Imaging examines rocket instability
Scientists generally have believed that powerful and unstable sound waves, created by energy supplied by the combustion process, were the cause of rocket failures in several US and Russian rockets. Scientists have also observed these mysterious oscillations in other propulsion and power-generating systems such as missiles and gas turbines. Recently, researchers at the Georgia Institute of Technology (Atlanta, GA, USA; www.gatech.edu) have developed a liquid rocket engine simulator and imaging techniques that can help demystify the cause of these explosive sound waves.
The Georgia Tech research team demonstrated that the phenomenon manifests itself in the form of spinning acoustic waves that gain destructive power as they rotate around the rocket’s combustion chamber. Working with Oleksandr Bibik, a visiting physicist and research scientist from Ukraine, the Georgia Tech research team developed an experimental setup and imaging technique that provides detailed information on how these waves form and behave. First, the researchers developed a low-pressure combustor that serves as a true simulator of larger rocket engines. Bibik then used a very-high-speed camera in combination with series of optical filters and fiberoptic probes that together allowed researchers to clearly observe the formation and behavior of excited spinning sound waves within the engine.
THz imaging aids drug analysis
TeraView (Cambridge, UK; www.teraview.com) has conducted successful proof-of-principle testing for high-speed terahertz (THz; 30 μm–3 mm) measurements of coating thickness on pharmaceutical tablets. This development represents a step toward addressing one of the most difficult problems to be overcome in on-line pharmaceutical inspection—measuring product attributes such as coating thickness accurately and rapidly while the tablets are in random motion in a coating pan.
This capability opens up the opportunity for deployment of THz sensors in rapid, nondestructive tablet inspection to ensure that pharmaceutical products remain within the specifications necessary to maintain therapeutic efficacy and drug performance. Ultimately, these sensors could be used in feedback systems to control production parameters (for example, coating spray rates and tablet compression force for single and multiple layer tablets) in real time. The technique could also support the pharmaceutical industry’s future plans to implement continuous process systems in drug manufacture.
Pedestrian tracking
The demand for smart surveillance systems is increasing. At many places, including subway stations, airports, and theme parks, there are far too many cameras installed to implement real-time observation by human operators. The Institute for Digital Image Processing at Joanneum Research (Graz, Austria; www.joanneum.at) recently designed and implemented high-level computer vision algorithms for object detection, classification, and tracking applications.
Using these algorithms, the institute is trying to address topics such as how to detect and track pedestrians in video streams. This is no simple inspection with a pass/fail result. It involves tracking objects of different sizes, velocities, accelerations, directions, and colors. Unlike bottles, microchips, or fruit, each person has a mind of his own, adding another level of difficulty.
Polar Bear tracks
RealVNC’s Virtual Network Computing (Cambridge, UK; www.realvnc.com) technology has been used to control and maintain a network of remote cameras in sub-zero temperatures on the shores of Hudson Bay in Canada to track the movement and behavior of polar bears. The digital system was set up by SeeMore Wildlife Systems (Homer, AK, USA; www.seemorewildlife.com), which specializes in remote wildlife monitoring, to help Polar Bears International (Sebastopol, CA, USA; www.polarbearsinternational.org) researchers from the University of Florida to film the dwindling number of polar bears as they prepared to head off to the Arctic for the winter.
The project comprised an IP-based network system of digital microwave links to transmit images across the tundra from Cape Churchill cameras to the remote town of Churchill, which was in turn connected to the control center in Alaska via the Internet. The work also involved a Tundra Buggy that fed live Polar Bear Cam streaming video through a 45-Mbyte wireless link to the town of Churchill and then to the National Geographic Web site (www.nationalgeographic.com).
Holographic microscopy meets microbes
By applying holographic microscopy to marine biology, researchers from The Johns Hopkins University (Baltimore, MD, USA; www.jhu.edu) and the University of Maryland Biotechnology Institute (Baltimore, MD, USA; www.umbi.umd.edu) have identified the swimming and attack patterns of two tiny, but deadly, microbes linked to fish death in Chesapeake Bay. The study focused on the aquatic hunting tactics of two single-celled creatures classified as dinoflagellates, which produce toxins that can kill large numbers of fish.
Studying the predators under a conventional microscope is difficult because they can quickly swim out of the microscope’s shallow field of focus. Researchers solved this problem using digital holographic microscopy to capture 3-D images of the microbes.
The technique consists of illuminating a sample water volume with a collimated laser beam and recording the interference pattern generated by light scattered from organisms with the remainder of the beam. The interference pattern—the hologram—is magnified and recorded by a high-speed digital camera. Computational reconstruction and subsequent data analysis produces 3-D views of activity. The study has shown how dinoflagellate predators respond to cues and alter the way in which they swim to become more formidable hunters. Gaining an understanding of the behavior of these microbes may lead to ways of averting fish death attributed to these toxins.
