Review and future directions in the modelling and control of continuous drum granulation

Many granulation plants operate well below design capacity, suffering from high recycle rates and even periodic instabilities. This behaviour cannot be fully predicted using the present models. The main objective of the paper is to provide an overview of the current status of model development for granulation processes and suggest future directions for research and development. The end-use of the models is focused on the optimal design and control of granulation plants using the improved predictions of process dynamics. The development of novel models involving mechanistically based structural switching methods is proposed in the paper. A number of guidelines are proposed for the selection of control relevant model structures. (C) 2002 Published by Elsevier Science B.V.

Teacher Use of Learners' Native Language in the Foreign Language Classroom

This article reports on an exploratory study into the use of students' native language (NL) by teachers in the foreign language (FL) classroom. The project was undertaken by four teachers of beginner French at the University of Queensland. The teachers' aim was to investigate the use of NL in a context which actively promotes an immersion approach to FL teaching. The audio recordings of the teachers' speech were transcribed to provide data for estimating the amount of NL, and for analyzing the various instances of NL use. The study indicates that the activity type is a significant variable affecting NL amount. It also isolates two strategic uses of NL, translating FL words into NL, and contrasting NL and FL forms, both of which involve intrasentential code switching with NL words embedded in an FL sentence. The study suggests that these strategies may facilitate acquisition during immersion in FL, but experimental research is needed to test the hypothesis that translation and contrast facilitate learning of FL vocabulary and grammar.

Microstructural evolution of the Serido Belt, NE-Brazil: the effect of two tectonic events on development of c-axis preferred orientation in quartz

The polyphase evolution of the Serido Belt (NE-Brazil) includes D, crust formation at 2.3-2.1 Ga, D-2 thrust tectonics at 1.9 Ga and crustal reworking by D-3 strike-slip shear zones at 600 Ma. Microstructural investigations within mylonites associated with D-2 and D-3 events were used to constrain the tectono-thermal evolution of the belt. D-2 shear zones commenced at deeper crustal levels and high amphibolite facies conditions (600-650 degreesC) through grain boundary migration, subgrain rotation and operation of quartz Q-prism slip. Continued shearing and exhumation of the terrain forced the re-equilibration of high-T fabrics and the switching of slip systems from (c)-prism to positive and negative (a)-rhombs. During D-3, enhancement of ductility by dissipation of heat that came from syn-D-3 granites developed wide belts of amphibolite facies mylonites. Continued shearing, uplift and cooling of the region induced D-3 shear zones to act in ductile-brittle regimes, marked by fracturing and development of thinner belts of greenschist facies mylonites. During this event, switching from (a)-prism to a basal slip indicates a thermal path from 600 to 350 degreesC. Therefore, microstructures and quartz c-axis fabrics in polydeformed rocks from the Serido Belt preserve the record of two major events, which includes contrasting deformation mechanisms and thermal paths. (C) 2003 Elsevier Ltd. All rights reserved.

Influence of magnetically-induced E-fields on cardiac electric activity during MRI: A modeling study

In modern magnetic resonance imaging (MRI), patients are exposed to strong, time-varying gradient magnetic fields that may be able to induce electric fields (E-fields)/currents in tissues approaching the level of physiological significance. In this work we present theoretical investigations into induced E-fields in the thorax, and evaluate their potential influence on cardiac electric activity under the assumption that the sites of maximum E-field correspond to the myocardial stimulation threshold (an abnormal circumstance). Whole-body cylindrical and planar gradient coils were included in the model. The calculations of the induced fields are based on an efficient, quasi-static, finite-difference scheme and an anatomically realistic, whole-body model. The potential for cardiac stimulation was evaluated using an electrical model of the heart. Twelve-lead electrocardiogram (ECG) signals were simulated and inspected for arrhythmias caused by the applied fields for both healthy and diseased hearts. The simulations show that the shape of the thorax and the conductive paths significantly influence induced E-fields. In healthy patients, these fields are not sufficient to elicit serious arrhythmias with the use of contemporary gradient sets. However, raising the strength and number of repeated switching episodes of gradients, as is certainly possible in local chest gradient sets, could expose patients to increased risk. For patients with cardiac disease, the risk factors are elevated. By the use of this model, the sensitivity of cardiac pathologies, such as abnormal conductive pathways, to the induced fields generated by an MRI sequence can be investigated. (C) 2003 Wiley-Liss, Inc.

Digitally-implemented naturally sampled PWM suitable for multilevel converter control

For dynamic closed loop control of a multilevel converter with a low pulse number (ratio of switching frequency to synthesized fundamental), natural sampled pulse-width modulation (PWM) is the best form of modulation. Natural sampling does not introduce distortion or a delayed response to the modulating signal. However previous natural sampled PWM implementations have generally been analog. For a modular multilevel converter, a digital implementation has advantages of accuracy and flexibility. Re-sampled uniform PWM is a novel digital modulation technique which approaches the performance of natural PWM. Both hardware and software implementations for a five level multilevel converter phase are presented, demonstrating the improvement over uniform PWM.

Identification and characterization of pptA: a gene involved in the phase-variable expression of phosphorylcholine on pili of Neisseria meningitidis

Pili of pathogenic Neisseria are major virulence factors associated with adhesion, cytotoxicity, twitching motility, autoaggregation, and DNA transformation. Pili are modified posttranslationally by the addition of phosphorylcholine. However, no genes involved in either the biosynthesis or the transfer of phosphorylcholine in Neisseria meningitidis have been identified. In this study, we identified five candidate open reading frames (ORFs) potentially involved in the biosynthesis or transfer of phosphorylcholine to pilin in N. meningitidis. Insertional mutants were constructed for each ORF in N. meningitidis strain C311#3 to determine their effect on phosphorylcholine expression. The effect of the mutant ORFs on the modification by phosphorylcholine was analyzed by Western analysis with phosphorylcholine-specific monoclonal antibody TEPC-15. Analysis of the mutants showed that ORF NMB0415, now defined as pptA (pilin phosphorylcholine transferase A), is involved in the addition of phosphorylcholine to pilin in N. meningitidis. Additionally, the phase variation (high frequency on-off switching of expression) of phosphorylcholine on pilin is due to changes in a homopolymeric guanosine tract in pptA.