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Murray Riley Chandrasekaran Venkat Wierman Adam 《Foundations of Computational Mathematics》2021,21(6):1703-1737
Foundations of Computational Mathematics - Certifying function nonnegativity is a ubiquitous problem in computational mathematics, with especially notable applications in optimization. We study the... 相似文献
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A crucial step in the Erdös-Rényi (1960) proof that the double-jump threshold is also the planarity threshold for random graphs is shown to be invalid. We prove that whenp=1/n, almost all graphs do not contain a cycle with a diagonal edge, contradicting Theorem 8a of Erdös and Rényi (1960). As a consequence, it is proved that the chromatic number is 3 for almost all graphs whenp=1/n.Research supported U.S. National Science Foundation Grants DMS-8303238 and DMS-8403646. The research was conducted on an exchange visit by Professor Wierman to Poland supported by the national Academy of Sciences of the USA and the Polish Academy of Sciences. 相似文献
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C. L. Platt K. W. Wierman J. K. Howard A. G. Roy D. E. Laughlin 《Journal of magnetism and magnetic materials》2003,260(3):487-491
The influence of oxide additives on the magnetic and structural properties of FePt L10 thin films has been studied. FePt films with HfO2 additive grown on a 5 nm MgO buffer showed a primarily random texture for both as-deposited and annealed samples. The average grain size was limited to 10 nm and the perpendicular coercivity was 1.3 kOe for a 10 nm thick FePt +20% HfO2 film annealed at 650°C for 10 min. In direct contrast, MnO additive neither limited grain size nor L10 ordering in annealed FePt films. A 10 nm thick FePt+20% MnO film grown on a 5 nm MgO buffer showed a unique discontinuous microstructure composed of clusters of (0 0 1) textured L10 grains after being annealed at 650°C for 10 min. The average size of the grains making up these clusters was 50 nm and the perpendicular coercivity of the film exceeded 7 kOe. 相似文献
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Mor Harchol-Balter Takayuki Osogami Alan Scheller-Wolf Adam Wierman 《Queueing Systems》2005,51(3-4):331-360
We present the first near-exact analysis of an M/PH/k queue with m > 2 preemptive-resume priority classes. Our analysis introduces a new technique, which we refer to as Recursive Dimensionality
Reduction (RDR). The key idea in RDR is that the m-dimensionally infinite Markov chain, representing the m class state space, is recursively reduced to a 1-dimensionally infinite Markov chain, that is easily and quickly solved.
RDR involves no truncation and results in only small inaccuracy when compared with simulation, for a wide range of loads and
variability in the job size distribution.
Our analytic methods are then used to derive insights on how multi-server systems with prioritization compare with their single
server counterparts with respect to response time. Multi-server systems are also compared with single server systems with
respect to the effect of different prioritization schemes—“smart” prioritization (giving priority to the smaller jobs) versus
“stupid” prioritization (giving priority to the larger jobs). We also study the effect of approximating m class performance by collapsing the m classes into just two classes.
Supported by NSF Career Grant CCR-0133077, NSF Theory CCR-0311383, NSF ITR CCR-0313148, and IBM Corporation via Pittsburgh
Digital Greenhouse Grant 2003.
AMS subject classification: 60K25, 68M20, 90B22, 90B36 相似文献
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A partially ordered set is called acircle containment order provided one can assign to each element of the poset a circle in the plane so thatxy iff the circle assigned tox is contained in the circle assigned toy. It has been conjectured that every finite three-dimensional partially ordered set is a circle containment order. We show that the infinite three dimensional posetZ
3 isnot a circle containment order.Research supported in part by the Office of Naval Research, contract number N00014-85-K0622.Research supported in part by National Science Foundation, grant number DMS-8403646. 相似文献
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John C. Wierman 《Random Structures and Algorithms》2002,20(4):507-518
Rigorous bounds for the bond percolation critical probability are determined for three Archimedean lattices: .7385 < pc((3, 122) bond) < .7449, .6430 < pc((4, 6, 12) bond) < .7376, .6281 < pc((4, 82) bond) < .7201. Consequently, the bond percolation critical probability of the (3, 122) lattice is strictly larger than those of the other ten Archimedean lattices. Thus, the (3, 122) bond percolation critical probability is possibly the largest of any vertex‐transitive graph with bond percolation critical probability that is strictly less than one. © 2002 Wiley Periodicals, Inc. Random Struct. Alg., 20: 507–518, 2002 相似文献
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