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  • Polymer and Materials Science  (6)
  • Mathematics and Statistics  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 1939-1947 
    ISSN: 0887-624X
    Keywords: polytetrahydrofuran ; acetylhexachloro-antimonate ; chain transfer ; THF ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the presence of acetic anhydride, the catalyst containing protons makes the polymerization complex.1,2 Thus, whether the living center, during the polymerization process of THF, transfers to the acetic anhydride is a difficult problem to answer. In this article, CH3COSbCl6 is used as the catalyst to avoid the interference of the protons. It is found that acetic anhydride is an effective chain transfer agent, by the experiment at different temperatures for two systems in the presence or absence of acetic anhydride, and by the comparison of kinetic behavior. In the system without acetic anhydride at the temperature of 7, 15, and 22°C, the propagation rate constants of THF, kp are 7.90, 14.23, and 23.35 10-3L/Mol.S, respectively. In the presence of acetic anhydride, kp are 1.51, 2.85, and 4.98 10-3L/Mol.S; and ktr are 2.04, 3.59, and 6.49 10-4L/Mol.S, respectively. © 1994 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 695-702 
    ISSN: 0887-624X
    Keywords: ABA-type block copolymers ; ring-opening polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ABA-type block copolymers of poly(trimethylene carbonate) with poly(ethylene glycol) (Mn 6820), PTMC-b-PEG-b-PTMC, were synthesized by the ring-opening polymerization of 1,3-dioxan-2-one (trimethylene carbonate) in the presence of poly-(ethylene glycol) with stannous octoate catalyst, and the copolymers with various compositions were obtained. The PTMC-b-PEG-b-PTMC copolymers were characterized with Fourier transform infrared and nuclear magnetic resonance spectroscopies. The intrinsic viscosities of resulting copolymers increased with the increase of 1,3-dioxan-2-one content in feed while the molar ratio of monomer over catalyst kept constant. It has been observed that the glass transition temperature (Tg) of the PTMC segments in copolymers, recorded from differential scanning calorimetry, was dependent on the composition of copolymers. The melting temperature (Tm) of PEG blocks in copolymer was lower than that of PEG polymer, and then disappeared as the length of PTMC blocks increased. The results of dynamic contact angle measurement clearly revealed that the hydrophilicity of resulting copolymers increased greatly with the increase of PEG content in copolymers. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 695-702, 1998
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1301-1307 
    ISSN: 0887-624X
    Keywords: 1,4-dioxan-2-one ; trimethylene carbonate ; stannous octoate ; drug delivery system ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(1,4-dioxan-2-one-co-trimethylene carbonate), P(DON-co-TMC), copolymers with different compositions were synthesized by copolymerizations of 1,4-dioxan-2-one (DON) and trimethylene carbonate (TMC) at 120°C in the presence of Sn(Oct)2. Their structures and compositions were determined with FT-IR and 1H-NMR spectroscopies. The intrinsic viscosities of copolymers increased with the increase of the TMC fraction in feed. The DSC results of copolymers showed that the glass transition temperatures (Tgs) of copolymers are lower than those of homopolymers. Most copolymers are amorphous except for one with a high DON composition. The hydrophilicity of the copolymers is in proportion with the DON molar fraction in the copolymers. It was found that the Levonorgestrel (LNG) release rate is dependent of the composition and flexibility of polymer chains. The fastest one is the copolymer with nearly a equivalent fraction of DON to TMC. Among copolymers with other compositions, a higher DON fraction would be favorable to the release of LNG. All measurements demonstrate an almost constant release rate in the period of 1 month. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1301-1307, 1998
    Additional Material: 8 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 2339-2346 
    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: Porous polydimethylsiloxane (PDMS) membranes with α-amylase or glucose oxidase activity were prepared by catalytic hydrosilylation cure of PDMS in the presence of the enzymewater solution. The pores in the membrane are the result of hydrogen foams, which are generated during the curing reaction. The enzyme reactions were examined in batch and permeation experiments by using glucose and starch solutions as substrates. For the permeation set-up, the reaction yields of the immobilized α -amylase increased as the permeation rate of the starch solution decreased. The Michaelis-Menten type of reaction kinetics for the immobilized enzyme indicated that the permeation system is effective for the diffusion through the solute of the matrix, as compared with the batch system. © 1996 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 44 (1992), S. 789-797 
    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: Medium molecular weight, novel polyfunctional elastomers, namely epoxy groups on poly(n-butylacrylate) (ETPnBA) and carboxyl groups on poly(n-butylacrylate) (CTPnBA) were photosynthesized for evaluation as the toughening agents in epoxy resins. The effect of the functionality and kind of functional group of the elastomers upon the toughening of epoxy resins modified with these rubbery copolymers as a second phase was investigated by tensile tests, impact test, and electron microscopy. It was found that there exists an optimum functionality of elastomers for maximum impact resistance in epoxy groups (ETPnBA) and carboxyl groups (CTPnBA) copolymer-modified systems. Studies on morphology of the modified epoxy resin system indicated that the better toughening effects of multiple distribution of particle sizes. The aggregation of rubber particles occurring in carboxyl group CTPnBA modified epoxy resin caused a loss of toughness.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 41 (1990), S. 2587-2593 
    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: Tribochemical reactions of PTFE with aluminum, silicon, and iron during rubbing were detected by ESCA. No apparent relationship between this chemical reaction of the fillers with the PTFE in the composite and the wear-reducing action of those fillers on the composite material was found.
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Numerical Methods for Partial Differential Equations 13 (1997), S. 617-661 
    ISSN: 0749-159X
    Keywords: characteristic methods ; Eulerian-Langrangian methods ; numerical solution of first-order hyperbolic equations ; Runge-Kutta methods ; Mathematics and Statistics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We develop two Runge-Kutta characteristic methods for the solution of the initial-boundary value problems for first-order linear hyperbolic equations. One of the methods is based on a backtracking of the characteristics, while the other is based on forward tracking. The derived schemes naturally incorporate inflow boundary conditions into their formulations and do not need any artificial outflow boundary condition. They are fully mass conservative and can be viewed as higher-order time integration schemes improved over the ELLAM (Eulerian-Lagrangian localized adjoint method) method developed previously. Moreover, they have regularly structured, well-conditioned, symmetric, and positive-definite coefficient matrices. Extensive numerical results are presented to compare the performance of these methods with many well studied and widely used methods, including the Petrov-Galerkin methods, the streamline diffusion methods, the continuous and discontinuous Galerkin methods, the MUSCL, and the ENO schemes. The numerical experiments also verify the optimal-order convergence rates of the Runge-Kutta methods developed in this article. © 1997 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 13: 617-661, 1997
    Additional Material: 27 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Numerical Methods for Partial Differential Equations 11 (1995), S. 1-31 
    ISSN: 0749-159X
    Keywords: Mathematics and Statistics ; Numerical Methods
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: Eulerian-Langrangian localized adjoint methods (ELLAM) were developed to solve convection-diffusion-reaction equations governing contaminant transport in groundwater flowing through a porous medium, subject to various combinations of boundary conditions. In this article, we prove optimal-order error estimates and some superconvergence results for the ELLAM schemes. In contrast to many existing estimates for a variety of numerical methods, which often contain the temporal derivatives of the exact solution, our error estimates contain the total derivatives of the exact solution but do not involve any temporal derivatives of the exact solution. © 1995 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
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  • 9
    ISSN: 0749-159X
    Keywords: Mathematics and Statistics ; Numerical Methods
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: The microbial degradation of organic contaminants in the subsurface holds significant potential as a mechanism for in-situ remediation strategies. The mathematical models that describe contaminant transport with biodegradation involve a set of advective-diffusive-reactive transport equations. These equations are coupled through the nonlinear reaction terms, which may involve reactions with all of the species and are themselves coupled to growth equations for the subsurface bacterial populations. In this article, we develop Eulerian-Lagrangian localized adjoint methods (ELLAM) to solve these transport equations. ELLAM are formulated to systematically adapt to the changing features of governing partial differential equations. The relative importance of retardation, advection, diffusion, and reaction is directly incorporated into the numerical method by judicious choice of the test functions that appear in the weak form of the governing equation. Different ELLAM schemes for linear variable-coefficient advective-diffusive-reactive transport equations are developed based on different operator splittings. Specific linearization techniques are discussed and are combined with the ELLAM schemes to solve the nonlinear, multispecies transport equations. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Numerical Methods for Partial Differential Equations 14 (1998), S. 739-780 
    ISSN: 0749-159X
    Keywords: advection-diffusion-reaction transport equations ; characteristic methods ; error estimates ; Eulerian-Lagrangian methods ; Mathematics and Statistics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: A family of ELLAM (Eulerian-Lagrangian localized adjoint method) schemes is developed and analyzed for linear advection-diffusion-reaction transport partial differential equations with any combination of inflow and outflow Dirichlet, Neumann, or flux boundary conditions. The formulation uses space-time finite elements, with edges oriented along Lagrangian flow paths, in a time-stepping procedure, where space-time test functions are chosen to satisfy a local adjoint condition. This allows Eulerian-Lagrangian concepts to be applied in a systematic mass-conservative manner, yielding numerical schemes defined at each discrete time level. Optimal-order error estimates and superconvergence results are derived. Numerical experiments are performed to verify the theoretical estimates. © 1998 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 14: 739-780, 1998
    Additional Material: 2 Tab.
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