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THE DEVELOPMENT OF A LOW NOISE 230 GHZ SIS RECEIVER IN NAGOYA UNIVERSITY
XIAO K. C.,OGAWA H.,FUKUI Y.,SUZUKI H. The Korean Astronomical Society 1996 Journal of The Korean Astronomical Society Vol.29 No.suppl1
A 230 GHz SIS tunnel junction receiver has been being developed for radio astronomy in Nagoya University. In this heterodyne receiver, we use a $\~$1/3 reduced hight rectangular waveguide SIS mixer with two tuning elements as front end. The mixer block with SIS junction was cooled to 4K with a closed cycle He-gas refrigerator. So far, a double sideband receiver noise temperature lower than l00K in 222-237 GHz is obtained. The receiver exhibits a best DSB noise temperature of 69K at 236 GHz as well as 228 GHz.
Kinetics studies of dimethyl carbonate synthesis from urea and methanol over ZnO catalyst
Wei Wei,Junliang Zhang,Feng Wang,Fukui Xiao,Yuhan Sun 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.6
A kinetic experiment of dimethyl carbonate (DMC) synthesis by urea methanol over ZnO catalyst was carried out in an isothermal fixed-bed reactor. A kinetic model based on the mole fraction was proposed and the kinetic parameters were estimated from the experimental results. The model predictions were compared with the experimental data and fair agreements were found. The effects of the reaction temperature (443-473 K), space time (0-4.7 h mol−1kgcat) and urea mass percent (5-9%) in feed on DMC mole fraction were investigated. It was found that the reactions are mainly influenced by the reaction temperature and space time rather than urea mass percent in feed. The experimental and simulated results indicated that the reaction from MC to DMC was the rate-controlling step in the DMC synthesis process from urea and methanol. It is important to remove the DMC and byproduct ammonia to achieve a high selectivity of DMC. This implies that reactive distillation might be used in the DMC synthesis on an industrial scale to achieve a higher selectivity of DMC.