88,849 research outputs found

    Perfect single error-correcting codes in the Johnson Scheme

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    Delsarte conjectured in 1973 that there are no nontrivial pefect codes in the Johnson scheme. Etzion and Schwartz recently showed that perfect codes must be k-regular for large k, and used this to show that there are no perfect codes correcting single errors in J(n,w) for n <= 50000. In this paper we show that there are no perfect single error-correcting codes for n <= 2^250.Comment: 4 pages, revised, accepted for publication in IEEE Transactions on Information Theor

    The Political Boycott: An Unprivileged Form of Expression

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    In this paper we generalize the Fourier transform from the space of tempered distributions to a bigger space called exponential generalized distributions. For that purpose we replace the Schwartz space S by a smaller space X0 of smooth functions such that, among other properties, decay at infinity faster than any exponential. The construction of X0 is such that this space of test functions is closed for derivatives, for Fourier transform and for translations. We equip X0 with an appropriate locally convex topology and we study it’s dual X'0; we call X&#8242;0 the space of exponential generalized distributions. The space X&#8242;0 contains all the Schwartz tempered distributions, is closed for derivatives, and both, translations and Fourier transform, are vector and topological automorphisms in X&#8242;0. As non trivial examples of elements in X&#8242;0, we show that some multipole series appearing in physics are convergent in this space.</p

    Transverse-Longitudinal Coupling by Space Charge in Cyclotrons

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    A method is presented that enables to compute the parameters of matched beams with space charge in cyclotrons with emphasis on the effect of the transverse-longitudinal coupling. Equations describing the transverse-longitudinal coupling and corresponding tune-shifts in first order are derived for the model of an azimuthally symmetric cyclotron. The eigenellipsoid of the beam is calculated and the transfer matrix is transformed into block-diagonal form. The influence of the slope of the phase curve on the transverse-longitudinal coupling is accounted for. The results are generalized and numerical procedures for the case of an AVF cyclotron are presented. The algorithm is applied to the PSI Injector II and Ring cyclotron and the results are compared to TRANSPORT.Comment: 8 pages, 2 figure

    Longwave spectral dependence of emission from warm dust clouds

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    Observations of the continuum emission from warm dust clouds at 230 GHz, or 1300 microns, enables the determination of the frequency dependence of the optically thin longwave emission. Integrating the emission over the solid angle of the clouds gives a flux independent of the beam size and of the internal temperature structure of the clouds. The frequency resolving power of 64 allows the correction of these fluxes for the contribution of free-free emission from nearby H II regions at a price of reduced sensitivity. These observations were combined with similar observations made by others in the submillimeter and far infrared regimes to determine the continuum spectra of the dust clouds. Mean characteristics were determined for these clouds, fitting the spectra with simple transfer equations. Results are briefly discussed

    Identification and analysis of email and contacts artefacts on iOS and OS X

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    Choosing a Company's Building Design: Models for Strategic Design Decisions

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    Improving the linkage between real estate strategy and building design can help competitive business strategy. Differentiating building design from product design is important. Problems in making design choices derive from received paradigmatic knowledge that misrepresents the design decision processes. Architectural selection problems are explained with reference to design decision processes and dilemmas of testing the design. Because comparison is the underlying method of evaluation, the design competition is discussed as a model to evaluate the design of a company’s proposed high profile buildings in relation to corporate strategy. The Appendix describes the process and the recent and past history of competitions.