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121.
Cross-linking of the cholesteric liquid-crystalline order in a hydroxypropyl cellulose (HPC) aqueous solution was attempted and the swelling and mechanical (static and dynamic) properties of cast films were determined. HPC solid films cast from the liquid-crystalline aqueous solution with dialdehyde (glyoxal or glutaraldehyde) and hydrochloric acid were insoluble in water and retained the right-handed cholesteric liquid-crystalline order. The swelling and static tensile properties exhibited a general behaviour with respect to the concentration of the cross-linking agent and to the heat treatment. However, dynamic and loss moduli exhibited an opposite behaviour to the static tensile modulus. A cross-linking mechanism is proposed for HPC molecules and dialdehydes based on the swelling and mechanical properties of HPC films cast from two dialdehyde systems. 相似文献
122.
This paper describes the technical details of an experimental HDTV digital VTR with a bit rate of 1.188 Gbps. This newly developed machine satisfies the proposed parameter values in the CCIR Report 801. The basic technologies developed to achieve such an ultra-high speed recording are: metal particle tape and Sendust sputtered type head, a high performance head assembly, and parallel signal processing. Using 8 recording heads, the recording rate per channel is 148.5 Mbps and the minimum recording wavelength is 0.69 pm. The error control mechanism, based on Reed-Solomon product code, worked sufficiently well with the overhead for parity, sync code and ID code in the blanking period. Even after 20th generation dubbing, no picture quality degradation has been observed. 相似文献
123.
R. Yoshinaka T.V. Tran M. Osada 《International Journal of Rock Mechanics and Mining Sciences》1998,35(7):941-955
Four saturated Miocene soft rocks of Japan i.e. Ohya tuff, Yokohama siltstone, Kobe mudstone and sandstone were tested under consolidated-undrained, cyclic loading conditions. The deformation behavior, pore pressure changes and strength mobilization, and contraction/dilation characteristics of these rocks were studied with emphasis on the non-linearity, stress- and strain-dependence of their mechanical properties. A procedure was introduced to locate the yield point, to estimate Young's modulus and to study the deformation behavior of these soft rocks. Deformation modulus was found to depend on plastic straining according to an exponential equation, whose coefficients in turn, depend on confining pressure. In addition, it also depends on the deviatoric stress levels causing hysteresis to occur. Patterns of pore pressure changes and associated failure modes were interpreted in terms of the initiation/propagation of micro- and macro-cracks inside the specimens. Characteristic stress levels were found, based on which the “true” rock strength components — cohesion and internal friction angle — were determined and their mobilization with respect to stress and strain levels was analyzed using a new interpretation method. Volume change tendencies were inferred from pore pressure changes whose rate was related to the contraction/dilation behavior of soft rocks. On that basis the dilation angle was estimated and its variation and stress- and strain-dependence was analyzed. A simple equation was introduced to characterize the variation of both internal friction and dilation angles with plastic straining, whereas their stress-dependence was studied through the variation of fit coefficients with confining pressure. 相似文献
124.
Yoshinori Sato Hikaru Nishizaka Shunichi Sawano Atsushi Yoshinaka Kazutaka Hirano Shinji Hashiguchi Takayuki Arie Seiji Akita Go Yamamoto Toshiyuki Hashida Hisamichi Kimura Kenichi Motomiya Kazuyuki Tohji 《Carbon》2012,50(1):34-39
We prepared and characterized multi-walled carbon nanotube (MWCNT) solids by de-fluorination of fluorinated MWCNTs using spark plasma sintering. In order to investigate the influence of the structure of MWCNT on the mechanical strength of the resulting solids, MWCNTs used in this experiment were as-defected MWCNTs modified by nitric acid and as-purified ones as non-defected nanotubes by comparison. The bend strength and modulus of the resulting solids were lower than those of de-fluorinated MWCNT solids derived from as-purified MWCNTs. The mechanical properties of the resulting MWCNT solids were found to be strongly dependent on the structure of the MWCNT. 相似文献
125.
Franois‐Xavier Jett AkioC. Yoshinaka AndrewJ. Higgins Fan Zhang 《Propellants, Explosives, Pyrotechnics》2003,28(5):240-248
The factors influencing initiation of detonation in gap tests for liquid explosives are investigated experimentally. A calibrated donor charge (nitromethane) and PMMA attenuator disk arrangement are used to transmit shocks of known strength (2–10 GPa) into a test explosive of nitromethane sensitized with 5% diethylenetriamine. The test explosive is contained in capsules of different wall materials (PVC, Teflon, aluminum), and the dimensions of the charges vary from 25 mm to 100 mm in diameter. For the small‐scale charges, the presence of the confining wall of the test capsule is seen to have a pronounced effect on the detonation initiation. Certain wall materials (PVC, Teflon) exhibit a multi‐valued critical gap thickness, meaning that a weaker shock may result in initiation while a stronger shock does not. The effect of the wall materials could not be correlated with their acoustic or shock impedance, and the only way to eliminate these effects was to make the diameter of the test charge larger than the donor charge. When the size of the donor charge was increased, the critical pressure required for initiation decreased. These results could be correlated to “ideal” shock initiation experiments that use flyer plates as shock sources assuming that lateral rarefactions quench detonation initiation if they reach the central axis of the charge before the onset of detonation is complete. 相似文献
126.
127.
Masayuki Imose Yoshihiko Takano Masaru Yoshinaka Ken Hirota Osamu Yamaguchi 《Journal of the American Ceramic Society》1998,81(6):1537-1540
Boehmite (AlO(OH)) solid-solution gel, which yields stoichiometric mullite (3Al2 O3 2SiO2 ) at high temperatures, has been prepared by the hydrazine method. The formation process leading to 3Al2 O3 2SiO2 is discussed. The as-prepared powder and powders heated below 1200°C consist of very fine particles showing needlelike morphology, whereas the particles of mullite powder show thin prismatic morphology. The mullite powder after heating at 1300°C has a high surface area (87 m2 /g). 相似文献
128.
Noriyuki Yoshida Yoshihiko Takano Masaru Yoshinaka Ken Hirota Osamu Yamaguchi 《Journal of the American Ceramic Society》1998,81(8):2213-2215
Picrochromite (MgCr2 O4 ) crystallizes at 480° to 530°C from an amorphous material prepared by the hydrazine method. The MgCr2 O4 powders were characterized for particle size and surface area. Individual particles tend toward a hexagonal morphology above 1000°C. Dense MgCr2 O4 ceramics (99.5% of theoretical) with an average grain size of 2 μm have been fabricated by spark plasma sintering for 5 min at 1400°C and 30 MPa. Their fracture toughness and bending strength are 3.7 MPa·m1/2 and 310 MPa, respectively. 相似文献