title: Extracting information from time series data from rechargable batteries

authors: Wilson, Marcus T.

abstract: In practical applications such as electric vehicles, mobile phones, etc, rechargable batteries are continually charged and discharged, resulting in time-varying voltages and currents. The relationship between voltage and current depends on the properties of the battery and analysis of the time-series can yield useful information about battery performance. However, analysis is complicated because the charge-discharge cycles are not periodic or regular.  For example, in an electric vehicle the battery might undergo intensive periods of discharge and charge, corresponding to acceleration and regenerative braking respectively, while the vehicle is in use, followed by long periods of inactivity.  There is structure on the timescales of seconds through to days. We have recorded voltage, current and temperature of several batteries in a laboratory as they have been continually cycled over many months using both regular and irregular cycles, the latter mimicking cycles experienced in practical applications. We have used established methods of time-series analysis such as the Hilbert Transform to investigate the relationships between voltage and current, and have shown that results agree with more sophisticated but less practical methods of battery characterisation such as electrical impedance spectroscopy. The relationships imply that several different processes occur, depending on time-scale.

text: Extracting information from time series data from rechargable batteries In practical applications such as electric vehicles, mobile phones, etc, rechargable batteries are continually charged and discharged, resulting in time-varying voltages and currents. The relationship between voltage and current depends on the properties of the battery and analysis of the time-series can yield useful information about battery performance. However, analysis is complicated because the charge-discharge cycles are not periodic or regular.  For example, in an electric vehicle the battery might undergo intensive periods of discharge and charge, corresponding to acceleration and regenerative braking respectively, while the vehicle is in use, followed by long periods of inactivity.  There is structure on the timescales of seconds through to days. We have recorded voltage, current and temperature of several batteries in a laboratory as they have been continually cycled over many months using both regular and irregular cycles, the latter mimicking cycles experienced in practical applications. We have used established methods of time-series analysis such as the Hilbert Transform to investigate the relationships between voltage and current, and have shown that results agree with more sophisticated but less practical methods of battery characterisation such as electrical impedance spectroscopy. The relationships imply that several different processes occur, depending on time-scale.

year: 2023-09-15

title: Laptops for teachers: An evaluation of the TELA scheme in schools (Years 4 to 6)

authors: Cowie, Bronwen

subjects: Laptop for Teachers Scheme

abstract: The purpose of this evaluation was to investigate the impacts of the Laptops for Teachers Scheme (referred to from here as the TELA scheme) on Years 4 to 6 teachers’ work over a period of three years (2004-2006) and to record emerging changes in laptop use. The investigation focused on the Ministry of Education expectation (Ministry of Education, 2004) that teacher access to a laptop for their individual professional use would lead to gains in confidence and expertise in the use of ICTs, to efficiencies in administration, would contribute to teacher collaboration and support the preparation of high quality lesson resources. It was also anticipated that teacher would use their laptop in the classroom for teaching and learning.

text: Laptops for teachers: An evaluation of the TELA scheme in schools (Years 4 to 6) The purpose of this evaluation was to investigate the impacts of the Laptops for Teachers Scheme (referred to from here as the TELA scheme) on Years 4 to 6 teachers’ work over a period of three years (2004-2006) and to record emerging changes in laptop use. The investigation focused on the Ministry of Education expectation (Ministry of Education, 2004) that teacher access to a laptop for their individual professional use would lead to gains in confidence and expertise in the use of ICTs, to efficiencies in administration, would contribute to teacher collaboration and support the preparation of high quality lesson resources. It was also anticipated that teacher would use their laptop in the classroom for teaching and learning.

year: 2010

title: Te Kōtihitihi: Ngā Tuhinga Reo Māori, Putanga 3

authors: Temara, Pou

abstract: Koinei te katoa o te Putanga 3 o te puka hautaka, Te Kōtihitihi.

text: Te Kōtihitihi: Ngā Tuhinga Reo Māori, Putanga 3 Koinei te katoa o te Putanga 3 o te puka hautaka, Te Kōtihitihi.

year: 2016