Applicability of offshore mooring and foundation technologies for marine renewable energy (MRE) device arrays

Published onlineThe marine renewable energy (MRE) sector is progressing from single device units to device arrays. Currently, the mooring/foundation technologies used in MRE are based on offshore oil/gas industry practices. For MRE arrays to reach commercialization, several issues need to be addressed including the hy-drodynamic array layout, electrical infrastructure, operations, maintenance, control, moorings, foundations, installation and logistics. The DTOcean (The Optimal Design Tools for Ocean Energy Arrays) project is aimed at accelerating the industrial development of ocean energy power generation knowledge, and providing design tools for deploying the first generation of wave and tidal energy converter arrays. In this paper, the ap-plicability of offshore mooring/foundation technologies for marine renewable energy (MRE) device arrays are assessed. The paper introduces the criteria which can be used to appraise technologies and approaches rele-vant to MRE devices. Existing mooring/foundation technologies used in the offshore industry are summarized with examples given of MRE device deployments. The guidance from certification agencies which is used for the design and analysis of mooring/foundation systems is summarized. If not addressed, the failure to opti-mize the design of ocean energy arrays and failure to properly understand economic, environmental, or relia-bility impacts of individual components could have significant consequences for the overall project and sec-tor. The function and type of mooring and/or foundation system are determined by a number of factors including the cost, site characteristics, expected environmental loading and environmental or legislative con-straints and these factors are discussed

Cell cycle regulation of proliferation versus differentiation in the central nervous system

Formation of the central nervous system requires a period of extensive progenitor cell proliferation, accompanied or closely followed by differentiation; the balance between these two processes in various regions of the central nervous system gives rise to differential growth and cellular diversity. The correlation between cell cycle lengthening and differentiation has been reported across several types of cell lineage and from diverse model organisms, both in vivo and in vitro. Furthermore, different cell fates might be determined during different phases of the preceding cell cycle, indicating direct cell cycle influences on both early lineage commitment and terminal cell fate decisions. Significant advances have been made in the last decade and have revealed multi-directional interactions between the molecular machinery regulating the processes of cell proliferation and neuronal differentiation. Here, we first introduce the modes of proliferation in neural progenitor cells and summarise evidence linking cell cycle length and neuronal differentiation. Second, we describe the manner in which components of the cell cycle machinery can have additional and, sometimes, cell-cycle-independent roles in directly regulating neurogenesis. Finally, we discuss the way that differentiation factors, such as proneural bHLH proteins, can promote either progenitor maintenance or differentiation according to the cellular environment. These intricate connections contribute to precise coordination and the ultimate division versus differentiation decision

Size of supernumerary teats in sheep correlates with complexity of the anatomy and microenvironment.

Supernumerary nipples or teats (polythelia) are congenital accessory structures that may develop at any location along the milk line and have been implicated in the pathogenesis of mastitis. We describe the anatomy and histology of 27 spontaneously occurring supernumerary teats from 16 sheep, delineating two groups of teats - simple and anatomically complex - according to the complexity of the anatomy and microenvironment. Anatomically complex supernumerary teats exhibited significantly increased length and barrel diameter compared with simple supernumerary teats. A teat canal and/or teat cistern was present in anatomically complex teats, with smooth muscle fibres forming a variably well-organised encircling teat sphincter. Complex supernumerary teats also exhibited immune cell infiltrates similar to those of normal teats, including lymphoid follicle-like structures at the folds of the teat cistern-teat canal junction, and macrophages that infiltrated the peri-cisternal glandular tissue. One complex supernumerary teat exhibited teat end hyperkeratosis. These anatomical and histological features allow inference that supernumerary teats may be susceptible to bacterial ingress through the teat canal and we hypothesise that this may be more likely in those teats with less well-organised encircling smooth muscle. The teat cistern of anatomically complex teats may also constitute a focus of milk accumulation and thus a possible nidus for bacterial infection, potentially predisposing to mastitis. We suggest that size of the supernumerary teat, and relationship to the main teats, particularly in the case of 'cluster teats', should be considerations if surgical removal is contemplated.British Veterinary Association Animal Welfare Foundation (BVA AWF) Norman Hayward Fun

Specific requirements for MRE foundation analysis

PublishedMarine Renewable Energy (MRE) systems involve single or arrays of devices that are secured to the seafloor via foundations and/or anchors. These MRE devices will transmit long-term cyclic loads to the seafloor sediment or rock, which may affect seafloor material properties and hence the overall physical performance of the MRE system. The response of seafloor sediments or rock formations is uncertain for the novel MRE systems and especially large arrays of 10s to >1000s of devices. This report summarizes critical inputs and tools for the design and analysis of foundations, anchors, and the response of the seafloor materials. Followed by an introduction in Section 1, Section 2 reviews the offshore structure and MRE literature to highlight current approaches and needed inputs for assessing interactions between foundations or anchors and seafloor materials, including potential environmental impacts. Section 3 addresses relevant marine geological settings that control key geotechnical engineering properties. Data collection activities are described, including in-situ site surveys and laboratory testing. Section 4 considers the unique interactions between MRE systems and seafloor materials, particularly cyclic loading and sediment response. Section 5 describes analytical and numerical tools and associated inputs for the design process of MRE foundations and anchors. Constitutive models are key to simulating sediment response and thus are discussed in detail. Important summary tables relate key variables of geology, geotechnical parameters, foundation or anchor type, and quantitative assessment tools including numerical analysis. Section 5 also addresses the incorporation of the geotechnical analysis into system-level tools to support decision making for MRE arrays. Section 6 presents conclusions and recommendations for future work.European Commission’s 7th Framework; Grant agreement number: 60859

Verification of a Rapid Mooring and Foundation Design Tool

This is the author accepted manuscript. The final version is available from SAGE Publications via the DOI in this record.Marine Renewable Energy (MRE) devices require mooring and foundation systems that are suitable in terms of device operation, are robust and also cost effective. In the initial stages of mooring and foundation development a large number of possible configuration permutations exist. Filtering of unsuitable designs is possible using information specific to the deployment site (i.e. bathymetry, environmental conditions) and device (i.e. mooring and/or foundation system role and cable connection requirements). The identification of a final solution requires detailed analysis, which includes load cases based on extreme environmental statistics following certification guidance processes. Static and/or quasi-static modelling of the mooring and/or foundation system serves as an intermediate design filtering stage enabling dynamic time-domain analysis to be focused on a small number of potential configurations. Mooring and foundation design is therefore reliant on logical decision making throughout this stage-gate process. The open-source DTOcean (Optimal Design Tools for Ocean Energy Arrays) Tool includes a Mooring and Foundation (MF) module, which automates the configuration selection process for fixed and floating wave and tidal energy devices. As far as the authors are aware this is one of the first tools to be developed for the purpose of identifying potential solutions during the initial stages of MRE design. Whilst the MF module does not replace a full design assessment, it provides in addition to suitable configuration solutions, assessments in terms of reliability, economics and environmental impact. This paper provides insight into the solution identification approach used by the module and features the verification of both the mooring system calculations and the foundation design using commercial software. Several case studies are investigated; a floating wave energy converter and several anchoring systems. It is demonstrated that the MF module is able to provide device and/or site developers with rapid mooring and foundation design solutions to appropriate design criteria.S.D. Weller, J. Hardwick, N. Mclean and L. Johanning were funded from the European Community's Seventh Framework Programme for DTOcean Project, Grant agreement number: 608597. S. Gomez, J. Heath, R. Jensen, and J. Roberts were funded by the Department of Energy’s (DOE) Energy Efficiency and Renewable Energy (EERE) Program’s Wind and Water Power Technologies Office. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND Number: 2013-6867

Bifurcations and chaos in semiconductor superlattices with a tilted magnetic field

We study the effects of dissipation on electron transport in a semiconductor superlattice with an applied bias voltage and a magnetic field that is tilted relative to the superlattice axis.In previous work, we showed that although the applied fields are stationary,they act like a THz plane wave, which strongly couples the Bloch and cyclotron motion of electrons within the lowest miniband. As a consequence,the electrons exhibit a unique type of Hamiltonian chaos, which creates an intricate mesh of conduction channels (a stochastic web) in phase space, leading to a large resonant increase in the current flow at critical values of the applied voltage. This phase-space patterning provides a sensitive mechanism for controlling electrical resistance. In this paper, we investigate the effects of dissipation on the electron dynamics by modifying the semiclassical equations of motion to include a linear damping term. We demonstrate that even in the presence of dissipation,deterministic chaos plays an important role in the electron transport process. We identify mechanisms for the onset of chaos and explore the associated sequence of bifurcations in the electron trajectories. When the Bloch and cyclotron frequencies are commensurate, complex multistability phenomena occur in the system. In particular, for fixed values of the control parameters several distinct stable regimes can coexist, each corresponding to different initial conditions. We show that this multistability has clear, experimentally-observable, signatures in the electron transport characteristics.Comment: 14 pages 11 figure

Magnetic resonance diffusion tensor microimaging reveals a role for Bcl-x in brain development and homeostasis

A new technique based on diffusion tensor imaging and computational neuroanatomy was developed to efficiently and quantitatively characterize the three- dimensional morphology of the developing brains. The technique was used to analyze the phenotype of conditional Bcl-x knock-out mice, in which the bcl-x gene was deleted specifically in neurons of the cerebral cortex and hippocampus beginning at embryonic day 13.5 as cells became postmitotic. Affected brain regions and associated axonal tracts showed severe atrophy in adult Bcl-x-deficient mice. Longitudinal studies revealed that these phenotypes are established by regressive processes that occur primarily during the first postnatal week, whereas neurogenesis and migration showed no obvious abnormality during embryonic stages. Specific families of white matter tracts that once formed normally during the embryonic stages underwent dramatic degeneration postnatally. Thus, this technique serves as a powerful tool to efficiently localize temporal and spatial manifestation of morphological phenotype

Plasticity and Damage Modeling of Stress Asymmetry and Dynamic Behavior of AFS Additive Manufactured Aluminum Alloy 2219

The Solid State Additive Manufacturing (AM) process referred as MELD that fabricated the samples in this study, provides a new path for repairing, coating, joining and additive manufacturing metals and metal matrix composites. This research will be the first application of a physics-based microstructure dependent internal state variable (ISV) plasticity and damage material model to capture the mechanical response of an AM Aluminum Alloy (AA) 2219 via the MELD process. In this research, a microstructure-based internal state variable (ISV) plasticity-damage model was used to capture the mechanical behavior of AFS 2219 aluminum alloy. Aeroprobe Corporation, creator and patent holder for the MELD process, fabricated the material by pushing a solid filler rod of AA2219-T861 material through a hollow rotating tool onto an AA2219 T851 plate substrate. As feedstock, solid or powder precursor metals are pushed through a nonconsumable rotating cylindrical tool. Herein, added layers are deposited and metallurgically bonded to substrate material or previously deposited layers by the heat generated from the rotating tool through plastic deformation of the filler material. Once a layer has been added, the tool height increases, and starts the deposition of the next layer. This process results in beneficial properties such as grain refinement, homogenization and reduced porosity (fully dense). This process will experience temperatures similar to those in the weld nugget zone (WNZ) in friction stir welding (FSW), ranging from 0.6-0.9 Tm, with Tm being the melting point of the material. MELD is highly scalable with AA deposition rates reaching over 1000 cm3/hr, which allows for MELD being used for repairs, coatings, and building components. A motivating factor driving the research for physics-based history dependent material modeling of MELD components is the ability to accurately capture the stress-state and strain rate dependence in the material caused by variations in material microstructure from the MELD processing of new or repaired components. The ISV model incorporates microstructural content and is consistent with continuum level kinematics, kinetics, and thermodynamics. These features allow the ISV model to capture large deformations at the structural scale using the kinematic and isotropic hardening, while microscale damage is obtained from the microstructural features. The benefits of the ISV model arise from the inclusion of structure-property relationships identified from microstructural characterization and experimentation. The Bauschinger effect (BE) is an important concept, vital in the accurate prediction of cyclic stress-strain response of ductile materials such as metals. The ISV model has been successfully used to capture the behavior and damage, and the BE of different aluminum alloys and steels. The ISV model uses kinematic and isotropic hardening to help capture deformations of the material at the macro scale. To understand this hardening relationship, calculating the kinematic and isotropic hardening relationship in the material is warranted for a high-fidelity model. Electron Backscattered Diffraction (EBSD) was used to characterize the as-fabricated microstructure, where a fully-dense equiaxed grain morphology with average grain size of 2.5 m was observed. Microhardness mapping of the as-built structures, monotonic tension and compression experiments at both quasi-static (0.001/s) strain rates, tension-followed-by-compression and compression-followed-by-tension experiments were performed to obtain the set of plasticity and damage constants necessary to capture strain rate and stress state behavior of this additive material. To calibrate the plasticity-damage model, a single set of constants were determined to capture the different stress states the MELD AA2219. One set of the constants was determined from experimental true stress-strain curves for the tension and compression data. Additionally, microstructural information and data from the open literature were used as the other model constants. This research is a first of its kind for AFS AA2219, includes correlating the ISV model to the monotonic experimental results that capture the isotropic and kinematic plasticity mechanical response