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Visar resultat 1 - 5 av 74 avhandlingar som matchar ovanstående sökkriterier.

1. 1. Systematic Antenna Design Using the Theory of Characteristic Modes

   Författare :Zachary Miers; Institutionen för elektro- och informationsteknik; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Theory of Characteristic Modes; Antenna Design; Antenna; Characteristic Modes; Computational Electromagnetics; MIMO Systems; MIMO Antenna; MIMO; Mutual Coupling; Mobile Antenna;

   Sammanfattning : The day Faraday moved a magnet in and out of a wire loop and detected the time-varying magnetic field, the first wireless transmitter / receiver system was created and the world was changed forever. However, it took almost fifty years for Heinrich Hertz to use Maxwell's equations and Faraday's insights in his professorship at Karlsruhe to create the first electromagnetic wireless communication system using a spark gap dipole transmitter and a loop antenna-based receiver. LÄS MER

3. 2. Computational Tools for Antenna Analysis and Design

   Författare :Doruk Tayli; Teoretisk elektroteknik; []
   Nyckelord :Antenna theory; Fundamental bounds; method of moments MoM ; Characteristic modes; macro basis functions MBFs ; adaptive cross approximation ACA ; endfire arrays;

   Sammanfattning : Many engineers and scientists prevalently use computational tools in electromagnetics, which is also the predominant case for antennas. The ever-increasing number of applications and technologies that employ antennas create a constant demand to improve and extend existing tools and develop new ones. LÄS MER

4. 3. Public procurement of engineering services : Task characteristics, control modes and effects on adaptability

   Författare :Klara Granheimer; Tina Karrbom Gustavsson; Per-Erik Eriksson; Göran Lindahl; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; client; construction management; engineering services; organizational control; public procurement; beställare; infrastrukturprojekt; offentlig upphandling; organisationsteori; tekniska konsulttjänster; Real Estate and Construction Management; Fastigheter och byggande;

   Sammanfattning : Previous research has emphasized the importance of engineering services and adaptability in the early stages of construction projects. Public clients usually procure engineering services from private companies, which makes their procurement strategies important in creating incentives for adaptability and innovation for the service providers. LÄS MER

5. 4. Dilute Nitride Lasers and Spectrally Engineered Semiconductor Laser Resonators

   Författare :Göran Adolfsson; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; single mode laser; transfer matrix method; threshold current; InGaAs; GaAs; multiple quantum wells; dilute nitrides; two-color laser; GaInNAs; Semiconductor lasers; molecular beam epitaxy; characteristic temperature; temperature dependence; ambipolar diusion; Fabry-Perot resonator; spectral engineering;

   Sammanfattning : The first part of this thesis deals with long wavelength (1.2-1.3 um) InGaAs(N)multiple quantum-well (QW) lasers grown on GaAs, with the aim of understandingand improving their threshold and temperature characteristics. The epitaxialmaterial is grown by molecular beam epitaxy (MBE). LÄS MER

7. 5. Acoustical Measurements of Material Nonlinearity and Nonequilibrium Recovery

   Författare :Kristian Haller; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; nonlinear acoustics; nondestructive testing; activation density; slow dynamics; nonequilibrium recovery; resonance frequency; nonlinear wave modulation spectroscopy; harmonic generation; trapped modes; open resonator; sweep rate; constant strain sweep;

   Sammanfattning : A damaged material or a material with non perfect atomic geometry, dislocations or cracks, exhibits two types of characteristic responses to acoustic excitations. First is the fast nonlinear dynamics response that is present as long as the material is excited. As soon as the excitation stops the response disappear. LÄS MER