Evaluation and optimal design of spectral sensitivities for digital color imaging

The quality of an image captured by color imaging system primarily depends on three factors: sensor spectral sensitivity, illumination and scene. While illumination is very important to be known, the sensitivity characteristics is critical to the success of imaging applications, and is necessary to be optimally designed under practical constraints. The ultimate image quality is judged subjectively by human visual system. This dissertation addresses the evaluation and optimal design of spectral sensitivity functions for digital color imaging devices. Color imaging fundamentals and device characterization are discussed in the first place. For the evaluation of spectral sensitivity functions, this dissertation concentrates on the consideration of imaging noise characteristics. Both signal-independent and signal-dependent noises form an imaging noise model and noises will be propagated while signal is processed. A new colorimetric quality metric, unified measure of goodness (UMG), which addresses color accuracy and noise performance simultaneously, is introduced and compared with other available quality metrics. Through comparison, UMG is designated as a primary evaluation metric. On the optimal design of spectral sensitivity functions, three generic approaches, optimization through enumeration evaluation, optimization of parameterized functions, and optimization of additional channel, are analyzed in the case of the filter fabrication process is unknown. Otherwise a hierarchical design approach is introduced, which emphasizes the use of the primary metric but the initial optimization results are refined through the application of multiple secondary metrics. Finally the validity of UMG as a primary metric and the hierarchical approach are experimentally tested and verified

Réalisation d'un système de conversion des couleurs pour un capteur d'images CMOS à photodétecteur sans filtre optique

RÉSUMÉ L’équipe de recherche de mon directeur de recherche, monsieur Yves Audet, travail sur un capteur d’images CMOS (Complementary Metal-Oxide-Semiconductor) sans filtre optique novateur. Les capteurs CCD (Charge-Coupled Device) et CMOS actuellement sur le marché sont basés sur des photodétecteurs sensibles à l’intensité lumineuse et non pas à la longueur d’onde. Pour les rendre sensible à la couleur, des filtres chromatiques sont déposés sur chaque photodétecteur afin que chaque photodétecteur ne détecte qu’une longueur d’onde spécifique. Cette façon de faire a deux inconvénients majeurs. Premièrement, l’utilisation du filtre chromatique réduit la sensibilité du capteur puisque ce filtre absorbe une partie de l’intensité lumineuse. Deuxièmement, chaque photodétecteur ne détecte qu’une couleur obligeant le recours à des algorithmes mathématiques d’extrapolation pour déduire les deux couleurs manquantes pour chaque pixel à partir des couleurs des pixels adjacents. Le nouveau capteur novateur remédie à ces deux inconvénients en ne nécessitant pas le dépôt des filtres optiques chromatiques sur les photodétecteurs. Il détecte les couleurs en utilisant la propriété d’un matériau semi-conducteur selon laquelle la profondeur de pénétration des ondes électromagnétiques varie avec la longueur d’onde. En utilisant cette propriété, le capteur permet de détecter trois couleurs avec chaque pixel. Le nouveau capteur est réalisable entièrement en technologie CMOS contrairement à un capteur de la compagnie Foveon qui a vue le jour en 2002 et qui utilise le même principe d’absorption de la lumière dans un semi-conducteur pour filtrer la lumière selon la longueur d’onde. Ce capteur n’est pas compatible avec la technologie CMOS parce qu’il utilise trois photodiodes enfouies verticalement dans le semi-conducteur. Ceci rend la réalisation de ce capteur coûteuse. Le présent travail de recherche est une continuité dans les efforts de développement du nouveau capteur d’images. Il consiste à trouver une méthode pour la conversion des couleurs de l’espace de couleurs du capteur en couleurs dans un espace standard. La conversion des couleurs est réalisée à l’aide d’une matrice 3x3 de conversion des couleurs.----------ABSTRACT The research team of my supervisor, Mr Yves Audet, work on an innovator CMOS (Complementary Metal-Oxide-Semiconductor) image sensor without optical filter. The CCD (Charge-Coupled Device) and CMOS sensors on the market today are based on photodetectors which are sensitive to the light intensity and not to the wavelength. To make them sensitive to color, color filters are deposited on each photodetector so that each photodetector detects only a specific wavelength. This approach has two major drawbacks. First, the use of the color filter reduces the sensitivity of the sensor as the filter absorbs some of the light intensities. Second, each photodetector detects only one color requiring the use of mathematical extrapolation algorithms to deduce the two missing colors at each pixel from the colors of adjacent pixels. The new innovative image sensor overcomes these disadvantages by not requiring the deposit of the color optical filters on the photodetectors. It detects color by using the property of a semiconductor material that the penetration depth of electromagnetic waves varies with wavelength. Using this property, the sensor can detect three colors with each pixel. The new sensor is made entirely in CMOS technology as opposed to a Foveon sensor, a company founded in 2002 and uses the same principle of light absorption in a semiconductor to filter the light according to the wavelength. This sensor is not compatible with CMOS technology because it uses three photodiodes buried vertically into the semiconductor. This makes the realization of this sensor expensive. This research work is a continuity in the development effort of the new sensor. It is to find a method for color conversion from sensor color space to a standard color space. The color conversion is performed using a 3x3 color conversion matrix. A method of calculating this matrix while considering the noise in the image has been identified and implemented as a Matlab GUI. The consideration of noise in the image is essential because of the nature of the sensor for which the conversion matrix can have large coefficients in the diagonal. However, they are responsible for the degradation of noise performance. Subsequently, a digital circuit for color conversion was designed in VHDL

Post-earthquake damage assessment and residual capacity of concrete and RC beams.

The assessment of damage and remaining capacity after an earthquake is an immediate measure to determine whether a reinforced concrete (RC) building is usable and safe for occupants. The recent Christchurch earthquake (22 February 2011) caused a uniquely severe level of structural damage to modern buildings, resulting in extensive damage to the building stock. About 60% of damaged multistorey concrete buildings (3 storeys and up) were demolished after the earthquake, and the cost of reconstruction amounted to 40 billion NZD. The aftermath disclosed issues of great complexities regarding the future of the RC buildings damaged by the earthquakes. This highlighted the importance of post-event decision-making, as the outcome will allow the appropriate course of action—demolition, repair or acceptance of the existing building—to be considered. To adopt the proper strategy, accurate assessment of the residual capacity and the level of damage is required. This doctoral dissertation aims to assess the damage and remaining capacity at constituent material and member level (i.e., concrete material and beams) through a systematic approach in an attempt to address part of an existing gap in the available literature. Since the residual capacity of RC members is not unique and depends on previously applied loading history, post-event residual capacity in this study was assessed in terms of fraction of fatigue life (i.e., the number of cycles required to failure). This research comprises three main parts: (1) residual capacity and damage assessment at material level (i.e., concrete), (2) post-yield bond deterioration and damage assessment at the interface of steel and concrete, and, finally, (3) residual capacity and damage assessment at member level (i.e., RC beam). The first part of this research focused on damage assessment and the remaining capacity of concrete from a material point of view. It aimed to employ appropriate and reliable durability-based testing and image-detection techniques to quantify deterioration in the mechanical properties of concrete on the basis that stress-induced damage occurred in the microstructural system of the concrete material. To this end, in the first phase, a feasibility study was conducted in which a combination of oxygen permeability, electrical resistivity and porosity tests were assessed to determine if they were robust and reliable enough to reveal damage which occurred in the microstructural system of concrete. The results, in terms of change in permeability, electrical resistivity and porosity features of disk samples taken from the middle third of damaged concrete cylinders (200 mm × 100 mm) monotonically pre-loaded to 50%, 70%, 90% and 95% of the ultimate strength (f′c), showed the permeability test is a reliable tool to identify the degree of damage, due to its high sensitivity to the load-induced microcracking. In parallel, to determine the residual capacity, the companion damaged concrete cylinders already loaded to the same level of compressive strength were reloaded up to failure. Comparing the stress–strain relationship of damaged concrete with intact material, it was also found that the strain capacity of the reloaded pre-damaged concrete cylinders decreases while strength remained virtually unchanged. In the second phase of the first part, a fluorescent microscopy technique was used to assess the damage and develop a correlation between material degradation, by virtue of the geometrical features, and damage to the concrete. To account for the effect of confinement and cyclic loading, in the third phase, the residual capacity and damage assessment of unconfined and GFRP confined concrete cylinders subjected to low-cycle fatigue loading, was investigated. Similar to the first phase, permeability testing technique was used to provide an indirect evaluation of fatigue damage. Finally, in the fourth phase of the first part, the suitability of permeability testing technique to assess damage was evaluated for cored concrete taken from three types of RC members: columns, beams and a beam-column joint. In view of the fact that the composite action of an RC member is highly dependent on the bond between reinforcement and surrounding concrete, understanding the deterioration of the bond in the post-yield range of strain in steel was crucial to assess damage at member level. Therefore, in the second phase of this research, a state-of-the- art distributed fibre optic strain sensor system (DFOSSS) system was used to evaluate bond deterioration in a cantilever RC beam subjected to monotonic lateral loading. The technology allowed the continuous capture of strain, every 2.6 mm along the length, in both reinforcing bars and cover concrete. The strain profile provided a basis by which the slip, axial stress and bond stress distributions were then established. In the third part, the study focused on the damage assessment and residual capacity of seven half-scale RC beams subjected to a constant-amplitude cyclic loading protocol. In the first stage, the structural performances of three specimens under constant-amplitude fatigue at 1%, 2% and 4% chord rotation (drift) were examined. In parallel, the number of cycles to failure, degradation in strength, stiffness and energy dissipation were characterized. In the second stage, four RC beams were subjected to loading up to 70% and 90% of their fatigue life, at 2% and 4% drift, and then monotonically pulled up to failure. To determine the residual flexural capacity, the lateral force–displacement results of pre-damaged specimens were compared with an undamaged specimen subjected to only monotonic loading. The study showed significant losses in strength, deformability, stiffness and energy dissipation capacity. A nonlinear finite element analysis (FEA) using concrete damage plasticity (CDP) model was also conducted in ABAQUS to numerically investigate the behaviour of the tested specimen. The results of the FE simulations indicated a reasonable response compared with the behaviour of the test specimen in terms of force–displacement and cracking pattern. During the Christchurch earthquake it was observed that the loading history has a significant influence on structural responses. While in conventional pseudo-static loading protocol, internal forces can be redistributed along the plastic length: there is little chance for structures undergoing high initial loading amplitude to redistribute pertinent stresses. As a result, in the third phase of this part, the effect of high rate of loading on the behaviour of seismically designed RC beams was investigated. Two half-scale cantilever RC beams were subjected to similar constant-amplitude cyclic loading at 2% and 4% drifts, but at a rate of 500 mm/s. Due to the incapability of conventional measuring techniques, a motion-tracking system was employed for data acquisition with the high-speed tests. The effect of rate of loading on the fatigue life of specimens (i.e., the number of cycles required to failure), secant stiffness, failure mode, cracking pattern, beam elongations and bar fracture surface were analysed. Integrating the results of all parts of this research has resulted in a better understanding of residual capacity and the development of damage at both the material and member level by using a low-cycle fatigue approach

Special Issue of the Manufacturing Engineering Society (MES)

This book derives from the Special Issue of the Manufacturing Engineering Society (MES) that was launched as a Special Issue of the journal Materials. The 48 contributions, published in this book, explore the evolution of traditional manufacturing models toward the new requirements of the Manufacturing Industry 4.0 and present cutting-edge advances in the field of Manufacturing Engineering focusing on additive manufacturing and 3D printing, advances and innovations in manufacturing processes, sustainable and green manufacturing, manufacturing systems (machines, equipment and tooling), metrology and quality in manufacturing, Industry 4.0, product lifecycle management (PLM) technologies, and production planning and risks

Safety and Reliability - Safe Societies in a Changing World

The contributions cover a wide range of methodologies and application areas for safety and reliability that contribute to safe societies in a changing world. These methodologies and applications include: - foundations of risk and reliability assessment and management - mathematical methods in reliability and safety - risk assessment - risk management - system reliability - uncertainty analysis - digitalization and big data - prognostics and system health management - occupational safety - accident and incident modeling - maintenance modeling and applications - simulation for safety and reliability analysis - dynamic risk and barrier management - organizational factors and safety culture - human factors and human reliability - resilience engineering - structural reliability - natural hazards - security - economic analysis in risk managemen