Dynamic Analysis of a Floating Vertical Axis Wind Turbine Under Emergency Shutdown Using Hydrodynamic Brake

Emergency shutdown is always a challenge for an operating vertical axis wind turbine. A 5-MW vertical axis wind turbine with a Darrieus rotor mounted on a semi-submersible support structure was examined in this study. Coupled non-linear aero-hydro-servo-elastic simulations of the floating vertical axis wind turbine were carried out for emergency shutdown cases over a range of environmental conditions based on correlated wind and wave data. When generator failure happens, a brake should be applied to stop the acceleration of the rotor to prevent the rotor from overspeeding and subsequent disaster. In addition to the traditional mechanical brake, a novel hydrodynamic brake was presented to apply to the shutdown case. The effects of the hydrodynamic brake on the platform motions and structural loads under normal operating conditions and during the emergency shutdown events were evaluated. The use of both the hydrodynamic brake and mechanical brake was also investigated. The application of the hydrodynamic brake is expected to be efficient for rotor shutdown and for reducing the platform motions and structural loads

Field Dependence of the Superconducting Basal Plane Anisotropy of TmNi2B2C

The superconductor TmNi2B2C possesses a significant four-fold basal plane anisotropy, leading to a square Vortex Lattice (VL) at intermediate fields. However, unlike other members of the borocarbide superconductors, the anisotropy in TmNi2B2C appears to decrease with increasing field, evident by a reentrance of the square VL phase. We have used Small Angle Neutron Scattering measurements of the VL to study the field dependence of the anisotropy. Our results provide a direct, quantitative measurement of the decreasing anisotropy. We attribute this reduction of the basal plane anisotropy to the strong Pauli paramagnetic effects observed in TmNi2B2C and the resulting expansion of vortex cores near Hc2.Comment: 8 pages, 6 figures, 1 tabl

Dimensional Evolution of Spin Correlations in the Magnetic Pyrochlore Yb2Ti2O7

The pyrochlore material Yb2Ti2O7 displays unexpected quasi-two-dimensional (2D) magnetic correlations within a cubic lattice environment at low temperatures, before entering an exotic disordered ground state below T=265mK. We report neutron scattering measurements of the thermal evolution of the 2D spin correlations in space and time. Short range three dimensional (3D) spin correlations develop below 400 mK, accompanied by a suppression in the quasi-elastic (QE) scattering below ~ 0.2 meV. These show a slowly fluctuating ground state with spins correlated over short distances within a kagome-triangular-kagome (KTK) stack along [111], which evolves to isolated kagome spin-stars at higher temperatures. Furthermore, low-temperature specific heat results indicate a sample dependence to the putative transition temperature that is bounded by 265mK, which we discuss in the context of recent mean field theoretical analysis.Comment: 5 pages, 6 figure

Are people in residential care entitled to receive rehabilitation services following hip fracture? Views of the public from a citizens' jury.

BACKGROUND:Access to rehabilitation services for people living in residential care facilities is frequently limited. A randomised trial of a hospital outreach hip fracture rehabilitation program in residential care facilities has demonstrated improvements in mobility at four weeks and quality of life at 12 months but was not considered cost-effective by standard health economic metrics. The current study aimed to explore the general public's views on issues involved in the allocation of rehabilitation resources for residents of care facilities. METHODS:A citizens' jury comprising 13 purposively sampled members of the general public, representative of the South Australian age, gender and household income profile. The jury considered the questions "Should there be an investment of physical rehabilitation services in residential care for older people following a hip fracture? If so, what is the best way of providing this service (considering funding, models of service delivery and equity)?" Deliberations were in the context of a state-wide health reform program. The jury was conducted over two days with an experienced independent facilitator, addressing questions developed by a steering group of research academics and clinicians. RESULTS:The mean age of the citizens' jury members was 43 (range 26 to 61). Eleven members voted for investment in outreach hospital rehabilitation services in residential aged care. All jurors agreed a number of strategies in addition to investment should be implemented, including health care planning and decision making, increased emphasis on hip fracture prevention, training of aged care staff in rehabilitation and routine provision of hospital discharge summaries to families. The jury further advocated for an increased focus on rehabilitation in residential care, potentially through accreditation criteria, increasing health literacy of residents and families, implementation of age friendly environment strategies and improving connections of care facilities with community, hospital and tertiary services. CONCLUSIONS:This citizens' jury representative of the general public recommends that regardless of dementia and frailty, people who live in residential care and are walking and fracture their hips should have access to hospital outreach rehabilitation and recovery services

The declining representativeness of the British party system, and why it matters

In a recent article, Michael Laver has explained ‘Why Vote-Seeking Parties May Make Voters Miserable’. His model shows that, while ideological convergence may boost congruence between governments and the median voter, it can reduce congruence between the party system and the electorate as a whole. Specifically, convergence can increase the mean distance between voters and their nearest party. In this article we show that this captures the reality of today’s British party system. Policy scale placements in British Election Studies from 1987 to 2010 confirm that the pronounced convergence during the past decade has left the Conservatives and Labour closer together than would be optimal in terms of minimising the policy distance between the average voter and the nearest major party. We go on to demonstrate that this comes at a cost. Respondents who perceive themselves as further away from one of the major parties in the system tend to score lower on satisfaction with democracy. In short, vote-seeking parties have left the British party system less representative of the ideological diversity in the electorate, and thus made at least some British voters miserable

Modelling societal transitions with agent transformation

Transition models explain long-term and large-scale processes fundamentally changing the structure of a societal system. Our concern is that most transition models are too static. Although they capture a move of focus from static equilibria to transitions between dynamic equilibria, they are still rooted in an "equilibriumist" approach. Improvement is possible with agent-based models that give attention to endogenous system processes called "transformation processes". These models can render far more dynamic pictures of societal systems in transition, and are no longer remote from descriptions in the emerging transition literature