The Experts below are selected from a list of 40143 Experts worldwide ranked by ideXlab platform
José Carlos Pinto - One of the best experts on this subject based on the ideXlab platform.
-
A stochastic flow model for a tubular Solution Polymerization reactor
Polymer Engineering & Science, 2007Co-Authors: Ardson Dos S. Vianna, Evaristo C. Biscaia, José Carlos PintoAbstract:Residence time distributions were evaluated experimentally for three tubular Solution Polymerization reactors to analyze aspects of the fluid-dynamic behavior of these reactors. The analysis of the available experimental data indicates that the flow characteristics of these reactors may be subject to stochastic perturbations. A stochastic flow model is then proposed by assuming that a viscous polymer layer is formed in the proximities of the reactor walls and that plugs of polymer material are released at random during the operations. This model is able to represent the available experimental data fairly well for three tubular reactors with different configurations. POLYM. ENG. SCI., 47:1839–1846, 2007. © 2007 Society of Plastics Engineers
-
Periodic oscillations in continuous free-radical Solution Polymerization reactors—a general approach
Chemical Engineering Science, 2001Co-Authors: Príamo A. Melo, Evaristo C. Biscaia, João G Sampaio, José Carlos PintoAbstract:Abstract Previous studies regarding the bifurcation behavior of continuous stirred tank Polymerization reactors have reported a multitude of different nonlinear responses. The nonlinear responses reported most often are steady-state multiplicity and self-sustained oscillatory behavior, which have been confirmed experimentally. Particularly, Freitas Filho, Biscaia, and Pinto (Chemical Engineering Science 49 (22) (1994) 3745–3755) used a generic model to describe the dynamic behavior of continuous free-radical Solution Polymerizations and were able to show that most reactors can present as many as five distinct steady-state Solutions, regardless of the particular chemical system analyzed. The work of Freitas Filho, Biscaia, and Pinto is extended here to show that self-sustained oscillatory responses may also be considered to be generic reactor responses, regardless of the particular chemical system analyzed. The effect of both physico-chemical and operational reactor parameters on the topology of the branches of periodic Solutions is also investigated. It is shown that most continuous Solution Polymerization systems may present regions where limit cycles are present and that the increase of the gel effect decreases the probability of observing sustained oscillatory responses.
William R. Cluett - One of the best experts on this subject based on the ideXlab platform.
-
Adaptive control of conversion in a simulated Solution Polymerization continuous stirred tank reactor
Industrial & Engineering Chemistry Research, 1990Co-Authors: Sergio A. Mendoza-bustos, Alexander Penlidis, William R. CluettAbstract:An adaptive controller that account for unmodeled dynamics and unmeasured disturbances is applied to the control of monomer conversion of a continuous Solution Polymerization reactor in the presence of reactive impurities with drifting concentration levels. This control approach is evaluated at the simulation level using the initiator concentration in the feed as the control variable. The performance is compared against those of a minimum variance and a self-tuning controller
Alexander Penlidis - One of the best experts on this subject based on the ideXlab platform.
-
High‐temperature Solution Polymerization of butyl acrylate/methyl methacrylate: Reactivity ratio estimation
Journal of Applied Polymer Science, 2000Co-Authors: Malik Hakim, V. Verhoeven, Neil T. Mcmanus, Marc A. Dubé, Alexander PenlidisAbstract:Solution coPolymerizations of butyl acrylate/methyl methacrylate in toluene were performed over an expanded temperature range (60–140°C) compared to more typical ranges that do not exceed 80°C. From a large amount of data collected independently at two laboratories, reactivity ratios were estimated at five different temperatures. The reactivity ratios were estimated from low conversion copolymer composition data using both the error-in-variables model method and a nonlinear parameter estimation based on the integrated copolymer composition equation. Using all of the available data, temperature-dependent expressions were developed for the reactivity ratios and compared to previously published bulk coPolymerization values. No significant differences appeared to exist between the bulk and Solution Polymerization reactivity ratios. Furthermore, the copolymer composition data conformed to the Mayo-Lewis kinetic model over the entire temperature range. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 602–609, 2000
-
high temperature Solution Polymerization of butyl acrylate methyl methacrylate reactivity ratio estimation
Journal of Applied Polymer Science, 2000Co-Authors: Malik Hakim, V. Verhoeven, Neil T. Mcmanus, Marc A. Dubé, Alexander PenlidisAbstract:Solution coPolymerizations of butyl acrylate/methyl methacrylate in toluene were performed over an expanded temperature range (60–140°C) compared to more typical ranges that do not exceed 80°C. From a large amount of data collected independently at two laboratories, reactivity ratios were estimated at five different temperatures. The reactivity ratios were estimated from low conversion copolymer composition data using both the error-in-variables model method and a nonlinear parameter estimation based on the integrated copolymer composition equation. Using all of the available data, temperature-dependent expressions were developed for the reactivity ratios and compared to previously published bulk coPolymerization values. No significant differences appeared to exist between the bulk and Solution Polymerization reactivity ratios. Furthermore, the copolymer composition data conformed to the Mayo-Lewis kinetic model over the entire temperature range. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 602–609, 2000
-
Adaptive control of conversion in a simulated Solution Polymerization continuous stirred tank reactor
Industrial & Engineering Chemistry Research, 1990Co-Authors: Sergio A. Mendoza-bustos, Alexander Penlidis, William R. CluettAbstract:An adaptive controller that account for unmodeled dynamics and unmeasured disturbances is applied to the control of monomer conversion of a continuous Solution Polymerization reactor in the presence of reactive impurities with drifting concentration levels. This control approach is evaluated at the simulation level using the initiator concentration in the feed as the control variable. The performance is compared against those of a minimum variance and a self-tuning controller
-
One-step optimal control of a continuous Solution Polymerization reactor
Proceedings of 1995 34th IEEE Conference on Decision and Control, 1Co-Authors: A.b. Ogunye, Alexander PenlidisAbstract:This paper describes the application of minimum variance and one-step optimal controllers to the control of conversion in a Solution Polymerization reactor. The objective is the servo control of polymer conversion. A new saturation and controller windup algorithm proposed in Ogunye (1994) was implemented for the set-point tracking control policies. The improvement in closed-loop performance using this saturation algorithm over that obtained when the input saturates (open-loop response) was demonstrated at the simulation level.
Sang-jin Lee - One of the best experts on this subject based on the ideXlab platform.
-
crystallization and densification of nano size amorphous cordierite powder prepared by a pva Solution Polymerization route
Journal of the American Ceramic Society, 2005Co-Authors: Sang-jin Lee, Waltraud M. KrivenAbstract:A homogeneous and stable amorphous-type cordierite (2MgO2Al2O35SiO2) powder was prepared by a Solution-Polymerization route employing a Pechini resin or a poly(vinyl alcohol) (PVA) Solution as the polymeric carrier. After calcination at 800°C for 1 h under atmospheric conditions, the bulky precursor changed into a very soft and porous powder. A 30 nm size, amorphous-type cordierite powder was prepared by attrition milling the calcined powder, which was made using a PVA precursor Solution. The nano-size powder, which had a high specific surface area of 181 m2/g, was obtained after milling for <1 h. The sintered cordierite grains did not show the presence of any amorphous SiO2 phase and had a dense microstructure with a relative density of 99% and a thermal expansion coefficient of 2.1 10-6/°C.
-
preparation of portland cement components by poly vinyl alcohol Solution Polymerization
Journal of the American Ceramic Society, 2004Co-Authors: Sang-jin Lee, Elizabeth A. Benson, Waltraud M. KrivenAbstract:The four components portland cement-dicalcium silicate, C2S (Ca2SiO4); tricalcium silicate, C3S (Ca3SiO5); tricalcium aluminate, C3A (Ca3Al2O6); and tetracalcium aluminate iron oxide, C4AF (Ca4Al2Fe3O10)-were formed using a Solution-Polymerization route based on poly(vinyl alcohol) (PVA) as the polymer carrier. The powders were characterized using X-ray diffraction techniques, BET specific surface area measurements, and scanning electron microscopy. This method produced relatively pure, synthetic cement components of submicrometer or nanometer crystallite dimensions, high specific surface areas, as well as extremely high reactivity at relatively low calcining temperatures. The PVA content and its degree of Polymerization had a significant influence on the homogeneity of the final powders. Two types of degree of Polymerization (DP) PVA were used. Lower crystallization temperatures and smaller particle size powders were obtained from the low-DP-type PVA at optimum content.
-
Preparation of Portland Cement Components by PVA Solution Polymerization
1998Co-Authors: Elizabeth A. Benson, Sang-jin Lee, Waltraud M. KrivenAbstract:Abstract : The four components of Portland cement: dicalcium silicate, C2S (Ca2SiO4), tricalcium silicate, C3S (Ca3SiO5), tricalcium aluminate, C3A (Ca3Al2O6), and tetracalcium aluminate iron oxide, C4AF (Ca4Al2Fe3O10), were formed using a Solution-Polymerization route based on polyvinyl alcohol (PVA) as the polymer carrier. The powders were characterized using X-ray diffraction techniques, BET specific surface area, and scanning electron microscopy. This method produced relatively pure, synthetic cement components of sub-micron or nanometer crystallite dimensions, high specific surface area and extremely high reactivity at relatively low calcining temperatures. The PVA content and its degree of Polymerization had a significant influence on the homogeneity of the final powders. Two types of degree of Polymerization (D.P.) PVA were used. Lower crystallization temperatures and smaller particle size powders were obtained from the low D.P. type of PVA at optimum content.
-
Processing of cordierite and hexacelsian precursor powders through Solution-Polymerization route
Journal of the Ceramic Society of Japan, 1998Co-Authors: Sang-jin LeeAbstract:Amorphous-type cordierite (2MgO⋅2Al2O3⋅5SiO2) and hexacelsian (BaO⋅Al2O3⋅2SiO2) precursor powders were prepared by a Solution-Polymerization route employing a Pechini resin or a PVA Solution as a polymeric carrier. After calcination at 800°C for 1h under atmospheric conditions, the bulky precursors changed into very soft and porous powders. In case of the cordierite precursor prepared using PVA Solution, the densification proceeded at lower temperature than in the case of the Pechini resin process. The densification was inhibited by the crystallization of amorphous silica in both cases and it was the reason for the coarse microstructure of the sintered cordierite. Sintered cordierite was closer to pure cordierite with low amount of amorphous-type cordierite phases as was observed in the case of the Solution-Polymerization route employing PVA Solution. Hexacelsian precursor powder, which was prepared by the PVA Solution process, was faster crystallized to hexacelsian and showed more sluggish reconstructive transformation behavior than the powder derived from the Pechini resin process.
-
A preparation of hexacelsian powder by Solution-Polymerization route and its phase transformation behavior
1997Co-Authors: Sang-jin Lee, Young-soo YoonAbstract:Hexacelsian () powder was prepared by a Solution-Polymerization route employing PVA Solution as a polymeric carrier. A fine amorphous-type hexacelsian powder with an average particle size of 0.8 and a BET specific surface area of /g was made by a ball-milling the powder precursor for 12 h after calcination at for :1 h. A densified hexacelsian was obtained through sintering at for 2 h under an air atmosphere. The and displacive phase transformation in polycrystalline hexacelsia,n was examined by using dilatometry and differential scanning calorimtry. The reconstructive transformation between hexacelsian and celsian was obtained by annealing at for 72h. Volume contraction of 5.6% was accompanied by the reconstructive transformation.
A.b. Ogunye - One of the best experts on this subject based on the ideXlab platform.
-
Online multivariable control of conversion and molecular weight in a continuous Solution Polymerization reactor
Proceedings of the 1997 American Control Conference (Cat. No.97CH36041), 1997Co-Authors: A.b. OgunyeAbstract:This paper presents a brief overview of some of the results from a comprehensive experimental study (Ogunye, 1994) wherein multivariable and multi-loop stochastic and non-stochastic control policies were applied to a pilot scale methyl methacrylate continuous Solution Polymerization reactor. The control objectives were the servo-control of conversion and square root of weight-average molecular weight. The multi-loop PID and LQG control strategies applied at the simulation level, proved effective for the servo-control of conversion and square root of weight-average molecular weight using the reactor temperature set-point and initiator flow rate as manipulated variables.
-
Adaptive control of a continuous Solution Polymerization reactor
Proceedings of 28th Southeastern Symposium on System Theory, 1Co-Authors: A.b. OgunyeAbstract:This paper focuses on the application of an explicit self-tuning linear quadratic Gaussian controller to the simulation servo control of conversion in a continuous stirred tank Solution Polymerization reactor under isothermal conditions. A new saturation and controller windup algorithm proposed in Ogunye (1994, 1996) was implemented for the set-point tracking-control policies. The improvement in closed-loop performance using this saturation algorithm over that obtained when the input saturates was demonstrated at the simulation level.
-
One-step optimal control of a continuous Solution Polymerization reactor
Proceedings of 1995 34th IEEE Conference on Decision and Control, 1Co-Authors: A.b. Ogunye, Alexander PenlidisAbstract:This paper describes the application of minimum variance and one-step optimal controllers to the control of conversion in a Solution Polymerization reactor. The objective is the servo control of polymer conversion. A new saturation and controller windup algorithm proposed in Ogunye (1994) was implemented for the set-point tracking control policies. The improvement in closed-loop performance using this saturation algorithm over that obtained when the input saturates (open-loop response) was demonstrated at the simulation level.
