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BEGIN:VEVENT
UID:news245@dmi.unibas.ch
DTSTAMP;TZID=Europe/Zurich:20180716T211238
DTSTART;TZID=Europe/Zurich:20151106T110000
SUMMARY:Seminar in Numerical Analysis: Sanna Mönkölä (University of Jyv
 äskylä)
DESCRIPTION:A wide range of numerical methods have been used for solving  t
 ime-harmonic wave equations. Typically\, the methods are based on  complex
 -valued formulations leading to large-scale indefinite linear  equations. 
 An alternative is to simulate time-dependent equations in  time\, until th
 e time-harmonic solution is reached. However\, this  approach suffers from
  poor convergence\, particularly in the case of  large wavenumbers and com
 plicated domains. We accelerate the convergence  rate by employing a contr
 ollability method. The problem is formulated  as a least-squares optimizat
 ion problem\, which is solved by the  conjugate gradient algorithm. The ef
 ficiency of the method relies on  smart discretizations. For spatial discr
 etization we use the spectral  element method or the discrete exterior cal
 culus\, and for time evolution  we consider leap-frog style discretization
  with non-uniform timesteps  or higher-order schemes. For constructing spa
 tially isotropic grids for  complex geometries\, we use non-uniform polygo
 nal structures imitating  the close packing in crystal lattices.
X-ALT-DESC:A wide range of numerical methods have been used for solving  ti
 me-harmonic wave equations. Typically\, the methods are based on  complex-
 valued formulations leading to large-scale indefinite linear  equations. A
 n alternative is to simulate time-dependent equations in  time\, until the
  time-harmonic solution is reached. However\, this  approach suffers from 
 poor convergence\, particularly in the case of  large wavenumbers and comp
 licated domains. We accelerate the convergence  rate by employing a contro
 llability method. The problem is formulated  as a least-squares optimizati
 on problem\, which is solved by the  conjugate gradient algorithm. The eff
 iciency of the method relies on  smart discretizations. For spatial discre
 tization we use the spectral  element method or the discrete exterior calc
 ulus\, and for time evolution  we consider leap-frog style discretization 
 with non-uniform timesteps  or higher-order schemes. For constructing spat
 ially isotropic grids for  complex geometries\, we use non-uniform polygon
 al structures imitating  the close packing in crystal lattices. 
DTEND;TZID=Europe/Zurich:20151106T120000
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