The objective of this research project has been to develop a computer controlled cyclic simple shear apparatus and to investigate the repeated load behaviour of local basecourse aggregates with regard to their shear modulus and volume change properties. A detailed discussion of the construction of the apparatus and the development of the control systems is presented. A review of the litreature regarding cyclic load testing of basecourse aggregates has been undertaken and presented in this thesis. A large number of shear displacement controlled cyclic simple shear tests were carried out using three types of local Auckland aggregate. A comparison of the performance of these materials is presented with particular emphasis placed on the shear modulus, volume change and particle degredation properties. High repitition cyclic simple shear tests have revealed an apparent stiffness recovery for granular specimens between test runs. This behaviour is difficult to explain, however it is thought to be related to the transition from a dynamic to a static state of friction within the specimen. The volume change properties of granular specimens have been found to be equivalent to the 'normally consolidated - over consolidated' behaviour of fine grained soils. This observation is consistent with that reported by Youd (1970) who performed similar tests using specimens of sand. The implications of this result are discussed with respect to the potential application to highway engineering. A number of shear stress controlled cyclic simple shear tests have been performed to investigate the applicability of a stability threshold for basecourse materials. The stability threshold, or shakedown behaviour, has been observed and is incorporated in a philosophy for pavement design. An example of this method has been performed to show the potential merits of including stability threshold data in the pavement design procedure.

This model study is concerned with attempting to identify some of the mechanics of pile-soil interaction under the influence of static loads, as a pre-requisite to defining the mechanics of the soil response to pile transmitted dynamic (i.e. seismic) lateral soil loads. The emphasis has been directed at the mechanics of the response of the soil to loads transmitted through the pile, rather than the more usual approach of defining an analytical pile model and assuming a soil response. The work contained herein follows the incremental deformations occurring within a soil mass throughout the process of installation through to the ultimate lateral loading condition. To enable this to be done the comparatively recent developments in soil mechanics involving the application of the techniques of stereophotogrammetry and radiography, have been employed. The study is mainly involved with short rigid models in dry dense sand. A more general aim of the research project has been to attempt to draw the more research orientated and practical aspects of the statically loaded pile problem closer together. To this end, state-of –the-art reviews of both the axial and lateral loading situations have been conducted and an attempt made to relate them to the mechanics of soil response, as identified both in this research project and from full scale tests reported in the literature. An attempt has been made to apply some of the more general observations resulting from the study, to the Type A prediction, (i.e. before the event), of the ground line displacements of a full scale pile under real site conditions when subjected to various loads.

Outage probability calculations are presented for the analogue land mobile radio situation where in order to obtain satisfactory radio reception both a sufficient CNR and CIR need to be achieved simultaneously. Such calculations can be used in the design and analysis of mobile radio systems and may be particularly useful for investigating the effects of cochannel interference in cellular systems. The outage probability expressions are derived using previously reported statistical descriptions of mobile radio propagation. Attention is generally focussed on situations where signals suffer Rayleigh fading and/or lognormal shadowing. However calculations for Nakagami-m, Rice and Weibull fading are also considered. The rapid growth in cellular mobile radio systems has stimulated the development of outage probability calculations for multiple interferer situations. Previously, while single interferer situations had been treated exactly, multiple interferers had been treated by approximate methods. In this thesis exact multiple interferer outage probability expressions are presented for the Rayleigh fading and the joint 'fading and shadowing' (Suzuki) situations. Similar expressions, but for more limited cases, are also presented for lognormal and Nakagami-m statistics. Using results from these expressions the accuracies of several approximate outage probability methods are assessed. The exact outage probability expressions for multiple Suzuki interferer situations are closely related to those for multiple Rayleigh interferer situations. Indeed, the exact analytic expressions for Rayleigh statistics form an integral part of the corresponding outage probability expressions for Suzuki statistics. These latter expressions can be readily evaluated using Gauss-Hermite numerical integration. In order to demonstrate the use of such calculations for mobile radio system analysis several theoretical examples are presented. Outage probability calculations for multiple interferer systems which employ diversity reception as a means of improving communications reliability are considered. Similarly, the extension of outage probability concepts to digital systems is briefly outlined.

Local scour at cylindrical bridge piers in both uniform and non-uniform cohesionless sediments was investigated experimentally. The aim of the study was to improve understanding of local scour around bridge piers with sediment transport. Three empirical functions which relate the equilibrium depth of scour with approach velocity, flow depth and sediment size were obtained for uniform sediments. The effects of armouring and sediment sizes were also investigated for non-uniform sediments. The experimental results for the variation of equilibrium scour depth (normalised with the pier diameter) with approach velocity show that the equilibrium scour depth reaches a maximum at the threshold condition of the bed sediment. Above the threshold velocity, the scour depth first decreases and then increases again with increasing velocity to a maximum at the transition flat bed condition. At still higher velocities, the equilibrium scour depth decreases due to the formation of antidunes. Lesser scour depths are recorded with ripple forming sediment at threshold conditions because the bed associated with a ripple forming sediment is unable to remain planar. In live-bed conditions, the effect of rippling diminishes for increasing velocity and becomes negligible for UO/UOC > 2. The experimental results for the variation of equilibrium scour depth with flow depth show that the trend for live-bed scour of increasing scour depth with increasing YO/D until a maximum influence of YO/D is reached, is similar to that for clear water scour as shown by Ettema (1980). A flow depth adjustment factor, K(YO/D), which is related to YO/D with D/d50 as the third parameter is presented which indicates to a designer the sequence of estimation of the effect of flow depth on the equilibrium depth of scour. The effect of sediment size on the eguilibrium scour depth is presented in terms of the relative size of pier to sediment, D/d50. A family of curves, at various values of UO/UOC, which relate dav/D and D/d50 for live-bed scour was obtained. The curves show that the equilibrium scour depth increases almost linearly for increasing values of D/d50 until it reaches the value of D/d50 = 50 after which the scour depth becomes independent of D/d50. A similar trend was obtained by Ettema (1980) for clear water scour. For design purposes, the data for large values of YO/D are presented in terms of a sediment adjustment factor, K(D/d), which is shown to be independent of the flow velocity. Both flow depth and sediment size functions include results by Shen et al (1966), Ettema (1980), Chee (1982), and the present study. Armouring and sediment size play an important role in reducinq the equilibrium scour depth for non-uniform sediments. The latter is particularly significant in laboratory experiments where the size of the pier is generally small relative to the size of the coarse particles in non-uniform sediments. Experiments were conducted under dynamic equilibrium conditions where there is continuous sediment input from upstream of the scour hole such that at equilibrium, the amount of sediment entering the bridge site is equal to that leaving. Both the effects of armouring and sediment size diminish for increasing velocity. At high velocity where all the sediment particles are mobile, the non-uniform sediment behaves like a uniform sediment. Hence, armouring does not occur and the equivalent size used for sediment adjustment is based on the d50 size of the sediment bed. At low velocity, armouring at the base of the scour hole is prominent and adjustment of D/d is based on the d90 size of the original mixture. An alternative condition can exist in natural rivers in contrast to the dynamic equilibrium conditions simulated in this study. This is where the upstream river is armoured such that there is little or no sediment input to the scour hole. It is postulated that, in this case, the equilibrium scour depth can approach the maximum equilibrium scour depth for clear water conditions (i.e. dav/D + 2.3) when the approach velocity is equal to the critical velocity of the non-uniform sediment. Finally, a design flow chart is presented for estimation of the equilibrium depth of local scour for design purposes. In live-bed scour where bed features are present, the results show that half the height of the bed features can be added to the estimated equilibrium scour depth.

This study examines the one dimensional response of sand. For this purpose a compression shear apparatus based on a multi-ring consolidometer has been developed in which one dimensional loading and unloading tests can be performed without wall friction, and in which simple shear distortion of an enclosed sand can be evaluated. The apparatus is also used to examine one dimensional unloading following horizontal shearing of a vertically loaded sample, which is of special interest for one dimensional behaviour in liquefaction associated phenomena. The one dimensional experimental results obtained from this apparatus are modelled using a mechanistic theory proposed by Dr G. R. Martin. In addition, particulate techniques are developed to investigate the underlying mechanisms occurring in the sand. To assist in this investigation special one dimensional, triaxial, and shear tests were performed and use was made of experimental results from published sources.

This thesis presents a theoretical basis and the practical implications for using small-scale (up to 50 kW) low-cost power generating systems comprising an ungoverned turbine, a three phase self-excited induction generator, a variable VAr source for voltage regulation, and an electronic load governor. The thrust of this work is towards the reduction of cost by replacing the more conventional synchronous generator by an induction machine and, by eliminating the site-specific fully-governed turbine. An electronic load governor, utilising zero-voltage switching to minimise waveform distortion, is used to regulate the system frequency by controlling the generator loading. The performance of the load governor is analysed in conjunction with both synchronous and induction generators, and the conditions under which the governed system is stable are determined. The induction machine is shown to have better operating characteristics than the synchronous machine and has the further advantages of low maintenance and ready availability making it particularly suitable for isolated applications. A theoretical explanation of the process by which an induction machine self-excites when capacitance is connected across its terminals is developed, and methods of guaranteeing excitation are proposed. It is shown that the remanent magnetism, present in the rotor, plays a significant role in the machine excitation and the conditions leading to loss of remanence are investigated. Once excited, the operation of the induction generator is analysed for both balanced and unbalanced loadings. The practical implications of these results are taken into account in proposals for single phase supplies, these being more desirable in smaller systems. A range of static VAr sources, including a switched capacitor VAr source and an inductively loaded ac-to-dc converter, are considered for controlling the machine’s excitation. The VAr sources are compared on the basis of harmonic distortion and system stability. The thesis considers the application of these devices to micro-hydro and wind generating systems. Preliminary investigations have been carried out into the use of two-speed induction machines to improve the efficiency of CSCF Constant Speed Constant Frequency wind generating schemes and into the use of centrifugal pumps as ungoverned turbines. Practical results obtained from laboratory experiments and tests on existing micro-hydro installations are included. It is shown that significant reductions in cost are obtainable by employing the methods discussed in this thesis. The resultant systems may incur a reduction in efficiency but there is little reduction in performance and in many respects the quality of supply is improved.

Digitised pictures have both cosmetic and scientific image aspects. This thesis presents an image coding system that compresses monochromatic digital image information in such a way that the cosmetic-or viewed-image aspects of a reconstructed picture are indistinguishable from the original to a (human) observer. The coding system is concerned with viewed aspects of digitised images and is based on a simplified 2-channel model of the human eye, with the image information being separated into slowly varying texture information and rapidly changing edge information corresponding to those two channels. Each of the two types of image data is coded using techniques suited to its individual characteristics. Texture information is coded using predictive waveform coding where the predictive filter coefficients are generated by linear predictive coding (LPC) techniques. Since the waveform prediction is not perfect, this thesis evaluates several different methods of differential pulse code modulation (DPCM) coding the residual prediction error. This signal is then used to improve the texture coding quality. Image edges are isolated from the digital image data by an asymptotically optimal edge detector known as the Laplacian of Gaussian (LOG) filter. Using two image edge models, the LOG isolated edges produce contours which are used to define edge position, shape, and "sharpness". The edge position data is then compressed using a chain-coding system. The thesis also considers the effect the edge characteristics have on the coding system and develops two methods for reducing the number of coded edges. Reconstruction of the coded image is in two parts corresponding to the two channels of the coding system. The texture information is reconstructed by predicting texture pixels and adding the decoded DPCM error signal. Edge information not contained in the texture coding channel is reconstructed using only edge information corresponding to the high spatial frequency channels of the human eye. These two channels are added together producing the final coded image reconstruction. Also considered are the effects of varying the original image sampling density. The 2-channel coding system is applicable to a wide variety of images, producing coded images with a high visual quality and coding bitrates as low as 0.6 bits/pixel (256 x 256 pixel images), while maintaining a relatively low computational overhead both at the encoder and the decoder.

In the 1950's and early 1960's a considerable amount of effort was devoted by Dr. H.A. Whale and others at the Seagrove Radio Research Station (now the Radio Research Centre, University of Auckland), to the examination of some of the problems involved in HF radio propagation. Among these were the evaluation of the effects of large-scale ionospheric tilts, the scattering which occurs at the earth and ionosphere, and the measurement and prediction of incoming bearing and elevation angles of signals from distant stations. In the latter stages of this work it became obvious that little was known about effects occurring at antipodal distances, so attempts were made to examine these and to postulate a propagation model consistent with the effects observed. The results presented in this thesis are a logical extension of this early work, and comprise investigations in three main areas: (1) The shape and size of the antipodal focussing area, (2) The development of a more general and less idealised propagation model, (3) The shape of the incoming angular power spectrum at antipodal distances. A summary of the theory and experimental results contained in chapters 4, 5, 6 and 7 has been published (Bold, 1969), and that contained in chapters 8 and 9 will be submitted for publication shortly.

Networked control systems (NCSs) are a type of distributed control systems where sensors, actuators, and controllers are interconnected through a communication network. This system setup has the advantage of low cost, °exibility, and less wiring, but it also inevitably invites some delays and data loss into the design procedure. The focus of this thesis is to address the problem of analysis and design of networked control systems when the communication delays are varying in a random fashion. This random feature of the time delays is typical for commercially used networks, such as a DeviceNet (which is a controller area network (CAN)) and Ethernet network. Models for communication network delays are ¯rst developed, in which Markov processes are used to model these random network-induced delays. Based on such models, we establish novel methodologies for stability analysis, control with disturbance attenuation, and fault estimation for a class of uncertain linear/nonlinear uncertain NCSs with random communication network-induced delays in both sensor-to-controller and controller-to- actuator channels. Data packet dropouts in the communication channels also have been taken into consideration in the modelling and design procedure. The main technique used in this thesis is based on the Lyapunov-Razumikhin method, which results in delay-dependent controllers. We ¯rst consider the design prob- lems for uncertain linear NCSs. In this case, state feedback controllers and dynamic output feedback controllers are designed to satisfy both stability and disturbance at- tenuation requirements for this class of NCSs. Moreover, a robust fault estimator that ensures the fault estimation error is less than a prescribed performance level is designed. We further go on to address the control problems for uncertain nonlinear NCSs. The nonlinear plant is ¯rst described by the T-S fuzzy model. Based on this model, stability analysis, disturbance attenuation, and fault estimation problems are studied for uncer- tain nonlinear NCSs. It should be noted that system uncertainties, disturbances and noises are addressed in both cases. The existence of such controllers and fault estimators are given in terms of the solvability of bilinear matrix inequalities. Iterative algorithms are proposed to change this non-convex problem into quasi-convex optimization problems, which can be solved e®ectively by available mathematical tools. Finally, to demonstrate the e®ectiveness and advantages of the proposed design methodologies in this thesis, numerical examples are given in each designed control systems. The simulation results show that the proposed design methodologies can achieve the prescribed performance requirements.

The aim of this thesis is the development of an understanding of some of the Limitations involved in the design of active filters. This introduces the idea of imposing an upper bound on the amplitude of the input voltage to an active filter such that the distortion, introduced, in the input stage of the operational amplifier, is Less then a value specified in the design, and investigating theoretically the errors in the frequency response of the actual circuit, caused by the operational amplifier which is considered linear but nonideal in that the analysis includes the finite input impedance and output conductance as well as the single-pole rolloff characteristic. The results of this theoretical research have been incorporated into a package of highly interactive computer programs, collectively called the Active Filter synthesis program, for the design of minimum-phase lowpass, highpass, bandpass, and bandstop active filters, the group-delay equalization of these filters and also of both unloaded, and loaded telephone Lines, and the displaying of their ideal frequency responses. The above-mentioned research arose from the design and construction of an experimental 600/1200 Baud, Modem, the filters in which provide a practical application of these developments. / Whole document restricted, but available by request, use the feedback form to request access.