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Visar resultat 1 - 5 av 179 avhandlingar som matchar ovanstående sökkriterier.

  1. 1. Photonic terahertz-wave generation, radiation and quasioptical integration

    Författare :Biddut Kumar Banik; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; semiconductor device modelling; semiconductor diodes; III-V semiconductors; Catadioptric lens; imaging; dipole antennas; slot antennas; lens antennas; semiconductor heterojunctions; dielectric loaded antennas; optical mixers; photomixers; near-field imaging; computer aided engineering; indium compounds; millimetre wave imaging; near-field optics; submillimeter wave generation; photodiodes; terahertz sources; millimetre wave generation; submillimetre wave integrated circuits; microwave imaging; uni-travelling-carrier photodiodes;

    Sammanfattning : This thesis deals with the uni-travelling-carrier photodiode (UTC-PD) based photonic generation of terahertz waves, antenna designs for the terahertz radiation and a novelcatadioptric lens for quasioptical integration.The ongoing and accomplished research work on the UTC-PD, its limitations and optimisation scopes for attaining higher bandwidth and higher output power have been discussed. LÄS MER

  3. 2. Inductive Pulse Generation

    Författare :Adam Lindblom; Hans Bernhoff; Jan Isberg; Anders Larsson; Owen Farish; Uppsala universitet; []
    Nyckelord :Technology; Pulsed Power; Inductive Pulse Generator; High Voltage; Semicon; XLPE; TEKNIKVETENSKAP; TECHNOLOGY; TEKNIKVETENSKAP;

    Sammanfattning : Pulsed power generators are a key component in compact systems for generation of high-power microwaves (HPM). HPM generation by virtual cathode devices such as Vircators put high demands on the source. The rise time and the pulse length of the source voltage are two key issues in the generation of HPM radiation. LÄS MER

  4. 3. Intense laser-plasma interactions

    Författare :Joel Magnusson; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; radiation reaction; radiation generation; particle-in-cell; plasma; pair production cascades; ion acceleration; laser;

    Sammanfattning : In the interaction of ultra-intense laser fields with matter, the target is rapidly ionized and a plasma is formed. The ability of a plasma to sustain acceleration gradients, orders of magnitude larger than achievable with conventional accelerators, has led to a great interest in laser-driven plasma-based particle and radiation sources, with applications in materials science, biology and medicine. LÄS MER

  5. 4. Radiation Therapy Patient Scheduling: An Operations Research Approach

    Författare :Sara Frimodig; Per Enqvist; Jan Kronqvist; Mats Carlsson; Willem-Jan van Hoeve; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Radiation therapy scheduling; patient scheduling; multi-appointment scheduling; operations research; integer programming; constraint programming; column generation; Schemaläggning; strålterapi; operationsanalys; heltalsprogrammering; villkorsprogrammering; kolumngenerering; Optimeringslära och systemteori; Optimization and Systems Theory;

    Sammanfattning : The manual scheduling of patients for radiation therapy is difficult and labor-intensive. With the increase in cancer patient numbers, efficient resource planning is an important tool to achieve short waiting times and equal right to care. This thesis studies an operations research approach to the radiation therapy scheduling problem. LÄS MER

  7. 5. Utilizing Problem Structure in Optimization of Radiation Therapy

    Författare :Fredrik Carlsson; Anders Forsgren; Edwin Romeijn; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Optimization; intensity-modulated radiation therapy; conjugate-gradient method; step-and-shoot delivery; column generation; quasi-Newton method; regularization; sequential quadratic programming; Optimization; systems theory; Optimeringslära; systemteori;

    Sammanfattning : In this thesis, optimization approaches for intensity-modulated radiation therapy are developed and evaluated with focus on numerical efficiency and treatment delivery aspects. The first two papers deal with strategies for solving fluence map optimization problems efficiently while avoiding solutions with jagged fluence profiles. LÄS MER