Mobility-awareness in group key management protocols within MANETs

Several sensitive applications deployed within wireless networks require group communications. A high level of security is often required in such applications, like military or public security applications. The most suitable solution to ensure security in these services is the deployment of a group key management protocol, adapted to the characteristics ofManets, especially to mobility of nodes. In this paper, we present theOmct (Optimized Multicast Cluster Tree) algorithm for dynamic clustering of multicast group, that takes into account both nodes localization and mobility, and optimizes the energy and bandwidth consumptions. Then, we show how we integrateOmct within our group key management protocolBalade, in a sequential multi-source model. The integration ofBalade andOmct allows an efficient and fast key distribution process, validated through simulations, by applying various models of mobility (individual mobility and group mobility). The impact of the mobility model on the performance and the behaviour of the group key management protocolBalade coupled withOmct, is also evaluated.     

Buckling behavior improvement of steel plate shear wall systems

To improve buckling stability and to prevent early elastic buckling of infill plates, vertical and horizontal plate stiffeners are designed for steel plate shear wall (SPSW) systems. Furthermore, effective design of stiffeners for SPSW systems results in improved structural behavior, such as increase of stiffness, capacity and energy absorption. In this paper, the effect of stiffeners is studied on SPSW structural behavior and consequently a rational method is proposed to determine the minimum required moment of inertia for stiffeners resulting in local buckling mode of the infill plate. The proposed requirement is then compared to results obtained from tests previously conducted, as well as those gained from finite element (FE) analyses performed for this study. Copyright © 2007 John Wiley & Sons, Ltd.     

Retinal vessel segmentation using a probabilistic tracking method

Vessel structures such as retinal vasculature are important features for computer-aided diagnosis. In this paper, a probabilistic tracking method is proposed to detect blood vessels in retinal images. During the tracking process, vessel edge points are detected iteratively using local grey level statistics and vessel's continuity properties. At a given step, a statistic sampling scheme is adopted to select a number of vessel edge points candidates in a local studying area. Local vessel's sectional intensity profiles are estimated by a Gaussian shaped curve. A Bayesian method with the Maximum a posteriori (MAP) probability criterion is then used to identify local vessel's structure and find out the edge points from these candidates. Evaluation is performed on both simulated vascular and real retinal images. Different geometric shapes and noise levels are used for computer simulated images, whereas real retinal images from the REVIEW database are tested. Evaluation performance is done using the Segmentation Matching Factor (SMF) as a quality parameter. Our approach performed better when comparing it with Sun's and Chaudhuri's methods. ROC curves are also plotted, showing effective detection of retinal blood vessels (true positive rate) with less false detection (false positive rate) than Sun's method.     

Utilisation of modified atmosphere packaging to extend the shelf life of Khalas fresh dates

Completely matured tamr stage dates are widely available and consumed throughout the year. However, for some date varieties, the earlier khalal stage crunchy fruit is considered a premium product. This work examines the use of modified atmosphere packaging to extend the shelf life of khalal dates under refrigerated conditions. Modified atmosphere packaging with 10% or 20% CO₂ in air was successful in reducing the rate of the ripening processes while control‐packaged dates showed signs of ripening development such as significant weight loss and darkening in date colour (identified visually and as low lactic acid bacteria measurements at 18 and 27 days after packaging), similar to that observed in tamr stage fruit.     

Polyether-based polyrotaxane synthesis with controlled β-cyclodextrin threading ratio

An effective one-pot polyrotaxane synthesis with control of the threading ratio is realized. 2,5-Bis(chloromethyl)-4-methoxy-1-octoxybenzene (PMOC) is condensed with a starting rotaxane consisting of a bisphenol A salt threaded into β-cyclodextrin (βCD), to lead to a βCD-threaded polyether. We demonstrate that the threading ratio of βCD on the polyether chain (ratio between the polymer repeat units and the βCD in polyrotaxane) can be varied from zero to unity depending on two parameters: the reactant concentration and the bulkiness of the counter-ion stopper in the starting rotaxane.     

Antifungal and antiovarian cancer properties of α Fe2 O3 and α Fe2 O3 /ZnO nanostructures synthesised by Spirulina platensis

Candida albicans (C. albicans) infection shows a growing burden on human health, and it has become challenging to search for treatment. Therefore, this work focused on the antifungal activity, and cytotoxic effect of biosynthesised nanostructures on human ovarian tetracarcinoma cells PA1 and their corresponding mechanism of cell death. Herein, the authors fabricated advanced biosynthesis of uncoated α‐Fe₂ O₃ and coated α‐Fe₂ O₃ nanostructures by using the carbohydrate of Spirulina platensis. The physicochemical features of nanostructures were characterised by UV–visible, high resolution transmission electron microscopy, Fourier transform infrared spectroscopy, and X‐ray diffraction. The antifungal activity of these nanostructures against C. albicans was studied by the broth dilution method, and examined by 2′, 7′‐dichlorofluorescein diacetate staining. However, their cytotoxic effects against PA1 cell lines were evaluated by MTT and comet assays. Results indicated characteristic rod‐shaped nanostructures, and increasing the average size of α‐Fe₂ O₃ @ZnO nanocomposite (105.2 nm × 29.1 nm) to five times as compared to α‐Fe₂ O₃ nanoparticles (20.73nm × 5.25 nm). The surface coating of α‐Fe₂ O₃ by ZnO has increased its antifungal efficiency against C. albicans. Moreover, the MTT results revealed that α‐Fe₂ O₃ @ZnO nanocomposite reduces PA1 cell proliferation due to DNA fragmentation (IC₅₀ 18.5 μg/ml). Continual advances of green nanotechnology and promising findings of this study are in favour of using the construction of rod‐shaped nanostructures for therapeutic applications.Inspec keywords: nanocomposites, toxicology, nanofabrication, cellular biophysics, X‐ray diffraction, iron compounds, biochemistry, cancer, antibacterial activity, transmission electron microscopy, biomedical materials, wide band gap semiconductors, DNA, II‐VI semiconductors, visible spectra, molecular biophysics, ultraviolet spectra, nanomedicine, zinc compounds, nanoparticles, microorganisms, Fourier transform infrared spectraOther keywords: Spirulina platensis, antifungal activity, α‐Fe₂ O₃ nanoparticles, antiovarian cancer properties, Candida albicans infection, cytotoxic effect, biosynthesised nanostructures, human ovarian tetracarcinoma cell PA1, cell death, uncoated α‐Fe₂ O₃ , coated α‐Fe₂ O₃ nanostructures, α‐Fe₂ O₃ ‐ZnO nanocomposite, carbohydrate, physicochemical features, UV‐visible spectroscopy, high resolution transmission electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, broth dilution method, 2′, 7′‐dichlorofluorescein diacetate staining, PA1 cell lines, comet assays, MTT assays, rod‐shaped nanostructures, surface coating, PA1 cell proliferation, DNA fragmentation, green nanotechnology, Fe₂ O₃ ‐ZnO, Fe₂ O₃      

On the accuracy of two analytical models for evaluating the performance of Gigabit Ethernet hosts

In this paper we develop and assess the accuracy of two analytical models that capture the behavior of network hosts when subjected to heavy load such as that of Gigabit Ethernet. The first analytical model is based on Markov processes and queuing theory, and the second is a pure Markov process. In order to validate the models and assess their accuracy, two different numerical examples are presented. The two numerical examples use system parameters that are realistic and appropriate for modern hardware. Both analytical models give closed-form solutions that facilitate the study of a number of important system performance metrics. These metrics include throughput, latency, stability condition, CPU utilizations of interrupt handling and protocol processing, and CPU availability for user applications. The two models give mathematically equivalent closed-form solutions for all metrics except for latency. To address latency, we compare the results of both models with the results of a discrete-event simulation. The latency accuracy of the two models is assessed relative to simulation in terms of differences and percentage errors. The paper shows that the second model is more accurate.     

A family of languages for architecture constraint specification

During software development, architecture decisions should be documented so that quality attributes guaranteed by these decisions and required in the software specification could be persisted. An important part of these architectural decisions is often formalized using constraint languages which differ from one stage to another in the development process. In this paper, we present a family of architectural constraint languages, called ACL. Each member of this family, called a profile, can be used to formalize architectural decisions at a given stage of the development process. An ACL profile is composed of a core constraint language, which is shared with the other profiles, and a MOF architecture metamodel. In addition to this family of languages, this paper introduces a transformation-based interpretation method of profiles and its associated tool.     

Extending software component models with the master–worker paradigm

Recent advances in computing and networking technologies—such as multi-core processors and high bandwidth wide area networks—lead parallel infrastructures to reach a higher degree of complexity. Programmers have to face with both parallel and distributed programming paradigms when designing an application. This is especially true when dealing with e-Science applications. Moreover, as parallel processing is moving to the mainstream, it does not seem appropriate to rely on low-level solutions requiring expert knowledge. This paper studies how to combine modern programming practices such as those based on software components and one of the most important parallel programming paradigms which is the well-known master–worker paradigm. The goal is to provide a simple and resource transparent model while enabling an efficient utilization of resources. The paper proposes a generic approach to embed the master–worker paradigm into software component models and describes how this generic approach can be implemented within an existing software component model. The overall approach is validated with synthetic experiments on clusters and the Grid’5000 testbed.