A graph G was defined in [16] as P4-reducible, if no vertex in G belongs to more than one chordless path on four vertices or P4. A graph G is defined in [15] as P4-sparse if no set of five vertices induces more than one P4, in G. P4-sparse graphs generalize both P4-reducible and the well known class of p4-free graphs or cographs. In an extended abstract in [11] the first author introduced a method using the modular decomposition tree of a graph as the framework for the resolution of algorithmic problems. This method was applied to the study of P4-sparse and extendedP4-sparse graphs.
In this paper, we begin by presenting the complete information about the method used in [11]. We propose a unique tree representation of P4-sparse and a unique tree representation of P4-reducible graphs leading to a simple linear recognition algorithm for both classes of graphs. In this way we simplify and unify the solutions for these problems, presented in [16–19]. The tree representation of an n-vertex P4-sparse or a P4-reducible graph is the key for obtaining O(n) time algorithms for the weighted version of classical optimization problems solved in [20]. These problems are NP-complete on general graphs.
Finally, by relaxing the restriction concerning the exclusion of the C5 cycles from P4-sparse and P4-reducible graphs, we introduce the class of the extendedP4-sparse and the class of the extendedP4-reducible graphs. We then show that a minimal amount of additional work suffices for extending most of our algorithms to these new classes of graphs. 相似文献
In modern heterogeneous environments, such as mobile, pervasive and ad-hoc networks, architectures based on web services
offer an attractive solution for effective communication and inter-operation. In such dynamic and rapidly evolving environments,
efficient web service discovery is an important task. Usually this task is based on the input/output parameters or other functional
attributes, however this does not guarantee the validity or successful utilization of retrieved web services. Instead, non-functional
attributes, such as device power features, computational resources and connectivity status, that characterize the context
of both service providers and consumers play an important role to the quality and usability of discovery results. In this
paper we introduce context-awareness in web service discovery, enabling the provision of the most appropriate services at
the right location and time. We focus on context-based caching and routing for improving web service discovery in a mobile
peer-to-peer environment. We conducted a thorough experimental study, using our prototype implementation based on the JXTA
framework, while simulations are employed for testing the scalability of the approach. We illustrate the advantages that this
approach offers, both by evaluating the context-based cache performance and by comparing the efficiency of location-based
routing to broadcast-based approaches.
Recommended by: Zakaria Maamar 相似文献
The Maximum Weight Independent Set (MWIS) problem on graphs with vertex weights asks for a set of pairwise nonadjacent vertices of maximum total weight. Being one of the most investigated and most important problems on graphs, it is well known to be -complete and hard to approximate. The complexity of MWIS is open for hole-free graphs (i.e., graphs without induced subgraphs isomorphic to a chordless cycle of length at least five). By applying a combination of clique separator and modular decomposition, we obtain a polynomial time solution of MWIS for hole- and co-chair-free graphs (the co-chair consists of five vertices four of which form a clique minus one edge – a diamond – and the fifth has degree one and is adjacent to one of the degree two vertices of the diamond). 相似文献
Gas/liquid down-flow in packed beds is studied, under periodic liquid feeding (at sufficiently high frequencies to be classified as “fast” mode of pulsing), in a range of mean liquid and gas flow rates within the steady “trickling flow regime”. The aim is to identify periodic feeding conditions resulting in improved fluid-mechanical characteristics (e.g. uniform fluids distribution) and possibly enhanced transport rates in this flow regime, which is common in industrial processes. From instantaneous, cross-sectionally averaged holdup measurements, at various locations along the packed bed, quantitative information is obtained on the axial propagation and attenuation of induced pulses. A phenomenological treatment of the pulse decay process facilitates data interpretation and leads to the determination of a characteristic attenuation factor for the various conditions tested. Key parameters of the process studied include, in addition to dynamic holdup, pressure drop, pulse celerity and intensity, as a function of fluid feed rates (G,L) and liquid cyclic frequency. Under the conditions of these tests, and for fixed mean rates G,L, the time averaged holdup and the pulse celerity are practically constant along the bed; furthermore, these quantities as well as the pressure drop do not seem to be affected by the imposed cyclic liquid feeding frequency. An expression to tentatively correlate pulse celerity data is recommended.The computed attenuation factors indicate that there is a rather narrow band of mean gas and liquid rates (along the so-called “pseudo-transition” boundary to pulsing flow) where pulse decay is at a minimum. Based on these results as well as on pulse intensity vs. bed length data, recommendations are made on preferred conditions for induced pulsing (from the fluid-mechanical standpoint) which would maximize expected benefits. 相似文献
A series of laboratory experiments was carried out on a sandy loam soil, for testing the predictive ability of a linearized analytical solution of the kinematic wave equation used for runoff estimation in micro-catchment water harvesting design. The experimental set-up comprised an inclined flume containing the soil sample and a rainfall simulator. The flume represented the Contributing Area (CA) of a micro-catchment. By applying various rainfall intensities, the runoff from the flume was recorded for a variety of conditions, including the initial soil water content and the slope of the flume. Comparison between experimental and predicted runoff hydrographs showed satisfactory agreement. 相似文献
The main objective of this paper is to review the existing methodologies for the estimation and analysis of regional drought. As a first step, point drought methods are presented. Further emphasis is given to the definition and estimation of regional drought characteristics. Stochastic processes for simulating the time-space variability of drought, are presented. Finally, illustrative examples are shown and recommendations for further research are given. 相似文献
The heterogeneity of schizophrenia has led to a multitude of diagnostic criteria systems. Thus, the best strategy for schizophrenia research might be the use of several diagnostic systems simultaneously. This polydiagnostic approach can be associated with isolating subtypes of symptoms or patients. In this way, the authors present several approaches such as, first, dimensional approaches, second, cluster analyses, and third the selection of a very homogeneous subtype with standardized criteria. One homogeneous subtype can be represented by deficit schizophrenia according to Carpenter as defined by the Schedule of Deficit Syndrome. 相似文献
We present a tool that combines two main trends of knowledge base refinement. The first is the construction of interactive knowledge acquisition tools and the second is the development of machine learning methods that automate this procedure. The tool presented here is interactive and gives experts the ability to evaluate an expert system and provide their own diagnoses on specific problems, when the expert system behaves erroneously. We also present a database scheme that supports the collection of specific instances. The second aspect of the tool is that knowledge base refinement and machine learning methods can be applied to the database, in order to automate the procedure refining the knowledge base. In this paper we examine the application of inductive learning algorithms within the proposed framework. Our main goal is to encourage the experts to evaluate expert systems and to introduce new knowledge, based on their experience. 相似文献