Application of active power sensitivity to frequency and voltage variations on load shedding

The occurrence of a large disturbance in a power system can lead to a decline in the system frequency and bus voltages due to a real and reactive power deficiency or due to the formation of islands with generation–load imbalance. Load shedding is an emergency control action that can prevent a blackout in the power system by relieving the overload in some parts of the system. This paper shows that rate of change of frequency can be utilized to determine the magnitude of generation–load imbalance, while the rate of change of voltage with respect to active power can be utilized to identify the sensitive bus for load shedding. The frequency, voltages and their rate of change can be obtained by means of measurements in real-time from various devices such as digital recorders or phasor measurement units or these parameters can be estimated from the voltage data by other means such as an optimal estimation method like Kalman filtering. The rate of change of system frequency, along with the equivalent system inertia may be used to estimate the magnitude of the disturbance prior to each load shedding step. The buses with a higher rate of change of voltage may be identified as the critical ones for load shedding and load can be first shed at these buses, depending on the change in the power flow at each bus. This application is tested on the IEEE 30 bus system and the preliminary results demonstrate that it is feasible to be used in load shedding to restore system voltage and frequency.     

Enhancement in Creep Strength of Modified 9CR–1MO Steel Through Thermo-Mechanical Treatment

In the present investigation, microstructure of the modified 9Cr–1Mo (T91) steel was refined through thermo-mechanical treatment (TMT). The finer precipitation of M₂₃C₆ and MX precipitates were observed in the TMT processed T91 steel. Creep deformation behaviour of T91 steel and TMT processed T91 steel was carried out at 923 K. The minimum creep rate of the TMT processed steel was significantly lowered as compared to T91 steel. The TMT processing of modified 9Cr–1Mo steel resulted in enhancement of creep strength due to presence of finer precipitates which relatively delayed the recovery of dislocation structure and coarsening of sub-boundaries than the steel in the normalized and tempered condition.     

Surface Modifications for Improved Delivery and Function of Therapeutic Bacteria

Live therapeutic bacteria (LTBs) hold promise to treat microbiome‐related diseases. However, few approaches to improve the colonization of LTBs in the gastrointestinal tract exist, despite colonization being a prerequisite for efficacy of many LTBs. Here, a modular platform to rapidly modify the surface of LTBs to enable receptor‐specific interactions with target surfaces is reported. Inspired by bacterial adhesins that facilitate colonization, synthetic adhesins (SAs) are developed for LTBs in the form of antibodies conjugated to their surface. The SA platform is nontoxic, does not alter LTB growth kinetics, and can be used with any antibody or bacterial strain combination. By improving adhesion, SA‐modified bacteria demonstrate enhanced in vitro pathogen exclusion from cell monolayers. In vivo kinetics of SA‐modified LTBs is tracked in the feces and intestines of treated mice, demonstrating that SA‐modified bacteria alter short‐term intestinal transit and improve LTB colonization and pharmacokinetics. This platform enables rapid formation of an intestinal niche, leading to an increased maximum concentration and a 20% improvement in total LTB exposure. This work is the first application of traditional pharmacokinetic analysis to design and evaluate LTB drug delivery systems and provides a platform toward controlling adhesion, colonization, and efficacy of LTBs.     

Corrosion behavior of SiC reinforced magnesium composites

The corrosion behavior of two SiC reinforced Mg-based metal matrix composites, Mg-6SiC and Mg-16SiC (in volume percent), has been studied in freely aerated 1 M NaCl solution and compared with that of pure Mg. The presence of SiC particles deteriorated the corrosion resistance of magnesium. Corrosion resistance decreased with increasing SiC volume fraction. The galvanic corrosion current density between pure SiC and pure Mg has been experimentally measured using zero resistance ammeter technique and theoretically determined using mixed potential theory. Galvanic corrosion between Mg matrix and SiC reinforcement in the composites did not contribute significantly to the overall corrosion rate. Electrochemical impedance spectroscopy indicated that the higher corrosion rates for the composites could be related to the defective nature of surface film.     

A novel parallel prefix adder for optimized Radix-2 FFT processor

Multidimensional Systems and Signal Processing - The Fast Fourier Transform (FFT) is the basic building block for DSP applications where high processing speed is the critical requirement. Resource...     

A frequency‐constrained geometric Pontryagin maximum principle on matrix Lie groups

We present a geometric discrete‐time Pontryagin maximum principle (PMP) on matrix Lie groups that incorporates frequency constraints on the control trajectories in addition to pointwise constraints on the states and control actions directly at the stage of the problem formulation. This PMP gives first‐order necessary conditions for optimality and leads to two‐point boundary value problems that may be solved by numerical techniques to arrive at optimal trajectories. We demonstrate our theoretical results with numerical simulations on the optimal trajectory generation of a wheeled inverted pendulum and an attitude control problem of a spacecraft on the Lie group SO(3).     

Revisit of Moving Average Technique for Smoothing GNSS Based Timing Data

A new moving average technique with a unique way of assigning weight has been proposed to reduce the influence of the bad/stray data points or large short term fluctuations automatically. A simple iterative technique is introduced wherein the weights of elements are dynamically optimised. This method has been compared with another proposed method which finds the average of a set of data by applying Fuzzy logic through generation of a special membership function. These two methods have been applied on some arbitrarily generated test data for establishing their validation. Finally this technique has been used to smooth the GNSS based timing data. The capabilities of smoothing data utilizing these techniques have been analyzed.