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51.
When three dimensional measurements are conducted with fringe projection, the quality of the grating used for the generation of the fringes is important. It has a direct influence on the achievable depth resolution in a given measurement setup. In the past, Ronchi grating or gratings written in nematic liquid-crystal displays or in digital micromirror devices have been used. We report on the application of a reflective ferroelectric liquid-crystal-on-silicon display as the fringe-generating element in a setup based on a stereo microscope. With this device the depth resolution of measurements by use of phase-shifting algorithms can be significantly improved compared with the application of a Ronchi grating or a nematic liquid-crystal display. 相似文献
52.
Kouamé D Girault JM Patat F 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2003,50(3):257-266
Real-time flow velocity measurement is a practical issue in industrial and biomedical applications. Because their good frequency resolution, parametric methods such as autoregressive (AR) modeling and time-frequency distributions (TFD) are generally preferred to Fourier analysis. However, these methods become highly inaccurate in the presence of colored noise. We review here the principal parametric and nonparametric techniques and show their limitations in the estimation of Doppler frequency in the presence of strong colored noise. Different solutions to overcome these limitations are then proposed and compared using synthetic Doppler signals with colored noise. 相似文献
53.
Kouamé D Girault JM Remenieras JP Chemla JP Lethiecq M 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2003,50(3):267-278
For pt.I see ibid., vol.50, no.3, p.267-78 (2003). This paper presents an application of continuous wave ultrasound Doppler velocity measurements to two-phase flow in pipes. In many petroleum wells, the multiphase flow is separated into two phases: the first is a liquid phase and the second is a gas phase with small scatterers. The problem of multiphase velocity profile measurements has not been satisfactorily solved by classical approaches due to the multiphase nature of the fluid and the presence of colored noise, which introduces a significant bias in classical frequency estimators. We propose the use of resolution frequency techniques to overcome the classical limitations. Direct estimation of Doppler frequency then obtained using either time frequency maximum frequency or arguments of poles of the parametric model that identifies the Doppler part of the signal is discussed. The tests made with synthetic Doppler signals and two-phase flow have demonstrated the excellent performance of the high resolution techniques based on reassignment and parametric techniques. 相似文献
54.
Frédéric?Dreux Stéphane?MaraisEmail author Fabienne?Poncin-Epaillard Michel?Metayer Michel?Labbe Jean-Marc?Saiter 《Materials Research Innovations》2003,7(3):183-190
CF4 and CO2 plasma treatments have been used to modify the barrier properties of a polyamide 12 (PA12) towards permeant molecules, which
present opposing characteristics: water and toluene. The surface modifications were observed by atomic force microscopy, X-ray
photoelectron spectroscopy and surface Gibbs function measurements. Both treatments lead to different surfaces; one is rather
hydrophobic (with CF4) whereas the other is more hydrophilic (with CO2. The effect of this modification on permeametric properties has been investigated by liquid water and liquid toluene permeation
measurements. Our results show opposite effects of the two treatments. CF4 plasma treatment leads to a reduction of water and toluene permeability. With CO2 plasma treatment, in terms of permeation, two different behaviours were observed, an increase and a decrease of permeancy
for water and toluene respectively. These results are in full agreement with those obtained for the surface characterization,
and confirms change in the polymeric surface affinity for the permeant leading to a variation of the materials permeancy. 相似文献
55.
Eric Royer Maxime Lhuillier Michel Dhome Jean-Marc Lavest 《International Journal of Computer Vision》2007,74(3):237-260
This paper presents a new real-time localization system for a mobile robot. We show that autonomous navigation is possible
in outdoor situation with the use of a single camera and natural landmarks. To do that, we use a three step approach. In a
learning step, the robot is manually guided on a path and a video sequence is recorded with a front looking camera. Then a
structure from motion algorithm is used to build a 3D map from this learning sequence. Finally in the navigation step, the
robot uses this map to compute its localization in real-time and it follows the learning path or a slightly different path
if desired. The vision algorithms used for map building and localization are first detailed. Then a large part of the paper
is dedicated to the experimental evaluation of the accuracy and robustness of our algorithms based on experimental data collected
during two years in various environments. 相似文献
56.
57.
Nathalie Perrier Bruno Agard Pierre Baptiste Jean-Marc Frayret André Langevin Robert Pellerin Diane Riopel Martin Trépanier 《Computers & Operations Research》2013
Emergency response operations in electric distribution systems involve a host of decision-making problems at the reliability and contingency planning levels. Those operations include fault diagnosis, fault location, fault isolation, restoration, and repair. As the first of a two-part survey, this paper reviews optimization models and solution methodologies for reliability planning problems with fault considerations related to electric distribution operations. Contingency planning problems of emergency distribution response are discussed in the second part. The present paper surveys research on determining a distribution substation single-fault capacity, reallocating excess load, configuring distribution systems, partitioning a geographical area into service territories, and locating material stores and depots. 相似文献
58.
Jean-Marc Valin Author Vitae Daniel V. Smith Author Vitae Timothy B. Terriberry Author Vitae 《Computers & Electrical Engineering》2010,36(4):603-616
Signal processing applications use sinusoidal modelling for speech synthesis, speech coding, and audio coding. Estimation of the model parameters involves non-linear optimisation methods, which can be very costly for real-time applications. We propose a low-complexity iterative method that starts from initial frequency estimates and converges rapidly. We show that for N sinusoids in a frame of length L, the proposed method has a complexity of O(LN), which is significantly less than the matching pursuits method. Furthermore, the proposed method is shown to be more accurate than the matching pursuits and time-frequency reassignment methods in our experiments. 相似文献
59.
60.
Dominique Bigot Jean-Marc Roelandt Hocine Kebir 《Journal of Materials Processing Technology》2009,209(7):3226-3235
Nowadays, the simulation of forming process is rather well integrated in the industrial numerical codes. However, in order to take into account the possible modifications of the tool during rates of working, a dedicated numerical software is currently developed within the laboratory Roberval, this software allows to simulate forming process. The tool is discretized by boundary elements and the product, which is subjected to non-linearities, is discretized by finite elements. For the product, an isotrope law of behaviour is integrated, and the damage is taken into account by the uncoupled Rice and Tracey model. This paper deals with a contact algorithm, coupling boundary elements and finite elements, programmed in the software KSP. For that, friction is described by the Coulomb law and the resolution of contact problems is done by the penalty method. An adaptive step has been developed in order to increase the robustness of the contact algorithm. 相似文献