4,242 research outputs found

    Trellis decoding complexity of linear block codes

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    In this partially tutorial paper, we examine minimal trellis representations of linear block codes and analyze several measures of trellis complexity: maximum state and edge dimensions, total span length, and total vertices, edges and mergers. We obtain bounds on these complexities as extensions of well-known dimension/length profile (DLP) bounds. Codes meeting these bounds minimize all the complexity measures simultaneously; conversely, a code attaining the bound for total span length, vertices, or edges, must likewise attain it for all the others. We define a notion of “uniform” optimality that embraces different domains of optimization, such as different permutations of a code or different codes with the same parameters, and we give examples of uniformly optimal codes and permutations. We also give some conditions that identify certain cases when no code or permutation can meet the bounds. In addition to DLP-based bounds, we derive new inequalities relating one complexity measure to another, which can be used in conjunction with known bounds on one measure to imply bounds on the others. As an application, we infer new bounds on maximum state and edge complexity and on total vertices and edges from bounds on span lengths

    Time evolution, cyclic solutions and geometric phases for general spin in an arbitrarily varying magnetic field

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    A neutral particle with general spin and magnetic moment moving in an arbitrarily varying magnetic field is studied. The time evolution operator for the Schr\"odinger equation can be obtained if one can find a unit vector that satisfies the equation obeyed by the mean of the spin operator. There exist at least 2s+12s+1 cyclic solutions in any time interval. Some particular time interval may exist in which all solutions are cyclic. The nonadiabatic geometric phase for cyclic solutions generally contains extra terms in addition to the familiar one that is proportional to the solid angle subtended by the closed trace of the spin vector.Comment: revtex4, 8 pages, no figur

    Readability of Dutch online patient-directed health information on breast reconstruction

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    Background The Netherlands and Belgium are among the top five worldwide of highest incidence in breast cancer, leading to an increase in post-mastectomy reconstruction interest. This study aims to analyze readability of Dutch-written online patient-directed information on breast reconstruction. Methods An online patient query for the term borstreconstructie was simulated using the largest search engine, Google. Content from the 10 most popular web sites from the Netherlands and Belgium was collected and formatted into plain text. Readability level assessment was performed using four available tools for the Dutch language: Accesibility.nl, Klinkende Taal, Texamen, and WizeNote, which measure readability according to the Common European Framework of Reference for Languages (CEFR). Results Of the 20 websites (10 Dutch and Belgian), breast reconstruction content was mainly written in B2/C1 and exceeded the recommended B1 level. The readability tool "Klinkende Taal" was found to have the lowest average CEFR level at B2 (average 4.01, 2.40-5.00), WizeNote (average 4.57, 3.00-5.00), and Accesibility.nl (average 4.58, 3.40-5.50). Both had a CEFR level B2/C1, while Texamen scored the highest average at C1 (average 4.77, 3.60-5.25). Kiesbeter.nl, a Dutch government web site, was found to comply with the recommended B1 level on their breast reconstruction information. Conclusions Readability of online health information on breast reconstruction was generally found to be too advanced for the lay population. Therefore, it may hold benefit for patient-directed health information to be analyzed and revised in order to tailor the information to the targeted population

    Fast solar electrons, interplanetary plasma and km-wave type-III radio bursts observed from the IMP-6 spacecraft

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    IMP-6 spacecraft observations of low frequency radio emission, fast electrons, and solar wind plasma are used to examine the dynamics of the fast electron streams which generate solar type-III radio bursts. Of twenty solar electron events observed between April, 1971 and August, 1972, four were found to be amenable to detailed analysis. Observations of the direction of arrival of the radio emission at different frequencies were combined with the solar wind density and velocity measurements at 1 AU to define an Archimedean spiral trajectory for the radio burst exciter. The propagation characteristics of the exciter and of the fast electrons observed at 1 AU were then conpared. We find that: (1) the fast electrons excite the radio emission at the second harmonic; (2) the total distance travelled by the electrons was between 30 and 70% longer than the length of the smooth spiral defined by the radio observations; (3) this additional distance travelled is the result of scattering of the electrons in the interplanetary medium; (4) the observations are consistent with negligible true energy loss by the fast electrons.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43740/1/11207_2004_Article_BF00153227.pd
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