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| Registros recuperados: 35 | |
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| Plaisant, M. |
| Empirical models already exist for ambient noise spectral density function of frequency, sea state or wind speed but they give no information on the spatial structure or coherence of the noise field which is essential as soon as array beamforming is involved. We have developed a model which computes the spatial coherence matrix of the noise field due to a continuous distribution of sources located at the sea surface, and also the noise power spectral density after classical beamforming on an equidistant hydrophones linear array. In this model, propagation effects like rays bending due to variations of index of refraction and multiple bottom and surface reflections are taken into account. Principles of the modeling are presented and results demonstrate that... |
| Tipo: Text |
Palavras-chave: Spectral analysis; Models; Wind speed; Sea surface; Surface water waves; Acoustic equipment; Sound waves; Underwater noise; Ambient noise. |
| Ano: 1990 |
URL: http://archimer.ifremer.fr/doc/1990/acte-1143.pdf |
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| Royer, Francois; Fromentin, Jean-marc. |
| This paper provides an exploratory analysis aiming to seek whether the colour of environmental noise theory could help in understanding the intriguing reproductive strategy of Atlantic bluefin tuna (BFT). A frequency-based approach based on spectral exponents, f(beta) with beta < 0, is chosen and applied on 10 biogeographical provinces covering the North Atlantic. The major BFT spawning area, i.e. the Mediterranean Sea, was the only one to display a pink power spectrum, whereas open ocean regions displayed more reddened fluctuations, i.e. greater variance at low frequencies. Environmental noise in the Mediterranean could, thus, offer more favourable characteristics on the long-term than the open ocean. The implications of these findings are discussed in... |
| Tipo: Text |
Palavras-chave: Thunnus thynnus; Spectral analysis; Spawning; Sea surface temperature; Environmental noise. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2437.pdf |
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| Sultan, Sar; Ahmad, F; Elghribi, Nm. |
| Analyses of the daily means of the sea level at Jeddah and Port Sudan for the year 1991 reveal that a large proportion (60%) of the energy is concentrated in the seasonal variations. The seasonal signal is approximated as the sum of an annual and semi-annual components. The amplitudes of the annual component are 20.3 and 12.7 cm respective! y and constitute about 44% of the total variance. The amplitudes of the semi-annual cycle are 9.6 cm and 7.7 cm and explain about 10% and 16% of the variance respcctively. At Jeddah cross-spectral anal ysis between the sea-level and the wind stress components shows that the annual cycle is mainly induced by the long-shore component. In contrast no correlation exists between the sea leve! and the cross-shore wind-stress... |
| Tipo: Text |
Palavras-chave: Niveau de la mer; Tension du vent; Analyse spectrale; Mer Rouge; Sea leve; Wind stress; Spectral analysis; Red Sea. |
| Ano: 1996 |
URL: http://archimer.ifremer.fr/doc/00096/20766/18392.pdf |
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| Lin, Jing-yi; Sibuet, Jean-claude; Hsu, S. |
| The acoustic basement map of the East China Sea, established by the Shanghai Offshore Petroleum Bureau with all available industry seismic data, shows the existence of a 30-km-wide, 10-km-deep basin, that we named the Ho Basin. The Ho Basin belongs to a series of elongated deep basins extending over 600 km east of the Taiwan-Sinzi Ridge and flanked to the East by a ridge named the Longwan Ridge in its northern part. This new system of basin and ridge was probably formed during middle Miocene, sometimes in between rifting episodes occurring in the Taipei Basin and Okinawa Trough. It. complements the already defined system of five belts of back-arc basins and associated arc volcanic ridges in the East China Sea, which are progressively younger from the... |
| Tipo: Text |
Palavras-chave: Depth of magnetic sources; Spectral analysis; Backarc basins; East China Sea. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/2005/publication-1342.pdf |
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| Vilibic, I; Leder, N. |
| The aim of this paper is to investigate long-period climatic variations in the Mediterranean sea level, as well as some meteorological parameters and the influence of atmospheric forcing on sea-level fluctuations. Data for the annual mean sea level at seven stations (Trieste, Genoa, Marseilles, Alicante, Oran, La Goulette and Sfax), located in the Western Mediterranean, together with mean air pressure and temperature data for Zagreb, have been spectrally analysed. Various peaks in the power, coherence and phase spectra have been detected. The period of about 5.1 years corresponds to the quasi-meridional fluctuation in the paths of Atlantic cyclones. The period of about 2.7 years may be excited by variations of currents and sea-surface temperature in the... |
| Tipo: Text |
Palavras-chave: Sea-level series; Meteorological series; Spectral analysis; Long-period climatic oscillations. |
| Ano: 1996 |
URL: http://archimer.ifremer.fr/doc/00096/20763/18389.pdf |
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| Horng, Cs; Roberts, Ap; Liang, Wt. |
| We present a 2.14-Myr astronomically tuned relative geomagnetic paleointensity record from the western Philippine Sea. Pseudosingle-domain titanomagnetite is the only magnetic mineral identified and variations in titanomagnetite concentration fall well within the accepted limits for relative paleointensity variations. No significant temporally persistent periodicities are observed in wavelet analyses of the paleointensity time series or in the rock magnetic parameters used for relative paleointensity normalization. This suggests that our paleointensity record is largely free of rock magnetic or lithological artefacts and that it represents a reliable record of geomagnetic behavior with no evidence for modulation of the field at Earth orbital periods. The... |
| Tipo: Text |
Palavras-chave: Geomagnetic paleointensity; Magnetostratigraphy; Spectral analysis; Wavelet analysis; Philippine Sea. |
| Ano: 2003 |
URL: https://archimer.ifremer.fr/doc/00224/33554/31978.pdf |
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| Jezequel, Youenn; Bonnel, Julien; Coston-guarini, Jennifer; Guarini, Jean-marc; Chauvaud, Laurent. |
| Experiments in marine behavioural ecology rely heavily on observations made in tanks. However, when studying acoustic behaviours of marine animals in confined volumes, the effects of reverberation must be characterized, something that has been overlooked in parts of the marine ecology literature. In this study, we characterized reverberation in tanks using an artificial sound source and examined the implications for bioacoustic studies using sounds emitted by the European lobster Homarus gammarus during feeding and in response to stress. Broadband and transient sounds commonly produced by crustaceans were severely impacted by reverberation such that their spectral characteristics and pulse width durations could not be assessed. In contrast, low-frequency... |
| Tipo: Text |
Palavras-chave: European lobster; Passive acoustics; Tanks; Reverberation; Rattle; Buzzing sound; Spectral analysis. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00439/55080/56512.pdf |
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| Cuadra, T. de la. |
| Datos de madurez sexual de la pinchagua (Ophisthonema spp.) y varios parámetros oceanográficos fueron comparados y analizados en forma de series de tiempo. Un análisis de Funciones Ortogonales Empíricas (EOF) mostro una fuerte relación con el índice de la Oscilación Decadal del Pacífico (PDO); en contraste no mostró nivel de asociación entre las variables oceanográficas locales y los estadios de madurez sexual de la pinchagua, ya que la variabilidad obtenida no fue común a todas las series. Por otro lado, el Análisis Espectral, determinó que existen varios aportes de energía a las series de tiempo con diferente origen que estarán asociados a la señal interanual identificada por un ciclo bienal irregular con periodicidades entre 1.5 y 2.5 años que... |
| Tipo: Journal Contribution |
Palavras-chave: Climate; El Nino phenomena; Spectral analysis; Sexual maturity; Oceanographic data; Reproduction (biology). |
| Ano: 2010 |
URL: http://hdl.handle.net/1834/4800 |
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| Fierro, J.; Castillo, M.; Valenzuela, C.. |
| During the research cruise Cimar-Fiordo 2, carried out in late 1996, sea level was recorded in three stations located in channels, Messier (Puerto Edén), Wide (Punta Beresford) and Concepción (Caleta Patria). The measurements were of short term, starting in October 20th and finishing in December 13th, 1996. The sea level in those stations, was analyzed in the time and frequency dominion, and some tide non harmonic values were calculated. Results showed that tides evident influence in sea level signal, with a clear mixt semidiurnal behavior, and a daily inequality between high and low waters. The highest tide range was observed in puerto Edén, showing the effect of the local orography configuration while the wave propagates into the channel, and... |
| Tipo: Journal Contribution |
Palavras-chave: Tides; Harmonic analysis; Spectral analysis; Sea level; Cruises; Sea level changes; Monitoring systems; Tidal dynamics; Tidal waves; Ice fields; Tides; Spectral analysis; Sea level; Http://aims.fao.org/aos/agrovoc/c_7764; Http://aims.fao.org/aos/agrovoc/c_28964; Http://aims.fao.org/aos/agrovoc/c_34115. |
| Ano: 2003 |
URL: http://hdl.handle.net/1834/1579 |
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| Martínez, R.. |
| Usando series de tiempo de promedios diarios de presión atmosférica, temperatura ambiental, temperatura superficial y nivel medio del mar en los años 1994-1995 en cinco estaciones costeras de Ecuador y Colombia y una estación en las Islas galápagos (Ecuador) se aplicaron las técnicas del análisis espectral para determinar las oscilaciones existentes en el océano y la atmósfera. Se obtuvieron con alto niveles de coherencia, cinco modos predominantes en la atmósfera tropical: la oscilación de 37 días, muy próxima a la oscilación de Madden-Julian (1972), un modo de tres semanas con características de la " autooscilación" de 21 días, Murakami, 1974 y que es de naturaleza planetaria, una tercera oscilación de 17 días, de características muy similares a la onda... |
| Tipo: Journal Contribution |
Palavras-chave: Barotropic motion; Water waves; Spectral analysis; Time series; Oceanographic data; Fixed stations; Water temperature data; Air temperature; Atmospheric pressure; Mean sea level; Atmospheric pressure; Spectral analysis; Air temperature; Http://aims.fao.org/aos/agrovoc/c_693; Http://aims.fao.org/aos/agrovoc/c_28964; Http://aims.fao.org/aos/agrovoc/c_230. |
| Ano: 1998 |
URL: http://hdl.handle.net/1834/2199 |
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| Rossato,Roberta; Prete,Cássio Egídio Cavenaghi; Castro,César de; Tomm,Gilberto Omar; Leite,Rodrigo Santos; Mandarino,José Marcos Gontijo; Araújo,Pedro Mário de; Carvalho,Claudio Guilherme Portela de. |
| The objective of this work was to establish a calibration equation and to estimate the efficiency of near-infrared reflectance (NIR) spectroscopy for evaluating rapeseed oil content in Southern Brazil. Spectral data from 124 half-sib families were correlated with oil contents determined by the chemical method. The accuracy of the equation was verified by coefficient of determination (R²) of 0.92, error of calibration (SEC) of 0.78, and error of performance (SEP) of 1.22. The oil content of ten genotypes, which were not included in the calibration with NIR, was similar to the one obtained by the standard chemical method. NIR spectroscopy is adequate to differentiate oil content of rapeseed genotypes. |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Brassica napus; NIR; Oilseed; Soxhlet; Spectral analysis. |
| Ano: 2013 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-204X2013001200010 |
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| Registros recuperados: 35 | |
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