Water Soluble Polymer Flocculants: Synthesis,Characterization, and Performance Assessment

Water soluble polymer flocculants are important constituents of solid–liquid separation units for the treatment of a variety of process‐affected effluents. The systematic development of a flocculant relies on a good understanding of flocculation process, polymer synthesis, polymer characterization, and, not the least, flocculation performance assessment as desired for a particular treatment process, all of which are essential to establish meaningful relationships between flocculant microstructure and flocculation efficiency. The aim of this article is to communicate the bigger picture of this research area to the readers. The recent advances in the application of bio/natural, synthetic, and stimuli‐responsive flocculants are reviewed. Then, the basic polymer reaction engineering tools to control the microstructure of flocculants are provided and the techniques for the quantification of flocculant microstructure are concisely discussed. This is followed by a review of the methods used for the characterization of particle‐polymer force measurement, and flocculation/dewatering assessment with attention to the characterization of aggregate structures.     

The effect of anisotropy on wrinkling of tube under rotary draw bending

Rotary draw tube bending is one of the most complex tube forming processes subject to different process parameters such as material properties and geometry. This process is being practiced in more and more applications in industry due to its high efficiency, high forming precision and quality. However, improper process parameters can lead to wrinkling which restrict the thin walled tube bending. Therefore, the prediction and prevention of wrinkling is very important. Despite its importance, the effect of anisotropy on the occurrence of wrinkling was not considered in the literature up to now. In this investigation, a quantitative study on the wrinkling of thin walled tube bending is carried out through a finite element model of the process using velocity integral parameter, which is used for the detection of wrinkles. The other methods usually warn the wrinkling initiation with no precise location prediction. In addition, the effects of some process parameters, specially normal and planar anisotropy on the tube wrinkling are investigated. It is shown that increasing normal and planar anisotropy (increasing r0 and r90 values) result in a decrease in tube wrinkling.     

Throughput improvement by mode selection in hybrid duplex wireless networks

Wireless Networks - Hybrid duplex wireless networks, use half duplex (HD) as well as full duplex (FD) modes to utilize the advantages of both technologies. This paper tries to determine the...     

Relations between transformational leadership, organizational learning, knowledge management, organizational innovation, and organizational performance: an empirical investigation of manufacturing firms

The aim of this study is to determine relations between transformational leadership, organizational learning, knowledge management, organizational innovation, and organizational performance among Iranian manufacturing companies through structural equation modeling. Two hundred eighty senior, executive, administrative, and other-level managers are selected from among 106 companies having more than 50 employees. Data are analyzed using structural equation modeling. The following findings are found: transformational leadership directly influenced organizational learning and knowledge management. Organizational learning directly and positively influenced knowledge management of manufacturing firms. Transformational leadership positively influenced organizational innovation and organizational performance of manufacturing firms. Organizational learning and knowledge management directly influenced organizational innovation; whereas organizational learning and organizational innovation directly influenced organizational performance among manufacturing firms. Meanwhile, transformational leadership positively and indirectly influenced organizational innovation through organizational learning and knowledge management. Knowledge management and organizational learning effected organizational performance indirectly by organizational innovation. The fit indices shows that the proposed model have an appropriate fit (χ ²/df?=?2.33, RMSEA?=?0.069, NFI?=?0.95, NNFI?=?0.95, CFI?=?97). If leaders of manufacturing firms undertake a transformational role and use organizational learning and knowledge management, this will facilitate organizational innovation and will consequently improve organizational performance to a great extent in manufacturing firms.     

Clarification of tomato juice by cross‐flow microfiltration

Clarification of fruit and vegetable juice is one of the integrated parts of modern industrial juice processing. This paper describes the clarification of tomato juice through microfiltration process. In this regard, the influence of transmembrane pressure (1, 2 and 3 bar), cross‐flow velocity which corresponds with Reynolds number (300, 1500 and 2500) and temperature (30, 40 and 50 °C) on permeate flux and some properties of clarified juice such as colour, turbidity, density, viscosity, pH and total soluble solid have been studied. The results revealed that the investigated parameters had an increasing effect on the permeate flux and colour and the greatest effect on the permeate flux and colour was supplied by cross‐flow velocity. The other permeate properties did not significantly change with variations of the operating parameters. Eventually, the statistical analysis indicated that the interactional effect of cross‐flow velocity and TMP on the permeate flux was significant.     

Three-dimensional macro/mesoporosity developments in polydimethylsiloxane

Macro/mesoporous polydimethylsiloxanes (PDMS) were prepared with the purpose of vascular grafts. Oligoester-containing semi-interpenetrating polymer networks (semi-IPNs) can be used as precursors for generation of networks with tunable pore sizes. Novel poly(methyl methacrylate)/PDMS semi-IPNs were prepared by varying structural parameters. Extraction of uncrosslinked oligoester subchains from semi-IPNs was investigated. To tailor the morphology of porous structure, influence of some factors including porogen type, different polymerization conditions, monomer type, and concentration, crosslinking agent concentration were studied. PDMS networks were examined by field emission scanning electron microscopy. A uniform porous structure with interconnected pores was detected in horizontal and vertical cross sections of PDMS.     

Adsorptive removal of petroleum hydrocarbons from aqueous solutions by novel zinc oxide nanoparticles grafted with polymers

Zinc oxide nanoparticles were synthesized and modified by a three-stage method. Elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning and transmission electron microscopy, and Brunauer–Emmett–Teller method were applied to characterize the nanoparticles. These nanoparticles were evaluated for toluene adsorption from aqueous solutions as a representative of petroleum hydrocarbon removal. The optimum adsorption condition achieved at pH of 6 and contact time of 30 min. The adsorption isotherms were fitted to the Langmuir model. The measured adsorption capacity was 12.8 mg g^?1. This study demonstrated that these nanoparticles could be used as an effective adsorbent for petroleum hydrocarbon removal.     

Equilibrium,kinetic and isotherm of some metal ion biosorption

Trichoderma reesei was used as a biosorbent for the removal of Co²⁺, Cu²⁺, Ni²⁺, Pb²⁺ and Zn²⁺ ions. The influence of factors such as pH, mass of biomass, contact time and temperature on biosorption efficiency was optimized. To calculate the isotherm parameters for the biosorption of Co²⁺, Cu²⁺, Ni²⁺, Pb²⁺ and Zn²⁺ ions at optimized conditions, the experimental equilibrium data were fitted to Langmuir and Freundlich models. The calculated thermodynamic parameters, ΔG°, ΔH° and ΔS° showed that the biosorption of Co²⁺, Cu²⁺, Ni²⁺, Pb²⁺ and Zn²⁺ ions onto T. reesei biomass was feasible, spontaneous and endothermic at the optimized conditions. The results of kinetic analysis showed that the biosorption of the selected metal ions onto T. reesei biomass obeys pseudo second order kinetics.     

The impacts of tomato residuum extract with Arabic gum and dill essential oil on the shelf life improvement of trout fillets stored at chilly condition

The objective of this study was to evaluate the effects of tomato residuum extract (TRE) dipping and Arabic gum (AG) coating enriched with dill essential oil (DEO) on the shelf life extension of refrigerated trout fillets. Gas chromatography/mass spectrometry analysis revealed that the main constituents of DEO were alpha-phellandrene (30.17%), limonene (28.31%), and carvone (21.31%). Antioxidant activities of acetone, ethanol, methanol, cold, and hot water extracts of tomato residuum were examined using reducing power and 2,2-azinobis-3-ethylbenzothiazoline-6-sulphonic acid assays in maceration, ultrasound, and combined ultrasound and maceration extraction methods. The strongest antioxidant activities were found in the ultrasound-assisted extraction with ethanol 50%. Thiobarbituric acid, total volatile basic nitrogen, and peroxide values indicated that TRE 3%–AG–DEO 2% and TRE 6%–AG–DEO 2% treatments could significantly (p ≤ .05) extend the shelf life of the fillets. Also, sensory evaluation showed that TRE along with DEO had significant (p ≤ .05) pleasant effects on the sensory characteristics of the fillets. It was concluded that TRE dipping along with AG coating containing DEO could be a suitable alternative for the synthetic preservative in the refrigerated trout fillets.