Compact optical isolator for near-infrared radiation

Compact Faraday rotation isolators have been developed for near-infrared radiation. Two types of Faraday rotators were used: one was composed of two permanent magnets, the other of a closed magnetic circuit with a permanent magnet. 2.0 dB insertion loss and 30 dB isolation ratio at 1.15 ?m wavelength have been obtained.     

Synthesis and properties of elastomeric ionenes I. Polybutadiene ionenes

Polybutadiene ionene (PBI) carrying quaternary ammonium ions in the main chain was synthesized from dimethylamino-terminated polybutadiene and 1,4-dibromobutane. Dimethylamino-terminated polybutadiene was prepared by the reaction of isocyanate-terminated polybutadiene with 2-dimethylaminoethanol. The swelling property and the mechanical properties of PBI were compared with those of polybutadiene urethane (PBU), which was prepared by the reaction of hydroxy-terminated polybutadiene with a diisocyanate. The following points were found: (1) PBI shows almost the same solubility parameter δ_p as that of PBU; (2) PBI attains a four time greater tensile strength at break than PBU at room temperature; (3) PBI shows a thermoplastic behavior.     

Synthesis and properties of urethane elastomer-modified epoxy resin having hydroxymethyl group

Synthesis and properties of urethane elastomer-modified epoxy resins were studied. The urethane elastomer-modified epoxy resins were synthesized by the reaction of a 4-cresol type epoxy compound having hydroxymethyl groups (EPCDA) with isocyanate prepolymer. The structure was identified by IR, ¹H NMR and GPC. These epoxy resins (EPCDATDI) were mixed with a commercial epoxy resin (DGEBA) in various ratios. The mixed epoxy resins were cured with a mixture of 4,4′-diaminodiphenylmethane and 3-phenylenediamine (molar ratio 6:4) as a hardener. The curing behaviour of these epoxy resins was studied by DSC. The higher the concentration of EPCDATDI, the higher the onset temperature and the smaller the rate constant (k) of the exothermic cure reaction were. It was considered that the ratio of hydroxymethyl group to epoxide group was very small and the molecular weight of EPCDATDI was large. Therefore, the accelerating effect of the hydroxymethyl group on the epoxide–amine reaction was cancelled by the retardant effect of increased molecular weight and viscosity, and decreased molecular motion. Toughness was estimated by Izod impact strength and fracture toughness (K_1C). On addition of 10 wt% EPCDATDI with low molecular weight (M?_n 6710, estimated by GPC using polystyrene standard samples), Izod impact strength and K_1C increased by 70% and 60%, respectively, compared with unmodified epoxy resin. Glass transition temperatures (T_g) for the cured epoxy resins mixed with EPCDATDI measured by dynamic mechanical spectrometry were the same as those of unmodified epoxy resin. The storage modulus (E′) at room temperature decreased with increasing concentration of EPCDATDI. Toughness and dynamic mechnical behaviour of cured epoxy resin systems were studied based on the morphology.     

CLA production from ricinoleic acid by lactic acid bacteria

The ability to produce CLA from ricinoleic acid is widely distributed in lactic acid bacteria. Washed cells of Lactobacillus plantarum JCM 1551 were selected as a potential catalyst for CLA production from ricinoleic acid. Cells cultivated in medium supplemented with a mixture of α-linolenic acid and linoleic acid showed enhanced CLA productivity. Under optimal reaction conditions, with the free acid form of ricinoleic acid as the substrate and washed cells of L. plantarum as the catalyst, 2.4 mg/mL CLA was produced from 3.4 mg/mL ricinoleic acid in 90 h, with a molar yield with respect to ricinoleic acid of 71%. The CLA produced, which was obtained in the FFA form, consisted of a mixture of two CLA isomers, cis-9,trans-11-octadecadienoic acid (21% of total CLA) and trans-9,trans-11-octadecadienoic acid (79% of total CLA), and accounted for 72% of the total FA obtained.     

Relaxation of elastoresistance in thin metal films

The change in the resistance of thin evaporated metal films in response to a step strain has been studied. Among the several metal films examined, aluminium and bismuth films exhibited remarkable relaxation, with a time constant of about 1 min at room temperature for a thickness of around 1000 Å. In the case of aluminium films, the time constant was found to decrease with increase of deposition temperature, thickness, annealing period and annealing temperature. In the case of bismuth films, such a clear tendency to decrease was not observed, at least for films thinner than 2 μm. It is suggestef that the resistance relaxation is related to the unusually large stress-strain relaxation which is known to exist in bismuth films. The thickness dependence of the gauge factors of both films is also illustrated.     

Solution copolymerization of ethylene with α-olefin by vanadium catalyst

Summary Copolymerization of ethylene with an -olefin, i.e. propylene, butene-1 and 4-methyl-pentene-1(4-MP-1), was carried out by vanadium catalyst prepared by treating VOCl₃ with (n-C₈H₁₇)₃Al in decane in combination with Et₃Al and CHCl₃. The copolymerization system was homogeneous at a temperature as high as 170 °C. It has been revealed that the monomer insertion reaction of irregular direction, i.e. the insertion giving rise to the growing end of secondary alkyl / catalyst bond, occurs occasionally at the propagation of the -olefin comonomer. The irregular insertion takes place most frequently with 4-MP-1. The chain transfer with hydrogen takes place more preferentially at the irregular propagation end in comparison with the regular one.     

Elastic Effect on Domain Morphology and Kinetics of Spinodal Decomposition in the Tetragonal System

A method was proposed for calculation of the effect of elastic strain on spinodal decomposition in the tetragonal system. An effective free energy for the composition field was derived by eliminating elastic fields which are coherently induced by composition inhomogeneities It was shown that anisotropic long-range interactions between composition fields play a major role in determining both the domainmorphology and domain growth law of spinodal decomposition with the coherence of the lattice. Computers simulations were performed on the basis of a two-dimensional model by taking into account those long-range interactions. The results demonstrated the appearance of lamella structure and its coarsening in the late stage of the phase separation The calculation for the TiO₂-SnO₂ system showed slow coarsening due to the anisotropic elastic long -range interactions The asymptotic growth of the lamella size was described by λα tⁿ, where n is 0.18.     

A new approach for evaluating crack growth resistance curve of mode II delamination by doubly end-notched tension tests

Quantitative determination of interlaminar fracture toughness that governs onset and growth of delamination is essential for engineering of composite materials and structures. This study proposes a new approach to evaluate both the initial fracture toughness and the crack growth resistance property of pure mode II delamination by tensile tests of specimens having two initial cracks, which were conceived from double-lap joints. The proposed test method achieves stable growth of mode II delamination using a fundamental testing system. This study presents the specimen configuration, the theory to evaluate the energy release rate, and experiment results. The mode II initial fracture toughness measured by the present approach agreed well with the results of conventional end-notched flexure tests. Furthermore, the crack growth resistance curves were evaluated by unloading-reloading tests of the proposed doubly end-notched tension specimens.     

Numerical study by large-eddy simulation on effects and mechanism of air-cooling enhancing technologies

ABSTRACT

Learning from the lessons of the Fukushima Daiichi Nuclear Power Station incident in which a long-term station blackout occurred, we have been developing an air-cooling system that can operate without electricity for a virtually indefinite time. We developed air-cooling enhancing technologies by using heat transfer fins, turbulence-enhancing ribs and a micro-fabrication surface. To achieve further improvement of the heat transfer performance, it is important to understand the mechanism of the air-cooling enhancing technologies. In this study, we used numerical analysis to investigate the effects and the mechanism of the developed air-cooling enhancing technologies. We confirmed that the Nusselt number was increased 75% by the heat transfer fins. In the heat transfer enhancement by the turbulence- enhancing ribs, the Nusselt number was increased 43% by the turbulence-enhancing ribs. The enhancement ratio of the Nusselt number by the micro-fabrication surface can be explained by the apparent thermal conductivity. The Nusselt number was increased 4%–8% by adding the micro-fabrication to the surface of the pipe with the turbulence-enhancing ribs. For the combination of the micro-fabrication surface and the turbulence-enhancing ribs, the interaction between the better heat transport in the thermally conductive layer and the mixing effect by the large-scale vortex is the heat transfer enhancement mechanism.