Optimal Design of Multi-Machine Power System Stabilizer Using Genetic Algorithm

Power system stabilizers (PSSs) are used to generate supplementary control signals for the excitation system to damp electromechanical oscillations. This paper presents an approach based on genetic algorithm for tuning the parameters of PSSs in a multi-machine power system. The stabilizers are tuned to simultaneously shift the lightly damped and undamped electromechanical modes of all plants to a prescribed zone in the s-plane. A multiobjective problem is formulated to optimize a composite set of objective functions comprising the damping factor, and the damping ratio of the lightly damped electromechanical modes. The performance of the proposed PSSs under different disturbances, loading conditions, and system configurations is investigated for different multi-machine power systems. The non-linear simulation results are presented under wide range of operating conditions; disturbances at different locations as well as for various fault clearing sequences to show the effectiveness and robustness of the proposed PSSs and their ability to provide efficient damping of low frequency oscillations

Focusing versus defocusing properties of truly naked black holes

We study the properties of the congruence of null geodesics propagating near the so-called truly naked horizons (TNH) - objects having finite Kretschmann scalar but with diverging tidal acceleration for freely falling observers. The expansion of outgoing rays near the future horizon always tends to vanish for the non-extremal case but may be non-zero for the distorted (ultra)extremal one. It tends to diverge for the ingoing ones if the the null energy condition (NEC) is satisfied in the vicinity of the horizon outside. However, it also tends to zero for NEC violating cases except the remote horizons. We also discuss the validity of test particle approximation for TNHs and find the sufficient condition for backreaction remaining small.Comment: 16 pages. To appear in IJMP

Synthesis, Characterization and Pharmacological evaluation of some newer Benzothiazole derivatives

The objective of the present work is to develop safer new chemical entities that show good anticonvulsant effects and antimicrobial actions. The current work describes the synthesis of Benzothiazole derivatives with encouraging anticonvulsant activity against MES and scPTZ tests with interesting pattern of antimicrobial effects. The synthesized Benzothiazole derivatives could be considered as lead molecule for the development of therapeutic agents. Many polycyclic and fused ring systems containing the thiazolenucleus(I) are well known. The most important is bicyclic system wherein the second ring benzene is fused to the 4,5 position of thiazole ring i.e. Benzothiazole.(II