7,732 research outputs found

    Towards A Practical High-Assurance Systems Programming Language

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    Writing correct and performant low-level systems code is a notoriously demanding job, even for experienced developers. To make the matter worse, formally reasoning about their correctness properties introduces yet another level of complexity to the task. It requires considerable expertise in both systems programming and formal verification. The development can be extremely costly due to the sheer complexity of the systems and the nuances in them, if not assisted with appropriate tools that provide abstraction and automation. Cogent is designed to alleviate the burden on developers when writing and verifying systems code. It is a high-level functional language with a certifying compiler, which automatically proves the correctness of the compiled code and also provides a purely functional abstraction of the low-level program to the developer. Equational reasoning techniques can then be used to prove functional correctness properties of the program on top of this abstract semantics, which is notably less laborious than directly verifying the C code. To make Cogent a more approachable and effective tool for developing real-world systems, we further strengthen the framework by extending the core language and its ecosystem. Specifically, we enrich the language to allow users to control the memory representation of algebraic data types, while retaining the automatic proof with a data layout refinement calculus. We repurpose existing tools in a novel way and develop an intuitive foreign function interface, which provides users a seamless experience when using Cogent in conjunction with native C. We augment the Cogent ecosystem with a property-based testing framework, which helps developers better understand the impact formal verification has on their programs and enables a progressive approach to producing high-assurance systems. Finally we explore refinement type systems, which we plan to incorporate into Cogent for more expressiveness and better integration of systems programmers with the verification process

    Beam scanning by liquid-crystal biasing in a modified SIW structure

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    A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

    Novel 129Xe Magnetic Resonance Imaging and Spectroscopy Measurements of Pulmonary Gas-Exchange

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    Gas-exchange is the primary function of the lungs and involves removing carbon dioxide from the body and exchanging it within the alveoli for inhaled oxygen. Several different pulmonary, cardiac and cardiovascular abnormalities have negative effects on pulmonary gas-exchange. Unfortunately, clinical tests do not always pinpoint the problem; sensitive and specific measurements are needed to probe the individual components participating in gas-exchange for a better understanding of pathophysiology, disease progression and response to therapy. In vivo Xenon-129 gas-exchange magnetic resonance imaging (129Xe gas-exchange MRI) has the potential to overcome these challenges. When participants inhale hyperpolarized 129Xe gas, it has different MR spectral properties as a gas, as it diffuses through the alveolar membrane and as it binds to red-blood-cells. 129Xe MR spectroscopy and imaging provides a way to tease out the different anatomic components of gas-exchange simultaneously and provides spatial information about where abnormalities may occur. In this thesis, I developed and applied 129Xe MR spectroscopy and imaging to measure gas-exchange in the lungs alongside other clinical and imaging measurements. I measured 129Xe gas-exchange in asymptomatic congenital heart disease and in prospective, controlled studies of long-COVID. I also developed mathematical tools to model 129Xe MR signals during acquisition and reconstruction. The insights gained from my work underscore the potential for 129Xe gas-exchange MRI biomarkers towards a better understanding of cardiopulmonary disease. My work also provides a way to generate a deeper imaging and physiologic understanding of gas-exchange in vivo in healthy participants and patients with chronic lung and heart disease

    Colour technologies for content production and distribution of broadcast content

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    The requirement of colour reproduction has long been a priority driving the development of new colour imaging systems that maximise human perceptual plausibility. This thesis explores machine learning algorithms for colour processing to assist both content production and distribution. First, this research studies colourisation technologies with practical use cases in restoration and processing of archived content. The research targets practical deployable solutions, developing a cost-effective pipeline which integrates the activity of the producer into the processing workflow. In particular, a fully automatic image colourisation paradigm using Conditional GANs is proposed to improve content generalisation and colourfulness of existing baselines. Moreover, a more conservative solution is considered by providing references to guide the system towards more accurate colour predictions. A fast-end-to-end architecture is proposed to improve existing exemplar-based image colourisation methods while decreasing the complexity and runtime. Finally, the proposed image-based methods are integrated into a video colourisation pipeline. A general framework is proposed to reduce the generation of temporal flickering or propagation of errors when such methods are applied frame-to-frame. The proposed model is jointly trained to stabilise the input video and to cluster their frames with the aim of learning scene-specific modes. Second, this research explored colour processing technologies for content distribution with the aim to effectively deliver the processed content to the broad audience. In particular, video compression is tackled by introducing a novel methodology for chroma intra prediction based on attention models. Although the proposed architecture helped to gain control over the reference samples and better understand the prediction process, the complexity of the underlying neural network significantly increased the encoding and decoding time. Therefore, aiming at efficient deployment within the latest video coding standards, this work also focused on the simplification of the proposed architecture to obtain a more compact and explainable model

    Northern Powerhouses: the homes of the industrial elite, c.1780-1875

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    This thesis explores the world of the industrial elites of Manchester and Liverpool in the period c.1780-1875, through their houses. The homes of the industrial elites, namely merchants and manufacturers, were extremely important tangible communicators of wealth, taste, and comfort. Whilst status-building was closely connected to the house, this thesis argues that the industrial elites carved their own identities into their domestic spheres and that emulation was not solely linked with aspiration. The findings of this thesis are based around its three research aims regarding the changing location of houses in Manchester and Liverpool in the eighteenth and nineteenth centuries, the appearance and use of houses, and the daily routines and involvement of the industrial elite in their domestic routines. An analysis of elite residential patterns in Manchester and Liverpool across the eighteenth and nineteenth centuries has created a more nuanced look at urban geographies of the region in this period. Though some residential patterns differed because of economic and political structure, a key finding has been that the process of suburbanisation in and around Manchester and Liverpool commenced earlier than previous scholarship has suggested. Suburbanisation among the elites began in the latter decades of the eighteenth century and into the early decades of the nineteenth century, with elite suburban communities being firmly established by the 1820s. This thesis discovered that despite socio-economic and political differences, the industrial elites of Manchester and Liverpool used their houses, gardens, and landed estates in very similar ways. This was a result of conformity which arose from emulation at both a community-based level and the emulation and aspiration of elite, gentrified lifestyle. Also, the merchants and manufacturers analysed within this work were involved in their home at every level of domesticity, from the construction of the house to the financial management of the household, although this latter theme was often a cooperative effort between spouses and family members, adding more to our understanding of gender, domesticity, and familial relations. Through detailed case studies and a combination of sources, the private lives of the industrial elites have been revaluated and redefined, including showing how their houses functions metaphorically and in reality

    Globalizing the Library

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    Globalizing the Library focuses on the globalization of information and the library in the period following the Second World War. Providing an examination of the ideas and aspirations surrounding information and the library, as well as the actual practices and actions of information professionals from the United States, Britain, and those working with organizations such as Unesco to develop library services, this book tells an important story about international history that also provides insight into the history of information, globalization, and cultural relations. Exploring efforts to help build library services and train a cohort of professional librarians around the globe, the book examines countries in Asia, Africa, and the Pacific during the period of the Cold War and decolonization. Using the ideas of ‘library diplomacy’ and ‘library imperialism’ to frame Anglo-American involvement in this work, Laugesen examines the impact library development work had on various countries. The book also considers what might have motivated nations in the global South to use foreign aid to help develop their library services and information infrastructure. Globalizing the Library prompts reflection on the way in which library services are developed and the way professional knowledge is transferred, while also illuminating the power structures that have shaped global information infrastructures. As a result, the book should be essential reading for academics and students engaged in the study of libraries, development, and information. It should also be of great interest to information professionals and information historians who are reflecting critically on the way information has been transferred, consumed, and shaped in the modern world

    The Anthropocene Hypothesis

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    Myanmar higher education in transition: the interplay between state authority, student politics and international actors.

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    The Myanmar “period of transition” (2011-2021) has often been described as a puzzle. Various scholars have begun to engage with the Myanmar context in an effort to grasp the essence of the transition it underwent during President Thein Sein’s USPD and Aung San Suu Kyi’s NLD governments. My work focuses on a specific policy sector, higher education, with a view to contributing to this scholarly debate regarding what was actually happening inside this complex country “transition”, especially in terms of collective participation in the process of political and social change. Reviewing existing scholarly literature on the politics of higher education, my study employs a triangle of analysis in which higher education reform is framed as the interplay of action on the part of “state authority”, “student politics” and “international actors”. What does this interplay lens reveal if we consider Myanmar’s “period of transition”? I argue that it shows the ambiguity and contradiction of tangible pushes for progressive social change that coexisted with authoritarian currents and the reinforcement of the societal position of dominant elites. At the policy level, ultimately, a convergence of interests between international actors and state authority served as the force driving the new higher education reform towards a neo-liberal model of governance and autonomy. This work unpacks the higher education reform process thanks to qualitative data gathered through extensive participant observation, in-depth interviewing and critical discourse analysis, shedding light on the rich narratives of those involved in the politics of higher education in Myanmar
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