On-line efficiency improvement of induction motor vector controlled

Efficiency improvement is an important challenge for electric motor driven systems. For an induction motor, operation under rated conditions (at rated load with rated flux) is very efficient. However, in many situations, operation with rated flux causes low efficiency especially at light load ranges. In these applications, induction motor should operate at reduced flux which causes a balance between iron losses and copper losses leading to an improved efficiency. This paper concerns energy optimization, i.e. efficiency improvement is carried out via a controller designed on the basis of imposing the rated power factor, by finding a relationship between rotor flux and torque current component which can optimize the compromise between torque and efficiency in steady state as well as in transient state. Experimental results are presented to prove the effectiveness and validity of the proposed controller

A data-driven functional projection approach for the selection of feature ranges in spectra with ICA or cluster analysis

Prediction problems from spectra are largely encountered in chemometry. In addition to accurate predictions, it is often needed to extract information about which wavelengths in the spectra contribute in an effective way to the quality of the prediction. This implies to select wavelengths (or wavelength intervals), a problem associated to variable selection. In this paper, it is shown how this problem may be tackled in the specific case of smooth (for example infrared) spectra. The functional character of the spectra (their smoothness) is taken into account through a functional variable projection procedure. Contrarily to standard approaches, the projection is performed on a basis that is driven by the spectra themselves, in order to best fit their characteristics. The methodology is illustrated by two examples of functional projection, using Independent Component Analysis and functional variable clustering, respectively. The performances on two standard infrared spectra benchmarks are illustrated.Comment: A paraitr

Study of electropolymerized PEDOT:PSS transducers for application as electrochemical sensors in aqueous media

Electropolymerized poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) onto screen-printed platinum electrodes was tested for stable charge/discharge cycle using cyclic voltammetry (CV) in aqueous media and its adhesion to the electrode surface was also examined. Electropolymerized PEDOT:PSS maintained most of its initial CV behavior after water-flow test (flow rate = 1 ml/s), whereas drop-cast PEDOT:PSS did not, indicating better adhesion and retention of the polymer's mechanical and electrical properties. Field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDS) suggest that film structure influence the stability of the redox current measurements. These results prove that careful electropolymerization techniques for synthesizing the PEDOT:PSS transducer are worth pursuing in developing robust electrochemical sensors suitable for continuous use in aqueous media. Developing such transducers is important for developing electrochemical sensors for biomedical and/or environmental monitoring where aqueous flow usually occurs on electrode surfaces

Effectiveness of multi-walled carbon nanotubes and activated carbon for capturing E. coli 0157:H7 for application in water filtration

The ability of unmodified and functionalized carbon nanotubes (MWCNTs) to capture Escherichia coli 0157:H7 from water was tested and compared with activated carbon (AC). This study aims to test the effectiveness of these materials to filter out this bacteria strain. Chemical oxidation was used to functionalize MWCNTs to achieve the desired oxygenated functional groups, which was analysed with Fourier transform infrared spectroscopy (FTIR). Field emission scanning electron microscopy (FESEM) was used to verify bacteria capture after water filtration on both functionalized and unmodified MWCNTs and AC respectively. Results showed that the bacteria were captured on functionalized MWCNTs and unmodified AC; however, the bacteria were not detectable on unmodified MWCNTs and functionalized AC. The results indicate that the presence of specific carboxyl functional groups on the surface of functionalized MWCNTs and morphology of the unmodified AC is relevant for Escherichia coli 0157:H7 capture

Mutual information for the selection of relevant variables in spectrometric nonlinear modelling

Data from spectrophotometers form vectors of a large number of exploitable variables. Building quantitative models using these variables most often requires using a smaller set of variables than the initial one. Indeed, a too large number of input variables to a model results in a too large number of parameters, leading to overfitting and poor generalization abilities. In this paper, we suggest the use of the mutual information measure to select variables from the initial set. The mutual information measures the information content in input variables with respect to the model output, without making any assumption on the model that will be used; it is thus suitable for nonlinear modelling. In addition, it leads to the selection of variables among the initial set, and not to linear or nonlinear combinations of them. Without decreasing the model performances compared to other variable projection methods, it allows therefore a greater interpretability of the results

AUTHENTIFICATION D’INDIVIDUS PAR RECONNAISSANCE DE VISAGES

La vérification de visage est un outil important pour l'authentification d'un individu. Elle peut être de valeur significative dansla sécurité et les applications de commerce. Le but assigné à ce travail est de faire l’authentification d’individus. Pour cela,nous avons utilisé un modèle Biométrique. La biométrie est la science qui étudie les méthodes de vérification d’identité(authentification), identification, ou même de chiffrement basées sur la reconnaissance de caractéristiques physiologiques del’individu. Pour être efficaces dans leur exploitation Ces caractéristiques doivent bien entendu posséder certaines qualitésintrinsèques pour permettre le développement de systèmes fiables et robustes. Les qualités indispensables pour chaquecaractéristique sont les suivantes : l’universalité, unicité, permanence, collectabilité et mesurabilité. Celles-ci assurent quechaque personne possède la caractéristique considérée, qu’elle est unique pour chaque individu, qu’elle ne change pas ou peudans le temps, qu’il est possible d’en récolter un échantillon et de l’analyser. Pour notre application, nous avons choisi pourl’extraction des caractéristiques la méthode de ACP (analyse en composantes principales) [1]. Une fois que le vecteurcaractéristique du visage est extrait, l’étape suivante consiste à le comparer avec le vecteur caractéristique de l’identitéproclamée. Ici, il s'agit de classer l'utilisateur comme un vrai utilisateur ou un imposteur. Par la suite le taux d’erreur est calculédans les deux ensembles, de validation et de test pour la base de données XM2VTS [2] selon le protocole de Lausanne [3]

Resampling methods for parameter-free and robust feature selection with mutual information

Combining the mutual information criterion with a forward feature selection strategy offers a good trade-off between optimality of the selected feature subset and computation time. However, it requires to set the parameter(s) of the mutual information estimator and to determine when to halt the forward procedure. These two choices are difficult to make because, as the dimensionality of the subset increases, the estimation of the mutual information becomes less and less reliable. This paper proposes to use resampling methods, a K-fold cross-validation and the permutation test, to address both issues. The resampling methods bring information about the variance of the estimator, information which can then be used to automatically set the parameter and to calculate a threshold to stop the forward procedure. The procedure is illustrated on a synthetic dataset as well as on real-world examples

PEDOT:PSS–MODIFIED PLATINUM MICROELECTRODES FOR MEASUREMENTS IN AQUEOUS MEDIA: EFFECT OF POLYMER SURFACE AREA ON LONG-TERM ANODIC PEAK CURRENT STABILITY

Contamination of drinking water by hazardous agents is becoming a serious global threat, so it is necessary to develop more efficient sensing technologies for applications in liquid media. The limited working lifetime of electrochemical biosensors, especially when measurements are made continuously in liquid media, remains an unsolved challenge. We studied the effect of PEDOT:PSS surface area on platinum microelectrodes with respect to electrode ability to conduct reversible ion-to-electron transduction in liquid media. Electropolymerization of 3,4-ethylenedioxythiophene:poly(styrene sulfonate) EDOT:PSS to poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) was conducted on microplatinum electrodes 5 and 10 mm long using a galvanostatic mode. Cyclic voltammetry was used to determine capacitive peak current; higher peak current indicates higher redox capacitance. Field-emisison scanning-electron microscopy was used to study the surface morphology of the PEDOT:PSS transucer layer after measurement in liquid media. The anodic capacitive peak currents did not differ significantly between the two electrodes at day one (~0.20 mA); however, peak current decreased by ~ 20% and ~ 80% at day six for 10- and-5 mm electrode lengths, respectively. The results imply that PEDOT:PSS surface area plays a role in transduction of PEDOT:PSS in aqueous media