Masson M.-H.,University of Picardie Jules Verne |
Masson M.-H.,French National Center for Scientific Research |
Denoeux T.,University Of Technology Of Compigne |
Denoeux T.,French National Center for Scientific Research
International Journal of Approximate Reasoning | Year: 2011
In this paper, belief functions, defined on the lattice of intervals partitions of a set of objects, are investigated as a suitable framework for combining multiple clusterings. We first show how to represent clustering results as masses of evidence allocated to sets of partitions. Then a consensus belief function is obtained using a suitable combination rule. Tools for synthesizing the results are also proposed. The approach is illustrated using synthetic and real data sets. © 2010 Elsevier Inc. All rights reserved.
Randall R.B.,University of New South Wales |
Antoni J.,University Of Technology Of Compigne
Mechanical Systems and Signal Processing | Year: 2011
This tutorial is intended to guide the reader in the diagnostic analysis of acceleration signals from rolling element bearings, in particular in the presence of strong masking signals from other machine components such as gears. Rather than being a review of all the current literature on bearing diagnostics, its purpose is to explain the background for a very powerful procedure which is successful in the majority of cases. The latter contention is illustrated by the application to a number of very different case histories, from very low speed to very high speed machines. The specific characteristics of rolling element bearing signals are explained in great detail, in particular the fact that they are not periodic, but stochastic, a fact which allows them to be separated from deterministic signals such as from gears. They can be modelled as cyclostationary for some purposes, but are in fact not strictly cyclostationary (at least for localised defects) so the term pseudo-cyclostationary has been coined. An appendix on cyclostationarity is included. A number of techniques are described for the separation, of which the discrete/random separation (DRS) method is usually most efficient. This sometimes requires the effects of small speed fluctuations to be removed in advance, which can be achieved by order tracking, and so this topic is also amplified in an appendix. Signals from localised faults in bearings are impulsive, at least at the source, so techniques are described to identify the frequency bands in which this impulsivity is most marked, using spectral kurtosis. For very high speed bearings, the impulse responses elicited by the sharp impacts in the bearings may have a comparable length to their separation, and the minimum entropy deconvolution technique may be found useful to remove the smearing effects of the (unknown) transmission path. The final diagnosis is based on "envelope analysis" of the optimally filtered signal, but despite the fact that this technique has been used for 40 years in analogue form, the advantages of more recent digital implementations are explained. © 2010 Elsevier Ltd.All rights reserved.
Sbodio M.L.,Hewlett - Packard |
Martin D.,SRI International |
Moulin C.,University Of Technology Of Compigne
Journal of Web Semantics | Year: 2010
This paper describes a novel approach to the description and discovery of Semantic Web services. We propose SPARQL as a formal language to describe the preconditions and postconditions of services, as well as the goals of agents. In addition, we show that SPARQL query evaluation can be used to check the truth of preconditions in a given context, construct the postconditions that will result from the execution of a service in a context, and determine whether a service execution with those results will satisfy the goal of an agent. We also show how certain optimizations of these tasks can be implemented in our framework. © 2010 Elsevier B.V. All rights reserved.
Chen D.,Beijing University of Technology |
Bonis M.,University Of Technology Of Compigne |
Zhang F.,Harbin Institute of Technology |
Dong S.,Harbin Institute of Technology
Precision Engineering | Year: 2011
This paper proposes a thermo-mechanical error model of a hydrostatic spindle for a high precision machine tool. By predicting the variation of motion error induced by thermal effects on a machine worktable during machining, this model allows deeper insights into the underlying mechanisms that result in evolutions of the spindle accuracy. The heat power generated in the spindle elements and the coefficients of convection heat transfer over its outer surface have been evaluated. Then, the distribution of temperature and deformation of the spindle have been simulated by a finite element coupled thermo-elastic model, from which the influence on notably spindle stiffness variation was deduced. Experimental measurement of the thrust plate axial displacement under thermal expansion is in close agreement with the computed axial thermal expansion. © 2011 Elsevier Inc.
Grimi N.,University Of Technology Of Compigne |
Mamouni F.,Sultan Moulay Slimane University |
Lebovka N.,University Of Technology Of Compigne |
Lebovka N.,Ukrainian Academy of Sciences |
And 2 more authors.
Journal of Food Engineering | Year: 2011
The purpose of this study was to compare the effects of pulsed electric field (PEF) on apple juice characteristics (turbidity, polyphenolic content and antioxidant capacities). The pressing was used as a standard method for juice extraction. Experiments were carried out at a constant pressure (P = 3 bar) using a laboratory press cell. Two different methods for PEF application at 400 V/cm were investigated (PEF treatment of whole samples before cutting and PEF treatment of apple slices after cutting). PEF treatment resulted in increase of the juice yield from 44 g/100 g apple (untreated samples) to 58 g/100 g apple (treatment of whole apples) and 64 g/100 g apple (treatment of slices) after 30 min of pressing. The analysis of pH and conductivity showed no significant difference between untreated and PEF-treated samples. However, the total soluble matter content of juice increased after PEF treatment. The obtained turbidity and transmittance data evidence a noticeable improvement of juice clarity for PEF-treated samples. The PEF pre-treatment was accompanied by an increase of the content of polyphenols and intensification of the antioxidant capacities of juice. Most of these effects (juice clarity and content of antioxidants) were more pronounced for the whole treated apples as compared to untreated apples and PEF-treated apple slices. The evolution of apple browning before and after PEF treatment was more pronounced for whole samples. PEF treatment accelerates browning. The obtained data can contribute to the determination of an optimum time for PEF application. The results evidence that PEF-enhanced expression is promising for production of higher quality juices. PEF treatment of whole apples reduces the energy consumption and is advantageous for industrial applications as compared to the treatment of apple slices. PEF combined with pressing can become a good alternative to traditional process. © 2010 Elsevier Ltd. All rights reserved.