title: Sunspot and Starspot lifetimes in a turbulent erosion model

authors: Litvinenko, Yuri E.

subjects: magnetic field

abstract: Quantitative models of sunspot and starspot decay predict the timescale of magnetic diffusion and may yield important constraints in stellar dynamo models. Motivated by recent measurements of starspot lifetimes, we investigate the disintegration of a magnetic flux tube by nonlinear diffusion. Previous theoretical studies are extended by considering two physically motivated functional forms for the nonlinear diffusion coefficient D: an inverse power-law dependence D ∝ B⁻ᵛ and a step-function dependence of D on the magnetic field magnitude B. Analytical self-similar solutions are presented for the power-law case, including solutions exhibiting "superfast" diffusion. For the step-function case, the heat-balance integral method yields approximate solutions, valid for moderately suppressed diffusion in the spot. The accuracy of the resulting solutions is confirmed numerically, using a method which provides an accurate description of long-time evolution by imposing boundary conditions at infinite distance from the spot. The new models may allow insight into the differences and similarities between sunspots and starspots.

text: Sunspot and Starspot lifetimes in a turbulent erosion model Quantitative models of sunspot and starspot decay predict the timescale of magnetic diffusion and may yield important constraints in stellar dynamo models. Motivated by recent measurements of starspot lifetimes, we investigate the disintegration of a magnetic flux tube by nonlinear diffusion. Previous theoretical studies are extended by considering two physically motivated functional forms for the nonlinear diffusion coefficient D: an inverse power-law dependence D ∝ B⁻ᵛ and a step-function dependence of D on the magnetic field magnitude B. Analytical self-similar solutions are presented for the power-law case, including solutions exhibiting "superfast" diffusion. For the step-function case, the heat-balance integral method yields approximate solutions, valid for moderately suppressed diffusion in the spot. The accuracy of the resulting solutions is confirmed numerically, using a method which provides an accurate description of long-time evolution by imposing boundary conditions at infinite distance from the spot. The new models may allow insight into the differences and similarities between sunspots and starspots.

year: 2017

title: Wireless Energy Harvesting by Direct Voltage Multiplication on Lateral Waves from a Suspended Dielectric layer

authors: Liu, Louis W.Y.

subjects: Energy harvesting

abstract: This paper explores the feasibility of wireless energy harvesting by direct voltage multiplication on lateral waves. Whilst free space is undoubtedly a known medium for wireless energy harvesting, space waves are too attenuated to support realistic transmission of wireless energy. A layer of thin stratified dielectric material suspended in mid-air can form a substantially less attenuated pathway, which efficiently supports propagation of wireless energy in the form of lateral waves. The conductivity of the suspended dielectric layer does not appear to be a critical factor rendering propagation of lateral waves impossible. In this paper, a mathematical model has been developed to simulate wireless energy harvesting over a suspended layer of stratified dielectric material. The model has been experimentally verified with the help of a novel open-ended voltage multiplier designed to harvest energy from ambient electromagnetic fields.

text: Wireless Energy Harvesting by Direct Voltage Multiplication on Lateral Waves from a Suspended Dielectric layer This paper explores the feasibility of wireless energy harvesting by direct voltage multiplication on lateral waves. Whilst free space is undoubtedly a known medium for wireless energy harvesting, space waves are too attenuated to support realistic transmission of wireless energy. A layer of thin stratified dielectric material suspended in mid-air can form a substantially less attenuated pathway, which efficiently supports propagation of wireless energy in the form of lateral waves. The conductivity of the suspended dielectric layer does not appear to be a critical factor rendering propagation of lateral waves impossible. In this paper, a mathematical model has been developed to simulate wireless energy harvesting over a suspended layer of stratified dielectric material. The model has been experimentally verified with the help of a novel open-ended voltage multiplier designed to harvest energy from ambient electromagnetic fields.

year: 2017

title: Editorial: Special Issue: Ignored no longer: Emerging Indigenous researchers on Indigenous psychologies

authors: Groot, Shiloh Ann Maree

abstract: In this special issue, edited by Mohi, Bridgette, Shiloh, Pat and Darren, we showcase work conducted within several such Indigenous psychologies. This collection of papers from emerging Indigenous scholars reflect a vibrant, healthy and supportive research environment in which conversations relevant to Indigenous peoples are taking place, and where culturally diverse perspectives and methods are valued and accepted. Here, culture is not simply seen as an abstract set of concepts. Culture constitutes a field of human action, meaning making, and self-production. It is through culture that all people construct themselves and make sense of the world (Groot, Hodgetts, Nikora, & Leggat-Cook, 2011; Nikora, Rua, & Te Awekōtuku, 2007).

text: Editorial: Special Issue: Ignored no longer: Emerging Indigenous researchers on Indigenous psychologies In this special issue, edited by Mohi, Bridgette, Shiloh, Pat and Darren, we showcase work conducted within several such Indigenous psychologies. This collection of papers from emerging Indigenous scholars reflect a vibrant, healthy and supportive research environment in which conversations relevant to Indigenous peoples are taking place, and where culturally diverse perspectives and methods are valued and accepted. Here, culture is not simply seen as an abstract set of concepts. Culture constitutes a field of human action, meaning making, and self-production. It is through culture that all people construct themselves and make sense of the world (Groot, Hodgetts, Nikora, & Leggat-Cook, 2011; Nikora, Rua, & Te Awekōtuku, 2007).

year: 2012