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  • 201.
    Åhlén, Julia
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Sundgren, David
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för matematik och statistik.
    Recognition of video signal by matching with the original video sequence2008In: Proceedings on CD-ROM, IADIS International Conference, 2008Conference paper (Refereed)
    Abstract [en]

    An adequate analysis of the originality of the video is of a great importance in video processing field. This paper presents a method for feature matching between two video streams. One of the video streams is subjected for severe compression, noise and rotation. These two copies represent the same movie but only one of the versions is original. Examples of reliable recognition of an original scene that is subjected for compression and noise are presented. The algorithm is invariant to image scale and rotation, providing robust matching across a substantial range of video signals. This paper shows an approach to using descriptive features for randomly chosen unstructured frames from video stream. By involving color information as a feature together with intensity profile for frame blocks we increase the robustness of the identification process. The median of low frequencies is measured, followed by an average of spectral information from the same frame to identify clusters belonging to a scene in a film. Finally, a comparison of mean squares of the difference is done to verify the originality of the film.

  • 202.
    Åhlén, Julia
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Sundgren, David
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för matematik och statistik.
    Bengtsson, Ewert
    CBA.
    Application of underwater hyperspectral data for color correction purposes2007In: Pattern recognition and image analysis, ISSN 1555-6212, Vol. 17, no 1, p. 170-173Article in journal (Refereed)
    Abstract [en]

    Color correction of underwater images has been considered a difficult task for a number of reasons. Those include severe absorption of the water column, the unpredictable behavior of light under the water surface, limited access to reliable data for correction purposes, and the fact that we are only able to process three spectral channels, which is insufficient for most color correction applications. Here, the authors present a method to estimate a hyperspectral image from an RGB image and pointwise hyperspectral data. This is then used to color correct the hyperspectral underwater image and transform it back into RGB color space.

  • 203.
    Åhlén, Julia
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Sundgren, David
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för matematik och statistik.
    Bengtsson, Ewert
    Pre-Processing of Underwater Images Taken in Shallow Waters for Color Reconstruction Purposes2005In: Proceedings of the 7th IASTED International Conference on Signal and Image Processing, 2005Conference paper (Refereed)
    Abstract [en]

    Coral reefs are monitored with different techniques in order to examine their health. Digital cameras, which provide an economically defendable tool for marine scientists to collect underwater data, tend to produce bluish images due to severe absorption of light at longer wavelengths. In this paper we study the possibilities of correcting for this color distortion through image processing. The decrease of red light by depth can be predicted by Beer's law. Another parameter that has to be taken into account is the image enhancement functions built into the camera. We use a spectrometer and a reflectance standard to obtain the data needed to approximate the joint effect of these functions. This model is used to pre-process the underwater images taken by digital cameras so that the red, green and blue channels show correct values before the images are subjected to correction for the effects of water column through application of Beer's law. This process is fully automatic and the amount of processed images is limited only by the speed of computer system. Experimental results show that the proposed method works well for correcting images taken at different depths with two different cameras.

  • 204.
    Åhlén, Julia
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Sundgren, David
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för matematik och statistik.
    Lindell, Tommy
    Dissolved Organic Matters Impact on Color Reconstruction of Underwater Images2005In: Proceedings of the 14th Scandinavian Conference on Image Analysis, 2005, p. 1148-1156Conference paper (Refereed)
    Abstract [en]

    The natural properties of water column usually affect underwater imagery by supressing high-energy light. In application such as color correction of underwater images estimation of water column parameters is crucial. Diffuse attenuation coefficients are estimated and used for further processing of underwater taken data. The coeeficients will give information on how fast light of different wavelengths decreases with increasing depth. Based on the exact depth measurements and data from a spectrometrer the calculation of downwelling irradiance will be done. Chlorophyll concentration and a yellow substance factor contribute to a great variety of values of attenuation coefficients at different depth. By taking advantage of variations in depth, a method is presented to estimate the influence of dissolved organic matters and chlorophyll on color correction. Attenuation coefficients that depends on concentration of dissolved organic matters in water gives an indication on how well any spectral band is suited for color correction algorithm.

  • 205.
    Åhman, Fredrik
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Hillström, Lars
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för naturvetenskap.
    Using a Game Theoretical Approach for Experimental Simulation of Brood Reduction: Conflict and Co-Operation, Effect on Brood Size with Limited Resources2005In: Proceedings of the Seventh International Conference on Enterprise Information Systems, 2005, p. 220-225Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    The evolution of parental care includes typical caring behaviour, such as protecting or feeding offspring. Sibling rivalry is anthropogenic viewed as conflicting behaviour, and can ultimately lead to brood reduction. In this study we have used object oriented programming to simulate different scenarios in this sibling rivalry conflict. A number of hypotheses have been proposed to explain the complex interactions occurring during brood reduction, but few simulation models successfully combines it with a hypothesis necessary to describe an ESS. In our solution we present a simple experimental simulation for brood reduction, where each sibling acts as an autonomous agent that has the ability to initiate actions for cooperation and competition against other siblings. Agents have a limited set of actions that can be activated during the onset of some specific environmental conditions, such as prey density, different climate variables etc. Parameters for food distribution are determined on a basis of a former known theory for maximizing inclusive fitness. In the computer simulations we have studied effects on sizes of siblings and fitness measures with varying degree of hatching patterns and prey density for siblings within the artificial brood. Results from the experimental simulations demonstrate interesting similarities with brood reduction in a real world setting, such as in raptorial birds that practice facultative siblicidal behaviour. Agents within the artificial brood respond with stronger conflicting behaviour whenever resources are limited and simulating increased hatching asynchrony lead to a lower survival rate (because of increased size hierarchy) of siblings within the simulated brood.

  • 206.
    Åström, Jesper
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Designvisualisering ur ”First person”-perspektiv2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    För att skapa kraftfullare presentationer måste nya metoder implementeras för att visualisera projekt. Ett aktivitetshus för ungdomar visualiseras i detta projekt genom att 3D-modellen av huset placeras i ett filmklipp från den plats där huset skall stå. Stegen som togs för att realisera detta var förarbete i form av inskaffande av ritningar, filmande, matchmoving, 3D-modellering, rendering, compositing och ljuddesign. Resultatet blev ett filmklipp som ur ett första persons perspektiv både visar exteriören och interiören.

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    FULLTEXT02
  • 207.
    Öman, Maria
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Jonsson, Torsten
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Om ett pedagogiskt arbete på en högskoleavdelning2004In: Kunskap och lärande i den högre utbildningen: lärarreflexioner från praktiken / [ed] Sara Dahlström och Göran Fransson, Gävle: Högskolan i Gävle , 2004, p. 39-52Chapter in book (Other (popular science, discussion, etc.))
  • 208.
    Östholm, John
    University of Gävle, Department of Mathematics, Natural and Computer Sciences. University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för datavetenskap.
    Spelkaraktär: En kreativ designprocess2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Designprocessen för en ”next-gen”-spelkaraktär är i dag förhållandevis invecklad och innehåller många olika moment innan den når sitt slutgiltiga stadium med en färdig karaktär som resultat. Den här artikeln dokumenterar designprocessen för en spelkaraktär från början till slut och kommer att se mycket till den kreativa men även den tekniska aspekten av detta arbete. Arbetet resulterar i en karaktär som modelleras, skulpteras, animeras och slutligen importeras till Unreal Editor 3.0.

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    FULLTEXT02
2345 201 - 208 of 208
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