• Journal of Environmental Science International
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• v.6 no.6
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• pp.679-688
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• 1997

In order to analyze the water quality variation of surface water around the Sudokwon landfill site, seasonal variations of water temperature, pH, DO. HOD, COD, SS, NH3-N, NO2-N, and NO3-N were examined at 10 sites from January to December, 1996. It was found that the estimates of COD, DO. SS, and $NH_3-N$ were Increased compared with the results of environmental Impact assessment carried out In 1988. Higher estimates of COD, DO, and SS were due to Industrial and agricultural wastewater, and the Increase of NH3-N at Jangdo reservoir strate was due to the leachate from the landfill. In particular, the estimate of 55 was found to be increased by the soil wash from the landfill during the heavy rainy days.

• The KSFM Journal of Fluid Machinery
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• v.19 no.3
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• pp.19-24
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• 2016

Oil sands are a mixture of sand, clay, and a high-viscosity petroleum called bitumen. Steam-Assisted Gravity Drainage (SAGD) is the most viable and environmentally safe recovery technology for extracting bitumen. It extracts the viscosity-lowered bitumen by high pressure, high temperature steam injected into the bitumen reservoir. The steam is produced at the Central Processing Facility (CPF). Typically, more than 90% of the energy consumed in producing bitumen are used to generate the steam. Fuels are employed in the process, which cause economic and environmental problems. This paper explores the retrofit of heat exchanger network to reduce the usage of hot and cold utilities. The hot and cold utilities are reduced respectively 6% and 37.3% which in turn resulted in 5.3% saving of total annual cost by improving the existing heat exchanger network of the CPF.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.45-48
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• 2008

This paper presents a passive air-breathing direct methanol fuel cell (DMFC) which has been designed and tested. The single cell is fuelled by methanol vapor that is supplied through flow channel from a methanol reservoir at the anode, and the oxygen is supplied via natural air-breathing at the cathode. The methods for supplying the methanol vapor to the single cell were parallel channel and chamber. This research investigates various methods to identify the effects of using flow channels for providing the methanol vapor at the anode, and the opening ratio between the inlet and outlet ports for the methanol flow at the anode. The best flow channel condition for passive DMFC was a chamber, and the opening ratio was 0.8. Under these conditions, the peak power was 10.2mW/$cm^2$ at room temperature and ambient pressure. The key issues for the Passive DMFCs for using methanol vapor are that sufficient methanol needs to be supplied using a large as possible opening ratio. However, it is shown that the performance of the passive DMFC, which has a channel at the anode,is low due to the low differential pressure and insufficient methanol supply rate.

• Proceedings of the KIPE Conference
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• 2001.12a
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• pp.109-114
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• 2001

Photovoltaic systems normally use a maximum power point tracking (MPPT) technique to continuously deliver the highest possible power to the load when variations in the insolation and temperature occur. A simple method of tracking the maximum power points (MPPs) and forcing the boost converter system to operate close to these points is presented through deriving small-signal model and transfer function of boost converter. This paper aims at modeling boost converter including equivalent series resistance of input reservoir capacitor by state-space-averaging method. In the future, properly designed controller for compensation will be constructed for maximum photovoltaic power tracking control.

• Journal of Korean Society of Rural Planning
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• v.7 no.1 s.13
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• pp.89-98
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• 2001

This study was carried out to provide the basic informations for the water quality management in Boryung fresh water reservoir watershed. Four agricultural reservoirs were selected and the water qualify of the reservoirs were investigated from November 1998 to December 2000, periodically. Including storage rate, temporal variation of water quality constituents such as water temperature, pH, EC, total nitrogen, total phosphorus were analysed. The result showed that pH ranged $6.7{\sim}10.4$, EC $56.1{\sim}1079{\mu}S/cm$, COD $0.75{\sim}8.0mg/L$, respectively. And, total-N concentration affected by the livestock wastes and agricultural activity ranged from 0.21 to 4.66mg/L and which was almost over the agricultural water quality standard(1.0mg/L). Total-P ranged from 0.001 to 0.080mg/L as lower than the agricultural water quality standard(0.1mg/L).

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.582-589
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• 1988

A rapid expansion of moist air or steam in a supersonic nozzle gives rise to condensation, and the total pressure of the flow is decreased due to this irreversibility of condensation phenomenon. In the present paper, the loss in total pressure during the condensation process has been studied, by numerical analysis and pressure measurement, in the case of moist air expanding in a supersonic nozzle. The effects of the degree of supersaturation at the stagnation condition and expansion rate of the nozzle on the total pressure loss have been studied. The length of the region where the total pressure decreases during the condensation process is longer than that of the nonequilibrium condensation region, and of difference between the length of these two increases with the increase of the degree of supersaturation at the stagnation condition. Furthermore, the larger the expansion rate of the nozzle and the higher the temperature and the degree of supersaturation at the reservoir are, the larger the total pressure loss of the flow becomes. And, it is turned out that the total pressure loss be about 2 to 8 percent in the present study.

• Bulletin of the Korean Chemical Society
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• v.24 no.2
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• pp.209-218
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• 2003

Ecosystems in the Keweenaw Peninsula region of Lake Superior, USA, were disturbed by over 500 million tons of copper-rich mine tailings during the period 1850-1968. Metals leaching from these mine residues have had dramatic effects on the ecosystems. Vast acreages of exposed tailings that are over 100 years old remain unvegetated because of the combination of metal toxicity, absence of nutrients, and temperature and water stress. Therefore, it is important to characterize and fractionate solid copper phases for assessing labile forms of copper in soils and sediments contaminated by the mining wastes. X-ray diffraction analyses indicate that calcite, quartz, hematite, orthoclase, and sanidine minerals are present as major minerals, whereas cuprite,tenorite, malachite, and chalcopyrite might be present as copper minerals in the mining wastes. Sequential extraction technique revealed that carbonate and oxide fractions were the largest pools of copper (ca. 50-80%) in lakeshore and wetland stamp sands whereas the organic matter fraction was the largest reservoir (ca. 32%) in the lake sediments. The concentrations of iron and copper were inversely correlated in the oxide fraction suggesting that copper may occur as a surface coating on iron oxides. As particle size and water contents decrease, the percent of the copper bound to the labile carbonate fraction increases.

• Journal of the Korean Solar Energy Society
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• v.29 no.6
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• pp.1-13
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• 2009

Photovoltaic conditioning systems normally use a maximum power point tracking (MPPT) technique to deliver the highest possible power to the load continuously when variations occur in the insolation and temperature. A unique method of tracking the maximum power points (MPPs) and forcing the boost converter system to operate close to these points is presented through deriving small-signal model and transfer function of boost converter considering input capacitor. This paper aims at modeling boost converter including fairly large equivalent series resistance(ESR) of input reservoir capacitor by state-space-averaging method and PWM switch model and compares both methods using Bode plots. In the future, properly designed controller for compensation will be constructed in 3kw real system for maximum photovoltaic power tracking control.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.172-176
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• 2009

We developed a program, "CogenSim-$\mu$," to simulate the operation of micro-combined heat and power (${\mu}CHP$) system. The CogenSim-$\mu$ can reflect the variation of energy efficiency by handling the real-time loads (heat and power) fluctuation. The result obtained using this program was compared with the real operation of 30 kWe gas engine driven ${\mu}CHP$. It was found that the CogenSim-$\mu$ could predict the amount of generated-power, recovered-heat and consumed-fuel with the error less than 3%, and heat and power efficiency with the error less than 4%. The CogenSim-$\mu$ reconstructed the profile of on-off cycle, which represented the operation of a facility, with more than 93% accuracy. The CogenSim-$\mu$ can reflect the effects of various factors such as size of thermal storage tank, desired temperature of reservoir water, natural frequency of generator, etc. As a result, the CogenSim-$\mu$ can be used to optimize the ${\mu}CHP$ operation.

• Membrane and Water Treatment
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• v.9 no.3
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• pp.173-179
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• 2018

Microcystin-LR, one of algal toxins induced by the eutrophication of a reservoir, is known to be harmful to human by adversely affecting our liver and brain. Hypochlorous acid is very efficient to remove Microcystin-LR in a clear well. The previous researches showed that CT, pH and temperature affected removal rate in batch tests. It was noted that hydrodynamic properties of clear well could also influence its removal rate. A mathematical model was built using an axial dispersion reactor model and software was used to simulate the removal rate. The model consisted of the second order differential equations including dispersion, convection, Microcystin-LR reaction with chlorine. Kinetic constants were obtained through batch tests with chlorine. They were $0.430{\times}10^{-3}L/mg/sec$ and $0.143{\times}10^{-3}L/mg/sec$ for pH 7.0 and 8.1, respectively. The axial dispersion reactor model was shown to be useful for the numerical model through conservative tracer tests. The numerical model successfully estimated the removal rate of Microcyctin-LR in a clear well. Numerical simulations showed that a small dispersion number, low pH and long hydraulic retention time were critical for higher removal rate with same chlorine dosage. This model could be used to optimize the operation of a clear well during an eutrophication season.