Corrosion Inhibition of Mild Steel in Aqueous HCl using Bitter Leaf and Fenugreek Seed Oils

Protection of Metals and Physical Chemistry of Surfaces - Bitter leaf and Fenugreek seed oils were extracted from their parent seed plants for use as corrosion inhibitors for mild steel in HCl....     

The effect of cognitive and affective aspects on usability

Studies on customer’s needs, desires and preferences have become highly important in the product design and development process. One consideration in usability is the cognitive aspect, which is related to the accommodation and evaluation of human cognitive capabilities, limitations and tendencies. In addition to the cognitive aspect, a recent study has shown that the affective aspect has been considered in the evaluation of product usability. Thus, both cognitive and affective aspects are deemed to be important for product design and the development process. Inherently, both aspects deliver complete human and product interaction and experience. However, studies that consider the affective process as a complement to the cognitive process for usability are relatively rare. To address this gap, this study discusses how an integrative framework of the cognitive and affective aspects can be applied to a product for usability assessment via empirical studies on e-commerce and e-learning platforms. The sample involved 230 respondents, using purposive sampling. The result shows that both cognitive and affective aspects have a significant effect, although with different weights. The affective aspect has been shown to improve product usability and user’s acceptance.     

Metasurface based pattern reconfigurable antenna for 2.45 GHz ISM band applications

In this article, a Z‐shaped antenna is designed for 2.45 GHz ISM band applications. The proposed antenna is surrounded by metasurface‐based unit cells. The unit cells are designed to reflect for the proposed frequency. Each of this unit cells are activated with the help of a diode. Unit cell is considered active by switching on the diode of respective unit cell. According to the activation of unit cell the pattern of the antenna will be reconfigured. The 2.45 GHz ISM band pattern reconfigurable microstrip antenna is presented. The radiation pattern of the antenna can be steered toward a desired direction by activating appropriate metasurface unit cell, minimizing the interference and optimizing medium usage. The proposed antenna performance is presented with the help of reflection coefficient and the pattern steerable capability by activating metasurface unit cells. The proposed antenna is having azimuth‐pattern reconfigurable capability around 360°.     

Bidirectional energy storage photovoltaic grid-connected inverter application system

A novel topology of the bidirectional energy storage photovoltaic grid-connected inverter was proposed to reduce the negative impact of the photovoltaic grid-connected system on the grid caused by environmental instability. Using the proposed Inverter as a UPS power supply in case of a grid failure, storage electrical energy and regulating the energy delivered to the grid for reducing the pressure on the grid. A new artificial fish-swarm algorithm and variable step voltage perturbation method were presented to track the maximum power point of the solar panels. Analysis was done to reduce the output ripple of the inverter and sinusoidal pulse width modulation (SPWM) was selected to control the inverter. Model simulation was performed using PSpice software to obtain the volt-ampere characteristic curve of the solar panel output. The solar array simulator was used to verify the effect of maximum power point tracking at different light intensities. The study concludes that the maximum power point tracking (MPPT) efficiency of the bidirectional energy storage photovoltaic grid-connected inverter designed was as high as 99.9%. The distortion rate of the grid-connected current waveform was within 2% and the DC current component was less than 0.5%. The output voltage and power were in full compliance with the grid connection standard.     

Wind characteristics and energy potential assessment in Akure,South West Nigeria: econometrics and policy implications

This paper analysed 11 years of daily mean wind-speed data, measured at Akure, Ondo State, Nigeria, using Weibull and Rayleigh distribution functions. While both distributions showed good agreements in extreme-value estimation patterns, investigation of their wind-speed characteristics modelling criteria, using goodness-of-fit statistics, revealed that the wind data followed the Weibull more than Rayleigh. Monthly wind-speed of Akure city ranged from 1.41 to 4.24 m/s by the Weibull fittings and from 1.40 to 4.16 m/s by the Rayleigh fittings. Overall results, of 2.71 m/s (Weibull) or 2.70 m/s (Rayleigh) mean wind-speed and 18.51 W/m² (Weibull) or 22.26 W/m² (Rayleigh) mean power density, indicated Akure a low wind-speed site, requiring low wind-speed turbine for generating wind energy. Econometric analyses of power output simulations using such turbine system resulted in affordable wind energy cost. These bear policy implications for sustainable wind energy usage in this and similar regions of the world.     

Statistical method‐based calibration and validation of a solid oxide fuel cell model

A 2‐stage model validation strategy for the previously developed solid oxide fuel cell model using the data from custom‐designed experiments is presented. The strategy is based on the identification of model structural and parametric errors. In the preliminary validation, the causes that can result in the voltage error during changing temperature and fuel flow rate conditions are analysed. It is identified that the convection heat transfer process contributes significantly towards the cell performance in a temperature controlled test environment. Rectification of this error results in the reduction of the maximum voltage error from 14% to 0.5%. Graphical methods for data visualisation are utilised to examine goodness of fit of the model. Input sensitivity analysis reveals that the air flow rate has negligible influence on the output quantities of current density, fuel utilisation, and cell temperature owing to temperature‐controlled conditions of the test. Parameter sensitivity analysis through the elementary effects method reveals that most of the electrochemical parameters in general and the activation energies in particular have dominant effects on the considered system outputs. Model validation is carried out through a classical statistical method of hypothesis testing by using the parameter uncertainty information obtained through nonlinear least squares fitting. The efficacy of the model validation strategy is demonstrated through the model acceptance with 8% maximum error in cell current.     

Influence of substrate temperature on crystalline copper aluminium oxide thin films synthesized through chemical spray pyrolysis (CSP) technique

Copper aluminium oxide (CuAlO₂) of well ordered crystalline films were deposited on to glass substrates with Cu/Al ratio r = 0.8 at the substrate temperatures of 250, 300, 350, 400 and 450 °C. Films which were characterized had a thickness of the order of few micrometers. Films deposited at the optimized deposition temperature (450 °C) revealed well-crystalline CuAlO₂ phase with XRD peak at 2θ = 31.7° corresponds to (006) reflection. The peak positions of the core level XPS spectra, confirm the presence of delafossite CuAlO₂ phase. The optical transmission of 80 % has been observed in the visible spectrum. The obtained band gap energy is 4.1 eV. From the observed results it was evidenced that the substrate temperature has strong influence on the structural and optical properties of the spray pyrolysed copper aluminium oxide films.