力学与湍流重点实验室学术报告（报告人：Prof. M.E. Kassner、Prof. Hai Wang）
发布时间: 2009-07-13 11:12:00
SEMINAR SERIES
北京大学工学院 
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力学与空天技术系
湍流与复杂系统国家重点实验室
题目一：New Developments in Understanding Long-Range Internal Stresses in Materials
Department of Aerospace and Mechanical Engineering,
and Chemical Engineering and Materials Science,
University of Southern California
题目二：Nanoparticle Transport in Low-Density Gases
报告人 Prof. Hai Wang
University of Southern California
主持人：王建祥 教授
时 间：7月14日（周二）下午
2:00~3:30 (报告一)
3:30~5:00 (报告二)
地 点：力学楼434会议室
欢迎广大师生光临！
报告一内容摘要：
Long-range internal stresses (LRIS) are widely suggested to exist in materials as a result of dislocation heterogeneities in plastically deformed microstructures. The dislocation heterogeneities include cell and subgrain walls in monotonically deformed materials and edge-dislocation dipole bundles (veins) and the edge dipole walls of persistent slip bands (PSBs) in cyclically deformed materials. Long-range internal stress have often been suggested to be responsible for the Bauschinger effect in reversed and cyclic deformation. Evidence for long-range internal stresses (LRIS) includes stress-dip tests, dislocation pinning of loaded materials, in-situ deformation experiments, and asymmetric x-ray line broadening analysis. Other experiments, including recent dipole separation observations and convergent beam electron diffraction experiments, may be ambiguous. Most recently, long-range internal stress, was investigated by us using advanced x-ray microbeam diffraction experiments. These were accomplished using a synchrotron at the Advanced Photon Source at Argonne National Laboratory that is able to determine the elastic strains in very small volumes (e.g. 0.1 cubic micron) within the cell interiors, and very recently, within the cell walls. These were accomplished using oriented monotonically deformed Cu single crystals. The results suggest that long-range internal stresses are present. The magnitude and variation of these stresses with position within the microstructure will be described. These results are placed in the context of earlier experiments.
Dr. M.E. Kassner简介：
Michael Kassner graduated with a Bachelors in Science-Engineering from Northwestern University in 1972, and an M.S. and Ph.D. in Materials Science and Engineering from Stanford University in 1979 and 1981.Kassner accepted a position at Lawrence Livermore National Laboratory in 1981 and was employed there until 1990. During that period he performed basic research on the mechanical behavior of metals, as well as a variety of defense-related projects. He was promoted to Head of the Physical Metallurgy and Welding Section and was the Thrust Leader for Physical Metallurgy Research. In 1984 he spent a year on leave at the Univ. of Groningen in The Netherlands as a Fulbright Senior Scholar. Kassner accepted a faculty position in the Mechanical Engineering Department at Oregon State University in 1990 where he was Northwest Aluminum Professor of Mechanical Engineering and Director of the interdisciplinary PhD program in materials science. He received the College of Engineering Outstanding Sustained Research Award in 1995. While at Oregon State, Professor Kassner was detailed to Basic Energy Sciences of the U.S. Department of Energy and a Program Manager. He was also on leave for one year at the NSF Institute of Mechanics and Materials at the University of California at San Diego, where he was an Adjunct Professor. Prof. Kassner moved in 2003 to accept a position as Chairman, Mechanical and Aerospace Engineering Department ant the University of Southern California (USC). Prof. Kassner is currently active in pursuing research at USC on creep, fracture, fatigue, severe plastic deformation and nanostructures and thermodynamics.
Prof. Kassner has published two books, one on the fundamentals of creep plasticity in metals and another on phase diagrams and has authored or co-authored over 200 published articles. He serves on several editorial and review boards for major scientific journals. He is a Fellow of the ASM International.
报告二内容摘要：
Recently, a theoretical framework for nanoparticle transport in laminar flow regime has been proposed (Li & Wang. 2003. Phys. Rev. E. 68: papers 061206, & 061207; Li & Wang. 2004. Phys. Rev. E. 70: paper 021205). The theory features a rigorous gas-kinetic theory analysis. It considers the effect of non-rigid body collision, and the theory is shown to reproduce the Chapman-Enskog theory of molecular transport in the small particle size limit, Epstein's model of particle drag in the rigid-body limit, and Stokes-Cunningham equation for the drag on micrometer size particles. This theoretical framework provides the hope that bits and pieces of particle transport theories formulated over the last century may now be unified into a generalized theory. This talk discusses an unresolved fundamental issue relating to this generalized theory, namely, the transition from specular scattering applicable to molecule-molecule collision to diffuse scattering governing molecule-"particle" collision. The implication of this transition on a broad range of theories, including nucleation and nanocatalysis, will be discussed briefly. Lastly, the application of the thermophoretic transport theory in fabricating large-area, thin-film solar cells in highly reacting flows will also be presented.
Dr. Wang简介：
Hai Wang graduated with a Bachelors degree in Polymer Materials Science and Engineering from East China University of Science and Technology in 1984, an M.S. in Chemical Engineering from Michigan Technological University in 1986 and a Ph.D. in Fuel Science from Pennsylvania State University in 1992. He carried out research as a postdoctoral fellow and later, a research assistant professor, at Penn State from 1992 to 1994. He joined Princeton University as a Research Staff in 1994 and moved on to become an Assistant Professor of Mechanical Engineering at the University of Delaware in 1997. He joined the faculty of the University of Southern California as an Associate Professor of Mechanical Engineering in 2004. Currently, he is a Professor and Associate Chair of the Aerospace and Mechanical Engineering Department at USC.Though the primary focus of his research is in combustion, Professor Wang’s research spans several areas of disciplines. He was instrumental in developing the much-celebrated GRI-Mech, a reaction model for natural gas combustion. He pioneered the science of modeling soot formation in flames. He developed the understanding of the mechanism of diamond thin-film deposition in chemical vapor deposition, and explained the origin of carbonaceous matters in interstellar media. He applied quantum mechanical and reaction rate theories to fundamental chemical kinetics of gas-phase elementary reactions. His recent work include the development of the mobility sizing method to explore the mechanism of soot formation in flames, the development of JetSurF, a standard reaction model for the combustion of jet fuel surrogates, and heterogeneous reaction kinetics of salt aerosols with atmospheric trace pollutant gases. He advanced the transport theory of small particles that will potentially unify the Chapman-Enskog theory of molecular diffusion and Einstein-Stokes theory of brownian diffusion. He is currently heavily engaged in solar cell research.
Professor Wang is an author or coauthor of over 100 refereed journal articles. His work on the mechanism and modeling of polycyclic aromatic hydrocarbon formation in flames is one of the highest cited paper in combustion literature. He is a co-editor of a recent book on Combustion Generated Fine Carbonaceous Particles, to be published by the Karlsruhe University Press. He served on the editorial boards of International Journal of Chemical Kinetics and Combustion and Flame. He is currently serving on the editorial board of Progress in Energy and Combustion Science and is an Associate Editor of Proceedings of the Combustion Institute. He was a co-chair of the soot and large molecules colloquia of the 30th and 31st International Symposium on Combustion.