A Survey on the Low-Dimensional-Model-based Electromagnetic Imaging

2018 ◽  
Vol 12 (2) ◽  
pp. 107-199 ◽  
Author(s):  
Lianlin Li ◽  
Martin Hurtado ◽  
Feng Xu ◽  
Bing Chen Zhang ◽  
Tian Jin ◽  
...  
2018 ◽  
Author(s):  
Lianlin Li ◽  
Martin Hurtado ◽  
Feng Xu ◽  
Bing Chen Zhang ◽  
Tian Jin ◽  
...  

2011 ◽  
Vol 137 ◽  
pp. 72-76
Author(s):  
Wei Zhang ◽  
Xian Wen ◽  
Yan Qun Jiang

A proper orthogonal decomposition (POD) method is applied to study the global stability analysis for flow past a stationary circular cylinder. The flow database at Re=100 is obtained by CFD software, i.e. FLUENT, with which POD bases are constructed by a snapshot method. Based on the POD bases, a low-dimensional model is established for solving the two-dimensional incompressible NS equations. The stability of the flow solution is evaluated by a POD-Chiba method in the way of the eigensystem analysis for the velocity disturbance. The linear stability analysis shows that the first Hopf bifurcation takes place at Re=46.9, which is in good agreement with available results by other high-order accurate stability analysis methods. However, the calculated amount of POD is little, which shows the availability and advantage of the POD method.


2012 ◽  
Vol 8 (6) ◽  
pp. e1002546 ◽  
Author(s):  
Ezequiel M. Arneodo ◽  
Yonatan Sanz Perl ◽  
Franz Goller ◽  
Gabriel B. Mindlin

2017 ◽  
Author(s):  
Matthias Morzfeld ◽  
Jesse Adams ◽  
Spencer Lunderman ◽  
Rafael Orozco

Abstract. Many applications in science require that computational models and data be combined. In a Bayesian framework, this is usually done by defining likelihoods based on the mismatch of model outputs and data. However, matching model outputs and data in this way can be unnecessary or impossible. For example, using large amounts of steady state data is unnecessary because these data are redundant, it is numerically difficult to assimilate data in chaotic systems, and it is often impossible to assimilate data of a complex system into a low-dimensional model. These issues can be addressed by selecting features of the data, and defining likelihoods based on the features, rather than by the usual mismatch of model output and data. Our goal is to contribute to a fundamental understanding of such a feature-based approach that allows us to assimilate selected aspects of data into models. Specifically, we explain how the feature-based approach can be interpreted as a method for reducing an effective dimension, and derive new noise models, based on perturbed observations, that lead to computationally efficient solutions. Numerical implementations of our ideas are illustrated in four examples.


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