Migration Method Research Articles

Upside-down Rayleigh-Marchenko: A practical redatuming scheme for seabed seismic acquisitions

Ocean-bottom seismic plays a crucial role in resource exploration and monitoring. However, despite their undoubted potential, the use of coarse receiver geometries poses challenges to accurate wavefield redatuming. This in turn affects the quality of subsequent imaging and reservoir characterization products. We develop a reciprocal version of the Rayleigh-Marchenko (RM) method, called the upside-down RM method, in which all spatial integrals are performed over the (usually much better-sampled) source carpet; this results in a redatuming scheme that naturally accommodates irregular and sparse receiver geometries. Our method requires the availability of multicomponent receivers and either dual sources or a preprocessing step of model-based source deghosting and uses only the down-going component of the receiver-side wavefield; as such, it can be interpreted as a full-wavefield extension of the mirror migration method commonly used in seabed settings. Two synthetic examples are used to showcase the effectiveness of our method, starting from the ideal scenario of finely and regularly sampled source and receiver arrays and subsequently considering different levels of decimation for the receiver geometry. Migrated images as well as common-angle gathers reveal that our method can be used to produce structural and amplitude-friendly imaging outputs with minimal data preprocessing.

One-step sparse-matrix method for full wave equation depth migration

By completely solving the second-order full-acoustic wave equation, two-way/full wave equation migration generates images up to arbitrary angles in inhomogeneous media. Full wave equation depth migration (FWDM) necessitates less wavefield storage during imaging, generates clearer imaging results, and has more computational flexibility compared with conventional reverse time migration. Conventionally, FWDM uses Runge-Kutta or two explicit one-way operators to extrapolate the data, which involves either a multirecursive process or complex square root computations of the Helmholtz operator, causing implementation complexities and inconveniences. To overcome these challenges, a novel algorithm called the one-step sparse-matrix method for FWDM (OSM-FWDM) is developed and executed. This method involves a straightforward calculation of the full wave equation propagator through a Taylor expansion and using the so-called precise integration method. The computational efficiency can be significantly improved by using sparse-matrix multiplication in the implementation of wavefield extrapolation. Building upon that, the method serves as a basic solution complemented by FWDM, offering straightforward, efficient, and easy coding characteristics. Our OSM-FWDM method is simpler and faster compared with conventional FWDM, all while maintaining imaging accuracy. In addition, a new solution that uses an extended velocity model to remove source-related artifacts in FWDM is developed and illustrated. These improvements are demonstrated through a series of numerical examples and a real data application.

Evaluation of fiber orientation of SFRP during molding by numerical method of local area migration

Evaluation of fiber orientation of SFRP during molding by numerical method of local area migration

THE INFLUENCE OF CHLORIDE IONS CONTENT ON THE MECHANICAL PROPERTIES OF CONCRETE

This paper presents an analysis of the effect of concrete salinity on the splitting tensile strength of specimens taken directly from the HC-500 floor slab and the flexural and compressive strength and the value of the modulus of elasticity of specimens made under laboratory conditions from lightweight concrete and ordinary concrete. The tests were carried out in two variants: in the first, chloride ions were introduced into the concrete by the migration method and in the second, as an additive introduced directly with the batch water. The analysis showed that the additive can affect certain mechanical properties of concrete both favorably and unfavorably. The results indicate that it is important to examine the issue of the influence of salinity on concrete’s mechanical properties. This knowledge can be applied to the modeling of damage in reinforced concrete structures resulting from exposure to chloride-rich environments.

Mapping 10-m harvested area in the major winter wheat-producing regions of China from 2018 to 2022.

Winter wheat constitutes approximately 20% of China's total cereal production. However, calculations of total production based on multiplying the planted area by the yield have tended to produce overestimates. In this study, we generated sample points from existing winter wheat maps and obtained samples for different years using a temporal migration method. Random forest classifiers were then constructed using optimized features extracted from spectral and phenological characteristics and elevation information. Maps of the harvested and planted areas of winter wheat in Chinese eight provinces from 2018 to 2022 were then produced. The resulting maps of the harvested areas achieved an overall accuracy of 95.06% verified by the sample points, and the correlation coefficient between the CROPGRIDS dataset is about 0.77. The harvested area was found to be about 13% smaller than the planted area, which can primarily be attributed to meteorological hazards. This study represents the first attempt to map the winter wheat harvested area at 10-m resolution in China, and it should improve the accuracy of yield estimation.

Shallow crustal structure of the northern Longmen Shan fault zone revealed by a dense seismic array with ambient noise analysis

The Longmen Shan (LMS) fault zone located in the southwest of China is not only the boundary tectonic zone of the Tibetan Plateau and South China block, but also an important part of the north–south seismic belt of China. To investigate the detailed crustal structure of the LMS fault zone, we deployed a dense seismic array of 151 short-period temporary stations in its northern section from March 16 to April 6, 2023. Continuous vertical component ambient noise waveforms recorded by these stations were cross-correlated for all station pairs, enabling the extraction of Rayleigh wave phase velocity dispersion curves across periods ranging from 0.5 s to 6 s. We then inverted these data to derive the crustal shear wave velocity using direct surface wave tomography. Meanwhile, a linear sub-array consisting of 54 stations and crossing the surface rupture of the 2008 Wenchuan earthquake was used to image the fault structure by applying the Transmitted Surface Wave Reverse Time Migration method (TSW-RTM). The ambient noise tomography results show that strong lateral heterogeneity exists in the shallow crust in the study area, with a high shear velocity in the northwest and a low shear velocity in the southeast. The low shear velocity is generally distributed between the Yingxiu-Beichuan fault (YBF) and the Guanxian-Jiangyou fault (GJF). The results of TSW-RTM indicate that the Wenchuan-Maoxian fault (WMF) and the YBF are both characterized with a steep dip to the northwest. Our results could serve as the important basis for the study of segmentation characteristics of the LMS fault and seismic hazard preparation and mitigation.

Effect of tannic acid modification on antioxidant activity, antibacterial activity, environmental stability and release characteristics of quercetin loaded zein-carboxymethyl chitosan nanoparticles

The stability of quercetin remains a challenge for their application in industrial food production. In order to solve this shortcoming, zein-tannic acid covalent complex was prepared. Fourier transform infrared spectroscopy demonstrated the formation of CN bond between zein and tannic acid. Quercetin loaded nanoparticles (QZTC) were prepared by zein-tannic acid complex and carboxymethyl chitosan by anti-solvent co-precipitation and pH migration method. The structure of the nanoparticles was characterized and the effects of tannic acid modification and carboxymethyl chitosan addition on the encapsulation efficiency, oxidation resistance, antibacterial property, environmental stability and microstructure of the nanoparticles were studied. The results showed that compared with zein nanoparticles, QZTC had higher encapsulation rate, smaller and more uniform spherical microstructure. Compared with free quercetin and the other two nanoparticles, QZTC showed higher light, heat, storage stability, antioxidant and antibacterial abilities (p < 0.05). It was also found that the improvement of stability mainly depended on the formation of CN covalent bond, hydrogen bond, electrostatic interaction and hydrophobic interaction between components. This study provides new ideas for improving the environmental stability, antioxidant and antibacterial properties of quercetin and for developing nanoparticles that can be used in food processing.

Routing Task in Dynamic Fog Computing Network

Relevance. In the context of traffic growth, transition to IMT-2030 networks and Telepresence services, the tasks of efficient management of network and computing resources occupy a special place. Fog computing as the next stage of decomposition of the architecture of multi access edge cloud computing is designed to radically change the models and methods of distributing computing tasks, influencing, among other things, the user-operator interaction models. At the moment, there is a whole layer of scientific problems for revealing the possibilities of fog computing. They can be divided into a number of areas, such as: study of models and methods for implementing services of ultra-reliable and ultra-low latency communications, defined in IMT-2020 networks; study of models and methods for ensuring quality of service, including quality of experience; study of methods for live migration of microservices, as well as groups of typical microservices; study of models and methods for distributing resources of dynamic fog computing while ensuring the stability of fog computing forms (clusters, nebulae); one of the potentially effective areas is research in the field of combining federated learning with dynamic fog computing. This paper solves a routing problem that can be attributed to the direction of infrastructure research in dynamic fog computing.Problem statement: research and develop the effective methods for routes determination in a dynamic fog computing network, including tasks of migrating microservices of telepresence services. Goal of the work: research and development of an effective method for ways determination to migrate microservices in communication networks using fog computing technologies, which could take into account not only the characteristics of connections (edges of the network graph), but also the computing capabilities and limitations of fog computing devices, as well as their features - the dynamics of computing devices. Methods: in order to test the proposed method, the program model was developed in the NS-3 modeling environment. Result. Analysis of the results showed the effectiveness of the proposed method within the framework of the task and various application scenarios. Novelty. A microservice migration method has been developed as a new routing protocol in a dynamic fog computing environment, which differs from the known ones in that this method ensures the interaction of fog computing devices for migrating microservices, while achieving a reduction in energy consumption by fog computing devices by 41% and reducing the share of lost packages on average up to 34%. Practical significance: The developed method can be used to implement fog computing in conditions of mobility of end devices in order to achieve the requirements of promising services of IMT-2030 networks.

Circular phase shift migration based photoacoustic computational tomography

Abstract In the recent several decades, photoacoustic technique has proved to be capable of noninvasive biomedical imaging with scalable spatial resolution and high penetration depth. To achieve faithful image reconstruction, various method has been proposed, such as back projection, phase shift migration, model-based method, etc. These methods have simple implementations in homogeneous media, whereas in the cases of heterogeneous media (e.g., layered media), complicated modifications with respect to wave propagation at layer interface are always necessary. Here, we propose a frequency domain algorithm extension of phase shift migration in polar coordinates, which is obtained by making second order approximation to the optoacoustic point spread function in cylindrical coordinates and thereafter step by step wavenumber-frequency domain wave field extrapolation along the axial direction. Theoretical simulation and phantom experimental results demonstrate that the proposed circular phase shift migration method can well solve the layered heterogeneous reconstructive problem without modifying the wave propagation model. The acoustic diffraction limited acoustic resolution (up to 225 μm) and high imaging SNR (at least 16 dB) are obtained.

Applying Bulldog Clamps to Prevent Stone Migration in Laparoscopic Upper Ureteral Stone Surgery

Background: Urolithiasis can be managed by endoscopic, laparoscopic, percutaneous, or open approaches. We introduce an effective and safe method for stone migration during laparoscopic ureterolithotomy. Description of Technique: We used laparoscopic intraperitoneal approach, with three ports. Stone is localized and the ureter occluded proximally and distally to the stone using bulldog clamps to minimize the risk of stone migration. Patients and Methods: Case 1 had a 15 mm left upper ureteral stone — refractory to ESWL. Case 2 had a 17mm right upper ureteral stone without previous stone procedure. Case 3 had a history of failed ESWL for a 17mm left upper ureteral stone. Results: Mean operation time was 55 minutes, mean hospital stay was two days, and SFR was 100%. No complications occurred during this minimally invasive surgery, either intra-operatively or post-operatively. Conclusion: This is a safe and effective maneuver, increasing the stone-free rate of the procedure, which facilitates stone surgery by releasing the surgeon’s hands and preventing stone migration.

Classification and spatio-temporal evolution analysis of coastal wetlands in the Liaohe Estuary from 1985 to 2023: based on feature selection and sample migration methods

Classification and spatio-temporal evolution analysis of coastal wetlands in the Liaohe Estuary from 1985 to 2023: based on feature selection and sample migration methods

An efficient illumination compensation method for reverse time migration

AbstractBy directly solving the full two‐way wave equation, reverse time migration has superiority over other imaging algorithms in handling steeply dipping structures and other complicated geological models. Moreover, by incorporating the asymptotic inversion operator into reverse time migration imaging condition, the imaging algorithm is able to give a quantitative estimation of parameter perturbation in high‐frequency approximation sense. However, because conventional asymptotic inversion only accounts for geometrical spreading, uneven illumination due to irregular acquisition geometry and inhomogeneous subsurface at each image point is neglected. The omit of illumination compensation significantly affects the imaging quality. Wave‐equation‐based illumination compensation methods have been extensively studied in the past. However, the traditional wave‐equation‐based illumination compensation methods usually require high computational cost and huge storage. In this paper, we propose an efficient wave‐equation‐based illumination compensation method. Under high‐frequency approximation, we first define a Jacobian determinant to measure the regularity of subsurface illumination, and then illumination compensation operators are proposed based on the Jacobian. Through boundary integration, we further express the illumination compensation operators through extrapolated wavefields; the explicit computation of asymptotic Green's functions is thus avoided, and an efficient illumination compensation implementation for reverse time migration is achieved. Numerical results with both synthetic and field data validate the effectiveness and efficiency of the presented method.

Spontaneous cytokine production by the cells from peripheral blood, lymph nodes, spleen, thymus and skin in a murine model of acute psoriasis-like dermatitis

Imiquimod-induced model of psoriasis in mice is used for the studies in psoriasis. Imiquimod administered as skin application triggers a complex multi-stage process simulating psoriatic inflammation of the skin, accompanied by changes in production of cytokines. The aim of this work was a comprehensive study of their contents in cell supernatants isolated from skin, blood, from central and peripheral lymphoid organs and the effect of imiquimod on these parameters. Forty-six C57BL/6 mice were divided into two groups: (1) control (n = 22), and (2) experimental (n = 24). Development of experimental pathology was evaluated by van de Fits et al. The mice from experimental group were treated with a cream containing 5% imiquimod (62.5 mg/ cm2/ day/mouse) for 7 days. On the 7th day of experiment, the animals were subject to blood sampling, extraction of spleen, lymph nodes, thymus, and skin biopsies were also made. To obtain cell suspensions, the tissues of spleen, lymph nodes, and thymus were crushed in a homogenizer, and then passed through cell filters (50 mcm pore size). The method of spontaneous migration was used to isolate skin cells. The cultures of blood, spleen, lymph nodes, thymus, and skin cells were incubated for 24 hours in RPMI-1640 followed by assessment of spontaneous cytokine production in supernatants. The cytokine level (IFNγ, IL-1β, IL-5, IL-6, IL-10, IL- 17, TNFα, IL-10) was determined using the murine Th1/Th2/Th17 Panel test system. Our study revealed that the cells isolated from blood and lymphoid organs synthesize increased amounts of pro-inflammatory cytokines: IL-1 and IL-17. The most pronounced changes in the cytokine profile are observed in cell supernatants from blood, skin and spleen cultures.

Generating microstructures of long fiber reinforced composites by the fused sequential addition and migration method

Generating microstructures of long fiber reinforced composites by the fused sequential addition and migration method

Spatiotemporal variation and driving factors of oases in the arid region of Northwest China.

Based on Landsat images and digital elevation model data during 2000-2020, we investigated the spatio-temporal variations and driving forces of oases in the arid region of Northwest China, using an object-oriented method for oasis classification, and employing trends analysis, centroid migration, and geographic detectors methods. The results showed that from 2000 to 2020, the oasis area in the arid region of Northwest China exhibited a linear increasing trend, with a rate of 1079.66 km2·a-1. The growth rate of oasis area, from highest to lowest, was Alxa, Southern Xinjiang, Hexi Corridor and Northern Xinjiang, respectively. Oases in the arid region of Northwest China were mainly distributed in bands or dots along the northern and southern foothills of Tianshan Mountain, Kunlun Mountain, the northern foothills of Qilian Mountain, and the Alxa Plateau. The oasis area in Northern Xinjiang increased while that in the south decreased. Oases in Southern Xinjiang mainly expanded along rivers, with some edges experiencing recession. Expansion and recession of oases in the Hexi Corridor occurred along the rivers in the northwest. Alxa oasis expanded in a scattered pattern with no significant recession areas. The centroids of oases in Northern and Southern Xinjiang generally shifted northeastward, while that in the Hexi Corridor moved northwestward. The centroid of Alxa oasis fluctuated in a north-south direction. The interpretations of agricultural production potential for spatial differentiation of oases in Northern Xinjiang and the Hexi Corridor were the most significant, at 43.6% and 45.3% respectively. Precipitation was the strongest environmental factor affecting Alxa oasis distribution, with an interpretation of 27.6%. Soil types were the strongest factor affecting the distribution of oases in Sou-thern Xinjiang, with an interpretation of 44.9%. The interaction among human activities in oases in the arid region of Northwest China was mainly enhanced by two factors, while the interaction among natural factors was enhanced by both two factors and nonlinear enhancement.

Image style migration method based on transformer generative adversarial network combined with contrast learning strategy

Abstract Aiming at the problems of large loss of image patch embedding information and lack of stylized features in the generated image during transformer style migration, a style migration model combining contrast learning with transformer backbone generative adversarial network is established. Firstly, overlapping patch embedding is used to serialize the input images to get richer features; then the style and content contrast loss of contrast learning is used to mine the non-significant information between stylized images to reduce the style and content loss; finally, a multi-scale discriminator discriminates the true and false of stylized images to optimize the generator to get more stylistic features. The results on MS-COCO and WikiArt datasets show that the model improves the effectiveness and transformation efficacy of stylized images in style migration.

Ultrasonic Imaging of Deeper Bone Defect Using Virtual Source Synthetic Aperture with Phased Shift Migration: A Phantom Study.

Ultrasound imaging for bone is a difficult task in the field of medical ultrasound. Compared with other phase array techniques, the synthetic aperture (SA) has a better lateral resolution but a limited imaging depth due to the limited ultrasonic energy emitted by the single emitter in each transmission. In contrast, the virtual source (VS) synthetic aperture allows a simultaneous multi-element emission and could provide a higher ultrasonic incident energy in each transmission. Therefore, the VS might achieve a high imaging quality at a deeper depth for bone imaging than the traditional SA. In this study, we proposed the virtual source phase shift migration (VS-PSM) method to achieve ultrasonic imaging of the deeper bone defect featured in the multilayer structure. The proposed VS-PSM method was validated using standard soft tissue phantom and printed bone phantom with artificial defects. The image quality was evaluated in terms of contrast-to-noise ratios (CNR) and amplitudes of scatters and defects at different imaging depths. The results showed that the VS-PSM method could achieve a high imaging quality of the soft tissues with a significant improvement in the scattering amplitude and without a significant sacrifice of the lateral and axial resolution. The PSM was superior to the DAS in suppressing the background noise in the images. Compared with the traditional SA-PSM, the VS-PSM method could image deeper bone defects at different ultrasonic frequencies, with an average improvement of 50% in CNR. In conclusion, this study demonstrated that the proposed VS-PSM method could image deeper bone defects and might help the diagnosis of bone disease using ultrasonic imaging.

Kirchhoff Prestack time migration of crooked-line seismic data

Abstract Crooked-line seismic survey has been widely used in oil and gas exploration in complex areas of western China. However, due to the unconventional acquisition geometry, current migration methods cannot fully account for the characteristics of crooked-line seismic data and may lead to poorly-resolved images with inaccurate kinematics. To mitigate this problem, we present in this paper a modified Kirchhoff prestack time migration well adapted to crooked-line seismic data. We first carry out a theoretical analysis on the propagation geometry of crooked-line seismic data and demonstrate problems associated with conventional 3D traveltime-based migration. Then, we present a modified 2D migration scheme based on the projection between the actual imaging trace within the vertical plane of seismic reflections and the output imaging trace. Compared with the 3D traveltime-based migration, our method not only ensures the accuracy of imaging depth but also improves the focusing and continuity of the migrated image. We use both synthetic and real data tests to validate the correctness and effectiveness of the proposed method.

2D acoustic equation prestack reverse-time migration based on an optimized combined compact difference scheme

Abstract Reverse-time migration (RTM) is widely regarded as one of the most accurate migration methods available today. A crucial step in RTM involves extending seismic wavefields forward and backward. Compared to the conventional central finite-difference (CFD) scheme, the combined compact difference (CCD) scheme offers several advantages, including a shorter difference operator and the suppression of numerical dispersion under coarse grids. These attributes conserve memory and enhance effectiveness while maintaining the same level of differential precision. In this article, we begin with the five-point eighth-order CCD scheme and utilize the least squares method and Lagrange multiplier method to optimize the difference coefficients. This optimization is guided by the concept of dispersion-relation-preserving (DRP). The result is the acquisition of an optimized combined compact difference (OCCD) scheme, further enhancing the ability to suppress numerical dispersion. We thoroughly compare and analyze dispersion relationships and stability conditions. In addition, we examine several crucial steps in the RTM of the second-order acoustic wave equation. These steps include absorption boundary conditions, boundary storage strategy, and Poynting vector imaging conditions. Finally, we apply both the CCD and OCCD schemes in the RTM of the layered model, graben model, and SEG/EAGE salt model. We compare these results with those obtained from CFD's RTM. Numerical findings demonstrate that, in contrast to the CFD scheme, the CCD scheme effectively suppresses numerical dispersion and enhances imaging accuracy. Moreover, the optimized OCCD scheme further improves the ability to suppress numerical dispersion and can obtain better imaging results, which is an effective RTM method suitable for coarse grid conditions.

Marsh decrease was much faster than the water increase among the Yellow River Source wetlands during 1986–2022

Wetlands are valuable and sensitive ecosystems that make them imperative to tracking the dynamics in their extent for sustainable management under global warming. Here we focused on the Yellow River Source (YRS) wetlands, which is renowned for hosting one of the world's largest plateau peat bog, unfortunately, it had experienced sharp degradation, threatening the safety of water supply for approximately 110 million people of the lower Yellow River basin. However, the lack of long-term, dense time-series data makes it challenging to assess its evolution trends and driving factors. Therefore, we developed a decision tree sample migration method based on Euclidean distance and Land Surface Water Index, and successfully generated annual wetland mapping of YRS from 1986 to 2022 by utilizing the Landsat 5/7/8 datasets and Random Forest method. The average sample migration rate was 89.21 %, with an average overall accuracy of 95.49 %. We observed that the marsh area decreased by 2031 km2, marking a decline of 12.98 %, while the water area increased by 710 km2 (31.24 %) compared to 1986. Spatially, 10.96 % of marsh composition presents significant (P < 0.05) decline trend, which are mainly converted to grass (86 %), followed by impervious (10 %). There were 6.69 % of water composition showing significant (P < 0.05) increase trend, which are mainly sourced from impervious (82 %) and marsh (12 %). Grazing activities were more important driving forces than climate change for marsh degradation, while the water expansion was associated with recent rising temperature in YRS. The sample migration method is proved to be feasible, robust, and effective for long-term wetland mapping. We suggest that wetland decision-makers need to focus on marsh degradation and reduce grazing intensity, so that fostering the sustainable and healthy wetlands in the Qinghai-Tibetan Plateau.