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排序方式: 共有3927条查询结果,搜索用时 31 毫秒
91.
Abdul Jabbar Justin P. Rohrer Victor S. Frost James P.G. Sterbenz 《Computer Communications》2011,34(16):1942-1955
Millimeter-wave mesh networks have the potential to provide cost-effective high-bandwidth solutions to many current bandwidth-constrained networks including cellular backhaul. However, the availability of such networks is severely limited due to their susceptibility to weather, such as precipitation and humidity. In this paper, we present a rigorous approach to survivable millimeter-wave mesh networks based on experimentation, modeling, and simulation. Individual link performance is characterised using frame error-rate measurements from millimeter-wave transmissions on test links over a period of one year. A geometric model based on radar-reflectivity data is used to characterise rain storms and determine their impact on spatially correlated links of a mesh network. To mitigate the impact of link impairments on network services, we present two cross-layered routing protocols to route around the failures: P-WARP (predictive weather-assisted routing protocol) and XL-OSPF (cross-layered open shortest-path first). We conduct a performance analysis of the proposed mesh network under the presence of actual weather events as recorded by the US National Weather Service. Results show that the proposed approach yields the highest dependability when compared against existing routing methods. 相似文献
92.
Chouvarda I Rosso V Mendez MO Bianchi AM Parrino L Grassi A Terzano M Cerutti S 《Computer methods and programs in biomedicine》2011,104(3):e16-e28
The present study quantitatively analyzes the EEG characteristics during activations (Act) that occur during NREM sleep, and constitute elements of sleep microstructure (i.e. the Cyclic Alternating Pattern). The fractal dimension (FD) and the sample entropy (SampEn) measures were used to study the different sleep stages and the Act that build up the sleep structure. Polysomnographic recordings from 10 good sleepers were analyzed. The complexity indexes of the Act were compared with the non-activation (NAct) periods during non-REM sleep. In addition, complexity measures among the different Act subtypes (A1, A2 and A3) were analyzed. A3 presented a quite similar complexity independently of the sleep stage, while A1 and A2 showed higher complexity in light sleep than during deep sleep. The current results suggest that Act present a hierarchic complexity between subtypes A3 (higher), A2 (intermediate) and A1 (lower) in all sleep stages. 相似文献
93.
94.
Deepak Kapur Victor L. Winter Raymond S. Berg 《Electronic Notes in Theoretical Computer Science》2001,50(1)
The use of formal methods for analyzing and synthesizing a controller for a multi-train multi-track railway system is discussed. The research was motivated by a case study involving the Bay Area Rapid Transit (BART) system. The overall goal is to design a train acceleration control function that enables trains to be safely placed but also increases system throughput. The use of a modeling language for specifying safety properties and a control function is illustrated. The program transformation methodology supported in the HATS system is employed to generate an efficient implementation from a high-level specification of a controller. This implementation can then be used to simulate the controller behavior, thus further enhancing confidence in the design. Properties of optimization transformations can be verified using an rewrite-rule based induction theorem prover Rewrite Rule Laboratory (RRL). 相似文献
95.
Filtered Jitter 总被引:1,自引:1,他引:0
R. Victor Klassen 《Computer Graphics Forum》2000,19(4):223-230
Jitter is one popular way of generating samples for stochastic sampling in computer graphics. The Poisson disk distribution better approximates that of the human photomosaic. In this paper we examine the spatial and frequency space behaviour of a number of existing algorithms for generating stochastic samples and propose a new algorithm based on low pass filtering a jittered set of displacements. The distribution is at least as much like that of the human photomosaic as any existing algorithm, while being fast to compute. 相似文献
96.
Johnson GP Calo VM Gaither KP 《IEEE transactions on visualization and computer graphics》2008,14(6):1420-1427
A stand-alone visualization application has been developed by a multi-disciplinary, collaborative team with the sole purpose of creating an interactive exploration environment allowing turbulent flow researchers to experiment and validate hypotheses using visualization. This system has specific optimizations made in data management, caching computations, and visualization allowing for the interactive exploration of datasets on the order of 1TB in size. Using this application, the user (co-author Calo) is able to interactively visualize and analyze all regions of a transitional flow volume, including the laminar, transitional and fully turbulent regions. The underlying goal of the visualizations produced from these transitional flow simulations is to localize turbulent spots in the laminar region of the boundary layer, determine under which conditions they form, and follow their evolution. The initiation of turbulent spots, which ultimately lead to full turbulence, was located via a proposed feature detection condition and verified by experimental results. The conditions under which these turbulent spots form and coalesce are validated and presented. 相似文献
97.
Leveraging online communities in fostering adaptive schools 总被引:1,自引:0,他引:1
David Hung Kenneth Y. T. Lim Der-Thanq Victor Chen Thiam Seng Koh 《International Journal of Computer-Supported Collaborative Learning》2008,3(4):373-386
There has long been a call for schools to prepare students for the twenty-first century where skills and dispositions differ
significantly from much of what has historically characterized formal education. The knowledge based economy calls for policy
and pedagogical efforts that would transform schools. Schools are to foster communities of learners. This paper suggests that
para-communities may be points of leverage in the fostering of adaptive schools. A critical analysis is done on the differences
between para-communities (such as online communities) and schools; and an argument is made that they each serve differing
goals and should be left distinct because they achieve different societal and economic demands. 相似文献
98.
Model checking based on the causal partial order semantics of Petri nets is an approach widely applied to cope with the state
space explosion problem. One of the ways to exploit such a semantics is to consider (finite prefixes of) net unfoldings—themselves
a class of acyclic Petri nets—which contain enough information, albeit implicit, to reason about the reachable markings of
the original Petri nets. In [19], a verification technique for net unfoldings was proposed, in which deadlock detection was reduced to a mixed integer linear
programming problem. In this paper, we present a further development of this approach. The essence of the proposed modifications
is to transfer the information about causality and conflicts between the events involved in an unfolding, into a relationship
between the corresponding integer variables in the system of linear constraints. Moreover, we present some problem-specific
optimisation rules, reducing the search space. To solve other verification problems, such as mutual exclusion or marking reachability
and coverability, we adopt Contejean and Devie's algorithm for solving systems of linear constraints over the natural numbers
domain and refine it, by taking advantage of the specific properties of systems of linear constraints to be solved.
Another contribution of this paper is a method of re-formulating some problems specified in terms of Petri nets as problems
defined for their unfoldings. Using this method, we obtain a memory efficient translation of a deadlock detection problem
for a safe Petri net into an LP problem. We also propose an on-the-fly deadlock detection method.
Experimental results demonstrate that the resulting algorithms can achieve significant speedups.
相似文献
Maciej KoutnyEmail: |
99.
100.
We consider weighted finite transducers over arbitrary groups, that is finite transducers having a counter in which, at any
step, a value of the group is stored but no information regarding the content of this counter is available until the computation
is finished. The computation is valid if the counter value is the neutral element of the group. We generalize here some results
from [8] and [17].
Received: 28 January 2001 / 5 June 2001 相似文献