• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.370-371
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• 2018

Recently, interest in renewable energy is increasing due to energy depletion and environmental problems. Among them, solar energy is the most popular feature for its infinite, eco-friendly, easy to maintain and high utilization. In these solar power systems, solar cells have either a current-voltage characteristic curve or a power-voltage characteristic curve with non-linear properties. Therefore, the Maximum Power Point Tracking (MPPT) technique is important to control this. In this thesis, we will discuss MPPT techniques using a boost converter and demonstrate their behavior using the PSIM program. Also, the MPPT control algorithm for solar energy generation will be proposed.

• Magazine of the Korean Society of Agricultural Engineers
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• v.32 no.E
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• pp.1-19
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• 1990

Abstract Over the last several decades, crop production in the United States increased largely due to the extensive use of animal waste and fertilizers as plant nutrient supplements, and pesticides for crops pests and weed control. Without the application of animal waste best management, the use of animal waste can result in nonpoint source pollution from agricultural land area. In order to increase nutrient levels and decrease contamination from agricultural lands, nonpoint source pollution is responsible for water quality degradation. Nonpoint source pollutants such as animal waste, ferilizers, and pesticides are transported primarily through runoff from agricultural areas. Nutrients, primarily nitrogen and phosphorus, can be a major water quality problem because they cause eutrophic algae growth. In 1985, it was presented that Watershed/Water Quality Monitoring for Evaluation BMP Effectiveness was implemented for Nomini Creek Watershed, located in Westmoreland County, Virginia. The watershed is predominantly agricultural and has an aerial extent of 1505 ha of land, with 43% under cropland, 54% under woodland, and 3% as homestead and roads. Rainfall data was collected at the watershed from raingages located at sites PNI through PN 7. Streams at stations QN I and QN2 were being measured with V-notch weirs. Water levels at the stream was measured using an FW-l Belfort (Friez FWl). The water quality monitoring system was designed to provide comprehensive assessment of the quality of storm runoff and baseflow as influenced by changes in landuse, agronomic, and cultural practices ill the watershed. As this study was concerned with the Nomini Creek Watershed, the separation of storm runoff and baseflow measured at QNI and QN2 was given by the master depletion curve method, and the loadings of baseflow and storm runoff for TN (Total Nitrogen) and TP (Total Phosphorus) were analyzed from 1987 through 1989. The results were studied for the best management practices to reduce contamination and loss of nutrients, (e.g., total nitrogen and total phosphorus) by nonpoint source pollution from agricultural lands.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.126-126
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• 2012

기후변화는 전 세계적으로 다양한 영향을 미치고 있으며 특히, 홍수나 대설로 인한 수문변화에 영향을 준다. 본 연구는 준분포형 연속 모형인 SWAT (Soil and Water Assessment Tool)모형을 이용하여 우리나라 3대 대설지역에 속하는 다목적댐인 충주댐유역(6642.0 m)의 기후변화에 따른 융설이 수문과 수질에 미치는 영향을 분석하고자 한다. 먼저, 융설 모형의 매개변수인 적설분포면적감소곡선 (Snow Cover Depletion Curve; SCDC)을 구축하기 위하여 10년(2000-2010)동안의 Terra MODIS (MODerate resolution Imaging Spectroradiometer) 위성영상자료와 6개 기상관측소(충주, 제천, 원주, 영월, 대관령, 태백)의 최심적설자료를 이용하여 연도별 SCDC을 구축하였다. 구축 결과, 눈이 50% 피복 일 때 snow volume은 연 평균 0.47로 분석되었다. 이를 SWAT 모형에 적용하여 수문과 수질에 대한 적용성 평가를 실시한 결과, 유출의 경우 NSE는 융설기간 동안 평균 0.8, 전체기간은 평균 0.6으로 나타났으며 수질(Sediment, T-N, T-P)의 경우 각각 평균 0.72, 0.70, 0.85을 나타내었다. 미래 기후자료는 IPCC(Intergovernmental Panel on Climate Change)에서 제공하는 SRES(Special Report on Emission Scenarios) A1B, B1 기후변화시나리오의 HadCM3 모델의 결과 값을 이용하였으며 기간은 과거 30년 기후자료(1981-2010, baseline)를 바탕으로 2040s(2020-2059), 2080s(2060-2099)의 두 기간으로 나누어 각각 분석하였으며 기후변화 결과 값의 불확실성을 줄이고자 과거 자료와 GCM의 1981년에서 2000년까지의 값을 비교하여 온도와 강수량의 보정을 실시한 후 LARS-WG를 이용하여 온도와 강수량 자료를 구축하였다. SWAT 모형을 적용한 결과, 평균 1.92 증가한 것으로 나타났으며 유출은 융설기간(Nov-Apr)이 비융설기간(May-Oct)보다 10% 더 증가하였다. 본 연구에서는 SWAT 모형을 통한 유출 및 환경부하량 전망을 목표로 하여 미래 기후변화를 고려한 융설이 다목적댐에서의 유출과 수질 (Sediment, Total Nitrogen, Total Phosphorus)에 미치는 영향을 평가해 보고자 한다.

• Water for future
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• v.12 no.1
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• pp.56-59
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• 1979

A prompt subsurface runoff producing mechanism whih creaters a depletion curve of direct runoff hydrograph is simulated by a dead zone dispersion model technique. Runoff processes are carried out by routing of the outflow resulted from previous linear channel and effective rainfall from its corresponding subwatershed through a series of conceptual linear channels representing subwatersheds of a catchment. Working rules are explained for evaluation the model parameters such as translatory velocity, diffusive factor, and parameters concerning the infiltration and relative magnitude of the prompt subsurface flow region.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.194-198
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• 2007

융설 모형의 중요 매개변수인 적설분포면적은 실제 우리나라에서 적설과 관련한 관측 자료의 부족으로 인해 매개변수 추정이 어렵다. 이러한 문제점 해결을 위해 원격탐사기법을 활용하여 적설분포면적을 추출하였다. 본 연구에서는 1997년부터 2006년까지의 겨울철 NOAA (National Oceanic and Atmospheric Administration)의 AVHRR(Advanced Very High Resolution Radiometer) 위성영상의 8 sets의 총 108개 영상을 이용하여 적설분포면적을 추출하였고, 기상청의 지상기상관측소의 최심적설심 자료를 이용하여 GIS 자료를 구축함으로써 적설심의 공간적 분포를 추출하였다. 이를 국내 5대유역인 한강, 낙동강, 금강, 영산강, 섬진강 유역에 대하여 융설모형의 주요 매개변수인 적설분포면적, 유역 평균, 최대 적설심과 적설분포감소비곡선을 구축하였다. 그 중 적설분포면적감소곡선 (SDC : Snow cover Depletion Curve)는 적설분포면적의 감소형태를 나타내주는 지표로써 융설의 가장 민감한 매개변수이다. 이를 국내 5대강 유역에 대해 구축하여 정량화하였다.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.254-259
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• 2005

The shape of a streamflow hydrograph is very much controlled by the area and depth of snow cover in mountain area. The purpose of this study is to suggest extraction methods for snow cover area and depth using NOAA/AVHRR images in Soyanggang watershed. Snow cover area maps ware derived form channel 1, 3, 4 images of NOAA/AVHRR based on threshold value. In order to extract snow cover depth, snow cover area maps were overlaid daily snow depth data form 7 meteorological observation stations. Snow cover area and depth was mapped for period of Dec. 2002 and Mar. 2003. For evaluating snowmelt changes, depletion curve was created using daily snow cover area in the same period. It is necessary to compare these results with observed data and check the applicability of the suggested method in snowmelt simulation.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1471-1473
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• 2000

In this study capacitance and dielectric loss factor were measured with low-voltage signal and the simulation of equivalent circuits for the data were conducted. As the result it was showed that the equivalent circuit model considered the gram-boundary structure with semiconducting layer, dielectric layer and depletion layer was well approximated with the observed data. Various parameters were determined by a optimum curve-fitting method and could be used to analyze the varistor-voltages and the nonlinear coefficient of varistors. It also seems that the proposed equivalent circuit model will be adopted for other BL type varistors.

• Journal of Plant Biology
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• v.36 no.1
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• pp.59-66
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• 1993

In maize coleoptile segments where auxin transport capacity decreases with time following excision, susceptability of the tissue to transport inhibitors such as N-1-naphthylphthalamic acid (NPA), 3,4,5-triiodobenzoic acid (TIBA) or high concentrations of IAA was found to be rather increased. A time-dependent increase in the sensitivity to NPA can be postulated since the dose-response curve for NPA was shifted in the‘aged’tissue to the left (i.e. lower concentration). Preincubation of the tissue at a low temperature abolished the time-dependent sensitivity change, suggesting that cellular metabolism could be involved. The NPA-sensitive state was also brought about by calcium depletion of the tissue, which can be partially reversed by addition of calcium. Presence of exogenous IAA in the preincubation medium kept the auxin transport system from decay, implicating auxin as an endogenous controlling factor. Results of our experiments indicate a reversible, time-dependent changes of auxin transport system in which transport capacity and sensitivity to NPA are tightly coupled. Changes in the sensitivity to NPA were also seen in auxin action as well.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.5
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• pp.678-685
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• 2010

GTAW was carried out to the austenitic 304(STS 304) and 22 APU stainless steels. In this case, difference of the corrosion characteristics of welded zone with STS 304 and 22APU mentioned above was investigated with electrochemical methods. Vickers hardness of weld metal in case of STS 304 (Hv-250) showed a relatively higher value than this of 22 APU(Hv-217). The corrosion current densities of weld metal of 22APU and heat affected zone of STS 304 were observed at the highest value compared to those of other welding zone respectively. This is probably because chromium depletion field due to chromium carbide formed to weld metal of 22APU and to heat affected zone of STS 304 can preferentially easily be corroded with more active anode than other fields. Consequently it is thought that application of the other welding methods like as laser welding or using of the optimum filler metals is necessary to improve the corrosion resistance of welding parts of these steels.

• Nuclear Engineering and Technology
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• v.51 no.6
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• pp.1708-1714
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• 2019

The purpose of the critical evaluation of the spent fuel pool (SFP) is to verify that the maximum effective multiplication factor ($K_{eff}$) is less than the critical safety limit at 100% stored condition of the spent fuel with the maximum reactivity. At nuclear power plants, the storage standard of spent fuel, ie, the loading curve, is established to prevent criticality from being generated in SFP. Here, the loading curve refers to a graph showing the minimum discharged burnup versus the initial enrichment of spent fuel. Recently, US NRC proposed the new critical safety assessment guideline (DSS-ISG-2010-01, Revision 0) of PWR SFPs and most of utilities in US is following it. Of course, the licensed criterion of the maximum effective multiplication factor of SFP remains unchanged and it should be less than 0.95 from the 95% probability and the 95% confidence level. However, the new guideline is including the new evaluation methodologies like the application of the axial burnup profile, the validation of depletion and criticality code, and trend analysis. Among the new evaluation methodologies, the most important factor that affects $K_{eff}$ is the axial burnup profile of spent fuel. US NRC recommends to consider the axial burnup profiles presented in NUREG-6801 in criticality analysis. In this paper, criticality effect was evaluated considering three profiles, respectively: i) Axial burnup profiles presented in NUREG-6801. ii) Representative PWR axial burnup profile. iii) Uniform axial burnup profile. As the result, the case applying the axial burnup profiles presented in NUREG-6801 showed the highest $K_{eff}$ among three cases. Therefore, we need to introduce a new methodology because it can be issued if the axial burnup profiles presented in NUREG/CR-6801 are applied to the domestic nuclear power plants without any other consideration.