Wyniki wyszukiwania - BazTech

1

Introducing and solving the hesitant fuzzy system AX = B

Babakordi Fatemeh, Allahviranloo Tofigh

Control and Cybernetics

|

2021

|

Vol. 50, No. 4

553--574

EN

In this paper the solution for hesitant fuzzy system as AX = B is introduced where A is an n×n known hesitant fuzzy matrix, B is an n×1 known hesitant fuzzy vector and X is an n×1 unknown hesitant fuzzy vector. First, L∞-norm and L1-norm of a hesitant fuzzy vector are introduced. Then, the concepts of hesitant fuzzy zero, ’almost equal’ and ’less than’ and ’equal’ are defined for two hesitant fuzzy numbers. Finally, using a minimization problem; the hesitant fuzzy system is solved. At the end, some numerical examples are presented to show the effectiveness of the proposed method.

2

Multiples inversion imaging using a one way propagation operator

Li Qiang, Wang Deli

Acta Geophysica

|

2019

|

Vol. 67, no. 5

1341--1348

EN

The one-way propagation operator in the frequency-space domain has the advantages of fast calculation speed and good adaptability to medium with lateral velocity variation. The full wavefeld model constructed by the one-way propagation operator is iterative. As the number of iterations increases, the components of wavefeld are more and more abundant. In the full wavefeld model, the propagation and scattering processes are independent of each other. The former is determined by the propagation operator, while the latter is determined by the scattering operator. As each iteration increases, the wavefeld component will increase by one order. As an inverse migration operator, the full wavefeld model could feed back the imaging result to the data. By calculating the residual between the simulated data and the actual data, the refectivity is updated. This is an inversion process. In this process, multiples will be imaged. In this way, the subsurface information contained in multiples is utilized and the imaging quality is greatly improved. The L1-norm is used to constrain the imaging result, which further suppresses the artifacts and improves the imaging resolution. We have made some numerical examples in 2D case, explaining the principles and advantages of this methodology.

3

Suppressing multiples using an adaptive multichannel filter based on L1-norm

Shi Y., Jing H., Zhang W., Ning D.

Acta Geophysica

|

2017

|

Vol. 65, no. 4

667--681

EN

Adaptive subtraction is an important link for removing surface-related multiples in the wave equation-based method. In this paper, we propose an adaptive multichannel subtraction method based on the L1-norm. We achieve enhanced compensation for the mismatch between the input seismogram and the predicted multiples in terms of the amplitude, phase, frequency band, and travel time. Unlike the conventional L2-norm, the proposed method does not rely on the assumption that the primary and the multiples are orthogonal, and also takes advantage of the fact that the L1-norm is more robust when dealing with outliers. In addition, we propose a frequency band extension via modulation to reconstruct the high frequencies to compensate for the frequency misalignment. We present a parallel computing scheme to accelerate the subtraction algorithm on graphic processing units (GPUs), which significantly reduces the computational cost. The synthetic and field seismic data tests show that the proposed method effectively suppresses the multiples.