Three-Story Structure Slammed in Magnitude 8 Earthquake on Shake Table

Wednesday, May 7, 2008

Engineering researchers are subjecting a three-story structure resembling a parking garage to a sequence of earthquake "shake test" jolts as powerful as magnitude 8.0 as part of a series of seismic tests to help improve building codes across the nation.

The 1 million-pound precast concrete structure has the largest footprint of any structure ever tested on a shake table in the United States; the shaking of the structure will continue through May with the most violent shakes coming in June. The increasing intensity of the seismic shaking will duplicate ground motions measured in actual earthquakes and adapted specific conditions in Knoxville, TN., Seattle, WA., and Northridge, CA.  Engineers are testing the seismic response of precast concrete floor systems that are used in parking garages, college dormitories, hotels, stadiums, prisons and increasingly in office buildings.

“This is a landmark test that will enable a very fast and economically advantageous high technology construction method to be used in seismically active regions of the United States,” said Gilbert A. Hegemier, director of UC San Diego’s Powell Structural Research Laboratories, and professor and chair of the Jacobs School of Engineering’s Department of Structural Engineering.

The seismic tests of the one-half-scale structure involve a collaboration among UC San Diego, the University of Arizona, and Lehigh University. The $2.3 million project is being funded by the Precast/Prestressed Concrete Institute and its member companies and organizations, the National Science Foundation, the Charles Pankow Foundation, and the Network for Earthquake Engineering Simulation (NEES).

The goal of the project is to design a building by 2012 that can withstand a major earthquake. In the past, due in part to lack of industry knowledge, individual precast elements pulled apart, much like what happened with the collapse of the nine parking garages during the Northridge Earthquake in Los Angeles in 1994.  Since that quake occurred in the early morning, one only one person died. However, experts say the death toll could have been much higher. The other problem is the seismic code for these types of precast buildings is 20 years old. The Precast/Prestressed Concrete Institute recently launched a competition to design better floors for such buildings. 

 “There are significant construction advantages in assembling concrete structures from pieces that are built ahead of time, but the challenge in using precast concrete is that the structure is not one continuous piece of concrete, but many individual ones that are connected together,” said Robert Fleischman, a civil engineering professor at the University of Arizona and principal investigator of this research project. “The floor section edges are interconnected and they sit on ledges; you can see these in any parking garage. These connections have had problems in earthquakes.”

The earthquake tests are being conducted at the Jacobs School of Engineering’s Englekirk Structural Engineering Center, which is about eight miles east of the university’s main campus. The $9 million Englekirk shake table is one of 15 earthquake testing facilities for NEES. The UCSD-NEES shake table, the largest in the United States and the only outdoor shake table in the world, is ideally suited for testing tall, full-scale buildings.

“The earthquake simulator at UC San Diego was designed to conduct state-of-the-art research and ultimately mitigate the disastrous impact of earthquakes in our communities,” said Jose Restrepo, co-principal investigator for the shake test and UCSD structural engineering professor.  “The test on the precast concrete building is an example of how to use the latest construction and testing techniques to develop the next generation of design methodologies.”

Source: University of California, San Diego / Jacobs School of Engineering

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Time Stamp: 5/7/2008 at 4:32:19 PM UTC

Getting Wired for Terahertz

Tuesday, April 15, 2008

A step toward circuits for superfast far-infrared computers

University of Utah engineers took an early step toward building superfast computers that run on far-infrared light instead of electricity: They made the equivalent of wires that carried and bent this form of light, also known as terahertz radiation, which is the last unexploited portion of the electromagnetic spectrum.

"We have taken a first step to making circuits that can harness or guide terahertz radiation," says Ajay Nahata, study leader and associate professor of electrical and computer engineering. "Eventually - in a minimum of 10 years - this will allow the development of superfast circuits, computers and communications."

Electricity is carried through metal wires. Light used for communication is transmitted through fiberoptic cables and split into different colors or "channels" of information using devices called waveguides. In a study to be published Friday, April 18 in the online journal Optics Express, Nahata and colleagues report they designed stainless steel foil sheets with patterns of perforations that successfully served as wire-like waveguides to transmit, bend, split or combine terahertz radiation.

"A waveguide is something that allows you to transport electromagnetic radiation from one point to another point, or distribute it across a circuit," Nahata says.

If terahertz radiation is to be used in computing and communication, it not only must be transmitted from one device to another, "but you have to process it," he adds. "This is where terahertz circuits are important. The long-term goal is to develop capabilities to create circuits that run faster than modern-day electronic circuits so we can have faster computers and faster data transfer via the Internet."

Nahata conducted the study with two doctoral students in electrical and computer engineering: Wenqi Zhu and Amit Agrawal.

Developing Terahertz Technology

The electromagnetic spectrum, which ranges from high to low frequencies (or short to long wavelengths), includes: gamma rays, X-rays, ultraviolet light, visible light (violet, blue, green, yellow, orange and red), infrared light (including radiant heat and terahertz radiation), microwaves, FM radio waves, television, short wave and AM radio.

Fiberoptic phone and data lines now use near-infrared light and some visible light. The only part of the spectrum not now used for communications or other practical purposes is terahertz-frequency or far-infrared radiation - also nicknamed T-rays - located on the spectrum between mid-infrared and microwaves.

With so much of the spectrum clogged by existing communications, engineers would like to harness terahertz frequencies for communication, much faster computing and even for anti-terrorism scanners and sensors able to detect biological, chemical or other weapons. Nahata says the new study is relevant mainly to computers that would use terahertz radiation to run at speeds much faster than current computers.

In March 2007, Nahata, Agrawal and others published a study in the journal Nature showing it was possible to control a signal of terahertz radiation using thin stainless steel foils perforated with round holes arranged in semi-regular patterns.

This February, British researchers reported they used computer simulations and some experiments to show that indentations punched across an entire sheet of copper-clad polymer could hold terahertz radiation close to the sheet's surface. That led them to conclude the far-infrared light could be guided along such a material's surface.

But the London researchers did not actually manipulate the direction the terahertz radiation moved, such as by bending or splitting it.

"We have demonstrated the ability to do this, which is a necessary requirement for making terahertz guided-wave circuits," Nahata says.

Circuits: From Electrical to Optical to Terahertz

Wires act as waveguides for electricity. Wires connect active devices such as transistors, which switch or adjust the electric signal. That is the basis for how computers work today. An electronic integrated circuit is a computer processor made of wires, transistors, resistors and capacitors on a semiconductor chip made of silicon.

In optical communications, the waveguides carry laser-generated light in fiberoptic cables and lines etched or deposited on an insulator or semiconductor surface. Nahata says photonic integrated circuits now are used for phone and Internet communications, mainly for combining or "multiplexing" different colors or channels of light entering a fiberoptic cable and separating or "demultiplexing" the different wavelengths exiting the cable.

"Electronic circuits today work at gigahertz frequencies - billions of cycles per second. Electronic devices like a computer chip can operate at gigahertz," Nahata says. "What people would like to do is develop capabilities to transport and manipulate data at terahertz frequencies [trillions of hertz]. It's a speed issue. People want to be able to transfer data at higher speeds. People would like to download a movie in a few seconds."

"In this study, we've demonstrated the first step toward making circuits that use terahertz radiation and ultimately might work at terahertz speeds," or a thousand times faster than today's gigahertz-speed computers, Nahata says.

Channeling, Bending, Splitting and Coupling T-Rays

"People have been working on terahertz waveguides for a decade," he says. "We've shown how to make these waveguides on a flat surface so that you can make circuits just like electronic circuits on silicon chips."

The researchers used pieces of stainless steel foil about 4 inches long, 1 inch wide and 625 microns thick, or 6.25 times the thickness of a human hair. They perforated the metal with rectangular holes, each measuring 500 microns (five human hair widths) by 50 microns (a half a hair width). The rectangular holes were arranged side by side in three different patterns to form "wires" for terahertz radiation:

• One line of rectangles that served as a "wire" and carried terahertz radiation.

• A line that becomes two lines - like the letter Y - to split the far-infrared light, similar to a splitter used to route a home cable TV signal to separate television sets.

• Two lines that curve close to each other in the middle -- like an X where the two lines come close but don't touch -- so the radiation could be "coupled," or moved from one line or "wire" to another.

The straight pattern successfully carried terahertz radiation in a straight line. The other two patterns "changed the direction the terahertz radiation was moving" by splitting it or coupling it, Nahata says. The study showed the terahertz radiation was closely confined both vertically (within 1.69 millimeters of the foil's surface) and horizontally (within 2 millimeters of the pattern of rectangles as it moved over them).

"All we've done is made the wires" for terahertz circuits, Nahata says. "Now the issue is how do we make devices [such as switches, transistors and modulators] at terahertz frequencies?"

When terahertz radiation is fed into the stainless steel waveguides, it spans a range of frequencies. One frequency is guided across the steel surface. That frequency is determined by the size of perforations in the foil. The engineers chose a frequency they could generate and measure: about 0.3 terahertz, or 300 gigahertz. Terahertz radiation is defined as ranging from 0.1 terahertz (or 100 gigahertz) to 10 terahertz.

The design of the waveguide means that it carries terahertz radiation in the form of surface plasma waves - also known as plasmons or plasmon polaritons - which are analogous to electrons in electrical devices or photons of light in optical devices. The surface plasma waves are waves of electromagnetic radiation at a terahertz frequency that are bound to the surface of the steel foil because they are interacting with moving electrons in the metal, Nahata says.

Nahata's department is part of the University of Utah's College of Engineering, which has six academic departments plus a School of Computing, with a total of 130 full-time faculty members, 2,047 undergraduate students and 812 graduate students.

Source: University of Utah

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Time Stamp: 4/15/2008 at 11:34:46 AM CST

Hubble Maps The Changing Constellation Of Internet 'Black Holes'

Tuesday, April 8, 2008

You're trying to log on to a Web site and it's not working. You try again and again. But persistence doesn't pay off. The site you want is inexplicably, frustratingly, out of reach.

The other computer might just be turned off, but the causes could be more mysterious. At any given moment, a proportion of computer traffic ends up being routed into information black holes. These are situations where a path between two computers does exist, but messages -- a request to visit a Web site, an outgoing e-mail -- get lost along the way.

A University of Washington system named Hubble looks for these black holes and maps them on a Web site, providing an ever-changing constellation of the Internet's weak points.

The Hubble map lets visitors see a map of problems worldwide or type in a specific Web page or network address to check its status. The work is being presented next week in San Francisco at the Usenix Symposium on Networked Systems Design and Implementation.

"There's an assumption that if you have a working Internet connection then you have access to the entire Internet," said Ethan Katz-Bassett, a UW doctoral student in computer science and engineering. "We found that's not the case."

The project is named for the Hubble Space Telescope, which can observe black holes in deep space, because the UW tool performs a similar function for the maze of routers and fiber-optic cables that make up the Internet. In fact, research on the Internet's structure and performance is sometimes described as Internet astronomy.

"It's the idea of peering into the depths of something and trying to figure out what's going on, without having direct access," Katz-Bassett said.

The UW researchers send test messages around the world to look for computers that can be reached from some but not all of the Internet, a situation known as partial reachability. Short communication blips are ignored; a problem has to register in two consecutive 15-minute trials to appear on the site. A test last fall found that more than 7 percent of computers worldwide experienced this type of error at least once during a three-week period.

"When we started this project, we really didn't expect to find so many problems," said Arvind Krishnamurthy, a UW research assistant professor of computer science and engineering and Katz-Bassett's doctoral adviser. "We were very surprised by the results we got."

Now the team has created an online global map, updated every 15 minutes, showing locations currently experiencing problems. Hubble shows a flag on the area that's experiencing problems and lists the numerical address for the group of computers affected. Each address typically describes a few hundred to a few thousand individual computers. Hubble also reports what percentage of test probes was successful, and how long each problem has persisted.

Clicking a flag reveals which locations were and were not able to reach that machine. Future versions of Hubble will try to pinpoint the cause of each black hole.

Hubble's virtual eye on the Internet is made possible by PlanetLab, a shared worldwide network of academic, industrial and government computers. The UW researchers use about 100 PlanetLab computers in about 40 countries to send virtual probes to computers around the globe. Hubble monitors about 90 percent of the Internet, researchers said.

The new map can satisfy a frustrated user's idle curiosity about why a Web site is not loading. But the tool promises to be especially useful to professional network operators who keep the Internet running smoothly. Right now, when a computer network experiences a problem the administrator typically turns to online discussion boards.

"You would think that the network operators of Internet service providers would have access to better data," said Katz-Bassett. "That's not the case. The general approach has been to mail something out to a listserv and say, 'Hey, can you try this and see if you have a problem?'"

In a world that relies increasingly on online communication for e-mail, banking, television, phone calls, medical information and emergency communications, researchers want to make the overall network more transparent and more reliable.

"We want to give operators a way to tell what's going on quicker, catch problems quicker and solve them quicker," Krishnamurthy said.

Link to Hubble Map: http://hubble.cs.washington.edu/

Source: University of Washington / Hannah Hickey

Permalink: http://www.sflorg.com/comm_center/unv_tech/p371_35.html

Time Stamp: 4/8/2008 at 12:25:15 PM CST

Hybrid Computer Materials May Lead To Faster, Cheaper Technology

Thursday, April 3, 2008

MU professor receives part of $6.5 million to research nano-magnetic devices

A modern computer contains two different types of components: magnetic components, which perform memory functions, and semiconductor components, which perform logic operations. A University of Missouri researcher, as part of a multi-university research team, is working to combine these two functions in a single hybrid material. This new material would allow seamless integration of memory and logical functions and is expected to permit the design of devices that operate at much higher speeds and use considerably less power than current electronic devices.

Giovanni Vignale, MU physics professor in the College of Arts and Science and expert in condensed matter physics, says the primary goal of the research team, funded by a $6.5 million grant from the Department of Defense, is to explore new ways to integrate magnetism and magnetic materials with emerging electronic materials such as organic semiconductors. The research may lead to considerably more compact and energy-efficient devices. The processing costs for these hybrid materials are projected to be much less than those of traditional semiconductor chips, resulting in devices that should be less expensive to produce.

"In this approach, the coupling between magnetic and non-magnetic components would occur via a magnetic field or flow of electron spin, which is the fundamental property of an electron and is responsible for most magnetic phenomena," Vignale said. "The hybrid devices that we target would allow seamless integration of memory and logical function, high-speed optical communication and switching, and new sensor capabilities."

Vignale studies processes by which magnetic information can be transferred from a place to another.

"One of the main theoretical tools I will be using for this project is the time-dependent, spin-current density functional theory," Vignale said. "It is a theory to which I have made many contributions over the years. The results of these theoretical calculations will be useful both to understand and to guide the experimental work of other team members."

The research grant was awarded to the University of Iowa as part of a multi-university research initiative (MURI). Vignale joins Michael Flatté (University of Iowa), Andy Kent (New York University), Yuri Suzuki (University of California, Berkeley) and Jeremy Levy (University of Pittsburgh). John Prater of the Army Research Office will monitor the program.

Source: University of Missouri

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Time Stamp: 4/3/2008 at 2:14:27 PM CST

Super-slippery surfaces developed by Swedish researchers

Wednesday, April 2, 2008

How to decrease friction between surfaces? Researchers at KTH, Stockholm University and the Institute for Surface Chemistry (YKI) have been able to reduce friction and produce super slippery surfaces by selecting material based on the van der Waals forces.

In a cooperative effort between the researchers Mark Rutland (KTH), Lennart Bergström, (Stockholm University) and Adam Feiler (YKI) it has been possible to demonstrate for the first time that the friction between two surfaces that are exposed to the van der Waals repulsion force is very close to zero. Results have been published in the Langmuir scientific journal.

Van der Waals forces usually attract, which results in adhesion, i.e. the molecular attraction that exists between two bodies in close contact achieves a considerable level between individual molecules and between surfaces. However in a few systems (when two surfaces are in close contact with a liquid between them) this attraction can be transformed into repulsion which increases in strength the closer the surfaces come to each other. These surfaces are then more attracted to the liquid than they are to each other, and consequently do not wish to come into contact with each other if they are immersed in the liquid.

“The unique thing with van der Waals repulsion forces is that they prevent contact between surfaces, even when the surfaces are pressed together,” says Professor Lennart Bergström, Stockholm University.

By utilizing the van der Waals repulsion forces when selecting material, the researchers have been able to eliminate adhesion and drastically reduce friction, thus producing super-slippery surfaces.

“For example our results show that the friction between a particle of gold and a Teflon surface immersed in cyclohexane is actually so low that it is not measurable, not even with an atomic force microscope; an instrument that is routinely used to measure forces between molecules,” reports Professor Mark Rutland, Department of Surface Chemistry at KTH.

Low friction levels are extremely important if, for example, turbines in windmills, micro engines or hip joint replacements are to work well. According to researchers there are a number of material combinations that can provide super-slippery, low friction surfaces.

“For example there could be a ball bearing made of metal in a Teflon ring, or perhaps make engine components that are exposed to friction from certain combinations of ceramic material,” states Professor Mark Rutland, KTH.

Source: KTH - Royal Institute of Technology

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Time Stamp: 4/2/2008 at 11:34:32 AM CST