title: Why your battery meter tells lies and it's hard to fix: Effect of pauses in cycling on submillihertz battery impedance

authors: Wilson, Marcus T.

subjects: battery

abstract: Rechargeable lithium-ion batteries are an increasing part of our world, found in small devices such as medical implants and mobile phones, up to much larger applications in electric vehicles and the huge battery electric storage systems (BESS) that support the modern electricity grid. But despite the advances in design and manufacturing, your battery meter still does not tell you the truth: "75% charge remaining" most likely does not mean 75% charge remaining. On a trivial scale this means your phone battery goes flat unexpectedly; less trivially your car runs out of charge before you get home, and on a cold winter's morning the electricity grid might not actually be able to provide the peak power that its operators think it can. The reason that producing an accurate meter is so challenging is that battery history matters. A battery's response to an electrical stimulus doesn't just depend on its state now, but also on its state in the past. In mathematical terms, its behaviour is described by fractional differential equations, where the order of the equation is non-integer. In this presentation, we discuss an experiment where we have looked at the effect of a long (56 day) break in battery battery charge/discharge cycling on electrical properties of the battery. On recommencement of cycling, we can discern the effect of the pause on impedance for around 30 days after the break. To see the effect we have constructed the impedance spectrum at ultra-low frequencies (10 μHz - 10 mHz) by applying wavelet methods to time-series data of voltage and current. However, if uncontrolled, other factors such as the shape of stimulating waveforms will mask much of this history effect, and thus in practice history may only matter on the scale of a few days. Nonetheless, results show that answering a simple question "what is my battery charge" does not have a simple physical answer, and thus producing a battery meter that does not lie remains a real challenge for theoretical physicists and mathematicians.

text: Why your battery meter tells lies and it's hard to fix: Effect of pauses in cycling on submillihertz battery impedance Rechargeable lithium-ion batteries are an increasing part of our world, found in small devices such as medical implants and mobile phones, up to much larger applications in electric vehicles and the huge battery electric storage systems (BESS) that support the modern electricity grid. But despite the advances in design and manufacturing, your battery meter still does not tell you the truth: "75% charge remaining" most likely does not mean 75% charge remaining. On a trivial scale this means your phone battery goes flat unexpectedly; less trivially your car runs out of charge before you get home, and on a cold winter's morning the electricity grid might not actually be able to provide the peak power that its operators think it can. The reason that producing an accurate meter is so challenging is that battery history matters. A battery's response to an electrical stimulus doesn't just depend on its state now, but also on its state in the past. In mathematical terms, its behaviour is described by fractional differential equations, where the order of the equation is non-integer. In this presentation, we discuss an experiment where we have looked at the effect of a long (56 day) break in battery battery charge/discharge cycling on electrical properties of the battery. On recommencement of cycling, we can discern the effect of the pause on impedance for around 30 days after the break. To see the effect we have constructed the impedance spectrum at ultra-low frequencies (10 μHz - 10 mHz) by applying wavelet methods to time-series data of voltage and current. However, if uncontrolled, other factors such as the shape of stimulating waveforms will mask much of this history effect, and thus in practice history may only matter on the scale of a few days. Nonetheless, results show that answering a simple question "what is my battery charge" does not have a simple physical answer, and thus producing a battery meter that does not lie remains a real challenge for theoretical physicists and mathematicians.

year: 2025

title: Geochemical zones and environmental gradients for soils from the central Transantarctic Mountains, Antarctica

authors: Diaz, Melisa A.

abstract: Previous studies have established links between biodiversity and soil geochemistry in the McMurdo Dry Valleys, Antarctica, where environmental gradients are important determinants of soil biodiversity. However, these gradients are not well established in the central Transantarctic Mountains, which are thought to represent some of the least hospitable Antarctic soils. We analyzed 220 samples from 11 ice-free areas along the Shackleton Glacier (∼ 85° S), a major outlet glacier of the East Antarctic Ice Sheet. We established three zones of distinct geochemical gradients near the head of the glacier (upper), its central part (middle), and at the mouth (lower). The upper zone had the highest water-soluble salt concentrations with total salt concentrations exceeding 80 000 μ g-1, while the lower zone had the lowest water-soluble N:P ratios, suggesting that, in addition to other parameters (such as proximity to water and/or ice), the lower zone likely represents the most favorable ecological habitats. Given the strong dependence of geochemistry on geographic parameters, we developed multiple linear regression and random forest models to predict soil geochemical trends given latitude, longitude, elevation, distance from the coast, distance from the glacier, and soil moisture (variables which can be inferred from remote measurements). Confidence in our random forest model predictions was moderately high with R2 values for total water-soluble salts, water-soluble N:P, ClO-4, and ClO-3 of 0.81, 0.88, 0.78, and 0.74, respectively. These modeling results can be used to predict geochemical gradients and estimate salt concentrations for other Transantarctic Mountain soils, information that can ultimately be used to better predict distributions of soil biota in this remote region.

text: Geochemical zones and environmental gradients for soils from the central Transantarctic Mountains, Antarctica Previous studies have established links between biodiversity and soil geochemistry in the McMurdo Dry Valleys, Antarctica, where environmental gradients are important determinants of soil biodiversity. However, these gradients are not well established in the central Transantarctic Mountains, which are thought to represent some of the least hospitable Antarctic soils. We analyzed 220 samples from 11 ice-free areas along the Shackleton Glacier (∼ 85° S), a major outlet glacier of the East Antarctic Ice Sheet. We established three zones of distinct geochemical gradients near the head of the glacier (upper), its central part (middle), and at the mouth (lower). The upper zone had the highest water-soluble salt concentrations with total salt concentrations exceeding 80 000 μ g-1, while the lower zone had the lowest water-soluble N:P ratios, suggesting that, in addition to other parameters (such as proximity to water and/or ice), the lower zone likely represents the most favorable ecological habitats. Given the strong dependence of geochemistry on geographic parameters, we developed multiple linear regression and random forest models to predict soil geochemical trends given latitude, longitude, elevation, distance from the coast, distance from the glacier, and soil moisture (variables which can be inferred from remote measurements). Confidence in our random forest model predictions was moderately high with R2 values for total water-soluble salts, water-soluble N:P, ClO-4, and ClO-3 of 0.81, 0.88, 0.78, and 0.74, respectively. These modeling results can be used to predict geochemical gradients and estimate salt concentrations for other Transantarctic Mountain soils, information that can ultimately be used to better predict distributions of soil biota in this remote region.

year: 2021

title: The Māori language curriculum for New Zealand schools: Spiral lesson/ lesson sequence design

authors: Johnson, Diane

subjects: Māori language teaching

abstract: A draft curriculum document for the teaching and learning of te reo Māori as a subject in mainstream schools in New Zealand (that is, in schools other than Kura Kaupapa Māori schools) was designed and trialled in 2004 and 2005. That draft is currently being reworked in line with the advice of those who trialled the document as well as that of a team of advisers set up by the Ministry of Education. The revised curriculum document will be submitted to the Ministry of Education in May 2006. As is the case with all new curriculum documents, the implementation phase will be critical. The extent to which this flexible, outcomes-focused curriculum document will genuinely inform new approaches to teaching and learning will depend not only upon the good will of teachers and communities, but also upon their ability to interpret the curriculum and to use it in a way that informs the design of language programmes, including the planning of units of work and of lessons and lesson sequences. In balancing language development and language practice, a communicative core and spiral approach is recommended, an approach in which there are core lessons (where the focus is language development) and spiral lessons (where the focus is language practice). In an earlier issue of this Journal (Johnson, 2003), one of us discussed core lesson design. Here, the design of spiral lessons is discussed and exemplified in the context of an outcomes-based curriculum.

text: The Māori language curriculum for New Zealand schools: Spiral lesson/ lesson sequence design A draft curriculum document for the teaching and learning of te reo Māori as a subject in mainstream schools in New Zealand (that is, in schools other than Kura Kaupapa Māori schools) was designed and trialled in 2004 and 2005. That draft is currently being reworked in line with the advice of those who trialled the document as well as that of a team of advisers set up by the Ministry of Education. The revised curriculum document will be submitted to the Ministry of Education in May 2006. As is the case with all new curriculum documents, the implementation phase will be critical. The extent to which this flexible, outcomes-focused curriculum document will genuinely inform new approaches to teaching and learning will depend not only upon the good will of teachers and communities, but also upon their ability to interpret the curriculum and to use it in a way that informs the design of language programmes, including the planning of units of work and of lessons and lesson sequences. In balancing language development and language practice, a communicative core and spiral approach is recommended, an approach in which there are core lessons (where the focus is language development) and spiral lessons (where the focus is language practice). In an earlier issue of this Journal (Johnson, 2003), one of us discussed core lesson design. Here, the design of spiral lessons is discussed and exemplified in the context of an outcomes-based curriculum.

year: 2005