Trailing Edge Noise Reduction by Passive and Active Flow Controls

This paper presents the results on the use of porous metal foams (passive control) and dielectric barrier surface plasma actuations (active control) for the reduction of vortex shedding tonal noises from the nonflat plate type trailing edge serration in a NACA0012 airfoil previously discussed in Chong et al. (AIAA J. Vol. 51, 2013, pp. 2665-2677). The use of porous metal foams to fill the interstices between adjacent members of the sawtooth can almost completely suppress the vortex shedding tonal noise, whilst the serration effect on the broadband noise reduction is retained. This concept will promote the nonflat plate type serrated trailing edge to become a genuine alternative to the conventional flat plate type serrated trailing edge, which is known to have drawbacks in the structural stability, aerodynamic performances and implementation issues. For the plasma actuators, configuration which produces electric wind in a tangential direction is found to be not very effective in suppressing the vortices emanated from the serration blunt root. On the other hand, for the plasma configuration which produces electric wind in a vertical direction, good level of vortex shedding tonal noise reduction has been demonstrated. However, the self noise produced by the plasma actuators negates the noise benefits on the tonal noise reduction. This characteristic illustrates the need to further develop the plasma actuators in a two pronged approach. First is to increase the electric wind speed, thereby allowing the plasma actuators to be used in a higher free jet velocity which naturally produces a larger level of jet noise. Second, the self noise radiated by the plasma actuators should be reduced

Coherent Dipole Modes for Multiple Interaction Regions

In the Large Hadron Collider (LHC) two proton beams of similar strength will collide at several interaction points. For a single interaction point it is known that the head-on collision of two equally strong beams with the same betatron tune, excites two coherent dipole modes whose frequencies are different from the frequencies of oscillation of individual particles in the beam. Because of this frequency difference Landau damping does not act on the dipole modes and the beams can be unstable. In this paper we extend these studies to several interaction points and explore the possibility of cancellation of the dipole coherent modes by carefully adjusting the phase difference between the beams from one collision to the next. We also study the collision of the two beams with LHC optics V 6.1. Special attention should be paid to coherent resonances that are excited due to local phase advance correlations. It will be shown also that a tune split of 0.03 between the two beams suppresses these coherent dipole modes

Hybrid Fast Multipole Method Applied to Beam-Beam Collisions in the Strong-Strong Regime

The strong-strong interactions of two colliding beams are simulated by tracking the motion of a set of macroparticles. The field generated by each distribution is evaluated using the Fast Multipole Method (FMM) together with some elements of particle-mesh methods. This technique allows us to check the exact frequencies of the coherent modes and the frequencies of oscillations of individual particles in the beam. The agreement between the simulations and analytical calculations is largely improved. Furthermore it is an efficient method to study the coherent modes in the case of separated beams

Rationale for a Stronger Disposition of Chardonnay Wines for Stuck and Sluggish Fermentation

The aim of this study was to identify and evaluate factors that contribute to fermentation problems inChardonnay, since this variety is reported to have frequent problems. Analytical methods included gaschromatography mass spectrometry, as well as atomic absorption spectroscopy and FT-MIR spectroscopy.Chardonnay, Pinot blanc, Pinot noir and Pinot noir précoce were screened to relate observations to specificvarietal properties. The results show a significant distinction in the amino acid profile of Chardonnay,which can be correlated with sluggish fermentation. A comparison between the fatty acid profile ofChardonnay and Pinot blanc reveals that Chardonnay contains more toxic compounds, which inhibityeast metabolism. Mineral supply and potential metal toxicity were also analysed. The concentrationsof iron, copper, magnesium, zinc and manganese show significant variations among the grape varieties.In conclusion, the possible causes for stuck fermentation in Chardonnay could be more related more tovariety than to oenological decisions

Quantum Control of the Hyperfine Spin of a Cs Atom Ensemble

We demonstrate quantum control of a large spin-angular momentum associated with the F=3 hyperfine ground state of 133Cs. A combination of time dependent magnetic fields and a static tensor light shift is used to implement near-optimal controls and map a fiducial state to a broad range of target states, with yields in the range 0.8-0.9. Squeezed states are produced also by an adiabatic scheme that is more robust against errors. Universal control facilitates the encoding and manipulation of qubits and qudits in atomic ground states, and may lead to improvement of some precision measurements.Comment: 4 pages, 4 figures (color

Coherent Beam-Beam Effects in the LHC

In the Large Hadron Collider (LHC) two proton beams of similar intensities collide in several interaction points. It is well known that the head-on collision of two beams of equal strength can excite coherent modes whose frequencies are separated from the incoherent spectrum of oscillations of individual particles. This can lead to the loss of Landau damping and possibly to unstable motion. The beam-beam effect in the LHC is further complicated by a large number of bunches (2808 per beam), a finite crossing angle and gaps in the bunch train. The coherent beam-beam effects under various conditions and operational scenarios are studied analytically and with multiparticle simulations. We give an overview of the main results and present proposals to overcome these difficulties together with possible side effects

Towards a new theory of practice for community health psychology

The article sets out the value of theorizing collective action from a social science perspective that engages with the messy actuality of practice. It argues that community health psychology relies on an abstract version of Paulo Freire’s earlier writing, the Pedagogy of the Oppressed, which provides scholar-activists with a ‘map’ approach to collective action. The article revisits Freire’s later work, the Pedagogy of Hope, and argues for the importance of developing a ‘journey’ approach to collective action. Theories of practice are discussed for their value in theorizing such journeys, and in bringing maps (intentions) and journeys (actuality) closer together