Search results for "waves"

The use of sea waves for generation of electrical energy: a linear tubular asynchronous electrical generator

2007

A linear tubular asynchronous generator to be used as generator driven by seawave is presented. The design criteria of a TLIM with hollowed iron induced part as well as the technological processes to be adopted and the materials utilized in the various parts are described. The methodologies for mechanical assembling and electric wiring are considered too. Finally, the prototype with bimetallic induced part that has been designed and built is presented and some experimental results on electrical and mechanical variables are shown.

A Ferrite Tubular Linear Permanent Magnet Generator (FTLPMG) analysis and design

2014

Several linear synchronous generators for the exploitation of sea wave energy have been proposed. Such machines do not require reactive power for the magnetization since they use permanent magnets for the excitation. The use of permanent magnets in a rough environment such as the marine environment may be a very weak point in the application of these kind of devices. In order to overcome this difficulty, the authors in this paper propose a linear synchronous electrical generator. Its excitation uses ferrites as suitable solutions to extract energy from sea waves. This paper describes the analysis and design of an improved axially magnetized tubular permanent-magnet machine in which several …

"The wrathful sunset glared...": The Krakatoa Sunsets in Victorian Science and Art

2020

The eruption of Krakatoa on August 27, 1883 was an event both tragic and spectacular. Thousands of lives were lost; sea waves and atmospheric disturbances were detected around the globe. Billions of tons of volcanic ash were thrown into the atmosphere producing multi-coloured sunsets caused by the scattering of light by aerosol particles. The paper discusses the ways in which these so-called Krakatoa sunsets, which were experienced by most of the world, were reflected in Victorian scientific and artistic discourse. The accounts included in the section “Descriptions of the Unusual Twilight Glows in Various Parts of the World, in 1883–84” of the Royal Society report The Eruption of Krakatoa a…

Cyclostratigraphy and high-frequency carbon isotope fluctuations in Upper Cretaceous shallow-water carbonates, southern Italy

2002

A detailed carbon isotope study has been carried out on a Santonian (Upper Cretaceous) carbonate platform succession that crops out at Monte Sant'Erasmo (southern Italy). Previous centimetre-scale studies on this succession have shown that high-frequency eustatic changes, resulting from the Earth's orbital fluctuations, controlled the hierarchical organization of the depositional and early diagenetic features in elementary cycles, bundles (groups of three to five elementary cycles) and superbundles (groups of three or four bundles). The elementary cycles, which correspond to single beds, suggest a control caused by Earth's precession; the bundles and superbundles record the short ( 100 kyr)…

Understanding seismic path biases and magmatic activity at Mount St Helens volcano before its 2004 eruption

2020

SUMMARY In volcanoes, topography, shallow heterogeneity and even shallow morphology can substantially modify seismic coda signals. Coda waves are an essential tool to monitor eruption dynamics and model volcanic structures jointly and independently from velocity anomalies: it is thus fundamental to test their spatial sensitivity to seismic path effects. Here, we apply the Multiple Lapse Time Window Analysis (MLTWA) to measure the relative importance of scattering attenuation vs absorption at Mount St Helens volcano before its 2004 eruption. The results show the characteristic dominance of scattering attenuation in volcanoes at lower frequencies (3–6 Hz), while absorption is the primary atte…

Mechanics and self-organization in tissue development

2021

Self-organization is an all-important feature of living systems that provides the means to achieve specialization and functionality at distinct spatio-temporal scales. Herein, we review this concept by addressing the packing organization of cells, the sorting/compartmentalization phenomenon of cell populations, and the propagation of organizing cues at the tissue level through traveling waves. We elaborate on how different theoretical models and tools from Topology, Physics, and Dynamical Systems have improved the understanding of self-organization by shedding light on the role played by mechanics as a driver of morphogenesis. Altogether, by providing a historical perspective, we show how i…

Self-Organization of Polarization State in Optical Fibers

2017

Exploiting the optical quadratic nonlinearity of zinc-blende semiconductors for guided-wave terahertz generation: A material comparison

2010

We present a detailed analysis and comparison of dielectric waveguides made of CdTe, GaP, GaAs and InP for modal phase matched optical difference frequency generation (DFG) in the terahertz domain. From the form of the DFG equations, we derived the definition of a very general figure of merit (FOM). In turn, this FOM enabled us to compare different configurations, by taking into account linear and nonlinear susceptibility dispersion, terahertz absorption, and a rigorous evaluation of the waveguide modes properties. The most efficient waveguides found with this procedure are predicted to approach the quantum efficiency limit with input optical power in the order of kWs.

Improved variables for measuring theΛbpolarization

1996

We discuss a few possible strategies for measuring the polarization of the {Lambda}{sub {ital b}} baryons produced in {ital e}{sup +}{ital e}{sup {minus}} annihilation at the {ital Z} resonance through their inclusive semileptonic decays. After reviewing the existing methods, an extension is proposed, based on the ratio of the averages of the squared electron and neutrino energies, including both perturbative and nonperturbative corrections. This variable minimizes the statistical error on the {Lambda}{sub {ital b}} polarization, while keeping the systematic theoretical errors at the level of 1{endash}2{percent}. A number of other polarization-sensitive variables are also discussed, such as…

STUDY OF LEG MOVEMENT IN ONE- AND TWO-LEGGED HOPPING

2012

This study was based on the previous research where mechanics of the leg-pushing phase in shot put was studied. The present paper examined the functional mechanics of leg movements during the ground contact of the jumps on one leg and on two legs. The principle of the measuring method was to photograph the movement in series of subject images on one frame where the marker lights attached to the subject can be seen as broken light-lines. The measuring accuracy of the system (time and distance) proved to be very high. This new measuring method is a useful complement to the existing methods. The aim of the study was to approximate the measured points by a suitable curve. Two equations (represe…