Investigation of thermal conductivity and rheological properties of nanofluids containing graphene nanoplatelets

In the present study, stable homogeneous graphene nanoplatelet (GNP) nanofluids were prepared without any surfactant by high-power ultrasonic (probe) dispersion of GNPs in distilled water. The concentrations of nanofluids were maintained at 0.025, 0.05, 0.075, and 0.1 wt.% for three different specific surface areas of 300, 500, and 750 m²/g. Transmission electron microscopy image shows that the suspensions are homogeneous and most of the materials have been well dispersed. The stability of nanofluid was investigated using a UV-visible spectrophotometer in a time span of 600 h, and zeta potential after dispersion had been investigated to elucidate its role on dispersion characteristics. The rheological properties of GNP nanofluids approach Newtonian and non-Newtonian behaviors where viscosity decreases linearly with the rise of temperature. The thermal conductivity results show that the dispersed nanoparticles can always enhance the thermal conductivity of the base fluid, and the highest enhancement was obtained to be 27.64% in the concentration of 0.1 wt.% of GNPs with a specific surface area of 750 m²/g. Electrical conductivity of the GNP nanofluids shows a significant enhancement by dispersion of GNPs in distilled water. This novel type of nanofluids shows outstanding potential for replacements as advanced heat transfer fluids in medium temperature applications including solar collectors and heat exchanger systems.     

Highly‐Cyclable Room‐Temperature Phosphorene Polymer Electrolyte Composites for Li Metal Batteries

Despite significant interest toward solid‐state electrolytes owing to their superior safety in comparison to liquid‐based electrolytes, sluggish ion diffusion and high interfacial resistance limit their application in durable and high‐power density batteries. Here, a novel quasi‐solid Li⁺ ion conductive nanocomposite polymer electrolyte containing black phosphorous (BP) nanosheets is reported. The developed electrolyte is successfully cycled against Li metal (over 550 h cycling) at 1 mA cm^?2 at room temperature. The cycling overpotential is dropped by 75% in comparison to BP‐free polymer composite electrolyte indicating lower interfacial resistance at the electrode/electrolyte interfaces. Molecular dynamics simulations reveal that the coordination number of Li⁺ ions around (trifluoromethanesulfonyl)imide (TFSI^?) pairs and ethylene‐oxide chains decreases at the Li metal/electrolyte interface, which facilitates the Li⁺ transport through the polymer host. Density functional theory calculations confirm that the adsorption of the LiTFSI molecules at the BP surface leads to the weakening of N and Li atomic bonding and enhances the dissociation of Li⁺ ions. This work offers a new potential mechanism to tune the bulk and interfacial ionic conductivity of solid‐state electrolytes that may lead to a new generation of lithium polymer batteries with high ionic conduction kinetics and stable long‐life cycling.     

Effects of Ageing on Selected Cooking Quality Parameters of Rice

Ageing can improve cooking quality of rice by influencing major cooking quality parameters i.e., kernel expansion, water absorption, alkali digestion value, and gelatinization temperature along with changes in internal structure of rice grains. In this research, the effects of natural and artificial ageing on the selected cooking quality parameters of two Malaysian rice cultivars, named Mahsuri and Puteri, were studied. A relation was observed between water absorption and elongation ratio in both varieties under different aging conditions. Alkali digestion value and gelatinization temperature were also influenced by varieties and ageing conditions. This study revealed the potentiality of ageing for the improvement of rice cooking quality.     

Kernel elongation in rice

Kernel elongation after cooking is an important character of fine rice and most rice consumers prefer length‐wise elongation. Although improvement of aromatic rice began early in the 1970s, until now the mechanisms and genetics of kernel elongation has remained unrevealed. Kernel elongation is considered as a physical phenomenon and is influenced by several physicochemical and genetic factors, including genotypes, aging temperature, aging time, water uptake, amylose content and gelatinization temperature. Recently the complete genetic map of fine rice has been created and the gene responsible for kernel length identified; moreover, this gene is tightly linked with the cooked kernel elongation trait. Several molecular markers linked with cooked kernel elongation have been developed. These tools will be helpful for the improvement of this important trait. For the proper study of cooked kernel elongation of rice, this review paper will provide the basis and directional materials for further studies.© 2012 Society of Chemical Industry     

Aluminum-based composites reinforced with SiC particles and NiTi fibers: influence of fiber dimensions and aging time on mechanical properties

NiTi short fiber and SiC particle reinforced 6061 Al alloy composites have been prepared by pressure-assisted induction heating method in ambient atmosphere. Two different composites with significant difference in NiTi fiber diameter (127 and 51 μm) have been prepared. It is found that 51-μm NiTi fibers are better bonded with the Al matrix; de-bonding has seldom been observed. There is better microstructural compatibility, i.e., fiber diameter is of the same order as the Al matrix grain size for this case. However, when 127-μm NiTi fibers are used, de-bonding and “pull-out” mechanism can be frequently observed. Aging effect on the properties of the composite has also been investigated. TEM and EDS experiments indicate that there is no evidence that the bonding of NiTi/Al is affected by either aging or size of NiTi fiber.     

Processing and structural optimization of PEEK composites

The objective of this experimental program was to understand how changes in processing conditions affect the morphology and ultimately, the performance of polyetheretherketone (PEEK)-based carbon fiber composites. Based on some initial differential scanning calorimetry (DSC) work, various molding and aging conditions were implemented on compression molded plaques made from PEEK APC-2 prepreg. These conditions included samples that were physically aged, annealed just below the melting point, slow cooled, prepared under low pressure, and under fast cooling. Using DSC, the crystallinity of plaques prepared according to the ICI procedure, low pressure, and physical aging conditions were found to be 31–33 percent, while the slow cooling and annealing conditions resulted in crystallinity of 42 percent, with slow cooling displaying a „shoulder”︁ on the primary melting endotherm. Optical and plasma etching/scanning electron microscopy on faster cooled plaques generally revealed a mixture of isolated and graphite fiber nucleated spherulites, while the slow-cooled condition revealed larger fiber nucleated spherulites exclusively. Fracture toughness and impact delamination as measured by ultrasonic C-scan indicates that slow cooling resulted in the lowest properties, while simultaneously resulting in the highest compression strength, all of which suggests reduced matrix toughness. The annealing condition, which allowed high crystallinity but in a matrix of smaller spherulites, resulted in properties intermediate between slow and fast cooling, suggesting that both spherulite size and degree of crystallinity are important in characterizing these materials. In contrast, physical aging resulted in no degradation in mechanical properties.     

Electricity consumption and economic growth nexus in Bangladesh: Revisited evidences

In this paper, an attempt is being made to examine the causal relationship between per capita electricity consumption and per capita GDP of Bangladesh using the vector error correction specified Granger causality test to search their short-run, long-run and joint causal relationships for the period of 1971–2008. Empirical findings reveal that there is a short-run unidirectional causal flow running from per capita electricity consumption to per capita GDP without feedback. The presence of a positive short-run causality explains that an increase in electricity consumption directly affects economic activity in Bangladesh. Likewise, results from joint causality exhibit the same as in short-run. By contrast, long-run results show a bi-directional causality running from electricity consumption to economic growth with feedback. These findings can provide essential policy insights to design immediate and long-term growth prospect for Bangladesh keeping in mind its present planned growth strategy and dismal power and energy sector.     

Intraoperative radiofrequency microbipolar coagulation to replace incisions of maze III procedure for correcting atrial fibrillation in patients with rheumatic valvular disease

The objective of this study was to determine the transcellular metabolism of leukotriene A4 by rabbit blood cells. mixed peripheral blood leukocyte preparations with and without platelets in a ratio of 1:40 were challenged with the Ca(2+)-ionophore A23187. 5-Lipoxygenase metabolites production was assessed by RP-HPLC coupled with diode-array UV detection. In light of the observation that leukotriene C4 production in leukocyte-platelet coincubation was the same as with leukocytes alone, mixed coincubation of human and rabbit blood cells was tested. Rabbit leukocytes with human platelets resulted in a significant increase of leukotriene C4 production, while no changes were observed in human leukocytes with or without rabbit platelets. In agreement with these results, intact rabbit platelets or rabbit platelet lysates, unlike human platelets, were not able to convert synthetic leukotriene A4 free acid to leukotriene C4. These data provide evidence that rabbit leukocytes are able to make a significant amount of leukotriene A4 available for transcellular metabolism, while rabbit platelets, unlike human platelets, lack leukotriene C4-synthase activity.     

Adaptive Delay-Aware Energy Efficient TDM-PON

Passive Optical Networks (PONs) are widely adopted as the last-mile technology due to the large bandwidth capacity it provides to end users. In addition, PON is viewed as a green access technology since it reduces energy consumption compared to other access technologies (e.g. Fiber to the Node). However, there is still room for enhancing the energy efficiency of PON further, and we can find many attempts along those lines in academia and industry. A widely used approach to save energy in Time Division Multiplexing (TDM)-PON is to keep the Optical Network Units (ONUs) in sleep mode when they do not have anything to receive or transmit. However, sleep intervals have a direct negative impact on increasing traffic delay. Therefore, energy efficiency in a TDM-PON presents a clear trade-off: the longer an ONU sleeps, the less energy it consumes, but the higher the delay experienced by the downlink traffic, and vice versa. In this paper, we propose an Adaptive Delay-Aware Energy Efficient (ADAEE) TDM-PON solution. The ADAEE aims at saving as much energy as possible while meeting the PON access delay restrictions imposed by the operator. We evaluate our solution in terms of energy consumption and delay performance using real traffic traces. The results demonstrate that the proposed solution can meet delay requirements while being more energy efficient solution compared to the existing solutions.     

Voice transmission over ad hoc network adapting optimum approaches to maximize the performance

Although a lot of research and implementations have been performed for voice transmission over regular network and internet, a little is done for mobile ad hoc network (MANET). Like other computer networks, in MANET voice transmission is also very much demanding and necessary. Since the wireless links in an ad hoc network are highly error prone and may go down frequently because of node mobility, interference, channel fading, and the lack of infrastructure, it is very difficult and challenging to implement voice transmission over MANET. In this research, to maximize the performance of MANET during voice transmission we choose some parameters and methodological approaches e.g. Method of media access, selection of audio codec, selection of routing protocol etc in efficient and optimum way. Since voice applications consume more energy than typical applications, we use an energy aware routing protocol known as WEAC for the study. During the selection process of routing protocol we have a performance comparison study between Improved DSR and WEAC, where WEAC performs better consuming less energy in case of larger network. We also have a comparative study among several audio codecs (G.711, G.729 and G.723.1) where by simulation we show that the G.729 codec is more suitable to use for voice transmission over MANET in terms of latency. Finally, we show that it is possible to launch voice transmission with acceptable quality and throughput over MANET using G.729 and WEAC protocol.