Fluorinated acrylic polymers: Surface properties and XPS investigations

A series of polymers based on methylmethacrylate, butylacrylate, and ω‐perfluorooctylalkylacrylate were prepared by radical polymerization. By changing both the length of the hydrocarbon spacer, between the fluorinated chain and the ester function of the fluorinated monomer, and its concentration, the surface properties of the resulting terpolymers were greatly influenced. Polymers containing small amounts of fluorinated comonomer units had considerably reduced surface energies compared to the copolymer poly (methylmethacrylate‐co‐butylacrylate) taken as reference. The outermost surface composition has been investigated by the XPS technique, confirming the strong fluorine enrichment. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 821–827, 2006     

A grammar approach for combining product configuration modelling with behavioural aspects and simulations

The effective modelling of configurable products must handle the complex problem of representation of the configurable products, learning new configurable products and analysis of their behaviour. However, currently in advanced CAD systems, there exists no systematic and effective method for designing configurations and integrating behavioural aspects and simulations. This paper proposes and develops a grammar-based design approach to support both the computer-aided design for configuration and computing in CAD systems. Two interrelated questions are taken into account: (1) What are the hypothesis, properties and features for product configuration? (2) How can the product based on configuration features be represented and how can the configuration representation method integrate the numerical computing in design? This approach, under the guide of the proposed formal modelling, is implemented in computers. A design case study illustrates the proposed approach.     

Synergistic effect of organoclay fillers based on fluorinated surfmers for preparation of polystyrene nanocomposites

Novel fluorinated reactive surfactants were used for the organic modification of monmorillonite clays. These organoclays were used for the preparation of polystyrene?clay nanocomposites by in‐situ free radical polymerization. Reference systems based on hydrocarbon homologous surfmer and nonpolymerizable surfactants were also used to deduce the effect of the fluorine moiety and the polymerizable function on the morphology and thermal stability of the prepared nanocomposites. Different structural parameters of the surfactants were investigated and modulated for the clay modification including: the nature of surfactant (surfmer/classical surfactant, fluorinated, or hydrocarbonated), the length of the fluorinated chain as well as the length of the hydrocarbon spacers linking the ammonium head to the fluorine chain or the polymerizable acrylic function. Wide angle‐X‐ray scattering (WAXD), thermogravimetric analysis (TGA), and electronic microcopies (TEM and SEM) were used to establish a structure‐morphology, thermal properties relationships, and to highlight the key parameters governing the exfoliation process. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42347.     

Handwritten characters recognition based on nature-inspired computing and neuro-evolution

The enormous services obtainable by bank and postal systems are not 100 % guaranteed due to variability of handwriting styles. Various methods based on neural networks have been suggested to address this issue. Unfortunately, they often fall into local optima that arises from the use of old learning methods. Global optimization methods provided new directions for neural networks evolution that may be useful in recognition. This paper develops efficient algorithms that compute globally optimal solutions by exploiting the benefits of both swarm intelligence and neuro-evolution in a way to improve the overall performance of a character recognition system. Various adaptations implied to both MLP and RBF networks have been suggested namely: particle swarm optimization (PSO) and the bees algorithm (BA) for characters classification, MLP training or RBF design by co-evolution and effective combinations of MLPs, RBFs or SVMs as an attempt to overcome the drawbacks of old recognition methods. Results proved that networks combination proposals ensure the highest improvement compared to either standard MLP and RBF networks, the co-evolutionary alternatives or other classifiers combination based on common combination rules namely majority voting, the fusion rules of min, max, sum, average, product and Bayes, Decision template and the Behavior Knowledge Space (BKS).     

High solids content emulsion polymerisation without intermediate seeds. Part I. Concentrated monomodal latices

In order to produce high solid content latexes in an unseeded process it is necessary to first begin by generating a concentrated latex with a monomodal particle size distribution and high solid contents. A process for the emulsion polymerisation of methyl methacrylate with butyl acrylate at solid contents of over 60% per unit volume is presented. The process relies on the use of an electrically neutral initiation system, combined with a stabilisation system rich in non-ionic surfactant. It was demonstrated that during the critical semi-batch growth stage, it is necessary to add the surfactant at a variable flow rate in order to avoid accumulating it in the water phase, and thereby ensuring that particles created by homogeneous nucleation are not stabilised. It is also shown that correctly adjusting the flow rate leads to a robust, reproducible process. Finally, a ‘stability band’ is clearly identified, and it is clear that the system is ‘self-regulating’ in the sense that an equilibrium between auto-flocculation and stabilisation of new particles leads to a latex with a surface coverage of 80-95% at high solid contents.     

Improved Turbo Decoding Using Soft Combining Principle

One great challenge in wireless communication systems is to ensure reliable communications. Turbo codes are known by their interesting capabilities to deal with transmission errors. In this paper, we present a novel turbo decoding scheme based on soft combining principle. Our method improves decoding performance using soft combining technique inside the turbo decoder. Working on Max-Log-Maximum a Posteriori (Max-Log-MAP) turbo decoding algorithm and using an Additive White Gaussian Noise (AWGN) channel model and 16 Quadrature Amplitude Modulation (16QAM), simulation results show that the suggested solution is efficient and outperforms the conventional Max-Log-MAP algorithm in terms of Bit Error Rate (BER). The performance analysis is carried out in terms of BER by varying parameters such as the Energy per bit to Noise power spectral density ratio ( \(\text {E}_{\text {b}}/\text {N}_{\text {o}}\) ), and decoding iterations number. We call our proposed solution Soft Combined Turbo Codes.     

Micromechanical modeling of the work-hardening behavior of single- and dual-phase steels under two-stage loading paths

Work-hardening behavior of single-phase steel and dual-phase steel which is made of hard martensite surrounded by soft ferrite is analyzed by using an elastoplastic crystal plasticity model in conjunction with the incremental self-consistent model. Two-stage loading paths consisting of uniaxial tension, unloading and subsequent uniaxial tension/compression for various directions are applied. Bauschinger effect and transitional re-yielding behavior, which depends on the direction of the second loading path, are predicted and analyzed with respect to the distribution of the residual resolved shear stresses within the material. These features, which are caused by the inhomogeneity of the residual stress field, are especially pronounced in the case of the dual-phase steel because of the strong mechanical contrast between ferrite and martensite phases.     

Adsorption and surface complexation study of L-DOPA on Rutile (α-TiO₂) in NaCl solutions

Dihydroxyphenylalanine (DOPA) and similar molecules are of considerable interest in studies of bioadhesion to minerals, solar cells involving titanium dioxide, and biomedical imaging. However, the extent and mechanisms of DOPA adsorption on oxides in salt solutions are unknown. We report measurements of DOPA adsorption on well-characterized rutile (α-TiO?) particles over a range of pH, ionic strength, and surface coverage as well as a surface complexation model analysis establishing the stoichiometry, model surface speciation, and thermodynamic equilibrium constants, which permits predictions in more complex systems. DOPA forms two surface species on rutile, the proportions of which vary strongly with pH but weakly with ionic strength and surface loading. At pH < 4.5 a species involving four attachment points ("lying down") is important, whereas at pH > 4.5 a species involving only two attachment points via the phenolic oxygens ("standing up") predominates. Based on evidence of strong attachment of DOPA to titanium dioxide from single molecule AFM (Lee, H. et al., Proc. Natl. Acad. Sci.2006, 103, 12999-12003) and studies of catechol adsorption, one or more of the DOPA attachments for each species is inner-sphere, the others are likely to be H-bonds.     

Effect of mixed solvents on PCDTBT:PC70BM based solar cells

We investigated the effect of solvents on the morphology, charge transport and device performance of poly[N-9″-hepta-decanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) and [6,6]-phenyl C71-butyric acid methyl ester (PC₇₀BM) based solar cells. To carry out this investigation, chloroform and 1,2-dichlorobenzene were chosen as good solvents of the two compounds. Films prepared with chloroform exhibit larger domains than those prepared with 1,2-dichlorobenzene and their size increases with the amount of PC₇₀BM. Fine tuning of the domain size was realized by using a solvent of mixed chloroform and 1,2-dichlorobenzene. At a mixing ratio of 50%:50%, a power conversion efficiency of 6.1% was achieved on PCDTBT:PC₇₀BM (1:3) devices with an active area of 1 cm², under air mass 1.5 global (AM 1.5 G) irradiation at 100 mW/cm².     

Removal of cyanide in aqueous solution by oxidation with hydrogen peroxide in presence of copper-impregnated activated carbon

This work is devoted to the removal of free cyanide from aqueous solution by oxidation with hydrogen peroxide H₂O₂ catalyzed by copper-impregnated activated carbon. Effects of initial molar ratio [H₂O₂]₀/[CN⁻]₀, copper-impregnated activated carbon amount, pH and the temperature on cyanide removal have been investigated.The presence of copper-impregnated activated carbon has increased the reaction rate showing thus a catalytic activity. The rate of cyanides removal increases with the raise of the initial molar ratio [H₂O₂]₀/[CN⁻]0 and decreases with the increase in the pH from 8 to 12. The increase in the copper-impregnated activated carbon amount from 1.5 to 10 g/L in reaction solution has a beneficial effect. Beyond this value, the impact of activated carbon amount is not anymore significant. The temperature does not have a significant effect between 20 and 35 °C. The four successive times re-use of catalyst shows a good stability. The kinetics of cyanide removal has been found to be of pseudo-second-order with respect to cyanide and the rate constants have been determined. This process seems very interesting because the rate of cyanides removal is very fast, the reaction does not use soluble metal catalyst and it consumes only hydrogen peroxide as chemical product.