Crosslinking of poly(ethylene glycol) with divalent metal salts of mono(hydroxyethyl) phthalate,anhydride, and bisepoxide

Poly(ethylene glycol)s (PEG) were crosslinked with divalent metal salts of mono(hydroxyethyl) phthalate, anhydride, and bisepoxide to give metal-containing cured rubbers. As the anhydride, hexahydrophthalic anhydride was used, and bisphenol A diglycidyl ether was the bisepoxide used. As for the physical properties of the cured rubbers obtained, the rubbers containing Mg showed much better physical properties than those containing Ca. In addition, the rubbers with high hard block contents and high overall crosslinking densities exhibited high tensile strength and Shore A hardness, and so did the rubbers having a high degree of crystallinity of the PEG soft block. The occurrence of crystallization became easy as the soft block length became longer and the soft block content became higher, or as the crosslinking density of the hard block became lower. The PEG-based rubbers showed much higher water absorption than the previously reported poly(propylene glycol)-based rubbers, due to the much higher hydrophilicity of the PEG block. Resistance to chemical attack and stress–relaxation are also discussed.     

Applications of genetic algorithm to aesthetic design of dam structures

In this paper, an attempt is made to develop a decision-making supporting system for the aesthetic design of dam structures. The present system is based on genetic algorithm and computer graphics. Genetic algorithm is able to produce many design alternatives, whereas computer graphics is useful to prepare their view simulations. In order to evaluate the alternatives, the analytical hierarchy process method is used to reflect the preference of designers. A numerical example of coloring a dam structure is presented to demonstrate the applicability of the system developed here.     

Reduction characteristics of Fe-Bi-P mixed oxide catalysts and their ammoxidation activities of propylene

The characteristics of Fe-Bi-P mixed oxide catalysts of different compositions for reduction by propylene or ammonia and the ammoxidation activities of propylene were studied using a McBain type thermobalance and the pulse reaction technique respectively. By comparing the dependency of the reduction characteristics and catalytic activity with oxide composition and also the reduction rates and reoxidation rates of the reduced catalyst it was concluded that the ammoxidation of propylene on Fe-Bi-P mixed oxide catalyst proceeds through alternate repetition of reduction by propylene and reoxidation by oxygen, and that abstraction of allylic hydrogen from adsorbed C₃H₆ is the rate determining step.     

Effect of sulfur on supersaturation in aluminum deoxidized liquid iron

The effect of sulfur addition on supersaturation observed in aluminum deoxidized liquid iron was studied at 1873 K, by using CaO-Al₂O₃ slags in an alumina or lime crucible. The contents of supersaturated oxygen for a given aluminum level were not influenced by the addition of sulfur (mass contents of 1×10^?5 ～ 0.42%) in the experiments where the sample was rapidly quenched. However, in the experiments in which the sample was cooled from 1873 to 1723 K at a cooling rate of 2.7 K/min, the effect of sulfur on supersaturation was observed for mass contents of more than 0.01% sulfur. The critical supersaturation for alumina precipitation was discussed based on the variation of the interfacial energy between liquid iron and alumina.     

Effect of tellurium on supersaturation in aluminum deoxidized liquid iron

The effect of tellurium addition on supersaturation observed in aluminum deoxidized liquid iron was studied at 1873 K, using CaO-Al₂O₃ slags in an alumina crucible. Supersaturated oxygen content for a given aluminum level decreased with the addition of tellurium as a result of lowering the interfacial energy between liquid iron and alumina and promoting the elimination of precipitated alumina by flotation. Furthermore, the degree of lowering of oxygen content was found to increase with a decrease in cooling rate. Tellurium distribution ratio between liquid iron and CaO-Al₂O₃ slags was determined as a function of aluminum content.     

Mean message waiting times in symmetric multi-queue systems with cyclic service

A new performance analysis is provided for a cyclic service system consisting of statistically identical stations where at most one message is served for any station in a cycle. We assume that the time is slotted and that the number of message arrivals at each station in any slot is independent and generally distributed. The switch-over time and message service time (integral multiples of the slot size) are also generally distributed. For this system (called limited service system) we find the mean message waiting time explicitly. In the case of Poisson arrivals we show that our mean message waiting time is greater than that for the gated service system which is greater than that for the exhaustive service system. We also summarize the corresponding results for the three types of services in continuous-time systems.     

Preparation of Semiconducting Barium Titanate by Excimer Laser Irradiation

A drastic drop of the electrical resistivity was observed on a ferroelectric insulator BaTiO₃ surface, after KrFlaser irradiation in air at atmospheric pressure. The temperature dependence of the resistivity was employed to demonstrate semiconducting behavior. Such behavior was seen when the resistance was measured in nitrogen. When measured in air, the semiconducting layer was oxidized and the insulating behavior restored.     

Tunable All-Optical Wavelength Conversion of 160-Gb/s RZ Optical Signals by Cascaded SFG-DFG Generation in PPLN Waveguide

We report, for the first time, tunable all-optical wavelength conversion of 160-Gb/s return-to-zero (RZ) optical signals based on cascaded sum- and difference-frequency generation in a periodically poled LiNbO₃ waveguide. The distorted signals due to limited phase-matching bandwidth during conversion were compensated by spectral reshaping. We achieved error-free tunable wavelength conversion with a bit-error rate of less than 10^-9 for 160-Gb/s RZ signals in a 23-nm tuning range over the C-band