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排序方式: 共有415条查询结果,搜索用时 11 毫秒
1.
Ashish Goel Monika R. Henzinger Serge Plotkin Eva Tardos 《Journal of Algorithms in Cognition, Informatics and Logic》2003,48(2):314-332
In this paper we consider the online ftp problem. The goal is to service a sequence of file transfer requests given bandwidth constraints of the underlying communication network. The main result of the paper is a technique that leads to algorithms that optimize several natural metrics, such as max-stretch, total flow time, max flow time, and total completion time. In particular, we show how to achieve optimum total flow time and optimum max-stretch if we increase the capacity of the underlying network by a logarithmic factor. We show that the resource augmentation is necessary by proving polynomial lower bounds on the max-stretch and total flow time for the case where online and offline algorithms are using same-capacity edges. Moreover, we also give polylogarithmic lower bounds on the resource augmentation factor necessary in order to keep the total flow time and max-stretch within a constant factor of optimum. 相似文献
2.
A two-dimensional linear analysis of the planar flame front stability for a compressible fluid is presented. The analysis shows that there are two types of perturbations. The first type, corresponding to waves in incompressible media, has already been studied by Landau. It predicts absolute instability of the flame front. The second type of perturbations is due to fluid compressibility and the dependence on upstream flow parameters of the flame front velocity. Three different regimes for these perturbations are possible: stable, acoustically unstable, and absolutely unstable. The instability results in a pronounced pressure wave generation.A one-dimensional analysis of the interaction of the flame front with flow boundaries is performed. Under some circumstances, this interaction is shown to cause exponential growth of the perturbations. 相似文献
3.
A data set of 29 experimentally determined Newby shifts in rare-earth nuclei is examined for the reliability of each values.
Using this data set, Newby shifts are obtained which are free from the Coriolis and the particle-particle coupling effects.
These new empirical values help resolve the failure of a recently proposed rule for the sign of the Newby shift in the {5/2[413]p − 5/2[642]n} configuration of160Tb and the {5/2[402]p − 5/2[512]n} configuration of174Lu. Also the Newby shifts are significantly modified in two other cases namely the {1/2[411]p − 1/2[521]n} configuration in168Tm and the {1/2[541]p − 1/2[521]n} configuration in172Lu. Only marginal changes are seen in the rest of the cases in the rare-earth nuclei. 相似文献
4.
Howard C. Clark Anil B. Goel Chun S. Wong 《Journal of organometallic chemistry》1980,190(4):C101-C104
Simple synthetic routes to the mixed ligand complexes PtLL'X2 and PtLL'XY (L' = PEt3; L = phosphine, arsine, etc.; X = Cl and Y = Cl, H or Me) are described; unexpectedly, these display an extensive chemistry without disproportionation, although in some cases ligand scrambling does occur. 相似文献
5.
6.
The relationship between Wiener's topological index and the antiepileptic activity of a series ofN-aryl-isoxazole carboxamides/N-isoxazolylbenzamide analogs has been investigated. Values of Wiener's topological index for 69 compounds constituting the training set were computed and an active range was identified. Each analog was subsequently assigned an activity which was then compared with the reported antiepileptic activity against the maximal electroshock seizure (MES) test. Due to significant correlation between antiepileptic activity and Wiener's topological index, it was possible to predict antiepileptic activity with an accuracy of 91 % in the active range. 相似文献
7.
The reactions of various main-group metal hydrides with 1-halo-5-hexenes and with 1-halo-2,2-dlmethyl-5-hexenes produce both straight chain and cyclized reduction products. The formation of cyclic hydrocarbons clearly indicates the presence of radical intermediates during the course of these reactions. 相似文献
8.
Goel SK 《Journal of colloid and interface science》1999,212(2):604-606
Effects of anionic surfactants, hydrotropes, and electrolytes on the cloud point of Triton X-100 have been studied over six decades of additives concentrations. A comprehensive look at all the data reveals significant new learnings. While anionic surfactants and hydrotropes affect the cloud point of non-ionics at ultra low (monomeric) concentrations, electrolytes exhibit a minimum critical concentration above which they cast their effect. This suggests that the former work by modifying the surface charge of non-ionic micelles (i.e., by affecting the solute), whereas the latter work by modifying the properties of the bulk medium. Above their respective critical concentrations, salting-out electrolytes decrease the cloud point while salting-in electrolytes increase it, the trends being linear with additive concentration in either case. The magnitude of the effect of anionic surfactants and hydrotropes increases gradually with increasing concentration till their respective cmc's are reached and then there is a sharp rise in the cloud point. Copyright 1999 Academic Press. 相似文献
9.
Using radiotracer solutions of Hg (203Hg) and Os (185Os), techniques have been developed for sampling these elements presumably suitable for ion probe measurements. Mercury has been electrodeposited on the cross-sectional area (5 mm2) of an electrochemically pure Cu wire giving a recovery 25 to 30% at the tip. Similar efficiency is found for Hg distillate solutions. Osmium has been collected in a Ni–NiS bead after loading its thiourea complex solution on filter paper. The recovery in the bead is 80–90%. These methods should be of help for isotopic study of these elements by ion microprobe. The suitability of these samples for measurements remains unconfirmed. 相似文献
10.
Diamagnetic susceptibilities of trimethyl(imino-oxy)silanes,Me
3SiON CMeR, and dimethyldi(imino-oxy)silanes,Me
2Si(ON CMeR)2, containing Si–O bonds are reported.
M
of these silicon compounds has been calculated theoretically from the method ofBaudet et al. and a good agreement has been obtained between the observed
M
values and the corresponding calculated values.
Si
in these compounds has been calculated graphically and the lower values have been explained on the basis of back-bonding to the silicon atom from the oxygen lone pair. 相似文献