Researchers at the University of California, Irvine (UCI) have made a groundbreaking discovery in the field of materials science. By expanding on a classic model developed over 70 years ago, scientists in UCI’s Samueli School of Engineering have gained new insights into the behavior of advanced materials critical to energy systems, space exploration, and nuclear applications.

The traditional Frank-Read theory attributed slip band formation to continuous dislocation multiplication at active sources. However, the UC Irvine team found that extended slip bands emerge from source deactivation followed by the dynamic activation of new dislocation sources. This process was observed at the atomic scale through mechanical compression on micropillars made of a chromium-cobalt-nickel alloy.

Using advanced microscopy techniques and large-scale atomistic modeling, researchers were able to visualize the confined slip band as a thin glide zone with minimal defects and the extended slip band with a high density of planar defects. This understanding has shed new light on collective dislocation motion and microscopic deformation instability in advanced structural materials.

Deformation banding, where strain concentrates in local zones, is a common phenomenon in various substances and systems, including crystalline solids, metals, granular media, and even geologic faults under compressive stress. The discovery of extended slip bands challenges the classic model developed by physicists Charles Frank and Thornton Read in the 1950s.

“This foundational knowledge will accelerate the discovery of materials with tailored and predictable mechanical properties to meet the rising demand for advanced materials resilient to extreme environments across energy and aerospace sectors,” said corresponding author Penghui Cao, UC Irvine associate professor of mechanical and aerospace engineering.

The research was funded by the U.S. Department of Energy, UC Irvine, and the National Science Foundation (through the UC Irvine Center for Complex and Active Materials). The project involved graduate students, research specialists, and other professors from UCI’s Department of Mechanical and Aerospace Engineering and Department of Materials Science and Engineering.

The article discusses a recent study led by University College London researchers that suggests using existing large planes, like the Boeing 777F, to inject particles into the atmosphere to reflect sunlight and cool the planet. This approach, known as stratospheric aerosol injection, is a geoengineering technique that has been previously researched but assumed to require specially designed aircraft flying at high altitudes.

The study found that injecting sulphur dioxide particles at an altitude of 13 km above the polar regions could meaningfully cool the planet, albeit less effectively than at higher altitudes closer to the equator. This approach would require using three times the amount of aerosol and would have increased side effects like acid rain.

However, climate change is a serious problem, and it’s essential to understand all options for policy-makers to make informed decisions. The researchers used simulations in the UK’s Earth System Model 1 (UKESM1) to estimate the impact of stratospheric aerosol injection at different altitudes, latitudes, and seasons.

Injecting 12 million tonnes of sulphur dioxide a year at 13 km would cool the planet by around 0.6°C, which is roughly the same amount added to the atmosphere by the eruption of Mount Pinatubo in 1991. This strategy is not as effective as injecting particles at higher altitudes but could begin sooner.

The study’s lead author noted that any stratospheric aerosol injection would need to be introduced gradually and reduced gradually to avoid catastrophic impacts from sudden warming or cooling, and would not eliminate the need for emissions reductions. The researchers emphasized that long-term climate stability can only be achieved with net-zero greenhouse gas emission reductions.

The study, led by Professor Sunny Jung of the College of Agriculture and Life Sciences, aimed to explore how hand clapping generates sound depending on various factors such as hand shape, size, and technique. The researchers used high-speed cameras to track the motion, air flow, and sound produced by 10 volunteers clapping their hands in different ways.

The results showed that the larger the cavity between the palms, the lower the frequency of the clap. This is because the air column pushed by the jet flow of air coming out of the hand cavity causes the disturbance in the air, producing the sound we hear. The researchers also found that the softness of the hands plays a role in dampening the sound.

The study compared human data to theoretical projections using a traditional resonator called a Helmholtz resonator and confirmed that it can predict the frequency of the human handclap. This finding has potential implications for bioacoustics, as it may help explain various phenomena involving soft material collision and jet flow.

Moreover, the researchers discovered that claps are so short compared to sound made through a traditional resonator due to the softness of the hands vibrating after impact and absorbing energy. This knowledge can be used to design handclapping shapes that make the hand more rigid, resulting in a longer-lasting sound.

The study opens the door to using a handclap as a personal identifier or signature, with another researcher testing its potential for taking attendance in a class. The connection between the physics of hand clapping and its applications is new, and this research provides a comprehensive understanding of the phenomenon.

This study was supported in part by funding from the National Science Foundation and involved co-authors from Cornell University and the University of Mississippi’s National Center for Physics and Astronomy.