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DIELECTRONIC RECOMBINATION FOR F-LIKE AND NE-LIKE GERMANIUM IONS

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS 1992年第4期25卷 791-798页

作者： YANG, HY QIU, YH LI, SC SUN, YS YANG, YL Inst. of Appl. Phys. & Comput. Math. Beijing China

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.

关键词： Germanium

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EXACT-SOLUTIONS FOR A CHARGED-PARTICLE IN A UNIFORM ELECTRIC-FIELD WITH ALTERNATING SITE ENERGIES - PERTURBATION-THEORY

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JOURNAL OF PHYSICS-CONDENSED MATTER 1991年第32期3卷 6021-6032页

作者： ZHAO, XG Inst. of Appl. Phys. & Comput. Math. Beijing China

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.

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PONDEROMOTIVE FORCE IN UNMAGNETIZED VLASOV-PLASMA

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PLASMA PHYSICS AND CONTROLLED FUSION 1993年第3期35卷 291-299页

作者： ZHU, SP HE, XT Centre for Nonlinear Studies Inst. of Appl. Phys. & Comput. Math. Beijing China

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.

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ON LEARNING TO RECOGNIZE 3-D OBJECTS FROM EXAMPLES

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IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE 1993年第8期15卷 833-837页

作者： EDELMAN, S Dept. of Appl. Math. & Comput. Sci. Weizmann Inst. of Sci. Rehovot Israel

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.

关键词： COMPLEXITY LEARNING FROM EXAMPLES OBJECT RECOGNITION REPRESENTATION VISION

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SPACE MARCHING DIFFERENCE-SCHEMES IN THE NONLINEAR INVERSE HEAT-CONDUCTION PROBLEM

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INVERSE PROBLEMS 1992年第1期8卷 25-43页

作者： CARASSO, AS Comput. & Appl. Math. Lab. Nat. Inst. of Stand. & Technol. Gaithersburg MD USA

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.

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HOMOCLINIC TANGLES - CLASSIFICATION AND appl.CATIONS

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NONLINEARITY 1994年第2期7卷 441-473页

作者： ROMKEDAR, V Dept. of Appl. Math. & Comput. Sci. Weizmann Inst. of Sci. Rehovot Israel

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.

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STEADY-STATE SOLUTIONS OF THE EULER EQUATIONS IN 2 DIMENSIONS .2. LOCAL ANALYSIS OF LIMITING V-STATES

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SIAM JOURNAL ON appl.ED math.MATICS 1986年第5期46卷 765-800页

作者： OVERMAN, EA Inst. Comput. Math. Appl. Dep. Math. and Stat. Univ. Pittsburgh Pittsburgh PA 15260 USA

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.

关键词： 76C05 65R20 Euler equations vorticity-stream function form steady-state solutions limiting solutions

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An axially twice acceleration low impedance HPM source 12

An axially twice acceleration low impedance HPM source

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12th International Conference on High-Power Particle Beams, BEAMS 1998

作者： Ding, Wu Inst. of Appl. Phys. and Comput. Math. P.O.Box 8009 Beijing China

ISBN: (纸本)0780342879

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 the diode into one;(2) The impedance of the diode is very low due to being coaxial, thus allowing larger input and output powers. We try to make two improvements for the device: (1) Add a accelerating section after the diode/ oscillator, make the bunched beam to be accelerated again, then extract the radiation emitted by the bunched and postaccelerated beam in the extraction cavity. Therefore one can not only raise the power and conversion efficiency of the beam, but also select output frequency of the waves. While in the Radial Acceletron, the conversion efficiency is not high enough, and the output frequency can not be tuned;(2) Change the radial acceleration to axial acceleration. In the configuration of radial outward twice acceleration, radius of the cavity should be very large, and the field and beam in it are divergence. In the configuration of radial inward acceleration, the power capacity is very small;While the new configuration of axially twice acceleration does not have these problems. The coaxial axially twice acceletron needs no magnetic guide field like the Super-Reltron. But its modulation cavity is TTO rather than SCO, and compared to SCO, it is not easy to breakdown due to its larger power capacity and the bunching of the beam is much better because of the combining of the oscillator with the diode. © 1998 Beam Organizing Committee.

关键词： Diodes

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Methodology for GPS Synchronization Evaluation with High Accuracy

Methodology for GPS Synchronization Evaluation with High Acc...

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IEEE Vehicular Technology Conference

作者： Zan Li Torsten Braun Desislava C. Dimitrova Inst. of Comput. Sci. & Appl. Math. Univ. of Bern Bern Switzerland

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.

关键词： clock skew clock recovery Network operations Signal processing algorithms NANOSECOND Skew key factors

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A Performance Prediction Approach for MPI Routines on Multi-clusters

A Performance Prediction Approach for MPI Routines on Multi-...

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Euromicro Conference on Parallel, Distributed and Network-Based Processing

作者： Sami Achour Wahid Nasri Higher Inst. of Appl. Math. & Comput. Sci. Kairouan Tunisia Higher School of Sciences and Techniques Tunis Tunisia

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.

关键词： Predictive models Time measurement Measurement uncertainty Size measurement Emulation Accuracy Benchmark testing

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