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  • 1
    Electronic Resource
    Electronic Resource
    New Evidence of Azimuthal Variations at Campi Flegrei: Attenuation and Predominant Frequency (1997)
    Springer
    Pure and applied geophysics 150 (1997), S. 285-304 
    Details
    ISSN: 1420-9136
    Keywords: Key words: Campi Flegrei, attenuation, predominant frequency, azimuthal variations.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —In this paper we have determined apparent Q from body-wave dispersion and a spectral ratio method for the Campi Flegrei area. A contour map of azimuthal variations of apparent Q (ranging from Q = 4 to Q = 40) reveals that the lower Q (higher attenuation) corresponds to an area that includes the Solfatara Crater (with active fumaroles), near the site of maximum uplift produced during the bradyseismic crisis of 1984, and just over the site evidencing the presence of a magmatic body. A strong azimuthal variation of the predominant frequency of the first pulse of the P wave has been found and is interpreted in terms of a vertical travel time in a surficial resonant layer (∼ 1 km thick) over a halfspace. The attenuation maps, the interpretation of the resonant frequencies, and the additional information provided by the P-wave velocity suggest the presence of a circular structure in the area. Not only does the distribution of the thickness of the resonant layer (obtained through the estimation of the contribution of different harmonics) show the circular structure, but it also agrees with the presence of a thin layer of lighter sediments, determined by means of a microgravimetric study, and with the total magnetic map, previously obtained for this area. The results of the azimuthal variation provide new evidence of the structure that can be used to improve the knowledge of the area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000240050077
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  • 2
    Electronic Resource
    Electronic Resource
    Bright seismic reflections and fluid movement by porous flow in the lower crust
    Amsterdam : Elsevier
    Earth and Planetary Science Letters 126 (1994), S. 161-169 
    Details
    ISSN: 0012-821X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0012-821X(94)90248-8
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  • 3
    Electronic Resource
    Electronic Resource
    A Treatment of Ill-Conditioned Systems In Expansions of Group Velocity Rayleigh Waves (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 97 (1989), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: When travel times of group velocities of fundamental mode Rayleigh waves are expressed by means of some functional expansion, spherical harmonics in our case, the singularities appearing in the system of equations lead to the non-uniqueness of the developments. In accordance with a theory about the generation of compatible solutions, different sets of spherical harmonic coefficients are obtained, all of them fitting the experimental travel times with the same accuracy. Due to the linearity between the travel-time data and the spherical harmonic coefficients, the generation and testing of the compatible solutions becomes a very easy process. Imposing physical constraints on the group velocity maps significantly reduces the number of compatible models. Comparison of different compatible models allows an assessment of uncertainty in the group velocity distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1989.tb00484.x
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  • 4
    Electronic Resource
    Electronic Resource
    Time-dependent probability density of statistical mechanics (1974)
    Springer
    Journal of statistical physics 11 (1974), S. 379-390 
    Details
    ISSN: 1572-9613
    Keywords: Probability density ; density matrix ; tunneling phenomena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Methods based on the density matrix for calculating the time-dependent probability density of a quantum system approaching equilibrium are presented. Explicit expressions are derived for the time-dependent probability density for a double-well potential. The effects of tunneling and transitions between energy levels on the probability density are discussed. For the case of closely spaced energy levels, a partial differential form of the density matrix equation is derived and used to calculate time-dependent probability densities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01026729
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  • 5
    Electronic Resource
    Electronic Resource
    Tunneling and transport problems for a quantum mechanical Brownian particle (1979)
    Springer
    Journal of statistical physics 21 (1979), S. 301-311 
    Details
    ISSN: 1572-9613
    Keywords: Quantum mechanical friction ; tunneling ; Brownian motion ; transport ; energy dissipation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Kanai model of a quantum mechanical Brownian particle is used to examine the effect of interactions between particles and their environment. Random forces cause the thermalization of the particle. Reflection of a particle from a step barrier is analyzed. The problem of tunneling of the Brownian particle through a rectangular barrier is solved. Finally, a solution for a Brownian particle in a box is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01011472
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  • 6
    Electronic Resource
    Electronic Resource
    Effectiveness factors and mass transfer in trickle-bed reactors (1979)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 25 (1979), S. 272-283 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Rates of hydrogenation of α-methyl styrene were measured at 40.6°C and 1 atm in a recycle, trickle-bed reactor using a palladium/aluminum oxide catalyst. Data for different hydrogen concentrations in the gas and liquid feed streams suggested that except, at high liquid flow rates, on part of the outer surface of the catalyst the mass transfer limitation was very small, indicating a gas covered type of surface. A procedure was developed for evaluating effectiveness factors for the nonuniform boundary conditions existing when part of the particle surface is covered by gas.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690250209
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  • 7
    Electronic Resource
    Electronic Resource
    Longitudinal and lateral thermal dispersion in packed beds. Part II: Comparison between theory and experiment (1985)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 591-602 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The thermal response of a packed bed subject to step changes in fluid temperature was measured in the Peclet number range from 10 to 103. Fluid temperature and particle temperatures were measured independently at six different axial locations in the bed as a function of time. From the temperature breakthrough curves we were able to calculate the spatial separation between the fluid and solid temperature fronts. The measured values were higher by a factor of 2 to 3 than those predicted by traditional heat transfer models. Longitudinal effective thermal conductivities were also computed and compared to theoretical predictions. The new heat transfer model developed in a previous paper is able to account for these differences between experimental results and the predictions of the dispersionconcentric and continuous solid phase models used by previous investigators. Steady-state experiments were used to measure lateral effective thermal conductivities. A temperature gradient was imposed at the top of the bed perpendicular to the flow direction and its spread was measured at different axial locations in the Peclet number range from 10 to 103. The predicted lateral effective thermal conductivities calculated using mass transfer data to estimate the hydrodynamic dispersion effect were significantly lower than the measured values. This is possibly due to the influence of viscosity and density gradients in the flow field in the packed bed.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690310409
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  • 8
    Electronic Resource
    Electronic Resource
    Longitudinal and lateral dispersion in packed beds: Effect of column length and particle size distribution (1985)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 277-288 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Longitudinal and lateral dispersion coefficients were measured at various axial positions in a packed bed in the Peclet number range from 102 to 104. Three different types of packings were used: uniform size particles, a narrow size distribution, and a wide size distribution. For the case of uniform particles the longitudinal dispersivities were found to be strong functions of position in the bed unless the dispersion length satisfies a constraint dependent on the value of the Peclet number. Generally, the larger the Peclet number, the larger the required length for constant axial dispersivities to be achieved. For the case of the wide size distribution, longitudinal dispersivities were larger than in the uniform particle case, and they required a longer dispersion length to achieve a constant value. This suggests a characteristic length for dispersion larger than the mean hydraulic radius. The lateral dispersivities were found to be insensitive to the distribution of particle sizes or location in the bed.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690310215
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  • 9
    Electronic Resource
    Electronic Resource
    The hysteretic behavior of pressure drop and liquid holdup in trickle beds (1988)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 1027-1030 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690340615
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  • 10
    Electronic Resource
    Electronic Resource
    Diffusion of gases through surfactant films: Interfacial resistance to mass transfer (1979)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 25 (1979), S. 1015-1024 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model is proposed for mass transfer of gases across surface-active films and into an aqueous phase. The interfacial region (1) obeys local equilibrium conditions, (2) has a capacity for the dissolved gases greater than the solubility in water, and (3) has a diffusion coefficient three orders of magnitude less than for that in water. The model is solved for and compared with three different experiments: the transient diffusion through monomolecular films into quiescent liquids studied by Plevan and Quinn (1966), the gas absorption through surfactant films into falling liquid films investigated by Emmert and Pigford (1954), and the frequency response of concentration pulses in surfactant films reported by Whitaker and Pigford (1966). The model consistently describes these experiments previously explained by three different models that either ignored the capacitance of the film or assumed local non-equilibrium.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690250613
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