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排序方式: 共有361条查询结果,搜索用时 93 毫秒
31.
Lotfi Ben Amor Louis-A. Dessaint Ouassima Akhrif Guy Olivier 《International Journal of Adaptive Control and Signal Processing》1993,7(2):117-136
In this paper a non-linear adaptive feedback-linearizing control is designed for a fifth-order model of a three-phase switched reluctance motor (SRM) which includes both electrical and mechanical dynamics. This non-linear adaptive control structure compensates for all the non-linearities between inputs and outputs, allows the use of a linear controller for motion tracking and improves the performance by reducing torque ripple of the SRM. A validated non-linear model of the SRM is used for the system simulation, while the control algorithm contains an adaptive scheme based on the parametrized model. Simulation results are given to demonstrate the effectiveness of the control method. 相似文献
32.
Damage evolution and infrared thermography in woven composite laminates under fatigue loading 总被引:2,自引:0,他引:2
An analytical model based on cumulative damage has been used for predicting the damage evolution in composite materials. The model is verified with experimental data from a carbon/epoxy composite fatigued under tension–tension load. Fatigue tests of specimens have been monitored with an infra-red thermography system. By analysing the temperature of the external surface during the application of cyclic loading, it is possible to evaluate the damage evolution. The model agrees well with the experimental data, and it can be used to predict the evolution of damage in composites. 相似文献
33.
Résumé Dans cet article, les auteurs comparent les propriétés structurales et hydriques de deux pates de ciment durcies, l'une ordinaire
(CO) et l'autre (CH) représentative de bétons à très hautes performances dont l'utilisation est croissante à l'heure actuelle
dans le domaine de la construction.
L'analyse de la structure poreuse montre le caractère fortement compact de la microstructure de la pate de ciment durcie CH.
Ce caractère est également illustré par les isothermes de désorption et d'adsorption de vapeur d'eau. Les courbes obtenues
dans deux laboratoires sont comparées. Elles mettent en évidence la faible sensibilité des matériaux à très hautes performances
vis-à-vis des variations de l'humidité relative de leur environnement, dans le domaine HR>50%. Ceci laisse prévoir des déformations
hygrométriques (retrait de dessiccation) réduites dans ce domaine, par rapport aux matériaux ordinaires.
Les résultats des mesures de perméabilité à la vapeur d'eau montrent l'influence du paramètre teneur en eau. La pate CH présente,
dans le domaine des fortes humidités relatives, une perméabilité plus faible que celle de la pate CO. La perméabilité à la
vapeur d'eau de ces pates de ciment durcies reste toutefois très faible par rapport à celle d'autres matériaux de construction.
Note de la rédaction Mme V. Baroghel Bouny travaille au Laboratoire Central des Ponts et Chaussées (LCPC), Membre Titulaire de la RILEM. 相似文献
Experimental determination of moisture properties of hardened cement pastes, showing hysteresis effects
In this paper, the structure and moisture properties of two hardened cement pastes are compared. One paste (CO) is an ordinary mix. The other paste (CH) is representative of high-performance concretes which are today more and more widely used in construction. The pore structure analysis shows the very dense microstructure of the hardened cement paste CH. This feature is also pointed out with water vapour desorption and adsorption isotherms. The curves obtained in two laboratories are compared. They highlight that high-performance materials are fairly insensitive to environmental relative humidity variations, in the range RH>50%. Smaller hygral strains (drying shrinkage) can be expected in this range, as compared to ordinary mixes. The results of water vapour permeability measurements show the influence of the water content. The permeability obtained for the hardened cement paste CH is lower than for CO, in the high relative humidity range. The water vapour permeability of these hardened cement pastes is, however, very low as compared to other building materials.
Note de la rédaction Mme V. Baroghel Bouny travaille au Laboratoire Central des Ponts et Chaussées (LCPC), Membre Titulaire de la RILEM. 相似文献
34.
Mourad Loulou Dominique Dallet Nouri Masmoudi Philippe Marchegay Lotfi Kamoun 《Analog Integrated Circuits and Signal Processing》2004,39(1):81-87
This article presents a low-pass sigma-delta modulator for Analogue-to-Digital conversion. The circuit uses a switched-current technique which presents a well known drawback called clock feedthrough. This phenomenon induces an error on the output signal value. In order to cancel the clock feedthrough effect, we use a new method based on a current feedback loop. The circuit is designed in 0.8 μm AMS “Austria Mikro Systems” single poly CMOS process. Measurements of the modulator are performed under A/D converters characterisation system, and show 55 dB dynamic range at 2.048 MHz sampling rate with 8 kHz input frequency bandwidth. These characteristics are suitable for audio applications. 相似文献
35.
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37.
Generating a Condensed Representation for Association Rules 总被引:1,自引:0,他引:1
Nicolas?PasquierEmail author Rafik?Taouil Yves?Bastide Gerd?Stumme Lotfi?Lakhal 《Journal of Intelligent Information Systems》2005,24(1):29-60
Association rule extraction from operational datasets often produces several tens of thousands, and even millions, of association rules. Moreover, many of these rules are redundant and thus useless. Using a semantic based on the closure of the Galois connection, we define a condensed representation for association rules. This representation is characterized by frequent closed itemsets and their generators. It contains the non-redundant association rules having minimal antecedent and maximal consequent, called min-max association rules. We think that these rules are the most relevant since they are the most general non-redundant association rules. Furthermore, this representation is a basis, i.e., a generating set for all association rules, their supports and their confidences, and all of them can be retrieved needless accessing the data. We introduce algorithms for extracting this basis and for reconstructing all association rules. Results of experiments carried out on real datasets show the usefulness of this approach. In order to generate this basis when an algorithm for extracting frequent itemsets—such as Apriori for instance—is used, we also present an algorithm for deriving frequent closed itemsets and their generators from frequent itemsets without using the dataset. 相似文献
38.
The nature of the stannite ion, produced by the anodic dissolution of tin, in sodium hydroxide solutions was determined by emf measurements. The results are best explained if the ion has the formula Sn(OH)?3. A new value for the standard potential of the reaction is proposed. 相似文献
39.
Said Barkati Lotfi Baghli El Madjid Berkouk Mohamed-Seghir Boucherit 《Electric Power Systems Research》2008
This paper describes two evolutionary algorithms for the optimized harmonic stepped–waveform technique. Genetic algorithms and particle swarm optimization are applied to compute the switching angles in a three-phase seven-level inverter to produce the required fundamental voltage while, at the same time, specified harmonics are eliminated. Furthermore, these algorithms are also used to solve the starting point problem of the Newton-Raphson conventional method. This combination provides a very effective method for the harmonic elimination technique. This strategy is useful for different structures of seven-level inverters. The diode-clamped topology is considered in this study. 相似文献
40.
Nadir Ouldhamadouche Amine Achour Raul Lucio-Porto Mohammad Islam Shahram Solaymani Ali Arman Azin Ahmadpourian Hamed Achour Laurent Le Brizoual Mohamed Abdou Djouadi Thierry Brousse 《材料科学技术学报》2018,34(6):976-982
Vanadium nitride(VN) was deposited by DC-sputtering on a vertically aligned carbon nanotube(CNTs)template for the purpose of nano-structuration. This led to the fabrication of hierarchically composite electrodes consisting of porous and nanostructured VN grown on vertically aligned CNTs in a nano-treelike configuration for micro-supercapacitor application. The electrodes show excellent performance with an areal capacitance as high as 37.5 m F cm~(-2) at a scan rate of 2 mV s~(-1) in a 0.5 MK_2SO_4 mild electrolyte solution. Furthermore, the capacitance decay was only 15% after 20,000 consecutive cycles. Moreover,the capacitance was found to increase with VN deposit thickness. The X-ray photoelectron spectroscopy analyses of the electrodes before and after cycling suggest that the oxide layers that form at the VN surface is the responsible for the redox energy storage in this material. Such electrodes can compete with other transition metal nitride based electrodes for micro-supercapacitors. 相似文献