Applications of analysis of variance in wool marketing

Analysis of variance could be described as a statistical technique for analysing measurements depending on several kinds of effects operating simultaneously so as to decide which kinds of effects are important and to estimate the effects. Although probably not susceptible of a very precise definition, it in general consists of a body of tests of hypotheses and methods of estimation using statistics which are linear combinations of sums of squares of linear functions of the observed values. Having been developed mainly in connection with problems of agricultural experimentation, the application thereof in the South African Wool Trade seems non existent. I hope that this thesis will illustrate some of the very useful applications, especially to the extent where the rejection of all (or some) of the hypotheses under consideration is in itself as significant as the acceptance thereof would have been

The management and governance conundrum in South African public schools: principals’ perspectives

The introduction of school governing bodies (hereinafter SGBs) changed the roles and functions of principals dramatically when this new approach to school governance and professional management (referred to as a participatory decision-making approach) was activated when the South African Schools Act 84 of 1996 (hereinafter SASA) was implemented in January 1997. Consequently, the principal is no longer the only decision-maker in the school. The principal as the protagonist in school management and governance (implementing SGB policy) is the role-player most affected by the introduction of the participatory decision-making approach. In this article, we discuss principals’ perspectives regarding the shared participatory decision-making approach and the effects thereof on the relationship between the principal and the SGB. In this regard, it is important to note that the perceptions the two parties have of each other are established by the SGB’s encroachment on the professional management functions of the principal and vice versa. The research findings concluded that the relationship between the principal and the SGB is often a relationship characterised by tension, no trust and irrational actions by the SGB. The relationship is further influenced by the functionality or lack of functionality of SGBs as well as prevailing socio-economic conditions and SGB members’ levels of literacy. On the other hand, principals who do not adapt to participatory decision-making, and who still implement an assertive autocratic management approach, also contribute to a turbulent relationship

ACODV : Ant Colony Optimisation Distance Vector routing in ad hoc networks

A mobile ad hoc network is a collection of wireless mobile devices which dynamically form a temporary network, without using any existing network infrastructure or centralised administration. Each node in the network effectively becomes a router, and forwards packets towards the packet’s destination node. Ad hoc networks are characterized by frequently changing network topology, multi-hop wireless connections and the need for dynamic, efficient routing protocols. The overarching requirement for low power consumption, as battery powered sensors may be required to operate for years without battery replacement; An emphasis on reliable communication as opposed to real-time communication, it is more important for packets to arrive reliably than to arrive quickly; and Very scarce processing and memory resources, as these sensors are often implemented on small low-power microprocessors. This work provides overviews of routing protocols in ad hoc networks, swarm intelligence, and swarm intelligence applied to ad hoc routing. Various mechanisms that are commonly encountered in ad hoc routing are experimentally evaluated under situations as close to real-life as possible. Where possible, enhancements to the mechanisms are suggested and evaluated. Finally, a routing protocol suitable for such low-power sensor networks is defined and benchmarked in various scenarios against the Ad hoc On-Demand Distance Vector (AODV) algorithm.Dissertation (MSc)--University of Pretoria, 2005.Computer ScienceUnrestricte

A critique on previous work in vision aided navigation

This paper presents a critique on previous work in the field of vision aided navigation, particularly in the fusion of visual and inertial sensors for navigation. Several improvements and updates are proposed for the existent systems. GPS receivers have allowed for accurate navigation for many vehicles and robotic platforms. GPS based navigation can, however, prove to be impractical in applications where there is no GPS reception such as underground, indoors or in some urban areas. This pertains, in particular, to many robotic applications where position must be known in global coordinates or relative to a reference point. An inertial navigation system (INS) can be used to calculate one’s relative navigation state via dead-reckoning calculations. The downfall of a low-cost INS is the errors associated with the system. While these errors are initially small, integration causes large drift errors over time. To combat this problem, cameras can be used to estimate the errors present in the INS readings. These results can then be used to correct the navigation state output from the INS. While the motion estimations from the cameras are not error-free, this method is made highly effective because of the complementary nature of the errors from the cameras and INS. Several improvements are proposed for this method; algorithmically, in updates to its hardware, and with the introduction of graphics processors to improve computational performance. The overall system performance, individual steps, algorithms, and results are compared to results from similar works to those of the proposed improvements. It is shown that the accuracy, responsiveness and overall performance of the system can potentially be greatly improved

The management and governance conundrum in South African public schools : principals perspectives

The introduction of school governing bodies (hereinafter SGBs) changed the roles and functions of principals dramatically when this new approach to school governance and professional management (referred to as a participatory decision-making approach) was activated when the South African Schools Act 84 of 1996 (hereinafter SASA) was implemented in January 1997. Consequently, the principal is no longer the only decision-maker in the school. The principal as the protagonist in school management and governance (implementing SGB policy) is the role-player most affected by the introduction of the participatory decision-making approach. In this article, we discuss principals’ perspectives regarding the shared participatory decision-making approach and the effects thereof on the relationship between the principal and the SGB. In this regard, it is important to note that the perceptions the two parties have of each other are established by the SGB’s encroachment on the professional management functions of the principal and vice versa. The research findings concluded that the relationship between the principal and the SGB is often a relationship characterised by tension, no trust and irrational actions by the SGB. The relationship is further influenced by the functionality or lack of functionality of SGBs as well as prevailing socio-economic conditions and SGB members’ levels of literacy. On the other hand, principals who do not adapt to participatory decision-making, and who still implement an assertive autocratic management approach, also contribute to a turbulent relationship.http://journals.ufs.ac.za/index.php/pieam2023Education Management and Policy Studie

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

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

Structural and gas-sensing properties of CuO–CuxFe3−xO4 nanostructured thin films

Nanocrystalline CuO–CuxFe3−xO4 thin films were developed using a radio-frequency sputtering method followed by a thermal oxidation process. Thin films were deposited applying two very different conditions by varying the argon pressure and the target-to-substrate distance. Structural, microstructural and gas-sensing characteristics were performed using grazing incidence X-ray diffraction (GXRD), Raman spectroscopy, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and electrical measurements. Their sensing properties were examined using hydrogen gas in dry synthetic air. The shortest response and recovery times were observed between 280 and 300 °C independently of the deposition conditions

Paraffin (kerosene) poisoning in childhood is prevention affordable in South Africa?

Paraffin (known in some Western countries as kerosene) ingestion is the most common form of acute childhood poisoning in most developing countries. South African black communities reflect a similar pattern, yet the true size and cost of the problem are not known. Without such baseline data the effect of interventions cannot be evaluated.The aim of the study was to determine the incidence and treatment cost of paraffin poisoning in the Cape Peninsula, to identify high-risk areas and to discuss which measures offered the most economical and best preventive potential for this paediatric hazard.A 12-month retrospective study was undertaken in 1990. Relevant patient data were extracted from the files of 6 major Cape Peninsula hospitals. Treatment costs were calculated based on differential hospital costs per inpatient per day, with outpatient costs at one-third of the costs per day. Age-specific rates for affected residential areas were calculated to identify high-risk areas. A total of 436 children (62,5% male), mostly between the ages of 12 and 36 months, were treated at an estimated cost of R111 673. This amount would have been sufficient to provide 95% of households in the 8 identified high-risk areas with child-resistant paraffin containers. In these areas age-specific paraffin poisoning rates ranged from 1,8/1 000 to 7,7/1 000. Strategically planned interventions can be cost-effective when weighed against the treatment cost of cases of paraffin poisoning