title: Laplace transform-based theoretical foundations and experimental validation: low-frequency supercapacitor circulation for efficiency improvements in linear regulators

authors: Kankanamge, Kosala

subjects: supercapacitors

abstract: Supercapacitor circulation techniques can be used to improve the end-to-end efficiency of linear regulators based on commercial low drop-out regulators (LDO). In this approach, one or more supercapacitors are used in series and parallel to the input of an LDO IC, and circulated at a very low frequency to increase the end-to-end efficiency by a multiplication factor compared with the efficiency of a linear regulator circuit with the same input–output voltages. This study presents the essential theory of supercapacitor circulation, together with analytical results and comparisons with experimental measurements from a practical 12–5 V implementation. The new technique achieved overall end-to-end efficiencies in the range of 70 to 80%, compared with the maximum theoretical efficiency of 42% for a 12–5 V linear regulator.

text: Laplace transform-based theoretical foundations and experimental validation: low-frequency supercapacitor circulation for efficiency improvements in linear regulators Supercapacitor circulation techniques can be used to improve the end-to-end efficiency of linear regulators based on commercial low drop-out regulators (LDO). In this approach, one or more supercapacitors are used in series and parallel to the input of an LDO IC, and circulated at a very low frequency to increase the end-to-end efficiency by a multiplication factor compared with the efficiency of a linear regulator circuit with the same input–output voltages. This study presents the essential theory of supercapacitor circulation, together with analytical results and comparisons with experimental measurements from a practical 12–5 V implementation. The new technique achieved overall end-to-end efficiencies in the range of 70 to 80%, compared with the maximum theoretical efficiency of 42% for a 12–5 V linear regulator.

year: 2012

title: Kelvin-Helmholtz instability in aluminium reduction cells

authors: Shin, Sung Nam

abstract: In aluminium reduction cells the intense magnetic fields and associated Lorentz forces drive steady flows in the cryolite and aluminium layers. Generally there is a discontinuity in velocity between the layers, which gives rise to a Kelvin-Helmholtz instability, and the study of this effect is the subject of the thesis. 

The role of the basic steady flow is focused in this analysis, while most previous MHD analyses neglect it and emphasise on the interaction between the interface wave and the electromagnetic field by the electromagnetic perturbation. The stationary magnetic field is considered important as a strong driving source for the steady velocity in our model. 

Steady velocity fields are studied in terms of a stream function and global stability criteria are discussed with disturbances. Non-linear evolution of flow is investigated to find a steady condition and show that steady flows are stable. A normal mode analysis is used to formulate wave evolution equations, which are integrated forwards in time. 

Also an improved treatment of electromagnetic damping is developed, which includes the effect of the induced electric field. 

Using a normal mode form of the steady-state current, magnetic field or flow, the scheme developed in this research is suitable for industrial application where these would be calculated numerically.

text: Kelvin-Helmholtz instability in aluminium reduction cells In aluminium reduction cells the intense magnetic fields and associated Lorentz forces drive steady flows in the cryolite and aluminium layers. Generally there is a discontinuity in velocity between the layers, which gives rise to a Kelvin-Helmholtz instability, and the study of this effect is the subject of the thesis. 

The role of the basic steady flow is focused in this analysis, while most previous MHD analyses neglect it and emphasise on the interaction between the interface wave and the electromagnetic field by the electromagnetic perturbation. The stationary magnetic field is considered important as a strong driving source for the steady velocity in our model. 

Steady velocity fields are studied in terms of a stream function and global stability criteria are discussed with disturbances. Non-linear evolution of flow is investigated to find a steady condition and show that steady flows are stable. A normal mode analysis is used to formulate wave evolution equations, which are integrated forwards in time. 

Also an improved treatment of electromagnetic damping is developed, which includes the effect of the induced electric field. 

Using a normal mode form of the steady-state current, magnetic field or flow, the scheme developed in this research is suitable for industrial application where these would be calculated numerically.

year: 2000

title: Hoera Te Mimiha

authors: Hart, Philip

abstract: Hoera Te Mimiha was a rangatira of Ngati Koi, an inferior hapu to Ngati Tamatera, and had affiliations to other hapu. Although to Pakeha he was a mere labourer, in Maori society in Ohinemuri in the 1870s and 1880s he was a leading figure. Details have been traced of his whakapapa, his wider family, and especially his children, one of whom married Hone Werahiko. 
Mimiha spent much time in the Maori Land Court trying to prove his entitlement to be included as an owner of several blocks of land, not always successfully, for he could not prove some of his cases either through ancestry or occupation. Other rangatira with superior whakapapa were able to show the weaknesses of some of his claims, forcing him into giving evasive answers to cross-examination. His evidence did reveal what land he had occupied and farmed.
Mimiha willingly sold land, including his interest in the Ohinemuri goldfield (the boundaries of which he had pointed out to surveyors), and obtained a good income, for a time. Being interested in mining from the early 1870s onwards, he was one of the few Maori willing to descend a shaft at Thames, an experience that encouraged him to push for opening Ohinemuri to mining, even, it seemed, if that endangered Maori control of their land. Having prospected at Karangahake before it was opened to mining in 1875, he participated in this rush and subsequently in the Te Aroha one of 1880, having interests in claims at all three portions of the latter field. When his daughter’s partner was murdered at Te Aroha, he calmed Maori anger, once again winning the gratitude of Pakeha.
Because of selling much of his land, he struggled financially, although unlike some Maori he did not drink his money away. Cutting off part of the ear of a Pakeha accused of raping his wife resulted in several court cases marked by dubious evidence presented by both sides. After being imprisoned for perjury, efforts by Pakeha to have his conviction reviewed resulted in his being judged to have been the only witness not to have lied to the court, but this sordid affair blackened his character.

text: Hoera Te Mimiha Hoera Te Mimiha was a rangatira of Ngati Koi, an inferior hapu to Ngati Tamatera, and had affiliations to other hapu. Although to Pakeha he was a mere labourer, in Maori society in Ohinemuri in the 1870s and 1880s he was a leading figure. Details have been traced of his whakapapa, his wider family, and especially his children, one of whom married Hone Werahiko. 
Mimiha spent much time in the Maori Land Court trying to prove his entitlement to be included as an owner of several blocks of land, not always successfully, for he could not prove some of his cases either through ancestry or occupation. Other rangatira with superior whakapapa were able to show the weaknesses of some of his claims, forcing him into giving evasive answers to cross-examination. His evidence did reveal what land he had occupied and farmed.
Mimiha willingly sold land, including his interest in the Ohinemuri goldfield (the boundaries of which he had pointed out to surveyors), and obtained a good income, for a time. Being interested in mining from the early 1870s onwards, he was one of the few Maori willing to descend a shaft at Thames, an experience that encouraged him to push for opening Ohinemuri to mining, even, it seemed, if that endangered Maori control of their land. Having prospected at Karangahake before it was opened to mining in 1875, he participated in this rush and subsequently in the Te Aroha one of 1880, having interests in claims at all three portions of the latter field. When his daughter’s partner was murdered at Te Aroha, he calmed Maori anger, once again winning the gratitude of Pakeha.
Because of selling much of his land, he struggled financially, although unlike some Maori he did not drink his money away. Cutting off part of the ear of a Pakeha accused of raping his wife resulted in several court cases marked by dubious evidence presented by both sides. After being imprisoned for perjury, efforts by Pakeha to have his conviction reviewed resulted in his being judged to have been the only witness not to have lied to the court, but this sordid affair blackened his character.

year: 2016