Smart Ice System Improves Flight Safety A smart ice-management system being developed at the University of Illinois would sense the effect of accreted ice on the performance and handling qualities of an aircraft, then alert the pilot, restrict the aircraft from potentially dangerous maneuvers, and adapt the flight control system to maintain safe operation.

"Current ice-protection systems attempt to prevent or remove an ice accretion and may provide limited sensing of the presence of ice," said Michael Bragg, professor and head of aeronautical and astronautical engineering at the U of I.  "But these systems use little, if any, information about the present state of the aircraft.  Our approach is to provide the pilot with a near real-time characterization of the effect that ice is actually having upon the aircraft."

When ice accumulates on flight surfaces, it can change an aircraft's performance, stability, and controllability.  Accidents can occur not only from degraded aerodynamic performance but also from well-intentioned pilots making bad decisions in the absence of adequate information.

"Pilots expect an aircraft to respond in a certain way to their commands, and when it doesn't, they might assume the wrong reason and take improper measures that can result in a dangerously unstable aircraft," said Tamer Basar, the Fredric G. and Elizabeth H. Nearing Professor of Electrical and Computer Engineering at the U of I.   "We have to provide more relevant information to the pilots so that they can make informed decisions and safely fly an aircraft under severe icing conditions."

Using systems identification techniques, the researchers first modeled the effects that ice can have on an aircraft's flight dynamics.  Then they developed methods to detect and characterize those effects.

"Instead of relying only upon an ice-thickness sensor, for example, we're measuring the changes in aircraft performance and control during an icing encounter," said James Melody, a graduate student in the university's Coordinated Science Laboratory.  "We use a neural network to extract information from the flight dynamics and various other sensors to better inform the pilot of the current state of the aircraft."

Ultimately, the researchers want their ice-management system to automatically adapt the flight control system to make an aircraft easier—and safer—to fly when iced.  For larger, newer aircraft, the system could operate autonomously, while still keeping the pilot properly informed.

A prototype of the smart ice-management system will be flight-tested following tests to validate the researchers' models and algorithms.

This work is supported in part by the National Aeronautics and Space Administration.
—James E. Kloeppel, University of Illinois News Bureau

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Microchannel Technology Bodes Well for Ammonia as Refrigerant

Modern microchannel tube technology—widely used in the automotive industry for heat exchangers—offers an excellent opportunity to rethink the use of ammonia as a refrigerant, say scientists at the University of Illinois.

In a recent feasibility study, U of I researchers used a commercially available microchannel heat exchanger to create a 15-kilowatt refrigeration system with the smallest ammonia charge in the world.  A similar technique could be used to significantly reduce the amount of ammonia in large chillers.

Ammonia is widely accepted as the most efficient and environmentally friendly refrigerant.  But its unpleasant odor and mild toxicity have limited its use to industrial plants away from heavily populated areas.  To reduce risk and expand applications in urban areas, the amount of ammonia required to charge refrigeration and air conditioning systems must be substantially reduced.

"New designs in microchannel heat exchangers allow much smaller refrigerant charges to be used than in conventional heat exchangers," said Pega Hrnjak, a U of I professor of mechanical and industrial engineering and co-director of the university's Air Conditioning and Refrigeration Center.  "Charges in these systems could be hundreds of times smaller than in conventional systems."

To explore the feasibility of using air-cooled condensers with microchannel tubes and ammonia as the refrigerant, Hrnjak and graduate research assistant Andrew Litch constructed an experimental chiller facility.  The researchers then evaluated two similarly sized aluminum condensers: one with a parallel microchannel tube arrangement and the other with a single serpentine macrochannel tube.

"The microchannel system significantly outperformed the conventional system," Hrnjak said.  "The amount of refrigerant was reduced several times, while significantly increasing the heat transfer capability."

Using microchannel tubes, Hrnjak and Litch successfully reduced the refrigerant charge to 2.5 ounces of ammonia per ton of evaporator capacity—considerably lower than the 12.5 ounces per ton used in current air-cooled ammonia chillers. Further charge reduction would be possible through better design of the condenser headers and optimization of the heat exchanger as a whole, Hrnjak said.

A paper discussing the researchers' findings has been accepted by the International Journal of Refrigeration.  The Modine Manufacturing Co., Hydro Aluminum, and the International Institute of Ammonia Refrigeration funded the research.
—James E. Kloeppel, University of Illinois News Bureau

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Student-Built Satellite Is Space Bound

Nothing is too ambitious or too challenging for Illinois engineering students—not even the task of designing and building a satellite that will be launched into space.  Thirty engineering students are enrolled in a new two-semester senior design course that will culminate in the November 2002 launch of their satellite from a Russian rocket.

Illinois is one of several universities worldwide taking advantage of Cubesat satellite technology.  Developed by a Stanford University professor, the technology converts Cold War weapons to launch vehicles.  Cubesat satellites are small (4 x 4 x 4 inches) and are mostly launched from a converted Russian Intercontinental Ballistic Missile (ICBM) launch vehicle.  The satellites fly in a low earth orbit (600 km).

"This project provides a unique learning experience," said Gary Swenson, an electrical and computer engineering professor serving as the course co-director with Victoria Coverstone, an aerospace engineering professor.  "Engineers from several departments are involved.  They have to learn to work with each other and appreciate each other's problems, including engineering interfaces and schedules."

The Illinois project will be the first Cubesat satellite to be equipped with thrusters, which will enable the students to have an unprecedented level of control of their satellite.  The thrusters act as a form of propulsion, and they can be used to turn the satellite while it's orbiting or can even be used to change the orbit.  Alemeda Applied Sciences Corp. donated engineering model and flight thrusters, valued at $20,000.

"With a thruster system, we could do formation flying," said electrical engineering senior Daniel Chen, assistant program manager of the project.  "We can do tests where other satellites cannot reach."

"We'll be able to control how it's oriented when it is orbiting—whether it's spinning as it goes around, or whether it's on its side, which way it's pointed," added Ryan Kuester, an electrical engineering senior and leader of the communications and data handling team.  "Also, you can change your orbit shape a little—change how high you are or the shape of your orbit."

According to Kuester, the U of I satellite's primary mission is to qualify the thrusters for space.  "These particular thrusters have never been flown in space before, so we're proving that these parts work in space."

A secondary mission is to fly a sensor to look at the airglow layer.  An airglow layer near 90 km altitude provides information about waves in the atmosphere.  This will offer a global survey of the waves.

To learn more about this project, explore http://courses.ece.uiuc.edu/cubesat.
—Laura Schmitt.  Excerpted from Ingenuity, published by the Department of Electrical and Computer Engineering.

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Random Noise Reveals Internal Structure

By picking up the tiny vibrations of thermal energy that exist naturally in all objects, researchers at the University of Illinois have performed ultrasonic measurements without using a source.  Potential applications range from seismology to materials science.

As reported in the Sept. 24, 2001, issue of Physical Review Letters, U of I professor of theoretical and applied mechanics Richard Weaver and research associate Oleg Lobkis measured minuscule sound waves—called phonons—propagating within a block of aluminum at room temperature.

"The sound we were listening to was created by arbitrary thermal fluctuations generated elsewhere in the sample, such as an electron hitting a lattice imperfection or an air molecule striking the surface," Weaver said.  "While no one had really doubted that these tiny fluctuations existed, no one had ever measured them before."

Weaver and Lobkis not only proved that the vibrations were indeed measurable, they also showed that by correlating what appeared to be random noise, considerable information could be gleaned about an object's interior.  First, they listened to the noise, then they used mathematical operations that looked for patterns and repetitions—a process called autocorrelation.

"Like BBs rattling inside a box, phonons will bounce off the walls of the aluminum, ricochet off some internal structure, and bounce off the walls again, corresponding to the round-trip travel time of an echo," Weaver said.  "We looked for correlations within the echoes."

Weaver and Lobkis validated their technique by autocorrelating the noise from a passive piezoelectric transducer mounted to the sample and then comparing that result with an active measurement they obtained using conventional ultrasonics.

"The waveforms were almost identical," Weaver said.  "When you autocorrelate the ambient noise, you see nearly the same signal as when you pulse the transducer and listen to the echoes."

This surprising result is something scientists have been overlooking for decades, Weaver said.  "We've been throwing away this noise—not realizing that it's full of useful information."

In principle, the passive technique could work on nearly any object, but would be most helpful in applications where conventional sound sources are scarce.  At very low frequencies, for example, seismologists could pick up the random vibrations from distant earthquakes to obtain local stratigraphic information without setting off directed explosives.  At extremely high frequencies, the technique could be used to noninvasively probe micron-sized features and material properties in microchips.

"The technique also might be useful for monitoring building vibrations to anticipate potential collapse," Weaver said. "By measuring the natural frequencies of the building as it responds to random vibrations in the neighborhood, even subtle changes in structural rigidity could be detected."

The National Science Foundation funded this research.
—James E. Kloeppel, University of Illinois News Bureau

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Enhanced Model Assesses Impact of Climate Variability

By adding topographic features to their hydrologic model, researchers at the University of Illinois can better assess the impact of climate variability and global warming on terrestrial systems such as stream ecology, water quality, and water resources management.

"Hydrologic models provide an essential link between the physical climate and terrestrial systems," said Praveen Kumar, a U of I professor of civil and environmental engineering.  "Modeling the terrestrial hydrologic dynamics properly is crucial to predicting the atmospheric dynamics as well as predicting the climate's impact on terrestrial systems."

The natural unit for the representation of hydrologic processes is a river basin, Kumar said.  "By using a large-area, basin-scale model, we can better characterize the variation of moisture distribution between land surface and atmosphere, so we can more effectively study key feedback mechanisms."

For their study, Kumar and graduate student Ji Chen combined digital elevation data from the U.S. Geological Survey (USGS) along with hydrologic characteristics such as river basin boundaries and drainage networks.  Then they added topographic parameters—water table fluctuations and vertical and horizontal ground water transport—to the model.  To compare results, they ran the model both with and without these topographic enhancements.

Simulations for the entire North American continent were performed using the International Satellite Land Surface Climatology Project datasets for the years 1987 and 1988.  The researchers validated their model by comparing model predictions against streamflow data collected by the USGS on rivers such as the Mississippi, Missouri, and Ohio.

"When run with the enhancements, the model captured both the seasonal and the inter-annual variability quite realistically," Kumar said.  "For example, seasonal patterns of streamflow in the tributaries of the Mississippi River basin were consistent with the actual measurements.  The model also correctly predicted the winter-spring runoff from the Appalachian mountain range."

The researchers described their model in the May 1, 2001, issue of the Journal of Climate.  The National Aeronautics and Space Administration and the National Science Foundation supported this work.
—James E. Kloeppel, University of Illinois News Bureau

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Nanoparticles Tailor Complex Fluids

Researchers at the University of Illinois have discovered a fundamentally new approach for tailoring the stability of colloidal suspensions.

Colloidal suspensions are complex fluids utilized in numerous applications ranging from advanced materials to drug delivery.  Controlling the stability of these fluids can influence such characteristics as flow behavior, structure, and mechanical response, and may result in materials with improved optical and electrical properties.

As reported in the July 31, 2001, issue of the Proceedings of the National Academy of Sciences, Jennifer Lewis and her colleagues have devised a process that they call nanoparticle haloing.  This self-organizing process imparts stability to otherwise attractive colloidal microspheres by decorating regions near their surface with highly charged nanoparticles.

"Using this nanoparticle haloing approach, we can control the phase behavior and structure of materials assembled from colloidal systems," said Lewis, a U of I professor of materials science and engineering and of chemical engineering.  "Our approach complements traditional stabilization techniques, such as electrostatic stabilization, by allowing systems of negligible charge or high ionic strength to be stabilized."

Tailoring the interactions between particles allows the researchers to engineer the desired degree of colloidal stability into the mixture.

"That means we can create designer colloidal fluids, gels, and even crystals," Lewis said.  "Our ability to control colloidal forces and phase behavior depends not only on the charge of the nanoparticles but also on their size.  Through nanoparticle engineering, we can assemble structures with properties that would not be possible through traditional stabilization routes."

For example, Lewis has teamed up with co-author Paul Braun, a U of I professor of materials science and ngineering, to explore the use of these nanoparticle-stabilized colloidal microsphere mixtures in assembling robust periodic templates for photonic band gap materials.  The researchers recently were awarded funding by the National Science Foundation to pursue such efforts.

Lewis and her students are also studying the structure and flow behavior of colloidal fluids and gels assembled from these microsphere-nanoparticle mixtures.  By compositionally modulating interparticle forces, the researchers can produce systems whose properties vary dramatically.  Such studies provide the foundation of ongoing efforts in the area of colloidal processing of electrical ceramics.

In addition to Lewis and Braun, the research team included U of I doctoral students Valeria Tohver and James Smay and Carnegie Mellon University graduate student Alan Braem.  The National Aeronautics and Space Administration Microgravity Research Program funded the work.
—James E. Kloeppel, University of Illinois News Bureau

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Lithographic Technique Creates Neuronal Networks in a Dish

Using a lithographic technique called microstamping, a University of Illinois scientist has produced patterned surfaces on glass substrates that integrate biocompatible materials and live nerve cells.

Manipulating the attachment and growth patterns of individual nerve cells has potential application to biosensors, drug screening, implants, and prosthetics.

"Controlling tissue response is particularly important for implants, which tend to work for a while, then lose electrical sensitivity," said Bruce Wheeler, a U of I professor of electrical and computer engineering and a researcher at the university's Beckman Institute for Advanced Science and Technology.  "If we can better understand and control the interface between electronic components and nerve cells, we could build more sophisticated and longer lasting implants."

Wheeler's microstamping technique precisely reproduces a master pattern with biologically relevant materials.  To culture nerve cells in a dish, he works with graduate students John Chang and Johnny Nam.  He also works with Gregory Brewer, a professor of medical microbiology at the Southern Illinois University School of Medicine in Springfield, who first removes brain cells from developing rat embryos. The cells are chemically and mechanically separated, then poured onto the patterned polylysine where they selectively attach to the surface.

"Within a few days, the cells send out processes that explore the environment, preferring areas that have intact polylysine," Wheeler said. "The cells soon mature and begin sending electrical signals."

Microlithographic techniques also can be used to fabricate planar microelectrode arrays. Confining the neurons to narrow tracks that intersect electrodes creates a technological basis for robust, designable neural networks useful for studying basic neuroscience or for constructing elaborate neural biosensors.

"One problem with biomaterials growing on a micropatterned array, however, is the long-term stability and retention of biological activity," Wheeler said.  "Also, because the brain has ordered layers of cells, we believe that orderly growth will lead to greater insight to brain activity, and we have had to develop techniques for maintaining the orderly growth of the neurons in culture."

Working with Deborah Leckband, a U of I professor of chemical engineering, the researchers have placed a layer of polyethylene glycol to reduce unwanted protein adhesion and cell growth in portions of the array.

"The nerve cells maintained compliance to the microstamped patterns and remained viable for up to one month," said Wheeler, who presented the team's latest findings at an international workshop on cells on solid substrates, held in summer 2001, in Tegernsee, Germany.
—James E. Kloeppel, University of Illinois News Bureau

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Slick Research Finds Speed Affects How Fluids Slip

When it comes to predicting boundary conditions of fluids flowing over solid surfaces, the textbooks are all wet, say researchers at the University of Illinois.

How fluids behave on extremely smooth surfaces is important in such high-tech applications as moving materials through microfluidic devices and lubricating computer hard drives.

"We found that if surfaces are smooth enough, and if the liquid is moving fast enough, the liquid will slip over the surface like ice skates gliding over ice," said Steve Granick, a professor of materials science at the U of I and a researcher at the Frederick Seitz Materials Research Laboratory on campus.

Liquids may be attracted poorly to a solid surface, like beads of water on a freshly waxed car, or they may be attracted strongly, like cooking oil on an old iron skillet.  A basic tenet of textbook fluid dynamics—called the "no-slip" boundary condition—says that a layer of fluid molecules flowing across a solid surface will be stuck in place, regardless of the strength of attraction.

To explore the no-slip boundary condition, Granick and doctoral student Yingxi (Elaine) Zhu placed drops of liquid between molecularly smooth mica surfaces within a modified surface forces apparatus.  Surface spacing was measured using optical interferometry and dynamic forces were measured using piezoelectric methods.  The team's findings were reported in the Aug. 27, 2001, issue of Physical Review Letters.

By first coating the mica with a smooth monolayer of octadecyltriethoxysiloxane, the researchers studied the behavior of two dissimilar fluids—tetradecane (an oil) and water.  Each drop was squeezed until the fluid was only a few layers thick.  Not only did none of the layers in either fluid "stick" to the surface (as textbooks claim they should), the amount of slip depended on the velocity of the fluid.

The researchers also saw the same effect when, instead of first modifying the solid surface, they added soap-like molecules to the flowing liquid.

"The surfactant migrated to the surface where it formed a smooth coating that lessened the attraction of the liquid for that surface," Granick said.  "This means we can achieve the same lubrication goal without going through the complicated protocols of producing a perfect surface."

This could be an easy and inexpensive way to save energy when transporting fluids through pipelines and for reducing friction in engines and machinery, Granick said.  "There will be many other applications down the road, when we know more about manipulating the no-slip boundary condition."

The National Science Foundation and the U.S. Department of Energy supported the research.
—James E. Kloeppel, University of Illinois News Bureau

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Engineering Alumnus Selected for University Honors
Thomas M. Siebel, chairman and CEO of Siebel Systems Inc., received the University of Illinois Presidential Award and Medallion, which honors alumni and friends of the university whose professional and humanitarian contributions have been noteworthy.

U of I President James J. Stukel made the award in recognition of Siebel's "commitment to excellence in software engineering, computer science research, and graduate education, and to his continuing commitment and generosity to his alma mater."

Siebel earned a bachelor's degree in history (1975) and master's degrees in business administration (1983) and computer science (1985), all from the U of I.   He founded Siebel Systems Inc., the world's leading provider of eBusiness application software, in 1993.

"The University of Illinois is recognized as a global leader in information technology," Siebel said.  "I am honored to receive this recognition.  As someone who has benefited greatly from the leadership of the university, it is my pleasure to play a continued role in the success of this institution."

Siebel received the award at the fall 2001 meeting of the Silicon Valley Roundtable, held at the Garden Court Hotel in Palo Alto, Calif.  Established in 1997, the group is composed of business leaders who are U of I alumni working on the West Coast.  They advise Stukel and the U of I Foundation on technology, business, and alumni issues.

In 1999, Siebel donated $32 million to the Urbana campus to help construct the Thomas M. Siebel Center for Computer Science, scheduled for completion in 2003. 

In addition, a corporate gift from Siebel Systems established the Siebel Scholars Fellowship Program at the nation's top graduate schools of computer science and business, including the computer science department at the Urbana campus.  Five U of I students recently received 2002 Siebel Scholars awards for their outstanding work in the computer science graduate program and their leadership excellence.

Each student received a $25,000 cash award to defray tuition costs and expenses for their final year of graduate study.  Bhaskar Borthakur and Albert Chu are focused on systems software and networking.  Hui Fang's research deals with computational science as it applies to astronomy.  James Jackson is working in the area of artificial intelligence, and Ryan Szypowski's research interest is numerical methods.

Siebel Systems employees, including chairman Siebel, assist Siebel Scholars by providing mentoring services, job search assistance, and help with business and public service initiatives.
—From University of Illinois News Bureau reports.

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