Simulating marine current turbine wakes with advanced turbulence models

Work is presented which compares the abilities of the Detached Eddy Simulation turbulence model to a Reynolds-Averaged Navier-Stokes turbulence model, for CFD simulations of a horizontal axis tidal turbine under different ambient turbulence conditions. Comparisons are made of the abilities of the respective models to predict both performance characteristics as well as wake length and character. It is demonstrated that whilst Detached Eddy Simulation holds little advantage over ak-! SST model for predicting mean performance characteristics, significant advantages are shown when predicting wake length, as well as allowing the prediction of the magnitude of fluctuations. It is expected that, despite the higher computational expense, hybrid LES-RANS turbulence models such as Detached Eddy Simulation will be of interest to engineers designing arrays of tidal turbines, which are anticipated if tidal energy is to make a significant contribution to the world’s energy resources

Anything You Can Do, You Can Do Better: Neural Substrates of Incentive-Based Performance Enhancement

Performance-based pay schemes in many organizations share the fundamental assumption that the performance level for a given task will increase as a function of the amount of incentive provided. Consistent with this notion, psychological studies have demonstrated that expectations of reward can improve performance on a plethora of different cognitive and physical tasks, ranging from problem solving to the voluntary regulation of heart rate. However, much less is understood about the neural mechanisms of incentivized performance enhancement. In particular, it is still an open question how brain areas that encode expectations about reward are able to translate incentives into improved performance across fundamentally different cognitive and physical task requirements

Understanding user behavior using cognitive models

We consider the application of cognitive models to a range of problems in mobile telecommunications. In particular, con- sideration is given to the characteristic patterns that emerge in how people use mobile content in a natural environment. Using cognitive models drawn from the literature on decision- making, preference and semantics, we show that the mobile content environment possesses a range of interesting psycho- logical properties, which can be used to further both pure and applied research goals.Daniel J. Navarro ; Marisa Maio Mackay ; Kieran O'Dohert

Recent and future trends in synthetic greenhouse gas radiative forcing

Atmospheric measurements show that emissions of hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons are now the primary drivers of the positive growth in synthetic greenhouse gas (SGHG) radiative forcing. We infer recent SGHG emissions and examine the impact of future emissions scenarios, with a particular focus on proposals to reduce HFC use under the Montreal Protocol. If these proposals are implemented, overall SGHG radiative forcing could peak at around 355 mW m[superscript −2] in 2020, before declining by approximately 26% by 2050, despite continued growth of fully fluorinated greenhouse gas emissions. Compared to “no HFC policy” projections, this amounts to a reduction in radiative forcing of between 50 and 240 mW m[superscript −2] by 2050 or a cumulative emissions saving equivalent to 0.5 to 2.8 years of CO2 emissions at current levels. However, more complete reporting of global HFC emissions is required, as less than half of global emissions are currently accounted for.Natural Environment Research Council (Great Britain) (Advanced Research Fellowship NE/I021365/1)United States. National Aeronautics and Space Administration (Upper Atmospheric Research Program Grant NNX11AF17G)United States. National Oceanic and Atmospheric Administratio

Motor Preparatory Activity in Posterior Parietal Cortex is Modulated by Subjective Absolute Value

For optimal response selection, the consequences associated with behavioral success or failure must be appraised. To determine how monetary consequences influence the neural representations of motor preparation, human brain activity was scanned with fMRI while subjects performed a complex spatial visuomotor task. At the beginning of each trial, reward context cues indicated the potential gain and loss imposed for correct or incorrect trial completion. FMRI-activity in canonical reward structures reflected the expected value related to the context. In contrast, motor preparatory activity in posterior parietal and premotor cortex peaked in high “absolute value” (high gain or loss) conditions: being highest for large gains in subjects who believed they performed well while being highest for large losses in those who believed they performed poorly. These results suggest that the neural activity preceding goal-directed actions incorporates the absolute value of that action, predicated upon subjective, rather than objective, estimates of one's performance

Ozone-depleting substances (ODSs) and related chemicals

The amended and adjusted Montreal Protocol continues to be successful at reducing emissions and atmospheric abundances of most controlled ozone-depleting substances (ODSs).Global Ozone Research and Monitoring Projec

Comparative Study of Four Passive Building Energy Simulations DOE 2.1, BLAST, SUNCAT 2.4, DEROB-III

Four building energy analysis codes are compared using two direct gain building models with Madison TMY weather data. Hourly temperature profiles and annual heating and cooling loads are compared and discussed. An analytic verification technique is described and used to investigate performance of the four codes. An anomaly is discovered in one of the codes, and the analytic verification technique is used to test a modified version of this code