Sample records for gaussian speckle fields

  1. Spatial Behaviour of Singularities in Fractal- and Gaussian Speckle Fields

    DEFF Research Database (Denmark)

    Angelsky, Oleg V.; Maksimyak, Alexander P.; Maksimyak, Peter P.


    Peculiarities of the spatial behaviour of the dislocation lines resulting from scattering of coherent radiation from random and fractal rough surfaces are studied. The technique of optical correlation is proposed for diagnostics of phase singularities in a complex speckle field by comparing...

  2. Image Enhancement and Speckle Reduction of Full Polarimetric SAR Data by Gaussian Markov Random Field (United States)

    Mahdian, M.; Motagh, M.; Akbari, V.


    In recent years, the use of Polarimetric Synthetic Aperture Radar (PolSAR) data in different applications dramatically has been increased. In SAR imagery an interference phenomenon with random behavior exists which is called speckle noise. The interpretation of data encounters some troubles due to the presence of speckle which can be considered as a multiplicative noise affecting all coherent imaging systems. Indeed, speckle degrade radiometric resolution of PolSAR images, therefore it is needful to perform speckle filtering on the SAR data type. Markov Random Field (MRF) has proven to be a powerful method for drawing out eliciting contextual information from remotely sensed images. In the present paper, a probability density function (PDF), which is fitted well with the PolSAR data based on the goodness-of-fit test, is first obtained for the pixel-wise analysis. Then the contextual smoothing is achieved with the MRF method. This novel speckle reduction method combines an advanced statistical distribution with spatial contextual information for PolSAR data. These two parts of information are combined based on weighted summation of pixel-wise and contextual models. This approach not only preserves edge information in the images, but also improves signal-to-noise ratio of the results. The method maintains the mean value of original signal in the homogenous areas and preserves the edges of features in the heterogeneous regions. Experiments on real medium resolution ALOS data from Tehran, and also high resolution full polarimetric SAR data over the Oberpfaffenhofen test-site in Germany, demonstrate the effectiveness of the algorithm compared with well-known despeckling methods.

  3. Speckle fields in holographic interferometry (United States)

    Lockshin, Gennady R.; Kozel, Stanislav M.; Bielonuchkin, V. E.


    The objects which are investigated which are investigated with the help of the holographic interferometry methods as a rule scatter light diffusely, therefore the two-expositional hologram reconstructs the result of interference of the speckle-fields f ('4 and f() scattered by th object at the initial (1) and final (2) states.

  4. Enhanced deterministic phase retrieval using a partially developed speckle field

    DEFF Research Database (Denmark)

    Almoro, Percival F.; Waller, Laura; Agour, Mostafa


    A technique for enhanced deterministic phase retrieval using a partially developed speckle field (PDSF) and a spatial light modulator (SLM) is demonstrated experimentally. A smooth test wavefront impinges on a phase diffuser, forming a PDSF that is directed to a 4f setup. Two defocused speckle...... intensity measurements are recorded at the output plane corresponding to axially-propagated representations of the PDSF in the input plane. The speckle intensity measurements are then used in a conventional transport of intensity equation (TIE) to reconstruct directly the test wavefront. The PDSF in our...

  5. Run-and-tumble particles in speckle fields

    International Nuclear Information System (INIS)

    Paoluzzi, M; Di Leonardo, R; Angelani, L


    The random energy landscapes developed by speckle fields can be used to confine and manipulate a large number of micro-particles with a single laser beam. By means of molecular dynamics simulations, we investigate the static and dynamic properties of an active suspension of swimming bacteria embedded into speckle patterns. Looking at the correlation of the density fluctuations and the equilibrium density profiles, we observe a crossover phenomenon when the forces exerted by the speckles are equal to the bacteria’s propulsion. (paper)

  6. Integration of non-Gaussian fields

    DEFF Research Database (Denmark)

    Ditlevsen, Ove Dalager; Mohr, Gunnar; Hoffmeyer, Pernille


    The limitations of the validity of the central limit theorem argument as applied to definite integrals of non-Gaussian random fields are empirically explored by way of examples. The purpose is to investigate in specific cases whether the asymptotic convergence to the Gaussian distribution is fast...... enough to justify that it is sufficiently accurate for the applications to shortcut the problem and just assume that the distribution of the relevant stochastic integral is Gaussian. An earlier published example exhibiting this problem concerns silo pressure fields. [Ditlevsen, O., Christensen, C......, 1994](1) The numerical technique applied to obtain approximate information about the distribution of the integral is based on a recursive application of Winterstein approximations (moment fitted linear combinations of Hermite polynomials of standard Gaussian variables). The method uses the very long...

  7. Polar Functions for Anisotropic Gaussian Random Fields

    Directory of Open Access Journals (Sweden)

    Zhenlong Chen


    Full Text Available Let X be an (N, d-anisotropic Gaussian random field. Under some general conditions on X, we establish a relationship between a class of continuous functions satisfying the Lipschitz condition and a class of polar functions of X. We prove upper and lower bounds for the intersection probability for a nonpolar function and X in terms of Hausdorff measure and capacity, respectively. We also determine the Hausdorff and packing dimensions of the times set for a nonpolar function intersecting X. The class of Gaussian random fields that satisfy our conditions includes not only fractional Brownian motion and the Brownian sheet, but also such anisotropic fields as fractional Brownian sheets, solutions to stochastic heat equation driven by space-time white noise, and the operator-scaling Gaussian random field with stationary increments.

  8. Gaussian processes and constructive scalar field theory

    International Nuclear Information System (INIS)

    Benfatto, G.; Nicolo, F.


    The last years have seen a very deep progress of constructive euclidean field theory, with many implications in the area of the random fields theory. The authors discuss an approach to super-renormalizable scalar field theories, which puts in particular evidence the connections with the theory of the Gaussian processes associated to the elliptic operators. The paper consists of two parts. Part I treats some problems in the theory of Gaussian processes which arise in the approach to the PHI 3 4 theory. Part II is devoted to the discussion of the ultraviolet stability in the PHI 3 4 theory. (Auth.)

  9. Perturbative Gaussianizing transforms for cosmological fields (United States)

    Hall, Alex; Mead, Alexander


    Constraints on cosmological parameters from large-scale structure have traditionally been obtained from two-point statistics. However, non-linear structure formation renders these statistics insufficient in capturing the full information content available, necessitating the measurement of higher order moments to recover information which would otherwise be lost. We construct quantities based on non-linear and non-local transformations of weakly non-Gaussian fields that Gaussianize the full multivariate distribution at a given order in perturbation theory. Our approach does not require a model of the fields themselves and takes as input only the first few polyspectra, which could be modelled or measured from simulations or data, making our method particularly suited to observables lacking a robust perturbative description such as the weak-lensing shear. We apply our method to simulated density fields, finding a significantly reduced bispectrum and an enhanced correlation with the initial field. We demonstrate that our method reconstructs a large proportion of the linear baryon acoustic oscillations, improving the information content over the raw field by 35 per cent. We apply the transform to toy 21 cm intensity maps, showing that our method still performs well in the presence of complications such as redshift-space distortions, beam smoothing, pixel noise and foreground subtraction. We discuss how this method might provide a route to constructing a perturbative model of the fully non-Gaussian multivariate likelihood function.

  10. Single field inflation and non-Gaussianity

    International Nuclear Information System (INIS)

    Gangui, Alejandro; Martin, Jerome; Sakellariadou, Mairi


    We study non-Gaussian signatures on the cosmic microwave background (CMB) radiation predicted within inflationary models with non-vacuum initial states for cosmological perturbations. The model incorporates a privileged scale, which implies the existence of a feature in the primordial power spectrum. This broken-scale-invariant model predicts a vanishing three-point correlation function for the CMB temperature anisotropies (or any other odd-numbered-point correlation function) whilst an intrinsic non-Gaussian signature arises for any even-numbered-point correlation function. We thus focus on the first non-vanishing moment, the CMB four-point function at zero lag, namely the kurtosis, and compute its expected value for different locations of the primordial feature in the spectrum, as suggested in the literature to conform with observations of large scale structure. The excess kurtosis is found to be negative and the signal to noise ratio for the dimensionless excess kurtosis parameter is equal to |S/N|≅4x10 -4 , almost independently of the free parameters of the model. This signature turns out to be undetectable. We conclude that, subject to current tests, Gaussianity is a generic property of single field inflationary models. The only uncertainty concerning this prediction is that the effect of back reaction has not yet been properly incorporated. The implications for the trans-Planckian problem of inflation are also briefly discussed

  11. Speckle photography applied to the density field of a flame (United States)

    Shu, J.-Z.; Li, J.-Y.


    An optical arrangement combining a set-up for taking speckle records with a shearing interferometer using a Wollaston prism is applied to the study of a fluctuating Bunsen burner flame. The simultaneous recording, in real time, of the interferogram facilitates the interpretation of the data field derived by the point-by-point analysis of the specklegram. The pattern of Young's fringes obtained by analysis of the specklegram at 16 different positions in the field of view is shown, displaying the random variation of the light deflection in the flame.

  12. Near-field to far-field characterization of speckle patterns generated by disordered nanomaterials. (United States)

    Parigi, Valentina; Perros, Elodie; Binard, Guillaume; Bourdillon, Céline; Maître, Agnès; Carminati, Rémi; Krachmalnicoff, Valentina; De Wilde, Yannick


    We study the intensity spatial correlation function of optical speckle patterns above a disordered dielectric medium in the multiple scattering regime. The intensity distributions are recorded by scanning near-field optical microscopy (SNOM) with sub-wavelength spatial resolution at variable distances from the surface in a range which spans continuously from the near-field (distance ≪ λ) to the far-field regime (distance ≫ λ). The non-universal behavior at sub-wavelength distances reveals the connection between the near-field speckle pattern and the internal structure of the medium.

  13. Speckle Interferometry (United States)

    Chiang, F. P.; Jin, F.; Wang, Q.; Zhu, N.

    Before the milestone work of Leedertz in 1970 coherent speckles generated from a laser illuminated object are considered noise to be eliminated or minimized. Leedertz shows that coherent speckles are actually information carriers. Since then the speckle technique has found many applications to fields of mechanics, metrology, nondestructive evaluation and material sciences. Speckles need not be coherent. Artificially created socalled white light speckles can also be used as information carriers. In this paper we present two recent developments of speckle technique with applications to micromechanics problems using SIEM (Speckle Interferometry with Electron Microscopy), to nondestructive evaluation of crevice corrosion and composite disbond and vibration of large structures using TADS (Time-Average Digital Specklegraphy).

  14. Higher moments of weighted integrals of non-Gaussian fields

    DEFF Research Database (Denmark)

    Mohr, Gunnar


    In general, the exact probability distribution of a definite integral of a given non-Gaussian random field is not known. Some information about this unknown distribution can be obtained from the 3rd and 4th moment of the integral. Approximations to these moments can be calculated by discretizing...... the integral and replacing the integrand by third-degree polynomials of correlated Gaussian Variables which reproduce the first four moments and the correlation function of the field correctly. The method described (see Ditlevsen O, Mohr G, Hoffmeyer P. Integration of non-Gaussian fields. Probabilistic...

  15. Gaussian vector fields on triangulated surfaces

    DEFF Research Database (Denmark)

    Ipsen, John H


    proven to be very useful to resolve the complex interplay between in-plane ordering of membranes and membrane conformations. In the present work we have developed a procedure for realistic representations of Gaussian models with in-plane vector degrees of freedoms on a triangulated surface. The method...

  16. Measurement of eye aberrations in a speckle field

    International Nuclear Information System (INIS)

    Larichev, A V; Ivanov, P V; Iroshnikov, N G; Shmalgauzen, V I


    The influence of speckles on the performance of a Shark-Hartmann wavefront sensor is investigated in the eye aberration studies. The dependence of the phase distortion measurement error on the characteristic speckle size is determined experimentally. Scanning of the reference source was used to suppress the speckle structure of the laser beam scattered by the retina. The technique developed by us made it possible to study the time dependence of the human eye aberrations with a resolution of 30 ms. (laser applications and other topics in quantum electronics)

  17. Statistics of polarization speckle: theory versus experiment

    DEFF Research Database (Denmark)

    Wang, Wei; Hanson, Steen Grüner; Takeda, Mitsuo


    In this paper, we reviewed our recent work on the statistical properties of polarization speckle, described by stochastic Stokes parameters fluctuating in space. Based on the Gaussian assumption for the random electric field components and polar-interferometer, we investigated theoretically...... and experimentally the statistics of Stokes parameters of polarization speckle, including probability density function of Stokes parameters with the spatial degree of polarization, autocorrelation of Stokes vector and statistics of spatial derivatives for Stokes parameters....

  18. 3D shape measurement using deterministic phase retrieval and a partially developed speckle field

    DEFF Research Database (Denmark)

    Almoro, Percival F.; Waller, Laura; Agour, Mostafa


    Fourier domain. The local variations of the recorded speckle patterns and the defocus distance approximate the axial intensity derivative which, in turn, is required to recover the wavefront phase via the transport of intensity equation (TIE). The SLM setup reduces the speckle recording time and the TIE...... allows direct (i.e., non-iterative) calculation of the phase. The pre-requisite partially-developed speckle field in our technique facilitates high image contrast and significant axial intensity variation. Wavefront reconstruction for the 3D refractive test object used demonstrates the effectiveness...... of the technique....

  19. Simulations of multi-contrast x-ray imaging using near-field speckles

    Energy Technology Data Exchange (ETDEWEB)

    Zdora, Marie-Christine [Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching (Germany); Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom and Department of Physics & Astronomy, University College London, London, WC1E 6BT (United Kingdom); Thibault, Pierre [Department of Physics & Astronomy, University College London, London, WC1E 6BT (United Kingdom); Herzen, Julia; Pfeiffer, Franz [Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching (Germany); Zanette, Irene [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE (United Kingdom); Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching (Germany)


    X-ray dark-field and phase-contrast imaging using near-field speckles is a novel technique that overcomes limitations inherent in conventional absorption x-ray imaging, i.e. poor contrast for features with similar density. Speckle-based imaging yields a wealth of information with a simple setup tolerant to polychromatic and divergent beams, and simple data acquisition and analysis procedures. Here, we present a simulation software used to model the image formation with the speckle-based technique, and we compare simulated results on a phantom sample with experimental synchrotron data. Thorough simulation of a speckle-based imaging experiment will help for better understanding and optimising the technique itself.

  20. Study of microparticles' anomalous diffusion in active bath using speckle light fields (Presentation Recording) (United States)

    Pince, Ercag; Sabareesh, Sabareesh K. P.; Volpe, Giorgio; Gigan, Sylvain; Volpe, Giovanni S.


    Particles undergoing a stochastic motion within a disordered medium is a ubiquitous physical and biological phenomenon. Examples can be given from organelles as molecular machines of cells performing physical tasks in a populated cytoplasm to human mobility in patchy environment at larger scales. Our recent results showed that it is possible to use the disordered landscape generated by speckle light fields to perform advanced manipulation tasks at the microscale. Here, we use speckle light fields to study the anomalous diffusion of micron size silica particles (5 μm) in the presence of active microswimmers. The microswimmers we used in the experiments are motile bacteria, Escherichia coli (E.coli). They constitute an active background constantly agitating passive silica particles within complex optical potentials. The speckle fields are generated by mode mixing inside a multimode optical fiber where a small amount of incident laser power (maximum power = 12 μW/μm2) is needed to obtain an effective random landscape pattern for the purpose of optical manipulation. We experimentally show how complex potentials contribute to the anomalous diffusion of silica particles undergoing collisions with swimming bacteria. We observed an enhanced diffusion of particles interacting with the active bath of E.coli inside speckle light fields: this effect can be tuned and controlled by varying the intensity and the statistical properties of the speckle pattern. Potentially, these results could be of interest for many technological applications, such as the manipulation of microparticles inside optically disordered media of biological interests.

  1. Folded resonant non-Gaussianity in general single field inflation

    International Nuclear Information System (INIS)

    Chen, Xingang


    We compute a novel type of large non-Gaussianity due to small periodic features in general single field inflationary models. We show that the non-Bunch-Davies vacuum component generated by features, although has a very small amplitude, can have significant impact on the non-Gaussianity. Three mechanisms are turned on simultaneously in such models, namely the resonant effect, non-Bunch-Davies vacuum and higher derivative kinetic terms, resulting in a bispectrum with distinctive shapes and running. The size can be equal to or larger than that previously found in each single mechanism. Our full results, including the resonant and folded resonant non-Gaussianities, give the leading order bispectra due to general periodic features in general single field inflation

  2. Quantitative X-ray dark-field and phase tomography using single directional speckle scanning technique

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hongchang, E-mail:; Kashyap, Yogesh; Sawhney, Kawal [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom)


    X-ray dark-field contrast tomography can provide important supplementary information inside a sample to the conventional absorption tomography. Recently, the X-ray speckle based technique has been proposed to provide qualitative two-dimensional dark-field imaging with a simple experimental arrangement. In this letter, we deduce a relationship between the second moment of scattering angle distribution and cross-correlation degradation of speckle and establish a quantitative basis of X-ray dark-field tomography using single directional speckle scanning technique. In addition, the phase contrast images can be simultaneously retrieved permitting tomographic reconstruction, which yields enhanced contrast in weakly absorbing materials. Such complementary tomography technique can allow systematic investigation of complex samples containing both soft and hard materials.

  3. Higher Moments of Weighted Integrals of Non-Gaussian Fields

    DEFF Research Database (Denmark)

    Mohr, Gunnar


    In general , the exact probability distribution of a definite non-Gaussian random field is not known. Some information about this unknown distribution can be obtained from the 3rd and 4th moment of the integral. Approximations to these moments are calculated by a numerical technique based...

  4. Point-wise and whole-field laser speckle intensity fluctuation measurements applied to botanical specimens (United States)

    Zhao, Yang; Wang, Junlan; Wu, Xiaoping; Williams, Fred W.; Schmidt, Richard J.


    Based on multi-scattering speckle theory, the speckle fields generated by plant specimens irradiated by laser light have been studied using a pointwise method. In addition, a whole-field method has been developed with which entire botanical specimens may be studied. Results are reported from measurements made on tomato and apple fruits, orange peel, leaves of tobacco seedlings, leaves of shihu seedlings (a Chinese medicinal herb), soy-bean sprouts, and leaves from an unidentified trailing houseplant. Although differences where observed in the temporal fluctuations of speckles that could be ascribed to differences in age and vitality, the growing tip of the bean sprout and the shihu seedling both generated virtually stationary speckles such as were observed from boiled orange peel and from localised heat-damaged regions on apple fruit. Our results suggest that both the identity of the botanical specimen and the site at which measurements are taken are likely to critically affect the observation or otherwise of temporal fluctuations of laser speckles.

  5. Gaussian likelihood inference on data from trans-Gaussian random fields with Matérn covariance function

    KAUST Repository

    Yan, Yuan


    Gaussian likelihood inference has been studied and used extensively in both statistical theory and applications due to its simplicity. However, in practice, the assumption of Gaussianity is rarely met in the analysis of spatial data. In this paper, we study the effect of non-Gaussianity on Gaussian likelihood inference for the parameters of the Matérn covariance model. By using Monte Carlo simulations, we generate spatial data from a Tukey g-and-h random field, a flexible trans-Gaussian random field, with the Matérn covariance function, where g controls skewness and h controls tail heaviness. We use maximum likelihood based on the multivariate Gaussian distribution to estimate the parameters of the Matérn covariance function. We illustrate the effects of non-Gaussianity of the data on the estimated covariance function by means of functional boxplots. Thanks to our tailored simulation design, a comparison of the maximum likelihood estimator under both the increasing and fixed domain asymptotics for spatial data is performed. We find that the maximum likelihood estimator based on Gaussian likelihood is overall satisfying and preferable than the non-distribution-based weighted least squares estimator for data from the Tukey g-and-h random field. We also present the result for Gaussian kriging based on Matérn covariance estimates with data from the Tukey g-and-h random field and observe an overall satisfactory performance.

  6. Discretisation Schemes for Level Sets of Planar Gaussian Fields (United States)

    Beliaev, D.; Muirhead, S.


    Smooth random Gaussian functions play an important role in mathematical physics, a main example being the random plane wave model conjectured by Berry to give a universal description of high-energy eigenfunctions of the Laplacian on generic compact manifolds. Our work is motivated by questions about the geometry of such random functions, in particular relating to the structure of their nodal and level sets. We study four discretisation schemes that extract information about level sets of planar Gaussian fields. Each scheme recovers information up to a different level of precision, and each requires a maximum mesh-size in order to be valid with high probability. The first two schemes are generalisations and enhancements of similar schemes that have appeared in the literature (Beffara and Gayet in Publ Math IHES, 2017.; Mischaikow and Wanner in Ann Appl Probab 17:980-1018, 2007); these give complete topological information about the level sets on either a local or global scale. As an application, we improve the results in Beffara and Gayet (2017) on Russo-Seymour-Welsh estimates for the nodal set of positively-correlated planar Gaussian fields. The third and fourth schemes are, to the best of our knowledge, completely new. The third scheme is specific to the nodal set of the random plane wave, and provides global topological information about the nodal set up to `visible ambiguities'. The fourth scheme gives a way to approximate the mean number of excursion domains of planar Gaussian fields.

  7. Quasi-single field inflation and non-Gaussianities

    International Nuclear Information System (INIS)

    Chen, Xingang; Wang, Yi


    In quasi-single field inflation models, massive isocurvature modes, that are coupled to the inflaton and have mass of order the Hubble parameter, can have nontrivial impacts on density perturbations, especially non-Gaussianities. We study a simple example of quasi-single field inflation in terms of turning inflaton trajectory. Large bispectra with a one-parameter family of novel shapes arise, lying between the well-known local and equilateral shape. The trispectra can also be very large and its magnitude t NL can be much larger than f NL 2

  8. Shape and deformation measurements of 3D objects using volume speckle field and phase retrieval

    DEFF Research Database (Denmark)

    Anand, A; Chhaniwal, VK; Almoro, Percival


    Shape and deformation measurement of diffusely reflecting 3D objects are very important in many application areas, including quality control, nondestructive testing, and design. When rough objects are exposed to coherent beams, the scattered light produces speckle fields. A method to measure the ......-sized deformation induced on a metal sheet was obtained upon subtraction of the phase, corresponding to unloaded and loaded states. Results from computer simulations confirm the experiments. (C) 2009 Optical Society of America....

  9. Holographic non-Gaussianities in general single-field inflation

    International Nuclear Information System (INIS)

    Isono, Hiroshi; Noumi, Toshifumi; Shiu, Gary; Wong, Sam S.C.; Zhou, Siyi


    We use holographic techniques to compute inflationary non-Gaussianities for general single-field inflation, including models with a non-trivial sound speed. In this holographic approach, the inflationary dynamics is captured by a relevant deformation of the dual conformal field theory (CFT) in the UV, while the inflationary correlators are computed by conformal perturbation theory. In this paper, we discuss the effects of higher derivative operators, such as (∂ μ ϕ∂ μ ϕ) m , which are known to induce a non-trivial sound speed and source potentially large non-Gaussianities. We compute the full inflationary bispectra from the deformed CFT correlators. We also discuss the squeezed limit of the bispectra from the viewpoint of operator product expansions. As is generic in the holographic description of inflation, our power spectrum is blue tilted in the UV region. We extend our bispectrum computation to the IR region by resumming the conformal perturbations to all orders. We provide a self-consistent setup which reproduces a red tilted power spectrum, as well as all possible bispectrum shapes in the slow-roll regime.

  10. Holographic non-Gaussianities in general single-field inflation

    Energy Technology Data Exchange (ETDEWEB)

    Isono, Hiroshi [Department of Physics, Faculty of Science,Chulalongkorn University, Bangkok 10330 (Thailand); Noumi, Toshifumi [Department of Physics and Jockey Club Institute for Advanced Study,Hong Kong University of Science and Technology (Hong Kong); Department of Physics,Kobe University, Kobe 657-8501 (Japan); Shiu, Gary [Department of Physics and Jockey Club Institute for Advanced Study,Hong Kong University of Science and Technology (Hong Kong); Department of Physics, University of Wisconsin-Madison,Madison, WI 53706 (United States); Wong, Sam S.C.; Zhou, Siyi [Department of Physics and Jockey Club Institute for Advanced Study,Hong Kong University of Science and Technology (Hong Kong)


    We use holographic techniques to compute inflationary non-Gaussianities for general single-field inflation, including models with a non-trivial sound speed. In this holographic approach, the inflationary dynamics is captured by a relevant deformation of the dual conformal field theory (CFT) in the UV, while the inflationary correlators are computed by conformal perturbation theory. In this paper, we discuss the effects of higher derivative operators, such as (∂{sub μ}ϕ∂{sup μ}ϕ){sup m}, which are known to induce a non-trivial sound speed and source potentially large non-Gaussianities. We compute the full inflationary bispectra from the deformed CFT correlators. We also discuss the squeezed limit of the bispectra from the viewpoint of operator product expansions. As is generic in the holographic description of inflation, our power spectrum is blue tilted in the UV region. We extend our bispectrum computation to the IR region by resumming the conformal perturbations to all orders. We provide a self-consistent setup which reproduces a red tilted power spectrum, as well as all possible bispectrum shapes in the slow-roll regime.

  11. Simulations of x-ray speckle-based dark-field and phase-contrast imaging with a polychromatic beam

    Energy Technology Data Exchange (ETDEWEB)

    Zdora, Marie-Christine, E-mail: [Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching (Germany); Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom); Department of Physics & Astronomy, University College London, London WC1E 6BT (United Kingdom); Thibault, Pierre [Department of Physics & Astronomy, University College London, London WC1E 6BT (United Kingdom); Pfeiffer, Franz [Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching (Germany); Zanette, Irene [Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching (Germany); Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom)


    Following the first experimental demonstration of x-ray speckle-based multimodal imaging using a polychromatic beam [I. Zanette et al., Phys. Rev. Lett. 112(25), 253903 (2014)], we present a simulation study on the effects of a polychromatic x-ray spectrum on the performance of this technique. We observe that the contrast of the near-field speckles is only mildly influenced by the bandwidth of the energy spectrum. Moreover, using a homogeneous object with simple geometry, we characterize the beam hardening artifacts in the reconstructed transmission and refraction angle images, and we describe how the beam hardening also affects the dark-field signal provided by speckle tracking. This study is particularly important for further implementations and developments of coherent speckle-based techniques at laboratory x-ray sources.

  12. Full-field illumination approach with multiple speckle for optical-resolution photoacoustic microscopy (Conference Presentation) (United States)

    Poisson, Florian; Bossy, Emmanuel


    Optical-resolution photoacoustic endomicroscopy (OR-PAE) allows going beyond the limited penetration depth of conventional optical-resolution photoacoustic systems. Recently, it has been shown that OR-PAE may be performed through minimally invasive multimode fibers, by raster scanning a focus spot with optical wavefront shaping [1]. Here we introduce for the first time an approach to perform OR-PAE through a multimode fiber with a full-field illumination approach. By using multiple known speckle patterns, we show that it is possible to obtain optical-diffraction limited photoacoustic images, with the same resolution as that obtained by raster scanning a focus spot, i.e that of the speckle grain size. The fluctuations patterns of the photoacoustic amplitude at each pixel in the sample plane with the series of multiple speckle illumination were used to encode each pixel. This approach with known speckle illumination requires an initial calibration stage, that consists in learn a set of fluctuation patterns pixel per pixel, which will encode patterns each pixel of the scanned area. A point-like absorber was scanned across the filed-of-view during the calibration stage to acquire the reference patterns. Image reconstruction may be carried out by cross-correlating the series of photoacoustic amplitude measured with the sample to the reference patterns obtained during the calibration stage. In this work, the approach above was carried out both theoretically with Monte-carlo simulations and experimentally through a multi-mode fiber with samples made of absorbing spheres. [1] Papadopoulos et al., " Optical-resolution photoacoustic microscopy by use of a multimode fiber", Appl. Phys. Lett., 102(21), 2013

  13. Non-Gaussianity from Self-Ordering Scalar Fields

    CERN Document Server

    Figueroa, Daniel G; Kamionkowski, Marc


    The Universe may harbor relics of the post-inflationary epoch in the form of a network of self-ordered scalar fields. Such fossils, while consistent with current cosmological data at trace levels, may leave too weak an imprint on the cosmic microwave background and the large-scale distribution of matter to allow for direct detection. The non-Gaussian statistics of the density perturbations induced by these fields, however, permit a direct means to probe for these relics. Here we calculate the bispectrum that arises in models of self-ordered scalar fields. We find a compact analytic expression for the bispectrum, evaluate it numerically, and provide a simple approximation that may be useful for data analysis. The bispectrum is largest for triangles that are aligned (have edges $k_1\\simeq 2 k_2 \\simeq 2 k_3$) as opposed to the local-model bispectrum, which peaks for squeezed triangles ($k_1\\simeq k_2 \\gg k_3$), and the equilateral bispectrum, which peaks at $k_1\\simeq k_2 \\simeq k_3$. We estimate that this non-...

  14. Superpositions of higher-order bessel beams and nondiffracting speckle fields

    CSIR Research Space (South Africa)

    Dudley, Angela L


    Full Text Available stream_source_info Dudley_d1_2009.pdf.txt stream_content_type text/plain stream_size 16165 Content-Encoding UTF-8 stream_name Dudley_d1_2009.pdf.txt Content-Type text/plain; charset=UTF-8 Superpositions of higher...: ( )∑∞= −+= 0 )exp()()exp()(),( m mm imrSimrCr ϕϕϕτ . (1) In the case of generating a nondiffracting speckle field, the transmission function ),( ϕτ r is dependent on both the radius, r...

  15. Some Metric Properties of Planar Gaussian Free Field (United States)

    Goswami, Subhajit

    In this thesis we study the properties of some metrics arising from two-dimensional Gaussian free field (GFF), namely the Liouville first-passage percolation (Liouville FPP), the Liouville graph distance and an effective resistance metric. In Chapter 1, we define these metrics as well as discuss the motivations for studying them. Roughly speaking, Liouville FPP is the shortest path metric in a planar domain D where the length of a path P is given by ∫Pe gammah(z)|dz| where h is the GFF on D and gamma > 0. In Chapter 2, we present an upper bound on the expected Liouville FPP distance between two typical points for small values of gamma (the near-Euclidean regime). A similar upper bound is derived in Chapter 3 for the Liouville graph distance which is, roughly, the minimal number of Euclidean balls with comparable Liouville quantum gravity (LQG) measure whose union contains a continuous path between two endpoints. Our bounds seem to be in disagreement with Watabiki's prediction (1993) on the random metric of Liouville quantum gravity in this regime. The contents of these two chapters are based on a joint work with Jian Ding. In Chapter 4, we derive some asymptotic estimates for effective resistances on a random network which is defined as follows. Given any gamma > 0 and for eta = {etav}v∈Z2 denoting a sample of the two-dimensional discrete Gaussian free field on Z2 pinned at the origin, we equip the edge ( u, v) with conductance egamma(etau + eta v). The metric structure of effective resistance plays a crucial role in our proof of the main result in Chapter 4. The primary motivation behind this metric is to understand the random walk on Z 2 where the edge (u, v) has weight egamma(etau + etav). Using the estimates from Chapter 4 we show in Chapter 5 that for almost every eta, this random walk is recurrent and that, with probability tending to 1 as T → infinity, the return probability at time 2T decays as T-1+o(1). In addition, we prove a version of subdiffusive

  16. Axial acoustic radiation force on a sphere in Gaussian field

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Rongrong; Liu, Xiaozhou, E-mail:; Gong, Xiufen [Key Laboratory of Modern Acoustics, Institute of Acoustics and School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)


    Based on the finite series method, the acoustical radiation force resulting from a Gaussian beam incident on a spherical object is investigated analytically. When the position of the particles deviating from the center of the beam, the Gaussian beam is expanded as a spherical function at the center of the particles and the expanded coefficients of the Gaussian beam is calculated. The analytical expression of the acoustic radiation force on spherical particles deviating from the Gaussian beam center is deduced. The acoustic radiation force affected by the acoustic frequency and the offset distance from the Gaussian beam center is investigated. Results have been presented for Gaussian beams with different wavelengths and it has been shown that the interaction of a Gaussian beam with a sphere can result in attractive axial force under specific operational conditions. Results indicate the capability of manipulating and separating spherical spheres based on their mechanical and acoustical properties, the results provided here may provide a theoretical basis for development of single-beam acoustical tweezers.


    International Nuclear Information System (INIS)

    Cen, Renyue


    While the Sersic profile family provides adequate fits for the surface brightness profiles of observed galaxies, its physical origin is unknown. We show that if the cosmological density field is seeded by random Gaussian fluctuations, as in the standard cold dark matter model, galaxies with steep central profiles have simultaneously extended envelopes of shallow profiles in the outskirts, whereas galaxies with shallow central profiles are accompanied by steep density profiles in the outskirts. These properties are in accord with those of the Sersic profile family. Moreover, galaxies with steep central profiles form their central regions in smaller denser subunits that possibly merge subsequently, which naturally leads to the formation of bulges. In contrast, galaxies with shallow central profiles form their central regions in a coherent fashion without significant substructure, a necessary condition for disk galaxy formation. Thus, the scenario is self-consistent with respect to the correlation between observed galaxy morphology and the Sersic index. We further predict that clusters of galaxies should display a similar trend, which should be verifiable observationally

  18. Speckle phase near random surfaces (United States)

    Chen, Xiaoyi; Cheng, Chuanfu; An, Guoqiang; Han, Yujing; Rong, Zhenyu; Zhang, Li; Zhang, Meina


    Based on Kirchhoff approximation theory, the speckle phase near random surfaces with different roughness is numerically simulated. As expected, the properties of the speckle phase near the random surfaces are different from that in far field. In addition, as scattering distances and roughness increase, the average fluctuations of the speckle phase become larger. Unusually, the speckle phase is somewhat similar to the corresponding surface topography. We have performed experiments to verify the theoretical simulation results. Studies in this paper contribute to understanding the evolution of speckle phase near a random surface and provide a possible way to identify a random surface structure based on its speckle phase.

  19. Wegner estimates, Lifshitz tails, and Anderson localization for Gaussian random magnetic fields (United States)

    Ueki, Naomasa


    The Wegner estimate for the Hamiltonian of the Anderson model for the special Gaussian random magnetic field is extended to more general magnetic fields. The Lifshitz tail upper bounds of the integrated density of states as analyzed by Nakamura are reviewed and extended so that Gaussian random magnetic fields can be treated. By these and multiscale analysis, the Anderson localization at low energies is proven.

  20. A note on moving average models for Gaussian random fields

    DEFF Research Database (Denmark)

    Hansen, Linda Vadgård; Thorarinsdottir, Thordis L.

    basis, a general modeling framework which includes several types of non-Gaussian models. We propose a new one-parameter spatial correlation model which arises from a power kernel and show that the associated Hausdorff dimension of the sample paths can take any value between 2 and 3. As a result...

  1. Prediction of Geological Subsurfaces Based on Gaussian Random Field Models

    Energy Technology Data Exchange (ETDEWEB)

    Abrahamsen, Petter


    During the sixties, random functions became practical tools for predicting ore reserves with associated precision measures in the mining industry. This was the start of the geostatistical methods called kriging. These methods are used, for example, in petroleum exploration. This thesis reviews the possibilities for using Gaussian random functions in modelling of geological subsurfaces. It develops methods for including many sources of information and observations for precise prediction of the depth of geological subsurfaces. The simple properties of Gaussian distributions make it possible to calculate optimal predictors in the mean square sense. This is done in a discussion of kriging predictors. These predictors are then extended to deal with several subsurfaces simultaneously. It is shown how additional velocity observations can be used to improve predictions. The use of gradient data and even higher order derivatives are also considered and gradient data are used in an example. 130 refs., 44 figs., 12 tabs.

  2. Excitation Of A Funnel-Shape Optical Near Field By The Laguarre-Gaussian Doughnut Beam


    Iftiquar, S. M.; Ito, Haruhiko; Takamizawa, Akifumi; Ohtsu, Motoichi


    Optical near field has been generated by Laguarre-Gaussian doughnut beam on inner surface of "atom funnel". The resulting optical near field has been measured with the help of fiber probe and a consequent effect on cold atoms- released from MOT, has been estimated. Atoms with temperature less than 10 micro_kelvin can be reflected by the optical near field.

  3. Vectorial field propagation through high NA objectives using polarized Gaussian beam decomposition (United States)

    Worku, N.; Gross, H.


    Scalar fields can be propagated through non-paraxial systems using the Gaussian beam decomposition method. However, for high NA objectives, this scalar treatment is not sufficient to correctly describe the electromagnetic fields inside the focal region due to high ray bendings, which result in a significant change in the polarization state of light. To model these vectorial effects, the Gaussian beam decomposition method has to be extended to include the polarization state of light. In this work we have combined it with the three dimensional polarization ray tracing in order to propagate vectorial fields through high NA optical systems. During the Gaussian beam decomposition, the polarization state of each individual beamlet is represented by a polarization vector [𝐸𝑥, 𝐸𝑦, 𝐸𝑧 ] associated with its central ray. Individual Gaussian beams are then propagated through the system using the complex ray tracing method. The effect of the optical system on the polarization state of each beam is computed by applying the three dimensional polarization ray tracing of the corresponding central rays. Finally the individual beams are superposed coherently in the plane of interest resulting in the complete vectorial field. We apply the proposed method to compute the vectorial field inside the focal region of a high NA microscope objective lens and compare our result to the vectorial Debye integral method. We find that the Gaussian beam decomposition method overcomes serious limitations of algorithms relying on Fourier transforms, i.e. the field sampling requirements are less critical in high NA focusing and in the presence of large aberrations. However, sharp edges in the amplitude profile are difficult to handle as they should be replaced with smooth Gaussian edge.

  4. Super-Gaussian transport theory and the field-generating thermal instability in laser–plasmas

    International Nuclear Information System (INIS)

    Bissell, J J; Ridgers, C P; Kingham, R J


    Inverse bremsstrahlung (IB) heating is known to distort the electron distribution function in laser–plasmas from a Gaussian towards a super-Gaussian, thereby modifying the equations of classical transport theory (Ridgers et al 2008 Phys. Plasmas 15 092311). Here we explore these modified equations, demonstrating that super-Gaussian effects both suppress traditional transport processes, while simultaneously introducing new effects, such as isothermal (anomalous Nernst) magnetic field advection up gradients in the electron number density n e , which we associate with a novel heat-flow q n ∝∇n e . Suppression of classical phenomena is shown to be most pronounced in the limit of low Hall-parameter χ, in which case the Nernst effect is reduced by a factor of five, the ∇T e × ∇n e field generation mechanism by ∼30% (where T e is the electron temperature), and the diffusive and Righi–Leduc heat-flows by ∼80 and ∼90% respectively. The new isothermal field advection phenomenon and associated density-gradient driven heat-flux q n are checked against kinetic simulation using the Vlasov–Fokker–Planck code impact, and interpreted in relation to the underlying super-Gaussian distribution through simplified kinetic analysis. Given such strong inhibition of transport at low χ, we consider the impact of IB on the seeding and evolution of magnetic fields (in otherwise un-magnetized conditions) by examining the well-known field-generating thermal instability in the light of super-Gaussian transport theory (Tidman and Shanny 1974 Phys. Fluids 12 1207). Estimates based on conditions in an inertial confinement fusion (ICF) hohlraum suggest that super-Gaussian effects can reduce the growth-rate of the instability by ≳80%. This result may be important for ICF experiments, since by increasing the strength of IB heating it would appear possible to inhibit the spontaneous generation of large magnetic fields. (paper)

  5. Super-Gaussian transport theory and the field-generating thermal instability in laser-plasmas (United States)

    Bissell, J. J.; Ridgers, C. P.; Kingham, R. J.


    Inverse bremsstrahlung (IB) heating is known to distort the electron distribution function in laser-plasmas from a Gaussian towards a super-Gaussian, thereby modifying the equations of classical transport theory (Ridgers et al 2008 Phys. Plasmas 15 092311). Here we explore these modified equations, demonstrating that super-Gaussian effects both suppress traditional transport processes, while simultaneously introducing new effects, such as isothermal (anomalous Nernst) magnetic field advection up gradients in the electron number density ne, which we associate with a novel heat-flow qn∝∇ne. Suppression of classical phenomena is shown to be most pronounced in the limit of low Hall-parameter χ, in which case the Nernst effect is reduced by a factor of five, the ∇Te × ∇ne field generation mechanism by ˜30% (where Te is the electron temperature), and the diffusive and Righi-Leduc heat-flows by ˜80 and ˜90% respectively. The new isothermal field advection phenomenon and associated density-gradient driven heat-flux qn are checked against kinetic simulation using the Vlasov-Fokker-Planck code impact, and interpreted in relation to the underlying super-Gaussian distribution through simplified kinetic analysis. Given such strong inhibition of transport at low χ, we consider the impact of IB on the seeding and evolution of magnetic fields (in otherwise un-magnetized conditions) by examining the well-known field-generating thermal instability in the light of super-Gaussian transport theory (Tidman and Shanny 1974 Phys. Fluids 12 1207). Estimates based on conditions in an inertial confinement fusion (ICF) hohlraum suggest that super-Gaussian effects can reduce the growth-rate of the instability by ≳80%. This result may be important for ICF experiments, since by increasing the strength of IB heating it would appear possible to inhibit the spontaneous generation of large magnetic fields.

  6. Signed zeros of Gaussian vector fields - density, correlation functions and curvature

    CERN Document Server

    Foltin, G


    We calculate correlation functions of the (signed) density of zeros of Gaussian distributed vector fields. We are able to express correlation functions of arbitrary order through the curvature tensor of a certain abstract Riemann Cartan or Riemannian manifold. As an application, we discuss one- and two-point functions. The zeros of a two-dimensional Gaussian vector field model the distribution of topological defects in the high-temperature phase of two-dimensional systems with orientational degrees of freedom, such as superfluid films, thin superconductors and liquid crystals.

  7. Speckle suppression via sparse representation for wide-field imaging through turbid media. (United States)

    Jang, Hwanchol; Yoon, Changhyeong; Chung, Euiheon; Choi, Wonshik; Lee, Heung-No


    Speckle suppression is one of the most important tasks in the image transmission through turbid media. Insufficient speckle suppression requires an additional procedure such as temporal ensemble averaging over multiple exposures. In this paper, we consider the image recovery process based on the so-called transmission matrix (TM) of turbid media for the image transmission through the media. We show that the speckle left unremoved in the TM-based image recovery can be suppressed effectively via sparse representation (SR). SR is a relatively new signal reconstruction framework which works well even for ill-conditioned problems. This is the first study to show the benefit of using the SR as compared to the phase conjugation (PC) a de facto standard method to date for TM-based imaging through turbid media including a live cell through tissue slice.

  8. State of the Art of X-ray Speckle-Based Phase-Contrast and Dark-Field Imaging

    Directory of Open Access Journals (Sweden)

    Marie-Christine Zdora


    Full Text Available In the past few years, X-ray phase-contrast and dark-field imaging have evolved to be invaluable tools for non-destructive sample visualisation, delivering information inaccessible by conventional absorption imaging. X-ray phase-sensing techniques are furthermore increasingly used for at-wavelength metrology and optics characterisation. One of the latest additions to the group of differential phase-contrast methods is the X-ray speckle-based technique. It has drawn significant attention due to its simple and flexible experimental arrangement, cost-effectiveness and multimodal character, amongst others. Since its first demonstration at highly brilliant synchrotron sources, the method has seen rapid development, including the translation to polychromatic laboratory sources and extension to higher-energy X-rays. Recently, different advanced acquisition schemes have been proposed to tackle some of the main limitations of previous implementations. Current applications of the speckle-based method range from optics characterisation and wavefront measurement to biomedical imaging and materials science. This review provides an overview of the state of the art of the X-ray speckle-based technique. Its basic principles and different experimental implementations as well as the the latest advances and applications are illustrated. In the end, an outlook for anticipated future developments of this promising technique is given.

  9. Theory and generation of conditional, scalable sub-Gaussian random fields (United States)

    Panzeri, M.; Riva, M.; Guadagnini, A.; Neuman, S. P.


    Many earth and environmental (as well as a host of other) variables, Y, and their spatial (or temporal) increments, ΔY, exhibit non-Gaussian statistical scaling. Previously we were able to capture key aspects of such non-Gaussian scaling by treating Y and/or ΔY as sub-Gaussian random fields (or processes). This however left unaddressed the empirical finding that whereas sample frequency distributions of Y tend to display relatively mild non-Gaussian peaks and tails, those of ΔY often reveal peaks that grow sharper and tails that become heavier with decreasing separation distance or lag. Recently we proposed a generalized sub-Gaussian model (GSG) which resolves this apparent inconsistency between the statistical scaling behaviors of observed variables and their increments. We presented an algorithm to generate unconditional random realizations of statistically isotropic or anisotropic GSG functions and illustrated it in two dimensions. Most importantly, we demonstrated the feasibility of estimating all parameters of a GSG model underlying a single realization of Y by analyzing jointly spatial moments of Y data and corresponding increments, ΔY. Here, we extend our GSG model to account for noisy measurements of Y at a discrete set of points in space (or time), present an algorithm to generate conditional realizations of corresponding isotropic or anisotropic random fields, introduce two approximate versions of this algorithm to reduce CPU time, and explore them on one and two-dimensional synthetic test cases.

  10. Interplay of nonclassicality and entanglement of two-mode Gaussian fields generated in optical parametric processes

    Czech Academy of Sciences Publication Activity Database

    Arkhipov, Ie.I.; Peřina, Jan; Peřina, J.; Miranowicz, A.


    Roč. 94, č. 1 (2016), 1-15, č. článku 013807. ISSN 2469-9926 R&D Projects: GA ČR GAP205/12/0382 Institutional support: RVO:68378271 Keywords : two-mode Gaussian fields * optical parametric processes Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.925, year: 2016


    International Nuclear Information System (INIS)

    James, J. Berian


    We report a technique to calculate the impact of distinct physical processes inducing non-Gaussianity on the cosmological density field. A natural decomposition of the cosmic genus statistic into an orthogonal polynomial sequence allows complete expression of the scale-dependent evolution of the topology of large-scale structure, in which effects including galaxy bias, nonlinear gravitational evolution, and primordial non-Gaussianity may be delineated. The relationship of this decomposition to previous methods for analyzing the genus statistic is briefly considered and the following applications are made: (1) the expression of certain systematics affecting topological measurements, (2) the quantification of broad deformations from Gaussianity that appear in the genus statistic as measured in the Horizon Run simulation, and (3) the study of the evolution of the genus curve for simulations with primordial non-Gaussianity. These advances improve the treatment of flux-limited galaxy catalogs for use with this measurement and further the use of the genus statistic as a tool for exploring non-Gaussianity.


    Energy Technology Data Exchange (ETDEWEB)

    Snodin, A. P. [Department of Mathematics, Faculty of Applied Science, King Mongkut’s University of Technology North Bangkok, Bangkok 10800 (Thailand); Ruffolo, D. [Department of Physics, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand); Matthaeus, W. H. [Bartol Research Institute and Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)


    The magnetic field line random walk (FLRW) plays an important role in the transport of energy and particles in turbulent plasmas. For magnetic fluctuations that are transverse or almost transverse to a large-scale mean magnetic field, theories describing the FLRW usually predict asymptotic diffusion of magnetic field lines perpendicular to the mean field. Such theories often depend on the assumption that one can relate the Lagrangian and Eulerian statistics of the magnetic field via Corrsin’s hypothesis, and additionally take the distribution of magnetic field line displacements to be Gaussian. Here we take an ordinary differential equation (ODE) model with these underlying assumptions and test how well it describes the evolution of the magnetic field line diffusion coefficient in 2D+slab magnetic turbulence, by comparisons to computer simulations that do not involve such assumptions. In addition, we directly test the accuracy of the Corrsin approximation to the Lagrangian correlation. Over much of the studied parameter space we find that the ODE model is in fairly good agreement with computer simulations, in terms of both the evolution and asymptotic values of the diffusion coefficient. When there is poor agreement, we show that this can be largely attributed to the failure of Corrsin’s hypothesis rather than the assumption of Gaussian statistics of field line displacements. The degree of non-Gaussianity, which we measure in terms of the kurtosis, appears to be an indicator of how well Corrsin’s approximation works.

  13. Laser speckle contrast imaging in biomedical optics. (United States)

    Boas, David A; Dunn, Andrew K


    First introduced in the 1980s, laser speckle contrast imaging is a powerful tool for full-field imaging of blood flow. Recently laser speckle contrast imaging has gained increased attention, in part due to its rapid adoption for blood flow studies in the brain. We review the underlying physics of speckle contrast imaging and discuss recent developments to improve the quantitative accuracy of blood flow measures. We also review applications of laser speckle contrast imaging in neuroscience, dermatology and ophthalmology.

  14. Reversible wavefront shaping between Gaussian and Airy beams by mimicking gravitational field (United States)

    Wang, Xiangyang; Liu, Hui; Sheng, Chong; Zhu, Shining


    In this paper, we experimentally demonstrate reversible wavefront shaping through mimicking gravitational field. A gradient-index micro-structured optical waveguide with special refractive index profile was constructed whose effective index satisfying a gravitational field profile. Inside the waveguide, an incident broad Gaussian beam is firstly transformed into an accelerating beam, and the generated accelerating beam is gradually changed back to a Gaussian beam afterwards. To validate our experiment, we performed full-wave continuum simulations that agree with the experimental results. Furthermore, a theoretical model was established to describe the evolution of the laser beam based on Landau’s method, showing that the accelerating beam behaves like the Airy beam in the small range in which the linear potential approaches zero. To our knowledge, such a reversible wavefront shaping technique has not been reported before.

  15. Non-Gaussian statistics, classical field theory, and realizable Langevin models

    International Nuclear Information System (INIS)

    Krommes, J.A.


    The direct-interaction approximation (DIA) to the fourth-order statistic Z ∼ left-angle λψ 2 ) 2 right-angle, where λ is a specified operator and ψ is a random field, is discussed from several points of view distinct from that of Chen et al. [Phys. Fluids A 1, 1844 (1989)]. It is shown that the formula for Z DIA already appeared in the seminal work of Martin, Siggia, and Rose (Phys. Rev. A 8, 423 (1973)] on the functional approach to classical statistical dynamics. It does not follow from the original generalized Langevin equation (GLE) of Leith [J. Atmos. Sd. 28, 145 (1971)] and Kraichnan [J. Fluid Mech. 41, 189 (1970)] (frequently described as an amplitude representation for the DIA), in which the random forcing is realized by a particular superposition of products of random variables. The relationship of that GLE to renormalized field theories with non-Gaussian corrections (''spurious vertices'') is described. It is shown how to derive an improved representation, that realizes cumulants through O(ψ 4 ), by adding to the GLE a particular non-Gaussian correction. A Markovian approximation Z DIA M to Z DIA is derived. Both Z DIA and Z DIA M incorrectly predict a Gaussian kurtosis for the steady state of a solvable three-mode example

  16. Field dose radiation determination by active learning with Gaussian Process for autonomous robot guiding

    International Nuclear Information System (INIS)

    Freitas Naiff, Danilo de; Silveira, Paulo R.; Pereira, Claudio M.N.A.


    This article proposes an approach for determination of radiation dose pro le in a radiation-susceptible environment, aiming to guide an autonomous robot in acting on those environments, reducing the human exposure to dangerous amount of dose. The approach consists of an active learning method based on information entropy reduction, using log-normally warped Gaussian Process (GP) as surrogate model, resulting in non-linear online regression with sequential measurements. Experiments with simulated radiation dose fields of varying complexity were made, and results showed that the approach was effective in reconstruct the eld with high accuracy, through relatively few measurements. The technique was also shown some robustness in presence measurement noise, present in real measurements, by assuming Gaussian noise. (author)

  17. Field dose radiation determination by active learning with Gaussian Process for autonomous robot guiding

    Energy Technology Data Exchange (ETDEWEB)

    Freitas Naiff, Danilo de; Silveira, Paulo R.; Pereira, Claudio M.N.A., E-mail:, E-mail:, E-mail: [Coordenacao de Pos-Graduacao e Pesquisa de Engenharia (PEN/COPPE/UFRJ), Rio de Janeiro, RJ (Brazil); Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil)


    This article proposes an approach for determination of radiation dose pro le in a radiation-susceptible environment, aiming to guide an autonomous robot in acting on those environments, reducing the human exposure to dangerous amount of dose. The approach consists of an active learning method based on information entropy reduction, using log-normally warped Gaussian Process (GP) as surrogate model, resulting in non-linear online regression with sequential measurements. Experiments with simulated radiation dose fields of varying complexity were made, and results showed that the approach was effective in reconstruct the eld with high accuracy, through relatively few measurements. The technique was also shown some robustness in presence measurement noise, present in real measurements, by assuming Gaussian noise. (author)

  18. Speckle interferometry (United States)

    Sirohi, Rajpal S.


    Illumination of a rough surface by a coherent monochromatic wave creates a grainy structure in space termed a speckle pattern. It was considered a special kind of noise and was the bane of holographers. However, its information-carrying property was soon discovered and the phenomenon was used for metrological applications. The realization that a speckle pattern carried information led to a new measurement technique known as speckle interferometry (SI). Although the speckle phenomenon in itself is a consequence of interference among numerous randomly dephased waves, a reference wave is required in SI. Further, it employs an imaging geometry. Initially SI was performed mostly by using silver emulsions as the recording media. The double-exposure specklegram was filtered to extract the desired information. Since SI can be configured so as to be sensitive to the in-plane displacement component, the out-of-plane displacement component or their derivatives, the interferograms corresponding to these were extracted from the specklegram for further analysis. Since the speckle size can be controlled by the F number of the imaging lens, it was soon realized that SI could be performed with electronic detection, thereby increasing its accuracy and speed of measurement. Furthermore, a phase-shifting technique can also be incorporated. This technique came to be known as electronic speckle pattern interferometry (ESPI). It employed the same experimental configurations as SI. ESPI found many industrial applications as it supplements holographic interferometry. We present three examples covering diverse areas. In one application it has been used to measure residual stress in a blank recordable compact disk. In another application, microscopic ESPI has been used to study the influence of relative humidity on paint-coated figurines and also the effect of a conservation agent applied on top of this. The final application is to find the defects in pipes. These diverse applications

  19. Excitation kinetics of impurity doped quantum dot driven by Gaussian white noise: Interplay with external field

    Energy Technology Data Exchange (ETDEWEB)

    Pal, Suvajit [Department of Chemistry, Hetampur Raj High School, Hetampur, Birbhum 731124, West Bengal (India); Sinha, Sudarson Sekhar [Department of Chemistry and Biochemistry, Jackson State University, Mississippi, MS 39217-0510 (United States); Ganguly, Jayanta [Department of Chemistry, Brahmankhanda Basapara High School, Basapara, Birbhum 731215, West Bengal (India); Ghosh, Manas, E-mail: [Department of Chemistry, Physical Chemistry Section, Visva Bharati University, Santiniketan, Birbhum 731 235, West Bengal (India)


    Highlights: • The excitation kinetics of impurity doped quantum dot has been investigated. • The dot is subject to Gaussian white noise. • External oscillatory field is also applied. • Noise strength and field intensity fabricate the kinetics. • Role of dopant location has also been analyzed. - Abstract: We investigate the excitation kinetics of a repulsive impurity doped quantum dot initiated by simultaneous application of Gaussian white noise and external sinusoidal field. We have considered both additive and multiplicative noise (in Stratonovich sense). The combined influences of noise strength (ζ) and the field intensity (∊) have been capsuled by invoking their ratio (η). The said ratio and the dopant location have been found to fabricate the kinetics in a delicate way. Moreover, the influences of additive and multiplicative nature of the noise on the excitation kinetics have been observed to be widely different. The investigation reveals emergence of maximization/minimization and saturation in the excitation kinetics as a result of complex interplay between η and the dopant coordinate (r{sub 0}). The present investigation is believed to provide some useful insights in the functioning of mesoscopic devices where noise plays some significant role.

  20. Excitation kinetics of impurity doped quantum dot driven by Gaussian white noise: Interplay with external field

    International Nuclear Information System (INIS)

    Pal, Suvajit; Sinha, Sudarson Sekhar; Ganguly, Jayanta; Ghosh, Manas


    Highlights: • The excitation kinetics of impurity doped quantum dot has been investigated. • The dot is subject to Gaussian white noise. • External oscillatory field is also applied. • Noise strength and field intensity fabricate the kinetics. • Role of dopant location has also been analyzed. - Abstract: We investigate the excitation kinetics of a repulsive impurity doped quantum dot initiated by simultaneous application of Gaussian white noise and external sinusoidal field. We have considered both additive and multiplicative noise (in Stratonovich sense). The combined influences of noise strength (ζ) and the field intensity (∊) have been capsuled by invoking their ratio (η). The said ratio and the dopant location have been found to fabricate the kinetics in a delicate way. Moreover, the influences of additive and multiplicative nature of the noise on the excitation kinetics have been observed to be widely different. The investigation reveals emergence of maximization/minimization and saturation in the excitation kinetics as a result of complex interplay between η and the dopant coordinate (r 0 ). The present investigation is believed to provide some useful insights in the functioning of mesoscopic devices where noise plays some significant role

  1. Using convex quadratic programming to model random media with Gaussian random fields

    International Nuclear Information System (INIS)

    Quintanilla, John A.; Jones, W. Max


    Excursion sets of Gaussian random fields (GRFs) have been frequently used in the literature to model two-phase random media with measurable phase autocorrelation functions. The goal of successful modeling is finding the optimal field autocorrelation function that best approximates the prescribed phase autocorrelation function. In this paper, we present a technique which uses convex quadratic programming to find the best admissible field autocorrelation function under a prescribed discretization. Unlike previous methods, this technique efficiently optimizes over all admissible field autocorrelation functions, instead of optimizing only over a predetermined parametrized family. The results from using this technique indicate that the GRF model is significantly more versatile than observed in previous studies. An application to modeling a base-catalyzed tetraethoxysilane aerogel system given small-angle neutron scattering data is also presented

  2. Non-Gaussianity and statistical anisotropy from vector field populated inflationary models

    CERN Document Server

    Dimastrogiovanni, Emanuela; Matarrese, Sabino; Riotto, Antonio


    We present a review of vector field models of inflation and, in particular, of the statistical anisotropy and non-Gaussianity predictions of models with SU(2) vector multiplets. Non-Abelian gauge groups introduce a richer amount of predictions compared to the Abelian ones, mostly because of the presence of vector fields self-interactions. Primordial vector fields can violate isotropy leaving their imprint in the comoving curvature fluctuations zeta at late times. We provide the analytic expressions of the correlation functions of zeta up to fourth order and an analysis of their amplitudes and shapes. The statistical anisotropy signatures expected in these models are important and, potentially, the anisotropic contributions to the bispectrum and the trispectrum can overcome the isotropic parts.

  3. Multi-fidelity Gaussian process regression for prediction of random fields

    Energy Technology Data Exchange (ETDEWEB)

    Parussini, L. [Department of Engineering and Architecture, University of Trieste (Italy); Venturi, D., E-mail: [Department of Applied Mathematics and Statistics, University of California Santa Cruz (United States); Perdikaris, P. [Department of Mechanical Engineering, Massachusetts Institute of Technology (United States); Karniadakis, G.E. [Division of Applied Mathematics, Brown University (United States)


    We propose a new multi-fidelity Gaussian process regression (GPR) approach for prediction of random fields based on observations of surrogate models or hierarchies of surrogate models. Our method builds upon recent work on recursive Bayesian techniques, in particular recursive co-kriging, and extends it to vector-valued fields and various types of covariances, including separable and non-separable ones. The framework we propose is general and can be used to perform uncertainty propagation and quantification in model-based simulations, multi-fidelity data fusion, and surrogate-based optimization. We demonstrate the effectiveness of the proposed recursive GPR techniques through various examples. Specifically, we study the stochastic Burgers equation and the stochastic Oberbeck–Boussinesq equations describing natural convection within a square enclosure. In both cases we find that the standard deviation of the Gaussian predictors as well as the absolute errors relative to benchmark stochastic solutions are very small, suggesting that the proposed multi-fidelity GPR approaches can yield highly accurate results.

  4. Multi-fidelity Gaussian process regression for prediction of random fields

    International Nuclear Information System (INIS)

    Parussini, L.; Venturi, D.; Perdikaris, P.; Karniadakis, G.E.


    We propose a new multi-fidelity Gaussian process regression (GPR) approach for prediction of random fields based on observations of surrogate models or hierarchies of surrogate models. Our method builds upon recent work on recursive Bayesian techniques, in particular recursive co-kriging, and extends it to vector-valued fields and various types of covariances, including separable and non-separable ones. The framework we propose is general and can be used to perform uncertainty propagation and quantification in model-based simulations, multi-fidelity data fusion, and surrogate-based optimization. We demonstrate the effectiveness of the proposed recursive GPR techniques through various examples. Specifically, we study the stochastic Burgers equation and the stochastic Oberbeck–Boussinesq equations describing natural convection within a square enclosure. In both cases we find that the standard deviation of the Gaussian predictors as well as the absolute errors relative to benchmark stochastic solutions are very small, suggesting that the proposed multi-fidelity GPR approaches can yield highly accurate results.

  5. Full-field displacement and strain measurement of small complex bony structures with digital speckle pattern interferometry and shearography (United States)

    Soons, Joris; Dirckx, Joris J. J.


    We have developed a simple digital speckle pattern interferometry (DSPI) and shearography setup to measure the displacement and the corresponding strains of small complex bony structures. We choose both optical techniques because we want to obtain very small deformations (+/- 20 μm) of small objects (+/- 1cm). Furthermore full field and in situ measurements are preferred. We first use a Michelson DSPI arrangement with phase shifting. In this way we can obtain the out-of-plane displacements precisely. Second, shearography is introduced to measure the derivative of the out-ofplane displacement. In this way some intrinsic disadvantages of DSPI can be overcome. We have developed these setups to measure the out-of-plane deformations of (small) bird beaks when realistic external forces are applied. In this way, we have a full field validation measurement to which we can compare the outcome of realistic finite element models. The aim is to determine whether the shape, and not only the size, of the bird beaks are optimized to deal with the biting forces that a species encounters. This quantitative analysis will help biologists to investigate if beak morphology is adapted to feeding habits. Applying the method to the famous evolution model of the Darwin's finches will provide scientific proof of functional evolution. In this paper we will present both the DSPI and shearography setup, a comparison of the performance of both techniques on a simple deflection of a cantilever beam and the first results obtained on loaded bird beaks.

  6. Optimized digital speckle patterns for digital image correlation by consideration of both accuracy and efficiency. (United States)

    Chen, Zhenning; Shao, Xinxing; Xu, Xiangyang; He, Xiaoyuan


    The technique of digital image correlation (DIC), which has been widely used for noncontact deformation measurements in both the scientific and engineering fields, is greatly affected by the quality of speckle patterns in terms of its performance. This study was concerned with the optimization of the digital speckle pattern (DSP) for DIC in consideration of both the accuracy and efficiency. The root-mean-square error of the inverse compositional Gauss-Newton algorithm and the average number of iterations were used as quality metrics. Moreover, the influence of subset sizes and the noise level of images, which are the basic parameters in the quality assessment formulations, were also considered. The simulated binary speckle patterns were first compared with the Gaussian speckle patterns and captured DSPs. Both the single-radius and multi-radius DSPs were optimized. Experimental tests and analyses were conducted to obtain the optimized and recommended DSP. The vector diagram of the optimized speckle pattern was also uploaded as reference.

  7. A biorthogonal decomposition for the identification and simulation of non-stationary and non-Gaussian random fields

    Energy Technology Data Exchange (ETDEWEB)

    Zentner, I. [IMSIA, UMR EDF-ENSTA-CNRS-CEA 9219, Université Paris-Saclay, 828 Boulevard des Maréchaux, 91762 Palaiseau Cedex (France); Ferré, G., E-mail: [CERMICS – Ecole des Ponts ParisTech, 6 et 8 avenue Blaise Pascal, Cité Descartes, Champs sur Marne, 77455 Marne la Vallée Cedex 2 (France); Poirion, F. [Department of Structural Dynamics and Aeroelasticity, ONERA, BP 72, 29 avenue de la Division Leclerc, 92322 Chatillon Cedex (France); Benoit, M. [Institut de Recherche sur les Phénomènes Hors Equilibre (IRPHE), UMR 7342 (CNRS, Aix-Marseille Université, Ecole Centrale Marseille), 49 rue Frédéric Joliot-Curie, BP 146, 13384 Marseille Cedex 13 (France)


    In this paper, a new method for the identification and simulation of non-Gaussian and non-stationary stochastic fields given a database is proposed. It is based on two successive biorthogonal decompositions aiming at representing spatio–temporal stochastic fields. The proposed double expansion allows to build the model even in the case of large-size problems by separating the time, space and random parts of the field. A Gaussian kernel estimator is used to simulate the high dimensional set of random variables appearing in the decomposition. The capability of the method to reproduce the non-stationary and non-Gaussian features of random phenomena is illustrated by applications to earthquakes (seismic ground motion) and sea states (wave heights).

  8. Statistics of spatially integrated speckle intensity difference

    DEFF Research Database (Denmark)

    Hanson, Steen Grüner; Yura, Harold


    We consider the statistics of the spatially integrated speckle intensity difference obtained from two separated finite collecting apertures. For fully developed speckle, closed-form analytic solutions for both the probability density function and the cumulative distribution function are derived h...... here for both arbitrary values of the mean number of speckles contained within an aperture and the degree of coherence of the optical field. Additionally, closed-form expressions are obtained for the corresponding nth statistical moments....

  9. Solvation in atomic liquids: connection between Gaussian field theory and density functional theory

    Directory of Open Access Journals (Sweden)

    V. Sergiievskyi


    Full Text Available For the problem of molecular solvation, formulated as a liquid submitted to the external potential field created by a molecular solute of arbitrary shape dissolved in that solvent, we draw a connection between the Gaussian field theory derived by David Chandler [Phys. Rev. E, 1993, 48, 2898] and classical density functional theory. We show that Chandler's results concerning the solvation of a hard core of arbitrary shape can be recovered by either minimising a linearised HNC functional using an auxiliary Lagrange multiplier field to impose a vanishing density inside the core, or by minimising this functional directly outside the core — indeed a simpler procedure. Those equivalent approaches are compared to two other variants of DFT, either in the HNC, or partially linearised HNC approximation, for the solvation of a Lennard-Jones solute of increasing size in a Lennard-Jones solvent. Compared to Monte-Carlo simulations, all those theories give acceptable results for the inhomogeneous solvent structure, but are completely out-of-range for the solvation free-energies. This can be fixed in DFT by adding a hard-sphere bridge correction to the HNC functional.

  10. Accurate and balanced anisotropic Gaussian type orbital basis sets for atoms in strong magnetic fields (United States)

    Zhu, Wuming; Trickey, S. B.


    In high magnetic field calculations, anisotropic Gaussian type orbital (AGTO) basis functions are capable of reconciling the competing demands of the spherically symmetric Coulombic interaction and cylindrical magnetic (B field) confinement. However, the best available a priori procedure for composing highly accurate AGTO sets for atoms in a strong B field [W. Zhu et al., Phys. Rev. A 90, 022504 (2014)] yields very large basis sets. Their size is problematical for use in any calculation with unfavorable computational cost scaling. Here we provide an alternative constructive procedure. It is based upon analysis of the underlying physics of atoms in B fields that allow identification of several principles for the construction of AGTO basis sets. Aided by numerical optimization and parameter fitting, followed by fine tuning of fitting parameters, we devise formulae for generating accurate AGTO basis sets in an arbitrary B field. For the hydrogen iso-electronic sequence, a set depends on B field strength, nuclear charge, and orbital quantum numbers. For multi-electron systems, the basis set formulae also include adjustment to account for orbital occupations. Tests of the new basis sets for atoms H through C (1 ≤ Z ≤ 6) and ions Li+, Be+, and B+, in a wide B field range (0 ≤ B ≤ 2000 a.u.), show an accuracy better than a few μhartree for single-electron systems and a few hundredths to a few mHs for multi-electron atoms. The relative errors are similar for different atoms and ions in a large B field range, from a few to a couple of tens of millionths, thereby confirming rather uniform accuracy across the nuclear charge Z and B field strength values. Residual basis set errors are two to three orders of magnitude smaller than the electronic correlation energies in multi-electron atoms, a signal of the usefulness of the new AGTO basis sets in correlated wavefunction or density functional calculations for atomic and molecular systems in an external strong B field.

  11. Accurate and balanced anisotropic Gaussian type orbital basis sets for atoms in strong magnetic fields. (United States)

    Zhu, Wuming; Trickey, S B


    In high magnetic field calculations, anisotropic Gaussian type orbital (AGTO) basis functions are capable of reconciling the competing demands of the spherically symmetric Coulombic interaction and cylindrical magnetic (B field) confinement. However, the best available a priori procedure for composing highly accurate AGTO sets for atoms in a strong B field [W. Zhu et al., Phys. Rev. A 90, 022504 (2014)] yields very large basis sets. Their size is problematical for use in any calculation with unfavorable computational cost scaling. Here we provide an alternative constructive procedure. It is based upon analysis of the underlying physics of atoms in B fields that allow identification of several principles for the construction of AGTO basis sets. Aided by numerical optimization and parameter fitting, followed by fine tuning of fitting parameters, we devise formulae for generating accurate AGTO basis sets in an arbitrary B field. For the hydrogen iso-electronic sequence, a set depends on B field strength, nuclear charge, and orbital quantum numbers. For multi-electron systems, the basis set formulae also include adjustment to account for orbital occupations. Tests of the new basis sets for atoms H through C (1 ≤ Z ≤ 6) and ions Li + , Be + , and B + , in a wide B field range (0 ≤ B ≤ 2000 a.u.), show an accuracy better than a few μhartree for single-electron systems and a few hundredths to a few mHs for multi-electron atoms. The relative errors are similar for different atoms and ions in a large B field range, from a few to a couple of tens of millionths, thereby confirming rather uniform accuracy across the nuclear charge Z and B field strength values. Residual basis set errors are two to three orders of magnitude smaller than the electronic correlation energies in multi-electron atoms, a signal of the usefulness of the new AGTO basis sets in correlated wavefunction or density functional calculations for atomic and molecular systems in an external strong B

  12. Exploitation of the speckle field statistics as an aid to diagnosis of the acute irradiation cutaneous syndrome: comparison of biophysical and biological results

    International Nuclear Information System (INIS)

    Carvalho, O.


    The objective of this research thesis is to demonstrate the possibility of using a non-invasive optical method for the in-vivo diagnosis and prognosis of the acute irradiation cutaneous syndrome. The author first describes the choice of an optical investigation method for application in dermatology. A conventional frequency analysis of the speckle field sampling is completed by a stochastic approach in order to extract parameters which characterize speckle patterns. An experimental protocol is then tested in order to better understand the parameter behaviour with respect to some physical properties of synthetic diffusing media. The author then reports the in-vivo application of this method to the acute irradiation cutaneous syndrome in the case of swine. Results obtained on several animals demonstrate the possibility of discrimination between irradiated areas of normal areas several weeks before the emergence of the first clinical signs. The author tries to understand the results obtained on a radiological burn comparing with histological results. A correlation appears between speckle parameters and histological analysis. Results are also compared with those obtained on other tested media

  13. Speckle averaging system for laser raster-scan image projection (United States)

    Tiszauer, Detlev H.; Hackel, Lloyd A.


    The viewers' perception of laser speckle in a laser-scanned image projection system is modified or eliminated by the addition of an optical deflection system that effectively presents a new speckle realization at each point on the viewing screen to each viewer for every scan across the field. The speckle averaging is accomplished without introduction of spurious imaging artifacts.

  14. Discriminative learning of receptive fields from responses to non-Gaussian stimulus ensembles.

    Directory of Open Access Journals (Sweden)

    Arne F Meyer

    Full Text Available Analysis of sensory neurons' processing characteristics requires simultaneous measurement of presented stimuli and concurrent spike responses. The functional transformation from high-dimensional stimulus space to the binary space of spike and non-spike responses is commonly described with linear-nonlinear models, whose linear filter component describes the neuron's receptive field. From a machine learning perspective, this corresponds to the binary classification problem of discriminating spike-eliciting from non-spike-eliciting stimulus examples. The classification-based receptive field (CbRF estimation method proposed here adapts a linear large-margin classifier to optimally predict experimental stimulus-response data and subsequently interprets learned classifier weights as the neuron's receptive field filter. Computational learning theory provides a theoretical framework for learning from data and guarantees optimality in the sense that the risk of erroneously assigning a spike-eliciting stimulus example to the non-spike class (and vice versa is minimized. Efficacy of the CbRF method is validated with simulations and for auditory spectro-temporal receptive field (STRF estimation from experimental recordings in the auditory midbrain of Mongolian gerbils. Acoustic stimulation is performed with frequency-modulated tone complexes that mimic properties of natural stimuli, specifically non-Gaussian amplitude distribution and higher-order correlations. Results demonstrate that the proposed approach successfully identifies correct underlying STRFs, even in cases where second-order methods based on the spike-triggered average (STA do not. Applied to small data samples, the method is shown to converge on smaller amounts of experimental recordings and with lower estimation variance than the generalized linear model and recent information theoretic methods. Thus, CbRF estimation may prove useful for investigation of neuronal processes in response to

  15. Statistics on gene-based laser speckles with a small number of scatterers: implications for the detection of polymorphism in the Chlamydia trachomatis omp1 gene (United States)

    Ulyanov, Sergey S.; Ulianova, Onega V.; Zaytsev, Sergey S.; Saltykov, Yury V.; Feodorova, Valentina A.


    The transformation mechanism for a nucleotide sequence of the Chlamydia trachomatis gene into a speckle pattern has been considered. The first and second-order statistics of gene-based speckles have been analyzed. It has been demonstrated that gene-based speckles do not obey Gaussian statistics and belong to the class of speckles with a small number of scatterers. It has been shown that gene polymorphism can be easily detected through analysis of the statistical characteristics of gene-based speckles.

  16. Superpositions of higher-order bessel beams and nondiffracting speckle fields - (SAIP 2009)

    CSIR Research Space (South Africa)

    Dudley, Angela L


    Full Text Available stream_source_info Dudley_d2_2009.pdf.txt stream_content_type text/plain stream_size 9714 Content-Encoding UTF-8 stream_name Dudley_d2_2009.pdf.txt Content-Type text/plain; charset=UTF-8 Superpositions of Higher... (1987). [4] P. A. Khilo, L. I. Kramoreva, and N. A. Khilo, “Optically controlled rotation of multibeam light field,” Proc. SPIE Vol. 4358, 250-253 (2001). Figure 1: (a): The experiment developed by Durnin[3] to generate a zero order Bessel beam...

  17. On the representation of the diffracted field of Hermite-Gaussian modes in an alien basis and the young diffraction principle

    International Nuclear Information System (INIS)

    Smirnov, V.N.; Strokovskii, G.A.


    An analytical form of expansion coefficients of a diffracted field for an arbitrary Hermite-Gaussian beam in an alien Hermite-Gaussian basis is obtained. A possible physical interpretation of the well-known Young phenomenological diffraction principle and experiments on diffraction of Hermite-Gaussian beams of the lowest types (n = 0 - 5) from half-plane are discussed. The case of nearly homogenous expansion corresponding to misalignment and mismatch of optical systems is also analyzed. 7 refs., 2 figs

  18. Full-field mapping of internal strain distribution in red sandstone specimen under compression using digital volumetric speckle photography and X-ray computed tomography

    Directory of Open Access Journals (Sweden)

    Lingtao Mao


    Full Text Available It is always desirable to know the interior deformation pattern when a rock is subjected to mechanical load. Few experimental techniques exist that can represent full-field three-dimensional (3D strain distribution inside a rock specimen. And yet it is crucial that this information is available for fully understanding the failure mechanism of rocks or other geomaterials. In this study, by using the newly developed digital volumetric speckle photography (DVSP technique in conjunction with X-ray computed tomography (CT and taking advantage of natural 3D speckles formed inside the rock due to material impurities and voids, we can probe the interior of a rock to map its deformation pattern under load and shed light on its failure mechanism. We apply this technique to the analysis of a red sandstone specimen under increasing uniaxial compressive load applied incrementally. The full-field 3D displacement fields are obtained in the specimen as a function of the load, from which both the volumetric and the deviatoric strain fields are calculated. Strain localization zones which lead to the eventual failure of the rock are identified. The results indicate that both shear and tension are contributing factors to the failure mechanism.


    Directory of Open Access Journals (Sweden)

    F. J. Aguilar


    Full Text Available Digital Elevation Models (DEMs are considered as one of the most relevant geospatial data to carry out land-cover and land-use classification. This work deals with the application of a mathematical framework based on a Gaussian Markov Random Field (GMRF to interpolate grid DEMs from scattered elevation data. The performance of the GMRF interpolation model was tested on a set of LiDAR data (0.87 points/m2 provided by the Spanish Government (PNOA Programme over a complex working area mainly covered by greenhouses in Almería, Spain. The original LiDAR data was decimated by randomly removing different fractions of the original points (from 10% to up to 99% of points removed. In every case, the remaining points (scattered observed points were used to obtain a 1 m grid spacing GMRF-interpolated Digital Surface Model (DSM whose accuracy was assessed by means of the set of previously extracted checkpoints. The GMRF accuracy results were compared with those provided by the widely known Triangulation with Linear Interpolation (TLI. Finally, the GMRF method was applied to a real-world case consisting of filling the LiDAR-derived DSM gaps after manually filtering out non-ground points to obtain a Digital Terrain Model (DTM. Regarding accuracy, both GMRF and TLI produced visually pleasing and similar results in terms of vertical accuracy. As an added bonus, the GMRF mathematical framework makes possible to both retrieve the estimated uncertainty for every interpolated elevation point (the DEM uncertainty and include break lines or terrain discontinuities between adjacent cells to produce higher quality DTMs.

  20. Microscopy using randomized speckle illumination (United States)

    Perinchery, Sandeep M.; Shinde, Anant; Murukeshan, V. M.


    It is well known for structured illumination microscopy (SIM) that the lateral resolution by a factor of two beyond the classical diffraction limit is achieved using spatially structured illumination in wide-field fluorescence microscope. In the state of art SIM systems, grating patterns are generally generated by physical gratings or by spatial light modulators such as digital micro mirrors (DMD), liquid crystal displays (LCD). In this study, using a combination of LCD and ground glasses, size controlled randomized speckle patterns are generated as an illumination source for the microscope. Proof of concept of using speckle illumination in SIM configuration is tested by imaging fixed BPAE cells.

  1. Microarray analyzer based on wide field fluorescent microscopy with laser illumination and a device for speckle suppression (United States)

    Lysov, Yuri; Barsky, Victor; Urasov, Dmitriy; Urasov, Roman; Cherepanov, Alecksey; Mamaev, Dmitryi; Yegorov, Yegor; Chudinov, Alexander; Surzhikov, Sergey; Rubina, Alla; Smoldovskaya, Olga; Zasedatelev, Alexander


    A microarray analyzer was developed to obtain images and measure the fluorescence intensity of microarrays at three wavelengths from 380 nm to 850 nm. The analyzer contains lasers to excite fluorescence, barrier filters, optics to project images on an image detector, and a device for suppressing laser speckles on the microarray support. The speckle suppression device contains a fibre-optic bundle and a rotating mirror positioned in a way to change the distance between the bundle butt and mirror surface during each mirror revolution. The analyzer provides for measurements with accuracy within ± 5%. Obtaining images at several exposure times allowed a significant expansion in the range of measured fluorescence intensities. The analyzer is useful for high throughput analysis of the same type of microarrays. PMID:29188082

  2. Advances in speckle metrology and related techniques

    CERN Document Server

    Kaufmann, Guillermo H


    Speckle metrology includes various optical techniques that are based on the speckle fields generated by reflection from a rough surface or by transmission through a rough diffuser. These techniques have proven to be very useful in testing different materials in a non-destructive way. They have changed dramatically during the last years due to the development of modern optical components, with faster and more powerful digital computers, and novel data processing approaches. This most up-to-date overview of the topic describes new techniques developed in the field of speckle metrology over the l

  3. Highly directive and Gaussian far-field emission from “giant” photonic trumpets

    DEFF Research Database (Denmark)

    Stepanov, Petr; Delga, Adrien; Gregersen, Niels


    Photonic trumpets are broadband dielectric antennas that efficiently funnel the emission of a pointlike quantum emitter—such as a semiconductor quantum dot—into a Gaussian free-space beam. After describing guidelines for the taper design, we present a “giant” photonic trumpet. The device features...

  4. Effect of interdiffusion and external magnetic field on electronic states and light absorption in Gaussian-shaped double quantum ring (United States)

    Aziz-Aghchegala, V. L.; Mughnetsyan, V. N.; Kirakosyan, A. A.


    The effect of interdiffusion and magnetic field on confined states of electron and heavy hole as well as on interband absorption spectrum in a Ga1-xAlxAs/GaAs Gaussian-shaped double quantum ring are investigated. It is shown that both interdiffusion and magnetic field lead to the change of the charge carriers' quantum states arrangement by their energies. The oscillating behavior of the electron ground state energy as a function of magnetic field induction gradually disappears with the increase of diffusion parameter due to the enhanced tunneling of electron to the central region of the ring. For the heavy hole the ground state energy oscillations are not observable in the region of the values of magnetic field induction B = 0 - 10 T . For considered transitions both the magnetic field and the interdiffusion lead to a blue-shift of the absorption spectrum and to decreasing of the absorption intensity. The obtained results indicate on the opportunity of purposeful manipulation of energy states and absorption spectrum of a Gaussian-shaped double quantum ring by means of the post growth annealing and the external magnetic field.

  5. Scattering of Gaussian Beams by Disordered Particulate Media (United States)

    Mishchenko, Michael I.; Dlugach, Janna M.


    A frequently observed characteristic of electromagnetic scattering by a disordered particulate medium is the absence of pronounced speckles in angular patterns of the scattered light. It is known that such diffuse speckle-free scattering patterns can be caused by averaging over randomly changing particle positions and/or over a finite spectral range. To get further insight into the possible physical causes of the absence of speckles, we use the numerically exact superposition T-matrix solver of the Maxwell equations and analyze the scattering of plane-wave and Gaussian beams by representative multi-sphere groups. We show that phase and amplitude variations across an incident Gaussian beam do not serve to extinguish the pronounced speckle pattern typical of plane-wave illumination of a fixed multi-particle group. Averaging over random particle positions and/or over a finite spectral range is still required to generate the classical diffuse speckle-free regime.

  6. Applicability of quantitative optical imaging techniques for intraoperative perfusion diagnostics: a comparison of laser speckle contrast imaging, sidestream dark-field microscopy, and optical coherence tomography (United States)

    Jansen, Sanne M.; de Bruin, Daniel M.; Faber, Dirk J.; Dobbe, Iwan J. G. G.; Heeg, Erik; Milstein, Dan M. J.; Strackee, Simon D.; van Leeuwen, Ton G.


    Patient morbidity and mortality due to hemodynamic complications are a major problem in surgery. Optical techniques can image blood flow in real-time and high-resolution, thereby enabling perfusion monitoring intraoperatively. We tested the feasibility and validity of laser speckle contrast imaging (LSCI), optical coherence tomography (OCT), and sidestream dark-field microscopy (SDF) for perfusion diagnostics in a phantom model using whole blood. Microvessels with diameters of 50, 100, and 400 μm were constructed in a scattering phantom. Perfusion was simulated by pumping heparinized human whole blood at five velocities (0 to 20 mm/s). Vessel diameter and blood flow velocity were assessed with LSCI, OCT, and SDF. Quantification of vessel diameter was feasible with OCT and SDF. LSCI could only visualize the 400-μm vessel, perfusion units scaled nonlinearly with blood velocity. OCT could assess blood flow velocity in terms of inverse OCT speckle decorrelation time. SDF was not feasible to measure blood flow; however, for diluted blood the measurements were linear with the input velocity up to 1 mm/s. LSCI, OCT, and SDF were feasible to visualize blood flow. Validated blood flow velocity measurements intraoperatively in the desired parameter (mL·g-1) remain challenging.

  7. X-ray speckle correlation interferometer

    International Nuclear Information System (INIS)

    Eisenhower, Rachel; Materlik, Gerhard


    Speckle Pattern Correlation Interferometry (SPCI) is a well-established technique in the visible-light regime for observing surface disturbances. Although not a direct imaging technique, SPCI gives full-field, high-resolution information about an object's motion. Since x-ray synchrotron radiation beamlines with high coherent flux have allowed the observation of x-ray speckle, x-ray SPCI could provide a means to measure strains and other quasi-static motions in disordered systems. This paper therefore examines the feasibility of an x-ray speckle correlation interferometer

  8. Acoustic radiation force on a multilayered sphere in a Gaussian standing field (United States)

    Wang, Haibin; Liu, Xiaozhou; Gao, Sha; Cui, Jun; Liu, Jiehui; He, Aijun; Zhang, Gutian


    We develop a model for calculating the radiation force on spherically symmetric multilayered particles based on the acoustic scattering approach. An expression is derived for the radiation force on a multilayered sphere centered on the axis of a Gaussian standing wave propagating in an ideal fluid. The effects of the sound absorption of the materials and sound wave on acoustic radiation force of a multilayered sphere immersed in water are analyzed, with particular emphasis on the shell thickness of every layer, and the width of the Gaussian beam. The results reveal that the existence of particle trapping behavior depends on the choice of the non-dimensional frequency ka, as well as the shell thickness of each layer. This study provides a theoretical basis for the development of acoustical tweezers in a Gaussian standing wave, which may benefit the improvement and development of acoustic control technology, such as trapping, sorting, and assembling a cell, and drug delivery applications. Project supported by National Key R&D Program (Grant No. 2016YFF0203000), the National Natural Science Foundation of China (Grant Nos. 11774167 and 61571222), the Fundamental Research Funds for the Central Universities of China (Grant No. 020414380001), the Key Laboratory of Underwater Acoustic Environment, Institute of Acoustics, Chinese Academy of Sciences (Grant No. SSHJ-KFKT-1701), and the AQSIQ Technology R&D Program of China (Grant No. 2017QK125).

  9. Speckle dynamics under ergodicity breaking (United States)

    Sdobnov, Anton; Bykov, Alexander; Molodij, Guillaume; Kalchenko, Vyacheslav; Jarvinen, Topias; Popov, Alexey; Kordas, Krisztian; Meglinski, Igor


    Laser speckle contrast imaging (LSCI) is a well-known and versatile approach for the non-invasive visualization of flows and microcirculation localized in turbid scattering media, including biological tissues. In most conventional implementations of LSCI the ergodic regime is typically assumed valid. However, most composite turbid scattering media, especially biological tissues, are non-ergodic, containing a mixture of dynamic and static centers of light scattering. In the current study, we examined the speckle contrast in different dynamic conditions with the aim of assessing limitations in the quantitative interpretation of speckle contrast images. Based on a simple phenomenological approach, we introduced a coefficient of speckle dynamics to quantitatively assess the ratio of the dynamic part of a scattering medium to the static one. The introduced coefficient allows one to distinguish real changes in motion from the mere appearance of static components in the field of view. As examples of systems with static/dynamic transitions, thawing and heating of Intralipid samples were studied by the LSCI approach.

  10. A multiresolution wavelet analysis and Gaussian Markov random field algorithm for breast cancer screening of digital mammography

    Energy Technology Data Exchange (ETDEWEB)

    Lee, C.G.; Chen, C.H. [Univ. of Massachusetts, North Dartmouth, MA (United States)


    In this paper a novel multiresolution wavelet analysis (MWA) and non-stationary Gaussian Markov random field (GMRF) technique is introduced for the identification of microcalcifications with high accuracy. The hierarchical multiresolution wavelet information in conjunction with the contextual information of the images extracted from GMRF provides a highly efficient technique for microcalcification detection. A Bayesian teaming paradigm realized via the expectation maximization (EM) algorithm was also introduced for edge detection or segmentation of larger lesions recorded on the mammograms. The effectiveness of the approach has been extensively tested with a number of mammographic images provided by a local hospital.

  11. Incorporating covariance estimation uncertainty in spatial sampling design for prediction with trans-Gaussian random fields

    Directory of Open Access Journals (Sweden)

    Gunter eSpöck


    Full Text Available Recently, Spock and Pilz [38], demonstratedthat the spatial sampling design problem forthe Bayesian linear kriging predictor can betransformed to an equivalent experimentaldesign problem for a linear regression modelwith stochastic regression coefficients anduncorrelated errors. The stochastic regressioncoefficients derive from the polar spectralapproximation of the residual process. Thus,standard optimal convex experimental designtheory can be used to calculate optimal spatialsampling designs. The design functionals ̈considered in Spock and Pilz [38] did nottake into account the fact that kriging isactually a plug-in predictor which uses theestimated covariance function. The resultingoptimal designs were close to space-fillingconfigurations, because the design criteriondid not consider the uncertainty of thecovariance function.In this paper we also assume that thecovariance function is estimated, e.g., byrestricted maximum likelihood (REML. Wethen develop a design criterion that fully takesaccount of the covariance uncertainty. Theresulting designs are less regular and space-filling compared to those ignoring covarianceuncertainty. The new designs, however, alsorequire some closely spaced samples in orderto improve the estimate of the covariancefunction. We also relax the assumption ofGaussian observations and assume that thedata is transformed to Gaussianity by meansof the Box-Cox transformation. The resultingprediction method is known as trans-Gaussiankriging. We apply the Smith and Zhu [37]approach to this kriging method and show thatresulting optimal designs also depend on theavailable data. We illustrate our results witha data set of monthly rainfall measurementsfrom Upper Austria.

  12. Scattering of Gaussian beams by disordered particulate media

    International Nuclear Information System (INIS)

    Mishchenko, Michael I.; Dlugach, Janna M.


    A frequently observed characteristic of electromagnetic scattering by a disordered particulate medium is the absence of pronounced speckles in angular patterns of the scattered light. It is known that such diffuse speckle-free scattering patterns can be caused by averaging over randomly changing particle positions and/or over a finite spectral range. To get further insight into the possible physical causes of the absence of speckles, we use the numerically exact superposition T-matrix solver of the Maxwell equations and analyze the scattering of plane-wave and Gaussian beams by representative multi-sphere groups. We show that phase and amplitude variations across an incident Gaussian beam do not serve to extinguish the pronounced speckle pattern typical of plane-wave illumination of a fixed multi-particle group. Averaging over random particle positions and/or over a finite spectral range is still required to generate the classical diffuse speckle-free regime. - Highlights: • Electromagnetic scattering by a disordered particulate medium is studied. • The superposition T-matrix solver of the Maxwell equations is used. • Finite width of an incident Gaussian beam does not extinguish interference speckles. • Ensemble or spectral averaging is required to generate diffuse speckle-free patterns.

  13. Polynomial Chaos Acceleration for the Bayesian Inference of Random Fields with Gaussian Priors and Uncertain Covariance Hyper-Parameters

    KAUST Repository

    Le Maitre, Olivier


    We address model dimensionality reduction in the Bayesian inference of Gaussian fields, considering prior covariance function with unknown hyper-parameters. The Karhunen-Loeve (KL) expansion of a prior Gaussian process is traditionally derived assuming fixed covariance function with pre-assigned hyperparameter values. Thus, the modes strengths of the Karhunen-Loeve expansion inferred using available observations, as well as the resulting inferred process, dependent on the pre-assigned values for the covariance hyper-parameters. Here, we seek to infer the process and its the covariance hyper-parameters in a single Bayesian inference. To this end, the uncertainty in the hyper-parameters is treated by means of a coordinate transformation, leading to a KL-type expansion on a fixed reference basis of spatial modes, but with random coordinates conditioned on the hyper-parameters. A Polynomial Chaos (PC) expansion of the model prediction is also introduced to accelerate the Bayesian inference and the sampling of the posterior distribution with MCMC method. The PC expansion of the model prediction also rely on a coordinates transformation, enabling us to avoid expanding the dependence of the prediction with respect to the covariance hyper-parameters. We demonstrate the efficiency of the proposed method on a transient diffusion equation by inferring spatially-varying log-diffusivity fields from noisy data.

  14. Neighborhood binary speckle pattern for deformation measurements insensitive to local illumination variation by digital image correlation. (United States)

    Zhao, Jian; Yang, Ping; Zhao, Yue


    Speckle pattern-based characteristics of digital image correlation (DIC) restrict its application in engineering fields and nonlaboratory environments, since serious decorrelation effect occurs due to localized sudden illumination variation. A simple and efficient speckle pattern adjusting and optimizing approach presented in this paper is aimed at providing a novel speckle pattern robust enough to resist local illumination variation. The new speckle pattern, called neighborhood binary speckle pattern, derived from original speckle pattern, is obtained by means of thresholding the pixels of a neighborhood at its central pixel value and considering the result as a binary number. The efficiency of the proposed speckle pattern is evaluated in six experimental scenarios. Experiment results indicate that the DIC measurements based on neighborhood binary speckle pattern are able to provide reliable and accurate results, even though local brightness and contrast of the deformed images have been seriously changed. It is expected that the new speckle pattern will have more potential value in engineering applications.

  15. Speckle-based spectrometer

    DEFF Research Database (Denmark)

    Chakrabarti, Maumita; Jakobsen, Michael Linde; Hanson, Steen Grüner


    A novel spectrometer concept is analyzed and experimentally verified. The method relies on probing the speckle displacement due to a change in the incident wavelength. A rough surface is illuminated at an oblique angle, and the peak position of the covariance between the speckle patterns observed...

  16. Probabilistic inference of multi-Gaussian fields from indirect hydrological data using circulant embedding and dimensionality reduction (United States)

    Laloy, Eric; Linde, Niklas; Jacques, Diederik; Vrugt, Jasper A.


    We present a Bayesian inversion method for the joint inference of high-dimensional multi-Gaussian hydraulic conductivity fields and associated geostatistical parameters from indirect hydrological data. We combine Gaussian process generation via circulant embedding to decouple the variogram from grid cell specific values, with dimensionality reduction by interpolation to enable Markov chain Monte Carlo (MCMC) simulation. Using the Matérn variogram model, this formulation allows inferring the conductivity values simultaneously with the field smoothness (also called Matérn shape parameter) and other geostatistical parameters such as the mean, sill, integral scales and anisotropy direction(s) and ratio(s). The proposed dimensionality reduction method systematically honors the underlying variogram and is demonstrated to achieve better performance than the Karhunen-Loève expansion. We illustrate our inversion approach using synthetic (error corrupted) data from a tracer experiment in a fairly heterogeneous 10,000-dimensional 2-D conductivity field. A 40-times reduction of the size of the parameter space did not prevent the posterior simulations to appropriately fit the measurement data and the posterior parameter distributions to include the true geostatistical parameter values. Overall, the posterior field realizations covered a wide range of geostatistical models, questioning the common practice of assuming a fixed variogram prior to inference of the hydraulic conductivity values. Our method is shown to be more efficient than sequential Gibbs sampling (SGS) for the considered case study, particularly when implemented on a distributed computing cluster. It is also found to outperform the method of anchored distributions (MAD) for the same computational budget.

  17. Highly porous nanoberyllium for X-ray beam speckle suppression

    Energy Technology Data Exchange (ETDEWEB)

    Goikhman, Alexander, E-mail:; Lyatun, Ivan; Ershov, Petr [Immanuel Kant Baltic Federal University, Nevskogo str. 14, Kaliningrad 236041 (Russian Federation); Snigireva, Irina [European Synchrotron Radiation Facility, BP 220, 38043 Grenoble (France); Wojda, Pawel [Immanuel Kant Baltic Federal University, Nevskogo str. 14, Kaliningrad 236041 (Russian Federation); Gdańsk University of Technology, 11/12 G. Narutowicza, Gdańsk 80-233 (Poland); Gorlevsky, Vladimir; Semenov, Alexander; Sheverdyaev, Maksim; Koletskiy, Viktor [A. A. Bochvar High-Technology Scientific Research Institute for Inorganic Materials, Rogova str. 5a, Moscow 123098 (Russian Federation); Snigirev, Anatoly [Immanuel Kant Baltic Federal University, Nevskogo str. 14, Kaliningrad 236041 (Russian Federation); European Synchrotron Radiation Facility, BP 220, 38043 Grenoble (France)


    A speckle suppression device containing highly porous nanoberyllium is proposed for manipulating the spatial coherence length and removing undesirable speckle structure during imaging experiments. This paper reports a special device called a ‘speckle suppressor’, which contains a highly porous nanoberyllium plate squeezed between two beryllium windows. The insertion of the speckle suppressor in an X-ray beam allows manipulation of the spatial coherence length, thus changing the effective source size and removing the undesirable speckle structure in X-ray imaging experiments almost without beam attenuation. The absorption of the nanoberyllium plate is below 1% for 1 mm thickness at 12 keV. The speckle suppressor was tested on the ID06 ESRF beamline with X-rays in the energy range from 9 to 15 keV. It was applied for the transformation of the phase–amplitude contrast to the pure amplitude contrast in full-field microscopy.

  18. Highly porous nanoberyllium for X-ray beam speckle suppression

    International Nuclear Information System (INIS)

    Goikhman, Alexander; Lyatun, Ivan; Ershov, Petr; Snigireva, Irina; Wojda, Pawel; Gorlevsky, Vladimir; Semenov, Alexander; Sheverdyaev, Maksim; Koletskiy, Viktor; Snigirev, Anatoly


    A speckle suppression device containing highly porous nanoberyllium is proposed for manipulating the spatial coherence length and removing undesirable speckle structure during imaging experiments. This paper reports a special device called a ‘speckle suppressor’, which contains a highly porous nanoberyllium plate squeezed between two beryllium windows. The insertion of the speckle suppressor in an X-ray beam allows manipulation of the spatial coherence length, thus changing the effective source size and removing the undesirable speckle structure in X-ray imaging experiments almost without beam attenuation. The absorption of the nanoberyllium plate is below 1% for 1 mm thickness at 12 keV. The speckle suppressor was tested on the ID06 ESRF beamline with X-rays in the energy range from 9 to 15 keV. It was applied for the transformation of the phase–amplitude contrast to the pure amplitude contrast in full-field microscopy

  19. Dynamical properties of speckled speckles

    DEFF Research Database (Denmark)

    Hanson, Steen Grüner; Iversen, Theis Faber Quist; Hansen, Rene Skov


    the static diffuser and the plane of observation consist of an optical system that can be characterized by a complex-valued ABCD-matrix (e.g. simple and complex imaging systems, free space propagation in both the near-and far-field, and Fourier transform systems). The use of the complex ABCD-method means...

  20. About a solvable mean field model of a Gaussian spin glass (United States)

    Barra, Adriano; Genovese, Giuseppe; Guerra, Francesco; Tantari, Daniele


    In a series of papers, we have studied a modified Hopfield model of a neural network, with learned words characterized by a Gaussian distribution. The model can be represented as a bipartite spin glass, with one party described by dichotomic Ising spins, and the other party by continuous spin variables, with an a priori Gaussian distribution. By application of standard interpolation methods, we have found it useful to compare the neural network model (bipartite) from one side, with two spin glass models, each monopartite, from the other side. Of these, the first is the usual Sherrington-Kirkpatrick model, the second is a spin glass model, with continuous spins and inbuilt highly nonlinear smooth cut-off interactions. This model is an invaluable laboratory for testing all techniques which have been useful in the study of spin glasses. The purpose of this paper is to give a synthetic description of the most peculiar aspects, by stressing the necessary novelties in the treatment. In particular, it will be shown that the control of the infinite volume limit, according to the well-known Guerra-Toninelli strategy, requires in addition one to consider the involvement of the cut-off interaction in the interpolation procedure. Moreover, the control of the ergodic region, the annealed case, cannot be directly achieved through the standard application of the Borel-Cantelli lemma, but requires previous modification of the interaction. This remark could find useful application in other cases. The replica symmetric expression for the free energy can be easily reached through a suitable version of the doubly stochastic interpolation technique. However, this model shares the unique property that the fully broken replica symmetry ansatz can be explicitly calculated. A very simple sum rule connects the general expression of the fully broken free energy trial function with the replica symmetric one. The definite sign of the error term shows that the replica solution is optimal. Then

  1. The Gaussian Atomic Orbital Multiplied by a Field-Dependent Gauge Phase for the Hydrogen Molecular Ion in Non-aligned Magnetic Fields

    International Nuclear Information System (INIS)

    Song, Xuanyu; Li, Cun; Wang, Xiaofeng; Qiao, Haoxue


    We multiply the anisotropic Gaussian atomic orbital by a field-dependent gauge phase to describe the wave function for the hydrogen molecular ion in non-aligned magnetic fields. With the kind of basis set, the convergence of the total energy at the equilibrium distance for the 1 u state is much improved compared to the same atomic orbital without the gauge phase. For 2.35 × 10 4 ≤ B ≤ 10 7 T, better total energies of the 1 u state at the corresponding equilibrium are obtained for the deviations 15°–90° of the magnetic field relative to the molecular axis. The result also shows that, there is a transition of the equilibrium configuration from the vertical orientation to the parallel orientation with increasing field strength. (author)

  2. Speckle Reduction in Projection Systems


    Riechert, Falko


    A speckle pattern is a quasi-random interference pattern which typically emerges when lasers are used as illumination sources in projection applications and which severely degrades the image quality. Since in most projection applications high speckle disturbance is not tolerable, speckle reduction is a major issue. This work gives an introduction into the theoretical description of speckle and investigates different practical methods for speckle reduction in laser projection systems.

  3. Diffusion Effects on the Breakdown of a Linear Amplifier Model Driven by the Square of a Gaussian Field (United States)

    Asselah, A.; Dai Pra, P.; Lebowitz, J. L.; Mounaix, Ph.


    We investigate solutions to the equation ∂ t ℰ-D Δℰ= λS 2ℰ, where S( x, t) is a Gaussian stochastic field with covariance C( x- x', t, t'), and x∈{R} d . It is shown that the coupling λ cN ( t) at which the N-th moment diverges at time t, is always less or equal for D>0 than for D=0. Equality holds under some reasonable assumptions on C and, in this case, λ cN ( t)= Nλ c ( t) where λ c ( t) is the value of λ at which diverges. The D=0 case is solved for a class of S. The dependence of λ cN ( t) on d is analyzed. Similar behavior is conjectured when diffusion is replaced by diffraction, D→ i D, the case of interest for backscattering instabilities in laser-plasma interaction.

  4. Primordial non-Gaussianities of gravitational waves in the most general single-field inflation model with second-order field equations. (United States)

    Gao, Xian; Kobayashi, Tsutomu; Yamaguchi, Masahide; Yokoyama, Jun'ichi


    We completely clarify the feature of primordial non-Gaussianities of tensor perturbations in the most general single-field inflation model with second-order field equations. It is shown that the most general cubic action for the tensor perturbation h(ij) is composed only of two contributions, one with two spacial derivatives and the other with one time derivative on each h(ij). The former is essentially identical to the cubic term that appears in Einstein gravity and predicts a squeezed shape, while the latter newly appears in the presence of the kinetic coupling to the Einstein tensor and predicts an equilateral shape. Thus, only two shapes appear in the graviton bispectrum of the most general single-field inflation model, which could open a new clue to the identification of inflationary gravitational waves in observations of cosmic microwave background anisotropies as well as direct detection experiments.

  5. Excursion probabilities of non-homogeneous Gaussian scalar fields based on maxima considerations

    DEFF Research Database (Denmark)

    Nielsen, Michael Havbro Faber; Rackwitz, R.


    Many uncertain natural or technical phenomena are most realistically described by random fields. A typical example of a random field is the load effect in a floor slab which is loaded by a spatially distributed gravity load. Other examples of random fields include the sea-level around off......-shore platforms. the distribution of material strength in a cross-section of a structural component. the concentration of detergents in ground water. the velocities or pressures in a turbulent medium or on surfaces....

  6. Stochastic mean-field theory: Method and application to the disordered Bose-Hubbard model at finite temperature and speckle disorder

    International Nuclear Information System (INIS)

    Bissbort, Ulf; Hofstetter, Walter; Thomale, Ronny


    We discuss the stochastic mean-field theory (SMFT) method, which is a new approach for describing disordered Bose systems in the thermodynamic limit including localization and dimensional effects. We explicate the method in detail and apply it to the disordered Bose-Hubbard model at finite temperature, with on-site box disorder, as well as experimentally relevant unbounded speckle disorder. We find that disorder-induced condensation and re-entrant behavior at constant filling are only possible at low temperatures, beyond the reach of current experiments [M. Pasienski, D. McKay, M. White, and B. DeMarco, e-print arXiv:0908.1182]. Including off-diagonal hopping disorder as well, we investigate its effect on the phase diagram in addition to pure on-site disorder. To make connection to present experiments on a quantitative level, we also combine SMFT with an LDA approach and obtain the condensate fraction in the presence of an external trapping potential.

  7. Markov random field and Gaussian mixture for segmented MRI-based partial volume correction in PET

    International Nuclear Information System (INIS)

    Bousse, Alexandre; Thomas, Benjamin A; Erlandsson, Kjell; Hutton, Brian F; Pedemonte, Stefano; Ourselin, Sébastien; Arridge, Simon


    In this paper we propose a segmented magnetic resonance imaging (MRI) prior-based maximum penalized likelihood deconvolution technique for positron emission tomography (PET) images. The model assumes the existence of activity classes that behave like a hidden Markov random field (MRF) driven by the segmented MRI. We utilize a mean field approximation to compute the likelihood of the MRF. We tested our method on both simulated and clinical data (brain PET) and compared our results with PET images corrected with the re-blurred Van Cittert (VC) algorithm, the simplified Guven (SG) algorithm and the region-based voxel-wise (RBV) technique. We demonstrated our algorithm outperforms the VC algorithm and outperforms SG and RBV corrections when the segmented MRI is inconsistent (e.g. mis-segmentation, lesions, etc) with the PET image. (paper)

  8. Controlling the evolution of nondiffracting speckle by complex amplitude modulation on a phase-only spatial light modulator

    CSIR Research Space (South Africa)

    Dudley, Angela L


    Full Text Available amplitude modulation on a phase-only spatial light modulator to implement controlled ring-slit experiments for the generation of nondiffracting speckle fields. The structure of the nondiffracting speckle due to binary and continuous phase modulations...

  9. Preprocessing of 18F-DMFP-PET Data Based on Hidden Markov Random Fields and the Gaussian Distribution

    Directory of Open Access Journals (Sweden)

    Fermín Segovia


    Full Text Available 18F-DMFP-PET is an emerging neuroimaging modality used to diagnose Parkinson's disease (PD that allows us to examine postsynaptic dopamine D2/3 receptors. Like other neuroimaging modalities used for PD diagnosis, most of the total intensity of 18F-DMFP-PET images is concentrated in the striatum. However, other regions can also be useful for diagnostic purposes. An appropriate delimitation of the regions of interest contained in 18F-DMFP-PET data is crucial to improve the automatic diagnosis of PD. In this manuscript we propose a novel methodology to preprocess 18F-DMFP-PET data that improves the accuracy of computer aided diagnosis systems for PD. First, the data were segmented using an algorithm based on Hidden Markov Random Field. As a result, each neuroimage was divided into 4 maps according to the intensity and the neighborhood of the voxels. The maps were then individually normalized so that the shape of their histograms could be modeled by a Gaussian distribution with equal parameters for all the neuroimages. This approach was evaluated using a dataset with neuroimaging data from 87 parkinsonian patients. After these preprocessing steps, a Support Vector Machine classifier was used to separate idiopathic and non-idiopathic PD. Data preprocessed by the proposed method provided higher accuracy results than the ones preprocessed with previous approaches.

  10. (Small) Resonant non-Gaussianities: Signatures of a Discrete Shift Symmetry in the Effective Field Theory of Inflation

    Energy Technology Data Exchange (ETDEWEB)

    Behbahani, Siavosh R.; /SLAC /Stanford U., Phys. Dept. /Boston U.; Dymarsky, Anatoly; /Princeton, Inst. Advanced Study; Mirbabayi, Mehrdad; /New York U., CCPP /New York U.; Senatore, Leonardo; /Stanford U., Phys. Dept. /KIPAC, Menlo Park


    We apply the Effective Field Theory of Inflation to study the case where the continuous shift symmetry of the Goldstone boson {pi} is softly broken to a discrete subgroup. This case includes and generalizes recently proposed String Theory inspired models of Inflation based on Axion Monodromy. The models we study have the property that the 2-point function oscillates as a function of the wavenumber, leading to oscillations in the CMB power spectrum. The non-linear realization of time diffeomorphisms induces some self-interactions for the Goldstone boson that lead to a peculiar non-Gaussianity whose shape oscillates as a function of the wavenumber. We find that in the regime of validity of the effective theory, the oscillatory signal contained in the n-point correlation functions, with n > 2, is smaller than the one contained in the 2-point function, implying that the signature of oscillations, if ever detected, will be easier to find first in the 2-point function, and only then in the higher order correlation functions. Still the signal contained in higher-order correlation functions, that we study here in generality, could be detected at a subleading level, providing a very compelling consistency check for an approximate discrete shift symmetry being realized during inflation.


    Jin, Ick Hoon; Yuan, Ying; Bandyopadhyay, Dipankar


    Research in dental caries generates data with two levels of hierarchy: that of a tooth overall and that of the different surfaces of the tooth. The outcomes often exhibit spatial referencing among neighboring teeth and surfaces, i.e., the disease status of a tooth or surface might be influenced by the status of a set of proximal teeth/surfaces. Assessments of dental caries (tooth decay) at the tooth level yield binary outcomes indicating the presence/absence of teeth, and trinary outcomes at the surface level indicating healthy, decayed, or filled surfaces. The presence of these mixed discrete responses complicates the data analysis under a unified framework. To mitigate complications, we develop a Bayesian two-level hierarchical model under suitable (spatial) Markov random field assumptions that accommodates the natural hierarchy within the mixed responses. At the first level, we utilize an autologistic model to accommodate the spatial dependence for the tooth-level binary outcomes. For the second level and conditioned on a tooth being non-missing, we utilize a Potts model to accommodate the spatial referencing for the surface-level trinary outcomes. The regression models at both levels were controlled for plausible covariates (risk factors) of caries, and remain connected through shared parameters. To tackle the computational challenges in our Bayesian estimation scheme caused due to the doubly-intractable normalizing constant, we employ a double Metropolis-Hastings sampler. We compare and contrast our model performances to the standard non-spatial (naive) model using a small simulation study, and illustrate via an application to a clinical dataset on dental caries.

  12. Blood vessel segmentation in modern wide-field retinal images in the presence of additive Gaussian noise. (United States)

    Asem, Morteza Modarresi; Oveisi, Iman Sheikh; Janbozorgi, Mona


    Retinal blood vessels indicate some serious health ramifications, such as cardiovascular disease and stroke. Thanks to modern imaging technology, high-resolution images provide detailed information to help analyze retinal vascular features before symptoms associated with such conditions fully develop. Additionally, these retinal images can be used by ophthalmologists to facilitate diagnosis and the procedures of eye surgery. A fuzzy noise reduction algorithm was employed to enhance color images corrupted by Gaussian noise. The present paper proposes employing a contrast limited adaptive histogram equalization to enhance illumination and increase the contrast of retinal images captured from state-of-the-art cameras. Possessing directional properties, the multistructure elements method can lead to high-performance edge detection. Therefore, multistructure elements-based morphology operators are used to detect high-quality image ridges. Following this detection, the irrelevant ridges, which are not part of the vessel tree, were removed by morphological operators by reconstruction, attempting also to keep the thin vessels preserved. A combined method of connected components analysis (CCA) in conjunction with a thresholding approach was further used to identify the ridges that correspond to vessels. The application of CCA can yield higher efficiency when it is locally applied rather than applied on the whole image. The significance of our work lies in the way in which several methods are effectively combined and the originality of the database employed, making this work unique in the literature. Computer simulation results in wide-field retinal images with up to a 200-deg field of view are a testimony of the efficacy of the proposed approach, with an accuracy of 0.9524.

  13. Laguerre Gaussian beam multiplexing through turbulence

    CSIR Research Space (South Africa)

    Trichili, A


    Full Text Available We analyze the effect of atmospheric turbulence on the propagation of multiplexed Laguerre Gaussian modes. We present a method to multiplex Laguerre Gaussian modes using digital holograms and decompose the resulting field after encountering a...

  14. Digital simulation of two-dimensional random fields with arbitrary power spectra and non-Gaussian probability distribution functions

    DEFF Research Database (Denmark)

    Yura, Harold; Hanson, Steen Grüner


    Methods for simulation of two-dimensional signals with arbitrary power spectral densities and signal amplitude probability density functions are disclosed. The method relies on initially transforming a white noise sample set of random Gaussian distributed numbers into a corresponding set with the......Methods for simulation of two-dimensional signals with arbitrary power spectral densities and signal amplitude probability density functions are disclosed. The method relies on initially transforming a white noise sample set of random Gaussian distributed numbers into a corresponding set...... with the desired spectral distribution, after which this colored Gaussian probability distribution is transformed via an inverse transform into the desired probability distribution. In most cases the method provides satisfactory results and can thus be considered an engineering approach. Several illustrative...

  15. Effects of hydrogen-like impurity and electromagnetic field on quantum transition of an electron in a Gaussian potential with QD thickness (United States)

    Xin, Wei; Zhao, Yu-Wei; Sudu; Eerdunchaolu


    Considering Hydrogen-like impurity and the thickness effect, the eigenvalues and eigenfunctions of the electronic ground and first exited states in a quantum dot (QD) are derived by using the Lee-Low-Pins-Pekar variational method with the harmonic and Gaussian potentials as the transverse and longitudinal confinement potentials, respectively. A two-level system is constructed on the basis of those two states, and the electronic quantum transition affected by an electromagnetic field is discussed in terms of the two-level system theory. The results indicate the Gaussian potential reflects the real confinement potential more accurately than the parabolic one; the influence of the thickness of the QD on the electronic transition probability is interesting and significant, and cannot be ignored; the electronic transition probability Γ is influenced significantly by some physical quantities, such as the strength of the electron-phonon coupling α, the electric-field strength F, the magnetic-field cyclotron frequency ωc , the barrier height V0 and confinement range L of the asymmetric Gaussian potential, suggesting the transport and optical properties of the QD can be manipulated further though those physical quantities.

  16. Inhomogeneous non-Gaussianity

    CERN Document Server

    Byrnes, Christian T; Tasinato, Gianmassimo; Wands, David


    We propose a method to probe higher-order correlators of the primordial density field through the inhomogeneity of local non-Gaussian parameters, such as f_NL, measured within smaller patches of the sky. Correlators between n-point functions measured in one patch of the sky and k-point functions measured in another patch depend upon the (n+k)-point functions over the entire sky. The inhomogeneity of non-Gaussian parameters may be a feasible way to detect or constrain higher-order correlators in local models of non-Gaussianity, as well as to distinguish between single and multiple-source scenarios for generating the primordial density perturbation, and more generally to probe the details of inflationary physics.

  17. Multiple speckle illumination for optical-resolution photoacoustic imaging (United States)

    Poisson, Florian; Stasio, Nicolino; Moser, Christophe; Psaltis, Demetri; Bossy, Emmanuel


    Optical-resolution photoacoustic microscopy offers exquisite and specific contrast to optical absorption. Conventional approaches generally involves raster scanning a focused spot over the sample. Here, we demonstrate that a full-field illumination approach with multiple speckle illumination can also provide diffraction-limited optical-resolution photoacoustic images. Two different proof-of-concepts are demonstrated with micro-structured test samples. The first approach follows the principle of correlation/ghost imaging,1, 2 and is based on cross-correlating photoacoustic signals under multiple speckle illumination with known speckle patterns measured during a calibration step. The second approach is a speckle scanning microscopy technique, which adapts the technique proposed in fluorescence microscopy by Bertolotti and al.:3 in our work, spatially unresolved photoacoustic measurements are performed for various translations of unknown speckle patterns. A phase-retrieval algorithm is used to reconstruct the object from the knowledge of the modulus of its Fourier Transform yielded by the measurements. Because speckle patterns naturally appear in many various situations, including propagation through biological tissue or multi-mode fibers (for which focusing light is either very demanding if not impossible), speckle-illumination-based photoacoustic microscopy provides a powerful framework for the development of novel reconstruction approaches, well-suited to compressed sensing approaches.2

  18. Lagrangian speckle model and tissue-motion estimation--theory. (United States)

    Maurice, R L; Bertrand, M


    It is known that when a tissue is subjected to movements such as rotation, shearing, scaling, etc., changes in speckle patterns that result act as a noise source, often responsible for most of the displacement-estimate variance. From a modeling point of view, these changes can be thought of as resulting from two mechanisms: one is the motion of the speckles and the other, the alterations of their morphology. In this paper, we propose a new tissue-motion estimator to counteract these speckle decorrelation effects. The estimator is based on a Lagrangian description of the speckle motion. This description allows us to follow local characteristics of the speckle field as if they were a material property. This method leads to an analytical description of the decorrelation in a way which enables the derivation of an appropriate inverse filter for speckle restoration. The filter is appropriate for linear geometrical transformation of the scattering function (LT), i.e., a constant-strain region of interest (ROI). As the LT itself is a parameter of the filter, a tissue-motion estimator can be formulated as a nonlinear minimization problem, seeking the best match between the pre-tissue-motion image and a restored-speckle post-motion image. The method is tested, using simulated radio-frequency (RF) images of tissue undergoing axial shear.

  19. Speckle Image Reconstruction. (United States)


    the well-known close binary Capella and the resolved red supergiant Betelgeuse , (including a diffraction limited differential speckle image of the...current space object identification requirements, and the set of images of the red supergiant Betelgeuse . 2.1 Asteroid/Planetary Science Our work on... Betelgeuse with the measured point xource response superimposed for comparison. Figure 4 shows an example of a full two-dimensional reduction, this time

  20. Speckle suppressing anisotropic diffusion filter for medical ultrasound images. (United States)

    Ovireddy, Saraniya; Muthusamy, Ezhilarasi


    Ultrasonography is often preferred over the other medical imaging modalities due to its noninvasive nature, cost-effectiveness, and portability. However, the resolution of the ultrasound image greatly depends upon the presence of speckle noise. Speckle noise generally tends to reduce the image resolution and contrast, thereby reducing the diagnostic resolution of this imaging modality. In this paper, we propose a speckle suppressing anisotropic diffusion (SSAD) filter, to remove the speckle noise from B-Mode Ultrasound images. The performance of the SSAD filter is compared with the existing diffusion filters. The evaluation is based on their application to images simulated by Field II (developed by Jensen et al.). The algorithms were also tested for clinical ultrasound images of polycystic ovaries obtained from HDI 5000 Ultrasound Scanner. Performance evaluation was done by both numerical and functional parameters. The proposed filter yields better results in terms of greatest structural similarity index map (SSIM) of 0.95 and accuracy of 99.5.

  1. GPC light shaper for speckle-free one- and two-photon contiguous pattern excitation

    DEFF Research Database (Denmark)

    Bañas, Andrew Rafael; Palima, Darwin; Villangca, Mark Jayson


    Generalized Phase Contrast (GPC) is an efficient method for generating speckle-free contiguous optical distributions useful in diverse applications such as static beam shaping, optical manipulation and recently, for excitation in two-photon optogenetics. To fully utilize typical Gaussian lasers...

  2. The implementation of laser speckle reduction based on MEMS two-dimensional scanning mirror (United States)

    Wang, Tingting; Shen, Wenjiang; Wu, Shengli; Zhou, Peng; He, Jiahui; Yu, Huijun


    Laser speckle on the screen of laser display system is due to the strong coherence characteristic of laser. In order to eliminate the influence of the speckle on image quality, the method of laser speckle reduction based on MEMS two-dimensional scanning mirror is proposed in this paper. The experimental results show that the speckle contrast can be reduced to 3.7%, which meets the requirement of laser display. And this system could be used in laser display field and improve the display performance.

  3. Speckle pattern processing by digital image correlation

    Directory of Open Access Journals (Sweden)

    Gubarev Fedor


    Full Text Available Testing the method of speckle pattern processing based on the digital image correlation is carried out in the current work. Three the most widely used formulas of the correlation coefficient are tested. To determine the accuracy of the speckle pattern processing, test speckle patterns with known displacement are used. The optimal size of a speckle pattern template used for determination of correlation and corresponding the speckle pattern displacement is also considered in the work.

  4. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Screw dislocations of laser speckle fields in interferograms with a circular line structure (United States)

    Bobrov, B. D.


    Experimental results are used to show that circular interferograms are of interest in studies of screw dislocations of speckle-distorted laser beams because of a close correspondence between the symmetry of these interferograms and defects. The presence of dislocations transforms a system of the usual rings into a split network. Typical structure elements of such interferograms are right- and left-handed spirals connecting singular points of dislocations. Spiral fragments can be used in the diagnostics of dislocations regarded as independent defects. A method is suggested for the formation of highly directed optical beams with a low level of the usual aberrations, but with a complex phase surface topology. Screw dislocations are shown to be a natural analog of helical waves known in optics and capable of deliberate generation.

  5. Emitting far-field multicolor patterns and characters through plastic diffractive micro-optics elements illuminated by common Gaussian lasers in the visible range. (United States)

    Zhang, Xinyu; Li, Hui; Liu, Kan; Luo, Jun; Xie, Changsheng; Ji, An; Zhang, Tianxu


    Far-field multicolor patterns and characters are emitted effectively in a relatively wide and deep spatial region by plastic diffractive micro-optics elements (DMOEs), which are illuminated directly by common Gaussian lasers in the visible range. Phase-only DMOEs are composed of a large number of fine step-shaped phase microstructures distributed sequentially over the plastic wafer selected. The initial DMOEs in silicon wafer are fabricated by an innovative technique with a combination of a single-mask ultraviolet photolithography and low-cost and rapid wet KOH etching. The fabricated silicon DMOEs are further converted into a nickel mask by the conventional electrochemical method, and they are finally transferred onto the surface of the plastic wafer through mature hot embossing. Morphological measurements show that the surface roughness of the plastic DMOEs is in the nanometer range, and the feature height of the phase steps in diffractive elements is in the submicrometer scale, which can be designed and adjusted flexibly according to requirements. The dimensions of the DMOEs can be changed from the order of millimeters to centimeters. A large number of pixel phase microstructures with a square microappearance employed to construct the phase-only DMOEs are created by the Gerchberg-Saxton algorithm, according to the target patterns and characters and common Gaussian lasers manipulated by the DMOEs fabricated. © 2011 Optical Society of America

  6. Speckle imaging of globular clusters

    International Nuclear Information System (INIS)

    Sams, B.J. III


    Speckle imaging is a powerful tool for high resolution astronomy. Its application to the core regions of globular clusters produces high resolution stellar maps of the bright stars, but is unable to image the faint stars which are most reliable dynamical indicators. The limits on resolving these faint, extended objects are physical, not algorithmic, and cannot be overcome using speckle. High resolution maps may be useful for resolving multicomponent stellar systems in the cluster centers. 30 refs

  7. Electron acceleration from rest to GeV energy by chirped axicon Gaussian laser pulse in vacuum in the presence of wiggler magnetic field (United States)

    Kant, Niti; Rajput, Jyoti; Singh, Arvinder


    This paper presents a scheme of electron energy enhancement by employing frequency - chirped lowest order axicon focussed radially polarised (RP) laser pulse in vacuum under the influence of wiggler magnetic field. Terawatt RP laser can be focussed down to ∼5μm by an axicon optical element, which produces an intense longitudinal electric field. This unique property of axicon focused Gaussian RP laser pulse is employed for direct electron acceleration in vacuum. A linear frequency chirp increases the time duration of laser-electron interaction, whereas, the applied magnetic wiggler helps in improving the strength of ponderomotive force v→ ×B→ and periodically deflects electron in order to keep it traversing in the accelerating phase up to longer distance. Numerical simulations have been carried out to investigate the influence of laser, frequency chirp and magnetic field parameters on electron energy enhancement. It is noticed that an electron from rest can be accelerated up to GeV energy under optimized laser and magnetic field parameters. Significant enhancement in the electron energy gain of the order of 11.2 GeV is observed with intense chirped laser pulse in the presence of wiggler magnetic field of strength 96.2 kG.

  8. Wave Localization Does not Affect the Breakdown of a Schrödinger-Type Amplifier Driven by the Square of a Gaussian Field (United States)

    Mounaix, Philippe; Collet, Pierre


    We study the divergence of the solution to a Schrödinger-type amplifier driven by the square of a Gaussian noise in presence of a random potential. We follow the same approach as Mounaix, Collet, and Lebowitz (MCL) in terms of a distributional formulation of the amplified field and the use of the Paley-Wiener theorem (Mounaix et al. in Commun. Math. Phys. 264:741-758, 2006, Erratum: ibid. 280:281-283, 2008). Our results show that the divergence is not affected by the random potential, in the sense that it occurs at exactly the same coupling constant as what was found by MCL without a potential. It follows a fortiori that the breakdown of the amplifier is not affected by the possible existence of a localized regime in the amplification free limit.

  9. Speckle Imaging of Binary Stars with Large-Format CCDs (United States)

    Horch, E.; Ninkov, Z.; Slawson, R. W.; van Altena, W. F.; Meyer, R. D.; Girard, T. M.


    In the past, bare (unintensified) CCDs have not been widely used in speckle imaging for two main reasons: 1) the readout rate of most scientific-grade CCDs is too slow to be able to observe at the high frame rates necessary to capture speckle patterns efficiently, and 2) the read noise of CCDs limits the detectability of fainter objects where it becomes difficult to distinguish between speckles and noise peaks in the image. These facts have led to the current supremacy of intensified imaging systems (such as intensified-CCDs) in this field, which can typically be read out at video rates or faster. We have developed a new approach that uses a large format CCD not only to detect the incident photons but also to record many speckle patterns before the chip is read out. This approach effectively uses the large area of the CCD as a physical ``memory cache'' of previous speckle data frames. The method is described, and binary star observations from the University of Toronto Southern Observatory 60-cm telescope and the Wisconsin-Indiana-Yale-NOAO (WIYN) 3.5-m telescope are presented. Plans for future observing and instrumentation improvements are also outlined.

  10. Non-gaussian turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Hoejstrup, J. [NEG Micon Project Development A/S, Randers (Denmark); Hansen, K.S. [Denmarks Technical Univ., Dept. of Energy Engineering, Lyngby (Denmark); Pedersen, B.J. [VESTAS Wind Systems A/S, Lem (Denmark); Nielsen, M. [Risoe National Lab., Wind Energy and Atmospheric Physics, Roskilde (Denmark)


    The pdf`s of atmospheric turbulence have somewhat wider tails than a Gaussian, especially regarding accelerations, whereas velocities are close to Gaussian. This behaviour is being investigated using data from a large WEB-database in order to quantify the amount of non-Gaussianity. Models for non-Gaussian turbulence have been developed, by which artificial turbulence can be generated with specified distributions, spectra and cross-correlations. The artificial time series will then be used in load models and the resulting loads in the Gaussian and the non-Gaussian cases will be compared. (au)

  11. Laser speckle analysis of retinal vascular dynamics

    DEFF Research Database (Denmark)

    Neganova, Anastasiia Y.; Postnov, Dmitry D.; Jacobsen, Jens Christian B.


    -field laser speckle imaging to evaluate vascular responses of the retinal network. Image segmentation and vessel recognition algorithms together with response mapping allow us to analyze diameter changes and blood flow responses in the intact retinal network upon systemic administration of the vasoconstrictor......Studies of vascular responses are usually performed on isolated vessels or on single vessels in vivo. This allows for precise measurements of diameter or blood flow. However, dynamical responses of the whole microvascular network are difficult to access experimentally. We suggest to use full...

  12. Multiple rotation assessment through isothetic fringes in speckle photography

    International Nuclear Information System (INIS)

    Angel, Luciano; Tebaldi, Myrian; Bolognini, Nestor


    The use of different pupils for storing each speckled image in speckle photography is employed to determine multiple in-plane rotations. The method consists of recording a four-exposure specklegram where the rotations are done between exposures. This specklegram is then optically processed in a whole field approach rendering isothetic fringes, which give detailed information about the multiple rotations. It is experimentally demonstrated that the proposed arrangement permits the depiction of six isothetics in order to measure either six different angles or three nonparallel components for two local general in-plane displacements

  13. Coherence and Polarization of Polarization Speckle Generated by Depolarizers and Their Changes through Complex ABCD Matrix

    DEFF Research Database (Denmark)

    Ma, Ning; Hanson, Steen Grüner; Lee, Tim K.


    Recent research work on speckle patterns indicates a variation of the polarization state during propagation and its nonuniformly spatial distribution. The preliminary step for the investigation of this polarization speckle is the generation of the corresponding field. In this paper, a kind of spe...... of coherence (DoC). and degree of polarization (DoP) P. The changes of the coherence and polarization when the speckle field propagates through any optical system are analysed within the framework of the complex ABCD-matrix theory....

  14. How Gaussian can our Universe be?

    NARCIS (Netherlands)

    Cabass, Giovanni; Pajer, Enrico; Schmidt, Fabian

    Gravity is a non-linear theory, and hence, barring cancellations, the initial super-horizon perturbations produced by inflation must contain some minimum amount of mode coupling, or primordial non-Gaussianity. In single-field slow-roll models, where this lower bound is saturated, non-Gaussianity is

  15. Rotating quantum Gaussian packets

    International Nuclear Information System (INIS)

    Dodonov, V V


    We study two-dimensional quantum Gaussian packets with a fixed value of mean angular momentum. This value is the sum of two independent parts: the ‘external’ momentum related to the motion of the packet center and the ‘internal’ momentum due to quantum fluctuations. The packets minimizing the mean energy of an isotropic oscillator with the fixed mean angular momentum are found. They exist for ‘co-rotating’ external and internal motions, and they have nonzero correlation coefficients between coordinates and momenta, together with some (moderate) amount of quadrature squeezing. Variances of angular momentum and energy are calculated, too. Differences in the behavior of ‘co-rotating’ and ‘anti-rotating’ packets are shown. The time evolution of rotating Gaussian packets is analyzed, including the cases of a charge in a homogeneous magnetic field and a free particle. In the latter case, the effect of initial shrinking of packets with big enough coordinate-momentum correlation coefficients (followed by the well known expansion) is discovered. This happens due to a competition of ‘focusing’ and ‘de-focusing’ in the orthogonal directions. (paper)

  16. Tailoring speckles with Weibull intensity statistics (United States)

    Amaral, João P.; Fonseca, Eduardo J. S.; Jesus-Silva, Alcenisio J.


    We use a phase-only computer-generated hologram to encode both phase and amplitude of a power of Rayleigh speckles. This method allows us to generate speckles with enhanced and reduced contrast without any optimization process. We explore non-Rayleigh speckles and unveil, theoretically and experimentally, their first-order statistical properties. These speckles may find applications in syntheses of disordered optical potentials for cold atoms and colloidal particles, in speckle illumination imaging, and in wave interference studied through spatial intensity correlation.

  17. Inference of multi-Gaussian property fields by probabilistic inversion of crosshole ground penetrating radar data using an improved dimensionality reduction (United States)

    Hunziker, Jürg; Laloy, Eric; Linde, Niklas


    Deterministic inversion procedures can often explain field data, but they only deliver one final subsurface model that depends on the initial model and regularization constraints. This leads to poor insights about the uncertainties associated with the inferred model properties. In contrast, probabilistic inversions can provide an ensemble of model realizations that accurately span the range of possible models that honor the available calibration data and prior information allowing a quantitative description of model uncertainties. We reconsider the problem of inferring the dielectric permittivity (directly related to radar velocity) structure of the subsurface by inversion of first-arrival travel times from crosshole ground penetrating radar (GPR) measurements. We rely on the DREAM_(ZS) algorithm that is a state-of-the-art Markov chain Monte Carlo (MCMC) algorithm. Such algorithms need several orders of magnitude more forward simulations than deterministic algorithms and often become infeasible in high parameter dimensions. To enable high-resolution imaging with MCMC, we use a recently proposed dimensionality reduction approach that allows reproducing 2D multi-Gaussian fields with far fewer parameters than a classical grid discretization. We consider herein a dimensionality reduction from 5000 to 257 unknowns. The first 250 parameters correspond to a spectral representation of random and uncorrelated spatial fluctuations while the remaining seven geostatistical parameters are (1) the standard deviation of the data error, (2) the mean and (3) the variance of the relative electric permittivity, (4) the integral scale along the major axis of anisotropy, (5) the anisotropy angle, (6) the ratio of the integral scale along the minor axis of anisotropy to the integral scale along the major axis of anisotropy and (7) the shape parameter of the Matérn function. The latter essentially defines the type of covariance function (e.g., exponential, Whittle, Gaussian). We present

  18. Objective speckle velocimetry for autonomous vehicle odometry. (United States)

    Francis, D; Charrett, T O H; Waugh, L; Tatam, R P


    Speckle velocimetry is investigated as a means of determining odometry data with potential for application on autonomous robotic vehicles. The technique described here relies on the integration of translation measurements made by normalized cross-correlation of speckle patterns to determine the change in position over time. The use of objective (non-imaged) speckle offers a number of advantages over subjective (imaged) speckle, such as a reduction in the number of optical components, reduced modulation of speckles at the edges of the image, and improved light efficiency. The influence of the source/detector configuration on the speckle translation to vehicle translation scaling factor for objective speckle is investigated using a computer model and verified experimentally. Experimental measurements are presented at velocities up to 80  mm s(-1) which show accuracy better than 0.4%.

  19. Speckle filtering of medical ultrasonic images using wavelet and guided filter. (United States)

    Zhang, Ju; Lin, Guangkuo; Wu, Lili; Cheng, Yun


    Speckle noise is an inherent yet ineffectual residual artifact in medical ultrasound images, which significantly degrades quality and restricts accuracy in automatic diagnostic techniques. Speckle reduction is therefore an important step prior to the analysis and processing of the ultrasound images. A new de-noising method based on an improved wavelet filter and guided filter is proposed in this paper. According to the characteristics of medical ultrasound images in the wavelet domain, an improved threshold function based on the universal wavelet threshold function is developed. The wavelet coefficients of speckle noise and noise-free signal are modeled as Rayleigh distribution and generalized Gaussian distribution respectively. The Bayesian maximum a posteriori estimation is applied to obtain a new wavelet shrinkage algorithm. The coefficients of the low frequency sub-band in the wavelet domain are filtered by guided filter. The filtered image is then obtained by using the inverse wavelet transformation. Experiments with the comparison of the other seven de-speckling filters are conducted. The results show that the proposed method not only has a strong de-speckling ability, but also keeps the image details, such as the edge of a lesion. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Synchronized renal blood flow dynamics mapped with wavelet analysis of laser speckle flowmetry data

    DEFF Research Database (Denmark)

    Brazhe, Alexey R; Marsh, Donald J; von Holstein-Rathlou, Niels-Henrik


    Full-field laser speckle microscopy provides real-time imaging of superficial blood flow rate. Here we apply continuous wavelet transform to time series of speckle-estimated blood flow from each pixel of the images to map synchronous patterns in instantaneous frequency and phase on the surface...... of rat kidneys. The regulatory mechanism in the renal microcirculation generates oscillations in arterial blood flow at several characteristic frequencies. Our approach to laser speckle image processing allows detection of frequency and phase entrainments, visualization of their patterns, and estimation...

  1. Laser speckle velocimetry applied to Rayleigh-Benard convection

    International Nuclear Information System (INIS)

    Arroyo, M.P.; Yonte, T.; Quintanilla, M.; Saviron, J.M.


    An application of speckle velocimetry technique to Rayleigh-Benard convection is presented. A 5-mW He-Ne laser allows precise determination of the two-dimensional velocity flow field, up to several mm/sec. The digital techniques used to analyze automatically the multiexposed photographs and to generate velocity and vorticity fields are described. The obtained results are in good agreement with previously reported data. The ability of the technique to cover other experimental conditions is discussed. 14 references

  2. The Magnetic Nanoparticle Movement in Magnetic Fluid Characterized by the Laser Dynamic Speckle Interferometry

    Directory of Open Access Journals (Sweden)

    Xijun Wang


    Full Text Available A dual scanning laser speckle interferometry experiment was designed to observe the dynamic behavior of the magnetic fluid actuated by a magnetic field. In order to improve the spatial resolution of the dynamic speckle measurement, the phase delay scanning was used to compensate the additional phase variation which was caused by the transverse scanning. The correlation coefficients corresponding to the temporal dynamic speckle patterns within the same time interval scattering from the nanoparticles were calculated in the experiment on nanoscale magnetic clusters. In the experiment, the speckle of the magnetic nanoparticle fluid movement has been recorded by the lens unmounted CCD within the interferometry strips, although the speckle led to the distinguished annihilation of the light coherence. The results have showed that the nanoparticle fluid dynamic properties appeared synergistically in the fringe speckles. The analyses of the nanoparticle's relative speed and the speckle pattern moving amount in the fringes have proved the nanoparticle’s movement in a laminar flow in the experiment.

  3. Color digital holography using speckle illumination by means of a multi-mode fiber (United States)

    Funamizu, Hideki; Shimoma, Shohei; Aizu, Yoshihisa


    We present color digital holography using speckle illumination by means of a multi-mode fiber. In this technique, speckle fields emitted from the fiber are used as both a reference wave and a wavefront illuminating an object. For three wavelengths, the interference patterns of two coherent waves are recorded as digital holograms on a CCD camera. A speckle method is used for suppressing DC terms and reducing a twin image in an in-line color digital holography. The speckle fields are changed by vibrating the multi-mode fiber using a vibrator, and a number of holograms are acquired to average reconstructed images. The dependence of the averaged number of holograms on color quality of reconstructed images is evaluated by chromaticity coordinates and color differences in colorimetry.

  4. Laser Speckle Contrast Imaging: theory, instrumentation and applications. (United States)

    Senarathna, Janaka; Rege, Abhishek; Li, Nan; Thakor, Nitish V


    Laser Speckle Contrast Imaging (LSCI) is a wide field of view, non scanning optical technique for observing blood flow. Speckles are produced when coherent light scattered back from biological tissue is diffracted through the limiting aperture of focusing optics. Mobile scatterers cause the speckle pattern to blur; a model can be constructed by inversely relating the degree of blur, termed speckle contrast to the scatterer speed. In tissue, red blood cells are the main source of moving scatterers. Therefore, blood flow acts as a virtual contrast agent, outlining blood vessels. The spatial resolution (~10 μm) and temporal resolution (10 ms to 10 s) of LSCI can be tailored to the application. Restricted by the penetration depth of light, LSCI can only visualize superficial blood flow. Additionally, due to its non scanning nature, LSCI is unable to provide depth resolved images. The simple setup and non-dependence on exogenous contrast agents have made LSCI a popular tool for studying vascular structure and blood flow dynamics. We discuss the theory and practice of LSCI and critically analyze its merit in major areas of application such as retinal imaging, imaging of skin perfusion as well as imaging of neurophysiology.

  5. Speckle Interferometry. I. A Test on an Earth Orbital Satellite. (United States)


    16 3. Short Exposure Speckle Photos for Betelgeuse , Point Source, and Binary Star...another star, the supergiant star Betelgeuse . The resemblence of these photos to laser speckle photos has led to the process being called "speckle

  6. Gaussian processes for machine learning. (United States)

    Seeger, Matthias


    Gaussian processes (GPs) are natural generalisations of multivariate Gaussian random variables to infinite (countably or continuous) index sets. GPs have been applied in a large number of fields to a diverse range of ends, and very many deep theoretical analyses of various properties are available. This paper gives an introduction to Gaussian processes on a fairly elementary level with special emphasis on characteristics relevant in machine learning. It draws explicit connections to branches such as spline smoothing models and support vector machines in which similar ideas have been investigated. Gaussian process models are routinely used to solve hard machine learning problems. They are attractive because of their flexible non-parametric nature and computational simplicity. Treated within a Bayesian framework, very powerful statistical methods can be implemented which offer valid estimates of uncertainties in our predictions and generic model selection procedures cast as nonlinear optimization problems. Their main drawback of heavy computational scaling has recently been alleviated by the introduction of generic sparse approximations.13,78,31 The mathematical literature on GPs is large and often uses deep concepts which are not required to fully understand most machine learning applications. In this tutorial paper, we aim to present characteristics of GPs relevant to machine learning and to show up precise connections to other "kernel machines" popular in the community. Our focus is on a simple presentation, but references to more detailed sources are provided.

  7. Polarization speckles and generalized Stokes vector wave: a review [invited

    DEFF Research Database (Denmark)

    Takeda, Mitsuo; Wang, Wei; Hanson, Steen Grüner


    Stokes parameters proposed by Korotkova and Wolf, and introduce its time-domain representation to describe the space-time evolution of the correlation between random electric vector fields at two different space-time points. This time-domain generalized Stokes vector, with components similar to those......We review some of the statistical properties of polarization-related speckle phenomena, with an introduction of a less known concept of polarization speckles and their spatial degree of polarization. As a useful means to characterize twopoint vector field correlations, we review the generalized...... of the beam coherence polarization matrix proposed by Gori, is shown to obey the wave equation in exact analogy to a coherence function of scalar fields. Because of this wave nature, the time-domain generalized Stokes vector is referred to as generalized Stokes vector wave in this paper....

  8. Gravitational Lensing Mass Mapping with Gaussian Processes (United States)

    Schneider, Michael; Ng, Karen; Dawson, William; Marshall, Phil; Meyers, Joshua; Bard, Deborah


    We infer gravitational lensing shear and convergence fields from galaxy ellipticity catalogs under a Gaussian Process prior for the lensing potential. We demonstrate the performance of our algorithm with simulated Gaussian-distributed cosmological lensing shear maps and a reconstruction of the mass distribution of the merging galaxy cluster Abell 781 using galaxy ellipticities measured with the Deep Lens Survey. Given interim posterior samples of lensing shear or convergence fields on the sky, we describe an algorithm to infer cosmological parameters via lens field marginalization. In the most general formulation of our algorithm we make no assumptions about weak shear orGaussian-distributed shape noise or shears. Because we require solutions and matrix determinants of a linear system of dimension that scales with the number of galaxies, we present computational performance metrics with approximate algorithms that introduce sparsity in the Gaussian Process kernel.

  9. Evolution of the scintillation index and the optical vortex density in speckle fields after removal of the least-squares phase

    CSIR Research Space (South Africa)

    Chen, M


    Full Text Available Knowledge of the behavior of stochastic optical fields can aid the understanding of the scintillation of light propagating through a turbulent medium. For this purpose, the authors perform a numerical investigation of the evolution...

  10. Methods for determination of mean speckle size in simulated speckle pattern

    Czech Academy of Sciences Publication Activity Database

    Hamarová, Ivana; Šmíd, Petr; Horvath, P.; Hrabovský, M.


    Roč. 14, č. 3 (2014), 177-182 ISSN 1335-8871 R&D Projects: GA ČR GA13-12301S Institutional support: RVO:68378271 Keywords : simulation * speckle * speckle pattern * mean speckle size * autocorrelation function Subject RIV: BH - Optics, Masers, Lasers Impact factor: 0.989, year: 2014

  11. Speckle photography applied to measure deformations of very large structures (United States)

    Conley, Edgar; Morgan, Chris K.


    Fundamental principles of mechanics have recently been brought to bear on problems concerning very large structures. Fields of study include tectonic plate motion, nuclear waste repository vault closure mechanisms, the flow of glacier and sea ice, and highway bridge damage assessment and residual life prediction. Quantitative observations, appropriate for formulating and verifying models, are still scarce however, so the need to adapt new methods of experimental mechanics is clear. Large dynamic systems often exist in environments subject to rapid change. Therefore, a simple field technique that incorporates short time scales and short gage lengths is required. Further, the measuring methods must yield displacements reliably, and under oft-times adverse field conditions. Fortunately, the advantages conferred by an experimental mechanics technique known as speckle photography nicely fulfill this rather stringent set of performance requirements. Speckle seemed to lend itself nicely to the application since it is robust and relatively inexpensive. Experiment requirements are minimal -- a camera, high resolution film, illumination, and an optically rough surface. Perhaps most important is speckle's distinct advantage over point-by-point methods: It maps the two dimensional displacement vectors of the whole field of interest. And finally, given the method's high spatial resolution, relatively short observation times are necessary. In this paper we discuss speckle, two variations of which were used to gage the deformation of a reinforced concrete bridge structure subjected to bending loads. The measurement technique proved to be easily applied, and yielded the location of the neutral axis self consistently. The research demonstrates the feasibility of using whole field techniques to detect and quantify surface strains of large structures under load.

  12. Gaussian and Non-Gaussian operations on non-Gaussian state: engineering non-Gaussianity

    Directory of Open Access Journals (Sweden)

    Olivares Stefano


    Full Text Available Multiple photon subtraction applied to a displaced phase-averaged coherent state, which is a non-Gaussian classical state, produces conditional states with a non trivial (positive Glauber-Sudarshan Prepresentation. We theoretically and experimentally demonstrate that, despite its simplicity, this class of conditional states cannot be fully characterized by direct detection of photon numbers. In particular, the non-Gaussianity of the state is a characteristics that must be assessed by phase-sensitive measurements. We also show that the non-Gaussianity of conditional states can be manipulated by choosing suitable conditioning values and composition of phase-averaged states.

  13. Ectoparasites and intestinal helminths of speckled pigeon ...

    African Journals Online (AJOL)

    Ectoparasites and intestinal helminths of speckled pigeon ( Columba guinea Hartlaub and Finsch 1870) in Zaria, Nigeria. ... Science World Journal ... A total of 30 (20 males and 10 females) Speckled Pigeons trapped from the wild in Zaria and its environs, Nigeria, were examined for ectoparasites and intestinal helminths, ...

  14. New developments in NDT through electronic speckle pattern interferometry

    International Nuclear Information System (INIS)

    Mohan, S.; Murugesan, P; Mas, R.H.


    Full text: Optical holography and speckle interferometry are the emerging optical techniques that can be used for the measurements of microscopic parameters such as displacement, strain, stress and slope. These techniques are applied in various fields such as surface studies, non destructive testing, speckle metrology and steller interferometry. Even though many new NDT methods are available, the suitability for a specific application is based on the material property, nature of defects and sensitivity of detection. Difficulty in radiographic technique is that it fails in detecting tight cracks, planar defects and debonds. Microwave techniques has limited sensitivity for the defect detection and it is not suitable for the objects with metallic cases since the metals are perfect reflectors for the microwaves. Low modulus material attenuates the acoustic energy completely, making ultrasonic testing techniques not feasible. The recently evolved optoelectronic technique namely Electronic Speckle Pattern interferometry (ESPI) is a fast developing optical technique widely used for measuring displacement components, their derivatives, surface roughness, surface contours, shape and others. Due to non contact nature and high sensitivity, this technique has been used as a powerful on line inspection tool for non destructive pattern of materials in industrial environment. The salient feature of ESPI is its capability to display the correlation fringes in a real time on a monitor without the need of photographic processing or optical filtering. ESPI is an alternate non destructive technique suitable for propellant grains and other low modulus materials used in space vehicle systems. The optoelectronic technique can be used to detect cracks, voids and residual stresses etc.., in the components in the industrial environment. In the present investigation, speckle non destructive testing has been carried out on some selected low modulus materials used in space vehicles. The

  15. SU-D-BRA-05: Prostatectomy Patient's Bladder and Rectum Inter-Fraction Organ Motion and Deformation Can Be Described by a Gaussian Signed Distance Field. (United States)

    Hu, E; Zhou, S


    The inter-fraction organ motion/deformation can be conveniently modeled using Bayesian theory with Normal-gamma conjugate prior if signed distance from any fixed point in space to surface of the organ of interest obeys normal distribution. In this study, we investigated whether the inter-fraction motion/deformation of bladder and rectum observed from clinical prostatectomy patients satisfy this normality condition. 285 treatment planning CT and daily CT-on-rails scans from 7 prostatectomy patients were used in this study. Both bladder and rectum were contoured on all scans. Each patient's daily CT-on-rails scans were registered to his treatment planning CT and the bladder/rectum contours were mapped into treatment planning CT space for analysis. A cubic box with orientations along treatment planning CT image axes is defined to contain all bladders/rectums with 2cm margin. For each voxel inside this box (size: 2mm×2mm×1.5mm), its distance to the bladder/rectum surfaces was measured. Sign is added to the distance to indicate whether a point is inside or outside of an organ of interest. Now the inter-fraction motion/deformation of bladder/rectum can be characterized by the distance variation from the voxels to the bladder/rectum surface. Jarque-Bera normality statistical test was employed to examine whether the signed distances obey normal distribution. For each patient, the signed distance to bladder or rectum from at least 99.99% of the voxels passed the Jarque-Bera test with p-value 0.05. For prostatectomy patients, their bladder or rectum inter-fraction organ motion/deformation can be statistically described by a Gaussian signed distance field. This makes it possible to use Bayesian statistics model with Normal-gamma conjugate prior to predict bladder or rectum daily location and shape during a prostatectomy patient fractionated radiotherapy. © 2012 American Association of Physicists in Medicine.

  16. Vortices in Gaussian beams

    CSIR Research Space (South Africa)

    Roux, FS


    Full Text Available , t0)} = P(du, dv) {FR{g(u, v, t0)}} Replacement: u→ du = t− t0 i2 ∂ ∂u′ v → dv = t− t0 i2 ∂ ∂v′ CSIR National Laser Centre – p.13/30 Differentiation i.s.o integration Evaluate the integral over the Gaussian beam (once and for all). Then, instead... . Gaussian beams with vortex dipoles CSIR National Laser Centre – p.2/30 Gaussian beam notation Gaussian beam in normalised coordinates: g(u, v, t) = exp ( −u 2 + v2 1− it ) u = xω0 v = yω0 t = zρ ρ = piω20 λ ω0 — 1/e2 beam waist radius; ρ— Rayleigh range ω ω...

  17. Gaussian operations and privacy

    International Nuclear Information System (INIS)

    Navascues, Miguel; Acin, Antonio


    We consider the possibilities offered by Gaussian states and operations for two honest parties, Alice and Bob, to obtain privacy against a third eavesdropping party, Eve. We first extend the security analysis of the protocol proposed in [Navascues et al. Phys. Rev. Lett. 94, 010502 (2005)]. Then, we prove that a generalized version of this protocol does not allow one to distill a secret key out of bound entangled Gaussian states

  18. HE11 radiation patterns and gaussian approximations

    International Nuclear Information System (INIS)

    Rebuffi, L.; Crenn, J.P.


    The possibility of approximating the HE11 radiation pattern with a Gaussian distribution is presented. A numerical comparison between HE11 far-field theoretical patterns and Abrams and Crenn approximations permits an evaluation of the validity of these two approximations. A new numerically optimized HE11 Gaussian approximation for the far-field, extended to great part of the near field, has been found. In particular, the value given for the beam radius at the waist, has been demonstrated to give the best HE11 Gaussian approximation in the far-field. The Crenn approximation is found to be very close to this optimal approximation, while the Abrams approximation is shown to be less precise. Universal curves for intensity, amplitude and power distribution are given for the HE11 radiated mode. These results are of interest for laser waveguide applications and for plasma ECRH transmission systems


    Directory of Open Access Journals (Sweden)

    Anna A. Isaeva


    Full Text Available The paper presents the application of speckle correlometry method with the spatial ring filtration of back scattered field with the usage of localized radiation source for the study of dynamic thermally activated processes in gel-like structures containing submicron particles and nanoparticles. Speckle-modulated images contain information about the processes taking place inside the investigated medium; therefore, they are effectively used in biomedicine and materials science. The transformation process from lysol to gel was considered in media based on technical gelatin dissolved in water with weight fraction equal to 0.28% containing titanium dioxide nanoparticles TiO2 (volume fraction of particles is equal to 0.1% and 0.01% and media based on food gelatin dissolved in water with weight fraction equal to 0.3% containing titanium dioxide nanoparticles TiO2 (volume fraction of particles is equal to 0.01% and 0.01%. The temperature of the medium during the structural transformation of "sol-gel" system was changed from 50 to 25°C. To estimate the experimentally obtained distribution of space-time intensity fluctuations of backscattered speckle fields, the correlation analysis and the formalism of Kolmogorov structure functions were used. The estimations of activation temperatures for the “sol-gel” transition process for technical and food gelatin were obtained. This approach can be successfully applied for the study of dynamic systems, for example, the demonstration of Brownian particle movements.

  20. Excitation of helium Rydberg states and doubly excited resonances in strong extreme ultraviolet fields: Full-dimensional quantum dynamics using exponentially tempered Gaussian basis sets

    Czech Academy of Sciences Publication Activity Database

    Kaprálová-Žďánská, Petra Ruth; Šmydke, Jan; Civiš, S.


    Roč. 139, č. 10 (2013), s. 104314 ISSN 0021-9606 R&D Projects: GA AV ČR IAAX00100903; GA MŠk(CZ) ME10046; GA ČR GAP205/11/0571 Institutional support: RVO:68378271 Keywords : Gaussian distribution * helium * oscillator strengths * quantum chemistry * rotational states * Rydberg states * two-photon processes Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.122, year: 2013

  1. Nonclassicality by Local Gaussian Unitary Operations for Gaussian States

    Directory of Open Access Journals (Sweden)

    Yangyang Wang


    Full Text Available A measure of nonclassicality N in terms of local Gaussian unitary operations for bipartite Gaussian states is introduced. N is a faithful quantum correlation measure for Gaussian states as product states have no such correlation and every non product Gaussian state contains it. For any bipartite Gaussian state ρ A B , we always have 0 ≤ N ( ρ A B < 1 , where the upper bound 1 is sharp. An explicit formula of N for ( 1 + 1 -mode Gaussian states and an estimate of N for ( n + m -mode Gaussian states are presented. A criterion of entanglement is established in terms of this correlation. The quantum correlation N is also compared with entanglement, Gaussian discord and Gaussian geometric discord.

  2. Position control of ECRH launcher mirrors by laser speckle sensor

    International Nuclear Information System (INIS)

    Michelsen, Poul K.; Bindslev, Henrik; Hansen, Rene Skov; Hanson, Steen G.


    The planned ECRH system for JET included several fixed and steerable mirrors some of which should have been fixed to the building structure and some to the JET vessel structure. A similar system may be anticipated for ITER and for other fusion devices in the future. In order to have high reproducibility of the ECRH beam direction, it is necessary to know the exact positions of the mirrors. This is not a trivial problem because of thermal expansion of the vessel structures and of the launcher itself and of its support structure, the mechanical load on mirrors and support structures, and the accessibility to the various mirrors. We suggest to use a combination of infrared diagnostic of beam spot positions and a new technique published recently, which is based on a non-contact laser speckle sensor for measuring one- and two-dimensional angular displacement. The method is based on Fourier transforming the scattered field from a single laser beam that illuminates the target. The angular distribution of the light field at the target is linearly mapped onto an array image sensor placed in the Fourier plane. Measuring the displacement of this so-called speckle pattern facilitates the determination of the mirror orientation. Transverse target movement can be measured by observing the speckle movement in the image plane of the object. No special surface treatment is required for surfaces having irregularities of the order of or larger than the wavelength of the incident light. For the JET ECRH launcher it is mainly for the last mirror pointing towards the plasma where the technique may be useful. This mirror has to be steerable in order to reflect the microwave beam in the correct direction towards the plasma. Maximum performance of the microwave heating requires that the beam hits this mirror at its centre and that the mirror is turned in the correct angle. Inaccuracies in the positioning of the pull rods for controlling the mirror turning and thermal effects makes it

  3. White Light Optical Processing Of Speckle Interferograms (United States)

    Yu, F. T.; Ruterbusch, P. H.; Gerhart, G. R.


    A technique of white-light color encoding of misfocused speckle interferometric fringe patterns is presented. The encoding is performed in the spatial frequency plane with color filters. This technique allows the viewing of a multiset of encoded speckle interferograms simultaneously. Thus it may provide new informational interferometric aspects of the object under stress or vibration. The effect on the speckle fringe pattern due to the spatial filtering is briefly discussed and experimental demonstrations of color encoded fringe patterns are presented. Due to the simplicity and versatility of the processing technique, we feel that the technique may develop into a practical tool for strain, stress and vibrational measurement.

  4. Speckle imaging algorithms for planetary imaging

    Energy Technology Data Exchange (ETDEWEB)

    Johansson, E. [Lawrence Livermore National Lab., CA (United States)


    I will discuss the speckle imaging algorithms used to process images of the impact sites of the collision of comet Shoemaker-Levy 9 with Jupiter. The algorithms use a phase retrieval process based on the average bispectrum of the speckle image data. High resolution images are produced by estimating the Fourier magnitude and Fourier phase of the image separately, then combining them and inverse transforming to achieve the final result. I will show raw speckle image data and high-resolution image reconstructions from our recent experiment at Lick Observatory.

  5. Learning conditional Gaussian networks

    DEFF Research Database (Denmark)

    Bøttcher, Susanne Gammelgaard

    This paper considers conditional Gaussian networks. The parameters in the network are learned by using conjugate Bayesian analysis. As conjugate local priors, we apply the Dirichlet distribution for discrete variables and the Gaussian-inverse gamma distribution for continuous variables, given...... a configuration of the discrete parents. We assume parameter independence and complete data. Further, to learn the structure of the network, the network score is deduced. We then develop a local master prior procedure, for deriving parameter priors in these networks. This procedure satisfies parameter...... independence, parameter modularity and likelihood equivalence. Bayes factors to be used in model search are introduced. Finally the methods derived are illustrated by a simple example....

  6. Dynamic speckle analysis using multivariate techniques

    International Nuclear Information System (INIS)

    López-Alonso, José M; Alda, Javier; Rabal, Héctor; Grumel, Eduardo; Trivi, Marcelo


    In this work we use principal components analysis to characterize dynamic speckle patterns. This analysis quantitatively identifies different dynamics that could be associated to physical phenomena occurring in the sample. We also found the contribution explained by each principal component, or by a group of them. The method analyzes the paint drying process over a hidden topography. It can be used for fast screening and identification of different dynamics in biological or industrial samples by means of dynamic speckle interferometry. (paper)

  7. Vegetation Detection in Stress of Moisture Shortage Based on Laser Speckle Recognition (United States)

    Ishizawa, Hiroaki; Matsuo, Tsukasa; Miki, Takashi

    This paper describes a new measuring method of plant vigor by using Laser speckle pattern. Furthermore, this proposes a practical application of this presented measurement system. The measuring instrument is consisted by a He-Ne Laser as the light source, and a set of optics, such as reflectors, a beam expander. The speckle pattern could be measured by a CCD camera through lenses. A Pothos (Epiremnum aureum) and Japanese morning glory (Ipomoea nil) were used as the sample plant. Their intact leaves were measured the speckle pattern images. Visible but small vigor veins could be clearly observed in the images obtained by the speckle patterns. On the other hand, withered ones have shown different images. The relationship has been obtained between the feature of the images and the chlorophyll degradation. It would be expected that the symptom of plant against some stress could be detected by measuring the Laser speckle pattern. It could be used as the sensor of the field server system at every field monitoring site.


    International Nuclear Information System (INIS)

    Lindner, Robert R.; Vera-Ciro, Carlos; Murray, Claire E.; Stanimirović, Snežana; Babler, Brian; Heiles, Carl; Hennebelle, Patrick; Goss, W. M.; Dickey, John


    We present a new algorithm, named Autonomous Gaussian Decomposition (AGD), for automatically decomposing spectra into Gaussian components. AGD uses derivative spectroscopy and machine learning to provide optimized guesses for the number of Gaussian components in the data, and also their locations, widths, and amplitudes. We test AGD and find that it produces results comparable to human-derived solutions on 21 cm absorption spectra from the 21 cm SPectral line Observations of Neutral Gas with the EVLA (21-SPONGE) survey. We use AGD with Monte Carlo methods to derive the H i line completeness as a function of peak optical depth and velocity width for the 21-SPONGE data, and also show that the results of AGD are stable against varying observational noise intensity. The autonomy and computational efficiency of the method over traditional manual Gaussian fits allow for truly unbiased comparisons between observations and simulations, and for the ability to scale up and interpret the very large data volumes from the upcoming Square Kilometer Array and pathfinder telescopes

  9. Bounded Gaussian process regression

    DEFF Research Database (Denmark)

    Jensen, Bjørn Sand; Nielsen, Jens Brehm; Larsen, Jan


    We extend the Gaussian process (GP) framework for bounded regression by introducing two bounded likelihood functions that model the noise on the dependent variable explicitly. This is fundamentally different from the implicit noise assumption in the previously suggested warped GP framework. We...


    Energy Technology Data Exchange (ETDEWEB)

    Lindner, Robert R.; Vera-Ciro, Carlos; Murray, Claire E.; Stanimirović, Snežana; Babler, Brian [Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706 (United States); Heiles, Carl [Radio Astronomy Lab, UC Berkeley, 601 Campbell Hall, Berkeley, CA 94720 (United States); Hennebelle, Patrick [Laboratoire AIM, Paris-Saclay, CEA/IRFU/SAp-CNRS-Université Paris Diderot, F-91191 Gif-sur Yvette Cedex (France); Goss, W. M. [National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville, Socorro, NM 87801 (United States); Dickey, John, E-mail: [University of Tasmania, School of Maths and Physics, Private Bag 37, Hobart, TAS 7001 (Australia)


    We present a new algorithm, named Autonomous Gaussian Decomposition (AGD), for automatically decomposing spectra into Gaussian components. AGD uses derivative spectroscopy and machine learning to provide optimized guesses for the number of Gaussian components in the data, and also their locations, widths, and amplitudes. We test AGD and find that it produces results comparable to human-derived solutions on 21 cm absorption spectra from the 21 cm SPectral line Observations of Neutral Gas with the EVLA (21-SPONGE) survey. We use AGD with Monte Carlo methods to derive the H i line completeness as a function of peak optical depth and velocity width for the 21-SPONGE data, and also show that the results of AGD are stable against varying observational noise intensity. The autonomy and computational efficiency of the method over traditional manual Gaussian fits allow for truly unbiased comparisons between observations and simulations, and for the ability to scale up and interpret the very large data volumes from the upcoming Square Kilometer Array and pathfinder telescopes.

  11. The SKED: speckle knife edge detector

    International Nuclear Information System (INIS)

    Sharpies, S D; Light, R A; Achamfuo-Yeboah, S O; Clark, M; Somekh, M G


    The knife edge detector—also known as optical beam deflection—is a simple and robust method of detecting ultrasonic waves using a laser. It is particularly suitable for detection of high frequency surface acoustic waves as the response is proportional to variation of the local tilt of the surface. In the case of a specular reflection of the incident laser beam from a smooth surface, any lateral movement of the reflected beam caused by the ultrasonic waves is easily detected by a pair of photodiodes. The major disadvantage of the knife edge detector is that it does not cope well with optically rough surfaces, those that give a speckled reflection. The optical speckles from a rough surface adversely affect the efficiency of the knife edge detector, because 'dark' speckles move synchronously with 'bright' speckles, and their contributions to the ultrasonic signal cancel each other out. We have developed a new self-adapting sensor which can cope with the optical speckles reflected from a rough surface. It is inelegantly called the SKED—speckle knife edge detector—and like its smooth surface namesake it is simple, cheap, compact, and robust. We describe the theory of its operation, and present preliminary experimental results validating the overall concept and the operation of the prototype device

  12. Color quality improvement of reconstructed images in color digital holography using speckle method and spectral estimation (United States)

    Funamizu, Hideki; Onodera, Yusei; Aizu, Yoshihisa


    In this study, we report color quality improvement of reconstructed images in color digital holography using the speckle method and the spectral estimation. In this technique, an object is illuminated by a speckle field and then an object wave is produced, while a plane wave is used as a reference wave. For three wavelengths, the interference patterns of two coherent waves are recorded as digital holograms on an image sensor. Speckle fields are changed by moving a ground glass plate in an in-plane direction, and a number of holograms are acquired to average the reconstructed images. After the averaging process of images reconstructed from multiple holograms, we use the Wiener estimation method for obtaining spectral transmittance curves in reconstructed images. The color reproducibility in this method is demonstrated and evaluated using a Macbeth color chart film and staining cells of onion.

  13. The possibilities laser and computer Speckle-holographic of the interferometer for study concentrated flow to energy

    International Nuclear Information System (INIS)

    Goncharov, A.V.; Lonin, Yu.F.; Kudryavtsev, V.I.; Poddubko, N.S.; Tolstolutskij, A.G.


    Proposed solution to the problem of measuring small energies can be carried out by creating a new measuring device based on the unique properties of speckle holography with modern developments in the field of video and computer equipment. The developed laser speckle computer holographic interferometer (LKSGI) is a rapid analysis instrument movements at the nanometer scale, and with it the energy level mJ with the spatial and temporal resolution.

  14. Convergence of posteriors for discretized log Gaussian Cox processes

    DEFF Research Database (Denmark)

    Waagepetersen, Rasmus Plenge


    In Markov chain Monte Carlo posterior computation for log Gaussian Cox processes (LGCPs) a discretization of the continuously indexed Gaussian field is required. It is demonstrated that approximate posterior expectations computed from discretized LGCPs converge to the exact posterior expectations...... when the cell sizes of the discretization tends to zero. The effect of discretization is studied in a data example....

  15. Characterization of spatial polarization fluctuations in scattered field

    International Nuclear Information System (INIS)

    Kumar Singh, Rakesh; Naik, Dinesh N; Itou, Hitoshi; Miyamoto, Yoko; Takeda, Mitsuo


    We extend the concept of Poincare vector correlations for the characterization of spatial polarization fluctuations of scattered fields. Spatial (rather than temporal) dynamics of polarization in the scattered field is investigated experimentally by detecting instantaneous polarization with a specially designed polarization interferometer. Use of the Poincare-vector correlation in characterization is demonstrated by determining polarization dynamics of three different cases of scattered fields. This confirms usefulness of the proposed technique in diagnosis of scatterers. Under the condition of spatial ergodicity and Gaussian statistics of the scattered field, we replace the ensemble average of the instantaneous field with the space average, and estimate generalized Stokes parameters (GSPs) of the polarization speckles. Results of GSPs are used to obtain spatial correlation of the Poincare vectors. (paper)

  16. The Gaussian entropy of fermionic systems

    Energy Technology Data Exchange (ETDEWEB)

    Prokopec, Tomislav, E-mail: [Institute for Theoretical Physics (ITP) and Spinoza Institute, Utrecht University, Postbus 80195, 3508 TD Utrecht (Netherlands); Schmidt, Michael G., E-mail: [Institut fuer Theoretische Physik, Heidelberg University, Philosophenweg 16, D-69120 Heidelberg (Germany); Weenink, Jan, E-mail: [Institute for Theoretical Physics (ITP) and Spinoza Institute, Utrecht University, Postbus 80195, 3508 TD Utrecht (Netherlands)


    We consider the entropy and decoherence in fermionic quantum systems. By making a Gaussian Ansatz for the density operator of a collection of fermions we study statistical 2-point correlators and express the entropy of a system fermion in terms of these correlators. In a simple case when a set of N thermalised environmental fermionic oscillators interacts bi-linearly with the system fermion we can study its time dependent entropy, which also represents a quantitative measure for decoherence and classicalization. We then consider a relativistic fermionic quantum field theory and take a mass mixing term as a simple model for the Yukawa interaction. It turns out that even in this Gaussian approximation, the fermionic system decoheres quite effectively, such that in a large coupling and high temperature regime the system field approaches the temperature of the environmental fields. - Highlights: Black-Right-Pointing-Pointer We construct the Gaussian density operator for relativistic fermionic systems. Black-Right-Pointing-Pointer The Gaussian entropy of relativistic fermionic systems is described in terms of 2-point correlators. Black-Right-Pointing-Pointer We explicitly show the growth of entropy for fermionic fields mixing with a thermal fermionic environment.

  17. OCT Amplitude and Speckle Statistics of Discrete Random Media

    NARCIS (Netherlands)

    Almasian, Mitra; van Leeuwen, Ton G.; Faber, Dirk J.


    Speckle, amplitude fluctuations in optical coherence tomography (OCT) images, contains information on sub-resolution structural properties of the imaged sample. Speckle statistics could therefore be utilized in the characterization of biological tissues. However, a rigorous theoretical framework

  18. Quantization analysis of speckle intensity measurements for phase retrieval

    DEFF Research Database (Denmark)

    Maallo, Anne Margarette S.; Almoro, Percival F.; Hanson, Steen Grüner


    Speckle intensity measurements utilized for phase retrieval (PR) are sequentially taken with a digital camera, which introduces quantization error that diminishes the signal quality. Influences of quantization on the speckle intensity distribution and PR are investigated numerically and experimen...

  19. Systematic and random errors in self-mixing measurements: effect of the developing speckle statistics. (United States)

    Donati, Silvano; Martini, Giuseppe


    We consider the errors introduced by speckle pattern statistics of a diffusing target in the measurement of large displacements made with a self-mixing interferometer (SMI), with sub-λ resolution and a range up to meters. As the source on the target side, we assume a diffuser with randomly distributed roughness. Two cases are considered: (i) a developing randomness in z-height profile, with standard deviation σ(z), increasing from ≪λ to ≫λ and uncorrelated spatially (x,y), and (ii) a fully developed z-height randomness (σ(z)≫λ) but spatially correlated with various correlation sizes ρ(x,y). We find that systematic and random errors of all types of diffusers converge to that of a uniformly illuminated diffuser, independent of the actual profile of radiant emittance and phase distribution, when the standard deviation σ(z) is increased or the scale of correlation ρ(x,y) is decreased. This convergence is a sign of speckle statistics development, as all distributions end up with the same errors of the fully developed diffuser. Convergence is earlier for a Gaussian-distributed amplitude than for other spot distributions. As an application of simulation results, we plot systematic and random errors of SMI measurements of displacement versus distance, for different source distributions standard deviations and correlations, both for intra- and inter-speckle displacements.

  20. Speckle technologies and measurement of retinal visual acuity in cataract patients (United States)

    Akchurin, Garif G.; Bakutkin, Valery V.; Radchenko, Elena Y.; Tuchin, Valery V.; Akchurin, Alexander G.


    Special features of speckle-modulated laser fields arising at in vitro measurements of different types of human cataractous lenses have been investigated experimentally. Computer analysis of digital images has allowed for estimation of destruction of the spatial coherence of a laser beam scattered by a turbid lens. Applied speckle-technologies have permitted the range of retinal angular resolution to be estimated with the help of laser retinometer at the stage of preoperative cataract diagnosis. An extent of laser retinometry at measuring visual acu9ity in patients with any type of cataract, and an incorrectness of its estimation by means of opto types charts have been set up.

  1. Three-dimensional displacement measurement by fringe projection and speckle photography

    International Nuclear Information System (INIS)

    Barrientos, B.; Garcia-Marquez, J.; Cerca, M.; Hernandez-Bernal, C.


    3D displacement fields are measured by the combination of two optical methods, fringe projection and speckle photography. The use of only one camera recording the necessary information implies that no calibration procedures are necessary as is the case in techniques based on stereoscopy. The out-of-plane displacement is measured by fringe projection whereas speckle photography yields the 2-D in-plane component. To show the feasibility of the technique, we analyze a detailed morphological spatio-temporal evolution of a model of the Earth's crust while subjected to compression forces. The results show that the combination of fringe projection and speckle photography is well suited for this type of studies

  2. Laser speckle-imaging of blood microcirculation in the brain cortex of laboratory rats in stress (United States)

    Vilensky, M. A.; Semyachkina-Glushkovskaya, Oxana V.; Timoshina, P. A.; Kuznetsova, Jana V.; Semyachkin-Glushkovskii, I. A.; Agafonov, Dmitry N.; Tuchin, Valerii V.


    The results of experimental approbation of the method of laser full-field speckle-imaging for monitoring the changes in blood microcirculation state of the brain cortex of laboratory rats under the conditions of developing stroke and administration of vasodilating and vasoconstrictive agents are presented. The studies aimed at the choice of the optimal conditions of speckle-image formation and recording were performed and the software implementing an adaptive algorithm for processing the data of measurements was created. The transfer of laser radiation to the probed region of the biotissue was implemented by means of a silica-polymer optical fibre. The problems and prospects of speckle-imaging of cerebral microcirculation of blood in laboratory and clinical conditions are discussed.

  3. In vivo lateral blood flow velocity measurement using speckle size estimation. (United States)

    Xu, Tiantian; Hozan, Mohsen; Bashford, Gregory R


    In previous studies, we proposed blood measurement using speckle size estimation, which estimates the lateral component of blood flow within a single image frame based on the observation that the speckle pattern corresponding to blood reflectors (typically red blood cells) stretches (i.e., is "smeared") if blood flow is in the same direction as the electronically controlled transducer line selection in a 2-D image. In this observational study, the clinical viability of ultrasound blood flow velocity measurement using speckle size estimation was investigated and compared with that of conventional spectral Doppler of carotid artery blood flow data collected from human patients in vivo. Ten patients (six male, four female) were recruited. Right carotid artery blood flow data were collected in an interleaved fashion (alternating Doppler and B-mode A-lines) with an Antares Ultrasound Imaging System and transferred to a PC via the Axius Ultrasound Research Interface. The scanning velocity was 77 cm/s, and a 4-s interval of flow data were collected from each subject to cover three to five complete cardiac cycles. Conventional spectral Doppler data were collected simultaneously to compare with estimates made by speckle size estimation. The results indicate that the peak systolic velocities measured with the two methods are comparable (within ±10%) if the scan velocity is greater than or equal to the flow velocity. When scan velocity is slower than peak systolic velocity, the speckle stretch method asymptotes to the scan velocity. Thus, the speckle stretch method is able to accurately measure pure lateral flow, which conventional Doppler cannot do. In addition, an initial comparison of the speckle size estimation and color Doppler methods with respect to computational complexity and data acquisition time indicated potential time savings in blood flow velocity estimation using speckle size estimation. Further studies are needed for calculation of the speckle stretch method

  4. Speckle perception and disturbance limit in laser based projectors (United States)

    Verschaffelt, Guy; Roelandt, Stijn; Meuret, Youri; Van den Broeck, Wendy; Kilpi, Katriina; Lievens, Bram; Jacobs, An; Janssens, Peter; Thienpont, Hugo


    We investigate the level of speckle that can be tolerated in a laser cinema projector. For this purpose, we equipped a movie theatre room with a prototype laser projector. A group of 186 participants was gathered to evaluate the speckle perception of several, short movie trailers in a subjective `Quality of Experience' experiment. This study is important as the introduction of lasers in projection systems has been hampered by the presence of speckle in projected images. We identify a speckle disturbance threshold by statistically analyzing the observers' responses for different values of the amount of speckle, which was monitored using a well-defined speckle measurement method. The analysis shows that the speckle perception of a human observer is not only dependent on the objectively measured amount of speckle, but it is also strongly influenced by the image content. As is also discussed in [Verschaffelt et al., Scientific Reports 5, art. nr. 14105, 2015] we find that, for moving images, the speckle becomes disturbing if the speckle contrast becomes larger than 6.9% for the red, 6.0% for the green, and 4.8% for the blue primary colors of the projector, whereas for still images the speckle detection threshold is about 3%. As we could not independently tune the speckle contrast of each of the primary colors, this speckle disturbance limit seems to be determined by the 6.9% speckle contrast of the red color as this primary color contains the largest amount of speckle. The speckle disturbance limit for movies thus turns out to be substantially larger than that for still images, and hence is easier to attain.

  5. Integration of speckle de-noising and image segmentation using ...

    Indian Academy of Sciences (India)

    In addition to speckle suppres- sion, an ideal filter must preserve edges and texture information. In the literature, adaptive filters for speckle removal are preferred for this purpose, since most of the well-known speckle removal filters perform the calculation of the local observed mean along with normalized standard deviation.

  6. Integration of speckle de-noising and image segmentation using ...

    Indian Academy of Sciences (India)

    Aperture Radar (SAR) image because of its imperviousness to unfavourable weather conditions. However, they suffer from the speckle noise. Hence, the processing of SAR image is applied in two stages: speckle removal filters and image segmentation methods for flood mapping. The speckle noise has been reduced.

  7. Dynamic speckle study of microbial growth (United States)

    Vincitorio, F. M.; Mulone, C.; Marcuzzi, P. A.; Budini, N.; Freyre, C.; Lopez, A. J.; Ramil, A.


    In this work we present a characterization of yeast dynamic speckle activity during growth in an isolated agar culture medium. We found that it is possible to detect the growth of the microorganisms even before they turn out to be visible. By observing the time evolution of the speckle activity at different regions of the culture medium we could extract a map of the growth process, which served to analyze how the yeast develops and spreads over the agar's medium. An interesting point of this study concerns with the influence of the laser light on the yeast growth rate. We have found that yeast finds hard to develop at regions with higher laser light illumination, although we used a synchronous system to capture the speckle pattern. The results obtained in this work would serve us as a starting point to fabricate a detector of growing microorganism colonies, with obvious interesting applications in diverse areas.

  8. Interconversion of pure Gaussian states requiring non-Gaussian operations (United States)

    Jabbour, Michael G.; García-Patrón, Raúl; Cerf, Nicolas J.


    We analyze the conditions under which local operations and classical communication enable entanglement transformations between bipartite pure Gaussian states. A set of necessary and sufficient conditions had been found [G. Giedke et al., Quant. Inf. Comput. 3, 211 (2003)] for the interconversion between such states that is restricted to Gaussian local operations and classical communication. Here, we exploit majorization theory in order to derive more general (sufficient) conditions for the interconversion between bipartite pure Gaussian states that goes beyond Gaussian local operations. While our technique is applicable to an arbitrary number of modes for each party, it allows us to exhibit surprisingly simple examples of 2 ×2 Gaussian states that necessarily require non-Gaussian local operations to be transformed into each other.

  9. Sums and Gaussian vectors

    CERN Document Server

    Yurinsky, Vadim Vladimirovich


    Surveys the methods currently applied to study sums of infinite-dimensional independent random vectors in situations where their distributions resemble Gaussian laws. Covers probabilities of large deviations, Chebyshev-type inequalities for seminorms of sums, a method of constructing Edgeworth-type expansions, estimates of characteristic functions for random vectors obtained by smooth mappings of infinite-dimensional sums to Euclidean spaces. A self-contained exposition of the modern research apparatus around CLT, the book is accessible to new graduate students, and can be a useful reference for researchers and teachers of the subject.

  10. Cardiac functional analysis by laser speckle interferometry (United States)

    Ramachandran, G.; Singh, M.

    The laser speckle interference pattern during movement of a rough surface is employed to measure the respective displacements. The purpose of this work is to apply this technique in the form of laser speckle displacement cardiography to analyse the displacement patterns during the I and II heart sounds. The recording is performed by illuminating the chest over the cardiac region by collimated laser beam controlled by an ECG operated electric shutter. By analysis the 3-D displacement patterns are obtained. A comparison shows that the displacement at the apex, right ventricle, aortic and mitral valvular regions are significantly higher during I sound than that of II sound.

  11. Estimators for local non-Gaussianities

    International Nuclear Information System (INIS)

    Creminelli, P.; Senatore, L.; Zaldarriaga, M.


    We study the Likelihood function of data given f NL for the so-called local type of non-Gaussianity. In this case the curvature perturbation is a non-linear function, local in real space, of a Gaussian random field. We compute the Cramer-Rao bound for f NL and show that for small values of f NL the 3- point function estimator saturates the bound and is equivalent to calculating the full Likelihood of the data. However, for sufficiently large f NL , the naive 3-point function estimator has a much larger variance than previously thought. In the limit in which the departure from Gaussianity is detected with high confidence, error bars on f NL only decrease as 1/ln N pix rather than N pix -1/2 as the size of the data set increases. We identify the physical origin of this behavior and explain why it only affects the local type of non- Gaussianity, where the contribution of the first multipoles is always relevant. We find a simple improvement to the 3-point function estimator that makes the square root of its variance decrease as N pix -1/2 even for large f NL , asymptotically approaching the Cramer-Rao bound. We show that using the modified estimator is practically equivalent to computing the full Likelihood of f NL given the data. Thus other statistics of the data, such as the 4-point function and Minkowski functionals, contain no additional information on f NL . In particular, we explicitly show that the recent claims about the relevance of the 4-point function are not correct. By direct inspection of the Likelihood, we show that the data do not contain enough information for any statistic to be able to constrain higher order terms in the relation between the Gaussian field and the curvature perturbation, unless these are orders of magnitude larger than the size suggested by the current limits on f NL . (author)

  12. Speckle photo-electromotive force in Bi12SiO20: Effect of the speckle size (United States)

    Salazar, Ángel


    A study of the speckle photo-electromotive force (PEMF) in a photorefractive sensor of amplitudes of micro-oscillations is presented. The experimental behavior of the first harmonic of the photocurrent generated as a function of the average speckle diameter and the oscillation amplitude of the speckle pattern is analyzed for a sensor implemented with a Bi12SiO20 (BSO) crystal. For a given light intensity, a nearly constant value of the maximum amplitude of the first harmonic was experimentally observed for the range of speckle sizes considered. This experimental result and the linear dependence of the vibration amplitude yielding the maximum of the photocurrent as a function of the speckle diameter were appropriately described by the mathematical model considered. Results show the possibility of adequately selecting the speckle size to optimize the output of speckle PEMF-based sensors depending on the oscillation amplitude to be measured.

  13. Polynomials of Gaussians and vortex-Gaussian beams as complete, transversely confined bases. (United States)

    Gutiérrez-Cuevas, Rodrigo; Alonso, Miguel A


    A novel type of discrete basis for paraxial beams is proposed, consisting of monomial vortices times polynomials of Gaussians in the radial variable. These bases have the distinctive property that the effective size of their elements is roughly independent of element order, meaning that the optimal scaling for expanding a localized field does not depend significantly on truncation order. This behavior contrasts with that of bases composed of polynomials times Gaussians, such as Hermite-Gauss and Laguerre-Gauss modes, where the scaling changes roughly as the inverse square root of the truncation order.


    Directory of Open Access Journals (Sweden)

    Richard A Vitale


    Full Text Available For several decades, the topics of the title have had a fruitful interaction. This survey will describe some of these connections, including the GB/GC classification of convex bodies, Ito-Nisio singularities from a geometric viewpoint, Gaussian representation of intrinsic volumes, theWills functional in a Gaussian context, and inequalities.

  15. Spectral representation of Gaussian semimartingales

    DEFF Research Database (Denmark)

    Basse-O'Connor, Andreas


    The aim of the present paper is to characterize the spectral representation of Gaussian semimartingales. That is, we provide necessary and sufficient conditions on the kernel K for X t =∫ K t (s) dN s to be a semimartingale. Here, N denotes an independently scattered Gaussian random measure...

  16. Recovering dark-matter clustering from galaxies with Gaussianization (United States)

    McCullagh, Nuala; Neyrinck, Mark; Norberg, Peder; Cole, Shaun


    The Gaussianization transform has been proposed as a method to remove the issues of scale-dependent galaxy bias and non-linearity from galaxy clustering statistics, but these benefits have yet to be thoroughly tested for realistic galaxy samples. In this paper, we test the effectiveness of the Gaussianization transform for different galaxy types by applying it to realistic simulated blue and red galaxy samples. We show that in real space, the shapes of the Gaussianized power spectra of both red and blue galaxies agree with that of the underlying dark matter, with the initial power spectrum, and with each other to smaller scales than do the statistics of the usual (untransformed) density field. However, we find that the agreement in the Gaussianized statistics breaks down in redshift space. We attribute this to the fact that red and blue galaxies exhibit very different fingers of god in redshift space. After applying a finger-of-god compression, the agreement on small scales between the Gaussianized power spectra is restored. We also compare the Gaussianization transform to the clipped galaxy density field and find that while both methods are effective in real space, they have more complicated behaviour in redshift space. Overall, we find that Gaussianization can be useful in recovering the shape of the underlying dark-matter power spectrum to k ˜ 0.5 h Mpc-1 and of the initial power spectrum to k ˜ 0.4 h Mpc-1 in certain cases at z = 0.

  17. Thermo-mechanical toner transfer for high-quality digital image correlation speckle patterns (United States)

    Mazzoleni, Paolo; Zappa, Emanuele; Matta, Fabio; Sutton, Michael A.


    The accuracy and spatial resolution of full-field deformation measurements performed through digital image correlation are greatly affected by the frequency content of the speckle pattern, which can be effectively controlled using particles with well-defined and consistent shape, size and spacing. This paper introduces a novel toner-transfer technique to impress a well-defined and repeatable speckle pattern on plane and curved surfaces of metallic and cement composite specimens. The speckle pattern is numerically designed, printed on paper using a standard laser printer, and transferred onto the measurement surface via a thermo-mechanical process. The tuning procedure to compensate for the difference between designed and toner-transferred actual speckle size is presented. Based on this evidence, the applicability of the technique is discussed with respect to surface material, dimensions and geometry. Proof of concept of the proposed toner-transfer technique is then demonstrated for the case of a quenched and partitioned welded steel plate subjected to uniaxial tensile loading, and for an aluminum plate exposed to temperatures up to 70% of the melting point of aluminum and past the melting point of typical printer toner powder.

  18. NESSI and `Alopeke: Two new dual-channel speckle imaging instruments (United States)

    Scott, Nicholas J.


    NESSI and `Alopeke are two new speckle imagers built at NASA's Ames Research Center for community use at the WIYN and Gemini telescopes, respectively. The two instruments are functionally similar and include the capability for wide-field imaging in additional to speckle interferometry. The diffraction-limited imaging available through speckle effectively eliminates distortions due to the presence of Earth's atmosphere by `freezing out' changes in the atmosphere by taking extremely short exposures and combining the resultant speckles in Fourier space. This technique enables angular resolutions equal to the theoretical best possible for a given telescope, effectively giving space-based resolution from the ground. Our instruments provide the highest spatial resolution available today on any single aperture telescope.A primary role of these instruments is exoplanet validation for the Kepler, K2, TESS, and many RV programs. Contrast ratios of 6 or more magnitudes are easily obtained. The instrument uses two emCCD cameras providing simultaneous dual-color observations help to characterize detected companions. High resolution imaging enables the identification of blended binaries that contaminate many exoplanet detections, leading to incorrectly measured radii. In this way small, rocky systems, such as Kepler-186b and the TRAPPIST-1 planet family, may be validated and thus the detected planets radii are correctly measured.


    Directory of Open Access Journals (Sweden)

    N. D. Abramovich


    Full Text Available Speckle fields are widely used in optical diagnostics of biotissues and evaluation of the functional state of bioobjects. The speckle field is formed by laser radiation scattered from the object under study. It bears information about the average dimensions of the scatterers, the degree of surface roughness makes it possible to judge the structural and biophysical characteristics of individual tissue cells (particles, on the one hand, and the integral optical characteristics of the entire biological tissue. The aim of the study was – the determination of connections between the biophysical and structural characteristics of the biotissue and the light fields inside the biotissues.The model developed of the medium gives a direct relationship between the optical and biophysical parameters of the biotissue. Calculations were carried out using known solutions of the radiation transfer equation, taking into account the multilayer structure of the tissue, multiple scattering in the medium, and multiple reflection of irradiation between the layers.With the increase wavelength, the size of speckles formed by the non-scattered component (direct light of laser radiation increases by a factor of 2 from 400 to 800 μm in the stratum corneum and 5 times from 0.6 to 3 μm for the epidermis and from 0.27 to 1.4 μm to the dermis. Typical values of sizes of speckles formed by the diffraction component of laser radiation for the stratum corneum and epidermis range from 0.02 to 0.15 μm. For the dermis typical spot sizes are up to 0.03 μm. The speckle-spot size of the diffusion component in the dermis can vary from ±10 % at 400 nm and up to ±23 % for 800 nm when the volume concentration of blood capillaries changes. Characteristic dependencies are obtained and biophysical factors associated with the volume concentration of blood and the degree of it’s oxygenation that affect the contrast of the speckle structure in the dermis are discussed.The of speckles

  20. Influence of error sources in speckle interferometry using only two speckle patterns (United States)

    Arai, Yasuhiko


    Speckle interferometry is an important deformation measurement method for objects with rough surfaces. Recently, a fringe analysis method that uses only one speckle pattern before deformation and one after deformation was proposed. The measurement accuracy of this method is known to depend on experimental conditions. In this paper, the improvement of the measurement accuracy of this method is discussed in comparison with the advanced technologies of off-axis digital holography. It is highly effective to introduce the experiences of the advanced technologies of digital holography to speckle interferometry. However, it should also be considered that both technologies have different purposes. Because digital holography is basically a technology which records images, the influence of the quantity of deformation has never been discussed in digital holography in detail. In this study, the measurement accuracy of speckle interferometry is investigated through a precise comparison of the experimental results from both technologies. It was confirmed that the conditions for digital holography are not always suitable for improving the measurement accuracy of speckle interferometry.

  1. Very low rate compression of speckled SAR imagery

    Energy Technology Data Exchange (ETDEWEB)

    Eichel, P.H. [Sandia National Labs., Albuquerque, NM (United States); Ives, R.W. [Navy (United States)


    Synthetic aperture radars produce coherent, and speckled, high resolution images of the ground. Because modern systems can generate large amounts of imagery, there is substantial interest in applying image compression techniques to these products. In this paper, the authors examine the properties of speckled imagery relevant to the task of data compression. In particular, they demonstrate the advisability of compressing the speckle mean function rather than the literal image. The theory, methodology, and an example are presented.

  2. Superconductor ceramics behavior analyses during service by speckle metrology (United States)

    Recuero, S.; Andres, N.; Arroyo, M. P.; Lera, F.; Angurel, L. A.


    This paper shows the feasibility of applying speckle techniques as a non-destructive evaluation of the performance of ceramic high temperature superconducting materials. Firstly, Digital Speckle Pattern Interferometry has been applied to test these materials during service, with the sample cooled to liquid nitrogen temperatures, to detect where a hot spot will be generated. Surface degradation due to humidity has also been studied. Speckle Photography, whose optical setup is simpler, has been selected for this study.

  3. Speckle Tracking Imaging in Normal Stress Echocardiography. (United States)

    Leitman, Marina; Tyomkin, Vladimir; Peleg, Eli; Zyssman, Izhak; Rosenblatt, Simcha; Sucher, Edgar; Gercenshtein, Vered; Vered, Zvi


    Exercise stress echocardiography is a widely used modality for the diagnosis and follow-up of patients with coronary artery disease. During the last decade, speckle tracking imaging has been used increasingly for accurate evaluation of cardiac function. This work aimed to assess speckle-tracking imaging parameters during nonischemic exercise stress echocardiography. During 2011 to 2014 we studied 46 patients without history of coronary artery disease, who completed exercise stress echocardiography protocol, had normal left ventricular function, a nonischemic response, and satisfactory image quality. These exams were analyzed with speckle-tracking imaging software at rest and at peak exercise. Peak strain and time-to-peak strain were measured at rest and after exercise. Clinical follow-up included a telephone contact 1 to 3 years after stress echo exam, confirming freedom from coronary events during this time. Global and regional peak strain increased following exercise. Time-to-peak global and regional strain and time-to-peak strain adjusted to the heart rate were significantly shorter in all segments after exercise. Rest-to-stress ratio of time-to-peak strain adjusted to the heart rate was 2.0 to 2.8. Global and regional peak strain rise during normal exercise echocardiography. Peak global and regional strain occur before or shortly after aortic valve closure at rest and after exercise, and the delay is more apparent at the basal segments. Time-to-peak strain normally shortens significantly during exercise; after adjustment to heart rate it shortens by a ratio of 2.0 to 2.8. These data may be useful for interpretation of future exercise stress speckle-tracking echocardiography studies. © 2016 by the American Institute of Ultrasound in Medicine.

  4. Speckle Shearing Interferometry And Its Application (United States)

    Jingtang, Ke; Hongqing, Zhang; Yeling, He; Yanfu, Chang


    The paper deals with experiments made to verify the theory of bending of plates and related problems by method of speckle shearing interferometry, which is proved to be highly sensitive. Tests carried out on rubber products: (such as tires)and thin-walled containers have demonstrated the prospects of using image-shearing camera in nondestructive in-situ testing of industrial products, suggesting a potentiality still wider than that of holographic interferometry.

  5. Twisted speckle entities inside wave-front reversal mirrors

    International Nuclear Information System (INIS)

    Okulov, A. Yu


    The previously unknown property of the optical speckle pattern reported. The interference of a speckle with the counterpropagating phase-conjugated (PC) speckle wave produces a randomly distributed ensemble of a twisted entities (ropes) surrounding optical vortex lines. These entities appear in a wide range of a randomly chosen speckle parameters inside the phase-conjugating mirrors regardless to an internal physical mechanism of the wave-front reversal. These numerically generated interference patterns are relevant to the Brillouin PC mirrors and to a four-wave mixing PC mirrors based upon laser trapped ultracold atomic cloud.

  6. Early detection and treatment of Speckled leukoplakia

    Directory of Open Access Journals (Sweden)

    Selviana Tampoma


    Full Text Available Background: Leukoplakia is one of potentially malignant disorders that can be found on oral mucosa. Speckled leukoplakia is a rare type of leukoplakia with a very high risk of premalignant growth. Approximately 3 % of worldwide population has suffered from leukoplakia, 5-25% of which tend to be malignant leukoplakia. Purpose: This case report was aimed to discuss about early detection of speckled leukoplakia as one of potentially malignant disorders. Case: A 62 year old male patient came with chief complaint of bald and painful tongue since one month ago. The patient has a history of allergic reaction, hypertension, uric acid, and hepatitis B. He had been a heavy smoker since young until 10 years ago. Intra oral examination showed a firm, rough, non scrapable white plaque lesion with a size of 1 x 1.5 cm, surrounded by painful erosion with diffuse boundary. Case Management: Based on cytology examination, the patient was reffered to oncologist to get an excisional biopsy. Next, the patient succesfully underwent the excisional biopsy and came for control. The results showed the healing process of the lesion with a minimal complaint of bald tongue, especially when eating spicy or hot meal. To improve healing process, the patient then was given an antibacterial mouth rinse containing zinc and mulvitamin. Conclusion: Speckled leukoplakia could show high malignant transformation rate, therefore, early detection and treatment are necessary.

  7. Methodology for the conception of speckle reduction elements in the case of short pulse illumination (United States)

    Lutz, Yves; Poyet, Jean-Michel


    One of the most efficient ways to decrease the speckle contrast in the field of laser illumination is to increase the spatial diversity of coherent laser sources. For very short laser pulses such as those required for flash laser imaging, the spatial diversity should take place instantaneously and no time averaging effect can be used. The spatial diversity is realized by sampling the laser beam into m beamlets with increased optical path length. This path length has to be greater than or equal to the coherence length of the laser beam. In this case, the beamlets are no longer able to create interferences which each other. According to the Goodman's theory of speckle reduction, the speckle contrast is then reduced by a factor of 1/√m. Unfortunately, in the case of multimode lasers, the number of uncorrelated beamlets is not infinite but is limited by a periodicity function resulting from the laser resonator length itself. The speckle reduction possibility is therefore limited and is directly linked to each laser source where the coherence length and cavity length are defined. In this work we present a methodology to determine experimentally the optical path length difference as well as the number of beamlets for de-speckling a laser source. An experimental realization is presented where both, coherence length and periodicity function are measured with a Michelson interferometer where only the speckle contrast of the two beams from each arm is analyzed. For the validation of the method, the chosen laser source is a single emitter 660 nm laser diode. Two cylindrical steppers made with diamond turned PMMA have been realized. Both elements yield interesting results with close values and in accordance with the theory of spatial diversity. The speckle contrast could be reduced from about 10% to a value close to 4%. These values confirm and validate the methodology presented in this work. Steppers can also be a promising solution for the reduction of interference fringes

  8. Speckle correlation technique to determine roughness in the dermatologic interval. (United States)

    Dalmases, F; Cibrián, R; Buendía, M; Romero, C; Salvador, R; Montilla, J


    A non-invasive method is proposed to determine human skin roughness. The technique is based on measurement of the correlation between two field distributions scattered by a metallised triafol (cellulose acetate foil) replica of the epidermal area to be analysed. The two speckle patterns are produced from the same rough surface illuminated by two coherent plane waves (He-Ne laser) under two slightly different angles. The accuracy of the method is highlighted by measurements made on a set of standard samples with roughnesses previously determined by mechanical profilometry. Analysis of the results indicates a precision of around 10%, and an applicability within the interest range of very rough surfaces in excess of 4-5 microns.

  9. Nephron blood flow dynamics measured by laser speckle contrast imaging

    DEFF Research Database (Denmark)

    von Holstein-Rathlou, Niels-Henrik; Sosnovtseva, Olga V; Pavlov, Alexey N


    Tubuloglomerular feedback (TGF) has an important role in autoregulation of renal blood flow and glomerular filtration rate (GFR). Because of the characteristics of signal transmission in the feedback loop, the TGF undergoes self-sustained oscillations in single-nephron blood flow, GFR, and tubular...... simultaneously. The interacting nephron fields are likely to be more extensive. We have turned to laser speckle contrast imaging to measure the blood flow dynamics of 50-100 nephrons simultaneously on the renal surface of anesthetized rats. We report the application of this method and describe analytic...... techniques for extracting the desired data and for examining them for evidence of nephron synchronization. Synchronized TGF oscillations were detected in pairs or triplets of nephrons. The amplitude and the frequency of the oscillations changed with time, as did the patterns of synchronization...

  10. Contrast-enhanced imaging of cerebral vasculature with laser speckle. (United States)

    Murari, K; Li, N; Rege, A; Jia, X; All, A; Thakor, N


    High-resolution cerebral vasculature imaging has applications ranging from intraoperative procedures to basic neuroscience research. Laser speckle, with spatial contrast processing, has recently been used to map cerebral blood flow. We present an application of the technique using temporal contrast processing to image cerebral vascular structures with a field of view a few millimeters across and approximately 20 microm resolution through a thinned skull. We validate the images using fluorescent imaging and demonstrate a factor of 2-4 enhancement in contrast-to-noise ratios over reflectance imaging using white or spectrally filtered green light. The contrast enhancement enables the perception of approximately 10%-30% more vascular structures without the introduction of any contrast agent.

  11. On the Shaker Simulation of Wind-Induced Non-Gaussian Random Vibration

    Directory of Open Access Journals (Sweden)

    Fei Xu


    Full Text Available Gaussian signal is produced by ordinary random vibration controllers to test the products in the laboratory, while the field data is usually non-Gaussian. Two methodologies are presented in this paper for shaker simulation of wind-induced non-Gaussian vibration. The first methodology synthesizes the non-Gaussian signal offline and replicates it on the shaker in the Time Waveform Replication (TWR mode. A new synthesis method is used to model the non-Gaussian signal as a Gaussian signal multiplied by an amplitude modulation function (AMF. A case study is presented to show that the synthesized non-Gaussian signal has the same power spectral density (PSD, probability density function (PDF, and loading cycle distribution (LCD as the field data. The second methodology derives a damage equivalent Gaussian signal from the non-Gaussian signal based on the fatigue damage spectrum (FDS and the extreme response spectrum (ERS and reproduces it on the shaker in the closed-loop frequency domain control mode. The PSD level and the duration time of the derived Gaussian signal can be manipulated for accelerated testing purpose. A case study is presented to show that the derived PSD matches the damage potential of the non-Gaussian environment for both fatigue and peak response.

  12. Equi-Gaussian curvature folding

    Indian Academy of Sciences (India)

    curvature kf (p) i.e., kp = kf (p). In this case f will map curves to curves with equal equi-. Gaussian curvature at corresponding points. It will also map area with sectional curvature k(σ, p) into areas with the same sectional curvature, and so on. The set of all equi-Gaussian curvature foldings of M into N will be denoted by.

  13. Noncontact speckle-based optical sensor for detection of glucose concentration using magneto-optic effect (United States)

    Ozana, Nisan; Beiderman, Yevgeny; Anand, Arun; Javidi, Baharam; Polani, Sagi; Schwarz, Ariel; Shemer, Amir; Garcia, Javier; Zalevsky, Zeev


    We experimentally verify a speckle-based technique for noncontact measurement of glucose concentration in the bloodstream. The final device is intended to be a single wristwatch-style device containing a laser, a camera, and an alternating current (ac) electromagnet generated by a solenoid. The experiments presented are performed in vitro as proof of the concept. When a glucose substance is inserted into a solenoid generating an ac magnetic field, it exhibits Faraday rotation, which affects the temporal changes of the secondary speckle pattern distributions. The temporal frequency resulting from the ac magnetic field was found to have a lock-in amplification role, which increased the observability of the relatively small magneto-optic effect. Experimental results to support the proposed concept are presented.

  14. Integration of instrumentation and processing software of a laser speckle contrast imaging system (United States)

    Carrick, Jacob J.

    Laser speckle contrast imaging (LSCI) has the potential to be a powerful tool in medicine, but more research in the field is required so it can be used properly. To help in the progression of Michigan Tech's research in the field, a graphical user interface (GUI) was designed in Matlab to control the instrumentation of the experiments as well as process the raw speckle images into contrast images while they are being acquired. The design of the system was successful and is currently being used by Michigan Tech's Biomedical Engineering department. This thesis describes the development of the LSCI GUI as well as offering a full introduction into the history, theory and applications of LSCI.

  15. Scalable Gaussian Processes and the search for exoplanets

    CERN Multimedia

    CERN. Geneva


    Gaussian Processes are a class of non-parametric models that are often used to model stochastic behavior in time series or spatial data. A major limitation for the application of these models to large datasets is the computational cost. The cost of a single evaluation of the model likelihood scales as the third power of the number of data points. In the search for transiting exoplanets, the datasets of interest have tens of thousands to millions of measurements with uneven sampling, rendering naive application of a Gaussian Process model impractical. To attack this problem, we have developed robust approximate methods for Gaussian Process regression that can be applied at this scale. I will describe the general problem of Gaussian Process regression and offer several applicable use cases. Finally, I will present our work on scaling this model to the exciting field of exoplanet discovery and introduce a well-tested open source implementation of these new methods.

  16. Speckle processing for OCT image based on Bayesian least mean square error criterion

    Directory of Open Access Journals (Sweden)

    WANG Rong


    Full Text Available This paper presents a noise reduction algorithm for the speckle noise in optical coherence tomography images based on Bayesian criterion.First,the noisy imaging data is put into the logarithmic space and sample is extracted from the data with noise of Gaussian distribution.Then pixels within the sample are given relevant weights based on the correlation between adjacent pixels in the image.Finally,the posterior distribution is estimated by using a weighted histogram approach and the noise-free data is estimated using generic Bayesian least mean square error estimate.Compared with traditional wavelet transformation noise reduction and median filtering denoising,this method obviously improves the signal-to-noise ratio (SNR and the equivalent apparent number (ENL of OCT image.Thus the image quality is enhanced to some extent.

  17. Comparison of laboratory grating-based and speckle-tracking x-ray phase-contrast imaging (United States)

    Romell, J.; Zhou, T.; Zdora, M.; Sala, S.; Koch, F. J.; Hertz, H. M.; Burvall, A.


    Phase-contrast imaging with x-rays is a developing field for imaging weakly absorbing materials. In this work, two phase-contrast imaging methods, grating- and speckle-based imaging, that measure the derivative of the phase shift, have been implemented with a laboratory source and compared experimentally. It was found that for the same dose conditions, the speckle-tracking differential phase-contrast images have considerably higher contrast-to-noise ratio than the grating-based images, but at the cost of lower resolution. Grating-based imaging performs better in terms of resolution, but would require longer exposure times, mainly due to absorption in the grating interferometer.

  18. Imprint of primordial non-Gaussianity on dark matter halo profiles

    Energy Technology Data Exchange (ETDEWEB)

    Dizgah, Azadeh Moradinezhad; Dodelson, Scott; Riotto, Antonio


    We study the impact of primordial non-Gaussianity on the density profile of dark matter halos by using the semi-analytical model introduced recently by Dalal {\\it et al.} which relates the peaks of the initial linear density field to the final density profile of dark matter halos. Models with primordial non-Gaussianity typically produce an initial density field that differs from that produced in Gaussian models. We use the path-integral formulation of excursion set theory to calculate the non-Gaussian corrections to the peak profile and derive the statistics of the peaks of non-Gaussian density field. In the context of the semi-analytic model for halo profiles, currently allowed values for primordial non-Gaussianity would increase the shapes of the inner dark matter profiles, but only at the sub-percent level except in the very innermost regions.

  19. Gaussian Process-Mixture Conditional Heteroscedasticity. (United States)

    Platanios, Emmanouil A; Chatzis, Sotirios P


    Generalized autoregressive conditional heteroscedasticity (GARCH) models have long been considered as one of the most successful families of approaches for volatility modeling in financial return series. In this paper, we propose an alternative approach based on methodologies widely used in the field of statistical machine learning. Specifically, we propose a novel nonparametric Bayesian mixture of Gaussian process regression models, each component of which models the noise variance process that contaminates the observed data as a separate latent Gaussian process driven by the observed data. This way, we essentially obtain a Gaussian process-mixture conditional heteroscedasticity (GPMCH) model for volatility modeling in financial return series. We impose a nonparametric prior with power-law nature over the distribution of the model mixture components, namely the Pitman-Yor process prior, to allow for better capturing modeled data distributions with heavy tails and skewness. Finally, we provide a copula-based approach for obtaining a predictive posterior for the covariances over the asset returns modeled by means of a postulated GPMCH model. We evaluate the efficacy of our approach in a number of benchmark scenarios, and compare its performance to state-of-the-art methodologies.

  20. Angular displacement and deformation analyses using speckle-based wavefront sensor

    DEFF Research Database (Denmark)

    Almoro, Percival; Giancarlo, Pedrini; Arun, Anand


    Wavefronts incident on a random phase plate are reconstructed via phase retrieval utilizing axially displaced speckle intensity measurements and the wave propagation equation. Retrieved phases and phase subtraction facilitate the investigations of wavefronts from test objects before and after und...... thermal loading. The technique offers simple, high resolution, noncontact, and whole field evaluation of three-dimensional objects before and after undergoing rotation or deformation. (C) 2009 Optical Society of America...

  1. Speckle evolution with multiple steps of least-squares phase removal

    CSIR Research Space (South Africa)

    Chen, M


    Full Text Available 84, 023846 (2011) Speckle evolution with multiple steps of least-squares phase removal Mingzhou Chen* and Chris Dainty Applied Optics, School of Physics, National University of Ireland Galway, Galway, Ireland Filippus S. Roux? National Laser...- arithmically with each step. The result is that the vortex density decreases according to a power law as a function of propagation distance. In some cases one or two vortex dipoles still remain in the final field. The separation distances between...

  2. Palm distributions for log Gaussian Cox processes

    DEFF Research Database (Denmark)

    Coeurjolly, Jean-Francois; Møller, Jesper; Waagepetersen, Rasmus Plenge


    This paper establishes a remarkable result regarding Palm distributions for a log Gaussian Cox process: the reduced Palm distribution for a log Gaussian Cox process is itself a log Gaussian Cox process that only differs from the original log Gaussian Cox process in the intensity function. This new...

  3. Effect of focusing optics on X-ray speckle contrast

    International Nuclear Information System (INIS)

    Retsch, C. C.; Wang, Y.; Frigo, S. P.; McNulty, I.; Lurio, L. B.; Stephenson, G. B.


    The authors investigated the behavior of speckle contrast and size under various experimental conditions using 1.82 keV x-rays. In this paper, they report the comparison of two different setups for x-ray speckle experiments: one employing a focusing zone plate and one in which a pinhole selects the size of the coherent x-ray beam. They found a strong dependence of the speckle contrast and size on the type of setup. In general, the pinhole setup results in higher contrast but smaller speckle size. On the other hand the zone plate setup allows one to target much smaller areas of interest in the sample, down to submicron dimensions, and also to adjust the speckle size. The authors anticipate that these results will be useful in future time-correlation spectroscopy experiments

  4. Alternating minimization algorithm for speckle reduction with a shifting technique. (United States)

    Woo, Hyenkyun; Yun, Sangwoon


    Speckles (multiplicative noise) in synthetic aperture radar (SAR) make it difficult to interpret the observed image. Due to the edge-preserving feature of total variation (TV), variational models with TV regularization have attracted much interest in reducing speckles. Algorithms based on the augmented Lagrangian function have been proposed to efficiently solve speckle-reduction variational models with TV regularization. However, these algorithms require inner iterations or inverses involving the Laplacian operator at each iteration. In this paper, we adapt Tseng's alternating minimization algorithm with a shifting technique to efficiently remove the speckle without any inner iterations or inverses involving the Laplacian operator. The proposed method is very simple and highly parallelizable; therefore, it is very efficient to despeckle huge-size SAR images. Numerical results show that our proposed method outperforms the state-of-the-art algorithms for speckle-reduction variational models with a TV regularizer in terms of central-processing-unit time.

  5. Speckle reduction in digital holography with resampling ring masks (United States)

    Zhang, Wenhui; Cao, Liangcai; Jin, Guofan


    One-shot digital holographic imaging has the advantages of high stability and low temporal cost. However, the reconstruction is affected by the speckle noise. Resampling ring-mask method in spectrum domain is proposed for speckle reduction. The useful spectrum of one hologram is divided into several sub-spectra by ring masks. In the reconstruction, angular spectrum transform is applied to guarantee the calculation accuracy which has no approximation. N reconstructed amplitude images are calculated from the corresponding sub-spectra. Thanks to speckle's random distribution, superimposing these N uncorrelated amplitude images would lead to a final reconstructed image with lower speckle noise. Normalized relative standard deviation values of the reconstructed image are used to evaluate the reduction of speckle. Effect of the method on the spatial resolution of the reconstructed image is also quantitatively evaluated. Experimental and simulation results prove the feasibility and effectiveness of the proposed method.

  6. Real time laser speckle imaging monitoring vascular targeted photodynamic therapy (United States)

    Goldschmidt, Ruth; Vyacheslav, Kalchenko; Scherz, Avigdor


    Laser speckle imaging is a technique that has been developed to non-invasively monitor in vivo blood flow dynamics and vascular structure, at high spatial and temporal resolution. It can record the full-field spatio-temporal characteristics of microcirculation and has therefore, often been used to study the blood flow in tumors after photodynamic therapy (PDT). Yet, there is a paucity of reports on real-time laser speckle imaging (RTLSI) during PDT. Vascular-targeted photodynamic therapy (VTP) with WST11, a water-soluble bacteriochlorophyll derivative, achieves tumor ablation through rapid occlusion of the tumor vasculature followed by a cascade of events that actively kill the tumor cells. WST11-VTP has been already approved for treatment of early/intermediate prostate cancer at a certain drug dose, time and intensity of illumination. Application to other cancers may require different light dosage. However, incomplete vascular occlusion at lower light dose may result in cancer cell survival and tumor relapse while excessive light dose may lead to toxicity of nearby healthy tissues. Here we provide evidence for the feasibility of concomitant RTLSI of the blood flow dynamics in the tumor and surrounding normal tissues during and after WST11-VTP. Fast decrease in the blood flow is followed by partial mild reperfusion and a complete flow arrest within the tumor by the end of illumination. While the primary occlusion of the tumor feeding arteries and draining veins agrees with previous data published by our group, the late effects underscore the significance of light dose control to minimize normal tissue impairment. In conclusion- RTSLI application should allow to optimize VTP efficacy vs toxicity in both the preclinical and clinical arenas.

  7. Measurement of natural convection by speckle photography

    International Nuclear Information System (INIS)

    Wernekinck, U.; Merzkirch, W.


    The principle of speckle photography can be applied to the measurement of density variations in fluids. A modification of existing experimental arrangements allows for the measurement of large values of the light deflection angles as they may occur in heat and mass transfer situations. The method is demonstrated for the case of a helium jet exhausting into still air and the natural convective flow along a heated plate. The obtained data are compared with results measured with classical optical interferometers, and good agreement is found. The advantages of the new technique over the classical optical methods are briefly discussed. 11 references

  8. Ten Years of Speckle Interferometry at SOAR (United States)

    Tokovinin, Andrei


    Since 2007, close binary and multiple stars are observed by speckle interferometry at the 4.1 m Southern Astrophysical Research (SOAR) telescope. The HRCam instrument, observing strategy and planning, data processing and calibration methods, developed and improved during ten years, are presented here in a concise way. Thousands of binary stars were measured with diffraction-limited resolution (29 mas at 540 nm wavelength) and a high accuracy reaching 1 mas; 200 new pairs or subsystems were discovered. To date, HRCam has performed over 11,000 observations with a high efficiency (up to 300 stars per night). An overview of the main results delivered by this instrument is given.

  9. Analysis of laser speckle patterns from fingertips

    DEFF Research Database (Denmark)

    Iversen, Theis Faber Quist; Hanson, Steen Grüner


    The trend in human-machine interface technology is heading towards optical solutions for tracking and movement detection. Especially, interactive touch screens and pads, in which the movement of the user’s fingertips is detected and tracked, are of great commercial interest. The applications range...... from mobile phones to laptops and PDA´s. However, the dynamics of scattered light from live tissue must be taken into account when designing optical sensor systems for tracking e.g. fingertips in touch-applications. Especially, when using coherent light sources, the statistics of the speckle...

  10. CMB constraints on running non-Gaussianity


    Oppizzi, Filippo; Liguori, Michele; Renzi, Alessandro; Arroja, Frederico; Bartolo, Nicola


    We develop a complete set of tools for CMB forecasting, simulation and estimation of primordial running bispectra, arising from a variety of curvaton and single-field (DBI) models of Inflation. We validate our pipeline using mock CMB running non-Gaussianity realizations and test it on real data by obtaining experimental constraints on the $f_{\\rm NL}$ running spectral index, $n_{\\rm NG}$, using WMAP 9-year data. Our final bounds (68\\% C.L.) read $-0.3< n_{\\rm NG}

  11. Observations of binary stars by speckle interferometry

    International Nuclear Information System (INIS)

    Morgan, B.L.; Beckmann, G.K.; Scaddan, R.J.


    This is the second paper in a series describing observations of binary stars using the technique of speckle interferometry. Observations were made using the 2.5-m Isaac Newton Telescope and the 1-m telescope of the Royal Greenwich Observatory and the 1.9-m telescope of the South African Astronomical Observatory. The classical Rayleigh diffraction limits are 0.050 arcsec for the 2.5-m telescope, 0.065 arcsec for the 1.9-m telescope and 0.125 arcsec for the 1-m telescope, at a wavelength of 500 nm. The results of 29 measurements of 26 objects are presented. The objects include long period spectroscopic binaries from the 6th Catalogue of Batten, close visual binary systems from the 3rd Catalogue of Finsen and Worley and variable stars. Nine of the objects have not been previously resolved by speckle interferometry. New members are detected in the systems β Cep, p Vel and iota UMa. (author)

  12. Characterization of Atherosclerotic Plaques by Laser Speckle Imaging (United States)

    Nadkarni, Seemantini K.; Bouma, Brett E.; Helg, Tina; Chan, Raymond; Halpern, Elkan; Chau, Alexandra; Minsky, Milan Singh; Motz, Jason T.; Houser, Stuart L.; Tearney, Guillermo J.


    Background A method capable of determining atherosclerotic plaque composition and measuring plaque viscoelasticity can provide valuable insight into intrinsic features associated with plaque rupture and can enable the identification of high-risk lesions. In this article, we describe a new optical technique, laser speckle imaging (LSI), that measures an index of plaque viscoelasticity. We evaluate the potential of LSI for characterizing atherosclerotic plaque. Methods and Results Time-varying helium-neon laser speckle images were acquired from 118 aortic plaque specimens from 14 human cadavers under static and deforming conditions (0 to 200 μm/s). Temporal fluctuations in the speckle patterns were quantified by exponential fitting of the normalized cross-correlation of sequential frames in each image series of speckle patterns to obtain the exponential decay time constant, τ. The decorrelation time constants of thin-cap fibroatheromas (TCFA) (τ=47.5±19.2 ms) were significantly lower than those of other atherosclerotic lesions (P90%. Speckle decorrelation time constants demonstrated strong correlation with histological measurements of plaque collagen (R=0.73, P0.05). Conclusions The measurement of speckle decorrelation time constant from laser speckle images provides an index of plaque viscoelasticity and facilitates the characterization of plaque type. Our results demonstrate that LSI is a highly sensitive technique for characterizing plaque and identifying thin-cap fibroatheromas. PMID:16061738

  13. Primordial black holes from inflation and non-Gaussianity (United States)

    Franciolini, G.; Kehagias, A.; Matarrese, S.; Riotto, A.


    Primordial black holes may owe their origin to the small-scale enhancement of the comoving curvature perturbation generated during inflation. Their mass fraction at formation is markedly sensitive to possible non-Gaussianities in such large, but rare fluctuations. We discuss a path-integral formulation which provides the exact mass fraction of primordial black holes at formation in the presence of non-Gaussianity. Through a couple of classes of models, one based on single-field inflation and the other on spectator fields, we show that restricting to a Gaussian statistics may lead to severe inaccuracies in the estimate of the mass fraction as well as on the clustering properties of the primordial black holes.

  14. The Multivariate Gaussian Probability Distribution

    DEFF Research Database (Denmark)

    Ahrendt, Peter


    This technical report intends to gather information about the multivariate gaussian distribution, that was previously not (at least to my knowledge) to be found in one place and written as a reference manual. Additionally, some useful tips and tricks are collected that may be useful in practical...

  15. On Gaussian conditional independence structures

    Czech Academy of Sciences Publication Activity Database

    Lněnička, Radim; Matúš, František


    Roč. 43, č. 3 (2007), s. 327-342 ISSN 0023-5954 R&D Projects: GA AV ČR IAA100750603 Institutional research plan: CEZ:AV0Z10750506 Keywords : multivariate Gaussian distribution * positive definite matrices * determinants * gaussoids * covariance selection models * Markov perfectness Subject RIV: BA - General Mathematics Impact factor: 0.552, year: 2007

  16. Maximal trace distance between isoenergetic bosonic Gaussian states (United States)

    Volkoff, T. J.


    We locate the set of pairs (ρ1, ρ2) of Gaussian states of a single mode electromagnetic field that exhibit maximal trace distance subject to the energy constraint ⟨a†a⟩ ρ1=⟨a†a⟩ ρ2=E . Any such pair allows to achieve the minimum possible error in the task of binary distinguishability of two single mode, isoenergetic Gaussian quantum signals. In particular, we show that the logarithm of the minimal error probability for distinguishing two maximally trace distant, isoenergetic Gaussian states scales as -E2, less than the achievable scaling of the minimal error probability for distinguishing, e.g., a pair of isoenergetic Heisenberg-Weyl coherent states with energy E or a pair of isoenergetic quadrature squeezed states with energy E. For the case of a field consisting of M > 1 modes, we locate the set of pairs of maximally trace distant isoenergetic, isocovariant Gaussian states. These results have basic applications in the theory of continuous variable quantum communications with Gaussian states of light.

  17. A Comparison of Speckle Reduction Techniques in Medical Ultrasound Imaging

    Directory of Open Access Journals (Sweden)



    Full Text Available Speckle noise is a multiplicative noise that degrades the visual evaluation in ultrasound imaging. In addition, it limits the efficient application of intelligent image processing algorithms, such as segmentation techniques. Thus, speckle noise reduction is considered an essential pre-processing step. The objective of this paper is to carry out a comparative evaluation of speckle filtering techniques, based on two image quality evaluation metrics, the Peak Signal to Noise Ratio (PSNR, and the Structural SIMilarity (SSIM index, and visual evaluation.

  18. White-Light Optical Processing Of Misfocused Speckle Interferograms (United States)

    Yu, F. T. S.; Ruterbusch, P. H.; Gheen, G.; Gerhard, Grant


    A technique of white-light color encoding of misfocused speckle interferometric fringe patterns is presented. The encoding is performed in the spatial frequency plane with color filters. This technique allows the viewing of a multiset of encoded speckle interferograms simultaneously. Thus, it may provide new informational interferometric aspects of the object under stress or vibration. The effect on the speckle fringe pattern due to the spatial filtering is briefly discussed, and experimental demonstrations of color encoded fringe patterns are presented. Due to the simplicity and versatility of the processing technique, we feel that the technique may develop into a practical tool for strain, stress, and vibrational measurement.

  19. Superresolution Imaging of Optical Vortices in a Speckle Pattern (United States)

    Pascucci, Marco; Tessier, Gilles; Emiliani, Valentina; Guillon, Marc


    We characterize, experimentally, the intensity minima of a polarized high numerical aperture optical speckle pattern and the topological charges of the associated optical vortices. The negative of a speckle pattern is imprinted in a uniform fluorescent sample by photobleaching. The remaining fluorescence is imaged with superresolution stimulated emission depletion microscopy, which reveals subdiffraction fluorescence confinement at the center of optical vortices. The intensity statistics of saturated negative speckle patterns are predicted and measured. The charge of optical vortices is determined by controlling the handedness of circular polarization, and the creation or annihilation of a vortex pair along propagation is shown.

  20. Acousto-electrical speckle pattern in Lorentz force electrical impedance tomography (United States)

    Grasland-Mongrain, Pol; Destrempes, François; Mari, Jean-Martial; Souchon, Rémi; Catheline, Stefan; Chapelon, Jean-Yves; Lafon, Cyril; Cloutier, Guy


    Ultrasound speckle is a granular texture pattern appearing in ultrasound imaging. It can be used to distinguish tissues and identify pathologies. Lorentz force electrical impedance tomography is an ultrasound-based medical imaging technique of the tissue electrical conductivity. It is based on the application of an ultrasound wave in a medium placed in a magnetic field and on the measurement of the induced electric current due to Lorentz force. Similarly to ultrasound imaging, we hypothesized that a speckle could be observed with Lorentz force electrical impedance tomography imaging. In this study, we first assessed the theoretical similarity between the measured signals in Lorentz force electrical impedance tomography and in ultrasound imaging modalities. We then compared experimentally the signal measured in both methods using an acoustic and electrical impedance interface. Finally, a bovine muscle sample was imaged using the two methods. Similar speckle patterns were observed. This indicates the existence of an ‘acousto-electrical speckle’ in the Lorentz force electrical impedance tomography with spatial characteristics driven by the acoustic parameters but due to electrical impedance inhomogeneities instead of acoustic ones as is the case of ultrasound imaging.

  1. Stable and Efficient Gaussian Process Calculations (United States)

    National Aeronautics and Space Administration — The use of Gaussian processes can be an effective approach to prediction in a supervised learning environment. For large data sets, the standard Gaussian process...

  2. Gaussian process regression analysis for functional data

    CERN Document Server

    Shi, Jian Qing


    Gaussian Process Regression Analysis for Functional Data presents nonparametric statistical methods for functional regression analysis, specifically the methods based on a Gaussian process prior in a functional space. The authors focus on problems involving functional response variables and mixed covariates of functional and scalar variables.Covering the basics of Gaussian process regression, the first several chapters discuss functional data analysis, theoretical aspects based on the asymptotic properties of Gaussian process regression models, and new methodological developments for high dime

  3. Analytic matrix elements with shifted correlated Gaussians

    DEFF Research Database (Denmark)

    Fedorov, D. V.


    Matrix elements between shifted correlated Gaussians of various potentials with several form-factors are calculated analytically. Analytic matrix elements are of importance for the correlated Gaussian method in quantum few-body physics.......Matrix elements between shifted correlated Gaussians of various potentials with several form-factors are calculated analytically. Analytic matrix elements are of importance for the correlated Gaussian method in quantum few-body physics....

  4. Laser speckle velocimetry for robot manufacturing (United States)

    Charrett, Thomas O. H.; Bandari, Yashwanth K.; Michel, Florent; Ding, Jialuo; Williams, Stewart W.; Tatam, Ralph P.


    A non-contact speckle correlation sensor for the measurement of robotic tool speed is presented for use in robotic manufacturing and is capable of measuring the in-plane relative velocities between a robot end-effector and the workpiece or other surface. The sensor performance was assessed in the laboratory with the sensor accuracies found to be better than 0:01 mm/s over a 70 mm/s velocity range. Finally an example of the sensors application to robotic manufacturing is presented where the sensor was applied to tool speed measurement for path planning in the wire and arc additive manufacturing process using a KUKA KR150 L110/2 industrial robot.

  5. Speckle interferometry of asteroids. I - 433 Eros (United States)

    Drummond, J. D.; Cocke, W. J.; Hege, E. K.; Strittmatter, P. A.; Lambert, J. V.


    Analytical expressions are derived for the semimajor and semiminor axes and orientation angle of the ellipse projected by a triaxial asteroid, and the results are applied speckle-interferometry observations of the 433 Eros asteroid. The expressions were calculated as functions of the dimensions and pole of the body and of the asterocentric position of the earth and the sun. On the basis of the analytical expressions, the dimensions of 433 Eros are obtained. The light curve from December 18, 1981 is compared to the dimensions to obtain a geometric albedo of 0.156 (+ or - 0.010). A series of two-dimensional power spectra and autocorrelation functions for 433 Eros show that it is spinning in space.

  6. Lifting Primordial Non-Gaussianity Above the Noise

    NARCIS (Netherlands)

    Welling, Yvette; Woude, Drian van der; Pajer, Enrico


    Primordial non-Gaussianity (PNG) in Large Scale Structures is obfuscated by the many additional sources of non-linearity. Within the Effective Field Theory approach to Standard Perturbation Theory, we show that matter non-linearities in the bispectrum can be modeled sufficiently well to strengthen

  7. Laser speckle imaging based on photothermally driven convection (United States)

    Regan, Caitlin; Choi, Bernard


    Laser speckle imaging (LSI) is an interferometric technique that provides information about the relative speed of moving scatterers in a sample. Photothermal LSI overcomes limitations in depth resolution faced by conventional LSI by incorporating an excitation pulse to target absorption by hemoglobin within the vascular network. Here we present results from experiments designed to determine the mechanism by which photothermal LSI decreases speckle contrast. We measured the impact of mechanical properties on speckle contrast, as well as the spatiotemporal temperature dynamics and bulk convective motion occurring during photothermal LSI. Our collective data strongly support the hypothesis that photothermal LSI achieves a transient reduction in speckle contrast due to bulk motion associated with thermally driven convection. The ability of photothermal LSI to image structures below a scattering medium may have important preclinical and clinical applications.

  8. Evaluating platelet aggregation dynamics from laser speckle fluctuations. (United States)

    Hajjarian, Zeinab; Tshikudi, Diane M; Nadkarni, Seemantini K


    Platelets are key to maintaining hemostasis and impaired platelet aggregation could lead to hemorrhage or thrombosis. We report a new approach that exploits laser speckle intensity fluctuations, emanated from a drop of platelet-rich-plasma (PRP), to profile aggregation. Speckle fluctuation rate is quantified by the speckle intensity autocorrelation, g 2 (t) , from which the aggregate size is deduced. We first apply this approach to evaluate polystyrene bead aggregation, triggered by salt. Next, we assess dose-dependent platelet aggregation and inhibition in human PRP spiked with adenosine diphosphate and clopidogrel. Additional spatio-temporal speckle analyses yield 2-dimensional maps of particle displacements to visualize platelet aggregate foci within minutes and quantify aggregation dynamics. These findings demonstrate the unique opportunity for assessing platelet health within minutes for diagnosing bleeding disorders and monitoring anti-platelet therapies.

  9. Assessment of Fevicol (adhesive Drying Process through Dynamic Speckle Techniques

    Directory of Open Access Journals (Sweden)

    Mohammad Z. Ansari


    Full Text Available Dynamic laser speckle (or biospeckle analysis is a useful measurement tool to analyze micro-motion on a sample surface via temporal statistics based on a sequence of speckle images. The aim of this work was to evaluate the use of dynamic speckles as an alternative tool to monitoring Fevicol drying process. Experimental demonstration of intensity-based algorithm to monitor Fevicol drying process is reported. The experiment was explored with the technique called Inertia Moment of co-occurrence matrix. The results allowed verifying the drying process and it was possible to observe different activity stages during the drying process. Statistical Tukey test at 5% significance level allowed differentiating different stages of drying. In conclusion, speckle activity, measured by the Inertia Moment, can be used to monitor drying processes of the Fevicol.


    Directory of Open Access Journals (Sweden)

    V. S. Nikiforov


    Full Text Available Speckle-tracking echocardiography is promising modern technique for evaluation of structural and functional changes in the myocardium. It evaluates the indicator of global longitudinal myocardial deformation, which is more sensitive than ejection fraction to early changes of left ventricular contractility. The diagnostic capabilities of speckle tracking echocardiography are reflected in clinical recommendations and consensus statements of European Society of Cardiology (ESC, European Association of Cardiovascular Imaging (EACVI and American Society of Echocardiography (ASE. The aim of this paper is describe basic principles of speckle tracking echocardiography and clinical applications of this new technology. Attention is paid to the use of speckle tracking echocardiography in such heart pathologies as heart failure, coronary heart disease and myocardial infarction, left ventricular hypertrophy in arterial hypertension, hypertrophic cardiomyopathy and amyloidosis of the heart, valvular heart disease, constrictive pericarditis and cancer therapy-induced cardiotoxicity.

  11. Assessing blood coagulation status with laser speckle rheology (United States)

    Tripathi, Markandey M.; Hajjarian, Zeinab; Van Cott, Elizabeth M.; Nadkarni, Seemantini K.


    We have developed and investigated a novel optical approach, Laser Speckle Rheology (LSR), to evaluate a patient’s coagulation status by measuring the viscoelastic properties of blood during coagulation. In LSR, a blood sample is illuminated with laser light and temporal speckle intensity fluctuations are measured using a high-speed CMOS camera. During blood coagulation, changes in the viscoelastic properties of the clot restrict Brownian displacements of light scattering centers within the sample, altering the rate of speckle intensity fluctuations. As a result, blood coagulation status can be measured by relating the time scale of speckle intensity fluctuations with clinically relevant coagulation metrics including clotting time and fibrinogen content. Our results report a close correlation between coagulation metrics measured using LSR and conventional coagulation results of activated partial thromboplastin time, prothrombin time and functional fibrinogen levels, creating the unique opportunity to evaluate a patient’s coagulation status in real-time at the point of care. PMID:24688816

  12. Polarization coupling of vector Bessel–Gaussian beams

    International Nuclear Information System (INIS)

    Takeuchi, Ryushi; Kozawa, Yuichi; Sato, Shunichi


    We report polarization coupling of radial and azimuthal electric field components of a vector light beam as predicted by the fact that the vector Helmholtz equation is expressed as coupled differential equations in cylindrical coordinates. To clearly observe the polarization variation of a beam as it propagates, higher order transverse modes of a vector Bessel–Gaussian beam were generated by a gain distribution modulation technique, which created a narrow ring-shaped gain region in a Nd:YVO 4 crystal. The polarization coupling was confirmed by the observation that the major polarization component of a vector Bessel–Gaussian beam alternates between radial and azimuthal components along with the propagation. (paper)

  13. Gaussian-state entanglement in a quantum beat laser

    International Nuclear Information System (INIS)

    Tahira, Rabia; Ikram, Manzoor; Nha, Hyunchul; Zubairy, M. Suhail


    Recently quantum beat lasers have been considered as a source of entangled radiation [S. Qamar, F. Ghafoor, M. Hillery, and M. S. Zubairy, Phys. Rev. A 77, 062308 (2008)]. We investigate and quantify the entanglement of this system when the initial cavity modes are prepared in a Gaussian two-mode state, one being a nonclassical state and the other a thermal state. It is investigated how the output entanglement varies with the nonclassicality of the input Gaussian state, thermal noise, and the strength of the driving field.

  14. Perturbative corrections for approximate inference in gaussian latent variable models

    DEFF Research Database (Denmark)

    Opper, Manfred; Paquet, Ulrich; Winther, Ole


    Expectation Propagation (EP) provides a framework for approximate inference. When the model under consideration is over a latent Gaussian field, with the approximation being Gaussian, we show how these approximations can systematically be corrected. A perturbative expansion is made of the exact b...... illustrate on tree-structured Ising model approximations. Furthermore, they provide a polynomial-time assessment of the approximation error. We also provide both theoretical and practical insights on the exactness of the EP solution. © 2013 Manfred Opper, Ulrich Paquet and Ole Winther....

  15. Separated Component-Based Restoration of Speckled SAR Images (United States)


    systems such as SAR, holography , ultra- sound, and synthetic aperture sonar suffer from a multiplicative noise known as speckle [1]. Speckle appears when...Award from the Office of Technology Commercialization, and an Outstanding GEMSTONE Mentor Award from the Honors College. He received the Outstanding...and Technology (University of London), London, England, in 1980 and 1984, respectively. From October 1984 to December 1984 he worked for IBM (UK) as a

  16. Characterization of blood flow rate in dental pulp by speckle patterns of backscattered light from an in vivo tooth (United States)

    Dick, Sergey K.; Chistyakova, Galina G.; Terekh, Alex S.; Smirnov, Alex V.; Salimi Zadeh, Mehrnush M.; Barun, Vladimir V.


    Experimental data on the hemodynamics of dental pulp at different stages of caries treatment are given. Observations of speckle patterns in backscattered laser light are used as a measurement method to qualitatively characterize changes in blood flow rate through the dental pulp. The measurements were made by the author-designed experimental setup. Theoretical estimations showed that stationary reflected light from an in vivo tooth contains a negligibly small information body on changes in the pulpal blood flow due to the shadowing of the pulp by optically thick enamel and dentin. Therefore, the temporal variations in the speckle patterns are the only possible way that can provide monitoring of blood conditions in the pulp by using backscattered light. Various statistical characteristics of the random reflected light fields are studied as indicators of blood flow rate changes. There were selected five statistical parameters of backscattered speckle images that give self-consistent data on these changes. The parameters include four combinations of integrals of the Fourier transforms of the observed temporal variations as well as the speckle image contrast. The selected parameters are shown to qualitatively agree with general considerations on the effects of reduced or increased blood flow rates on the selected integral quantities.

  17. General Galilei Covariant Gaussian Maps (United States)

    Gasbarri, Giulio; Toroš, Marko; Bassi, Angelo


    We characterize general non-Markovian Gaussian maps which are covariant under Galilean transformations. In particular, we consider translational and Galilean covariant maps and show that they reduce to the known Holevo result in the Markovian limit. We apply the results to discuss measures of macroscopicity based on classicalization maps, specifically addressing dissipation, Galilean covariance and non-Markovianity. We further suggest a possible generalization of the macroscopicity measure defined by Nimmrichter and Hornberger [Phys. Rev. Lett. 110, 16 (2013)].

  18. Equi-Gaussian curvature folding

    Indian Academy of Sciences (India)

    have the same equi-Gaussian curvature 1/a2, where a is the radius of the sphere. Now let f : S2 → Pn be a cellular folding. Then we have the following possibilities: Firstly, there are no cellular foldings f : S2 → Pn, for any n > 3 [2]. Secondly, any cellular folding f : S2 → P3 for which Gf forms a regular graph is equivalent to ...

  19. Gaussian Embeddings for Collaborative Filtering


    Dos Santos , Ludovic; Piwowarski , Benjamin; Gallinari , Patrick


    International audience; Most collaborative ltering systems, such as matrix factorization, use vector representations for items and users. Those representations are deterministic, and do not allow modeling the uncertainty of the learned representation, which can be useful when a user has a small number of rated items (cold start), or when there is connict-ing information about the behavior of a user or the ratings of an item. In this paper, we leverage recent works in learning Gaussian embeddi...

  20. Continuous-variable quantum teleportation with non-Gaussian resources

    International Nuclear Information System (INIS)

    Dell'Anno, F.; De Siena, S.; Albano, L.; Illuminati, F.


    We investigate continuous variable quantum teleportation using non-Gaussian states of the radiation field as entangled resources. We compare the performance of different classes of degaussified resources, including two-mode photon-added and two-mode photon-subtracted squeezed states. We then introduce a class of two-mode squeezed Bell-like states with one-parameter dependence for optimization. These states interpolate between and include as subcases different classes of degaussified resources. We show that optimized squeezed Bell-like resources yield a remarkable improvement in the fidelity of teleportation both for coherent and nonclassical input states. The investigation reveals that the optimal non-Gaussian resources for continuous variable teleportation are those that most closely realize the simultaneous maximization of the content of entanglement, the degree of affinity with the two-mode squeezed vacuum, and the, suitably measured, amount of non-Gaussianity

  1. Differential detection of Gaussian MSK in a mobile radio environment (United States)

    Simon, M. K.; Wang, C. C.


    Minimum shift keying with Gaussian shaped transmit pulses is a strong candidate for a modulation technique that satisfies the stringent out-of-band radiated power requirements of the mobil radio application. Numerous studies and field experiments have been conducted by the Japanese on urban and suburban mobile radio channels with systems employing Gaussian minimum-shift keying (GMSK) transmission and differentially coherent reception. A comprehensive analytical treatment is presented of the performance of such systems emphasizing the important trade-offs among the various system design parameters such as transmit and receiver filter bandwidths and detection threshold level. It is shown that two-bit differential detection of GMSK is capable of offering far superior performance to the more conventional one-bit detection method both in the presence of an additive Gaussian noise background and Rician fading.

  2. Laser speckle imaging of atherosclerotic plaques through optical fiber bundles (United States)

    Nadkarni, Seemantini K.; Bouma, Brett E.; Yelin, Dvir; Gulati, Amneet; Tearney, Guillermo J.


    Laser speckle imaging (LSI), a new technique that measures an index of plaque viscoelasticity, has been investigated recently to characterize atherosclerotic plaques. These prior studies demonstrated the diagnostic potential of LSI for detecting high-risk plaques and were conducted ex vivo. To conduct intracoronary LSI in vivo, the laser speckle pattern must be transmitted from the coronary wall to the image detector in the presence of cardiac motion. Small-diameter, flexible optical fiber bundles, similar to those used in coronary angioscopy, may be incorporated into an intravascular catheter for this purpose. A key challenge is that laser speckle is influenced by inter-fiber leakage of light, which may be exacerbated during bundle motion. In this study, we tested the capability of optical fiber bundles to transmit laser speckle patterns obtained from atherosclerotic plaques and evaluated the influence of motion on the diagnostic accuracy of fiber bundle-based LSI. Time-varying helium-neon laser speckle images of aortic plaques were obtained while cyclically moving the flexible length of the bundle to mimic coronary motion. Our results show that leached fiber bundles may reliably transmit laser speckle images in the presence of cardiac motion, providing a viable option to conduct intracoronary LSI. PMID:19021396

  3. Non-Gaussian signatures arising from warm inflation driven by geometric tachyon

    International Nuclear Information System (INIS)

    Bhattacharjee, Anindita; Deshamukhya, Atri


    In a warm inflationary scenario, the initial seeds of density perturbation arise from thermal fluctuations of the inflaton field. These fluctuations in principle have Gaussian distribution. In a Gaussian distribution the density perturbation can be expressed as the two point correlation function. Thus if in an inflationary model the density perturbation is expressed as correlation function of order higher than two, these fluctuations are non-Gaussian in nature. A simple inflationary model containing single scalar field, slow roll, canonical kinetic term and vacuum initial state can produce a tiny amount of non-Gaussianity which are very small to be detected by any experiment. Non-Gaussianity can also arise in inflationary models containing multiple scalar fields. For an inflationary scenario with single scalar field, non-Gaussianity can be expressed in terms of bi-spectrum however for multi field Inflation, it is expressed in terms of trispectrum etc. In this piece of work, the warm inflationary scenario, driven by a D3 brane due to the presence of a stack of k coincident NS 5 branes is considered and the non-Gaussian effects in such an inflationary scenario has been analysed by measuring the bispectrum of the gravitational field fluctuations generated during the warm inflation in strong dissipative regime. The bi-spectrum of the Inflation is expressed in terms of the parameter f NL and it is seen that the value of f NL parameter lies well within the limit observed by WMAP7

  4. Prosthetic clone and natural human tooth comparison by speckle interferometry (United States)

    Slangen, Pierre; Corn, Stephane; Fages, Michel; Raynal, Jacques; Cuisinier, Frederic J. G.


    transducers to perform "4-buckets" phase shifting leading to phase variations during the compression test. In-plane displacement fields from speckle interferometry already showed very interesting data concerning the mechanical behaviour of teeth: the dentine-enamel junction (DEJ) and the glue junction have been shown including their interfacing function. Mechanical action of the tooth surrounding medium will also be discussed.

  5. Exploiting the speckle-correlation scattering matrix for a compact reference-free holographic image sensor. (United States)

    Lee, KyeoReh; Park, YongKeun


    The word 'holography' means a drawing that contains all of the information for light-both amplitude and wavefront. However, because of the insufficient bandwidth of current electronics, the direct measurement of the wavefront of light has not yet been achieved. Though reference-field-assisted interferometric methods have been utilized in numerous applications, introducing a reference field raises several fundamental and practical issues. Here we demonstrate a reference-free holographic image sensor. To achieve this, we propose a speckle-correlation scattering matrix approach; light-field information passing through a thin disordered layer is recorded and retrieved from a single-shot recording of speckle intensity patterns. Self-interference via diffusive scattering enables access to impinging light-field information, when light transport in the diffusive layer is precisely calibrated. As a proof-of-concept, we demonstrate direct holographic measurements of three-dimensional optical fields using a compact device consisting of a regular image sensor and a diffusor.

  6. Gaussian beam shooting algorithm based on iterative frame decomposition


    Ghannoum, Ihssan; Letrou, Christine; Beauquet, Gilles


    International audience; Adaptive beam re-shooting is proposed as a solution to overcome essential limitations of the Gaussian Beam Shooting technique. The proposed algorithm is based on iterative frame decompositions of beam fields in situations where usual paraxial formulas fail to give accurate enough results, such as interactions with finite obstacle edges. Collimated beam fields are successively re-expanded on narrow and wide window frames, allowing for re-shooting and further propagation...

  7. A statistical theory on the turbulent diffusion of Gaussian puffs

    International Nuclear Information System (INIS)

    Mikkelsen, T.; Larsen, S.E.; Pecseli, H.L.


    The relative diffusion of a one-dimensional Gaussian cloud of particles is related to a two-particle covariance function in a homogeneous and stationary field of turbulence. A simple working approximation is suggested for the determination of this covariance function in terms of entirely Eulerian fields. Simple expressions are derived for the growth of the puff's standard deviation for diffusion times that are small compared to the integral time scale of the turbulence. (Auth.)

  8. Non-contact measurement of ocular microtremor using laser speckle (United States)

    Kenny, E.; Coakley, D.; Boyle, G.


    The human eye moves continuously even while it appears to be at rest. The involuntary eye movements causing this motion are called fixational eye movements. Ocular Microtremor (OMT) is the smallest (150 - 2500nm amplitude) and fastest (~ 80Hz) of these eye movements. OMT has been proven to provide useful clinical information regarding depth of consciousness and neurological disorders. Most quantitative clinical investigations of OMT have been carried out using an eye-contacting piezoelectric probe. However, this measurement procedure suffers from a number of disadvantages which limit the potential of the technique in the clinical environment. The need for eye contact requires the eye to be anaesthetised and not all subjects can tolerate the procedure. A promising alternative to the piezoelectric technique is speckle metrology. A speckle correlation instrument for measuring OMT was first described by Al-Kalbani et al. The approach presented in this paper is a non contact measurement technique implementing laser speckle correlation and using a highly light sensitive video camera operating at 500Hz. The OMT measurement technique in this paper was investigated using a human subject and an eye movement simulator. Using this system, measurement of speckle on the eye takes only a few minutes, no eye drops are necessary and no discomfort is caused to the subject. The paper describes the preliminary results of capturing speckle from the simulator and from the human eye in-vivo at eye safe laser powers. The effects of tear flow, biospeckle and speckle shifting by larger eye movements on the displacement information carried by the speckle are also discussed.

  9. Miniaturization of speckle interferometry for rapid strain analysis (United States)

    Wegner, Ronny; Ettemeyer, Andreas


    Today's industry demands high-performance components meeting toughest mechanical features and ultimate safety standards. Especially in automotive and aircraft industry the development focuses on tailor-made design and solutions according to customer specifications. To reconcile economy, light-weight construction has become a key issue. Many companies are looking for new advanced strain/stress analysis techniques to improve cost efficiency and the limitations of classical methods. Detection of weak points and fatigue tests are carried out mainly with strain gauges which need careful application and experience. ESPI (electronic speckle pattern interferometry) allows a rapid, full field and 3D-measurement without contact. This paper presents the principle and application of a new miniaturized laser optical sensor combining contour and deformation measurement. In its basic employment ESPI is an interferometric method measuring deformations at modern working materials with high accuracy. Here also a module for contouring was developed and integrated into a single interferometer. Therefore even at complex components it is possible to measure and display strain-fields and -gradients with respect to the underlying contour. The new sensor is a unique device for flexible strain-analysis at welded-materials, extrusions, engines, car-bodies, etc. Without preparation and due to the full field and 3D- measurement 'hot spots' are shown, reducing the testing procedure and increasing the reliability of the complex component testing significantly. In this paper the recent development of a miniaturized ESPI-interferometer for strain and stress measurement is described. Advanced features according to classical techniques are specified and new applications in material and component testing are presented.

  10. A novel approach to speckle noise filtering based on Artificial Bee Colony algorithm: an ultrasound image application. (United States)

    Latifoğlu, Fatma


    In this study a novel approach based on 2D FIR filters is presented for denoising digital images. In this approach the filter coefficients of 2D FIR filters were optimized using the Artificial Bee Colony (ABC) algorithm. To obtain the best filter design, the filter coefficients were tested with different numbers (3×3, 5×5, 7×7, 11×11) and connection types (cascade and parallel) during optimization. First, the speckle noise with variances of 1, 0.6, 0.8 and 0.2 respectively was added to the synthetic test image. Later, these noisy images were denoised with both the proposed approach and other well-known filter types such as Gaussian, mean and average filters. For image quality determination metrics such as mean square error (MSE), peak signal-to-noise ratio (PSNR) and signal-to-noise ratio (SNR) were used. Even in the case of noise having maximum variance (the most noisy), the proposed approach performed better than other filtering methods did on the noisy test images. In addition to test images, speckle noise with a variance of 1 was added to a fetal ultrasound image, and this noisy image was denoised with very high PSNR and SNR values. The performance of the proposed approach was also tested on several clinical ultrasound images such as those obtained from ovarian, abdomen and liver tissues. The results of this study showed that the 2D FIR filters designed based on ABC optimization can eliminate speckle noise quite well on noise added test images and intrinsically noisy ultrasound images. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  11. Mixed non-Gaussianity in multiple-DBI inflation

    Energy Technology Data Exchange (ETDEWEB)

    Emery, Jon; Tasinato, Gianmassimo; Wands, David, E-mail:, E-mail:, E-mail: [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Portsmouth, PO1 3FX (United Kingdom)


    We study a model of multiple-field DBI inflation leading to mixed form of primordial non-Gaussianity, including equilateral and local bispectrum shapes. We present a general formalism based on the Hamilton-Jacobi approach, allowing us to go beyond slow-roll, combining the three-point function for the fields at Hubble-exit with the non-linear evolution of super-Hubble scales. We are able to obtain analytic results by taking a separable Ansatz for the Hubble rate. We find general expressions for both the equilateral and local type non-Gaussianity parameter f{sub NL}. The equilateral non-Gaussianity includes the usual enhancement for small sound speeds, but multiplied by an analytic factor which can lead to a suppression. We illustrate our results with two scenarios. In the first model, previously found to have detectable local non-Gaussianity, we find that the equilateral signal is not sufficiently suppressed to evade current observational bounds. In our second scenario we construct a model which exhibits both a detectable equilateral f{sub NL} and a negative local f{sub NL}.

  12. Speckle noise suppression using a helix-free ferroelectric liquid crystal cell

    Energy Technology Data Exchange (ETDEWEB)

    Andreev, A L; Andreeva, T B; Kompanets, I N [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Zalyapin, N V [National Research Nuclear University ' ' MEPhI' ' (Russian Federation)


    We have studied the method for suppressing speckle noise in patterns produced by a laser based on a fast-response electro-optical cell with a ferroelectric liquid crystal (FLC) in which helicoid is absent, i.e., compensated for. The character of smectic layer deformation in an electric field is considered along with the mechanism of spatially inhomogeneous phase modulation of a laser beam passing through the cell which is accompanied by the destruction of phase relations in the beam. Advantages of a helix-free FLC cell are pointed out as compared to helical crystal cells studied previously. (liquid crystal devices)

  13. Speckle-based off-axis holographic detection for non-contact photoacoustic tomography

    Directory of Open Access Journals (Sweden)

    Buj C.


    Full Text Available A very fast innovative holographic off-axis non-contact detection method for Photoacoustic Tomography (PAT is introduced. It overcomes the main problems of most state-of-the-art photoacoustic imaging approaches that are long acquisition times and the requirement of acoustic contact. In order to increase the acquisition speed significantly, the surface displacements of the object, caused by the photoacoustic pressure waves, are measured interferometrically in two dimensions. Phase alterations in the observed speckle field are used to identify changes in the object’s topography. A sampling rate of up to 80 MHz is feasible, which reduces the occurrence of motion artefacts.

  14. Speckle Interferometry at SOAR in 2014 (United States)

    Tokovinin, Andrei; Mason, Brian D.; Hartkopf, William I.; Mendez, Rene A.; Horch, Elliott P.


    The results of speckle interferometric observations at the Southern Astrophysical Research Telescope (SOAR) telescope in 2014 are given. A total of 1641 observations were taken, yielding 1636 measurements of 1218 resolved binary and multiple stars and 577 non-resolutions of 441 targets. We resolved for the first time 56 pairs, including some nearby astrometric or spectroscopic binaries and ten new subsystems in previously known visual binaries. The calibration of the data is checked by linear fits to the positions of 41 wide binaries observed at SOAR over several seasons. The typical calibration accuracy is 0.°1 in angle and 0.3% in pixel scale, while the measurement errors are on the order of 3 mas. The new data are used here to compute 194 binary star orbits, 148 of which are improvements on previous orbital solutions and 46 are first-time orbits. Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).

  15. Laser speckle decorrelation for fingerprint acquisition (United States)

    Schirripa Spagnolo, Giuseppe; Cozzella, Lorenzo


    Biometry is gaining popularity as a physical security approach in situations where a high level of security is necessary. Currently, biometric solutions are embedded in a very large and heterogeneous group of applications. One of the most sensible is for airport security access to boarding gates. More airports are introducing biometric solutions based on face, fingerprint or iris recognition for passenger identification. In particular, fingerprints are the most widely used biometric, and they are mandatorily included in electronic identification documents. One important issue, which is difficult to address in traditional fingerprint acquisition systems, is preventing contact between subsequent users; sebum, which can be a potential vector for contagious diseases. Currently, non-contact devices are used to overcome this problem. In this paper, a new contact device based on laser speckle decorrelation is presented. Our system has the advantage of being compact and low-cost compared with an actual contactless system, allowing enhancement of the sebum pattern imaging contrast in a simple and low-cost way. Furthermore, it avoids the spreading of contagious diseases.

  16. Laser speckle decorrelation for fingerprint acquisition

    International Nuclear Information System (INIS)

    Schirripa Spagnolo, Giuseppe; Cozzella, Lorenzo


    Biometry is gaining popularity as a physical security approach in situations where a high level of security is necessary. Currently, biometric solutions are embedded in a very large and heterogeneous group of applications. One of the most sensible is for airport security access to boarding gates. More airports are introducing biometric solutions based on face, fingerprint or iris recognition for passenger identification. In particular, fingerprints are the most widely used biometric, and they are mandatorily included in electronic identification documents. One important issue, which is difficult to address in traditional fingerprint acquisition systems, is preventing contact between subsequent users; sebum, which can be a potential vector for contagious diseases. Currently, non-contact devices are used to overcome this problem. In this paper, a new contact device based on laser speckle decorrelation is presented. Our system has the advantage of being compact and low-cost compared with an actual contactless system, allowing enhancement of the sebum pattern imaging contrast in a simple and low-cost way. Furthermore, it avoids the spreading of contagious diseases. (paper)

  17. Detecting periodicities with Gaussian processes

    Directory of Open Access Journals (Sweden)

    Nicolas Durrande


    Full Text Available We consider the problem of detecting and quantifying the periodic component of a function given noise-corrupted observations of a limited number of input/output tuples. Our approach is based on Gaussian process regression, which provides a flexible non-parametric framework for modelling periodic data. We introduce a novel decomposition of the covariance function as the sum of periodic and aperiodic kernels. This decomposition allows for the creation of sub-models which capture the periodic nature of the signal and its complement. To quantify the periodicity of the signal, we derive a periodicity ratio which reflects the uncertainty in the fitted sub-models. Although the method can be applied to many kernels, we give a special emphasis to the Matérn family, from the expression of the reproducing kernel Hilbert space inner product to the implementation of the associated periodic kernels in a Gaussian process toolkit. The proposed method is illustrated by considering the detection of periodically expressed genes in the arabidopsis genome.

  18. The use of digital speckle radiography to study the ballistic deformation of a polymer bonded sugar (an explosive simulant)


    Prentice, H.J.; Proud, W.G.; Walley, S.M.; Field, J.E.


    Abstract This paper reports an initial study into the benefits of determining two-dimensional flow fields for low velocity impact on a small-scale model of explosive reactive armour (ERA) using digital speckle radiography (DSR). The model system consisted of a polymer-bonded sugar (PBS) (otherwise known as a sugarmock) confined between two mild steel plates. The DSR technique relies upon creating a layer within the specimen that is seeded with lead particles. So although radiograph...

  19. Deformation measurements of materials at low temperatures using laser speckle photography method

    International Nuclear Information System (INIS)

    Sumio Nakahara; Yukihide Maeda; Kazunori Matsumura; Shigeyoshi Hisada; Takeyoshi Fujita; Kiyoshi Sugihara


    The authors observed deformations of several materials during cooling down process from room temperature to liquid nitrogen temperature using the laser speckle photography method. The in-plane displacements were measured by the image plane speckle photography and the out-of-plane displacement gradients by the defocused speckle photography. The results of measurements of in-plane displacement are compared with those of FEM analysis. The applicability of laser speckle photography method to cryogenic engineering are also discussed

  20. Assessing White Wine Viscosity Variation Using Polarized Laser Speckle: A Promising Alternative to Wine Sensory Analysis


    Abou Nader, Christelle; Loutfi, Hadi; Pellen, Fabrice; Le Jeune, Bernard; Le Brun, Guy; Lteif, Roger; Abboud, Marie


    In this paper, we report measurements of wine viscosity, correlated to polarized laser speckle results. Experiments were performed on white wine samples produced with a single grape variety. Effects of the wine making cellar, the grape variety, and the vintage on wine Brix degree, alcohol content, viscosity, and speckle parameters are considered. We show that speckle parameters, namely, spatial contrast and speckle decorrelation time, as well as the inertia moment extracted from the temporal ...

  1. Drug packaging security by means of white-light speckle (United States)

    Cozzella, Lorenzo; Simonetti, Carla; Schirripa Spagnolo, Giuseppe


    Protecting pharmaceutical products against counterfeiting or the fraudulent importation of donated and discounted drugs will remain a permanent challenge in light of the increased frequency of counterfeiting. The increasing complexity of the supply chain in today's global economy complicates certification of each individual supply source. This complexity is a key factor in the rapid increase of counterfeiting attacks, including those in countries where the supply chains are well established and trustworthy. In this article, an innovative solution based on the white-light speckle theory (visible speckle obtained as ultraviolet fluorescence) is applied to an ultraviolet source, which allows drug packages to be linked with a barcode. The basis of the proposed method is the biometric paradigm, applied to nonliving matter, which requires the identification of a unique distinctive matter characteristic for the unique identification of the related object. The identified characteristic is not an inherent characteristic of the object itself; instead, a white-light speckle pattern will be artificially added. This speckle pattern becomes a sort of fingerprint for the drug package. Starting from this pattern, drug packages can be authenticated by a biometric-like approach. This paper presents a concise review of pharmaceutical product anti-counterfeiting and introduces our white-light speckle method.

  2. Analysis of strawberry ripening by dynamic speckle measurements (United States)

    Mulone, C.; Budini, N.; Vincitorio, F. M.; Freyre, C.; López Díaz, A. J.; Ramil Rego, A.


    This work seeks to determine the age of a fruit from observation of its dynamic speckle pattern. A mobile speckle pattern originates on the fruit's surface due to the interference of the wavefronts reflected from moving scatterers. For this work we analyzed two series of photographs of a strawberry speckle pattern, at different stages of ripening, acquired with a CMOS camera. The first day, we took ten photographs at an interval of one second. The same procedure was repeated the next day. From each series of images we extracted several statistical descriptors of pixel-to-pixel gray level variation during the observation time. By comparing these values from the first to the second day we noticed a diminution of the speckle activity. This decay demonstrated that after only one day the ripening process of the strawberry can be detected by dynamic speckle pattern analysis. For this study we employed a simple new algorithm to process the data obtained from the photographs. This algorithm allows defining a global mobility index that indicates the evolution of the fruit's ripening.

  3. Speckle reduction methods in laser-based picture projectors (United States)

    Akram, M. Nadeem; Chen, Xuyuan


    Laser sources have been promised for many years to be better light sources as compared to traditional lamps or light-emitting diodes (LEDs) for projectors, which enable projectors having wide colour gamut for vivid image, super brightness and high contrast for the best picture quality, long lifetime for maintain free operation, mercury free, and low power consumption for green environment. A major technology obstacle in using lasers for projection has been the speckle noise caused by to the coherent nature of the lasers. For speckle reduction, current state of the art solutions apply moving parts with large physical space demand. Solutions beyond the state of the art need to be developed such as integrated optical components, hybrid MOEMS devices, and active phase modulators for compact speckle reduction. In this article, major methods reported in the literature for the speckle reduction in laser projectors are presented and explained. With the advancement in semiconductor lasers with largely reduced cost for the red, green and the blue primary colours, and the developed methods for their speckle reduction, it is hoped that the lasers will be widely utilized in different projector applications in the near future.

  4. Identification of a chemical inhibitor for nuclear speckle formation: Implications for the function of nuclear speckles in regulation of alternative pre-mRNA splicing

    Energy Technology Data Exchange (ETDEWEB)

    Kurogi, Yutaro; Matsuo, Yota; Mihara, Yuki; Yagi, Hiroaki; Shigaki-Miyamoto, Kaya; Toyota, Syukichi; Azuma, Yuko [Department of Biological Sciences, Graduate School of Science and Technology, Kumamoto University, Chuo-ku, Kumamoto 860-8555 (Japan); Igarashi, Masayuki [Laboratory of Disease Biology, Institute of Microbial Chemistry, Shinagawa-ku, Tokyo 141-0021 (Japan); Tani, Tokio, E-mail: [Department of Biological Sciences, Graduate School of Science and Technology, Kumamoto University, Chuo-ku, Kumamoto 860-8555 (Japan)


    Highlights: • We identified tubercidin as a compound inducing aberrant formation of the speckles. • Tubercidin causes delocalization of poly (A){sup +}RNAs from nuclear speckles. • Tubercidin induces dispersion of splicing factors from nuclear speckles. • Tubercidin affects alternative pre-mRNA splicing. • Nuclear speckles play a role in regulation of alternative pre-mRNA splicing. - Abstract: Nuclear speckles are subnuclear structures enriched with RNA processing factors and poly (A){sup +} RNAs comprising mRNAs and poly (A){sup +} non-coding RNAs (ncRNAs). Nuclear speckles are thought to be involved in post-transcriptional regulation of gene expression, such as pre-mRNA splicing. By screening 3585 culture extracts of actinomycetes with in situ hybridization using an oligo dT probe, we identified tubercidin, an analogue of adenosine, as an inhibitor of speckle formation, which induces the delocalization of poly (A){sup +} RNA and dispersion of splicing factor SRSF1/SF2 from nuclear speckles in HeLa cells. Treatment with tubercidin also decreased steady-state MALAT1 long ncRNA, thought to be involved in the retention of SRSF1/SF2 in nuclear speckles. In addition, we found that tubercidin treatment promoted exon skipping in the alternative splicing of Clk1 pre-mRNA. These results suggest that nuclear speckles play a role in modulating the concentration of splicing factors in the nucleoplasm to regulate alternative pre-mRNA splicing.

  5. Coherence of the vortex Bessel-Gaussian beam in turbulent atmosphere (United States)

    Lukin, Igor P.


    In this paper the theoretical research of coherent properties of the vortex Bessel-Gaussian optical beams propagating in turbulent atmosphere are developed. The approach to the analysis of this problem is based on the analytical solution of the equation for the transverse second-order mutual coherence function of a field of optical radiation. The behavior of integral scale of coherence degree of vortex Bessel-Gaussian optical beams depending on parameters of an optical beam and characteristics of turbulent atmosphere is particularly considered. It is shown that the integral scale of coherence degree of a vortex Bessel-Gaussian optical beam essentially depends on value of a topological charge of a vortex optical beam. With increase in a topological charge of a vortex Bessel-Gaussian optical beam the value of integral scale of coherence degree of a vortex Bessel-Gaussian optical beam are decreased.

  6. Experimental demonstration of Generalized Phase Contrast based Gaussian beam-shaper

    DEFF Research Database (Denmark)

    Tauro, Sandeep; Bañas, Andrew Rafael; Palima, Darwin


    -cost binary-phase optics fabricated using photolithography and chemical etching techniques can replace the SLM in static and high power beam shaping applications. The design parameters for the binary-phase elements of the module are chosen according to the results of our previously conducted analysis......We report the first experimental demonstration of Gaussian beam-shaping based on the Generalized Phase Contrast (GPC) approach. We show that, when using a dynamic spatial light modulator (SLM), this approach can rapidly generate arbitrarily shaped beams. Moreover, we demonstrate that low...... and numerical demonstrations [Opt. Express 15, 11971 (2007)]. Beams with a variety of cross-sections such as circular, rectangular and square, with near flat-top intensity distributions are demonstrated. GPC-based beam shaping is inherently speckle-free and the shaped beams maintain a flat output phase. The non...


    Directory of Open Access Journals (Sweden)

    H. Wang


    Full Text Available Image registration is a fundamental in remote sensing applications such as inter-calibration and image fusion. Compared to other multi sensor image registration problems such as optical-to-IR, the registration for SAR and optical images has its specials. Firstly, the radiometric and geometric characteristics are different between SAR and optical images. Secondly, the feature extraction methods are heavily suffered with the speckle in SAR images. Thirdly, the structural information is more useful than the point features such as corners. In this work, we proposed a novel Gaussian Mixture Model (GMM based Optical-to-SAR image registration algorithm. The feature of line support region (LSR is used to describe the structural information and the orientation attributes are added into the GMM to avoid Expectation Maximization (EM algorithm falling into local extremum in feature sets matching phase. Through the experiments it proves that our algorithm is very robust for optical-to- SAR image registration problem.

  8. Breaking Gaussian incompatibility on continuous variable quantum systems

    Energy Technology Data Exchange (ETDEWEB)

    Heinosaari, Teiko, E-mail: [Turku Centre for Quantum Physics, Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Kiukas, Jukka, E-mail: [Department of Mathematics, Aberystwyth University, Penglais, Aberystwyth, SY23 3BZ (United Kingdom); Schultz, Jussi, E-mail: [Turku Centre for Quantum Physics, Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Dipartimento di Matematica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano (Italy)


    We characterise Gaussian quantum channels that are Gaussian incompatibility breaking, that is, transform every set of Gaussian measurements into a set obtainable from a joint Gaussian observable via Gaussian postprocessing. Such channels represent local noise which renders measurements useless for Gaussian EPR-steering, providing the appropriate generalisation of entanglement breaking channels for this scenario. Understanding the structure of Gaussian incompatibility breaking channels contributes to the resource theory of noisy continuous variable quantum information protocols.

  9. Anomalous dimensions and non-gaussianity

    Energy Technology Data Exchange (ETDEWEB)

    Green, Daniel; Lewandowski, Matthew; Senatore, Leonardo; Silverstein, Eva; Zaldarriaga, Matias


    We analyze the signatures of inflationary models that are coupled to interacting field theories, a basic class of multifield models also motivated by their role in providing dynamically small scales. Near the squeezed limit of the bispectrum, we find a simple scaling behavior determined by operator dimensions, which are constrained by the appropriate unitarity bounds. Specifically, we analyze two simple and calculable classes of examples: conformal field theories (CFTs), and large-N CFTs deformed by relevant time-dependent double-trace operators. Together these two classes of examples exhibit a wide range of scalings and shapes of the bispectrum, including nearly equilateral, orthogonal and local non-Gaussianity in different regimes. Along the way, we compare and contrast the shape and amplitude with previous results on weakly coupled fields coupled to inflation. This signature provides a precision test for strongly coupled sectors coupled to inflation via irrelevant operators suppressed by a high mass scale up to ~ 103 times the inflationary Hubble scale.

  10. Optical Processing of Speckle Images with Bacteriorhodopsin for Pattern Recognition (United States)

    Downie, John D.; Tucker, Deanne (Technical Monitor)


    Logarithmic processing of images with multiplicative noise characteristics can be utilized to transform the image into one with an additive noise distribution. This simplifies subsequent image processing steps for applications such as image restoration or correlation for pattern recognition. One particularly common form of multiplicative noise is speckle, for which the logarithmic operation not only produces additive noise, but also makes it of constant variance (signal-independent). We examine the optical transmission properties of some bacteriorhodopsin films here and find them well suited to implement such a pointwise logarithmic transformation optically in a parallel fashion. We present experimental results of the optical conversion of speckle images into transformed images with additive, signal-independent noise statistics using the real-time photochromic properties of bacteriorhodopsin. We provide an example of improved correlation performance in terms of correlation peak signal-to-noise for such a transformed speckle image.

  11. DMD based digital speckle illumination for high resolution imaging (United States)

    Shinde, Anant; Mishra, Ayush; Perinchery, Sandeep M.; Murukeshan, V. M.


    Spatially non-uniform illumination patterns have shown significant potential to improve the imaging. Recent developments in the patterned illumination microscopy have demonstrated that the use of an optical speckle as an illumination pattern significantly improves the imaging resolution at the same time reducing the computational overheads. We present a DMD based method for generation of digital speckle pattern. The generated digital speckle and uniform white light illumination are used as two illuminations to acquire images. The image reconstruction algorithm for blind structured illumination microscopy is used to get the high resolution image. Our approach does not require any calibration step or stringent control of the illumination, and dramatically simplifies the experimental set-up.

  12. Color speckle measurement errors using system with XYZ filters (United States)

    Kinoshita, Junichi; Yamamoto, Kazuhisa; Kuroda, Kazuo


    Measurement errors of color speckle are analyzed for a measurement system equipped with revolving XYZ filters and a 2D sensor. One of the errors is caused by the filter characteristics unfitted to the ideal color matching functions. The other is caused by uncorrelations among the optical paths via the XYZ filters. The unfitted color speckle errors of all the pixel data can be easily calibrated by conversion between the measured BGR chromaticity triangle and the true triangle obtained by the BGR wavelength measurements. For the uncorrelated errors, the measured BGR chromaticity values spread over around the true values. As a result, it would be more complicated to calibrate the uncorrelated errors, repeating the triangular conversion pixel by pixel. Color speckle and its errors greatly affect also chromaticity measurements and image quality of displays using coherent light sources.

  13. Beam shape coefficients of the most general focused Gaussian laser beam for light scattering applications

    International Nuclear Information System (INIS)

    Lock, James A.


    The vector wave equation for electromagnetic waves, when subject to a number of constraints corresponding to propagation of a monochromatic beam, reduces to a pair of inhomogeneous differential equations describing the transverse electric and transverse magnetic polarized beam components. These differential equations are solved analytically to obtain the most general focused Gaussian beam to order s 4 , where s is the beam confinement parameter, and various properties of the most general Gaussian beam are then discussed. The radial fields of the most general Gaussian beam are integrated to obtain the on-axis beam shape coefficients of the generalized Lorenz–Mie theory formalism of light scattering. The beam shape coefficients are then compared with those of the localized Gaussian beam model and the Davis–Barton fifth-order symmetrized beam. -- Highlights: ► Derive the differential equation for the most general Gaussian beam. ► Solve the differential equation for the most general Gaussian beam. ► Determine the properties of the most general Gaussian beam. ► Determine the beam shape coefficients of the most general Gaussian beam

  14. Trapping induced nonlinear behavior of backward stimulated Raman scattering in multi-speckled laser beams

    International Nuclear Information System (INIS)

    Yin, L.; Albright, B. J.; Rose, H. A.; Bowers, K. J.; Bergen, B.; Montgomery, D. S.; Kline, J. L.; Kirkwood, R. K.; Hinkel, D. E.; Langdon, A. B.; Michel, P.


    In inertial confinement fusion experiments, stimulated Raman scattering (SRS) occurs when electron density fluctuations are amplified resonantly by the incident laser beams and scattered light. These beams comprise several thousands of individual laser speckles. We have found in single-speckle studies that electron trapping lowers the threshold intensity for SRS onset to a value below that from linear theory and enhances scattering. The trapping-induced plasma-wave frequency shift leads to wave-front bowing and filamentation processes that saturate SRS and limit scattering within a speckle. With large-scale simulations, we have now examined how laser speckles interact with one another through three-dimensional (3D) particle-in-cell (PIC) simulations of two interacting speckles and 2D PIC simulations of ensembles of laser speckles (hundreds of speckles). Our work shows that kinetic trapping physics also governs the onset and saturation of SRS in ensembles of speckles. Speckles interact in a manner that is nonlinear and nonlocal: An intense speckle can destabilize its neighbors through transport of hot electrons and SRS waves, resulting in enhanced emission of particles and waves that, in turn, act upon the original speckle. In this manner, speckles below threshold when in isolation can be above the threshold in multi-speckled beams under conditions for laser-driven fusion experiments at the National Ignition Facility (NIF) and ensembles of speckles are thus found to collectively lower the SRS onset threshold. Simulations of the hohlraum interior where laser beams overlap show that multi-speckled laser beams at low average intensity (a few times 10 14 W/cm 2 ) have correspondingly lower thresholds for enhanced SRS and that the sub-ps bursts of SRS saturate through trapping induced nonlinearities. Because of electron trapping effects, SRS reflectivity grows slowly with average laser intensity. While SRS reflectivity saturates under NIF conditions, SRS hot electron

  15. Speckle Suppression in Ultrasonic Images Based on Undecimated Wavelets (United States)

    Argenti, Fabrizio; Torricelli, Gionatan


    An original method to denoise ultrasonic images affected by speckle is presented. Speckle is modeled as a signal-dependent noise corrupting the image. Noise reduction is approached as a Wiener-like filtering performed in a shift-invariant wavelet domain by means of an adaptive rescaling of the coefficients of an undecimated octave decomposition. The scaling factor of each coefficient is calculated from local statistics of the degraded image, the parameters of the noise model, and the wavelet filters. Experimental results demonstrate that excellent background smoothing as well as preservation of edge sharpness and fine details can be obtained.

  16. Speckle Interferometry with the OCA Kuhn 22" Telescope (United States)

    Wasson, Rick


    Speckle interferometry measurements of double stars were made in 2015 and 2016, using the Kuhn 22-inch classical Cassegrain telescope of the Orange County Astronomers, a Point Grey Blackfly CMOS camera, and three interference filters. 272 observations are reported for 177 systems, with separations ranging from 0.29" to 2.9". Data reduction was by means of the REDUC and Speckle Tool Box programs. Equipment, observing procedures, calibration, data reduction, and analysis are described, and unusual results for 11 stars are discussed in detail.

  17. Mutual Information between Reflected and Transmitted Speckle Images (United States)

    Fayard, N.; Goetschy, A.; Pierrat, R.; Carminati, R.


    We study theoretically the mutual information between reflected and transmitted speckle patterns produced by wave scattering from disordered media. The mutual information between the two speckle images recorded on an array of N detection points (pixels) takes the form of long-range intensity correlation loops that we evaluate explicitly as a function of the disorder strength and the Thouless number g . Our analysis, supported by extensive numerical simulations, reveals a competing effect of cross-sample and surface spatial correlations. An optimal distance between pixels is proven to exist that enhances the mutual information by a factor N g compared to the single-pixel scenario.

  18. Gaussian queues in light and heavy traffic

    NARCIS (Netherlands)

    Dębicki, K.; Kosiński, K.M.; Mandjes, M.


    In this paper we investigate Gaussian queues in the light-traffic and in the heavy-traffic regime. Let $Q^{(c)}_{X}\\equiv\\{Q^{(c)}_{X}(t):t\\ge0\\}$ denote a stationary buffer content process for a fluid queue fed by the centered Gaussian process X≡{X(t):t∈ℝ} with stationary increments, X(0)=0,

  19. Palm distributions for log Gaussian Cox processes

    DEFF Research Database (Denmark)

    Coeurjolly, Jean-Francois; Møller, Jesper; Waagepetersen, Rasmus

    This paper reviews useful results related to Palm distributions of spatial point processes and provides a new result regarding the characterization of Palm distributions for the class of log Gaussian Cox processes. This result is used to study functional summary statistics for a log Gaussian Cox...

  20. Conditional and unconditional Gaussian quantum dynamics (United States)

    Genoni, Marco G.; Lami, Ludovico; Serafini, Alessio


    This article focuses on the general theory of open quantum systems in the Gaussian regime and explores a number of diverse ramifications and consequences of the theory. We shall first introduce the Gaussian framework in its full generality, including a classification of Gaussian (also known as 'general-dyne') quantum measurements. In doing so, we will give a compact proof for the parametrisation of the most general Gaussian completely positive map, which we believe to be missing in the existing literature. We will then move on to consider the linear coupling with a white noise bath, and derive the diffusion equations that describe the evolution of Gaussian states under such circumstances. Starting from these equations, we outline a constructive method to derive general master equations that apply outside the Gaussian regime. Next, we include the general-dyne monitoring of the environmental degrees of freedom and recover the Riccati equation for the conditional evolution of Gaussian states. Our derivation relies exclusively on the standard quantum mechanical update of the system state, through the evaluation of Gaussian overlaps. The parametrisation of the conditional dynamics we obtain is novel and, at variance with existing alternatives, directly ties in to physical detection schemes. We conclude our study with two examples of conditional dynamics that can be dealt with conveniently through our formalism, demonstrating how monitoring can suppress the noise in optical parametric processes as well as stabilise systems subject to diffusive scattering.

  1. Study of photo activation reaction of experimental graphene dental nanocomposites through dynamic laser speckle (United States)

    Salas, Marianne; Yebra, Ana; Pozo, Antonio M.; Lucena, Cristina; Pérez, María. M.


    The objective of this study was to characterize the photo activation reaction of experimental graphene dental nanocomposites and to compare this reaction between commercial nanocomposite by dynamic laser speckle patterns. One commercial nanocomposite and two experimental graphene nanocomposites were used. LED curing unit was used to produce the photo activation reaction and the speckle patterns were generated by the incident light from the laser diode. These patterns were captured with the CMOS camera; later the speckle correlation was calculated. The photo activation process originates different speckle patterns between the commercial and the experimental graphene nanocomposites; having this less speckle activity.

  2. Dedicated hardware processor and corresponding system-on-chip design for real-time laser speckle imaging. (United States)

    Jiang, Chao; Zhang, Hongyan; Wang, Jia; Wang, Yaru; He, Heng; Liu, Rui; Zhou, Fangyuan; Deng, Jialiang; Li, Pengcheng; Luo, Qingming


    Laser speckle imaging (LSI) is a noninvasive and full-field optical imaging technique which produces two-dimensional blood flow maps of tissues from the raw laser speckle images captured by a CCD camera without scanning. We present a hardware-friendly algorithm for the real-time processing of laser speckle imaging. The algorithm is developed and optimized specifically for LSI processing in the field programmable gate array (FPGA). Based on this algorithm, we designed a dedicated hardware processor for real-time LSI in FPGA. The pipeline processing scheme and parallel computing architecture are introduced into the design of this LSI hardware processor. When the LSI hardware processor is implemented in the FPGA running at the maximum frequency of 130 MHz, up to 85 raw images with the resolution of 640×480 pixels can be processed per second. Meanwhile, we also present a system on chip (SOC) solution for LSI processing by integrating the CCD controller, memory controller, LSI hardware processor, and LCD display controller into a single FPGA chip. This SOC solution also can be used to produce an application specific integrated circuit for LSI processing.

  3. Gaussian vs non-Gaussian turbulence: impact on wind turbine loads

    DEFF Research Database (Denmark)

    Berg, Jacob; Natarajan, Anand; Mann, Jakob


    taking into account the safety factor for extreme moments. Other extreme load moments as well as the fatigue loads are not affected because of the use of non-Gaussian turbulent inflow. It is suggested that the turbine thus acts like a low-pass filter that averages out the non-Gaussian behaviour, which......From large-eddy simulations of atmospheric turbulence, a representation of Gaussian turbulence is constructed by randomizing the phases of the individual modes of variability. Time series of Gaussian turbulence are constructed and compared with its non-Gaussian counterpart. Time series from the two...

  4. Productive interactions: heavy particles and non-Gaussianity

    International Nuclear Information System (INIS)

    Flauger, Raphael; Mirbabayi, Mehrdad; Senatore, Leonardo; Silverstein, Eva


    We analyze the shape and amplitude of oscillatory features in the primordial power spectrum and non-Gaussianity induced by periodic production of heavy degrees of freedom coupled to the inflaton φ. We find that non-adiabatic production of particles can contribute effects which are detectable or constrainable using cosmological data even if their time-dependent masses are always heavier than the scale φ̇ 1/2 , much larger than the Hubble scale. This provides a new role for UV completion, consistent with the criteria from effective field theory for when heavy fields cannot be integrated out. This analysis is motivated in part by the structure of axion monodromy, and leads to an additional oscillatory signature in a subset of its parameter space. At the level of a quantum field theory model that we analyze in detail, the effect arises consistently with radiative stability for an interesting window of couplings up to of order ∼< 1. The amplitude of the bispectrum and higher-point functions can be larger than that for Resonant Non-Gaussianity, and its signal/noise may be comparable to that of the corresponding oscillations in the power spectrum (and even somewhat larger within a controlled regime of parameters). Its shape is distinct from previously analyzed templates, but was partly motivated by the oscillatory equilateral searches performed recently by the Planck collaboration. We also make some general comments about the challenges involved in making a systematic study of primordial non-Gaussianity.

  5. Assessing White Wine Viscosity Variation Using Polarized Laser Speckle: A Promising Alternative to Wine Sensory Analysis. (United States)

    Nader, Christelle Abou; Loutfi, Hadi; Pellen, Fabrice; Jeune, Bernard Le; Le Brun, Guy; Lteif, Roger; Abboud, Marie


    In this paper, we report measurements of wine viscosity, correlated to polarized laser speckle results. Experiments were performed on white wine samples produced with a single grape variety. Effects of the wine making cellar, the grape variety, and the vintage on wine Brix degree, alcohol content, viscosity, and speckle parameters are considered. We show that speckle parameters, namely, spatial contrast and speckle decorrelation time, as well as the inertia moment extracted from the temporal history speckle pattern, are mainly affected by the alcohol and sugar content and hence the wine viscosity. Principal component analysis revealed a high correlation between laser speckle results on the one hand and viscosity and Brix degree values on the other. As speckle analysis proved to be an efficient method of measuring the variation of the viscosity of white mono-variety wine, one can therefore consider it as an alternative method to wine sensory analysis.

  6. Three-dimensional speckle-noise reduction by using computational integral imaging and statistical point estimator (United States)

    Moon, Inkyu


    In this paper we overview a method which can remove speckle noises to exist in coherent imaging systems. Integral imaging (II) system under coherent illumination records the elemental image set with speckle noise patterns of a threedimensional (3D) object. The computational geometrical ray propagation and statistical point estimation algorithms are applied to the elemental image set in order to reconstruct the speckle reduced 3D integral imaging. As performance metrics, the SNR and speckle index are calculated. The results are used to compare the speckle reduced 3D image reconstructed by the presented method with the coherent image having speckle patterns. It is shown in experiments that the presented method can three dimensionally reduce the speckle noise in the 3D object reconstruction.

  7. Representation of Gaussian semimartingales with applications to the covariance function

    DEFF Research Database (Denmark)

    Basse-O'Connor, Andreas


    stationary Gaussian semimartingales and their canonical decomposition. Thirdly, we give a new characterization of the covariance function of Gaussian semimartingales, which enable us to characterize the class of martingales and the processes of bounded variation among the Gaussian semimartingales. We...

  8. Thermoregulation under semi-natural conditions in speckled ...

    African Journals Online (AJOL)

    We recorded body temperature (Tb) in speckled mousebirds (Colius striatus) under semi-natural conditions in outdoor aviaries, and examined interactions between behavioural and metabolic thermoregulation by experimentally manipulating food availability and communal roosting behaviour. When food was available ad ...

  9. Laser speckle reduction based on compressive sensing and edge detection (United States)

    Wen, Dong-hai; Jiang, Yue-song; Hua, Hou-qiang; Yu, Rong; Gao, Qian; Zhang, Yan-zhong


    Polarization active imager technology obtains images encoded by parameters different than just the reflectivity and therefore provides new information on the image. So polarization active imager systems represent a very powerful observation tool. However, automatic interpretation of the information contained in the reflected intensity of the polarization active image data is extremely difficult because of the speckle phenomenon. An approach for speckle reduction of polarization active image based on the concepts of compressive sensing (CS) theory and edge detection. First, A Canny operator is first utilized to detect and remove edges from the polarization active image. Then, a dictionary learning algorithm which is applied to sparse image representation. The dictionary learning problem is expressed as a box-constrained quadratic program and a fast projected gradient method is introduced to solve it. The Gradient Projection for Square Reconstruction (GPSR) algorithm for solving bound constrained quadratic programming to reduce the speckle noise in the polarization active images. The block-matching 3-D (BM3D) algorithm is used to reduce speckle nosie, it works in two steps: The first one uses hard thresholding to build a relatively clean image for estimating statistics, while the second one performs the actual denoising through empirical Wiener filtering in the transform domain. Finally, the removed edges are added to the reconstructed image. Experimental results show that the visual quality and evaluation indexes outperform the other methods with no edge preservation. The proposed algorithm effectively realizes both despeckling and edge preservation and reaches the state-of-the-art performance.

  10. Spatial blurring in laser speckle imaging in inhomogeneous turbid media

    NARCIS (Netherlands)

    Vitomir, Luka; Sprakel, Joris; Gucht, Van Der Jasper


    Laser speckle imaging (LSI) has developed into a versatile tool to image dynamical processes in turbid media, such as subcutaneous blood perfusion and heterogeneous dynamics in soft materials. Spatially resolved information about local dynamics is obtained by measuring time-dependent correlation

  11. Pointwise intensity-based dynamic speckle analysis with binary patterns (United States)

    Stoykova, Elena; Mateev, Georgy; Nazarova, Dimana; Berberova, Nataliya; Ivanov, Branimir


    Non-destructive detection of physical or biological activity through statistical processing of speckle patterns on the surface of diffusely reflecting objects is an area of active research. A lot of pointwise intensity-based algorithms have been proposed over the recent years. Efficiency of these algorithms is deteriorated by the signal-dependent speckle data, non-uniform illumination or varying reflectivity across the object, especially when the number of the acquired speckle patterns is limited. Pointwise processing of a sequence of 2D images is also time-consuming. In this paper, we propose to transform the acquired speckle images into binary patterns by using for a sign threshold the mean intensity value estimated at each spatial point from the temporal sequence of intensities at this point. Activity is characterized by the 2D distribution of a temporal polar correlation function estimated at a given time lag from the binary patterns. Processing of synthetic and experimental data confirmed that the algorithm provided correct activity determination with the same accuracy as the temporal normalized correlation function. It is efficient without the necessity to apply normalization at non-uniform distribution of intensity in the illuminating laser beam and offers acceleration of computation.

  12. A method to transfer speckle patterns for digital image correlation

    International Nuclear Information System (INIS)

    Chen, Zhenning; He, Xiaoyuan; Quan, Chenggen; Zhu, Feipeng


    A simple and repeatable speckle creation method based on water transfer printing (WTP) is proposed to reduce artificial measurement error for digital image correlation (DIC). This technique requires water, brush, and a piece of transfer paper that is made of prefabricated decal paper, a protected sheet, and printed speckle patterns. The speckle patterns are generated and optimized via computer simulations, and then printed on the decal paper. During the experiments, operators can moisten the basement with water and the brush, so that digital patterns can be simply transferred to the carriers’ surfaces. Tensile experiments with an extended three-dimensional (3D) DIC system are performed to test and verify the validity of WTP patterns. It is shown that by comparing with a strain gage, the strain error is less than 50με in a uniform tensile test. From five carbon steel tensile experiments, Lüders bands in both WTP patterns and spray paint patterns are demonstrated to propagate symmetrically. In the necking part where the strain is up to 66%, WTP patterns are proved to adhere to the specimens well. Hence, WTP patterns are capable of maintaining coherence and adherence to the specimen surface. The transfer paper, working as the role of strain gage in the electrometric method, will contribute to speckle creation. (paper)

  13. Simultaneous laser speckle imaging and positron emission tomography (United States)

    Gramer, M.; Feuerstein, D.; Backes, H.; Takagaki, M.; Kumagai, T.; Graf, R.


    Complex biological systems often require measurements of multiple parameters with high temporal and spatial resolution. Multimodal approaches and the combination of methods are therefore a powerful tool to address such scientific questions. Laser speckle imaging (LSI) is an optical method that monitors dynamic changes in cortical blood flow (CBF) with high temporal resolution. Positron emission tomography (PET) allows for quantitative imaging of physiological processes and is a gold standard method to determine absolute cerebral blood flow. We developed a setup that allows simultaneous measurement with both modalities. Here, we simultaneously measured CBF with PET and LSI in rats and analyzed how the correlation of PET and LSI is modified when (1) different methods are used for the calculation of speckle inverse correlation time (ICT), (2) speckle data is acquired through thinned or craniectomized skull, (3) influence of surface vessels is removed from the speckle data. For the latter, a method for automated vessel segmentation from LSI data was developed. We obtained the best correlation (R² = 0.890, pICT. Thus, LSI provides CBF in absolute units at high temporal resolution.

  14. Powertrain engineering using holographic/electronic speckle pattern interferometry (United States)

    Chen, Fang; Marchi, Mitchell M.; Allen, Thomas E.


    Novel applications of computer aided holographic interferometry and electronic speckle pattern interferometry in automotive powertrain engineering are presented. Four applications are described: engine manifold/cylinder head interface deformation measurement, engine camcover strain analysis, throttle bore deformation measurement, and alternator modal characterization.

  15. An Exchange of Views on "The Great Speckled Bird." (United States)

    Waugh, Dexter; Cornbleth, Catherine


    Responds to critical commentary about the authors' article, "The Great Speckled Bird" (1993), which addressed educational policymaking within a social context characterized by multicultural backlash. The authors point to their critics' attempts to deflect from the article's main focus, how these educational policies came to be, by…

  16. 3-color photometry of a sunspot using speckle masking techniques

    NARCIS (Netherlands)

    Wiehr, E.; Sütterlin, P.


    A three-colour photometry is used to deduce the temperature of sunspot fine-structures. Using the Speckle-Masking method for image restoration, the resulting images (one per colour and burst) have a spatial resolution only limited by the telescope's aperture, i.e. 95km (blue), 145 km (red) and

  17. Scattering property based contextual PolSAR speckle filter (United States)

    Mullissa, Adugna G.; Tolpekin, Valentyn; Stein, Alfred


    Reliability of the scattering model based polarimetric SAR (PolSAR) speckle filter depends upon the accurate decomposition and classification of the scattering mechanisms. This paper presents an improved scattering property based contextual speckle filter based upon an iterative classification of the scattering mechanisms. It applies a Cloude-Pottier eigenvalue-eigenvector decomposition and a fuzzy H/α classification to determine the scattering mechanisms on a pre-estimate of the coherency matrix. The H/α classification identifies pixels with homogeneous scattering properties. A coarse pixel selection rule groups pixels that are either single bounce, double bounce or volume scatterers. A fine pixel selection rule is applied to pixels within each canonical scattering mechanism. We filter the PolSAR data and depending on the type of image scene (urban or rural) use either the coarse or fine pixel selection rule. Iterative refinement of the Wishart H/α classification reduces the speckle in the PolSAR data. Effectiveness of this new filter is demonstrated by using both simulated and real PolSAR data. It is compared with the refined Lee filter, the scattering model based filter and the non-local means filter. The study concludes that the proposed filter compares favorably with other polarimetric speckle filters in preserving polarimetric information, point scatterers and subtle features in PolSAR data.

  18. The POKEMON Speckle Survey of Nearby M-Dwarfs (United States)

    van Belle, Gerard; von Braun, Kaspar; Horch, Elliott; Clark, Catherine; DSSI Speckle Team


    The POKEMON (Pervasive Overview of Kompanions of Every M-dwarf in Our Neighborhood) survey of nearby M-dwarfs intends to inspect, at diffraction-limited resolution, every low-mass star out to 15pc, along with selected additional objects to 25pc. The primary emphasis of the survey is detection of low-mass companions to these M-dwarfs for refinement of the low-mass star multiplicity rate. The resultant catalog of M-dwarf companions will also guide immediate refinement of transit planet detection results from surveys such as TESS. POKEMON is using Lowell Observatory's 4.3-m Discovery Channel Telescope (DCT) with the Differential Speckle Survey Instrument (DSSI) speckle camera, along with the NN-Explore Exoplanet Stellar Speckle Imager (NESSI) speckle imager on 3.5-m WIYN; the survey takes advantage of the extremely rapid observing cadence rates possible with WIYN and (especially) DCT. The current status and preliminary results from the first 20+ nights of observing will be presented. Gotta observe them all!

  19. Analysis of Flow and Transport in non-Gaussian Heterogeneous Formations Using a Generalized Sub-Gaussian Model (United States)

    Guadagnini, A.; Riva, M.; Neuman, S. P.


    Environmental quantities such as log hydraulic conductivity (or transmissivity), Y(x) = ln K(x), and their spatial (or temporal) increments, ΔY, are known to be generally non-Gaussian. Documented evidence of such behavior includes symmetry of increment distributions at all separation scales (or lags) between incremental values of Y with sharp peaks and heavy tails that decay asymptotically as lag increases. This statistical scaling occurs in porous as well as fractured media characterized by either one or a hierarchy of spatial correlation scales. In hierarchical media one observes a range of additional statistical ΔY scaling phenomena, all of which are captured comprehensibly by a novel generalized sub-Gaussian (GSG) model. In this model Y forms a mixture Y(x) = U(x) G(x) of single- or multi-scale Gaussian processes G having random variances, U being a non-negative subordinator independent of G. Elsewhere we developed ways to generate unconditional and conditional random realizations of isotropic or anisotropic GSG fields which can be embedded in numerical Monte Carlo flow and transport simulations. Here we present and discuss expressions for probability distribution functions of Y and ΔY as well as their lead statistical moments. We then focus on a simple flow setting of mean uniform steady state flow in an unbounded, two-dimensional domain, exploring ways in which non-Gaussian heterogeneity affects stochastic flow and transport descriptions. Our expressions represent (a) lead order autocovariance and cross-covariance functions of hydraulic head, velocity and advective particle displacement as well as (b) analogues of preasymptotic and asymptotic Fickian dispersion coefficients. We compare them with corresponding expressions developed in the literature for Gaussian Y.

  20. Operation of a quasi-optical gyrotron with a gaussian output coupler

    International Nuclear Information System (INIS)

    Hogge, J.P.; Tran, T.M.; Paris, P.J.; Tran, M.Q.


    The operation of a 92 GHz quasi-optical gyrotron (QOG) having a resonator formed by a spherical mirror and a diffraction grating placed in -1 order Littrow mount is presented. A power of 150 kW with a gaussian output pattern was measured. The gaussian content in the output was 98% with less than 1% of depolarization. By optimizing the magnetic field at fixed frequency, a maximum efficiency of 15% was reached. (author) 12 figs., 2 tabs., 22 refs

  1. Application of the fractional Fourier transformation to digital holography recorded by an elliptical, astigmatic Gaussian beam. (United States)

    Nicolas, F; Coëtmellec, S; Brunel, M; Allano, D; Lebrun, D; Janssen, A J E M


    The authors have studied the diffraction pattern produced by a particle field illuminated by an elliptic and astigmatic Gaussian beam. They demonstrate that the bidimensional fractional Fourier transformation is a mathematically suitable tool to analyse the diffraction pattern generated not only by a collimated plane wave [J. Opt. Soc. Am A 19, 1537 (2002)], but also by an elliptic and astigmatic Gaussian beam when two different fractional orders are considered. Simulations and experimental results are presented.

  2. Non-Gaussian signatures of tachyacoustic cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Bessada, Dennis, E-mail: [UNIFESP — Universidade Federal de São Paulo, Laboratório de Física Teórica e Computação Científica, Rua São Nicolau, 210, 09913-030, Diadema, SP (Brazil)


    I investigate non-Gaussian signatures in the context of tachyacoustic cosmology, that is, a noninflationary model with superluminal speed of sound. I calculate the full non-Gaussian amplitude A, its size f{sub NL}, and corresponding shapes for a red-tilted spectrum of primordial scalar perturbations. Specifically, for cuscuton-like models I show that f{sub NL} ∼ O(1), and the shape of its non-Gaussian amplitude peaks for both equilateral and local configurations, the latter being dominant. These results, albeit similar, are quantitatively distinct from the corresponding ones obtained by Magueijo et al. in the context of superluminal bimetric models.

  3. Gaussian mixture model of heart rate variability.

    Directory of Open Access Journals (Sweden)

    Tommaso Costa

    Full Text Available Heart rate variability (HRV is an important measure of sympathetic and parasympathetic functions of the autonomic nervous system and a key indicator of cardiovascular condition. This paper proposes a novel method to investigate HRV, namely by modelling it as a linear combination of Gaussians. Results show that three Gaussians are enough to describe the stationary statistics of heart variability and to provide a straightforward interpretation of the HRV power spectrum. Comparisons have been made also with synthetic data generated from different physiologically based models showing the plausibility of the Gaussian mixture parameters.

  4. Loop corrections to primordial non-Gaussianity (United States)

    Boran, Sibel; Kahya, E. O.


    We discuss quantum gravitational loop effects to observable quantities such as curvature power spectrum and primordial non-Gaussianity of cosmic microwave background (CMB) radiation. We first review the previously shown case where one gets a time dependence for zeta-zeta correlator due to loop corrections. Then we investigate the effect of loop corrections to primordial non-Gaussianity of CMB. We conclude that, even with a single scalar inflaton, one might get a huge value for non-Gaussianity which would exceed the observed value by at least 30 orders of magnitude. Finally we discuss the consequences of this result for scalar driven inflationary models.

  5. Some continual integrals from gaussian forms

    International Nuclear Information System (INIS)

    Mazmanishvili, A.S.


    The result summary of continual integration of gaussian functional type is given. The summary contains 124 continual integrals which are the mathematical expectation of the corresponding gaussian form by the continuum of random trajectories of four types: real-valued Ornstein-Uhlenbeck process, Wiener process, complex-valued Ornstein-Uhlenbeck process and the stochastic harmonic one. The summary includes both the known continual integrals and the unpublished before integrals. Mathematical results of the continual integration carried in the work may be applied in the problem of the theory of stochastic process, approaching to the finding of mean from gaussian forms by measures generated by the pointed stochastic processes

  6. Multipoint propagators for non-Gaussian initial conditions

    International Nuclear Information System (INIS)

    Bernardeau, Francis; Sefusatti, Emiliano; Crocce, Martin


    We show here how renormalized perturbation theory calculations applied to the quasilinear growth of the large-scale structure can be carried on in presence of primordial non-Gaussian (PNG) initial conditions. It is explicitly demonstrated that the series reordering scheme proposed in Bernardeau, Crocce, and Scoccimarro [Phys. Rev. D 78, 103521 (2008)] is preserved for non-Gaussian initial conditions. This scheme applies to the power spectrum and higher-order spectra and is based on a reorganization of the contributing terms into the sum of products of multipoint propagators. In case of PNG, new contributing terms appear, the importance of which is discussed in the context of current PNG models. The properties of the building blocks of such resummation schemes, the multipoint propagators, are then investigated. It is first remarked that their expressions are left unchanged at one-loop order irrespective of statistical properties of the initial field. We furthermore show that the high-momentum limit of each of these propagators can be explicitly computed even for arbitrary initial conditions. They are found to be damped by an exponential cutoff whose expression is directly related to the moment generating function of the one-dimensional displacement field. This extends what had been established for multipoint propagators for Gaussian initial conditions. Numerical forms of the cutoff are shown for the so-called local model of PNG.

  7. Method for aortic wall strain measurement with three-dimensional ultrasound speckle tracking and fitted finite element analysis. (United States)

    Karatolios, Konstantinos; Wittek, Andreas; Nwe, Thet Htar; Bihari, Peter; Shelke, Amit; Josef, Dennis; Schmitz-Rixen, Thomas; Geks, Josef; Maisch, Bernhard; Blase, Christopher; Moosdorf, Rainer; Vogt, Sebastian


    Aortic wall strains are indicators of biomechanical changes of the aorta due to aging or progressing pathologies such as aortic aneurysm. We investigated the potential of time-resolved three-dimensional ultrasonography coupled with speckle-tracking algorithms and finite element analysis as a novel method for noninvasive in vivo assessment of aortic wall strain. Three-dimensional volume datasets of 6 subjects without cardiovascular risk factors and 2 abdominal aortic aneurysms were acquired with a commercial real time three-dimensional echocardiography system. Longitudinal and circumferential strains were computed offline with high spatial resolution using a customized commercial speckle-tracking software and finite element analysis. Indices for spatial heterogeneity and systolic dyssynchrony were determined for healthy abdominal aortas and abdominal aneurysms. All examined aortic wall segments exhibited considerable heterogenous in-plane strain distributions. Higher spatial resolution of strain imaging resulted in the detection of significantly higher local peak strains (p ≤ 0.01). In comparison with healthy abdominal aortas, aneurysms showed reduced mean strains and increased spatial heterogeneity and more pronounced temporal dyssynchrony as well as delayed systole. Three-dimensional ultrasound speckle tracking enables the analysis of spatially highly resolved strain fields of the aortic wall and offers the potential to detect local aortic wall motion deformations and abnormalities. These data allow the definition of new indices by which the different biomechanical properties of healthy aortas and aortic aneurysms can be characterized. Copyright © 2013 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

  8. Applying laser speckle images to skin science: skin lesion differentiation by polarization (United States)

    Lee, Tim K.; Tchvialeva, Lioudmila; Dhadwal, Gurbir; Sotoodian, Bahman; Kalai, Sunil; Zeng, Haishan; Lui, Harvey; McLean, David I.


    Skin cancer is a worldwide health problem. It is the most common cancer in the countries with a large white population; furthermore, the incidence of malignant melanoma, the most dangerous form of skin cancer, has been increasing steadily over the last three decades. There is an urgent need to develop in-vivo, noninvasive diagnostic tools for the disease. This paper attempts to response to the challenge by introducing a simple and fast method based on polarization and laser speckle. The degree of maintaining polarization estimates the fraction of linearly maintaining polarization in the backscattered speckle field. Clinical experiments of 214 skin lesions including malignant melanomas, squamous cell carcinomas, basal cell carcinomas, nevi, and seborrheic keratoses demonstrated that such a parameter can potentially diagnose different skin lesion types. ROC analyses showed that malignant melanoma and seborrheic keratosis could be differentiated by both the blue and red lasers with the area under the curve (AUC) = 0.8 and 0.7, respectively. Also malignant melanoma and squamous cell carcinoma could be separated by the blue laser (AUC = 0.9), while nevus and seborrheic keratosis could be identified using the red laser (AUC = 0.7). These experiments demonstrated that polarization could be a potential in-vivo diagnostic indicator for skin diseases.

  9. Laser speckle contrast imaging of skin blood perfusion responses induced by laser coagulation

    Energy Technology Data Exchange (ETDEWEB)

    Ogami, M; Kulkarni, R; Wang, H; Reif, R; Wang, R K [University of Washington, Department of Bioengineering, Seattle, Washington 98195 (United States)


    We report application of laser speckle contrast imaging (LSCI), i.e., a fast imaging technique utilising backscattered light to distinguish such moving objects as red blood cells from such stationary objects as surrounding tissue, to localise skin injury. This imaging technique provides detailed information about the acute perfusion response after a blood vessel is occluded. In this study, a mouse ear model is used and pulsed laser coagulation serves as the method of occlusion. We have found that the downstream blood vessels lacked blood flow due to occlusion at the target site immediately after injury. Relative flow changes in nearby collaterals and anastomotic vessels have been approximated based on differences in intensity in the nearby collaterals and anastomoses. We have also estimated the density of the affected downstream vessels. Laser speckle contrast imaging is shown to be used for highresolution and fast-speed imaging for the skin microvasculature. It also allows direct visualisation of the blood perfusion response to injury, which may provide novel insights to the field of cutaneous wound healing. (laser biophotonics)

  10. Quantum Information Protocols with Gaussian States of Light

    DEFF Research Database (Denmark)

    Jacobsen, Christian Scheffmann

    Quantum cryptography is widely regarded as the most mature field within the context of quantum information in the sense that its application and development has produced companies that base their products on genuine quantum mechanical principles. Examples include quantum random number generators...... of Gaussian states. A quantum information protocol is essentially a sequence of state exchanges between some number of parties and a certain ordering of quantum mechanical unitary operators performed by these parties. An example of this is the famous BB84 protocol for secret key generation, where photons...... with Gaussian states is a promising avenue for the development of practical quantum key distribution with a relay network structure in environments where the distances are relatively short and there is a high number of users, such as an urban environment. In addition to this we consider various point...

  11. Speckle reduction using deformable mirrors with diffusers in a laser pico-projector. (United States)

    Chen, Hsuan-An; Pan, Jui-Wen; Yang, Zu-Po


    We propose a design for speckle reduction in a laser pico-projector adopting diffusers and deformable mirrors. This research focuses on speckle noise suppression by changing the angle of divergence of the diffuser. Moreover, the speckle contrast value can be further reduced by the addition of a deformable mirror. The speckle reduction ability obtained using diffusers with different divergence angles is compared. Three types of diffuser designs are compared in the experiments. For Type 1 which uses a circular symmetric diffuser the speckle contrast value can be decreased to 0.0264. For Type 2, the speckle contrast value can be reduced to 0.0267 because of the inclusion of an elliptical distribution diffuser. With Type 3 which includes a combination of the circular distribution diffuser and elliptical distribution diffuser, the speckle contrast value can be reduced to 0.0236. For all three types, the speckle contrast value is lower than 0.05. Under this speckle value, the speckle phenomenon is invisible to the human eye.

  12. Understanding the exposure-time effect on speckle contrast measurements for laser displays (United States)

    Suzuki, Koji; Kubota, Shigeo


    To evaluate the influence of exposure time on speckle noise for laser displays, speckle contrast measurement method was developed observable at a human eye response time using a high-sensitivity camera which has a signal multiplying function. The nonlinearity of camera light sensitivity was calibrated to measure accurate speckle contrasts, and the measuring lower limit noise of speckle contrast was improved by applying spatial-frequency low pass filter to the captured images. Three commercially available laser displays were measured over a wide range of exposure times from tens of milliseconds to several seconds without adjusting the brightness of laser displays. The speckle contrast of raster-scanned mobile projector without any speckle-reduction device was nearly constant over various exposure times. On the contrary to this, in full-frame projection type laser displays equipped with a temporally-averaging speckle-reduction device, some of their speckle contrasts close to the lower limits noise were slightly increased at the shorter exposure time due to the noise. As a result, the exposure-time effect of speckle contrast could not be observed in our measurements, although it is more reasonable to think that the speckle contrasts of laser displays, which are equipped with the temporally-averaging speckle-reduction device, are dependent on the exposure time. This discrepancy may be attributed to the underestimation of temporal averaging factor. We expected that this method is useful for evaluating various laser displays and clarify the relationship between the speckle noise and the exposure time for a further verification of speckle reduction.

  13. Granger Causality and Transfer Entropy Are Equivalent for Gaussian Variables (United States)

    Barnett, Lionel; Barrett, Adam B.; Seth, Anil K.


    Granger causality is a statistical notion of causal influence based on prediction via vector autoregression. Developed originally in the field of econometrics, it has since found application in a broader arena, particularly in neuroscience. More recently transfer entropy, an information-theoretic measure of time-directed information transfer between jointly dependent processes, has gained traction in a similarly wide field. While it has been recognized that the two concepts must be related, the exact relationship has until now not been formally described. Here we show that for Gaussian variables, Granger causality and transfer entropy are entirely equivalent, thus bridging autoregressive and information-theoretic approaches to data-driven causal inference.

  14. Measuring object shape by using in-plane electronic speckle pattern interferometry with divergent illumination

    International Nuclear Information System (INIS)

    Parra-Michel, Jorge; Martínez, Amalia; Rayas, J A; Anguiano-Morales, Marcelino


    Electronic speckle pattern interferometry is a useful technique for displacement, deformation and contouring measurements. Traditionally, for contouring measurements, collimated illumination with a constant sensitivity vector is used, and the surface area analysis is limited to the illuminated area. In some industrial applications, large surfaces require to be analyzed in restricted space conditions. Considering this situation, an optical system with divergent illumination for whole-field measurements can be used. It is known that displacement fields and the optical phase are related by the sensitivity vector. Therefore, to compute the sensitivity vector, illumination position and superficial shape need to be considered, a condition that becomes an impediment for surface contouring if the superficial shape is unknown. In this work, a simple iterative algorithm based on the Gauss–Seidel technique is presented to compute contouring measurements. Contouring measurements from both ESPI and a coordinate-measuring machine (CMM) are compared. In addition, a measurement comparison considering supposed collimated and divergent illumination is presented

  15. A non-Gaussian multivariate distribution with all lower-dimensional Gaussians and related families

    KAUST Repository

    Dutta, Subhajit


    Several fascinating examples of non-Gaussian bivariate distributions which have marginal distribution functions to be Gaussian have been proposed in the literature. These examples often clarify several properties associated with the normal distribution. In this paper, we generalize this result in the sense that we construct a pp-dimensional distribution for which any proper subset of its components has the Gaussian distribution. However, the jointpp-dimensional distribution is inconsistent with the distribution of these subsets because it is not Gaussian. We study the probabilistic properties of this non-Gaussian multivariate distribution in detail. Interestingly, several popular tests of multivariate normality fail to identify this pp-dimensional distribution as non-Gaussian. We further extend our construction to a class of elliptically contoured distributions as well as skewed distributions arising from selections, for instance the multivariate skew-normal distribution.

  16. Permutation entropy based speckle analysis in metal cutting (United States)

    Nair, Usha; Krishna, Bindu M.; Namboothiri, V. N. N.; Nampoori, V. P. N.


    Machine tool chatter is an unfavorable phenomenon during metal cutting, which results in heavy vibration of cutting tool. With increase in depth of cut the cutting regime changes from chatter- free cutting to one with chatter. In this paper, we propose the use of permutation entropy (PE), a conceptually simple and computationally fast measure to detect the onset of chatter from the time series generated using laser speckle pattern recorded using Charge Couple Device (CCD) camera. Laser speckle is an interference pattern produced by light reflected or scattered from different parts of the illuminated surface. It is the superposition of many wave fronts with random phases, scattered from different parts of the rough surface. If a speckle pattern is produced by coherent light incident on a rough surface, then surely the speckle pattern, or at least the statistics of the speckle pattern, must depend upon the detailed surface properties. Therefore we propose PE as an ideal measure, which can efficiently distinguish regular and complex nature of any signal, to extract information about the roughness of the reflecting surface. In the present study two work pieces, one taper cut and one step cut are machined to form cylindrical pieces, by continuously varying the depth of cut. As the depth of cut increases the surface finish is expected to deteriorate, mainly due to the onset of chatter vibrations. To analyze the surface texture characteristics, the speckle pattern is obtained by illuminating this curved surface using a collimated laser beam (5mW Diode Laser at 676nm wavelength.). The laser beam is made to incident obliquely to the curved surface of the work piece, and the speckle pattern is recorded using a CCD camera. The beam is scanned along the axis of the work-piece and the speckle pattern is recorded at different regions at constant intervals. A time series is generated from the speckle data and analyzed using PE. Permutation entropy is a complexity measure suitable

  17. Bipartite and Multipartite Entanglement of Gaussian States (United States)

    Adesso, Gerardo; Illuminati, Fabrizio

    In this chapter we review the characterization of entanglement in Gaussian states of continuous variable systems. For two-mode Gaussian states, we discuss how their bipartite entanglement can be accurately quantified in terms of the global and local amounts of mixedness, and efficiently estimated by direct measurements of the associated purities. For multimode Gaussian states endowed with local symmetry with respect to a given bipartition, we show how the multimode block entanglement can be completely and reversibly localized onto a single pair of modes by local, unitary operations. We then analyze the distribution of entanglement among multiple parties in multimode Gaussian states. We introduce the continuous-variable tangle to quantify entanglement sharing in Gaussian states and we prove that it satisfies the Coffman-Kundu-Wootters monogamy inequality. Nevertheless, we show that pure, symmetric three-mode Gaussian states, at variance with their discrete-variable counterparts, allow a promiscuous sharing of quantum correlations, exhibiting both maximum tripartite residual entanglement and maximum couplewise entanglement between any pair of modes. Finally, we investigate the connection between multipartite entanglement and the optimal fidelity in a continuous-variable quantum teleportation network. We show how the fidelity can be maximized in terms of the best preparation of the shared entangled resources and, viceversa, that this optimal fidelity provides a clearcut operational interpretation of several measures of bipartite and multipartite entanglement, including the entanglement of formation, the localizable entanglement, and the continuous-variable tangle.

  18. Non-Gaussian halo assembly bias

    International Nuclear Information System (INIS)

    Reid, Beth A.; Verde, Licia; Dolag, Klaus; Matarrese, Sabino; Moscardini, Lauro


    The strong dependence of the large-scale dark matter halo bias on the (local) non-Gaussianity parameter, f NL , offers a promising avenue towards constraining primordial non-Gaussianity with large-scale structure surveys. In this paper, we present the first detection of the dependence of the non-Gaussian halo bias on halo formation history using N-body simulations. We also present an analytic derivation of the expected signal based on the extended Press-Schechter formalism. In excellent agreement with our analytic prediction, we find that the halo formation history-dependent contribution to the non-Gaussian halo bias (which we call non-Gaussian halo assembly bias) can be factorized in a form approximately independent of redshift and halo mass. The correction to the non-Gaussian halo bias due to the halo formation history can be as large as 100%, with a suppression of the signal for recently formed halos and enhancement for old halos. This could in principle be a problem for realistic galaxy surveys if observational selection effects were to pick galaxies occupying only recently formed halos. Current semi-analytic galaxy formation models, for example, imply an enhancement in the expected signal of ∼ 23% and ∼ 48% for galaxies at z = 1 selected by stellar mass and star formation rate, respectively

  19. Impact of transducer frequency setting on speckle tracking measures. (United States)

    Olsen, Flemming Javier; Svendsen, Jesper Hastrup; Køber, Lars; Højberg, Søren; Haugan, Ketil; Jensen, Jan Skov; Biering-Sørensen, Tor


    Speckle tracking echocardiography is an emerging technique, which is currently being included in clinical guidelines. We sought to investigate the impact of transducer frequency settings on speckle tracking derived measures. The study comprised of 22 subjects prospectively enrolled for a randomized controlled trial (LOOP-study, Patients were above 70 years of age with increased risk of stroke, and had an echocardiogram performed, which included focused images of the left ventricle. Focused images were obtained with the transducer frequency set at both 1.7/3.3 and 1.5/3.0 MHz. The images were obtained immediately after each other at the exact same position for the two settings. Speckle tracking was performed in three apical projections, allowing for acquisition of layered global longitudinal strain (GLS) and strain rate measures. Concordance between the frequency settings was tested for endo-, mid-, and epicardial GLS and strain rates by coefficients of variation, bias coefficients and visually displayed by Bland-Altman plots. Bland-Altman plots did not reveal any significant over- or underestimation of any speckle tracking measure. Bias coefficients showed that none of the measurements differed significantly between the two settings (bias for GLS endo  = - 0.07 ± 2.94, p = 0.91; GLS mid  = 0.02 ± 2.70, p = 0.98, GLS epi  = 0.07 ± 2.53, p = 0.90). Coefficients of variation were as follows: GLS endo  = 15.11%, GLS mid  = 15.28%, GLS epi  = 17.26%, systolic strain rate = 15.66%, early diastolic strain rate = 38.46%, late diastolic strain rate = 11%. Changing between transducer frequency settings does not systematically derange speckle tracking measures. One can safely reduce the transducer frequency without compromising the validity of speckle tracking derived measures.

  20. Molecular integrals evaluated over contracted Gaussian functions by using auxiliary contracted hyper-Gaussian functions (United States)

    Honda, Hiroaki; Yamaki, Takayoshi; Obara, Shigeru


    General recurrence formulas for evaluating molecular integrals over contracted Cartesian Gaussian functions are derived by introducing auxiliary contracted hyper-Gaussian (ACH) functions. By using a contracted Gaussian function, this ACH represents an extension of the Gaussian function named derivative of Fourier-kernel multiplied Gaussian [J. Chem. Phys. 94, 3790 (1991)]. The ACH is reducible to contracted Cartesian Gaussian functions, contracted modified Hermite Gaussian functions, and to contracted Gaussian functions multiplied by phase factors, or the so-called GIAO, and is also reducible to various spatial operators necessary for ab initio molecular orbital calculations. In our formulation, all molecular integrals are expressed in terms of ACH. Therefore, the formulations have wide applicability for calculating various kinds of molecular integrals in ab initio calculations. Recursive calculations based on our formulation do not depend on the number of contraction terms, because the contraction step is completed at the evaluation of the initial integrals. Therefore, we expect that more efficient recursive calculations will be accomplished by using our formulas for evaluating molecular integrals over contracted Gaussian functions.

  1. Adaptive Laguerre-Gaussian variant of the Gaussian beam expansion method. (United States)

    Cagniot, Emmanuel; Fromager, Michael; Ait-Ameur, Kamel


    A variant of the Gaussian beam expansion method consists in expanding the Bessel function J0 appearing in the Fresnel-Kirchhoff integral into a finite sum of complex Gaussian functions to derive an analytical expression for a Laguerre-Gaussian beam diffracted through a hard-edge aperture. However, the validity range of the approximation depends on the number of expansion coefficients that are obtained by optimization-computation directly. We propose another solution consisting in expanding J0 onto a set of collimated Laguerre-Gaussian functions whose waist depends on their number and then, depending on its argument, predicting the suitable number of expansion functions to calculate the integral recursively.

  2. Non-Gaussian isocurvature perturbations from Goldstone modes generated during inflation

    International Nuclear Information System (INIS)

    Bucher, M.; Zhu, Y.


    We investigate non-Gaussian isocurvature perturbations generated by the evolution of Goldstone modes during inflation. If a global symmetry is broken before inflation, the resulting Goldstone modes are disordered during inflation in a precise and predictable way. After inflation these Goldstone modes order themselves in a self-similar way, much as Goldstone modes in field ordering scenarios based on the Kibble mechanism. For (H inf 2 /M Pl 2 )∼10 -6 , through their gravitational interaction these Goldstone modes generate density perturbations of approximately the right magnitude to explain the cosmic microwave background (CMB) anisotropy and seed the structure seen in the universe today. We point out that for the pattern of symmetry breaking in which a global U(1) is completely broken, the inflationary evolution of the Goldstone field may be treated as that of a massless scalar field. Unlike the more commonly discussed case in which a global U(1) is completely broken in a cosmological phase transition, in the inflationary case the production of defects can be made exponentially small, so that Goldstone field evolution is completely linear. In such a model non-Gaussian perturbations result because to lowest order density perturbations are sourced by products of Gaussian fields. Consequently, in this non-Gaussian model N-point correlations may be calculated by evaluating Feynman diagrams. We explore the issue of phase dispersion and conclude that this non-Gaussian model predicts Doppler peaks in the CMB anisotropy. copyright 1997 The American Physical Society

  3. Speckle-modulating optical coherence tomography in living mice and humans (United States)

    Liba, Orly; Lew, Matthew D.; Sorelle, Elliott D.; Dutta, Rebecca; Sen, Debasish; Moshfeghi, Darius M.; Chu, Steven; de La Zerda, Adam


    Optical coherence tomography (OCT) is a powerful biomedical imaging technology that relies on the coherent detection of backscattered light to image tissue morphology in vivo. As a consequence, OCT is susceptible to coherent noise (speckle noise), which imposes significant limitations on its diagnostic capabilities. Here we show speckle-modulating OCT (SM-OCT), a method based purely on light manipulation that virtually eliminates speckle noise originating from a sample. SM-OCT accomplishes this by creating and averaging an unlimited number of scans with uncorrelated speckle patterns without compromising spatial resolution. Using SM-OCT, we reveal small structures in the tissues of living animals, such as the inner stromal structure of a live mouse cornea, the fine structures inside the mouse pinna, and sweat ducts and Meissner's corpuscle in the human fingertip skin--features that are otherwise obscured by speckle noise when using conventional OCT or OCT with current state of the art speckle reduction methods.

  4. A novel method for repeatedly generating speckle patterns used in digital image correlation (United States)

    Zhang, Juan; Sweedy, Ahmed; Gitzhofer, François; Baroud, Gamal


    Speckle patterns play a key role in Digital Image Correlation (DIC) measurement, and generating an optimal speckle pattern has been the goal for decades now. The usual method of generating a speckle pattern is by manually spraying the paint on the specimen. However, this makes it difficult to reproduce the optimal pattern for maintaining identical testing conditions and achieving consistent DIC results. This study proposed and evaluated a novel method using an atomization system to repeatedly generate speckle patterns. To verify the repeatability of the speckle patterns generated by this system, simulation and experimental studies were systematically performed. The results from both studies showed that the speckle patterns and, accordingly, the DIC measurements become highly accurate and repeatable using the proposed atomization system.

  5. Spiking cortical model-based nonlocal means method for speckle reduction in optical coherence tomography images (United States)

    Zhang, Xuming; Li, Liu; Zhu, Fei; Hou, Wenguang; Chen, Xinjian


    Optical coherence tomography (OCT) images are usually degraded by significant speckle noise, which will strongly hamper their quantitative analysis. However, speckle noise reduction in OCT images is particularly challenging because of the difficulty in differentiating between noise and the information components of the speckle pattern. To address this problem, the spiking cortical model (SCM)-based nonlocal means method is presented. The proposed method explores self-similarities of OCT images based on rotation-invariant features of image patches extracted by SCM and then restores the speckled images by averaging the similar patches. This method can provide sufficient speckle reduction while preserving image details very well due to its effectiveness in finding reliable similar patches under high speckle noise contamination. When applied to the retinal OCT image, this method provides signal-to-noise ratio improvements of >16 dB with a small 5.4% loss of similarity.

  6. An approximate fractional Gaussian noise model with computational cost

    KAUST Repository

    Sørbye, Sigrunn H.


    Fractional Gaussian noise (fGn) is a stationary time series model with long memory properties applied in various fields like econometrics, hydrology and climatology. The computational cost in fitting an fGn model of length $n$ using a likelihood-based approach is ${\\\\mathcal O}(n^{2})$, exploiting the Toeplitz structure of the covariance matrix. In most realistic cases, we do not observe the fGn process directly but only through indirect Gaussian observations, so the Toeplitz structure is easily lost and the computational cost increases to ${\\\\mathcal O}(n^{3})$. This paper presents an approximate fGn model of ${\\\\mathcal O}(n)$ computational cost, both with direct or indirect Gaussian observations, with or without conditioning. This is achieved by approximating fGn with a weighted sum of independent first-order autoregressive processes, fitting the parameters of the approximation to match the autocorrelation function of the fGn model. The resulting approximation is stationary despite being Markov and gives a remarkably accurate fit using only four components. The performance of the approximate fGn model is demonstrated in simulations and two real data examples.

  7. Generation of correlated finite alphabet waveforms using gaussian random variables

    KAUST Repository

    Jardak, Seifallah


    Correlated waveforms have a number of applications in different fields, such as radar and communication. It is very easy to generate correlated waveforms using infinite alphabets, but for some of the applications, it is very challenging to use them in practice. Moreover, to generate infinite alphabet constant envelope correlated waveforms, the available research uses iterative algorithms, which are computationally very expensive. In this work, we propose simple novel methods to generate correlated waveforms using finite alphabet constant and non-constant-envelope symbols. To generate finite alphabet waveforms, the proposed method map the Gaussian random variables onto the phase-shift-keying, pulse-amplitude, and quadrature-amplitude modulation schemes. For such mapping, the probability-density-function of Gaussian random variables is divided into M regions, where M is the number of alphabets in the corresponding modulation scheme. By exploiting the mapping function, the relationship between the cross-correlation of Gaussian and finite alphabet symbols is derived. To generate equiprobable symbols, the area of each region is kept same. If the requirement is to have each symbol with its own unique probability, the proposed scheme allows us that as well. Although, the proposed scheme is general, the main focus of this paper is to generate finite alphabet waveforms for multiple-input multiple-output radar, where correlated waveforms are used to achieve desired beampatterns. © 2014 IEEE.

  8. Analysis of error functions in speckle shearing interferometry

    International Nuclear Information System (INIS)

    Wan Saffiey Wan Abdullah


    Electronic Speckle Pattern Shearing Interferometry (ESPSI) or shearography has successfully been used in NDT for slope (∂w/ (∂x and / or (∂w/ (∂y) measurement while strain measurement (∂u/ ∂x, ∂v/ ∂y, ∂u/ ∂y and (∂v/ (∂x) is still under investigation. This method is well accepted in industrial applications especially in the aerospace industry. Demand of this method is increasing due to complexity of the test materials and objects. ESPSI has successfully performed in NDT only for qualitative measurement whilst quantitative measurement is the current aim of many manufacturers. Industrial use of such equipment is being completed without considering the errors arising from numerous sources, including wavefront divergence. The majority of commercial systems are operated with diverging object illumination wave fronts without considering the curvature of the object illumination wavefront or the object geometry, when calculating the interferometer fringe function and quantifying data. This thesis reports the novel approach in quantified maximum phase change difference analysis for derivative out-of-plane (OOP) and in-plane (IP) cases that propagate from the divergent illumination wavefront compared to collimated illumination. The theoretical of maximum phase difference is formulated by means of three dependent variables, these being the object distance, illuminated diameter, center of illuminated area and camera distance and illumination angle. The relative maximum phase change difference that may contributed to the error in the measurement analysis in this scope of research is defined by the difference of maximum phase difference value measured by divergent illumination wavefront relative to the maximum phase difference value of collimated illumination wavefront, taken at the edge of illuminated area. Experimental validation using test objects for derivative out-of-plane and derivative in-plane deformation, using a single illumination wavefront

  9. Sensitivity evaluation of dynamic speckle activity measurements using clustering methods

    International Nuclear Information System (INIS)

    Etchepareborda, Pablo; Federico, Alejandro; Kaufmann, Guillermo H.


    We evaluate and compare the use of competitive neural networks, self-organizing maps, the expectation-maximization algorithm, K-means, and fuzzy C-means techniques as partitional clustering methods, when the sensitivity of the activity measurement of dynamic speckle images needs to be improved. The temporal history of the acquired intensity generated by each pixel is analyzed in a wavelet decomposition framework, and it is shown that the mean energy of its corresponding wavelet coefficients provides a suited feature space for clustering purposes. The sensitivity obtained by using the evaluated clustering techniques is also compared with the well-known methods of Konishi-Fujii, weighted generalized differences, and wavelet entropy. The performance of the partitional clustering approach is evaluated using simulated dynamic speckle patterns and also experimental data.

  10. Optical design of the comet Shoemaker-Levy speckle camera

    Energy Technology Data Exchange (ETDEWEB)

    Bissinger, H. [Lawrence Livermore National Lab., CA (United States)


    An optical design is presented in which the Lick 3 meter telescope and a bare CCD speckle camera system was used to image the collision sites of the Shoemaker-Levy 9 comet with the Planet Jupiter. The brief overview includes of the optical constraints and system layout. The choice of a Risley prism combination to compensate for the time dependent atmospheric chromatic changes are described. Plate scale and signal-to-noise ratio curves resulting from imaging reference stars are compared with theory. Comparisons between un-corrected and reconstructed images of Jupiter`s impact sites. The results confirm that speckle imaging techniques can be used over an extended time period to provide a method to image large extended objects.

  11. Dynamic speckle image segmentation using self-organizing maps (United States)

    Pra, Ana L. Dai; Meschino, Gustavo J.; Guzmán, Marcelo N.; Scandurra, Adriana G.; González, Mariela A.; Weber, Christian; Trivi, Marcelo; Rabal, Héctor; Passoni, Lucía I.


    The aim of this work is to build a computational model able to automatically identify, after training, dynamic speckle pattern regions with similar properties. The process is carried out using a set of descriptors applied to the intensity variations with time in every pixel of a speckle image sequence. An image obtained by projecting a self-organized map is converted into regions of similar activity that can be easily distinguished. We propose a general procedure that could be applied to numerous situations. As examples we show different situations: (a) an activity test in a simplified situation; (b) a non-biological example and (c) biological active specimens. The results obtained are encouraging; they significantly improve upon those obtained using a single descriptor and will eventually permit automatic quantitative assessment.

  12. Separated Component-Based Restoration of Speckled SAR Images (United States)


    TYPE New Reprint 17. LIMITATION OF ABSTRACT UU 15. NUMBER OF PAGES 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 5c. PROGRAM ELEMENT...radar. I. INTRODUCTION COHERENT imaging systems such as synthetic aper -ture radar (SAR), holography, ultrasound, and synthetic aperture sonar suffer...noise variance by a factor of L. However, this often results in the reduction of the spatial resolution. Other types of speckle reduction methods are

  13. Speckle imaging with the PAPA detector. [Precision Analog Photon Address (United States)

    Papaliolios, C.; Nisenson, P.; Ebstein, S.


    A new 2-D photon-counting camera, the PAPA (precision analog photon address) detector has been built, tested, and used successfully for the acquisition of speckle imaging data. The camera has 512 x 512 pixels and operates at count rates of at least 200,000/sec. In this paper, technical details on the camera are presented and some of the laboratory and astronomical results are included which demonstrate the detector's capabilities.

  14. Analysis of the speckle properties in a laser projection system based on a human eye model. (United States)

    Cui, Zhe; Wang, Anting; Ma, Qianli; Ming, Hai


    In this paper, the properties of the speckle that is observed by humans in laser projection systems are theoretically analyzed. The speckle pattern on the fovea of the human retina is numerically simulated by introducing a chromatic human eye model. The results show that the speckle contrast experienced by humans is affected by the light intensity of the projected images and the wavelength of the laser source when considering the paracentral vision. Furthermore, the image quality is also affected by these two parameters. We believe that these results are useful for evaluating the speckle noise in laser projection systems.

  15. Speckle-free digital holographic recording of a diffusely reflecting object. (United States)

    Kim, You Seok; Kim, Taegeun; Woo, Sung Soo; Kang, Hoonjong; Poon, Ting-Chung; Zhou, Changhe


    We demonstrate holographic recording without speckle noise using the digital holographic technique called optical scanning holography (OSH). First, we record a complex hologram of a diffusely reflecting (DR) object using OSH. The incoherent mode of OSH makes it possible to record the complex hologram without speckle noise. Second, we convert the complex hologram to an off-axis real hologram digitally and finally we reconstruct the real hologram using an amplitude-only spatial light modulator (SLM) without twin-image noise and speckle noise. To the best of our knowledge, this is the first time demonstrating digital holographic recording of a DR object without speckle noise.

  16. Setup for studying speckle noise of spectroradiometer diffusers in Earth observation applications (United States)

    Vaskuri, Anna; Greenwell, Claire; Woolliams, Emma


    Diffusers in in-orbit spectroradiometers cause speckle under partially coherent solar radiation. A speckle pattern entering a spectroradiometer through a small slit creates systematic spectral deviations in measured spectra. We have developed a setup to characterise the spatial speckle of diffusers and the related spectral features. The decorrelation angles measured at 532 nm for Spectralon, Diffusil, and Heraeus diffusers were 0.021°, 0.014°, and 0.005° respectively. This information can be used for compensating speckle-related spectral features from the radiometric satellite measurements by averaging over multiple decorrelated spectra.

  17. Speckle reduction of reconstructions of digital holograms using three dimensional filtering (United States)

    Maycock, Jonathan; McDonald, John B.; Hennelly, Bryan M.


    We report on a new digital signal processing technique that reduces speckle in reconstructions of digital holograms. This is achieved by convolving the three dimensional intensity pattern (the intensity of the propagated DH at a series of different distances) with a 3D point spread function in all three dimensions (x,y,z). It is based on the fact that the addition of different independent speckle images on an intensity basis reduces the speckle content. We provide quantitative results in terms of speckle index and resolution, and show that filtering in the z direction has the added benefit of an increase in the depth of focus of the digital hologram reconstruction.

  18. The hatching results of indigenous Hungarian speckled hens

    Directory of Open Access Journals (Sweden)

    Ákos Benk


    Full Text Available In the pilot farm of Szeged University Faculty of Agriculture we keep two varieties of the Hungarian speckled hen, the feathered-neck variant and the naked-neck type since 1977. The three colour variations of the domestic hen species were bred from the Hungarian lea-land bird by the middle of the 20th Century. Because of the spread of intensive poultry keeping the population of this species has become endangered. Programs supporting ecological-biological farming that began in the last two decades placed the domestically bred birds in the forefront both as purebreds and as candidates in projects for developing merchandisable bio-poultry. Beside the gene preservation, we endeavor to find the best way for the production-purpose utilisation of the speckled hen stock. On the basis of our experiments the laying hens can be used in small scale egg production. We examined the hatching results of both type of speckled hens, during more than 20 generations.

  19. Impact of transducer frequency setting on speckle tracking measures

    DEFF Research Database (Denmark)

    Olsen, Flemming Javier; Svendsen, Jesper Hastrup; Køber, Lars


    Speckle tracking echocardiography is an emerging technique, which is currently being included in clinical guidelines. We sought to investigate the impact of transducer frequency settings on speckle tracking derived measures. The study comprised of 22 subjects prospectively enrolled for a randomized.......5/3.0 MHz. The images were obtained immediately after each other at the exact same position for the two settings. Speckle tracking was performed in three apical projections, allowing for acquisition of layered global longitudinal strain (GLS) and strain rate measures. Concordance between the frequency...... that none of the measurements differed significantly between the two settings (bias for GLSendo = - 0.07 ± 2.94, p = 0.91; GLSmid = 0.02 ± 2.70, p = 0.98, GLSepi = 0.07 ± 2.53, p = 0.90). Coefficients of variation were as follows: GLSendo = 15.11%, GLSmid = 15.28%, GLSepi = 17.26%, systolic strain rate = 15...

  20. Gold-Speckled Multimodal Nanoparticles for Noninvasive Bioimaging (United States)


    In this report the synthesis, characterization, and functional evaluation of a multimodal nanoparticulate contrast agent for noninvasive imaging through both magnetic resonance imaging (MRI) and photoacoustic tomography (PAT) is presented. The nanoparticles described herein enable high resolution and highly sensitive three-dimensional diagnostic imaging through the synergistic coupling of MRI and PAT capabilities. Gadolinium (Gd)-doped gold-speckled silica (GSS) nanoparticles, ranging from 50 to 200 nm, have been prepared in a simple one-pot synthesis using nonionic microemulsions. The photoacoustic signal is generated from a nonuniform, discontinuous gold nanodomains speckled across the silica surface, whereas the MR contrast is provided through Gd incorporated in the silica matrix. The presence of a discontinuous speckled surface, as opposed to a continuous gold shell, allows sufficient bulk water exchange with the Gd ions to generate a strong MR contrast. The dual imaging capabilities of the particles have been demonstrated through in silicio and in vitro methods. The described particles also have the capacity for therapeutic applications including the thermal ablation of tumors through the absorption of irradiated light. PMID:19466201

  1. Twinkle Twinkle Little Star - Speckle Imaging for Exoplanet Characterization (United States)

    Howell, Steve B.; Scott, Nic; Horch, Elliott


    The NASA K2 mission is finding many high-value exoplanets and world-wide follow-up is ensuing. The NASA TESS mission will soon be launched, requiring additional ground-based observations as well. As a part of the NASA-NSFNN-EXPLORE program to enable exoplanet research, our group is building two new speckle interferometry cameras for the Kitt Peak WIYN 3.5-m telescope and the Gemini-N 8-m telescope. Modeled after the successful DSSI visitor instrument that has been used at these telescopes for many years, speckle observations provide the highest resolution images available today from any ground- or space-based single telescope. They are the premier method through which small, rocky exoplanets can be validated. Available for public use in early 2017, WIYNSPKL and GEMSPKL will obtain simultaneous images in two filters with fast EMCCD readout, "speckle" and “wide-field” imaging modes, and user support for proposal writing, observing, and data reduction. We describe the new cameras, their design, and their benefits for exoplanet follow-up, characterization, and validation. Funding for this project comes from the NASA Exoplanet Exploration Program and NASA HQ.

  2. Speckle imaging with the SOAR and the very large telescopes (United States)

    Rengaswamy, Sridharan; Girard, Julien H.; Montagnier, Guillaume


    Astronomical speckle imaging is a well established technique for obtaining diffraction limited images of binary and multiple stars, low contrast solar features and nearby extended objects such as comets and solar system planets, with large ground-based telescopes. We have developed a speckle masking code to reconstruct images of such objects from the corresponding specklegrams. This code uses speckle interferometry for estimating the Fourier amplitudes and bispectrum for estimating the Fourier phases. In this paper, we discuss a few technical issues such as: What is the photometric and astrometric accuracy that can be achieved with this code? What is the closest separation between the components of a binary star that can be clearly resolved with sufficient signal to noise ratio with this code? What is the maximum dynamic range? What kind of calibration schemes can be used in the absence of a bright calibrator close to the object of interest? We address these questions based on computer simulations. We present a few sample reconstructions from the real data obtained from the SOAR telescope. We also present the details of a technical feasibility study carried out with NACO-cube mode at the VLT.

  3. Semiparametric inference on the fractal index of Gaussian and conditionally Gaussian time series data

    DEFF Research Database (Denmark)

    Bennedsen, Mikkel

    Using theory on (conditionally) Gaussian processes with stationary increments developed in Barndorff-Nielsen et al. (2009, 2011), this paper presents a general semiparametric approach to conducting inference on the fractal index, α, of a time series. Our setup encompasses a large class of Gaussian...

  4. The transition of a Gaussian chain end-grafted at a penetrable surface

    NARCIS (Netherlands)

    Skvortsov, A.M.; Klusken, L.I.; Male, van J.; Leermakers, F.A.M.


    A Gaussian chain at a liquid–liquid interface is considered. The solvents are represented by an external potential field u that has a constant value in one half-space and is zero elsewhere. One end of the chain is fixed at the boundary where the external potential field changes its value. For this

  5. EDITORIAL: Non-linear and non-Gaussian cosmological perturbations Non-linear and non-Gaussian cosmological perturbations (United States)

    Sasaki, Misao; Wands, David


    In recent years there has been a resurgence of interest in the study of non-linear perturbations of cosmological models. This has been the result of both theoretical developments and observational advances. New theoretical challenges arise at second and higher order due to mode coupling and the need to develop new gauge-invariant variables beyond first order. In particular, non-linear interactions lead to deviations from a Gaussian distribution of primordial perturbations even if initial vacuum fluctuations are exactly Gaussian. These non-Gaussianities provide an important probe of models for the origin of structure in the very early universe. We now have a detailed picture of the primordial distribution of matter from surveys of the cosmic microwave background, notably NASA's WMAP satellite. The situation will continue to improve with future data from the ESA Planck satellite launched in 2009. To fully exploit these data cosmologists need to extend non-linear cosmological perturbation theory beyond the linear theory that has previously been sufficient on cosmological scales. Another recent development has been the realization that large-scale structure, revealed in high-redshift galaxy surveys, could also be sensitive to non-linearities in the primordial curvature perturbation. This focus section brings together a collection of invited papers which explore several topical issues in this subject. We hope it will be of interest to theoretical physicists and astrophysicists alike interested in understanding and interpreting recent developments in cosmological perturbation theory and models of the early universe. Of course it is only an incomplete snapshot of a rapidly developing field and we hope the reader will be inspired to read further work on the subject and, perhaps, fill in some of the missing pieces. This focus section is dedicated to the memory of Lev Kofman (1957-2009), an enthusiastic pioneer of inflationary cosmology and non-Gaussian perturbations.

  6. Approximate reversal of quantum Gaussian dynamics (United States)

    Lami, Ludovico; Das, Siddhartha; Wilde, Mark M.


    Recently, there has been focus on determining the conditions under which the data processing inequality for quantum relative entropy is satisfied with approximate equality. The solution of the exact equality case is due to Petz, who showed that the quantum relative entropy between two quantum states stays the same after the action of a quantum channel if and only if there is a reversal channel that recovers the original states after the channel acts. Furthermore, this reversal channel can be constructed explicitly and is now called the Petz recovery map. Recent developments have shown that a variation of the Petz recovery map works well for recovery in the case of approximate equality of the data processing inequality. Our main contribution here is a proof that bosonic Gaussian states and channels possess a particular closure property, namely, that the Petz recovery map associated to a bosonic Gaussian state σ and a bosonic Gaussian channel N is itself a bosonic Gaussian channel. We furthermore give an explicit construction of the Petz recovery map in this case, in terms of the mean vector and covariance matrix of the state σ and the Gaussian specification of the channel N .

  7. Coherence and polarization speckle generated by a rough-surfaced retardation plate depolarizer

    DEFF Research Database (Denmark)

    Ma, Ning; Hanson, Steen Grüner; Takeda, Mitsuo


    of position introducing random phase differences between the two orthogonal components of the electric vector. Under the assumption of Gaussian statistics with zero mean, the surface model for the depolarizer of the rough-surfaced retardation plate is obtained. The propagation of the modulated fields through...... any quadratic optical system is examined within the framework of the complex ABCD matrix theory to show how the degree of coherence and polarization of the beam changes on propagation, including propagation in free space...

  8. Three-Dimensional Dynamic Deformation Measurements Using Stereoscopic Imaging and Digital Speckle Photography

    International Nuclear Information System (INIS)

    Prentice, H. J.; Proud, W. G.


    A technique has been developed to determine experimentally the three-dimensional displacement field on the rear surface of a dynamically deforming plate. The technique combines speckle analysis with stereoscopy, using a modified angular-lens method: this incorporates split-frame photography and a simple method by which the effective lens separation can be adjusted and calibrated in situ. Whilst several analytical models exist to predict deformation in extended or semi-infinite targets, the non-trivial nature of the wave interactions complicates the generation and development of analytical models for targets of finite depth. By interrogating specimens experimentally to acquire three-dimensional strain data points, both analytical and numerical model predictions can be verified more rigorously. The technique is applied to the quasi-static deformation of a rubber sheet and dynamically to Mild Steel sheets of various thicknesses

  9. Strain rate measurement by Electronic Speckle Pattern Interferometry: A new look at the strain localization onset

    Energy Technology Data Exchange (ETDEWEB)

    Guelorget, Bruno [Universite de Technologie de Troyes (UTT), Laboratoire des Systemes Mecaniques et d' ingenierie Simultanee (LASMIS, CNRS FRE 2719), 12 rue Marie Curie, B.P. 2060, 10010 Troyes Cedex (France)]. E-mail:; Francois, Manuel [Universite de Technologie de Troyes (UTT), Laboratoire des Systemes Mecaniques et d' ingenierie Simultanee (LASMIS, CNRS FRE 2719), 12 rue Marie Curie, B.P. 2060, 10010 Troyes Cedex (France); Vial-Edwards, Cristian [Departemento de Ingenieria Mecanica y Metalurgica, Pontificia Universidad Catolica de Chile, Vicuna Mackenna 4860, 6904411 Santiago (Chile); Montay, Guillaume [Universite de Technologie de Troyes (UTT), Laboratoire des Systemes Mecaniques et d' ingenierie Simultanee (LASMIS, CNRS FRE 2719), 12 rue Marie Curie, B.P. 2060, 10010 Troyes Cedex (France); Daniel, Laurent [Universite de Technologie de Troyes (UTT), Laboratoire des Systemes Mecaniques et d' ingenierie Simultanee (LASMIS, CNRS FRE 2719), 12 rue Marie Curie, B.P. 2060, 10010 Troyes Cedex (France); Lu, Jian [Universite de Technologie de Troyes (UTT), Laboratoire des Systemes Mecaniques et d' ingenierie Simultanee (LASMIS, CNRS FRE 2719), 12 rue Marie Curie, B.P. 2060, 10010 Troyes Cedex (France)


    In-plane Electronic Speckle Pattern Interferometry has been successfully used during tensile testing of semi-hard copper sheets in order to measure the strain rate. On one hand, heterogeneity in strain rate field has been found before the maximum of the tensile force ({epsilon} {sup t} {approx_equal} 19.4 and 25.4%, respectively). Thus, a localization phenomenon occurs before the classic Considere's criterion (dF = 0) for the diffuse neck initiation. On the other hand, strain rate measurement before fracture shows the moment where one of the two slip band systems becomes predominant, then strain concentrates in a small area, the shear band. Uncertainty evaluation has been carried out, which shows a very good accuracy of the total strain and the strain rate measurements.

  10. Measurement of simple shear strain with a uniaxial speckle strain meter; Laser speckle yugamikei wo mochiita sendan yugami no keisoku

    Energy Technology Data Exchange (ETDEWEB)

    Muto, H.; Sakai, M. [Toyohashi University of Technology, Aichi (Japan)


    Elastic and viscoelastic shear strains induced in test specimens with double-shear geometry are measured by extending the conventional uniaxial speckle extensometry. The test results for soda-lime glass give excellent agreements with the shear modulus G at room temperature and the shear viscosity {eta} reported in the literature at temperatures from 530 to 555degC. The G and {eta} values are also in agreement with those measured by a strain-gage foil and by an electro-optical extensometer, respectively. This agreement confirms that the proposed technique and analysis for the measurement of shear strain with a uniaxial laser speckle strain meter are not only applicable for characterizing the mechanical properties of brittle materials in a small scale deformation, but also provide a powerful tool for studying the high-temperature deformation and flow of engineering materials in a large scale deformation. The issue of affine transformation of polycrystalline materials with local heterogeneity and anisotropy is also discussed by comparing the test results of speckle and electro-optical extensometries. 11 refs., 6 figs.

  11. Gaussian free turbulence: structures and relaxation in plasma models

    International Nuclear Information System (INIS)

    Gruzinov, A.V.


    Free-turbulent relaxation in two-dimensional MHD, the degenerate Hasegawa-Mima equation and a two-dimensional microtearing model are studied. The Gibbs distributions of these three systems can be completely analyzed, due to the special structure of their invariants and due to the existence of ultraviolet catastrophe. The free-turbulent field is seen to be a sum of a certain coherent structure (statistical attractor) and Gaussian random noise. Two-dimensional current layers are shown to be statistical attractors in 2D MHD. (author)

  12. Development of a speckle-based portable device for in situ metrology of synchrotron X-ray mirrors. (United States)

    Kashyap, Yogesh; Wang, Hongchang; Sawhney, Kawal


    A portable device for in situ metrology of synchrotron X-ray mirrors based on the near-field speckle scanning technique has been developed. Ultra-high angular sensitivity is achieved by scanning a piece of abrasive paper or filter membrane in the X-ray beam. In addition to the compact setup and ease of implementation, a user-friendly graphical user interface has been developed to ensure that optimizing active X-ray mirrors is simple and fast. The functionality and feasibility of this device have been demonstrated by characterizing and optimizing X-ray mirrors.

  13. Semisupervised Gaussian Process for Automated Enzyme Search. (United States)

    Mellor, Joseph; Grigoras, Ioana; Carbonell, Pablo; Faulon, Jean-Loup


    Synthetic biology is today harnessing the design of novel and greener biosynthesis routes for the production of added-value chemicals and natural products. The design of novel pathways often requires a detailed selection of enzyme sequences to import into the chassis at each of the reaction steps. To address such design requirements in an automated way, we present here a tool for exploring the space of enzymatic reactions. Given a reaction and an enzyme the tool provides a probability estimate that the enzyme catalyzes the reaction. Our tool first considers the similarity of a reaction to known biochemical reactions with respect to signatures around their reaction centers. Signatures are defined based on chemical transformation rules by using extended connectivity fingerprint descriptors. A semisupervised Gaussian process model associated with the similar known reactions then provides the probability estimate. The Gaussian process model uses information about both the reaction and the enzyme in providing the estimate. These estimates were validated experimentally by the application of the Gaussian process model to a newly identified metabolite in Escherichia coli in order to search for the enzymes catalyzing its associated reactions. Furthermore, we show with several pathway design examples how such ability to assign probability estimates to enzymatic reactions provides the potential to assist in bioengineering applications, providing experimental validation to our proposed approach. To the best of our knowledge, the proposed approach is the first application of Gaussian processes dealing with biological sequences and chemicals, the use of a semisupervised Gaussian process framework is also novel in the context of machine learning applied to bioinformatics. However, the ability of an enzyme to catalyze a reaction depends on the affinity between the substrates of the reaction and the enzyme. This affinity is generally quantified by the Michaelis constant KM

  14. Evaluation of digital image correlation techniques using realistic ground truth speckle images

    International Nuclear Information System (INIS)

    Cofaru, C; Philips, W; Van Paepegem, W


    Digital image correlation (DIC) has been acknowledged and widely used in recent years in the field of experimental mechanics as a contactless method for determining full field displacements and strains. Even though several sub-pixel motion estimation algorithms have been proposed in the literature, little is known about their accuracy and limitations in reproducing complex underlying motion fields occurring in real mechanical tests. This paper presents a new method for evaluating sub-pixel motion estimation algorithms using ground truth speckle images that are realistically warped using artificial motion fields that were obtained following two distinct approaches: in the first, the horizontal and vertical displacement fields are created according to theoretical formulas for the given type of experiment while the second approach constructs the displacements through radial basis function interpolation starting from real DIC results. The method is applied in the evaluation of five DIC algorithms with results indicating that the gradient-based DIC methods generally have a quality advantage when using small sized blocks and are a better choice for calculating very small displacements and strains. The Newton–Raphson is the overall best performing method with a notable quality advantage when large block sizes are employed and in experiments where large strain fields are of interest

  15. Construction of Capacity Achieving Lattice Gaussian Codes

    KAUST Repository

    Alghamdi, Wael


    We propose a new approach to proving results regarding channel coding schemes based on construction-A lattices for the Additive White Gaussian Noise (AWGN) channel that yields new characterizations of the code construction parameters, i.e., the primes and dimensions of the codes, as functions of the block-length. The approach we take introduces an averaging argument that explicitly involves the considered parameters. This averaging argument is applied to a generalized Loeliger ensemble [1] to provide a more practical proof of the existence of AWGN-good lattices, and to characterize suitable parameters for the lattice Gaussian coding scheme proposed by Ling and Belfiore [3].

  16. Model selection for Gaussian kernel PCA denoising

    DEFF Research Database (Denmark)

    Jørgensen, Kasper Winther; Hansen, Lars Kai


    We propose kernel Parallel Analysis (kPA) for automatic kernel scale and model order selection in Gaussian kernel PCA. Parallel Analysis [1] is based on a permutation test for covariance and has previously been applied for model order selection in linear PCA, we here augment the procedure to also...... tune the Gaussian kernel scale of radial basis function based kernel PCA.We evaluate kPA for denoising of simulated data and the US Postal data set of handwritten digits. We find that kPA outperforms other heuristics to choose the model order and kernel scale in terms of signal-to-noise ratio (SNR...

  17. Speckle Interferometry with the McMath-Pierce East Auxiliary Telescope (United States)

    Harshaw, Richard; Ray, Jimmy; Douglass, David; Prause, Lori; Genet, Russell


    Engineering runs and tests on the McMath-Pierce 0.8 meter East Auxiliary telescope successfully configured the telescope for speckle interferometry observations of close visual double stars. This paper reports the procedure and results of the speckle analysis of four double stars.

  18. Visual based laser speckle pattern recognition method for structural health monitoring (United States)

    Park, Kyeongtaek; Torbol, Marco


    This study performed the system identification of a target structure by analyzing the laser speckle pattern taken by a camera. The laser speckle pattern is generated by the diffuse reflection of the laser beam on a rough surface of the target structure. The camera, equipped with a red filter, records the scattered speckle particles of the laser light in real time and the raw speckle image of the pixel data is fed to the graphic processing unit (GPU) in the system. The algorithm for laser speckle contrast analysis (LASCA) computes: the laser speckle contrast images and the laser speckle flow images. The k-mean clustering algorithm is used to classify the pixels in each frame and the clusters' centroids, which function as virtual sensors, track the displacement between different frames in time domain. The fast Fourier transform (FFT) and the frequency domain decomposition (FDD) compute the modal properties of the structure: natural frequencies and damping ratios. This study takes advantage of the large scale computational capability of GPU. The algorithm is written in Compute Unifies Device Architecture (CUDA C) that allows the processing of speckle images in real time.

  19. Spatial filtering velocimetry of objective speckles for measuring out-of-plane motion

    DEFF Research Database (Denmark)

    Jakobsen, Michael Linde; Yura, H. T.; Hanson, Steen Grüner


    This paper analyzes the dynamics of objective laser speckles as the distance between the object and the observation plane continuously changes. With the purpose of applying optical spatial filtering velocimetry to the speckle dynamics, in order to measure out-of-plane motion in real time...

  20. Tandem-pulsed acousto-optics: an analytical framework of modulated high-contrast speckle patterns

    NARCIS (Netherlands)

    Resink, Steffen; Steenbergen, Wiendelt


    Recently we presented acousto-optic (AO) probing of scattering media using addition or subtraction of speckle patterns due to tandem nanosecond pulses. Here we present a theoretical framework for ideal (polarized, noise-free) speckle patterns with unity contrast that links ultrasound-induced optical

  1. Predicting Paroxysmal Atrial Fibrillation in Cerebrovascular Ischemia Using Tissue Doppler Imaging and Speckle Tracking Echocardiography

    DEFF Research Database (Denmark)

    Olsen, Flemming Javier; Jørgensen, Peter Godsk; Møgelvang, Rasmus


    , tissue Doppler imaging (TDI), and speckle tracking. TDI was performed to acquire myocardial peak velocities during systole/ventricular contraction (global s'), early diastole/ventricular filling (global e'), and late diastole/atrial contraction (global a'). Speckle tracking was performed for myocardial...

  2. Remarks on non-Gaussian fluctuations of the inflaton and constancy of ζ outside the horizon

    International Nuclear Information System (INIS)

    Mahajan, N; Rangarajan, R


    We have pointed out that the non-Gaussianity arising from cubic self interactions of the inflaton field is proportional to ξN e . For scales of interest N e = 60, and for models such as new inflation, natural inflation, and running mass inflation ξ is large compared to the slow roll parameter. Therefore, the contribution from self interactions should not be outrightly ignored while retaining other terms in the non-Gaussianity parameter f NL . But the N e dependent term seems to imply the growth of non-Gaussianities outside the horizon. Therefore, we have briefly discussed the issue of the constancy of correlations of the curvature perturbation ζ outside the horizon. We have then presented our results on the 3-point function of ζ k , and found that the N e dependent contribution to f NL from self interactions of the inflaton field is cancelled by contributions from other terms associated with non-linearities in cosmological perturbation theory

  3. Statistically tuned Gaussian background subtraction technique for ...

    Indian Academy of Sciences (India)

    ground, small objects, moving background and multiple objects are considered for evaluation. The technique is statistically compared with frame differencing technique, temporal median method and mixture of Gaussian model and performance evaluation is done to check the effectiveness of the proposed technique after ...

  4. Log Gaussian Cox processes on the sphere

    DEFF Research Database (Denmark)

    Pacheco, Francisco Andrés Cuevas; Møller, Jesper

    We define and study the existence of log Gaussian Cox processes (LGCPs) for the description of inhomogeneous and aggregated/clustered point patterns on the d-dimensional sphere, with d = 2 of primary interest. Useful theoretical properties of LGCPs are studied and applied for the description of sky...

  5. Open problems in Gaussian fluid queueing theory

    NARCIS (Netherlands)

    Dȩbicki, K.; Mandjes, M.


    We present three challenging open problems that originate from the analysis of the asymptotic behavior of Gaussian fluid queueing models. In particular, we address the problem of characterizing the correlation structure of the stationary buffer content process, the speed of convergence to

  6. Fourth Power Diophantine Equations in Gaussian Integers

    Indian Academy of Sciences (India)


    Fourth Power Diophantine Equations in Gaussian Integers. 7. 7. U. Schneiders and H.G. Zimmer, The rank of elliptic curves upon quadratic extensions,. Computational Number Theory (A. Petho, H.C. Williams,H.G. Zimmer, eds.), de Gruyter,. 239-260, Berlin, (1991). 8. Y. Suzuki, On the Diophantine Equation 2aX4 + 2bY 4 ...

  7. Statistically tuned Gaussian background subtraction technique for ...

    Indian Academy of Sciences (India)

    The non-parametric background modelling approach proposed by Martin Hofmann et al (2012) involves modelling of foreground by the history of recently ... background subtraction system with mixture of Gaussians, deviation scaling factor and max– min background model for outdoor environment. Selection of detection ...

  8. The Wehrl entropy has Gaussian optimizers

    DEFF Research Database (Denmark)

    De Palma, Giacomo


    We determine the minimum Wehrl entropy among the quantum states with a given von Neumann entropy and prove that it is achieved by thermal Gaussian states. This result determines the relation between the von Neumann and the Wehrl entropies. The key idea is proving that the quantum-classical channel...

  9. Gaussian curvature on hyperelliptic Riemann surfaces

    Indian Academy of Sciences (India)

    Indian Acad. Sci. (Math. Sci.) Vol. 124, No. 2, May 2014, pp. 155–167. c Indian Academy of Sciences. Gaussian curvature on hyperelliptic Riemann surfaces. ABEL CASTORENA. Centro de Ciencias Matemáticas (Universidad Nacional Autónoma de México,. Campus Morelia) Apdo. Postal 61-3 Xangari, C.P. 58089 Morelia,.

  10. Bregman Cost for Non-Gaussian Noise

    DEFF Research Database (Denmark)

    Burger, Martin; Dong, Yiqiu; Sciacchitano, Federica

    estimator for the Bregman cost if the image is corrupted by Gaussian noise. In this work we extend this result to other noise models with log-concave likelihood density, by introducing two related Bregman cost functions for which the CM and the MAP estimates are proper Bayes estima-tors. Moreover, we also...

  11. Non-Gaussianity effects in petrophysical quantities (United States)

    Koohi Lai, Z.; Jafari, G. R.


    It has been proved that there are many indicators (petrophysical quantities) for the estimation of petroleum reservoirs. The value of information contained in each indicator is yet to be addressed. In this work, the most famous and applicable petrophysical quantities for a reservoir, which are the gamma emission (GR), sonic transient time (DT), neutron porosity (NPHI), bulk density (RHOB), and deep induced resistivity (ILD), have been analyzed in order to characterize a reservoir. The implemented technique is the well-logging method. Based on the log-normal model defined in random multiplicative processes, the probability distribution function (PDF) for the data sets is described. The shape of the PDF depends on the parameter λ2 which determines the efficiency of non-Gaussianity. When non-Gaussianity appears, it is a sign of uncertainty and phase transition in the critical regime. The large value and scale-invariant behavior of the non-Gaussian parameter λ2 is an indication of a new phase which proves adequate for the existence of petroleum reservoirs. Our results show that one of the indicators (GR) is more non-Gaussian than the other indicators, scale wise. This means that GR is a continuously critical indicator. But by moving windows with various scales, the estimated λ2 shows that the most appropriate indicator for distinguishing the critical regime is ILD, which shows an increase at the end of the measured region of the well.

  12. Fourth Power Diophantine Equations in Gaussian Integers

    Indian Academy of Sciences (India)


    Fourth Power Diophantine Equations in Gaussian. Integers. Farzali Izadi · Rasool Naghdali. Forooshani · Amaneh Amiryousefi. Varnousfaderani . Received: date / Accepted: date. Abstract In this paper we examine a class of fourth power Diophantine equa- tions of the form x4 + kx2y2 + y4 = z2 and ax4 + by4 = cz2, in the ...

  13. Gaussian shaping filter for nuclear spectrometry

    International Nuclear Information System (INIS)

    Menezes, A.S.C. de.


    A theorical study of a gaussian shaping filter, using Pade approximation, for using in gamma spectroscopy is presented. This approximation has proved superior to the classical cascade RC integrators approximation in therms of signal-to-noise ratio and pulse simmetry. An experimental filter was designed, simulated in computer, constructed, and tested in the laboratory. (author) [pt

  14. Gaussian processes for prediction in intensive care


    Guiza Grandas, Fabian; Ramon, Jan; Blockeel, Hendrik


    In this paper we present the use of Gaussian Processes for regression in the application of prediction in Intensive Care. We propose a preliminary solution to predicting the evolution of a patient's state during his stay in intensive care by means of defined patient specific characteristics.

  15. Survival Exponents for Some Gaussian Processes

    Directory of Open Access Journals (Sweden)

    G. Molchan


    Full Text Available The problem is a power-law asymptotics of the probability that a self-similar process does not exceed a fixed level during long time. The exponent in such asymptotics is estimated for some Gaussian processes, including the fractional Brownian motion (FBM in , and the integrated FBM in , .

  16. Study of drying process of paint by dynamic speckle with B/D pixel counting technique (United States)

    Balamurugan, R.; Rajarajan, G.


    The aim of the work is the assessment of drying process of latex paint by dynamic Laser speckle method. The basic concept of dynamic speckle technique is described. Laser light scattering by water borne sample is a time dependent surface activity. The variation of laser speckle intensity is due to the change of refractive index and the particle movements of the latex paint. A novel method, B/D counting technique to measure the dynamic activity of drying paint using co-occurrence matrix of Time History of Speckle Pattern (THSP) is presented. The result of drying process of latex paint by dynamic laser speckle method is compared with the gravimetric method and agreed well.

  17. A Gaussian graphical model approach to climate networks

    Energy Technology Data Exchange (ETDEWEB)

    Zerenner, Tanja, E-mail: [Meteorological Institute, University of Bonn, Auf dem Hügel 20, 53121 Bonn (Germany); Friederichs, Petra; Hense, Andreas [Meteorological Institute, University of Bonn, Auf dem Hügel 20, 53121 Bonn (Germany); Interdisciplinary Center for Complex Systems, University of Bonn, Brühler Straße 7, 53119 Bonn (Germany); Lehnertz, Klaus [Department of Epileptology, University of Bonn, Sigmund-Freud-Straße 25, 53105 Bonn (Germany); Helmholtz Institute for Radiation and Nuclear Physics, University of Bonn, Nussallee 14-16, 53115 Bonn (Germany); Interdisciplinary Center for Complex Systems, University of Bonn, Brühler Straße 7, 53119 Bonn (Germany)


    Distinguishing between direct and indirect connections is essential when interpreting network structures in terms of dynamical interactions and stability. When constructing networks from climate data the nodes are usually defined on a spatial grid. The edges are usually derived from a bivariate dependency measure, such as Pearson correlation coefficients or mutual information. Thus, the edges indistinguishably represent direct and indirect dependencies. Interpreting climate data fields as realizations of Gaussian Random Fields (GRFs), we have constructed networks according to the Gaussian Graphical Model (GGM) approach. In contrast to the widely used method, the edges of GGM networks are based on partial correlations denoting direct dependencies. Furthermore, GRFs can be represented not only on points in space, but also by expansion coefficients of orthogonal basis functions, such as spherical harmonics. This leads to a modified definition of network nodes and edges in spectral space, which is motivated from an atmospheric dynamics perspective. We construct and analyze networks from climate data in grid point space as well as in spectral space, and derive the edges from both Pearson and partial correlations. Network characteristics, such as mean degree, average shortest path length, and clustering coefficient, reveal that the networks posses an ordered and strongly locally interconnected structure rather than small-world properties. Despite this, the network structures differ strongly depending on the construction method. Straightforward approaches to infer networks from climate data while not regarding any physical processes may contain too strong simplifications to describe the dynamics of the climate system appropriately.

  18. A Gaussian graphical model approach to climate networks

    International Nuclear Information System (INIS)

    Zerenner, Tanja; Friederichs, Petra; Hense, Andreas; Lehnertz, Klaus


    Distinguishing between direct and indirect connections is essential when interpreting network structures in terms of dynamical interactions and stability. When constructing networks from climate data the nodes are usually defined on a spatial grid. The edges are usually derived from a bivariate dependency measure, such as Pearson correlation coefficients or mutual information. Thus, the edges indistinguishably represent direct and indirect dependencies. Interpreting climate data fields as realizations of Gaussian Random Fields (GRFs), we have constructed networks according to the Gaussian Graphical Model (GGM) approach. In contrast to the widely used method, the edges of GGM networks are based on partial correlations denoting direct dependencies. Furthermore, GRFs can be represented not only on points in space, but also by expansion coefficients of orthogonal basis functions, such as spherical harmonics. This leads to a modified definition of network nodes and edges in spectral space, which is motivated from an atmospheric dynamics perspective. We construct and analyze networks from climate data in grid point space as well as in spectral space, and derive the edges from both Pearson and partial correlations. Network characteristics, such as mean degree, average shortest path length, and clustering coefficient, reveal that the networks posses an ordered and strongly locally interconnected structure rather than small-world properties. Despite this, the network structures differ strongly depending on the construction method. Straightforward approaches to infer networks from climate data while not regarding any physical processes may contain too strong simplifications to describe the dynamics of the climate system appropriately

  19. Body size evolution in insular speckled rattlesnakes (Viperidae: Crotalus mitchellii.

    Directory of Open Access Journals (Sweden)

    Jesse M Meik


    Full Text Available Speckled rattlesnakes (Crotalus mitchellii inhabit multiple islands off the coast of Baja California, Mexico. Two of the 14 known insular populations have been recognized as subspecies based primarily on body size divergence from putative mainland ancestral populations; however, a survey of body size variation from other islands occupied by these snakes has not been previously reported. We examined body size variation between island and mainland speckled rattlesnakes, and the relationship between body size and various island physical variables among 12 island populations. We also examined relative head size among giant, dwarfed, and mainland speckled rattlesnakes to determine whether allometric differences conformed to predictions of gape size (and indirectly body size evolving in response to shifts in prey size.Insular speckled rattlesnakes show considerable variation in body size when compared to mainland source subspecies. In addition to previously known instances of gigantism on Angel de la Guarda and dwarfism on El Muerto, various degrees of body size decrease have occurred frequently in this taxon, with dwarfed rattlesnakes occurring mostly on small, recently isolated, land-bridge islands. Regression models using the Akaike information criterion (AIC showed that mean SVL of insular populations was most strongly correlated with island area, suggesting the influence of selection for different body size optima for islands of different size. Allometric differences in head size of giant and dwarf rattlesnakes revealed patterns consistent with shifts to larger and smaller prey, respectively.Our data provide the first example of a clear relationship between body size and island area in a squamate reptile species; among vertebrates this pattern has been previously documented in few insular mammals. This finding suggests that selection for body size is influenced by changes in community dynamics that are related to graded differences in area over

  20. Rat retinal vasomotion assessed by laser speckle imaging

    DEFF Research Database (Denmark)

    Neganova, Anastasiia Y; Postnov, Dmitry D; Sosnovtseva, Olga


    vasomotion occurs in anesthetized animals and (ii) vasomotion can be initiated by systemic administration of the thromboxane analogue U-46619 and the nitric-oxide donor S-nitroso-acetylDL-penicillamine (SNAP). Although these drugs activate different cellular pathways responsible for vasomotion, our approach...... that can address the role and dynamical properties of vasomotion in vivo. We apply laser speckle imaging to study spontaneous and drug induced vasomotion in retinal network of anesthetized rats. The results reveal a wide variety of dynamical patterns. Wavelet-based analysis shows that (i) spontaneous...

  1. Effect of low-frequency vibrations on speckle interferometry fringes

    International Nuclear Information System (INIS)

    Vikram, C.S.; Pechersky, M.J.


    The effects of low-frequency vibrations on speckle correlation fringes have been investigated. The relatively short capture time of the camera in the low-frequency case may yield usable fringe contrast in spite of vibration. It has been shown that the fringes also shift due to the vibration. The study is in agreement with experimental observations of good-contrast correlation fringes even if the object is not on a vibration-isolated table. Some such experimental observations are also presented. copyright 1998 Society of Photo-Optical Instrumentation Engineers

  2. Optoelectronic imaging of speckle using image processing method (United States)

    Wang, Jinjiang; Wang, Pengfei


    A detailed image processing of laser speckle interferometry is proposed as an example for the course of postgraduate student. Several image processing methods were used together for dealing with optoelectronic imaging system, such as the partial differential equations (PDEs) are used to reduce the effect of noise, the thresholding segmentation also based on heat equation with PDEs, the central line is extracted based on image skeleton, and the branch is removed automatically, the phase level is calculated by spline interpolation method, and the fringe phase can be unwrapped. Finally, the imaging processing method was used to automatically measure the bubble in rubber with negative pressure which could be used in the tire detection.

  3. Speckle tracking echocardiography in mature Irish Wolfhound dogs

    DEFF Research Database (Denmark)

    Westrup, Ulrik; McEvoy, Fintan


    Two-dimensional strain measurements obtained by speckle tracking echocardiography (STE) have been reported in both humans and dogs. Incorporation of this technique into canine clinical practice requires the availability of measurements from clinically normal dogs, ideally of the same breed, taken...... under normal clinical conditions.The aims of this prospective study were to assess if it is possible to obtain STE data during a routine echocardiographic examination in Irish Wolfhound dogs and that these data will provide reference values and an estimation of measurement error....

  4. Excitonic Coherence in Semiconductor Nanostructures Measured by Speckle Analysis

    DEFF Research Database (Denmark)

    Langbein, Wolfgang; Hvam, Jørn Märcher


    A new method to measure the time-dependent coherence of optical excitations in solids is presented, in which the coherence degree of light emission is deduced from its intensity fluctuations over the emission directions (speckles). With this method the decays of intensity and coherence...... are determined separately, thus distinguishing lifetime from pure dephasing. In particular, the secondary emission of excitons in semiconductor quantum wells is investigated. Here, the combination of static disorder and inelastic scattering leads to a partially coherent emission. The temperature dependence...

  5. Ocular microtremor measurement using laser-speckle metrology (United States)

    Kenny, Emer; Coakley, Davis; Boyle, Gerard


    We describe a novel, noninvasive measurement approach for recording a small involuntary tremor of the eye known as ocular microtremor. The method is based on measuring out-of-plane angular displacements of a target by using laser-speckle correlation of images recorded in the Fourier plane of a lens. The system has a dynamic range of 4 to 5000 μrad, resolution of 4 μrad, and a bandwidth of 250 Hz. The design and optimization of the system is presented with an in vitro validation of the system against its specification.

  6. Lensless Photoluminescence Hyperspectral Camera Employing Random Speckle Patterns.

    Czech Academy of Sciences Publication Activity Database

    Žídek, Karel; Denk, Ondřej; Hlubuček, Jiří


    Roč. 7, č. 1 (2017), č. článku 15309. ISSN 2045-2322 R&D Projects: GA MŠk(CZ) LO1206; GA ČR(CZ) GJ17-26284Y Institutional support: RVO:61389021 Keywords : compressed sensing * photoluminescence imaging * laser speckles * single-pixel camera Subject RIV: BH - Optics, Masers, Lasers OBOR OECD: Optics (including laser optics and quantum optics) Impact factor: 4.259, year: 2016

  7. Gaussian-input Gaussian mixture model for representing density maps and atomic models. (United States)

    Kawabata, Takeshi


    A new Gaussian mixture model (GMM) has been developed for better representations of both atomic models and electron microscopy 3D density maps. The standard GMM algorithm employs an EM algorithm to determine the parameters. It accepted a set of 3D points with weights, corresponding to voxel or atomic centers. Although the standard algorithm worked reasonably well; however, it had three problems. First, it ignored the size (voxel width or atomic radius) of the input, and thus it could lead to a GMM with a smaller spread than the input. Second, the algorithm had a singularity problem, as it sometimes stopped the iterative procedure due to a Gaussian function with almost zero variance. Third, a map with a large number of voxels required a long computation time for conversion to a GMM. To solve these problems, we have introduced a Gaussian-input GMM algorithm, which considers the input atoms or voxels as a set of Gaussian functions. The standard EM algorithm of GMM was extended to optimize the new GMM. The new GMM has identical radius of gyration to the input, and does not suddenly stop due to the singularity problem. For fast computation, we have introduced a down-sampled Gaussian functions (DSG) by merging neighboring voxels into an anisotropic Gaussian function. It provides a GMM with thousands of Gaussian functions in a short computation time. We also have introduced a DSG-input GMM: the Gaussian-input GMM with the DSG as the input. This new algorithm is much faster than the standard algorithm. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

  8. MCEM algorithm for the log-Gaussian Cox process


    Delmas, Celine; Dubois-Peyrard, Nathalie; Sabbadin, Regis


    Log-Gaussian Cox processes are an important class of models for aggregated point patterns. They have been largely used in spatial epidemiology (Diggle et al., 2005), in agronomy (Bourgeois et al., 2012), in forestry (Moller et al.), in ecology (sightings of wild animals) or in environmental sciences (radioactivity counts). A log-Gaussian Cox process is a Poisson process with a stochastic intensity depending on a Gaussian random eld. We consider the case where this Gaussian random eld is ...

  9. Spatial pattern formation induced by Gaussian white noise. (United States)

    Scarsoglio, Stefania; Laio, Francesco; D'Odorico, Paolo; Ridolfi, Luca


    The ability of Gaussian noise to induce ordered states in dynamical systems is here presented in an overview of the main stochastic mechanisms able to generate spatial patterns. These mechanisms involve: (i) a deterministic local dynamics term, accounting for the local rate of variation of the field variable, (ii) a noise component (additive or multiplicative) accounting for the unavoidable environmental disturbances, and (iii) a linear spatial coupling component, which provides spatial coherence and takes into account diffusion mechanisms. We investigate these dynamics using analytical tools, such as mean-field theory, linear stability analysis and structure function analysis, and use numerical simulations to confirm these analytical results. Copyright © 2010 Elsevier Inc. All rights reserved.

  10. Laser-driven acceleration with Bessel and Gaussian beams

    International Nuclear Information System (INIS)

    Hafizi, B.; Esarey, E.; Sprangle, P.


    The possibility of enhancing the energy gain in laser-driven accelerators by using Bessel laser beams is examined. Scaling laws are derived for the propagation length, acceleration gradient, and energy gain in various accelerators for both Gaussian and Bessel beam drivers. For equal beam powers, the energy gain can be increased by a factor of N 1/2 by utilizing a Bessel beam with N lobes, provided that the acceleration gradient is linearly proportional to the laser field. This is the case in the inverse free electron laser and the inverse Cherenkov accelerators. If the acceleration gradient is proportional to the square of the laser field (e.g., the laser wakefield, plasma beat wave, and vacuum beat wave accelerators), the energy gain is comparable with either beam profile. copyright 1997 American Institute of Physics

  11. Linking network usage patterns to traffic Gaussianity fit

    NARCIS (Netherlands)

    de Oliveira Schmidt, R.; Sadre, R.; Melnikov, Nikolay; Schönwälder, Jürgen; Pras, Aiko

    Gaussian traffic models are widely used in the domain of network traffic modeling. The central assumption is that traffic aggregates are Gaussian distributed. Due to its importance, the Gaussian character of network traffic has been extensively assessed by researchers in the past years. In 2001,

  12. A photonic nanowire trumpet for interfacing a quantum dot and a Gaussian free-space mode

    DEFF Research Database (Denmark)

    Gregersen, Niels; Munsch, Mathieu; Malik, Nitin S.


    potential. However, the device requires a delicate, sharp needle-like taper with performance sensitive to minute geometrical details. To overcome this limitation we demonstrate the photonic trumpet, exploiting an opposite tapering strategy. The trumpet features a strongly Gaussian far-field emission...

  13. Ability of the Gaussian plume model to predict and describe spore dispersal over a potato crop

    NARCIS (Netherlands)

    Spijkerboer, H.P.; Beniers, J.E.; Jaspers, D.; Schouten, H.J.; Goudriaan, J.; Rabbinge, R.; Werf, van der W.


    The Gaussian plume model (GPM) is considered as a valuable tool in predictions of the atmospheric transport of fungal spores and plant pollen in risk assessments. The validity of the model in this important area of application has not been extensively evaluated. A field experiment was set up to test

  14. Generation of Radial Laguerre-Gaussian modes with a lower threshold using a digital laser

    CSIR Research Space (South Africa)

    Bell, Teboho


    Full Text Available Zulu-Natal, Westville, Private Bag X 54001, Durban 4000, South Africa. 3Centre de Développement des Techniques Avancées, Division Milieux Ionisés et Lasers, P.O. Box 17 Baba Hassan, Algiers 16303, Algeria. 2Electrical field of Laguerre-Gaussian beams with radial...

  15. Gaussian-to-top-hat beam shaping: an overview of parameters, methods, and applications (United States)

    Homburg, O.; Mitra, T.


    Direct laser patterning of various materials is today widely used in several micro-system production lines like inkjet printing, solar cell technology, flat-panel display production, LEDs, OLEDs, semiconductors and medicine. Typically single-mode solid state lasers and their higher harmonics (e. g. 266, 355, 532 and 1064 nm) are used especially for machining of holes and grooves. The striking advantages of flat top intensity distributions compared to Gaussian beam profiles with respect to the efficiency and quality of these processes were already demonstrated. Here we will give an overview of parameters, methods and applications of Gaussian-to-top-hat beam shaping. The top hat field size can start from about 30 μm with no upper size limitation in the far field of the optics. Beam shaping for various wavelengths were realized with field geometries of squares, rectangles and circles. With LIMO's compact Gaussian-to-top-hat converter an inhomogeneity better than 5% contrast was reached. Special focus is put on the integration of Gaussian-to-top-hat beam shapers in fast scanning systems employing Galvo mirrors and a specially developed f-Theta lens to avoid destruction of the top hat profile within the scan field. Results with a 50x50μm2 top hat size (inhomogeneity down to solar panels.

  16. Optical characterization of display screens by speckle patterns (United States)

    Pozo, Antonio M.; Castro, José J.; Rubiño, Manuel


    In recent years, flat-panel display (FPD) technology has undergone great development, and now FPDs appear in many devices. A significant element in FPD manufacturing is the display front surface. Manufacturers sell FPDs with different types of front surfaces, which can be matte (also called anti-glare) or glossy screens. Users who prefer glossy screens consider these displays to show more vivid colors compared with matte-screen displays. However, on the glossy screens, external light sources may cause unpleasant reflections that can be reduced by a matte treatment in the front surface. In this work, we present a method to characterize FPD screens using laser-speckle patterns. We characterize three FPDs: a Samsung XL2370 LCD monitor of 23 in. with matte screen, a Toshiba Satellite A100 LCD laptop of 15.4 in. with glossy screen, and a Grammata Papyre 6.1 electronic book reader of 6 in. with ePaper screen (E-ink technology). The results show great differences in speckle-contrast values for the three screens characterized and, therefore, this work shows the feasibility of this method for characterizing and comparing FPDs that have different types of front surfaces.

  17. Intraoperative multi-exposure speckle imaging of cerebral blood flow. (United States)

    Richards, Lisa M; Kazmi, Sm Shams; Olin, Katherine E; Waldron, James S; Fox, Douglas J; Dunn, Andrew K


    Multiple studies have demonstrated that laser speckle contrast imaging (LSCI) has high potential to be a valuable cerebral blood flow monitoring technique during neurosurgery. However, the quantitative accuracy and sensitivity of LSCI is limited, and highly dependent on the exposure time. An extension to LSCI called multi-exposure speckle imaging (MESI) overcomes these limitations, and was evaluated intraoperatively in patients undergoing brain tumor resection. This clinical study ( n = 8) recorded multiple exposure times from the same cortical tissue area spanning 0.5-20 ms, and evaluated images individually as single-exposure LSCI and jointly using the MESI model. This study demonstrated that the MESI estimates provided the broadest flow sensitivity for sampling the flow magnitude in the human brain, closely followed by the shorter exposure times. Conservation of flow analysis on vascular bifurcations was used to validate physiological accuracy, with highly conserved flow estimates (flow changes after tissue cautery. Results from this study demonstrate that intraoperative MESI can be performed with high quantitative accuracy and sensitivity for cerebral blood flow monitoring.

  18. Calibration of a speckle-based compressive sensing receiver (United States)

    Sefler, George A.; Shaw, T. Justin; Stapleton, Andrew D.; Valley, George C.


    Optical speckle in a multimode waveguide has been proposed to perform the function of a compressive sensing (CS) measurement matrix (MM) in a receiver for GHz-band radio frequency (RF) signals. Unlike other devices used for the CS MM, e.g. the digital micromirror device (DMD) used in the single pixel camera, the elements of the speckle MM are not known before use and must be measured and calibrated. In our system, the RF signal is modulated on a repetitively pulsed chirped wavelength laser source, generated from mode-locked laser pulses that have been dispersed in time or from an electrically addressed distributed Bragg reflector laser. Next, the optical beam with RF propagates through a multimode fiber or waveguide, which applies different weights in wavelength (or equivalently time) and space and performs the function of the CS MM. The output of the guide is directed to or imaged on a bank of photodiodes with integration time set to the pulse length of the chirp waveform. The output of each photodiode is digitized by an analog-to-digital converter (ADC), and the data from these ADCs are used to form the CS measurement vector. Accurate recovery of the RF signal from CS measurements depends critically on knowledge of the weights in the MM. Here we present results using a stable wavelength laser source to probe the guide.

  19. Real time speckle monitoring to control retinal photocoagulation (United States)

    Bliedtner, Katharina; Seifert, Eric; Brinkmann, Ralf


    Photocoagulation is a treatment modality for several retinal diseases. Intra- and inter-individual variations of the retinal absorption as well as ocular transmission and light scattering makes it impossible to achieve a uniform effective exposure with one set of laser parameters. To guarantee a uniform damage throughout the therapy a real-time control is highly requested. Here, an approach to realize a real-time optical feedback using dynamic speckle analysis in-vivo is presented. A 532 nm continuous wave Nd:YAG laser is used for coagulation. During coagulation, speckle dynamics are monitored by a coherent object illumination using a 633 nm diode laser and analyzed by a CMOS camera with a frame rate up to 1 kHz. An algorithm is presented that can discriminate between different categories of retinal pigment epithelial damage ex-vivo in enucleated porcine eyes and that seems to be robust to noise in-vivo. Tissue changes in rabbits during retinal coagulation could be observed for different lesion strengths. This algorithm can run on a FPGA and is able to calculate a feedback value which is correlated to the thermal and coagulation induced tissue motion and thus the achieved damage.

  20. Distributed Remote Vector Gaussian Source Coding for Wireless Acoustic Sensor Networks

    DEFF Research Database (Denmark)

    Zahedi, Adel; Østergaard, Jan; Jensen, Søren Holdt


    In this paper, we consider the problem of remote vector Gaussian source coding for a wireless acoustic sensor network. Each node receives messages from multiple nodes in the network and decodes these messages using its own measurement of the sound field as side information. The node’s measurement...... encoding multiple sources. We focus on the case where node measurements are in form of noisy linearly mixed combinations of the sources and the acoustic channel mixing matrices are invertible. For this problem, we derive the rate-distortion function for vector Gaussian sources and under covariance...

  1. Partial summations of stationary sequences of non-Gaussian random variables

    DEFF Research Database (Denmark)

    Mohr, Gunnar; Ditlevsen, Ove Dalager


    The distribution of the sum of a finite number of identically distributed random variables is in many cases easily determined given that the variables are independent. The moments of any order of the sum can always be expressed by the moments of the single term without computational problems...... of convergence of the distribution of a sum (or an integral) of mutually dependent random variables to the Gaussian distribution. The paper is closely related to the work in Ditlevsen el al. [Ditlevsen, O., Mohr, G. & Hoffmeyer, P. Integration of non-Gaussian fields. Prob. Engng Mech 11 (1996) 15-23](2)....

  2. On Alternate Relaying with Improper Gaussian Signaling

    KAUST Repository

    Gaafar, Mohamed


    In this letter, we investigate the potential benefits of adopting improper Gaussian signaling (IGS) in a two-hop alternate relaying (AR) system. Given the known benefits of using IGS in interference-limited networks, we propose to use IGS to relieve the inter-relay interference (IRI) impact on the AR system assuming no channel state information is available at the source. In this regard, we assume that the two relays use IGS and the source uses proper Gaussian signaling (PGS). Then, we optimize the degree of impropriety of the relays signal, measured by the circularity coefficient, to maximize the total achievable rate. Simulation results show that using IGS yields a significant performance improvement over PGS, especially when the first hop is a bottleneck due to weak source-relay channel gains and/or strong IRI.

  3. Interweave Cognitive Radio with Improper Gaussian Signaling

    KAUST Repository

    Hedhly, Wafa


    Improper Gaussian signaling (IGS) has proven its ability in improving the performance of underlay and overlay cognitive radio paradigms. In this paper, the interweave cognitive radio paradigm is studied when the cognitive user employs IGS. The instantaneous achievable rate performance of both the primary and secondary users are analyzed for specific secondary user sensing and detection capabilities. Next, the IGS scheme is optimized to maximize the achievable rate secondary user while satisfying a target minimum rate requirement for the primary user. Proper Gaussian signaling (PGS) scheme design is also derived to be used as benchmark of the IGS scheme design. Finally, different numerical results are introduced to show the gain reaped from adopting IGS over PGS under different system parameters. The main advantage of employing IGS is observed at low sensing and detection capabilities of the SU, lower PU direct link and higher SU interference on the PU side.

  4. Geometrical approach to gaussian beam propagation. (United States)

    Laures, P


    The curvature of the wavefront and the spot size of a propagating Gaussian beam may be determined from simple geometrical transformations of the lateral foci. The analysis starts from the construction of the lateral foci in the case of a spherical Fabry-Perot. Then the cases of Gaussian beam propagation through media with different refractive indices, lenses, and simple optical systems are treated. Constructions show how propagation in the image space is readily determined in each case. This analysis is the generalization of the technique outlined by Deschamps and Mast. The geometrical constructions developed for simple cases are applied to the design of some special cases of interest in laser optics: cavities by a lens, laser zoom telescope, and ring cavity.

  5. Extended Linear Models with Gaussian Priors

    DEFF Research Database (Denmark)

    Quinonero, Joaquin


    In extended linear models the input space is projected onto a feature space by means of an arbitrary non-linear transformation. A linear model is then applied to the feature space to construct the model output. The dimension of the feature space can be very large, or even infinite, giving the model...... a very big flexibility. Support Vector Machines (SVM's) and Gaussian processes are two examples of such models. In this technical report I present a model in which the dimension of the feature space remains finite, and where a Bayesian approach is used to train the model with Gaussian priors...... on the parameters. The Relevance Vector Machine, introduced by Tipping, is a particular case of such a model. I give the detailed derivations of the expectation-maximisation (EM) algorithm used in the training. These derivations are not found in the literature, and might be helpful for newcomers....

  6. Environmental Modeling Framework using Stacked Gaussian Processes


    Abdelfatah, Kareem; Bao, Junshu; Terejanu, Gabriel


    A network of independently trained Gaussian processes (StackedGP) is introduced to obtain predictions of quantities of interest with quantified uncertainties. The main applications of the StackedGP framework are to integrate different datasets through model composition, enhance predictions of quantities of interest through a cascade of intermediate predictions, and to propagate uncertainties through emulated dynamical systems driven by uncertain forcing variables. By using analytical first an...

  7. Adaptive multiple importance sampling for Gaussian processes

    Czech Academy of Sciences Publication Activity Database

    Xiong, X.; Šmídl, Václav; Filippone, M.


    Roč. 87, č. 8 (2017), s. 1644-1665 ISSN 0094-9655 R&D Projects: GA MŠk(CZ) 7F14287 Institutional support: RVO:67985556 Keywords : Gaussian Process * Bayesian estimation * Adaptive importance sampling Subject RIV: BB - Applied Statistics, Operational Research OBOR OECD: Statistics and probability Impact factor: 0.757, year: 2016

  8. Dimensionality Reduction by Local Discriminative Gaussians


    Parrish, Nathan; Gupta, Maya


    We present local discriminative Gaussian (LDG) dimensionality reduction, a supervised dimensionality reduction technique for classification. The LDG objective function is an approximation to the leave-one-out training error of a local quadratic discriminant analysis classifier, and thus acts locally to each training point in order to find a mapping where similar data can be discriminated from dissimilar data. While other state-of-the-art linear dimensionality reduction methods require gradien...

  9. Recognition of Images Degraded by Gaussian Blur

    Czech Academy of Sciences Publication Activity Database

    Flusser, Jan; Farokhi, Sajad; Höschl, Cyril; Suk, Tomáš; Zitová, Barbara; Pedone, M.


    Roč. 25, č. 2 (2016), s. 790-806 ISSN 1057-7149 R&D Projects: GA ČR(CZ) GA15-16928S Institutional support: RVO:67985556 Keywords : Blurred image * object recognition * blur invariant comparison * Gaussian blur * projection operators * image moments * moment invariants Subject RIV: JD - Computer Applications, Robotics Impact factor: 4.828, year: 2016

  10. Stochastic Energetics for Non-Gaussian Processes (United States)

    Kanazawa, Kiyoshi; Sagawa, Takahiro; Hayakawa, Hisao


    By introducing a new stochastic integral, we investigate the energetics of classical stochastic systems driven by non-Gaussian white noises. In particular, we introduce a decomposition of the total energy difference into the work and the heat for each trajectory, and derive a formula to calculate the heat from experimental data on the dynamics. We apply our formulation and results to a Langevin system driven by a Poisson noise.

  11. A Gaussian IV estimator of cointegrating relations

    DEFF Research Database (Denmark)

    Bårdsen, Gunnar; Haldrup, Niels


    -nonparametricestimators. Theoretically ideal instruments can be defined to ensure a limitingGaussian distribution of IV estimators, but unfortunately such instruments areunlikely to be found in real data. In the present paper we suggest an IV estimatorwhere the Hodrick-Prescott filtered trends are used as instruments forthe regressors...... in cointegrating regressions. These instruments are almost idealand simulations show that the IV estimator using such instruments alleviatethe endogeneity problem extremely well in both finite and large samples....

  12. Modeling text with generalizable Gaussian mixtures

    DEFF Research Database (Denmark)

    Hansen, Lars Kai; Sigurdsson, Sigurdur; Kolenda, Thomas


    We apply and discuss generalizable Gaussian mixture (GGM) models for text mining. The model automatically adapts model complexity for a given text representation. We show that the generalizability of these models depends on the dimensionality of the representation and the sample size. We discuss ...... the relation between supervised and unsupervised learning in the test data. Finally, we implement a novelty detector based on the density model....

  13. Efficient method of evaluation for Gaussian Hartree-Fock exchange operator for Gau-PBE functional. (United States)

    Song, Jong-Won; Hirao, Kimihiko


    We previously developed an efficient screened hybrid functional called Gaussian-Perdew-Burke-Ernzerhof (Gau-PBE) [Song et al., J. Chem. Phys. 135, 071103 (2011)] for large molecules and extended systems, which is characterized by the usage of a Gaussian function as a modified Coulomb potential for the Hartree-Fock (HF) exchange. We found that the adoption of a Gaussian HF exchange operator considerably decreases the calculation time cost of periodic systems while improving the reproducibility of the bandgaps of semiconductors. We present a distance-based screening scheme here that is tailored for the Gaussian HF exchange integral that utilizes multipole expansion for the Gaussian two-electron integrals. We found a new multipole screening scheme helps to save the time cost for the HF exchange integration by efficiently decreasing the number of integrals of, specifically, the near field region without incurring substantial changes in total energy. In our assessment on the periodic systems of seven semiconductors, the Gau-PBE hybrid functional with a new screening scheme has 1.56 times the time cost of a pure functional while the previous Gau-PBE was 1.84 times and HSE06 was 3.34 times.

  14. Image illumination enhancement with an objective no-reference measure of illumination assessment based on Gaussian distribution mapping

    Directory of Open Access Journals (Sweden)

    Gholamreza Anbarjafari


    Full Text Available Illumination problems have been an important concern in many image processing applications. The pattern of the histogram on an image introduces meaningful features; hence within the process of illumination enhancement, it is important not to destroy such information. In this paper we propose a method to enhance image illumination using Gaussian distribution mapping which also keeps the information laid on the pattern of the histogram on the original image. First a Gaussian distribution based on the mean and standard deviation of the input image will be calculated. Simultaneously a Gaussian distribution with the desired mean and standard deviation will be calculated. Then a cumulative distribution function of each of the Gaussian distributions will be calculated and used in order to map the old pixel value onto the new pixel value. Another important issue in the field of illumination enhancement is absence of a quantitative measure for the assessment of the illumination of an image. In this research work, a quantitative measure indicating the illumination state, i.e. contrast level and brightness of an image, is also proposed. The measure utilizes the estimated Gaussian distribution of the input image and the Kullback-Leibler Divergence (KLD between the estimated Gaussian and the desired Gaussian distributions to calculate the quantitative measure. The experimental results show the effectiveness and the reliability of the proposed illumination enhancement technique, as well as the proposed illumination assessment measure over conventional and state-of-the-art techniques.

  15. Resonant non-Gaussianity with equilateral properties

    International Nuclear Information System (INIS)

    Gwyn, Rhiannon; Rummel, Markus


    We discuss the effect of superimposing multiple sources of resonant non-Gaussianity, which arise for instance in models of axion inflation. The resulting sum of oscillating shape contributions can be used to ''Fourier synthesize'' different non-oscillating shapes in the bispectrum. As an example we reproduce an approximately equilateral shape from the superposition of O(10) oscillatory contributions with resonant shape. This implies a possible degeneracy between the equilateral-type non-Gaussianity typical of models with non-canonical kinetic terms, such as DBI inflation, and an equilateral-type shape arising from a superposition of resonant-type contributions in theories with canonical kinetic terms. The absence of oscillations in the 2-point function together with the structure of the resonant N-point functions, imply that detection of equilateral non-Gaussianity at a level greater than the PLANCK sensitivity of f NL ∝O(5) will rule out a resonant origin. We comment on the questions arising from possible embeddings of this idea in a string theory setting.

  16. Neutron inverse kinetics via Gaussian Processes

    International Nuclear Information System (INIS)

    Picca, Paolo; Furfaro, Roberto


    Highlights: ► A novel technique for the interpretation of experiments in ADS is presented. ► The technique is based on Bayesian regression, implemented via Gaussian Processes. ► GPs overcome the limits of classical methods, based on PK approximation. ► Results compares GPs and ANN performance, underlining similarities and differences. - Abstract: The paper introduces the application of Gaussian Processes (GPs) to determine the subcriticality level in accelerator-driven systems (ADSs) through the interpretation of pulsed experiment data. ADSs have peculiar kinetic properties due to their special core design. For this reason, classical – inversion techniques based on point kinetic (PK) generally fail to generate an accurate estimate of reactor subcriticality. Similarly to Artificial Neural Networks (ANNs), Gaussian Processes can be successfully trained to learn the underlying inverse neutron kinetic model and, as such, they are not limited to the model choice. Importantly, GPs are strongly rooted into the Bayes’ theorem which makes them a powerful tool for statistical inference. Here, GPs have been designed and trained on a set of kinetics models (e.g. point kinetics and multi-point kinetics) for homogeneous and heterogeneous settings. The results presented in the paper show that GPs are very efficient and accurate in predicting the reactivity for ADS-like systems. The variance computed via GPs may provide an indication on how to generate additional data as function of the desired accuracy.

  17. Resonant non-Gaussianity with equilateral properties

    Energy Technology Data Exchange (ETDEWEB)

    Gwyn, Rhiannon [Max-Planck-Institut fuer Gravitationsphysik (Albert-Einstein-Institut), Potsdam (Germany); Rummel, Markus [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Westphal, Alexander [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)


    We discuss the effect of superimposing multiple sources of resonant non-Gaussianity, which arise for instance in models of axion inflation. The resulting sum of oscillating shape contributions can be used to ''Fourier synthesize'' different non-oscillating shapes in the bispectrum. As an example we reproduce an approximately equilateral shape from the superposition of O(10) oscillatory contributions with resonant shape. This implies a possible degeneracy between the equilateral-type non-Gaussianity typical of models with non-canonical kinetic terms, such as DBI inflation, and an equilateral-type shape arising from a superposition of resonant-type contributions in theories with canonical kinetic terms. The absence of oscillations in the 2-point function together with the structure of the resonant N-point functions, imply that detection of equilateral non-Gaussianity at a level greater than the PLANCK sensitivity of f{sub NL} {proportional_to}O(5) will rule out a resonant origin. We comment on the questions arising from possible embeddings of this idea in a string theory setting.

  18. Gaussian Hypothesis Testing and Quantum Illumination. (United States)

    Wilde, Mark M; Tomamichel, Marco; Lloyd, Seth; Berta, Mario


    Quantum hypothesis testing is one of the most basic tasks in quantum information theory and has fundamental links with quantum communication and estimation theory. In this paper, we establish a formula that characterizes the decay rate of the minimal type-II error probability in a quantum hypothesis test of two Gaussian states given a fixed constraint on the type-I error probability. This formula is a direct function of the mean vectors and covariance matrices of the quantum Gaussian states in question. We give an application to quantum illumination, which is the task of determining whether there is a low-reflectivity object embedded in a target region with a bright thermal-noise bath. For the asymmetric-error setting, we find that a quantum illumination transmitter can achieve an error probability exponent stronger than a coherent-state transmitter of the same mean photon number, and furthermore, that it requires far fewer trials to do so. This occurs when the background thermal noise is either low or bright, which means that a quantum advantage is even easier to witness than in the symmetric-error setting because it occurs for a larger range of parameters. Going forward from here, we expect our formula to have applications in settings well beyond those considered in this paper, especially to quantum communication tasks involving quantum Gaussian channels.

  19. Persistent homology and non-Gaussianity (United States)

    Cole, Alex; Shiu, Gary


    In this paper, we introduce the topological persistence diagram as a statistic for Cosmic Microwave Background (CMB) temperature anisotropy maps. A central concept in 'Topological Data Analysis' (TDA), the idea of persistence is to represent a data set by a family of topological spaces. One then examines how long topological features 'persist' as the family of spaces is traversed. We compute persistence diagrams for simulated CMB temperature anisotropy maps featuring various levels of primordial non-Gaussianity of local type. Postponing the analysis of observational effects, we show that persistence diagrams are more sensitive to local non-Gaussianity than previous topological statistics including the genus and Betti number curves, and can constrain Δ fNLloc= 35.8 at the 68% confidence level on the simulation set, compared to Δ fNLloc= 60.6 for the Betti number curves. Given the resolution of our simulations, we expect applying persistence diagrams to observational data will give constraints competitive with those of the Minkowski Functionals. This is the first in a series of papers where we plan to apply TDA to different shapes of non-Gaussianity in the CMB and Large Scale Structure.

  20. Fixing convergence of Gaussian belief propagation

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Jason K [Los Alamos National Laboratory; Bickson, Danny [IBM RESEARCH LAB; Dolev, Danny [HEBREW UNIV


    Gaussian belief propagation (GaBP) is an iterative message-passing algorithm for inference in Gaussian graphical models. It is known that when GaBP converges it converges to the correct MAP estimate of the Gaussian random vector and simple sufficient conditions for its convergence have been established. In this paper we develop a double-loop algorithm for forcing convergence of GaBP. Our method computes the correct MAP estimate even in cases where standard GaBP would not have converged. We further extend this construction to compute least-squares solutions of over-constrained linear systems. We believe that our construction has numerous applications, since the GaBP algorithm is linked to solution of linear systems of equations, which is a fundamental problem in computer science and engineering. As a case study, we discuss the linear detection problem. We show that using our new construction, we are able to force convergence of Montanari's linear detection algorithm, in cases where it would originally fail. As a consequence, we are able to increase significantly the number of users that can transmit concurrently.

  1. Production and propagation of Hermite-sinusoidal-Gaussian laser beams. (United States)

    Tovar, A A; Casperson, L W


    Hermite-sinusoidal-Gaussian solutions to the wave equation have recently been obtained. In the limit of large Hermite-Gaussian beam size, the sinusoidal factors are dominant and reduce to the conventional modes of a rectangular waveguide. In the opposite limit the beams reduce to the familiar Hermite-Gaussian form. The propagation of these beams is examined in detail, and resonators are designed that will produce them. As an example, a special resonator is designed to produce hyperbolic-sine-Gaussian beams. This ring resonator contains a hyperbolic-cosine-Gaussian apodized aperture. The beam mode has finite energy and is perturbation stable.

  2. Detection of radiation deformation in crystalline polymers using the speckle photography technique

    International Nuclear Information System (INIS)

    El-Ghandoor, H.; Hashem, A.A.; Sharaf, F.


    In order to measure the resulting deformation due to gamma irradiation of polymers, a new optical technique, namely speckle-photography, was established and used. Thin films of tetrafluoroethene, with constant thickness were irradiated by different doses of gamma rays and the diffraction patterns of a laser beam passing through these films were recorded using the speckle photography technique. This technique has been applied to detect the radiation deformation in (Teflon) TFE, which is a crystalline polymer. A diffraction pattern due to the TFE thin layer is obtained and superimposed on the interference pattern displaying the speckle pattern pairs recorded on the same emulsion. (author)

  3. Single tracking location methods suppress speckle noise in shear wave velocity estimation. (United States)

    Elegbe, Etana C; McAleavey, Stephen A


    In ultrasound-based elastography methods, the estimation of shear wave velocity typically involves the tracking of speckle motion due to an applied force. The errors in the estimates of tissue displacement, and thus shear wave velocity, are generally attributed to electronic noise and decorrelation due to physical processes. We present our preliminary findings on another source of error, namely, speckle-induced bias in phase estimation. We find that methods that involve tracking in a single location, as opposed to multiple locations, are less sensitive to this source of error since the measurement is differential in nature and cancels out speckle-induced phase errors.

  4. Investigation of Portevin-Le Chatelier band with temporal phase analysis of speckle interferometry (United States)

    Jiang, Zhenyu; Zhang, Qingchuan; Wu, Xiaoping


    A new method combining temporal phase analysis with dynamic digital speckle pattern interferometry is proposed to study Portevin-Le Chatelier effect quantitatively. The principle bases on that the phase difference of interference speckle patterns is a time-dependent function related to the object deformation. The interference speckle patterns of specimen are recorded with high sampling rate while PLC effect occurs, and the 2D displacement map of PLC band and its width are obtained by analyzing the displacement of specimen with proposed method.

  5. A new optical pressure sensor interrogated by speckles pattern for oil industry (United States)

    Sperandio, Vinicius M.; Pontes, Maria J.; Neto, Anselmo F.; Webster, Lucas G.


    A new optical pressure control concept in petroleum industry based on laser speckle analysis, with inherent safety light, is investigated in this work. A plastic optical fiber (POF) utilized to instrument a conventional manometer enabled pressure monitoring of a system that is interrogated by speckle photography technique. Specklegrams were imaged on a CCD camera and then analyzed, after Mathematical Morphology Filter, regarding its movement. Tests demonstrated that the speckle pattern movement is radial towards the center of pressure and accordingly reverse during depressurization within 5% maximum error.

  6. Dynamics of laser speckle imaging of blood flow and morphological changes in tissues with a full time local ischemia of pancreas

    Directory of Open Access Journals (Sweden)

    Alexandrov D.A.


    Full Text Available The purpose: to establish influence of a full ischemia of different duration and the subsequent reperfusionon pathology development in pancreas of rats by means of laser speckle-visualization and lifetime digital microscopy. Materials and Methods. The work has been performed on 42 white rats of line Wistar in weight of 200-250 Research of properties of a blood-groove was made by means of methods laser Doppler flowmetry, digital biomicroscopy and a method of laser speckle-contrast visualization. Results. After the termination of a 5-minute full ischemia the speed of bloodflow has been increased in 2-3 times, clinic pancreatic necrosis is marked does not develop. After the termination of 20-minute full ischemia the increase in speed of a bloodflow did not occur, there were morphological and clinical signs of pancreatic necrosis. Conclusion, the efficiency of monitoring of microhemodynamics of pancreas in rats by the method of speckle-capillary of full field has been shown. Multidirectional phase of perfusion changes in pancreas have been revealed after reversible infringement of blood supply of different duration.

  7. Co-exposure to sunlight enhances the toxicity of naturally weathered Deepwater Horizon oil to early lifestage red drum (Sciaenops ocellatus) and speckled seatrout (Cynoscion nebulosus). (United States)

    Alloy, Matthew; Garner, Thomas Ross; Bridges, Kristin; Mansfield, Charles; Carney, Michael; Forth, Heather; Krasnec, Michelle; Lay, Claire; Takeshita, Ryan; Morris, Jeffrey; Bonnot, Shane; Oris, James; Roberts, Aaron


    The 2010 Deepwater Horizon oil spill resulted in the accidental release of millions of barrels of crude oil into the Gulf of Mexico. Photo-induced toxicity following co-exposure to ultraviolet (UV) radiation is 1 mechanism by which polycyclic aromatic hydrocarbons (PAHs) from oil spills may exert toxicity. Red drum and speckled seatrout are both important fishery resources in the Gulf of Mexico. They spawn near-shore and produce positively buoyant embryos that hatch into larvae in approximately 24 h. The goal of the present study was to determine whether exposure to UV as natural sunlight enhances the toxicity of crude oil to early lifestage red drum and speckled seatrout. Larval fish were exposed to several dilutions of high-energy water-accommodated fractions (HEWAFs) from 2 different oils collected in the field under chain of custody during the 2010 spill and 3 gradations of natural sunlight in a factorial design. Co-exposure to natural sunlight and oil significantly reduced larval survival compared with exposure to oil alone. Although both species were sensitive at PAH concentrations reported during the Deepwater Horizon spill, speckled seatrout demonstrated a greater sensitivity to photo-induced toxicity than red drum. These data demonstrate that even advanced weathering of slicks does not ameliorate the potential for photo-induced toxicity of oil to these species. Environ Toxicol Chem 2017;36:780-785. © 2016 SETAC. © 2016 SETAC.

  8. Fast and robust automatic calibration for single-shot dual-wavelength digital holography based on speckle displacements. (United States)

    Khodadad, Davood; Bergström, Per; Hällstig, Emil; Sjödahl, Mikael


    The objective of this paper is to describe a fast and robust automatic single-shot dual-wavelength holographic calibration method that can be used for online shape measurement applications. We present a model of the correction in two terms for each lobe, one to compensate the systematic errors caused by off-axis angles and the other for the curvature of the reference waves, respectively. Each hologram is calibrated independently without a need for an iterative procedure or information of the experimental set-up. The calibration parameters are extracted directly from speckle displacements between different reconstruction planes. The parameters can be defined as any fraction of a pixel to avoid the effect of quantization. Using the speckle displacements, problems associated with phase wrapping is avoided. The procedure is shown to give a shape accuracy of 34 μm using a synthetic wavelength of 1.1 mm for a measurement on a cylindrical test object with a trace over a field of view of 18  mm×18  mm.

  9. Imaging of nanoparticle-labeled stem cells using magnetomotive optical coherence tomography, laser speckle reflectometry, and light microscopy (United States)

    Cimalla, Peter; Werner, Theresa; Winkler, Kai; Mueller, Claudia; Wicht, Sebastian; Gaertner, Maria; Mehner, Mirko; Walther, Julia; Rellinghaus, Bernd; Wittig, Dierk; Karl, Mike O.; Ader, Marius; Funk, Richard H. W.; Koch, Edmund


    Cell transplantation and stem cell therapy are promising approaches for regenerative medicine and are of interest to researchers and clinicians worldwide. However, currently, no imaging technique that allows three-dimensional in vivo inspection of therapeutically administered cells in host tissues is available. Therefore, we investigate magnetomotive optical coherence tomography (MM-OCT) of cells labeled with magnetic particles as a potential noninvasive cell tracking method. We develop magnetomotive imaging of mesenchymal stem cells for future cell therapy monitoring. Cells were labeled with fluorescent iron oxide nanoparticles, embedded in tissue-mimicking agar scaffolds, and imaged using a microscope setup with an integrated MM-OCT probe. Magnetic particle-induced motion in response to a pulsed magnetic field of 0.2 T was successfully detected by OCT speckle variance analysis, and cross-sectional and volumetric OCT scans with highlighted labeled cells were obtained. In parallel, fluorescence microscopy and laser speckle reflectometry were applied as two-dimensional reference modalities to image particle distribution and magnetically induced motion inside the sample, respectively. All three optical imaging modalities were in good agreement with each other. Thus, magnetomotive imaging using iron oxide nanoparticles as cellular contrast agents is a potential technique for enhanced visualization of selected cells in OCT.

  10. Oscillator strength of impurity doped quantum dots: Influence of Gaussian white noise

    Energy Technology Data Exchange (ETDEWEB)

    Pal, Suvajit [Department of Chemistry, Hetampur Raj High School, Hetampur, Birbhum 731124, West Bengal (India); Ganguly, Jayanta [Department of Chemistry, Brahmankhanda Basapara High School, Basapara, Birbhum 731215, West Bengal (India); Saha, Surajit [Department of Chemistry, Bishnupur Ramananda College, Bishnupur, Bankura 722122, West Bengal (India); Ghosh, Manas, E-mail: [Department of Chemistry, Physical Chemistry Section, Visva Bharati University, Santiniketan, Birbhum 731 235, West Bengal (India)


    We make a rigorous analysis of profiles of oscillator strength of a doped quantum dot in the presence and absence of noise. The noise employed here is a Gaussian white noise. The quantum dot is doped with repulsive Gaussian impurity. Noise has been administered additively and multiplicatively to the system. A perpendicular magnetic field is also present and a static external electric field has been applied. Profile of OS has been minutely monitored with variation of several important quantities such as confinement energy, electric field strength, dopant location, magnetic field strength, dopant potential, noise strength, Al concentration, and mode of application of noise. The profiles are enriched with significant subtleties and often reveal enhancement and maximization of oscillator strength in the presence of noise. These observations are indeed useful in the study of linear and nonlinear optical properties of doped QD systems which bear sufficient technological importance.

  11. Segmentation of Rumex obtusifolius using Gaussian Markov random fields

    NARCIS (Netherlands)

    Atni Hiremath, S.; Tolpekin, V.A.; Heijden, van der G.; Stein, A.


    Rumex obtusifolius is a common weed that is difficult to control. The most common way to control weeds-using herbicides-is being reconsidered because of its adverse environmental impact. Robotic systems are regarded as a viable non-chemical alternative for treating R. obtusifolius and also other

  12. High-Order Local Pooling and Encoding Gaussians Over a Dictionary of Gaussians. (United States)

    Li, Peihua; Zeng, Hui; Wang, Qilong; Shiu, Simon C K; Zhang, Lei


    Local pooling (LP) in configuration (feature) space proposed by Boureau et al. explicitly restricts similar features to be aggregated, which can preserve as much discriminative information as possible. At the time it appeared, this method combined with sparse coding achieved competitive classification results with only a small dictionary. However, its performance lags far behind the state-of-the-art results as only the zero-order information is exploited. Inspired by the success of high-order statistical information in existing advanced feature coding or pooling methods, we make an attempt to address the limitation of LP. To this end, we present a novel method called high-order LP (HO-LP) to leverage the information higher than the zero-order one. Our idea is intuitively simple: we compute the first- and second-order statistics per configuration bin and model them as a Gaussian. Accordingly, we employ a collection of Gaussians as visual words to represent the universal probability distribution of features from all classes. Our problem is naturally formulated as encoding Gaussians over a dictionary of Gaussians as visual words. This problem, however, is challenging since the space of Gaussians is not a Euclidean space but forms a Riemannian manifold. We address this challenge by mapping Gaussians into the Euclidean space, which enables us to perform coding with common Euclidean operations rather than complex and often expensive Riemannian operations. Our HO-LP preserves the advantages of the original LP: pooling only similar features and using a small dictionary. Meanwhile, it achieves very promising performance on standard benchmarks, with either conventional, hand-engineered features or deep learning-based features.

  13. Closed form formula for Mie scattering of nonparaxial analogues of Gaussian beams. (United States)

    Moore, Nicole J; Alonso, Miguel A


    A closed form formula is found for the Mie scattering coefficients of incident complex focus beams (which are a nonparaxial generalization of Gaussian beams) with any numerical aperture. This formula takes the compact form of multipoles evaluated at a single complex point. Included are the cases of incident scalar fields as well as electromagnetic fields with many polarizations, such as linear, circular, azimuthal and radial. Examples of incident radially and azimuthally polarized beams are presented.

  14. Beam conditions for radiation generated by an electromagnetic Gaussian Schell-model source. (United States)

    Korotkova, Olga; Salem, Mohamed; Wolf, Emil


    It was shown recently that the basic properties of a fluctuating electromagnetic beam can be derived from knowledge of a 2 x 2 cross-spectral density matrix of the electric field in the source plane. However, not every such matrix represents a source that will generate a beamlike field. We derive conditions that the matrix must satisfy for the source to generate an electromagnetic Gaussian Schell-model beam.

  15. Calculating emittance for Gaussian and Non-Gaussian distributions by the method of correlations for slits

    International Nuclear Information System (INIS)

    Tan, Cheng-Yang; Fermilab


    One common way for measuring the emittance of an electron beam is with the slits method. The usual approach for analyzing the data is to calculate an emittance that is a subset of the parent emittance. This paper shows an alternative way by using the method of correlations which ties the parameters derived from the beamlets to the actual parameters of the parent emittance. For parent distributions that are Gaussian, this method yields exact results. For non-Gaussian beam distributions, this method yields an effective emittance that can serve as a yardstick for emittance comparisons

  16. Stochastic differential calculus for Gaussian and non-Gaussian noises: A critical review (United States)

    Falsone, G.


    In this paper a review of the literature works devoted to the study of stochastic differential equations (SDEs) subjected to Gaussian and non-Gaussian white noises and to fractional Brownian noises is given. In these cases, particular attention must be paid in treating the SDEs because the classical rules of the differential calculus, as the Newton-Leibnitz one, cannot be applied or are applicable with many difficulties. Here all the principal approaches solving the SDEs are reported for any kind of noise, highlighting the negative and positive properties of each one and making the comparisons, where it is possible.

  17. Evaluation of detectable defect size for inner defect of pressure vessel using laser speckle

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyeoung Suk; Seon, Sang Woo; Choi, Tae Ho; Kang, Chan Geun; Na, Man Gyun; Jung, Hyun Chul [Chsoun University, Gwangju (Korea, Republic of)


    Pressure vessels are used in various industrial fields. If a defect occurs on the inner or outer surface of a pressure vessel, it may cause a massive accident. A defect on the outer surface can be detected by visual inspection. However, a defect on the inner surface is generally impossible to detect with visual inspection. Nondestructive testing can be used to detect this type of defect. Laser speckle shearing interferometry is one nondestructive testing method that can optically detect a defect; its advantages include noncontact, full field, and real time inspection. This study evaluated the detectable size for an internal defect of a pressure vessel. The material of the pressure vessel was ASTM A53 Gr.B. The internal defect was detected when the pressure vessel was loaded by internal pressure controlled by a pneumatic system. The internal pressure was controlled from 0.2 MPa to 0.6 MPa in increments of 0.2 MPa. The results confirmed that an internal defect with a 25 % defect depth could be detected even at 0.2 MPa pressure variation.

  18. Investigation of Rock Failure Pattern in Creep by Digital Speckle Correlation Method

    Directory of Open Access Journals (Sweden)

    Yunliang Tan


    Full Text Available In order to study the mechanical characteristics from creep deformation to failure of rock, the tests of uniaxial compression and pushing steel-plate anchored in rock were performed, by using RLJW-2000 servo test synchronizing with Digital Speckle Correlation Method (DSCM. The investigations showed that for a uniaxial compressive specimen, when load arrived at 0.5σc, displacement clusters orderly formed, which was ahead of the macrocreep strain occurring in a slight jump mode when load arrived at 0.7σc. When the load level arrived at 0.8σc, displacement clusters gathered to be a narrow band. After that, the specimen abruptly fractured in a shear mode. In the creep pushing steel-plate test, when pushing force arrived at 25 kN, crack began to occur, the horizontal displacement field as well as shear strain field concentrated continuously along the interface between steel-plate and rock, and a new narrow concentrating band gathered in the upper layer. When pushing force arrived at 27.5 kN, another new narrow shear deformation band formed in the lower layer. Then, the steel-plate was pushed out quickly accompanying strong creep deformation.

  19. Uncloaking diffusive-light invisibility cloaks by speckle analysis. (United States)

    Niemeyer, Andreas; Mayer, Frederik; Naber, Andreas; Koirala, Milan; Yamilov, Alexey; Wegener, Martin


    Within the range of validity of the stationary diffusion equation, an ideal diffusive-light invisibility cloak can make an arbitrary macroscopic object hidden inside of the cloak indistinguishable from the surroundings for all colors, polarizations, and directions of incident visible light. However, the diffusion equation for light is an approximation which becomes exact only in the limit of small coherence length. Thus, one expects that the cloak can be revealed by illumination with coherent light. The experiments presented here show that the cloaks are robust in the limit of large coherence length but can be revealed by analysis of the speckle patterns under illumination with partially coherent light. Experiments on cylindrical core-shell cloaks and corresponding theory are in good agreement.

  20. Angular diameters of Magellanic Cloud plantary nebulae. I. Speckle interferometry

    International Nuclear Information System (INIS)

    Wood, P.R.; Bessell, M.S.; Dopita, M.A.


    Speckle interferometric angular diameters of Magellanic Cloud planetary nebulae are presented. The mass of ionized gas in each nebula has been derived from the angular diameter and published H-beta line fluxes; the derives masses range from less than 0.006 to more than 0.19 solar mass. The planetary nebulae observed were the brightest in the Magellanic Clouds; consequently, they are all relatively small, young, bright, and dense. They are almost certainly only partially ionized, so that the masses derived for the ionized parts of the nebula are lower limits to the total nebula mass. The properties of the Magellanic Cloud nebulae are compared with those of planetary nebulae at the galactic center. 27 references

  1. Speckle reduction via higher order total variation approach. (United States)

    Wensen Feng; Hong Lei; Yang Gao


    Multiplicative noise (also known as speckle) reduction is a prerequisite for many image-processing tasks in coherent imaging systems, such as the synthetic aperture radar. One approach extensively used in this area is based on total variation (TV) regularization, which can recover significantly sharp edges of an image, but suffers from the staircase-like artifacts. In order to overcome the undesirable deficiency, we propose two novel models for removing multiplicative noise based on total generalized variation (TGV) penalty. The TGV regularization has been mathematically proven to be able to eliminate the staircasing artifacts by being aware of higher order smoothness. Furthermore, an efficient algorithm is developed for solving the TGV-based optimization problems. Numerical experiments demonstrate that our proposed methods achieve state-of-the-art results, both visually and quantitatively. In particular, when the image has some higher order smoothness, our methods outperform the TV-based algorithms.

  2. Surface Roughness Measurement on a Wing Aircraft by Speckle Correlation

    Directory of Open Access Journals (Sweden)

    Alberto Barrientos


    Full Text Available The study of the damage of aeronautical materials is important because it may change the microscopic surface structure profiles. The modification of geometrical surface properties can cause small instabilities and then a displacement of the boundary layer. One of the irregularities we can often find is surface roughness. Due to an increase of roughness and other effects, there may be extra momentum losses in the boundary layer and a modification in the parasite drag. In this paper we present a speckle method for measuring the surface roughness on an actual unmanned aircraft wing. The results show an inhomogeneous roughness distribution on the wing, as expected according to the anisotropic influence of the winds over the entire wing geometry. A calculation of the uncertainty of the technique is given.

  3. Surface roughness measurement on a wing aircraft by speckle correlation. (United States)

    Salazar, Félix; Barrientos, Alberto


    The study of the damage of aeronautical materials is important because it may change the microscopic surface structure profiles. The modification of geometrical surface properties can cause small instabilities and then a displacement of the boundary layer. One of the irregularities we can often find is surface roughness. Due to an increase of roughness and other effects, there may be extra momentum losses in the boundary layer and a modification in the parasite drag. In this paper we present a speckle method for measuring the surface roughness on an actual unmanned aircraft wing. The results show an inhomogeneous roughness distribution on the wing, as expected according to the anisotropic influence of the winds over the entire wing geometry. A calculation of the uncertainty of the technique is given.

  4. Modelling and control of dynamic systems using gaussian process models

    CERN Document Server

    Kocijan, Juš


    This monograph opens up new horizons for engineers and researchers in academia and in industry dealing with or interested in new developments in the field of system identification and control. It emphasizes guidelines for working solutions and practical advice for their implementation rather than the theoretical background of Gaussian process (GP) models. The book demonstrates the potential of this recent development in probabilistic machine-learning methods and gives the reader an intuitive understanding of the topic. The current state of the art is treated along with possible future directions for research. Systems control design relies on mathematical models and these may be developed from measurement data. This process of system identification, when based on GP models, can play an integral part of control design in data-based control and its description as such is an essential aspect of the text. The background of GP regression is introduced first with system identification and incorporation of prior know...

  5. Primordial perturbations and non-Gaussianities from modulated trapping

    International Nuclear Information System (INIS)

    Langlois, David; Sorbo, Lorenzo


    We propose a new mechanism to generate primordial curvature perturbations, based on the resonant production of particles during inflation. It is known that this phenomenon can trap the inflaton for a fraction of e-fold. This effect is governed by the mass of the produced particles and by their coupling to the inflaton, parameters which can depend on the expectation value of other fields. If one of such additional fields—a modulaton—is light, then its fluctuations, acquired during the earlier stages of inflation, will induce a spatial modulation of the trapping, and thus of the end of inflation, corresponding to a curvature perturbation. We calculate the power spectrum, bispectrum and trispectrum of the curvature perturbations generated by this mechanism, taking into account the perturbations due to the inflaton fluctuations as well. We find that modulated trapping could provide the main contribution to the observed power spectrum and lead to detectable primordial non-gaussianities

  6. Lifting primordial non-Gaussianity above the noise

    International Nuclear Information System (INIS)

    Welling, Yvette; Woude, Drian van der; Pajer, Enrico


    Primordial non-Gaussianity (PNG) in Large Scale Structures is obfuscated by the many additional sources of non-linearity. Within the Effective Field Theory approach to Standard Perturbation Theory, we show that matter non-linearities in the bispectrum can be modeled sufficiently well to strengthen current bounds with near future surveys, such as Euclid. We find that the EFT corrections are crucial to this improvement in sensitivity. Yet, our understanding of non-linearities is still insufficient to reach important theoretical benchmarks for equilateral PNG, while, for local PNG, our forecast is more optimistic. We consistently account for the theoretical error intrinsic to the perturbative approach and discuss the details of its implementation in Fisher forecasts.

  7. Optimization of Vehicular Trajectories under Gaussian Noise Disturbances

    Directory of Open Access Journals (Sweden)

    Joan Garcia-Haro


    Full Text Available Nowadays, research on Vehicular Technology aims at automating every single mechanical element of vehicles, in order to increase passengers’ safety, reduce human driving intervention and provide entertainment services on board. Automatic trajectory tracing for vehicles under especially risky circumstances is a field of research that is currently gaining enormous attention. In this paper, we show some results on how to develop useful policies to execute maneuvers by a vehicle at high speeds with the mathematical optimization of some already established mobility conditions of the car. We also study how the presence of Gaussian noise on measurement sensors while maneuvering can disturb motion and affect the final trajectories. Different performance criteria for the optimization of such maneuvers are presented, and an analysis is shown on how path deviations can be minimized by using trajectory smoothing techniques like the Kalman Filter. We finalize the paper with a discussion on how communications can be used to implement these schemes.

  8. Evaluation and Correction for Optical Scattering Variations in Laser Speckle Rheology of Biological Fluids (United States)

    Hajjarian, Zeinab; Nadkarni, Seemantini K.


    Biological fluids fulfill key functionalities such as hydrating, protecting, and nourishing cells and tissues in various organ systems. They are capable of these versatile tasks owing to their distinct structural and viscoelastic properties. Characterizing the viscoelastic properties of bio-fluids is of pivotal importance for monitoring the development of certain pathologies as well as engineering synthetic replacements. Laser Speckle Rheology (LSR) is a novel optical technology that enables mechanical evaluation of tissue. In LSR, a coherent laser beam illuminates the tissue and temporal speckle intensity fluctuations are analyzed to evaluate mechanical properties. The rate of temporal speckle fluctuations is, however, influenced by both optical and mechanical properties of tissue. Therefore, in this paper, we develop and validate an approach to estimate and compensate for the contributions of light scattering to speckle dynamics and demonstrate the capability of LSR for the accurate extraction of viscoelastic moduli in phantom samples and biological fluids of varying optical and mechanical properties. PMID:23705028


    Energy Technology Data Exchange (ETDEWEB)

    Horch, Elliott P.; Bahi, Lizzie Anne P.; Gaulin, Joseph R. [Department of Physics, Southern Connecticut State University, 501 Crescent Street, New Haven, CT 06515 (United States); Howell, Steve B. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Sherry, William H. [National Optical Astronomy Observatories, 950 North Cherry Avenue, Tucson, AZ 87719 (United States); Baena Galle, Roberto [Observatori Fabra, Reial Academia de Ciencies i Arts de Barcelona, Cami de l' Observatori s/n, E-08002 Barcelona (Spain); Van Altena, William F., E-mail:, E-mail:, E-mail:, E-mail:, E-mail:, E-mail:, E-mail: [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520 (United States)


    Five hundred thirty-one speckle measures of binary stars are reported. These data were taken mainly during the period 2008 June through 2009 October at the WIYN 3.5 m Telescope at Kitt Peak and represent the last data set of single-filter speckle observations taken in the WIYN speckle program prior to the use of the current two-channel speckle camera. The astrometric and photometric precision of these observations is consistent with previous papers in this series: we obtain a typical linear measurement uncertainty of approximately 2.5 mas, and the magnitude differences reported have typical uncertainties in the range of 0.1-0.14 mag. In combination with measures already in the literature, the data presented here permit the revision of the orbit of A 1634AB (= HIP 76041) and the first determination of visual orbital elements for HDS 1895 (= HIP 65982).


    Directory of Open Access Journals (Sweden)

    E.S. Samundeeswari


    Full Text Available Breast cancer, commonly found in women is a serious life threatening disease due to its invasive nature. Ultrasound (US imaging method plays an effective role in screening early detection and diagnosis of Breast cancer. Speckle noise generally affects medical ultrasound images and also causes a number of difficulties in identifying the Region of Interest. Suppressing speckle noise is a challenging task as it destroys fine edge details. No specific filter is designed yet to get a noise free BUS image that is contaminated by speckle noise. In this paper M2 filter, a novel hybrid of linear and nonlinear filter is proposed and compared to other spatial filters with 3×3 kernel size. The performance of the proposed M2 filter is measured by statistical quantity parameters like MSE, PSNR and SSI. The experimental analysis clearly shows that the proposed M2 filter outperforms better than other spatial filters by 2% high PSNR values with regards to speckle suppression.

  11. Speckle-based three-dimensional velocity measurement using spatial filtering velocimetry

    DEFF Research Database (Denmark)

    Iversen, Theis Faber Quist; Jakobsen, Michael Linde; Hanson, Steen Grüner


    We present an optical method for measuring the real-time three-dimensional (3D) translational velocity of a diffusely scattering rigid object observed through an imaging system. The method is based on a combination of the motion of random speckle patterns and regular fringe patterns. The speckle ...... spatial filters designed to measure the three components of the object’s translational velocity. Furthermore, experimental data are presented that demonstrate full 3D velocity measurement.......We present an optical method for measuring the real-time three-dimensional (3D) translational velocity of a diffusely scattering rigid object observed through an imaging system. The method is based on a combination of the motion of random speckle patterns and regular fringe patterns. The speckle...

  12. Software phantom with realistic speckle modeling for validation of image analysis methods in echocardiography (United States)

    Law, Yuen C.; Tenbrinck, Daniel; Jiang, Xiaoyi; Kuhlen, Torsten


    Computer-assisted processing and interpretation of medical ultrasound images is one of the most challenging tasks within image analysis. Physical phenomena in ultrasonographic images, e.g., the characteristic speckle noise and shadowing effects, make the majority of standard methods from image analysis non optimal. Furthermore, validation of adapted computer vision methods proves to be difficult due to missing ground truth information. There is no widely accepted software phantom in the community and existing software phantoms are not exible enough to support the use of specific speckle models for different tissue types, e.g., muscle and fat tissue. In this work we propose an anatomical software phantom with a realistic speckle pattern simulation to _ll this gap and provide a exible tool for validation purposes in medical ultrasound image analysis. We discuss the generation of speckle patterns and perform statistical analysis of the simulated textures to obtain quantitative measures of the realism and accuracy regarding the resulting textures.

  13. Speckle tracking evaluation of right ventricular functions in children with sickle cell disease

    Directory of Open Access Journals (Sweden)

    Osama Abd Rab Elrasol Tolba


    Conclusions: Children with SCD have impaired right ventricular systolic and diastolic functions when compared to healthy children with early evaluation of the systolic dysfunction by speckle tracking imaging technique.

  14. Speeding up 3D speckle tracking using PatchMatch (United States)

    Zontak, Maria; O'Donnell, Matthew


    Echocardiography provides valuable information to diagnose heart dysfunction. A typical exam records several minutes of real-time cardiac images. To enable complete analysis of 3D cardiac strains, 4-D (3-D+t) echocardiography is used. This results in a huge dataset and requires effective automated analysis. Ultrasound speckle tracking is an effective method for tissue motion analysis. It involves correlation of a 3D kernel (block) around a voxel with kernels in later frames. The search region is usually confined to a local neighborhood, due to biomechanical and computational constraints. For high strains and moderate frame-rates, however, this search region will remain large, leading to a considerable computational burden. Moreover, speckle decorrelation (due to high strains) leads to errors in tracking. To solve this, spatial motion coherency between adjacent voxels should be imposed, e.g., by averaging their correlation functions.1 This requires storing correlation functions for neighboring voxels, thus increasing memory demands. In this work, we propose an efficient search using PatchMatch, 2 a powerful method to find correspondences between images. Here we adopt PatchMatch for 3D volumes and radio-frequency signals. As opposed to an exact search, PatchMatch performs random sampling of the search region and propagates successive matches among neighboring voxels. We show that: 1) Inherently smooth offset propagation in PatchMatch contributes to spatial motion coherence without any additional processing or memory demand. 2) For typical scenarios, PatchMatch is at least 20 times faster than the exact search, while maintaining comparable tracking accuracy.

  15. Humanoid environmental perception with Gaussian process regression

    Directory of Open Access Journals (Sweden)

    Dingsheng Luo


    Full Text Available Nowadays, humanoids are increasingly expected acting in the real world to complete some high-level tasks humanly and intelligently. However, this is a hard issue due to that the real world is always extremely complicated and full of miscellaneous variations. As a consequence, for a real-world-acting robot, precisely perceiving the environmental changes might be an essential premise. Unlike human being, humanoid robot usually turns out to be with much less sensors to get enough information from the real world, which further leads the environmental perception problem to be more challenging. Although it can be tackled by establishing direct sensory mappings or adopting probabilistic filtering methods, the nonlinearity and uncertainty caused by both the complexity of the environment and the high degree of freedom of the robots will result in tough modeling difficulties. In our study, with the Gaussian process regression framework, an alternative learning approach to address such a modeling problem is proposed and discussed. Meanwhile, to debase the influence derived from limited sensors, the idea of fusing multiple sensory information is also involved. To evaluate the effectiveness, with two representative environment changing tasks, that is, suffering unknown external pushing and suddenly encountering sloped terrains, the proposed approach is applied to a humanoid, which is only equipped with a three-axis gyroscope and a three-axis accelerometer. Experimental results reveal that the proposed Gaussian process regression-based approach is effective in coping with the nonlinearity and uncertainty of the humanoid environmental perception problem. Further, a humanoid balancing controller is developed, which takes the output of the Gaussian process regression-based environmental perception as the seed to activate the corresponding balancing strategy. Both simulated and hardware experiments consistently show that our approach is valuable and leads to a

  16. Modulated reheating and large non-gaussianity in string cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Cicoli, M.; Quevedo, F. [Abdus Salam ICTP, Strada Costiera 11, Trieste 34014 (Italy); Tasinato, G. [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Portsmouth, PO1 3FX (United Kingdom); Zavala, I. [Centre for Theoretical Physics, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands); Burgess, C.P., E-mail:, E-mail:, E-mail:, E-mail:, E-mail: [Department of Physics and Astronomy, McMaster University, Hamilton ON (Canada)


    A generic feature of the known string inflationary models is that the same physics that makes the inflaton lighter than the Hubble scale during inflation often also makes other scalars this light. These scalars can acquire isocurvature fluctuations during inflation, and given that their VEVs determine the mass spectrum and the coupling constants of the effective low-energy field theory, these fluctuations give rise to couplings and masses that are modulated from one Hubble patch to another. These seem just what is required to obtain primordial adiabatic fluctuations through conversion into density perturbations through the 'modulation mechanism', wherein reheating takes place with different efficiency in different regions of our Universe. Fluctuations generated in this way can generically produce non-gaussianity larger than obtained in single-field slow-roll inflation; potentially observable in the near future. We provide here the first explicit example of the modulation mechanism at work in string cosmology, within the framework of LARGE Volume Type-IIB string flux compactifications. The inflationary dynamics involves two light Kähler moduli: a fibre divisor plays the rôle of the inflaton whose decay rate to visible sector degrees of freedom is modulated by the primordial fluctuations of a blow-up mode (which is made light by the use of poly-instanton corrections). We find the challenges of embedding the mechanism into a concrete UV completion constrains the properties of the non-gaussianity that is found, since for generic values of the underlying parameters, the model predicts a local bi-spectrum with f{sub NL} of order 'a few'. However, a moderate tuning of the parameters gives also rise to explicit examples with f{sub NL} ∼ O(20) potentially observable by the Planck satellite.

  17. Entanglement rate for Gaussian continuous variable beams (United States)

    Jiao Deng, Zhi; Habraken, Steven J. M.; Marquardt, Florian


    We derive a general expression that quantifies the total entanglement production rate in continuous variable systems, where a source emits two entangled Gaussian beams with arbitrary correlators. This expression is especially useful for situations where the source emits an arbitrary frequency spectrum, e.g. when cavities are involved. To exemplify its meaning and potential, we apply it to a four-mode optomechanical setup that enables the simultaneous up- and down-conversion of photons from a drive laser into entangled photon pairs. This setup is efficient in that both the drive and the optomechanical up- and down-conversion can be fully resonant.

  18. Non-Gaussianity from Broken Symmetries

    CERN Document Server

    Kolb, Edward W; Vallinotto, A; Kolb, Edward W.; Riotto, Antonio; Vallinotto, Alberto


    Recently we studied inflation models in which the inflaton potential is characterized by an underlying approximate global symmetry. In the first work we pointed out that in such a model curvature perturbations are generated after the end of the slow-roll phase of inflation. In this work we develop further the observational implications of the model and compute the degree of non-Gaussianity predicted in the scenario. We find that the corresponding nonlinearity parameter, $f_{NL}$, can be as large as 10^2.

  19. Ripple Tank Demonstration of Gaussian Beam Propagation (United States)

    Jude, Kathy J.; Wilson, Thomas E.


    We have reproduced a ripple tank experimentfootnote 'Ripple Tank Studies of Wave Motion' by W. Llowarch (Oxford University Press, 1961) in order to illustrate the effects of focusing and diffraction of a capillary planewave by a bi-convex carbon tetrachloride 'lens'. We compare the experimental results, captured by a video camera, to the theoretical results obtained using the ABCD matrix method for the gaussian beam propagation through this paraxial 'optical' systemfootnote 'Lasers' by Anthony Siegman (University Science Book, Mill Valley, CA, 1986). The diffraction-limited focusing of the propagating wave is clearly visible; this is a feature not easily demonstrable in optics.

  20. Return probability: Exponential versus Gaussian decay

    Energy Technology Data Exchange (ETDEWEB)

    Izrailev, F.M. [Instituto de Fisica, BUAP, Apdo. Postal J-48, 72570 Puebla (Mexico)]. E-mail:; Castaneda-Mendoza, A. [Instituto de Fisica, BUAP, Apdo. Postal J-48, 72570 Puebla (Mexico)


    We analyze, both analytically and numerically, the time-dependence of the return probability in closed systems of interacting particles. Main attention is paid to the interplay between two regimes, one of which is characterized by the Gaussian decay of the return probability, and another one is the well-known regime of the exponential decay. Our analytical estimates are confirmed by the numerical data obtained for two models with random interaction. In view of these results, we also briefly discuss the dynamical model which was recently proposed for the implementation of a quantum computation.

  1. Optical trapping with Super-Gaussian beams

    CSIR Research Space (South Africa)



    Full Text Available stream_source_info McLaren1_2013.pdf.txt stream_content_type text/plain stream_size 2236 Content-Encoding UTF-8 stream_name McLaren1_2013.pdf.txt Content-Type text/plain; charset=UTF-8 JT2A.34.pdf Optics in the Life... Sciences Congress Technical Digest © 2013 The Optical Society (OSA) Optical trapping with Super-Gaussian beams Melanie McLaren, Thulile Khanyile, Patience Mthunzi and Andrew Forbes* National Laser Centre, Council for Scientific and Industrial Research...

  2. Holographic interferometry and laser speckle photography as aids to assessment of pressurized components

    International Nuclear Information System (INIS)

    Martin, D.J.V.


    This paper gives details of the defect detection holographic technique and describes laser speckle photography to evaluate in phase movement and strain in pressurized components. The new fibre optic technique and system appraisal is included. The holographic tests show that it is possible to detect on the outside of tubes defects in the bore approximately 10% of thickness deep. Speckle photography gives object lateral movement, direction and strain. (Auth.)

  3. Potential of the McMath-Pierce 1.6-Meter Solar Telescope for Speckle Interferometry (United States)

    Harshaw, Richard; Jones, Gregory; Wiley, Edward; Boyce, Patrick; Branston, Detrick; Rowe, David; Genet, Russell


    We explored the aiming and tracking accuracy of the McMath-Pierce 1.6 m solar telescope at Kitt Peak National Observatory as part of an investigation of using this telescope for speckle interferometry of close visual double stars. Several slews of various lengths looked for hysteresis in the positioning system (we found none of significance) and concluded that the 1.6 m telescope would make a useful telescope for speckle interferometry.

  4. Single Tracking Location Methods Suppress Speckle Noise in Shear Wave Velocity Estimation


    Elegbe, Etana C.; McAleavey, Stephen A.


    In ultrasound-based elastography methods, the estimation of shear wave velocity typically involves the tracking of speckle motion due to an applied force. The errors in the estimates of tissue displacement, and thus shear wave velocity, are generally attributed to electronic noise and decorrelation due to physical processes. We present our preliminary findings on another source of error, namely, speckle-induced bias in phase estimation. We find that methods that involve tracking in a single l...

  5. Estimation of vessel diameter and blood flow dynamics from laser speckle images

    DEFF Research Database (Denmark)

    Postnov, Dmitry D.; Tuchin, Valery V.; Sosnovtseva, Olga


    Laser speckle imaging is a rapidly developing method to study changes of blood velocity in the vascular networks. However, to assess blood flow and vascular responses it is crucial to measure vessel diameter in addition to blood velocity dynamics. We suggest an algorithm that allows for dynamical...... masking of a vessel position and measurements of it's diameter from laser speckle images. This approach demonstrates high reliability and stability....

  6. Simultaneous Gaussian and exponential inversion for improved analysis of shales by NMR relaxometry (United States)

    Washburn, Kathryn E.; Anderssen, Endre; Vogt, Sarah J.; Seymour, Joseph D.; Birdwell, Justin E.; Kirkland, Catherine M.; Codd, Sarah L.


    Nuclear magnetic resonance (NMR) relaxometry is commonly used to provide lithology-independent porosity and pore-size estimates for petroleum resource evaluation based on fluid-phase signals. However in shales, substantial hydrogen content is associated with solid and fluid signals and both may be detected. Depending on the motional regime, the signal from the solids may be best described using either exponential or Gaussian decay functions. When the inverse Laplace transform, the standard method for analysis of NMR relaxometry results, is applied to data containing Gaussian decays, this can lead to physically unrealistic responses such as signal or porosity overcall and relaxation times that are too short to be determined using the applied instrument settings. We apply a new simultaneous Gaussian-Exponential (SGE) inversion method to simulated data and measured results obtained on a variety of oil shale samples. The SGE inversion produces more physically realistic results than the inverse Laplace transform and displays more consistent relaxation behavior at high magnetic field strengths. Residuals for the SGE inversion are consistently lower than for the inverse Laplace method and signal overcall at short T2 times is mitigated. Beyond geological samples, the method can also be applied in other fields where the sample relaxation consists of both Gaussian and exponential decays, for example in material, medical and food sciences.

  7. Simultaneous Gaussian and exponential inversion for improved analysis of shales by NMR relaxometry (United States)

    Washburn, Kathryn E.; Anderssen, Endre; Vogt, Sarah J.; Seymour, Joseph D.; Birdwell, Justin E.; Kirkland, Catherine M.; Codd, Sarah L.


    Nuclear magnetic resonance (NMR) relaxometry is commonly used to provide lithology-independent porosity and pore-size estimates for petroleum resource evaluation based on fluid-phase signals. However in shales, substantial hydrogen content is associated with solid and fluid signals and both may be detected. Depending on the motional regime, the signal from the solids may be best described using either exponential or Gaussian decay functions. When the inverse Laplace transform, the standard method for analysis of NMR relaxometry results, is applied to data containing Gaussian decays, this can lead to physically unrealistic responses such as signal or porosity overcall and relaxation times that are too short to be determined using the applied instrument settings. We apply a new simultaneous Gaussian-Exponential (SGE) inversion method to simulated data and measured results obtained on a variety of oil shale samples. The SGE inversion produces more physically realistic results than the inverse Laplace transform and displays more consistent relaxation behavior at high magnetic field strengths. Residuals for the SGE inversion are consistently lower than for the inverse Laplace method and signal overcall at short T2 times is mitigated. Beyond geological samples, the method can also be applied in other fields where the sample relaxation consists of both Gaussian and exponential decays, for example in material, medical and food sciences.

  8. Developing and setting up optical methods to study the speckle patterns created by optical beam smoothing

    International Nuclear Information System (INIS)

    Surville, J.


    We have developed three main optical methods to study the speckles generated by a smoothed laser source. The first method addresses the measurement of the temporal and spatial correlation functions of the source, with a modified Michelson interferometer. The second one is a pump-probe technique created to shoot a picture of a speckle pattern generated at a set time. And the third one is an evolution of the second method dedicated to time-frequency coding, thanks to a frequency chirped probe pulse. Thus, the speckles can be followed in time and their motion can be described. According to these three methods, the average size and duration of the speckles can be measured. It is also possible to measure the size and the duration of each of them and mostly their velocity in a given direction. All the results obtained have been confronted to the different existing theories. We show that the statistical distributions of the measured speckles'size and speckles'intensity agree satisfactorily with theoretical values

  9. Inflation with multiple sound speeds: A model of multiple DBI type actions and non-Gaussianities

    International Nuclear Information System (INIS)

    Cai Yifu; Xia Haiying


    In this Letter we study adiabatic and isocurvature perturbations in the frame of inflation with multiple sound speeds involved. We suggest this scenario can be realized by a number of generalized scalar fields with arbitrary kinetic forms. These scalars have their own sound speeds respectively, so the propagations of field fluctuations are individual. Specifically, we study a model constructed by two DBI type actions. We find that the critical length scale for the freezing of perturbations corresponds to the maximum sound horizon. Moreover, if the mass term of one field is much lighter than that of the other, the entropy perturbation could be quite large and so may give rise to a growth outside sound horizon. At cubic order, we find that the non-Gaussianity of local type is possibly large when entropy perturbations are able to convert into curvature perturbations. We also calculate the non-Gaussianity of equilateral type approximately.

  10. Approximation problems with the divergence criterion for Gaussian variablesand Gaussian processes

    NARCIS (Netherlands)

    A.A. Stoorvogel; J.H. van Schuppen (Jan)


    textabstractSystem identification for stationary Gaussian processes includes an approximation problem. Currently the subspace algorithm for this problem enjoys much attention. This algorithm is based on a transformation of a finite time series to canonical variable form followed by a truncation.

  11. Gaussian-log-Gaussian wavelet trees, frequentist and Bayesian inference, and statistical signal processing applications

    DEFF Research Database (Denmark)

    Møller, Jesper; Jacobsen, Robert Dahl

    We introduce a promising alternative to the usual hidden Markov tree model for Gaussian wavelet coefficients, where their variances are specified by the hidden states and take values in a finite set. In our new model, the hidden states have a similar dependence structure but they are jointly Gaus...... detection problems in two-dimensional images....

  12. Frequentist and Bayesian inference for Gaussian-log-Gaussian wavelet trees and statistical signal processing applications

    DEFF Research Database (Denmark)

    Jacobsen, Christian Robert Dahl; Møller, Jesper


    We introduce new estimation methods for a subclass of the Gaussian scale mixture models for wavelet trees by Wainwright, Simoncelli and Willsky that rely on modern results for composite likelihoods and approximate Bayesian inference. Our methodology is illustrated for denoising and edge detection...... problems in two-dimensional images....

  13. On the structure of Gaussian pricing models and Gaussian Markov functional models

    NARCIS (Netherlands)

    C.D.D. Neumann


    textabstractThis article investigates the structure of Gaussian pricing models (that is, models in which future returns are normally distributed). Although much is already known about such models, this article differs in that it is based on a formulation of the theory of derivative pricing in which

  14. Multimodal Similarity Gaussian Process Latent Variable Model. (United States)

    Song, Guoli; Wang, Shuhui; Huang, Qingming; Tian, Qi


    Data from real applications involve multiple modalities representing content with the same semantics from complementary aspects. However, relations among heterogeneous modalities are simply treated as observation-to-fit by existing work, and the parameterized modality specific mapping functions lack flexibility in directly adapting to the content divergence and semantic complicacy in multimodal data. In this paper, we build our work based on the Gaussian process latent variable model (GPLVM) to learn the non-parametric mapping functions and transform heterogeneous modalities into a shared latent space. We propose multimodal Similarity Gaussian Process latent variable model (m-SimGP), which learns the mapping functions between the intra-modal similarities and latent representation. We further propose multimodal distance-preserved similarity GPLVM (m-DSimGP) to preserve the intra-modal global similarity structure, and multimodal regularized similarity GPLVM (m-RSimGP) by encouraging similar/dissimilar points to be similar/dissimilar in the latent space. We propose m-DRSimGP, which combines the distance preservation in m-DSimGP and semantic preservation in m-RSimGP to learn the latent representation. The overall objective functions of the four models are solved by simple and scalable gradient decent techniques. They can be applied to various tasks to discover the nonlinear correlations and to obtain the comparable low-dimensional representation for heterogeneous modalities. On five widely used real-world data sets, our approaches outperform existing models on cross-modal content retrieval and multimodal classification.

  15. Overlay Spectrum Sharing using Improper Gaussian Signaling

    KAUST Repository

    Amin, Osama


    Improper Gaussian signaling (IGS) scheme has been recently shown to provide performance improvements in interference limited networks as opposed to the conventional proper Gaussian signaling (PGS) scheme. In this paper, we implement the IGS scheme in overlay cognitive radio system, where the secondary transmitter broadcasts a mixture of two different signals. The first signal is selected from the PGS scheme to match the primary message transmission. On the other hand, the second signal is chosen to be from the IGS scheme in order to reduce the interference effect on the primary receiver. We then optimally design the overlay cognitive radio to maximize the secondary link achievable rate while satisfying the primary network quality of service requirements. In particular, we consider full and partial channel knowledge scenarios and derive the feasibility conditions of operating the overlay cognitive radio systems. Moreover, we derive the superiority conditions of the IGS schemes over the PGS schemes supported with closed form expressions for the corresponding power distribution and the circularity coefficient and parameters. Simulation results are provided to support our theoretical derivations.

  16. An innovation approach to non-Gaussian time series analysis


    Ozaki, Tohru; Iino, Mitsunori


    The paper shows that the use of both types of random noise, white noise and Poisson noise, can be justified when using an innovations approach. The historical background for this is sketched, and then several methods of whitening dependent time series are outlined, including a mixture of Gaussian white noise and a compound Poisson process: this appears as a natural extension of the Gaussian white noise model for the prediction errors of a non-Gaussian time series. A stati...

  17. Prediction and retrodiction with continuously monitored Gaussian states

    DEFF Research Database (Denmark)

    Zhang, Jinglei; Mølmer, Klaus


    Gaussian states of quantum oscillators are fully characterized by the mean values and the covariance matrix of their quadrature observables. We consider the dynamics of a system of oscillators subject to interactions, damping, and continuous probing which maintain their Gaussian state property......(t)$ to Gaussian states implies that the matrix $E(t)$ is also fully characterized by a vector of mean values and a covariance matrix. We derive the dynamical equations for these quantities and we illustrate their use in the retrodiction of measurements on Gaussian systems....

  18. Gaussian polynomials and content ideal in trivial extensions

    International Nuclear Information System (INIS)

    Bakkari, C.; Mahdou, N.


    The goal of this paper is to exhibit a class of Gaussian non-coherent rings R (with zero-divisors) such that wdim(R) = ∞ and fPdim(R) is always at most one and also exhibits a new class of rings (with zerodivisors) which are neither locally Noetherian nor locally domain where Gaussian polynomials have a locally principal content. For this purpose, we study the possible transfer of the 'Gaussian' property and the property 'the content ideal of a Gaussian polynomial is locally principal' to various trivial extension contexts. This article includes a brief discussion of the scopes and limits of our result. (author)


    Energy Technology Data Exchange (ETDEWEB)



    Electron cooling together with intra-beam scattering results in a transverse distribution that can best be described by a sum of two gaussians, one for the high-density core and one for the tails of the distribution. Simulation studies are being performed to understand the beam-beam interaction of these double-gaussian beams. Here we report the effect of low-frequency random tune modulations on diffusion in double-gaussian beams and compare the effects to those in beam-beam interactions with regular gaussian beams and identical tune shift parameters.


    International Nuclear Information System (INIS)



    Electron cooling together with intra-beam scattering results in a transverse distribution that can best be described by a sum of two gaussians, one for the high-density core and one for the tails of the distribution. Simulation studies are being performed to understand the beam-beam interaction of these double-gaussian beams. Here we report the effect of loW--frequency random tune modulations on diffusion in double-gaussian beams and compare the effects to those in beam-beam interactions with regular gaussian beams and identical tune shift parameters