<p>Communication tools such as text-based instant messaging, voice and video relay services, real-time video chat and mobile SMS and MMS have successfully been used among Deaf people.&nbsp / Several years of field research with a local Deaf community revealed that disadvantaged South African Deaf people preferred to communicate with both Deaf and hearing peers in South African&nbsp / Sign Language as opposed to text. Synchronous video chat and video relay services provided such opportunities. Both types of services are commonly available in developed regions, but not in&nbsp / developing countries like South Africa. This thesis reports on a workaround approach to design and develop an asynchronous video communication tool that adapted synchronous video codecs&nbsp / to store-and-forward video delivery. This novel asynchronous video tool provided high quality South African Sign Language video chat at the expense of some additional latency. Synchronous video&nbsp / codec adaptation consisted of comparing codecs, and choosing one to optimise in order to minimise latency and preserve video quality. Traditional quality of service metrics only addressed real-time video quality and related services. There was no such standard for asynchronous video communication. Therefore, we also enhanced traditional objective video quality&nbsp / metrics with subjective assessment metrics conducted with the local Deaf community.&nbsp / </p>

Microorganisms have the potential to remove heavy metals from polluted waters and effluents and may be used in clean-up processes. Microbial associations were enriched for and adapted to grow in nutrient solutions containing various concentrations of different metals. As immobilised cells are known to be more stable and more efficient in metal uptake than are corresponding planktonic or free-living cells the attachment of the microbial associations was investigated using a model stream and it was found that biofilm development was better on rough surfaces such as ground glass and polystyrene than on smooth surfaces such as unetched glass plates and glass beads. When comparing metal uptake by planktonic and attached microorganisms, attached populations were found to have a greater metal-uptake capacity. The uptake of individual metals from various metal combinations was tested with various proportions of pregrown metal-adapted microbial populations as inoculum and it was found that a particular metal was taken up more readily by microbial associations which had previously been exposed to that metal. Lead (Pb2+) appeared to be taken up more readily than copper (Cu2+) or cadmium (Cd2+) while Cd2+ was more actively removed than Cu2+ from solution. pH also affected metal uptake and the optimum range for Cu2+ uptake by the Cu2+ -adapted microbial association was found to be between 5.8 and 7.0. Dead microbial biomass was investigated and found to have efficient metal uptake capacity. Living mycelium from an isolated Aspergillus species showed poor uptake of Cu2+ initially, but when this fungus was pregrown and subsequently killed by moist heat treatment the non-living mycelium was efficient in removal of Pb2+ and Cu2+ ions. The optimum mycelial biomass concentration for metal uptake was also determined. The mechanism of metal uptake by this Aspergillus species was determined, using electron microscopy and EDX techniques, to be metabolism-independent biosorption onto the hyphal surface. Thus the microbial associations and fungal cultures used in this study were shown to have the potential for use in the removal of heavy metals from polluted waters. / Thesis (Ph.D.)-University of Natal, Pietermartizburg, 1995.

Software engineering is a discipline concerned with manufacturing or developing software. Software plays a pivotal role in everyday life, an absence of which will be devastating to a number of governmental, recreational and financial activities, amongst many others. One of the latest branches of software engineering, component-based software engineering, is concerned with the development of software systems using already existing components which speculatively will ensure rapid and inexpensive software development processes. Parallel with the advances in software engineering, the field of digital libraries — a field dealing with Web-based access to and management of structured digital content — has adopted this development model from software engineering to shift focus from developing and using traditionally monolithic software systems to developing and using more flexible component-oriented software systems. Since componentised development approaches are relatively recent, other areas such as packaging and managing component-based software systems still remain unattended to. This dissertation presents research on techniques and methodologies for packaging customisable component-based digital libraries such that deployment is rapid and flexibility is not compromised. Although the reference point of this research was that of component-based digital library systems, it is believed that this research can be generalised across the family of Web-based component-based software systems. An outcome of this research was a prototype packaging system consisting of a pair of tools: a package builder tool and a package installer tool. This packaging system was developed to model the ideas and methodologies that were identified as important to the processes of packaging and installing component-based digital library systems. These tools consequently underwent a user evaluation study whereby they were evaluated for understandability, usability and usefulness to the processes of packaging and installing component-based digital libraries. A key contribution of this research was identifying requirements for a generic component packaging framework. For a component to be seen as ”fit-to-package”, it must posses the following at the very least: the component must be configurable automatically; the component must have a formal description of its dependency software; there must be formal descriptions that describe individual components as well as systems composed of components; and there must be a way whereby installation questions are formally encoded such that components are able to correctly receive configuration information. In totality, this research has shown that component-oriented software development approaches can benefit from an infrastructure which allows for component-based software systems to be composed, distributed and installed effortlessly.

The growth of the World Wide Web has in large part been made possible by the technologies that power it. These are the Web servers and Web browsers that many take for granted. Each has evolved to support the changing needs of users of the WWW from simple static text to highly interactive and dynamic multimedia. The Web servers, in particular, have evolved into a spectrum of different technologies to support what are now known as Web applications. These are usually installed and accessed through a Web server. Security is a problem in Web server environments and therefore the Web servers are usually run as an un-privileged user. Performance is another problem as some of these technologies require re-initialization of the execution environment with every subsequent request. These security and performance shortcomings have been dealt with by numerous Web application technologies. Most of these technologies are language-centric and seek solutions to the security and performance shortcomings independently of each other. The universal Web application server is proposed as an alternative solution addressing the security, language dependence and performance shortcomings of existing technologies. It has support for multiple authors in a secure environment with support for multiple implementation technologies (languages) using persistent interpreters to enhance performance. Test results from the performance evaluation show that the introduction of the layers of processing contributes a small percentage to the total request processing time and that the universal Web application server can perform comparably to other Web application servers. Tests with twenty users also showed that packaging and deploying Web applications in the universal Web application server is an easy and viable approach. Moreover, the installation of PhpBB2 in the universal Web application server demonstrates that it can be used with realistic Web applications. A universal Web application server that provides an efficient, secure and language independent environment has been developed and thoroughly evaluated demonstrating that a Web application server that addresses the shortcomings of existing technologies is feasible.

Customs administrations, worldwide, are adopting the trend towards risk-based processing of international cargoes as a means of facilitating trade. This has lead to the introduction of innovative processes ably supported by technology to realize improvements in customs effectiveness and overall efficiency. Widespread use of e-commerce in trade-customs transactions and exchanges, likewise necessitates complimentary technical support where Customs has need to intervene in a specific import, export or transit consignment. South African Revenue Service (SARS) is presently developing and enhancing its core competencies through training of its personnel in the disciplines of risk management, anti-smuggling and post clearance audit. It therefore becomes essential that these capacity building initiatives be complimented with the most appropriate tools for conducting cargo examination. The current physical examination process and inspection techniques are both time consuming and costly for business and render the goods liable to damage and theft. Recent historical events, specifically the 9/11 tragedy in New York, has caused international organizations such as the G8 and World Customs Organization (WCO) to consider the implications and effects of terrorism on international maritime transportation. The G8 adopted a Co-operative Action Plan on Security covering all aspects of transportation security and the WCO adopted a Resolution on Security and Facilitation of the International Supply Chain. Both initiatives aim to ensure safer and more secure maritime trade on the global scale. Fundamental to SARS Customs ability to successfully implement such measures are the following: Availability of advance electronic customs data Automated risk profiling and targeting capability Availability of non-intrusion inspectional devices (X-ray cargo scanners) to examine cargo. These three criteria are essential for SARS to participate in supply chain security initiatives and to facilitate the transportation of international consignment. Accordingly this research project explores how the external and internal environment impacts on SARS. It further critically analyses the core competencies and resource strengths of SARS. To support SARS in its effort and in its process of starting a project to improve controls and facilitation of goods at ports of entry within the Republic, this study explores and expounds on infrastructure and business application needs of SARS. Finally the research project concludes with a recommendation of the most effective approach towards the implementation of cargo scanner 'shared, outsourced service." / Thesis (MBA)-University of Natal, Durban, 2003.

With the exceptions of mixing and heating mechanisms, and the recycling of settled solids, no radical changes or improvements have been made to conventional anaerobic digesters treating municipal sewage. These digesters usually function with a hydraulic retention time of 30 to 60 days and at a total solids concentration of 2.6 %(m/v). Volumetric loading is limited since high loadings effect the displacement of the slow growing methanogens. Thus, the hydraulic retention time is coupled to the solids retention time. A crossflow microfiltration unit has been constructed at Northern Waste Water Treatment Works, Durban, to concentrate sludge from a conventional anaerobic digester and, thus, facilitate operation with a higher solids concentration. In addition, this process should result in the retention of the active biomass which would otherwise be lost as a waste product of the treatment process. The solids retention time is, thus, decoupled from the hydraulic retention time. The net result could be higher volumetric loadings, increased microbial activity and increased volatile solids destruction and, hence, improvement in the efficiency of anaerobic digestion of sewage sludge. To test these, different experiments were conducted to specifically determine the effect of higher solids loads. Preliminary experiments were undertaken to determine the biodegradability of primary sludge from the Northern Waste Water Treatment Works. Results showed that primary sludge of 76% VS could be reduced to approximately 48 to 50% VS during an experimental period of 85 days. Reduction of the first 20% VS was rapid if conditions were optimum but subsequent reduction from 55 to 50% VS was slow. It was calculated that approximately 0.88 l gas was produced for every g volatile solids catabolised. Further experiments were conducted to investigate the effects of different solids concentrations on microbial activity. The results showed that the volume of gas produced increased as the solids concentration increased from 2 to 6%(m/v). Digesters with solids concentrations of 6 to 13%(m/v) produced similar volumes of gas. Digesters with solids concentrations of 6 to 13%(m/v) TS produced approximately 300 ml more gas than the control during the 20 days experimental period. The rate of gas production also increased as the solids concentration increased. However, digesters containing 11%(m/v) and 13%(m/v) TS produced similar rates. These results indicate that the introduction of concentrated sludge into the digester improves digestion efficiency. Finally, a semi-continuous digester was operated at a 30 days retention time and at optimum temperature to investigate the efficacy of digesters with increased solids concentrations. The results showed that the rate of gas production increased as the solids concentration increased from 2%(m/v)(control) to 3.8%(m/v). However, the digester operated with 4.7%(m/v) TS produced gas at a rate lower that the digester with 3.8%(m/v) TS. The volatile solids concentrations of all four digesters were similar, indicating neither favourable nor unfavourable effects from increased solids concentrations. The digesters operated with 3.8%(m/v) and 4.7%(m/v) TS produced higher concentrations of volatile acids than the control. The alkalinity concentrations (>_4000 mg t-1 ) were similar for all four digesters. / Thesis (M.Sc.)-University of Natal, Durban, 1995.

No description available.

No description available.

No description available.

No description available.