Modeling and Observer-Based Monitoring of RAFT Homopolymerization Reactions

Reversible addition–fragmentation chain–transfer (RAFT) polymerization of methyl methacrylate (MMA) is modeled and monitored using a multi-rate multi-delay observer in this work. First, to fit the RAFT reaction rate coefficients and the initiator efficiency in the model, in situ 1 H nuclear magnetic resonance (NMR) experimental data from small-scale (<2 mL) NMR tube reactions is obtained and a least squares optimization is performed. 1 H NMR and size exclusion chromatography (SEC) experimental data from large-scale (>400 mL) reflux reactions is then used to validate the fitted model. The fitted model accurately predicts the polymer properties of the large-scale reactions with slight discordance at late reaction times. Based on the fitted model, a multi-rate multi-delay observer coupled with an inter-sample predictor and dead time compensator is designed, to account for the asynchronous multi-rate measurements with non-constant delays. The multi-rate multi-delay observer shows perfect convergence after a few sampling times when tested against the fitted model, and is in fair agreement with the real data at late reaction times when implemented based on the experimental measurements.

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The Usefulness of Video Learning Analytics in Small Scale E-Learning Scenarios

Applied Sciences ◽

10.3390/app112110366 ◽

2021 ◽

Vol 11 (21) ◽

pp. 10366

Author(s):

César Córcoles ◽

Germán Cobo ◽

Ana-Elena Guerrero-Roldán

Keyword(s):

Learning Process ◽

Teaching And Learning ◽

Large Scale ◽

Real Data ◽

Small Scale ◽

E Learning ◽

Learning Scenarios ◽

Real Scenario ◽

Teaching Learning ◽

Learning Data

A variety of tools are available to collect, process and analyse learning data obtained from the clickstream generated by students watching learning resources in video format. There is also some literature on the uses of such data in order to better understand and improve the teaching-learning process. Most of the literature focuses on large scale learning scenarios, such as MOOCs, where videos are watched hundreds or thousands of times. We have developed a solution to collect clickstream analytics data applicable to smaller scenarios, much more common in primary, secondary and higher education, where videos are watched tens or hundreds of times, and to analyse whether the solution is useful to teachers to improve the learning process. We have deployed it in a real scenario and collected real data. Furthermore, we have processed and presented the data visually to teachers for those scenarios and have collected and analysed their perception of their usefulness. We conclude that the collected data are perceived as useful by teachers to improve the teaching and learning process.

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Critically evaluated propagation rate coefficients for radical polymerizations: acrylates and vinyl acetate in bulk (IUPAC Technical Report)

Pure and Applied Chemistry ◽

10.1515/pac-2018-1108 ◽

2019 ◽

Vol 91 (11) ◽

pp. 1883-1888

Author(s):

Robin A. Hutchinson ◽

Sabine Beuermann

Keyword(s):

Vinyl Acetate ◽

Propagation Rate ◽

Size Exclusion ◽

Rate Coefficients ◽

Data Sets ◽

Chromatography Method ◽

Benchmark Data ◽

Technical Report ◽

Exclusion Chromatography ◽

Secondary Radical

Abstract Arrhenius parameters capturing the temperature dependence of radical polymerization propagation rate coefficients, kp, for methyl acrylate, butyl acrylate, and vinyl acetate in bulk are reported, based on the fitting of benchmark data sets compiled from independent laboratories using the pulsed-laser polymerization/size exclusion chromatography method. The reported kp values for acrylates hold for secondary-radical propagation and are needed to calculate effective propagation rate coefficients in situations where there is a significant population of mid-chain acrylate radicals resulting from backbiting, as will be the case at technically relevant temperatures. The results are compared to those previously reported for styrene and methacrylates to highlight the large differences in kp values seen between the major monomer families.

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Detailed Analysis of the Wake Structure of a Straight-Blade H-Darrieus Wind Turbine by Means of Wind Tunnel Experiments and Computational Fluid Dynamics Simulations

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4037906 ◽

2017 ◽

Vol 140 (3) ◽

Cited By ~ 14

Author(s):

Alessandro Bianchini ◽

Francesco Balduzzi ◽

Giovanni Ferrara ◽

Lorenzo Ferrari ◽

Giacomo Persico ◽

...

Keyword(s):

Fluid Dynamics ◽

Experimental Data ◽

Computational Fluid Dynamics ◽

Wind Tunnel ◽

Wind Turbines ◽

Large Scale ◽

Vertical Axis ◽

Performance Estimation ◽

Small Scale ◽

Dynamics Simulations

Darrieus vertical axis wind turbines (VAWTs) have been recently identified as the most promising solution for new types of applications, such as small-scale installations in complex terrains or offshore large floating platforms. To improve their efficiencies further and make them competitive with those of conventional horizontal axis wind turbines, a more in depth understanding of the physical phenomena that govern the aerodynamics past a rotating Darrieus turbine is needed. Within this context, computational fluid dynamics (CFD) can play a fundamental role, since it represents the only model able to provide a detailed and comprehensive representation of the flow. Due to the complexity of similar simulations, however, the possibility of having reliable and detailed experimental data to be used as validation test cases is pivotal to tune the numerical tools. In this study, a two-dimensional (2D) unsteady Reynolds-averaged Navier–Stokes (U-RANS) computational model was applied to analyze the wake characteristics on the midplane of a small-size H-shaped Darrieus VAWT. The turbine was tested in a large-scale, open-jet wind tunnel, including both performance and wake measurements. Thanks to the availability of such a unique set of experimental data, systematic comparisons between simulations and experiments were carried out for analyzing the structure of the wake and correlating the main macrostructures of the flow to the local aerodynamic features of the airfoils in cycloidal motion. In general, good agreement on the turbine performance estimation was constantly appreciated.

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The influence of hydrogen bonding on radical chain-growth parameters for butyl methacrylate/2-hydroxyethyl acrylate solution copolymerization

Polymer Chemistry ◽

10.1039/c6py00834h ◽

2016 ◽

Vol 7 (27) ◽

pp. 4567-4574 ◽

Cited By ~ 19

Author(s):

Jan E. S. Schier ◽

Robin A. Hutchinson

Keyword(s):

Growth Parameters ◽

Propagation Rate ◽

Size Exclusion ◽

Rate Coefficients ◽

Butyl Methacrylate ◽

Chain Growth ◽

Copolymer Composition ◽

Radical Chain ◽

Effect Of Solvent ◽

Exclusion Chromatography

Pulsed laser polymerizations coupled with size exclusion chromatography (PLP-SEC) and NMR analyses were performed to determine radical kinetic parameters for BMA/HEA, with a focus on the effect of solvent choice and H-bonding on both copolymer composition and copolymer-averaged propagation rate coefficients.

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Screening optimized protein purification protocols by coupling small-scale expression and mini-size exclusion chromatography

Protein Expression and Purification ◽

10.1016/j.pep.2010.05.014 ◽

2010 ◽

Vol 74 (2) ◽

pp. 231-235 ◽

Cited By ~ 18

Author(s):

Elisa Sala ◽

Ario de Marco

Keyword(s):

Protein Purification ◽

Size Exclusion Chromatography ◽

Size Exclusion ◽

Small Scale ◽

Exclusion Chromatography

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Molecular Weight and Tacticity of Oligoacrylates by Capillary Electrophoresis - Mass Spectrometry

Australian Journal of Chemistry ◽

10.1071/ch10088 ◽

2010 ◽

Vol 63 (8) ◽

pp. 1219 ◽

Cited By ~ 17

Author(s):

Marianne Gaborieau ◽

Tim J. Causon ◽

Yohann Guillaneuf ◽

Emily F. Hilder ◽

Patrice Castignolles

Keyword(s):

Capillary Electrophoresis ◽

Raft Polymerization ◽

Degree Of Polymerization ◽

Size Exclusion ◽

Separation Mechanism ◽

Ionization Mass ◽

Polymeric Particles ◽

Reversible Addition ◽

Exclusion Chromatography

Oligo(acrylic acid) efficiently stabilizes polymeric particles, especially particles produced by reversible addition–fragmentation chain transfer (RAFT) (as hydrophilic block of an amphiphilic copolymer). Capillary electrophoresis (CE) has a far higher resolution power to separate these oligomers than the commonly used size exclusion chromatography. Coupling CE to electrospray ionization mass spectrometric detection unravels the separation mechanism. CE separates these oligomers, not only according to their degree of polymerization, but also according to their tacticity, in agreement with NMR analysis. Such analysis will provide insight into the role of these oligomers as stabilizers in emulsion polymerization, and into the mechanism of the RAFT polymerization with respect to degree of polymerization and tacticity.

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Kinetics of RAFT polymerization and copolymerization of vinyl monomers by size exclusion chromatography

European Polymer Journal ◽

10.1016/j.eurpolymj.2019.109356 ◽

2020 ◽

Vol 122 ◽

pp. 109356 ◽

Cited By ~ 4

Author(s):

Vaidas Klimkevicius ◽

Medeina Steponaviciute ◽

Ricardas Makuska

Keyword(s):

Size Exclusion Chromatography ◽

Raft Polymerization ◽

Size Exclusion ◽

Vinyl Monomers ◽

Exclusion Chromatography ◽

Kinetics Of

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Gas transfer under breaking waves: experiments and an improved vorticity-based model

Annales Geophysicae ◽

10.5194/angeo-26-2131-2008 ◽

2008 ◽

Vol 26 (8) ◽

pp. 2131-2142 ◽

Cited By ~ 1

Author(s):

V. K. Tsoukala ◽

C. I. Moutzouris

Keyword(s):

Experimental Data ◽

Oxygen Transfer ◽

Large Scale ◽

Breaking Waves ◽

Small Scale ◽

Gas Transfer ◽

Transfer Coefficients ◽

Wave Flume ◽

Proposed Model ◽

Sloping Beach

Abstract. In the present paper a modified vorticity-based model for gas transfer under breaking waves in the absence of significant wind forcing is presented. A theoretically valid and practically applicable mathematical expression is suggested for the assessment of the oxygen transfer coefficient in the area of wave-breaking. The proposed model is based on the theory of surface renewal that expresses the oxygen transfer coefficient as a function of both the wave vorticity and the Reynolds wave number for breaking waves. Experimental data were collected in wave flumes of various scales: a) small-scale experiments were carried out using both a sloping beach and a rubble-mound breakwater in the wave flume of the Laboratory of Harbor Works, NTUA, Greece; b) large-scale experiments were carried out with a sloping beach in the wind-wave flume of Delft Hydraulics, the Netherlands, and with a three-layer rubble mound breakwater in the Schneideberg Wave Flume of the Franzius Institute, University of Hannover, Germany. The experimental data acquired from both the small- and large-scale experiments were in good agreement with the proposed model. Although the apparent transfer coefficients from the large-scale experiments were lower than those determined from the small-scale experiments, the actual oxygen transfer coefficients, as calculated using a discretized form of the transport equation, are in the same order of magnitude for both the small- and large-scale experiments. The validity of the proposed model is compared to experimental results from other researchers. Although the results are encouraging, additional research is needed, to incorporate the influence of bubble mediated gas exchange, before these results are used for an environmental friendly design of harbor works, or for projects involving waste disposal at sea.

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Unsteady aerodynamic analysis for offshore floating wind turbines under different wind conditions

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2014.0080 ◽

2015 ◽

Vol 373 (2035) ◽

pp. 20140080 ◽

Cited By ~ 18

Author(s):

B. F. Xu ◽

T. G. Wang ◽

Y. Yuan ◽

J. F. Cao

Keyword(s):

Experimental Data ◽

Wind Turbine ◽

Wind Turbines ◽

Large Scale ◽

Aerodynamic Performance ◽

Small Scale ◽

Floating Platform ◽

Unsteady Aerodynamic ◽

Blade Root ◽

Platform Motions

A free-vortex wake (FVW) model is developed in this paper to analyse the unsteady aerodynamic performance of offshore floating wind turbines. A time-marching algorithm of third-order accuracy is applied in the FVW model. Owing to the complex floating platform motions, the blade inflow conditions and the positions of initial points of vortex filaments, which are different from the fixed wind turbine, are modified in the implemented model. A three-dimensional rotational effect model and a dynamic stall model are coupled into the FVW model to improve the aerodynamic performance prediction in the unsteady conditions. The effects of floating platform motions in the simulation model are validated by comparison between calculation and experiment for a small-scale rigid test wind turbine coupled with a floating tension leg platform (TLP). The dynamic inflow effect carried by the FVW method itself is confirmed and the results agree well with the experimental data of a pitching transient on another test turbine. Also, the flapping moment at the blade root in yaw on the same test turbine is calculated and compares well with the experimental data. Then, the aerodynamic performance is simulated in a yawed condition of steady wind and in an unyawed condition of turbulent wind, respectively, for a large-scale wind turbine coupled with the floating TLP motions, demonstrating obvious differences in rotor performance and blade loading from the fixed wind turbine. The non-dimensional magnitudes of loading changes due to the floating platform motions decrease from the blade root to the blade tip.

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