title: Simple harmonic error cancellation in time of flight range imaging

authors: Streeter, Lee

subjects: Three-dimensional image acquisition

abstract: Amplitude modulated continuous wave (AMCW) time of flight (ToF) range imaging provides a full field of distance measurement, but common hardware is implemented with digital technology which leads to unwanted harmonic content, a principle source of error in the distance measurements. Existing strategies for correction of harmonics require auxiliary measurements and amplify noise. A small modification of the data acquisition procedure is described which, intrinsically, is invariant to at least one harmonic. The third harmonic, the main cause of harmonic error, is targeted. Compared to traditional measurements the third harmonic is eliminated with no significant increase in noise variance observed.

text: Simple harmonic error cancellation in time of flight range imaging Amplitude modulated continuous wave (AMCW) time of flight (ToF) range imaging provides a full field of distance measurement, but common hardware is implemented with digital technology which leads to unwanted harmonic content, a principle source of error in the distance measurements. Existing strategies for correction of harmonics require auxiliary measurements and amplify noise. A small modification of the data acquisition procedure is described which, intrinsically, is invariant to at least one harmonic. The third harmonic, the main cause of harmonic error, is targeted. Compared to traditional measurements the third harmonic is eliminated with no significant increase in noise variance observed.

year: 2015

title: Anisotropic three-dimensional MHD turbulence

authors: Matthaeus, William H.

subjects: MHD

abstract: Direct spectral method simulation of the three-dimensional magnetohydrodynamics (MHD) equations is used to explore anisotropy that develops from initially isotropic fluctuations as a consequence of a uniform applied magnetic field. Spectral and variance anisotropies are investigated in both compressible and incompressible MHD. The nature of the spectral anisotropy is consistent with the model of Shebalin et al. [1983] in which the spectrum broadens in the perpendicular wavenumber direction, the anisotropy being greater for smaller wavenumbers. Here this effect is seen for both incompressible and polytropic compressible MHD. In contrast, the longitudinal (compressive) velocity fluctuations remain isotropic. Variance anisotropy is observed for low plasma beta compressible MHD but not for incompressible MHD. Solar wind observations are qualitatively consistent with both variance and spectral anisotropies of the type discussed here.

text: Anisotropic three-dimensional MHD turbulence Direct spectral method simulation of the three-dimensional magnetohydrodynamics (MHD) equations is used to explore anisotropy that develops from initially isotropic fluctuations as a consequence of a uniform applied magnetic field. Spectral and variance anisotropies are investigated in both compressible and incompressible MHD. The nature of the spectral anisotropy is consistent with the model of Shebalin et al. [1983] in which the spectrum broadens in the perpendicular wavenumber direction, the anisotropy being greater for smaller wavenumbers. Here this effect is seen for both incompressible and polytropic compressible MHD. In contrast, the longitudinal (compressive) velocity fluctuations remain isotropic. Variance anisotropy is observed for low plasma beta compressible MHD but not for incompressible MHD. Solar wind observations are qualitatively consistent with both variance and spectral anisotropies of the type discussed here.

year: 1996

title: E hoki mai nei ki te ūkaipō | Return to your place of nourishment [Te Kōputu a te Whanga a Toi | Whakatāne Art Gallery]

authors: Apiata, Hāwea

subjects: toi Māori

abstract: E Hoki Mai Nei ki te Ūkaipō | Return to Your Place of Nourishment brings together works by four wāhine Māori artists, Aimee Ratana, Aisha Roberts, Hollie Tawhiao and Maraea Timutimu, which explore narratives of pakanga
(conflict) through toi (art). In this show, the four artists weave together their unique practices and stories to present a cohesive yet diverse examination of conflicts, with a particular focus on the artists’ own whānau, hapū, and iwi narratives.
Curated by Hāwea Apiata.

text: E hoki mai nei ki te ūkaipō | Return to your place of nourishment [Te Kōputu a te Whanga a Toi | Whakatāne Art Gallery] E Hoki Mai Nei ki te Ūkaipō | Return to Your Place of Nourishment brings together works by four wāhine Māori artists, Aimee Ratana, Aisha Roberts, Hollie Tawhiao and Maraea Timutimu, which explore narratives of pakanga
(conflict) through toi (art). In this show, the four artists weave together their unique practices and stories to present a cohesive yet diverse examination of conflicts, with a particular focus on the artists’ own whānau, hapū, and iwi narratives.
Curated by Hāwea Apiata.

year: 2025-04-17