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Item Open Access Acoustic emission pulse analysis: an integrated system for transducer calibration and signal processing(1982-10) Oliveras, Juan M.; Bannister, R. H.The present thesis covers the pioneering effort of establishing an infrastructure for conducting research into the analysis of Acoustic Emission signatures, with emphasis being placed upon the recovery of the true surface waveform for a given transient input. The topics covered in this work are: The p·rovi s ion of the necessary computer software for the handling and processing of the data. Here, a method is included for the correction of phase errors introduced by the sampling/multiplexing of ·the signals, which provides the basis for the implementation of data convolution.techniques in the frequency domain. J°he development of an experimental rig and source of excitation, later applied to the design of transducers. The development of a new transducer configuration, capable of producing a relatively flat frequency response (±7dB) over the frequency range 300 KHz - 2 MHz. The development of a procedure for the calibration of transducers, based upon a modified reciprocity method. The technique produces the calibration of transducers in relative terms, requiring a comple- . . mentary method to provide the reference level for the calibration. As a means of assessing the proposed techniques, the transducer calibration was applied to the de-convolution of pulses generated with a step forcing function, and the results compared with an equivalent theoretical model previously published.Item Open Access Aerodynamic surface pressure measurement in atmosphere and wind tunnel on a vertical axis wind turbine blade using pressure transducers(1989-09) Oram, C. E.; Garside, A. J.; Hales, R. L.; Moss, J. B.Blade aerodynamic loads during operation of a wind turbine are poorly understood. Better measurements of these forces are needed for the design of more cost effective turbines. Existing estimates have been inferred from strain gauges in the blade structure, but such measurements are confused by the complexity of the blade's structural response. This present work has pressure tapped the blade surface and recorded at high speed, giving a highly detailed picture of dynamic events and blade loads. A modular blade was constructed for the 6m diameter Rutherford Appleton Vertical Axis Wind Turbine and instrumented with 32 semiconductor pressure transducers. A flow probe using a further three transducers projected ahead of the blade during some of the tests. The instrumented module was also operated in the oscillating mounting of the University of Glasgow's 1.6m by 2.4m wind tunnel. 1760 revolutions of data were collected in atmosphere with blade speed ratios down to about 2.0 and with a variety of blade leanout angles. Some 118 runs of a variety of waveform types and Reynolds numbers from 0.3 to 1.1 million, were collected from the blade in tunnel. Analysis of transducer calibrations concluded that the novel temperature correction technique used allowed pressure readings to 40Pa or better with 95% confidence. Confidence in measured pressures has allowed use of leading edge stagnation point pressure and position as a measure of wind in the rotor flowfield and as a surrogate measure of blade angle of attack. Blade surface pressures and integrated forces show the progression of dynamic stall with increase in wind speed, the dominance of the upstream blade pass in usefulness at low and moderate windspeeds and the rough equality at high windspeeds. Comparisons of wind tunnel and on-rotor data show much lower force and moment coefficients in atmosphere. Rotor 'goodness1 ratios of average blade tangential force to maximum blade and rotor force coefficients peak at a blade speed ratio of about 2.8. Goodness ratios show a mixed pattern with blade leanout. Analysis of pressure coefficient traces through stall indicate a mixed stall type starting at mid chord, moving to leading edge and thence to trailing edge.Item Open Access The aerodynamics of slender aircraft forebodies at high angle of attack.(2001-08) Petterson, Kristian; Poll, D. I. A.; Sillén, M.; Arlinger, B.High angle-of-attack aerodynamics has been the focus of much attention as a result of the drive to increase combat aircraft manoeuverability and thereby improve survivability. A key factor in this regime is the behaviour of the complex vortical wake generated by the forebody. Even at zero yaw, the shear layers and vortex pairs which are symmetric at moderate angles of attack (alpha) can become highly asymmetric as alpha is increased. This can lead to large sideforces and yawing moments which may exceed available control power. Computationally simulating high-alpha forebody flowfields is known to be a challenging problem. This thesis details the evaluation and enhancement of the CFD code NSMB with the objective of improving qualitative and quantitive predictions of the flowfield around fighter-type forebodies throughout the angle-of-attack range. Results on a tangent-ogive body confirmed that computing asymmetric flow required the introduction of a space- and time-fixed surface excrescence or the use of a non-symmetric solution algorithm to simulate flow instabilities via transient numerical error. Although solution stability problems were encountered, results with the non-symmetric algorithm showed promise. Suspected turbulence modelling issues were addressed by implementing the k-w family. Having established a methodology, solutions were obtained for the forebody of a current fighter aircraft, the Saab JAS-39 Gripen. The computed data shows excellent experimental agreement for 0° ≤ a ≤50° over the clean geometry but the inclusion of a nose pitot probe was seen to destabilise the calculation and prevent convergence. Finally, a single vertical nose strake or ‘rhino horn’ was added. When undeflected, this stabilised the flowfield, reduced solution oscillation and negated sideforce. Deflecting the hom produced a stable flowfield with non-zero sideforce. Similar devices may be used, together with engine thrust-vectoring, in the next generation of combat aircraft and may also be added to existing airframes as a MLU.Item Open Access The aeroelastic behaviour and response to turbulence of a class of high performance tailless sailplanes.(1978-09) Banerjee, J. R.; Griffin, K. H.The symmetric flutter and response characteristics of a class of tailless .sailplanes-:are investigated combining rigid--body dynamics with elastic modes of deformation. The methods used are based on the normal mode approach through the use of finite element techniques and unsteady aerodynamic theories in two dimensional flow. The flutter speed and. aeroelastic modes are critically examined and the results are compared with those of a tailed sailplane. The flutter speed of the tailless sailplane is found to be low in comparison with those of orthodox layout and a parametric study is undertaken to locate-the reason for this; recommendations are made for improvements. A method is proposed for the analysis of the. short period oscillation characteristics of flexible aircraft allowing for the-effects of unsteady aerodynamics. - It is then applied to the type of tailless sailplane under investigation. The response to gusts and turbulence is evaluated using both statistical and discrete gust methods. Comments are made from the calculated results about the aeroelastic behaviour of tailless sailplanes in general. Computer programs developed for detailed aero-elastic calculations are presented.Item Open Access Airblast atomization : the effect of linear scale on the mean drop size(1978-12) El-Shanawany, M. S. M. R.; Lefebvre, A. H.Stationary prefilming-cup airblast atomizers, in which the fuel is first spread into a thin cylindrical sheet and then exposed on both sides to high velocity air, have several important advantages over other common methods of fuel injection in their application to continuous combustion systems. This thesis reports the results of a detailed programme of research on airblast atomization directed primarily to the investigation of the effect of atomizer linear scale, or size, on the mean drop diameter of sprays and, to the provision of a comprehensive picture of the performance of thin-sheet airblast atomizers over a wide range of working conditions. Three geometrically similar atomizers giving cross-sectional areas in the ratio of 1 : 4 : 16 were used; covering the range of prefilming cup diameter, D, from 19.05mm. to 76.20 millimeters, and were capable of handling various liquids at flow rates from 0.003kg/s up to 0.225 kg/s, at fuel pressures below 33 x 10^ N/m^ (about 50 p.s.i.). . It was found that atomizer scale has an appreciable direct effect on atomization quality. The Sauter mean diameter of low liquid viscosity sprays increases with the 0.44 power of atomizer linear dimension (D), while for liquids of high viscosity this effect is slightly higher.Item Open Access Airline deregulation: an analysis under different regulatory and operating environments(1989-07) Etemadi-Nejad Alamdari, F.; Cordey-Hayes, M.Like other transportation modes the airline industry has a long history of government regulation. In recent years however the theoretical and empirical bases for air service regulatory schemes have been questioned by opponents of such policies. In Western Europe there have been pressures for relaxation of regulation of the air transport industry with respect to air fares, service frequency and market access. Because changes in such public policies are likely to have a major impact, there is a considerable interest in their possible implications. It is the objective of this study to explore the interactions between fare and service frequency in different competitive environments, and to examine the rivalrous behaviour of airlines and their possible equilibrium position under deregulation. The study also considers the effect of a competing mode (rail) on air carriers performance under various competitive conditions. The individual carrier's performance is quantified in terms of fare, service frequency, resulting generalised costs, market share and financial results. A competition model is developed by which the objectives set above are achieved. The study is divided into three parts. The first part provides a framework within which the competition model can be built. This part also generates the policy questions which must be addressed, should relaxation of regulation take place in Europe. The second part explains the structure of the competition model and its characteristics. The assumptions upon which the model is built and its limitations are also discussed. The model consists of three sub-models: the market share model, the costing model and the reaction model. In the third part, with the aid of the model the policy questions generated in the first part are addressed and the general implications for carriers operating under different competitive conditions are discussed. Finally the technical and the policy conclusions are discussed. It is generally concluded that: competition results in lower fares and a more efficient airline industry; the impacts of competition are not evenly distributed amongst markets, routes and carriers; and the competition on equal terms amongst carriers plays an important role in maintaining the effectiveness of deregulation.Item Open Access An alternative approach to inventory control and forecasting methods in the public and private sectors(1989-10) Southworth, M. S.; Saw, R.This research was spawned by the questions and answers from the 33rd report of the committee of Public Accounts session 1983-84. The Key to the ensuing arguments about the report hinged on 3 words "Best Commercial Practice". In order to deduce a baseline the present systems of public and private concerns were investigated to find out what is actually being done. The thesis research examined what is actually happening today and in certain instances where companies have been prepared to speculate (and be open) what they believe they will be doing in the future. A review of the American and Germany Army systems has been included to ensure that the question 'best practice' could be examined between other systems having identical constraints^ The research includes both new and old literature by both academics and practitioners of the science of inventory. The hypothesis is that inventory is regarded in the singular whereas for all large concerns it should be considered in the plural, how the plural should be defined, what and how these sub inventories are and how they should be identified. The hypothesis whilst proven has the caveat that it only relates to inventories which are subject to similar structures and constraints. The effect of implementing the hypothesis in a working environment, possible areas for future work and research, largely due to the embryonic technical breakthroughs in information technology are examined briefly. The recommendations and conclusions represent an alternative approach to inventory control and forecasting not previously covered by either theoretical or practical work.Item Open Access Analysis and prediction of the low speed flow over a highly swept wing(2000-11) Shires, Andrew; Garry, Kevin P.; Fulker, J. L.A combined experimental and theoretical study is described of the low speed flow over a highly swept and cambered wing that simulates the flow features of a transonic manoeuvre condition. The thesis is divided into two parts: Part I examines the research objectives from a customer perspective, with background information on the project history and funding sources. Since the research is aimed at improving the aerodynamic performance of low observable configurations, stealth technologies are discussed and their implications for combat aircraft wing flows. The management chapter of the thesis then discusses the influences affecting the decision making process for the acquisition of weapon systems in the UK. Part II describes the design of a highly swept and cambered wing that generates strong adverse pressure gradients near the trailing edge, leading to three-dimensional separations in this region. Using surface flow visualisation the nature of these flows is defined, indicating how the position of a separated streamline moves forward with increasing angle of incidence. These observations are confirmed by flow predictions using the SAUNA Computational Fluid Dynamics (CFD) method that solves the Reynolds Averaged Navier-Stokes equations, employing a two-equation turbulence model. The mechanism of the flow separation is also predicted using CFD, indicating that a separated stream surface reattaches at the wing trailing edge, forming a ‘tunnel’ of separated flow. To the authors knowledge this represents the first time that the main physical features of such a complex three-dimensional separated flow has been modelled using a CFD method. From an evaluation of the CFD methods employed, a design process has been proposed by which a wing designer can determine if wing flows over similar configurations remain attached. Additionally, the velocity magnitudes within parts of the separated shear layers and the wake are obtained using an optical non-intrusive measurement technique and give good agreement with the theory. -Item Open Access An analysis of fibre optic interferometer configurations for optical coherence tomography applications(2003-10) Beddows, Ruth; Tatam, Ralph P.The Michelson Interferometer has been the principal interferometer configuration for Optical Coherence Tomography (OCT) imaging. For OCT applications, in particular endoscopy, there may be polarisation induced signal fading due to environmental changes within the sample arm. The most significant cause of polarisation induced fading within OCT systems is suggested to be due to changes within the optical fibres. The Fizeau interferometer has been shown to eliminate this polarisation induced fading as the sample and reference arm experience the same environmental effects. However the Signal to Noise Ratio (SNR) o f the Fizeau configuration is lower than that o f the Michelson because a second processing interferometer is required. An investigation into suitable interferometer configurations for OCT was carried out in order to increase the performance o f the Fizeau interferometer compared with Michelson configuration. It was shown theoretically that by using a circulator and balanced detection, a standard Fizeau interferometer could achieve a signal to noise ratio (SNR) up to I8dB greater than the conventional Michelson interferometer and a comparable SNR to the Michelson interferometer optimised for power conservation. An analysis into the optical components used in OCT systems was carried out and the optimal Fizeau interferometer design was constructed. The Optimal design was shown to give an increase o f 26dB compared to the standard Fizeau interferometer relative to theoretical results using the same optical components. It was experimentally shown that the use o f an optical circulator within the Fizeau interferometer improves the SNR compared to the standard configuration.Item Open Access The application of computational techniques to the design of thermal ice protection systems(1990-03) Leah, C. W.; Eshelby, M. E.A bibliography citing 1350 references related to all aspects of aircraft icing is presented. An ice adhesion database has been compiled, and a survey of ice adhesion test rig designs is presented. An ice shear adhesion test rig is designed, manufactured and operated. The results are added to and compared with those in the database. The adhesion of ice accreted on metal and non-metallic composite aircraft propeller blades in flight is assessed. A one-dimensional thermodynamic study of ice accreted on a non-metallic composite propeller blade with ’built-in1 electrothermal de-icing system is effected and compared with a solid metal blade. A two-dimensional aerofoil icing prediction program is modified and executed in series with additionally created software to predict icing on aircraft engine air intake duct lips in flight. Hence a new de-icing system design method is developed to replace and improve upon an existing one. Validation of the new design method is initiated and a programme for its completion is presented. Icing predictions produced using the new method correlate well with expected values derived by several methods. The new design method is incorporated in the sponsoring companies business with an appropriate computer hardware/software system and employed, in parallel with the ’old’ approach (till validation completion), on commercial projects. Market response indicates a definite preference for the new design method. The ’non-technical’ and other related practical topics of implementing the new de-icing system design method, including specification and installation of computer hardware and software are discussed. Marketing, financial and other commercially oriented subjects are addressed in justifying the research and the implications of introducing the new design method into the commercial business of the sponsoring organisation are considered. This research programme forms a part of a large, long term icing research commitment. Continued research subjects and investigative routes including the integration of ice adhesion mechanical characteristics into the de-icing system design method are discussed together with their relationship to this and the overall icing research plan.Item Open Access The application of electrolytic photoetching and photopolishing to AISI 304 stainless steel and the electrolytic photoetching of amorphous cobalt alloy(1986-01) Talib, Talib Naji; Allen, DavidThe results presented cover broad aspects of a quantitative investigation into the elecrolytic etching and polishing of metals and alloys through photographically produced dielectric stencils (Photoresists). A study of the potential field generated between a cathode and relatively smaller anode sites as those defined by a dielectric stencil was carried out. Numerical, analytical and graphical methods yielded answers to the factors determining lateral dissolution (undercut) at the anode/stencil interface. A quasi steady state numerical model simulating the transient behavior of the partially masked electrodes undergoing dissolution was obtained. AISI 304 stainless steel was electrolytically photoetched in 10% w/w HC1 electrolyte. The optimised process parameters were utilised for quantifying the effects of galvanostatic etching of the anode as that defined by a relatively narrow adherent resist stencil. Stainless steel was also utilised in investigating electrolytic photopolishing. A polishing electrolyte (orthophosphoric acid —glycerol) was modified by the addition of a surfactant which yielded surface texture values of 70nm (Ra) and high levels of specular reflectance. These results were used in the production of features upon the metal surface through photographically produced precision stencils. The process was applied to the production of edge filters requiring high quality surface textures in precision recesses. Some of the new amorphous material exhibited high resistance to dissolution in commercially used spray etching formulations. One of these materials is a cobalt based alloy produced by chill block spinning. This material was also investigated and electro etched in 10% w/w HC1 solution. Although passivity was not overcome, by selecting suitable operating parameters the successful electro photoetching of precision magnetic recording head laminations was achieved. Similarly, a polycrystalline nickel based alloy also exhibiting passivity in commercially used etchants was successfully etched in the above electrolyte.Item Open Access The application of neural networks to spacecraft control(1994-08) Cooper, A.; Lewis, D. J. G.This thesis investigates how two neural network-based control techniques can be applied to a specific spacecraft control problem. The neural networks used are simple backpropagation networks, consisting of one or more tansigmoidal neurons (neurons with tanh transfer functions) in a hidden layer, and a linear neuron in the output layer. The neural network control techniques investigated here are Direct Model Inversion and Indirect Model Inversion. The spacecraft control problem is that of reducing the vibrations of a spacecraft payload. The source of the vibrations is a mass imbalance in one of the reaction wheels of the spacecraft. Four components are represented in the spacecraft model. These are rigid body inertia, solar array flexure, fuel slosh and payload vibration. A simple sinusoidal signal is used to model the disturbance torque produced by the reaction wheel mass imbalance. The complete model is broadly based on the Solar Heliospheric Observatory (SOHO) that is due for launch in 1995. Each of the neural network control techniques used is shown to be successful in reducing the effects of the disturbance torques on the spacecraft payload. However, in each case, a simple positional feedback gain term provides more effective and reliable control.Item Open Access Application of nonlinear control theory in weapon guidance and control(2001-03) Brundle, D.; Thomasson, P. G.This thesis considers the application of nonlinear control theory in two subjects pertinent to weapon applications. Initially, Section 2 considers the development of a simple nonlinear autopilot for a Laser Guided Bomb (LGB). Later a nonlinear autopilot design is developed using a Pulse-Width Modulated (PWM) controller derived from the method developed by Bemelli-Zazzera et al4. This is applied to an LGB utilising a “bang-bang” actuator, enabling the control surfaces to achieve a pseudo-proportional response. The PWM design stems from an equivalent Pulse Amplitude Modulated controller, which required a design technique to be developed for a linear autopilot and, in addition, simulation of an electro-mechanical actuator. Simulation demonstrated that the PWM controller can achieve the desired response but the design must incorporate actuator dynamics. Section 3 considers the use of nonlinear control theory to examine the nonlinear intercept equations using a Proportional Navigation (PN) guidance law. Using a simple heuristic example, PN is introduced and vector algebra used to develop a simple model of the intercept. The model is then used to illustrate the importance of the kinematic gain. Using the method pioneered by Ha et al16, Lyapunov theory is used to demonstrate that PN is a robust guidance law. Although generally derived assuming the target maintains rectilinear flight, Lyapunov theory is used to demonstrate interception is always possible provided the pursuer has sufficient manoeuvre advantage over the target. Noting that many missiles incorporate a 1 directional warhead, Lyapunov theory is used to design a time-varying rate bias that controls the direction of approach to the target. Simulation demonstrates that the guidance requirements are indeed achieved by this law but additional effort is required by the control system. In Section 3 it is demonstrated that the PN guidance law will always ensure an intercept, i.e. it does not by itself generate miss-distance. In the final part of Section 3, using adjoint software designed by Zarchan42, it is demonstrated that miss-distance develops in practical systems as the result of sub-system dynamicsItem Open Access The application of relative navigation to civil air traffic management(2000-08) Sangpetchsong, K; Allerton, David J.This thesis addresses navigation and guidance which will be required for air traffic management in Future Air Navigation Systems (FANS) and Free Flight. In particular, the thesis covers the issues of data fusion and integrity monitoring, to provide an adequate level of aircraft separation assurance, based on relative navigation (RELNAV). The evolution of air navigation systems is described. The principles of Kalman filtering and Joint Tactical Information Distribution System (JTIDS) RELNAV are covered. Sensor models of strapdown Inertial Navigation System (INS), Global Positioning System (GPS), and Automatic Dependent Surveillance-Broadcast (ADS-B) are developed in Matlab and integrated to form a hybrid navigation system. RELNAV algorithms for centralised and decentralised Kalman filtering are formulated, and their respective performances are analysed using Monte Carlo simulations for an airspace containing several aircraft. It is shown that RELNAV, based on the integration of INS and ADS-B, can enable aircraft to maintain safe separation independent of GPS, where it is assumed that an ADS-B datalink provides accurate time synchronisation. An alternative approach that integrates INS, GPS, and ADS-B is developed and analysed. It is shown that this approach is more applicable to civil aviation because it eliminates the needs to establish and manage several navigation communities simultaneously, in effect, exploiting GPS as the navigation controller. The source selection functions used for RELNAV are also developed, and the stability and performance of this technique is evaluated from simulation studies. A failure detection algorithm that monitors the residuals of a Kalman filter is derived and evaluated using Monte Carlo simulations of GPS failures. It is shown that this algorithm combines the use of likelihood functions and chi-squared tests, allowing both a false alarm rate to be selected and a failed sensor to be identified. Finally, an algorithm is developed for separation assurance to determine the probability that aircraft are closer than a pre-determined distance, taking into account flight path prediction errors. It is shown that this algorithm simplifies aircraft conflict detection in three dimensions and allows the conflict probability at a particular time to be determined. This approach is validated using Monte Carlo simulations of aircraft trajectories which include near-misses.Item Open Access The application of signal analysis techniques based on chaos theory to flow regime identification.(1996-12) Rawes, W; Yeung, H.The aim of the research presented in this thesis has been to develop an objective measurement technique to improve the detection of flow patterns in closed ducts. This activity is important for the safe and efficient running of many processes, particularly within the oil production, nuclear power, chemical and process industries. Signal analysis techniques based on nonlinear dynamic (chaos) theory have been applied to simulated and experimental transducer signals measuring properties of gas-liquid (air-water) flows in horizontal and vertical pipes. The techniques provide a method of measuring properties of the signals that are related to patterns within the signals. Signals from various non-invasive transducers (including differential pressure transducers, an electrical conductance transducer, a light attenuation transducer, an ultrasonic transducer and a gamma-ray densitometer) have been analysed. Signal analysis techniques include the use of singular value decomposition, the correlation integral and power spectra analysis. The results of signal analysis on the simulated signals illustrate their potential for flow regime identification. When applied to experimental signals it is shown that changes in some of the signal characteristics correlate well with changes in the flow regimes. Discernment between horizontal stratified-wavy, plug and slug and vertical slug and bubbly flow regimes has been achieved. The most successful analysis technique (using singular value composition) is more robust than previously used techniques and can be computed much more efficiently.Item Open Access An approach to configuration design synthesis of subsonic transport aircraft using artificial intelligence techniques(1991-12) Pasaribu, H. M.; Fielding, JohnThis thesis outlines a computer system developed to tackle the configuration design synthesis of subsonic transport aircraft. The system provides an interactive design environment which combines the reasoning process of the aircraft configuration definition and the numerical analyses that lie behind the reasoning. The system applies Artificial Intelligence (AI) techniques to the configuration analysis. This gives the system the capability to reason with the configuration choices. The system is built in modules, with each module is clearly separated to deal with a complete analysis in a specific aspect of design. The integration of the modules is done through an intelligent interface and a common database. The interface also incorporates AI techniques in deciding the sequence of execution of the modules and the processing of the input/output data for a particular module. The interface permits the sharing of information among the modules and supports modularity and flexibility of the system for future development. Since each module is independent, it can be easily modified or replaced without disturbing the balance of the system. An extensive library of application programs is included in the engineering analysis module which enable detailed analysis to be performed. The system is equipped with a simplified database management and a special purpose graphics module which is extensively used for the presentation of the output. The system has been validated and tested. It can handle both propeller driven and jet engined aircraft. An example of the case studies is presented. The improvement of the system for future development is also considered. These include the extension of the knowledge base for dealing with problems in other modules, the enhancement of the application programs in the engineering module, and a possible interface with an established Computer Aided Drafting (CAD) system.Item Open Access The behaviour of polyurethane foam beams reinforced with thin walled steel sections for use in bus structures(1980-08) Gaafar, Labib A.; Tidbury, G. H.The thesis is directed to the theoretical determination of the behaviour of rigid skin polyurethane foam beams reinforced with thin walled steel sections. The aim is to enable the designer to predict the behaviour of bus body structure during accident situations in order to build safe buses. A literature search has revealed that very little work has been done in this particular field of research. Thus a preliminary test programme was made to investigate the beam behaviour in bending particularly at high deflection. The test results shown in Chapter 1 gave promising results for continuing the research. Chapter 2 is directed to elastic analysis of composite beams. One of the advanced methods to predict the elastic stiffness of sandwich beams is the interfacial shear method. This assumes an interfacial shear between the core and the faces of sandwich beams. So, by considering a similar assumption, i.e. an interfacial shear between the matrix and the reinforcement, an analysis was made to predict the stiffness of composite beams. Although this method highly overestimated the stiffness, it represents a good basis for the inelastic bending analysis which is more important for the present study. Chapter • 3 shows the inelastic bending analysis of composite beams. This analysis is based on TIMOSHENKO and JAMES curvature area method. The experimental verification of the theory is shown in Chapter 4. The theory shows good agreement with the experimental results. The shape of the reinforcement was optimised for uniaxial bending. This optimum composite section showed a weight saving when it was compared with equivalent energy absorbing rectangular steel tube. Impact tests were made using a pendulum designed specially to test cantilever beams at different speed and impact energies. The test results are presented in Chapter 5. These results showed that the composite beams behaviour is similar for both static and dynamic loading. To compare the composite beam with the constituent beams, the large deflection behaviour of thin walled channel section beams made of thin sheet steel has been investigated. The experiments consisted of cantilever bending tests with the beam loaded through the shear centre and through the centroid. When loaded through the shear centre the beam buckling took place in the compression flange at the root of the cantilever. When loaded through the centroid however, it was noted that the compression flange buckled at a fixed distance from the fixed end. The general theory of thin walled beams developed by Vlasov was applied to the problem and indicated that the maximum compression stress at the free edge of the flange would be a maximum at some distance from the fixed end. The value of the maximum compression stress obtained by the general linear theory was small and its position did not coincide with the experimental position. The Vlasov analysis has been modified to include the increase in the twisting moment due to the lateral deformation- of the beam along its length. Good agreement between the modified theory and experiment both for the position of the maximum compressive stress and for the twist of the cantilever at three points along its length. Because of the very low torsional stiffness of thin walled channel sections, the small deflection theory is only applicable for small bending loads applied through the centroid and the modified theory should be used for practical loading cases.Item Open Access Biosensor and bioelectrocatalysis studies of enzymes immobilized on graphite electrode materials(1987-05) Schneider, B. H.; Higgins, I. J.; Turner, Anthony P. F.The immobilization of glucose oxidase and lipoamide dehydrogenase on graphite electrodes was studied for their application in mediated bioelectrochemical systems. These are techniques where the electrons involved in an enzymatic redox reaction are either supplied by, or given to an electrode from the enzyme. In the biosensor mode, where a current is measured due to product oxidation, the immobilized enzyme may be used to monitor its substrate, for example a biosensor for glucose based on the enzyme glucose oxidase. In the bioelectrosynthesis mode, when a cathodic potential is applied to the electrode, electrons may be transferred to the enzyme via a mediator thereby driving a thermodynamically difficult reaction, such as the reduction of the coenzyme NAD+ . A glucose sensor based on glucose oxidase immobilized onto graphite foil electrodes which had been doped with the mediator dimethylferrocene was found to produce both a linear and rapid response to changes in glucose concentration in solution. The kinetics of this particular system were studied in depth in order to explain its behaviour. Results showed that the porous nature of the electrode material resulted in immobilization of the enzyme throughout a number of layers• Consequently, diffusion of glucose into the electrode became the rate limiting process at low glucose concentrations, which resulted in linear calibration curves. This was characterized by a substrate modulus, which was found to be sufficiently large to predict diffusional limitations. From this the effective rate of glucose diffusion within the electrode was estimated, and found to be up to 5 times smaller than that in free solution. The rapid response of the sensor, on the other hand, was due to the absence of any mass transfer limitations external to the electrode surface. When lipoamide dehydrogenase was employed in the same system it was found that complications arose due to coupling of NADH oxidation with the adsorbed mediator. By employing a less anodic potential of +150 mV vs. Ag/AgCl at NADH concentrations below 1 mM the detection of enzymatic oxidation of the coenzyme was achieved. Enzymatic reduction of NAD+ was achieved using lipoamide dehydrogenase immobilized onto graphite felt electrodes. This reaction was mediated by methyl viologen, with the enzyme-modified electrode used to reduce the mediator at a potential of -0.7 V ( vs. SCE ). In this fashion the reduced form of methyl viologen was recycled, thereby driving the reduction of NAD . By coupling this system to lactate dehydrogenase it was possible to effect the reduction of pyruvate.Item Open Access Buckling of corrugated core sandwich panels(1969-09-19) Patel, N. G.; Griffin, K. H.A computer program is developed to determine the buckling stress and deflections of symmetric corrugated core sandwich panels. In the program freedom for lateral deflections at core to face-plate junction is allowed for. Provision is also made to study the effect of variation of core bend radius. A range of test specimens using four basic core configurations is designed to assess the effect of core bend radius on the buckling stress of the panel. The computer program indicates that above a certain value of core bend radius there is a marked drop in the value of critical buckling stress and a change in buckling Mode. The values of deflections at core to face-plate junctions at low buckling wave-lengths are not reliable* Due to the limited range of the experimental work, it is not possible to draw any conclusions on the effect of core bend radius on the buckling stress. The method used for determining the experimental buckling load is somewhat subjective in application, and its accuracy is difficult to assess. In general, the experimental values of buckling stresses are 15% higher than those predicted by the computer program. These discrepancies are not large when dimensional and material property variations are considered and indicate that the computer results are giving the correct trend and are conservative. Recommendations are made for : (i) Investigation of the buckling deflections at low values of buckling wave-lengths for specimens with high face-plateto-core thickness ratio. (ii) A test programme covering a wider range of specimens than that covered by the test programme in this study. and (iii) Trying out the other two methods of determining the buckling load.Item Open Access Characterisation of dwelling electricity demand with reference to DCHP(2002-04) Geslot, Olivier; Newborough, MarcusThe research relates to the introduction of dwelling micro combined heat and power to the domestic sector as a mean of improving the efficiency with which primary energy is used, and the economic efficiency of supplying electricity via the national grid. Such small generators may constitute Stirling engine or solid polymer fuel cells. This research is orientated towards the electrical demand side issues. The context is to maximise the feasibility of such technologies when the typical domestic consumer's heat demand varies significantly with season and the associated electrical power varies substantially every minute of the day. The main issue was to ensure that the system could effectively and economically satisfy a considerable proportion of the electricity demand the typical demand profile is very peaky by virtue of the way inhabitants behave at home and the design of domestic appliances. To derive the characteristic of dwelling electricity demand, a total of 45 dwellings were sampled, monitored and classified, in order to analyse the parameters influencing the shape, magnitude and duration of the profile data collected. A survey was issued to . complete the research regarding appliances time of use. Then a model was designed with an interface allowing dynamism. The research concluded there are attractive reasons for micro combined heat and power to be implemented in dwelling. It could save up to 15% of primary fuel. On an annual basis, and with the 15 dwelling data provided by British Gas, the average saving for a constant lkWe DCHP is determined to be £44.78, and the saving is increased to £124.61 for a system that would allows a tumdown from lkWe DCHP during winter to 500We DCHP during summer. Furthermore utility companies should be gaining from this introduction because peak power demand reduction on the grid should reduce costs.