The aim of this research was to investigate the ink release characteristics of anilox rolls. This was successfully achieved by the development and use of experimental and analysis methods. Techniques were developed using white light interferometry for accurate user independent characterisation of single ani lox cells. An experimental trial printing UV curable ink onto a non-porous film substrate using banded C02 and Y AG laser engraved anilox rolls was designed and undertaken. Optical print densities and physical printed dot geometries were used to quantify the ink released for various print parameters. The Y AG anilox roll released a higher percentage of ink than the C02 anilox at comparable volumes and cell profiles. As the cell volume and depth-to-opening ratio increased the percentage of ink released from both anilox rolls decreased. The optimum ink release was found at a depth-to-opening ratio of20%. The percentage of ink released from both rolls was dependent on plate coverage, screen ruling, speed and anilox to plate engagement. As plate coverage increased, the percentage of ink released from the anilox roll decreased. As plate screen ruling increased, the percentage of ink released from the anilox roll increased. Increasing press speed decreased the optical print density due to a reduction in ink transfer. Increasing anilox to plate engagement had variable effects on the printed samples and subsequent release from the anilox. Increasing engagement increased the optical print density and physical dot area. Physical dot volume was increased for the first engagement increase, but then decreased at the highest engagement. A method was successfully developed and tested using white light interferometry and a printability tester for the direct measurement and quantification of fluid within a cell, pre and post printed. Results for the percentage ink released were comparable to those obtained from the experimental trial and were also dependent on plate coverage and engagement force.

Due to the enhanced level of national security currently required due to the possibility of terrorist attack, monitoring devices for trace levels of explosive materials are now of the upmost importance. One such method that offers a possible route towards the development of a system for the detection of such analytes is via an electrochemical regime, coupled to the use of disposable sensor technology. Within this study, the use of modified carbon screen-printed sensors for the detection and analysis of such analytes of importance has been investigated. The modification of the base carbon substrate has been undertaken in a two-fold manner; firstly the incorporation of an enhanced electroactive mediator (Cobalt Phthalocyanine) has been investigated as an aid to facilitate the signal response and secondly the use of a novel surface modification technique to produce microelectrode arrays upon the carbon has also been employed. Microelectrodes hold intrinsic advantages over planar electrodes, such as stir independence, low detection limits and increased sensitivity due to their hemispherical diffusional profile. An array of microelectrodes can retain these properties whilst including the added advantage of enhancing the current response. The integration of these two approaches, the microelectrode array coupled with the mediated electrodes, has been developed with the ultimate objective to develop an accurate and sensitive detection system for trace quantities of explosives, namely 2,4,6-trinitrotoluene (TNT). This thesis describes work focussed towards the optimisation of each of the individual components involved in the formation of a sensing device for the detection and measurement of trace levels of explosive materials. In particular, factors and techniques that may facilitate the enhanced sensitivity of the measurement device are described. At every stage, each modification step was also undertaken with a suitable redox probe, ferrocenemonocarboxylic acid to allow for a quantitative assessment to be made. The use of unmediated and mediated carbon ink has been assessed in terms of suitability as a host material for the detection of TNT, with concentrations of 400 nM being measured on these base substrates. Further to this, microelectrode arrays were then formed upon these planar carbon surfaces via insulation with poly(phenylenediamine) coating and subsequent ultrasonic ablation. These thin film microelectrode arrays (~40 nm, pore population ~7.0 x 104 cm- 2 ) were also investigated in terms of response to TNT and were seen to offer an enhanced response in terms of signal differentiation. A final stage was then applied where the microelectrode array was further modified to incorporate a conductively grown polymer from the pore areas. Within this conductive growth, an enzyme/co-factor matrix specific to TNT was deposited which was seen to further increase signal responses, although displaying a lack of sensitivity at lower concentrations. As a final step the developed sensor methodologies were then used in conjunction with an airsampling system, the Coriolis®µ cyclone, to mimic the use of the sensors in realistic environments for practical employment. The sensors were used to successfully measure TNT samples from a concentrated stock sample of 4.4 mM collected via the cyclone technique.

The work investigates an extension and improvement to reliability prediction in single crystal silicon MEMS by utilising dynamic Raman spectroscopy to allow fracture test data collected directly from devices thereby taking account of actual geometrical tolerances, dynamic load conditions and effects from the microfabrication process. Micro-cantilever beam MEMS devices microfabricated from (100) crystalline silicon wafers having [110] beam direction were used in this experiment. A piezo actuator was used to vibrate the devices. The fracture data was taken by increasing the supply voltage to bring each device to rupture whilst a continuous beam HeNe laser was directed from the [100] direction to particular positions on the sample allowing for capture of the LO_z photons. The resulting Raman profile, broadened by the vibration of the device, was fit using a Voigt profile and compared to the no load condition. A calibration step was used to convert the Raman signal to volumetric μstrain. The reliability prediction methodology used in this work was developed under the Weibull distribution function that is based on the concept of weakest link theory describing distribution of flaws in brittle material. As each device was fabricated from semiconductor grade single crystalline silicon, it can be considered to have no mechanical defects with the flaws on the device only existing as surface flaws induced from the microfabrication process during manufacturing. Differently processed surfaces each have their own Weibull parameters. The failure prediction of a particular MEMS device is calculated from these parameters with the simulated structure responses due to applied load being predicted from the finite element package ANSYS. The failure prediction method shows a good agreement with the experimental results with accuracy of 10%. However, visual observations were necessary as a number of ruptured specimens started to fail from the bottom side of the clamped end and propagated through [111] direction so from the upper side the failure looks like it started from a distance from the clamped end. The experimental work was carried out utilising [100] Raman scattering. This limits the ability of the system to only capture the strain condition in one direction; the other strain directions were approximated using silicon orthotropic material properties and assuming that the load is a uniaxial load. This limitation forces the failure prediction distribution function to treat silicon as an isotropic material with the strength ii characteristic scale parameter in the Weibull distribution being the same value for all directions. This limitation together with extending the work towards implementing an “off-axis” Raman characterisation able to characterise all the strain directions is discussed for future work.

No description available.

In recent years, many instruments have been developed to capture distance and reflectance information. They have been incorporated into various applications, with two of these applications forming the focus of this work: (1) range cameras for obstacle detection and (2) integrated-path differential-absorption (IPDA) light detection and ranging (LIDAR) systems for space-borne remote sensing applications. Conventional range cameras are based either on triangulation or time-of-flight distance measurement principles. The former is constrained to indoor applications and the latter suffers from distance ambiguity. For space-borne IPDA LIDAR systems, the conventional pulsed approach takes two time-multiplexed measurements with laser pulses of different wavelengths, which results in measurement errors, due to the distance misalignment between the successive beams. The aforementioned problems have been solved in this work either by signal processing techniques or by deriving more suitable modulation schemes. In the first part of this thesis, the ToF camera captured range image has been enhanced by applying two modulation frequencies and Markov random field (MRF) modelling. This extends the non-ambiguous range and at the same time reduces noise. After which, the range images are then utilised in a novel obstacle detection system, which is described. In the second part of this thesis, a novel range imaging technique based on the random-modulation continuous wave (RMCW) scheme has been proposed. This technique extends the non-ambiguous distance and allows multi-user operation without the need for a software pre-processing procedure. In the last chapter of this thesis, the RMCW scheme has been extended to be applied in satellite remote sensing applications. This enables the use of continuous wave (CW) laser sources. Not only do CW sources offer a greater power efficiency, but this set-up also removes the beam misalignment problem. Together, this work has brought several innovations to the field of range measurement techniques and their applications.

This project involves the study of new molecular sensors based on luminescent compounds that can change their emission properties in the presence of an analyte, in particular 'spectroscopically silent' metals, particularly those important in nature, such as Zn or Cu. Gold(l) complexes exhibiting Au--Au (aurophilic) interactions are often highly luminescent, and their emission can be related to the presence of such weak interactions. There is, however, a lack of understanding on how to control the extent of the interactions and the influence that these may have on the structures and optical behaviour of the compounds. The present work involves the systematic study of the influence that Au--Au and other weak interactions (Au--X, X = 0, S) have on the overall structures of digold(l) compounds as well as on their luminescence spectra, both in solid and solution states. These secondary interactions were investigated by varying both the heteroatom present in the bridging diphosphine ligand and the range of thiolate and alkyne co-ligands coordinated through the Au(l) atom. The potential of the compounds as optical sensors towards other metal ions has been investigated. Within this study, some very interesting X-ray crystal structures were obtained and described e.g. an unusual Au4Ag4 cluster.

Zone plates are commonly used in soft X-ray microscopy due to the high spatial resolutions achievable, however the performance is somewhat limited due to their small numerical aperture, combined with chromatic aberration and the multiple diffraction orders that are produced. Microstructured Optical Arrays (MOAs) have been proposed as an alternative method of focusing soft X-rays, using grazing incidence reflections from an array of channels, with the cumulative effect producing a small focused spot. The development and focusing properties of MOAs are described and simulated within this thesis, with comparison made to zone plates and other methods of focusing X-rays. -- Experimental characterisation of MOAs and zone plates was achieved using a microfocused electron bombardment X-ray source. Necessary developments required to examine MOAs using the X-ray source and detector system are described, along with current calibration measurements, providing insight into the overall performance of the source. -- The use of a CCD detector with the microfocus source has allowed comparison to be made between experimental measurements made to characterise the optical performance of MOAs and computer simulation.

Since current meters are generally calibrated by towing in still water, their ability to measure the mean flow velocity under the sometimes totally different field conditions has come under considerable question. In an effort to answer some of the questions posed the work described in this thesis was undertaken. The analytical and experimental studies described are divided into three main chapters. (1) An Investigation into the Principles of Current Meters under Steady Flow Conditions. The analysis attempted in this chapter has been carried out because the existing theories appeared inadequate, and totally unconfirmed experimentally. A fundamental study is therefore made of the forces experienced by such meters, and a theory developed and used, in conjunction with some unique experimental measurements, to predict quantitatively the shape of the steady state calibration curves. The agreement between predicted and measured calibration curves for the three OTT meters tested is generally good. The theory is then further developed to show that temperature changes and symmetrical velocity gradients can cause registration errors, but under normal working conditions it is shown that these are unlikely to be excessively large. It is also noted with interest that asymmetrical velocity profiles can cause this type of meter to overestimate the mean flow velocity. (2) The Errors of Current Meters in Pulsating Flow. A meter situated in a stream can be exposed to fluctuating velocities both parallel and transverse to the meter axis, and since such flow conditions contravene the calibration conditions the question arises as to the accuracy of such measurements. It is shown in the initial experiments of this chapter that sinusoidal flow fluctuations parallel to the mean velocity vector cause the meter to over-register the mean liquid velocity, and transverse fluctuations generally cause the meter to underestimate. From the results of these tests general suggestions are made concerning the choice of meter design and station in order that such errors can be minimised. A theoretical attempt at predicting the measured errors is also undertaken, and it is found, using simple aerodynamic principles, that all the trends experienced by the meter when subjected to axially pulsating flow could be estimated. The agreement between this completely theoretical approach and the experiments is found to be good; and from this investigation further comment is made about the optimisation of the meter design. However it is found, after much work, that this and a subsequent approach somewhat oversimplifies the problem, since it is shown using a more rigorous approach, along similar lines to the initial theory, that the quantitative agreement with the measured error under axially pulsating conditions is not as good as that previously found. In this rigorous approach the equation of motion is formed using experimentally measured torques, and the overestimation obtained by solving this equation on an Analogue Computer. It was thought that this deviation, between experiment and theory, could have been caused either by the viscous effects of the liquid or by its inertia, of which no account had been taken in the theory. In order to minimise these effects similar tests were conducted in air flow, and the agreement between measured and estimated errors, under axially pulsating conditions was found to be surprisingly good; which partially proved the hypothesis. A rough estimation is also made at predicting the error due to transverse pulsations; again using the Analogue Computer to solve the relevant differential equation. It is conclusively shown in the appendices of this chapter that current meters tend to overestimate more when the axial flow fluctuations contain large negative accelerations; and also that the measured error is unaffected by prolonged vibration over quite considerable lengths of time. It would appear for this work that, for most practical cases of flow measurement where no large amplitudes and high frequency pulsations are present, the current meter system is surprisingly accurate. Indeed it is shown that a sinusoidal axial fluctuation in flow of;l; 101'0 about the mean velocity can only cause a maximum overestimation of ~. However, if the fluctuations are large then it is shown that a rough estimation of the % error incurred can be made if the approximate mean velocity, size and shape of the fluctuations, and the rotor torque characteristics are known. (3) The Transient Response of Current Meters and Turbine Type Flowmeters. Because of the unusual results of the preceding chapter it was thought tbat a more fundamental study should be mode into dynamic effects on current meters. It was decided to study the response of propeller type flowmeters to rising step-inputs since this appeared to be the simplest way of subjecting the meter to dynamic flow conditions. There was also a need for such an analysis because of its direct application in the mechanics of rocket propulsion servo-systems, where propeller flowmeters are used. In this work, using some novel experimental techniques, it is shown that a theory which neglects the fluid inertia can only be used accurately to predict the response times of such meters under certain limited conditions. It is again found that the response under gaseous flow conditions (where the fluid inertia term is negligible compared with th~t of the rotor) can be fully explained; and with liquid flow the inertia term causes the theory to underestimate the actual time constant at a given flow velocity. The amount or deviation from the theory is shown to depend on the dimensions and density of the rotor and on the fluid density. In the appendices of this chapter it is shown that the effect of symmetrical velocity profiles on the time constant is, for most practical cases, unlikely to be excessive. A possible system for measuring the rotor revolutions is also discussed, which seems to have a number of advantages over the mechanism now used in laboratory current meters. From the results of these three chapters general conclusions are drawn and a brief outline is given of a proposed future research programme.

Experimental investigation and theoretical analysis of an electromagnetic flowmeter designed for use with dielectric liquids has been carried out. An extensive survey of the industrial users of flowmeters has been made, involving the participation of over 47 companies, which provides information about the current industrial use, attitudes and attributes of electromagnetic and other types of flowmeters. The design of the flowmeter is mainly concerned with overcoming the charge noise that is associated with the flow of dielectric liquids so as to effectively detect the weak flow signal. It is shown that the working of the flowmeter depends heavily on the design of the eddy current free electrostatic shield. The result of the mathematical analysis of the design is a simplified formula for predicting the sensitivity of the meter. It is adjusted to take account of such factors as end-effects and electrical properties of the flow conduit of the meter. Experimental results show that not only an induction flowmeter based on Faraday's principle is possible but also the measured values of the flow signal closely matches those obtained from the formula. It is suggested that the formula can be generalised to include moderately conducting liquids which is supported by results achieved from experiments on water. Finally, recommendations for future work are put forward for further improvement of the design.

This thesis discusses the construction, analysis, performance and applications of "Novel Knitted Fibre Meshed Transducers" (KFMTs). Unobtrusive transducers play a major role in the wearable computing field. These transducers are being used in wearable personalized monitoring systems. Common practice is to embed sensors that are made separately into garments at a later stage, and therefore, these systems are not truly unobtrusive in nature. To overcome these disadvantages a new generation of more robust and unobtrusive sensors is required. One scenario is to make such sensors by using smart materials and integrating them into intelligent textile structures using mechanical methods of fibre assembling (weaving knitting and braiding). These are called fabric or textile sensors. Research has been carried out mostly into woven structures due to their structural stability. On the other hand, knitted structures are very attractive due to their superior adaptability. When a knitted fabric is subjected to biaxial stress in the fabric plane the geometry of the individual pattern elements is deformed and followed by the structure as a whole. The structures are knitted with yarns made out of smart materials that are capable of converting the deformations into variations of electrical parameters (resistance capacitance inductance). This new generation of transducers is named Fibre-Meshed Transducers (FMTs). These sensors can be used to measure proximity, touch, pressure, acceleration, force, displacement, vibration, sound, temperature, chemical & biological substances, light and radio frequencies and bio-potentials. Initially the feasibility of making resistive, capacitive and inductive knitted transducers has been explored by using conductive yarns and knitted structures. As a first attempt, a knitted resistive strain gauge and a knitted resistive displacement sensor were constructed. It was concluded that these types of KFMTs could be used to measure relative readings. A capacitive knitted transducer was made and used as a touch sensitive switch. A knitted solenoid was constructed by using conductive yarns and nonconductive elastomeric yarn in a tubular structure and was used as a strain and displacement measurement in wearable physiological information measuring systems. Knitted bio-potential electrodes were constructed by using stainless steel yarns, Ag coated polyester and Cu yarns and they were tested for their performance in ECG measurements. It was concluded that the performance of the wet electrodes were degraded over time.