Measurement of electrical characteristics of ZnO microvaristors

A measurement technique is developed to measure the characteristics of zinc oxide (ZnO) microvaristors directly. We used Cu wires, a micromanipulator, and an optical microscope to gain ohmic contact of the measurement apparatus with ZnO particles. With our system, the I−V characteristics and C⁻²−V characteristics were measured for 25 µm ZnO microvaristors. Our measurements show that these microparticles behave as varistors. Further measurement on the ZnO microvaristors and observation of their fine structure may help to understand the varistor behavior. It also can pave the way to the understanding of the electrical characteristics of grain boundaries as well as the double Schottky barrier formed at the grain boundaries. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

CFD analysis of the convection flow in the pan during induction heating and gas range heating

One difference between induction heating (IH) and gas range heating (GRH) is that, because the heating location of the pan is different, the convection in the pan is different. In particular, in cooking situations in which solids are mixed with liquids, such as the boiling of soup containing solid foods, the natural convection flow in the pan may affect food quality. The convection in the pan during IH and GRH was analyzed by using computational fluid dynamics (CFD), and the temperature distribution and the flow velocity distribution in the pan were obtained. These results were then compared with the measurement results. In GRH, the heat flux at the wall of the pan was obtained by experiment, and it was used for the analysis as a boundary condition. In IH, the heat generation distribution obtained by electromagnetic field analysis was used for the analysis as the boundary condition. Differences in convection flow in the pan during IH and GRH were observed by CFD modeling especially at the initial stage of heating. The simulated convection in the pan showed the same tendency as the captured movement of the tracer particle using flow visualization.     

A Homogeneous Catalyst for Reduction of Optically Active Esters to the Corresponding Chiral Alcohols without Loss of Optical Purities

A ruthenium complex was found to catalyze the hydrogen reduction of esters under mild and neutral conditions. A variety of optically active esters can be reduced to the corresponding alcohols in excellent yield without loss of their optical purity or causing undesirable side reactions. Hydrogen reduction needs such simple operations – reaction, concentration, and purification – that the violent quench step and extraction step, which accompany conventional sodium borohydride or lithium aluminum hydride reduction, can be omitted.     

Decomposition kinetics of umami component during meat cooking

We developed a kinetic model for the decomposition reaction of inosine monophosphate (IMP), which is a umami component, and obtained kinetic parameters based on the amount of IMP in an isothermal experiment. The amount of remaining IMP decreased with heating time, and its reduction rate was the highest at 40 °C. We assumed that the activity of IMP decomposition enzyme is temperature-dependent above 40 °C, and constant below 40 °C. The predicted results using this kinetic model are in good agreement with the experimental ones. Unsteady-state three-dimensional heat transfer analysis of meat during sous-vide cooking was conducted, and the distribution of remaining IMP was predicted. By the end of sous-vide cooking, the ratio of the amount of IMP in the interior of the meat decreased, whereas at the surface region, it was almost the same as the initial value, because the surface temperature reached the inactivation temperature immediately.