title: Misconceptions arising from the Infinite Solenoid Magnetic Field Formula

authors: Wilson, Marcus T.

abstract: Many high school and first-year university courses include discussion of the magnetic effect of currents. Frequently discussed textbook examples include long, straight wires, circular current loops, and solenoids, partly because these examples are tractable mathematically. The solenoid naturally leads to discussion on magnetic materials since it is readily demonstrated that a paramagnetic core significantly boosts the strength of an electromagnet. However, magnetic effects of solid and even liquid materials are subtle and confusing¹ and the mathematics is not straightforward. This leads to confusion amongst students (and their teachers), which, when taken to more advanced study, leads to significant misconceptions about the nature of magnetic properties and fields. These misconceptions can become problematic when practical (rather than stereotyped) magnetic design and analysis is required such as for transformers,² magnetic recording materials, geomagnetic sensors,³ or biological stimulators4 to name a few. In this article, I highlight examples of this confusion, in particular the failure in realistic situations of the well-quoted formula for an infinite solenoid with a paramagnetic core, and the physical interpretation of the relative permeability of a material, µr.

text: Misconceptions arising from the Infinite Solenoid Magnetic Field Formula Many high school and first-year university courses include discussion of the magnetic effect of currents. Frequently discussed textbook examples include long, straight wires, circular current loops, and solenoids, partly because these examples are tractable mathematically. The solenoid naturally leads to discussion on magnetic materials since it is readily demonstrated that a paramagnetic core significantly boosts the strength of an electromagnet. However, magnetic effects of solid and even liquid materials are subtle and confusing¹ and the mathematics is not straightforward. This leads to confusion amongst students (and their teachers), which, when taken to more advanced study, leads to significant misconceptions about the nature of magnetic properties and fields. These misconceptions can become problematic when practical (rather than stereotyped) magnetic design and analysis is required such as for transformers,² magnetic recording materials, geomagnetic sensors,³ or biological stimulators4 to name a few. In this article, I highlight examples of this confusion, in particular the failure in realistic situations of the well-quoted formula for an infinite solenoid with a paramagnetic core, and the physical interpretation of the relative permeability of a material, µr.

year: 2021

title: The influence of the COVID-19 pandemic on the hedging functionality of Chinese financial markets

authors: Corbet, Shaen

subjects: Social Sciences

abstract: In this paper, we investigate both constant and time-varying hedge ratios in terms of the effectiveness of CSI300 index futures during the COVID-19 crisis. Using naïve, OLS and EC/ROLS strategies to estimate constant hedge ratios, results indicate that the CSI300 spot index presents decreased effectiveness using the naïve hedging strategy; however, increased effectiveness of OLS and EC hedge ratios are identified. Differential behaviour is identified when considering five newly introduced COVID-19 concept-based stock indices. Time-varying hedge ratios indicate the weakened effectiveness, ranging between 20% and 40% variance reduction. Evidence suggests that the capability of the CSI300 index futures to hedge against the risks of the COVID-19 is impaired, regardless of whether constant or time-varying hedge ratios are used. Such results provide important implications to both local and foreign investors in the Chinese stock market.

text: The influence of the COVID-19 pandemic on the hedging functionality of Chinese financial markets In this paper, we investigate both constant and time-varying hedge ratios in terms of the effectiveness of CSI300 index futures during the COVID-19 crisis. Using naïve, OLS and EC/ROLS strategies to estimate constant hedge ratios, results indicate that the CSI300 spot index presents decreased effectiveness using the naïve hedging strategy; however, increased effectiveness of OLS and EC hedge ratios are identified. Differential behaviour is identified when considering five newly introduced COVID-19 concept-based stock indices. Time-varying hedge ratios indicate the weakened effectiveness, ranging between 20% and 40% variance reduction. Evidence suggests that the capability of the CSI300 index futures to hedge against the risks of the COVID-19 is impaired, regardless of whether constant or time-varying hedge ratios are used. Such results provide important implications to both local and foreign investors in the Chinese stock market.

year: 2022

title: Older adult education in a New Zealand university: Developments and issues

authors: Findsen, Brian

abstract: This article explores a case study of educational provision for older adults in the context of continuing education in one of New Zealand’s universities. It explains how developments in older adult education at the University of Waikato have reflected historical and cultural trends related to the wider field of adult and community education (ACE) inside a higher education setting. It discusses issues of tertiary education policy and funding, what constitutes curriculum and provision for older adults and how university-community partnerships have shaped opportunities for both indigenous Māori and Pakeha (European) seniors. Government removal of funding to all universities in New Zealand for ACE at the end of 2012 ended formal provision but older adult education groups, formerly supported by the Centre for Continuing Education in the University of Waikato, have assumed a more proactive stance in planning and implementing their own programmes.

text: Older adult education in a New Zealand university: Developments and issues This article explores a case study of educational provision for older adults in the context of continuing education in one of New Zealand’s universities. It explains how developments in older adult education at the University of Waikato have reflected historical and cultural trends related to the wider field of adult and community education (ACE) inside a higher education setting. It discusses issues of tertiary education policy and funding, what constitutes curriculum and provision for older adults and how university-community partnerships have shaped opportunities for both indigenous Māori and Pakeha (European) seniors. Government removal of funding to all universities in New Zealand for ACE at the end of 2012 ended formal provision but older adult education groups, formerly supported by the Centre for Continuing Education in the University of Waikato, have assumed a more proactive stance in planning and implementing their own programmes.

year: 2014