A New Inverse Method Using Model Synthesis: Application to Thermal Systems

We propose a new inverse method which consists of building an “inverse model.” The model synthesis [1 G. Lefebvre , E. Palomo , and A. Ait-Yahia , Substructured Modelling of Linear Thermal Systems: The Model Synthesis , Numer. Heat Transfer B , vol. 39 , pp. 303 – 324 , 2001 . [CSA] [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]], which allows us to gather several coupled elementary models in a single one, can be used to permute some outputs with some inputs of the direct model, solving a special coupling between the direct model and a particular one called “inversor.”

The model synthesis then provides an inverse model which can be used to perform usual simulations. We show the principles of the method, the practical “ticks,” and demonstrate with an example that it is an easy-to-use and efficient method.     

Optimization of the Mechanical Strength of PP/TALC Micro-Composite after Immersion in Benzene

Strength of Materials - In this study, the degradation of mechanical properties of polypropylene(PP)/talc composite after immersion in benzene was evaluated experimentally. Tensile tests were...     

Seasonal occurrence and toxicity of Microcystis spp. and Oscillatoria tenuis in the Lebna Dam, Tunisia

Physicochemical and biological water quality, including the total microcystin concentrations, was investigated for the first time from January to December 2005 in the Lebna Dam, Tunisia. Microcystin levels and characterization of the different microcystin variants present were measured by protein phosphatase (PP2A) inhibition assays and by LC/MS/MS, respectively. Nutrient values were high, with total inorganic nitrogen and phosphorus concentrations ranging from 0.05 to 8.4 mg L(-1) and from 0.03 to 1.37 mg L(-1), respectively. However, the chlorophyll-a concentrations were very low with a peak (5.32 microg L(-1)) on 20 September 2005 at 9 m depth water samples. Microscopic examination of the phytoplankton samples showed the dominance in the autumn of three morphospecies of the genus Microcystis and the species Oscillatoria tenuis. The total (particulate and dissolved) microcystin concentrations at the surface and at 9 m depth water samples ranged between 0.008 and 1.73, and 0.005 and 5.57 microg microcystin (MC)-LR equivalent L(-1), respectively, with a peak on 20 September. The presence of the microcystin synthetase genes (mcyA, -B, and -C) in the lysates of the three morphospecies of the genus Microcystis and the species O. tenuis indicated that these species were responsible for the microcystin production in this system. The analysis of the field cyanobacterial sample extract containing these species by LC/MS/MS revealed the presence of two microcystin variants: microcystin-LR (MC-LR) and microcystin-YR (MC-YR).     

Study of clay's mineralogy effect on mechanical properties of ceramic body using an experimental design

Three clays minerals namely illite (I), montmorillonite (M), and kaolin (K) were chosen as references to study the effect of mixture composition of clays on the mechanical properties and the shrinkage of the fired ceramic. The study was accomplished using the experimental design methodology. More specifically, a mixture design was carried out in order to establish relationships between mechanical strength and shrinkage of finished products and the proportions of the three clay mineral references in the mixture. The statistical study shows that the fitted models were adequate to describe these properties of fired ceramic bodies. The results demonstrate that the mechanical resistance was mainly governed by the amount of montmorillonite mineral. In fact, the mixture design performed in this study shows clearly that montmorillonite can be incorporated in industrial ceramic products up to 45 wt% with high mechanical resistance. On the other hand, the shrinkage decreases strongly with the amount of kaolin in the mixture and increases with the amount of illite while montmorillonite exhibits moderate effect on this property. The higher strength was shown in mixture in which mullite and anorthite appear together due to the presence of kaolinite and illite and give, as a consequence, a synergic power.     

Design and Characterization of a New Food Packaging Material by Recycling Blends Virgin and Recovered polyethylene terephthalate

This research is dealing with plastic wastes recycling environmental problem. The objective is the polyethylene terephthalate (PET) valorization from postconsumer bottles by the optimization of the most suitable virgin and recycled PET mixture to be used as food contact packaging. Mixtures of these materials were elaborated by extrusion and injection molding using different recycled PET rates. Rheological, mechanical, and thermal analyses were achieved, and then migration tests were investigated to assess the recycled PET compatibility for food contact packaging. The rheological analysis showed a PET degradation after the mechanical recycling, with PET viscosity decrease, compared to that of the virgin material. The blends properties showed that at low deformation, mechanical properties were significantly improved by adding recycled PET. Consequently, the new material was more rigid with a crystallinity degree improvement, increasing the materials resistance that enhanced their tenacity. However, at great deformations, the PET mixed materials were deteriorated through drastic ductility losses. The mixture 30/70 recycled/virgin PET seems to be the best blend. For all the studied mixtures, the overall migrations conformed the European Standard, allowing the use of the recycled PET for packaging as an issue in circular economy principles for a sustainable development. POLYM. ENG. SCI., 60: 250–256, 2019. © 2019 Society of Plastics Engineers     

Prediction of surface characteristics obtained by burnishing

To reduce the irregularities of machined surface, burnishing is used as a finishing process by plastic deformation. This process does not only improve surface finish but also generates compressive residual stresses throughout the surface. In this work, an analytical study and a finite element modelling were performed to provide a fundamental understanding of the burnishing on an AISI 1042 workpiece. The analytical results were concentrated on the surface roughness and on some burnishing parameter effects. The simulations were devoted to the study of the surface profile, the residual stresses and the influence of burnishing parameters (penetration depth, feed rates, diameter of the ball of burnishing tool and initial surface quality) on surface roughness and the residual stress distribution. It has been noted that burnishing improves surface quality and introduces compressive residual stresses. These results were successfully compared to experimental data obtained in previous works.     

Purification and Biochemical Characterization of Lipase from <Emphasis Type="Italic">Ficus carica</Emphasis> Latex of Tunisian East Coast Zidi Variety

Lipase from Ficus carica L. (Moraceae) latex of the Zidi variety was purified 80.5-fold with 68.5 % recovery using silica gel chromatography. The molecular weight of the enzyme was 29 kDa as determined by SDS-PAGE. High lipolytic activity was found in the crude extract during the fruit ripening process. The activity of purified lipase (ZL) seemed to depend strongly on chain length and showed a preference to long chain triacylglycerols. Indeed, ZL specific activity was 370.3 UI/mg using olive oil as a substrate at 45 °C and pH 5.5. In contrast, activity towards short chain triacylglycerols (tributyrin) was 12-fold lower (32 UI/mg). The enzyme was quite stable in the pH range 4–8, and thermally stable at 60 °C displaying t _1/2 about 90 min using olive oil as a substrate. The values of K _m app and V _m were found to be 14.3 mM and 294.1 μmol/min/mg, respectively. ZL activity was strongly reduced by Fe²⁺, Mg²⁺ and Zn²⁺, while significantly increased by Ca²⁺ and Cu²⁺. The enzyme was stimulated by sodium dodecyl sulfate, and Tween-80, while Triton X-100 and EDTA had a slight inhibitory effect. No Effect was observed in addition of PMSF and iodoacetic acid.