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Your search keyword '"Sheikh, Nadeem Ahmed"' showing total 256 results
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256 results on '"Sheikh, Nadeem Ahmed"'

19. Experimental and numerical study on thin silicon wafer CO2 laser cutting and damage investigation.

Author

Moghadasi, Kaveh, Tamrin, Khairul Fikri, Sheikh, Nadeem Ahmed, Kram, Abdul Rahman, Barroy, Pierre, Mahmud, Fahizan, and Khan, Amir Azam

Subjects
LASER machining, LASER measurement, CUTTING machines, OPTICAL measurements, MACHINING, LASER beam cutting
Abstract

This study investigates laser-induced damage in thin silicon (Si) wafer ablation both experimentally and numerically. A 40-W continuous-wave CO2 laser is employed as the volumetric heat source. Experiments are conducted that involve variations in the laser cutting speed from 5 to 20 mm/s and the number of passes from one to three while maintaining a constant laser power of 40 W for investigation. The measured output parameters include surface morphologies, heat-affected zone (HAZ), and kerf width. For the first time, a finite element solution based on the brittle–ductile transition (BDT) phenomenon is introduced to predict temperature-stress gradients in the laser cutting region. Johnson–Cook (J-C) plasticity, along with the introduced damage criteria, are employed to analyse the cutting characteristics. The results show that the lowest CO2 laser speed and minimal number of passes enhance Si wafer quality. Nevertheless, increasing cutting speed and the number of passes significantly intensify material ablation and oxidisation due to elevated laser heat input. Using optimal parameters, numerical analysis shows a high level of agreement with experimental findings. Transverse/longitudinal stresses correlate with temperature, while the longitudinal stress is substantially lower compared to the transverse stresses due to thermal expansion and the direction of heat transfer. Following that, computed assessments of compressive and tensile stresses are used to refine specific laser parameters and locations for experimental setup. [ABSTRACT FROM AUTHOR]

Published
2024
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35. Impaled trans-palatal crochet needle impacted at skull base; a multidisciplinary management challenge.

Author

Sheikh, Nadeem Ahmed, Butt, Khalid Pervaiz, and Hussain, Zahid

Subjects
*MEDICAL personnel, *ARTERIAL injuries, *INJURY complications, *CHILDREN'S injuries, *FOREIGN bodies
Abstract

Pediatric oro-pharyngeal trauma is a common observation in hospital accidents & emergencies reception. Immense responsibility rests with specialized health care providers to instantly diagnose and manage a rather small proportion of life-threatening complication associated with such injuries. Postero-lateral oropharyngeal trauma carries a significant risk of major neurovascular insult. More-over such patients are exposed to high radiation exposure to face, head & neck regions. A multi-disciplinary approach involving high dependency nursing, neuro-observation, meticulous imaging, prompt surgical exploration where indicated and a cautious follow-up must be considered as neurovascular manifestation may become apparent after some days of initial injury. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
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