5,654 research outputs found

    Converging organoids and extracellular matrix::New insights into liver cancer biology

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    Right Place, Right Time:Proactive Multi-Robot Task Allocation Under Spatiotemporal Uncertainty

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    For many multi-robot problems, tasks are announced during execution, where task announcement times and locations are uncertain. To synthesise multi-robot behaviour that is robust to early announcements and unexpected delays, multi-robot task allocation methods must explicitly model the stochastic processes that govern task announcement. In this paper, we model task announcement using continuous-time Markov chains which predict when and where tasks will be announced. We then present a task allocation framework which uses the continuous-time Markov chains to allocate tasks proactively, such that robots are near or at the task location upon its announcement. Our method seeks to minimise the expected total waiting duration for each task, i.e. the duration between task announcement and a robot beginning to service the task. Our framework can be applied to any multi-robot task allocation problem where robots complete spatiotemporal tasks which are announced stochastically. We demonstrate the efficacy of our approach in simulation, where we outperform baselines which do not allocate tasks proactively, or do not fully exploit our task announcement models

    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

    An empirical investigation of the relationship between integration, dynamic capabilities and performance in supply chains

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    This research aimed to develop an empirical understanding of the relationships between integration, dynamic capabilities and performance in the supply chain domain, based on which, two conceptual frameworks were constructed to advance the field. The core motivation for the research was that, at the stage of writing the thesis, the combined relationship between the three concepts had not yet been examined, although their interrelationships have been studied individually. To achieve this aim, deductive and inductive reasoning logics were utilised to guide the qualitative study, which was undertaken via multiple case studies to investigate lines of enquiry that would address the research questions formulated. This is consistent with the author’s philosophical adoption of the ontology of relativism and the epistemology of constructionism, which was considered appropriate to address the research questions. Empirical data and evidence were collected, and various triangulation techniques were employed to ensure their credibility. Some key features of grounded theory coding techniques were drawn upon for data coding and analysis, generating two levels of findings. These revealed that whilst integration and dynamic capabilities were crucial in improving performance, the performance also informed the former. This reflects a cyclical and iterative approach rather than one purely based on linearity. Adopting a holistic approach towards the relationship was key in producing complementary strategies that can deliver sustainable supply chain performance. The research makes theoretical, methodological and practical contributions to the field of supply chain management. The theoretical contribution includes the development of two emerging conceptual frameworks at the micro and macro levels. The former provides greater specificity, as it allows meta-analytic evaluation of the three concepts and their dimensions, providing a detailed insight into their correlations. The latter gives a holistic view of their relationships and how they are connected, reflecting a middle-range theory that bridges theory and practice. The methodological contribution lies in presenting models that address gaps associated with the inconsistent use of terminologies in philosophical assumptions, and lack of rigor in deploying case study research methods. In terms of its practical contribution, this research offers insights that practitioners could adopt to enhance their performance. They can do so without necessarily having to forgo certain desired outcomes using targeted integrative strategies and drawing on their dynamic capabilities

    Contributions to autonomous robust navigation of mobile robots in industrial applications

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    151 p.Un aspecto en el que las plataformas móviles actuales se quedan atrás en comparación con el punto que se ha alcanzado ya en la industria es la precisión. La cuarta revolución industrial trajo consigo la implantación de maquinaria en la mayor parte de procesos industriales, y una fortaleza de estos es su repetitividad. Los robots móviles autónomos, que son los que ofrecen una mayor flexibilidad, carecen de esta capacidad, principalmente debido al ruido inherente a las lecturas ofrecidas por los sensores y al dinamismo existente en la mayoría de entornos. Por este motivo, gran parte de este trabajo se centra en cuantificar el error cometido por los principales métodos de mapeado y localización de robots móviles,ofreciendo distintas alternativas para la mejora del posicionamiento.Asimismo, las principales fuentes de información con las que los robots móviles son capaces de realizarlas funciones descritas son los sensores exteroceptivos, los cuales miden el entorno y no tanto el estado del propio robot. Por esta misma razón, algunos métodos son muy dependientes del escenario en el que se han desarrollado, y no obtienen los mismos resultados cuando este varía. La mayoría de plataformas móviles generan un mapa que representa el entorno que les rodea, y fundamentan en este muchos de sus cálculos para realizar acciones como navegar. Dicha generación es un proceso que requiere de intervención humana en la mayoría de casos y que tiene una gran repercusión en el posterior funcionamiento del robot. En la última parte del presente trabajo, se propone un método que pretende optimizar este paso para así generar un modelo más rico del entorno sin requerir de tiempo adicional para ello

    Post-Growth Geographies: Spatial Relations of Diverse and Alternative Economies

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    Post-Growth Geographies examines the spatial relations of diverse and alternative economies between growth-oriented institutions and multiple socio-ecological crises. The book brings together conceptual and empirical contributions from geography and its neighbouring disciplines and offers different perspectives on the possibilities, demands and critiques of post-growth transformation. Through case studies and interviews, the contributions combine voices from activism, civil society, planning and politics with current theoretical debates on socio-ecological transformation

    Towards a framework for the study of ongoing socio-technical transitions: explored through the UK self-driving car paradigm

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    The UK government set out to see self-driving cars on roads by 2021. The idea of a self-driving car has been around for almost a century, and more recent technological developments have made self-driving cars a real-life possibility. While a fully self-driving automobility system is some distance away, real-life testing is bringing autonomous driving closer to consumers. Some claim this to be the biggest disruption to mobility systems since the invention of the car. Claims about the potential of self-driving mobility range from economic and social benefits to environmental improvements. A significant ambiguity however remains concerning how they will be deployed and how the technological innovation will affect mobility aims and related transport and infrastructure systems. So far, the vast majority of studies on AVs have focused on the technology aspect of this transition lacking contributions that address this from a broader socio-technical perspective. With the accelerated adoption of new technologies, Sustainability Transitions has come to prominence as a research area that seeks to understand and guide socio-technical transitions toward sustainable trajectories. Socio-technical transitions theoretical framework has been used to understand historical transitions in the majority of empirical applications. The ability to apply the same framework to ongoing transitions and to guide these towards sustainable outcomes remains unsubstantiated. To address this gap this thesis examines the foundations of multi-level perspective (MLP) – a socio-technical transitions analytical framework – and develops an analytical framework (SRPM – System Rules Pathways Mechanisms) that is appropriate for the study of ongoing transitions. The refocused framework incorporates critical realism to focus analysis on causation and causal mechanisms. It is used to analyse the ongoing socio-technical transition to self-driving cars in the UK through a four-step analytical process. The study is framed as a case-based process mechanism study. The four steps are: i) contextualisation of the ongoing transition to AVs in the UK as a socio-technical transition based on the MLP theoretical framework; ii) identification of internal and external structural relations within the transition through the notion of rules and the morphogenetic cycle; iii) aligning observed processes with transition pathways to theorise about the trajectories of the transition; iv) identification of causal mechanisms in the observed processes through identification of demi-regularities through data analysis of grey literature and theorisation about mechanisms through the development of mechanism sketches and schemata. The thesis makes two contributions to knowledge: i) methodological and ii) empirical. The methodological contribution is the development of the SRPM analytical framework to study an ongoing socio-technical transition, and the empirical contribution is the application of this framework to the study of the ongoing transition to driverless cars in the UK
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