English
norskBlar i forfatter "Johansen, Tor Arne"
Viser treff 1-13 av 13
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Characterization of seabed properties from Scholte waves acquired on floating ice on shallow water
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-09)Seismic surveying of the coastal areas in the Arctic is best facilitated during wintertime when the sea ice is land‐fast. This eases the logistics of the operation and assures that there is no damage made to the vulnerable tundra. Seismic experiments on floating ice on shallow water performed in a fjord in Svalbard in the Norwegian Arctic show prominent Scholte waves. The dispersion relation of ... -
Integrated Monitoring of Mola mola Behaviour in Space and Time
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-08-05)Over the last decade, ocean sunfish movements have been monitored worldwide using various satellite tracking methods. This study reports the near-real time monitoring of fine-scale (< 10 m) behaviour of sunfish. The study was conducted in southern Portugal in May 2014 and involved satellite tags and underwater and surface robotic vehicles to measure both the movements and the contextual environment ... -
Measured sound levels in ice-covered shallow water caused by seismic shooting on top of and below floating ice, reviewed for possible impacts on true seals
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-01-01)Seismic surveying of the Arctic is important for several reasons, but also introduces some challenges. One is the concern that seismic data may affect the hearing of marine mammals living there, including true seals. We performed two seismic experiments on floating ice on Svalbard in the Norwegian Arctic in early March 2016 and late May 2017, just before and right after the ringed seal breeding ... -
Mission Performance Trade-offs of Battery-powered sUAS
(Chapter; Bokkapittel, 2017-07-27)A sensitivity analysis is presented on the influence of the weight, altitude and speed of battery-powered sUAS on the resulting stall speed, endurance and range. To aid in the determination of the aircraft performance prior to flight, a method is being brought forth that quantifies the impact of these mission parameters. As a case study the P31015 sUAS is used. The P31015 is a concept model of a ... -
Monitoring Algal Blooms with Complementary Sensors on Multiple Spatial and Temporal Scales
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-01-19)Climate change, and other human-induced impacts, are severely increasing the intensity and occurrences of algal blooms in coastal regions (IPCC, 2022). Ocean warming, marine heatwaves, and eutrophication promote suitable conditions for rapid phytoplankton growth and biomass accumulation. An increase in such primary producers provides food for marine organisms, and phytoplankton play an important ... -
Passive seismic recording of cryoseisms in Adventdalen, Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-20)A series of transient seismic events were discovered in passive seismic recordings from 2-D geophone arrays deployed at a frost polygon site in Adventdalen, Svalbard. These events contain a high proportion of surface wave energy and produce high-quality dispersion images using an apparent offset re-sorting and inter-trace delay minimisation technique to locate the seismic source, followed by ... -
Path planning for UAV harvesting information from dynamical wireless sensor nodes at sea
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-16)A system of several wireless sensor nodes and one unmanned aerial vehicle (UAV) is considered in this research. The nodes are only floating and drifting with the sea stream. The UAV will be operating as a data mule to gather sensing information from wireless sensor nodes. Unlike prior studies, this paper addressed a realistic ocean model for the nodes movements which will be the references to the ... -
Potential use of time-lapse surface seismics for monitoring thawing of the terrestrial arctic
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-09)The terrestrial Arctic is warming rapidly, causing changes in the degree of freezing of the upper sediments, which the mechanical properties of unconsolidated sediments strongly depend upon. This study investigates the potential of using time-lapse surface seismics to monitor thawing of currently (partly) frozen ground utilizing synthetic and real seismic data. First, we construct a simple geological ... -
PSO and Kalman Filter-Based Node Motion Prediction for Data Collection from Ocean Wireless Sensors Network with UAV
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-13)In this paper, we consider a wireless sensor network of nodes at the sea surface drifting due to wind and sea currents. In our scenario an Unmanned Aerial Vehicle (UAV) will be used to gather data from the sensor nodes. The goal is to find a flyable path which is optimal in terms of sensor node energy consumption, total channel throughput between the UAV and sensor nodes, flight time for the UAV and ... -
PSO and Kalman Filter-Based Node Motion Prediction for Data Collection from Ocean Wireless Sensors Network with UAV
(Conference object; Konferansebidrag, 2021-01)In this paper, we consider a wireless sensor network of nodes at the sea surface drifting due to wind and sea currents. In our scenario an Unmanned Aerial Vehicle (UAV) will be used to gather data from the sensor nodes. The goal is to find a flyable path which is optimal in terms of sensor node energy consumption, total channel throughput between the UAV and sensor nodes, flight time for the ... -
Quantitative interpretation using inverse rock-physics modeling on AVO data
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-08-16)Quantitative seismic interpretation has become an important and critical technology for improved hydrocarbon exploration and production. However, this is typically a resource-demanding process that requires information from several well logs, building a representative velocity model, and, of course, high-quality seismic data. Therefore, it is very challenging to perform in an exploration or appraisal ... -
Sea ice thickness from air-coupled flexural waves
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-28)Air-coupled flexural waves (ACFWs) appear as wave trains of constant frequency that arrive in advance of the direct air wave from an impulsive source travelling over a floating ice sheet. The frequency of these waves varies with the flexural stiffness of the ice sheet, which is controlled by a combination of thickness and elastic properties. We develop a theoretical framework to understand these ... -
Seismic on floating ice: data acquisition versus flexural wave noise
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-09)Geophysical surveying of the Arctic will become increasingly important in future prospecting and monitoring of the terrestrial and adjacent areas in this hemisphere. Seismic data acquired on floating ice are hampered with extensive noise due to ice vibrations related to highly dispersive ice flexural waves generated by the seismic source. Several experiments have been conducted on floating ice in ...
