排序方式: 共有16条查询结果,搜索用时 296 毫秒
1.
Bucataru Ioan Constantinescu Oana Creţu Georgeta 《Annals of Global Analysis and Geometry》2022,62(4):815-827
Annals of Global Analysis and Geometry - We prove that in a Finsler manifold with vanishing $$\chi $$ -curvature (in particular with constant flag curvature) some non-Riemannian geometric... 相似文献
2.
A system of third order differential equations, whose coefficients do not depend explicitly on time, can be viewed as a third
order vector field, which is called a semispray, and lives on the second order tangent bundle. We prove that a regular second
order Lagrangian induces such a semispray, which is uniquely determined by two associated Poincaré-Cartan one-forms. To study
the geometry of this semispray, we construct a horizontal distribution, which is a Lagrangian subbundle for an associated
Poincaré-Cartan two-form. Using this semispray and the associated nonlinear connection we define dynamical covariant derivatives
of first and second order. With respect to this, the second order dynamical derivative of the Lagrangian metric tensor vanishes. 相似文献
3.
In this paper we characterize sprays that are metrizable by Finsler functions of constant flag curvature. By solving a particular case of the Finsler metrizability problem, we provide the necessary and sufficient conditions that can be used to decide whether or not a given homogeneous system of second order ordinary differential equations represents the geodesic equations of a Finsler function of constant flag curvature. The conditions we provide are tensorial equations on the Jacobi endomorphism. We identify the class of homogeneous SODE where the Finsler metrizability is equivalent with the metrizability by a Finsler function of constant flag curvature. 相似文献
4.
We formulate coordinate-free conditions for identifying all the symmetry classes of the elasticity tensor and prove that these conditions are both necessary and sufficient. Also, we construct a natural coordinate system of this tensor without the a priory knowledge of the symmetry axes. 相似文献
5.
Material symmetries of elasticity tensors 总被引:1,自引:0,他引:1
6.
7.
Using orthogonal projections, we investigate distance of a given elasticity tensor to classes of elasticity tensors exhibiting
particular material symmetries. These projections depend on the orientation of the elasticity tensor; hence the distance is
obtained as the minimization of corresponding expressions with respect to the action of the orthogonal group. These expressions
are stated in terms of the eigenvalues of both the given tensor and the projected one. The process of minimization is facilitated
by the fact that, as we prove, the traces of the corresponding Voigt and dilatation tensors are invariant under these orthogonal
projections. For isotropy, cubic symmetry and transverse isotropy, we formulate algorithms to find both the orientation and
the eigenvalues of the elasticity tensor endowed with a particular symmetry and closest to the given elasticity tensor.
相似文献
8.
Nicholas Stanley Georgiana Bucataru Yong Miao Audrey Favrelle Marc Bria Francois Stoffelbach Patrice Woisel Philippe Zinck 《Journal of polymer science. Part A, Polymer chemistry》2014,52(15):2139-2145
The polymerization of ε‐caprolactone (ε‐CL) has been assessed in water using various Brønsted acids as catalysts. The reaction was found to be quantitative at 100 °C, leading to number–average molecular weights up to 5000 g mol?1. The Brønsted acid‐catalyzed polymerization of ε‐CL in water was further conducted in the presence of water‐soluble polysaccharides thereby affording graft copolymers. The approach enables an easy, mild access to dextran hydroxyesters. For low degree of substitution, the latter self‐assembles in water to form nanoparticles. Poly(ε‐CL)‐graft‐methylcellulose copolymers can also be obtained via a similar approach. It is noteworthy that the methodology reported herein is a one‐step route to poly(ε‐CL)‐graft‐water‐soluble polysaccharides, operating in mild conditions, that is, at low temperatures, using readily available metal‐free catalysts and water as a solvent. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2139–2145 相似文献
9.
10.
Ioan Bucataru 《Differential Geometry and its Applications》2007,25(3):335-343
For a system of second order differential equations we determine a nonlinear connection that is compatible with a given generalized Lagrange metric. Using this nonlinear connection, we can find the whole family of metric nonlinear connections that can be associated with a system of SODE and a generalized Lagrange metric. For the particular case when the system of SODE and the metric structure are Lagrangian, we prove that the canonical nonlinear connection of the Lagrange space is the only nonlinear connection which is metric and compatible with the symplectic structure of the Lagrange space. For this particular case, the metric tensor determines the symmetric part of the canonical nonlinear connection, while the symplectic structure determines the skew-symmetric part of the nonlinear connection. 相似文献