Load-sharing system model and its application to the real data set

This study deals with the classical and Bayesian estimation of the parameters of a k-components load-sharing parallel system model in which each component's lifetime follows Lindley distribution. Initially, the failure rate of each of the k components in the system is h(t,θ₁) until the first component failure. However, upon the first failure within the system, the failure rates of the remaining (k − 1) surviving components change to h(t,θ₂) and remain the same until next failure. After second failure, the failure rates of (k − 2) surviving components change to h(t,θ₃) and finally when the (k − 1)th component fails, the failure rate of the last surviving component becomes h(t,θ_k). In classical set up, the maximum likelihood estimates of the load share parameters, system reliability and hazard rate functions along with their standard errors are computed. 100 × (1 − γ)% confidence intervals and two bootstrap confidence intervals for the parameters have also been constructed. Further, by assuming Jeffrey's invariant and gamma priors of the unknown parameters, Bayes estimates along with their posterior standard errors and highest posterior density credible intervals of the parameters are obtained. Markov Chain Monte Carlo technique such as Metropolis–Hastings algorithm has been utilized to generate draws from the posterior densities of the parameters.     

Bayes estimation of the mixture of hazard-rate model

Engineering systems are subject to continuous stresses and shocks which may (or may not) cause a change in the failure pattern of the system with unknown probability q( =1 − p), 0 < p < 1. Conceptualising a mixture of hazard-rate or failure-rate patterns representing a realistic situation, the failure time distribution is given in the corresponding case. Classical and Bayesian estimation of the parameters and reliability characteristics of this failure time distribution is the subject matter of the present study.     

Hydrogenation of Carboxylic Acids and Synergistic Catalysts

Rhenium heptoxide, a known catalyst for hydrogenation of car-boxylic acids to alcohols, forms synergistic combinations with palladium, platinum, rhodium and ruthenium catalysts. This effect is also seen at lower presures (500 psi). Synergism is also mainfest when rhenium and palladium (or rhodium) are used as supported catalysts on silica and used in a flow mode. An interaction of un-known nature between the metals suggests itself. The process is not very efficient at lower pressures giving lower conversion in the flow mode. At higher temperatures needed for higher rates, significant participation of side reactions such as decarboxylation of the acid and hydrogenolysis of the alcohol occurs yielding hydrocarbons.     

Ecotoxicity of as‐synthesised copper nanoparticles on soil bacteria

Release of metallic nanoparticles in soil poses a serious threat to the ecosystem as they can affect the soil properties and impose toxicity on soil microbes that are involved in the biogeochemical cycling. In this work, in vitro ecotoxicity of as‐synthesised copper nanoparticles (CuNPs) on Bacillus subtilis (MTCC No. 441) and Pseudomonas fluorescens (MTCC No. 1749), which are commonly present in soil was investigated. Three sets of colloidal CuNPs with identical physical properties were synthesised by chemical reduction method with per batch yield of 0.2, 0.3 and 0.4 gm. Toxicity of CuNPs against these soil bacteria was investigated by MIC (minimum inhibitory concentration), MBC (minimum bactericidal concentration), cytoplasmic leakage and ROS (reactive oxygen species) assay. MIC of CuNPs were in the range of 35–60 µg/ml and 35–55 µg/ml for B. subtilis and P. fluorescens respectively, while their MBC ranged from 40–70 µg/ml and 40–60 µg/ml respectively. MIC and MBC tests reveal that Gram‐negative P. fluorescens was more sensitive to CuNPs as compared to Gram positive B. subtilis mainly due to the differences in their cell wall structure and composition. CuNPs with smaller hydrodynamic size (11.34 nm) were highly toxic as revealed by MIC, MBC tests, cytoplasmic leakage and ROS assays, which may be due to the higher active surface area of CuNPs and greater membrane penetration. Leakage of cytoplasmic components and generation of extra‐cellular oxidative stress by reactive oxygen species (ROS) causes cell death. The present study realizes in gauging the negative impact of inadvertent release of nanoparticles in the environment, however, in situ experiments to know its overall impact on soil health and soil microflora can help in finding solution to combat ecotoxicity of nanoparticles.     

CORROSION INHIBITION OF MILD STEEL IN 1 N HCL SOLUTION BY MERCAPTO-QUINOLINE SCHIFF BASE

Corrosion inhibition of mild steel in 1 N HCl solutions was investigated in the absence and presence of different concentrations of some mercapto-quinoline derivatives namely, 3-((phenylimino)methyl)quinoline-2-thiol (PMQ) and 3-((5-methylthiazol-2-ylimino)methyl)quinoline-2-thiol (MMQT) by using conventional weight loss, potentiodynamic polarization, linear polarization, electrochemical impedance spectroscopy, and scanning electron microscopic studies. By EIS and weight loss measurements, it was found that PMQ and MMQT were effective inhibitors and their inhibition efficiency was significantly increased with increasing concentrations of inhibitors. Polarization curves showed that the evaluated PMQ and MMQT both act as mixed inhibitions. The adsorptions of these inhibitors on the mild steel were found to follow the Langmuir adsorption isotherm. Results show that the rate of corrosion of mild steel increased with increasing temperature over the range 25°–45°C both in the presence of inhibitors and in their absence. Activation energies in the presence and absence of PMQ and MMQT were obtained.     

Performance and emission study of preheated Jatropha oil on medium capacity diesel engine

Diesel engines have proved its utility in transport, agriculture and power sector. Environmental norms and scared fossil fuel have attracted the attention to switch the energy demand to alternative energy source. Oil derived from Jatropha curcas plant has been considered as a sustainable substitute to diesel fuel. However, use of straight vegetable oil has encountered problem due to its high viscosity. The aim of present work is to reduce the viscosity of oil by heating from exhaust gases before fed to the engine, the study of effects of FIT (fuel inlet temperature) on engine performance and emissions using a dual fuel engine test rig with an appropriately designed shell and tube heat exchanger (with exhaust bypass arrangement). Heat exchanger was operated in such a way that it could give desired FIT. Results show that BTE (brake thermal efficiency) of engine was lower and BSEC (brake specific energy consumption) was higher when the engine was fueled with Jatropha oil as compared to diesel fuel. Increase in fuel inlet temperature resulted in increase of BTE and reduction in BSEC. Emissions of NO_x from Jatropha oil during the experimental range were lower than diesel fuel and it increases with increase in FIT. CO (carbon monoxide), HC (hydrocarbon), CO₂ (carbon dioxide) emissions from Jatropha oil were found higher than diesel fuel. However, with increase in FIT, a downward trend was observed. Thus, by using heat exchanger preheated Jatropha oil can be a good substitute fuel for diesel engine in the near future. Optimal fuel inlet temperature was found to be 80 °C considering the BTE, BSEC and gaseous emissions.     

Experimental investigations on flame stabilization behavior in a diverging micro channel with premixed methane–air mixtures

In the present paper, experimental investigations on the characterization of flame stabilization behavior in a 2.0 mm wide diverging channel are carried out with premixed methane–air mixtures. The effect of mixture equivalence ratio (Ф) and flow rate on flame shape, position, stability and emissions are reported in this work. The diverging portion of channel is preheated from the bottom side with a sintered metal burner to provide a positive temperature gradient along the direction of fluid flow which helps in stabilizing a flame in the channel. For a range of velocities and equivalence ratios, different types of stable and partially stable flame propagation modes were observed. Flames obtained for rich mixtures exhibited more stable nature as compared to lean mixtures. The flame stability limits were observed to vary between 0.2 m/s and 1.9 m/s for a range of mixture equivalence ratios.