Auger rates, average absorption oscillator strengths (corresponding average wavelengths) and level-to-level dielectronic recombination rate coefficients describing dielectronic recombination for F-like and Ne-like ger...
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Auger rates, average absorption oscillator strengths (corresponding average wavelengths) and level-to-level dielectronic recombination rate coefficients describing dielectronic recombination for F-like and Ne-like germanium ions are explicitly calculated. Our calculations are based on Cowan's non-relativistic multi-configuration Hartree-Fock (HFR) code which includes relativistic mass-velocity and Darwin corrections and successive subroutines for calculating average oscillator strengths and average wavelengths and dielectronic recombination rate coefficients are developed. The dielectronic recombination rate coefficients as the function of temperature of free electrons are given in an analytical form which is very convenient in practice.
The energy spectrum and the eigenvectors of a charged particle in a uniform electric field with alternating site energies are studied for infinite systems. For the case of large energy mismatch, exact solutions are pr...
The energy spectrum and the eigenvectors of a charged particle in a uniform electric field with alternating site energies are studied for infinite systems. For the case of large energy mismatch, exact solutions are presented by using perturbation theory, from which it is found that the spectrum is that of two interspaced Stark ladders. The character of these Stark ladders is that the difference of the ratio of the energy and the field between two energies on a same rung is an even number.
An expression for ponderomotive force caused by electromagnetic fields is derived from Valsov-Maxwell equations in a non-stationary, unmagnetized plasma. Comparison between our result and earlier ones is given.
An expression for ponderomotive force caused by electromagnetic fields is derived from Valsov-Maxwell equations in a non-stationary, unmagnetized plasma. Comparison between our result and earlier ones is given.
Previous results on nonlearnability of visual concepts relied on the assumption that such concepts are represented as sets of pixels [1]. This correspondence uses an approach developed by Haussler [2] to show that und...
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Previous results on nonlearnability of visual concepts relied on the assumption that such concepts are represented as sets of pixels [1]. This correspondence uses an approach developed by Haussler [2] to show that under an alternative, feature-based representation, recognition is PAC learnable from a feasible number of examples in a distribution-free manner.
For ill-posed initial value problems, step by step marching comput.tions are unconditionally unstable, and necessarily blow-up numerically as the mesh is refined. However, for the 1D nonlinear inverse heat conduction ...
For ill-posed initial value problems, step by step marching comput.tions are unconditionally unstable, and necessarily blow-up numerically as the mesh is refined. However, for the 1D nonlinear inverse heat conduction problem, we show how to construct consistent marching schemes that blow-up much more slowly than the counterpart analytical problem. Several new space marching finite difference schemes are formulated and compared with existing schemes relative to their error amplification properties. Using the Lax-Richtmyer theory, we evaluate the L2 norms of the linearized discrete solution operators mapping the sensor data into the desired temperature and gradient histories at the inaccessible active surface. Various combinations of space and time differencing are examined, leading to 18 different algorithms. A non-dimensional parameter-OMEGA, involving the time step DELTA-t, the effective thermal diffusivity-alpha, and the distance-iota from the sensor to the active surface, is shown to provide a measure of the numerical difficulty of the inverse calculation. All 18 schemes blow-up like 10-lambda-OMEGA, where the constant-lambda depends on the particular numerical method. There are substantial differences in the lambda's however, and some new algorithms, employing forward time differences at non-adjacent mesh points, are shown to produce relatively low values of lambda. Next, using synthetic noisy data, a nonlinear reconstruction problem is considered for which OMEGA = 25. This problem simulates heat transfer in gun barrels when a shell is fired. It is shown that while most of the 18 schemes cannot recover the thermal pulses at the gun tube wall, two of the new methods provide reasonably accurate results. A tendency to underestimate peak values in fast, narrow thermal pulses, is also noted.
Here we develop the Topological Approximation Method (TAM) which gives a new description of the mixing and transport processes in chaotic two-dimensional time-periodic Hamiltonian flows. It is based upon the structure...
Here we develop the Topological Approximation Method (TAM) which gives a new description of the mixing and transport processes in chaotic two-dimensional time-periodic Hamiltonian flows. It is based upon the structure of the homoclinic tangle, and supplies a detailed solution to a transport problem for this class of systems, the characteristics of which are typical to chaotic, yet not ergodic dynamical systems. These characteristics suggest some new criteria for quantifying transport and mixing-hence chaos-in such systems. The results depend on several parameters, which are found by perturbation analysis in the near integrable case, and numerically otherwise. The strength of the method is demonstrated on a simple model. We construct a bifurcation diagram describing the changes in the homoclinic tangle as the physical parameters are varied. From this diagram we find special regions in the parameter space in which we approximate the escape rates from the vicinity of the homoclinic tangle, finding non-trivial self-similar solutions as the forcing magnitude tends to zero. We compare the theoretical predictions with brute force calculations of the escape rates, and obtain satisfactory agreement.
Steady-state solutions of the 2D incompressible Euler equations (which we call V-states) are studied analytically. That is, a local expansion is done in the neighborhood of any point on the boundary of a V-state (whic...
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Steady-state solutions of the 2D incompressible Euler equations (which we call V-states) are studied analytically. That is, a local expansion is done in the neighborhood of any point on the boundary of a V-state (which consists of piecewise constant regions of vorticity). The analytical results contained in paper I by Wu, Overman, and Zabusky are proven. In particular, the limiting V-states for the numerically calculated translating and rotating V-states have $90^\circ$ corners and not cusps. It is also proven that at a point which lies on the boundary of only one region and at which the tangent angle has a jump discontinuity then the difference in tangent angles can only be $90^\circ$ (a corner) or $180^\circ$ (a cusp). The analytical behavior of doubly and triply connected rotating V-states is also investigated.
M.J. Arman presented a new low impedance HPM source-Radial Acceletron (1996), it has the following new characteristics: (1) There are very high harmonic currents in the device because it combines the oscillator and th...
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Clock synchronization in the order of nanoseconds is one of the critical factors for time-based localization. Currently used time synchronization methods are developed for the more relaxed needs of network operation. ...
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ISBN:
(纸本)9781479980895
Clock synchronization in the order of nanoseconds is one of the critical factors for time-based localization. Currently used time synchronization methods are developed for the more relaxed needs of network operation. Their usability for positioning should be carefully evaluated. In this paper, we are particularly interested in GPS-based time synchronization. To judge its usability for localization we need a method that can evaluate the achieved time synchronization with nanosecond accuracy. Our method to evaluate the synchronization accuracy is inspired by signal processing algorithms and relies on fine-grain time information. The method is able to calculate the clock offset and skew between devices with nanosecond accuracy in real time. It was implemented using software defined radio technology. We demonstrate that GPS-based synchronization suffers from remaining clock offset in the range of a few hundred of nanoseconds but the clock skew is negligible. Finally, we determine a corresponding lower bound on the expected positioning error.
Performance is one of the key features of parallel and distributed comput.ng systems. For that reason, a significant research effort was invested in the development of approaches in the area of performance modeling an...
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Performance is one of the key features of parallel and distributed comput.ng systems. For that reason, a significant research effort was invested in the development of approaches in the area of performance modeling and prediction. Since many parallel appl.cations from scientific comput.ng use MPI communication operations to distribute or collect data, we present in this paper a novel (off-line) approach that addresses the performance prediction of MPI routines in multi-clusters platforms. The main objective of this approach is to predict accurately and efficiently the performance of a given routine. Our solution is based principally on models for point to point (P2P) MPI routines which are obtained after a short profiling procedure. Since collective communication routines are composed of P2P routines, the performance prediction of the formers is done on the basis of a rapid emulation of these routines and on an evaluation of P2P routines models. Experimental results obtained on a grid platform demonstrated the interest of the proposed approach.
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