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: Computer science & Control theory. The organization has 1138 authors who have published 1381 publications receiving 7798 citations.

Quadrature oscillator using operational transresistance amplifier

Abstract: Quadrature oscillator based on the operational transresistance amplifier (OTRA) is presented in this paper. The proposed quadrature oscillator circuit uses two OTRAs as main active building blocks and a few external passive components to generate the oscillations. The circuit provides independent control over the condition of oscillation and frequency of oscillation. A prototype circuit is implemented on a laboratory breadboard using commercially available current feedback operational amplifier ICs (AD844 AN) and passive components are connected externally and tested for waveform generation. Both the SPICE simulation and experimental results are given to verify the theoretical analysis.

Effects of System Design on Fatigue Life of Solder Joints in BGA Packages Under Vibration at Random Frequencies

Abstract: Fatigue life predictions for ball grid arrays (BGA) in electronic devices under random vibration have been made using the finite element method (FEM). Three different circuit board configurations were investigated to determine the best system design for longer fatigue lifetime. Moreover, to reveal the effect of the input frequency, different acceleration power spectral density (PSD) values were applied to the systems. The root-mean-square peeling stress was selected as the failure indicator. FEM results showed that the maximum peeling stress occurred at the outermost corners of solder joints adjacent to the printed circuit board in BGA packages. It was also found that, with increase in the input PSD, solder joints in BGA packages were more exposed to failure. Furthermore, it was revealed that the location of different parts of the system on the board can influence the stress distribution. The results show that a system with a heat sink at the corner of the board, away from the BGA packages, showed the longest fatigue life among the designed configurations.

Performance Analysis of Partition and Evolutionary Clustering Methods on Various Cluster Validation Criteria

Abstract: Large quantity of data has been accumulating tremendously due to digitalization. But the accumulated data are not converted into useful patterns. This gap is conquered by using exploratory data analysis techniques. Clustering is one of the vital technologies in exploratory data analysis. It is a methodology to arrange data objects as per their characteristics. Traditional clustering approaches, namely leader, K-means, ISODATA and evolutionary-based approaches like genetic algorithm, particle swarm optimization, social group optimization methods, are also implemented on benchmark data set. Evolutionary-based clustering methods are derived from the existing hard clustering methods for finding optimal results. Performance analysis of the above clustering techniques should be validated through different cluster validation methods. The performance analysis reveals evolutionary clustering methods convergence rate is better than partition clustering methods. ISODATA performs better in various aspects on large data. In this work analyzed performance of hard and evolutionary clustering methods on execution time, internal cluster validity criteria.