Metal to ceramic joining for high temperature applications

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The phenomenal growth rate for the use of engineering ceramics is attributed to successful scientific responses to industrial demand. These materials are replacing metal and its alloys in diverse applications from cutting tools and heat engine components to integrated circuits. Joining technology plays a vital role in this changing and evolving technology as success and failure comes with breaking new barriers. It is important to improve existing techniques and to develop new techniques that reliably join simple shape components to form complex assemblies or join dissimilar materials such as metal to ceramic. Joining of ceramics is not simple due to their high chemical stability and low coefficient of thermal expansion (CTE). Joining between metal and ceramic is usually carried out at elevated temperatures and upon cooling thermal residual stresses are induced that lead to joint failure or poor strength. Most metal-ceramic joints cannot be used over 500°C primarily due to the low melting temperature of the interlayer. This investigation was concerned with the successful joining for higher temperature applications (above 500°C) of two dissimilar high temperature oxidation and corrosion resistant materials, Fecralloy and silicon nitride. The primary focus was on the effects of process conditions upon the microstructure and mechanical properties of the joint and to also study/identify the joining mechanism. Two novel techniques were employed to join successfully the metal to ceramic. The first was by use of a thin Cu foil that did not remain after joining. Joining occurs by a process that results in partial melting of the Fecralloy interface, where Fe, Cr, Al and Cu reactively infiltrate into the silicon nitride. This liquid mixture causes partial dissolution of the silicon nitride interface, where Si and N diffuse into the Fecralloy. A thin reaction product layer was formed at the silicon nitride interface and our results suggested that this was AIN. The free surface Si and porosity of the silicon nitride along with the eutectic temperatures above 1100°C are all vital for this joining process. The highest average shear strength of a Fecralloy-silicon nitride joint produced by the method was 67.5 MPa. The second route was that of a powder metallurgy one, where cold pressed Ni-Al (1:1 molar) compacts were used to join successfully the Fecralloy to silicon nitride. The formation of NiAl from its constituents is highly exothermic and this is initiated between 500-650°C. The high temperature reached causes partial melting of the Fecralloy interface and dissolution/reactive wetting at the silicon nitride interface. Mostly Fe infiltrates the NiAl improving room temperature ductility, fracture toughness and yield strength. Molten Al from the interlayer reacts and wets the silicon nitride interface with small amount of infiltration and no reaction product forming. The reaction synthesis of NiAl was studied using DTA and TGA, where the effects of Ni particle size and heating rate were investigated. This joining process is highly dependant upon process conditions, the most important of which are applied pressure, heating rate and Ni/A1 particle size. The highest average shear strength attained was 94.30 MPa and this is attributed to good interfacial bonding, high pressure, moderate process temperature and dwell time. The exothermic formation of the NiAl interlayer that is densified and monophase was paramount for this joining process. The Bansal-Doremus kinetic model for evaluating the kinetic parameters from non-isothermal DTA data was shown to be valid. The results obtained were identical to those by other authors who used a different model and approach

To compare the efficacy of progesterone between oral versus vaginal routes of administration in the treatment of first trimester threatened miscarriage

Objective: To determine the efficacy of oral versus vaginal progesterone in the treatment of the first trimester threatened miscarriage. Methodology: This randomized controlled trial study was conducted at Gynaecology and Obstetrics Department of Mardan Medical Complex, Mardan from September 2019 to March 2020. A total of 126 women between ages 18-45 years presenting in their first trimester with threatened miscarriage were included. All patients were randomly allocated in two equal groups A and B by lottery method (63 in each group). Patients in group A were given oral progesterone 10 mg bid for one week and group B patients were given vaginal progesterone 400 mg for one week under the supervision of obstetrician. All patients were followed up till 20th week of pregnancy. The efficacy of the drug was evaluated based on the absence of bleeding per vagina and pregnancy proceeding beyond 20 weeks of gestation. Results: A total of 126 women were included. The majority of the patients 64 (50.79%) were between 18 to 30 years of age. The mean age of women in group A was 30.52 ± 4.52 years and in group, B was 30.73 ± 4.23 years. Efficacy of Oral progesterone (group A) was seen in 57 (90.48%) women and of vaginal progesterone (group B) was seen in 46 (73.02%) women. This showed a highly significant difference between the two routes of administration with p-value of 0.01. Conclusion: Oral progesterone is more effective than vaginal progesterone in treating first trimester threatened miscarriage in terms of prevention of blood loss and continuing the pregnancy beyond 20 weeks

Genetic characterization of human echinococcosis in Southern Punjab, Pakistan

IntroductionEchinococcosis is a neglected tropical zoonotic infection that affects both the human and livestock populations. In Pakistan, the infection is long-standing, but data on its molecular epidemiology and genotypic characterization in the southern Punjab region are limited. The aim of the current study was the molecular characterization of human echinococcosis in southern Punjab, Pakistan.MethodsEchinococcal cysts were obtained from a total of 28 surgically treated patients. Patients’ demographic characteristics were also recorded. The cyst samples were subjected to further processing to isolate DNA in order to probe the Nad1 and Cyt-b genes, followed by DNA sequencing and phylogenetic analysis for genotypic identification.ResultsThe majority of the echinococcal cysts were from male patients (60.7%). The liver was the most commonly infected organ (60.71%), followed by the lungs (25%), spleen (7.14%), and the mesentery (7.14%). Molecular and genotypic identification through sequencing and phylogenetic tree analysis showed that most of the cysts (24/28, 85.7%) were caused by the species Echinococcus granulosus sensu stricto (E. granulosus s.s.) (G1 and G3), followed by Echinococcus multilocularis (E. multilocularis) and Echinococcus canadensis (E. canadensis) (G6/G7) (3/28, 10.8%, and 1/28, 3.5%, respectively).ConclusionThe current study concluded that the majority of human infections were caused by E. granulosus s.s., followed by the E. multilocularis and E. canadensis species (G6/G7). Genotypic characterization among both human and livestock populations is needed to explore the genetic diversity of echinococcosis

ECONOMIC VALUE ADDITION IMPLICATIONS: A STUDY OF THE PAKISTANI BANKING INDUSTRY

Human beings are mostly concerned about value additionin almost every aspect of life. Does this reality prove accurate insecondary markets investment? This empirical study deals with theEconomic Value Addition of major seventeen banks of Pakistanincluding national and public limited banks. In this research, ROE,ROCE, and OCF are taken as parameters of profitability whilemarketability parameters are PE and MB ratio. Two sample t-testsshow that a new banks value creation is more in comparison withold banks in the context of EVA. Private and Government bank arenot significantly different in EVA. Fixed effect modeling and Clusterestimation infer that Profitability parameters positively impact EVA.Marketability parameter MB positively impacts EVA while PE ratiois statistically insignificant. Correlation analysis shows thatinvestors of the banking sector in Pakistan do not pay specialattention to EVA in their investment decisions

FINANCIAL DEVELOPMENT : A CONTRIBUTING AGENT OF ECONOMIC GROWTH - STUDY OF SELECTED ASIAN COUNTRIES

It has been a self-proclaimed fact that financial development boosts economic growth in the short as well as in the long run. This particular study has taken financial development indicators from banking and secondary market perspectives into consideration. We find the banking sector more prominent and more influential in contrast to secondary markets as by revealed their coefficients. The study adopts financial deepening, foreign direct investment, banking credit to private sector, stock market size, stock market efficiency and stock market liquidity as independent variables along with economic growth as dependent variables. All the variables except banking credit to private sector have a significant and positive relationship with economic growth. Results show that financial development affects economic growth positively. Financial deepening, stock market liquidity and foreign direct investment have only one way causality while stock market size has two-way causality

Cognitive dual coprime frequency diverse array MIMO radar network for target discrimination and main-lobe interference mitigation.

The authors propose a novel dual coprime frequency diverse array (FDA) multiple input multiple output (DCFDA-MIMO) radar network design, empowered by cognitive capabilities, aimed at target discrimination and mitigation of interference present in the standalone radar systems. That is, the proposed DCFDA-MIMO design capitalises on the complementary advantages of FDAs for target discrimination and coprime arrays for enhanced resolution, resulting in superior performance. Additionally, the proposed DCFDA-MIMO network employs a 2D multiple signal classification algorithm to achieve high-resolution target localisation. By incorporating cognitive techniques based on the action-perception cycle, the proposed approach demonstrates notable improvements in multiple target detection and tracking accuracy with fewer number of antenna elements as compared to existing techniques. Furthermore, it enhances individual radar beamforming performance for interference suppression and true target detection without prior information

Cataract prevalence, cataract surgical coverage and barriers to uptake of cataract surgical services in Pakistan: the Pakistan National Blindness and Visual Impairment Survey.

AIM: To estimate the prevalence of visual impairment and blindness caused by cataract, the prevalence of aphakia/pseudophakia, cataract surgical coverage (CSC) and to identify barriers to the uptake of cataract services among adults aged >or=30 years in Pakistan. METHODS: Probability proportional-to-size procedures were used to select a nationally representative sample of adults. Each subject underwent interview, visual acuity measurement, autorefraction, biometry and ophthalmic examination. Those that saw <6/12 in either eye underwent a more intensive examination procedure including corrected visual acuity, slit lamp and dilated fundus examination. CSC was calculated for different levels of visual loss by person and by eye. Individuals with <6/60 in the better eye as a result of cataract were interviewed regarding barriers. RESULTS: 16 507 Adults were examined (95.5% response rate). The crude prevalence of blindness (presenting <3/60 in the better eye) caused by bilateral cataract was 1.75% (95% CI 1.55%, 1.96%). 1317 Participants (633 men; 684 women) had undergone cataract surgery in one or both eyes, giving a crude prevalence of 8.0% (95% CI 7.6%, 8.4%). The CSC (persons) at <3/60, <6/60 and <6/18 were 77.1%, 69.3% and 43.7%, respectively. The CSC (eyes) at <3/60, <6/60 and <6/18 were 61.4%, 52.2% and 40.7%, respectively. Cost of surgery (76.1%) was the main barrier to surgery. CONCLUSION: Approximately 570 000 adults are estimated to be blind (<3/60) as a result of cataract in Pakistan, and 3,560000 eyes have a visual acuity of <6/60 because of cataract. Overall, the national surgical coverage is good but underserved populations have been identified

Organic petrography and thermal maturity of the permian roseneath and murteree shales in the cooper basin, Australia

The Permo-Triassic Cooper Basin is one of the largest intracratonic basins in Australia, covering approximately 130,000 km2 in South Australia and Queensland. The basin is one of Australia's major onshore hydrocarbon province and most prospective region for both conventional and unconventional hydrocarbon explorations. Organic petrography and thermal maturity of two Permian lacustrine shale units in the Cooper Basin, the Murteree and Roseneath shales, were investigated on 21 wells with the objective of evaluating the gas generating potential of these units. Vitrinite reflectance values for the Murteree and Roseneath shales range between 1.17% and 2.00%. Macerals show systematic changes in properties relative to maturity rank. A range of maceral compositions, dominated by vitrinite group macerals, are present in both units, which vary between rich and very rich in organic content. Rock-Eval data suggest fair to very good kerogen quality (of kerogen types II, III, and IV ranging from immature to mature) and imply a mostly gas-prone generation potential in the shales

Prevalence of Diabetic Retinopathy and Correlation with HbA1c in Patients Admitted in Khyber Teaching Hospital Peshawar

Objective: To determine the prevalence of diabetic retinopathy in patients admitted in Khyber Teaching Hospital Peshawar and to correlate different stages of diabetic retinopathy with HbA1C levels. Methodology: This cross sectional study was conducted at Department of Ophthalmology, Khyber Teaching Hospital, MTI, Peshawar from December 2019 to May 2020. All patients over the age of 15 years who were diagnosed with diabetes mellitus were included in the study while patients with cataract or retinopathy due to other pathologies were excluded. All diabetic patients were admitted through outpatient department. In the ward their blood pressures were recorded and HbA1c levels were also measured. Visual acuity (VA) was checked. Screening for diabetic retinopathy was done by a consultant ophthalmologist by Optos Ultrawide Field Imaging of retina and Optical Coherence Tomography (OCT) of macula to establish stages of diabetic retinopathy and presence of diabetic macular edema respectively. Results: A total of 103 diabetic patients were included. Their retina was photographed, viewed and analyzed. Diabetic retinopathy, irrespective of the type, was found in 69 patients with a prevalence of 66.9%. Patients with lower ranges of HbA1c (below 6%) showed no evidence of DR. The clustering of majority of patients with diabetic retinopathy with HbA1c levels of 8 to 12 %, showed a significant relationship between high blood sugar levels and severity. Conclusion: In our study the higher frequency of retinopathy is alarming by considering it one of the leading causes of blindness in working class. It is highly recommended that routine ophthalmologic examination may be carried out along with optimal diabetic control