Prediction of central bursting defects in rod extrusion process with upper bound analysis method

The prediction of central bursting defects in the rod extrusion process through conical dies using the upper bound analysisis investigated. A kinematically admissible velocity field, including the radial and angular velocity components, is proposed. A newcriterion is presented to predict the occurrence of the central bursting defects. Parameter bobt, which represents the risk probability ofcracking, is proposed. It is calculated using the shape of the boundary at the entrance by minimizing the total power dissipationduring the extrusion process. When bobt is equal to or greater than bcr, central bursting occurs. Furthermore, the quantitativerelationships between central bursting defects and process parameters （semi die angle, reduction in area and frictional factor） arestudied. The results show that the central bursting defects are affected primarily by the reduction in area and the friction factor. Thepresented criterion is verified by comparing with the FEM simulation data and the results of the published paper.

Epidemiological Review of Macular Hole in Ekiti, Southwestern Nigeria

Background: Macular hole is a known cause of central visual defect with varying etiologies in different parts of the world. It was considered an untreatable condition until 1991 when varying treatment techniques began to emerge with resultant restoration of central vision. This study was carried out to evaluate the prevalence and pattern of Macular hole in a tertiary eye centre in Nigeria. Method: This is a prospective hospital-based study over a 5 year period spanning from November 2013 to October 2018. All patients with macular hole seen within this period were included in the study. Relevant data were recorded with a structured questionnaire and analysed with SPSS version 20. Results: There were 46 eyes of 42 patients which constituted about 0.5% of all new patients seen over the study period. Male to female ratio was 1:1.3 with age ranged between 15 and 91years (mean = 61.8 ± 16.5 years). The majority of the patients (95.7%) had Idiopathic macular hole. Half of the patients (54.8%) had visual acuity less than 3/60 in the affected eye at the time of presentation. The majority (95.7%) of the patients did not accept the recommended surgical treatment option because of financial incapacitation. Conclusion: Macular hole is a disease of marked visual consequence. Available treatment option is still not within the reach of the majority because of the high cost.