7,946 research outputs found
Beam scanning by liquid-crystal biasing in a modified SIW structure
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
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
Explainable fault prediction using learning fuzzy cognitive maps
IoT sensors capture different aspects of the environment and generate high throughput data streams. Besides capturing these data streams and reporting the monitoring information, there is significant potential for adopting deep learning to identify valuable insights for predictive preventive maintenance. One specific class of applications involves using Long Short-Term Memory Networks (LSTMs) to predict faults happening in the near future. However, despite their remarkable performance, LSTMs can be very opaque. This paper deals with this issue by applying Learning Fuzzy Cognitive Maps (LFCMs) for developing simplified auxiliary models that can provide greater transparency. An LSTM model for predicting faults of industrial bearings based on readings from vibration sensors is developed to evaluate the idea. An LFCM is then used to imitate the performance of the baseline LSTM model. Through static and dynamic analyses, we demonstrate that LFCM can highlight (i) which members in a sequence of readings contribute to the prediction result and (ii) which values could be controlled to prevent possible faults. Moreover, we compare LFCM with state-of-the-art methods reported in the literature, including decision trees and SHAP values. The experiments show that LFCM offers some advantages over these methods. Moreover, LFCM, by conducting a what-if analysis, could provide more information about the black-box model. To the best of our knowledge, this is the first time LFCMs have been used to simplify a deep learning model to offer greater explainability
Fish investigations in the Barents Sea Winter 2022
Annual catch quotas and other regulations of the Barents Sea fisheries are set through negotiations between Norway and Russia. Assessment of the state of the stocks and quota advice are based on survey results and international landings statistics. The results from the demersal fish winter surveys in the Barents Sea are an important source of information for the annual stock assessment.Fish investigations in the Barents Sea Winter 2022publishedVersio
The place where curses are manufactured : four poets of the Vietnam War
The Vietnam War was unique among American wars. To pinpoint its uniqueness, it was necessary to look for a non-American voice that would enable me to articulate its distinctiveness and explore the American character as observed by an Asian. Takeshi Kaiko proved to be most helpful. From his novel, Into a Black Sun, I was able to establish a working pair of 'bookends' from which to approach the poetry of Walter McDonald, Bruce Weigl, Basil T. Paquet and Steve Mason. Chapter One is devoted to those seemingly mismatched 'bookends,' Walt Whitman and General William C. Westmoreland, and their respective anthropocentric and technocentric visions of progress and the peculiarly American concept of the "open road" as they manifest themselves in Vietnam. In Chapter, Two, I analyze the war poems of Walter McDonald. As a pilot, writing primarily about flying, his poetry manifests General Westmoreland's technocentric vision of the 'road' as determined by and manifest through technology. Chapter Three focuses on the poems of Bruce Weigl. The poems analyzed portray the literal and metaphorical descent from the technocentric, 'numbed' distance of aerial warfare to the world of ground warfare, and the initiation of a 'fucking new guy,' who discovers the contours of the self's interior through a set of experiences that lead from from aerial insertion into the jungle to the degradation of burning human
feces. Chapter Four, devoted to the thirteen poems of Basil T. Paquet, focuses on the continuation of the descent begun in Chapter Two. In his capacity as a medic, Paquet's entire body of poems details his quotidian tasks which entail tending the maimed, the mortally wounded and the dead. The final chapter deals with Steve Mason's JohnnY's Song, and his depiction of the plight of Vietnam veterans back in "The World" who are still trapped inside the interior landscape of their individual "ghettoes" of the soul created by their war-time experiences
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An Agile Musicology: Improvisation in Corporate Management and Lean Startups
The last decade of the twentieth century saw a proliferation of publications that use jazz as a metaphor for corporate management, arguing that in the contemporary knowledge economy, jazz is superior to the symphonic model that governed mid-century factory floors. As the literature on the jazz metaphor, and organizational improvisation more broadly, continued to develop into the twenty-first century, another managerial methodology became widely adopted by entrepreneurs: agile. While agile is yet to be fully theorized as an improvisatory practice, agile shares several core tenets with the models promoted by organizational improvisation scholars, including the use of small teams, an emphasis on feedback, and an openness to change. In this dissertation, I argue that agile methods, and the adjacent lean methodology, are inherently improvisatory and that understanding them as improvisatory offers opportunities not only for their deployment within growing businesses, but also for adoption at-scale in large corporations.
I draw on an array of disciplinary perspectives, including management science, organizational studies, musicology, and critical improvisation studies, as well as a wide range of sources, from peer-reviewed journal publications to trade manuals. Each chapter builds upon the former: a substantial and critical review of the jazz metaphor literature is followed by a dissection of its main themes under a musicological lens; after securing the foundations of organizational improvisation, the next chapter reveals the improvisatory nature of agile and lean startup practices and links them to concepts discussed within the jazz metaphor literature. Drawing on insights from large-scale improvisatory musical practices, the final chapter reveals how improvisation, as a set of practices shared between corporate management and agile methodologies, provides avenues for agile to be scaled up as startups grow or for its widespread adoption within established companies
Towards ultrasound full-waveform inversion in medical imaging
Ultrasound imaging is a front-line clinical modality with a wide range of applications. However, there are limitations to conventional methods for some medical imaging problems, including the imaging of the intact brain. The goal of this thesis is to explore and build on recent technological advances in ultrasonics and related areas such as geophysics, including the ultrasound data parallel acquisition hardware, advanced computational techniques for field modelling and for inverse problem solving. With the significant increase in the computational power now available, a particular focus will be put on exploring the potential of full-waveform inversion (FWI), a high-resolution image reconstruction technique which has shown significant success in seismic exploration, for medical imaging applications. In this thesis a range of technologies and systems have been developed in order to improve ultrasound imaging by taking advantage of these recent advances.
In the first part of this thesis the application of dual frequency ultrasound for contrast enhanced imaging of neurovasculature in the mouse brain is investigated. Here we demonstrated a significant improvement in the contrast-to-tissue ratio that could be achieved by using a multi-probe, dual frequency imaging system when compared to a conventional approach using a single high frequency probe. However, without a sufficiently accurate calibration method to determine the positioning of these probes the image resolution was found to be significantly reduced. To mitigate the impact of these positioning errors, a second study was carried out to develop a sophisticated dual probe ultrasound tomography acquisition system with a robust methodology for the calibration of transducer positions. This led to a greater focus on the development of ultrasound tomography applications in medical imaging using FWI. A 2.5D brain phantom was designed that consisted of a soft tissue brain model surrounded by a hard skull mimicking material to simulate a transcranial imaging problem. This was used to demonstrate for the first time, as far as we are aware, the experimental feasibility of imaging the brain through skull using FWI. Furthermore, to address the lack of broadband sensors available for medical FWI reconstruction applications, a deep learning neural network was proposed for the bandwidth extension of observed narrowband data. A demonstration of this proposed technique was then carried out by improving the FWI image reconstruction of experimentally acquired breast phantom imaging data. Finally, the FWI imaging method was expanded for3D neuroimaging applications and an in silico feasibility of reconstructing the mouse brain with commercial transducers is demonstrated.Open Acces
A Transcendent View of Things: The Persistence of Metaphysics in Modern German Lyric Poetry, 1771–1908
This dissertation explores the lyric poetry of Johann Wolfgang von Goethe, Eduard Mörike, and Rainer Maria Rilke, and it contends that these modern poets retain, albeit uneasily, a view of things as symbols of the transcendent divine. It thus disputes the secularization theory of post-Enlightenment aesthetics. This study specifically challenges the view of symbolism as mere metaphor—an image constructed of arbitrary signs (Nietzsche)—by showing how the epiphanies of modern lyric poetry remain grounded in the metaphysics of analogia, even where (as in Mörike) the writer seems to have left such entanglements behind. The modern poet’s desire to unveil a significant reality beyond subjective impression reveals that symbolic vision necessarily unfolds within the difference between the visible world and the transcendent divine. If signification entails likeness, yet lyric poetry always signifies in and through difference, then a constitutive analogy—that is, the simultaneity of likeness and even greater difference—emerges from within the dynamism of the lyric image itself. Part 1 begins by describing the symbolic image in Goethe’s lyric poetry to recover his view of things as expressing the “holy open mystery” of the cosmos. I show how his symbolism overcomes Enlightenment naturalism by depicting the antecedent order of analogia. Drawing primarily on Neoplatonic metaphysics, the Goethean symbol reveals the partial yet indisputable relatedness of things to the transcendent. Turning to Mörike, part 2 charts his transition to an equivocal understanding of symbol that would sever the image from its numinous source of significance by confining the image to the scope of the poet’s own gaze. Yet Mörike’s poetry also evinces a counter-veiling tendency to de-subjectivize the image, thus yielding a vision of things as they are prior to epistemic concerns, sentiment, and subjective preference. Part 3 contends that Rilke’s thing-poetry evinces a similar tendency to neutralize modernity’s biases against metaphysics. For his poetry recovers an apophatic understanding of symbolism as grounded in analogia that draws on Dionysian theology. His poems thus focus our attention on the thing’s unfathomable capacity for initiating a vision of the divine, of which the thing itself is a partial and fleeting manifestation.Doctor of Philosoph
The Politics of Historical Memory and Commemoration in Africa
The volume re-centres Africa and African history in memory studies, with each chapter drawing parallels to comparable cases in Africa and the world. An underlying assumption is that what can be learned from the politics of historical memory in Africa will have relevance for contemporary politics globally and for understanding how memories can be mobilised for political ends
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