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61.
Recently multiserver queues with setup times have been extensively studied because they have applications in power-saving data centers. A challenging model is the M/M/c/Setup queue where a server is turned off when it is idle and is turned on if there are some waiting jobs. Recently, Gandhi et al. (in: Proceedings of the ACM SIGMETRICS, pp. 153–166, ACM, 2013; Queueing Syst. 77(2):177–209, 2014) obtain the generating function of the number of jobs in the system, as well as the Laplace transform of the response time using the recursive renewal reward approach and the distributional Little’s law (Keilson and Servi in Oper Res Lett 7(5):223– 227, 1988). In this paper, we derive exact solutions for the joint stationary queue length distribution of the same model using two alternative methodologies: generating function approach and matrix analytic method. The generating function approach yields exact closed form expressions for the joint stationary queue length distribution and the conditional decomposition formula. On the other hand, the matrix analytic approach leads to an exact recursive algorithm to calculate the joint stationary distribution and performance measures so as to provide some application insights. 相似文献
62.
Khaled?ElbassioniEmail author Amr?Elmasry Ibrahim?Kamel 《Distributed and Parallel Databases》2005,17(3):215-249
We consider the problem of indexing a set of objects moving in d-dimensional spaces along linear trajectories. A simple external-memory indexing scheme is proposed to efficiently answer
general range queries. The following are examples of the queries that can be answered by the proposed method: report all moving
objects that will (i) pass between two given points within a specified time interval; (ii) become within a given distance
from some or all of a given set of other moving objects. Our scheme is based on mapping the objects to a dual space, where
queries about moving objects are transformed into polyhedral queries concerning their speeds and initial locations. We then
present a simple method for answering such polyhedral queries, based on partitioning the space into disjoint regions and using
a B+-tree to index the points in each region. By appropriately selecting the boundaries of each region, we guarantee an average
search time that matches a known lower bound for the problem. Specifically, for a fixed d, if the coordinates of a given set of N points are statistically independent, the proposed technique answers polyhedral queries, on the average, in O((N/B)1−1/d⋅(log B N)1/d+K/B) I/O's using O(N/B) space, where B is the block size, and K is the number of reported points. Our approach is novel in that, while it provides a theoretical upper bound on the average
query time, it avoids the use of complicated data structures, making it an effective candidate for practical applications.
The proposed index is also dynamic in the sense that it allows object insertion and deletion in an amortized update cost of
log B(N) I/O's. Experimental results are presented to show the superiority of the proposed index over other methods based on R-trees.
recommend Ahmed Elmagarmid 相似文献
63.
Exploring spatial datasets with histograms 总被引:2,自引:0,他引:2
Chengyu Sun Nagender Bandi Divyakant Agrawal Amr El Abbadi 《Distributed and Parallel Databases》2006,20(1):57-88
As online spatial datasets grow both in number and sophistication, it becomes increasingly difficult for users to decide whether
a dataset is suitable for their tasks, especially when they do not have prior knowledge of the dataset. In this paper, we
propose browsing as an effective and efficient way to explore the content of a spatial dataset. Browsing allows users to view the size of
a result set before evaluating the query at the database, thereby avoiding zero-hit/mega-hit queries and saving time and resources.
Although the underlying technique supporting browsing is similar to range query aggregation and selectivity estimation, spatial
dataset browsing poses some unique challenges. In this paper, we identify a set of spatial relations that need to be supported
in browsing applications, namely, the contains, contained and the overlap relations. We prove a lower bound on the storage required to answer queries about the contains relation accurately at a given resolution. We then present three storage-efficient approximation algorithms which we believe
to be the first to estimate query results about these spatial relations. We evaluate these algorithms with both synthetic
and real world datasets and show that they provide highly accurate estimates for datasets with various characteristics.
Recommended by: Sunil Prabhakar
Work supported by NSF grants IIS 02-23022 and CNF 04-23336. An earlier version of this paper appeared in the 17th International
Conference on Data Engineering (ICDE 2001). 相似文献
64.
In studying the problem of the nonlinear viscous barotropic non-divergent vorticity equation on - and - planes, the method of Lie group has been applied. The method reduces the number of independent variables by one, and consequently, for the case of three independent variables we applied the method successively twice and the nonlinear partial differential equation reduces to ordinary differential equation. Investigation of exact solutions of the viscous barotropic non-divergent vorticity equation on - and - planes, via the application of Lie group, provides large classes of new exact solutions which include both Rossby and Rossby–Haurwitz waves as special cases. Also, The Lie symmetries of the viscous barotropic non-divergent vorticity equation with two parameters and , are determined. The possible reductions of the viscous barotropic vorticity equation with two parameters and have been investigated by means of one- dimensional Lie subalgebras. 相似文献
65.
66.
Fadl Sondos Megahed Amr Han Qi Qiong Li 《Multimedia Tools and Applications》2020,79(25-26):17619-17643
Multimedia Tools and Applications - Nowadays, due to the increasing crime and theft around the world, surveillance security systems play an important role. On the other hand, the availability of... 相似文献
67.
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69.
Ahmed Abdelaal Ahmed Mahmoud M. Alkhatip Michail Georgakis Lucio R. Montero Valenzuela Mohamed Hamza Ehab Farag Jaqui Hodgkinson Hisham Hosny Ahmed M. Kamal Mohamed Wagih Amr Naguib Hany Yassin Haytham Algameel Mohamed Elayashy Mohamed Abdelhaq Mohamed I. Younis Hassan Mohamed Mohammed Abdulshafi Mohamed A. Elramely 《International journal of molecular sciences》2021,22(6)
SARS-CoV-2 currently lacks effective first-line drug treatment. We present promising data from in silico docking studies of new Methisazone compounds (modified with calcium, Ca; iron, Fe; magnesium, Mg; manganese, Mn; or zinc, Zn) designed to bind more strongly to key proteins involved in replication of SARS-CoV-2. In this in silico molecular docking study, we investigated the inhibiting role of Methisazone and the modified drugs against SARS-CoV-2 proteins: ribonucleic acid (RNA)-dependent RNA polymerase (RdRp), spike protein, papain-like protease (PlPr), and main protease (MPro). We found that the highest binding interactions were found with the spike protein (6VYB), with the highest overall binding being observed with Mn-bound Methisazone at −8.3 kcal/mol, followed by Zn and Ca at −8.0 kcal/mol, and Fe and Mg at −7.9 kcal/mol. We also found that the metal-modified Methisazone had higher affinity for PlPr and MPro. In addition, we identified multiple binding pockets that could be singly or multiply occupied on all proteins tested. The best binding energy was with Mn–Methisazone versus spike protein, and the largest cumulative increases in binding energies were found with PlPr. We suggest that further studies are warranted to identify whether these compounds may be effective for treatment and/or prophylaxis. 相似文献
70.
Situational awareness of construction equipment using GPS, wireless and web technologies 总被引:3,自引:0,他引:3
Situational awareness refers to the ability by equipment operators to sense their environment with the objective of increasing safety and improving productivity on construction sites. This paper reports on research related to situational awareness of construction equipment using differential Global Positioning System (DGPS), wireless and web-based technologies. In this investigation, the researchers developed and implemented technologies for vehicle tracking, and collision detection. The paper concludes with a summary of these applications, along with a discussion of the limitations of current implementations, and the required augmentation by other technologies. 相似文献