Rolling contact fatigue of thermal spray coatings

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The practical advantages of thermal spray coatings like high deposition rates, low cost and tribological properties of high wear resistance have enabled these coatings to become an integral part of aircraft and automobile industry. Recent advancements in thermal spraying techniques like high particle speed and temperature call for new applications for these coatings. This experimental study addresses the Rolling Contact Fatigue performance of thermal spray coatings deposited by a variety of techniques like High Velocity Oxy-Fuel (HVOF), Detonation Gun (D-Gun) and Plasma spraying. RCF tests were conducted using a modified four ball machine in conventional steel ball bearing and hybrid ceramic bearing configurations. Tribological conditions during the RCF tests were varied by changing the test lubricant and the lubrication mechanism, contact load and shape of the drive coated rolling element to vary the roll/slip ratio. RCF tests were analyzed on the basis of the performance, coating failures using surface and subsurface observations, and residual stress studies. Experimental and theoretical studies of the ball kinematics have also been included. These tests revealed that the performance of the coated rolling elements was dependent upon the coating and the substrate properties. The coating thickness, substrate hardness, tribological conditions during the test, coating and substrate material as well as the coating process and the substrate preparation significantly affect the coating performance and the failure modes. Three different failure modes of these coatings have been discussed along with the changes in the near surface residual stress behaviour of the coated rolling elements

Determining the most efficient geometry through simulation study of ZnO nanorods for the development of high-performance tactile sensors and energy harvesting devices

The piezoelectric nanomaterial ZnO exhibits an excellent piezoelectric response that can transduce mechanical energy into electrical signals by applying pressure. The piezoelectric behavior of ZnO nanostructures (especially nanorods or microrods) is getting considerable attention in the fabrications of piezo tactile sensors, energy harvesting devices, and other self-powering implantable devices. Especially vertically aligned ZnO nanorods are of high interest due to their higher value of piezoelectric coefficient along the z-direction. In this report, various geometries and alignments of ZnO nanorods are explored and their effect on strength of piezoelectric output potential has been simulated by COMSOL Multiphysics software. Best suited geometry and inclination are explored in this simulation to achieve high piezoelectric output in haptic and energy harvester devices. The simulation results show out of many geometries and inclinations the highest piezoelectric output is demonstrated by the inclined ZnO nanorods due to the application of higher torque force or shear stress in similar applied force. The high torque force or shear stress at 60 degree orientation and optimized contributions from all the piezoelectric coefficients resulted in a high piezoelectric output potential close to 215 mV which is much higher than the vertically aligned ZnO nanorod which is approximately 25 mV. The results are contrary to the accepted understanding that the vertical ZnO nanorods should produce the highest output voltage due to the high piezoelectric coefficient along the z-axis.Comment: 22 pages, 8 figure

Right-sided congenital diaphragmatic hernia and myelomeningocele: a rare association

Congenital diaphragmatic hernia (CDH) is a rare birth defect with a prevalence of \u3c 0.5 per 1,000 live births. Majority of these defects are left-sided as most studies suggest that frequency of right-sided CDH was 10% of the total. The association of CDH with myelomeningocele (MMC) is extremely rare; as in Sweed\u27s study of 116 consecutive cases of CDH, the incidence of associated MMC with CDH was stated as 4.3%. There has been one previous case report of leftsided CDH, MMC and hydrocephalus prenatally diagnosed; but to the best of authors\u27 knowledge, this is the first reported case of the above constellation with a right-sided CDH diagnosed prenatally

Cognitive disposition to respond in postgraduate trainees of general surgery at Rawalpindi Medical University

Introduction: Cognitive biases leading to diagnostic errors are associate with adverse outcomes and compromise patient safety and contribute to morbidity and mortality. Exploration and identification of cognitive biases have been a difficult task for the clinicians and medical educators. The literature is deficient in the identification of cognitive biases in surgical trainees. The objective of the study was to identify various cognitive biases that may negatively impact clinical reasoning skills and lead to diagnostic errors in trainees of general surgery. Materials and Methods: A quantitative study was conducted involving 48 trainees of general surgery to explore the various cognitive biases. The questionnaire was devised and consisted of ten items devised to explore five biases. .Descriptive statistical analysis was done on SPSS 20 and the respondents with score >25 were categorized as predisposed to error scores of 20-25 were taken as a borderline and overall score of <25 was insignificant for the presence of cognitive bias. Results: Premature closure was the most frequent cognitive bias found significant in 34 (70 %) of trainees followed by anchoring bias in 14 (58, 3 %) trainees. The relative frequencies of different biases are shown in Table 2. The mean score of the questionnaire was 22.7 (range 10 to 38) SD 7.2. Ten out of forty-eight (21%) trainees with a mean score of >25 showed a clear inclination toward cognitive errors whereas 11 (22%) with a score in the range of 21 to 25 were categorized as having an equivocal tendency towards committing an error, Whereas 27 (56%) with a score of less than 20 were less prone to cognitive errors. Conclusion: The two most common errors seen in the study were anchoring bias and premature closure and both are related to information gathering. A larger study is required to explore the association of cognitive bias with different specialties and experience of clinicians

Design Of 3.3V Digital Standard Cells Libraries For Leon3

The scope of the research work was to develop 3.3Vdigital standard cell library for LEON3 operable at 200˚C using Peregrine 0.5m process. The dimension of the transistors was determined based on the work of Singravelan Vishwanathan. Layout and abstracted view were generated for the library. In total we have 259 cells. The cell library is characterized for timing and power data. The characterized data of the cells are documented in html format along with the lib format. The lib format file is used for synthesis and place and route.School of Electrical & Computer Engineerin