In the last few decades, Titanium dioxide (also called Titania or TiO2) has experienced significant scientific interest due to its range of properties and possibility for further developments in a range of applications, including photocatalysis. Initially, the material was widely used in this application in powder form for water decontamination applications. It was later developed as a thin film coating onto glasses and metals (industrial, construction scale) for its self-cleaning properties. Indeed, the scientific community realised that TiO2 coatings could present both antimicrobial properties (via degradation of cell walls) and a strong hydrophilic behaviour. Recently, thin films technologies, and more particularly magnetron sputtering processes, have undergone a new expansion: the HiPIMS (High Power Impulse Magnetron Sputtering) process. The HiPIMS process is 15 years old and its principal aim is to provide a more ionized deposition flux (by an order of magnitude), easing the control of the deposited film properties (density, structure, composition, targeted areas on the substrate, etc ...). It has also been shown to facilitate low substrate temperatures during operation. The combination of both characteristics should lead to the possible deposition of crystalline films at low temperature. The first aim in this work is to provide the reader with a deep understanding of the HiPIMS discharge and how it can influence the deposition process. To do so, plasma diagnostics have been carried out on different coating systems (rigs) and using different power supplies to show how both of these aspects can drastically change the processes occurring within the discharge. For the rig used for deposition of the films, thermal and deposition rates measurements have also been carried out. This leads to the establishment of a process envelope, suitable for the deposition of crystalline titanium dioxide films. Subsequently, TiO2 coatings have been deposited by HiPIMS onto various substrates and the influences of the deposition parameters studied to better understand the plasma behaviour and its consequences on the thin film properties, in order to optimize the latter’s crystallography. The final aim of this project is to deposit a crystalline photo-active (i.e. photocatalytic, hydrophilic) film onto a polymeric substrate at low temperature. This project implies the use of a large range of characterisation techniques. The structural, mechanical, chemical and crystallographic properties have been studied by using a large array of techniques including X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Raman spectroscopy, etc... The photocatalytic activity was assessed using dye degradation tests under UV light, and the hydrophilicity by contact angle measurements. In this project, it has been shown that a modification of the deposition rig can bring drastic changes to the plasma. These changes are even more important when it comes to the reactive plasma. Each rig has its own process envelope and transferring from a laboratory scaled rig to an industrial rig is not a simple task. Parameters influences on the plasma can also vary from one configuration to another and optimized deposition conditions are not necessarily repeatable from one rig to another. Mainly, it seems that the oxidation process is greatly modified by the rig configuration. This thesis presents plasma diagnostic conducted using only an oscilloscope, to show that this is a simple and cheap way for industrials to deposit in reactive atmosphere. Here, the author has optimized deposition conditions on a given apparatus, where crystalline Anatase (TiO2) has been deposited at low temperature, typically, below 60 °C. These films have also been deposited onto polymeric substrates with no destruction of the latter. The oxygen content during deposition appears to be the more important point to control during deposition. For the rig used here, films have been deposited in the poisoned mode, at low pressure, high frequency and short pulse width as it seemed to provide the more ionized discharge, facilitating the films crystallization.

This thesis presents a feasibility study of using microwave and millimetre wave radiations to assess burn wounds and the potential for monitoring the healing process under dressing materials, without their removal. As interaction of these types of radiations with the human body is almost exclusively with the skin, there is potential in others areas of medicine such as early skin cancer detection and the diagnosis of skin conditions such as eczema and psoriasis. This study involves developments of experimental methodologies, electromagnetic modelling, and measurements conducted on human skin (in vivo from 150 healthy participants), porcine skin samples (ex vivo from 20 fresh samples), and dressing materials (20 samples). Radiometric measurements obtained from the human skin over the frequency band (80-100) GHz show that the emissivity of the skin varies consistently over different regions of the hand and forearm, with gender, ethnicity, body mass index, age, and hydration level of the skin. A half space electromagnetic model of human skin has been developed and simulations using this model indicate that the human skin can be modelled as a single layer over the band 30 GHz to 300 GHz. The model also indicates that the band could be used to detect burns and a range of medical conditions associated with the skin. Experimental data collected from samples (human and porcine) have been measured by passive and active imaging systems and the results analysed in terms of the emissivity and the reflectivity of the skin. The major outcomes of the thesis are that microwave and millimetre wave radiations are capable of discriminating burn-damaged skin from healthy tissue and these measurements can be made through bandages without the sensor making any physical contact with the skin or the bandage.

There is a broad range of technologies available for wireless communications for moving vehicles, such as Worldwide Interoperability for Microwave Access (WiMax), 3G, Dedicated Short Range Communication (DSRC)/ Wireless Access for Vehicular Environment (WAVE) and Mobile Broadband Wireless Access (MBWA). These technologies are needed to support delay-sensitive safety related applications such as collision avoidance and emergency breaking. Among them, the IEEE802.11p standard (aka DSRC/WAVE), a Wi-Fi based medium RF range technology, is considered to be one of the best suited draft architectures for time-sensitive safety applications. In addition to safety applications, however, services of non-safety nature like electronic toll tax collection, infotainment and traffic control are also becoming important these days. To support delay-insensitive infotainment applications, the DSRC protocol suite also provides facilities to use Internet Protocols. The DSRC architecture actually consists of WAVE Short Messaging Protocol (WSMP) specifically formulated for realtime safety applications as well as the conventional transport layer protocols TCP/UDP for non-safety purposes. But the layer four protocol TCP was originally designed for reliable data delivery only over wired networks, and so the performance quality was not guaranteed for the wireless medium, especially in the highly unstable network topology engendered by fast moving vehicles. The vehicular wireless medium is inherently unreliable because of intermittent disconnections caused by moving vehicles, and in addition, it suffers from multi-path and fading phenomena (and a host of others) that greatly degrade the network performance. One of the TCP problems in the context of vehicular wireless network is that it interprets transmission errors as symptomatic of an incipient congestion situation and as a result, reduces the throughput deliberately by frequently invoking slow-start congestion control algorithms. Despite the availability of many congestion control mechanisms to address this problem, the conventional TCP continues to suffer from poor performance when deployed in the Vehicular Ad-hoc Network (VANET) environment. Moreover, the way non-safety applications, when pressed into service, will treat the existing delay-sensitive safety messaging applications and the way these two types of applications interact between them are not (well) understood, and therefore, in order for them to coexist, the implication and repercussion need to be examined closely. This is especially important as IEEE 802.11p standards are not designed keeping in view the issues TCP raises in relation to safety messages. This dissertation addresses the issues arising out of this situation and in particular confronts the congestion challenges thrown up in the context of heterogenous communication in VANET environment by proposing an innovative solution with two optimized congestion control algorithms. Extensive simulation studies conducted by the author shows that both these algorithms have improved TCP performance in terms of metrics like Packet Delivery Fraction (PDF), Packet Loss and End-to-End Delay (E2ED), and at the same time they encourage the non-safety TCP application to behave unobtrusively and cooperatively to a large extent with DSRC’s safety applications. The first algorithm, called vScalable-TCP – a modification of the existing TCPScalable variant – introduces a reliable transport protocol suitable for DSRC. In the proposed approach, whenever packets are discarded excessively due to congestion, the slow-start mechanism is purposely suppressed temporarily to avoid further congestion and packet loss. The crucial idea here is how to adjust and regulate the behaviour of vScalable-TCP in a way that the existing safety message flows are least disturbed. The simulation results confirm that the new vScalable-TCP provides better performance for real-time safety applications than TCP-Reno and other TCP variants considered in this thesis in terms of standard performance metrics. The second algorithm, named vLP-TCP – a modification of the existing TCP-LP variant – is designed to test and demonstrate that the strategy developed for vScalable-TCP is also compatible with another congestion control mechanism and achieves the same purpose. This expectation is borne out well by the simulation results. The same slow-start congestion management strategy has been employed but with only a few amendments. This modified algorithm also improves substantially the performance of basic safety management applications. The present work thus clearly confirms that both vScalable-TCP and vLP-TCP algorithms – the prefix ‘v’ to the names standing for ‘vehicular’ – outperform the existing unadorned TCP-Scalable and TCP-LP algorithms, in terms of standard performance metrics, while at the same time behaving in a friendly manner, by way of sharing bandwidth non-intrusively with DSRC safety applications. This paves the way for the smooth and harmonious coexistence of these two broad, clearly incompatible or complementary categories of applications – viz. time-sensitive safety applications and delay-tolerant infotainment applications – by narrowing down their apparent impedance or behavioural mismatch, when they are coerced to go hand in hand in a DSRC environment.

When a train driver’s error results in a red, stop signal being passed without authority there is the potential for disaster. These events are termed a “SPAD”, signal passed at danger without authority. Occasionally these incidents have led to tragedies such as the Ladbroke Grove accident in 1999. This accident led to 31 fatalities and over 523 injuries. Investigations of incidents have resulted in safety advancements that decreased the number of incidents and accidents. Despite all these efforts SPADs still occur and very little is known about the cognitive effects that the track-side signalling system has on the driver during normal operational conditions. The motivation for understanding the cognitive and behavioural effects of the routine patterns of railway signalling is to identify potential high and low risk situations. The identification of neural correlates that predict the driver’s state of readiness prior to a potentially dangerous situation. The combination of knowledge of these events and the insights into their causes could allow better systems, operational methods and logistics to be designed. This is an Electroencephalograph, (EEG) study to identify neural correlates that are used to identify high and low risk response and perceptual accuracy situations. The behavioural data is recorded from the keyboard responses and used to guide the EEG analysis. The tools applied to solving the research problem are artefact detection and removal from the EEG data, followed by analysis for patterns and features. The phase-locking functional-connectivity reveals repetition priming, antipriming, and neural precursors to correct and erroneous responses. The phase-locking for certain graph metrics are found to vary significantly prior to response errors. The EEG analysis reveals that multiple cortical region coordinated cognitive activity is required to successfully perform multiple paradigm tasks. Certain channels and regions of the brain are important in creating a cognitive state that facilitated future correct responses. Different states are required to promote response accuracy for different forthcoming events.

Healthcare systems worldwide are facing growing demands on their resources due to an ageing population and increase in prevalence of chronic diseases. Innovative residential healthcare monitoring systems, using a variety of sensors are being developed to help address these needs. Interpreting the vast wealth of data generated is key to fully exploiting the benefits offered by a monitoring system. This thesis presents the application of topic models, a machine learning algorithm, to detect behaviour patterns in different types of data produced by a monitoring system. Latent Dirichlet Allocation was applied to real world activity data with corresponding ground truth labels of daily routines. The results from an existing dataset and a novel dataset collected using a custom mobile phone app, demonstrated that the patterns found are equivalent of routines. Long term monitoring can identify changes that could indicate an alteration in health status. Dynamic topic models were applied to simulated long term activity datasets to detect changes in the structure of daily routines. It was shown that the changes occurring in the simulated data can successfully be detected. This result suggests potential for dynamic topic models to identify changes in routines that could aid early diagnosis of chronic diseases. Furthermore, chronic conditions, such as diabetes and obesity, are related to quality of diet. Current research findings on the association between eating behaviours, especially snacking, and the impact on diet quality and health are often conflicting. One problem is the lack of consistent definitions for different types of eating event. The novel application of Latent Dirichlet Allocation to three nutrition datasets is described. The results demonstrated that combinations of food groups representative of eating event types can be detected. Moreover, labels assigned to these combinations showed good agreement with alternative methods for labelling eating event types.

No description available.

Patterning, the utilisation and manipulation of geometric properties, is important both for the rational design of technological devices and also to the understanding of many natural phenomena. In this thesis I examine the way in which micro and nano patterning can alter optical properties across a large range of wavelength scales and how these novel phenomena can be utilised. Micro patterned electrodes can tune the geometry of radio frequency electric fields to generate dielectrophoretic microfluidic devices. These devices use the dielectrophoretic force to sort, position and characterise the properties of micro and nano particles. I develop a new image processing algorithm that radically improves experimental efficiency allowing for real-time supervisor free dielectrophoretic characterisation of nanoparticles. Metamaterials are composite structures that have repeating units that are much smaller than the wavelength of radiation they are designed to work with. The optical properties of the materials are derived from these units rather than the bulk characteristics of the materials they are composed of. I demonstrate the development of novel THz metamaterial absorber devices. These devices provide a means to design and control the absorption of THz radiation, modulating bandwidth, polarization dependence and frequency in a form that is readily integrable with other standard fabrication processes. Finally by periodically patterning materials on the nanometer scale I demonstrate the development of novel photonic crystal devices and complementary optical components. In these devices the periodicity of the electromagnetic wave is modulated by the periodicity of the structures themselves resulting in band gaps and resonances analogous to the band gaps and defect states found commonly in semi-conductor physics. I demonstrate the theory, fabrication and measurement of these devices using novel broadband supercontinuum sources and propose a future application for biosensing. Further topics covered in the appendix include the development of a spin out technology, a $100 open source atomic force microscope developed while spending time in China. Finally I examine the role of patterning for optimising the performance of nanomechanical cantilever biosensors, and show how geometrical effects on the microscopic scale are crucial to understanding the workings of the vancomycin family of antibiotics, as screened using microcantilevers. Portions of this report are edited extracts from published articles resulting from this work, a full list of which is given in Appendix A.

Metallic nanoparticles and nanostructures have spawned significant interest in a wide area of science. Nanoparticles in glass show unique linear and nonlinear optical properties due to surface plasmon resonances. These induce absorption and scattering of light around the resonance wavelength, which can be tuned by changing size, shape or spatial distribution of the nanoparticles. Metallic nanostructures show local field enhancement effects, which are used for example in surface enhanced Raman scattering. Their large surface area compared to bulk materials makes them interesting for applications in chemistry and life science. In this thesis the synthesis of two different types of silver-glass nanocomposites is investigated. Both materials are prepared from silver ion-exchanged glass, which is also prepared and characterised in house. The first type of nanocomposite is glass doped with silver nanoparticles. It is formed by annealing silver ion-exchanged glass at a temperature close to the transition point. This induces the reduction of silver to atoms and the agglomeration in nanoparticles with a diameter of less than 10nm, which are located in a layer beneath the glass surface, which has a thickness of tens of micrometres. These nanoparticles are responsible for a characteristic absorption band centred around 410nm due to plasmon resonances. The second nanocomposite, which was first produced in the course of this work, is called glass-silver composite. It is created by pulsed laser irradiation of silver ion-exchanged glass. It contains nanoparticles with a diameter of 100nm or more, which are distributed homogeneously in a dense single monolayer at the glass surface. This material shows a strong metal-like reflection of light. The location of nanoparticles at the surface makes it interesting for applications utilising the field enhancement effect of the nanoparticles, such as surface enhanced Raman scattering and enhancement of light conversion. Both nanocomposites and the ion-exchanged glass are characterised by optical microscopy, scanning electron microscopy and optical spectroscopy. The work is divided in four chapters, starting with an introduction in chapter 1. In chapter 2 the method of production of the silver ion-exchanged glass and the properties of the material are presented. Generation of nanoparticles inside the glass by annealing is covered in chapter 3 and an analysis of laser processing of ion-exchanged glasses is shown in chapter 4. The concluding chapter consists of a summary of the work and an outlook.

Scale formation on surfaces can normally be divided into two distinct processes: a “deposition process” which refers to the process of heterogeneous nucleation and growth at the asperities of the surface in the bulk solution and an “adhesion process” which refers to the sticking of pre-existing crystals, which have nucleated in the bulk solution, and which build up as a layer on the surface. The presented work represents an experimental study of scaling tests to assess the effect of hydrodynamic conditions in a complex scaling environment, supersaturated with sulphate/carbonate-dominated brine solutions, on the stainless steel substrate coated with a range of commercially-available coatings. Due to the complexity of the brine solutions, the formed scale deposits are the product of the coprecipitation process. The morphology of the scale deposits along with the chemical composition of the surface scale deposits in different conditions was analysed and characterised. In addition, the effect of the surface energy and surface roughness on both processes have been studied. The thesis provides data that will assist in the understanding of the controlling parameters in scale formation in different conditions, and also describes what characteristics of the surface can make it a good anti-scaling surface for inorganic scale; however, the results have shown that merely one parameter cannot assure a surface as a good antifouling surface. Since most of the surface scaling studies have been focused on laboratory experiments and very little data are available to demonstrate such results are relevant and can be scaled-up to field environment, the current study focuses on correlating the systematic laboratory results with field trials. The current study shows that if properly selected, surface engineering offers great promise as an approach to prevent mineral scale deposition in the piping system of oilfields.

Las aleaciones con memoria de forma al ser unos materiales con nuevas propiedades abren ante sí un nuevo campo de aplicaciones tecnológicas respecto a los materiales convencionales. Estas aleaciones además de presentar las propiedades típicas de un metal, presentan otras propiedades que las hacen diferentes de estos como es la superelasticidad, el efecto memoria de forma y la capacidad de amortiguamiento. Se conocen diferentes familias de materiales con memoria de forma entre los que destacan los polímeros, los cerámicos y los metales. Dentro de los metales tres grupos son los más importantes: las aleaciones base NiTi utilizadas en la actualidad, sobre todo en el campo biomédico debido a su biocompatibilidad, las aleaciones base cobre muy utilizadas en investigación por sus buenas propiedades de memoria de forma, su bajo coste y su fácil preparación y por último las aleaciones férreas con memoria de forma que están en proceso de desarrollo, pero que su buena resistencia a la corrosión y bajo coste, las hace tener un futuro prometedor.En la presente investigación, todos los trabajos experimentales se han centrado en el estudio de las aleaciones base cobre CuZnAl. Se han estudiado tres aspectos poco conocidos en estas aleaciones como son la cinética de crecimiento de grano, el desgaste y la corrosión. Además todas las aleaciones estudiadas han sido preparadas en el laboratorio dando lugar al Capítulo II de la presente tesis.En el Capítulo III se caracteriza la cinética de crecimiento de grano de la aleación CuZnAl observando como el crecimiento de grano de esta aleación es muy rápido y como los tratamientos térmicos, provocan aumentos muy elevados en el tamaño de grano, que junto con la anisotropía de los diferentes cristales provocan una disminución de las propiedades mecánicas y fragilidad intercristalina. Para reducir este problema, se estudia el efecto de diferentes aleantes, con el fin de reducir el tamaño de grano. Asimismo se determina, el efecto del tamaño de grano en las temperaturas de transformación y se ha estudiado el efecto que ejercen los límites de grano en el mecanismo de fractura. En este sentido se ha observado un importante mecanismo de deformación como es la propagación de placas de martensita a través de los límites de grano, entre aquellos granos que presentan una elevada coherencia cristalográfica y también otros mecanismos de deformación no menos importantes como son la formación de martensita -, el maclado y el entrecruzamiento de placas de martensita.En el Capítulo IV se detalla el trabajo experimental realizado para caracterizar el comportamiento a desgaste adhesivo de la aleación CuZnAl con memoria de forma cuando es sometida a ensayos de desgaste Pin-on-Disk frente a un disco de acero inoxidable 316L. Se evalúan los efectos que tienen los diferentes parámetros de ensayo, como son la carga y la velocidad lineal de deslizamiento sobre el desgaste en las diferentes microestructuras que presenta el material (, + martensita y martensita). Se evalúa también para una carga y velocidad constante, la microestructura del material que presenta un mejor comportamiento a desgaste adhesivo, a la vez que se relaciona este comportamiento con la temperatura de transformación Ms que presente el material. Se determina la pérdida de peso del material en función de la distancia recorrida para aleaciones que presentan temperaturas de transformación Ms comprendidas entre -93 y 78ºC. Se observa que son las aleaciones que presentan fase  + martensita y fase  con temperaturas de transformación Ms cercanas a la temperatura de trabajo las que presentan un mejor comportamiento a desgaste, siendo las aleaciones en fase  con temperaturas de transformación Ms pequeñas las que presentan una menor resistencia al desgaste. Se observa también que los residuos de desgaste independientemente de la microestructura que presente la aleación, presentan fase martensita, que al ser más blanda que la fase  no provocará ralladuras en el material. Por último en el Capítulo V, se detalla el trabajo experimental realizado para caracterizar electroquímicamente el comportamiento a corrosión de las aleaciones con memoria de forma CuZnAl utilizadas en el estudio del desgaste. Se utilizan diferentes técnicas electroquímicas como son:-Curvas E-t-Curvas de polarización -Ensayos potenciostáticos-Espectroscopia de impedanciasA parte de estas técnicas electroquímicas, también se utiliza la microscopía electrónica de barrido con microanálisis EDX acoplado, para caracterizar las superficies de corrosión y la técnica de espectroscopia de masas inducida por plasma (ICP-MS) para evaluar la liberación de iones al medio. A partir de los resultados obtenidos mediante la técnica de espectroscopia de impedancias se ha modelizado, un circuito eléctrico análogo al sistema físico estudiado, también llamado circuito equivalente. No se han observado diferencias significativas en el comportamiento electroquímico de las diferentes aleaciones estudiadas en función de la microestructura presente y en función de la composición química, para el rango de composiciones químicas estudiado.