Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references. Also available in electronic version.

Oilseed rape has become an important weed in arable rotations and a feral plant of field margins, soil dumps and roadsides. Seed persistence in the soil following induced secondary dormancy is thought to perpetuate these weed and feral populations. Potential variation between cultivars has been suggested in previous work in the extent of secondary dormancy and other germination traits, and in underlying genetic heterogeneity. The aim of this work was to quantify in more detail inter- and intra- cultivar variation in germination traits for six oilseed rape cultivars, to confirm that variation was consistent in laboratory and field, and to ascertain whether there is a genetic base to this variation. The cultivars are Askari, Bristol, Gazelle, Libravo, Martina and Rocket, selected on the basis of their suspected heterogeneity. Laboratory germination tests were conducted at 4°C, 10°C and 19°C on a thermal plate and confirmed substantial inter-cultivar variation in germination rate, induction of secondary dormancy and the temperature stimuli required for dormancy break. The phenotypic traits were quantified by mathematical parameters and cultivars ranked in order of decreasing heterogeneity. DNA analysis was made on leaf tissue of early, middle and late germinating phenotypes using two simple sequence repeat primers. There was heterogeneity and phenotypic variability generally, but a direct association between phenotype and genotype was found only in the cultivar Martina. Field emergence trials revealed non-linearity in emergence and a strong similarity between laboratory germination and field emergence curves. Cultivar heterogeneity was found to be similar for emergence rate and post-winter emergence. Again there was evidence of an association between heterogeneity in emergence and genetic heterogeneity in the DNA markers. The results suggest that standard seed testing should be carried out at low temperatures to detect any hidden variability in germination. Plant breeders should be cautious about introducing variability into new breeding lines as this might increase the potential persistence of feral populations and the risk of gene transfer to later.

Water resources development around the world has taken many different forms and directions since the dawn of civilization. Water shortage in arid and semiarid regions has encouraged the search for additional sources currently not exploited intensively. Hence, knowledge of the infiltration process is a requirement for understanding water management. The main aim here is to solve the one-dimensional nonlinear time-dependent Richard's equation for water flow in an unsaturated uniform soil. The main theory of soil infiltration is introduced using a mathematical-physical approach to describe water movement in unsaturated soils. This gives rise to Richard's flow equation; which is presented for both unsaturated and also saturated soil. Methods for solving Richard's equation by both analytical and numerical techniques are then introduced. This gives rise to a discussion of the similarity methods first used by Philip to determine analytical solutions of Richard's equation in an unsaturated soil. This is then generalised to determine a broader class of solutions using the Lie (classical) symmetry approach. The non-classical symmetries of Bluman and Cole are also determined. Although these group methods provide the most widely applicable technique to find solutions of ordinary and partial differential equations, a large number of tedious calculations are involved. With the help of computer algebra it is shown that the determining equations for the non-classical case lead to four new highly non-linear equations which are solved in five particular cases. Each case of classical and non-classical solutions is then reduced to an ordinary differential equation and explicit solutions are produced when possible. The potential classical and non-classical method, first suggested by Bluman, Reid and Kumei, is also discussed and presented. The potential non-classical method produced new results, which the potential classical method did not. The solution is useful as a tool by which to judge the quality of numerical methods. A practical solution of classical (Lie/ potential) and non-classical symmetry of Richard's equation is presented. Finally, conclusions and suggestions for further work are discussed.

This thesis describes an investigation into the use of dual modality tomography to measure component concentrations within a cross-section. The benefits and limitations of using dual modality compared with single modality are investigated and discussed. A number of methods are available to provide imaging systems for process tomography applications and seven imaging techniques are reviewed. Two modalities of tomography were chosen for investigation (i.e. Electrical Impedance Tomography (EIT) and optical tomography) and the proposed dual modality system is presented. Image reconstruction algorithms for EIT (based on modified Newton-Raphson method), optical tomography (based on back-projection method) and with both modalities combined together to produce a single tomographic imaging system are described, enabling comparisons to be made between the individual and combined modalities. To analyse the performance of the image reconstruction algorithms used in the EIT, optical tomography and dual modality investigations, a sequence of reconstructions using a series of phantoms is performed on a simulated vessel. Results from two distinct cases are presented, a) simulation of a vertical pipe in which the cross-section is filled with liquid or liquid and objects being imaged and b) simulation of a horizontal pipe where the conveying liquid level may vary from pipe full down to 14% of liquid. A computer simulation of an EIT imaging system based on a 16 electrode sensor array is used. The quantitative images obtained from simulated reconstruction are compared in term of percentage area with the actual cross-section of the model. It is shown from the results that useful reconstructions may be obtained with widely differing levels of liquid, despite the limitations in accuracy of the reconstructions. The test results obtained using the phantoms with optical tomography, based on two projections each of sixteen views, show that the images produced agree closely on a quantitative basis with the physical models. The accuracy of the optical reconstructions, neglecting the effects of aliasing due to only two projections, is much higher than for the EIT reconstructions. Neglecting aliasing, the measured accuracies range from 0.1% to 0.8% for the pipe filled with water. For the sewer condition, i.e. the pipe not filled with water, the major phase is measured with an accuracy of 1% to 3.4%. For the single optical modality the minor components are measured with accuracies 6.6% to 19%. The test results obtained using the phantoms show that the images produced by combining both EIT and optical tomography method agree quantitatively with the physical models. The EIT eliminates most of the aliasing and the results now show that the optical part of the system provides accuracies for the minor components in the range 1% to 5%. It is concluded that the dual modality system shows a measurable increase in accuracy compared with the single modality systems. The dual modality system should be investigated further using laboratory flow rigs in order to check accuracies and determine practical limitations. Finally, suggestions for future work on improving the accuracy, speed and resolution of the dual modality imaging system is presented.

No description available.

Submitted in partial fulfilment of the requirements for the degree of Master of Education in the Department of Planning and Administration in the University of Zululand, 1990. / This study looks into the problem of failure in Matric in Black schools in KwaZulu. Some researchers have focused on causes for academic failure before. Some of these researchers are: Souper, (1976); Bryant, (1978); Havinghurst, (1979); Donald, (1980); Simons, (1980). Failure is rarely, if ever, attributable to one simple cause. There are likely to be a multiplicity of interrelated causes. Some' of these causes are : family disorganisation; family size and education; poor study facilities at home and teacher-pupil ratio. Failure at school may imply that one may fail in life. Society believes that school subjects are the means of i equipping pupils with the knowledge of understanding certain socio-economic and political demands. School subjects, it is believed, reveal the r, ealities that they should know in their society. It is through these school subjects that the child will know how to live comfortable with other people (Social Studies); how to look after his/her body, (Physiology and Hygiene); how other organisms are important in her/his life, (Biology/ Ecology; (Geography) .

Quasi static and intermediate strain rate (5 s-1 and 500 s-1) tests are conducted on various aluminum and steel ASTM E8 subsize tensile specimens to validate a newly developed testing method which combines a previously developed serpentine bar for load monitoring and a newly described high-speed actuator. This new actuator is controlled by a semi-passive piezoelectrically actuated brake system mounted to a standard actuator, which allows for the actuator to produce high loads and quick response times (≈100 µs). Limitations of this experimental method are that tests must be monotonic (tension or compression but not cyclic loading) and strain rate rise times limit this method to the intermediate strain rate regime (below 500 s-1).

No description available.

Source coding, a central concept in information theory, is the study of encoding and decoding data. Depending on the topological structure of the sources, i.e. how the sources are connected with encoders, different rate distortion functions are used. In this thesis two different encoding schemes---distributed and decentralized---are discussed and compared with a benchmark (centralized) coding structure. Specifically, all structures for two and three sources are discussed and a special case for the multi-source (more than three sources) is calculated. This work gives a pathway to characterize the generalized multiterminal source coding systems by finding the difference in the rate distortion limits from the optimal centralized coding system. It is shown that in specific cases, some decentralized systems can achieve the Shannon lower bound in a high resolution regime. / Thesis / Master of Science (MSc)

Soybean [Glycine max (L.) Merr.] seed cost has increased dramatically with the introduction and adoption of herbicide-resistant cultivars, generating interest from growers to reduce seeding rates to the lowest possible level that does not affect yield. Research indicates that greater seeding rates are needed to maximize yield under low-yielding environments and less seed is needed in high-yielding environments, but this has not been confirmed with recent research in Virginia. The objectives of this research was to 1) determine the yield response of soybean cultivars with differing growth habits and maturities grown in full-season and double-crop systems to seeding rate under different yield environments; and 2) compare two seeding rates in large on-farm strip-plots to determine if the growth environment within the field affects the yield response to seeding rate. For objective 1, small-plot research was conducted on Piedmont and Coastal Plain sites across Virginia from 2017 thru 2020. Maturity group (MG) 4 or 5 cultivars were planted in 46-cm rows at the following seeding rates: full-season soybean – 74,130, 148,260, 222,390, 296,520, 370,650, and 444,780 seed ha-1; and double-crop soybean – 197,680, 296,520, 395,360, 494,200, 543,620, and 593,040 seed ha-1. One cultivar per MG was used in 2017 and 2018, but the experiments were expanded to include two cultivars, differing in canopy structure, within each MG in 2019 and 2020. On-farm research compared a high and low seeding rate with a 100,000 seed ha-1 difference based upon grower current practices. To determine growth influence on the yield response, normal difference vegetative index (NDVI) was measured at 2-week intervals from late-vegetative to late-reproductive stages in small-plot and on-farm experiments. Double-crop soybean required an average of 205,000 more seed ha-1 than full-season soybean. Although yield response varied with site and year, MG 4 cultivars usually yielded more than MG 5 at higher seeding rates, but less at lower seeding rate. No differences between cultivar canopy structure were present in full-season systems; differences were revealed in double-crop systems but were not consistent over sites. To obtain 95% of maximum yield, 170,000 to 390,000 seed ha-1 were required in full-season soybean and 470,000 to 550,000 seed ha-1 were required in double-crop soybean. While the NDVI response to seeding rate generally reflected the yield response at most site-years, relationship between yield and NDVI was weak. In on-farm experiments, higher seeding rates yielded more at 3 of 6 sites, but differences varied within the field. The yield-NDVI relationship was stronger due to greater variability within the field, but these differences due to seeding rate could not be discerned. Growing environment, primarily amount and distribution of rainfall, greatly influenced these results; therefore, more exact site-specific seed rate recommendations will be difficult in Virginia's environment. / Master of Science / Soybean is one of the world's most important seed legumes and contributes a major portion of global protein concentrate for livestock feeding and oil for human consumption therefore, it is essential to continually and sustainably increase yield while maintaining profitability for growers. Through adoption of precision agriculture technology by Southeastern farmers, site-specific management using variable rate application and/or automatic section control of inputs are able to be utilized when field variability is assessed. Additionally, on-farm experiments validate small plot research with larger field-scale evaluations with proper technology and design. In this study various seeding rates on soybean yield in both small-plot and on-farm experiments, as influenced by variable growth and yield differences within the field, was determined. On-farm research allowed better observation of yield response to seeding rate for each field, allowing the evaluation of production practices under realistic growing conditions. Ultimately, it is expected that more early-season growth in areas of the field with greater productivity will result in greater yields using less seed per hectare. The utilization of vegetative indices as well as remote sensing technology contributed largely to the analysis of yield and varying seeding rates. Accordingly, measurements were correlated with one another to determine if remote sensing techniques can be substituted for ground measurements in predicting yields.