24,524 research outputs found

    Re-Scaling of Energy in the Stringy Charged Black Hole Solutions using Approximate Symmetries

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    This paper is devoted to study the energy problem in general relativity using approximate Lie symmetry methods for differential equations. We evaluate second-order approximate symmetries of the geodesic equations for the stringy charged black hole solutions. It is concluded that energy must be re-scaled by some factor in the second-order approximation.Comment: 18 pages, accepted for publication in Canadian J. Physic

    Dynamics of coherent structures in a plane mixing layer

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    An incompressible, time developing 3-D mixing layer with idealized initial conditions was simulated numerically. Consistent with the suggestions from experimental measurements, the braid region between the dominant spanwise vortices or rolls develops longitudinal vortices or ribs, which are aligned upstream and downstream of a roll and produce spanwise distortion of the rolls. The process by which this distortion occurs is explained by studying a variety of quantities of dynamic importance (e.g., production of enstrophy, vortex stretching). Other quantities of interest (dissipation, helicity density) are also computed and discussed. The currently available simulation only allows the study of the early evolution (before pairing) of the mixing layer. New simulations in progress will relieve this restriction

    Ultracompact Generation of Continuous-Variable Cluster States

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    We propose an experimental scheme that has the potential for large-scale realization of continuous-variable (CV) cluster states for universal quantum computation. We do this by mapping CV cluster-state graphs onto two-mode squeezing graphs, which can be engineered into a single optical parametric oscillator (OPO). The desired CV cluster state is produced directly from a joint squeezing operation on the vacuum using a multi-frequency pump beam. This method has potential for ultracompact experimental implementation. As an illustration, we detail an experimental proposal for creating a four-mode square CV cluster state with a single OPO.Comment: 4 pages, 1 figure; v2 improved discussion of the implications of our result; added discussion of finite squeezing effect

    Fixed points of dynamic processes of set-valued F-contractions and application to functional equations

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    The article is a continuation of the investigations concerning F-contractions which have been recently introduced in [Wardowski in Fixed Point Theory Appl. 2012:94,2012]. The authors extend the concept of F-contractive mappings to the case of nonlinear F-contractions and prove a fixed point theorem via the dynamic processes. The paper includes a non-trivial example which shows the motivation for such investigations. The work is summarized by the application of the introduced nonlinear F-contractions to functional equations

    Land and water productivity of wheat in the Western Indo-Gangetic Plains of India and Pakistan: a comparative analysis

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    Wheat / Crop yield / Productivity / Climate / Irrigation canals / Watercourses / Water distribution / Water allocation / Policy / India / Pakistan / Gangetic Plains / Kaithal Irrigation Circle / Bhakra Canal / Chaj Sub-Basin / Lower Jehlum Canal

    Clinical Outcomes of the Ilizarov Method After an Infected Tibial Non Union

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    Background: The Ilizarov technique has been used in the UK for the last 20 years in the management of infected non-union of long bones. This method uses fine wires inserted percutaneously which are attached and tensioned to provide a strong frame construct. The majority of tibial and femoral non unions can be treated successfully by internal fixation. However, an infected non-union of the tibia can prove a difficult problem. The Ilizarov method can prove useful for treating these complex injuries. Objectives: To assess whether a new limb reconstruction centre in the UK has comparable results. Patients and Methods: Twelve patients (10 M: 2 F; Avg age 43.3 years) who had an infected tibial non-union between March 2009 and August 2010 treated with the Ilizarov technique. Intervention method was Ilizarov technique and main outcome measures include functional and radiological outcomes assessed using the Association for the Study and Application of Methods of Ilizarov (ASAMI) criteria, American Orthopaedic Foot and Ankle Score (AOFAS) and Visual Analogue Pain scores. Results: All twelve patients united. None required amputation. Mean time to union was 46 weeks (range 24 - 70/median 50). The average follow up time was 62 weeks (39 - 164/ median 59). According to the ASAMI score bone/radiological results ten were classed as excellent with the remainder being good. Functionally six were graded as excellent, four as good and two as poor. The average AOFAS score was 83/100 (70 - 90) and pain visual analogue scale (VAS) was two. Conclusions: Our results in terms of ASAMI scores are comparable with the published literature. Furthermore, our return to work is better than most European studies (63%). All our patients said they would have the procedure again. We attribute this success partly to the multidisciplinary approach. We recommend early referral to a dedicated unit if there is any evidence of a non-union

    Comparison of Two Powder Processing Techniques on the Properties of Cu-NbC Composites

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    An in situCu-NbC compositewas successfully synthesized fromCu,Nb, and C powders using ball milling and high pressure torsion (HPT) techniques. The novelty of the new approach, HPT, is the combination of high compaction pressure and large shear strain to simultaneously refine, synthesize, and consolidate composite powders at roomtemperature.The HPTed Cu-NbC composite was formed within a short duration of 20 min without Fe contamination from the HPT’s die. High porosity of 3–9%, Fe and niobium oxidations, fromgrindingmedia and ethanol during ball milling led to low electrical conductivity of the milled Cu-NbC composite. The electrical conductivity of the HPTed Cu-NbC composite showed a value 50% higher than that of milled Cu-NbC composite of the same composition
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