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11.
A woven fabric can be described as a surface made of two families of fibers: in this work we study how the geometry of the
weave pattern affects the symmetry properties of the elastic energy of the surface. Four basic symmetry classes of weave patterns
are possible, depending on the angle between the fibers and their material properties. The properties of the pattern determine
the material symmetry group of the network, under which the elastic energy is invariant. We derive representations for the
energy of a woven fabric that are invariant under the symmetry group of the network, and discuss the relation of these invariants
with the curvature and twist of the fibers.
相似文献
12.
Borghetti P Goldoni A Castellarin-Cudia C Casalis L Herberg F Floreano L Cossaro A Verdini A Gebauer R Ghosh P Sangaletti L 《Langmuir : the ACS journal of surfaces and colloids》2010,26(24):19007-19013
The role of potassium in the formation of synthetic eumelanin aggregates is investigated by atomic force microscopy and soft-X-ray spectroscopy. Control over the thin film granularity is achieved by using K salts, in both drop casting and electrodeposition of eumelanin thin films. Further control over orientation is made possible by a suitable choice of the substrate: evidence of self-assembly is found for thin films deposited on gold. Finally, it is shown that the potassium content affects not only the samples morphology, but also the low-lying states in the valence band, where a transfer of spectral weight across the HOMO-LUMO gap is observed, disclosing possible applications of this multifunctional biomacromolecule. 相似文献
13.
Gianfranco Ciani Vincenzo G. Albano Attilio Immirzi 《Journal of organometallic chemistry》1976,121(2):237-248
The structure of the title compound, (NEt4)2[H4Re4(CO)15], is reported in two crystallographic modifications, I and II. Both forms axe monoclinic and the cell constants are as follows: I, a 11.355(2), b 21.204(4), c 17.416(3) Å, β 94.15(2)°, space group P21/c; II, a 21.831(4), b 17.584(3), c 11.446(2) Å, β 96.02(2)°, space group P21,/n. Two sets of 3042 (I) and 2870 (II) independent diffraction intensities, collected by counter methods, were used for the solution and refinement of the two structures. The final conventional R factors have values 5.5% (I) and 6.3% (II), respectively. The crystal packings are compared, showing different conformations of the (NEt4)+ cations. The anions contain a tetrametal cluster formed by an isosceles triangle plus an apically bound metal atom; the carbonyl groups are all terminally bonded to the rhenium atoms. Some differences, present both in the metal atom clusters and in the carbonyl dispositions, are discussed and compared with a third, previously reported, crystallographic modification of the same compound. 相似文献
14.
Vincenzo G. Albano Carlo Castellari Cristina Femoni M. Carmela Iapalucci Giuliano Longoni Magda Monari Stefano Zacchini 《Journal of Cluster Science》2001,12(1):75-87
The new Au8{Fe(CO)4}4(P^P)2 and Au6Cu2{Fe(CO)4}4(P^P)2 (P^P=dppm, dppe) neutral cluster compounds were isolated in good yields by condensation of the [Au3{Fe(CO)4}2(P^P)]- anions with Au(SEt2)Cl and CuCl, respectively, and have been characterized by IR, NMR and microanalyses. The molecular structures of Au8{Fe(CO)4}4(dppe)2 and Au6Cu2{Fe(CO)4}4(dppe)2 have been determined by X-ray diffraction studies. Both molecules adopt a stereogeometry of the heavy atoms consisting of a triangulated and corrugated ribbon twisted around the elongation direction. Contrary to the expectations the latter displays the two copper atoms in the sites of highest connectivity. This implies that site exchange between copper and gold occurs during the synthesis. 相似文献
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17.
Few results are available in the mathematical literature for studying the structure of the singular set of a weak solution u of F(x,u,Du)=0. This paper provides new techniques to analyse such a set when u is semiconcave and F is a nonlinear convex function with respect to p. The main objective achieved here is a classification of the singularities of u that propagate along Lipschitz arcs. Such a propagation phenomenon is also described by means of a generalized characteristics inclusion. 相似文献
18.
Albano Brand 《Fresenius' Journal of Analytical Chemistry》1887,26(1):222-226
Ohne Zusammenfassung 相似文献
19.
We study the analytic singularities of viscosity solutions of equations of eikonal type and obtain that the analytic singular
support of these functions has an analytic stratification. The singular support can be identified with the cut locus of the
distance to the boundary of an open set, when the interior is equipped with a degenerate Riemannian metric. We apply the result
to elliptic equations as well as to model operators of Grušin type. 相似文献
20.
The theory of non-equilibrium thermodynamics is applied to a system of two immiscible fluids and their interface. A singular energy density at the interface, which is related to the phenomenon of surface tension, is taken into account. Furthermore the momentum and the heat currents are allowed to be singular at the interface. Using the conservation laws and the Gibbs' relation for the surface, an expression for the singular entropy production density at the interface is obtained. The linear phenomenological laws between fluxes and thermodynamic forces occurring in this singular entropy production density are given. Some of these linear laws are boundary conditions for the solution of the differential equations governing the evolution of the state variables in the bulk. 相似文献