• Aerospace Engineering and Technology
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• v.9 no.1
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• pp.151-157
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• 2010

The tracking radars in NARO space center are precious, long-range tracking systems for tracking the launch vehicle (KSLV-1) and transmitting TSPI (Time, Space and Position Information) data to MCC (Mission Control Center). Because TSPI data from tracking radars to MCC are important information for the launch mission and flight safety control, TSPI data are required to be more accurate. In this paper, we analyzed theoretically the required specification of the random noise error in tracking radar and verified the real random noise error. In this analysis, we evaluated the TSPI data of several flight tests performed in NARO space center.

• The KIPS Transactions:PartC
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• v.12C no.3 s.99
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• pp.437-442
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• 2005

The measurement of RTT (Round Trip Time) can be used for the analysis of Internet congestion. However, simple measuring of RTT which measures only hun around time of a packet can not infer a packet forward/backward delay variation. In this thesis, we present a new algorithm which can be used for the estimation of forward/backward delay variation of packets. These delay variations are implication of network congestion state. In this algorithm, the reference forward/backward delay can be determined based on the minimum RTT value. The delay variation of each packet can be calculated by comparing reference delay with the packet delay. We verified our proposed algorithm by NS-2 simulation and delay measuring in a real network.

• Proceedings of the Korean Information Science Society Conference
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• 2010.06c
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• pp.221-225
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• 2010

본 연구에서는 제한된 온도 영역에서 보통 정밀 온도 측정 소자로 많이 쓰이는 NTC 써미스터를 사용하여 전압 분배 회로(voltage divider circuits)를 구성하였다. 분압 저항이 온도측정 해상도에 미치는 영향을 분석하고, 회로의 분압 저항을 결정하는 방법으로서 측정하고자 하는 온도 구간의 최대 온도와 최저 온도의 NTC 써미스터 저항 값을 조화평균을 사용하여 분압 저항(divider resistance)으로 사용하였다. 선택한 분압 저항이 이상적인 저항인지에 대하여 조화평균으로 계산한 분압 저항과 대조군 저항으로 전압 분배 회로를 병렬로 구성하였다. 센서들을 항온조 넣어 설정온도($50^{\circ}C$, $70^{\circ}C$, $90^{\circ}C$)에서 각각의 온도를 측정한 후 측정 데이터의 표준편차를 구하여 평균 온도 분해능을 비교 하는 실험을 하였다. 실험결과 측정온도 구간의 최대 온도와 최소 온도에서의 NTC 써미스터 저항 값을 조화평균으로 계산한 분압 저항 값이 대조군 저항에 비해 설정온도에서 보다 높은 평균 온도 분해능(sensing resolution)을 보였다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.5 s.57
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• pp.101-108
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• 2009

Mathematical basis of interpretation of data from nondestructive evaluation (NDE) methods in condition assessment of structures is presented. In structural inspection with NDE methods, NDE data are not directly used for the condition assessment. Instead, NDE data must be interpreted as condition of inspected element. Correct assessments of conditions depend on many factors such as the inaccuracy and the variability in NDE measurements and the uncertainty in correlation between attributes (what is measured) and conditions (what is sought in the inspection). A full description of the performance of NDE methods considers the relation of test data to conditions of elements. The quality of the test itself is important, but equally important is the interpretation that occurs after the test. The effects of variability in test data and uncertainty in correlations of attributes and conditions are presented in three examples of field testing methods.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.11a
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• pp.1243-1247
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• 2011

센서 네트워크는 많은 수의 센서들로 구성되며 물질세계와 상호작용하여 실시간 감시를 할 수 있는 큰 규모의 네트워크이다. 현실 세계의 물리적 변화를 지속적으로 감시하기 위하여 센서 네트워크에 속해 있는 각 센서들은 주기적으로 측정값을 읽어서 기지국(base station)에 전달하는 기능을 수행한다. 이러한 경우, 각 센서들의 지속적인 통신에 따른 에너지 낭비가 발생하여 센서 네트워크 전체의 수명을 단축시키게 된다. 따라서 데이터 모니터링에 있어서 예측을 통한 근사 데이터 수집을 통해 센서 네트워크의 수명을 연장하고자 하는 연구들이 진행되고 있다. 그러나 현재의 예측을 통한 근사 데이터 수집은 측정값의 변화가 클수록 예측 모델의 갱신이 잦다. 따라서 본 논문에서는 지연 갱신을 이용한 효율적인 예측 모델 갱신 기법을 제안한다. 제안된 기법에서는 예측이 실패하였을 경우 즉시 예측 모델을 갱신하는 대신 문제가 되는 구간의 측정값들을 지연, 근사화하여 전송함으로써 예측 모델의 잦은 갱신을 방지할 수 있다.

• Progress in Medical Physics
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• v.11 no.2
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• pp.123-130
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• 2000

The performance of an electrometer directly affects on the accuracy and precision in radiation dosimetry. This study is to list of the quality control for maintaining performance and to perform evaluation tests of an electrometer. Performance tests selected include proper polarizing voltages, warm-up and equalization time, leakages, long-term stability, linearity, and effect of ambient conditions. An electrometer connected with a rigid stem ionization chamber was evaluated with a Strontium-90 check device. Bias voltage was measured directly on the input socket. Equalization time is the time required for reaching threshold of charged state after the power is on or the bias voltage is changed. Pre- and post-signal leakages are defined as the accumulation of signal with no exposure and after exposure, respectively. Over three months period, the electrometer's long-term stability was measured by comparison of the temperature-pressure corrected readings. Linearity was expressed as the deviation of readings from multiple short exposures from one continuous exposure. Effect of ambient conditions was expressed as the zero drift of the electrometer over 17-34$^{\circ}C$ temperature ranges. For two nominal values, 300 and 500 volts, measured voltages were lower by 2.5 and 5.8%, respectively. The warm-up time, 20 minutes, was longer than the lamp time by 9 minutes and the equalization time was less than 1 minute. Without exposure, the zero-drift was 0.002 scale-unit in 15 minutes and the leakage after 10 minutes exposure was minimal. The IQ-4 was stable over 99.4% for three-month periods. Deviation from the linearity was 0.9% for measurement scale, 0.000-9.991. Over 17-34$^{\circ}C$ temperature range, the zero-drift was minimal, less than 0.2%. For a clinically-used electrometer, a list for the basic peformance evaluations is proposed. By running this program, the measurement error using an electrometer can be reduced and in turn the improvement in accuracy and precision of radiation dosimetry can be achieved.

• The Journal of the Korea Contents Association
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• v.12 no.8
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• pp.240-247
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• 2012

Marginal and internal fit is an important part of the longevity of dental restorations. The purpose of this study was to analysis the marginal and internal fit of zirconia core by dental CAD/CAM system using innovative and non-destructive methods such as optical coherence tomography(OCT) and compare with conventional method such as silicone replica technique(SRT). Ten dental stone models of abutment of maxillary right central incisal were manufactured and scanned. Ten zirconia cores were fabricated with commercial CAD/CAM system. To measure the marginal and internal fit of each sample, five point of fitness were measured using 2 different methods(OCT and SRT). Statistical analysis was performed using independent sample t-test(${\alpha}$=0.05). OCT and SRT groups were not significantly different(P>0.05). By this results, analysis the fitness of dental restorations using OCT were acceptable measuring method.

• Journal of the Korean Chemical Society
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• v.44 no.1
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• pp.10-16
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• 2000

In general, acid rain is unbuffered solution with low ionic strength and high resistance. Therefore during the pH measurement of acid rain, error can be occurred due to the liquid junction potential difference between the sample and the standard solution. Actually the average conductivity of rain in Taeduk Science Town during 1998 is 12.8 ${\mu}S/cm$, while that of pH standmd solutions is about 5,980 ${\mu}S/cm$. There is a large difference in ionic strength. To compensate the bias due to residual liquid junction potentials, a quality control standard(QCS) of dilute sulfuric acid, which has the conductivity and pH values simikw to rain, was prepared. The pH of QCS solution was determined using the hydrogen electrode system without liquid junction, and compensation has been made for the bias terms by performing the pH measurements with glass electrode. On the basis of this compensation method, the pH vaiues of rain in Taeduk Science Town during 1998 were measured.

• KSBB Journal
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• v.15 no.3
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• pp.243-246
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• 2000

One of recent topics in the case of hepatits B virus(HVB) is the value of hepatitis B surface antigen(HBsAg) concentration as a prognostic maker. We developed uantitative method of rapid immunochromatographic assay(ICA) kit for HBsAg using computer image analysis (CIA) for the purpose of home diagnosis. uantitative ICA using CIA demonstrated integrated optical density(IOD) values proportional to log of reference HBsAg concentrations in the range of 2-200 ng/mL and enzyme-linked immunosorbent assay(ELISA) demonstrated the same in the range of 0.1-100 ng/mL however the test results with sample sear showed the same concentration on both kits. Furthermore repeated tests with the same samples revealed that this quantitative ICA using CIA would be reproducible and coefficient of variation(CV) of the results was 1.38~6.30%.

• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.40-41
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• 2002

차세대 반도체 및 나노소자 산업에 대한 국제적 기술은 고밀도 직접화의 추세에 따라서 .게이트 산화막의 두께가 급속히 작아지는 추세이다. 지금까지 이산화규소(A1₂O₃)가 게이트 산화막으로 주로 사용되어 왔으나 점차 SiON 혹은 high k 박막으로 바뀌고 있다. 본 연구에서는 차세대 반도체 소자에 사용될 게이트 산화막 물질인 SiON 박막과 Al₂O₃박막에 대한 SE(Spectroscopic Ellipsometry)분석 모델을 확립하였고, SE 측정결과를 TEM, MEIS, XRR의 결과들과 비교하였다. SiON 박막의 굴절률 값은 Si₃N₄와 SiO₂가 물리적으로 혼합되어 있다고 가정하여 Bruggeman effective medium approximation을 사용하여 구하였다. 동일한 시료를 절단하여 TEM, MEIS, 그리고 XRR에 의하여 SiON 박막의 두께를 측정하였으며, 그 결과 SE와 XRR에 의해 얻어진 박막두께가 TEM과 MEIS의 결과 값보다 약 0.5 nm 크게 주어짐을 알 수 있었다(Table 1 참조). 본 연구결과는 비파괴적이며 비접촉식 측정방법인 SE가 2～4nm 두께의 초미세 SiON 박막의 두께와 N 농도의 상대적 값을 빠르고 쉽게 구할 수 있는 유용한 측정방법 임을 보여주었다. 기존의 게이트 산화물인 SiO₂를 대체할 후보 물질들 중의 하나인 A1₂O₃의 유전함수를 구하기 위하여 8 inch, p-type 실리콘 기판 위에 성장된 5 nm, 10 nm, 및 20 nm 두께의 A1₂O₃ 박막의 유전함수와 두께를 측정하였다. 이 시료들에 대한 SE data는 vacuum-UV spectroscopic ellipsometer를 사용하여 세 개의 입사각에서 0.75 eV에서 8.75 eV까지 0.05 eV 간격으로 측정되었다. A1₂O₃ 박막의 유전함수와 두께를 얻기 위하여 공기층/A1₂O₃ 박막/Si 기판으로 구성된 3상계 모델을 사용하였다. Si 기판에 대한 복소 유전함수는 문헌상의 값(1)을 사용하였고, A1₂O₃ 박막의 유전함수는 5개의 미지상수를 갖는 Tauc- Lorentz(TL) 분산함수(2)를 사용하였다. A1₂O₃ 박막의 경우 두께가 증가함에 따라서 굴절률이 커짐을 알 수 있었다.