Carbon nanotube-textured sand for controlling bioavailability of contaminated sediments

Sand particles textured with multi-walled carbon nanotubes (MWCNTs) can efficiently control the mobility and bioavailability of contaminants found in aquatic sediments. Adsorption measurements for a wide variety of aquatic contaminants (chlorinated hydrocarbons) on MWCNT-textured sand showed orders of magnitude increase in their sorption coefficients compared to traditional materials (sand) when used for physically separating contaminated sediments from overlying water. Molecular dynamics simulations performed on model experimental systems emphasize that the hydrophobic interactions of the MWCNT surfaces play a crucial role in driving the water molecules away, promoting such enhanced contaminant uptake. The MWCNT-textured sand significantly reduced the migration of contaminants from sediments to overlying water and possesses suitable parameters needed for contaminant sequestration and sediment remediation technologies. The single step and scalable procedure described here for synthesizing robust MWCNT-textured sand surfaces will provide important improvements in the field of remediation/aquatic environment restoration technologies.     

High frequency electromagnetism, heat transfer and fluid flow coupling in ANSYS multiphysics.

The goal of this study was to numerically predict the temperature of a liquid product heated in a continuous-flow focused microwave system by coupling high frequency electromagnetism, heat transfer, and fluid flow in ANSYS Multiphysics. The developed model was used to determine the temperature change in water processed in a 915 MHz microwave unit, under steady-state conditions. The influence of the flow rates on the temperature distribution in the liquid was assessed. Results showed that the average temperature of water increased from 25 degrees C to 34 degrees C at 2 l/min, and to 42 degrees C at 1 l/min. The highest temperature regions were found in the liquid near the center of the tube, followed by progressively lower temperature regions as the radial distance from the center increased, and finally followed by a slightly higher temperature region near the tube's wall corresponding to the energy distribution given by the Mathieu function. The energy distribution resulted in a similar temperature pattern, with the highest temperatures close to the center of the tube and lower at the walls. The presented ANSYS Multiphysics model can be easily improved to account for complex boundary conditions, phase change, temperature dependent properties, and non-Newtonian flows, which makes for an objective of future studies.     

Capacity of wireless networks under SINR interference constraints

A fundamental problem in wireless networks is to estimate their throughput capacity—given a set of wireless nodes and a set of connections, what is the maximum rate at which data can be sent on these connections. Most of the research in this direction has focused either on random distributions of points, or has assumed simple graph-based models for wireless interference. In this paper, we study the capacity estimation problem using a realistic Signal to Interference Plus Noise Ratio (SINR) model for interference, on arbitrary wireless networks without any assumptions on node distributions. The problem becomes much more challenging for this setting, because of the non-locality of the SINR model. Recent work by Moscibroda et al. (IEEE INFOCOM 2006, ACM MobiHoc 2006) has shown that the throughput achieved by using SINR models can differ significantly from that obtained by using graph-based models. In this work, we develop polynomial time algorithms to provably approximate the throughput capacity of wireless network under the SINR model.     

RF energy harvesting systems: An overview and design issues

One of the main challenges in implementing sensor devices for internet of things (IoTs), is the means for the operating power supply. RF energy harvesting (RFEH) presents a promising solution as RF power is a suitable choice particularly for cases where solar harvesting is not feasible. However, in spite of RF communication system design being a well‐established, there are several challenges poised for the implementation of the RFEH systems especially for harvesting the ambient RF signals. The challenges can be widely categorized as the overall conversion efficiency, bandwidth, and form factor. In this article, an exhaustive survey on the different RFEH system that is reported is carried out and discussed. Important design issues are identified with insights drawn. First, we have presented the challenges in designing antennas for RFEH systems. This is followed by rectifier circuits and matching networks, and eventually a general frame work for designing of ambient RFEH systems is deduced.     

Hybrid edge-based fractal image encoding using K-NN search

Multimedia Tools and Applications - A hybrid algorithm is proposed for edge-based image encoding using a fractal paradigm. This algorithm exercises spatial domain adaptive techniques on a fractal...     

Standalone and ensemble-based machine learning techniques for particle Froude number prediction in a sewer system

Neural Computing and Applications - The hydraulic capacity of a channel is impacted due to sediment deposition in urban drainage and sewer system. As a result, the self-cleansing mechanism is a...     

Study of Solubility Efficiency of Polycyclic Aromatic Hydrocarbons in Single Surfactant Systems

Water solubility enhancements of two polycyclic aromatic hydrocarbons i.e., naphthalene (Naph) and anthracene (Anth) in single surfactants system have been measured by UV–VIS-Spectrophotometer. The relationships between solubilizing capacity and their solubilization efficiency towards polycyclic aromatic hydrocarbons (PAH) have been quantified and discussed in terms of the molar solubilization ratio (MSR), the micelle-water partition coefficient (K _m) and standard free energy of solubilization (ΔG°_s). The micellar and surface properties of some cationic and anionic surfactants have been investigated by conductivity, surface tension and fluorescence measurements at 300 K. Above the CMC, maximum solubilization occurs in cationic surfactants where as the solubilization is least in the presence of anionic surfactants. The negative value of ΔG°_s shows spontaneity of the solubilization process. The MSR values are larger in naphthalene than anthracene (Naph > Anth). The present studies provide valuable information for the selection of surfactants for solubilizing water-insoluble compounds.     

Manganese recovery from secondary resources: a green process for carbothermal reduction and leaching of manganese bearing hazardous waste

During the hydrometallurgical extraction of zinc by electrowinning process, a hazardous solid waste called anode mud is generated. It contains large quantity of manganese oxides (55-80%) and lead dioxide (6-16%). Due to the presence of a large quantity of lead, the anode mud waste is considered hazardous and has to be disposed of in secure landfills, which is costly, wastes available manganese and valuable land resources. For recovery of manganese content of anode mud, a process comprising of carbothermal treatment using low density oil (LDO) followed by sulphuric acid leaching is developed.     

Fly ash-supported cerium triflate as an active recyclable solid acid catalyst for Friedel–Crafts acylation reaction

An efficient solid Lewis acid, has been synthesized by loading cerium triflate (7 wt%) on the acid activated fly ash with high silica content (81%). The physico-chemical properties of synthesized fly ash-supported cerium triflate catalyst (CFT) were monitored by XRD, FT-IR spectroscopy, FT-IR spectroscopy of the ammonia adsorbed catalyst, SEM-EDAX, TEM, Flame Atomic Absorption Spectrophotometer and TG-DTA study. The increased concentration of silica surface hydroxyl groups on activated fly ash have a major influence on the loading of cerium triflate. The catalytic activity of the catalyst CFT was tested in the acylation of veratrole using acetic anhydride as the acylating agent. The proposed model structure of CFT shows that the triflate species withdraws the electron density from the surface cerium making it electron deficit and generate Lewis acidity on the surface of fly ash as confirmed by NH₃ adsorbed FT-IR spectrum. The activity data indicate that this heterogeneous catalyst is very active, corresponding to high conversion (88%) of veratrole to 3,4-dimethoxyacetophenone. The catalyst could be easily recovered and reused giving similar conversion up to three reaction cycles indicating its stability under experimental conditions. Thus fly ash-supported cerium triflate is a novel and efficient catalyst and is a promising way of bulk utilization of waste fly ash by developing cost effective catalyst system for industrially important Friedel–Crafts acylation reactions.     

Evaluating Cell Disruption Strategies for Aqueous Lipid Extraction from Oleaginous Scenedesmus obliquus at High Solid Loadings

Among various renewable energy sources, the production of biofuels derived from algal lipids holds bright prospects. One of the major roadblocks in the successful commercialization of microalgal biofuels is the existing energy‐intensive lipid extraction. In the present investigation, an attempt is made to assess aqueous lipid extraction strategies from oleaginous Scenedesmus obliquus at a high solid loading of 15% (w/v). In this study, four surfactants and five enzymes are evaluated for cell disruption of S. obliquus. It is the first report citing cetyl pyridinium bromide as the most suitable cationic detergent for surfactant‐assisted extraction, with a lipid recovery as high as 31.4%. However, during the evaluation of enzyme‐based cell disruption, neutral protease emerges as the best biocatalyst resulting in a lipid recovery of ≈75%. Total lipid extraction is accomplished using a two solvent system comprising of water‐immiscible ethyl acetate, followed by chloroform addition. The study revalidates the fact that the biochemical composition of Scenedesmus sp. plays a vital role while identifying and formulating an efficient and green process for microalgal cell disruption for enhanced lipid extraction under aqueous conditions. Practical Applications: The results of the present study demonstrate that if the biochemical composition of any oleaginous algal cell wall is known, aqueous enzymatic lipid extraction can be employed rather than taking up the conventional route of drying followed by Soxhlet extraction. The combination of using the cheap sources of enzymes and water‐immiscible green solvents like ethyl acetate can be lucrative downstream procedures for the lipid recovery from wet algal biomass when compared to traditional procedures.