11,286 research outputs found

    Self-induced structure in the current-voltage characteristics of RSQUIDs

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    Resistive two-junction SQUIDs (RSQUIDs) made from high-temperature superconductors are being developed as narrow-linewidth tunable oscillators in the GHz frequency range. We present here the results of numerical simulation of RSQUIDs of this type. These studies have identified conditions where sub-harmonic steps and other features are apparent in the current-voltage characteristics, driven by the internally-generated heterodyne frequency. The behavior is sensitive to the frequency (set by the voltage across the resistive element in the RSQUID), the temperature and also the loop inductance. We have studied the effects of thermal noise on these features. We also assess how these effects might be observed, and consider how they might affect practical applications of high frequency heterodyne RSQUID oscillators

    Test, Control and Monitor System (TCMS) operations plan

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    The purpose is to provide a clear understanding of the Test, Control and Monitor System (TCMS) operating environment and to describe the method of operations for TCMS. TCMS is a complex and sophisticated checkout system focused on support of the Space Station Freedom Program (SSFP) and related activities. An understanding of the TCMS operating environment is provided and operational responsibilities are defined. NASA and the Payload Ground Operations Contractor (PGOC) will use it as a guide to manage the operation of the TCMS computer systems and associated networks and workstations. All TCMS operational functions are examined. Other plans and detailed operating procedures relating to an individual operational function are referenced within this plan. This plan augments existing Technical Support Management Directives (TSMD's), Standard Practices, and other management documentation which will be followed where applicable

    Towards the disintermediation of creative music search: Analysing queries to determine important facets

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    Purpose: Creative professionals search for music to accompany moving images in films, advertising, television. Some larger music rights holders (record companies and music publishers) organise their catalogues to allow online searching. These digital libraries are organised by various subjective musical facets as well as by artist and title metadata. The purpose of this paper is to present an analysis of written queries relating to creative music search, contextualised and discussed within the findings of text analyses of a larger research project whose aim is to investigate meaning making in this search process. Method: A facet analysis of a collection of written music queries is discussed in relation to the organisation of the music in a selection of bespoke search engines. Results: Subjective facets, in particular Mood, are found to be highly important in query formation. Unusually, detailed Music Structural aspects are also key. Conclusions: These findings are discussed in relation to disintermediation of this process. It is suggested that there are barriers to this, both in terms of classification and also commercial / legal factors

    Direct measurement of penetration length in ultra-thin and/or mesoscopic superconducting structures

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    We describe a method for direct measurement of the magnetic penetration length in thin (10 - 100 nm) superconducting structures having overall dimensions in the range 1 to 100 micrometers. The method is applicable for broadband magnetic fields from dc to MHz frequencies.Comment: Accepted by Journal of Applied P:hysics (Jun 2006).5 pages, 5 figure

    Higher order BRST and anti-BRST operators and cohomology for compact Lie algebras

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    After defining cohomologically higher order BRST and anti-BRST operators for a compact simple algebra {\cal G}, the associated higher order Laplacians are introduced and the corresponding supersymmetry algebra Σ\Sigma is analysed. These operators act on the states generated by a set of fermionic ghost fields transforming under the adjoint representation. In contrast with the standard case, for which the Laplacian is given by the quadratic Casimir, the higher order Laplacians WW are not in general given completely in terms of the Casimir-Racah operators, and may involve the ghost number operator. The higher order version of the Hodge decomposition is exhibited. The example of su(3) is worked out in detail, including the expression of its higher order Laplacian W.Comment: 31 pages, two figures, latex2e file. Replacement (May 14, 1999): a comment and references added. To appear in JM

    Quantum mechanics over a q-deformed (0+1)-dimensional superspace

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    We built up a explicit realization of (0+1)-dimensional q-deformed superspace coordinates as operators on standard superspace. A q-generalization of supersymmetric transformations is obtained, enabling us to introduce scalar superfields and a q-supersymmetric action. We consider a functional integral based on this action. Integration is implemented, at the level of the coordinates and at the level of the fields, as traces over the corresponding representation spaces. Evaluation of these traces lead us to standard functional integrals. The generation of a mass term for the fermion field leads, at this level, to an explicitely broken version of supersymmetric quantum mechanics.Comment: 11 pages, Late
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