The present study used a Microsoft Visual Basic computer program to examine the effects of changing reinforcement schedule components on response allocation following previously extinguished responding. In Experiment 1, participants allocated responses to three different colored buttons that moved around the screen after each successive click. Components were arranged such that clicking on one button resulted in reinforcer delivery on a programmed variable-interval (VI) 10 s schedule while clicking either of the other two buttons did not result in programmed reinforcer deliveries. Results of Experiment 1 may have been confounded by an unintended signaling of component changes, so an identical experiment was repeated without a point counter visible to the participants. The results of Experiment 2 indicated an induced responding on the button most recently associated with reinforcement when the reinforcement schedule changed. This induction effect is discussed in relation to current conceptions of relapse effects in the scientific literature and implications for treatment of challenging behavior.

The objective of this thesis is to combine computational flow modelling, flow visualization and point measurements of mean flow and turbulence properties to obtain a better, more detailed, understandýing of the effects of alternative throttling devices on mixture preparation and turbulence generation in spark ignition engines. In so doing, it also seeks to assess the wider diagnostic potential of flow field computational techniques in internal combustion engine designs. Full-scale models, comprising simplified representations of the induction tract, throttling device, inlet valve and cylinder, have been manufactured in Perspex for steady-state water analogy tests. The resulting photographs of flow tracers in a variety of viewing planes provide a clear, but qualitative, picture of the princi - pal features of the flow in the models under study. The essentially qualitative data obtained from water analogy tests are complemented by limited hot wire velocity measurements at particular stations in the Perspex models, with air replacing the water as the flow medium. These data, supplemented by information in the literature, provide the framework for comparisons with an extensive computational simulation of induction flows which are performed using the general purpose PHOENICS code developed by CHAM. These studies include both transient and steady state predictions. The statistically stationary turbulent flow field through alternative induction system throttling devices -a conventional butterfly valve and a variable geometry ramp restriction- are modelled computationally and compared with water analogy flow visualization. The principal flow field characteristics are satisfactorily reproduced, including in particular the extent of the recirculation zone in the lee of the throttle and the relative persistence of the turbulence generated downstream for varying throat apertures. That generated by the two-dimensional variable geometry ramp is predicted to be both higher and persist beyond the inlet valve into the cylinder producing discernible swirl at high throttle settings. The limited quantitative comparisons with hot wire velocity measurements lend further support to the more detailed aspects of the computational predictions. Finally, comparisons are made between PHOENICS predictions and Laser-Doppler measurements of velocity for transient flow inside an axisymmetric motored piston-cylinder assembly, for different valve seat angles, reported in the literature. The agreement is again very encouraging, reinforcing the view that general purpose computer codes of the kind investigated can play an important role in detailed design assessment and evaluation.

A finite difference algorithm for solving the forward modelling problem of geo-electromagnetic induction in three-dimensional structures has been developed in this thesis. Novel features of the method include the incorporation of a thin sheet of anomalous conductance at the surface of an otherwise quite general three-dimensional structure in which the anomalous region is allowed to approach two-dimensional configurations at infinity; the use of magnetic rather than the electric field components for obtaining the solution; the use of integral boundary conditions at the top and bottom of the model; and the application of new cell-integral finite difference equations to the main body of the model. The algorithm has been tested for synthetic models against results delivered by existing two and three dimensional modelling programs which are already well established. The results are found to be very satisfactory. Applications of the algorithm have been shown for two cases. First, the dependence of the induction vectors on the period ranging from 10 to 10000 s has been studied for a model with two perpendicular lateral conductivity contrasts; the directions of induction vectors vary from site to site reflecting the combined effect of the two perpendicular contrasts. In the second case, the distortion effect due to small surface inhomogeneities over a buried 2D anomaly was studied using induction vectors and difference vectors. There is evidence of mutual coupling in a certain region which invalidates a simple subtraction of the vectors to reveal the form of the buried anomaly, but elsewhere the procedure appears to be quite valid. Since surface anomalies can be simulated by an anomalous thin sheet over the general 3D structure, it is suggested that this algorithm could be very useful for testing the validity of existing schemes for impedance tensor decompositions used in MT studies when surface anomalies are thought to be distorting the real data. / Graduate

M.Ing. (Electrical & Electronic Engineering) / In recent years, there has been a renewed interest in the synchronous reluctance machine, because it holds so many promises according to the mathematics. In the past very little research has been done in this field, due to the problems of controlling the machine and the necessary technology had not yet- been developed. When the machine is running synchronously, it can be very accurately controlled and is therefore suited for applications in the paper or textile industry. In this dissertation the possibility of accurately controlling the machine without the use of a position/speed sensor on the rotor will be investigated.

[No abstract available] / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Understanding the trajectories of particulate solids inside a flow-through reactor, such as the riser of a recirculating fluidized bed, is a basic requisite to accurately modelling the reactor. However, these trajectories, which are complicated by gross internal recirculation, are not readily measurable. Conventional means of measuring the residence time distribution can be applied to closed boundaries, such as the exit of the riser. Doing so, however, does not directly provide the details of the trajectories within the riser. In order to determine these trajectories, meaningful measurements must be made at the open boundaries between the adjacent axial regions which, in total, make up the riser. Transient tracer concentration measurements at open boundaries are ambiguous because, as tracer material recirculates past the sensor, its concentration is repeatedly recorded, with no distinction as to which region (above or below the boundary) it has just resided in. A method designed to eliminate this ambiguity at open boundaries is reported in this thesis. By repeatedly introducing single tracer particles into the riser, and measuring the time of passage through each axial region, the residence time distributions for each region can be obtained from the frequency density of these times. The crux of this approach is being able to sense individual tracer particles. The major thrust of this investigation has been to find a practical means to this end. The final sensor considered in this investigation is based on electromagnetic induction: a magnetic primary field induces an eddy current in a conductive tracer particle, and the resulting secondary field is sensed, indicating the presence of the tracer particle in the sensing volume. Noise, resulting from direct coupling between transmitter and receiver coils, electrostatics, and vibrations, determines the sensitivity of the device. The final prototype sensor is limited in sensitivity to relatively large tracer particles, and it is incapable of measuring tracer velocity. Nevertheless, the trajectory of large particles is of practical significance for circulating fluidized beds. Limited tests were conducted in a 0.15 m ID x 9.14 m tall acrylic riser where the tracer particles were injected opposite the solids re-entry point, and were sensed by a single sensor located at an open boundary 7.5 m downstream. At each of the two superficial gas velocities considered, and above a threshold solids flux, the time-of-flight frequency density between the injector and the sensor for these large tracer particles does not change with increasing flux of the fine solids. This result is incongruous with obvious changes in the macro-flow structure occurring in the riser. Recommended changes in the sensor would allow measurement of the direction and speed of the tracer, as it passes by the sensor, as well as potentially reducing noise. With these improvements, it would be useful to install multiple sensors along the full length of the riser. The information obtainable from such a configuration would greatly enhance understanding of the detailed trajectories within the riser. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

A recent theory describes the fluxgate magnetometer as a modulated inductor. In that theory, hysteresis and demagnetization are implicitly incorporated in the sense-coil inductance, an easily measured quantity. In this thesis, the principle equation of that theory is experimentally tested. Expressions relating the open-circuit and short-circuit output from a fluxgate magnetometer to the magnetic field are derived from the principle equation. In order to test the proposed relations, the writer assembled a ring-core fluxgate a computer-controlled current source to drive the fluxgate, and circuits required to monitor the open-circuit and short-circuit output signals, initial tests showed that the integrated open-circuit output voltage from the fluxgate is proportional to the magnetic field. The constant of proportionality is simply the product of the length-to-turns ratio of the sense-coil and the maximum change in the sense-coil inductance caused the drive current. This result was correctly predicted by the aforementioned fluxgate equation. Test results from the short-circuit experiment were also correctly predicted by the fluxgate equation. Therefore, experimental data is provided that supports the validity of the fluxgate equation. The same fluxgate theory is used to predict specific values of drive current parameters that maximize the fluxgate output signal. The computer-controlled current source was used to generate a bipolar square-pulse waveform with an adjustable amplitude, frequency, and duty cycle. A sinusoidal drive waveform was also used. Experimental data confirm the validity of all the predicted relations, and thus, provide substantial support for theoretical work that has been recently published. As a final application, the fluxgate theory was used to quantify the behavior of a ring-core fluxgate immersed in a magnetic fluid. A fluxgate was put in magnetic fluid in an attempt to discover if the fluxgate responds primarily to the ambient flux density, and consequently, to determine whether the output signal could be enhanced by simply placing the sensor in a container filled with magnetic fluid, The experiment was terminated when inductance measurements taken on the immersed sensor showed that stray flux from the toroidal drive-coil significantly altered the permeability of the magnetic fluid, and thus altered the calculated values of flux density in the magnetic fluid. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

A detailed study of electromagnetic induction in a sequence of conductive layers has been completed for the case when the inducing fields are generated by an alternating current in a horizontal loop. The study was undertaken with a view to the development of a computer program to perform automatic inversion of horizontal loop electromagnetic (HLEM) frequency soundings taken over horizontally stratified ground. The program constitutes a new implementation of the general approach of Backus and Gilbert (1967, 1968, 1970). By means of a linearised iterative scheme, it constructs layered conductivities which satisfy a given set of observations to an accuracy consistent with the observational uncertainties. Subsequently, the non-uniqueness admitted by the limited amount of data can be appraised by computing averages of the original constructed model and comparing them with averages corresponding to other dissimilar models which also satisfy the data. In examples the Backus-Gilbert averages faithfully reflect the character of the "true" conductivity in regions of high conductivity, but they are of limited value in delineating resistive zones. The program has been applied successfully to the inversion of real data from Grass Valley, Nevada. A uniqueness theorem is presented for inversion of HLEM frequency soundings. It has been proved that an unlimited quantity of perfectly accurate HLEM frequency soundings (at a fixed receiver location) suffices to completely determine the conductivity as a function of depth. This result, which is believed to be new, enhances the credibility of conclusions based on inversion of HLEM soundings. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Ocean bottom magnetometer data from a site on the Pacific plate above 3 my old lithosphere are inverted for electrical conductivity as a function of depth. Magnetotelluric impedances are calculated by the vertical gradient method using the fields at the OBM in conjuction with those measured at the Victoria Geomagnetic Observatory. The approximations involved are examined. Winnowing criteria are proposed which isolate those impedances compatible with all the model and source field assumptions. These then define the best possible data set. A number of inversion algorithms are applied to the data and a wide range of acceptable conductivity profiles are constructed. All profiles exhibit a uniform, relatively high conductivity of about 0.2 S/m from the surface down to a depth of 100 km. Exact and approximate bounds on the conductance are calculated in an effort to quantify the non-uniqueness of the diverse conductivity models. Profiles with a minimum of structure are used to calculate the partial melting and temperature variations beneath the 3 my old site. All results are compared with three other magnetotelluric analyses above 1, 30 and 72 my old lithosphere. The 3 my old datum is discordant and does not fit the trends interpreted from the other three studies. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

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