Electrical properties and microstructure in the system ceria-alkaline earth oxide

The ionic conduction of oxygen in the ceria-alkaline earth oxide system was investigated as a function of temperature, partial pressure of oxygen and oxide composition, together with its crystal structure, density, and microstructure. Undoped ceria and its solid solution with alkaline earth oxides have a cubic fluorite structure. The ionic conductivity of ceria is greatly enhanced by additions of calcia and strontia, even when they are added in excess of the solubility limit. The conductivities of ceria-calcia and ceria-strontia were much higher than those of calcia-and yttria-stabilized zirconia. Up to the limit of calcia and strontia, the ionic transference number was nearly unity in the temperature range between 600 and 900°C. With an increase in calcia and strontia content, the ionic conductivity was little affected by the presence of a second phase of CaO and SrCeO₃.     

Product design logic for an intelligent product modelling system

Recent research in CAD systems has been conducted to realize intelligent processing. Several CAD systems and product modelling systems have been developed using AI techniques. However, in order to develop more intelligent CAD systems, the design logic which connects the functional requirement to the geometric and the technological information of the designed product must be evaluated.

A product model used in such intelligent CAD systems has to include not only the geometric and the technological information of the product but also the designer's thought process which explains the design logic.

Design logic is generally divided into two parts. One is the generalized design logic which is commonly used in the conceptual design of mechanical products. The other is the product specified design logic which is used in the fundamental and detailed design phase. Different logic is applied to each product. This type of design logic is often used in modification design and compilation design, where the dimensions of parts have to be modified according to different functional requirements. When the dimensions and accuracies of the products are defined in connection with the functional requirements through design logic, the CAD system can automatically make decisions according to the given requirements. In this paper, suitable presentation formats and processing functions for these two types of design logic are discussed.

The importance of design logic in product modelling is proven through several case studies in this paper. As a conclusion, the intelligent product modelling system is developed, which should expedite the progress of design automation in the near future. In conceptual design, the design logic is processed in the modelling system and the product structure, with the technological information decided automatically from the functional requirement. Automation in the detailed design phase is also facilitated by the modelling system using the product specified design logic in the product model.     

Advanced microwave scanning radiometer (AMSR): requirements andpreliminary design study

An investigation on users' requirements for future passive microwave scanning radiometers, especially the advanced microwave scanning radiometer (AMSR), which is one of the Earth Observing System instruments, has been conducted together with a preliminary design of the AMSR system. As a result, mission parameters for the AMSR have been determined while the feasibility of the electronically scanning type of AMSR has been confirmed. In particular, it is found that a beam-switching antenna system that was developed makes possible multifrequency measurement, and multiple beam conical scanning, while preserving polarization purity     

Photocatalytic activities of CdS crystallites embedded in TiO2 gel as a stable semiconducting matrix

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Thermal rollover characteristics up to 150°C of buried-stripetype 980-nm laser diodes with a current injection window delineated by aSiNx layer

In order to improve device robustness of buried-stripe type 980-nm laser diodes against excess current injection even under high temperature operation, we have introduced a current injection window delineated by a SiN_x layer to suppress current injection near the facets. The devices showed complete thermal rollover characteristics at temperatures up to 150°C with 800-mA continuous-wave current injection while devices without the layer failed due to front facet degradation during high temperature tests. We think the improvement of device robustness with a SiN_x layer is attributable to suppression of nonradiative recombination of carriers overflowing from the active layers near the facet and to reduced light absorption at the facet brought about by suppression of carrier-induced bandgap shrinkage     

Broadband four-wave mixing generation in short optical fibres

Several advantages of using a short length of fibre to generate broadband four-wave mixing are proposed and verified using wavelength conversion experiments for different lengths of a previously developed high-nonlinearity fibre with a nonlinear coefficient of 13.8 W^-1 km^-1. Consequently, 91.3 nm broadband simultaneous wavelength conversion is demonstrated using a 100 m long section of the developed fibre     

Oxidation behavior of ytterbium silicide

Si-rich ytterbium silicide was fabricated by through an arc-melting technique for applying use as a bond coat material in an environmental barrier coating system. Evaluation of its potential was accomplished through oxidation tests in dry air and an inert atmosphere. The experimental results showed that the changes in weight and morphologies of ytterbium silicide observed after the tests depended on the oxygen partial pressure. Extensive oxidation and weight gain occurred after oxidation in air. In order to apply this material for hot structures, improvement of the oxidation resistance is needed.     

The functional implications of the dimerization of the catalytic subunits of the mammalian brain platelet-activating factor acetylhydrolase (Ib)

The mammalian brain contains significant amounts of the cytosolicisoform Ib of the platelet-activating factor acetylhydrolase(PAF-AH), a unique type of PLA2. This oligomeric protein complexcontains three types of subunits: two homologous (63% identity)26 kDa catalytic subunits (     

Far infrared optical properties of amorphous semiconductors As−S systems

Far infrared reflection, Raman, and Brillouin spectra of amorphous semiconductor As?S systems are measured. From the reflection spectra, the optical constants are calculatured by the Kramers Kronig analysis. The existence of some intermediate range interaction among molecular units AsS₃ is suggested. From the analysis of the Boson peak at low frequency region in Raman scattering, the correlation length is obtained to be ca. 6 Å. From the absorption coefficient in the low frequency region about 3% fluctuation of charge is suggested for As₂S₃ by schlömann theory.