RESEARCH NOTES
Dr. Philippe Van
Cappellen, left, associate professor in Georgia Tech's School of
Earth and Atmospheric Sciences, and Tech graduate student Alakendra
Roychoudhury prepare to take a core water sample from Georgia salt
marsh.
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This environment is the object of an important interdisciplinary study at Sapelo Island, Ga. Here, scientists associated with the Georgia Institute of Technology have been trying to understand the biogeochemical processes at work in the marsh — that is, the exchange of biogeochemical elements such as carbon, phosphorus, nutrients and metals between living and non-living components of the environment. They want to know how these processes relate to the productivity, faunal activity and hydrology of the marsh system. An understanding of these relationships is crucial to predicting the effects of global warming on the coastal environment.
The scientists presented their work earlier this year at a joint meeting of the Ecological Society of America and the American Society of Limnology and Oceanography. The conference was titled "Land-Water Interface: Science for a Sustainable Biosphere."
"We had among some of the highest rates of organic matter decomposition ever measured in marine systems," says senior author Dr. Joel Kostka, a Georgia Tech adjunct professor and researcher at the Skidaway Institute of Oceanography, a research unit of the University System of Georgia. One reason for the higher than expected results may have been the length of time the study was conducted; very few studies have looked at decomposition rates by microorganisms over a two- year study period, as it was in this study, Kostka explains.
Researchers believe microorganisms in salt marsh sediments play a significant role in the cycling of materials in and out of the ecosystem. By examining microorganisms, such as bacteria, which occur in all of the sediments in the salt marsh, the scientists hope to determine what drives the microbial activity. By looking at the total marsh environment across several seasons, they are learning how nutrients flow through the system.
Numerous variables affect microbial activity in the soils, says Dr. Philippe Van Cappellen, an associate professor in Georgia Tech's School of Earth and Atmospheric Sciences. He and Tech graduate student Alakendra Roychoudhury are working with Kostka on this continuing study. Those variables include temperature, inundation by the tides, plant composition in the area, the hydrology of the area, the input of organic material, runoff from the adjoining land area and mixing of the sediment.
Along with the microorganisms at work in the marsh, larger forms of animal life also affect nutrient cycling in the marsh. Large populations of fiddler crabs that inhabit the mud flats in the salt marsh can greatly enhance productivity in the area, Koskta says. Their burrows, which can extend 20 centimeters into the soil, allow salt water to infiltrate the mud, which in turn introduces oxygen into the sediments.
"The injection of oxygen changes microbial activity," Kostka says, "and that changes chemical and nutrient releases."
The research was funded by Georgia Tech's Earth and Atmospheric Sciences program, the Georgia Sea Grant College program, the Office of Naval Research, the Skidaway Institute and the National Science Foundation through an initiative aimed at encouraging interdisciplinary studies.
— Patricia J. West
For the full-text news release, see www.gtri.gatech.edu/res-news/WARMING.html. .For more information, you may contact Dr. Joel Kostka, Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, GA 31411. (Telephone: 912/598-2395) (E-mail: joel@skio.peachnet.edu); or Dr. Philippe Van Cappellen, School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332-0340. (Telephone: 404/894-3883) (E-mail: philippe.vancappellen@eas.gatech.edu)
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Tiny Computers Of Carbon? |
Georgia Tech researchers
observed ballistic conductance — a phenomenon in
which electrons pass through a conductor without
heating it — at room temperature
in multi-walled carbon nanotubes up to five microns long.
photo by Stanley Leary
U. S. Army Capt. Scott Rauer, a pilot and former graduate student at Georgia
Tech, operates a flight simulator developed by NTI Inc. of Dayton, Ohio, with
assistance from GTRI researcher Dr. Brian Stevens. It is a very realistic flight
simulator that will record the needed data and run on a relatively inexpensive, off-
the-shelf personal computer.
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Yet military doctors face an unusual dilemma in treating pilots: the extensive array of the modern pharmacopeia. Which drugs, both prescription and over-the-counter, can affect pilot performance? How much of a given drug can a pilot take before becoming impaired?
Obviously, a flight simulator would be the safest way to measure the effects of medication use among pilots. But conventional flight simulators are not designed for drug impairment studies, and they are not easy to reconfigure. Also, the availability of flight simulators is limited, and time on simulators is expensive. So how do you test for the effects of medication? The answer — recently developed by NTI Inc. of Dayton, Ohio, with assistance from the Georgia Tech Research Institute (GTRI) — is a very realistic flight simulator that will record the needed data and run on a relatively inexpensive, off-the-shelf personal computer.
"The part that makes it more realistic is very high fidelity aircraft mathematical models and aerodynamic data, many tables of aerodynamic data," says Dr. Brian L. Stevens, a GTRI senior research engineer and principal investigator for the NTI contract. Rauer, with his pilot training and relevant aerospace engineering coursework, was the ideal graduate research assistant. He assisted in the model development.
The mathematical models use the data — some of it from NASA and the U.S. Air Force — to provide realistic aircraft dynamics in various flight conditions. These conditions range from combat maneuvering to flying a precise course in severe weather or turbulence. The mathematical models coupled with computer graphics and a set of flight controls — stick, throttle and rudder pedals — provide a realistic flight simulator.
The heart of the simulation is a computer model of the F-16 fighter jet. Stevens developed the model for a book on aircraft controls and simulation. Subsequently NTI contracted with Stevens to develop the aircraft flight models for the simulator program for use in tests of how pilots react to unusual circumstances.
The program, known as the Situation Awareness Flight Test Evaluator (SAFTE), uses Stevens' computer model as its core. The graphics in the program provide an area of about 60 by 150 nautical miles in which aircraft can fly. This area includes mountains, four towns, a river and other topographical features suggested by a former F-16 pilot consulting for NTI. The program combines all the data and graphics and can operate in as little as two-millisecond steps, making the simulation extremely realistic — especially in comparison with most personal or game simulations, which operate in 50-millisecond steps.
NTI used the simulation at the University of North Dakota on 100 subjects who were trained to fly the simulator, and then tested. Yet, there were limitations to the simulation. Time and cost constraints prevented the graphics from being very realistic. Data on a tricycle landing gear, used by the F-16 and most fighter and trainer aircraft, were not readily available, so researchers substituted a bicycle landing gear.
Perhaps the most significant limitation was the power of the computers on which the program runs. Researchers ran the program on two personal computers — one dedicated to graphics and one to run the flight calculations that made the program realistic. To do this required the team to write a special real-time "executive program" to control operations.
Subsequently, NTI developed its Flight Performance Assessment Simulation System (FPASS) to evaluate the effects of medications on U.S. Air Force pilot performance. That development gave Stevens the chance to upgrade and expand the flight simulation. In addition to the F-16, it now includes the T-1 and T-38 training aircraft, and each has a tricycle landing gear. Perhaps more importantly, it allows simulation modifications that take advantage of advances in personal computer technology.
"This effort brings everything in line with current commercial standards," Stevens says. NTI modified the program to run on the Windows '95 operating system on a single 300-megahertz computer. Now, the simulation can use Microsoft scenery files, providing more realistic graphics and allowing the simulation to use thousands of already available files. In addition, researchers can use more complete aerodynamic data sets on the newer system.
Of course, researchers had to make some compromises because of changes to the simulation system. The original simulation ran in real-time because it was a DOS program, which allows the simulation to have exclusive control of the computer and its resources. The Windows operating system does not allow this control, but provides near real-time operations. Windows '98, the next generation of the Windows operating system will provide a better interface with the flight controls, Stevens says.
In addition to more realistic scenery, the improved simulation features a realistic working cockpit. The new image shows gauges that are accurately reacting to simulation conditions. A new audio capability allows instructions or other data to be "radioed" to the pilot, and may even allow them to acknowledge that the transmission was received.
The result of this work is an extremely realistic flight simulator, which according to Stevens is "equivalent to the official simulators and other professional training simulators in terms of the accuracy of its aircraft models." The difference is, this simulator collects data on the pilot's actions, allowing scientists to gather data if and when common medications affect pilot performance.
— C. Blake Powers
For more information on this simulator, contact Dr. Brian Stevens, Sensors and Electromagnetic Applications Laboratory, Georgia Tech Research Institute, Atlanta, GA 30332-0856. (Telephone: 770/528-7765) (E-mail: brian.stevens@gtri.gatech.edu)
The southeastern United States consistently has the nation's highest
rate of fatal traffic crashes. These southeastern states — Alabama,
Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina
and Tennessee — also have a significantly higher proportion of fatal
crashes in which drivers were not wearing, or not properly wearing,
their seat belts, according to a preliminary study done by the Georgia
Institute of Technology, the
Federal Highway Administration (FHWA)
and the National Highway Safety Administration (NHTSA).
Traffic Fatalities and Seat Belts
New study to investigate higher
fatality rate in Southeast.
This chart illustrates the
traffic fatality rates in southeastern states compared to other regions
and the nation as a whole. Click on graphic to see larger, 55k
version.
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"The Southeast systematically ranks poorly with respect to fatal crashes compared to the remainder of the U.S. — we need to identify the causal factors and implement effective countermeasures," said lead researcher Dr. Simon Washington, an assistant professor in the School of Civil and Environmental Engineering.
Now, with preliminary results in hand, that is exactly what Washington, assistant civil engineering professor Dr. Karen Dixon and transportation officials from each southeastern state are doing. They have just begun a two-year study to determine the causes for this disturbing trend. State safety officials will use this information to formulate solutions. Washington is coordinating the research effort, which will include university researchers from each of the southeastern states.
The entire research team will investigate the top five potential contributing factors to fatal crash occurrence. They expected to choose the top five by the end of the summer based on each state's informal top 10 list.
"Among some of the factors likely to be studied are: alcohol and drug related crashes; occupant restraint use; speeding and police enforcement; fixed objects crashes; intersection-related crashes; and rural versus urban crashes," Washington said. "Studies of these and other factors are likely to reveal new and detailed insight into the relative importance of these factors on fatal crash occurrence.
"This large regional study is unusual because each state will have researchers studying and analyzing crash factors in their states, while Georgia Tech provides analysis coordination and regional analysis support," Washington said. "Also, the Federal Highway Administration and the National Highway Traffic Safety Administration are working together to provide oversight of the research effort. As a result of the inter-state cooperation of researchers and safety officials, we are hopeful that the results are likely to be used to implement safety policies and programs."
— Jane M. Sanders
For the full-text news release, see www.gtri.gatech.edu/res-news/TRAFFIC2.html. For more information, you may contact Dr. Simon Washington, School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0355. (Telephone: 404/894-6476) (E-mail: simon.washington@ce.gatech.edu)
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And That Which Is Old Shall Be New Again |
GTRI researchers are making sure the strengths and limitations of humans
will be considered central to the redesign of Kaman SH-2 Seasprite helicopters for
the Royal Australian Navy.
photo by David Scott
Habitat mitigation is one of the topics covered in a new book co-edited by a
Georgia Tech professor. A habitat mitigation project near Augusta, Ga., provided an artificial
foraging site called Kathwood Ponds for the endangered wood stork. The storks had
been feeding in the Savannah River Swamp before the habitat was damaged by hot
water effluent from nuclear reactors at the U.S. Department of Energy's Savannah
River Site in Aiken, S.C.
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Environmental Methods Review: Retooling Impact Assessment for the New Century was published this past spring. It was edited by Dr. Alan Porter, a Georgia Institute of Technology professor of industrial and systems engineering, and John Fittipaldi, a 1978 master's graduate of Tech's city planning degree program, who is a senior fellow at the Army Environmental Policy Institute (AEPI). AEPI relocated to Georgia Tech in 1994 to collaborate with Tech faculty on environmental policy projects such as this book. The book features articles by an international group of experts on various environmental assessment (EA) and impact assessment (IA) tools and techniques.
The book's intention is to point readers to the state of the art of good practice in EA and IA, the editors say. It also emphasizes the need for improved methods, particularly with increased demand for sustainable development.
Environmental assessment practitioners in the Army and other military branches, military contractors and others outside of the armed services can use the book for guidance, the editors say. The editors also expect the book will alert graduate students and faculty to methodological issues needing further research.
Seven sections in the book deal with the themes represented in the authors' papers. They are: Perspectives on the Field, Overviews, Strategic Assessments, Processes, Risk Assessment, Domain-Oriented IA and Models in Environmental IA.
Among the writers offering perspectives are Lynton Caldwell, the person most recognized with crafting the National Environmental Policy Act of 1969 (NEPA). The other paper reflects upon the Army's interest in introducing relevance and efficiency often lacking in many environmental assessments.
The overview section features five papers. Two reflect upon the performance of EA in developed economies. The third paper presents a contrasting view of recent changes in Chinese EA practice. The fourth provides an overview of EA and IA methods. And the fifth article poses critical environmental sustainability concepts that can guide various EA approaches.
The strategic environmental assessment section focuses on what one of the authors calls the single most important direction in the field. All six of the papers in this section focus on the application of EA above the project level.
Papers in the processes section share a theme of "doing," the editors say. They range from selecting methods to training. The section also includes papers on "cheaper, better, faster" ways to conduct EA and the integration of NEPA into IA and ecological management.
The risk assessment (RA) section seeks to open communication between the RA and EA/IA communities. One paper contrasts RA guidelines, and the other considers risk communication issues in EA.
The focus is on methods applied to particular IA disciplines in the domain-oriented IA section of the book. Eight papers address social, economic, climate, health, ecological systems and environmental justice.
The EIA models section contains three papers: one on the selection of models and parameters for analysis of environmental impacts; another points to the value of health risk assessments in EA; the third makes the case for consideration of transportation activities in EA.
— Jane M. Sanders
For more information, you may contact Alan Porter, Technology Policy and Assessment Center, Georgia Institute of Technology, Atlanta, GA 30332-0205. (Telephone: 404/894-2330) (E-mail: alan.porter@isye.gatech.edu).
Molecular dynamics
simulations show how oscillating the gap between two sliding surfaces
reduces the order of thin-film lubricant molecules. In the lower image,
molecules that had been confined within the surface have moved out into
the bulk lubricant not confined, and molecules from the bulk areas have
moved into the gap.
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Researchers at the Georgia Institute of Technology reported in the June 25 Journal of Physical Chemistry that by rapidly oscillating the width of the lubricant-filled gap separating two sliding surfaces, they can significantly reduce friction between them.
The technique keeps the lubricant in a state of dynamic disorder, preventing the formation of molecular layering that can increase friction. Based on molecular dynamics simulations, the findings would be of particular interest to designers of micro-scale machines.
"This is a novel way of controlling friction," said Dr. Uzi Landman, director of Georgia Tech's Center for Computational Materials Science (GTCMS). "Through the use of small amplitude oscillations of the gap between two solid surfaces, the ordering process of the lubricant is frustrated, which maintains the lubricant in a liquid state. This allows steady motion of the surfaces with a small coefficient of friction."
Studies by Landman and colleagues Jianping Gao and W.D. Luedtke suggest that varying the gap by as little as 5 percent can maintain the necessary level of disorder.
The research builds on earlier studies showing that thin-film lubricant molecules confined between two solid surfaces organize themselves into well-ordered layers. In a confined film of approximately 20 Angstroms, a lubricant such as hexadecane forms four to five layers in which the long-chain molecules all lie parallel to the sliding plane.
The molecular organization creates what Landman calls a "semisolid." Such a structure resists the shearing forces necessary to slide the two surfaces it separates, increasing the force necessary to make them move.
Creating small variations in the distance between the sliding surfaces upsets the ability of the lubricant molecules to fit "comfortably" between the surfaces, he said. Decreasing the gap forces some molecules out, while increasing it allows more molecules in. This constant rearranging of molecules prevents formation of the ordered layers in the lubricant film.
The research was sponsored by the U.S. Air Force Office of Scientific Research and the U.S. Department of Energy. The molecular dynamics simulations were performed at the Pittsburgh Supercomputing Center, the National Energy Research Scientific Supercomputing Center at Berkeley and at Georgia Tech.
— John Toon
For the full-text news release, see www.gtri.gatech.edu/res-news/FRICTION.html.
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