Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Granular materials not so puzzling after all, physicists find

25.08.2003


Understanding the physics of granular materials is important in industries that handle and process large amounts of the materials, such as pills and powders in the pharmaceutical and food industries and sand in the construction business.



But the problem of how to model granular materials has perplexed physicists. In particular, they’d like to better understand how the temperature within an assemblage of granular material affects the system’s dynamics. That understanding will help scientists determine whether the same thermodynamic principles that apply to systems at equilibrium also apply to systems that are far from equilibrium, such as living organisms.

In a paper to be published in the Aug. 21 issue of the journal Nature, a multinational team that includes University of Michigan physicist Franco Nori describes experiments in which the team devised an unusual "thermometer" and used it to test the soundness of the temperature concept in a continuously shaken container of tiny beads.


Temperature measurements actually are a reflection of how excited individual particles in a material are, be they molecules of air or grains of sand. In a gas, for instance, molecules vibrate and constantly collide with one another like extremely bouncy rubber balls. If the gas was trapped in a box, the microscopic motion would never stop and the temperature would remain constant. This so-called equilibrium state is possible because no loss of energy occurs in the molecules’ chaotic dancing.

In the work described in the Nature paper, the researchers explored the question of whether temperature can be similarly defined for systems that are not at equilibrium, especially those in which energy is dissipated during collisions. If it can, that means that equilibrium thermodynamic concepts can be generalized to far-from-equilibrium situations.

The question has practical implications for understanding natural phenomena such as the formation of order from disorder (a process known as pattern formation) and the extraction of motion out of randomness (biological Brownian motors). For these non-equilibrium situations, the lack of a definition of temperature and related parameters has prevented scientists from completely understanding the systems involved.

The researchers used an experimental set-up that they compare to a pinball machine, with balls moving around in a closed space. In a standard pinball machine, however, the balls are launched one at a time and bounce from one obstacle to the next. In the experimental system, thousands of tiny beads move almost imperceptibly due to the gentle shaking of the container in which they are held, colliding with each other and with the container walls. Because the beads are not perfectly elastic, energy is dissipated during these collisions. Only the external vibration of the container maintains the beads’ chaotic motion; if the container isn’t constantly shaken, the beads quickly stop moving.

In this experimental model of a non-equilibrium system, the researchers used a device called a torsion oscillator to act as a thermometer. The torsion oscillator---a wire with a cone-shaped probe at the end---was immersed in the container of beads. When the container was shaken, the beads bombarded the probe, causing the wire to oscillate back and forth like a clock spring.

By looking at the resulting motion of the wire, the scientists were able to determine whether the measured "temperature" followed the rules one would expect in an equilibrium energy conserving system ---a system in which energy is not dissipated in collisions. To their surprise, they found that temperature did follow the expected rules, leading them to conclude that even for a dissipative system, a few parameters---such as temperature---can be used to extract essential information concealed in the disordered motion of billions of particles.

In addition to Nori of the Institute of Physical and Chemical Research (RIKEN) in Japan and the Center for Theoretical Physics at the University of Michigan, the research team included: Gianfranco D’Anna and Patrick Mayor of the Ecole Polytechnique Federale de Lausanne in Lausanne, Switzerland; Alain Barrat of the Universite de Paris-Sud in Paris, France; Vittorio Loreto of the Center for Statistical Mechanics and Complexity in Rome, Italy; and Franco Nori of the Institute of Physical and Chemical Research (RIKEN) in Japan and the.

The researchers hope their results will stimulate new ideas in the description of non-equilibrium physics.


###

Nancy Ross Flanigan | EurekAlert!
Further information:
http://www-personal.engin.umich.edu/~nori/
http://www.riken.go.jp/engn/r-world/research/lab/frontier/quantum/digital/index.html
http://igahpse.epfl.ch/htc/

More articles from Physics and Astronomy:

nachricht Discovery of an Extragalactic Hot Molecular Core
29.09.2016 | National Astronomical Observatory of Japan

nachricht Swiss space research reaches for the sky
29.09.2016 | Schweizerischer Nationalfonds SNF

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New welding process joins dissimilar sheets better

Friction stir welding is a still-young and thus often unfamiliar pressure welding process for joining flat components and semi-finished components made of light metals.
Scientists at the University of Stuttgart have now developed two new process variants that will considerably expand the areas of application for friction stir welding.
Technologie-Lizenz-Büro (TLB) GmbH supports the University of Stuttgart in patenting and marketing its innovations.

Friction stir welding is a still-young and thus often unfamiliar pressure welding process for joining flat components and semi-finished components made of...

Im Focus: First quantum photonic circuit with electrically driven light source

Optical quantum computers can revolutionize computer technology. A team of researchers led by scientists from Münster University and KIT now succeeded in putting a quantum optical experimental set-up onto a chip. In doing so, they have met one of the requirements for making it possible to use photonic circuits for optical quantum computers.

Optical quantum computers are what people are pinning their hopes on for tomorrow’s computer technology – whether for tap-proof data encryption, ultrafast...

Im Focus: OLED microdisplays in data glasses for improved human-machine interaction

The Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP has been developing various applications for OLED microdisplays based on organic semiconductors. By integrating the capabilities of an image sensor directly into the microdisplay, eye movements can be recorded by the smart glasses and utilized for guidance and control functions, as one example. The new design will be debuted at Augmented World Expo Europe (AWE) in Berlin at Booth B25, October 18th – 19th.

“Augmented-reality” and “wearables” have become terms we encounter almost daily. Both can make daily life a little simpler and provide valuable assistance for...

Im Focus: Artificial Intelligence Helps in the Discovery of New Materials

With the help of artificial intelligence, chemists from the University of Basel in Switzerland have computed the characteristics of about two million crystals made up of four chemical elements. The researchers were able to identify 90 previously unknown thermodynamically stable crystals that can be regarded as new materials. They report on their findings in the scientific journal Physical Review Letters.

Elpasolite is a glassy, transparent, shiny and soft mineral with a cubic crystal structure. First discovered in El Paso County (Colorado, USA), it can also be...

Im Focus: Complex hardmetal tools out of the 3D printer

For the first time, Fraunhofer IKTS shows additively manufactured hardmetal tools at WorldPM 2016 in Hamburg. Mechanical, chemical as well as a high heat resistance and extreme hardness are required from tools that are used in mechanical and automotive engineering or in plastics and building materials industry. Researchers at the Fraunhofer Institute for Ceramic Technologies and Systems IKTS in Dresden managed the production of complex hardmetal tools via 3D printing in a quality that are in no way inferior to conventionally produced high-performance tools.

Fraunhofer IKTS counts decades of proven expertise in the development of hardmetals. To date, reliable cutting, drilling, pressing and stamping tools made of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

HLF: From an experiment to an establishment

29.09.2016 | Event News

European Health Forum Gastein 2016 kicks off today

28.09.2016 | Event News

Laser use for neurosurgery and biofabrication - LaserForum 2016 focuses on medical technology

27.09.2016 | Event News

 
Latest News

New Multiferroic Materials from Building Blocks

29.09.2016 | Materials Sciences

Silicon Fluorescent Material Developed Enabling Observations under a Bright “Biological Optical Window”

29.09.2016 | Materials Sciences

X-shape Bio-inspired Structures

29.09.2016 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>