• Journal of Electrochemical Science and Technology
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• 제8권4호
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• pp.265-273
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• 2017

Solid-state alkaline water electrolysis is a promising method for producing hydrogen using renewable energy sources such as wind and solar power. Despite active investigations of component development for anion exchange membrane water electrolysis (AEMWE), understanding of the device performance remains insufficient for the commercialization of AEMWE. The study of assembled AEMWE devices is essential to validate the activity and stability of developed catalysts and electrolyte membranes, as well as the dependence of the performance on the device operating conditions. Herein, we review the development of catalysts and membranes reported by different AEMWE companies such as ACTA S.p.A. and Proton OnSite and device operating conditions that significantly affect the AEMWE performance. For example, $CuCoO_x$ and $LiCoO_2$ have been studied as oxygen evolution catalysts by Acta S.p.A and Proton OnSite, respectively. Anion exchange membranes based on polyethylene and polysulfone are also investigated for use as electrolyte membranes in AEMWE devices. In addition, operation factors, including temperature, electrolyte concentration and acidity, and solution feed methods, are reviewed in terms of their influence on the AEMWE performance. The reaction rate of water splitting generally increases with increase in operating temperature because of the facilitated kinetics and higher ion conductivity. The effect of solution feeding configuration on the AEMWE performance is explained, with a brief discussion on current AEMWE performance and device durability.

• 한국수소및신에너지학회논문집
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• 제7권1호
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• pp.29-37
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• 1996

Alkaline water electrolysis has been commercialized as the only large-scale method for a long time to produce hydrogen and the technology is superior to other methods such as photochemical, thermochemical water splitting, and thermal decomposition method in view of efficiency and related technical problem. However, such conventional electrolyzer do not have high electric efficiency and productivity to apply to large scale hydrogen production for energy or chemical feedstocks. Solid polymer electrolyte water electrolysis using a perfluorocation exchange membrane as an $H^+$ ion conductor is considered to be a promising method, because of capability for operating at high current densities and low cell voltages. So, this is a good technology for the storage of electricity generated by photovoltaic power plants, wind generators and other energy conversion systems. One of the most important R&D topics in electrolyser is how to minimize cell voltage and maximize current density in order to increase the productivity of the electrolyzer. A commercialized technology is the hot press method which the film type electrocatalyst is hot-pressed to soild polymer membrane in order to eliminate the contact resistance. Various technologies, electrocatalyst formed over Nafion membrane surface by means of nonelectrolytic plating process, porous sintered metal(titanium powder) or titanium mesh coated with electrocatalyst, have been studied for preparation of membrane-electrocatalyst composites. In this study some experiments have been conducted at a solid polymer electrolyte water electrolyzer, which consisted of single cell stack with an electrode area of $25cm^2$ in a unipolar arrangement using titanium mesh coated with electrocatalyst.

• 전기전자학회논문지
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• 제24권2호
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• pp.392-402
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• 2020

본 논문은 광센서 없는 태양광 추적 시스템을 제안한다. 태양광 추적, MPPT, ESS, 모니터링의 4가지 기능을 모듈화하여 시스템을 구현하였다. 9개의 태양광 패널을 기본단위로, 바람의 영향을 저감하고, 광센서 없이 태양광 추적이 가능하도록 상하좌우 패널의 높낮이를 다르게 한 격자형 구조를 채택하였다. 저가형 MCU를 이용한 부스트 컨버터 PWM 스위칭을 위해 기존 MPPT의 연산 방법을 개선하였다. ESS 모듈은 리튬 이온 배터리 12개(직렬 3셀과 병렬 4셀)를 기본 단위로 구성하여 온도 및 전기 특성의 이상 유무 감시가 가능하게 하였다. 각 모듈의 MCU는 Atmega128 또는 Raspberry PI로 구성하였으며 운전 정보를 상호 교환하고, IoT 기술을 응용하여 실시간 원격 모니터링과 클라우드에 데이터베이스를 구축하여 유지보수가 가능하게 하였다. 실험을 위해 제작된 태양광 발전 시스템의 운전 데이터는 각 모듈의 분산 및 원격 모니터링의 가능성, 유지보수의 편의성 및 광추적 성능을 증명한다.

• 대한기계학회논문집B
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• 제26권1호
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• pp.82-93
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• 2002

The effects of the interaction between the flow and temperature field and a boundary layer due to a variety of the height of a vortex generator are experimentally investigated. The test facility consists of a boundary-layer wind tunnel with the vortex generator protruding from the bottom surface. In order to control the strength of the longitudinal vortices, the angle of attack and the spacing distance of the vortex generator are 20 degree and 40 mm, respectively. The height of the vortex generator (H) is 15 mm, 20 mm and 30 mm and the cord length of it is 50 mm. Three-component mean velocity measurements are made using a 5-hole probe system and the surface temperature distribution is measured by the hue capturing method using thermochromatic liquid crystals. By using the method mentioned above, the following conclusions are obtained from the present experiment. The boundary layer is thinned in the downwash region where the strong downflow and the lateral outflow of the boundary layer fluid occur and thickened in the upwash re,3ion where the longitudinal vortex sweeps low momentum fluid away from the bottom surface. In case that the height of the vortex generator increases, the averaged circulation and the maximum vorticity of the vortex pair decrease. The contours of the non-dimensional temperature show the similar trends fur all the cases (H=15 mm, 20 mm and 30 mm). The peak augmentation of the distribution of the local non-dimensional temperature occurs in the downwash region near the point of minimum boundary-layer thickness.

• 자원환경지질
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• 제32권1호
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• pp.73-82
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• 1999

The objectives of this study are to investigate soil contamination in the vicinity of abandoned Au-Ag mine and to apply a remediation technique of liming to tailings. In the study area of the Imcheon Au-Ag mine, soils were sampled in and around the mine the analyzed by Atomic Absorption Spectrometry extracted by both 0.1N HCl and aqua regia. Elevated levels of Cd, Cu, Pb and Zn concentrations extracted by 0.1N HCl were found in soils taken from tailings site. These high contents directly influenced metal concentrations in soils taken in the vicinity of the site. This is mainly due to clastic movement by wind and effluent of mine waste water. In addition, relatively enriched concentrations of the metals were found in soils extrated by aqua regia due to strong decomposition of the samples compared with 0.1N HCl extration. According to the statistical approach, metal concentrations in soils by 0.1N HCl had a positive correlation with those by aqua regia extraction. Mine waste waters and stream waters were also sampled around the mine in spring and summer and analyzed by AAS for Cd, Cu, Pb and Zn, and by Ion Chromatography for anions. Like soils developed over tailings, significant levels of metals and sulphates were found in the mine waste waters ranging of 0.2~0.3, 0.5~2.0, 0.2~2.8, 30~50 and 1,240~4,700 mg/l of Cd, Cu, Pb, Zn and $SO_4^{2-}$, respectively. These elevated levels influenced in the stream waters in the vicinity of the tailings site. In seasonal variation of metal and anion contents, relatively high levels were found in waters sampled on summer due to leaching the metals and anions from tailings by rain. This study also examined the possibility of lime treatment for remediation of acid mine tailings and assumed to be 46 tones of pulverized lime for neutralization of the tailings.

• 한국환경과학회지
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• 제13권12호
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• pp.1079-1088
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• 2004

In order to understand chemical characteristics and dewfall formation in western Busan area, we analysed monthly distribution of dewfall, and investigated the correlation between dewfall formation amount and meteoro­logical factors. This study used the modified teflon plate $(1m{\times}1m)$ at Silla university in Busan from August 2002 to April 2003. In order to estimate qualitatively water soluble components, IC, ICP and UV methods for water soluble ions are also used respectively. Dewfall amount of sampling periods (47 day) collected 3.8 mm. Meteorological conditions for the formation of dewfall above $50\;g/m^{2}$ showed that temperature diurnal $range(^{\circ}C)\;was\;5.6^{\circ}C$ above, cloud amounts (1/10) at dawn of the sampling day was 7/10 below, mean wind speed at dawn (0~6hr) of the sampling day was 4.4 m/sec below, and mixing ratio at 6hr of the sampling day was 3.2 g/kg above. Distribution of water soluble ions in dewfall founded the highest concentration (206.1\;{\mu}eq/{\ell}\;for\;SO_{4}^{2-},\;42.4\;{\mu}eq/{\ell}\;for\;NH_{4}^{+},\;249.2\;{\mu}eq/{\ell}\;for\;Ca^{2+},\;and\;42.0\;{\mu}eq/{\ell}\;for\;Mg^{2+})$ during the March, the lowest concentration $(73.0\;{\mu}eq/{\ell}\;for\;SO_{4}^{2-},\;4.6\;{\mu}eq/{\ell}\;for\;NH_{4}^+\;and\;72.7\;{\mu}eq/{\ell}\;for\;Ca^{2+})$ during the August. Monthly equivalent ratio of $[SO_{4}^{2-}]/[NO_{3}^-]$ showed the highest value (4.99) during the October, the lowest value (1.84) during the August, and the mean value was 3.45.

• 천문학회보
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• 제37권2호
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• pp.101.2-101.2
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• 2012

Shocks are ubiquitous in astrophysical plasmas: bow shocks are formed by the interaction of solar wind with planetary magnetic fields, and supernova explosions and jets produce shocks in interstellar and intergalactic spaces. The global morphologies of these shocks are usually described by a set of magnetohydrodynamic (MHD) equations which tacitly assumes local thermal equilibrium, and the resulting Rankine-Hugoniot shock jump conditions are applied to obtain the relationship between the upstream and downstream physical quantities. While thermal equilibrium can be achieved easily in collisional fluids, it is generally believed that collisions are infrequent in astrophysical settings. In fact, shock widths are much smaller than collisional mean free paths and a variety of kinetic phenomena are seen at the shock fronts according to in situ observations of planetary shocks. Hence, both the MHD and kinetic equations have been adopted in theoretical and numerical studies to describe different aspects of the physical phenomena associated with astrophysical shocks. In this paper, we present the results of 3D relativistic particle-in-cell (PIC) simulations for ion-electron plasmas, with focus on the shock structures: when a jet propagates into an unmagnetized ambient plasma, a shock forms in the nonlinear stage of the Weibel instability. As the shock shows the structures that resemble those predicted in MHD systems, we compare the results with those predicted in the MHD shocks. We also discuss the thermalization processes of the upstream flows based on the time evolutions of the phase space and the velocity distribution, as well as the wave spectra analyses.

• 한국산학기술학회논문지
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• 제19권7호
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• pp.384-395
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• 2018

본 연구는 교래자연휴양림 지역을 A와 B 지역으로 나누어서 대기질의 음이온과 양이온수를 측정하여 일별 그 분포와 변이에 대한 연구가 목적이었다. 이온수 측정은 이온수 측정기로 2017년 6월 28일-7월 13일 사이에 실시하였다. A지역의 5개 지점의 전체 평균 음이온수는 $734.5ions/cm^3$, 양이온 수는 $463.3ions/cm^3$, 대기온도는 $25.51^{\circ}C$, 습도는 81.6%, 풍속은 0.28 m/sec, 해발 고도는 455.7 m 이었다. B지역의 4개 지역 전체 측정한 평균 음이온수는 $780ions/cm^3$, 양이온수는 $379.55ions/cm^3$, 대기온도는 $27.6^{\circ}C$, 습도는 80%, 풍속은 0.1 m/sec, 측정지역의 해발고도는 477 m 이었다. 교래지역 A와 B전체의 음이온수의 평균치는 $757.5ions/cm^3$, 양이온수의 평균치는 $419.41ions/cm^3$이었다. 이온의수는 시간별로 측정별로 변이성이 높았다. 음이온수가 양이온수보다 평균 $275.73ions/cm^3$ 만큼 더 높게 유지되었다. A와 B점의 음이온과 양이온수의 측정치를 Pearson 분산분석에서는 음이온 측정지점별 및 측정지점 내의 분석이 유의하게 나타났으며(p<.001), 양이온의 측정지점별 및 측정지점 내의 분석에서도 유의하게 나타났다(p<.001). 음이온과 양이온수의 지역별 평균측정치 간의 상관관계분석에 서 r=.386으로 유의한 정적인 상관관계가 있었다(p<.001). 결론적으로 상기 음이온과 양이온 함량의 시간적 분포와 변이를 나타낸 결과는 교래자연휴양림의 대기질의 성분과 변화에 대한 기초정보를 제공하고 있다고 본다.

• 한국토양비료학회지
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• 제8권3호
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• pp.135-152
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• 1975

제주도(濟州道) 감귤원토양(柑橘園土壤)의 이화학적(理化學的) 특성(特性)과 과수(果樹)의 영양조사(營養調査)에 의(依)하여 다음과 같은 점들이 알려졌다. 1. 한라산려(漢拏山麗)의 대지(臺地)와 분석구(憤石口)에 위치(位置)하여 토양수분(土壤水分)이나 과원미세기상(果園微細氣象)에 지형(地形)의 영향(影響)이 클것같다 2. 배수(排水)가 잘되고 토심(土深)이 적으며 사력함량(砂礫含量)이 많고 고상율(固相率)이 적은에다가 강풍(强風)이 있어 토양(土壤)의 풍식(風蝕)과 토양수분(土壤水分)이 문제가 될 것이며 보비력(保肥力)과 보수력(保水力) 및 근발달(根發達)을 위해 토심확대(土深擴大)가 필요(必要)하다. 3. 토양유효(土壤有效) 수분함량(水分含量)은 유기물함량(有機物含量)과 고도(高度)의 유의정상관(有意正相關)을 보이며 점토(粘土)가 다음으로 기여하였다. 비닐 피복은 수분보존(水分保存), 풍식방지(風蝕防止) 동계지온상승(冬季地溫上昇) 등에 효과(效果)가 클 것으로 보였다. 4. 다량(多量)의 비정질(非晶質) 양성(兩性) 알로판 (Ampoteric Amorphous Allophane)은 인산(燐酸)의 고정(固定)과 양(陽)ion 용탈(溶脫)의 순환작용(巡環作用)에 의(依)하여 비효(肥效)가 결정(決定)되며 석회(石灰)와 인산(燐酸)의 심층시비(深層施肥)가 요망(要望)되며 고토(固定) 인산(隣酸)의 용출(溶出)이 재평가(再平價)되어야 할 것이다. 5. 비효(肥效)는 해초(海草)와 같은 유기물(有機物)에 의(依)하여 증대(增大)되며 춘계시비효과(春季施肥效果)가 적은것은 토양수분함량(土壤水分含量)과 관계(關係)가 큰것같다. 6. 엽분석(葉分析)은 N는 많으며 Mg는 충분하나 P, Ca가 부족(不足)하고 과실분석(果實分析)은 K가 부족(不足)하였다. 인산시용(燐酸施用)은 감미비(甘味比)를 증가(增加)시켰으며 K는 과피율(果皮率)을 감소시켰다. 7. Mn의 과잉과 부족(不足)증상이 부분적으로 나타났으며 Fe와 B는 문제가 없으며 Ca는 대부분 과잉이나 부족한 원(園)이 있으며 Zn도 부족(不足)한 곳이 보였다. 8. 암반(岩盤)을 제거한후 심토(心土)와 표토(表土)를 혼합(混合)하고 다량(多量)의 유기물(有機物)과 완용성비료(緩溶性肥料)를 시용(施用)하며 비닐피복을 하고 점적관개(點滴灌漑)를 하므로서 시비효과(施肥效果)가 발현(發現)되며 수량(收量)이 급증(急增)할 것으로 보인다.

• 기술경영경제학회:학술대회논문집
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• 기술경영경제학회 1997년도 제12회 동계학술발표회 논문집
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• pp.159-176
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• 1997

This paper deals with demand surveys for big science and technology research facilities and equipments to advance national S'||'&'||'T research infrastructure. We perform surveys thrice based on applied Delphi method on the future demand of big S'||'&'||'T research facilities and equipments among Korean scientists and engineers. We employ the concept of big S'||'&'||'T research facilities and equipments as follows: \circled1 The operating size of it is equivalent to that of an institute or research center, and/or \circled2 The users in various disciplines are many, and/or \circled3 The application areas or spill-over effects are large, and/or \circled4 The scale and scope of research objects is equivalent to that of mega science area such as earth.oceanography.space, and/or \circled5 The expenses for installing and operating it are to be supported by government, and/or \circled5 The facilities are expected as necessary for international joint research, and/or \circled7 It is necessary for promoting creative basic science and developing creative technology. We ask the respondents to answer the following questionnaire: - How to prioritize the equipments according to the degree of importance\ulcorner $\square$ Promotion of basic science and mega science, the development of the technologies to enhance the public welfare, the competitiveness of industrial technologies, the job creation for the S'||'&'||'T personnel, and international cooperation. - Who should be in charge of acquisition and operation of the equipments\ulcorner $\square$ Industry, Government Research Institutes, Academy, ERC and SRC. - When shall we acquire the equipment\ulcorner $\square$ Within 2000, 2002, 2007, 2012, and 2017. - How shall we acquire the equipments\ulcorner $\square$ International Joint Development, Domestic Development, Acquisition from Overseas, - How much will the equipment generate spill-over effects to national competitiveness\ulcorner $\square$ Promotion of basic science, contribution to the economy, supply of S'||'&'||'T personnel, and international cooperation. We suggest the following equipments as prioritized candidates after consulting the officers from MOST, MOE, MIC, MOEN and experts from KBSI and STEPI:(table omitted) where, #1, Korea Advanced Liquid Metal Reactor, #2. 800 MHz Superconduction Fourier-Transform Nuclear Magnetic Resonance Spectrometer, #3. Ion Accelerator, #4. Seismic Test Facility, #5. Transonic Wind Tunnel, #6. Radio Telescope for Very Long Baseline Interferometer, #7. 3000t Universal(or Large Structure) Testing Machine, #8. Compost Facility or Plasma Pyrolysis Facility.