Browsing by Subject "Experiments"

Now showing 1 - 3 of 3
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    Local and Non-local Geomorphic Effects of Hydrokinetic Turbines: Bridging Renewable Energy and River Morphodynamics
    (2019-06) Musa, Mirko
    Marine and Hydrokinetic (MHK) energy is an emerging renewable and sustainable technology which harnesses kinetic energy of natural water flows such as tides, rivers and ocean currents. In particular, rivers are currently an overlooked source of local and continuous kinetic energy that can be exploited using the available in-stream converters technology. The uncertainties regarding the interaction between these devices and the surrounding environment complicate the regulatory permitting processes, slowing down the expansion of MHK industry. A crucial issue that needs further attention is the interaction between these devices and the physical fluvial environment such as the bathymetry, sediment transport, and the associated morphodynamic processes. Analytical and experimental research conducted at Saint Anthony Falls Laboratory (SAFL) addressed this topic, unveiling the local and non-local (far from the device location) effects of hydrokinetic turbines on channel bathymetry and morphology. A theoretical model framework based on the phenomenology of turbulence was derived to predict the scour at the base of MHK device. Asymmetric installations of turbine array models within multi-scale laboratory channels were observed to trigger river instabilities known as forced-bars. Results suggest that the amplitude of these instabilities might be reduced by limiting the power plant lateral obstruction within the channel cross-section. A 12-turbine staggered array also proved to be resilient to intense flooding conditions, encouraging the expansion of this technology to large sandy rivers. Current research is investigating how hydrokinetic technology can be synergistically integrated in rivers, not only minimizing the environmental costs but also providing a positive feedback on the channel. Experiments suggest that turbines strategically installed in the river (i.e. at the side bank in yawed condition or in a vane-shaped array) could be used as stream bank protection systems and, eventually, be integrated in stream restoration projects.
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    The relationship between multiple identity attributes and diversity, and individual decision making and group performance: experimental evidence.
    (2009-08) Kramer, Amit
    The effect of diversity on individual behavior and team and organizational performance is a rapidly growing field of study. Another growing field of study involves the effect of identity-based behavior on individual, team, and organizational outcomes. Diversity and identity, although related to each other, have not been combined in a single framework. A serious of lab studies is used to explore the effect of similarity across different identity attributes at the individual and group level, and diversity of the group, on decisions, behavior, and performance within the context of (a) multiple identity attributes and both deep and surface-level diversity; (b) task complexity; and (c) task interdependence. The results indicate that individuals do make decision and act based on similarity across multiple identity attributes and multiple diversity dimensions. Furthermore, the effect of attribute similarity is cumulative: similarity across multiple deep-level attributes, simultaneously, increases favoritism toward similar others. In addition, homogeneous groups outperformed diverse groups in tasks that were characterized by high interdependence when communication between group members was not allowed, but diverse groups outperformed homogeneous groups in the same tasks when communication between group members was allowed.