Dopant-Free Ultraviolet-Sensitive Calcium Aluminate Glasses

Dopant-free calcium aluminate glasses are very sensitive to ultraviolet radiation; new optical absorption bands rapidly appear around 400 nm on illumination and are easily bleached when the glass is heated to >100° to 250°C. This coloringbleaching process is reversible when the illumination and heating cycles are repeated, A clear correlation was found between the intensities of the uv-induced optical absorption and the ESR signal of Al-OHC.     

Growth mechanism of AlGaAs on terraced substrates by low pressure MOVPE

AlGaAs layers were grown on recessed GaAs substrates by MOVPE at 5 and 100 Torr. The two mechanisms, the gas phase diffusion through the stagnant layer and the surface migration of the growing species, are responsible for the surface step height after the growth. Since the mean free path in the gas phase at 5 Torr (≈20μm) is longer than the recess height (≈1μm), only the surface migration determines the growth at 5 Torr, while both mechanisms contribute to the growth at 100 Torr. The surface diffusion equation is solved to find out the relation between the growth conditions and the surface step height after the growth. It was found that the surface migration length on the (111)A surface is much longer than that on the (100) plane. The optical waveguide is fabricated by growing a double-heterostructure on the recessed substrate, and light confinement in the channel is verified. On leave from Matsushita Kotobuki Electronics Ltd. Fukutake, Saijo 793, Japan     

Development of three-dimensional electric field computation system by surface charge method

This paper describes development of three-dimensional electric field computation system by surface charge method. Using this system, both potential and electric field in the case which includes resistance or true electric charge can be calculated. And this system is able to be connected to the pre-post processors, which is useful for us to make arbitrary shape and to display results of analysis.     

Removal of suspended solids by coagulation and foam separation using surface-active protein

By using several kinds of surface-active proteins as a chemical agent that combined collector with frother, removal of suspended substances by coagulation and foam separation with dispersed air was examined. Milk casein showed the greatest capability of suspension removal, and coagulating flocs formed by clay particles and iron hydroxide were almost perfectly recovered in foam generated from the liquid, even in the case of freshwater and seawater suspension at neutral pH. In contrast, the removal efficiency was extremely low using sodium dodecyl sulfate (SDS). Casein had a much greater capability for removing solids than SDS as a result of the high adsorptive activity of casein on the floc. For municipal wastewater treatment, the removal efficiency of turbidity and suspended solids was over 98% with the condition of iron coagulant (FeCl3) 20 mg-Fe/L and casein 3 mg/L and pH 5-6. Moreover, this method proved to be an effective treatment for polluted saline water (salinity 1.5%), and the suspended solids were almost perfectly recovered in foam. Here, we show a new method for quickly removing (within 7 min) suspended solids from polluted wastewater utilizing casein and bubbles.     

Stable and controlled amphoteric doping by encapsulation of organic molecules inside carbon nanotubes

Single-walled carbon nanotubes (SWNTs) have strong potential for molecular electronics, owing to their unique structural and electronic properties. However, various outstanding issues still need to be resolved before SWNT-based devices can be made. In particular, large-scale, air-stable and controlled doping is highly desirable. Here we present a method for integrating organic molecules into SWNTs that promises to push the performance limit of these materials for molecular electronics. Reaction of SWNTs with molecules having large electron affinity and small ionization energy achieved p- and n-type doping, respectively. Optical characterization revealed that charge transfer between SWNTs and molecules starts at certain critical energies. X-ray diffraction experiments revealed that molecules are predominantly encapsulated inside SWNTs, resulting in an improved stability in air. The simplicity of the synthetic process offers a viable route for the large-scale production of SWNTs with controlled doping states.     

Mutual diffusion process for continuous fabrication of graded-index plastic rod lenses

We propose a new process for fabrication of plastic rod lenses based on the traditional method of fiber extrusion. The process consists of the following steps: multilayer conjugate extrusion, monomer diffusion between adjacent layers, and photopolymerization of an uncured strand fiber. We call this process a mutual diffusion process for continuous plastic rod lens fabrication. Characteristics of this process are as follows: fast production speed (approximately 100 cm/min), precision control of refractive-index distribution, high angular aperture, and long-term reliability. The optical resolution of the rod-lens array is 300 dpi, which is high enough for application to G3 facsimiles with transmission time of less than 1 min and monochromatic scanners.     

Future potential of nuclear heat utilization in energy, economy and environment

In this study quantitative analyses are made to clarify the possible roles of S-HTGRs (Small-sized modular High Temperature Gas-cooled Reactors) in our future energy systems. The results obtained show the good possibility of S-HTGRs to compete economically with L-HTGRs (Large-sized HTGR) taking into account the effects of modularization, learning, mass production, and simplification of safety systems. In the electricity market, S-HTGRs can well compete with coal steam electric power and LWR electric power if they are located close to demand areas. In addition the high temperature nuclear heat from small-sized modular gas-cooled reactors has the potential of contributing to reduce the amount of imported fossil fuels and also SO₂, NO_x, and CO₂ emissions.     

Preparation and properties of LiTaO3-based solid solutions with cation vacancies

It has been found that nonstoichiometric solid solutions $\text{(}\text{Li}{}_{\mathrm{<mtext>1?</mtext><mtext>x</mtext>}}\text{M}{}^{\mathrm{2+}}{}_{\mathrm{<mtext>x</mtext><mtext>2</mtext>}}\text{□}{}_{\mathrm{<mtext>x</mtext><mtext>2</mtext>}}\text{)}\text{TaO}\text{3}$ with M=Zn, Ni, Mg and Ca exist over wide ranges. In the case of the Zn-system, especially, a LiTaO₃ structure was still stable even at x=0.5, where 25% of the Li sites are vacant. A new series of solid solutions shows ferroelectric properties. The Curie temperature is closely related with the axial ratio c/a of the hexagonal cell.     

Comparison of quantized Hall resistances RH(2) andRH(4) of a GaAs/AlGaAs heterostructure device

Quantized Hall resistances R_H(4) and R_H(2) of a GaAs/AlGaAs heterostructure were compared with reference resistors whose values are close to h/4e² or h/2e². The values of the reference resistors were compared with a 100 ohm standard resistor via a cryogenic current comparator (CCC) resistance bridge. Results showed that (4×R_H(4)-2×R_H(2))/2×R_H (2)=(0.037±0.019)×10^-6     

Preparation of Monolithic Porous Titania-Silica Ceramics

Monolithic porous ceramics composed of TiO₂ (67 mol%) and SiO₂ (33 mol%) were prepared via casting a melt in the Na₂O-CaO-TiO₂-P₂O₅-SiO₂ system and subsequent acid leaching of the resultant ceramics which are constituted of NaCaPO₄, TiO₂, and amorphous SiO₂. The median pore diameter and specific surface area of the resulting porous ceramics are approximately 1 μm and 40 m², respectively. Amorphous silica surrounds the submicrometer-sized particles of TiO₂ acting as a binder and retaining monolithic forms. No significant shrinkage in the pore size occurred upon heating up to 1000°C.