Introduction Temporal fluctuations in a magnetic field produce artifacts and distortion in MR images. The main sources of such fluctuations are eddy currents, which are induced by gradient switching. Fluctuations induced by gradient switching cause significant effects in MR images, especially in DWEPI (diffusion weighted echo-planar imaging), that uses MPG (motion probing gradient) pulses with ...

The ability to control the speed and polarisation of light pulses will allow for faster data flow in optical networks of the future. Optical delay and switching have been achieved using slow-light techniques in various media, including atomic vapour. Most of these vapour schemes utilise resonant narrowband techniques for optical switching, but suffer the drawback of having a limited frequency r...

A unified graphical modeling technique, “Switching Flow-Graph” is developed to study the nonlinear dynamic behavior of pulse-width-modulated (PWM) switching converters. Switching converters are variable structure systems with linear subsystems. Each subsystem can be represented by a flow-graph. The Switching Flow-Graph is obtained by combining the flowgraphs of the subsystems through the use of...

High quality GGG:Cr,Ca crystal for passive Q-switching Nd:garnet lasers has been grown by the Czochralski method. Thermal treatment of GGG crystals co-doped with Cr4+ and Ca2+ at different temperatures is investigated. The absorption spectra were resolved into different peaks, of modified Gaussian line-shape. Transition from octahedral sites to tetrahedral ones is thermally activated. An...

This paper presents techniques to assist the power supply designer in accurately modeling and designing the control loop of a switchmode DC/DC power supply. The three major components of the power supply control loop (i.e., the power stage, the pulse width modulator and the error amplifier) are presented with power stage modeling being the focus of this presentation. The power stage is modeled ...