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  • Chemical Engineering  (4,929)
  • Q
  • 1995-1999  (1,638)
  • 1990-1994  (3,297)
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  • 1
    Electronic Resource
    Electronic Resource
    Mt. Melbourne volcano, antarctica: Evidence of seismicity related to volcanic activity (1996)
    Springer
    Pure and applied geophysics 146 (1996), S. 305-318 
    Details
    ISSN: 1420-9136
    Keywords: Volcanic seismicity ; polarization analysis ; Q ; volcanic processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Characterization of the microseismic activity (M L 〈2.0) has been performed at Mt. Melbourne since 1990. We recorded a group of low frequency events with common morphological characteristics, i.e., an emerging onset, an unclear second phase and a sharply dropping coda. Spectral analysis of events recorded at more than one station indicates that the seismogram characteristics and spectral content are largely due to source effects. A polarization filter applied to a set of three component data revealed a first phase made up ofP waves followed (after about 0.9–1.4 sec.) by a second phase probably composed ofSH-type waves. Particle motion analysis detected a seismic ray angle direction mainly between N70°E and N110°E and apparent angle of incidence between 35° and 48° for the first phase. The studied seismicity was localized in an area on the eastern slope of Mt. Melbourne Volcano which presents a surface temperature anomaly (Mazzarini andSalvini, 1994). We formulate two hypotheses for the type of earthquakes recorded: 1) long-period events involving active presence of magmatic fluids in the source processes; 2) or the result of fracturing processes (shear?) in a medium characterized by transition between brittle and plastic behaviors. In the latter hypothesis the superficial thermal anomaly may be a symptom of this behavior at depth and is confirmed by the lown values observed for the exponential fit in the codaQ analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00876495
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  • 2
    Electronic Resource
    Electronic Resource
    Q structure of the oceanic crust (1991)
    Springer
    Marine geophysical researches 13 (1991), S. 227-237 
    Details
    ISSN: 1573-0581
    Keywords: Q ; attenuation ; ophiolite ; oceanic crust ; velocity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Compressional wave attenuations and velocities have been measured as a function of confining pressure in ophiolite samples representing a cross-section of the oceanic crust and uppermost mantle. Data are presented for basalts, diabase dikes, gabbros and a suite of serpentinites and peridotites showing a range of serpentization. An ultrasonic pulse-echo spectral ratio technique was used to determine the attenuations to confining pressures of 500 MPa. From this data a Q profile for the oceanic crust and upper mantle is presented. Q is found to moderately increase with depth through the pillow basalts of the upper oceanic crust. The sheeted dike rocks of Layer 2C show an increase in Q with depth due to progressive metamorphism (from greenschist to amphibolite facies). Q drops abruptly from Layer 2C to Layer 3, though it is not clear why the gabbros have such low Q's. The crust-mantle boundary is a Q discontinuity; however, the Q contrast between Layer 3 and the upper mantle could be altered by upper mantle serpentinization, interlayered gabbros and peridotites at the boundary, or serpentinized peridotite diapirs intruding the gabbroic section. Q varies significantly with the percentage of serpentinization in the ultramafic samples, with the largest changes in Q being at the extremes of zero and full serpentinization. Q is sensitive to the overburden pressure for all of the samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369151
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  • 3
    Electronic Resource
    Electronic Resource
    Stratigraphic filtering (1990)
    Springer
    Pure and applied geophysics 132 (1990), S. 49-65 
    Details
    ISSN: 1420-9136
    Keywords: Multiple scattering ; dispersion ; earth filter ; Q ; random scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A plane-wave signal traveling at normal incidence through the earth's sedimentary layers attenuates, spreads, and changes waveform as it propagates, partly in response to “stratigraphic filtering” resulting from the buildup in the medium of intrabed multiples caused by the layering, and partly in response to absorption. This paper consists of a review of one-dimensional stratigraphic filtering. The action of stratigraphic filtering resembles that of absorption, and the filter's spectrum can be characterized by an effective quality factor. A comparison between the spectra of field data and synthetic data derived from absorption-free one-dimensional models suggests that in some geologic formations, stratigraphic filtering causes a significant fraction of the total attenuation evident on seismic records. In such studies, however, the simplicity of one-dimensional models leaves some uncertainty regarding the generality of the results. Nonetheless, one-dimensional stratigraphic filtering can serve as a useful metaphor that provides insight into the workings of more complex multi-dimensional scattering models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00874357
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  • 4
    Electronic Resource
    Electronic Resource
    Unified approach to amplitude attenuation and coda excitation in the randomly inhomogeneous lithosphere (1990)
    Springer
    Pure and applied geophysics 132 (1990), S. 93-121 
    Details
    ISSN: 1420-9136
    Keywords: Scattering ; attenuation ; coda ; Q ; heterogeneity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A unified model is proposed for explaining the frequency dependent amplitude attenuation and the coda wave excitation on the basis of the single scattering process in the randomly inhomogeneous lithosphere. Adopting Birch's law and a direct proportion between density and wave velocity, we statistically describe the inhomogeneous medium by one random function characterized by the von Karman autocorrelation function. We calculate the amplitude attenuation from the solid angle integral of scattered wave energy on the basis of the Born approxiimation after subtracting the travel-time fluctuation effect caused by slowly varying velocity inhomogeneities. This subtraction is equivalent to neglect energy loss by scattering within a cone around the forward direction. The random inhomogeneity of the von Karman autocorrelation function of order 0.35 with the mean square fractional fluctuation of 7.2×10−3 ≈1.3×10−2 and the correlation distance of 2.1≈5.1 km well explains observed backward scattering coefficientg π and the ratioQ P −1 /Q S −1 , and observed and partially conjecturedQ S −1 for frequencies between 0.5 Hz and 30 Hz.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00874359
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  • 5
    Electronic Resource
    Electronic Resource
    Overbreak and underbreak in underground openings Part 2: causes and implications (1996)
    Springer
    Geotechnical and geological engineering 14 (1996), S. 325-340 
    Details
    ISSN: 1573-1529
    Keywords: overbreak ; underbreak ; digital image processing ; tunnelling ; blasting assessment ; tunnel profiling ; RMR ; Q ; powder factor ; perimeter powder factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Summary The newly developed light sectioning method has been used to investigate some of the causes and costs of overbreak and underbreak. Investigations at the Aquamilpa Hydroelectric Project in Mexico have shown decreased overbreak and increased underbreak as a result of increased rock quality and decreased explosive energy. A new measure of explosive energy, the ‘perimeter powder factor’ (PPF), has been defined and shown to be useful in the context of tunnel-wall rock damage. Tentative results indicate that explosive energy (PPF) may be a more important factor in producing underbreak, whereas rock quality may be a greater factor in producing overbreak. A site-specific equation is given for predicting overbreak or underbreak as a function of rock quality and explosive energy, with an evaluation of the cost of underbreak and overbreak.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00421947
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  • 6
    Electronic Resource
    Electronic Resource
    Polymer blend containing a thermotropic polyester with long flexible spacer in the main chain (1990)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 22-29 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Polymer blends of nylon 66 and thermotropic polyester with long flexible spacers in the main chains were prepared by melt mixing. The samples were made as single filaments by passing the polymer blend through a small and round die of a capillary rheometer. Mechanical properties of blends showed that the modulus and strength of nylon 66 could be improved without reduction of extensibility. The morphology of fractured surfaces was observed by a scanning electron microscope (SEM). It showed that the microfibrillar structure of a thermotropic polyester was formed by extensional flow while the spherical and ellipsoidal particles in the nylon 66 (matrix polymer) were produced by shear flow. The polyester particles were occasionally covered with adhering matrix polymer because of good adhesion between these two polymers. They were highly elongated by tensile stress without loss of elongational characteristics of blends. This fact was explained by very good adhesion between the two phases.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760300105
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  • 7
    Electronic Resource
    Electronic Resource
    Gelation in thermosets formed by chain addition polymerization (1990)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 83-89 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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 physical behavior of the diglycidyl ether of bisphenol A, cured with different concentrations of 2-ethyl-4-methylimidazole, was examined with dynamic mechanical and dielectric analyses, differential scanning calorimetry, and solvent extraction studies, ‘The network formation process was shown to depend strongly on the imidazole concentration’. At high imidazole concentrations, the gel point was characterized by a decrease in sol fraction, the crossover of the dynamic moduli and a rapid increase in viscosity. At low imidazole concentrations, the viscosity remained low until the sol fraction approached zero. For this system, the gel point, which occurred prior to the dynamic moduli crossover, was characterized by comparing the thermal properties of the network with the viscosity and dielectric behavior of the resin system during cure.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760300204
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  • 8
    Electronic Resource
    Electronic Resource
    Calculated stresses in dual coated optical fibers (1990)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 108-117 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: We examine several practically important problems, related to the mechanical behavior of dual coated optical fibers: low temperature microbending, evaluation of spring constant due to coating layers, strength of the end portions of fibers clamped in terminal fixtures, and prediction of stresses caused by the misalignment of the openings in the frame and in the terminal fixture. The developed formulas are simple, easy-to-use, and clearly indicate the role of the major factors affecting the mechanical behavior of the fibers. The obtained results can be of help in physical design of dual coated fibers and optical interconnections.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760300207
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  • 9
    Electronic Resource
    Electronic Resource
    Energy absorption characteristics of polymeric foams used as cushioning materials (1990)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 129-133 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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 “Efficiency of Energy Absorption” (or “Efficiency”) and “Ideality” parameters were evaluated for several plastic foams and were found to be very useful in choosing an appropriate cushion for the protection of a specific product. The maxima in these parameters were found to be in the same range of stresses, when derived from dynamic measurements or from predicted stress-strain curves based on previously proposed “Reference” and “Modified Boltzman Superposition” Models. For the rate independent foams the maxima in these parameters do not change with strain rate and can therefore be derived from slow, constant rate (“static”) experiments. For rate dependent foams however, the maxima from “static” measurements were found to be in a lower range of stresses than those derived from dynamic ones. As a result, slow rate compressive measurements do not predict well the behavior of the foams during impact and the use of the “Reference” and “Modified Boltzman Superposition” Models is required for good predictions. It was found that the suffer PS and PE foams attain maximum Efficiency and Ideality at higher stresses than the more flexible PUR foams.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760300210
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  • 10
    Electronic Resource
    Electronic Resource
    Crystallization kinetics of poly(ethylene terephthalate). Part I: Kinetic equation with variable growth rate (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 110-115 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: A new crystallization kinetic equation has been derived considering the decrease in growth rate. The average linear growth rate of spherulite was assumed to be proportional to the m-th order of the uncrystallized fraction of the crystallizing material. A modified Avrami equation, 1 - Vc = exp[-Kf(t)n], was used where f(t) is the integral of the growth function, (1 - Vc)m. The validity of the equation was tested by analyzing the isothermal crystallization kinetic data of poly(ethylene terephthalate) from the melt using differential scanning calorimetry.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310209
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