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Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences

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https://www.readbyqxmd.com/read/29986922/analysis-of-time-varying-signals-using-continuous-wavelet-and-synchrosqueezed-transforms
#1
Jean Baptiste Tary, Roberto Henry Herrera, Mirko van der Baan
The continuous wavelet transform (CWT) has played a key role in the analysis of time-frequency information in many different fields of science and engineering. It builds on the classical short-time Fourier transform but allows for variable time-frequency resolution. Yet, interpretation of the resulting spectral decomposition is often hindered by smearing and leakage of individual frequency components. Computation of instantaneous frequencies, combined by frequency reassignment, may then be applied by highly localized techniques, such as the synchrosqueezing transform and ConceFT, in order to reduce these effects...
August 13, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/29986921/on-the-use-of-wavelets-to-reveal-oscillatory-patterns-in-stellar-flare-emission
#2
J López-Santiago
Wavelet analysis is a powerful tool to investigate non-stationary signals such as amplitude modulated sinusoids or single events lasting for a small percentage of the observing time. Wavelet analysis can be used, for example, to reveal oscillations in the light curve of stars during coronal flares. A careful treatment of the background in the wavelet scalogram is necessary to determine robust confidence levels required to distinguish between patterns caused by actual oscillations and noise. This work describes the method using synthetic light curves and investigates the effect of background noise when determining confidence levels in the scalogram...
August 13, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/29986920/continuous-wavelet-transform-in-the-study-of-the-time-scale-properties-of-intracranial-pressure-in-hydrocephalus
#3
María García, Jesús Poza, David Santamarta, Roberto Romero-Oraá, Roberto Hornero
Normal pressure hydrocephalus (NPH) encompasses a heterogeneous group of disorders generally characterized by clinical symptoms, ventriculomegaly and anomalous cerebrospinal fluid (CSF) dynamics. Lumbar infusion tests (ITs) are frequently performed in the preoperatory evaluation of patients who show NPH features. The analysis of intracranial pressure (ICP) signals recorded during ITs could be useful to better understand the pathophysiology underlying NPH and to assist treatment decisions. In this study, 131 ICP signals recorded during ITs were analysed using two continuous wavelet transform (CWT)-derived parameters: Jensen divergence (JD) and spectral flux (SF)...
August 13, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/29986919/quantitative-feature-analysis-of-continuous-analytic-wavelet-transforms-of-electrocardiography-and-electromyography
#4
Mark P Wachowiak, Renata Wachowiak-Smolíková, Michel J Johnson, Dean C Hay, Kevin E Power, F Michael Williams-Bell
Theoretical and practical advances in time-frequency analysis, in general, and the continuous wavelet transform (CWT), in particular, have increased over the last two decades. Although the Morlet wavelet has been the default choice for wavelet analysis, a new family of analytic wavelets, known as generalized Morse wavelets, which subsume several other analytic wavelet families, have been increasingly employed due to their time and frequency localization benefits and their utility in isolating and extracting quantifiable features in the time-frequency domain...
August 13, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/29986918/continuous-wavelet-transform-and-higher-order-spectrum-combinatory-potentialities-in-breath-sound-analysis-and-electroencephalogram-based-pain-characterization
#5
REVIEW
Leontios J Hadjileontiadis
The combination of the continuous wavelet transform (CWT) with a higher-order spectrum (HOS) merges two worlds into one that conveys information regarding the non-stationarity, non-Gaussianity and nonlinearity of the systems and/or signals under examination. In the current work, the third-order spectrum (TOS), which is used to detect the nonlinearity and deviation from Gaussianity of two types of biomedical signals, that is, wheezes and electroencephalogram (EEG), is combined with the CWT to offer a time-scale representation of the examined signals...
August 13, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/29986917/a-wavelet-neural-control-scheme-for-a-quadrotor-unmanned-aerial-vehicle
#6
F Jurado, S Lopez
Wavelets are designed to have compact support in both time and frequency, giving them the ability to represent a signal in the two-dimensional time-frequency plane. The Gaussian, the Mexican hat and the Morlet wavelets are crude wavelets that can be used only in continuous decomposition. The Morlet wavelet is complex-valued and suitable for feature extraction using the continuous wavelet transform. Continuous wavelets are favoured when high temporal and spectral resolution is required at all scales. In this paper, considering the properties from the Morlet wavelet and based on the structure of a recurrent high-order neural network model, a novel wavelet neural network structure, here called a recurrent Morlet wavelet neural network, is proposed in order to achieve a better identification of the behaviour of dynamic systems...
August 13, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/29986916/wavelet-based-analysis-of-time-variant-adaptive-structures
#7
Kajetan Dziedziech, Alexander Nowak, Alexander Hasse, Tadeusz Uhl, Wiesław J Staszewski
Wavelet analysis is applied to identify the time-variant dynamics of adaptive structures. The wavelet-based power spectrum of the structural response, wavelet-based frequency response function (FRF) and wavelet-based coherence are used to identify continuously and abruptly varying natural frequencies. A cantilever plate with surface-bonded macro fibre composite-which alters the structural stiffness-is used to demonstrate the application of the methods. The results show that the wavelet-based input-output characteristics-i...
August 13, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/29986915/branch-mode-competition-in-the-flow-induced-vibration-of-a-square-cylinder
#8
Jisheng Zhao, András Nemes, David Lo Jacono, John Sheridan
The flow-induced vibration response of a square cross-sectional cylinder with low mass and damping ratio is analysed using continuous wavelet transforms (CWT) for three representative angles of attack of the cylinder to the incoming flow. The amplitude and frequency responses over a range of flow velocities map out multiple regimes (branches) of oscillation. Analysis of the time-frequency domain for boundary regions between branches using CWT reveals intermittency at the synchronization region boundaries as well as mode competition at branch boundaries...
August 13, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/29986914/wavelet-analysis-techniques-in-cavitating-flows
#9
Paul A Brandner, James A Venning, Bryce W Pearce
Cavitating and bubbly flows involve a host of physical phenomena and processes ranging from nucleation, surface and interfacial effects, mass transfer via diffusion and phase change to macroscopic flow physics involving bubble dynamics, turbulent flow interactions and two-phase compressible effects. The complex physics that result from these phenomena and their interactions make for flows that are difficult to investigate and analyse. From an experimental perspective, evolving sensing technology and data processing provide opportunities for gaining new insight and understanding of these complex flows, and the continuous wavelet transform (CWT) is a powerful tool to aid in their elucidation...
August 13, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/29986913/a-review-of-morlet-wavelet-analysis-of-radial-profiles-of-saturn-s-rings
#10
REVIEW
Matthew S Tiscareno, Matthew M Hedman
Spiral waves propagating in Saturn's rings have wavelengths that vary with radial position within the disc. The best-quality observations of these waves have the form of radial profiles centred on a particular azimuth. In that context, the wavelength of a given spiral wave is seen to change substantially with position along the one-dimensional profile. In this paper, we review the use of Morlet wavelet analysis to understand these waves. When signal to noise is high and the cause of the wave is well understood, wavelet analysis has been used to solve for wave parameters that are diagnostic of local disc properties...
August 13, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/29986912/introduction-to-redundancy-rules-the-continuous-wavelet-transform-comes-of-age
#11
Paul S Addison
Redundancy: it is a word heavy with connotations of lacking usefulness. I often hear that the rationale for not using the continuous wavelet transform (CWT)-even when it appears most appropriate for the problem at hand-is that it is 'redundant'. Sometimes the conversation ends there, as if self-explanatory. However, in the context of the CWT, 'redundant' is not a pejorative term, it simply refers to a less compact form used to represent the information within the signal. The benefit of this new form-the CWT-is that it allows for intricate structural characteristics of the signal information to be made manifest within the transform space, where it can be more amenable to study: resolution over redundancy...
August 13, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/29986911/nonlinear-analysis-of-natural-folds-using-wavelet-transforms-and-recurrence-plots
#12
Alison Ord, Bruce Hobbs, Greg Dering, Klaus Gessner
Three-dimensional models of natural geological fold systems established by photogrammetry are quantified in order to constrain the processes responsible for their formation. The folds are treated as nonlinear dynamical systems and the quantification is based on the two features that characterize such systems, namely their multifractal geometry and recurrence quantification. The multifractal spectrum is established using wavelet transforms and the wavelet transform modulus maxima method, the generalized fractal or Renyi dimensions and the Hurst exponents for longitudinal and orthogonal sections of the folds...
August 13, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/29986910/california-s-carbon-market-and-energy-prices-a-wavelet-analysis
#13
Luís Aguiar-Conraria, Maria Joana Soares, Rita Sousa
Carbon price is a key variable in management and risk decisions in activities related to the burning of fossil fuels. Different major players in this market, such as polluters, regulators and financial actors, have different time horizons. We use innovative multivariate wavelet analysis tools, including partial wavelet coherence and partial wavelet gain, to study the link between carbon prices and final energy prices in the time and frequency dimensions in California's carbon market, officially known as the California cap-and-trade programme...
August 13, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/29941632/andreev-bound-states-and-their-signatures
#14
J A Sauls
Many of the properties of superconductors related to quantum coherence are revealed when the superconducting state is forced to vary in space in response to an external magnetic field, a proximity contact, an interface to a ferromagnet or to impurities embedded in the superconductor. Among the earliest examples is Andreev reflection of an electron into a retro-reflected hole at a normal-superconducting interface. In regions of strong inhomogeneity, multiple Andreev reflection leads to the formation of sub-gap states, Andreev bound states , with excitation energies below the superconducting gap...
August 6, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/29941631/correction-to-building-equity-in-strategies-for-integrating-equity-into-modelling-for-a-1-5%C3%A2-c-world
#15
Sonja Klinsky, Harald Winkler
No abstract text is available yet for this article.
August 6, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/29941630/multifaceted-properties-of-andreev-bound-states-interplay-of-symmetry-and-topology
#16
T Mizushima, K Machida
Andreev bound states (ABSs) ubiquitously emerge as a consequence of non-trivial topological structures of the order parameter of superfluids and superconductors and significantly contribute to thermodynamics and low-energy quantum transport phenomena. We here share the current status of our knowledge on their multifaceted properties such as Majorana fermions and odd-frequency pairing. A unified concept behind ABSs originates from a soliton state in the one-dimensional Dirac equation with mass domain wall and interplay of ABSs with symmetry and topology enrich their physical characteristics...
August 6, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/29941629/out-of-equilibrium-spin-transport-in-mesoscopic-superconductors
#17
REVIEW
C H L Quay, M Aprili
The excitations in conventional superconductors, Bogoliubov quasi-particles, are spin-[Formula: see text] fermions but their charge is energy-dependent and, in fact, zero at the gap edge. Therefore, in superconductors (unlike normal metals) spin and charge degrees of freedom may be separated. In this article, we review spin injection into conventional superconductors and focus on recent experiments on mesoscopic superconductors. We show how quasi-particle spin transport and out-of-equilibrium spin-dependent superconductivity can be triggered using the Zeeman splitting of the quasi-particle density of states in thin-film superconductors with small spin-mixing scattering...
August 6, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/29941628/study-on-green-s-function-on-topological-insulator-surface
#18
Bo Lu, Yukio Tanaka
In the theory of superconducting junctions, Green's function has an important role for obtaining Andreev bound states, local density of states and Josephson current in a systematic way. In this article, we show how to construct Green's function on the surface of a topological insulator following McMillan's formalism where the energy spectrum of electrons obeys a linear dispersion. For a model of a superconductor (S)/ferromagnet (F)/normal metal (N) junction, we show that the generation of a Majorana fermion gives rise to the enhanced local density of states and pair amplitude of odd-frequency pairing...
August 6, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/29941627/non-equilibrium-charge-and-spin-transport-in-superconducting-ferromagnetic-superconducting-point-contacts
#19
REVIEW
C Holmqvist, W Belzig, M Fogelström
The conventional Josephson effect may be modified by introducing spin-active scattering in the interface layer of the junction. Here, we discuss a Josephson junction consisting of two s-wave superconducting leads coupled over a classical spin that precesses with the Larmor frequency due to an external magnetic field. This magnetically active interface results in a time-dependent boundary condition with different tunnelling amplitudes for spin-up and -down quasi-particles and where the precession produces spin-flip scattering processes...
August 6, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/29941626/weyl-nodes-in-periodic-structures-of-superconductors-and-spin-active-materials
#20
Ahmet Keles, Erhai Zhao
Motivated by recent progress in epitaxial growth of proximity structures of s -wave superconductors (S) and spin-active materials (M), in this paper we show that certain periodic structures of S and M can behave effectively as superconductors with pairs of point nodes, near which the low-energy excitations are Weyl fermions. A simple model, where M is described by a Kronig-Penney potential with both spin-orbit coupling and exchange field, is proposed and solved to obtain the phase diagram of the nodal structure, the spin texture of the Weyl fermions, as well as the zero-energy surface states in the form of open Fermi lines (Fermi arcs)...
August 6, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
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