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991.
992.
The Heavy Ion Research Facility and Cooling Storage Ring(HIRFL-CSR)accelerator in Lanzhou offers a unique possibility for the generation of high density and short pulse heavy ion beams by non-adiabatic bunch compression longitudinally,which is implemented by a fast jump of the RF-voltage amplitude.For this purpose,an RF cavity with high electric field gradient loaded with Magnetic Alloy cores has been developed.The results show that the resonant frequency range of the single-gap RF cavity is from 1.13 MHz to 1.42 MHz,and a maximum RF voltage of 40 kV with a total length of 100 cm can be obtained,which can be used to compress heavy ion beams of 238U72+ with 250 MeV/u from the initial bunch length of 200 ns to 50 ns with the coaction of the two single-gap RF cavity mentioned above. 相似文献
993.
The peak algebra
is a unital subalgebra of the symmetric group algebra, linearly spanned by sums of permutations with a common set of peaks.
By exploiting the combinatorics of sparse subsets of [n−1] (and of certain classes of compositions of n called almost-odd and thin), we construct three new linear bases of
. We discuss two peak analogs of the first Eulerian idempotent and construct a basis of semi-idempotent elements for the peak
algebra. We use these bases to describe the Jacobson radical of
and to characterize the elements of
in terms of the canonical action of the symmetric groups on the tensor algebra of a vector space. We define a chain of ideals
of
, j = 0,...,
, such that
is the linear span of sums of permutations with a common set of interior peaks and
is the peak algebra. We extend the above results to
, generalizing results of Schocker (the case j = 0).
Aguiar supported in part by NSF grant DMS-0302423
Orellana supported in part by the Wilson Foundation 相似文献
994.
The gradient method for the symmetric positive definite linear system
is as follows
where
is the residual of the system at xk and αk is the stepsize. The stepsize
is optimal in the sense that it minimizes the modulus
, where λ1 and λn are the minimal and maximal eigenvalues of A respectively. Since λ1 and λn are unknown to users, it is usual that the gradient method with the optimal stepsize is only mentioned in theory. In this
paper, we will propose a new stepsize formula which tends to the optimal stepsize as
. At the same time, the minimal and maximal eigenvalues, λ1 and λn, of A and their corresponding eigenvectors can be obtained.
This research was initiated while the first author was visiting The Hong Kong Polytechnic University.
This author was supported by the Chinese NSF grants (No. 40233029 and 101071104) and an innovation fund of Chinese Academy
of Sciences.
This author was supported by a grant from the Research Committee of the Hong Kong Polytechnic University (A-PC36). 相似文献
(1) |
995.
Zdzislaw Brzezniak Yuhong Li 《Transactions of the American Mathematical Society》2006,358(12):5587-5629
We introduce a notion of an asymptotically compact (AC) random dynamical system (RDS). We prove that for an AC RDS the -limit set of any bounded set is nonempty, compact, strictly invariant and attracts the set . We establish that the D Navier Stokes Equations (NSEs) in a domain satisfying the Poincaré inequality perturbed by an additive irregular noise generate an AC RDS in the energy space . As a consequence we deduce existence of an invariant measure for such NSEs. Our study generalizes on the one hand the earlier results by Flandoli-Crauel (1994) and Schmalfuss (1992) obtained in the case of bounded domains and regular noise, and on the other hand the results by Rosa (1998) for the deterministic NSEs.
996.
In this paper we study ambiguous chance constrained problems where the distributions of the random parameters in the problem
are themselves uncertain. We focus primarily on the special case where the uncertainty set of the distributions is of the form where ρp denotes the Prohorov metric. The ambiguous chance constrained problem is approximated by a robust sampled problem where each
constraint is a robust constraint centered at a sample drawn according to the central measure The main contribution of this paper is to show that the robust sampled problem is a good approximation for the ambiguous
chance constrained problem with a high probability. This result is established using the Strassen-Dudley Representation Theorem
that states that when the distributions of two random variables are close in the Prohorov metric one can construct a coupling of the random variables such that the samples are close with a high probability. We also show that the robust sampled problem can be solved efficiently both in theory
and in practice.
Research partially supported by NSF grant CCR-00-09972.
Research partially supported by NSF grants CCR-00-09972, DMS-01-04282, and ONR grant N000140310514. 相似文献
997.
This paper is concerned with nonlinear partial differential equations of the calculus of variation (see [13]) perturbed
by noise. Well-posedness of the problem was proved by Pardoux in the seventies (see [14]), using monotonicity methods.
The aim of the present work is to investigate the asymptotic behaviour of the corresponding transition semigroup Pt. We show existence and, under suitable assumptions, uniqueness of an ergodic invariant measure ν. Moreover, we solve the
Kolmogorov equation and prove the so-called "identite du carre du champs". This will be used to study the Sobolev space W1,2(H,ν) and to obtain information
on the domain of the infinitesimal generator of Pt. 相似文献
998.
999.
1000.
P.J. Cregg Kieran Murphy Adriele Prina-Mello 《Journal of magnetism and magnetic materials》2010,322(15):2087-2094
The implant assisted magnetic targeted drug delivery system of Avilés, Ebner and Ritter is considered both experimentally (in vitro) and theoretically. The results of a 2D mathematical model are compared with 3D experimental results for a magnetizable wire stent. In this experiment a ferromagnetic, coiled wire stent is implanted to aid collection of particles which consist of single domain magnetic nanoparticles (radius ). In order to model the agglomeration of particles known to occur in this system, the magnetic dipole-dipole and hydrodynamic interactions for multiple particles are included. Simulations based on this mathematical model were performed using open source C++ code. Different initial positions are considered and the system performance is assessed in terms of collection efficiency. The results of this model show closer agreement with the measured in vitro experimental results and with the literature. The implications in nanotechnology and nanomedicine are based on the prediction of the particle efficiency, in conjunction with the magnetizable stent, for targeted drug delivery. 相似文献