Contrary to common intuition, free jets of fluid can ``bounce'' off each other on collision in mid-air, through the effect of a lubricating air film that separates the jets. While there has been much work on coalescing jets of fluid and non-coalescence in other systems like drop-drop, drop on a bath, jet on a bath, non-coalescence of fluid jets has been little studied. A simple experimental setup was developed to stably demonstrate and study the non-coalescence of jets upon collision. This thesis presents the results of an experimental investigation of oblique collision between two fluid jets. The transition from bouncing to coalescence of jets is examined for various jet sizes and angles. Results indicate that the transition from bouncing to coalescence can be rationalized in terms of critical value of the dimensionless parameter Normal Weber Number, which represents the ratio between inertial and surface tension forces. A parametric study of the characteristic of bouncing jets, conducted by varying the nozzle diameter, jet velocity, angle of inclination and fluid viscosity reveals the scaling laws for the quantities involved such as contact time. These scaling laws help us in elucidating the role of various physical forces at play such as viscous stresses, capillary force and inertia / Master of Science

Problem: Running is one of the most widespread physical activities. Incorrect running technique, training quantity but also the runner's equipment can strongly affect health condition of the individual, both positively and negatively. For that reason various trends emerge in the area of running footwear. They include classical sports shoes with different types of impact attenuation as well as the minimalist footwear made to imitate barefoot running, which should be much more natural for humans, as insisted by B. Nigg in his book "Born to Run" - where he says that man was born to walk and run barefooted. Inappropriate shoes can cause various health complications, not only in the foot area. Objective: To find out how foot strike changes in the area of the foot-shoe interaction in running on flat ground when an amateur runner uses minimalist and sports footwear and to draw conclusions for training practice on the basis of the results. Methods: The thesis deals with amateur endurance running in different shoe types (minimalist and sports shoes). The study specimen consisted of 14 female runners (mean body weight 63,31 ± 4,89 kg, height 169,69 ± 4,71 cm, age 31,92 ± 5,34 years, speed in minimalist shoes (MO) 3,34 ± 0,06 m.s- 1 , speed in sports shoes (SO) 3,29 ± 0,06 m.s-1 , weekly mileage 37,54 ± 9,43...

The purpose of this study was to compare ground contact time between an optical measurement system and a force platform. Participants in this study included six collegiate level athletes who performed drop jumps and sprint strike steps for a total of 15 repetitions each. Ground contact data was simultaneously collected from an optical measurement system and a force platform, at a sampling frequency of 1000 Hz. Data was then analyzed with Pearson’s correlation and paired sample t-tests. The measures from the optical measurement system were found to be significantly higher (p < 0.001) than measures from the force platform in both conditions. Although significantly different, the extremely large relationships (0.979, 0.993) found between the two devices suggest the optical sensor is able to detect similar changes in performance to that of a force platform. Practitioners may continue to utilize optical sensors to monitor performance as it may provide a superior user-friendly alternative to more traditional based monitoring procedures, but must comprehend the inherent limitations due to the design of the optical sensors.

Self-cleaning, anti-corrosion, anti-icing, dropwise-condensation, and drag-reduction are some applications in which superhydrophobic surfaces are implemented. To date, all the studies associated with superhydrophobic surfaces have been dedicated to understanding the liquid interaction with surfaces that are macroscopically smooth. The current study investigates the solid-liquid interaction of such surfaces which are fully decorated with macroscopic ridges (ribbed surfaces). In particular, the drop motion and impact on our newly designed non-wettable ribbed surface have been investigated in this work. Our experimental investigations have shown that liquid drops move faster on the ribbed surfaces due to lower friction induced by such a surface pattern. Moreover, an impacting droplet shows shorter contact time on ribbed surfaces. This concludes that ribbed surface pattern can be an efficient alternative design for the related applications. Besides the experimental studies, the theoretical analyses done in this work have led to, firstly a scaling model to predict descent velocity of a rolling viscous drops on an inclined non-wettable surface more accurately. Secondly, for curved superhydrophobic surfaces a scaling model which correlates the contact time of the impacting drop to its impact velocity has been developed. At the end, the knowledge obtained from this work has led to a special surface design which exhibits a contact time shorter than the inertial-capillary time scale, an unprecedented phenomenon.

<p><font size="3"> <p>The aim of this research was to investigate the use of social media (SM) in improving the quantity and quality of passes in computer programming in South Africa&rsquo / s Further Education and Training (FET) colleges. The study addresses the high learner failure rates in computer programming at National Certificate (Vocational) (NCV) level 3. A preliminary investigation identified that increased lecturer contact time with the students could positively affect the quantity and quality of passes in computer programming. The social medium of Facebook (FB) was studied to assess whether it could enhance contact time with students.</p> <p>In investigating factors affecting computer programming passes at the College of Cape Town, the study identified how SM technologies can assist in increasing contact time for students outside normal college time. Four groups on FB were created to allow learners to ask questions, interact with the lecturer and peers on the subject. A mixed approach was employed using qualitative and quantitative data. Test scores for previous years (2011) were compared to current (2012) test scores for the NCV 3 learners. Statistical functions calculated the average passes and total number of passes. Furthermore, a total of thirty questionnaires were used to check the learners&rsquo / perceptions toward the use of SM outside the class to enhance performance..</p> <p>More lecturer contact time on FB for one student group scored better in terms of the quantity and quality of passes. The groups using FB (with more practice time or more technical contact time) produced results which were far better than in previous years (2010 and 2011). The fourth group using FB for more peer interaction also did fairly well with an increase at the end of the year (2012) of 35% pass in programming at level 3 - up from 30% in 2011. It is the researcher&rsquo / s view that, once internet access is evenly spread, it has the potential to increase performance in subjects like computer programming. A further look at the certification of level 4 learners for programming subjects indicated an improvement could be possible by the introduction of SM at level 3 - where much of the bottleneck lies.</p> <p>As this research was limited to a single FET college it cannot be generalised. Further research spread across various FET colleges countrywide will serve to confirm these findings and determine new insights into the whole process of using SM to improve passes in computer programming at NCV level 3.. The practical recommendation is that FB should be used for this stated purpose. In respect of academic recommendations, the researcher intends to implement the same study with learners at level two and level four.</p> </font></p>

<p><font size="3"> <p>The aim of this research was to investigate the use of social media (SM) in improving the quantity and quality of passes in computer programming in South Africa&rsquo / s Further Education and Training (FET) colleges. The study addresses the high learner failure rates in computer programming at National Certificate (Vocational) (NCV) level 3. A preliminary investigation identified that increased lecturer contact time with the students could positively affect the quantity and quality of passes in computer programming. The social medium of Facebook (FB) was studied to assess whether it could enhance contact time with students.</p> <p>In investigating factors affecting computer programming passes at the College of Cape Town, the study identified how SM technologies can assist in increasing contact time for students outside normal college time. Four groups on FB were created to allow learners to ask questions, interact with the lecturer and peers on the subject. A mixed approach was employed using qualitative and quantitative data. Test scores for previous years (2011) were compared to current (2012) test scores for the NCV 3 learners. Statistical functions calculated the average passes and total number of passes. Furthermore, a total of thirty questionnaires were used to check the learners&rsquo / perceptions toward the use of SM outside the class to enhance performance..</p> <p>More lecturer contact time on FB for one student group scored better in terms of the quantity and quality of passes. The groups using FB (with more practice time or more technical contact time) produced results which were far better than in previous years (2010 and 2011). The fourth group using FB for more peer interaction also did fairly well with an increase at the end of the year (2012) of 35% pass in programming at level 3 - up from 30% in 2011. It is the researcher&rsquo / s view that, once internet access is evenly spread, it has the potential to increase performance in subjects like computer programming. A further look at the certification of level 4 learners for programming subjects indicated an improvement could be possible by the introduction of SM at level 3 - where much of the bottleneck lies.</p> <p>As this research was limited to a single FET college it cannot be generalised. Further research spread across various FET colleges countrywide will serve to confirm these findings and determine new insights into the whole process of using SM to improve passes in computer programming at NCV level 3.. The practical recommendation is that FB should be used for this stated purpose. In respect of academic recommendations, the researcher intends to implement the same study with learners at level two and level four.</p> </font></p>

This research used the tracer study method to determine more accurate disinfectant contact times in the City of Carbondale Water Treatment Plant. In this investigation, three clarifiers were selected to be the experimental segments. Water samples coming from each clarifier and the confluence of the three clarifiers were analyzed to obtain the disinfectant contact times. Based on a continuous source of infinite duration model and the tool "Solver" in Microsoft Excel, this study optimized the experimental data. The experimental data and the optimized data were then analyzed to determine the disinfectant contact times using the graphical method and the numerical method. The disinfectant contact times obtained between using the experimental data and the optimized data, and between using the graphical method and the numerical method were then compared. The results from the numerical method on the optimized data were most accurate and reliable according to these comparisons. The results suggested that the disinfectant contact times were 192.7 min for the first clarifier when its flow rate was 5.72 ML/d; 161.46 min for the second clarifier when its flow rate was 5.99 ML/d; 156.06 min for the third clarifier when its flow rate was 6.26 ML/d; and 168.48 min for the confluence of all clarifiers when its flow rate was 17.5 ML/d, respectively. The feed flows increase down the distribution manifold changing the disinfectant contact times for the clarifiers.

Magister Commercii (Infomation Management) / The aim of this research was to investigate the use of social media (SM) in improving the quantity and quality of passes in computer programming in South Africa’s Further Education and Training (FET) colleges. The study addresses the high learner failure rates in computer programming at National Certificate (Vocational) (NCV) level 3. A preliminary investigation identified that increased lecturer contact time with the students could positively affect the quantity and quality of passes in computer programming. The social medium of Facebook (FB) was studied to assess whether it could enhance contact time with students. In investigating factors affecting computer programming passes at the College of Cape Town, the study identified how SM technologies can assist in increasing contact time for students outside normal college time. Four groups on FB were created to allow learners to ask questions, interact with the lecturer and peers on the subject. A mixed approach was employed using qualitative and quantitative data. Test scores for previous years (2011) were compared to current (2012) test scores for the NCV 3 learners. Statistical functions calculated the average passes and total number of passes. Furthermore, a total of thirty questionnaires were used to check the learners’ perceptions toward the use of SM outside the class to enhance performance.. More lecturer contact time on FB for one student group scored better in terms of the quantity and quality of passes. The groups using FB (with more practice time or more technical contact time) produced results which were far better than in previous years (2010 and 2011). The fourth group using FB for more peer interaction also did fairly well with an increase at the end of the year (2012) of 35% pass in programming at level 3 - up from 30% in 2011. It is the researcher’s view that, once internet access is evenly spread, it has the potential to increase performance in subjects like computer programming. A further look at the certification of level 4 learners for programming subjects indicated an improvement could be possible by the introduction of SM at level 3 - where much of the bottleneck lies. As this research was limited to a single FET college it cannot be generalised. Further research spread across various FET colleges countrywide will serve to confirm these findings and determine new insights into the whole process of using SM to improve passes in computer programming at NCV level 3.. The practical recommendation is that FB should be used for this stated purpose. In respect of academic recommendations, the researcher intends to implement the same study with learners at level two and level four.

Magister Scientiae (Physiotherapy) - MSc(Physio) / Sprinting can be described as the ability to cover a short distance in the fastest possible time. It requires enormous stability, strength and speed to achieve this goal. Any improvements in technique or speed can be the difference between winning and losing and ultimately gold or silver. Many coaches focus their training on improving the mechanics of the lower limb in order to achieve their goal. They often neglect to consider the effect the upper limb, head, neck and trunk has on the sprinters technique. This study aimed to determine the effect the muscles that assist in stabilising the head and neck namely the deep neck flexors, has on sprinting technique. A systematic review was conducted to determine the factors that influence the acquisition of the correct and most efficient sprint technique. Thereafter assessments were done to determine the prevalence of neck discomfort and how it impacts the athlete’s life by use of the Disability Neck Index. In addition, the endurance of the participant’s deep neck flexors using the Craniocervical Flexion Test and an analysis of their sprinting technique through video analysis were conducted. Variables for each assessment were coded and analysed with Chisquared tests to determine statistically significant relationships. Results show that there was to prevalence of neck pain among participants and although the participants have poor deep neck flexor endurance and an inadequate sprinting technique, no statistically significant relationships could be found between these two variables. Thus poor endurance in the deep neck flexors has no effect on sprinting technique. The results of the study was limited due to a small sample size and lack of equipment, thus further research is required in order to completely reject the possibility that the deep neck flexors effects a sprinters ability to acquire an efficient sprinting technique.

Problem: Running is one of the most widespread physical activities. Incorrect running technique, training quantity but also the runner's equipment can strongly affect health condition of the individual, both positively and negatively. For that reason various trends emerge in the area of running footwear. They include classical sports shoes with different types of impact attenuation as well as the minimalist footwear made to imitate barefoot running, which should be much more natural for humans, as insisted by B. Nigg in his book "Born to Run" - where he says that man was born to walk and run barefooted. Inappropriate shoes can cause various health complications, not only in the foot area. Objective: To find out how foot strike changes in the area of the foot-shoe interaction in running on flat ground when an amateur runner uses minimalist and sports footwear and to draw conclusions for training practice on the basis of the results. Methods: The thesis deals with amateur endurance running in different shoe types (minimalist and sports shoes). The study specimen consisted of 14 female runners (mean body weight 63,31 ± 4,89 kg, height 169,69 ± 4,71 cm, age 31,92 ± 5,34 years, speed in minimalist shoes (MO) 3,34 ± 0,06 m.s- 1 , speed in sports shoes (SO) 3,29 ± 0,06 m.s-1 , weekly mileage 37,54 ± 9,43...