|| Speaker (Affiliation)
|| 2013. 05.21 (Tue.) 16:30
|| Dr. Takemasa Miyoshi, Team Leader (RIKEN, Advanced Institute for Computational Science)
Title: Chaos, Predictability, and Data Assimilation
Abstract: Data assimilation is a cross-disciplinary science to synergize numerical simulations and observational data, using statistical methods and applied mathematics. As computers become more powerful and enable more precise simulations, it will become more important to compare the simulation with actual observations. Data assimilation is also considered as chaos synchronization, a science field investigating synchronization of two chaotic dynamical systems through a limited exchange of information. In this presentation, I will introduce essential ideas of data assimilation for chaotic dynamical systems to maximize the predicting capability.
|| 2013. 06.11 (Tue.) 17:00
|| Dr. Takayuki Muranushi, Assistant Professor (Kyoto Univ., The HAKUBI Project)
Title: Automated Generation and Optimization of PDE solvers
Abstract: I am Takayuki Muranushi, an astrophysicist. My approach is to design
and implement new programming languages for astrophysical simulations.
Paraiso is a domain specific language embedded in functional
programming language Haskell, for automated tuning of explicit solvers
of partial differential equations (PDEs) on Graphic Processing Units
(GPUs) as well as multicore CPUs. In Paraiso, one can describe PDE
solving algorithms succinctly using tensor equations notation.
Hydrodynamic properties, interpolation methods and other building
blocks are described in abstract, modular, re-usable and combinable
forms, which lets us generate versatile solvers from little set of
Paraiso source codes.
A Navier-Stokes solver has been implemented and tested by Paraiso. A
single source code less than 500 lines can be used to generate solvers
of arbitrary dimensions, for both multicore CPUs and GPUs. We
demonstrate both manual annotation based tuning and evolutionary
computing based automated tuning of the program, that provides
faster-than-hand-tuned codes on CPUs and an order of magnitude faster
code on GPUs.
Recently, I've been trying to solve problems with such long timescales
that explicit methods are not applicative. Also explicit solvers of
PDEs, especially when combined with phenomenological models, tend to
develop pathologically small timesteps or NaNs. As an alternative,
I've been trying to formulate PDE solving methods methods as
optimization problems on f(t,x) thus eliminating needs of causal time
integral. I'm looking forward to the discussion with applied
|| 2013. 07.23 (Tue.) 16:30
|| Dr. Hiroshi Kori, Associate Professor (Ochanomizu Univ., Dept. Information Science)
Title: Novel dynamical behavior and coarse-grained description in oscillator networks
Abstract: Oscillator networks exhibit a rich variety of dynamical behavior, including synchronization, clustering, waves, and spatio-temporal chaos. In this talk, I will present our recent studies on novel
dynamical behavior in coupled and forced oscillators: (i) Synchronization-chaos transition in oscillator networks, (ii)
instability due to interplay between noise and nonlinearity, (iii) common-noise-induced synchronization in an infinite number of globally coupled oscillators (i.e., the Kuramoto model). Finally, I will talk
about a new method for the coarse-grained description of oscillator networks.
|| 2013. 09.20 (Fri.) 16:30
|| Dr. Tsuguo Kondoh (Toyota Central R&D Labs., INC.)
Title: Numerical investigation on optimal body shapes in low Reynolds number flows
(Drag minimization and lift maximization in laminar flows via topology optimization method)Novel dynamical behavior and coarse-grained description in oscillator networks
|| 2013. 10. 15 (Tue.) 17:00
|| Dr. Elliott Ginder (Hokkaido University, RIES)
Title: Interfacial dynamics and free boundary problems
for oscillating membrane motions
Abstract: We will present results on a model equation
related to droplet and bubble motions. The target equation is
a hyperbolic free boundary problem with volume and contact
angle constraints. By constructing a minimizing movement,
we are able to approximate the evolution and we show how
to obtain the convergence to a weak solution in the
one-dimensional (spatial) setting.
A different approach is needed for the case of "overhanging"
contact angles, and so we have developed an approximation
method, using thresholding dynamics, for computing motion
by multiphase, volume preserving, mean curvature flow
(with prescribed contact angles). Since this approach only
specifies the velocity of the interface, we will also consider
the case where the interface is allowed to oscillate.
The numerical methods for our approximation schemes have
also been constructed and we would also like to show the
numerical results of their implementation.
This is joint work with K. Svadlenka.
|| 2013. 12. 3. (Tue.) 16:30
|| Dr. Pinaki Chakraborty, Associate Professor (Okinawa Institute of Science and Technology)
Title: The Spectral Link in Turbulent Frictional Drag and Turbulent Mean Velocity Profile
Abstract: Please click here.
|| 2014.1.21 (Tue.) 16:30
|| Dr. Marcio Gameiro, Associate Professor (ICMC-USP Brazil & RIMS)
Title: Rigorous Numerics for Nonlinear PDEs
Abstract: We present a rigorous numerical method to compute solutions of infinite dimensional
nonlinear problems. The method combines classical predictor corrector algorithms,
analytic estimates and the uniform contraction principle to prove existence of smooth
branches of solutions of nonlinear PDEs. The method is applied to compute equilibria
and time periodic orbits for PDEs defined on two- and three-dimensional spatial domains.
|| 2014.2.18 (Tue.) 16:30
|| Dr. Wagatsuma Hiroaki, Associate Professor (Kyushu Institute of Technology)
Abstract: This talk is given in Japanese.