Optimisation of Defibrillation for Ventricular Fibrillation

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Ethical dimension of cult in the book of Isaiah

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Wear characterizations of polyoxymethylene (POM) reinforced with carbon nanotubes (POM/CNTs) using the paraffin oil dispersion technique.

The wear of polyoxymethylene (POM) is considered a key design parameter of polymer gears and some mechanical applications, and it determines the service time span. This work investigates the influence of carbon nanotubes (CNTs) on the specific wear rate of POM/CNT nanocomposites by using a pin-on-disk test rig (sliding only). The CNTs were synthesized with a fully automatic machine via the arc-discharge multi-electrode technique and subsequently dispersed in a POM matrix to manufacture test specimens. The CNT weight percentages were varied within the range 0-0.03 wt.% in three different operating media (air, distilled water, and mineral oil). The wear mechanism was examined by microscopy. The mechanical and thermal properties of POM/CNT were studied by using calorimetric analysis and by mechanical tensile testing. In addition, the thermal and mechanical properties were improved to an optimum CNT ratio of 0.02 wt.% due to the improvement in crystallinity of POM and a decrease in the fusion defects. The crystallinity degree increased by 7%, and the melting temperature also increased. The results further indicate that the specific wear rate (Ws) for POM/CNT containing 0.03 wt.% CNT in air and water media was improved by 73% and 66%, respectively, compared with virgin POM. In addition, the tensile strength of the mechanical properties and Young's modulus increased by 31% and 29%, respectively

Mechanical performance of single lap polymeric joints welded by a portable diode laser

The polymer laser welding can be successfully used to join two or more parts of plastic surfaces and it can be used in several fields, such as the biomaterials and microelectronics. Thermoplastic materials are welded by a localized energy input without the use of any organic solvents and formation of particulate.The employment of a portable diode laser can personalize the welding joint area and it let to draw the welding geometry, like a pen in a very easy and fast process. In this research, we studied single lap joints made by biomedical grade polyethylene (UHMWPE) pure and filled with carbon nanomaterials, necessary to make the polymer laser absorbent, added in amount of 0,2% in weight.The joints were irradiated by a diode laser operating at 970 nm (fundamental harmonic), in repetition rate of 10Hz, with a maximum pulse energy of 200 mJ and a laser spot of . 4 mm2 (no focusing lens were employed). The portable laser was employed to realize four types of welding geometries (points, continuous and discontinuous lines, cross lines) in the overlapped area. The joints were characterized by mechanical shear tests and hardness Shore D test and observed by a morphological analysis (optical microscopy). The results suggested that the welding strength depends not only on the welded area, but also on the continuity of the welded geometry and on the stress direction. The points welding exhibits the worse mechanical performance, while is the cross lines welding the best one among these investigated