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Experimental Curves (experimental + curve)

Distribution by Scientific Domains

Chemistry	50%
Polymers and Materials Science	33%

Selected Abstracts

Separation of mono- and dibranched hydrocarbons on silicalite

AICHE JOURNAL, Issue 9 2002
E. Jolimaitre
Breakthrough curves for mixtures of C5 and C6 hydrocarbons with different degrees of branching were obtained experimentally on a silicalite molecular sieve by fixed-bed experiments. The kinetic separation of di- from monobranched hydrocarbons was feasible on this type of zeolite: dimethyl molecules enter silicalite crystals very slowly, whereas monomethyl molecules are quickly adsorbed. Experimental results were compared to a theoretical isothermal model, considering the variation of diffusivity with concentration according to the Maxwell,Stefan theory. The parameters of the model (adsorption equilibria and diffusivities) were determined from single-component breakthrough curves. Experimental curves were generally well represented by the model, but the variation of diffusivity with concentration, as predicted by the Maxwell,Stefan theory, did not significantly improve the model prediction of experimental breakthrough curves by using a mean value of diffusivity. [source]

Kinetics and mechanism of the hydrolytic disproportionation of iodine

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 11 2004
Krisztina Seb, k-Nagy
Kinetics of the hydrolytic disproportionation of I2 was studied by UV,VIS spectrophotometry at 298 K and at the ionic strength 0.2 M (NaClO4) in buffered solutions in the pH range 8.91,10.50 at different initial iodide concentrations. The characterization of this reaction is fundamental for modeling oscillatory and front reactions in the presence of iodine as reactant or intermediate as well as for drinking water treatment. A matrix rank analysis confirmed three absorbing species in the beginning of the reaction, whereas later assumption of two species is enough to describe the experimental data in the visible part of the spectrum. A reaction mechanism was proposed for disproportionation by using fitting/simulation with a multipurpose program package ZiTa, by simultaneous evaluation of 17,906 points in 79 experimental curves. A parameter set was suggested, which was obtained by absolute, relative, and orthogonal fittings of the experimental data. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 596,602, 2004 [source]

MATHEMATICAL MODEL FOR THE SURVIVAL OF LISTERIA MONOCYTOGENES IN MEXICAN-STYLE SAUSAGE

JOURNAL OF FOOD SAFETY, Issue 4 2005
M.N. HAJMEER
ABSTRACT Survival of Listeria monocytogenes in chorizos (Mexican-style sausages) was modeled in relation to initial water activity (aw0) and storage conditions using the Weibull cumulative distribution function. Twenty survival curves were generated from chorizos formulated at aw0 = 0.85,0.97 then stored under four temperature (T) and air inflow velocity (F) conditions. The Weibull model parameters (, and ,) were determined for every curve. Predicted survival curves agreed with experimental curves with R2 = 0.945,0.992. Regression models (R2 = 0.981,0.984) were developed to relate , and , to operating conditions. The times to one- and two-log reduction in count (t1D and t2D) were derived from the Weibull model in terms of , and ,. A parametric study revealed that L. monocytogenes survival was most sensitive to aw0 between 0.90 and 0.95. The inactivation of L. monocytogenes could be maximized with higher T and lower aw0; however, F did not significantly influence survival. [source]

Dielectric modeling of transmittance and ellipsometric spectra of thin In2O3:Sn films

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2010
Zhaohui Qiao
Abstract Thin ITO films with thickness between 0.05 and 0.4,µm were deposited on quartz substrates by direct-current magnetron-sputtering. The films' ellipsometric and transmittance spectra between 280 and 2500,nm were simulated simultaneously with a computer program based on dielectric modeling. The dielectric function used is the sum of three types of electronic excitations: intraband transitions of free electrons (extended Drude model), band gap transitions, and interband transitions into the upper half of the conduction band. A successful fit of the simulated to the experimental curves was obtained with a two-layer model (bulk and surface layers) and applying the Bruggeman effective-medium approach. From the simulation, film thickness, refractive index, band gap, and free carrier density can be obtained. The thickness of the surface layer is comparable with the surface roughness determined by AFM measurements. [source]

Tensile creep of a long-fibre glass mat thermoplastic (GMT) composite.

POLYMER COMPOSITES, Issue 9 2009

In Part I of this article, the short-term tensile creep of a 3-mm-thick continuous long-fibre glass mat thermoplastic composite was characterized and found to be linear viscoelastic up to 20 MPa. Subsequently, a nonlinear viscoelastic model has been developed for stresses up to 60 MPa for relatively short creep durations. The creep response was also compared with the same composite material having twice the thickness for a lower stress range. Here in Part II, the work has been extended to characterize and model longer term creep and recovery in the 3-mm composite for stresses up to near failure. Long-term creep tests consisting of 1-day loading followed by recovery were carried out in the nonlinear viscoelastic stress range of the material, i.e., 20,80 MPa in increments of 10 MPa. The material exhibited tertiary creep at 80 MPa and hence data up-to 70 MPa has been used for model development. It was found that viscoplastic strains of about 10% of the instantaneous strains were developed under load. Hence, a non-linear viscoelastic,viscoplastic constitutive model has been developed to represent the considerable plastic strains for the long-term tests. Findley's model which is the reduced form of the Schapery non-linear viscoelastic model was found to be sufficient to model the viscoelastic behavior. The viscoplastic strains were modeled using the Zapas and Crissman viscoplastic model. A parameter estimation method which isolates the viscoelastic component from the viscoplastic part of the nonlinear model has been developed. The model predictions were found to be in good agreement with the average experimental curves. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source]

Kinetic analysis of thermo-oxidative degradation of PEEK/thermotropic liquid crystalline polymer blends

POLYMER ENGINEERING & SCIENCE, Issue 2 2006
M. Naffakh
The thermal degradation behavior of blends of poly(aryl ether ether ketone), PEEK, with a thermotropic liquid crystalline polymer (TLCP), Vectra®, were investigated in an oxidative atmosphere, using thermogravimetric analysis under dynamic conditions. The theoretical weight loss curves of the blends were compared with the experimental curves in order to explain the effect of blending on the thermal stability of the pure polymers. The thermo-oxidative degradation of PEEK/Vectra® blends of different compositions takes place in various steps and the characteristic degradation temperatures and the kinetic parameters such as activation energy are strongly influenced by blending. Polymer blends based on this TLCP polymer had not been previously studied from kinetic viewpoint. POLYM. ENG. SCI. 46:129,138, 2006. © 2005 Society of Plastics Engineers [source]