Sökning: "sigma phase"

Visar resultat 1 - 5 av 44 avhandlingar innehållade orden sigma phase.

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

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

    Sammanfattning : 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. LÄS MER

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

    Författare :Joel Ekstrand; Maxim Zabzine; Anton Alekseev; Uppsala universitet; []
    Nyckelord :NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; Chiral de Rham complex; Conformal field theory; Poisson vertex algebra; Sigma model; String theory; Vertex algebra; Theoretical Physics; Teoretisk fysik;

    Sammanfattning : 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. LÄS MER

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

    Författare :Andreas Bredthauer; Ulf G. Lindström; Bengt E.W. Nilsson; Uppsala universitet; []
    Nyckelord :Theoretical physics; Theoretical Physics; String Theory; Tensionless Strings; Supergravity Backgrounds; Plane Wave; Supersymmetry; Non-linear Sigma Models; Generalized Complex Geometry; Teoretisk fysik;

    Sammanfattning : 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. LÄS MER

  4. 4. Evolution of Microstructure in Two Austenitic Alloys at High Temperatures

    Författare :Jenny M Erneman; Chalmers University of Technology; []
    Nyckelord :N ; Thermo-Calc; Nb C; gamma prime; DICTRA; APFIM; quantitative metallography; AISI 347; Alloy 800; energy filtered TEM; sigma phase;

    Sammanfattning : A niobium stabilised AISI 347 austenitic stainless steel was investigated after static ageing and creep deformation at temperatures between 500°C and 800°C for times up to 88 000 h. Coarse and fine NbX precipitates and also s-phase precipitates were formed in the temperature range 500-700°C. LÄS MER

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

    Författare :Jian Chen; Li-Rong Zheng; Fredrik Jonsson; Hannu Tenhunen; Georges Gielen; KTH; []
    Nyckelord :ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; 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.;

    Sammanfattning : 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. LÄS MER