Search for dissertations about: "hydroacoustics"

Found 5 swedish dissertations containing the word hydroacoustics.

2. 1. Studies on Baltic Sea mysids

   Author : Martin Ogonowski; Sture Hansson; Jörgen Berge; Stockholms universitet; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; Mysids; hydroacoustics; Baltic Sea; abundance; stable isotopes; specific dynamic action SDA ; diel vertical migration; partial migration; trophic interactions; physiology; benthic-pelagic coupling; protein:DNA; C:N ratio; genetic structure; Marine Ecology; marin ekologi;

   Abstract : Mysid shrimps (Mysidacea, Crustacea) are efficient zooplanktivores in both marine and freshwater systems as well as lipid rich prey for many species of fish.  Although some efforts have been made to study the role of mysids in the Baltic Sea, very few studies have been carried out in recent time and there are still knowledge gaps regarding various aspects of mysid ecology. READ MORE

4. 2. Numerical prediction of propeller induced hull pressure pulses and noise

   Author : Muye Ge; Chalmers tekniska högskola; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; RANS; Transition; IDDES; Cavitation; Pressure pulses; Sheet cavitation inception; Ship noise; k − ω SST; FWH acoustic analogy; Hydroacoustics;

   Abstract : An operating marine propeller is one of the major sources inducing hull pressure pulses, onboard noise and vibration as well as underwater radiated noise. There are rising concerns of environmental impacts and comfort and welfare of passengers and crews due to these negative effects. READ MORE

5. 3. Design and implementation of a programmable, wideband sonar for sediment mapping

   Author : Peter Jonsson; Teknisk geologi; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; centroid; programmable sonar; sediment mapping; underwater acoustics; hydroacoustics; echosounder;

   Abstract : To be able to explore different signal types and processing techniques, apt for sediment mapping, programmable, fully digital profiling systems has been built and tested. The systema are designed to be deployed also at small water depths from small boats, without special handling equipment. READ MORE

6. 4. Physical modelling of acoustic shallow-water communication channels

   Author : Elin Svensson; Ilkka Karasalo; Finn Jensen; KTH; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; underwater acoustics; hydroacoustics; time variability; ray tracing; Gaussian beam summation; sound propagation models; shallow water; waveguides; caustics; underwater communication; undervattensakustik; hydroakustik; tidsvariabilitet; strålgång; gaussisk strålsummation; ljudutbredningsmodeller; grunt vatten; vågledare; kaustikor; undervattenskommunikation; Acoustics; Akustik;

   Abstract : Akustiska kanaler för undervattenskommunikation är flervägskanaler där ljudet reflekteras från havets yta och botten och bryts vid ljudhastighetsförändringar. I grunt vatten är impulssvaret långt jämfört med symbolernas tidslängd i ett utskickat meddelande. READ MORE

7. 5. Distribution and activity of pelagic fish - acoustic studies in the Baltic Sea

   Author : Tomas Didrikas; Sture Hansson; Thomas Mehner; Stockholms universitet; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; Pelagic; fish; hydroacoustic; distribution; activity; Baltic; Biology; Biologi;

   Abstract : Fisheries agencies around the Baltic Sea use hydroacoustics to assess stock sizes of herring and sprat. These assessments rely on the assumption that the acoustic properties of Baltic clupeids are the same as North Sea herring. READ MORE