Study of Micro-grinding of Glass using On-machine Fabricated Polycrystalline Diamond (PCD) by Micro-EDM

Ph.DDOCTOR OF PHILOSOPH

Applications of Laser Welding in Dentistry: A State-of-the-Art Review

The dental industry without lasers is inconceivable right now. This captivating technology has outlasted other possible alternative technologies applied in dentistry in the past due to its precision, accuracy, minimal invasive effect as well as faster operating time. Other alternatives such as soldering, resistance (spot) welding, plasma (torch) welding, and single pulse tungsten inert gas welding have their pros and cons; nevertheless, laser welding remains the most suitable option so far for dental application. This paper attempts to give an insight into the laser principle and types of lasers used for dental purposes, types of dental alloys used by the dentist, and effect of laser parameters on prosthesis/implants. It is apparent from the literature review that laser assisted dental welding will continue to grow and will become an unparalleled technology for dental arena

Impact of Total, Internal and External Government Debt on Interest Rate in Pakistan

The objective of the study is to examine impact of total, internal and external government debt on nominal interest rate in Pakistan. To attain these objectives, the study used annual time series data from 1973 to 2016. The study used loanable fund theory as theoretical model and ARDL bound testing approach for cointegration and Granger causality test to estimate the results. The results of the study found negative relation between total government debt, external debt and nominal interest rate in long run, while the study found no evidence of long run relation between internal government debt and nominal interest rate. In short run, positive relation exists between total government debt and nominal interest rate, while negative relation exists between external government debt and nominal interest rate. The results found unidirectional causality between total government debt and nominal interest rate. Government decrease nominal interest rate to lessen the repayment of government borrowing, which lead to decrease in interest rate. Reforms should be made to lessen the burden of government debt and to stabilize the interest rate

Impact of Total, Internal and External Government Debt on Interest Rate in Pakistan

The objective of the study is to examine impact of total, internal and external government debt on nominal interest rate in Pakistan. To attain these objectives, the study used annual time series data from 1973 to 2016. The study used loanable fund theory as theoretical model and ARDL bound testing approach for cointegration and Granger causality test to estimate the results. The results of the study found negative relation between total government debt, external debt and nominal interest rate in long run, while the study found no evidence of long run relation between internal government debt and nominal interest rate. In short run, positive relation exists between total government debt and nominal interest rate, while negative relation exists between external government debt and nominal interest rate. The results found unidirectional causality between total government debt and nominal interest rate. Government decrease nominal interest rate to lessen the repayment of government borrowing, which lead to decrease in interest rate. Reforms should be made to lessen the burden of government debt and to stabilize the interest rate

Electro-Discharge Machining of Ceramics: A Review

Conventional machining techniques of ceramics such as milling, drilling, and turning experience high cutting forces as well as extensive tool wear. Nevertheless, non-contact processes such as laser machining and electro-discharge machining (EDM) remain suitable options for machining ceramics materials, which are considered as extremely brittle and hard-to-machine. Considering the importance of ceramic machining, this paper attempts to provide an insight into the state of the art of the EDM process, types of ceramics materials and their applications, as well as the machining techniques involved. This study also presents a concise literature review of experimental and theoretical research studies conducted on the EDM of ceramics. Finally, a section summarizing the major challenges, proposed solutions, and suggestions for future research directions has been included at the end of the paper

Clinicopathological Study of Patients Presenting with Adnexal Masses

Background: To assess the clinicopathological outcome of women with adnexal masses . Method: In this observational study patients with a diagnosis of adnexal mass, who underwent laparotomy, were included. All the patients were evaluated by a complete history, general abdominal and pelvic examination, followed by ultrasonography. Their preoperative findings are then correlated with surgical findings and histopathological diagnosis. Descriptive statistics are applied and results shown in the form of frequencies and percentages. Result: In 50 patients commonest presenting symptom was pain abdomen followed by mass abdomen. Ultrasound features correlate well with histopathological features. Majority (94.6%) patients had benign adnexal pathology and 5.4% had malignant pathology. Most common neoplasms were surface epithelial tumours followed by dermoid cyst. Conclusion:Demographic detail, ultrasonography and CA-125 are good preoperative indicators of malignant nature or benign nature of adnexal masses. Most common adnexal tumours are surface epithelial tumours followed by dermoid cysts and malignant tumours are common in postmenopausal group

STUDY OF SLA PRINTING PARAMETERS AFFECTING THE DIMENSIONAL ACCURACY OF THE PATTERN AND CASTING IN RAPID INVESTMENT CASTING

Dimensional accuracy and geometric characteristics of the manufactured parts bear significant importance in product assembly. In Rapid Investment Casting, these characteristics can be affected by the printing parameters of the Additive Manufacturing method used in the pattern production process. Stereolithography is one of the important AM techniques mostly exploited in RIC due to its accuracy, smooth surface, and precision. However, the effect of SLA printing parameters on the dimensional accuracy and geometric characteristics have not been studied thoroughly. This study considers an experimental approach to study the effect of SLA printing parameters such as layer thickness, build angle, support structure density, and support touchpoint size on the dimensional accuracy and geometrical characteristics of the Castable Wax printed patterns and the Al cast parts. Taguchi’s Design of Experiment was used to define the number of experimental runs. SolidCast simulation was used to design the orientation of casting feeder to achieve directional solidification. Coordinate Measuring Machine measurements of deviations in the printed and cast parts were analyzed using the “Smaller-the-better” scheme in the two-step optimization method of Taguchi experiments. Build angle and Layer thickness were identified to be the first and the second most impactful parameters, respectively, affecting both the dimensional and geometric accuracy of Castable Wax patterns and Al cast parts, with optimal values of 0 deg and 0.25 μm, respectively. Both printed and cast parts had twice as many deviations in geometry as in dimensions. The sphere roundness and angularity were found to be the most and least accurate geometric characteristics, respectively. The dimensions in the Z direction were more accurate than in the X-Y directions, showing the smallest size deviations for height measurements and large deviations in the length, width, and diameter of the hole

Social support and mental health among female employees: the moderating effect of age

The association between social support and mental health at work has been widely established; nevertheless, notably among working women, the significance of age in that relationship remains controversial. This research used age as a moderator to determine mental health from social support. The Interpersonal Support Evaluation List–12 (ISEL-12) and the Mental Health Inventory–18 (MHI-18) was answered by 100 working women (Mage=41.20; SDage=9.80). A significant association between social support and mental health were reported but not between age and mental health. Age moderated the connection between social support and mental health. Younger women demonstrated greater mental health than older women in low-social support environments. With increasing social support, older working women reported better mental health. The findings of this study can be implemented by companies to develop and implement social support methods and policies to improve overall mental health in the workplace

THE POST-PROCESSING OF ADDITIVE MANUFACTURED POLYMERIC AND METALLIC PARTS

The traditional manufacturing industry has been revolutionized with the introduction of additive manufacturing which is based on layer-by-layer manufacturing. Due to these tool-free techniques, complex shape manufacturing becomes much more convenient in comparison to traditional machining. However, additive manufacturing comes with its inherent process characteristics of high surface roughness, which in turn effect fatigue strength as well as residual stresses. Therefore, in this paper, common post-processing techniques for additive manufactured (AM) parts were examined. The main objective was to analyze the finishing processes in terms of their ability to finish complicated surfaces and their performance were expressed as average surface roughness (Sa and Ra). The techniques were divided according to the materials they applied to and the material removal mechanism. It was found that chemical finishing significantly reduces surface roughness and can be used to finish parts with complicated geometry. Laser finishing, on the other hand, cannot be used to finish intricate internal surfaces. Among the mechanical abrasion methods, abrasive flow finishing shows optimum results in terms of its ability to finish complicated freeform cavities with improved accuracy for both polymer and metal parts. However, it was found that, in general, most mechanical abrasion processes lack the ability to finish complex parts. Moreover, although most of post-processing methods are conducted using single finishing processes, AM parts can be finished with hybrid successive processes to reap the benefits of different post-processing techniques and overcome the limitation of individual process

Modeling of Material Removal Rate and Surface Roughness Generated during Electro-Discharge Machining

This study reports on the numerical model development for the prediction of the material removal rate and surface roughness generated during electrical discharge machining (EDM). A simplified 2D numerical heat conduction equation along with additional assumptions, such as heat effect from previously generated crater on a subsequent crater and instantaneous evaporation of the workpiece, are considered. For the material removal rate, an axisymmetric rectangular domain was utilized, while for the surface roughness, a rectangular domain where every discharge resides at the end of previous crater was considered. Simulated results obtained by solving the heat equation based on a finite element scheme suggested that results are more realistic by considering instantaneous evaporation of the material from the workpiece and the effect of residual heat generated from each spark. Good agreement between our model and previously published data validated the newly proposed models and demonstrate that instantaneous evaporation, as well as residual heat, provide more realistic predictions of the EDM process