An investigation of Lagrangian Riemann methods incorporating material strength

The application of Riemann Methods formulated in the Lagrangian reference frame to the numerical simulation of non-linear events in solid materials is investigated. Here, solids are characterised by their ability to withstand shear distortion since they possess material strength. In particular, numerical techniques are discussed for simulating the transient response of solids subjected to extreme loading. In such circumstances, the response of solids will often be highly non-linear, displaying elastic and plastic behaviour, and even moderate compressions will produce strong shock waves.This work reviews the numerical schemes or 'hydrocodes' which have been adopted in the past in order to simulate such systems, identifying the advantages and limitations of such techniques. One of the most prominent limitations of conventional Lagrangian methods is that the computational mesh or grid has fixed-connectivity i.e. mesh nodes are connected to the same nodes for all time. This has significant disadvantages since the computational mesh can easily become tangled as the simulated material distorts. The majority of conventional hydrocodes are also constructed using outdated artificial viscosity schemes which are known to diffuse shock waves and other steep features which may be present in the solution.In the work presented here, a novel two-dimensional Lagrangian solver has been developed Vucalm-EP which overcomes many of the limitations of conventional techniques. By employing the Free-Lagrange Method, whereby the connectivity of the computational mesh is allowed to evolve as the material distorts, problems of arbitrarily large deformation can be simulated. With the implementation of a spatially second-order accurate, finite-volume, Godunov-type solver, non-linear waves such as shocks are represented with higher resolution than previously possible with contemporary schemes. The Vucalm-EP solver simulates the transient elastic-perfectly plastic response of solids and displays increased accuracy over alternative Lagrangian techniques developed to simulate large material distortion such as Smoothed particle Hydrodynamics (SPH). Via a variety of challenging numerical simulations the Vucalm-EP solver is compared with contemporary Euler, fixed-connectivity Lagrangian, and meshless SPH solvers. These simulations include the solution of one- and two dimensional shock tube problems in aluminium, simulating the collapse of cylindrical shells and modelling high-velocity projectile impacts. Validation against previously published results, solutions obtained using alternative numerical techniques and analytical models illustrates the versatility and accuracy of the technique. Thus, the Vucalm-EP solver provides a numerical scheme for the Lagrangian simulation of extensive material distortion in materials with strength, which has never previously been possible with mesh-based techniques

Implementation and perceived benefits of an after-school soccer program designed to promote social and emotional learning: A multiple case study

Social and emotional learning (SEL) competencies such as self-awareness and relationship skills are predictors of academic success, overall well-being, and avoidance of problematic behaviors. Among school-aged children, research has demonstrated that well-implemented programs teach SEL competencies and life skills (e.g., leadership, responsible decision making) that can transfer to other settings. Similar claims have been made in the field of sport-based youth development (SBYD), however, the SEL framework has not been widely applied in sport programming. Implementation, student learning, and transfer of learning in SBYD programs designed to promote SEL require further exploration. Therefore, the current study examined the implementation and perceived benefits of an after-school soccer program designed to promote SEL. Participants were six coaches and 51 students from three different sites where this program is offered. A multiple case study design was used, integrating data from customized feedback surveys, interviews, systematic observation, and field notes. Results indicated the program reflects many SBYD best practices. Although implementation varied between sites, program culture and core values were consistent. Evidence indicated students learned and applied SEL lessons in the soccer program and that transfer beyond the program was promoted. Participants were most likely to report transfer to the school setting, therefore, future studies should examine this topic more directly. Other implications for research and program implementation are discussed

The detection efficiency of on-axis short gamma ray burst optical afterglows triggered by aLIGO/Virgo

Assuming neutron star (NS) or neutron star/stellar-mass black hole (BH) mergers as progenitors of the short gamma ray bursts, we derive and demonstrate a simple analysis tool for modelling the efficiency of recovering on-axis optical afterglows triggered by a candidate gravitational wave event detected by the Advanced LIGO and Virgo network. The coincident detection efficiency has been evaluated for different classes of operating telescopes using observations of gamma ray bursts. We show how the efficiency depends on the luminosity distribution of the optical afterglows, the telescope features, and the sky localisation of gravitational wave triggers. We estimate a plausible optical afterglow and gravitational wave coincidence rate of 1 yr$^{-1}$ (0.1 yr$^{-1}$) for NS-NS (NS-BH), and how this rate is scaled down in detection efficiency by the time it takes to image the gravitational wave sky localization and the limiting magnitude of the telescopes. For NS-NS (NS-BH) we find maximum detection efficiencies of $>80$ when the total imaging time is less than 200 min (80 min) and the limiting magnitude fainter than 20 (21). We show that relatively small telescopes $(m<18)$ can achieve similar detection efficiencies to meter class facilities $(m<20)$ with similar fields of view, only if the less sensitive instruments can respond to the trigger and image the field within 10-15 min. The inclusion of LIGO India into the gravitational wave observatory network will significantly reduce imaging time for telescopes with limiting magnitudes $\sim20$ but with modest fields of view. An optimal coincidence search requires a global network of sensitive and fast response wide field instruments that could effectively image relatively large gravitational-wave sky localisations and produce transient candidates for further photometric and spectroscopic follow-up.Comment: 6 pages, 2 figures, version 2, reference added typo correction, Accepted by MNRA

Biotic and Abiotic Characteristics Influencing Nest Location and Trophic Relationships of the Fungus-Growing Ant \u3ci\u3eTrachymyrmex septentrionalis\u3c/i\u3e (Formicidae: \u3ci\u3eAttini)\u3c/i\u3e

Trachymyrmex septentrionalis represents the only species of fungus-growing ant in the southeastern United States. T. septentrionalis cultivates a symbiotic fungus on which the ants feed. Worker ants collect plant and animal debris to feed the fungus. These ants are common in Florida, but increasingly scarce as they near the northern extent of their range in New Jersey. Colonies of T. septentrionalis occur in patches throughout Blackwater Ecological Preserve, a longleaf pine forest in southeastern Virginia. Blackwater Ecologic Preserve is a 129 hectare tract of land, located in Isle of Wight county, that is undergoing a regimen of controlled burning to increase the population of longleaf pines ( Pinus palustris). Over an 8 year period, multiple abiotic and biotic factors were studied to better understand what conditions determine the distribution of T. septentrionaliscolonies within an ecosystem and how those factors may affect the ability of individual colonies to collect sufficient substrate to sustain the fungal symbiont and feed the colony. Soil temperature (23.5 vs. 25.1°C), air temperature (22.3 vs. 26.4°C), and light intensity (302.8 vs. 595.2 lumens) were all found to be significantly higher around inactive nests. Plant cover, which would affect light intensity around the nests, was significantly higher above active nests (71.1%) than over inactive nests (57.9%). Soil samples from T. septentrionalis populated and adjacent, unpopulated sites resulted in soil moisture being significantly lower in the upper 60 cm of soil in populated versus unpopulated areas. No consistent differences were found for soil organic matter, cation exchange capacity, or pH between populated and unpopulated sites. Colony densities, calculated for each nesting site, ranged from 0.072 to 0.145 nests/m 2, and these densities can be correlated to soil and air temperatures, light intensity, and vegetation cover. In an attempt to understand the patchy distribution of T. septentrionalis in Blackwater Ecologic Preserve, the composition of ant and plant communities in areas with and without T. septentrionalis nests were analyzed. A total of 34 ant species was collected, with 27 species from sites with T. septentrionalis and 30 from those without. Only Aphaenogaster treatae displayed significantly different numbers between sites, but there were numerous species that occurred only in one or the other. A total of 15 plant species were identified in areas populated by T. septentrionalis, but 22 were identified in unpopulated areas. As with the ant community, numerous species could be located in one site but not the other. Just as air temperatures affect the overall activity of T. septentrionalis colonies, they also influence foraging rates. Field preference of forage falls into four categories (Berry, Pteridium aquilinum, Quercus sp., Unknown Materials). Carbon and nitrogen concentrations increase as the elements are tracked from the substrate to the fungus then to the ants themselves. During a season of activity, a nest of 356 workers, alates, and pupae is expected to capture approximately 29.58 kcal/m 2 of energy through substrate collection. From this total, the T. septentrionalis/fungus symbiont is estimated to assimilate between 11.1 and 12.79 kcal/nest/yr. T. septentrionalis appears to be highly sensitive to environmental conditions such as temperatue and light intensity both for daily activities and the foundation of new colonies. Soil moisture may also be considered as an important factor, either directly as it influences chamber excavation and stability or indirectly by determining vegetative cover. Overall, ant and plant communities did not affect the presence or absence of T. septentrionalis. T. septentrionalis acquires limited nutrients and energy from the surrounding ecosystem, this may be due to an inability to exploit the environment or the higher energetic demands required to acquire richer sources of nutrients and energy by leaf cutting

The UK offshore wind job creation capacity, O&M costs and content analysis

This paper focuses on exploring the operation and maintenance costs and job creation capacity of the UK offshore wind sector. The UK Government long-term target is to use the offshore wind farm (OWF) renewable energy to meet 15% of its renewable energy target by 2020. OWF operation and maintenance market opportunities have been encouraging firm to make major investment in the sector. This emerging market presents opportunities to turbine manufacturers, wind farm developers and small & medium enterprises (SMEs), thereby leading to significant job creation capacity. About 1,183 offshore wind turbines have been installed in the UK with capacity of 4,042 megawatt (MW) and this sector currently provides skilled jobs to about 6,830 full-time employees. Cost reduction in the operation and maintenance and a strong supply chain are necessary if the UK Government targets for the sector is to be achieved