In this research project the study was conducted on conductivity of acrylonitrile butadiene styrene (ABS)/Nylon 6 blend with carbon black as conductive filler. Three different blends of ABS/carbon black, Nylon 6/carbon black and ABS/Nylon 6/carbon black with various compositions were prepared by mixing together by using a single screw extruder. Each compound was reblended to achieve homogeneous mixture and the effect of processing was studied. Conductivity of the low resistance of blends were obtained by measuring sheet resistance using four-point probe as according to ASTM F 1529. The sheet resistance could only be detected for ABS/carbon black 20 wt % and above, and ABS/Nylon 6 with 80:20 ratio with 10 wt % of carbon black. Whereas, for Nylon 6/carbon black blends and the others high resistance of blends, their resistances were measured by Teraohmeter according to ASTM D 257 method. Percolation threshold (critical volume fraction) of the blends was studied to find actual conductive filler contents to avoid deterioration of mechanical properties. In this case, tensile tests were conducted according to ASTM D 638 to establish their mechanical properties. Meanwhile, scanning electron microscopy (SEM) was used to study the morphology of blended polymers, interface of polymer/carbon black and aggregation phenomenon between carbon black and polymers. The correlation between conductivity, mechanical properties and morphological characterisation of all the blends was studied. The results show that, the addition of carbon black up to 10%, increases conductivity and tensile strength of ABS/carbon black and Nylon 6/carbon black blends. Conductivity continues to increase with further addition of carbon black, but at the expense of tensile strength reduction due to the effect of brittle nature of carbon black. By adding ABS in ABS/Nylon 6/carbon black blends, conductivity increases, whereas tensile strength decreases. However, tensile strength of ABS/Nylon 6/carbon black blends were too low to compare with individual polymer blended with carbon black, due to immiscibility between ABS and Nylon 6. Reblending the compound for the third time increases conductivity and mechanical properties due to increase in homogeneity and uniform distribution of carbon black dispersion. Both ABS and conductive carbon black absorb moisture that can effect the properties of compound. Drying of the compound will remove moisture which will result in improvements in conductivity and tensile strength.

An experimental apparatus has been developed with the object of providing a test plant, based on commercially available electro-hydraulic components, for the investigation of multivariable control system design methodologies. A mathematical model has been produced for this experimental plant and a preliminary analysis of the plant carried out. A selection of controller design techniques has been investigated. Designs have been produced for two state feedback controllers in which the feedback coefficients were based on LQR theory, one of which used a full order estimator based on a Kalman Filter, the other using a reduced order observer whose poles were chosen arbitrarily. In addition, forward path compensators have been developed using the Characteristic Locus and the Hinfinity/Mixed Sensitivity methods. These controller designs were based on computations and simulations utilising Matlab and a selection of its control engineering toolboxes and Simulink. The completed designs were implemented in digital form and tested on the actual plant. A series of tests were carried out to assess the robustness of the various controllers in the presence of plant uncertainty. The physical plant was modified and the controllers based on the nominal plant model used in conjunction with this modified plant. As a design technique which enabled robustness issues to be addressed explicitly, the Hinfinity approach was used to improve the robustness of the original Hinfinity controller.

Results are presented from a series of simulations undertaken to determine whether dynamic processes observed in device-scale liquid crystal cells confined between aligning substrates can be simulated in a molecular system using parallel molecular dynamics of the Gay-Berne model. In a nematic cell, on removal of an aligning field, initial near-surface director relaxation can induce flow, termed 'backflow', in the liquid. This, in turn, can cause director rotation, termed 'orientational kickback', in the centre of the cell. Simulations are performed of the relaxation in nematic systems confined between substrates with a common alignment on removal of an aligning field. Results show that relaxation timescales of medium sized systems are accessible. Following this, simulations are performed of relaxation in hybrid aligned nematic systems, where each surface induces a different alignment. Flow patterns associated with director reorientation are observed. The damped oscillatory nature of the relaxation process suggests that the behaviour of these systems is dominated by orientational elastic forces and that the observed director motion and flow do not correspond to the macroscopic processes of backflow and kickback. Chevron structures can occur in confined smectic cells which develop two domains of equal and opposite layer tilt on cooling. Layer tilting is thought to be caused by a need to reconcile a mismatch between bulk and surface smectic layer spacing. Here, simulations are performed of the formation of structures in confined smectic systems where layer tilt is induced by an imposed surface pretilt. Results show that bookshelf, chevron and tilted layer structures are observable in a confined Gay-Berne system. The formation and stability of the chevron structure are shown to be influenced by surface slip.

Powered passenger train door unreliability is a major source of in-service delay and cancellation to passenger train services. This unreliability costs UK Train Operating Companies significant amounts of money through Railtrack charges, customer compensation payments and loss of revenue as well as door maintenance and repair procedures. The successful and reliable identification of incipient powered door faults could therefore help to reduce these charges and subsequent maintenance costs, increase train reliability and potentially reduce safety-related incidents. This thesis presents the research and development of an off-line condition monitoring tool for electric powered passenger train doors, the Door Analysis Tool. The Door Analysis Tool was developed through a two-year, collaborative TCS project between Sheffield Hallam University and Interfleet Technology, an international railway engineering consultancy. The project was partly funded by the Department of Trade and Industry. This thesis focuses on a number of primary areas of work, namely: Introduction to powered train doors and condition monitoring in the railway industry; Identification of suitable data collection and condition monitoring equipment forpowered train doors; Development of suitable data analysis and interpretation algorithms; Development of a commercially viable prototype condition monitoring product forpowered passenger train doors, the Door Analysis Tool; Validation of the Door Analysis Tool through theoretical and practical testing; Identification of further development opportunities and further future work. The Door Analysis Tool uses clamp-on current probes to measure the door motor current characteristic and traction interlock status during opening and closing cycles to monitor the performance of train doors. It offers a range of opportunities to different parties within the railway industry to help reduce the impact of powered train door unreliability and thereby improve train performance through the identification of faulty train doors prior to costly in-service failures. The practical testing of the prototype Door Analysis Tool showed that it functions as intended in a train maintenance depot environment and that it is capable of collecting, analysing and classifying data relating to train door performance. The theoretical tests presented the prototype Door Analysis Tool with nine different sets of data, each representing a range of faulty and fault-free door operations. The Door Analysis Tool was able to correctly classify six of the nine tests. Three of the tests incorporating minor fault conditions were not highlighted by the door performance classification, however all of the theoretical faults were identifiable through inspection of the analysis parameters, which can be stored after each test. The sensitivity of the Door Analysis Tool analysis routines can be adjusted to tailor the tool to different systems.

The work in this thesis investigates the properties of the IR diffuse wireless link with regard to: the use of sets of signature sequences with good message separation properties (hence providing low BER), the suitability of a hPIM-CDMA scheme for the IR diffuse wireless systems under the constraint of eye safety regulations (i.e. when all users are transmitting simultaneously), the quality of message separation due to multipath propagation. The suitability of current DS-CDMA systems using other modulation techniques are also investigated and compared with hPIM-CDMA for the performances in power efficiency, data throughput enhancement and error rate. A new algorithm has also been proposed for generating large sets of (n,3,1,1)OOC practically with reduced computation time. The algorithm introduces five conditions that are well refined and help in speeding up the code construction process. Results for elapsed computation times for constructing the codes using the proposed algorithm are compared with theory and show a significant achievement. The models for hPIM-CDMA and hPPM-CDMA systems, which were based on passive devices only, were also studied. The technique used in hPIM-CDMA, which uses a variable and shorter symbol duration, to achieve higher data throughput is presented in detail. An in-depth analysis of the BER performance was presented and results obtained show that a lower BER and higher data throughput can be achieved. A corrected BER expression for the hPPM-CDMA was presented and the justification for this detailed. The analyses also show that for DS-CDMA systems using certain sets of signature sequences, the BER performance cannot be approximated by a Gaussian function.

No description available.

No description available.

The canine stifle joint is one of the most vulnerable joints within the musculoskeletal system and the cranial cruciate ligament (CCL) is the most susceptible ligament to rupture within the joint. When this ligament is damaged, the stifle joint becomes mechanically unstable leading to abnormal load distribution within the joint. This physiological change is associated with osteophyte formation at the joint margins, thickening of the medial aspect of the joint capsule and the medial collateral ligament, softening of the articular cartilage resulting in osteoarthritis (OA). Ligament injury can be either purely traumatic or a degenerative non-contact form. The aetiopathogenesis of non-contact cranial cruciate ligament rupture (CCLR) is unclear, however alterations in the composition of the extracellular matrix (ECM) has been implicated as one of its causes. This thesis aimed to advance the current understanding of the biomechanical behaviour of the canine CCL and investigated the contribution of proteoglycans (PGs) to the viscoelastic behaviour of the CCL. The objectives comprise of experimental and numerical studies, including the development and utilisation of a novel full-field three-dimensional digital image correlation method (3D DIC) and a representative FEM of the whole canine stifle joint. Experimental Study I on the canine CCLs was the first to focus on characterising slow strain rate sensitivity and hysteresis behaviour of the ligament at the toe-region of stress-strain behaviour. This study showed that arranging mechanical tests in different orders of strain rates resulted in different tissue response, such that tensile responses of the CCL during the ascending (increasing order of strain rates from 0.1 to 1%/min, and 1 to 10%/min) tests were significantly different from the descending tests (decreasing order of strain rates from 10 to 1%/min, and 1 to 0.1%/min). Only during ascending tests were the CCLs strain rate sensitive and hysteresis was strain rate dependent. The different tensile responses of the CCLs during the ascending and descending order of strain rate may be associated with strain history of the tissue. In Experimental Study II, two groups of the CCLs (control and treatment (PG depletion)) were tested under tensile load at slow strain rates (0.1, 1 and 10%/min). PG content in the treatment group was depleted by 21.11 ± 14.51% (p=0.45). Water content in the treatment group reduced by approximately 5.2% (p=0.048). Although there were no statistically significant values; stress-strain, tangent modulus, hysteresis and creep behaviour in the treatment was different from the control groups. Stress relaxation rate was significantly higher in the control than the treatment group (p=0.039). The lower relaxation rate in the treatment group could be associated with sGAGs which provides cross-links between collagen molecules. Hence, it is possible that an efficient depletion of PGs in canine CCLs could result in significant mechanical changes in the tissue. A full-field 3D DIC method was developed to generate five CCL-specific FEM and provide load-deformation behaviour across the middle region of the CCLs. This information was utilised to predict stress-strain behaviour of the CCLs through inverse analysis. In addition, an anatomically representative FEM of the canine stifle joint was developed and employed to investigate the joint when PGs in the CCL were depleted. Results showed reduction in joint stability in joints with depleted CCLs (p=0.56). Hence, PG content in the CCL could be one of the ECM components contributing to the mechanical behaviour of the ligament, and affecting the stability in canine stifle joints. This research leads to a better understanding of the biomechanical behaviour of canine CCL, and it is useful for researchers in the field of biomechanics and biomedical science who are seeking advanced experimental and numerical works in tissue mechanics.

No description available.

Split sleeve cold expansion is one of the most widely used methods in the aerospace industry to enhance the fatigue performance of fastener holes in airframe structures. The initial motivation, which led to this research programme, was to develop an understanding of the behaviour of fatigue cracks emanating from cold-expanded holes, with a particular emphasis on the influence of these cracks on the surrounding compressive residual stresses. There are two strands of the research presented in this thesis: first being related to the study of hole deformation resulting from split sleeve cold expansion; and the second one focused on the fatigue behaviour of cracks emanating from cold-expanded holes. The strain fields developed from cold expansion were measured using stereoscopic digital image correlation (DIC) technique in aluminium specimens of two different thicknesses giving thickness to hole diameter ratio of 0.25 and 1. The capability of DIC in providing full-field strain data was exploited to determine the shape and size of the plastic zones developed from cold expansion. The results showed that the existing split sleeve cold expansion process is not as effective in creating an axisymmetric compressive residual elastic stress zone around the fastener holes in thin as it is in the thick specimens. The thin specimens used in this investigation were equivalent in thickness to sheet material commonly used in an aircraft fuselage or wing skins and the results indicate that there is a need to review the use of cold expansion process using a split sleeve and mandrel for holes in thin sheets. A simple approach utilising DIC was presented to analyse the strain fields resulting from cold expansion in stacked specimens. The results showed that stacking offers some improvement in the cold expansion of thin sheet components. They also demonstrated the workability of this approach which can be applied effectively to analyse cold expansion of fastener holes associated with a real joint configuration in an airframe. The propagation of fatigue cracks initiating from the cold-expanded holes was investigated by employing the thermoelastic stress analysis (TSA) technique and their influence on the surrounding residual stresses was determined using synchrotron x-ray diffraction (SXRD) technique. A long-standing ambiguity in the literature regarding the potential relaxation of beneficial compressive residual stresses, as a result of fatigue crack propagation, was addressed; and it was established, from TSA and SXRD results, that the formation or propagation of a fatigue crack does not cause any significant relaxation of these residual stresses. The results also clearly identify the loading conditions under which the residual stresses are expected to relax. This information is important in improving the theoretical models for fatigue life assessment of cold-expanded holes. The results should also be useful for the engineers in the aerospace industry to realise the full potential of the cold expansion process and to utilise it more effectively in the manufacturing of airframes leading to improved fatigue endurance under different loading conditions.