Final results from the EU project AVATAR: aerodynamic modelling of 10 MW wind turbines

This paper presents final results from the EU project AVATAR in which aerodynamic models are improved and validated for wind turbines on a scale of 10 MW and more. Special attention is paid to the improvement of low fidelity engineering (BEM based) models with higher fidelity (CFD) models but also with intermediate fidelity free vortex wake (FVW) models. The latter methods were found to be a good basis for improvement of induction modelling in engineering methods amongst others for the prediction of yawed cases, which in AVATAR was found to be one of the most challenging subjects to model. FVW methods also helped to improve the prediction of tip losses. Aero-elastic calculations with BEM based and FVW based models showed that fatigue loads for normal production cases were over predicted with approximately 15% or even more. It should then be realised that the outcome of BEM based models does not only depend on the choice of engineering add-ons (as is often assumed) but it is also heavily dependent on the way the induced velocities are solved. To this end an annulus and element approach are discussed which are assessed with the aid of FVW methods. For the prediction of fatigue loads the so-called element approach is recommended but the derived yaw models rely on an annulus approach which pleads for a generalised solution method for the induced velocities

Latest results from the EU project AVATAR: aerodynamic modelling of 10 MW wind turbines

This paper presents the most recent results from the EU project AVATAR in which aerodynamic models are improved and validated for wind turbines on a scale of 10 MW and more. Measurements on a DU 00-W-212 airfoil are presented which have been taken in the pressurized DNW-HDG wind tunnel up to a Reynolds number of 15 Million. These measurements are compared with measurements in the LM wind tunnel for Reynolds numbers of 3 and 6 Million and with calculational results. In the analysis of results special attention is paid to high Reynolds numbers effects. CFD calculations on airfoil performance showed an unexpected large scatter which eventually was reduced by paying even more attention to grid independency and domain size in relation to grid topology. Moreover calculations are presented on flow devices (leading and trailing edge flaps and vortex generators). Finally results are shown between results from 3D rotor models where a comparison is made between results from vortex wake methods and BEM methods at yawed conditions

The impact of corporate philanthropy on reputation for corporate social performance

This study seeks to examine the mechanisms by which a corporation’s use of philanthropy affects its reputation for corporate social performance (CSP), which the authors conceive of as consisting of two dimensions: CSP awareness and CSP perception. Using signal detection theory (SDT), the authors model signal amplitude (the amount contributed), dispersion (number of areas supported), and consistency (presence of a corporate foundation) on CSP awareness and perception. Overall, this study finds that characteristics of firms' portfolio of philanthropic activities are a greater predictor of CSP awareness than of CSP perception. Awareness increases with signal amplitude, dispersion, and consistency. CSP perception is driven by awareness and corporate reputation. The authors’ contention that corporate philanthropy is a complex variable is upheld, as we find that CSP signal characteristics influence CSP awareness and perception independently and asymmetrically. The authors conclude by proposing avenues for future research

Total and Differential Cross Sections for the pp-->pp eta-prime Reaction Near Threshold

The eta-prime meson production in the reaction pp-->pp eta-prime has been studied at excess energies of Q = 26.5, 32.5 and 46.6 MeV using the internal beam facility COSY-11 at the cooler synchrotron COSY. The total cross sections as well as one angular distribution for the highest Q-value are presented. The excitation function of the near threshold data can be described by a pure s-wave phase space distribution with the inclusion of the proton-proton final state interaction and Coulomb effects. The obtained angular distribution of the eta-prime mesons is also consistent with pure s-wave production.Comment: 6 pages, 5 figures, submitted to Eur. Phys. J.

In the absence of ATPase activity, pre-RC formation is blocked prior to MCM2-7 hexamer dimerization

The origin recognition complex (ORC) of Saccharomyces cerevisiae binds origin DNA and cooperates with Cdc6 and Cdt1 to load the replicative helicase MCM2–7 onto DNA. Helicase loading involves two MCM2–7 hexamers that assemble into a double hexamer around double-stranded DNA. This reaction requires ORC and Cdc6 ATPase activity, but it is unknown how these proteins control MCM2–7 double hexamer formation. We demonstrate that mutations in Cdc6 sensor-2 and Walker A motifs, which are predicted to affect ATP binding, influence the ORC–Cdc6 interaction and MCM2–7 recruitment. In contrast, a Cdc6 sensor-1 mutant affects MCM2–7 loading and Cdt1 release, similar as a Cdc6 Walker B ATPase mutant. Moreover, we show that Orc1 ATP hydrolysis is not involved in helicase loading or in releasing ORC from loaded MCM2–7. To determine whether Cdc6 regulates MCM2–7 double hexamer formation, we analysed complex assembly. We discovered that inhibition of Cdc6 ATPase restricts MCM2–7 association with origin DNA to a single hexamer, while active Cdc6 ATPase promotes recruitment of two MCM2–7 hexamer to origin DNA. Our findings illustrate how conserved Cdc6 AAA+ motifs modulate MCM2–7 recruitment, show that ATPase activity is required for MCM2–7 hexamer dimerization and demonstrate that MCM2–7 hexamers are recruited to origins in a consecutive process

Drift chamber with a c-shaped frame

We present the construction of a planar drift chamber with wires stretched between two arms of a c-shaped aluminium frame. The special shape of the frame allows to extendthe momentum acceptance of the COSY-11 detection system towards lower momenta without suppressing the high momentum particles. The proposed design allows for construction of tracking detectors covering small angles with respect to the beam, which can be installed and removed without dismounting the beam-pipe. For a three-dimensional track reconstruction a computer code was developed using a simple algorithm of hit preselection.Comment: submitted to Nucl. Instr. & Meth

Near-Threshold eta Meson Production in Proton-Proton Collisions

The production of eta mesons has been measured in the proton-proton interaction close to the reaction threshold using the COSY-11 internal facility at the cooler synchrotron COSY. Total cross sections were determined for eight different excess energies in the range from 0.5 MeV to 5.4 MeV. The energy dependence of the total cross section is well described by the available phase-space volume weighted by FSI factors for the proton-proton and proton-eta pairs.Comment: 9 pages, 1 table, 5 figure