PROPORTIONAL FEEDBACK CONTROL OF DUTY CYCLE FOR DC HYBRID ACTIVE POWER FILTER

This thesis deals with the design and implementation of a feedback control scheme for a DC Hybrid Active Power Filter used to filter harmonics from a Switched Reluctance Motor (SRM) Drive load. Power electronic systems are non-linear & dynamic [1,3,5]. Power electronic systems employ switching circuits to maximize their efficiency at the penalty that switching circuits generate electrical noise called ripple current and voltage or conducted electromagnetic interference (EMI). The ripple current drawn by the power electronic systems needs to be attenuated to an acceptable level. Filters attenuate this to an acceptable level. Traditionally filters with passive inductors and capacitors are used. Active filters contain switching elements in addition to passive inductors and capacitors which reduce overall size of passive components used. Two control approaches, full-state state space, and plain proportional feedback, are evaluated for this filter. Circuit models are simulated in SPICE and mathematical models are simulated in Matlab/Simulink for evaluating these control approaches. Proportional feedback control was chosen for implementation and the reason for this is provided in the thesis. The active filter was tested with chosen feedback control and experimental results were compared with simulation results. Inferences and scope for further work are finally presented

CONTEMPORARY PERSPECTIVES ON AYURVEDA & CHANGING PARADIGMS

Medical science is advancing by leaps and bounds, exploring the intricacies and unravelling the mysteries of human life. Ever since the dawn of his turbulent history, man has evolved several ways of coping with illness. Every country has developed a medical system presenting a unique configuration designed to be compatible with its future, meeting the needs of its population. Thus the ‘traditional medicine’, which is full of experiences, astute observations and fancy formulae reflecting a combination of inspiration, intuition, information, facts and results, has incarnated.Ayurveda, literally meaning “the science of lifespan”, is the traditional medicine system of India. Its natural healing modality has been in existence for about 5000 years. Ayurveda is widely acknowledged to be the world’s oldest system of healthcare. WHO regards it as “the world’s most ancient, scientific, holistic, complete, natural system of healthcare and is the forerunner of all other great systems practiced today.

Prediction of Electronic Excited States of Adsorbates on Metal Surfaces from First Principles

We present the first ab initio prediction of localized electronic excited states in a periodically infinite condensed phase, a heretofore intractable goal. In particular, we examined local excitations within a CO molecule adsorbed on Pd(111). The calculation allows a configuration interaction treatment of a local region, while its interaction with the extended condensed phase is described via an embedding potential obtained from periodic density functional theory. Our work lays the foundation of a microscopic understanding of photochemistry and spectroscopy on metal surfaces

Experimental determination of the electrical resistivity of beef

 A. K. Mahapatra, B. L. Jones, C. N. Nguyen, G. Kannan(Agricultural Research Station, Fort Valley State University, 1005 State University Drive, Fort Valley, GA 31030, USA) Abstract: Electrical resistivity properties of beef were investigated.  The resistivity behavior under three frequencies of 1, 10 and 100-kHz, different temperatures (5, 10, 15, and 20℃), different length and cross-sectional areas (width: 7 cm, two depths:  3 and 5 cm, and four lengths: 7, 11, 15, and 19 cm) were determined.  The electrical series circuit was found to be adequate to measure the resistivity properties of beef.  Samples with warmer temperatures offered much less resistance and the resistivity values obtained at temperatures 5℃ and below were not consistent.  Increasing temperature had a significant effect on the resistivity values of beef (p<0.05).  Increase in frequency did not have any significant effect on the resistivity properties of beef (p>0.05).  It was observed that resistivity was higher across the myofiber axes than along the myofiber axes.  However, there was no significant difference between the fiber directions in terms of resistivity (p>0.05).  The mean resistivity of beef at 20℃ for across the myofiber and along the myofiber directions was found to be 365.42 Ohms.cm and 346.67 Ohms.cm, respectively.Keywords: electrical resistivity, beef, anisotropy Citation: Mahapatra A. K., B. L. Jones, C. N. Nguyen, and G. Kannan.  Experimental determination of the electrical resistivity of beef.  Agric Eng Int: CIGR Journal, 2010, 12(3): 124-128. &nbsp

Investigation of Micro-indentation Hardness of Bi2Te3 Based Composite Thermoelectric Materials

We have successfully synthesized Bi0.5Sb1.7Te3+x (x = 0, 0.12, 0.14) composite thermoelectric materials via solid state reaction followed by Spark Plasma Sintering (SPS). The structural characterization of these materials carried out by X-ray diffraction reveals to be composite phase consisting of Bi2Te3-type phase with small amount of Te and Sb phase. The micro-hardness performed on samples Bi0.5Sb1.7Te3+x(x = 0, 0.12, 0.14) reveals the reduction of VHN with increasing Te concentration as compared to that of single phase state-of-the-art Bi0.5Sb1.5Te3 thermoelectric materials

Assessment of optical, mechanical and nonlinear properties of potassium acid phthalate single crystal: a potential candidate for optoelectronic applications

A good optical quality semi-organic single crystal of Potassium Acid Phthalate (KAP) was harvested from aqueous solution by using slow evaporation solution growth technique (SEST) at ambient condition. The defect free single crystal of KAP was analyzed by different instrumentation techniques, for checking its compatibility for different applications. Its unit cell dimensions and phase purity was examined by powder X-ray diffraction (PXRD) and found that it crystallizes in orthorhombic with non-centrosymmetric in nature. The quality of the grown ingot was assessed by high resolution X-ray diffraction (HRXRD) technique and found that, the crystalline quality is better with less grain boundaries. Its optical properties were scrutinized by UV-vis., photoluminescence (PL) and time resolved photoluminescence (TRPL) measurements respectively. The mechanical stability of the grown crystal was tested by Vickers microhardness method and found that the grown crystal shows indentation size effect (ISE) which was explained using different theoretical models. Its third order nonlinear optical properties were studied by Z-scan measurement by using Ti:Sapphire laser as a source and determined its nonlinear absorption coefficient (beta) and it was found that the KAP crystal is one of the preferable choices for optical limiting applications

Two-soliton solution for the derivative nonlinear Schr\"odinger equation with nonvanishing boundary conditions

An explicit two-soliton solution for the derivative nonlinear Schr\"odinger equation with nonvanishing boundary conditions is derived, demonstrating details of interactions between two bright solitons, two dark solitons, as well as one bright soliton and one dark soliton. Shifts of soliton positions due to collisions are analytically obtained, which are irrespective of the bright or dark characters of the participating solitons.Comment: 11 pages, 4 figures. Phys. Lett. A 2006 (in press

Hydrogel route to nanotubes of metal oxides and sulfates

A tripodal cholamide-based hydrogel has been employed as a template to synthesize inorganic nanotubes. Besides nanotubes of oxides such as SiO2, TiO2, ZrO2, WO3 and ZnO, nanotubes of sulfates such as the water-soluble ZnSO4 as well as of BaSO4 have been obtained using this method. An advantage of the use of the hydrogel is that metal alkoxides are not required for the synthesis of the oxide nanotubes. The nanotubes have been characterized by X-ray diffraction and transmission electron microscopy