title: Resolving Multiple Propagation Paths in Time of Flight Range Cameras using Direct and Global Separation Methods

authors: Whyte, Refael

subjects: time of flight imaging

abstract: Time of flight (ToF) range cameras illuminate the scene with an amplitude-modulated continuous wave light source and measure the returning modulation envelopes: phase and amplitude. The phase change of the modulation envelope encodes the distance travelled. This technology suffers from measurement errors caused by multiple propagation paths from the light source to the receiving pixel. The multiple paths can be represented as the summation of a direct return, which is the return from the shortest path length, and a global return, which includes all other returns. We develop the use of a sinusoidal pattern from which a closed form solution for the direct and global returns can be computed in nine frames with the constraint that the global return is a spatially lower frequency than the illuminated pattern. In a demonstration on a scene constructed to have strong multipath interference, we find the direct return is not significantly different from the ground truth in 33∕136 pixels tested; where for the full-field measurement, it is significantly different for every pixel tested. The variance in the estimated direct phase and amplitude increases by a factor of eight compared with the standard time of flight range camera technique.

text: Resolving Multiple Propagation Paths in Time of Flight Range Cameras using Direct and Global Separation Methods Time of flight (ToF) range cameras illuminate the scene with an amplitude-modulated continuous wave light source and measure the returning modulation envelopes: phase and amplitude. The phase change of the modulation envelope encodes the distance travelled. This technology suffers from measurement errors caused by multiple propagation paths from the light source to the receiving pixel. The multiple paths can be represented as the summation of a direct return, which is the return from the shortest path length, and a global return, which includes all other returns. We develop the use of a sinusoidal pattern from which a closed form solution for the direct and global returns can be computed in nine frames with the constraint that the global return is a spatially lower frequency than the illuminated pattern. In a demonstration on a scene constructed to have strong multipath interference, we find the direct return is not significantly different from the ground truth in 33∕136 pixels tested; where for the full-field measurement, it is significantly different for every pixel tested. The variance in the estimated direct phase and amplitude increases by a factor of eight compared with the standard time of flight range camera technique.

year: 2015

title: Correcting English text using PPM models

authors: Teahan, W.J.

subjects: computer science

abstract: An essential component of many applications in natural language processing is a language modeler able to correct errors in the text being processed. For optical character recognition (OCR), poor scanning quality or extraneous pixels in the image may cause one or more characters to be mis-recognized; while for spelling correction, two characters may be transposed, or a character may be inadvertently inserted or missed out. 
This paper describes a method for correcting English text using a PPM model. A method that segments words in English text is introduced and is shown to be a significant improvement over previously used methods. A similar technique is also applied as a post-processing stage after pages have been recognized by a state-of-the-art commercial OCR system. We show that the accuracy of the OCR system can be increased from 95.9% to 96.6%, a decrease of about 10 errors per page.

text: Correcting English text using PPM models An essential component of many applications in natural language processing is a language modeler able to correct errors in the text being processed. For optical character recognition (OCR), poor scanning quality or extraneous pixels in the image may cause one or more characters to be mis-recognized; while for spelling correction, two characters may be transposed, or a character may be inadvertently inserted or missed out. 
This paper describes a method for correcting English text using a PPM model. A method that segments words in English text is introduced and is shown to be a significant improvement over previously used methods. A similar technique is also applied as a post-processing stage after pages have been recognized by a state-of-the-art commercial OCR system. We show that the accuracy of the OCR system can be increased from 95.9% to 96.6%, a decrease of about 10 errors per page.

year: 1997-11

title: Whānau aspirations, extracurricular activity  and positive youth development:  The leisure activity patterns and narratives of successful young Māori men and how they might inform  urban whānau raising tamatāne.

authors: Clarke, Gloria Hinemoa

subjects: Leisure

abstract: The purpose of this research is to offer parents and whānau (extended family groups) insight about the kinds of leisure activities that might make a positive contribution to their boys’ development. Focused on the positive developmental benefits of leisure participation in relation to Māori boys, and employing a kaupapa Māori framework and qualitative methods, this study represents a foray into new territory. 
	Conducted ‘by, with, and for’ Māori (the indigenous people of Aotearoa New Zealand), and guided by the question ‘How might the leisure activity patterns and narratives of successful young Māori men inform urban whānau raising tamatāne (Māori boys/sons)?’ the three-phase research design was strengths-based, collaborative, and both retrospective and prospective. In phase one, a group of 11 parents participated in focus group hui (gatherings) in which they established the criteria for ‘successful young Māori men’ (SYMM) based on their aspirations for their primary-school aged boys. In phase two, this whānau of interest then selected six SYMM from a pool of eight volunteers, who, along with one or both of their parents participated in one-off semi-structured interviews. In these interviews, we co-constructed life and leisure maps, and discussed how their childhood leisure activities and experiences contributed to their development and who they are today. In phase three, a selection of raw data from these interviews was prepared for a group analysis, during which the whānau of interest made three key observations: (1) As children and youth, these SYMM had participated in a number and range of organised and informal leisure activities including sport, kapa haka (Māori cultural performance), music, art, and for three of them, faith-based activities; (2) they were “connected” to their parent(s) and whānau; and (3) their leisure activities had brought them into contact with positive male role models. Consequently, the whānau of interest talked about increasing the number and variety of their boys’ leisure activities; how they could further support their boys’ leisure participation; and bringing more male role models into their boys’ lives. 
	The findings of this study support the current literature regarding extracurricular activity participation in relation to positive youth development, but also highlight some methodological issues and cultural and contextual nuances. The research supports international and local studies in which high-performing students participated in a number and combination of extracurricular activities. In contrast, however, the experiences and reflections of the SYMM in this study highlight the limitations of combining all sports and all arts into broad activity categories. The research participants’ leisure activities also point to the relevance and applicability of the Te Whare Tapa Whā model of health and wellbeing. Their involvement in kapa haka contrasts with the (North American) literature in which males are a minority in the performing arts, and while some studies indicate that participation in music making declines in high school, these young men began playing musical instruments in high school. Moreover, the salience and significance of the research participants’ casual leisure activities challenges the tendency to cast informal leisure as the antithesis of extracurricular activity participation. These findings raise questions about the applicability of using international activity categories in Aotearoa New Zealand research, and consequently the need to conduct our own leisure and positive youth development studies. 
Other topics raised in this thesis include rugby and masculinity, spirituality, and the tensions involved in building and honouring our children’s rangatiratanga (independence). The short answer to the research question is that a variety and balance of leisure activities has the potential to make positive contributions to boys’ lives. Implications, limitations, and recommendations for future research are also discussed.

text: Whānau aspirations, extracurricular activity  and positive youth development:  The leisure activity patterns and narratives of successful young Māori men and how they might inform  urban whānau raising tamatāne. The purpose of this research is to offer parents and whānau (extended family groups) insight about the kinds of leisure activities that might make a positive contribution to their boys’ development. Focused on the positive developmental benefits of leisure participation in relation to Māori boys, and employing a kaupapa Māori framework and qualitative methods, this study represents a foray into new territory. 
	Conducted ‘by, with, and for’ Māori (the indigenous people of Aotearoa New Zealand), and guided by the question ‘How might the leisure activity patterns and narratives of successful young Māori men inform urban whānau raising tamatāne (Māori boys/sons)?’ the three-phase research design was strengths-based, collaborative, and both retrospective and prospective. In phase one, a group of 11 parents participated in focus group hui (gatherings) in which they established the criteria for ‘successful young Māori men’ (SYMM) based on their aspirations for their primary-school aged boys. In phase two, this whānau of interest then selected six SYMM from a pool of eight volunteers, who, along with one or both of their parents participated in one-off semi-structured interviews. In these interviews, we co-constructed life and leisure maps, and discussed how their childhood leisure activities and experiences contributed to their development and who they are today. In phase three, a selection of raw data from these interviews was prepared for a group analysis, during which the whānau of interest made three key observations: (1) As children and youth, these SYMM had participated in a number and range of organised and informal leisure activities including sport, kapa haka (Māori cultural performance), music, art, and for three of them, faith-based activities; (2) they were “connected” to their parent(s) and whānau; and (3) their leisure activities had brought them into contact with positive male role models. Consequently, the whānau of interest talked about increasing the number and variety of their boys’ leisure activities; how they could further support their boys’ leisure participation; and bringing more male role models into their boys’ lives. 
	The findings of this study support the current literature regarding extracurricular activity participation in relation to positive youth development, but also highlight some methodological issues and cultural and contextual nuances. The research supports international and local studies in which high-performing students participated in a number and combination of extracurricular activities. In contrast, however, the experiences and reflections of the SYMM in this study highlight the limitations of combining all sports and all arts into broad activity categories. The research participants’ leisure activities also point to the relevance and applicability of the Te Whare Tapa Whā model of health and wellbeing. Their involvement in kapa haka contrasts with the (North American) literature in which males are a minority in the performing arts, and while some studies indicate that participation in music making declines in high school, these young men began playing musical instruments in high school. Moreover, the salience and significance of the research participants’ casual leisure activities challenges the tendency to cast informal leisure as the antithesis of extracurricular activity participation. These findings raise questions about the applicability of using international activity categories in Aotearoa New Zealand research, and consequently the need to conduct our own leisure and positive youth development studies. 
Other topics raised in this thesis include rugby and masculinity, spirituality, and the tensions involved in building and honouring our children’s rangatiratanga (independence). The short answer to the research question is that a variety and balance of leisure activities has the potential to make positive contributions to boys’ lives. Implications, limitations, and recommendations for future research are also discussed.

year: 2020