• 멤브레인
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• 제17권4호
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• pp.345-351
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• 2007

본 연구에서는 선택적 Gas-Liquid Contactor의 성능을 향상시키기 위하여 polyethersulfone(PES), polysulfone(PSf), polyvinylidenefluoride (PVDF) 등의 막에 $F_2$ gas를 이용하여 표면개질하였다. 표면개질된 막의 특성을 알아보기 위해 SEM, 표면접촉각, XPS, 물 투과 최소 압력 실험을 수행하였다. SEM 측정으로부터 막의 표면형태를 살펴본 결과 불소처리 시간이 증가함에 따라 막 표면의 roughness가 증가함을 알 수 있었다. 표면불소화한 막 표면에 $-CF_2$, $-CF_3$의 perfluoro group이 화학적으로 결합되어 막의 소수성이 증가된 것으로 나타났다. 또한 표면접촉각 및 물 투과 최소 압력 실험으로부터 표면불소화 처리시간이 증가함에 따라 측정값이 증가하여 막의 특성이 향상됨을 알 수 있었다.

• 한국농공학회지
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• 제38권1호
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• pp.116-127
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• 1996

This paper dealt with FEM analysis of foundation improved with pack drain. The theory on pack drain was scrutinized and observed values in the field were compared with numerical results. Work site of Kwangyang container pier was selected as a ease study in which measurement of settlement and pore water pressure was accurately carried out. Biot's consolidation equation was selected as governing One, coupled with modified Camclay model as constitutive one. Christian and Boehmer's numerical technique was adopted. Behavior of foundation with pack drain is not simple but very complicated. Discontinuity resulted from rigidity difference between adjacent materials, smear effect and complicated boundary conditions should be considered in the behavior analysis of foundation behavior. The results of numerical analysis were influenced by smear zone. In relevant to this effect, finite element analysis was carried out using the reduced horizontal coefficient of permeability in the smear zone; The numerical results were compared with observed values in surface settlement. including pore water pressure. However only lateral di5plaoement by numerical ana1Ysis was shown since its measurement was not performed in the field. The predication of settlement to be developed later can be effectively employed for the obtimization of construction. The predication of residual settlement using the data measured in the field was made by Hoshino, Asaoka and hyperbolic method. Among them, the hyperbolic method proved best one. Settlements accorded well between numsrical and observed values while pore pressure showed a slight difference. Lateral displacement showed largest values at constant distance from ground surface. The validation of foundation analysis improved with pack drain by computer program employed in this study selecting modified Cam-clay model was satisfactorily secured.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.185-185
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• 2011

ZnTe semiconductor is very attractive materials for optoelectronic devices in the visible green spectral region because of it has direct bandgap of 2.26 eV. The prototypes of ZnTe light emitting diodes (LEDs) have been reported [1], showing that their green emission peak closely matches the most sensitive region of the human eye. Another application to photovoltaics proved that ZnTe is useful for the production of high-efficiency multi-junction solar cells [2,3]. By using the pulse laser deposition system, ZnTe thin films were deposited on ZnO thin layer, which is grown on (0001) Al2O3substrates. To produce the plasma plume from an ablated ZnO and ZnTe target, a pulsed (10 Hz) YGA:Nd laser with energy density of 95 mJ/$cm^2$ and wavelength of 266 nm by a nonlinear fourth harmonic generator was used. The laser spot focused on the surface of the ZnO and ZnTe target by using an optical lens was approximately 1 mm2. The base pressure of the chamber was kept at a pressure around $10^{-6}$ Torr by using a turbo molecular pump. The oxygen gas flow was controlled around 3 sccm by using a mass flow controller system. During the ZnTe deposition, the substrate temperature was $400^{\circ}C$ and the ambient gas pressure was $10^{-2}$ Torr. The structural properties of the samples were analyzed by XRD measurement. The optical properties were investigated by using the photoluminescence spectra obtained with a 325 nm wavelength He-Cd laser. The film surface and carrier concentration were analyzed by an atomic force microscope and Hall measurement system.

• International Journal of Air-Conditioning and Refrigeration
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• 제13권1호
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• pp.51-60
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• 2005

This paper reviews the studies on the pressure drop and the heat transfer in microchannels. Although a lot of studies about the single-phase flow have been done until now, conflicting results are occasionally reported about flow transition from laminar flow to turbulent flow, friction factor, and Nusselt number. Some studies reported the early flow transition due to relatively greater wall effect like surface roughness, but the other studies showed that the flow transition occurred at the Reynolds number of about 2300 and the early flow transition might be due to less accurate measurement of the channel geometry. Also, there have been arguments whether the conventional relation based upon continuum theory can be applied to the fluid flow and the heat transfer in microchannels without modification or not. The studies about the two-phase flow in microchannels have been mostly about investigating the flow pattern and the pressure drop in rectangular channels using two-component, two-phase flow like air/water mixture. Some studies proposed correlations to predict two-phase flow pressure drop in microchannels. They were mostly based on Lockhart-Martinelli model with modification on C-coefficient, which was dependent on channel geometry, Reynolds number, surface tension, and so on. Others investigated the characteristics of flow boiling heat transfer in microchannels with respect to test parameters such as mass flux, heat flux, system pressure, and so on. The existing studies have not been fully satisfactory in providing consistent results about the pressure drop and the heat transfer in microchannels. Therefore, more in-depth studies should be done for understanding the fundamentals of the transport phenomena in the microchannels and giving the basic guidelines to design the micro devices.

• 센서학회지
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• 제27권6호
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• pp.397-402
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• 2018

Proper seat design is critical to the safety, comfort, and ergonomics of automotive driver's seats. To ensure effective seat design, quantitative methods should be used to evaluate the characteristics of automotive seats. This paper presents a system that is capable of simultaneously monitoring body pressure distribution and surface deformation in a textile material. In this study, a textile-based capacitive sensor was used to detect the body pressure distribution in an automotive seat. In addition, a strain gauge sensor was used to detect the degree of curvature deformation due to high-pressure points. The textile-based capacitive sensor was fabricated from the conductive fabric and a polyurethane insulator with a high signal-to-noise ratio. The strain gauge sensor was attached on the guiding film to maximize the effect of its deformation due to bending. Ten pressure sensors were placed symmetrically in the hip area and six strain gauge sensors were distributed on both sides of the seat cushion. A readout circuit monitored the absolute and relative values from the sensors in realtime, and the results were displayed as a color map. Moreover, we verified the proposed system for quantifying the body pressure and fabric deformation by studying 18 participants who performed three predefined postures. The proposed system showed desirable results and is expected to improve seat safety and comfort when applied to the design of various seat types. Moreover, the proposed system will provide analytical criteria in the design and durability testing of automotive seats.

• 한국결정성장학회지
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• 제6권3호
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• pp.406-414
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• 1996

본 연구에서는 금속타겟을 이용한 반응성 스퍼터링법을 이용하여 PZT 박막 증착후 냉각시 산소분압에 따른 박막의 상형성 거동 및 전기적 특성에 미치는 영향을 고찰하였다. 냉각시 산소분압의 감소에 따라 박막 표면의 휘발에 기인하여 표면거칠기는 증가하였고 입성장은 거의 일어나지 않았다. 산소분압이 증가할수록 각형비가 보다 우수한 hysteresis 특성을 얻을 수 있었고 산소분압이 감소함에 따라 remanent polarization과 retained polarization이 감소하였으며, 항전계의 감소가 관찰되었다. 산소분압에 따른 유전율-전압 특성 측정에서 산소분입이 감소함에 따라 internal bias field의 증가가 관찰되었으며, 유전율도 조금씩 감소하였다. Field accelerated retention 시험결과 냉각시 산소분압이 감소함에 따라 nonswitched polarization의 증가가 관찰되었고 bias time이 증가함에 따라 nonswitched polarization이 감소하였다.

• 한국유체기계학회 논문집
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• 제11권6호
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• pp.31-37
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• 2008

Film cooling effectiveness on the convergent or divergent channel was measured by pressure sensitive paint technique. The channel convergent or divergent angle was changed from $-5^{\circ}$ to $10^{\circ}$ and the tested blowing ratios were 0.5, 1 and 2. Results showed that the film cooling effectiveness on the convergent channel was not much affected by the convergent angle. With divergent film cooled surface, the film cooling effectiveness near the injection hole decreased as the divergent angle increases. However, the film cooling effectiveness at far downstream from the hole showed opposite trend. For the non-film cooled surface inclined case, the film cooling effectiveness was not much affected by the divergent angle.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 센서 박막재료 반도체재료 기술교육
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• pp.86-89
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• 2002

We give pressure stimulation into organic thin films and then manufacture a device under the accumulation condition that the state surface pressure is 10[mN/m]. In processing of a device manufacture, we can see the process is good from the change of a surface pressure for organic thin films and transfer ratio of area per molecule. The structure of manufactured device is Au/Poly-${\gamma}$ Benzyl $_D$-Glutamate/Al and Au/Poly-${\gamma}$ Benzyl $_D$-Glutamate/Au; the number of accumulated layers is 1, 3, 5 and 7. Also, we then examined of the MIM device by means of I-V. The I-V characteristic of the device is measured from 0 to +2[V]. We determined electrochemical measurement by using cyclic voltammetry with a three-electrode system. LB film accumulated by monolayer on an ITO. In the cyclicvoltammetry, An Ag/AgCl reference electrode, a platinum wire counter electrode and LB film-coated ITO working electrode measured in $LiBF_4$ solution, stable up to 0.9V vs. Ag/AgCl.

• 한국유체기계학회 논문집
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• 제2권4호
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• pp.40-47
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• 1999

A hot water layer (HWL hereinafter) was installed at the depth of 1.2 m from the pool surface to reduce the radiation level at the pool top. After the HWL system was improved by the replacement of the filter with the Ion Exchanger to capture the Na-24, to purify the pool water of HWL and finally to reduce the radiation at the pool top. It was confirmed by the performance test of the pump and the measurement of the pressure difference through the Ion Exchanger and the strainer, that the flow characteristics of HWL system was not adversely affected after the system modification. Also the flow analysis using the pressure loss coefficients of the Ion Exchanger and strainer, calculated by the Darcy formula, could predict the flow variations by pressure changes within $10\%$ error in comparison with the field test results. It was also confirmed that HWL was maintained with the depth of 1.2 m from the pool surface because each electric water heater was electrically and thermodynamically maintained at 30 kW and the temperature of HWL was maintained with $5^{\circ}C$ higher temperature than that of pool water. Finally, it was confirmed that the pool top radiation was saturated and stabilized below 10000 nG/hr within 24 hours as the ion exchanger captured the main nucleus, Na-24 and purified the pool water of HWL.

• Wind and Structures
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• 제13권2호
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• pp.127-144
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• 2010

Pressure measurements on static and autorotating flat plates have been recently reported by Lin et al. (2006), Holmes, et al. (2006), and Richards, et al. (2008), amongst others. In general, the variation of the normal force with respect to the angle of attack appears to stall in the mid attack angle range with a large scale separation in the wake. To date however, no surface pressures have been measured on auto-rotating plates that are typical of a certain class of debris. This paper presents the results of an experiment to measure the aerodynamic forces on a flat plate held stationary at different angles to the flow and allowing the plate to auto-rotate. The forces were determined through the measurement of differential pressures on either side of the plate with internally mounted pressure transducers and data logging systems. Results are presented for surface pressure distributions and overall integrated forces and moments on the plates in coefficient form. Computed static force coefficients show the stall effect at the mid range angle of attack and some variation for different Reynolds numbers. Normal forces determined from autorotational experiments are higher than the static values at most pitch angles over a cycle. The resulting moment coefficient does not compare well with current analytical formulations which suggest the existence of a flow mechanism that cannot be completely described through static tests.