Relevant bibliographies by topics / P wave polarisation

Academic literature on the topic 'P wave polarisation'

Author: Grafiati
Published: 10 December 2022
Last updated: 19 February 2023

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Journal articles on the topic "P wave polarisation"

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Hendrick, N., and S. Hearn. "VECTOR WAVEFIELD-SEPARATION TECHNIQUES FOR IMPROVED MULTI-COMPONENT SEISMIC EXPLORATION." APPEA Journal 42, no. 1 (2002): 613. http://dx.doi.org/10.1071/aj01037.

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Analysis of multi-component seismic data commonly involves scalar processing of the vertical component to provide a conventional P-wave image, and scalar processing of the horizontal component(s) to yield an Swave image. A number of convincing examples now exist where such S-wave imagery has significantly enhanced hydrocarbon exploration.There is potential to achieve cleaner P- and S-wave images by more fully exploiting the true vector nature of multi-component reflection data. The simplest form of vector analysis, termed polarisation analysis, allows identification of different wave types. It does not, however, generally lead to effective wavefield separation, due to significant interference between the different waves in a typical exploration-seismic recording.More effective vector separation is possible if the particle-motion information from polarisation analysis is coupled with the more familiar tools of frequency and velocity filtering. Three related separation algorithms, termed MUSIC, IWSA and PIM are considered here. These techniques all utilise a parametric approach whereby wavefield slowness and polarisation are modelled simultaneously in the frequency domain.Synthetic and ocean-bottom cable examples are used to demonstrate practical issues relating to the use of these tools. The PIM algorithm is considered to be the most generally useful of the three multi-component wavefield separation algorithms. Implementation of these tools in a highly automated production environment is considered non-trivial. Hence, it is envisaged that such vector separation schemes will have most application for specialised data processing over identified target zones. Vector wavefield separation has the potential to amplify the considerable success already achieved with integrated P- and S-wave exploration.
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Teubner, P. J. O., V. Karaganov, and K. A. Stockman. "Coherence and Correlation in Electron Scattering from the Alkalis." Australian Journal of Physics 52, no. 3 (1999): 421. http://dx.doi.org/10.1071/ph98081.

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A series of superelastic electron scattering experiments from lithium and from potassium is described in which the total polarisation parameter P+ is measured. We report significant departures from the coherence condition P+ = 1 for both targets. The structure observed in the parameter P+ can be interpreted by a qualitative wave mechanical model that had been introduced by our research group to explain similar structure in superelastic electron scattering experiments from sodium.
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Scharien, R. K., J. Landy, and D. G. Barber. "Sea ice melt pond fraction estimation from dual-polarisation C-band SAR – Part 1: In situ observations." Cryosphere Discussions 8, no. 1 (January 27, 2014): 805–44. http://dx.doi.org/10.5194/tcd-8-805-2014.

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Abstract. An understanding of the evolution of melt ponds on Arctic sea ice is important for climate model parameterizations, weather forecast models, and process studies involving mass, energy and biogeochemical exchanges across the ocean-sea ice–atmosphere interface. A field campaign was conducted on landfast first-year sea ice in the Canadian Arctic Archipelago during the summer of 2012, to examine the potential for estimating melt pond fraction from C-band synthetic aperture radar (SAR). In this study, in situ dual-polarisation radar scatterometer observations of pond covered ice are combined with surface physical measurements to analyse the effects of radar and surface parameters on backscatter. LiDAR measurements of ice surface roughness and ultrasonic wind-wave height profiles of melt ponds are used to quantify the sea ice surface rms-height. Variables contributing to the roughness of wind-generated melt pond surface waves within the fetch-limited pond environment are evaluated, and we show that pond roughness and backscatter cannot be explained by wind speed alone. The utility of the VV / HH polarisation ratio (PR) for retrieving melt pond properties including pond fraction, due to the dielectric contrast between free surface water and sea ice, is demonstrated and explained using Bragg scattering theory. Finally, the PR approach is discussed in the context of retrievals from satellite C-, L-, and P-band dual-polarisation SAR.
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Ramkumar, Madhu A., and Chandrika Sudhendra. "Novel Ultra Wide Band Polarisation Independent Capacitive Jaumann Radar Absorber." Defence Science Journal 68, no. 1 (December 18, 2017): 64. http://dx.doi.org/10.14429/dsj.68.12025.

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<p style="margin-bottom: 0.14in; line-height: 115%;" align="justify">An ultra wide band (UWB), reduced thickness four layers capacitive jaumann absorber (CJA) with measured reflectivity of -15 dB (minimum) from 2 GHz to 19 GHz is presented in this paper. The novel CJA is designed and implemented by modifying the jaumann absorber (JA) design. The crucial impedance matching layers of CJA are designed by conceptualizing hexagonal resistive grid on dielectric substrates. Reduced thickness of 24.8 mm is realised by capacitive loading of hexagonal resistive grids with hexagonal resistive patches. Absorption performance of CJA is verified by full wave analysis using high frequency structural simulator software. Polarisation independent absorption performance is realised. Absorption of 96.5 per cent (minimum) is achieved with variation in angles of incidence from 0° to 30°. Resistive capacitive layers of CJA are developed as electrically thin printed circuit boards and integrated with alternating low loss, low density foam dielectric spacers backed by metallic conducting plane. Size of panel CJA is 280 mm × 280 mm. Fabricated panel CJA is evaluated for radar cross section (RCS) performance in microwave anechoic chamber. Matching results are obtained in simulation and measurements. The reduced thickness, low weight, UWB CJA finds application in RCS reduction of air vehicles/unmanned air vehicle. <span class="Apple-converted-space"> </span></p>
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Kumar, Praveen, Dr MBalasubramaniam, BS Murty, and KM Rajan. "Infrared and Structural Studies of Micro and Nano-crystalline Ta Doped Lead Zirconate Titanate Ceramics." Defence Science Journal 68, no. 4 (June 26, 2018): 412. http://dx.doi.org/10.14429/dsj.68.12314.

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<p> In this paper, influence of additives on structural properties of Tantalum (<em>Ta</em>) doped PZT ceramics, prepared by solid-state oxide and mechanical activation (MA) routes, has been studied. The Fourier transformation infrared spectroscopy (FTIR) studies, are done to understand the structural interactions, confirmed that the wave number and bond energy decreases with the increase in Ta content accompanied by decrease in grain size. FTIR spectrum becomes broader in nanocrystalline Ta-PZT. The fraction of tetragonal phase decrease along with reduction in grain size as the <em>Ta </em>content increase. The remnant polarisation and coercive field also follows the similar trend on <em>Ta </em>doping. It is seen that infrared spectroscopy results corroborate the structure and ferroelectric properties of PZT materials.</p>
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Del Gaudio, V., J. Wasowski, and S. Muscillo. "New developments in ambient noise analysis to characterise the seismic response of landslide-prone slopes." Natural Hazards and Earth System Sciences 13, no. 8 (August 20, 2013): 2075–87. http://dx.doi.org/10.5194/nhess-13-2075-2013.

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Abstract. We report on new developments in the application of ambient noise analysis applied to investigate the dynamic response of landslide-prone slopes to seismic shaking, with special attention to the directional resonance phenomena recognised in previous studies. These phenomena can be relevant for seismic slope susceptibility, especially when maximum resonance orientation is close to potential sliding directions. Therefore, the implementation of an effective technique for site response directivity detection is of general interest. In this regard methods based on the calculation of horizontal-to-vertical noise spectral ratio (HVNR) are promising. The applicability of such methods is investigated in the area of Caramanico Terme (central Italy), where ongoing accelerometer monitoring of slopes with different characteristics offers the possibility of validation of HVNR analysis. The noise measurements, carried out in different times to test the result repeatability, revealed that sites affected by response directivity persistently show major peaks with a common orientation, consistent with the resonance direction inferred from accelerometer data. In some cases such a directivity turned out parallel to maximum slope direction, but this cannot be considered a systematic feature of slope dynamic response. At sites where directivity is absent, the HVNR peaks do not generally show a preferential orientation, with rare exceptions that could be linked to the presence of temporarily active sources of polarised noise. The observed variations of spectral ratio amplitude can be related to temporal changes in site conditions (e.g. groundwater level/soil water content variations affecting P wave velocity and Poisson's ratio of surficial layer), which can hinder the recognition of main resonance frequencies. Therefore, we recommend conducting simultaneous measurements at nearby sites within the same study area and repeating measurements at different times in order to distinguish significant systematic polarisation caused by site-specific response directivity from polarisation controlled by properties of noise sources. Furthermore, an analysis of persistence in noise recordings of signals with systematic directivity showed that only a portion of recordings contains wave trains having a clear polarisation representative of site directional resonance. Thus a careful selection of signals for HVNR analysis is needed for a correct characterisation of site directional properties.
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Palmer, Michael H., John A. Blair-Fish, Paul Sherwood, and Martyn F. Guest. "Halogen Nuclear Quadrupole Coupling Constants: Comparison of ab initio Calculations which include Correlation, with Experiment." Zeitschrift für Naturforschung A 53, no. 6-7 (July 1, 1998): 383–95. http://dx.doi.org/10.1515/zna-1998-6-719.

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Abstract Ab initio determination of the electric field gradient (EFG) tensors at halogen and other centres ena-bled determination of the nuclear quadrupole coupling constants (NQCC) for a diverse set of axially symmetric (C3v , C∞v, D∞h and other symmetries) inorganic and organic molecules, where the heavy ele-ments are Cl, Br, and I with C, Si, Ge, and Sn hydrides. The latter elements are in an approximately tetrahedral environment. The study presents results at a standardised level of calculation, triple-zeta in the valence space (TZV) plus polarisation functions (TZVP) for the equilibrium geometry stage; all-electron MP2 correlation is included in all these studies. f-Orbital exponents were optimised for both Br and I centres in the methanes; the atomic populations of the f-orbital components are very small for the Br-and I-atoms, confirming their role as polarisation functions rather than having any bonding character. The EFG are determined at equilibrium with the TZVP basis set, except Sn and I centres where the basis set is TZV + MP2. For the bromo and iodo compounds, especially the latter, it is essential to allow for core polarisation, by decontraction of the p,d-functions. This is conveniently done by initial optimization of the structure with a partly contracted basis, followed by reestablishment of the equilibrium structure with the decontracted basis. A close correlation of the observed (microwave spectral) data with the calculations was observed, using the 'best' values for the atomic quadrupole moments for Cl, Br, and I; thus there seems no need to postulate that the value of QBr for 79Br and 81Br are in error. The SCF and MP2 wave-functions were converted into localised molecular orbitals by the Boys Method. This allowed a study of the differing s/p/d-hybridisation ratios, and the centroid positions, to be compared with the quadrupole coupling constants. The charge distributions for the atoms were converted into local bond dipoles, which in turn are correlated with the electronegativity differences of the bonded atoms.
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Buckingham, AD. "Linear and Nonlinear Light Scattering from the Surfaces of Liquids." Australian Journal of Physics 43, no. 5 (1990): 617. http://dx.doi.org/10.1071/ph900617.

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The linear optical properties of matter, e.g. the refractive index, the absorption coefficient and the reflectivity, can be interpreted in terms of the oscillating charge and current densities induced by the optical field. For most purposes, it is sufficient to consider the oscillating dipole moment 11= OI.E = OI.E(O) exp(-ioot+ik. r), where 01. is the mean polarisability of a molecule, or of a unit cell, in a plane wave propagating with wave vector k, angular frequency 00 and amplitude E(O). A static electric field F polarises the material and may affect the reflected light linearly in F. If F is in the plane of incidence there is a change of phase of the reflected light, and if F is perpendicular to the plane of incidence there is a change in polarisation and intensity. If the intensity of the optical field is high, nonlinear scattering is observed from the surface of a liquid. The surface breaks the symmetry of the fluid, leading to partial molecular orientation and hence to a non�vanishing first hyperpolarisability P that gives the induced dipole at the frequency 200 proportional to the square of E. With intense laser sources a molecular monolayer or sub-monolayer can be detected. Surface selectivity can be achieved by tuning an infrared laser of frequency oolR to a vibrational frequency of the monolayer and detecting a coherent beam at the sum frequency oo+ooIR, when the surface is simultaneously subjected to pulses at 00 and oolR.
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Córdoba-Jabonero, Carmen, Michaël Sicard, María-Ángeles López-Cayuela, Albert Ansmann, Adolfo Comerón, María-Paz Zorzano, Alejandro Rodríguez-Gómez, and Constantino Muñoz-Porcar. "Aerosol radiative impact during the summer 2019 heatwave produced partly by an inter-continental Saharan dust outbreak – Part 1: Short-wave dust direct radiative effect." Atmospheric Chemistry and Physics 21, no. 8 (April 30, 2021): 6455–79. http://dx.doi.org/10.5194/acp-21-6455-2021.

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Abstract. The short-wave (SW) direct radiative effect (DRE) during the summer 2019 heatwave produced partly by a moderate, long-lasting Saharan dust outbreak over Europe is analysed in this study. Two European sites (periods) are considered: Barcelona, Spain (23–30 June), and Leipzig, Germany (29 and 30 June), 1350 km apart from each other. Major data are obtained from AERONET and polarised Micro-Pulse Lidar (P-MPL) observations. Modelling is used to describe the different dust pathways, as observed at both sites. The coarse dust (Dc) and fine dust (Df) components (with total dust, DD = Dc + Df) are identified in the profiles of the total particle backscatter coefficient using the POLIPHON (POlarisation LIdar PHOtometer Networking) method in synergy with P-MPL measurements. This information is used to calculate the relative mass loading and the centre-of-mass height, as well as the contribution of each dust mode to the total dust DRE. Several aspects of the ageing of dust are put forward. The mean dust optical depth and its Df/DD ratios are, respectively, 0.153 and 24 % in Barcelona and 0.039 and 38 % in Leipzig; this Df increase in Leipzig is attributed to a longer dust transport path in comparison to Barcelona. The dust produced a cooling effect on the surface with a mean daily DRE of −9.1 and −2.5 W m−2, respectively, in Barcelona and Leipzig, but the Df/DD DRE ratio is larger for Leipzig (52 %) than for Barcelona (37 %). Cooling is also observed at the top of the atmosphere (TOA), although less intense than on the surface. However, the Df/DD DRE ratio at the TOA is even higher (45 % and 60 %, respectively, in Barcelona and Leipzig) than on the surface. Despite the predominance of Dc particles under dusty conditions, the SW radiative impact of Df particles can be comparable to, even higher than, that induced by the Dc ones. In particular, the Df/DD DRE ratio in Barcelona increases by +2.4 % d−1 (surface) and +2.9 % d−1 (TOA) during the dusty period. This study is completed by a second paper about the long-wave and net radiative effects. These results are especially relevant for the next ESA EarthCARE mission (planned in 2022) as it is devoted to aerosol–cloud–radiation interaction research.
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"Physiological ECG Value for Polish Half-Bred Anglo-Arab Horses." Bulletin of the Veterinary Institute in Pulawy 56, no. 4 (December 1, 2012): 631–35. http://dx.doi.org/10.2478/v10213-012-0111-4.

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Abstract The electrocardiographic examination was performed in 33 training horses (2-16 years of age, 11 males and 22 females). Einthoven and precordial leads (I, II, III, aVR, aVL, aVF, CV1, CV2, CV4) were used. The ECG was performed in resting horses and immediately after exercise (10 min walk, 15 min trot, 10 min canter) using a portable Schiller AT-1 3-channel electrocardiograph, with a paper speed of 25 mm sec-1 and a sensitivity of 10 mm.mV-1. The heart rate, wave amplitudes, and duration time were estimated manually. All horses presented a significant increase in heart rate after exercise (rest 43.83 ±10.33 vs. exercise 73.2 ±14.8). QT intervals were significantly shortened in most of the leads. In resting horses, all P waves in the lead I were positive and almost all II, III and CV4 leads were positive. Simple negative P wave dominated in aVR and only simple negative T wave was found in the leads I. The biphasic shape was observed. After exercise, the amplitude of P and T waves rose, however, clear changes were not observed in wave polarisation and form. In the absence of specific racial characteristics of the electrocardiogram in the Polish Anglo- Arabians, electrocardiographic findings can be interpreted according to ECG standards adopted for horses.
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Dissertations / Theses on the topic "P wave polarisation"

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Goy, Jérôme. "Mesures des observables tensorielles dans la réaction H(p,d)pion pour des énergies comprises entre 580 et 1300 MeV et stabilité des systèmes borroméens." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10019.

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L'essentiel du travail de cette these se rapporte a la mesure des observables tensorielles de polarisation dans la reaction h(p,d)pion pour des energies comprises entre 580 et 1300 mev. Ces observables sont obtenues en mesurant la polarisation des protons incidents et la polarisation tensorielle des deutons de recul par le polarimetre polder. Les resultats concernant les pouvoirs polarisants et les coefficients de transfert de spin de cette reaction apportent des contraintes nouvelles sur les analyses en ondes partielles et permettent d'acceder a une meilleure comprehension du processus d'absorption du pion pour des energies superieures au pic d'excitation de la resonance delta. La mesure du pouvoir d'analyse vectoriel fait egalement ressortir une structure autour de l'energie centre de masse de 2. 38 gev qui n'est pas reproduite par les analyses en ondes partielles. L'etude detaillee des erreurs systematiques associees aux mesures de polarisation du deuton servira aussi dans l'analyse d'une experience de diffusion elastique electron-deuton qui se monte actuellement au tnjaf (usa) et qui doit permettre d'isoler les facteurs de forme de charge et quadrupolaire du deuton a haut moment de transfert. La seconde partie de la these se refere a un travail effectue sur les systemes borromeens. L'objectif etait de determiner par une methode variationnelle, le jeu des constantes de couplage des potentiels d'interaction qui autorise la stabilite a trois corps sans qu'aucun sous-systeme a deux corps ne puisse etre lie
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Margerin, Ludovic. "Diffusion multiple des ondes élastiques dans la lithosphère." Phd thesis, Université Joseph Fourier (Grenoble), 1998. http://tel.archives-ouvertes.fr/tel-00749704.

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Nous étudions la dépendance spatio-temporelle de l'énergie de la coda courte-période (> 1Hz) des seismes. Pour celà, nous développons des solutions de l'équation de Transfert Radiatif (TR) pour les ondes élastiques dans des milieux réalistes. Deux approches sont adoptées, l'une numérique basée sur les méthodes de Monte-Carlo, l'autre analytique basée sur l'équation de diffusion. Dans l'approximation acoustique, nous résolvons l'équation de TR pour la croûte terrestre représentée par un guide d'ondes hétérogène. Pour ce modèle, l'énergie de la coda décroît exponentiellement en raison des fuites d'énergie à la base de la croûte. Nous confrontons cette théorie de façon critique à des données du Mexique. Nous concluons que notre modèle avec fuite rend parfaitement compte des observations et nous montrons que l'anélasticité des roches est faible. Enfin nous introduisons le temps de résidence des ondes diffuses pour décrire la décroissance énergétique de la coda. Nous abordons ensuite le problème de diffusion multiple en élasticité complète. Nous tenons compte des conversions entre ondes P et S, ainsi que de leur polarisation, décrite par 5 paramètres de Stokes. Nous montrons que l'énergie de la coda est rapidement dominée par les ondes S. Un équilibre d'énergie universel s'établit rapidement entre les modes P et S, en accord avec le principe d'équipartition . Le phénomène d'équilibrage de l'énergie est également observé pour les ondes de coda du Mexique, démontrant leur caractère diffusif. Enfin, nous calculons le cône de rétro-diffusion cohérente dynamique en champ proche. Nous montrons qu'après un régime transitoire, le cône se stabilise et s'étend sur une longueur d'onde autour de la source. L'ensemble des modèles et observations nous permettent de confirmer la nature diffusive de la coda.
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(12547160), Jennifer Kay Hafner. "Earthquake backazimuth determination using a single three-component digital seismograph." Thesis, 1997. https://figshare.com/articles/thesis/Earthquake_backazimuth_determination_using_a_single_three-component_digital_seismograph/19769053.

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Earthquake backazimuth estimation using a single three -component digital seismograph has been investigated. A three-dimensional principal components method formed the basic computational technique. Other details of the backazimuth estimation procedure were varied to determine the optimum approach. The data set comprised aftershocks of the 1988 Tennant Creek earthquakes, recorded on a number of stations in, or close to, the source zone. Epicentral distances (3.5 to 25 km) were unusually small compared to the data sets of others who have used similar techniques.

Complex geology challenged the accuracy of results. The most likely causes of error were believed to be the interruption of source -receiver wave travel paths by fault planes, and complex site geology. This included outcrops of highly deformed rocks, and proximity to a large intrusive body of anomalous character. Errors of 180° were common, possibly due to the low velocity surface layers.

Single station estimates were compared to reference backazimuths from network locations, determined by "EQLOCL" (SRC, RMIT), a program based on the least -squares travel -time approach. Approximately 75% of backazimuth discrepancies, projected into the range -90 to +90°, were less than or equal to 20°. This outcome indicates that the investigated technique can be successfully used to estimate earthquake backazimuth in at least some complex geologic receiver settings, and at short epicentral distances.

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