Imagerie 3D de particules individuelles

peer reviewedIn recent years, impressive progress has been made in digital imaging and in particular in three dimensional visualisation and analysis of objects. This paper reviews the most recent literature on three dimensional imaging with a special attention to particulate systems analysis. After an introduction recalling some important concepts in spatial sampling and digital imaging, the paper reviews a series of techniques with a clear distinction between the surfometric and volumetric principles. The literature review is as broad as possible covering materials science as well as biology while keeping an eye on emerging technologies in optics and physics. The paper should be of interest to any scientist trying to picture particles in 3D with the best possible resolution for accurate size and shape estimation. Though techniques are adequate for nanoscopic and microscopic particles, no special size limit has been considered while compiling the review

Wide-field anterior ocular surface morphometrics

The current understanding of anterior eye shape in humans is limited due to available technology and its accessibility. Accurate curvature metrics of specific areas of the peripheral cornea, corneo-limbal junction and anterior sclera have remained obscured by the limits of the palpebral aperture, since the upper and lower eyelids cover most of the vertical aspect. This thesis starts by comparing the ‘gold standard’ keratometry measurements to commonly used topographic systems. Keratometric analogues were found to be significantly different and in addition provided spurious vertical anterior ocular surface (AOS) profiles. These findings revealed a need to establish an accurate model. Magnetic resonance imaging (MRI) potentially offers the best opportunity to image the entire AOS structure. However, preliminary studies in this thesis demonstrated that the use of a 3-Tesla MRI scanner was unable to obtain sufficiently resolute data to meet requirements. As an alternative, ocular impression taking techniques were adopted during the remainder of this work to acquire the AOS data. Eye casts from impression moulds were scanned using active laser triangulation and virtual 3-dimensional surfaces rendered. Further investigations defined the most suitable material for impression taking and the amount of deformation of the AOS caused by the procedure. The ocular impression casting and scanning process was examined for accuracy and reliability. This protocol was used to sample a population of normal white European eyes in order to establish a database and define wide-field AOS variability. Volumetric and 2-dimensional topographic profiles were extracted from the digital 3-dimensional representation obtained, allowing for the analysis of point-to-point curvature differences. For the first time, the entire AOS shape has been defined with known accuracy. In addition, effects of myopic refractive error and gender are presented. This data is of potential importance to ophthalmic surgeons, ocularists, contact lens practitioners, vision scientists and researchers, in the form of a digital archive of normal white European wide-field AOS topography as a reference source.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Wide-field anterior ocular surface morphometrics

The current understanding of anterior eye shape in humans is limited due to available technology and its accessibility. Accurate curvature metrics of specific areas of the peripheral cornea, corneo-limbal junction and anterior sclera have remained obscured by the limits of the palpebral aperture, since the upper and lower eyelids cover most of the vertical aspect. This thesis starts by comparing the ‘gold standard’ keratometry measurements to commonly used topographic systems. Keratometric analogues were found to be significantly different and in addition provided spurious vertical anterior ocular surface (AOS) profiles. These findings revealed a need to establish an accurate model. Magnetic resonance imaging (MRI) potentially offers the best opportunity to image the entire AOS structure. However, preliminary studies in this thesis demonstrated that the use of a 3-Tesla MRI scanner was unable to obtain sufficiently resolute data to meet requirements. As an alternative, ocular impression taking techniques were adopted during the remainder of this work to acquire the AOS data. Eye casts from impression moulds were scanned using active laser triangulation and virtual 3-dimensional surfaces rendered. Further investigations defined the most suitable material for impression taking and the amount of deformation of the AOS caused by the procedure. The ocular impression casting and scanning process was examined for accuracy and reliability. This protocol was used to sample a population of normal white European eyes in order to establish a database and define wide-field AOS variability. Volumetric and 2-dimensional topographic profiles were extracted from the digital 3-dimensional representation obtained, allowing for the analysis of point-to-point curvature differences. For the first time, the entire AOS shape has been defined with known accuracy. In addition, effects of myopic refractive error and gender are presented. This data is of potential importance to ophthalmic surgeons, ocularists, contact lens practitioners, vision scientists and researchers, in the form of a digital archive of normal white European wide-field AOS topography as a reference source.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Wide-field anterior ocular surface morphometrics

The current understanding of anterior eye shape in humans is limited due to available technology and its accessibility. Accurate curvature metrics of specific areas of the peripheral cornea, corneo-limbal junction and anterior sclera have remained obscured by the limits of the palpebral aperture, since the upper and lower eyelids cover most of the vertical aspect. This thesis starts by comparing the ‘gold standard’ keratometry measurements to commonly used topographic systems. Keratometric analogues were found to be significantly different and in addition provided spurious vertical anterior ocular surface (AOS) profiles. These findings revealed a need to establish an accurate model. Magnetic resonance imaging (MRI) potentially offers the best opportunity to image the entire AOS structure. However, preliminary studies in this thesis demonstrated that the use of a 3-Tesla MRI scanner was unable to obtain sufficiently resolute data to meet requirements. As an alternative, ocular impression taking techniques were adopted during the remainder of this work to acquire the AOS data. Eye casts from impression moulds were scanned using active laser triangulation and virtual 3-dimensional surfaces rendered. Further investigations defined the most suitable material for impression taking and the amount of deformation of the AOS caused by the procedure. The ocular impression casting and scanning process was examined for accuracy and reliability. This protocol was used to sample a population of normal white European eyes in order to establish a database and define wide-field AOS variability. Volumetric and 2-dimensional topographic profiles were extracted from the digital 3-dimensional representation obtained, allowing for the analysis of point-to-point curvature differences. For the first time, the entire AOS shape has been defined with known accuracy. In addition, effects of myopic refractive error and gender are presented. This data is of potential importance to ophthalmic surgeons, ocularists, contact lens practitioners, vision scientists and researchers, in the form of a digital archive of normal white European wide-field AOS topography as a reference source

New advances in vehicular technology and automotive engineering

An automobile was seen as a simple accessory of luxury in the early years of the past century. Therefore, it was an expensive asset which none of the common citizen could afford. It was necessary to pass a long period and waiting for Henry Ford to establish the first plants with the series fabrication. This new industrial paradigm makes easy to the common American to acquire an automobile, either for running away or for working purposes. Since that date, the automotive research grown exponentially to the levels observed in the actuality. Now, the automobiles are indispensable goods; saying with other words, the automobile is a first necessity article in a wide number of aspects of living: for workers to allow them to move from their homes into their workplaces, for transportation of students, for allowing the domestic women in their home tasks, for ambulances to carry people with decease to the hospitals, for transportation of materials, and so on, the list don’t ends. The new goal pursued by the automotive industry is to provide electric vehicles at low cost and with high reliability. This commitment is justified by the oil’s peak extraction on 50s of this century and also by the necessity to reduce the emissions of CO2 to the atmosphere, as well as to reduce the needs of this even more valuable natural resource. In order to achieve this task and to improve the regular cars based on oil, the automotive industry is even more concerned on doing applied research on technology and on fundamental research of new materials. The most important idea to retain from the previous introduction is to clarify the minds of the potential readers for the direct and indirect penetration of the vehicles and the vehicular industry in the today’s life. In this sequence of ideas, this book tries not only to fill a gap by presenting fresh subjects related to the vehicular technology and to the automotive engineering but to provide guidelines for future research. This book account with valuable contributions from worldwide experts of automotive’s field. The amount and type of contributions were judiciously selected to cover a broad range of research. The reader can found the most recent and cutting-edge sources of information divided in four major groups: electronics (power, communications, optics, batteries, alternators and sensors), mechanics (suspension control, torque converters, deformation analysis, structural monitoring), materials (nanotechnology, nanocomposites, lubrificants, biodegradable, composites, structural monitoring) and manufacturing (supply chains). We are sure that you will enjoy this book and will profit with the technical and scientific contents. To finish, we are thankful to all of those who contributed to this book and who made it possible.info:eu-repo/semantics/publishedVersio

The application of pulsed laser Electronic Speckle Pattern Interferometry to the measurement of in-plane strain on high speed rotating components

Increasingly sophisticated rotating system designs demand a need for more advanced experimental measurement systems, providing highly accurate data over a large number of measurement points. Described within is an interferometric measurement system based upon a speckle correlation technique, referred to in the literature as Electronic Speckle Pattern Interferometry (ESPI), TV holography or Digital Speckle Pattern Interferometry (DSPI). The interferometer is configured to measure radial in-plane displacement. A pulsed laser, necessary because of the rotary motion of the specimen, provides the illumination source. The output from the ESPI system is a fringe pattern, which must be further processed to yield useful data. The work is a continuation of an existing project, and focuses on three main aspects: • To increase the operable speed range and reliability of the system. • To extract quantitative engineering data from the fringe patterns. • To develop the existing design into a 'user-friendly' system, capable of transfer into an industrial environment. A set of two-dimensional Fourier transform programs, running on an 80486 computer, enable accurate phase data to be extracted from the fringes, delivering quantitative measurements of radial strain to subfringe accuracy. Major advancements include the construction of a new electronic system to control the pulsed laser, enabling interferograms to be obtained at rotational speeds up to 23,842rpm, with a tip speed increase of 2.75 times any previous result (from 132m s'1 to 364m s"1). The new control unit, unlike its predecessor, is designed to be immune to the electromagnetic interference generated by the laser, and allows speckle patterns to be obtained at any rotational speed, up to 24,000rpm, which is the maximum speed of the drive motor. An innovative shaft encoder was also incorporated into the system, producing highly reliable timing data from the rotating specimen. Efforts to increase the reliability of the measurements concentrated on the vibration and windage generated by the disc. A significant increase in the repeatability at all speeds up to approximately 14,000rpm is reported. Above this speed, the vibrations are too severe to enable repeatable results to be obtained. However, high contrast fringes are still obtained, establishing that speckle correlation occurs, and is likely to at even higher speeds. Results from static specimens indicate that the computer software functions effectively, showing close correlation with measured strains. When used with rotating specimens, the system yields results which are generally higher than the established theory. Investigation into this phenomenon suggests that windage heating of the disc surface induces additional stresses in the specimen, as shown in a series of windage tests. Tests conducted under conditions which minimise the windage heating have good agreement with the analytical theory

Adaptive Methods for Robust Document Image Understanding

A vast amount of digital document material is continuously being produced as part of major digitization efforts around the world. In this context, generic and efficient automatic solutions for document image understanding represent a stringent necessity. We propose a generic framework for document image understanding systems, usable for practically any document types available in digital form. Following the introduced workflow, we shift our attention to each of the following processing stages in turn: quality assurance, image enhancement, color reduction and binarization, skew and orientation detection, page segmentation and logical layout analysis. We review the state of the art in each area, identify current defficiencies, point out promising directions and give specific guidelines for future investigation. We address some of the identified issues by means of novel algorithmic solutions putting special focus on generality, computational efficiency and the exploitation of all available sources of information. More specifically, we introduce the following original methods: a fully automatic detection of color reference targets in digitized material, accurate foreground extraction from color historical documents, font enhancement for hot metal typesetted prints, a theoretically optimal solution for the document binarization problem from both computational complexity- and threshold selection point of view, a layout-independent skew and orientation detection, a robust and versatile page segmentation method, a semi-automatic front page detection algorithm and a complete framework for article segmentation in periodical publications. The proposed methods are experimentally evaluated on large datasets consisting of real-life heterogeneous document scans. The obtained results show that a document understanding system combining these modules is able to robustly process a wide variety of documents with good overall accuracy