Sökning: "periodic loading"

Visar resultat 1 - 5 av 24 avhandlingar innehållade orden periodic loading.

1. 1. Next Generation Wideband Antenna Arrays for Communications and Radio Astrophysics

   Författare :Christos Kolitsidas; Lars Jonsson; Christophe Craeye; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; array figure of merit; fundamental limits; wideband array; wide scan-angle array; strongly coupled asymmetric dipole array; periodic loading; soft Vivaldi array; 21cm Cosmology; Epoch of Reionization; Electrical Engineering; Elektro- och systemteknik;

   Sammanfattning : Wideband, wide-scan antenna arrays are a promising candidate for the future wireless networks and as well as an essential part of experimental radio astrophysics. Understanding the underline physics of the element performance in the array environment is paramount to develop and improve the performance of array systems. LÄS MER

3. 2. Ultracold rubidium atoms in periodic potentials

   Författare :Robert Saers; Anders Kastberg; Svante Jonsell; Jan W. Thomsen; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Bose-Einstein condensation; optical lattice; quantum phase transition; experiment; theory; Condensed matter physics; Kondenserade materiens fysik;

   Sammanfattning : This thesis includes both experimental and theoretical investigations, presented in a series of eight papers. The experimental part ranges from the construction procedures of an apparatus for Bose-Einstein condensates, to full scale experiments using three different set-ups for ultracold atoms in optical lattices. LÄS MER

4. 3. Miniaturized Hard Waveguides in Multifunction Array Antennas

   Författare :Malcolm Ng Mou Kehn; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; interlaced arrays; Floquet theorem; reflector antennas; focal plane array; multifunction antennas; miniaturized waveguides; multilayer structures; spectral domain technique; periodic structures; aperture reuse; method of moments; soft and hard surfaces; array antennas;

   Sammanfattning : Recent advances in technologies of wireless communications systems have led to an increasing desire for several antennas performing diverse functions at different frequencies to be integrated into a common radiating aperture. This gives rise to the so-called multifunction antenna, which affords the saving of scarce premium real estate and can alleviate problems arising from excessive antenna protrusions in aspects such as aerodynamics, aesthetics, and stealth capability in military applications. LÄS MER

5. 4. Growth of fatigue cracks subjected to non-proportional Mode I and II

   Författare :Peter Dahlin; Mårten Olsson; Veronique École; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Fatigue crack growth; Mode II overloading; Crack closure; Sequential mixed mode loading; Other engineering mechanics; Övrig teknisk mekanik;

   Sammanfattning : This thesis deals with some aspects of crack growth in the presence of cyclic loading, i.e. fatigue. The cyclic load cases studied here are primary of non-proportional mixed mode type. LÄS MER

7. 5. Numerical Modeling of Plasticity in FCC Crystalline Materials Using Discrete Dislocation Dynamics

   Författare :Arash Hosseinzadeh Delandar; Pavel Korzhavyi; Rolf Sandström; Mikko Alava; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Dislocations; crystal plasticity; discrete dislocation dynamics; Cu single crystal; high strain rate deformation; strain rate sensitivity; plastic anisotropy; slip band formation; Teknisk materialvetenskap; Materials Science and Engineering;

   Sammanfattning : Plasticity in crystalline solids is controlled by the microscopic line defects known as “dislocations”. Decisive role of dislocations in crystal plasticity in addition to fundamentals of plastic deformation are presented in the current thesis work. LÄS MER