Sökning: "ulf jonsson avhandling"

Hittade 2 avhandlingar innehållade orden ulf jonsson avhandling.

  1. 1. Detecting Inclusions in a Silicone Rubber Phantom Using Standing Lamb Waves and Multiple Frequency Footprints

    Författare :Ulf G Jonsson; Britt Andersson; Olof A Lindahl; Jacques Ohayon; Umeå universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Piezoelectric; Silicone rubber; Impedance; Resonance; Lamb waves; Phantom; Electronics; elektronik;

    Sammanfattning : The thesis deals with one major question: is it possible, using one piezoelectric sensor/vibrator, to detect a hard inclusion in a silicone rubber phantom? The question was approached with an open mind and the task was subdivided into three clearly identifiable parts: characterization of the piezoelectric sensor/vibrator (paper I), creating a model of the visco-elastic properties of a tissue-like material (phantom) in contact with the sensor/vibrator (paper II), and to detect the presence of a hard inclusion in the phantom (paper III). All vibrations of the sensor/vibrator and phantom was modeled using a finite element method (FEM). LÄS MER

  3. 2. Unraveling the importance of solid and adsorbed phase mercury speciation for methylmercury formation, evasion and bioaccumulation

    Författare :Sofi Jonsson; Erik Björn; Ulf Skyllberg; Erik Lundberg; Per Persson; Robert Mason; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; mercury; methylmercury; aquatic systems; estuary; Hg; MeHg; bioaccumulation; methylation; demethylation; evasion; sediment; water; terrestrial sources; atmospheric sources; climate change; eutrophication;

    Sammanfattning : Monomethylmercury, MeHg, is formed under anoxic conditions in waters, sediments and soils and then bioaccumulated and biomagnified in aquatic food webs, negatively effecting both human and wildlife health. It is generally accepted that precipitation of mercury, Hg, and adsorption of Hg to e.g. LÄS MER