Synthesis and characterization of functionalized carbon nanotubes with different wetting behaviors and their influence on the wetting properties of carbon nanotubes/polymethylmethacrylate coatings

The synthesis and characterization of hydrophobic functionalized multi-wall carbon nanotubes (MWCNTs) were investigated and their influence on the wetting properties of organic coatings and composites was studied. Functionalization was performed using oxidation, 1,3-dipolar cycloaddition, and silanization. Silanization was conducted using three hydrophobic silane precursors: 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, and triethoxyoctylsilane. Functionalization was directly confirmed and characterized by Fourier transform infrared spectroscopy, thermal gravimetric analysis, and scanning electron microscopy. The water contact angle of the functionalized MWCNTs was 40–142° for different surface functionalities and the functionalized MWCNTs were incorporated into an acidic solution of polymethylmethacrylate. The effect of surface functionality and the concentration of the functionalized MWCNTs on the wetting properties of these composites were studied by measuring the water contact angle. Under optimum conditions, composite surfaces with water contact angles greater than 110° were obtained. Atomic force microscopy was used to determine the topography of the surface and energy dispersion spectroscopy was used to determine the distribution of the functionalized MWCNTs in the composite film. It was shown that the hydrophobic functionalized MWCNTs migrated to the surface; this was more pronounced for the more hydrophobic MWCNTs.     

Analytical performance models for resource allocation schemes of cloudlet in mobile cloud computing

The Journal of Supercomputing - In the cloudlet architecture of mobile cloud computing (MCC), the mobile users offload their resource-intensive tasks to a local cloud (i.e., Cloudlet) via WiFi...     

Synthesis and characterization of diethylene glycol monobutyl ether—Blocked diisocyanate crosslinkers

Typically blocked isocyanate systems are used to obtain the performance of two component polyurethane (PU) system in a one-component mixture. In this study four types of isocyanates namely, hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI) and toluene diisocyanate (TDI) were blocked with diethylene glycol monobutyl ether (DEGMBE). Elimination of the isocyanate groups and the formation of urethane bonds were studied by FTIR spectroscopy and titration methods. Thermal dissociation of blocked diisocyanates was analyzed by DSC and TGA techniques.     

An Entropy-Based Approach to Fuzzy Multi-objective Optimization of Reservoir Water Quality Monitoring Networks Considering Uncertainties

In this study, a new fuzzy methodology for a multi-objective optimization of reservoir Water Quality Monitoring Stations (WQMS) was developed, based on Transinformation Entropy (TE), the IRanian Water Quality Index (IRWQI), and fuzzy social choice considering uncertainties. The approach was utilized in the Karkheh Dam reservoir in Iran. The objective functions were: 1) minimizing costs, 2) minimizing redundant information and uncertainties, and 3) maximizing the spatial coverage of the network. A CE-QUAL-W2 model was used for the simulation of water quality variables. The IRWQI was computed to reveal a complete picture of the reservoir water quality. The TE quantities were calculated for each pair of potential stations. The TE values were plotted against the spatial distances among potential WQMS to obtain the TE–Distance (TE–D) curve, and minimize redundant information among stations, while providing coverage of the entire network. A multi-objective Genetic Algorithm (NSGA-II) was applied to obtain Pareto-optimal solutions taking stakeholder preference into account. The most preferred solution was then obtained using fuzzy social choice approaches to achieve a consensus. The fuzziness embedded in the decision-making procedure, the uncertainty in the value of mutual information, and the uncertainty in identifying the optimal distance among WQMS were also investigated. Results indicated that the three fuzzy social choice approaches (Borda Count, Minimax, and Approval Voting) led to the same number of optimized WQMS in each fuzzy alpha-cut. Based on the fuzzy linguistic quantifiers method, the number of optimized WQMS was increased.     

Effects of Packaging Materials,Modified Atmospheric Conditions,and Storage Temperature on Physicochemical Properties of Roasted Pistachio Nut

Pistachio is one of the most important non-oil export items for Iran and also has the ability to adapt itself to adverse conditions including salinity, moisture stress, soil, and low water irrigation. It is one of the economical crops of desertic and dry areas and is recommended for such places. In this research, the effect of different packaging materials including five layers of compound film, modified polypropylene and metallized plastic, and packaging atmosphere on the quality of roasted pistachio nut were investigated. Atmospheric conditions were N₂/CO₂, vacuum, and ambient air at temperatures of 20 °C and 40 °C. Samples were tested in defined time intervals and then data were statistically analyzed. Results showed that packaging pistachio nut in metallized film and five-layer films with gases N₂/CO₂ and vacuum conditions kept the quality of pistachio better and lengthened shelf-life. A temperature of 40 °C compared to 20 C was a favorable condition for pistachio quality.     

Effect of stirring speed and time on microstructure and mechanical properties of Cast Al–Ti–Zr–B<Subscript>4</Subscript>C composite produced by stir casting

A new aluminum matrix composite reinforced with B₄C particles was manufactured using different stirring speeds and time. Stirring speeds of 600 and 700 rpm and stirring time of 5, 10, and 15 minutes were chosen for casting the aluminum-B₄C composites The effects of these parameters on the microstructure and mechanical properties of the produced composites were analyzed using reflected light microscopy (RLM), scanning electron microscopy (SEM and FESEM), image analysis, density measurement, and tensile test. Image analysis of the as-cast microstructures revealed that longer stirring speeds and time resulted in higher reinforcement content in the as-cast microstructure and consequently the sample under 700 rpm stirring speed with 15 min total stirring time had incorporated most of the added B₄C particles. Interface characterization performed by FESEM showed that the added Ti and Zr had accumulated at the interface. Tensile test results revealed that higher stirring speed and longer stirring time resulted in the reduction of ultimate tensile strength and total elongation for 700 rpm stirring speed. It was concluded that a 700 rpm stirring speed with 15 min stirring time could produce a composite sample with the incorporation of most of the added particles distributed almost uniformly throughout the microstructure.