• Membrane Journal
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• v.23 no.1
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• pp.61-69
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• 2013

The effect of humic acid (HA), and the roles of microfiltration (MF), PES (polyethersulfone) beads adsorption, and photo-oxidation were investigated in hybrid process of ceramic MF and PES beads loaded with titanium dioxide ($TiO_2$) photocatalyst for advanced drinking water treatment. Those were compared and studied in viewpoints of membrane fouling resistance ($R_f$), permeate flux (J), and total permeate volume ($V_T$). Because membrane fouling increased dramatically as decreasing HA, $R_f$ increased and J decreased, and finally $V_T$ was the highest at 2 mg/L HA. In the experiment to investigate the roles of photo-oxidation and adsorption at humic acid 4 mg/L and 6 mg/L. In both conditions, $R_f$ was the lowest and $V_T$ was the highest in MF + $TiO_2$ + UV process. The average treatment efficiencies of turbidity and dissolved organic matters were the highest in MF + $TiO_2$ + UV process, too.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.5
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• pp.558-562
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• 2006

Filtration experiments were conducted to determine the characteristics of manganese removal in filtration using 4 different filter media including sand and manganese sand(MS). Filtration velocity was 123 m/d and the flow rate was $3.9m^3/d$ per column. Duration of these experiments was about one year, and manganese dioxide accumulation, turbidity removal, manganese removal, and organic material removal were examined depending on filter media. When filter influent(residual chlorine 1.0 mg/L) with an average manganese concentration of 0.208 mg/L was fed through a filter column, the sand+MS and MS columns removed 98.9% and 99.2% of manganese respectively on an annual basis. When there is need to replace the sand filters with a MS filter to remove manganese, it was shown that the replacement of a partial sand filter with MS had adequate manganese removal.

• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.191-197
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• 2012

Acrylic terminated polyurethane prepolymers were synthesized by capping the NCO groups of polyurethane prepolymers, prepared from isophorone diisocyanate (IPDI), polycarbonate diol (PCD) and dimethylol propionic acid (DMPA), with pentaerythritol triacrylate (PETA). Subsequently, silylated acrylic terminated prepolymers were prepared by capping the NCO groups of acrylic terminated polyurethane prepolymers with different types of silane coupling agents, glycidoxypropyl trimethoxysilane (GPTMS) or aminopropyl triethoxysilane (APS). The average particle size of pure waterborne polyurethane solution, measured by the dynamic light scattering method, was increased from 14.3 nm to 208.6 nm by adding PETA and APS. Also, the coating film of silylated acrylic terminated waterborne polyurethane showed better abrasion resistance and pencil hardness than that of pure waterborne polyurethane.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1729-1733
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• 2010

본 연구에서는 7개 지점(여주, 적성, 왜관, 진동, 공주, 구례2, 나주)에 대해 유사량 특성 분석을 수행하였다. 부유사량은 강우가 집중되는 홍수기와 이의 전 후시기인 저 평수기(2회)로 나누어 왕복수심적분법(D-74)으로 측정하였고, 하상토는 BM-54, Grab Sampler(60 L), 선격자 등을 이용하여 홍수기 전 후로 2회 채취하였다. 채취된 시료는 그 목적에 따라 여과법(부유사농도), BW관법(부유사입도분포), 체분석법(하상토입도분포)으로 분석하였고, 그 결과로 작성된 평균 부유사농도 및 Oden Curve와 입도분포곡선과 수리량(수위, 유속, 측정수심, 수면폭, 수면경사, 수온)등의 자료를 이용하여 총유사량(미측정구간의 유사량 포함)을 추정(실측+계산: Modified Einstein)하였다. 총유사량 추정시, 세류사량을 제외한 부유사량을 적용하였다. 유량-부유사농도와 부유사량 및 총유사량 관계에 대한 결과는 다음과 같다: 1) 하나의 강우사상의 수위 상승-첨두-하강에 대한 측정성과는 대체적으로 Loop 형태를 보였고 이로 인해 일부 지점에서 측정성과들 간의 산포도가 다소 크게 나타났으며 수위 하강 때보다 상승시 초기 탁도의 증가 현상으로 부유사농도가 더 높은 것을 볼 수 있었다. 2) 유량-부유사농도, 부유사량, 총유사량 관계에서 왜관과 공주 지점의 경우, 첨두 수위에서 값들의 최고치를 보였고 나머지 지점들은 첨두 수위의 앞선 측정 수위에서 최고치를 보였다. 이는 강우사상별, 강우강도, 댐 방류량, 수위 상승-하강부, 유량에 따른 부유사농도와 부유사량의 특성이 각각 다른 점과 총유사량 추정시, 추정방법에서 추천하는 범위에서 벗어나는 자료를 적용해서 나타나는 결과로 판단된다. 여기서 유량, 수심, 하상토의 입도크기 등 자료의 범위가 추정공식들이 추천하는 범위에서 벗어나면 그 분석 결과도 서로 다르게 나타난다는 것은 그만큼 총유사량 공식의 범용성이 적다는 것을 의미한다. 이러한 점에서 때로는 자료 전체에 대해 전반적으로 양호한 결과를 보이는 공식보다는 정확한 답을 원하는 자료의 범위 내에서 예측하는 공식을 선정하는 것이 필요하다. 즉, 공식을 적용하여 유사량을 추정하고자 하는 하천이나 수로의 특성에 맞는 유사량 공식을 선정하는 것이 중요하다는 것이다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.6
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• pp.1959-1970
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• 1996

Effects of oscillatory flow upon heat transfer characteristics have been studied experimentally for oscillating flow in a circular tube. The experimental apparatus was designed to simulate the heat exchangers of the Stirling or Vuilleumier cycle machines and the test section consists of heater and cooler. Measurements were presented of heat flux, axial wall temperature distribution, and radial temperature profile of the working fluid for several cases of oscillation frequency and swept distance ratio. The influences of two main parameters, frequency and tidal displacement of the oscillation were investigated. Then the heat transfer coefficient at the heater is obtained. The carried by the authors with a assumption of oscillatory laminar slug flow.

• 한국해양학회지
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• v.26 no.3
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• pp.242-254
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• 1991

Southern sea of Korea was investigated for primary productivity during four scientific cruises of Korea Ocean research and Development Institute. Frontal structure appeared to be an important physical characteristic in enhancing the phytoplankton production in the study area. Relatively high productivity was occurred near the front between Tsushima Warm Current Water and Coastal Waters of China continent in March 1990 and in November 1989, and near the front between Tsushima Warm Current Water and Korean coastal Water in April 1989. In August 1988 high productive zone was limited to the tidal front off the southwestern coast of Korea. Nutrient supply related to the frontal structure might play a dominant role in increasing the primary productivity but mechanisms of nutrient enrichment are not clear. Average column productivity showed its maximum in April 1989 (1727 mgC/m$^2$/day). In the costal Waters of the china Continent incident light may be an important factor in regulating the regulating the phytoplankton production because of low light penetration rate resulting from high turbidity.

• KIPS Transactions on Computer and Communication Systems
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• v.8 no.4
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• pp.93-102
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• 2019

As interest in wellness grows, There is a lot of research about monitoring individual health using wearable devices. Accordingly, a variety of methods have been studied to distinguish exercise from daily activities using wearable devices. Most of these existing studies are machine learning methods. However, there are problems with over-fitting on individual person's learning, data discontinuously recognition by independent segmenting and fake activity. This paper suggests a detection method for exercise activity based on the physiological response principle of heart rate up and down during exercise. This proposed method calculates activity intensity and heart rate from triaxial and photoplethysmography sensor to determine a heart rate recovery, then detects exercise by estimating activity intensity or detecting a heart rate rising state. Experimental results show that our proposed algorithm has 98.64% of averaged accuracy, 98.05% of averaged precision and 98.62% of averaged recall.

• Journal of Korea Society of Industrial Information Systems
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• v.14 no.5
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• pp.61-73
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• 2009

Many software reliability growth models(SRGM) have been proposed since the software reliability issue was raised in 1972. The technology to estimate and grow the reliability of developing S/W to target value during testing phase were developed using them. Most of these propositions assumed the S/W debugging testing efforts be constant or even did not consider them. A few papers were presented as the software reliability evaluation considering the testing effort was important afterwards. The testing effort forms which have been presented by this kind of papers were exponential, Rayleigh, Weibull, or Logistic functions, and one of these 4 types was used as a testing effort function depending on the S/W developing circumstances. I propose the methology to evaluate the SRGM using least square estimater and maximum likelihood estimater for those 4 functions, and then examine parameters applying actual data adopted from real field test of developing S/W.

• Korean Journal of Environmental Agriculture
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• v.28 no.3
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• pp.249-257
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• 2009

Surface runoff and erosion are responsible for extensive losses of top soil and agricultural productivity. In this study, a laboratory experiment was conducted to investigate the effects of different polyacrylamides (PAM) on the protection of soil from erosion and turbidity in loamy sand soil. To accomplish this, 10 and 40 kg $ha^{-1}$ of PAM were applied to the soil surface. The effects of rainfall on 10 and 20% slopes were then evaluated in the laboratory using a rainfall simulator. After air drying, the surface was subjected to rain at 30 mm $hr^{-1}$. The silt+clay of the runoff from samples treated with 10 kg PAM $ha^{-1}$ reduced by 43% and 13% when the 10% and 20% slopes were evaluated, respectively, when compared with the tap water without PAM treatment as control. The mean contents of silt+clay were reduced as the amount of PAMs applied increased at both slopes. Specifically, samples treated with 40 kg PAM $ha^{-1}$ showed reductions in the silt+clay of the runoff to 88% and 85% when the 10% and 20% slopes were evaluated, respectively, when compared to control. Furthermore, the mean turbidity of runoff in the 40 kg PAM $ha^{-1}$ treatment was reduced to 94.7% and 84.8% when the samples were subjected to 10% and 20% slopes, respectively, when compared to the control. Taken together, these findings indicate that PAM treatment will improve water pollution and agricultural productivity on sloped land via a reduction in soil erosion.

• Economic and Environmental Geology
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• v.35 no.5
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• pp.395-406
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• 2002

The sixty natural springs and community wells used as a drinking water in the Daejeon area are mainly located at the parks and the natural green districts. The purpose of this study is to investigate the characteristics of water quality and the contamination of the springs and the wells, and to suggest the management strategy for the springs and wells. For this study, we undertook water quality data from Daejeon City. According to the statistic analysis of water quality data, unacceptable rate as a drinking water was about 28 percent in 1999 and 24.5 percent in 2000, respectively. Major unacceptable factor is coliform, and others are bacteria, yersinia, color, turbidity, Fe and F. The unacceptable rate shows a roughly positive relationship with precipitation, that is, it shows highest rate during a rainy season between June and September. The major contamination source is likely to be the excrement of wild animals around natural springs and wells. Most of springs are vulnerable to the contamination of coliform and bacteria because of short residence time and shallow circulation in subsurface environment. The water samples collected from 31 springs or wells show weak acidic pHs, the electrical conductivity ranging from 63 to 357 $\mu\textrm{S}$/cm, and the hydrochemical types of Na(Ca)-HC0$_3$ and Ca-HC0$_3$. The groundwater samples of low total dissolved solid(TDS) belong to Na(Ca)-HC0$_3$. type, and the groundwater of high total dissolved solid is shifted towards Ca-HC0$_3$ type in the chemical composition. These hydrochemical characteristics indicate that most natural springs is in the early stage of geochemical evolution. The natural springs should be closed during a rainy season, which shows a high contamination rate. We suggest that a protection barrier around the springs should be built to keep wild animals away from the springs.