Search for dissertations about: "Sigma phase"

Showing result 1 - 5 of 35 swedish dissertations containing the words Sigma phase.

  1. 1. Transformation phenomena in a super duplex stainless steel

    University dissertation from Stockholm : Materialvetenskap

    Author : Anders Wilson; KTH.; [2001]
    Keywords : Duplex stainless steel; Microstructure; Phase transformations; Precipitates; Sigma phase; Kinetics; Thermodynamic calculation; Continuous cooling transformation diagram; Time temperature transformation diagram; Computer model.;

    Abstract : Duplex stainless steels consist of about equal fractions offerrite and austenite and are attractive due to their highcorrosion resistance against pitting corrosion and stresscorrosion cracking. The pitting corrosion resistance can bedescribed by the PREN value which is defined asPREN=%Cr+3.3*%Mo+16*%N. READ MORE

  2. 2. Going Round in Circles From Sigma Models to Vertex Algebras and Back

    University dissertation from Uppsala : Acta Universitatis Upsaliensis

    Author : Joel Ekstrand; Uppsala universitet.; [2011]
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; Chiral de Rham complex; Conformal field theory; Poisson vertex algebra; Sigma model; String theory; Vertex algebra; Theoretical Physics; Teoretisk fysik;

    Abstract : In this thesis, we investigate sigma models and algebraic structures emerging from a Hamiltonian description of their dynamics, both in a classical and in a quantum setup. More specifically, we derive the phase space structures together with the Hamiltonians for the bosonic two-dimensional non-linear sigma model, and also for the N=1 and N=2 supersymmetric models. READ MORE

  3. 3. Tensionless Strings and Supersymmetric Sigma Models Aspects of the Target Space Geometry

    University dissertation from Uppsala : Acta Universitatis Upsaliensis

    Author : Andreas Bredthauer; Uppsala universitet.; [2006]
    Keywords : Theoretical physics; Theoretical Physics; String Theory; Tensionless Strings; Supergravity Backgrounds; Plane Wave; Supersymmetry; Non-linear Sigma Models; Generalized Complex Geometry; Teoretisk fysik;

    Abstract : In this thesis, two aspects of string theory are discussed, tensionless strings and supersymmetric sigma models.The equivalent to a massless particle in string theory is a tensionless string. Even almost 30 years after it was first mentioned, it is still quite poorly understood. READ MORE

  4. 4. Low Noise Oscillator in ADPLL toward Direct-to-RF All-digital Polar Transmitter

    University dissertation from Stockholm : KTH Royal Institute of Technology

    Author : Jian Chen; KTH.; KTH.; [2012]
    Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; all-digital; digitally-intensive; frequency modualtion; phase modulation; amplitude modulation; polar; transmitter; oscillator; digital controled oscillator; DCO; VCO; voltage controled oscillator; class-C oscillator; class-D PA; ADPLL; phase noise; RF; CMOS.;

    Abstract : In recent years all-digital or digitally-intensive RF transmitters (TX) have attracted great attention in both literature and industry. The motivation is to implement RF circuits in a manner suiting advanced nanometer CMOS processes. To achieve that, information is encoded in the time-domain rather than voltage amplitude. READ MORE

  5. 5. Influence of multiple welding cycles on microstructure and corrosion resistance of a super duplex stainless steel

    University dissertation from Trollhättan : University West

    Author : Vahid Hosseini; Högskolan Väst.; [2016]
    Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Super duplex stainless steel; autogenous TIG welding; multiple welding thermal cycles; sensitization; nitrogen loss; sigma phase; ferrite content; production technology; Production Technology; Produktionsteknik; Manufacturing and materials engineering; Produktions- och materialteknik;

    Abstract : Super duplex stainless steel (SDSS) has found a wide use in demanding applications such as offshore, chemical and petrochemical industries thanks to its excellent combination of mechanical properties and corrosion resistance. Welding of SDSS, however, is associated with the risk of precipitation of secondary phases and formation of excessive amounts of ferrite in the weld metal and heat affected zone. READ MORE