排序方式: 共有39条查询结果,搜索用时 15 毫秒
1.
聚合物驱油作为一种重要的三次采油方法,在国内外油气田开发中得到了广泛应用.聚合物驱油效果的好坏取决于多种因素,其中很重要的一个因素是聚合物的注入能力,这一因素直接决定了聚合物驱油的成败.本文利用实验方法研究了聚合物的分子质量、岩样的渗透率以及注入速度等因素对聚合物注入能力的影响.结果表明,聚合物溶液具有粘弹性,注入速度增大,注入性变差.同时聚合物分子量越大,岩心渗透率越低,聚合物注入性越差.对于孤岛中一区,平均孔隙半径与聚合物分子折算半径之比大于10时,聚合物可顺利注入地层.研究结果可用于指导现场聚合物的选取,从而有效保证聚合物的注入能力,使聚合物驱油达到预期效果. 相似文献
2.
M Büttiker 《Pramana》2002,58(2):241-257
We introduce a hierarchy of density of states to characterize the charge distribution in a mesoscopic conductor. At the bottom
of this hierarchy are the partial density of states which represent the contribution to the local density of states if both
the incident and the out-going scattering channel is prescribed. The partial density of states play a prominent role in measurements
with a scanning tunneling microscope on multiprobe conductors in the presence of current flow. The partial density of states
determine the degree of dephasing generated by a weakly coupled voltage probe. In addition the partial density of states determine
the frequency-dependent response of mesoscopic conductors in the presence of slowly oscillating voltages applied to the contacts
of the sample. The partial density of states permit the formulation of a Friedel sum rule which can be applied locally. We
introduce the off-diagonal elements of the partial density of states matrix to describe charge fluctuation processes. This
generalization leads to a local Wigner-Smith life-time matrix. 相似文献
3.
Wilderich Tuschmann 《Proceedings of the American Mathematical Society》2002,130(1):303-306
A recent injectivity radius estimate and previous sphere theorems yield the following smooth diameter sphere theorem for manifolds of positive Ricci curvature: For any given and there exists a positive constant 0$">such that any -dimensional complete Riemannian manifold with Ricci curvature , sectional curvature and diameter is Lipschitz close and diffeomorphic to the standard unit -sphere. A similar statement holds when the diameter is replaced by the first eigenvalue of the Laplacian.
4.
本文证明,在Gromov-Hausdorff拓扑下,Ricci曲率平行,截面曲率和单一半径有下界,体积有上界的Riemann流形的集合是c∞紧的.作为应用,我们证明一个pinching结果,即在某些条件下,Rucci平坦的流形必定平坦. 相似文献
5.
Marius Radulescu Sorin Radulescu 《Journal of Mathematical Analysis and Applications》2011,382(2):559-564
We discuss the problem of global invertibility of nonlinear maps defined on the finite dimensional Euclidean space via differential tests. We provide a generalization of the Fujisawa-Kuh global inversion theorem and introduce a generalized ratio condition which detects when the pre-image of a certain class of linear manifolds is non-empty and connected. In particular, we provide conditions that also detect global injectivity. 相似文献
6.
Hong Ding 《Applicable analysis》2013,92(9):1838-1850
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Let ƒ∈C
1 (R
1, R
2), ƒ(0) = 0. The Jacobian Conjecture states that if for any x∈R
2, the eigenvalues of the Jacobian matrix Dƒ(x) have negative real parts, then the zero solution of the differential equation x = ƒ(x) is globally asymptotically stable. In this paper we prove that the conjecture is true.
This work is supported by the National Natural Science Foundation of China 相似文献
10.
Nobuhiro Innami 《Proceedings of the American Mathematical Society》1999,127(10):3049-3055
We show some relations among the volumes of domains in Euclidean spaces, their surface areas and the inward injectivity radii from their boundaries. In particular, we give an estimate for the upper bound of the ratios of their surface areas and volumes by means of inward injectivity radii. The upper bound seems to depend on their topological structures.