Adjacent Shots Research Articles

Simultaneous random plus outlier attenuation and deblending based on L1‐norm misfit function

AbstractDeblending technology aims at separating simultaneous source seismic data between adjacent shots by allowing multiple sources to be shot simultaneously. Conventional deblending methods based on sparse inversion assume that the primary source is coherent, and the secondary source is randomized. The L2‐norm minimization constraint can effectively minimize the Gaussian random noise while deblending in the transform domain. Nonetheless, the L2‐norm misfit function is highly sensitive to outliers, negatively influencing the deblending performance. An effective optimization strategy is developed with deblending in pre‐stack seismic data to eliminate outliers and enhance deblending accuracy. For this reason, we introduce the deblending algorithm in the morphological component analysis framework, modify the L2‐norm misfit function to outlier‐robust L1‐norm and provide the corresponding derivation in detail via the alternating direction method of multipliers. Applications to synthetic and field data sets prove the improved robustness and efficiency of our deblending method.

Hardness Determination of Thin Film Structural Materials Using Laser-Induced Breakdown Spectroscopy

The hardness of a thin film structural material is a direct reflection of its comprehensive mechanical properties, which are dependent on the film thickness. In recent years, laser-induced breakdown spectroscopy (LIBS) has been gradually applied to the determination of the hardness of materials; however, there is no relevant studies have been conducted on thin film structural materials. In this study, Q235 steels with different copper plating thicknesses on the surface were used to determine the correlation between the hardness and spectroscopic parameters. Nanoindentation was used for the hardness analysis. First, a linear relationship was obtained between the sample hardness and copper film thickness and the goodness-of-fit value was 0.9961. Second, we calibrated the plasma temperature and Cu ionic-to-atomic line intensity ratio of the surface spectra to the hardness and found that the spectroscopic parameters of the surface spectra of the samples were not sufficient to characterize their hardness. Finally, the number of shots reaching the Cu-substrate interface is determined by the similarity between the spectra obtained from two adjacent shots, 2, 5, 21, and 96, respectively. We determined a more accurate linear relationship between the plasma temperature, ionic-to-atomic line intensity ratio of the spectra at the film-substrate interface, and sample hardness. The goodness-of-fit values were 0.9923 and 0.9973. This demonstrates that the spectra at the film-substrate interface are more suitable for sample hardness analysis and LIBS is a potential method for the estimation of the hardness of thin film structural materials.

Deep neural network-based workflow for attenuating seismic interference noise and its application to marine towed-streamer data from the northern Viking Graben

To separate seismic interference (SI) noise while ensuring high signal fidelity, we have developed a deep neural network (DNN)-based workflow applied to common-shot gathers (CSGs). In our design, a small subset of the entire to-be-processed data set is first processed by a conventional algorithm to obtain an estimate of the SI noise (from now on called the SI noise model). By manually blending the SI noise model with SI-free CSGs and a set of simulated random noise, we obtain training inputs for the DNN. The SI-free CSGs can be either real SI-free CSGs from the survey or SI-attenuated CSGs produced in parallel with the SI noise model from the conventional algorithm depending on the specific project. To enhance the DNN’s output signal fidelity, adjacent shots on both sides of the to-be-processed shot are used as additional channels of the input. We train the DNN to output the SI noise into one channel and the SI-free shot along with the intact random noise into another. Once trained, the DNN can be applied to the entire data set contaminated by the same types of SI in the training process, producing results efficiently. For demonstration, we applied our DNN-based workflow to 3D seismic field data acquired from the northern Viking Graben of the North Sea and compared it with a conventional algorithm. The studied area has a challenging SI contamination problem with no sail lines free from SI noise during the acquisition. The comparison finds that our DNN-based workflow outperformed the conventional algorithm in processing quality with less noise residual and better signal preservation. This validates its feasibility and value for real processing projects.

Multiparameter Elastic Full Waveform Inversion Based on Random Source-Encoding and Projection Regularization

Multi-parameter elastic full waveform inversion (FWI) makes full use of the dynamic and kinematic information of all seismic wavefield. Through the mutual constraint and verification of the three parameters of P-wave velocity, S-wave velocity, and density, the joint evaluation is carried out, which is helpful to understand the structural and lithologic information of underground media more comprehensively. The bottleneck restricting the multi-parameter FWI is the large amount of calculation and low efficiency. To improve this problem, multiple shots are directly superimposed to form super shots. While it usually results in an unstable inversion due to that a large amount of crosstalk noise will be easily generated between adjacent shots. In this paper, we introduce the random source-encoding strategy to improve the inversion efficiency and load the total-variation (TV) regularization term to suppress the crosstalk noise, but it also brings the problem of regularization parameters selection for multi-parameter FWI. Thus, the projection method is applied to directly load the regularization term into the model as a constraint, which avoids the unsatisfactory results caused by the improper selection of regularization parameters and effectively improves the ill-posedness of inversion. Finally, three examples of the graben, the 1994BP, and the overthrust model are used to prove that the proposed algorithm based on random source-encoding and projection regularization can effectively improve the inversion efficiency, suppress noise, and has good practicability and adaptability.

A novel method for fabricating micro-dimple arrays with good surface quality on metallic glass substrate by combining laser irradiation and mechanical polishing under wax sealing

Surface micro-patterning is an emerging technique to endow a wide range of materials with specific functions, such as superhydrophobicity and anti-reflection, but it is still technically challenging and inordinately expensive via existing manufacturing approaches. Compared with crystalline metals, metallic glasses (MGs) are talented with some unique mechanical and chemical properties due to their isotropic internal structure. Here, a novel two-step method, involving nanosecond pulsed laser irradiation and mechanical polishing, was proposed to fabricate micro-dimple arrays with good surface quality on the MG substrate. In the first step, multi-pulse laser irradiation experiments were performed to study the correlation between the peak laser power intensity and the feature sizes of the micro-dimple (i.e. the depth and diameter of the micro-dimple as well as the height of the pile-up), and then various micro-dimple arrays were fabricated on the MG substrate by adjusting the peak laser power intensity and the interval between adjacent laser shots. Subsequently, aiming at improving the surface quality, the micro-dimple arrays were mechanically polished under wax sealing. The experimental results indicated that after polishing, the pile-ups around the micro-dimples were completely removed, and at the same time, the surface quality of their inner walls was improved. Furthermore, based on experimental results, the possible material removal mechanism during polishing was discussed. This study provides a convenient method to fabricate micro-dimple arrays with good surface quality on the MG substrate, which would be one of the potential alternatives for large-area, low-cost micro/nano-manufacturing.

A direct noise attenuation approach in processing of land continuous records

Blended source acquisition has drawn great attention in industry due to its increased efficiency and reduced overall cost for acquiring seismic data. It eliminates the requirement of a minimum time (usually determined by record length) between adjacent shots and allows multiple sources to be activated simultaneously and independently. Conventional processing simply converts continuous records into fixed-length records using the source excitation time and then applies traditional denoising techniques to the fixed-length records. Source excitation time is used to extract fixed-length records that are the equivalent of traditional synchronous recording. Here, we elaborate on the usage of continuous records for land noise attenuation. Compared to conventional common shot/receiver/midpoint/offset domains, continuous records represent the data in the naturally recorded domain. This domain offers flexible and much longer record lengths to work with and, moreover, enables exploiting the characteristics of noise prior to correlation, shot slicing, or other preprocessing. We limit our discussions to the techniques and methods for attenuating coherent environmental and source-generated noise on vibroseis data. We have found that incoherent noise can be handled effectively by traditional noise suppression methods after deblending. We illustrate the effectiveness of noise attenuation in the continuously recorded domain for three different types of noise using field examples from the North Slope of Alaska and the Permian Basin.

Numerical simulation of surface topography and residual stress after abrasive water jet sequential peening

In this paper, the theoretical models of the surface topography and residual stress (RS) were proposed, and the abrasive water jet sequential peening (AWJSP) finite element models were established by using ABAQUS. Then, the formation mechanism of the surface topography in multiple passes AWJSP process and the coupling mechanism of RS in a single and multiple passes AWJSP process were analyzed. After that, the influence of the number of shots (i.e. N), the distance between the center of adjacent shots Dc, shot velocity v, and shot radius R on the surface topography and residual stress field (RSF) of the target were investigated. Results show that successive dimples were formed by single-pass AWJSP, the RSF formed by the impact of each shot will influence the previous RSF, and that will be coupled with it. In multiple passes AWJSP process, decreasing Dc can decrease the surface roughness, the surface smoothness of the target material will gradually become better, and the RSF will also be uniform. Under full coverage condition, the surface roughness Rt and mean width of the profile Rsm will gradually decrease with the decrease of Dc, while the change of Dc has little influence on the RSF. Increasing the v can increase Rt and Rsm, and it is beneficial to induce a large and deep compressive RS layer. Increasing the R can decrease Rt, Rsm remains unchanged, and it is beneficial to induce a deep compressive RS layer.

Numerical investigation of surface topography and residual stress after abrasive water jet sequential peening (AWJSP)

This article reveals the formation mechanism of surface topography and the formation and coupling mechanism of residual stress field (RSF) after abrasive water jet sequential peening (AWJSP) that can sequential peening on the material surface at a certain distance interval, and proposes a mathematical model of surface dimple characteristic verified by simulation results. In addition, the influences of shot velocity v0, shot radius R and the distance between the center of adjacent shots DC on surface topography and RSF were also investigated. Results show the surface dimple forms resulting from the material plastic strain, and the residual stress (RS) is mainly induced by the unrecovered elastic strain resulting from the hindering of plastic strain. Decreasing v0, R or DC can decrease the surface roughness Rt, while increasing v0 and R is beneficial to induce a large and deep compressive RS layer. DC influences the whole distribution of compressive RS layer directly.

VIDEO SCENE SEGMENTATION OF TV SERIES USING MULTI-MODAL NEURAL FEATURES

Scene segmentation of a video, a book or TV series allows to organize them into Logical Story Units and is an essential step for representing, extracting and understanding their narrative structures. We propose an automatic scene segmentation method for TV series based on the grouping of adjacent shots and relying on a combination of multimodal neural features: visual features and textual features, further augmented with the temporal information which may improve the clustering of adjacent shots. Reported experiments compare early and late fusion of the features, video frames subsampling and various shot clustering algorithms. The proposed method achieved good recall, precision and F-measure when tested on several seasons of two popular TV series.

Simultaneous Sources Separation via an Iterative Rank-Increasing Method

Simultaneous sources acquisition attracts intensive attention from both academia and industry due to its greatly improved efficiency in acquiring high-density seismic data. Unfortunately, its merits are compromised by the strong interference noise between adjacent shots. In this letter, we propose a stepwise rank-increasing (RI) method to estimate the crosstalk noise in simultaneous sources acquisition. The proposed algorithm assumes that an ideal common offset gather (COG) can be represented via a low-rank matrix in the time-space domain. The coherent signals are estimated from low-rank decomposition and transformed to the crosstalk noise by employing a priori information about random dithering code, and then the blending noise is subtracted from the blended data. By increasing the rank of coherent signals step-by-step, the crosstalk noise can be gradually estimated with high accuracy. In this letter, singular value decomposition is utilized to increase the rank of COG data. Applications on synthetic and field data sets demonstrate the better performance of the proposed RI method not only by more effectively suppressing noise but also by accelerating the convergence rate.

Anatomical-based model for simulation of HIFU-induced lesions in atherosclerotic plaques

Purpose: The aim of this study was to simulate the effect of high intensity focused ultrasound (HIFU) in non-homogenous medium for targeting atherosclerotic plaques in vivo. Materials and methods: A finite-difference time-domain heterogeneous model for acoustic and thermal tissue response in the treatment region was derived from ultrasound images of the treatment region. A 3.5 MHz dual mode ultrasound array suitable for targeting peripheral vessels was used. The array has a lateral and elevation focus at 40 mm with fenestration in its centre through which a 7.5 MHz diagnostic transducer can be placed. Two cases were simulated where seven adjacent HIFU shots (∼5000 W/cm2, 2-s exposure time) were targeted on the plaque tissue within the femoral artery. The transient bioheat equation with a convective term to account for blood flow was used to predict the thermal dose. The results of the simulation model were then validated against the histology data. Results: The simulation model predicted the HIFU-induced damage for both cases, and correlated well with the histology data. For the first case thermal damage was detected within the targeted plaque, while for the second case thermal damage was detected in the pre-focal region. Conclusion: The results suggest that a realistic, image-based acoustic and thermal model of the treatment region is capable of predicting the extent of thermal damage to target plaque tissue. The model considered the effect of the wall thickness of large arteries and the heat-sink effect of flowing blood. The model is used for predicting the size and pattern of HIFU damage in vivo.

Quality assurance of stereotactic alignment and patient positioning mechanical accuracy for robotized Gamma Knife radiosurgery

The automatic patient positioning system and its alignment is critical and specified to be less than 0.35 mm for a radiosurgical treatment with the latest robotized Gamma Knife Perfexion (GKPFX). In this study, we developed a quantitative QA procedure to verify the accuracy and robustness of such a system. In particular, we applied the test to a unit that has performed >1000 procedures at our institution. For the test, a radiochromic film was first placed inside a spherical film phantom and then irradiated with a sequence of linearly placed shots of equal collimator size (e.g. 4 mm) via the Leksell Gamma Knife Perfexion system (PFX). The shots were positioned with either equal or unequal gaps of approximately 8 mm both at center and off-center positions of the patient positioning system. Two independent methods of localizing the irradiation shot center coordinates were employed to measure the gap spacing between adjacent shots. The measured distance was then compared with the initial preset values for the test. On average, the positioning uncertainty for the PFX delivery system was found to be 0.03 ± 0.2 mm (2σ). No significant difference in the positioning uncertainty was noted among measurements in the x-, y- and z-axis orientations. In conclusion, a simple, fast, and quantitative test was developed and demonstrated for routine QA of the submillimeter PFX patient positioning system. This test also enables independent verification of any patient-specific shot positioning for a critical treatment such as a tumor in the brainstem.

SU-E-T-563: A Fast and Quantative Picket-Fence Test of a Submillimeter Patient Positioning System for Stereotactic Radiosurgery

Purpose: Picket-fence test is a qualitative TG142-recommended quality assurance (QA) test for multileaf collimators. In study, we adopted the same concept and developed a fast but quantatitive QA test for an automatic patient positioning system that requires submilleter accuracy for a radiosurgical treatment. Methods: A piece of radiochromic film was first placed inside a spherical solid water phantom and then irradiated with a sequenence of linearly placed shots of same collimator size (e.g. 4-mm) via the Leskell Gamma Knife Perfexion system (PFX). The shots were positioned with either equal or non-equal gaps of approximately 4 mm to 8 mm depending on the location of the region of interest. A pattern recognization program was developed and then applied to measure the gap spacing between two adjacent shots. The measured distance was then compared with the initial preset values for the test. Results: By introducing variable systematic and random shifts of 0.1 mm to 0.5 mm to the shot sequence, the maximum gap variation from the described test was found to be 0.35 mm or less. On average the positioning uncertainty for the PFX delivery system was found to be 0.1±0.2 mm. No significant difference in the positioning uncertainty was noted for the centrally aligned shot sequence locations versus the peripherally aligned shot sequence locations. Conclusion: A new quantitative picket-fence type test was developed and demonstrated for routine QA of the submillimeter PFX patient positioning sytem. This test also enables independent verification of any patient-specific shot positioning for a critical treatment such as a tumor in brainstem. Dr Ma is currently on the board of international society of stereotactic Radiosurgery

First‐time viewers' comprehension of films: Bridging shot transitions

Which perceptual and cognitive prerequisites must be met in order to be able to comprehend a film is still unresolved and a controversial issue. In order to gain some insights into this issue, our field experiment investigates how first-time adult viewers extract and integrate meaningful information across film cuts. Three major types of commonalities between adjacent shots were differentiated, which may help first-time viewers with bridging the shots: pictorial, causal, and conceptual. Twenty first-time, 20 low-experienced and 20 high-experienced viewers from Turkey were shown a set of short film clips containing these three kinds of commonalities. Film clips conformed also to the principles of continuity editing. Analyses of viewers' spontaneous interpretations show that first-time viewers indeed are able to notice basic pictorial (object identity), causal (chains of activity), as well as conceptual (links between gaze direction and object attention) commonalities between shots due to their close relationship with everyday perception and cognition. However, first-time viewers' comprehension of the commonalities is to a large degree fragile, indicating the lack of a basic notion of what constitutes a film.

Numerical Simulation of Stress Peen Forming with Regular Indentation

Stress peen forming is widely used to form the thin components with complex shapes in the aerospace industry. The prestress has an influence on the residual stress profiles, thereby influencing the peen forming forces: bending moment and stretching force for shaping the component. A static one-shot FE model was performed to investigate the residual stress profiles of single shot indenting under different prestresses and loads. A static four-shot FE model was performed to investigate the overlapping of the stress fields of adjacent shots indenting. The simulation results reveal that the tensile prestress enhances the indentation diameter and the plastic region size resulting in larger and deeper compressive residual stresses. The average peen forming forces of regular distributed four shots are four times the forming forces of one of shots when the separation distance of adjacent shots is larger than the plastic region size of one shot indenting. Experiments with different prebending arc heights and indenting gaps were carried out on aluminum alloy 2024-T351 strips with a developed Brinell hardness tester. The experimental results validated the simulation results.

A NOVEL TECHNIQUE FOR SIZE CONSTRAINED VIDEO STORYBOARD GENERATION USING STATISTICAL RUN TEST AND SPANNING TREE

Storyboard consisting of key-frames is a popular format of video summarization as it helps in efficient indexing, browsing and partial or complete retrieval of video. In this paper, we have presented a size constrained storyboard generation scheme. Given the shots i.e. the output of the video segmentation process, the method has two major steps: extraction of appropriate key-frame(s) from each shot and finally, selection of a specified number of key-frames from the set thus obtained. The set of selected key-frames should retain the variation in visual content originally possessed by the video. The number of key-frames or representative frames in a shot may vary depending on the variation in its visual content. Thus, automatic selection of suitable number of representative frames from a shot still remains a challenge. In this work, we propose a novel scheme for detecting the sub-shots, having consistent visual content, from a shot using Wald–Wolfowitz runs test. Then from each sub-shot a frame rendering the highest fidelity is extracted as key-frame. Finally, a spanning tree based novel method is proposed to select a subset of key-frames having specific cardinality. Chronological arrangement of such frames generates the size constrained storyboard. Experimental result and comparative study show that the scheme works satisfactorily for a wide variety of shots. Moreover, the proposed technique rectifies mis-detection error, if any, incurred in video segmentation process. Similarly, though not implemented, the proposed hypothesis test has ability to rectify the false-alarm in shot detection if it is applied on pair of adjacent shots.

NUMERICAL SIMULATION FOR SHOT-PEENING BASED ON SPH-COUPLED FEM

In dealing with shot-peening simulation, existing literatures adopt finite element method (FEM), which establishes models of a single shot or several shots only, thus the effect of a large number of shots repeat impacting and the influence among adjacent shots are ignored. To overcome these disadvantages of FEM models, smoothed particle hydrodynamics (SPH)-coupled FEM modeling is presented, in which the shots are modeled by SPH particles and the target material is modeled by finite elements. The two parts interact through contact algorithm to simulate a number of shots impinging the target. Utilizing this model, a material model for shots is established, the relationships between compressive residual stress and peening frequencies, coverage, and velocities are analyzed. Steady compressive residual stress can be obtained by multiple peening; higher coverage can improve the compressive residual stress; faster velocities can induce greater and deeper maximum residual stress in target subsurface. The simulation results agree well with the existing experimental data. The study would not only provide a new powerful tool for the simulation of shot-peening process, but also be benefit to optimize the operating parameters.

Light-shield border impact on the printability of extreme-ultraviolet mask

When a thinner absorber mask is applied to extreme ultraviolet (EUV) lithography for chip production, it becomes essential to a introduce light-shield border in order to suppress the leakage of EUV light from the adjacent exposure shots. In this paper, we evaluate the leakage of both EUV and out-of-band from light-shield border and clarify the dependence of lithographic performance on light-shield border structure using a small field exposure tool with/without spectral purify filter (SPF). Then we evaluate the lithographic performance of a thin absorber EUV mask with light-shield border of the etched multilayer type and demonstrate the merit of its structure using a full-field scanner operating under the currently employed condition of EUV source in which SPF is not installed.

Shot peening simulation based on SPH method

Shot peening is a complex surface-treating process which is usually employed to improve the fatigue strength of metallic part or members. In dealing with shot peening simulation, existing literatures apply finite element method (FEM) to establish only a single shot or several shots models, thus the effect of a mass of shots impacting repeatedly and the interaction among adjacent shots are ignored. To overcome these defects of FEM models, smoothed particle hydrodynamics (SPH) coupled FEM modeling is presented, in which the shots are modeled by SPH particles and the target material is modeled by finite elements. Contact algorithm is used to simulate the interaction between shots and target. Utilizing this model, material model for shots is established, the relationships between compressive residual stress and peening frequencies, coverage, and velocities are analyzed. Steady compressive residual stress can be gotten by multiple peening; higher coverage can improve the compressive residual stress; faster velocities can induce greater and deeper maximum residual stress in target subsurface. The simulation results agree well with the existing experimental data. The study will not only provide a new powerful tool for the simulation of shot peening process, but also be benefit to optimize the operating parameters.

Online Plasma Shape Reconstruction for EAST Tokamak

An online plasma shape reconstruction, based on the offline version of the EFIT code and MPI library, can be carried out between two adjacent shots in EAST. It combines online data acquisition, parallel calculation, and data storage together. The program on the master node of the cluster detects the termination of the discharge promptly, reads diagnostic data from the EAST mdsplus server on the completion of data storing, and writes the results onto the EFIT mdsplus server after the calculation is finished. These processes run automatically on a nine-nodes IBM blade center. The total time elapsed is about 1 second to several minutes, depending on the duration of the shot. With the results stored in the mdsplus server, it is convenient for operators and physicists to analyze the behavior of plasma using visualization tools.