Analysis of harmonics using wavelet technique

This paper develops an approach based on wavelet technique for the estimation of harmonic presents in power system signals. The proposed technique divides the power system signals into different frequency sub-bands corresponding to the odd harmonic components of the signal. The algorithm helps to determine both the time and frequency information from the harmonic frequency bands. The comparative study will be done with the input and the results attained from the wavelet transform (WT) for different conditions and Simulation results are given

P A STAGNATION POINT FLOW OVER A STRETCHING SHEET WITH NEWTONIAN HEATING USING LAPLACE ADOMIAN DECOMPOSITION METHOD

Abstract: Our aim in this piece of work is to demonstrate the power of Laplace Adomian decomposition method in approximating the solution of nonlinear differential equations governing stagnation point flow over a stretching sheet with Newtonian heating

Implementation of Low-Cost Direct Torque Control Algorithm for Induction Motor without AC Phase Current Sensors

ABSTRACT: This paper presents a novel low -cost and simple phase-current reconstruction algorithm for three-phase induction motor (IM) under direct torque Control (DTC) using the information obtained from only one shunt resistor (in series with low side switches in a conventional three -phase inverter). The main objective is to develop a low -cost high-performance IM drive. The proposed algorithm is robust and very simple. It uses the dc current to reconstruct the stator currents needed to estimate the motor flux and the electromagnetic torque. A theoretical concept is developed, the modified look -up table is presented and current -access tables are designed and used in the phase-current reconstruction. The limitations are also studied and presented. Simulation results are given to prove the ability of the proposed scheme of reproducing the performances of a traditional DTC IM drive. KEYWORDS: Direct torque control (DTC), Induction motor (IM), sensor count reduction, single current sensor. I.INTRODUCTION Direct torque control (DTC) of induction motors has gained popularity in industrial applications mainly due to its simple control structure from its first introduction in 1986. An electric motor drive controlled with the DTC technique exhibits performance similar to a field oriented drive despite a simpler structure. In fact, a DTC scheme achieves the closed-loop control of the motor stator flux and the Electromagnetic torque without using any current loop or shaft sensor. Many researchers are interested in this control technique because of its wide area applications used with various ac machine types as induction motor, PMSM, PM Brushless, and reluctance motor. The DTC scheme requires information about the stator currents and the dc -link voltage, which is used with the inverter, switches states, to estimate the values of stator flux and electromagnetic torque. The current feedback for the closed -loop control is usually obtained by sensing instantaneous phase currents by current sensors. In general, galvanically isolated current sensors such as Hall Effect sensors and current transducers are widely used in many applications. They are typically used on, at least, two outputs of the power inverter to provide current feedback signals. Such a kind of sensors performs well, but brings disadvantages to the overall drive system in terms of cost, Encumbrance and somehow nonlinearity. Recently, single current sensor operation has been proposed to reconstruct phase currents from the DC link current sensor. In this way, various approaches have been proposed in the literature. Some methods adjust the pulse -width modulation (PWM) signals to ensure that two-phase currents can be sampled in each control period. Other strategies introduce modifications of the modulation algorithm in order to guarantee the reliability of the measurements from the dc -link current sensors under all the operating conditions. Other interesting approaches are based on the estimation of the motor phase currents using prediction-correction algorithms, thus introducing additional computational burden to the drive system. Only a few papers deal with the DTC technique for induction motor and PMSM. The algorithm used in these works operates in two stages. First, it predicts the stator currents from a model of the motor and then adjusts the prediction on the basis of the sensed dc -link current. This algorithm requires an additional computation burden and the knowledge of the stator transient inductance. In this paper

PHENOTYPIC AND GENOTYPIC CHARACTERIZATION OF FLUOROQUINOLONE DRUG RESISTANCE AMONG STAPHYLOCOCCUS AUREUS IN A TERTIARY CARE HOSPITAL

Objective: The objective of the study was to determine whether recent use of topical fluoroquinolones is a risk factor for in vitro fluoroquinolone resistance in Staphylococcus aureus ocular isolates. Fluoroquinolone antibiotics such as ciprofloxacin (CIP) are useful drugs against infections caused by Staphylococcus aureus and mutations in deoxyribonucleic acid (DNA) gyrase which control bacterial DNA topology, can be one of the reasons of occurrence resistance to this class of antibiotics. Therefore, finding new mutations and study of the quinolone interaction with mutated GyrA can provide important issues for explanation resistance. Methods: Bacterial identification was confirmed by appropriate morphological, cultural, and biochemical tests. The antibiotic susceptibility pattern was determined for all isolates. The possible involvement of efflux pumps in mediating fluoroquinolone resistance as well as changes in the quinolone resistance-determining region (QRDR) of gyrA gene was investigated. Results: Differences in methicillin resistance among staphylococci were observed based on patient age, with higher rates observed in older patients (p<0.0001). Out of 91 isolates, 77 (84.61%) were resistant to CIP and 47 (51.65%) were resistant to ofloxacin (OF). Confirmation with agar dilution test showed that 57 samples were resistant to CIP, 38 samples were resistant to OF, and 29 samples were resistant to both CIP and OF. By polymerase chain reaction (PCR) testing, gyrA genes in resistance strains were amplified. All the five resistant isolates were found to be positive for the presence of a fluoroquinolones resistance gene (gyrA gene) and the two sensitive isolates were found to be negative. Resistance among CIP and OF in isolated harboring a mutation GyrA was of statistical significance among S. aureus (p<0.001). Conclusion: The result of this study will be useful to update the antibiotic policy in our hospital set up and controlling the irrational use of antibiotics among health care workers. The information obtained will provide a baseline data that can be used to design further research for prevention of drug resistance caused by Staphylococcus aureus