Extraction of decision alternatives in construction management projects: Application and adaptation of NSGA-II and MOPSO

The time-cost trade-off problem is a known bi-objective problem in the field of project management. Recently, a new parameter, the quality of the project has been added to previously considered time and cost parameters. The main specification of the time-cost trade-off problem is discretization of the decision space to limited and accountable decision variables. In this situation the efficiency of the traditional methods decrease and applying of the evolutionary algorithms is necessary. In this paper, two evolutionary algorithms that originally search the decision space in a continuous manner including: (1) multi-objective particle swarm optimization (MOPSO) and (2) nondominated sorting genetic algorithm (NSGA)-II, are considered as the optimization tools to solve two construction project management problems. These problems are both in discrete domain including two or tree objectives, separately. In this regard, some procedures has been suggested and then applied to adopt both algorithms capable in solving the problems in a discrete domain. Results show the advantages and effectiveness of the used procedures in reporting the optimal Pareto for the optimization problems. Moreover, the NSGA-II is more successful in determining optimal alternatives in both time-cost trade-off (TCTO) and time-cost-quality trade-off (TCQTO) problems than the MOPSO algorithm.     

Ultrasonic-assisted ball burnishing of aluminum 6061 and AISI 1045 steel

In the present work, experimental study was carried out to enhance the surface properties of aluminum 6061 and AISI 1045 steel plates by ultrasonic-assisted ball burnishing process. Full factorial experimental design was utilized here to find the effect of ultrasonic vibration, feed rate, and pass number on surface roughness and hardness. The results were discussed according to interaction effect of process factors for different material. It is found from the results that for conventional burnishing process, the highest surface hardness is attained at 5000?mm/min feed rate and 5 pass number, while for ultrasonic-assisted burnishing, the highest hardness is attained at 1000?mm/min feed rate and 5 pass number. On the other hand, it is found from the results that exerting ultrasonic vibration significantly enhances the hardness value and hardened depth. Also, it is found that irrespective of type of operation and material, increase in feed rate causes higher roughness, whereas increase in pass number causes reduction in roughness. Furthermore, surface roughness of ultrasonic-assisted burnishing is lower than that of conventional burnishing process. This enhancement is due to the association of both static and dynamic loading in ultrasonic-assisted burnishing process that causes microstructure modification and limits the elastic recovery of the surface.     

Mechanical performance of tubular composites reinforced by innovative 3D integrated knitted spacer fabrics

This article aimed to investigate the mechanical performance of 3D integrated knitted spacer composites with a tubular shape, in term of internal hydrostatic and external static pressures (ESP). All the tubular‐knitted fabrics were produced on a modern flat knitting machine using untwisted glass and HT‐nylon yarns. Then, the epoxy resin was transferred through the whole fabric structure via vacuum infusion molding process. Produced tubular composites were subjected to internal hydrostatic and ESP. Accordingly, force–displacement curves were obtained and experimental results were discussed. The results revealed that the tubular composite samples containing non‐knitting yarns show 27.33 and 37.50% improvement in internal hydrostatic and ESP, respectively, compared with the plain knitted fabric reinforced composite. Also, the finding demonstrated that mechanical performance of the tubular‐knitted spacer composites is highly affected by aspect ratio and the number of connecting layers. Knitted spacer reinforced composite containing 5 and 10 connecting layers can improve the resistance against internal hydrostatic pressure 35.08 and 51.29%, respectively, compared with the plain knitted reinforced composites. In this case, 84.20 and 89.86% improvement can be achieved in term of the resistance against ESP. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46074.     

Synthetic-based blended electrospun scaffolds in tissue engineering applications

Journal of Materials Science - Electrospinning, as one of the most common methodologies in nanofibers production, involves applying high voltages to a polymeric solution that is entrapped in a...     

On the influence of individual differences in cross-modal Mulsemedia QoE

Multimedia Tools and Applications - Quality of Experience (QoE) is inextricably linked to the human side of the multimedia experience. Whilst there has been a considerable amount of research...     

Carbon-ceramic supported bimetallic Pt–Ni nanoparticles as an electrocatalyst for electrooxidation of methanol and ethanol in acidic media

The electrooxidation of methanol and ethanol was investigated in acidic media on the platinum–nickel nanoparticles carbon-ceramic modified electrode (Pt–Ni/CCE) via cyclic voltammetric analysis in the mixed 0.5 M methanol (or 0.15 M ethanol) and 0.1 M H₂SO₄ solutions. The Pt–Ni/CCE catalyst, which has excellent electrocatalytic activity for methanol and ethanol oxidation than the Pt–Ni particles glassy carbon modified electrode (Pt–Ni/GCE), Pt nanoparticles carbon-ceramic modified electrode (Pt/CCE) and smooth Pt electrode, shows great potential as less expensive electrocatalyst for these fuels oxidation. These results showed that the presence of Ni in the structure of catalyst and application of CCE as a substrate greatly enhance the electrocatalytic activity of Pt towards the oxidation of methanol and ethanol. Moreover, the presence of Ni contributes to reduce the amount of Pt in the anodic material of direct methanol or ethanol fuel cells, which remains one of the challenges to make the technology of direct alcohol fuel cells possible. On the other hand, the Pt–Ni/CCE catalyst has satisfactory stability and reproducibility for electrooxidation of methanol and ethanol when stored in ambient conditions or continues cycling making it more attractive for fuel cell applications.     

Application of tin(IV) porphyrin complexes as novel catalysts for the synthesis of new copolyurethanes with cyclopeptide moiety

New electron deficient tin(IV) porphyrins were used as efficient catalysts for the reaction of 4,4′‐methylene‐bis‐(4‐phenylisocyanate) (MDI), with L‐leucine anhydride cyclodipeptide (LAC) and polyethyleneglycol‐400 (PEG‐400) and the results were compared with those obtained in the presence of a commercial catalyst, dibutyltin dilaurate (DBTDL). Molar ratio of catalysts to MDI, polymerization reaction time, viscosity, and yield of the resulting poly(ether‐urethane‐urea)s (PEUU) were compared in the presence of different catalysts. The rate of N?C?O conversion in the presence of each catalysts under the same reaction conditions was also compared and followed by FT‐IR N?C?O absorption band. FT‐IR, GPC, and viscosity studies have shown that tin(IV) porphyrins afford higher viscosity and reaction progress. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Pyridine‐2,6‐diamine‐functionalized Fe3O4 nanoparticles as a novel sorbent for determination of lead and cadmium ions in cosmetic samples

A novel sorbent based on pyridine‐2,6‐diamine‐functionalized Fe₃O₄ nanoparticles was developed and characterized by X‐ray powder diffraction (XRD), elemental analysis, IR spectroscopy and scanning electron microscopy (SEM). The application of the sorbent was investigated for pre‐concentration and determination of lead and cadmium ions in aqueous samples. Effects of various factors such as the sample pH, eluent parameters (type, concentration and volume) and time (adsorption and desorption) were appraised. The effects of several interfering ions on method recovery were also investigated. The limit of detection (LOD) was found to be 1.3 and 0.089 μg L^?1 for lead and cadmium ions, respectively. Recovery and precision (RSD%) of the method were above 97.9% and below 0.6%, respectively. Validation of the outlined method was performed by analysing several certified reference materials. This method was successfully used for determination of lead and cadmium ions in several cosmetic samples, which are usually contaminated by lead and cadmium ions.