3,800 research outputs found

    Geodetic monitoring of complex shaped infrastructures using Ground-Based InSAR

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    In the context of climate change, alternatives to fossil energies need to be used as much as possible to produce electricity. Hydroelectric power generation through the utilisation of dams stands out as an exemplar of highly effective methodologies in this endeavour. Various monitoring sensors can be installed with different characteristics w.r.t. spatial resolution, temporal resolution and accuracy to assess their safe usage. Among the array of techniques available, it is noteworthy that ground-based synthetic aperture radar (GB-SAR) has not yet been widely adopted for this purpose. Despite its remarkable equilibrium between the aforementioned attributes, its sensitivity to atmospheric disruptions, specific acquisition geometry, and the requisite for phase unwrapping collectively contribute to constraining its usage. Several processing strategies are developed in this thesis to capitalise on all the opportunities of GB-SAR systems, such as continuous, flexible and autonomous observation combined with high resolutions and accuracy. The first challenge that needs to be solved is to accurately localise and estimate the azimuth of the GB-SAR to improve the geocoding of the image in the subsequent step. A ray tracing algorithm and tomographic techniques are used to recover these external parameters of the sensors. The introduction of corner reflectors for validation purposes confirms a significant error reduction. However, for the subsequent geocoding, challenges persist in scenarios involving vertical structures due to foreshortening and layover, which notably compromise the geocoding quality of the observed points. These issues arise when multiple points at varying elevations are encapsulated within a singular resolution cell, posing difficulties in pinpointing the precise location of the scattering point responsible for signal return. To surmount these hurdles, a Bayesian approach grounded in intensity models is formulated, offering a tool to enhance the accuracy of the geocoding process. The validation is assessed on a dam in the black forest in Germany, characterised by a very specific structure. The second part of this thesis is focused on the feasibility of using GB-SAR systems for long-term geodetic monitoring of large structures. A first assessment is made by testing large temporal baselines between acquisitions for epoch-wise monitoring. Due to large displacements, the phase unwrapping can not recover all the information. An improvement is made by adapting the geometry of the signal processing with the principal component analysis. The main case study consists of several campaigns from different stations at Enguri Dam in Georgia. The consistency of the estimated displacement map is assessed by comparing it to a numerical model calibrated on the plumblines data. It exhibits a strong agreement between the two results and comforts the usage of GB-SAR for epoch-wise monitoring, as it can measure several thousand points on the dam. It also exhibits the possibility of detecting local anomalies in the numerical model. Finally, the instrument has been installed for continuous monitoring for over two years at Enguri Dam. An adequate flowchart is developed to eliminate the drift happening with classical interferometric algorithms to achieve the accuracy required for geodetic monitoring. The analysis of the obtained time series confirms a very plausible result with classical parametric models of dam deformations. Moreover, the results of this processing strategy are also confronted with the numerical model and demonstrate a high consistency. The final comforting result is the comparison of the GB-SAR time series with the output from four GNSS stations installed on the dam crest. The developed algorithms and methods increase the capabilities of the GB-SAR for dam monitoring in different configurations. It can be a valuable and precious supplement to other classical sensors for long-term geodetic observation purposes as well as short-term monitoring in cases of particular dam operations

    The role of nursing in multimorbidity care

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    Background Multimorbidity (the co-occurrence of two or more chronic conditions in the same person) affects around one in three persons, and it is strongly associated with a range of negative outcomes including worsening physical function, increased health care use, and premature death. Due to the way healthcare is provided to people with multimorbidity, treatment can become burdensome, fragmented and inefficient. In people with palliative conditions, multimorbidity is increasingly common. Better models of care are needed. Methods A mixed-methods programme of research designed to inform the development of a nurse-led intervention for people with multimorbidity and palliative conditions. A mixed-methods systematic review explored nurse-led interventions for multimorbidity and their effects on outcomes. A cross-sectional study of 63,328 emergency department attenders explored the association between multimorbidity, complex multimorbidity (≥3 conditions affecting ≥3 body systems), and disease-burden on healthcare use and inpatient mortality. A focussed ethnographic study of people with multimorbidity and life-limiting conditions and their carers (n=12) explored the concept of treatment burden. Findings Nurse-led interventions for people with multimorbidity generally focus on care coordination (i.e., case management or transitional care); patients view them positively, but they do not reliably reduce health care use or costs. Multimorbidity and complex multimorbidity were significantly associated with admission from the emergency department and reattendance within 30 and 90 days. The association was greater in those with more conditions. There was no association with inpatient mortality. People with multimorbidity and palliative conditions experienced treatment burden in a manner consistent with existing theoretical models. This thesis also noted the effect of uncertainty on the balance between capacity and workload and proposes a model of how these concepts relate to one another. Discussion This thesis addresses a gap in what is known about the role of nurses in providing care to the growing number of people with multimorbidity. A theory-based nurse-led intervention is proposed which prioritises managing treatment burden and uncertainty. Conclusions Nursing in an age of multimorbidity necessitates a perspective shift which conceptualises chronic conditions as multiple overlapping phenomena situated within an individual. The role of the nurse should be to help patients navigate the complexity of living with multiple chronic conditions

    Understanding the complexities of supporting children’s career aspirations and preparedness for the changing world of work

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    Aspiring to and preparing for a career is becoming an increasingly complex activity for children and adolescents. A young person entering the job market is now more likely to experience multiple career transitions. Recent technological advances are making many routine and some non-routine jobs more susceptible to automation, as well as changing the skill and task requirements within occupations. These changing career conditions are raising complexities for those who support children’s and adolescents’ career aspirations and preparedness. Career theories and interventions incorporating person-occupation matching approaches may increasingly encounter problems as it may become more difficult to explore rapidly evolving occupational requirements with young people and achieve good-fitting or sustained matches between their career aspirations/choices and future job opportunities. Possible mismatches could mean that more young people experience unemployment and/or various opportunity costs from pursuing or failing to adequately prepare for careers affected by automation. To contribute to an enhanced understanding of these problems, this thesis investigated the complexities of supporting children’s and adolescents’ career aspirations and preparedness for the changing world of work. To understand different aspects of the problem, this thesis reports three consecutive and interrelated studies carried out using a mixed methods design. These studies were conducted to address the following overarching research question: what are the complexities of supporting children’s career aspirations and preparedness for automation and job change? The research studies were informed by Social Cognitive Career Theory. First, to estimate the automation-related career risks different groups of school students may encounter over the coming decades, an analysis was conducted using large-scale survey data covering primary and secondary school students’ career aspirations and probability statistics on job automation. Study results revealed that adolescents, male students, lower-income groups, and students’ parental occupation were associated with a greater likelihood of aspiring to an occupation at higher risk of automation. While the results from Study One highlighted possible automation-related risks for school children and different subgroups, these risks are potentially nuanced, affecting some higher status and non-routine occupations as well as routine roles. Due to this emerging complexity, it was important to review how recent career aspiration interventions have approached the changing career conditions to critically evaluate a range of possible approaches to the problem. The second study comprised of a systematic review of career aspiration intervention studies involving children (aged 5-18) to gain insights and identify gaps in how recent intervention approaches have/have not addressed job change. Review findings showed that the interventions often focused on select demographic groups and job sectors, with STEM occupations, females, and adolescents targeted more frequently. It was also shown that the intervention objectives and learning content largely did not address changes within occupations or job markets. Because of the limited approaches to addressing job change identified in Study Two, along with the automation-related career risks estimated in Study One, there was reason to explore how a contemporary career education provision could address automation and job change with children. Considering the context-specific complexities involved in supporting children’s preparedness for automation and job change, it was important to examine the perspectives of stakeholders who contribute to children’s career education to reveal possible conceptual issues and the practical opportunities and challenges they encounter. Focusing on the Scottish career education system, a case study was conducted using a thematic analysis of career documentation, a focus group, and interviews with career policymakers, practitioners, and a sample of primary and secondary schoolteachers. Findings revealed that the career education stakeholders conceptualised automation as creating new occupations rather than resulting in the mass displacement of jobs. However, despite recognising that specific job types were becoming more susceptible to automation and that different groups of children tend to aspire to certain types of occupations, stakeholders did not infer that automation may contribute to differential career impacts across groups. Several practical challenges were raised by stakeholders, including managing some children’s anxiety due to future career uncertainty. Consistent with insights from Study Two, Study Three findings showed stakeholders focused on general career skills and adaptability without also exploring the reasons and principles underlying automation and job change. Fostering this meta understanding of job change could aid young people in their career preparedness and decision making by enabling them to discern likely changes to occupations and job markets. After synthesising findings from the three studies, recommendations for advancing career theory and practice were provided. A key contribution of this research was highlighting potential limitations of aspiration-occupation matching theories and interventions by identifying automation-related career risks and supplementary approaches to address the nuanced changes within occupations and job markets. In sum, this thesis revealed how automation and job change may serve as both an environmental barrier and a potential source of inspiration for children as they pursue and prepare for their future careers

    Resource-aware scheduling for 2D/3D multi-/many-core processor-memory systems

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    This dissertation addresses the complexities of 2D/3D multi-/many-core processor-memory systems, focusing on two key areas: enhancing timing predictability in real-time multi-core processors and optimizing performance within thermal constraints. The integration of an increasing number of transistors into compact chip designs, while boosting computational capacity, presents challenges in resource contention and thermal management. The first part of the thesis improves timing predictability. We enhance shared cache interference analysis for set-associative caches, advancing the calculation of Worst-Case Execution Time (WCET). This development enables accurate assessment of cache interference and the effectiveness of partitioned schedulers in real-world scenarios. We introduce TCPS, a novel task and cache-aware partitioned scheduler that optimizes cache partitioning based on task-specific WCET sensitivity, leading to improved schedulability and predictability. Our research explores various cache and scheduling configurations, providing insights into their performance trade-offs. The second part focuses on thermal management in 2D/3D many-core systems. Recognizing the limitations of Dynamic Voltage and Frequency Scaling (DVFS) in S-NUCA many-core processors, we propose synchronous thread migrations as a thermal management strategy. This approach culminates in the HotPotato scheduler, which balances performance and thermal safety. We also introduce 3D-TTP, a transient temperature-aware power budgeting strategy for 3D-stacked systems, reducing the need for Dynamic Thermal Management (DTM) activation. Finally, we present 3QUTM, a novel method for 3D-stacked systems that combines core DVFS and memory bank Low Power Modes with a learning algorithm, optimizing response times within thermal limits. This research contributes significantly to enhancing performance and thermal management in advanced processor-memory systems

    LIPIcs, Volume 251, ITCS 2023, Complete Volume

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    LIPIcs, Volume 251, ITCS 2023, Complete Volum

    Robust estimation in exponential families: from theory to practice

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    On the Computation of Multi-Scalar Multiplication for Pairing-Based zkSNARKs

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    Multi-scalar multiplication refers to the operation of computing multiple scalar multiplications in an elliptic curve group and then adding them together. It is an essential operation for proof generation and verification in pairing-based trusted setup zero-knowledge succinct non-interactive argument of knowledge (zkSNARK) schemes, which enable privacy-preserving features in many blockchain applications. Pairing-based trusted setup zkSNARKs usually follow a common paradigm. A public string composed of a list of fixed points in an elliptic curve group called common reference string is generated in a trusted setup and accessible to all parties involved. The prover generates a zkSNARK proof by computing multi-scalar multiplications over the points in the common reference string and performing other operations. The verifier verifies the proof by computing multi-scalar multiplications and elliptic curve bilinear pairings. Multi-scalar multiplication in pairing-based trusted setup zkSNARKs has two characteristics. First, all the points are fixed once the common reference string is generated. Second, the number of points n is typically large, with the thesis targeting at n = 2^e (10 ≤ e ≤ 21). Our goal in this thesis is to propose and implement efficient algorithms for computing multi-scalar multiplication in order to enable efficient zkSNARKs. This thesis primarily includes three aspects. First, the background knowledge is introduced and the classical multi-scalar multiplication algorithms are reviewed. Second, two frameworks for computing multi-scalar multiplications over fixed points and five corresponding auxiliary set pairs are proposed. Finally, the theoretical analysis, software implementation, and experimental tests on the representative instantiations of the proposed frameworks are presented

    Fluid dynamics and mass transfer in porous media: Modelling fluid flow and filtration inside open-cell foams

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    Quality of experience and access network traffic management of HTTP adaptive video streaming

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    The thesis focuses on Quality of Experience (QoE) of HTTP adaptive video streaming (HAS) and traffic management in access networks to improve the QoE of HAS. First, the QoE impact of adaptation parameters and time on layer was investigated with subjective crowdsourcing studies. The results were used to compute a QoE-optimal adaptation strategy for given video and network conditions. This allows video service providers to develop and benchmark improved adaptation logics for HAS. Furthermore, the thesis investigated concepts to monitor video QoE on application and network layer, which can be used by network providers in the QoE-aware traffic management cycle. Moreover, an analytic and simulative performance evaluation of QoE-aware traffic management on a bottleneck link was conducted. Finally, the thesis investigated socially-aware traffic management for HAS via Wi-Fi offloading of mobile HAS flows. A model for the distribution of public Wi-Fi hotspots and a platform for socially-aware traffic management on private home routers was presented. A simulative performance evaluation investigated the impact of Wi-Fi offloading on the QoE and energy consumption of mobile HAS.Die Doktorarbeit beschäftigt sich mit Quality of Experience (QoE) – der subjektiv empfundenen Dienstgüte – von adaptivem HTTP Videostreaming (HAS) und mit Verkehrsmanagement, das in Zugangsnetzwerken eingesetzt werden kann, um die QoE des adaptiven Videostreamings zu verbessern. Zuerst wurde der Einfluss von Adaptionsparameters und der Zeit pro Qualitätsstufe auf die QoE von adaptivem Videostreaming mittels subjektiver Crowdsourcingstudien untersucht. Die Ergebnisse wurden benutzt, um die QoE-optimale Adaptionsstrategie für gegebene Videos und Netzwerkbedingungen zu berechnen. Dies ermöglicht Dienstanbietern von Videostreaming verbesserte Adaptionsstrategien für adaptives Videostreaming zu entwerfen und zu benchmarken. Weiterhin untersuchte die Arbeit Konzepte zum Überwachen von QoE von Videostreaming in der Applikation und im Netzwerk, die von Netzwerkbetreibern im Kreislauf des QoE-bewussten Verkehrsmanagements eingesetzt werden können. Außerdem wurde eine analytische und simulative Leistungsbewertung von QoE-bewusstem Verkehrsmanagement auf einer Engpassverbindung durchgeführt. Schließlich untersuchte diese Arbeit sozialbewusstes Verkehrsmanagement für adaptives Videostreaming mittels WLAN Offloading, also dem Auslagern von mobilen Videoflüssen über WLAN Netzwerke. Es wurde ein Modell für die Verteilung von öffentlichen WLAN Zugangspunkte und eine Plattform für sozialbewusstes Verkehrsmanagement auf privaten, häuslichen WLAN Routern vorgestellt. Abschließend untersuchte eine simulative Leistungsbewertung den Einfluss von WLAN Offloading auf die QoE und den Energieverbrauch von mobilem adaptivem Videostreaming
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