This research work deals with the manufacture, properties and characterisation of layered silicate (LS) reinforced novel spent polymer nanocomposites. Three different materials used for nanocomposites preparation were polyamide 12 (PA-12), DuraForm polyamide 11 (EX) and Glass Filled polyamide 12 (GF-12). Various concentrations (1, 3, 5 and 7 wt. %) of the layered silicates were dispersed in three different types of spent polyamide matrix by the melt compounding method, in order to investigate the effect of LS reinforcement on mechanical and thermal properties of spent polymer. The interlayer d-spacing, interlamellar structure and surface morphologies were investigated by wide angle x-ray diffraction (WXRD), transmission electron microscope (TEM) and scanning electron microscope (SEM), respectively. The tensile strength and modulus of the un-reinforced spent PA-12 samples were found to increase with the incorporation of LS. This improvement in the tensile strength and modulus appear to be directly related to the LS loading. Similarly, the flexural strength and modulus were found to increase significantly with incorporation of the LS reinforcement. Nanoindentation test results were used to evaluate the nanomechanical properties (i.e. hardness and modulus) of spent PA-12/nanocomposites. The results show that the hardness and modulus of LS reinforced spent PA-12 nanocomposites were higher compared to the un-reinforced spent PA-12 sample. Crystallisation temperature measured using DSC showed a gradual decrease as the LS loading increased. For spent PA-12 nanocomposites samples the melting temperature slightly increased with 1 and 3 wt. % of LS loading when compared with the unreinforced spent PA-12 sample. However, samples with 5 and 7 wt. % of LS have approximately the same melting temperature of the un-reinforced spent PA-12 sample. Glass transition temperature (Tg) of the spent PA-12 nanocomposites slightly decreased in comparison to the un-reinforced spent PA-12 sample. It was found that the incorporation of LS does not affect or improve the tensile strength and modulus of the spent EX nanocomposites. However, flexural strength and modulus for the spent EX nanocomposites are improved when compared with the un-reinforced spent EX sample. The nanoindentation results show that as the LS concentration increased up to 3 wt.%, the hardness and modulus were improved. Different levels of layered silicates dispersion as characterised by XRD, TEM and SEM correlated strongly with improvements in mechanical and thermal performances. The crystallisation temperature of spent EX and GF-12 nanocomposites samples shows gradual increases with increasing LS loading. The measured crystallisation temperature was approximately 6˚C higher for the spent EX nanocomposites samples than for the un-reinforced spent EX sample. Secondary heating of the un-reinforced spent EX sample and the nanocomposites samples resulted in an increase in melting temperature which corresponded to increasing LS loading. However, the melting temperature for all the spent GF-12 nanocomposites samples was similar to the one for the un-reinforced spent GF-12 sample. It was found that Tg values decreased with increased in LS loading for spent GF-12 samples. The presence of layered silicate did not contribute in improving tensile and flexural strength of spent GF-12 matrix. However, the hardness and elastic modulus were found to increase with increased layered silicates loading up to 7 wt.%.

Recently, femoroacetabular impingement (FAI) was introduced as a pathomechanical concept that could explain idiopathic cartilage and labral degeneration. FAI can be subdivided into three mechanisms: 'Cam'- and 'pincer'-type impingement and the 'contracoupe' mechanism. The suggested concept aims to create a link between retrospective findings of cartilaginous tissue degeneration and mild abnormal structural deformations of the hip joint. The theoretical concept focuses on abnormal articulation rather than increased axial-overloading. Although clinical evidence seems to be given, prospective biomechanical verification would be desirable to provide further justification for early joint reconstruction surgery. A comprehensive research program has been carried out to highlight elevated stresses, contact pressures, affected fluid-load support, abnormal articulation and increased femoral head motion evoked by mild to severe abnormal conditions of the hip joint. Contact pressure, stress distributions and femoral head motion, indicating joint stability, were studied using three dimensional finite element models of normal and abnormal hip joint conditions; the considered abnormal conditions included a varying degree of acetabular and femoral version and manifestation of femoral protrusions (hump) at the femoral head-neck junction. The cartilogenous tissues were considered as linear elastic isotropic materials. The highlighted abnormal articulation confirmed the suggested concept of FAI; the predicted abnormal stress and contact pressure distribution corresponded to clinical findings. The fluid-load support, solid-on-solid stress, stress components, within the solid extracellular matrix of the cartilaginous tissues, and total contact pressure were studied during normal and isolated 'cam'-type impinged articulation. The cartilogenous tissues were considered as linear biphasic orthotropic materials. While the maximum total contact pressure, predicted during distinct 'cam'-type impingement, did not exceed the maxima obtained for normal articulation, the fluid-load support was severely affected at the zone of impingement. Vigorous elevated solid-on-solid stresses found at the zone of impingement, suggest a local increase in the coefficient of friction, which might lead to cartilage wear and progresses to severe osteoarthritis.

Creativity is widely recognised as a vital element in modern-day engineering design. It is through creative behaviour that engineering designers produce creative solutions to their problems, and through creative solutions that many companies succeed. However, research into creative behaviour within engineering design has to date focused largely on the design process in general or on early-stage design; neglecting the often complex and constrained engineering practice that occurs during later design stages. It is to this research focus that the work presented here has been completed. Defined through its production of outputs that are original, of appropriate quality, and surprising, creative design behaviour is a culmination of several aspects within the engineering process; that of a person or team; working within a specific context; actively completing a process; that will produce an output for a particular design brief. At the centre of this situation is then the designer; it is through their individual behaviours that creative outputs are formed. Due to the nature of the later stage engineering design process, the accompanying influences under which designers work, and the types of activity that they complete, it presents a very different situation to early-stage design. It is therefore not possible to assume that understanding based on study of either early-stage design or the design process in general is entirely applicable to later-stage design processes or to the type of support that designers working within may need. Thus, when linked to creative behaviour, this presents an opportunity for research; there is possibility to gain valuable understanding of the manner in which creative solutions are produced through the study of designers’ creative behaviour in later-stage design. It is to this goal that this research has been performed, namely to characterise the creative behaviour of designers within the later-stages of the engineering design process. To this end, this thesis presents a detailed review of the field of creativity, the field of engineering design, and current understanding of designer behaviour. From the understanding that each of these provides, a framework and coding scheme are then developed, which are designed to identify creative behaviour within the individual tasks of designers throughout the design process. This coding scheme is then used within three studies; one based on seven less-experienced designers working within a 22-week project, one of eighteen designers of varying experience undertaking a design brief set by the author, and one of four designers working within industry. Through analysis of the data produced by these studies, this thesis contributes several characterisations of designer behaviour within later-stage design. These include typical task-types in which all designers are creative, two distinct creative approaches that correlate with a designers personal creative style, and types of tasks to complete in order encourage streamlining of the design process; in addition to more general characterisations concerning designer focus within early and late-stage design, and differences in behaviour between expert and less-experienced designers. Through the understanding that this research has gained and presents within this thesis there are many opportunities for further work on the subject of the improvement and support of designer behaviour. Both within an academic and industrial context, detailed and specific characterisation of creative behaviour in later-stage design has the potential to provide the means to improve both the process and output of engineering design.

In many image-processing applications, one object of interest must be segmented. The techniques used for segmentation vary depending on the particular situation and the specifications of the problem at hand. In methods that rely on a learning process, the lack of a sufficient number of training samples is usually an obstacle, especially when the samples need to be manually prepared by an expert. The performance of some other methods may suffer from frequent user interactions to determine the critical segmentation parameters. Also, none of the existing approaches use online (permanent) feedback, from the user, in order to evaluate the generated results. Considering the above factors, a new multi-stage image segmentation system, based on Reinforcement Learning (RL) is introduced as the main contribution of this research. In this system, the RL agent takes specific actions, such as changing the tasks parameters, to modify the quality of the segmented image. The approach starts with a limited number of training samples and improves its performance in the course of time. In this system, the expert knowledge is continuously incorporated to increase the segmentation capabilities of the method. Learning occurs based on interactions with an offline simulation environment, and later online through interactions with the user. The offline mode is performed using a limited number of manually segmented samples, to provide the segmentation agent with basic information about the application domain. After this mode, the agent can choose the appropriate parameter values for different processing tasks, based on its accumulated knowledge. The online mode, consequently, guarantees that the system is continuously training and can increase its accuracy, the more the user works with it. During this mode, the agent captures the user preferences and learns how it must change the segmentation parameters, so that the best result is achieved. By using these two learning modes, the RL agent allows us to optimally recognize the decisive parameters for the entire segmentation process.

Vehicle tracking in environments containing occlusion and clutter is an active research area. The problem of tracking vehicles through such environments presents a variety of challenges. These challenges include vehicle track initialization, tracking an unknown number of targets and the variations in real-world lighting, scene conditions and camera vantage. Scene clutter and target occlusion present additional challenges. A stochastic framework is proposed which allows for vehicles tracks to be identified from a sequence of images. The work focuses on the identification of vehicle tracks present in transportation scenes, namely, vehicle movements at intersections. The framework combines background subtraction and motion history based approaches to deal with the segmentation problem. The tracking problem is solved using a Monte Carlo Markov Chain Data Association (MCMCDA) method. The method includes a novel concept of including the notion of discrete, independent regions in the MCMC scoring function. Results are presented which show that the framework is capable of tracking vehicles in scenes containing multiple vehicles that occlude one another, and that are occluded by foreground scene objects.

This research explores the development of vibration-based haptic feedback for a mouse-like computer input device. The haptic feedback is intended to be used in 3D virtual environments to provide users of the environment with information that is difficult to convey visually, such as collisions between objects. Previous research into vibrotactile haptic feedback can generally be split into two broad categories: single tactor handheld devices; and multiple tactor devices that are attached to the body. This research details the development of a vibrotactile feedback device that merges the two categories, creating a handheld device with multiple tactors. Building on previous research, a prototype device was developed. The device consisted of a semi-sphere with a radius of 34 mm, mounted on a PVC disk with a radius of 34 mm and a height of 18 mm. Four tactors were placed equidistantly about the equator of the PVC disk. Unfortunately, vibrations from a single tactor caused the entire device to shake due to the rigid plastic housing for the tactors. This made it difficult to accurately detect which tactor was vibrating. A second prototype was therefore developed with tactors attached to elastic bands. When a tactor vibrates, the elastic bands dampen the vibration, reducing the vibration in the rest of the device. The goal of the second prototype was to increase the accuracy in localizing the vibrating tactor. An experiment was performed to compare the two devices. The study participants grasped one of the device prototypes as they would hold a computer mouse. During each trial, a random tactor would vibrate. By pushing a key on the keyboard, the participants indicated when they detected vibration. They then pushed another key to indicate which tactor had been vibrating. The procedure was then repeated for the other device. Detection of the vibration was faster (p < 0.01) and more accurate (p < 0.001) with the soft shell design than with the hard shell design. In a post-experiment questionnaire, participants preferred the soft shell design to the hard shell design. Based on the results of the experiment, a mould was created for building future prototypes. The mould allows for the rapid creation of devices from silicone. Silicone was chosen as a material because it can easily be moulded and is available in different levels of hardness. The hardness of the silicone can be used to control the amount of damping of the vibrations. To increase the vibration damping, a softer silicone can be used. Several recommendations for future prototypes and experiments are made.

In many image-processing applications, one object of interest must be segmented. The techniques used for segmentation vary depending on the particular situation and the specifications of the problem at hand. In methods that rely on a learning process, the lack of a sufficient number of training samples is usually an obstacle, especially when the samples need to be manually prepared by an expert. The performance of some other methods may suffer from frequent user interactions to determine the critical segmentation parameters. Also, none of the existing approaches use online (permanent) feedback, from the user, in order to evaluate the generated results. Considering the above factors, a new multi-stage image segmentation system, based on Reinforcement Learning (RL) is introduced as the main contribution of this research. In this system, the RL agent takes specific actions, such as changing the tasks parameters, to modify the quality of the segmented image. The approach starts with a limited number of training samples and improves its performance in the course of time. In this system, the expert knowledge is continuously incorporated to increase the segmentation capabilities of the method. Learning occurs based on interactions with an offline simulation environment, and later online through interactions with the user. The offline mode is performed using a limited number of manually segmented samples, to provide the segmentation agent with basic information about the application domain. After this mode, the agent can choose the appropriate parameter values for different processing tasks, based on its accumulated knowledge. The online mode, consequently, guarantees that the system is continuously training and can increase its accuracy, the more the user works with it. During this mode, the agent captures the user preferences and learns how it must change the segmentation parameters, so that the best result is achieved. By using these two learning modes, the RL agent allows us to optimally recognize the decisive parameters for the entire segmentation process.

Vehicle tracking in environments containing occlusion and clutter is an active research area. The problem of tracking vehicles through such environments presents a variety of challenges. These challenges include vehicle track initialization, tracking an unknown number of targets and the variations in real-world lighting, scene conditions and camera vantage. Scene clutter and target occlusion present additional challenges. A stochastic framework is proposed which allows for vehicles tracks to be identified from a sequence of images. The work focuses on the identification of vehicle tracks present in transportation scenes, namely, vehicle movements at intersections. The framework combines background subtraction and motion history based approaches to deal with the segmentation problem. The tracking problem is solved using a Monte Carlo Markov Chain Data Association (MCMCDA) method. The method includes a novel concept of including the notion of discrete, independent regions in the MCMC scoring function. Results are presented which show that the framework is capable of tracking vehicles in scenes containing multiple vehicles that occlude one another, and that are occluded by foreground scene objects.

This research explores the development of vibration-based haptic feedback for a mouse-like computer input device. The haptic feedback is intended to be used in 3D virtual environments to provide users of the environment with information that is difficult to convey visually, such as collisions between objects. Previous research into vibrotactile haptic feedback can generally be split into two broad categories: single tactor handheld devices; and multiple tactor devices that are attached to the body. This research details the development of a vibrotactile feedback device that merges the two categories, creating a handheld device with multiple tactors. Building on previous research, a prototype device was developed. The device consisted of a semi-sphere with a radius of 34 mm, mounted on a PVC disk with a radius of 34 mm and a height of 18 mm. Four tactors were placed equidistantly about the equator of the PVC disk. Unfortunately, vibrations from a single tactor caused the entire device to shake due to the rigid plastic housing for the tactors. This made it difficult to accurately detect which tactor was vibrating. A second prototype was therefore developed with tactors attached to elastic bands. When a tactor vibrates, the elastic bands dampen the vibration, reducing the vibration in the rest of the device. The goal of the second prototype was to increase the accuracy in localizing the vibrating tactor. An experiment was performed to compare the two devices. The study participants grasped one of the device prototypes as they would hold a computer mouse. During each trial, a random tactor would vibrate. By pushing a key on the keyboard, the participants indicated when they detected vibration. They then pushed another key to indicate which tactor had been vibrating. The procedure was then repeated for the other device. Detection of the vibration was faster (p < 0.01) and more accurate (p < 0.001) with the soft shell design than with the hard shell design. In a post-experiment questionnaire, participants preferred the soft shell design to the hard shell design. Based on the results of the experiment, a mould was created for building future prototypes. The mould allows for the rapid creation of devices from silicone. Silicone was chosen as a material because it can easily be moulded and is available in different levels of hardness. The hardness of the silicone can be used to control the amount of damping of the vibrations. To increase the vibration damping, a softer silicone can be used. Several recommendations for future prototypes and experiments are made.

Capacitive micromachined ultrasonic transducers (CMUTs) have proven themselves to be excellent candidates for medical ultrasonic imaging applications. The use of semiconductor fabrication techniques facilitates the fabrication of high quality arrays of uniform cells and elements, broad acoustic bandwidth, the potential to integrate the transducers with the necessary electronics, and the opportunity to exploit the benefits of batch fabrication. In this thesis, the design, fabrication and testing of one- and two-dimensional CMUT arrays using a novel wafer bonding process whereby the membrane and the insulation layer are both silicon nitride is reported. A user-grown insulating membrane layer avoids the need for expensive SOI wafers, permits optimization of the electrode size, and allows more freedom in selecting the membrane thickness, while also enjoying the benefits of wafer bonding fabrication. Using a row-column addressing scheme for an NxN two-dimensional array permits three-dimensional imaging with a large reduction in the complexity of the array when compared to a conventional 2D array with connections to all N2 elements. Only 2N connections are required and the image acquisition rate has the potential to be greatly increased. A simplification of the device at the imaging end will facilitate the integration of a three-dimensional imaging CMUT array into either an endoscope or catheter which is the ultimate purpose of this research project. To date, many sizes of transducers which operate at different frequencies have been successfully fabricated. Initial characterization in terms of resonant frequency and, transmission and reception in immersion has been performed on most of the device types. Extensive characterization has been performed with a linear 32 element array transducer and a 32x32 element row-column transducer. Two- and three-dimensional phased array imaging has been demonstrated.