Relay Selection Approach in Underwater Acoustic WSNs Using Bi-Partite Graph

Wireless Personal Communications - In an underwater wireless sensor networks, it is very difficult to communicate data over the 3-D underwater acoustic signal. In acoustic communication, there is...     

Extracellular synthesis of silver nanoparticles using the leaf extract of Coleus amboinicus Lour.

In the present investigation, Coleus amboinicus Lour. leaf extract-mediated green chemistry approach for the synthesis of silver nanoparticles was described. The nanoparticles were characterized by ultraviolet-visible (UV-Vis) spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The influence of leaf extract on the control of size and shape of silver nanoparticles is reported. Upon an increase in the concentration of leaf extract, there was a shift in the shape of nanoparticles from anisotrophic nanostructures like triangle, decahedral and hexagonal to isotrophic spherical nanoparticles. Crystalline nature of fcc structured nanoparticles was confirmed by XRD spectrum with peaks corresponding to (1 1 1), (2 0 0), (2 2 0) and (3 1 1) planes and bright circular spots in the selected-area electron diffraction (SAED). Such environment friendly and sustainable methods are non-toxic, cheap and alternative to hazardous chemical procedures.     

Experimental investigations on polymer-modified concrete subjected to elevated temperatures

This paper presents the effect of elevated temperature and duration of exposures on polymer-modified concrete (PMC). Styrene Butadiene Rubber latex polymer solids were added in terms of 0, 5, 10 and 20 % by mass of cement. Curing of PMC specimen was done by the combination of wet and dry conditions. At appropriate ages, specimens were exposed to 200–800 °C for 1–3 h. The residual compressive strength was tested at 7 and 28 days. Micro structural properties were studied by XRD and SEM analysis. It was found that PMC and conventional concrete can be exposed to 400 °C for 3 h exposure without any adverse effect on strength properties. Addition of 20 % polymer was detrimental to concrete subjected to elevated temperature. Duration of exposure does not have much influence on the residual compressive strength properties of conventional concrete and PMC specimens.     

Experimental investigation on the performance of RC beams strengthened with external bars at soffit

This paper presents the findings of the comprehensive experimental investigation on the use of non-prestressed external reinforcing bars at soffit of the RC beams for enhancing the flexural strength. Based on the encouraging results of the preliminary experimental study conducted by the authors, a comprehensive experimental investigation was carried out by testing 20 numbers of RC beams with varying internal and external bar ratio in order to further explore the viability of this technique. External reinforcing bars technique has already been used by keeping the reinforcement at the sides of the beam using deflectors, mechanical anchoring devices and with strengthening end anchorage zones. The reported technique uses external reinforcing bars at the soffit, which eliminates the need of deflectors, and the anchoring was done by adopting a very simple technique, which eliminates the use of mechanical anchoring devices. The proposed technique is found to be cost effective, easy to execute, enhances moment carrying capacity and effective in deflection and crack control.     

Application of response surface method on machining of Al–SiC nano-composites

The newly fabricated metal matrix nano-composite (MMNC) of Al 7075 reinforced with 1.5 wt% SiC nano-particles was prepared by a novel ultrasonic cavitation method. The high resolution scanning electron micrograph (SEM) and field emission scanning electron micrograph (FESEM) shows uniform distribution and good dispersion of the SiC nanoparticles within the aluminum metal matrix. Electrical discharge machining (EDM) was employed to machine MMNC with copper electrode by adopting face centered central composite design of response surface methodology. Analysis of variance was applied to investigate the influence of process parameters and their interactions. Further a mathematical model has been formulated in order to estimate the machining characteristics. It has been observed that pulse current was found to be the most important factor affecting all the three output parameters such as material removal rate (MRR), electrode wear rate (EWR) and surface roughness (SR). The optimum parameter of combination setting has been identified for the MMNC are voltage 50.00 V, pulse current 8.00 A, Pulse on time 8.00 μs and pulse off time 9.00 μs. Finally the parameters were optimized for maximizing MRR, minimizing EWR and SR using desirability function approach.     

Yttrium dependent space charge effect on modulating the conductivity of barium zirconate electrolyte for solid oxide fuel cell

Development of high proton conducting, chemically stable electrolyte for solid oxide fuel cell application still remains as a major challenge. In this work, yttrium (0, 5, 10, 15 and 20 mol%) doped barium zirconate synthesised by hydrothermal assisted coprecipitation exhibited highly crystalline cubic perovskite. The results demonstrate that the proton conductivity is higher than oxygen ion conductivity measured in the temperature range of 200–600 °C. The 20 mol% Y doped BaZrO₃ exhibited higher protonic conductivity (6.1 mScm^?1) with an activation energy 0.64 eV under the reducing atmosphere. The Mott–Schottky analysis carried out in hydrogen atmosphere at 200 °C revealed that the barrier height of doped BaZrO₃ reduced from 0.6 to 0.2 V. The Schottky depletion layer width also decreased from 4 to 2 nm with the increase in yttrium concentration and the boiling water test showed good phase stability. Our study highlights the critical role of space charge in the grain boundary and its suppression with the increase in dopant concentration. The results demonstrate that Y doped BaZrO₃ sintered at low temperature is a promising candidate as the electrolyte material for the intermediate temperature proton conducting solid oxide fuel cells.     

Start up study of UASB reactor treating press mud for biohydrogen production

Anaerobic digestion of press mud mixed with water for biohydrogen production was performed in continuous fed UASB bioreactor for 120 days. Experiment was conducted by maintaining constant HRT of 30 h and the volume of biohydrogen evolved daily was monitored. Various parameters like COD, VFA, Alkalinity, EC, Volatile solids, pH with respect to biohydrogen production were monitored at regular interval of time. SBPR was 10.98 ml g⁻¹ COD reduced d⁻¹ and 12.77 ml g⁻¹ VS reduced d⁻¹ on peak yield of biohydrogen. COD reduction was above 70 ± 7%. Maximum gas yield was on the 78th day to 2240 ml d⁻¹. The aim of the experiment is to study the startup process of UASB reactor for biohydrogen production by anaerobic fermentation of press mud. The inoculum for the process is cow dung and water digested in anaerobic condition for 30 days with municipal sewage sludge. The study explores the viability of biohydrogen production from press mud which is a renewable form of energy to supplement the global energy crisis.     

Role of Silicon Carbide in Phase-Evolution and Oxidation Behaviors of Pulse Electrodeposited Nickel-Tungsten Coating

Silicon carbide (SiC) was reinforced in the pulse electrodeposited nickel-tungsten (Ni-W) coatings deposited on the steel substrate, and isothermal oxidation test was performed at 1273 K (1000 °C) for 24 hours. Addition of just 2 vol pct of SiC showed 26 pct increase in the relative oxidation resistance of Ni-W coating. The increased oxidation resistance was attributed to the phase evolution (SiO₂, Cr₂O₃, CrSi₂, Ni₂SiO₄, Cr₇C₃, Cr₃C₂, and Cr₃Si), which suppressed the spallation of the oxide scale in Ni-W-2 vol pct SiC. The presence of Fe₂O₃ phase in the oxidized Ni-W coating was mainly responsible for the major multiple spallations at the interface and in the bulk, which resulted in the degradation of oxidation resistance.

     

Phytosynthesis of gold nanoparticles using leaf extract of Coleus amboinicus Lour

Present study reports a green chemistry approach for the biological synthesis of gold nanoparticles by using the leaf extract of Coleus amboinicus Lour. The nanoparticles were structurally characterized by UV–Vis spectroscopy, XRD, TEM and SAED analyses. Elemental and vibrational analyses were done with EDAX and FT–IR spectroscopies respectively. Bioreduction of gold ions by C. amboinicus leaf extract resulted in the synthesis of spherical, truncated triangle, triangle, hexagonal and decahedral nanoparticles. These nanoparticles showed an absorption peak at 536 nm in UV–Vis spectrum corresponding to the plasmon resonance of gold nanoparticles. The size of gold nanoparticles ranged from 4.6 to 55.1 nm. FT–IR spectrum confirmed the involvement of aromatic amines, amide (II) groups and secondary alcohols in capping and reduction of gold nanoparticles. Extracellular synthesis of gold nanoparticles is a simple, cheap and environmentally benign alternative to physical and chemical procedures.     

A study on the bond strength of tension lap splices in self compacting concrete

The primary objective of the research reported in this paper was to evaluate the effect of using self compacting concrete on the bond strength and mode of bond failure of tension lap splices anchored in normal strength concrete (NSC). Studies on the effect of transverse reinforcement on anchored reinforcement in self compacting concrete to prevent brittle mode of failure is limited. To meet this objective, full-scale NSC beam specimens were tested. Each beam was designed with bars spliced in a constant moment region at mid-span with various levels of stirrup confinement. The slip of the reinforcement with respect to concrete is also measured by providing notches at the end of the splices. Test results indicated that there is an increase in the bond strength when self compacting concrete is used in place of vibrated concrete. Ductility and splice strength increased as the confinement increased. When the stirrup spacing is less than 150 mm, the failure in the splice region was by yielding of steel. The influence of confinement on the crack formation of the beams is also reported.