Effect of Post Heat Treatment on Corrosion Resistance of Phytic Acid Conversion Coated Magnesium

An environment friendly chemical conversion coating for magnesium was obtained by using a phytic acid solution. The effect of post-coating 1heat treatment on the microstructures and corrosion properties of phytic acid conversion coated magnesium was investigated. It was observed that the microstructure and corrosion resistive properties were improved for the heat treated samples. The corrosion current density for bare magnesium, phytic acid conversion coated magnesium, and post-coating heat treated magnesium was calculated to be 2.48×105 , 1.18×106 , and 9.27×107 A/cm2 , respectively. The lowest corrosion current density for the heat treated sample indicated its highest corrosion resistive effect for the magnesium. The maximum corrosion protective nature of the heat treated sample was further confirmed by the largest value of impedance in electrochemical impedance spectroscopy studies.     

Energy and exergy analysis of a 747-MW combined cycle power plant Guddu

ABSTRACT

The paper presents a detailed study based on the energy and exergy analysis of a combined cycle power plant (CCPP) Guddu having triple pressure heat recovery steam generator (HRSG). The energy loss and the energy efficiency of each plant component with HRSG as a whole is calculated. The exergy destruction of these components and the sub-parts of the HRSG are also found out. All the three stages of the steam turbine are analysed individually. The combustion chamber is found to have the maximum share of exergy destruction while the condenser is having a maximum of energy loss. The total net power output, energy and exergy efficiency of the whole plant is calculated as 737.8?MW, 59.12% and 58.24%, respectively. The error in getting the designed power output of 747?MW is 3.16%. The thermal efficiency of the Brayton and Rankine cycle is 62.01% and 56.38%, respectively.     

Forecasting of daily air quality index in Delhi

As the impact of air pollutants on human health through ambient air address much attention in recent years, the air quality forecasting in terms of air pollution parameters becomes an important topic in environmental science. The Air Quality Index (AQI) can be estimated through a formula, based on comprehensive assessment of concentration of air pollutants, which can be used by government agencies to characterize the status of air quality at a given location. The present study aims to develop forecasting model for predicting daily AQI, which can be used as a basis of decision making processes. Firstly, the AQI has been estimated through a method used by US Environmental Protection Agency (USEPA) for different criteria pollutants as Respirable Suspended Particulate Matter (RSPM), Sulfur dioxide (SO₂), Nitrogen dioxide (NO₂) and Suspended Particulate Matter (SPM). However, the sub-index and breakpoint concentrations in the formula are made according to Indian National Ambient Air Quality Standard. Secondly, the daily AQI for each season is forecasted through three statistical models namely time series auto regressive integrated moving average (ARIMA) (model 1), principal component regression (PCR) (model 2) and combination of both (model 3) in Delhi. The performance of all three models are evaluated with the help of observed concentrations of pollutants, which reflects that model 3 agrees well with observed values, as compared to the values of model 1 and model 2. The same is supported by the statistical parameters also. The significance of meteorological parameters of model 3 has been assessed through principal component analysis (PCA), which indicates that daily rainfall, station level pressure, daily mean temperature, wind direction index are maximum explained in summer, monsoon, post-monsoon and winter respectively. Further, the variation of AQI during the weekends (holidays) and weekdays are found negligible. Therefore all the days of week are accounted same in the models.     

Mechanical and bond properties of coconut shell concrete

The properties of concrete using coconut shell as coarse aggregate were investigated in an experimental study. Compressive, flexural, splitting tensile strengths, impact resistance and bond strength were measured and compared with the theoretical values as recommended by the standards. For the selected mix, two different water–cement ratios have been considered to study the effect on the flexural and splitting tensile strengths and impact resistance of coconut shell concrete. The bond properties were determined through pull-out test. Coconut shell concrete can be classified under structural lightweight concrete. The results showed that the experimental bond strength of coconut shell concrete is much higher than the bond strength as estimated by BS 8110 and IS 456:2000 for the mix selected.     

Chrome ore beneficiation challenges & opportunities - A review

Supply of world chromite (chrome ore) has come under severe pressure over the past year driven by strong demand for ferrochrome used in ferroalloy production for making stainless steel. Many of the strategic minerals are inputs into products in fast-changing markets. This article reviews the major process flow sheets in practice for the recovery of chromite values from various types of ores and critical issues related to chromite ore beneficiation. The comprehensive condensation of pertinent facts is intended to provide a single reference source rather than the reader perusing many articles. Emphasis is placed on different processes developed in identifying and solving critical plant problems.     

Context-driven mean residual life estimation of mining machinery

Maintenance is crucial to ensure production/output and customer satisfaction in the mining sector. The cost of maintenance of mechanised and automated mining systems is very high, necessitating efforts to enhance the effectiveness of maintenance systems and organisation. For effective maintenance planning, it is important to have a good understanding of the reliability and availability characteristics of the systems. Determining the Mean Residual Life (MRL) of systems allows organisations to more effectively plan maintenance tasks. In this paper, we use a statistical approach to estimate MRL and consider a Weibull proportional hazard model (PHM) with time-independent covariates to model the hazard function so that the operating environment could be integrated into the reliability analysis. The paper explains our methods for calculating the conditional reliability function and computing the MRL as a function of the current conditions. The model is verified and validated using data from the hydraulic system of LHD equipment in a Swedish mine. The results are useful to estimate the remaining useful life of such systems; the method can be used for maintenance planning, helping to control unplanned stoppages of highly mechanised and automated systems.     

Synthesis of non-Gaussian wind pressure time series on low building roofs

This paper presents an efficient and practical method for the digital generation of univariate non-Gaussian wind pressure time series on low building roofs. The method, based on the Fast Fourier Transform (FFT) approach, essentially inverts the Fourier coefficients which are a linear combination of Fourier amplitude and phase. In this study, the Fourier amplitude part is assumed to be known. The Fourier phase capable of inducing non-normality to the time series is carefully modelled and a simple stochastic model with a single parameter is suggested for its simulation. The computation of this single parameter is accomplished by minimizing the sum of the squared errors in higher order statistics such as skewness and kurtosis. The simplicity and effectiveness of this methodology have been demonstrated using several measured non-Gaussian pressure data from various low building roofs under different conditions.     

Miscibility of chitosan–hydroxyethylcellulose blends in aqueous acetic acid solutions at 35°C

The miscibility of blends of chitosan and hydroxyethylcellulose in a 2% acetic acid solution was studied by viscometry, densitometry, and refractometry at 35°C. The data suggest that the blends were completely miscible in all proportions. Further, the membranes were fabricated from concentrated blend solutions. The solid‐state compatibility of the blends was confirmed by scanning electron microscopy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1996–1998, 2005