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美国华盛顿大学 Prof. Lawrence A. Crum 学术讲座通知 2014-09-11 16:40:36 讲座时间: 9 月 17 日 讲座地点: 教二北楼 讲座人: 9:30-12:00 308 室 Lawrence A. Crum 讲座内容: 1. Sonofusion: Star in a Jar? Abstract: When a sound wave of moderate intensity is propagated through water, light emissions can be observed. This conversion of sound energy into light energy is called Sonoluminescence (SL) and represents an energy amplification per molecule of over eleven orders of magnitude. The discovery in our laboratory (J. Acoust. Soc. Am. 91, 3166-3183 (1992) that a single, stable gas bubble, acoustically levitated in a liquid, can emit optical emissions each cycle for an unlimited period of time stimulated considerable interest in this topic. Presumably, the oscillations of the bubble cause the gas in the interior to be heated to incandescent temperatures during the compression portion of the cycle. Because the lifetime of the optical pulse can be on the order of 50 picoseconds, it is likely that some rather unusual physics is occurring. One explanation for the short pulse length is that a shock wave is created in the gas which is then elevated to high temperatures by inertial confinement. If shock waves are the mechanism for SL emission, then optimization of the process has been speculated to lead to extraordinary physics, including thermonuclear fusion. Recent reports from Taleyarkhan, et al. (Science, vol. 295, 1868-1873, 2002; Phys Rev Lett. 2006 Jan 27;96(3):034301.) have even provided evidence for the nuclear emissions that should be associated with this phenomenon. Since this mechanism (thermonuclear fusion) is the energy source that drives our sun, one can even speculate that a miniature “star in a jar” has been created. A broad overview of this intriguing phenomenon will be presented as well a critical review of the potential for acoustic inertial confinement fusion. 2. Space travel, Special Relativity, Transhumanism, and the Singularity Abstract: There was a recent TV Program in which Stephen Hawking described how one day humans would travel to planets on other stars and what they might find. I dug out my old Special Relativity Lecture Notes and did some calculations. First of all, I think Hawking is wrong; Humans will never travel to other star systems—physics, and physiology, doesn’t allow it. Then, I did some research on what serious futurists believe will be the technologies of the next one hundred, even one thousand years. My thesis in this lecture is that unless humans evolve beyond their present mental capabilities and physical limitations, humans as we now know them, will never travel beyond our own solar system, and, according, never find (by ourselves) other intelligent life forms. On the other hand, we could evolve into transhumans that might solve some of the challenges of intra-galactic space travel. Finally, there are those who have estimated when computers will have vastly superior “intellectual” powers to humans—the so-called “Singularity”—and what this might imply. This lecture is for general audiences, but may offend personal sensitivities. 讲座人简介:Dr. Lawrence A. Crum is currently Principal Physicist and Founder/Former Director of the Center for Industrial and Medical Ultrasound in the Applied Physics Laboratory, and Research Professor of Bioengineering and Electrical Engineering at the University of Washington.He has held previous positions at Harvard University, the U. S. Naval Academy, and the University of Mississippi, where he was F. A. P. Barnard Distinguished Professor of Physics and Director of the National Center for Physical Acoustics. He has published over 200 articles in professional journals, holds an honorary doctorate from the Universite Libre de Bruxelles, and was recently awarded the HelmholtzRayleigh Silver Medal and the Gold Medal of the Acoustical Society of America. He is Past President of the Acoustical Society of America, the Board of the International Commission for Acoustics, and the International Society for Therapeutic Ultrasound. His principal areas of interest are therapeutic ultrasound, physical acoustics, and image-guided therapy.