Vegar Johansen - Academia.edu (original) (raw)
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Bangladesh University of Engineering and Technology
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Papers by Vegar Johansen
Aquaculture, 2009
We constructed a Lagrangian (individual-based) model of the behaviour of Atlantic salmon in sea-c... more We constructed a Lagrangian (individual-based) model of the behaviour of Atlantic salmon in sea-cages. The behaviour of individual fish was affected by a set of environmental factors and the other individuals in the population. The model was based on behavioural parameters derived from literature and comparisons between model performance and published quantitative data sets. Simulations demonstrated that the model was
Volume 8A: Ocean Engineering, 2014
Oceans '04 MTS/IEEE Techno-Ocean '04 (IEEE Cat. No.04CH37600), 2004
This paper deals with the issue of estimating the trajectory of a vehicle or object moving underw... more This paper deals with the issue of estimating the trajectory of a vehicle or object moving underwater based on camera measurements. The proposed approach consists of a diffusion-based trajectory observer [1] processing whole segments of a trajectory at a time. Additionally, the observer contains a Tikhonov regularizer for smoothing the estimates. Then, a method for including the camera measurements in an appropriate manner is proposed.
Volume 4: Materials Technology; Ocean Engineering, 2007
Journal of Physical Oceanography, 2009
... Bubbles in bubble plumes behave hydrodynamically cleaner than isolated bubbles (Leifer andde ... more ... Bubbles in bubble plumes behave hydrodynamically cleaner than isolated bubbles (Leifer andde Leeuw 2006). ... 51.300′W; 65 m) measured an upwelling flow V up (z o ), of 30 cm s −1 . Dye releases by scuba divers in communication with surface observers at Shane Seep (34 ...
International Journal of Non-Linear Mechanics, 2006
The recognition of very stiff axial elastic motion compared to the motion in the transverse direc... more The recognition of very stiff axial elastic motion compared to the motion in the transverse direction for cable dynamics motivates separation of the axial and transversal dynamics. For certain applications, e.g. real-time model-based control, fast calculation of the transverse motion may be of high importance, motivating the development of numerically efficient software code. Separation of axial dynamics renders possible neglection or simplification of the axial dynamics if appropriate for the system studied. A model is proposed with the assumption of axial inextensible material and negligible bending, torsion and shear stiffness in the cable. Experiments are carried out to verify the model, and the results are compared with simulations. The comparison between the experiments and numerical simulations showed good agreement up to the second frequency range with resonant behavior and the corresponding motion amplitudes. ᭧
Aquaculture, 2009
We constructed a Lagrangian (individual-based) model of the behaviour of Atlantic salmon in sea-c... more We constructed a Lagrangian (individual-based) model of the behaviour of Atlantic salmon in sea-cages. The behaviour of individual fish was affected by a set of environmental factors and the other individuals in the population. The model was based on behavioural parameters derived from literature and comparisons between model performance and published quantitative data sets. Simulations demonstrated that the model was
Volume 8A: Ocean Engineering, 2014
Oceans '04 MTS/IEEE Techno-Ocean '04 (IEEE Cat. No.04CH37600), 2004
This paper deals with the issue of estimating the trajectory of a vehicle or object moving underw... more This paper deals with the issue of estimating the trajectory of a vehicle or object moving underwater based on camera measurements. The proposed approach consists of a diffusion-based trajectory observer [1] processing whole segments of a trajectory at a time. Additionally, the observer contains a Tikhonov regularizer for smoothing the estimates. Then, a method for including the camera measurements in an appropriate manner is proposed.
Volume 4: Materials Technology; Ocean Engineering, 2007
Journal of Physical Oceanography, 2009
... Bubbles in bubble plumes behave hydrodynamically cleaner than isolated bubbles (Leifer andde ... more ... Bubbles in bubble plumes behave hydrodynamically cleaner than isolated bubbles (Leifer andde Leeuw 2006). ... 51.300′W; 65 m) measured an upwelling flow V up (z o ), of 30 cm s −1 . Dye releases by scuba divers in communication with surface observers at Shane Seep (34 ...
International Journal of Non-Linear Mechanics, 2006
The recognition of very stiff axial elastic motion compared to the motion in the transverse direc... more The recognition of very stiff axial elastic motion compared to the motion in the transverse direction for cable dynamics motivates separation of the axial and transversal dynamics. For certain applications, e.g. real-time model-based control, fast calculation of the transverse motion may be of high importance, motivating the development of numerically efficient software code. Separation of axial dynamics renders possible neglection or simplification of the axial dynamics if appropriate for the system studied. A model is proposed with the assumption of axial inextensible material and negligible bending, torsion and shear stiffness in the cable. Experiments are carried out to verify the model, and the results are compared with simulations. The comparison between the experiments and numerical simulations showed good agreement up to the second frequency range with resonant behavior and the corresponding motion amplitudes. ᭧