• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.567-570
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• 1989

A constant V/F control system of voltage contrlled PWM inverter has a unstable operation of the low- speed and the light-load. In this paper, the authors propose stability control with idealized operation of induction motor by the neglect of primary leakage inductance and resistance. Also ldealized operation system is adopted voltage error, feed back impedance circuit, and increasing resistance from dead time of switching is compensated by the soft ware with u-processors. The proposed simulation of the idealized control method is proved at the low-speed operation for three phase induction motor.

• Speech Sciences
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• v.4 no.1
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• pp.7-17
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• 1998

The purpose of this preliminary study on Korean vowel duration was to find how different syllable types and kinds of plosives influence vowel duration. The vowel duration of the Front Mid and Low vowels (/$\varepsilon$/(에), /e/(어), /${\ae}$/(애), /a/(아)) was found to be longer than that of High and Back vowels (/i/(이), /i/(으), /u/(우), /o/(오)). Compared with single vowels (V), Vowels followed by a consonant (CV) were shortened by 79.3% and vowels between consonants (CVC) were shortened by 38.5%, respectively. These results suggest that the influence of consonants upon Korean vowel duration depend on syllble types and the manner or place of articulation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.7
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• pp.956-965
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• 1998

Hot-wire measurement of the longitudinal and radial velocity components and Reynolds stresses are reported for developing turbulent flow in a strongly curved 180 deg. pipe and its tangents. Slanted wire is rotated to 6 directions and the voltage outputs of them are combined to obtain the mean velocities and Reynolds stresses. Significant double maxima in the longitudinal velocity component appear in the bend. V-profiles reveal the development of a strong secondary flow. This secondary flow is induced by the transverse pressure gradient set up between the outer(r$\sub$o/) and inner(r$\sub$i/) wall region of the bend. Another second cross-stream flow develops after .theta.=135 deg. and its direction is opposed to that of main second flow.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.410.1-410.1
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• 2014

A soft-lithographic top-down approach is combined with an epitaxial layer transfer process to fabricate high quality III-V compound semiconductor nanowires (NWs) and integrate them on Si/SiO2 substrates, using MBE-grown ultrathin InAs as a source wafer. The channel width of the InAs nanowires is controlled by using solvent-assisted nanoscale embossing (SANE), descumming, and etching processes. By optimizing these processes, the NW width is scaled to less than 50 nm, and the InAs NWFETs has ${\sim}1,600cm^2/Vs$ peak electron mobility, which indicates no mobility degradation due to the size.

• Electrical & Electronic Materials
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• v.1 no.4
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• pp.303-310
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• 1988

본 논문에서는 Langmuir-Blodgett법으로 유기초박막을 제작하기 위하여 시료인 (N-docosyl pyridinium)-TCNQ(1:2) 작제를 합성하고 이를 초박막으로 제작한 다음, U.V측정, capacitance측정, 그리고 기판과 수직한 방향의 도전율등을 측정하여 막이 잘 이루어지고 있음을 확인하였다. 한편, 하부 전극을 Al로 할 경우 전극표면에 생기는 자연 산화막(Al$_{2}$O$_{3}$)의 두께는 37.1.angs.정도이었으며 기관과 수직한 방향의 도전율은 약 $10^{-14}$S/cm로 양호한 절연성이었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.69-69
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• 2011

다이아몬드는 절연 물질이지만, 합성 다이아몬드를 생성할 때 결정 내에 도핑(doping) 과정을 통해 불순물을 혼입함으로써 반도체 성질을 가지게 된다. 본 연구에서는 마이크로웨이브 CVD 장치를 이용하여 다이아몬드 박막의 생성 조건을 최적화하고 여기에 다이아몬드 박막 생성시 디보란(Diborane, B2H6)을 주입하여 전기적 특성을 갖는 보론-도핑 된 다이아몬드 박막을 생성하였다. 실험 조건으로는 방전전력 1.4 Kw, 진공압력 40 Torr의 상태에서 디보란의 주입량을 각각 다르게 하여 실험을 진행하였다. 이 때 사용된 기판으로는 전기적 특성이 서로 다른 사파이어($Al_2O_3$), Si, Ti 기판을 사용하여 박막과 기판과의 연관성도 조사하였다. 각각의 보론-도핑 농도와 기판에 따른 다이아몬드 결정구조를 Micro Raman, SEM으로 분석하였고, 다이아몬드 박막의 I-V특성을 통해 다이아몬드의 전기적 특성을 조사하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.6
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• pp.952-958
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• 2000

다양한 구조위 트랜스미션 라인과 힌지들을 갖는 고주파용 마이크로머신드 용량성 스위치들이 새롭게 디자인되었고 전기도금 기술, 저온 공정기술, 그리고 건식 식각기술들을 이용하여 제작되었다. 특히, 집적화된 용량성 스위치들이 높은 스위칭 on/off ratio와 on 캐패시턴스를 갖도록 하기 위하여 고유전율을 갖는 SrTiO3라는 상유전체를 절연체로 사용하였다. 제작된 스위치들은 8V의 구동전압, 0.08dB의 삽입손실, 42dB의 높은 isolation, 600의 on/off ratio, 그리고 50pF의 on 캐패시턴스의 특성들을 갖는다.

• Computers and Concrete
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• v.26 no.1
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• pp.53-62
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• 2020

Concrete is the most widely used substance in construction industry, so it's been required to improve its quality using new technologies. Nowadays, nanotechnology offers new frontiers for improving construction materials. In this paper, we study the stability analysis of the Single Walled Carbon Nanotubes (SWCNT) reinforced concrete cylindrical shell embedded in elastic foundation using the Donnell cylindrical shell theory. In this regard, we propose a new explicit analytical formula of the critical buckling load which takes into account the distribution of SWCNT reinforcement through the thickness of the concrete shell using the U, X, O and V forms and the elastic foundation using Winkler and Pasternak models. The rule of mixture is used to calculate the effective properties of the reinforced concrete cylindrical shell. The influence of diverse parameters on the stability behavior of the reinforced concrete shell is also discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.342-342
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• 2011

산화막은 반도체 공정 중 가장 핵심적이며 기본적인 물질이다. 반도체 소자에서 내부의 캐리어들의 이동을 막고 전기를 절연시켜주는 절연체로서 역할을 하게 된다. 실제로 제작된 산화막에서는 dangling bond 혹은 내부에 축적되는 charge들의 의해 leakage가 생기게 되고 그에 따라 산화막의 특성은 저하되게 된다. 내부에서 특성을 저하시키는 defect을 감소시키기 위해 Plasma Treatment에 따른 특성변화를 관찰하였다. 본 연구에서는 최적화 시킨 Flexible TFT제작을 위해 저온에서 Silicon Oxide로 형성한 Gate Insulator에 각각 N2O, H2, NH3가스를 주입 후 Plasma처리를 하였다. 특성화 시킨 Gate Insulator를 이용하여 MIS(Metal-Insulator-Semiconductor)구조를 제작 후 C-V curve특성변화, Dit의 감소, Stress bias에 따른 stability를 확인 하였다.

• Journal of Korean Society for Atmospheric Environment
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• v.9 no.E
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• pp.358-363
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• 1993

Total particulate mater (TPM), $NO_2$ and $NH_3$ were measured simultaneously in the smoking and non-smoking locations during an eleven month period from March 1986 to January 1987 at three sites in Chicago : Illinois Institute of Technology Cafeteria, Rush-Presbyterian St. Lukes Medical Center Cafeteria and a downtown office building. From this study, the mean concentrations of $NO_2$ and $NH_3$ were not significantly different between the smoking and non-smoking locations at any sampling site ; however, there was a statistical difference for TPM between the smoking and non-smoking locations. Activity factor was useful for describing the contribution from indoor source. The linear regression analysis was reasonable method for discriminating the individual contribution of source to determine the emission factor. The TPM emission factor determined from this technique was in good agreement with value from the literature.