• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권3호
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• pp.137-142
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• 2004

A voltage transformer(VT) used for the estabilishment of high voltage national standard, has generally ratio error and phase angle error. Both errors in VT depend critically on values of external burden of VT used. Both ratio ewer and phase angle error in existence of the external burden is calculated. These calculated values are very well consistent with the experimental result. The principle and the measurement method of VT in our institute are also explained.

• 전기학회논문지P
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• 제57권4호
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• pp.437-443
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• 2008

We have developed an evaluation technique for both ratio error and phase displacement of current transformer (CT) comparator by using the precise standard capacitors and resistors. By applying this technique to equivalent circuit of CT comparator evaluation system, we can obtain the calculated and measured ratio errors (or phase displacements) in the CT comparator. Thus we can evaluate ratio errors and phase displacement of CT comparator by comparing the calculated and measured ratio errors (or phase displacements). The method was applied to CT comparator under test with the ratio errors and phase displacement ranges of $0{\sim}{\pm}10%$ and $0{\sim}{\pm}7.5$ crad, respectively. Finally we have compared the ratio error and phase displacement of the CT comparator obtained in this method with specifications of two companies.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권4호
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• pp.213-217
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• 2004

A current transformer(CT) used for the estabilishment of high current national standard, has generally very small ratio error and phase angle error. Both the errors of CT depend critically on the external burden used. When both the ratio and phase angle errors at two different burdens including zero burden are known, those at any other burdens are calculated theoretically. The theoretical values are well consistent with the experimental results within the $82{\times}10$-6, implying the measurement system of CT in KRISS is well maintained.

• Current Optics and Photonics
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• 제2권2호
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• pp.119-124
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• 2018

The errors in retrieved aerosol backscattering coefficients due to different lidar ratios are analyzed quantitatively in this paper. The actual calculation shows that the inversion error of the aerosol backscattering coefficients using the Fernald backward-integration method increases with increasing inversion distance. The greater the error in the lidar ratio, the faster the error in the aerosol backscattering coefficient increases. For the same error in lidar ratio, the smaller actual aerosol backscattering coefficient will get the larger relative error of the retrieved aerosol backscattering coefficient. The errors in the lidar ratios for dust or the cirrus layer have great impact on the retrievals of backscattering coefficients. The interval between the retrieved height and the reference range is one of the important factors for the derived error in the aerosol backscattering coefficient, which is revealed quantitatively for the first time in this paper. The conclusions of this article can provide a basis for error estimation in retrieved backscattering coefficients of background aerosols, dust and cirrus layer. The errors in the lidar ratio of an aerosol layer influence the retrievals of backscattering coefficients for the aerosol layer below it.

• 치위생과학회지
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• 제11권3호
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• pp.155-161
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• 2011

본 연구는 치근단 필름 촬영에 있어서 촬영법에 따른 실책율을 살펴봄으로써 향후 효율적인 촬영기술 습득과 학생의 지도를 위한 기초 자료를 얻고자 시행되었다. 2009년 3월부터 2010년 12월까지 D 보건대학 및 S 보건대학 치위생과 학생들을 대상으로 촬영한 필름 14,402매를 분석하고, 등각촬영법과 평행촬영법의 촬영 실습수업을 이수한 학생 263명을 대상으로 현상과정에서 가장 어려웠던 점에 관한 설문조사를 실시하여 다음과 같은 결과를 얻었다. 1. 등각촬영법으로 촬영한 경우 상 하악 모두 대구치부에서 실책율이 가장 높았다. 2. 평행촬영법으로 촬영한 경우 상악에서는 소구치부, 하악에서는 대구치부에서 실책율이 가장 높았다. 3. 촬영기술상의 실책은 등각촬영법과 평행촬영법 모두 필름위치의 부정확이 가장 높게 나타났으며, 등각촬영법이 평행촬영법에 비해 실책율이 높게 나타났다. 4. 현상기술상의 실책은 등각촬영법과 평행촬영법 모두 어두운 상과 밝은 상이 가장 높게 나타났으며, 등각 촬영법이 평행촬영법에 비해 실책율이 높게 나타났다. 5. 학생들은 현상과정에서 현상의 정도를 파악하는 것을 가장 어려워하는 것으로 나타났다. 이상의 결과로 살펴볼 때, 치근단 촬영 시 실책율을 줄이기 위해서는 구강 내 형태학적, 해부학적 구조의 이해가 필요하며, 충분한 시간을 가지고 여러 번 반복 촬영하여 숙련도를 높이는 것이 중요하다고 생각된다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권6호
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• pp.317-322
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• 2006

A accurate potential transformer(PT) with the nominal ratio errors in the wide range of - 9 % to + 11 % has been developed. The developed wide ratio error PT can be used to evaluate the linearity of the PT comparator by comparing both the theoretical values as standard values and experimental values of the PT. The new method has been successfully applied for calibration and correction in the PT comparator including very low ratio error values from ${\pm}0.005%$ to ${\pm}0.3%$ belonging to industry.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권11호
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• pp.503-507
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• 2005

Both ratio error and phase angle error in voltage transformer(VT) depend on values of VT burden used. Thus, precise measurement of burden is very important for the evaluation of VT. A method of evaluation for VT burden has been developed by employing the portable decade resistor, with AC-DC resistance difference less than 10-3. The burden value(value and power factor) can be obtained by conductance and susceptance, obtained by measuring the change of ratio error and phase angle error caused by the resistance change of decade resistor. The burden value and power factor obtained by the method are consistent with those obtained using power analyzer within corresponding uncertainties.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권5호
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• pp.250-256
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• 2006

Both ratio error and phase angle error in current transformer(CT) depend critically on values of CT burden. Thus, precise measurement of CT burden is very important for the evaluation of CT. A method for the measurement of CT burden has been developed by employing the portable shunt precise resistor with negligible AC-DC resistance difference less than $10^{-5}$. The burden value(value and power factor) can be calculated from resistance and reactance obtained by measuring the change of ratio error and phase angle error caused by the change of shunt resistor. The uncertainty for the method is evaluated and found to be abut 2 %.

• 인터넷정보학회논문지
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• 제11권4호
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• pp.59-72
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• 2010

WIM(Weigh-In-Motion) 시스템은 고속으로 이동 중인 차량의 무게를 측정하는 시스템이다. 기존의 WIM 시스템에서는 등속을 기준으로 차량의 무게를 측정하며 오차율이 10% 범위에 있다. 하지만 운전자의 가 감속 조작과 같은 비정상 주행패턴을 고려하고 있지 않으므로 실제 오차율은 더욱 크다. 이러한 오차를 최소화하기 위해서 비정상적인 주행패턴을 찾고 이를 적용한 개선된 WIM 시스템이 필요하다. 본 논문에서는 기존의 WIM 시스템의 오차율에 영향을 미치는 비정상 주행패턴을 분석하고 오차율을 최소화하는 개선된 WIM 시스템을 설계한다. 개선된 WIM 시스템은 기존의 시스템에 루프센서를 추가한 다단 루프 구조를 가진다. 또한 내부적으로 정의된 측정 함수를 개선하여 비정상 주행패턴별로 측정된 무게를 보정한다. 실험 분석 결과 개선된 WIM 시스템은 기존의 최대 평균 오차율 22.98% 에서 8% 미만으로 오차율이 감소한 사실을 알 수 있다.

• 한국정밀공학회지
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• 제18권6호
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• pp.102-108
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• 2001

This paper addresses an analytical approach to the mechanical error analysis of gear train and tolerance design and manufacture of gear train in restricted space considering motor driving torque, driving system inertia, motor acceleration, motor rotor inertia and friction torque. The gear train is designed to have optimum gear ratio in restricted space and each gear is manufactured to have the lowest weight and each gear tooth is heat-treated to have robustness. Based on the small difference between the mechanical error analysis and measurement, gear train design with optimum gear ratio and restricted space and robustness is proposed.