Rheological models comparison

Interesting ice samples from Antarctica and Greenland have been and are being recovered. We studied samples of the Byrd core, which is a 12-cm-diameter core that extended to bedrock at 2100-m depth [1]. This core is presently kept at the Central Ice Core Storage Facility at S.U.N.Y. Buffalo (C. C. Langway, Jr., Curator). Its age-depth relationship has been calculated on the basis of rheological models [3,4,5], and comparisons of the 6180 variations of the core with those in the Camp Century (Greenland) core. The age calculated for the bottom ice is between 50 x 103 and 100 x 103 years. 

Figures 2-4 show that no experimental data were recorded at low impeller shear rates. Experimental data began at y = 8.53 s4 for 21% solids, 5.15 s 1 for 23% solids, and 3.43 s 1 for 25% solids. The reason for the missing data is that the helical impeller viscometer has limitations. Owing to possible viscometer error, data were not recorded until the impeller torque was >10% of the full-scale torque. Therefore, no experimental data were recorded at low impeller rotational speeds. The lack of experimental data at low shear rates made comparison of rheologic models at low shear rates and the prediction of yield stress impossible.

Figure 2 7. Comparison of fit of power law, Bingham plastic and Robertson-Stiff rheological models to experimental data from bentonite drilling fluid. (Data from reference 106.)...

D. Quemada, Rheology of concentrated disperse systems. III. General features of the proposed non-Newtonian model. Comparison with experimental data, Rheol. Acta 17 (1978) 643-653. 

Kairn, T., Daivis, P. J., Ivanov, I., and Bhattacharya, S. N., Molecular-dynamics simulation of model polymer nanocomposite rheology and comparison with experiment, J. Chem. Phys., 123, 194905-1 (2005). 

FIGURE 4 Comparison of rheological model of Eqs. (47)-(49) with experiment for natural rubber, (a) Steady-state shear viscosity, (b) Transient shear viscosity at beginning of flow, (c) Stress, relaxation following now. 

Rheology is a branch of physics concerned with the time-dependent deformation of solids and the viscous flow of liquids. Rheological models can be used to illustrate the nonlinear viscoelastic response of rPET polymer concrete. These models are mechanical comparisons that demonstrate the interrelationship between the elastic and viscous response of polymers. Simple and complex models can be proposed to... 

A transient numerical analysis has been carried out of the EHL shut-down conditions examined experimentally by Glovnea and Spikes [1]. The main features of the experimental measurements are reproduced in the numerical results obtained. There are differences observed in the detailed comparison of film thickness profiles. These may be the result of the particular form of non-Newtonian rheological model adopted for the numerical analysis. If so, such comparisons may be a means of distinguishing between such models within an EHL contact. 

A comparison between the Eg values listed in tables I and II with theoretical Gg values is not possible at present, since for calculation of Gg one needs to know the polymer-solvent interaction parameter as a function of Na2S04 concentration. Moreover, an assumption must be made about the segment distribution of the adsorbed layer. In the absence of such information, it is not possible to calculate Gg. However, the values of Eg obtained from rheology (tables I and II) are reasonable, considering the approximation made and the crude model used for calculating Es. 

Alvarez, M. D., Canet, W. (2002). A comparison of various rheological properties for modelling the kinetics of thermal softening of potato tissue (cv. Monalisa) by water cooking and pressure steaming. Int. J. Food Sci. Technol., 37, 41-55. 

Structures 13C, 2H and 2H NMR spectroscopy (T2 relaxation times, signal intensity ratio versus generation) rheology studies electron microscopy computer-assisted molecular simulations, comparison to CPK models electrospray mass spectroscopy fluorescence probe analysis. 

Two-fluid simulations have also been performed to predict void profiles (Kuipers et al, 1992b) and local wall-to-bed heat transfer coefficients in gas fluidized beds (Kuipers et al., 1992c). In Fig. 18 a comparison is shown between experimental (a) and theoretical (b) time-averaged porosity distributions obtained for a 2D air fluidized bed with a central jet (air injection velocity through the orifice 10.0 m/s which corresponds to 40u ). The experimental porosity distributions were obtained with the aid of a nonintrusive light transmission technique where the principles of liquid-solid fluidization and vibrofluidization were employed to perform the necessary calibration. The principal differences between theory and experiment can be attributed to the simplified solids rheology assumed in the hydrodynamic model and to asymmetries present in the experiment. 

To allow a comparison with rheological and SANS data, the stress and scattering intensity have been calculated for the Rouse model as a function of time and strain rate for simple elcngational flow. L being the chain length, the n normal mode is given by [1] ... 

A first comparison between the model and our rheological data for sample SI shows that... 

Part 2 presents a summary of the theoretical considerations and basic assumptions that lead to the model equations. Part 3 discusses some experimental aspects and focuses on the measmements in various shear and uniaxial elongational flow situations. Part 4 and 5 are devoted to the comparisons between experimental and predicted rheological functions. Problems encountered in the choice of correct sets of parameters or related to the use of each type of equation will be discussed in view of discrepancies between model and data. 

Poly(methylmethacrylate), PMMA, latex particles have also served as a model colloidal system for many years (mainly as hard spheres with hydroxy stearic acid (HSA) chains being the grafting choice [91,113,114]). Tunability was achieved by varying the core size and the size of the corona chains. The comparison between chemically grafted (stable) and end-adsorbed temperature-sensitive chains (usually surfactants) has shown that the adsorbed chain particles exhibit similar rheological behavior with chemically grafted particles [115]. 

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