Journal of Imaging

Research

21 pages, 3646 KiB

Open AccessArticle

Seismic Waveform Inversion Capability on Resource-Constrained Edge Devices

by Daniel Manu, Petro Mushidi Tshakwanda, Youzuo Lin, Weiwen Jiang and Lei Yang

J. Imaging 2022, 8(12), 312; https://doi.org/10.3390/jimaging8120312 - 22 Nov 2022

Cited by 6 | Viewed by 1835

Seismic full wave inversion (FWI) is a widely used non-linear seismic imaging method used to reconstruct subsurface velocity images, however it is time consuming, has high computational cost and depend heavily on human interaction. Recently, deep learning has accelerated it’s use in several [...] Read more.

Seismic full wave inversion (FWI) is a widely used non-linear seismic imaging method used to reconstruct subsurface velocity images, however it is time consuming, has high computational cost and depend heavily on human interaction. Recently, deep learning has accelerated it’s use in several data-driven techniques, however most deep learning techniques suffer from overfitting and stability issues. In this work, we propose an edge computing-based data-driven inversion technique based on supervised deep convolutional neural network to accurately reconstruct the subsurface velocities. Deep learning based data-driven technique depends mostly on bulk data training. In this work, we train our deep convolutional neural network (DCN) (UNet and InversionNet) on the raw seismic data and their corresponding velocity models during the training phase to learn the non-linear mapping between the seismic data and velocity models. The trained network is then used to estimate the velocity models from new input seismic data during the prediction phase. The prediction phase is performed on a resource-constrained edge device such as Raspberry Pi. Raspberry Pi provides real-time and on-device computational power to execute the inference process. In addition, we demonstrate robustness of our models to perform inversion in the presence on noise by performing both noise-aware and no-noise training and feeding the resulting trained models with noise at different signal-to-noise (SNR) ratio values. We make great efforts to achieve very feasible inference times on the Raspberry Pi for both models. Specifically, the inference times per prediction for UNet and InversionNet models on Raspberry Pi were 22 and 4 s respectively whilst inference times for both models on the GPU were 2 and 18 s which are very comparable. Finally, we have designed a user-friendly interactive graphical user interface (GUI) to automate the model execution and inversion process on the Raspberry Pi. Full article

(This article belongs to the Special Issue Recent Advances in Image-Based Geotechnics)

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19 pages, 4837 KiB

Open AccessArticle

Using Transparent Soils to Observe Soil Liquefaction and Fines Migration

by Jisun Chang and David Airey

J. Imaging 2022, 8(9), 253; https://doi.org/10.3390/jimaging8090253 - 19 Sep 2022

Cited by 5 | Viewed by 2045

Abstract

The cyclic liquefaction of soils and associated mud-pumping can lead to costly repairs of roads, railways, and other heavy-haul infrastructure. Over the last decade, several laboratory studies have been conducted to investigate these phenomena, but, due to the opacity of soil, the typical [...] Read more.

The cyclic liquefaction of soils and associated mud-pumping can lead to costly repairs of roads, railways, and other heavy-haul infrastructure. Over the last decade, several laboratory studies have been conducted to investigate these phenomena, but, due to the opacity of soil, the typical experimental observations of cyclic liquefaction have been limited to post-test observations of fine movement and the data of water pressures and soil settlements. In this paper, we show how partially transparent soil models can be used to provide the visualization of a moving saturation front and that fully transparent models can be used to observe fine migration during the cycling loading of a soil column. The changing saturation degree was tracked using a correlation between the degree of saturation, soil transparency, and grayscale image values, while particle movements of fines and larger particles were measured using a small number of fluorescent particles and particle tracking velocimetry. Another innovation of the work was in using mixtures of ethyl benzoate and ethanol as a low-viscosity pore fluid with the refractive index matching the fused silica soil particles. The benefits and challenges of these visualization tests are discussed. Full article

(This article belongs to the Special Issue Recent Advances in Image-Based Geotechnics)

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21 pages, 5811 KiB

Open AccessArticle

On Acquisition Parameters and Processing Techniques for Interparticle Contact Detection in Granular Packings Using Synchrotron Computed Tomography

by Fernando Alvarez-Borges, Sharif Ahmed and Robert C. Atwood

J. Imaging 2022, 8(5), 135; https://doi.org/10.3390/jimaging8050135 - 12 May 2022

Viewed by 2318

Abstract

X-ray computed tomography (XCT) is regularly employed in geomechanics to non-destructively measure the solid and pore fractions of soil and rock from reconstructed 3D images. With the increasing availability of high-resolution XCT imaging systems, researchers now seek to measure microfabric parameters such as [...] Read more.

X-ray computed tomography (XCT) is regularly employed in geomechanics to non-destructively measure the solid and pore fractions of soil and rock from reconstructed 3D images. With the increasing availability of high-resolution XCT imaging systems, researchers now seek to measure microfabric parameters such as the number and area of interparticle contacts, which can then be used to inform soil behaviour modelling techniques. However, recent research has evidenced that conventional image processing methods consistently overestimate the number and area of interparticle contacts, mainly due to acquisition-driven image artefacts. The present study seeks to address this issue by systematically assessing the role of XCT acquisition parameters in the accurate detection of interparticle contacts. To this end, synchrotron XCT has been applied to a hexagonal close-packed arrangement of glass pellets with and without a prescribed separation between lattice layers. Different values for the number of projections, exposure time, and rotation range have been evaluated. Conventional global grey value thresholding and novel U-Net segmentation methods have been assessed, followed by local refinements at the presumptive contacts, as per recently proposed contact detection routines. The effect of the different acquisition set-ups and segmentation techniques on contact detection performance is presented and discussed, and optimised workflows are proposed. Full article

(This article belongs to the Special Issue Recent Advances in Image-Based Geotechnics)

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20 pages, 13517 KiB

Open AccessArticle

Comparison of 2D Optical Imaging and 3D Microtomography Shape Measurements of a Coastal Bioclastic Calcareous Sand

by Ryan D. Beemer, Linzhu Li, Antonio Leonti, Jeremy Shaw, Joana Fonseca, Iren Valova, Magued Iskander and Cynthia H. Pilskaln

J. Imaging 2022, 8(3), 72; https://doi.org/10.3390/jimaging8030072 - 14 Mar 2022

Cited by 12 | Viewed by 2957

Abstract

This article compares measurements of particle shape parameters from three-dimensional (3D) X-ray micro-computed tomography (μCT) and two-dimensional (2D) dynamic image analysis (DIA) from the optical microscopy of a coastal bioclastic calcareous sand from Western Australia. This biogenic sand from a high energy environment [...] Read more.

This article compares measurements of particle shape parameters from three-dimensional (3D) X-ray micro-computed tomography (μCT) and two-dimensional (2D) dynamic image analysis (DIA) from the optical microscopy of a coastal bioclastic calcareous sand from Western Australia. This biogenic sand from a high energy environment consists largely of the shells and tests of marine organisms and their clasts. A significant difference was observed between the two imaging techniques for measurements of aspect ratio, convexity, and sphericity. Measured values of aspect ratio, sphericity, and convexity are larger in 2D than in 3D. Correlation analysis indicates that sphericity is correlated with convexity in both 2D and 3D. These results are attributed to inherent limitations of DIA when applied to platy sand grains and to the shape being, in part, dependent on the biology of the grain rather than a purely random clastic process, like typical siliceous sands. The statistical data has also been fitted to Johnson Bounded Distribution for the ease of future use. Overall, this research demonstrates the need for high-quality 3D microscopy when conducting a micromechanical analysis of biogenic calcareous sands. Full article

(This article belongs to the Special Issue Recent Advances in Image-Based Geotechnics)

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23 pages, 10515 KiB

Open AccessArticle

Visualization of Interstitial Pore Fluid Flow

by Linzhu Li and Magued Iskander

J. Imaging 2022, 8(2), 32; https://doi.org/10.3390/jimaging8020032 - 30 Jan 2022

Cited by 7 | Viewed by 3625

Abstract

Pore scale analysis of flow through porous media is of interest because it is essential for understanding internal erosion and piping, among other applications. Past studies have mainly focused on exploring macroscopic flow to infer microscopic phenomena. An innovative method is introduced in [...] Read more.

Pore scale analysis of flow through porous media is of interest because it is essential for understanding internal erosion and piping, among other applications. Past studies have mainly focused on exploring macroscopic flow to infer microscopic phenomena. An innovative method is introduced in this study which permits visualization of interstitial fluid flow through the pores of a saturated synthetic transparent granular medium at the microscale. Several representative images of Ottawa sand were obtained using dynamic image analysis (DIA), for comparison with flow through perfect cylinders. Magnified transparent soil particles made of hydrogel were cast in 3D printed molds. Custom 3D printed jigs were employed for accurate positioning of the particles to ensure that particles have the same flow area within the soil. The pore fluid was embedded with silver-coated hollow microspheres that allowed for their florescence and tracking their movement within the model when illuminated by a laser light source. Images of the flow were captured from the model using a high-speed camera. This, along with particle image velocimetry (PIV) provided for the velocity and direction analysis of fluid flow movements within the pore space of a planar 2D model. Comparison of interstitial flow through homogeneous porosity-controlled Ottawa-shaped and cylindrical particles demonstrates that the magnitude of turbulence is related to particle roundness. Full article

(This article belongs to the Special Issue Recent Advances in Image-Based Geotechnics)

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13 pages, 5112 KiB

Open AccessArticle

How Do Roots Interact with Layered Soils?

by Nina Kemp, Vasileios Angelidakis, Saimir Luli and Sadegh Nadimi

J. Imaging 2022, 8(1), 5; https://doi.org/10.3390/jimaging8010005 - 5 Jan 2022

Cited by 2 | Viewed by 2867

Abstract

Vegetation alters soil fabric by providing biological reinforcement and enhancing the overall mechanical behaviour of slopes, thereby controlling shallow mass movement. To predict the behaviour of vegetated slopes, parameters representing the root system structure, such as root distribution, length, orientation and diameter, should [...] Read more.

Vegetation alters soil fabric by providing biological reinforcement and enhancing the overall mechanical behaviour of slopes, thereby controlling shallow mass movement. To predict the behaviour of vegetated slopes, parameters representing the root system structure, such as root distribution, length, orientation and diameter, should be considered in slope stability models. This study quantifies the relationship between soil physical characteristics and root growth, giving special emphasis on (1) how roots influence the physical architecture of the surrounding soil structure and (2) how soil structure influences the root growth. A systematic experimental study is carried out using high-resolution X-ray micro-computed tomography (µCT) to observe the root behaviour in layered soil. In total, 2 samples are scanned over 15 days, enabling the acquisition of 10 sets of images. A machine learning algorithm for image segmentation is trained to act at 3 different training percentages, resulting in the processing of 30 sets of images, with the outcomes prompting a discussion on the size of the training data set. An automated in-house image processing algorithm is employed to quantify the void ratio and root volume ratio. This script enables post processing and image analysis of all 30 cases within few hours. This work investigates the effect of stratigraphy on root growth, along with the effect of image-segmentation parameters on soil constitutive properties. Full article

(This article belongs to the Special Issue Recent Advances in Image-Based Geotechnics)

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16 pages, 12889 KiB

Open AccessArticle

Characterisation of Single-Phase Fluid-Flow Heterogeneity Due to Localised Deformation in a Porous Rock Using Rapid Neutron Tomography

by Maddi Etxegarai, Erika Tudisco, Alessandro Tengattini, Gioacchino Viggiani, Nikolay Kardjilov and Stephen A. Hall

J. Imaging 2021, 7(12), 275; https://doi.org/10.3390/jimaging7120275 - 14 Dec 2021

Cited by 5 | Viewed by 2632

Abstract

The behaviour of subsurface-reservoir porous rocks is a central topic in the resource engineering industry and has relevant applications in hydrocarbon, water production, and CO

_{2}

sequestration. One of the key open issues is the effect of deformation on the hydraulic properties of [...] Read more.

The behaviour of subsurface-reservoir porous rocks is a central topic in the resource engineering industry and has relevant applications in hydrocarbon, water production, and CO

_{2}

sequestration. One of the key open issues is the effect of deformation on the hydraulic properties of the host rock and, specifically, in saturated environments. This paper presents a novel full-field data set describing the hydro-mechanical properties of porous geomaterials through in situ neutron and X-ray tomography. The use of high-performance neutron imaging facilities such as CONRAD-2 (Helmholtz-Zentrum Berlin) allows the tracking of the fluid front in saturated samples, making use of the differential neutron contrast between “normal” water and heavy water. To quantify the local hydro-mechanical coupling, we applied a number of existing image analysis algorithms and developed an array of bespoke methods to track the water front and calculate the 3D speed maps. The experimental campaign performed revealed that the pressure-driven flow speed decreases, in saturated samples, in the presence of pre-existing low porosity heterogeneities and compactant shear-bands. Furthermore, the observed complex mechanical behaviour of the samples and the associated fluid flow highlight the necessity for 3D imaging and analysis. Full article

(This article belongs to the Special Issue Recent Advances in Image-Based Geotechnics)

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29 pages, 44702 KiB

Open AccessArticle

Quantitative Evaluation of Soil Structure and Strain in Three Dimensions under Shear Using X-ray Computed Tomography Image Analysis

by Shintaro Nohara and Toshifumi Mukunoki

J. Imaging 2021, 7(11), 230; https://doi.org/10.3390/jimaging7110230 - 29 Oct 2021

Cited by 4 | Viewed by 2748

Abstract

The objective of this study is to quantitatively evaluate the soil structure behavior when under shear stress to understand the mechanism of shear zone formation using a micro-focus X-ray computed tomography (CT) scanner to visualize the internal samples without causing disturbance. A new [...] Read more.

The objective of this study is to quantitatively evaluate the soil structure behavior when under shear stress to understand the mechanism of shear zone formation using a micro-focus X-ray computed tomography (CT) scanner to visualize the internal samples without causing disturbance. A new image-analysis method was proposed to systematically evaluate the particle length and direction by fitting the particle as an ellipsoid. Subsequently, a direct shear experiment was conducted on soil materials, and shear band was scanned using a micro-focus X-ray CT scanner. After validating the proposed method, the soil structure was evaluated in the shear zone via image analysis on the CT images. Furthermore, the strain inside the specimen was evaluated using digital image correlation. The results showed that a partial change in the particle direction occurred when the volume expansion inside the shear zone exceeded the peak. In addition, the width of the shear zone was ~7.1 times the median grain size of the sand used; however, the region exhibiting a change in the direction of the particles was narrow and confined to the vicinity of the shear plane. Full article

(This article belongs to the Special Issue Recent Advances in Image-Based Geotechnics)

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