7,186 research outputs found

    Non-Rectangular Convolutions and (Sub-)Cadences with Three Elements

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    The discrete acyclic convolution computes the 2n-1 sums sum_{i+j=k; (i,j) in [0,1,2,...,n-1]^2} (a_i b_j) in O(n log n) time. By using suitable offsets and setting some of the variables to zero, this method provides a tool to calculate all non-zero sums sum_{i+j=k; (i,j) in (P cap Z^2)} (a_i b_j) in a rectangle P with perimeter p in O(p log p) time. This paper extends this geometric interpretation in order to allow arbitrary convex polygons P with k vertices and perimeter p. Also, this extended algorithm only needs O(k + p(log p)^2 log k) time. Additionally, this paper presents fast algorithms for counting sub-cadences and cadences with 3 elements using this extended method

    Operational experience with crab cavities at KEKB

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    KEKB was in operation from December 1988 to June 2010. The crab cavities were installed at KEKB in February 2007 and worked very stably until the end of KEKB operation. Operational experience of the crab cavities with beams is described.Comment: 10 pages, contribution to the ICFA Mini-Workshop on Beam-Beam Effects in Hadron Colliders, CERN, Geneva, Switzerland, 18-22 Mar 201

    Beam-size effect and particle losses at SuperBB factory (Italy)

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    In the colliders, the macroscopically large impact parameters give a substantial contribution to the standard cross section of the e+ee+eγe^+ e^- \to e^+ e^- \gamma process. These impact parameters may be much larger than the transverse sizes of the colliding bunches. It means that the standard cross section of this process has to be substantially modified. In the present paper such a beam-size effect is calculated for bremsstrahlung at SuperBB factory developed in Italy. We find out that this effect reduces beam losses due to bremsstrahlung by about 40%.Comment: 11 pages, 4 figure

    Finite element analysis of magnetic circuits composed of axisymmetric and rectangular regions

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    A new approximate method is developed for calculating three-dimensional magnetic fields in magnetic circuits composed of connected axisymmetric and rectangular regions. Using this new method, fairly accurate solutions can be obtained when the leakage flux from the magnetic circuit is small. In this paper, the new method is explained and then the usefulness of the technique is clarified by comparing calculated and measured flux densities.</p
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