A comparison of conventional and ultrasonic seams in swimwear
- Authors: Tyalana, Nommiselo
- Date: 2018
- Subjects: Textile finishing , Textile finishing agents Seams (Sewing) Textile fabrics Textile fibers Textile design
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/36727 , vital:34048
- Description: Ultrasonic welding technology is a relatively new technology in apparel construction, this research forms part of a study to assess its effectiveness as a joining technology that can be used in ladies swimwear. The ultimate aim was to determine whether the ultrasonic welding joining technique could be successfully used in assembling ladies swimwear garments, comprising only synthetic fibres, namely polyester/Lycra, polyamide/Lycra, polyamide/Lycra power-net and polyamide/Lycra mesh warp knitted fabrics. These specific swimwear fabrics were selected since they comprise 100% thermoplastic synthetic fibres, considered ideal for ultrasonic welding. This study essentially compares and contrasts the performance of two seam joining techniques: namely conventional sewing and ultrasonic welding, in terms of seam strength, when used in the above mentioned four fabrics. Conventionally sewn and ultrasonically welded seams were produced, straight and curved, in both the wale and course directions of the fabrics. The conventionally sewn seams were produced using two sewing machines; namely an overlocker, also known as a mock safety sewing machine, and a cover seam machines. All conventionally sewn seams were stitched and tested under similar conditions. The ultrasonic welded seams were produced using three different wheels, a Medium Male Knurled pattern wheel, a Staggered Triple Stitch pattern wheel and a Single Stitch pattern wheel. The amplitude and speed of the welding machine, during the ultrasonic seaming, were kept constant, except when welding the polyamide/Lycra power-net and the polyamide/Lycra mesh fabrics when the pressure had to be drastically reduced in order to avoid excessively softened seams. The results of the study are presented in the form of line charts, scatter charts and tables. The ultrasonic welded seams, joined with the Medium Male Knurled wheel, exhibited surface waviness, as opposed to those joined with the Staggered Triple Stitch wheel which were smooth. It was found that, in terms of seam strength, the ultrasonic seams produced with the Single Stitch and Medium Male Knurled pattern wheels out performed those produced with the Staggered Triple Stitch wheels. The polyester/Lycra fabric was found easier to handle during the ultrasonic seaming process than the polyamide/Lycra fabric, although the strength of the ultrasonic seams in the polyester/Lycra fabric did not differ consistently from those of the polyamide/Lycra fabric. It was found that the conventional sewn seams were consistently stronger, and had a better appearance, than the ultrasonic welded seams. Although some promising results were obtained, in terms of the strength of the ultrasonic welded seams, the results overall were far too variable, inconsistent and unsatisfactory for this technique of seaming to be recommended at this stage for any of the swimwear fabrics covered. Further, more in depth, studies are required in order to gain a better understating of the effect of the various ultrasonic seaming parameters, as well as fabric parameters on ultrasonic seam strength and consistency.
- Full Text:
- Date Issued: 2018
- Authors: Tyalana, Nommiselo
- Date: 2018
- Subjects: Textile finishing , Textile finishing agents Seams (Sewing) Textile fabrics Textile fibers Textile design
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/36727 , vital:34048
- Description: Ultrasonic welding technology is a relatively new technology in apparel construction, this research forms part of a study to assess its effectiveness as a joining technology that can be used in ladies swimwear. The ultimate aim was to determine whether the ultrasonic welding joining technique could be successfully used in assembling ladies swimwear garments, comprising only synthetic fibres, namely polyester/Lycra, polyamide/Lycra, polyamide/Lycra power-net and polyamide/Lycra mesh warp knitted fabrics. These specific swimwear fabrics were selected since they comprise 100% thermoplastic synthetic fibres, considered ideal for ultrasonic welding. This study essentially compares and contrasts the performance of two seam joining techniques: namely conventional sewing and ultrasonic welding, in terms of seam strength, when used in the above mentioned four fabrics. Conventionally sewn and ultrasonically welded seams were produced, straight and curved, in both the wale and course directions of the fabrics. The conventionally sewn seams were produced using two sewing machines; namely an overlocker, also known as a mock safety sewing machine, and a cover seam machines. All conventionally sewn seams were stitched and tested under similar conditions. The ultrasonic welded seams were produced using three different wheels, a Medium Male Knurled pattern wheel, a Staggered Triple Stitch pattern wheel and a Single Stitch pattern wheel. The amplitude and speed of the welding machine, during the ultrasonic seaming, were kept constant, except when welding the polyamide/Lycra power-net and the polyamide/Lycra mesh fabrics when the pressure had to be drastically reduced in order to avoid excessively softened seams. The results of the study are presented in the form of line charts, scatter charts and tables. The ultrasonic welded seams, joined with the Medium Male Knurled wheel, exhibited surface waviness, as opposed to those joined with the Staggered Triple Stitch wheel which were smooth. It was found that, in terms of seam strength, the ultrasonic seams produced with the Single Stitch and Medium Male Knurled pattern wheels out performed those produced with the Staggered Triple Stitch wheels. The polyester/Lycra fabric was found easier to handle during the ultrasonic seaming process than the polyamide/Lycra fabric, although the strength of the ultrasonic seams in the polyester/Lycra fabric did not differ consistently from those of the polyamide/Lycra fabric. It was found that the conventional sewn seams were consistently stronger, and had a better appearance, than the ultrasonic welded seams. Although some promising results were obtained, in terms of the strength of the ultrasonic welded seams, the results overall were far too variable, inconsistent and unsatisfactory for this technique of seaming to be recommended at this stage for any of the swimwear fabrics covered. Further, more in depth, studies are required in order to gain a better understating of the effect of the various ultrasonic seaming parameters, as well as fabric parameters on ultrasonic seam strength and consistency.
- Full Text:
- Date Issued: 2018
A congestion aware ant colony optimisation-based routing and wavelength assignment algorithm for transparent flexi-grid optical burst switched networks
- Authors: Oladipo, Joshua Femi
- Date: 2018
- Subjects: Ants -- Behavior -- Mathematical models , Distributed algorithms
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/34733 , vital:33432
- Description: Optical Burst Switching (OBS) over transparent exi-grid optical networks, is considered a potential solution to the increasing pressure on backbone networks due to the increase in internet use and widespread adoption of various high bandwidth applications. Both technologies allow for more e cient usage of a networks resources. However, transmissions over exi-grid networks are more susceptible to optical impairments than transmissions made over xed-grid networks, and OBS suers from high burst loss due to contention. These issues need to be solved in order to reap the full benets of both technologies. An open issue for OBS whose solution would mitigate both issues is the Routing and Wavelength Assignment (RWA) algorithm. Ant Colony Optimisation (ACO) is a method of interest for solving the RWA problem on OBS networks. This study aims to improve on current dynamic ACO-based solutions to the Routing and Wavelength Assignment problem on transparent exi-grid Optical Burst Switched networks.
- Full Text:
- Date Issued: 2018
- Authors: Oladipo, Joshua Femi
- Date: 2018
- Subjects: Ants -- Behavior -- Mathematical models , Distributed algorithms
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/34733 , vital:33432
- Description: Optical Burst Switching (OBS) over transparent exi-grid optical networks, is considered a potential solution to the increasing pressure on backbone networks due to the increase in internet use and widespread adoption of various high bandwidth applications. Both technologies allow for more e cient usage of a networks resources. However, transmissions over exi-grid networks are more susceptible to optical impairments than transmissions made over xed-grid networks, and OBS suers from high burst loss due to contention. These issues need to be solved in order to reap the full benets of both technologies. An open issue for OBS whose solution would mitigate both issues is the Routing and Wavelength Assignment (RWA) algorithm. Ant Colony Optimisation (ACO) is a method of interest for solving the RWA problem on OBS networks. This study aims to improve on current dynamic ACO-based solutions to the Routing and Wavelength Assignment problem on transparent exi-grid Optical Burst Switched networks.
- Full Text:
- Date Issued: 2018
A seismic characterization of the crustal structure underlying the offshore Natal valley within the south-west Indian Ocean
- Authors: Moorcroft, David
- Date: 2018
- Subjects: Seismology , Seismology -- Kwa Zulu Natal -- Research Coasts -- Kwa Zulu Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/22387 , vital:29965
- Description: The Natal Valley is a ~1000 km long, elongated depression in the seafloor, located within the south-west Indian Ocean, between the coastline of south-east Africa and the offshore aseismic Mozambique Ridge. Knowledge of its present-day crustal structure is important to reconstruct the Gondwana supercontinent break-up history and the concurrent opening of the Indian Ocean, which started during the Jurassic, some ~180 – 150 million years ago. Major geological events relating to this supercontinent break-up including continental rifting, magmatism, the emplacement of extensive oceanic flood basalt as submarine plateaus, vertical processes associated with tectonic uplift, flexural subsidence of the margin and relative global sea-level change are recorded within the crust underlying the south-west Indian Ocean. Although these events have been well modelled, fundamental questions remain regarding the nature and tectonic structure of the crust. Today, the Natal Valley region represents a frontier for geophysical exploration. Early attempts at imaging the crust beneath the seafloor within the south-west Indian Ocean made use of now primitive seismic reflection data acquisition and processing techniques available to them at the time (1960’s - 1970’s). Considering the advancements made in marine seismic reflection imaging, these vintage datasets lacked the horizontal and vertical resolution necessary to most accurately account for and describe features of the upper crust underlying the northern Natal Valley. This study is based on the acquisition, processing and preliminary interpretation of a newly acquired, regional seismic reflection profile, Profile Mz5-007, acquired across the northernmost region of the Natal Valley during the PAMELA-Moz5 cruise in 2016. The methods of marine seismic reflection data acquisition, processing and interpretation are described. The seismic reflection data presented in this dissertation provides a regional-scaled appraisal of the upper crust underlying the northern Natal Valley for the first time. The imagery allows a comprehensive description of crustal structures and features from the very northern Natal Valley, close to the Mozambique coastline, southwards into the southern Natal Valley offshore of Durban. The findings presented here support the notion that the crust underlying the northern Natal Valley experienced roughly N-S orientated trans-tensional stresses in relation to the breakup of West Gondwana. At least two major phases of volcanism are imaged within the seismic stratigraphy. The lower-most event underlies the Limpopo Fan in the northernmost regions of the Natal Valley at a depth of 2 seconds TWT and is interpreted as a seismic expression of the upper surface of the Lower – Middle Jurassic Karoo LIP. The progressive disappearance of this horizon towards the south coincides with the emergence of a second, overlying, as yet unreported volcanic horizon, which extends southwards throughout the Natal Valley. On the basis of its regional distribution, spatial relationship with the underlying event boundary and its deformation history, this volcanic horizon is interpreted to represent a series of basaltic lava outpourings during the Lower Cretaceous, initiated in response to trans-tensional crustal deformation associated with the breakup of West Gondwana. In addition to these two major phases of flood basalt outpouring, a number of localized volcanic flows are imaged throughout the stratigraphy, most notably over the Central Terrace. In addition, at least four major unconformities are identified, all of which are well developed within the Limpopo Fan. One of these is interpreted to represent the well-developed Mid-Cretaceous hiatus in sedimentation, providing a relative seismo-stratigraphic constraint to overlying and underlying seismic units. A review of the structural elements of the crust reveals how the northern Natal Valley is partitioned into two sub-basins separated by a prominent basement high, the Central Terrace, imaged across the central portions of Profile Mz5-007. To the north of the Central Terrace, structural deformation appears largely extensional, characterized by a large (~37 km wide) asymmetrical depression directly to the north of the Central Terrace and only minor structural faulting. To the south of the Central Terrace, trans-tensional stresses associated with withdrawal of the Falkland Malvinas Plateau have deformed the upper crust into a series of apparently southwards tilted crustal blocks, producing a series of deep (3.5 s TWT) half graben-like structures, within which syn-rift fill has an apparent dip towards the south. There is evidence to suggest ongoing reactivation of these fault structures. This zone of deformation is shown to bear resemblances to the faulting mapped onshore of the Kwa-Zulu Natal coastline, providing reason to consider the two regions as a continuous zone of deformation associated with the withdrawal of the Falkland-Malvinas Plateau during the breakup of West Gondwana. Furthermore, a number of post-sedimentary intrusive features are imaged, the largest of which is the Naude Ridge; a large pinnacle-like feature which has penetrated the upper crust towards the southern limit of the profile. This feature corresponds to an abrupt change in seafloor depth and upper crustal structure, suggesting that this feature may mark the transition between subsided continental crust interpreted to underlie the northern Natal Valley to the north and oceanic crust known to underlie the southern Natal Valley to the south.
- Full Text:
- Date Issued: 2018
- Authors: Moorcroft, David
- Date: 2018
- Subjects: Seismology , Seismology -- Kwa Zulu Natal -- Research Coasts -- Kwa Zulu Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/22387 , vital:29965
- Description: The Natal Valley is a ~1000 km long, elongated depression in the seafloor, located within the south-west Indian Ocean, between the coastline of south-east Africa and the offshore aseismic Mozambique Ridge. Knowledge of its present-day crustal structure is important to reconstruct the Gondwana supercontinent break-up history and the concurrent opening of the Indian Ocean, which started during the Jurassic, some ~180 – 150 million years ago. Major geological events relating to this supercontinent break-up including continental rifting, magmatism, the emplacement of extensive oceanic flood basalt as submarine plateaus, vertical processes associated with tectonic uplift, flexural subsidence of the margin and relative global sea-level change are recorded within the crust underlying the south-west Indian Ocean. Although these events have been well modelled, fundamental questions remain regarding the nature and tectonic structure of the crust. Today, the Natal Valley region represents a frontier for geophysical exploration. Early attempts at imaging the crust beneath the seafloor within the south-west Indian Ocean made use of now primitive seismic reflection data acquisition and processing techniques available to them at the time (1960’s - 1970’s). Considering the advancements made in marine seismic reflection imaging, these vintage datasets lacked the horizontal and vertical resolution necessary to most accurately account for and describe features of the upper crust underlying the northern Natal Valley. This study is based on the acquisition, processing and preliminary interpretation of a newly acquired, regional seismic reflection profile, Profile Mz5-007, acquired across the northernmost region of the Natal Valley during the PAMELA-Moz5 cruise in 2016. The methods of marine seismic reflection data acquisition, processing and interpretation are described. The seismic reflection data presented in this dissertation provides a regional-scaled appraisal of the upper crust underlying the northern Natal Valley for the first time. The imagery allows a comprehensive description of crustal structures and features from the very northern Natal Valley, close to the Mozambique coastline, southwards into the southern Natal Valley offshore of Durban. The findings presented here support the notion that the crust underlying the northern Natal Valley experienced roughly N-S orientated trans-tensional stresses in relation to the breakup of West Gondwana. At least two major phases of volcanism are imaged within the seismic stratigraphy. The lower-most event underlies the Limpopo Fan in the northernmost regions of the Natal Valley at a depth of 2 seconds TWT and is interpreted as a seismic expression of the upper surface of the Lower – Middle Jurassic Karoo LIP. The progressive disappearance of this horizon towards the south coincides with the emergence of a second, overlying, as yet unreported volcanic horizon, which extends southwards throughout the Natal Valley. On the basis of its regional distribution, spatial relationship with the underlying event boundary and its deformation history, this volcanic horizon is interpreted to represent a series of basaltic lava outpourings during the Lower Cretaceous, initiated in response to trans-tensional crustal deformation associated with the breakup of West Gondwana. In addition to these two major phases of flood basalt outpouring, a number of localized volcanic flows are imaged throughout the stratigraphy, most notably over the Central Terrace. In addition, at least four major unconformities are identified, all of which are well developed within the Limpopo Fan. One of these is interpreted to represent the well-developed Mid-Cretaceous hiatus in sedimentation, providing a relative seismo-stratigraphic constraint to overlying and underlying seismic units. A review of the structural elements of the crust reveals how the northern Natal Valley is partitioned into two sub-basins separated by a prominent basement high, the Central Terrace, imaged across the central portions of Profile Mz5-007. To the north of the Central Terrace, structural deformation appears largely extensional, characterized by a large (~37 km wide) asymmetrical depression directly to the north of the Central Terrace and only minor structural faulting. To the south of the Central Terrace, trans-tensional stresses associated with withdrawal of the Falkland Malvinas Plateau have deformed the upper crust into a series of apparently southwards tilted crustal blocks, producing a series of deep (3.5 s TWT) half graben-like structures, within which syn-rift fill has an apparent dip towards the south. There is evidence to suggest ongoing reactivation of these fault structures. This zone of deformation is shown to bear resemblances to the faulting mapped onshore of the Kwa-Zulu Natal coastline, providing reason to consider the two regions as a continuous zone of deformation associated with the withdrawal of the Falkland-Malvinas Plateau during the breakup of West Gondwana. Furthermore, a number of post-sedimentary intrusive features are imaged, the largest of which is the Naude Ridge; a large pinnacle-like feature which has penetrated the upper crust towards the southern limit of the profile. This feature corresponds to an abrupt change in seafloor depth and upper crustal structure, suggesting that this feature may mark the transition between subsided continental crust interpreted to underlie the northern Natal Valley to the north and oceanic crust known to underlie the southern Natal Valley to the south.
- Full Text:
- Date Issued: 2018
An appraisal of warm temperate mangrove estuaries as food patches using zooplankton and RNA: DNA ratios of Gilchristella aestuaria larvae as indicators
- Authors: Bornman, Eugin
- Date: 2018
- Subjects: Mangrove swamps Fishes -- Larvae , Mangrove ecology , Zooplankton
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/17908 , vital:28481
- Description: Mangrove habitats are considered as the ideal fish nursery as they are known to increase the growth and survival of juvenile fishes by providing enhanced food availability and protection. However, most studies have focused on tropical mangroves with a few recent warm temperate studies finding conflicting results. Furthermore, the nursery value of South African mangroves to fishes remain understudied in subtropical areas, while warm temperate mangroves are yet to be evaluated. This study aimed to assess whether mangrove presence leads to any advantage to the larvae of an important estuarine resident fish species, Gilchristella aestuaria, by comparing the food patch quality of South African warm temperate mangrove and non-mangrove estuaries. Results indicate that larvae fed primarily on the dominant prey species, Pseudodiaptomus hessei, Paracrtia longipatella, and Acartiella natalensis. However, postflexion larvae consumed more of the larger species, P. hessei, within the two mangrove estuaries (16.09 %V in Nahoon and 13.79 %V in Xhora) than the two nonmangrove estuaries (12.20 %V in Gonubie and 7.05 %V in Qora), despite other prey species occurring at similar densities. Results indicate that mangrove habitats acted as sediment sinks, slightly reducing the turbidity of these estuaries which resulted in postflexion larvae actively selecting larger, more nutritious prey, which in turn, significantly increased their individual instantaneous growth rates (0.11 ± 0.21 Gi) when compared to postflexion larvae in non-mangrove estuaries (0.09 ± 0.12 Gi). This study found that mangrove presence was significantly related to postflexion larval densities when coupled with abiotic (such as temperature and turbidity) and biotic factors (such as predator-prey interactions). Understanding the spatial and temporal dynamics, predator-prey interactions as well as the growth and survival of G. aestuaria is particularly important as they are key zooplanktivores that are prey to other species in estuarine food webs.
- Full Text:
- Date Issued: 2018
- Authors: Bornman, Eugin
- Date: 2018
- Subjects: Mangrove swamps Fishes -- Larvae , Mangrove ecology , Zooplankton
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/17908 , vital:28481
- Description: Mangrove habitats are considered as the ideal fish nursery as they are known to increase the growth and survival of juvenile fishes by providing enhanced food availability and protection. However, most studies have focused on tropical mangroves with a few recent warm temperate studies finding conflicting results. Furthermore, the nursery value of South African mangroves to fishes remain understudied in subtropical areas, while warm temperate mangroves are yet to be evaluated. This study aimed to assess whether mangrove presence leads to any advantage to the larvae of an important estuarine resident fish species, Gilchristella aestuaria, by comparing the food patch quality of South African warm temperate mangrove and non-mangrove estuaries. Results indicate that larvae fed primarily on the dominant prey species, Pseudodiaptomus hessei, Paracrtia longipatella, and Acartiella natalensis. However, postflexion larvae consumed more of the larger species, P. hessei, within the two mangrove estuaries (16.09 %V in Nahoon and 13.79 %V in Xhora) than the two nonmangrove estuaries (12.20 %V in Gonubie and 7.05 %V in Qora), despite other prey species occurring at similar densities. Results indicate that mangrove habitats acted as sediment sinks, slightly reducing the turbidity of these estuaries which resulted in postflexion larvae actively selecting larger, more nutritious prey, which in turn, significantly increased their individual instantaneous growth rates (0.11 ± 0.21 Gi) when compared to postflexion larvae in non-mangrove estuaries (0.09 ± 0.12 Gi). This study found that mangrove presence was significantly related to postflexion larval densities when coupled with abiotic (such as temperature and turbidity) and biotic factors (such as predator-prey interactions). Understanding the spatial and temporal dynamics, predator-prey interactions as well as the growth and survival of G. aestuaria is particularly important as they are key zooplanktivores that are prey to other species in estuarine food webs.
- Full Text:
- Date Issued: 2018
An investigation of the movement of sediment through the Noordhoek headland bypass dunefield system at Cape Recife, South Africa
- Authors: Goosen, Gerrit Pieter
- Date: 2018
- Subjects: Sedimentation and deposition , Fluvial geomorphology Geomorphology Sand dunes -- Environmental aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/22101 , vital:29840
- Description: A detailed study of the movement of sediment across the Cape Recife headland via the Noordhoek headland bypass dunefield was conducted. The Noordhoek HBD is important because of the environmental impacts anticipated on the sewerage works, settling ponds, and road to the Cape Recife lighthouse situated in the migration path of the dunefield to the ENE of its active boundary. The primary objective of the study was to investigate the movement of sediment in and through the Noordhoek HBD system. This study has provided sand transportation and dune migration rates by making use of various dune monitoring techniques. In doing so, useful predictions have been made as to when the settling ponds and the road to the lighthouse will be inundated. An indication has also been given as to how much sand moves through the system. Some key findings from this research included: the net migration direction of the Noordhoek HBD was found to be towards the east-north-east; the wind environment at the study area was classified as a high energy wind environment; this study has highlighted that various climatic factors such as rainfall and temperature influence the movement of sediment through dune systems; sediment transport was found to be directly related to the source area and topography; the central zone of the dunefield proved to be a groundwater recharge zone for the western and eastern zones; and the leading lobes of the migrating Noordhoek dunefield are gradually covering stabilising vegetation by pulses of dunes moving through. In this study, it was calculated that presently a total volume of about 26 000 m3 of sand is migrating into the vegetation at the leading lobes annually. If the Noordhoek HBD is left to run its natural course and migrate across the Cape Recife headland to the downwind beach, an approximate volume of 26 000 m3 of sand could be supplied to the downwind beach by this system. In doing so, it has the potential to play a role in replenishing some of the sand to Port Elizabeth’s eroded southern beaches via a natural process.
- Full Text:
- Date Issued: 2018
- Authors: Goosen, Gerrit Pieter
- Date: 2018
- Subjects: Sedimentation and deposition , Fluvial geomorphology Geomorphology Sand dunes -- Environmental aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/22101 , vital:29840
- Description: A detailed study of the movement of sediment across the Cape Recife headland via the Noordhoek headland bypass dunefield was conducted. The Noordhoek HBD is important because of the environmental impacts anticipated on the sewerage works, settling ponds, and road to the Cape Recife lighthouse situated in the migration path of the dunefield to the ENE of its active boundary. The primary objective of the study was to investigate the movement of sediment in and through the Noordhoek HBD system. This study has provided sand transportation and dune migration rates by making use of various dune monitoring techniques. In doing so, useful predictions have been made as to when the settling ponds and the road to the lighthouse will be inundated. An indication has also been given as to how much sand moves through the system. Some key findings from this research included: the net migration direction of the Noordhoek HBD was found to be towards the east-north-east; the wind environment at the study area was classified as a high energy wind environment; this study has highlighted that various climatic factors such as rainfall and temperature influence the movement of sediment through dune systems; sediment transport was found to be directly related to the source area and topography; the central zone of the dunefield proved to be a groundwater recharge zone for the western and eastern zones; and the leading lobes of the migrating Noordhoek dunefield are gradually covering stabilising vegetation by pulses of dunes moving through. In this study, it was calculated that presently a total volume of about 26 000 m3 of sand is migrating into the vegetation at the leading lobes annually. If the Noordhoek HBD is left to run its natural course and migrate across the Cape Recife headland to the downwind beach, an approximate volume of 26 000 m3 of sand could be supplied to the downwind beach by this system. In doing so, it has the potential to play a role in replenishing some of the sand to Port Elizabeth’s eroded southern beaches via a natural process.
- Full Text:
- Date Issued: 2018
Application of hidden Markov models and their extensions to animal movement data
- Authors: Van Niekerk, Bracken
- Date: 2018
- Subjects: Markov processes Animal locomotion Time-series analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23835 , vital:30624
- Description: Hidden Markov Models (HMMs) have become increasingly popular in animal movement studies as they provide a flexible modelling approach and take the correlation between successive observations into account. They can segment the movement paths into latent states, which can be considered as rough proxies for the behaviours of the animals. This study comprises of two sections, both involving the application of HMMs to large terrestrial mammal movement data. Usually step lengths representing the displacement distances between successive observations, turning angles measuring the tortuosity, or a bivariate input of both variables are used as inputs in the models. It has been found in the literature that the turning angle is either included in the modelling process or it is excluded without much justification for doing so. The first part of this study investigates the nfluence of the turning angle on the model output and resultant interpretations of the HMMs when modelling the trajectories of large terrestrial mammals in southern Africa. Results revealed at different time scales, and for both predator and herbivore species in this study, that the turning angle does not influence the state allocation of the HMMs, which is the main output in terms of interpreting the behaviours of the animals. It is thought in most cases that the inclusion of the turning angle overcomplicates the models unnecessarily without contributing any additional information in terms of the behavioural interpretations or improving the overall fit of the models. This was found for the variety of movements of the species under observation in this study. The second part of this study attempts to validate the state allocation of the HMMs fitted to eland trajectories in the Greater Addo Elephant National Park in the Eastern Cape, with the use of camera trap data. This presented a unique opportunity as this type of data is mainly used for abundance or capture-recapture studies, and the HMMs are rarely validated as the true behaviours of the animals are seldom known. Results revealed that the same diel patterns were detected by the HMMs that were shown by the classified camera trap data. Direct comparisons of the observations where the dates and times matched for the telemetry and camera trap data could be done in several rare instances, which revealed many similarities. Although it was not an ideal comparison, the camera trap data provided a rough validation of the state allocation of the HMMs used in the study.
- Full Text:
- Date Issued: 2018
- Authors: Van Niekerk, Bracken
- Date: 2018
- Subjects: Markov processes Animal locomotion Time-series analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23835 , vital:30624
- Description: Hidden Markov Models (HMMs) have become increasingly popular in animal movement studies as they provide a flexible modelling approach and take the correlation between successive observations into account. They can segment the movement paths into latent states, which can be considered as rough proxies for the behaviours of the animals. This study comprises of two sections, both involving the application of HMMs to large terrestrial mammal movement data. Usually step lengths representing the displacement distances between successive observations, turning angles measuring the tortuosity, or a bivariate input of both variables are used as inputs in the models. It has been found in the literature that the turning angle is either included in the modelling process or it is excluded without much justification for doing so. The first part of this study investigates the nfluence of the turning angle on the model output and resultant interpretations of the HMMs when modelling the trajectories of large terrestrial mammals in southern Africa. Results revealed at different time scales, and for both predator and herbivore species in this study, that the turning angle does not influence the state allocation of the HMMs, which is the main output in terms of interpreting the behaviours of the animals. It is thought in most cases that the inclusion of the turning angle overcomplicates the models unnecessarily without contributing any additional information in terms of the behavioural interpretations or improving the overall fit of the models. This was found for the variety of movements of the species under observation in this study. The second part of this study attempts to validate the state allocation of the HMMs fitted to eland trajectories in the Greater Addo Elephant National Park in the Eastern Cape, with the use of camera trap data. This presented a unique opportunity as this type of data is mainly used for abundance or capture-recapture studies, and the HMMs are rarely validated as the true behaviours of the animals are seldom known. Results revealed that the same diel patterns were detected by the HMMs that were shown by the classified camera trap data. Direct comparisons of the observations where the dates and times matched for the telemetry and camera trap data could be done in several rare instances, which revealed many similarities. Although it was not an ideal comparison, the camera trap data provided a rough validation of the state allocation of the HMMs used in the study.
- Full Text:
- Date Issued: 2018
Assessing growth response patterns of microalgae to varying environmental conditions using sediments from ephemeral wetlands
- Authors: Mazwane, Sixolile
- Date: 2018
- Subjects: Microalgae -- South Africa , Wetland conservation -- South Africa Landscape ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/22398 , vital:29966
- Description: Ephemeral wetlands serve as habitats for different fauna and flora. Microalgae make up a bulk of primary production in newly inundated wetlands and have a big influence on the aquatic community structure. As ephemeral wetlands have cyclical drying and wetting phases, algal species found in these habitats have evolved adaptations (i.e. dormancy and cysts) to survive during dry periods and become productive upon inundation. Algae have been used as ecological indicators in many aquatic ecosystems including wetlands, particularly associated with water quality and with varying inundation states. Whilst temperature and water level have been shown to affect microalgal biomass independently, this study aims to assess the effects of these two factors simultaneously on microalgal biomass, species diversity and community changes. The aim of the study was to investigate microalgal dynamics using two ephemeral wetlands in the Nelson Mandela Bay Municipality. The growth response patterns of microalgal communities to varying temperatures and inundation levels through experiments using dry temporary wetland sediments was also assessed. Dry sediments were collected from two depression wetlands with different sediment characteristics (1592 and Elephant Wallow (EW)). The study consisted of replicated treatments with three different surface area: volume ratios (SA:V) (Low surface area: volume (LSAV), Medium (MSAV) and High (HSAV)), inundated with distilled water. The microcosms were placed inside a Conviron environmental growth chamber and illuminated at between 106 to 138 μmol.m-2s-1, with a 12:12 light-dark cycle at constant temperatures of 12 °C (mean winter) and 22 °C (mean summer). Physicochemical data were recorded, and biological samples were collected every 4 days over a 28-day inundation period. In the field, Electrical conductivity (EC) and pH showed a gradual increase over the inundation period. The systems were well oxygenated (6-10 mg L-1). Overall, phytoplankton biomass in the field was ~10 μg L-1 whereas benthic biomass (MPB) was significantly higher 10 – 300 mg L-1. Within the experiments, the phytoplankton biomass showed a pattern while MPB biomass increased gradually for both experiments. There were no significant (p>0.05) differences between the 1592 and EW phytoplankton biomass. However, the MPB biomass showed significant (p<0.05) differences between the two sediments (EW high, 1592 low) and the experiments, respectively. In the winter experiment, the 1592 sediment had high phytoplankton biomass compared to EW, the reverse was observed for the MPB biomass. In summer experiment, similar results were observed in terms of phytoplankton biomass. For the MPBs, 1592 had greater biomass for all treatments compared to EW. The phytoplankton community for both field samples and experiments was dominated by chlorophytes (>50 %), followed by cyanophytes and euglenophytes (with cryptophytes in summer experiment) for both field and experiments. The MPB community was dominated by bacillariophytes (55 %) and chlorophytes (25 %) in the 1592 sediments and this was also the case with EW sediments bacillariophytes (70 %), although cyanophytes (15 %) made up the remainder of the MPB community. The 1592 sediments supported higher diatom abundances under the HSAV compared to the same treatment from the EW wetland suggesting that possibly grain size or texture might be responsible. In contrast, sediments from EW under LSAV conditions showed higher diatom cell numbers possibly indicating that increased water depth has the propensity to support greater diatom assemblages compared with the same water level for sediments from 1592. The results indicate that microalgae community is influenced by sediment type more than it is by water level. From this study it was also established that microalgae were able to reemerge from their dormancy state upon inundation and that tank experiments were successful in simulating natural ephemeral wetland conditions. The findings from this study will add to the available baseline data on microalgal dynamics in the ephemeral wetlands in South Africa, especially in semi-arid areas. This information can be valuable in enhancing our understanding regarding the role of microalgae in ephemeral wetlands in order to conserve them.
- Full Text:
- Date Issued: 2018
- Authors: Mazwane, Sixolile
- Date: 2018
- Subjects: Microalgae -- South Africa , Wetland conservation -- South Africa Landscape ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/22398 , vital:29966
- Description: Ephemeral wetlands serve as habitats for different fauna and flora. Microalgae make up a bulk of primary production in newly inundated wetlands and have a big influence on the aquatic community structure. As ephemeral wetlands have cyclical drying and wetting phases, algal species found in these habitats have evolved adaptations (i.e. dormancy and cysts) to survive during dry periods and become productive upon inundation. Algae have been used as ecological indicators in many aquatic ecosystems including wetlands, particularly associated with water quality and with varying inundation states. Whilst temperature and water level have been shown to affect microalgal biomass independently, this study aims to assess the effects of these two factors simultaneously on microalgal biomass, species diversity and community changes. The aim of the study was to investigate microalgal dynamics using two ephemeral wetlands in the Nelson Mandela Bay Municipality. The growth response patterns of microalgal communities to varying temperatures and inundation levels through experiments using dry temporary wetland sediments was also assessed. Dry sediments were collected from two depression wetlands with different sediment characteristics (1592 and Elephant Wallow (EW)). The study consisted of replicated treatments with three different surface area: volume ratios (SA:V) (Low surface area: volume (LSAV), Medium (MSAV) and High (HSAV)), inundated with distilled water. The microcosms were placed inside a Conviron environmental growth chamber and illuminated at between 106 to 138 μmol.m-2s-1, with a 12:12 light-dark cycle at constant temperatures of 12 °C (mean winter) and 22 °C (mean summer). Physicochemical data were recorded, and biological samples were collected every 4 days over a 28-day inundation period. In the field, Electrical conductivity (EC) and pH showed a gradual increase over the inundation period. The systems were well oxygenated (6-10 mg L-1). Overall, phytoplankton biomass in the field was ~10 μg L-1 whereas benthic biomass (MPB) was significantly higher 10 – 300 mg L-1. Within the experiments, the phytoplankton biomass showed a pattern while MPB biomass increased gradually for both experiments. There were no significant (p>0.05) differences between the 1592 and EW phytoplankton biomass. However, the MPB biomass showed significant (p<0.05) differences between the two sediments (EW high, 1592 low) and the experiments, respectively. In the winter experiment, the 1592 sediment had high phytoplankton biomass compared to EW, the reverse was observed for the MPB biomass. In summer experiment, similar results were observed in terms of phytoplankton biomass. For the MPBs, 1592 had greater biomass for all treatments compared to EW. The phytoplankton community for both field samples and experiments was dominated by chlorophytes (>50 %), followed by cyanophytes and euglenophytes (with cryptophytes in summer experiment) for both field and experiments. The MPB community was dominated by bacillariophytes (55 %) and chlorophytes (25 %) in the 1592 sediments and this was also the case with EW sediments bacillariophytes (70 %), although cyanophytes (15 %) made up the remainder of the MPB community. The 1592 sediments supported higher diatom abundances under the HSAV compared to the same treatment from the EW wetland suggesting that possibly grain size or texture might be responsible. In contrast, sediments from EW under LSAV conditions showed higher diatom cell numbers possibly indicating that increased water depth has the propensity to support greater diatom assemblages compared with the same water level for sediments from 1592. The results indicate that microalgae community is influenced by sediment type more than it is by water level. From this study it was also established that microalgae were able to reemerge from their dormancy state upon inundation and that tank experiments were successful in simulating natural ephemeral wetland conditions. The findings from this study will add to the available baseline data on microalgal dynamics in the ephemeral wetlands in South Africa, especially in semi-arid areas. This information can be valuable in enhancing our understanding regarding the role of microalgae in ephemeral wetlands in order to conserve them.
- Full Text:
- Date Issued: 2018
Assessment of indigenous forest degradation and deforestation along the wild coast, near Port St John’s, Eastern Cape Province, South Africa
- Katende, Lukyamuzi Lucky Fulgentius
- Authors: Katende, Lukyamuzi Lucky Fulgentius
- Date: 2018
- Subjects: Deforestation -- South Africa -- Eastern Cape , Forest degradation -- South Africa -- Eastern Cape Forest management -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30649 , vital:31006
- Description: Indigenous forests along the Wild Coast of the Eastern Cape Province have experienced both degradation and deforestation over the past decades. In early 2000, steps were taken to rehabilitate some of the degraded areas. Nevertheless, there is no monitoring mechanism in place, so little is known about the extent of degradation and impact of the rehabilitation efforts. The present study assesses the extent to which deforestation and degradation of the indigenous forests have occurred, and evaluates rehabilitation efforts in the study area around Port Saint John’s. Forest degradation was defined as the decrease in forest cover density while deforestation was defined as an increase in the trend of light forests and/ or a decrease in dense forests. The details for this study were obtained from multi – temporal remotely sensed data for a period between 1982 and 2013 (31 years). Multi-temporal Landsat satellite imagery for 1982, 1986, 1989, 2002, 2009 and 2013 was acquired and analysed. On the basis of prior knowledge of the area, the supervised classification approach was used. The Maximum likelihood supervised classification technique was used to extract information from satellite data. The classified images were filtered using a majority filtering procedure to reduce noise. Google Earth (Astrium) ancillary images were used to refine the classification based on expert rules. The derived changes in the degraded and rehabilitated areas were further validated through field visits. The overall image classification accuracy generated from Landsat image data ranged from 80% to 90%. It was noted that the area of dense forest almost doubled between 1986 and 1989, coinciding with a 59% decrease in the light forest. Subsequently, dense forests increased by 14,820 ha while light forests decreased by 16,690 ha between 1989 and 2002. The subsequent reduction in light forest coverage is explained by the establishment of the Participatory Forest Management (PFMA) approach by Department of Water Affairs and Forestry (DWAF) which reversed the degradation trend. However, specific degradation hotspots were identified, particularly where new settlements have been established. The emergence of the non-vegetated area increased gradually from 7% in 1986 to 23.4% in 2013. Notably, dense forest was observed to have experienced higher rates of forest degradation and deforestation than the light forest. The highest number patches were 4 recorded between 2002 and 1998, followed by between 2010 and 2013 and lastly 1986. Based on spatial connectedness of patches, the year 1986 had the highest landscape connectedness of forest vegetation (CONAT = 35.3) followed by 2002 and 1996 while the year 2010 and 2013 had the lowest landscape contiguity. Over the study period, the distribution of patches clearly shows that forest degradation and deforestation rates were lower in the years 1986, 1998 and tremendously increased in the later period of between 2010 and 2013. However, as a result of rehabilitation efforts, dense forest was seen to steadily gain more land than light forest. Finer details of degradation trends could not be easily picked from the images used in the study, given their spatial resolution limitations. That notwithstanding, the trends identified are good for overview decisions. The study has also established that de-agraianisation, forest restoration and rehabilitation greatly contributed to increased forest cover. Therefore, with more use of GIS by forest managers, and imagery of the high resolution being readily available, forests will in future be easily monitored using remote sensing.
- Full Text:
- Date Issued: 2018
- Authors: Katende, Lukyamuzi Lucky Fulgentius
- Date: 2018
- Subjects: Deforestation -- South Africa -- Eastern Cape , Forest degradation -- South Africa -- Eastern Cape Forest management -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30649 , vital:31006
- Description: Indigenous forests along the Wild Coast of the Eastern Cape Province have experienced both degradation and deforestation over the past decades. In early 2000, steps were taken to rehabilitate some of the degraded areas. Nevertheless, there is no monitoring mechanism in place, so little is known about the extent of degradation and impact of the rehabilitation efforts. The present study assesses the extent to which deforestation and degradation of the indigenous forests have occurred, and evaluates rehabilitation efforts in the study area around Port Saint John’s. Forest degradation was defined as the decrease in forest cover density while deforestation was defined as an increase in the trend of light forests and/ or a decrease in dense forests. The details for this study were obtained from multi – temporal remotely sensed data for a period between 1982 and 2013 (31 years). Multi-temporal Landsat satellite imagery for 1982, 1986, 1989, 2002, 2009 and 2013 was acquired and analysed. On the basis of prior knowledge of the area, the supervised classification approach was used. The Maximum likelihood supervised classification technique was used to extract information from satellite data. The classified images were filtered using a majority filtering procedure to reduce noise. Google Earth (Astrium) ancillary images were used to refine the classification based on expert rules. The derived changes in the degraded and rehabilitated areas were further validated through field visits. The overall image classification accuracy generated from Landsat image data ranged from 80% to 90%. It was noted that the area of dense forest almost doubled between 1986 and 1989, coinciding with a 59% decrease in the light forest. Subsequently, dense forests increased by 14,820 ha while light forests decreased by 16,690 ha between 1989 and 2002. The subsequent reduction in light forest coverage is explained by the establishment of the Participatory Forest Management (PFMA) approach by Department of Water Affairs and Forestry (DWAF) which reversed the degradation trend. However, specific degradation hotspots were identified, particularly where new settlements have been established. The emergence of the non-vegetated area increased gradually from 7% in 1986 to 23.4% in 2013. Notably, dense forest was observed to have experienced higher rates of forest degradation and deforestation than the light forest. The highest number patches were 4 recorded between 2002 and 1998, followed by between 2010 and 2013 and lastly 1986. Based on spatial connectedness of patches, the year 1986 had the highest landscape connectedness of forest vegetation (CONAT = 35.3) followed by 2002 and 1996 while the year 2010 and 2013 had the lowest landscape contiguity. Over the study period, the distribution of patches clearly shows that forest degradation and deforestation rates were lower in the years 1986, 1998 and tremendously increased in the later period of between 2010 and 2013. However, as a result of rehabilitation efforts, dense forest was seen to steadily gain more land than light forest. Finer details of degradation trends could not be easily picked from the images used in the study, given their spatial resolution limitations. That notwithstanding, the trends identified are good for overview decisions. The study has also established that de-agraianisation, forest restoration and rehabilitation greatly contributed to increased forest cover. Therefore, with more use of GIS by forest managers, and imagery of the high resolution being readily available, forests will in future be easily monitored using remote sensing.
- Full Text:
- Date Issued: 2018
Assessment of the microalgal community structure and biomass in surface waterbodies of the Eastern Cape Karoo region earmarked for shale gas exploration
- Authors: Roussouw, Natasha Kimberlee
- Date: 2018
- Subjects: Fresh water -- Eastern Cape , Water-supply -- South Africa -- Eastern Cape Water-supply, Rural -- South Africa -- Eastern Cape Constructed wetlands Watershed management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/35234 , vital:33655
- Description: The Eastern Cape Karoo region of South Africa typically displays low rainfall and high temperatures, which is particularly concerning considering the shale gas exploration/extraction project proposed recently. Almost 90% of the fracking fluid consists of water and with the Karoo region already classified as a water-stressed region, the increased demand for freshwater for fracking could put further pressure on water resources of the region. By understanding the ecological functioning of the lower trophic levels, likely implications for higher trophic levels can be determined, and ultimately, recommendations for mitigation actions can be made. Here, observations aimed at understanding the dynamics of lower trophic levels are presented, that is, the microalgal biomass and assemblage composition within three characteristic surface waterbodies of the region. In addition, the work focuses on the smaller, more dynamic temporary wetland systems typical of this water-scarce region, with the aim of understanding the significance of single species macrophyte cover in relation to the lower trophic levels. Thirty-three waterbodies were sampled (natural depressions = 13, dams = 9, rivers = 11) during November 2014 (austral spring) and April 2015 (austral autumn). Waterbody physico-chemistry, hydro-morphometry, habitat cover and surrounding land-use, as well as microalgal biomass and assemblage composition within each waterbody type were measured. Thirteen natural depression wetlands were sampled during October 2015, December 2015 and March 2016. Once again, waterbody physico-chemistry, microalgal biomass and assemblage composition were measured. However, in addition, Schoenoplectus decipiens macrophyte cover and microalgal (diatom) species composition were also determined. In general, no significant differences in microalgal biomass between the three main waterbody types of the Eastern Cape Karoo region were found; however, the different waterbody types each displayed distinct microalgal assemblage compositions. Also, Schoenoplectus decipiens cover had negligible effects on microalgal biomass and assemblages in the temporary wetlands investigated here. These results suggest that the generalist nature of species occupying these systems allows them to adapt to the ever-changing conditions typical of this region. Ongoing monitoring initiatives considering impending hydraulic fracturing activities should include a comprehensive species-level diversity census, which could further inform management of any impacts associated with this potential disturbance.
- Full Text:
- Date Issued: 2018
- Authors: Roussouw, Natasha Kimberlee
- Date: 2018
- Subjects: Fresh water -- Eastern Cape , Water-supply -- South Africa -- Eastern Cape Water-supply, Rural -- South Africa -- Eastern Cape Constructed wetlands Watershed management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/35234 , vital:33655
- Description: The Eastern Cape Karoo region of South Africa typically displays low rainfall and high temperatures, which is particularly concerning considering the shale gas exploration/extraction project proposed recently. Almost 90% of the fracking fluid consists of water and with the Karoo region already classified as a water-stressed region, the increased demand for freshwater for fracking could put further pressure on water resources of the region. By understanding the ecological functioning of the lower trophic levels, likely implications for higher trophic levels can be determined, and ultimately, recommendations for mitigation actions can be made. Here, observations aimed at understanding the dynamics of lower trophic levels are presented, that is, the microalgal biomass and assemblage composition within three characteristic surface waterbodies of the region. In addition, the work focuses on the smaller, more dynamic temporary wetland systems typical of this water-scarce region, with the aim of understanding the significance of single species macrophyte cover in relation to the lower trophic levels. Thirty-three waterbodies were sampled (natural depressions = 13, dams = 9, rivers = 11) during November 2014 (austral spring) and April 2015 (austral autumn). Waterbody physico-chemistry, hydro-morphometry, habitat cover and surrounding land-use, as well as microalgal biomass and assemblage composition within each waterbody type were measured. Thirteen natural depression wetlands were sampled during October 2015, December 2015 and March 2016. Once again, waterbody physico-chemistry, microalgal biomass and assemblage composition were measured. However, in addition, Schoenoplectus decipiens macrophyte cover and microalgal (diatom) species composition were also determined. In general, no significant differences in microalgal biomass between the three main waterbody types of the Eastern Cape Karoo region were found; however, the different waterbody types each displayed distinct microalgal assemblage compositions. Also, Schoenoplectus decipiens cover had negligible effects on microalgal biomass and assemblages in the temporary wetlands investigated here. These results suggest that the generalist nature of species occupying these systems allows them to adapt to the ever-changing conditions typical of this region. Ongoing monitoring initiatives considering impending hydraulic fracturing activities should include a comprehensive species-level diversity census, which could further inform management of any impacts associated with this potential disturbance.
- Full Text:
- Date Issued: 2018
Biological activity of macrofungi in South Africa against respiratory and lung disease
- Authors: Didloff, Jenske
- Date: 2018
- Subjects: Macrofungi , Microbiology Medical microbiology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30138 , vital:30835
- Description: Macrofungi represent an untapped source of natural bioactive compounds for various diseases, which have been targeted as potential therapeutic agents. The medicinal uses of macrofungi discovered to date include anticancer, antidiabetic, antioxidant, antimicrobial, and immunomodulatory properties. The knowledge regarding the medicinal uses of macrofungi in Africa is limited; however, it is believed that Africa may contain a large number of unidentified species of macrofungi. The objectives of this study were to: (i) screen the macrofungal extracts for antimicrobial activity against microorganisms responsible for respiratory diseases (e.g. Pseudomonas aeruginosa, Klebsiella pneumoniae, Streptococcus pneumoniae, Streptococcus pyogenes, Staphylococcus aureus, Mycobacterium tuberculosis, HIV-1), (ii) determine the effect of macrofungal extracts on bacterial morphology, (iii) investigate the cytotoxicity of macrofungal extracts against human lung carcinoma cells, and to elucidate the mechanism/s of action of cytotoxicity/anticancer activity. In vitro bioassays for antimicrobial activity included: ρ-iodonitrotetrazolium chloride assays and microplate alamar blue assay (MABA), while the HIV-1 reverse transcriptase colorimetric ELISA and HIV-1 protease fluorometric assay kits were used for anti-HIV activity. Cytotoxicity of the macrofungal species against A549 lung cancer cell line was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, and the IC50 values determined for the most cytotoxic macrofungal spp. The mechanism of cytotoxicity was investigated by cell cycle analysis and fluorescent staining to observe morphological and biochemical changes (i.e. acridine orange, caspase activation). Ethanol extracts of Amanita foetidissima, Gymnopilus junonius, Pisolithus tinctorius, Fomitopsis lilacinogilva, Stereum hirsutum and Pycnoporus sanguineus showed higher antimicrobial activity against the Gram-positive bacteria than aqueous extracts, with S. pneumoniae being the most susceptible. The ethanol extracts of Agaricus campestris, Chlorophyllum molybdites, Gymnopilus penetrans, Pseudophaeolus baudonii and Laetiporus sulphureus exhibited anti-TB (tuberculosis) activity with minimum inhibitory concentrations (MICs) ranging between 500-1,000 μg/mL. C. molybdites ethanol extract inhibited HIV-1 protease activity (IC50: 49.7 μg/mL). The macrofungal extracts did not inhibit HIV-1 reverse transcriptase activity. Ethanol extracts of F. lilacinogilva, G. junonius, P. sanguineus and the aqueous extract iv of P. baudonii were cytotoxic against A549 lung cancer cells at IC50 values of 69.2±3.6, 57±5, 7.4±1.1 and 53.6±1.1 μg/mL, respectively. Cell cycle arrest was observed in the G2 phase for both P. sanguineus and P. baudonii, and G2/M and early M phases for G. junonius and F. lilacinogilva, respectively. Apoptosis induced by macrofungal extracts was confirmed by fluorescent staining. Morphological and biochemical changes included chromatin condensation, membrane blebbing, loss of cytoskeletal structure, caspase activation and phosphatidylserine translocation. This study demonstrates the biological activities of selected macrofungal extracts and their potential mechanisms of action. Isolation and identification of active compounds require further analysis.
- Full Text:
- Date Issued: 2018
- Authors: Didloff, Jenske
- Date: 2018
- Subjects: Macrofungi , Microbiology Medical microbiology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30138 , vital:30835
- Description: Macrofungi represent an untapped source of natural bioactive compounds for various diseases, which have been targeted as potential therapeutic agents. The medicinal uses of macrofungi discovered to date include anticancer, antidiabetic, antioxidant, antimicrobial, and immunomodulatory properties. The knowledge regarding the medicinal uses of macrofungi in Africa is limited; however, it is believed that Africa may contain a large number of unidentified species of macrofungi. The objectives of this study were to: (i) screen the macrofungal extracts for antimicrobial activity against microorganisms responsible for respiratory diseases (e.g. Pseudomonas aeruginosa, Klebsiella pneumoniae, Streptococcus pneumoniae, Streptococcus pyogenes, Staphylococcus aureus, Mycobacterium tuberculosis, HIV-1), (ii) determine the effect of macrofungal extracts on bacterial morphology, (iii) investigate the cytotoxicity of macrofungal extracts against human lung carcinoma cells, and to elucidate the mechanism/s of action of cytotoxicity/anticancer activity. In vitro bioassays for antimicrobial activity included: ρ-iodonitrotetrazolium chloride assays and microplate alamar blue assay (MABA), while the HIV-1 reverse transcriptase colorimetric ELISA and HIV-1 protease fluorometric assay kits were used for anti-HIV activity. Cytotoxicity of the macrofungal species against A549 lung cancer cell line was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, and the IC50 values determined for the most cytotoxic macrofungal spp. The mechanism of cytotoxicity was investigated by cell cycle analysis and fluorescent staining to observe morphological and biochemical changes (i.e. acridine orange, caspase activation). Ethanol extracts of Amanita foetidissima, Gymnopilus junonius, Pisolithus tinctorius, Fomitopsis lilacinogilva, Stereum hirsutum and Pycnoporus sanguineus showed higher antimicrobial activity against the Gram-positive bacteria than aqueous extracts, with S. pneumoniae being the most susceptible. The ethanol extracts of Agaricus campestris, Chlorophyllum molybdites, Gymnopilus penetrans, Pseudophaeolus baudonii and Laetiporus sulphureus exhibited anti-TB (tuberculosis) activity with minimum inhibitory concentrations (MICs) ranging between 500-1,000 μg/mL. C. molybdites ethanol extract inhibited HIV-1 protease activity (IC50: 49.7 μg/mL). The macrofungal extracts did not inhibit HIV-1 reverse transcriptase activity. Ethanol extracts of F. lilacinogilva, G. junonius, P. sanguineus and the aqueous extract iv of P. baudonii were cytotoxic against A549 lung cancer cells at IC50 values of 69.2±3.6, 57±5, 7.4±1.1 and 53.6±1.1 μg/mL, respectively. Cell cycle arrest was observed in the G2 phase for both P. sanguineus and P. baudonii, and G2/M and early M phases for G. junonius and F. lilacinogilva, respectively. Apoptosis induced by macrofungal extracts was confirmed by fluorescent staining. Morphological and biochemical changes included chromatin condensation, membrane blebbing, loss of cytoskeletal structure, caspase activation and phosphatidylserine translocation. This study demonstrates the biological activities of selected macrofungal extracts and their potential mechanisms of action. Isolation and identification of active compounds require further analysis.
- Full Text:
- Date Issued: 2018
Capacitance spectroscopy of GaAs p-i-n solar cells embedded with GaNAs quantum wells
- Authors: Venter, Danielle Ahlers
- Date: 2018
- Subjects: Solar cells , Photocatalysis Nanotechnology Fuel cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/21593 , vital:29713
- Description: The search for higher efficiencies in solar cell technology has brought forth competitive ideas, among them tandem solar cells (TSC) and intermediate-band solar cells (IBSC). These cells deliver higher efficiencies by absorbing a wider range of the electro-magnetic spectrum compared to conventional cells, but do come with unique challenges. This includes, amongst others, the need to find suitable material systems, which can fully realise the requirements behind the concept. In this study, the notion of using dilute nitrides in III-V systems as a candidate for the IBSC is considered. Incorporation of GaNAs QW structures into GaAs p-i-n solar cells are structurally, optically and electrically characterised. At a first estimate the photovoltaic properties of the material is obtained through current-voltage (I-V) measurements under illumination. It is observed that the open circuit voltage (𝑉𝑂𝐶), short circuit current (𝐼𝑆𝐶) and conversion efficiency decrease upon the incorporation of the QWs. Electrically active defect levels are notorious for reducing the life time of electron-hole pairs, directly impacting cell efficiency. In an effort to gain a clearer understanding of this behavior, the study of electrically active deep level center present in such devices were investigated. A comprehensive understanding of defects in semiconductors remains of fundamental importance and thus reinforces this approach. This was done using two of the most commonly used semiconductor defect spectroscopy techniques viz. admittance spectroscopy (AS) and deep level transient spectroscopy (DLTS). Since in principle, these two techniques are similar, deep level related results were compared in order to verify the validity of the results. The devices under study, GaNAs/GaAs embedded QW p-i-n solar cells, were grown by molecular beam epitaxy (MBE). In particular, the doping of the quantum wells was varied and this effect on the electrical properties investigated. Four samples were studied and their electrical, optical and structural properties compared. The sample series consisted of a reference GaAs p-i-n diode that contained no embedded QWs and three GaAs p-i-n diodes each containing ten equally spaced and equally thick GaNAs QW layers. These layers were either Beryllium (Be) doped (p-type), un-doped or Silicon (Si) doped (n-type) respectively. Both AS and DLTS revealed deep level centers present in the devices. Each technique presented its own list of advantages and disadvantages and the collaborative use of both of them was found to be complementary in their determination of deep level defect centers. The correlation of these defects with the QWs is not clear as the structures were not optimized for capacitance spectroscopic measurements. NextNano++ simulation software was also used to theoretically model the electronic structure of the sample. The addition of the applied bias and its effect on the cross-over point of the Fermi level and the deep level energy, as well as the depletion width was investigated. This was a useful and essential tool for the interpretation of the results obtained and for the design of optimal structures for future studies.
- Full Text:
- Date Issued: 2018
- Authors: Venter, Danielle Ahlers
- Date: 2018
- Subjects: Solar cells , Photocatalysis Nanotechnology Fuel cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/21593 , vital:29713
- Description: The search for higher efficiencies in solar cell technology has brought forth competitive ideas, among them tandem solar cells (TSC) and intermediate-band solar cells (IBSC). These cells deliver higher efficiencies by absorbing a wider range of the electro-magnetic spectrum compared to conventional cells, but do come with unique challenges. This includes, amongst others, the need to find suitable material systems, which can fully realise the requirements behind the concept. In this study, the notion of using dilute nitrides in III-V systems as a candidate for the IBSC is considered. Incorporation of GaNAs QW structures into GaAs p-i-n solar cells are structurally, optically and electrically characterised. At a first estimate the photovoltaic properties of the material is obtained through current-voltage (I-V) measurements under illumination. It is observed that the open circuit voltage (𝑉𝑂𝐶), short circuit current (𝐼𝑆𝐶) and conversion efficiency decrease upon the incorporation of the QWs. Electrically active defect levels are notorious for reducing the life time of electron-hole pairs, directly impacting cell efficiency. In an effort to gain a clearer understanding of this behavior, the study of electrically active deep level center present in such devices were investigated. A comprehensive understanding of defects in semiconductors remains of fundamental importance and thus reinforces this approach. This was done using two of the most commonly used semiconductor defect spectroscopy techniques viz. admittance spectroscopy (AS) and deep level transient spectroscopy (DLTS). Since in principle, these two techniques are similar, deep level related results were compared in order to verify the validity of the results. The devices under study, GaNAs/GaAs embedded QW p-i-n solar cells, were grown by molecular beam epitaxy (MBE). In particular, the doping of the quantum wells was varied and this effect on the electrical properties investigated. Four samples were studied and their electrical, optical and structural properties compared. The sample series consisted of a reference GaAs p-i-n diode that contained no embedded QWs and three GaAs p-i-n diodes each containing ten equally spaced and equally thick GaNAs QW layers. These layers were either Beryllium (Be) doped (p-type), un-doped or Silicon (Si) doped (n-type) respectively. Both AS and DLTS revealed deep level centers present in the devices. Each technique presented its own list of advantages and disadvantages and the collaborative use of both of them was found to be complementary in their determination of deep level defect centers. The correlation of these defects with the QWs is not clear as the structures were not optimized for capacitance spectroscopic measurements. NextNano++ simulation software was also used to theoretically model the electronic structure of the sample. The addition of the applied bias and its effect on the cross-over point of the Fermi level and the deep level energy, as well as the depletion width was investigated. This was a useful and essential tool for the interpretation of the results obtained and for the design of optimal structures for future studies.
- Full Text:
- Date Issued: 2018
Causes and impacts of delays in low-income housing projects in the greater Nelson Mandela Bay and Buffolo City Municipality
- Authors: Xongo, Nwabisa
- Date: 2018
- Subjects: Project management -- South Africa -- Nelson Mandela Bay Municipality , Project management -- South Africa -- Buffalo City Municipality Low-income housing -- South Africa -- Eastern Cape Public housing -- South Africa -- Eastern Cape Housing development -- South Africa Construction industry -- Management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/36259 , vital:33916
- Description: A construction project depends upon having correct people with the correct skills and usable equipment, therefore to deliver the project on time, on budget and specified quality. Project success can be attained if the construction works moves professionally within the time schedule. Delays to projects mean the go slow of process and all other related fields. The main aim of this study is to assess the numerous causes of delays and reasons for those delays that are currently affecting the project in low income housing projects in Nelson Mandela Bay and Buffalo City Metropolitan Municipality.
- Full Text: false
- Date Issued: 2018
- Authors: Xongo, Nwabisa
- Date: 2018
- Subjects: Project management -- South Africa -- Nelson Mandela Bay Municipality , Project management -- South Africa -- Buffalo City Municipality Low-income housing -- South Africa -- Eastern Cape Public housing -- South Africa -- Eastern Cape Housing development -- South Africa Construction industry -- Management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/36259 , vital:33916
- Description: A construction project depends upon having correct people with the correct skills and usable equipment, therefore to deliver the project on time, on budget and specified quality. Project success can be attained if the construction works moves professionally within the time schedule. Delays to projects mean the go slow of process and all other related fields. The main aim of this study is to assess the numerous causes of delays and reasons for those delays that are currently affecting the project in low income housing projects in Nelson Mandela Bay and Buffalo City Metropolitan Municipality.
- Full Text: false
- Date Issued: 2018
Challenges facing the state of construction health and safety management practices within the Eastern Cape: a case of the Sarah Baartman District
- Authors: Mafuya, Nomakhwezi
- Date: 2018
- Subjects: Industrial safety -- Management , Construction industry -- South Africa -- Eastern Cape Construction industry -- Safety measures -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/31532 , vital:31504
- Description: The construction industry has a poor Health and Safety (H&S) record globally and South Africa is no exception (Haupt, 2016: 1). The construction industry is integrally a high-impact and dangerous industry with less than a 50% ratio in compliance to H&S standards (PricewaterhouseCoppers (PwC), 2016). This study is aimed towards evolving a solution to mitigate the fatalities and injuries, occupational health hazards, non-compliance with legislation and design originated hazards and the reoccurring problems experienced by the Eastern Cape Department of Public Works (ECDPW) on projects. Literature points out that H&S performance is attributable to a lack of management commitment, inadequate supervision, inadequate H&S training, and lack of worker involvement (construction industry development board (cidb), 2009: 36). Huang and Hinze (2006: 179) contend that clients‟ participation in project H&S can significantly influence project performance. Various researchers have amplified the importance of leadership roles and involvement of clients in H&S. A quantitative survey and qualitative inquiry were utilised to gather and analyse data within the Eastern Cape province of South Africa. Three questionnaires were developed and distributed to a target population, and interviews were conducted. The study focuses on seven schools, namely; Stormsriver, Jubilee, Mfesane, Bongweni, David Livingstone, Kaiser Ngxwane and Bethelsdorp, which are on-going for the 2016/2017 financial period during which the research study was conducted. A total of 136 responses were used to analyse the data. All project stakeholders, namely: project managers, contractors‟ site managers, and workers contributed to the study. The frequency of H&S actions varied with each stakeholder dependent on the stage in which they were involved. The study determined that extensive inadequacy of construction expertise in terms of H&S including H&S consultants and departmental H&S personnel, inadequate management and supervision on site, inadequate workers participation, inadequate H&S training, inadequate expertise in H&S management, inadequate designer report, inadequate H&S knowledge and awareness, negligence, unsafe acts, unskilled workers, unsafe conditions, non-compliance with H&S regulations, Safe v Operating Procedure (SOPs) and Safe Working Procedures (SWPs), inadequate commitment of various project stakeholders, ignorance, poor client H&S leadership throughout certain aspects of the ECDPW projects are the primary cause of fatalities and injuries, ill-health, design originated hazards, non-compliance and the reoccurrence of problems. Recommendations were for H&S to be integrated within the Departments internal project systems from project inception to project close out, and to enhance H&S knowledge and skills in order to mitigate the reoccurrences of problems on projects.
- Full Text:
- Date Issued: 2018
- Authors: Mafuya, Nomakhwezi
- Date: 2018
- Subjects: Industrial safety -- Management , Construction industry -- South Africa -- Eastern Cape Construction industry -- Safety measures -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/31532 , vital:31504
- Description: The construction industry has a poor Health and Safety (H&S) record globally and South Africa is no exception (Haupt, 2016: 1). The construction industry is integrally a high-impact and dangerous industry with less than a 50% ratio in compliance to H&S standards (PricewaterhouseCoppers (PwC), 2016). This study is aimed towards evolving a solution to mitigate the fatalities and injuries, occupational health hazards, non-compliance with legislation and design originated hazards and the reoccurring problems experienced by the Eastern Cape Department of Public Works (ECDPW) on projects. Literature points out that H&S performance is attributable to a lack of management commitment, inadequate supervision, inadequate H&S training, and lack of worker involvement (construction industry development board (cidb), 2009: 36). Huang and Hinze (2006: 179) contend that clients‟ participation in project H&S can significantly influence project performance. Various researchers have amplified the importance of leadership roles and involvement of clients in H&S. A quantitative survey and qualitative inquiry were utilised to gather and analyse data within the Eastern Cape province of South Africa. Three questionnaires were developed and distributed to a target population, and interviews were conducted. The study focuses on seven schools, namely; Stormsriver, Jubilee, Mfesane, Bongweni, David Livingstone, Kaiser Ngxwane and Bethelsdorp, which are on-going for the 2016/2017 financial period during which the research study was conducted. A total of 136 responses were used to analyse the data. All project stakeholders, namely: project managers, contractors‟ site managers, and workers contributed to the study. The frequency of H&S actions varied with each stakeholder dependent on the stage in which they were involved. The study determined that extensive inadequacy of construction expertise in terms of H&S including H&S consultants and departmental H&S personnel, inadequate management and supervision on site, inadequate workers participation, inadequate H&S training, inadequate expertise in H&S management, inadequate designer report, inadequate H&S knowledge and awareness, negligence, unsafe acts, unskilled workers, unsafe conditions, non-compliance with H&S regulations, Safe v Operating Procedure (SOPs) and Safe Working Procedures (SWPs), inadequate commitment of various project stakeholders, ignorance, poor client H&S leadership throughout certain aspects of the ECDPW projects are the primary cause of fatalities and injuries, ill-health, design originated hazards, non-compliance and the reoccurrence of problems. Recommendations were for H&S to be integrated within the Departments internal project systems from project inception to project close out, and to enhance H&S knowledge and skills in order to mitigate the reoccurrences of problems on projects.
- Full Text:
- Date Issued: 2018
Construction company joint ventures in South Africa
- Authors: Sisilana, Owethu
- Date: 2018
- Subjects: Construction industry -- South Africa , Joint ventures Strategic alliances (Business) Project management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/35554 , vital:33756
- Description: In the construction industry, construction joint ventures (CJVs) have become one of the major organisational forms utilised in large-scale projects. However, because of the complexity of CJVs, the management of CJVs is much more difficult than that of usual projects undertaken by a single construction firm. In South Africa the existence of a clear and effective strategy for the successful transformation of organisational culture in a CJV is not clear. Similarly, poorly organised administrative structures in a CJV can also be a barrier to organisational performance. In South Africa there seems to be no evidence of a common understanding on the CJV formation process. According to CIDB (2004) there is no standard CJV agreement document. Therefore, a need arises to establish guidelines on the formation of a CJV agreement. Secondly, there is a need to establish strategies for the successful transformation of organisational culture in CJV. The research obtains an inside view with contractors who have participated in CJV’s, therefore, utilising the qualitative research method. The choice of data collection method was semi-structured one-on-one face to face interviews. In deriving the findings of the research, the ATLAS.ti software was used throughout the research process to manage both the secondary and primary data. The main factors which cause major problems in CJV's is the preliminary agreement, the partner selection and cultural differences. There is no evidence of a collective understanding among CJV partners regarding the successful formation processes of a CJV. The concept that the industry needs a standardised CJV agreement has been welcomed by the participants, the existence of a common CJV agreement would certainly resolve many problems in the way things are done currently including the implementation of joint venture projects. There is consensus between all participants that there is no standard CJV agreement in use in the South African construction industry and exploring a common approach is an idea that is viewed reasonable and to be one of the practical solutions to the problems in the industry. There are several limitations in this study. First, the sample included emerging and established contractors who are currently registered with the CIDB under Contractor Development Program only. While the sample size is relatively small, the researcher was cautious when interpreting the results. Secondly the targeted population for this research was selected using a sample of convenience method as opposed to a random sample, then the results of the study cannot be generally applied to a larger population. Thirdly, an obvious weakness of the research is the methodological difficulties related to qualitative research which relies on the inferences that are made by the researcher based on their own understanding of the data collected. It is therefore crucial that the data gathered is credible and that the findings represent the truth and actual sentiments as they appear from the data collection process. The research is of importance to managers and supervisors of construction companies of all sizes. The findings of this study will assist in ensuring that CJV are efficiently managed irrespective of the cultural differences.
- Full Text:
- Date Issued: 2018
- Authors: Sisilana, Owethu
- Date: 2018
- Subjects: Construction industry -- South Africa , Joint ventures Strategic alliances (Business) Project management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/35554 , vital:33756
- Description: In the construction industry, construction joint ventures (CJVs) have become one of the major organisational forms utilised in large-scale projects. However, because of the complexity of CJVs, the management of CJVs is much more difficult than that of usual projects undertaken by a single construction firm. In South Africa the existence of a clear and effective strategy for the successful transformation of organisational culture in a CJV is not clear. Similarly, poorly organised administrative structures in a CJV can also be a barrier to organisational performance. In South Africa there seems to be no evidence of a common understanding on the CJV formation process. According to CIDB (2004) there is no standard CJV agreement document. Therefore, a need arises to establish guidelines on the formation of a CJV agreement. Secondly, there is a need to establish strategies for the successful transformation of organisational culture in CJV. The research obtains an inside view with contractors who have participated in CJV’s, therefore, utilising the qualitative research method. The choice of data collection method was semi-structured one-on-one face to face interviews. In deriving the findings of the research, the ATLAS.ti software was used throughout the research process to manage both the secondary and primary data. The main factors which cause major problems in CJV's is the preliminary agreement, the partner selection and cultural differences. There is no evidence of a collective understanding among CJV partners regarding the successful formation processes of a CJV. The concept that the industry needs a standardised CJV agreement has been welcomed by the participants, the existence of a common CJV agreement would certainly resolve many problems in the way things are done currently including the implementation of joint venture projects. There is consensus between all participants that there is no standard CJV agreement in use in the South African construction industry and exploring a common approach is an idea that is viewed reasonable and to be one of the practical solutions to the problems in the industry. There are several limitations in this study. First, the sample included emerging and established contractors who are currently registered with the CIDB under Contractor Development Program only. While the sample size is relatively small, the researcher was cautious when interpreting the results. Secondly the targeted population for this research was selected using a sample of convenience method as opposed to a random sample, then the results of the study cannot be generally applied to a larger population. Thirdly, an obvious weakness of the research is the methodological difficulties related to qualitative research which relies on the inferences that are made by the researcher based on their own understanding of the data collected. It is therefore crucial that the data gathered is credible and that the findings represent the truth and actual sentiments as they appear from the data collection process. The research is of importance to managers and supervisors of construction companies of all sizes. The findings of this study will assist in ensuring that CJV are efficiently managed irrespective of the cultural differences.
- Full Text:
- Date Issued: 2018
Construction management’s perceptions of health and safety
- Authors: Sigama, Takalani
- Date: 2018
- Subjects: Construction industry -- Management , Building -- Safety measures Construction industry -- Health aspects Construction industry -- Safety regulations
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/35713 , vital:33784
- Description: Projects in the construction sector are reputed for poor health and safety (H&S) performance, compared to other industries. This can be attributed to, inter alia, a relatively uncontrolled working environment, inherent operational risks, workers' behaviour in relation to H&S commitment, cultural and religious beliefs, and uncertainties inherent in projects. Hazards and risk arising from poor H&S practices result in injuries, and in some cases, fatalities. The aim of this study is to explore the perceptions of construction management regarding H&S on construction sites. This study investigates the relationship between behaviours, attitudes, perceptions, and behaviours towards H&S, and compares cultural divergences among levels of construction personnel, namely construction management, construction supervision, construction H&S personnel, and H&S representatives. The construction industry has for many years developed and maintained a very bad reputation for coping with project cost, H&S, quality, and schedule. The industry often delivers projects late, and contributes to a disproportionate rate of work-related injuries, and fatalities. Project H&S management is acknowledged as one of the techniques that could be improved on construction projects to enhance performance of construction contractors in South Africa. To answer the research question: ‘Why construction management perceive H&S as a hindrance to production?” the mixed-method research approach was used. An indepth literature review with respect to project H&S was carried out, followed by qualitative and quantitative empirical research. The study established the need for H&S training and awareness of Construction Managers, Construction Supervisors, Construction Health and Safety Managers (CHSMs), Officers (CHSOs), and H&S Representatives. The study recommends that an H&S training needs analysis is critical for all employees, since it raises H&S awareness among all stakeholders in the construction industry, and enables the development of training plans, thereby supporting the reduction of accidents and related incident.
- Full Text:
- Date Issued: 2018
- Authors: Sigama, Takalani
- Date: 2018
- Subjects: Construction industry -- Management , Building -- Safety measures Construction industry -- Health aspects Construction industry -- Safety regulations
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/35713 , vital:33784
- Description: Projects in the construction sector are reputed for poor health and safety (H&S) performance, compared to other industries. This can be attributed to, inter alia, a relatively uncontrolled working environment, inherent operational risks, workers' behaviour in relation to H&S commitment, cultural and religious beliefs, and uncertainties inherent in projects. Hazards and risk arising from poor H&S practices result in injuries, and in some cases, fatalities. The aim of this study is to explore the perceptions of construction management regarding H&S on construction sites. This study investigates the relationship between behaviours, attitudes, perceptions, and behaviours towards H&S, and compares cultural divergences among levels of construction personnel, namely construction management, construction supervision, construction H&S personnel, and H&S representatives. The construction industry has for many years developed and maintained a very bad reputation for coping with project cost, H&S, quality, and schedule. The industry often delivers projects late, and contributes to a disproportionate rate of work-related injuries, and fatalities. Project H&S management is acknowledged as one of the techniques that could be improved on construction projects to enhance performance of construction contractors in South Africa. To answer the research question: ‘Why construction management perceive H&S as a hindrance to production?” the mixed-method research approach was used. An indepth literature review with respect to project H&S was carried out, followed by qualitative and quantitative empirical research. The study established the need for H&S training and awareness of Construction Managers, Construction Supervisors, Construction Health and Safety Managers (CHSMs), Officers (CHSOs), and H&S Representatives. The study recommends that an H&S training needs analysis is critical for all employees, since it raises H&S awareness among all stakeholders in the construction industry, and enables the development of training plans, thereby supporting the reduction of accidents and related incident.
- Full Text:
- Date Issued: 2018
Correlation of photovoltaics plant performance metrics
- Authors: Vumbugwa, Monphias
- Date: 2018
- Subjects: Photovoltaic cells , Perfomance -- Evaluation , Thin films
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/45657 , vital:38924
- Description: The generation of electrical energy using Photovoltaic (PV) technology has increased globally with the decrease in the cost of PV systems and the rise in electrical power demand. In South Africa, the support by the government in implementing the Renewable Energy Independent Power Producer Procurement Programme (REIPPPP) has seen a growth in PV system deployment and investment in roof and ground mounted, stand alone and grid connected PV plants. This rapid growth shows that the PV industry is becoming highly competitive as there is a shift to low carbon emissions and it is anticipated to be the most affordable source of electricity. Hence, there is need to develop maintenance and fault diagnosis expertise and capabilities in the PV industry, which can in turn improve the dependability, productiveness and lifespan of PV systems. Solar PV modules directly receive and convert solar irradiance into electricity and may not generate the expected optimum energy due to abnormalities which arise when they are exposed to harsh unfavorable environmental conditions in the field. Thermal Infrared (TIR) imaging is widely used as a fault diagnosis tool in operating PV modules and mostly in large PV power plants. Therefore, there is need to research the interpretation of the observed thermal signatures and the impact that the anomalies have on electrical output of the system so as to improve the PV maintenance systems. This research focuses on identifying performance limiting defects using an Infra-Red (I-R) camera, mounted on an Unmanned Aerial Vehicle (UAV), to understand the effect of thermal signatures on current-voltage (I-V) characteristics of PV module strings. Aerial TIR imaging using a UAV can rapidly identify abnormalities in operational PV modules strings as hotspots. Any deviation of the string I-V curve, from the expected, indicates a problem with one or more PV modules in the string. However, locating the faulty module involves measuring I-V parameters of the individual modules in a string, which is not feasible in large PV power plants. Therefore, there is a need to estimate the power loss associated with the thermal signatures in PV module strings. Visual inspection may help in identifying the exact cause of some hotspots, while other hotspots need special characterization techniques, such as Electroluminescence (EL) and UV Fluorescence (UV-F), which can indicate if a solar cell is cracked or has weak busbars or contact finger connections.
- Full Text:
- Date Issued: 2018
- Authors: Vumbugwa, Monphias
- Date: 2018
- Subjects: Photovoltaic cells , Perfomance -- Evaluation , Thin films
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/45657 , vital:38924
- Description: The generation of electrical energy using Photovoltaic (PV) technology has increased globally with the decrease in the cost of PV systems and the rise in electrical power demand. In South Africa, the support by the government in implementing the Renewable Energy Independent Power Producer Procurement Programme (REIPPPP) has seen a growth in PV system deployment and investment in roof and ground mounted, stand alone and grid connected PV plants. This rapid growth shows that the PV industry is becoming highly competitive as there is a shift to low carbon emissions and it is anticipated to be the most affordable source of electricity. Hence, there is need to develop maintenance and fault diagnosis expertise and capabilities in the PV industry, which can in turn improve the dependability, productiveness and lifespan of PV systems. Solar PV modules directly receive and convert solar irradiance into electricity and may not generate the expected optimum energy due to abnormalities which arise when they are exposed to harsh unfavorable environmental conditions in the field. Thermal Infrared (TIR) imaging is widely used as a fault diagnosis tool in operating PV modules and mostly in large PV power plants. Therefore, there is need to research the interpretation of the observed thermal signatures and the impact that the anomalies have on electrical output of the system so as to improve the PV maintenance systems. This research focuses on identifying performance limiting defects using an Infra-Red (I-R) camera, mounted on an Unmanned Aerial Vehicle (UAV), to understand the effect of thermal signatures on current-voltage (I-V) characteristics of PV module strings. Aerial TIR imaging using a UAV can rapidly identify abnormalities in operational PV modules strings as hotspots. Any deviation of the string I-V curve, from the expected, indicates a problem with one or more PV modules in the string. However, locating the faulty module involves measuring I-V parameters of the individual modules in a string, which is not feasible in large PV power plants. Therefore, there is a need to estimate the power loss associated with the thermal signatures in PV module strings. Visual inspection may help in identifying the exact cause of some hotspots, while other hotspots need special characterization techniques, such as Electroluminescence (EL) and UV Fluorescence (UV-F), which can indicate if a solar cell is cracked or has weak busbars or contact finger connections.
- Full Text:
- Date Issued: 2018
Corrosion resistance of nanocrystalline titanium zirconium nitride layers deposited on ZIRLO
- Nyembe, Hlanganani Siphelele
- Authors: Nyembe, Hlanganani Siphelele
- Date: 2018
- Subjects: Zirconium alloys , Titanium alloys Nanocrystals Nanotechnology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/34744 , vital:33435
- Description: Zirconium (Zr) alloys are used as nuclear fuel cladding in water-cooled nuclear reactors. Being in contact with steam, the Zr-alloy is oxidised and it absorbs hydrogen. The hydrogen pickup in Zr-alloys induces embrittlement of the tubes due to hydride formation. In this study, effectiveness of corrosion resistant nanocrystalline titanium zirconium nitride (nc-TiZrN) coatings on the surface of a Zr-alloy for the reduction of corrosion and hydrogen pickup is investigated. The nc-TiZrN layers were deposited onto the surface of ZIRLO® using the cathodic arc vapour deposition (CAVD) technique. The influence of nc-TiZrN coatings on the corrosion performance of ZIRLO® was investigated under the following conditions: (a) In an oxygen atmosphere at various temperatures from 400 to 900 ℃ for 30 minutes, (b) for various exposure times from 6 – 24 hours with the temperature kept constant at 500 ℃ in a tube furnace, and (c) in pure steam for 30 days at 360 ℃ and 18.7 MPa in an autoclave. The corrosion properties of the nc-TiZrN coated ZIRLO were compared to uncoated ZIRLO for all experiments. Following corrosion testing, the TiZrN coatings and oxide layers were investigated by scanning and transmission electron microscopy and energy dispersive X-ray spectroscopy. The TiZrN coating had a thickness of ~3.8 μm with a small number of Ti-rich and Nb-rich inclusions. The coating exhibited a single phase solid solution of Ti0.42Zr0.58N with a NaCl-type crystal structure and columnar nanocrystals. These columnar nanocrystals showed a strong {111} preferred orientation and the {111} planes of the TiZrN crystals are oriented parallel to the (001) planes of α-ZIRLO grains with <001> direction perpendicular to the coating/ZIRLO interface. The corrosion testing at various temperatures from 400 to 900 ℃ for 30 minutes showed that the TiZrN coating oxidises slowly and retained its microstructure, composition and crystallinity up to 600 ℃. At higher temperatures above 600 ℃, the TiZrN layer completely oxidised to a non-protective TiZr-oxide layer and resulted in rapid corrosion of the underlying ZIRLO substrate. The rapid corrosion was not observed in the uncoated ZIRLO sample for all temperatures. The results of samples subjected to annealing treatment at 500 ℃ in an oxygen atmosphere at various times up to 24 hours revealed that the TiZrN layer oxidises faster than ZIRLO. This was confirmed by sub-cubic and sub-parabolic oxide growth kinetics observed in the uncoated ZIRLO which are slower than the parabolic kinetics of TiZrN coated samples. In all coated samples, the spallation was observed near the edges of the samples. The spallation was caused by rapid corrosion of the underlying ZIRLO substrate which resulted from the penetration of oxygen ions between the TiZrN coating and ZIRLO substrate along the edges of the samples. In pure steam for 30 days at 360 ℃, a complete loss of the TiZrN layer occurred but the results show that the coating might have delayed the corrosion of ZIRLO. In summary, corrosion resistance of nc-TiZrN coated ZIRLO was lower than that of uncoated ZIRLO. The study shows that the failure of TiZrN coatings leads to rapid corrosion of the underlying ZIRLO substrate which was not observed on the uncoated ZIRLO. It is not yet understood why the presence TiZrN coatings reduced the oxidation resistance of ZIRLO.
- Full Text:
- Date Issued: 2018
- Authors: Nyembe, Hlanganani Siphelele
- Date: 2018
- Subjects: Zirconium alloys , Titanium alloys Nanocrystals Nanotechnology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/34744 , vital:33435
- Description: Zirconium (Zr) alloys are used as nuclear fuel cladding in water-cooled nuclear reactors. Being in contact with steam, the Zr-alloy is oxidised and it absorbs hydrogen. The hydrogen pickup in Zr-alloys induces embrittlement of the tubes due to hydride formation. In this study, effectiveness of corrosion resistant nanocrystalline titanium zirconium nitride (nc-TiZrN) coatings on the surface of a Zr-alloy for the reduction of corrosion and hydrogen pickup is investigated. The nc-TiZrN layers were deposited onto the surface of ZIRLO® using the cathodic arc vapour deposition (CAVD) technique. The influence of nc-TiZrN coatings on the corrosion performance of ZIRLO® was investigated under the following conditions: (a) In an oxygen atmosphere at various temperatures from 400 to 900 ℃ for 30 minutes, (b) for various exposure times from 6 – 24 hours with the temperature kept constant at 500 ℃ in a tube furnace, and (c) in pure steam for 30 days at 360 ℃ and 18.7 MPa in an autoclave. The corrosion properties of the nc-TiZrN coated ZIRLO were compared to uncoated ZIRLO for all experiments. Following corrosion testing, the TiZrN coatings and oxide layers were investigated by scanning and transmission electron microscopy and energy dispersive X-ray spectroscopy. The TiZrN coating had a thickness of ~3.8 μm with a small number of Ti-rich and Nb-rich inclusions. The coating exhibited a single phase solid solution of Ti0.42Zr0.58N with a NaCl-type crystal structure and columnar nanocrystals. These columnar nanocrystals showed a strong {111} preferred orientation and the {111} planes of the TiZrN crystals are oriented parallel to the (001) planes of α-ZIRLO grains with <001> direction perpendicular to the coating/ZIRLO interface. The corrosion testing at various temperatures from 400 to 900 ℃ for 30 minutes showed that the TiZrN coating oxidises slowly and retained its microstructure, composition and crystallinity up to 600 ℃. At higher temperatures above 600 ℃, the TiZrN layer completely oxidised to a non-protective TiZr-oxide layer and resulted in rapid corrosion of the underlying ZIRLO substrate. The rapid corrosion was not observed in the uncoated ZIRLO sample for all temperatures. The results of samples subjected to annealing treatment at 500 ℃ in an oxygen atmosphere at various times up to 24 hours revealed that the TiZrN layer oxidises faster than ZIRLO. This was confirmed by sub-cubic and sub-parabolic oxide growth kinetics observed in the uncoated ZIRLO which are slower than the parabolic kinetics of TiZrN coated samples. In all coated samples, the spallation was observed near the edges of the samples. The spallation was caused by rapid corrosion of the underlying ZIRLO substrate which resulted from the penetration of oxygen ions between the TiZrN coating and ZIRLO substrate along the edges of the samples. In pure steam for 30 days at 360 ℃, a complete loss of the TiZrN layer occurred but the results show that the coating might have delayed the corrosion of ZIRLO. In summary, corrosion resistance of nc-TiZrN coated ZIRLO was lower than that of uncoated ZIRLO. The study shows that the failure of TiZrN coatings leads to rapid corrosion of the underlying ZIRLO substrate which was not observed on the uncoated ZIRLO. It is not yet understood why the presence TiZrN coatings reduced the oxidation resistance of ZIRLO.
- Full Text:
- Date Issued: 2018
Cost and time overruns on Mpumalanga Province infrastructure projects
- Authors: Phalanndwa, Shonisani Aaron
- Date: 2018
- Subjects: Project management -- South Africa -- Mpumalanga , Infrastructure (Economics) industrial management -- South Africa -- Mpumalanga Business enterprises -- South Africa -- Mpumalanga -- Finance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/34169 , vital:33248
- Description: Cost and time overruns in construction projects are a common issue affecting project performance, and Mpumalanga is no exception. Completion of any project within the estimated cost of a project is a basic criterion for success of any project. The success of any project highly depends on adequate availability and efficient management of various resources. Construction projects often face a lot of uncertainties, which places building construction projects at the risk of cost, time overruns as well as poor quality delivery. This study assesses the causes, effects and measures of minimising construction project cost and time overrun in the Mpumalanga Province. The data used in this study were derived from both primary and secondary sources. The primary data was collected through case study interviews with construction professionals, project owners, contractors and consultants involved in Mpumalanga construction projects. Findings from the case study revealed that clients inability to meet payment obligations on time, additional work requested by the client, proper feasibility study not done, ensuring transparency in awarding of contracts, contractors financial difficulties, late delivery of materials, contractors lack of experience, bribery and corruption involving the contractor or contractor’s team, and poor site management and consultants insufficient geotechnical investigations, insufficient/unknown information regarding site conditions during design phase, mistakes and discrepancies in design documents are the major causes of cost and time overruns that are incidental to project implementation in Mpumalanga. Furthermore the study also reveals that the major effect of cost and time overrun are: poor quality workmanship, total abandonment, and disputes, discouragement of investors, community unrest and service delivery is negatively affected. It was revealed that all stakeholders of construction parties are deeply involved in contributing to the causes of the problems, clients should bear the greatest responsibility and play the most important role in lessening the impact of cost and time overrun. Thus, interventions that could be adopted by the Mpumalanga province to achieve project delivery that is within estimated cost and time are: Government must adopt ‘financial assignment’ to deal with suppliers in order to supply materials to the contractor and have available funds for projects on time, soil investigation and testing should be conducted by clients prior to the commencement of a project; encourage whistleblowing and punish fraudsters more severely. Contractors must have enough cash before commencing of projects, v monitor financial spending of the projects and payments; consultants must review and approve design documents, shop drawings, and payments of contractor. It is recommended that training courses, seminars and workshops on project management should be made available to help improve the abilities of construction teams responsible for management and supervision of sites and client organisations should encourage whistleblowing, punish fraudsters more efficiently and pay commensurate reward to whistle-blowers in order to minimise cost and time overruns.
- Full Text:
- Date Issued: 2018
- Authors: Phalanndwa, Shonisani Aaron
- Date: 2018
- Subjects: Project management -- South Africa -- Mpumalanga , Infrastructure (Economics) industrial management -- South Africa -- Mpumalanga Business enterprises -- South Africa -- Mpumalanga -- Finance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/34169 , vital:33248
- Description: Cost and time overruns in construction projects are a common issue affecting project performance, and Mpumalanga is no exception. Completion of any project within the estimated cost of a project is a basic criterion for success of any project. The success of any project highly depends on adequate availability and efficient management of various resources. Construction projects often face a lot of uncertainties, which places building construction projects at the risk of cost, time overruns as well as poor quality delivery. This study assesses the causes, effects and measures of minimising construction project cost and time overrun in the Mpumalanga Province. The data used in this study were derived from both primary and secondary sources. The primary data was collected through case study interviews with construction professionals, project owners, contractors and consultants involved in Mpumalanga construction projects. Findings from the case study revealed that clients inability to meet payment obligations on time, additional work requested by the client, proper feasibility study not done, ensuring transparency in awarding of contracts, contractors financial difficulties, late delivery of materials, contractors lack of experience, bribery and corruption involving the contractor or contractor’s team, and poor site management and consultants insufficient geotechnical investigations, insufficient/unknown information regarding site conditions during design phase, mistakes and discrepancies in design documents are the major causes of cost and time overruns that are incidental to project implementation in Mpumalanga. Furthermore the study also reveals that the major effect of cost and time overrun are: poor quality workmanship, total abandonment, and disputes, discouragement of investors, community unrest and service delivery is negatively affected. It was revealed that all stakeholders of construction parties are deeply involved in contributing to the causes of the problems, clients should bear the greatest responsibility and play the most important role in lessening the impact of cost and time overrun. Thus, interventions that could be adopted by the Mpumalanga province to achieve project delivery that is within estimated cost and time are: Government must adopt ‘financial assignment’ to deal with suppliers in order to supply materials to the contractor and have available funds for projects on time, soil investigation and testing should be conducted by clients prior to the commencement of a project; encourage whistleblowing and punish fraudsters more severely. Contractors must have enough cash before commencing of projects, v monitor financial spending of the projects and payments; consultants must review and approve design documents, shop drawings, and payments of contractor. It is recommended that training courses, seminars and workshops on project management should be made available to help improve the abilities of construction teams responsible for management and supervision of sites and client organisations should encourage whistleblowing, punish fraudsters more efficiently and pay commensurate reward to whistle-blowers in order to minimise cost and time overruns.
- Full Text:
- Date Issued: 2018
Deep learning applied to the semantic segmentation of tyre stockpiles
- Barfknecht, Nicholas Christopher
- Authors: Barfknecht, Nicholas Christopher
- Date: 2018
- Subjects: Neural networks (Computer science)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23947 , vital:30647
- Description: The global push for manufacturing which is environmentally sustainable has disrupted standard methods of waste tyre disposal. This push is further intensified by the health and safety risks discarded tyres pose to the surrounding population. Waste tyre recycling initiatives in South Africa are on the increase; however, there is still a growing number of undocumented tyre stockpiles developing throughout the country. The plans put in place to eradicate these tyre stockpiles have been met with collection, transport and storage logistical issues caused by the remoteness and distant locales. Eastwood (2016) aimed at optimising the logistics associated with collection, by estimating the number of visible tyres from images of tyre stockpiles. This research was limited by the need for manual segmentation of each tyre stockpile located within each image. This research proposes the use of semantic segmentation to automatically segment images of tyre stockpiles. An initial review of neural network, convolutional network and semantic segmentation literature resulted in the selection of Dilated Net as the semantic segmentation architecture for this research. Dilated Net builds upon the VGG-16 classification architecture to perform semantic segmentation. This resulted in classification experiments which were evaluated using precision, recall and f1-score. The results indicated that regardless of tyre stockpile image dimension, fairly accurate levels of classification accuracy can be attained. This was followed by semantic segmentation experiments which made use of intersection over union (IoU) and pixel accuracy to evaluate the effectiveness of Dilated Net on images of tyre stockpiles. The results indicated that accurate tyre stockpile segmentation regions can be obtained and that the trained model generalises well to unseen images.
- Full Text:
- Date Issued: 2018
- Authors: Barfknecht, Nicholas Christopher
- Date: 2018
- Subjects: Neural networks (Computer science)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23947 , vital:30647
- Description: The global push for manufacturing which is environmentally sustainable has disrupted standard methods of waste tyre disposal. This push is further intensified by the health and safety risks discarded tyres pose to the surrounding population. Waste tyre recycling initiatives in South Africa are on the increase; however, there is still a growing number of undocumented tyre stockpiles developing throughout the country. The plans put in place to eradicate these tyre stockpiles have been met with collection, transport and storage logistical issues caused by the remoteness and distant locales. Eastwood (2016) aimed at optimising the logistics associated with collection, by estimating the number of visible tyres from images of tyre stockpiles. This research was limited by the need for manual segmentation of each tyre stockpile located within each image. This research proposes the use of semantic segmentation to automatically segment images of tyre stockpiles. An initial review of neural network, convolutional network and semantic segmentation literature resulted in the selection of Dilated Net as the semantic segmentation architecture for this research. Dilated Net builds upon the VGG-16 classification architecture to perform semantic segmentation. This resulted in classification experiments which were evaluated using precision, recall and f1-score. The results indicated that regardless of tyre stockpile image dimension, fairly accurate levels of classification accuracy can be attained. This was followed by semantic segmentation experiments which made use of intersection over union (IoU) and pixel accuracy to evaluate the effectiveness of Dilated Net on images of tyre stockpiles. The results indicated that accurate tyre stockpile segmentation regions can be obtained and that the trained model generalises well to unseen images.
- Full Text:
- Date Issued: 2018
Determining productivity, residual damage and cost of two alternative harvesting systems in pinus elliottii thinning
- Dembure, Tigere Pasca, Spinelli, Raffaele, Ramantswana, Muedanyi
- Authors: Dembure, Tigere Pasca , Spinelli, Raffaele , Ramantswana, Muedanyi
- Date: 2018
- Subjects: Pinus caribaea , Forests and forestry Logging Harvesting -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/22016 , vital:29813
- Description: Pinus elliottii is the second most dominant softwood grown in the South African plantation forestry industry. It possesses desirable timber characteristics and is useful for production of solid wood products. In the silviculture of softwoods (grown for solid wood products), thinning is an important tending operation. It is necessary for stand hygiene and volume increment of residual trees through the creation of growing space. The selection of a suitable harvesting system for thinning is vital. The system of choice has to attain higher productivity, cause the least damage to residual trees and must be cost effective. From as early as 2000 the South African forestry industry witnessed a general shift towards the use of fully mechanised cut-to-length harvesting systems. This has been a result of high labour turnover, increased labour costs, increased timber demand and the effects of HIV and AIDS on forestry workers. With this recent introduction of mechanised systems, they have not been benchmarked against conventional harvesting systems. In this regard, two harvesting systems were studied side-by-side for productivity, residual damage and cost in a seventh row second thinning operation in P. elliottii stands. First thinnings generate poor financial returns since small trees are harvested and they have a relatively low financial value but have a relatively high operational cost per unit harvested. The second thinning operation is usually the thinning operation that is most likely to result in an intermediate financial return for the organisation, hence the need to benchmark these harvesting systems during the second thinning. These systems were a fully mechanised cut-to-length (CTL) and a semi-mechanised tree length (TL) system. The fully mechanised system comprised of a harvester (felling) and a forwarder (extracting) and the semi-system consisted of felling by chainsaw, tractor extraction, roadside processing by chainsaw and stacking by three-wheeled logger. Two uniform compartments planted with P. elliottii were selected for the study. A total number of 32 plots (16 plots per compartment) were marked and randomly assigned between the two treatments, each plot comprised of seven rows, with the middle row clear-cut and three rows on either side, where marked trees were selectively removed. Within each plot, the number of removal trees ranged from 80 to 105. The diameter, height and form of each removal tree were measured to determine tree volume and ultimately determine productivity. Before analysis, plot characteristics were compared to determine if conditions were equal for both treatments using the Mann-Whitney test at alpha level ˂ 0.05. There was a statistically significant difference in total operator efficiency between the two systems (p ˂ 0.0001). The fully mechanised system attained higher levels of productivity than the semi-mechanised system (15.58 m3/SMH versus 5.26 m3/SMH, for felling and 15.56 m3/SMH versus 5.29 m3/SMH, for the extraction operation). Operator productivity comparisons were restricted to the two harvester operators, and one operator achieved 16.9 m3/SMH while the other operator achieved 14.3 m3/SMH. Different operator working technique contributed to the productivity differences with one operator spending (on average) four seconds less per tree on the fell-process work element. Residual tree damage was assessed immediately after all felling and extraction had taken place. Damage size was measured as ellipse surface area. For each record of residual damage, the damage type was noted, damage position along the stem, and tree position from extraction trail. The most predominant damage type was bark peel. The motor-manual system caused five per cent damage and the fully mechanised system inflicted only three per cent damage to the residual trees. Residual tree damage from the semi-mechanised system mainly occurred at the root zone, and occurred more frequently on edge trees. The mechanised CTL system was characterised by high investment and operational costs. The mechanised system incurred 3037.75 R/SMH while the semi-mechanised system incurred 1667.10 R/SMH. The difference in total costs per year between both systems was 56.29 per cent, with the fully mechanised system being more expensive. The high capacity and the superior technology of mechanised harvesting systems may not be fully exploited in thinnings, therefore harvesting systems with lower capital costs and reasonable productivity can be competitive.
- Full Text:
- Date Issued: 2018
- Authors: Dembure, Tigere Pasca , Spinelli, Raffaele , Ramantswana, Muedanyi
- Date: 2018
- Subjects: Pinus caribaea , Forests and forestry Logging Harvesting -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/22016 , vital:29813
- Description: Pinus elliottii is the second most dominant softwood grown in the South African plantation forestry industry. It possesses desirable timber characteristics and is useful for production of solid wood products. In the silviculture of softwoods (grown for solid wood products), thinning is an important tending operation. It is necessary for stand hygiene and volume increment of residual trees through the creation of growing space. The selection of a suitable harvesting system for thinning is vital. The system of choice has to attain higher productivity, cause the least damage to residual trees and must be cost effective. From as early as 2000 the South African forestry industry witnessed a general shift towards the use of fully mechanised cut-to-length harvesting systems. This has been a result of high labour turnover, increased labour costs, increased timber demand and the effects of HIV and AIDS on forestry workers. With this recent introduction of mechanised systems, they have not been benchmarked against conventional harvesting systems. In this regard, two harvesting systems were studied side-by-side for productivity, residual damage and cost in a seventh row second thinning operation in P. elliottii stands. First thinnings generate poor financial returns since small trees are harvested and they have a relatively low financial value but have a relatively high operational cost per unit harvested. The second thinning operation is usually the thinning operation that is most likely to result in an intermediate financial return for the organisation, hence the need to benchmark these harvesting systems during the second thinning. These systems were a fully mechanised cut-to-length (CTL) and a semi-mechanised tree length (TL) system. The fully mechanised system comprised of a harvester (felling) and a forwarder (extracting) and the semi-system consisted of felling by chainsaw, tractor extraction, roadside processing by chainsaw and stacking by three-wheeled logger. Two uniform compartments planted with P. elliottii were selected for the study. A total number of 32 plots (16 plots per compartment) were marked and randomly assigned between the two treatments, each plot comprised of seven rows, with the middle row clear-cut and three rows on either side, where marked trees were selectively removed. Within each plot, the number of removal trees ranged from 80 to 105. The diameter, height and form of each removal tree were measured to determine tree volume and ultimately determine productivity. Before analysis, plot characteristics were compared to determine if conditions were equal for both treatments using the Mann-Whitney test at alpha level ˂ 0.05. There was a statistically significant difference in total operator efficiency between the two systems (p ˂ 0.0001). The fully mechanised system attained higher levels of productivity than the semi-mechanised system (15.58 m3/SMH versus 5.26 m3/SMH, for felling and 15.56 m3/SMH versus 5.29 m3/SMH, for the extraction operation). Operator productivity comparisons were restricted to the two harvester operators, and one operator achieved 16.9 m3/SMH while the other operator achieved 14.3 m3/SMH. Different operator working technique contributed to the productivity differences with one operator spending (on average) four seconds less per tree on the fell-process work element. Residual tree damage was assessed immediately after all felling and extraction had taken place. Damage size was measured as ellipse surface area. For each record of residual damage, the damage type was noted, damage position along the stem, and tree position from extraction trail. The most predominant damage type was bark peel. The motor-manual system caused five per cent damage and the fully mechanised system inflicted only three per cent damage to the residual trees. Residual tree damage from the semi-mechanised system mainly occurred at the root zone, and occurred more frequently on edge trees. The mechanised CTL system was characterised by high investment and operational costs. The mechanised system incurred 3037.75 R/SMH while the semi-mechanised system incurred 1667.10 R/SMH. The difference in total costs per year between both systems was 56.29 per cent, with the fully mechanised system being more expensive. The high capacity and the superior technology of mechanised harvesting systems may not be fully exploited in thinnings, therefore harvesting systems with lower capital costs and reasonable productivity can be competitive.
- Full Text:
- Date Issued: 2018