Mass Transport in Shallow Turbulent Wake Flow by Planar Concentration Analysis Technique

A planar concentration analysis (PCA) system is used for observing the transport and mixing of a tracer mass in a shallow turbulent free-surface wake flow of a large cylindrical obstacle. The nonintrusive, fieldwise PCA measuring technique is applied to evaluate depth-averaged mass concentrations by making use of light attenuation due to absorption and scattering processes related to a dissolved tracer mass. The scalar fields are decomposed into a low-frequency quasiperiodic part, the coherent flow, and a randomly fluctuating part. From accompanying near-surface velocity measurements, large-scale coherent structures are identified and related to the coherent mass fields. This allows one to assess the role of the large-scale vortices for advection and diffusion in shallow wake flows. The time–mean wake flow displays a self-similar spanwise distribution both for mass and velocity. The longitudinal development of shallow wakes initially shows the growth of unbounded wakes; in the wake far field an attenuated behavior applies.     

A highly stable 30 W average power mode-locked Nd:YAG laser

Mode locking of a CW pumped Nd:YAG laser operating in the TEM01or donut mode using an intracavity acoustooptic AM modulator is described. Mode-locking investigations to date have concentrated on obtaining as short pulses as possible at the expense of average and peak laser output power. We describe a mode-locked system for field use having an average output of 30 W, with pulses recurring at a 100 MHz rate and having a peak power in excess of 0.5 kW. Detector limited pulses of 0.6 ns duration were recorded and the mode locking was stable for several hours requiring no feedback loop or fine adjustment.     

Laser radar in robotics

In this paper we describe the basic operating principles of laser radar sensors and the typical algorithms used to process laser radar imagery for robotic applications. We review 12 laser radar sensors to illustrate the variety of systems that have been applied to robotic applications wherein information extracted from the laser radar data is used to automatically control a mechanism or process. Next we describe selected robotic applications in seven areas: autonomous vehicle navigation, walking machine foot placement, automated service vehicles, manufacturing and inspection, automotive, military and agriculture. We conclude with a discussion of the status of laser radar technology and suggest trends we see in the application of laser radar sensors to robotics. Many new applications are expected as the maturity level progresses and system costs are reduced