• Korean Journal of Remote Sensing
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• v.31 no.2
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• pp.149-160
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• 2015

A comparative study was conducted for alternative consecutive procedures of detection of cloud-contaminated pixels and gap-filling and smoothing of time-series data to produce high-quality gapless satellite vegetation index (i.e. Normalized Difference Vegetation Index, NDVI). Performances of five alternative methods for detecting cloud contaminations were tested with ground-observed cloudiness data. The data gap was filled with a simple linear interpolation and then, it was applied two alternative smoothing methods (i.e. Savitzky-Golay and Wavelet transform). Moderate resolution imaging spectroradiometer (MODIS) data were used in this study. Among the alternative cloud detection methods, a criterion of MODIS Band 3 reflectance over 10% showed best accuracy with an agreement rate of 85%, which was followed by criteria of MODIS Quality assessment (82%) and Band 3 reflectance over 20% (81%), respectively. In smoothing process, the Savitzky-Golay filter was better performed to retain original NDVI patterns than the wavelet transform. This study demonstrated an operational framework of gapdetection, filling, and smoothing to produce high-quality satellite vegetation index.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.617-620
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• 2008

지열에너지는 지구 내부의 깊은 곳에서부터 발생하는 열과 상부 지각에서 방사성 동위원소의 붕괴에 의한 열에 의해 발생한다. 지열에너지는 다른 신재생에너지(수력, 풍력, 태양력, 조력, 바이오 매스등)에 비하여 가동효율이 높고, 지속가능한 재활용 자원으로 경제적 효율성이 높아 전 세계적으로 활용도와 잠재성이 높은 신재생에너지의 하나로 각광 받고 있다. 따라서, 지열에너지의 사용은 화석 연료 사용의 상당부분을 대체할 수 있고, 온실가스의 배출도 줄일 수 있다. 현재 우리나라의 지열에너지 이용은 저온성 지열에너지를 이용한 냉난방에 국한되어 있지만, 앞으로의 지열에너지 이용은 Enhanced Geothermal System(EGS) 을 이용한 지열에너지 개발에 초점이 맞추어질 것이다. 현재의 지열에너지 개발을 용이하게 하고, 또한 미래의 지열에너지 개발에 대비하여 우리나라의 이용가능한 지열에너지 부존량을 파악하기 위해 본 연구를 수행하였다. 연구 수행에는1560개 열물성 자료(밀도, 비열, 열전도도), 353개 지표 지열류량 자료, 180개 열생산율 자료와 54개의 지표온도 자료가 사용되었다. 우리나라의 지표에서부터 1 km 깊이 간격별로 5 km 깊이까지 지열에너지 부존량을 산출한 결과 지표에서 부터 5 km 깊이까지의 추출 가능한 지열에너지의 총 부존량은 $1.01{\times}10^{23}$ J로 산출되었다. 지열에너지 부존량을 Toe(석유환산톤) 로 환산하면 $2.40{\times}10^{12}$ Toe 가 된다. 추출한 지열에너지 자원의 2%를 사용한다고 가정 했을때 약 480억 Toe 이다. 이는 2006년 우리나라 전체 1차 에너지 총 소비량(2.33억 Toe)을 고려 했을때 약 200년 동안 사용할 수 있는 양이다.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.1
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• pp.41-48
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• 2010

Uranium deposits from an electrorefining process contain about 30% salt. In order to recover pure uranium and transform it into an ingot, the salts have to be removed from the uranium deposits. Major process variables for the salt distillation process of the uranium deposits are hold temperature and vacuum pressure. Effects of the variables on the salt removal efficiency were studied in the previous study[1]. By applying the Hertz-Langmuir relation to the salt evaporation of the uranium deposits, the evaporation coefficients were obtained at the various conditions. The operational conditions for achieving above 99% salt removal were deduced. The salt distilled uranium deposits tend to form the eutectic melt with iron, nickel, chromium for structural material of salt evaporator. In this study, we investigated the hold temperature limitation in order to prevent the formation of the eutetic melt between urnaium and other metals. The reactions between the uranium metal and stainless steel were tested at various conditions. And for enhancing the evaporation rate of the salt and the efficient recovery of the distilled salt, the thermal analysis of the salt distiller was conducted by using commercial CFX software. From the thermal analysis, the effect of Ar gas flow on the evaporation of the salt was studied.

• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.442-448
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• 2012

The effects of zeolite-type catalysts addition on the thermal decomposition of the PP resin have been studied in a thermal analyzer, a Pyrolyser GC-mass, and a small batch reactor. The zeolite type catalysts tested were natural zeolite, used FCC catalyst, and ZSM-5. As the results of TGA experiments, the pyrolysis starting temperature for PP varied in the range of $330{\sim}360^{\circ}C$ according to the heating rate. Addition of the zeolite type catalysts in the PP resin increased the pyrolysis rate in the order of used FCC catalyst> natural zeolite> ZSM-5 > PP resin. Adding the used FCC catalyst in the PP reduced most effectively the pyrolysis finishing temperature. In the PY-G.C. mass experiments, addition of zeolite type catalysts decreased the molecular weight of pyrolyzed product. In the batch system experiments, the mixing of used FCC catalyst enhanced best the initial yield of fuel oil, but the final yield of fuel oil was 2% higher in the case of mixing of natural zeolite. Also in the carbon number analysis, used FCC catalyst was the most useful one in this experiments for fuel oil.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.33 no.2
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• pp.138-145
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• 1988

The effect of directions (north to south vs east to west) of planting row, planting intensities (10/15, 15/15, 20/15, 25/15 cm/cm) and the number of rows consecutively (1,2, 3,4) for both the CMS and pollen parent in alternation, on the seed yield of CMS of rice was tested with a breeding line V20A/Iri342$\^$*8/. When the planting row was made in vertical direction to the wind direction during anthesis, the seed yield was higher than the other direction regardless the planting densities and number of rows consecutive. Seed yield increased as high as 46.9%. The higher planting intensities up to 10/15 cm/cm yielded the higher hybrid seeds. The highest yield was 81.2 kg/ha. The yield variation among plants within a plot and among the plants within a replication was relatively large. Increased pollen parent row numbers caused increased grain fertility per plant, but the seed yield was increased by reduced pollen parent row number. Reduced CMS parental row numbers caused increased grain fertility per plant, but the seed yield was increased by increased CMS parental row numbers. Considering the hybrid seed yield, parental seed yield and operational convenience, 4 rows of CMS and 1 row of pollen parent in alternate with 20/15 or 25/15 (cm/cm) planting densities seemed to be the rational layout.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.11
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• pp.1154-1161
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• 2006

Air drying equipment was built as a device for reduction of dewatered cake from wastewater and waterworks sludge and to reproduce it by reusable matter. Dewatered cake was supplied into the air drying equipment which operated by air velocity of 80 m/sec, air rate 30 $m^3/min$ and air temperature of $40^{\circ}C$, and dried to produce the dried powder. The air drying equipment was composed of the air ejector which made high-speed fluid field, and cyclone which made circling fluid field. Dewatered cake was crushed at the high-speed zone as first step, and formed into dried powder of sphere shape by the collision between particles at the circling fluid zone.. Wastewater sludge with water content of 82.5 wt% was supplied 1.0 kg/min into air drying equipment and produced the dried powder which had the water content of 62.3 wt% and mass median diameter of 2.4 mm after process. At that time, it was analyzed that water removal rate was 0.1 $H_2O{\Delta}kg/min{\cdot}DS$ kg and air consumption was 170 $m^3/DS$ kg. Under same experimental conditions, when waterworks sludge was dried, water content of dried powder decrease to 47.5 wt% and mass median diameter decrease 2.1 mm and water removal rate increase 0.13 $H_2O{\Delta}kg/min{\cdot}DS$ kg. Air consumption increase 180 $m^3/DS$ kg with comparison to the results of wastewater sludge. Therefore, this technology was evaluated that drying the dewatered cake of waterworks sludge was more efficient than wastewater sludge, and also economical sludge handling technology due to drying the cake by only air.

• Tunnel and Underground Space
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• v.31 no.6
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• pp.520-533
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• 2021

It is necessary to increase the blasting efficiency in order to minimize the economic loss caused when the excavation cross section is reduced due to the stability problem of underground mining development, and for this, a new blasting design is proposed. In this study, the blasting efficiency of the general design in the field, the suggestion designI, which added two columns to production blasting, and the suggestion design II, which added one column to create asymmetry, is compared. Advance rate and fragmentation were selected as the evaluation index of the blasting efficiency. In the case of advance rate, compared to the normal, the suggestionI improved by 6.07% and the suggestionII improved by 4.65%. In the case of fragmentation, based on P80, compared to the normal, the suggestionI reduced about 58% and the suggestionII was about 47%. Accoording to the evaluation index, the suggestion designI shows better blasting efficiency than the suggestion designII. But considering the additional work time and cost required for the suggestion designI due to the insignificant difference in the evaluation index results, the asymmetry V-cut, the suggestion designII, is judged to be a more suitable blasting design for the site.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.246.1-246.1
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• 2010

본 연구는 바이오가스의 에너지효율성을 높이기 위한 연구로서 바이오가스 정제공정과 초저온액화공정을 통하여 액화바이오메탄을 생산하는 바이오가스 고질화기술개발 연구이다. 바이오가스 정제공정은 탈황, 제습, 흡착, 압축, $CO_2/CH_4$ 분리공정으로 구성하고, 초저온액화공정은 열교환기, $CO_2$ 제거설비, 질소냉매 공급공정으로 구성하여 혐기성소화조에서 발생하는 바이오가스($CH_4$ 농도: 60~65%, $H_2S$: 1,500~2,500ppm)를 $200Nm^3/hr$의 유량으로 인입시켜 액화바이오메탄을 생산하였다. 연구결과, 탈황공정에서는 가성소다 세정법을 이용하여 1,500~2,500ppm으로 인입되는 $H_2S$를 100ppm 이하로 제거한 후, 흡착법을 이용하여 $H_2S$를 완전히 제거하였다. 바이오가스에 포화된 수분은 냉각제습과 흡착제습공정을 통해 Dew point $-70{\sim}-90^{\circ}C$까지 제거하여 안정적으로 $CO_2/CH_4$ 분리공정에 인입시켰다. $CO_2/CH_4$ 분리공정은 흡착방식을 적용하여 $CH_4$ 순도가 95% 이상인 바이오메탄을 생산하였으며, 이때 메탄 회수율은 약 87%이였다. $CO_2$가 분리된 바이오메탄은 초저온액화공정을 이용하여 액화바이오메탄으로 전환시켰다. 이때 초저온액화공정은 Reverse Brayton cycle로 구성하였으며, 냉매로는 질소를 사용하였다. 액화바이오메탄의 생산은 바이오메탄을 등엔트로피과정인 단열팽창을 통하여 $-155{\sim}-159^{\circ}C$의 초저온으로 냉각되는 질소냉매와 열교환기에서 열교환시켜 이루어졌으며 그 생산량은 $3.46m^3$/day(1bar, $-161^{\circ}C$)이었다.

• Environmental and Resource Economics Review
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• v.15 no.4
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• pp.673-692
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• 2006

In order to test for the dynamic optimality condition for the use of nonrenewable resource, it is necessary to estimate the shadow value of the resource in situ. In the previous literatures, a time series for in situ price has been derived either as the difference between marginal revenue and marginal cost or by differentiating with respect to the quantity of ore extracted the restricted cost function in which the quantity of ore is quasi-fixed. However, not only inconsistent estimates are likely to be generated due to the nonmalleability of capital, but the estimate of marginal revenue will be affected by market power. Since firms will likely fail to minimize the cost of the reproducible inputs subject to market prices under realistic circumstances where imperfect factor markets, strikes, or government regulations are present, the shadow in situ values obtained by estimating the restricted cost function can be biased. This paper provides a valid methodology for checking the dynamic optimality condition for a nonrenewable resource by using the input distance function. Our methodology has some advantages over previous ones: only data on quantities of inputs and outputs are required; nor is the maintained hypothesis of cost minimization required; adoption of linear programming enables us to circumvent autocorrelated errors problem caused by use of time series or panel data. The dynamic optimality condition for domestic coal mining does not hold for constant discount rates ranging from 2 to 20 percent over the period 1970~1993. The dynamic optimality condition also does not hold for variable rates ranging from fourth to four times the real interest rate.

• Korean Chemical Engineering Research
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• v.54 no.4
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• pp.443-447
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• 2016

The microalgae have cellulose as a main structural component of their cell wall and the lignin content in microalgae is much lower than other lignocellulosic biomass. Therefore, fermentable sugar production from microalgae (Tetraselmis KCTC 12236BP) can be carried out under pretreatment without high temperature and high pressure. It was investigated that the effect of hot-water pretreatment using sulfuric acid for lipid extracted algae which is expected to be a next generation biomass. The effects of three major variables including extraction temperature, acid concentration and time on the enzymatic hydrolysis were investigated. Among the tested variables, temperature and acid concentration showed significant effects and optimum pretreatment conditions for the economic operation criteria were obtained as follows: reaction temperature of $120^{\circ}C$, sulfuric acid concentration of 2 mol and pretreatment time of 40 min. Under the optimum conditions of acidic hot water pretreatment, experimentally obtained hydrolysis yield were 95.9% which showed about 2.1 fold higher compared with enzymatic hydrolysis process. Therefore, acid pretreatment under mild condition was proven to be an effective method for fermentable sugar production from lipid extracted microalgae.