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Three-parameter Model (three-parameter + model)

Distribution by Scientific Domains

Chemistry	60%

Selected Abstracts

VISCOELASTICITY OF A SIMULATED POLYMER AND COMPARISON WITH CHICKPEA FLOUR DOUGHS

JOURNAL OF FOOD PROCESS ENGINEERING, Issue 3 2006
NIDHI YADAV
ABSTRACT An integrated approach consisting of compression and stress relaxation is performed with a simulated model system of poly dimethyl siloxane (PDMS), a viscoelastic polymer material when the compressive strain, height of sample and crosshead speed were varied. The parameters derived are the forces at the end of compression and relaxation, energy for compression and the extent of elasticity of the sample based on the ratios of forces as well as the proposed energy values. The results were verified with food doughs undergoing large deformations that show a nonlinear behavior. The proposed extent of elasticity based on the ratios of energy stored and compression can be used as an index for the characterization of viscoelasticity. A nonlinear three-parameter model had also been proposed to predict the stress decay characteristics as a function of time, which was found suitable for the PDMS system, and was better than the two-parameter Peleg model as judged by lower variance values (0.0006,0.018 and 0.002,0.048, respectively). Further, an actual system of food doughs in the form of chickpea (Cicer arietinum L.) flour dough was used to verify the proposed model and viscoelastic index at different moisture contents (27,39%) subjected to compressive strains of 25,75%. The nonlinear relaxation characteristics of the food dough are sensitive to moisture content as well as to strain level. [source]

Linearized transport model for nanofiltration: Development and assessment

AICHE JOURNAL, Issue 4 2002
W. Richard Bowen
Finite difference linearization of pore concentration gradient in nanofiltration membranes greatly simplifies the solution of a three-parameter model (pore radius, membrane charge, and pore dielectric constant) for electrolyte rejection by removing the requirement for numerical integration of the extended Nernst,Planck equation. The validity of the linearized model is first experimentally tested by comparing with a rigorous characterization of the Desal-DK nanofiltration membrane, the linearized model closely agreeing with the numerical solution of the full model. Investigation of pore concentration profiles showed the assumption of linearity to be valid over a wide range of nanofiltration conditions. The linearized model was also successfully extended to ternary electrolyte mixtures, highlighting its main advantage over analytic solutions. Overall, the model is a powerful tool for characterization of nanofiltration membranes and subsequent prediction of separation performance. Computational demands are modest in terms of time and complexity. [source]

QSAR modeling of photosynthesis-inhibiting nostoclide derivatives

PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 2 2010
Róbson Ricardo Teixeira
Abstract BACKGROUND: A statistical model, built using the CODESSA software package, was developed to describe the relationship between the structure of nostoclide derivatives and their ability to interfere with the electron transport chain in the Hill reaction. RESULTS: A QSAR treatment was carried out on a series of compounds designed using the naturally occurring toxin nostoclides to correlate molecular descriptors with their in vitro biological activity (the ability to interfere with light-driven reduction of ferricyanide by isolated spinach chloroplast thylakoid membranes). The treatment using the CODESSA software package resulted in a three-parameter model with n = 19, R2 = 0.83, F = 23.8 and R2cv = 0.72. In the proposed model, the Image of Onsager Kirkwood solvation energy, which gives a measure of the polarity of a given compound, is the most important descriptor. The model was internally validated. CONCLUSIONS: The results obtained in this study indicate that polarity, as expressed by the dipole moment, is the most relevant molecular property determining efficiency of photosynthetic inhibitory activity. Copyright © 2009 Society of Chemical Industry [source]

Who Is Mobilized to Vote?

AMERICAN JOURNAL OF POLITICAL SCIENCE, Issue 1 2009
A Re-Analysis of 11 Field Experiments
Many political observers view get-out-the-vote (GOTV) mobilization drives as a way to increase turnout among chronic nonvoters. However, such a strategy assumes that GOTV efforts are effective at increasing turnout in this population, and the extant research offers contradictory evidence regarding the empirical validity of this assumption. We propose a model where only those citizens whose propensity to vote is near the indifference threshold are mobilized to vote and the threshold is determined by the general interest in the election. Our three-parameter model reconciles prior inconsistent empirical results and argues that low-propensity voters can be effectively mobilized only in high-turnout elections. The model is tested on 11 randomized face-to-face voter mobilization field experiments in which we specifically analyze whether subjects' baseline propensity to vote conditions the effectiveness of door-to-door GOTV canvassing. The evidence is consistent with the model and suggests that face-to-face mobilization is better at stimulating turnout among low-propensity voters in prominent elections than it is in quiescent ones. [source]

Horizontal resolution impact on short- and long-range forecast error

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 649 2010
Roberto Buizza
Abstract The impact of horizontal resolution increases from spectral truncation T95 to T799 on the error growth of ECMWF forecasts is analysed. Attention is focused on instantaneous, synoptic-scale features represented by the 500 and 1000 hPa geopotential height and the 850 hPa temperature. Error growth is investigated by applying a three-parameter model, and improvements in forecast skill are assessed by computing the time limits when fractions of the forecast-error asymptotic value are reached. Forecasts are assessed both in a realistic framework against T799 analyses, and in a perfect-model framework against T799 forecasts. A strong sensitivity to model resolution of the skill of instantaneous forecasts has been found in the short forecast range (say up to about forecast day 3). But sensitivity has shown to become weaker in the medium range (say around forecast day 7) and undetectable in the long forecast range. Considering the predictability of ECMWF operational, high-resolution T799 forecasts of the 500 hPa geopotential height verified in the realistic framework over the Northern Hemisphere (NH), the long-range time limit ,(95%) is 15.2 days, a value that is one day shorter than the limit computed in the perfect-model framework. Considering the 850 hPa temperature verified in the realistic framework, the time limit ,(95%) is 16.6 days for forecasts verified in the realistic framework over the NH (cold season), 14.1 days over the SH (warm season) and 20.6 days over the Tropics. Although past resolution increases have been providing continuously better forecasts especially in the short forecast range, this investigation suggests that in the future, although further increases in resolution are expected to improve the forecast skill in the short and medium forecast range, simple resolution increases without model improvements would bring only very limited improvements in the long forecast range. Copyright © 2010 Royal Meteorological Society [source]