Brushless Doubly Fed Machines (BDFM) have potential advantages in variable
speed generation and adjustable speed drive applications. The most significant of these
advantages is a reduction in the power electronic converter rating, and therefore a
reduction in overall system cost. Presently, efforts are being directed at optimizing the
design of...
This thesis presents both an analysis and simulations of a passively controlled variable-speed generator system, which can be applied for renewable energy sources such as wind turbines. Parallel connected passive/external resistors and inductors are connected to the slip rings of a wound rotor induction machine to provide an acceptable speed...
With the increased attention on high efficiency and energy savings, power electronic energy conversion equipment is increasingly incorporated in all levels of the power system. The drawback of such equipment is the generation of nonsinusoidal currents in the power distribution network due to the nonlinear operation. Harmonic currents may distort...
With the increased attention on high efficiency and controllability of industrial processes, as well as reduced weight, volume and cost of consumer products, the applications of nonlinear power electronic converters such as adjustable speed drives (ASDs) are showing a rapid rise. Power Quality (PQ) is becoming an increasing concern with...
The study investigated the impact of Thai preservice middle school mathematics teachers' knowledge of subject matter and of students' conceptions of division of rational numbers with respect to their classroom practices in a teaching environment controlled by a required national curriculum. Four preservice teachers were selected with different knowledge of...
This dissertation investigates the use of a hardware mechanism called Eager Data Transfer (EDT) for achieving the reduction of communication latency for user-level network protocol. To reach the goal, the dissertation addresses the following research issues. First, the development of a communication system performance evaluation tool called Linux/SimOS is presented....
Generation of electricity from the wind is becoming increasing popular as an
environmentally responsible resource. Current methods for generating electricity from
the wind involve the use of fixed-speed generators. However, the use of variable-speed
generators increases the amount of energy that can be extracted from the wind.
Most variable-speed technologies...
We construct an implicit derivative matching (IDM) technique for restoring the accuracy of the Yee scheme for Maxwell's equations in dispersive media with material interfaces in one dimension. We consider media exhibiting orientational polarization, which are represented using a Debye dispersive model, examples of which are water and living tissue....
This research employed both quantitative and qualitative research methodologies to
explore the impact of mobile wireless technology (MWT) in higher education classrooms.
The methodology was developed using systems engineering concepts. A methodology to
evaluate and compare the cost, cost-effectiveness and cost-utility of different MWT
configurations was also developed. Five outcomes...
In the first part of this dissertation, low frequency l/f or flicker noise in the frequency range of Hz to kHz has been identified and demonstrated to be described by temperature fluctuations in heat conduction in bipolar transistors operated at higher power densities. This noise phenomenon is not described by...