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Automated software engineering 1997年第2期4卷 243-245页

作者： Pfleeger, Shari Lawrence Center for Research in Evaluating Software Technology (CREST) Department of Systems and Computer Science School of Engineering Howard University Washington USA

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Design and implementation of a distributed workflow enactment service

Design and implementation of a distributed workflow enactmen...

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International Conference on Cooperative Information Systems

作者： E. Gokkoca M. Altinel R. Cingil E.N. Tatbul P. Koksal A. Dogac Software Research and Development Center Department of Computer Engineering Middle East Technical University Ankara Turkey

Workflows are activities involving the coordinated execution of multiple tasks performed by different processing entities, mostly in distributed heterogeneous environments, which are very common in enterprises of even moderate complexity. In current commercial workflow systems, the workflow scheduler is a single centralized component. A distributed workflow enactment service, on the other hand, should contain several schedulers on different nodes of a network, each executing a part of the process instances. Such an architecture would fit naturally into the distributed heterogeneous environments. Further advantages of a distributed enactment service are failure resiliency and increased performance, since a centralized scheduler is a potential bottleneck. In this paper, we present the design and implementation of a distributed workflow enactment service based on the work of M. Singh (1996). By starting with a block-structured workflow specification language, we avoid a very general set of dependencies and their related problems. In this way, it is possible to present a simple algorithm for the distributed scheduling of process instances. Further benefits of the approach are the ease of testing and debugging the system, and the execution efficiency through having a reduced number of messages.

关键词： Distributed computing software performance Research and development Neck Scheduling algorithm System testing Debugging Performance evaluation Councils Humans

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SYSTOLIC ALGORITHMS FOR THE SOLUTION OF TOEPLITZ MATRICES

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Parallel Algorithms and Applications 1997年第4期12卷 321-339页

作者： D. J. Evans[a] S. A. Amin[b] [a] Computer Studies Department Parallel Algorithms Research Center (PARC) Lougborough University Lougborough Leices UK [b] Informatic and Software Engineering Research Centre (ISERC) Chatham Kent UK

In this paper a factorisation of certain symmetric circulant banded linear systems proposed by Evans [Evans 1981] is described. It can be shown that a banded Toeplitz matrix can be factorised into the product of easily inverted cyclic matrices. By using this factorisation, a solution can be derived for such *** matrices have become increasingly important with the rapid growth of signal and image processing. To achieve high performance, new systolic array designs for the algorithm shown above are implemented, A full description of the systolic array designs are given in a later section. The performance of the designs are discussed.

关键词： Toeplitz circulant systolic array

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Constrained multipoint aerodynamic shape optimization using an adjoint formulation and parallel computers 35th

Constrained multipoint aerodynamic shape optimization using ...

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35th Aerospace Sciences Meeting and Exhibit, 1997

作者： Reuther, J. Jameson, A. Alonso, J.J. Rimlinger, M.J. Saunders, D. Research Institute for Advanced Computer Science NASA Ames Research Center MS 227-6 Moffett FieldCA94035 United States Department of Mechanical and Aerospace Engineering Princeton University PrincetonNJ08544 United States Sterling Software NASA Ames Research Center MS 227-6 Moffett FieldCA94035 United States

An aerodynamic shape optimization method that treats the design of complex aircraft configurations subject to high fidelity computational fluid dynamics (CFD), geometric constraints and multiple design points is described. The design process will be greatly accelerated through the use of both control theory and distributed memory computer architectures. Control theory is employed to derive the adjoint differential equations whose solution allows for the evaluation of design gradient information at a fraction of the computational cost required by previous design methods [5, 4, 24, 18]. The resulting problem is implemented on parallel distributed memory architectures using a domain decomposition approach, an optimized communication schedule, and the MPI (Message Passing Interface) standard for portability and efficiency. The final result achieves very rapid aerodynamic design based on a higher order CFD method. In order to facilitate the integration of these high fidelity CFD approaches into future multi-disciplinary optimization (MDO) applications, new methods must be developed which are capable of simultaniously addressing complex geometries, multiple objective functions, and geometric design constraints. In our earlier studies [8,9,10,11, 19,15, 20,21,22, 23,1], we coupled the adjoint based design formulations with unconstrained optimization algorithms and showed that the approach was effective for the aerodynamic design of airfoils, wings, wing-bodies, and complex aircraft configurations. In many of the results presented in these earlier works, geometric constraints were satisfied either by a projection into feasible space or by posing the design space parameterization such that it automatically satisfied constraints. Furthermore, with the exception of reference [9] where the second author initially explored the use of multipoint design in conjunction with adjoint formulations, our earlier works have focused on single point design efforts. Here we demonstrate that

关键词： Computational fluid dynamics

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Characterization and application of rapid thermal oxide surface passivation for the highest efficiency RTP silicon solar cells

Characterization and application of rapid thermal oxide surf...

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Conference Record of the Twenty Sixth IEEE Photovoltaic Specialists Conference - 1997

作者： P. Doshi J. Moschner J. Jeong A. Rohatgi R. Singh S. Narayanan School of Electrical and Computer Engineering Georgia Institute of Technology University Center of Excellence for Photovoltaics Research and Education Atlanta GA USA Department of Electrical and Computer Engineering Clemson University Clemson SC USA Solarex Corporation Frederick MD USA

This paper presents the development and analysis of the first 19%-efficient silicon solar cells fabricated by rapid thermal processing (RTP). These cells required no high-temperature conventional furnace processing (CFP). Improved front surface passivation by rapid thermal oxidation (RTO) was found to reduce S/sub front/ from 7.5/spl times/10/sup 5/ to 2/spl times/10/sup 4/ cm/s, decrease J/sub 0e/ by almost an order of magnitude, and increase cell efficiency by about 1% (absolute). An additional 1% gain in efficiency was achieved by applying a thicker screen-printed, RTP-alloyed Al-BSF instead of the standard 1 /spl mu/m evaporated Al-BSF. Because of the rapid heating rate in RTP, the RTP Al-BSF also gives a more uniform and effective BSF compared with the CFP Al-BSF. In comparison with furnace processed cells, this RTP/RTO process reduced the time for diffusion and oxidation from 330 to 10 min without sacrificing efficiency. To reduce back surface recombination further, RTO can be grown on the back. PCD characterization of RTO on 1.3 /spl Omega/cm Si reveals an S/sub back/ well below 100 cm/s, which can result in >20% efficient RTP/RTO cells.

关键词： Passivation Silicon Furnaces Photovoltaic cells Oxidation Production Lithography Annealing Degradation Application software

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Back surface field and emitter passivation effects in the record high efficiency n-type dendritic web silicon solar cell

Back surface field and emitter passivation effects in the re...

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Conference Record of the Twenty Sixth IEEE Photovoltaic Specialists Conference - 1997

作者： S. Narasimha G. Crotty T. Krygowski A. Rohatgi D.L. Meier Department of Electrical and Computer Engineering Georgia Institute of Technology University Center of Excellence for Photovoltaics Research and Education Atlanta GA USA EBARA Solar Inc. PA USA

A solar cell efficiency of 17.3% (4 cm/sup 2/ area) has been achieved on 11 /spl Omega/-cm, n-type dendritic web silicon. This is the highest reported efficiency to date on any silicon ribbon material. Detailed characterization and modeling show that, due to the reduced substrate thickness (100 /spl mu/m) and long diffusion length (>400 /spl mu/m), device performance is strongly dependent on the back surface recombination velocity (S/sub b/). In this study, an n/sup +/ phosphorus back surface field was implemented to reduce the effective S/sub b/ to approximately 20 cm/s, and increase the device efficiency by nearly 4% (absolute) above the case of infinite S/sub b/. Additionally, thermal oxide passivation of the boron emitter was found to improve the cell performance by more than 0.5% (absolute). By extending model calculations to "mirror" solar cells (identically doped n/sup +/-p-p/sup +/ and p/sup +/-n-n/sup +/ devices with equivalent bulk lifetimes), it is shown that substrate type plays only a minor role in determining the overall device efficiency.

关键词： Passivation Photovoltaic cells Silicon Boron Etching Annealing Coatings Photovoltaic systems Solar power generation computer science education

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Model-checking of real-time systems: A telecommunications application - Experience report 97

Model-checking of real-time systems: A telecommunications ap...

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19th International Conference on software engineering (ICSE 97) - Pulling Together

作者： Alur, R Jagadeesan, LJ Kott, JJ VonOlnhausen, JE Computing Sciences Research Center Bell Laboratories and Department of Electrical Engineering & Computer Science University of California Berkeley CA Software Production Research Department Bell Laboratories 1000 E. Warrenville Rd. Naperville IL Network Systems Platform Development Lucent Technologies 1200 E. Warrenville Rd. Naperville IL

ISBN: (纸本)0897919149

We describe the application of model checking tools to analyze a real-time software challenge in the design of Lucent Technologies' 5ESS telephone switching system. We use two tools: COSPAN for checking real-time properties, and TPWB for checking probabilistic specifications. We report on the feedback given by the tools, and based on our experience, discuss the advantages and the limitations of the approach used.

关键词： telecommunications software formal methods model checking real-time verification probabilistic verification

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Multi-attribute lexicon generation by hyperlinked embedded access structure

Multi-attribute lexicon generation by hyperlinked embedded a...

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International Symposium on Database engineering and Applications (IDEAS)

作者： Wen-Jann Yang R. Sridhar P. Palumbo Center of Excellence for Document Analysis and Recognition State University of New York University at Buffalo Buffalo NY USA Department of Electrical and Computer Engineering State University of New York University at Buffalo Buffalo NY USA

Providing a lexicon for all possible postal addresses can support decision making for handwritten address interpretation. The possibility of uncertainty can be reduced by choosing the highest confident record in the provided lexicon as the target postal address. For a large database with multi-attribute records, traditional access methods are not efficient enough to generate the lexicon. This paper proposes a hyperlinked embedded access structure (HEAS) which combines the features of inverted file structure and doubly-chained tree structure with unique data compression schemes. The raw United State Postal Service (USPS) database is organized according to the proposed access structure, and the organized database serves as a knowledge base for interpreting handwritten addresses. The organization cost, storage requirement, and query cost are analyzed and compared to conventional inverted file and doubly-chained tree structures.

关键词： Tree data structures Spatial databases Text analysis Decision making Costs Information retrieval Indexes Distributed power generation Uncertainty Postal services

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Color clustering techniques for color-content-based image retrieval from image databases

Color clustering techniques for color-content-based image re...

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IEEE International Conference on Multimedia Computing and Systems (ICMCS)

作者： Jia Wang Wen-Jann Yang R. Acharya Department of Electrical & Computer Engineering State University of New York University at Buffalo Buffalo NY USA Center of Excellence for Ducument Analysis and Recognition State University of New York University at Buffalo Buffalo NY USA

Image retrieval based on color content is an auxiliary function for traditional text-annotated image databases. Most color-based image retrieval systems adopt color histograms as the feature of color content. One of the most important steps in these systems is to reduce histogram dimensions with the least loss in color content. A good clustering technique is vital for this purpose. This paper examines the color conservation property by applying different clustering techniques in perceptually uniform color spaces and different images. For studying color spaces, the perceptual uniform spaces, such as Mathematical Transformation to Munsell system (MTM) and C.I.E. L*a*b*, are investigated. For evaluating clustering techniques, the equalized quantization approach, the hierarchical clustering approach, and the Color-Naming-System (CNS) supervised clustering approach are studied. For analyzing color loss, the error bound, the quantized error in color space conversion, and the average quantized error of 400 color images are explored. An image retrieval application based on color content is shown to demonstrate the difference in applying these clustering techniques. These simulation results suggest that good clustering techniques usually lead to more effective retrieval.

关键词： Information retrieval Image retrieval Image databases Content based retrieval Image color analysis Histograms Quantization Image analysis Spatial databases Visual databases

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Pulsed Laser Deposition of Highly Crystalline Gan Films on Sapphire

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MRS Online Proceedings Library 1997年第1期482卷 410-415页

作者： R. D. Vispute V. Talyansky S. Chupoon R. Enck T. Dahmas S. B. Ogale R. P. Sharma T. Venkatesan Y. X. Li L. G. Salamanca-Riba A. A. Iliadis M. He X. Tang J. B. Halpern M. G. Spencer M. A. Khan K. A. Jones V. Bel’kov V. Botnaryuk I. Diakonu L. Fedorov Y. Zhilyaev CSR Dept. of Physics University of Maryland College Park USA Department of Materials and Nuclear Engineering University of Maryland Collge Park USA Department of Electrical Engineering University of Maryland Collge Park USA Materials Science Research Center of Excellence Howard University Washington DC USA Department of Electrical and Computer Engineering University of South Carolina Columbia USA U.S. Army Research Laboratory Adelphi USA A.F. Ioffe Physical-Technical Institute St. Petersburg Russia

We report high quality epitaxial growth of GaN film by pulsed laser deposition technique. In this method, a KrF pulsed excimer laser was used for ablation of a polycrystalline, stoichiometric GaN target. The ablated material was deposited on a substrate kept at a distance of ~7 cm from the target surface and in an NH3 background pressure of 10−5 Torr and temperature of 750°C. The films (~0.5 μm thick) grown on AIN buffered sapphire showed a x-ray diffraction rocking curve FWHM of 4–6 arc minutes. The ion channeling minimum yield in the surface region was ~3% indicating a high degree of crystallinity. The optical band gap was found to be 3.4 eV. The epitaxial films were shiny, and the surface RMS roughness was ∼ 5–15 nm. The electrical resistivity of these films was in the range of 10−2–102 Ω-cm with a mobility in excess of 60 cm2V−1s−1 and carrier concentration of 1017–1019cm−3.

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