This thesis presents an effective technique for interference control with the use of frequency selective surfaces (FSSs) in indoor wireless environments. An FSS with a bandstop frequency response was applied to an existing wall as a wallpaper to transform the wall into a frequency- selective (FS) wall. The FS-Wall can be made to deliberately filter out undesired interference, and accordingly improve wireless system performance. In-situ measurements have shown that the FS-Wall prototype can attenuate 5.3GHz{5.8GHz (IEEE802.11a) transmissions by 15dB in addition to the unmodified wall attenuation, whereas other radio services, such as cellular telephony at 1.8GHz, experience only little attenuation. The FS-Wall created performed consistently (with acceptable attenuation levels) with varying signal incident angles from 0± to 56±. The 15dB reduction in signal strength is considered sufficient to isolate a system from external interference, and could potentially improve a WLAN system throughput by 2.2 times. The FSS performance has been examined intensely by both equivalent circuit modelling and practical measurements. Factors that influence FSS performance such as the FSS element dimensions, element conductivities, dielectric substrates adjacent to the FSS, and signal incident angles were investigated. By keeping the elements small and densely packed, a largely angle- insensitive FSS was developed as a promising prototype for FS-wallpaper. Such an FS-wallpaper can be applied directly to the wall (with no intervening spacing) with insignificant mutual interaction between the FSS and the wall. Accordingly, the resultant FS-Wall can be modelled by cascading the effects of the FS-wallpaper and the wall. Good agreement between the modelled and the measured results was observed, which suggests that the equivalent circuit model can be used confidently to assist FSS design. Fabrication techniques and practical installation issues associated with the development of FSS for indoor wireless applications were also investigated in this thesis. With the use of an angle-insensitive bandstop FSS, this research has demonstrated a feasible solution for mitigating external interference into indoor wireless systems. This research work has linked the fields of antenna design, communication systems and building architecture.

This thesis considers the scattering of small amplitude water waves, obliquely incident on a set of floating elastic plates occupying the entire water surface. The problem is twodimensional and assumes invariance in the width of the plates. All non-linear physical effects are neglected. The plates are floating on a body of water of finite depth and each plate has uniquely defined properties. The problem is formulated by imposing boundary conditions on the eigenfunction expansion of Laplace’s equation. A set of transmission and reflection coefficients is generated, which is solved by applying the edge conditions and matching at each plate boundary. We label this solution method the Matched Eigenfunction Expansion Method (MEEM). The problem is solved for a variety of edge conditions including free, clamped, sliding, springed and hinged. To verify the MEEM results, the problem is also solved using a Green Function Method. The convergence of the two methods is compared and found to be almost identical. The MEEM is used to simulate wave–ice interaction in the Marginal Ice Zone (MIZ). The model removes the resonance effects and predicts that the transmitted energy is independent of floe length, provided the wavelength is more than three times the floe length. The model predicts an exponential decay of wave energy with distance of propagation through the MIZ, which agrees with experimental findings. The results have been summarised in a graph with the attenuation coefficient expressed as a function of period for various floe thicknesses. We also provide an estimate of the attenuation coefficient using an approximation theory. The displacements of the MEEM are compared against a series of laboratory experiments performed in a two-dimensional wave-tank and show good agreement. The attenuation model results are compared against a series of field experiments carried out in the Arctic and off the West Antarctic Peninsula. Generally, the decay rates of the model agree well with the field experiments in diffuse ice. We suggest that factors other than wave scatter are relevant in models of wave-attenuation in non-diffuse ice.

The development of a large-signal power transistor model applicable at radio frequencies is described. This model which has its basis in the classical large-signal models is valid for cut-off and active region operation but does not include saturation operation. The model is intended primarily for use in broadband linear radio frequency amplifier applications and is useful up to frequencies of the order of 1/15 f┬. The model is described by two first order nonlinear differential equations and a number of algebraic equations. Equation coefficients are determined from measurements made on the devices under study. Two methods are described for the solution of the model equations. The first and principal method is an iterative one requiring computer assistance whilst the second is analytical and depends upon piecewise linearisation of the device transfer characteristic. This analytical method whilst in some respects inadequate, e.g. distortion level predictions, is easy to implement and despite its limitations affords useful insight into output power capability and frequency limitations of specific devices. The model contains all transistor nonlinearities and parasitic elements of significance and an important feature is the inclusion of device temperature as a model variable, resulting in good accuracy over a wide range of operating conditions. A simplified input impedance representation is evolved and it is demonstrated that input impedance measurements provide a useful window on model structure and aid in the evaluation of parameter values.

The increasing use of fibre reinforced polymers in structural components often requires an accurate assessment of the strength of the component. The strength of composite materials is usually based on the strength of an individual lamina. This is then combined in a manner depending on the orientation of the plies within the laminate. The actual failure process is often ignored in this type of analysis. Composite failure is the result of damage accumulation from a number of failure modes, in particular, fibre failure, matrix failure and failure of the interface between the fibres and matrix. Measurement of the interfacial strength requires specialised testing techniques in order to obtain accurate characterization of the interfacial failure processes. This research uses a double torsion specimen reinforced with fibres in a number of configurations. The testing techniques developed allow the interaction of a matrix crack with fibres, resulting in the failure of the interface. Finite element analysis has been used to gain an insight into the deformation mechanisms. A compliance change analysis has been developed so that the load in the fibres can be calculated. Results from the finite element analysis confirm the analytical procedures and show that, for the fibre/resin combination tested, the interface has a lower fracture toughness than the matrix material. The interaction between the fibres and matrix shows that the mechanism of fibre bridging inhibits the propagation of matrix cracks. This produces an apparent increase in the toughness of the composite system. To confirm the failure processes occurring, the technique of acoustic emission has been used to monitor the development of the specimen failure. In line with other workers, it is shown that matrix failure produces low amplitude events and interfacial failure produces mid amplitude events. Fibre failure did not occur to any significant degree. This thesis shows how the contribution from the presence of an interface affects the fracture of composite materials and how, via the reinforced double torsion specimen, this contribution can be measured and interpreted.

This thesis explores the seismic analysis and design of post-tensioning concrete masonry (PCM) walls. Using unbonded post-tensioning, walls are vertically prestressed by means of strands or bars which are passed through vertical ducts inside the walls. As the walls are subjected to lateral displacements (in-plane loading), gaps form at the horizontal joints, reducing the system stiffness. As long as the prestressing strands are kept within the elastic limit, or at least maintain a considerable amount of the initial prestressing force, they can provide a restoring force, which will return the walls to their original alignment upon unloading. The key feature in this behaviour is attributable to the tendons being unbonded over the entire wall height, allowing for distribution of tendon strain over the entire length of the tendon. An extensive literature review found that post-tensioning of masonry has had limited application in seismic areas and that there currently are no specific code requirements for it’s use for ductile seismic design, largely as a consequence of little knowledge about the ductility capacity and energy dissipation characteristics. It was concluded that structural testing of PCM walls and concrete masonry creep and shrinkage testing were essential to advance the understanding of this construction type. Creep and shrinkage experiments confirmed that long term prestress losses are considerable in both grouted and ungrouted concrete masonry, and must be taken into account in design. It was concluded that it is essential to use high strength steel for prestressing of PCM in order to reduce long term losses. Structural testing confirmed that fully grouted unbonded post-tensioned concrete masonry is a competent material combination for ductile structural wall systems. In particular, PCM walls strengthened in the flexural compression zones with confining plates are expected to successfully withstand severe ground shaking from an earthquake. It was suggested that partially and ungrouted PCM walls may suitably be used in strength design (non-ductile). The proposed prediction method for wall in-plane behaviour was validated by experimental results. Good correlation between predictions and results was found. Displacement spectra were developed for ductile seismic design of PCM walls. These can be used to accurately estimate the displacement demand imposed on multi-storey PCM cantilever walls.

This thesis is divided into four parts. The first part discusses the problem of using prestressed concrete for earthquake resistant structures, and examines the "equivalent viscous damping" approach to the measurement of structural damping. Part two describes the reversed cyclic testing of prestressed concrete members: end moments were applied to the members to simulate earthquake loading, and measurements were made of stiffness and damping energy. An analytical method of obtaining moment - rotation curves for prestressed members, taking account of curvature concentration at the tension cracks, is presented in part three. The last part is a study of the response of an idealized prestressed concrete structure to a recorded earthquake ground motion. The test results given in part two are used to define the properties of the idealized structure.

System-on-a-chip (SoC) designs have gained immense popularity as they provide designers with the ability of integrating all components (called IPs) of an application-specific computer system onto a single chip. However, one of the main bottlenecks of the SoC design cycle is the validation of complex designs. As system size grows, validation time increases beyond manageable limits. It is desirable that design inconsistences are found and fixed early in the design process, as validation overheads are significantly higher after IPs are integrated. This thesis presents a range of techniques for the automatic verification and design of SoCs that aim to reduce post-integration validation costs. Firstly, local module checking algorithm, a practical implementation of module checking, is presented. This technique allows for the comprehensive verification of IPs such that they guarantee the satisfaction of critical specifications regardless of the SoC they are used in. Local module checking is shown to be able to validate IPs in much lesser time on average than global module checking, and can help in handling many important validation tasks much before the integration stage. Next, a number of protocol conversion techniques that assist in the composition of IPs with incompatible protocols is presented. The inconsistencies between IP protocols, called mismatches, are bridged by the automatic generation of some extra glue-logic, called a converter. Converters generated by the proposed techniques can handle control, datawidth and clock mismatches between multiple IPs in a unified manner. These approaches ensure that the integration of IPs is correct-by-construction, such that the final system is guaranteed to satisfy key specifications without the need for further validation. Finally, a technique for automatic IP reuse using forced simulation is presented, which involves automatically generating an adaptor that guides an IP such that it satisfies desired specifications. The proposed technique can generate adaptors in many cases where existing IP techniques fail. As it is guaranteed that reused IPs satisfy desired specifications, post-integration validation costs are significantly reduced. For each proposed technique, a comprehensive set of results is presented that highlights the significance of the solution. It is noted that the proposed approaches can help automate SoC design and achieve significant savings in post-integration validation costs.

A new model is presented to explain the results of tracer tests of reservoirs. The flow field model is two-dimensional and can include multiple wells, background flow and a high permeability fracture of finite length or a barrier of finite length - likely features of a reservoir in fractured rock. The flow field is represented by a complex potential. This enables the accurate calculation of the time for tracer to travel along the streamline linking the release position and the observation well. The shape of the concentration curve measured at the observation well is governed by dispersion. Two types of dispersion are considered – small scale dispersion and large scale dispersion. Small scale dispersion is due to interaction with the rock matrix and to small scale variations in velocity (not included in the flow field model), in the neighbourhood of a streamline. Large scale dispersion is due to the spread of tracer over streamlines which have different travel times to the observation well and may go to different observation wells. In the literature, small scale dispersion models are used to match the concentration curves for individual wells. Here it is shown that models with differing small scale mechanisms give equally good matches to Wairakei data and that response curves for small scale dispersion and large scale dispersion are similar. This means that the shape of a concentration response curve gives little information about reservoir structure. The important results from a tracer test are whether tracer is detected at each observation well and the travel times to the wells that respond, in conjunction with the locations of the release and production wells. This new approach to analysing tracer tests is used together with the flow field model to deduce the permeability structure and flow field of a simple hypothetical reservoir and of the Wairakei (New Zealand) geothermal reservoir.

This thesis describes the development of a bus crew scheduling method, based on a set partitioning model, for the Christchurch Transport Board, New Zealand. It also examines in detail the effects of the high degree of degeneracy in scheduling set partitioning models. Degeneracy can cause severe computational difficulties because it inflates the number of simplex iterations needed to solve the set partitioning linear programme. In this thesis, it is shown that a maximum-pivot leaving variable criterion can considerably improve the performance of the simplex method, but that this alone is insufficient. Experiments with several degeneracy-resolving techniques have been performed on a class of highly degenerate problems arising from an air crew rostering application, and the results are discussed. Before the set partitioning model can be applied to scheduling, the problem size must be heuristically reduced. Therefore the overall Christchurch system is divided into several subsystems which are solved sequentially. Also, a three-stage method has been developed which essentially considers each type of duty individually. At the first stage, meal-breaks are allocated carefully to reduce the effects of the loss of interaction among the subproblems. A further heuristic reduction technique is then applied to each subproblem, not only to reduce its size but also to improve its integer properties. The resulting solution method has been applied to the Christchurch weekday scheduling problem. A special technique for the Sunday scheduling problem has also been developed. The two methods are described and the promising results which have been achieved are discussed. / Whole document restricted, but available by request, use the feedback form to request access.

This work presents a numerical model for simulating the response of a geothermal reservoir to exploitation. The techniques developed are more efficient and in many ways superior to those of previous investigators. The model is capable of yielding a description of transient mass and heat flow in either a one- or two-dimensional reservoir defined by Cartesian or cylindrical coordinates. The techniques enable simulation of a geothermal flow in all three thermodynamic states – compressed water, two-phase and superheated steam regions – and transitions between these states. The model is able to simulate a geothermal system where the presence of carbon dioxide as a second component influences exploitation response. Results are presented for a range of reservoir states. The effects of different physical parameters are considered. The usefulness of the model for looking at real systems is demonstrated by simulating the development of Wairakei and Broadlands geothermal areas in New Zealand.