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71.
Michell’s problem of optimizing truss topology for stress or compliance constraints under a single load condition is solved
analytically for plane trusses having a square-shaped line support. Geometrical characteristics of the Hencky nets giving
the truss layout are expressed in terms of Lommel functions. Analytically derived truss volumes for the above problem are
compared with those of trusses supported along circles of equivalent area. Some general implications of the results are also
discussed. 相似文献
72.
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: |
73.
Comments on the effect of yttrium on the early stages of oxidation of alumina formers 总被引:3,自引:0,他引:3
Jerzy Jedliński 《Oxidation of Metals》1993,39(1-2):55-60
74.
The precipitation process in alloys containing 4% Ti and 5 to 16% Ni was investigated using transmission electron microscopy, hardness and electrical conductivity measurements. After ageing, spherical -Ni3Ti precipitates with ordered DO22 superlattice were observed in alloys CuTiNi5 to 10 and the L12 superlattice in the CuTi4Ni16 alloy. With increasing nickel content the size of precipitates decreases; this has only a minor influence on the age hardening. The CuTiNi10 alloy has the best electrical conductivity approaching 18m–1mm–2. 相似文献
75.
Edyta Szymańska 《Information Processing Letters》2012,112(23):899-902
76.
77.
Maciej Dabrowski Thomas Acton Hans van der Heijden 《Expert systems with applications》2012,39(9):8279-8287
This paper proposes a novel method for preference relaxation in online product search, which enables consumers to make quality choices without suffering from the commonly experienced information overload. In online shopping scenarios that involve multi-attribute choice tasks, it can be difficult for consumers to process the vast amounts of information available and to make satisfactory buying decisions. In such situations consumers are likely to eliminate potentially good choices early on, using hard-constraint filtering tools. Our approach uses edge sets to identify the alternatives on the soft boundary and the principle of alternative domination to suppress the alternatives on this boundary that are irrelevant. We demonstrate how our approach outperforms existing methods for product search in a set of simulations using two sets of 2650 car advertisements and 1813 digital cameras gathered from a popular online store. 相似文献
78.
Quattor: Tools and Techniques for the Configuration,Installation and Management of Large-Scale Grid Computing Fabrics 总被引:1,自引:0,他引:1
R. García Leiva M. Barroso López G. Cancio Meliá B. Chardi Marco L. Cons P. Poznański A. Washbrook E. Ferro A. Holt 《Journal of Grid Computing》2004,2(4):313-322
This paper describes the quattor tool suite, a new system for the installation, configuration, and management of operating systems and application software for computing fabrics. At present Unix derivatives such as Linux and Solaris are supported. Quattor is a powerful, portable and modular open source solution that has been shown to scale to thousands of computing nodes and offers a significant reduction in management costs for large computing fabrics. The quattor tool suite includes innovations compared to existing solutions which make it very useful for computing fabrics integrated into grid environments. Evaluations of the tool suite in current large scale computing environments are presented. 相似文献
79.
Wies?aw Ostachowicz Marek Krawczuk Matthew Cartmell Michael Gilchrist 《Computers & Structures》2004,82(6):475-483
The wave propagation model investigated herein is based on the known fact that material discontinuities affect the propagation of elastic waves in solids. The change in certain material characteristics, such as a local change in stiffness or inertia caused by a crack or the presence of material damage, will affect the propagation of transmitted elastic waves and will modify the received signal. Wave frequencies associated with the highest detection sensitivity depend, among other things, on the type of structure, the type of material, and the type of damage. This paper presents a method of wave propagation, which can be further used to detect small delaminations in beam-like structures. The considered beam is modelled by spectral finite elements. 相似文献
80.
In this paper, we investigate formulation of non-local memory effect hysteretic loops in presliding domain of friction by examining the dynamic responses of a single-degree-of-freedom friction oscillator. We modify the Maxwell slip model introducing characteristic features of asperities and perform detailed examination of the system from two perspectives. The first one, termed by us as microscale, presents contribution of each individual asperity to the total friction force, whereas the second one, termed by us as macroscale, concerns friction force behaviour of the whole model treated as the unity, with a special emphasis on non-local memory effect hysteretic loops formulation, complemented by time responses. 相似文献