25,549 research outputs found
Series Prediction based on Algebraic Approximants
It is described how the Hermite-Pad\'e polynomials corresponding to an
algebraic approximant for a power series may be used to predict coefficients of
the power series that have not been used to compute the Hermite-Pad\'e
polynomials. A recursive algorithm is derived and some numerical examples are
given.Comment: 9 pages, ISRN Applied Mathematics, in pres
Correlation Energy Estimators based on M{\o}ller-Plesset Perturbation Theory
Some methods for the convergence acceleration of the M{\o}ller-Plesset
perturbation series for the correlation energy are discussed. The
order-by-order summation is less effective than the Feenberg series. The latter
is obtained by renormalizing the unperturbed Hamilton operator by a constant
factor that is optimized for the third order energy. In the fifth order case,
the Feenberg series can be improved by order-dependent optimization of the
parameter. Alternatively, one may use Pad{\'e} approximants or a further method
based on effective characteristic polynomials to accelerate the convergence of
the perturbation series. Numerical evidence is presented that, besides the
Feenberg-type approaches, suitable Pad{\'e} approximants, and also the
effective second order characteristic polynomial, are excellent tools for
correlation energy estimation.Comment: 21 pages, 87 references, LaTeX2e, elsart.cls, uuencoded compressed
tar file created by csh script uufiles. J. Mol. Struct. (THEOCHEM), in press.
Postscript and dvi also available via
http://www.chemie.uni-regensburg.de/preprint.html and
ftp://rchs1.uni-regensburg.de/pub/preprint/TC-QM-96-
Design of a high-speed valve
A high‐speed valve has been designed for opening a deLaval nozzle in times less than 10^(−3) sec
A computer program for the generation of logic networks from task chart data
The Network Generation Program (NETGEN), which creates logic networks from task chart data is presented. NETGEN is written in CDC FORTRAN IV (Extended) and runs in a batch mode on the CDC 6000 and CYBER 170 series computers. Data is input via a two-card format and contains information regarding the specific tasks in a project. From this data, NETGEN constructs a logic network of related activities with each activity having unique predecessor and successor nodes, activity duration, descriptions, etc. NETGEN then prepares this data on two files that can be used in the Project Planning Analysis and Reporting System Batch Network Scheduling program and the EZPERT graphics program
DISCUSSION: FINANCING AGRICULTURAL RESEARCH AND EDUCATION IN A PERIOD OF TIGHT BUDGETS
Public Economics,
A multigrid continuation method for elliptic problems with folds
We introduce a new multigrid continuation method for computing solutions of nonlinear elliptic eigenvalue problems which contain limit points (also called turning points or folds). Our method combines the frozen tau technique of Brandt with pseudo-arc length continuation and correction of the parameter on the coarsest grid. This produces considerable storage savings over direct continuation methods,as well as better initial coarse grid approximations, and avoids complicated algorithms for determining the parameter on finer grids. We provide numerical results for second, fourth and sixth order approximations to the two-parameter, two-dimensional stationary reaction-diffusion problem: Δu+λ exp(u/(1+au)) = 0.
For the higher order interpolations we use bicubic and biquintic splines. The convergence rate is observed to be independent of the occurrence of limit points
Spin-Lattice Relaxation in Metal-Organic Platinum(II) Complexes
The dynamics of spin-lattice relaxation (slr) of metal-organic Pt(II)
compounds is studied. Often, such systems are characterized by pronounced
zero-field splittings (zfs) of the lowest-lying triplets. Previous expressions
for the Orbach slr process do not allow to treat such splitting patterns
properly. We discuss the behavior of a modified Orbach expression for a model
system and present results of a fit of the temperature dependence of the
spin-lattice relaxation rate of Pt(2-thpy) based on the modified
expression.Comment: 9 pages, 3 figures (made from 4 .eps files), elsart.cls. Using dvips
(dvipsk 5.58f), it may be necessary to manually edit the generated file
letter.ps to change in the first line from PS-Adobe-2.0 to PS-Adobe-3.0.
Chemical Physics Letters, in pres
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