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  • 1
    Electronic Resource
    Electronic Resource
    Hydrodynamic characteristics of dual Rushton impeller stirred vessels (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 332-346 
    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 flows generated in vessels stirred by two Rushton impellers were investigated in two vessels of diameter (T) 100 and 294 mm with impellers of diameter D = T/3 using flow visualization, power consumption, mixing time, and 360° ensemble-averaged and 1° angle-resolved LDA measurement techniques. The flows depended strongly on the clearance of the lower impeller above the base of the vessel (C1), the separation between the impellers (C2), and the submergence (C3) of the upper impeller below the top of the liquid column height (H). When these distances were varied, three stable and four unstable flow patterns were observed. Comparisons between the two LDA techniques showed that while the 360° ensemble-averaged measurements are useful for characterizing the overall flow structure and turbulence levels in the vessel, care must be exercised when interpreting such data, since in the impeller region they include periodic variations in the mean velocity in addition to the turbulent fluctuations. The trailing vortex structure and flow periodicity produced by the Rushton impellers is shown to decay significantly within a cylindrical region of height 1.2D and radius 1.0D centered around the middle of the vessel, when C1 = C2 = T/3. The turbulence structure within this region is anisotropic, while outside this region it might be considered mostly isotropic. The main flow features scaled well between the vessels.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690420204
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  • 2
    Electronic Resource
    Electronic Resource
    Local shell-side heat transfer coefficients and pressure drop in a tubular heat exchanger with orifice baffles (1960)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 6 (1960), S. 669-675 
    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: By means of a moveable sensing probe previously described2 local shell-side heat transfer coefficients and friction losses were measured on a model tubular heat exchanger containing orifice baffles. The heat exchanger shell was 6-in. nominal I.D. and 45 in. in length and contained four tubes in triangular arrangement passing through orifice baffles. Baffle hole diameters of 1-/16, 1-2/16, 1-3/16, and 1-5/16 in. and baffle spacings of 4.0 and 9.0 in. were studied. Data were taken at several air flow rates for each of the four baffle hole diameters.The average heat transfer coefficient for the region between two central baffles was correlated with an empirical equation based on only two baffle spacings.An increase in the baffle-to-tube clearance caused a decrease in heat transfer. An increase in the baffle spacing also resulted in a decrease in heat transfer. Four flow zones in the baffle space are postulated from the analysis of Nusselt number distribution along the tube. The heat transfer characteristics in each of the four flow zones were analyzed in terms of the mechanism of the fluid flow.The pressure-drop data were correlated in terms of an annular orifice coefficient of discharge and an orifice-pressure-drop function. As a result of this study a method was developed by which one can predict the average of the local coefficients at the baffle position from the knowledge of pressure drop across a single baffle.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690060430
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  • 3
    Electronic Resource
    Electronic Resource
    On-line optimizing control of a nonadiabatic fixed bed reactor (1985)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 667-675 
    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 scheme of on-line optimizing control is presented for a nonadiabatic fixed bed reactor which experiences a highly exothermic reaction. The control scheme has been devised to perform adaptive control of bed temperature and on-line steady state optimization simultaneously.Experiments were conducted with a pilot scale fixed bed reactor where partial oxidation of n-butane to maleic anhydride occurs. The reactor system was interfaced with a microcomputer for real-time control and optimization. With an objective function consisting of a net profit by producing maleic anhydride plus a penalty term on high bed temperature, it was clearly shown that the reaction conditions were driven to the expected optimum region.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690310417
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  • 4
    Electronic Resource
    Electronic Resource
    Revisit of MALDI for small proteins (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 1315-1320 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Matrix-assisted laser desorption/ionization (MALDI) was used for several small proteins (such as insulin) and for peptides. It was found that the detection efficiencies of MALDI for the insulin B chain and the insulin A chain are drastically different. Similar phenomena were also observed for various types of peptides. The positive-ion signal of MALDI in detecting proteins or peptides was found to be greatly enhanced by the presence of a basic amino acid in their chains. The experimental results indicate that this enhancement may arise from proton transfer in solution by an acid-base reaction between the protein/peptide and matrix molecule. This pre-protonated mechanism provides a low energy barrier for the ionization of peptides in a MALDI process, and greatly reduces the energy threshold of MALDI. Matrix effects on the ionization mechanism are discussed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290091318
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  • 5
    Electronic Resource
    Electronic Resource
    Structure and property development in poly(p-phenylene terephthalamide) during heat treatment under tension (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 1-14 
    Details
    ISSN: 0887-6266
    Keywords: poly (p-phenylene terepthalamide) ; Kevlar® ; heat treatment ; structure development ; mechanical properties ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The evolution of several structural characteristics during isothermal heat treatment of poly(p-phenylene terephthalamide) was studied. In this work, heat treatment was interrupted after different treatment times, with the specimens immediately quenched to room temperature. These specimens were then characterized by tensile testing, wide- and small-angle x-ray scattering, and optical microscopy. Structural parameters obtained from these measurements relate to crystal perfection (via the paracrystalline axial distortion parameter), axial crystallite size, transverse crystallite size, degree of chain misorientation, and degree of pleating. Structural and mechanical parameters were then plotted against heat-treatment time to obtain kinetic isotherms for each parameter. The kinetics of the removal of chain misorientation parallels that of tensile modulus increase under all conditions. Of the other structural parameters, only the kinetics of pleat removal mimics that of modulus change, indicating that pleat removal is the effective cause of increased chain alignment and thereby of increased axial stiffness. ©1995 John Wiley & Sons, Inc.
    Additional Material: 27 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1995.090330101
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  • 6
    Electronic Resource
    Electronic Resource
    Gas permeation and viscoelastic deformation of prepregs in composite manufacturing processes (1995)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 16 (1995), S. 370-377 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Gas permeation and creep deformation of a commercial prepreg, which exhibits viscoelastic characteristics, were investigated as a function of time, temperature, and consolidation pressure. Experiments using a prepreg stack demonstrated that the material exhibited a linear viscoelastic bulk deformation under vacuum/autoclave pressure and furthermore, the in-plane gas flow exhibited non-Darcian flow behavior with a permeation hysteresis. This behavior was viewed and analyzed by two viscoelastic relaxation processes: (1) bulk dimensional relaxation, and (2) microscopic pore structure rearrangement. A modified standard linear solid (SLS) viscoelastic model was used to interpret the creep compliance and dynamic gas permeability utilizing two independent relaxation parameters. By visual investigation of pore sizes and their distribution, air permeation was found to take place mostly through the interlaminar porosity network for the prepreg system examined.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750160505
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  • 7
    Electronic Resource
    Electronic Resource
    The effect of chelation on the selective transport of alkaline-earth metal ions in asymmetric cellulose acetate hyperfiltration membranes (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 21 (1977), S. 1795-1800 
    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 rejection of calcium and/or magnesium ion by asymmetric cellulose acetate hyperfiltration membranes is increased significantly by formation of the corresponding alkaline-earth metal chelate. Typically solute fluxes are reduced by a factor of 5 consequent to chelation with ethylenediaminetetraacetic acid (EDTA) at pH 6.0. Selective chelation and, in turn, selective transport of magnesium is observed when equimolar solute mixtures corresponding to 1:1:1 magnesium:calcium:EDTA are hyperfiltered. Under these conditions, calcium successfully competes for the stoichiometrically limiting EDTA, and the rejection of magnesium is lower than the rejection observed for the hyperfiltration of the MgEDTA2- complex in the absence of competitive calcium. Alternatively, the rejection of the CaEDTA2- complex is increased under these identical conditions, presumably as a consequence of specific interactions between the available free magnesium and the cellulose acetate membrane. The effects reported here all seem to be related to reductions in solute diffusivity associated with the increased size of the alkaline-earth metal ion complex.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1977.070210707
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  • 8
    Electronic Resource
    Electronic Resource
    Batch and semicontinuous emulsion copolymerization of vinylidene chloride and butyl methacrylate. I. Kinetics in VDC-BMA emulsion polymerization and surface and colloidal properties of VDC-BMA latexes (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 2207-2219 
    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: Vinylidene chloride (VDC) - butyl methacrylate (BMA) comonomer mixtures with various composition (83 : 17, 60 : 40, 33 : 67 in mol %) were polymerized at 25°C using redox catalyst by batch and seeded semicontinuous emulsion copolymerization. The reactivity ratios determined in VDC (M1) - BMA (M2) emulsion copolymerization system were r1 = 0.22 and r2 = 2.41. Seven 35% solids (83 : 17 mol %) VDC-BMA copolymer latexes were prepared: one batch (G), one seeded batch (F), and 5 seeded semicontinuous polymerizations of 5 different monomer feed rates ranging from 0.27 (A) to 1.10 wt %/min (E). The kinetic studies of seeded semicontinuous polymerizations A-E showed that the rates of polymerizations (Rp) were controlled by the monomer addition rates (Ra). The conversion versus time curves for the polymerizations of 0 : 100-100 : 0 VDC-BMA mixtures by batch polymerization showed that the rate of polymerization (Rp) was a function of the number of particles, and that the rate of polymerization in a latex particle (Rpp) increased with increasing proportions of butyl methacrylate in the monomer mixture. All of the latexes had narrow particle size distributions. The greater particle number density in VDC polymerization and the greater water solubility of VDC suggest that the homogeneous nucleation mechanism is operative in VDC-BMA copolymerizations. The latex copolymers prepared by semicontinuous polymerization had lower number-and weight-average molecular weights than those of the corresponding batch copolymers, resulting from the monomer starvation occurring during the semicontinuous polymerization. The surface characterization study of the cleaned latexes showed that for the latexes by batch process, the surface charge density derived from strong-acid groups decreased with increasing proportion of VDC in the monomer mixture. On the other hand, for the latexes prepared by semicontinuous polymerization, the surface charge density derived from strong-acid groups did not depend on the monomer composition of the copolymers.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070451217
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  • 9
    Electronic Resource
    Electronic Resource
    Batch and semicontinuous emulsion copolymerization of vinylidene chloride and butyl methacrylate. II. Physical and mechanical properties of copolymer latex films (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 2221-2234 
    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: Vinylidene chloride (VDC)-butyl methacrylate (BMA) copolymer latex films of various compositions (83 : 17, 60 : 40, 33 : 67 in mol %), prepared by batch and semicontinuous processes, were investigated for their physical properties by infrared spectroscopy, 13C solidstate NMR spectroscopy, X-ray diffraction, solubility in various solvents, differential scanning calorimetry (DSC), and water vapor transmission rates (WVTR), and for their mechanical properties by dynamic mechanical spectroscopy (DMS), and tensile strength measurements. Semicontinuous latex films were found to be homogeneous in composition and amorphous in character. On the other hand, batch latex films containing high VDC monomer content were heterogeneous in composition and crystalline in character. These differences were found to reflect the effect of mode of monomer addition during the emulsion polymerization process, and correlated well to the results on kinetics, colloidal, and surface properties of the VDC-BMA copolymer latexes, as described in the first part of this study.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070451218
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  • 10
    Electronic Resource
    Electronic Resource
    The effect of chelation on the selective transport of alkaline earth metal ions in asymmetric cellulose acetate hyperfiltration membranes. II (1978)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 22 (1978), S. 1093-1104 
    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 effects of chelation on the transport of calcium and magnesium, both separately and in a variety of admixtures, in a controlled series of asymmetric cellulose acetate membranes were characterized. Ethylenediaminetetraacetic acid (EDTA) and ethylenebis(oxyethylenenitrilo)tetraacetic acid (EGTA) were used as chelating agents for the alkaline earth metal ions. Asymmetric cellulose acetate membranes annealed at 70°, 75°, and 85°C were studied. Chelation of each of these alkaline earth metals ions in aqueous solutions at pH 6, by either EDTA or EGTA, significantly increased the overall hyperfiltration rejections of these metals by all the membranes studied. The increase in rejection varied montonically with the fraction of metal ion complexed. The higher rejection of metal chelates, compared to the rejection of unbound metal ions, was considered to be the result of the significantly larger size of the chelated species. Calculations suggested that selective (or competitive) chelation took place at pH 6 in a mixture of calcium and magnesium ions in the presence of a stoichiometrically limiting amount of chelating agent. Calcium successfully competed for most of the available chelating agent in equimolar aqueous solutions of chelating agent, calcium, and magnesium. The calcium rejection was explained primarily in terms of the effects of chelation per se on the effective size of the formed complex even in feeds comprised of these ternary solute mixtures. The complexation reaction between magnesium and EGTA is, however, so unfavorable at pH 6 that the Mg2+ ion remains uncomplexed even in the presence of an equivalent amount of EGTA. The observed increased rejection of magnesium ions, therefore, in ternary systems was explained by electroneutrality criteria and by solute-membrane interactions involving the various calcium species and the membranes.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1978.070220418
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