Development of novel method for prediction of gas density in operational conditions

The performance of gas industries is extensively function of gas properties such as gas density. Due to this importance in the present work, a novel grid partitioning based fuzzy inference system method applied to predict gas density base on pressure, temperature and molecular weight of gas. To this end, the required experimental data are collected from reliable sources. Different comparison scenarios are used to evaluate the ability of model. The coefficients of determination (R²) for training and testing phases are calculated as 0.9985 and 0.9980 respectively. The determined indexes and graphical evaluations show that predicting model can estimate gas density in high degree of accuracy. According to the obtained results, the predicting model can be used as a simple and powerful software in gas industries to predict different processes.     

Filtered gradient active fuzzy neural network noise control in an enclosure backed by a clamped plate

The performance of conventional linear algorithms in active noise control applications deteriorates facing nonlinearities in the system mainly because of loudspeakers. On the other hand, fuzzy logic and neural networks are good candidates to overcome this drawback. In this paper, the acoustic attenuation of noise in a rectangular enclosure with a flexible panel and five rigid walls is presented both theoretically and experimentally using filtered gradient fuzzy neural network (FGFNN) error back propagation algorithm in which the secondary path effect is implemented in derivation of updating rules. Considering this effect in updating rules leads to faster convergence and stability of the active noise control system. On the other hand, the primary path in the investigated system comprises an identified nonlinear model of loudspeaker inside the aforementioned box, parameters of which vary with the input current. The loudspeaker is identified using series‐parallel neural network model identification method. As a comparison, the performance of filtered‐x least mean squares and FGFNN algorithms are compared. It is observed that FGFNN controller exhibits far better results in the presence of loudspeakers with nonlinear behavior in primary path.Copyright © 2012 John Wiley & Sons, Ltd.     

Physicochemical and antibacterial properties of chitosan‐polyvinylpyrrolidone films containing self‐organized graphene oxide nanolayers

Chitosan films have a great potential to be used for wound dressing and food‐packaging applications if their physicochemical properties including water vapor permeability, optical transparency, and hydrophilicity are tailored to practical demands. To address these points, in this study, chitosan (CS) was combined with polyvinylpyrrolidone (PVP) and graphene oxide (GO) nanosheets (with a thickness of ～1 nm and lateral dimensions of few micrometers). Flexible and transparent films with a high antibacterial capacity were prepared by solvent casting methods. By controlling the evaporation rate of the utilized solvent (1 vol % acidic acid in deionized water), self‐organization of GO in the polymer matrix was observed. The addition of PVP to the CS/GO films significantly increased their water vapor permeability and optical transmittance. A blue shift in the optical absorption edge was also noticed. Thermal analysis coupled with Fourier transform infrared spectroscopy suggested that the superior thermal stability of the nanocomposite films was due to the formation of hydrogen bonds between the functional groups of chitosan with those of the graphene oxide. An improved bactericidal capacity of the nanocomposite films against gram‐positive Staphylococcus aureus and gram‐negative Escherichia coli bacteria was also observed. Highly flexible, transparent (opacity of 6.95), and antimicrobial CS/25 vol % PVP/1 wt % GO films were prepared. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43194.     

Evaluation of Thermodynamic Models for Prediction of Sorption Behavior into the Polydimethylsiloxane Membrane in Pervaporation Process

This work focuses on modeling of the sorption step as a main step in the mass transport through the pervaporation process. For this purpose, four thermodynamic models including Flory–Huggins (FH), Universal Quasichemical (UNIQUAC), modified Non-Random Two-Liquid (M-NRTL), and modified Wilson (M-Wilson) were used to predict the equilibrium sorption of ethanol/water mixtures into the polydimethylsiloxane (PDMS) membrane. In the M-Wilson model, the reference state based on pure enthalpy of components was used to determine the residual term. Moreover, the influences of ethanol feed content and temperature on the liquid sorption level and sorption selectivity were studied experimentally and theoretically. The results indicated that the proposed models were successfully able to determine the sorption level of the ethanol aqueous solutions into the PDMS membrane. Moreover, the M-NRTL and M-Wilson models were found to be much more accurate than the FH and UNIQUAC models to determine the volume fraction of the penetrants in the PDMS membrane. It was also observed that the total and ethanol sorptions increased with an enhancement in the ethanol feed concentration, while the membrane sorption selectivity decreased. Moreover, increasing the operating temperature led to higher sorption of both ethanol and water, whereas the sorption selectivity did not show significant changes with temperature.     

Combined method of complex coacervation and electrospray for encapsulate preparation

Encapsulate beads composed of alginate and chitosan as shell and bovine serum albumin (BSA) as core were prepared by combined method of complex coacervation and electrospray. The main objective of this work was to produce mono‐sized and spherical capsule of chitosan‐alginate with controlled sizes of capsules and shell. However, the effects of applied voltage, flow rate, and molecular weight of chitosan were investigated on the size, size distribution, membrane thickness of the prepared capsules, as well as the release rate of BSA. The results revealed that by the method developed in this study, it was possible to produce spherical capsules with controlled size and narrow size distribution. Increasing the voltage and decreasing the flow rate reduced the radius of capsule and its shell thickness from 2.09 mm to 750 μm and from 1.31 mm to 490 μm, respectively. Furthermore, the molecular weight of chitosan had no significant effect on the capsules' size and the release rate of BSA, whereas the rate of BSA release was increased with increase of the voltage. The later effect would be due to the increase of shell porosity at the higher voltages. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A comparative study on the free volume theories for diffusivity through polymeric membrane in pervaporation process

In this work, free volume theories are coupled with a thermodynamic model and generalized Fick's law to develop a mass transfer model based on solution‐diffusion mechanism for pervaporation process with a hydrophobic polymeric membrane. The Wesselingh, Fujita and Vrentas‐Duda's theories are used to calculate concentration‐dependent diffusion coefficient of permeants inside polydimethylsiloxane membrane. The sorption and pervaporation experiments on aqueous ethanol solutions are performed to validate the sorption and pervaporation models. The results reveal that the proposed models are able to predict influences of feed concentration and temperature as well as permeate‐side pressure on partial fluxes through the membrane. The comparative investigation indicated that Wesselingh's free volume theory underestimated the diffusion coefficients inside the membrane and the accuracy of the model used this theory is very low for prediction of the permeation flux. Generally, Fujita and Vrentas‐Duda's theories are found to be much more accurate especially for dilute aqueous feed solutions. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40581.     

Environmental impacts of desalination on the ecology of Lake Urmia

Lake Urmia, the second largest hypersaline lake by area in the world, has fluctuated in salinity over time, but in recent years, it has reached a maximum of 340 g/L. The lake is the main habitat for the endemic Iranian brine shrimp, Artemia urmiana, and is a protected aquatic environment. Efforts have been made by the Iranian government to enhance the diversity of its wildlife. One approach has been to look for a method to reduce the salt content of the lake. We investigate the feasibility of this by first considering the water chemistry of Lake Urmia and then the various technologies used to extract salt from marine and brackish waters. Average concentrations of Na, Mg, K, Ca, Cl, SO₄, and HCO₃ were 125 g/L, 11.3 g/L, 2.63 g/L, 0.55 g/L, 216 g/L, 22.4 g/L, and 1.38 g/L, respectively, and cations and anions were balanced, However, Lake Urmia waters have a ‘very high’ salinity hazard and a high sodium adsorption ratio (SAR). Moreover, the saturation index (SI) for each of the major cations was greater than zero, indicating that the water in Lake Urmia is supersaturated, and precipitation is likely. The extraction of available salts from the lake for the use in petrochemical industries is economically feasible. However, technologies based on removing salts by distillation or reverse osmosis and then using this fresh water to dilute lake salinity are problematic. A better strategy would be better to allow more fresh water to reach the lake rather than creating fresh water through reverse osmosis and distillations processes. While concerns have been raised about the salinity tolerance of A.urmiana, it has successfully tolerated various salinity ranges from 166 to 340 g/L, and so the species is not threatened, unless the lake desiccates. Because the lake is saturated with salts, it seems unlikely that salinity could increase much higher.     

Clarification of pomegranate juice by microfiltration with PVDF membranes

Microfiltration was used to clarify pomegranate juice using two polyvinylidene fluoride membranes with pore sizes of 0.22 and 0.45 μm. Changes were studied in the chemical properties of the juice after passing through each membrane. Characteristics such as turbidity changed for both membranes (more than 95%). The permeate flux decreased over time as a result of membrane fouling. The degree of decline in the membrane with pore size of 0.22 μm was greater than another one. In both membranes, fouling resistance increased over time from 5 × 10⁹ m²/kg to 4.43 × 10¹⁰ m²/kg for 0.22 μm and to 1.29 × 10¹⁰ m²/kg for 0.45 μm after 45 min. This increase had a sharp slope in the first stages of the testing. Fouling index changes over time showed similar behavior. Scanning electron microscopy images showed that the cake layer had the greatest impact on membrane fouling after processing by preventing turbid components from entering pores.     

Pyrolytic carbon coating for cytocompatibility of titanium oxide nanoparticles: a promising candidate for medical applications

Nanoparticles for biomedical use must be cytocompatible with the biological environment that they are exposed to. Current research has focused on the surface functionalization of nanoparticles by using proteins, polymers, thiols and other organic compounds. Here we show that inorganic nanoparticles such as titanium oxide can be coated by pyrolytic carbon (PyC) and that the coating has cytocompatible properties. Pyrolization and condensation of methane formed a thin layer of pyrolytic carbon on the titanium oxide core. The formation of the PyC shell retards coalescence and sintering of the ceramic phase. Our MTT assay shows that the PyC-coated particles are cytocompatible at employed doses.