An Online Calibration System for Digital Input Electricity Meters Based on Improved Nuttall Window

OAPA This paper proposes an improved online calibration technique for digital input electricity meters. The technique employs a double spectral line interpolation fast Fourier transform algorithm with four-item, three-order Nuttall window to reduce the measurement error caused by spectrum leakage, frequency fluctuation, noise pollution and harmonic interference. A calibration system of friendly human-computer interaction is designed using LabVIEW. Simulation and practical results show that the proposed calibration system with improved Nuttall window algorithm is of high accuracy and reliability when compared with the traditional calibration algorithm currently used by industry practice

Doctor of Philosophy

dissertationOil shale is a complex material that is composed of organic matter, mineral matrix and trace amount of bound and/or unbound water. The endothermic decomposition of the organic matter generates liquid and gaseous products. The yield and the desired quality of the product (shale oil) are controlled by the operational conditions. Pyrolysis of a small batch of finely ground oil shale provides chemically controlled intrinsic kinetic rate of organic decomposition. Pyrolysis of large size block/core samples is governed by temperature distributions and the time required for product expulsion. Heat and mass transfer considerations influence the distribution of products and alter the yield and quality. The experimental studies on oil shale pyrolysis performed in this work were designed to understand the relevant coupled phenomena at multiple scales. Oil shale in the Mahogany zone of the Green River formation was used in all experiments. Experiments were conducted at four scales, powdered samples (100 mesh) and core samples of ¾", 1" and 2.5" diameters. Batch, semibatch and continuous flow pyrolysis experiments were designed to study the effect of temperature (300°C to 500°C), heating rate (1°C/min to 10°C/min), pressure (ambient and 500 psi) and size of the sample on product formation. Comprehensive analyses were performed on reactants and products - liquid, gas and spent shale. The activation energies of organic decomposition derived from advanced isoconversional method were in the range of 93 to 245 kJ/mol with an uncertainty of about 10%. Lighter hydrocarbons evolved slightly earlier and their amounts were higher in comparison to heavier hydrocarbons. Higher heating rates generated more alkenes compared to respective alkanes and as the carbon number increased, this ratio decreased. Oil yield decreased and the amount of coke formed increased as the sample size and/or pressure increased. Higher temperature, higher heating rate and low pressure favored more oil yield. The quality of oil improved with an increase in the temperature, pressure and size of the sample. A model in COMSOL multiphysics platform was developed. A general kinetic model was integrated with important physical and chemical phenomena that occur during pyrolysis. The secondary reactions of coking and cracking in the product phase were addressed. The multiscale experimental data generated and the models developed, provide an understanding of the simultaneous effects of chemical kinetics, heat and mass transfers on oil quality and yield. The comprehensive data collected in this study will help advance the move to large scale oil production from the pyrolysis of shale

African cities and collaborative futures

African cities and collaborative futures: Urban platforms and metropolitan logistics brings together scholars from across the globe to discuss the nature of African cities – the interactions of residents with infrastructure, energy, housing, safety and sustainability, seen through local narratives and theories. This groundbreaking collection, drawing on a variety of fields and extensive first-hand research, offers a fresh perspective on some of the most pressing issues confronting urban Africa in the twenty-first century. Each of the chapters, using case studies from Ethiopia, Kenya, Malawi, Niger, Nigeria, South Africa and Tanzania, explores how the rapid growth of African cities is reconfiguring the relationship between urban social life and its built forms. While the most visible transformations in cities today can be seen as infrastructural, these manifestations are cultural as well as material, reflecting the different ways in which the city is rationalised, economised and governed. How can we ‘see like a city’ in twenty-first-century Africa, understanding the urban present to shape its future? This is the central question posed throughout this volume, with a practical focus on how academics, local decision-makers and international practitioners can work together to achieve better outcomes