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11.
12.
P. Chadwick 《Journal of sound and vibration》1976,47(1):39-52
A pure surface mode in a semi-infinite elastic body with a traction-free boundary is a progressive harmonic surface wave in which the displacement is everywhere co-planar with the wave and surface normals. When the elastic material has orthorhombic symmetry, with one of the 2-fold symmetry axes normal to the bounding plane, there are generally only two directions in which a pure surface mode may propagate, but additional directions appear when the transmitting material has higher symmetry. It is shown that for all the possibilities arising in this way the positive definiteness of the strain energy is a sufficient condition for the existence of a unique pure surface mode. The properties of pure modes in elastic materials belonging to the orthorhombic, tetragonal, hexagonal and cubic systems are discussed with particular reference to conditions under which the motion has the same features as a Rayleigh wave. 相似文献
13.
W. Ochs V. Davidson A. Dzierba A. Firestone W. Ford R. Gomez F. Nagy C. Peck C. Rosenfeld J. Ballam J. Carroll G. Chadwick D. Linglin K. Moffeit R. Ely D. Grether P. Oddone 《Nuclear Physics B》1976,102(3):405-428
We present data on momentum correlations both in and out of the production plane for the reactions π+p→πf+(π+n) and π?p→πf?(π?Δ++). The dissociation products show strikingly similar transverse momentum distributions which in terms of exchange models suggest an equal amount of pion and baryon exchange. For both reactions, we find an approximate factorization in the projectile frame between the transverse momentum of πf and the longitudinal momenta of the dissociation products. Exchange models predict this result equally in both reactions, but it appears much more clearly in the Δ reaction. Finally, we relate the observed longitudinal and transverse momentum distributions in a way suggested by an isotropic decay model. 相似文献
14.
Canepa P Schofield E Chadwick AV Alfredsson M 《Physical chemistry chemical physics : PCCP》2011,13(28):12826-12834
Comparison and prediction of the experimental XANES spectrum is a good measurement of the quality of the electronic structure calculations employed, and their ability to predict electronic transitions in solids. Here we present a comparison between BLYP + U and hybrid-BLYP calculations regarding the geometric, magnetic and electronic structures of α-Fe(2)O(3) (hematite). Several values of U and different percentages of Fock-exchange have been screened to see how their contributions affect different properties of hematite, paying particular attention to the electronic structure. To estimate the quality of the various methods the calculated density-of-states were compared to the experimentally collected XANES spectrum of the iron K-edge, providing information about the orbitals describing the conduction band. We find that in agreement with previous studies DFT + U and hybrid-functional simulations can correctly predict the character of the valence band, but only Fock-exchange higher than 30% or U-values equal or larger than 6 eV properly reproduce the order between the t(g) and e orbitals in the conduction band, and can, therefore, be used to study and predict XANES spectra and electronic transitions in hematite. 相似文献
15.
Aharonian F Akhperjanian AG Barres de Almeida U Bazer-Bachi AR Becherini Y Behera B Beilicke M Benbow W Bernlöhr K Boisson C Bochow A Borrel V Braun I Brion E Brucker J Brun P Bühler R Bulik T Büsching I Boutelier T Carrigan S Chadwick PM Charbonnier A Chaves RC Chounet LM Clapson AC Coignet G Costamante L Dalton M Degrange B Deil C Dickinson HJ Djannati-Ataï A Domainko W Drury LO Dubois F Dubus G Dyks J Egberts K Emmanoulopoulos D Espigat P Farnier C Feinstein F Fiasson A Förster A Fontaine G 《Physical review letters》2008,101(17):170402
In the past few decades, several models have predicted an energy dependence of the speed of light in the context of quantum gravity. For cosmological sources such as active galaxies, this minuscule effect can add up to measurable photon-energy dependent time lags. In this Letter a search for such time lags during the High Energy Stereoscopic System observations of the exceptional very high energy flare of the active galaxy PKS 2155-304 on 28 July 2006 is presented. Since no significant time lag is found, lower limits on the energy scale of speed of light modifications are derived. 相似文献
16.
The sensitivity of tin oxide is dependent on various factors, one of which is the grain size. Three methods have been investigated with the aim of stabilising the grain size in the nanometer range, namely; (i) encapsulation within a silica matrix, (ii) coating the crystallites with hexamethyldisilazane and (iii) pinning the grain boundaries with a second metal oxide nanocrystal. The resulting materials have been characterised by X-ray powder diffraction (XRPD), Extended X-ray absorption fine structure (EXAFS) and conductivity measurements. 相似文献
17.
Chadwick C. Rasmussen Sulabh K. Dhanuka James F. Driscoll 《Proceedings of the Combustion Institute》2007,31(2):2505-2512
Laser-induced fluorescence of OH and CH2O was imaged to investigate the flame stabilization mechanism in a flameholder with a Mach 2.4 free stream. Ethylene was burned in a rectangular cavity with two points of injection: the aft wall and the cavity floor. When injected from the aft wall, the fuel came into immediate contact with hot combustion products from the reaction zone under the shear layer. Primary combustion occurred under the shear layer and in the aft region of the cavity volume. In contrast, when fuel was injected from the floor, a jet-driven recirculation zone of hot products near the upstream wall of the cavity served as a flameholder. The reaction then occurred on the underside of the shear layer. In conditions near lean blowout, significant changes in the flameholding mechanisms were observed. Improved CH2O fluorescence signal was obtained by taking advantage of the long fluorescence lifetime at low pressures and delaying the camera gate to reduce the background signal. 相似文献
18.
Nileshkumar Kukalyekar Luigi Balzano Gerrit W. M. Peters Sanjay Rastogi John C. Chadwick 《大分子反应工程》2009,3(8):448-454
Bimodal polyethylenes comprising varying proportions of high‐ and low‐molecular‐weight fractions are synthesized in a single polymerization stage, via the co‐immobilization of a chromium and an iron catalyst on an MgCl2/AlEtn(OEt)3?n support. Changes observed in the viscoelastic response of the polymer melt with increasing content of the high‐molecular‐weight fraction indicate effective mixing in the bimodal blend. In flow, chains in the high‐molecular weight fraction tend to orient and stretch under shear. Due to the longer relaxation time of the high‐molecular‐weight component, X‐ray diffraction and scattering reveal that shear‐induced crystallization takes place at temperatures close to the equilibrium melting point of linear polyethylene. The so‐crystallized high‐molecular‐weight component suppresses the nucleation barrier for further crystallization, leading to the formation of a “shish‐kebab” polymer morphology.
19.
Abe F Amidei D Apollinari G Atac M Auchincloss P Baden AR Bamberger A Barbaro-Galtieri A Barnes VE Bedeschi F Behrends S Belforte S Bellettini G Bellinger J Bensinger J Beretvas A Berge JP Bertolucci S Bhadra S Binkley M Blair R Blocker C Booth AW Brandenburg G Brown D Buckley E Byon A Byrum KL Campagnari C Campbell M Carey R Carithers W Carlsmith D Carroll JT Cashmore R Cervelli F Chadwick K Chiarelli G Chinowsky W Cihangir S Clark AG Connor D Contreras M Cooper J Cordelli M Crane D Curatolo M 《Physical review letters》1989,63(7):720-723
20.
Abe F Amidei D Apollinari G Ascoli G Atac M Auchincloss P Baden AR Barbaro-Galtieri A Barnes VE Bedeschi F Behrends S Belforte S Bellettini G Bellinger J Bensinger J Beretvas A Berge P Bertolucci S Bhadra S Binkley M Blair R Blocker C Bofill J Booth AW Brandenburg G Brown D Byon A Byrum KL Campbell M Carey R Carithers W Carlsmith D Carroll JT Cashmore R Cervelli F Chadwick K Chapin T Chiarelli G Chinowsky W Cihangir S Cline D Connor D Contreras M Cooper J Cordelli M Curatolo M Day C DelFabbro R 《Physical review letters》1989,62(26):3020-3023