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    <title>DRS Collection: Engineering &amp; Instrumentation</title>
    <link>http://drs.nio.org/drs/handle/2264/4</link>
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      <title>The Channel Image</title>
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      <link>http://drs.nio.org/drs/handle/2264/4</link>
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      <title>The Collection's search engine</title>
      <description>Search the Channel</description>
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      <title>In situ profiling of eastern Arabian Sea coastal waters using a new autonomous vertical profiler</title>
      <link>http://drs.nio.org/drs/handle/2264/4253</link>
      <description>Title: In situ profiling of eastern Arabian Sea coastal waters using a new autonomous vertical profiler
&lt;br/&gt;
&lt;br/&gt;Authors: Desa, E.S.; Madhan, R.; Dabholkar, N.A.; Prabhudesai, S.P.; Navelkar, G.S.; Mascarenhas, A.A.M.Q.; Afzulpurkar, S.; Phaldesai, M.; Maurya, P.
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&lt;br/&gt;Abstract: The autonomous vertical profiler (AVP) presented here offers a fast, cost-effective, optimized approach to profiling in coastal waters. It consists of a hands-free, slightly buoyant, motor-driven in situ robot profiler that requires no operator skill or deployment gear, but fulfills the requirements of repetitive profiling of the water column. It uses standard oceanographic sensors to measure vertical structure at high resolution (10 cm) in waters as shallow as 5 m and as deep as 200 m. The detailed engineering design, hydrodynamics, safety systems, endurance, and performance of the AVP relative to other profilers are covered in this paper. Proof-of-concept experiments in coastal waters present a clear picture, for the first time, of stable interactions between constant density contours and chlorophyll maxima in the waters of the Coral Island of Kavaratti (in the Lakshadweep Archipelago). The AVP has also been used in deep dives to 200 m in shelf regions of the Arabian Sea to record the presence of anoxic layers and phytoplankton existing in low-oxygen conditions.</description>
      <pubDate>Mon, 29 Oct 2012 22:58:59 GMT</pubDate>
    </item>
    <item>
      <title>A multi-sensor autonomous platform for fast ocean observation studies</title>
      <link>http://drs.nio.org/drs/handle/2264/4216</link>
      <description>Title: A multi-sensor autonomous platform for fast ocean observation studies
&lt;br/&gt;
&lt;br/&gt;Authors: Afzulpurkar, S.; Navelkar, G.S.; Desa, E.; Madhan, R.; Dabholkar, N.A.; Prabhudesai, S.P.; Mascarenhas, A.A.M.Q.; Maurya, P.
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&lt;br/&gt;Abstract: A new platform Autonomous Vertical Profiler (AVP) has been developed at CSIR - National Institute of Oceanography in Goa, India that can rapidly and autonomously collect repetitive data to 200m water depth. It is equipped with sensors to measure conductivity-temperature-depth (CTD), dissolved oxygen (DO), PAR, chlorophyll-a, turbidity and backscatter. A typical profile is obtained within ten minutes. The ability to collect profiles and transmit data to remote places over a radio or satellite link makes the AVP an appropriate tool for ocean observations related to climate, water quality studies etc. The AVP can be deployed for 12 days with four profiles per day to a depth of 100m and it is being enhanced to 30 days endurance. This enables several dives to be executed in a short duration to determine the movement of OMZ with respect to depth. Compared to the AVP, ARGO floats are designed for deep water operations with cm/sec descent rates and limited sensor payloads, although this situation is now improving with the advent BIO ARGO floats equipped with sensors for DO, and chlorophyll-a. The AVP's initial tests were carried out in fresh water bodies at Amthane Dam, Goa and at Tillari dam, Maharashtra. AVP's subsequent deployments were at locations off Goa, off Ratnagiri, in Maharashtra and in Coral Islands of Lakshadweep Archipelago from depths of 30 m to 200 meters. It was generally observed that DO values declined rapidly beyond 30 meters to 100 meters depth and by 150m were practically zero indicating anoxic waters. During a cruise onboard RV Sindhu Sankalp the AVP was deployed off Kavaratti Island, Lakshadweep, India to a depth of 200 m. The data indicates presence of very low DO values, possibly the presence of an OMZ signature. Similarly, during a mid December 2010 cruise on RV Sindhu Sankalp, an OMZ was detected at 200m close to shelf waters off Goa (West cost of India). This again points to the possible intrusion of the OMZ waters from the Central Arabian Sea to coastal waters of the West coast of India. The detection of anoxic waters found by many AVP profiles proves conclusively its use in the detection of low oxygen waters in rapid ocean observation studies. Currently, the AVP is also being used in satellite sensor validation experiments for the OceanSat 2 satellite launched by India, and in other wide ranging observations of anoxia in freshwater dams and in coastal waters off Goa, Vizag, and Kochi.</description>
      <pubDate>Sat, 29 Oct 2011 22:58:59 GMT</pubDate>
    </item>
    <item>
      <title>An autonomous underwater vehicle "Maya", for monitoring coastal waters, estuaries, rivers and dams</title>
      <link>http://drs.nio.org/drs/handle/2264/4204</link>
      <description>Title: An autonomous underwater vehicle "Maya", for monitoring coastal waters, estuaries, rivers and dams
&lt;br/&gt;
&lt;br/&gt;Authors: Mascarenhas, A.A.M.Q.; Navelkar, G.S.; Madhan, R.; Dabholkar, N.A.; Prabhudesai, S.P.; Maurya, P.K.; Desa, E.; Afzulpurkar, S.; Suresh, T.; Matondkar, S.G.P.; Mahalunkar, A.
&lt;br/&gt;
&lt;br/&gt;Abstract: This article demonstrates the use of Maya, Autonomous Underwater Vehicle (AUV) for monitoring coastal waters, estuaries, rivers and dams. Maya is a mono hull structure with detachable nose and tail cones. The nose cone is mission specific, and offers the following sensor combinations: (a) dissolved oxygen and fluorometer, (b) conductivity temperature and depth, (c) hyperspectral irradiance, radiance and fluorometer. During a yoyo mission off-Goa in Nov 2006, a sensor suite (option c) was used to simultaneously measure the upwelling radiance (Lu) and down welling Irradiance (Ed) spectra, along with fluorescence Chlorophyll-a. The sampling frequency was 0.1 Hz. All sensors exhibited consistency during the various mission segments, consisting of surface, dive to 2m, cruise at 2m and accent to the surface. Maya was operated away from the mother ship, so as to decouple the optical measurements from all ship borne disturbances, like ship shadow and vibration of winch wire. Using the Ed and Lu spectra the hyperspectral remote sensing reflectance (Rrs), was derived along the mission track. Both irradiance and radiance, show an exponential decrease and increase respectively during the mission decent and assent segments. Fluorometer recorded chlorophyll-a values averaged at 0.52 ug/l. Water samples were collected along the path for estimating the Chlorophyll-a pigment using HPLC method. During another expedition at the SUPA dam in Karnataka during January 08, the spatial variations of dissolved oxygen, chlorophyll-a &amp; backscatter was studied. A 3.3km path following, waypoint guided yoyo mission at 1m depth was executed at noon in the east to west direction. Maya was programmed to pop up for a GPS fix every 500m. A similar mission was executed at 2m depth in quick succession but in the west to east direction for a distance of 1.7km. The sensor time series outputs are presented. More recently under the biogeochemistry program, Maya was used to study the spatial (horizontal &amp; vertical) salinity distribution in rivers and estuaries during the onset of tides. An improved path following algorithm was implemented to achieve minimal cross-track errors. Simulations carried out using hardware in loop technique for the deployment sites are presented.</description>
      <pubDate>Sat, 29 Oct 2011 22:58:59 GMT</pubDate>
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    <item>
      <title>Direct bed stress measurements under solitary tsunami-type waves and breaking tsunami wave fronts</title>
      <link>http://drs.nio.org/drs/handle/2264/4170</link>
      <description>Title: Direct bed stress measurements under solitary tsunami-type waves and breaking tsunami wave fronts
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&lt;br/&gt;Authors: JayaKumar, S.; Baldock, T.E.
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&lt;br/&gt;Abstract: During their propagation tsunamis often traverse continental slopes that are relatively steep compared to deeper oceans. Further due to the change of bed slope from offshore to near shore, there is every likely possibility that a tsunami might steepen and eventually break, thereby generating large pressure gradients that could enhance the likelihood of liquefaction of the seabed. In the drawdown, high shear stresses could trigger debris flow in submarine canyons and on steep ridges. Therefore estimation of the bed stress is important in estimation of the forces induced during tsunami wave propagation, both on the seabed as well as on the subsurface installations. Bed and shear stresses generated by wave forms that represent tsunami (a solitary wave and broken solitary wave in the form of a bore) are measured using a shear cell. This paper deals with the measurements and modeling of the bed stress under the solitary waves.</description>
      <pubDate>Wed, 29 Oct 2008 22:58:59 GMT</pubDate>
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