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11.
12.
S. Zouari M. Maatar T. Fakhfakh M. Haddar 《Journal of Failure Analysis and Prevention》2010,10(6):531-539
The objective of this study was to follow the crack propagation in the tooth foot of a spur gear by using Linear Elastic Fracture
Mechanics (LEFM) and the Finite Element Method (FEM). The tooth foot crack propagation is a function of Stress Intensity Factors
(SIF) that play a very crucial role in the life span of the gear. A two-dimensional quasi-static analysis is carried out using
a program that determines the gear geometry, coupled with the Finite Element Code (ANSYS). The study estimates the stress
intensity factors and monitors their variations on the tooth foot according to crack depth, crack propagation angle, and the
crack position. An appropriate methodology for predicting the crack propagation path is applied by considering gear tooth
behavior in bending fatigue. The results are used to predict/prevent catastrophic rim fracture failure modes from occurring
in critical components. 相似文献
13.
Protection should fundamentally be flexible for devices roaming in Beyond 3G networks. In this federation of heterogeneous access networks, each sub-network comes with its own security requirements, policies, and protocols. Foundational element of device security, the embedded OS itself, should become adaptable to make it possible to tune its protection mechanisms to the current security context, notably to support multiple authorization policies. We show how flexibility can be applied to the kernel authorization architecture by adopting a component-based OS design, the component serving as single abstraction for reconfiguration and security. We present a policy-neutral access control architecture called CRACKER (Component-based Reconfigurable Access Control for KERnels) for component-based operating systems. CRACKER supports a wide range of authorization policies, and permits policy reconfiguration, in the same or in different security models. Specified in the Fractal component model, and implemented in the Think OS, CRACKER illustrates how flexible kernel authorization can be realized while maintaining acceptable system performance. 相似文献
14.
This study aims at gaining a better understanding of the microstructural features that control the mechanical and the tribological performances of WC–12 wt.% Co coatings under High Velocity Oxygen Fuel (HVOF) spraying conditions. This paper looks at the influences of the HVOF process parameters for WC–12Co material on the microstructural and the tribological behaviours of the coatings. The correlation between the coating microstructure and the wear behaviour is investigated by observing and analysing the microstructure and by studying the friction moment using enhanced statistical tool based on neural computations. According to the experimental and the numerical results, it has been shown that the spray parameters affect the phase composition, hardness and porosity of HVOF sprayed WC–12Co coatings and the correlations with HVOF process parameters are fully predictable in the steady-state regime. 相似文献
15.
Tahar Boubellouta Romdhane Karoui Annick Lebecque Éric Dufour 《European Food Research and Technology》2010,231(6):873-882
Twelve samples of cheeses (three types of Saint-Nectaire PDO cheeses and Savaron cheeses) differing by manufacturing and ripening
conditions, from 12 different producers, were characterised by attenuated total reflectance mid-infrared (MIR) and front-face
fluorescence spectroscopies, dynamic testing rheology and physico-chemical analysis. Fluorescence spectra (tryptophan residues,
vitamin A and riboflavin) and MIR (3,000–2,800 (fat region), 1,700–1,500 (protein region) and 1,500–900 cm−1 (fingerprint region)) spectra were recorded on cheese samples. The potential of the data tables was investigated for discriminating
the four different groups of cheeses. The results of factorial discriminant analysis (FDA) performed on the fluorescence and
mid-infrared spectra showed a good discrimination of the four cheese groups. Considering cross-validation results, the best
classifications (100%) were achieved from mid-infrared and fluorescence spectra, while only 91.7 and 72.2% of correct classification
were obtained by applying FDA to rheology and physico-chemical data, respectively. Spectroscopic techniques could provide
useful fingerprints and allow the identification of investigated cheeses according to manufacturing conditions. Simple and
rapid spectroscopic methods offer a promising approach to the authentication of cheeses. 相似文献
16.
Amr?T.?Abdel-HamidEmail author Sofiéne?Tahar El?Mostapha?Aboulhamid 《Design Automation for Embedded Systems》2004,9(3):211-227
Intellectual property (IP) block reuse is essential for facilitating the design process of system-on-a-chip. Sharing IP designs poses significant high security risks. Recently, digital watermarking emerged as a candidate solution for copyright protection of IP blocks. In this paper, we survey and classify different techniques used for watermarking IP designs. To this end, we defined several evaluation criteria, which can also be used as a benchmark for new IP watermarking developments. Furthermore, we established a comprehensive set of requirements for future IP watermarking techniques. 相似文献
17.
Molka Attia Hili Tahar Fakhfakh Mohamed Haddar 《Journal of Engineering Mathematics》2007,57(4):351-363
Free vibrations of a spinning disk–shaft system are analysed using the finite-element method. The spinning disk is described
by the Kirchhoff plate theory. The shaft is modelled by a rotating beam. Using Lagrange’s principle and including the rigid-body
translation and tilting motion, equations of motion of the spinning flexible disk and shaft are derived consistently to satisfying
the geometric compatibility conditions on the internal boundaries among the substructures. The finite-element method is then
used to discretize the derived governing equations. The method is applied to the shaft–disk spinning system. The sensitivity
to the running speed as well as the effect of both disk flexibility and boundary condition on the natural frequencies of the
spinning system are numerically investigated. 相似文献
18.
L. Ben Tahar M. Artus F. Herbst S. Ammar F. Fiévet 《Materials Research Bulletin》2007,42(11):1888-1896
Pure nanoparticles of the CoFe2−xRExO4 (RE = Gd, Sm; x = 0.0, 0.1) system have been prepared by forced hydrolysis in polyol. The insertion of Sm3+ and Gd3+ cations into the cobalt ferrite structure has been investigated. X-ray micro-analysis (EDX) shows that the RE contents are close to the nominal ones. X-ray diffraction (XRD) evidences a cell size increase with slight distortions in the spinel-like lattice indicating the entrance of RE3+ ions. Micro-Raman spectroscopy confirms the cubic inverse-spinel structure and rules out the existence of impurities like hematite. Magnetic measurements (SQUID) show important differences in the magnetic properties of the unsubstituted and substituted particles. All the particles are superparamagnetic at room temperature and ferrimagnetic at low temperature. However, their main magnetic characteristics appear to be directly dependent on the RE content. 相似文献
19.
Markov chains are extensively used in modeling different aspects of engineering and scientific systems, such as performance of algorithms and reliability of systems. Different techniques have been developed for analyzing Markovian models, for example, Markov Chain Monte Carlo based simulation, Markov Analyzer, and more recently probabilistic model-checking. However, these techniques either do not guarantee accurate analysis or are not scalable. Higher-order-logic theorem proving is a formal method that has the ability to overcome the above mentioned limitations. However, it is not mature enough to handle all sorts of Markovian models. In this paper, we propose a formalization of Discrete-Time Markov Chain (DTMC) that facilitates formal reasoning about time-homogeneous finite-state discrete-time Markov chain. In particular, we provide a formal verification on some of its important properties, such as joint probabilities, Chapman-Kolmogorov equation, reversibility property, using higher-order logic. To demonstrate the usefulness of our work, we analyze two applications: a simplified binary communication channel and the Automatic Mail Quality Measurement protocol. 相似文献
20.
A comparative evaluation of filter-based feature selection methods for hyper-spectral band selection
Bo Wu Chongcheng Chen Tahar Mohand Kechadi Liya Sun 《International journal of remote sensing》2013,34(22):7974-7990
Band selection (dimensionality reduction) plays an essential role in hyper-spectral image processing and applications. This article presents a unified comparison framework for systematic performance comparison of filter-based feature selection models and conducts a comparative evaluation of four methods: maximal minimal associated index (MMAIQ), mutual information-based max-dependency criterion (mRMR), relief feature selection (Relief-F), and correlation-based feature selection (CFS) for hyper-spectral band selection. The evaluation is based on the performance of effectiveness, robustness, and classification accuracy, which involves five measuring indices: class separability, feature entropy, feature stability, feature redundancy, and classification accuracy. Three images acquired by different sensors were used to investigate the performance of the metrics. Experimental results show the best results for MMAIQ for all data sets in terms of used measurements, except for feature stability where mRMR and Relief-F exhibit their superiority. 相似文献