3-D resistive MHD calculations for tokamak plasmas: beyond the simple reduced set of equations

Numerical studies of the resistive stability of tokamak plasmas in cylindrical geometry have been performed using: (1) the full set of resistive Magnetohydrodynamic (MHD) equations and (2) an extended version of the reduced set of resistive MHD equations including diamagnetic and electron temperature effects. In particular, the nonlinear interaction of tearing modes of many helicities has been investigated. The numerical results confirm many of the features uncovered previously using the simple reduced equations

Impacts of offshore oil spill accidents on island bird communities:a test run study around Orkney and Svalbard archipelagos

Abstract The sea area around the Orkney archipelago, Scotland is subjected to substantial maritime shipping activities. By contract, the Svalbard archipelago, Norway currently has a rather low marine traffic profile. Future projections, however, indicate that the Trans-Arctic route might change the whole transportation picture and Svalbard may be at the centre of maritime activities. Both archipelagos have sensitive environmental resources at sea and inland, including bird communities. There are, for instance, 13 Red Listed species present in Orkney and 2 in Svalbard. In this regard, it is important to address oil spill risks along existing and projected shipping routes. Hypothetical spills were simulated in twelve scenarios for both the Orkney and Svalbard archipelagos with the OpenDrift open-source software. The results indicate risks to seabird communities. For Orkney, the spills resulted in the most extensive contamination of the sea and land environments in autumn. For Svalbard, autumn spills on the contrary presented the lowest risk to seabirds. Based on the simulations, we recommend increased caution for shipping activities in the problematic seasons, improved local readiness for ship accidents and sufficient pre-incident planning

Comparative studies reveal variability in the use of tidal stream environments by seabirds

The global increase in tidal stream turbine installations creates a need to identify and mitigate any impacts on seabird populations. Within Scotland, UK, the vulnerability of black guillemots Cepphus grylle and European shags Phalacrocorax aristotelis is dependent on their tendency to exploit microhabitats characterised by fast mean horizontal current speeds (≥2 ms–1), and tidal states with maximum current speeds, within tidal stream environments. Identifying consistencies in their relative use of different microhabitats (fast versus slow mean horizontal current speeds) and tidal states (increasing/decreasing versus maximum currents) across these habitats could assist risk assessment and mitigation measures at both a regional and development site level. Datasets from shore-based surveys collated across 6 tidal stream environments showed that the probability of detecting foraging black guillemots and European shags tended to be higher in fast and slow microhabitats, respectively. However, differences between microhabitats were reversed and/or marginal in 3 out of the 5 sites used for each species. Differences between tidal states were almost always marginal. These variabilities show that a species' vulnerability could differ greatly among development sites, and environmental impact assessments (EIA) must quantify habitat-use using dedicated and site-specific surveys to reduce uncertainty. However, a greater understanding of the mechanisms underlying variation in the use of tidal stream environments is needed when selecting a suite of potential development sites that reduce the possibility of population-level impacts. The current collection of physical and biological data across tidal stream environments could therefore prove invaluable for the protection of seabird populations

Equilibrium and stability studies for high-beta plasmas in torsatron/heliotron devices

The equilibrium and stability properties of high-..beta.. plasmas in torsatron/heliotron devices have been investigated. Three numerical approaches have been used to study plasma equilibria for a range of coil configurations. The method of averaging permits fast equilibrium and stability calculations. Two fully 3-D codes, namely the Chodura-Schluter code, and the NEAR code recently developed at ORNL, are used to explore selected regions of parameter space. The resulting equilibria calculated with different methods are in good agreement. This validates the average method approach and enhances its usefulness. Results are presented for configurations with different aspect ratios and number of field periods. The role of the vertical field has also been studied in detail. The main conclusion is that for moderate aspect ratios (A/sub p/ less than or equal to 8), the self-stabilizing effect of the magnetic-axis shift is large enough to open a direct path to the second-stability regime

Resolving environmental effects of wind energy

Concerns for potential wildlife impacts resulting from land-based and offshore wind energy have created challenges for wind project development. Research is not always adequately supported, results are neither always readily accessible nor are they satisfactorily disseminated, and so decisions are often made based on the best available information, which may be missing key findings. The potential for high impacts to avian and bat species and marine mammals have been used by wind project opponents to stop, downsize, or severely delay project development. The global nature of the wind industry—combined with the understanding that many affected species cross-national boundaries, and in many cases migrate between continents—also points to the need to collaborate on an international level. The International Energy Agency (IEA) Wind Technology Collaborative Programs facilitates coordination on key research issues. IEA Wind Task 34— WREN: Working Together to Resolve Environmental Effects of Wind Energy–is a collaborative forum to share lessons gained from field research and modeling, including management methods, wildlife monitoring methods, best practices, study results, and successful approaches to mitigating impacts and addressing the cumulative effects of wind energy on wildlife. WREN develops products such as white papers, fact sheets, and short science summaries, and is involved in a number of activities including hosting a webinar series and outreach and information dissemination through participation in meetings, workshops, and conferences to increase and expand the knowledge base pertaining to wildlife challenges at wind energy facilities. This information is available on WREN Hub, hosted on the Tethys website. adaptive management, cumulative impacts, dissemination, environmental effects, environmental trade-offs, population impacts, risk estimation, Tethys, wind energyResolving environmental effects of wind energyacceptedVersio

Methods to quantify avian airspace use in relation to wind energy development

It is likely that there will continue to be a substantial increase in the number of wind turbines as we aim to meet global energy demands through renewable sources. However, these structures can have adverse impacts on airborne wildlife, such as posing a potential collision risk with the turbine structure. A range of methods and technologies have been applied to the collection of bird flight parameters, such as height and speed, to improve the estimation of potential collision compared with traditional visual methods, but these are currently not applied in a consistent and systematic way. To this end, a systematic literature search was conducted to (1) examine the methods and technologies that can be used to provide bird flight data to assess the impact of wind energy developments and (2) provide an updated framework to guide how they might be most usefully applied within the impact assessment process. Four empirical measurement methods were found that improve the estimation of bird flight parameters: radar, telemetry, ornithodolite and LiDAR. These empirical sensor-based tools were typically more often applied in academic peer-reviewed papers than in report-based environmental statements. Where sensor-based tools have been used in the report-based literature, their inconsistent application has resulted in an uncertain regulatory environment for practitioners. Our framework directly incorporates sensor-based methods, together with their limitations and data requirements, from pre-deployment of infrastructure to post-consent monitoring of impacts. This revised approach will help improve the accuracy of estimation of bird flight parameters for ornithological assessment of wind energy. Sensor-based tools may not be the most cost-effective. However, a precedent has been set for wind energy development consent refusal based on ornithological impact assessment, and therefore the cost of collecting accurate and reliable flight data may be balanced favourably against the cost of development consent refusalacceptedVersio

Magnetoresistance and non-Ohmic conductivity of thin platinum films at low temperatures

The electrical conductivity of thin Pt films is measured as a function of temperature T, magnetic field B, and electric field E. A logarithmic temperature dependence is observed. The magnetoresistance is positive and anisotropic, increasing as B2/T in small perpendicular fields and logarithmically in high B⊥. The electric field causes the resistance to drop proportional to E2 at low E and logarithmically at high E, in agreement with localization theory. Our data on the magnetoresistance, however, disagree with theory