High Thermal Conductivity Polymer Composites Fabrication through Conventional and 3D Printing Processes: State-of-the-Art and Future Trends

The lifespan and the performance of flexible electronic devices and components are affected by the large accumulation of heat, and this problem must be addressed by thermally conductive polymer composite films. Therefore, the need for the development of high thermal conductivity nanocomposites has a strong role in various applications. In this article, the effect of different particle reinforcements such as single and hybrid form, coated and uncoated particles, and chemically treated particles on the thermal conductivity of various polymers are reviewed and the mechanism behind the improvement of the required properties are discussed. Furthermore, the role of manufacturing processes such as injection molding, compression molding, and 3D printing techniques in the production of high thermal conductivity polymer composites is detailed. Finally, the potential for future research is discussed, which can help researchers to work on the thermal properties enhancement for polymeric materials.     

A review on conversion of triglycerides to on‐specification diesel fuels without additional inputs

Dependence on fossil fuels for global energy supply has continued to generate concerns about climate change and sustainable development. It has motivated the search for carbon‐neutral alternative resources for the production of transportation fuels to replace crude oil. Although biodiesels have recently emerged as a close substitute to petrol diesel, their use in compression ignition engines designed to run on petro‐diesel fuels are linked to adverse effects on the engines' performance and life span. This informed efforts at upgrading biodiesel or direct conversion of triglycerides to hydrocarbon mixtures that are identical or similar to that of petro‐diesel through hydrodeoxygenation. Moreover, it seems that commercial methods for the conversion of triglycerides to diesel fuels depends on inputs (methanol and hydrogen) derived from fossil fuels. However, it will be desirable to do so without inputs from fossil fuels. Hence, reaction paths for direct conversion of triglycerides to on‐specification hydrocarbons fuels without hydrogen gas input are discussed and suggested strategies are in cognisance of green chemistry principles. Copyright © 2012 John Wiley & Sons, Ltd.     

Efficient solutions to various routing issues involved in mobile ad hoc bio-sensor networks: applying appropriate motion trajectories

Ad hoc bio-sensor networks have a very characteristic structure with three types of nodes: the command centre, the sensor nodes (animals such as rats) and the relaying nodes. We have taken up such networks and measured the throughput of such systems and suggest ways in which the throughput can be increased. It was also found that to increase the throughput of such systems, no sophisticated routing techniques or expensive transmission techniques are needed. This can be achieved by simply adopting the appropriate motion trajectories of the nodes. We have also explained the structure of these networks in detail and the routing issues involved in these networks. A Hot-Spot problem at the command centre has also been discussed. The suggestions of appropriate motions target this problem and show how an even distribution of nodes can alleviate this problem to a large extent. In addition to this, a constraint on the number of messages the sensor node can send per unit time can also make the network more efficient.     

Evaluation of the Effectiveness of Water Management Policies in Bangladesh

Water resources development and management policies initiatives in Bangladesh are primarily driven by the need for sufficient food grain production for the country's teeming population and curtailing the perennial flooding problems. It is therefore necessary to investigate whether or not these objectives are being met. The aim of this study is to evaluate the impacts of past water resources development and management strategies on agriculture, food security, flood management and socio-economic development in Bangladesh. The research is based on the historical data of the relevant parameters of the water resources management over the period 1947–2005. The outcomes of the study demonstrate that past policies and strategies of water development have resulted in significant irrigation expansion, especially through intensified groundwater utilization, which has helped to achieve the country's primary objective of self-sufficiency in food production. However, the provision of safe drinking water and sanitation facilities still remains a challenge in the country. Similarly, the impact of the flood control policies was diverse with success mostly apparent with regard to protection against modest events, while catastrophic, extreme events still effectively defying answer.     

Spinel-Coated Graphite for Carbon Containing Refractory Castables

Oxidation resistance and water wettability of graphite flakes have been improved by a thin sol–gel film of magnesium aluminate spinel (MgAl₂O₄) over its surface. The hydrosol has been synthesized by less expensive precursors and the spinel formation has been studied by scanning electron microscopy (SEM), supplemented with energy dispersive spectral analysis. After an easy-to-use mixing procedure, drying (110°C), and subsequent calcination (550°C), coated graphites were sieved to below 75 μm. The coating over the powder contained 1.5 wt% MgAl₂O₄, which enormously increased the oxidation resistance (performed at 600°, 900°, and 1200°C) and water wettability, as revealed by hydrophilic functional groups from infrared spectra. Defective, intermediate spinel structure of fine, lamellar Mg-doped γ-Al₂O₃ has been considered to be significant for this improvement. An approximate (1:2) stoichiometry of (Mg:Al) in the coating composition was confirmed by an X-ray photoelectron spectroscopy test. Castables prepared by this graphite remarkably improved their bulk density and apparent porosity compared with those prepared by the as-received graphite. Casting water was reduced along with the amount of antioxidants. This also enhanced the resistance toward the basic slag by retaining the graphite in the refractory.     

Toughening of bone cement using nanoparticle: The effect of solvent

Drawbacks of poly(methyl methacrylate) (PMMA)‐based bone cement as a grouting agent for in vivo fixation of orthopedic and dental implants such as considerable low mechanical strength have been improved using nanotechnology. Bone cement‐layered silicate nanocomposites have been prepared without any heat treatment in the presence of polar (dimethyl formamide, DMF) and nonpolar (benzene) solvents. Solvents have been removed completely from the bone cement after its preparation. Nanostructure is very much dependent on the solvent used for nanocomposite preparation, and benzene‐based nanocomposites are highly intercalated, whereas DMF‐based nanocomposites do not exhibit intercalation. Thermal stability of bone cement has improved in the presence of nanoclays. The relative enhanced interaction in case of benzene‐based nanocomposites has been shown through FTIR and UV–vis studies. The significant improvement in modulus and toughness of bone cement has been demonstrated in the presence of minimum amount of nanoclay for benzene‐based nanocomposites, whereas no change in modulus and reduced toughness have been observed for DMF‐based nanocomposites. The decrease of contact angle has been witnessed with increasing nanoclay concentration indicating better hydrophilic materials suitable for biomedical applications for greater cell growth. The reason for varying property enhancement in different solvents has been discussed considering the polarity effect and interactions. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Toward Optimal Network Fault Correction in Externally Managed Overlay Networks

We consider an end-to-end approach of inferring probabilistic data forwarding failures in an externally managed overlay network, where overlay nodes are independently operated by various administrative domains. Our optimization goal is to minimize the expected cost of correcting (i.e., diagnosing and repairing) all faulty overlay nodes that cannot properly deliver data. Instead of first checking the most likely faulty nodes as in conventional fault localization problems, we prove that an optimal strategy should start with checking one of the candidate nodes, which are identified based on a potential function that we develop. We propose several efficient heuristics for inferring the best node to be checked in large-scale networks. By extensive simulation, we show that we can infer the best node in at least 95 percent of time, and that first checking the candidate nodes rather than the most likely faulty nodes can decrease the checking cost of correcting all faulty nodes.     

Screening selected strains of probiotic lactic acid bacteria for their ability to produce biogenic amines (histamine and tyramine)

The aim of this study was to investigate the production of biogenic amines (BA), histamine and tyramine by some probiotic lactic acid bacteria (LAB). Fifteen strains representing six LAB species were screened qualitatively by growing them in a decarboxylase medium. Quantitative analysis was carried out by HPLC analysis with direct derivatization of acid extracts. Lactobacillus casei (TISTR 389) and Lactobacillus delbrueckii subsp. bulgaricus (TISTR 895) were found to produce BA. The highest levels of histamine (1820.9 ± 3.5 mg L^?1) and tyramine (5486.99 ± 47.6 mg L^?1) formation were observed for the TISTR 389 strain, while TISTR 895 produced only histamine (459.1 ± 0.63 mg L^?1) in the decarboxylase broth. Biogenic amine potential was not observed for the Lactobacillus acidophilus, Lactobacillus lactis subsp. lactis, Lactococcus lactis subsp. lactis, and Lactobacillus plantarum strains studied. This study confirmed that BA formation is strain dependent and not related to the species. Therefore, careful screening for amino acid decarboxylase activity is recommended before selecting LAB as appropriate starter or probiotic strains in food and dairy industry.