utilization. One hundred and eighty broilers were randomly allotted to six dietary treatments(1) control, basal diet; (2) BFMl00, Fish meal replacing at 100% level with bacillus sp. inoculated feather meal; (3) BSM20, Soybean meal replacing at 20% level with bacillus sp. inoculated feather meal; (4) BFMl00+BSM20, Fish meal and soybean meal replacing at 100% level and 20% level with bacillus sp. inoculated feather meal, respectively; (5) GFMl00, Fish meal replacing at 100% level with general feather meal; and (6) GSM20, Soybean meal replacing at 20% level with general feather meal) in a 5 week feeding trial. In overall period, body weight gain of control was the highest(1,623g) and those of BFM 100, BFM 100+ BSM 20 and GFM 100 were 1,572g, 1,564g, and 1,078g, respectively. And that of GFM 100(1,078.3g) was the lowest(p<0.05) among treatments. Digestibility of dry matter for BFM 100+BSM 20(81.46%) was higher(p<0.05) than that for other treatments, and that of crude protein was the lowest (p<0.05). Digestibilities of organic matter were significantly(p<0.05) improved when Bacillus sp. inoculated feather meal was replaced at 100% level with fish meal in the basal diet. Methane and hydrogen sulfide gases from the feces were significantly(p<0.05) decreased in chicks fed the control, BFM 100 and GFM 100 diets, when observed after 3 weeks of feeding trials. Feed costs of the control and BFM 100 were 417 and 384 won, respectively but that of BSM 20 was 558 won. Therefore, replacement of fish meal with Bacillus sp. inoculated feather meal in the diets for chicks could be useful for economic production.