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21.
In this note we study constant mean curvature surfaces in asymptotically flat 3-manifolds. We prove that, outside a given compact subset in an asymptotically flat 3-manifold with positive mass, stable spheres of given constant mean curvature are unique. Therefore we are able to conclude that the foliation of stable spheres of constant mean curvature in an asymptotically flat 3-manifold with positive mass outside a given compact subset is unique.
22.
[1]中提出了具有功能反应的三种群捕食者——食饵系统的两种模型(Ⅰ)、(Ⅱ),并给出了局部渐近稳定的条件。本文研究了另外两种模型(Ⅲ)和(Ⅳ)的局部渐近稳定的条件。 相似文献
23.
E. Alper Yildirim Xiaofei Fan-Orzechowski 《Computational Optimization and Applications》2006,33(2-3):229-247
We study the maximum stable set problem. For a given graph, we establish several transformations among feasible solutions
of different formulations of Lovász's theta function. We propose reductions from feasible solutions corresponding to a graph
to those corresponding to its induced subgraphs. We develop an efficient, polynomial-time algorithm to extract a maximum stable
set in a perfect graph using the theta function. Our algorithm iteratively transforms an approximate solution of the semidefinite
formulation of the theta function into an approximate solution of another formulation, which is then used to identify a vertex
that belongs to a maximum stable set. The subgraph induced by that vertex and its neighbors is removed and the same procedure
is repeated on successively smaller graphs. We establish that solving the theta problem up to an adaptively chosen, fairly
rough accuracy suffices in order for the algorithm to work properly. Furthermore, our algorithm successfully employs a warm-start
strategy to recompute the theta function on smaller subgraphs. Computational results demonstrate that our algorithm can efficiently
extract maximum stable sets in comparable time it takes to solve the theta problem on the original graph to optimality.
This work was supported in part by NSF through CAREER Grant DMI-0237415. Part of this work was performed while the first author
was at the Department of Applied Mathematics and Statisticsat Stony Brook University, Stony Brook, NY, USA. 相似文献
24.
25.
在超声快速制取组织细胞病理切片的过程中,发现激励信号对切片制取效果有明显的影响.为了掌握超声激励信号对组织细胞的影响规律,达到快速制取病理切片的最佳状态,从气泡空化模型入手,通过改变激励信号频率、声压、气泡初始半径和液体黏滞系数等参量,研究了声孔效应中气泡动力学激励机制.数值计算表明:空化泡振动随激励声压增强而升高,随液体黏滞系数增强而减弱;一定频率范围内空化泡振动能保持在膨胀、收缩和振荡的稳定空化状态,存在空化泡稳态振动的最佳激励频率;一定初始半径能保证空化泡产生稳定的振动,存在空化泡稳态振动幅度最大的初始半径.实际操作中,在频率、声压、初始半径和黏滞系数综合作用的若干空化阈内,声孔效应使超声快速法制取细胞组织切片获得最佳效果.
关键词:
声孔效应
超声空化
气泡振动
稳态空化域 相似文献
26.
M. Froese C. Champagne J. R. Crespo López-Urrutia S. Epp G. Gwinner A. Lapierre J. Pfister G. Sikler J. Ullrich J. Dilling 《Hyperfine Interactions》2006,173(1-3):85-92
The precision of atomic mass measurements in a Penning trap is directly proportional to the charge state q of the ion and,
hence, can be increased by using highly charged ions (HCI). For this reason, charge breeding with an electron beam ion trap
(EBIT) is employed at TRIUMF’s Ion Trap for Atomic and Nuclear science (TITAN) on-line facility in Vancouver, Canada. By bombarding
the injected and trapped singly charged ions with an intense beam of electrons, the charge state of the ions is rapidly increased
inside the EBIT. To be compatible with the on-line requirements of short-lived isotopes, very high electron beam current densities
are needed. The TITAN EBIT includes a 6 Tesla superconducting magnet and is designed to have electron beam currents and energies
of up to 5 A and 60 keV, respectively. Once operational at full capacity, most species can be bred into a He-like configuration
within tens of ms. Subsequently, the HCI are extracted, pass a Wien filter to reduce isobaric contamination, are cooled, and
injected into a precision Penning trap for mass measurement. We will present the first results and current status of the TITAN
EBIT, which has recently been moved to TRIUMF after assembly and commissioning at the Max-Planck-Institute (MPI) for Nuclear
Physics in Heidelberg, Germany. 相似文献
27.
28.
通过考虑同类核子相干对间的四极相互作用,在IBM2中对Ce偶-偶同位素^128Ce-^138Ce的低激发态能谱和E2跃迁几率及分支比进行了理论分析,计算结果有效地改善了IBM中这些核的γ带能谱的Staggering现象描述,与实验观察到的低激发态结果基本一致。 相似文献
29.
Manuel Fernández-López Eduardo García-Río Demir N. Kupeli 《Annals of Global Analysis and Geometry》2002,21(1):1-13
A characterization of time functions on a spacetime is made by using theMöbius equation. It is shown that a time function characterized in this wayyields past timelike geodesic incompleteness and local Lorentzian warpedproduct decomposition of spacetime, provided that the stress-energy tensoris a fluid. Also, by imposing additional assumptions on the stress-energytensor and global analytic structure of the spacetime, more restrictivedecompositions closer to Robertson–Walker spacetimes are obtained. 相似文献
30.
温香彩 《河南师范大学学报(自然科学版)》1994,22(1):10-13
本文分别利用向量Lyapunov函数方法和标量Lyapunov函数方法,给出了判定离散大系统解的有界性与周期解的存在性的充分条件,并讨论了一类具有非线性时变周期离散大系统的平稳振荡存在性问题. 相似文献