54 research outputs found

    Design and implementation of a tool for teaching programming

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    Recently, computers have been widely used in almost all fields of education. Our approach to computer aided education is mainly concerned with programming. Here, it is intended to teach the Pascal language for problem solving in a visual manner. In this project, we have used an object oriented approach for the implementation of an educational tool for programming. The paper mainly discusses the topics related to computer aided education, user interface, object oriented programming and ongoing research related to the project. © 1989

    Automated LASCO CME catalog for solar cycle 23: are CMEs scale invariant?

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    In this paper we present the first automatically constructed LASCO CME catalog, a result of the application of the Computer Aided CME Tracking software (CACTus) on the LASCO archive during the interval September 1997 - January 2007. We have studied the CME characteristics and have compared them with similar results obtained by manual detection (CDAW CME catalog). On average CACTus detects less than 2 events per day during solar minimum up to 8 events during maximum, nearly half of them being narrow (< 20 degrees). Assuming a correction factor, we find that the CACTus CME rate is surprisingly consistent with CME rates found during the past 30 years. The CACTus statistics show that small scale outflow is ubiquitously observed in the outer corona. The majority of CACTus-only events are narrow transients related to previous CME activity or to intensity variations in the slow solar wind, reflecting its turbulent nature. A significant fraction (about 15%) of CACTus-{\it only} events were identified as independent events, thus not related to other CME activity. The CACTus CME width distribution is essentially scale invariant in angular span over a range of scales from 20 to 120 degrees while previous catalogues present a broad maximum around 30 degrees. The possibility that the size of coronal mass outflows follow a power law distribution could indicate that no typical CME size exists, i.e. that the narrow transients are not different from the larger well-defined CMEs.Comment: 13 pages. ApJ, accepte

    A knowledge-based space planning system

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    Knowledge-based systems are potentially powerful tools for improving the results of automated or interactive design procedures. Expert Space Planner is a prototype of such a system that uses production rules in the spatial planning of panel houses. © 1992 Taylor and Francis Group, LLC

    Keyframe reduction techniques for motion capture data

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    Two methods for keyframe reduction of motion capture data are presented. Keyframe reduction of motion capture data enables animators to easily edit motion data with smaller number of keyframes. One of the approaches achieves keyframe reduction and noise removal simultaneously by fitting a curve to the motion information using dynamic programming. The other approach uses curve simplification algorithms on the motion capture data until a predefined threshold of number of keyframes is reached. Although the error rate varies with different motions, the results show that curve fitting with dynamic programming performs as good as curve simplification methods. ©2008 IEEE

    Tests of sunspot number sequences: 1. Using ionosonde data

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    More than 70 years ago it was recognised that ionospheric F2-layer critical frequencies [foF2] had a strong relationship to sunspot number. Using historic datasets from the Slough and Washington ionosondes, we evaluate the best statistical fits of foF2 to sunspot numbers (at each Universal Time [UT] separately) in order to search for drifts and abrupt changes in the fit residuals over Solar Cycles 17-21. This test is carried out for the original composite of the Wolf/Zürich/International sunspot number [R], the new “backbone” group sunspot number [RBB] and the proposed “corrected sunspot number” [RC]. Polynomial fits are made both with and without allowance for the white-light facular area, which has been reported as being associated with cycle-to-cycle changes in the sunspot number - foF2 relationship. Over the interval studied here, R, RBB, and RC largely differ in their allowance for the “Waldmeier discontinuity” around 1945 (the correction factor for which for R, RBB and RC is, respectively, zero, effectively over 20 %, and explicitly 11.6 %). It is shown that for Solar Cycles 18-21, all three sunspot data sequences perform well, but that the fit residuals are lowest and most uniform for RBB. We here use foF2 for those UTs for which R, RBB, and RC all give correlations exceeding 0.99 for intervals both before and after the Waldmeier discontinuity. The error introduced by the Waldmeier discontinuity causes R to underestimate the fitted values based on the foF2 data for 1932-1945 but RBB overestimates them by almost the same factor, implying that the correction for the Waldmeier discontinuity inherent in RBB is too large by a factor of two. Fit residuals are smallest and most uniform for RC and the ionospheric data support the optimum discontinuity multiplicative correction factor derived from the independent Royal Greenwich Observatory (RGO) sunspot group data for the same interval

    Object-Space Parallel Polygon Rendering on Hypercubes

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    This paper presents algorithms for object-space parallel polygon rendering on hypercube-connected multicomputers. A modified scanline z-buffer algorithm is proposed for local rendering phase. The proposed algorithm avoids message fragmentation by packing local foremost pixels in consecutive memory locations efficiently, and it eliminates the initialization of scanline z-buffer for each scanline. Several algorithms, utilizing different communication strategies and topological embeddings, are proposed for global z-buffering of local foremost pixels during the pixel merging phase. The performance comparison of these pixel merging algorithms are presented based on the communication overhead incurred in each scheme. Two adaptive screen subdivision heuristics are proposed for load balancing in the pixel merging phase. These heuristics utilize the distribution of foremost pixels on the screen for the subdivision. Experimental results obtained on an Intel&apos;s iPSC/2 hypercube multicompu..

    Active Pixel Merging on Hypercube Multicomputers

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    This paper presents algorithms developed for pixel merging phase of object-space parallel polygon rendering on hypercube-connected multicomputers. These algorithms reduce volume of communication in pixel merging phase by only exchanging local foremost pixels. In order to avoid message fragmentation, local foremost pixels should be stored in consecutive memory locations. An algorithm, called modified scanline z-buffer, is proposed to store local foremost pixels efficiently. This algorithm also avoids the initialization of scanline z-buffer for each scanline on the screen. Good processor utilization is achieved by subdividing the image-space among the processors in pixel merging phase. Efficient algorithms for load balancing in the pixel merging phase are also proposed and presented. Experimental results obtained on a 16-processor Intel&apos;s iPSC/2 hypercube multicomputer are presented

    Object-Space Parallel Polygon Rendering On Hypercube-Connected Multicomputers

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    This paper presents algorithms developed for object-space parallelism for polygon rendering on hypercube-connected multicomputers. In object-space parallelism, each processor is given the responsibility to render a portion of the input polygons. Each processor shades and z-buffers the locally generated pixels. After this local rendering, the remaining pixels in each processor should be globally z-buffered. Efficient parallelization of this pixel merging operation is important. This is the only place where an overhead is incurred due to parallelization. In this paper, efficient algorithms are presented to perform local rendering and global pixel merging operations. A modified scanline based z-buffer algorithm is proposed. This algorithm reduces the number of pixels sent and received in the pixel merging operation and avoids the re-initialization of the z-buffer for each scanline. Various algorithms are proposed for pixel merging phase. These algorithms use different communication charac..
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