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21.
The minimum sequence lengths (nc) of vinyl acetate (VAc) units necessary to form a colored iodine complex were determined to be 4 and 17 for radically polymerized VAc/vinyl propionate (VPr) and VAc/isopropenyl acetate (IPAc) copolymers, respectively. The iodine affinities (I/VAc) of VAc/VPr copolymers (SP-series) obtained by propionylation of partially saponified polyvinyl acetate (PVAc) were remarkably affected by the saponification conditions. An increase of the water content in acetone/water mixture as saponification solvent brought about a decrease of the iodine affinities of the SP-series. The dependence of the iodine affinity on the saponification of monomer units in the SP-series was compared with that in the radically polymerized VAc/VPr copolymers by taking the sequence probability as the measure of monomer unit distribution. The results strongly supported an occurence of the slide fastener reaction at high degrees of saponification, which was well-known in the saponification of PVAc. Furthermore, it was found that the saponification mode of PVAc at low degrees of saponification was influenced uniquely by the water content in saponification solvents and the saponification temperature. 相似文献
22.
The effect of the reaction kinetics on the ionic conductivity for a comblike‐type polyether (MEO) electrolyte with lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) was characterized by DSC, complex impedance measurements, and 1H pulse NMR spectroscopy. The ionic conductivity of these electrolytes was affected by the reaction condition of the methacrylate monomer and revealed by the glass transition temperature (Tg), spin–spin relaxation time (T2), steric effects of the terminal groups, and the number of charge carriers indicated by the VTF kinetic parameter. In this system, the electrolytes prepared by the reaction heating rate of 10°C/min of MEO–H and 15°C/min of MEO–CH3 showed maximum ionic conductivity, σi, two to three times higher in magnitude than that of the σi of the others at room temperature. As experimental results, the reaction kinetic rate affected the degree of conversion, the ionic conductivity, and the relaxation behaviors of polyether electrolytes. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2149–2156, 2003 相似文献
23.
Ken Kihara Hirotaka Fujisaki Sakuichi Ohtsuka Masaru Miyao Jun Shimamura Hiroyuki Arai Yukinobu Taniguchi 《Journal of the Society for Information Display》2014,22(7):329-336
Some stereoblind observers do not perceive depth of 3D stimuli that depends on binocular disparity. These individuals, who have no disabilities, comprise over 5% of the general population. In addition, 17–30% of nonstereoblind young and young–middle people do not use disparity information in certain 3D environments, a phenomenon known as pseudo‐stereoblindness. This study aimed to investigate the relationship between aging and the proportion of pseudo‐stereoblindness in the general population. In an experiment, 134 nonstereoblind participants, ranging in age from 17 to 83 years, judged subjective depth of 3D stimuli containing binocular disparity and pictorial depth cues. Results showed that the proportion of pseudo‐stereoblindness among young (17–24 years old) and young–middle aged observers (25–39 years old) was 29%, in both cases. However, the proportion of pseudo‐stereoblind observers increased in older populations: 65% and 82% in the middle (40–54 years old) and senior (55–83 years old) age groups, respectively. These results suggest that a number of people, especially in elderly populations, have trouble perceiving depth from binocular disparity in 3D graphic contents despite their essential ability to use disparity information. 相似文献
24.
Poly(ethylene phthalate) (PEP) and poly(ethylene phthalate–co‐ethylene terephthalate) were used to improve the brittleness of the cycloaliphatic epoxy resin 3,4‐epoxycyclohexylmethyl 3,4‐epoxycyclohexane carboxylate (Celoxide 2021?), cured with methyl hexahydrophthalic anhydride. The aromatic polyesters used were soluble in the epoxy resin without solvents and effective as modifiers for toughening the cured epoxy resin. For example, the inclusion of 20 wt % PEP (MW, 7400) led to a 130% increase in the fracture toughness (KIC) of the cured resin with no loss of mechanical and thermal properties. The toughening mechanism is discussed in terms of the morphological and dynamic viscoelastic behaviors of the modified epoxy resin system. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 388–399, 2002; DOI 10.1002/app.10363 相似文献
25.
Radical polymerization of butyl acrylate (BA) and random copolymerizations of styrene (St) and BA and St and methyl methacrylate (MMA) in the presence of 7-aza-15-hydroxydispiro[5.1.5.3]hexadecane-7-yloxyl (1) and 1-aza-2,2-dimethyl-4-hydroxyspiro[5.6]dodecane-1-yloxyl (2) were carried out. Radical polymerization of BA at 120 °C in the presence of 1 gave poly(BA) with Mn=20200 and Mw/Mn=1.30 at 23% conversion. The termination of polymerization observed around ∼20% conversion was solved to a certain extent by an addition of small amounts of dicumyl peroxide, and poly(BA) with Mn=37400 and Mw/Mn=1.33 was obtained in 46% yield. Random copolymerizations of St and BA and St and MMA in the presence of 1 and 2 at 80 °C gave the corresponding random copolymers with narrow polydispersities of 1.12-1.38 at the molar fraction above 0.30 of St in feed. The kinetic study for the NO-C bond homolysis of the corresponding alkoxyamines prepared from 1 and 2 were carried out, and evaluation of the preexponential factors (Aact) and the activation parameters (Eact) showed that the steric factors of the nitroxides are reflected mainly on Eact. 相似文献
26.
Masao Tomikawa Frank W. Harris Stephen Z. D. Cheng Edward Galentier 《Reactive and Functional Polymers》1996,30(1-3):101-107
A series of new, substituted pyromellitic dianhydrides were synthesized from 1,2,4,5-tetramethylbenzene. New soluble rigid-rod polyimides were obtained from the dianhydrides and 2,2′-bis(trifluoromethyl)-4,4′-biphenyl (PFMB) in phenolic solvents in the presence of isoquinoline as a catalyst. The polyimides are soluble in N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), m-cresol and other solvents, in spite of having no bending in their rigid structures.
UV irradiation changed color of the polyimide solutions and also their viscosity. We observed new absorbance in the 700-nm region and an ESR signal by UV irradiation. The new visible absorbance and the ESR signal are derived from the same origin. They are attributed to the anion radical of the diimide moiety in the polyimide as deduced from the hyper fine structure of the ESR signal. In addition, UV irradiation diminishes the solution viscosity. 相似文献
27.
Shigeji Taniguchi Toshio Shibata Naoyuki Asanuma Hanyi Lou Fuhui Wang Weitao Wu 《Oxidation of Metals》1993,39(5-6):457-473
The oxidation behavior of TiAl coupons coated with a fine-grain Co-30Cr-4Al (mass %) film of about 30-m thickness has been studied at 1100–1400 K in a flow of purified oxygen at atmospheric pressure for up to 500 ks. Three oxidation stages were recognized: initial transient, parabolic, and accelerated stages. However, at 1100 K a parabolic stage continues for more than 800 ks. The activation energy for parabolic oxidation agrees with reported values for the oxidation of alumina-former alloys, although the mass gains during the parabolic stages are relatively small at 1200 and 1300 K. Micropores developed mainly at the scale/coating and coating/substrate interfaces as oxidation proceeded. This is attributable to recrystallization of the coating during oxidation and a Kirkendall effect due to preferential diffusion of Co into the substrate. The accelerated oxidation can be explained in terms of the formation of rutile mounds on the scale. 相似文献
28.
Sun-Chan Jeong Ichiro Katayama Hirokane Kawakami Yutaka Watanabe Hironobu Ishiyama Nobuaki Imai Yoshikazu Hirayama Hiroari Miyatake Masao Sataka Satoru Okayasu Hiroyuki Sugai Shin-Ichi Ichikawa Katsuhisa Nishio Shinichi Mitsuoka Takamitsu Nakanoya Masahito Yahagi Takanori Hashimoto Kazunori Takada Mamoru Watanabe Tomoko Ishikawa Akihiro Iwase 《Journal of Phase Equilibria and Diffusion》2005,26(5):472-476
For the effective use of short-lived radioactive beams, soon to be available at the Tokai Radioactive Ion Accelerator Complex, the authors have developed a radiotracer method for diffusion studies in solids. The experimental test was performed by the measurement of the diffusion coefficients of Li in a sample of the compound βLiAl using an α-emitting radiotracer of 8Li (T1/2=0.84 s). It was found that the time-dependent yields of the α particles from the diffusing 8Li that was initially implanted in the sample could be used as a measure of the diffusivity of the tracer in a nondestructive way. The method was applied to measure the self-diffusion coefficients of Li in βLiGa, and for investigating how the Li diffusion in the Li ionic conductors is affected by the concentration of atomic defects (i.e., the existence of the atomic vacancies of Li and the defects in Ga sites that are replaced by Li). 相似文献
29.
Masahiro Hayashi Masahiko Jin Sutasn Thipprakmas Masao Murakawa Jung-Chung Hung Yu-Chung Tsai Ching-Hua Hung 《Journal of Materials Processing Technology》2003,140(1-3):30-35
In ultrasonic-vibration drawing, wires are drawn while ultrasonic vibration is applied to a drawing die. Prior studies provide experimental proof that ultrasonic-vibration drawing reduces drawing resistance, improves lubrication and prevents wire breakage. In the future, ultrasonic-vibration drawing is expected to contribute to the drawing of difficult-to-draw materials and operations, such as shaped wires, ultrafine wires, and the wire drawing operation in semidry or dry condition. However, a detailed analysis and understanding of the mechanism of improvement is not possible on the basis of conventional experimental observations because the ultrasonic-vibration processing phenomenon occurs at high speed. Therefore, we attempted to understand the processing mechanism of ultrasonic-vibration drawing using the finite element method (FEM). ABAQUS was used for the FEM. Drawing force and stress–strain distributions in drawn wires were analyzed. From these studies, we quantitatively clarified the mechanism of improved drawing characteristics, such as decreased drawing force. 相似文献
30.
Emad Shihab Akinori Ihara Yasutaka Kamei Walid M. Ibrahim Masao Ohira Bram Adams Ahmed E. Hassan Ken-ichi Matsumoto 《Empirical Software Engineering》2013,18(5):1005-1042
Bug fixing accounts for a large amount of the software maintenance resources. Generally, bugs are reported, fixed, verified and closed. However, in some cases bugs have to be re-opened. Re-opened bugs increase maintenance costs, degrade the overall user-perceived quality of the software and lead to unnecessary rework by busy practitioners. In this paper, we study and predict re-opened bugs through a case study on three large open source projects—namely Eclipse, Apache and OpenOffice. We structure our study along four dimensions: (1) the work habits dimension (e.g., the weekday on which the bug was initially closed), (2) the bug report dimension (e.g., the component in which the bug was found) (3) the bug fix dimension (e.g., the amount of time it took to perform the initial fix) and (4) the team dimension (e.g., the experience of the bug fixer). We build decision trees using the aforementioned factors that aim to predict re-opened bugs. We perform top node analysis to determine which factors are the most important indicators of whether or not a bug will be re-opened. Our study shows that the comment text and last status of the bug when it is initially closed are the most important factors related to whether or not a bug will be re-opened. Using a combination of these dimensions, we can build explainable prediction models that can achieve a precision between 52.1–78.6 % and a recall in the range of 70.5–94.1 % when predicting whether a bug will be re-opened. We find that the factors that best indicate which bugs might be re-opened vary based on the project. The comment text is the most important factor for the Eclipse and OpenOffice projects, while the last status is the most important one for Apache. These factors should be closely examined in order to reduce maintenance cost due to re-opened bugs. 相似文献