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The Utility of Instability

08-08-16

Professors Dennis M. Kochmann and Chiara Daraio along with colleagues from Harvard have designed and created mechanical chains made of soft matter that can transmit signals across long distances. Because they are flexible, the circuits could be used in machines such as soft robots or lightweight aircraft constructed from pliable, nonmetallic materials. "Engineers tend to shy away from instability. "Though there are many applications, the fundamental principles that we explore are most exciting to me," Kochmann says. "These nonlinear systems show very similar behavior to materials at the atomic scale but these are difficult to access experimentally or computationally. Now we have built a simple macroscale analogue that mimics how they behave." [Caltech story]

Tags: research highlights Chiara Daraio GALCIT MCE Dennis Kochmann

Community Seismic Network Detected Air Pulse From Refinery Explosion

06-30-16

The Community Seismic Network’s (CSN) tight network of low-cost detectors are improving the resolution of seismic data gathering and could offer city inspectors crucial information on building damage after a quake. On February 18, 2015, an explosion rattled the ExxonMobil refinery in Torrance, causing ground shaking equivalent to that of a magnitude-2.0 earthquake and blasting out an air pressure wave similar to a sonic boom. Traveling at 343 meters per second the air pressure wave reached a 52-story high-rise in downtown Los Angeles 66 seconds after the blast. The building's seismometers, which are part of the CSN, noted and recorded the motion of each individual floor. "We want first responders, structural engineers, and facilities engineers to be able to make decisions based on what the data say," explained Monica Kohler, Research Assistant Professor of Mechanical and Civil Engineering, and the lead author of a paper detailing the high-rise's response that recently appeared in the journal Earthquake Spectra. [Caltech story]

Tags: research highlights MCE Monica Kohler

Microseismicity and Large Earthquakes

06-10-16

Nadia Lapusta, Professor of Mechanical Engineering and Geophysics, and Caltech alumnus Dr. Junle Jiang, have linked the patterns of microseismicity to the depth extension of large earthquakes, both through modeling and observationally. They argue that fault segments which do not have concentrated microseismicity at the bottom of the seismogenic zone must have had deeper, larger earthquakes than currently believed. A number of segments on the San Andreas fault appear to fall into that category. The potential for such deeper earthquakes in the future would imply higher seismic hazard. [Science article] [KPCC coverage] [New Yorker Article]

Tags: research highlights MCE Nadia Lapusta alumni Junle Jiang

Tiny Diatoms Boast Enormous Strength

02-08-16

Researchers in the lab of Julia R. Greer, Professor of Materials Science and Mechanics, have recently found that diatom shells have the highest specific strength—the strength at which a structure breaks with respect to its density—of any known biological material, including bone, antlers, and teeth. [Caltech story]

Tags: APhMS research highlights MedE MCE Julia Greer

Extending a Battery's Lifetime with Heat

10-03-15

The research of alumnus Asghar Aryanfar (’15 PhD, ME) along with Professors Goddard and Hoffmann has shown that heat can break down the damaging branch-like structures that grow inside batteries, which may possibly be used to extend battery lifetimes. [Learn more] [Read the paper]

Tags: research highlights MCE ESE William Goddard alumni Michael Hoffmann Asghar Aryanfar

Atomic Fractals in Metallic Glasses

09-18-15

Julia R. Greer, Professor of Materials Science and Mechanics, and colleagues including graduate student David Chen have shown that metallic glasses has an atomic-level structure although it differs from the periodic lattices that characterize crystalline metals. "Our group has solved this paradox by showing that atoms are only arranged fractally up to a certain scale," Greer says. "Larger than that scale, clusters of atoms are packed randomly and tightly, making a fully dense material, just like a regular metal. So we can have something that is both fractal and fully dense." [Caltech story]

Tags: APhMS research highlights MedE MCE Julia Greer David Chen

Preparing for Earthquakes with ShakeAlert

08-03-15

United States Geological Survey (USGS) has announced an approximately $4 million in awards to Caltech, University of California Berkeley, the University of Washington and the University of Oregon, for the expansion and improvement of the ShakeAlert, an earthquake early-warning system. "Caltech's role in ShakeAlert will focus on research and development of the system so that future versions will be faster and more reliable," said Professor Thomas Heaton. "We currently collect data from approximately 400 seismic stations throughout California. The USGS grant will allow Caltech to upgrade or install new stations in strategic locations that will significantly improve the performance of ShakeAlert." [Caltech story]

Tags: research highlights MCE Thomas Heaton

Srivatsan Hulikal Wins Seismo-Engineering, Prediction, and Protection Prize

06-09-15

Graduate student, Srivatsan Hulikal, was the recipient of the the 2015 Demetriades - Tsafka - Kokkalis Prize in Seismo-Engineering, Prediction, and Protection. In his thesis, Dr. Hulikal successfully took on the multifaceted and challenging problem of linking macroscopic frictional properties of interfaces to their micromechanics. His advisor Professor Lapusta explains, “Understanding this connection is key to addressing fundamental problems in seismo-mechanics and seismo-engineering, such as creating predictive physical models of earthquakes.”

Tags: honors research highlights MCE Nadia Lapusta Srivatsan Hulikal

An Earthquake Warning System in Our Pockets?

04-10-15

Thomas H. Heaton, Professor of Engineering Seismology, and colleagues’ recent study suggests that all of our phones and other personal electronic devices could function as a distributed network, detecting any ground movements caused by a large earthquake, and, ultimately, giving people crucial seconds to prepare for a temblor. "Thirty years ago it took months to assemble a crude picture of the deformations from an earthquake. This new technology promises to provide a near-instantaneous picture with much greater resolution," says Professor Heaton. [Caltech story]

Tags: research highlights MCE Thomas Heaton