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81.
Juan E. Nápoles Valdés 《Results in Mathematics》2002,41(3-4):337-345
Qualitative behavior of second order nonlinear differential equations of type y″+p(t)y+q(t)f(y)=0, is studied. It includes properties such as positivity, number of zeros, oscillating nature, boundedness and monotonicity of the solutions. 相似文献
82.
83.
84.
Jaume GINE 《数学学报(英文版)》2006,22(6):1613-1620
The centers of the polynomial differential systems with homogeneous polynomials have been studied for the degrees s = 2, 3, 4, 5. for s = 2, 3, and partially classified for s = 4, 5. In this paper we recall and we give new centers for s = 6, 7 a linear center perturbed by They are completely classified these results for s = 2, 3, 4, 5, 相似文献
85.
86.
Summary. The perfectly matched layer (PML) is an efficient tool to simulate propagation phenomena in free space on unbounded domain.
In this paper we consider a new type of absorbing layer for Maxwell's equations and the linearized Euler equations which is
also valid for several classes of first order hyperbolic systems. The definition of this layer appears as a slight modification
of the PML technique. We show that the associated Cauchy problem is well-posed in suitable spaces. This theory is finally
illustrated by some numerical results. It must be underlined that the discretization of this layer leads to a new discretization
of the classical PML formulation.
Received May 5, 2000 / Published online November 15, 2001 相似文献
87.
It is shown that the condition υ > υp (ω), which is necessary in order to trigger the Vavilov-Cherenkov effect, determines the interval of radiated frequencies
and it alone cannot establish a strong restriction to the velocity of the particle. It is exhibited that it is possible to
define a general lower bound for the velocity of the particle, which does not depend on the frequency when both, a specific
response of the medium is taken into account and the mentioned condition is considered. The minimum value of the phase velocity
of light in the medium determines the existence of such general lower bound. 相似文献
88.
It was studied the tin phase composition of the electrodeposited alloys produced at different temperatures and current densities from an acid chloride/fluoride electrolyte and an acid chloride bath. Mössbauer spectra were consistent with a Ni3Sn4 intermetallic compound, dissolved tin, and a Cu?Sn intermetallic compound formed at the interface of the copper substrate. 相似文献
89.
A simple High performance liquid chromatographic (HPLC) method for the specific determination of the molecular weight and concentration of hyaluronic acid (HA) in complex mixtures has been developed. Hyaluronate-binding proteins isolated from bovine cartilage labelled by 125I or fluoresceinisothiocyanate were used as specific markers. The specific binding affinities of the markers were compared and were found to have association constants of 1.6 x 10(7) M-1 and 1.2 x 10(7) M-1 respectively. The HA levels and molecular weight distributions can be easily determined in the range 10-500 ng/mL in complex mixtures by the use of markers, molecular sieving HPLC columns and appropriate detectors. It has been demonstrated clearly that the method is useful for the highly specific determination of the parameters in complex biological samples such as serum and synovial fluids and is recommended for clinical applications. 相似文献
90.
We study percolation in the following random environment: let Z be a Poisson process of constant intensity on ℝ2, and form the Voronoi tessellation of ℝ2 with respect to Z. Colour each Voronoi cell black with probability p, independently of the other cells. We show that the critical probability is 1/2. More precisely, if p>1/2 then the union of the black cells contains an infinite component with probability 1, while if p<1/2 then the distribution of the size of the component of black cells containing a given point decays exponentially. These
results are analogous to Kesten's results for bond percolation in ℤ2.
The result corresponding to Harris' Theorem for bond percolation in ℤ2 is known: Zvavitch noted that one of the many proofs of this result can easily be adapted to the random Voronoi setting.
For Kesten's results, none of the existing proofs seems to adapt. The methods used here also give a new and very simple proof
of Kesten's Theorem for ℤ2; we hope they will be applicable in other contexts as well.
Research supported in part by NSF grant ITR 0225610 and DARPA grant F33615-01-C-1900
Research partially undertaken during a visit to the Forschungsinstitut für Mathematik, ETH Zürich, Switzerland 相似文献