Wednesday, November 11, 2009


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When you kick over a garbage can, it doesn't make a pure, musical tone. That's why the sound is so hard to synthesize.

But now Cornell computer scientists have developed a practical method to generate the crashing and rumbling sounds of objects made up of thin "harmonic shells," including the sounds of cymbals, falling garbage cans and lids, and plastic water-cooler bottles and recycling bins.

The work by graduate students Jeffrey Chadwick and Steven An and Doug James, associate professor of computer science, will be presented at the SIGGRAPH Asia conference in Yokohama, Japan, in December.

As virtual environments become more realistic and immersive, the researchers point out, computers will have to generate sounds that match the behavior of objects in real time. Even in an animated movie, where sound effects can be dubbed in after the fact from recordings of real sounds, synthesized sounds can match more realistically to the action. So the goal is to start with the computer model of an object already created by animators, analyze how such an object would vibrate when dropped or struck, and how that vibration would be transferred to the air to radiate as sound.

When a thin-shelled object is struck or falls, the metal or plastic sheet slightly deforms and snaps back, triggering a vibration. To simulate the deformation, the computer divides the shell into many small triangles and calculates how the angles between triangles change and how much the sides of the triangles are stretched. What makes this difficult is that the shell vibrates in several different ways at once, and these modes of vibration are "coupled" -- energy transfers from one to another and back again. Previous methods of sound synthesis for shells did not take this into account, James said, and the result was a clean, clear sound, appropriate for bells and wind chimes, but not for things that crash and rumble.

The calculation must be stepped through time at audio frequencies, in this case seeing how the object will look every 1/44,100 of a second. Time-stepping a large mesh of triangles would take weeks of computer time, so the researchers approximate the response by sampling a few hundred triangles (out of thousands) and interpolate between them, a process they call "cubature."

The final step is to map out how the sound waves radiate to determine how the event will sound to a listener at any particular location. Calculating how vibrations of the object move the air is a standard, off-the-shelf process used by engineers who design real-world objects (a lot of work goes into making machinery quieter), but it's too slow for sound synthesis, so the radiation model is pre-computed to save time.

Even with these refinements, the system is not ready for real time, James reported. The computations for simple demonstrations still take about an hour on a laptop computer.

"There's some hope that we can speed this up," he said, "by making other approximations." Nevertheless, he said, previous methods of generating these sounds could take weeks, "but now we can do it in hours."

The work on thin shells is part of a larger project in James' lab to synthesize a variety of sounds, including those of dripping and splashing fluids, small objects clattering together and shattering glass.

(Photo: James Lab/Cornell University)

Cornell University


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Imagine taking all of the data on a Blu-ray disk, adding 40 times more information and shrinking it down to the size of a dime. Imagine that disk having enough memory to record an entire human life.

Sandipan Pramanik, a professor in the Department of Electrical and Computer Engineering, is developing a new way of storing memory that will dramatically alter entire industries. Pramanik's ambitious vision has won the first annual Disruptive Technology Challenge sponsored by TRLabs, a national high-tech research consortium based in Edmonton.

Pramanik is researching what amounts to the Holy Grail of computer engineering-a universal memory circuit that will render static and dynamic random-access memory used in PCs and laptop computers as well as hard disc drives, compact discs and flash memory, obsolete.

Using present technology, selecting one of these types of memory systems always involves a trade off in speed, cost, storage density, power consumption and durability or volatility, says Pramanik.

Pramanik is taking a unique approach to the problem, applying nanotechnology and spintronics. Simply put, Pramanik is fastening carbon nanotubes onto a pitted surface. The electrical resistance of each nanotube-weak or strong, represents a "zero" or "one" as a single bit of information.

Because he is working at the nanoscale, Pramanik's memory circuit can be shrunk to unprecedented levels. Pramanik envisions a single universal memory chip with a storage capacity of 1,000 gigabytes in an area of one square centimetre, compared to approximately 25 gigabytes for a Blu-ray disc (and 5 gigabytes for a normal DVD) that typically occupies 100 square centimetres.

The Disruptive Technology Challenge is designed to nurture information and communications technology innovation that has the potential to disrupt or create markets, disrupt current thinking in a field, or provoke new avenues of research with strong commercialization potential. The award Pramanik received will help fund three PhD student scholarships for three years.

Pramanik said winning the award is an honour.

"It is really great. This project has several technological challenges, and this award enables us to assemble a team of researchers, build the necessary infrastructure, and address these problems in a systematic manner," he said. "At present we are anticipating hiring three PhD students."

Pramanik is optimistic about reaching his goals. There are challenges "but we have plans on how to tackle those issues, and if everything goes well we are hoping to develop a prototype by the end of this funding period."

(Photo: U. Alberta)

University of Alberta


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Just in time for Halloween, researchers have announced the discovery of a new, real-world “monster” – what they are calling a “unicorn” fly that lived about 100 million years ago and is being described as a new family, genus and species of fly never before observed.

A single, incredibly well-preserved specimen of the tiny but scary-looking fly was preserved for eternity in Burmese amber, and it had a small horn emerging from the top of its head, topped by three eyes that would have given it the ability to see predators coming. But despite that clever defense mechanism, it was apparently an evolutionary dead end that later disappeared.

“No other insect ever discovered has a horn like that, and there’s no animal at all with a horn that has eyes on top,” said George Poinar, Jr., a professor of zoology at Oregon State University who just announced the new species in Cretaceous Research, a professional journal.

“It was probably a docile little creature that fed on the pollen and nectar of tiny tropical flowers,” Poinar said. “But it was really bizarre looking. One of the reviewers of the study called it a monster, and I have to admit it had a face only another fly could have loved. I was thinking of making some masks based on it for Halloween.”

This fly lived in the jungles of Myanmar and was found trapped in amber that was from 97 to 110 million years old. The gooey, viscous tree sap that flowed down over the fly and later turned to stone preserved its features in lifelike detail, including its strange horn topped by three functional eyes.

“If we had seen nothing but the wings of this insect, it would have looked similar to some other flies in the family Bibionomorpha,” Poinar said. “But this was near the end of the Early Cretaceous when a lot of strange evolutionary adaptations were going on. Its specialized horn and eyes must have given this insect an advantage on very tiny flowers, but didn’t serve as well when larger flowers evolved. So it went extinct.”

Poinar named the new fly Cascoplecia insolitis – from the Latin “cascus” for old and “insolates” for strange and unusual.

The fly also had other very unusual characteristics, the study found, such as an odd-shaped antenna, unusually long legs that would have helped it crawl over flowers and extremely small vestigial mandibles that would have limited it to nibbling on very tiny particles of food.

Pollen grains found on the legs of the fly suggest that it primarily must have fed on flowers.

This fly lived during the time of the dinosaurs, but also in a period when Triassic and Jurassic species were becoming extinct, modern groups were appearing and angiosperms, or flowering plants, were diversifying. Some of the characteristics of the fly were common to other families found around that time, but others were extremely different – especially the horn with eyes on top.

The specimen found in amber was well-preserved, lacking only the rear left portion of the abdomen and a portion of the left hind leg. It’s rare to find specimens with essentially a complete body as well as wings, scientists noted in the report. The fossil came from an amber mine in the Hukawng Valley of Myanmar, first excavated in 2001.

Poinar is an expert on insects and other life forms that have been preserved in amber, and has used them as clues to create detailed portraits of ancient ecosystems.

“None of the specialized body characters of Cascoplecia occurs on previously reported Cretaceous bibionids,” the report concluded. “This ‘unicorn’ fly was one of the oddities of the Cretaceous world and was obviously an evolutionary dead end.”

Unless, of course, it shows up once again as a scary looking Halloween costume – with wings, grasping claws, and a horn with three piercing eyes on top.

(Photo: George Poinar)

Oregon State University




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