An improved approach to application-specific power electronicseducation-switch characterization and modeling

An integrated power electronics curriculum has been implemented in the Department of Electrical and Computer Engineering at the University of Illinois, Chicago. This paper describes the development of a set of hands-on laboratory experiments to accompany classroom lectures. Content is based on switching converter topologies and commercial power semiconductor devices. Unlike most experiments, which focus on circuit- or control-level characteristics, our approach emphasizes the circuit-device-load interactions. The concept presented is innovative in that it creates a 3×3 matrix of experiment variation-devices, circuits-control, and machines-loads-with one set of hardware. The lab development is ongoing with future experiments to address three-phase converters and motor control applications. Experiment content is described, as well as the means by which the material has been integrated within the course sequence. Lab station construction and safety issues are also addressed. The experiments require hands-on measurement and circuit connection and complement the established course elements of theory and computer-based circuit modeling. Laboratory experiments and computer simulations collectively provide quantitative evidence of mixed circuit and device optimization     

Application of Sequential Learning Neural Networks to Civil Engineering Modeling Problems

A sequential orthogonal approach to the building and training of a single hidden layer neural network is presented in this paper. The Sequential Learning Neural Network (SLNN) model proposed by Zhang and Morris [1]is used in this paper to tackle the common problem encountered by the conventional Feed Forward Neural Network (FFNN) in determining the network structure in the number of hidden layers and the number of hidden neurons in each layer. The procedure starts with a single hidden neuron and sequentially increases in the number of hidden neurons until the model error is sufficiently small. The classical Gram–Schmidt orthogonalization method is used at each step to form a set of orthogonal bases for the space spanned by output vectors of the hidden neurons. In this approach it is possible to determine the necessary number of hidden neurons required. However, for the problems investigated in this paper, one hidden neuron itself is sufficient to achieve the desired accuracy. The neural network architecture has been trained and tested on two practical civil engineering problems – soil classification, and the prediction o strength and workability of high performance concrete.     

On the various stages of spinodal decomposition in an Al-38 at % Zn alloy

Spinodal decomposition of an Al-38 at % Zn alloy in the temperature range 293 to 573 K has been studied by transmission electron microscopy. Microstructural evidences for the existence of various stages of spinodal decomposition, namely, the initial, the corsening and the particulate stages have been established. The morphological characteristics and the different diffusion regimes under which these stages are operative are explained.     

Influence of Coating Parameter and Sintering Atmosphere on the Corrosion Resistance Behavior of Electrophoretically Deposited Composite Coatings

The purpose of this study is to synthesize and characterize nanosized titania (TiO₂), zinc oxide (ZnO), and its composite coating on Ti–6Al–4V to enhance its corrosion protection behavior in Ringer's solution. Nanosized powders of TiO₂ and ZnO was characterized by Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD), and scanning electron microscopy - energy dispersive atomic spectroscopy (SEM-EDAX) analysis. As a result of antibacterial activity, both ZnO and TiO₂/ZnO have produce remarkable inhibition zone on Escherichia coli. The antibacterial activity of composites are due to the combined effect of ZnO on TiO₂. The adherence and surface uniformity of TiO₂/ZnO composite film on titanium implant was examined by optical microscopy and Vickers microhardness test. Corrosion resistant behavior of the coating on titanium implant was investigated by tafel polarization and impedance analysis. The composite coatings on Ti–6Al–4V have produced improved corrosion resistance with a pronounced shift in the anodic corrosion potential (E_corr) with a corresponding less corrosion current density (I_corr) compared to monophase coating. Similar results have been obtained for impedance analysis which indicated a reduction in double layer capacitance (C_dl) and with enhancement in charge transfer resistance (R_ct). These observations suggest improved corrosion resistance property of TiO₂/ZnO composite coating on Ti–6Al–4V.     

Inverted emulsion polymerization route to polyaniline‐3D nanofiber network using sulfonated‐p‐cresol as novel dopant

Sulfonated‐p‐cresol (SPC) was used as novel dopant for the first time in the synthesis of polyaniline in 3D nanofiber networks (PANI‐3D). Polyaniline in 3D nanofiber network was prepared using organic solvent soluble benzoyl peroxide as oxidizing agent in presence of SPC and sodium lauryl sulfate (SLS) surfactant via inverted emulsion polymerization pathway. The influence of synthesis conditions such as the concentration of the reactants, stirring/static condition, and temperature etc., on the properties and formation of polyaniline nanofiber network were investigated. Polyaniline in 3D nanofiber network with 40–160 nm (diameter), high yield (134 wt % with respect to aniline used), and reasonably good conductivity (0.1 S/cm) was obtained in 24 h time. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Performance and emission study in manifold hydrogen injection with diesel as an ignition source for different start of injection

Over the past two decades there has been a considerable effort to develop and introduce alternative transportation fuels to replace conventional fuels, gasoline and diesel. Environmental issues are the principal driving forces behind this effort. To date the bulk of research has focused on the carbon-based fuels such as reformulated gasoline, methanol and natural gas. One alternative fuel to carbon-based fuels is hydrogen which is considered to be low polluting fuel. In the present experimental investigation hydrogen was injected into the intake manifold by using an injector. Using an electronic control unit (ECU) the injection timing and the duration were controlled. From the results it is observed that the optimum injection timing is at gas exchange top dead center (GTDC). The efficiency improved by about 15% with an increase in NO_X emission by 3% compared to diesel. The smoke emission decreased by almost 100%. A net reduction in carbon emissions was also noticed due to the use of hydrogen. By adopting manifold injection technique the hydrogen–diesel dual fuel engine operates smoothly with a significant improvement in performance and reduction in emissions.     

Corrosion behavior of Cr electrodeposited from Cr(VI) and Cr(III)-baths using direct (DCD) and pulse electrodeposition (PED) techniques

A comparison was made between the electrochemical corrosion behaviors of chromium deposited from hexavalent [Cr(VI)] and trivalent [Cr(III)] chromium baths using direct current (DCD) and pulse electro deposited (PED) techniques. Chromium coatings were deposited on mild-steel (MS) substrate. The corrosion behavior of both DCD and PED chromium from Cr(VI) and Cr(III)-baths in 3.5%NaCl solution was studied using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results indicated that PED chromium from Cr(VI) and Cr(III)-baths have higher charge-transfer resistance R_ct and very low I_corr than that of DCD chromium on mild-steel substrate.     

Surface chemistry and adsorption mechanism of cadmium ion on activated carbon derived from Garcinia mangostana shell

A detailed surface characterizations and adsorption mechanism of Cd²⁺ on chemical activated carbon (CAC) prepared from Garnicia mangostana shell were investigated. The activation is accomplished in self-generating atmosphere using phosphoric acid as activating agent. The characterizations performed are elemental analysis, functional group identification, N₂ adsorption isotherm and surface charges. Adsorption mechanism of metal ion was tested using Cd²⁺ as model ion. CAC achieved BET surface area of 1,498 m²/g with a mixture of micro and mesopores. The point of zero charge is observed to be at pH 2.8 and the optimum pH for Cd²⁺ adsorption on CAC is 12. The adsorption isotherm followed the Freundlich model, and the adsorption kinetics was explained by pseudo-second order kinetic model. From thermodynamic studies, the adsorption was found to be physical adsorption. X-ray photoelectron spectroscopy (XPS) confirmed the adsorption of Cd²⁺ onto CAC as +2 oxidation state.     

Thermal stability,morphology, and X-ray diffraction studies of dynamically vulcanized natural rubber/chitosan blends

The thermal degradation behavior of cross-linked Natural Rubber/Chitosan (NR/CS) blends was studied by thermogravimetric analysis (TGA). Dicumyl peroxide (DCP) was selected as a cross-linking agent. Peroxide-cured NR/CS blends exhibit very good overall thermal properties. The activation energy of degradation was analyzed using the Horowitz–Metzger equation. Vulcanization of rubber phase in the blend increased the activation energy. From the activation energy values, it is found that among the series of the blend compositions, NR₈₅CS₁₅ blend vulcanized with 3 pphr DCP exhibits better thermal stability. Better adhesion between the two phases with the incorporation of DCP is achieved which results in an enhancement in the thermal stability. The DSC curve shows that, the T _g of chitosan in the blend increased to 242 °C by dynamic vulcanization. The morphology of the vulcanized blends was studied by scanning electron microscopy. More uniform distribution was exhibited by the vulcanization of NR phase in the blend. X-ray diffraction (XRD) study shows an enhancement in the crystallinity by vulcanization.     

Experimental investigation on a DI dual fuel engine with hydrogen injection

Over the past two decades considerable efforts have been undertaken to develop and introduce new alternative fuels for the conventional gasoline and diesel. Many alternative fuels, both liquid and gaseous, have been experimented and some have even been commercialized such as ethanol, natural gas, etc. Hydrogen has been considered as an excellent fuel to replace the petroleum‐based fuels due to its clean burning characteristics. In the present experimental investigation, hydrogen was injected in the intake manifold and diesel fuel was injected inside the engine cylinder in the conventional manner. Hydrogen injection parameters such as injection timing, injection duration and quantity of hydrogen injected were optimized based on the performance and emission characteristics. Exhaust gas recirculation (EGR) technique was adopted to reduce the oxides of nitrogen emission. From the results it was observed that for hydrogen diesel dual fuel (DF) engine, the optimal operating parameters for hydrogen injection were start of injection at gas exchange top dead centre with injection duration of 30° crank angle with the hydrogen flow rate of 7.5 litres per minute (lpm). With EGR the optimized condition was found to be 20% for the entire load. The brake thermal efficiency with 20% EGR increases by 16% at 75% load as compared with diesel, while at full load it reduces by 8% due to the recirculation of exhaust gases that results in a reduction of intake oxygen concentration compared with part load. NO_X emission decreases by five and half times, while other emissions increase by 1.4 times as compared with DF engine. Copyright © 2008 John Wiley & Sons, Ltd.