Division of Applied Mathematics

Seminars for Sep 11 - Sep 15, 2000

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• Monday, September 11, 2000
  
  

  Lefschetz Center for Dynamical Systems Seminar

  Speaker:	Yong Wang,
  Title:	Bifurcation Control with Applications to Active Control of Rotating Stall in Gas Turbine Engines
  Time/Place:	4:00 p.m., B&H 155

  Abstract:   For systems described by ordinary differential equations, we consider the problem of how to design a feedback law to alter a subcritical steady-state/Hopf bifurcation to a supercritical one, when the bifurcating mode is linearly unstabilizable. Under certain nondegeneracy conditions, algebraic necessary and sufficient conditions of stabilizability are given. The effect of magnitude saturation of feedback controllers are analyzed. Geometric interpretations of stabilizability are given for some of the conditions. And sufficient conditions are obtained for systems governed by functional differential equations.

  In models describing rotating stall in gas turbine engines, subcritical Hopf bifurcations are asssociated with abrupt inception of instabilities and hysteresis. We give a qualitative analysis on the effects of magnitude saturation, dandwidth, and rate limits on active control of rotating stall. The theoretical analysis is compared with experiments n a low speed, single stage compressor.

• Wednesday, September 13, 2000
  
  

  Brown Analysis Seminar

  Speaker:	Lee Rudolph, Clark University
  Title:	Compact Stein Surfaces with Boundary as Branched Covers of $D^{4}$
  Time/Place:	4:15 p.m., Kassar 105

• Friday, September 15, 2000
  
  

  PDE Seminar

  Speaker:	Dr. Chris Hallstrom, Brown University Division of Applied Mathematics
  Title:	Bounds on Heat Transfer in Rotating Rayleigh-Benard Convection
  Time/Place:	3:00 p.m., Kassar 105

  <---   2000  Index

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