In modern microprocessors, thermal management has become one of the main hurdles in continued performance enhancement. Cooling schemes utilizing single phase microfluidics have been investigated extensively for enhanced heat dissipation from microprocessors. However, two-phase fluidic cooling devices are becoming a promising approach, and are less understood. This study aims to examine two-phase flow and heat transfer within a pin-fin enhanced micro-gap. The pin-fin array covered an area of 1cm x 1cm and had a pin diameter, height and pitch of 150μm, 200μm and 225μm, respectively, (aspect ratio of 1.33). This study covers both uniformly and partially heated scenarios. The working fluid used was R245fa. The average heat transfer coefficient and high speed flow visualization results indicated a rapid transition to the annular flow regime with a strong dependence on heat flux. Also, unique, conically-shaped two-phase wakes were observed, demonstrating the lateral spreading capability of the pin-fin array geometry.

The composition of orthopaedic wear testing lubricants used to mimic synovial fluid (SF) is known to significantly affect in vitro polyethylene (PE) wear; however, some wear testing standards may be promoting the use of lubricants that are not clinically relevant. The present thesis evaluated the biochemical composition of human osteoarthritic and periprosthetic SF in order to propose changes to lubricant specifications in current wear testing standards. Using this data, pin-on-disc wear tests were conducted to explore the effects of more clinically relevant lubricants on PE wear. Results showed that wear decreased using a more clinically relevant lubricant. Samples of these lubricants were biochemically evaluated and compared to the SF results previously obtained, which showed that current standards for wear testing lubricants are biochemically different from SF. The findings from the present thesis encourage the modification of standardized lubricant specifications to improve wear testing protocols and guarantee clinically relevant wear testing.

The composition of orthopaedic wear testing lubricants used to mimic synovial fluid (SF) is known to significantly affect in vitro polyethylene (PE) wear; however, some wear testing standards may be promoting the use of lubricants that are not clinically relevant. The present thesis evaluated the biochemical composition of human osteoarthritic and periprosthetic SF in order to propose changes to lubricant specifications in current wear testing standards. Using this data, pin-on-disc wear tests were conducted to explore the effects of more clinically relevant lubricants on PE wear. Results showed that wear decreased using a more clinically relevant lubricant. Samples of these lubricants were biochemically evaluated and compared to the SF results previously obtained, which showed that current standards for wear testing lubricants are biochemically different from SF. The findings from the present thesis encourage the modification of standardized lubricant specifications to improve wear testing protocols and guarantee clinically relevant wear testing.

The cervical spine must provide structural support for the head, allow large range of motion and protect both the spinal cord and branching nerves. There are two types of spinal joints: the intervertebral discs which are flexible connections and the facets, which are articulating synovial joints. Both types degenerate with age. Current surgical treatments include spinal fusion and articulating disc replacement implants. If both disc and facet joints are degenerated, fusion is the only option. In spinal fusion, the disc is removed and the adjacent vertebrae are fused which causes abnormally high stress levels in adjacent discs. In disc replacement, an articulating device is inserted to restore intervertebral motion and mimic healthy spinal kinematics. Disc arthroplasty does not significantly increase adjacent level stress but the lack of rotational constraint causes increased facet contact pressures. Thus, there is a need for a cervical total level arthroplasty system (CTLAS) that has a disc implant specifically designed to preserve the facet joints and implants for facet arthroplasty that can act independently or in-unison with the disc replacement. The conceptual design of a CTLAS implant system was proposed that would replace the disc and the facet joints. To facilitate medical imaging, PEEK (polyetheretherkeytone) was selected as the structural and bearing material. In the present thesis, multi-station pin-on-plate wear testing was initiated for pairs of unfilled (OPT) and carbon-fiber-reinforced (CFR) PEEK. Wear is important in arthroplasty implant design because wear particles can cause osteolysis leading to loosening. A variety of experiments were performed to investigate the effects of load, contact geometry and lubricant composition on wear. CFR PEEK was found to have much lower and more predictable wear than OPT PEEK in the present experiments. The wear of OPT PEEK pairs showed sensitivity to lubricant protein concentration. The coefficient of friction during testing was found to be quite high (up to 0.5), which might have clinical implications. Also, some subsurface fatigue was found, exposing carbon fibers of CFR PEEK. This remains a concern for its long-term application. Further wear testing is recommended using actual implants in a spine wear simulator.

Mémoire (M.Ress.Renouv.)--Université du Québec à Chicoutimi, 2001. / Document électronique également accessible en format PDF. CaQCU

Thèse (M. Ress.Renouv.) -- Université du Québec à Chicoutimi, 2004. / Bibliogr.: f. [44]-53. Document électronique également accessible en format PDF. CaQCU

Thèse (M.Ress.Renouv.) -- Université du Québec à Chicoutimi, 2004. / Bibliogr.: f. [72]-78. Document électronique également accessible en format PDF. CaQCU

Thèse (M.Ress.Renouv.) -- Université du Québec à Chicoutimi, 2005. / Bibliogr.: f. 62-66. Document électronique également accessible en format PDF. CaQCU

Thèse (M.Sc.)--Université Laval, 2005. / Titre de l'écran-titre (visionné le 23 février 2006). Bibliogr.

Thèse (M.Sc.)--Université Laval, 2004. / Bibliogr. Publié aussi en version électronique.