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  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 179 (1978), S. 1209-1217 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Studies on the relative efficiencies of 3d-transition metal oxides as catalysts for the polymerization of vinyl ethers revealed that V2O5 is the most efficient catalyst. Some kinetic studies with the system isobutyl vinyl ether/V2O5/benzene were carried out at ambient temperature. It was found that the rate is second order in isobutyl vinyl ether (IBVE) concentration (0,25 to 2,0mol.1-1) and the inhibition of the polymerization by pyridine suggests a cationic mechanism. Rp increases by the use of benzaldehyde along with V2O5, whereas water (3.10-3mol.1-1) seems to have no effect on Rp. Over the temperature range of 15 to 60°C, Rp as well as [η] attain a maximum value at about 32°C. [η] is unaffected by varying the amounts of oxides, whereas it increases with increasing IBVE concentration. No stereoregularity in the product polymer was observed by using V2O5 alone or in combination with modifiers such as benzaldehyde or carbon disulfide. The kinetics are interpreted in terms of the Hinshelwood-Langmuire mechanism assuming a single point adsorption.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 72 (1978), S. 57-66 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Poly(N-vinylcarbazol) wurde mit verschiedenen Reagenzien sulfoniert und die Ionenaustauschkapazität der erhaltenen Harze bestimmt. Eine maximale Kapazität von 4,5 meq · g-1 des trockenen Harzes wurde durch 10stündige Reaktion mit 98,8proz. H2SO4 bei 30°C erhalten. Die pH-Titrationskurven lassen einen starken monofunktionellen Kationenaustauscher mit einem pK-Wert von 2,2 erkennen. Das Harz zeigt eine mäßige Austauschgeschwindigkeit mit NaCl und ist bis zu 250°C thermisch stabil.
    Notes: Poly(N-vinyl carbazole) was sulfonated with different sulfonating agents and ion exchange capacities of the resins produced were evaluated. A maximum capacity of 4.5 meq · g-1 of dry resin was realized when sulfonation was done with 98.8% H2SO4 at 30°C for 10 h. The pH titration curves reveal the nature of a strong monofunctional cation exchanger with a pK value of 2.2. The resin exhibits a moderate rate of exchange with NaCl and is thermally stable up to ca. 250°C.
    Additional Material: 4 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 73 (1978), S. 53-61 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Ein Kationenaustauscher wurde durch Kondensation von Polyisobutylvinyläther und Furfural hergestellt. Als Katalysator diente konzentrierte Schwefelsäure. Der Austauscher wurde durch Messen der Austauschkapazität, durch Untersuchen seiner thermischen Belastbarkeit und durch Bestimmen seines Verhaltens bei der pH-Titration charakterisiert. Es scheint sich um einen Austauscher mit schwachen Säregruppen zu handlen, die wohl als —COOH-Gruppen vorliegen und durch Oxidation aus den Furfuralgruppen entstanden sein dürften.
    Notes: A cation exchange resin was synthesized from the condensation product of poly(iso-butyl vinyl ether) and furfural by treating it with concentration sulphuric acid. The resin produced was characterized by measuring its total and salt splitting capacities, and by studying its thermal characteristics and behaviour to pH metric titration. The latter suggests the resin to be a weak one possibly containing —COOH groups, which result from the oxidation of the furfural aldehyde group by sulphuric acid.
    Additional Material: 2 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 23 (1979), S. 2327-2334 
    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: Cation-exchange resins have been synthesized through the condensation of N-vinylcarbazole and poly(N-vinylcarbazole) with furfural in presence of anhydrous AlCl3 and subsequent sulfonation of the condensates. The resins have been characterized in respect to their polyfunctionality, exchange capacity, and thermal stability.
    Additional Material: 3 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 24 (1979), S. 683-692 
    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: Influence of hydrofuramide and ethanolamines on efficient vulcanization (EV), semi-EV, and conventional sulfur vulcanization accelerated by tetramethyl thiuram disulfide is reported. In the case of thiuram vulcanization, the amines increase the cure rate but reduce the crosslink density. The interaction of tetramethyl thiuram disulfide with amines has been studied. The amines interact with thiuram disulfide (TMTD) giving rise to the formation of gaseous products. Thermogravimetric analysis shows weight loss of about 50% in case of TMTD-ethanolamine system and 25% in case of TMTD-hydrofuramide system. Gas chromatographic studies of the gaseous products indicate that it consists mainly of H2S. The other constituents in the gaseous product are CO2 and a thiol. A possible reaction based on these observations to account for decrease in crosslink density in thiuram vulcanization caused by amines is reported.
    Additional Material: 4 Ill.
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  • 6
    Publication Date: 2019-07-13
    Description: In this paper we study the performance of the Lustre file system using five scientific and engineering applications representative of NASA workload on large-scale supercomputing systems such as NASA s Pleiades. In order to facilitate the collection of Lustre performance metrics, we have developed a software tool that exports a wide variety of client and server-side metrics using SGI's Performance Co-Pilot (PCP), and generates a human readable report on key metrics at the end of a batch job. These performance metrics are (a) amount of data read and written, (b) number of files opened and closed, and (c) remote procedure call (RPC) size distribution (4 KB to 1024 KB, in powers of 2) for I/O operations. RPC size distribution measures the efficiency of the Lustre client and can pinpoint problems such as small write sizes, disk fragmentation, etc. These extracted statistics are useful in determining the I/O pattern of the application and can assist in identifying possible improvements for users applications. Information on the number of file operations enables a scientist to optimize the I/O performance of their applications. Amount of I/O data helps users choose the optimal stripe size and stripe count to enhance I/O performance. In this paper, we demonstrate the usefulness of this tool on Pleiades for five production quality NASA scientific and engineering applications. We compare the latency of read and write operations under Lustre to that with NFS by tracing system calls and signals. We also investigate the read and write policies and study the effect of page cache size on I/O operations. We examine the performance impact of Lustre stripe size and stripe count along with performance evaluation of file per process and single shared file accessed by all the processes for NASA workload using parameterized IOR benchmark.
    Keywords: Computer Systems
    Type: ARC-E-DAA-TN6025 , HiPC 2012; Dec 18, 2012 - Dec 21, 2012; Pune; India
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  • 7
    Publication Date: 2019-07-13
    Description: The high performance computing (HPC) community has shown tremendous interest in exploring cloud computing as it promises high potential. In this paper, we examine the feasibility, performance, and scalability of production quality scientific and engineering applications of interest to NASA on NASA's cloud computing platform, called Nebula, hosted at Ames Research Center. This work represents the comprehensive evaluation of Nebula using NUTTCP, HPCC, NPB, I/O, and MPI function benchmarks as well as four applications representative of the NASA HPC workload. Specifically, we compare Nebula performance on some of these benchmarks and applications to that of NASA s Pleiades supercomputer, a traditional HPC system. We also investigate the impact of virtIO and jumbo frames on interconnect performance. Overall results indicate that on Nebula (i) virtIO and jumbo frames improve network bandwidth by a factor of 5x, (ii) there is a significant virtualization layer overhead of about 10% to 25%, (iii) write performance is lower by a factor of 25x, (iv) latency for short MPI messages is very high, and (v) overall performance is 15% to 48% lower than that on Pleiades for NASA HPC applications. We also comment on the usability of the cloud platform.
    Keywords: Computer Systems
    Type: ARC-E-DAA-TN5169 , 14th IEEE International Conferenc eon HPCC-2012; Jun 25, 2012; Liverpool; United Kingdom
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  • 8
    Publication Date: 2019-07-12
    Description: From its bold start nearly 30 years ago and continuing today, the NASA Advanced Supercomputing (NAS) facility at Ames Research Center has enabled remarkable breakthroughs in the space agency s science and engineering missions. Throughout this time, NAS experts have influenced the state-of-the-art in high-performance computing (HPC) and related technologies such as scientific visualization, system benchmarking, batch scheduling, and grid environments. We highlight the pioneering achievements and innovations originating from and made possible by NAS resources and know-how, from early supercomputing environment design and software development, to long-term simulation and analyses critical to design safe Space Shuttle operations and associated spinoff technologies, to the highly successful Kepler Mission s discovery of new planets now capturing the world s imagination.
    Keywords: Computer Systems
    Type: ARC-E-DAA-TN4714
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  • 9
    Publication Date: 2019-07-13
    Description: NASA has increasingly relied on high-performance computing (HPC) re- sources for computational modeling, simulation, and data analysis to meet the science and engineering goals of its missions in space exploration, aeronautics, and Earth and space science. The NASA Advanced Supercomputing (NAS) Division at Ames Research Center in Silicon Valley, Calif., hosts NASAs premier supercomputing resources, integral to achieving and enhancing the success of the agencys missions. NAS provides a balanced environment, funded under the High-End Computing Capability (HECC) project, comprised of world-class supercomputers, including its flagship distributed-memory cluster, Pleiades; high-speed networking; and massive data storage facilities, along with multi-disciplinary support teams for user support, code porting and optimization, and large-scale data analysis and scientific visualization. However, as scientists have increased the fidelity of their simulations and engineers are conducting larger parameter-space studies, the requirements for supercomputing resources have been growing by leaps and bounds. With the facility housing the HECC systems reaching its power and cooling capacity, NAS undertook a prototype project to investigate an alternative approach for housing supercomputers. Modular supercomputing, or container-based computing, is an innovative concept for expanding NASAs HPC capabilities. With modular supercomputing, additional containerssimilar to portable storage podscan be connected together as needed to accommodate the agencys ever-increasing demand for computing resources. In addition, taking advantage of the local weather permits the use of cooling technologies that would additionally save energy and reduce annual water usage. The first stage of NASAs Modular Supercomputing Facility (MSF) prototype, which resulted in a 1,000 square-foot module on a concrete pad with room for 16 compute racks, was completed in Fall 2016 and an SGI (now HPE) computer system, named Electra, was deployed there in early 2017. Cooling is performed via an evaporative system built into the module, and preliminary experience shows a Power Usage Effectiveness (PUE) measurement of 1.03. Electra achieved over a petaflop on the LINPACK benchmark, sufficient to rank number 96 on the November 2016 TOP500 list [14]. The system consists of 1,152 InfiniBand-connected Intel Xeon Broadwell-based nodes. Its users access their files on a facility-wide file system shared by all HECC compute assets via Mellanox MetroX InfiniBand extenders, which connect the Electra fabric to Lustre routers in the primary facility over fiber-optic links about 900 feet long. The MSF prototype has exceeded expectations and is serving as a blueprint for future expansions. In the remainder of this chapter, we detail how modular data center technology can be used to expand an existing compute resource. We begin by describing NASAs requirements for supercomputing and how resources were provided prior to the integration of the Electra module-based system.
    Keywords: Computer Operations and Hardware
    Type: ARC-E-DAA-TN47639 , Contemporary High Performance Computing: From Petascale toward Exascale; 3
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  • 10
    Publication Date: 2019-07-13
    Description: An overview regarding NASA Ames Advanced Computing Systems. This presentation will discuss the modeling, simulation, analysis, and decision-making in relation to the Advanced Computing Systems.
    Keywords: Computer Systems
    Type: ARC-E-DAA-TN22019 , High Performance Computing Day; Apr 06, 2015; Blacksburg, VA; United States
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