Model-based Aeroservoelastic Design and Load Alleviation of Large Wind Turbine Blades

This paper presents an aeroservoelastic modeling approach for dynamic load alleviation in large wind turbines with trailing-edge aerodynamic surfaces. The tower, potentially on a moving base, and the rotating blades are modeled using geometrically non-linear composite beams, which are linearized around reference conditions with arbitrarily-large structural displacements. Time-domain aerodynamics are given by a linearized 3-D unsteady vortexlattice method and the resulting dynamic aeroelastic model is written in a state-space formulation suitable for model reductions and control synthesis. A linear model of a single blade is used to design a Linear-Quadratic-Gaussian regulator on its root-bending moments, which is finally shown to provide load reductions of about 20% in closed-loop on the full wind turbine non-linear aeroelastic model

Electrophysiological evidence for different effects of working memory load on interference control in adolescents than adults

The present study investigated how the development of interference control is influenced by the development of working memory (WM) capacity during adolescence. In a dual-task, 17 adolescents (12-16years) and 19 adults (18-48years) performed a gender word-face Stroop task, while WM-capacity was manipulated by a concurrently performed N-back task. Behavior (reaction times, % errors and % misses) and event-related potentials associated with the detection (N450) of the Stroop conflict and response selection (sustained positivity; SP) were measured without or with a concurrent WM load. Adolescents had lower accuracy on N-back and Stroop trials than adults. N450 results showed Stroop conflict above temporal-occipital cortex which was suggested to be caused by processing of distracter faces. This N450 conflict response was smaller in adults and only present when holding a simultaneous WM-load, whereas adolescents' N450 conflict responses were already present without a concurrent WM-load and did not further increase with load. These N450 results indicate poorer distracter suppression in adolescence which is suggested to be due to insufficient attentional resources for top-down control. Irrespective of WM-load, adolescents also had larger parietal SP conflict responses than adults, suggesting inefficient response selection in case of activation of two conflicting responses. The main conclusion is that adolescents have worse distracter suppression than adults, caused by lower availability of resources for top-down control. (PsycINFO Database Record (c) 2011 APA, all rights reserved) (journal abstract

Electronic spin drift in graphene field effect transistors

We studied the drift of electron spins under an applied DC electric field in single layer graphene spin valves in a field effect transport geometry at room temperature. In the metallic conduction regime ($n \simeq 3.5 \times 10^{16}$ m$^{-2}$), for DC fields of about $\pm$70 kV/m applied between the spin injector and spin detector, the spin valve signals are increased/decreased, depending on the direction of the DC field and the carrier type, by as much as $\pm$50%. Sign reversal of the drift effect is observed when switching from hole to electron conduction. In the vicinity of the Dirac neutrality point the drift effect is strongly suppressed. The experiments are in quantitative agreement with a drift-diffusion model of spin transport.Comment: 4 figure

Controlling the efficiency of spin injection into graphene by carrier drift

Electrical spin injection from ferromagnetic metals into graphene is hindered by the impedance mismatch between the two materials. This problem can be reduced by the introduction of a thin tunnel barrier at the interface. We present room temperature non-local spin valve measurements in cobalt/aluminum-oxide/graphene structures with an injection efficiency as high as 25%, where electrical contact is achieved through relatively transparent pinholes in the oxide. This value is further enhanced to 43% by applying a DC current bias on the injector electrodes, that causes carrier drift away from the contact. A reverse bias reduces the AC spin valve signal to zero or negative values. We introduce a model that quantitatively predicts the behavior of the spin accumulation in the graphene under such circumstances, showing a good agreement with our measurements.Comment: 4 pages, 3 color figure

Epidermolysis bullosa acquisita

Epidermolysis bullosa acquisita (EBA) is a subtype of pemphigoid that may present with scarring similar to hereditary dystrophic epidermolysis bullosa, of which the naming of EBA was derived. The clinical subtype of EBA with scarring is named mechanobullous EBA, because blisters are evoked by sudden mechanical trauma to the skin. The other subtype of EBA with erythematous lesions without scarring is named inflammatory EBA, and may look like bullous pemphigoid. The mucous membranes can be involved in both subtypes. The pathogenesis is mediated by IgG or IgA against type VII collagen, which is the component of anchoring fibrils below the lamina densa. Diagnosis is confirmed by detection of a u-serrated linear pattern of immune depositions by direct immunofluorescence microscopy of a skin biopsy. The pathogenesis of both clinical subtypes is unknown, and is not related to binding of a particular epitope of the auto-antigen. EBA is associated with systemic lupus erythematosus and colitis ulcerosa. The disease is relative refractory to treatment.</p

Bullous systemic lupus erythematosus

Bullous systemic lupus erythematosus (BSLE) is rare heterogeneous cutaneous manifestation in patient with systemic lupus erythematosus (SLE). BSLE encompasses a subepidermal autoimmune bullous disease with type VII collagen autoantibodies, leading to epidermolysis bullosa acquisita in patients with SLE. Alternatively, an acute generalized hemorrhagic vesiculo-bullous eruption may also occur in patients with SLE caused by the extensive inflammatory reaction without the presence of type VII collagen. Vesicular eruptions can also be seen in subacute cutaneous lupus erythematosus due to severe inflammatory reaction with subepidermal clefting, which in extreme cases may resemble erythema multiforme (Rowell syndrome) or toxic epidermal necrolysis.</p