26 research outputs found

    A Novel Sequence Generation Approach to Diagnose Faults in Reconfigurable Scan Networks

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    With the complexity of nanoelectronic devices rapidly increasing, an efficient way to handle large number of embedded instruments became a necessity. The IEEE 1687 standard was introduced to provide flexibility in accessing and controlling such instrumentation through a reconfigurable scan chain. Nowadays, together with testing the system for defects that may affect the scan chains themselves, the diagnosis of such faults is also important. This article proposes a method for generating stimuli to precisely identify permanent high-level faults in a IEEE 1687 reconfigurable scan chain: the system is modeled as a finite state automaton where faults correspond to multiple incorrect transitions; then, a dynamic greedy algorithm is used to select a sequence of inputs able to distinguish between all possible faults. Experimental results on the widely-adopted ITC'02 and ITC'16 benchmark suites, as well as on synthetically generated circuits, clearly demonstrate the applicability and effectiveness of the proposed approach: generated sequences are two orders of magnitude shorter compared to previous methodologies, while the computational resources required remain acceptable even for larger benchmarks

    New techniques for functional testing of microprocessor based systems

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    Electronic devices may be affected by failures, for example due to physical defects. These defects may be introduced during the manufacturing process, as well as during the normal operating life of the device due to aging. How to detect all these defects is not a trivial task, especially in complex systems such as processor cores. Nevertheless, safety-critical applications do not tolerate failures, this is the reason why testing such devices is needed so to guarantee a correct behavior at any time. Moreover, testing is a key parameter for assessing the quality of a manufactured product. Consolidated testing techniques are based on special Design for Testability (DfT) features added in the original design to facilitate test effectiveness. Design, integration, and usage of the available DfT for testing purposes are fully supported by commercial EDA tools, hence approaches based on DfT are the standard solutions adopted by silicon vendors for testing their devices. Tests exploiting the available DfT such as scan-chains manipulate the internal state of the system, differently to the normal functional mode, passing through unreachable configurations. Alternative solutions that do not violate such functional mode are defined as functional tests. In microprocessor based systems, functional testing techniques include software-based self-test (SBST), i.e., a piece of software (referred to as test program) which is uploaded in the system available memory and executed, with the purpose of exciting a specific part of the system and observing the effects of possible defects affecting it. SBST has been widely-studies by the research community for years, but its adoption by the industry is quite recent. My research activities have been mainly focused on the industrial perspective of SBST. The problem of providing an effective development flow and guidelines for integrating SBST in the available operating systems have been tackled and results have been provided on microprocessor based systems for the automotive domain. Remarkably, new algorithms have been also introduced with respect to state-of-the-art approaches, which can be systematically implemented to enrich SBST suites of test programs for modern microprocessor based systems. The proposed development flow and algorithms are being currently employed in real electronic control units for automotive products. Moreover, a special hardware infrastructure purposely embedded in modern devices for interconnecting the numerous on-board instruments has been interest of my research as well. This solution is known as reconfigurable scan networks (RSNs) and its practical adoption is growing fast as new standards have been created. Test and diagnosis methodologies have been proposed targeting specific RSN features, aimed at checking whether the reconfigurability of such networks has not been corrupted by defects and, in this case, at identifying the defective elements of the network. The contribution of my work in this field has also been included in the first suite of public-domain benchmark networks

    Sensors Fault Diagnosis Trends and Applications

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    Fault diagnosis has always been a concern for industry. In general, diagnosis in complex systems requires the acquisition of information from sensors and the processing and extracting of required features for the classification or identification of faults. Therefore, fault diagnosis of sensors is clearly important as faulty information from a sensor may lead to misleading conclusions about the whole system. As engineering systems grow in size and complexity, it becomes more and more important to diagnose faulty behavior before it can lead to total failure. In the light of above issues, this book is dedicated to trends and applications in modern-sensor fault diagnosis

    A study assessing the viability of using Fused Filament Fabrication (FFF) Additive Manufacturing (AM) technology to manufacture customised Class I medical devices

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    Additive manufacturing (AM) is becoming an increasingly common manufacturing method for medical devices due to the benefits of advanced customisation, improved fit and opportunities for innovation. However, many AM medical devices remain inaccessible due to high costs of hardware and consumables, and the large infrastructural requirements required for operation. Fused filament fabrication (FFF) is a highly accessible AM technique due to its open-source nature, which has led to an extensive market of affordable desktop 3D printers. In this work FFF has been demonstrated as a potentially viable technique to fabricate low-risk medical devices in two case studies presented in this thesis: a customised daily living aid and a range of medical devices in response to the COVID-19 pandemic. Although the potential of the technology has been demonstrated, research around the practical suitability of FFF for medical applications remained limited, with much of the research in the field focussing on proof-of-concept applications, which did not explore the necessary requirements for the integration of the technology into daily clinical practices. This thesis investigates the fundamental requirements of the FFF AM technique for it to be used for Class I medical device applications in three identified use cases: non-specialist, research and industrial use. In keeping with the ambition for FFF to provide accessible solutions, mid-range hardware aimed at professional printing applications was selected to carry out this work, which encompasses the activities present in each of the three identified use cases. A methodology was presented to determine the repeatability and reproducibility of FFF across three potential use cases, which revealed varying process capability between the X-, Y- and Z- printing directions for individual machines, and significant variation between multiple machines of the same make and model. The repeatability and reproducibility of the FFF technique was identified as a key limitation for the widespread adoption of FFF technology for specialist and industrial use. The smallest tolerance achieved from a professional desktop FFF printer was 0.3mm in both the X- and Y- directions, and 0.4mm in the Z-direction. Additional variable factors were studied, including the condition of filament with respect to its storage environment and duration of storage, the influence of different colours and pigments present in filament and the use of an air management add-on unit intended to enhance the hardware. The glass transition temperature of Tough PLA remained largely unaffected from variable storage conditions, which when submerged in water decreased by around 1.4ºC from that of ambiently stored filament. The mechanical properties of printed parts were influenced by filament colour, with white filament producing parts with increased elongation and tensile strength than other colours studied. Dimensional accuracy in the Z-printing direction was affected by air management, where samples produced with air management were measured higher than the nominal value, and without air management lower than the nominal value. This thesis is the first known work to explore the suitability of FFF technology for Class I medical devices, from the perspective of both specialist and non-specialist users. The key barriers to widespread adoption were identified as the repeatability and reproducibility of the technique, and the influence of variable factors on the process and part performance. The exploration of these continually referenced medical device regulations, whilst consideration was given to how the experimental work can be applied to real-world Class I medical device manufacturing applications

    Pilot\u27s Handbook of Aeronautical Knowledge, 2016

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    The Pilot’s Handbook of Aeronautical Knowledge provides basic knowledge that is essential for pilots. This handbook introduces pilots to the broad spectrum of knowledge that will be needed as they progress in their pilot training. Except for the Code of Federal Regulations pertinent to civil aviation, most of the knowledge areas applicable to pilot certification are presented. The Pilot’s Handbook of Aeronautical Knowledge provides basic knowledge for the student pilot learning to fly, as well as pilots seeking advanced pilot certification. For detailed information on a variety of specialized flight topics, see specific Federal Aviation Administration (FAA) handbooks and Advisory Circulars (ACs). Occasionally the word “must” or similar language is used where the desired action is deemed critical. The use of such language is not intended to add to, interpret, or relieve a duty imposed by Title 14 of the Code of Federal Regulations (14 CFR). It is essential for persons using this handbook to become familiar with and apply the pertinent parts of 14 CFR and the Aeronautical Information Manual (AIM). The AIM is available online at www.faa.gov. The current Flight Standards Service airman training and testing material and learning statements for all airman certificates and ratings can be obtained from https://www.faa.gov

    Local-global geographies of tacit knowledge production in London and New York's advertising and law professional service firms

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    For economic geographers interest in the role of knowledge in economic activities and a ‘knowledge economy’ raises questions about how geography enables (and disables) learning and whether the production of tacit knowledge has exclusively local or multiple overlapping geographies. This thesis engages with this debate and considers its relevance to the geographies of tacit knowledge production (learning) in the employees of global advertising and law professional service firms operating in London and New York City. It begins by critically engaging with theories of knowledge, learning and their geographies to develop a spatially sensitive approach to examine learning. Such an analysis is then applied in order to understand the geographies of knowledge production in global advertising and law firms. Three themes are addressed. First, why is tacit knowledge important in the work of these firms? Second, what are the key practices involved in producing such knowledge? Third, what are the geographies of these practices and how important is the local scale (the communities within London and New York) and the global scale (the communities stretched between offices of the global firms studied) for knowledge production. Research findings from semistructured interviews highlight the multiple geographies of learning in the firms studied at both local and global scales. This is enabled by a number of ‘embedding’ forces that ‘smooth’ the learning process and that have multiple geographies themselves. It is therefore argued that a relational and topological analysis that traces the learning networks across space most usefully provides insights into the geographies of knowledge production. This reveals that the ‘networks and spaces of learning’ are fluid and transcend spatial scales when suitable constructed
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