• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1779-1781
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• 2003

For reliability of high voltage test results in test laboratory, traceability of measuring systems is to be needed. In this paper, it deals with traceability and uncertainty of AC voltage measuring system which is tested by comparison with reference divider.

• The Korean Journal of Nuclear Medicine Technology
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• v.18 no.1
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• pp.158-162
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• 2014

Purpose: Reference material (RM) is defined as material that is safe and homogeneous enough about specified characteristic that is made with a purpose of using test of measurement or nominal characteristic. Certified reference material (CRM), which is issued by authorized organization, is defined as reference material that provides characteristic value, link uncertainty and retroactivity. The purpose of this paper was to evaluate recovery of radioimmunoassay by Certified Reference Material enclosed with a certificate and therefore to enhance reliability of test. Materials and Methods: WHO certified reference material is purchased from NIBSC (National Institute for Biological Standard and Control, United Kingdom) and made of 3 levels that are C-1 (low concentration), C-2 (medium concentration) and C-3 (high concentration) and measured for kit at the Seoul National University Hospital. Recovery rate is evaluated after measurement at four different days. Results: Recovery rate results using WHO certified reference material are T4 90%, Ferritin 88%, PSA 94%, Prolactin 99%, AFP 94% and TSH 93%. Conclusion: A procedure that appropriate accuracy, precision, specificity, sensitivity, reproducibility, and validate on the subject of kit for radioimmunoassay is essential. Recovery rate assay as extraction efficiency of analysis process is percent about already measuring results of analysis result after all measuring process. This is very important assessment standards of performance evaluation of immunoassay kit. Recovery rate results of 6 type used WHO CRM are satisfactory to 88~99%. This demonstrates that the radioimmunoassay is a very accurate measurement, which is very effectively utilized in clinical practice.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.928-930
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• 2000

교류전력을 측정하기 위하여 알고 있는 직류전력과 동시에 비교할 수 있는 전력비교기를 개발하였으며 이 비교기를 기본으로 하여 정밀 전력계와 전자식 전력량계를 교정하거나 시험검사 할 수 있는 기준시스템인 전력표준기를 개발하였다. 특히 Push-Pull 기술을 이용한 전력비교기는 간단하며 정확도가 매우 높은 것으로 평가되었으며 전력비교기의 전체 불확도는 30 $\mu$ W/VA로 평가되었다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.10
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• pp.699-705
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• 2001

Six types of planar thermal converters from TC 1 to TC 6 were designed and fabricated for the purpose of being used as practical standards to alternating current. The respective voltage responses in air and in a vacuum of TC 6, which has the smallest thermal loss, were about 4.03mV/mW and about 6.38 mV/mW. Thermal time constant of TC 6, which has also the smallest heater thermal inertia, was about 8 ms. The respective variations of AC-DC voltage and current transfer errors from sample to sample, which were measured by FRDC(fast reversed DC) method, were about $\pm$0.41 ~$\pm$0.85 ppm and about $\pm$0.15~$\pm$1.16 ppm in the frequent range of 40 Hz~10 KHz with appling 1 V and 5 mA rms sine waves to the converters. All converters investigated exhibited sufficiently low AC-DC transfer errors to be used as practical standards.

• Journal of the Korean Electrochemical Society
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• v.2 no.1
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• pp.23-26
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• 1999

The Langmuir adsorption isotherm at the $(Pt)/0.1M\;H_2SO_4$ electrolyte interface has been qualitatively analyzed using the ac impedance measurement and phase-shift method. The phase shift $(\phi)$ depends on both the cathode potential (E<0) and frequency (f) and is inversely proportional to the factional surface coverage $(\theta)$. At an intermediate frequency band (ca. $1\~100$ Hz), the phase-shift profile $(\phi\;vs.\;E)$ can be related to the fractional surface coverage $(\theta\;vs.\;E)$. The phase-shift profile $(\phi\;vs.\;E)$ can be used as an experimental method to estimate and analyze the Langmuir adsorption isotherm $(\theta\;vs.\;E)$. The equilibrium constant (K) and the standard free energy $({\Delta}G_{ads})$ of the adsorbed hydrogen atom $(H_{ads})\;and\;3\times10^{-4}$ and 20.1 kJ/mol, respectively.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.828-830
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• 2001

잘 교정된 유도성 전압 분할기는 다른 교류 전압 분할기들을 비교 교정하기 위한 전압비의 표준기로서 사용되어질 뿐 만 아니라 각종 임피던스 정밀측정용 브리지의 비례 arm으로서 사용이 되어진다. 이러한 유도성 전압 분할기를 비교교정 하기 위한 교정시스템이 연구제작이 되었다. 본 연구 논문에서는 제작방법, 교정방법, 그리고 오차 등에 대하여 관하여 논의하고 실제교정결과와 분석된 결과를 비교한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.693-696
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• 2006

In this study, we made the system to measure variation of blood flow using bio-electrical impedance analysis method. The system, which could measure variation of impedance according to pressure change by artificial pressure, consists of pressure measurement and impedance measurement by 4-electrode method. Pressure measurement splits into semiconducting pressure sensor and electronic circuit for processing output signal. In addition, impedance measurement splits into constant current source circuit and lock-in amplifier for detection impedance signal. We experimented feature of impedance measurement using standard resistance to evaluate the system characteristic. As well as, we experimented to estimate variation of blood flow by measuring impedance and blood flow resistance ratio using mean arterial pressure and variation of blood flow with experimental group. As result of this study, blood flow resistance ratio and variation of blood flow were definitely in inverse proportion and were -0.96776 as correlation coefficient by correlation analysis.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.463-463
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• 2010

고휘도 고효율 백색 LED (lighting emitting diode)가 차세대 조명광원으로 급부상하고 있다. 백색 LED를 생산하기 위한 공정에서 MOCVD (유기금속화학증착)장비를 이용한 Epi wafer공정은 에피층과 기판의 격자상수 차이와 열팽창계수차이로 인하여 생성되는 에피결함의 제거를 위하여 기판과 GaN 박막층 사이에 완충작용을 해줄 수 있는 버퍼층 (Buffer layer)을 만들고 그 위에 InGaN/GaN MQW (Multi Quantum Well)공정을 하여 고휘도 고효율 백색 LED를 구현할 수 있다. 이 공정에서 기판의 온도가 불균일해지면 wafer 파장 균일도가 나빠지므로 백색 LED의 yield가 떨어진다. 균일한 기판 온도를 갖기 위한 조건으로 기판과 induction heater의 간격, 가스의 흐름, 기판의 회전, 유도가열코일의 디자인 등이 장비의 설계 요소이다. 코일에 교류전류를 흘려주면 이 코일 안 또는 근처에 있는 도전체에 와전류가 유도되어 가열되는 유도가열 방식은 가열 효율이 높아 경제적이고, 온도에 대한 신속한 응답성으로 인하여 열 손실을 줄일 수 있으며, 출력 온도 제어의 용이성 및 배출 가스 등의 오염 없다는 장점이 있다. 본 연구에서는 유도가열방식의 induction heater를 이용하여 회전에 의한 기판의 온도 균일도 측정을 하였다. 기초 실험으로 저항 가열 히터를 통하여 대류에 의한 온도 균일도를 평가하였다. 그 결과 gap이 3 mm일 때, 평균 온도 $166.5^{\circ}C$ 에서 불균일도 6.5 %를 얻었으며 이를 바탕으로 induction heater와 graphite susceptor의 간격이 3 mm일 때, 회전에 의한 온도 균일도를 측정을 하였다. 가열원은 induction heater (viewtong, VT-180C2)를 사용하였고, 가열된 graphite 표면의 온도를 2차원적으로 평가하기 위하여 적외선 열화상 카메라(Fluke, Ti-10)을 이용하여 온도를 측정하였다. 기판을 회전하면서 표면 온도의 평균과 표준 편차를 측정한 결과 2.5 RPM일 때 평균온도 $163^{\circ}C$ 에서 가장 좋은 5.5 %의 불균일도를 확인할 수 있었고, 이를 상용화 전산 유체 역학 코드인 CFD-ACE+의 모델링 결과와 비교 분석 하였다.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.9
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• pp.81-92
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• 1998

A new hybrid technique using several sub-populations having completely different evolutionary behaviors is proposed to increase the possibility to quickly find the global optimum of continuous optimization problem. It has three sub-populations. Two NPOSA algorithms showing good performance in the problem having a rugged fitness function are applied to two sub-populations and a self-adaptive evolutionary algorithm to the other sub-population. Sub-populations evolve in different manners and the interaction among these sub-populations lead to the global optimum quickly. The efficiency of this technique is verified through benchmark test functions. Finally, the algorithm with three sub-populations has been applied to seek for the optimal camera calibration parameters. After an error function has been defined using measured feature points of a calibration block, it has been shown that the algorithm searches for the camera parameters that minimize the error function.

• Korean Journal of Social Welfare Studies
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• v.41 no.4
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• pp.345-368
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• 2010

The purpose of this study is to develop the School Multicultural Climate(SMC) scale for students and to evaluate its reliability and validity. This study comprises of both qualitative and quantitative research. Preliminary items were developed based on the theoretical literature and interviews with students. The scale was evaluated with students in grades 4 through 6 in the seven elementary schools. Exploratory factor analysis was determined that the scale was composed of four components: Equal Status, Mutual Cooperation, Friendly Relations, Supportive Norms. The scale demonstrated that Cronbach's alpha=.943 for the internal consistency of total items. And the standard error of the measurement, another way of evaluating reliability, was 3.33. Criteria-related validity was evaluated by showing that the differences of the students' recognition of the school multicultural climate level, which depend on the availability of the multiculture-related policy, was statistically significant. The correlation analysis for the convergent validity was performed with the theoretically related variables such as self esteem and school adjustment. It was found that the SMC scale was a reliable and valid measure for evaluating the multicultural climate level of elementary school.