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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of systems integration 3 (1993), S. 23-42 
    ISSN: 1573-8787
    Keywords: Real-time ; valid ratio ; concurrency control ; prescheduling ; performance evaluation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A new priority management policy, aprescheduling policy, is proposed. This policy can be applied on any conventional concurrency control protocol to schedule a real-time transaction. Costly preemption is avoided by the prescheduling policy, and parsing dataset of a transaction is not needed. Three widely used conventional concurrency control protocols (dynamic two-phase locking, basic timestamp ordering, and optimistic) are incorporated with the prescheduling policy to form three real-time concurrency control protocols. Performance of the three protocols is evaluated from three different viewpoints: database management systems, protocols, and transaction. From a database management system viewpoint, we show the prescheduling policy can improve the performance of protocols by raising thevalid ratio and reducingrestart counts. In general, two-phase locking with the prescheduling policy performs the best in most cases and yields the best choice for concurrency control in a real-time application. Deciding factors that affect performance of each protocol are identified from protocol viewpoint. Some suggestions are given for writing a timely transaction from the aspect of transaction viewpoint.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 182 (1990), S. 193-203 
    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: Polyurethanpräpolymere (PU) auf der Basis von Poly(butylenadipaten) (PBA) bzw. Poly(oxytetramethylen) polyolen (PTMO) wurden als Vernetzer für Bisphenol-A-diglycidylether (DGEBA) eingesetzt. Anschließend wurde DGEBA mit einem tertiären Amin zu einem PU-vernetzten DGEBA ausgehärtet. Die Reißfestigkeit sowohl von PU(PBA)-als auch von PU(PTMO)-vernetzten Systemen stieg mit steigendem PU-Gehalt bis zu einem Maximum an, um bei noch höheren Gehalten von PU wieder abzufallen. Hinsichtlich der Izod-Schlagzähigkeit brachte die Vernetzung des DGEBA mit PU(PBA) eine wesentlich bedeutendere Verbesserung als mit PU(PTMO). Andererseits zeigten PU(PTMO)-vernetzte DGEBA-Polymere viel höhere Werte der Bruchenergie G1 C als PU(PBA)-vernetzte.
    Notes: Polyurethane (PU) prepolymers based on poly(butylene adipate) (PBA) and poly(oxytetramethylene) (PTMO) polyols were employed as a crosslinking agent to the diglycidyl ether of bisphenol A (DGEBA). Then the DGEBA was cured with a tertiary amine catalyst to form PU-crosslinked DGEBA.The tensile strength of both the PU(PBA)-crosslinked DGEBA and PU(PTMO)-crosslinked DGEBA systems increased to a maximum value with increasing PU content in the system and then decreased with further increasing PU content.Izod impact property of these PU-crosslinked DGEBA indicated that the PU(PBA)-crosslinked DGEBA had much more significant improvement than the PU(PTMO)-crosslinked DGEBA. On the contrary, the fracture energy (G1 C value) of the resultant PU-crosslinked DGEBA showed that the PU(PTMO)-crosslinked DGEBA had much higher G1 C values than the PU(PBA)-crosslinked DGEBA.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 184 (1991), S. 89-97 
    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: Polyurethan(PU)-vernetzte Bisphenol-A-diglycidylether (DGEBA) wurden durch Reaktion der sekundären Hydroxygruppe im DGEBA-Präpolymeren mit den im PU-Präpolymeren vorhandenen freien Isocyanatendgruppen hergestellt. Obwohl das PU als Vernetzer für das DGEBA wirkte, fanden sich in der Morphologie und im dynamisch mechanischen Verhalten je nach Typ und Molekulargewicht der eingesetzten Polyole Unterschiede. Es gab keine signifikante Verschiebung der Lage des Maximums des Verlustmoduls (E′″) zwischen den Polyester-und den Polyether-vernetzten DGEBA-Polymertypen, aber die Intensität des E″-Peaks stieg mit der Verwendung des Polyesterpräpolymeren an. Die Morphologie dieser Polyester-PU-vernetzten DGEBA-Polymeren war homogen einphasig, während die Polyether-PU-Typen eine Zweiphasenmorphologie mit PU-Teilchen, dispergiert in der DGEBA-Matrix zeigten.
    Notes: The polyurethane(PU)-crosslinked diglycidyl ether of bisphenol A (DGEBA) was prepared from the reaction of the pendent secondary hydroxy group in DGEBA with the isocyanate-terminated group present in the PU prepolymer. Though the PU acted as a crosslinking agent for the DGEBA, the morphology and dynamic mechanical behaviour of these PU-crosslinked DGEBA could be different among themselves depending on the type and molecular weight of polyols employed in the PU. There was no significant shift in the loss modulus (E″) peaks of the DGEBA crosslinked with the polyester-type and polyether-type polyurethanes, but the intensity of the E″ peaks increased as the polyester-type PU employed. The morphology of this polyester-type PU-crosslinked DGEBA exhibited a homogeneous one-phase system, while the DGEBA crosslinked with the polyether-type PU showed a two-phase morphology with the PU particles dispersed in DGEBA matrix.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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