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  • 11
    Electronic Resource
    Electronic Resource
    Nuclear resonant scattering using synchrotron radiation (1999)
    Springer
    Hyperfine interactions 120-121 (1999), S. 169-173 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A one-dimensional quantum model for nuclear resonant scattering using synchrotron radiation has been developed. This model gives a clear physical interpretation of the most prominent features of the coherent forward scattering process namely, the “speed-up” and “dynamical beat” effects. The form of the solution, for the time-dependent forward scattered intensity of the resonant radiation from the resonant medium after synchrotron radiation excitation, is a finite series. This unique solution can be interpreted in terms of a summation over all multiple forward scattering paths the radiation takes in reaching the detector. The resonant medium is represented by a linear chain of N effective resonant nuclei. The analysis starts from a coupled set of quantum mechanical equations for the relevant amplitudes in frequency space. Transformation to the time domain gives an analytical expression for the forward scattered intensity. The contribution of every order of the multiple scattering processes from the N effective nuclei appears naturally. The expression gives a clear physical understanding of all relevant aspects of resonant forward nuclear scattering. Furthermore, the present formalism allows the consideration of incoherent processes. This permits the study of processes in which there is gamma emission with recoil or emission of internal-conversion electrons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017098617489
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  • 12
    Electronic Resource
    Electronic Resource
    Nuclear ground states dressed with rf photons in Mössbauer–Zeeman 57Fe spectroscopy (1999)
    Springer
    Hyperfine interactions 120-121 (1999), S. 175-179 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have applied the “dressed” state concept, developed in quantum electronics, to the situation in which spin 1/2 ground-state nuclear levels are coupled by rf photons. In particular, we have studied Mössbauer spectroscopy when there is Zeeman splitting of the nuclear levels and a further interaction due to an applied rf-radiation field when the rf frequency is in the neighborhood of the ground-state splitting. The dressed-state approach treats the coupling of the ground nuclear Zeeman levels, due to a radio frequency field, by considering the total system made up of: nucleus, static magnetic field, and rf field as one global quantum system. The energy levels and corresponding eigenstates of the system are calculated as a function of the rf frequency and the magnitude of the rf magnetic flux density. Mössbauer spectra are calculated for the 57Fe case in which the source is subjected to both the static and radiation fields while the absorber nuclear levels are unsplit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017050701559
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  • 13
    Electronic Resource
    Electronic Resource
    Tourism and advertising: Evidence from Virginia beach (1998)
    Springer
    International advances in economic research 4 (1998), S. 384-397 
    Details
    ISSN: 1573-966X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract In recent years, the City of Virginia Beach, Virginia, has been spending more than two million dollars per year to promote tourism for the city. However, very little is known about the effects of such advertising on overnight visitors. On the basis of a survey of 1,200 overnight visitors during the summer of 1991, this study estimates the effect on tourism and the subsequent fiscal effect of tourism advertising expenditures. The study also calculates a rate of return from advertising from the perspective of a governmental revenue maximization objective function. This paper develops a travel cost model of the impact of advertising on overnight visitation to the city. The model provides, ceteris paribus, that advertising expenditures of 2.4 million dollars in 1991 resulted in an estimated 600,000 additional visitors. The paper concludes that if the City's objective is to maximize public profit, then it should expand its advertising budget.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02295692
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  • 14
    Electronic Resource
    Electronic Resource
    Preparation of high-strength/high-modulus regenerated cellulose fibers from lyotropic mesophases (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 58 (1995), S. 1365-1370 
    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: Cellulose triacetate (CTA) fibers were spun from a 35% (w/v) solution of CTA (molecular weight, 95,000) in trifluoroacetic acid (TFA)/CH2CL2 (60/40, v/v) using laboratory-scale spinning equipment, an air gap, and cold MeOH as the coagulant. The resulting fibers, of large diameter (ca. 80 μm) were saponified with a variety of reagents. The regenerated cellulose fibers had tenacities and moduli as high as 1.6 and 50 GPa, respectively. The fiber properties did not show a dependence on which cellulose polymorph was present. It is suggestes that for highly oriented fibers, the cellulose molecular weight is the primary parameter that determines the strength and modulus. This emphasizes the advantages of using a lyotropic cellulosic mesophase which permits relatively low solution viscosities at high concentrations and high polymer molecular weights. © 1995 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070580818
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  • 15
    Electronic Resource
    Electronic Resource
    Preparation of ultrahigh molecular weight polyacrylonitrile and its terpolymers (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 58 (1995), S. 2067-2075 
    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 synthesis of high molecular weight (in excess of 106 million Daltons) poly(acrylonitrile) and poly(acrylonitrile-co-methylacrylate-co-itaconic acid) is described. An inverse emulsion polymerization formulation with AIBN as the initiator was used. However, polymer precipitation occurred early in the polymerization. In each case, the molecular weight distribution was surprisingly narrow (M̄w/M̄n ∼ 1.5). Conversion vs. time plots with monomers containing the inhibitor had the “S” shape typical of emulsion polymerizations. The terpolymer composition and molecular weight were quite uniform throughout the polymerization. With inhibitor-free monomers, the initial molecular weights were very high (∼ 3 × 106 Daltons), but gelation occurred at ca. 50% conversion. There was an inverse relationship between the monomer inhibitor content and the polymer molecular weight. It is suggested that the growing polymer radicals are occluded in the precipitated polymer particles and are terminated by inhibitor diffusing into the particles, accounting for the narrow molecular weight distribution. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070581119
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  • 16
    Electronic Resource
    Electronic Resource
    ANALYTICAL MODEL OF PROGRESSIVE SLOPE FAILURE IN WASTE CONTAINMENT SYSTEMS (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 20 (1996), S. 35-56 
    Details
    ISSN: 0363-9061
    Keywords: waste containment systems ; slope failure ; strain-softening ; landfill ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The potential for progressive failure in waste containment systems is an important design consideration. Many common interfaces between components in containment systems exhibit strain-softening behaviour; however, slopes are presently designed using limit equilibrium methods that do not account for these effects. An analytical model is developed to investigate the potential for progressive failure due to strain softening. Results are presented in a non-dimensional form relating the potential for strain softening to the slope geometry, the waste properties and the properties of the containment system interface. The potential for progressive failure increases as (i) the waste stiffness decreases relative to the initial stiffness of the interface resistance, (ii) the length of the slip surface increases and (iii) the rate of strain softening with displacement increases. Analysis of a case study slope failure indicates that the analytical approach produces results that are consistent with field observations and comparable to results from a more sophisticated, numerical analysis. Although simple, this analytical approach serves as a useful design guide to identify cases where it is unsafe to use the peak shear strength in a limit equilibrium analysis.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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