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  • 1
    Electronic Resource
    Electronic Resource
    Design of advanced process controllers (1981)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 27 (1981), S. 793-805 
    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: This paper deals with defining the relation between modeling of process units and controller design. In the process industries, it is often difficult to obtain accurate process models. It is shown that advanced algorithms such as dead-time compensators require more detailed process information for design than do with PI and PID controllers. A method is described to systematically evaluate the relation between process identification and controller design, stability, and performance. It is shown that conventional gain and phase margins do not provide proper safety margins for dead-time compensators and optimal controllers. Methods for safe design of dead-time compensators are derived, and the approach could be useful in a wide class of problems.To illustrate the approach presented, the design of PI controllers by conventional methods is analyzed. The conditions, as well as the exceptions, are specified in which methods such as described by Ziegler and Nichols or Cohen and Coon will give good results. It is shown that for any stable nonlinear system with an input/output function y = G*p(u), a linearized design function G′pd can be constructed and identified that guarantees stability and reasonable performance of the controller (Eqs. 21 and 22 and Figures 4-7) over a wide range of operating conditions. A rigorous framework for identifying the exceptions and understanding the reason why such methods work is presented.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690270513
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of aging and moisture on the reactivity of a graphite epoxy prepreg (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 474-482 
    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 effect of moisture on the curing reaction of Hercules 3501-6/AS graphite-epoxy prepreg was investigated. Test samples of prepreg were aged under humid conditions, while control samples were aged under identical temperature conditions but with negligible humidity. Determinations of the amounts of moisture absorbed and desorbed fom the samples were accomplished gravimetrically. Dielectric analysis was used to monitor the relative reaction rates and overall activation energies of the prepreg after various aging periods. Changes taking place in monomer concentrations were observed using high performance liquid chromatography (HPLC). As aging continued, samples aged under humid conditions displayed, significant decrease in the overall activation energy accompanied by increased reaction rates. This change did not occur in the control samples. Samples aged in high humidity showed increased conversion of monomers to polymer when compared to dry aged samples. The aging time required before the above changes became apparent was temperature dependent; the higher the aging temperature, the sooner the changes in reactivity occurred.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760210807
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  • 3
    Electronic Resource
    Electronic Resource
    Electrical properties of carbon black filled crosslinked polyethylene (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1049-1054 
    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 electrical resistivity of peroxide and radiation crosslinked polyethylene/carbon black compounds was studied as a function of black concentration and, temperature in heating/cooling cycles. Different carbon blacks in compounds with polyethylene responded differently, regarding electrical resistivity, to the effect of crosslinking. In one case (fine black) the resistivity and PTC (positive temperature coefficient) effect did not significantly change, whereas in another case (coarse black) the effect of crosslinking-was to significantly increase the resistivity and reduce the PTC effect. The main advantages of crosslinking were to give compounds having good electrical reproducibility and to practically eliminate the NTC (negative temperature coefficient) effect in compounds containing fine, coarse, or mixtures of carbon blacks. Crosslinked compounds containing mixtures of carbon blacks have shown good conductivity, electrical reproducibility, and switching properties.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760211602
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  • 4
    Electronic Resource
    Electronic Resource
    Nylon-6 containing metal halides II: Tensile properties (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 223-226 
    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: Following the reported pronounced effects of metal halides incorporated into nylon-6 on its glass transition temperature, melting temperature, melt viscosity, crystallization rate and final crystallinity, the tensile mechanical properties and crystallinity of nylon-6 as affected by the absorption of metal halides were studied. At low salt content, some of the mechanical properties are substantially altered and at higher salt concentrations the ductile polymer becomes brittle. There is no marked difference between the salts studied (CuCl2, CuBr2, FeCl3) regarding their effects on the polymer mechanical properties. In the concentration range studied, absorbed Cu salts do not significantly change the polymer's degree of crystallinity, whereas absorbed FeCl3 results in a pronounced reduction, indicating its effect also on the crystalline phase.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760210408
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  • 5
    Electronic Resource
    Electronic Resource
    Residence time distribution in a real single screw extruder (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1194-1202 
    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 residence time distribution in an industrial single screw extruder was investigated experimentally in the case of melt and plasticating extrusion. The investigations performed proved that the extrusion parameters influence strongly the residence time distribution in the extruder. It was found that the resistance to flow through the die-head of the extruder is very important from this point of view, as well as other parameters like rotational speed of the screw and the screw channel depth. Variation of these parameters can change the residence time distribution over a broad range between the extreme idealized cases of plug flow and flow with perfect mixing. In order to obtain quantitative dependences three moduli were used and a correlation equation was obtained. This equation enables an estimation of residence time distribution on the basis of experimental characteristics of the extruder and the actual extrusion parameters.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760211804
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