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31.
The development philosophy and implementation of IFECS (an interactive finite element computing system) is described. The system, written in BASIC-PLUS for the RSTS/E computing system, provides solutions for various classes of stress problems in two dimensions. IFECS contains an automatic mesh generator, solution routines and an interactive means of interrogating the program output. This latter feature provides the user with the means of directly selecting relevant information, rather than having to wade through vast reams of the total output. The system, which may be implemented on a very simple computing configuration, is very easy to use and for many problems reduces the effective solution time to a few hours. 相似文献
32.
McArthur EA Ye T Cross JP Petoud S Borguet E 《Journal of the American Chemical Society》2004,126(8):2260-2261
Detection and quantification of submonolayer coverage surface species is not trivial. We have developed a novel method sensitive to surface-bound chemical functional groups as low as 10(11) molecules/cm(2) by specific covalent attachment of fluorescent chromophores. This enables the intermediates of the UV photochemistry of alkylsiloxane self-assembled monolayers to be identified. 相似文献
33.
We investigated the rheological properties of a thin film of a lyotropic lamellar phase with a Dynamic Surface Forces Apparatus. The minimum thickness of the film is varied between one to several tens of layers by confining the materials between solid surfaces. The rheometric properties are measured with the application of a small harmonic compression. These properties depend clearly on the smectic order of the material. Whole mechanical properties may be easily described by taking into account interactions between membranes and motion of the dislocation line loops. In particular, it is shown that at the dynamical frequencies investigated in this study, the solvent flows between membranes which remain undeformed. Consequences and perspectives of this study will be discussed.Received: 22 April 2004, Published online: 11 August 2004PACS:
61.30.St Lyotropic phases - 61.30.Jf Defects in liquid crystals - 83.80.Qr Surfactant and micellar systems, associated polymers 相似文献
34.
N-heterocyclic carbenes as highly efficient catalysts for the cyclotrimerization of isocyanates 总被引:2,自引:0,他引:2
[reaction: see text] A series of N-heterocyclic carbenes (NHCs) were evaluated as potential catalysts for the cyclotrimerization of isocyanates to afford isocyanurates. 1,3-Bis-(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene (SIPr) was found to be a highly efficient catalyst for the cyclotrimerization of a variety of isocyanates. 相似文献
35.
A method for the systematic cryopreservation of potato apices was developed by the Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH (DSMZ) and the Institute for Crop and Grassland Science of the Federal Agricultural Research Centre (FAL, Braunschweig). Designed specifically for routine use in genebanks, this method uses a very simple ultra-rapid freezing approach and was applied to a wide range of varieties within the Federal Centre for Breeding Research on Cultivated Plants (BAZ, Quedlinburg) Potato Collection. After several years of storage in liquid nitrogen, shoot tips from a random sample of 51 varieties were thawed and the survival and shoot regeneration percentages compared to those measured immediately after freezing. There were no major changes in either survival or recovery of frozen apices. Data presented are not the outcome of a systematic experiment but from that accumulated during our work from 1992 to 1999. 相似文献
36.
Aerosol assisted chemical vapour deposition of polyoxotungstate precursors [n-Bu4N]2[W6O19] and [n-Bu4N]4H3[PW11O39] produces films of WO(3 - x) and WO3 on glass substrates; the WO3 films show significant photocatalytic decomposition of a test organic pollutant--stearic acid--when irradiated with either 254 or 365 nm radiation. 相似文献
37.
The effect of phonon scattering by surface roughness on the thermal conductance in mesoscopic systems at low temperatures is calculated using full elasticity theory. The low frequency behavior of the scattering shows novel power law dependences arising from the unusual properties of the elastic modes. This leads to new predictions for the low temperature depression of the thermal conductance below the ideal universal value. Comparison with the data of Schwab et al. [Nature (London) 404, 974 (2000)] suggests that surface roughness on a scale of the width of the thermal pathway is important in the experiment. 相似文献
38.
Bratman VL Cross AW Denisov GG He W Phelps AD Ronald K Samsonov SV Whyte CG Young AR 《Physical review letters》2000,84(12):2746-2749
First bandwidth measurements of a novel gyrotron amplifier are presented. The coupling between the second harmonic cyclotron mode of a gyrating electron beam and the radiation field occurred in the region of near infinite phase velocity over a broad bandwidth by using a cylindrical waveguide with a helical corrugation on its internal surface. With a beam energy of 185 keV, the amplifier achieved a maximum output power of 1.1 MW, saturated gain of 37 dB, linear gain of 47 dB, saturated bandwidth of 8.4 to 10.4 GHz ( 21% relative bandwidth), and an efficiency of 29%, in good agreement with theory. 相似文献
39.
High resolution x-ray powder diffraction measurements on poled PbZr1-xTixO3 (PZT) ceramic samples close to the rhombohedral-tetragonal phase boundary (the so-called morphotropic phase boundary) have shown that for both rhombohedral and tetragonal compositions the piezoelectric elongation of the unit cell does not occur along the polar directions but along those directions associated with the monoclinic distortion. This work provides the first direct evidence for the origin of the very high piezoelectricity in PZT. 相似文献
40.
G. Lunge C. F. Cross E. J. Bevan und Herm Rey 《Fresenius' Journal of Analytical Chemistry》1891,30(1):471-472
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