title: Current singularities in planar magnetic X points of finite compressibility

authors: Craig, Ian J.D.

subjects: mathematics

abstract: The formation of current singularities in nonresistive, line-tied magnetic X points is addressed. It is pointed out that, although gas pressure suppresses the current singularity development when strictly antiparallel, one-dimensional magnetic fields implode, the pressure is likely to be less effective in the more realistic case of two-dimensional magnetic fields. Detailed nonlinear relaxation computations at various levels of compressibility confirm that singularity is present even in the incompressible limit, but its strength, as determined by the amplitude and morphology of the current density, is considerably reduced. The singularity strength is quantified by computing the scalings of the peak current density with resolution. The scalings show that localized current structures can be expected only for negligible gas pressures. The numerical results imply that the inclusion of gas pressure effectively stalls fast magnetic reconnection in line-tied X-point geometries.

text: Current singularities in planar magnetic X points of finite compressibility The formation of current singularities in nonresistive, line-tied magnetic X points is addressed. It is pointed out that, although gas pressure suppresses the current singularity development when strictly antiparallel, one-dimensional magnetic fields implode, the pressure is likely to be less effective in the more realistic case of two-dimensional magnetic fields. Detailed nonlinear relaxation computations at various levels of compressibility confirm that singularity is present even in the incompressible limit, but its strength, as determined by the amplitude and morphology of the current density, is considerably reduced. The singularity strength is quantified by computing the scalings of the peak current density with resolution. The scalings show that localized current structures can be expected only for negligible gas pressures. The numerical results imply that the inclusion of gas pressure effectively stalls fast magnetic reconnection in line-tied X-point geometries.

year: 2005-07-15

title: Non-continuous and variable rate processes: Optimisation for energy use

authors: Morrison, Andrew S.

subjects: energy optimization

abstract: The need to develop new and improved ways of reducing energy use and increasing energy intensity in industrial processes is currently a major issue in New Zealand. Little attention has been given to optimisation of non-continuous processes in the past, due to their complexity, yet they remain an essential and often energy intensive component of many industrial sites. Novel models based on pinch analysis that aid in minimising utility usage have been constructed here through the adaptation of proven continuous techniques. The knowledge has been integrated into a user friendly software package, and allows the optimisation of processes under variable operating rates and batch conditions. An example problem demonstrates the improvements in energy use that can be gained when using these techniques to analyse non-continuous data. A comparison with results achieved using a pseudo-continuous method show that the method described can provide simultaneous reductions in capital and operating costs.

text: Non-continuous and variable rate processes: Optimisation for energy use The need to develop new and improved ways of reducing energy use and increasing energy intensity in industrial processes is currently a major issue in New Zealand. Little attention has been given to optimisation of non-continuous processes in the past, due to their complexity, yet they remain an essential and often energy intensive component of many industrial sites. Novel models based on pinch analysis that aid in minimising utility usage have been constructed here through the adaptation of proven continuous techniques. The knowledge has been integrated into a user friendly software package, and allows the optimisation of processes under variable operating rates and batch conditions. An example problem demonstrates the improvements in energy use that can be gained when using these techniques to analyse non-continuous data. A comparison with results achieved using a pseudo-continuous method show that the method described can provide simultaneous reductions in capital and operating costs.

year: 2007-02-01

title: Racism and Employment: A Narrative Review of Aotearoa New Zealand and International Qualitative Studies

authors: Tan, Kyle K. H.

abstract: In Aotearoa New Zealand, employment inequities exist for minoritised ethnic groups (Māori, Pasifika, Asian, racialised migrants and refugees) in the forms of barriers to employment, occupation inequities, differences in promotion to leadership roles, ethnic pay gaps and discriminatory experiences at workplaces. In this review, we compiled Aotearoa qualitative studies to depict the dynamics of racism alongside other intersectional forms of prejudices that disadvantage the employment processes and career progression of minoritised ethnicities. Literature gaps in Aotearoa research were identified through reviewing international literature published between 2016 and 2021. Reviewed Aotearoa studies were categorised into three themes: unemployment and underemployment, workplace discrimination, and strategies for navigating racism. Drawing upon a framework that recognises racialised processes as spanning across micro- (individual), meso- (organisational) and macro- (institutional) levels, we found most Aotearoa studies analysing racism in the workplace focus on micro-level experiences. Compared with international literature, research in Aotearoa has yet to consider the roles of organisations and technologies as racialised structures that engender employment inequities, and the interaction of individuals in response to meso- and macro-structures that build on settler colonialism and racism. Our review echoes the call of Aotearoa scholars to name racism as the overarching oppressive mechanism embedded within organisations and to use anti-racism praxes such as te Tiriti o Waitangi as a way forward to promote employment equity.

text: Racism and Employment: A Narrative Review of Aotearoa New Zealand and International Qualitative Studies In Aotearoa New Zealand, employment inequities exist for minoritised ethnic groups (Māori, Pasifika, Asian, racialised migrants and refugees) in the forms of barriers to employment, occupation inequities, differences in promotion to leadership roles, ethnic pay gaps and discriminatory experiences at workplaces. In this review, we compiled Aotearoa qualitative studies to depict the dynamics of racism alongside other intersectional forms of prejudices that disadvantage the employment processes and career progression of minoritised ethnicities. Literature gaps in Aotearoa research were identified through reviewing international literature published between 2016 and 2021. Reviewed Aotearoa studies were categorised into three themes: unemployment and underemployment, workplace discrimination, and strategies for navigating racism. Drawing upon a framework that recognises racialised processes as spanning across micro- (individual), meso- (organisational) and macro- (institutional) levels, we found most Aotearoa studies analysing racism in the workplace focus on micro-level experiences. Compared with international literature, research in Aotearoa has yet to consider the roles of organisations and technologies as racialised structures that engender employment inequities, and the interaction of individuals in response to meso- and macro-structures that build on settler colonialism and racism. Our review echoes the call of Aotearoa scholars to name racism as the overarching oppressive mechanism embedded within organisations and to use anti-racism praxes such as te Tiriti o Waitangi as a way forward to promote employment equity.

year: 2024-01-01