1,854 research outputs found

    Diagnosis of Machining Conditions Based on Logical Analysis of Data

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    RÉSUMÉ : Un élément clé pour un système d'usinage automatisé sans surveillance est le développement de systèmes de surveillance et de contrôle fiables et robustes. Plusieurs modèles mathématiques et statistiques, qui modélisent la relation entre les variables indépendantes et les variables dépendantes d’usinage, sont suggérés dans la littérature, en commençant par le modèle de Taylor jusqu’aux modèles de régression les plus sophistiqués. Tous ces modèles ne sont pas dynamiques, dans le sens que leurs paramètres ne changent pas avec le temps. Des modèles basés sur l'intelligence artificielle ont résolu de nombreux problèmes dans ce domaine, mais la recherche continue. Dans la présente thèse, je propose l'application d'une approche appelée Analyse Logique de Données (LAD) pour prédire le sortant d’un processus d’usinage. Cette approche a démontré une bonne performance et des capacités additionnelles une fois comparée à la conception traditionnelle des expériences ou à la modélisation mathématique et statistique. Elle est aussi comparée dans cette thèse à la méthode bien connue des réseaux de neurones. Elle est basée sur l'exploitation des données saisies par des capteurs et l'extraction des informations utiles à partir de ces dernières. LAD est utilisé pour déterminer les meilleures conditions d'usinage, pour détecter l'usure de l'outil, pour identifier le moment optimal de remplacement de l’outil d’usinage, et pour surveiller et contrôler les processus d'usinage. Étant donné que les capteurs et les technologies de l'information sont tous les deux en expansion rapide et continue, il serait prévu qu'un outil d’analyse tels que LAD aidera à tracer un chemin dans l'amelioration des processus d'usinage en utilisant les techniques de pointe afin de réduire considérablement le coût ces processus. Les résultats de mon travail pourraient avoir un impact important sur l'optimisation de ces processus.----------ABSTRACT : A key issue for an unattended and automated machining system is the development of reliable and robust monitoring and controlling systems. Research in Artificial Intelligence-based monitoring of machining systems covers several issues and has solved many problems, but the search continues for a robust technique that does not depend on a statistical learning background and that does not have ambiguous procedures. In this thesis, I propose the application of an approach called Logical Analysis of Data (LAD) which is based on the exploitation of data captured by sensors, and the extraction of useful information from this data. LAD is used for determining the best machining conditions, detecting the tool wear, identifying the optimal replacement time for machining tools, monitoring, and controlling machining processes. LAD has demonstrated good performance and additional capabilities when it is compared to the famous statistical technique, Proportional Hazard Model (PHM), and the well known machine learning technique, Artificial Neural Network (ANN). Since sensors’ and information technologies are both expanding rapidly and continuously, it is expected that an analysis tool such as LAD will help in blazing a new trail in machining processes by using state of the art techniques in order to significantly reduce the cost of machining process

    Critical literature review on concrete crack repairs

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    This dissertation focuses on an in-depth review of literature on concrete crack repairs. Deterioration of concrete affects both the aesthetics and the integrity of structures. As a result, there is need to repair such defects in order to restore the aesthetics and the integrity of concrete structures. This research discusses concrete crack repairs taking into consideration the mechanisms resulting in concrete cracking, techniques to determine concrete cracking, practices for prevention of concrete cracking and concrete crack repair techniques. Causes of cracking include alkali silica reactions (ASR), steel reinforcement corrosion, shrinkage, thermal variations, foundation movements, soil settlement, vegetation effects and cracking related to earthquale effects. Non-destructive and destructive techniques to determine conrete cracking shall be discussed. Destructive techniques usually involve core drilling of samples whilst non-destructive techniques include visual inspections, ultrasonic pulse velocity test, acoustic emission, spectral analysis of surface waves, modal analysis, petrographic analysis and infrared thermography. Several concrete crack repair techniques are to be discussed such as epoxy injection, routing and sealing, near surface reinforcement, additional reinforcement, gravity filling, grouting, dry packing, crack arrest, polymer impregnation, overlay and surface treatments, crack filling, crack sealing, blanketing, stitching and external stressing. These techniques are applied differently depending on the nature and cause of the concrete cracks. Further discussions will be on various case studies around the world on concrete crack repair which demonstrate the application of various concrete crack repair techniques to different types of concrete cracking scenarios. The case studies also highlight recent developments in technology, repair materials, application fields for various techniques and limitations to concrete crack repair. Some of the case studies discussed include concrete crack repair due to ASR damage on transport infrastructure in USA, ASR effects and crack repairs on a two storey building in California (USA), ASR effects and crack repairs to concrete structures in Hokuriku District in Japan, ASR effects and crack repairs to a gravity dam in India, crack repairs at Buttermarket Shopping Center due to shrinkage cracking and concrete crack repairs in Cheshire due to thermal effects

    SciTech News Volume 71, No. 1 (2017)

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    Columns and Reports From the Editor 3 Division News Science-Technology Division 5 Chemistry Division 8 Engineering Division Aerospace Section of the Engineering Division 9 Architecture, Building Engineering, Construction and Design Section of the Engineering Division 11 Reviews Sci-Tech Book News Reviews 12 Advertisements IEEE

    Smart FRP Composite Sandwich Bridge Decks in Cold Regions

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    INE/AUTC 12.0

    3D printed sensing systems for upper extremity assessment

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    Book of abstracts of the 2nd International Conference of TEMA: mobilizing projects

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    Based on its Human Capital and Capacities, the Centre for Mechanical Technology and Automation (TEMA) embraces a mission aiming to contribute to a sustainable industry, with specially focus on the surrounding SMEs, and to the wellbeing of society. Sustainable manufacturing aims to contribute to the development of a sustainable industry by developments and innovations on manufacturing engineering and technologies, to increase productivity, improve products quality and reduce waste in production processes. Technologies for the Wellbeing wishes to contribute to the wellbeing of society by the development of supportive engineering systems focusing on people and their needs and intending to improve their quality of life. TEMA intends to maximize its national and international impact in terms of scientific productivity and its transfer to society by tackling the relevant challenges of our time. TEMA is aware of the major challenges of our days, not only confined to scientific issues but also the societal ones, (a strategic pillar of the Horizon 2020 program), at the same time placing an effort to have its research disseminated, in high impact journals to the international scientific community. (...)publishe

    Optimal sensor placement in structural health monitoring (SHM) with a field application on a RC bridge

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    Structural health monitoring (SHM) is a research field that targets detecting and locating damage in structures. The main objective of SHM is to detect damage at its onset and inform authorities about the type, nature and location of the damage in the structure. Successful SHM requires deploying optimal sensor networks. We present a probabilistic approach to identify optimal location of sensors based on a priori knowledge on damage locations while considering the need for redundancy in sensor networks. The optimal number of sensors is identified using a multi-objective optimization approach incorporating information entropy and cost of the sensor network. As the size of the structure grows, the advantage of the optimal sensor network in damage detection becomes obvious. We also present an innovative field application of SHM using Field Programmable Gate Array (FPGA) and wireless communication technologies. The new SHM system was installed to monitor a reinforced concrete (RC) bridge on interstate I-40 in Tucumcari, New Mexico. The new monitoring system is powered with renewable solar energy. The integration of FPGA and photovoltaic technologies make it possible to remotely monitor infrastructure with limited access to power. Using calibrated finite element (FE) model of the bridge with real data collected from the sensors installed on the bridge, we establish fuzzy sets describing different damage states of the bridge. Unknown states of the bridge performance are then identified using degree of similarity between these fuzzy sets. The proposed SHM system will reduce human intervention significantly and can save millions of dollars currently spent on prescheduled inspection by enabling performance based monitoring

    NASA Tech Briefs, August 2010

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    Topics covered include: Technology Focus: Mechanical Components; Electronics/Computers; Software; Materials; Mechanics/Machinery; Manufacturing; Bio-Medical; Physical Sciences; Information Sciences; and Books and Reports

    Durability problems of 20th century reinforced concrete heritage structures and their restorations

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    This paper presents a study on the 20th century reinforced concrete heritage structures, thier durability problems, thier repair and restorations according to the conservation principles of heritage structures and the repair principles of reinforced concrete structures.The common problems on reinforced concrete heritage structures such as reinforcement corrosion, alkali aggregate reaction, freeze thaw and overloading of the structure are identified and thier respective repair methods presented. Even though so many causes exist that contribute for durability problems of reinforced concrete heritage structures, the mentioned ones are the most common appearing in most cases
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