• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.205-208
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• 2008

The wind load on building surface is numerically investigated. The geometry of target building is a square cross section and aspect ratio (height (H) to width (d)) is 6. On building surface, the pressure was measured, compared to obtained value from numerical simulation. The numerical simulations were done using URANS with three different turbulence models such as v2-f model, k-${\omega}$model, and k-${\varepsilon}$ model, respectively. The v2-f model showed the best agreement with experimental data in simulating mean pressure coefficients on front, rear and side surface. But unsteady characteristics of pressure history measured on surface is shown a discrepancy between experiment and numerical simulation.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1995년도 추계학술대회 논문집
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• pp.158-162
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• 1995

We report rf and power characteristics of AlGaAs/GaAs Heterojunction Bipolar Transistor (HBTs) for X-band power applications. HBTs have been fabricated with polyimide a an interlayer dielectric. By characterizing the DC and RF characteristics we obtained the maximum current gain of 45, BV$\_$CEO/ of 10 V, fT of 30 GHz and f$\_$max/ of 17 GHz for device with 6x14$\mu\textrm{m}$$^2$emitter size. To extract accurate equivalent parameters, the De-embedded method was applied for extraction of parasitic parameters and the calculation of circuit equations for intrinsic parameters. Based on the Load-pull method, power characteristics was simulated and measured to get the maximum output power of the device.

• Restorative Dentistry and Endodontics
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• 제22권1호
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• pp.396-412
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• 1997

The purpose of this study is to observe the corrosion characteristics of five dental amalgams(CAULK FINE CUT, OPTALLOY II, DISPERSALLOY, TYTIN, and VALIANT) in the solutions with fluoride compound through the anodic polarization curve obtained by using a potentiostat. After each amalgam alloy and Hg being triturated, the triturated mass was inserted into the cylindrical metal mold, and condensed by hydraulic pressure(160 kg/$cm^2$). Each specimen was removed from the metal mold. Specimens were polished with the silicone carbide grinding paper 24 hours after condensation and stored at room temperature for 1 week. The anodic polarization curves were employed to compare the corrosion behaviours of the amalgams in 0.9 % saline solution and in the saline solutions with 2.2 ppm, 0.05 %, 2 % NaF, and 8 % $SnF_2$ at $37^{\circ}C$ with 3-electrode potentiostat. After the immersion of specimen in electrolyte for 30 minutes, the potential scan was begun. The potential scan range was -1500m V to + 800m V(vs. S.C.E.) in the working electrode and the scan rate was 50 mV/sec. The results were as follows, 1. The corrosion potential, the potential of anodic current peak, and transpassive potential in the saline solutions with NaF shifted to lower direction than those in normal saline solution, and the current density in the saline solutions with NaF was higher than that in normal saline solution. The differences were increased as the concentrations of NaF became higher. 2. The corrosion potential and transpassive potential in the saline solution with $SnF_2$ shifted to higher direction than those in normal saline solution, and the current density in the saline solution with $SnF_2$ was higher than that in normal saline solution after the corrosion potential. The anodic polarization curves in the saline solution with $SnF_2$ had no outstanding anodic current peak. 3. The corrosion potentials for high-copper amalgams were much higher than those for CAULK FINE CUT and OPTALLOY II in normal saline solution, but, as the concentrations of fluoride compound became higher, the differences in corrosion potentials between them were decreased. The corrosion potentials had the similarity in the saline solution with 2% NaF or 8% $SnF_2$. 4. The current density for TYTIN was the lowest among the others in normal saline solution and in the saline solution with 2.2 ppm or 0.05 % NaF. 5. There was no significant difference in current density between Pd-enriched VALIANT and other high-copper amalgams.

• ALGAE
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• 제25권2호
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• pp.89-97
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• 2010

To test the feasibility of using chlorophyll ${\alpha}$ fluorescence to assess the establishment success of seagrass transplants, photosynthetic characteristics of eelgrass Zostera marina transplants were measured using a Diving-pulsed amplitude modulation fluorometer in Jindong Bay on the southern coast of Korea. Maximum quantum yield ($F_v/F_m$), photosynthetic efficiency ($\alpha$), saturating irradiance ($E_k$) and maximum electron transport rate ($ETR_{max}$) of transplants and reference plants in a nearby transplant site were measured using the fluorometer for 5 months. Additionally, shoot morphology, individual shoot weight and productivity of transplants and reference plants were also monitored. Shoot height, leaf weight and productivity of transplants were significantly reduced during the first two or three months after transplantation compared to those of reference plants, and then increased to the levels of reference plants Characteristics of chlorophyll a fluorescence, including $F_v/F_m$, $\alpha$, $E_k$ and $ETR_{max}$ of transplants were also significantly reduced in the initial period, but recovered slightly sooner than shoot morphology or leaf productivity. These results indicated that after transplantation, Z. marina transplant photosynthesis recovered faster than shoot morphology, biomass or productivity. Thus, chlorophyll a fluorescence can be used as an indicator for early assessment of the status of eelgrass transplants without destructive sampling.

• 한국항행학회논문지
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• 제15권4호
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• pp.596-601
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• 2011

본 논문에서는 간단한 회로구조와 높은 효율을 갖는 스위칭 방식의 E급 주파수 체배기에 대한 연구를 수행하였다. 주파수 체배는 능동소자의 비선형성에 의해 발생하는데 본 논문에서는 FET 능동소자를 간단한 스위치 및 기생소자 성분 모델로 근사하여 특성을 해석하고자 하였다. FET를 입력에 의해 동작하는 스위치 및 기생소자로 모델링하고 E급 주파수 체배기의 정합소자 값을 유도하였다. ADS시뮬레이터를 이용하여 출력 전압과 전류 파형 및 효율을 시뮬레이션하고 기생성분에 따른 변화를 연구하였다. 기생 커패시턴스, 저항, 인덕턴스에 의한 영향을 시뮬레이션하였으며 입력주파수 2.9GHz, 바이어스전압 2V일 때, 출력주파수 5.8GHz에서 기생커패시턴스가 0pF에서 1pF으로 변화함에 따라 드레인효율은 98%에서 28%로 감소하여 기생커패시턴스 CP가 FET의 기생 성분 중 가장 큰 영향을 끼친 것을 확인했다.

• 한국진공학회지
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• 제6권1호
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• pp.91-96
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• 1997

평면형 유도 결합 플라즈마의 전기적 특성을 측정하였고 Langmuir probe를 이용하 여 전자의 밀도와 온도를 측정하였다. 코일과 플라즈마를 포함한 총 부하의 저항 성분은 1 에서 4$\Omega$까지 변하였고 인덕턱스는 $1.5\mu$H와 2$\mu$H사이의 값을 가졌다. $10^{11}/\textrm{cm}^3$ 이상의 고밀 도 플라즈마를 발생시켰으며 전자의 온도는 공정 조건에 따라 3에서 5eV까지 변하였다. 산 화막 식각시 선택도를 개선하기 위한 방법으로 바이어스 전압을 변조하는 방법을 모색하였 다. C4F8플라즈마에서 바이어스 변조 방법을 사용하였을 때 선택도는 크게 향상 되었으나 산화막 식각율이 400$\AA$/min 이하였다. 선택도 향상을 위해 수소를 첨가한 실험에서 $C_4F_8$ 플 라즈마에 60% $H_2$를 첨가하였을 때 선택도 50이상, 산화막 식각율 2000$\AA$/min 이상의 결과 를 얻을 수 있었다.

• 전기화학회지
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• 제3권4호
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• pp.235-240
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• 2000

고출력 전기화학 캐패시터를 위한 전극제조공정으로 screen printing과 doctor blade법이 연구되었다. Screen printing에 의해서 제작된 비정질 $MnO_2$전극으로 측정된 CV (cyclic voltammogram)는 이상적인 캐패시터에 가까운 특성을 보여주었다. 50mV/s의 scan rate에서의 CV로부터 계산된 비용량은 $140{\mu}m,\;24{\mu}m,\; 3{\mu}m$의 전극두께에 대해서 각각 5.8F/g과, 81.8F/g, 172.0F/g의 값을 나타내었다. Screen printing전극에서의 $MnO_2$활물질의 이용율을 $100\%$로 하였을 때, paste와 doctor blade법의 이용율은 각각 $3.4\%$와 $47.6\%$이었다. Screen printing은 고출력 응용을 위한 얇은 전극의 코팅 방법으로 우수한 특성을 보였다.

• 한국안전학회지
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• 제11권3호
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• pp.81-88
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• 1996

In order to investigate the electrical properties of transformer oils for large power, the characteristics of AC and Impulse breakdown in gap length of 1.0~2.5mm and that of volume resistivity were researched in temperature range of 20~$100^{\circ}C$. An geometrical capacitance of electrode with coaxial cylindrical shape for measuring the volume resistivity was 16pF, and highmegohm meter with model no. VMG-1000 was used, and also the applied voltage were DC 100, 250 and 500V. In the dependance of breakdown characteristics due to electrode gap length, it was confirmed that breakdown voltage was nearly uniform by volume effect according to the increase of gap. In the characteristics for AC breakdown, the dielectric strength was increased to $90^{\circ}C$ but decreased over $90^{\circ}C$, and also in case of impulse breakdown, it was increased to 7$0^{\circ}C$ and at dated $70^{\circ}C$ over in temperature range. The calculated mobility of oils in the characteristics for impulse breakdown were about $10^{-5}$~$10^{-4}cm^2/V{\cdot}S$, and the value of volume resistivity was almost invariable in low temperature range, regardless of voltage by the stable thermal properties, and it indicated a peak at $50^{\circ}C$ and had a sudden change to decrease over that temperature, and also the value of volume resistivity in 250V/mm at $80^{\circ}C$ is suitable for the International electrical standards, it was confirmed.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.147-147
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• 2015

The multilayer structure of the organic light emitting diode has merits of improving interfacial characteristics and helping carriers inject into emission layer and transport easier. There are many reports to control hole injection from anode electrode by using transition metal oxide as an anode buffer layer, such as V2O5, MoO3, NiO, and Fe3O4. In this study, we apply thin films of LiF which is usually inserted as a thin buffer layer between electron transport layer(ETL) and cathode, as an anode buffer layer to reduce the hole injection barrier height from ITO. The thickness of LiF as an anode buffer layer is tested from 0 nm to 1.0 nm. As shown in the figure 1 and 2, the luminous efficiency versus current density is improved by LiF anode buffer layer, and the threshold voltage is reduced when LiF buffer layer is increased up to 0.6 nm then the device does not work when LiF thickness is close to 1.0 nm As a result, we can confirm that the thin layer of LiF, about 0.6 nm, as an anode buffer reduces the hole injection barrier height from ITO, and this results the improved luminous efficiency. This study shows that LiF can be used as an anode buffer layer for improved hole injection as well as cathode buffer layer.

• 센서학회지
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• 제23권3호
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• pp.185-191
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• 2014

The width of depletion region in a varactor diode can be modulated by varying a reverse bias voltage. Thus, the preferred characteristics of depletion capacitance can obtained by the change in the width of depletion region so that it can select only the desirable frequencies. In this paper, the TV tuner varactor diode fabricated by hyper-abrupt profile control technique is presented. This diode can be operated within 3.3 V of driving voltage with capability of UHF band tuning. To form the hyperabrupt profile, firstly, p+ high concentration shallow junction with $0.2{\mu}m$ of junction depth and $1E+20ions/cm^3$ of surface concentration was formed using $BF_2$ implantation source. Simulation results optimized important factors such as epitaxial thickness and dose quality, diffusion time of n+ layer. To form steep hyper-abrupt profile, Formed n+ profile implanted the $PH_3$ source at Si(100) n-type epitaxial layer that has resistivity of $1.4{\Omega}cm$ and thickness of $2.4{\mu}m$ using p+ high concentration Shallow junction. Aluminum containing to 1% of Si was used as a electrode metal. Area of electrode was $30,200{\mu}m^2$. The C-V and Q-V electric characteristics were investigated by using impedance Analyzer (HP4291B). By controlling of concentration profile by n+ dosage at p+ high concentration shallow junction, the device with maximum $L_F$ at -1.5 V and 21.5~3.47 pF at 0.3~3.3 V was fabricated. We got the appropriate device in driving voltage 3.3 V having hyper-abrupt junction that profile order (m factor) is about -3/2. The deviation of capacitance by hyper-abrupt junction with C0.3 V of initial capacitance is due to the deviation of thermal process, ion implantation and diffusion. The deviation of initial capacitance at 0.3 V can be reduced by control of thermal process tolerance using RTP on wafer.