Search for dissertations about: "Periodic conditions"

Showing result 6 - 10 of 173 swedish dissertations containing the words Periodic conditions.

2. 6. On the Analysis of Horns, Reflectors, and Periodic Structures

   Author : Martin Johansson; Chalmers tekniska högskola; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY;

   Abstract : The design and manufacturing of a dual-frequency horn is presented. The dual-depth corrugated horn is fed by a circular and a coaxial waveguide, in the upper and lower frequency band, respectively. The reason for choosing a waveguide-only feeding network is discussed. READ MORE

4. 7. Control and Analysis of Pulse-Modulated Systems

   Author : Stefan Almér; Ulf Jönsson; Gilead Tadmor; KTH; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; Pulse-width modulation; Periodic systems; Stability analysis; Harmonic analysis; Lyapunov methods; Dynamic phasors; Harmonic transfer function; Switched mode power converters; Sampled data modeling; H-infinity synthesis; Optimization; systems theory; Optimeringslära; systemteori;

   Abstract : The thesis consists of an introduction and four appended papers. In the introduction we give an overview of pulse-modulated systems and provide a few examples of such systems. Furthermore, we introduce the so-called dynamic phasor model which is used as a basis for analysis in two of the appended papers. READ MORE

5. 8. A hybrid finite element method for electromagnetics with applications in time-domain

   Author : DAVID DEGERFELDT; Chalmers tekniska högskola; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Nitsche s method; antenna arrays; NASA almond; edge elements; scattering; explicit-implicit time-stepping; Maxwell s equations; Finite Element Method; mass lumping; stability analysis; Finite-Differences Time-Domain; periodic structures; shape and material optimization;

   Abstract : In this thesis, a new hybrid method that combines the Finite Element Method (FEM) with the Finite-Difference in Time-Domain (FDTD) method is presented. Tetrahedrons in the unstructured FEM region are connected directly to thehexahedrons in the structured FDTD region. READ MORE

6. 9. Transient Phenomena in CO and Hydrocarbon Oxidation over Supported Platinum Catalysts

   Author : Per-Anders Carlsson; Chalmers tekniska högskola; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; mean-field kinetics simulations; ignition; environmental heterogeneous catalysis; flow-reactor studies; periodic operation; extinction; low-temperature activity; transient methods; in situ spectroscopy;

   Abstract : The aim with this thesis work was to better understand transient phenomena involved in the low-temperature oxidation of CO and hydrocarbons by oxygen over typical oxidation catalysts. Supported platinum catalysts were prepared and carefully studied under transient conditions by means of flow-reactor experiments, different in situ spectroscopic (FTIR and XANES) methods in combination with mass spectrometry and mean-field kinetics simulations. READ MORE

7. 10. Underactuated mechanical systems : Contributions to trajectory planning, analysis, and control

   Author : Pedro La Hera; Anton Shiriaev; Ambarish Goswami; Umeå universitet; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Underactuated mechanical systems; mechanical systems with impacts; trajectory planning; periodic trajectories; orbital stabilization; walking robots; virtual holonomic constraints; transverse linearization; Automatic control; Reglerteknik; Automatic Control; reglerteknik;

   Abstract : Nature and its variety of motion forms have inspired new robot designs with inherentunderactuated dynamics. The fundamental characteristic of these controlled mechanicalsystems, called underactuated, is to have the number of actuators less than the number ofdegrees of freedom. READ MORE