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Fall 2002 Departmental Distinguished Seminar SeriesProfessor Daniel Lacks
Tulane University Daniel Lacks discussed how simulations are used to address nonequilibrium properties of materials systems under stress, and how the results are analyzed in terms of the many-body function (landscape) that controls the system dynamics. Lacks and others have shown that stress causes distortions of landscapes, including the disappearance of peaks and valleys. These landscape distortions alter the system dynamics, and ultimately the system properties. Based on this landscape picture, they show that: (1) shear thinning and shear-induced diffusion in flowing fluids arise from strain-activated relaxation events associated with the distortions of the energy landscape; (2) fracture propagation in glasses occurs by a series of these discrete strain-activated relaxation events; and (3) ordered colloidal phases cannot exist even as metastable states at high polydispersities, due to polydispersity-induced distortions of the energy landscape. This landscape analysis also led to their prediction of a new amorphous-to-amorphous phase transition in silica, which has subsequently been observed experimentally. Lacks’ visit was hosted by Ben McCoy. Scott Ostrowski, CSP, PE
ExxonMobil The seminar provided an overview of pressure relief devices commonly in use in the chemical processing industry. Topics of discussion included basic terminology, pressure vessel code requirements, and a general introduction to pressure relief valves, rupture disks, and rupture pins. Discussion of each pressure-relieving device included a summary of their uses, advantages, and disadvantages. Concepts were reinforced with numerous field photographs. Ostrowski’s visit was hosted by Ralph Pike. Edgar Bristol, Fellow Emeritus
Foxboro Company Edgar Bristol put together a Control Idiom Documentation Tool as a demonstration. The tool excerpts the ICL Idiom notation, based on a degree of freedom algebra. This expresses each cascaded stage by its controlled variable footnoted with various Idiom operators defining the detailed control Intents (including feedforwards and overrides). The tool reformats the statements for readability echoed with corresponding graphics. It permits systematic application documentation of most standard control practices. The tool generates PostScript output either as multipage PostScript documents or as Encapsulated PostScript figures which can be inserted in separate text or graphic documents. The GhostScript display tool can convert the documents to Acrobat format. The website http://homepage.mac.com/ebristol/ was also referred to in the demonstration. Bristol’s visit was hosted by Armand Corripio. Professor Daniel Resasco
University of Oklahoma Daniel Resasco discussed how the constant discovery of new and exciting properties of SWNT keeps amazing the scientific community as well as the general public. However, he stressed that the development of commercial applications will remain a dream as long as they are made by the laboratory methods available today. The full realization of the technological potential of nanotubes is contingent upon the development of industrial- scale synthesis. An important step in advancing this technology is the development of techniques to produce tons of nanotubes per year. Resasco explained that they have developed what they call “controlled production”, which implies the ability to control the selectivity towards SWNT by changing catalyst formulations and operating conditions, combined with an effective purification strategy and a quantitative determination of the SWNT obtained. Resasco went on to describe the catalysts and methods used to create a scalable, cost-effective process. Resasco’s visit was hosted by Kerry Dooley.
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