Real time feature-based facial tracking using Lie algebras

We have developed a novel human facial tracking system that operates in real time at a video frame rate without needing any special hardware. The approach is based on the use of Lie algebra, and uses three-dimensional feature points on the targeted human face. It is assumed that the roughly estimated facial model (relative coordinates of the three-dimensional feature points) is known. First, the initial feature positions of the face are determined using a model fitting technique. Then, the tracking is operated by the following sequence: (1) capture the new video frame and render feature points to the image plane; (2) search for new positions of the feature points on the image plane; (3) get the Euclidean matrix from the moving vector and the three-dimensional information for the points; and (4) rotate and translate the feature points by using the Euclidean matrix, and render the new points on the image plane. The key algorithm of this tracker is to estimate the Euclidean matrix by using a least square technique based on Lie algebra. The resulting tracker performed very well on the task of tracking a human face.

Centrifuge modelling of submarine landslide flows

Landslides occur both onshore and offshore, however little attention has been given to offshore landslides (submarine landslides). The unique characteristics of submarine landslides include large mass movements and long travel distances at very gentle slopes. Submarine landslides have significant impacts and consequences on offshore and coastal facilities. This paper presents data from a series of centrifuge tests simulating submarine landslide flows on a very gentle slope. Experiments were conducted at different gravity levels to understand the scaling laws involved in simulating submarine landslide flows through centrifuge modelling. The slope was instrumented with miniature sensors for measurements of pore pressure beneath the flow. A series of digital cameras were used to capture the flow in flight. The results provide a better understanding of the scaling laws that needs to be adopted for centrifuge experiments involving submarine landslide flows and gives an insight into the flow mechanisms. © 2010 Taylor & Francis Group, London.

Contact dynamics in a gently vibrated granular pile.

We use multispeckle diffusive wave spectroscopy to probe the micron-scale dynamics of a water-saturated granular pile submitted to discrete gentle taps. The typical time scale between plastic events is found to increase dramatically with the number of applied taps. Furthermore, this microscopic dynamics weakly depends on the solid fraction of the sample. This process is largely analogous to the aging phenomenon observed in thermal glassy systems. We propose a heuristic model where this slowing-down mechanism is associated with a slow evolution of the distribution of the contact forces between particles. This model accounts for the main features of the observed dynamics.