1,269 research outputs found

    Wiggly Strings in Linearized Brans-Dicke Gravity

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    The metric around a wiggly cosmic string is calculated in the linear approximation of Brans-Dicke theory of gravitation. The equations of motion for relativistic and non-relativistic particles in this metric are obtained. Light propagation is also studied and it is shown that photon trajectories can be bounded.Comment: 10 pages, LaTeX, added reference

    Time boundary terms and Dirac constraints

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    Time boundary terms usually added to action principles are systematically handled in the framework of Dirac's canonical analysis. The procedure begins with the introduction of the boundary term into the integral Hamiltonian action and then the resulting action is interpreted as a Lagrangian one to which Dirac's method is applied. Once the general theory is developed, the current procedure is implemented and illustrated in various examples which are originally endowed with different types of constraints.Comment: 12 page

    Defect Detection System for Smartphone Front Camera Based on Improved Template Matching Algorithm

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    Automatic defect detection plays crucial role in resilient manufacturing in terms of product quality and cost effectiveness. With reference to the smartphone front cameras production process, the most recurrent defects can be classified into no hole, inner hole burr, outer circle damage, hole deformation, outer circle fracture and hole position offset. Due to the fast production lines and the defects micro size, Sampling-based methods has huge uncertainty and limitation, and Machine learning-based methods are characterised by low efficiency. To tackle these issues, this paper proposes a machine vision-based detection methods of smartphone front camera based on a multi-step template matching algorithm to reduce the computational effort. Specifically, in order to improve the algorithm efficiency, the images of the smartphone front cameras, acquired using industrial image acquisition devices are pre-processed by performing Hough circle and line transformations respectively, then locate the exact defect area as a region of interest (ROI). Finally, a multi-step template matching algorithm is used to detect and classify a number of common defects. Experimental results show an excellent suitability of the proposed system in detecting front camera surface defects. A benchmarking with other available technologies highlights how the proposed system yields an improvement in the detection speed by 46%, along with an improvement in the detection accuracy by 9%. The successful industrial implementation is discussed with reference to the integration into an automatic defect detection system in a smartphone front camera manufacturing context

    Adiabatic renormalization in theories with modified dispersion relations

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    We generalize the adiabatic renormalization to theories with dispersion relations modified at energies higher than a new scale MCM_C. We obtain explicit expressions for the mean value of the stress tensor in the adiabatic vacuum, up to the second adiabatic order. We show that for any dispersion relation the divergences can be absorbed into the bare gravitational constants of the theory. We also point out that, depending on the renormalization prescription, the renormalized stress tensor may contain finite trans-Planckian corrections even in the limit MCM_C\to\infty.Comment: Typos corrected; to appear in the Proceedings of IRGAC 06, Journal of Physics

    Stability of Chaplygin gas thin-shell wormholes

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    In this paper we construct spherical thin-shell wormholes supported by a Chaplygin gas. For a rather general class of geometries we introduce a new approach for the stability analysis of static solutions under perturbations preserving the symmetry. We apply this to wormholes constructed from Schwarzschild, Schwarzschild-de Sitter, Schwarzschild-anti de Sitter and Reissner-Nordstrom metrics. In the last two cases, we find that there are values of the parameters for which stable static solutions exist.Comment: 14 pages, 5 figures; v2: minor changes and new references added. Accepted for publication in Physical Review

    Eco-intelligent factories: Timescales for environmental decision support

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    Manufacturing decisions are currently made based on considerations of cost, time and quality. However there is increasing pressure to also routinely incorporate environmental considerations into the decision making processes. Despite the existence of a number of tools for environmental analysis of manu-facturing activities, there does not appear to be a structured approach for gener-ating relevant environmental information that can be fed into manufacturing decision making. This research proposes an overarching structure that leads to three approaches, pertaining to different timescales that enable the generation of environmental information, suitable for consideration during decision making. The approaches are demonstrated through three industrial case studies

    Activity-dependent heteromerization of the hyperpolarization-activated, cyclic-nucleotide gated (HCN) channels: role of N-linked glycosylation.

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    Formation of heteromeric complexes of ion channels via co-assembly of different subunit isoforms provides an important mechanism for enhanced channel diversity. We have previously demonstrated co-association of the hyperpolarization activated cyclic-nucleotide gated (HCN1/HCN2) channel isoforms that was regulated by network (seizure) activity in developing hippocampus. However, the mechanisms that underlie this augmented expression of heteromeric complexes have remained unknown. Glycosylation of the HCN channels has been implicated in the stabilization and membrane expression of heteromeric HCN1/HCN2 constructs in heterologous systems. Therefore, we used in vivo and in vitro systems to test the hypothesis that activity modifies HCN1/HCN2 heteromerization in neurons by modulating the glycosylation state of the channel molecules. Seizure-like activity (SA) increased HCN1/HCN2 heteromerization in hippocampus in vivo as well as in hippocampal organotypic slice cultures. This activity increased the abundance of glycosylated HCN1 but not HCN2-channel molecules. In addition, glycosylated HCN1 channels were preferentially co-immunoprecipitated with the HCN2 isoforms. Provoking SA in vitro in the presence of the N-linked glycosylation blocker tunicamycin abrogated the activity-dependent increase of HCN1/HCN2 heteromerization. Thus, hippocampal HCN1 molecules have a significantly higher probability of being glycosylated after SA, and this might promote a stable heteromerization with HCN2
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