• 한국수자원학회논문집
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• 제54권7호
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• pp.495-507
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• 2021

최근 도시와 산업의 발달과 함께 하천, 호소 등 수환경에서의 수질 오염사고가 빈번하게 일어나고 있어 어류폐사, 취수중단, 친수활동 저해 등 심각한 수생태계 및 사회경제적 피해가 발생하고 있다. 따라서 이에 대한 대응책으로 수질모델링을 통한 오염물질의 이동 및 확산에 대한 사전 예측이 필요하다. 본 연구에서는 2차원 하천흐름/수질해석 프로그램인 RAMS+의 현장 적용성 및 예측 정확도를 검증하기 위해 만곡하천인 섬강에서 현장실험을 수행하였다. 모의결과 흐름해석모형 HDM-2Di와 수질해석모형 CTM-2D-TX는 현장실험에서 관측된 2차원 흐름 특성과 오염물질의 거동 및 혼합 양상을 정확하게 재현하였다. 특히 하천의 양안과 만곡부에서 국부적으로 발생하는 저유속 흐름에 의해 오염물질의 거동이 지체되는 저장대 효과를 정확하게 모의하였다. 나아가서 하천 만곡부에서 이차류가 야기하는 오염물질 3차원적 혼합 양상을 2차원 분산계수를 통해 효과적으로 재현하였다. 오염물질의 위험농도 체류시간은 취수중단 기간을 결정하는데 있어 매우 중요한 요소이다. 본 연구에서는 CTM-2D-TX 모의결과를 기반으로 오염물질 위험농도 체류시간을 계산하였고, 위험농도 체류시간의 공간적 분포가 하폭방향으로 큰 편차를 지니고 있음을 확인하였다. 이러한 오염물질의 2차원적 체류 특성은 1차원 수질모형을 통해서는 예측이 불가능하기 때문에 효율적이고 정확한 수질사고대응을 위해 2차원 수질모형의 활용이 필요함을 본 연구의 결과는 시사하고 있다.

• 한국수자원학회논문집
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• 제44권7호
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• pp.591-599
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• 2011

도달시간 산정식에서 강우강도는 고려되어야 할 매우 중요한 요소이지만 일반적으로 강우강도식의 복잡함 때문에 도달시간 산정에서 강우강도를 충분히 고려하지 못하고 있는 실정이다. 본 연구에서는 도달시간 계산의 정확성을 높이기 위하여 강우강도와 재현기간을 도달시간 산정식의 유도에 포함시켰다. 강우강도식으로는 Sherman형 식을 사용하였고, 건설교통부에서 발행한 확률강우량도에서 독취한 강우강도 값으로 수식의 지역상수를 추정하였다. 그리고 확률강우량을 간결하게 계산하기 위하여 Sherman형 식의 지역상수를 등치선도로 나타냈다. 기존의 연구에서는 일반형 강우강도식을 대입하여 반복계산으로 도달시간을 산정하였지만, 본 연구에서는 Sherman형 강우강도식을 도달시간 수식에 대입함으로써 반복계산이 필요 없는 간단한 도달시간 식이 유도되었다. 연구 결과로부터, 도달시간 계산에 강우강도의 영향을 반영하기 위하여 Sherman형 식의 사용을 추천한다. 그리고 재현기간과 우리나라에서 위치가 정해지면, 강우강도식의 지역상수를 간편하게 추정할 수 있고, 강우강도가 고려된 도달시간을 계산할 수 있다.

• 성인간호학회지
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• 제27권1호
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• pp.83-93
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• 2015

Purpose: This study was to investigate the relationship among the symptom recognition, health behavior compliance, and the hospital arrival time to identify factors influencing the hospital arrival time in patient with acute myocardial infarction (AMI). Methods: The subjects of this study were 200 patients with AMI in C hospital in D city. Data were analyzed using descriptive statistics, independent t-test, One way ANOVA, Pearson's correlation coefficients, and stepwise multiple liner regression tests. Results: Level of symptom recognition and health behavior compliance was low. The median value of hospital arrival time was 4.48 hours (ST-segment Elevation Ml was 2.43 hours and Non ST-segment Elevation MI was 7.83 hours). Among the studied factors, only symptom recognition had a statistically significant positive correlation with health behavior compliance (r=0.38, p<.001). Factors influencing the hospital arrival time were MI classification, diabetes mellitus (DM) and transport vehicle to the 1st hospital, and they accounted for 13% of the variance for hospital arrival time in AMI patients. Conclusion: To prevent the delay of hospital arrival time in MI patients, a more robust nursing strategic intervention according to MI classification and DM is necessary; further education on the importance of transportation utilization is also mandated.

• 지질공학
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• 제3권2호
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• pp.203-214
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• 1993

액체 산업폐기물을 심층지하에 방출시, 폐기물의 이동은 지하매체의 낮은 투수율로 인하여 분자확산에 의해 좌우된다. 하편 확산에 의한 이동은 Fick의 제2법칙으로 예측할 수 있다. 본 연구에서는 실험을 통한 Cr(VI)의 확산 이동계수를 구하였다. 다공질내에서의 Cr(VI)이동을 추적하기 위해 방사성 동위원소인 $^{51}Cr$을 사용하였으며, Fick의 제2법칙에 대한 해석해를 구해 Cr(VI)의 확산계수를 결정하였다. 본 연구에서는 온도, $^{51}Cr$의 양, 염소 이온의 양, 매체의 건조밀도를 환경적 변화인자로 이용하였다.

• 설비공학논문집
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• 제16권6호
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• pp.589-598
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• 2004

Flow condensation heat transfer coefficients (HTCs) of R22 and R134a were measured on a horizontal 9 hole aluminum multi-channel tube. The main test section in the refrigerant loop was made of a flat multi-channel aluminum tube of 1.4 mm hydraulic diameter and 0.53 m length. Refrigerant was cooled by passing cold water through an annulus surrounding the test section. Data were obtained in the vapor qualities of 0.1∼0.9 at mass flux of 200∼400 kg/$m^2$s and heat flux of 7.3∼7.7 ㎾/$m^2$ at the saturation temperature of 4$0^{\circ}C$. All popular correlations in single-phase subcooled liquid and flow condensation originally developed for large single tubes predicted the present data of the flat tube within 20% deviation when effective heat transfer area is used in determining experimental data. This suggests that there is little change in flow characteristics and patterns when the tube diameter is reduced down to 1.4 mm diameter range. Thermal insulation for the outer tube section surrounding the test tube for the transport of heat transfer fluid is very important in fluid heat-ing or cooling type heat transfer experimental apparatus.

• Journal of Advanced Marine Engineering and Technology
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• 제36권8호
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• pp.1003-1009
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• 2012

열교환기는 에너지전달을 필요로 하는 산업분야에 널리 사용되고 있으며 효율이 좋은 판형 열교환기의 비중이 크게 증가되고 있다. 본 연구는 판형열교환기의 최적설계를 위하여 주요설계인자를 분석하고 방정식을 유도하였으며 상용코드와 비교 분석하였다. 판의 쉐브론각에 따른 열전달계수와 압력강하 설계식을 도입하였으며 각각의 설계식은 레이놀즈 수의 함수로 표현되었다. 이 설계식을 이용해 쉐브론 각이 동일한 판을 사용하였을 경우와 쉐브론각이 다른 두 판을 교차한 경우에 대하여 성능 해석하였으며 상용프로그램의 결과와 비교분석하였다. 성능해석을 한 결과 대류열전달계수는 8%이내, 압력강하는 5%이내의 오차로 만족할 만한 결과를 나타냈다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2009년도 학술발표회 초록집
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• pp.2179-2183
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• 2009

As urbanization is progressed, the network for distributing water in a basin become complex due to the spatial expansion and parameter uncertainties of water supply systems. When a long range water supply plan is determined, the total construction and operation cost has to be evaluated with the system components and parameter uncertainties as many as possible. In this paper, the robust optimization approach of Bertsimas and Sim is applied in a hypothetical system to find a solution which remains feasible under the possible parameter uncertainties having the correlation effect between the uncertain coefficients. The system components to supply, treatment, and transport water are included in the developed water supply system and construction and expansion of the system is allowed for a long-range period. In this approach, the tradeoff between system robustness and total cost of the system is evaluated in terms of the degree of conservatism which can be converted to the probability of constraint violation. As a result, the degree of conservatism increases, the total cost is increased due to the installation of large capacity of treatment and transportation systems. The applied robust optimization technique can be used to determine a long-range water supply plan with the consideration of system failure.

• 한국응용과학기술학회지
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• 제28권1호
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• pp.102-108
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• 2011

The study of wave propagation and scattering in biological media has become increasingly important in recent years. The propagation of light within tissues is an important problem that confronts the dosimetry of therapeutic laser delivery and the development of diagnostic spectroscopy. In the clinical application of photodynamic therapy(PDT) and in photobiology, the photon deposition within a tissue determines the spatial distribution of photochemical reactions. Scattered light is measured as a function of the distance (r) between the axis of the incident beam and the detection spot. Consequently, knowledge of the photosensitizer(Chlorophyll-a) function that characterizes a phantom is measured. To obtain the results of scattering coefficients(${\mu}s$) of a turbid material from diffusion described by experimental approach. It was measured the energy fluency of photon radiation at the position of penetration depth. From fluorescence experimental method obtained the analytical expression for the scattered light as the values of $(I/I_o)_{wavelength}$ vs the distance between the center of the incident beam and optical fiber in terms of the condition of "in situ spectroscopy(optically thick)" and real time by fluorometric measurements. The result was compromised with transport of intensities though a random distribution of scatters.

• 한국농공학회지
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• 제39권2호
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• pp.62-73
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• 1997

The application of nutrients and pesticides to agricultural lands has been reported to contribute to groundwater contamination, which can be explained by preferential flow in lieu of convective-dispersive flow. An one-dimensional numerical model depicting preferential water and solute movement was modified to describe multi-layer flows. The model is based on a piecewise linear conductivity function. By combining conservation of mass and Darcy's law and using the method of characteristics a solution is obtained for water flow in which water moves at distinct velocities in different flow regions instead of an average velocity for the whole profile. The model allows transfer ofqr solutes between pore groups. The transfer is characterized by assuming mixing coefficients. The model was applied to undisturbed soil columns and an experiment site with structured sandy clay loam soil. Chloride, bromide, and 2, 4-D were used as tracers. Simulated solutes concentrations were in good agreement with the soil column data and field data in which preferential flow of solute is significant. The proposed model is capable of describing preferential solute transport under laboratory and field conditions.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2003년도 한국우주과학회보 제12권2호
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• pp.40-40
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• 2003

When the magnetotail is disturbed by an impulsive input such as the substorm onset, compressional magnetohydrodynamic (MHD) waves play an important role in delivering perturbed energy and exciting various wave modes and currents. The plasmasheet, in which relatively hot plasmas exist, is surrounded by relatively cold plasmas at the plasma sheet boundary layer (PSBL) and the equatorial plasmasphere. Since the Alfven speed significantly varies near these regions, the compressional waves are expected to undergo mode conversion by inhomogeneity at the boundary between cold and hot plasma regions. We investigate how the initial compressional MHD wave energy is reflected, transmitted, and absorbed across that boundary by adopting the invariant imbedding method (IIM) which gives the exact reflection, transmission, and absorption coefficients without any theoretical approximations for given frequencies and wave numbers. The IIM method is very useful in quantifying the reflection and transmission of compressional waves in the sense that we can calculate how much fast mode wave energy is delievered into shear Alfven waves or field-aligned currents. Our results show that strongly localized absorption occurs at the boundary region. This feature suggests that localized field-aligned currents can be impulsively excited at such boundary regions by any compressional disturbances, which is highly associated with impulsive auroral brightening at the substorm onset. We compare our results with previous studies in cold inhomogeneous plasmas.