Impact parameter treatments of certain hydrogen-proton and hydrogen-hydrogen excitation collisions

1958 ◽  
Vol 245 (1242) ◽  
pp. 299-311 ◽  
Keyword(s):  
Impact Parameter ◽  
Stationary State ◽  
Born Approximation ◽  
Order Approximation ◽  
Hydrogen Atoms ◽  
First Order ◽  
Normal Hydrogen ◽  
First Order Approximation ◽  
The Impact

Consideration is given to the impact parameter form of the Born approximation and of the pRA approximation (i.e. the first-order approximation to which the perturbed stationary state, or PSS, approximation tends). Calculations are carried out on the excitation of normal hydrogen atoms to the 2 s or 2 p states in encounters with protons and other normal hydrogen atoms. The results obtained provide some information on the range of validity of the Born approximation. The impact-parameter treatment corresponding to a simplified version of the second Born approximation is given and discussed. Attention is drawn to the fact that for certain transitions the pRA approximation fails seriously when the encounter is very close.

On the Electronic Structure of Metal Hydrides I. Exposition of a Many-Electron Theory

1979 ◽  
Vol 34 (12) ◽  
pp. 1373-1384
Author(s):  
F. Wahl ◽  
G. Baumann
Keyword(s):  
Order Approximation ◽  
Energy Difference ◽  
Host Lattice ◽  
Hydrogen Atoms ◽  
Electron Theory ◽  
First Order ◽  
Structure Of Metal ◽  
Self Consistent ◽  
First Order Approximation ◽  
Dynamical Potential

Abstract We present the concept of a many-electron theory for the calculation of the energy difference between an undisturbed metallic host lattice and a crystal disturbed by stored hydrogen atoms. With the help of an elimination procedure a multidimensional system of equations is reduced to a one-particle Schrödinger equation for the electron of the hydrogen. The interaction with the electrons of the metal is then described by a dynamical potential depending on the state of the electron itself. A first order approximation with static screening is discussed and then generalized to a self-consistent calculation of one-electron functions which are used as a basis for expansions.

scholarly journals Spectral Analyses of Wolf-Rayet Stars: The Impact of Clumping

1999 ◽  
Vol 169 ◽  
pp. 239-242 ◽  
Author(s):  
Wolf-Rainer Hamann ◽  
Lars Koesterke
Keyword(s):  
Mass Loss ◽  
Electron Scattering ◽  
Loss Rate ◽  
Order Approximation ◽  
Mass Loss Rate ◽  
Spectral Analyses ◽  
First Order ◽  
Homogeneous Models ◽  
First Order Approximation ◽  
The Impact

AbstractInhomogeneities are accounted for in our non-LTE stellar wind models in a first-order approximation. When applied for spectral analyses, clumpy models yield lower mass-loss rates than homogeneous models, while other parameters are not affected. For representative WR stars, we determine the density contrast from the electron-scattering line wings and obtain mass-loss rate reductions by a factor of two, typically.

Improved first-order approximation of eigenvalues and eigenvectors

AIAA Journal ◽  
1998 ◽  
Vol 36 ◽  
pp. 1721-1727
Author(s):  
Prasanth B. Nair ◽  
Andrew J. Keane ◽  
Robin S. Langley
Keyword(s):  
Order Approximation ◽  
Eigenvalues And Eigenvectors ◽  
First Order ◽  
First Order Approximation

Analytical solution for unsteady flow behind ionizing shock wave in a rotational axisymmetric non-ideal gas with azimuthal or axial magnetic field

2021 ◽  
Vol 76 (3) ◽  
pp. 265-283
Author(s):  
G. Nath
Keyword(s):  
Magnetic Field ◽  
Shock Wave ◽  
Analytical Solution ◽  
Axial Magnetic Field ◽  
Order Approximation ◽  
Ideal Gas ◽  
Field Region ◽  
First Order ◽  
First Order Approximation ◽  
Flow Variables

Abstract The approximate analytical solution for the propagation of gas ionizing cylindrical blast (shock) wave in a rotational axisymmetric non-ideal gas with azimuthal or axial magnetic field is investigated. The axial and azimuthal components of fluid velocity are taken into consideration and these flow variables, magnetic field in the ambient medium are assumed to be varying according to the power laws with distance from the axis of symmetry. The shock is supposed to be strong one for the ratio C 0 V s 2 ${\left(\frac{{C}_{0}}{{V}_{s}}\right)}^{2}$ to be a negligible small quantity, where C 0 is the sound velocity in undisturbed fluid and V S is the shock velocity. In the undisturbed medium the density is assumed to be constant to obtain the similarity solution. The flow variables in power series of C 0 V s 2 ${\left(\frac{{C}_{0}}{{V}_{s}}\right)}^{2}$ are expanded to obtain the approximate analytical solutions. The first order and second order approximations to the solutions are discussed with the help of power series expansion. For the first order approximation the analytical solutions are derived. In the flow-field region behind the blast wave the distribution of the flow variables in the case of first order approximation is shown in graphs. It is observed that in the flow field region the quantity J 0 increases with an increase in the value of gas non-idealness parameter or Alfven-Mach number or rotational parameter. Hence, the non-idealness of the gas and the presence of rotation or magnetic field have decaying effect on shock wave.

FIRST-ORDER APPROXIMATION OF THE NUMBER-PROJECTED SO(2N) TAMM-DANCOFF EQUATION AND ITS REDUCTION BY THE SCHUR FUNCTION

1999 ◽  
Vol 08 (05) ◽  
pp. 461-483
Author(s):  
SEIYA NISHIYAMA
Keyword(s):  
Wave Function ◽  
Order Approximation ◽  
Approximate Equation ◽  
Variation Principle ◽  
Schur Function ◽  
Soliton Theory ◽  
First Order ◽  
Fermion Systems ◽  
Group Manifold ◽  
First Order Approximation

First-order approximation of the number-projected (NP) SO(2N) Tamm-Dancoff (TD) equation is developed to describe ground and excited states of superconducting fermion systems. We start from an NP Hartree-Bogoliubov (HB) wave function. The NP SO(2N) TD expansion is generated by quasi-particle pair excitations from the degenerate geminals in the number-projected HB wave function. The Schrödinger equation is cast into the NP SO(2N) TD equation by the variation principle. We approximate it up to first order. This approximate equation is reduced to a simpler form by the Schur function of group characters which has a close connection with the soliton theory on the group manifold.

Chaotic Amplitude Dynamics for Parametrically Excited Systems With Quadratic Nonlinearities

1995 ◽  
Author(s):  
Bappaditya Banerjee ◽  
Anil K. Bajaj
Keyword(s):  
Harmonic Balance ◽  
Chaotic Dynamics ◽  
Degrees Of Freedom ◽  
Order Approximation ◽  
Amplitude Equations ◽  
Analytical Technique ◽  
First Order ◽  
Numerical Studies ◽  
Quadratic Nonlinearities ◽  
First Order Approximation

Abstract Dynamical systems with two degrees-of-freedom, with quadratic nonlinearities and parametric excitations are studied in this analysis. The 1:2 superharmonic internal resonance case is analyzed. The method of harmonic balance is used to obtain a set of four first-order amplitude equations that govern the dynamics of the first-order approximation of the response. An analytical technique, based on Melnikov’s method is used to predict the parameter range for which chaotic dynamics exist in the undamped averaged system. Numerical studies show that chaotic responses are quite common in these quadratic systems and chaotic responses occur even in presence of damping.

scholarly journals Analytical quality assessment of iteratively reweighted least-squares (IRLS) method

2014 ◽  
Vol 20 (1) ◽  
pp. 132-141 ◽  
Author(s):  
Jianfeng Guo
Keyword(s):  
Least Squares ◽  
Order Approximation ◽  
Diagnostic Tools ◽  
Iteratively Reweighted Least Squares ◽  
First Order ◽  
Iterative Reweighting ◽  
First Order Approximation ◽  
Detectable Bias ◽  
Theoretical Analyses ◽  
Exact Analytical Method

The iteratively reweighted least-squares (IRLS) technique has been widely employed in geodetic and geophysical literature. The reliability measures are important diagnostic tools for inferring the strength of the model validation. An exact analytical method is adopted to obtain insights on how much iterative reweighting can affect the quality indicators. Theoretical analyses and numerical results show that, when the downweighting procedure is performed, (1) the precision, all kinds of dilution of precision (DOP) metrics and the minimal detectable bias (MDB) will become larger; (2) the variations of the bias-to-noise ratio (BNR) are involved, and (3) all these results coincide with those obtained by the first-order approximation method.

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