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991.
We consider a multi-class feedforward queueing network with first come first serve queueing discipline and deterministic services
and routing. The large deviation asymptotics of tail probabilities of the distribution of the workload vector can be characterized
by convex path space minimization problems with non-linear constraints. So far there exists no numerical algorithm which could
solve such minimization problems in a general way. When the queueing network is heavily loaded it can be approximated by a
reflected Brownian motion. The large deviation asymptotics of tail probabilities of the distribution of this heavy traffic
limit can again be characterized by convex path space minimization problems with non-linear constraints. However, due to their
less complicated structure there exist algorithms to solve such minimization problems. In this paper we show that, as the
network tends to a heavy traffic limit, the solution of the large deviation minimization problems of the network approaches
the solution of the corresponding minimization problems of a reflected Brownian motion. Stated otherwise, we show that large
deviation and heavy traffic asymptotics can be interchanged. We prove this result in the case when the network is initially
empty. Without proof we state the corresponding result in the stationary case. We present an illuminating example with two
queues.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
992.
A. Nowak W. Urban M. Rejmund J.L. Durell M.J. Leddy M.A. Jones W.R. Phillips A.G. Smith B.J. Varley I. Ahmad L.R. Morss M. Bentaleb E. Lubkiewicz N. Schulz 《The European Physical Journal A - Hadrons and Nuclei》1998,3(2):111-113
Neutron-rich, N=84 nuclei from the 132Sn region, populated in spontaneous fission of 248Cm, have been studied with EUROGAM 2. Excited states and their spins and parities in the 136Te nucleus were established up to 17ħ. OXBASH code calculations support the experimental identification of maximum aligned
configurations in 136Te. Empirical shell model calculations for the Iπ= 14+ level in 136Te indicate that the adopted mass of the 134Te nucleus should be lowered by 200(80) keV.
Received: 3 August 1998 相似文献
993.
A. Tomiyama S. Suga A. Okiji 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):351-359
The elementary excitation spectrums for the Anderson model at finite temperatures are calculated by using the Bethe-ansatz
solution. The formulation is based on the method of Yang and Yang, which was developed for the one-dimensional boson systems
with the -function type interaction. We obtain the temperature dependence of the spin and the charge excitation spectrums. When the
impurity level lies deeply from the Fermi level and the Coulomb interaction is suitably large, the resonant peak structure
develops in the low energy region of the spin excitation spectrum and the hump structure grows around the impurity level of
the charge excitation spectrum with decreasing temperature.
Received: 21 January 1998 / Accepted: 17 March 1998 相似文献
994.
A.A. Aligia E. Gagliano L. Arrachea K. Hallberg 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):371-378
We consider a generalized Hubbard model with on-site and nearest-neighbour repulsions U and V respectively, and nearest-neighbour hopping for spin up (down) which depends on the total occupation nb of spin down (up) electrons on both sites involved. The hopping parameters are t
AA
, tAB and tBB for n
b
=0,1,2 respectively. We briefly summarize results which support that the model exhibits s-wave superconductivity for certain parameters and extend them by studying the Berry phases. Using a generalized Hartree-Fock(HF)
BCS decoupling of the two and three-body terms, we obtain that at half filling, for t
AB
<t
AA
=t
BB
and sufficiently small U and V the model leads to triplet p-wave superconductivity for a simple cubic lattice in any dimension. In one dimension, the resulting phase diagram is compared
with that obtained numerically using two quantized Berry phases (topological numbers) as order parameters. While this novel
method supports the previous results, there are quantitative differences.
Received: 2 February 1998 / Accepted: 17 March 1998 相似文献
995.
The electronic structure of heavy fermion compound LiV2O4 has been calculated using a self-consistent full-potential LMTO method. The results show that the conduction bands in this
compound are formed from V 3 d states with a bandwidth of 2.5 eV. The symmetric characteristics of conduction bands are of
t2g in principle. The energy gap between conduction bands and fully occupied oxygen 2p bands is 1.9 eV. The band dispersions
near Fermi energy display complicated structures. Furthermore, the N( EF) and ycal are 11.1 (states/eV/f.u.) and 26.7 mJ/mol.K2 determined numerically by LDA calculation, respectively. It is insufficient to clarify the origin of local moment in LiV2O4 from plain LDA calculations. In addition to the above LDA calculation, we also found a LSDA solution of LiV2O4 that is lower in total energy than that of LDA calculation. Similarly, LSDA + GGA calculation yields almost the identical
result as that in LSDA. We conclude that the mechanism responsible for heavy fermion properties in LiV2O4 might be somewhat different from the plain Kondo mechanism in conventional 4f and 5f heavy fermion compounds and perhaps
the quantum transition might play an adequate role in heavy-ferrnion behaviors in LiV2O4. 相似文献
996.
在Skyrme相互作用下讨论了径向膨胀能量对平均场、核子-核子碰撞截面的依赖关系,得到了有关状态方程的信息.在计算中发现,中能区重离子碰撞中径向膨胀能量受平均场影响较大,而截面对它的影响很小. 相似文献
997.
A M Porcellato V Palmieri L Bertazzo A Capuzzo D Giora F Stivanello S Y Stark S Kar 《Pramana》2002,59(5):871-880
Eight cryostats, each housing 4 sputtered Nb/Cu, 160 MHz, quarter wave resonators (QWR), are now in operation in ALPI[1].
Two of them house high β cavities; the others are equipped with medium β resonators. Another medium β cryostat is ready and will be installed in the early 2002. Pb/Cu medium β accelerating cavities are now present only in four cryostats and they will have their Pb superconducting (SC) layer replaced
by sputtered Nb soon.
The substitution of the Pb SC layer in ALPI medium β resonators did not interfere with ALPI operation; the upgrading of resonators went on parallel to the cryostat maintenance
programme. The average accelerating field of these resonators, at the design power of 7 W, overcomes 4 MV/m, whereas, when
Pb electroplated, their average value was 2.7 MV/m. The sputtered resonator combines the good SC characteristics of Nb with
the higher thermal conductivity and better stability to change of He bath pressure, which is typical of copper resonators.
This leads to a very high reliability, as routinely experienced during beam acceleration. 相似文献
998.
999.
A year ago, we presented a new approach to treat hadronic interactions or the initial stage of nuclear collisions [1,2]. It
is an effective theory based on the Gribov-Regge formalism, where the internal structure of the Pomerons at high energies
is governed by perturbative parton evolution, therefore the nameparton-based Gribov-Regge theory. The main improvement compared to models used so far is the appropriate treatment of the energy sharing between the different
elementary interactions in case of multiple scattering. It is clear that the above formalism is not yet complete. At high
energies (RHIC, LHC), the multiple elementary interactions (Pomerons) cannot be purely parallel, they interact. So we introduce
multiple Pomeron vertices into the theory. 相似文献
1000.
从菲尔德–费曼的叠代模型出发,考虑到入射夸克的味结构,研究了π介子的碎裂函数Duπ+,Ddπ+,和Dsπ+,并将分析结果和实验数据进行了比较,对K介子的碎裂函数DsK+(z),DuK+(z),DsK+(z)和DdK+(z)作出的预言将被进一步的实验检验。 相似文献