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  • 1
    Electronic Resource
    Electronic Resource
    Theory of quantum dynamics in fermionic environment: An influence functional approach (1987)
    Springer
    Journal of statistical physics 47 (1987), S. 17-55 
    Details
    ISSN: 1572-9613
    Keywords: Path integral ; influence functional ; fermion bath ; real-time density matrix ; Grassmann algebra ; quantum Langevin equation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Quantum dynamics of a particle coupled to a fermionic environment is considered, with particular emphasis on the formulation of macroscopic quantum phenomena. The framework is based on a path integral formalism for the real-time density matrix. After integrating out of the fermion variables of the environment, we embed the whole environmental effects on the particle into the so-called influence functional in analogy to Feynman and Vernon's initial work. We then show that to the second order of the coupling constant, the exponent of the influence functional is in exact agreement with that due to a linear dissipative environment (boson bath). Having obtained this, we turn to a specific model in which the influence functional can be exactly evaluated in a long-time limit (long compared to the inverse of the cutoff frequency of the environmental spectrum). In this circumstance, we mainly address our attention to the quantum mechanical representation of the system-plus-environment from the known classical properties of the particle. It is shown that, in particular, the equivalence between the fermion bath and the boson bath is generally correct for a singlechannel coupling provided we make a simple mapping between the nonlinear interaction functions of the baths. Finally, generalizations of the model to more complicated situations are discussed and significant applications and connections to certain practically interesting problems are mentioned.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01009034
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  • 2
    Electronic Resource
    Electronic Resource
    A new method for quantum processes in fermionic heat baths (1987)
    Springer
    Journal of statistical physics 49 (1987), S. 811-826 
    Details
    ISSN: 1572-9613
    Keywords: Adiabatic transformation ; fermion bath ; Grassmann algebra ; influence functional ; path integral ; real-time density matrix
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The general path-integral formalism for real-time dynamics for a quantum system in a fermionic environment proposed previously is investigated by using a new method called local adiabatic transformation. This method is based on the observation that in the long-time limit (the time scale of the system is much larger than that of the environment, typically characterized by the inverse of the cutoff frequency of the environment), most degrees of freedom of the environment will follow the dynamics adiabatically. This feature is utilized by transforming the original problem of coordinate coupling into a problem of velocity coupling. This is achieved by making some simple unitary transformation on the fermion field (before path-integrating out of that field). By doing perturbations on the new problem, all the previous important results are recovered. Further-more, generalizations to more realistic situations [for example, a particle traveling over a large distance and coupled to a Fermi gas through the phase factor exp(ik·R) (the coupling may involve many channels of angular momentum)] are considered and significant results obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01009357
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  • 3
    Electronic Resource
    Electronic Resource
    Poly(methacrylates) with different kinds of dendritic moieties as side groups (1996)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 17 (1996), S. 401-407 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Alkyl methacrylate monomers with three kinds of dendritic fragments as alkyl groups, two kinds of Fréchet-type and a new type with 3,5-diphenoxybenzyl as first generation, were prepared by reaction of the corresponding dendritic bromides with methacrylic acid in good yield and were homopolymerized with a radical initiator. Polymers with side groups in first generation had a degree of polymerization (P̄n) of 17-24, markedly higher than those with side groups in second generation, P̄n ≈ 6-7.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1996.030170606
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  • 4
    Electronic Resource
    Electronic Resource
    Interpenetrating polymer networks of polyurethane and vinyl ester resin for reactive injection molding process (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 46 (1992), S. 2075-2080 
    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: Three kinds of polyurethane (PU) and vinyl ester resin interpenetrating polymer network (IPN) have been synthesized to study their morphologies and mechanical properties for the potential application in the reinforced reactive injection molding process. For the PU prepared from uretonimine modified pure MDI, the macrophase separation of the IPNs between the rubber and plastic phases was found by DSC measurement and scanning electron microscopy (SEM) observation, whereas the interpenetration between the two networks was also observed on SEM photos at least around the area of interface. However, for the IPN systems including PU prepared from TDI or graft polyol, which was synthesized by using macromer technique, the compatibility between the two phases is excellent. The mechanical properties of these IPNs were measured and could be correlated well enough with their morphologies. The IPN prepared with graft polyol exhibited the best mechanical properties over all IPN specimens studied in this work. © 1992 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070461202
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  • 5
    Electronic Resource
    Electronic Resource
    Photocrosslinking of polyethylene. I. Photoinitiators, crosslinking agent, and reaction kinetics (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 4051-4075 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High density polyethylene has been photocrosslinked in the melt by using 4-chlorobenzophenone (4-CBP) as photoinitiator and triallylcyanurate (TAC) as crosslinking agent. Various factors affecting the crosslinking process (photoinitiator used and its concentration, irradiation temperature and time, atmosphere, UV light source, light intensity) were examined. By optimizing the irradiation conditions, it was found that samples up to 2 mm thick could readily be crosslinked to high gel content (≈ 90%) with satisfactory homogeneity within very short irradiation times (≈ 15 s). The kinetic analysis of the crosslinking process showed a linear relation between log S and log t (S is the sol fraction t is the irradiation time). An induction period was observed, the length of which decreased with increasing concentration of 4-CBP and increasing light intensity. An upper limit of gel content was also found for long irradiation times at a level depending on the concentration of 4-CBP. The crosslinking rate was proportional to the second order of light intensity at lower intensity and changed to first order at higher light intensity. A mechanism based on the recombination of chain radicals through both allyl and alkyl type radicals of TAC was proposed.
    Additional Material: 22 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1989.080271214
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  • 6
    Electronic Resource
    Electronic Resource
    Photocrosslinking of polyethylene. III. Thermal oxidative stability of photocrosslinked polyethylene (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 1847-1859 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal oxidative stability of photocrosslinked high density polyethylene was studied. The relative effectiveness of various antioxidants (hindered phenols and amines, aromatic amine, organic sulfides, and phosphites) was examined by comparing the oxidation induction time (OIT) which was measured using differential scanning calorimetry. Hindered phenol antioxidants were found to be most effective. At an antioxidant concentration of 0.20 wt % which gave an OIT value of 20 min at 200°C, the photocrosslinking rate was decreased only to a limited extent as evidenced by a small drop in gel content. However, the efficiency of the antioxidants as stabilizers decreased to a considerable extent after the photocrosslinking process. Serious surface deterioration was found which was ascribed to depletion of antioxidant at the surface mainly due to high rate of oxidation and evaporation.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080280717
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  • 7
    Electronic Resource
    Electronic Resource
    Photocrosslinking of polyethylene. II. Properties of photocrosslinked polyethylene (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 4077-4086 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Some properties of photocrosslinked high density polyethylene (2 mm thick sheets) have been studied. The homogeneity of the network is greatly improved by the application of triallylcyanurate (TAC) as crosslinking agent. The role of TAC in promoting the crosslinking is discussed. The crosslinked PE is found to be durable towards immersion in boiling water. Oxygen permeability increases while density and melting point decrease with increasing degree of crosslinking. The network chain density is obtained using conventional swelling method in boiling xylene, which together with data from melting point depression show that contribution of chain entanglement is insignificant to the gel formation of PE in this work.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1989.080271215
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  • 8
    Electronic Resource
    Electronic Resource
    Photocrosslinking of ultra high strength polyethylene fibersThis is Part IV of a series of papers on “Photocrosslinking of Polyethylene”. Part I, II and III will appear in Journal Polymer Science, Polymer Chemistry Edition, 1989. (1990)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 1 (1990), S. 103-107 
    Details
    ISSN: 1042-7147
    Keywords: Benzophenone ; Ultraviolet light ; Gel content ; Tensile strength ; Young's modulus ; Elongation at break ; Creep behaviour ; 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: Ultra high strength polyethylene (HSPE) fibers have been successfully photocrosslinked using benzophenone as photoinitiator. The introduction of photoinitiator without disturbing the fiber structure is a difficult problem which was solved by vapor absorption at elevated temperature while keeping the fiber under constant strain. The crosslinked fiber showed no decrease in mechanical properties at room temperature as is the case when fibers are crosslinked by other reported methods such as radiation and chemical crosslinking. The crosslinked fiber showed enhanced high temperature resistance as well as much lower creep rate on prolonged stressing. Photocrosslinking of HSPE fiber is superior to other crosslinking methods reported in the literature.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pat.1990.220010112
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