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- Volkan Akcelik, George Biros, Omar Ghattas
- SC
- 2002

One of the outstanding challenges of computational science and engineering is large-scale nonlinear parameter estimation of systems governed by partial differential equations. These are known as <i>inverse problems</i>, in contradistinction to the <i>forward problems</i> that usually characterize large-scale simulation. Inverse problems are significantly… (More)

- Volkan Akcelik, Jacobo Bielak, +8 authors John Urbanic
- SC
- 2003

For earthquake simulations to play an important role in the reduction of seismic risk, they must be capable of high resolution and high fidelity. We have developed algorithms and tools for earthquake simulation based on multiresolution hexahedral meshes. We have used this capability to carry out 1 Hz simulations of the 1994 Northridge earthquake in the LA… (More)

In contrast to traditional terascale simulations that have known, fixed data inputs, dynamic data-driven (DDD) applications are characterized by unknown data and informed by dynamic observations. DDD simulations give rise to inverse problems of determining unknown data from sparse observations. The main difficulty is that the optimality system is a boundary… (More)

- Volkan Akcelik, George Biros, Andrei Draganescu, Omar Ghattas, Judith Hill, Bart G. van Bloemen Waanders
- International Conference on Computational Science
- 2006

We are interested in a DDDAS problem of localization of airborne contaminant releases in regional atmospheric transport models from sparse observations. Given measurements of the contaminant over an observation window at a small number of points in space, and a velocity field as predicted for example by a mesoscopic weather model, we seek an estimate of the… (More)

We consider the inverse problem of determining an arbitrary source in a time-dependent convective-diffusive transport equation, given a velocity field and pointwise measurements of the concentration. Applications that give rise to such problems include determination of groundwater or airborne pollutant sources from measurements of concentrations, and… (More)

- Volkan Akcelik, Kwok Ko, Lie-Quan Lee, Zenghai Li, Cho-Kuen Ng, Liling Xiao
- J. Comput. Physics
- 2008

The measured physical parameters of a superconducting cavity differ from those of the designed ideal cavity. This is due to shape deviations caused by both loose machine tolerances during fabrication and by the tuning process for the accelerating mode. We present a shape determination algorithm to solve for the unknown deviations from the ideal cavity using… (More)

- V. Akcelik, A. Candel, +4 authors L. Xiao
- 2008

The successful operation of accelerator cavities has to satisfy both rf and mechanical requirements. It is highly desirable that electromagnetic, thermal and structural effects such as cavity wall heating and Lorentz force detuning in superconducting rf cavities can be addressed in an integrated analysis. Based on the SLAC parallel finite-element code… (More)

SLAC has developed a multi-physics simulation code TEM3P for simulating integrated effects of electromagnetic, thermal and structural loads. TEM3P shares the same software infrastructure with SLAC's paralell finite element electromagnetic codes, thus enabling all physics simulations within a single framework. The finite-element approach allows… (More)

- H. P. Flath, Lucas C. Wilcox, Volkan Akcelik, Judith Hill, Bart G. van Bloemen Waanders, Omar Ghattas
- SIAM J. Scientific Computing
- 2011