Effect of maleic anhydride and liquid natural rubber as compatibilizers on the mechanical properties and impact resistance of the NR‐NBR blend

The degree of compatibilization between natural rubber (NR) and acrylonitrile‐butadiene rubber (NBR) was investigated by two different methods. NBR was chemically modified with maleic anhydride in a screw twin mixer with and without reaction initiator, benzoyl peroxide. Also, the effects of molecular weight of liquid natural rubber (LNR) as a compatibilizer were studied. The degree of compatibilization between NBR and NR is determined indirectly through measurements of mechanical properties and impact resistance. The maleic anhydride and benzoyl peroxide concentrations influence the mechanical properties and impact resistance of the blends. Also, the mechanical properties of the blends showed that the molecular weight of LNR played an important role in determing their performance. Copyright © 2004 John Wiley & Sons, Ltd.     

Effect of the Formation of Inclusion Complexes With β-Cyclodextrin on the Photoisomerization and Fluorescence Properties of Aromatic Norbornadiene Derivatives

The valence photoisomerization of four aromatic norbornadiene (NBD)derivatives has been studied in ethanol and in 0.01 M -cyclodextrin(-CD) water–ethanol (v/v, 99/1) solution (WECD). Observedfirst-order rate constants are found to be of the same order of magnitude inethanol and WECD, ranging between 0.1 and 0.28 s^-1, accordingto the compound. These photoisomerization kinetic properties are attributedto the formation of inclusion complexes between NBDs and -CD. Thestoichiometry is 1 : 1, and association constants ranging between 310 and390 M^-1 have been determined fluorimetrically, usingBenesi–Hildebrand plots and a nonlinear regression method. Thestructure of the inclusion complexes is discussed on the basis of AMIsemiempirical dimension calculations and photophysical properties.     

Synthesis of Spiro and Fused Five Membered N-Heterocycles from Alkylidenephosphoranes

Triketoindan-2-oxime reacted readily with ethoxycarbonylmethylene triphenylphosphorane to give mainly the corresponding spiro-pyrrole (38%) along with the fused 1-hydroxydihydropyrrole (14%), whereas the spiro-dimer (29%) was obtained from the reaction of the oxime with methoxycarbonylmethylenetriphenyl phosphorane in addition to the corresponding 1-hydroxydihydropyrrole (31%). Conversely, Wittig products, mono-olefin (52%) and diolefin (<7%) along with the reduced substrate (10%), were observed when the oxime was treated with a cyano ylide. The reactions of the oxime with allyl- and vinyl phosphonium salts proceeded under phase-transfer catalysis to afford fused oxazole (46%) and spiro[2]oxazole (17%), while with the latter the fused 1-hydroxypyrrole (55%) was produced.     

A New Method for the Estimation of Mass Functions in?the?Dempster�CShafer��s Evidence Theory: Application to Colour Image Segmentation

In this paper, the problem of colour image segmentation is addressed using the Dempster–Shafer (DS) theory. Examples are provided showing that this theory is able to take into account a large variety of special situations that occur and which are not well solved using classical approaches. Modelling both uncertainty and imprecision, and computing the conflict between images and introducing a priori information are the main features of this theory. Consequently, the performance of such a segmentation scheme is largely conditioned by the appropriate estimation of mass functions in the DS evidence theory. In this paper, a new method of automatically determining the mass function for colour-image segmentation problems is presented. The mass function of each pixel is determined by applying possibilistic c-means (PCM) clustering to the grey levels of the three primitive colours. A reliability criterion, associated with each pixel and the mass functions of its neighbouring pixels, is used into a fuzzy based reasoning system in order to decide on the appropriate segmentation. Experimental segmentation results on medical and textured colour images highlight the effectiveness of the proposed method.     

An interior-proximal method for convex linearly constrained problems and its extension to variational inequalities

In this paper, an entropy-like proximal method for the minimization of a convex function subject to positivity constraints is extended to an interior algorithm in two directions. First, to general linearly constrained convex minimization problems and second, to variational inequalities on polyhedra. For linear programming, numerical results are presented and quadratic convergence is established.Corresponding author. His research has been supported by C.E.E grants: CI1* CT 92-0046.     

Impact dynamics of surfactant laden drops: dynamic surface tension effects

We study the impact and subsequent retraction of aqueous surfactant-laden drops upon high-speed impact on hydrophobic surfaces. Without surfactants, a rapid expansion of the drop due to the fluid inertia is followed by a rapid retraction, due to the wetting incompatibility. With surfactants, the retraction can be partly or completely inhibited. We provide quantitative measurements showing that both the expansion and the retraction dynamics depend not only on the equilibrium surface tension (ST) but also on the dynamic tension of the surfactant solutions; the latter varies significantly between different surfactants.     

Improvement in energy conversion of electrostrictive composite materials by new approach via piezoelectric effect: Modeling and experiments

This study proposes a new model that couples the piezoelectric and electrostrictive behavior to minimize the polarization power of composite polymer. The development of this model is capable to predict the energy harvesting abilities of an electrostrictive composite. To improve the dielectric permittivity of electrostrictive polymer, the particles of PZT have been incorporated in order to increase the conversion efficiency of the composite. Dielectric characterization tests showed an increase in dielectric permittivity by a factor of 4.5 compared to pure polymer. Experimental measurements of harvested power validate the analytical model and demonstrate a good correlation between the two data. An equivalent of an electrical scheme has been developed, which allows modeling the two behaviors. The harvested power density under low frequency at 2% of strain can reach 0.30 μW/cm³ for 33% of PZT without the polarization field, including the conversion efficiency becomes higher. The energy harvester property of this material composite has excellent potential for several self‐powered applications such as wireless sensor networks and the internet of things.