Steady-State and Dynamic Modeling of Gas-Phase Polypropylene Processes Using Stirred-Bed Reactors

2004 ◽  
Vol 43 (4) ◽  
pp. 884-900 ◽  
Author(s):  
Neeraj P. Khare ◽  
Bruce Lucas ◽  
Kevin C. Seavey ◽  
Y. A. Liu ◽  
Ashuraj Sirohi ◽  
...  
Keyword(s):  
Steady State ◽  
Gas Phase ◽  
Dynamic Modeling

Steady-state and dynamic modeling of a gas absorber-stripper system

1985 ◽  
Vol 24 (3) ◽  
pp. 288-295 ◽  
Author(s):  
Martin M. Suenson ◽  
Christos Georgakis ◽  
Lawrence B. Evans
Keyword(s):  
Steady State ◽  
Dynamic Modeling

Mitochondrial function in the presence of myoglobin

1982 ◽  
Vol 53 (5) ◽  
pp. 1116-1124 ◽  
Author(s):  
R. P. Cole ◽  
P. C. Sukanek ◽  
J. B. Wittenberg ◽  
B. A. Wittenberg
Keyword(s):  
Oxygen Consumption ◽  
Steady State ◽  
Liquid Phase ◽  
Gas Phase ◽  
Oxygen Pressure ◽  
Oxygen Electrode ◽  
Oxygen Binding ◽  
Atp Production ◽  
Skeletal Muscle Mitochondria ◽  
The Difference

The effect of myoglobin on oxygen consumption and ATP production by isolated rat skeletal muscle mitochondria was studied under steady-state conditions of oxygen supply. A method is presented for the determination of steady-state oxygen consumption in the presence of oxygen-binding proteins. Oxygen consumed in suspensions of mitochondria was replenished continuously by transfer from a flowing gas phase. Liquid-phase oxygen pressure was measured with an oxygen electrode; the gas-phase oxygen concentration was held constant at a series of fixed values. Oxygen consumption was determined from the characteristic response time of the system and the difference in the steady-state gas- and liquid-phase oxygen concentrations. ATP production was determined from the generation of glucose 6-phosphate in the presence of hexokinase. During steady-state mitochondrial oxygen consumption, the oxygen pressure in the liquid phase is enhanced when myoglobin is present. Functional myoglobin present in the solution had no effect on the relation of mitochondrial respiration and ATP production to liquid-phase oxygen pressure. Myoglobin functions in this system to enhance the flux of oxygen into the myoglobin-containing phase. Myoglobin may function in a similar fashion in muscle by increasing oxygen flux into myocytes.

scholarly journals A semi-analytical method for calculating rates of new sulfate aerosol formation from the gas phase

2007 ◽  
Vol 7 (1) ◽  
pp. 2169-2196 ◽  
Author(s):  
J. Kazil ◽  
E. R. Lovejoy
Keyword(s):  
Steady State ◽  
Gas Phase ◽  
Nucleation Rate ◽  
Atmospheric Modeling ◽  
Sulfate Aerosol ◽  
Nucleation Theory ◽  
Rate Coefficients ◽  
Classical Nucleation Theory ◽  
Aerosol Formation ◽  
Aerosol Model

Abstract. The formation of new sulfate aerosol from the gas phase is commonly represented in atmospheric modeling with parameterizations of the steady state nucleation rate. Such parameterizations are based on classical nucleation theory or on aerosol nucleation rate tables, calculated with a numerical aerosol model. These parameterizations reproduce aerosol nucleation rates calculated with a numerical aerosol model only imprecisely. Additional errors can arise when the nucleation rate is used as a surrogate for the production rate of particles of a given size. We discuss these errors and present a method which allows a more precise calculation of steady state sulfate aerosol formation rates. The method is based on the semi-analytical solution of an aerosol system in steady state and on parameterized rate coefficients for H2SO4 uptake and loss by sulfate aerosol particles, calculated from laboratory and theoretical thermodynamic data.

Graphenylene and Inorganic Graphenylene Nanopores for Gas-Phase 4He/3He Separation: Kinetic and Steady-State Considerations

2021 ◽  
Author(s):  
Maryam Sadat Motallebipour ◽  
Javad Karimi-Sabet
Keyword(s):  
Steady State ◽  
Gas Phase ◽  
Quantum Tunneling ◽  
Zero Point ◽  
Selective Membrane ◽  
Quantum Phenomena ◽  
Mass Dependent

Selective membrane-based separation of light isotopes is considered to be possible based on the quantum phenomena. In this regard, the role of the two mass-dependent effects, quantum tunneling and zero-point...

Kinetics of NO2 air space absorption in isolated rat lungs

1992 ◽  
Vol 73 (5) ◽  
pp. 1939-1945 ◽  
Author(s):  
E. M. Postlethwait ◽  
S. D. Langford ◽  
A. Bidani
Keyword(s):  
Steady State ◽  
Tidal Volume ◽  
Gas Phase ◽  
Initial Rate ◽  
Quasi Steady State ◽  
Closed Chamber ◽  
First Order ◽  
First Order Kinetics ◽  
Rat Lungs ◽  
Kinetics Of

We previously showed, during quasi-steady-state exposures, that the rate of inhaled NO2 uptake displays reaction-mediated characteristics (J. Appl. Physiol. 68: 594–603, 1990). In vitro kinetic studies of pulmonary epithelial lining fluid (ELF) demonstrated that NO2 interfacial transfer into ELF exhibits first-order kinetics with respect to NO2, attains [NO2]-dependent rate saturation, and is aqueous substrate dependent (J. Appl. Physiol. 71: 1502–1510, 1991). We have extended these observations by evaluating the kinetics of NO2 gas phase disappearance in isolated ventilating rat lungs. Transient exposures (2–3/lung at 25 degrees C) employed rebreathing (NO2-air) from a non-compliant continuously stirred closed chamber. We observed that 1) NO2 uptake rate is independent of exposure period, 2) NO2 gas phase disappearance exhibited first-order kinetics [initial rate (r*) saturation occurred when [NO2] > 11 ppm], 3) the mean effective rate constant (k*) for NO2 gas phase disappearance ([NO2] < or = 11 ppm, tidal volume = 2.3 ml, functional residual capacity = 4 ml, ventilation frequency = 50/min) was 83 +/- 5 ml/min, 4) with [NO2] < or = 11 ppm, k* and r* were proportional to tidal volume, and 5) NO2 fractional uptakes were constant across [NO2] (< or = 11 ppm) and tidal volumes but exceeded quasi-steady-state observations. Preliminary data indicate that this divergence may be related to the inspired PCO2. These results suggest that NO2 reactive uptake within rebreathing isolated lungs follows first-order kinetics and displays initial rate saturation, similar to isolated ELF.(ABSTRACT TRUNCATED AT 250 WORDS)

A hemodynamic model representation of the dog lung

1991 ◽  
Vol 70 (1) ◽  
pp. 15-26 ◽  
Author(s):  
S. T. Haworth ◽  
J. H. Linehan ◽  
T. A. Bronikowski ◽  
C. A. Dawson
Keyword(s):  
Steady State ◽  
Dynamic Modeling ◽  
Power Law ◽  
Transmural Pressure ◽  
Morphometric Data ◽  
Pressure Flow ◽  
Average Ratio ◽  
Vascular Bed ◽  
Hemodynamic Model ◽  
Arteries And Veins

The published morphometric data from human, cat, and dog lungs suggest that the power-law relationships between the numbers (Na and Nv) and diameters (Da and Dv) of arteries and veins and between the lengths (La and Lv) and diameters of the arteries and veins could be used as scaling rules for assigning dimensions and numbers to the intrapulmonary vessels of the arterial and venous trees of the dog lung. These rules, along with the dimensions of the extrapulmonary arteries and capillary sheet and the distensibility coefficients of the vessels obtained from the literature, were used to construct a steady-state hemodynamic model of the dog lung vascular bed. The model can be characterized approximately by 15 orders of arteries with Na approximately 2.07 Da-2.58 and 13 orders of veins with Nv approximately 2.53 Dv-2.61. For the intrapulmonary vessels (orders 1–12), La approximately 4.85 Da1.01, and Lv approximately 6.02 Da1.07. The average ratio of the numbers of vessels in consecutive orders is approximately 3.2 for the arteries and veins. These arterial and venous trees are connected by the capillary sheet with an undistended thickness of approximately 3.5 microns and an area of 33 m2. The average distensibility (% increase in diameter over the undistended diameter/Torr increase in transmural pressure) for the model arteries and veins is approximately 2.4%/Torr, and the distensibility of the capillary sheet (% increase in thickness over the undistended thickness/Torr increase in transmural pressure) is approximately 3.6%/Torr. The calculated arterial-capillary-venous volumes and compliances of the model agree well with experimental estimates of these variables in dogs. In addition, the model appears consistent with certain aspects of the pressure-flow relationships measured in dog lungs. The model appears to be a useful summary of some of the available data on pulmonary morphometry and vessel properties. It is anticipated that the model will provide the basis for dynamic modeling of the dog lung in the future.

Modelling post-discharge nitriding and nitrocarburising

2004 ◽  
Vol 120 ◽  
pp. 239-247
Author(s):  
T. Belmonte ◽  
C. Jaoul ◽  
H. Michel
Keyword(s):  
Steady State ◽  
Ternary System ◽  
Gas Phase ◽  
Gas Flow ◽  
State Of The Art ◽  
Active Species ◽  
Surface Phenomena ◽  
Post Discharge ◽  
Two Phase ◽  
Adsorption Surface

In this paper, the state of the art in the modelling of nitriding and nitrocarburising using late post-discharge processes is described. In a first part, interstitial diffusion in ternary system is treated. The problem of the diffusion in two-phase domains is evoked. The chemical pathways in N2-H2 and N2-CH4 post-discharges creating active species are next presented to try to identify the precursors responsible for the transport of nitrogen and carbon to the surface of the solid. Finally, attention is paid to the coupling between the gas phase and the solid. Two different approaches are proposed, either by considering a steady state or a transient gas flow. The latter requires to introduce a sequence of surface phenomena (adsorption, surface diffusion, recombination, dissolution…) that provides a rigorous way to couple processes in the gas phase and in the solid.

Pseudo-Dynamic Modeling to Evaluate a Remote Gas-to-Liquids Process

2011 ◽  
Vol 6 (1) ◽  
Author(s):  
Glen Hay ◽  
John Nighswander
Keyword(s):  
Steady State ◽  
Dynamic Model ◽  
Dynamic Modeling ◽  
Model Development ◽  
Liquid Fuels ◽  
Sensitivity Analyses ◽  
Small Scale ◽  
Process Viability ◽  
Gas To Liquids ◽  
Steady State Simulation

A project team was given the task of evaluating various technology options for design of a small-scale gas-to-liquids (GTL) process operated remotely at or near an individual gas source. For this study, small-scale plants were considered those producing between 100 and 500 barrels per day of liquid fuels. In addition, being remote enforced limitations on utility sources available to the plant site such as water and grid power. A secondary goal was development of a dynamic model of the plant to use in operator training. To accomplish these objectives, the authors investigated the suitability of a process-simulation application. The conceptual design of the GTL unit included many different possibilities, such as front-end design, back-end design, heat integration, and recycling of materials. Complications associated with plant start-up and shutdown, utilities, process reliability, and economics were included in the decision-making process. The authors present selective results from a steady-state model and sensitivity studies. Considerations for the development of the dynamic model included both a fully rigorous dynamic model and a pseudo-dynamic steady-state-based model; results of the latter model are provided. The study concluded that an industrial steady-state simulation tool provided sufficient flexibility to complete the material and energy-balance calculations, sensitivity analyses, and pseudo-dynamic modeling. This study yielded significant insights into the importance of model assumptions and their impact on the overall process viability. The pseudo-dynamic model also provided insight for improving the process control design. During the work completed the authors determined that the object-oriented structure adopted for the model enabled an efficient, rapid model development.

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