title: Radial evolution of cross helicity at low and high latitudes in the solar wind

authors: Breech, Ben

subjects: MHD turbulence

abstract: We employ a turbulence transport theory to the radial evolution of the solar wind at both low and high latitudes. The theory includes cross helicity, magnetohydrodynamic (MHD) turbulence, and driving by shear and pickup ions. The radial decrease of cross helicity, observed in both low and high latitudes, can be accounted for by including sufficient shear driving to overcome the tendency of MHD turbulence to produce Alfvénic states. The shear driving is weaker at high latitudes leading to a slower evolution. Model results are compared with observations from Ulysses and Voyager.

text: Radial evolution of cross helicity at low and high latitudes in the solar wind We employ a turbulence transport theory to the radial evolution of the solar wind at both low and high latitudes. The theory includes cross helicity, magnetohydrodynamic (MHD) turbulence, and driving by shear and pickup ions. The radial decrease of cross helicity, observed in both low and high latitudes, can be accounted for by including sufficient shear driving to overcome the tendency of MHD turbulence to produce Alfvénic states. The shear driving is weaker at high latitudes leading to a slower evolution. Model results are compared with observations from Ulysses and Voyager.

year: 2005

title: 3D-printed Acoustic Directional Couplers

authors: MacDonell, Marcus Scott Glengarry

subjects: Acoustical engineering

abstract: Acoustic Directional Couplers permit separation of forward and reverse sound pressure waves. This separation opens the way to traceable precision acoustic reflection measurements. In order to span the audio frequency range, multiple couplers will be required, as each operates over a frequency range of slightly more than one octave. To reach 20kHz or above requires vary small, mechanically precise construction. We achieve this by 3D printing techniques. We manufactured two otherwise-identical couplers, one made with a powder-type 3D printer with photopolymer support structure, the other made with an ABS-filament thermoplastic-type 3D printer. We compare the measured acoustic performance of these two couplers. The wavelength of sound at 20 kHz is comparable to that encountered at a microwave frequency of 18 GHz. We expect to be able to fabricate couplers that reach 55 kHz where the wavelength is 6 mm, corresponding to a frequency of 50 GHz in the electromagnetic spectrum.

text: 3D-printed Acoustic Directional Couplers Acoustic Directional Couplers permit separation of forward and reverse sound pressure waves. This separation opens the way to traceable precision acoustic reflection measurements. In order to span the audio frequency range, multiple couplers will be required, as each operates over a frequency range of slightly more than one octave. To reach 20kHz or above requires vary small, mechanically precise construction. We achieve this by 3D printing techniques. We manufactured two otherwise-identical couplers, one made with a powder-type 3D printer with photopolymer support structure, the other made with an ABS-filament thermoplastic-type 3D printer. We compare the measured acoustic performance of these two couplers. The wavelength of sound at 20 kHz is comparable to that encountered at a microwave frequency of 18 GHz. We expect to be able to fabricate couplers that reach 55 kHz where the wavelength is 6 mm, corresponding to a frequency of 50 GHz in the electromagnetic spectrum.

year: 2014

title: Hau

authors: Lodge, Martin

subjects: music

abstract: The article presents reflections on some issues encountered when combining traditional Maori and Western concert music. These issues include tradition and repertoire versus innovation, control versus freedom, collaboration versus appropriation, and the overlapping roles of creator and performer. Focal to the article is "Hau," a Maori word meaning breath or wind. The author also presents a comparison of Western music with traditional Maori instrumental music.

text: Hau The article presents reflections on some issues encountered when combining traditional Maori and Western concert music. These issues include tradition and repertoire versus innovation, control versus freedom, collaboration versus appropriation, and the overlapping roles of creator and performer. Focal to the article is "Hau," a Maori word meaning breath or wind. The author also presents a comparison of Western music with traditional Maori instrumental music.

year: 2007