• 한국농공학회논문집
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• 제60권3호
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• pp.15-25
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• 2018

Estimating the reference evapotranspiration is an important factor to consider in irrigation system design and agricultural water use. However, there is a limitation in using the FAO Penman-Monteith (FAO P-M) equation, which requires various meteorological data. The purpose of this study is to compare three reference evapotranspiration (ETo) equations in the case of meteorological data missing for 11 study weather stations. Firstly, the FAO P-M equation is used for reference potential evapotranspiration estimation with the actual solar radiation data $R_n$ and the actual vapor pressure $e_a$. Then, in the case of $R_n$, and $e_a$ are missed, the reference evapotranspirations applying FAO P-M, Priestley-Taylor (P-T), Hargreaves (HG) equation were calculated using other meteorological factors. Secondly, MAE, RMSE, $R^2$ were calculated to compare ETo relationship from the ETo equations. From the results, ETo with Hargreaves equation in coastal areas and the Priestley-Taylor equation in the inland areas showed relatively high correlation with FAO P-M when $e_a$ data is missed. In the case of $R_n$ data is missed or two weather data, $e_a$, and $R_n$ data are all missed, $R^2$ value in Priestley-Taylor equation was highest in coastal areas, and $R^2$ values in Hargreaves equation were the high values for 7 inland areas. The results of sensitivity analysis showed that net radiation was the most sensitive for P-T and HG equation, and for FAO P-M, the most sensitive factor was net radiation and relative humidity, air temperature and wind speed were follows. Therefore, in considering of the accessibility to the coast, the types of the missing wether data, and the correlation and the magnitude of error, the reference evapotranspiration equations would be selected in sense of different conditions.

• 대한기계학회논문집A
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• 제26권11호
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• pp.2442-2449
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• 2002

This paper provides an reference stress based J estimation equation fur cylinders with finite internal axial surface cracks under internal pressure. In part 1, the J estimation equation based on deformation plasticity using Ramberg-Osgood (R-0) materials is proposed. In this paper, the developed CE/EPRI -type solutions ale then re-formulated based on the reference stress concept. Such a re-formulation provides a simpler equation for J. estimation are then further extended to combined internal pressure and bending. The proposed reference stress based J estimation equation is compared with elastic-plastic 3-D FE results using actual stress-strain data for a Type 304 stainless steel. Good agreement between the FE results and the proposed reference stress based J estimations provides confidence in the use of the proposed method to elastic -plastic fracture mechanics of pressurised piping.

• Tuberculosis and Respiratory Diseases
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• 제69권2호
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• pp.108-114
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• 2010

Background: The aim was to estimate the differences between pulmonary disability grades according to the spirometry reference equations (the Korean equation and the Morris equation). Methods: Spirometry was performed on 16,916 male and 1,353 female special examination for pneumoconiosis, in the period of 2007~2009. Changes in predictive values for forced expiratory volume in one second ($FEV_1$), forced vital capacity (FVC) and $FEV_1$/FVC and in disability grade were evaluated using both equations. Results: Mean FVCs for men and women were 4,218.7 mL and 2,801.5 mL in predictive values after the application of the Korean equation, and 3,763.9 mL and 2,395.6 mL after the Morris equation, respectively. Compared with the Morris equation, the Korean equation showed 10.8% and 14.5% of excesses for men and women (p<0.001). Mean $FEV_1s$ for men and women were 3,102.5 mL and 2,107.1 mL in the Korean equation, and 2,667.8 mL and 1,699.6 mL in the Morris equation, respectively. Compared with the Morris equation, the Korean equation showed 14.0% and 19.3% of excesses for men and women (p<0.001). Men and women who showed the changes of disability grades using the Korean equation in place of the Morris equation were 23.9% (4,052/16,916) and 22.9% (311/1,353) on FVC, and 23.1% (3,913/16,916) and 10.7% (145/1,353) on $FEV_1$. Conclusion: Applying different reference equations for spirometry has resulted in changes for disability grades in special examination for pneumoconiosis.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.143-148
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• 2003

This paper provides two types of engineering J estimation equations for cylinders with finite internal axial surface cracks under internal pressure. The first type is the so-called GE/EPRI type J estimation equation based on Ramberg-Osgood materials. Based on detailed 3-D FE results the GE/EPRI-type J estimation equation along the crack front is proposed and validated for Ramberg-Osgood materials. For more general application, the developed GE/EPRI-type solutions are then re-formulated based on the reference stress concept. The proposed reference stress based J estimation equation has good agreement between the FE results and the proposed reference stress based J estimation provides confidence in the use of the proposed method for elastic-plastic fracture mechanics of pressurised piping

• 한국수자원학회논문집
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• 제46권9호
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• pp.933-946
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• 2013

유역의 수문기상학적 특성을 분석하거나 수자원계획을 수립하는 과정에서 필수적인 사항은 증발산에 대한 정량적인 특성을 파악하는 것이다. 일반적으로 증발산량에 대한 정량적인 분석은 기온, 풍속 등 기상학적 인자를 바탕으로 잠재증발산량 또는 기준증발산량을 추정하는 방법을 이용하고 있으며, Hargreaves 공식은 기온자료를 이용하여 기준증발산량을 산정할 수 있는 간단한 경험식이라 할 수 있다. 본 연구에서는 Hargreaves 공식을 우리나라에 적용함에 있어 보다 정확한 기준증발산량 추정이 가능하도록 공식의 매개변수를 지역화하기 위한 연구를 수행하였다. 먼저 일사량 관측자료와 기온과의 관계를 검토하여 수정 관계식을 도출하였으며, 수정 관계식과 Penman-Monteith 방법에 의한 기준증발산량 산정결과를 이용하여 Hargreaves 공식의매개변수지역화를 수행하였다. 또한 매개변수와 기온과의 관계분석을 통해 기온자료로부터 Hargreaves 공식의 매개변수를 추정할 수 있는 관계식을 제안하였으며, 이에 대한 검증을 수행하였다. 연구결과, 우리나라에서 기존 Hargreaves 공식을 그대로 이용할 경우 Penman-Monteith 방법에 비해 과대 또는 과소 산정될 수 있음을 확인하였으며, 지역화된 매개변수를 이용할 경우 정확도가 크게 개선되고 있음을 확인하였다. 또한 기온자료로부터 Hargreaves 공식의 매개변수를 추정할 수 있는 관계식에 대한 검증을 통해 본 연구에서 제안한 관계식의 적용 가능성을 확인할 수 있었다.

• 대한기계학회논문집A
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• 제26권10호
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• pp.2122-2129
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• 2002

Creep damage using a reference stress(RS) was analyzed for type 316LN stainless steel. The generalized K-R equation was reconstructed into the RS equation using a critical stress value $\sigma$. The RS equation was derived from the critical stress in failure time $t_f$ instead of material damage parameter $\omega$, which indicates the critical condition of collapse or approach to gross instability of materials during creep. For obtaining the reference stress, a series of creep tests and tensile tests were conducted with at 55$0^{\circ}C$ and $600^{\circ}C$. The stress-time data obtained from creep tests were applied to the RS equations to characterize the creep damage of type 316LN stainless steel. The value of creep constant r with stress levels was about 18 at 55$0^{\circ}C$ and 21 at $600^{\circ}C$. This value was almost similar with r = 24 in the K-R equation, which was obtained by using damage parameter $\omega$. Relationship plots of creep failure strain and life fraction $(t_f /t_r)$ were also obtained with different λ values. The RS equation was therefore more convenient than the generalized K-R equation, because the measuring process to quantify the damage parameter $\omega$ such as voids or micro cracks in crept materials was omitted. The RS method can be easily used by designers and plant operator as a creep design tool.

• 대한토목학회논문집
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• 제28권6B호
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• pp.675-681
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• 2008

기상자료가 부족하거나 결측인 지역의 기준 증발산량 산정을 위해서는 Hargreaves 공식의 매개변수 추정을 수행할 필요가 있다. 본 연구에서는 우리나라 전역에 걸쳐 1997년-2006년 기상자료를 바탕으로 Hargreaves 공식을 이용하여 기준 증발산량(이하 ETo)을 산정하였다. 각 지점별로 PM공식에 의해 산정한 값을 증발산량의 정해로 가정하여 Hargreaves 매개변수를 지점별로 추정하였다. 최소의 오차가 발생하도록 Hargreaves 계수를 조정한 후 Root Mean Square Error와 Nash Sutcilffe Coefficient of Efficiency분석을 통하여 추정효율이 크게 향상되는 것을 알 수 있었다. 또한 추정된 매개변수를 바탕으로 기온 자료만의 의한 Hargreaves 증발산량을 추정할 수 있도록 일반화된 하나의 회귀직선을 도출하여 보았다. 온도-Hargreaves 계수의 선형 상관관계를 이용한 Hargreaves 계수의 일반화에서는 개선의 여지가 있지만 만족스러운 결과를 보여주는 것으로 나타났다. 이 연구결과는 우리나라의 수자원, 관개분야 및 환경 운용에 많은 도움이 될 것으로 판단된다.

• Tuberculosis and Respiratory Diseases
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• 제64권2호
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• pp.80-86
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• 2008

연구배경: 폐확산능을 해석하는 데 필요한 정상예측식으로는 한국인을 대상으로 하여 박 등이 개발한 식(박 식)이 있으나 아직 외국 정상예측식을 많이 사용하고 있다. 이에 국내에서 많이 사용하는 외국 정상예측식인 Burrows 식과 박 식의 임상적 유용성과 정확성을 비교하고자 하였다. 방법: 1. 임상적 유용성 연구; 2006년 7월부터 12월까지 6개월간 폐확산능검사를 시행한 환자 중 두 식을 각각 정상예측식으로 적용하였을 때 폐확산능 해석이 다른 276명(대상군 A)을 대상으로 하였다. 대상군 A에게 두 식을 각각 적용하였을 때 폐확산능 해석과 임상적 판단과의 일치도를 비교하여 임상적 유용성을 평가하였다. 2. 간질성폐질환 진단의 정확성 비교; 2001년부터 2006년까지 폐조직검사를 시행하여 확진된 간질성폐질환군과 서울아산병원에서 모집한 정상군을 대상으로 하여 정상예측식으로 두 식을 각각 적용하였을 때 폐확산능 해석의 정확도를 비교하였고, 두 식이 차이가 나는지 맥니머의 카이스퀘어 검정을 하였다. 결과: 1. 임상적 판단과의 일치도 비교; 276명을 임상정보를 토대로 폐확산능을 예측하여 분류한 결과 정상 54명, 감소 220명, 불분명이 2명이었다. 예측식으로 박 식과 Burrows 식을 적용하였을 때 임상적 판단과 일치하는 환자는 각각 78%와 22%이었다(p<0.001). 2. 간질성폐질환 진단의 정확성 비교; 박 식은 민감도 90.1%, 특이도 100%이었고 Burrows 식은 민감도 64.2%, 특이도 100%로 민감도가 통계학적으로 유의하게 박 식이 높았다(p<0.001). 결론: 우리나라 정상예측식인 박 식이 외국 정상예측식인 Burrows 식을 정상예측식으로 적용하는 것보다 임상적 유용성이나 간질성폐질환 진단의 민감도에서 더 우월하였다. 향후 폐확산능검사의 정상예측식으로 박 식을 사용해야 할 것으로 사료된다.

• Nutrition Research and Practice
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• 제11권1호
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• pp.51-56
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• 2017

BACKGROUND/OBJECTIVES: The purpose of this study was to assess the accuracy of a dietary reference intake (DRI) predictive equation for estimated energy requirements (EER) in female college tennis athletes and non-athlete students using doubly labeled water (DLW) as a reference method. MATERIALS/METHODS: Fifteen female college students, including eight tennis athletes and seven non-athlete subjects (aged between 19 to 24 years), were involved in the study. Subjects' total energy expenditure (TEE) was measured by the DLW method, and EER were calculated using the DRI predictive equation. The accuracy of this equation was assessed by comparing the EER calculated using the DRI predictive equation ($EER_{DRI}$) and TEE measured by the DLW method ($TEE_{DLW}$) based on calculation of percentage difference mean and percentage of accurate prediction. The agreement between the two methods was assessed by the Bland-Altman method. RESULTS: The percentage difference mean between the methods was -1.1% in athletes and 1.8% in non-athlete subjects, whereas the percentage of accurate prediction was 37.5% and 85.7%, respectively. In the case of athletic subjects, the DRI predictive equation showed a clear bias negatively proportional to the subjects' TEE. CONCLUSIONS: The results from this study suggest that the DRI predictive equation could be used to obtain EER in non-athlete female college students at a group level. However, this equation would be difficult to use in the case of athletes at the group and individual levels. The development of a new and more appropriate equation for the prediction of energy expenditure in athletes is proposed.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권2호
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• pp.107-115
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• 2006

In this paper, a new speed sensorless control based on an instantaneous reactive power is proposed for the interior permanent magnet synchronous motor(IPMSM) drives. In proposed algorithm, the current observer estimates the line currents and the estimated speed can be yielded from the voltage equation because the information of speed is included in back EMF. To implement speed sensorless control, the current observer is composed by using the voltage equation of the IPMSM in the stationary reference frame fixed to the stator. The estimated speed of the rotor is composed by using the voltage equation of the IPMSM in the rotating reference frame fixed to the rotor The estimated speeds to minimize the speed error compensated by using the instantaneous reactive power. The instantaneous reactive power is calculated on the rotating reference frame fixed to the rotor. The effectiveness of the preposed algorithm is confirmed by the experiments.