Passivity based visual servoing of mobile robots with dynamics compensation

This paper presents an image-based dynamic visual servoing to make a mobile robot able to track a moving object on the workspace by using a calibrated on board vision system. The stability of the proposed system is proved based on its passivity properties. A robustness analysis and an L₂-gain performance analysis are also presented. Experimental results are shown to illustrate the system performance.     

Real-Time Speaker Verification System Implemented on Reconfigurable Hardware

Nowadays, biometrics is considered as a promising solution in the market of security and personal verification. Applications such as financial transactions, law enforcement or network management security are already benefitting from this technology. Among the different biometric modalities, speaker verification represents an accurate and efficient way of authenticating a person’s identity by analyzing his/her voice. This identification method is especially suitable in real-life scenarios or when a remote recognition over the phone is required. The processing of a signal of voice, in order to extract its unique features, that allows distinguishing an individual to confirm or deny his/her identity is, usually, a process characterized by a high computational cost. This complexity imposes that many systems, based on microprocessor clocked at hundreds of MHz, are unable to process samples of voice in real-time. This drawback has an important effect, since in general, the response time needed by the biometric system affects its acceptability by users. The design based on FPGA (Field Programmable Gate Arrays) is a suited way to implement systems that require a high computational capability and the resolution of algorithms in real-time. Besides, these devices allow the design of complex digital systems with outstanding performance in terms of execution time. This paper presents the implementation of a MFCC (Mel-Frequency Cepstrum Coefficients)—SVM (Support Vector Machine) speaker verification system based on a low-cost FPGA. Experimental results show that our system is able to verify a person’s identity as fast as a high-performance microprocessor based on a Pentium IV personal computer.     

Identification and fine tuning of closed‐loop processes under discrete EWMA and PI adjustments

Conventional process identification techniques of a open‐loop process use the cross‐correlation function between historical values of the process input and of the process output. If the process is operated under a linear feedback controller, however, the cross‐correlation function has no information on the process transfer function because of the linear dependency of the process input on the output. In this paper, several circumstances where a closed‐loop system can be identified by the autocorrelation function of the output are discussed. It is assumed that a proportional integral controller with known parameters is acting on the process while the output data were collected. The disturbance is assumed to be a member of a simple yet useful family of stochastic models, which is able to represent drift. It is shown that, with these general assumptions, it is possible to identify some dynamic process models commonly encountered in manufacturing. After identification, our approach suggests to tune the controller to a near‐optimal setting according to a well‐known performance criterion. Copyright © 2001 John Wiley & Sons, Ltd.     

Changes of volatile compounds in wine vinegars during their elaboration in barrels made from different woods

Changes in the volatile components of red wine vinegars and balsamic vinegars were investigated during 1 year of aging in wood barrels and bottles. Barrels of four different woods (oak, chestnut, acacia and cherry) were used. A total of 57 volatile compounds were analysed by Gas Chromatography–Flame Ionization Detection (GC–FID) and Headspace Sorptive Extraction GC–Mass Spectrometry (HSSE-TD–GC–MS). We observed significant increases in the total content of volatile compounds only for balsamic vinegars. The concentrations of ethyl furoate, ethyl benzoate, benzaldehyde and acetophenone were highest in cherry barrels. These compounds, then, seem to be characteristic of this wood. Oak lactones presented the highest increases for vinegars aged in oak. Eugenol was only present in vinegars aged in chestnut and oak barrels. Oak and cherry seem to be the best type of wood for aging of vinegar due to their distinctive aromatic characteristics.     

Identification of New Coloured Anthocyanin–Flavanol Adducts in Pressure-Extracted Pomegranate (<Emphasis Type=BoldItalic>Punica granatum</Emphasis> L.) Juice by High-Performance Liquid Chromatography/Electrospray Ionization Mass Spectrometry

Pomegranate (Punica granatum L.) juice, obtained by pressure extraction of the whole fruit, contains coloured flavanol–anthocyanin adducts (the flavanol occupies the upper part of the dimmer) from the direct condensation between anthocyanidins delphinidin, cyanidin and pelargonidin and flavan-3-ols (epi)gallocatechin, (epi)catechin and (epi)afzelechin. The presence of adducts between these same flavanols and anthocyanidins, but belonging to the coloured anthocyanin–flavanol adduct type (anthocyanin occupies the upper part of the dimmer) has been revealed by reversed-phase liquid chromatography coupled to tandem mass spectrometry (ion trap), with positive electrospray ionization (LC–ESI/MS ⁿ ). These new adducts are isotopic with their corresponding counterparts (flavanol–anthocyanin adducts) and indistinguishable from them by comparison of the mass spectra from the MS² of the isotopic parent ions. However, they can be distinguished by comparison of the mass spectra from the MS³ of their corresponding isotopic aglycons. Hence, the MS³ of the aglycon from a given flavanol–anthocyanin adduct always yields a mass spectrum containing five characteristic ions, the three with smaller m/z being only dependent on the anthocyanidin and the other two on both the anthocyanidin and the flavanol. In contrast, the mass spectrum from the MS³ of the aglycon of its counterpart anthocyanin–flavanol adduct gives only two of the above five characteristic ions, where the ion with smaller m/z only depends on the anthocyanidin and the other on both the anthocyanidin and the flavanol. Ten 3-hexoside derivatives of coloured anthocyanin–flavanol adducts were detected in pomegranate juice being reported for the first time this type of adducts from a natural source.     

Evaluation of high oleic-high stearic sunflower hard stearins for cocoa butter equivalent formulation

Cocoa butter equivalents (CBEs) are produced from vegetable fats by blending palm mid fraction (PMF) and tropical butters coming from shea, mango kernel or kokum fat. In this regard, high oleic-high stearic (HOHS) sunflower hard stearins from solvent fractionation can be used in CBE production since their compositions and physical properties are similar to those found in the above-mentioned tropical butters. In this work, three sunflower hard stearins (SHS) ranging from 65% to 95% of disaturated triacylglycerols and a shea stearin (used as reference) were blended with PMF to evaluate their potential use in CBEs formulation. Isosolid phase diagrams of mixtures of PMF/SHS showed eutectic formation for SHS 65 and SHS 80, but monotectic behaviour with softening effect for SHS 95. Three CBEs from SHS and shea stearin were formulated according to phase behaviour diagrams and solid fat content data at 25 °C. Isosolid phase diagrams of mixtures of these CBEs with cocoa butter showed no eutectic behaviour. Therefore, CBEs elaborated from SHS exhibited full compatibility with cocoa butter.