title: Observations of wave energy fluxes and swash motions on a low-sloping, dissipative beach

authors: Guedes, Rafael M. C.

subjects: swash

abstract: Field observations of swash and ocean waves show that runup saturation at infragravity frequencies (<0.05 Hz) can occur under mild offshore energy conditions if the beach slope is sufficiently gentle. Infragravity saturation was observed for higher-frequency (>0.025–0.035 Hz) infragravity waves, where typically less than 5% of the (linear) energy flux was reflected from the beach and where, similar to the sea swell band, the swash energy was independent of offshore wave energy. The infragravity frequency range of saturation was determined by the tide, with saturation extending to lower frequencies at low tide when the local beach face slope over the concave-shaped profile was gentler. Runup was strongly dominated by infragravity frequencies, which accounted on average for 96% of the runup variance, and its energy levels were entirely consistent with strong infragravity wave dissipation observed in the surfzone, particularly when including the nonlinear contributions to the wave energy fluxes. The infragravity wave dissipation was strongly associated with breaking of sea swell waves, which abruptly decreased nonlinear transfers to infragravity frequencies and made infragravity dissipation prevail over forcing within the breaking region. Our observations show evidence of nonlinear interactions involving infragravity and high-frequency, harmonic waves and suggest that these harmonics could play a role in the wave energy balance near the shoreline on low-sloping, dissipative beaches.

text: Observations of wave energy fluxes and swash motions on a low-sloping, dissipative beach Field observations of swash and ocean waves show that runup saturation at infragravity frequencies (<0.05 Hz) can occur under mild offshore energy conditions if the beach slope is sufficiently gentle. Infragravity saturation was observed for higher-frequency (>0.025–0.035 Hz) infragravity waves, where typically less than 5% of the (linear) energy flux was reflected from the beach and where, similar to the sea swell band, the swash energy was independent of offshore wave energy. The infragravity frequency range of saturation was determined by the tide, with saturation extending to lower frequencies at low tide when the local beach face slope over the concave-shaped profile was gentler. Runup was strongly dominated by infragravity frequencies, which accounted on average for 96% of the runup variance, and its energy levels were entirely consistent with strong infragravity wave dissipation observed in the surfzone, particularly when including the nonlinear contributions to the wave energy fluxes. The infragravity wave dissipation was strongly associated with breaking of sea swell waves, which abruptly decreased nonlinear transfers to infragravity frequencies and made infragravity dissipation prevail over forcing within the breaking region. Our observations show evidence of nonlinear interactions involving infragravity and high-frequency, harmonic waves and suggest that these harmonics could play a role in the wave energy balance near the shoreline on low-sloping, dissipative beaches.

year: 2013-07

title: Energy-Efficient SMPS-Based Pulse Generator for Neurostimulators

authors: Seshadri, Sinduja

subjects: pulse generator

abstract: There is a need in the neuromodulation industry for a very energy-efficient pulse generator. Little data is observed in literature to develop a power efficient pulse generator that can deliver the required stimulus. A typical stimulator has a boost stage, a low-dropout (LDO) stage and an analog circuit that delivers the stimulus in the form of a pulse to the patient. Such a system is found to be ∼ 40% efficient. There are two new methods that can improve this efficiency rating significantly. (1) A mod- ification to existing pulse generator by adding microprocessors to control the output voltages of boost and LDO in the circuit, as proposed by the manufacturer; (2) a Single-Ended Primary Inductance Converter (SEPIC) based design proposed by the authors, with the input connected to a battery and the output to electrodes. Comparing with existing design, the modification offered a consistent 75% efficiency for output voltages from 3.9V to 6.6V. SEPIC had an efficiency rating of 80% to 86% across the same voltage range.

text: Energy-Efficient SMPS-Based Pulse Generator for Neurostimulators There is a need in the neuromodulation industry for a very energy-efficient pulse generator. Little data is observed in literature to develop a power efficient pulse generator that can deliver the required stimulus. A typical stimulator has a boost stage, a low-dropout (LDO) stage and an analog circuit that delivers the stimulus in the form of a pulse to the patient. Such a system is found to be ∼ 40% efficient. There are two new methods that can improve this efficiency rating significantly. (1) A mod- ification to existing pulse generator by adding microprocessors to control the output voltages of boost and LDO in the circuit, as proposed by the manufacturer; (2) a Single-Ended Primary Inductance Converter (SEPIC) based design proposed by the authors, with the input connected to a battery and the output to electrodes. Comparing with existing design, the modification offered a consistent 75% efficiency for output voltages from 3.9V to 6.6V. SEPIC had an efficiency rating of 80% to 86% across the same voltage range.

year: 2019

title: Indigenizing outdoor play in New Zealand: A conversation analysis approach

authors: Bateman, Amanda

abstract: This chapter focuses on a single case analysis of one trip to a local bush reserve in New Zealand. The observations included in this chapter begin by exploring the way in which a promise to the Maori God Tane Mahuta is managed by the teachers and children at the beginning of the excursion. The promise made is part of the mundane, everyday activity engaged in by these children and teachers during their weekly visit to the bush reserve, where every child is required to recite a phrase that promises not to hurt the creatures, animals or plants of Tane Mahuta when they are playing in the forest. In the first of the video-recorded episodes, explicit reference to Tane Mahuta is initially oriented through one of the children reciting the promise, unprompted, at the beginning of the recording. The second observation reveals one of the teachers explaining to a child the rules of entering the forest: that you have to ask permission from Tane Mahuta before you enter. When a child does not want to say the promise, he is encouraged to do so collaboratively with the teacher before entering the forest. Only once the child has said the promise does he enter, demonstrating the importance of the verbal commitment and participation in the accountable action of promise-making by the participants prior to entering the forest.

text: Indigenizing outdoor play in New Zealand: A conversation analysis approach This chapter focuses on a single case analysis of one trip to a local bush reserve in New Zealand. The observations included in this chapter begin by exploring the way in which a promise to the Maori God Tane Mahuta is managed by the teachers and children at the beginning of the excursion. The promise made is part of the mundane, everyday activity engaged in by these children and teachers during their weekly visit to the bush reserve, where every child is required to recite a phrase that promises not to hurt the creatures, animals or plants of Tane Mahuta when they are playing in the forest. In the first of the video-recorded episodes, explicit reference to Tane Mahuta is initially oriented through one of the children reciting the promise, unprompted, at the beginning of the recording. The second observation reveals one of the teachers explaining to a child the rules of entering the forest: that you have to ask permission from Tane Mahuta before you enter. When a child does not want to say the promise, he is encouraged to do so collaboratively with the teacher before entering the forest. Only once the child has said the promise does he enter, demonstrating the importance of the verbal commitment and participation in the accountable action of promise-making by the participants prior to entering the forest.

year: 2017