Micro- and nanoparticles are being widely investigated for pharmaceutical purposes and are beginning to see application in clinical practice. There are numerous techniques to produce such therapeutic particles, including emulsion-based techniques and spray drying, each with their advantages. Electrospraying provides an alternative technique for preparing drug-loaded particles in the micro-scale with a good control of important particle characteristics, such as size and shape. In this work, electrospraying was used to investigate its potential for producing microparticles intended for oral administration of low solubility drugs. Different processing parameters including flow rate, solute concentration, drug loading and type of solvent and their influence on particle characteristics and drug release were studied using Celecoxib as a model drug and poly(lactic-co-glycolic acid) as a carrier material. The role of solvent mixtures were studied in detail with respect to particle characteristics and drug release kinetics and additional studies were performed for microparticles prepared with Celecoxib and the polymer Hypromellose Acetate Succinate. The electrosprayed particles were then compared with particles prepared with spray drying using similar experimental conditions and their performance was tested. Electrosprayed microparticles were prepared with diameters between 2-8 m and a near-monodisperse size distribution was obtained in most cases. The morphology of the particles ranged from smooth and spherical to rough and non-spherical depending on parameters used and were mainly attributed the evaporation rate and solubility of solute in the solvents. They are different from the spray dried particles which were all smooth, spherical and with a broader size distribution. Electrosprayed particles also showed more porosity and a different drug distribution compared with spray dried particles. The drug molecules were in an amorphous form in particles prepared using both techniques and remained stable after 8 months of storage. Drug release studies showed differences in release profiles depending on the parametric values. The drug release rates were directly related to the particle size, morphology, porosity and drug distribution observed and hence influenced by the studied process parameters. Spray dried particles generally had a slower drug release rate compared with electrosprayed particles attributed to differences in the particles characteristics observed. The results indicated that electrospraying is an attractive technique for producing drug loaded microparticles that can be tailored towards an intended drug delivery application. Compared with the more conventional spray drying process it provides better control of particle characteristics and demonstrated its suitability for preparing particle-based solid dispersion formulations in which the drug is molecularly dispersed and is released in a sustained manner to potentially improve oral bioavailability of low solubility drugs.

Rolling element bearings find widespread use in numerous machines and they are one of key components in involved systems. Bearing failures can cause catastrophic events if they are not detected in time and result in increasing downtime and maintenance cost. The need for longer endurance life with less cost drives research on bearing condition monitoring. Abstract Load monitoring provides significant information for bearing design and residual service life prediction as load applied by each rolling element on a bearing raceway controls friction and wear. It is possible to infer bearing load from load cells or strain gauges on the shaft or bearing housing. However this is not always simply and uniquely related to the real load transmitted by rolling elements directly to the raceway. Firstly, the load sharing between rolling elements in the raceway is statically indeterminate. And secondly, in a machine with non-steady loading the load path is complex and highly transient being subject to dynamic behavior of the transmission. This project develops a non-invasive, safe and portable technique to measure the load that transmitted directly by a rolling element to the raceway by using ultrasound. Abstract The technique works by monitoring the time-of-flight (ToF) of ultrasound that travels in a raceway and reflects back from the contact face. A piezoelectric sensor was permanently bonded onto the external surface of the stationary raceway in a rolling element bearing. The ToF of an ultrasonic pulse from the sensor to the raceway-rolling element contact was measured which depends on the wave speed and the thickness of the raceway. Abstract The speed of an ultrasonic wave in a component changes with the state of the stress; known as the acoustoelastic effect. The thickness of the element varies when deflection occurs as the contacting surfaces are subjected to load. Therefore, the ultrasonic ToF in a raceway is load dependent. In practical measurements, it was found that the phase of the wave reflected from rolling contacts varied with contact conditions. The phase was determined by the contact stiffness and in simple peak to peak measurement, this appeared as a change in the ToF. For typical rolling contacts, the ToF changes caused by deflection and acoustoelastic effect are of the order of nanoseconds, while the apparent time shift from the phase change effect is in the same order. Abstract Despite the phase change having effect on reflected signals, it does not affect the envelope of these signals. In this work the Hilbert transform was used to calculate the envelope of the reflected pulses and thus this contact dependent phase shift was eliminated. Time difference between the envelope of reflected pulses in unloaded and loaded state was a result of load effect alone. Abstract Ultrasonic measurements have been carried out on a model line contact formed between a steel plate and a cylindrical bearing steel roller, and line contacts in a cylindrical roller bearing which was used for the planet gear of a wind turbine epicyclic gearbox, as well as on elliptical contacts in a radially loaded ball bearing (deep groove). The ToF changes under different contact loads were recorded and used to determine the deflection of the raceway. This was then related to load using a simple elastic contact model. Measured load from the ultrasonic reflection was compared with the applied load upon the contact and good agreement has been achieved. The ultrasonic ToF technique shows promise as an effective method for load monitoring in real bearing applications.

No description available.

Nowadays, the global environmental pollution regulations drives the increase in the use of low-carbon sources as an alternative to conventional power generation. Moreover, the UK current energy policy, the Electricity Market Reform (EMR), has a strong focus on the security, affordability and decarbonisation of the energy system. In order to determine the optimal operation strategy from a techno-economics aspect under the EMR in the energy system, a Combined Economic and Emission Dispatch (CEED) model is investigated to solve the optimization problem in the energy system. This is able to find a security and affordability solution for the energy system. In addition, a wind-storage combined system (WSCS) is incorporated in the model. Furthermore, the Carbon Price Floor (CPF) and an Emission Performance Standard (EPS) are applied to model the support of EMR. The research in this thesis is progressive. The CEED model is investigated for a steady state energy system with conventional and wind power. Then the investigated model is developed to a dynamic state model; additionally, the dynamic model takes into account WSCS, which is in order to reduce renewable power uncertainty and the possible cost of waste and reserve power; finally, practical cases are studied using the model. To conclude, increasing the CPF at a low emission limit leads to an increase in the cost of an electrical system, but the increasing cost rate is mitigated by decreasing the emission limit. Furthermore, the CPF is able to dominate the dispatch at high emission limits. Nevertheless, at low emission limits, the EPS has a high impact on the dispatch. In addition, the renewable power has the superiority in both the economics and environment for a mid to long-term strategy for the UK. Moreover, the benefit of the WSCS is noticeable in economics, emissions and robustness.

An investigation of various ceramic bandpass filters with an improved spurious performance for use in cellular base station filtering applications is presented in this thesis. Monolithic integrated ceramic bandpass filters offer more than 50% size reduction compared to air-filled coaxial resonator filters with the same unloaded Q-factor. However, the stopband performance of these filters is deteriorated by spurious frequencies of the fundamental mode and higher order modes. The probable solution to reducing the effects of these undesired modes is to add a low-pass filter or band-stop filter at the expense of higher in-band losses and bulky volumes. In this work, multiple geometrical design techniques are explored to achieve the optimum out of band performance without any need for a low-pass filter. The improvement in spurious performance of Chebyshev ceramic bandpass waveguide filters is explored. In particular, its design solution aimed to improve the stopband attenuation for these filters. The design of the Chebyshev monolithic ceramic bandpass filter is reviewed, and some realizations are proposed and compared with the filter. The sixth order Chebyshev ceramic bandpass filters with posts were designed with improved spurious performance. The input/output couplings are realized through the use of a coaxial cable placed at the center of the external resonator. The inter-resonator couplings are achieved by placing various metal plated through-holes in the broad dimension of a waveguide. The broad dimension of integrated ceramic waveguide resonators can be utilized as an extra degree of freedom that can be integrated into filter design procedure and a better spurious performance is achieved by mixing resonators of non-uniform widths. Chebyshev ceramic bandpass filters are designed with two and three non-uniform width resonators and significant improvement has been achieved in the stopband performance of the filters. Other solutions involve the mixing of resonators with posts and non-uniform width resonator. The six order ceramic waveguide bandpass filters are simulated and fabricated in an air filled waveguide with tuning screws. Metal tuning screws are included to overcome mechanical discrepancies and imperfections. The stepped impedance resonators were previously applied to both planar, coaxial and air-filled rectangular waveguide filters. Here, for the first time, their use has been extended to monolithic integrated ceramic waveguide filters, accomplishing an exceptional spurious free stopband bandwidth for the filters. Finally, sixth order ceramic loaded waveguide filters were designed and fabricated with ridge and non-uniform width ceramic blocks. Their top and bottom surfaces are metalized through the silver paint with the conductivity of 4 x 10⁷ s/m. Inductive irises are used for inter-resonator coupling where the coaxial probe excites the external resonators of the filter and the excellent stopband attenuation of up to 2.45 *f_o is achieved.

No description available.

Cutting tools with ceramic inserts are often used in the process of machining many types of super alloys, mainly due to their high strength and thermal resistance. Nevertheless, during the cutting process, the plastic flow wear generated in these inserts enhances and propagates cracks due to high temperature and high mechanical stress. This leads to a very variable failure of the cutting tool. Furthermore, in high-speed rough machining of nickel-based super alloys, such as Inconel 718 and Waspalloy, it is recommended to avoid the use of any type of coolant. This in turn, enables the clear visualization of cutting sparks, which in these machining tasks are quite distinctive. The present doctoral thesis attempts to set the basis of a potential Tool Condition Monitoring (TCM) system that could use vison-based sensing to calculate the amount of tool wear. This TCM system would work around the research hypothesis that states that a relationship exists between the continuous wear that ceramic SiAlON (solid solutions based on the Si3N4 structure) inserts experience during a high-speed machining process, and the evolution of sparks created during the same process. A successful TCM system such as this could be implemented at an industrial level to aid in providing a live status of the cutting tool’s condition, potentially improving the effectiveness of these machining tasks, whilst preventing tool failure and workpiece damage. During this research, sparks were analyzed through various visual methods in three main experiments. Four studies were developed using the mentioned experiments to support and create a final predictive approach to the TCM system. These studies are described in each thesis chapter and they include a wear assessment of SiAlON ceramics, an analysis of the optimal image acquisition systems and parameters appropriate for this research, a study of the research hypothesis, and finally, an approach to tool wear prediction using Neural Networks (NN). To carry out some of these studies, an overall methodology was structured to perform experiments and to process spark evolution data, as image processing algorithms were built to extract spark area and intensity. Towards the end of this thesis, these spark features were used, along with measured values of tool wear, namely notch, flank and crater wear, to build a Neural Network for tool wear prediction.

No description available.

Aeroelasticity and fracture mechanics are two fields that commonly known will result in a structural failure. However, small attention is given in assessing the structural integrity of any flying object in aerospace application subjected to aerodynamic or aeroelastic loads especially the aircraft wing. The current research in the aircraft industry is focusing on the development of advanced composite wing structure, which there are still not well explored widely. Due to the higher strength of composite materials, a stronger wing could be designed to sustain the aerodynamic loads or any gust turbulence during flying at high altitude. This situation will be severely dangerous in the event of having a crack or damage on the surface of the cruising wing structure. This research aims at investigating the structural integrity of composite plate, either undamaged or with damage (with crack) subjected to the aerodynamic loads. The purpose of this study is to provide a novel numerical modelling in predicting the application of aerodynamic loads, by observing the flight maneuver safety margin including the flutter speed determination. Initially, the flutter speed was computed based on the coupled of finite element method (FEM) for the structural modelling and the doublet lattice method (DLM) in MSC Nastran for the unsteady aerodynamic modelling. Both structural and aerodynamic models were connected by interpolation using spline. In the end, the safety flight envelope for the composite plate was plotted based on the regulations provided by the Federal Aviation Regulations (FAR) 23. The numerical predictions of crack propagations of the damaged composite structure were determined by implementing the extended finite element model (XFEM), subjected to the aerodynamic loads intercorrelated through Fourier Series Function (FSF). Significantly, the aerodynamic loads were predicted by the implementation of gust, which produced the same level of maximum deflection analysed via aero-static analysis. The results show that the fibre orientation of the composite plate contributes significant crack propagations under the cruising aerodynamic loads. The same procedures were repeated to the wing box prototype developed under the joint program of Indonesian Aerospace, National Institute of Aeronautics and Space of Indonesia and Agency for Assessment and Application of Technology of Indonesia. For this work, the wing fracture was investigated by the influence of turbulence, called discrete 'gust loads'. From here, FSF was used to combine the wingtip deflection under the gust load influence, and hence applied XFEM to model the crack propagations. The results show that the crack propagated at the lower-front skin near to the wing root.

No description available.