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991.
Summary Conventional numerical methods, when applied to the ordinary differential equations of motion of classical mechanics, conserve the total energy and angular momentum only to the order of the truncation error. Since these constants of the motion play a central role in mechanics, it is a great advantage to be able to conserve them exactly. A new numerical method is developed, which is a generalization to arbitrary order of the discrete mechanics described in earlier work, and which conserves the energy and angular momentum to all orders. This new method can be applied much like a corrector as a modification to conventional numerical approximations, such as those obtained via Taylor series, Runge-Kutta, or predictor-corrector formulae. The theory is extended to a system of particles in Part II of this work. 相似文献
992.
Robert Schumacher 《manuscripta mathematica》1976,19(2):133-142
Cheney and others [2] have shown that, with respect to the norm of uniform convergence, the Fourier operator Fn:C2pn is the only minimal projection. For a more detailed study of operators A:C2Pn we investigate the evaluation functionals
respectively the mean of their norms
. We give a complete characterization of polynomial operators which minimize this quantity. As an application we can simplify the proof in [2]. Moreover, we show that the trigonometric interpolation operators, having the above minimal-property,are exactly those with equidistant nodes.
Diese Arbeit enthält die wesentlichen Resultate einer Diplomarbeit, die der Verfasser an der Eberhard-Karls-Universität Tübingen unter der Anleitung von A.Schönhage angefertigt hat. 相似文献
Diese Arbeit enthält die wesentlichen Resultate einer Diplomarbeit, die der Verfasser an der Eberhard-Karls-Universität Tübingen unter der Anleitung von A.Schönhage angefertigt hat. 相似文献
993.
Hans Robert Müller 《Journal of Geometry》1976,8(1-2):1-7
A generalisation of a ruled surface in n-dimensional euclidean space may be generated by euclidean motion of a s-plane As. For this one-parametric family {As} the curve of striction is defined and the following theorems are proved:
- The generators As are parallel along the curve of striction, i.e. the multivectors representing As form a parallel vector field along the curve of striction.
- If the curve of striction is geodesic on {As}, it is also an isogonal trajectory of the family of generators {As}.
994.
G. Bender 《Zeitschrift für Physik B Condensed Matter》1976,23(3):285-288
Wegner's model for magnetic phase transitions on elastic isotropic lattices is generalized to elastic anisotropy and the general spin-lattice coupling linear in lattice distortion. Cyclic boundary conditions are employed. The elimination of the elastic degrees of freedom gives rise to an effective spin Hamiltonian which consists of a shortrange and a long-range part. Renormalization group analysis yields the following result: If the lattice couples to a relevant operator with an exponenty >d/2, the long-range part contains a relevant contribution with exponent 2y—d leading away from any fixed pointH
* associated with the short-range interactions. In particular,H
* is unstable for positive specific heat exponent, and, in most cases, if a spin-anisotropy is involved. 相似文献
995.
996.
We look for singlevalued solutions of the squared modulus M of the traveling wave reduction of the complex cubic-quintic Ginzburg-Landau equation. Using Clunie??s lemma, we first prove that any meromorphic solution M is necessarily elliptic or degenerate elliptic. We then give the two canonical decompositions of the new elliptic solution recently obtained by the subequation method. 相似文献
997.
A simple observation about the action for geodesics in a stationary spacetime with separable geodesic equations leads to a natural class of slicings of that spacetime whose orthogonal geodesic trajectories represent the world lines of freely falling fiducial observers. The time coordinate function can then be taken to be the observer proper time, leading to a unit lapse function, although the time coordinate lines still follow Killing trajectories to retain the explicitly stationary nature of the coordinate grid. This explains some of the properties of the original Painlevé-Gullstrand coordinates on the Schwarzschild spacetime and their generalization to the Kerr-Newman family of spacetimes, reproducible also locally for the Gödel spacetime. For the static spherically symmetric case the slicing can be chosen to be intrinsically flat with spherically symmetric geodesic observers, leaving all the gravitational field information in the shift vector field. 相似文献
998.
999.
Robert Pendrill Ole W. Sørensen Göran Widmalm 《Magnetic resonance in chemistry : MRC》2014,52(3):82-86
Site‐specific 13C isotope labeling is a useful approach that allows for the measurement of homonuclear 13C,13C coupling constants. For three site‐specifically labeled oligosaccharides, it is demonstrated that using the J‐HMBC experiment for measuring heteronuclear long‐range coupling constants is problematical for the carbons adjacent to the spin label. By incorporating either a selective inversion pulse or a constant‐time element in the pulse sequence, the interference from one‐bond 13C,13C scalar couplings is suppressed, allowing the coupling constants of interest to be measured without complications. Experimental spectra are compared with spectra of a nonlabeled compound as well as with simulated spectra. The work extends the use of the J‐HMBC experiments to site‐specifically labeled molecules, thereby increasing the number of coupling constants that can be obtained from a single preparation of a molecule. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
1000.