• Transactions on Electrical and Electronic Materials
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• 제18권2호
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• pp.97-102
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• 2017

A current transformer (CT) is a type of sensor that consists of a combination of electric and magnetic circuits, and it measures large ac currents. When a large amount of current flows into the primary winding, the alternating magnetic flux in the iron core induces an electromotive force in the secondary winding. The characteristics of a CT are determined by the iron core design because the iron core is saturated above a certain magnetic flux density. In particular, when a large current, such as a current surge, is input into a CT, the iron core becomes saturated and the induced electromotive force in the secondary winding fluctuates severely. Under these conditions, the CT no longer functions as a sensor. In this study, the characteristics of the secondary winding were investigated using the time-difference finite element method when a current surge was provided as an input. The CT was modeled as a two-dimensional analysis object using constraints, and the saturation characteristics of the iron core were evaluated using the Newton-Rhapson method. The results of the calculation were compared with the experimental data. The results of this study will prove useful in the designs of the iron core and the windings of CTs.

• Clinical and Experimental Reproductive Medicine
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• 제29권3호
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• pp.215-222
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• 2002

Objective : Previous studies have suggested that hyperhomocysteinemia and methylenetetrahydrofolate reductase (MTHFR C677T) mutations are associated with increased risk of recurrent spontaneous abortion (RSA). Recently, a second site polymorphism in MTHFR, 1298A-->C, which changes a glutamic acid into an alanine residue, was shown to be associated with a decreased enzyme activity. We tested whether the variant alleles of MTHFR C677T and A1298C are risk factor (biomarker) for RSA. Materials and Methods: We analyzed DNA from a case-control study in the Korean DNA was extracted from blood samples of 118 patients with RSA and 123 healthy fertile patients as the controls. MTHFR variant alleles were determined by a PCR-restriction fragment length polymorphism assay. Results: We found no evidence for an association between 677TT genotype and risk of RSA (OR=1.95, 95% CI=$0.84{\sim}4.50$, p=0.12). However, the MTHFR 1298AC (OR=0.36, 95% CI=$0.20{\sim}0.63$, p=0.0004) and 1298AC+CC (OR=0.35, 95% CI=$0.20{\sim}0.61$, p=0.0002) genotypes were lower among 118 RSA cases compared with 123 controls, conferring a 2.8-fold decrease in risk of RSA, respectively. Moreover, the combined genotypes of MTHFR 677CC/1298AC (OR=0.30, 95% CI=$0.10{\sim}0.88$, p=0.029) and 677CT/1298AC (OR=0.77, 95% CI=$0.60{\sim}0.99$, p=0.043) also showed significantly lower risk than those with MTHFR 677CC/1298AA type. Conclusion: MTHFR 1298AC, MTHFR 677CC/1298AC and 677CT/1298AC genotypes may represent genetic markers for the protection of RSA at least in Korean women.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.427-428
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• 2008

We have studied design and application about an self generation equipment for underground power transmission cable. The split CT(Current Transformer), which has the applicable underground power transmission cable, was manufactured through electromagnetic simulation of magnetic core. And manufactured the AC-DC converter that supplied stable DC power for PLC modem when current of power line has more than 150A. An self generation equipment using the CT and AC-DC converter get into operation the PLC modem consistently. As a result, the underground power transmission cable was showed the application possibility through the stable communication and network characteristics.

• 공업화학
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• 제4권1호
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• pp.153-161
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• 1993

$700-900^{\circ}C$의 온도범위와 여러 산소분압 조건에서 고체전해질 연료전지의 양극인 $La_{0.9}Sr_{0.1}MnO_3$에서 산소의 환원반응특성을 조사하였다. AC 임피던스법과 전류중단법에 의해 산소환원반응의 전하전달저항을 측정하였는데 두 방법으로 구한 간이 서로 잘 일치하였다. 전기화학적 산소환원반응의 활성화에너지는 대기압 조건에서 174kJ/mol의 값을 보였고, 산소분압에 따른 전하전달저항의 측정결과로 부터 이 전극에서 전기화학적 산소환원반응의 율속단계는 전하전달과정임을 알 수 있었다.

• 한국방사선학회논문지
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• 제18권3호
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• pp.213-222
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• 2024

본 연구는 폐 방사선 치료를 위한 컴퓨터 단층촬영의 관전압, 관전류 조건에 따라 딥 러닝과 아틀라스기반 자동분할 방법에 따른 생성된 볼륨과 Dice 유사도 계수와 95% 하우스도르프 거리를 분석하였다. 첫 번째 결과로 관전압 관전 류의 변화에 생성된 볼륨의 결과에서는 아틀라스기반인 smart segmentation 방법이 가장 적은 볼륨 변화를 보여주었으며, 딥 러닝을 사용한 Aview RT ACS와 OncoStudio에서는 100 mAs보다 낮은 관전류에서는 볼륨이 작아지는 걸 확인했다. 두 번째 결과인 Dice 유사도 계수에서는 Aview RT ACS가 OncoStuido 보다 2% 높은 결과를 보여주고 있으며, 95% 하우스도르프거리 결과에서도 Aview RT ACS가 OncoStudio 보다 평균 0.2~0.5% 높게 분석되었다. 하지만 관전류와 관전압에 따라 각각의 결과의 표준편차에서는 오히려 OncoStudio가 낮으므로 볼륨의 변화에서도 일관성 있을 거라 사료된다. 따라서 폐 방사선 치료를 위한 CT 촬영조건에서 낮은 관전압과 낮은 관전류에서 딥 러닝 기반 자동분할 프로그램을 사용할 때는 주의가 필요하며, 일정 관전압, 관전류 이상에서 기존에 사용하고 있는 아틀라스기반 자동분할 프로그램과 유사한 결과를 도출할 수 있었다.

• Clinical and Experimental Reproductive Medicine
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• 제33권1호
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• pp.61-61
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• 2006

목 적: 본 연구는 methylenetetrahydrofolate reductase (MTHFR C677T와 A1298C) 유전자 돌연변이형이 자연유산아 발생의 원인 유전자로 작용하는지에 대해 알아보고자 시도하였다. 연구방법: 95명의 자연유산아 조직과 대조군으로 100명의 정상 소아의 혈액 그리고 449명의 정상 성인의 혈액을 채취하여 DNA를 분리하여 사용하였다. 유전자형은 분리된 DNA를 이용하여 중합효소 연쇄반응과 제한효소 절편다형 분석방법으로 결정하였다. 결 과: 자연유산아 그룹은 소아대조군에서 보다 MTHFR 677CC 형 (p=0.014)은 높게, 677CT형 (p=0.063)은 낮게 나타났다. 성인대조군과의 비교에서도 MTHFR 677CT 형의 빈도는 현저히 낮게 나타났다 (p=0.032). 그리고 MTHFR 677CC/1298AC 조합형 유전자의 경우 소아대조군 (p=0.034)과의 비교에서는 현저히 높은 빈도를 나타냈으나, 성인대조군 (p=0.063)과의 비교에서는 높은 경향성은 있었으나 통계학적으로 유의한 차이는 없었다. 결 론: MTHFR 677CC와 MTHFR 677CC/1298AC 유전자형은 자연유산아 발생의 위험인자일 가능성이 높으며, 지속적인 연구가 요구된다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.61-66
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• 2003

In this paper, the effect of binder additive on the fracture toughness was metal matrix composite produced by squeeze casting method. In this study using the matrix is AC4CH and reinforcement used Aluminum borate whisker. Each MMC was produced by add inanimate binder ($SiO_2,\;Al2O_3,\;TiO_2$) to whiskers for increase the binding together of whiskers. Fracture toughness test were carry out in accordance with the ASTM E-399 standard test method, W=25mm, b=12.5mm CT(half size) specimen. However Base metal AC4CH was not meet the qualification of $P_m/P_Q<1.1$, so that test were performed $J_{IC}$ test. $K_{J_{IC}}$ value was measuring by $J_{IC}$ value change into $K_{IC}$. $J_{IC}$ test was carry out in accordance with the ASTM 1820.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.154-154
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• 2009

본 연구는 고전압 전력기기인 몰드형변압기와 계기용 변성기인 CT, PT 절연특성에 유용한 Epoxy/Nano-Micro Mixture Composites(이하,ENMMC)를 개발하기위해 무엇보다 중요한 것은 Nano입자인 $SiO_2$_10nm입자의 표면을 제어하여 즉, 표면의 소수성을 크게 하여 나노입자의 균질한 분산을 얻은것이 무엇보다 중요하다. 개발된 Epoxy/$SiO_2$_10nm Nanocomposites와 Microcomposites을 기계적 전단응력을 이용하여 균질 혼합을 실시하였다. 이런 조건을 이용한 전기적특성을 측정하기위해 구대구 전극이 완전함침된 평등전계하에서 절연파괴전압을 측정하기 시편을 제조하였다. 마이크로입자의 충진함량을 일정하게 유지하여 나노입자 충진함량비율을 4가지로 변화시켜 절연파괴특성을 연구하였다. 충진함량이 나노입자의 경우 1wt%이하의 값이 상대적으로 우수한 절연파괴특성으로 와이블 플롯을 통하여 알수있었다. 상대적으로 멀티나노콤포지트의 형상파라미터가 큰 결과값을 얻을수 있었다. 그리고 스케일파리미터는 누적확률 밀도함수로서 63.2%에서 대단히 큰 초절연성의 절연소재를 개발할수 있었다.

• 대한의용생체공학회:의공학회지
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• 제26권1호
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• pp.43-47
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• 2005

We have developed a small bore x-ray CT for small animal imaging with a linear x-ray detector array and small-scale slip rings. The linear x-ray detector array consists of 1024 elements of 400□m×400□m with a gadolinium oxysulfide (GOS) scintillator on top of them. To avoid use of expensive large diameter slip rings for projection data transmission from the X­ray detector to the image reconstruction system, we used the wireless LAN technology. The projection data are temporally stored in the data acquisition system residing on the rotating gantry during the scan and they are transmitted to the image reconstruction system after the scan. With the wireless LAN technology, we only needed to use small-scale slip rings to deliver the AC electric power to the X-ray generator and the power supply on the rotating gantry. The performances of the small animal CT system, such as SNR, contrast, and spatial resolution, have been evaluated through experiments using various phantoms. It has been experimentally found that the SNR is almost linearly proportional to the tube current and tube voltage, and the minimum resolvable contrast is less than 30 CT numbers at 40kVp/3.0㎃. The spatial resolution of the small animal CT system has been found to be about 0.9Ip/㎜. Postmortem images of a piglet is also presented.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.373-378
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• 2002

Metal matrix composites have a great interest in recent years because high specific strength, high specific stiffness characteristics, and application ranges of the composites are extend to variety industry. In this paper, an investigation was performed on the plane strain fracture toughness and slinding wear properties of AC4CH alloy(Al-Si-Mg line) reinforced with 20wt% aluminum borate whisker expect one, which contained a inorganic binder($TiO_2$). the binder led to the formation of strengthen the whisker each other. The test of fracture toughness was using CT(half size) specimen of thickness 12.5mm, width 25mm. and test of slinding wear of using tribo a pin-on-disk machine and lubricant is used without paraffine 8.2CST at room temperature. As results, Fracture toughness $K_{IC}$ is $8.7MPa-m^{05}$ for ABOw/AC4CH, $9.28MPa-m^{05}$ for ABOw/AC4CH added $TiO_2$. but AC4CH alloy was violated the critical stipulated by ASTM standard for valid measurement of $K_{IC}$. In case of, it was performed $J_{IC}$ test instead of $K_{IC}$ based on ASTM E 1820.