Bibliografie tematiche / Atmospheric long-range propagation

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Letteratura scientifica selezionata sul tema "Atmospheric long-range propagation"

Autore: Grafiati

Pubblicato: 15 marzo 2023

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Articoli di riviste sul tema "Atmospheric long-range propagation"

Averbuch, Gil, Jelle D. Assink e Läslo G. Evers. "Long-range atmospheric infrasound propagation from subsurface sources". Journal of the Acoustical Society of America 147, n. 2 (febbraio 2020): 1264–74. http://dx.doi.org/10.1121/10.0000792.

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Gibson, Robert G., e David E. Norris. "Long‐range infrasound propagation modeling using updated atmospheric characterizations". Journal of the Acoustical Society of America 112, n. 5 (novembre 2002): 2380. http://dx.doi.org/10.1121/1.4779677.

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Hart, Carl R., D. Keith Wilson, Chris L. Pettit e Edward T. Nykaza. "Machine-learning of long-range sound propagation through simulated atmospheric turbulence". Journal of the Acoustical Society of America 149, n. 6 (giugno 2021): 4384–95. http://dx.doi.org/10.1121/10.0005280.

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Eisenmann, Shmuel, Einat Louzon, Yiftach Katzir, Tala Palchan, Arie Zigler, Yonatan Sivan e Gadi Fibich. "Control of the filamentation distance and pattern in long-range atmospheric propagation". Optics Express 15, n. 6 (2007): 2779. http://dx.doi.org/10.1364/oe.15.002779.

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Lim, Tea Heung, Minho Go, Chulhun Seo e Hosung Choo. "Analysis of the Target Detection Performance of Air-to-Air Airborne Radar Using Long-Range Propagation Simulation in Abnormal Atmospheric Conditions". Applied Sciences 10, n. 18 (16 settembre 2020): 6440. http://dx.doi.org/10.3390/app10186440.

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In this paper, we propose the analysis of the target detection performance of air-to-air airborne radars using long-range propagation simulations with a novel quad-linear refractivity model under abnormal atmospheric conditions. The radar propagation characteristics and the target detection performance are simulated using the Advanced Refractive Effects Prediction System (AREPS) software, where the refractivity along the altitude, array antenna pattern, and digital terrain elevation data are considered as inputs to obtain the path loss of the wave propagation. The quad-linear model is used to approximate the actual refractivity data, which are compared to the data derived using the conventional trilinear refractivity model. On the basis of the propagation simulations, we propose a detection performance metric in terms of the atmosphere (DPMA) for intuitively examining the long-range propagation characteristics of airborne radars in air-to-air situations. To confirm the feasibility of using the DPMA map in various duct scenarios, we employ two actual refractive indices to observe the DPMA results in relation to the height of the airborne radar.

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Drob, D. P., D. Broutman, M. A. Hedlin, N. W. Winslow e R. G. Gibson. "A method for specifying atmospheric gravity wavefields for long-range infrasound propagation calculations". Journal of Geophysical Research: Atmospheres 118, n. 10 (20 maggio 2013): 3933–43. http://dx.doi.org/10.1029/2012jd018077.

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Rajendran, K., e A. Kitoh. "Modulation of Tropical Intraseasonal Oscillations by Ocean–Atmosphere Coupling". Journal of Climate 19, n. 3 (1 febbraio 2006): 366–91. http://dx.doi.org/10.1175/jcli3638.1.

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Abstract The impact of ocean–atmosphere coupling on the structure and propagation characteristics of 30–60-day tropical intraseasonal oscillations (TISOs) is investigated by analyzing long-term simulations of the Meteorological Research Institute coupled general circulation model (CGCM) and its stand-alone atmospheric general circulation model (AGCM) version forced with SSTs derived from the CGCM and comparing them with recent observation datasets [Global Precipitation Climatology Project (GPCP) precipitation, 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40), and Reynolds SST]. Composite events of (i) eastward propagating Madden–Julian oscillations (MJOs) during boreal winter and (ii) northward propagating intraseasonal oscillations (NPISOs) during boreal summer, constructed based on objective criteria, show that the three-dimensional structure, amplitude, and speed of propagation, and the phase relationship among surface fluxes, SST, and convection, are markedly improved in the CGCM simulation. Consistent with the frictional wave conditional instability of the second kind mechanism, successive development of low-level convergence to the east (north) of deep convection was found to be important for eastward (northward) propagation of MJO (NPISO). Complex interaction between large-scale dynamics and convection reveals the importance of atmospheric dynamics and suggests that they are intrinsic modes in the atmosphere where coupling is not essential for their existence. However, as in observations, realistic coupling in the CGCM is found to result in the evolution of TISOs as coupled modes through a coherent coupled feedback process. This acts as an amplifying mechanism for the existing propagating convective anomalies and plays an important modifying role toward a more realistic simulation of TISOs. In contrast, the simulated TISOs in its atmosphere-alone component lack many of the important features associated with their amplitude, phase, and life cycle. Thus, a realistic representation of the interaction between sea surface and the atmospheric boundary layer is crucial for a better simulation of TISOs.

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Tahira, Makoto. "A Study of the Long Range Propagation of Infrasonic Waves in the Atmosphere". Journal of the Meteorological Society of Japan. Ser. II 66, n. 1 (1988): 17–26. http://dx.doi.org/10.2151/jmsj1965.66.1_17.

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Hussain, Hammad, e Guillaume Dutilleux. "A parametric study of long-range atmospheric sound propagation using Bellhop Ray-tracing Model". Journal of the Acoustical Society of America 148, n. 4 (ottobre 2020): 2562. http://dx.doi.org/10.1121/1.5147110.

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Waxler, Roger, Claus H. Hetzer, Jelle D. Assink e Philip Blom. "A two-dimensional effective sound speed parabolic equation model for infrasound propagation with ground topography". Journal of the Acoustical Society of America 152, n. 6 (dicembre 2022): 3659–69. http://dx.doi.org/10.1121/10.0016558.

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A terrain capable parabolic equation (PE) propagation algorithm for long range infrasound propagation modeling has been implemented using Padé approximations for the various operator valued functions that arise in PE algorithms. In this work, the influence of the winds are captured by the effective sound speed approximation and propagation is restricted to the range-altitude plane. The ground topography is included by the addition of an impenetrable fluid below the ground surface. The impedance condition at the ground is handled explicitly, including both vertical and radial components. It is found that including terrain can have a large influence on long range propagation. In particular, reflections from a sufficiently steep slope can change the inclination angle enough to move the propagation path from one atmospheric duct to another.

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Più fonti

Tesi sul tema "Atmospheric long-range propagation"

Moloney, Jerome V., Kolja Schuh, Paris Panagiotopoulos, M. Kolesik e S. W. Koch. "Long range robust multi-terawatt MWIR and LWIR atmospheric light bullets". SPIE-INT SOC OPTICAL ENGINEERING, 2017. http://hdl.handle.net/10150/626498.

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There is a strong push worldwide to develop multi-Joule femtosecond duration laser pulses at wavelengths around 3.5-4 and 9-11 mu m within important atmospheric transmission windows. We have shown that pulses with a 4 mu m central wavelength are capable of delivering multi-TW powers at km range. This is in stark contrast to pulses at near-IR wavelengths which break up into hundreds of filaments with each carrying around 5 GW of power per filament over meter distances. We will show that nonlinear envelope propagators fail to capture the true physics. Instead a new optical carrier shock singularity emerges that can act to limit peak intensities below the ionization threshold leading to low loss long range propagation. At LWIR wavelengths many-body correlations of weakly-ionized electrons further suppress the Kerr focusing nonlinearity around 10 mu m and enable whole beam self-trapping without filaments.

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Bonnafont, Thomas. "Modélisation de la propagation atmosphérique d'ondes électromagnétiques sur de longues distances en 3D à partir de la transformée en ondelettes". Electronic Thesis or Diss., Toulouse 3, 2020. http://www.theses.fr/2020TOU30173.

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La propagation troposphèrique des ondes électromagnétiques sur de longues distances est un sujet important pour de nombreuses applications. L'objectif de cette thèse est de développer une méthode rapide et précise pour la propagation dans des domaines 3D. Celle-ci devra être efficace en taille mémoire. Dans le but d'atteindre cet objectif, trois contributions majeures ont été obtenues. Une méthode locale de propagation basée sur les ondelettes a été introduite en 2D. Une borne pour l'erreur de compression de cette méthode a été démontrée. Enfin, la méthode locale a été étendue à la 3D. La méthode split-step Fourier est très utilisée dans le contexte de la propagation sur de longues distances. Cependant, dans le cas de la 3D elle n'est pas très efficace en taille mémoire et temps de calcul. Une méthode basée sur les ondelettes en 2D, matrix split-step wavelet (mSSW), a été introduite pour réduire le temps de calcul. En effet à l'aide de la transformée rapide en ondelettes et de la compression, la méthode est très efficace en temps de calcul. La compression introduit une erreur qui s'accumule pendant la propagation. C'est pourquoi nous avons proposé une formule qui permet de choisir les seuils de compression pour une erreur donnée. La taille mémoire est un problème majeur pour le passage à la 3D de mSSW. Une méthode locale SSW (lSSW) a été développée pour la réduire. Dans celle-ci, seule l'information essentielle à la propagation est stockée réduisant l'occupation mémoire au minimum. Des tests numériques ont montré que cette méthode est plus efficace que mSSW en taille mémoire. Cette méthode a donc été étendue à la 3D. Des tests numériques dans des cas canoniques ont montré l'efficacité de cette méthode. Le problème de la propagation au dessus d'île en 3D a été étudié. Nous avons montré que dans ce cas la discrete-mixed Fourier transform, largement utilisée pour les sols impédants, n'est pas valide dans ce cas
The tropospheric long-range propagation of electromagnetic waves is a topic of major concern in many applications. The objective of this Ph.D. thesis is to develop a method to model the propagation in a realistic 3D domain. This method should be fast, accurate, and low in memory occupation. Three main milestones toward this objective are achieved. First, a 2D wavelet-based method has been improved. Second, a theoretical bound for the accuracy has been proposed. Lastly, a wavelet-based 3D propagation method has been developped.In the context of long-range propagation, the split-step Fourier method is widely used. For large domain propagation and 3D, the time and memory occupation become a major issue. Therefore, a matrix split-step wavelet (mSSW) method has been developed. Using compression and the fast wavelet transform, this method is fast. Compression is used to increase the efficiency of the method, but it introduces an accumulation of error throughout the propagation. We propose a formula for setting the compression thresholds in order to obtain a chosen accuracy in a given domain. Numerical tests have shown that the memory size of the propagator becomes an issue for large domains. Using wavelet properties, a local method of SSW (lSSW) has been proposed to reduce this requirement while keeping the computation time low. It is based on the computation of a minimal set of wavelet propagations, for which only the essential information is stored. Numerical tests have shown that this method is lower than mSSW in terms of memory occupation. Using the 2D wavelet representation, a 3D lSSW method has been proposed. Numerical tests have been performed to show validate the method on canonical scenarios. Finally, propagation over islands has been studied. We have shown that the discrete mixed Fourier transform, widely used in case of impedance ground, is not valid in this case

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Libri sul tema "Atmospheric long-range propagation"

van den Dool, Huug. Empirical Methods in Short-Term Climate Prediction. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780199202782.001.0001.

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This clear and accessible text describes the methods underlying short-term climate prediction at time scales of 2 weeks to a year. Although a difficult range to forecast accurately, there have been several important advances in the last ten years, most notably in understanding ocean-atmosphere interaction (El Nino for example), the release of global coverage data sets, and in prediction methods themselves. With an emphasis on the empirical approach, the text covers in detail empirical wave propagation, teleconnections, empirical orthogonal functions, and constructed analogue. It also provides a detailed description of nearly all methods used operationally in long-lead seasonal forecasts, with new examples and illustrations. The challenges of making a real time forecast are discussed, including protocol, format, and perceptions about users. Based where possible on global data sets, illustrations are not limited to the Northern Hemisphere, but include several examples from the Southern Hemisphere.

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Capitoli di libri sul tema "Atmospheric long-range propagation"

van den Dool, Huug. "Empirical Wave Propagation". In Empirical Methods in Short-Term Climate Prediction. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780199202782.003.0010.

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The purpose of this chapter is to demonstrate that, given a long data set of global extent, one can design a simple forecast method called Empirical Wave Propagation (EWP), which has modest forecast skill and allows us to explore aspects of atmospheric dynamics empirically, most notably aspects that help to explain mechanisms of teleconnection. The highlight of this chapter are dispersion experiments where we ask the question what happens to an isolated source at t = 0? Even though Nature has never done such an experiment, we will address this question empirically. In case the reader does not need/want to know the technical details of deriving wavespeeds he/she can skip to page 22 (EWP diagnostics sct 3.2) of this chapter. We will also discuss the skill of one-day EWP forecasts, in comparison to skill controls like “persistence”, as a function of season, hemisphere, level and variable. While short-range (1 day) forecasts are certainly not the topic of this book, we note that the short-term wave propagation features described here do nourish and maintain the teleconnection patterns thought to be important for longer range forecasts. EWP uses either zonal harmonic waves (sin/cos pairs) along each latitude circle separately, or global domain spherical harmonics (see Parkinson and Washington (1986) for the basics on spherical harmonics). The orthogonal functions used here are thus analytical. The atmosphere is to first order rotation-symmetric and obviously periodic in the east–west direction, which makes the zonal Fourier transform a natural. Moreover, many weather systems, wave-like in the upper levels, are seen to move from west to east (east to west) in the mid-latitudes (tropics), so a decomposition in sin/ cos functions should inform us about phase propagation and energy dispersion on the sphere. For any initial time we decompose the state of the atmosphere into harmonic waves. If we knew the wave speed, and made an assumption about the future amplitude, we could make forecasts by analytical means. But how do we know the phase speed? One way to proceed, with data alone, is to calculate from a large data set the climatological speeds of anomaly waves. This is where the empirical aspects come in.

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López-De-Castro, Marcos, Andrea Trucchia, Umberto Morra di Cella, Paolo Fiorucci, Antonio Cardillo e Gianni Pagnini. "Fire-spotting modelling: A comparative study of an Italian test case". In Advances in Forest Fire Research 2022, 593–601. Imprensa da Universidade de Coimbra, 2022. http://dx.doi.org/10.14195/978-989-26-2298-9_91.

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Wildfire propagation is a non-linear and multiscale system in which there are involved multiple physical and chemical processes. One critical mechanism in the spread of wildfires is the so-called fire-spotting: a random phenomenon which occurs when embers are transported over large distances by the wind, causing the start of new spotting ignitions which jeopardize fire fighting actions. Due to its nature, fire-spotting is usually modeled as a probabilistic process. Three principal processes are involved during the fire-spotting: firebrands generation, transport and landing, and spot ignition. In this work, the physical parametrization of fire-spotting RandomFront (Trucchia et al. 2019) has been implemented into the operational wildfire spread simulator PROPAGATOR (Trucchia et al. 2020), that is based on a cellular automata approach. In the RandomFront parametrization the downwind landing distribution of firebrands is modeled by the means of a lognormal distribution, which is parameterized taking into account the physics involved in the phenomenon. The considered physical parameters are wind field, fire-line intensity, fuel density, firebrand radius, maximum loftable height, as well as factors related to atmospheric stability and flame geometry (Trucchia et al. 2019; Egorova et al. 2020,2022). We have reproduced the evolution of a wildfire occured in Italy, in which the fire-spotting effects played a critical role in its spread, to test how RandomFront is able to reproduce it accurately. In addition, we have already implemented some established fire-spotting empirical parametrizations for cellular automata-based wildfire models to compare also the performance between the three firebrand landings models. The results show that the RandomFront parametrization on the one hand reproduces the main spotting effects given by the available literature parametrizations (Alexandridis et al. 2011; Perryman et al. 2013), while, on the other hand, generates a variety of fire-spotting situations as well as long range fluctuations of the burning probability. The physical parametrization allows for complex patterns of fire spreading in this operational simulator context.

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Frangieh, Nicolas, Gilbert Accary, Jean-Louis Rossi, Dominique Morvan, François-Joseph Chatelon, Thierry Marcelli, Sofiane Meradji et al. "Fuelbreaks design: from CFD modelling to operational tools". In Advances in Forest Fire Research 2022, 222–26. Imprensa da Universidade de Coimbra, 2022. http://dx.doi.org/10.14195/978-989-26-2298-9_36.

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Dimensioning a fuelbreak remains always a challenging problem. For a long time, this problem was tackled using an empirical approach from the experience of operational users such as the fire fighters and the foresters. During the last decades, new approaches coming from fire safety engineering have completed the set of tools adapted to study this problem. These tools are all based on physical considerations, more or- less sophisticated. The simplest ones, consist in assimilating the flame as a radiant panel, calculating the distribution of radiant heat flux as a function of the distance separating the flame to a potential target and defining at what distance this heat flux reached a critical threshold level susceptible to produce damages on this target (pain for people or ignition for materials). The most complex ones, consist in solving the conservation equations (mass, momentum, energy ...) governing the behaviour of complex coupled problem formed by the vegetation, the flame front and the surrounding atmosphere. This new generation of engineering tool, based on CFD approach allows to directly predict the behaviour of a fire front propagating toward a fuelbreak, in order to evaluate its efficiency as a function of the amount of surface fuel (grass, shrubs) removed to reduce locally the fuel load and therefore the intensity of an incoming fire. These two approaches are fully complementary, only the first one has the potentiality to be spread operationally on the field, whereas the second one can contribute to improve the first one and to study with more detail some very sensitive situations such as those encountered in the wildland urban interface (WUI). The main part of this study concerns numerical simulations of the propagation of a fire front through a homogeneous vegetation layer (a grassland) in the vicinity of a fuelbreak represented by a band more or less wide inside which all the fuel was removed. The simulations were performed using a fully physical wildfire model (FIRESTAR3D), three variable parameters were considered in this study: the 1m open wind speed (U1 ranged between 3 and 10 m/s), the fuel height (HFuel ranged between 0.25 and 1m) and the fuelbreak width (LFB). With these conditions, the simulations covered a large range of values of the Byramâ€™s convective number NC (0.3 < NC < 60) in order to explore wind as well driven fires (NC < 2) and plume dominated fires (NC > 10). The 72 simulations carried out in this study have been classified in three categories: 1/ Propagation (if the fire has crossed the fuelbreak with a propagation after); 2/ Overshooting or Marginal (if the fire has crossed the fuelbreak without a propagation after); 3/ No-propagation (if the fuelbreak has stopped the fire). The main objective of this study was to determine the optimal fuelbreak width LFBx separating between the Propagation and the No-propagation regimes, in order to generalize the conclusion, the results have been presented in dimensionless form (similitude theory) in representing as an example the ratio LFBx/HFuel versus the Byramâ€™s convective number NC.

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Atti di convegni sul tema "Atmospheric long-range propagation"

Chatterjee, Monish R., e Ali A. Mohamed. "Mitigation of image intensity distortion using chaos-modulated image propagation through gamma-gamma atmospheric turbulence". In Long-Range Imaging III, a cura di Eric J. Kelmelis. SPIE, 2018. http://dx.doi.org/10.1117/12.2306482.

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Hussain, Hammad, e Guillaume Dutilleux. "A parametric study of long-range atmospheric sound propagation using underwater acoustics software". In 18th International Symposium on Long Range Sound Propagation. ASA, 2020. http://dx.doi.org/10.1121/2.0001321.

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Gainville, Olaf, Pierre-Franck Piserchia, Philippe Blanc-Benon e Julian Scott. "Ray Tracing for Long Range Atmospheric Propagation of Infrasound". In 12th AIAA/CEAS Aeroacoustics Conference (27th AIAA Aeroacoustics Conference). Reston, Virigina: American Institute of Aeronautics and Astronautics, 2006. http://dx.doi.org/10.2514/6.2006-2451.

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PRUSZYNSKI, C. "Atmospheric propagation losses for long-range airborne radar systemsanalysis". In 23rd Aerospace Sciences Meeting. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1985. http://dx.doi.org/10.2514/6.1985-267.

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Vanleer, Ann, e Christopher R. Anderson. "Characterization of Atmospheric Variability on Long Range 3.4 GHz Propagation". In 2023 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM). IEEE, 2023. http://dx.doi.org/10.23919/usnc-ursinrsm57470.2023.10043171.

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Bertin, Michaël, Christophe Millet, Daniel Bouche e Jean-Christophe Robinet. "The Role of Atmospheric Uncertainties on Long Range Propagation of Infrasounds". In 42nd AIAA Fluid Dynamics Conference and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2012. http://dx.doi.org/10.2514/6.2012-3346.

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Sivan, Yonatan, Gadi Fibich, Shmuel Eisenmann, Einat Louzon, Yiftach Katzir e Arie Zigler. "Control of the filamentation distance and pattern in long range atmospheric propagation". In Nonlinear Photonics. Washington, D.C.: OSA, 2007. http://dx.doi.org/10.1364/np.2007.nwb2.

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Montmerle Bonnefois, A., R. Biérent, N. Védrenne, M. Lefebvre, V. Michau, M. T. Velluet, A. Godard, S. Derelle, A. Durécu e M. Raybaut. "SCALPEL: a long range free-space optical communication system with adaptive optics in the MIR bandwidth". In Optics in Atmospheric Propagation and Adaptive Systems. SPIE, 2010. http://dx.doi.org/10.1117/12.865022.

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Churnside, James H. "Remote Sensing of Refractive Turbulence with Optical Spatial Filters". In Laser and Optical Remote Sensing: Instrumentation and Techniques. Washington, D.C.: Optica Publishing Group, 1987. http://dx.doi.org/10.1364/lors.1987.tha2.

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If a point source of light is allowed to propagate some distance through atmospheric turbulence, it will generate a random pattern of irradiance containing a wide range of spatial scales. Similarly, if an extended light source is viewed through atmospheric turbulence by a point detector, the irradiance at the detector will vary as if the extended source was a random pattern containing a wide range of spatial scales. These phenomena can be analyzed by assuming that light scattered by each scale size of refractive fluctuations in the atmosphere at each position along the propagation path reaches the observation plane with no perturbations from refractive fluctuations at other scale sizes or path positions. This analysis will be valid as long as the path-integrated turbulence is low and saturation of scintillation can be neglected.

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Harris, M., G. N. Pearson, J. M. Vaughan, C. Karlsson, D. Letalick e I. Renhorn. "Eye-Safe Semiconductor Lasers for Lidar: Experimental Studies of Coherence and Atmospheric Propagation". In Coherent Laser Radar. Washington, D.C.: Optica Publishing Group, 1995. http://dx.doi.org/10.1364/clr.1995.thd5.

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Shorter-wavelength lasers (with λ of order 1.5-2.5 μm), both semiconductor and solid-state, are showing increasing promise for lidar applications, with improved power levels and frequency stability. Advantages over existing long-wavelength systems include: compactness and robustness, compatibility with cheap components and optical fibres from the telecommunications industry, and the lack of need for cooled detectors. It is thus becoming important to investigate the primary aspects of such lasers to establish their performance characteristics. The potential for semiconductor lasers in lidar/rangefinder systems is currently limited by their relatively low output power and short coherence length (or equivalently, their broad spectral bandwidth). This reduces the level of performance in range and velocity resolution, as well as leading to a degraded signal-to-noise ratio. In fact, the two considerations of power and linewidth are closely linked, because attempts to increase the output by turning up the laser drive current eventually lead to a significant increase in bandwidth. This "rebroadening" effect is poorly understood; it imposes a limit on the coherence performance of this type of laser, and hence also on its capabilities in laser radar applications. The work reported here could benefit understanding of the serious problem of rebroadening. Further limitations to the use of semiconductor lasers may result from the increased effects of atmospheric turbulence at these wavelengths.

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Rapporti di organizzazioni sul tema "Atmospheric long-range propagation"

Hart, Carl R., D. Keith Wilson, Chris L. Pettit e Edward T. Nykaza. Machine-Learning of Long-Range Sound Propagation Through Simulated Atmospheric Turbulence. U.S. Army Engineer Research and Development Center, luglio 2021. http://dx.doi.org/10.21079/11681/41182.

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Conventional numerical methods can capture the inherent variability of long-range outdoor sound propagation. However, computational memory and time requirements are high. In contrast, machine-learning models provide very fast predictions. This comes by learning from experimental observations or surrogate data. Yet, it is unknown what type of surrogate data is most suitable for machine-learning. This study used a Crank-Nicholson parabolic equation (CNPE) for generating the surrogate data. The CNPE input data were sampled by the Latin hypercube technique. Two separate datasets comprised 5000 samples of model input. The ﬁrst dataset consisted of transmission loss (TL) ﬁelds for single realizations of turbulence. The second dataset consisted of average TL ﬁelds for 64 realizations of turbulence. Three machine-learning algorithms were applied to each dataset, namely, ensemble decision trees, neural networks, and cluster-weighted models. Observational data come from a long-range (out to 8 km) sound propagation experiment. In comparison to the experimental observations, regression predictions have 5–7 dB in median absolute error. Surrogate data quality depends on an accurate characterization of refractive and scattering conditions. Predictions obtained through a single realization of turbulence agree better with the experimental observations.

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