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101.
Soluble polyimides (PIs) were prepared as random or multiblock types with 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (s‐BPDA) as acid dianhydride components and 4,4′‐bis(m‐aminophenoxy) diphenyl sulfone (m‐BAPS) as a diamine component by a one‐pot process and used to improve the brittleness of the cyanate ester resin. Random‐type PIs were more effective as modifiers than multiblock‐type PIs. The morphologies of the modified resins depended on PI structure, molecular weight, and concentration. The most effective modification of the cyanate ester resin was attained because of a heterogeneous phase structure composed of a flat matrix phase and phase‐inverted structures of the modified resin; a 15 wt % inclusion of a random PI (weight‐average molecular weight = 63,400) composed of 6FDA, s‐BPDA, and m‐BAPS (0.5/0.5/1.0 molar ratio) led to a 65% increase in the fracture toughness for the modified resin with a slight loss of flexural strength and a retention of flexural modulus and glass‐transition temperature, compared with the values for the unmodified resin. Water absorptivity of the modified resin was comparable to that of the unmodified resin up to 400 h, and then, water absorption of the modified resins increased considerably. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1–11, 2003 相似文献
102.
Masaaki Yokoyama Tomohiro Zaita 《International journal for numerical methods in engineering》1992,35(6):1277-1288
In order to obtain accurate results and to reduce computation time, we have proposed in this paper a new strategic method, where quadratic elements are used at the corner points and linear elements at the points off the corner points. A computer program using this method has been developed and applied to several problems of various shapes. The usefulness of this method was illustrated by the application results. 相似文献
103.
Tomohiro Higashihara Kumiko Kinoshita Seichi Sato Tamotsu Kozaki 《Applied Clay Science》2004,26(1-4):91
Sodium ions spiked with 22Na as a tracer were migrated by electromigration and electro-osmosis in the water-saturated compacted Na-montmorillonite at dry densities 1.0×103 kg m−3, under an electric potential gradient. Dissolved helium was also migrated by electro-osmosis in the montmorillonite. After migration, concentration profiles of the sodium ions and helium were obtained by γ-spectrometry and mass-spectrometric methods, respectively. From the profiles of both chemical species, not only migration due to electrokinetic phenomena but also mechanical dispersion was observed in the montmorillonite. The dispersion coefficients, Di, and apparent migration rates, Uia, of 22Na and helium were found in the compacted Na-montmorillonite at 1.0×103 kg m−3. The migration of helium in the montmorillonite under an electric potential gradient reflects that of water because helium migrates as an electrically neutral species. The parameters DHem, UHea, and αHe correspond to those of water. The mechanical dispersion coefficients, DNam, of 22Na+ ions are much smaller than those of water obtained by helium. The dispersivity parameters, αNa, for 22Na+ obtained from these DNa and UNaa values are 10−5 m and those for water (αHe) are 10−3 m. This indicates that 22Na+ ions migrate in different spaces than water in the compacted montmorillonite under a potential gradient. This finding suggests that the migration of Na+ ions occurs in the interlayer and/or on the outer surfaces of the montmorillonite; whereas dissolved helium migrates in the pore water. 相似文献
104.
Encapsulation of lead-free Sn/Zn/Bi solder alloy particles by coating with wax powder for improving oxidation resistance 总被引:2,自引:0,他引:2
Tomohiro Iwasaki Jeong Hwan Kim Shohei Mizuhashi Munetake Satoh 《Journal of Electronic Materials》2005,34(5):647-654
An encapsulation treatment of lead-free Sn/Zn/Bi solder powder was investigated for improving the oxidation resistance. Sn-8mass%Zn-3mass%Bi
alloy particles were coated with a wax (12-hydroxystearic acid) powder by means of a dry mechanical treatment method using
a ball mill. In order to determine the optimum operating conditions of the ball mill in the wax-coating treatments, the compressive
energy required for deforming a single Sn/Zn/Bi alloy particle was measured with an unconfined compression tester and the
mechanical energy applied to the alloy particles in the ball mill was estimated using the results of the compression test.
The optimum operating conditions were determined based on both the applied energy and the flowability of solder pastes, and
the wax-coated alloy particles maintaining the spherical shape were obtained under the conditions. The wettability test and
the solder balling test for the solder pastes containing the wax-coated alloy particles stored at room temperature in air
were carried out to evaluate the oxidation resistance performance. The wax-coated alloy particles had an excellent wettability
compared with the original alloy particles, and the oxidation resistance of the Sn/Zn/Bi solder powder was improved by the
encapsulation treatment. 相似文献
105.
The allowable maximum coating speed of optical fibers has been correlated to the flow properties of the coating material itself. The maximum smooth coating speed has been measured from the coating thickness fluctuation-coating speed curves using several types of silicone resins. Flow curves of the silicone resins also have been measured by two different viscometers, i.e., cone-plate and capillary viscometers. The maximum smooth coating speed, at which the coating thickness fluctuation begins to increase, has been found to correspond to the critical shear rate at which the flow curve deviates from a power law. This correspondence probably results from the fact that the slip occurs both at the fiber-coating material interface and at the viscometer (cone, plate, or capillary)-coating material interface. Accordingly, the maximum smooth coating speed can be predicted from the critical shear rate value without the actual fiber coating experiments. 相似文献
106.
Hiroyuki Miyamura Aya Suzuki Tomohiro Yasukawa Sh Kobayashi 《Advanced Synthesis \u0026amp; Catalysis》2015,357(18):3761-3761
107.
Alexandru I. Petrisor Sandra Szyjka Tomohiro Kawaguchi Pieter T. Visscher Robert Sean Norman Alan W. Decho 《International journal of molecular sciences》2014,15(1):850-877
Microspatial arrangements of sulfate-reducing microorganisms (SRM) in surface microbial mats (~1.5 mm) forming open marine stromatolites were investigated. Previous research revealed three different mat types associated with these stromatolites, each with a unique petrographic signature. Here we focused on comparing “non-lithifying” (Type-1) and “lithifying” (Type-2) mats. Our results revealed three major trends: (1) Molecular typing using the dsrA probe revealed a shift in the SRM community composition between Type-1 and Type-2 mats. Fluorescence in-situ hybridization (FISH) coupled to confocal scanning-laser microscopy (CSLM)-based image analyses, and 35SO4
2−-silver foil patterns showed that SRM were present in surfaces of both mat types, but in significantly (p < 0.05) higher abundances in Type-2 mats. Over 85% of SRM cells in the top 0.5 mm of Type-2 mats were contained in a dense 130 μm thick horizontal layer comprised of clusters of varying sizes; (2) Microspatial mapping revealed that locations of SRM and CaCO3 precipitation were significantly correlated (p < 0.05); (3) Extracts from Type-2 mats contained acylhomoserine-lactones (C4-, C6-, oxo-C6 C7-, C8-, C10-, C12-, C14-AHLs) involved in cell-cell communication. Similar AHLs were produced by SRM mat-isolates. These trends suggest that development of a microspatially-organized SRM community is closely-associated with the hallmark transition of stromatolite surface mats from a non-lithifying to a lithifying state. 相似文献
108.
Tetsuya Yamamoto Azamat Zhumagazin Takuma Furusawa Ryoji Tanaka Tetsu Yamakawa Yohei Oe Tetsuo Ohta 《Advanced Synthesis \u0026amp; Catalysis》2014,356(17):3525-3529
Cyclometallated NHC palladium complexes prepared from palladium(II) acetate [Pd(OAc)2] and unsymmetrical 1,3‐diarylimidazolinium salts catalyzed the hydroxymethylation of (hetero)arylboronic acids using an excess amount of formalin to afford (hetero)arylmethanols in good to satisfactory yields.
109.
110.
Hosokai S Kasiwaya Y Matsui K Okinaka N Akiyama T 《Environmental science & technology》2011,45(2):821-826
This paper describes the reduction of hematite with ammonia for ironmaking, in which the effect of temperature on the products was examined. The results showed that the reduction process began at 430 °C during heating, and with an increase in temperature, the reduction mechanism changed apparently from a direct reduction of ammonia (Fe(2)O(3) + 2NH(3) → 2Fe + N(2) + 3H(2)O) to an indirect reduction via the thermal decomposition of ammonia (2NH(3) → N(2) + 3H(2), Fe(2)O(3) + 3H(2) → 2Fe + 3H(2)O) at temperatures over 530 °C. The final product obtained at 600 and 700 °C was pure metallic iron, in contrast with that formed at 450 °C, that is, a mixture of metallic iron and iron nitride. The results suggest the possibility of using ammonia as a reducing agent for carbonless ironmaking, which is operated at a much lower temperature than 900 °C in conventional coal-based ironmaking. 相似文献