Aerospace and Mechanical Engineering
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AEM alum awarded Best Dissertation Award

Each year approximately two hundred students are nominated to receive the Graduate School’s highly competitive Best Dissertation Award.  We are pleased to announce that AEM alum, Liping Liu, has been selected to receive this award. 

liping liu
Each year the Graduate School recognizes the University's top recent Ph.D. graduates by presenting these awards.  The recipients receive an honorarium of $1,000 and a special certificate.
 
 
Upon receiving the award, Liu was “deeply honored” and expressed gratitude to his AEM faculty advisors, Professors Perry Leo and Richard James, for their “invaluable guidance and support.”

The Research

While at the University, Liu worked with James and Leo on composites of magnetostrictive materials, particularly composites of a recently discovered class of materials called ferromagnetic shape memory materials.
 
One problem with these materials was that they could only be used in single crystal form, which are very hard to grow.   The most promising of these, Ni_2MnGa, can also be quite brittle.  One way to get around these difficulties is to turn brittleness into a virtue by grinding a polycrystal into its individual grains and make a composite by casting the resulting powder into a polymer.  Liu showed this is feasible and provided precise predictions of the behavior of these composites under a magnetic field.
 
Additionally, as a byproduct of this work, Liu was led to solve a problem that has baffled scientists for nearly 50 years, since the famous work of Eshelby. If one has a magnetized inclusion in a nonmagnetic medium it produces a magnetic field, like an ordinary magnet, but usually the field isn’t constant on the inclusion. 
 
There is a very special shape, the ellipsoid, for which this is true.  It was widely believed that in three dimensions this was the only such shape.  Liu’s work disproved that belief and gave a new variational principle for such shapes.  He discovered a plethora of new "Eshelby inclusions", including those that are periodic and can have any volume fraction between 0 and 1.  Liu found collections of 2, 3 and 5 inclusions with the constant field property. (see right)
 
These shapes have unexpectedly useful properties.  They seem to be natural inclusions for giving optimal composites.  Researchers at Micron Corp. have speculated that they would also be the ideal shape for magnetic bits in magnetic storage devices. 
 
Liu's inclusions have a rapidly expanding list of fascinating properties and the race to understand them has opened up a new field of research.

 


Last Modified: Monday, 19-May-2008 09:07:08 CDT -- this is in International Standard Date and Time Notation