Master of Science / Division of Biology / John M. Blair / Temperate grasslands are among the most threatened biomes in the world, with the largest historical losses due to conversion to agricultural land. While much of this biome has already been converted, there is concern the last remaining remnants in North America will be converted in response to increasing demand for crops used for ethanol production. Thus, restoring grasslands post-anthropogenic disturbance is increasingly important for conserving grassland biodiversity. Two major challenges for prairie restorations are establishing the many subdominant and rarer species found in native prairie, and offsetting the typical decline in richness and diversity over time as restorations age. Repeated seed addition of targeted species is commonly used to override low and declining plant richness and diversity. While this is generally effective early in restoration (i.e., as communities are establishing), its effectiveness in later stages (i.e., when established communities are often losing diversity) remains unknown. I investigated plant community responses to combinations of resource manipulations and disturbances coupled with a seed addition in a 15-yr old restored grassland to test the hypothesis that spatial resource heterogeneity increases the rate of colonization into established prairie restoration communities. Seeds were added to a long-term restoration experiment involving soil depth manipulations (deep, shallow) crossed with nutrient manipulations (reduced N, ambient N, enriched N). Seedling emergence was generally low and only 8 of the 14 forb species added were detected in the first growing season. I found no effect of increased resource heterogeneity on the abundance or richness of seedlings. There was a significant nutrient effect (p<0.1, α=0.1) on seedling abundance, with higher emergence in the enriched N than the ambient N treatment. I also found unexpected nutrient effects on richness, diversity and Mean C (Mean C = Σ CoCi*Ai, where CoC=Coefficient of Conservatism and A=relative abundance of the ith species). All values, except Mean C, were higher in the enriched N treatment than in either the reduced or ambient N treatments. Mean C was lowest in the enriched N treatment, and highest in the whole-plot control, suggesting that the majority of species contributing to higher richness and diversity in the enriched N treatment were “weedier” species. In a separate experiment, I found no effect of small-scale disturbances (aboveground biomass removal or soil disturbance) on seedling abundance or seedling richness. I did find a marginal effect of disturbance type on seedling richness (p=0.11, α=0.1), with higher seedling richness in the soil disturbance than the aboveground biomass removal treatment. I did not find any disturbance effects on community response variables. These results indicate that recruitment from seed additions into well-established restored communities is relatively low in the first year following a seed addition, regardless of resource availability and heterogeneity. Follow-up studies to determine recruitment rates in subsequent years are needed to elucidate whether recruitment responses are driven more by individual species differences or by environmental mechanisms.

Sasol Infragas uses various maintenance information systems that support operational and maintenance personnel in their everyday environment. These systems have been in operation for more than two years. Currently, there are four maintenance information systems in use at Infragas, these are; alarm management, deviation management, overall efficiency management, and rotating equipment management. The information from these systems is stored on intranet portals which are accessible to all Infragas employees. This paper aimed to analyse the extent to which these portals are being utilised by Infragas employees, if at all. This paper also investigated the employees’ mind-set towards the maintenance information systems. This will assist in understanding which systems enhancements can be made to further improve employee engagement. These objectives were achieved by means of two methods. The first method was an actual usage measurement. This identified which employees were using the portals, as well as the usage frequency. This investigation method gave a real indication of the system usage and highlighted any shortfalls in employees’ interaction with the portals. The second method was a questionnaire, given to Infragas employees. The first section analysed whether the Infragas maintenance information systems are an accepted technology by investigating whether systems are being used by portal users. This was done by means of a technology acceptance model. The questionnaire also aimed to gather information on portal quality characteristics. This would indicate which quality characteristics are important to Infragas employees. Maintenance information system quality needs will differ from employee to employee. This information could improve the quality of interaction between the employees and the portals. The questionnaire also aimed to examine employees’ attitudes towards maintenance information systems. This section investigated whether employees felt that maintenance information systems improved plant performance and were beneficial to the Infragas environment. These investigations revealed valuable information for the improvement of these systems. The connection between the results of the two methods also indicated if both methods were valid. The information gathered from this study was communicated back to the Sasol Infragas management team. Recommendations for possible system improvements, which would increase employee system interaction, were also made. / MIng (Development and Management Engineering), North-West University, Potchefstroom Campus, 2014

Network failures can originate from or be located in any one of several network layers as described by the OSI model. This investigation focuses on the role of physical topological design parameters in determining network reliability and performance as can be expected from the point of view of a typical client-server based connection in an Ethernet local area network. This type of host-to-host IP connection is found in many commercial, military and industrial network based systems. Using Markov modelling techniques reliability and performability models are developed for common network topologies based on the redundancy mechanism provided by IEEE spanning tree protocols. The models are tested and validated using the OPNET network simulation environment. The reliability and performability metrics calculated from the derived models for different topologies are compared leading to the following conclusions. The reliability of the entry-nodes into a redundant network is a determining factor in connection availability. Redundancy mechanisms must be extended from the entry-node to the connecting hosts to gain a significant benefit from redundant network topologies as network availability remains limited to three-nines. The hierarchical mesh network offers the highest availability (sevennines) and performability. Both these metrics can be accurately predicted irrespective of the position of the entry-node in the mesh. Ring networks offer high availability (five to sevennines) and performability if the ring remains small to medium sized, however for larger rings (N≥32) the availability is highly dependant on the relative position of the entry-node in the ring. Performability also degrades significantly as the ring size increases. Although star networks offer predictable and high performability the availability is low (four-nines) because of the lack of redundancy. The star should therefore not be used in IP networked systems requiring more than four-nines availability. In all the topologies investigated the reliability and performability can be increased significantly by introducing redundant links instead of single links interconnecting the various nodes, with the star topology availability increasing from four-nines to seven-nines and performance doubling. / MIng (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2014

Reliability-Cenetred Maintenance (RCM) is a well-known maintenance process developed in the aviation industry. It has yielded great success and hence was the process adapted to be used in the more industrial environments, such as the process developed by Moubray (1997) called RCM2. The RCM process is considered by many to be a very effective and comprehensive maintenance process that can, if implemented correctly, improve reliability and plant availability substantially. However, many maintenance practitioners and maintenance experts who have used RCM will tell you that it is an overcomplicated process and that it is difficult to implement. In many cases the process is abandoned and left incomplete due to the amount of resources required and the slow initial results delivered by the process. This dissertation investigates the reason for this and considers the viability of implementing the RCM process on an industrial level. The Hot Strip Mill (HSM) at the ArcelorMittal Vanderbijlpark plant was used as a case study. The viability of using RCM to improve the HSM maintenance practices was investigated. A suggested maintenance improvement plan was developed that is more suitable for the HSM maintenance environment and culture. / MSc (Development and Management Engineering), North-West University, Potchefstroom Campus, 2015

Sasol Infragas uses various maintenance information systems that support operational and maintenance personnel in their everyday environment. These systems have been in operation for more than two years. Currently, there are four maintenance information systems in use at Infragas, these are; alarm management, deviation management, overall efficiency management, and rotating equipment management. The information from these systems is stored on intranet portals which are accessible to all Infragas employees. This paper aimed to analyse the extent to which these portals are being utilised by Infragas employees, if at all. This paper also investigated the employees’ mind-set towards the maintenance information systems. This will assist in understanding which systems enhancements can be made to further improve employee engagement. These objectives were achieved by means of two methods. The first method was an actual usage measurement. This identified which employees were using the portals, as well as the usage frequency. This investigation method gave a real indication of the system usage and highlighted any shortfalls in employees’ interaction with the portals. The second method was a questionnaire, given to Infragas employees. The first section analysed whether the Infragas maintenance information systems are an accepted technology by investigating whether systems are being used by portal users. This was done by means of a technology acceptance model. The questionnaire also aimed to gather information on portal quality characteristics. This would indicate which quality characteristics are important to Infragas employees. Maintenance information system quality needs will differ from employee to employee. This information could improve the quality of interaction between the employees and the portals. The questionnaire also aimed to examine employees’ attitudes towards maintenance information systems. This section investigated whether employees felt that maintenance information systems improved plant performance and were beneficial to the Infragas environment. These investigations revealed valuable information for the improvement of these systems. The connection between the results of the two methods also indicated if both methods were valid. The information gathered from this study was communicated back to the Sasol Infragas management team. Recommendations for possible system improvements, which would increase employee system interaction, were also made. / MIng (Development and Management Engineering), North-West University, Potchefstroom Campus, 2014

Network failures can originate from or be located in any one of several network layers as described by the OSI model. This investigation focuses on the role of physical topological design parameters in determining network reliability and performance as can be expected from the point of view of a typical client-server based connection in an Ethernet local area network. This type of host-to-host IP connection is found in many commercial, military and industrial network based systems. Using Markov modelling techniques reliability and performability models are developed for common network topologies based on the redundancy mechanism provided by IEEE spanning tree protocols. The models are tested and validated using the OPNET network simulation environment. The reliability and performability metrics calculated from the derived models for different topologies are compared leading to the following conclusions. The reliability of the entry-nodes into a redundant network is a determining factor in connection availability. Redundancy mechanisms must be extended from the entry-node to the connecting hosts to gain a significant benefit from redundant network topologies as network availability remains limited to three-nines. The hierarchical mesh network offers the highest availability (sevennines) and performability. Both these metrics can be accurately predicted irrespective of the position of the entry-node in the mesh. Ring networks offer high availability (five to sevennines) and performability if the ring remains small to medium sized, however for larger rings (N≥32) the availability is highly dependant on the relative position of the entry-node in the ring. Performability also degrades significantly as the ring size increases. Although star networks offer predictable and high performability the availability is low (four-nines) because of the lack of redundancy. The star should therefore not be used in IP networked systems requiring more than four-nines availability. In all the topologies investigated the reliability and performability can be increased significantly by introducing redundant links instead of single links interconnecting the various nodes, with the star topology availability increasing from four-nines to seven-nines and performance doubling. / MIng (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2014

Reliability-Cenetred Maintenance (RCM) is a well-known maintenance process developed in the aviation industry. It has yielded great success and hence was the process adapted to be used in the more industrial environments, such as the process developed by Moubray (1997) called RCM2. The RCM process is considered by many to be a very effective and comprehensive maintenance process that can, if implemented correctly, improve reliability and plant availability substantially. However, many maintenance practitioners and maintenance experts who have used RCM will tell you that it is an overcomplicated process and that it is difficult to implement. In many cases the process is abandoned and left incomplete due to the amount of resources required and the slow initial results delivered by the process. This dissertation investigates the reason for this and considers the viability of implementing the RCM process on an industrial level. The Hot Strip Mill (HSM) at the ArcelorMittal Vanderbijlpark plant was used as a case study. The viability of using RCM to improve the HSM maintenance practices was investigated. A suggested maintenance improvement plan was developed that is more suitable for the HSM maintenance environment and culture. / MSc (Development and Management Engineering), North-West University, Potchefstroom Campus, 2015

ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California / This paper compares telemetry link performance of the PCM/FM waveform when simultaneously transmitting in two different frequency bands, S-Band and C-Band. A description of the aircraft and ground station is presented followed by flight test results. These results are presented in the form of received signal strength and accumulated bit errors, versus time and link availability, over the flight paths. Conclusions are drawn based upon the presented flight test results.

Home availability of both healthful and unhealthful foods may influence consumption among rural adolescent populations. In conjunction, the availability of food in an individual’s local food environment has the potential to significantly impact what is procured for the home and eaten away from the home. The purpose of this study was to determine how in-store food availability and parental purchases influences home availability and, ultimately, dietary intake among adolescents. This study measured perceived home availability, using the University of Minnesota Project EAT Survey, and dietary intake, using the NHANES Dietary Screener Questionnaire, of (n=28) adolescent participants in two Kentucky counties during 2013. Availability of food in local stores was measured using the Nutrition Environment Measures Survey in Stores (NEM-S). The results of multiple linear regression analysis suggest that overall store availability does not significantly impact parental purchases. However, in-store availability of specific unhealthy food categories, such as snacks, junk food, candy, and pop, was associated with increased parental purchases of similar unwholesome items and a greater predicted intake of sugar. Therefore, it may be beneficial to develop interventions aimed at decreasing the availability of unhealthy food items in stores in order to improve diet quality among rural adolescents.

The size and trend of a population is fundamental to the assessment of its conservation status, yet cetacean abundance data are often biased and lack statistical power to detect trends. As a result, the conservation status of many species is unknown and the population-level effects of conservation pressures such as anthropogenic sound cannot be quantified. Failing to account for cetaceans that are unavailable for detection at the surface during abundance surveys will negatively bias estimates of abundance. Analysis of time-depth data revealed that pilot whale dive and surface interval durations, and availability for detection, varied with time of day, but this bias was accurately estimated using the mean dive and surface interval durations. A global analysis of cetacean density estimates compiled from multiple line-transect surveys incorporated covariates describing availability bias, and other sources of variability, to facilitate the detection of underlying temporal trends. Decadal global trends in cetacean density were detected for four species, while significant yearly ocean-scale trends were detected for six families. Exploratory analysis of data compiled from line-transect surveys found some evidence that trends in the density of minke whales and sperm whales in the northeast Atlantic varied between areas with and without seismic survey effort. However, there were insufficient data to clearly identify chronic exposure to anthropogenic sound from seismic surveys as a driver of population change. Analysis of strandings data from the UK and Ireland identified some evidence that harbour porpoise and sperm whale stranding rates were related to seismic survey effort and wind farm construction, but the results were not conclusive. Large-scale cetacean surveys provide valuable information on the density and spatial and temporal distribution of cetaceans that is vital for monitoring populations, but these surveys cannot replace dedicated studies of the population-level effects of sound on cetaceans.