1,152 research outputs found

    Academic Freedom: How Does Florida Stand?

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    Spectroscopic diagnostics of plasma during laser processing of aluminium

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    The role of the plasma in laser–metal interaction is of considerable interest due to its influence in the energy transfer mechanism in industrial laser materials processing. A 10 kW CO2 laser was used to study its interaction with aluminium under an argon environment. The objective was to determine the absorption and refraction of the laser beam through the plasma during the processing of aluminium. Laser processing of aluminium is becoming an important topic for many industries, including the automobile industry. The spectroscopic relative line to continuum method was used to determine the electron temperature distribution within the plasma by investigating the 4158 ° Ar I line emission and the continuum adjacent to it. The plasmas are induced in 1.0 atm pure Ar environment over a translating Al target, using f/7 and 10 kW CO2 laser. Spectroscopic data indicated that the plasma composition and behaviour were Ar-dominated. Experimental results indicated the plasma core temperature to be 14 000–15 300 K over the incident range of laser powers investigated from 5 to 7 kW. It was found that 7.5–29% of the incident laser power was absorbed by the plasma. Cross-section analysis of the melt pools from the Al samples revealed the absence of any key-hole formation and confirmed that the energy transfer mechanism in the targets was conduction dominated for the reported range of experimental data.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/58114/2/d7_19_021.pd

    Task Feasibility Maximization using Model-Free Policy Search and Model-Based Whole-Body Control

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    Producing feasible motions for highly redundant robots, such as humanoids, is a complicated and high-dimensional problem.Model-based whole-body control of such robots, can generate complex dynamic behaviors through the simultaneous execution of multiple tasks.Unfortunately, tasks are generally planned without close consideration for the underlying controller being used, or the other tasks being executed, and are often infeasible when executed on the robot. Consequently, there is no guarantee that the motion will be accomplished.In this work, we develop an optimization loop which automatically improves task feasibility using model-free policy search in conjunction with model-based whole-body control.This combination allows problems to be solved, which would be otherwise intractable using simply one or the other.Through experiments on both the simulated and real iCub humanoid robot, we show that by optimizing task feasibility, initially infeasible complex dynamic motions can be realized --- specifically, a sit-to-stand transition

    The effectiveness of national strategic guidelines at a local level: a case study of the UK general aviation industry.

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    The thesis is concerned with the prospects for reducing strategic-local tensions in the British planning process. It examines the conflicts surrounding small general aviation aerodromes as a means of understanding these tensions, why they have evolved, and if they might be reconciled through planning reform. The only prior academic research to have touched upon this issue through general aviation has been an ESRC funded project undertaken by Gallent and colleagues (1999), who found aerodromes provided a microcosm of planning's issues. Building on this work, the thesis develops what is meant by strategic-local tensions, which in broad terms are described as differences between national and regional guidance/plans and what actually takes place locally. Moving from a basic research question it develops a wide planning perspective based on the literature by discussing the meaning of planning, its history and issues for example, how conflicts in planning might be influenced by the broader socio-political environment. The thesis then arrives at three hypotheses which question the effectiveness of the existing strategic guideline implementation process, develops a local planning authority framework and addresses issues of reflectivity and bias. Results from three national surveys of pilots, aerodromes and manufacturers, plus longitudinal analysis of government and other datasets, are then used to detail a comprehensive and unique description of general aviation, which includes a costing based account of the direct expenditure of flying activity. This provides a substantive foundation for a local planning authority survey which both extends previous boundaries and enables the process of implementing strategic objectives to be disaggregated and evaluated. Field visits to twenty six aerodromes and five local authorities are subsequently used to explore gaps within the strategic implementation process and to develop conclusions, within the wider landscape of planning, about the nature of strategic local tensions and implications for planning reform

    Intraoperative Neurophysiological Monitoring for Endoscopic Endonasal Approaches to the Skull Base: A Technical Guide.

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    Intraoperative neurophysiological monitoring during endoscopic, endonasal approaches to the skull base is both feasible and safe. Numerous reports have recently emerged from the literature evaluating the efficacy of different neuromonitoring tests during endonasal procedures, making them relatively well-studied. The authors report on a comprehensive, multimodality approach to monitoring the functional integrity of at risk nervous system structures, including the cerebral cortex, brainstem, cranial nerves, corticospinal tract, corticobulbar tract, and the thalamocortical somatosensory system during endonasal surgery of the skull base. The modalities employed include electroencephalography, somatosensory evoked potentials, free-running and electrically triggered electromyography, transcranial electric motor evoked potentials, and auditory evoked potentials. Methodological considerations as well as benefits and limitations are discussed. The authors argue that, while individual modalities have their limitations, multimodality neuromonitoring provides a real-time, comprehensive assessment of nervous system function and allows for safer, more aggressive management of skull base tumors via the endonasal route

    Invariant Manifolds and Rate Constants in Driven Chemical Reactions

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    Reaction rates of chemical reactions under nonequilibrium conditions can be determined through the construction of the normally hyperbolic invariant manifold (NHIM) [and moving dividing surface (DS)] associated with the transition state trajectory. Here, we extend our recent methods by constructing points on the NHIM accurately even for multidimensional cases. We also advance the implementation of machine learning approaches to construct smooth versions of the NHIM from a known high-accuracy set of its points. That is, we expand on our earlier use of neural nets, and introduce the use of Gaussian process regression for the determination of the NHIM. Finally, we compare and contrast all of these methods for a challenging two-dimensional model barrier case so as to illustrate their accuracy and general applicability.Comment: 28 pages, 13 figures, table of contents figur

    Towards Logistics 4.0: A Skill-Based OPC UA Communication between WMS and the PLC of an Automated Storage and Retrieval System

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    In order to bring intralogistics systems to the same level of interoperability as today’s modern production systems, logistics must take the essential steps towards Industry 4.0. This requires an increasing abstraction level of control logic as an enabler for horizontal and vertical integration. The abstraction will lead to the interconnection of manufacturing and logistics control with the production planning and warehouse management systems (WMS). A main enabler for these communication paths are service-oriented architectures (SoA). OPC UA has established itself as a widely used and already adopted SoA-based communication standard in industry. The paper describes the realization of an OPC UA-based approach for the communication between a WMS and a PLC of an automated storage and retrieval system (ASRS). The conceptual basis of communication design are skills of the ASRS. The work is supported by an architectural design with a subsequent prototypical implementation
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