Search for dissertations about: "variable frequency"

Showing result 21 - 25 of 229 swedish dissertations containing the words variable frequency.

  2. 21. Impact of Tissue Characteristics on Radio-Frequency Lesioning and Navigation in the Brain : Simulation, experimental and clinical studies

    Author : Johannes Johansson; Karin Wårdell; Hans von Holst; Linköpings universitet; []
    Keywords : MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; Brain; Radio frequency ablation; Finite element method; Monte Carlo simulation; light reflectance; Radiological research; Radiologisk forskning;

    Abstract : Radio-Frequency (RF) lesioning, or RF ablation, is a method that uses high frequency currents for thermal coagulation of pathological tissue or signal pathways. The current is delivered from an electrode, which also contains a temperature sensor permitting control of the current at a desired target temperature. In the brain, RF lesioning can e.g. READ MORE

  4. 22. Dynamics of ecological communities in variable environments : local and spatial processes

    Author : Linda Kaneryd; Bo Ebenman; Peter Münger; Michael S. Fowler; Linköpings universitet; []
    Keywords : ;

    Abstract : The ecosystems of the world are currently facing a variety of anthropogenic perturbations, such as climate change, fragmentation and destruction of habitat, overexploitation of natural resources and invasions of alien species. How the ecosystems will be affected is not only dependent on the direct effects of the perturbations on individual species but also on the trophic structure and interaction patterns of the ecological community. READ MORE

  5. 23. Estimation of Forest Biomass and Faraday Rotation using Ultra High Frequency Synthetic Aperture Radar

    Author : Gustaf Sandberg; Chalmers tekniska högskola; []
    Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; NATURVETENSKAP; NATURAL SCIENCES; LANTBRUKSVETENSKAPER; AGRICULTURAL SCIENCES; Forest Biomass; Ultra High Frequency; Faraday Rotation; Synthetic Aperture Radar;

    Abstract : Synthetic Aperture Radar (SAR) data in the Ultra High Frequency (UHF; 300 MHz – 3 GHz)) band have been shown to be strongly dependent of forest biomass, which is a poorly estimated variable in the global carbon cycle. In this thesis UHF-band SAR data from the fairly flat hemiboreal test site Remningstorp in southern Sweden were analysed. READ MORE

  6. 24. Run-Up Transient Analysis for Salient Pole Wound Field Synchronous Motors : Field winding and power electronics implications for a smoother and cooler asynchronous start

    Author : Roberto Felicetti; Urban Lundin; Andreas Binder; Uppsala universitet; []
    Keywords : apparent resistance; cable modeling; current control; transmission line model; eddy currents; field winding; frequency analysis response; Fourier Transform; impedance mismatch; main inductance; overvoltage; parasitic capacitance; partial discharge; quality factor; ringing; slew rate; stray inductance; voltage gradient; winding resonance frequency; asynchronous start; run-up; torque ripple; reluctance torque; Engineering Science with specialization in Science of Electricity; Teknisk fysik med inriktning mot elektricitetslära;

    Abstract : Salient Pole Wound Field Synchronous Machines have better efficiency at full load than asynchronous machines of the same capability. Moreover, where asynchronous machines need inherently to draw a magnetizing current from the grid, Salient Pole Wound Field Synchronous Machines can work efficiently at unity power factor. READ MORE

  7. 25. Essays on Macroeconomics, Monetary Policy and Firm Heterogeneity

    Author : Claire Thürwächter; Per Krusell; Timo Boppart; Mathias Klein; Stockholms universitet; []
    Keywords : SAMHÄLLSVETENSKAP; SOCIAL SCIENCES; Macroeconomics; Monetary Economics; Monetary Policy Transmission; Firm Heterogeneity; Investment Frictions; High-frequency Identification; Granular Instrumental Variable; Corporate Debt; Corporate Leverage; Economics; nationalekonomi;

    Abstract : Firm Heterogeneity and Monetary Policy TransmissionThis paper studies sources of heterogeneity in the response of firm investment to monetary policy. I estimate firm-level semi-elasticities of investment to plausibly exogenous changes in interest rates for a comprehensive firm-level dataset for ten euro area countries. READ MORE