Comparative ozonization of LDPE and HDPE and grafting of some monomers to elaborate new ion exchange membranes

A comparative study of the ozonization of low density polyethylene (LDPE) and high density polyethylene (HDPE) was carried out. A grafting study of acrylic acid (AA), N,N‐dimethylamino‐2‐ethylmethacrylate (MADAME) and vinyl phosphonic acid (VPA) on LDPE and HDPE was performed in mass and solution. The ozonized polyethylene and the grafting polymers were characterized by IR spectroscopy and elementary analysis. Ion exchange membranes were prepared from grafted copolymers and characterized by the exchange capacity and electrical resistance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4423–4429, 2006     

Optimization of fluoride removal from brackish water by electrodialysis

The study showed that desired potable water can be easily obtained by electrodialysis from fluoride-rich brackish water. Studies have been performed to defluoridate brackish water containing 3000 ppm of total dissolved solids (TDS) and 3 ppm of fluoride using electrodialysis. The behaviour of water parameters (ion contents, TDS, pH, total hardness) with electrodialysis parameters (duration, flow rate, temperature, voltages) is followed. Optimal operational conditions for obtaining desired potable water have been proposed.     

Machine Learning Techniques for Software Maintainability Prediction: Accuracy Analysis

Maintaining software once implemented on the end-user side is laborious and, over its lifetime, is most often considerably more expensive than the initial software development. The prediction of software maintainability has emerged as an important research topic to address industry expectations for reducing costs, in particular, maintenance costs. Researchers and practitioners have been working on proposing and identifying a variety of techniques ranging from statistical to machine learning (ML) for better prediction of software maintainability. This review has been carried out to analyze the empirical evidence on the accuracy of software product maintainability prediction (SPMP) using ML techniques. This paper analyzes and discusses the findings of 77 selected studies published from 2000 to 2018 according to the following criteria: maintainability prediction techniques, validation methods, accuracy criteria, overall accuracy of ML techniques, and the techniques offering the best performance. The review process followed the well-known systematic review process. The results show that ML techniques are frequently used in predicting maintainability. In particular, artificial neural network (ANN), support vector machine/regression (SVM/R), regression &; decision trees (DT), and fuzzy &; neuro fuzzy (FNF) techniques are more accurate in terms of PRED and MMRE. The N-fold and leave-one-out cross-validation methods, and the MMRE and PRED accuracy criteria are frequently used in empirical studies. In general, ML techniques outperformed non-machine learning techniques, e.g., regression analysis (RA) techniques, while FNF outperformed SVM/R, DT, and ANN in most experiments. However, while many techniques were reported superior, no specific one can be identified as the best.

     

Synthesis and characterization of new ion-exchange membranes

The synthesis of grafted polymers of polyethylene (PE) with acrylic acid and N,N-dimethylamino-2 ethyl acrylate is performed in two steps. The first one needed the ozonization of powder of PE in well-defined conditions to obtain an expected activation. The second one consisted in bulk grafting the two monomers by thermal decomposition of the above hydroperoxides and peroxides of the activated PE. After elimination of homoacrylated by selective solubilization, we obtained films by pressing the copolymers either alone or the mixture of the two copolymers to prepare the anion (or cation) exchange membrane and the amphoteric ion-exchange membrane. The second part of the study deals with the physicochemical characterization of these membranes: thickness, exchange capacity, electrical resistance, transport number, and water content. These characteristics are given for various concentrations of equilibrating solutions and for various pH. The results show that we have perfectly corrected membranes that are competitive with the commercial ones.     

Nitrate removal of brackish underground water by chemical adsorption and by electrodialysis

Nitrate content has increased in Morocco, especially in underground water of agrarian areas. Several processes including degradation processes and separation processes can remove nitrate from water. Two separating processes were studied to remove nitrate from brackish underground water: adsorption on industrial animal waste and electrodialysis equipped by anion monovalent membrane. The results show that a desired product water quality can easily be obtained by electrodialysis contrary to chemical adsorption which requires a great reactional surface.     

Economic evaluation of fluoride removal by electrodialysis

An economic study was conducted to evaluate the costs of fluoride removal by electrodialysis on the basis of industrial and economic data. The investment and operating costs were estimated for an industrial plant with a capacity of 2200 m³/d water consumption for 50,000 per capita according to Moroccan standards for rural areas. The capital cost was estimated to be € 833,207 and the calculated operating cost to be € 0.154/m³.     

An optimization model for a mechanical vapor compression desalination plant driven by a wind/PV hybrid system

A renewable hybrid system to produce domestic water is presented. It consists of a photovoltaic module, a wind turbine, a mechanical vapor compression desalination plant and a storage unit. An optimization model based on a mathematical programming is developed to control the energy flows exchanged among the system components in order to satisfy the domestic water demand. The model has been solved for three specific case studies in Morocco, where two of them are located in Rabat which aim to satisfy the hourly and monthly water demand of 20 households, whereas, the last one is in Essaouira, which aims to ensure the monthly water demand of 40 households. The main motivations behind selecting these specific case studies are the evaluation of the efficiency and feasibility of such system in two coastal sites having different characteristics of renewable energy sources. The obtained results show that the domestic water demands are satisfied in each time interval at a reasonable economic cost comparable to the current average cost of water in Morocco which is about 0.7 € m⁻³.