No description available.

This thesis covers research in the field of non-cooperative target recognition given the limitations of modern air defence surveillance radars. The potential presence of low observable manned or unmanned targets within the vast surveillance volume demand highly sensitive systems. This may again introduce unwanted detections of single birds of comparable radar cross section, previously avoided by use of wide clutter rejection filters and sensitivity time control. The demand for methods effectively separating between birds and slow moving manmade targets is evident. The research questions addressed are connected to identification of characteristic features of birds and manmade targets of comparable size. Ultimately the goal has been to find methods that can utilize such features to effectively distinguish between the classes. In contrast to the vast majority of non-cooperative target recognition publications, this thesis includes non-rigid targets covering a range of dielectric properties and targets falling in the resonant and Rayleigh scattering regions. These factors combined with insufficient spatial resolution for classification require alternative approaches such as utilization of periodic RCS modulation, micro-Doppler- and polarimetric signatures. Signatures of birds and UAVs are investigated through electromagnetic prediction and radar measurements. A flexible and fully polarimetric radar capable of simultaneous operation in both L- and S-band is developed for collection of relevant signatures. Inspired by the use of polarimetric radar for classification of precipitation covered in the weather radar literature, focus has been on using similar methods to recognize signatures of rotors, propellers and bird wings. Novel micro-Doppler signatures combining polarimetric information from this sensor is found to hold information about the orientation of such target parts. This information combined with several other features is evaluated for classification. The benefit from involving polarimetric measurements is especially investigated, and is found to be highly valuable when information provided by other methods is limited.

The main effect of noise on the performance of a non-linear oscillator may be characterised in two ways: a) by a broadening in the output spectrum, or b) by an uncertainty in the oscillator frequency (i.e. as measured by zero counting method). There are many methods for analysing this problem. In this work a new method using generalised definitions of amplitude and phase is presented. The contents of the chapters are as follows: Chapter 1. An introduction to the problem of noise in non-linear oscillators is made. After describing main sources and effects of noise, a brief account of existing methods is given. Method of the work is introduced and compared with other approaches. Finally, a statement of originality is made. Chapter 2. Normalized equations are derived from physical circuits. Various solutions of the noiseless oscillator equation are presented. Chapter 3. The potential function are developed and their relationship to amplitude and phase demonstrated. A generalisation of phase and amplitude is made. Chapter 4. Analysis of the noise is made by transforming the oscillator equation into the curvilinear co-ordinates formed by the equipotentials of the potential functions. Chapter 5. Discussion of the results and suggestions for future work are made.

In this thesis, the application of state space theory to the analysis and synthesis of electrical networks is considered. The state equations consist of a set of first order linear differential equations of the form dx/dt = Ax + Bu where u is the input vector and x the,state vector. The problem of setting up these equations for the case of RLC active networks, containing controlled generators, is examined. A topological approach is taken which gives a method for finding, by inspection, the maximum number of state equations, the maximum order of complexity, for a class of networks. An algebraic approach is also taken. A method is suggested for forming the equations and a way of determining the order of complexity given. It is shown that, with very small restrictions the problem of finding the maximum order of complexity can be greatly simplified. Necessary and sufficient conditions are given for the network to possess a unique solution. The relationship between the concepts of system theory and network synthesis are considered. In particular, the relationship between the order of complexity and the degree is considered. The problems associated with poles at infinity are considered and a more general transformation suggested for generating all equivalent irreducible realizations for systems with poles at infinity. The use of state space theory for network synthesis is reviewed and the problems of active network synthesis are considered.

The problems of high speed photography are discussed with special reference to the high framing rates mad high sensitivities which can be obtained using image tube cameras. A photoelectronic electron image store and analyser which can be used to overcome the problems of synchronisation is discussed and its constructional details and associated electronic circuitry are described. The shuttering action of the device is analysed in detail in terms of the design of the gating electrode structure and the shape of the applied electrical pulses. The spatial and temporal resolution of the device is discussed. A deflection system is developed so that the device can be operated at a framing rate of ~ 109 f.p.s. using an oscilloscope trace as a simulated event. Synchronisation to the breakdown of a 20 millijoule spark is demonstrated.

With recent developments in power systems the demand on alternators to operate in the leading var region at light loads is increasing. With these developments in view, the effect of automatic direct and quadrature axis excitation regulators on the stability of an alternator connected to an infinite bus through a series reactance is investigated. The study is limited to small oscillations, and the stability analysis is done using conventional techniques, such as, the root-locus, the Nyquist, the Routh, and some consideration is also given to state variable methods. A proportionate voltage regulator in conjunction with the field current feedback for the direct-axis excitation regulation is investigated. The limitations and the usefulness of the scheme are discussed. It is mathematically shown that at zero power no direct-axis excitation regulation scheme can extend the steady state reactive absorption beyond a limit de-pending on the quadrature-axis synchronous reactance. On the other hand the quadrature-axis excitation regulation can extend the steady state reactive absorption limit. Out of the various signals theoretically considered for the quadrature-axis excitation regulation the rotor angle signal proves to be the most effective. A proportionate angle regulator on the quadrature-axis acts like a position control servo-system and ideally can extend the steady state reactive absorption limit depending on the transient reactance at all power levels, but the gain range of such a regulator is poor. A proportionate regulator with first and second derivative terms can however increase the reactive absorption limit and the gain range many times compared with a proportionate regulator. Experiments were performed on a model machine in conjunction with simulated regulators to determine the steady state stability limit curves as a function of regulator gain. For some regulators the open-loop frequency response loci were determined from the closed-loop frequency response test for small oscillations. All the experimental and theoretical results show reasonable agreement.

Much importance has been ascribed by historians from a number of traditions to co-operation between academic scientists and their counterparts in industry. However, while some knowledge of the extent of this 'science-industry relationship' in Britain has been gained, little of the historical work done so far has been sufficiently detailed to bring out the nature of this link - especially in the period after industrial research began to be formalised in separate departments dedicated to scientific research and development. Though a general overview of the situation nationwide has been gained, we have little evidence of how firms and universities cooperated in concrete instances in the changing context of post-WWI Britain. The present thesis aims to help £ill this gap by concentrating on Manchester, Britain's largest industrial region in the period from WWI to the 1960s, and investigating one of the two large sciencebased firms in the area to have had extensive contacts with the local university science departments. The thesis adopts an approach which focuses on the wide variety of cooperative ventures which were undertaken by local actors, in terms of the importance which they themselves attributed to them. This methodology underlines the multi-faceted nature of the 'science-industry relationship' which, in the case of Manchester, ranged from the scientific and educational, to the institutional and political. A number of new archival sources are used including the research department reports of Metropolitan Vickers Co. Ltd. and the personal papers of the scientists, industrialists and university managers who collaborated in furthering cooperation in scientific research in Manchester. It is demonstrated that a university-industrygovernment relationship existed from the very beginning of the period considered, but that it was initially largely informal, depending on individuals and the networks they formed, was varied, that it grew and developed only as and when concrete needs and opportunities arose and, far from being determined by government policy, was actually fundamental in shaping it.

The major problem encountered by an airborne bistatic radar is the suppression of bistatic clutter. Unlike clutter echoes for a sidelooking airborne monostatic radar, bistatic clutter echoes are range dependent. Using training data from nearby range gates will result in widening of the clutter notch of STAP (space-time adaptive processing) processor. This will cause target returns from slow relative velocity aircraft to be suppressed or even go undetected. Some means of Doppler compensation for mitigating the clutter range dependency must be carried out. This thesis investigates the nature of the clutter echoes with different radar configurations. A novel Doppler compensation method using Doppler interpolation in the angle-Doppler domain and power correction for a JDL (joint domain localized) processor is proposed. Performing Doppler compensation in the Doppler domain, allows several different Doppler compensations to be carried out at the same time, using separate Doppler bins compensation. When using a JDL processor, a 2-D Fourier transformation is required to transform space-time domain training data into angular-Doppler domain. Performing Doppler compensation in the spacetime domain requires Fourier transformations of the Doppler compensated training data to be carried out for every training range gate. The whole process is then repeated for every range gate under test. On the other hand, Fourier transformations of the training data are required only once for all range gates under test, when using Doppler interpolation. Before carrying out any Doppler compensation, the peak clutter Doppler frequency difference between the training range gate and the range gate under test, needs to be determined. A novel way of calculating the Doppler frequency difference that is robust to error in pre-known parameters is also proposed. Reducing the computational cost of the STAP processor has always been the desire of any reduced dimension processors such as the JDL processor. Two methods of further reducing the computational cost of the JDL processor are proposed. A tuned DFT algorithm allow the size of the clutter sample covariance matrix of the JDL processor to be reduced by a factor proportional to the number of array elements, without losses in processor performance. Using alternate Doppler bins selection allows computational cost reduction, but with performance loss outside the clutter notch region. Different systems parameters are also used to evaluate the performance of the Doppler interpolation process and the JDL processor. Both clutter range and Doppler ambiguity exist in radar systems operating in medium pulse repetitive frequency mode. When suppressing range ambiguous clutter echoes, performing Doppler compensation for the clutter echoes arriving from the nearest ambiguous range alone, appear to be sufficient. Clutter sample covariance matrix is estimated using training data from the range or time or both dimension. Investigations on the number of range and time training data required for the estimation process in both space-time and angular-Doppler domain are carried out. Due to error in the Doppler compensation process, a method of using the minimum amount of range training data is proposed. The number of training data required for different clutter sample covariance matrix sizes is also evaluated. For Doppler interpolation and power correction JDL processor, the number of Doppler bins used can be increased, to reduce the amount of training data required, while maintaining certain desirable processor performance characteristics.

Radars and airborne electronic support measures (ESMs) systems are locked in a tactical battle to detect each other whilst remaining undetected. Traditionally, the ESM system has a range advantage. Low probability of intercept (LPI) waveform designers are, however, more heavily exploiting the matched filter radar advantage and hence degrading the range advantage. There have been literature and internal, SELEX Galileo proposals to regain some ESM processing gain of low probability of intercept (LPI) waveforms. This study, however, has sought digital signal processing (DSP) solutions which are: (1) computationally simple; (2) backward-compatible with existing SELEX Galileo digital receivers (DRxs) and (3) have low resource requirements. The two contributions are complementary and result in a detector which is suitable for detection of most radar waveforms. The first contribution is the application of spatially variant apodization (SVA) in a detection role. Compared to conventional window functions, SVA was found to be beneficial for the detection of sinusoidal radar waveforms as it surpassed the fixed window function detectors in all scenarios tested. The second contribution shows by simulation that simple spectral smoothing techniques improved DRx LPI detection capability to a level similar to more complicated non-parametric spectral estimators and far in excess of the conventional (modified) periodogram. The DSP algorithms were implemented using model-based design (MBD). The implication is that a detector with improved conventional and LPI waveform detection capability can be created from the intellectual property (IP). Estimates of the improvement in SELEX Galileo DRx system detection range are provided in the conclusion.

A simple water balance model was applied to a micro-catchment water harvesting system for a semi-arid area in the North-Eastern part of Jordan. Two Negarim micro-catchment water harvesting systems were built at Al-Khanasri research station. A Randomized complete block design (RCBD) in factorial combination was used with six treatments and three replicates. Each plot was divided into two parts; a runoff area, and a run-on area. Two different treatments were used for the catchment area, these were: compacted (T1) and Natural treatments (T2). Three treatments were used for the run-on area, these were: disturbed (S1), stones (S2), and crop residue mulch (S3). Soil water content was measured over a depth of 0-1 m during the seasons 96-97 in these micro-catchments. In this model; daily rainfall, runoff, and evaporation were used. Runoff was calculated by the curve number method; evaporation was calculated by the Penman equation, the Priestley and Taylor method and the Class A pan approach. The least squares method was used for optimizing model parameters. The performance of the model was assessed by different criteria, such as root mean square error, relative root mean square error, coefficient of determination and the Nash-Sutcliffe efficiency method. The performance of the micro-catchments system was also evaluated. Results showed that with limited but reliable hydrological data good agreement between predicted and observed values could be obtained. The ratio of water storage in a one meter soil depth to the rainfall falling on each catchment indicated that T1S2 and T1S3 have the highest values in size1 plots while T2S1 and T2S2 have the highest values in size 2 plots. Modelling results showed that for all the size 1 plots, the required ratio of the cultivated to catchment area, (C/CA), required to ensure sufficient harvested water, was less than the actual ratio used in the experimental design. For the size 2 plots this was only true for the T1 treatments. Consequently for the majority of plot sizes and treatments, the results showed that a smaller catchment area is capable of providing sufficient harvested water to meet crop growth requirements. The experimental ratio was based on a typical yearly design rainfall for the region having either a 50% or 67% probability of occurrence. Results also indicated that using stones and crop residue as mulch on the soil surface in the cultivated area was effective in decreasing the evaporation rate. S3 was more efficient than S2 as it stored more water due to the higher infiltration rate (12.4 cm/hr) when compared to S2 (4.1 cm/hr).