• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 208
  • 116
  • 2
  • 2
  • Tagged with
  • 336
  • 336
  • 336
  • 256
  • 64
  • 63
  • 55
  • 47
  • 46
  • 44
  • 43
  • 40
  • 28
  • 25
  • 23
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Odour management at landfills.

Roebuck, Duncan. January 2005 (has links)
Landfill sites that are situated near residential zones pose significant management challenges. One of the key issues concerns odour emissions; they can be a major cause of public opposition to the existence of landfills. Mounting opposition can result in costly and premature closure of waste management facilities. The Bisasar Road landfill in Durban is one of the largest general waste landfills in South Africa, and is surrounded by residential areas on three sides. Odour emissions are therefore of primary concern. The situation at Bisasar provided an opportunity to involve the surrounding residents as odour "receptors" in order to undertake research that would provide a better understanding of odour emissions and how best to manage them. Effective management of odour emissions requires a model to accurately predict the occurrence and extent of the problem. For effective modelling and prediction of odour at a landfill, it becomes necessary to characterize the odour sources in terms of their odour emission rates and also to establish the population's response to the odour over a wide range of concentrations. This thesis describes the application of numerical dispersion modelling, coupled with interactive community involvement, in order to indirectly estimate odour emission rates, where the community acts as an odour assessment panel. A reanalysis of data captured from a 2002 community survey was performed in order to investigate the odour emission rate from the open waste piles - transfer station and working face - at the Bisasar road Landfill site. The odour emission rate from these similar odour sources was found to lie in the range 102-103 OU/m2/s. For the duration of the survey, the working face contributed 82% to the odour perceived at the receptors and the Transfer Station contributed 18% to the overall offsite odour. The 2002 survey required receptors to fill out a weekly diary of odour observations, but a new community survey in 2004 used direct telephonic communication with receptors to establish the odour impact. Residents were contacted telephonically at their homes on a regular basis to ascertain whether they perceived an odour at the time of call. This data, in conjunction with the concentration predictions form the odour prediction model, allowed for an emission rate for the open waste piles to be inferred through backward dispersion. The emission rate from an open waste pile was estimated at being 250 OU/m2/s. The individual response of each receptor as well as the combined response for the panel to a range of odour concentrations was assessed in terms of probability of detection and perceived odour intensity. The odour emission rate, inferred through backward dispersion using the 2004 community survey data, was used to establish the impact of the odour from the open waste piles on the surrounding community through long term forward dispersion calculations. This provided a scientifically defensible methodology for the specification of buffer zones around sources that emit nuisance odours. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2005.

The characterization of stormwater runoff from road surfaces.

Chrystal, Clinton Paul. January 2006 (has links)
The water quality of stormwater runoff from various road surfaces in Durban, KwaZulu- Natal was characterised by monitoring programmes established at four study areas. The investigation focussed on obtaining representative stormwater samples in order to quantitatively identify pollutant constituents transported within stormwater runoff from road surfaces during rainfall events. Stormwater runoff is a leading cause of degradation in the water quality of receiving water bodies. A review of sampling methods and equipment, informed by the objectives and resources of this investigation, resulted in the development of a stormwater runoff sampler. An economical flow weighted composite sampler was designed, developed and tested. The sampler produces one representative composite event mean concentration sample. Controlled laboratory experiments, computer simulations and field tests were conducted in order to test and calibrate the sampler. The product of the event mean concentration and total runoff volume estimated provide an estimation of the total pollutant loading from a particular drainage area. Twenty stormwater runoff event mean concentration (EMC) and atmospheric deposition samples were collected over an eighteen month period. The characterisation of stormwater runoff for this investigation included heavy metals, oxygen demanding substances, sediments and physico-chemical analysis for pH, conductivity and water hardness. Chemical analysis indicates that the pollutant levels of constituents sometimes exceeded EMCs reported internationally. The majority of contaminant EMCs exceeded the South African wastewater discharge general and special limits. The results also indicate a 60% reduction in lead (Pb) levels since the introduction of lead-free fuel in South Africa in January 2006. The findings from this investigation will provide decision-makers with an improved local data base for estimating the impacts of road transportation systems on water quality. A comparison between the four study areas also provides guidance concerning the variability of stormwater quality from different road surfaces and usage patterns. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2006.

The breaching of temporary open/closed estuaries.

Parkinson, Michael. January 2007 (has links)
Intermittent breaching of sand barriers at temporary open estuaries plays a key role in the functioning of these systems. Breaching events lead to large and rapid changes in the physico-chemical environment which in turn triggers major biological responses. The breaching process can cause significant morphological changes as strong breach outflows can scour large quantities of accumulated sediments from an estuary. Simple laboratory experiments are reported that investigate the temporal evolution of the breach and the scaling of the breach characteristics namely the breach width W, volume Vb, formation time Tf and peak outflow Qp. The experiments were specifically designed to investigate the influence of the outflow volume S, the hydraulic head H and the barrier breadth B on the breach characteristics. The breach width W was found to be proportional to S1/3, whilst the breach volume Vb was found to be proportional to HBS1/ 3. The breach formation time Tf was found to be proportional to (g/S1/3)-1/2 (H/S1/3)-3/2 (B/S1/3)1 and the peak outflow Qp was found to be proportional to (gS5/3)1/2 (H/S1/3)3/2 (B/S1/3)-1. These scalings are also shown to be consistent with observed breach characteristics for actual estuaries and earth dam failures where outflow volumes are typically six orders of magnitude larger than for the models. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2007.

Contributions to hydraulic engineering.

James, William. January 1984 (has links)
No abstract available. / Thesis (Ph.D.)-University of Natal, Durban, 1984.

Experimental cadmium contamination of the echinoid Stomopneustes variolaris (Echinodermata: Echinoidea) : influence of dosage and distribution of the metal in the organism.

Bachoo, Santosh. January 2002 (has links)
Cd levels were measured in three different body compartments of the echinoid Stomopneustes variolaris after exposure to concentrations of 5 ug 1l, 20 ug 1l and 50 ug 1l Cd for a period of two weeks. The body compartments investigated included the intestine, gonads and skeleton. The gonads did not exhibit dose-dependent bioaccumulation. The levels of cadmium in the intestine and skeleton were significantly different between the treatments, suggesting that dose dependent bioaccumulation had occurred in these compartments (except in the skeleton where higher levels -were recorded for those exposed to 20 ug 1l than those exposed to 50 ug 1l) The levels recorded in the intestine were higher than those recorded in the gonads and skeleton at the higher Cd exposures of 20 and 50 ug 1i. The levels accumulated in the gonads and skeleton were not significantly different from each other. A separate group, exposed to 20 ug 1`1Cd over a period of two weeks, was placed in uncontaminated seawater to determine if the echinoids were capable of bioremediation. Bioremediation was found to lower the Cd levels in the gonads, but not in the intestine and skeleton. Cadmium levels for the three body compartments were also recorded from specimens collected from the field, indicating the presence of this element in the environment. In addition to using atomic absorption spectroscopy (AAS), energy dispersive X-ray analysis (EDX) was used as a comparative technique to detect the presence of Cd in the skeleton of the urchin. Cadmium was detected in the skeleton with AAS, but not with EDX. S. variolaris proved to be a capable biomonitor of Cd contamination. / Thesis (M.Sc.Eng.)-University of Durban-Westville, 2002.

The development of a latent heat thermal energy storage system using a phase change material for solar energy application.

Zulu, Njabulo Mziwandile. January 2010 (has links)
This investigation forms part of an attempt to provide an alternative to conventional power generation technologies that use fossil fuels which have impact on global warming. The field of this investigation covers the development of a latent heat thermal storage system which has a potential of conserving available solar energy. The advantages of using thermal energy storage that have been found previously include reduced energy cost, energy consumption, equipment size and pollutant emissions, also increased flexibility of operation, efficiency and effectiveness of equipment utilization. Traditionally, available heat has been stored in the form of sensible heat (typically by raising the temperature of the energy storage medium) for later use. Latent heat storage on the other hand, is a young and developing technology which has found considerable interest in recent times due to its advantages over sensible heat storage which include smaller temperature swing, smaller size and lower weight per unit of storage capacity. It has been demonstrated that, for the development of a latent heat thermal energy storage system, the choice of the phase change material (PCM) as well as the heat transfer mechanism in the PCM play important roles. In this study, a suitable phase change material and an appropriate heat transfer enhancement technique are identified for utilization in a proposed latent heat thermal energy storage system. Also included, is the design of the proposed heat storage system. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.

Long term emissions from pretreated waste : lysimeter studies.

19 October 2010 (has links)
Landfill emissions are the major environmental impact associated with the landfilling of / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2007

Evaluation of PCI reverse osmosis membrane on landfill leachate.

20 October 2010 (has links)
The specific objective of this study was to evaluate a PCI reverse osmosis membrane for / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2006

Management and production techniques in the manufacturing and service industries and how it relates to the construction industry.

21 January 2011 (has links)
This dissertation is concerned with the future of the construction industry in South Africa and the ability to improve. Continuous growth is predicted through to the year 2015 and beyond, it is considered that to meet this challenge the South African construction industry must achieve substantial improvement and change. South Africa is a developing nation with ambitious objectives to improve social development and growth through delivery of infrastructure and other areas including, municipal development, hospitals, roads, water, electricity and government facilities. It is essential that South Africa has a construction industry that can develop capability and capacity to achieve sustainable growth. Current management thinking acknowledges that the best management and production principles are transferable. This is not a new concept or proposal, early management and production theorists and applicators such as Frederick Taylor, Frank B Gilbreth and Henry Ford all held the view that best practice techniques are transferable in application. By researching and presenting current successful management and production practices it intends to identify principles that can be adopted for change and improvement by the South African construction industry. A current general review of the South African construction industry has been undertaken to place it in context regarding the adoption of these best practice principles. The research will adopt a qualitative approach; it will be subjective and contain descriptions of techniques, people interactions, observations and assumptions. The principles addressed in this research are Benchmarking, Lean Production and Supply Chain Management; they have been selected as current best practice and as having significant use and proven continued success. They are presented in a format to allow understanding of the principles now developed and to illustrate via existing case studies, successes in application. Conclusions are made on individual aspects, on common core practices existing in all three principles and the current state of the South African construction industry. Recommendations are made and further areas of research suggested. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2007.

Radar reflectivity infilling techniques.

January 2005 (has links)
Weather radar provides a detailed spatial representation of rainfall over a large area and in a real time basis. It has proven to be a valuable tool for hydrologists, agriculturalists and organisations that require accurate and real time information of rainfall and overcomes many of the disadvantages associated with the traditional raingauge estimate. However one of the shortcomings of the rainfall estimates supplied by weather radars is that there are quality problems associated with radar rainfall images that include ground clutter, beam blocking and anomalous propagation to name a few. To obtain the best rainfall estimate possible, techniques for removing ground clutter (non-meteorological echoes that influence radar data quality) on two-dimensional (20) and three-dimensional (3D) radar rainfall image data sets were developed in this study. The chosen method for estimating the "true" values behind the contaminated data was Kriging, which is considered to be the optimal technique for the spatial prediction of Gaussian data. Kriging has various advantages and disadvantages, which need to be taken into consideration in this type of application. For the radar rainfall images to be repaired in real time a computationally fast and efficient method of estimating the missing contaminated data was needed. This is achieved by exploiting the various properties associated with Kriging. In South Africa, radar volume scan data are currently only available on one-kilometre horizontal grids at one-kilometre intervals above the earth's surface. This may not be an accurate representation of the rainfall that actually reaches ground level. To provide an estimate of the "true" rainfall reaching the earth's surface, an algorithm has been developed that extrapolates the radar data down to ground level. The extrapolation is carried out using a combination of 3D Universal and Ordinary Kriging which is preceded by a rainfall classification algorithm developed and calibrated in this study. The techniques proposed for ground clutter infilling and the extrapolation of radar data to ground level have been tested for their effectiveness and efficiency on a wide range of selected rainfall events and indicate that the methodology is practically useful. The South African Weather Service (SAWS) has recently installed the software to "cleanse" the radar data as it is received in real time. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2005.

Page generated in 0.1018 seconds