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排序方式: 共有405条查询结果,搜索用时 18 毫秒
161.
In this paper, we obtain all the Leibniz 2-cocycles of the twisted N = 2 superconformal algebra ℒ, which determine its second Leibniz cohomology group. 相似文献
162.
Microtubes/rods of the layered metal hydroxide salt compound Cd2(OH)3(DS).nH2O, where DS stands for dodecyl sulfate sandwiched between two adjacent inorganic sheets, have been synthesized for the first time through a mild hydrothermal reaction route. The microtubes/rods have a diameter of about 1 μm and a length ranging from several microns to 20 μm. The growth process of microtubes/rods under the experimental conditions employed follows a dissolution-recrystallization route. 相似文献
163.
Low-shear viscosities have been studied for isotropic dispersions of uncharged colloidal silica rods in cyclohexane as a function of volume fraction Φ and aspect ratiorp. Intrinsic viscosities in the limit Φ → 0 agree with theoretical results [Brenner, H.,Int. J. Multiphase Flow1,195 (1974)] for colloidal cylinders. The Φ2term in the low-shear viscosity, accounting for two-particle interactions, is considerably larger than predicted by D. H. Berry and W. B. Russel [J. Fluid Mech.180,475 (1987)] for dilute hard-rod dispersions. The discrepancy is very likely due to weak interparticle attractions, which also account for the novel observation of an isotropic–isotropic phase separation in the silica rod dispersions. Our results demonstrate that, in comparison to spheres, high aspect ratios markedly increase both the shear viscosity and its sensitivity to even minor attractions. 相似文献
164.
Quan-Xin Sun 《Acta Mechanica Solida Sinica》1992,5(1):111-123
In this paper, the field equations for a directed rod are given. The form of the reaction forces with respect to a general internal constraint imposed on the rod is also derived, based on the assumption that the reaction forces do no work in any deformation compatible with the constraint. Finally, the rod subjected to both special and fundamental internal constraints is treated. 相似文献
165.
We demonstrate the equoivalence of two seemingly disparate dynamical systems. One consits of three hard rods sliding along a frictionless ring and making elastic collisions. The other consists of one ball moving on a frictionless triangular table with elastic rails. Several applications of this result are discussed. 相似文献
166.
We consider twisted convolution operators with kernels having singularities on a sphere and having as Fourier transform the oscillatory symbol mα(|ξ|) = |ξ|–αei|ξ|, 0 ≤ ??α < 2n. We give integral representations for such operators and, as a principal result, we study Lp–Lq estimates for them. 相似文献
167.
Scott Allen 《Journal of statistical physics》1995,79(1-2):165-181
A detailed analysis is reported examining the local magnetic susceptibility (r), in relation to the correlation functionG(R) and correlation length , of a spherical model ferromagnet confined to geometry =L
d –d
×
d
(
d
2,d>2) under a continuous set oftwisted boundary conditions. The twist parameter
in this problem may be interpreted as a measure of the geometry-dependent doping level of interfacial impurities (or antiferromagnetic seams) in theextended system at various temperatures. For
j
0, jd-d, no seams are present except at infinity, whereas if
j
= 1/2, impurity saturation occurs. For 0 <
j
< 1/2 the physical domain
phys =D
d –d
×
d
(D>L), defining the region between seams containing the origin, depends on temperature above a certain threshold (T>T
0). Below that temperature (T>T
0), seams are frozen at the same position (DL/2,d-d'=1), revealing a smoothly varying largescale structural phase transition. 相似文献
168.
It is shown that the system of partial differential equations governing small amplitude vibrations of an elastic ring has solutions describing motions in which the axial curve C of the ring remains rigid, but executes a rocking motion while the cross-sections undergo torsional rotations about C that vary periodically both in time and in distance along C. This type of flexure-free torsional vibration can occur both in rings that are stress-free in a circular equilibrium configuration and in rings formed by bringing together and sealing, with or without the addition of twist, the ends of rods that are stress-free when straight.
Sommario Si mostra che le equazioni che governano le oscillazioni di piccola ampiezza di travi elastiche anulari hanno soluzioni che corrispondono a moti nei quali l'asse C della trave è sottoposto a un'oscillazione rigida e le sezioni trasversali subiscono una rotazione torsionale che varia periodicamente nel tempo e con l'ascissa lungo C. Questo tipo di vibrazione torsionale, non accompagnata da flessione dell'asse, si presenta sia quando la configurazione anulare è priva di sforzi sia quando tale configurazione può pensarsi ottenuta inflettendo una trave che in uno stato privo di sforzi è ad asse rettilineo, imprimendo ad essa una eventuale deformazione torsionale, e collegando fra loro le sue estremità.相似文献
169.
非平面扭曲构象对1,3-二苯基吡唑啉衍生物荧光性质的影响 总被引:2,自引:0,他引:2
研究了1,3-二苯基吡唑啉(DPP)和1-苯基-3-(4-硝基苯基)吡唑啉(PNP)在室温及77K时不同溶剂中的荧光光谱,发现在非极性溶剂中77K时DPP的荧光强度远比其在室温时的低,而PNP则完全没有荧光,表明这些化合物激发态的构象松驰,形成非平面扭曲构象对分子的发光性质十分重要。同时发现这两个化合物具有不同的关键性扭曲部位,形成各自有利于发光的构象,N-1上及C-3上苯环的扭曲分别对DPP和PNP的发光态的形成起着重要作用。 相似文献
170.
Lin Shan 《Journal of Functional Analysis》2008,255(6):1480-1496
In this paper, we define an equivariant higher index map from to K∗(C∗Γ(X)) if a torsion-free discrete group Γ acts on a manifold X properly, where C∗Γ(X) is the norm closure of all locally compact, Γ-invariant operators with finite propagation. When Γ acts on X properly and cocompactly, this equivariant higher index map coincides with the Baum-Connes map [P. Baum, A. Connes, K-theory for discrete groups, in: D. Evens, M. Takesaki (Eds.), Operator Algebras and Applications, Cambridge Univ. Press, Cambridge, 1989, pp. 1-20; P. Baum, A. Connes, N. Higson, Classifying space for proper actions and K-theory of group C∗-algebras, in: C∗-Algebras: 1943-1993, San Antonio, TX, 1993, in: Contemp. Math., vol. 167, Amer. Math. Soc., Providence, RI, 1994, pp. 240-291]. When Γ is trivial, this equivariant higher index map is the coarse Baum-Connes map [J. Roe, Coarse cohomology and index theory on complete Riemannian manifolds, Mem. Amer. Math. Soc. 104 (497) (1993); J. Roe, Index Theory, Coarse Geometry, and the Topology of Manifolds, CBMS Reg. Conf. Ser. Math., vol. 90, Amer. Math. Soc., Providence, RI, 1996]. If X is a simply-connected complete Riemannian manifold with nonpositive sectional curvature and Γ is a torsion-free discrete group acting on X properly and isometrically, we prove that the equivariant higher index map is injective. 相似文献