The motivation for this research project arose from the realisation that many South African rural water supply schemes fail due to the over abstraction of groundwater from single boreholes. The main reason for this mis-management of groundwater is a result of inappropriate borehole yield recommendation methods. This research project set out to review existing borehole yield assessment methods and establish new methods which take the shortcomings of existing methods into account. The study is concerned with borehole yield assessment methods applicable to secondary aquifers, since these aquifers are by far the most common in South Africa. The yield assessment methods have been grouped into those that are based on aquifer yield analyses, and on the analysis of single borehole test pump data. In order to assess which methods give suitable yield recommendations, it was necessary to compare the yields obtained using the various methods, with established yields from production boreholes. The focus of the aquifer yield component of the study, was to develop a method for estimating the proportion of recharge that can be abstracted from a single borehole located in a relatively small aquifer. The method was developed by computer simulations of aquifers with different hydraulic properties, and by establishing a formula which describes the relationship between recharge and the abstractable proportion of recharge. Under specific hydrogeological conditions, the recharge based method proved to be reliable in relation to established yields from production boreholes. Of the borehole yield assessment methods based on the analysis of test pump data, none of the existing methods proved to be reliable. However, the yields obtained using the two newly developed methods compared favourably to the established yield of existing production boreholes. Both of these methods are based on the application of the Cooper-Jacob approximation of the Theis equation. This study reviews existing methods and presents newly developed methods for recommending borehole abstraction rates in secondary aquifers. While existing borehole yield assessment methods were found to be unreliable, some of the newly developed methods, if correctly applied, give acceptable yield recommendations.

This thesis describes the design of a magnetometer for recording geomagnetic micropulsations. The nuclear magnetic resonance phenomenon of hydrogen nuclei in water is utilized in the sensing unit of a feedback system, the feedback current being recorded as a measure of the geomagnetic variation. The thesis establishes the feasibility of a feedback system magnetometer. The system transfer function is derived and from it the sensitivity, stability, steady state error and dynamic range are determined. The dispersion mode signal of nuclear magnetic resonance obtained experimentally is shown and compared with that predicted theoretically. The advantages of a feedback system are indicated. The difficulty in closing the feedback loop is discussed and methods for overcoming this problem are suggested. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Bullying is a subset of aggressive behaviour that is characterised by three features: intention to cause harm, repetitiveness, and an imbalance of power between the perpetrator of the aggression and his or her victim (Olweus, 2010). This definition is widely accepted and widely used in academic research on bullying (Cornell & Bandyopadhyay, 2010), but lacks empirical evidence of construct validity (Finkelhor, Turner, & Hamby, 2012). This dissertation explores the construct validity of bullying in two ways. The first study examines the validity of the definition of bullying in terms of its ability to predict student functioning and identify a distinct group. The second study examines the validity of a widely used bullying measurement strategy in terms of its ability to identify aggression that meets the definition of bullying. Marginal evidence for the construct validity of bullying as currently measured and defined was found. While the characteristics of bullying do predict several measures of functioning above and beyond the presence of generic aggression or victimization, the differences predicted appear to be differences of magnitude only. This indicates that bullying may be related to more severe, but not unique, outcomes. In addition, the individual characteristics of bullying contained within the overall definition (repetition, intention to harm, power imbalance) are shown to be highly related and better thought of indicators that bullying has occurred rather than additive constructs that define a certain subclass of aggressive behaviour. Finally, regarding measurement, the results of this study show that peer-report responses using definitional measurement strategies are not strongly related to the definitional criteria of bullying. Implications for the field of bullying research are discussed. Theoretically informed empirical work on clarifying the bullying construct is identified as a research priority.

The U.B.C. Hanson-McKibben type Long Counter has been modified to permit insertion of a larger diameter BF₃ proportional counter. An investigation was made to determine the effects of the modification on the neutron detection characteristics of the counter. 2.60 MeV and 3.09 MeV neutrons were obtained from the reaction D(d,n)³ He and 4.5 MeV neutrons from a standard²⁴¹AmBe source. The efficiency of the Long Counter was determined in terms of counting rate per unit neutron flux occurring at the effective centre of the counter. The count rate used was that due to the ¹ºB(n,α)⁷Li pulses from the BF₃ counter located in the centre of the Long Counter. The effective centre was defined as that point inside the counter such that the counting rate varied as the inverse square of the distance of the source from the effective centre. The following table lists the neutron energy, efficiency and distance from the front reference face of the Long Counter to the effective centre. [ Formulas omitted ] The efficiency for 4.5 MeV neutrons was found to have increased by at least an order of magnitude from that of the original Long Counter. However, the dependence of the efficiency on energy has been increased, varying by 50% over the range of energies measured. The shielding on the sides of the Long Counter was found to reduce the intrinsic efficiency for neutrons incident from the side to 0.4 of that for neutrons incident on the front face. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Analytical and experimental studies of the behaviour of equipment vibration isolators under seismic conditions are presented. A preliminary parametric study of the effect of equipment-structure interaction on the ultimate equipment response of general equipment-structure systems is considered first. The results of this study indicate the conditions under which a non-interactive approach can yield adequate ultimate equipment response estimates. A model of a prototype air handling unit mounted on vibration isolators was constructed for use in the experimental studies. Two types of vibration isolators -elastomeric isolators and open spring isolators with uni-directional restraint - were tested under static and dynamic conditions. The frequency and seismic response characteristics of these vibration isolated systems were obtained. The experimental results indicate that the vibration isolators have nonlinear stiffness characteristics and high damping values. The results also show that the elastomeric isolators can survive a substantially higher level of base excitation than the open spring isolators with uni-directional restraint Analytical models of the vibration isolated systems, based on the model identification test results, have been formulated. A numerical procedure, utilizing time series analysis, was used to solve the equations of motion of the systems. Good agreement between the experimental results and the analytical results was observed. This study indicates that the analytical procedure can be used to accurately predict the response characteristics of vibration isolated equipment systems subjected to known base excitation inputs. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The self-boring pressuremeter which is inserted into the ground without disturbing the surrounding soil has two drawbacks. Skilled operators are needed to insert the probe into the ground without disturbing the soil, and the self-boring process requires a jetting action or a rotating cutter and drilling mud. One method of simplifying the pressuremeter installation procedure is to install the probe in a full displacement manner. A solid tip is placed oh the end of the probe and then the pressuremeter is pushed into the ground in the same manner as a cone penetrometer. This research project was performed to examine the suitability of using the full displacement pressuremeter for determining shear modulus, insitu horizontal stresses, and undrained shear strength. The variables examined were; the type of pressuremeter, whether the pressuremeter was run in a stress or a strain controlled manner, the size of the tip pushed in front of the pressuremeter, and whether time was allowed for the dynamic pore pressures to dissipate. Tests were conducted in sand, silt, and clay. When the shear moduli measured with the full displacement pressuremeter were adjusted to account for the differences in strain level, and mean effective stress they compared very well with the dynamic shear moduli measured with the seismic cone. The attempts to determine the insitu horizontal stress by examining the liftoff pressure were unsuccessful. The undrained shear strengths of clay determined using cavity expansion theory compared very well with undrained shear strengths determined using the field vane. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The characteristics of several types of heated sensors used for measuring oceanic turbulence have been examined. The author measured the steady heat flux from glass coated ellipsoidal microbead thermistors, computed numerically the unsteady heat flux from an ideal constant temperature flat plate, and analyzed the steady flow calibration data of a paralene-c coated plate thermistor as well as the steady and unsteady calibration data of two conical constant temperature hot film anemometers. In order to understand the behaviour of probes alone, thermal models of these sensors have been developed. The models incorporate a Nusselt number governed steady heat flux from the wetted surface and the thermal effects of a surface coating and a supportive substrate. Derived functional relationships between the steady heat flux and the flow rate agree favourably with the available calibration data. The quasi-steady sensitivity of these probes when used as anemometers or thermometers as well as their signal contamination by temperature or velocity are calculated using the functional heat flux relationships. The substrate and the coating reduce the sensitivity to temperature and to speed as well as the ratio of speed-to-temperature sensitivity. The response of sensors is not governed by the Nusselt number when the boundary layer is unsteady. The unsteady response of a sensor to velocity oscillations is governed by its unsteady viscous boundary layer and may increase with increasing frequency over some frequency ranges. The response bandwidth is wider for velocity than for temperature. The ratio of unsteady temperature-to-velocity sensitivity is highest at zero frequency. Frequency response calibrations methods must realistically simulate the sensor's unsteady viscous boundary layer. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

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No description available.

Poor sleep measured across many dimensions has been linked to adverse physical and mental health outcomes including cardiovascular disease, diabetes, cancer, increased mortality, depression, and anxiety. Current research typically relies upon brief, subjective, inadequately validated methods to assess limited dimensions of sleep, resulting in inaccurate measurements and possibly faulty conclusions. Specifically, research validating objective (e.g., actigraphy) and subjective (e.g., sleep diaries, retrospective surveys) measurement methods against the gold standard of polysomnography (PSG, an overnight sleep study) is primarily limited by a) a lack of reliability based on too short (e.g., 24 or 48 hours) of an assessment period to capture night-to-night variability, b) a lack of ecological validity (e.g., full PSG in a laboratory setting), and c) a lack of generalizability due to limited or special populations (e.g., individuals with insomnia). Barriers such as prohibitive cost, extensive setup time, and personnel training requirements diminish the ability of researchers to conduct measurement comparison studies using gold standard measures like traditional PSG. These barriers can be circumvented with the use of low-cost, minimally invasive single-channel EEG devices (e.g., Zmachine), but to date few studies have employed these devices. The current study evaluated the accuracy of retrospective surveys, sleep diaries, and actigraphy compared to a single-channel EEG device for assessment of sleep timing, duration, and efficiency in participants' homes over one week using a broad community sample (N = 80). Actigraphy generally demonstrated the best agreement with Zmachine across sleep variables, followed by diary and then survey. Circadian midpoint was the most consistent across measures, followed by sleep duration and then sleep efficiency. Implications and future directions are discussed.