Hydrodynamic changes due to large seabed installations in coastal waters off west coast of India

Offshore marine environment can very well be utilized for mass storage of liquids which are not harmful to that environment. Improper placement of large tanks on the seabed, to store large quantities of liquids, would adversely affect the hydrodynamics of adjoining environment. Thorough understanding on the hydrodynamics of the adjoining environment is thus required before and after placing such tanks so as to properly plan the placement of these large tanks. A two dimensional numerical hydrodynamic model is used to study influence of placing large number of tanks in a dynamic marine environment. Cylindrical tanks (5 m dia.) are arranged in three rows with 50 tanks placed in each row with their length (100 m) aligned perpendicular to the coast. These tanks cover an area of about 36000 m2 and are placed on seabed in water depths about 15 m. Hydrodynamic simulations carried out with tidal forcing for cases of (a) before and (b) after placement of tanks showed that current speeds increase up to 65% in the region where the tanks are placed compared to currents without placement of tanks. However, up to 85% increase in current speeds is observed in regions beyond the tanks. In this manuscript results of the effects on the hydrodynamics of a region due to placing large number of tanks in shallow waters are presented

On the origin of the various types of radio emission in GRS 1915+105

We investigate the association between the radio ``plateau'' states and the large superluminal flares in GRS 1915+105 and propose a qualitative scenario to explain this association. We identify several candidate superluminal flare events from available monitoring data on this source and analyze the contemporaneous RXTE pointed observations. We detect a strong correlation between the average X-ray flux during the ``plateau'' state and the total energy emitted in radio during the subsequent radio flare. We find that the sequence of events is similar for all large radio flares with a fast rise and exponential decay morphology. Based on these results, we propose a qualitative scenario in which the separating ejecta during the superluminal flares are observed due to the interaction of the matter blob ejected during the X-ray soft dips, with the steady jet already established during the ``plateau'' state. This picture can explain all types of radio emission observed from this source in terms of its X-ray emission characteristics.Comment: Corrected typo in the author names, contents unchanged, accepted in Ap

Nonlinear Mode Coupling and Internal Resonances in MoS2 Nanoelectromechanical System

Atomically thin two dimensional (2D) layered materials have emerged as a new class of material for nanoelectromechanical systems (NEMS) due to their extraordinary mechanical properties and ultralow mass density. Among them, graphene has been the material of choice for nanomechanical resonator. However, recent interest in 2D chalcogenide compounds has also spurred research in using materials such as MoS2 for NEMS applications. As the dimensions of devices fabricated using these materials shrink down to atomically thin membrane, strain and nonlinear effects have become important. A clear understanding of nonlinear effects and the ability to manipulate them is essential for next generation sensors. Here we report on all electrical actuation and detection of few layers MoS2 resonator. The ability to electrically detect multiple modes and actuate the modes deep into nonlinear regime enables us to probe the nonlinear coupling between various vibrational modes. The modal coupling in our device is strong enough to detect three distinct internal resonances

Discrete Electronic Warfare Signal Processing using Compressed Sensing Based on Random Modulator Pre-Integrator

Electronic warfare receiver works in the wide electromagnetic spectrum in dense radar signal environment. Current trends in radar systems are ultra wideband and low probability of intercept radar technology. Detection of signals from various radar stations is a concern. Performance and probability of intercept are mainly dependent on high speed ADC technology. The sampling and reconstruction functions have to be optimized to capture incoming signals at the receiver to extract characteristics of the radar signal. The compressive sampling of the input signal with orthonormal base vectors, projecting the basis in the union of subspaces and recovery through convex optimisation techniques is the current traditional approach. Modern trends in signal processing suggest the random modulator pre-integrator (RMPI), which sample the input signal at information rate non-adaptively and recovery by the processing of discrete and finite vectors. Analysis of RMPI theory, application to EW receiver, simulation and recovery of EW receiver signals are discussed