Offshore reliability approach for floating renewable energy devices

30th International Conference on Ocean, Offshore and Arctic Engineering, Rotterdam, The Netherlands, 19 – 24 June 2011The viability and success of Marine Renewable Energy installations is strongly dependent on the reliability of devices as this determines the amount of generated electricity and the cost for operation and maintenance. Reliability testing of critical components could mitigate these difficulties and provide device developers with a possibility to reveal early failures, gain information on lifetime criteria and provide project developers, investors and certification agencies with the required reliability demonstration and evidence of suitable risk control. The application of component reliability testing can reveal design weaknesses prior to deployment and establish necessary reliability and maintenance information. Components tested under service simulated conditions could be evaluated regarding performance, expected lifetime and subsequently be (cost-)optimised. Two test facilities that enable component reliability testing for marine renewable energy converters developed within the Peninsula Research Institute for Marine Renewable Energy (PRIMaRE) group at the University of Exeter are described. Those two facilities will allow measuring loads that are experienced in the field through prototype testing at the South Western Mooring Test Facility (SWMTF) and subsequently replicate those load conditions (or information from device developers) at the DMaC for accelerated reliability testing and design enhancement. The (SWMTF) is a unique mooring load and response test facility, at large scale in real sea condition and has been recently installed. The Dynamic Marine Component Test facility (DMaC) is capable to perform accelerated component testing under simulated in-service field conditions in four degree of freedom. This paper will describe the test facilities developed within the PRIMaRE group and discuss the approach of the group to mitigate risk for marine renewable energy installations. Furthermore load and response data from sea trial will be used to highlight the importance of this research activity.South West Regional Development Agency: PRIMaREEngineering and Physical Sciences Research Council (EPSRC) : SUPERGEN Marine Doctoral Programm

A comparative analysis of Simplified General Circulation Models of the atmosphere of Venus

Within the context of a working group supported by ISSI (Bern, Switzerland), we have made an intercomparison work between Global Circulation Models using simpli?ed parameterizations for radiative forcing and other physical processes. Even with similar schemes and parameters, the different GCMs produce different circulations, illustrating interesting differences between dynamical model cores

Asymmetric Fermi superfluid with different atomic species in a harmonic trap

We study the dilute fermion gas with pairing between two species and unequal concentrations in a harmonic trap using the mean field theory and the local density approximation. We found that the system can exhibit a superfluid shell structure sandwiched by the normal fermions. This superfluid shell structure occurs if the mass ratio is larger then certain critical value which increases from the weak-coupling BCS region to the strong-coupling BEC side. In the strong coupling BEC regime, the radii of superfluid phase are less sensitive to the mass ratios and are similar to the case of pairing with equal masses. However, the lighter leftover fermions are easier to mix with the superfluid core than the heavier ones. A partially polarized superfluid can be found if the majority fermions are lighter, whereas phase separation is still found if they are heavier.Comment: 12 pages, 7 figure

Pairing in spin polarized two-species fermionic mixtures with mass asymmetry

We discuss on the pairing mechanism of fermions with mismatch in their fermi momenta due to a mass asymmetry. Using a variational ansatz for the ground state we also discuss the BCS -BEC crossover of this system. It is shown that the breached pairing solution with a single fermi surface is stable in the BEC regime. We also include the temperatures effect on the fermion pairing within an approximation that is valid for temperatures much below the critical temperature.Comment: 8 pages and 6 figures, few typos corrected, version to appear in EPJ

Chronic viral infection promotes sustained Th1-derived immunoregulatory IL-10 via BLIMP-1

During the course of many chronic viral infections, the antiviral T cell response becomes attenuated through a process that is regulated in part by the host. While elevated expression of the immunosuppressive cytokine IL-10 is involved in the suppression of viral-specific T cell responses, the relevant cellular sources of IL-10, as well as the pathways responsible for IL-10 induction, remain unclear. In this study, we traced IL-10 production over the course of chronic lymphocytic choriomeningitis virus (LCMV) infection in an IL-10 reporter mouse line. Using this model, we demonstrated that virus-specific T cells with reduced inflammatory function, particularly Th1 cells, display elevated and sustained IL-10 expression during chronic LCMV infection. Furthermore, ablation of IL-10 from the T cell compartment partially restored T cell function and reduced viral loads in LCMV-infected animals. We found that viral persistence is needed for sustained IL-10 production by Th1 cells and that the transcription factor BLIMP-1 is required for IL-10 expression by Th1 cells. Restimulation of Th1 cells from LCMV-infected mice promoted BLIMP-1 and subsequent IL-10 expression, suggesting that constant antigen exposure likely induces the BLIMP-1/IL-10 pathway during chronic viral infection. Together, these data indicate that effector T cells self-limit their responsiveness during persistent viral infection via an IL-10-dependent negative feedback loop.This work was supported by an Australian NHMRC Overseas Biomedical Postdoctoral Fellowship (to I.A. Parish); a Yale School of Medicine Brown-Coxe Postdoctoral Fellowship (to I.A. Parish); the Alexander von Humboldt Foundation (SKA2010, to P.A. Lang); a CIHR grant (to P.S. Ohashi); and by the Howard Hughes Medical Institute and NIH grant RO1AI074699 (to S.M. Kaech). P.S. Ohashi holds a Canada Research Chair in Autoimmunity and Tumor immunity

Fulde-Ferrell-Larkin-Ovchinnikov states in one-dimensional spin-polarized ultracold atomic Fermi gases

We present a systematic study of quantum phases in a one-dimensional spin-polarized Fermi gas. Three comparative theoretical methods are used to explore the phase diagram at zero temperature: the mean-field theory with either an order parameter in a single-plane-wave form or a self-consistently determined order parameter using the Bogoliubov-de Gennes equations, as well as the exact soluble Bethe ansatz method. We find that a spatially inhomogeneous Fulde-Ferrell-Larkin-Ovchinnikov phase, which lies between the fully paired BCS state and the fully polarized normal state, dominates most of the phase diagram of a uniform gas. The phase transition from the BCS state to the Fulde-Ferrell-Larkin-Ovchinnikov phase is of second order, and therefore there are no phase separation states in one-dimensional homogeneous polarized gases. This is in sharp contrast to the three-dimensional situation, where a phase separation regime is predicted to occupy a very large space in the phase diagram. We conjecture that the prediction of the dominance of the phase separation phases in three dimension could be an artifact of the non-self-consistent mean-field approximation, which is heavily used in the study of three-dimensional polarized Fermi gases. We consider also the effect of a harmonic trapping potential on the phase diagram, and find that in this case the trap generally leads to phase separation, in accord with the experimental observations for a trapped gas in three dimension. We finally investigate the local fermionic density of states of the Fulde-Ferrell-Larkin-Ovchinnikov ansatz. A two-energy-gap structure is shown up, which could be used as an experimental probe of the Fulde-Ferrell-Larkin-Ovchinnikov states.Comment: 22 papes, 19 figure

p-wave phase shift and scattering length of 6^6Li

We have calculated the p-wave phase shifts and scattering length of $^6$Li. For this we solve the $p$ partial wave Schr\"odinger equation and analyze the validity of adopting the semiclassical solution to evaluate the constant factors in the solution. Unlike in the $s$ wave case, the semiclassical solution does not provide unique value of the constants. We suggest an approximate analytic solution, which provides reliable results in special cases. Further more, we also use the variable phase method to evaluate the phase shifts. The p-wave scattering lengths of $^{132}$Cs and $^{134}$Cs are calculated to validate the schemes followed. Based on our calculations, the value of the $p$ wave scattering length of $^6$Li is $-45a_o$.Comment: 10 figure

SPECIFIC INHIBITION OF LYMPHOID COMPLEMENT RECEPTORS BY ANTI-H-2 SERA: EVIDENCE FOR A NEW H-2 LINKED POLYMORPHISM

Certain anti-H-2 sera contain an antibody-like activity which specifically inhibits EAC rosette formation by lymphoid (and not myeloid) cells of certain mouse strains. Studies in congenic recombinant mouse strains strongly indicate that at least part of the control of susceptibility to inhibition by these antisera is mediated by H-2 linked genes, mapping in the I-C subregion or the S region. The strain distribution of the trait CRIS indicates that certain H-2 identical mice behave differently from one another, pointing toward a component of non-H-2 modulation of the H-2 linked gene (or to a previously unsuspected H-2 difference). Positive sera were usually raised across differences in the D end of the H-2 complex. The complex implications of this system must be considered in the light of known S region involvement in complement metabolism.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73055/1/j.1744-313X.1975.tb00549.x.pd