title: Arithmetic coding revisited

authors: Moffat, Alistair

subjects: Coding and information theory

abstract: Over the last decade, arithmetic coding has emerged as an important compression tool. It is now the method of choice for adaptive coding on multisymbol alphabets because of its speed,
low storage requirements, and effectiveness of compression. This article describes a new implementation of arithmetic coding that incorporates several improvements over a widely used earlier version by Witten, Neal, and Cleary, which has become a de facto standard. These improvements include fewer multiplicative operations, greatly extended range of alphabet sizes and symbol probabilities, and the use of low-precision arithmetic, permitting implementation by fast shift/add operations. We also describe a modular structure that separates the coding, modeling, and probability estimation components of a compression system. To motivate the improved coder, we consider the needs of a word-based text compression program. We report a range of experimental results using this and other models. Complete source code is available.

text: Arithmetic coding revisited Over the last decade, arithmetic coding has emerged as an important compression tool. It is now the method of choice for adaptive coding on multisymbol alphabets because of its speed,
low storage requirements, and effectiveness of compression. This article describes a new implementation of arithmetic coding that incorporates several improvements over a widely used earlier version by Witten, Neal, and Cleary, which has become a de facto standard. These improvements include fewer multiplicative operations, greatly extended range of alphabet sizes and symbol probabilities, and the use of low-precision arithmetic, permitting implementation by fast shift/add operations. We also describe a modular structure that separates the coding, modeling, and probability estimation components of a compression system. To motivate the improved coder, we consider the needs of a word-based text compression program. We report a range of experimental results using this and other models. Complete source code is available.

year: 1998-07-01

title: Sticky trapping of adult mayflies, stoneflies and caddisflies alongside three contrasting streams near Hamilton, New Zealand

authors: Collier, Kevin J.

subjects: adult insects

abstract: Sticky traps were used to catch adult mayflies (Ephemeroptera), stoneflies (Plecoptera) and caddisflies (Trichoptera) alongside three second order streams bordered by pines (Pinus radiata), willow (Salix sp.) or native forest (predominantly kanuka, Kunzea ericoides) near Hamilton, New Zealand. Five traps were attached to tree trunks at each of three heights (0.5 m, 1.5 m and 5.0 m from base), and were changed monthly between September 1993 and February 1994. During this period, species richness and numbers of mayflies, stoneflies and caddisflies were highest atthe willow site (31 species and 75% of total numbers), followed by the native site (17 species and 19% of numbers) and the pine site (14 species and 6% of numbers). Catches at the pine site were dominated by mayflies (78% of numbers), whereas mayflies and stoneflies were both relatively abundant atthe native site (49% and 33%, respectively), and mayflies and caddisflies atthe willow site (53% and 44%, respectively). Highest numbers at each site were recorded in December-January, but there did not appear to be a seasonal pattern in species richness. Trap height did not have a significant effect on numbers of mayflies or caddisflies caught at the willow site in December. Sticky traps represent a cheap and passive means of catching predominantly flying adults where numbers are high. Our trap design is likely to be most effective alongside larger streams where the area of streambed relative to trap area is greater.

text: Sticky trapping of adult mayflies, stoneflies and caddisflies alongside three contrasting streams near Hamilton, New Zealand Sticky traps were used to catch adult mayflies (Ephemeroptera), stoneflies (Plecoptera) and caddisflies (Trichoptera) alongside three second order streams bordered by pines (Pinus radiata), willow (Salix sp.) or native forest (predominantly kanuka, Kunzea ericoides) near Hamilton, New Zealand. Five traps were attached to tree trunks at each of three heights (0.5 m, 1.5 m and 5.0 m from base), and were changed monthly between September 1993 and February 1994. During this period, species richness and numbers of mayflies, stoneflies and caddisflies were highest atthe willow site (31 species and 75% of total numbers), followed by the native site (17 species and 19% of numbers) and the pine site (14 species and 6% of numbers). Catches at the pine site were dominated by mayflies (78% of numbers), whereas mayflies and stoneflies were both relatively abundant atthe native site (49% and 33%, respectively), and mayflies and caddisflies atthe willow site (53% and 44%, respectively). Highest numbers at each site were recorded in December-January, but there did not appear to be a seasonal pattern in species richness. Trap height did not have a significant effect on numbers of mayflies or caddisflies caught at the willow site in December. Sticky traps represent a cheap and passive means of catching predominantly flying adults where numbers are high. Our trap design is likely to be most effective alongside larger streams where the area of streambed relative to trap area is greater.

year: 1995

title: Te Whatu Kakahu: Assessment in Kaupapa Maori Early Childhood Practice

authors: Rameka, Lesley Kay

subjects: Kaupapa Maori

abstract: Through the exploration of Kaupapa Māori assessment approaches, I examine the reclaiming and reframing of Māori ways of knowing and being within early childhood practice. Assessment is the vehicle for reclaiming and reframing while Kaupapa Māori theory is the fuel that ignites and drives the vehicle.

The effects of successive education policies remain today with Māori children, and their families continuing to disengage from education and consistently receiving disproportionately lower outcomes, opportunities and benefits. Reclaiming and reframing Māori ways of knowing and being within early childhood assessment thinking and practice is a means of addressing the cultural and educational disparities faced by Māori children within an education system that upholds western cultural and educational superiority, privilege and truths.  Key questions in this process of reclaiming and reframing are: Who has the power to define?  Whose truths are being reflected and how are these truths constructed? 

The metaphor of whatu kākahu or weaving of clothing has been used to frame this thesis. The process has involved weaving the Kaupapa Māori theory elements of conscientisation, resistance, transformative praxis and Māori ways of knowing and being, across and within historical, cultural and educational paradigms and understandings, to fashion assessment kākahu that afford comfort, warmth and flexibility in a contemporary early childhood context. This research case studies the progress of three Māori early childhood services and kōhanga reo towards the development of Kaupapa Māori early childhood assessment understandings and framings (kākahu), that reflect their particular ways of knowing and being, context and aspirations for children. This thesis has been about their assessment journeys. These journeys are a work in progress and that work continues.

A qualitative, Kaupapa Māori research methodology was used to gather, collate and analyse data in this research.  In accordance with Kaupapa Māori research aspirations and expectations, this research focuses on areas of importance and concern for Māori, and involved retrieving space for Māori voices to be heard. This research can be seen as a means of privileging Māori approaches, perspectives and ways of knowing and being in early childhood assessment practice.

Kaupapa Māori assessment is an important agenda for early childhood.   It builds upon Māori philosophical and epistemological understandings that express Māori ways of knowing and being. Kaupapa Māori assessment is able to contribute significantly to children’s learning and potential growth and is an important tool in constructing educational outcomes for Māori children. It is therefore an important agenda for early childhood.

text: Te Whatu Kakahu: Assessment in Kaupapa Maori Early Childhood Practice Through the exploration of Kaupapa Māori assessment approaches, I examine the reclaiming and reframing of Māori ways of knowing and being within early childhood practice. Assessment is the vehicle for reclaiming and reframing while Kaupapa Māori theory is the fuel that ignites and drives the vehicle.

The effects of successive education policies remain today with Māori children, and their families continuing to disengage from education and consistently receiving disproportionately lower outcomes, opportunities and benefits. Reclaiming and reframing Māori ways of knowing and being within early childhood assessment thinking and practice is a means of addressing the cultural and educational disparities faced by Māori children within an education system that upholds western cultural and educational superiority, privilege and truths.  Key questions in this process of reclaiming and reframing are: Who has the power to define?  Whose truths are being reflected and how are these truths constructed? 

The metaphor of whatu kākahu or weaving of clothing has been used to frame this thesis. The process has involved weaving the Kaupapa Māori theory elements of conscientisation, resistance, transformative praxis and Māori ways of knowing and being, across and within historical, cultural and educational paradigms and understandings, to fashion assessment kākahu that afford comfort, warmth and flexibility in a contemporary early childhood context. This research case studies the progress of three Māori early childhood services and kōhanga reo towards the development of Kaupapa Māori early childhood assessment understandings and framings (kākahu), that reflect their particular ways of knowing and being, context and aspirations for children. This thesis has been about their assessment journeys. These journeys are a work in progress and that work continues.

A qualitative, Kaupapa Māori research methodology was used to gather, collate and analyse data in this research.  In accordance with Kaupapa Māori research aspirations and expectations, this research focuses on areas of importance and concern for Māori, and involved retrieving space for Māori voices to be heard. This research can be seen as a means of privileging Māori approaches, perspectives and ways of knowing and being in early childhood assessment practice.

Kaupapa Māori assessment is an important agenda for early childhood.   It builds upon Māori philosophical and epistemological understandings that express Māori ways of knowing and being. Kaupapa Māori assessment is able to contribute significantly to children’s learning and potential growth and is an important tool in constructing educational outcomes for Māori children. It is therefore an important agenda for early childhood.

year: 2012