Vignan University

About: Vignan University is a education organization based out in Guntur, Andhra Pradesh, India. It is known for research contribution in the topics: Control theory & CMOS. The organization has 1138 authors who have published 1381 publications receiving 7798 citations.

A Novel Switching Sequence for Asymmetrical 15-Level Packed U Cell Inverter Topology with Improved Total Harmonic Distortion

Abstract: Multilevel inverters (MLIs) have a major drawback of a utilizing more number of power semiconductor components (PSC), switching losses, increasing of voltage stress on the switches while going for higher level generations. In this work, drawbacks of conventional MLI topologies have been overcome through an advanced MLI topology called packed U cell (PUC). PUC-15 level MLI topology is developed by using lesser number of PSC, so that losses and voltage stress on switch is less when compared to conventional topologies. In this article, the novel switching sequence of PUC-15 topology is developed. It controls the switching stress due to its random switching operation. The PUC-15 switching sequence is controlled by using advanced sawtooth carrier- and triangular carrier- based multi-carrier sinusoidal pulse width modulation. The functionality of novel switching sequence and PWM techniques are confirmed via simulations, and results are compared in terms of total harmonic distortion (THD) at disparate modulation indexes. The measured FFT analysis of %THD is lesser than 5% which is under IEEE-519 standard for both voltage and current.

Characterization of electrospun polyurethane/polyacrylonitrile nanofiber for protective textiles

Abstract: A system of polyurethane (PU) and polyacrylonitrile (PAN) with a polymer composition of 60:40 electrospun nanofibrous web has been developed as barriers to pesticides liquid (Dimethoate) penetration in protective clothing systems for agricultural workers. Barrier performance of different polymer compositions of PU and PAN layered systems has been evaluated with different areal densities of electrospun web ranging from 0.5 to 3 g/m2. This was done to improve the barrier performance of a nanofiber against a pesticide liquid. In this process, an ultra-thin layer of PU and PAN has been taken in the ratio of 60:40 and its top it is coated with polyvinylidene fluoride (PVDF). Application of PU and PAN web with PVDF and PU has significantly improved its effectiveness which has been measured when accessing the overall comfort performance of a nanofiber which includes parameters like air permeability and water vapor transmission within a layered system. Further, it is observed that the electrospun areal density has been altered due to the effect of air permeability and because of the penetration of the pesticide liquid. On other hand, the polymer compositions also affect the air permeability and rate of penetration of pesticides. It was observed that the electrospun web area has a massive impact on a web area density which reduces a pore size distribution when web area increases. Increasing the percentage of polyacrylonitrile with thermoplastic polyurethane the penetration is reduced without affecting the moisture vapor transition and which had a significant effect on air permeability. Hence PU and PAN along with PVDF nanofibrous mat have a prospective application in agro-textile industries.

A high slew rate, low voltage CMOS class-AB amplifier

Abstract: A simple low voltage operational amplifier is introduced with an efficient class-AB output stage. Two biasing transistors are present in between common source stage. This amplifier is simulated in 0.18 µm CMOS technology. The proposed class-AB amplifier is designed to operate from ±500 mV supplies. The simulated phase margin of proposed class-AB amplifier is 87° at the load of 10 kΩ∥1 pF. The class-AB amplifier's total compensation capacitance is 5 pF, which is less than 50% of conventional amplifiers. The unity gain frequency of proposed class-AB amplifier is 21.17 MHz, when driving a resistive load from 10 kΩ to 500 kΩ and capacitive loads from 1 pF to 5 pF. The slew rates of modified amplifier are 7.5 V/µs and 8.57 V/µs. This modified amplifier greatly increases the slew rate compared to the conventional circuits.

Hybrid membrane process: an emerging and promising technique toward industrial wastewater treatment

Abstract: Over the past decade, essential requisite for fresh water has been potentially intensified along with the rapid growth of the world’s population and rapid industrialization. Industrial wastewaters are complex water, which contains numerous verities of compounds such as heavy metals, salts, different nutrients, cyanides, and dyes is increasing globally and needs to be concentrated as this will lead to water scarcity as well as water quality. The lack of freshwater has therefore strengthened activities toward the upgradation of existing water treatment processes and to develop advanced techniques to treat, purify, recycle, and reuse water sustainably. Different traditional techniques viz. adsorption, coagulation, biological treatment, and oxidation have been used toward the treatment of wastewater but they each have some limitations. Membrane separation techniques have become one of the promising and emerging technologies for wastewater treatment due to their discrete advantages over traditional methods. The main disadvantage of membrane technologies is membrane fouling, which decreases the membrane permeate flux and separation efficiency. This present book chapter focuses on the hybrid or integrated approach to increase the treatment efficiency and overcome the shortcoming of single membrane separation techniques. This chapter provide the knowledge on hybrid membrane techniques and huge potential toward the removal of waste effluent from industrial wastewater.