Razvoj robusnog diskretnog regulatora za silazni pretvarač s dvostrukom frekvencijom preklapanja

A discrete controller is designed for high efficiency double frequency buck converter. This double frequency buck converter is comprised of two buck cells: one works at high frequency, and another works at low frequency. It operates in a way that current in the high frequency switch is diverted through the low frequency switch. Thus, the converter can operate at very high frequency without adding any additional control circuits. Moreover, the switching loss of the converter remains small. The proposed converter exhibits improved steady -- state and transient response with low switching loss. A digital compensator further improves the dynamic performance of the closed loop system. Simulation of digitally controlled double frequency buck converter is performed with MATLAB / Simulink. Experimental results are given to demonstrate the effectiveness of the controller using LabVIEW with a Data Acquisition Card (NI - 9221).Dikretni regulator je projektiran za postizanje visoke efikasnosti silaznog pretvarača s dvostrukom frekvencijom preklapanja. Ovaj silazni pretvarač s dvostrukom frekvencijom preklapanja sastoji se od dvaju ćelija: po jedna za rad na visokim i niskim frekvencijama preklapanja. Regulator funkionira tako da se struja preklapanja na visokim frekvencijama preusmjerava kroz prekidač za preklapanje na niskim frekvencijama. Tako pretvarač može funkcionirati na vrlo visokim frekvencijama bez dodatnih upravljačkih krugova. štoviše, gubici prekidanja pretvarača ostaju mali. Prikazani pretvarač pokazuje poboljšanja kod odzivu u ustaljenom stanju te u prijelaznim pojavama uz male gubitke prilikom prekidanja. Digitalni kompenzator nadalje poboljšava dinamičke performanse sustava u zatvorenom krugu. Simulacije digitalno upravljanog silaznog pretvarača s dvostrukom frekvencijom preklapanja su provedene korištenjem MATLAB / Simulink-a. Eksperimentalni rezultati su prikazani kako bi se demonstrirala efikasnost regulatora korištenjem LabVIEW-a i kartice za prikupljanje podataka (NI - 9221)

Symmetric Multi-Level Boost Inverter with Single DC Source Using Reduced Number of Switches

In this paper a novel multilevel boost DC to DC converter with H-Bridge inverter circuit for single DC source is proposed. The proposed scheme has two stages: the first one is a multilevel boost converter which gives a multilevel dc output for a single dc source and the second level is a H-Bridge converter which converts multilevel DC to multilevel AC at required frequency. This DC-DC converter not only reduces the DC source but also reduces the switches, diodes and capacitors. This leads to decrease of the amount and the inverter space installation in order to increase the required output voltage by increasing the number of capacitors and diodes in the DC to DC converter. Comparison between the number of power switches for the suggested topology and other topologies in the recent literature is presented. Simulation results are conveyed through MatLAB/Simulink domain and the working of the suggested converter is realized

Screening and Anti-Inflammatory Activity of Methanolic and Aqueous Extracts of Seaweed Gracillaria Edulis

Abstract: Seaweeds were collected from coastal area (Mandabam, Tamilnadu, India).Out of 9 species Gracillaria edulis expressed both antimicrobial and anti inflammatory activity. In this study, the aqueous and methanolic extracts of seaweeds were subjected to anti inflammatory activity using experimental animal model,in the presence of the positive control drugs.The inflammation was induced by carrageenan. The aqueous extract of Gracillaria edulis showed highest activity for anti-inflammation. However the methanolic extract did not exhibited any appreciable activity. The aqueous extract of seaweed contains compound may be a novel drug for anti-inflammatory activity

Numerical control of laser processing and simulation of microstructures and temperature profiles - a fuzzy approach

The use of high power density laser beam for surface modification of many important alloys often leads to appreciable changes in the composition & tribological properties. These changes are dependent on process variables such as beam size, energy, scan rate, laser mode and the Chemistry and metallurgy of steel. Appro-ximate solutions to heat flow equations are combined with kinetic models to predict the microstructures and temperature distributions. A transient fuzzy logic based heat flow model is developed to predict temperature zones instead of discrete temperature calculations. A set of separate membership functions are formulated for dete-rmining temperature zones by means of continuous iteration process the same method is adopted to evaluate micro-structures for a specific temperature zone by incorporat-ing the kinetic and thermal datas available. Alloy steel of CK45 grade and stainless steel of 316 grade are used for this investigations and the results obtained are compared with the temperature profiles obtained from conventional methods and hence their microstructures. An attempt is also made to compute the dendrite cell width distribution during laser melt solidification of 316 LN steel by means of the above mentioned method

Intelligent approach on sensorless control of permanent magnet synchronous generator

In this paper, a standalone permanent magnet synchronous generator (PMSG) system is designed to generate power at maximum power point (MPP). The variable speed operation of wind energy conversion system consists of PMSG, controlled rectifier and voltage source inverter co to the load. Proportional integral (PI), sliding mode (SM), and feed forward neural network (FFNN) control strategies are applied in field oriented control (FOC) at generator side converter. A comparative study on power generated at maximum power point (MPP) is done with these controllers using simulation. Hill climb search (HCS) method is applied to attain MPP. Load side inverter control strategy involves the PI and SM controllers in order to maintain the unity power factor and to control the active and reactive power for nonlinear load. The control strategies are modelled and simulated with MATLAB/Simulink. The effectiveness of proposed control method is demonstrated using simulation results

Cotton fibre development: Genes and physiological determinants of fibre length

Cotton fibres, single-celled extensions of the seed epidermis, progress through a series of developmental stages. This review explores fibre developments' genetic and physiological components, focusing on factors that affect fibre length. An attempt has been made to summarize the evolution of cotton species, highlighting the transition from wild to cultivated types and the selection for improved fibre traits. The stages of fibre development–initiation, elongation, secondary wall synthesis and maturation, as well as the roles of specific genes and physiological determinants governing fibre length during these processes, are discussed. The prospects for improving cotton fibre length to meet the industry standards, supported by the wealth of research information generated, are also outlined

Glycerol conversion to 1, 3-Propanediol is enhanced by the expression of a heterologous alcohol dehydrogenase gene in Lactobacillus reuteri

In this work, Lactobacillus reuteri has been metabolically engineered for improving 1, 3-propanediol (1, 3-PD) production by the expression of an Escherichia coli alcohol dehydrogenase, yqhD, that is known to efficiently convert the precursor 3-hydroxypropionaldehyde (3-HPA) to 1, 3-PD. The engineered strain exhibited significantly altered formation rates for the product and other metabolites during the fermentation. An increase in the 1, 3-PD specific productivity of 34% and molar yield by 13% was achieved in the clone, relative to the native strain. A concomitant decrease in the levels of toxic intermediate, 3-HPA, was observed, with the specific productivity levels being 25% lesser than that of the native strain. Interestingly, the recombinant strain exhibited elevated rates of lactate and ethanol formation as well as reduced rate of acetate production, compared to the native strain. The preferential utilization of NADPH by YqhD with a possible decrease in the native 1, 3-PD oxidoreductase (NADH-dependent) activity, could have resulted in the diversion of surplus NADH towards increased lactate and ethanol productivities

Pulsed electric field and combination processing of mango nectar: effect on volatile compounds and HMF formation

Mango nectar is a commercially familiar and preferred product. The traditional processing of mango nectar has been by thermal processing which resulted in the alteration of the flavour of the product due to the effect of high temperature. The thermal processing of the nectar also resulted in the production of byproducts of non-enzymatic browning such as 5- hydroxy methyl furfural (HMF). These process induced effects, affect both the nutritive and sensory attributes of the fruit product, making it less preferable. With the growing interest and awareness about the benefits of alternative non-thermal technologies, such as pulsed electric field (PEF), the present work was proposed to use PEF to minimize the loss of volatiles and formation of HMF. The study involves thermal (96 ºC for 300 s and 600 s), PEF (24 µs, 120 Hz and 38 kV/cm) and combination processing (PEF + Thermal (96 ºC for 90 s)) of mango nectar. The effect of these treatments on the volatile composition of mango nectar has been analysed using GC-MS technique. The reduction in the volatile compounds was significant (p 0.05) different from unprocessed sample, proving the fresh-like character of the product

Epidemiological studies on somatic cell count and subclinical mastitis in buffaloes of Puducherry, India

The present study was conducted to investigate the normal somatic cell count (SCC), associated factors in hygienic management and to define subclinical mastitis in buffaloes in Puducherry. Samples were collected from 50 clinically normal buffaloes stationed at different farms of Puducherry region. Somatic cell count was measured for all the milk samples using Newman-Lampert staining technique. The upper limit of SCC was determined as ≥2, 00,000/ml of milk based on the mean ± 2SD of a total SCC. California mastitis test (CMT) was conducted for all the animals. In the present study subclinical mastitis was diagnosed on the basis of samples with SCCs ≥ 2, 00,000/ml. In the present study 96% of the milk samples were negative for California mastitis test (CMT). The SCC of CMT positive quarter was significantly higher (P<0.01) than CMT negative quarters. Subclinical mastitis was found only in three buffaloes in the present study. Somatic cell counts were significantly higher in the buffaloes with subclinical mastitis. Regarding the hygiene, all the farms had poor management and improper housing. Proper education on hygienic management is need of the hour for buffalo owners of Puducherry region

Synthesis, characterization and anti-microbial screening of novel heterocyclic system containing bridgehead nitrogen atom

ABSTRACT The nicotino hydrazide (1) on reaction with carbon disulphide and ethanolic potassium hydroxide followed by treatment with hydrazine hydrate give 4-amino-5-(pyridin-3-yl)-4H-1,2,4-triazole-3-thiol (3). The compound (3) when treated carbon disulphide in ethanolic potassium hydroxide undergo cycloaddition to produce 3-(pyridin-3-yl)