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排序方式: 共有238条查询结果,搜索用时 350 毫秒
71.
P. Soffitta L. Barbanera E. Costa G. Di Persio M. Feroci B. Martino L. Piro A. Rubini E. Massaro G. Medici G. C. Perola A. Santangelo S. Giarrusso G. La Rosa G. Manzo G. Fazio P. Kaaret R. Novick I. Lapshov R. Sunyaev 《Il Nuovo Cimento C》1993,16(6):703-707
Summary The Stellar X-Ray Polarimeter SXRP will be flown at the focus of the SODART X-ray telescope aboard the Russian satellite SPECTRUM-X-Gamma
by the end of 1995. Four imaging proportional counters will detect photons diffracted by a graphite crystal (2.6 and 5.2 keV)
and scattered from a lithium rod enclosed in a beryllium case (from 5 to 20 KeV). The counters are position-sensitive by the
Wedge and Strip (WS) readout method. The gas mixture is 80% xenon, 10% argon and 10% methane. In this contribution we resume
the results of the measurements performed on the engineering models of the counters. Position resolution of about 1.5 mm is
attained with an energy resolution of about 25%. The pulse shape discrimination offers more than 98%60Co events rejection, with at least 90% X-ray acceptance. Some improvements are foreseen for the flight units in terms of sensitivity
and uniformity of response. 相似文献
72.
Dirichlet problem Characterization of regularity 总被引:5,自引:0,他引:5
G. Di Fazio 《manuscripta mathematica》1994,84(1):47-56
73.
Riccardo Fazio 《Journal of Computational and Applied Mathematics》1990,30(3):341-349
Three problems of physical interest, which are described by first-order quasilinear hyperbolic systems in conservative form, are considered. These systems are invariant with respect to the stretching group of transformations and, more important, they admit an associated group. So we are able to characterize both the profile of the shock and discontinuity velocity; the latter by making use of the concept of “discrete perturbation stability analysis”. 相似文献
74.
A free boundary formulation for the numerical solution of boundary value problems on infinite intervals was proposed recently in Fazio (SIAM J. Numer. Anal. 33 (1996) 1473). We consider here a survey on recent developments related to the free boundary identification of the truncated boundary. The goals of this survey are: to recall the reasoning for a free boundary identification of the truncated boundary, to report on a comparison of numerical results obtained for a classical test problem by three approaches available in the literature, and to propose some possible ways to extend the free boundary approach to the numerical solution of problems defined on the whole real line. 相似文献
75.
A Regge pole analysis is employed to explain the oscillatory patterns observed in numerical simulations of integral cross section for the F+H(2)(v=0,j=0)-->HF(v(')=2,j(')=0)+H reaction in the translational collision energy range 25-50 meV. In this range the integral cross section for the transition, affected by two overlapping resonances, shows nearly sinusoidal oscillations below 38 meV and a more structured oscillatory pattern at larger energies. The two types of oscillations are related to the two Regge trajectories which (pseudo) cross near the energy where the resonances are aligned. Simple estimates are given for the periods of the oscillations. 相似文献
76.
De Fazio D Cavalli S Aquilanti V Buchachenko AA Tscherbul TV 《The journal of physical chemistry. A》2007,111(49):12538-12549
We study scattering resonances in the F+HD-->HF+D reaction using a new method for direct evaluation of the lifetime Q-matrix [Aquilanti et al., J. Chem. Phys. 2005, 123, 054314]. We show that most of the resonances are due to van der Waals states in the entrance and exit reaction channels. The metastable states observed in the product reaction channel are assigned by calculating the energy levels and wave functions of the HF...D van der Waals complex. The behavior of resonance energies, widths, and decay branching ratios as functions of total angular momentum is analyzed. The effect of isotopic substitution on resonance energies and lifetimes is elucidated by comparison with previous results for the F+H2 reaction. It is demonstrated that HF(v'=3) products near threshold are formed by decay of the narrow resonances supported by van der Waals wells in the exit channel. State-to-state differential cross sections in the HF(v'=3) channel exhibit characteristic forward-backward peaks due to the formation of a long-lived metastable complex. The role of the exit-channel resonances in the interpretation of molecular beam experiments is discussed. 相似文献
77.
BVPs on infinite intervals: A test problem,a nonstandard finite difference scheme and a posteriori error estimator 下载免费PDF全文
Riccardo Fazio Alessandra Jannelli 《Mathematical Methods in the Applied Sciences》2017,40(18):6285-6294
As far as the numerical solution of boundary value problems defined on an infinite interval is concerned, in this paper, we present a test problem for which the exact solution is known. Then we study an a posteriori estimator for the global error of a nonstandard finite difference scheme previously introduced by the authors. In particular, we show how Richardson extrapolation can be used to improve the numerical solution using the order of accuracy and numerical solutions from 2 nested quasi‐uniform grids. We observe that if the grids are sufficiently fine, the Richardson error estimate gives an upper bound of the global error. 相似文献
78.
Mustapha Mourragui Enza Orlandi 《Annales de l'Institut Henri Poincaré (B) Probabilités et Statistiques》2007,43(6):677-715
We consider a lattice gas in a periodic d-dimensional lattice of width γ−1, γ>0, interacting via a Kac's type interaction, with range and strength γd, and under the influence of a random one body potential given by independent, bounded, random variables with translational invariant distribution. The system evolves through a conservative dynamics, i.e. particles jump to nearest neighbor empty sites, with rates satisfying detailed balance with respect to the equilibrium measures. In [M. Mourragui, E. Orlandi, E. Saada, Macroscopic evolution of particles systems with random field Kac interactions, Nonlinearity 16 (2003) 2123–2147] it has been shown that rescaling space as γ−1 and time as γ−2, in the limit γ→0, for dimensions d3, the macroscopic density profile ρ satisfies, a.s. with respect to the random field, a non-linear integral partial differential equation, having the diffusion matrix determined by the statistical properties of the external random field. Here we show an almost sure (with respect to the random field) large deviations principle for the empirical measures of such a process. The rate function, which depends on the statistical properties of the external random field, is lower semicontinuous and has compact level sets. 相似文献
79.
AbstractWe have prepared novel nanohybrid Li2xMn1?xPS3/GO films consisting of graphene oxide (GO) and exfoliated MnPS3 nanosheets via an easy mixing protocol at room temperature. These films were investigated by SEM and AFM, as well as XRD, Raman and XPS spectroscopies, obtaining information about the nature of the interaction between MnPS3 and GO. In particular, the dark colour of the nanocomposite film and, more to the point, the analysis of (i) the C1s core level XPS spectra, (ii) the interlayer spacing obtained by XRD measurements and (iii) the increment in the intensity ratio ID/IG of the two bands typical of the carbon region of GO Raman spectra, suggest that a partial reduction of GO can be obtained right upon intercalation into Li2xMn1?xPS3. 相似文献
80.
The fibrils that yielded the Shroud body image show a stochastic distribution on the Linen of Turin. In fact, the probability of a fibril yellowing is a function of the energy, while this is not the case for the optical density value. This means that the above image is a latent image. We suggest thermal radiation or low-temperature chemical processes as possible natural energy sources to explain, by stochastic effects, the Shroud body image formation. Unfortunately, due to the nature of the phenomenon, we are not able to extract the energy source. 相似文献