A SEM and X-ray study for investigation of solidified/stabilized arsenic-iron hydroxide sludge

Despite the fact that the solidification/stabilization of arsenic containing wastes with Portland cement and lime has an extensively documented history of use, the physical and chemical phenomena as a result of the interaction between arsenic and cement components have not been fully characterized. The study investigates the behavior of synthesized arsenic-iron hydroxide sludge, the by-product of arsenic removal by coagulation with ferric chloride, in solidified/stabilized matrices as well as its binding mechanisms by exploring the cementitious matrices in the micro-scale by scanning electron microscopy equipped with energy dispersive X-ray spectrometer (SEM-EDS). It was revealed that arsenic can be chemically fixed into cementitious environment of the solidified/stabilized matrices by three important immobilization mechanisms; sorption onto C-S-H surface, replacing SO4(2-) of ettringite, and reaction with cement components to form calcium-arsenic compounds, the solubility limiting phases.     

Scanning near-field optical microscopy as a tool for the characterization of multimode interference devices

We report the scanning near-field optical microscopy (SNOM) characterization of a 4 x 4 multimode interference (MMI) device working at a wavelength of 1.55 microm and designed for astronomical signal recombination. A comprehensive analysis of the mapped propagating field is presented. We compare SNOM measurements with beam-propagation-method simulations and thus are able to determine the MMI structure's refractive-index contrast and show that the measured value is higher than the expected value. Further investigation allows us to demonstrate that good care must be taken with the refractive-index profile used in simulation when one deals with low-index contrast structures. We show evidence that a step-index contrast is not suitable for adequate simulation of our structure and present a model that permits good agreement between measured and simulated propagating fields.     

A Framework for the Generation of Adaptive Courses Based on Semantic Metadata

This approach proposes the creation and management of adaptive learning systems by combining component technology, semantic metadata, and adaptation rules. A component model allows interaction among components that share consistent assumptions about what each provides and each requires of the other. It allows indexing, using, reusing, and coupling of components in different contexts powering adaptation. Our claim is that semantic metadata are required to allow a real reusing and assembling of educational component. Finally, a rule language is used to define strategies to rewrite user query and user model. The former allows searching components developing concepts not appearing in the user query but related with user goals, whereas the last allow inferring user knowledge that is not explicit in user model.John Freddy Duitama received his M.Sc. degree in system engineering from the University of Antioquia -Colombia (South America). He is currently a doctoral candidate in the GET – Institut National des Télécommunications, Evry France. This work is sponsored by the University of Antioquia, where he is assistant professor.His research interest includes semantic web and web-based learning systems, educational metadata and learning objects.Bruno Defude received his Ph.D. in Computer Science from the University of Grenoble (I.N.P.G) in 1986. He is currently Professor in the Department of Computer Science at the GET - Institut National des Télécommunications, Evry France where he leads the SIMBAD project (Semantic Interoperability for MoBile and ADaptive applications).His major field of research interest is databases and semantic web, specifically personalized data access, adaptive systems, metadata, interoperability and semantic Peer-to-peer systems with elearning as a privileged application area.He is a member of ACM SIGMOD.Amel Bouzeghoub received a degree of Ph.D. in Computer Sciences at Pierre et Marie Curie University, France.In 2000, she joined the Computer Sciences Department of GET-INT (Institut National des Telecommunications) at Evry (France) as an associate professor.Her research interests include topics related to Web-based Learning Systems, Semantic Metadata for learning resources, Adaptive Learning Systems and Intelligent Tutoring Systems.Claire Lecocq received an Engineer Degree and a Ph.D. in Computer Sciences respectively in 1994 and 1999. In 1997, she joined the Computer Sciences Department at GET-INT (Institut National des Télécommunications) of Evry, France, as an associate professor. Her first research interests included spatial databases and visual query languages. She is now working on adaptive learning systems, particularly on semantic metadata and user models.     

Assessment of exposure rate and collective effective dose equivalent in the city of Baghdad due to natural gamma radiation

Exposure rate measurements in the city of Baghdad were initiated in June 1981. The average exposure rate, the average annual effective dose equivalent and the collective effective dose equivalent are assessed. The data are presented according to the eleven municipal divisions of the city. The average exposure rate was 6.9 microR h-1 and an average annual effective dose equivalent of 4.5 x 10(-4) Sv year-1. The collective effective dose equivalent is 1.81 x 10(3) man Sv year-1.     

Microstructure of In-Situ composites

In this paper, the results of several years of research work by the authors on the microstructure of In-Situ composites are reviewed. Alloy systems investigated are the fibrous Al? Ni and cobalt-base superalloy Co? Cr? C, and the lamellar Al? Cu and Co? W. The effect of solidification variables and off-eutectic compositions on the micro-structure of Al? Ni Co? W and Al? Cu systems was studied. The influence of heat flow direction on the microstructure of Al? Ni was examined. Post solidification isothermal annealing was performed for Al? Cu and Co? Cr? C alloy and thermal cycling regimes were imposed on the Co? Cr? C alloy and the microstructure variations were examined. Computer simulation of directional, solidification to study the heat flow pattern in the metal and mould was also performed. It was found that low growth rates, high temperature gradients, eutectic composition and pure materials favor a planar solidification front and an aligned structure. Increasing the growth rate resulted in finer structures. The thermal stability of In-Situ composites was found to be reasonably good due to the strong interfacial bond between matrix and reinforcement in this class of composites.     

Poly[ethylene‐co‐(vinyl alcohol)]‐graft‐poly(ε‐caprolactone) Synthesis by Reactive Extrusion, 1 ‐ Structural and Kinetic Study

Chemical modification of EVOH in the molten state at 185 °C by a grafting from process of poly(ε‐caprolactone) in batch was studied. ¹H NMR was used to characterize the structure evolutions of PCL grafts. In addition to grafting reactions, dynamic covalent transesterification reactions between EVOH residual alcohols and the polyester grafts led to a redistribution of the PCL grafts length. up to 27 and SR up to 80% were obtained. Experiments made in a corotating mini twin‐screw extruder also confirmed these results. The effect of the alcohol to caprolactone ratio and catalyst concentration (SnOct₂) on kinetic evolution showed that few minutes were necessary to complete the polymerization. A kinetic model was proposed and adequate conditions for the synthesis by reactive extrusion were defined.

     

Effect of Reciproc blue,XP‐endo shaper,and WaveOne gold instruments on dentinal microcrack formation: A micro‐computed tomographic evaluation

The purpose of this study was to evaluate and compare the effect of Reciproc Blue (RPCB), XP‐endo Shaper (XPS), and WaveOne Gold (WOG) single‐files on dentinal microcrack formation using micro‐computed tomography (micro‐CT). Twenty‐four mesial roots (24 mesio‐buccal and 24 mesio‐lingual canals) of mandibular molar teeth were prepared using RPCB, XPS, and WOG files (n = 8/each group). The samples were scanned with micro‐CT in the pre‐ and post‐preparation. Then, before preparation and after preparation cross‐sectional images of the teeth were evaluated to detect the presence of microcracks. For each group, the number of microcracks was calculated as a percentage rate. The data were statistically analyzed using McNemar at 5% significance level (p < .05). Dentinal microcracks were observed in 25.99% (2,103 of 7,813), 31.99% (2,482 of 7,758), and 36.66% (2,836 of 7,731) of cross‐sectional images of the XPS, WOG, and RPCB groups, respectively. In all the groups, all the dentinal microcracks seen in the post‐treatment cross‐sectional images were present in the corresponding pre‐treatment images. Within the limitations of this study, the XPS, WOG, and RPCB files did not cause new dentinal microcrack formation or propagation of existing dentinal microcracks.     

Fuzzy-modeling with Particle Swarm Optimization for enhancing the production of biodiesel from Microalga

Biodiesel is one of the promising energy sources that could replace petroleum oil in the near future. Microalgae is occupying a distinguished position among the promising sources for biodiesel production. Enhancement of the lipids production during the pretreatment is a key factor for the biodiesel production. High-pressure homogenizer is a better pretreatment procedure to enhance the lipid extraction from microalgae. In this research, a robust model of biodiesel system using fuzzy logic is built based on the experimental data for biodiesel system. Then, Particle Swarm Optimization (PSO) optimizer is applied for determining the best operating parameters of biodiesel system. The decision variables used in the optimization process are; pressure, number of passes, and reaction time that maximizes the percentage of recovery lipids of biodiesel. A comparison study was carried out between the optimized results thought PSO algorithm and those obtained by the experimental results and the optimized results through the Response Surface Methodology (RMS). Results demonstrated that using the proposed optimization methodology is significantly better than RSM, a nearly 78.7% increase in lipids extraction could be achieved according to the current model.     

Antimicrobial materials based on poly(ethylene-co-vinyl alcohol) and silver acetate produced by reactive extrusion

The use of silver as an antimicrobial agent has exhibited great interest in recent years. In this research, poly(ethylene-co-vinyl alcohol) (EVOH)–silver acetate-based antimicrobial materials were prepared at high temperature by reactive extrusion. Silver acetates were used without pretreatment. The thermal reaction of silver acetates in the material and their effect on the thermal and mechanical properties of the polymer were investigated as a function of their concentration. The dispersed silver acetate salts within the EVOH matrix have displayed a significant thermal reaction. This reaction of metallic salts was partial when the extrusion temperature was fixed at 190 °C and completed at 230 °C. The antimicrobial agents also had significant effects on the properties of the matrix. Reductions of glass temperature and storage modulus were observed by the analyses. All the variations were dependent on both the concentration of silver acetate and the extrusion parameters. The antimicrobial activity was studied and demonstrated a promising potential to create an antimicrobial material in a one-step solvent free extrusion method. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47799.     

Multi-criteria decision making in workforce choice using AHP,WSM and WPM

This paper focuses on the implementation of Multi-Criteria Decision Making (MCDM) methods to evaluate the workforce competence in apparel industry. In this study, the Analytic Hierarchy Process (AHP), the Weighted Sum Model (WSM) and the Weighted Product Model (WPM) are suggested to solve workforce selection problem. The use of these methods is expected to help choose the best operator among several alternatives. Based on three criteria, each worker is evaluated in each executed operation. The criteria are a Quality Index ‘QI’, an Activity ‘A’ and an Attendance Rate ‘AR’. Thanks to the MCDM methods, scores allowing an objective classification of operators are obtained. Experimental results on AHP, WSM and WPM methods show the same decisions with the same workers’ classification from the best to the worst alternative. The resulting database contributes to the line balancing optimization by choosing for each operation, and as far as possible, the most competent operator.