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This work covers laboratory studies in the excavation of selected rock materials with mechanical cutters. Cutting head design of rock excavation systems employing drag tools or disc cutters is investigated by considering their practical cutting action. Effects of tool tilt angle on the performance of roadheaders with longitudinal cutting heads are investigated in detail. Along with tilt angle, optimum tool spacing between adjacent cutters, cutting head geometry and mode of operation of roadheaders are also studied. Experiments with disc cutters covered mainly the effect of disc edge angle on disc performance. When the practical cutting action of drag tools is considered the trend of forces and specific energy becomes somewhat different from those obtained during flat rock surface cutting trials; however, the definition of optimum tool spacing with respect to drag tools confirms previous findings. Tilt angle has a significant influence on the performance of cutting tools; in particular, with corner cutting tools. It was found that individual tool forces are proportional to the cross-sectional area cut by the corresponding tool. Roadheader cutting heads with combined geometry offer better performances than those with spherical geometry when the tool spacing is kept constant around the cutting head. In arcing mode tool duties are also affected by boom length. Cyclic deepening of grooves exists when cutting with discs, discs having smaller edge angles requiring more successive passes to produce a complete breakout between adjacent grooves.

The mitral valve in the heart sometimes struggles with diseases and complications, and needs to be replaced. This problem becomes more frequent with the ageing of the population in developed countries. The most common practice consists of suturing a prosthetic valve into place. However, newer methods are being devised and tested to make the surgery faster and less invasive. In particular, various types of new sutureless heart valve systems exist on the market. However, there is still a need for a tool designed for the intracardiac delivery and anchoring of a prosthetic mitral valve, as addressed here. A number of criteria and specifications were set by researchers at the Robarts Research Institute (London, ON) who came up with the design task. To address their request, ten conceptual designs of a sutureless, virtual-reality guided, self-anchoring, intracardiac system were developed to hold a prosthetic mitral valve, deliver it safely, and quickly affix it in position. The winning concept adequately met the design criteria. Two prototypes were manufactured. The attachment of a prosthetic valve to a simulated mitral valve annulus was tested with the first prototype to verify feasibility and measure leakage. The second prototype was pressure tested in a dynamic surgical phantom reproducing the circulatory conditions during surgery. While the preliminary feasibility of the concept was established, recommendations were made to develop a less bulky design.

No description available.

The mitral valve in the heart sometimes struggles with diseases and complications, and needs to be replaced. This problem becomes more frequent with the ageing of the population in developed countries. The most common practice consists of suturing a prosthetic valve into place. However, newer methods are being devised and tested to make the surgery faster and less invasive. In particular, various types of new sutureless heart valve systems exist on the market. However, there is still a need for a tool designed for the intracardiac delivery and anchoring of a prosthetic mitral valve, as addressed here. A number of criteria and specifications were set by researchers at the Robarts Research Institute (London, ON) who came up with the design task. To address their request, ten conceptual designs of a sutureless, virtual-reality guided, self-anchoring, intracardiac system were developed to hold a prosthetic mitral valve, deliver it safely, and quickly affix it in position. The winning concept adequately met the design criteria. Two prototypes were manufactured. The attachment of a prosthetic valve to a simulated mitral valve annulus was tested with the first prototype to verify feasibility and measure leakage. The second prototype was pressure tested in a dynamic surgical phantom reproducing the circulatory conditions during surgery. While the preliminary feasibility of the concept was established, recommendations were made to develop a less bulky design.

The mitral valve in the heart sometimes struggles with diseases and complications, and needs to be replaced. This problem becomes more frequent with the ageing of the population in developed countries. The most common practice consists of suturing a prosthetic valve into place. However, newer methods are being devised and tested to make the surgery faster and less invasive. In particular, various types of new sutureless heart valve systems exist on the market. However, there is still a need for a tool designed for the intracardiac delivery and anchoring of a prosthetic mitral valve, as addressed here. A number of criteria and specifications were set by researchers at the Robarts Research Institute (London, ON) who came up with the design task. To address their request, ten conceptual designs of a sutureless, virtual-reality guided, self-anchoring, intracardiac system were developed to hold a prosthetic mitral valve, deliver it safely, and quickly affix it in position. The winning concept adequately met the design criteria. Two prototypes were manufactured. The attachment of a prosthetic valve to a simulated mitral valve annulus was tested with the first prototype to verify feasibility and measure leakage. The second prototype was pressure tested in a dynamic surgical phantom reproducing the circulatory conditions during surgery. While the preliminary feasibility of the concept was established, recommendations were made to develop a less bulky design.

Tooling design for manufacturing processes refers to direct tooling for making a part such as molds and dies for injection molded parts and metal stampings, or for supporting machining operations such as jigs and fixtures. This paper summarizes some of the R&D activities in those areas over a period of 20 years in the Department of Mechanical Engineering, National University of Singapore. It is notable that increasing use of computer tools has turned what is used to be known as a “black art” into a discipline embracing both heuristic and scientific analyses. / Singapore-MIT Alliance (SMA)