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排序方式: 共有93条查询结果,搜索用时 15 毫秒
1.
Dynamic composition and optimization of Web services 总被引:1,自引:0,他引:1
Liangzhao Zeng Anne H. H. Ngu Boualem Benatallah Rodion Podorozhny Hui Lei 《Distributed and Parallel Databases》2008,24(1-3):45-72
Process-based composition of Web services has recently gained significant momentum for the implementation of inter-organizational business collaborations. In this approach, individual Web services are choreographed into composite Web services whose integration logics are expressed as composition schema. In this paper, we present a goal-directed composition framework to support on-demand business processes. Composition schemas are generated incrementally by a rule inference mechanism based on a set of domain-specific business rules enriched with contextual information. In situations where multiple composition schemas can achieve the same goal, we must first select the best composition schema, wherein the best schema is selected based on the combination of its estimated execution quality and schema quality. By coupling the dynamic schema creation and quality-driven selection strategy in one single framework, we ensure that the generated composite service comply with business rules when being adapted and optimized. 相似文献
2.
Hierarchically Distributed Peer-to-Peer Document Clustering and Cluster Summarization 总被引:1,自引:0,他引:1
Hammouda Khaled M. Kamel Mohamed S. 《Knowledge and Data Engineering, IEEE Transactions on》2009,21(5):681-698
In distributed data mining, adopting a flat node distribution model can affect scalability. To address the problem of modularity, flexibility and scalability, we propose a Hierarchically-distributed Peer-to-Peer (HP2PC) architecture and clustering algorithm. The architecture is based on a multi-layer overlay network of peer neighborhoods. Supernodes, which act as representatives of neighborhoods, are recursively grouped to form higher level neighborhoods. Within a certain level of the hierarchy, peers cooperate within their respective neighborhoods to perform P2P clustering. Using this model, we can partition the clustering problem in a modular way across neighborhoods, solve each part individually using a distributed K-means variant, then successively combine clusterings up the hierarchy where increasingly more global solutions are computed. In addition, for document clustering applications, we summarize the distributed document clusters using a distributed keyphrase extraction algorithm, thus providing interpretation of the clusters. Results show decent speedup, reaching 165 times faster than centralized clustering for a 250-node simulated network, with comparable clustering quality to the centralized approach. We also provide comparison to the P2P K-means algorithm and show that HP2PC accuracy is better for typical hierarchy heights. Results for distributed cluster summarization match those of their centralized counterparts with up to 88% accuracy. 相似文献
3.
Asif Iqbal Naeem U. Dar Ning He Muhammad M. I. Hammouda Liang Li 《Journal of Intelligent Manufacturing》2010,21(6):761-776
The foremost challenge faced by expert systems, for their applicability to real world problems, is their inherent deficiency
of dynamism. For an expert system to be more pragmatic and applicable, the whole structure of an expert system—including rule-base,
fuzzy sets, and even user-interface—needs to be upgraded continuously. This continuous up gradation demands full-time, repetitive,
and cumbersome involvement of knowledge engineers. Machine learning is an answer to this problem, but unfortunately, the solutions
that have been provided are limited in scope. For example, most of the researchers put forward techniques of either generating
just rules from data, or self-expanding and self-correcting knowledge-base only. The innovative approach presented in this
paper is broader in scope. It enhances the efficacy and viability of expert systems to be more capable of coping with dynamic
and ever-changing industrial environments. The objective is facilitated by rendering, concurrently, the self-learning, self-correcting,
and self-expanding abilities to the expert system, without requiring knowledge engineering skills of the developers. This
means that the user needs just to feed data in form of the values of input/output variables and the complete development of
expert system is done automatically. The superiority of the proposed expert system, regarding its continuous self-development,
has been explained with the help of three examples related to prediction and optimization of milling and welding processes. 相似文献
4.
Z. Sereir N. Boualem Ea. Adda-Bedia 《International Journal of Mechanics and Materials in Design》2005,2(3-4):61-78
This paper presents an analytical method to assess the transient hygroscopic stresses in laminated composite plates due to asymmetrical constant environmental conditions. The developed method permits us to determine directly the values of such stresses without the calculation of the moisture concentration through laminated plates. The present method is the extension of the method developed by Tounsi and Adda-Bedia [Tounsi, A., Adda-Bedia, E.A.: Appl Compos Mater 10, 1–18 (2003)] which is limited only to the problems with symmetrical environmental conditions. Thus by the present method, we can study the effect of symmetrical and asymmetrical environmental conditions. A validation was made with the results of the same authors [Tounsi, A., Adda-Bedia, E.A.: Appl Compos Mater 10, 1–18 (2003); Sereir, Z., et al.: J. Thermal Stres. 28(9), 889–910 (2005)] for symmetrical environmental conditions and the results of benkeddad [Benkeddad, A., et al.: Compos. Struct. 30(2), 201–215 (1995)] for asymmetrical environmental conditions. In order to evaluate the performances of each balanced [θ/−θ]
S
laminate proposed for this applications, we use the polar method introduced by Verchery [Vannucci, P., Verchery, G.: Int. J. Solids Struct. 38, 9281–9294 (2001), Vincenti, A., et al.: Composites: Part A, 1525–1532 (2001), Valot, E., et al.: Compos. Struct. 60, 413–429 (2003), Vannucci, P., Verchery, G.: Compos. Sci. Technol. 61, 1465–1473 (2001)]. This method enables us to locate the favourite directions of the mechanical characteristics and to estimate the degree of anisotropy of all stacking sequences. Therefore, we can reduce the transient hygroscopic stresses, particularly at the edges of laminated plates. Through this theoretical study presented here, we hope to contribute to the understanding of hygrothermal behaviour of composite laminated plates. 相似文献
5.
6.
When fiber-reinforced polymer plates are exposed to cyclic environmental conditions, polymer matrix absorbs or desorbs continuously
the moisture due to the variation in service temperature and relative humidity. Both temperature and moisture concentration
produce an important hygrothermal transverse stresses, which are maximum on both edges of the composite plates. These transverse
stresses which are more important at first times of moisture diffusion, can produce a probable damage of composite plates.
To extend the durability of our composite plate, interplay hybrid composites are adopted to reduce the transverse stresses
on edges. Therefore, a variation of the relationship between thicknesses of unidirectional hybrid composites constituents
AS/3501-5 and T300/5208 is carried out in order to find minimal transverse stresses. This thicknesses variation enables us
to find the best configuration which gives favourable service conditions of our hybrid composite, i.e., to predict firstly
a considerable reduction of hygrothermal transverse stresses at both edges of our hybrid plate, secondly to reduce or to attenuate
the edge effect developed in 6 days and 6 weeks periods. 相似文献
7.
Facilitating the Rapid Development and Scalable Orchestration of Composite Web Services 总被引:8,自引:1,他引:8
The development of new Web services through the composition of existing ones has gained a considerable momentum as a means to realise business-to-business collaborations. Unfortunately, given that services are often developed in an ad hoc fashion using manifold technologies and standards, connecting and coordinating them in order to build composite services is a delicate and time-consuming task. In this paper, we describe the design and implementation of a system in which services are composed using a model-driven approach, and the resulting composite services are orchestrated following a peer-to-peer paradigm. The system provides tools for specifying composite services through statecharts, data conversion rules, and multi-attribute provider selection policies. These specifications are interpreted by software components that interact in a peer-to-peer way to coordinate the execution of the composite service. We report results of an experimental evaluation showing the relative advantages of this peer-to-peer approach with respect to a centralised one. 相似文献
8.
A trust negotiation system for digital library Web services 总被引:1,自引:0,他引:1
Halvard?SkogsrudEmail author Boualem?Benatallah Fabio?Casati 《International Journal on Digital Libraries》2004,4(3):185-207
A scalable approach to trust negotiation is required in digital library (DL) environments that have large and dynamic user populations. In this paper we introduce Trust-Serv, a model-driven trust negotiation framework for Web services, and show how it can be used to effectively handle trust negotiation in DLs. The framework employs a model for trust negotiation based on state machines, extended with security abstractions. High-level specifications expressed with the state-machine-based model are then translated into formats suitable for automating the trust negotiation process. The proposed framework also supports negotiation policy lifecycle management, an important trait in the dynamic environments that characterize DLs. In particular, we present a set of policy change operations that enable the dynamic evolution of negotiation policies without disrupting ongoing negotiations. The proposed approach has been implemented as a container-centric mechanism that is transparent to the DL and to the developers of DL Web services, simplifying DL development and management as well as enabling scalable deployments. 相似文献
9.
A new technique has been developed to generate dendritic‐equiaxed structures in aluminium alloy casting processes, not only to improve the mechanical properties but also to study the effect of crystal structure on the chemical and physical properties of alloys to be cast. The investigation combined laboratory experimental work, metallographic examination and mathematic modelling. The laboratory experimental work involved different superheats for Al‐4.5%Cu alloy in cast ingots. Measurements of temperature distributions were conducted to verify the solidification model. A metallographic study combined macro and micro structural evolution of cast ingot samples. Two‐dimensional mathematical models of fluid flow and heat transfer were developed to characterise the natural convection streams and thermal fields. The model predictions were compared to temperature and isotherms measurements where a good agreement was found. The formation of cast structure and columnar, equiaxed transition (CET) and macro segregation phenomena were studied and discussed, based not only on the theories of nucleation but also on the thermal effects in the mushy and liquid zones. 相似文献
10.
Mohamed A. Taha Nahed A. El-Mahallawy Rawia M. Hammouda Sherif I. Nassef 《Journal of Coatings Technology and Research》2010,7(6):793-800
Although magnesium alloys have the advantage of high specific strength, they have poor atmospheric corrosion resistance. An
important method of improving the corrosion resistance is by applying a coating layer. In this work, the physical vapor deposition
(PVD) technique is used for coating a magnesium (Mg) AZ31 sheet substrate with a thin layer of high purity aluminum (Al) and
Al–12.6% Si. Aluminum is expected to be suitable as a coating layer on Mg sheets, due to its corrosion resistance and its
formability. Before coating, the substrate was subjected to several consecutive surface preparations, including sand-blasting,
mechanical grinding, mirror-like polishing, ultrasonic etching, and finally ion etching by magnetron sputtering (MS). PVD
coating was conducted using a PVD machine with max electron beam power and voltage of 100 kW and 40 kV, respectively. This
was either with or without plasma activation, and with variable substrate speeds ranging between 10 and 70 mm/s. During MS
ion etching and coating, the substrate temperature increased. The substrate temperature increased with the application of
plasma activation and with lower substrate speeds. The coating-layer thickness varied inversely with substrate speed. A thinner
coat with finer morphology was obtained in the case of plasma activation. Other results included coating layer characteristics,
diffusion between the AZ 31 substrate and the Al coating layer, adhesion of the coating layer to the substrate, and corrosion
resistance by a humidity test. 相似文献