• 한국태양에너지학회 논문집
• /
• 제37권4호
• /
• pp.23-33
• /
• 2017

A great deal of study for loss reduction of photovoltaic system is conducted currently. It is hard to distinct the fault of photovoltaic system with the naked eye. For that reason, it is essential to repair and maintain the PV system by monitoring the system. The fault of individual modules can cause the huge loss of the entire system because of the mismatch. Therefore, the method of diagnosing the PV array is necessary by measuring the multi-channel arrays simultaneously. In this paper, it is presented the method of measuring I-V curve of multi-channel arrays simultaneously by using the charge and discharge characteristics of capacitor. Generated DC power at PV arrays is charged and discharged at the capacitors in a moment. By measuring the charged voltage and current, it is possible to diagnose of performance of PV arrays.

• Journal of Magnetics
• /
• 제10권3호
• /
• pp.122-127
• /
• 2005

New classes of LC resonators for micro magnetic sensor device were proposed and fabricated. The first type LC resonator (Type I) consists of a small piece of microwire and two cylindrical electrodes at the end of the microwire without direct contact to its ferromagnetic core. In type I resonator the ferromagnetic core of the microwire and cylindrical electrodes act as an inductor and two capacitors respectively to form a LC circuit. The second type LC resonator (Type II) consists of a solenoidal micro-inductor with a bundle of soft magnetic microwires as a core. The solenoidal micro-inductors fabricated by MEMS technique were $500\sim1,000\;\mu{m}$ in length with $10\sim20$ turns. A capacitor is connected in parallel to the micro-inductor to form a LC circuit. A tiny glass coated $CO_{83.2}B_{3.3}Si_{5.9}Mn_{7.6}$ microwire was fabricated by a glass-coated melt spinning technique. A supergiant magneto-impedance effect was found in a type I resonator as much as 400,000% by precise tuning frequency at around 518.51 MHz. In type II resonator the changes of inductance as a function of external magnetic field in micro-inductors with properly annealed microwire cores were varied as much as 370%. The phase angle between current and voltage was also strongly dependent on the magnetic field. The drastic increments of magnetoimpedance at near the resonance frequency were observed in both types of LC resonators. Accordingly, the sudden change of the phase angle, as large as $180^{\circ}C$, evidenced the occurrence of the resonance at a given external magnetic field.

• 센서학회지
• /
• 제31권5호
• /
• pp.318-323
• /
• 2022

Barium titanate (BaTiO₃) is considered to be a beneficial ceramic material for multilayer ceramic capacitor (MLCC) applications because of its high dielectric constant and low dielectric loss. Numerous attempts have been made to improve the physical properties of BaTiO₃ in response to recent market trends by employing multicomponent alloying strategies. However, owing to its significant number of atomic combinations and unpredictable physical properties, finding a traditional experimental approach to develop multicomponent systems is difficult; the development of such systems is also time-consuming. In this study, 168 new structures were fabricated using special quasi-random structures (SQSs) of Ba_1-xCa_xTi_1-yZryO₃, and 1680 physical properties were extracted from first-principles calculations. In addition, we built an integrated database to manage the computational results, and will provide big data solutions by performing data analysis combined with AI modeling. We believe that our research will enable the global materials market to realize digital transformation through datalization and intelligence of the material development process.

• 한국재료학회지
• /
• 제4권7호
• /
• pp.759-766
• /
• 1994

본 연구에서는 Ta 박막 밑에 $SnO_{2}$박막층을 입혀서 $Ta/SnO_2$이중박막이 산화될 때 산소의 공급원을 2원화 함으로써 $Ta_2O_5$의 stoichiomitry를 향상시켜 $Ta_2O_5$박막 커패시터의 주설전류를 줄이고자 하였다. Tantalum을 실리콘 웨이퍼 위에 기판온도를 변화시켜 가면서 전자빔증착이나 스퍼터링 방밥으로 입히고 $500^{\circ}C$~$900^{\circ}C$에서 산화시켜 Al/$Ta_2O_5$p-Si/Al또는Al/$Ta_2O_5$/p-Si/Al과 같은 MIS형 커패시터를 만들어 유전상수 및 누설전류를 측정하였으며 XRD, AES, ESCA등을 이용하여 박막의 결정성 및 특성을 분석하였다. $SnO_{2}$박막층을 입힌 커패시터는$SnO_{2}$층을 입히지 않은 커패시터보다 10배 이상 큰 200정도의 유전상수 값을 나타내었다. 그리고 산화온도가 높으면 박막의 결정화로 인하여 유전상수는 증가하지아는 누설전류도 약간 증가하는 것이 확인되었다. 또한 높은 증착온도는 일반적으로 누설전류를 낮추는 것으로 나타났다. 특히 $SnO_{2}$층을 입힌 경우에 기판온도를 $200^{\circ}C$로 하고 $800^{\circ}C$에서 산화시켜 만든 커패스터의 경우에 $4 \times 10^{5}$V/cm의 전장강도에서 $10^{-7}A/\textrm{cm}^2$의 낮은 누설전류 값을 나타내었다. $Ta_2O_5$박막은 $700^{\circ}C$ 이상에서 박막이 결정되고, Ta /$SnO_{2}$ 이중박막을 산화시키면 처음에는 Ta박막과 $SnO_{2}$박막 계면에서 $SnO_{2}$로부터 Ta박막에 산소가 공급되지마는 점차 Sn이 Ta박막쪽으로 확산되어 결국에는 Ta-Sn-O계의 새로운 ternary oxide가 생성되는 것으로 나타났다.

• 대한전자공학회논문지SD
• /
• 제44권5호
• /
• pp.8-14
• /
• 2007

본 논문에서는 MOS 소자의 게이트 유전체로 사용될 고유전 박막으로 $HfO_2$/Hf 박막을 제조하여 그 전기적 특성을 관찰하였다. $HfO_2$박막은 TEMAH와 $O_3$ 전구체를 사용한 ALD 방법으로 p-type (100) 실리콘 웨이퍼 위에 증착하였다. $HfO_2$막을 증착시키기 전에 중간층으로써 Hf 금속 층을 증착하였다. Round-type의 MOS 커패시터 제작을 위해, 상부 전극은 Al 또는 Pt을 이용하여 약 2000 ${\AA}$ 두께의 전극을 형성하였다. $HfO_2$ 박막은 화학정량적 특성을 보였으며, $HfO_2$/Si 계면에서 Si-O 결합 대신 Hf-Si 결합과 Hf-Si-O 결합이 관찰되었다. $HfO_2$와 Si 사이의 Hf 중간층은 $SiO_x$의 성장이 억제되었고, $HfSi_xO_y$으로 변형되었다. 이러한 결과로 $HfO_2$/Hf/Si 구조에서 Hf 중간층이 있음으로 게이트 유전체의 고유전율이 유지되면서 계면 특성이 개선됨을 확인하였다.

• 한국환경보건학회지
• /
• 제27권2호
• /
• pp.127-137
• /
• 2001

Polychlorinated biphenyls(PCBs) are halogenated aromatic compounds with the empirical formula $C_{12}$ $H_{10-n}$C $l_{n}$(n=1~10), and are a mixture of possible 209 different chlorinated congeners. PCBs were widely used as dielectric fluids for capacitors and transformers, plasticizers, lubricant inks and paint addirives. Once released into the environment, PCBs persist for years because they are so resistant to degradation. In addition to their persistence in the environment, PCBs in ecological food chains undergo biomagnification because of their high degree of lipophilicity. In 1970s, the worldwide production of PCBs was ceased and the import of PCBs was prohibited since 1983 in Korea. In spite of these actions, many PCBs seems to be still in use. The environmental load of PCBs will continue to be recycled through air, land, water, and the biosphere for decades to come. This study was conducted to measure the concentrations of PCBs in the serum samples of 112 women by GC/MSD and GC/ECD. The main results of this study were as follows. 1. PCBs were detected in all samples. The mean $\pm$SD levels of PCBs in the serum were 3.613$\pm$0.759 ppb, and median were 3.828 ppb. 2. The correlation coefficients of the concentrations of 13 PCB congeners were from minimum, 0.7913 to maximum, 0.9985, and all was significant(p=0.0001). The correlation coefficient between the concentrations of PCBs and p,p'-DDE was 0.9641(p=0.0001). 3. There was a positive association between age and PCBs' concentrations (simple linear regression ; $R^2$=0.86, $\beta$=0.08023, p<0.001). 4. There was a positive association between total lipids in the serum and PCBs' concentrations (simple linear regression ; $R^2$=0.7058, $\beta$=0.00486, p<0.001). 5. For possible predictors of PCBs and p,p' -DDE levels in the serum, age adjusted model (Y=$\beta$$_{0}$+$\beta$$_1$age+ $B_2$X) was applied. For BMI, major residential area, wether to eat caught fish by angling, where to eat caught fish by angling(by parents in the past), fish consumption, meat consumption, meat consumption, and dairy consumption, there was no association. For total conception frequency and lactation frequency and lactation period, there was negative association.ion.

• 조명전기설비학회논문지
• /
• 제20권4호
• /
• pp.21-28
• /
• 2006

본 논문에서는 Ballard사의 1.2[kW]급 연료전지와 연료전지의 저전압($28{\sim}43[VDC]$)을 승압(380([VDC])시키기 위한 풀-브리지 직류-직류 컨버터, 그리고 승압된 직류 링크전압을 교류 전압(220[VAC]), 60[Hz]으로 변환하기 위한 단상 풀-브리지 인버터로 구성된 연료전지 발전용 전력변환시스템 중 풀-브리지 고주파 절연형 영전압 영전류 스위칭 위상 천이 펄스폭 변조 직류-직류 컨버터를 제안하였다. 제안한 풀-브리지 고주파 절연형 영전압 영전류 스위칭 위상 천이 펄스폭 변조 직류-직류는 프리휠링 다이오드를 포함한 탭부 인덕터 필터를 이용하여 순환 전류를 저감시켰으며, 스위치 및 변압기의 턴-온, 턴-오프시에 오버슈트 전압이나 과도현상이 발생하지 않는다. 그리고 넓은 출력 전압 조정에도 효율을 $93{\sim}97[%]$정도 얻을 수 있으며, 출력 부하전류의 변화에 대해 거의 일정한 출력 전압 특성을 가졌다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
• /
• pp.254-255
• /
• 2012

Interest in nano-crystalline silicon (nc-Si) thin films has been growing because of their favorable processing conditions for certain electronic devices. In particular, there has been an increase in the use of nc-Si thin films in photovoltaics for large solar cell panels and in thin film transistors for large flat panel displays. One of the most important material properties for these device applications is the macroscopic charge-carrier mobility. Hydrogenated amorphous silicon (a-Si:H) or nc-Si is a basic material in thin film transistors (TFTs). However, a-Si:H based devices have low carrier mobility and bias instability due to their metastable properties. The large number of trap sites and incomplete hydrogen passivation of a-Si:H film produce limited carrier transport. The basic electrical properties, including the carrier mobility and stability, of nc-Si TFTs might be superior to those of a-Si:H thin film. However, typical nc-Si thin films tend to have mobilities similar to a-Si films, although changes in the processing conditions can enhance the mobility. In polycrystalline silicon (poly-Si) thin films, the performance of the devices is strongly influenced by the boundaries between neighboring crystalline grains. These grain boundaries limit the conductance of macroscopic regions comprised of multiple grains. In much of the work on poly-Si thin films, it was shown that the performance of TFTs was largely determined by the number and location of the grain boundaries within the channel. Hence, efforts were made to reduce the total number of grain boundaries by increasing the average grain size. However, even a small number of grain boundaries can significantly reduce the macroscopic charge carrier mobility. The nano-crystalline or polymorphous-Si development for TFT and solar cells have been employed to compensate for disadvantage inherent to a-Si and micro-crystalline silicon (${\mu}$-Si). Recently, a novel process for deposition of nano-crystralline silicon (nc-Si) thin films at room temperature was developed using neutral beam assisted chemical vapor deposition (NBaCVD) with a neutral particle beam (NPB) source, which controls the energy of incident neutral particles in the range of 1~300 eV in order to enhance the atomic activation and crystalline of thin films at room temperature. In previous our experiments, we verified favorable properties of nc-Si thin films for certain electronic devices. During the formation of the nc-Si thin films by the NBaCVD with various process conditions, NPB energy directly controlled by the reflector bias and effectively increased crystal fraction (~80%) by uniformly distributed nc grains with 3~10 nm size. The more resent work on nc-Si thin film transistors (TFT) was done. We identified the performance of nc-Si TFT active channeal layers. The dependence of the performance of nc-Si TFT on the primary process parameters is explored. Raman, FT-IR and transmission electron microscope (TEM) were used to study the microstructures and the crystalline volume fraction of nc-Si films. The electric properties were investigated on Cr/SiO2/nc-Si metal-oxide-semiconductor (MOS) capacitors.

• 한국전자파학회논문지
• /
• 제22권12호
• /
• pp.1069-1077
• /
• 2011

본 논문에서는 선택적 산화 알루미늄(SAAO: Selectively Anodized Aluminum Oxide) 기판을 이용하여 2.5 GHz 8 W급 소형 GaN HEMT 전력 증폭기 모듈을 설계, 제작하였다. SAAO 기판 공정은 최근 Wavenics사에서 제안한 특허 기술로서, 알루미늄을 웨이퍼로 이용한다. 본 연구에 사용된 능동 소자는 최근 발표된 TriQuint사의 칩 형태 의 GaN HEMT이다. 최적의 임피던스는 수동 조정 소자가 내장된 지그를 사용하여 실험적으로 결정하였다. 결정된 임피던스를 이용하여, 입 출력 임피던스 정합 회로를 EM co-시뮬레이션을 이용하여 F급으로 설계를 수행하였으며, SAAO 기판에 구현하였다. 이때, 소형의 패키지(모듈)에 집적하기 위하여 인덕터와 커패시터는 각각 spiral inductor, single layer capacitor를 사용하였다. 소형으로($4.4{\times}4.4\;mm^2$) 패키지된 전력 증폭기 모듈의 경우, 출력은 8 W, 효율은 40 % 그리고 2차 및 3차 고조파에 대한 고조파 억제는 30 dBc 이상의 특성을 보였다.

• 한국전자파학회논문지
• /
• 제24권11호
• /
• pp.1064-1073
• /
• 2013

본 논문에서는 내부 고조파 조정 회로로 구성되는 셀룰러와 L-대역용 소형의 고효율 370 W GaN(Gallium Nitride) HEMT(High Electron Mobility Transistor) 소형 전력 증폭기(PA)를 구현하였다. 원천 및 2차 고조파 주파수에서 동시에 높은 효율을 내기 위해 새로운 회로 정합 형태를 적용했다. 소형화를 위하여 새로운 41.8 mm GaN HEMT와 2개의 MOS(Metal Oxide Semiconductor) 캐패시터를 구성 물질의 변화를 이용하여 열 저항을 개선한 $10.16{\times}10.16{\times}1.5Tmm^3$ 크기의 새로운 패키지에 와이어 본딩으로 결합하였다. 드레인 바이어스 48 V 인가 시, 개발된 GaN HEMT 전력 증폭기는 370 W 포화 출력 전력(Psat.)과 770~870 MHz에서 80 % 이상, 1,805~1,880 MHz에서 75 % 이상의 드레인 효율(DE)을 나타내었다. 이는 지금까지 보고된 셀룰러와 L대역에서 GaN HEMT 전력 증폭기 중 최고의 효율과 출력 전력 특성이다.