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41.
Ying Chen Frank Dehne Todd Eavis Andrew Rau-Chaplin 《Distributed and Parallel Databases》2008,23(2):99-126
We present “Pipe ’n Prune” (PnP), a new hybrid method for iceberg-cube query computation. The novelty of our method is that
it achieves a tight integration of top-down piping for data aggregation with bottom-up a priori data pruning. A particular
strength of PnP is that it is efficient for all of the following scenarios: (1) Sequential iceberg-cube queries, (2) External memory iceberg-cube queries, and (3) Parallel
iceberg-cube queries on shared-nothing PC clusters with multiple disks.
We performed an extensive performance analysis of PnP for the above scenarios with the following main results: In the first
scenario PnP performs very well for both dense and sparse data sets, providing an interesting alternative to BUC and Star-Cubing. In the second scenario PnP shows a surprisingly
efficient handling of disk I/O, with an external memory running time that is less than twice the running time for full in-memory
computation of the same iceberg-cube query. In the third scenario PnP scales very well, providing near linear speedup for
a larger number of processors and thereby solving the scalability problem observed for the parallel iceberg-cubes proposed
by Ng et al.
Research partially supported by the Natural Sciences and Engineering Research Council of Canada. A preliminary version of
this work appeared in the International Conference on Data Engineering (ICDE’05). 相似文献
42.
Adigitized plane of sizeM is a rectangular M × M array of integer lattice points called pixels. A M × M mesh-of-processors in which each processorP
ij
represents pixel (i,j) is a natural architecture to store and manipulate images in ; such a parallel architecture is called asystolic screen. In this paper we consider a variety of computational-geometry problems on images in a digitized plane, and present optimal algorithms for solving these problems on a systolic screen. In particular, we presentO(M)-time algorithms for determining all contours of an image; constructing all rectilinear convex hulls of an image (peeling); solving the parallel and perspective visibility problem forn disjoint digitized images; and constructing the Voronoi diagram ofn planar objects represented by disjoint images, for a large class of object types (e.g., points, line segments, circles, ellipses, and polygons of constant size) and distance functions (e.g., allL
p
metrics). These algorithms implyO(M)-time solutions to a number of other geometric problems: e.g., rectangular visibility, separability, detection of pseudo-star-shapedness, and optical clustering. One of the proposed techniques also leads to a new parallel algorithm for determining all longest common subsequences of two words.Research supported by the Naural Sciences and Engineering Research Council of Canada. With the Editor-in-Chief's permission, this paper was sent to the referees in a form which kept them unaware of the fact that the Guest Editor is one of the co-authors. 相似文献
43.
Frank Dehne Russ Miller Andrew Rau-Chaplin 《International journal of parallel programming》1991,20(6):475-486
In this paper, we present optimal parallel algorithms for optical clustering on a mesh-connected computer.Optical clustering is a clustering technique based on the principal of optical resolution, and is of particular interest in picture analysis. The algorithms we present are based on the application of parallel algorithms in computational geometry and graph theory. In particular, we show that given a setS ofN points in the Euclidean plane, the following problems can be solved in optimal
time on a mesh-connected computer of sizeN.
Research partially supported by the Natural Sciences and Engineering Research Council of Canada and the National Science Foundation under Grant IRI-9108288. 相似文献
1. | Determine the optical clusters ofS with respect to a given separation parameter. |
2. | Given an interval [a, b] representing the number of optical clusters desired in the clustering ofS, determine the range of the separation parameter that will result in such an optical clustering. |
44.
Comment to the vfdb‐guidelines “Methods of fire safety engineering”. In the last eight years the vfdb Working Group 4 elaborated the Guidelines “Methods of fire safety engineering“. They shall give help to choose appropriate methods and input data for fire safety engineering in the framework of a fire safety concept. This paper explains the overall concept and the relations between the different chapters of the Guidelines. Safety objectives and related performance requirements are discussed in more detail because they are important for the choice of relevant fire scenarios and design criteria and appropriate calculation methods. The application of the Guidelines is demonstrated for a convention building which is investigated with respect to smoke control and fire protection of the roof construction. 相似文献
45.
46.
Andreas Jankiewicz Werner Baltes Klaus Werner Bgl Lutz Ingo Dehne Annette Jamin Andreas Hoffmann Dieter Haustein Stefan Vieths 《Journal of the science of food and agriculture》1997,75(3):359-370
Celery roots were processed by microwave heating, cooking, drying, γ-irradiation, ultra high pressure treatment and high voltage impulse treatment. The immunochemical stabilities of the three known allergenic structures of celery were tested with sera from patients who were sensitised to celery. In addition, rabbit antisera were used to detect the allergens profilin and Api g 1 on celery immunoblots. The specificity and reactivity of IgE from the patients' sera were investigated by immunoblotting, by an enzyme allergosorbent test (EAST) and by dose-related IgE inhibition experiments. The results of all three methods agreed closely and indicated high antigenic and allergenic activity in native celery which was reduced by thermal processing. The heat-stability of the known celery allergens decreased in the following order: carbohydrate epitopes> profilin>Api g 1. In contrast, the allergenicity was only mildly reduced by non-thermal processing. The results obtained with human IgE were confirmed by an in vitro mediator-release assay that is based on rat basophil leukemia cells (RBL cells) which were passively sensitised with celery-specific murine IgE. With sera from mice that had been immunised with native celery, the native sample and non-thermal celery preparations elicited the strongest mediator release, whereas a weak response was obtained with samples from heat-processed celery. These results agreed closely with the data obtained in allergic patients whose IgE antibodies were directed against the major protein allergen Api g 1. Our results may be helpful in risk assessment and in selecting food preparations which can be consumed without symptoms by a subgroup of celery-allergic patients with a known sensitisation pattern. ©1997 SCI 相似文献
47.
48.
49.
T. Zimmermann G. W. Fischer J. Teller H. Dehne B. Olk 《Advanced Synthesis \u0026amp; Catalysis》1989,331(5):843-852
Pyrylium Compounds. 43. Arylsubstituted 5-(2-Dialkylamino-thiazol-5-yl)-pentadienones from 2,4,6-Triarylpyrylium Salts and 2-Dialkylamino-4-aryl-thiazoles 2,4,6-Triarylpyrylium salts 1 react with 2-dialkylamino-4-aryl-thiazoles 7 (used in substance or prepared in situ from α-thiocyanato-acetophenones 9 ) in the presence of an appropriate acid-binding agent (e.g. piperidine acetate or sodium acetate) to give 5-(2-dialkylamino-4-aryl-thiazol-5-yl)-1,3,5-triaryl-penta-2,4-dien-1-ones 8 . As reaction medium aliphatic alcohols (ethanol, n-propanol), dipolar aprotic solvents (acetonitrile) or chlorinated hydrocarbons (methylene chloride, chloroform) can be used. On the other hand, under the same conditions 2-amino-4-phenyl-thiazole ( 10 ) reacts with salts of type 1 via pyrylium ring transformation yielding 2,4,6-triaryl-1-(4-phenyl-thiazol-2-yl)-pyridinium perchlorates 11 . 相似文献
50.
The synthesis of 4-thiazoline 2-iminium sulfinates ( 3 ) is described. From the salts 3 and NBS the 2-(arylsulfonylimino)-4-thiazolines ( 4 ) were formed, which have also been prepared by oxidation of 2-(arylsulfenylimino)-4-thiazolines ( 5 ) and by reaction of the arylsulfonyl chlorides ( 6 ) with 2-imino-4-thiazolines ( 2 ). The treatment of 5 with NBS (or NIS) in dry solvents results in 2-(arylsulfenylimino)-5-bromo (or iodo)-4-thiazolines ( 7 ); in the presence of NaHCO3 2-(arylsulfonylimino)-5-bromo-4-thiazolines ( 8 ) are formed. 2-(Arylsulfinylimino)-4-thiazolines ( 10 ) have also been halo- genated in the same manner with NBS or NIS to give the products ( 11 ). 相似文献