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排序方式: 共有1777条查询结果,搜索用时 15 毫秒
41.
The reactions of ruthenium VIII tetroxide (RuO4) and the ruthenium VII and VI oxyanions, perruthenate (RuO4
−) and ruthenate (RuO4
=) with hydroxy substituted and unsaturated fatty acids have been studied. At a 1:1 molar ratio, ruthenium tetroxide (RuO4) and both oxyanions (RuO4
− and RuO4
=) oxidized 12-hydroxystearic acid to 12-ketostearic acid. With 9, 10-dihydroxystearic acid, the type of oxidation products
obtained depended on the amount of ruthenium oxidant used. At high ratios of oxidant to substrate, cleavage to pelargonic
and azelaic acids occurred whereas at lower ratios, partial oxidation to diketo and acyloin derivatives predominated. The
oxidation of oleic acid with excess ruthenium tetroxide (RuO4) or perruthenate anion (RuO4
−) gave the cleavage products pelargonic and azelaic acid through the intermediate formation of dihydroxy and diketo intermediates.
Ruthenate anion (RuO4
=) did not react with the double bond of oleic acid.
Agricultural Research Service, U.S. Department of Agriculture. 相似文献
42.
The purpose of this paper is to present a metod to calculate real molecular weight averages of polymer samples from GPC chromatograms where the instrumental spreading functions are skewed and the concentration effect exists. In this method, it is assumed that (1) the skewed chromatograms of monodisperse polymer samples can be represented as resultant of halves of two different Gaussians, (2) the resolution factors are regarded as constant in the case of low sample loading, and (3) the peak elution volume is independent of the presence of other components in the case of low sample loading. Adequate monodisperse polystyrenes and the mixtures (binary, seven and ten components) were examined for this purpose; and the molecular weight averages calculated by this method were compared with the ones obtained by Rosen and Provder's method. From the results in our study, it is found that this method can be available for correcting molecular weight from GPC chromatograms except for very narrow high molecular weight samples. 相似文献
43.
Ismayil Nurulla Akitoshi TanimotoKouichi Shiraishi Shintaro SasakiTakakazu Yamamoto 《Polymer》2002,43(4):1287-1293
Polycondensation by Stille coupling of 2-decyl-4,7-dibromobenzimidazoles and N-methyl-2-decyl-4,7-dibromobenzimidazole with 2,5-bis(trimethylstannyl)thiophene and 5,5′-bis(trimethylstannyl)-2,2′-bithiophene gave the corresponding π-conjugated polymers, poly(2-decylbenzimidazole-4,7-diyl-thiophene-2,5-diyl) 1b, poly(2-decylbenzimidazole-4,7-diyl-bithiophene-2,5-diyl) 1c and poly(N-methyl-2-decylbenzimidazole-4,7-diyl-thiophene-2,5-diyl) 2b, in 98-99% yields. The polymers 1b and 2b were fully soluble in CF3COOH, and partially soluble in DMF (about 60 and 40% for 1b and 2b, respectively) and NMP (about 70 and 40%, respectively). The NMP soluble part of 1b and DMF soluble part of 2b gave values of 0.36 and 0.24 dl g−1 in NMP and DMF, respectively. The DMF soluble part of 1b, 1c and 2b showed absorption peaks at about 458, 465 and 388 nm, respectively, in DMF. In an alkaline medium the absorption peaks of 1b and 1c are shifted to a longer wavelength by 92-101 nm; the observed shifts in the acidic medium and alkaline medium were much larger than those observed with usual benzimidazoles with low molecular weights. Packing structures of 1b, 1c and 2b are discussed based on their XRD patterns. 相似文献
44.
Gopal P. Khanal Ichiro Fujii Shintaro Ueno Satoshi Wada 《Journal of the American Ceramic Society》2021,104(9):4649-4658
The <110>-oriented BaTiO3 ceramics were fabricated using BaCO3 matrix and H1.08Ti1.73O4.nH2O (HTO) template particles, and the mechanism of BaTiO3 phase formation was investigated. The dielectric, ferroelectric, and piezoelectric properties were also investigated. The transformation of the HTO phase into the TiO2 bronze or TiO2 (B) phase was observed at 600°C, where the BaTiO3 nucleation was accompanied by the formation of a Ba2TiO4 phase. The TiO2 phase reacted with the Ba2TiO4 phase at 800°C to give a BaTiO3 phase, whereas its reaction with the BaTiO3 resulted in the formation of BaTi2O5 phase that got decomposed into BaTiO3 and Ba6Ti17O40 phase at sintering temperature ≥1300°C. Sintering with samples’ embedding in BaTiO3 powders prevented the formation of the Ba6Ti17O40 secondary phase. The crystallographic orientation along the <110> direction (F110) was developed by the epitaxial grain growth mechanism. In addition to the contribution of the grain-size increment for enhancing the F110, the preservation of the platelike structure was also found to have a significant impact. The ceramics prepared by the embedded sintering (grain size ≈12.4 µm and F110 = 83%) exhibited the room-temperature dielectric constant of 1708 and piezoelectric strain constant of 445 pm/V, which are higher than those of the BaTiO3 ceramics with randomly oriented grains. 相似文献
45.
Hatem S. Zurob Jinichiro Nakano Gary R. Purdy 《Journal of Phase Equilibria and Diffusion》2006,27(6):699-706
The presence of a concentration gradient across a thin liquid film leads to the phenomenon of isothermal liquid film migration
(LFM). In most cases, the concentration gradient is due to coherency stresses, and the migration of the liquid film results
in the relaxation of these stresses. It is also possible to envisage cases in which LFM occurs as a result of chemical solubility
differences between stable and metastable phases. Both situations are examined in this contribution with special emphasis
on the effect of adding a second solute element to the liquid phase. The kinetics of LFM is examined as a function of the
initial liquid concentration and the ratio of the solute diffusion coefficients in a model coherency-driven ternary system.
The growth of the Γ2 inside δ particles in the Zn-Fe-Al system is presented as a possible example of chemically driven LFM.
This article was presented at the Multicomponent-Multiphase Diffusion Symposium in Honor of Mysore A. Dayananda, which was
held during TMS 2006, the 135th Annual Meeting and Exhibition, March 12–16, 2006, in San Antonio, TX. The symposium was organized
by Yongho Sohn of University of Central Florida, Carelyn E. Campbell of National Institute of Standards and Technology, Richard
D. Sisson, Jr., of Worcester Polytechnic Institute, and John E. Morral of Ohio State University. 相似文献
46.
Kazunori Sakata Kosuke Nakano Hirofumi Miyahara Yasuhiro Matsubara Keisaku Ogi 《Journal of Thermal Spray Technology》2007,16(5-6):991-997
This article describes microstructure control aimed for wear-resistance improvement of Co-based (Co-Cr-W-B-Si) self-fluxing
alloy coating by diffusion treatment. The diffusion treatments of thermally sprayed Co-based self-fluxing alloy coating on
steel substrate were carried out at 1370-1450 K for 600-6000 s under an Ar gas atmosphere. Microstructural variations of the
coating and the interface between the substrate and the coating were investigated in detail. A proper diffusion treatment
precipitates two kinds of fine compounds in Co-based matrix. X-ray diffractometer (XRD) and electron probe microanalyzer (EPMA)
analysis revealed these precipitates to be a chromium boride dissolving cobalt and a tungsten boride containing cobalt and
chromium. The size of each precipitate became larger with increasing treatment temperature and time. A coating with the proper
size borides showed a superior wear-resistance.
This article is an invited paper selected from presentations at the 2007 International Thermal Spray Conference and has been
expanded from the original presentation. It is simultaneously published in Global Coating Solutions, Proceedings of the 2007 International Thermal Spray Conference, Beijing, China, May 14-16, 2007, Basil R. Marple, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain
Montavon, Ed., ASM International, Materials Park, OH, 2007. 相似文献
47.
48.
Hiroshi Mukawa Katsuyuki Akutsu Ikuo Matsumura Satoshi Nakano Takuji Yoshida Mieko Kuwahara Kazuma Aiki 《Journal of the Society for Information Display》2009,17(3):185-193
Abstract— A full‐color eyewear display with over 85% see‐through transmittance with a 16° horizontal field of view was developed. Very low color crosstalk, less than 0.008 Δu′v′ uniformity, and 120% NTSC color gamut were achieved. Waveguides with two in‐ and out‐coupling reflection volume hologram elements enabled a simple configuration that has an optical engine beside the user's temples. The reflection volume hologram elements used on the waveguides realized a small thickness of 1.4 mm for each waveguide, and an out‐coupling reflection volume hologram used as an optical combiner contributed a high see‐through transmittance of 85% due to its wavelength selectivity. However, there are technical challenges in achieving a reasonable screen size and quality color images with optics that utilize holographic waveguides because holograms have large chromatic dispersions compared to conventional optical elements such as lenses and mirrors. Approaches to overcome these issues are described. 相似文献
49.
Keisuke Fujita Kohji Higuchi Kazushi Nakano Koji Matsushita Tatsuyoshi Kajikawa Fumiho Chino 《Artificial Life and Robotics》2009,14(3):433-439
There is a need for robust current control of a pulse width modulation (PWM) power amplifier whose transient response characteristics
do not deteriorate with extensive load changes and/or direct-current power supply voltage changes. In this article, we propose
a digital robust controller with bumpless mode switching to control the current of a PWM power amplifier to satisfy the demands
and extend the range of an inductive load width. It is necessary to measure the value of the load in order to implement this
bumpless mode switching automatically depending on the load range. Therefore, a method of estimating the inductive load is
shown. The bumpless mode switching is automatically performed by estimating an inductive value without specifying the value
of the inductive load beforehand. That is, the value of the inductive load is estimated during the DDC execution, and the
control mode is automatically switched bumplessly according to this estimated value. A digital controller equipped with inductance
estimation and bumpless mode switching is realized by a DSP. Some experiments show that the digital controller with the proposed
bumpless mode switching can satisfy larger specifications. 相似文献
50.
Yamagishi J. Kobayashi T. Nakano Y. Ogata K. Isogai J. 《IEEE transactions on audio, speech, and language processing》2009,17(1):66-83
In this paper, we analyze the effects of several factors and configuration choices encountered during training and model construction when we want to obtain better and more stable adaptation in HMM-based speech synthesis. We then propose a new adaptation algorithm called constrained structural maximum a posteriori linear regression (CSMAPLR) whose derivation is based on the knowledge obtained in this analysis and on the results of comparing several conventional adaptation algorithms. Here, we investigate six major aspects of the speaker adaptation: initial models; the amount of the training data for the initial models; the transform functions, estimation criteria, and sensitivity of several linear regression adaptation algorithms; and combination algorithms. Analyzing the effect of the initial model, we compare speaker-dependent models, gender-independent models, and the simultaneous use of the gender-dependent models to single use of the gender-dependent models. Analyzing the effect of the transform functions, we compare the transform function for only mean vectors with that for mean vectors and covariance matrices. Analyzing the effect of the estimation criteria, we compare the ML criterion with a robust estimation criterion called structural MAP. We evaluate the sensitivity of several thresholds for the piecewise linear regression algorithms and take up methods combining MAP adaptation with the linear regression algorithms. We incorporate these adaptation algorithms into our speech synthesis system and present several subjective and objective evaluation results showing the utility and effectiveness of these algorithms in speaker adaptation for HMM-based speech synthesis. 相似文献