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  • Chemistry  (11)
  • Computer Systems  (10)
  • Fluid Mechanics and Thermodynamics  (2)
  • TEM  (2)
  • 1995-1999  (23)
  • 1925-1929  (2)
  • 11
    Electronic Resource
    Electronic Resource
    Polymer-anchored metal complexes. III. Preparation, structural, thermal stability, dielectric, and conductivity characterization of polycondensates from Cu(II)-1, 10-phenanthroline and trimellitic anhydride/pryromellitic dianhydride (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 56 (1995), S. 501-508 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Trimellitic anhydride and pyromellitic dianhydride have been polycondensed with Cu(II)-phenanthroline complex as a comonomer in the presence of anhydrous ZnCl2 under selective conditions. Elemental diffuse reflectance and infrared spectroscopic and X-ray diffraction (XRD) analysis data of these polymers have been correlated with the tentative structure Proposed for these polycondensates. Thermal stability and dielectric and conductivity characteristics of these polycondensates have been evaluated to understand the effect of the ligand and the anhydride moieties on these properties. Unlike the polymer-anchored 3d-metal complexes, these polycondensates fail to initiate the cationic polymerization of N-vinylcarbazole. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070560412
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    Paper (German National Licenses)
    Fulltext
  • 12
    Electronic Resource
    Electronic Resource
    Cure synergism in XNBR vulcanization in presence of thiophosphoryl disulfides and amine disulfide/thiazole accelerators (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 1349-1359 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The study deals with the vulcanization of carboxylated nitrile butadiene rubber (XNBR) having synergistic combinations of accelerators comprising thiophosphoryl disulfide as one of the components. Other constituent accelerators employed in the present investigation are 2-mercaptobenzothiazole (MBT), 2-mercaptobenzothiazyl disulfide (MBTS), bis(N-oxydiethylene)disulfide (ODDS), N-oxydiethylene 2-benzothiazole sulfenamide (OBTS), etc. The binary combinations of thiophosphoryl disulfides with OBTS exhibited the highest mutual activity in the respective areas, so far as the physical properties are concerned. Structural characterization of different thiophosphoryl disulfide-accelerated XNBR vulcanizates, including those formed from the synergistic combinations with OBTS, were studied using a methyl iodide probe. It was found that the amount of sulfidic crosslinks arising from the reaction between —COOH groups of XNBR and thiophosphoryl disulfides, actually controls the network structure as wellas the physical properties of the vulcanizates. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 13
    Electronic Resource
    Electronic Resource
    Fabric-reinforced thermoplastics: Simulation of the forming process (1996)
    Hoboken, NJ : Wiley-Blackwell
    Advances in Polymer Technology 15 (1996), S. 165-170 
    Details
    ISSN: 0730-6679
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The Institut für Kunststoffverarbeitung in Aachen, Germany is undertaking investigations in a simulation program of the process of forming fabric-reinforced thermoplastics, in order to attain an efficient instrument for the layout of components as early as in the desing stage. The current state of the investigations provides instruments for the determination of several data crucial for industrial applications. These are fiber placement and wall thickness distribution after forming, displacement paths required, interlaminar sliding, minimum blank size required, as well as the heat transfer during forming. Current and future investigations will enhance the program's range of performance. Of particular interest are calculation of three-dimensional anisotropic temperature distribution, of the mechanical characteristic values, as well as of shrinkage and warpage behaviors. As these investigations are concluded, the designer will have a comprehensive computer-assisted engineering system at hand for the layout and dimensioning of components made of fiber-reinforced thermoplastics produced in a forming process. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 14
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    Tetrahedral and Hexahedral Mesh Adaptation for CFD Problems (1997)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: This paper presents two unstructured mesh adaptation schemes for problems in computational fluid dynamics. The procedures allow localized grid refinement and coarsening to efficiently capture aerodynamic flow features of interest. The first procedure is for purely tetrahedral grids; unfortunately, repeated anisotropic adaptation may significantly deteriorate the quality of the mesh. Hexahedral elements, on the other hand, can be subdivided anisotropically without mesh quality problems. Furthermore, hexahedral meshes yield more accurate solutions than their tetrahedral counterparts for the same number of edges. Both the tetrahedral and hexahedral mesh adaptation procedures use edge-based data structures that facilitate efficient subdivision by allowing individual edges to be marked for refinement or coarsening. However, for hexahedral adaptation, pyramids, prisms, and tetrahedra are used as buffer elements between refined and unrefined regions to eliminate hanging vertices. Computational results indicate that the hexahedral adaptation procedure is a viable alternative to adaptive tetrahedral schemes.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: NAS-96-007
    Format: text
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  • 15
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    A New Approach to Parallel Dynamic Partitioning for Adaptive Unstructured Meshes (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Classical mesh partitioning algorithms were designed for rather static situations, and their straightforward application in a dynamical framework may lead to unsatisfactory results, e.g., excessive data migration among processors. Furthermore, special attention should be paid to their amenability to parallelization. In this paper, a novel parallel method for the dynamic partitioning of adaptive unstructured meshes is described. It is based on a linear representation of the mesh using self-avoiding walks.
    Keywords: Computer Systems
    Type: IPPS''99; Apr 12, 1999 - Apr 16, 1999; San Juan; Puerto Rico
    Format: application/pdf
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  • 16
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    Communication Studies of DMP and SMP Machines (1997)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Understanding the interplay between machines and problems is key to obtaining high performance on parallel machines. This paper investigates the interplay between programming paradigms and communication capabilities of parallel machines. In particular, we explicate the communication capabilities of the IBM SP-2 distributed-memory multiprocessor and the SGI PowerCHALLENGEarray symmetric multiprocessor. Two benchmark problems of bitonic sorting and Fast Fourier Transform are selected for experiments. Communication-efficient algorithms are developed to exploit the overlapping capabilities of the machines. Programs are written in Message-Passing Interface for portability and identical codes are used for both machines. Various data sizes and message sizes are used to test the machines' communication capabilities. Experimental results indicate that the communication performance of the multiprocessors are consistent with the size of messages. The SP-2 is sensitive to message size but yields a much higher communication overlapping because of the communication co-processor. The PowerCHALLENGEarray is not highly sensitive to message size and yields a low communication overlapping. Bitonic sorting yields lower performance compared to FFT due to a smaller computation-to-communication ratio.
    Keywords: Computer Systems
    Type: NAS-96-005
    Format: application/pdf
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  • 17
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    Large-Scale Distributed Computational Fluid Dynamics on the Information Power Grid Using Globus (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper describes an experiment in which a large-scale scientific application development for tightly-coupled parallel machines is adapted to the distributed execution environment of the Information Power Grid (IPG). A brief overview of the IPG and a description of the computational fluid dynamics (CFD) algorithm are given. The Globus metacomputing toolkit is used as the enabling device for the geographically-distributed computation. Modifications related to latency hiding and Load balancing were required for an efficient implementation of the CFD application in the IPG environment. Performance results on a pair of SGI Origin 2000 machines indicate that real scientific applications can be effectively implemented on the IPG; however, a significant amount of continued effort is required to make such an environment useful and accessible to scientists and engineers.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: Frontiers; Feb 21, 1999 - Feb 25, 1999; Annapolis, MD; United States
    Format: application/pdf
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  • 18
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    Efficient Load Balancing and Data Remapping for Adaptive Grid Calculations (1997)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Mesh adaption is a powerful tool for efficient unstructured- grid computations but causes load imbalance among processors on a parallel machine. We present a novel method to dynamically balance the processor workloads with a global view. This paper presents, for the first time, the implementation and integration of all major components within our dynamic load balancing strategy for adaptive grid calculations. Mesh adaption, repartitioning, processor assignment, and remapping are critical components of the framework that must be accomplished rapidly and efficiently so as not to cause a significant overhead to the numerical simulation. Previous results indicated that mesh repartitioning and data remapping are potential bottlenecks for performing large-scale scientific calculations. We resolve these issues and demonstrate that our framework remains viable on a large number of processors.
    Keywords: Computer Systems
    Type: NASA-CR-204487 , NAS 1.26:204487 , RIACS-TR-97-03 , Parallel Algorithms and Architectures; Jun 22, 1997 - Jun 25, 1997; Newport, RI; United States
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  • 19
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    Efficient Parallelization of a Dynamic Unstructured Application on the Tera MTA (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The success of parallel computing in solving real-life computationally-intensive problems relies on their efficient mapping and execution on large-scale multiprocessor architectures. Many important applications are both unstructured and dynamic in nature, making their efficient parallel implementation a daunting task. This paper presents the parallelization of a dynamic unstructured mesh adaptation algorithm using three popular programming paradigms on three leading supercomputers. We examine an MPI message-passing implementation on the Cray T3E and the SGI Origin2OOO, a shared-memory implementation using cache coherent nonuniform memory access (CC-NUMA) of the Origin2OOO, and a multi-threaded version on the newly-released Tera Multi-threaded Architecture (MTA). We compare several critical factors of this parallel code development, including runtime, scalability, programmability, and memory overhead. Our overall results demonstrate that multi-threaded systems offer tremendous potential for quickly and efficiently solving some of the most challenging real-life problems on parallel computers.
    Keywords: Computer Systems
    Type: Supercomputing; Nov 13, 1999 - Nov 19, 1999; Portland, OR; United States
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  • 20
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    Satisfiability Test with Synchronous Simulated Annealing on the Fujitsu AP1000 Massively-Parallel Multiprocessor (1996)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Solving the hard Satisfiability Problem is time consuming even for modest-sized problem instances. Solving the Random L-SAT Problem is especially difficult due to the ratio of clauses to variables. This report presents a parallel synchronous simulated annealing method for solving the Random L-SAT Problem on a large-scale distributed-memory multiprocessor. In particular, we use a parallel synchronous simulated annealing procedure, called Generalized Speculative Computation, which guarantees the same decision sequence as sequential simulated annealing. To demonstrate the performance of the parallel method, we have selected problem instances varying in size from 100-variables/425-clauses to 5000-variables/21,250-clauses. Experimental results on the AP1000 multiprocessor indicate that our approach can satisfy 99.9 percent of the clauses while giving almost a 70-fold speedup on 500 processors.
    Keywords: Computer Systems
    Type: NASA-CR-200964 , NAS 1.26:200964 , RIACS-TR-96-07 , 10th ACM International Conference on Supercomputing; May 25, 1996 - May 28, 1996; Philadelphia, PA; United States
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