Sökning: "sigma"

Visar resultat 11 - 15 av 151 avhandlingar innehållade ordet sigma.

1. 11. Digitally Enhanced Continuous-Time Sigma-Delta Analogue-to-Digital Converters

   Författare :Julian Garcia; Ana Rusu; Maurits Ortmanns; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; analogue-to-digital conversion; sigma-delta modulation; digital enhancement; continuous-time; multi-channel applications;

   Sammanfattning : The continuous downscaling of CMOS technology presents advantagesand difficulties for IC design. While it allows faster, denser and more energy efficient digital circuits, it also imposes several challenges which limit the performance of analogue circuits. LÄS MER

3. 12. Strings as Sigma Models and in the Tensionless Limit

   Författare :Jonas Persson; Ulf Lindström; Joseph Minahan; Fawad Hassan; Uppsala universitet; []
   Nyckelord :Theoretical physics; Theoretical Physics; String Theory; Tensionless Strings; Supergravity Backgrounds; Plane Wave; Extended Supersymmetry; Non-Linear Sigma Models; Generalized Complex Geometry; T-duality; Teoretisk fysik;

   Sammanfattning : This thesis considers two different aspects of string theory, the tensionless limit of the string and supersymmetric sigma models with extended supersymmetry. First, the tensionless limit is used to find a IIB supergravity background generated by a tensionless string. The background has the characteristics of a gravitational shock-wave. LÄS MER

4. 13. The Complex World of Superstrings : On Semichiral Sigma Models and N=(4,4) Supersymmetry

   Författare :Malin Göteman; Ulf Lindström; Daniel Waldram; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Non-linear sigma models; extended supersymmetry; semichiral superfields; neutral hyperkähler geometry; generalized Kähler geometry; T-duality; vector multiplets; Theoretical Physics; Teoretisk fysik;

   Sammanfattning : Non-linear sigma models with extended supersymmetry have constrained target space geometries, and can serve as effective tools for investigating and constructing new geometries. Analyzing the geometrical and topological properties of sigma models is necessary to understand the underlying structures of string theory. LÄS MER

5. 14. Power-Efficient Continuous-Time Incremental Sigma-Delta Analog-to-Digital Converters

   Författare :Sha Tao; Ana Rusu; Franco Maloberti; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; analog-to-digital conversion; sigma-delta modulation; incre- mental ADC; two-step ADC; continuous-time; biosensor applications.;

   Sammanfattning : Over the past decade, there has been a growing interest in the devel- opment of integrated circuits (ICs) for wearable or implantable biosensors, aiming at providing personalized healthcare services and reducing the health-care expenses. In biosensor ICs, the analog-to-digital converter (ADC) is a key building block that acts as a bridge between analog signals and digital processors. LÄS MER

7. 15. Sigma-Delta-over-Fiber for High-Speed Wireless Communication Systems

   Författare :Ibrahim Can Sezgin; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Sigma-delta-over-fiber; Ultra-high speed communication; Distributed-MIMO; Vertical-cavity surface-emitting-laser;

   Sammanfattning : Future mobile communication networks aim to increase the communication speed, provide better reliability and improve the coverage. It needs to achieve all of these enhancements, while the number of users are increasing drastically. LÄS MER