Fault Detection and Prognostic Health monitoring of Towed array sonars

Sonars are used to detect underwater targets and are especially important in maintaining naval superiority. Towed array sonars can operate at very low frequencies thus giving larger ranges and can be deployed to any desired depth of operation. Towed array sonars offer long range surveillance capability and is the sensor of choice for sustained surveillance operations. Reliable operation and maintenance of towed array sonars need effective methods of health monitoring and reliability prediction. For any prognostic health monitoring to be done we need to identify certain parameters which can be observed and will give system health status in the present condition. This paper proposes some metrics which are easily measurable in-situ and which offer insights into the health of the sonar system. These metrics give direct measureable impact for each of the failure modes and offer insights into the current health of an operational towed array sonar. Simulation results are shown to demonstrate the effectiveness of the proposed metrics and detailed trial data results from different towed array trials are analysed to validate them in operational scenarios

Vibration Signature Analysis of Shipboard Machinery

A brief description of Vibration Signature Analysis as an effective tool in anticipation and prevention of Shipboard Machinery failures is provided. A case history of marine steam turbine and gearbox vibration signature analysis is given

Scalar Field Dark Energy Perturbations and their Scale Dependence

We estimate the amplitude of perturbation in dark energy at different length scales for a quintessence model with an exponential potential. It is shown that on length scales much smaller than hubble radius, perturbation in dark energy is negligible in comparison to that in in dark matter. However, on scales comparable to the hubble radius ($\lambda_{p}>1000\mathrm{Mpc}$) the perturbation in dark energy in general cannot be neglected. As compared to the $\Lambda$CDM model, large scale matter power spectrum is suppressed in a generic quintessence dark energy model. We show that on scales $\lambda_{p} < 1000\mathrm{Mpc}$, this suppression is primarily due to different background evolution compared to $\Lambda$CDM model. However, on much larger scales perturbation in dark energy can effect matter power spectrum significantly. Hence this analysis can act as a discriminator between $\Lambda$CDM model and other generic dark energy models with $w_{de} \neq -1$.Comment: 12 pages, 13 figures, added new section, accepted for publication in Phys. Rev.

Mouthpart morphology of phyllosoma of the tropical spiny lobster Panulirus homarus (Linnaeus, 1758)

Mouthpart morphology of Panulirus homarus phyllosoma larva was studied under scanning electron microscope in order to analyse the developmental changes during growth. Phyllosoma larvae have six pairs of mouthparts (mandibles, maxillule, maxilla, maxillipeds I, II, and III), labrum, and paired paragnaths. Increased length of second and third maxillipeds in late stage phyllosoma resulted in the increase of oral field, thus increasing its ability to catch prey. Labrum and paired paragnaths form a semienclosed oral chamber where mastication by the mandibles occurs. The improved threshing and tearing efficiency in late instars (stage VI-VIII) is facilitated by morphological changes in the mouthparts viz., increase in oral field, increased robustness and number of spinose setations of maxillule, and lengthy maxillipeds, indicating that the late instar larvae can process fleshier prey as compared to the early instar counterparts

Measurements of plasma temperature and electron density in laser-induced copper plasma by time-resolved spectroscopy of neutral atom and ion emissions

Plasma produced by a 355 nm pulsed Nd:YAG laser with a pulse duration of 6 ns focussed onto a copper solid sample in air at atmospheric pressure is studied spectroscopically. The temperature and electron density characterizing the plasma are measured by time-resolved spectroscopy of neutral atom and ion line emissions in the time window of 300-2000 ns. An echelle spectrograph coupled with a gated intensified charge coupled detector is used to record the plasma emissions. The temperature is obtained using the Boltzmann plot method and the electron density is determined using the Saha-Boltzmann equation method. Both parameters are studied as a function of delay time with respect to the onset of the laser pulse. The results are discussed. The time window where the plasma is optically thin and is also in local thermodynamic equilibrium (LTE), necessary for the laser-induced breakdown spectroscopy (LIBS) analysis of samples, is deduced from the temporal evolution of the intensity ratio of two Cu I lines. It is found to be 700-1000 ns

Spectroscopy of laser-produced plasmas: setting up of high-performance laser-induced breakdown spectroscopy system

It is a well-known fact that laser-induced breakdown spectroscopy (LIBS) has emerged as one of the best analytical techniques for multi-elemental compositional analysis of samples. We report assembling and optimization of LIBS set up using high resolution and broad-range echelle spectrograph coupled to an intensified charge coupled device (ICCD) to detect and quantify trace elements in environmental and clinical samples. Effects of variations of experimental parameters on spectroscopy signals of copper and brass are reported. Preliminary results of some plasma diagnostic calculations using recorded time-resolved optical emission signals are also reported for brass samples

Vizhinjam Marine Aquarium Haven for Marine Ornamentals

There has been a huge growth of public aquaria since the opening of the first public aquarium display in the Fish House at the London Zoo in t 826, and particularly in the past 20 years (Hall and Douglas 2003)

Studies on the remote setting of two commercially important Indian bivalves

The concept of remote setting, which involves transporting bivalve larvae, under moist condition and at 5- 10°C lower than the atmospheric temperture, to distant areas for settlement was tried for thejirst time on two species of Indian bivalves. About 68% of the 'pediveliger' larvae of Indian backwater oyster, Crassostrea madrasensis which were transported at 27±1 °C for 18 hours metamorphosed to settle as spat The post-set survived rates were 66.2% to 73.4% in 30ppt and 71.3% to 87.5% in 15 ppt salinity. Higher settlement rate and post-set swvival was observed in larvae transported under low temperature than in atmospheric temperature. Transportation of late 'umbo' larvae of Indian pearl oyster Pinctada fucata gave high survival rate, but failed to metamorphose as spa

Standard and derived Planck quantities: selected analysis and derivations

We provide an overview of the fundamental units of physical quantities determined naturally by the values of fundamental constants of nature. We discuss a comparison between the 'Planck units', now widely used in theoretical physics and the pre-quantum 'Stoney units' in which, instead of the Planck constant, the charge of the electron is used with very similar quantitative results. We discuss some of the physical motivation for these special units, attributed much after they were introduced, and also put forth a summary of the arguments supporting various cases for making specific physical interpretations of the meanings of some of these units. The new aspects we discuss are a possible physical basis for the Stoney units, their link to the Planck units, and also the importance of Planck units for thermodynamical quantities in the context of quantum gravity.Comment: 22 pages, 1 tabl