Morphology development in polyethylene/polystyrene blends: the influence of processing conditions and interfacial modification

The influence of processing conditions and interfacial modification on the morphology evolution and the composition range within which fully co‐continuous high density polyethylene/polystyrene blend structures can exist during blending in a single screw extruder was studied. Blends ranging from pure A to pure B component, with and without compatibilizer, were prepared under two different shear rates. It was found that high shear rates displaced the breakdown–coalescence balance of the dispersed nodules to the side of coalescence, narrowing the percolation domain and the critical composition for full co‐continuity decreased with increasing shear rates. The addition of a tri‐block compatibilizer induced the percolation threshold of the polystyrene phase to begin at lower percentages of polyethylene but the phase inversion point did not change. The experimental results are discussed in the light of various theoretical models. Copyright © 2005 Society of Chemical Industry     

A branch and bound algorithm for extracting smallest minimal unsatisfiable subformulas

Explaining the causes of infeasibility of Boolean formulas has practical applications in numerous fields, such as artificial intelligence (repairing inconsistent knowledge bases), formal verification (abstraction refinement and unbounded model checking), and electronic design (diagnosing and correcting infeasibility). Minimal unsatisfiable subformulas (MUSes) provide useful insights into the causes of infeasibility. An unsatisfiable formula often has many MUSes. Based on the application domain, however, MUSes with specific properties might be of interest. In this paper, we tackle the problem of finding a smallest-cardinality MUS (SMUS) of a given formula. An SMUS provides a succinct explanation of infeasibility and is valuable for applications that are heavily affected by the size of the explanation. We present (1) a baseline algorithm for finding an SMUS, founded on earlier work for finding all MUSes, and (2) a new branch-and-bound algorithm called Digger that computes a strong lower bound on the size of an SMUS and splits the problem into more tractable subformulas in a recursive search tree. Using two benchmark suites, we experimentally compare Digger to the baseline algorithm and to an existing incomplete genetic algorithm approach. Digger is shown to be faster in nearly all cases. It is also able to solve far more instances within a given runtime limit than either of the other approaches.     

A C5 parallel robot identification and control

The paper proposes a controller scheme based on a priori identification for a C5 parallel robot. First we realize the identification of dynamic parameters of the robot using the Least Squares technique. Different data are used for this step of identification. The cross validation permitted to select and confirm the identified parameters. After, a control scheme (computed torque) is applied to control the C5 parallel robot. The functions of this control scheme are based on precedent identified parameters. In order to reduce the effect of the identification error, we have added a robustness term based on sliding mode technique. The stability of the system in closed loop is presented using the Lyapunov principle. Experimental results of identification and control are presented and show the effectiveness of our methodology.     

A review on renewable energy conceptual perspectives in North Africa using a polynomial optimization scheme

In this review, general features of the renewable energy sources in the North African upper zone have been studied. The primal renewable sources of energy have been identified in Algeria, Morocco and Tunisia. Taking into account concordances and divergences of the different actors in the region, a polynomial optimization scheme has been performed in order to predict future potentials and perspectives.     

Preliminary evaluation of biogenic amines content in Chilean young varietal wines by HPLC

Biogenic amines are organic nitrogenous compounds produced in wines mainly during malolactic fermentation. Its presence is a health risk for sensitive individuals and it could negatively affect the wine quality. The objective of this work was to determine the biogenic amines content in Chilean young varietal wines. For that, a liquid chromatographic method with pre-column derivatization was optimized and validated to achieve a reliable quantification of the most important biogenic amines in wines, i.e. histamine, tyramine, spermine, spermidine, putrescine, cadaverine and phenylethylamine. Using a face-centered central composite design derivatization and chromatographic conditions were optimized. Derivatization with dansyl chloride showed an optimum yield for all biogenic amines at 60 °C during 60 min. These derivatives were optimally separated with a C₁₈ YMC-Pack ODS-A column set a 40 °C using a mobile phase composed of acetonitrile and water under gradient conditions. An effective separation and quantification of the biogenic amines was achieved in 40 min using ultraviolet detection at 254 nm. Validation was established according to ICH guidelines, calibrations in matrix fitted a linear regression model with R² > 0.997. Repeatability (n = 6) and intermediate precision (n = 3) in matrix showed RSD values <2.34% and <3.16%, respectively. This method was applied to determine for the first time the biogenic amines content in Chilean wines. Twenty-seven samples of young varietal wines, i.e. Cabernet Sauvignon (n = 9), Merlot (n = 8) and Carménère (n = 10) were analyzed finding a biogenic amines content from 18.12 to 39.84 mg L^-1, where putrescine showed the highest concentration in all grape varieties. No significant difference was found between grapes varieties regarding total biogenic amines content (P = 0.7842, df = 26). Along with putrescine, histamine and tyramine were the most abundant biogenic amines but similar levels were also observed with spermidine.     

Thermal Analysis of Non-linear Convective–Radiative Hyperbolic Lumped Systems with Simultaneous Variation of Temperature-Dependent Specific Heat and Surface Emissivity by MsDTM and BPES

With the advent of temperatures near absolute zero, it is often claimed that at very low temperatures the effect of thermal wave propagation must be included by the hyperbolic heat conduction equation (HHCE). In this paper the non-linear convective–radiative HHCE is investigated. Opposite to common numerical analyses, analytical expressions are obtained for the temperature variations by the multi-step differential transformation method. Some conclusions about alteration of the specific heat of the material, temperature steeping, and Vernotte number have been formulated.     

Biosorption potential of the mediterranean plant (Posidonia oceanica) for the removal of Cu2+ ions from aqueous media : Equilibrium,kinetic, thermodynamic and mechanism analysis

The biosorption characteristics of copper(II) ions using Posidonia oceanica biomass were investigated. Experimental parameters affecting the biosorption process such as pH level, contact time, biosorbent dosage and temperature were studied. The equilibrium data were applied to the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. The Langmuir model fitted very well the equilibrium data, and the maximum uptake of Cu(II) by Posidonia oceanica was found to be 76.92 mg/g. The mean free energy E (10.78 kJ/mol) from the D-R isotherm indicated a chemical ion-exchange mechanism. Kinetic results showed that the pseudo-second-order kinetic model was well fitted to the experimental data. Thermodynamic parameters depicted the exothermic nature of biosorption and the process was feasible and spontaneous. The results of FTIR (Fourier-transform infrared spectroscopy) revealed that carboxyl, amine, and hydroxyl groups on the biomass surface were involved in the biosorption of Cu(II) ions.     

Dispersed phase morphology and fractionated crystallization of high-density polyethylene in PET/HDPE blends

The fractionated crystallization of high density polyethylene dispersed in a poly(ethylene terephthalate) matrix at composition of 15 wt-% was studied. The effect of the molecular weight of polyethylene with and without compatibilization was particularly addressed regarding its influence on the morphology of the blends. For non-compatibilized blends, the dramatic influence of the molecular weight of the polyethylene on the viscosity ratio and therefore on the dispersion is reflected on the relative intensities of the twin crystallization peaks of polyethylene that are developed upon cooling. These peaks reflect two sets of particles that are nucleated by more or less active heterogeneities. The influence of the addition of an ethylene-glycidyl methacrylate copolymer on the morphology and on the crystallization of the blends was also investigated. For a high molecular weight polyethylene, the compatibilizer shows less efficiency as far as dispersion is concerned.     

Boubaker polynomials expansion scheme (BPES) solution to Boltzmann diffusion equation in the case of strongly anisotropic neutral particles forward–backward scattering

A polynomial expansion scheme is used to solve Boltzmann neutron transport equation in the case of strongly anisotropic neutral particles forward–backward scattering.     

Estimating the Long-Memory Parameter in Nonstationary Processes Using Wavelets

In this article, we propose two new semiparametric estimators in the wavelet domain in order to estimate the parameter of nonstationary long memory models. Compared to the Fourier transform, the advantage of the wavelet approach to analyze the behavior of nonstationary time series is that it can localize a process simultaneously in time and scale. We thus develop a Wavelet Exact Local Whittle estimator and a Wavelet Feasible Exact Local Whittle estimator, which extend the estimators of Phillips and Shimotsu (Ann Stat 32(2):656–692, 2004), Shimotsu and Phillips (Ann Stat 33(4):1890–1933, 2005; J Econom 130:209–233, 2006) and Shimotsu (Econom Theory 26(2):501–540, 2010) into the wavelet domain. Simulation experiments show that the new estimators perform better under most situations in the stationary and nonstationary cases. We also applied these two new semiparametric estimators to some financial series (daily stock market indices and exchange rates).