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Full-Text Articles in Biomedical Engineering and Bioengineering

Angular Momentum In Human Walking, Marko Popovic, Hugh Herr Dec 2007

Angular Momentum In Human Walking, Marko Popovic, Hugh Herr

Marko B. Popovic

Angular momentum is a conserved physical quantity for isolated systems where no external moments act about a bodyʼs center of mass (CM). However, in the case of legged locomotion, where the body interacts with the environment (ground reaction forces), there is no a priori reason for this relationship to hold. A key hypothesis in this paper is that angular momentum is highly regulated throughout the walking cycle about all three spatial directions [ (t) ≈0], and therefore horizontal ground reaction forces and the center of pressure trajectory can be explained predominantly through an analysis that assumes zero net moment about …


Optimal Roughness For Minimal Adhesion, Nancy Burnham, D-L Liu, J Martin Jul 2007

Optimal Roughness For Minimal Adhesion, Nancy Burnham, D-L Liu, J Martin

Nancy A. Burnham

Roughness has a significant affect on adhesion. The authors used a single-asperity model to describe a smooth tip in contact with a rough surface and predicted that an optimal size of asperity yields a minimum of adhesion. Experimentally, adhesive forces on silicon wafers with varying roughness were measured using atomic-force-microscopy cantilevers with varying tip radii. It was found that minima do exist, and for all tip radii, the adhesion falls significantly for roughness greater than 1–2nm and drops at higher roughness for larger tips. This work should help minimize stiction in microelectromechanical systems and progress the understanding of nanoscale-contact mechanics.


3d Thoracoscopic Ultrasound Volume Measurement Validation In An Ex Vivo And In Vivo Porcine Model Of Lung Tumours, V. Hornblower, E. Yu, A. Fenster, J. Battista, R. Malthaner Jan 2007

3d Thoracoscopic Ultrasound Volume Measurement Validation In An Ex Vivo And In Vivo Porcine Model Of Lung Tumours, V. Hornblower, E. Yu, A. Fenster, J. Battista, R. Malthaner

Edward Yu

The purpose of this study was to validate the accuracy and reliability of volume measurements obtained using three-dimensional (3D) thoracoscopic ultrasound (US) imaging. Artificial "tumours" were created by injecting a liquid agar mixture into spherical moulds of known volume. Once solidified, the "tumours" were implanted into the lung tissue in both a porcine lung sample ex vivo and a surgical porcine model in vivo. 3D US images were created by mechanically rotating the thoracoscopic ultrasound probe about its long axis while the transducer was maintained in close contact with the tissue. Volume measurements were made by one observer using the …