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991.
Takafumi Kawaguchi Hiroyuki Nishimura Fumiaki Miwa Kazuhiro Abe Takashi Kuriyama Ikuo Narisawa 《Polymer Engineering and Science》1999,39(2):268-273
The environmental stress cracking (ESC) of acrylonitrile-butadiene-styrene (ABS) copolymer caused by a non-ionic surfactant (poly-oxyethylene alkylether) was studied by constant-load tensile creep tests and edge crack tension (ECT) tests. The fracture surfaces were investigated by a scanning electron microscope (SEM) and the morphology of the crack tip was investigated by a transmission electron microscope (TEM). It was found that the results of the creep tests performed in the non-ionic surfactant were very different from those performed in air. SEM images of the fracture surfaces showed that there were three different mechanisms of fracture and that specimens had a tendency to rupture by ESC when the stress was small. The results of the ECT tests and the TEM images showed that the change in the mechanism of the fracture was attributable to the change of morphology at the crack tip. 相似文献
992.
Summary Copolystyrenes complexed with macrocyclic compounds through hydrogen bonding have been synthesized by the copolymerization of styrene with the complex of 4-vinylbenzoic acid and crown ethers containing a 2,6-pyridyl moiety. The glass transition temperatures of the copolymeric complexes are significantly lower than that of the simple copolymer, which shows that the carboxylic acid groups in the polymer backbone do not intermolecularly dimerize. The UV absorption spectra of polymeric complexes suggest that they have complex structures similar to that of the low-molecular-weight complexes of 4-ethylbenzoic acid and the crown ethers. Received: 31 March 1999/Accepted: 27 April 1999 相似文献
993.
Methanol decomposition to synthesis gas over supported Pd catalysts prepared from synthetic anionic clays 总被引:2,自引:0,他引:2
Ryuji Shiozaki Takashi Hayakawa Yan-yong Liu Tomoko Ishii Mikio Kumagai Satoshi Hamakawa Kunio Suzuki Tatehiko Itoh Tetsuya Shishido Katsuomi Takehira 《Catalysis Letters》1999,58(2-3):131-140
Supported Pd or Rh catalysts were prepared by the solid-phase crystallization method starting from hydrotalcite anionic clay minerals based on [Mg6Al2(OH)16CO 2 2− ]·4H2O as the precursors. The precursors were prepared by a coprecipitation method from the raw materials containing Pd2+ and various trivalent metal ions which can replace each site of Mg2+ and Al3+ in the hydrotalcite. Rh3+ was also used for preparing the catalyst as comparison. The precursors were then thermally decomposed and reduced to form supported Pd or Rh catalysts and used for the methanol decomposition to synthesis gas. Among the precursors tested, use of Mg–Cr hydrotalcite containing Pd2+ resulted in the formation of efficient Pd supported catalysts for the production of synthesis gas by selective decomposition of methanol at low temperature. Although Pd2+ cannot well replace the Mg2+ site in the hydrotalcite, the Pd supported catalyst (Pd/Mg–Cr) prepared by the solid-phase crystallization method formed highly dispersed Pd metal particles and showed much higher activity than that prepared by the conventional impregnation method. When the precursor was prepared under mild conditions, more fine particles of Pd metal were formed over the catalyst, resulting in high activity. It is likely that the high activity may be due to the highly dispersed and stable Pd metal particles assisted by the role of Cr as the co-catalyst. This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
994.
Design criteria for gas entrainments (GE) from the liquid surface in a fast breeder reactor system were proposed in this paper for the two types of GE phenomena from a vortex dimple based on a computational fluid dynamics (CFD) method. The first gas entrainment phenomenon is a gas core extension directly to the outlet piping level, which induces large amount of GE to the flow system. The second is continuous bubble detachments from the tip of the vortex dimple. Based on CFD calculations for elemental experiments of the surface vortex, local CFD non-dimensional numbers were defined as the design criteria to prevent GE. In conclusion, it was found that the CFD non-dimensional numbers are useful for the design parameters of GE prevention. 相似文献
995.
Sergey Zherebtsov Takashi Naoe Katsuhiro Maekawa 《Surface & coatings technology》2007,201(12):6035-6043
The effect of laser surface alloying of type 316 stainless steel on the erosion resistance in mercury has been investigated. The alloying was produced by melting predeposited Al-Si powder and a portion of underlying substrate with a pulsed Nd:YAG laser beam. The microhardness of the modified layer was found to be 2.5 times higher than that of untreated steel. The erosion test of laser alloyed surface and steel in mercury was carried out by using the electromagnetic impact testing machine. The laser alloyed surface was found to be less damaged after 105 cycles of impacts compared to untreated stainless steel. However, after 106 cycles the erosion resistance of the modified layer is much lower than that of untreated steel. Liquid metal embrittlement in contact with mercury and residual stresses were considered as factors impairing the erosion resistance of the laser alloyed surface. 相似文献
996.
Takashi Masuoka Yasuyuki Takatsu Tomomi Inoue 《Nanoscale and Microscale Thermophysical Engineering》2013,17(4):347-357
An experimental study has been made of the chaotic behavior in the transition to turbulence of flow through porous media consisting of a bank of tubes in a narrow gap. Judging from the examination of the correlation dimension and the maximum Lyapunov exponents, we can identify the chaotic behavior in porous media for Re > ~60. Rapid increase in the maximum Lyapunov exponents was observed for Re > ~300. Also, the spatial distribution of the Lyapunov exponents is discussed. 相似文献
997.
Uphill transport of ammonium ions through a membrane with sulfonic acid groups were investigated with pH-controllers which keep the solution at a constant pH. A membrane with sulfonic acid groups was prepared by casting an aqueous solution containing poly(styrenesulfonic acid) and poly(vinyl alcohol) on a glass plate. When a membrane with one side alkaline and the other acidic was fixed as a diaphragm in a cell, ammonium ions were transported from the alkaline side to the acidic side through the membrane against the concentration gradient of the adjacent solutions. Uphill transport of ammonium ions with pH-controllers was more efficient than without, thus keeping the pH difference between both sides of the membrane constant, which is a driving force for the uphill transport. Furthermore, the effect of pH of the acidic side on the uphill transport was investigated and the mechanism of the pH-controlled uphill transport is discussed. 相似文献
998.
Shi-Guang Li Ryosuke Matsubara Toshio Matsusue Masatoshi Sakai Kazuhiro Kudo Masakazu Nakamura 《Organic Electronics》2013,14(4):1157-1162
Innovative sensing systems based on THz electromagnetic waves have been attracting a great deal of attention. Although many THz detectors have been developed over the years, it is currently difficult to manufacture low-cost THz sensing/imaging devices. In the present study, we propose to use organic field-effect transistors (OFETs) and small potential fluctuation against the carriers within them (N. Ohashi, H. Tomii, R. Matsubara, M. Sakai, K. Kudo, M. Nakamura, Appl. Phys. Lett. 91 (2007) 162105). We use THz time-domain spectroscopy for OFETs in which the carrier density in the pentacene active layer is modulated by the gate bias. We found evidence that the accumulated free holes in pentacene films can be excited by THz photons to overcome the surrounding barriers in the fluctuating potential. The Drude–Lorentz model could not account for the shape of the absorption spectra, which suggests that the holes are weakly restricted by the potential fluctuation. The integrated absorption intensity was proportional to the transfer characteristics of the OFETs. The present findings represent an important step toward developing a new class of THz-wave sensors. 相似文献
999.
Dr. Takashi Sakamoto Rikuto Yamada 《Chembiochem : a European journal of chemical biology》2019,20(10):1242-1245
A new label-free in situ monitoring system for the hybridization chain reaction (HCR) based on DNA minor-groove-binding fluorophores [Hoechst 33258 (Hoe) or quinone cyanine-dithiazole (QCy-DT)] has been developed. Use of two unmodified hairpin oligodeoxyribonucleotides containing incomplete double-stranded AATT sequences enabled target-dependent formation of probe binding sites—that is, AATT double strand—in the HCR product, together with fluorescence enhancement of minor-groove-binding fluorophores in situ. This system allows target DNA to be detected through the fluorescence enhancement of Hoe and QCy-DT in real time and in situ. Further development of a label-free, isothermal detection system might provide a cost-effective and user-friendly method for nucleic acid detection. 相似文献
1000.
Takashi Nozawa Takaaki Koyanagi Yutai Katoh Hiroyasu Tanigawa 《Journal of the European Ceramic Society》2019,39(8):2634-2647
SiC/SiC composites are promising structural candidate materials for various nuclear applications over the wide temperature range of 300–1000 °C. Accordingly, irradiation tolerance over this wide temperature range needs to be understood to ensure the performance of these composites. In this study, neutron irradiation effects on dimensional stability and mechanical properties to high doses (11–44 dpa) at intermediate irradiation temperatures (?600 °C) were evaluated for Hi-Nicalon Type-S or Tyranno-SA3 fiber–reinforced SiC matrix composites produced by chemical vapor infiltration. The influence of various fiber/matrix interfaces, such as a 50–120 nm thick pyrolytic carbon (PyC) monolayer interphase and 70–130 nm thick PyC with a subsequent PyC (?20 nm)/SiC (?100 nm) multilayer, was evaluated and compared with the previous results for a thin-layer PyC (?20 nm)/SiC (?100 nm) multilayer interphase. Four-point flexural tests were conducted to evaluate post-irradiation strength, and SEM and TEM were used to investigate microstructure. Regardless of the fiber type, monolayer composites showed considerable reduction of flexural properties after irradiation to 11–12 dpa at 450–500 °C; and neither type showed the deterioration identified at the same dose level at higher temperatures (>750 °C) in a previous study. After further irradiation to 44 dpa at 590–640 °C, the degradation was enhanced compared with conventional multilayer composites with a PyC thickness of ?20 nm. Multilayer composites have shown comparatively good strength retention for irradiation to ?40 dpa, with moderate mechanical property degradation beginning at 70–100 dpa. Irradiation-induced debonding at the F/M interface was found to be the major cause of deterioration of various composites. 相似文献