title: A strategy for the correction of effects of jitter in AMCW lidar images

authors: Streeter, Lee

subjects: Science & Technology

abstract: Full-field range imaging cameras, which are an example of amplitude modulated continuous wave (AMCW) lidar, are subject to multiple error sources. In this paper we consider the possibility that a global jitter and/or drift occurs between the modulation signals to the active illumination source and the camera sensor. A model for jitter is presented and is used to characterise the jitter in a real camera system. Correction of the effects of jitter in real acquired range images is demonstrated by a reduction of the standard deviation of random noise by up to a factor of five, with the best reductions occurring in pixels that receive a strong signal.

text: A strategy for the correction of effects of jitter in AMCW lidar images Full-field range imaging cameras, which are an example of amplitude modulated continuous wave (AMCW) lidar, are subject to multiple error sources. In this paper we consider the possibility that a global jitter and/or drift occurs between the modulation signals to the active illumination source and the camera sensor. A model for jitter is presented and is used to characterise the jitter in a real camera system. Correction of the effects of jitter in real acquired range images is demonstrated by a reduction of the standard deviation of random noise by up to a factor of five, with the best reductions occurring in pixels that receive a strong signal.

year: 2013

title: Interstellar neutral hydrogen in the heliosphere: new horizons observations in the context of models

authors: Swaczyna, P

subjects: mathematics

abstract: Interstellar neutral (ISN) hydrogen is the most abundant species in the outer heliosheath and the very local interstellar medium (VLISM). Charge-exchange collisions in the outer heliosheath result in filtration, reducing the ISN hydrogen density inside the heliosphere. Additionally, these atoms are intensively ionized close to the Sun, resulting in a substantial reduction of their density within a few astronomical units from the Sun. The products of this ionization—pickup ions (PUIs)—are detected by charged particle detectors. The Solar Wind Around Pluto instrument on New Horizons provides, for the first time, PUI observations from the distant heliosphere. We analyze the observations collected between 22 and 52 au from the Sun to find the ISN hydrogen density profile and compare the results with predictions from global heliosphere models. We conclude that the density profile derived from the observations is inconsistent with steady-state model predictions. This discrepancy is not explained by time variations close to the Sun and thus may be related to the temporal evolution of the outer boundaries or VLISM conditions. Furthermore, we show that the cold and hot models of ISN hydrogen distribution are not a good approximation closer to the termination shock. Therefore, we recommend a new fiduciary point based on the available New Horizons observations at 40 au from the Sun, at ecliptic direction (285.°62, 1.°94), where the ISN hydrogen density is 0.11 cm−3. The continued operation of New Horizons should give better insight into the source of the discussed discrepancy.

text: Interstellar neutral hydrogen in the heliosphere: new horizons observations in the context of models Interstellar neutral (ISN) hydrogen is the most abundant species in the outer heliosheath and the very local interstellar medium (VLISM). Charge-exchange collisions in the outer heliosheath result in filtration, reducing the ISN hydrogen density inside the heliosphere. Additionally, these atoms are intensively ionized close to the Sun, resulting in a substantial reduction of their density within a few astronomical units from the Sun. The products of this ionization—pickup ions (PUIs)—are detected by charged particle detectors. The Solar Wind Around Pluto instrument on New Horizons provides, for the first time, PUI observations from the distant heliosphere. We analyze the observations collected between 22 and 52 au from the Sun to find the ISN hydrogen density profile and compare the results with predictions from global heliosphere models. We conclude that the density profile derived from the observations is inconsistent with steady-state model predictions. This discrepancy is not explained by time variations close to the Sun and thus may be related to the temporal evolution of the outer boundaries or VLISM conditions. Furthermore, we show that the cold and hot models of ISN hydrogen distribution are not a good approximation closer to the termination shock. Therefore, we recommend a new fiduciary point based on the available New Horizons observations at 40 au from the Sun, at ecliptic direction (285.°62, 1.°94), where the ISN hydrogen density is 0.11 cm−3. The continued operation of New Horizons should give better insight into the source of the discussed discrepancy.

year: 2024

title: Conscientisation and Resistance: Experiences from implementing a culturally responsive pedagogy of relations

authors: Lawrence, Dawn Cherie

subjects: culturally responsive pedagogy of relations

abstract: Consciousness of being part of a particular hegemonic force (that is to say,political consciousness) is the first stage towards a further progressive self –conscious in which theory and practice will finally be one. (Hoare & Smith,1971, p. 333)

Bishop, Berryman, Tiakiwai and Richardson, (2003) state that effective teachers of Māori students “positively and vehemently reject deficit theorizing as a means of explaining Māori students’ educational achievement” (p.95). This fundamental tenet of the Te Kotahitanga Effective Teaching Profile (ETP) moves beyond simply refraining from publicly articulating discourses that pathologise Māori students and their whānau (Bishop et al., 2003; Bishop & Berryman, 2006; Bishop, Berryman, Cavanagh, & Teddy. 2007). For many teachers it is a challenging, ongoing transformative process of critical self-reflection, which touches the very core of their own culture and identity.

This thesis contends that by working to discursively position themselves within a culturally responsive pedagogy of relations, teachers develop classroom practices that have been shown to positively affect outcomes for Māori students. It goes on to suggest that such discursive repositioning might be seen as praxis, with the potential to transform the inequities experienced by Māori within mainstream educational settings. With this understanding, the culture and leadership approach of the school context becomes a greater influence on teachers’ capacity to realize their agency within this pedagogy than any characteristic of the individual.

text: Conscientisation and Resistance: Experiences from implementing a culturally responsive pedagogy of relations Consciousness of being part of a particular hegemonic force (that is to say,political consciousness) is the first stage towards a further progressive self –conscious in which theory and practice will finally be one. (Hoare & Smith,1971, p. 333)

Bishop, Berryman, Tiakiwai and Richardson, (2003) state that effective teachers of Māori students “positively and vehemently reject deficit theorizing as a means of explaining Māori students’ educational achievement” (p.95). This fundamental tenet of the Te Kotahitanga Effective Teaching Profile (ETP) moves beyond simply refraining from publicly articulating discourses that pathologise Māori students and their whānau (Bishop et al., 2003; Bishop & Berryman, 2006; Bishop, Berryman, Cavanagh, & Teddy. 2007). For many teachers it is a challenging, ongoing transformative process of critical self-reflection, which touches the very core of their own culture and identity.

This thesis contends that by working to discursively position themselves within a culturally responsive pedagogy of relations, teachers develop classroom practices that have been shown to positively affect outcomes for Māori students. It goes on to suggest that such discursive repositioning might be seen as praxis, with the potential to transform the inequities experienced by Māori within mainstream educational settings. With this understanding, the culture and leadership approach of the school context becomes a greater influence on teachers’ capacity to realize their agency within this pedagogy than any characteristic of the individual.

year: 2014