230,802 research outputs found
J. Rist, Germania anelante la pace, a cura di R. De Pol. traduzione di R. De Pol e M. Gobber
No full textLong-wavelength Pol-InSAR for glacier ice extinction estimation
No full textIn recent years there has been increased interest in using synthetic aperture radar (SAR) to study and monitor glaciers for climate change research. This paper describes the estimation of ice extinctions through modelling of Pol-InSAR (polarimetric interferometric SAR) coherences as a combination of a surface contribution (from the snow-firn interface and wind-induced features) and a volume response. Ground-to-volume scattering ratios derived from a novel polarimetric decomposition are used in conjunction with Pol-InSAR interferometric coherence magnitudes to invert the extinction of the ice layer. The inversion is performed with experimental airborne Pol-InSAR data at L- and P-band collected using DLR's E-SAR system over the Austfonna ice cap in Svalbard, Norway as part of the 2007 ICESAR campaign. Extinction-dependencies on frequency and glacier zone are investigated, and validation is performed comparing P-band sounder data to inverted extinction values
Forcing, damping and detuning for single and coupled Van der Pol oscillators
No full textWe use Melnikov function techniques together with geometric methods of bifurcation theory to study the interactions of forcing, damping and detuning on resonant periodic orbits for single and coupled forced Van Der Pol oscillators. For a coupled pair the local bifurcation geometry is almost everywhere described in terms of the singularities of a line congruence in three dimensions
M. Pol Métayer
No full textM. Pol Métayer. In: Manuel général de l'instruction primaire : journal hebdomadaire des instituteurs. 75e année, tome 44, 1907. p. 652
Extinction estimation over land ice using long-wavelength Pol-InSAR
No full textIn recent years there has been increased interest in using SAR to study and monitor glaciers and ice sheets for glaciological and climate change research. This paper describes for the first time the estimation of ice extinction through the modelling of Pol-InSAR coherences as a combination of a surface contribution from the snow-ice interface and a volume response. Separation of the ground and volume contributions is obtained through decomposition of the polarimetric coherency matrix. Both model-based Freeman 2- and 3-component and eigenvector decompositions are examined. Ground-to-volume scattering ratios derived from polarimetry are used in conjunction with Pol-InSAR interferometric coherences to invert the extinction of the ice layer. Validation is performed with airborne Pol-InSAR data at L- and P-band collected using DLR's E-SAR system over the Austfonna ice cap in Svalbard, Norway as part of the ICESAR campaign
Estimation of glacier ice extinction using long-wavelength airborne Pol-InSAR
No full textIn recent years there has been increased interest in using synthetic aperture radar (SAR) to study and monitor glaciers and ice sheets for glaciological and climate change research. This paper describes the estimation of ice extinctions through modeling of Pol-InSAR (polarimetric interferometric SAR) coherences as a combination of a surface contribution (from the snow-firn interface and wind-induced sastrugi features) and a volume response. Ground-to-volume scattering ratios derived from a novel polarimetric decomposition are used in conjunction with Pol-InSAR coherence magnitudes to invert the extinction of the ice layer. The inversion is performed for experimental airborne Pol-InSAR data at L- and P-band acquired by DLR's E-SAR system over the Austfonna ice cap in Svalbard, Norway as part of the 2007 ICESAR campaign. Extinction-dependencies on frequency and glacier facie
are investigated, and validation is performed comparing ground penetrating radar data to SAR backscatter and extinction values
Complete set of 6,034 one-per-person, subtype-assigned HIV-1 group M complete pol sequences
No full textComplete set of 6,034 one-per-person, subtype-assigned HIV-1 group M complete pol sequences is in a tab-delimited file containing the aligned pol sequence, GenBank accession number, GenBank author list, GenBank submission title, PubMed ID, country, sample year, and assigned subtype/CR
Characterisation of oriented volumes in glacier ice and extinction inversion with Pol-InSAR
No full textIn recent years there has been increased interest in using SAR to study and monitor glaciers and ice sheets for glaciological and climate change research. This paper describes the estimation of ice extinctions through the modelling of Pol-InSAR coherences as a combination of a surface contribution from the snow-ice interface and a volume response from an oriented particle cloud. Separation of the ground and volume contributions is obtained using a novel decomposition of the polarimetric covariance matrix which allows for preferential particle orientations and accounts for the influence of the dielectric constants of ice and snow. Ground-to-volume scattering ratios derived from polarimetry are used in conjunction with Pol-InSAR interferometric coherences to invert the extinction of the ice layer. Validation is performed with airborne Pol-InSAR data at L- and P-band collected using DLR's E-SAR system over the Austfonna ice cap in Svalbard, Norway as part of the ICESAR campaign
Vertical profile reconstruction with Pol-InSAR data of a subpolar glacier
No full textThe last decade has seen an increasing demand for accurate mapping and wide-coverage monitoring of glaciers and ice sheets in order to measure and predict their response to global climate change and their contribution to sea level rise. This in turn requires a more complete understanding of their properties including topography, accumulation rates and vertical profiles. One promising new technique for vertical profile reconstruction using polarimetric interferometric SAR (Pol-InSAR) data is Polarization Coherence Tomography (PCT) and for the first time, PCT is adapted here to a glacier scenario. The inversion algorithm to reconstruct vertical ice profiles is applied to both simulated data to assess its accuracy and sensitivity to input parameters, and to airborne Pol-InSAR data at L- and P-band and InSAR data at X-band collected using DLR's E-SAR system over the Austfonna ice cap in Svalbard, Norway
Pine Forest Height Inversion Using Single-Pass X-Band Pol-InSAR Data
No full textInternational audienceA sparse pine forest is investigated at X-band on a single-pass polarimetric synthetic aperture radar interferometry (PolInSAR) data set using HH and HV channels. These first preliminary results show that the associated phase centers present a significant vertical separation (about 6 m) allowed by penetration through gaps in the canopy. Forest parameter inversion using the random volume over ground (RVoG) model is evaluated and adapted at this frequency. The forest height can be retrieved accurately by supposing a high mean extinction coefficient (around 1.6 (dB/m). The penetration depth is estimated to be around 4 m, based on the forest height ground measurements. Finally, a time-frequency analysis using a sublook decomposition is performed to increase the vertical separation of the polarimetric phase centers. As a consequence, RVoG-inversion performance is improved, and a penetration depth that is in better accordance with a previous work (of the order of 2 m) is found. This paper has shown that the height inversion of a pine forest was possible using PolInSAR X-band data and that the performance was more dependent on the forest density than at lower frequencies
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