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논문 : 노외기계시스템공학 ; 코어샘플을 이용한 질소 등 토양성분 현장 측정방법의 비교평가
권기영 ( G. Kweon ),( Eric Lund ),( Chase Maxton ),( Dreiling Kenton ) 한국농업기계학회 2011 바이오시스템공학 Vol.36 No.2
Several methods of in-field measurements of Nitrogen and other soil properties using cores extracted by a hydraulic soil sampler were evaluated. A prototype core scanner was built to accommodate Veris Technologies commercial Vis-NIRS equipment. The testing result for pH, P and Mg were close to RPD (Ratio of Prediction to Deviation=Standard deviation/RMSE) of 2, however the scanner could not achieve the goal of RPD of 2 on some other properties, especially on nitrate nitrogen (NO3) and potassium (K). In situ NIRS/EC probe showed similar results to the core scanner; pH, P and Mg were close to RPD of 2, while NO3 and K were RPD of 1.5 and 1.2, respectively. Correlations between estimations using the probe and the core scanner were strong, with r2>0.7 for P, Mg, Total N, Total C and CEC. Preliminary results for mid-IR spectroscopy showed an r2 of 0.068 and an RMSE for nitrate (N) of 18ppm, even after the removal of calcareous samples and possible N outlier. After removal of calcareous samples on a larger sample set, results improved considerably with an r2 of 0.64 and RMSE of 6 ppm. However, this was only possible after carbonate samples were detected and eliminated, which would not be feasible under in-field measurements. Testing of NO3 and K ion-selective electrodes (ISEs) revealed promising results, with acceptable errors measuring soil solutions containing nitrate and potassium levels that are typical of production agriculture fields.
권기영 ( Giyoung Kweon ),이상윤 ( Sangyoon Kee ),유승준 ( Seungjun Ryu ),박영기 ( Young-ki Park ),양재경 ( Jaekyung Yang ) 한국농업기계학회 2017 한국농업기계학회 학술발표논문집 Vol.22 No.2
무주군 3곳의 지역에서 172개의 토종다래 샘플을 수집하여, 각 86개씩 임의로 calibration과 validation 데이터로 분리하였다. 토종다래의 당도측정은 온도에 민감하게 반응함으로 변화하는 외기에서도 정확하게 예측하기 위하여 온도별 예측실험을 실시하였다. 각 10, 20, 30도로 설정한 항온기에 토종다래를 넣어두고 한 시간 이후 스펙트로미터(FieldSpec 4, ASD Inc., Colorado, USA)를 이용하여 샘플을 측정하였다. 스펙트로미터의 측정가능한 범위는 350~2500 nm이지만 당도예측과 상관관계가 낮은 파장대와 잡음이 많은 파장대를 제외하여 730~2300 nm 범위에서 토종다래를 측정하였다. 토종다래의 당도는 brix 0~55%의 측정범위를 가진 휴대형 디지털 당도측정기(SCM-1000, HM Digital, Korea)를 사용하였다. 전체 토종다래의 당도 평균값은 16.1, 표준편차는 3.9, 최대값은 25.8, 최소값은 9.8 brix로 측정되었다. 당도예측을 위한 데이터 분석과 모델생성은 Matlab (MathWorks, USA)과 PLS_Toolbox (Eigenvector Research Inc., USA)를 이용하였다. 스펙트로미터로 측정한 데이트는 전처리 과정(1st derivative, Standard Normal Variate, Mean Center Correction)을 거친 후 PLS regression을 행하였으며, Latent variable (LV)는 8로 설정하였다. 캘리브레이션을 위한 토종다래 샘플들은 leave-one-out cross validation을 통해 모델검증을 하였고 이후 validation 데이터로 예측성능을 검증하였다. 분석결과, 측정온도 10도에서의 캘리브레이션 모델의 R2는 0.80, cross validation의 R2는 0.70, 생성된 calibration 모델에 validation data를 사용하여 예측한 결과 R2는 0.74로 나타났다. 20도에서의 캘리브레이션 모델의 R2는 0.83, cross validation의 R2는 0.71, validation data에서의 예측한 결과는 R2는 0.86으로 나타났다. 30도에서의 캘리브레이션 모델의 R2는 0.83, cross validation의 R2는 0.73, validation data의 예측한 결과는 R2는 0.80으로 나타났다. 10, 20, 30도에서 측정한 데이터를 모두 통합하여 모델을 만들고 분석을 한 결과, 캘리브레이션 모델의 R2는 0.76, cross validation의 R2는 0.73, validation data의 예측한 결과는 R2는 0.74로 나타나 변화하는 외기온도에서도 비파괴로 토종다래의 당도분석이 가능함을 확인하였다.
김진범(Jin-Bum Kim),권기영(Ki-Yeoung Kweon),이학성(Hahk-Sung Lee) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
High-voltage auto-expansion circuit breakers utilize the ablation of polytetrafluoroethylene(PTFE) nozzle to produce adequate conditions for arc quenching at current zero. The high-current simulation provides information about the mixing process of the hot PTFE cloud with the SF? gas which is difficult to access for measurement. But it is also difficult to simulate flow phenomenon because the flow in interrupter with high current and SF?-PTFE mixture vapor, complex physical behavior including radiation. Using the PC based PHOENICS, a commercial computational fluid dynamics(CFD) package, the conservation equation for the gas and temperature, velocity and electric fields within breaker can be visualized and thermal interruption capability predicted. These numerical results will reduce the number of costly short-circuit test.
PTFE 용삭을 고려한 초고압 복합소호 차단기의 열챔버 압력 특성 평가
김진범(Jin-Bum Kim),권기영(Ki-Yeoung Kweon),이학성(Hahk-Sung Lee) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
Self-blast circuit breakers utilize the energy dissipated by the arc itself to create the required conditions for arc quenching during the current zero. During the arcing period, high pressure, temperature and radiation of the arc could burn in pure SF6 gas and PTFE nozzle. Ablated nozzle shape and SF6-PTFE mixture vapor affect the performance of an self-blast circuit breaker. But it is hard to simulate the behavior of hot gas, prediction because of complex physical behavior including radiation, calculation of electric field. Using computational fluid dynamics, the conservation equation for the gas and temperature, velocity and electric fields within breaker can be solved. Performance of ablated nozzle shape are compared with original model.
대용량 변압기용 쿨러의 냉각특성에 관한 수치해석적 연구
노경철(Kyoung-Chul Ro),권기영(Ki-Yeoung Kweon),최원호(Won-Ho Choi) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
The purpose of this study is to evaluate the thermal and hydrodynamic characteristics of the cooler system in a large power transformer. The cooling system consists of a pin-tube, fans and an oil pump. To predict the cooling capacity and the pressure drop according to the oil flow, numerical analysis has been conducted using the commercial finite-volume code, FLUENT and the results are compared with the experimental data. The experimental and numerical results shows a good agreement for all the range of oil flow rate.
수정된 Hardy-Cross법을 이용한 전동기내 유량 분배 해석
이창준(Chang-Jun Lee),권기영(Ki-Yeoung Kweon),이승구(Seung-Kuh Lee) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
Modified Hardy-Cross Method is introduced to analyze the flow rate distributions in a motor. The Hardy-Cross Method has been used to analyse the water pipe networks. In this paper, some calculation parts of this method are changed in order to apply the air pipe systems. The computed results were verified by the comparison with a commercial CFD package FLUENT analysis. The flow rate distributions in a motor are investigated analytically.