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121.
Jigang Yin Yin Hang Lianhan Zhang Jing Xiong Pengchao Hu 《Journal of luminescence》2010,130(8):1338-1342
The electronic structures of LiYF4 (YLF) crystals containing F color center (YLF-F) and Yb doped YLF crystals (Yb3+:YLF, Yb2+:YLF) are systematically studied within the framework of the density functional theory. The calculated results indicate that the 330 nm absorption band originates from the F center in YLF crystals. Thus the doping of Yb3+ can weaken the 330 nm absorption band by competing with F vacancies in capturing free electrons arising after γ-irradiation and change to Yb2. By analyzing the lattice relaxation and the electronic structure of YLF containing Yb2+, we can reasonably believe that once Yb2+ is formed in YLF crystal, its compensating hole will turn out to be shared by two F− nearest to Yb2+ forming a diatomic fluoride molecular ion () perturbed by Yb2+, or to say VF color center. According to the molecular-orbital linear combination of atomic orbital (MO-LCAOs) theory, compared to the alkali halides, e.g. LiF, the in VF center in LiYF4 peaks at about 340 nm, which is in agreement with the experimental results. 相似文献
122.
Konstantinos Spiliopoulos Richard B. Sowers 《Stochastic Processes and their Applications》2011,121(12):2861-2898
We consider the effect of recovery rates on a pool of credit assets. We allow the recovery rate to depend on the defaults in a general way. Using the theory of large deviations, we study the structure of losses in a pool consisting of a continuum of types. We derive the corresponding rate function and show that it has a natural interpretation as the favored way to rearrange recoveries and losses among the different types. Numerical examples are also provided. 相似文献
123.
Constrained diffusions, with diffusion matrix scaled by small ?>0, in a convex polyhedral cone G⊂Rk, are considered. Under suitable stability assumptions small noise asymptotic properties of invariant measures and exit times from domains are studied. Let B⊂G be a bounded domain. Under conditions, an “exponential leveling” property that says that, as ?→0, the moments of functionals of exit location from B, corresponding to distinct initial conditions, coalesce asymptotically at an exponential rate, is established. It is shown that, with appropriate conditions, difference of moments of a typical exit time functional with a sub-logarithmic growth, for distinct initial conditions in suitable compact subsets of B, is asymptotically bounded. Furthermore, as initial conditions approach 0 at a rate ?2 these moments are shown to asymptotically coalesce at an exponential rate. 相似文献
124.
Bo Göran Johansson 《Historia Mathematica》2011,38(3):338-367
The algorithms used in Arabic and medieval European mathematics for extracting cube roots are studied with respect to algebraic structure and use of external memory (dust board, table, paper). They can be separated into two distinct groups. One contains methods used in the eastern regions from the 11th century, closely connected to Chinese techniques, and very uniform in structure. The other group, showing much wider variation, contains early Indian methods and techniques developed in central and western parts of the Arabic areas and in Europe. This study supports hypotheses previously formulated by Luckey and Chemla on an early scientific connection between China and Persia. 相似文献
125.
Yoshiyuki Kagei 《Journal of Differential Equations》2011,251(11):3248-3295
The initial boundary value problem for the compressible Navier-Stokes equation is considered in an infinite layer of Rn. It is proved that if n?3, then strong solutions to the compressible Navier-Stokes equation around parallel flows exist globally in time for sufficiently small initial perturbations, provided that the Reynolds and Mach numbers are sufficiently small. The proof is given by a variant of the Matsumura-Nishida energy method based on a decomposition of solutions associated with a spectral property of the linearized operator. 相似文献
126.
We study three types of quotient maps of frames which are closely related to C- and C?-quotient maps. We call them C1-, strong C1-, and uplifting quotient maps. C1-quotient maps are precisely those whose induced ring homomorphisms contract maximal ideals to maximal ideals. We show that every homomorphism onto a frame is a C1-, a strong C1-, or an uplifting quotient map iff the frame is pseudocompact, compact, or almost compact and normal, respectively. These quotient maps are used to characterize normality and also certain weaker forms of normality in a manner akin to the characterization of normal frames as those for which every closed quotient map is a C-quotient map. Under certain conditions, we show that the Stone extension of a quotient map is C1-, strongly C1- or uplifting if the map has the corresponding property. 相似文献
127.
Igor Leite Freire Antonio Cândido Faleiros 《Nonlinear Analysis: Theory, Methods & Applications》2011,74(11):3478-3486
Using the classical Lie method we obtain the full Lie point symmetry group of the Aronsson equation in two independent variables. Some group invariant solutions of this equation are found and a conjecture on the Lie point symmetry group of the Aronsson equation in Rn is presented. 相似文献
128.
129.
Ultrashort-pulse fiber ring lasers 总被引:4,自引:0,他引:4
L.E. Nelson D.J. Jones K. Tamura H.A. Haus E.P. Ippen 《Applied physics. B, Lasers and optics》1997,65(2):277-294
Received: 18 February 1997/Revised version: 22 April 1997 相似文献
130.
Simeon M. Berman 《Annals of the Institute of Statistical Mathematics》1984,36(1):301-321
Summary Let {X
n,j,−∞<j<∞∼,n≧1, be a sequence of stationary sequences on some probability space, with nonnegative random variables. Under appropriate
mixing conditions, it is shown thatS
n=Xn,1+…+X
n,n has a limiting distribution of a general infinitely divisible form. The result is applied to sequences of functions {f
n(x)∼ defined on a stationary sequence {X
j∼, whereX
n.f=fn(Xj). The results are illustrated by applications to Gaussian processes, Markov processes and some autoregressive processes of
a general type.
This paper represents results obtained at the Courant Institute of Mathematical Sciences, New York University, under the sponsorship
of the National Sciences Foundation, Grant MCS 82-01119. 相似文献