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News Tip


September 4, 2002

For more information on these science news and feature story tips, please contact the public information officer at the end of each item at (703) 292-8070. Editor: Amber Jones

Model of Plane Impact at WTC Provides Clues to Structural Issues

Abolhassan Astaneh-Asl, a civil engineering professor at the University of California, Berkeley, has constructed a realistic computer simulation of the World Trade Center North Tower being hit by a jet airplane. Astaneh's model has simulated the first few seconds of the plane's impact and entry into the building, and he is refining the model to include damage to the plane, the building floors and the internal core columns. The next step will be to include the effect of fire heating the damaged structure and initiating its final collapse.

The simulation will help analyze the potential effects that different structural designs, such as more robust core walls or more fireproofing, might have had and the implications for the design of future buildings.

Shortly after Sept. 11, Astaneh, a structural engineer, obtained a National Science Foundation (NSF) quick-response grant to investigate the collapse of the World Trade Center towers and surrounding buildings. He examined portions of the steel structures removed from the site for recycling, recording damage caused by impact and intense heat. To build the model, he combined these reconnaissance data, details from the original building plans for the towers, photos of the disaster and a model representing a Boeing 767, using software donated by the MSC Software Corporation.

Astaneh's study is part of an ongoing national effort to provide engineers and architects with technologies to strengthen buildings, bridges and other physical infrastructure against disasters such as earthquakes, fire and explosions.Astaneh's NSF-supported research has included the study of flexible connections for semi-rigid steel frames in low- and mid-rise buildings, a steel cable mechanism to retrofit multi-story buildings to prevent progressive collapse due to blast, and a composite shear wall system combining reinforced concrete and steel plates in a new configuration for seismic and blast protection. [Amber Jones]

simulation of plane impact

simulation of plane impact

simulation of plane impact

Simulating the airplane's impact on the building structure and the ensuing fire.
Images courtesy: Abolhassan Astaneh-Asl, Univ. of Calif., Berkeley

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Oceanographers Probe Breaking Wave Bubbles, Ocean Processes with New "Bubblecam"

The relaxing atmosphere of a walk along the shore, especially the sounds of waves breaking on the beach, continually lures people to coastlines.

For Grant Deane and Dale Stokes, oceanographers at Scripps Institution of Oceanography at the University of California, San Diego, the sounds of hundreds of millions of air bubbles bursting at the shoreline represent a key to understanding ocean phenomena. The researchers, funded by NSF, used acoustical and optical observations to determine that bubbles created in breaking ocean waves play an important role in a variety of ocean and atmospheric processes, including air-sea gas transfer, heat and moisture exchange, aerosol production and climate change.

"Bubbles turn out to be the centerpiece for a range of ocean-based and culturally important phenomena," said Deane. "They play a part in global climate change because the global rates of carbon dioxide exchange are in part dictated by bubble-mediated gas transport."

The researchers developed a unique, high-tech instrument called "BubbleCam" to meticulously track the spectrum of bubble sizes, the most important property of breaking wave bubbles.

"BubbleCam is a high-speed video camera with an intricate lens and light-focusing system that lets us take finely sliced pictures as waves break," said Stokes. "We can gather all those images and feed them into a computer that does the bubble-counting for us."

The results will be incorporated into models of bubble-mediated, air-sea gas transport to help improve the models' accuracy. The research may lead to the development of new instruments that will allow scientists to remotely monitor greenhouse gas transfer. [Cheryl Dybas]

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What Makes a Perfect Graph? Students of Math Get an Answer

What makes a perfect graph? The number of colors and cliques, according to a group of NSF grantees which has solved this 40-year-old mathematical problem.

The researchers--Neil Robertson of Ohio State University, Paul Seymour and Maria Chudnovsky of Princeton University and Robin Thomas of the Georgia Institute of Technology--report they have proved the Strong Perfect Graph Conjecture after three years of study.

French mathematician Claude Berge proposed the conjecture in 1960, describing the conditions that he believed would characterize a perfect graph. Berge died on June 30, 2002, just after the team proved his predictions to be correct.

A graph is a collection of points of data and the lines that connect them. A graph can illustrate, for example, a network of radio transmitters or cellular phone towers (points), connected by lines wherever their transmission ranges overlap. The points can be colored to illustrate frequencies.

The conjecture concerns the smallest number of colors needed to allow the two endpoints of each connecting line in the graph to be different colors. This number is called the chromatic number, or chi, of the graph. A clique is any group of points within the graph that are all connected to one another. The minimum number of colors, or chi, of a graph is at least as large as the number of points in its largest clique. According to the conjecture, a graph is perfect if, for the graph and any subgraph created by deleting some of the points, the chi equals the number of points in the largest clique.

An example of a perfect graph can be visualized as an efficient data transmission network. Thus, a phone network based on a perfect graph would run most efficiently with the minimum number of frequencies or channels (colors) assigned to its transmitters (points) and would continue to operate efficiently even if some of the transmitters were knocked out. [Amber Jones]

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NSF-NIH Grants Will Integrate Mathematics and Biology

NSF and the National Institute of General Medical Sciences, National Institutes of Health, have announced about $24 million in funding over five years to encourage the use of quantitative methods and computational tools in biological research.

The 20 funded projects include statistical approaches to DNA sequencing and genomics; the modeling of microorganisms, pathogens, and acute inflammation; and studies involving proteins.

Traditionally, federal support for the mathematical sciences has come primarily from NSF. The new program provides an additional source of funding for mathematicians and encourages cross-discipline approaches. The partnership gives the medical sciences institute, which supports research and training in the basic biomedical sciences, access to a broader pool of math researchers.

Other areas of collaboration between NSF and NIH include training in bioengineering and bioinformatics and a cooperative biodiversity program. [Amber Jones]

For the list of grants, see:



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