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  • 1
    Electronic Resource
    Electronic Resource
    Estimation of the molecular weight distribution in batch polymerization (1988)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 1341-1353 
    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 filtering technique is proposed for on-line estimation of the temperature, monomer conversion, initiator conversion, and the entire molecular weight distribution in a batch methyl methacrylate polymerization reactor. The technique uses a detailed polymerization model combined with on-line measurements of conversion, temperature, and the molecular weight distribution, taken at different discrete time intervals. The polymerization model includes a chain-length-dependent termination rate constant which allows the prediction of the molecular weight distribution for common free-radical polymerization conditions. Comparisons between modeling and experimental results show that the polymerization model gives good predictions of the monomer conversion and the molecular weight distribution in the polymerization system. The performance of the estimation scheme is tested for cases of strong gel effect conditions leading to a bimodal molecular weight distribution, and poor initial conditions. Finally, off-line experimental data are used to test the algorithm under actual reactor operating conditions.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690340812
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    On-line molecular weight distribution estimation and control in batch polymerization (1994)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 445-462 
    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 molecular weight distribution (MWD) estimator for batch methyl methacrylate solution polymerization is implemented experimentally for on-line control and estimation of the MWD. The estimator is based on an extended Kalman filter and provides current estimates of the entire MWD, reaction temperature, monomer conversion, and initiator conversion. It uses a detailed polymerization model, on-line monomer conversion measurements, temperature measurements, and periodic, time-delayed measurements of the MWD from an on-line size-exclusion chromatograph. The estimator is shown to perform well with several on-line MWD estimation experiments. Real-time feedback control of the molecular weight is presented by utilizing the on-line MWD information. Temperature, monomer-addition, and simultaneous temperature and monomer-addition control are investigated experimentally to achieve a specific constant weight-average molecular weight. The on-line feedback control is effective in rejecting realistic disturbances which deteriorate molecular weight control.
    Additional Material: 34 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690400308
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Ejecting volume, filling volume and stroke volume gains: New indexes of inotropism and lusitropism (1992)
    Springer
    Heart and vessels 7 (1992), S. 57-65 
    Details
    ISSN: 1615-2573
    Keywords: Pump function ; Systole ; Diastole ; Preload ; Afterload ; Ventricular distensibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We propose new indexes to evaluate the effects of ventricular inotropism and lusitropism on stroke volume. The end-systolic pressure-volume relationship (ESPVR) or its slope (Emax) has been employed to assess ventricular inotropism. The end-diastolic pressure-volume relationship (EDPVR) or compliance has been used to express ventricular diastolic properties or lusitropism. However, their net effect on stroke volume under a given set of preload and afterload pressures has not quantitatively been evaluated.Ejecting volume gain (Ge) was proposed to quantify the inotropic effect on stroke volume by the change in end-systolic volume between the two ESPVR curves obtained before and during an inotropic intervention at a specified ejecting pressure. Ge is a function of afterload pressure.Filling volume gain (Gf) was proposed to quantify the lusitropic effect on stroke volume by the change in end-diastolic volume between the two EDPVR curves before and during a lusitropic intervention at a specified filling pressure. Gf is a function of preload pressure. The net effect of these inotropic and lusitropic effects on stroke volume at these specified preload and afterload pressures can be expressed by the sum of Ge and Gf. We call this sumstroke volume gain (Gsv). Gsv is a function of preload and afterload pressures. Using representative examples, we demonstrate that these new indexes are conceptually useful to quantitatively understand changes in the pumping ability of the heart under simultaneous inotropic and lusitropic effects as a function of ejecting and filling pressures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01744450
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Cardiac muscle fiber force versus length determined by a cardiac muscle crossbridge model (1992)
    Springer
    Heart and vessels 7 (1992), S. 200-205 
    Details
    ISSN: 1615-2573
    Keywords: Heart ; Mathematical model ; Crossbridge kinetics ; Computer simulation ; Calcium level
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A mathematical model incorporating Huxley's sliding filament crossbridge muscle model coupled with parallel and series elastic components was simulated to examine force-length relations under different external calcium concentrations. Several researchers have determined experimentally in both papillary muscle preparations and in situ heart experiments that the calcium concentration (or effective concentration from inotropic agents) will affect the strength and convexity of the cardiac muscle fiber force-length relations. Simulations were performed over a several-order-of-magnitude range of calcium concentrations in isometric contractions and these showed that the force-length curve convexity was changed. Simulation results demonstrated that increasing the stiffness in the model contractile element or series elasticity element did not change the force-length convexity. Increasing the series elasticity element stiffness did slightly change the shape of the force-length curve. The model predicts that the curve convexity changes as a result of the calcium-troponin interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01744605
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    Paper (German National Licenses)
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