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91.
A study of the alkylation of 3% Re2O7/60%Al2O3-40%SiO2 catalyst using tetraethyllead (Et4Pb)(TEL) shows that the reaction time and temperature affect the catalyst activity and selectivity in the methyl erucate metathesis
reaction.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
92.
Maxim A. Olshanskii Andriy Sokolov Stefan Turek 《Journal of Mathematical Fluid Mechanics》2010,12(4):485-502
In this paper a projection method for the Navier–Stokes equations with Coriolis force is considered. This time-stepping algorithm
takes into account the Coriolis terms both on prediction and correction steps. We study the accuracy of its semi-discretized
form and show that the velocity is weakly first-order approximation and the pressure is weakly order
\frac12\frac{1}{2} approximation. 相似文献
93.
Transition metal complex catalyzed cocyclotrimerization of protected alkynylpurine ribonucleosides 1 with various diynes 2 gave rise to a series of 6-arylpurine nucleosides 3 that were further deprotected to free nucleosides 4. Generally, the best yields of cyclotrimerizations were obtained with a catalytic system Ni(cod)2/2PPh(3). On the other hand, CoBr(PPh(3))3 proved to be a superior catalyst for cyclotrimerization of 1 with dipropargyl ether 2g. In addition, Ni catalysis is also suitable for direct cyclotrimerization of unprotected alkynylpurine ribonucleosides 5 to the corresponding 6-arylpurinylribosides 4. 相似文献
94.
M. Králík K. Turek V. Vondrá?ek J. Krása A. Velyhan M. Scholz I.M. Ivanova-Stanik 《Radiation measurements》2010,45(10):1245-1249
Paper presents results of measurements of neutron spectra with Bonner spheres spectrometer around radiotherapeutic linac producing undesirable photoneutrons and around plasma focus device PF-1000 in which neutrons are generated in 2H + 2H → n + 3He reaction. In the Bonner spheres an active detector, proportional counter filled with 3He, was replaced by passive one to avoid overloading of the active detector during very short period of neutrons generation. For the measurements around linac track detectors with 10B radiator were used and around plasma focus device pairs of TLDs (6LiF and 7LiF). 相似文献
95.
The longstanding open problem of approximating all singular vertex couplings in a quantum graph is solved. We present a construction in which the edges are decoupled; an each pair of their endpoints is joined by an edge carrying a δ potential and a vector potential coupled to the “loose” edges by a δ coupling. It is shown that if the lengths of the connecting edges shrink to zero and the potentials are properly scaled, the limit can yield any prescribed singular vertex coupling, and moreover, that such an approximation converges in the norm-resolvent sense. 相似文献
96.
97.
The catalytic activity of samples such as PPy(H4SiW12O40), PPy(H5PMo10V2O40), PPy(H2Fe(III)PMo10V2O40), PPy(H3Cu(II)PMo10V2O40) has been examined in two different test reactions. The acid-base and oxidation-reduction properties were studied using the conversion of isopropyl alcohol to propene and acetone. Redox ability of catalysts was examined in the reaction of oxidation of allyl alcohol to glycidol. It was found that the activity of catalysts in the oxidation of allyl alcohol increases as the oxidation properties determined from the conversion of isopropyl alcohol increase. It was also observed that stronger oxidation-reduction properties of the catalyst result in a high rate of the consecutive reaction of glycidol to 3-hydroxypropanone.The phase composition of catalysts was determined by means of X-ray diffraction (XRD). 相似文献
98.
The flux‐corrected‐transport paradigm is generalized to finite‐element schemes based on arbitrary time stepping. A conservative flux decomposition procedure is proposed for both convective and diffusive terms. Mathematical properties of positivity‐preserving schemes are reviewed. A nonoscillatory low‐order method is constructed by elimination of negative off‐diagonal entries of the discrete transport operator. The linearization of source terms and extension to hyperbolic systems are discussed. Zalesak's multidimensional limiter is employed to switch between linear discretizations of high and low order. A rigorous proof of positivity is provided. The treatment of non‐linearities and iterative solution of linear systems are addressed. The performance of the new algorithm is illustrated by numerical examples for the shock tube problem in one dimension and scalar transport equations in two dimensions. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
99.
100.
J. Kudrnovský V. Drchal I. Turek P. H. Dederichs P. Weinberger P. Bruno 《Journal of magnetism and magnetic materials》2002,240(1-3):177-179
The spin-polarized electron conductance perpendicular to layers of a random magnetic multilayer is evaluated from first principles. We employ the Landauer formulation in the framework of the tight-binding linear muffin-tin orbital approach and the surface Green-function technique. The disorder in the bulk and at interfaces is included in terms of lateral supercells confined to individual atomic layers. The application is made to interleave and separate multilayers with a different order of magnetic and non-magnetic layers with generally non-collinear alignments of layer magnetizations. 相似文献