• 한국세라믹학회지
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• 제31권9호
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• pp.995-1004
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• 1994

Phase relation and microwave dielectric properties of the system BaO.(Nd1-xSmx)2O3.TiO2 (n=4, 5) were studied. With n=5 (1 : 1 : 5), Ba2Ti9O20 and TiO2 formed in case of X$\leq$0.7, and Ba2Ti9O20 and Sm2Ti2O7 formed at X=1.0 as the second phases dispersed in fine-grained orthorhombic matrix phase. With n=4 (1 : 1 : 4). on the contrary, only fine grains of an ortho-rhombic phase were observed irrespective of Nd/Sm ratio. The compositions of these two stable orthorombic phases having distinct lattic constants even with the same Nd/Sm ratio were estimated as 4BaO.5(Nd1-xSmx)2O3.18TiO2 and BaO.(Nd1-xSmx)2O3.4TiO2 with n=5 and n=4 in the system BaO.(Nd1-xSmx)2O3.TiO2, respectively. Consequently the composition BaO.(Nd1-xSmx)2O3.5TiO2 lies in the compatible triangle of 4BaO.5(Nd1-xSmx)2O3.18TiO2 and the second phases mentioned above. The microwave dielectric properties (~4 GHz) of BaO.(Nd1-xSmx)2O3.5TiO2 can be controlled effectively by adjusting Sm content : with increasing X from 0 to 0.7, both dielectric constant and the temperature coefficient of resonant frequency decreased monotonically from 82 to 65 and from 91 (ppm/$^{\circ}C$) to -19(ppm/$^{\circ}C$), respectively, while unloaded Q(Qo) remained constant at about 2,600.

• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.858-867
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• 2018

Analytical modeling equations are proposed for the conventional and modified three-section branch-line couplers. The analytical equations are explicit and capable of determining the characteristic impedance of each branch line for the coupler at desired coupling level as well as the suitability of broadband S-parameters analysis. In addition, a bandwidth extension and miniaturization of three-section branch-line coupler using slow-wave and meandering line structures were designed. The modified coupler, which is able to operate within frequencies from 1.5 to 3.32 GHz has been fabricated, tested and compared. A bandwidth extension of 600 MHz and 53% reduced size of the modified coupler have been achieved compared to a conventional coupler. The modified coupler has roughly insertion loss and coupling of -4 dB and -3.2 dB, while the isolation and return loss, respectively less than -14 dB with fractional bandwidth of 77 %, as well as phase imbalances less than $2^{\circ}$ over the operating bandwidth. Overall, the derived analytical model, simulation and measurement results demonstrated a good agreement.

• 한국표면공학회지
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• 제47권5호
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• pp.263-268
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• 2014

Nanocrystalline diamond(NCD) coated SiC balls were applied in a ball-on-disk tribometer. After seeding in an ultrasonic bath containing nanometer diamond powders, $2.2{\mu}m$ thick NCD films were deposited on sintered 3 mm diameter SiC balls at $600^{\circ}C$ in a 2.45 GHz microwave plasma CVD system. Bare $ZrO_2$ and SiC balls were prepared for comparison as test balls. Tribology tests were performed in air with pairs of three different balls and mirror polished steel(SKH51) disk. The wear tracks on balls and disks were examined by optical microscope and alpha step profiler. Under the load of 3 N, the friction coefficients of steel against $ZrO_2$, SiC and NCD-coated balls were between 0.4 and 0.8. After a few thousands sliding laps, the friction coefficient of NCD-coated balls dropped from 0.45 to below 0.1 and maintained thereafter. Under a higher load of 10 N or 20 N with a long sliding distance of 2 km, $ZrO_2$ and SiC balls exhibited the similar friction coefficients as above. The friction coefficient of NCD-coated balls was less than 0.1 from the beginning and increased to above 0.1 steadily or with some fluctuations as sliding distance increased. NCD coating layers were found worn out after long duration and/or high load sliding test, which resulted in the friction coefficient higher than 0.1.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.611-614
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• 2004

[ $Ba(Zn_{1/3}Nb_{2/3})O_3$ ] (BZN) 세라믹스의 소결 온도는 약 $1350^{\circ}C$ 이다. 그러나 $B_2O_3$가 첨가된 경우, BZN 세라믹스는 $900^{\circ}C$에서 소결되었다. $BaB_4O_7$, $BaB_2O_4$ 그리고 $BaNb_2O_6$ 이차상이 $B_2O_3$가 첨가된 BZN 세라믹스에서 관찰되었다. $BaB_4O_7$과 $BaB_2O_4$ 이차상은 약 $900^{\circ}C$에서 공정 온도를 가지기 때문에 $B_2O_3$를 첨가한 BZN 세라믹스론 $900^{\circ}C$에서 소결하는 동안 액상으로 존재할 것으로 여겨지며, 그것이 BZN 세라믹스의 소결온도를 낮출 것으로 생각된다. 소결 온도의 증가에 따라 유전 상수 ($\varepsilon_r$)와 품질 계수 ($Q{\times}f$)의 값은 증가하였는데, 이는 밀도의 증가에 기인한다. 그러나 $B_2O_3$의 첨가량이 많은 경우 Q 값은 감소하는데, 이는 이차상의 존재가 품질계수의 저하를 초래한다고 생각된다. 2.0 mol% $B_2O_3$가 첨가된 BZN 세라믹스를 $950^{\circ}C$에서 2시간 동안 소결하는 경우, $Q{\times}f$=13.600 GHz, $\varepsilon_r$=37.6 그리고 공진 주파수 온도계수 ($\tau_f$) = 19 ppm/$^{\circ}C$의 유전특성을 얻을 수 있었다.

• 한국표면공학회지
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• 제46권2호
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• pp.68-74
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• 2013

For the coating of diamond films on WC-Co tools, a buffer interlayer is needed because Co catalyzes diamond into graphite. W and Ti were chosen as candidate interlayer materials to prevent the diffusion of Co during diamond deposition. W or Ti interlayer of $1{\mu}m$ thickness was deposited on WC-Co substrate under Ar in a DC magnetron sputter. After seeding treatment of the interlayer-deposited specimens in an ultrasonic bath containing nanometer diamond powders, $2{\mu}m$ thick nanocrystalline diamond (NCD) films were deposited at $600^{\circ}C$ over the metal layers in a 2.45 GHz microwave plasma CVD system. The cross-sectional morphology of films was observed by FESEM. X-ray diffraction and visual Raman spectroscopy were used to confirm the NCD crystal structure. Micro hardness was measured by nano-indenter. The coefficient of friction (COF) was measured by tribology test using ball on disk method. After tribology test, wear tracks were examined by optical microscope and alpha step profiler. Rockwell C indentation test was performed to characterize the adhesion between films and substrate. Ti and W were found good interlayer materials to act as Co diffusion barriers and diamond nucleation layers. The COFs on NCD films with W or Ti interlayer were measured as less than 0.1 whereas that on bare WC-Co was 0.6~1.0. However, W interlayer exhibited better results than Ti in terms of the adhesion to WC-Co substrate and to NCD film. This result is believed to be due to smaller difference in the coefficients of thermal expansion of the related films in the case of W interlayer than Ti one. By varying the thickness of W interlayer as 1, 2, and $4{\mu}m$ with a fixed $2{\mu}m$ thick NCD film, no difference in COF and wear behavior but a significant change in adhesion was observed. It was shown that the thicker the interlayer, the stronger the adhesion. It is suggested that thicker W interlayer is more effective in relieving the residual stress of NCD film during cooling after deposition and results in stronger adhesion.

• 한국자기학회지
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• 제5권5호
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• pp.782-785
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• 1995

In this paper, $Mn^{2+}$ ion was doped in Y-Ba-Cu-O as an EPR probe. The following samples were prepared by conventional solid-state reaction method : $YBa_{2}Cu_{2.96}Mn_{0.04}O_{7-\delta}$ (MN-I), annealed $YBa_{2}Cu_{2.96}Mn_{0.04}O_{7-\delta}$ (AMN) and $YBa_{2}Cu_{2.94}Mn_{0.06}O_{7-\delta}$ (MN-II). AMN sample was obtained from MN-I by annealing for 1 hr under the Ar gas atmosphere at $600^{\circ}C$. X-band (~9.05 GHz) EPR spectra were measured from 103 K to room temperature by employing a JES-RE3X spectroscopy with a $TE_{0.11}$ cylindrical cavity and 100 kHz modulation frequency. In MN-I we have observed only the $Cu^{2+}$ signal. The fact that no $Mn^{2+}$ signal was observed, in spite of $Mn^{2+}$ being a very sensitive EPR probe, indicates that most likely isolated $Mn^{2+}$ ions don't exist in the MN-I sample. Most probably $Mn^{2+}$ ions in the MN-I sample interact antiferromagnetically and hence are EPR silent. The AMN spectra of at room temperature and 103 K indicate not only the $Cu^{2+}$ signal but also an extra signal, which increases with decreasing temperature. It is suggested that the extra signal originates from Mn ions that were antiferromagnetically coupled before the annealing process. In MN-II, from 103 K to room temperature, also, the extra signal was observed together with the $Cu^{2+}$ signal. The extra signal in MN-II, however, decreases with decreasing temperature and nearly disappears at 103 K. The signal originates from Mn ions in impurity phases that include $Mn^{2+}$ ions. We suppose that there exist at least two $Mn^{2+}$ doped phases in Y-Ba-Cu-O. The $Mn^{2+}$ signal of one phase is undectable at all temperature and that of another phase decreases with decreasing temperature and disappears around 103 K.

• 대한전자공학회논문지SD
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• 제44권8호
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• pp.52-59
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• 2007

본 논문에서는 이더넷 광 네트워크 구현용 핵심 부품인 1.25 Gbps 단일집적 양방향 광전 SoC (Monolithic integrated hi-directional optoelectronic system-on-a- chip)의 전기적 혼신을 감소시키기 위한 임플란트의 전기적 절연 특성을 분석하였으며, 측정결과로부터 임플란트의 등가회로를 추출하였다. InP 기판상에 단일집적된 양방향 광전 SoC의 구성은 다음과 같다. 먼저 송신부는 전기신호를 광신호로 바꾸어 전송하는 레이저 다이오드(Laser Diode)와 레이저 다이오드의 출력을 모니터링하기 위한 모니터 포토다이오드(Monitor Photodiode)로 구성된다. 그리고 수신부는 디지털로 변조된 후 입력된 광신호를 전기신호로 변환하는 디지털 포토다이오드(Digital photodetector)로 구성된다. IEEE 802.3ah와 ITU-T G.983.3가 요구하는 기가비트 수동 광 네트워크 (Gigabit-Passive Optical Network)용 ONU (Optical Network Unit)의 양방향 광전 모듈의 규격을 만족하기 위해서는 수신부의 수신감도는 -24 dBm (@ BER (Bit Error Rate)=10-12)을 만족해야 하므로, 모듈 내의 전기적 혼신은 DC에서 3 GHz까지 -86 dB이하로 유지되어야 한다. 한편, 임플란트 구조의 측정 및 분석 결과, 단일 InP 기판상에 집적된 레이저 다이오드와 모니터 포토다이오드 간의 간격과, 그리고 모니터 포토다이오드와 디지털 포토다이오드간의 간격을 200 mm 이상을 유지하면서, 20 mm 폭의 임플란트를 삽입하였을 경우, -86 dB 이하의 전기적 혼신을 만족하였다. 본 논문에서 사용하고 분석한 임플란트 구조 및 특성은 단일집적 양방향 광전 SoC 뿐만 아니라, 아날로그/디지털 혼합모드 SOC의 설계 제작용 기본 데이터로 활용할 수 있다., 1.0 mm로 나타났다. 하체 고정기구를 사용한 환자군에서 디지털재구성사진과 모의 치료사진의 차이는 좌우, 전후, 두미 방향에 따라 각각 $1.3{\pm}1.9\;mm$, $1.8{\pm}1.5\;mm$, $1.1{\pm}1.1\;mm$, 디지털재구성사진과 조사영역사진 간의 차이는 각각 $1.0{\pm}1.8\;mm$, $1.2{\pm}0.9\;mm$, $1.2{\pm}0.8\;mm$, 조사영역사진 간의 평균 표준편차는 각각 0.9 mm, 1.6 mm, 0.8 mm로 고정기구를 사용하지 않았을 때보다 유의하게 재현성이 향상된 것으로 나타났다. 결 론: 본 연구에서 고안된 하체 고정기구는 골반부암 환자 치료 시 편안함을 제공해 주고 재현성 향상에 도움을 주는 것으로 사료된다..) 이 때 방사선 조사량의 중앙값은 3,600 cGy이었다. 이후 추가 방사선 치료 시 계획용 CT를 사용하지 않고 2-oblique fields 사용하여 치료한 경우가 87명(35.4%)이었는데 방사선 조사량의 중앙값은 1,800 cGy이었다. 전 환자에서 1일 1회 180 cGy로 치료하였다. 전 환자에서 조사된 총 방사선량의 중앙값은 5,580 cGy이었다. 수술 후 방사선 치료를 시행한 경우 중앙값은 5,040 cGy이었고 수술을 받지 않은 환자 중앙값은 5,940 cGy이었다. 근접조사 방사선 치료는 총 34명(13.8%)에서 시행되었고, 전 환자에서 high dose rate Iridium-192를 사용하였다. 조사범위는 종양에서 longitudinal margin의 중앙값은 1 cm, prescribed isodose curve에서 axial length의 평균값은 8.25 cm, 폭은 2 cm, 그리고 전후 폭의 중앙값도 2 cm이었다. Fraction size의 중앙값은