• 한국전기전자재료학회논문지
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• 제23권3호
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• pp.216-221
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• 2010

Employing statistical design of experiments, the difference in doping behaviors of rare-earth ions and their effects on the dielectric property and microstructure of $BaTiO_3$-MgO-$MnO_2$-($Ba_{0.4}Ca_{0.6}$) $SiO_3-Re_2O_3$ (Re = $Y_2O_3$, $Er_2O_3$) system were investigated. Through the statistical analysis we have found that the amount of $Re_2O_3$ are significantly affecting on the dielectric properties. The $Re_2O_3$ improved the dielectric constant, dielectric loss and R*C constant, so the appropriate contents of $Y_2O_3$ and $Er_2O_3$ were 0.8 ~ 1.2 mol% and 0.8 ~ 1.3 mol%, respectively. The MLCC(mutilayer chip capacitor) with $2.0{\times}1.2{\times}1.2mm$ size and 475 nF was also suited for X7R with the above composition. It showed that the dielectric constant and RC constant were 2,839 and 3,675 ${\Omega}F$, respectively in the sintering condition at $1250^{\circ}C$ in $Po_2$ $10^{-7}$ Mpa.

• Asian Pacific Journal of Cancer Prevention
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• 제13권9호
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• pp.4823-4826
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• 2012

Objective: To explore serum angiogenic factor expression in patients with osteosarcoma and its relationship with metastasis. Methods: Immunohistochemistry was used to test the expression of CD34 and FVIII-Rag in osteosarcoma tissues of 36 patients (osteosarcoma group) and microvessel density (MVD) was also recorded. In addition, ELISA was used to test the level of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), transforming growth factor-${\beta}1$ (TGF-${\beta}1$) and endostatin (ES) in the osteosarcoma group and in a control group. Results: VEGF and ES level were significantly higher than in the control group before operation (P<0.01), VEGF, bFGF and TGF-${\beta}1$ correlating with the ES level (P<0.01). Serum VEGF and ES levels of osteosarcoma patients before surgery were closely related to relapse and metastasis; moreover, serum VEGF increased with MVD (P<0.01). Postoperative VEGF and ES levels were lower than the preoperation values (P<0.01); ES level in relapse group was significantly higher than that of the non-relapse group (P<0.01). Conclusion: Preoperative serum VEGF and postoperative ES levels have great predictive value with regard to relapse of osteosarcoma patients.

• 방송공학회논문지
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• 제4권1호
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• pp.44-58
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• 1999

본 논문에서는 영역 인접성 그래프를 사용한 반복적 병합법으로 율왜곡 기반 영상 분할을 수행하는 알고리듬을 제안하였다. 제안한 기법에서는, 인접한 두 영역간의 이질성을 율왜곡적 관접에서 고려한 Lagrange 비용함수로 표현하였다. 이 때 각 병합 단계에 맞는 Lagrange 상수를 추정하고 율왜곡 기반 비용이 최소가 되는 인접 영역 쌍을 탐색하여 이들을 새로운 영역으로 병합하였다. 이러한 병합과정은 어떤 정지조건에 이를때까지 반복한다. 제안된 분할법은 영역기반 부호화 혹은 분할기반 부호화 기법에 적합한 분할법이다. 실험 결과, 256x256 L둠 에 대해서 영역기반 부호화를 수행하였을 때, 제안한 기법은 평균밝기 차이, 왜곡의 변화량 및 JPEG에 비하여 각각 2.5~3.5dB, 0.8~1.0 dB, 0.3~0.6 dB 정도의 PSNR 성능 개선이 있는 것으로 나타났다.

• Transactions on Electrical and Electronic Materials
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• 제11권3호
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• pp.126-129
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• 2010

(1-X) $(Na_{0.5}K_{0.5})NbO_3-X$ $K_4CuNb_8O_{23}$ (NKN-X KCN) ceramics were produced using the conventional solid state sintering method, and their sinterability and electric properties were investigated. The density, dielectric constant (${\varepsilon}_r$), piezoelectric constant $d_{33}$, electromechanical coupling factor $k_p$ and mechanical quality factor $Q_m$ value of the NKN ceramics depended upon the KCN content and the sintering temperature. In particular, the KCN addition to the NKN greatly improved the mechanical quality factor $Q_m$ value. The ceramic with X = 2.0 mol% sintered at $1,150^{\circ}C$ possesses the optimum properties (${\varepsilon}_r=241$, $d_{33}=78$, $k_p=0.34$ and $Q_m=1,121$). These results indicate that the ceramic is a promising candidate material for applications in lead free piezoelectric transformer and filter materials.

• 천문학회보
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• 제42권2호
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• pp.76.4-77
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• 2017

We have been performing a long term AGN Monitoring project, to measure the time lag of H beta line with respect to AGN optical continuum based on the reverberation mapping method. From October 2015, 69 AGNs have been monitored with BVR band photometry, using the MDM 1.3m & 2.4m and LOAO 1m telescopes, and long-slit spectroscopy, using the Lick 3m and MDM 2.4m telescopes. In this poster, we report the preliminary results of the variability study of a subsample of 9 AGNs, particularly with a few of tentative time rag measurements between B band magnitude and H beta luminosity based on the 1st year data set from February 2016 - January 2017.

• 한국전기전자재료학회논문지
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• 제21권5호
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• pp.440-446
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• 2008

To manufacture the MLCC with X7R for high voltage stability, $BaTiO_3-MgO-MnO_2-Y_2O_3$ with $(Ba_{0.4}Ca_{0.6})SiO_3$ glass frit was formulated. Based on this composition, the addition of $Er_2O_3$ showed that TCC(Temperature Coefficient Capacitance) at $85^{\circ}C$ was improved from 5 % to ${\sim}0\;%$, but the dielectric constant and IR (Insulation Resistance) were decreased. The glass frit improved the dielectric constant and IR, so the appropriate contents of $Er_2O_3$ and glass frit were 0.6 mol% and 1 wt%, respectively. It showed that the dielectric constant and RC constant were 2,550 and 2,000 (${\Omega}F$), respectively in the sintering condition at $1250^{\circ}C$ in PO2 $10^{-7}$ Mpa. The MLCC with $3.2{\times}1.6$ (mm) size and $1\;{\mu}F$ was also suited for X7R with the above composition.

• Nuclear Engineering and Technology
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• 제22권1호
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• pp.1-11
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• 1990

중수는 중수형 원자로의 감속재 및 냉각재로 사용되고 있으며 그 가격이 고가이기 때문에 일단 계통내에서 사용된 후 농도가 낮아진 저등급 중수는 중수승급기를 통해 99.8% 이상으로 농축 재생되어 중수로로 재주입되고 있다. 본 연구에서는 중수승급기의 공정을 면밀히 검토하였고 정상상태의 중수증류공정의 해석을 위하여 이론적인 모델을 제시하였으며 변수들간의 관계식을 설정하였다. 그리고 이 비선형 관계식을 단계적으로 처리하는 알고리즘의 전산 프로그램 UPGR을 개발하였다. 전산코드의 결과는 실제 운전 데이타와 잘 일치하였다. 월성 1호기에서 이를 이용한 운전지침의 제시, 운전효율의 평가, 성능평가 및 성능관리를 수행함으로써 중수승급기의 효율적인 운전에 기여하고 있다.

• 한국전기전자재료학회논문지
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• 제21권7호
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• pp.645-651
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• 2008

To reduce noise in high frequency and distortion of signal, the composition of $(Ca_{0.7}Sr_{0.3})(Zr_{0.97}Ti_{0.03})O_3$ and $(Ba_{0.2}Ca_{0.4}Sr_{0.4})TiO_3$ was developed. The composition was not solid solution, but mixtures of various phases composed of Ca, Sr, Zr, Ti and Ba oxides. The dielectric constant increased, the quality factor and the insulation resistance decreased with $(Ba_{0.2}Ca_{0.4}Sr_{0.4})TiO_3$ content. The composition of $0.4(Ba_{0.2}Ca_{0.4}Sr_{0.4})TiO_3$ satisfied the electric characteristics and the temperature coefficient of dielectric constant (TCC). In addition, the glass frit and $MnO_2$ also affected the electric characteristics. From the result of the best fit simulation, $MnO_2$ 0.3 mol%, the glass frit 0.6 wt% showed the insulation resistance $906{\Omega}{\cdot}F$, the quality factor 821, and the dielectric constant 92. With the selected composition, MLCC capacitors sized $4.5{\times}3.2{\times}2.5mm$ were manufactured with 105 layered of the dielectric thickness $16{\mu}m$ using Ni inner electrode, They represented the capacitance $98{\sim}102$ nF, the quality factor 1,200 and the insulation resistance $1,500{\Omega}{\cdot}F$. Also, they had high break-down voltage with $107{\sim}115V/{\mu}m$, and satisfied the SL TCC characteristics.

• Transactions on Electrical and Electronic Materials
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• 제10권5호
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• pp.152-155
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• 2009

The microstructure and the electrical properties of a ZnO varistor, which was composed of a ZnO-$Bi_2O_3$-$Sb_2O_3$-CoO- $MnO_2$ -NiO-$Nd_2O_3$ system, were investigated at various $Y_2O_3$ addition concentrations. $Y_2O_3$ played a role in the inhibition of the grain growth. As the $Y_2O_3$ content increased, the average grain size decreased from $6.8{\mu}m$ to $4{\mu}m$, and the varistor voltage($V_{1mA}$) greatly increased from 275 to 400 V/mm. The nonlinearity coefficient ($\alpha$) decreased from 72 to 65 with increasing $Y_2O_3$ amount. On the other hand, the leakage current ($I_L$) increased from 0.2 to 0.9 ${\mu}A$. These results confirmed that doping the varistors with $Y_2O_3$ is a promising production route for production of a higher fine-grained varistor voltage ($V_{1mA}$) which can dramatically reduce the size of the varistors.

• 한국ITS학회 논문지
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• 제12권1호
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• pp.28-42
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• 2013

전기를 이용한 신 교통 시스템인 무인궤도차량은 도심교통 완화, 관광지 교통지원, 공항 및 고속철도와 거점지역을 연결하는 목적을 가지고 있다. 무인궤도차량의 무인 운용에 따른 안전성과 신뢰성 보장을 위해 안전장치의 개발을 필요로 하고 있다. UWB 레이더는 낮은 전력소모와 낮은 간섭 및 높은 정밀도의 장점을 가지고 있어 무인궤도차량에 적합한 시스템이다. 본 논문에서는 무인궤도차량의 안전한 운행을 위한 필수 요소인 레이더에 적합하고, 다양한 잡음환경에서 개선된 성능을 보이는 적응형 CFAR 알고리즘을 제안하였다. 제안된 CFAR 알고리즘은 Mean Level 계열의 CFAR 알고리즘에 비하여 균질한 잡음상황과 다중표적상황에서 개선된 성능을 보였으며, 기존의 VI-CFAR이 가진 다중 표적 상황에서 성능저하를 개선하였다.