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201.
C.M. Andrei J.C. Walmsley H.W. Brinks R. Holmestad S.S. Srinivasan C.M. Jensen B.C. Hauback 《Applied Physics A: Materials Science & Processing》2005,80(4):709-715
NaAlH4 is a promising candidate material for hydrogen storage. Ti additives are effective in reducing the reaction temperatures and improving kinetics. In this work, the microstructure of NaAlH4 with 2% TiF3 has been studied in different conditions using a combination of transmission electron microscopy and scanning electron microscopy, both with energy-dispersive spectroscopic X-ray analysis. The effect of the additive on particle and grain size was examined after the initial ball-milling process and after 15 cycles. The additive has an uneven distribution in the sample after ball milling. Selected-area diffraction and high-resolution imaging confirmed the presence of TiF3. This phase accounts for most of the Ti in the material at this stage and showed limited mixing with the alanate. The grain size within particles for TiF3 is larger than for the alanate particles. Diffraction from the latter was dominated by metallic aluminium. After cycling, the TiF3 has decomposed and energy-dispersive spectroscopic X-ray analysis maps showed some combination of Ti with the alanate phase. There is no significant change in the measurable grain size of the Al-containing alanate particles between the ball-milled and the 15-cycled samples, but more cycles result in agglomeration of the material. PACS 61.14.-x; 68.37.LP; 68.37.Hk 相似文献
202.
We study the Lie algebra of infinitesimal isometries on compact Sasakian and K-contact manifolds. On a Sasakian manifold which is not a space form or 3-Sasakian, every Killing vector field is an infinitesimal automorphism of the Sasakian structure. For a manifold with K-contact structure, we prove that there exists a Killing vector field of constant length which is not an infinitesimal automorphism of the structure if and only if the manifold is obtained from the Konishi bundle of a compact pseudo-Riemannian quaternion-Kähler manifold after changing the sign of the metric on a maximal negative distribution. We also prove that nonregular Sasakian manifolds are not homogeneous and construct examples with cohomogeneity one. Using these results we obtain in the last section the classification of all homogeneous Sasakian manifolds. 相似文献
203.
Caio L. Firme Andrei V. Grafov Marcos L. Dias 《Journal of polymer science. Part A, Polymer chemistry》2005,43(18):4248-4259
Ethylene and propylene polymerization using Ind2ZrCl2 and Ind2Zr(CH3)2/MAO catalytic systems modified by the sterically demanding bridged alicyclic alcohols, adamantan‐1‐ol, adamantan‐2‐ol, 2‐methyladamantan‐2‐ol, and fenchyl alcohol, was investigated. Lower alcohols like isopropanol completely deactivate the system, whereas in the case of catalysts modified by these voluminous alcohols only a slight decrease in the catalytic activity proportional to alcohol/metallocene molar ratio was observed. The addition of the modifiers gives rise to polymers with higher molecular weights than the nonmodified systems, but no structural changes in the polyethylenes were observed. The addition of the sterically demanding alcohols to the reaction medium changes the regioregularity of polypropylenes, but does not significantly influence their stereoregularity, at 30 °C. Propylene–ethylene copolymers containing up to 8.6% of ethylene units derived from 1,3‐insertion and significant amount of rr‐centered pentads were obtained by single‐monomer polymerization of propylene with Ind2ZrCl2/MMAO/adamantan‐1‐ol, at 70 °C. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4248–4259, 2005 相似文献
204.
Andrei V. Grafov Eugene A. Mazurenko Giovanni A. Battiston Pierino Zanella Francesco Tisato Franco Braga Pietro Traldi 《应用有机金属化学》1995,9(3):259-266
The first three representatives of a new family of volatile organohafnium compounds suitable as metallo-organic chemical vapour deposition precursors were synthesized. A combination of cyclopentadienyl and alkoxo-ligands with a bicyclo[2.2.1]heptanc framework was used. Volatility at relatively low temperatures for hafnium compounds was found and the precursors were characterized by elemental analysis and spectroscopic methods (IR, 1H and 13C NMR, mass spectrometry and mass-analysed ion kinetic energy spectroscopy). The outlook for use in hafnium functional materials synthesis was derived from the fragmentation data. 相似文献
205.
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207.
Andrei Bourchtein Ludmila Bourchtein 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2007,49(5):926-939
In this study the problem of finding the conformal mapping from a sphere onto a plane with a given scale function independent
of longitude is solved for an arbitrary spherical domain. The obtained results are compared with the well-known projections
used in cartography and geophysical fluid dynamics. The problem of minimization of the distortion under conformal mappings
is solved for domains in the form of the spherical disk. The distortions of some extensively used conformal mappings are compared
with the distortions of orthogonal mappings. 相似文献
208.
209.
We study stability properties of the spectral Galerkin approximation of the solutions of semilinear problems. Assuming that
the data of the problem are known within a certain error, we investigate when the solution of the Galerkin approximate equation
provides a desired accuracy uniformly with respect to small perturbations of the data. We show that for certain classes of
semilinear problems an additional compactness assumption is sufficient to assure that the spectral Galerkin method provides
an accurate approximation to the exact solution uniformly with respect to small perturbations of the data.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
210.
We propose the new concept of a switchable multimode microlaser. As a generic, realistic model of a multimode microresonator a system of two coupled defects in a two-dimensional photonic crystal is considered. We demonstrate theoretically that lasing of the cavity into one selected resonator mode can be caused by injecting an appropriate optical pulse at the onset of laser action (injection seeding). Temporal mode-to-mode switching by reseeding the cavity after a short cooldown period is demonstrated by direct numerical solution. A qualitative analytical explanation of the mode switching in terms of the laser bistability is presented. 相似文献