title: NiMH battery forensics: Instrumentation, modelling and prognostics for identifying failure

authors: Leijen, Petrus Jozef Martinus

subjects: NiMH

abstract: Battery forensics is a growing research field that is becoming increasingly important with the introduction of hybrid-electric and electric vehicles. The need to correctly diagnose battery condition and predict signs of early failure is well recognised. Many presently used techniques are only applicable to laboratory situations where sensitive measurement is required or where complicated mathematical approaches are needed to assess battery condition. Advanced techniques are explored, such as extended Kalman filtering, to identify the challenges associated with analysis of multi-cell battery modules. Energy-recycling hardware is developed that is capable of efficiently cycling energy to and from cells connected in a series configuration. Switching a supercapacitor-bank-based energy store between series and parallel configurations, coupled with a bidirectional switch-mode power-supply, ensures that maximum energy is retained during the analysis cycle. Extended Kalman filtering (EKF) applied to three different battery models was used to quantify the internal component values of the battery equivalent circuits. The bulk-surface model was determined to be the most appropriate for the Toyota Prius battery modules as the EKF predicted component values converge to stable values, and the recovered voltage trace has a low error. However, the computational complexity when considering 12 series-connected NiMH cells, with their individual component variation with state-of-charge and state-of-health, make the EKF approach unviable. The data harvested during the energy recycling is used to calculate a new effective capacitance measure which relates directly to battery state-of-health. Not only is there a direct relationship between effective capacitance and state-of-health, but the (Q,V) coordinate of maximum effective capacitance on the charge-voltage plane, captured during battery discharge, is able to distinguish clearly between ordinary ageing and catastrophic cell failures.

text: NiMH battery forensics: Instrumentation, modelling and prognostics for identifying failure Battery forensics is a growing research field that is becoming increasingly important with the introduction of hybrid-electric and electric vehicles. The need to correctly diagnose battery condition and predict signs of early failure is well recognised. Many presently used techniques are only applicable to laboratory situations where sensitive measurement is required or where complicated mathematical approaches are needed to assess battery condition. Advanced techniques are explored, such as extended Kalman filtering, to identify the challenges associated with analysis of multi-cell battery modules. Energy-recycling hardware is developed that is capable of efficiently cycling energy to and from cells connected in a series configuration. Switching a supercapacitor-bank-based energy store between series and parallel configurations, coupled with a bidirectional switch-mode power-supply, ensures that maximum energy is retained during the analysis cycle. Extended Kalman filtering (EKF) applied to three different battery models was used to quantify the internal component values of the battery equivalent circuits. The bulk-surface model was determined to be the most appropriate for the Toyota Prius battery modules as the EKF predicted component values converge to stable values, and the recovered voltage trace has a low error. However, the computational complexity when considering 12 series-connected NiMH cells, with their individual component variation with state-of-charge and state-of-health, make the EKF approach unviable. The data harvested during the energy recycling is used to calculate a new effective capacitance measure which relates directly to battery state-of-health. Not only is there a direct relationship between effective capacitance and state-of-health, but the (Q,V) coordinate of maximum effective capacitance on the charge-voltage plane, captured during battery discharge, is able to distinguish clearly between ordinary ageing and catastrophic cell failures.

year: 2016

title: Applicability of contrarian strategy in the Bombay stock exchange

authors: Locke, Stuart

subjects: contrarian strategy

abstract: The application of contrarian strategies in the Bombay Stock Exchange (BSE) are examined in this paper, shedding further light on competing explanations underlying this anomaly. Three specific issues are investigated using several models. First, can a trader book a profit by employing a contrarian strategy? The test portfolio earned a contrarian profit of 74.40 per cent above the market return. Second, risk differences between Winner and Loser portfolios are found to be an independent phenomenon. Third, the size of the firm appears to play a vital role in explaining the overreaction hypothesis.

text: Applicability of contrarian strategy in the Bombay stock exchange The application of contrarian strategies in the Bombay Stock Exchange (BSE) are examined in this paper, shedding further light on competing explanations underlying this anomaly. Three specific issues are investigated using several models. First, can a trader book a profit by employing a contrarian strategy? The test portfolio earned a contrarian profit of 74.40 per cent above the market return. Second, risk differences between Winner and Loser portfolios are found to be an independent phenomenon. Third, the size of the firm appears to play a vital role in explaining the overreaction hypothesis.

year: 2009

title: Final report of the 2018 Census External Data Quality Panel

authors: Bedford, Richard

abstract: At the time this report was submitted for publication in January 2020, Stats NZ was finalizing its release schedule for census products that allow users to produce their own tabulations and statistical analyses using census data (see Appendix 2 for a summary of release dates for 2018 Census products).
In early 2020, Stats NZ will release 2018 Census data for use in the Data Lab, a distributed set of secure computer sites where users can access, with approval, microdata for research purposes. By March 2020, 2018 Census data will be in the Integrated Data Infrastructure (IDI) and available for use by approved researchers and policy analysts who wish to negotiate access to the IDI.

text: Final report of the 2018 Census External Data Quality Panel At the time this report was submitted for publication in January 2020, Stats NZ was finalizing its release schedule for census products that allow users to produce their own tabulations and statistical analyses using census data (see Appendix 2 for a summary of release dates for 2018 Census products).
In early 2020, Stats NZ will release 2018 Census data for use in the Data Lab, a distributed set of secure computer sites where users can access, with approval, microdata for research purposes. By March 2020, 2018 Census data will be in the Integrated Data Infrastructure (IDI) and available for use by approved researchers and policy analysts who wish to negotiate access to the IDI.

year: 2020