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991.
The concept of breakpoint graph, known from the theory of sorting by reversal, has been successfully applied in the theory of gene assembly in ciliates. We further investigate its usage for gene assembly, and show that the graph allows for an efficient characterization of the possible orders of loop recombination operations (one of the three types of molecular operations that accomplish gene assembly) for a given gene during gene assembly. The characterization is based on spanning trees within a graph built upon the connected components in the breakpoint graph. We work in the abstract and more general setting of so-called legal strings. 相似文献
992.
993.
Emanuel Makrlík Jiří Dybal Jan Budka Petr Vaňura 《Monatshefte für Chemie / Chemical Monthly》2009,140(10):1155-1158
994.
Heavy tailed durations of regional rainfall 总被引:1,自引:0,他引:1
Durations of rain events and drought events over a given region provide important information about the water resources of
the region. Of particular interest is the shape of upper tails of the probability distributions of such durations. Recent
research suggests that the underlying probability distributions of such durations have heavy tails of hyperbolic type, across
a wide range of spatial scales from 2 km to 120 km. These findings are based on radar measurements of spatially averaged rain
rate (SARR) over a tropical oceanic region. The present work performs a nonparametric inference on the Pareto tail-index of
wet and dry durations at each of those spatial scales, based on the same data, and compares it with conclusions based on the
classical Hill estimator. The results are compared and discussed.
The authors express sincere thanks to the Mathematisches Forschungsinstitut Oberwolfach (MFO) for facilitating their collaboration
under a “Research in Pairs” project hosted at MFO during March 5–25, 2006. The research of the second and third authors was supported by the project
LC06024. 相似文献
995.
996.
997.
We present an algebraic multigrid algorithm for fully coupled implicit Runge–Kutta and Boundary Value Method time-discretizations of the div-grad and curl-curl equations. The algorithm uses a blocksmoother and a multigrid hierarchy derived from the hierarchy built by any algebraic multigrid algorithm for the stationary version of the problem. By a theoretical analysis and numerical experiments, we show that the convergence is similar to or better than the convergence of the scalar algebraic multigrid algorithm on which it is based. The algorithm benefits from several possibilities for implementation optimization. This results in a computational complexity which, for a modest number of stages, scales almost linearly as a function of the number of variables. 相似文献
998.
Adaptive tensor product wavelet methods are applied for solving Poisson’s equation, as well as anisotropic generalizations, in high space dimensions. It will be demonstrated that the resulting approximations converge in energy norm with the same rate as the best approximations from the span of the best N tensor product wavelets, where moreover the constant factor that we may lose is independent of the space dimension n. The cost of producing these approximations will be proportional to their length with a constant factor that may grow with n, but only linearly. 相似文献
999.
1000.