• 한국농공학회지
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• 제44권4호
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• pp.129-138
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• 2002

This paper presents a study on the discharge capacity of geotextiles as a horizontal drain layer placed between the layers of earth fill and natural soft ground. Required discharge capacity of geotextiles as drain layers estimated by consolidation analysis is proportional to the consolidation coefficient of the ground soils and the width of the earth fills. The field discharge capacity of the geotextiles are measured by the hydraulic transmissivity test. And the results show wide variation according to the material characteristics of geotextiles, water content of the soils, vertical pressure, and etc. For the short horizontal drain length, geotextile filter mat can be used for the horizontal drain layer. And f3r the long drain($25{\sim}55m$), it is used for the drain together with Bord Drain.

• Ocean and Polar Research
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• 제38권4호
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• pp.331-338
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• 2016

Many studies using tracers have been conducted to understand a physical process in a system. Rain-on-snow could accelerate snowmelt processes, which influences the hydrological process in both temperate and polar regions. Hydrological and ecological conditions will be affected by the amount and timing of discharge reaching the bottom of a snowpack. The discharge consists of the rain-on-snow, pore water penetrating into the snowpack and natural meltwater. In this study, after a rain-on-snow experiment, we conducted an isotopic hydrograph separation to distinguish rainwater and pore water from meltwater. Using the isotopic data of snow and meltwater from Lee et al. (2010), two components were separated based on the assumption that rainwater and pore water are new water and natural meltwater is old water. After the second rain-on-snow experiment, the maximum contributions of rainwater and pore water reached up to 69% of the discharge and then decreased. During the study period, the measured total discharge was 4153 L and 40% (based on hydrogen isotope) of rainwater and pore water was calculated in the discharge, which is not consistent with what Lee et al. (2016) calculated using chemical separation (63%). This inconsistency can be explained by how an end-member was defined in both approaches. The contributions of artificial rainonsnow and pore water to melwater discharge range between the two methods. This study will suggest a mixing calculation from isotopic compositions of the Southern Ocean.

• Spatial Information Research
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• 제14권1호
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• pp.15-27
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• 2006

본 연구는 지형학적 단위도(geomorphoclimatic unit hydrograph, GIUH)로 미계측 소유역의 한계유출량을 산정에 관한 연구이다. GIUH는 수문특성예측에 많이 이용된다. 연구대상지역인 경북 감포지역에 대한 $5km^2$의 소유역으로 수문특성인자, 제방월류유량 및 합성단위도(Clark Nakayasu, S.C.S)에 의한 유출량도 함께 분석하였다. 그리고 지리정보시스템으로 지형인자를 추출하고 지형학적순간단위도에서 산정된 첨두유량을 감포지점의 실측자료와 비교함으로써 지형학적순간단위도의 타당성을 검증하였고, 이와 NRCS(Natural Resources Conservation Service)방법을 이용하여 돌발홍수 기준우량을 제시하기위한 한계유출량을 산정하였다.

• 한국해안·해양공학회논문집
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• 제25권2호
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• pp.103-111
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• 2013

방류 유무에 따른 유속, 잔차류 그리고 염분의 시공간적인 분포를 파악하기 위해서 영산강 하구둑에서 서쪽방향으로 7.5 km의 구간까지 방류 시와 미방류 시에 종단면의 유속, 수온 그리고 염분을 한 조석 주기 동안 1시간 간격으로 동시에 관측하였다. 미방류 시에 연구지역의 유속 형태는 창조지속 시간이 길고 낙조류가 강한 낙조우세 특성을 보인다. 방류 시에 표층 최대 유속은 최대 1.5 m/s의 제트류 형태로 방류되지만, 저층 유속은 미방류 시와 비교해보면 0.4 m/s로 크게 변하지 않는다. 방류 시의 수직 잔차류 분포는 담수의 영향으로 일반적인 하구에서 보이는 2층 흐름 구조를 가지는 반면에, 미방류 시에는 다층 흐름 구조가 나타난다. 일반적으로 방류로 인하여 하구둑 외측에서 강한 연직 혼합이 일어나는 것으로 알려져 있으나, 본 연구조사에서는 방류에 의해서 염분 성층이 발달하고, 표층과 저층간의 연직 혼합에 크게 기여하지 않는 것으로 나타났다. 이는 방류가 강하게 일어남에도 불구하고 하구둑 전면의 지형적 효과와 밀도 차에 의한 해수 흐름 특성에 의한 것으로 판단되며, 이를 통해 하구둑 방향의 물질수송은 수직 방향보다는 수평 방향으로 나타남을 알 수 있다.

• 한국지반신소재학회논문집
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• 제4권1호
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• pp.27-36
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• 2005

식물섬유에서 추출한 천연섬유를 이용하여 제작한 천연섬유배수재의 통수능을 평가하기 위해 수평배수재의 경우에는 투수시험 그리고 연직배수재의 경우에는 Delft 공대에서 개발한 통수능 시험과 교란 점토를 이용한 복합통수능 시험을 각각 수행하였다. 친환경 수평배수재에 대한 투수시험 결과 코코넛 껍질로 구성된 매트의 투수성은 모래에 비해 매우 우수한 것으로 나타났다. 또한, Delft 공대에서 개발한 통수능 시험으로 평가한 친환경 연직배수재의 통수능은 국산 플라스틱드레인보드의 통수능에 비해 매우 작은 것으로 나타났으나, 교란점토를 이용하여 실제 현장을 가깝게 모사한 복합통수능시험을 수행한 결과 친환경배수재와 플라스틱드레인보드를 설치한 지반의 침하나 간극수압 소산 양상이 서로 유사하게 나타나 친환경배수재가 배수재에 요구되는 최소통수능을 만족하는 것으로 나타났다.

• 한국재료학회지
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• 제25권6호
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• pp.279-287
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• 2015

In order to prepare anode materials for high power lithium ion secondary batteries, carbon composites were fabricated with a mixture of petroleum pitch and coke (PC) and a mixture of petroleum pitch, coke, and natural graphite (PC-NG). Although natural graphite has a good reversible capacity, it has disadvaantages of a sharp decrease in capacity during high rate charging and potential plateaus. This may cause difficulties in perceiving the capacity variations as a function of electrical potential. The coke anodes have advantages without potential plateaus and a high rate capability, but they have a low reversible capacity. With PC anode composites, the petroleum pitch/cokes mixture at 1:4 with heat treatment at $1000^{\circ}C$ (PC14-1000C) showed relatively high electrochemical properties. With PC-NG anode composites, the proper graphite contents were determined at 10~30 wt.%. The composites with a given content of natural graphite and remaining content of various petroleum pitch/cokes mixtures at 1:4~4:1 mass ratios were heated at $800{\sim}1200^{\circ}C$. By increasing the content of petroleum pitch, reversible capacity increased, but a high rate capability decreased. For a given composition of carbonaceous composite, the discharge rate capability improved but the reversible capacity decreased with an increase in heat treatment temperature. The carbonaceous composites fabricated with a mixture of 30 wt.% natural graphite and 70 wt.% petroleum pitch/cokes mixture at 1:4 mass ratio and heat treated at $1000^{\circ}C$ showed relatively high electrochemical properties, of which the reversible capacity, initial efficiency, discharge rate capability (retention of discharge capacity in 10 C/0.2 C), and charge capacity at 5 C were 330 mAh/g, 79 %, 80 %, and 60 mAh/g, respectively.

• Journal of Electrical Engineering and Technology
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• 제11권3호
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• pp.699-706
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• 2016

Partial discharges (PD) lead to the degradation of high voltage cables and accessories. PD activities occur due to the existence of impurities, voids, contaminants, defects and protrusions during the manufacture and installation of power cables. Commonly, insulation failures occur at cable joints and terminations, caused by inhomogeneous electric field distributions. In this work, a blend of natural rubber (NR) and linear low density polyethylene (LLDPE) was investigated, and the optimal formulation of the blend that could resist PD was discussed. The experiments were conducted under a constant high voltage stress test of 6.5 kV AC and the magnitude of partial discharge activities was recorded using the CIGRE method II. Pattern analysis of PD signals was performed along with the interpretation of morphological changes. The results showed that the addition of 10 wt% of NR and 5 wt% of Alumina Trihydrate (ATH) provided promising results in resisting PD activities. However, as the NR content increased, more micropores existed, thus resulting in increased PD activities within the samples.

• Advances in Energy Research
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• 제8권1호
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• pp.41-57
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• 2022

Electrochemical double-layer capacitors (EDLCs) based on solid polymer electrolytes (SPEs) have gained an immense recognition in the present world due to their unique properties. This study is about preparing and characterizing EDLCs using a natural rubber (NR) based SPE with natural graphite (NG) electrodes. NR electrolyte was consisted with 49% methyl grafted natural rubber (MG49) and zinc trifluoromethanesulfonate ((Zn(CF₃SO₃)₂-ZnTF). It was characterized using electrochemical impedance spectroscopy (EIS) test, dc polarization test and linear sweep voltammetry (LSV) test. NG electrodes were made using a slurry of NG and acetone. EIS test, cyclic voltammetry (CV) test and galvanostatic charge discharge (GCD) test have been done to characterize the EDLC. Optimized electrolyte composition with NR: 0.6 ZnTF (weight basis) exhibited a conductivity of 0.6 x 10^-4 Scm^-1 at room temperature. Conductivity was predominantly due to ions. The electrochemical stability window was found to be from 0.25 V to 2.500 V. Electrolyte was sandwiched between two identical NG electrodes to fabricate an EDLC. Single electrode specific capacitance was about 2.26 Fg^-1 whereas the single electrode discharge capacitance was about 1.17 Fg^-1. The EDLC with this novel NR-ZnTF based SPE evidences its suitability to be used for different applications with further improvement.

• Journal of Electrical Engineering and Technology
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• 제13권3호
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• pp.1337-1345
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• 2018

The reliability of power transmission and distribution depends up on the consistency of insulation in the high voltage power transformer. In recent times, considering the drawbacks of conventional mineral oils such as poor biodegradability and poor fire safety level, several research works are being carried out on natural ester based nanofluids. Earlier research works show that sunflower oil has similar dielectric characteristics compared with mineral oil. BIOTEMP oil which is now commercially available in the market for transformers is based on sunflower oil. Addition of nanofillers in the base oil improves the dielectric characteristics of liquid insulation. Only few results are available in the literature about the insulation characteristics of nano modified natural esters. Hence understanding the influence of addition of nanofillers in the dielectric properties of sunflower oil and collecting the database is important. Considering these facts, present work contributes to investigate the important characteristics such as partial discharge, lightning impulse, breakdown strength, tandelta, volume resistivity, viscosity and thermal characteristics of $SiO_2$ nano modified sunflower oil with different wt% concentration of nano filler material varied from 0.01wt% to 0.1wt%. From the obtained results, nano modified sunflower oil shows better performance than virgin sunflower oil and hence it may be a suitable candidate for power transformer applications.

• Journal of Electrical Engineering and information Science
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• 제3권3호
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• pp.316-321
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• 1998

In recent years, concern has been raised about the technique of controlling electrical breakdown by using laser in many fields. Especially, laser has attracted much attention in the Electro-Discharge Macining(EDM) because of its many merits. Therefore, this research has been performed to obtain fundamental data relevant to discharge processing by using a pulsed Nd:YAG laser. The experiments of laser-guided dc discharge by laser radiation have been carried out at low air pressure ranging from 0.2 to 20 torr. The minimum laser-guided dc discharge voltage V\ulcorner at the given pressures P and distances D between an anode and a cathode was measured. It is found that the minimum laser-guided dc discharge voltage is much lower than the natural discharge voltage V\ulcorner\ulcorner, and the values of V\ulcorner and V\ulcorner as a function of P.D has a similar tendency. The laser output energy Eout decreases with input pulse duration tp increasing, and the more the value of tp increases, the higher that of V\ulcorner is obtained because the number of photons during the discharge time N decreases with t\ulcorner increasing. There is the time lag frequently when the discharge by laser radiation is misguided under the condition of the applied voltage less than V_G.min.