The experiences of users of the Griffiths III

The Griffiths III was published in 2016 and has since then been used internationally by practitioners. The Association for Research in Infant and Child Development (ARICD) is currently planning and reviewing, refining, and improving the 2016 version of this assessment tool. Part of this process is to obtain feedback from all the key role players in the Griffiths III. The purpose of the present study was to explore and describe how users of the Griffiths III experience the measure. A qualitative methodology was utilised, and an exploratory-descriptive design was employed. A questionnaire was created by the ARICD and distributed to all 217 registered users of the Griffiths III. A total of 72 registered Griffiths users, who were using the Griffiths III at that stage, completed and returned the questionnaires to the ARICD. The data were analysed using thematic analysis to extract themes. The findings of the study revealed four overarching themes, namely 1) the purpose and use of the Griffiths III; 2) domains, content, and structure of the Griffiths III; 3) psychometric properties, standardisation, and norms; and 4) merits, limitations, and improvements. Based on the findings, recommendations were made regarding the revision of the Griffiths III. These recommendations relate to a specialised version for children with an autism spectrum disorder, psychometric properties, school readiness elements, universality of the scales, administration time, diagnosis and screening, cost, specific items, and report writing.Thesis (MA) -- Faculty of Health Sciencess, 202

The experiences of users of the Griffiths III

The Griffiths III was published in 2016 and has since then been used internationally by practitioners. The Association for Research in Infant and Child Development (ARICD) is currently planning and reviewing, refining, and improving the 2016 version of this assessment tool. Part of this process is to obtain feedback from all the key role players in the Griffiths III. The purpose of the present study was to explore and describe how users of the Griffiths III experience the measure. A qualitative methodology was utilised, and an exploratory-descriptive design was employed. A questionnaire was created by the ARICD and distributed to all 217 registered users of the Griffiths III. A total of 72 registered Griffiths users, who were using the Griffiths III at that stage, completed and returned the questionnaires to the ARICD. The data were analysed using thematic analysis to extract themes. The findings of the study revealed four overarching themes, namely 1) the purpose and use of the Griffiths III; 2) domains, content, and structure of the Griffiths III; 3) psychometric properties, standardisation, and norms; and 4) merits, limitations, and improvements. Based on the findings, recommendations were made regarding the revision of the Griffiths III. These recommendations relate to a specialised version for children with an autism spectrum disorder, psychometric properties, school readiness elements, universality of the scales, administration time, diagnosis and screening, cost, specific items, and report writing.Thesis (MA) -- Faculty of Health Sciencess, 202

Simplified grinding mill circuit models for use in process control

A grinding mill circuit forms a crucial part in the energy-intensive comminution process of extracting valuable metals and minerals from mined ore. The ability to control the grinding mill circuit is of primary importance to achieve the desired product specification with regards to quality and production rate. In order to achieve control objectives an accurate dynamic model of the milling circuit is required. Phenomenological models are preferred over linear-time-invariant models since the latter cannot describe the non-linear behaviour of the process. However, the available phenomenological models of grinding mill circuits are usually complex, use large parameter sets and are mostly aimed towards steady-state design of grinding mill circuits. This study investigates simplified non-linear dynamic models of grinding mill circuits suitable for process controller design. In the first part of this study, the number of size classes in a cumulative rates model of a grinding mill circuit is reduced to determine the minimum number required to provide a reasonably accurate model of the circuit for process control. Each reduced size class set is used to create a non-linear cumulative rates model which is linearized to design a linear model predictive controller. The accuracy of a model is determined by the ability of the corresponding model predictive controller to control important process variables in the grinding mill circuit as represented by the full non-linear cumulative rates model. The second part of the study validates a simple and novel non-linear model of a run-of-mine grinding mill circuit developed for process control and estimation purposes. This model is named the Hulbert-model and makes use of the minimum number of states and parameters necessary to produce responses that are qualitatively accurate. It consists of separate feeder, mill, sump and hydrocyclone modules that can be connected to model different circuit configurations. The model uses five states: rocks, solids, fines, water and steel balls. Rocks are defined as too large to be discharged from the mill, whereas solids, defined as particles small enough to leave the mill, consist of out-of-specification coarse ore and in-specification fine ore fractions. The model incorporates a unique prediction of the rheology of the slurry within the mill. A new hydrocyclone model is also presented. The Hulbert-model parameters are fitted to an existing plant’s sampling campaign data and a step-wise procedure is given to fit the model to steady-state data. Simulation test results of the model are compared to sampling campaign data of the same plant at different steady-state conditions.Dissertation (MEng)--University of Pretoria, 2012.Electrical, Electronic and Computer Engineeringunrestricte

Quality Control of a Laser Additive Manufactured Medical Implant by X-Ray Tomography

Published ArticleQuality control of laser additive manufactured medical implants is of interest, especially if nondestructive quality control can be performed on parts before implantation. X-ray micro-computed tomography (microCT or CT) can be used for defect/porosity analysis as well as for comparing the part surface with its computer-aided design (CAD) file. In both cases, the limited use of CT is partly due to the variation in scan types and the quality of scans that can occur. We present a simple method demonstrating the use of a light metal casting as a reference porosity sample, to confirm good CT image quality and to quantify minimum detectable pore size for the selected CT scan settings. This makes a good comparison for additive manufactured parts, since castings generally contain more porosity. A full part-to-CAD comparison shows how the part is compared with its CAD file, as a second-quality control. The accuracy of the CAD variance is given by the minimum detectable pore size. Finally, the part is sectioned and scanned at two higher resolution settings showing small porosity (10–50 lm diameter) present but well distributed, as expected

Reconstructing faulty measurements at a tailings treatment surge tank

Measurement faults in processing plants can cause the performance of a process to deteriorate. Once the failure of a sensor is identified, it is possible to reconstruct the missing measurement using the measurements of other sensors. Plant operators or controllers can use the reconstructed measurement to make informed decisions. Although the theory to reconstruct faulty measurements is well-developed, various issues remain when applying the method in practice. In this study, a tailings treatment surge tank, which is a very simple process, is used to investigate issues surrounding measurement reconstruction using Principal Component Analysis. Different sets of faulty and correct sensors were created to investigate measurement reconstruction accuracy. The state observability of the surge tank model states was compared to the ability to reconstruct faulty measurements. It was found that the system does not necessarily need to be observable in terms of the available correct measurements for successful reconstruction. In addition, a fault in the measurement of the volume of slurry in the tank could not be reconstructed, even if it was the only faulty measurement. This indicates that the success of measurement reconstruction by Principal Component Analysis may depend on the dynamics of the process and the associated model.https://www.journals.elsevier.com/ifac-papersonlineam2022Electrical, Electronic and Computer Engineerin

Directionality of Cavities and Porosity Formation in Powder-Bed Laser Additive Manufacturing of Metal Components Investigated Using X-Ray Tomography

Published ArticleEnsuring additive manufactured metal components are free of major defects is crucial to the application of this new technology in medical and aerospace industries. One source of defects in such parts is lack of fusion in individual locations or specific layers. Such lack of melting or fusion could be the result of a nonflat powder bed due to an imperfect recoating blade or loose support structures causing recoating problems. Another possible source is laser power fluctuations or beam size fluctuations, or even ambient humidity or temperature changes, among others. The aims of this article are to investigate lack of fusion with planned induced defects (cavities) with different three-dimensional (3D) geometries and analyze these using nondestructive 3D X-ray tomography. It is found that some fusion occurs in induced defect layers and lines perpendicular to the build direction (XY) up to 180 lm in height. This means fusion occurs through fused layers above cavities, minimizing defect formation in the plane of the build platform. In contrast, in the case of vertical cavities (cavity walls) parallel to the build direction, much larger defects are observed compared to the above case. This result may point to the build direction (vertical) being more favorable for porosity formation under nonideal conditions (i.e., a preferred directionality). An example of unexpected porosity trail formation in the build direction is also reported from such nonideal conditions for a real part in contrast to a designed cavity

Validation of a dynamic non-linear grinding circuit model for process control

A step-wise algebraic routine is used to fit a dynamic non-linear model, specifically developed for process control, to steady-state process data of an industrial single-stage grinding mill circuit. Step-test data from the industrial plant is used to validate the response of the non-linear model. The results indicate that the model provides a qualitatively accurate response of the main process variables. Because the non-linear model parameters can be calculated from steady-state data, it provides an advantage over classical system identification methods as it does not require an expensive and disruptive step-test campaign to develop linear transfer function models. The model is ideal for model-based predictive process control.https://www.elsevier.com/locate/minenghj2022Electrical, Electronic and Computer Engineerin

Controlling a grinding mill circuit using constrained model predictive static programming

A constrained Model Predictive Static Programming (MPSP) method is implemented in simulation to a single-stage grinding mill circuit model. The results are compared to a constrained Nonlinear Model Predictive Control (NMPC) method. Both the constrained MPSP and NMPC controllers were able to track the desired output set-points without exceeding any constraints. The comparison shows that the constrained MPSP has a faster computational time than that of the NMPC controller with similar performance. Therefore, constrained MPSP shows promise as a model-based controller for large processes where computational time limits the use of NMPC.National Research Foundation of South Africa (Grant Numbers: 137769)https://www.journals.elsevier.com/ifac-papersonlineElectrical, Electronic and Computer Engineerin

Psychiatric morbidity in children involved in bullying treated at the Free State Psychiatric Complex

Background: Bullying is a multifaceted problem with many consequences. Aim: This study aimed to determine the psychiatric morbidity of children involved in bullying, either as bullies or victims, treated at the Child and Adolescent Mental Health Care Centre of the Free State Psychiatric Complex (FSPC). Setting: Free State Psychiatric Complex, Bloemfontein, South Africa. Methods: This retrospective cross-sectional study included children under 18 years treated at the FSPC Care Centre between January and September 2017. Information was extracted from patient files. Results: Of 288 patients, 98 (34.0%) were involved in bullying: 66 were bullies, 28 victims, 3 bully-victims, and 1 unspecified. For gender and family structure, there were no statistically significant differences between children involved and those not involved in bullying and between bullies and victims. Almost all bullies (95.4%) had aggression as presenting complaint compared with 39.3% of the victims (p 0.01). Statistically significantly more victims, than bullies, reported sadness (21.4%, 4.6%, p = 0.02). Attention deficit/hyperactivity disorder (ADHD) was diagnosed in most children, both involved (73.5%) and not involved (63.2%). Statistically significant differences for the presence of conduct disorder were found between children involved and those not involved in bullying (31.6%, 10.0%, p 0.01) and between bullies and victims (39.4%, 14.3%, p = 0.02). Conclusion: The prevalence of conduct disorder diagnosis was more common in bullies than in victims and those involved in bullying as opposed to those not involved. Contribution: Psychiatric information of bullying victims and perpetrators in the Free State, which had a high prevalence of bullying in a national survey