Synthesis and characterization of nanoporous silica using dendrimer molecules

A water soluble porogen, e.g., poly(amido amine) dendrimer, has been used as a structure-directing agent to introduce porosity of nanometer scale in silica-based nanocomposite materials. Hydrothermal synthesis was carried out at different elevated temperatures (343-413 K) in a closed teflon-lined stainless steel autoclave under autogenerated pressure. The synthesis time varied from 2 to 6 days, depending upon pH, synthesis temperature, concentration of porogen, etc. X-ray diffraction, transmission and scanning electron microscopic analyses, as well as infrared absorption spectroscopic measurements, were carried out to characterize these materials. Mostly disordered mesostructures were observed. The porous silica particles with sphere-like morphology varied from 30 to 200 nm in size were prepared depending upon the conditions of preparation. The structure and nanoporosity were preserved after the removal of structure-directing porogen through calcination at 823 K. The pore size was in the range of the dendrimer molecule as a template, indicating the structure-directing role of the terminal amino groups in the dendrimer molecule for the synthesis of nanoporous silica, since the nanoporous silica could be prepared by the hydrogen bonding or electrostatic interaction of dendrimer amino groups and tetraethyl orthosilicate.     

Supporting collaborative learning in engineering design

In team-based project courses, collaborative learning is the dominant learning mode. Collaborative learning has been shown to increase individual learning through co-construction and personal reflection. Rapid adoption of web-based communication and mobile computing by students provide opportunities to take advantage of computer-supported collaboration for engineering education. We present preliminary findings on a computer environment, the Kiva Web, that supports the activities of group collaboration for interdisciplinary engineering design teams. We have employed methods from human–computer interaction (HCI) to iterate on the design in the context of use. In this paper, we discuss the evolution of the Kiva Web and the implications for both student design teams and professional design teams.     

Correction to: Benchmarking performance of machine and deep learning-based methodologies for Urdu text document classification

Neural Computing and Applications - The article [Benchmarking performance of machine and deep learning-based methodologies for Urdu text document classification], written by [Muhammad Nabeel Asim,...     

Design of NS3 VLC module and performance analysis of ad hoc network under VLC and Wi‐Fi layers

Visible light communication (VLC) is the branch of optical wireless communications that uses light‐emitting diodes for the dual purpose of illumination and very‐high‐speed data communication. The main motivation behind the current work is finding alternatives to the saturated radio frequency spectrum, radio frequency security issue, and vulnerability to interferences. The current work is aimed at developing a module for the physical layer of a VLC‐based ad hoc network in network simulation 3. The VLC physical layer module is developed by using the optical signal modules available in the network simulator. The work also includes modelling of VLC‐based transmitter, wireless optical channel, and the optical receiver. Furthermore, the implementation and evaluation of the VLC‐based physical layer is carried out over a typical ad hoc network under different performance metrics. The designed ad hoc network is also tested under Wi‐Fi module followed by its comparison with corresponding ad hoc network under VLC module. The comparison is based on bit error rate curves, system throughput, and gain in received signal‐to‐noise ratio mainly. Finally, the suitability of different modulation schemes is also investigated in the current work for both Wi‐Fi– and VLC‐based ad hoc networks.     

Effect of feed spacer arrangement on flow dynamics through spacer filled membranes

Operational issues arising from scaling and fouling of membranes are addressed by pre-treatment processes and alternative membrane or membrane secondary structures. In the present work the flow patterns associated with fluids within the membrane module are investigated using Computational Fluid Dynamics (CFD) tools. The effects on flow patterns through a spacer filled Reverse Osmosis (RO) membrane with the secondary structure of the membranes (feed spacer filaments) at various angles with the inlet flow are analyzed. The presence of the feed spacers in membrane module appears to generate secondary flow patterns enhancing the prospects for self induced backwashing increasing the allowable operational time and membrane efficiency. The flow visualization in the present study is useful in understanding the complex flow patterns generated in spacer filled RO membrane modules and could possibly lead to developing a new RO membrane which is more efficient, economical and appears to be a practically viable solution to reduce costs associated with the maintenance of RO membranes.     

Effects of water absorption on mechanical properties of hemp fiber composites

Effects of water absorption on mechanical properties of hemp fiber composites have been studied. Finite difference method modeling of water absorption in these composites showed the diffusion to be Fickian in nature. The residual tensile and flexural properties showed immediate decline following immersion in water, the loss in modulus being more pronounced than the loss in strength. The fracture of tensile tested composites following immersion in water was found to be more ductile than brittle, which showed the evidence of shear stresses being more significant in these conditions. For impact damaged composites immersed in water, most of the degradation in residual tensile properties occurred within first 100 h of immersion in water at same impact energy level and further immersion in water for up to 400 h did not result in any further degradation. No deterioration in fatigue strength and fatigue sensitivity of composites following immersion in water was observed. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

Effects of alkalization on tensile,impact, and fatigue properties of hemp fiber composites

The effects of alkalization surface treatment on hemp fiber properties and the properties of hemp fiber–reinforced polyester composites have been studied. Hemp fibers were exposed to 1, 5, and 10% sodium hydroxide (NaOH) solutions. The tensile properties and interfacial shear strength of all alkalized fibers were found to lie within the range of nonalkalized fibers. Laminates were made of alkalized fibers with unsaturated polyester resin, using hand lay‐up and compression moulding. Alkalization of fibers at low concentrations of 1 and 5% resulted in improvements in tensile and fatigue properties of composites made from these fibers, but no such improvements were observed for 10% alkalized fiber composites. The improvements were attributed to improvement in fiber/matrix bonding after this treatment, which was also confirmed by scanning electron microscopy images. No improvement in impact damage tolerance was observed for any of these three alkalized fiber composites. Immersion in distilled water reduced water absorption compared with nonalkalized fiber composites; however, the tensile properties in water were similar to those for nonalkalized fiber composites. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Evaluation of the extracellular proteins in full-scale activated sludges

The proteins present in the extracellular polymeric substances (EPS) of activated sludge flocs were investigated using three cation-associated extraction methods. The subproteomes generated from four full-scale activated sludges were subsequently fractionated by ammonium sulfate precipitation and analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The results showed that each extraction method led to unique SDS-PAGE protein profiles, which provided strong evidence that the extracted proteins are uniquely associated with specific cations in activated sludge flocs. The comparison of protein profiles across sludges from different treatment plants revealed that extracts obtained using a cation-exchange resin exhibited similar protein banding patterns while sulfide- and base-extracted EPS led to more variable protein profiles. Analysis of several SDS-PAGE bands by liquid chromatography-tandem mass spectrometry of tryptic digests led to the identification of several bacterial proteins as well as sewage-derived polypeptides (human elastase IIIA and keratins). Their putative roles in activated sludges and their association with targeted cations are proposed.