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Analysis of watersheds and river systems: short course
Get PDFShort course: Analysis of Watersheds and River Systems, Session I and II, held on May 28-June 1, 1979 and June 4-June 8, 1979 at Colorado State University, Fort Collins, Colorado.Speakers: Dr. E. V. Richardson, Dr. David Duttweiller, Mr. Lee Mulkey, Dr. Stanley A. Schumm, Dr. Daryl B. Simons, Dr. Ross Carder.Includes bibliographical references.This short course is designed for individuals dealing with the analysis of watersheds and rivers. Practical applications concerning physical processes will be emphasized.Chapter 1. General introduction / Daryl B. Simons and Ruh-Ming Li -- Chapter 2. Introduction to watershed and river analysis / Daryl B. Simons and Ruh-Ming Li -- Chapter 3. Physical processes governing response of watersheds and rivers / Daryl B. Simons, Timothy J. Ward and Ruh-Ming Li -- Chapter 4. Sediment transport / H. W. Shen -- Chapter 5. Alluvial bed roughness / H. W. Shen -- Chapter 6. Overview of flood routing methods / Ruh-Ming Li and V. Miguel Ponce -- Chapter 7. Water routing and yield from watersheds, Part I and II / Ruh-Ming Li, Daryl B. Simons, and Kenneth G. Eggert -- Chapter 8. Water routing in rivers / Yung-Hai Chen -- Chapter 9. Stage discharge relations / Robert K. Simons, Ruh-Ming Li, and Daryl B. Simons -- Chapter 10. Watershed sediment yield / Ruh-Ming Li, Daryl B. Simons, and Timothy J. Ward -- Chapter 11. Unsteady sediment routing models in rivers / Yung-Hai Chen and Daryl B. Simons -- Chapter 12. Known discharge sediment routing / Glenn O. Brown and Ruh-Ming Li -- Chapter 13. Landslide potential delineation / Timothy J. Ward, Ruh-Ming Li, and Daryl B. Simons -- Chapter 14. Application of Kalman filtering in watershed and river analysis / Nguyen Duong -- Chapter 15. Handheld calculator programs for analysis / Kenneth G. Eggert, Ruh-Ming Li, and Daryl B. Simons -- Chapter 16. Overview of case studies and data management / Daryl B. Simons, Ruh-Ming Li, and Nguyen Duong -- Chapter 17. Canal and channel design and river response analysis / Daryl B. Simons, Ruh-Ming Li, and Yung-Hai Chen -- Chapter 18. Degradation and aggradation analysis / Ruh-Ming Li and Daryl B. Simons -- Chapter 19. Watershed best management analysis / Ruh-Ming Li, Timothy J. Ward, and Daryl B. Simons -- Chapter 20. Large river basin analysis: Yazoo River Sedimentation Study / Daryl B. Simons and Ruh-Ming Li
Mechanisms of top-down facilitation in perception of visual objects studied by fMRI
Get PDFPrior knowledge regarding the possible identity of an object facilitates its recognition from a degraded visual input, though the underlying mechanisms are unclear. Previous work implicated ventral visual cortex but did not disambiguate whether activity-changes in these regions are causal to or merely reflect an effect of facilitated recognition. We used functional magnetic resonance imaging to study top-down influences on processing of gradually revealed objects, by preceding each object with a name that was congruent or incongruent with the object. Congruently primed objects were recognized earlier than incongruently primed, and this was paralleled by shifts in activation profiles for ventral visual, parietal, and prefrontal cortices. Prior to recognition, defined on a trial-by-trial basis, activity in ventral visual cortex rose gradually but equivalently for congruently and incongruently primed objects. In contrast, prerecognition activity was greater with congruent priming in lateral parietal, retrosplenial, and lateral prefrontal cortices, whereas functional coupling between parietal and ventral visual (and also left lateral prefrontal and parietal) cortices was enhanced in the same context. Thus, when controlling for recognition point and stimulus information, activity in ventral visual cortex mirrors recognition success, independent of condition. Facilitation by top-down cues involves lateral parietal cortex interacting with ventral visual areas, potentially explaining why parietal lesions can lead to deficits in recognizing degraded objects even in the context of top-down knowledge
Two-loop Sudakov form factor in ABJM
No full textThis article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited
Underwater detection, classification and localisation: Improving the capabilities of towed sonar arrays
No full textThe end of the Cold War and the collapse of the Warsaw pact have resulted in a change of operational theatre for the naval forces of the North Atlantic Treaty Organisation (NATO). In particular, the focus of Anti Submarine Warfare forces has shifted from tracking Soviet nuclear ballistic missile submarine in the deep waters of the Atlantic ocean to hunting smaller and quieter Diesel electric submarines in coastal water. In most scenarios, towed array sonars are the best sensor to detect, classify and localise submarines. The long passive towed array sonars used during the Cold war are more difficult to use in coastal waters and are being replaced by most Navies by Low Frequency Active Sonars (LFAS) using a towed source and shorter towed receiving array. These shorter towed arrays can be used in both active and passive modes. In passive mode, their reduced size offer limited performance compared to their longer equivalent. In active mode, they can detect submarines at long ranges in shallow waters but are plagued by false alarms caused by echoes from features of the seafloor. This thesis deals with algorithms improving Detection, Classification and Localisation for towed sonar arrays, with a specific focus on LFAS sonars. In Chapter 2, we derive, analyse and apply to measured data a method for improving detection performance with short passive towed arrays. An important issue in detection of quiet acoustic source with short towed arrays is the improvement in signal-to-noise ratio (SNR) and bearing resolution for targets emitting low frequency signals. One of the techniques believed to improve these characteristics is Synthetic Aperture Sonar (SAS). The method is based on the artificial enlargement of a sonar array by coherently integrating acoustic snapshots at different antenna positions. We first derive theoretical measures of performance of passive SAS and report on its application in combination with other signal-processing algorithms. Its theoretical performance is compared with that of the frequently used incoherent integration. The used passive SAS algorithm is the method known as Extended Towed Array Measurement (ETAM) or the overlap correlator. It is based on the correlation of data snapshots on overlapping hydrophones. Correlation is a key issue in this method and since it is affected by noisy targets, some gain can be expected from noise cancellation. The influence on the performance of ETAM of a method of tow ship noise cancelling at hydrophone level (Inverse Beam Forming, IBF) is analysed. This approach increases ETAM performance by removing a loud and highly correlated noise source, the tow ship, and thus enhancing the other targets in the beam pattern. The results of the algorithms applied to two experimental datasets show that they bring an improvement close to theoretical expectations. Port starboard discrimination and the successful combination of IBF with ETAM make this approach innovative. In Chapter 3, methods for improving the localisation of a source with a short towed array are analysed and applied to data, both simulated and measured at sea. Localisation performance with sonar towed array is related to the array length. The knowledge of the position of a given acoustic source gives a critical tactical advantage to a ship. There are a limited number of ways to estimate the range of a source with a towed passive sonar, most requiring the towing platform to execute a manoeuvre. These manoeuvres are undesirable as they take a lot of time, cause bending of the towed array and can even put the towing platform in harm’s way. We present a number of source position estimation methods for both broadband and narrowband sources suitable for short towed arrays. Recursive methods based on the extended Kalman filter are first examined. A new method based on the integration of time delay of arrival measurements along the sonar path is described. We derive theoretical performance indicators and show that this method gives the possibility to estimate the position and speed of a source without a manoeuvre. In Chapter 4, the Classification performance of a broadband waveform is analysed and measured on data collected at sea. Like any long-range active sonar system, LFAS produces a large amount of unwanted sea bottom echoes or clutter. These echoes give rise to false alarms that increase the computational load of target trackers and jeopardise the correct classification of each echo. The number of false alarms due to clutter can be reduced either through echo classification techniques or through Doppler filtering provided the targets of interest are in motion. Much research has been carried out on waveform investigation for the efficient use of bandwidth capabilities of modern sonar transmitters. Among the quantity of waveforms, Binary Phase Shift Keyed (BPSK) pulses have emerged as exhibiting cross-correlation properties relevant to Doppler filtering while maintaining a range resolution comparable to Frequency Modulated (FM) pulses. We have successfully applied a false alarm reduction technique using contacts obtained with an FM pulse subsequently processed by Doppler filtering with a BPSK pulse. The Doppler classification performance for this pulse is evaluated on an experimental dataset and a few limitations of BPSK are identified.Aircraft Transport and OperationAerospace Engineerin
Neural basis for priming of pop-out during visual search revealed with fMRI
No full textMalikovic and Nakayama first showed that visual search efficiency can be influenced by priming effects. Even "pop-out" targets (defined by unique color) are judged quicker if they appear at the same location and/or in the same color as on the preceding trial, in an unpredictable sequence. Here, we studied the potential neural correlates of such priming in human visual search using functional magnetic resonance imaging (fMRI). We found that repeating either the location or the color of a singleton target led to repetition suppression of blood oxygen level-dependent (BOLD) activity in brain regions traditionally linked with attentional control, including bilateral intraparietal sulci. This indicates that the attention system of the human brain can be "primed," in apparent analogy to repetition-suppression effects on activity in other neural systems. For repetition of target color but not location, we also found repetition suppression in inferior temporal areas that may be associated with color processing, whereas repetition of target location led to greater reduction of activation in contralateral inferior parietal and frontal areas, relative to color repetition. The frontal eye fields were also implicated, notably when both target properties (color and location) were repeated together, which also led to further BOLD decreases in anterior fusiform cortex not seen when either property was repeated alone. These findings reveal the neural correlates for priming of pop-out search, including commonalities, differences, and interactions between location and color repetition. fMRI repetition-suppression effects may arise in components of the attention network because these settle into a stable 1. attractor state" more readily when the same target property is repeated than when a different attentional state is required
Gravity coupled to a scalar field from a Chern-Simons action : describing rotating hairy black holes and solitons with gauge fields
No full textPublisher Copyright: © 2023, The Author(s).Einstein gravity minimally coupled to a scalar field with a two-parameter Higgs-like self-interaction in three spacetime dimensions is recast in terms of a Chern-Simons form for the algebra g+ ⊕ g− where, depending on the sign of the self-interaction couplings, g± can be so(2, 2), so(3, 1) or iso(2, 1). The field equations can then be expressed through the field strength of non-flat composite gauge fields, and conserved charges are readily obtained from boundary terms in the action that agree with those of standard Chern-Simons theory for pure gravity, but with non-flat connections. Regularity of the fields then amounts to requiring the holonomy of the connections along contractible cycles to be trivial. These conditions are automatically fulfilled for the scalar soliton and allow to recover the Hawking temperature and chemical potential in the case of the rotating hairy black holes presented here, whose entropy can also be obtained by the same formula that holds in the case of a pure Chern-Simons theory. In the conformal (Jordan) frame the theory is described by General Relativity with cosmological constant conformally coupled to a self-interacting scalar field, and its formulation in terms of a Chern-Simons form for suitably composite gauge fields is also briefly addressed
Alpert multiwavelets and Legendre-Angelesco multiple orthogonal polynomials
No full text© 2017 Society for Industrial and Applied Mathematics. We show that the multiwavelets, introduced by Alpert in 1993, are related to type I Legendre-Angelesco multiple orthogonal polynomials. We give explicit formulas for these Legendre-Angelesco polynomials and for the Alpert multiwavelets. The multiresolution analysis can be done entirely using Legendre polynomials, and we give an algorithm, using Cholesky factorization, for computing the multiwavelets and a method, using the Jacobi matrix for Legendre polynomials, for computing the matrices in the scaling relation for any size of the multiplicity of the multiwavelets.sponsorship: The work of the first author was partially supported by Simons Foundation grant 210169. The work of the second author was partially supported by Simons Foundation grant 280940. The work of the third author was supported by FWO research projects G.0934.13 and G.0864.16, and by KU Leuven research grant OT/12/073. (Simons Foundation|210169, Simons Foundation|280940, FWO|G.0934.13, FWO|G.0864.16, KU Leuven research grant|OT/12/073)status: Publishe
Over de stoomtuigen voor de droogmaking van het Haarlemmer Meer
No full textKort exposé met twee tekeningen inzake de stoomgemalen (de Cruquius, de Leeghwater en de Lijnden) die de Haarlemmermeer drooggemalen hebben. Informatie over ontwerp, maten en het proefdraaien
Comment on "Wandering minds: The default network and stimulus-independent thought"
No full textMason et al. (Reports, 19 January 2007, p. 393) attributed activity in certain regions of the "resting" brain to the occurrence of mind-wandering. However, previous research has demonstrated the difficulty of distinguishing this type of stimulus-independent thought from stimulus-oriented thought (e.g., watchfulness). Consideration of both possibilities is required to resolve this ambiguity
Riverbed sediment classification using multi-beam echo-sounder backscatter data
No full textA method has recently been developed that employs multi-beam echo-sounder backscatter data to both obtain the number of sediment classes and discriminate between them by applying the Bayes decision rule to multiple hypotheses [ Simons and Snellen, Appl. Acoust. 70, 1258–1268 (2009) ]. In deep water, the number of scatter pixels within the beam footprint is large enough to ensure Gaussian distributions for the backscatter strengths and to increase the discriminative power between acoustic classes. In very shallow water (<10?m), however, this number is too small. This paper presents an extension of this high-frequency methodology for these environments, together with a demonstration of its performance using backscatter data from the river Waal, The Netherlands. The objective of this work is threefold. (i) Increasing the discriminating power of the classification method: high-resolution bathymetry data allow precise bottom slope corrections for obtaining the true incident angle, and the high-resolution backscatter data reduce the statistical fluctuations via an averaging procedure. (ii) Performing a correlation analysis: the dependence of acoustic backscatter classification on sediment physical properties is verified by observing a significant correlation of 0.75 (and a disattenuated correlation of 0.90) between the classification results and sediment mean grain size. (iii) Enhancing the statistical description of the backscatter intensities: angular evolution of the K-distribution shape parameter indicates that the riverbed is a rough surface, in agreement with the results of the core analysis.Remote SensingAerospace Engineerin
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