• 센서학회지
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• 제17권3호
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• pp.162-167
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• 2008

In this paper we report on the electrical properties of carbon fiber which is an attractive material for strain gauges and can also be applied to resonating micro sensors. The carbon fibers used in this research was manufactured from polyactylonitrile (PAN). The fabricated carbon fibers had about $10\;{\mu}m$ in length and several centimeters in length. We employed a micro structure to measure electrical properties of the carbon fiber. The measured electrical resistivity of the carbon fibers were about $3{\times}10^{-3}{\Omega}{\cdot}cm$ A gauge factor of the carbon fiber is also observed with the same system and it was about 400, depending on the structure of the carbon fiber. For the sensor applications of the carbon fiber, it is selectively placed between the gap of Al electrodes using a dielectrophoresis method. When the carbon fiber is resonated by a piezoelectric ceramic, resistance change at a variety of resonance mode was observed through an electrical system.

• 대한기계학회논문집B
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• 제30권8호
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• pp.772-779
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• 2006

Window is a critical component in the design of energy-efficient buildings. To minimize the heat loss, insulation performance of the glazing has to be improved. Manufacturing of vacuum glazing has been motivated by the possibility of making windows of very good thermal insulation properties for such applications. It is made by maintaining vacuum in the gap between two glass panes. Pillars are placed between them to withstand the atmospheric pressure. Edge covers are applied to reduce conduction through the edge. Accurate measurements have been made of the radiative heat transfer, the pillar conduction and the gas conduction using a guarded hot plate apparatus. Vacuum glazing is found to have low thermal conductance roughly below $1W/m^2K$. Among the heat transfer modes of residual gas conduction, conduction through support pillar and the radiative heat transfer between the glass panes, the last one is the most dominant to the overall thermal conductance. Vacuum glazing using very low emittance AI-coated glass has an overall thermal conductance of about $0.7W/m^2K$.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 C
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• pp.941-943
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• 1998

Exploitation of equipment with cross linked polyethylene (XLPE) insulation requires its condition monitoring and diagnostic. Traditionally diagnostics of insulation is carried out by means of partial discharge detection. Many researchers have developed a lot of methods to identify the defect by the PD form. However, such identification of a defect, for example, void, inclusion or treeing, does not say about its danger from a point of view of full insulation gap breakdown and insulation construction failure. The information about the form and size of formed upon high voltage treeing is necessary for prediction of the remained resource of XLPE insulation. For this purpose we carry out experimental research for determination of the dependencies between PD characteristics in XLPE upon time and three dimension PD patterns of corresponding treeing. The investigations were carried out by means of electrical measurement of PD current and simultaneous optical recording of treeing image. Test results show that the PD patterns can be applied for detecting tree growth well.

• 한국철도학회논문집
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• 제10권6호
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• pp.786-791
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• 2007

고속열차의 속도가 300km/h 이상이 되면 난류의 박리나 와류발산 등에 의한 공력소음의 영향이 지배적이 된다. 본 연구에서는 KTX와 한국형고속열차의 외부에서 발생하는 공력소음, 특히 차간 공간에서 발생하는 소음의 특성을 시험을 통해 규명한다. 차량 실내외의 소음 측정을 통해 이 소음의 특성을 분석하였고, 풍동시험을 통해 머드플랩 사이의 틈의 크기가 저주파 소음 발생에 직접적인 영향을 준다는 것을 규명하였다. 또한 마이크로폰어에이 시험으로 고속열차의 외부에서 발생하는 소음의 주파수 특성을 분석하였다.

• 한국진공학회지
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• 제9권2호
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• pp.116-121
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• 2000

Molecular beam epitaxy(MBE)로 성장시킨 $Al_{0.24}Ga$$_{0.76}As/GaAs$ 에피층 구조의 표면 광전압을 측정하였다. 측정된 신호로부터 구한 $Al_{0.24}Ga$$_{0.76} As/GaAs$ 에피층, GaAs 기판 그리고 GaAs 완충층의 밴드갭 에너지는 각각 1.72, 1.40 그리고 1.42 eV이다. 이는 phoareflectance(PR) 측정 결과와 잘 일치하였다 그리고 $Al_{0.24}Ga $_{0.76} As/GaAs$ 에피층이 GaAs기판의 표면 광전압세기 보다 약 3배 정도 작게 나타났는데 이는 캐리어의 이동도 차이로 나타나는 현상으로 해석된다. 또한 표면 광전압의 온도 의존성으로부터 Varshni 식의 계수들을 구하였다.

• 한국자기학회지
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• 제4권2호
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• pp.179-183
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• 1994

자왜 또는 자기이방성의 측정에 사용되는 전자석의 여자전류를 측정에 필요한 수초간만 흘려서 에너지 소모 및 측정시의 최대난점인 시료의 온도변화의 문제를 극소화하였다. 따라서 전자석의 냉각장치는 생략되고 크기와 전원의 용량도 극소화되었다. 공기간격 22 mm, 자극의 단면적 $40{\times}25mm^{2}$에서 0.5 T의 자장발생에는 180 W의 전원으로 족하였다. 시료의 자왜와, 자기이방성에 의한 토크를 전기용량센서에 의하여 측정하여 $10^{-8}$의 자왜분해능과 1 nJ의 토크 분해능을 얻었다. $0.02{\times}0.8{\times}10mm^{2}$의 연자성 리본의 형상이방성을 이용하여 이방성 측정시의 토크값을 교정하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.395-398
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• 2009

Currently, a new generation of ducted fan UAVs (Unmanned Aerial Vehicles) is under development for a wide range of inspection, investigation and combat missions as well as for a variety of civil roles like traffic monitoring, meteorological studies, hazard mitigation etc. The current study presents extensive results obtained experimentally in order to investigate the tip clearance effects on performance characteristics of a ducted fan for small UAV systems. Three ducted fans having different tip clearance gap and with same rotor size were examined under three different yawed conditions of calibrated slanted hot-wire probe. Three dimensional velocity flow fields were measured from hub to tip at outlet of the ducted fan. The analysis of data were done by PLEAT (Phase locked Ensemble Averaging Technique) and three non-linear differential equations were solved simultaneously by using Newton -Rhapson numerical method. Flow field characteristics such as tip vortex and secondary flow were confirmed through axial, radial and tangential velocity contour plots. At the same time, the effects of tip clearance on axial thrust and input power were also investigated by using wind tunnel measurement system. For enhancing the performance of ducted fan, tip clearance level should be as small as possible.

• Journal of Information Display
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• 제7권1호
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• pp.25-29
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• 2006

By the voltage threshold (Vt) close-curve measurement method, the changes in the discharge characteristics such as a firing voltage and IR emission among the three electrodes were examined relative to the low or high panel temperature ranging from -10 to $80^{\circ}$. The variation in the panel temperature was found significantly influence the surface discharge between the MgO surfaces rather than the plate gap discharge between the MgO and phosphor layers. Based on this experimental observation, a modified reset waveform that alleviates the surface discharge during a ramp-up and -down period was deeloped. By adopting the proposed reset waveform, a stable address discharge could be obtained irrespective of the panel temperature variation.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.7-12
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• 2006

The high efficacy concept, featuring in this study an auxiliary electrode and a 200 ${\mu}m$ coplanar gap, is applied to AC-PDPs with a stripe - type and a closed - type barrier rib, respectively. The roles of the pulses applied to the auxiliary electrode create additional excitation during the sustain period and reduce a discharge current that flows into the display cells. The efficacy of the proposed panel with the closed barrier rib has maximum values when the auxiliary pulse voltage is 50 volts and 80 volts for the Ne+4%Xe and Ne+20%Xe gas-mixtures, respectively. The maximum luminous efficacy is more than 10 lm/W in terms of the measurement of the discharges in VGA resolution ($540{\mu}m{\times}720{\mu}m$) and the green cells.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.239-242
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• 2004

A stoichiometric mixture of evaporating materials for $CdIn_2S_4$ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, $CdIn_2S_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by hot wall epitaxy(HWE) system. The source and substrate temperatures were $630^{\circ}C$ and $420^{\circ}C$ respectively. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction(DCXD). The carrier density and mobility of $CdIn_2S_4$ single crystal thin films measured from Hall effect by van der Pauw method are $9.01{\times}10^{16}\;cm^{-3}$ and $219\;cm^2/V{\cdot}s$ at 293 K, respectively. From the optical absorption measurement, the temperature dependence of energy band gap on $CdIn_2S_4$ single crystal thin films was found to be $E_g(T)\;=\;2.7116\;eV\;-\;(7.74{\times}10^{-4}\;eV)T^2/(T+434)$. After the as-grown $CdIn_2S_4$ single crystal thin films was annealed in Cd-, S-, and In-atmospheres, the origin of point defects of $CdIn_2S_4$ single crystal thin films has been investigated by the photoluminescence(PL) at 10 K.