• 대한기계학회논문집B
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• 제40권3호
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• pp.139-148
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• 2016

터빈과 압축기의 1차 근사 모델을 대상으로 열역학적 해석을 하여 단열 효율의 특성을 파악하였다. 비단열 터빈과 압축기에 대해서는 엔트로피 평균 온도와 생성 엔트로피, 열원 온도, 열전달량 등의 값에 따라 단열 효율이 1보다 커질 수 있다. 즉, 단열 효율을 비단열 검사체적에 적용하면 실제보다 성능을 높게 평가하는 오류가 생길 수 있다. 이 문제를 해결하는 대안으로 실제 과정과 동일한 열이 전달되는 가역 비단열 과정을 이상 과정으로 채택하여 정의하는 비단열 효율을 제안한다. 이 비단열 효율은 항상 0과 1 사이에 있으며, 대부분의 경우 엑서지 효율보다 작음을 입증하였다. 비단열 효율은 단열 효율을 포함하는 더 일반적인 효율의 정의식으로 사용할 수 있다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.278-281
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• 2007

The purpose of this study is to develop snow and sea ice detection algorithm in Communication, Ocean and Meteorological Satellite (COMS) meteorological data processing system. Since COMS has only five channels, it is not affordable to use microwave or shortwave infrared data which are effective and generally used for snow detection. In order to estimate snow and sea ice coverage, combinations between available channel data(mostly visible and 3.7 ${\mu}m$) are applied to the algorithm based on threshold method. As a result, the COMS snow and sea ice detection algorithm shows reliable performance compared to MODIS products with channel limitation. Specifically, there is partial underestimation over the complicated vegetation area and overestimation over the area of high level clouds such as cirrus. Some corrections are performed by using water vapor and infrared channels to remove cloud contamination and by applying NDVI to detect more snow pixels for the underestimated area.

• 상하수도학회지
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• 제30권3호
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• pp.225-231
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• 2016

Peak load rate(i.e., maximum daily flow/average daily flow) has not been considered for industrial water demand planning in Korea to date, while area unit method based on average daily flow has been applied to decide capacity of industrial water treatment plants(WTPs). Designers of industrial WTPs has assumed that peak load would not exist if operation rate of factories in industrial sites were close to 100%. However, peak load rates were calculated as 1.10~2.53 based on daily water flow from 2009 to 2014 for 9 industrial WTPs which have been operated more than 9 years(9-38 years). Furthermore, average operation rates of 9 industrial WTPs was less than 70% which means current area unit method has tendency to overestimate water demand. Therefore, it is not reasonable to consider peak load for the calculation of water demand under current area unit method application to prevent overestimation. However, for the precise future industrial water demand calculation more precise data gathering for average daily flow and consideration of peak load rate are recommended.

• 대한핵의학회지
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• 제24권2호
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• pp.260-266
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• 1990

Scintigraphic measurement of gastric emptying time has been reported to be influenced by the variation in depth of radionuclide within the stomach. In order to determine the effect of tissue attenuation in the measurement of gastric emptying time, 15 gastric emptying studies were performed with Tc-99m labeled egg sandwiches. Single anterior detector method overestimated the T1/2 by an average of 13% than geometric mean method and range of overestimation was wide (from -13% to 132%). Therefore, to evaluate the gastric empthying time accurately, methods of attenuation correction are needed.

• 한국농공학회논문집
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• 제62권1호
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• pp.61-70
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• 2020

To estimate the ventilation volume of mechanically ventilated swine farms, various regression models were applied, and errors were compared to select the regression model that can best simulate actual data. Linear regression, linear spline, polynomial regression (degrees 2 and 3), logistic curve, generalized additive model (GAM), and gompertz curve were compared. Overfitting models were excluded even when the error rate was small. The evaluation criteria were root mean square error (RMSE) and mean absolute percentage error (MAPE). The evaluation results indicated that degree 3 exhibited the lowest error rate; however, an overestimation contradiction was observed in a certain section. The logistic curve was the most stable and superior to all the models. In the estimation of ventilation volume by all of the models, the estimated ventilation volume of the logistic curve was the smallest except for the model with a large error rate and the overestimated model.

• 한국농림기상학회지
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• 제7권2호
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• pp.171-183
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• 2005

In order to monitor the global terrestrial carbon cycle, NASA (National Aeronautics and Space Administration) provides 8-day GPP images by use of satellite remote-sensing reflectance data from MODIS (Moderate Resolution Imaging Spectroradiometer) at l-km nadir spatial resolution since December, 1999. MODIS GPP algorithm adopts DAO (Data Assimilation Office) meteorological data to calculate daily GPP. By evaluating reliability of DAO data with respect to surface weather station data, we examined the effect of errors from DAO data on MODIS GPP estimation in the Korean Peninsula from 2001 to 2003. Our analyses showed that DAO data underestimated daily average temperature, daily minimum temperature, and daily vapor pressure deficity (VPD), but overestimated daily shortwave radiation during the study period. Each meteorological variable resulted in different spatial patterns of error distribution across the Korean Peninsula. In MODIS GPP estimation, DAO data resulted in overestimation of GPP by $25\%$ for all biome types but up to $40\%$ for forest biomes, the major biome type in the Korean Peninsula. MODIS GPP was more sensitive to errors in solar radiation and VPD than in temperatures. Our results indicate that more reliable gridded meteorological data than DAO data are necessary for satisfactory estimation of MODIS GPP in the Korean Peninsula.

• Clinics in Shoulder and Elbow
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• 제9권1호
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• pp.27-33
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• 2006

Purpose: To investigate early complications after repair of massive rotator cuff tears and to find out factors that compromise the results. Materials and Methods: Fourteen patients who had two or more cuff tendons involved were included. All patients were operated by open acromioplasty and rotator cuff repair. At 3 months after operation, we investigated whether there were any early complications or not. We used ASES scoring system for preoperative and follow up evaluation. In addition, various preoperative factors, such as duration of symptom, degree of tendon retraction, degree of fatty degeneration, and acromio-humeral distance, were compared between the complicated patients and non-complicated patients. Results: At 3 months after operation, the ASES score and pain were improved in any degree in all patients. But 5 patients complained persisting pain, and three of them showed major complications such as re-rupture of rotator cuff or deltoid rupture. But no preoperative factors in complicated patients were significantly different from those in non-complicated patients. Conclusion: None of the preoperative factors were related to the complications. There was a tendency of overestimation of fatty degeneration in MRI. Some factors in surgical technique and rehabilitation were highly suspected to be related to the complications.

• Mass Spectrometry Letters
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• 제1권1호
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• pp.29-32
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• 2010

Cross reacting antibodies can cause an overestimation of the results of immunoassays. Therefore, alternative methods are needed for the accurate quantification of steroids. Gas chromatography combined with isotope-dilution mass spectrometry (GC-IDMS) is developed to quantify urinary active androgens, testosterone, epitestosterone and dihydrotestosterone, which are clinically relevant androgens to both hair-loss and prostate diseases. The method devised involves enzymatic hydrolysis with $\beta$-glucuronidase, solid-phase extraction, liquid-liquid extraction using methyl tert-butyl ether and subsequent conversion to pentafluorophenyldimethylsilyl-trimethylsilyl (flophemesyl-TMS) derivatives for sensitive and selective analysis in selected-ion monitoring mode. Flophemesyl-TMS derivatization not only eliminates matrix interference but also has a good peak resolution within a 6 min-run. A selective and sensitive GC technique with flophemesyl-TMS derivatives also allows accurate quantitative analysis of three active androgens when combined with IDMS. The limit of quantification of the three analytes was <50 pg/mL, and extraction recoveries ranged from 91.9 to 102.1%. The precision and accuracy were 1.2~6.5% and 89.0~106.7%, respectively. This GC-IDMS method can be useful for evaluating the drug efficacy and monitoring the biological processes responsible for male-pattern baldness and prostate diseases.

• 대한공간정보학회지
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• 제19권1호
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• pp.29-36
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• 2011

본 연구는 항공 라이다 자료를 이용하여 영역 기반 차폐율 지도를 제작하는데 목적이 있다. 영역 기반 차폐율을 산정하기 위하여 대표적인 영역 분할 기법인 유역 분할(Watershed) 기법을 라이다 자료의 고도값에 적용하였으며, 추출된 영역들을 기반으로 차폐율을 산정하였다. 포인트 기반의 라이다 분류 자료를 래스터 자료로 변환하는 과정에서 빈도수 방법을 사용함으로써 포인트 기반의 차폐율 산정법에서 발생하는 과소 과대 추정 문제를 해결하였다. 또한, 분할의 정도를 달리함으로써 필요에 따라 다양한 축척의 차폐율 지도를 작성할 수 있었다. 제안 기법을 통해 제작된 차폐율 지도는 기존 임상도에서 제공하는 소밀도에 비해 보다 정확하고 세밀한 정보를 제공함을 확인할 수 있었다.

• 한국지반공학회논문집
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• 제20권3호
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• pp.67-74
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• 2004

사례 연구를 통해서 실제 세립토 교량현장에 대해 기존 교량세굴 해석모델들의 적용성을 분석하였다. 하상이 실트질 점토로 구성된 강화 초지대교를 대상교량으로 선정하여 현장조사를 실시하였다. 초음파 센서장비를 이용하여 교각주변의 세굴심을 직접 측정하였으며, 불교란시료를 채취하여 지반공학적 특성을 결정하고, 또한 세굴률 실험을 통해 대상 지반의 유속별 세굴률을 분석하였다. 그 결과를 바탕으로 기존에 제안된 대표적인 교량세굴 해석모델들을 이용하여 주요 교각의 세굴심을 예측하여 실측 세굴심과 비교하였다. 지반의 침식특성을 고려하지 않는 기존의 교량세굴 해석모델들은 모두 3.6∼6.5의 비율로 세굴심을 과대평가하는 경향을 보였으며, SRICOS 방법은 실측세굴심에 비해 1.7배의 합리적인 결과를 보여주었다.