Publications
520 results found
Kazantsev D, Van Eyndhoven G, Lionheart WRB, et al., 2015, Employing temporal self-similarity across the entire time domain in computed tomography reconstruction, Philosophical Transactions of the Royal Society A: Mathematical, Physical & Engineering Sciences, Vol: 373, ISSN: 1364-503X
There are many cases where one needs to limit the X-ray dose, or the number of projections, or both, for high frame rate (fast) imaging. Normally, it improves temporal resolution but reduces the spatial resolution of the reconstructed data. Fortunately, the redundancy of information in the temporal domain can be employed to improve spatial resolution. In this paper, we propose a novel regularizer for iterative reconstruction of time-lapse computed tomography. The non-local penalty term is driven by the available prior information and employs all available temporal data to improve the spatial resolution of each individual time frame. A high-resolution prior image from the same or a different imaging modality is used to enhance edges which remain stationary throughout the acquisition time while dynamic features tend to be regularized spatially. Effective computational performance together with robust improvement in spatial and temporal resolution makes the proposed method a competitive tool to state-of-the-art techniques.
Lin Q, Neethling SJ, Dobson KJ, et al., 2015, Quantifying and minimising systematic and random errors in X-ray micro-tomography based volume measurements, COMPUTERS & GEOSCIENCES, Vol: 77, Pages: 1-7, ISSN: 0098-3004
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- Citations: 35
Cai B, Karagadde S, Rowley D, et al., 2015, Time-resolved synchrotron tomographic quantification of deformation-induced flow in a semi-solid equiaxed dendritic Al-Cu alloy, Scripta Materialia, Vol: 103, Pages: 69-72, ISSN: 1872-8456
The rheology of semi-solid alloys has been studied by a novel in situ tomographic technique. Via extruding an equiaxed Al–15 wt.%Cu alloy, theinhomogeneous coherent compression of the a-Al grains was quantified, including the interdendritic channel closure and formation of a liquid extrudate.This investigation not only provides important insights into the microstructural changes occurring during semi-solid deformation, but also offers a validation benchmark for segregation and rheological models.
Kazantsev D, Thompson WM, Lionheart WRB, et al., 2015, 4D-CT reconstruction with unified spatial-temporal patch-based regularization, Inverse Problems and Imaging, Vol: 9, Pages: 447-467, ISSN: 1930-8345
In this paper, we consider a limited data reconstruction problem for temporarily evolving computed tomography (CT), where some regions are static during the whole scan and some are dynamic (intensely or slowly changing). When motion occurs during a tomographic experiment one would like to minimize the number of projections used and reconstruct the image iteratively. To ensure stability of the iterative method spatial and temporal constraints are highly desirable. Here, we present a novel spatial-temporal regularization approach where all time frames are reconstructed collectively as a unified function of space and time. Our method has two main differences from the state-of-the-art spatial-temporal regularization methods. Firstly, all available temporal information is used to improve the spatial resolution of each time frame. Secondly, our method does not treat spatial and temporal penalty terms separately but rather unifies them in one regularization term. Additionally we optimize the temporal smoothing part of the method by considering the non-local patches which are most likely to belong to one intensity class. This modification significantly improves the signal-to-noise ratio of the reconstructed images and reduces computational time. The proposed approach is used in combination with golden ratio sampling of the projection data which allows one to find a better trade-off between temporal and spatial resolution scenarios.
Sercombe TB, Xu X, Challis VJ, et al., 2015, Failure modes in high strength and stiffness to weight scaffolds produced by Selective Laser Melting, MATERIALS & DESIGN, Vol: 67, Pages: 501-508, ISSN: 0264-1275
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- Citations: 66
Qiu C, Yue S, Adkins NJE, et al., 2015, Influence of processing conditions on strut structure and compressive properties of cellular lattice structures fabricated by selective laser melting, Materials Science and Engineering: A, Vol: 628, Pages: 188-197, ISSN: 0921-5093
Mostafavi M, Collins DM, Cai B, et al., 2015, Yield behavior beneath hardness indentations in ductile metals, measured by three-dimensional computed X-ray tomography and digital volume correlation, ACTA MATERIALIA, Vol: 82, Pages: 468-482, ISSN: 1359-6454
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- Citations: 58
Robinson JB, Engebretsen E, Brown LD, et al., 2015, Thermal gradients in solid oxide fuel cell anodes: X-ray diffraction, thermal imaging and model prediction, ECS Transactions, Vol: 68, Pages: 1053-1067, ISSN: 1938-5862
Thermal gradients can be induced within solid oxide fuel cells (SOFC) due to a range of design and operational considerations. These gradients coupled with the mismatched coefficient of thermal expansion between the anode and electrolyte layer can advance cell degradation and lead to cell failure. In this study a combined experimental and modelling approach is taken to investigate the effect of thermal gradients on the stresses within SOFC anodes. Experimental results obtained from investigations performed at Diamond Light Source using a concurrent X-ray diffraction and infrared thermal imaging approach are coupled with finite element analysis modelling to assess the impact of various parameters upon the cell. Operational considerations including cell polarisation and fuel flow configurations are examined to demonstrate the importance of optimization in minimising thermal gradients and subsequent stresses within the anode to prolong the lifetime of the cell whilst also maintaining the performance of the cell.
Seers TD, Hodgetts D, Andrew M, et al., 2015, From digital outcrops to digital rocks - Multiscale characterization of structural heterogeniety within porous sandstones, Pages: 4027-4031
Large scale faults are important structural elements within many conventional clastic reservoirs, acting as potential conduits, baffles or barriers to hydrocarbon or CO2 migration. Though inconspicuous within most seismic tomography datasets, smaller subsidiary faults, commonly within the damage zones of parent structures, may also play an important role. Within high porosity sandstones these smaller faults typically form through cataclasis (grain reorganisation, dilation, isovolumetric strain, grain fracturing and crushing), creating thin, tabular low permeability zones which serve to compartmentalize the reservoir. Though microfaults within high porosity sandstones are commonly assumed to adversely impact upon hydrocarbon production and CO2 injection, little is known about their volumetric properties at the continuum scale (esp. volumetric intensity), or the pore-scale processes which govern their capacity to trap mobile geofluids. In this paper, we seek to address these uncertainties, using a novel outcrop constrained discrete fracture network modelling code to obtain estimates of fault volumetric intensity, and employing high pressure-temperature synchrotron tomography to resolve pore-scale multiphase flow across a single cataclastic fault. The coupled studies indicate that whilst fault rocks may form a major fraction of a given rock mass, the presence of intra-fault capillary heterogeneity may significantly reduce their capacity to restrict the migration of geofluids.
Archilha NL, Missagia RM, Hollis C, et al., 2015, 3D experimental investigation of velocity-permeability controlling factors in carbonates rocks, Pages: 3000-3004, ISSN: 1052-3812
Pore geometrical parameters derived from digital image analysis (DIA) have recently been used to improve permeability and velocity versus porosity predictions (e.g. Weger et al., 2009). Despite a great improvement had been observed, no spatial information of the pore structure was considered from 2D dataset analyzes. Here, we link pore space parameters from 3D images to experimental physical properties of carbonate rocks to improve permeability and velocity predictions. Results show that applying a combination of porosity, pore size and 3D geometrical parameters to permeability and velocity significantly improves the adjusted coefficient of determination. These results reflect a pore size and geometrical control of velocity and permeability prediction.
Taiwo OO, Eastwood DS, Lee PD, et al., 2015, In-situ examination of microstructural changes within a lithium-ion battery electrode using synchrotron x-ray microtomography, Pages: 81-85, ISSN: 1938-6737
In this work, we use synchrotron X-ray microtomographic imaging to examine in-situ changes in a silicon / lithium half-cell before and after lithiation. We visualize volume expansion within the silicon electrode matrix and active particle fracturing as a result of the lithiation process. A change in volume fraction of silicon with respect to electrode state-of-charge was also characterized.
Prasad A, Yuan L, Lee PD, et al., 2015, On the solute diffusion length in the interdependence model: Dendritic versus non-dendritic interface, Pages: 461-467, ISSN: 0255-5476
The Interdependence model currently uses an analytical expression for a moving planar interface to calculate the solute diffusion length designated as x’dl in the model. Upon nucleation within an alloy melt (i.e. when the solid embryo starts to grow), the interface grows with a spherical front which then breaks down into a dendritic interface. The time required for this breakdown is a subject for separate research. In this paper, we explore the validity of using a planar interface in the early stages of nucleation and growth of metal alloys as used in the Interdependence model. The diffusion field ahead of a planar interface, in theory, has an exponentially changing composition of infinite length. In the Interdependence model, x’dl is assumed to be where this exponentially decreasing composition profile in the liquid ahead of the interface (for k < 1) reduces to within 1% of a quantity proportional to the nominal alloy composition, C0, far from the interface. A numerical solidification model, µMatIC, is used to simulate the growth of a single grain with a dendritic interface in 2D and 3D. The numerical model is capable of generating the solute profile ahead of the growing grain which is used to evaluate the solute diffusion length that can be compared with the results obtained from the planar interface model. The comparisons were made with both 1% and 0.1% cut-off criteria. The results indicate that the 1% assumption being used in the planar front diffusion length calculation is a good approximation for the Interdependence model.
Eastwood DS, Bayley PM, Chang HJ, et al., 2015, Three-dimensional characterization of electrodeposited lithium microstructures using synchrotron X-ray phase contrast imaging, CHEMICAL COMMUNICATIONS, Vol: 51, Pages: 266-268, ISSN: 1359-7345
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- Citations: 104
Cai B, Karagadde S, Marrow TJ, et al., 2015, Synchrotron X-ray Tomographic Quantification of Deformation Induced Strain Localisation in Semi-solid Al-15wt.% Cu, 14th International Conference on Modeling of Casting, Welding and Advanced Solidification Processes (MCWASP), Publisher: IOP PUBLISHING LTD, ISSN: 1757-8981
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- Citations: 4
Zhang Z, Yuan L, Lee PD, et al., 2014, Modeling of time dependent localized flow shear stress and its impact on cellular growth within additive manufactured titanium implants, Journal of Biomedical Materials Research Part B-Applied Biomaterials, Vol: 102B, Pages: 1689-1699, ISSN: 1552-4973
Bone augmentation implants are porous to allowcellular growth, bone formation and fixation. However, thedesign of the pores is currently based on simple empiricalrules, such as minimum pore and interconnects sizes. Wepresent a three-dimensional (3D) transient model of cellulargrowth based on the Navier–Stokes equations that simulatesthe body fluid flow and stimulation of bone precursor cellulargrowth, attachment, and proliferation as a function of localflow shear stress. The model’s effectiveness is demonstratedfor two additive manufactured (AM) titanium scaffold architectures.The results demonstrate that there is a complex interactionof flow rate and strut architecture, resulting in partiallyrandomized structures having a preferential impact on stimulatingcell migration in 3D porous structures for higher flowrates. This novel result demonstrates the potential newinsights that can be gained via the modeling tool developed,and how the model can be used to perform what-if simulationsto design AM structures to specific functional requirements
Betts C, Balint D, Lee J, et al., 2014, In situ microtensile testing and X-ray microtomography-based finite element modelling of open-cell metal foam struts and sandwich panels, JOURNAL OF STRAIN ANALYSIS FOR ENGINEERING DESIGN, Vol: 49, Pages: 592-606, ISSN: 0309-3247
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- Citations: 9
Kim TB, Yue S, Zhang Z, et al., 2014, Additive manufactured porous titanium structures: Through-process quantification of pore and strut networks, JOURNAL OF MATERIALS PROCESSING TECHNOLOGY, Vol: 214, Pages: 2706-2715, ISSN: 0924-0136
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- Citations: 96
Hughes AE, Trinchi A, Chen FF, et al., 2014, The application of multiscale quasi 4D CT to the study of SrCrO<sub>4</sub> distributions and the development of porous networks in epoxy-based primer coatings, PROGRESS IN ORGANIC COATINGS, Vol: 77, Pages: 1946-1956, ISSN: 0300-9440
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- Citations: 24
Karagadde S, Yuan L, Shevchenko N, et al., 2014, 3-D microstructural model of freckle formation validated using in situ experiments, ACTA MATERIALIA, Vol: 79, Pages: 168-180, ISSN: 1359-6454
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- Citations: 93
Puncreobutr C, Phillion AB, Fife JL, et al., 2014, In situ quantification of the nucleation and growth of Fe-rich intermetallics during Al alloy solidification, ACTA MATERIALIA, Vol: 79, Pages: 292-303, ISSN: 1359-6454
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- Citations: 82
Kareh KM, Lee PD, Atwood RC, et al., 2014, Pore behaviour during semi-solid alloy compression: Insights into defect creation under pressure, SCRIPTA MATERIALIA, Vol: 89, Pages: 73-76, ISSN: 1359-6462
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- Citations: 13
, 2014, Additions and corrections for Journal of Materials Chemistry B published 11th November 2013 to 10th June 2014., J Mater Chem B, Vol: 2, Pages: 5478-5479
Cai B, Karagadde S, Yuan L, et al., 2014, In situ synchrotron tomographic quantification of granular and intragranular deformation during semi-solid compression of an equiaxed dendritic Al-Cu alloy, ACTA MATERIALIA, Vol: 76, Pages: 371-380, ISSN: 1359-6454
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- Citations: 71
Robinson JB, Brown LD, Jervis R, et al., 2014, A novel high-temperature furnace for combined <i>in situ</i> synchrotron X-ray diffraction and infrared thermal imaging to investigate the effects of thermal gradients upon the structure of ceramic materials, JOURNAL OF SYNCHROTRON RADIATION, Vol: 21, Pages: 1134-1139, ISSN: 0909-0495
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- Citations: 7
Kazantsev D, Lionheart WR, Withers PJ, et al., 2014, Multimodal Image Reconstruction Using Supplementary Structural Information in Total Variation Regularization., Sensing and Imaging, Vol: 15, ISSN: 1557-2064
In this paper, we propose an iterative reconstruction algorithm which uses available information from one dataset collected using one modality to increase the resolution and signal-to-noise ratio of one collected by another modality. The method operates on the structural information only which increases its suitability across various applications. Consequently, the main aim of this method is to exploit available supplementary data within the regularization framework. The source of primary and supplementary datasets can be acquired using complementary imaging modes where different types of information are obtained (e.g. in medical imaging: anatomical and functional). It is shown by extracting structural information from the supplementary image (direction of level sets) one can enhance the resolution of the other image. Notably, the method enhances edges that are common to both images while not suppressing features that show high contrast in the primary image alone. In our iterative algorithm we use available structural information within a modified total variation penalty term. We provide numerical experiments to show the advantages and feasibility of the proposed technique in comparison to other methods.
Hughes AE, Trinchi A, Chen FF, et al., 2014, Revelation of Intertwining Organic and Inorganic Fractal Structures in Polymer Coatings, ADVANCED MATERIALS, Vol: 26, Pages: 4504-+, ISSN: 0935-9648
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- Citations: 29
Kareh KM, Lee PD, Atwood RC, et al., 2014, Revealing the micromechanisms behind semi-solid metal deformation with time-resolved X-ray tomography, Nature Communications, Vol: 5, Pages: 1-7, ISSN: 2041-1723
The behaviour of granular solid–liquid mixtures is key when deforming a wide range of materials from cornstarch slurries to soils, rock and magma flows. Here we demonstrate that treating semi-solid alloys as a granular fluid is critical to understanding flow behaviour and defect formation during casting. Using synchrotron X-ray tomography, we directly measure the discrete grain response during uniaxial compression. We show that the stress–strain response at 64–93% solid is due to the shear-induced dilation of discrete rearranging grains. This leads to the counter-intuitive result that, in unfed samples, compression can open internal pores and draw the free surface into the liquid, resulting in cracking. A soil mechanics approach shows that, irrespective of initial solid fraction, the solid packing density moves towards a constant value during deformation, consistent with the existence of a critical state in mushy alloys analogous to soils.
Staines KA, Parker S, Poulet B, et al., 2014, STR/Ort mice exhibit an endochondral growth deficit which may underpin their osteoarthritis, Autumn Meeting of the British-Society-for-Matrix-Biology, Publisher: WILEY-BLACKWELL, Pages: A30-A30, ISSN: 0959-9673
Kazantsev D, Ourselin S, Hutton BF, et al., 2014, A novel technique to incorporate structural prior information into multi-modal tomographic reconstruction, INVERSE PROBLEMS, Vol: 30, ISSN: 0266-5611
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- Citations: 18
Evans LM, Margetts L, Casalegno V, et al., 2014, Thermal characterisation of ceramic/metal joining techniques for fusion applications using X-ray tomography, FUSION ENGINEERING AND DESIGN, Vol: 89, Pages: 826-836, ISSN: 0920-3796
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- Citations: 13
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