Dispersion of phosphovanadates on silica gel chemically modified with silane coupling agents having an amino group and their catalytic activities for methanol oxidation

Phosphotetradecavanadate (PV14) was dispersed on a silica gel chemically modified with a silane coupling agent (AnPS-SiO₂) by an equilibrium adsorption method. The PV14 contents approximately correlated with the V(IV) spin contents by ESR. PV14 dispersed on AnPS-SiO₂ resulted in a quite high selectivity for formaldehyde such as 97% in methanol oxidation.     

Fabrication of Zirconia-Nickel Functionally Gradient Materials by Slip Casting and Pressureless-Sintering

A powder processing technique has been developed for the fabrication of tetragonal zirconia-nickel functionally gradient materials using slip casting and pressureless-sintering. Rheological behavior of slips was studied. Single-layer zirconia-nickel green compacts with various zirconia/nickel volume ratios were characterized by permeability and pore radius. A multilayer zirconia-nickel green compacts with a stepwise compositional gradient was formed and sintered in argon atmosphere. One of the keys to successful fabrication was to minimize differences in permeability and pore radius between neighbouring layers in a multilayer green compact to avoid fracture during drying in an ambient atmosphere.     

Stability of PZT Piezoelectric Ceramics under Vibration Level Change

Stability of the piezoelectric properties with changing vibration level was studied in lead zirconate–titanate (PZT) ceramics by using the constant-current/velocity driving method. The changes of Young's modulus Y^E₀ and mechanical loss factor Q^–1_m are a function of the square of effective vibration velocity v ₀. The nonlinear proportional constants of the above functions indicate the degree of stability under vibration level change. The stability of PZT estimated by these constants coincides with the results obtained through the heat generation study.     

Framework of a flexible computer communication network

With the increasing speed of computers and communication links, and the successful convergence of both fields, computers connected by high speed links now represent an enormously large distributed computing system. At the same time, communication between man and machine is also becoming more diverse and personalized. Networking issues such as evolution of user services, seamless communication between hosts, failure recovery and integration of new technologies arise daily. Problem-specific approaches and corresponding solutions are available at considerable cost. However, a common requirement is adaptability of the computer network to a variety of changes. In this paper, we propose Flexible Computer Communication Networks (FN) as a uniform solution to most of these networking problems. The framework of Flexible Networks can be considered as an intelligent shell enclosing existing networking architectures. An agent-oriented implementation of a flexible network is outlined. The conversion of existing networks to flexible networks is shown to be incremental, and therefore practicable.     

Effect of calcium chloride on vapor-liquid equilibria of alcohol-alcohol and alcohol-water binary systems

The vapor-liquid equilibria of three alcohol-alcohol binary mixtures (methanol-ethanol, methanol-1-propanol and ethanol-1-propanol) and three alcohol-water binary mixtures (methanol-water, ethanol-water and allyl alcohol-water) containing calcium chloride were measured at 298.15 K using a flow-type apparatus. The measured data of each ternary system were correlated by the use of a semi-empirical model proposed by Hála. It was found that the model with the optimal value of the exponent β = 5.0 in the electrostatic interaction term, originally given as 3/2 by Hála, gives reasonable prediction to all the systems in this study.     

Local structural analysis of hopeite crystals by the EXAFS curve-fitting method

Structural analysis of hopeite crystals was performed by the extended X-ray absorption fine structure (EXAFS) curve fitting method. Two types of hopeite crystals, Zn₃(PO₄)₂·4H₂O and Zn_3-xMn_x(PO₄)₂·4H₂O which is doped by manganese, were studied. Fourier transform of EXAFS gave Zn-O bond distances of 0.146 nm for the former and 0.144 nm for the latter. The real bond distances were determined by the reverse operation of Fourier transform and curve-fitting. By this procedure, the real bond distances of Zn-O were determined to be 0.194 and 0.196 nm, respectively. These distances indicated a Zn-O bond in [ZnO₄] of tetrahedral structure. Although the Mn-O bond distance in Zn_3-xMn_x(PO₄)₂·4H₂O was found to be 0.162 nm by the Fourier transform of EXAFS, the reverse operation of Fourier transform gave a real bond distance of 0.215 nm for the Mn-O bond in the hopeite crystal. The data supported the idea that the Mn-O bond refered to [MnO₂(H₂O)₄] of the octahedral structure in the crystal. The coordination numbers of the zinc and manganese components clarified their local structure in hopeite crystals.     

Recovery of Tritium from Wastewater Generated by Decommissioning of Gas Cooled Reactors (GCR)

The recovery of tritium from wastewater generated by the decommissioning of a 166‐MWe GCR, Tokai‐1, nuclear reactor was evaluated. The dimensions of two tritium separation columns, water distillation process and hydrogen‐isotope exchange with hydrophobic Pt‐catalyst, were evaluated numerically under the assumptions that the recovery of tritium from the wastewater would be completed in five years and the wastewater after the recovery of tritium would be suitable for release into the environment. It was found that, in addition to lower steam, the column was smaller than that for the water distillation process. The hydrogen‐isotope exchange process was suitable for the treatment of wastewater, not only for a process design point of view but also for a reduction of energy consumption.