Student Number : 0401422G - MSc dissertation - School of Chemical and Metallurgical Engineering - Faculty of Engineering / Mixing is an important operation that is carried out in food, paint, pharmaceutical and mineral processing industries. Ball mills are one of the many mixing vessels used in a mineral processing industry. During grinding, the mill’s efficiency depends on particle presentation to the grinding media and the adequate utilisation of the applied forces to effect breakage of particles (ore). Utilisation of applied forces is affected by how well particles and grinding media are mixed. The study of charge mixing is important as it affects the mill’s production rate and accelerates media wear, thus relevant to the cost reduction for the milling process. The kinetics of mixing in a batch ball mill were quantified both radially and axially. Experiments were conducted in a laboratory batch ball mill and two experimental programs were used to study the mixing process. Radial mixing of particles was observed to increase with increasing mill speed. For a mill used in this study, mixing of particles at Nc=90% took almost half the total time taken at Nc=75% to reach completion. A simplified mathematical model is presented, which can be used to predict the radial mixing of particles in a ball mill. Axial mixing of particles was observed to be affected by both the charge system used and segregation of particles from the grinding media. It took a minute for mixing to reach 80% completion for a mill used in the experiments. Mixing of particles was faster in a steel balls/plastic powders charge system than in a glass beads/quartz charge system. The distribution of particles in a batch mill was observed to vary along the axis of the mill. The centre of the mill was overfilled with particles, U>1, while the regions near the mill ends were underfilled, U<1. The opposite was true for the grinding media. The data reported was based on measurements of particle distribution along the mill as affected by different charge systems. The work presented in this thesis is a contribution to the continuing research on mixing of particles in ball mills.

The understanding of the subjective experience of a visually stable world despite the occurrence of an observer's eye movements has been the focus of extensive research for over 20 years. These studies have revealed fundamental mechanisms such as anticipatory receptive field (RF) shifts and the saccadic suppression of stimulus displacements, yet there currently exists no single explanatory framework for these observations. We show that a previously presented neuro-computational model of peri-saccadic mislocalization accounts for the phenomenon of predictive remapping and for the observation of saccadic suppression of displacement (SSD). This converging evidence allows us to identify the potential ingredients of perceptual stability that generalize beyond different data sets in a formal physiology-based model. In particular we propose that predictive remapping stabilizes the visual world across saccades by introducing a feedback loop and, as an emergent result, small displacements of stimuli are not noticed by the visual system. The model provides a link from neural dynamics, to neural mechanism and finally to behavior, and thus offers a testable comprehensive framework of visual stability.

The understanding of the subjective experience of a visually stable world despite the occurrence of an observer's eye movements has been the focus of extensive research for over 20 years. These studies have revealed fundamental mechanisms such as anticipatory receptive field (RF) shifts and the saccadic suppression of stimulus displacements, yet there currently exists no single explanatory framework for these observations. We show that a previously presented neuro-computational model of peri-saccadic mislocalization accounts for the phenomenon of predictive remapping and for the observation of saccadic suppression of displacement (SSD). This converging evidence allows us to identify the potential ingredients of perceptual stability that generalize beyond different data sets in a formal physiology-based model. In particular we propose that predictive remapping stabilizes the visual world across saccades by introducing a feedback loop and, as an emergent result, small displacements of stimuli are not noticed by the visual system. The model provides a link from neural dynamics, to neural mechanism and finally to behavior, and thus offers a testable comprehensive framework of visual stability.

This diploma thesis deals with the issue of the driver's view from the vehicle, respectively the measurement of the field of views and blind spots. This thesis takes into account the 360° view around the vehicle. The first part of the thesis is devoted to the theoretical outlook of the vehicle. The reader becomes acquainted with the progressive development of the 360° view in a vehicle, beginning with the past and leading up to the present enhancements in today's vehicles. The reader will also understand, the position and movement of the eyes in a vehicle, the detailed description of the direct forward look, and the indirect reverse look. Subsequently, the theoretical part is devoted to the methodology of visibility measurements according to the prescribed standards of SAE and EHK. The theoretical part concludes with a chapter explaining how the theory is used in the practical part of the thesis. The practical part is devoted to the design of the 360° views of the vehicle and the description of the methodology. Another element of the practical part is the measurement protocol. This section deals with all the calculations for the complete driver's view, which was shown as an example on one of the sixteen vehicles measured. The last chapter compares, evaluates and reviews the results of all measured 360° views and blind spots around the vehicle.