Effect of electron-beam irradiation followed by annealing on the physical properties of poly(vinyl alcohol)–chitosan blend films at different weight ratios

The aim of this study was to examine the effect of electron-beam irradiation followed by annealing on the physical properties of poly(vinyl alcohol) (PVA)–chitosan (CS) blend films. Solution-cast films containing various ratios of polymers were exposed to irradiation doses of 26, 39, and 52 kGy at room temperature and then annealed at 100 °C. The results show that at all doses, with an increase in the weight ratio of CS, the gel content of the samples decreased, and the water absorption of the samples increased. The irradiation dose ranged from 26 to 39 kGy; this led to an increased gel content and a decreased degree of swelling in the samples. However, at 52 kGy, an increase in the amount of swelling was observed. X-ray diffraction analysis and scanning electronic microscopy images of the samples revealed that the increase in the irradiation dose reduced the crystallinity and increased the surface heterogeneity, respectively. The tensile strength of the blends decreased with decreasing PVA–CS weight ratio. This property of the samples increased with dose from 26 to 39 kGy and decreased at 52 kGy. The elongation at break of the samples decreased with both an increase in the irradiation dose and a decrease in the CS content. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47820.     

Fabrication and Characterization of SiO2/(3-Aminopropyl)triethoxysilane-Coated Magnetite Nanoparticles for Lead(II) Removal from Aqueous Solution

A novel nano-adsorbent SiO₂/(3-aminopropyl)triethoxysilane-coated magnetite nanoparticles was synthesized for the adsorption of lead ions from water samples. Its structure and magnetic characteristics were characterized, by FTIR, powder X-ray diffraction, scanning electron microscope (SEM), transmission electron microscope (TEM) and vibrating sample magnetometry (VSM). Amino-functionalized SiO₂ coated Fe₃O₄ magnetite nano-adsorbent exhibited superparamagnetic behavior and strong magnetization at room temperature. The efficiency of the nano-adsorbent in separation of the metals was evaluated by adsorption technique. Kinetic data were analyzed using the pseudo-first-order and pseudo-second-order equations. The data fitted very well to the pseudo-second-order kinetic model.The linear Langmuir and Freundlich models were applied to describe equilibrium isotherms and Langmuir model fitted well. The monolayer adsorption capacity was found as 17.65 mg/g at pH 4.0. Thermodynamic parameters such as free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°) were also calculated. These parameters showed that the adsorption of Pb(II) onto nano-adsorbent was feasible, spontaneous and endothermic. The amino-functionalized SiO₂ coated Fe₃O₄ magnetic nano-adsorbent shows high adsorption capability for metal ions from aqueous solutions via the chelation mechanisms. The Pb(II) loaded nano-adsorbent can be easily recovered from aqueous solution with magnetic separation and regenerated readily by acid treatment. The product of this work can be used as an effective and recyclable nano-adsorbent for the removal of metal ions in wastewater treatment.     

Polyacrylamide-g-Reduced Graphene Oxide Supported Pd Nanoparticles as a Highly Efficient Catalyst for Suzuki–Miyaura Reactions in Water

Catalysis Letters - To improve the dispersibility of graphene oxide (GO) in solvents, the grafting of polyacrylamide (PAM) from the GO surface was performed by redox polymerization system. The...     

A green and efficient synthesis of 2-thioxoquinazolinone derivatives in water using potassium thiocyanate

Green chemistry is one of the most important routes for the synthesis of heterocyclic compounds. In this regard, the synthesis of 2-thioxoquinazolinone derivatives was achieved by condensation of versatile materials including isatoic anhydride, amine and potassium thiocyanate in the green medium of water. This convenient and ef?cient method affords the desired products with good to excellent yields.     

SYNTHESIS AND APPLICATIONS OF CROSS-LINKED POLY(DIALLYLDIMETHYL AMMONIUM CHLORIDE) AND ITS DERIVATIVE COPOLYMERS AS EFFICIENT PHASE TRANSFER CATALYST FOR NUCLEOPHILIC SUBSTITUTION REACTIONS

Cross-linked poly(diallyldimethylammonium chloride) and its derivative copolymers were synthesized and used as phase transfer catalyst in the nucleophilic substitution reaction especially halogen exchange reactions. In addition, the effect of hydrophilic-hydrophohic character of the polymers in the nucleophilic reactions was investigated.     

An investigation into the thermal performance of office buildings in Ghana

This paper comprises the outcome of a long-term monitoring of the thermal conditions in a selected number of office buildings in Kumasi, Ghana. The observed data was not only used to assess indoor environmental conditions in these offices, but also to calibrate a number of thermal simulation models of the buildings. Thus, a simulation-based exploration of thermal retrofit options towards a general reduction of cooling requirements could be conducted. Moreover, the impact of thermal retrofit measures towards reducing carbon dioxide (CO₂) emissions was assessed and the amortization times for investments in such retrofit measures were estimated. The results suggest that improvements in building fabric and controls (with payback times of 3–12 years) can reduce buildings’ cooling loads by around 20–35% and CO₂ emissions around 27%. Additionally, the outcome of interviews conducted showed that 45% and 70% of occupants in mixed-mode and naturally ventilated buildings were uncomfortable with the air quality during the dry season. The highest dissatisfaction with indoor environment was reported by 85% of the occupants in the naturally ventilated building. The importance attached to the operation of windows and shades was relatively high, 55–80%, depending on building type.     

Effort and effectiveness considerations in computational design evaluation: a case study

Computational building evaluation tools have the potential to provide an effective means to support informed design decision making. Computational modeling, however, comes with a cost. Thereby, the most important cost factor is not software acquisition, but the time needed for learning and using the software. The extent of required time and effort is believed to be one of the main hindrances toward the pervasive use of computational building performance assessment tools by designers: Currently, modeling applications are mostly used, if at all, in the later stages of design and by specialists, rather than architects. However, few studies have explicitly dealt with the ascertainment and quantification of the actual effort needed to understand, master, and apply computational building evaluation tools. Thus, little factual information is available as to the cost and burden of computational building evaluation and its effectiveness in building design support. In this context, the present paper describes a case study, whose motivation was to estimate the time and effort needed by novice designers to computationally evaluate the performance of building designs. A group of senior architecture students participated in the study, learning and using a software application to assess the energy performance of six project submissions for a school building design competition. The outcome of this study (time investment ranges for various components of the modeling activity) was evaluated and further extrapolated to estimate the effort needed for a more comprehensive computational assessment of the environmental performance of these designs.     

A flow matrix-based heuristic algorithm for cell formation and layout design in cellular manufacturing system

Cellular manufacturing is a successful application of group technology (GT) concepts. The aim of a cellular manufacturing system (CMS) is to identify similar manufacturing processes and features where machines are grouped into machine cells based on their contributions to the production process. In the last three decades of research in cell formation, researchers have mainly used zero-one machine component incidence matrix as the input data for the problem. However, recently efforts have been made to use other data structures, such as interval data and ordinal data (consisting of sequence of processing). Sequence data provide valuable information about the flow patterns of various jobs in a manufacturing system. This study develops a heuristic algorithm based on flow matrix for cell formation and layout design in a simultaneous fashion using sequence data. The numerical results of the algorithm on the available problems in the literature indicate the usefulness of the algorithm regarding to performance indices.     

Solving cell formation problem in cellular manufacturing using ant-colony-based optimization

Grouping the machines and parts in a cellular manufacturing system based on similarities is known as the cell formation problem. It has been shown that cell formation problem is a NP-hard problem. In this paper, the ant colony optimization (ACO) method is used as an evolutionary approach to solve the cell formation problem. This model uses a P?=?[P _ij ] _{(C)?×?(M?+?P)} pheromone matrix in which C, M, and P are the number of cells, machines, and parts, respectively. In order to represent the sequence of operations, the machine–part incidence matrix entries are considered as positive integers. Performance of the proposed algorithm is tested on some benchmark problems existing in the literature to show the applicability and effectiveness of the proposed model. Comparison of the solutions obtained by the proposed algorithm with those reported in the literature indicates that application of the proposed algorithm has resulted in 5.73% improvement in the total number of intercellular movements and voids on average.