345 research outputs found

    Heater Control for Thermionic Power Generation

    Get PDF
    The purpose of this report is to detail the conceptualization, analysis, budget, manufacturing, and assembly the heater for a thermionic energy converter for portable energy generation. This proof of concept will be created to provide a full thermionic energy converter with a reliable and satisfactory heater than can be used in future systems. The report highlights the feasibility and realities in the design and fabrication of the system

    Higgs-photon resonances

    Full text link
    We study models that produce a Higgs boson plus photon (h0γh^0 \gamma) resonance at the LHC. When the resonance is a Z′Z' boson, decays to h0γh^0 \gamma occur at one loop. If the Z′Z' boson couples at tree-level to quarks, then the h0γh^0 \gamma branching fraction is typically of order 10−510^{-5} or smaller. Nevertheless, there are models that would allow the observation of Z′→h0γZ' \to h^0 \gamma at s=13\sqrt{s} = 13 TeV with a cross section times branching fraction larger than 1 fb for a Z′Z' mass in the 200--450 GeV range, and larger than 0.1 fb for a mass up to 800 GeV. The 1-loop decay of the Z′Z' into lepton pairs competes with h0γh^0 \gamma, even if the Z′Z' couplings to leptons vanish at tree level. We also present a model in which a Z′Z' boson decays into a Higgs boson and a pair of collimated photons, mimicking an h0γh^0 \gamma resonance. In this model, the h0γh^0 \gamma resonance search would be the discovery mode for a Z′Z' as heavy as 2 TeV. When the resonance is a scalar, although decay to h0γh^0 \gamma is forbidden by angular momentum conservation, the h0h^0 plus collimated photons channel is allowed. We comment on prospects of observing an h0γh^0 \gamma resonance through different Higgs decays, on constraints from related searches, and on models where h0h^0 is replaced by a nonstandard Higgs boson.Comment: 22 page

    Constitutional Law - Right to Travel

    Get PDF
    The United States Supreme Court has held that state residency requirements for eligibility under federal welfare assistance programs are unconstitutional because they restrict the right to travel. Shapiro v. Thompson, 89 S. Ct. 1322 (1969)

    Intravascular ultrasound: a technique in evolution: methodological considerations

    Get PDF
    As the title of the thesis suggests, intravascular ultrasound has been, and continues to be, an imaging technique that is in active evolution. Image quality has improved dramatically from the crude, low resolution 'black and white' images of the first generation of intravascular ultrasound scanners and transducers are now small enough to image most arteries before intervention. Although intravascular ultrasound is increasingly seen as the most informative method of assessing the coronary arteries, there are outstanding problems that must be addressed and overcome before its full potential can be achieved.The aim of this thesis is to examine a number of these methodological shortcomings of intravascular ultrasound so that appropriate solutions can be found.After a general overview, provided in Chapter 1, the reproducibility of intravascular ultrasound quantitation is assessed in Chapter 2. For reasons elaborated above, ultrasound is seen as the best technique to study the acute and long term outcome of coronary interventions and the effect of plaque modifying agents. Without detailed data concerning its reproducibility, such studies are uninterpretable.Chapter 3 deals with the impact of catheter malfunction on the geometric integrity of intravascular ultrasound images. At present, the mechanical ultrasound devices are the most widely used systems. All mechanical systems are potentially subject to the problem of non -uniform rotation of the transducer, and to date its impact has been poorly characterised.The difficulty encountered in discriminating unstable coronary lesions is examined in Chapter 4. There is a widely held view that acute coronary lesions cannot be discriminated using intravascular ultrasound. Specific echographic markers are described that are found in the majority of unstable lesions. Close scrutiny of grey scale images allows identification of acute lesions and may allow discrimination of thrombus from underlying atheromatous plaque.In the last two chapters, methodological issues relating to the clinical application of intravascular ultrasound in guiding coronary stenting are explored. In chapter 5, the findings of an observational study confirm the potential of intravascular ultrasound to provide additional information in cases in which favourable angiographic appearances have been achieved. However, the choice of one particular 'expansion index' over another is seen to impact significantly on the proportion of lesions that are judged to be successful. Before ultrasound guidance based on the attainment of specific quantitative expansion criteria be advocated as a widely applied technique, the reproducibility of reference segment measurements must be known. This issue is studied in chapter 6.Separate studies are described in each of the data chapters. A similar layout is employed in each, consisting of the study aims, methods, findings, discussion and conclusion. At the risk of introducing a degree of repetition in the methods sections of each chapter, the ultrasound examination and image interpretation protocol are elaborated in each case, as important differences exist between the studies

    Temporal-Difference Learning to Assist Human Decision Making during the Control of an Artificial Limb

    Full text link
    In this work we explore the use of reinforcement learning (RL) to help with human decision making, combining state-of-the-art RL algorithms with an application to prosthetics. Managing human-machine interaction is a problem of considerable scope, and the simplification of human-robot interfaces is especially important in the domains of biomedical technology and rehabilitation medicine. For example, amputees who control artificial limbs are often required to quickly switch between a number of control actions or modes of operation in order to operate their devices. We suggest that by learning to anticipate (predict) a user's behaviour, artificial limbs could take on an active role in a human's control decisions so as to reduce the burden on their users. Recently, we showed that RL in the form of general value functions (GVFs) could be used to accurately detect a user's control intent prior to their explicit control choices. In the present work, we explore the use of temporal-difference learning and GVFs to predict when users will switch their control influence between the different motor functions of a robot arm. Experiments were performed using a multi-function robot arm that was controlled by muscle signals from a user's body (similar to conventional artificial limb control). Our approach was able to acquire and maintain forecasts about a user's switching decisions in real time. It also provides an intuitive and reward-free way for users to correct or reinforce the decisions made by the machine learning system. We expect that when a system is certain enough about its predictions, it can begin to take over switching decisions from the user to streamline control and potentially decrease the time and effort needed to complete tasks. This preliminary study therefore suggests a way to naturally integrate human- and machine-based decision making systems.Comment: 5 pages, 4 figures, This version to appear at The 1st Multidisciplinary Conference on Reinforcement Learning and Decision Making, Princeton, NJ, USA, Oct. 25-27, 201
    • …
    corecore