Multiple attenuation using λ–f domain high-resolution Radon transform

The parabolic Radon transform has been widely used in multiple attenuation. To further improve the accuracy and efficiency of the Radon transform, we developed the 2- fdomain high-resolution Radon transform based on the fast and modified parabolic Radon transform presented by Abbad. The introduction of a new variable 2 makes the transform operator frequency-independent. Thus, we need to calculate the transform operator and its inverse operator only once, which greatly improves the computational efficiency. Besides, because the primaries and multiples are distributed on straight lines with different slopes in the 2-fdomain, we can easily choose the filtering operator to suppress the multiples. At the same time, the proposed method offers the advantage of high-resolution Radon transform, which can greatly improve the precision of attenuating the multiples. Numerical experiments suggest that the multiples are well suppressed and the amplitude versus offset characteristics of the primaries are well maintained. Real data processing results further verify the effectiveness and feasibility of the method.

Optimization of multiple attenuation mechanisms by cation substitution in imidazolic MOFs-derived porous composites for superior broadband electromagnetic wave absorption

Metal-organic frameworks(MOFs)derived composites are extremely potential electromagnetic wave(EMW)absorbers.However,the permittivity of absorbers directly derived from MOFs with solid structure is usually relatively low,inevitably limiting their further applications.Cation substitution can primely overcome the problem by regulating the morphology and atomic space occupation to enhance multiple loss mechanisms and impedance matching characteristics.However,universal mechanisms of the effect on EMW absorption performance influenced by cation substitution are still comparatively inadequate,which prospectively requires further exploration.Herein,a series of imidazolic MOFs were fabricated by ultrasonic symbiosis method and tailored by subsequent cation substitution strategy to prepare target porous composites.At a low filling rate and thin thickness,the as-obtained samples reach the optimal reflection loss and effective absorption bandwidth values of–49.81 dB and 7.63 GHz,respectively.The intercoupling between multiple atoms lays a significant foundation for abundant heterogeneous interfaces and defect vacancies,which effectively ameliorate the attenuation mechanisms.Meanwhile,the porous structure introduced by cation substitution reduces the bulk density to enhance the impedance matching and multiple reflections simultaneously.This study provides a helpful idea to exceedingly improve the EMW absorbing performance of imidazolic MOFs-derived composites by cation substitution.

An improved predictive deconvolution based on maximization of non-Gaussianity

The predictive deconvolution algorithm （PD）, which is based on second-order statistics, assumes that the primaries and the multiples are implicitly orthogonal. However, the seismic data usually do not satisfy this assumption in practice. Since the seismic data （primaries and multiples） have a non-Gaussian distribution, in this paper we present an improved predictive deconvolution algorithm （IPD） by maximizing the non-Gaussianity of the recovered primaries. Applications of the IPD method on synthetic and real seismic datasets show that the proposed method obtains promising results.

Carbon-Based MOF Derivatives:Emerging Efficient Electromagnetic Wave Absorption Agents

To tackle the aggravating electromagnetic wave(EMW)pollution issues,high-efficiency EMW absorption materials are urgently explored.Metal-organic framework(MOF)derivatives have been intensively investigated for EMW absorption due to the distinctive components and structures,which is expected to satisfy diverse application requirements.The extensive developments on MOF derivatives demonstrate its significantly important role in this research area.Particularly,MOF derivatives deliver huge performance superiorities in light weight,broad bandwidth,and robust loss capacity,which are attributed to the outstanding impedance matching,multiple attenuation mechanisms,and destructive interference effect.Herein,we summarized the relevant theories and evaluation methods,and categorized the state-of-the-art research progresses on MOF derivatives in EMW absorption field.In spite of lots of challenges to face,MOF derivatives have illuminated infinite potentials for further development as EMW absorption materials.

Adaptive multiple subtraction using a constrained L1-norm method with lateral continuity

The Lt-norm method is one of the widely used matching filters for adaptive multiple subtraction. When the primaries and multiples are mixed together, the L1-norm method might damage the primaries, leading to poor lateral continuity. In this paper, we propose a constrained L1-norm method for adaptive multiple subtraction by introducing the lateral continuity constraint for the estimated primaries. We measure the lateral continuity using prediction-error filters （PEF）. We illustrate our method with the synthetic Pluto dataset. The results show that the constrained L1-norm method can simultaneously attenuate the multiples and preserve the primaries.

Combined Adaptive Multiple Subtraction Based on Optimized Event Tracing and Extended Wiener Filtering

The surface-related multiple elimination(SRME) method is based on feedback formulation and has become one of the most preferred multiple suppression methods used. However, some differences are apparent between the predicted multiples and those in the source seismic records, which may result in conventional adaptive multiple subtraction methods being barely able to effectively suppress multiples in actual production. This paper introduces a combined adaptive multiple attenuation method based on the optimized event tracing technique and extended Wiener filtering. The method firstly uses multiple records predicted by SRME to generate a multiple velocity spectrum, then separates the original record to an approximate primary record and an approximate multiple record by applying the optimized event tracing method and short-time window FK filtering method. After applying the extended Wiener filtering method, residual multiples in the approximate primary record can then be eliminated and the damaged primary can be restored from the approximate multiple record. This method combines the advantages of multiple elimination based on the optimized event tracing method and the extended Wiener filtering technique. It is an ideal method for suppressing typical hyperbolic and other types of multiples, with the advantage of minimizing damage of the primary. Synthetic and field data tests show that this method produces better multiple elimination results than the traditional multi-channel Wiener filter method and is more suitable for multiple elimination in complicated geological areas.