• 한국광학회:학술대회논문집
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• 한국광학회 2008년도 동계학술발표회 논문집
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• pp.429-430
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• 2008

We demonstrate coherent x-ray diffraction imaging using table-top x-ray laser at a wavelength of 13.9nm driven by 10-Hz ti:Sapphire laser system at the Advanced Photonics Research Institute in Korea. Since the flux of x-ray photons reaches as high as $10^9$ photons/pulse in a $20{\times}20{\mu}m^2$ field of view, we measured a ingle-pulse diffraction pattern of a micrometer-scale object with high dynamic range of diffraction intensities and successfully reconstructed to the image using phase retrieval algorithm with an oversampling ratio of 1:6. the imaging resolution is $^{\sim}150$ nm, while that is much improved by stacking the many diffraction patterns. This demonstration can be extended to the biological sample with the diffraction limited resolution.

• 천문학회지
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• 제50권5호
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• pp.139-149
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• 2017

The Korea Astronomy and Space Science Institute plans to develop a coronagraph in collaboration with National Aeronautics and Space Administration (NASA) and to install it on the International Space Station (ISS). The coronagraph is an externally occulted one-stage coronagraph with a field of view from 3 to 15 solar radii. The observation wavelength is approximately 400 nm, where strong Fraunhofer absorption lines from the photosphere experience thermal broadening and Doppler shift through scattering by coronal electrons. Photometric filter observations around this band enable the estimation of 2D electron temperature and electron velocity distribution in the corona. Together with a high time cadence (<12 min) of corona images used to determine the geometric and kinematic parameters of coronal mass ejections, the coronagraph will yield the spatial distribution of electron density by measuring the polarized brightness. For the purpose of technical demonstration, we intend to observe the total solar eclipse in August 2017 with the filter system and to perform a stratospheric balloon experiment in 2019 with the engineering model of the coronagraph. The coronagraph is planned to be installed on the ISS in 2021 for addressing a number of questions (e.g., coronal heating and solar wind acceleration) that are both fundamental and practically important in the physics of the solar corona and of the heliosphere.

• 한국초등과학교육학회지:초등과학교육
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• 제39권3호
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• pp.449-463
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• 2020

This study was to analysis teaching strategies, types of inquiry activities and the relationship between science concepts and inquiry activities presented in science textbooks. As a result of the study, first, the inquiry-based teaching strategies presented in science textbooks were experiment, simulation, demonstration, and field study. Second, there were 53 inquiry activities presented in 8 units related to the earth science area of science textbooks, and the types of inquiry activities were experimental observation (EO) 18, mock activity (SA) 20, investigation discussion and presentation (IP). It was analyzed as 12, data interpretation (ID) 2, and express (EX) 1 piece. Third, the relationship between inquiry activities and science concepts presented in science textbooks was analyzed. As a result of the analysis, out of a total of 42 inquiry activities, 21 inquiry activities corresponded to EA (explicit activities), in which the result of inquiry activities was directly and explicitly linked to science concepts. And IA (implicit activities), which is an implicit inquiry activity in which science concepts must be inferred using the results of inquiry activities, were analyzed as 21. In particular, IA (implicit activities), which is an implicit inquiry activity, can be said to be the result of reflecting the characteristics of earth science areas where many simulated activities (SA) are used. This is considered to be a matter to be considered in the process of developing various elementary science textbooks in the future.

• 한국수소및신에너지학회논문집
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• 제23권4호
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• pp.300-309
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• 2012

Long endurance is a key issue in the application of unmanned aerial vehicles. This study presents feasibility test results when fuel cell system as an alternative to the conventional engine is applied for the power of the UAV after the 150W fuel cell system is developed and packaged to the 1/4 scale super cub airplane. Fuel cell system is operated by dead-end method in the anode part and periodically purged to remove the water droplet in flow field during the operation. Oxygen in the air is supplied to the stack by the two air blowers. And fuel cell stack is water cooled by cooling circuit to dissipate the heat generated during the fuel cell operation. Weight balance is considered to integrate the stack and balance of plant (BOP) in package layout. In flight performance test, we demonstrated 4 times standalone take-off and landing. In the laboratory test simulating the flight condition to quantify the energy flow, the system is analyzed in detail. Sankey diagram shows that electric efficiency of the fuel cell system is 39.2%, heat loss 50.1%, parasitic loss 8.96%, and unreacted purged gas 1.67%, respectively compared to the total hydrogen input energy. Feasibility test results show that fuel cell system is high efficient and appropriate for the power of UAV.

• 방사성폐기물학회지
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• 제16권2호
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• pp.137-164
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• 2018

심지층처분장 공학적방벽의 성능 보장은 장기처분안전성 측면에서 뿐만 아니라 심지층처분장의 효율적인 설계를 위해서도 매우 중요하다. 따라서 지하실험시설에서 수행되는 현장실험들을 통해 심지층처분장 조건 하에서의 공학적방벽 성능을 입증할 필요가 있다. 이 논문에서는 심지층처분장 공학적방벽의 성능을 실증하기 위해, 지난 수십 년 동안 전 세계에서 수행되어온 주요 현장실험의 현황과 그 결과에 대해 검토하였다. 먼저 심지층처분장의 폐쇄 후 성능을 모사하는 공학적방벽시스템의 열-수리-역학적 복합거동을 규명하기 위한 현장실험들이 분석되었다. 아울러 실제 심지층처분장의 환경에서 완충재의 성능을 조사하기 위한 현장실험들이 검토되었다. 완충재-콘크리트 상호반응, 완충재, 뒷채움재 및 플러그의 설치, 그리고 근계암반 특성과 처분용기 재질의 부식 현상을 규명하기 위한 현장실험들의 기술현황도 분석되었다.

• 한국농공학회논문집
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• 제60권5호
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• pp.125-134
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• 2018

Recently, interest in alternative energy has been increasing to reduce greenhouse gas emissions and fossil fuel consumption in accordance with the United Nations Framework Convention on Climate Change(UNFCCC). Accordingly, there is a need to use waste heat that unused throughout industrial systems for lowering the concentration of energy on fossil fuels. In particular, government support projects for the energy recycling of agriculture and fisheries such as cultivation of tropical crops and aquaculture are being actively carried out by utilizing waste heat and thermal effluents caused from large-scale industrial complexes including power plants. The study was conducted on supplier (power plant), consumer (farmer) and stakeholders (constructor and local governments) of domestic demonstration areas using waste heat that is abandoned from the power plant in the form of thermal effluents. It investigated the overall improvement and feasibility of government funded projects through field interviews and questionnaire-type surveys. The results of this study are expected to provide basic directions for the operation of the project in terms of nationwide expansion and diffusion of the heat source supply project at horticultural greenhouse by utilizing the thermal effluents from power plant.

• 한국도로학회논문집
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• 제12권4호
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• pp.157-164
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• 2010

본 연구는 프리스트레스가 도입된 접속슬래브(Single-PTAS: Single Post-Tensioned Approach Slab)의 긴장력 도입에 따른 거동과 환경하중에 대한 거동을 분석하기 위하여 시험시공 현장에서 실험을 통해 수행되었다. 실험을 위해 온도측정센서를 슬래브의 깊이에 따라 장착하였으며, 변위측정게이지를 슬래브의 여러 위치에 설치하여 환경하중 및 긴장력 도입에 따른 슬래브의 변위 변화를 3차원적으로 측정하였다. 실험결과 접속슬래브는 길이가 짧아 긴장력 도입에 의한 급격한 종방향 변위 변화는 관찰되지 않았다. 접속슬래브의 깊이별 일일 온도변화는 깊이가 약 35cm보다 깊을 경우에는 거의 발생하지 않았으며, 수직온도구배는 접속슬래브의 두께가 큰 교대부근에서는 포장과 인접하는 부근에서 보다 작아졌다. 컬링 시 수직변위의 변화 양상 및 크기는 측정 지점의 수직온도구배와 직접적으로 관계가 있었다. Single-PTAS의 거동을 분석한 결과 콘크리트 포장 슬래브와 매우 유사한 거동을 보였으며, 따라서 차륜하중만을 고려하여 단순보로 설계하고 있는 접속슬래브에 포장체의 개념을 도입한 설계방안의 정립이 필요한 것으로 판단되었다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 1999년도 정기총회 및 춘계 공동 학술발표회
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• pp.149-156
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• 1999

In the United States (U.S.), the monitored natural attenuation (MNA) approach has been used as an alternative remedial option for organic and inorganic compounds retained in soil and dissolved in groundwater. The U.S. Environmental Protection Agency (EPA) defines the MNA as“in-situ naturally-occurring processes include biodegradation, diffusion, dilution, sorption, volatilization, and/or chemical and biochemical stabilization of contaminants and reduce contaminant toxicity, mobility or volume to the levels that are protective of human health and the environment”. The Department of Soil Environment. National Institute Environmental Research (NIER) is in the process for demonstrating the MNA approach as a potential remedial option for the BTEX contaminated site in Uiwang City. The project is charactering the research site in terms of the nature and extend of contamination, biological degradation rate, and geochemical and hydrological properties. The microbial-degradation rate and effectiveness of nutrient and redox supplements will be determined through laboratory batch and column tests. The geochemical process will be monitored for determining the concentration changes of chemical species involved in the electron transfer processes that include methanogenesis, sulfate and iron reduction, denitrification, and aerobic respiration. Through field works, critical soil and hydrogeologic parameters will be acquired to simulate the effects of dispersion, advection, sorption, and biodegradation on the fate and transport of the dissolved-phase BTEX plume using Bioplume III model. The objectives of this multi-years research project are (1) to evaluate the MNA approach using the BTEX contaminated site in Uiwang City, (2) to establish a standard protocol for future application of the approach, (3) to investigate applicability of the passive approach as a secondary treatment remedy after active treatments. In this presentation, the overall picture and philosophy behind the MNA approach will be reviewed. Detailed discussions of the site characterization/monitoring plans and risk-based decision-making processes for the demonstration site will be included.

• 스마트미디어저널
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• 제8권1호
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• pp.9-18
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• 2019

4차 산업혁명 시대에 사물인터넷과 모바일을 통해 수집된 다양한 정보를 이용해 공공 및 민간영역의 새로운 비즈니스모델을 위한 빅데이터 산업이 각광을 받고 있다. 하지만, 개인정보 비식별화 조치를 통한 빅데이터 통합 및 분석를 수행하면서 개인프라이버시가 노출될 위험성을 여전히 가지고 있다. 최근 개인정보를 노출하지 않고 데이터의 가치를 유지하는 방법에 대한 연구가 진행되고 있다. 본 논문에서는 빅데이터산업 활성화를 위해 의료, 농업 등 산업별로 개인정보 보호체계가 필요함을 강조하였다. 비식별화된 개인정보의 적정성 평가 기준을 개인 민감정보 중심의 의료분야는 k-익명성 최소값을 일반적인 산업분야의 평균값 보다 높은 5 이상으로 설정해야하며, 농업분야에서는 개인별 민감정보범위에 개인소유 반려견이나 농지 정보를 포함시켜서, 산업별 특성에 맞게 개인정보 보호체계를 보완해야하며, 해당 산업의 특정지역을 대상으로 먼저 실증을 거처 전국적으로 확산하는 것을 제안한다.

• 상하수도학회지
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• 제34권6호
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• pp.411-423
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• 2020

To remove phosphorus from the effluent of public wastewater treatment facilities, hundreds of enhanced phosphorus treatment processes have been introduced nationwide. However, these processes have a few problems including excessive maintenance cost and sludge production caused by inappropriate coagulant injection. Therefore, the optimal decision of coagulant dosage and automatic control of coagulant injection are essential. To overcome the drawbacks of conventional phosphorus removal processes, the integrated sedimentation and dissolved air flotation(SeDAF) process has been developed and a demonstration plant(capacity: 100 ㎥/d) has also been installed. In this study, various jar-tests(sedimentation and / or sedimentation·flotation) and multiple regression analyses have been performed. Particularly, we have highlighted the decision-making algorithms of optimal coagulant dosage to improve the applicability of the SeDAF process. As a result, the sedimentation jar-test could be a simple and reliable method for the decision of appropriate coagulant dosage in field condition of the SeDAF process. And, we have found that the SeDAF process can save 30 - 40% of coagulant dosage compared with conventional sedimentation processes to achieve total phosphorus (T-P) concentration below 0.2 mg/L of treated water, and it can also reduce same portion of sludge production.