New study allows scientists to visualize why free-moving objects jam when compressed
University of Oregon physicists using a supercomputer and mathematically rich formulas have captured fundamental insights about what happens when objects moving freely jam to a standstill.
Their approach captures jamming -- the point at which objects come together too tightly to move -- by identifying geometric signatures. The payoff, while likely far down the road, could be a roadmap to preventing overfilled conveyor belts from stopping in factories, separating oil deposits trapped in sand, or allowing for the rapid, efficient transfer of mass quantities of data packets on the Internet, say UO doctoral student Peter K. Morse and physics professor Eric I. Corwin.
Their paper "Geometric Signatures of Jamming in the Mechanical Vacuum" is online ahead of print in the journal Physical Review Letters.
"The history of the field has been looking at mechanical properties really close to the jamming transition, right where a sand pile starts to push back," said Corwin, whose research is supported by a National Science Foundation Faculty Early Career Development award. "What we're doing that is really different is we're asking what happens before the sand pile starts to push back. When it's not pushing back, you can't get any information about its mechanical properties. So, instead, we're looking at the geometry -- where particles are in relation to one another."
The problem, Corwin said, involves an ages-old question used to introduce physics in early education: Is sand a liquid, a solid or a gas? "Make a sand pile, step back and it holds its shape, so clearly it's a solid," he said. "But I can take that same sand and pour it into a bucket; it flows in and takes the shape of the container and has a level surface, so clearly sand is a liquid. Or I can put a top on the bucket and shake it around really hard, and when I do that the sand fills all of the space. Clearly sand is a gas. Except, it's none of those things.
"This has led to granular materials, or little chunks of things, being referred to as a fourth state of matter," he continued. "Is sand something else? One thing everyone agrees on -- the one feature about sand or piles of gravel or piles of glass spheres or ball bearings, that makes them really unique -- is that when spread out they can't support any load. If you keep compressing them, and they get denser and denser, you reach a density where it's like flipping a switch. All of a sudden they can support a load."
The key, the researchers said, is identifying the nearest neighbors of particles. This is done using the Voronoi construction, a method of dividing spaces into a number of regions that was devised by Georgy Feodosevich Voronoy, a Russian mathematician in the late 19th century.
"Imagine a cluster of islands in the ocean," Morse said. "If you found yourself dropped in the water you would swim to the nearest island. You could say that the island 'owns' the region of ocean closest to it and islands that 'own' adjacent patches of ocean are nearest neighbors. We use this to characterize the internal geometry of a sand pile."
To study what happens to this internal geometry as a sand pile is compressed, they entered data into the UO's new ACISS (Applied Computational Instrument for Scientific Synthesis) supercomputer, applying the Voronoi construction.
"Using these cells, called Voronoi tesslations, you can find out all you want to know about a geometric object -- its volume, surface area, number of sides -- you get it all," said Morse, who also is a fellow of the UO's GK-12 Science Outreach Program that links chemistry and physics graduate students with the state's elementary and middle schools. "All of the geometric features that we can think of so far show us that systems below jamming are very different than systems that are about to jam or that are jammed already. We end up finding that this purely geometric construct will exhibit this phase transition."
And by carrying out their computations into multidimensional spaces -- up to the eighth dimension in this project -- researchers learned that the physics of the jamming process can be simply identified by seeing what happens in the transition from 2-D to 3-D spaces. It's at that level, applying the knowledge to high-dimensional spaces, Corwin said, that application to expanding data transfer capabilities come into focus.
"The new ACISS supercomputer puts the UO at the forefront of a revolution that applies cloud computing to scientific investigation in physics, biology, chemistry, human brain science and computer science," said Kimberly Andrews Espy, vice president for research and innovation and dean of the UO Graduate School. "By incorporating the powerful ACISS computer into this project, Dr. Corwin and his team were able to examine the geometry of jamming and provide a new perspective on the process that has potential applications down the road for everything from manufacturing to computing to power production."
NSF grants DMR-1255370 and DGE-0742540 supported the research.
About the University of Oregon
The University of Oregon is among the 108 institutions chosen from 4,633 U.S. universities for top-tier designation of "Very High Research Activity" in the 2010 Carnegie Classification of Institutions of Higher Education. The UO also is one of two Pacific Northwest members of the Association of American Universities.
Corwin faculty page: http://physics.uoregon.edu/profile/ecorwin/
GK-12 Science Outreach Program: http://materialscience.uoregon.edu/GK12/Overview.html
UO Physics Department: http://physics.uoregon.edu/
Follow UO Science on Facebook: http://www.facebook.com/UniversityOfOregonScience
UO Science on Twitter: http://twitter.com/UO_Research
More UO Science/Research News: http://uoresearch.uoregon.edu
Note: The University of Oregon is equipped with an on-campus television studio with a point-of-origin Vyvx connection, which provides broadcast-quality video to networks worldwide via fiber optic network. In addition, there is video access to satellite uplink, and audio access to an ISDN codec for broadcast-quality radio interviews.
Jim Barlow | EurekAlert!
Neutron star merger directly observed for the first time
17.10.2017 | University of Maryland
Breaking: the first light from two neutron stars merging
17.10.2017 | American Association for the Advancement of Science
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
17.10.2017 | Life Sciences
17.10.2017 | Life Sciences
17.10.2017 | Earth Sciences