Stability Analysis of Networked Control in Smart Grids

A suitable networked control scheme and its stability analysis framework have been developed for controlling inherent electromechanical oscillatory dynamics observed in power systems. It is assumed that the feedback signals are obtained at locations away from the controller/actuator and transmitted over a communication network with the help of phasor measurement units (PMUs). Within the generic framework of networked control system (NCS), the evolution of power system dynamics and associated control actions through a communication network have been modeled as a hybrid system. The data delivery rate has been modeled as a stochastic process. The closed-loop stability analysis framework has considered the limiting probability of data dropout in computing the stability margin. The contribution is in quantifying allowable data-dropout limit for a specified closed loop performance. The research findings are useful in specifying the requirement of communication infrastructure and protocol for operating future smart grids

A moving control volume approach to computing hydrodynamic forces and torques on immersed bodies

We present a moving control volume (CV) approach to computing hydrodynamic forces and torques on complex geometries. The method requires surface and volumetric integrals over a simple and regular Cartesian box that moves with an arbitrary velocity to enclose the body at all times. The moving box is aligned with Cartesian grid faces, which makes the integral evaluation straightforward in an immersed boundary (IB) framework. Discontinuous and noisy derivatives of velocity and pressure at the fluid-structure interface are avoided and far-field (smooth) velocity and pressure information is used. We re-visit the approach to compute hydrodynamic forces and torques through force/torque balance equation in a Lagrangian frame that some of us took in a prior work (Bhalla et al., J Comp Phys, 2013). We prove the equivalence of the two approaches for IB methods, thanks to the use of Peskin's delta functions. Both approaches are able to suppress spurious force oscillations and are in excellent agreement, as expected theoretically. Test cases ranging from Stokes to high Reynolds number regimes are considered. We discuss regridding issues for the moving CV method in an adaptive mesh refinement (AMR) context. The proposed moving CV method is not limited to a specific IB method and can also be used, for example, with embedded boundary methods

Phase transitions in Lu2_2Ir3_3Si5_5

We report the results of our investigations on a polycrystalline sample of Lu$_2$Ir$_3$Si$_5$ which crystallizes in the U$_2$Co$_3$Si$_5$ type structure (Ibam). These investigations comprise powder X-ray diffraction, magnetic susceptibility, electrical resistivity and high temperature (120-300 K) heat capacity studies. Our results reveal that the sample undergoes a superconducting transition below 3.5 K. It also undergoes a first order phase transition between 150-250 K as revealed by an upturn in the resistivity, a diasmagnetic drop in the magnetic susceptibility and a large anomaly (20-30 J/mol K) in the specific heat data. We observe a huge thermal hysteresis of almost 45 K between the cooling and warming data across this high temperature transition in all our measurements. Low temperature X-ray diffraction measurements at 87 K reveals that the compound undergoes a structural change at the high temperature transition. Resistivity data taken in repeated cooling and warming cycles indicate that at the high temperature transition, the system goes into a highly metastable state and successive heating/cooling curves are found to lie above the previous one and the resistance keeps increasing with every thermal cycle. The room temperature resistance of a thermaly cycled piece of the sample decays exponentialy with time with a decay time constant estimated to be about 10$^4$ secs. The anomaly (upturn) in the resistivity and the large drop (almost 45%) in the susceptibility across the high temperature transition suggest that the observed structural change is accompanied or induced by an electronic transition.Comment: 7 figures, 1 table and 18 reference

Removal of Zn2+ and Pb2+ using new isolates of Bacillus spp. PPS03 and Bacillus subtilis PPS04 from Paper mill effluents using indigenously designed Bench-top Bioreactor

Biosorption processes have the potential to decrease environmental hazards through their factors such as initial metal ion concentration, temperature, pH and biomass concentration in the solution. In the present study biosorption process was performed using the strains of Bacillus spp. PPS 03 (KF710041) and Bacillus subtilis PPS 04 (KF710042) isolated from sediment core of Paper mill effluent (PME) for the removal of Zn2+and Pb2+ in an indigenously designed Bench-top Bioreactor. The temperature, initial pH, biomass and incubation period of PME for Zn2+ and Pb2+ reduction was standardized. The strains exhibited significant reduction in Zn2+ and Pb2+ of PME to the extent of 73.29% and 85.64% with PPS 03 and 78.15% and 87.57% respectively with PPS 04 after 120 hrs of aerobic treatment. The reduction in the metals occurred from first day of the treatment, but the maximum reduction in these metals was observed after 120 hrs. at pH (7.0±0.2), temperature (35±1.0°C) and biomass (5% v/ v) of the bacterial strains. The removal of metals with strain PPS 04 was more in comparison to the strain PPS 03. The Freundlich isotherms on the data showed that it was linearly fitted for Zn2+and Pb2+. The values of correlation coefficient (R2) of Freundlich isotherms were greater than 0.812 for Pb2+ and Zn2+. The kinetic study for the rate of removal of Pb2+ and Zn2+ by both species was found to best fit a Pseudo first order reaction. The rate constant was found to be inversely proportional to the concentration of parameters. Thus, the microbial strains were found efficient for the biosorption/removal of Pb2+ and Zn2+

Report on the 68-bus, 16-machine, 5-area system

The present report refers to a small-signal stability study carried over the 68-Bus, 16-Machine, 5-Area System and validated on a widely known software package: MATLAB-Simulink (ver. 2012b). The 68-bus system is a reduced order equivalent of the inter-connected New England test system (NETS) and New York power system (NYPS), with five geographical regions out of which NETS and NYPS are represented by a group of generators whereas, the power import from each of the three other neighboring areas are approximated by equivalent generator models. This report has the objective to show how the simulation of this system must be done using MATLAB in order to get results that are comparable (and exhibit a good match with respect to the electromechanical modes) with the ones obtained using other commercial software packages and presented on the PES Task Force website on Benchmark Systems for Stability Controls

Distribution of Steroid like Compounds in Plant Flora

Medicinal herbs constitute an effective source of traditional (Ayurvedic, Unani and Homeopathy) and modern medicine. The plant is a biosynthetic laboratory, not only for chemical compounds, but also a multitude of compounds like glycosides, alkaloids etc. These exert physiological and therapeutic effect. The compounds that are responsible for medicinal property of the drug are usually secondary metabolites. Alkaloids, glycosides, neutral principles, resins, oleoresins, sesquiterpene lactones are some of the common active constituents of medicinal herbs. The article reviews distribution of steroid like compounds and their pharmacological importance