Design of an automated grinding media charging system for ball mills

The parameters of mill load (ML) not only represent the load of the ball mill, but also determine the grinding production ratio (GPR) of the grinding process. Monitoring and recognition of milling conditions have significant effect on the operating efficiency, product quality, and energy and grinding media consumption for the milling circuit. This paper presents an automated grinding media charging system incorporating a multi-agent system developed in Java Agent Development Environment (JADE). A control logix program is designed to determine the precise quantities of grinding media to be charged in an incremental manner such that shock loading is avoided. The multi-agent system created in JADE monitors the power drawn and the mill load of the ball mill such that proper charging conditions are established. High quality of the regulation process is achieved through utilization of the control logix and the multi-agent system

Review and analysis of work sampling methods : the case of an automated labour performance measurement system using the work sampling method

Published ArticleThis paper analyses work sampling and time study as work measurement methods with the view of employing them in an automated labour performance measurement system. These are compared with respect to Hawthorn effect, labour intensiveness, cost, tediousness and knowledge extensiveness. The analysis proves that work sampling is a better option for developing an automated labour performance measurement system that employs computer vision. Web cameras are used to feed real-time images to a central computer via USB extenders. The computer runs a standalone C++ application that uses a random function to establish when measurements are to be taken. The developed video camera footage is converted into a pixel matrix using OpenCV. This matrix is then filtered and analysed, enabling the tracking of a worker. The data generated is stored in text files. After the work sampling period has elapsed, the data is transferred into Microsoft Excel for analysis. Finally a report of the labour utilisation is generated in Microsoft Excel and then send to the analyst for review

Academic staff development strategies in engineering fields of study : case study of Zimbabwe

Higher education is the basic instrument of economic growth and technological advancement in any society. The economic meltdown in Zimbabwe which climaxed 2008 with an inflation level of 231million % exacerbated the brain drain. After the economic meltdown, Zimbabwe is in the process of rebuilding the quality of staff and the staffing levels in its higher education institutions. The challenge has been the decision on the mode of study: whether to go via taught masters or masters by research; where to allow the faculty members to study: in the region, or beyond; on a fulltime or on a part-time basis or on a split-site basis. These challenges have been due to the need to have a quick but quality programme of staff development, while maximising on the resources available for staff development. A survey was undertaken of the engineering related departments in Zimbabwe universities focusing on the existing staffing levels, their qualifications, current numbers undergoing study and their levels. The challenges faced by each institution from the administrative side and from the staff side are summarised. Recommendations on staff development strategies are given in conclusion

Application of an automated labour performance measuring system at a confectionery company

Published ArticleThis paper focuses on the implementation of a labour performance measuring system at a confectionery company. The computer vision based system is based on the work sampling methodology. It consists of four cameras linked to a central computer via USB extenders. The computer uses a random function in C++ in order to determine when measurements are to be taken. OpenCV is used to track the movement of a target worker's dominant hand at a given work station. Tracking is accomplished through the use of a bandwidth colour filter. The speed of the worker's hand is used to identify whether the worker is busy, idle or out of the frame over the course of the sampling period. Data collected by the system is written into a number of text files. The stored data is then exported to a Microsoft Excel 2007 spread sheet where it is analysed and a report on the labour utilisation is generated

Antioxidant properties, protein binding capacity and mineral contents of some plants traditionally used in the management of animal wounds

Abstract: Please refer to full text to view abstrac

Development of a resource agent for an e-manufacturing system

Due to globalisation and distributed manufacturing systems the development and manufacture of products is no longer an isolated activity undertaken by either one discipline or a single organization but has become a global process. Using e-manufacturing companies can now outsource to manufacturers outside their geographical area and make them dependent on the production capabilities and responsiveness of the suppliers. Hence there is need for the suppliers to provide reliable information on the state of the orders being processed. E-manufacturing promises companies to exchange the required information with their suppliers by increased visibility to the shop floor and providing a platform for information interchange. The paper discusses the development of an e-manufacturing resource agent to enable manufactures to predict the probability of their outsourced machinery being available and the probability to complete an order without having a breakdown. The Maintenance Free Operation Period (MFOP) method is used to develop the agent. This means that the manufacturer will be expected to have a guarantee that no unscheduled maintenance activities will occur during each defined period of operation with the predefined level of confidence

Evaluation Of The Impact Of Scanning Strategies On Residual Stresses In Selective Laser Melting

Published ArticleThe occurrence of residual stresses in selective laser melting (SLM) presents challenges that limit the capability of the process to manufacture parts at industrial scale. These stresses can have irreversible effects such as warping and cracking of parts during and post manufacturing.One of the most important SLMparameters that should be controlled carefully in order to effectively manage residual stresses is the scanning strategy. This study presents an evaluation of four different scanning strategies, namely the island, successive, successive chessboard and least heat influence (LHI) scanning strategies with respect to their influence on residual stresses and distortions. All the scanning strategies were investigated by melting single tracks on tool steel substrates without powder. Measurement of residual stresses was performed on selected positions on the substrates before and after exposure to the laser beam using the x-ray diffraction technique. The successive chessboard scanning strategy was found to contribute to the least average residual stresses, and lowered residual stress by up to 40% relative to the default island scanning strategy. Further to this, the influence of the successive chessboard and island scanning strategies on distortions was evaluated. Similar to the residual stress findings, the successive chessboard contributed to lower form deviations compared to the island strategy. The scanning strategies were also evaluated based on their impact on total scanning times, with the successive chessboard strategy showing slightly lower scanning time than that for the island and LHI chessboard strategies

Micro-milling work-holding devices employing adhesive forces

IngenieursweseBedryfsingenieursweseMicro-parts are often very fragile rendering conventional, mechanical work-holding fixtures unsuitable for them since they exert large straining forces. Furthermore, macroworkholding devices occupy a large space which impedes high precision required in micromilling. Although some micro-clamping fixtures exist, they are limited to specific part shapes and in most cases expensive to manufacture. Hence this paper focuses on the application of adhesive forces namely electrostatic, surface tension and van-der-Waals forces; in work-holding strategies for micro-milling operations. An analysis is given as to their applicability with reference to micro-milling cutting forces

Micro-material handling, employing e-beam coatings of copper and silver

CITATION: Matope, S., Van der Merwe, A. F. & Rabinovich, Y. I. 2012. Micro-material handling, employing e-beam coatings of copper and silver. South African Journal of Industrial Engineering, 23(1):114-121, doi:10.7166/23-1-223.The original publication is available at http://sajie.journals.ac.zaENGLISH ABSTRACT: Van der Waals forces and other adhesive forces impose great challenges on micro-material handling. Mechanical grippers fail to release micro-parts reliably because of them. This paper explores how the problematic Van der Waals forces may be used for micro-material handling purposes using surface roughnesses generated by e-beam coatings of copper and silver on silicon. An atomic force microscope, model Asylum MFP 3 D-Bio with version 6.22A software, was used to measure the forces exerted by the surfaces. A silver coating of 1.41 nm rms surface roughness value is found to exert the highest Van der Waals force, followed by a copper coating of 2.72 nm rms; a copper coating of 217 nm rms exerts the least force. This implies that, in a reliable micro-material handling system, these coatings are suitable for the interactive surfaces of the placement position, micro-gripper, and the pick-up position respectively.AFRIKAANSE OPSOMMING: Van der Waalskragte en ander bindingskragte hou steeds groot uitdagings in vir mikromateriaalhantering. As gevolg van hierdie bindingskragte stel meganiese gryptoerusting nie die mikro-partikels vry nie. Hierdie artikel ondersoek hoe die Van der Waalskragte gebruik kan word vir die mikro-materiaalhanteringsproses deur die gebruik van oppervlakgrofheid gegenereer deur n e-straal-laagbedekking van koper en silwer op silikon. n Atoomkrag mikroskoop, model Asylum MFP 3 D-Bio met weergawe 6.22A programmatuur, is gebruik om die kragte deur die oppervlakke uitgeoefen te meet. Daar is gevind dat n silwer laagbedekking met n oppervlakgrofheid van 1.41nm wortel-gemiddelde-kwadraat (wgk) die hoogste Van der Waalskrag uitoefen, gevolg deur n koper laagbedekking met n oppervlakgrofheid van 2.72nm wgk; n koper laagbedekking met n grofheid van 217nm wgk het die kleinste krag uitgeoefen. Dit impliseer dat, vir n betroubare mikro-materiaalhanteringsisteem, hierdie laagbedekkings geskik is vir die interaktiewe oppervlakke van die plasingsposisie, die mikro-gryper en die optelposisie.http://sajie.journals.ac.za/pub/article/view/223Publisher's versio

Co-prevalent infections in adults with HIV-associated cryptococcal meningitis are associated with an increased risk of death: a nested analysis of the Advancing Cryptococcal meningitis Treatment for Africa (ACTA) cohort

Background: HIV-associated cryptococcal meningitis accounts for 15% of AIDS related deaths globally. In sub-Saharan Africa, acute mortality ranges from 24% to 100%. In addition to the mortality directly associated with cryptococcosis, patients with HIV-associated cryptococcal meningitis are at risk of a range of opportunistic infections (OIs) and hospital acquired nosocomial infections (HAIs). The attributable mortality associated with co-prevalent infections in cryptococcal meningitis has not been evaluated. Methods: As part of the Advancing Cryptococcal meningitis Treatment for Africa (ACTA) trial, consecutive HIV-positive adults with cryptococcal meningitis were randomised to one of five anti-fungal regimens and followed up until 10-weeks. We conducted a retrospective case note review of ACTA participants recruited from Queen Elizabeth Central Hospital in Blantyre, Malawi to describe the range and prevalence of OIs and HAIs diagnosed, and the attributable mortality associated with these infections. Results: We describe the prevalence of OIs and HAIs in 226 participants. Baseline median CD4 count was 29 cell/mm3, 57% (129/226) were on anti-retroviral therapy. 56% (127/226) had at least one co-prevalent infection during the 10-week study period. Data were collected for 187 co-prevalent infection episodes. Suspected blood stream infection was the commonest co-prevalent infection diagnosed (34/187, 18%), followed by community-acquired pneumonia (32/187, 17%), hospital-acquired pneumonia (13/187, 7%), pulmonary tuberculosis (12/187, 6%) and confirmed blood stream infections (10/187, 5%). All-cause mortality at 10-weeks was 35% (80/226), diagnosis of an OI or HAI increased the risk of death at 10 weeks by nearly 50% (HR 1.48, 95% CI 1.01-2.17, p=0.04). Conclusion: We demonstrate the high prevalence and broad range of OIs and HAIs occurring in patients with HIV-associated cryptococcal meningitis. These co-prevalent infections are associated with a significantly increased risk of death. Whether a protocolised approach to improve surveillance and proactive treatment of co-prevalent infections would improve cryptococcal meningitis outcomes warrants further investigation