Air blower has been widely used in many industrial fields such as wind tunnel and large ventilation systems. Its performance is affected by operating conditions and system geometry of inpeller and duct, and these design parameter optimization is essential for the effective development. CFD analysis is carried out to investigate the air flow field characteristics with outlet total pressure in a blower system. Intake air into the impeller blade through the inlet is compressed, and then gradually discharged from the outlet with ascending total pressure, and predicted results are compared with test data. Especially this overall pressure difference in the blower system severely depends on the flow rate. These results are expected to be used as applicable design data for blower performance improvement.

Transparent conductive tungsten (W) doped indium oxide (In2O3; IWO) films were deposited at different substrate bias voltage (-Vb) conditions at room temperature on glass substrates by radio frequency (RF) magnetron sputtering and the influence of the substrate bias voltage on the optical and electrical properties was investigated. As the substrate bias voltage increased to -350 Vb, the IWO films showed a lower resistivity of 2.06 × 10-4 Ωcm. The lowest resistivity observed for the film deposited at -350 Vb could be attributed to its higher mobility, of 31.8 cm2/Vs compared with that (6.2 cm2/Vs) of the films deposited without a substrate bias voltage (0 Vb). The highest visible transmittance of 84.1 % was also observed for the films deposited at the -350 Vb condition. The X-ray diffraction observation indicated the IWO films deposited without substrate bias voltage were amorphous phase without any diffraction peaks, while the films deposited with bias voltage were polycrystalline with a low In2O3 (222) diffraction peak and relatively high intensity (431) and (046) diffraction peaks. From the observed visible transmittance and electrical properties, it is concluded that the opto-electrical performance of the polycrystalline IWO film deposited by RF magnetron sputtering can be enhanced with effective substrate bias voltage conditions.

PURPOSES : Roller-compacted concrete pavement (RCCP) is a superstiff-consistency concrete pavement that exhibits excellent strength development owing to a hydration reaction and interlocking aggregates owing to the roller compaction. A zero-slump concrete mixture is generally used. Hence, it is important to control the consistency of the RCCP mixture to prevent the deterioration of the construction quality (such as material separation during paving). The workability of the RCCP is characterized by its consistency and controlled by the Vebe time, whereas a conventional concrete pavement is controlled based on the slump test. The consistency of the RCCP changes over time after concrete mixing owing to delivery, construction time delays, etc. Thus, it is necessary to use the optimum Vebe time to achieve the best construction quality. Therefore, this study aims to develop a Vebe time prediction model for efficiently controlling the consistency of RCCPs according to random time variations. METHODS : A Vebe time prediction model was developed using a multiple linear regression analysis. A dataset of 131 samples was used to develop the model. The collected data consisted of variables with large potential effects on the consistency of the RCCP, such as the water-cement ratio (W/C), sand/aggregate ratio (S/a), water content (ω), water content per unit volume (W), cement (C), fine aggregate (S), coarse aggregate (G), water reducing admixtrue (PNS), air-entraining admixture (AE), delay time (T), air temperature (TEM), and humidity (HUM). In the multiple linear regression analysis, the mentioned parameters were used as the independent variables, and the Vebe time was the dependent variable. The Vebe time prediction models were evaluated by considering the adjusted R2 and p-values. The selection of the model was based on the largest R2 value and an acceptable p-value (p<0.05). RESULTS : The Vebe time prediction model achieved an adjusted R2 value of 64.14% with a significance level (p-value) of less than 0.05. This shows that the predictive model is adequately described for the dependent variable, and that the model is suitable for Vebe time predictions. Moreover, the significance level of the independent variables is less than 0.05, indicating significant effects on the Vebe time (i.e., the dependent variable). CONCLUSIONS : The Vebe time prediction model developed in this study can be used to estimate Vebe times with an R2 of 63.33% between the measured and predicted values. The proposed Vebe time prediction model is expected to be effectively utilized for the quality control of RCCP mixtures. Moreover, it is expected to contribute to achieving good RCCP construction quality.

To improve ferroelectric properties of PZT, many studies have attempted to fabricate dense PZT films. The AD process has an advantage for forming dense ceramic films at room temperature without any additional heat treatment in low vacuum. Thick films coated by AD have a higher dielectric breakdown strength due to their higher density than those coated using conventional methods. To improve the breakdown strength, glass (SiO2-Al2O3-Y2O3, SAY) is mixed with PZT powder at various volume ratios (PZT-xSAY, x = 0, 5, 10 vol%) and coating films are produced on silicon wafers by AD method. Depending on the ratio of PZT to glass, dielectric breakdown strength and energy storage efficiency characteristics change. Mechanical impact in the AD process makes the SAY glass more viscous and fills the film densely. Compared to pure PZT film, PZT-SAY film shows an 87.5% increase in breakdown strength and a 35.3 % increase in energy storage efficiency.

휘어지며 투명한 전자기기의 개발을 위해서 최근 유기반도체, 탄소기반 나노소재, 금속산화물 반도체등의 다양한 신소재 반도체 개발에 대한 연구가 관심을 받으며 지속적으로 발전하고 있다. 그러나, 이러한 신소재 반도체 기술의 꾸준하고 지속적인 발전에도 불구하고 트랜지스터를 구성하는 주요 소재중 하나인 유전체에 대한 연구는 반도체의 개발속도에 크게 미치지 못하여, 기계적인 휘어짐의 특성을 갖추고, 높은 캐패시턴스와 좋은 누전전류 특성을 갖는 새로운 유전체 개발에 대한 요구가 지속적으로 커지고 있다. 이에 본 연구는 저전압에서 구동 가능한 박막트랜지스터를 위한 유기-무기 하이브리드소재 박막을 개발하며 이를 저전압 구동이 가능한 유기박막트랜지스터에 적용하였다. 상대적으로 높은 유전상수를 갖는 염화하프늄 (HfO2)과 소수성기를 갖고 있으며 금속산화물과 공유결합이 가능한 실란산 기반의 유기물 (octadecyltrimethoxysilane)을 혼합한 전구체 용액을 합성하며 상대적으로 낮은 온도에서 열처리를 통해 얻을 수 있었다. 제조된 하이브리드 게이트 유전체 박막은 우수한 절연 및 유전체 특성과 함께 소수성 표면 특성을 가질 수 있었고 펜타센 유기박막트랜지스터로 응용하여 저전압에서 구동이 되며 우수한 트랜지스터 성능을 갖는 소자를 개발하였다.

High voltage impulse (HVI) has been gained attention as an alternative technique that could control the CaCO3 scale problems encountered in water main, pipe, cooling tower and heat exchanger vessels. The aim of this study was to investigate the effect of electric field (E) and contact time (t) of HVI on reduction of Ca2+ concentration at two different temperatures of 25℃ and 60℃. A kinetic model on the effect of E and t was investigated too. As the E and t increased, the Ca2+ concentration decreased more than that of the control (= no HVI). The Ca2+ concentration decreased up to 81% at 15 kV/cm at 60℃, which was nearly 2 times greater than the control. With these experimental data-set of reduction of Ca2+ concentration under different E and t, the kinetic model was developed. The relationship between E and t required to reduce the concentration of Ca2+ by 30% was modeled at each temperature. The empirical model equations were; E0.83· t = 60.3 at 25℃ and E0.08· t = 1.1 at 60℃. These equations state the products of En and t is always constant, which means that the required contact time can be reduced in accordance with the increment of E and vice versa.

Although membrane bio-reactor (MBR) has been widely applied for wastewater treatment plants, the membrane fouling problems are still considered as an obstacle to overcome. Thus, many studies and commercial developments on mitigating membrane fouling in MBR have been carried out. Recently, high voltage impulse (HVI) has gained attention for a possible alternative technique for desalting, non-thermal sterilization, bromate-free disinfection and mitigation of membrane fouling. In this study, it was verified if the HVI could be used for mitigation of membrane fouling, particularly the internal pore fouling in MBR. The HVI was applied to the fouled membrane under different conditions of electric fields (E) and contact time (t) of HVI in order to investigate how much of internal pore fouling was reduced. The internal pore fouling resistance (Rf) after HVI induction was reduced as both E and t increased. For example, Rf decreased by 19% when the applied E was 5 kV/cm and t was 80 min. However, the Rf decreased by 71% as the E increased to 15 kV/cm under the same contact time. The correlation between E and t that needed for 20% of Rf reduction was modeled based on kinetics. The model equation, E1.54t = 1.2 × 103 was obtained by the membrane filtration data that were obtained with and without HVI induction. The equation states the products of En and t is always constant, which means that the required contact time can be reduced in accordance with the increase of E.

The ion-beam irradiated lanthanum zinc oxide (LZO) films were conducted as liquid crystal (LC) alignment layer to achieve uniform and homogeneous alignment of LC molecules. Polarized optical microscopy and the pre-tilt angle measurements revealed the alignment characteristics of LC molecules on the LZO film surface. Physical characteristics of the LZO film surface were analyzed by field emission scanning electron microscope and atomic force microscopy. The strong ion-beam irradiation on the LZO film changed surface rougher than before and induced physical anisotropic characteristics. Chemical composition of the LZO film was investigated by X-ray photoelectron spectroscopy and it was revealed that the ion-beam irradiation induced the breakage of the metal-oxide bonds. Due to this, anisotropic dipole moment which related with van der Waals force between LC molecules and alignment layer was induced. Because of this, LC molecules were anchored to the LZO film surface to achieve uniform LC alignment. Collecting the capacitance-voltage curve, residual DC of the LC cell with the LZO films was measured and it was verified that the LC cell with the LZO film had a nearly zero residual DC. Therefore, the ion-beam irradiated LZO film is an efficient method as an LC alignment layer

High voltage impulse(HVI) has been gained attention as an alternate technique controlling CaCO3 scale formation. Investigation of key operational parameters for HVI is important, however, those had not been reported yet. In this study, the effect of temperature and applied voltage of HVI on Ca2+ concentration was studied. As the applied voltage from 0 to 15kV and the temperature increased from 20 to 60°C, the Ca2+ concentration decreased, indicating that the aqueous Ca2+ precipitated to CaCO3. The Ca2+ concentration decreased up to 81% under the condition of 15kV and 60°C. Rate constant for the precipitation reaction, k was determined under different temper1ature and voltage. The reaction rate constant under the 15kV and 60°C condition was evaluated to 66☓10-3 L/(mmol·hr), which was 5 times greater than the k of the reaction without HVI at same temperature. The increases in k by HVI at higher temperature region(40 to 60°C) was much greater than at lower temperature region(20 to 40°C), which implies temperature is more important parameter than voltage for reducing Ca2+ concentration at high temperature region. These results show that the HVI induction accelerates the precipitation to CaCO3, particularly much faster at higher temperature.

본 논문에서는 안정적인 전력공급이 어려운 실제 현장에 적용하기 위해서 PSC 내부 텐던의 긴장력 관리를 위한 저전압 EM센싱기법을 검증하였다. 지난 국내외 PSC 구조물 사고 사례를 볼 수 있듯이, 공용간 구조적 안정성을 확보하기 위해서는 PS텐던의 긴장력 관리가 매우 중요함을 알 수 있었다. 이에 본 논문에서는 EM센서를 통해 탄성-자기이론을 기반한 강자성 체의 자기변형과 응력의 관계를 이용하여 전압 크기에 따른 긴장력에 대한 자기이력곡선을 계측하고자 하였다. 이를 위해 이중 원통코일형태의 EM센서를 제작하고 유압식 인장기를 이용한 PS텐던 인장 실험 장비를 구성하였다. 실험은 단계적으 로 전압을 감소시켜 긴장력 크기에 따른 자기이력곡선의 변화를 계측하면서 최대/최소 전압값에 대한 계측결과에 따른 투자 율의 변화와 긴장력의 관계를 비교·분석하였다. 그 결과, 전압이 감소하여 자기장의 크기가 작아짐에 따라 추정식에 대한 상수는 상이하지만 유사한 형태의 자기이력곡선 투자율의 변화를 확인할 수 있었다. 이를 통해 본 연구에서는 저전압 상태에 서 EM센싱기법을 이용한 PSC 내부 텐던에 대한 긴장력 관리가 가능할 것으로 판단된다.

In this paper, we investigate the relationship between fuel injection quantity and voltage and current energy of Bosch system and Delphi system by measuring the high and low voltage waveform, current waveform, fuel injection quantity and fuel pressure of A and J-engines. Waveform measurements are made using the PICO scope and the CDS tester. The injectors of A and J engines were tested under no load condition using injector with normal fuel injection quantity, injector with small fuel injection quantity and injector with many fuel injection quantity. In case of normal injector, A-engine has higher fuel pressure, injection interval time, voltage energy, and current energy than J-engine. The current energy of the A-engine changed linearly compared to that of the J-engine. For over and under injectors, the change in the previous physical quantity was greater for the A-engine than for the J-engine. However, the duration time of maintaining to open the injector is controlled differently, and so the voltage and current energy values are changed, and the change of the current energy is larger than the voltage energy.

In this study, a membrane electrode assembly(MEA) composed of three electrodes(anode, cathode, and reference electrode) is designed to investigate the effects of methanol concentration on the overpotentials of anode and cathode in direct methanol fuel cells(DMFCs). Using the three-electrode cell, in-situ analyses of the overpotentials are carried out during direct methanol fuel cell operation. It is demonstrated that the three-electrode cell can work effectively in transient state operating condition as well as in steady-state condition, and the anode and cathode exhibit different overpotential curves depending on the concentration of methanol used as fuel. Therefore, from the real-time separation of the anode and cathode overpotentials, it is possible to more clearly prove the methanol crossover effect, and it is expected that in-situ analysis using the three-electrode cell will provide an opportunity to obtain more diverse results in the area of fuel cell research.

본 연구에서는 가변 통기성 스마트 의류의 제작을 위해 필요한 형상기억합금 액추에이터의 작동 조건을 파악하였다. 의복의 개방, 폐쇄와 같은 양방향 작동 시 형태 변형 시에만 전력을 소모하는 저전력 소모 액추에이터 개발을 위해 복수 채널의 일방향 형상기억합금을 이용하여 스위치로 작동되는 액추에이터를 설계하였으며 가장 효율적으로 작동할 수 있는 와이어의 직경과 전압인가 단위시간을 도출하였다. 선행연구 결과 도출된 양방향 작동이 가능한 일방향 형상기억합금의 직경 범위 내에서 Arduino 스위치를 제작하여 3.7V 전압인가 시 변화량을 분석한 결과 0.4Φ의 액추에이터가 가장 적합한 것으로 나타났다. 0.4Φ 형상기억합금와이어를 사용한 양방향작동 액추에이터의 개방, 폐쇄에 필요한 최적전압인가 시간을 도출하기 위해 액추에이터의 최대개방, 최소폐쇄 도달 전압인가 시간으로부터 50ms씩 감소, 증가 시키며 냉각 후 액추에이터의 내경을 비교하는 방식으로 측정한 결과 개방 동작에 필요한 최적 전압인가 단위시간은 4,100ms로 나타났다. 각 채널간의 발열에 의한 간섭을 최소화하기 위한 양방향간 작동 시 필요 딜레이 분석을 위해 상온에서 형상기억합금에 최적 전압입가 시간인 4.1초 동안 전원을 공급하고 가열 후 냉각까지의 과정을 열화상카메라로 촬영하여 형상기억합금 와이의 온도가 냉각시의 상변태온 이하로 하강하는 시점을 파악한 결과, 액추에이터의 양방향간 작동 딜레이는 1.8초 이상이 확보되어야 함을 파악할 수 있었다.

본 연구에서는 이온교환막을 결합한 막 결합형 축전식 탈염공정으로 적용하여 진행하였다. 막 결합형 축전식 탈염공정에서 흡착전압과 이온교환막의 두께가 흡착성능에 미치는 영향을 알아보았다. 흡착전압을 0.5, 1, 1.4 V로 달리하였고 흡착전압이 증가함에 따라 강한인력으로 인해 많은 이온들의 흡착으로 배출수 농도의 최소점이 낮아지고 전극이 포화상태가 되기까지의 운전시간이 증가하였다. 이온교환막의 두께를 1, 2, 3회로 코팅횟수를 달리하였고 막이 두꺼울수록 막 내에서 이온들의 움직임이 원활하지 않아 감소된 흡착성능을 확인하였다. 이온교환막의 적합한 두께는 1회 코팅했을 때 3.85 ㎛의 두께를 보였다.

즉석조리식품 제품의 포장 후(in-package) 미생물 저해 기술로 대기압 콜드 플라스마에 대한 연구가 활발하게 진행되고 있다. 본 연구에서는 대기압 유전체 장벽 방전 콜드 플라스마(atmospheric dielectric barrier discharge cold plasma, ADCP)를 이용하여 코팅된 닭 가슴살 시료의 색도에 영향을 미치지 않고 Salmonella 저해를 최적화시키는 처리 전압과 시간을 결정하였다. 닭 가슴살을 삶은 후 1.5x1.5x1.5 cm의 큐브로 준비한 후 유청 분리 단백질로 코팅하여 처리 시료를 준비하였고 살균된 polyethylene terephthalate 용기 (16.3X12.5x3.5 cm)에 12개의 코팅된 닭 가슴살 큐브 처리 시료를 담고 28, 29, 30, 31, 또는 32 kV 의 처리 전압과 120, 150, 180, 210, 214, 또는 240초 처리하였다. 모든 ADCP 처리에서는 처리 중 45초 간격으로 15초씩 shaking이 이루어졌다. 32 kV에서 닭 가슴살 시료에 절연파괴(dielectric breakdown, arc)가 발생했으나 arc 발생은 닭가슴살 시료의 색 변화를 일으키지 않았다. 29, 30, 그리고 31 kV의 처리 또한 닭 가슴살 큐브의 색도에 유의적인 영향을 미치지 않았다(p>0.05). Salmonella 저해율은 처리 전압이 29, 30, 그리고 31 kV 일 때 1.5 0.1, 1.4 0.2, 그리고 1.9 0.0 log CFU/cube이었으며 31 kV 에서 ADCP 처리가 29, 30 kV에서 처리 보다 닭 가슴살 시료의 Salmonella를 더 효과적으로 저해시켰다(p<0.05). 처리 시간을 변수로 하였을 때, 31 kV 에서 180초 처리가 120초, 150초, 210초, 그리고 240초 처리했을 때보다 유의적으로 높은 Salmonella 저해 정도를 보였다(p<0.05). 연구에 사용된 arc를 발생하지 않은 전압과 시간 조건은 색도에 영향을 주지 않으면서 Salmonella를 효과적으로 저해하는 것을 알 수 있었으며 이때 미생물 저해 효과를 보여주는 최대 전압과 시간은 각각 31 kV, 180초로 결정되었다.

Recently, applications of high voltage impulse (hereafter HVI) technique to desalting, sludge solubilization and disinfection have gained great attention. However, information on how the operating condition of HVI changes the water qualities, particularly production of hydroxyl radical (·OH) is not sufficient yet. The aim of this study is to investigate the effect of operating conditions of the HVI on the generation of hydroxyl radical. Indirect quantification of hydroxyl radical using RNO which react with hydroxyl radical was used. The higher HVI voltage applied up to 15 kV, the more RNO decreased. However, 5 kV was not enough to produce hydroxyl radical, indicating there might be an critical voltage triggering hydroxyl radical generation. The concentration of RNO under the condition of high conductivity decreased more than those of the low conductivities. Moreover, the higher the air supplies to the HVI reactor, the greater RNO decreased. The conditions with high conductivity and/or air supply might encourage the corona discharge on the electrode surfaces, which can produce the hydroxyl radical more easily. The pH and conductivity of the sample water changed little during the course of HVI induction.