• 전기학회논문지P
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• 제57권3호
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• pp.291-295
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• 2008

We have developed an evaluation technique for ratio errors of current transformer (CT) comparator by using the precise standard capacitors. By applying this technique for equivalent circuit of CT comparator evaluation system, we can obtain the calculated and measured ratio errors in the CT comparator. Thus we can evaluate ratio errors of CT comparator by comparing the calculated and measured ratio errors. Because this method requires only the standard capacitors, it is simple and easy method to reliability and accuracy maintenance of CT comparator. The method was applied to CT comparator under test with the ratio error ranges of $0{\sim}{\pm}10%$. The ratio error of the CT comparator under test theoretically obtained in this method are consistent with that measured for same CT comparator under test by using wide ratio error CT within an estimated expanded uncertainty (k = 2) in the overall ratio error ranges.

• 전기학회논문지P
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• 제58권2호
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• pp.202-206
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• 2009

Evaluation system for calibrating Rogowski coiI(RC) up to primary current of 40,000 A have been established. The system consists of 40,000 A AC high current source, current transformer(CT) comparator, standard CT, RC under test, voltage to current convertor(VCC), buffer and CT burden. An AC high current is applied to the primary windings of both the standard CT and the RC under test, and then the CT comparator measures the ratio error and the phase displacement by comparing the secondary current of the standard CT with output current of VCC. For testing of RC, we have evaluated two RCs under test of primary current ranges of 0 A ${\sim}$ 2,000 A and 0 A ${\sim}$ 40,000 A with the accuracy class of 1 %. The extended uncertainty is 0.02 % ${\sim}$ 0.23 % for ratio error and 0.29 min ${\sim}$ 1.93 min for phase displacement in the primary current ranges of 10 ${\sim}$ 40,000 A.

• 전기학회논문지P
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• 제57권1호
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• pp.6-13
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• 2008

National standard system for calibrating current transformer(CT) up to primary current of 20,000A have been established. The system consists of 20,000 A AC high current source, CT comparator, standard CT, CT under test and CT burden. An AC high current is applied tn the primary windings of both the standard CT and the CT under test, and then the CT comparator measures the ratio error and the phase displacement by comparing the secondary currents of the two transformers. As a validity check for 20,000 A CT calibration system, the comparison with the two national standard institutes(NMIs) has been performed using same CTs. The comparison results of the CTs are consistent with those measured at two NMIs within 0.004 % for ratio error and 0.1 min for phase displacement in the primary current ranges of Ip = 10 - 20,000 A with a secondary current of Is = 5 A.

• 전기학회논문지P
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• 제57권2호
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• pp.153-159
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• 2008

We have developed an absolute evaluation method to obtain the ratio error and phase displacement of a current transformer (CT) without any precise standard CT by measuring four parameters in a CT equivalent circuit. The excitation admittance in the CT equivalent circuit can be obtained by employing standard resistors with negligible reactive component. The secondary leakage impedance in the CT equivalent circuit can be measured using a universal impedance bridge. The method was applied to CTs under test with the wide current ratios in the range of 5 A / 5 A - 5,000 A / 5 A and 5 A / 1 A - 5,000 A / 1 A. The ratio error and phase displacement of the CT under test obtained in this study are consistent with those measured at the national institute in Canada using the same CT under test within an expanded uncertainty (k = 2) in the overall current ratios.

• 대한기계학회논문집A
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• 제29권1호
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• pp.107-114
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• 2005

In order to analyze the elastic-plastic fracture behavior of a structure, the fracture resistance curve of the material should be known first. The standard CT specimen was used to obtain the fracture resistance curves of a piping system. However, it is known that the fracture resistance curve by the standard CT specimen is very conservative to evaluate the integrity of a structure. Also the fracture resistance curve is effected by the specimen geometry and the dimensions because of the constraint effect. The objective of this paper is to be certain the conservativeness of the fracture resistance curve by the standard CT specimen and to provide an additional safety margin. For these, the fracture tests using a real pipe specimen and the standard CT specimen test were performed. A 4-point bending jig was manufactured for the pipe test and the direct current potential drop method was used to measure the crack extension and the length for the pipe test. Also finite element analyses were performed with a CT specimen and a pipe in order to prove the additional safety margin. From the result of tests and analyses of the pipe and the standard CT specimen, it was observed that the fracture analysis with the standard CT specimen is conservative and the additional safety margin was proved.

• 전기학회논문지P
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• 제57권3호
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• pp.279-284
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• 2008

We have developed two absolute evaluation technology of inductor using current transformer (CT) comparator. One is the method that the reactance of inductor is obtained by analysing the equivalent circuit of CT with inductor connected to series at secondary terminal of CT. The other is the method that the reactance of inductor is obtained by comparing phase displacement of current flowing on inductor by using CT comparator. These technologies have the advantage to apply up to rated current and voltage of inductor. The method was applied to inductors under test in the range of $100 {\mu}H{\sim}1\;H$. The inductance of the inductor under test obtained in this study are consistent with those measured by LCR meter using the same inductor within an expanded uncertainty (k = 2) in the overall range of inductance.

• 한국의학물리학회지:의학물리
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• 제30권4호
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• pp.160-166
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• 2019

This study examined the clinical use of two newly installed computed tomography (CT) simulators in the Department of Radiation Oncology. The accreditation procedure was performed by the Korean Institute for Accreditation of Medical Imaging. An Xi R/F dosimeter was used to measure the CT dose index for each plug of the CT dose index phantom. Image qualities such as the Hounsfield unit (HU) value of water, noise level, homogeneity, existence of artifacts, spatial resolution, contrast, and slice thickness were evaluated by scanning a CT performance phantom. All test items were evaluated as to whether they were within the required tolerance level. CT calibration curves-the relationship between CT number and relative electron density-were obtained for dose calculations in the treatment planning system. The positional accuracy of the lasers was also evaluated. The volume CT dose indices for the head phantom were 22.26 mGy and 23.70 mGy, and those for body phantom were 12.30 mGy and 12.99 mGy for the first and second CT simulators, respectively. HU accuracy, noise, and homogeneity for the first CT simulator were -0.2 HU, 4.9 HU, and 0.69 HU, respectively, while those for second CT simulator were 1.9 HU, 4.9 HU, and 0.70 HU, respectively. Five air-filled holes with a diameter of 1.00 mm were used for assessment of spatial resolution and a low contrast object with a diameter of 6.4 mm was clearly discernible by both CT scanners. Both CT simulators exhibited comparable performance and are acceptable for clinical use.

• 전기학회논문지P
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• 제58권1호
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• pp.72-78
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• 2009

We have developed a current range extension method to obtain the ratio error and phase displacement of a current transformer (CT) by using absolute evaluation method and two different CTs. The method was applied to CTs under test with the current ratios in the range of 5,000 A / 1 A - 20,000 A / 1 A. The ratio error and phase displacement of the CT under test obtained in this study are consistent with those measured at the national institute in Germany using the same CT under test within an expanded uncertainty (k = 2) in the overall current ratios.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.2032-2033
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• 2008

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

• 한국방사선학회논문지
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• 제10권1호
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• pp.29-37
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• 2016

CT 조영검사 예약환자의 원활한 검사 진행과 조영검사로 인한 부작용을 줄일 수 있는 전처치 프로세스 시스템을 개발 및 적용하여 CT 조영검사 예약환자의 검사 만족도를 높이고자 하였다. 2014년 1월부터 2014년 2월까지 CT 조영검사를 예약하여 추적검사를 시행했던 2,846명의 환자들 중 예약시간에 검사를 시행하지 못하고 지연된 214명의 환자들을 대상으로 지연사유를 분석한 후 전처치 프로세스 시스템을 구상 및 개발하여 2015년 1월부터 2015년 2월까지 전처치 프로세스 시스템을 이용하여 전처치가 필요한 644명을 대상으로 SMS 전송 시행율, SMS 전송내역, 예약시간 준수율, 예약시간 지연 사유, 예약 시간보다 지연된 시간 등을 분석하였다. 2014년 1~2월 외래 CT 조영검사 예약환자는 2,846명이었고, 그 중 예약시간에 검사를 시행하지 못한 환자는 214건으로, 약 7.52%의 비중을 차지하고 있었다. 예약시간보다 지연된 세부적인 사례는 creatinine 미확인이 98건(46%), creatinine 1.3 이상이 40건(19%), 과거조영제부작용이 34건(16%), 금식 등 전처치 미흡이 25건(11%), 메트포민제제 당뇨약 복용이 4건(2%), 기타 이유가 13건(6%)으로 나타났으며, 평균 지연시간은 creatinine 미확인이 120분, creatinine 1.3이상이 30분, 과거조영제부작용이 40분, 금식 등 전처치 미흡이 120분, 메트포민제제 당뇨약 복용이 30분, 기타 사유가 60분으로 나타났다. 2015년 1월~2 월 전처치 프로세스 시스템을 적용하여 전처치가 필요한 대상자 644명중 SMS 전송시행율은 515건(80%)으로 나타났으며, SMS 전송내역을 분석한 결과 당일 검사가 283건(44%), 진료과 방문이 185건(29%), 전처치 불필요가 47건(7%), 외래과에서 전처치 프로세스 시스템 미확인으로 SMS 전송이 안 된 건수가 129(20%)건으로 나타났다. CT 조영검사 예약시간 준수율은 전체 644건 중 560건(87%)이 예약시간 안에 검사를 시행하였으며, 예약시간보다 지연된 세부적인 사례는 creatinine 미확인이 23건(28%), creatinine 1.3이상이 11건(13%), 과거조영제부작용이 7건(8%), 금식 등 전처치 미흡이 30건(36%), 메트포민제제 당뇨약 복용이 6건(7%), 기타 이유가 7건(8%) 이었다. 예약시간보다 평균 지연된 시간은 creatinine 미확인이 90분, creatinine 1.3이상이 20분, 과거조영제부작용이 30분, 금식 등 전처치 미흡이 120분, 메트포민제제 당뇨약 복용이 30분, 기타 사유가 60분으로 나타났다. 조영제 부작용의 효율적인 관리적 측면과 CT 조영검사 예약시간에 검사가 원활하게 진행될 수 있도록 전처치 프로세스 시스템을 적용해본 결과 적용 전에 비해 전처치 준비 시간이 줄어들고 CT실, 진료실, 채혈실, 주사처치실 등의 방문횟수 및 동선이 줄어들어 CT실을 찾는 고객들의 검사만족도와 의료서비스 향상에 기여가 될 것으로 사료된다.