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31.
A time-dependent model corresponding to an Oldroyd-B viscoelastic fluid is considered, the convective terms being disregarded.
Global existence in time is proved in Banach spaces provided the data are small enough, using the implicit function theorem
and a maximum regularity property for a three fields Stokes problem. A finite element discretization in space is then proposed.
Existence of the numerical solution is proved for small data, so as a priori error estimates, using again an implicit function
theorem.
Supported by the Swiss National Science Foundation. Fellowship PBEL2–114311. 相似文献
32.
Some authors claim that reporting the best result obtained by a stochastic algorithm in a number of runs is more meaningful
than reporting some central statistic. In this short note, we analyze and refute the main argument brought in favor of this
statement. 相似文献
33.
34.
Summary The radial evolution of Alfvénic correlation is such that its value decreases with increasing heliocentric distance. So far
this behaviour has been interpreted as an increase in the local production of ?inward? modes interacting destructively with
the ?outward? modes. This work, which deals with largescale turbulence, shows that local generation phenomena are not commonly
found in the solar wind and that the Alfvénic character of the fluctuations mainly depend on the ?outward? modes alone. The
interaction of these modes with density and/or magnetic-field structures convected by the wind causes their destruction and
a consequent depletion of the Alfvénic correlation. The same effect would be obtained if ?inward? modes were really present.
Our conclusions are that large-scale ?inward? modes are the spectral counterpart of non-propagating field and plasma structures
convected by the solar wind and identified as both compression regions and pressure balance structures.
Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990. 相似文献
35.
Marco Marletta 《Advances in Computational Mathematics》1994,2(2):155-184
This paper discusses the numerical solution of eigenvalue problems for Hamiltonian systems of ordinary differential equations.
Two new codes are presented which incorporate the algorithms described here; to the best of the author’s knowledge, these
are the first codes capable of solving numerically such general eigenvalue problems. One of these implements a new new method
of solving a differential equation whose solution is a unitary matrix. Both codes are fully documented and are written inPfort-verifiedFortran 77, and will be available in netlib/aicm/sl11f and netlib/aicm/sl12f. 相似文献
36.
37.
Marco Merkli 《Journal of Mathematical Analysis and Applications》2007,327(1):376-399
Level shift operators describe the second-order displacement of eigenvalues under perturbation. They play a central role in resonance theory and ergodic theory of open quantum systems at positive temperatures. We exhibit intrinsic properties of level shift operators, properties which stem from the structure of open quantum systems at positive temperatures and which are common to all such systems. They determine the geometry of resonances bifurcating from eigenvalues of positive temperature Hamiltonians and they relate the Gibbs state, the kernel of level shift operators, and zero energy resonances. We show that degeneracy of energy levels of the small part of the open quantum system causes the Fermi Golden Rule Condition to be violated and we analyze ergodic properties of such systems. 相似文献
38.
Modern trends in designing mechatronic systems call for a synergic design of the separated subsystems (mechanic, electronic parts, control modules, etc.) concurring to the overall performance. Following this point of view, this paper presents a control oriented model and a nonlinear control design for a Common Rail injection system. First a model is developed, which is tuned in a virtual simulation environment, representing the injection system in details in a reliable replication of reality. Then a sliding mode control is developed. Both the model of the injection process and of the control law are validated by a virtual detailed simulation environment. The prediction capability of the model and the control efficiency are clearly shown. 相似文献
39.
We study the asymptotic behaviour of non-negative solutions of Yamabe type equations on a complete Riemannian manifold. Then we provide a comparison result, based on a form of the weak maximum principle at infinity, which together with the “a priori” estimates previously obtained, yields uniqueness under very general Ricci assumptions. The paper ends with an existence result and an application to the non-compact Yamabe problem. 相似文献
40.
Bruno Després 《Comptes Rendus Mathematique》2006,342(1):73-78
We describe a Weak Rankine Hugoniot relation for constrained discontinuous solutions of conservation laws. The constraint is convex in the primitive variable. Various examples show the potential interest of this approach. To cite this article: B. Després, C. R. Acad. Sci. Paris, Ser. I 342 (2006). 相似文献