title: Adapting the bidirectional Kalman filter for use in multi-frequency Time-of-flight range imaging

authors: Alqassab, Ali

subjects: Time-of-flight

abstract: Time-of-flight range imaging cameras obtain range by producing amplitude modulated light and measuring the time taken for light to travel to the scene and back to the camera. Time-of-flight cameras require at least three raw measurements to calculate range. Raw frames are captured sequentially, and as such, motion in scenes during capture leads to inconsistent raw frame measurements and erroneous range calculations. Motion error constrains Time-of-flight cameras to non-dynamic scenes and limits their potential applications. The Time-of-flight bidirectional Kalman filter method is a state-of-the-art method known to reduce error due to transverse motion in cameras operating with a single modulation frequency. The method works by treating raw frames as a noisy time series and running the Kalman filter on it to produce a range estimation at every raw frame. The Kalman filter is then reapplied to the data in reverse to produce another set of range estimations, and a composite range is selected from the two set of range estimations. A number of commercial timeof-flight cameras, such as the Microsoft Kinect V2, use multiple modulation frequencies. In this thesis, we adapt the bidirectional Kalman filter method to multi-frequency operated cameras by having the prediction component of the Kalman filter take into account the change in amplitude and phase shift caused by the change in frequency. The amplitude component of the prediction is performed linearly by multiplication, while the phase shift component of the prediction is performed using the ratio of the modulation frequencies. The phase shift prediction across modulation frequencies requires the phase to be unwrapped. The unwrapping is performed between modulation frequencies by selecting the number of phase wraps that best predicts the two following raw frames. Finally, to ensure correct composite phase selection, an alternative method for selecting the composite phase is proposed for the adapted bidirectional Kalman filter. We perform quantitative and qualitative experiments to test the proposed method. In the quantitative experiment, the proposed method produces less error than the classical Discrete Fourier Transform approach in 70% of tested instances. The qualitative experiment shows that the proposed method significantly reduces motion blur.

text: Adapting the bidirectional Kalman filter for use in multi-frequency Time-of-flight range imaging Time-of-flight range imaging cameras obtain range by producing amplitude modulated light and measuring the time taken for light to travel to the scene and back to the camera. Time-of-flight cameras require at least three raw measurements to calculate range. Raw frames are captured sequentially, and as such, motion in scenes during capture leads to inconsistent raw frame measurements and erroneous range calculations. Motion error constrains Time-of-flight cameras to non-dynamic scenes and limits their potential applications. The Time-of-flight bidirectional Kalman filter method is a state-of-the-art method known to reduce error due to transverse motion in cameras operating with a single modulation frequency. The method works by treating raw frames as a noisy time series and running the Kalman filter on it to produce a range estimation at every raw frame. The Kalman filter is then reapplied to the data in reverse to produce another set of range estimations, and a composite range is selected from the two set of range estimations. A number of commercial timeof-flight cameras, such as the Microsoft Kinect V2, use multiple modulation frequencies. In this thesis, we adapt the bidirectional Kalman filter method to multi-frequency operated cameras by having the prediction component of the Kalman filter take into account the change in amplitude and phase shift caused by the change in frequency. The amplitude component of the prediction is performed linearly by multiplication, while the phase shift component of the prediction is performed using the ratio of the modulation frequencies. The phase shift prediction across modulation frequencies requires the phase to be unwrapped. The unwrapping is performed between modulation frequencies by selecting the number of phase wraps that best predicts the two following raw frames. Finally, to ensure correct composite phase selection, an alternative method for selecting the composite phase is proposed for the adapted bidirectional Kalman filter. We perform quantitative and qualitative experiments to test the proposed method. In the quantitative experiment, the proposed method produces less error than the classical Discrete Fourier Transform approach in 70% of tested instances. The qualitative experiment shows that the proposed method significantly reduces motion blur.

year: 2020

title: The effect of complement C5a on mitochondrial functions of PC12 cells

authors: Martinus, Ryan Dennis

subjects: C5a

abstract: C5a is thought to play a role during complement-activated neuronal apoptotic cell death in the central nervous system. The mechanisms responsible are however not well-understood. As mitochondria play a key role during apoptosis, we investigated mitochondria as a potential target for C5a. Using PC12 cells, we demonstrated that exposure to C5a led to inhibition of mitochondrial respiration, dehydrogenase and cytochrome c oxidase activities. Interestingly, an increase in expression of the mitochondrial stress protein chaperonin 60 was also observed, confirming a marked effect of C5a on mitochondrial functions. These observations are the first documented intracellular effects noted for the complement molecule C5a in in-vitro cultured cells.

text: The effect of complement C5a on mitochondrial functions of PC12 cells C5a is thought to play a role during complement-activated neuronal apoptotic cell death in the central nervous system. The mechanisms responsible are however not well-understood. As mitochondria play a key role during apoptosis, we investigated mitochondria as a potential target for C5a. Using PC12 cells, we demonstrated that exposure to C5a led to inhibition of mitochondrial respiration, dehydrogenase and cytochrome c oxidase activities. Interestingly, an increase in expression of the mitochondrial stress protein chaperonin 60 was also observed, confirming a marked effect of C5a on mitochondrial functions. These observations are the first documented intracellular effects noted for the complement molecule C5a in in-vitro cultured cells.

year: 2011-08

title: Representations of diversity in the revised New Zealand PictureBook Collection

authors: Daly, Nicola

subjects: picturebooks

abstract: Collections of children’s literature are used for a range of reasons including preservation, record keeping, and more recently the encouragement of intercultural understanding. Both the signifi- cance of learning about other cultures and the importance of children seeing themselves reflected in the books that they read have been discussed extensively. In 2010, the New Zealand PictureBook Collection (NZPBC) was developed in order to create a resource that reflected New Zealand national identity. In 2015 the NZPBC was revised and this article presents a visual and textual analysis of the diversity present in the sixty books nomi- nated through the lens of critical multicultural analysis, using four variables. Findings indicate considerable diversity is present in the collection in terms of representations of ethnicity and family; less so for representations of disability and languages.

text: Representations of diversity in the revised New Zealand PictureBook Collection Collections of children’s literature are used for a range of reasons including preservation, record keeping, and more recently the encouragement of intercultural understanding. Both the signifi- cance of learning about other cultures and the importance of children seeing themselves reflected in the books that they read have been discussed extensively. In 2010, the New Zealand PictureBook Collection (NZPBC) was developed in order to create a resource that reflected New Zealand national identity. In 2015 the NZPBC was revised and this article presents a visual and textual analysis of the diversity present in the sixty books nomi- nated through the lens of critical multicultural analysis, using four variables. Findings indicate considerable diversity is present in the collection in terms of representations of ethnicity and family; less so for representations of disability and languages.

year: 2017