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A geometric method for analysis of elastic and elastic-plastic solids is proposed. It involves operators on naturally discrete domains representing a material’s microstructure, rather than the classical discretisation of domains for solving continuum boundary value problems. Discrete microstructures are considered as general cell complexes, which are circumcentre-dual to simplicial cell complexes. The proposed method uses the separation of the total deformation energy into volumetric and distortional parts as a base for introducing elastoplastic material behaviour. Volumetric parts are obtained directly from volume changes of dual cells, and the distortional parts are calculated from the distance changes between primal and dual nodes. First, it is demonstrated that the method can accurately reproduce the elastic behaviour of solids with Poisson’s ratios in the thermodynamically admissible range from -0.99 to 0.49. Further verification of the method is demonstrated by excellent agreement between analytical results and simulations of the elastic deformation of a beam subjected to a vertical displacement. Second, the Prandtl operator approach is used to simulate the behaviour of the solid during cyclic loading, considering its elastoplastic material properties. Results from simulations of cyclic behaviour during alternating and variable load histories are compared to expected macroscopic behaviour as further support to the applicability of the method to elastic-plastic problems.

Purpose of Review This paper assesses social science research relating to BECCS and considers the applicability of research on CCS to BECCS. Recent Findings In recent years, social science research on CCS and BECCS has gone beyond an evaluation of public acceptance to provide a more nuanced analysis of the wider social political, ethical, and governance contexts in which large-scale deployment might be achieved. This raises issues at global, local, and regional scales, requiring a wide array of methods and approaches. Summary Awareness of the scale and urgency needed to act on climate change is growing and the role of BECCS in delivering carbon dioxide removal forms a central argument for the use of this family of technologies. Here, framing becomes a critical factor in how society responds to BECCS technologies and we argue that making the case for BECCS as a means of extending mitigation to make a ‘net zero’ goal achievable could be the key to its acceptable and sustainable deployment.

A semi-submersible wind platform with four floats of equal diameter, damping plates and relatively small drafts has been designed to support a 5 MW wind turbine at full scale. Motion and mooring forces from wave basin measurements have been compared with time domain linear diffraction modelling accounting for drag forces, mooring forces and mean forces due to zero-difference frequency components, as is standard, and due to damping associated with radiation and drag forces, not previously considered. The platform response in the form of rms acceleration is quite well predicted although peak values can be underestimated. The mean mooring forces are underestimated and peak values are considerably underestimated. In large waves moorings experience high snatch loads. The measured mean forces were applied in the model for further comparison. The mooring was primarily designed to prevent drift of the floater and improved designs could eliminate or reduce snatch loads. However, it is shown that hub acceleration is quite moderate, with peak values less than 4 m/s2 in even the largest waves. The rms platform acceleration is largely decoupled from the mooring forces, as shown by corresponding spectra. In extreme conditions hydrodynamic mooring forces require nonlinear effects due to steep, sometimes breaking, waves to be accounted for. The wind thrust is included in the model using a coefficient from blade element momentum theory based on relative wind velocity. The peak hydrodynamic force would be significantly larger than the maximum wind thrust although the mean hydrodynamic force is significantly smaller. A practical conclusion is that a semi-sub floater with damping plates giving sufficiently low accelerations for operation in large waves may be of relatively shallow draft, less than the depths of many ports which is convenient for deployment.

This work describes a local approach to cleavage fracture (LAF) incorporating the statistics of microcracks to characterize the cleavage fracture toughness distribution in structural steels. Fracture toughness testing conducted on standard compact tension C(T) specimens for a 22NiMoCr37 pressure vessel steel provides the cleavage fracture resistance data needed to determine the measured toughness distribution. Metallographic examination of etched surfaces for the tested steel also provides the distribution of carbides, which are assumed as the Griffith fracture-initiating particles, dispersed in the material from which the cleavage fracture toughness distribution is predicted. Overall, the analyses conducted in the present work show that LAFs incorporating the statistics of microcracks are a viable engineering procedure to describe the dependence of fracture toughness on temperature in the DBT region for ferritic steels.

Graphite is a candidate material for Generation IV concepts and is used as a moderator in Advanced Gas-cooled Reactors (AGR) in the UK. Spatial material variability is present within billets causing different material property values between different components. Variations in material properties and irradiation effects can produce stress concentrations and diverse mechanical responses in a nuclear reactor graphite core. In order to characterise the material variability, geostatistical techniques called variography and random field theory were adapted for studying the density and Young's modulus of a billet of Gilsocarbon and NBG-18 graphite grades. Variography is a technique for estimating the distance over which material property values have significant spatial correlation, known as the scale of fluctuation or spatial correlation length. The paper uses random field theory to create models that mimic the original spatial and statistical distributions of the original data set. This study found different values of correlation length for density and Young's modulus around the edges of a Gilsocarbon billet, while in the case of NBG-18, similar correlation lengths where found across the billet. Examples of several random fields are given to reproduce the spatial patterns and values found in the original data.

© 2019 The Royal Society of Chemistry. High electrostrain and breakdown strength (1 - x)BiFeO3-0.3BaTiO3-xNd(Li0.5Nb0.5)O3 (BF-BT-xNLN) ceramics were studied by in situ synchrotron X-ray diffraction (XRD) in combination with Rietveld refinement and conventional transmission electron microscopy. At zero field, compositions transformed from majority ferroelectric rhombohedral to pseudocubic as the NLN concentration increased, with 0.27% strain achieved at 60 kV cm-1 for x = 0.01. The large measured macroscopic strain was commensurate with peak shifting in XRD peak profiles, yielding 0.6% total strain at 150 kV cm-1. Strain anisotropy of ϵ200 > ϵ220 > ϵ111 was observed but despite the large applied field, no peak splitting was detected. We therefore concluded that the large electrostrain is not achieved through a conventional relaxor to field induced long-range ferroelectric transition. Instead, the data supports a model where local polar regions distort in the direction of the applied field within multiple local symmetries (pseudosymmetry) without long range correlation. We proposed that pseudosymmetry is maintained in BF-BT-xNLN even at high field (150 kV cm-1) due to the large ion radii mismatch and competing ionic/covalent bonding between Ba2+ and Bi3+ ions.

Distinctive structure-property relationships are revealed in the relaxor ferroelectric ceramic solid solution, (1-x)K0.5Bi0.5TiO3 - xBiMg0.5Ti0.5O3: 0.02 < x < 0.08. The constructed phase diagram and results of in-situ synchrotron X-ray diffraction provide explanations for temperature and electric field dependent anomalies in dielectric, ferroelectric and electromechanical properties. At room temperature a mixed phase tetragonal and pseudocubic phase field occurs for compositions 0 > x ≤ 0.07. As temperature rises to ≥ 150 °C, the ferroelectric tetragonal relaxor phase changes to a pseudocubic ergodic relaxor phase; this change in length scale of polar order is responsible for an inflection in relative permittivity - temperature plots. The transition is reversed by a sufficient electric field, thereby explaining the constricted form of polarisation-electric field loops measured at >150°C. It is also responsible for a change in slope of the strain-electric field (S-E) plots which are relatively linear in the ferroelectric regime i.e. at temperatures up to 150 °C, giving unipolar strains of 0.11 % at 20 °C and 0.14% at 150 °C (50 kV cm-1 field). The additional contribution from the effect of the field-induced pseudocubic to tetragonal transition, generates strains of ∼ 0.2 % at 185 °C. Unusual for a piezoelectric solid solution, the maximum strains and charge coefficients (d33 =150 pC N-1, 20 °C) do not coincide with a morphotropic or polymorphic phase boundary.

The response and power capture of the multi-float wave energy converter M4 has been shown to be approximately predicted by linear diffraction-radiation modelling, giving relatively high capture widths. In this study we model a 6-float configuration which has been investigated experimentally in irregular waves and take account of the mooring system. Second-order mean forces are included due to excitation forces as is standard, but also due to the rate of energy extraction from mechanical damping and radiation damping resulting from body motion. There are also second order effects due to coupling between heave and surge. Operational conditions with mechanical damping and extreme conditions without mechanical damping (giving worst case response) are investigated. The motion is almost independent of mooring forces from a single point mooring, known as slack-moored. In operational conditions mean mooring forces are in approximate agreement with experiment except for larger periods and peak forces are similar. For extreme waves large rotational response is predicted reasonably by linear diffraction-radiation modelling with a small representative drag coefficient, as is horizontal acceleration, although peak values may be underestimated for the largest wave heights. However mean mooring forces are markedly underestimated and peak values generally overestimated. The overall conclusion is that linear modelling gives reasonable prediction of response in all wave conditions, and power capture when operational, but resulting second order mean forces only give approximate predictions for smaller wave heights.

Bioenergy is given an important role in reaching national and international climate change targets. However, uncertainties relating to emission reductions and the timeframe for these reductions are increasingly recognised as challenges whether bioenergy can deliver the required reductions. This paper discusses and highlights the challenges and the importance of the real greenhouse gas (GHG) reduction potential of bioenergy systems and its relevance for a global 450 ppm CO2e stabilisation target in terms of uncertainties and temporal aspects. The authors aim to raise awareness and emphasise the need for dynamic and consequential approaches for the evaluation of climate change impacts of bioenergy systems to capture the complexity and challenges of their real emission reduction potential within a 2 °C target. This review does not present new research results. This paper shows the variety of challenges and complexity of the problem of achieving real GHG emission reductions from bioenergy systems. By reflecting on current evaluation methods of emissions and impacts from bioenergy systems, this review points out that a rethinking and going beyond static approaches is required, considering each bioenergy systems according to its own characteristics, context and feedbacks. With the development of knowledge and continuously changing systems, policies should be designed in a way that they provide a balance between flexibility to adapt to new information and planning security for investors. These will then allow considering if a bioenergy system will deliver the required emission saving in the appropriate timeframe or not.