Sökning: "Ulf Andersson"

Visar resultat 26 - 30 av 52 avhandlingar innehållade orden Ulf Andersson.

1. 26. 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. 27. Wear of piston rings in hydrostatic transmissions

   Författare :Ulf Skytte af Sätra; Sören Andersson; Kenneth Holmberg; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; piston ring; surface roughness; texture; coating; wear; hydraulic motor; Construction engineering; Konstruktionsteknik; Mechanical engineering; Maskinteknik;

   Sammanfattning : This study focuses on the wear of piston rings in a hydraulic radial piston motor. The piston ring has to satisfy increasing demands for reliability and longer service life. It has two contacting surfaces, the face and the flank, and operates under a boundary lubrication state. LÄS MER

4. 28. Model-based design of haptic devices

   Författare :Ahmad Aftab; Kjell Andersson; Ulf Sellgren; Per Wennhage; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Haptic device; model-based design; stiffness; SRA - ICT; SRA - Informations- och kommunikationsteknik;

   Sammanfattning : Efficient engineering design and development of high precision and reliable surgical simulators, like haptic devices for surgical training benefits from model-based and simulation driven design. The complexity of the design space, multi-domains, multicriteria requirements and multi-physics character of the behavior of such a product ask for a model based systematic approach for creating and validating compact and computationally efficient simulation models to be used for the design process. LÄS MER

5. 29. Designing for Transformational Change in School : Digitalizing the Digitized

   Författare :Annika Agélii Genlott; Åke Grönlund; Annika Andersson; Olga Viberg; Ulf Melin; Örebro universitet; []
   Nyckelord :SAMHÄLLSVETENSKAP; SOCIAL SCIENCES; Design Science Research; Digitalization; Information Systems artifact; School organization; School leadership;

   Sammanfattning : Digital technologies have gained a prominent role in education and schools, but research concerning how digital technologies can create better conditions for improved teaching and enhanced learning for students is scarce and inconclusive. Successful use of digital technologies requires a complex combination of interacting factors, including integrating technology and pedagogy as well as organizing and leading a structured transformation process. LÄS MER

7. 30. Food web structures and carbon transfer efficiencies in a brackish water ecosystem

   Författare :Kristin Dahlgren; Ulf Båmstedt; Agneta Andersson; Marja Koski; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Carbon transfer efficiency; Food web efficiency; zooplankton; production; pelagic; benthic; fatty acids; wax esters; Marine ecology; Marin ekologi;

   Sammanfattning : Two differently structured food webs can be distinguished in the pelagic habitat of aquatic systems; the classical one (autotrophic) with phytoplankton as a base and the microbial food web (heterotrophic) with bacteria as a base. Energy (produced at the basal trophic level) reaches higher trophic levels, i.e. LÄS MER