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Experimental study of relative permittivity of atmospheric ice
(Journal article; Peer reviewed; Tidsskriftartikkel, 2013-01-01)
Atmospheric icing on onshore and offshore structures
is problematic, if we don’t detect and remove it.
Despite of various ice detection techniques, capacitor
based ice sensing technique is interesting one, as it
is based on dielectric properties of material. This technique of measuring icing event is simple and cost-
effective. Based on the dielectric concept, an experi
mental ...
Numerical Study of Atmospheric Icing on Non Rotating Circular Cylinders in Tandem Arrangement
(Journal article; Tidsskriftartikkel; Peer reviewed, 2013-03-01)
Numerical study of atmospheric ice accretion on two non-rotating circular cylinders in tandem arrangement was carried out at different operating and geometric conditions. To validate the numerical model, initially the results of ice accretion on single circular cylinder were compared with the experimental data obtained from CIGELE atmospheric icing research wind tunnel (CAIRWT) [1, 2]. A good agreement ...
Atmospheric ice monitoring system operation at Remote locations in cold region
(Journal article; Peer reviewed; Tidsskriftartikkel, 2013)
The problems encountered in installation, maintenance and operations of equipment in the cold climate regions are far more complicated than others. The contributing factors and problems that can affect the system operation and performance should be identified, assessed and focused within well-defined parameters before its installation in cold climate regions. The harsh cold environment, could not ...
Underactuated Waypoint Tracking of a Fixed-Wing UAV
(Journal article; Peer reviewed; Tidsskriftartikkel, 2013)
In this paper a new method of performing waypoint tracking is shown for underactuated fixed-wing UAVs. The position error can be mapped onto the desired axis using a desired rotation matrix, while the velocity error can be mapped to the desired axis using a desired angular velocity. With all errors defined along one axis, the tracking problem is easily solved using only one thruster. A velocity ...
Underactuated Control of Quadrotors with Collision Avoidance
(Journal article; Peer reviewed; Tidsskriftartikkel, 2013)
In this paper a saturated controller is derived that solves the translational control problem for underactuated quadrotors. The controller is applied to multiple quadrotors during a formation reconfiguration where the quadrotors move from an initial position to a desired position. The null-space-based behavioral control method is a popular method for avoiding collisions between mobile agents, and ...
Real-Time Particle Tracking using a Formation of UAVs
(Journal article; Peer reviewed; Tidsskriftartikkel, 2013)
In this paper the problem of real-time particle tracking is studied. Using sensor measurements, a formation of UAVs autonomously find the closest point with high particle density where they enter a holding pattern. After converging to the holding pattern, one UAV will remain, while the rest will go looking for other maxima. To avoid collisions between the UAVs during the mission, a controller is ...
Weighted Hardy-Type Inequalities in Variable Exponent Morrey-Type Spaces
(Journal article; Peer reviewed; Tidsskriftartikkel, 2013)
We study the p(.) -> q(.) boundedness of weighted multidimensional Hardy-type operators H-w(alpha(.)) and H-w(alpha(.)) of variable order alpha(x), with radial weight w(vertical bar x vertical bar), from a variable exponent locally generalized Morrey space L-p(.),L-phi(.)(R-n, w) to another L-q(.),L-psi(.)(R-n, w). The exponents are assumed to satisfy the decay condition at the origin and infinity. ...
Optical water types of the Nordic Seas and adjacent areas
(Journal article; Tidsskriftartikkel; Peer reviewed, 2013-05-20)
A new map of Jerlov's optical water types in the Nordic Seas and adjacent waters at 139 locations, as well as a table with statistical and geographical properties of the vertical attenuation coefficient of downward irradiance at 475 nm, are presented. The data analysis is based on 715 recordings at different stations, at latitudes between 54° and 82°N, and longitudes between 31°W and 49°E, obtained ...
Local refinement of ERBS curves
(Journal article; Peer reviewed; Chapter, 2013-12-31)
Expo-rational B-splines (ERBS) provide a blending type construction where local functions at each knot are blended together by infinitely smooth basis functions. In this work we consider some specific ERBS curves that are approximations of parametric curves. We study local refinement to increase flexibility by inserting local control curves at points of interest on the ERBS curve. Inserting knots ...
Control of Spacecraft Formation with Disturbance Rejection and Exponential Gains
(Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
We address the problem of state feedback translational motion control of a spacecraft formation through a modified sliding surface controller using variable gains and I^2 action for disturbance rejection. The exponential varying gains ensure faster convergence of the state trajectories during attitude maneuver while keeping the gains small (and the system less stiff) for station keeping. Integral ...