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41.
Linear partial differential algebraic equations (PDAEs) of the form Au
t(t, x) + Bu
xx(t, x) + Cu(t, x) = f(t, x) are studied where at least one of the matrices A, B R
n×n
is singular. For these systems we introduce a uniform differential time index and a differential space index. We show that in contrast to problems with regular matrices A and B the initial conditions and/or boundary conditions for problems with singular matrices A and B have to fulfill certain consistency conditions. Furthermore, two numerical methods for solving PDAEs are considered. In two theorems it is shown that there is a strong dependence of the order of convergence on these indexes. We present examples for the calculation of the order of convergence and give results of numerical calculations for several aspects encountered in the numerical solution of PDAEs. 相似文献
42.
G.Ya. Korenman 《Hyperfine Interactions》1999,119(1-4):227-233
Effect of medium density on shift and broadening of (
) spectral lines is considered in the framework of binary-collision approximation with an effective (
)–He potential including the long-range attraction and short-range repulsion. Quantum calculations of the scattering phase
shifts at reasonable values of the potential parameters allow to explain the main features of the observed density effect
on the shape of (
) spectral lines in low-temperature helium.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
43.
Emilio Musso Lorenzo Nicolodi 《Abhandlungen aus dem Mathematischen Seminar der Universit?t Hamburg》1999,69(1):123-138
We study surfaces with plane lines of curvature in the framework of Laguerre geometry and provide explicit representation
formulae for these surfaces in terms of a potential function. As an application, we explicitly integrate allL- minimal surfaces with plane curvature lines.
Partially supported by MURST 40. 相似文献
44.
Based on unequidistant B-spline function, generalized spline subdomain displacement mode of rotational shell is obtained by taking double-direction interpolation of spline. The elastoplastic constitutive equation of shells is established by using the endochronic theory.According to the initial deflection theory of shells, the elastoplastic stress analysis of cylindrical shells with flat strip geometrical imperfection is studied. Numerical results show that the geometrical imperfection has a great effect on the stress distribution of shells. 相似文献
45.
Time dependent problems in Partial Differential Equations (PDEs) are often solved by the Method Of Lines (MOL). For linear parabolic PDEs, the exact solution of the resulting system of first order Ordinary Differential Equations (ODEs) satisfies a recurrence relation involving the matrix exponential function. In this paper, we consider the development of a fourth order rational approximant to the matrix exponential function possessing real and distinct poles which, consequently, readily admits a partial fraction expansion, thereby allowing the distribution of the work in solving the corresponding linear algebraic systems in essentially Backward Euler-like solves on concurrent processors. The resulting parallel algorithm possesses appropriate stability properties, and is implemented on various parabolic PDEs from the literature including the forced heat equation and the advection-diffusion equation.Dedicated to Professor J. Crank on the occasion of his 80th birthday 相似文献
46.
The collisional broadening and shift of four spectral lines of neon (747.2, 748.8, 753.5, 754.4 nm) arising from 2p5 3p - 2p5 3d transitions, emitted from a low-pressure glow discharge in pure neon and neon-helium mixtures have been measured using a Fabry-Perot interferometer. The values of pressure broadening and shift coefficients are determined and analyzed in terms of the impact theory. 相似文献
47.
Various transitions of a pressure tunable atomic fluorine laser have been observed over a rather wide spectral range, 634.8–755.2 nm, by exciting the atmospheric pressure of helium containing 0.2% F2 in a preionized Blumlein discharge device with a charging voltage of 10–15 kV. The intensity of two quartet transitions, 739.9 and 755.2 nm, increases with pressure, whereas that of the other quartet and doublet lines, 634.8, 641.4, 712.8 and 731.1 nm, decreases with increasing atmospheric fill-pressure. The pumping mechanisms at high pressures appear to be different from those at relatively low pressures. 相似文献
48.
Six FIR laser lines from CD3OH pumped by the 10R(36) and the 10R(18) CO2 laser lines are assigned to specific rotational energy levels in the excited C–0 stretch state. It is found that their upper laser levels are shifted by a Fermi resonance between the C–0 stretch vibration and the third and forth harmonics of the torsional mode. The Fermi resonance shifts are +0.332 cm–1 and +2.251 cm–1 for the upper laser levels pumped by the 10R(36) and the 10R(18) CO2 laser lines, respectively. Calculated frequencies of the pump and the laser transitions agree with those of the pump CO2 laser lines and the observed FIR laser lines within estimated accuracy. 相似文献
49.
P. Ruján 《Journal of statistical physics》1982,29(2):247-262
Systems with competing interactions can be often exactly solved on a restricted subspace of the parameter space, called an order or disorder trajectory. A simple method introduced within the transfer matrix formalism allows for the calculation of the free energy and spin-spin correlation functions along the order and disorder lines of the Ising model with all possible interactions around a face of the square lattice (IRF model). The general eight-vertex model is thoroughly examined and shows full analogy with the quantum spin chain results of the previous paper.On leave from and address after September 1, 1982: Institute for Theoretical Physics, Eötvös University, 1088 Budapest, Puskin U. 5–7, Hungary. 相似文献
50.
Z.?Simic M.?S.?DimitrijevicEmail author L.?C.?Popovic M.?D.?Dacic 《Journal of Applied Spectroscopy》2005,72(3):443-446
Using a semiclassical approach, we have considered electron-, proton-, and ionized helium-impact line widths and shifts for
the F III 2p3
4So-3s 4P resonant line. Moreover, for 10 F III multiplets where the full semiclassical perturbation approach is not applicable in
an adequate way due to the lack of reliable atomic data, electron-impact line widths have been calculated within the modified
semiempirical approach. Results are obtained as a function of temperature for perturber density of 1017 cm−3. The theoretical data obtained have been used to consider the influence of Stark broadening for A-type star atmosphere conditions.
__________
Published in Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 3, pp. 412–415, May–June, 2005. 相似文献