title: Multiple frequency range imaging to remove measurement ambiguity

authors: Payne, Andrew D.

subjects: range imaging system

abstract: Range imaging systems use a specialised sensor to capture an image where object distance (range) is measured for every pixel using time-of-flight. The scene is illuminated with an amplitude modulated light source, and the phase of the modulation envelope of the reflected light is measured to determine flight time, hence object distance for each pixel. As the modulation waveform is cyclic, an ambiguity problem exists if the phase shift exceeds 2π radians. To overcome this problem we demonstrate a method that superposes two different modulation frequencies within a single capture. This technique reduces the associated overhead compared with performing two sequential measurements, allowing the system to retain high range measurement precision at rapid acquisition rates. A method is also provided to avoid interference from aliased harmonics during sampling, which otherwise contaminate the resulting range measurement. Experimental results show the potential of the multiple frequency approach; producing high measurement precision while avoiding ambiguity. The results also demonstrate the limitation of this technique, where large errors can be introduced through a combination of a low signal to noise ratio and suboptimal selection of system parameters.

text: Multiple frequency range imaging to remove measurement ambiguity Range imaging systems use a specialised sensor to capture an image where object distance (range) is measured for every pixel using time-of-flight. The scene is illuminated with an amplitude modulated light source, and the phase of the modulation envelope of the reflected light is measured to determine flight time, hence object distance for each pixel. As the modulation waveform is cyclic, an ambiguity problem exists if the phase shift exceeds 2π radians. To overcome this problem we demonstrate a method that superposes two different modulation frequencies within a single capture. This technique reduces the associated overhead compared with performing two sequential measurements, allowing the system to retain high range measurement precision at rapid acquisition rates. A method is also provided to avoid interference from aliased harmonics during sampling, which otherwise contaminate the resulting range measurement. Experimental results show the potential of the multiple frequency approach; producing high measurement precision while avoiding ambiguity. The results also demonstrate the limitation of this technique, where large errors can be introduced through a combination of a low signal to noise ratio and suboptimal selection of system parameters.

year: 2009

title: Triumph displays inform eavesdropping little blue penguins of new dominance asymmetries

authors: Mouterde, Solveig C.

subjects: agonistic interaction

abstract: Agonistic signals used during contests over important resources have been extensively studied; postconflict signals have received comparatively little attention. While ‘triumph displays’, performed by winners following fights, have been described for many species, no experiment has yet assessed one of the main hypotheses explaining their existence: advertising victory to social eavesdroppers. Our experiments evaluated the impact of triumph calls on the behaviour and stress responses of surrounding penguins. We found that territorial male little blue penguins, Eudyptula minor, having previously been exposed to playback of a vocal exchange between conspecifics followed by the sounds of a fight, had higher heart rates in response to the winner’s call than that of the loser; females had high rates in response to both winners and losers. Males were also less likely to threaten winners than losers vocally during a simulated approach of their burrow, while females remained silent in both contexts. Our findings support the hypothesis that triumph calls facilitate an association of winners’ distinctive vocalizations with stress generated by nearby overt aggression. By advertising their victories, males may establish a ‘reputation’ for winning fights within the social group, potentially reducing the likelihood of being challenged by eavesdroppers in future contests.

text: Triumph displays inform eavesdropping little blue penguins of new dominance asymmetries Agonistic signals used during contests over important resources have been extensively studied; postconflict signals have received comparatively little attention. While ‘triumph displays’, performed by winners following fights, have been described for many species, no experiment has yet assessed one of the main hypotheses explaining their existence: advertising victory to social eavesdroppers. Our experiments evaluated the impact of triumph calls on the behaviour and stress responses of surrounding penguins. We found that territorial male little blue penguins, Eudyptula minor, having previously been exposed to playback of a vocal exchange between conspecifics followed by the sounds of a fight, had higher heart rates in response to the winner’s call than that of the loser; females had high rates in response to both winners and losers. Males were also less likely to threaten winners than losers vocally during a simulated approach of their burrow, while females remained silent in both contexts. Our findings support the hypothesis that triumph calls facilitate an association of winners’ distinctive vocalizations with stress generated by nearby overt aggression. By advertising their victories, males may establish a ‘reputation’ for winning fights within the social group, potentially reducing the likelihood of being challenged by eavesdroppers in future contests.

year: 2012

title: Dual cultural identity and tangihanga: Conflict, resolution and unexpected outcomes

authors: Edge, Kiri

subjects: bereavement

abstract: New Zealand has a significant number of dual-cultural whānau (families) which incorporate the identities of both Pākehā (New Zealander of European descent) and Māori (indigenous peoples of New Zealand). Little attention has been paid to the bereavement processes that will inevitably impact upon the lives of these whānau/families. As part of the Tangihanga Research Programme based at The University of Waikato, a directed study was conducted with a participant whose family/whānau included two life ways: Māori and Pākehā. An open-ended narrative approach was used to explore the participant’s bereavement after the death of his beloved wife. Two central themes emerged within the narrative, which related to conflict and eventual resolution. Decision-making processes and language played significant roles in the conflict experienced by the participant. Communication and compromise helped to resolve these conflicts. Unexpected outcomes included new understandings and strengthened connections between the participant and his wife’s marae.

text: Dual cultural identity and tangihanga: Conflict, resolution and unexpected outcomes New Zealand has a significant number of dual-cultural whānau (families) which incorporate the identities of both Pākehā (New Zealander of European descent) and Māori (indigenous peoples of New Zealand). Little attention has been paid to the bereavement processes that will inevitably impact upon the lives of these whānau/families. As part of the Tangihanga Research Programme based at The University of Waikato, a directed study was conducted with a participant whose family/whānau included two life ways: Māori and Pākehā. An open-ended narrative approach was used to explore the participant’s bereavement after the death of his beloved wife. Two central themes emerged within the narrative, which related to conflict and eventual resolution. Decision-making processes and language played significant roles in the conflict experienced by the participant. Communication and compromise helped to resolve these conflicts. Unexpected outcomes included new understandings and strengthened connections between the participant and his wife’s marae.

year: 2010