Effects of unequal reactivity of functional groups on gelation phenomena in polyurethane systems

A model to describe the effect of unequal reactivity on curing of a diisocyanate with water, polyol and a diol was developed. The model predicts whether a given initial composition would gel or not and the fractional conversions of functional groups at the gel point. It has been shown that the relative speeds of reaction of water and hydroxyl groups can be used to classify water's behaviour as that of a (i) nonreactive diluent (ii) monofunctional blocking agent and (iii) chain extender capable of connecting branch points.     

Une méthode d’optimisation discrète pour les filtres cascade à capacités commutées

A discrete optimization method using a noninteraction property between the different sections of cascade switched-capacitor filter is described. The optimization, realized with a reduced set of intermediate parameters caracterizing each section, yields to a non minimum capacitive area structure, but which has very accurate capacitor ratios and which could be realized with minimum unit capacitors. This method may be applied to switched-current filters (aspect ratios of transistor discretization). An eighth order band-pass Cauer filter and a fifth order low-pass Cauer filter show the effectiveness of this method.     

Regression-based weight generation algorithm in neural network for solution of initial and boundary value problems

This paper introduces a new algorithm for solving ordinary differential equations (ODEs) with initial or boundary conditions. In our proposed method, the trial solution of differential equation has been used in the regression-based neural network (RBNN) model for single input and single output system. The artificial neural network (ANN) trial solution of ODE is written as sum of two terms, first one satisfies initial/boundary conditions and contains no adjustable parameters. The second part involves a RBNN model containing adjustable parameters. Network has been trained using the initial weights generated by the coefficients of regression fitting. We have used feed-forward neural network and error back propagation algorithm for minimizing error function. Proposed model has been tested for first, second and fourth-order ODEs. We also compare the results of proposed algorithm with the traditional ANN algorithm. The idea may very well be extended to other complicated differential equations.     

A study of global vs. local properties for maleic anhydride modified polypropylene nanocomposites

Nanoindentation of organomodified clay filled maleated polypropylene (MAPP) was investigated. The study aims to identify the relative increase in local stiffness in comparison to the increase in mechanical properties of the bulk in polypropylene-based nanocomposites. Such a study allows one to assess confined material property in addition to increased filler volume at the local scale. A mixture of highly intercalated and well exfoliated clay structures, when dispersed in MAPP matrix, was observed under transmission electron microscopy. The degree of exfoliation was found to increase with clay loading, which was attributed to the higher viscosity and mechanical shear forces during melt compounding. Instrumented indentation was performed on (1) clay aggregate supported by MAPP matrix, (2) clay-matrix boundary, and (3) the MAPP matrix. The clay aggregated region generally showed higher stiffness as compared to the matrix. And, the relative increase in indentation stiffness is substantially higher than the relative increase in tensile and compressive stiffnesses for clay reinforced systems. Polymer chain confinement and topological constraint appeared to be operative to enhance local stiffness in the clay aggregated region. Good correlation was, however, obtained between the change in macroscopic stiffness and the change in highly local indentation stiffness as a result of clay reinforcement.     

Identification of leek-moth and diamondback-moth frass volatiles that stimulate parasitoid,Diadromus pulchellus

Acrolepiopsis assectella andPlutella xylostella frass volatiles, trapped on Tenax GC, were examined by capillary gas chromatography. In both moths, the same three disulfides, dimethyl, dipropyl, and methyl propyl, were the most abundant substances, but in different proportions. The synthetic disulfides elicited the same behavioral response by the parasitoid,Diadromus pulchellus as frass. The plant origin of these substances is discussed.     

Solving singular control problems using uniform trigonometrization method

This study investigates the application of a recently developed construct, the uniform trigonometrization method (UTM), to the singular control problems in chemical engineering. The UTM involves minimal modifications to the original problem, thereby generating near-singular control solutions that can be used for conceptual design and serve as an alternate to direct techniques like nested and simultaneous approaches. Eight classical singular control problems with known analytical solutions and three complex singular control problems from chemical engineering domain are solved in this study. The results obtained using the UTM for these problems are found to match well with the literature and are of higher resolution as compared to the results obtained using a direct pseudospectral-based solver. The ability of the UTM to handle complex chemical engineering problems with both singular controls and state path constraints has also been demonstrated in this study.     

Developing Faculty ICT Competencies Inside and Outside the Library

Despite all the financial resources that are directed to support and acquire learning technologies, the results have been generally disappointing. Faculty are eager to use technology but lack the technical skills, ability, and experience. Library staff includes a talent tool rich in Information and Communication Technologies (ICT)/WEB 2.0 technical expertise and experience. In terms of content sourcing and procurement, library technical services and selection staff have broad knowledge of the marketplace for online information and content as well as experience in licensing access. They have a firm grasp of the transaction process, workflows, pricing, and licensing negotiations. Content development and sourcing inevitably involves access management, online storage, copyright, and licensing—things at which libraries are good. ICT deployment is changing teaching and learning on campuses, and the roles of those involved in teaching and learning are also changing. Whether formally through mandated library services, or informally through back channels, library staff are supporting faculty new technology use as well as faculty teaching materials content sourcing and procurement.     

Kernel methods for software effort estimation

Analogy based estimation (ABE) generates an effort estimate for a new software project through adaptation of similar past projects (a.k.a. analogies). Majority of ABE methods follow uniform weighting in adaptation procedure. In this research we investigated non-uniform weighting through kernel density estimation. After an extensive experimentation of 19 datasets, 3 evaluation criteria, 5 kernels, 5 bandwidth values and a total of 2090 ABE variants, we found that: (1) non-uniform weighting through kernel methods cannot outperform uniform weighting ABE and (2) kernel type and bandwidth parameters do not produce a definite effect on estimation performance. In summary simple ABE approaches are able to perform better than much more complex approaches. Hence,—provided that similar experimental settings are adopted—we discourage the use of kernel methods as a weighting strategy in ABE.