Assessing the influence of lifter profiles on the velocity profile and the charge toe and shoulder using data from the PEPT system

Includes bibliographical references.The research focus of this thesis is lifter height effect on different charge characteristics. Thecharge characteristics identified were shoulder and toe angle, charge size and toe height. Anattempt was made to develop a model for the velocity profile incorporating lifter height.Therefore the objectives of the study are to: •Determine the effect of lifter height on the velocity profile using the particle tracking data. •Determine the effect the lifter height on the charge shoulder and toe. •Develop a velocity profile model including lifter height using granular flow theory and to compare the model to experimental data. The motivation for the study is that lifters are one of the most important design variables in a mill. Without lifters the mill’s energy efficiency would decrease. In Meaders & MacPherson, (1964) the effect of lifters on energy was quantified to be between 20% and 30%. The lifters control the height and angle of departure from the charge at the mill shell and therefore control the impact area and magnitude. The area and magnitude of the charge impact will affect the grind of the mill and energy utilization in the mill. The thesis was also aimed at generating data that can be used to model the velocity profile that can be incorporated in power models. Most of the power models do not account for the effect of lifters. The experiments involved collecting data from three dimensional particle tracking of selected particles in the charge. using the PEPT system. The PEPT experiments were conducted at IThemba Labs in Cape Town South Africa using a 300 mm x 285 mm experimental mill. The charge used for the experiments were glass beads with an approximate specific gravity (SG) of 2.7. The PEPT system operates by tracking the x, y and z coordinates with respect to time of an irradiated particle (tracer). The experiments were run under different conditions to evaluate the effect of the lifter height. The experiments were operated by varying mill speed (55%, 70% and 85%), mill fill (20%, 30% and 40%) and lifter heights (1.5 mm, 3 mm, 6 mm and 10 mm)

EVALUATION OF HOPKINSON BAR EXPERIMENTS USING MULTIPLE DIGITAL IMAGE CORRELATION SOFTWARE TOOLS

Three different tools for Digital Image Correlation (DIC) were used for evaluation of dynamic experiments performed using custom Open Hopkinson Pressure Bar (OHPB) apparatus. High strain-rate measurements were performed on specimens of advanced cellular materials with predefined structure and negative Poisson’s ratio. Low impedance polymethyl methacrylate (PMMA) bars instrumented with foil strain-gauges were used for dynamic loading of the specimens. Experiments were observed using a pair of high-speed cameras for imaging of loading process in sufficient quality. Custom developed evaluation DIC tool implemented in Matlab, open-source Matlab tool (NCorr) and commercial DIC software (ISTRA 4D) were all used for evaluation of image sequences recorded by high-speed cameras. Comparison of results obtained using all three different DIC tools and results of complementary strain-gauge measurement are shown in this paper. Verification of reliability of custom made DIC software tool is presented

Aktuelle statistische Befunde zu Ganztagsschulen

Dieser Beitrag soll den Leser*innen ei-nen differenzierten Überblick über ak-tuelle statistische Befunde zu Ganztags-schulen geben. Dies soll sowohl auf Bundes- und Länderebene, mit beson-derem Bezug auf die Situation Sach-sens, als auch auf Ebene der konkreten Umsetzung geschehen. Ebenfalls soll die Frage beantwortet werden, ob der Umbau zu Ganztagsschulen genügt, um den vielfachen gesellschaftlichen Erwartungen gerecht zu werden und an welchen Stellen Verbesserungsbe-darf besteht. Dabei werden die Per-spektiven unterschiedlicher beteiligter Personengruppen miteinbezogen

Surface Characterization of Retrieved Metal-on-Metal Total Hip Implants from Patients with Adverse Reaction to Metal Debris

The use of metal-on-metal (MoM) total hip implants has decreased recently due to reports of high failure rates and adverse local tissue reaction (ALTR). It has been hypothesized that wear metal debris released from CoCr bearing surfaces may provoke delayed hypersensitivity reactions. The goal of this study is to evaluate the microscopic bearing surface characteristics of implants revised due to evidence of ALTR. The bearing surface of each head and cup was analyzed using multiple microscopy techniques for characterization of the surface features. The presence of severe mechanical scratching was a common characteristic found in all of the implants evaluated. Mechanical factors seemed to be the prevalent failure mode related to the appearance of ALTR with this particular set of retrieved implants

Does expecting more pain make it more intense? Factors associated with the first week pain trajectories after breast cancer surgery

The aim of this study was to identify clinical risk factors for unfavorable pain trajectories after breast cancer surgery, to better understand the association between pain expectation, psychological distress, and acute postoperative pain. This prospective study included 563 women treated for breast cancer. Psychological data included questionnaires for depressive symptoms and anxiety. Experimental pain tests for heat and cold were performed before surgery. The amount of oxycodone needed for satisfactory pain relief after surgery was recorded. Pain intensity in the area of operation before surgery and during the first postoperative week and expected intensity of postoperative pain were recorded using the Numerical Rating Scale (NRS 0-10). Pain trajectories were formed to describe both initial intensity (the intercept) and the direction of the pain path (the slope). Factors associated with higher initial pain intensity (the intercept) were the amount of oxycodone needed for adequate analgesia, psychological distress, type of axillary surgery, preoperative pain in the area of the operation, and expectation of postoperative pain. The higher the pain initially was, the faster it resolved over the week. Expectation of severe postoperative pain was associated with higher scores of both experimental and clinical pain intensity and psychological factors. The results confirm that acute pain after breast cancer surgery is a multidimensional phenomenon. Psychological distress, pain expectation, and the patients' report of preoperative pain in the area to be operated should be recognized before surgery. Patients having axillary clearance need more efficient analgesic approaches.Peer reviewe