Optimal Pattern Synthesis of Linear Antenna Array Using Grey Wolf Optimization Algorithm

The aim of this paper is to introduce the grey wolf optimization (GWO) algorithm to the electromagnetics and antenna community. GWO is a new nature-inspired metaheuristic algorithm inspired by the social hierarchy and hunting behavior of grey wolves. It has potential to exhibit high performance in solving not only unconstrained but also constrained optimization problems. In this work, GWO has been applied to linear antenna arrays for optimal pattern synthesis in the following ways: by optimizing the antenna positions while assuming uniform excitation and by optimizing the antenna current amplitudes while assuming spacing and phase as that of uniform array. GWO is used to achieve an array pattern with minimum side lobe level (SLL) along with null placement in the specified directions. GWO is also applied for the minimization of the first side lobe nearest to the main beam (near side lobe). Various examples are presented that illustrate the application of GWO for linear array optimization and, subsequently, the results are validated by benchmarking with results obtained using other state-of-the-art nature-inspired evolutionary algorithms. The results suggest that optimization of linear antenna arrays using GWO provides considerable enhancements compared to the uniform array and the synthesis obtained from other optimization techniques

Students' Preferences Between Blackboard Teaching and PowerPoint Presentations: A Cross-Sectional Survey

INTRODUCTION: With evolution of technology, teachers have, or are shifting to various methods other that blackboard teaching (e.g. PowerPoint, Over Head Projectors, Integrated Learning, Online Apps, etc)AIM: To assess students’ Preferences between blackboard teaching and PowerPoint Presentations among different university students in the city of Melbourne, AustraliaMATERIALS AND METHOD: Data was collected using a pre-tested and pre-validated questionnaire and distributed online to students studying in various Universities in Melbourne, Australia. Statistical tests involved the Shapiro-Wilk test, Independent samples t-test, multivariate linear regression and the Pearson’s correlation coefficient. The analysis was done using SPSS version 21.0.RESULTS: There were a total of 827 complete responses (response rate: 82.6%) and females formed a majority of the study population (62%). Majority of the students (53.1%) preferred PowerPoint presentations as compared to blackboard teaching (46.9%), although the difference was minimal; responses of females was statistically significant (p=0.02). Significant differences (p=0.03) were also observed as 58.8 % students considered blackboard teaching more interesting as compared to PowerPoint Lectures.CONCLUSION: Students preferred PowerPoint presentations as compared to Blackboard teaching and the teachers should aim to make it as interesting as possible and allow student interaction in between

Robust Stability Analysis of PMSM with Parametric Uncertainty using Kharitonov Theorem

The permanent magnet synchronous motors (PMSM) are used as servo motor for precise motion control and are used as generator to generate electrical energy driven by wind energy. There is large variation in inertia due to varying load and parametric uncertainty in PMSM. The design objective of this paper is to analytically determine the relative robust stability of PMSM with parametric uncertainty using Kharitonov theorem and Routh stability criterion. The conventional integral controller (IC) and two robust internal model controllers (IMCs) are used for relative robust stability analysis of speed control of PMSM. The frequency domain performance specifications like gain margin (GM) and phase margin (PM) are taken for relative robust stability analysis, and the effect of controllers on time domain performance specifications such as settling time (ST), rise time (RT) and overshoot (OS) is also studied

Abnormal presentation of common sexually transmitted diseases in HIV-positive patients: A case series

Mucocutaneous diseases are the most common manifestation of human immunodeficiency virus and because of abnormal presentation, diagnosis and management is a challenge for clinicians. Here, we present three cases of unusual and severe presentation of common sexually transmitted diseases, out of which two patients had ulcerative lesions in genitals and one patient had cauliflower-like growth involving the pubic and anal region