Decentralising a service-oriented architecture

Service-oriented computing is becoming an increasingly popular paradigm for modelling and building distributed systems in open and heterogeneous environments. However, proposed service-oriented architectures are typically based on centralised components, such as service registries or service brokers, that introduce reliability, management, and performance issues. This paper describes an approach to fully decentralise a service-oriented architecture using a self-organising peer-to-peer network maintained by service providers and consumers. The design is based on a gradient peer-to-peer topology, which allows the system to replicate a service registry using a limited number of the most stable and best performing peers. The paper evaluates the proposed approach through extensive simulation experiments and shows that the decentralised registry and the underlying peer-to-peer infrastructure scale to a large number of peers and can successfully manage high peer churn rates.     

Study of mixing in an axisymmetric coflowing liquid jet by coupling L.D.A. to an electrochemical method

Local and simultaneous velocity and concentration fluctuations were analysed in an axisymmetric jet of an aqueous electrolyte solution moving in a codirectional water stream. The determination of the convection velocity of the turbulent eddies as well as correlation between axial velocity and concentration fluctuations was made possible by coupling L.D.A. to an electrochemical technique. The influence of the ratio of the coflowing stream velocity to the jet exit velocity was investigated. The mean velocity and concentration profiles, the turbulence intensity, the integral length scales relative to axial velocity and concentration were also determined.     

Testing for decreasing heterogeneity in a new time-varying frailty model

Frailty models adjust for between-cluster variability in survival data by including a cluster-specific random factor, the frailty term, in the Cox model. The frailty term is assumed to be constant over time. This assumption is questionable in some particular settings, e.g., in cancer clinical trials on chronic myeloid leukaemia. We therefore relax the time-constant heterogeneity assumption and consider frailty models with a time-varying frailty term. Instead of working with hazard models, we rather model the log cumulative hazard function, making use of the mixed model framework, and introduce a time-varying random effect at that level. Simulations demonstrate that the proposed method has acceptable size and power to detect time-dependent clustering. The method is applied to data from a large-scale multicentre clinical trial in patients with chronic myeloid leukaemia.     

Multiscale carbon fibre–reinforced polymer (CFRP) composites containing carbon nanotubes with tailored interfaces

Pristine and functionalized multiwalled carbon nanotubes (MWCNTs) with tailored interfaces were efficiently dispersed in an epoxy matrix using a three‐roll mill and further reinforced with carbon fibres. 1.3‐Dipolar cycloaddition of azomethine ylides was used for the chemical modification of MWCNTs by a solvent‐free approach. The influence of different loadings and types of MWCNTs on the final properties of the epoxy matrix was studied. Moreover, the most promising formulations were selected for manufacturing of prepreg sheets. The transversal tensile properties and the interlaminar fracture toughness under mode I loading (G_IC) of multiscale carbon fibre–reinforced polymer (CFRP) composites were characterized. The results point out that it is not straightforward to transfer the remarkable intrinsic properties of MWCNTs to the composite level, although an overall positive trend was found. Double cantilever beam experiments showed that G_IC of CFRP composites was improved 44% at ultralow content of functionalized MWCNTs (0.043 wt%).     

Influence of initial microstructuring of the cement paste in fresh mortar on early hydration-strength binding

This paper concerns the observation, interpretation and modelling of changes in mortar strength at the very beginning of its lifetime in relation to the advance of hydration, taking a special interest in the nature of the cement and that of the superplasticizer. A set of values was defined and determined experimentally in order to quantify the following:

Identifying frequent items in distributed data sets

Many practical problems in computer science require the knowledge of the most frequently occurring items in a data set. Current state-of-the-art algorithms for frequent items discovery are either fully centralized or rely on node hierarchies which are inflexible and prone to failures in massively distributed systems. In this paper we describe a family of gossip-based algorithms that efficiently approximate the most frequent items in large-scale distributed datasets. We show, both analytically and using real-world datasets, that our algorithms are fast, highly scalable, and resilient to node failures.     

Modeling and experimental validation of sharpening mechanism based on thermal oxidation for fabrication of ultra-sharp silicon nanotips

This paper aims at modeling the thermal oxidation of silicon pillars leading to the formation of very sharp silicon tips. The model is used to determine optimum process parameters with respect to the initial shape of the silicon pillars and the geometry of the desired tip. The modeling concept is to extend a previous approach, which predicts the oxidation mechanism of silicon cylinders versus their initial radius. The silicon pillar geometry is approximated by a superposition of silicon cylindrical structures featuring a local curvature radius. Experimental validation has been performed for several initial silicon pillar shapes, at 1000/spl deg/C and 1100/spl deg/C under dry oxidation conditions, leading to formation of very sharp silicon tips. The numerical predictions are shown to agree well with these experimental data. The motivation of this study aims at designing and fabricating a nanoelectromechanical filter device. Its vibrating part consists of a silicon nanotip, covered with a thin gold layer, the geometrical features of which affect the center frequency of the nanofilter device.     

Molecular basis for fibrinogen Dusart (A alpha 554 Arg-->Cys) and its association with abnormal fibrin polymerization and thrombophilia

The molecular defect in the abnormal fibrinogen Dusart (Paris V) that is associated with thrombophilia was determined by sequence analysis of genomic DNA that had been amplified using the polymerase chain reaction. The propositus was heterozygous for a single base change (C-->T) in the A alpha-chain gene, resulting in the amino acid substitution A alpha 554 Arg-->Cys. Restriction analysis of the amplified DNA derived from the family members showed that his father and his two sons were also heterozygous. Electron microscopic studies on fibrin formed from purified fibrinogen Dusart demonstrated fibers that were much thinner than in normal fibrin. In contrast to the previously observed defective binding of plasminogen, the binding of thrombospondin to immobilized fibrinogen Dusart was similar to that of normal fibrinogen. Immunoblot analysis of plasma fibrinogen demonstrated that a substantial part of the fibrinogen Dusart molecules were disulfide-linked to albumin. The plasma of the affected family members also contained fibrinogen-albumin complexes. Furthermore, small amounts of high molecular weight complexes containing fibrinogen were detected in all the heterozygous individuals. These data indicate that the molecular abnormality in fibrinogen Dusart (A alpha 554 Arg-->Cys) results in defective lateral association of the fibrin fibers and disulfide-linked complex formation with albumin, and is associated with a family history of recurrent thrombosis in the affected individuals.