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排序方式: 共有74条查询结果,搜索用时 31 毫秒
1.
2.
Nikolai V Ignat’ev Michael SchmidtUdo Heider Andriy KucherinaPeter Sartori Fatiah M Helmy 《Journal of fluorine chemistry》2002,113(2):201-205
The electrochemical fluorination (ECF) of N,N-dimethylperfluoroacylamides gives the corresponding perfluoro-N,N-dimethylacylamides in low yield. With increase of the number of carbon atoms in the perfluoroacyl radical the yield of the required perfluoro-N,N-dimethylacylamides is slightly increased. 相似文献
3.
[reaction: see text] Rhodium-catalyzed oxygen transfer was used to generate benzyl 2-silyl-2-oxoacetates in good yields. The hydrogenation of these compounds led to chiral alpha-silyl-substituted alpha-hydroxyacetic acids. Resolution by means of HPLC using a chiral stationary phase afforded an enantiomerically pure representative of this class of compounds, which was successfully applied as a chiral ligand in an asymmetric aldol-type reaction. 相似文献
4.
Heider Nasser ákos Rédey Tatiana Yuzhakova Zsolt Németh Tóth Tamás Ollár 《Reaction Kinetics and Catalysis Letters》2007,92(2):329-335
CO adsorption at low temperature has been used to probe Lewis acid sites created upon dehydroxylation of γ-Al2O3 and reduction of Mo/Al2O3 catalysts, using Fourier Transform Infrared spectroscopy (FTIR).
Carbon-monoxide adsorption on γ-Al2O3 and Mo/Al2O3 catalysts dehydroxylated and reduced at different temperatures was studied at 78 K by IR spectroscopy. However, our results
indicate that there is an approximately linear correlation between the increase either of dehydroxylation or the extent of
reduction of the catalysts and the increasing absorbance of CO due to CO adsorption on Lewis acid sites created upon dehydroxylation
of γ-Al2O3 and reduction of Mo/Al2O3. 相似文献
5.
Bei Zhou Yousef Heider Andreas Blaeser Stefan Raith Horst Fischer Bernd Markert 《PAMM》2016,16(1):117-118
The aim of this work is to numerically simulate the gelation of a crosslinking polymer, which is a very complex process involving chemical reactions and phase transitions from a viscous fluid to a viscoelastic solid. A phenomenological model is proposed to simulate the gelation process of agarose droplets, considering the thermal boundary conditions. The numerical model is implemented using the finite element package FlexPDE. The temperature- and time-dependent degree of gelation and the deformation of the droplets during the gelation process are investigated. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
6.
Rory?H.?Uibel Emily?C.?Heider Jennifer?L.?Gasser Joel?M.?HarrisEmail author Edward?M.?Eyring Sergio?Petrucci 《Journal of solution chemistry》2005,34(5):499-514
Advances have been made recently in broadening the accessible ultrasonic absorption frequency range and improving the detectability of minor species present in solution using Raman spectroscopy. Development of chemometric techniques in these areas needs to keep pace with the improvement of these experimental methods. Refinements in the analysis of ultrasonic and Raman data based on multivariable least squares and factor analysis, respectively, are examined to investigate the kinetics of zinc thiocyanate complex formation in water. Analysis of ultrasonic absorption relaxation spectra verified that the observed process in aqueous Zn(SCN)2 involves substitution of water from the first coordination shell of Zn2+. Use of a multivariable least-squares error surface is described that enhances the reliability of assigned frequencies of ultrasonic absorption maxima. Factor analysis of Raman scattering data provided direct evidence that at least four complex species, such as Zn(SCN)+ and Zn(SCN)2, are simultaneously present in the aqueous zinc thiocyanate solutions. 相似文献
7.
Composite materials containing metallic nickel and yttria stabilised zirconia (YSZ) have been prepared by a sol gel method.
Microstructural investigations show that metal particles with a diameter of less than 300 nm still remain present after sintering.
In the present work, the conductivity behaviour of such composites was investigated. Furthermore, ageing phenomena, in particular
the influence of the nickel content, were studied. A possible application of such materials as anodes in solid oxide fuel
cells will be discussed.
Paper presented at the 1st Euroconference on Solid State Ionics, Zakynthos, Greece, 11 – 18 Sept. 1994 相似文献
8.
Edward J. Kramer Heider G. Krenz Dieter G. Ast 《Journal of Polymer Science.Polymer Physics》1978,16(2):349-366
Methanol crazes are grown from sharp cracks in poly(methyl methacrylate) (PMMA). The craze thickness profile is measured using a replica technique after the craze opening displacement profile of the growing craze has been measured with holographic interferometry. The craze strain profile is then computed from these data. The craze surface stress profile is determined by two methods: (1) from the uniaxial strain profile of regions adjacent to the craze as measured from the fringe spacing on the reconstructed hologram and (2) from the craze opening displacement profile using the Fourier transform method of Sneddon. From the surface stress and craze-strain profiles a true stress-strain curve for the craze fibrils has been constructed. The extrapolated fibril yield stress is in good agreement with the yield stress of bulk PMMA plasticized with methanol indicating that surface tension effects do not contribute importantly to craze fibril mechanical properties at room temperature. The craze strain increases from 0.4 near the craze tip to 1.4 near the craze base implying that methanol crazes in PMMA thicken by further straining of the existing craze fibrils and not by drawing new material into the craze from the craze surfaces. The primordial craze thickness, i.e., the original thickness of polymer which fibrillates to form the craze fibrils, is approximately 1 μm and is constant over most of the craze length. This thickness may be determined by diffusion of methanol normal to the craze surfaces in a process zone just behind the craze tip. 相似文献
9.
Blaise Heider 《代数通讯》2013,41(5):2156-2162
To describe the representation theory of the quantum Weyl algebra at an lth primitive root γ of unity, Boyette, Leyk, Plunkett, Sipe, and Talley found all nonsingular irreducible matrix solutions to the equation yx ? γxy = 1, assuming yx ≠ xy. In this note, we complete their result by finding and classifying, up to equivalence, all irreducible matrix solutions (X, Y), where X is singular. 相似文献
10.
Ultrasonic welding (USW) is an alternative solution for the bonding process especially in automotive industry. Ultrasonic welding of metals is a joining technique as a combination of applying pressure and frictional vibrations within the range of ultrasonic frequencies. In automotive industry, ultrasonic welding is often used for wired connections. As an alternative for crimping technology of multi-strand aluminum cables in wire bonding, ultrasonic welding is used. This work presents a thermomechanical analysis of the interface between two mating parts in USW. For this reason, the temperature distribution at bonding locations inside a wire bundle due to frictional vibrations and pressure is investigated using the finite element method (FEM). The obvious difference in microsections from different welding samples, which originates from different local temperature rises, was the motivation for this study to further investigate the thermomechanical aspects of the USW by use of finite element simulations. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献