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Pulkki, Ville, Symeon Delikaris-Manias et Archontis Politis, dir. Parametric Time-Frequency Domain Spatial Audio. Chichester, UK : John Wiley & Sons, Ltd, 2017. http://dx.doi.org/10.1002/9781119252634.
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Ozin, Linda. Age differences in the shape of spatial frequency filters. Ottawa : National Library of Canada, 1994.
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Simons, Rainee N. Spatial frequency multiplier with active linearly tapered slot antenna array. [Washington, DC : National Aeronautics and Space Administration, 1994.
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Zahar, Yadh. Eléments d'hydrologie pour l'aménagement : Modélisation spatiale et temporelle des précipitations extrêmes et érosives en Tunisie centrale. [Manouba] : Université des lettres, des arts et des sciences humaines, Tunis I, Faculté des lettres de la Manouba, 1997.
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Gold, Jason M. The role of spatial frequency information in the identification of complex visual patterns. Ottawa : National Library of Canada, 1996.
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Chabane, G. The detection of chromatic and achromatic patterns by mechanismsworking in the spatial frequency range. Manchester : UMIST, 1993.
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G, Schaefer Melvin, Washington (State). Dept. of Transportation., Washington State Transportation Commission. Planning and Programming Service Center., MGS Engineering Consultants Inc et Oregon Climate Service, dir. Regional precipitation-frequency analysis and spatial mapping of precipitation for 24-hour and 2-hour durations in western Washington. [Olympia, Wash.] : Washington State Dept. of Transportation, 2002.
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Safford, Hugh D. Using fire return interval departure (FRID) analysis to map spatial and temporal changes in fire frequency on national forest lands in California. Albany, CA] : United States Department of Agriculture, Forest Service, Pacific Southwest Research Station, 2014.
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1953-, Wilson Charles A., United States. Minerals Management Service. Gulf of Mexico OCS Region. et Coastal Marine Institute (Baton Rouge, La.), dir. Seasonal and spatial variation in the biomass and size frequency distribution of the fish associated with oil and gas platforms in the northern Gulf of Mexico. New Orleans, La : U.S. Dept. of the Interior, Minerals Management Service, Gulf of Mexico OCS Region, 2000.
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Stanley, David R. Seasonal and spatial variation in the biomass and size frequency distribution of the fish associated with oil and gas platforms in the northern Gulf of Mexico. New Orleans, La : U.S. Dept. of the Interior, Minerals Management Service, Gulf of Mexico OCS Region, 2000.
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McCourt, Mark E., et Barbara Blakeslee. Grating Induction. Oxford University Press, 2017. http://dx.doi.org/10.1093/acprof:oso/9780199794607.003.0055.
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Grating induction is a brightness/lightness illusion in which a sinewave luminance grating induces the appearance of a counterphase sinusoidal grating in a homogeneous test field oriented orthogonally to the inducing grating. Induction is greatest at low spatial and temporal frequencies and declines with increasing frequency in both dimensions. Induction magnitude also declines with increasing test field height and scales as the product of inducing grating spatial frequency (c/d) and test field height. These properties of grating induction are difficult to explain using nonfiltering-based models but are readily accounted for by multiscale spatial filtering and lend support to such models of brightness/lightness induction.
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Pulkki, Ville, Symeon Delikaris-Manias et Archontis Politis. Parametric Time-Frequency Domain Spatial Audio. Wiley-Interscience, 2017.
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Pulkki, Ville, Symeon Delikaris-Manias et Archontis Politis. Parametric Time-Frequency Domain Spatial Audio. Wiley & Sons, Limited, John, 2017.
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Pulkki, Ville, Symeon Delikaris-Manias et Archontis Politis. Parametric Time-Frequency Domain Spatial Audio. Wiley & Sons, Incorporated, John, 2017.
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Pulkki, Ville, Symeon Delikaris-Manias et Archontis Politis. Parametric Time-Frequency Domain Spatial Audio. Wiley & Sons, Incorporated, John, 2017.
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National Aeronautics and Space Administration (NASA) Staff. Local Spatial Frequency Analysis for Computer Vision. Independently Published, 2018.
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Kramer, Patricia Elaine. Summation and uncertainty effects in the detection of spatial frequency. 1985.
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Anstis, Stuart. Adaptation to Brightness Change, Contours, Jogging, and Apparent Motion. Oxford University Press, 2017. http://dx.doi.org/10.1093/acprof:oso/9780199794607.003.0108.
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Frisby and Stone have dubbed adaptation the “psychophysicist’s electrode” and John Mollon once famously said, “If it adapts, it’s there.” Psychologists piously hope that their many experiments on visual adaptation will tell physiologists where to look inside the brain. This chapter describes visual adaptation to temporal ramps, spatial edges, and apparent motion and touches on kinesthetic aftereffects from jogging. Sawtooth adaptation, a ramp aftereffect that is produced by gazing at a spatially uniform patch whose luminance is temporally modulated by a repetitive sawtooth, either gradually dimming and turning sharply back on (rapid-on) or gradually brightening and turning sharply back off (rapid-off), is discussed. Related concepts that are covered include pattern-specific contrast adaptation, contour adaptation, adaptation to apparent motion, and adapting to flicker, which changes apparent spatial frequency.
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Oliva, Aude, et Philippe G. Schyns. Hybrid Image Illusion. Oxford University Press, 2017. http://dx.doi.org/10.1093/acprof:oso/9780199794607.003.0111.
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Artists, designers, photographers, and visual scientists are routinely looking for ways to create, out of a single image, the feeling that there is more to see than what meets the eye. Many well-known visual illusions are dual in nature, causing the viewer to experience two different interpretations of the same image. Hybrid images illustrate a double-image illusion, where different images are perceived depending on viewing distance, viewing duration, or image size: one that appears when the image is viewed up-close (displaying high spatial frequencies) and another that appears from afar (showing low spatial frequencies). This method can be used to create compelling dual images in which the observer experiences different percepts when interacting with the image.
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Congendo, Marco, et Fernando H. Lopes da Silva. Event-Related Potentials. Sous la direction de Donald L. Schomer et Fernando H. Lopes da Silva. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780190228484.003.0039.
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Event-related potentials (ERPs) can be elicited by a variety of stimuli and events in diverse conditions. This chapter covers the methodology of analyzing and quantifying ERPs in general. Basic models (additive, phase modulation and resetting, potential asymmetry) that account for the generation of ERPs are discussed. The principles and requirements of ensemble time averaging are presented, along with several univariate and multivariate methods that have been proposed to improve the averaging procedure: wavelet decomposition and denoising, spatial, temporal and spatio-temporal filtering. We emphasize basic concepts of principal component analysis, common spatial pattern, and blind source separation, including independent component analysis. We cover practical questions related to the averaging procedure: overlapping ERPs, correcting inter-sweep latency and amplitude variability, alternative averaging methods (e.g., median), and estimation of ERP onset. Some specific aspects of ERP analysis in the frequency domain are surveyed, along with topographic analysis, statistical testing, and classification methods.
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Piepmeier, Karen Swanson. Determining readability by computer analysis using the Fourier transform to calculate the spatial frequencies of words. 1987.
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Walsh, Bruce, et Michael Lynch. Using Molecular Data to Detect Selection : Signatures from Recent Single Events. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198830870.003.0009.
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Different types and phases of a selective sweep (hard, soft, partial, polygenic) generate different patterns of departures from neutrality, and hence require different tests. It is thus not surprising that a large number of tests have been proposed that use sequence information to detect ongoing, or very-recently completed, episodes of selection. This chapter critically reviews over 50 such tests, which use information on allele-frequency change, linkage disequilibrium patterns, spatial allele-frequency patterns, site-frequency spectrum data, allele-frequency spectrum data, and haplotype structure. This chapter discusses the domain of applicability for each test, and their strengths and weaknesses. Finally, this chapter examines application of these methods in the search for recent, or ongoing, selection in humans and for genes involved in the domestication process in plants and animals.
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Blakeslee, Barbara, et Mark E. McCourt. The White Effect. Oxford University Press, 2017. http://dx.doi.org/10.1093/acprof:oso/9780199794607.003.0039.
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The White effect is an illusion in which gray test patches of identical luminance placed on the black and white bars of a square-wave grating appear different in brightness/lightness. The effect has received much attention because the direction of the brightness change does not correlate with the amount of black or white border in contact with the gray test patch or its general vicinity. The test patch on the black bar appears lighter than the test patch on the white bar despite changes in test patch height or inducing grating spatial frequency. In addition, although the test patch shows a smooth change in brightness/lightness as its spatial position is varied relative to the inducing grating, spatial inhomogeneities in brightness/lightness within the test patch are also visible. A large number of “higher-level” explanations have been offered for the White effect; only the oriented-difference-of-Gaussians model can account for all of these properties.
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Furst, Eric M., et Todd M. Squires. Interferometric tracking. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199655205.003.0006.
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The purpose of this chapter is to present a survey of passive microrheology techniques that are important complements to more widely used particle tracking and light scattering methods. Such methods include back focal plane interferometry and extensions of particle tracking to measure the rotation of colloidal particles. Methods of passive microrheology using back focal plane interferometry are presented, including the experimental design and detector sensitivity and limits in frequency bandwidth and spatial resolution. The Generalized Stokes Einstein relation is derived from linear response theory of the particle position power spectrum and complex susceptibility. Applications of interoferometric tracking include high frequency microrheology and two-point measurements. Lastly, the chapter includes a discussion of rotational passive microrheology and the rotational GSER.
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Billings, Stephen A. Nonlinear System Identification : NARMAX Methods in the Time, Frequency, and Spatio-Temporal Domains. Wiley, 2013.
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Billings, Stephen A. Nonlinear System Identification : NARMAX Methods in the Time, Frequency, and Spatio-Temporal Domains. Wiley & Sons, Incorporated, John, 2013.
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Billings, Stephen. Nonlinear System Identification : Narmax Methods in the Time, Frequency, and Spatio-Temporal Domains. Wiley & Sons, Incorporated, John, 2013.
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Billings, Stephen A. Nonlinear System Identification : NARMAX Methods in the Time, Frequency, and Spatio-Temporal Domains. Wiley & Sons, Incorporated, John, 2013.
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Billings, Stephen. Nonlinear System Identification : NARMAX Methods in the Time, Frequency, and Spatio-Temporal Domains. Wiley & Sons, Limited, John, 2013.
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Billings, Stephen A. Nonlinear System Identification : NARMAX Methods in the Time, Frequency, and Spatio-Temporal Domains. Wiley & Sons, Incorporated, John, 2013.
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Chubb, Charles, Joshua A. Solomon et George Sperling. The Contrast Contrast Illusion. Oxford University Press, 2017. http://dx.doi.org/10.1093/acprof:oso/9780199794607.003.0041.
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To most observers, a patch of medium-contrast texture viewed against a background of high-contrast texture appears lower in contrast than an identical patch viewed against a homogeneous, mean gray background. This is the contrast contrast illusion. This chapter reviews basic findings concerning this illusion; for example, the contrast contrast illusion is selective for texture spatial frequency as well as for texture contrast polarity. Several theories to account for the illusion are discussed. Related concepts such as texture contrast, textual granularity, individual differences, contrast polarity, color and the contrast contrast illusion, and ecological accounts of the contrast contrast illusion are explored.
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Fermüller, Cornelia. Motion Illusions in Man and Machine. Oxford University Press, 2017. http://dx.doi.org/10.1093/acprof:oso/9780199794607.003.0006.
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At the level of mathematical abstraction, computing image motion amounts to an estimation problem and can be analyzed using the tools of statistics and signal processing. As shown in this chapter, intrinsic limitations to the estimation processes make it impossible to derive veridical estimates for all images. Image motion is estimated erroneously, and as a result higher level processes compute erroneous three-dimensional motion and moving scenes. Specifically, two limitations are discussed: (a) due to noise in image data, there is statistical bias that affects anisotropic patterns and (2) the filters computing changes in time are asymmetric (causal), using data only from the past but not the future, and misestimate on locally asymmetric intensity signals of certain spatial frequencies. Since these limitations are not an artifact of the hardware but are inherent to the computations, they will affect any system and thus create illusions in man and machine.
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Michel, Christoph M., et Bin He. EEG Mapping and Source Imaging. Sous la direction de Donald L. Schomer et Fernando H. Lopes da Silva. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780190228484.003.0045.
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This chapter describes methods to analyze the scalp electric field recorded with multichannel electroencephalography (EEG). With advances in high-density EEG, systems now allow fast and easy recording from 64 to 256 channels simultaneously. Pattern-recognition algorithms can characterize the topography of scalp electric fields and detect changes in topography over time and between experimental or clinical conditions. Methods for estimating the sources underlying the recorded scalp potential maps have increased the spatial resolution of EEG. The use of anatomical information in EEG source reconstruction has increased the precision of EEG source localization. Algorithms of functional connectivity applied to the source space allow determination of communication between large-scale brain networks in certain frequencies and identification of the directionality of this information flow and detection of crucial drivers in these networks. These methods have boosted the use of EEG as a functional neuroimaging method in experimental and clinical applications.
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Schomer, Donald L., Charles M. Epstein, Susan T. Herman, Douglas Maus et Bruce J. Fisch. Recording Principles. Sous la direction de Donald L. Schomer et Fernando H. Lopes da Silva. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780190228484.003.0005.
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This chapter reviews the technical aspects of recording and reviewing clinical electroencephalograms (EEGs) and related biopotentials. While advances in engineering technology have revolutionized EEG machines, the basic principles underlying accurate representation of brain activity are largely unchanged. The first section reviews the analog EEG components, and the second section discusses analog-to-digital conversion, digital filters, and display and storage parameters. Digital EEG machines are now less expensive and their capabilities far surpass those of analog machines. The third section reviews how electrode positions and systems of signal display (montages) can be used to determine the polarity and field of EEG signals. The final section describes how other biopotentials are acquired and displayed. Polygraphy can provide crucial information on other physiological processes that can impact EEG activity and can help identify potential artifactual signals. We highlight recent advances that allow the recording of a broader range of EEG frequencies and spatial distribution.
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Brophy, Philip. Parties in Your Head. Sous la direction de John Richardson, Claudia Gorbman et Carol Vernallis. Oxford University Press, 2013. http://dx.doi.org/10.1093/oxfordhb/9780199733866.013.0021.
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This article appears in theOxford Handbook of New Audiovisual Aestheticsedited by John Richardson, Claudia Gorbman, and Carol Vernallis. The sound of nightclubs and club music has transformed spatial scale, frequency range, and volume levels in film soundtracks for the past twenty-five years. Across this period, spatialization is intensified, the soundtrack gets noiser, and characterization favors unbalanced psychological states. Consequently, an aural “Other” becomes progressively encoded and registered. The texture of recorded sound on film becomes affected by non-cinematic aurality, responding to approaches to microphone placement in pop music, and the role that psycho-acoustics play in shaping psychological drama. Discussion ensues to audit the noise inside the addled heads of characters in a selection of films which exemplify this transformative audiovision in cinema:Scorpio Rising, Vinyl, Scarface, Blue Velvet, La Vie Nouvelle, andIrréversible.
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Seasonal and spatial variation in the biomass and size frequency distribution of the fish associated with oil and gas platforms in the northern Gulf of Mexico. New Orleans, La : U.S. Dept. of the Interior, Minerals Management Service, Gulf of Mexico OCS Region, 2000.
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Ślusarski, Marek. Metody i modele oceny jakości danych przestrzennych. Publishing House of the University of Agriculture in Krakow, 2017. http://dx.doi.org/10.15576/978-83-66602-30-4.
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The quality of data collected in official spatial databases is crucial in making strategic decisions as well as in the implementation of planning and design works. Awareness of the level of the quality of these data is also important for individual users of official spatial data. The author presents methods and models of description and evaluation of the quality of spatial data collected in public registers. Data describing the space in the highest degree of detail, which are collected in three databases: land and buildings registry (EGiB), geodetic registry of the land infrastructure network (GESUT) and in database of topographic objects (BDOT500) were analyzed. The results of the research concerned selected aspects of activities in terms of the spatial data quality. These activities include: the assessment of the accuracy of data collected in official spatial databases; determination of the uncertainty of the area of registry parcels, analysis of the risk of damage to the underground infrastructure network due to the quality of spatial data, construction of the quality model of data collected in official databases and visualization of the phenomenon of uncertainty in spatial data. The evaluation of the accuracy of data collected in official, large-scale spatial databases was based on a representative sample of data. The test sample was a set of deviations of coordinates with three variables dX, dY and Dl – deviations from the X and Y coordinates and the length of the point offset vector of the test sample in relation to its position recognized as a faultless. The compatibility of empirical data accuracy distributions with models (theoretical distributions of random variables) was investigated and also the accuracy of the spatial data has been assessed by means of the methods resistant to the outliers. In the process of determination of the accuracy of spatial data collected in public registers, the author’s solution was used – resistant method of the relative frequency. Weight functions, which modify (to varying degree) the sizes of the vectors Dl – the lengths of the points offset vector of the test sample in relation to their position recognized as a faultless were proposed. From the scope of the uncertainty of estimation of the area of registry parcels the impact of the errors of the geodetic network points was determined (points of reference and of the higher class networks) and the effect of the correlation between the coordinates of the same point on the accuracy of the determined plot area. The scope of the correction was determined (in EGiB database) of the plots area, calculated on the basis of re-measurements, performed using equivalent techniques (in terms of accuracy). The analysis of the risk of damage to the underground infrastructure network due to the low quality of spatial data is another research topic presented in the paper. Three main factors have been identified that influence the value of this risk: incompleteness of spatial data sets and insufficient accuracy of determination of the horizontal and vertical position of underground infrastructure. A method for estimation of the project risk has been developed (quantitative and qualitative) and the author’s risk estimation technique, based on the idea of fuzzy logic was proposed. Maps (2D and 3D) of the risk of damage to the underground infrastructure network were developed in the form of large-scale thematic maps, presenting the design risk in qualitative and quantitative form. The data quality model is a set of rules used to describe the quality of these data sets. The model that has been proposed defines a standardized approach for assessing and reporting the quality of EGiB, GESUT and BDOT500 spatial data bases. Quantitative and qualitative rules (automatic, office and field) of data sets control were defined. The minimum sample size and the number of eligible nonconformities in random samples were determined. The data quality elements were described using the following descriptors: range, measure, result, and type and unit of value. Data quality studies were performed according to the users needs. The values of impact weights were determined by the hierarchical analytical process method (AHP). The harmonization of conceptual models of EGiB, GESUT and BDOT500 databases with BDOT10k database was analysed too. It was found that the downloading and supplying of the information in BDOT10k creation and update processes from the analyzed registers are limited. An effective approach to providing spatial data sets users with information concerning data uncertainty are cartographic visualization techniques. Based on the author’s own experience and research works on the quality of official spatial database data examination, the set of methods for visualization of the uncertainty of data bases EGiB, GESUT and BDOT500 was defined. This set includes visualization techniques designed to present three types of uncertainty: location, attribute values and time. Uncertainty of the position was defined (for surface, line, and point objects) using several (three to five) visual variables. Uncertainty of attribute values and time uncertainty, describing (for example) completeness or timeliness of sets, are presented by means of three graphical variables. The research problems presented in the paper are of cognitive and application importance. They indicate on the possibility of effective evaluation of the quality of spatial data collected in public registers and may be an important element of the expert system.
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Isett, Philip. Hölder Continuous Euler Flows in Three Dimensions with Compact Support in Time. Princeton University Press, 2017. http://dx.doi.org/10.23943/princeton/9780691174822.001.0001.
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Motivated by the theory of turbulence in fluids, the physicist and chemist Lars Onsager conjectured in 1949 that weak solutions to the incompressible Euler equations might fail to conserve energy if their spatial regularity was below 1/3-Hölder. This book uses the method of convex integration to achieve the best-known results regarding nonuniqueness of solutions and Onsager's conjecture. Focusing on the intuition behind the method, the ideas introduced now play a pivotal role in the ongoing study of weak solutions to fluid dynamics equations. The construction itself—an intricate algorithm with hidden symmetries—mixes together transport equations, algebra, the method of nonstationary phase, underdetermined partial differential equations (PDEs), and specially designed high-frequency waves built using nonlinear phase functions. The powerful “Main Lemma”—used here to construct nonzero solutions with compact support in time and to prove nonuniqueness of solutions to the initial value problem—has been extended to a broad range of applications that are surveyed in the appendix. Appropriate for students and researchers studying nonlinear PDEs, this book aims to be as robust as possible and pinpoints the main difficulties that presently stand in the way of a full solution to Onsager's conjecture.
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Malawey, Victoria. A Blaze of Light in Every Word. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780190052201.001.0001.
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A Blaze of Light in Every Word presents a conceptual model for analyzing vocal delivery in popular song recordings focused on three overlapping areas of inquiry: pitch, prosody, and quality. The domain of pitch, which refers to listeners’ perceptions of frequency, considers range, tessitura, intonation, and registration. Prosody, the pacing and flow of delivery, comprises phrasing, metric placement, motility, embellishment, and consonantal articulation. Qualitative elements include timbre, phonation, onset, resonance, clarity, paralinguistic effects, and loudness. Intersecting all three domains is the area of technological mediation, which considers how external technologies, such as layering, overdubbing, pitch modification, recording transmission, compression, reverb, spatial placement, delay, and other electronic effects, impact voice in recorded music. Though the book focuses primarily on the sonic and material aspects of vocal delivery, it situates these aspects among broader cultural, philosophical, and anthropological approaches to voice with the goal to better understand the relationship between sonic content and its signification. Drawing upon transcription and spectrographic analysis as the primary means of representation, as well as modes of analysis, this book features in-depth analyses of a wide array of popular song recordings spanning genres from indie rock to hip-hop to death metal, develops analytical tools for understanding how individual dimensions make singing voices both complex and unique, and synthesizes how multiple aspects interact to better understand the multidimensionality of singing voices.
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Ramani, Ramachandran, dir. Functional MRI. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780190297763.001.0001.
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Functional MRI with BOLD (Blood Oxygen Level Dependent) imaging is one of the commonly used modalities for studying brain function in neuroscience. The underlying source of the BOLD fMRI signal is the variation in oxyhemoglobin to deoxyhemoglobin ratio at the site of neuronal activity in the brain. fMRI is mostly used to map out the location and intensity of brain activity that correlate with mental activities. In recent years, a new approach to fMRI was developed that is called resting-state fMRI. The fMRI signal from this method does not require the brain to perform any goal-directed task; it is acquired with the subject at rest. It was discovered that there are low-frequency fluctuations in the fMRI signal in the brain at rest. The signals originate from spatially distinct functionally related brain regions but exhibit coherent time-synchronous fluctuations. Several of the networks have been identified and are called resting-state networks. These networks represent the strength of the functional connectivity between distinct functionally related brain regions and have been used as imaging markers of various neurological and psychiatric diseases. Resting-state fMRI is also ideally suited for functional brain imaging in disorders of consciousness and in subjects under anesthesia. This book provides a review of the basic principles of fMRI (signal sources, acquisition methods, and data analysis) and its potential clinical applications.
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Bartkowicz, Leszek. Tekstura drzewostanów naturalnych w polskich parkach narodowych na tle teorii dynamiki lasu. Publishing House of the University of Agriculture in Krakow, 2021. http://dx.doi.org/10.15576/978-83-66602-20-5.
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The aim of the study was to compare a patch-mosaic pattern in the old-growth forest stands developed in various climate and soil conditions occurring in different regions of Poland. Based on the assumption, that the patch-mosaic pattern in the forest reflect the dynamic processes taking place in it, and that each type of forest ecosystem is characterized by a specific regime of natural disturbances, the following hypotheses were formulated: (i) the patches with a complex structure in stands composed of latesuccessional, shade-tolerant tree species are more common than those composed of early-successional, light-demanding ones, (ii) the patch-mosaic pattern is more heterogeneous in optimal forest site conditions than in extreme ones, (iii) in similar site conditions differentiation of the stand structure in distinguished patches is determined by the successional status of the tree species forming a given patch, (iv) the successional trends leading to changes of species composition foster diversification of the patch structure, (v) differentiation of the stand structure is negatively related to their local basal area, especially in patches with a high level of its accumulation. Among the best-preserved old-growth forest remaining under strict protection in the Polish national parks, nineteen research plots of around 10 ha each were selected. In each plot, a grid (50 × 50 m) of circular sample subplots (with radius 12,62 m) was established. In the sample subplots, species and diameter at breast height of living trees (dbh ≥ 7 cm) were determined. Subsequently, for each sample subplot, several numerical indices were calculated: local basal area (G), dbh structure differentiation index (STR), climax index (CL) and successional index (MS). Statistical tests of Kruskal- Wallis, Levene and Generalized Additive Models (GAM) were used to verify the hypotheses. All examined forests were characterized by a large diversity of stand structure. A particularly high frequency of highly differentiated patches (STR > 0,6) was recorded in the alder swamp forest. The patch mosaic in the examined plots was different – apart from the stands with a strongly pronounced mosaic character (especially subalpine spruce forests), there were also stands with high spatial homogeneity (mainly fir forests). The stand structure in the distinguished patches was generally poorly related to the other studied features. Consequently, all hypotheses were rejected. These results indicate a very complex, mixed pattern of forest natural dynamics regardless of site conditions. In beech forests and lowland multi-species deciduous forests, small-scale disturbances of the gap dynamics type dominate, which are overlapped with less frequent medium-scale disturbances. In more difficult site conditions, large-scale catastrophic disturbances, which occasionally appear in communities formed under the influence of gap dynamics (mainly spruce forests) or cohort dynamics (mainly pine forests), gain importance.
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Gao, Yanhong, et Deliang Chen. Modeling of Regional Climate over the Tibetan Plateau. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190228620.013.591.
Texte intégralRésumé :
The modeling of climate over the Tibetan Plateau (TP) started with the introduction of Global Climate Models (GCMs) in the 1950s. Since then, GCMs have been developed to simulate atmospheric dynamics and eventually the climate system. As the highest and widest international plateau, the strong orographic forcing caused by the TP and its impact on general circulation rather than regional climate was initially the focus. Later, with growing awareness of the incapability of GCMs to depict regional or local-scale atmospheric processes over the heterogeneous ground, coupled with the importance of this information for local decision-making, regional climate models (RCMs) were established in the 1970s. Dynamic and thermodynamic influences of the TP on the East and South Asia summer monsoon have since been widely investigated by model. Besides the heterogeneity in topography, impacts of land cover heterogeneity and change on regional climate were widely modeled through sensitivity experiments.In recent decades, the TP has experienced a greater warming than the global average and those for similar latitudes. GCMs project a global pattern where the wet gets wetter and the dry gets drier. The climate regime over the TP covers the extreme arid regions from the northwest to the semi-humid region in the southeast. The increased warming over the TP compared to the global average raises a number of questions. What are the regional dryness/wetness changes over the TP? What is the mechanism of the responses of regional changes to global warming? To answer these questions, several dynamical downscaling models (DDMs) using RCMs focusing on the TP have recently been conducted and high-resolution data sets generated. All DDM studies demonstrated that this process-based approach, despite its limitations, can improve understandings of the processes that lead to precipitation on the TP. Observation and global land data assimilation systems both present more wetting in the northwestern arid/semi-arid regions than the southeastern humid/semi-humid regions. The DDM was found to better capture the observed elevation dependent warming over the TP. In addition, the long-term high-resolution climate simulation was found to better capture the spatial pattern of precipitation and P-E (precipitation minus evapotranspiration) changes than the best available global reanalysis. This facilitates new and substantial findings regarding the role of dynamical, thermodynamics, and transient eddies in P-E changes reflected in observed changes in major river basins fed by runoff from the TP. The DDM was found to add value regarding snowfall retrieval, precipitation frequency, and orographic precipitation.Although these advantages in the DDM over the TP are evidenced, there are unavoidable facts to be aware of. Firstly, there are still many discrepancies that exist in the up-to-date models. Any uncertainty in the model’s physics or in the land information from remote sensing and the forcing could result in uncertainties in simulation results. Secondly, the question remains of what is the appropriate resolution for resolving the TP’s heterogeneity. Thirdly, it is a challenge to include human activities in the climate models, although this is deemed necessary for future earth science. All-embracing further efforts are expected to improve regional climate models over the TP.
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Szewczyk, Janusz. Rola zaburzeń w kształtowaniu struktury i dynamiki naturalnych lasów bukowo-jodłowo-świerkowych w Karpatach Zachodnich. Publishing House of the University of Agriculture in Krakow, 2018. http://dx.doi.org/10.15576/978-83-66602-35-9.
Texte intégralRésumé :
The aim of the study was to determine the influence of different disturbances (both natural and anthropogenic) on species composition and stand structure of old-growth mixed mountain forests in the Western Carpathians. These stands are usually dominated by beech, fir and spruce, mixed in different proportions. The tree main species represent different growth strategies, and they compete against each other. The longevity of trees makes the factors influencing the stand structure difficult to identify, even during longitudinal studies conducted on permanent research plots. That is why dendroecological techniques, based upon the annual variability of tree rings, are commonly used to analyze the disturbance histories of old-growth stands. Dendroecological methods make it possible to reconstruct the stand history over several centuries in the past by analyzing the frequency, intensity, duration and spatial scale of disturbances causing the death of trees. Combining the dendroecological techniques with the detailed measurements of stand structure, snag volume, CWD volume, and the analyses of regeneration species composition and structure allows us to identify the factors responsible for the changes in dynamics of mixed mountain forests. Various disturbance agents affect some species selectively, while some disturbances promote the establishment of tree seedlings of specific species by modifying environmental conditions. Describing the disturbance regime requires a broad scope of data on stand structure, on dead wood and tree regeneration, while various factors affecting all the stages of tree growth should be taken into consideration. On the basis of the already published data from permanent sample plots, combined with the available disturbance history analyses from the Western Carpathians, three research hypotheses were formulated. 1. The species composition of mixed mountain forests has been changing for at least several decades. These directional changes are the consequence of simultaneous conifer species decline and expansion of beech. 2. The observed changes in species composition of mixed mountain forests are the effect of indirect anthropogenic influences, significantly changing tree growth conditions also in the forests that are usually considered natural or near-natural. Cumulative impact of these indirect influences leads to the decrease of fir share in the tree layer (spruce decline has also been observed recently),and it limits the representation of this species among seedlings and saplings. The final effect is the decrease of fir and spruce share in the forest stands. 3. Small disturbances, killing single trees or small groups of trees, and infrequent disturbances of medium size and intensity dominate the disturbance regime in mixed mountain forests. The present structure of beech-fir-spruce forests is shaped both by complex disturbance regime and indirect anthropogenic influences. The data were gathered in permanent sample plots in strictly protected areas of Babia Góra, Gorce, and Tatra National Parks, situated in the Western Carpathians. All plots were located in the old-growth forest stands representing Carpathian beech forest community. The results of the measurements of trees, snags, coarse woody debris (CWD) and tree regeneration were used for detailed description of changes in the species composition and structure of tree stands. Tree ring widths derived from increment cores were used to reconstruct the historical changes in tree growth trends of all main tree species, as well as the stand disturbance history within the past two to three hundred years. The analyses revealed complex disturbance history in all of the three forest stands. Intermediate disturbances of variable intensity occurred, frequently separated by the periods of low tree mortality lasting from several decades up to over one hundred years. The intervals between the disturbances were significantly shorter than the expected length of forest developmental cycle, in commonly used theories describing the dynamics of old-growth stands. During intermediate disturbances up to several dozen percent of canopy trees were killed. There were no signs of stand-replacing disturbances, killing all or nearly all of canopy trees. The periods of intense tree mortality were followed by subsequent periods of increased sapling recruitment. Variability in disturbance intensity is one of the mechanisms promoting the coexistence of beech and conifer species in mixed forests. The recruitment of conifer saplings depended on the presence of larger gaps, resulting from intermediate disturbances, while beech was more successful in the periods of low mortality. However, in the last few decades, beech seems to benefit from the period of intense fir mortality. This change results from the influence of long-term anthropogenic disturbances, affecting natural mechanisms that maintain the coexistence of different tree species and change natural disturbance regimes. Indirect anthropogenic influence on tree growth was clearly visible in the gradual decrease of fir increments in the twentieth century, resulting from the high level of air pollution in Europe. Synchronous decreases of fir tree rings’ widths were observed in all three of the sample plots, but the final outcomes depended on the fir age. In most cases, the damage to the foliage limited the competitive abilities of fir, but it did not cause a widespread increase in tree mortality, except for the oldest firs in the BGNP (Babia Góra National Park) plot. BGNP is located in the proximity of industrial agglomeration of Upper Silesia, and it could be exposed to higher level of air pollution than the other two plots. High level of fir regeneration browsing due to the deer overabundance and insufficient number of predators is the second clear indication of the indirect anthropogenic influence on mixed mountain forests. Game impact on fir regeneration is the most pronounced in Babia Góra forests, where fir was almost completely eliminated from the saplings. Deer browsing seems to be the main factor responsible for limiting the number of fir saplings and young fir trees, while the representation of fir among seedlings is high. The experiments conducted in fenced plots located in the mixed forests in BGNP proved that fir and sycamore were the most preferred by deer species among seedlings and saplings. In GNP (Gorce National Park) and TNP (Tatra National Park), the changes in species composition of tree regeneration are similar, but single firs or even small groups of firs are present among saplings. It seems that all of the analysed mixed beech-fir-spruce forests undergo directional changes, causing a systematic decrease in fir representation, and the expansion of beech. This tendency results from the indirect anthropogenic impact, past and present. Fir regeneration decline, alongside with the high level of spruce trees’ mortality in recent years, may lead to a significant decrease in conifers representation in the near future, and to the expansion of beech forests at the cost of mixed ones.