Radial Basis Function Methods For Large-Scale Wave Propagation

Author(s):  
Jun-Pu Li ◽  
Qing-Hua Qin
2019 ◽  
Vol 16 (2) ◽  
pp. 627-632 ◽  
Author(s):  
S. Valarmathy ◽  
R. Ramani

The Magnetic Resonance Imaging (MRI) based classification process for the classification of dementia is presented in this work. The classifier's performance may be enhanced by means of improving the extracted features that are inputted into its classifier. These MRI images are all duly segmented by making use of the wavelet. For choosing a subset that has optimal features, it may become inflexible and all issues relating to the feature selection will be shown as the NonDeterministic Polynomial (NP)-hard. The work further deals with techniques of optimization that are used in the case of feature selection for picking an optimal feature set. The Principal Component Analysis (PCA) will find an application of a large scale in signal processing. The noise estimation and the source separation are all possible. For this, the Radial Basis Function (RBF) and its classifier have been optimized to this structure by making use of the Genetic Algorithm (GA)-Artificial Immune System (AIS) algorithm. Such an optimized classifier of the RBF will classify a feature set that is provided by the GA, the AIS and the GA-AIS algorithm of feature selection. A classifier will be evaluated on the basis of its performance metrics. All classifiers will be evaluated keeping the accuracy, specificity, and sensitivity in making use of an optimized set of features. The results of the experiment have clearly demonstrated the feature selection and its effectiveness to improve the accuracy of the classification of all the images.


Author(s):  
Anoop A. Mullur ◽  
Achille Messac

The process of constructing computationally benign approximations of expensive computer simulation codes, or metamodeling, is a critical component of several large-scale Multidisciplinary Design Optimization approaches. Such applications typically involve complex models, such as finite elements, computational fluid dynamics, or chemical processes. The decision regarding the most appropriate metamodeling approach usually depends on the type of application. However, several newly-proposed kernel-based metamodeling approaches can provide consistently accurate performance for a wide variety of applications. The authors recently proposed one such novel and effective metamodeling approach — the Extended Radial Basis Function approach — and reported encouraging results. To further understand the advantages and limitations of this new approach, we compare its performance to that of the typical radial basis function approach, and another closely related method — kriging. Several test functions with varying problem dimensions and degrees of nonlinearity are used to compare the accuracies of the metamodels using these metamodeling approaches. We consider several performance criteria, such as metamodel accuracy. effect of sampling technique, effect of problem dimension, and computational complexity. The results suggest that the E-RBF approach is a potentially powerful metamodeling approach for MDO-based applications.


Geophysics ◽  
2020 ◽  
pp. 1-52
Author(s):  
Han Wu ◽  
Chengyu Sun ◽  
Shizhong Li ◽  
Jie Tang ◽  
Ning Xu

Compared with one-way wave equation migration and ray-based migration, reverse time migration (RTM) using the two-way wave propagation information can produce accurate imaging result for complex structures. Its computational accuracy and efficiency are mainly determined by numerical method for wavefield simulation. When using traditional regular grids for seismic modeling, scattering artifacts may occur due to the stepped approximation of layer interfaces and rugged topography. On the other hand, the irregular grids requires complex grid generation algorithm, despite having certain geometric flexibility. Mesh-free RTM can effectively reduce the scattered noise under regular grids and avoid the extra computation in the process of irregular grids generation. For the implementation of mesh-free RTM method, an algorithm with fast generation of node distributions is used to discretize the underground velocity model, and radial-basis function generated finite-difference (RBF-FD) is used to realize the numerical simulation of wave propagation, cross-correlation imaging condition is adopted for imaging. The mesh-free RTM method which has both flexibility of simulation region and abundance of wavefield information, reduces the storage required for reverse time migration, shows the potential of high-accuracy migration in the case of undulating surface and provides more accurate migration imaging results for oil and gas exploration under complex geological conditions.


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