Academic literature on the topic 'Spectral wave period'
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Journal articles on the topic "Spectral wave period"
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Hamilton, L. J. "Methods to obtain representative surface wave spectra, illustrated for two ports of north-western Australia." Marine and Freshwater Research 48, no. 1 (1997): 43. http://dx.doi.org/10.1071/mf94220.
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Simple automatic methods of classifying surface wave spectra in terms of spectral shape are outlined and are used to examine the monthly wave climatology for the port approaches to Dampier and Port Hedland on the North West Shelf of Australia. Waves and swell at these shallow sites occur independently in three frequency bands. These correspond to low-energy long-period swell from distant sources (periods of 12 to 20 s), cyclones or energetic local storms (periods of 8 to 12 s), and local winds (periods of 4 to 8 s). Summer cyclones generate highest waves, but sea breezes are the dominant mode of wave generation. Waves and swell tend to occur episodically and independently in any month, and the peak frequency shifts during the wave generation process, so that a representative spectrum formed by simple averaging of spectra would be grossly oversmoothed. To overcome this, the monthly climatology is presented in terms of reference spectral shapes (the Ochi and Hubble 1976 North Atlantic formulations) that are most likely to occur for particular frequency bands and ranges of significant wave height. Measured spectra may then be selected as representative spectra from groupings associated with the most likely reference shapes, with further criteria such as spectral width being used to define what is typical. In some cases, the reference spectra provide good enough fits to enable them to be used directly as representative spectra.
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Aouf, Lotfi, Jean-Michel Lefèvre, and Danièle Hauser. "Assimilation of Directional Wave Spectra in the Wave Model WAM: An Impact Study from Synthetic Observations in Preparation for the SWIMSAT Satellite Mission." Journal of Atmospheric and Oceanic Technology 23, no. 3 (March 1, 2006): 448–63. http://dx.doi.org/10.1175/jtech1861.1.
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Abstract Within the framework of the Surface Waves Investigation and Monitoring from Satellite mission (SWIMSAT) proposed to the European Space Agency, an assimilation scheme has been implemented in the Wave Model (WAM) in order to estimate the impact of spectral information on wave prediction. The scheme uses an optimal interpolation and the “spectral partitioning” principle. The synthetic wave spectra are located along a SWIMSAT orbit track and are assimilated in a 4-day-period simulation. Random errors are included to simulate the uncertainties of SWIMSAT instrumentation. The sensitivity of the scheme to background and observational errors and the correlation length is examined. The assimilation impact is investigated for two cases of moderate and large errors of the first guess. The results show that the assimilation scheme works correctly and the rms errors of significant wave height, mean period, and direction are significantly reduced for both periods of analysis and forecast. The impact on significant wave height is noticeable during the period of analysis and stays efficient for 2-day forecasts. For a large error in the first guess, the impact increases and remains significant for 3-day forecasts. Statistical analysis of mean wave parameters clearly shows that the use of spectral information yields a better estimate of wave frequency, direction, and low-frequency wave height in comparison with the results based upon assimilation of wave heights only. However, total significant wave height is less sensitive to the addition of spectral information in the assimilation scheme. The use of correlation length depending on the latitude of grid points leads to a better spread of incremental observations and, hence, to better skills in terms of the rms errors of mean wave parameters. The use of several wavelength cutoffs concerning the SWIMSAT synthetic wave spectra suggests that the “assimilation index” of mean wave parameters decreases with the increasing wavelength cutoff.
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Guedes Soares, C., and M. C. Nolasco. "Spectral Modeling of Sea States With Multiple Wave Systems." Journal of Offshore Mechanics and Arctic Engineering 114, no. 4 (November 1, 1992): 278–84. http://dx.doi.org/10.1115/1.2919981.
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The spectral models of individual wave systems have one peak and are described by theoretical models that have gained general acceptance. This work deals with sea states with more than one wave system, leading to spectral models with two or more peaks. Use is made of spectra derived from measurements off the Portuguese Coast and data is provided as to their probability of occurrence as well as about the dependence of the spectral parameters on the significant wave height and peak period. It is shown that wind-dominated and swell-dominated two-peaked spectra tend to occur in different areas of the scatter diagram. The spectral parameters of the two-peaked spectra show little correlation with significant wave height and peak period.
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Nair, M. Anjali, and V. Sanil Kumar. "Wave spectral shapes in the coastal waters based on measured data off Karwar on the western coast of India." Ocean Science 13, no. 3 (May 3, 2017): 365–78. http://dx.doi.org/10.5194/os-13-365-2017.
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Abstract. An understanding of the wave spectral shapes is of primary importance for the design of marine facilities. In this paper, the wave spectra collected from January 2011 to December 2015 in the coastal waters of the eastern Arabian Sea using the moored directional waverider buoy are examined to determine the temporal variations in the wave spectral shape. Over an annual cycle for 31.15 % of the time, the peak frequency is between 0.08 and 0.10 Hz; the significant wave height is also relatively high (∼ 1.55 m) for waves in this class. The slope of the high-frequency tail of the monthly average wave spectra is high during the Indian summer monsoon period (June–September) compared to other months, and it increases with an increase in significant wave height. There is not much interannual variation in the slope for swell-dominated spectra during the monsoon, while in the non-monsoon period when wind-seas have a high level of influence, the slope varies significantly. Since the exponent of the high-frequency part of the wave spectrum is within the range of −4 to −3 during the monsoon period, the Donelan spectrum shows a better fit for the high-frequency part of the wave spectra in monsoon months compared to other months.
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Li, Jian-Guo, and Martin Holt. "Comparison of Envisat ASAR Ocean Wave Spectra with Buoy and Altimeter Data via a Wave Model." Journal of Atmospheric and Oceanic Technology 26, no. 3 (March 1, 2009): 593–614. http://dx.doi.org/10.1175/2008jtecho529.1.
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Abstract The Advanced Synthetic Aperture Radar (ASAR) on board the Envisat satellite is an important resource for observation of global ocean surface wave spectra. However, assessment of this valuable dataset is not straightforward as a result of a lack of other independent ocean wave spectral observations. The radar altimeter (RA-2) on board the same satellite measures ocean wave height at the same time as the ASAR but at a location about 200 km distant. A small number of moored buoys produce one-dimensional (1D) ocean wave spectra but few ASAR spectra fall on the buoy positions in a given period. Indirect comparison of the Envisat ASAR 2D wave spectra with the RA-2 wave heights and 1D spectra of three selected buoys from July 2004 to February 2006 is facilitated by a wave model, which provides coherent spatial and temporal links between these observations. In addition to the conventional significant wave height (SWH), four spectral subrange wave heights (SRWHs) are used to illustrate the spectral characteristics of these observations. A comparison of three Envisat ASAR 2D spectra with the closest model and buoy spectra is also attempted to illustrate the qualities of these different observations and to demonstrate the restrictions to their direct comparison. Results indicate that these three independent observations are in good agreement in terms of SWH, though the Envisat ASAR shows the largest variance. Comparison of SRWHs indicates that the ASAR spectra agree well with buoy and model in moderately long waves, but the ASAR instrument does not resolve high-frequency waves, especially along the satellite track.
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Ern, M., P. Preusse, M. Krebsbach, M. G. Mlynczak, and J. M. Russell III. "Equatorial wave analysis from SABER and ECMWF temperatures." Atmospheric Chemistry and Physics Discussions 7, no. 4 (August 8, 2007): 11685–723. http://dx.doi.org/10.5194/acpd-7-11685-2007.
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Abstract. Equatorial planetary scale wave modes such as Kelvin waves or Rossby-gravity waves are excited by convective processes in the troposphere. In this paper an analysis for these and other equatorial wave modes is carried out with special focus on the stratosphere using temperature data from the SABER instrument as well as ECMWF temperatures. Space-time spectra of symmetric and antisymmetric spectral power are derived to separate the different equatorial wave types and the contribution of gravity waves is determined from the spectral background of the space-time spectra. Both gravity waves and equatorial planetary scale wave modes are main drivers of the quasi-biennial oscillation (QBO) in the stratosphere. Temperature variances attributed to the different wave types are calculated for the period from February 2002 until March 2006 and compared to previous findings. A comparison between SABER and ECMWF wave analyses shows that in the lower stratosphere SABER and ECMWF spectra and temperature variances agree remarkably well while in the upper stratosphere ECMWF tends to overestimate Kelvin wave components. Gravity wave variances are partly reproduced by ECMWF but have a significant low-bias. A case study for the time period of the SCOUT-O3 tropical aircraft measurement campaign in Darwin/Australia (in November and December 2005) is performed and we find that in the lower stratosphere also the longitude-time distribution of the Kelvin waves is correctly reproduced by ECMWF.
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Ern, M., P. Preusse, M. Krebsbach, M. G. Mlynczak, and J. M. Russell. "Equatorial wave analysis from SABER and ECMWF temperatures." Atmospheric Chemistry and Physics 8, no. 4 (February 21, 2008): 845–69. http://dx.doi.org/10.5194/acp-8-845-2008.
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Abstract. Equatorial planetary scale wave modes such as Kelvin waves or Rossby-gravity waves are excited by convective processes in the troposphere. In this paper an analysis for these and other equatorial wave modes is carried out with special focus on the stratosphere using temperature data from the SABER satellite instrument as well as ECMWF temperatures. Space-time spectra of symmetric and antisymmetric spectral power are derived to separate the different equatorial wave types and the contribution of gravity waves is determined from the spectral background of the space-time spectra. Both gravity waves and equatorial planetary scale wave modes are main drivers of the quasi-biennial oscillation (QBO) in the stratosphere. Temperature variances attributed to the different wave types are calculated for the period from February 2002 until March 2006 and compared to previous findings. A comparison between SABER and ECMWF wave analyses shows that in the lower stratosphere SABER and ECMWF spectra and temperature variances agree remarkably well while in the upper stratosphere ECMWF tends to overestimate Kelvin wave components. Gravity wave variances are partly reproduced by ECMWF but have a significant low-bias. For the examples of a QBO westerly phase (October–December 2004) and a QBO easterly phase (November/December 2005, period of the SCOUT-O3 tropical aircraft campaign in Darwin/Australia) in the lower stratosphere we find qualitatively good agreement between SABER and ECMWF in the longitude-time distribution of Kelvin, Rossby (n=1), and Rossby-gravity waves.
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Ponce de León, Sonia, and C. Guedes Soares. "Extreme Waves in the Agulhas Current Region Inferred from SAR Wave Spectra and the SWAN Model." Journal of Marine Science and Engineering 9, no. 2 (February 2, 2021): 153. http://dx.doi.org/10.3390/jmse9020153.
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The influence of the Agulhas Current on the wave field is investigated. The study is conducted by performing high resolution spectral wave model simulations with and without ocean currents. The validation of the numerical simulations is performed for the Significant Wave Height (Hs) using all possible satellite altimetry data available in the study region for a winter period of 2018. Wave spectra and extreme waves parameters are examined in places where waves and current are aligned in the Agulhas Current. Sentinel-1 (S1) wave mode Synthetic Aperture Radar (SAR) spectra are used to estimate the composites of the Hs and BFI (Benjamin–Feir Index). SAR computed BFI and Hs were compared with the respective composites obtained from the Simulating Waves Nearshore (SWAN) model. From the Hs composites using SAR data and modeled data, it can be concluded that the Hs maxima values are distributed in the Agulhas Current Retroflection (ACR) and also in the southern limit of the domain that is affected by the strong circumpolar winds around Antarctic. In addition, the BFI composites exhibit the highest values in the ACR and some few values are observed in the southern border as occurred with the Hs. The results of this study indicate that there is direct correlation between the Agulhas Current strength, the Hs and the BFI. It was found that the modeled directional wave spectra are broadened when the ocean current is considered in the simulation. The analysis of the modeled wave spectra is performed over eddies, rings and meanders in the Agulhas Current region. The transformation of the wave spectra due to current refraction is discussed based on the numerical simulations. The effect of the Agulhas Current on the spectral shape is explored. The spectral wave energy grows when the wave and the current are aligned, resulting in peaked, elongated and widened spectra. A decrease of the peak period was observed before the occurrence of maximum values of BFI, which characterize abnormal sea states.
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Álvarez, Enrique, and Ramón Plaza. "Existence and spectral instability of bounded spatially periodic traveling waves for scalar viscous balance laws." Quarterly of Applied Mathematics 79, no. 3 (March 17, 2021): 493–544. http://dx.doi.org/10.1090/qam/1591.
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This paper studies both existence and spectral stability properties of bounded spatially periodic traveling wave solutions to a large class of scalar viscous balance laws in one space dimension with a reaction function of monostable or Fisher-KPP type. Under suitable structural assumptions, it is shown that this class of equations underlies two families of periodic waves. The first family consists of small amplitude waves with finite fundamental period which emerge from a Hopf bifurcation around a critical value of the wave speed. The second family pertains to arbitrarily large period waves which arise from a homoclinic bifurcation and tend to a limiting traveling (homoclinic) pulse when their fundamental period tends to infinity. For both families, it is shown that the Floquet (continuous) spectrum of the linearization around the periodic waves intersects the unstable half plane of complex values with positive real part, a property known as spectral instability. For that purpose, in the case of small-amplitude waves it is proved that the spectrum of the linearized operator around the wave can be approximated by that of a constant coefficient operator around the zero solution and determined by a dispersion relation which intersects the unstable complex half plane. In the case of large period waves, we verify that the family satisfies the assumptions of the seminal result by Gardner (Spectral analysis of long wavelength periodic waves and applications, J. Reine Angew. Math. 491 (1997), 149–181) of convergence of periodic spectra in the infinite-period limit to that of the underlying homoclinic wave, which is unstable. A few examples are discussed.
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Nguyen, Thu-Ha, Bas Hofland, Vu Dan Chinh, and Marcel Stive. "Wave Overtopping Discharge for Very Gently Sloping Foreshores." Water 12, no. 6 (June 13, 2020): 1695. http://dx.doi.org/10.3390/w12061695.
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The spectral wave period T m − 1 , 0 at the toe of sea-dikes is a crucial parameter to predict wave overtopping discharge over sea-dikes. It is known from literature that this period quickly increases when waves reach shallow foreshores; however, sometimes the assumption is made that the wave period remains constant from offshore to near-shore, leading to an underestimation of the near-shore wave period. Several formulae have been proposed to resolve the underestimation of wave overtopping discharges for very shallow foreshores. These corrective formulations confirm the tendency of underestimating the overtopping discharges over a very gently sloping foreshore but are not validated for foreshore slopes gentler than 1:500. The “equivalent slope” method based on a recent study is inappropriate for these very gently sloping foreshores due to the breaker parameter being much smaller than seven. This study proposes an extension of the correction and finds that spectral wave periods can reach values two times those offshore.
Dissertations / Theses on the topic "Spectral wave period"
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Berg, Caroline. "Validation of the WAM-model over the Baltic Sea." Thesis, Uppsala University, Department of Earth Sciences, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9139.
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In order to understand how waves influence the exchange of momentum, latent heat and other parameters, between the ocean surface and the atmosphere, one can use models. A coupling between a wave model and an atmospheric regional climate model, for the Baltic Sea, will be performed at the Meteorology Institute in Uppsala University. The wave model is a state of the art, third generation wave model called WAM.
The new version of the WAM model (cycle 4) needs to be validated. The aim of this thesis is to perform this validation and also to investigate what meteorological forcing one should use to achieve best results. Two different types of forcing are analyzed, ERA40 reanalysis and the RCA climate model. In order to do this, observations from six different buoys in the Baltic Sea will be compared with the model output from WAM. The parameters that will be compared in this study are significant wave height, direction and peak period.
A consistent phenomenon for all the buoys is a slightly overestimation by the model of what the rate of this increases with increasing wave height. If one compares the model output when WAM are forced with the RCA climate model and when it is forced with ERA40 reanalysis, the differences between them are notable but not large. ERA40 is slightly better.
Significant wave height is quite good and gives a reasonably result. Some buoys and periods are better and some are worse. There are some differences for the significant wave height between the east coast and the west coast of Sweden, when forcing the model with RCA. It is slightly better on the west coast. On the contrary, the results from ERA40 are very coherent. The quality of the hindcast for the direction and the peak period, in contrast to the significant wave height, is not that good. The results are not bad, but it only gives a rough picture of the sea state.
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Kotaška, Stanislav. "Měření větrových oscilačních vln na nádrži." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-391947.
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This diploma thesis deals with the measurement of wind oscillation waves on reservoirs, especially with regard to the determination of wave properties with a focus on the spectral density. The thesis presents the basics of the theory of creation and propagation of wind oscillation waves, the recherche of measuring devices and a description of the pilot measurement with the processing of measured data in the MATLAB environment using the software tool WAFO. Attached to the CD are sample scripts for data processing from the resistance sensor.
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Golkin, Stanislav. "Simulation de la propagation d'ondes SH dans des structures périodiques et de la diffusion multiple d'ondes de volume en milieux aléatoires." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR1A002/document.
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Cette thèse concerne l’étude de la propagation d’ondes acoustiques dans des structures hétérogènes. Le but essentiel de ces travaux est de confronter des résultats d’expériences numériques effectuées dans le domaine physique (espace, temps) à des prédictions analytiques pour la propagation des ondes de surface SH le long d’un demi-espace stratifié périodique produisant des spectres discontinus de dispersion pour les ondes, ainsi que pour la diffusion multiple dans des milieux aléatoires inclusionnaires (fissures, cavités). Le code numérique FDTD développé lors de cette étude a permis, en autres choses, de corroborer quantitativement les fenêtres spectrales théoriques d’existence des ondes de surface dans les demi-espaces périodiques,ainsi que de montrer des zones de validité fréquentielles des approches analytiques de diffusion multiple concernant les propriétés effectives de milieux aléatoiresThe study is concerned with acoustic waves in elastic media with a different nature of in homogeneity consisting in either periodically continuous or piece wise variation of material properties, or in random sets of defects embedded into a homogeneous matrix, with a given statistical distribution. The scope of problems is topical in non-destructive testing and other applications of ultrasound.Theoretical methods describing involved acoustic phenomena (complex dispersion features, coherent wave in random media, ensemble average techniques) often rely on certain a priori assumptions which render numerical verification especially important.The thesis presents results of analytical modelling of the propagation of surface acoustic waves along periodic half-space, for which the dispersion spectrum is rather complex (discontinuous spectrum of propagation for the surface waves). A 2nd order FDTD numerical code has been developed in order to perform numerical experiments in the space and time domains, and to corroborate the analytical predictions in the frequency domain. A good agreement of simulated results with analytical modelling demonstrates applicability and consistency of the numerical tool. Finally, the code has been used for extracting numerically the coherent wave regime (mean wave over ensemble averaging of the positions of scatterers) for the acoustic propagation in different types of populations of randomly distributed scatterers. The results indicate ranges of validity of some multiple scattering analytical techniques
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Wang, Yunli. "Etude expérimentale et numérique des oscillations hydrodynamiques en milieux poreux partiellement saturés." Thesis, Toulouse, INPT, 2010. http://www.theses.fr/2010INPT0127/document.
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Cette thèse vise à étudier expérimentalement, analytiquement et numériquement, les conséquences de variations et d'oscillations hydrodynamiques à forte variabilité temporelle en milieux poreux partiellement saturés. Les problèmes que nous étudions comportent des surfaces libres tant à l'extérieur qu'à l'intérieur des milieux poreux, celles-ci étant définies comme des isosurfaces de pression d'eau égale à la pression atmosphérique (Pwater = Patm). Les différentes études expérimentales réalisées en laboratoire sont, respectivement : une expérience d'imbibition dans une boite à sable avec effets capillaires importants; la transmission d'oscillations de la surface libre à travers un massif sableux intercalaire dans un petit canal à houle (IMFT, Toulouse); l'étude de la dynamique et de la propagation des oscillations des niveaux d'eau dans un grand canal à houle (HYDRALAB, Barcelone), partiellement recouvert d'un fond sableux incliné, avec mesures de niveaux d'eau en pleine eau et sous le sable, et mesures du fond sableux (érosion/dépôts). Pour les études théoriques, nous avons développés des solutions analytiques linéarisées. Un exemple de problème traité analytiquement est: l'équation linéarisée de Dupuit-Boussinesq (D-B) transitoire à surface libre, en hypothèse d'écoulements plans et vidange/remplissage instantané : oscillations forcées, transmission et dissipation d'ondes à travers une boite à sable rectangulaire. Nous avons aussi développé une solution de l'équation faiblement non linéaire de Dupuit- Boussinesq (D-B) pour étudier le problème d'imbibition avec variation abrupte du niveau d'eau amont (suivi temporel du front de saturation). Nous avons pu étudier les différents types de problèmes transitoires liés aux expériences citées plus haut par simulation numérique. En particulier, nous avons simulé des écoulements partiellement saturés et insaturés, en coupe verticale, à l'aide d'un code de calcul (BIGFLOW 3D) qui résoud l'équation de Richards généralisée en régime transitoire. Nous avons ainsi étudié numériquement en régime non saturé, l'expérience d'imbibition dans un sable initialement sec à frontières verticales (IMFT sandbox), puis l'expérience de propagation d'ondes dans le grand canal à houle de Barcelone (laboratoire HYDRALAB) comportant une plage de sable inclinée, avec un couplage complètement intégré entre les zones micro-poreuse (sable) et “macro-poreuse” (pleine eau). Pour analyser les résultats de cette dernière expérience et les comparer aux simulations, nous avons utilisé plusieurs méthodes de traitement et d'analyse des signaux : analyse de Fourier (spectres de fréquences) ; ondelettes discrètes multi-résolution (Daubechies) ; analyses corrélatoires simple et croisée. Ces méthodes sont combinées avec des méthodes de préfiltrage pour estimer dérives et résidus (moyennes mobiles ; ondelettes multi-résolution). Cette analyse des signaux a permis de comprendre et quantifier la propagation à travers une plage de sable. Au total, les différentes approches de modélisation mis en oeuvre, associé à des procédures de calage en situation de couplage transitoire non linéaire ont permis de reproduire globalement les phénomènes de propagation de teneur en eau et de niveau d'eau dans les différentes configurations étudiéesThis thesis aims at investigating experimentally, analytically and numerically, the consequences of hydrodynamic variations and oscillations with high temporal variability in partially saturated porous media. The problems investigated in this work involve “free surfaces” both outside and inside the porous media, the free surface being defined as the “atmospheric” water pressure isosurface (Pwater = Patm). The laboratory experiments studied in this work are, respectively: Lateral imbibition in a dry sand box with significant capillary effects; Transmission of oscillations of the free surface through a vertical sand box placed in a small wave canal (IMFT, Toulouse); Dynamics of free surface oscillations and wave propagation in a large wave canal (HYDRALAB, Barcelona), partially covered with sand, with measurements of both open water and groundwater levels, and of sand topography (erosion / deposition). For theoretical studies, we have developed linearized analytical solutions. Here is a sample problem that was treated analytically in this work: The linearized equation of Dupuit-Boussinesq (DB) for transient free surface flow, assuming horizontal flow and instantaneous wetting/drainage of the unsaturated zone: forced oscillations, wave transmission and dissipation through a rectangular sandbox. We also developed a weakly nonlinear solution of the Dupuit-Boussinesq equation to study the sudden imbibition (temporal monitoring of the wetting front). We have studied the different types of transient flow problems related to the experiments cited above by numerical simulation. In particular, we have simulated unsaturated or partially saturated transient flows in vertical cross-section, using a computer code (BIGFLOW 3D) which solves a generalized version of Richards’ equation. Thus, using the Richards / BIGFLOW 3D model, we have studied numerically the experiment of unsaturated imbibition in a dry sand (IMFT sandbox), and then, with the same model, we have also studied the partially saturated wave propagation experiment in the large Barcelona wave canal (HYDRALAB laboratory), focusing on the sloping sandy beach, with coupling between the micro-porous zone (sand) and the “macro-porous” zone (open water). To interpret the results of the latter experiment and compare them to simulations, we use several methods of signal analyzis and signal processing, such as: Fourier analysis, discrete multi-resolution wavelets (Daubechies), auto and cross-correlation functions. These methods are combined with pre-filtering methods to estimate trends and residuals (moving averages; discrete wavelet analyses). This signal analyzis has allowed us to interpret and quantify water propagation phenomena through a sandy beach. To sum up, different modeling approaches, combined with model calibration procedures, were applied to transient nonlinear coupled flow problems. These approaches have allowed us to reproduce globally the water content distributions and water level propagation in the different configurations studied in this work
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Sharpe, Matthew Michael. "The distribution of wave heights and periods for seas with unimodal and bimodal power density spectra." Thesis, 1990. http://hdl.handle.net/10945/24360.
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CIVINSApproved for public release ; distribution is unlimited
Observed distributions of wave heights and periods taken from one year of surface wave monitoring near Martha's Vineyard are compared to distributions based on narrow-band theory. The joint distributions of wave heights and periods and the marginal height distributions are examined. The observed significant wave heights and periods of the extreme waves are also studied. Seas are classified by the shapes of their power density spectra. Spectra with a single peak are designated as unimodal and spectra with two peaks as bimodal. Seas are further classified by spectral width, a function of the thee lowest spectral moments. The joint distributions of wave heights and periods from seas with narrow spectral widths take the general shape predicted by narrow-band theory and the statistics of extreme waves for these seas are well described. As spectral width increases, agreement between the theoretical and observed distributions diminishes and the significant wave heights and statistics of extreme waves show increasingly variability. Bimodal seas with wide-banded spectra are found to have larger significant and extreme wave heights and shorter extreme wave periods than unimodal seas of the same width. Theses.
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Ramberg, Andreas. "Ocean Waves Estimation : An Artificial Intelligence Approach." Thesis, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-35736.
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This thesis aims to solve the mathematical inverse problem of characterizing sea waves based on the responses obtained from a marine vessel sailing under certain sea conditions. By researching this problem the thesis contributes to the marine industry by improving products that are using ocean behavior for controlling ship's dynamics. Knowledge about the current state of the sea, such as the wave frequency and height, is important for navigation, control, and for the safety of a vessel. This information can be retrieved from specialized weather reports. However, such information is not at all time possible to obtain during a voyage, and if so usually comes with a certain delay. Therefore this thesis seeks solutions that can estimate on-line the waves' state using methods in the field of Artificial Intelligence. The specific investigation methods are Transfer Functions augmented with Genetic Algorithm, Artificial Neural Networks and Case-Based Reasoning. These methods have been configured and validated using the n-fold cross validation method. All the methods have been tested with an actual implementation. The algorithms have been trained with data acquired from a marine simulation program developed in Simulink. The methods have also been trained and tested using monitored data acquired from an actual ship sailing on the Baltic Sea as well as wave data obtained from a buoy located nearby the vessel's route. The proposed methods have been compared with state-of-the art reports in order evaluate the novelty of the research and its potential applications in industry. The results in this thesis show that the proposed methods can in fact be used for solving the inverse problem. It was also found that among the investigated methods it is the Transfer Function augmented with Genetic Algorithm which yields best results. This Master Thesis is conducted under the Master of Engineering Program in Robotics at Mälardalens högskola in Västerås, Sweden. The thesis was proposed by Q-TAGG R&D AB in Västerås, Sweden, a company which specializes in marine vessel dynamics research.
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Mohebbi, Hamid Reza. "Parametric Interaction in Josephson Junction Circuits and Transmission Lines." Thesis, 2011. http://hdl.handle.net/10012/5973.
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This research investigates the realization of parametric amplification in superconducting circuits and structures where nonlinearity is provided by Josephson junction (JJ) elements. We aim to develop a systematic analysis over JJ-based devices toward design of novel traveling-wave Josephson parametric amplifiers (TW-JPA). Chapters of this thesis fall into three categories: lumped JPA, superconducting periodic structures and discrete Josephson transmission lines (DJTL).
The unbiased Josephson junction (JJ) is a nonlinear element suitable for parametric amplification through a four-photon process. Two circuit topologies are introduced to capture the unique property of the JJ in order to efficiently mix signal, pump and idler signals for the purpose of signal amplification. Closed-form expressions are derived for gain characteristics, bandwidth determination, noise properties and impedance for this kind of parametric power amplifier. The concept of negative resistance in the gain formulation is observed. A design process is also introduced to find the regimes of operation for gain achievement. Two regimes of operation, oscillation and amplification, are highlighted and distinguished in the result section. Optimization of the circuits to enhance the bandwidth is also carried out.
Moving toward TW-JPA, the second part is devoted to modelling the linear wave propagation in a periodic superconducting structure. We derive closed-form equations for dispersion and s-parameters of infinite and finite periodic structures, respectively. Band gap formation is highlighted and its potential applications in the design of passive filters and resonators are discussed. The superconducting structures are fabricated using YBCO and measured, illustrating a good correlation with the numerical results.
A novel superconducting Transmission Line (TL), which is periodically loaded by Josephson junctions (JJ) and assisted by open stubs, is proposed as a platform to realize a traveling-wave parametric device. Using the TL model, this structure is modeled by a system of nonlinear partial differential equations (PDE) with a driving source and mixed-boundary conditions at the input and output terminals, respectively. This model successfully emulates parametric and nonlinear microwave propagation when long-wave approximation is applicable. The influence of dispersion to sustain three non-degenerate phased-locked waves through the TL is highlighted.
A rigorous and robust Finite Difference Time Domain (FDTD) solver based on the explicit Lax-Wendroff and implicit Crank-Nicolson schemes has been developed to investigate the device responses under various excitations. Linearization of the wave equation, under small-amplitude assumption, dispersion and impedance analysis is performed to explore more aspects of the device for the purpose of efficient design of a traveling-wave parametric amplifier.
Knowing all microwave characteristics and identifying different regimes of operation, which include impedance properties, cut-off propagation, dispersive behaviour and shock-wave formation, we exploit perturbation theory accompanied by the method of multiple scale to derive the three nonlinear coupled amplitude equations to describe the parametric interaction. A graphical technique is suggested to find three waves on the dispersion diagram satisfying the phase-matching conditions. Both cases of perfect phase-matching and slight mismatching are addressed in this work. The incorporation of two numerical techniques, spectral method in space and multistep Adams-Bashforth in time domain, is employed to monitor the unilateral gain, superior stability and bandwidth of this structure. Two types of functionality, mixing and amplification, with their requirements are described. These properties make this structure desirable for applications ranging from superconducting optoelectronics to dispersive readout of superconducting qubits where high sensitivity and ultra-low noise operation is required.
Books on the topic "Spectral wave period"
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Staelin, David H. Improved passive microwave sounding of the atmosphere: Annual report, NASA grant NAG 5-2545, covering the period March 15, 1995 - March 14, 1996. [Washington, DC: National Aeronautics and Space Administration, 1996.
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Deruelle, Nathalie, and Jean-Philippe Uzan. The wave vector of light. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198786399.003.0022.
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This chapter shows how simple world lines of zero length can describe an undulatory aspect of light—namely, its frequency. It first encodes the information about the frequency of a monochromatic light wave in the zeroth component of its wave vector. An alternative method of taking into account the wave nature of light is based on the fact that the emission of successive light corpuscles by the source also defines the period of a light signal. To illustrate, the chapter provides the example of a light source and a receiver moving along the X axis of a frame S. Finally, this chapter illustrates the idea of a particle horizon as well as the limits of validity of the spectral shift formulas introduced in the chapter by the example of two objects which exchange light signals.
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Chan, Felicia. Performing (Comic) Abjection in the Hong Kong Ghost Story. Edinburgh University Press, 2018. http://dx.doi.org/10.3366/edinburgh/9781474424592.003.0007.
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Horror films in Hong Kong cinema have eschewed terror in favour of comedy, where supernatural beings take the form of hopping vampires, wandering spirits and underworld demons rendered in latex masks and movie slime. This chapter explores the comic presentation of these subjects in Hong Kong horror, where the self-reflexive exposure of the cinematic machinery of costume and special effects appear to put it at odds with the spectral affectivity of the Hong Kong ghost story. This chapter returns to two classic films from the mid-1980s, A Chinese Ghost Story (Tsui Hark 1987) and Rouge (Stanley Kwan 1988), films from the ‘second wave’ period long noted to carry ‘Hong Kong’ as a subject of concern in the run up to the British handover of 1997, and revisits their historical positioning in the light of more recent post-1997 incarnations such as Visible Secret (Ann Hui 2001), My Left Eye Sees Ghosts (Johnnie To 2002), and Rigor Mortis (Juno Mak 2013).
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Duncan, Anthony, and Michel Janssen. Constructing Quantum Mechanics. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198845478.001.0001.
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This is the first of two volumes on the genesis of quantum mechanics. It covers the key developments in the period 1900–1923 that provided the scaffold on which the arch of modern quantum mechanics was built in the period 1923–1927 (covered in the second volume). After tracing the early contributions by Planck, Einstein, and Bohr to the theories of black‐body radiation, specific heats, and spectroscopy, all showing the need for drastic changes to the physics of their day, the book tackles the efforts by Sommerfeld and others to provide a new theory, now known as the old quantum theory. After some striking initial successes (explaining the fine structure of hydrogen, X‐ray spectra, and the Stark effect), the old quantum theory ran into serious difficulties (failing to provide consistent models for helium and the Zeeman effect) and eventually gave way to matrix and wave mechanics. Constructing Quantum Mechanics is based on the best and latest scholarship in the field, to which the authors have made significant contributions themselves. It breaks new ground, especially in its treatment of the work of Sommerfeld and his associates, but also offers new perspectives on classic papers by Planck, Einstein, and Bohr. Throughout the book, the authors provide detailed reconstructions (at the level of an upper‐level undergraduate physics course) of the cental arguments and derivations of the physicists involved. All in all, Constructing Quantum Mechanics promises to take the place of older books as the standard source on the genesis of quantum mechanics.
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J, Devenport William, and United States. National Aeronautics and Space Administration., eds. Perpendicular blade vortex interaction and its implications for helicopter noise prediction: Final report to NASA Langley on research performed under grant NAG-1-1119, "wave-number frequency spectra in a trailing vortex for BSI noise prediction" for the period ending 15th August, 1993. [Washington, DC: National Aeronautics and Space Administration, 1993.
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Esterhammer, Angela. Identity Crises. Edited by Paul Hamilton. Oxford University Press, 2016. http://dx.doi.org/10.1093/oxfordhb/9780199696383.013.39.
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This chapter addresses the European dimension of nineteenth-century celebrity culture, the extent to which it involves international media networks and figures who, in person and by reputation, crossed borders to engage with multiple publics. Fame on an international scale was facilitated by the reopening of the continent to travel and tourism after the Battle of Waterloo in 1815—but the post-Napoleonic era also altered the conditions of fame, and as the effects of celebrity culture made themselves felt, so did some ironic counter-currents. In the wake of the personality-driven poetry of Byron or the novels and essays of Mme de Staël, late Romantic literature manifests certain anti-celebrity impulses. All of this brings the issue of personal identity to the forefront in the literature and culture of the early nineteenth century, a moment when Romanticism’s recently awakened concern with unique subjectivity confronts the spectre of externalized, commodified, reproducible selves.
Book chapters on the topic "Spectral wave period"
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Priya, Prachi, Prashant Kumar, and Rajni. "Wave Spectral Analysis of Visakhapatnam Port Under the Resonance Conditions." In Advances in Transdisciplinary Engineering. IOS Press, 2023. http://dx.doi.org/10.3233/atde221335.
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The Visakhapatnam port, India is a major natural port, situated in between the Kolkata and Chennai on the East Coast and in terms of latitude and longitude its location is 17.6856∘ N, 83.2160∘ E has experienced an extreme wave oscillations 2.0 to 6.0 m in the midst of its severe weather events. In this paper numerical studies are performed to analyze the frequency distribution over the oceanic surface of standing waves in Visakhapatnam port at four respective synthetic record stations in presence of partially reflecting harbor. The convergence study is conducted to obtain the numerical accuracy of the scheme and simulation results are validated with the available studies experimentally from Ippen and Goda (1963) and Lee (1971) also with the analytical approximations. Further, the spectral density is determined corresponding to the wave period for the incident waves striking with several directions towards the Visakhapatnam port at four different record stations. The computation of the resonant frequencies is conducted in the Visakhapatnam port to examine the safe locations for the moored ship. Abstract goes here.
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Kraus, Eric B., and Joost A. Businger. "Surface Wind Waves." In Atmosphere-Ocean Interaction. Oxford University Press, 1995. http://dx.doi.org/10.1093/oso/9780195066180.003.0008.
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Rhythmic and monotonously repetitive, but quite unpredictable in its details, the structure of the sea surface is an epitome of the natural world. Surface waves have been studied actively by mathematicians and physicists since the dawn of modern science. Though the phenomenon seems deceptively simple, it cannot be explained or predicted rigorously by existing theories. Nonlinear interactions between wind, waves, and currents cause theoretical problems as well as make it difficult to obtain comprehensive, interactive data sets. In response to wind and pressure changes at the air-sea interface, the ocean reacts with waves that occupy some nine spectral decades: from capillary waves, which undulate within a fraction of a second over distances smaller than one centimeter, to planetary waves with periods measured in years and wavelengths of thousands of kilometers. The dynamics of all these waves can be related to the set of equations discussed in Section 4.1. For that reason, a consideration of all wave forms could have been combined in the same chapter, but we found it more convenient to divide the subject into two parts. The present chapter deals exclusively with wind-generated waves at the sea surface. They determine the small-scale configuration of the air-sea interface and that affects the turbulent transfers, which are the topic of the following chapter. On the other hand, information and energy transports from the sea surface into the ocean interior by internal and inertial waves, depend upon the state of the upper layers of the ocean. This made it desirable to discuss these wave forms in Chapter 7, after the consideration of planetary boundary layers in Chapter 6. Small-amplitude or linear, harmonic surface waves are considered in Section 4.2. Analysis of these waves has been the classic approach to the topic. Linear waves represent an idealized abstraction, but their analysis does provide basic insights into actual wave dynamics. Linear approximations have to be abandoned when one considers the energy and the momentum of wave fields. This is the topic of Section 4.3. In Section 4.4 we discuss the various sources and sinks of wave energy and momentum.
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Tabrej Khan, Md, and Ashish Adholiya. "Current Research Trends Machine Learning in 5G: A Bibliometric Analysis." In New Frontiers in Communication and Intelligent Systems, 437–51. Soft Computing Research Society, 2021. http://dx.doi.org/10.52458/978-81-95502-00-4-46.
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Researchers are attracted to emerging field 5G with machine learning. Many review articles have been carried out to analyze in a different direction of 5G with machine learning. However, no researcher presented bibliometric analysis on machine learning in the 5G research field to a detailed analysis of research status and future trend network in this research area. A bibliometric analysis was done in the current study using the bibliometric R tool and VOS viewer software. The relevant literature was collected period 2001 to 2021 from the Web of Science (WoS) Core Collection and Scopus database. The quantitative analysis was done in terms of a yearly published article, most trend research topic, and future direction in ML in 5G technology. Finally, the result indicated that China, the U.S.A., and India are the top countries to publish this field because China, the U.S.A., and the U.K. are the most cited countries. Beijing University of Posts and Telecommunications is the most relevant organization, Wang most appropriate and most influential author in this research area (5G in AI/ML). IEEE Access, IEEE transactions on vehicular technology, and Sensor are the most relevant journal. The main challenges in this field are low latency communication, resource allocation, resource management spectral efficiency, millimeter wave, 5G with the Internet of things (IoT), a device to device communication, power control, and massive MIMO. Deep learning, machine learning, cognitive radio, and reinforcement learning are artificial intelligence techniques used in 5G.
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Youssoufa, Mati, Ousmanou Dafounansou, Camus Gaston Latchio Tiofack, and Alidou Mohamadou. "Traveling Wave Solutions and Chaotic Motions for a Perturbed Nonlinear Schrödinger Equation with Power-Law Nonlinearity and Higher-Order Dispersions." In The Nonlinear Schrödinger Equation [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.100396.
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This chapter aims to study and solve the perturbed nonlinear Schrödinger (NLS) equation with the power-law nonlinearity in a nano-optical fiber, based upon different methods such as the auxiliary equation method, the Stuart and DiPrima’s stability analysis method, and the bifurcation theory. The existence of the traveling wave solutions is discussed, and their stability properties are investigated through the modulational stability gain spectra. Moreover, the development of the chaotic motions for the systems is pointed out via the bifurcation theory. Taking into account an external periodic perturbation, we have analyzed the chaotic behavior of traveling waves through quasiperiodic route to chaos.
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Ostlie, Dale A. "Revealing Secrets Hidden in Light and Matter." In Astronomy: The Human Quest for Understanding, 237–62. Oxford University PressOxford, 2022. http://dx.doi.org/10.1093/oso/9780198825821.003.0007.
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Abstract Revealing Secrets Hidden in Light and Matter presents the growing body of evidence, theory, and tools that ultimately allow scientists to study objects that are otherwise beyond human reach. The wave-like nature of light means that diffraction gratings can be used to separate light into its constituent colors, revealing hidden complexity and unique signatures of each element. General characteristics of objects, their temperatures, and their environments can produce continuous blackbody radiation, emission lines, or absorption lines. The chemical properties of the elements reveal patterns that can be represented by the periodic table. Atomic spectra even led to the discovery of helium in the Sun’s spectrum. The production of cathode rays in vacuum tubes led to the discovery of electrons and the fact that they have an elementary charge. The discovery of radioactivity also led to further insights into matter and provided a means for estimating ages through radiometric dating.
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Kumar Chourasia, Ritesh, Nitesh K. Chourasia, and Narendra Bihari. "Optical Properties of Hollow-Core Bragg Fiber Waveguides." In Photonic Materials: Recent Advances and Emerging Applications, 214–36. BENTHAM SCIENCE PUBLISHERS, 2023. http://dx.doi.org/10.2174/9789815049756123010014.
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The propagation and dispersion properties of hollow-core Bragg fibre waveguides for both high and low refractive index contrasts of cladding materials are explored and compared in this chapter using two design wavelengths: 1550 nm in the near-infrared area and 632.8nm in the visible range. The boundary matching approach was used to build a relationship between the incoming and outgoing light waves employing the transfer matrix method. The observed photonic band gaps are somewhat substantial in high refractive index contrast cladding Bragg fibre waveguides, i.e. HRBFW, and low periodic cladding layers are required to achieve a perfect photonic bandgap. The spectrum range and spectral location of photonic band gaps in both HRBFW and low refractive index contrast cladding Bragg fibre waveguides, i.e. LRBFW, are substantially dependent on the angle of incidence of a light beam, i.e. the optical path of the incident light. The sensitivity of the Bragg fibre waveguide for sensing applications may be determined by measuring the thickness of the photonic bandgap or the spectral shift of the photonic bandgap. HRBFW seems to have a high sensitivity when considering the change in spectral bandwidth of photonic bandgap with core refractive index, which grows with increasing design wavelength. LRBFW has a much higher sensitivity than HRBFW when considering the LBE (Left band edge) and RBE (Right band edge), hence it is suggested for sensing applications. HRBFW directed a greater number of modes than LRBFW, according to the assessment of dispersion characteristics.
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Wehrey, Frederic. "Introduction." In Beyond Sunni and Shia, 1–10. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780190876050.003.0001.
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Analysis of the modern Middle East using a sectarian lens is widespread, in academia, the media and in policy circles. A common approach is primordialism, which ascribes conflict in the region to “age-old” tensions within Islam, specifically between Sunnis and Shias. At the other end of the spectrum are the so-called “instrumentalists” who see religious identity as essentially malleable and driven by elite agency and geopolitics. This volume aims for a middle ground: acknowledging the salience of faith and belief while also emphasizing how religious tensions are inflamed through wordly factors like government policies, state collapse, geopolitics, media, and identity entrepreneurs. Furthermore, it situates the ebb and flow of sectarianism within several periods or waves: the aftermath of the 1979 Iranian revolution; the Iraq War of 2003 to 2010 and the period following the 2011 Arab uprisings to the present.
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Goody, R. M., and Y. L. Yung. "Absorption by Atmospheric Gases." In Atmospheric Radiation. Oxford University Press, 1989. http://dx.doi.org/10.1093/oso/9780195051346.003.0007.
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Digital archives offer the investigator an up-to-date analysis of an extensive and specialized literature. Periodic revisions are reported in the open literature and it seems unlikely that future investigators will attempt to use any other source where archives can provide the required data. For this reason, we shall confine our comments on permitted vibration-rotation transitions to describing the AFGL tape contents, but we shall add two areas not contained in it: first, electronic bands, and second, the related topics of forbidden transitions, collision-induced transitions, and polymer spectra. The AFGL tape lists data on one important set of electronic transitions, those giving rise to the near-infrared atmospheric bands of molecular oxygen. These bands behave in the same way as vibration rotation bands, except for the frequency displacement caused by the change in electronic energy and the symmetry conditions imposed by the electronic wave functions. Other electronic transitions usually involve larger differences between energy levels and cannot be understood as completely as the lower energy, vibrational and rotational transitions. Fortunately, visible and ultraviolet bands of importance for atmospheric problems are less complicated than vibration—rotation bands and they are usually less affected by state parameters. Atmospheric absorption calculations in the visible and ultraviolet spectrum are commonly made on the basis of empirical data without requiring the level of understanding developed in Chapters 3 and 4 for vibration-rotation bands. The altitude of unit optical depth for ultraviolet atmospheric bands is illustrated in Fig. 5.1. The intensity of solar radiation falls off rapidly with decreasing wavelength in the spectral region shown (the irradiance at 2000 Å compared to that at 3000 Å is 10-2 whereas at 1000 Å it is 10-5, see Appendix 9). For heating rate calculations at altitudes less than 100km, only O2 and O3 are important, except under special conditions when the atmosphere contains large amounts of volcanic aerosols, or polar stratospheric clouds at high latitudes. All of the absorptions shown in Fig. 5.1 are important for other reasons that do not directly concern us here.
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Kelz, Robert. "Enduring Competition." In Competing Germanies, 226–88. Cornell University Press, 2020. http://dx.doi.org/10.7591/cornell/9781501739859.003.0006.
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This chapter tracks the trajectory of Argentina's German theaters against a changing political landscape and new waves of European emigration. In the postwar period, director Paul Walter Jacob endeavored to attract all German speakers to the Free German Stage; however, his failed efforts at reconciliation underscored the polarized environment in the Argentine capital. Without ever renouncing fascism, Ludwig Ney adopted a strategy of interculturalism to succeed professionally in Peronist Argentina. German-speaking artists from across the political spectrum embarked on cross-cultural projects, and their transformative impact on theater in Argentina is still evident today. Meanwhile, in its crusade against communism, the West German embassy intervened at both stages. Carefully staged depictions of German heritage and reconciliation reflected a specious contrivance, contingent on edited memories of the recent past. The intractable animosity ultimately led to a move away from German dramatists in favor of canonical European playwrights, such as William Shakespeare.
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Sirven, Joseph I. "Adult EEG." In Clinical Neurophysiology, edited by Devon I. Rubin, 127–46. 5th ed. Oxford University PressNew York, 2021. http://dx.doi.org/10.1093/med/9780190067854.003.0008.
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Abstract The use of electroencephalography (EEG), particularly long-term bedside EEG in the hospital and intensive care unit, has grown dramatically over the past several years. The purpose of these studies has been to identify occult seizures and nonconvulsive status epilepticus. Often, the EEG in these circumstances reveals a spectrum of abnormal nonepileptiform activity. This chapter explores these abnormal nonepileptiform patterns inclusive of focal and diffuse slowing, named findings such as frontal intermittent rhythmic delta or triphasic waves and rhythmic periodic abnormalities that often reside on the border between epileptiform and nonepileptiform discharges. The chapter addresses specific patterns often seen in common neuropathologies and then discusses the use of EEG in prognostication and brain death.
Conference papers on the topic "Spectral wave period"
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Azimirad, M., A. R. M. Gharabaghi, and M. R. Chenaghlou. "Deterministic-Spectral Fatigue Analysis of a Typical Jacket Platform (SPD1) Using Directional Wave Spectrum." In ASME 2007 26th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2007. http://dx.doi.org/10.1115/omae2007-29418.
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Fixed offshore platforms or Jacket type platforms are the most common offshore structures used for oil & gas Exploration & Production industry in Persian Gulf, because water depth is such that the shallow water condition is dominant. Sea waves as dominant environmental loading are cyclic and have random nature. The applied cyclic sea wave forces will lead to fatigue damages in jacket’s joints. There are different methods to investigate the fatigue life of jackets such as deterministic method, simplified method, spectral method and transient method. Spectral method is a suitable method, which can consider the random nature of sea waves in fatigue analysis. Deterministic-spectral method developed by Bishop et al. is used to estimate the fatigue life of shallow water jacket platforms. However, in this method the frequency spectrum of waves is used in the analysis, but generally sea waves are propagating in different directions with different frequencies, so directional wave spectrum can consider wave randomness more properly. In this paper, frequency domain spectral method using Deterministic-Spectral approach has been used to estimate the fatigue life of a typical jacket platform (SPD1 at South Pars Field - Persian Gulf). Base wave cases were chosen from joint histogram of height & period that is calculated based on scatter diagrams of South Pars Field. First the jacket was modeled by ANSYS software, then by applying base wave cases to it and analyzing the critical TT joint under internal cyclic forces, hot spot stress transfer functions at 8 nodes around the intersection of joint were obtained. Using JONSWAP standard spectrum and the spreading function proposed by Goda, sea state’s Power Spectral Densities (PSD) and directional spectrums are multiplied to obtain stress spectra. The fatigue damage and fatigue life then are calculated. Results indicate that the fatigue life based on frequency spectrum is less than the fatigue life based on directional spectrum.
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Kitano, Toshikazu, Hajime Mase, and Wataru Kioka. "Theory of Significant Wave Period Based on Spectral Integrals." In Fourth International Symposium on Ocean Wave Measurement and Analysis. Reston, VA: American Society of Civil Engineers, 2002. http://dx.doi.org/10.1061/40604(273)43.
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Nunes, Luis Manoel Paiva, C. Guedes Soares, and Jose Antonio Moreira Lima. "Separation of Wave Systems in Time Series of Combined Sea States." In ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/omae2008-57643.
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In some oceanographic applications it is necessary to separate the individual sea state components, or wave systems, that are present in complex wave conditions represented by multipeaked wave energy spectra. Later on, it may be required to realign the original sea states having only the calculated parameters of the splitted spectrum. As an example, this situation may arise when trying to make correlation between time evolution of the sea states with meteorological forcings. To solve this problem a method was developed to follow the time evolution of a given initial sea state using a mathematical tracking procedure. It is based in a “similarity index” between one point of the time series and three previous points. The criterion uses wave parameters Hs (significant wave height), Tp (spectral peak period) and Dir (spectral peak wave direction) to calculate the similarity index. The method selects points that have the highest similarity index as a part of the same type of spectral component, following the time sequence of waves.
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Waseda, Takuji, Sho Asaumi, and Keiji Kiyomatsu. "Improving Resource Assessment of Wave Power Based on Spectral Wave Model." In ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-24492.
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Epistemic uncertainties of wave power estimation based on spectral wave model were assessed utilizing the community wave model WW3 of NOAA. A four tiered nested model was constructed covering the Pacific Ocean, the sea around Japan, the North-Eastern Japan and Kamaishi regional model at 100km, 10km, 1km and 100m resolutions respectively. The sensitivity of the model output to four wind products (NCEP-GFS, NCEP-CFSR, GSM/JMA, ERA-interim/ECWMF) was tested; the wave model outputs as well as wind products were validated against observations of NDBC buoys, JKEO/JAMSTEC buoy, TAO array and NOWPHAS buoy along the north-eastern Japan. The differences of the estimations using four wind products were relatively small whereas model errors were spatially inhomogeneous. The dependence on grid-resolution was relatively small at depth 100m or so. On the other hand, the modeled significant wave period had a large bias from the observation because of the inconsistency in the spectral moment used to estimate the significant wave period. The energy period (T-1,0) was 5% larger than the period from WW3 (T-0.5,0) and 20% larger than the period from NDBC (T0,2). The difference of wave period, dependent on the spectral shape and location, are often overlooked despite their significant impact on the resource estimate.
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Pontes, M. T., and M. Bruck. "Using Remote Sensed Data for Wave Energy Resource Assessment." In ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/omae2008-57775.
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The conversion of the energy contained in ocean waves into an useful form of energy namely electrical energy requires the knowledge at least of wave height and period parameters. Since 1992 at least one altimeter has been accurately measuring significant wave height Hs. To derive wave period parameters namely zero-crossing period Tz from the altimeter backscatter coefficient various models have been proposed. Another space-borne sensor that measures ocean waves is SAR (or the advanced ASAR) from which directional spectra are obtained. In this paper various models proposed to compute Tz from altimeter data are presented and verified against a collocated set of Jason altimeter and NDBC buoy data. A good fitting of altimeter estimates to buoy data was found. Directional spectra obtained from ENVISAT ASAR measurements were compared against NDBC buoy data. It was concluded that for the buoys that are more sensitive to long low-frequency wave components the fitting of wave parameters and spectral form is good for short spatial distances. However, since the cut-off ASAR frequency is low (reliable information is provided only for long waves) their use for wave energy resource assessment in areas where wind-waves are important is limited.
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Souza, Felipe Lopes de, Eduardo Aoun Tannuri, Pedro Cardozo de Mello, Guilherme Franzini, Jordi Mas-Soler, and Alexandre Nicolaos Simos. "Bayesian Estimation of Directional Wave-Spectrum Using Vessel Movements and Wave-Probes: Proposal and Preliminary Experimental Validation." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-61241.
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The measurement of the directional wave spectrum in oceans has been done by different approaches, mainly wave-buoys, satellite imagery and radar technologies; these methods, however, present some inherent drawbacks, e.g., difficult maintenance, low-resolution around areas of interest and high-cost. In order to overcome those problems, recent works in the area proposed a motion-based estimation procedure using the vessel, or the floating facility, as a wave sensor, what was called wave-buoy analogy. Despite of solving the issues, the solution is still incomplete, since it suffers from low estimation capabilities of the spectral energy below the cut-off period of the systems, around eight seconds, a frequency range that is responsible for the drift effects, that are critical for operation planning and dynamic positioning. This work studies the usage of wave-probes installed on the hull of a moored vessel to enhance the estimation capabilities of the motion-based strategy, using a high-order estimation method based on Bayesian statistics. The proposal is founded on the asymptotical response of the oceanic systems facing low period waves, which starts to behave like a wall, reflecting all the incoming energy, i.e., the worst the motion-based estimation is, the better the wave-elevation based estimation should be. Firstly, the measurements from the wave-probes are incorporated to the dynamic system of the vessel as new degrees-of-freedom, using a linear model extension, thus the Bayesian method can be expanded without additional reasoning. Secondly, the linear model hypothesis and the possible improvements are validated by experiments conducted in a wave-basin with a scale model of a moored FPSO-VLCC, concluding that the approach is able to improve not only the estimation of spectra with low peak period, but also the estimation in the entire range of expected spectra, mainly the significant height and the peak period properties. Lastly, some drawbacks are discussed, as the effect of the non-linear roll movement, which must be taken in account when calculating the wave-probe response; and the poor mean-direction estimation capability in some particular wave directions and low peak periods, in which even the vessel motions allied with the wave-probe response are not able to provide the proper direction discrimination.
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Ewans, Kevin, and Bas Buchner. "Wavelet Analysis of an Extreme Wave in a Model Basin." In ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/omae2008-57499.
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Analyses of laboratory wave records including extreme crests, based on the continuous wavelet transform, are reported. The analyses have provided further insight into the spectral characteristics of these extreme events. During the period of the extreme wave crest, spectral levels over all frequencies are substantially elevated by comparison with average spectrum for the complete wave record. This was also observed in a similar analysis of the famous New Year wave event that occurred at the Draupner platform. The analyses also indicate that nonlinear effects are active during the crest event, second-order effects being particular strong and indicating phase-locking of high frequency waves to freely-propagating waves with frequencies close to the spectral peak. These nonlinear effects appear to be strong only in the vicinity of the extreme.
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Katsardi, Vasiliki, and Chris Swan. "An Experimental Study of Shallow Water Wave Statistics on Mild Bed Slopes." In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49957.
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This paper describes a new series of laboratory observations, undertaken in a purpose built wave flume, in which a number of scaled simulations of realistic ocean spectra were allowed to evolve over a range of mild bed slopes. The purpose of the study was to examine the distribution of wave heights and its dependence on the local water depth, d, the local bed slope, m, and the nature of the input spectrum; the latter considering variations in the spectral peak period, Tp, the spectral bandwidth and the wave steepness. The results of the study show that for mild bed slopes the statistical distributions of wave heights are effectively independent of both the bed slope and the spectral bandwidth. However, the peak period plays a very significant role in the sense that it alters the effective water depth. Following detailed comparisons with the measured data, the statistical distributions for wave heights in relatively deep water are found to be in reasonable agreement with the Forristall [1] and Glukhovskii [2] distributions. For intermediate water depths, the Battjes & Groenendijk [3] distribution works very well. However, for the shallowest water depths none of the existing distributions provides good agreement with the measured data; all leading to an over-estimate of the largest wave heights.
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Feng, Qin, and Richard Large. "Prediction of Fatigue Life of Shallow Water Offshore Platforms Using Spectral Fatigue Analysis Method." In ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/omae2010-20796.
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Spectral fatigue analysis approach is highly recommended for fixed offshore platform design and reassessment by API. This method is a computationally efficient method, being able to handle the random nature of environmental ocean wave conditions during calculating wave loads on the offshore platforms and subsequent structural responses. However, its fundamental theory is based on the assumption of linearity of both structural system and wave loading mechanism. Although this method is critically appropriate to be applied in offshore platform design and fatigue assessment for deep water scenarios where wave and force nonlinearities are not very severe, it has still been widely utilized for the design and assessment of shallow water platforms in offshore industry without carefully considering possible errors caused by strong nonlinear factors between ocean waves and forces. The source giving rise to the errors is because of the difficulties in choosing suitably correct wave heights for a series of wave periods required for producing transfer functions between sea state spectra and structural response spectra. Therefore, the studies to justify the possible errors of the spectral fatigue analysis method for shallow water platforms have been provoked. This paper presents the results of the studies of investigating the errors from currently existing spectral fatigue analysis method. A new technical approach that can reduce the errors in the spectral fatigue analysis of shallow water platforms is introduced. The proposed technical approach is mainly focused on producing realistic transfer functions between sea state spectra and structural response spectra, which can reasonably reflect the individually local sea state data by using wave height-period joint probability density function. Hence the fatigue damage and life at the tubular joints of offshore platforms can be more precisely predicted. The spectral fatigue analysis of a practical shallow water jacket platform in the recent platform design project has been performed using the proposed approach and the results are discussed.
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Ren, Bing, and Yongxue Wang. "Spectral Analysis of Irregular Wave Impact on the Structure in Splash Zone." In ASME 2002 21st International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2002. http://dx.doi.org/10.1115/omae2002-28091.
Full textAbstract:
The spectral analysis from experimental data of irregular wave impact on the structures with large dimension in the splash zone is presented. The experiments were conducted in the large wave-current tank in the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology. In the experiment, the target spectrum is JONSWAP spectrum, the significant wave height H1/3 is in the range from 0.1m to 0.3m, and the peak period of spectrum Tp in the range from 1.0s to 2.0s. The ratio of s/H1/3, which refers to the clearance of the subface of the structure above still water level (s) to the incident wave height, is between −0.1 and 0.4. The spectral analysis results of the irregular wave impact pressure on the subface of the structure under various case studies are presented. The distribution of spectral moment of the impact pressure on the structure along the subface is given. And the influence of different incident wave parameters and relative clearance s/H1/3 on the average spectral moment of impact pressure are discussed.
Reports on the topic "Spectral wave period"
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Sharpe, Matthew M. The Distribution of Wave Heights and Periods for Seas with Unimodal Bimodal Power Density Spectra. Fort Belvoir, VA: Defense Technical Information Center, September 1990. http://dx.doi.org/10.21236/ada227040.
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