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排序方式: 共有416条查询结果,搜索用时 9 毫秒
31.
Summary The ring-opening polymerization of deoxophostone 5, a five-membered cyclic phosphinite, has been studied. Some cationic initiators gave polymer whereas anionic and radical initiators as well as metal chloride (Lewis acid) catalysts did not yield polymer. The polymer consisted of a phosphine oxide repeating unit 6. The polymerization proceeded via the Arbuzov-type reaction. The reduction of polymer 6 with a HSiCl3/Et3N system gave polyphosphine 7. 相似文献
32.
Shiro Seki Takeshi Kobayashi Nobuyuki Serizawa Yo Kobayashi Katsuhito Takei Hajime Miyashiro Kikuko Hayamizu Seiji Tsuzuki Takushi Mitsugi Yasuhiro Umebayashi Masayoshi Watanabe 《Journal of power sources》2010,195(18):6207-6211
The physicochemical and electrochemical properties of three 1-alkyl-2,3,5-trimethylpyrazolium cation-based room-temperature ionic liquids with various alkyl chain lengths were investigated. The temperature dependences of density, viscosity, and ionic conductivity were obtained by precise measurements. Electrolyte properties of these room-temperature ionic liquids were also examined from the viewpoint of their uses in lithium secondary batteries ([LiCoO2 positive electrode|electrolyte|lithium metal negative electrode]). It was found that the alkyl chain length affects the charge–discharge performances of cells. 相似文献
33.
Primbs T Simonich S Schmedding D Wilson G Jaffe D Takami A Kato S Hatakeyama S Kajii Y 《Environmental science & technology》2007,41(10):3551-3558
To estimate the emissions of anthropogenic semivolatile organic compounds (SOCs) from East Asia and to identify unique SOC molecular markers in Asian air masses, high-volume air samples were collected on the island of Okinawa, Japan between 22 March and 2 May 2004. Contributions from different source regions (China, Japan, the Koreas, Russia, and ocean/local) were estimated by use of source region impact factors (SRIFs). Elevated concentrations of hexachlorobenzene (HCB), hexachlorcyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs), and particulate-phase polycyclic aromatic hydrocarbons (PAHs) were attributed to air masses from China. A large proportion of the variation in the current-use pesticides, gas-phase PAHs, and polychlorinated biphenyl (PCB) concentrations was explained by meteorology. Chlordanes showed a technical mixture profile and similar concentrations regardless of source region. alpha/gamma HCH and trans/cis chlordane ratios did not vary significantly with different source regions and had regional averages of 2.5 +/- 1.0 and 1.2 +/- 0.3, respectively. Particulate-phase PAH concentrations were significantly correlated (p value < 0.05) with other incomplete combustion byproduct concentrations, including elemental mercury (Hg0), CO, NOx, black carbon, submicrometer aerosols, and SO2. By use of measured PAH, CO, and black carbon concentrations and estimated CO and black carbon emission inventories, the emission of six carcinogenic particulate-phase PAHs was estimated to be 1518-4179 metric tons/year for Asia and 778-1728 metric tons/year for China, respectively. These results confirm that East Asian outflow contains significant emissions of carcinogenic particulate-phase PAHs. 相似文献
34.
35.
Shiro Torizuka Kaoru Sato Hiroaki Nishio Teruo Kishi 《Journal of the American Ceramic Society》1995,78(6):1606-1610
Compacts of TiB2 with densities approaching 100% are difficult to obtain using pressureless sintering. The addition of SiC was very effective in improving the sinterability of TiB2 . The oxygen content of the raw TiB2 powder used in this research was 1.5 wt%. X-ray photoelectron spectroscopy showed that the powder surface consisted mainly of TiO2 and B2 O3 . Using vacuum sintering at 1700°C under 13–0.013 Pa, TiB2 samples containing 2.5 wt% SiC achieved 96% of their theoretical density, and a density of 99% was achieved by HIPing. TEM observations revealed that SiC reacts to form an amorphous phase. TEM-EELS analysis indicated that the amorphous phase includes Si, O, and Ti, and X-ray diffraction showed the reaction to be TiO2 + SiC → SiO2 + TiC. Therefore, the improved sinterability of TiB2 resulted from the SiO2 liquid phase that was formed during sintering when the raw TiB2 powder had 1.5 wt% oxygen. 相似文献
36.
Shiro Matsuoka 《Journal of research of the National Institute of Standards and Technology》1997,102(2):213-228
The high frequency end of the relaxation spectrum for polymer molecules involves the rotation of the segmental bonds. This fast relaxation process, however, cannot take place easily in the condensed state crowded by the densely packed conformers, necessitating the slower cooperatively synchronous relaxation. As the temperature is lowered, the domain of cooperativity grows towards the infinite size at the Kauzmann zero entropy temperature, though actually the system deviates from the equilibrium as the glass transition intervenes typically at 50 K above that temperature. The excess enthalpy and entropy drop faster than predicted by the rotational isomeric states which would reach zero only at 0 K. The real ΔCP is greater than that of the RIS value. The actual volume in excess of the crystalline lattice volume, however, points towards zero at 0 K. Thus, a polymer with higher Tg typically exhibits a lower density and modulus in the glassy state. Since the configurational entropy associated with the free volume is proportional to the logarithm of the latter, the Kauzmann temperature can be scaled by ln M, where M is the algebraic average of the conformer molecular weight. The temperature dependence of the most dominant, i.e., the largest equilibrium domain size will result in the Adam-Gibbs and Vogel equations for the characteristic relaxation time. The cooperative domain distribution leads to the relaxation spectrum that follows a power law. The relationship between the characteristic relaxation time and the rate of physical aging is derived. 相似文献
37.
38.
Shiro Usui Nilton Liuji Kamiji Tatsuki Taniguchi Naonori Ueda 《Neural computing & applications》2011,20(7):993-999
With the increasing amount of information available in recent years, searching for the desired content is becoming a challenging
task. In this work, a tool for searching abstracts submitted to scientific conferences is introduced. It not only searches
abstracts by the given keyword(s) but also displays abstracts related to a single or multiple selection. It also displays
highly relevant abstracts together with possible keywords to help users refine their search. Analysis of the conditional similarity
algorithm proposed here has shown that it does provide better output compared to ordinary cosine similarity, as well as the
list of possible keywords reflects results of latent topic analysis. An interface for storing and sorting selected abstracts
for future review and/or printing is also provided. 相似文献
39.
Dispersion polymerization of styrene in an aqueous alcohol solution using poly(2-ethyl-2-oxazoline) as a polymeric stabilizer was performed to prepare micron-size monodisperse polystyrene particles. As the water content of the solvent increased, the polymerization rate and the molecular weight of the polymer particles increased and the particle size decreased. Effects of concentrations of stabilizer and initiator upon the polymerization and the size of the resulting polystyrene particles have been examined in the solvent containing different water contents. 相似文献
40.
Case studies on process sequence design in cold forming of engine valve slider and self-locking nuts
Two cases on process sequence design are presented. One describes the procedure for manufacturing an engine valve slider, and the other for self-locking nut manufacturing. They are based on experts' experience. All operations required to produce final products, from raw material are shown, and general considerations and rules for forming sequence design are explained. For engine valve sliders several upsetting processes are used preforming operations and the final product is obtained by combined forward and backward extrusion. In manufacturing of self-locking nuts special features involved in design are shown in turning the workpiece upside down during the process sequence and producing intentionally a minor crack for the final operation of piercing. In addition, both macro structure and micro structure analysis for major deformation processes are shown. 相似文献