• 한국전산유체공학회지
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• 제21권4호
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• pp.102-111
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• 2016

In this paper a computation of turbulent natural convection in enclosures with the elliptic-blending based differential and algebraic flux models is presented. The primary emphasis of the study is placed on an investigation of accuracy of the treatment of turbulent heat fluxes with the elliptic-blending second-moment closure for the turbulent natural convection flows. The turbulent heat fluxes in this study are treated by the elliptic-blending based algebraic and differential flux models. The previous turbulence model constants are adjusted to produce accurate solutions. The proposed models are applied to the prediction of turbulent natural convections in a 1:5 rectangular cavity and in a square cavity with conducting top and bottom walls, which are commonly used for validation of the turbulence models. The relative performance between the algebraic and differential flux model is examined through comparing with experimental data. It is shown that both the elliptic-blending based models predict well the mean velocity and temperature, thereby the wall shear stress and Nusselt number. It is also shown that the elliptic-blending based algebraic flux model produces solutions which are as accurate as those by the differential flux model.

• Transactions on Electrical and Electronic Materials
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• 제15권2호
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• pp.103-111
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• 2014

This paper investigates the output powers of PV modules by predicting three unknown parameters: reverse saturation current, and series and shunt resistances. A theoretical model using the non-uniform physical parameters of solar cells, including the temperature coefficients, voltage, current, series and shunt resistances, is proposed to obtain the I-V characteristics of PV modules. The solar irradiation effect is included in the model to improve the accuracy of the output power. Analytical and Newton methods are implemented in MATLAB to calculate a module output. Experimental data of the non-uniform solar cells for both serial and parallel connections are used to extend the implementation of the model based on the I-V equation of the equivalent circuit of the cells and to extend the application of the model to m by n modules configuration. Moreover, the theoretical model incorporates, for the first time, the variations of series and shunt resistances, reverse saturation current and irradiation for easy implementation in real power generation. Finally, this model can be useful in predicting the degradation of a PV system because of evaluating the variations of series and shunt resistances, which are critical in the reliability analysis of PV power generation.

• Natural Product Sciences
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• 제17권4호
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• pp.328-336
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• 2011

A high-performance liquid chromatography (HPLC) with diode array detector (DAD) method was established for the discrimination of a folk medicine Forsythia suspensa and Forsythia viridissima. Five and three representative metabolites of the lignan and phenolic glycoside classes were selected for the analysis from F. suspensa and F. viridissima, respectively. The optimal chromatographic conditions were obtained on an ODS column (5 ${\mu}m$, $4.6{\times}250$ mm) with the column temperature at $40^{\circ}C$. The mobile phase was composed of methanol and 0.3% acetic acid using an isocratic elution with the flow rate 1 mL/min. Detection wavelength was set at 280 nm. All calibration curves showed good linear regression ($r^2$ > 0.996) within test ranges. Limits of detection (LOD) and limits of quantitation (LOQ) values were lower than 0.096 and 0.291 ${\mu}g/mL$, respectively. The developed method provided satisfactory precision and accuracy with overall intra-day and inter-day variations of 0.07-0.63% and 0.14-0.62%, respectively, and the overall recoveries of 97.79-102.46% for all of the compounds analyzed. In addition, effectiveness of diverse extraction methods was compared to each other for the development of standard analytical method. The verified method was successfully applied to the quantitative determination of representative metabolites in fifty-three commercial F. suspensa samples and fifteen commercial F. viridissima samples from diverse sources. The overall analytical results showed the unequivocal differences in bioactive constituents between F. suspensa and F. viridissima.

• 한국농공학회논문집
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• 제60권6호
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• pp.121-131
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• 2018

Climate change has caused changes in environmental factors that have a direct impact on agriculture such as temperature and precipitation. The meteorological disaster that has the greatest impact on agriculture is drought, and its forecasts are closely related to agricultural production and water supply. In the case of terrestrial data, the accuracy of the spatial map obtained by interpolating the each point data is lowered because it is based on the point observation. Therefore, acquisition of various meteorological data through satellite imagery can complement this terrestrial based drought monitoring. In this study, Evaporative Stress Index (ESI) was used as satellite data for drought determination. The ESI was developed by NASA and USDA, and is calculated through thermal observations of GOES satellites, MODIS, Landsat 5, 7 and 8. We will identify the difference between ESI and other satellite-based drought assessment indices (Vegetation Health Index, VHI, Leaf Area Index, LAI, Enhanced Vegetation Index, EVI), and use it to analyze the drought in South Korea, and examines the applicability of ESI as a new indicator of agricultural drought monitoring.

• Journal of Biosystems Engineering
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• 제35권5호
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• pp.310-315
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• 2010

The amount of salt intake of Korean people is 11.4 grams per a day, which is 2.3 times of the recommended daily salt intake by WHO - 5 grams of salt a day. The relationship between high salt consumption and increased risk of high blood pressure, observed not only in hypertensive but also in normotensive patients. High salt intake is also associated with an increased risk of heart attack, cerebral ischemia and osteoporosis. Therefore, this research is for developing a salt taste sensor to reduce sodium consumption and improve meal habits for the perception of a more bland taste of most foods. When the sensor was put into food sample, current intensity achieved with distribution cables. Current intensity was correlate with a simple equivalent of salt taste stimulus intensity. The salt taste sensor consists of salinity & temperature measuring probe, signal processing circuit and LCD display & LED warning light. When salinity is going over a set point, LCD displayer indicate salt taste on LCD panel by percent value (%), and at the same time, blue LED light change to red LED light. So we could know the grade of salt taste in soup before meals conveniently and objectively. The results show that operating range of 10 to $80^{\circ}C$ and accuracy of ${\pm}0.1%$ were achieved with an analysis time of about 2 or 3 sec. Moderate reductions in salt intake can help to avert adult diseases and lead a healthy life.

• 대한의용생체공학회:의공학회지
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• 제29권6호
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• pp.493-501
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• 2008

In this paper, a novel system is proposed to measure skin hydration using the susceptance method. This system largely consists of a low-voltage(${\pm}2.6$ V) driven circuit and minimized electrodes of size($5{\times}5mm^2$). To evaluate the accuracy of the novel system in measuring skin hydration, skin hydration values from 105 subjects are measured by the proposed system. The measurements are then compared to those obtained by the golden reference device based on the capacitance method in terms of Intraclass Correlation Coefficient(ICC) and correlation coefficient. All measurements are performed on 7 sites, which are forehead, Crow's foot, cheek, chin, volar forearm, dorsal forearm, and back of the hand, in a room where the temperature and humidity are maintained at an uniform level of $22{\pm}2^{\circ}C$ and $50{\pm}5%$, respectively. ICC values are above 0.9(p=0.001), signifying that the skin hydration values measured by the two methods show a good level of reliability. Correlation coefficient between the two methods is also 0.562(p=0.001). Based on these results, it is expected that the proposed system may be applicable in a variety of clinical or cosmetic areas.

• 한국산학기술학회논문지
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• 제14권8호
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• pp.3925-3932
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• 2013

감성은 인간의 삶과 밀접한 관련을 가지고 있으며 이는 집중력, 학습능력 등 많은 부분에 영향을 주어 다양한 행동 패턴을 가지게 한다. 따라서 본 논문의 목적은 부정감성을 구분하기 위하여 생체신호를 기반으로 주요한 특징들을 추출하는 것이다. 이를 위해 본 논문에서는 심전도, 뇌파, 피부 온도와 피부전도도를 기반으로 생체신호를 측정한 후, 선형분류기와 유전 알고리즘의 조합으로 정확하고 신속한 알고리즘 개발하고, 주요 특징을 추출하였다. 그 결과, 알고리즘은 최대 96.4%의 정확도를 가짐을 확인할 수 있었고, 추출된 파라미터는 심박변이도의 Mean, RMSSD, NN50과 뇌파의 전두엽 영역에서의 ${\sigma}$파와 ${\alpha}$파의 주파수 파워, 두정엽 영역에서 ${\alpha}$파, ${\beta}$파, ${\gamma}$파와 의 주파수 파워, 그리고 피부온도의 평균과 표준편차 값이었다. 이에 따라 각 각의 생체신호를 기반으로 한 추출 된 특징들은 부정감성의 분류에 있어 중요한 역할을 함을 확인할 수 있었다.

• 한국위성정보통신학회논문지
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• 제11권4호
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• pp.94-101
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• 2016

원격 관측 자료인 위성 자료는 한계점이 있으며, 특히 광학 관측기를 활용하면 구름이나 기타 요인에 의해 손실 자료가 발생한다. 본 연구에서는 MODerate resolution Imaging Spectrometer(MODIS)의 관측 자료 중, 지표면 온도 자료를 대상으로 손실 자료를 복원하기 위한 방법인 평균 편차 방법, 회귀 분석 방법, 지역 변동 방법의 세 가지 복원 방법을 개발하였다. 검증을 위해 2014년과 2015년의 위성 자료에서 관측 비율을 근거로 사례를 선택하였다. 검증 자료에서 확인된 지역 변동 방법의 평균 제곱근 편차(RMSE)는 일부 사례에서 약 2 K 이상으로 다른 복원 방법에 비해 낮은 정확도를 보였으며, 회귀 분석 방법의 RMSE는 평균 약 1.13 K으로 대부분의 사례에서 가장 좋은 결과를 보였다. 평균 편차 방법 사용 시, RMSE는 회귀 분석 방법 시와 유사하게 약 1.32 K으로 나타났다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2018년도 춘계학술대회
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• pp.457-459
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• 2018

태양광발전시스템은 태양광으로부터 에너지를 생산하는 발전기술이며, 신재생 에너지 기술 중 가장 빠르게 성장하고 있다. 태양광 발전 시스템은 부하에 안정적으로 에너지를 공급하는 것이 가장 중요시 된다. 그러나 날씨 및 기상 조건에 따라 에너지 생산이 불안정하기 때문에 에너지 생산량에 대한 정확한 예측이 필요하다. 본 논문에서는 강수량, 장 단파 복사선 평균, 온도 등 15가지 종류의 기상 데이터를 사용하여 태양광 에너지를 예측하는 인공 신경망(ANN)을 구현하고 성능을 평가한다. 인공 신경망은 은닉층을 구성하고 오버피팅을 방지하기 위한 페널티 ${\alpha}$와 같은 파라미터를 조절하여 구현한다. 예측모델의 정확도와 타당성을 검증하기 위해 성능지표로 MAPE(Mean Absolute Percentage Error)와 MAE(Mean Absolute Error)를 사용한다. 실험 결과 Hidden Layer $Sizes=^{\prime}16{\times}10^{\prime}$을 사용하였을 때 MAPE=19.54와 MAE=2155345.10776로 나타났다.

• 한국약용작물학회지
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• 제3권3호
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• pp.226-232
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• 1995

자호(紫胡) saikosaponin정량(定量)에 대한 추출방법(抽出方法) 및 기기분석조건별(器機分析條件別) 비교분석시험(比較分析試驗)결과는 다음과 같다. 1. HPLC를 이용한 시호 사포닌 정량은 산처리하는 방법에서 무처리 방법보다 분석시간이 더 단축되었다. 2. 추출방법상 상온추출이 수율이 높으나 가온 환류추출에 의해 분석시간이 짧고 양호한 크로마토그람을 얻을 수 있었다. 3. 시호 사포닌 분석시 HPTLC법이 HPLC법보다 대량신속측면에서 양호하나 신뢰도가 떨어졌다. 4. 따라서 시호 사포닌의 추출 및 분석은 가온환류추출과 산처리하는 분석방법이 신속한 분석방법으로 적당하였으며, 성분육종을 위한 간이검정기술로서는TLC 이용 분석이 유리할 것으로 생각되었다.