In this work, we have designed a novel gas inlet structure for efficient usage of growth and doping precursors. Our previous gas injection configuration is that the gas is mixed to one pipe first, then divided into two pipes, and finally entered the chamber symmetrically above the substrate without a jet nozzle. The distance between gas inlet and substrate is about 14.75 cm. Our new design is to add a new tube in the center of the susceptor, and the distance between the new tube and substrate is about 0.5 cm. In this new design, different gas injection configurations have been planned such that the gas flow in the reactor aids the transport of reaction species toward the sample surface, expecting the utilization efficiency of the precursors being improved in this method. Experiments have shown that a high doping efficiency and fast growth could be achieved concurrently in diamond growth when methane and diborane come from this new inlet, demonstrating a successful implementation of the design to a diamond microwave plasma chemical vapor deposition system. Compared to our previous gas injection configuration, the growth rate increases by 15-fold and the boron concentration increases by ~ 10 times. COMSOL simulation has shown that surface reaction and precursor supply both have a change in determining the growth rate and doping concentration. The current results could be further applied to other dopants for solving the low doping efficiency problems in ultra-wide-band-gap semiconductor materials.

In this paper, numerical simulations are performed for the drying process of potato chip in a microwave oven with multiple waveguides, with the purpose of enhancing the uniformity in temperature distribution. A simulation model is built and simulated using COMSOL Multiphysics software. The simulation model uses 5 different positions of waveguides to see whether it affects the heat distribution in the material. In order to know the final temperature result of the material after it comes out of the cavity on a moving conveyor belt, the average temperature values along the direction of the conveyor belt motion are calculated and plotted. From the results, the best waveguide position is determined to get the best temperature distribution in the potato chips.

Unreported dielectrics based on the binary system of MgO-SiO2 were investigated as potential candidates for microwave dielectric applications, particularly those demanding a high fired density and high quality factors. Extensive dielectric compositions having different molar ratios of MgO to SiO2, such as 2:1, 3:1, 4:1, and 5:1, were prepared by conventional solid state reactions between MgO and SiO2. 1 mol% of V2O5 was added to aid sintering for improved densification. The dielectric compositions were found to consist of two distinguishable phases of Mg2SiO4 and MgO beyond the 2:1 compositional ratio, which determined the final physical and dielectric properties of the corresponding composite samples. The increase of the ratio of MgO to SiO2 tended to improve fired density and quality factor (Q) without increasing grain size. As a promising composition, the 5MgO.SiO2 sample sintered at 1400 ˚C exhibited a low dielectric constant of 7.9 and a high Q × f (frequency) value of ~99,600 at 13.7 GHz.

In the reaction of gas-solid phases, the microwave energy plays a role as a catalyst, because it causes friction between adjacent molecules and enables an unique characteristics of interior heating of the materials. When the dipole gases are adsorbed inside of the pore of carbon materials, the gases are decomposed by the microwave energy and reacted with the carbon atoms. Using this principle, we could make the activated carbon from coconut shell within 20 minute, and this residence time for activation is about 1/16 of rotary kiln. The BET surface area of activated carbon made by microwave is about 1,100m2/g similar to conventional method of rotary kiln. In this study, the power of microwave generator was 400~1000W, and the gas for activation was steam mainly.

페르브스카이트 구조를 갖는 CaTiO3-La(Zn12/Ti12)O3계에서 소결 온도와 소결 시간의 증가에 따른 ZnO의 휘발과 이에 따른 고주파 유전 특성에 대하여 조사하였다. 시편 내부를 WDS 분석한 결과 위치에 따른 ZnO의 농도차를 관찰할 수 있었고, 시편의 두께를 달리하여 QxfO 값을 조사한 결과 ZnO가 많이 휘발된 가장자리에서 더 높은 QxfO 값을 얻을 수 있었다. 0.535CaTiO3-0. 465La(Zn12/Ti12/)O3몰비로 1550˚C, 2시간동안 합성한 결과 소결 밀도 5.31g/㎤, 유전율 50, Qxf034,000, 온도계수 +8ppm/˚C의 고주파 유전 특성을 갖는 소결체를 얻을 수 있었다.

In this study, global positioning system (GPS)-derived precipitable water vapor (PWV) and microwave radiometer(MWR)-measured integrated water vapor (IWV) were compared and their characteristics were analyzed. Comparingthose two quantities for two years from August 2009, we found that GPS PWV estimates were larger than MWR IWV. Theaverage differenceover the entire test period was 1.1 mm and the standard deviation was 1.2 mm. When the discrepanciesbetween GPS PWV and MWR IWV were analyzed depending on season, the average difference was 0.7 mm and 1.9mm in the winter and summer months, respectively. Thus, the average difference was about 2.5 times larger in summerthan that in winter. However, MWR IWV measurements in the winter months were over-estimated than those in the summermonths as the water vapor content got larger. The results of the diurnal analysis showed that MWR IWV was underestimatedin the daytime, showing a difference of 0.8 mm. In the early morning hours, MWR IWV has a tendency to beover-estimated, with a difference of 1.3 mm with respect to GPS PWV.

電波方向探知器나 레이다 等과 같은 電波航海計器를 갖추기 힘든 小型漁船을 위하여 마이크로波를 利用한 船位位測定方式을 開發하고