Three-channel buried-crescent InGaAsP laser with 1.51 ?m wavelength on semi-insulating InP

Laser diodes with current threshold as low as 16 mA for lasers of 300 ?m length and channel width of 2?3 ?m were obtained with operational wavelength of 1.51 ?m. These lasers are fabricated with one liquid-phase-epitaxy growth step and a lateral zinc diffusion process. Current confinement is achieved by use of the semi-insulating substrate material.     

Radical copolymerization of ethylene glycol bis(methyl fumarate) with N-vinylcarbazole

Summary For the purpose of elucidating copolymerizability of ethylene glycol bis(methyl fumarate), a new multifunctional monomer, its free-radical Copolymerization with N-vinylcarbazole has been studied. The results show that free-radical Copolymerization of ethylene glycol bis(methyl fumarate) with N-vinylcarbazole produces soluble copolymers at low conversions, the compositions of which vary from 1∶1 to increasingly VCZ rich (below 2.0) with an increase in the VCZ content in the monomer feed. It is suggested that 1∶1 alternating Copolymerization proceeds and that cyclo-propagation becomes predominant when the monomer feed composition becomes rich in VCZ. Gelation occurs at relatively high conversions.     

Formation of Microcrystalline α-Alumina by Glycothermal Treatment of Gibbsite

Microcrystalline α-aluminas (hexagonal plates, ∼0.1 μm wide and ∼0.025 μm thick) were prepared by treating fineparticle gibbsite in glycol at 300°C under the spontaneous vapor pressure of glycol (glycothermal treatment). The α-alumina was formed by the collapse of the glycol derivative of boehmite.     

Identification of a Sex Pheromone Component of Pseudococcus cryptus

A sex pheromone component of Pseudococcus cryptus has been isolated and identified. The crude pheromone extract obtained by airborne collection was fractionated by liquid chromatography (LC) on Florisil, and further purified by high performance liquid chromatography and preparative Gas Chromatography (GC). The pheromone component was shown to be an ester, the alcohol part of which was identical to the known alcohol moiety of the pheromone of Planococcus citri. The chemical structure was determined to be 3-isopropenyl-2,2-dimethylcyclobutylmethyl 3-methyl-3-butenoate by MS and ¹H NMR analyses. The absolute configuration of the pheromone was assigned as (1R,3R) by comparison of the retention time of the alcohol derived from the P. cryptus pheromone with those of the alcohol derived from P. citri pheromone, and a synthetic sample of alcohol enriched in the (1R,3R)-enantiomer, using a chiral GC stationary phase. The structure of the pheromone was confirmed by synthesis, and by bioassays in a glasshouse.     

CPG model for autonomous decentralized multi-legged robot system—generation and transition of oscillation patterns and dynamics of oscillators

A central pattern generator (CPG) model is proposed for the gait-pattern generation mechanism of an autonomous decentralized multi-legged robot system. The topological structure of the CPG is represented as a graph on which two time evolution systems, the Hamilton system and a gradient system, are introduced. The CPG model can generate oscillation patterns depending only on the network topology and can bifurcate different oscillation patterns according to the network energy, which means that the robot can generate gait patterns by connecting legs and transit gait patterns according to such parameters as the desired speed.     

Acoustic emission and disturbances in central solenoid model coil for International Thermonuclear Experimental Reactor

This paper presents acoustic emission (AE) signals induced from the Central Solenoid (CS) model coil of the International Thermonuclear Experimental Reactor (ITER) program. Envelopes of the AE signals were quasi-continuously measured with high-time resolution of 100 μs using six multi-channel AE sensors in order to detect the disturbances in the CS model coil during the process of the series of direct current (DC) operations. The AE signals were considered to be originally induced by motion of superconducting cables in cable-in-conduit (CIC) conductors and local motion of the conductors, judging from the close correlation between the AE signals and voltage spikes in the coil, especially during the virgin current operation. The multi-channel measurements provide us with information about the distribution of disturbances that could be detected acoustically by the AE sensors installed at each point of the CS model coil. The observation of AE envelopes with high-time resolution showed that the disturbances at each location of the CS model coil decreased by repeatedly charging-up the coil, judging from instantaneous AE levels, AE energy and the number of AE events. Direct measurements of the number of AE events that were carried out at another point on the coil confirmed that the disturbance dependence on the number of operations was similar to that mentioned above. The transfer function methods using one pair of AE sensors enabled us to analyze changes that might occur in either the coil structure or in the disturbance in frequency region during the repeating of the charging-up processes of the coil.     

The effect of nonlinear stress-strain relationship on the bend strength of isotropic graphite

Four-point bend tests on rectangular specimens of several different sizes of isotropic graphite 7477PT were made to study the effect of nonlinear stress-strain relationship on bend strengths. The measurements showed that the tensile and compressive strains at the outer fibers had a nonlinear relationship with the bending load and that the tensile fiber strains at fracture were 0.4–0.7%, as compared with the uniaxial tensile fracture strains 0.25–0.45%. From the observations the nonlinear stress-strain curves were determined for tension and compression, nonlinearity being larger in the former than in the latter. The true bend strengths were 10–15% smaller than the elastic ones. In calculations on Weibull's statistical theory, the probability distributions of bend fracture in terms of true bend strength agreed better with experiments than those in terms of elastic bend strength.