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Thomas Gmür Alain Schorderet 《International journal for numerical methods in engineering》2000,49(10):1267-1280
This paper describes an efficient and numerically stable algorithm for accurately computing the solutions of the quadratic eigenproblem associated to non‐proportionally viscously damped structures characterized by symmetric matrices. Combining the simultaneous inverse iteration with a generalized Rayleigh–Ritz analysis, the proposed procedure is well suited for extracting the subset of the lowest natural frequencies, the corresponding subcritical damping ratios and the mode shapes of large dissipative systems with non‐classical viscous damping. The iterative process exploits the specific nature of non‐proportionally damped structures, takes full advantage of the banded configuration of the structural matrices involved in the eigenproblem, avoids the computation of the left eigenvectors and circumvents the use of complex algebra owing to a unitary transformation strategy. An academic test case and an industrial numerical example are presented to highlight the effectiveness of the algorithm. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
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Caumes JP Younus A Salort S Chassagne B Recur B Ziéglé A Dautant A Abraham E 《Applied optics》2011,50(20):3604-3608
A monochromatic millimeter-wave imaging system coupled with an infrared temperature sensor has been used to investigate historic objects preserved at the Museum of Aquitaine (France). In particular, two-dimensional and three-dimensional analyses have been performed in order to reveal the internal structure of nearly 3500-year-old sealed Egyptian jars. 相似文献
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Alain Segundo Potts ;Basilio Thome de Freitas Jr. ;Jose Carlos Amaro 《能源与动力工程:英文版》2014,(7):1272-1278
This paper presents a fuzzy tuning system for real-time industrial PID (proportional-integral-derivative) controllers. The algorithm set the proportional gain, integral time and derivative time of a classical PID structure according to the set point, error and error derivative of the process, respectively. The tuning of the PID controller is based on a fuzzy inference machine. The set of rules of the fuzzy inference machine was obtained by experts engineering. The system is tested in an austempering process but can be applied in any industrial plant. Besides, an analysis between the response of the process with a PID controller and the system of fuzzy auto-tuning for P1D proposed was made. 相似文献
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Mazel V Richardin P Debois D Touboul D Cotte M Brunelle A Walter P Laprévote O 《Analytical chemistry》2007,79(24):9253-9260
A new protocol is implemented to demonstrate the presence of blood in the patina of African art objects from Mali. Divided into three steps, the protocol first consists in demonstrating the presence of proteins and localizing them in the sample's cross sections using time-of-flight secondary ion mass spectrometry (TOF-SIMS) and synchrotron-based infrared microspectrometry (microFT-IR). In a second time, TOF-SIMS is used to investigate heme, which is a blood marker. If heme is missing, which could mean that it is too degraded to be detected, X-ray microfluorescence (microXRF) and X-ray absorption near-edge microspectroscopy (microXANES) are used to prove the presence of iron in the protein area and to get a fingerprint of its chemical environment. This permits us thus to demonstrate that iron is indeed linked with proteins and not with mineral phases of the sample. Coupled with the ritual context of the objects, this constitutes a proof of the use of blood. Thanks to this protocol, which has the major advantage of avoiding false positive results, the presence of blood has been demonstrated in seven out of the eight studied samples. 相似文献
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Ecocomposites made up of polystyrene and starch were produced by co-grinding. The mechanism by which the composite is formed was identified by following the particle size and morphology. The size reduction of the matrix particles is favoured by the presence of starch which adheres on polystyrene surface, playing the role of agglomeration inhibitor between matrix particles. Thus, the filler is well dispersed in the matrix, permitting a good homogeneity of the composite properties. The hydrophilic behaviour of starch is reduced by co-grinding, resulting of a decrease of the acid and non dispersive components of the surface energies. Consequently the interactions between the initially hydrophobic matrix and hydrophilic filler are enhanced without using a compatibilizer. Thus, the water-resistance of the co-ground composite materials is better compared to blends since blends pellets introduced in water are rapidly disintegrated while an adapted co-grinding time permits to avoid this problem. It was seen that the diffusion coefficient of water in the composite pellets decreases with an increase of the co-grinding time for the lower filler rates, while it is the opposite for high filler rates. Moreover, the diffusion coefficient increases with the filler ratio. 相似文献
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Thomas Schareina Xiao-Feng Wu Alexander Zapf Alain Cotté Matthias Gotta Matthias Beller 《Topics in Catalysis》2012,55(7-10):426-431
The first copper-catalyzed trifluoromethylation of aryl halides was developed that utilizes inexpensive trifluoroacetates. Providing low concentrations of the most economically attractive and atom-efficient trifluoromethylation reagent this new protocol is advantageous compared to known procedures both economically and ecologically. 相似文献