Sökning: "High frequency approximations"
Visar resultat 16 - 20 av 36 avhandlingar innehållade orden High frequency approximations.
16. Silicon Carbide Microwave Devices
Sammanfattning : This work deals with silicon carbide (SiC) microwave devices. It treats two devices; the Schottky diode and the metal semiconductor field effect transistor (MESFET). Different MESFET materials, fabrication processes, theoretical models for physical simulation, and device models are presented. LÄS MER
17. Countermeasures against railway ground and track vibrations
Sammanfattning : Railway track and ground vibrations are considered, with anemphasis on methods of mitigation ("countermeasures"), forapplication to wayside disturbance problems.Original field measurements from two sites in Sweden, aswell as borrowed measurements from Norway, provide vibrationresults at many points on the track, on and underneath theground surface, for a variety of trains, both with and withoutcountermeasures in-place. LÄS MER
18. Topics in Analysis and Computation of Linear Wave Propagation
Sammanfattning : This thesis concerns the analysis and numerical simulation of wave propagation problems described by systems of linear hyperbolic partial differential equations. A major challenge in wave propagation problems is numerical simulation of high frequency waves. LÄS MER
19. Design of Low-Order Controllers using Optimization Techniques
Sammanfattning : In many applications, especially in the process industry, low-level controllers are the workhorses of the automated production lines. The aim of this study has been to provide simple tuning procedures, either optimization-based methods or tuning rules, for design of low-order controllers. The first part of this thesis deals with PID tuning. LÄS MER
20. On the Design of Ultra-fast Electro-Mechanical Actuators
Sammanfattning : The continuously increasing demand for connecting electric grids with remote renewable energy sources such as wind power and photovoltaic cells has rekindled interest in high voltage direct current (HVDC) multi-terminal networks. Although HVDC networks have numerous benefits, their adoption relies entirely on the availability of HVDC circuit breakers which, compared to traditional alternating current circuit breakers, have to operate in a time frame of milliseconds. LÄS MER