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991.
It is demonstrated by means of combined optical microscopy and field desorption mass spectrometry that alkali ions and cluster ions are emitted from microcrystals of KCl and NaCl exposed to positive high electric fields. The ion emission is very strong at temperatures where the sublimation of the sample is optically observable, indicating that an enhanced sample sublimation is a key precondition for enhanced ion emission. 相似文献
992.
A technique for efficient Raman conversion of an excimer pumped dye laser is described, based on the use of a Raman oscillator/amplifier combination. A photon conversion efficiency of 90% to first Stokes is demonstrated, with diffraction-limited beam quality. 相似文献
993.
Numerical solutions of relativistic hydrodynamic equations are obtained with essentially non-oscillatory (ENO) finite differencing schemes. The method is explicit, conservative, consistent with the entropy condition, and high order accurate in space and time. The present implementation is applicable to the most general, three-dimensional problems with an arbitrary equation of state. Numerical experiments, including computations of multi-dimensional flows, demonstrate that the method delivers sharp, non-oscillatory shock transitions without sacrificing high resolution of the smooth regions. This extends results already established for the Euler gas dynamics to the relativistic regime, suggesting the usefulness of ENO schemes for modelling relativistic nuclear collisions. 相似文献
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Richard T. Wong 《Mathematical Programming》1984,28(3):271-287
The Steiner tree problem on a directed graph (STDG) is to find a directed subtree that connects a root node to every node
in a designated node setV. We give a dual ascent procedure for obtaining lower bounds to the optimal solution value. The ascent information is also
used in a heuristic procedure for obtaining feasible solutions to the STDG. Computational results indicate that the two procedures
are very effective in solving a class of STDG's containing up to 60 nodes and 240 directed/120 undirected arcs.
The directed spanning tree and uncapacitated plant location problems are special cases of the STDG. Using these relationships,
we show that our ascent procedure can be viewed as a generalization ofboth the Chu-Liu-Edmonds directed spanning tree algorithm and the Bilde-Krarup-Erlenkotter ascent algorithm for the plant location
problem. The former comparison yields a dual ascent interpretation of the steps of the directed spanning tree algorithm. 相似文献
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