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  • Chemical Engineering  (29)
  • Air Transportation and Safety  (23)
  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 1 (1955), S. 302-304 
    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: 1 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 17 (1971), S. 428-435 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Modification of parameters in the conventional controller equation usually is necessitated by uncontrollable process parameter drifts which occur during the operation of the large scale continuous processes typically found in the chemical industry. To this end, a normalized version of the model reference adaptive control system, including suitable procedures for adjusting the adaptive loop gains, was developed and demonstrated to provide excellent adaptive performance for a single concentration control loop for a simulated stirred-tank chemical reactor. The three constants in a conventional PID controller were simultaneously adjusted to accomplish this adaptation. Equally excellent adaptive performance was achieved in an interacting control loop scheme simulated by control of both the concentration and the temperature in the same stirred-tank reactor. In both cases adaptation was achieved in a time interval which was sufficiently short to make this method of adaptive control feasible for use in a real processing situation. Models needed for implementation of the model reference adaptive control scheme were easily developed. In a real application these models could be easily developed from studies which could take place during prestartup or early operations of the process; hence no a priori knowledge would be required. A wide range of adaptive loop gains was demonstrated to provide a stable overall control system. A high degree of stability was demonstrated for the overall system despite the initiation of large extraneous load upsets occurring during the operation of the adaptive control system.The method presented has not been rigorously proven to be applicable to every real control problem requiring adaptive control. However, the method was demonstrated to be highly effective over a wide range of required controller adjustments in cases similar to those encountered in large continuous processes. Thus the method merits serious consideration for possible implementation whenever adaptive control is required.
    Additional Material: 10 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 32 (1986), S. 2079-2082 
    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: 3 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 33 (1987), S. 558-572 
    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 theoretical framework useful for predicting the steady state response of enzyme-pH electrodes is developed. The model takes into account that the catalytic activity of the enzymes as well as the degree of dissociation of the product acids and bases is strongly dependent upon the local pH, and that buffering salts present in solution facilitate the transport of H+ ions. It is shown that the electrode should operate under substrate diffusion-limited conditions and the concentration of H+ ions should not have steep variations within the enzymic membrane. This condition can be fulfilled by adjusting the buffer concentration in the bulk solution. In the latter conditions the electrode response does not depend on the actual kinetics of the enzymic reaction, and can be predicted by an algebraic equation. The predictions are in excellent agreement with the experiments on penicillinase-pH and urease-pH electrodes.
    Additional Material: 9 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 694-704 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Concentration profiles were determined in both phases for the system methyl isobutyl ketone (MIBK) - water-acetic acid in a Kühni 72.45-mm-dia. Extraction column of 25 stages. Mass transfer and backmixing parameters were estimated numerically from the profiles in terms of the backflow model. The results indicated that backmixing of the continuous phase was appreciable, while that of the dispersed phase was negligible. Independent values of the continuous-phase backmixing coefficient, αc, were also determined by both unsteady-state and continuous tracer injection, in the former case both with and without mass transfer. The results indicated that αc is increased by mass transfer, and that the tracer values, both with and without mass transfer, are greater than those obtained from the profile data.
    Additional Material: 9 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 5 (1959), S. 314-318 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In an investigation of the behavior of an air-fluidized bed of glass spheres under varying interparticle forces, the results obtained are explained by hypothesizing the coexistence of particulate and aggregative fluidization. As interparticle forces are increased, a greater portion of the particles are in aggregative fluidization, resulting in a decrease in bed height. In this study water added to the fluidizing air increased the interparticle forces. Up to 0.5 mass % water was used, with a fluidized bed of glass spheres 0.013 to 0.035 in. in diameter. The resulting decrease in bed height has been correlated by means of a theoretical equation for the increase in interparticle forces due to the added water.
    Additional Material: 10 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 1 (1955), S. 544-548 
    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 method is presented for determining the flow-rate - pressure-gradient relationship for the streamline flow of the large class of non-Newtonian, nonthixotropic fluids to which the Powell-Eyring equation applies. The general procedure and assumptions required in developing this method are the same as used in deriving the Hagen-Poiseuille equation except that the Powell-Eyring equation is used in place of Newton's equation to relate shear stress to shear rate.The method can be used to predict pipe-flow pressure gradients from both precision viscometer data and pipe-flow data. Its applicability is demonstrated for three typical non-Newtonian fluids, 3% carboxymethylcellulose in water, 15% napalm in kerosene, and 33% hydrated lime in water.When used with pipe-flow data, it resembles the method of Alves and associates, compensating for the inconvenience of an additional step in calculation procedure by providing a means of extrapolating beyond the range of the experimental data.The relationships developed facilitate the application of shear-stress - shear-rate data in the design of conduits for non-Newtonian fluids.
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 2 (1956), S. 271-272 
    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 method, based upon the pertinent flat-plate heat transfer equation, is presented for computing the local heat transfer coefficients for a boundary layer subjected to streamwise velocity and pressure gradients. No extensive mathematical background is required as the complexity of a rigorous solution for this type of problem is avoided. The validity of the method for gases is demonstrated by comparison of the predicted coeffcients with the experimental data for two widely different problems.
    Additional Material: 2 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 10 (1964), S. 944-951 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: With the development of relatively inexpensive control computers and on-stream analyzers, on-line dynamic optimization of nonlinear, multistage systems has become more feasible. Investigators have been concerned with the static optimization and control of single-stage and multistage systems, but few have considered the optimization of a multistage system whose behavior is nonstatic owing to stochastic changes in its input and environment, and whose optimal control policy is time varying.This paper looks at the problem of dynamic optimization as it applies to the analysis of a multistage continuous stirred-tank reactor system. A variational approach, in which the physical restraints on the manipulatable variables are included by a parametric representation, led to a bang-bang, sampled-data, optimal control law, or an equivalent analytical expression for continuous optimal control. Inclusion of the inequality relationships, specifying amplitude constraints on the manipulatable variables by a penalty function, resulted in a set of nonlinear Euler-Lagrange equations specifying the control law.
    Additional Material: 3 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 14 (1968), S. 591-599 
    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 dynamic behavior of a packed liquid extraction column was investigated by comparing experimental frequency response data obtained from pulse testing with theoretical frequency response data. The theoretical model, which assumed that the column can be represented by a series of perfectly mixed cells, did not adequately describe the frequency response characteristics of the extraction process. However, by the utilization of various magnitude and phase correction factors, a technique was developed to obtain a semiempirical model that could be used to duplicate the actual performance of the liquid extraction column.
    Additional Material: 13 Ill.
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