• Transactions on Electrical and Electronic Materials
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• 제16권1호
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• pp.1-4
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• 2015

(111)-oriented and random oriented $Pb_{0.8}Ba_{0.2}ZrO_3$ (PBZ) perovskite relaxor ferroelectric thin films were fabricated on Pt(111)/$TiO_x$/$SiO_2$/Si substrate by sol-gel method. Nano-scaled antiferroelectric and ferroelectric two-phase coexisted in both (111)-oriented and random oriented PBZ thin film. High dielectric tunability (${\eta}=75%$, E = 560 kV/cm) and figure-of-merit (FOM ~ 236) at room temperature was obtained in (111)-oriented thin film. Meanwhile, giant electrocaloric effect (ECE) (${\Delta}T=45.3K$ and ${\Delta}S=46.9JK^{-1}kg^{-1}$ at $598kVcm^{-1}$) at room temperature (290 K), rather than at its Curie temperature (408 K), was observed in random oriented $Pb_{0.8}Ba_{0.2}ZrO_3$ (PBZ) thin film, which makes it a promising material for the application to cooling systems near room temperature. The giant ECE as well as high dielectric tunability are attributed to the coexistence of AFE and FE phases and field-induced nano-scaled AFE to FE phase transition.

• 한국의학물리학회지:의학물리
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• 제23권1호
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• pp.15-25
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• 2012

부피적조절회전방사선치료(VMAT)의 정도관리를 TG-119에서 제시된 권고안을 통해 평가하고자 하였다. 또한 선택적 최적화 변수에 따른 치료계획의 평가와 그에 따른 선량학적 특성을 평가하고자 하였다. Varian사의 iX선형가속기와 Nucletron사의 Oncentra MasterPlan 치료계획장치를 결합하여 VMAT 치료계획을 수립하였다. TG-119에 제시된 5가지의 구조세트를 이용하여 아크 수, 겐트리 간격, 치료 시간 등의 선택적 최적화 변수(selectable optimization parameters)를 변화하여 치료 계획의 평가와 선량검증을 통해 정확성을 평가하였다. 치료계획의 평가는 선량체적히스토그램을 이용하여 표적과 위험장기의 평균값과 표준편차를 이용하였으며 선량검증은 이온 전리함과 $Delta^{4PT}$ bi-planar diode array를 이용하였다. 치료계획의 평가에서 싱글 아크의 경우 C-shape (hard)를 제외한 다른 구조세트에서 목표한 선량에 근접하는 결과를 보였으며 듀얼 아크의 경우에는 C-shape (hard)를 제외한 다른 구조세트에서 제시한 목표 선량에 도달하였다. 또한 선택 변수에 대한 평가에서는 전립선과 같은 간단한 구조 세트에서는 아크 수에 따른 치료계획의 차이는 거의 나타나지 않았으나, 두경부와 같은 복잡한 구조에서는 듀얼 아크가 위험장기에 대하여 좀 더 우수한 결과를 나타내었다. 겐트리 간격의 크기 변화에 의한 선량분포는 $6^{\circ}$에 비해 $4^{\circ}$의 겐트리 간격이 우수하였으나 $2^{\circ}$ 간격과는 거의 차이가 없었다. 점선 량의 정확성 평가에서는 표적과 위험장기에 대한 점선량의 측정값과 계산값의 평균오차는 싱글 아크와 듀얼 아크 모두 3% 이내였으며, 신뢰구간은 싱글아크와 듀얼 아크가 4% 내로 허용범위 안에 포함되었다. 겐트리 간격의 크기에 따른 점선량의 정확성 평가에서는 $2^{\circ}$, $4^{\circ}$, $6^{\circ}$ 모두 3% 이내였으며, 표적과 위험장기에 대한 신뢰한계(Confidence limit)는 5% 내로 허용범위 안에 포함되었다. $Delta^{4PT}$를 이용한 싱글 아크와 듀얼 아크의 선량분포 측정에서는 허용기준 3 mm/3%를 통과하는 감마인덱스는 평균 $98.72{\pm}1.52%$와 $98.30{\pm}1.50%$이었으며 신뢰한계는 2.99%와 3.74%로 허용범위 내에 포함되었다. 겐트리 간격의 크기에 따른 선량의 정확성은 간격이 적을수록 우수한 결과를 나타냈다. 본 연구에서는 VMAT의 정도관리를 TG-119에서 제시된 시험을 수행하였으며 제시된 모든 구조 세트에 대하여 허용기준을 모두 만족하였다. 또한 사용자가 선택할 수 있는 최적화 변수의 변화에 대한 치료계획과 선량학적 영향을 분석하였으며 각 상황에 따른 임상적 특성에 맞는 변수를 선택하는 것이 중요하다고 사료된다.

• Journal of Korean Vacuum Science & Technology
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• 제3권2호
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• pp.130-133
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• 1999

Paraelectric ZrTiO4 thin films were synthesized on a Si(100) substrate using DC magnetron reactive sputtering. Films deposited above-400$^{\circ}C$ exhibited crystalline characteristics. The dielectric constants ($\varepsilon$) and dielectric losses (tan$\delta$) of as-deposited and annealed films were measured in the 1 MHz range using a Pt upper electrode and a phosphorous-doped si bottom electrode. Preliminary data showed that as the deposition temperature increased, the dielectric losses decreased while the dielectric constants did not change significantly. similar trends for dielectric losses were observed when the as-deposited samples were annealed at 800$^{\circ}C$. The reduction of dielectric losses at high-deposition temperatures and post annealing correlated well with the x-ray diffraction peak widths.

• The Korean Journal of Ceramics
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• 제7권1호
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• pp.20-25
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• 2001

PbTiO$_3$ thin films were prepared by low-pressure thermal plasma deposition on (100)Pt/(100)MgO substrates. Mist of source material in which metal alkoxides are dissolved in 2-methoxyethanol was introduced into plasma through heating furnace and deposited onto substrates at $600^{\circ}C$. As-deposited PbTiO$_3$/Pt/MgO thin film prepared at 1.33$\times$10$^4$ Pa was grown epitaxially, but was consisted of many rectangular shaped grains, with many grain boundaries and it was impossible to measure electric properties. As-deposited film prepared at 1.00$\times$10$^4$ Pa showed weak peaks of X-ray diffraction and the film was not grown epitaxially. On the other hand, the film after annealed at $700^{\circ}C$ showed strong diffraction peaks and epitaxial growth was also observed. For annealed film, moreover, no clear grain boundaries were observed. The value of ${\varepsilon}_r$, tan${\delta}$, Pr and Ec of annealed film were 160, 3.2%, 10.4${\mu}$C.cm$^-2$ and 51.2kV.cm$^-1$, respectively. Since the composition, Pb/Ti, measured by EDS attaching to SEM changed point by point, the distribution of composition in annealed film was investigated and found out several relations between composition and electric properties. At stoichiometric composition, Pr and Ec showed the lowest value and they gradually became large as composition deviated from stoichiometric one. Moreover, the value of ${\varepsilon}_r$ became gradually large as the ratio of Ti became high.

• 신재생에너지
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• 제9권1호
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• pp.51-59
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• 2013

Tantalum carbide crystallites which is to be used for $H_2$ fuel cell has been synthesized via a temperature-programmed reduction of $Ta_2O_5$ with pure $CH_4$. The resultant Ta carbide crystallites prepared using two different heating rates and space velocity exhibit the different surface areas. The $O_2$ uptake has a linear relation with surface area, corresponding to an oxygen capacity of $1.36{\times}10^{13}\;O\;cm^{-2}$. Tantalum carbide crystallites are very active for hydrogen production form ammonia decomposition reaction. Tantalum carbides are as much as two orders of magnitude more active than Pt/C catalyst (Engelhard). The highest activity has been observed at a ratio of $C_1/Ta^{{\delta}+}=0.85$, suggesting the presence of electron transfer between metals and carbon in metal carbides.

• E2M - 전기 전자와 첨단 소재
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• 제3권4호
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• pp.271-278
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• 1990

본 논문에서는 내부전극 Pt를 갖는 적층형 압전액튜에이터의 제조와 적층수에 따른 압전액튜에이터 압전특성에 대해 조사 연구하였다. 먼저, Dr.blade방법을 사용하여 두께 ~220.mu.m의 PZT green sheet를 제작하였다. green sheet의 밀도는 결합제 양과 외부압력에 대해 크게 의존하였으며 소결체의 밀도는 green sheet의 밀도가 커질수록 더 높게 나타났다. 다음에는 적층수에 따른 압전정수의 변화에 대한 것으로써 압전정수(d$_{33}$)는 PZT세라믹스의 적층수가 증가할수록 매우 크게 증가되었으며 압전정수를 도입하여 계산된 변형량(.DELTA.l/l)은 10층 시편에 대해 2*$10^{6}$V/m의 전계에서 3*$10^{-3}$값을 얻었다. 이와같은 결과로써 적층형 압전액튜에이터는 저전압에서도 큰 변위를 나타내며 따라서 제어장치의 미세작동에 충분히 이용 될 수가 있다.다.

• 센서학회지
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• 제17권4호
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• pp.281-288
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• 2008

Polyacrylonitrile(PAN)/metal oxide(MO) nanocomposite mats with a thickness of 0.12 mm were electrospun by adding 0 to 10 wt% of MO nanoparticles ($Fe_2O_3$, ZnO, $SnO_2$, $Sb_2O_3-SnO_2$) into PAN. Pt electrode was patterned on $Al_2O_3$ substrate by DC sputtering and then the PAN(/MO) mats on the Pt patterned $Al_2O_3$ were electrically wired to investigate the $CO_2$ gas sensing properties. As the MO content rose, the fiber diameter decreased due to the presence of lumps caused by the presence of MOs in the fiber. The PAN/2% ZnO mat revealed a faster response time of 93 s and a relatively short recovery of 54 s with a ${\Delta}R$ of 0.031 M${\Omega}$ at a $CO_2$ concentration of 200 ppm. The difference in sensitivity was not observed significantly for the PAN/MO fiber mats in the $CO_2$ concentration range of 100 to 500 ppm. It can be concluded that an appropriate amount of MO nanoparticles in the PAN backbone leads to improvement of the $CO_2$ gas sensing properties.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.94-98
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• 2000

Polycrystalline SBTN ferroelectric thin films were prepared by sol-gel method with various Nb mole ratios on Pt/ $SiO_2$/Si (100) substrates. The films were annealed at different temperatures and characterized in terms of phase and microstructure. Relatively a well saturated hysteresis pattern was obtained at x =0.2 in S $r_{0.8}$B $i_{2.3}$(T $a_{1-x}$ N $b_{x}$)$_2$ $O_{9+}$$\alpha$/ thin films. At an applied voltage of 5V, the dielectric constant ($\varepsilon$$_{r}$) and dissipation factor (tan $\delta$) of typical S $r_{0.8}$B $i_{2.3}$(T $a_{1-x}$ N $b_{x}$)$_2$ $O_{9+}$$\alpha$/ thin film (x=0.2) were about 236.2 and 0.034. Measured remanent polarization (2Pr) and coercive field (Ec) were 4.28C/c $m_2$, and 38.88kv/cm respectively. No fatigue was observed up to 6$\times$10$_{10}$ switching cycles at 5V and the normalized polarization reduced by a factor of only 4%.%. 4%.%. 4%.%.%.%.%.

• 대한치과보철학회지
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• 제41권2호
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• pp.148-159
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• 2003

Statement of problem Metal-ceramic restorations have been used extensively by dental clinicians for nearly 40 years. Strength an functional ability of metal-ceramic restorations are proved to be satisfying, However esthetics and biocompatibility of metal alloy which is used in metal-ceramic restoration is not ideal. Using pure gold as an alternative, have advantage of esthetics, biocompatibility over conventional metal alloy. But there had been little article which studied on the color effect of pure gold on fual porcelain color. Purpose The purpose of this study was to spectrophotometrically evaluate the difference between color of metal alloy(Au-Pt, Ni-Cr) and pure gold, during color masking procedure with opaque porcelain and to analyze the differences, Material and Methods Three types of metal - base metal(Ni-Cr), high gold alloy(Au-Pt), pure gold(GES) - specimen were fabricated 1cm in diameter. Four steps were established - after finishing, after pre-coditioning, after application of first opaque porcelain(0.08mm in thickness), after application of second opaque porcelain(0.15mm in thickness)- and tested color with spectrophotometer every each steps and analyzed with $CIEL^*a^*b^*$ color order system. One-Way ANOVA test was used to and out if there were significant differences between groups tested and Shaffe multiple comparison was used to identify where the differences were. Results 1. After finishing and pre-conditioning, pure gold(GES) group showed most high values in $L^*,a^*,b^*$. 2. After application of first opaque porcelain(0.08mm in thickness), after application of second opaque porcelain(0.15mm in thickness), pure gold(GES) group showed the least difference in $L^*,a^*,b^*$ values and the lowest ${\Delta}E$ value(${\Delta}E$=0.63). 3. After application of first opaque porcelain and after application of second opaque porcelain differences that were significant (P<0.05) between groups were found only in $a^*$ values. 4. Base metal alloy group showed the lowest $a^*$ value in test after application of first opaque porcelain and the highest value in test after application of first opaque porcelain Conclusion Pure gold group and high gold group showed higher $a^*$ values than base metal group when tested after 0.08mm thickness of opaque porcelain was applied and pure gold group showed much similar $L^*,a^*,b^*$ values between 0.08mm thickness and 0.15mm thickness of opaque porcelain. This meant that pure gold was more easily masked by opaque porcelain than the other two groups.

• 한국식품영양과학회지
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• 제12권4호
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• pp.323-335
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• 1983

홍삼(紅蔘)과 백삼(白蔘) 항산화작용(抗酸化作用)에 의한 노화억제작용(老化抑制作用)을 구명(究明)하기 위하여 80% ethanol extract 및 수포화(水飽和)부탄올로 이행(移行)한 saponin을 시료(試料)로 하여 in vitro 및 in vivo 실험(實驗)을 통하여 홍삼(紅蔘)과 백삼(白蔘)의 노화억제작용(老化抑制作用)을 비교(比較)하였다. DPPH에 대한 전자공여능(電子供與能)(EDA), TBA value 및 peroxide value에 의한 과산화지질생성억제작용(過酸化脂質生成抑制作用), superoxide dismutase 및 peroxidase의 활성측정(活性測定)등으로 홍삼(紅蔘)과 백삼(白蔘)의 노화억제작용(老化抑制作用)을 비교(比較)한 결과(結果), 홍삼(紅蔘)은 장기간(長期間)에 걸친 연속투여(連續投與)에서 백삼(白蔘)보다 과산화지질생성억제작용(過酸化脂質生成抑制作用). superoxide dismutase 및 peroxidase의 활성(活性)을 유의성(有意性)있게 증가(增加)하였다. 생체내실험(生體內實驗)에서 홍삼(紅蔘)이 백삼(白蔘)보다 노화억제작용(老化抑制作用)이 현저한 것은 증삼(蒸參) 및 가공처리중(加工處理中) saponin pattern의 변화(變化)에 기인(起因)하며 백삼(白蔘)의 PT/PD ratio가 0.401인데 반(反)해 홍삼(紅蔘)의 PT/PD ratio가 0.561로서 triol saponin이 증가(增加)되었기 때문이다.