Second-order model for remote and close-up short-circuit faults currents on DC traction supply

A technique to calculate the current waveform for both close-up and remote short-circuit faults on DC supplied railways and subways is presented. Exact DC short-circuit current calculation is best performed by sophisticated computer transient simulations. However, an accurate simplified calculation method based on second-order approximation which can be easily executed with the help of a calculator or a spreadsheet program is proposed.

On Aspects of Mathematical Reasoning : Affect and Gender

This thesis explores two aspects of mathematical reasoning: affect and gender. I started by looking at the reasoning of upper secondary students when solving tasks. This work revealed that when not guided by an interviewer, algorithmic reasoning, based on memorising algorithms which may or may not be appropriate for the task, was predominant in the students reasoning. Given this lack of mathematical grounding in students reasoning I looked in a second study at what grounds they had for different strategy choices and conclusions. This qualitative study suggested that beliefs about safety, expectation and motivation were important in the central decisions made during task solving.  But are reasoning and beliefs gendered? The third study explored upper secondary school teachers conceptions about gender and students mathematical reasoning. In this study I found that upper secondary school teachers attributed gender symbols including insecurity, use of standard methods and imitative reasoning to girls and symbols such as multiple strategies especially on the calculator, guessing and chance-taking were assigned to boys. In the fourth and final study I found that students, both male and female, shared their teachers view of rather traditional feminities and masculinities. Remarkably however, this result did not repeat itself when students were asked to reflect on their own behaviour: there were some discrepancies between the traits the students ascribed as gender different and the traits they ascribed to themselves. Taken together the thesis suggests that, contrary to conceptions, girls and boys share many of the same core beliefs about mathematics, but much work is still needed if we should create learning environments that provide better opportunities for students to develop beliefs that guide them towards well-grounded mathematical reasoning. 

Teachers' conceptions about students' mathematical reasoning : Gendered or not?

This study looks at how upper secondary school teachers gender stereotype aspects of students' mathematical reasoning. Girls were attributed gender symbols including insecurity, use of standard methods and imitative reasoning. Boys were assigned the symbols such as multiple strategies especially on the calculator, guessing and chance-taking. 

Novel Statistical Methods in Quantitative Genetics : Modeling Genetic Variance for Quantitative Trait Loci Mapping and Genomic Evaluation

This thesis develops and evaluates statistical methods for different types of genetic analyses, including quantitative trait loci (QTL) analysis, genome-wide association study (GWAS), and genomic evaluation. The main contribution of the thesis is to provide novel insights in modeling genetic variance, especially via random effects models. In variance component QTL analysis, a full likelihood model accounting for uncertainty in the identity-by-descent (IBD) matrix was developed. It was found to be able to correctly adjust the bias in genetic variance component estimation and gain power in QTL mapping in terms of precision.  Double hierarchical generalized linear models, and a non-iterative simplified version, were implemented and applied to fit data of an entire genome. These whole genome models were shown to have good performance in both QTL mapping and genomic prediction. A re-analysis of a publicly available GWAS data set identified significant loci in Arabidopsis that control phenotypic variance instead of mean, which validated the idea of variance-controlling genes.  The works in the thesis are accompanied by R packages available online, including a general statistical tool for fitting random effects models (hglm), an efficient generalized ridge regression for high-dimensional data (bigRR), a double-layer mixed model for genomic data analysis (iQTL), a stochastic IBD matrix calculator (MCIBD), a computational interface for QTL mapping (qtl.outbred), and a GWAS analysis tool for mapping variance-controlling loci (vGWAS).

"Hey, I'm learning this"

The article offers a look at the benefits, as well as the negative impact, of using games in mathematics education. The views of teachers on the benefits of using games in teaching mathematics are explored. Information on the guestimate calculator game is provided. Details of a study on the use of guestimate game on Year 5 and 6 students is presented.

Students` impressions of the value of games for the learning of mathematics

The use of mathematical games in primary classrooms is commonplace in Australia. This paper reports on key findings from a larger investigation exploring the impact of games on mathematical learning, student attitudes, and behaviours. 222 Grade 5 and 6 children were taught multiplication and division of decimal numbers using calculator games. This paper raises questions about the students’ attitudes towards games as a vehicle for learning mathematics. One aspect reported in this paper is an apparent difference between students’ attitudes to games usage when data were
collected quantitatively compared with qualitatively.

Students' conflicting attitudes towards games as a vehicle for learning mathematics : a methodological dilemma

Mathematics games are widely employed in school classrooms for such reasons as a reward for early finishers or to enhance students' attitude towards mathematics. During a four week period, a total of 222 Grade 5 and 6 (9 to 12 years old) children from Melbourne, Australia, were taught multiplication and division of decimal numbers using calculator games or rich mathematical activities. Likert scale surveys of the children's attitudes towards games as a vehicle for learning mathematics revealed unexpectedly high proportions of negative attitudes at the conclusion of the research. In contrast, student interview data revealed positive associations between games and mathematical learning. This article reports on the methodological dilemma of resultant conflicting attitudinal data related to game- playing. Concerns arising from the divergence in the results are raised in this article. Implications based on the experience of this study may inform educational researchers about future methodological choices involving attitudinal research.

Estimating the increasing cost of commercial buildings in Australia due to greenhouse emissions trading

The ratification of the Kyoto Protocol by most industrial nations will result in an international greenhouse emissions trading market by or before 2008. Calculating the quantity of embodied energy in commercial buildings has therefore taken on added significance because it is in the creation of energy that most greenhouse gas that causes global warming is released. For energy efficient commercial buildings in Australia, the embodied energy can typically represent between 10 and 20 years of operational energy. When greenhouse emissions trading is introduced in Australia the cost of energy will rise significantly, particularly electricity which relies primarily on burning fossil fuels for generation. This will affect not only the operating energy costs of buildings (light, power & heating/cooling) but also the cost of building materials and construction. Early estimates of the potential cost of future greenhouse emission permits in Australia vary between $IO/tonne to $180Itonne. This cost would be imposed primarily on the producers of energy and passed on by them to consumers via higher energy costs. For a typical commercial building this could lead to an increase in the total procurement cost of buildings of up to 20% due to the energy embodied during the construction or refurbishment of the building. To assist in evaluating these potential cost increases McKean & Park, Sinclair Knight Merz and Deakin University have developed a web-based Carbon Cost Calculator for commercial buildings.

Using activity theory in researching young children's use of calculators

Constructivist and socio-cultural perspectives in mathematics education highlight the crucial role that activity plays in mathematical development and learning. Activity theory provides a socio-cultural lens to help analyse human behaviour, including that which occurs in classrooms. It provides a framework for co-ordinating constructivist and socio-cultural perspectives in mathematics learning. In this paper, we adopt Cole and Engeström's (1991) model of activity theory to examine the mediation offered by the calculator as a tool for creating and supporting learning processes of young children in the social environment of their classroom. By adopting this framework, data on young children's learning outcomes in number, when given free access to calculators, can be examined not only in terms of the mediating role of the calculator, but also within the broader context of the classroom community, the teachers' beliefs and intentions, and the classroom norms and the division of labour. Use of this model in a post hoc situation suggests that activity theory can play a significant role in the planning of future classroom research.

Calculators, mathematics and young children : a study of six children using calculators as part of the mathematics curriculum during their first two years of school

The thesis investigates the role a calculator can play in the developing number knowledge of three girls and three boys as part of their mathematics program, during their first two years at primary school. Random sampling was used initially to select six girls and six boys from the twenty-four children entering a 1993 prep class. These twelve children were interviewed on entrance to school and based on the performance of the twelve children on the initial interview, a girl and a boy were chosen from the higher, middle and lower achievers to take part in the full study. The class teachers involved were previously participants in the ‘Calculators in Primary Mathematics’ research program and were committed to the use of calculators in their mathematics program. A case study approach using qualitative methods within the activity theory framework is used to collect relevant data and information, an analysis of five interviews with each child and observations of the children in forty-one classroom lessons provides comprehensive data on the children's developing number knowledge during the two years. The analysis questionnaires establishes each teacher's perceptions of the children's number learning at the beginning and end of each year, compares teacher expectations with children's actual performance for the year and compares curriculum expectations with children's actual performance. A teacher interview established reasons for changes in teaching style; teacher expectations; children's number learning; and was used to confirm my research findings. An activity theory framework provides an appropriate means of co-coordinating perspectives within this research to enable a description of the child's number learning within a social environment. This framework allows for highlighting the mediation offered by the calculator supporting the children's number learning in the classroom. Levels of children's developing number knowledge reached when working with a calculator and as a result of calculator use are mapped against the levels recommended in ‘Mathematics in the National Curriculum’ (National Curriculum Council, December 1988), and the Curriculum and Standards Framework: Mathematics (Board of Studies 2000). Findings from this comparison illustrate that the six children's performance in number was enhanced when using a calculator and indicate that on-going development and understanding of number concepts occurred at levels of performance at least two years in advance of curriculum recommendations for the first two years of school.

In the office SFX

In the Office SFX is a sound effect of a busy office.

The mechanics of computation and human thought

Thousands of students are preparing for chemistry examinations in June. An unresolved debate is whether they should be permitted to use graphics and programmable calculators in those examinations. Some educators have not only advocated the use of graphics calculators, but have also pointed to the Danish system in which students are permitted to use computers in senior school examinations.

In some Australian jurisdictions, graphics calculators are permitted in year 12 mathematics examinations, but not in chemistry examinations. The reasoning is that information or methods of solving numerical chemical problems can be stored in the memory of graphics calculators, giving some students an unfair advantage. This means that chemistry students either have to learn how to use (and buy!) two types of calculators or, if they only have one calculator, are disadvantaged in using non-programmable calculators in mathematics examinations.

The use of technology (or its lack thereof) can limit how and what students learn. “The mechanics of computation and human thought” is an allusion to Asimov’s short story, “A Feeling of Power” in which, overuse of technology has caused people to forget how to do simple arithmetic. In our current assessment system, the insistence that students must be able to do simple chemical calculations has lead to underuse of available technology. The misperception is that the ability to do calculations is linked to understanding of concepts.

Graphics calculators, programmable calculators and computers are tools. Instead of banning or limiting technology, we should take the opportunity to rethink what is being assessed and how it is assessed. It is the proper use of technology, by combining the mechanics of computation and human thought to deepen understanding and to ask probing questions that truly leads to a feeling of power.

Consumer response to unit pricing for mobile telephony

This project is a co-operative study between ACCAN and Deakin University. It focuses on Unit Pricing, the practice of displaying the price of goods or services based on a standard quantity, to allow a direct comparison between competitive offers. This study aimed at gauging whether the new unit pricing information for mobile phone contracts assists consumers in assessing and comparing the value provided across alternative contracts within and between suppliers. Some 24 in-depth interviews were conducted with consumers who had recently bought or renewed a mobile phone contract.
The research showed that most consumers could use unit pricing information and some found it useful. Where consumers’ plans had unlimited or infinite capacity, unit pricing information was not relevant. Many consumers preferred voice allowances to be expressed in minutes, rather than in dollar allowances. Data was the most problematic category, as consumers typically had only limited understanding of the amount of data that various applications used. Most did have a broad understanding of what total capacity in data they would need, typically expressed in gigabytes.
Consumers commonly sought simplicity in deciding on which plan they would purchase or renew. A key issue for consumers was not “going over”, that is not exceeding their call, text or data allowances. For that reason, they were prepared to choose a plan that commonly resulted in them not using their full allowances each month. Some consumers used Apps on their smartphones to monitor their usage. Not all consumers had experienced advisory messages about nearing the limits of their plan’s allowances.
The Report recommended that:

R1. Unit pricing should be maintained
R2. Where unit pricing is provided for call costs, these should be expressed in terms of a one-minute call.
R3 Unit pricing for data should be expressed in terms of gigabytes or part thereof.
R4 In advertising mobile phone plans and at point of sales, customers should be provided with three levels of information – 1) overall plan features, 2) unit pricing information and 3) a data calculator.
R5 Level 2 and 3 information should be provided in a standard format across the industry, enabling consumers to make ready comparisons between plans and between competitive offers from different providers.
R6. Continuing public education is needed.
R7. Warnings about going over should always include the date when the allowance period ends and tell consumers what the rate will be if they “go over” based on the Level 2 information.
R8. The Consumer Protection Code should be reviewed in the light of these findings and recommendations.

Fire Hazard in Coconino County, Arizona

Fire is a major management issue in the southwestern United States. Three spatial models of fire risk for Coconino County, Northern Arizona. These models were generated using thematic data layers depicting vegetation, elevation, wind speed and direction, and precipitation for January (winter), June (summer), and July (start of monsoon season). ArcGIS 9.0 was used to weight attributes in raster layers to reflect their influence on fire risk and to interpolate raster data layers from point data. Final models were generated using the raster calculator in the Spatial Analyst extension of ArcGIS 9.0. Ultimately, the unique combinations of variables resulted in three different models illustrating the change in fire risk during the year.

A aquisição automática de dados proporcionando discussões conceituais na física térmica do ensino médio

Diante dos problemas vivenciados no ensino da Física cabe ao professor a tarefa de tentar combater as dificuldades de seus alunos, proporcionando-lhes experiências de aprendizagem eficazes, procurando atualizar, tanto quanto possível, os instrumentos pedagógicos que utiliza. Considerando a especificidade experimental da Física, a realização de atividades de laboratório faz-se de grande importância. Porém, uma reflexão a respeito de como utilizar tais atividades é necessária para que possam realmente contribuir para uma aprendizagem significativa. Nesta busca, a utilização da aquisição automática de dados através de dispositivos do tipo CBL (do inglês Calculator Based Laboratory) pode, sem dúvida, trazer grande contribuição. Aliando-se à grande potencialidade do uso destes dispositivos, à inexistência de trabalhos divulgados envolvendo seu uso no ensino de Física no Brasil e, finalmente, ao fato deste ser um equipamento adquirido recentemente pelo Centro Federal de Educação Tecnológica de Pelotas, instituição na qual este trabalho foi desenvolvido, optou-se por propor nesta dissertação a utilização de tais equipamentos em laboratório didático de Física Térmica no ensino médio. Dentre os assuntos abordados cita-se: calor, temperatura e energia interna; resfriamento de um corpo; mudança de estado físico e pressão de vapor; transmissão do calor. Alguns destes assuntos não são normalmente abordados no ensino médio, como a lei de resfriamento e análise da curva de pressão de vapor. Outros tópicos levam a uma maior contextualização da Física, como umidade relativa do ar e formação de geada. Esta proposta é fundamentada pela teoria da aprendizagem significativa de David Ausubel e pela teoria da interação social de Lev Vigotski Através desta experiência de implementação em aulas regulares de ensino médio, espera-se verificar a possibilidade de sua utilização neste nível de ensino. Como produto deste trabalho de dissertação, foi produzido material instrucional que compreende guias experimentais e textos envolvendo os conteúdos abordados, assim como material hipermídia sobre transmissão do calor contendo algumas animações e teste interativo desenvolvidos em Flash MX. Todo este material foi concebido e implementado buscando levar o aluno a uma aprendizagem significativa dos conceitos físicos.