Spatial Behaviour of Singularities in Fractal- and Gaussian Speckle Fields
DEFF Research Database (Denmark)
Angelsky, Oleg V.; Maksimyak, Alexander P.; Maksimyak, Peter P.
2009-01-01
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...
Directory of Open Access Journals (Sweden)
M. Mahdian
2013-09-01
Full Text Available 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.
Entendue invariance in speckle fields
International Nuclear Information System (INIS)
Medina, F.F.; Garcia-Sucerquia, J.; Henao, R.; Trivi, M.
2000-04-01
Experimental evidence is shown that confirms the Entendue invariance in speckle fields. Because of this condition, the coherence patch of the speckle field can be significantly greater than the mean size of the speckles, as is shown by double exposure speckle interferometry. (author)
Enhanced deterministic phase retrieval using a partially developed speckle field
DEFF Research Database (Denmark)
Almoro, Percival F.; Waller, Laura; Agour, Mostafa
2012-01-01
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...
Finding small displacements of recorded speckle patterns: revisited
DEFF Research Database (Denmark)
Hanson, Steen Grüner; Jakobsen, Michael Linde; Chakrabarti, Maumita
2015-01-01
An analytical expression for the bias effect in digital speckle correlation is derived based on a Gaussian approximation of the spatial pixel size and array extent. The evaluation is carried out having assumed an incident speckle field. The analysis is focused on speckle displacements in the order...
Gaussian processes and constructive scalar field theory
International Nuclear Information System (INIS)
Benfatto, G.; Nicolo, F.
1981-01-01
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.)
Integration of non-Gaussian fields
DEFF Research Database (Denmark)
Ditlevsen, Ove Dalager; Mohr, Gunnar; Hoffmeyer, Pernille
1996-01-01
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....... and Randrup-Thomsen, S. Reliability of silo ring under lognormal stochastic pressure using stochastic interpolation. Proc. IUTAM Symp., Probabilistic Structural Mechanics: Advances in Structural Reliability Methods, San Antonio, TX, USA, June 1993 (eds.: P. D. Spanos & Y.-T. Wu) pp. 134-162. Springer, Berlin...
Perturbative Gaussianizing transforms for cosmological fields
Hall, Alex; Mead, Alexander
2018-01-01
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.
Measurement of deformation field in CT specimen using laser speckle
International Nuclear Information System (INIS)
Jeon, Moon Chang; Kang, Ki Ju
2001-01-01
To obtain A 2 experimentally in the J-A 2 theory, deformation field on the lateral surface of a CT specimen was to be determined using laser speckle method. The crack growth was measured using direct current potential drop method and most procedure of experimental and data reduction was performed according to ASTM Standard E1737-96. Laser speckle images during crack propagation were monitored by two CCD cameras to cancel the effect of rotation and translation of the specimen. An algorithm to pursue displacement of a point from each image was developed and successfully used to measure A 2 continuously as the crack tip was propagated. The effects of specimen thickness on J-R curve and A 2 were explored
Dynamical properties of speckled speckles
DEFF Research Database (Denmark)
Hanson, Steen Grüner; Iversen, Theis Faber Quist; Hansen, Rene Skov
2010-01-01
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...... to be Gaussian but the derived expressions are not restricted to a plane incident beam. The results are applicable for speckle-based systems for determining mechanical displacements, especially for long-range systems, and for analyzing systems for measuring biological activity beyond a diffuse layer, e.g. blood...
Statistics of peaks of Gaussian random fields
International Nuclear Information System (INIS)
Bardeen, J.M.; Bond, J.R.; Kaiser, N.; Szalay, A.S.; Stanford Univ., CA; California Univ., Berkeley; Cambridge Univ., England; Fermi National Accelerator Lab., Batavia, IL)
1986-01-01
A set of new mathematical results on the theory of Gaussian random fields is presented, and the application of such calculations in cosmology to treat questions of structure formation from small-amplitude initial density fluctuations is addressed. The point process equation is discussed, giving the general formula for the average number density of peaks. The problem of the proper conditional probability constraints appropriate to maxima are examined using a one-dimensional illustration. The average density of maxima of a general three-dimensional Gaussian field is calculated as a function of heights of the maxima, and the average density of upcrossing points on density contour surfaces is computed. The number density of peaks subject to the constraint that the large-scale density field be fixed is determined and used to discuss the segregation of high peaks from the underlying mass distribution. The machinery to calculate n-point peak-peak correlation functions is determined, as are the shapes of the profiles about maxima. 67 references
Laser speckle contrast imaging using light field microscope approach
Ma, Xiaohui; Wang, Anting; Ma, Fenghua; Wang, Zi; Ming, Hai
2018-01-01
In this paper, a laser speckle contrast imaging (LSCI) system using light field (LF) microscope approach is proposed. As far as we known, it is first time to combine LSCI with LF. To verify this idea, a prototype consists of a modified LF microscope imaging system and an experimental device was built. A commercially used Lytro camera was modified for microscope imaging. Hollow glass tubes with different depth fixed in glass dish were used to simulate the vessels in brain and test the performance of the system. Compared with conventional LSCI, three new functions can be realized by using our system, which include refocusing, extending the depth of field (DOF) and gathering 3D information. Experiments show that the principle is feasible and the proposed system works well.
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).
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
2001-01-01
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)
Statistics of polarization speckle: theory versus experiment
DEFF Research Database (Denmark)
Wang, Wei; Hanson, Steen Grüner; Takeda, Mitsuo
2010-01-01
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....
Area of isodensity contours in Gaussian and non-Gaussian fields
International Nuclear Information System (INIS)
Ryden, B.S.
1988-01-01
The area of isodensity contours in a smoothed density field can be measured by the contour-crossing statistic N1, the number of times per unit length that a line drawn through the density field pierces an isodensity contour. The contour-crossing statistic distinguishes between Gaussian and non-Gaussian fields and provides a measure of the effective slope of the power spectrum. The statistic is easy to apply and can be used on pencil beams and slices as well as on a three-dimensional field. 10 references
Gaussian vector fields on triangulated surfaces
DEFF Research Database (Denmark)
Ipsen, John H
2016-01-01
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...
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)
2016-01-28
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.
A characterization of Markovian homogeneous multicomponent Gaussian fields
International Nuclear Information System (INIS)
Ekhaguere, G.O.S.
1980-01-01
Necessary and sufficient conditions are given for a certain class of homogeneous multicomponent Gaussian generalized stochastic fields to possess a Markov property equivalent to Nelson's. The class of Markov fields so characterized has a as a cubclass the class of Markov fields which lead by Nelson's Reconstruction Theorem to some covariant (free) quantum fields. (orig.)
A note on moving average models for Gaussian random fields
DEFF Research Database (Denmark)
Hansen, Linda Vadgård; Thorarinsdottir, Thordis L.
The class of moving average models offers a flexible modeling framework for Gaussian random fields with many well known models such as the Matérn covariance family and the Gaussian covariance falling under this framework. Moving average models may also be viewed as a kernel smoothing of a Lévy...... 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...
Energy Technology Data Exchange (ETDEWEB)
Wang, Hongchang, E-mail: hongchang.wang@diamond.ac.uk; Kashyap, Yogesh; Sawhney, Kawal [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom)
2016-03-21
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.
Energy Technology Data Exchange (ETDEWEB)
Wang, Yuan-Mei; Li, Jun-Gang, E-mail: jungl@bit.edu.cn; Zou, Jian
2017-06-15
Highlights: • Adaptive measurement strategy is used to detect the presence of a magnetic field. • Gaussian Ornstein–Uhlenbeck noise and non-Gaussian noise have been considered. • Weaker magnetic fields may be more easily detected than some stronger ones. - Abstract: By using the adaptive measurement method we study how to detect whether a weak magnetic field is actually present or not under Gaussian noise and non-Gaussian noise. We find that the adaptive measurement method can effectively improve the detection accuracy. For the case of Gaussian noise, we find the stronger the magnetic field strength, the easier for us to detect the magnetic field. Counterintuitively, for non-Gaussian noise, some weaker magnetic fields are more likely to be detected rather than some stronger ones. Finally, we give a reasonable physical interpretation.
Superpositions of higher-order bessel beams and nondiffracting speckle fields
CSIR Research Space (South Africa)
Dudley, Angela L
2009-08-01
Full Text Available speckle fields. The paper reports on illuminating a ring slit aperture with light which has an azimuthal phase dependence, such that the field produced is a superposition of two higher-order Bessel beams. In the case that the phase dependence of the light...
Superpositions of higher-order bessel beams and nondiffracting speckle fields - (SAIP 2009)
CSIR Research Space (South Africa)
Dudley, Angela L
2009-07-01
Full Text Available speckle fields. The paper reports on illuminating a ring slit aperture with light which has an azimuthal phase dependence, such that the field produced is a superposition of two higher-order Bessel beams. In the case that the phase dependence of the light...
Topological recursion for Gaussian means and cohomological field theories
Andersen, J. E.; Chekhov, L. O.; Norbury, P.; Penner, R. C.
2015-12-01
We introduce explicit relations between genus-filtrated s-loop means of the Gaussian matrix model and terms of the genus expansion of the Kontsevich-Penner matrix model (KPMM), which is the generating function for volumes of discretized (open) moduli spaces M g,s disc (discrete volumes). Using these relations, we express Gaussian means in all orders of the genus expansion as polynomials in special times weighted by ancestor invariants of an underlying cohomological field theory. We translate the topological recursion of the Gaussian model into recurrence relations for the coefficients of this expansion, which allows proving that they are integers and positive. We find the coefficients in the first subleading order for M g,1 for all g in three ways: using the refined Harer-Zagier recursion, using the Givental-type decomposition of the KPMM, and counting diagrams explicitly.
Yan, Yuan
2017-07-13
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.
Yan, Yuan; Genton, Marc G.
2017-01-01
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.
Phase statistics in non-Gaussian scattering
International Nuclear Information System (INIS)
Watson, Stephen M; Jakeman, Eric; Ridley, Kevin D
2006-01-01
Amplitude weighting can improve the accuracy of frequency measurements in signals corrupted by multiplicative speckle noise. When the speckle field constitutes a circular complex Gaussian process, the optimal function of amplitude weighting is provided by the field intensity, corresponding to the intensity-weighted phase derivative statistic. In this paper, we investigate the phase derivative and intensity-weighted phase derivative returned from a two-dimensional random walk, which constitutes a generic scattering model capable of producing both Gaussian and non-Gaussian fluctuations. Analytical results are developed for the correlation properties of the intensity-weighted phase derivative, as well as limiting probability densities of the scattered field. Numerical simulation is used to generate further probability densities and determine optimal weighting criteria from non-Gaussian fields. The results are relevant to frequency retrieval in radiation scattered from random media
Gaussian free fields at the integer quantum Hall plateau transition
Energy Technology Data Exchange (ETDEWEB)
Bondesan, R., E-mail: roberto.bondesan@phys.ox.ac.uk [Rudolf Peierls Centre for Theoretical Physics, 1 Keble Road, Oxford OX1 3NP (United Kingdom); Wieczorek, D.; Zirnbauer, M.R. [Institut für Theoretische Physik, Universität zu Köln, Zülpicher Straße 77, 50937 Köln (Germany)
2017-05-15
In this work we put forward an effective Gaussian free field description of critical wavefunctions at the transition between plateaus of the integer quantum Hall effect. To this end, we expound our earlier proposal that powers of critical wave intensities prepared via point contacts behave as pure scaling fields obeying an Abelian operator product expansion. Our arguments employ the framework of conformal field theory and, in particular, lead to a multifractality spectrum which is parabolic. We also derive a number of old and new identities that hold exactly at the lattice level and hinge on the correspondence between the Chalker–Coddington network model and a supersymmetric vertex model.
Discretisation Schemes for Level Sets of Planar Gaussian Fields
Beliaev, D.; Muirhead, S.
2018-01-01
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. https://doi.org/10.1007/s10240-017-0093-0; 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.
Non-gaussianity from the trispectrum and vector field perturbations
International Nuclear Information System (INIS)
Valenzuela-Toledo, Cesar A.; Rodriguez, Yeinzon
2010-01-01
We use the δN formalism to study the trispectrum T ζ of the primordial curvature perturbation ζ when the latter is generated by vector field perturbations, considering the tree-level and one-loop contributions. The order of magnitude of the level of non-gaussianity in the trispectrum, τ NL , is calculated in this scenario and related to the order of magnitude of the level of non-gaussianity in the bispectrum, f NL , and the level of statistical anisotropy in the power spectrum, g ζ . Such consistency relations will put under test this scenario against future observations. Comparison with the expected observational bound on τ NL from WMAP, for generic inflationary models, is done.
Non-gaussianity from the trispectrum and vector field perturbations
Energy Technology Data Exchange (ETDEWEB)
Valenzuela-Toledo, Cesar A., E-mail: cavalto@ciencias.uis.edu.c [Escuela de Fisica, Universidad Industrial de Santander, Ciudad Universitaria, Bucaramanga (Colombia); Rodriguez, Yeinzon, E-mail: yeinzon.rodriguez@uan.edu.c [Escuela de Fisica, Universidad Industrial de Santander, Ciudad Universitaria, Bucaramanga (Colombia); Centro de Investigaciones, Universidad Antonio Narino, Cra 3 Este 47A-15, Bogota D.C. (Colombia)
2010-03-01
We use the deltaN formalism to study the trispectrum T{sub z}eta of the primordial curvature perturbation zeta when the latter is generated by vector field perturbations, considering the tree-level and one-loop contributions. The order of magnitude of the level of non-gaussianity in the trispectrum, tau{sub NL}, is calculated in this scenario and related to the order of magnitude of the level of non-gaussianity in the bispectrum, f{sub NL}, and the level of statistical anisotropy in the power spectrum, g{sub z}eta. Such consistency relations will put under test this scenario against future observations. Comparison with the expected observational bound on tau{sub NL} from WMAP, for generic inflationary models, is done.
Singular trajectories: space-time domain topology of developing speckle fields
Vasil'ev, Vasiliy; Soskin, Marat S.
2010-02-01
It is shown the space-time dynamics of optical singularities is fully described by singularities trajectories in space-time domain, or evolution of transverse coordinates(x, y) in some fixed plane z0. The dynamics of generic developing speckle fields was realized experimentally by laser induced scattering in LiNbO3:Fe photorefractive crystal. The space-time trajectories of singularities can be divided topologically on two classes with essentially different scenario and duration. Some of them (direct topological reactions) consist from nucleation of singularities pair at some (x, y, z0, t) point, their movement and annihilation. They possess form of closed loops with relatively short time of existence. Another much more probable class of trajectories are chain topological reactions. Each of them consists from sequence of links, i.e. of singularities nucleation in various points (xi yi, ti) and following annihilation of both singularities in other space-time points with alien singularities of opposite topological indices. Their topology and properties are established. Chain topological reactions can stop on the borders of a developing speckle field or go to infinity. Examples of measured both types of topological reactions for optical vortices (polarization C points) in scalar (elliptically polarized) natural developing speckle fields are presented.
Yilmaz, Hasan
2016-03-01
Structured illumination enables high-resolution fluorescence imaging of nanostructures [1]. We demonstrate a new high-resolution fluorescence imaging method that uses a scattering layer with a high-index substrate as a solid immersion lens [2]. Random scattering of coherent light enables a speckle pattern with a very fine structure that illuminates the fluorescent nanospheres on the back surface of the high-index substrate. The speckle pattern is raster-scanned over the fluorescent nanospheres using a speckle correlation effect known as the optical memory effect. A series of standard-resolution fluorescence images per each speckle pattern displacement are recorded by an electron-multiplying CCD camera using a commercial microscope objective. We have developed a new phase-retrieval algorithm to reconstruct a high-resolution, wide-field image from several standard-resolution wide-field images. We have introduced phase information of Fourier components of standard-resolution images as a new constraint in our algorithm which discards ambiguities therefore ensures convergence to a unique solution. We demonstrate two-dimensional fluorescence images of a collection of nanospheres with a deconvolved Abbe resolution of 116 nm and a field of view of 10 µm × 10 µm. Our method is robust against optical aberrations and stage drifts, therefore excellent for imaging nanostructures under ambient conditions. [1] M. G. L. Gustafsson, J. Microsc. 198, 82-87 (2000). [2] H. Yilmaz, E. G. van Putten, J. Bertolotti, A. Lagendijk, W. L. Vos, and A. P. Mosk, Optica 2, 424-429 (2015).
Non-Gaussianity from self-ordering scalar fields
International Nuclear Information System (INIS)
Figueroa, Daniel G.; Caldwell, Robert R.; Kamionkowski, Marc
2010-01-01
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 ≅2k 2 ≅2k 3 ) as opposed to the local-model bispectrum, which peaks for squeezed triangles (k 1 ≅k 2 >>k 3 ), and the equilateral bispectrum, which peaks at k 1 ≅k 2 ≅k 3 . We estimate that this non-Gaussianity should be detectable by the Planck satellite if the contribution from self-ordering scalar fields to primordial perturbations is near the current upper limit.
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: marie-christine.zdora@diamond.ac.uk [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)
2015-09-21
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.
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)
2016-12-07
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.
The Gaussian streaming model and convolution Lagrangian effective field theory
Energy Technology Data Exchange (ETDEWEB)
Vlah, Zvonimir [Stanford Institute for Theoretical Physics and Department of Physics, Stanford University, Stanford, CA 94306 (United States); Castorina, Emanuele; White, Martin, E-mail: zvlah@stanford.edu, E-mail: ecastorina@berkeley.edu, E-mail: mwhite@berkeley.edu [Department of Physics, University of California, Berkeley, CA 94720 (United States)
2016-12-01
We update the ingredients of the Gaussian streaming model (GSM) for the redshift-space clustering of biased tracers using the techniques of Lagrangian perturbation theory, effective field theory (EFT) and a generalized Lagrangian bias expansion. After relating the GSM to the cumulant expansion, we present new results for the real-space correlation function, mean pairwise velocity and pairwise velocity dispersion including counter terms from EFT and bias terms through third order in the linear density, its leading derivatives and its shear up to second order. We discuss the connection to the Gaussian peaks formalism. We compare the ingredients of the GSM to a suite of large N-body simulations, and show the performance of the theory on the low order multipoles of the redshift-space correlation function and power spectrum. We highlight the importance of a general biasing scheme, which we find to be as important as higher-order corrections due to non-linear evolution for the halos we consider on the scales of interest to us.
Some Metric Properties of Planar Gaussian Free Field
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
GAUSSIAN RANDOM FIELD: PHYSICAL ORIGIN OF SERSIC PROFILES
International Nuclear Information System (INIS)
Cen, Renyue
2014-01-01
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
Density of states in an optical speckle potential
International Nuclear Information System (INIS)
Falco, G. M.; Fedorenko, A. A.; Giacomelli, J.; Modugno, M.
2010-01-01
We study the single-particle density of states of a one-dimensional speckle potential, which is correlated and non-Gaussian. We consider both the repulsive and the attractive cases. The system is controlled by a single dimensionless parameter determined by the mass of the particle, the correlation length, and the average intensity of the field. Depending on the value of this parameter, the system exhibits different regimes, characterized by the localization properties of the eigenfunctions. We calculate the corresponding density of states using the statistical properties of the speckle potential. We find good agreement with the results of numerical simulations.
International Nuclear Information System (INIS)
Mysina, N Yu; Maksimova, L A; Ryabukho, V P; Gorbatenko, B B
2015-01-01
Investigated are statistical properties of the phase difference of oscillations in speckle-fields at two points in the far-field diffraction region, with different shapes of the scatterer aperture. Statistical and spatial nonuniformity of the probability density function of the field phase difference is established. Numerical experiments show that, for the speckle-fields with an oscillating alternating-sign transverse correlation function, a significant nonuniformity of the probability density function of the phase difference in the correlation region of the field complex amplitude, with the most probable values 0 and p, is observed. A natural statistical interference experiment using Young diagrams has confirmed the results of numerical experiments. (laser applications and other topics in quantum electronics)
3D shape measurement using deterministic phase retrieval and a partially developed speckle field
DEFF Research Database (Denmark)
Almoro, Percival F.; Waller, Laura; Agour, Mostafa
2012-01-01
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...
Linear velocity fields in non-Gaussian models for large-scale structure
Scherrer, Robert J.
1992-01-01
Linear velocity fields in two types of physically motivated non-Gaussian models are examined for large-scale structure: seed models, in which the density field is a convolution of a density profile with a distribution of points, and local non-Gaussian fields, derived from a local nonlinear transformation on a Gaussian field. The distribution of a single component of the velocity is derived for seed models with randomly distributed seeds, and these results are applied to the seeded hot dark matter model and the global texture model with cold dark matter. An expression for the distribution of a single component of the velocity in arbitrary local non-Gaussian models is given, and these results are applied to such fields with chi-squared and lognormal distributions. It is shown that all seed models with randomly distributed seeds and all local non-Guassian models have single-component velocity distributions with positive kurtosis.
Prediction of Geological Subsurfaces Based on Gaussian Random Field Models
Energy Technology Data Exchange (ETDEWEB)
Abrahamsen, Petter
1997-12-31
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.
Evolution of the optical vortex density in phase corrected speckle fields
CSIR Research Space (South Africa)
Roux, FS
2010-09-01
Full Text Available In an attempt to understand the process whereby the phase modulation due to atmospheric turbulance causes phase singularities (also called optical vortices), the authors investigated the effect of phase perturbations in speckle beams. They perturb...
Speckle suppression via sparse representation for wide-field imaging through turbid media.
Jang, Hwanchol; Yoon, Changhyeong; Chung, Euiheon; Choi, Wonshik; Lee, Heung-No
2014-06-30
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.
State of the Art of X-ray Speckle-Based Phase-Contrast and Dark-Field Imaging
Directory of Open Access Journals (Sweden)
Marie-Christine Zdora
2018-04-01
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.
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
2013-01-01
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)
Super-Gaussian transport theory and the field-generating thermal instability in laser-plasmas
Bissell, J. J.; Ridgers, C. P.; Kingham, R. J.
2013-02-01
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.
Yeung, Chuck
2018-06-01
The assumption that the local order parameter is related to an underlying spatially smooth auxiliary field, u (r ⃗,t ) , is a common feature in theoretical approaches to non-conserved order parameter phase separation dynamics. In particular, the ansatz that u (r ⃗,t ) is a Gaussian random field leads to predictions for the decay of the autocorrelation function which are consistent with observations, but distinct from predictions using alternative theoretical approaches. In this paper, the auxiliary field is obtained directly from simulations of the time-dependent Ginzburg-Landau equation in two and three dimensions. The results show that u (r ⃗,t ) is equivalent to the distance to the nearest interface. In two dimensions, the probability distribution, P (u ) , is well approximated as Gaussian except for small values of u /L (t ) , where L (t ) is the characteristic length-scale of the patterns. The behavior of P (u ) in three dimensions is more complicated; the non-Gaussian region for small u /L (t ) is much larger than that in two dimensions but the tails of P (u ) begin to approach a Gaussian form at intermediate times. However, at later times, the tails of the probability distribution appear to decay faster than a Gaussian distribution.
Ding, Jian; Li, Li
2018-06-01
We initiate the study on chemical distances of percolation clusters for level sets of two-dimensional discrete Gaussian free fields as well as loop clusters generated by two-dimensional random walk loop soups. One of our results states that the chemical distance between two macroscopic annuli away from the boundary for the random walk loop soup at the critical intensity is of dimension 1 with positive probability. Our proof method is based on an interesting combination of a theorem of Makarov, isomorphism theory, and an entropic repulsion estimate for Gaussian free fields in the presence of a hard wall.
Signed zeros of Gaussian vector fields - density, correlation functions and curvature
Foltin, G
2003-01-01
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.
DEFF Research Database (Denmark)
Franchin, P.; Ditlevsen, Ove Dalager; Kiureghian, Armen Der
2002-01-01
The model correction factor method (MCFM) is used in conjunction with the first-order reliability method (FORM) to solve structural reliability problems involving integrals of non-Gaussian random fields. The approach replaces the limit-state function with an idealized one, in which the integrals ...
Self-consistent field theory of protein adsorption in a non-Gaussian polyelectrolyte brush
Biesheuvel, P.M.; Leermakers, F.A.M.; Stuart, M.A.C.
2006-01-01
To describe adsorption of globular protein molecules in a polyelectrolyte brush we use the strong-stretching approximation of the Edwards self-consistent field equation, combined with corrections for a non-Gaussian brush. To describe chemical potentials in this mixture of (globular) species of
Non-Gaussianities in a two-field generalization of natural inflation
Riquelme M., Simon
2018-04-01
We describe a two-field model that generalizes natural inflation, in which the inflaton is the pseudo-Goldstone boson of an approximate symmetry that is spontaneously broken, and the radial mode is dynamical. We analyze how the dynamics fundamentally depends on the mass of the radial mode and calculate/estimate the non-Gaussianities arising from such a scenario.
Czech Academy of Sciences Publication Activity Database
Arkhipov, Ie.I.; Peřina, Jan; Peřina, J.; Miranowicz, A.
2016-01-01
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)
Bertschinger, E.
1987-01-01
Path integrals may be used to describe the statistical properties of a random field such as the primordial density perturbation field. In this framework the probability distribution is given for a Gaussian random field subjected to constraints such as the presence of a protovoid or supercluster at a specific location in the initial conditions. An algorithm has been constructed for generating samples of a constrained Gaussian random field on a lattice using Monte Carlo techniques. The method makes possible a systematic study of the density field around peaks or other constrained regions in the biased galaxy formation scenario, and it is effective for generating initial conditions for N-body simulations with rare objects in the computational volume. 21 references
International Nuclear Information System (INIS)
Wu, Jinghe; Guo, Kangxian; Liu, Guanghui
2014-01-01
Polaron effects on nonlinear optical rectification in asymmetrical Gaussian potential quantum wells are studied by the effective mass approximation and the perturbation theory. The numerical results show that nonlinear optical rectification coefficients are strongly dependent on the barrier hight V 0 of the Gaussian potential quantum wells, the range L of the confinement potential and the electric field F. Besides, the numerical results show that no matter how V 0 , L and F change, taking into consideration polaron effects, the optical rectification coefficients χ 0 (2) get greatly enhanced.
PHYSICS OF NON-GAUSSIAN FIELDS AND THE COSMOLOGICAL GENUS STATISTIC
International Nuclear Information System (INIS)
James, J. Berian
2012-01-01
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.
On the non-Gaussian correlation of the primordial curvature perturbation with vector fields
DEFF Research Database (Denmark)
Kumar Jain, Rajeev; Sloth, Martin Snoager
2013-01-01
We compute the three-point cross-correlation function of the primordial curvature perturbation generated during inflation with two powers of a vector field in a model where conformal invariance is broken by a direct coupling of the vector field with the inflaton. If the vector field is identified...... with the electromagnetic field, this correlation would be a non-Gaussian signature of primordial magnetic fields generated during inflation. We find that the signal is maximized for the flattened configuration where the wave number of the curvature perturbation is twice that of the vector field and in this limit...
EVOLUTION OF THE MAGNETIC FIELD LINE DIFFUSION COEFFICIENT AND NON-GAUSSIAN STATISTICS
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)
2016-08-20
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.
Ma, S.; Ma, J.; Liu, L.; Liu, P.
2007-12-01
Digital speckle correlation method (DSCM) is one kind of photomechanical deformation measurement method. DSCM could obtain continuous deformation field contactlessly by just capturing speckle images from specimen surface. Therefore, it is suitable to observe high spatial resolution deformation field in tectonophysical experiment. However, in the general DSCM experiment, the inspected surface of specimen needs to be painted to bear speckle grains in order to obtain the high quality speckle image. This also affects the realization of other measurement techniques. In this study, an improved DSCM system is developed and utilized to measure deformation field of rock specimen without surface painting. The granodiorite with high contrast nature grains is chosen to manufacture the specimen, and a specially designed DSCM algorithm is developed to analyze this kind of nature speckle images. Verification and calibration experiments show that the system could inspect a continuous (about 15Hz) high resolution displacement field (with resolution of 5μm) and strain field (with resolution of 50μɛ), dispensing with any preparation on rock specimen. Therefore, it could be conveniently utilized to study the failure of rock structure. Samples with compressive en echelon faults and extensional en echelon faults are studied on a two-direction servo-control test machine. The failure process of the samples is discussed based on the DSCM results. Experiment results show that: 1) The contours of displacement field could clearly indicate the activities of faults and new cracks. The displacement gradient adjacent to active faults and cracks is much greater than other areas. 2) Before failure of the samples, the mean strain of the jog area is largest for the compressive en echelon fault, while that is smallest for the extensional en echelon fault. This consists with the understanding that the jog area of compressive fault subjects to compression and that of extensional fault subjects to
International Nuclear Information System (INIS)
Lian-Huang, Li; Fu-Yuan, Guo
2009-01-01
This paper analyzes the characteristic of matching efficiency between the fundamental mode of two kinds of optical waveguides and its Gaussian approximate field. Then, it presents a new method where the mode-field half-width of Gaussian approximation for the fundamental mode should be defined according to the maximal matching efficiency method. The relationship between the mode-field half-width of the Gaussian approximate field obtained from the maximal matching efficiency and normalized frequency is studied; furthermore, two formulas of mode-field half-widths as a function of normalized frequency are proposed
International Nuclear Information System (INIS)
Vasil'ev, Vasilii I; Soskin, M S
2013-01-01
A natural singular dynamics of elliptically polarised speckle-fields induced by the 'optical damage' effect in a photorefractive crystal of lithium niobate by a passing beam of a helium — neon laser is studied by the developed methods of singular optics. For the polarisation singularities (C points), a new class of chain reactions, namely, singular chain reactions are discovered and studied. It is shown that they obey the topological charge and sum Poincare index conservation laws. In addition, they exist for all the time of crystal irradiation. They consist of a series of interlocking chains, where singularity pairs arising in a chain annihilate with singularities from neighbouring independently created chains. Less often singular 'loop' reactions are observed where arising pairs of singularities annihilate after reversible transformations in within the boundaries of a single speckle. The type of a singular reaction is determined by a topology and dynamics of the speckles, in which the reactions are developing. (laser optics 2012)
A brain MRI bias field correction method created in the Gaussian multi-scale space
Chen, Mingsheng; Qin, Mingxin
2017-07-01
A pre-processing step is needed to correct for the bias field signal before submitting corrupted MR images to such image-processing algorithms. This study presents a new bias field correction method. The method creates a Gaussian multi-scale space by the convolution of the inhomogeneous MR image with a two-dimensional Gaussian function. In the multi-Gaussian space, the method retrieves the image details from the differentiation of the original image and convolution image. Then, it obtains an image whose inhomogeneity is eliminated by the weighted sum of image details in each layer in the space. Next, the bias field-corrected MR image is retrieved after the Υ correction, which enhances the contrast and brightness of the inhomogeneity-eliminated MR image. We have tested the approach on T1 MRI and T2 MRI with varying bias field levels and have achieved satisfactory results. Comparison experiments with popular software have demonstrated superior performance of the proposed method in terms of quantitative indices, especially an improvement in subsequent image segmentation.
Delpueyo, D.; Balandraud, X.; Grédiac, M.
2013-09-01
The aim of this paper is to present a post-processing technique based on a derivative Gaussian filter to reconstruct heat source fields from temperature fields measured by infrared thermography. Heat sources can be deduced from temperature variations thanks to the heat diffusion equation. Filtering and differentiating are key-issues which are closely related here because the temperature fields which are processed are unavoidably noisy. We focus here only on the diffusion term because it is the most difficult term to estimate in the procedure, the reason being that it involves spatial second derivatives (a Laplacian for isotropic materials). This quantity can be reasonably estimated using a convolution of the temperature variation fields with second derivatives of a Gaussian function. The study is first based on synthetic temperature variation fields corrupted by added noise. The filter is optimised in order to reconstruct at best the heat source fields. The influence of both the dimension and the level of a localised heat source is discussed. Obtained results are also compared with another type of processing based on an averaging filter. The second part of this study presents an application to experimental temperature fields measured with an infrared camera on a thin plate in aluminium alloy. Heat sources are generated with an electric heating patch glued on the specimen surface. Heat source fields reconstructed from measured temperature fields are compared with the imposed heat sources. Obtained results illustrate the relevancy of the derivative Gaussian filter to reliably extract heat sources from noisy temperature fields for the experimental thermomechanics of materials.
Non-Gaussianity at tree and one-loop levels from vector field perturbations
International Nuclear Information System (INIS)
Valenzuela-Toledo, Cesar A.; Rodriguez, Yeinzon; Lyth, David H.
2009-01-01
We study the spectrum P ζ and bispectrum B ζ of the primordial curvature perturbation ζ when the latter is generated by scalar and vector field perturbations. The tree-level and one-loop contributions from vector field perturbations are worked out considering the possibility that the one-loop contributions may be dominant over the tree-level terms [both (either) in P ζ and (or) in B ζ ] and vice versa. The level of non-Gaussianity in the bispectrum, f NL , is calculated and related to the level of statistical anisotropy in the power spectrum, g ζ . For very small amounts of statistical anisotropy in the power spectrum, the level of non-Gaussianity may be very high, in some cases exceeding the current observational limit.
Rubtsov, Vladimir; Kapralov, Sergey; Chalyk, Iuri; Ulianova, Onega; Ulyanov, Sergey
2013-02-01
Statistical properties of laser speckles, formed in skin and mucous of colon have been analyzed and compared. It has been demonstrated that first and second order statistics of "skin" speckles and "mucous" speckles are quite different. It is shown that speckles, formed in mucous, are not Gaussian one. Layered structure of colon mucous causes formation of speckled biospeckles. First- and second- order statistics of speckled speckles have been reviewed in this paper. Statistical properties of Fresnel and Fraunhofer doubly scattered and cascade speckles are described. Non-gaussian statistics of biospeckles may lead to high localization of intensity of coherent light in human tissue during the laser surgery. Way of suppression of highly localized non-gaussian speckles is suggested.
Sirohi, Rajpal S.
2002-03-01
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
Chang, Wen-Chi; Chen, Yu-Chi; Chien, Chih-Jen; Wang, An-Bang; Lee, Chih-Kung
2011-04-01
A testing system contains an advanced vibrometer/interferometer device (AVID) and a high-speed electronic speckle pattern interferometer (ESPI) was developed. AVID is a laser Doppler vibrometer that can be used to detect single-point linear and angular velocity with DC to 20 MHz bandwidth and with nanometer resolution. In swept frequency mode, frequency response from mHz to MHz of the structure of interest can be measured. The ESPI experimental setup can be used to measure full-field out-of-plane displacement. A 5-1 phase shifting method and a correlation algorithm were used to analyze the phase difference between the reference signal and the speckle signal scattered from the sample surface. In order to show the efficiency and effectiveness of AVID and ESPI, we designed a micro-speaker composed of a plate with fixed boundaries and two piezo-actuators attached to the sides of the plate. The AVID was used to measure the vibration of one of the piezo-actuators and the ESPI was adopted to measure the two-dimensional out-of-plane displacement of the plate. A microphone was used to measure the acoustic response created by the micro-speaker. Driving signal includes random signal, sinusoidal signal, amplitude modulated high-frequency carrier signal, etc. Angular response induced by amplitude modulated high-frequency carrier signal was found to be significantly narrower than the frequency responses created by other types of driving signals. The validity of our newly developed NDE system are detailed by comparing the relationship between the vibration signal of the micro-speaker and the acoustic field generated.
Non-Gaussian statistics, classical field theory, and realizable Langevin models
International Nuclear Information System (INIS)
Krommes, J.A.
1995-11-01
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
Edwards, Philip J.; Hobson, Peter R.; Rodgers, G. J.
2000-08-01
In-line particle holography is subject to image deterioration due to intrinsic speckle noise. The resulting reduction in the signal to noise ratio (SNR) of the replayed image can become critical for applications such as holographic particle velocimetry (HPV) and 3D visualisation of marine plankton. Work has been done to extend the mono-disperse model relevant to HPV to include poly-disperse particle fields appropriate for the visualisation of marine plankton. Continuous and discrete particle fields are both considered. It is found that random walk statistics still apply for the poly-disperse case. The speckle field is simply the summation of the individual speckle patters due to each scatter size. Therefor the characteristic speckle parameter (which encompasses particle diameter, concentration and sample depth) is alos just the summation of the individual speckle parameters. This reduces the SNR calculation to the same form as for the mono-disperse case. For the continuous situation three distributions, power, exponential and Gaussian are discussed with the resulting SNR calcuated. The work presented here was performed as part of the Holomar project to produce a working underwater holographic camera for recording plankton.
Non-Gaussian path integration in self-interacting scalar field theories
International Nuclear Information System (INIS)
Kaya, Ali
2004-01-01
In self-interacting scalar field theories kinetic expansion is an alternative way of calculating the generating functional for Green's functions where the zeroth order non-Gaussian path integral becomes diagonal in x-space and reduces to the product of an ordinary integral at each point which can be evaluated exactly. We discuss how to deal with such functional integrals and propose a new perturbative expansion scheme which combines the elements of the kinetic expansion with the usual perturbation theory techniques. It is then shown that, when the cutoff dependences of the bare parameters in the potential are chosen to have a well defined non-Gaussian path integral without the kinetic term, the theory becomes trivial in the continuum limit
International Nuclear Information System (INIS)
Freitas Naiff, Danilo de; Silveira, Paulo R.; Pereira, Claudio M.N.A.
2017-01-01
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)
Energy Technology Data Exchange (ETDEWEB)
Freitas Naiff, Danilo de; Silveira, Paulo R.; Pereira, Claudio M.N.A., E-mail: danilonai1992@poli.ufrj.br, E-mail: paulo@lmp.ufrj.br, E-mail: cmnap@ien.gov.br [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)
2017-11-01
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)
Electron acceleration by longitudinal electric field of a gaussian laser beam
International Nuclear Information System (INIS)
Takeuchi, Satoshi; Sugihara, Ryo; Shimoda, Koichi.
1991-11-01
It is shown that the longitudinal electric field of a transverse magnetic mode of a Gaussian laser beam accelerates an electron to an ultra-relativistic energy. The electron is captured and accelerated in a length of the order of the Rayleigh range. The ultimate energy increment of the electron with a single laser beam is given by the product of transverse field intensity and the beam waist, and can be of the order of 100MeV. This fact implies that a multi-stage acceleration enables TeV-order-acceleration in a length of a few kilometers with the present state of the art. (author)
Primordial non-Gaussianities in single field inflationary models with non-trivial initial states
Energy Technology Data Exchange (ETDEWEB)
Bahrami, Sina; Flanagan, Éanna É., E-mail: sb933@cornell.edu, E-mail: eef3@cornell.edu [Department of Physics, Cornell University, Ithaca, NY 14853 (United States)
2014-10-01
We compute the non-Gaussianities that arise in single field, slow roll inflationary models arising from arbitrary homogeneous initial states, as well as subleading contributions to the power spectrum. Non Bunch-Davies vacuum initial states can arise if the transition to the single field, slow roll inflation phase occurs only shortly before observable modes left the horizon. They can also arise from new physics at high energies that has been integrated out. Our general result for the bispectrum exhibits several features that were previously seen in special cases.
Addendum to foundations of multidimensional wave field signal theory: Gaussian source function
Directory of Open Access Journals (Sweden)
Natalie Baddour
2018-02-01
Full Text Available Many important physical phenomena are described by wave or diffusion-wave type equations. Recent work has shown that a transform domain signal description from linear system theory can give meaningful insight to multi-dimensional wave fields. In N. Baddour [AIP Adv. 1, 022120 (2011], certain results were derived that are mathematically useful for the inversion of multi-dimensional Fourier transforms, but more importantly provide useful insight into how source functions are related to the resulting wave field. In this short addendum to that work, it is shown that these results can be applied with a Gaussian source function, which is often useful for modelling various physical phenomena.
Addendum to foundations of multidimensional wave field signal theory: Gaussian source function
Baddour, Natalie
2018-02-01
Many important physical phenomena are described by wave or diffusion-wave type equations. Recent work has shown that a transform domain signal description from linear system theory can give meaningful insight to multi-dimensional wave fields. In N. Baddour [AIP Adv. 1, 022120 (2011)], certain results were derived that are mathematically useful for the inversion of multi-dimensional Fourier transforms, but more importantly provide useful insight into how source functions are related to the resulting wave field. In this short addendum to that work, it is shown that these results can be applied with a Gaussian source function, which is often useful for modelling various physical phenomena.
Stochastic generation of explicit pore structures by thresholding Gaussian random fields
Energy Technology Data Exchange (ETDEWEB)
Hyman, Jeffrey D., E-mail: jhyman@lanl.gov [Program in Applied Mathematics, University of Arizona, Tucson, AZ 85721-0089 (United States); Computational Earth Science, Earth and Environmental Sciences (EES-16), and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM 87544 (United States); Winter, C. Larrabee, E-mail: winter@email.arizona.edu [Program in Applied Mathematics, University of Arizona, Tucson, AZ 85721-0089 (United States); Department of Hydrology and Water Resources, University of Arizona, Tucson, AZ 85721-0011 (United States)
2014-11-15
We provide a description and computational investigation of an efficient method to stochastically generate realistic pore structures. Smolarkiewicz and Winter introduced this specific method in pores resolving simulation of Darcy flows (Smolarkiewicz and Winter, 2010 [1]) without giving a complete formal description or analysis of the method, or indicating how to control the parameterization of the ensemble. We address both issues in this paper. The method consists of two steps. First, a realization of a correlated Gaussian field, or topography, is produced by convolving a prescribed kernel with an initial field of independent, identically distributed random variables. The intrinsic length scales of the kernel determine the correlation structure of the topography. Next, a sample pore space is generated by applying a level threshold to the Gaussian field realization: points are assigned to the void phase or the solid phase depending on whether the topography over them is above or below the threshold. Hence, the topology and geometry of the pore space depend on the form of the kernel and the level threshold. Manipulating these two user prescribed quantities allows good control of pore space observables, in particular the Minkowski functionals. Extensions of the method to generate media with multiple pore structures and preferential flow directions are also discussed. To demonstrate its usefulness, the method is used to generate a pore space with physical and hydrological properties similar to a sample of Berea sandstone. -- Graphical abstract: -- Highlights: •An efficient method to stochastically generate realistic pore structures is provided. •Samples are generated by applying a level threshold to a Gaussian field realization. •Two user prescribed quantities determine the topology and geometry of the pore space. •Multiple pore structures and preferential flow directions can be produced. •A pore space based on Berea sandstone is generated.
International Nuclear Information System (INIS)
Pal, Suvajit; Sinha, Sudarson Sekhar; Ganguly, Jayanta; Ghosh, Manas
2013-01-01
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
Directory of Open Access Journals (Sweden)
Pablo Gregori
2014-03-01
Full Text Available This paper represents a survey of recent advances in modeling of space or space-time Gaussian Random Fields (GRF, tools of Geostatistics at hand for the understanding of special cases of noise in image analysis. They can be used when stationarity or isotropy are unrealistic assumptions, or even when negative covariance between some couples of locations are evident. We show some strategies in order to escape from these restrictions, on the basis of rich classes of well known stationary or isotropic non negative covariance models, and through suitable operations, like linear combinations, generalized means, or with particular Fourier transforms.
Non-Gaussianity in two-field inflation beyond the slow-roll approximation
Energy Technology Data Exchange (ETDEWEB)
Jung, Gabriel; Tent, Bartjan van, E-mail: gabriel.jung@th.u-psud.fr, E-mail: bartjan.van-tent@th.u-psud.fr [Laboratoire de Physique Théorique (UMR 8627), CNRS, Univ. Paris-Sud, Université Paris-Saclay, Bâtiment 210, 91405 Orsay Cedex (France)
2017-05-01
We use the long-wavelength formalism to investigate the level of bispectral non-Gaussianity produced in two-field inflation models with standard kinetic terms. Even though the Planck satellite has so far not detected any primordial non-Gaussianity, it has tightened the constraints significantly, and it is important to better understand what regions of inflation model space have been ruled out, as well as prepare for the next generation of experiments that might reach the important milestone of Δ f {sub NL}{sup local}=1. We derive an alternative formulation of the previously derived integral expression for f {sub NL}, which makes it easier to physically interpret the result and see which types of potentials can produce large non-Gaussianity. We apply this to the case of a sum potential and show that it is very difficult to satisfy simultaneously the conditions for a large f {sub NL} and the observational constraints on the spectral index n {sub s} . In the case of the sum of two monomial potentials and a constant we explicitly show in which small region of parameter space this is possible, and we show how to construct such a model. Finally, the new general expression for f {sub NL} also allows us to prove that for the sum potential the explicit expressions derived within the slow-roll approximation remain valid even when the slow-roll approximation is broken during the turn of the field trajectory (as long as only the ε slow-roll parameter remains small).
Non-Gaussianity and statistical anisotropy from vector field populated inflationary models
Dimastrogiovanni, Emanuela; Matarrese, Sabino; Riotto, Antonio
2010-01-01
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.
Statistics of spatially integrated speckle intensity difference
DEFF Research Database (Denmark)
Hanson, Steen Grüner; Yura, Harold
2009-01-01
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...... 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....
Chen, Zhenning; Shao, Xinxing; Xu, Xiangyang; He, Xiaoyuan
2018-02-01
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.
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: venturi@ucsc.edu [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)
2017-05-01
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.
Multi-fidelity Gaussian process regression for prediction of random fields
International Nuclear Information System (INIS)
Parussini, L.; Venturi, D.; Perdikaris, P.; Karniadakis, G.E.
2017-01-01
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.
Vanishing of local non-Gaussianity in canonical single field inflation
Bravo, Rafael; Mooij, Sander; Palma, Gonzalo A.; Pradenas, Bastián
2018-05-01
We study the production of observable primordial local non-Gaussianity in two opposite regimes of canonical single field inflation: attractor (standard single field slow-roll inflation) and non attractor (ultra slow-roll inflation). In the attractor regime, the standard derivation of the bispectrum's squeezed limit using co-moving coordinates gives the well known Maldacena's consistency relation fNL = 5 (1‑ns) / 12. On the other hand, in the non-attractor regime, the squeezed limit offers a substantial violation of this relation given by fNL = 5/2. In this work we argue that, independently of whether inflation is attractor or non-attractor, the size of the observable primordial local non-Gaussianity is predicted to be fNLobs = 0 (a result that was already understood to hold in the case of attractor models). To show this, we follow the use of the so-called Conformal Fermi Coordinates (CFC), recently introduced in the literature. These coordinates parametrize the local environment of inertial observers in a perturbed FRW spacetime, allowing one to identify and compute gauge invariant quantities, such as n-point correlation functions. Concretely, we find that during inflation, after all the modes have exited the horizon, the squeezed limit of the 3-point correlation function of curvature perturbations vanishes in the CFC frame, regardless of the inflationary regime. We argue that such a cancellation should persist after inflation ends.
A generalized non-Gaussian consistency relation for single field inflation
Bravo, Rafael; Mooij, Sander; Palma, Gonzalo A.; Pradenas, Bastián
2018-05-01
We show that a perturbed inflationary spacetime, driven by a canonical single scalar field, is invariant under a special class of coordinate transformations together with a field reparametrization of the curvature perturbation in co-moving gauge. This transformation may be used to derive the squeezed limit of the 3-point correlation function of the co-moving curvature perturbations valid in the case that these do not freeze after horizon crossing. This leads to a generalized version of Maldacena's non-Gaussian consistency relation in the sense that the bispectrum squeezed limit is completely determined by spacetime diffeomorphisms. Just as in the case of the standard consistency relation, this result may be understood as the consequence of how long-wavelength modes modulate those of shorter wavelengths. This relation allows one to derive the well known violation to the consistency relation encountered in ultra slow-roll, where curvature perturbations grow exponentially after horizon crossing.
Gaussian mixtures on tensor fields for segmentation: applications to medical imaging.
de Luis-García, Rodrigo; Westin, Carl-Fredrik; Alberola-López, Carlos
2011-01-01
In this paper, we introduce a new approach for tensor field segmentation based on the definition of mixtures of Gaussians on tensors as a statistical model. Working over the well-known Geodesic Active Regions segmentation framework, this scheme presents several interesting advantages. First, it yields a more flexible model than the use of a single Gaussian distribution, which enables the method to better adapt to the complexity of the data. Second, it can work directly on tensor-valued images or, through a parallel scheme that processes independently the intensity and the local structure tensor, on scalar textured images. Two different applications have been considered to show the suitability of the proposed method for medical imaging segmentation. First, we address DT-MRI segmentation on a dataset of 32 volumes, showing a successful segmentation of the corpus callosum and favourable comparisons with related approaches in the literature. Second, the segmentation of bones from hand radiographs is studied, and a complete automatic-semiautomatic approach has been developed that makes use of anatomical prior knowledge to produce accurate segmentation results. Copyright © 2010 Elsevier Ltd. All rights reserved.
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: gregoire.ferre@ponts.org [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)
2016-06-01
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).
Coupling the Gaussian Free Fields with Free and with Zero Boundary Conditions via Common Level Lines
Qian, Wei; Werner, Wendelin
2018-06-01
We point out a new simple way to couple the Gaussian Free Field (GFF) with free boundary conditions in a two-dimensional domain with the GFF with zero boundary conditions in the same domain: Starting from the latter, one just has to sample at random all the signs of the height gaps on its boundary-touching zero-level lines (these signs are alternating for the zero-boundary GFF) in order to obtain a free boundary GFF. Constructions and couplings of the free boundary GFF and its level lines via soups of reflected Brownian loops and their clusters are also discussed. Such considerations show for instance that in a domain with an axis of symmetry, if one looks at the overlay of a single usual Conformal Loop Ensemble CLE3 with its own symmetric image, one obtains the CLE4-type collection of level lines of a GFF with mixed zero/free boundary conditions in the half-domain.
Fano resonance of the ultrasensitve optical force excited by Gaussian evanescent field
International Nuclear Information System (INIS)
Yang, Yang; Li, Jiafang; Li, Zhi-Yuan
2015-01-01
In this paper, we study the angle-dependent Fano-like optical force spectra of plasmonic Ag nanoparticles, which exhibit extraordinary transformation from Lorentzian resonance to Fano resonance when excited by a Gaussian evanescent wave. We systematically analyze the behavior of this asymmetric scattering induced optical force under different conditions and find that this Fano interference-induced force is ultrasensitive to the excitation wavelength, incident angle and particle size, as well as the core–shell configuration, which could be useful for wavelength- and angle-dependent size-selective optical manipulation. The origin of this Fano resonance is further identified as the interference between the two adjacent-order multipolar plasmonic modes excited in the Ag particle under the excitation of an inhomogeneously distributed evanescent field. (paper)
International Nuclear Information System (INIS)
Carvalho, O.
2008-01-01
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
Ulyanov, Sergey S.; Ulianova, Onega V.; Zaytsev, Sergey S.; Saltykov, Yury V.; Feodorova, Valentina A.
2018-04-01
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.
Development of Speckle Interferometry Algorithm and System
International Nuclear Information System (INIS)
Shamsir, A. A. M.; Jafri, M. Z. M.; Lim, H. S.
2011-01-01
Electronic speckle pattern interferometry (ESPI) method is a wholefield, non destructive measurement method widely used in the industries such as detection of defects on metal bodies, detection of defects in intergrated circuits in digital electronics components and in the preservation of priceless artwork. In this research field, this method is widely used to develop algorithms and to develop a new laboratory setup for implementing the speckle pattern interferometry. In speckle interferometry, an optically rough test surface is illuminated with an expanded laser beam creating a laser speckle pattern in the space surrounding the illuminated region. The speckle pattern is optically mixed with a second coherent light field that is either another speckle pattern or a smooth light field. This produces an interferometric speckle pattern that will be detected by sensor to count the change of the speckle pattern due to force given. In this project, an experimental setup of ESPI is proposed to analyze a stainless steel plate using 632.8 nm (red) wavelength of lights.
Solvation in atomic liquids: connection between Gaussian field theory and density functional theory
Directory of Open Access Journals (Sweden)
V. Sergiievskyi
2017-12-01
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.
Auxiliary-field quantum Monte Carlo calculations of molecular systems with a Gaussian basis
International Nuclear Information System (INIS)
Al-Saidi, W.A.; Zhang Shiwei; Krakauer, Henry
2006-01-01
We extend the recently introduced phaseless auxiliary-field quantum Monte Carlo (QMC) approach to any single-particle basis and apply it to molecular systems with Gaussian basis sets. QMC methods in general scale favorably with the system size as a low power. A QMC approach with auxiliary fields, in principle, allows an exact solution of the Schroedinger equation in the chosen basis. However, the well-known sign/phase problem causes the statistical noise to increase exponentially. The phaseless method controls this problem by constraining the paths in the auxiliary-field path integrals with an approximate phase condition that depends on a trial wave function. In the present calculations, the trial wave function is a single Slater determinant from a Hartree-Fock calculation. The calculated all-electron total energies show typical systematic errors of no more than a few millihartrees compared to exact results. At equilibrium geometries in the molecules we studied, this accuracy is roughly comparable to that of coupled cluster with single and double excitations and with noniterative triples [CCSD(T)]. For stretched bonds in H 2 O, our method exhibits a better overall accuracy and a more uniform behavior than CCSD(T)
A novel approach to assess the treatment response using Gaussian random field in PET
Energy Technology Data Exchange (ETDEWEB)
Wang, Mengdie [Department of Biomedical Engineering, Tsinghua University, Beijing 100084, China and Center for Advanced Medical Imaging Science, Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, Boston, Massachusetts 02114 (United States); Guo, Ning [Center for Advanced Medical Imaging Science, Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, Boston, Massachusetts 02114 (United States); Hu, Guangshu; Zhang, Hui, E-mail: hzhang@mail.tsinghua.edu.cn, E-mail: li.quanzheng@mgh.harvard.edu [Department of Biomedical Engineering, Tsinghua University, Beijing 100084 (China); El Fakhri, Georges; Li, Quanzheng, E-mail: hzhang@mail.tsinghua.edu.cn, E-mail: li.quanzheng@mgh.harvard.edu [Center for Advanced Medical Imaging Science, Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, Boston, Massachusetts 02114 and Department of Radiology, Harvard Medical School, Boston, Massachusetts 02115 (United States)
2016-02-15
Purpose: The assessment of early therapeutic response to anticancer therapy is vital for treatment planning and patient management in clinic. With the development of personal treatment plan, the early treatment response, especially before any anatomically apparent changes after treatment, becomes urgent need in clinic. Positron emission tomography (PET) imaging serves an important role in clinical oncology for tumor detection, staging, and therapy response assessment. Many studies on therapy response involve interpretation of differences between two PET images, usually in terms of standardized uptake values (SUVs). However, the quantitative accuracy of this measurement is limited. This work proposes a statistically robust approach for therapy response assessment based on Gaussian random field (GRF) to provide a statistically more meaningful scale to evaluate therapy effects. Methods: The authors propose a new criterion for therapeutic assessment by incorporating image noise into traditional SUV method. An analytical method based on the approximate expressions of the Fisher information matrix was applied to model the variance of individual pixels in reconstructed images. A zero mean unit variance GRF under the null hypothesis (no response to therapy) was obtained by normalizing each pixel of the post-therapy image with the mean and standard deviation of the pretherapy image. The performance of the proposed method was evaluated by Monte Carlo simulation, where XCAT phantoms (128{sup 2} pixels) with lesions of various diameters (2–6 mm), multiple tumor-to-background contrasts (3–10), and different changes in intensity (6.25%–30%) were used. The receiver operating characteristic curves and the corresponding areas under the curve were computed for both the proposed method and the traditional methods whose figure of merit is the percentage change of SUVs. The formula for the false positive rate (FPR) estimation was developed for the proposed therapy response
Zhu, Wuming; Trickey, S B
2017-12-28
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
Zhu, Wuming; Trickey, S. B.
2017-12-01
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.
Discriminative learning of receptive fields from responses to non-Gaussian stimulus ensembles.
Meyer, Arne F; Diepenbrock, Jan-Philipp; Happel, Max F K; Ohl, Frank W; Anemüller, Jörn
2014-01-01
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 natural stimuli and
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
Directory of Open Access Journals (Sweden)
Lingtao Mao
2015-04-01
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.
Gaussian point count statistics for families of curves over a fixed finite field
Kurlberg, Par; Wigman, Igor
2010-01-01
We produce a collection of families of curves, whose point count statistics over F_p becomes Gaussian for p fixed. In particular, the average number of F_p points on curves in these families tends to infinity.
Advances in speckle metrology and related techniques
Kaufmann, Guillermo H
2010-01-01
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
International Nuclear Information System (INIS)
Smirnov, V.N.; Strokovskii, G.A.
1994-01-01
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
Complex-Valued ABCD Matrices and Speckle Metrology
DEFF Research Database (Denmark)
Hanson, Steen Grüner; Jakobsen, Michael Linde; Yura, Harold T.
2016-01-01
coherent light sources, optical elements of finite size, and distributed random inhomogeneity along the optical path. In many cases (e.g., laser beam propagation and Gaussian optics) we have been able to derive simple analytical expressions for the optical field quantities at an observation plane. A series......We demonstrate that within the paraxial ray approximation the propagation of light through a complex optical system can be formulated in terms of a Huygens principle expressed with the complete system’s ABCD-matrix elements. As such, propagation through an optical system reduces...... of laser-based optical measurement systems have been analyzed and analytical expressions for their main parameters have been given. Specifically, scattering from rough surfaces not giving rise to a fully developed speckle field, various anemometers and systems for measuring rotational velocity have been...
Cheraghalizadeh, Jafar; Najafi, Morteza N.; Mohammadzadeh, Hossein
2018-05-01
The effect of metallic nano-particles (MNPs) on the electrostatic potential of a disordered 2D dielectric media is considered. The disorder in the media is assumed to be white-noise Coulomb impurities with normal distribution. To realize the correlations between the MNPs we have used the Ising model with an artificial temperature T that controls the number of MNPs as well as their correlations. In the T → 0 limit, one retrieves the Gaussian free field (GFF), and in the finite temperature the problem is equivalent to a GFF in iso-potential islands. The problem is argued to be equivalent to a scale-invariant random surface with some critical exponents which vary with T and correspondingly are correlation-dependent. Two type of observables have been considered: local and global quantities. We have observed that the MNPs soften the random potential and reduce its statistical fluctuations. This softening is observed in the local as well as the geometrical quantities. The correlation function of the electrostatic and its total variance are observed to be logarithmic just like the GFF, i.e. the roughness exponent remains zero for all temperatures, whereas the proportionality constants scale with T - T c . The fractal dimension of iso-potential lines ( D f ), the exponent of the distribution function of the gyration radius ( τ r ), and the loop lengths ( τ l ), and also the exponent of the loop Green function x l change in terms of T - T c in a power-law fashion, with some critical exponents reported in the text. Importantly we have observed that D f ( T) - D f ( T c ) 1/√ ξ( T), in which ξ( T) is the spin correlation length in the Ising model.
ANALYSIS AND VALIDATION OF GRID DEM GENERATION BASED ON GAUSSIAN MARKOV RANDOM FIELD
Directory of Open Access Journals (Sweden)
F. J. Aguilar
2016-06-01
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.
Efficient 3D porous microstructure reconstruction via Gaussian random field and hybrid optimization.
Jiang, Z; Chen, W; Burkhart, C
2013-11-01
Obtaining an accurate three-dimensional (3D) structure of a porous microstructure is important for assessing the material properties based on finite element analysis. Whereas directly obtaining 3D images of the microstructure is impractical under many circumstances, two sets of methods have been developed in literature to generate (reconstruct) 3D microstructure from its 2D images: one characterizes the microstructure based on certain statistical descriptors, typically two-point correlation function and cluster correlation function, and then performs an optimization process to build a 3D structure that matches those statistical descriptors; the other method models the microstructure using stochastic models like a Gaussian random field and generates a 3D structure directly from the function. The former obtains a relatively accurate 3D microstructure, but computationally the optimization process can be very intensive, especially for problems with large image size; the latter generates a 3D microstructure quickly but sacrifices the accuracy due to issues in numerical implementations. A hybrid optimization approach of modelling the 3D porous microstructure of random isotropic two-phase materials is proposed in this paper, which combines the two sets of methods and hence maintains the accuracy of the correlation-based method with improved efficiency. The proposed technique is verified for 3D reconstructions based on silica polymer composite images with different volume fractions. A comparison of the reconstructed microstructures and the optimization histories for both the original correlation-based method and our hybrid approach demonstrates the improved efficiency of the approach. © 2013 The Authors Journal of Microscopy © 2013 Royal Microscopical Society.
X-ray speckle correlation interferometer
International Nuclear Information System (INIS)
Eisenhower, Rachel; Materlik, Gerhard
2000-01-01
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
Speckle dynamics under ergodicity breaking
Sdobnov, Anton; Bykov, Alexander; Molodij, Guillaume; Kalchenko, Vyacheslav; Jarvinen, Topias; Popov, Alexey; Kordas, Krisztian; Meglinski, Igor
2018-04-01
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.
Directory of Open Access Journals (Sweden)
Phil Diamond
2003-01-01
Full Text Available Sensitivity of output of a linear operator to its input can be quantified in various ways. In Control Theory, the input is usually interpreted as disturbance and the output is to be minimized in some sense. In stochastic worst-case design settings, the disturbance is considered random with imprecisely known probability distribution. The prior set of probability measures can be chosen so as to quantify how far the disturbance deviates from the white-noise hypothesis of Linear Quadratic Gaussian control. Such deviation can be measured by the minimal Kullback-Leibler informational divergence from the Gaussian distributions with zero mean and scalar covariance matrices. The resulting anisotropy functional is defined for finite power random vectors. Originally, anisotropy was introduced for directionally generic random vectors as the relative entropy of the normalized vector with respect to the uniform distribution on the unit sphere. The associated a-anisotropic norm of a matrix is then its maximum root mean square or average energy gain with respect to finite power or directionally generic inputs whose anisotropy is bounded above by a≥0. We give a systematic comparison of the anisotropy functionals and the associated norms. These are considered for unboundedly growing fragments of homogeneous Gaussian random fields on multidimensional integer lattice to yield mean anisotropy. Correspondingly, the anisotropic norms of finite matrices are extended to bounded linear translation invariant operators over such fields.
Energy Technology Data Exchange (ETDEWEB)
Li, Yu-Bin; Cai, Yi-Fu [CAS Key Laboratory for Researches in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Chinese Academy of Sciences, Hefei, Anhui 230026 (China); Quintin, Jerome [Department of Physics, McGill University, 3600 rue University, Montréal, QC, H3A 2T8 (Canada); Wang, Dong-Gang, E-mail: lyb2166@mail.ustc.edu.cn, E-mail: jquintin@physics.mcgill.ca, E-mail: wdgang@strw.leidenuniv.nl, E-mail: yifucai@ustc.edu.cn [Leiden Observatory, Leiden University, 2300 RA Leiden (Netherlands)
2017-03-01
We extend the matter bounce scenario to a more general theory in which the background dynamics and cosmological perturbations are generated by a k -essence scalar field with an arbitrary sound speed. When the sound speed is small, the curvature perturbation is enhanced, and the tensor-to-scalar ratio, which is excessively large in the original model, can be sufficiently suppressed to be consistent with observational bounds. Then, we study the primordial three-point correlation function generated during the matter-dominated contraction stage and find that it only depends on the sound speed parameter. Similar to the canonical case, the shape of the bispectrum is mainly dominated by a local form, though for some specific sound speed values a new shape emerges and the scaling behaviour changes. Meanwhile, a small sound speed also results in a large amplitude of non-Gaussianities, which is disfavored by current observations. As a result, it does not seem possible to suppress the tensor-to-scalar ratio without amplifying the production of non-Gaussianities beyond current observational constraints (and vice versa). This suggests an extension of the previously conjectured no-go theorem in single field nonsingular matter bounce cosmologies, which rules out a large class of models. However, the non-Gaussianity results remain as a distinguishable signature of matter bounce cosmology and have the potential to be detected by observations in the near future.
Maksimova, L. A.; Ryabukho, P. V.; Mysina, N. Yu.; Lyakin, D. V.; Ryabukho, V. P.
2018-04-01
We have investigated the capabilities of the method of digital speckle interferometry for determining subpixel displacements of a speckle structure formed by a displaceable or deformable object with a scattering surface. An analysis of spatial spectra of speckle structures makes it possible to perform measurements with a subpixel accuracy and to extend the lower boundary of the range of measurements of displacements of speckle structures to the range of subpixel values. The method is realized on the basis of digital recording of the images of undisplaced and displaced speckle structures, their spatial frequency analysis using numerically specified constant phase shifts, and correlation analysis of spatial spectra of speckle structures. Transformation into the frequency range makes it possible to obtain quantities to be measured with a subpixel accuracy from the shift of the interference-pattern minimum in the diffraction halo by introducing an additional phase shift into the complex spatial spectrum of the speckle structure or from the slope of the linear plot of the function of accumulated phase difference in the field of the complex spatial spectrum of the displaced speckle structure. The capabilities of the method have been investigated in natural experiment.
Aziz-Aghchegala, V. L.; Mughnetsyan, V. N.; Kirakosyan, A. A.
2018-02-01
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.
Acoustic radiation force on a multilayered sphere in a Gaussian standing field
Wang, Haibin; Liu, Xiaozhou; Gao, Sha; Cui, Jun; Liu, Jiehui; He, Aijun; Zhang, Gutian
2018-03-01
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).
Highly porous nanoberyllium for X-ray beam speckle suppression
Energy Technology Data Exchange (ETDEWEB)
Goikhman, Alexander, E-mail: agoikhman@ymail.com; 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)
2015-04-09
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.
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
2015-01-01
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
Goodman, Joseph W.
2013-05-01
Speckle appears whenever coherent radiation of any kind is used. We review here the basic properties of speckle, the negative effects it has on imaging systems of various kinds, and the positive benefits it offers in certain nondestructive testing and metrology problems.
DEFF Research Database (Denmark)
Chakrabarti, Maumita; Jakobsen, Michael Linde; Hanson, Steen Grüner
2015-01-01
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...
Post-Gaussian Effective Potential of Double sine-Gordon Field
International Nuclear Information System (INIS)
Cai Weiran; Lou Senyue
2005-01-01
In the framework of the functional integral formalism, we calculate the effective potential of the double sine-Gordon (DsG) model up to the second order with an optimized expansion and the Coleman's normal-ordering prescription. Within the range of convergence, we make a comparison among the classical and the effective potential of the first and second order. The numerical analysis shows that the DsG post-Gaussian EP possesses some fine global properties and makes a substantial and a concordant quantum correction to the features of the classical potential.
Multimode waveguide speckle patterns for compressive sensing.
Valley, George C; Sefler, George A; Justin Shaw, T
2016-06-01
Compressive sensing (CS) of sparse gigahertz-band RF signals using microwave photonics may achieve better performances with smaller size, weight, and power than electronic CS or conventional Nyquist rate sampling. The critical element in a CS system is the device that produces the CS measurement matrix (MM). We show that passive speckle patterns in multimode waveguides potentially provide excellent MMs for CS. We measure and calculate the MM for a multimode fiber and perform simulations using this MM in a CS system. We show that the speckle MM exhibits the sharp phase transition and coherence properties needed for CS and that these properties are similar to those of a sub-Gaussian MM with the same mean and standard deviation. We calculate the MM for a multimode planar waveguide and find dimensions of the planar guide that give a speckle MM with a performance similar to that of the multimode fiber. The CS simulations show that all measured and calculated speckle MMs exhibit a robust performance with equal amplitude signals that are sparse in time, in frequency, and in wavelets (Haar wavelet transform). The planar waveguide results indicate a path to a microwave photonic integrated circuit for measuring sparse gigahertz-band RF signals using CS.
Directory of Open Access Journals (Sweden)
Gunter eSpöck
2015-05-01
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.
Le Maitre, Olivier
2015-01-07
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.
Excursion probabilities of non-homogeneous Gaussian scalar fields based on maxima considerations
DEFF Research Database (Denmark)
Nielsen, Michael Havbro Faber; Rackwitz, R.
1988-01-01
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 p...
International Nuclear Information System (INIS)
Bissbort, Ulf; Hofstetter, Walter; Thomale, Ronny
2010-01-01
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.
Gao, Xian; Kobayashi, Tsutomu; Yamaguchi, Masahide; Yokoyama, Jun'ichi
2011-11-18
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.
A practical approach to optimizing the preparation of speckle patterns for digital-image correlation
International Nuclear Information System (INIS)
Lionello, Giacomo; Cristofolini, Luca
2014-01-01
The quality of strain measurements by digital image correlation (DIC) strongly depends on the quality of the pattern on the specimen’s surface. An ideal pattern should be highly contrasted, stochastic, and isotropic. In addition, the speckle pattern should have an average size that exceeds the image pixel size by a factor of 3–5. (Smaller speckles cause poor contrast, and larger speckles cause poor spatial resolution.) Finally, the ideal pattern should have a limited scatter in terms of speckle sizes. The aims of this study were: (i) to define the ideal speckle size in relation to the specimen size and acquisition system; (ii) provide practical guidelines to identify the optimal settings of an airbrush gun, in order to produce a pattern that is as close as possible to the desired one while minimizing the scatter of speckle sizes. Patterns of different sizes were produced using two different airbrush guns with different settings of the four most influential factors (dilution, airflow setting, spraying distance, and air pressure). A full-factorial DOE strategy was implemented to explore the four factors at two levels each: 36 specimens were analyzed for each of the 16 combinations. The images were acquired using the digital cameras of a DIC system. The distribution of speckle sizes was analyzed to calculate the average speckle size and the standard deviation of the corresponding truncated Gaussian distribution. A mathematical model was built to enable prediction of the average speckle size in relation to the airbrush gun settings. We showed that it is possible to obtain a pattern with a highly controlled average and a limited scatter of speckle sizes, so as to match the ideal distribution of speckle sizes for DIC. Although the settings identified here apply only to the specific equipment being used, this method can be adapted to any airbrush to produce a desired speckle pattern. (technical design note)
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
2012-01-01
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)
Nonlinear field theories and non-Gaussian fluctuations for near-critical many-body systems
International Nuclear Information System (INIS)
Tuszynski, J.A.; Dixon, J.M.; Grundland, A.M.
1994-01-01
This review article outlines a number of efforts made over the past several decades to understand the physics of near critical many-body systems. Beginning with the phenomenological theories of Landau and Ginzburg the paper discusses the two main routes adopted in the past. The first approach is based on statistical calculations while the second investigates the underlying nonlinear field equations. In the last part of the paper we outline a generalisation of these methods which combines classical and quantum properties of the many-body systems studied. (orig.)
Directory of Open Access Journals (Sweden)
Fermín Segovia
2017-10-01
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.
Analysis of the anomalous mean-field like properties of Gaussian core model in terms of entropy
Nandi, Manoj Kumar; Maitra Bhattacharyya, Sarika
2018-01-01
Studies of the Gaussian core model (GCM) have shown that it behaves like a mean-field model and the properties are quite different from standard glass former. In this work, we investigate the entropies, namely, the excess entropy (Sex) and the configurational entropy (Sc) and their different components to address these anomalies. Our study corroborates most of the earlier observations and also sheds new light on the high and low temperature dynamics. We find that unlike in standard glass former where high temperature dynamics is dominated by two-body correlation and low temperature by many-body correlations, in the GCM both high and low temperature dynamics are dominated by many-body correlations. We also find that the many-body entropy which is usually positive at low temperatures and is associated with activated dynamics is negative in the GCM suggesting suppression of activation. Interestingly despite the suppression of activation, the Adam-Gibbs (AG) relation that describes activated dynamics holds in the GCM, thus suggesting a non-activated contribution in AG relation. We also find an overlap between the AG relation and mode coupling power law regime leading to a power law behavior of Sc. From our analysis of this power law behavior, we predict that in the GCM the high temperature dynamics will disappear at dynamical transition temperature and below that there will be a transition to the activated regime. Our study further reveals that the activated regime in the GCM is quite narrow.
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
2012-06-06
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.
A SIMPLE HETERODYNE TEMPORAL SPECKLE-PATTERN INTERFEROMETER
International Nuclear Information System (INIS)
Wong, W. O.; Gao, Z.; Lu, J.
2010-01-01
A common light path design of heterodyne speckle pattern interferometer based on temporal speckle pattern interferometry is proposed for non-contact, full-field and real-time continuous displacement measurement. Double frequency laser is produced by rotating a half wave plate. An experiment was carried out to measure the dynamic displacement of a cantilever plate for testing the proposed common path heterodyne speckle pattern interferometer. The accuracy of displacement measurement was checked by measuring the motion at the mid-point of the plate with a point displacement sensor.
Lagrangian speckle model and tissue-motion estimation--theory.
Maurice, R L; Bertrand, M
1999-07-01
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.
Multiple speckle illumination for optical-resolution photoacoustic imaging
Poisson, Florian; Stasio, Nicolino; Moser, Christophe; Psaltis, Demetri; Bossy, Emmanuel
2017-03-01
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
Laguerre Gaussian beam multiplexing through turbulence
CSIR Research Space (South Africa)
Trichili, A
2014-08-17
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...
Yura, Harold T; Hanson, Steen G
2012-04-01
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 examples with relevance for optics are given.
Xin, Wei; Zhao, Yu-Wei; Sudu; Eerdunchaolu
2018-05-01
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.
Speckle interferometry of asteroids
International Nuclear Information System (INIS)
Drummond, J.
1988-01-01
By studying the image two-dimensional power spectra or autocorrelations projected by an asteroid as it rotates, it is possible to locate its rotational pole and derive its three axes dimensions through speckle interferometry under certain assumptions of uniform, geometric scattering, and triaxial ellipsoid shape. However, in cases where images can be reconstructed, the need for making the assumptions is obviated. Furthermore, the ultimate goal for speckle interferometry of image reconstruction will lead to mapping albedo features (if they exist) as impact areas or geological units. The first glimpses of the surface of an asteroid were obtained from images of 4 Vesta reconstructed from speckle interferometric observations. These images reveal that Vesta is quite Moon-like in having large hemispheric-scale albedo features. All of its lightcurves can be produced from a simple model developed from the images. Although undoubtedly more intricate than the model, Vesta's lightcurves can be matched by a model with three dark and four bright spots. The dark areas so dominate one hemisphere that a lightcurve minimum occurs when the maximum cross-section area is visible. The triaxial ellipsoid shape derived for Vesta is not consistent with the notion that the asteroid has an equilibrium shape in spite of its having apparently been differentiated
Laser-induced speckle scatter patterns in Bacillus colonies
Directory of Open Access Journals (Sweden)
Huisung eKim
2014-10-01
Full Text Available Label-free bacterial colony phenotyping technology called BARDOT (BActerial Rapid Detection using Optical scattering Technology provided successful classification of several different bacteria at the genus, species, and serovar level. Recent experiments with colonies of Bacillus species provided strikingly different characteristics of elastic light scatter (ELS patterns, which were comprised of random speckles compared to other bacteria, which are dominated by concentric rings and spokes. Since this laser-based optical sensor interrogates the whole volume of the colony, 3-D information of micro- and macro-structures are all encoded in the far-field scatter patterns. Here, we present a theoretical model explaining the underlying mechanism of the speckle formation by the colonies from Bacillus species. Except for Bacillus polymyxa, all Bacillus spp. produced random bright spots on the imaging plane, which presumably dependent on the cellular and molecular organization and content within the colony. Our scatter model-based analysis revealed that colony spread resulting in variable surface roughness can modify the wavefront of the scatter field. As the center diameter of the Bacillus spp. colony grew from 500 μm to 900 μm, average speckles area decreased 2-fold and the number of small speckles increased 7-fold. In conclusion, as Bacillus colony grows, the average speckle size in the scatter pattern decreases and the number of smaller speckle increases due to the swarming growth characteristics of bacteria within the colony.
DEFF Research Database (Denmark)
Yura, Harold; Hanson, Steen Grüner
2012-01-01
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...
Energy Technology Data Exchange (ETDEWEB)
Eley, John G.; Hogstrom, Kenneth R.; Matthews, Kenneth L.; Parker, Brent C.; Price, Michael J. [Department of Physics and Astronomy, Louisiana State University and Agricultural and Mechanical College, 202 Nicholson Hall, Tower Drive, Baton Rouge, Louisiana 70803-4001 (United States); Department of Physics and Astronomy, Louisiana State University and Agricultural and Mechanical College, 202 Nicholson Hall, Tower Drive, Baton Rouge, Louisiana 70803-4001 (United States) and Mary Bird Perkins Cancer Center, 4950 Essen Lane, Baton Rouge, Louisiana 70809-3482 (United States); Department of Physics and Astronomy, Louisiana State University and Agricultural and Mechanical College, 202 Nicholson Hall, Tower Drive, Baton Rouge, Louisiana 70803-4001 (United States); Department of Physics and Astronomy, Louisiana State University and Agricultural and Mechanical College, 202 Nicholson Hall, Tower Drive, Baton Rouge, Louisiana 70803-4001 (United States) and Mary Bird Perkins Cancer Center, 4950 Essen Lane, Baton Rouge, Louisiana 70809-3482 (United States)
2011-12-15
Purpose: The purpose of this work was to investigate the potential of discrete Gaussian edge feathering of the higher energy electron fields for improving abutment dosimetry in the planning volume when using an electron multileaf collimator (eMLC) to deliver segmented-field electron conformal therapy (ECT). Methods: A discrete (five-step) Gaussian edge spread function was used to match dose penumbras of differing beam energies (6-20 MeV) at a specified depth in a water phantom. Software was developed to define the leaf eMLC positions of an eMLC that most closely fit each electron field shape. The effect of 1D edge feathering of the higher energy field on dose homogeneity was computed and measured for segmented-field ECT treatment plans for three 2D PTVs in a water phantom, i.e., depth from the water surface to the distal PTV surface varied as a function of the x-axis (parallel to leaf motion) and remained constant along the y-axis (perpendicular to leaf motion). Additionally, the effect of 2D edge feathering was computed and measured for one radially symmetric, 3D PTV in a water phantom, i.e., depth from the water surface to the distal PTV surface varied as a function of both axes. For the 3D PTV, the feathering scheme was evaluated for 0.1-1.0-cm leaf widths. Dose calculations were performed using the pencil beam dose algorithm in the Pinnacle{sup 3} treatment planning system. Dose verification measurements were made using a prototype eMLC (1-cm leaf width). Results: 1D discrete Gaussian edge feathering reduced the standard deviation of dose in the 2D PTVs by 34, 34, and 39%. In the 3D PTV, the broad leaf width (1 cm) of the eMLC hindered the 2D application of the feathering solution to the 3D PTV, and the standard deviation of dose increased by 10%. However, 2D discrete Gaussian edge feathering with simulated eMLC leaf widths of 0.1-0.5 cm reduced the standard deviation of dose in the 3D PTV by 33-28%, respectively. Conclusions: A five-step discrete Gaussian edge
Speckle Suppression by Weighted Euclidean Distance Anisotropic Diffusion
Directory of Open Access Journals (Sweden)
Fengcheng Guo
2018-05-01
Full Text Available To better reduce image speckle noise while also maintaining edge information in synthetic aperture radar (SAR images, we propose a novel anisotropic diffusion algorithm using weighted Euclidean distance (WEDAD. Presented here is a modified speckle reducing anisotropic diffusion (SRAD method, which constructs a new edge detection operator using weighted Euclidean distances. The new edge detection operator can adaptively distinguish between homogenous and heterogeneous image regions, effectively generate anisotropic diffusion coefficients for each image pixel, and filter each pixel at different scales. Additionally, the effects of two different weighting methods (Gaussian weighting and non-linear weighting of de-noising were analyzed. The effect of different adjustment coefficient settings on speckle suppression was also explored. A series of experiments were conducted using an added noise image, GF-3 SAR image, and YG-29 SAR image. The experimental results demonstrate that the proposed method can not only significantly suppress speckle, thus improving the visual effects, but also better preserve the edge information of images.
Statistical characterization of speckle noise in coherent imaging systems
Yaroslavsky, Leonid; Shefler, A.
2003-05-01
Speckle noise imposes fundamental limitation on image quality in coherent radiation based imaging and optical metrology systems. Speckle noise phenomena are associated with properties of objects to diffusely scatter irradiation and with the fact that in recording the wave field, a number of signal distortions inevitably occur due to technical limitations inherent to hologram sensors. The statistical theory of speckle noise was developed with regard to only limited resolving power of coherent imaging devices. It is valid only asymptotically as much as the central limit theorem of the probability theory can be applied. In applications this assumption is not always applicable. Moreover, in treating speckle noise problem one should also consider other sources of the hologram deterioration. In the paper, statistical properties of speckle due to the limitation of hologram size, dynamic range and hologram signal quantization are studied by Monte-Carlo simulation for holograms recorded in near and far diffraction zones. The simulation experiments have shown that, for limited resolving power of the imaging system, widely accepted opinion that speckle contrast is equal to one holds only for rather severe level of the hologram size limitation. For moderate limitations, speckle contrast changes gradually from zero for no limitation to one for limitation to less than about 20% of hologram size. The results obtained for the limitation of the hologram sensor"s dynamic range and hologram signal quantization reveal that speckle noise due to these hologram signal distortions is not multiplicative and is directly associated with the severity of the limitation and quantization. On the base of the simulation results, analytical models are suggested.
Real time processor for array speckle interferometry
International Nuclear Information System (INIS)
Chin, G.; Florez, J.; Borelli, R.; Fong, W.; Miko, J.; Trujillo, C.
1989-01-01
With the construction of several new large aperture telescopes and the development of large format array detectors in the near IR, the ability to obtain diffraction limited seeing via IR array speckle interferometry offers a powerful tool. We are constructing a real-time processor to acquire image frames, perform array flat-fielding, execute a 64 x 64 element 2D complex FFT, and to average the power spectrum all within the 25 msec coherence time for speckles at near IR wavelength. The processor is a compact unit controlled by a PC with real time display and data storage capability. It provides the ability to optimize observations and obtain results on the telescope rather than waiting several weeks before the data can be analyzed and viewed with off-line methods
Speckle pattern processing by digital image correlation
Directory of Open Access Journals (Sweden)
Gubarev Fedor
2016-01-01
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.
Bobrov, B. D.
1991-07-01
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.
Color speckle in laser displays
Kuroda, Kazuo
2015-07-01
At the beginning of this century, lighting technology has been shifted from discharge lamps, fluorescent lamps and electric bulbs to solid-state lighting. Current solid-state lighting is based on the light emitting diodes (LED) technology, but the laser lighting technology is developing rapidly, such as, laser cinema projectors, laser TVs, laser head-up displays, laser head mounted displays, and laser headlamps for motor vehicles. One of the main issues of laser displays is the reduction of speckle noise1). For the monochromatic laser light, speckle is random interference pattern on the image plane (retina for human observer). For laser displays, RGB (red-green-blue) lasers form speckle patterns independently, which results in random distribution of chromaticity, called color speckle2).
Applications of polarization speckle in skin cancer detection and monitoring
Lee, Tim K.; Tchvialeva, Lioudmila; Phillips, Jamie; Louie, Daniel C.; Zhao, Jianhua; Wang, Wei; Lui, Harvey; Kalia, Sunil
2018-01-01
Polarization speckle is a rapidly developed field. Unlike laser speckle, polarization speckle consists of stochastic interference patterns with spatially random polarizations, amplitudes and phases. We have been working in this exciting research field, developing techniques to generate polarization patterns from skin. We hypothesize that polarization speckle patterns could be used in biomedical applications, especially, for detecting and monitoring skin cancers, the most common neoplasmas for white populations around the world. This paper describes our effort in developing two polarization speckle devices. One of them captures the Stokes parameters So and S1 simultaneously, and another one captures all four Stokes parameters So, S1, S2, and S3 in one-shot, within milliseconds. Hence these two devices could be used in medical clinics and assessed skin conditions in-vivo. In order to validate our hypothesis, we conducted a series of three clinical studies. These are early pilot studies, and the results suggest that the devices have potential to detect and monitor skin cancers.
Speckle imaging of globular clusters
International Nuclear Information System (INIS)
Sams, B.J. III
1990-01-01
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
Huang, N. E.; Long, S. R.; Bliven, L. F.; Tung, C.-C.
1984-01-01
On the basis of the mapping method developed by Huang et al. (1983), an analytic expression for the non-Gaussian joint probability density function of slope and elevation for nonlinear gravity waves is derived. Various conditional and marginal density functions are also obtained through the joint density function. The analytic results are compared with a series of carefully controlled laboratory observations, and good agreement is noted. Furthermore, the laboratory wind wave field observations indicate that the capillary or capillary-gravity waves may not be the dominant components in determining the total roughness of the wave field. Thus, the analytic results, though derived specifically for the gravity waves, may have more general applications.
Speckle Imaging of Binary Stars with Large-Format CCDs
Horch, E.; Ninkov, Z.; Slawson, R. W.; van Altena, W. F.; Meyer, R. D.; Girard, T. M.
1997-12-01
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.
Miranda, Rodrigo A.; Schelin, Adriane B.; Chian, Abraham C.-L.; Ferreira, José L.
2018-03-01
In a recent paper (Chian et al., 2016) it was shown that magnetic reconnection at the interface region between two magnetic flux ropes is responsible for the genesis of interplanetary intermittent turbulence. The normalized third-order moment (skewness) and the normalized fourth-order moment (kurtosis) display a quadratic relation with a parabolic shape that is commonly observed in observational data from turbulence in fluids and plasmas, and is linked to non-Gaussian fluctuations due to coherent structures. In this paper we perform a detailed study of the relation between the skewness and the kurtosis of the modulus of the magnetic field |B| during a triple interplanetary magnetic flux rope event. In addition, we investigate the skewness-kurtosis relation of two-point differences of |B| for the same event. The parabolic relation displays scale dependence and is found to be enhanced during magnetic reconnection, rendering support for the generation of non-Gaussian coherent structures via rope-rope magnetic reconnection. Our results also indicate that a direct coupling between the scales of magnetic flux ropes and the scales within the inertial subrange occurs in the solar wind.
Multiple rotation assessment through isothetic fringes in speckle photography
International Nuclear Information System (INIS)
Angel, Luciano; Tebaldi, Myrian; Bolognini, Nestor
2007-01-01
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
Speckles generated by skewed, short-coherence light beams
International Nuclear Information System (INIS)
Brogioli, D; Salerno, D; Ziano, R; Mantegazza, F; Croccolo, F
2011-01-01
When a coherent laser beam impinges on a random sample (e.g. a colloidal suspension), the scattered light exhibits characteristic speckles. If the temporal coherence of the light source is too short, then the speckles disappear, along with the possibility of performing homodyne or heterodyne scattering detection or photon correlation spectroscopy. Here we investigate the scattering of a so-called ‘skewed coherence beam’, i.e. a short-coherence beam modified such that the field is coherent within slabs that are skewed with respect to the wave fronts. We show that such a beam generates speckles and can be used for heterodyne scattering detection, despite its short temporal coherence. Moreover, we show that the heterodyne signal is not affected by multiple scattering. We suggest that the phenomenon presented here can be used as a means of carrying out heterodyne scattering measurement with any short-coherence radiation, including x-rays. (paper)
Kant, Niti; Rajput, Jyoti; Singh, Arvinder
2018-03-01
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.
Revell, James; Mirmehdi, Majid; McNally, Donal
2005-06-01
We present the development and validation of an image based speckle tracking methodology, for determining temporal two-dimensional (2-D) axial and lateral displacement and strain fields from ultrasound video streams. We refine a multiple scale region matching approach incorporating novel solutions to known speckle tracking problems. Key contributions include automatic similarity measure selection to adapt to varying speckle density, quantifying trajectory fields, and spatiotemporal elastograms. Results are validated using tissue mimicking phantoms and in vitro data, before applying them to in vivo musculoskeletal ultrasound sequences. The method presented has the potential to improve clinical knowledge of tendon pathology from carpel tunnel syndrome, inflammation from implants, sport injuries, and many others.
Speckle evolution with multiple steps of least-squares phase removal
CSIR Research Space (South Africa)
Chen, M
2011-08-01
Full Text Available vortex density and scintillation index. Statistical results show that almost all the optical vortices can be removed from a speckle field, which finally decays into a quasiplane wave after such an iterative process....
Tachyon mediated non-Gaussianity
International Nuclear Information System (INIS)
Dutta, Bhaskar; Leblond, Louis; Kumar, Jason
2008-01-01
We describe a general scenario where primordial non-Gaussian curvature perturbations are generated in models with extra scalar fields. The extra scalars communicate to the inflaton sector mainly through the tachyonic (waterfall) field condensing at the end of hybrid inflation. These models can yield significant non-Gaussianity of the local shape, and both signs of the bispectrum can be obtained. These models have cosmic strings and a nearly flat power spectrum, which together have been recently shown to be a good fit to WMAP data. We illustrate with a model of inflation inspired from intersecting brane models.
Dynamical speckles in watery surfaces
International Nuclear Information System (INIS)
Llovera-Gonzalez, J.J.; Moreno-Yeras, A.; Garcia-Diaz, M.; Alvarez-Salgado, Y.
2009-01-01
Recovery of watery surfaces with monolayer of surfactant substances is of interest in diverse technological applications. The format ion and study of molecular monolayer deposited in these surfaces require the application of measurements techniques that allow evaluating the recovery grade locally without modifying practically the studied surface. In this paper the preliminary results obtained by the authors it plows exposed applying the technique of dynamic speckle interferometry in watery surfaces and their consideration like to possible resource to measure the grade of local recovery of these surfaces on the it bases that the speckles pattern dog reveal the dynamics of evaporation that takes place in the same ones. (Author)
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)
1999-03-01
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)
Objective speckle velocimetry for autonomous vehicle odometry.
Francis, D; Charrett, T O H; Waugh, L; Tatam, R P
2012-06-01
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%.
Signal-to-noise based local decorrelation compensation for speckle interferometry applications
International Nuclear Information System (INIS)
Molimard, Jerome; Cordero, Raul; Vautrin, Alain
2008-01-01
Speckle-based interferometric techniques allow assessing the whole-field deformation induced on a specimen due to the application of load. These high sensitivity optical techniques yield fringe images generated by subtracting speckle patterns captured while the specimen undergoes deformation. The quality of the fringes, and in turn the accuracy of the deformation measurements, strongly depends on the speckle correlation. Specimen rigid body motion leads to speckle decorrelation that, in general, cannot be effectively counteracted by applying a global translation to the involved speckle patterns. In this paper, we propose a recorrelation procedure based on the application of locally evaluated translations. The proposed procedure implies dividing the field into several regions, applying a local translation, and calculating, in every region, the signal-to-noise ratio (SNR). Since the latter is a correlation indicator (the noise increases with the decorrelation) we argue that the proper translation is that which maximizes the locally evaluated SNR. The search of the proper local translations is, of course, an interactive process that can be facilitated by using a SNR optimization algorithm. The performance of the proposed recorrelation procedure was tested on two examples. First, the SNR optimization algorithm was applied to fringe images obtained by subtracting simulated speckle patterns. Next, it was applied to fringe images obtained by using a shearography optical setup from a specimen subjected to mechanical deformation. Our results show that the proposed SNR optimization method can significantly improve the reliability of measurements performed by using speckle-based techniques
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
2014-01-01
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......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 the extent of synchronization in renal cortex dynamics....
Gaussian limit of compact spin systems
International Nuclear Information System (INIS)
Bellissard, J.; Angelis, G.F. de
1981-01-01
It is shown that the Wilson and Wilson-Villain U(1) models reproduce, in the low coupling limit, the gaussian lattice approximation of the Euclidean electromagnetic field. By the same methods it is also possible to prove that the plane rotator and the Villain model share a common gaussian behaviour in the low temperature limit. (Auth.)
Directory of Open Access Journals (Sweden)
Xijun Wang
2014-01-01
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.
Rotating quantum Gaussian packets
International Nuclear Information System (INIS)
Dodonov, V V
2015-01-01
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)
Laser speckle velocimetry applied to Rayleigh-Benard convection
International Nuclear Information System (INIS)
Arroyo, M.P.; Yonte, T.; Quintanilla, M.; Saviron, J.M.
1986-01-01
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
Laser Speckle Contrast Imaging: theory, instrumentation and applications.
Senarathna, Janaka; Rege, Abhishek; Li, Nan; Thakor, Nitish V
2013-01-01
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.
DEFF Research Database (Denmark)
Frier, Christian; Sørensen, John Dalsgaard
2005-01-01
For many reinforced concrete structures corrosion of the reinforcement is an important problem since it can result in expensive maintenance and repair actions. Further, a significant reduction of the load-bearing capacity can occur. One mode of corrosion initiation occurs when the chloride content...... is modeled by a 2-dimensional diffusion process by FEM (Finite Element Method) and the diffusion coefficient, surface chloride concentration and reinforcement cover depth are modeled by multidimensional stochastic fields, which are discretized using the EOLE (Expansion Optimum Linear Estimation) approach....... As an example a bridge pier in a marine environment is considered and the results are given in terms of the distribution of the time for initialization of corrosion...
Polarization speckles and generalized Stokes vector wave: a review [invited
DEFF Research Database (Denmark)
Takeda, Mitsuo; Wang, Wei; Hanson, Steen Grüner
2010-01-01
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...... 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...... 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....
International Nuclear Information System (INIS)
McFadden, Paul; Skenderis, Kostas
2011-01-01
We investigate the non-Gaussianity of primordial cosmological perturbations within our recently proposed holographic description of inflationary universes. We derive a holographic formula that determines the bispectrum of cosmological curvature perturbations in terms of correlation functions of a holographically dual three-dimensional non-gravitational quantum field theory (QFT). This allows us to compute the primordial bispectrum for a universe which started in a non-geometric holographic phase, using perturbative QFT calculations. Strikingly, for a class of models specified by a three-dimensional super-renormalisable QFT, the primordial bispectrum is of exactly the factorisable equilateral form with f NL equil. = 5/36, irrespective of the details of the dual QFT. A by-product of this investigation is a holographic formula for the three-point function of the trace of the stress-energy tensor along general holographic RG flows, which should have applications outside the remit of this work
Tracking speckle displacement by double Kalman filtering
Institute of Scientific and Technical Information of China (English)
Donghui Li; Li Guo
2006-01-01
@@ A tracking technique using two sequentially-connected Kalman filter for tracking laser speckle displacement is presented. One Kalman filter tracks temporal speckle displacement, while another Kalman filter tracks spatial speckle displacement. The temporal Kalman filter provides a prior for the spatial Kalman filter, and the spatial Kalman filter provides measurements for the temporal Kalman filter. The contribution of a prior to estimations of the spatial Kalman filter is analyzed. An optical analysis system was set up to verify the double-Kalman-filter tracker's ability of tracking laser speckle's constant displacement.
Correcting for motion artifact in handheld laser speckle images
Lertsakdadet, Ben; Yang, Bruce Y.; Dunn, Cody E.; Ponticorvo, Adrien; Crouzet, Christian; Bernal, Nicole; Durkin, Anthony J.; Choi, Bernard
2018-03-01
Laser speckle imaging (LSI) is a wide-field optical technique that enables superficial blood flow quantification. LSI is normally performed in a mounted configuration to decrease the likelihood of motion artifact. However, mounted LSI systems are cumbersome and difficult to transport quickly in a clinical setting for which portability is essential in providing bedside patient care. To address this issue, we created a handheld LSI device using scientific grade components. To account for motion artifact of the LSI device used in a handheld setup, we incorporated a fiducial marker (FM) into our imaging protocol and determined the difference between highest and lowest speckle contrast values for the FM within each data set (Kbest and Kworst). The difference between Kbest and Kworst in mounted and handheld setups was 8% and 52%, respectively, thereby reinforcing the need for motion artifact quantification. When using a threshold FM speckle contrast value (KFM) to identify a subset of images with an acceptable level of motion artifact, mounted and handheld LSI measurements of speckle contrast of a flow region (KFLOW) in in vitro flow phantom experiments differed by 8%. Without the use of the FM, mounted and handheld KFLOW values differed by 20%. To further validate our handheld LSI device, we compared mounted and handheld data from an in vivo porcine burn model of superficial and full thickness burns. The speckle contrast within the burn region (KBURN) of the mounted and handheld LSI data differed by burns. Collectively, our results suggest the potential of handheld LSI with an FM as a suitable alternative to mounted LSI, especially in challenging clinical settings with space limitations such as the intensive care unit.
CSIR Research Space (South Africa)
Chen, M
2010-10-01
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...
Large deviations for Gaussian processes in Hoelder norm
International Nuclear Information System (INIS)
Fatalov, V R
2003-01-01
Some results are proved on the exact asymptotic representation of large deviation probabilities for Gaussian processes in the Hoeder norm. The following classes of processes are considered: the Wiener process, the Brownian bridge, fractional Brownian motion, and stationary Gaussian processes with power-law covariance function. The investigation uses the method of double sums for Gaussian fields
Inflation in random Gaussian landscapes
Energy Technology Data Exchange (ETDEWEB)
Masoumi, Ali; Vilenkin, Alexander; Yamada, Masaki, E-mail: ali@cosmos.phy.tufts.edu, E-mail: vilenkin@cosmos.phy.tufts.edu, E-mail: Masaki.Yamada@tufts.edu [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States)
2017-05-01
We develop analytic and numerical techniques for studying the statistics of slow-roll inflation in random Gaussian landscapes. As an illustration of these techniques, we analyze small-field inflation in a one-dimensional landscape. We calculate the probability distributions for the maximal number of e-folds and for the spectral index of density fluctuations n {sub s} and its running α {sub s} . These distributions have a universal form, insensitive to the correlation function of the Gaussian ensemble. We outline possible extensions of our methods to a large number of fields and to models of large-field inflation. These methods do not suffer from potential inconsistencies inherent in the Brownian motion technique, which has been used in most of the earlier treatments.
Speckle photography applied to measure deformations of very large structures
Conley, Edgar; Morgan, Chris K.
1995-04-01
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.
Real time processor for array speckle interferometry
Chin, Gordon; Florez, Jose; Borelli, Renan; Fong, Wai; Miko, Joseph; Trujillo, Carlos
1989-02-01
The authors are constructing a real-time processor to acquire image frames, perform array flat-fielding, execute a 64 x 64 element two-dimensional complex FFT (fast Fourier transform) and average the power spectrum, all within the 25 ms coherence time for speckles at near-IR (infrared) wavelength. The processor will be a compact unit controlled by a PC with real-time display and data storage capability. This will provide the ability to optimize observations and obtain results on the telescope rather than waiting several weeks before the data can be analyzed and viewed with offline methods. The image acquisition and processing, design criteria, and processor architecture are described.
Simple educational tool for digital speckle shearography
International Nuclear Information System (INIS)
Schirripa Spagnolo, Giuseppe; Martocchia, Andrea; Papalillo, Donato; Cozzella, Lorenzo
2012-01-01
In this study, an educational tool has been prepared for obtaining short-term and more economic training on digital speckle shearography (DSS). Shearography non-destructive testing (NDT) has gained wide acceptance over the last decade, providing a number of important and exciting inspection solutions in aerospace, electronics and medical device manufacturing. For exploring these motivations, it is important to develop didactic tools to understand the potential of digital shearography through training and didactic courses in the field of NDT. In this paper we describe a simple tool for making one familiar with the potential of DSS in the area of education and training. The system is realized with a simple and economic optical setup and a virtual instrument based on the LabVIEW™ and DAQ. (paper)
International Nuclear Information System (INIS)
Yarovoi, V V; Kirsanov, A V
2002-01-01
A model of the so-called short hologram, which does not exhibit in-depth diffraction deformation of the fine speckle pattern of the recording fields, is studied. The investigation is performed by the example of a thermal hologram recorded by two speckle waves, which is the output mirror of a ring laser produced as a result of this recording. It is shown that the ability of this short hologram to select a wave conjugated to a speckle signal in the mode of the holographic laser depends both on the degree of mutual mixing of the speckles of recording beams in the hologram volume and on the effects of its saturation by the beams. The maximum accuracy of phase conjugation of speckle radiation in the holographic Nd:YAG laser achieved upon the best selection of the conjugate wave by the short thermal hologram was 93%. (nonlinear optical phenomena)
Gaussian processes for machine learning.
Seeger, Matthias
2004-04-01
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.
Gaussian entanglement revisited
Lami, Ludovico; Serafini, Alessio; Adesso, Gerardo
2018-02-01
We present a novel approach to the separability problem for Gaussian quantum states of bosonic continuous variable systems. We derive a simplified necessary and sufficient separability criterion for arbitrary Gaussian states of m versus n modes, which relies on convex optimisation over marginal covariance matrices on one subsystem only. We further revisit the currently known results stating the equivalence between separability and positive partial transposition (PPT) for specific classes of Gaussian states. Using techniques based on matrix analysis, such as Schur complements and matrix means, we then provide a unified treatment and compact proofs of all these results. In particular, we recover the PPT-separability equivalence for: (i) Gaussian states of 1 versus n modes; and (ii) isotropic Gaussian states. In passing, we also retrieve (iii) the recently established equivalence between separability of a Gaussian state and and its complete Gaussian extendability. Our techniques are then applied to progress beyond the state of the art. We prove that: (iv) Gaussian states that are invariant under partial transposition are necessarily separable; (v) the PPT criterion is necessary and sufficient for separability for Gaussian states of m versus n modes that are symmetric under the exchange of any two modes belonging to one of the parties; and (vi) Gaussian states which remain PPT under passive optical operations can not be entangled by them either. This is not a foregone conclusion per se (since Gaussian bound entangled states do exist) and settles a question that had been left unanswered in the existing literature on the subject. This paper, enjoyable by both the quantum optics and the matrix analysis communities, overall delivers technical and conceptual advances which are likely to be useful for further applications in continuous variable quantum information theory, beyond the separability problem.
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, ...
New developments in NDT through electronic speckle pattern interferometry
International Nuclear Information System (INIS)
Mohan, S.; Murugesan, P; Mas, R.H.
2007-01-01
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
Gaussian statistics for palaeomagnetic vectors
Love, J.J.; Constable, C.G.
2003-01-01
With the aim of treating the statistics of palaeomagnetic directions and intensities jointly and consistently, we represent the mean and the variance of palaeomagnetic vectors, at a particular site and of a particular polarity, by a probability density function in a Cartesian three-space of orthogonal magnetic-field components consisting of a single (unimoda) non-zero mean, spherically-symmetrical (isotropic) Gaussian function. For palaeomagnetic data of mixed polarities, we consider a bimodal distribution consisting of a pair of such symmetrical Gaussian functions, with equal, but opposite, means and equal variances. For both the Gaussian and bi-Gaussian distributions, and in the spherical three-space of intensity, inclination, and declination, we obtain analytical expressions for the marginal density functions, the cumulative distributions, and the expected values and variances for each spherical coordinate (including the angle with respect to the axis of symmetry of the distributions). The mathematical expressions for the intensity and off-axis angle are closed-form and especially manageable, with the intensity distribution being Rayleigh-Rician. In the limit of small relative vectorial dispersion, the Gaussian (bi-Gaussian) directional distribution approaches a Fisher (Bingham) distribution and the intensity distribution approaches a normal distribution. In the opposite limit of large relative vectorial dispersion, the directional distributions approach a spherically-uniform distribution and the intensity distribution approaches a Maxwell distribution. We quantify biases in estimating the properties of the vector field resulting from the use of simple arithmetic averages, such as estimates of the intensity or the inclination of the mean vector, or the variances of these quantities. With the statistical framework developed here and using the maximum-likelihood method, which gives unbiased estimates in the limit of large data numbers, we demonstrate how to
Gaussian statistics for palaeomagnetic vectors
Love, J. J.; Constable, C. G.
2003-03-01
With the aim of treating the statistics of palaeomagnetic directions and intensities jointly and consistently, we represent the mean and the variance of palaeomagnetic vectors, at a particular site and of a particular polarity, by a probability density function in a Cartesian three-space of orthogonal magnetic-field components consisting of a single (unimodal) non-zero mean, spherically-symmetrical (isotropic) Gaussian function. For palaeomagnetic data of mixed polarities, we consider a bimodal distribution consisting of a pair of such symmetrical Gaussian functions, with equal, but opposite, means and equal variances. For both the Gaussian and bi-Gaussian distributions, and in the spherical three-space of intensity, inclination, and declination, we obtain analytical expressions for the marginal density functions, the cumulative distributions, and the expected values and variances for each spherical coordinate (including the angle with respect to the axis of symmetry of the distributions). The mathematical expressions for the intensity and off-axis angle are closed-form and especially manageable, with the intensity distribution being Rayleigh-Rician. In the limit of small relative vectorial dispersion, the Gaussian (bi-Gaussian) directional distribution approaches a Fisher (Bingham) distribution and the intensity distribution approaches a normal distribution. In the opposite limit of large relative vectorial dispersion, the directional distributions approach a spherically-uniform distribution and the intensity distribution approaches a Maxwell distribution. We quantify biases in estimating the properties of the vector field resulting from the use of simple arithmetic averages, such as estimates of the intensity or the inclination of the mean vector, or the variances of these quantities. With the statistical framework developed here and using the maximum-likelihood method, which gives unbiased estimates in the limit of large data numbers, we demonstrate how to
Modeling laser speckle imaging of perfusion in the skin (Conference Presentation)
Regan, Caitlin; Hayakawa, Carole K.; Choi, Bernard
2016-02-01
Laser speckle imaging (LSI) enables visualization of relative blood flow and perfusion in the skin. It is frequently applied to monitor treatment of vascular malformations such as port wine stain birthmarks, and measure changes in perfusion due to peripheral vascular disease. We developed a computational Monte Carlo simulation of laser speckle contrast imaging to quantify how tissue optical properties, blood vessel depths and speeds, and tissue perfusion affect speckle contrast values originating from coherent excitation. The simulated tissue geometry consisted of multiple layers to simulate the skin, or incorporated an inclusion such as a vessel or tumor at different depths. Our simulation used a 30x30mm uniform flat light source to optically excite the region of interest in our sample to better mimic wide-field imaging. We used our model to simulate how dynamically scattered photons from a buried blood vessel affect speckle contrast at different lateral distances (0-1mm) away from the vessel, and how these speckle contrast changes vary with depth (0-1mm) and flow speed (0-10mm/s). We applied the model to simulate perfusion in the skin, and observed how different optical properties, such as epidermal melanin concentration (1%-50%) affected speckle contrast. We simulated perfusion during a systolic forearm occlusion and found that contrast decreased by 35% (exposure time = 10ms). Monte Carlo simulations of laser speckle contrast give us a tool to quantify what regions of the skin are probed with laser speckle imaging, and measure how the tissue optical properties and blood flow affect the resulting images.
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.
2003-01-01
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
DEFF Research Database (Denmark)
Ma, Ning; Hanson, Steen Grüner; Lee, Tim K.
2015-01-01
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 special depolarizer: the random roughness birefringent screen (RRBS) is introduced to meet this requirement. The statistical properties of the field generated by the depolarizer is investigated and illustrated in terms of the 2x2 beam coherence and polarization matrix (BCPM) with the corresponding degree...... 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....
Speckle imaging algorithms for planetary imaging
Energy Technology Data Exchange (ETDEWEB)
Johansson, E. [Lawrence Livermore National Lab., CA (United States)
1994-11-15
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.
CSIR Research Space (South Africa)
Roux, FS
2009-01-01
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...
Gaussian operations and privacy
International Nuclear Information System (INIS)
Navascues, Miguel; Acin, Antonio
2005-01-01
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
Czech Academy of Sciences Publication Activity Database
Kaprálová-Žďánská, Petra Ruth; Šmydke, Jan; Civiš, S.
2013-01-01
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
Galaxy bias and primordial non-Gaussianity
Energy Technology Data Exchange (ETDEWEB)
Assassi, Valentin; Baumann, Daniel [DAMTP, Cambridge University, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Schmidt, Fabian, E-mail: assassi@ias.edu, E-mail: D.D.Baumann@uva.nl, E-mail: fabians@MPA-Garching.MPG.DE [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85748 Garching (Germany)
2015-12-01
We present a systematic study of galaxy biasing in the presence of primordial non-Gaussianity. For a large class of non-Gaussian initial conditions, we define a general bias expansion and prove that it is closed under renormalization, thereby showing that the basis of operators in the expansion is complete. We then study the effects of primordial non-Gaussianity on the statistics of galaxies. We show that the equivalence principle enforces a relation between the scale-dependent bias in the galaxy power spectrum and that in the dipolar part of the bispectrum. This provides a powerful consistency check to confirm the primordial origin of any observed scale-dependent bias. Finally, we also discuss the imprints of anisotropic non-Gaussianity as motivated by recent studies of higher-spin fields during inflation.
Galaxy bias and primordial non-Gaussianity
International Nuclear Information System (INIS)
Assassi, Valentin; Baumann, Daniel; Schmidt, Fabian
2015-01-01
We present a systematic study of galaxy biasing in the presence of primordial non-Gaussianity. For a large class of non-Gaussian initial conditions, we define a general bias expansion and prove that it is closed under renormalization, thereby showing that the basis of operators in the expansion is complete. We then study the effects of primordial non-Gaussianity on the statistics of galaxies. We show that the equivalence principle enforces a relation between the scale-dependent bias in the galaxy power spectrum and that in the dipolar part of the bispectrum. This provides a powerful consistency check to confirm the primordial origin of any observed scale-dependent bias. Finally, we also discuss the imprints of anisotropic non-Gaussianity as motivated by recent studies of higher-spin fields during inflation
Mitri, F G; Fellah, Z E A
2014-01-01
The present analysis investigates the (axial) acoustic radiation force induced by a quasi-Gaussian beam centered on an elastic and a viscoelastic (polymer-type) sphere in a nonviscous fluid. The quasi-Gaussian beam is an exact solution of the source free Helmholtz wave equation and is characterized by an arbitrary waist w₀ and a diffraction convergence length known as the Rayleigh range z(R). Examples are found where the radiation force unexpectedly approaches closely to zero at some of the elastic sphere's resonance frequencies for kw₀≤1 (where this range is of particular interest in describing strongly focused or divergent beams), which may produce particle immobilization along the axial direction. Moreover, the (quasi)vanishing behavior of the radiation force is found to be correlated with conditions giving extinction of the backscattering by the quasi-Gaussian beam. Furthermore, the mechanism for the quasi-zero force is studied theoretically by analyzing the contributions of the kinetic, potential and momentum flux energy densities and their density functions. It is found that all the components vanish simultaneously at the selected ka values for the nulls. However, for a viscoelastic sphere, acoustic absorption degrades the quasi-zero radiation force. Copyright © 2013 Elsevier B.V. All rights reserved.
ARTIFICIAL INCOHERENT SPECKLES ENABLE PRECISION ASTROMETRY AND PHOTOMETRY IN HIGH-CONTRAST IMAGING
Energy Technology Data Exchange (ETDEWEB)
Jovanovic, N.; Guyon, O.; Pathak, P.; Kudo, T. [National Astronomical Observatory of Japan, Subaru Telescope, 650 North A’Ohoku Place, Hilo, HI, 96720 (United States); Martinache, F. [Observatoire de la Cote d’Azur, Boulevard de l’Observatoire, F-06304 Nice (France); Hagelberg, J., E-mail: jovanovic.nem@gmail.com [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)
2015-11-10
State-of-the-art coronagraphs employed on extreme adaptive optics enabled instruments are constantly improving the contrast detection limit for companions at ever-closer separations from the host star. In order to constrain their properties and, ultimately, compositions, it is important to precisely determine orbital parameters and contrasts with respect to the stars they orbit. This can be difficult in the post-coronagraphic image plane, as by definition the central star has been occulted by the coronagraph. We demonstrate the flexibility of utilizing the deformable mirror in the adaptive optics system of the Subaru Coronagraphic Extreme Adaptive Optics system to generate a field of speckles for the purposes of calibration. Speckles can be placed up to 22.5 λ/D from the star, with any position angle, brightness, and abundance required. Most importantly, we show that a fast modulation of the added speckle phase, between 0 and π, during a long science integration renders these speckles effectively incoherent with the underlying halo. We quantitatively show for the first time that this incoherence, in turn, increases the robustness and stability of the adaptive speckles, which will improve the precision of astrometric and photometric calibration procedures. This technique will be valuable for high-contrast imaging observations with imagers and integral field spectrographs alike.
Vegetation Detection in Stress of Moisture Shortage Based on Laser Speckle Recognition
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.
Funamizu, Hideki; Onodera, Yusei; Aizu, Yoshihisa
2018-05-01
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.
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
2014-01-01
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
The SKED: speckle knife edge detector
Sharpies, S. D.; Light, R. A.; Achamfuo-Yeboah, S. O.; Clark, M.; Somekh, M. G.
2014-06-01
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.
Nonclassicality by Local Gaussian Unitary Operations for Gaussian States
Directory of Open Access Journals (Sweden)
Yangyang Wang
2018-04-01
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.
Generalized Gaussian Error Calculus
Grabe, Michael
2010-01-01
For the first time in 200 years Generalized Gaussian Error Calculus addresses a rigorous, complete and self-consistent revision of the Gaussian error calculus. Since experimentalists realized that measurements in general are burdened by unknown systematic errors, the classical, widespread used evaluation procedures scrutinizing the consequences of random errors alone turned out to be obsolete. As a matter of course, the error calculus to-be, treating random and unknown systematic errors side by side, should ensure the consistency and traceability of physical units, physical constants and physical quantities at large. The generalized Gaussian error calculus considers unknown systematic errors to spawn biased estimators. Beyond, random errors are asked to conform to the idea of what the author calls well-defined measuring conditions. The approach features the properties of a building kit: any overall uncertainty turns out to be the sum of a contribution due to random errors, to be taken from a confidence inter...
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....
Speckle techniques for determining stresses in moving objects
Murphree, E. A.; Wilson, T. F.; Ranson, W. F.; Swinson, W. F.
1978-01-01
Laser speckle interferometry is a relatively new experimental technique which shows promise of alleviating many difficult problems in experimental mechanics. The method utilizes simple high-resolution photographs of the surface which is illuminated by coherent light. The result is a real-time or permanently stored whole-field record of interference fringes which yields a map of displacements in the object. In this thesis, the time-average theory using the Fourier transform is developed to present the application of this technique to measurement of in-plane displacement induced by the vibration of an object.
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.
2008-01-01
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
Theoretical investigations on dual-beam illumination electronic speckle pattern interferometry
International Nuclear Information System (INIS)
Goudemand, Nicolas
2006-01-01
Contrary to what is found in most of the existing scientific literature,where a specific frame is developed, the theory of speckle interferometry is (conveniently) presented here as a particular case of the more general theory of holographic interferometry. In addition to the intellectual benefit of dealing with a single unified theory, this brings about many advantages when it comes to discuss fundamental topics such as the three-dimensional evolution of the complex amplitude of the diffuse optical wave fronts, the degree of approximation of the leading formulas, the loss of fringe contrast,the decorrelation effects, the real influence of the terms generally neglected in out-of-focus regions. In the same way, the statistical properties of the speckle fields, usually treated as a separate subject matter, are also integrated in the theory, thus providing a comprehensive knowledge of the qualitative features of speckle interferometry methods, otherwise difficult to understand
Theoretical investigations on dual-beam illumination electronic speckle pattern interferometry
Goudemand, Nicolas
2006-07-01
Contrary to what is found in most of the existing scientific literature, where a specific frame is developed, the theory of speckle interferometry is (conveniently) presented here as a particular case of the more general theory of holographic interferometry. In addition to the intellectual benefit of dealing with a single unified theory, this brings about many advantages when it comes to discuss fundamental topics such as the three-dimensional evolution of the complex amplitude of the diffuse optical wavefronts, the degree of approximation of the leading formulas, the loss of fringe contrast, the decorrelation effects, the real influence of the terms generally neglected in out-of-focus regions. In the same way, the statistical properties of the speckle fields, usually treated as a separate subject matter, are also integrated in the theory, thus providing a comprehensive knowledge of the qualitative features of speckle interferometry methods, otherwise difficult to understand.
AUTONOMOUS GAUSSIAN DECOMPOSITION
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: rlindner@astro.wisc.edu [University of Tasmania, School of Maths and Physics, Private Bag 37, Hobart, TAS 7001 (Australia)
2015-04-15
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.
Bounded Gaussian process regression
DEFF Research Database (Denmark)
Jensen, Bjørn Sand; Nielsen, Jens Brehm; Larsen, Jan
2013-01-01
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...... with the proposed explicit noise-model extension....
AUTONOMOUS GAUSSIAN DECOMPOSITION
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
2015-01-01
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
Speckle perception and disturbance limit in laser based projectors
Verschaffelt, Guy; Roelandt, Stijn; Meuret, Youri; Van den Broeck, Wendy; Kilpi, Katriina; Lievens, Bram; Jacobs, An; Janssens, Peter; Thienpont, Hugo
2016-04-01
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.
Speckle-learning-based object recognition through scattering media.
Ando, Takamasa; Horisaki, Ryoichi; Tanida, Jun
2015-12-28
We experimentally demonstrated object recognition through scattering media based on direct machine learning of a number of speckle intensity images. In the experiments, speckle intensity images of amplitude or phase objects on a spatial light modulator between scattering plates were captured by a camera. We used the support vector machine for binary classification of the captured speckle intensity images of face and non-face data. The experimental results showed that speckles are sufficient for machine learning.
Statistical Image Recovery From Laser Speckle Patterns With Polarization Diversity
2010-09-01
several techniques for speckle suppression in optical imaging [19]. However, averaging nonimaged laser speckle patterns does not yield the same result...Comparison”. Applied Optics , 21(15):2758–2769, August 1982. 13. Fienup, James R. “Image Formation from Nonimaged Laser Speckle Patterns”. S. R. Robinson...6 ν Optical Frequency . . . . . . . . . . . . . . . . . . . . . . 6 t Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 ϕ
Quantum information with Gaussian states
International Nuclear Information System (INIS)
Wang Xiangbin; Hiroshima, Tohya; Tomita, Akihisa; Hayashi, Masahito
2007-01-01
Quantum optical Gaussian states are a type of important robust quantum states which are manipulatable by the existing technologies. So far, most of the important quantum information experiments are done with such states, including bright Gaussian light and weak Gaussian light. Extending the existing results of quantum information with discrete quantum states to the case of continuous variable quantum states is an interesting theoretical job. The quantum Gaussian states play a central role in such a case. We review the properties and applications of Gaussian states in quantum information with emphasis on the fundamental concepts, the calculation techniques and the effects of imperfections of the real-life experimental setups. Topics here include the elementary properties of Gaussian states and relevant quantum information device, entanglement-based quantum tasks such as quantum teleportation, quantum cryptography with weak and strong Gaussian states and the quantum channel capacity, mathematical theory of quantum entanglement and state estimation for Gaussian states
Quantum beamstrahlung from gaussian bunches
International Nuclear Information System (INIS)
Chen, P.
1987-08-01
The method of Baier and Katkov is applied to calculate the correction terms to the Sokolov-Ternov radiation formula due to the variation of the magnetic field strength along the trajectory of a radiating particle. We carry the calculation up to the second order in the power expansion of B tau/B, where tau is the formation time of radiation. The expression is then used to estimate the quantum beamstrahlung average energy loss from e + e - bunches with gaussian distribution in bunch currents. We show that the effect of the field variation is to reduce the average energy loss from previous calculations based on the Sokolov-Ternov formula or its equivalent. Due to the limitation of our method, only an upper bound of the reduction is obtained. 18 refs
Convergence of posteriors for discretized log Gaussian Cox processes
DEFF Research Database (Denmark)
Waagepetersen, Rasmus Plenge
2004-01-01
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....
Chimera states in Gaussian coupled map lattices
Li, Xiao-Wen; Bi, Ran; Sun, Yue-Xiang; Zhang, Shuo; Song, Qian-Qian
2018-04-01
We study chimera states in one-dimensional and two-dimensional Gaussian coupled map lattices through simulations and experiments. Similar to the case of global coupling oscillators, individual lattices can be regarded as being controlled by a common mean field. A space-dependent order parameter is derived from a self-consistency condition in order to represent the collective state.
Improving the gaussian effective potential: quantum mechanics
International Nuclear Information System (INIS)
Eboli, O.J.P.; Thomaz, M.T.; Lemos, N.A.
1990-08-01
In order to gain intuition for variational problems in field theory, we analyze variationally the quantum-mechanical anharmonic oscillator [(V(x)sup(k) - sub(2) x sup(2) + sup(λ) - sub(4) λ sup(4)]. Special attention is paid to improvements to the Gaussian effective potential. (author)
Analysis of Minute Features in Speckled Imagery with Maximum Likelihood Estimation
Directory of Open Access Journals (Sweden)
Alejandro C. Frery
2004-12-01
Full Text Available This paper deals with numerical problems arising when performing maximum likelihood parameter estimation in speckled imagery using small samples. The noise that appears in images obtained with coherent illumination, as is the case of sonar, laser, ultrasound-B, and synthetic aperture radar, is called speckle, and it can neither be assumed Gaussian nor additive. The properties of speckle noise are well described by the multiplicative model, a statistical framework from which stem several important distributions. Amongst these distributions, one is regarded as the universal model for speckled data, namely, the Ã°ÂÂ’Â¢0 law. This paper deals with amplitude data, so the Ã°ÂÂ’Â¢A0 distribution will be used. The literature reports that techniques for obtaining estimates (maximum likelihood, based on moments and on order statistics of the parameters of the Ã°ÂÂ’Â¢A0 distribution require samples of hundreds, even thousands, of observations in order to obtain sensible values. This is verified for maximum likelihood estimation, and a proposal based on alternate optimization is made to alleviate this situation. The proposal is assessed with real and simulated data, showing that the convergence problems are no longer present. A Monte Carlo experiment is devised to estimate the quality of maximum likelihood estimators in small samples, and real data is successfully analyzed with the proposed alternated procedure. Stylized empirical influence functions are computed and used to choose a strategy for computing maximum likelihood estimates that is resistant to outliers.
Gaussian discriminating strength
Rigovacca, L.; Farace, A.; De Pasquale, A.; Giovannetti, V.
2015-10-01
We present a quantifier of nonclassical correlations for bipartite, multimode Gaussian states. It is derived from the Discriminating Strength measure, introduced for finite dimensional systems in Farace et al., [New J. Phys. 16, 073010 (2014), 10.1088/1367-2630/16/7/073010]. As the latter the new measure exploits the quantum Chernoff bound to gauge the susceptibility of the composite system with respect to local perturbations induced by unitary gates extracted from a suitable set of allowed transformations (the latter being identified by posing some general requirements). Closed expressions are provided for the case of two-mode Gaussian states obtained by squeezing or by linearly mixing via a beam splitter a factorized two-mode thermal state. For these density matrices, we study how nonclassical correlations are related with the entanglement present in the system and with its total photon number.
Speckle disturbance limit in laser-based cinema projection systems
Verschaffelt, Guy; Roelandt, Stijn; Meuret, Youri; van den Broeck, Wendy; Kilpi, Katriina; Lievens, Bram; Jacobs, An; Janssens, Peter; Thienpont, Hugo
2015-09-01
In a multi-disciplinary effort, we investigate the level of speckle that can be tolerated in a laser cinema projector based on a quality of experience experiment with movie clips shown to a test audience in a real-life movie theatre setting. 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. The speckle disturbance limit for movies turns out to be substantially larger than that for still images, and hence is easier to attain.
Speckle reduction techniques in digital holography
Energy Technology Data Exchange (ETDEWEB)
Monaghan, David; Kelly, Damien; Hennelly, Bryan [Department of Computer Science, National University of Ireland, Maynooth, Co. Kildare (Ireland); Javidi, Bahram, E-mail: bryanh@cs.nuim.i [University of Connecticut Electrical and Computer Engineering Department 371 Fairfield Road, Unit 2157 Storrs, CT 06269-2157 (United States)
2010-02-01
We have studied several speckle reduction techniques, applicable to digital holography. These include the use of optical diffusers, wavelet filtering, simulating temporal incoherence and filtering in the Fourier domain. The Digital Holograms (DHs) used in this study are captured using a Phase Shift Interferometric (PSI) in-line setup and subsequently reconstructed numerically.
International Nuclear Information System (INIS)
Liu Shixiong; Guo Hong; Liu Mingwei; Wu Guohua
2004-01-01
Propagation characteristics of focused Gaussian beam (FoGB) and fundamental Gaussian beam (FuGB) propagating in vacuum are investigated. Based on the Fourier transform and the angular spectral analysis, the transverse component and the second-order approximate longitudinal component of the electric field are obtained in the paraxial approximation. The electric field components, the phase velocity and the group velocity of FoGB are compared with those of FuGB. The spot size of FoGB is also discussed
Interconversion of pure Gaussian states requiring non-Gaussian operations
Jabbour, Michael G.; García-Patrón, Raúl; Cerf, Nicolas J.
2015-01-01
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.
Yurinsky, Vadim Vladimirovich
1995-01-01
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.
Simple form for the Gaussian equations in curved space
International Nuclear Information System (INIS)
Mazzitelli, F.D.; Paz, J.P.
1988-01-01
We show that the variational Gaussian equations for λphi 4 theory in an arbitrary background gravitational field admit a simple form, which allows the use of a Schwinger-DeWitt-type expansion in order to renormalize them
NESSI and `Alopeke: Two new dual-channel speckle imaging instruments
Scott, Nicholas J.
2018-01-01
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
2017-01-01
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
Estimators for local non-Gaussianities
International Nuclear Information System (INIS)
Creminelli, P.; Senatore, L.; Zaldarriaga, M.
2006-05-01
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)
How Gaussian can our Universe be?
Cabass, G.; Pajer, E.; Schmidt, F.
2017-01-01
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 controlled by two observables: the tensor-to-scalar ratio, which is uncertain by more than fifty orders of magnitude; and the scalar spectral index, or tilt, which is relatively well measured. It is well known that to leading and next-to-leading order in derivatives, the contributions proportional to the tilt disappear from any local observable, and suspicion has been raised that this might happen to all orders, allowing for an arbitrarily low amount of primordial non-Gaussianity. Employing Conformal Fermi Coordinates, we show explicitly that this is not the case. Instead, a contribution of order the tilt appears in local observables. In summary, the floor of physical primordial non-Gaussianity in our Universe has a squeezed-limit scaling of kl2/ks2, similar to equilateral and orthogonal shapes, and a dimensionless amplitude of order 0.1 × (ns-1).
How Gaussian can our Universe be?
Energy Technology Data Exchange (ETDEWEB)
Cabass, G. [Physics Department and INFN, Università di Roma ' ' La Sapienza' ' , P.le Aldo Moro 2, 00185, Rome (Italy); Pajer, E. [Institute for Theoretical Physics and Center for Extreme Matter and Emergent Phenomena, Utrecht University, Princetonplein 5, 3584 CC Utrecht (Netherlands); Schmidt, F., E-mail: giovanni.cabass@roma1.infn.it, E-mail: e.pajer@uu.nl, E-mail: fabians@mpa-garching.mpg.de [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching (Germany)
2017-01-01
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 controlled by two observables: the tensor-to-scalar ratio, which is uncertain by more than fifty orders of magnitude; and the scalar spectral index, or tilt, which is relatively well measured. It is well known that to leading and next-to-leading order in derivatives, the contributions proportional to the tilt disappear from any local observable, and suspicion has been raised that this might happen to all orders, allowing for an arbitrarily low amount of primordial non-Gaussianity. Employing Conformal Fermi Coordinates, we show explicitly that this is not the case. Instead, a contribution of order the tilt appears in local observables. In summary, the floor of physical primordial non-Gaussianity in our Universe has a squeezed-limit scaling of k {sub ℓ}{sup 2}/ k {sub s} {sup 2}, similar to equilateral and orthogonal shapes, and a dimensionless amplitude of order 0.1 × ( n {sub s}−1).
Twisted speckle entities inside wave-front reversal mirrors
International Nuclear Information System (INIS)
Okulov, A. Yu
2009-01-01
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.
Speckle Tracking and Transthyretin Amyloid Cardiomyopathy
Directory of Open Access Journals (Sweden)
Alexandre Marins Rocha
Full Text Available Abstract Background: Amyloidosis is a disease caused by deposits of insoluble fibrils in extracellular spaces. The most common type of familial amyloidosis is mediated by mutation of transthyretin, especially Val30Met. Symptoms and ejection fraction decrease may occur in cardiac amyloidosis only in case of poor prognosis. Myocardial strain detected by two-dimensional speckle tracking echocardiography can indicate changes in myocardial function at early stages of the disease. Objective: To determine the accuracy of left ventricular longitudinal strain by two-dimensional speckle tracking echocardiography in patients with familial amyloidosis caused by Val30Met transthyretin mutation. Methods: Eighteen consecutive patients, carriers of transthyretin mutation, were evaluated by two-dimensional speckle tracking echocardiography, by which myocardial strain curves were obtained, following the American Society of Echocardiography recommendations. Results: Patients were divided into three groups: 1- Val30Met with cardiac amyloidosis; 2-Val30Met with extracardiac amyloidosis; 3 - Val30Met without evidence of disease. As the three groups were compared by the Mann-Whitney test, we found a statistically significant difference between groups 1 and 2 in the mean longitudinal tension (p=0.01, mean basal longitudinal strain (p=0.014; in mean longitudinal tension and mean longitudinal strain between groups 1 and 3 (p=0.005; and in the ratio of longitudinal strain of apical septum segment to longitudinal strain of basal septum (p=0.041 between groups 2 and 3. Conclusion: Left ventricular longitudinal strain detected by two-dimensional speckle tracking echocardiography is able to diagnose left ventricular dysfunction in early stages of familial amyloidosis caused by transthyretin Val30Met mutation.
Dynamic laser speckle for non-destructive quality evaluation of bread
Stoykova, E.; Ivanov, B.; Shopova, M.; Lyubenova, T.; Panchev, I.; Sainov, V.
2010-10-01
Coherent illumination of a diffuse object yields a randomly varying interference pattern, which changes over time at any modification of the object. This phenomenon can be used for detection and visualization of physical or biological activity in various objects (e.g. fruits, seeds, coatings) through statistical description of laser speckle dynamics. The present report aims at non-destructive full-field evaluation of bread by spatial-temporal characterization of laser speckle. The main purpose of the conducted experiments was to prove the ability of the dynamic speckle method to indicate activity within the studied bread samples. In the set-up for acquisition and storage of dynamic speckle patterns an expanded beam from a DPSS laser (532 nm and 100mW) illuminated the sample through a ground glass diffuser. A CCD camera, adjusted to focus the sample, recorded regularly a sequence of images (8 bits and 780 x 582 squared pixels, sized 8.1 × 8.1 μm) at sampling frequency 0.25 Hz. A temporal structure function was calculated to evaluate activity of the bread samples in time using the full images in the sequence. In total, 7 samples of two types of bread were monitored during a chemical and physical process of bread's staling. Segmentation of images into matrixes of isometric fragments was also utilized. The results proved the potential of dynamic speckle as effective means for monitoring the process of bread staling and ability of this approach to differentiate between different types of bread.
Static speckle experiments using white synchrotron radiation
Energy Technology Data Exchange (ETDEWEB)
Sant, Tushar; Panzner, Tobias; Pietsch, Ullrich [Solid State Physics Group, University of Siegen (Germany)
2008-07-01
Static speckle experiments were performed using coherent white X-ray radiation from a bending magnet at BESSYII. Semiconductor and polymer surfaces were investigated under incidence condition smaller than the critical angle of total external reflection. The scattering pattern of the sample results from the illumination function modified by the surface undulations. The periodic oscillations are caused by the illumination function whereas other irregular features are associated with sample surface. The speckle map of reflection from a laterally periodic structure like GaAs grating is studied. Under coherent illumination the grating peaks split into speckles because of fluctuations on the sample surface. It is important to understand which length scales on the sample surface are responsible for the oscillations in reflectivity map. To investigate this experiments are done with a triangular shaped sample. Different parts of the sample are illuminated with the footprint on the sample larger or smaller than the actual sample length. This gives prior information about total illuminated area on the sample. Using this additional information a detailed surface profile of the sample is reconstructed.
Early detection and treatment of Speckled leukoplakia
Directory of Open Access Journals (Sweden)
Selviana Tampoma
2016-12-01
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.
Palm distributions for log Gaussian Cox processes
DEFF Research Database (Denmark)
Coeurjolly, Jean-Francois; Møller, Jesper; Waagepetersen, Rasmus Plenge
2017-01-01
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...... result is used to study functional summaries for log Gaussian Cox processes....
Geometry of Gaussian quantum states
International Nuclear Information System (INIS)
Link, Valentin; Strunz, Walter T
2015-01-01
We study the Hilbert–Schmidt measure on the manifold of mixed Gaussian states in multi-mode continuous variable quantum systems. An analytical expression for the Hilbert–Schmidt volume element is derived. Its corresponding probability measure can be used to study typical properties of Gaussian states. It turns out that although the manifold of Gaussian states is unbounded, an ensemble of Gaussian states distributed according to this measure still has a normalizable distribution of symplectic eigenvalues, from which unitarily invariant properties can be obtained. By contrast, we find that for an ensemble of one-mode Gaussian states based on the Bures measure the corresponding distribution cannot be normalized. As important applications, we determine the distribution and the mean value of von Neumann entropy and purity for the Hilbert–Schmidt measure. (paper)
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
2011-01-01
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...... pressure and flow. Nephrons interact by exchanging electrical signals conducted electrotonically through cells of the vascular wall, leading to synchronization of the TGF-mediated oscillations. Experimental studies of these interactions have been limited to observations on two or at most three nephrons...
Speckle Noise Reduction via Nonconvex High Total Variation Approach
Directory of Open Access Journals (Sweden)
Yulian Wu
2015-01-01
Full Text Available We address the problem of speckle noise removal. The classical total variation is extensively used in this field to solve such problem, but this method suffers from the staircase-like artifacts and the loss of image details. In order to resolve these problems, a nonconvex total generalized variation (TGV regularization is used to preserve both edges and details of the images. The TGV regularization which is able to remove the staircase effect has strong theoretical guarantee by means of its high order smooth feature. Our method combines the merits of both the TGV method and the nonconvex variational method and avoids their main drawbacks. Furthermore, we develop an efficient algorithm for solving the nonconvex TGV-based optimization problem. We experimentally demonstrate the excellent performance of the technique, both visually and quantitatively.
Damage monitoring in historical murals by speckle interferometry
Hinsch, Klaus D.; Gulker, Gerd; Joost, Holger
2003-11-01
In the conservation of historical murals it is important to identify loose plaster sections that threaten to fall off. Electronic speckle interferometry in combination with acoustic excitation of the object has been employed to monitor loose areas. To avoid disadvantages of high sound irradiation of the complete building a novel directional audio-sound source based on nonlinear mixing of ultrasound has been introduced. The optical system was revised for optimum performance in the new environment. Emphasis is placed on noise suppression to increase sensitivity. Furthermore, amplitude and phase data of object response over the frequency-range inspected are employed to gain additional information on the state of the plaster or paint. Laboratory studies on sample specimen supplement field campaigns at historical sites.
Cosmological information in Gaussianized weak lensing signals
Joachimi, B.; Taylor, A. N.; Kiessling, A.
2011-11-01
Gaussianizing the one-point distribution of the weak gravitational lensing convergence has recently been shown to increase the signal-to-noise ratio contained in two-point statistics. We investigate the information on cosmology that can be extracted from the transformed convergence fields. Employing Box-Cox transformations to determine optimal transformations to Gaussianity, we develop analytical models for the transformed power spectrum, including effects of noise and smoothing. We find that optimized Box-Cox transformations perform substantially better than an offset logarithmic transformation in Gaussianizing the convergence, but both yield very similar results for the signal-to-noise ratio. None of the transformations is capable of eliminating correlations of the power spectra between different angular frequencies, which we demonstrate to have a significant impact on the errors in cosmology. Analytic models of the Gaussianized power spectrum yield good fits to the simulations and produce unbiased parameter estimates in the majority of cases, where the exceptions can be traced back to the limitations in modelling the higher order correlations of the original convergence. In the ideal case, without galaxy shape noise, we find an increase in the cumulative signal-to-noise ratio by a factor of 2.6 for angular frequencies up to ℓ= 1500, and a decrease in the area of the confidence region in the Ωm-σ8 plane, measured in terms of q-values, by a factor of 4.4 for the best performing transformation. When adding a realistic level of shape noise, all transformations perform poorly with little decorrelation of angular frequencies, a maximum increase in signal-to-noise ratio of 34 per cent, and even slightly degraded errors on cosmological parameters. We argue that to find Gaussianizing transformations of practical use, it will be necessary to go beyond transformations of the one-point distribution of the convergence, extend the analysis deeper into the non
Integration of instrumentation and processing software of a laser speckle contrast imaging system
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.
Ozana, Nisan; Beiderman, Yevgeny; Anand, Arun; Javidi, Baharam; Polani, Sagi; Schwarz, Ariel; Shemer, Amir; Garcia, Javier; Zalevsky, Zeev
2016-06-01
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.
Controllable gaussian-qubit interface for extremal quantum state engineering.
Adesso, Gerardo; Campbell, Steve; Illuminati, Fabrizio; Paternostro, Mauro
2010-06-18
We study state engineering through bilinear interactions between two remote qubits and two-mode gaussian light fields. The attainable two-qubit states span the entire physically allowed region in the entanglement-versus-global-purity plane. Two-mode gaussian states with maximal entanglement at fixed global and marginal entropies produce maximally entangled two-qubit states in the corresponding entropic diagram. We show that a small set of parameters characterizing extremally entangled two-mode gaussian states is sufficient to control the engineering of extremally entangled two-qubit states, which can be realized in realistic matter-light scenarios.
Resource theory of non-Gaussian operations
Zhuang, Quntao; Shor, Peter W.; Shapiro, Jeffrey H.
2018-05-01
Non-Gaussian states and operations are crucial for various continuous-variable quantum information processing tasks. To quantitatively understand non-Gaussianity beyond states, we establish a resource theory for non-Gaussian operations. In our framework, we consider Gaussian operations as free operations, and non-Gaussian operations as resources. We define entanglement-assisted non-Gaussianity generating power and show that it is a monotone that is nonincreasing under the set of free superoperations, i.e., concatenation and tensoring with Gaussian channels. For conditional unitary maps, this monotone can be analytically calculated. As examples, we show that the non-Gaussianity of ideal photon-number subtraction and photon-number addition equal the non-Gaussianity of the single-photon Fock state. Based on our non-Gaussianity monotone, we divide non-Gaussian operations into two classes: (i) the finite non-Gaussianity class, e.g., photon-number subtraction, photon-number addition, and all Gaussian-dilatable non-Gaussian channels; and (ii) the diverging non-Gaussianity class, e.g., the binary phase-shift channel and the Kerr nonlinearity. This classification also implies that not all non-Gaussian channels are exactly Gaussian dilatable. Our resource theory enables a quantitative characterization and a first classification of non-Gaussian operations, paving the way towards the full understanding of non-Gaussianity.
Manoussakis, G.; Delikaraoglou, D.
2011-01-01
In this paper we form relations for the determination of the elements of the E\\"otv\\"os matrix of the Earth's normal gravity field. In addition a relation between the Gauss curvature of the normal equipotential surface and the Gauss curvature of the actual equipotential surface both passing through the point P is presented. For this purpose we use a global Cartesian system (X, Y, Z) and use the variables X, and Y to form a local parameterization a normal equipotential surface to describe its ...
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
2014-01-01
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...... in such applications, we analytically derive conditions for photon efficient light shaping with GPC. When combined with the conditions for optimal contrast developed in previous works, our analysis further simplifies GPCx2019;s implementation. The results of our analysis are applied to practical illumination shapes......, such as a circle and different rectangles commonly used in industrial or commercial applications. We also show simple and efficient beam shaping of arbitrary shapes geared towards biophotonics research and other contemporary applications. Optimized GPC configurations consistently give ~84% efficiency and ~3x...
Ma, Ning; Zhao, Juan; Hanson, Steen G.; Takeda, Mitsuo; Wang, Wei
2016-10-01
Laser speckle has received extensive studies of its basic properties and associated applications. In the majority of research on speckle phenomena, the random optical field has been treated as a scalar optical field, and the main interest has been concentrated on their statistical properties and applications of its intensity distribution. Recently, statistical properties of random electric vector fields referred to as Polarization Speckle have come to attract new interest because of their importance in a variety of areas with practical applications such as biomedical optics and optical metrology. Statistical phenomena of random electric vector fields have close relevance to the theories of speckles, polarization and coherence theory. In this paper, we investigate the correlation tensor for stochastic electromagnetic fields modulated by a depolarizer consisting of a rough-surfaced retardation plate. Under the assumption that the microstructure of the scattering surface on the depolarizer is as fine as to be unresolvable in our observation region, we have derived a relationship between the polarization matrix/coherency matrix for the modulated electric fields behind the rough-surfaced retardation plate and the coherence matrix under the free space geometry. This relation is regarded as entirely analogous to the van Cittert-Zernike theorem of classical coherence theory. Within the paraxial approximation as represented by the ABCD-matrix formalism, the three-dimensional structure of the generated polarization speckle is investigated based on the correlation tensor, indicating a typical carrot structure with a much longer axial dimension than the extent in its transverse dimension.
CSIR Research Space (South Africa)
Dudley, Angela L
2011-09-01
Full Text Available for both a uniform and a normal distribution is investigated. We find that we are able to engineer whether the nondiffracting field will appear as speckle or a structured zero-order Bessel beam by adjusting the standard deviation in the distribution. Having...
Handbook of Gaussian basis sets
International Nuclear Information System (INIS)
Poirier, R.; Kari, R.; Csizmadia, I.G.
1985-01-01
A collection of a large body of information is presented useful for chemists involved in molecular Gaussian computations. Every effort has been made by the authors to collect all available data for cartesian Gaussian as found in the literature up to July of 1984. The data in this text includes a large collection of polarization function exponents but in this case the collection is not complete. Exponents for Slater type orbitals (STO) were included for completeness. This text offers a collection of Gaussian exponents primarily without criticism. (Auth.)
Compound speckles and their statistical and dynamical properties
DEFF Research Database (Denmark)
Hanson, Steen Grüner; Jakobsen, Michael Linde; Skov Hansen, Rene
2008-01-01
Two issues will be treated in this presentation, both focusing on gaining a deeper understanding of dynamic speckles, aiming at the use for probing dynamical properties of scattering structures. The first issue to be addressed is the dynamics of speckles arising from illuminating a solid surface...
Correlation of Spatially Filtered Dynamic Speckles in Distance Measurement Application
International Nuclear Information System (INIS)
Semenov, Dmitry V.; Nippolainen, Ervin; Kamshilin, Alexei A.; Miridonov, Serguei V.
2008-01-01
In this paper statistical properties of spatially filtered dynamic speckles are considered. This phenomenon was not sufficiently studied yet while spatial filtering is an important instrument for speckles velocity measurements. In case of spatial filtering speckle velocity information is derived from the modulation frequency of filtered light power which is measured by photodetector. Typical photodetector output is represented by a narrow-band random noise signal which includes non-informative intervals. Therefore more or less precious frequency measurement requires averaging. In its turn averaging implies uncorrelated samples. However, conducting research we found that correlation is typical property not only of dynamic speckle patterns but also of spatially filtered speckles. Using spatial filtering the correlation is observed as a response of measurements provided to the same part of the object surface or in case of simultaneously using several adjacent photodetectors. Found correlations can not be explained using just properties of unfiltered dynamic speckles. As we demonstrate the subject of this paper is important not only from pure theoretical point but also from the point of applied speckle metrology. E.g. using single spatial filter and an array of photodetector can greatly improve accuracy of speckle velocity measurements
Speckle reduction in digital holography with resampling ring masks
Zhang, Wenhui; Cao, Liangcai; Jin, Guofan
2018-01-01
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.
An adaptive Kalman filter for speckle reductions in ultrasound images
International Nuclear Information System (INIS)
Castellini, G.; Labate, D.; Masotti, L.; Mannini, E.; Rocchi, S.
1988-01-01
Speckle is the term used to describe the granular appearance found in ultrasound images. The presence of speckle reduces the diagnostic potential of the echographic technique because it tends to mask small inhomogeneities of the investigated tissue. We developed a new method of speckle reductions that utilizes an adaptive one-dimensional Kalman filter based on the assumption that the observed image can be considered as a superimposition of speckle on a ''true images''. The filter adaptivity, necessary to avoid loss of resolution, has been obtained by statistical considerations on the local signal variations. The results of the applications of this particular Kalman filter, both on A-Mode and B-MODE images, show a significant speckle reduction
On the Shaker Simulation of Wind-Induced Non-Gaussian Random Vibration
Directory of Open Access Journals (Sweden)
Fei Xu
2016-01-01
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.
Measurement of natural convection by speckle photography
International Nuclear Information System (INIS)
Wernekinck, U.; Merzkirch, W.
1986-01-01
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
Scalable Gaussian Processes and the search for exoplanets
CERN. Geneva
2015-01-01
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.
Imprint of primordial non-Gaussianity on dark matter halo profiles
Energy Technology Data Exchange (ETDEWEB)
Dizgah, Azadeh Moradinezhad; Dodelson, Scott; Riotto, Antonio
2013-09-01
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.
Gaussian Process-Mixture Conditional Heteroscedasticity.
Platanios, Emmanouil A; Chatzis, Sotirios P
2014-05-01
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.
Phase-processing as a tool for speckle reduction in pulse-echo images
DEFF Research Database (Denmark)
Healey, AJ; Leeman, S; Forsberg, F
1991-01-01
. Traditional speckle reduction procedures regard speckle correction as a stochastic process and trade image smoothing (resolution loss) for speckle reduction. Recently, a new phase acknowledging technique has been proposed that is unique in its ability to correct for speckle interference with no image......Due to the coherent nature of conventional ultrasound medical imaging systems interference artefacts occur in pulse echo images. These artefacts are generically termed 'speckle'. The phenomenon may severely limit low contrast resolution with clinically relevant information being obscured...
Characterisation of random Gaussian and non-Gaussian stress processes in terms of extreme responses
Directory of Open Access Journals (Sweden)
Colin Bruno
2015-01-01
Full Text Available In the field of military land vehicles, random vibration processes generated by all-terrain wheeled vehicles in motion are not classical stochastic processes with a stationary and Gaussian nature. Non-stationarity of processes induced by the variability of the vehicle speed does not form a major difficulty because the designer can have good control over the vehicle speed by characterising the histogram of instantaneous speed of the vehicle during an operational situation. Beyond this non-stationarity problem, the hard point clearly lies in the fact that the random processes are not Gaussian and are generated mainly by the non-linear behaviour of the undercarriage and the strong occurrence of shocks generated by roughness of the terrain. This non-Gaussian nature is expressed particularly by very high flattening levels that can affect the design of structures under extreme stresses conventionally acquired by spectral approaches, inherent to Gaussian processes and based essentially on spectral moments of stress processes. Due to these technical considerations, techniques for characterisation of random excitation processes generated by this type of carrier need to be changed, by proposing innovative characterisation methods based on time domain approaches as described in the body of the text rather than spectral domain approaches.
Observations of binary stars by speckle interferometry
International Nuclear Information System (INIS)
Morgan, B.L.; Beckmann, G.K.; Scaddan, R.J.
1980-01-01
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)
Information geometry of Gaussian channels
International Nuclear Information System (INIS)
Monras, Alex; Illuminati, Fabrizio
2010-01-01
We define a local Riemannian metric tensor in the manifold of Gaussian channels and the distance that it induces. We adopt an information-geometric approach and define a metric derived from the Bures-Fisher metric for quantum states. The resulting metric inherits several desirable properties from the Bures-Fisher metric and is operationally motivated by distinguishability considerations: It serves as an upper bound to the attainable quantum Fisher information for the channel parameters using Gaussian states, under generic constraints on the physically available resources. Our approach naturally includes the use of entangled Gaussian probe states. We prove that the metric enjoys some desirable properties like stability and covariance. As a by-product, we also obtain some general results in Gaussian channel estimation that are the continuous-variable analogs of previously known results in finite dimensions. We prove that optimal probe states are always pure and bounded in the number of ancillary modes, even in the presence of constraints on the reduced state input in the channel. This has experimental and computational implications. It limits the complexity of optimal experimental setups for channel estimation and reduces the computational requirements for the evaluation of the metric: Indeed, we construct a converging algorithm for its computation. We provide explicit formulas for computing the multiparametric quantum Fisher information for dissipative channels probed with arbitrary Gaussian states and provide the optimal observables for the estimation of the channel parameters (e.g., bath couplings, squeezing, and temperature).
Quantization analysis of speckle intensity measurements for phase retrieval
DEFF Research Database (Denmark)
Maallo, Anne Margarette S.; Almoro, Percival F.; Hanson, Steen Grüner
2010-01-01
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 experimentally in the static wavefront sensing setup. Resultsshowthat 3 to 4 bits are adequate to represent the speckle intensities and yield acceptable reconstructions at relatively fast convergence rates. Computer memory requirements may be eased down by 2.4 times if a 4 bit instead of an 8 bit camera is used...
Analyzing speckle contrast for HiLo microscopy optimization
Mazzaferri, J.; Kunik, D.; Belisle, J. M.; Singh, K.; Lefrançois, S.; Costantino, S.
2011-07-01
HiLo microscopy is a recently developed technique that provides both optical sectioning and fast imaging with a simple implementation and at a very low cost. The methodology combines widefield and speckled illumination images to obtain one optically sectioned image. Hence, the characteristics of such speckle illumination ultimately determine the quality of HiLo images and the overall performance of the method. In this work, we study how speckle contrast influence local variations of fluorescence intensity and brightness profiles of thick samples. We present this article as a guide to adjust the parameters of the system for optimizing the capabilities of this novel technology.
Detectability of the effect of Inflationary non-Gaussianity on halo bias
Verde, Licia
2009-01-01
We consider the description of the clustering of halos for physically-motivated types of non-Gaussian initial conditions. In particular we include non-Gaussianity of the type arising from single field slow-roll, multi fields, curvaton (local type), higher-order derivative-type (equilateral), vacuum-state modifications (enfolded-type) and horizon-scale GR corrections type. We show that large-scale halo bias is a very sensitive tool to probe non-Gaussianity, potentially leading, for some planned surveys, to a detection of non-Gaussianity arising from horizon-scale GR corrections.
Acousto-electrical speckle pattern in Lorentz force electrical impedance tomography
International Nuclear Information System (INIS)
Grasland-Mongrain, Pol; Destrempes, François; Cloutier, Guy; Mari, Jean-Martial; Souchon, Rémi; Catheline, Stefan; Chapelon, Jean-Yves; Lafon, Cyril
2015-01-01
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. (paper)
Acousto-electrical speckle pattern in Lorentz force electrical impedance tomography
Grasland-Mongrain, Pol; Destrempes, François; Mari, Jean-Martial; Souchon, Rémi; Catheline, Stefan; Chapelon, Jean-Yves; Lafon, Cyril; Cloutier, Guy
2015-05-01
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.
CMB constraints on running non-Gaussianity
Oppizzi, Filippo; Liguori, Michele; Renzi, Alessandro; Arroja, Frederico; Bartolo, Nicola
2017-01-01
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}
Gaussian entanglement distribution via satellite
Hosseinidehaj, Nedasadat; Malaney, Robert
2015-02-01
In this work we analyze three quantum communication schemes for the generation of Gaussian entanglement between two ground stations. Communication occurs via a satellite over two independent atmospheric fading channels dominated by turbulence-induced beam wander. In our first scheme, the engineering complexity remains largely on the ground transceivers, with the satellite acting simply as a reflector. Although the channel state information of the two atmospheric channels remains unknown in this scheme, the Gaussian entanglement generation between the ground stations can still be determined. On the ground, distillation and Gaussification procedures can be applied, leading to a refined Gaussian entanglement generation rate between the ground stations. We compare the rates produced by this first scheme with two competing schemes in which quantum complexity is added to the satellite, thereby illustrating the tradeoff between space-based engineering complexity and the rate of ground-station entanglement generation.
Non-gaussianity versus nonlinearity of cosmological perturbations.
Verde, L
2001-06-01
Following the discovery of the cosmic microwave background, the hot big-bang model has become the standard cosmological model. In this theory, small primordial fluctuations are subsequently amplified by gravity to form the large-scale structure seen today. Different theories for unified models of particle physics, lead to different predictions for the statistical properties of the primordial fluctuations, that can be divided in two classes: gaussian and non-gaussian. Convincing evidence against or for gaussian initial conditions would rule out many scenarios and point us toward a physical theory for the origin of structures. The statistical distribution of cosmological perturbations, as we observe them, can deviate from the gaussian distribution in several different ways. Even if perturbations start off gaussian, nonlinear gravitational evolution can introduce non-gaussian features. Additionally, our knowledge of the Universe comes principally from the study of luminous material such as galaxies, but galaxies might not be faithful tracers of the underlying mass distribution. The relationship between fluctuations in the mass and in the galaxies distribution (bias), is often assumed to be local, but could well be nonlinear. Moreover, galaxy catalogues use the redshift as third spatial coordinate: the resulting redshift-space map of the galaxy distribution is nonlinearly distorted by peculiar velocities. Nonlinear gravitational evolution, biasing, and redshift-space distortion introduce non-gaussianity, even in an initially gaussian fluctuation field. I investigate the statistical tools that allow us, in principle, to disentangle the above different effects, and the observational datasets we require to do so in practice.
Revisiting non-Gaussianity from non-attractor inflation models
Cai, Yi-Fu; Chen, Xingang; Namjoo, Mohammad Hossein; Sasaki, Misao; Wang, Dong-Gang; Wang, Ziwei
2018-05-01
Non-attractor inflation is known as the only single field inflationary scenario that can violate non-Gaussianity consistency relation with the Bunch-Davies vacuum state and generate large local non-Gaussianity. However, it is also known that the non-attractor inflation by itself is incomplete and should be followed by a phase of slow-roll attractor. Moreover, there is a transition process between these two phases. In the past literature, this transition was approximated as instant and the evolution of non-Gaussianity in this phase was not fully studied. In this paper, we follow the detailed evolution of the non-Gaussianity through the transition phase into the slow-roll attractor phase, considering different types of transition. We find that the transition process has important effect on the size of the local non-Gaussianity. We first compute the net contribution of the non-Gaussianities at the end of inflation in canonical non-attractor models. If the curvature perturbations keep evolving during the transition—such as in the case of smooth transition or some sharp transition scenarios—the Script O(1) local non-Gaussianity generated in the non-attractor phase can be completely erased by the subsequent evolution, although the consistency relation remains violated. In extremal cases of sharp transition where the super-horizon modes freeze immediately right after the end of the non-attractor phase, the original non-attractor result can be recovered. We also study models with non-canonical kinetic terms, and find that the transition can typically contribute a suppression factor in the squeezed bispectrum, but the final local non-Gaussianity can still be made parametrically large.
Local features with large spiky non-Gaussianities during inflation
International Nuclear Information System (INIS)
Abolhasani, Ali Akbar; Firouzjahi, Hassan; Khosravi, Shahram; Sasaki, Misao
2012-01-01
We provide a dynamical mechanism to generate localized features during inflation. The local feature is due to a sharp waterfall phase transition which is coupled to the inflaton field. The key effect is the contributions of waterfall quantum fluctuations which induce a sharp peak on the curvature perturbation which can be as large as the background curvature perturbation from inflaton field. Due to non-Gaussian nature of waterfall quantum fluctuations a large spike non-Gaussianity is produced which is narrowly peaked at modes which leave the Hubble radius at the time of phase transition. The large localized peaks in power spectrum and bispectrum can have interesting consequences on CMB anisotropies
Application of laser speckle to randomized numerical linear algebra
Valley, George C.; Shaw, Thomas J.; Stapleton, Andrew D.; Scofield, Adam C.; Sefler, George A.; Johannson, Leif
2018-02-01
We propose and simulate integrated optical devices for accelerating numerical linear algebra (NLA) calculations. Data is modulated on chirped optical pulses and these propagate through a multimode waveguide where speckle provides the random projections needed for NLA dimensionality reduction.
The Study Of Optometry Apparatus Of Laser Speckles
Bao-cheng, Wang; Kun, Yao; Xiu-qing, Wu; Chang-ying, Long; Jia-qi, Shi; Shi-zhong, Shi
1988-01-01
Based on the regularity of laser speckles movement the method of exam the uncorrected eyes is determined. The apparatus with micro-computer and optical transformation is made. Its practical function is excellent.
MODERN POSSIBILITIES OF SPECKLE TRACKING ECHOCARDIOGRAPHY IN CLINICAL PRACTICE
Directory of Open Access Journals (Sweden)
V. S. Nikiforov
2017-01-01
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.
A decade of innovation with laser speckle metrology
Ettemeyer, Andreas
2003-05-01
Speckle Pattern Interferometry has emerged from the experimental substitution of holographic interferometry to become a powerful problem solving tool in research and industry. The rapid development of computer and digital imaging techniques in combination with minaturization of the optical equipment led to new applications which had not been anticipated before. While classical holographic interferometry had always required careful consideration of the environmental conditions such as vibration, noise, light, etc. and could generally only be performed in the optical laboratory, it is now state of the art, to handle portable speckle measuring equipment at almost any place. During the last decade, the change in design and technique has dramatically influenced the range of applications of speckle metrology and opened new markets. The integration of recent research results into speckle measuring equipment has led to handy equipment, simplified the operation and created high quality data output.
Differential expression of speckled POZ protein, SPOP: Putative ...
Indian Academy of Sciences (India)
2014-05-01
May 1, 2014 ... In other mouse tissues and human cancer cell lines analysed, only low SPOP ... speckled POZ protein; SRC-3, steroid receptor co-activator-3; TNF, tumour necrosis factor; ...... complexity of primary human prostate cancer.
Laser speckle imaging based on photothermally driven convection
Regan, Caitlin; Choi, Bernard
2016-02-01
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.
SPECKLE INTERFEROMETRY AT SOAR IN 2014
International Nuclear Information System (INIS)
Tokovinin, Andrei; Mason, Brian D.; Hartkopf, William I.; Mendez, Rene A.; Horch, Elliott P.
2015-01-01
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
Laser speckle velocimetry for robot manufacturing
Charrett, Thomas O. H.; Bandari, Yashwanth K.; Michel, Florent; Ding, Jialuo; Williams, Stewart W.; Tatam, Ralph P.
2017-06-01
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.
Wen, Xian-Huan; Gómez-Hernández, J. Jaime
1998-03-01
The macrodispersion of an inert solute in a 2-D heterogeneous porous media is estimated numerically in a series of fields of varying heterogeneity. Four different random function (RF) models are used to model log-transmissivity (ln T) spatial variability, and for each of these models, ln T variance is varied from 0.1 to 2.0. The four RF models share the same univariate Gaussian histogram and the same isotropic covariance, but differ from one another in terms of the spatial connectivity patterns at extreme transmissivity values. More specifically, model A is a multivariate Gaussian model for which, by definition, extreme values (both high and low) are spatially uncorrelated. The other three models are non-multi-Gaussian: model B with high connectivity of high extreme values, model C with high connectivity of low extreme values, and model D with high connectivities of both high and low extreme values. Residence time distributions (RTDs) and macrodispersivities (longitudinal and transverse) are computed on ln T fields corresponding to the different RF models, for two different flow directions and at several scales. They are compared with each other, as well as with predicted values based on first-order analytical results. Numerically derived RTDs and macrodispersivities for the multi-Gaussian model are in good agreement with analytically derived values using first-order theories for log-transmissivity variance up to 2.0. The results from the non-multi-Gaussian models differ from each other and deviate largely from the multi-Gaussian results even when ln T variance is small. RTDs in non-multi-Gaussian realizations with high connectivity at high extreme values display earlier breakthrough than in multi-Gaussian realizations, whereas later breakthrough and longer tails are observed for RTDs from non-multi-Gaussian realizations with high connectivity at low extreme values. Longitudinal macrodispersivities in the non-multi-Gaussian realizations are, in general, larger than
Speckle imaging using the principle value decomposition method
International Nuclear Information System (INIS)
Sherman, J.W.
1978-01-01
Obtaining diffraction-limited images in the presence of atmospheric turbulence is a topic of current interest. Two types of approaches have evolved: real-time correction and speckle imaging. A speckle imaging reconstruction method was developed by use of an ''optimal'' filtering approach. This method is based on a nonlinear integral equation which is solved by principle value decomposition. The method was implemented on a CDC 7600 for study. The restoration algorithm is discussed and its performance is illustrated. 7 figures
Non-Gaussianity from tachyonic preheating in hybrid inflation
International Nuclear Information System (INIS)
Barnaby, Neil; Cline, James M.
2007-01-01
In a previous work we showed that large non-Gaussianities and nonscale-invariant distortions in the cosmic microwave background power spectrum can be generated in hybrid inflation models, due to the contributions of the tachyon (waterfall) field to the second order curvature perturbation. Here we clarify, correct, and extend those results. We show that large non-Gaussianity occurs only when the tachyon remains light throughout inflation, whereas n=4 contamination to the spectrum is the dominant effect when the tachyon is heavy. We find constraints on the parameters of warped-throat brane-antibrane inflation from non-Gaussianity. For F-term and D-term inflation models from supergravity, we obtain nontrivial constraints from the spectral distortion effect. We also establish that our analysis applies to complex tachyon fields
The Multivariate Gaussian Probability Distribution
DEFF Research Database (Denmark)
Ahrendt, Peter
2005-01-01
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 ...
On Gaussian conditional independence structures
Czech Academy of Sciences Publication Activity Database
Lněnička, Radim; Matúš, František
2007-01-01
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
Prosthetic clone and natural human tooth comparison by speckle interferometry
Slangen, Pierre; Corn, Stephane; Fages, Michel; Raynal, Jacques; Cuisinier, Frederic J. G.
2010-09-01
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.
Lee, KyeoReh; Park, YongKeun
2016-10-31
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.
Analytic matrix elements with shifted correlated Gaussians
DEFF Research Database (Denmark)
Fedorov, D. V.
2017-01-01
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....
Gaussian process regression analysis for functional data
Shi, Jian Qing
2011-01-01
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
Reproducing kernel Hilbert spaces of Gaussian priors
Vaart, van der A.W.; Zanten, van J.H.; Clarke, B.; Ghosal, S.
2008-01-01
We review definitions and properties of reproducing kernel Hilbert spaces attached to Gaussian variables and processes, with a view to applications in nonparametric Bayesian statistics using Gaussian priors. The rate of contraction of posterior distributions based on Gaussian priors can be described
Lifting Primordial Non-Gaussianity Above the Noise
Welling, Yvette; Woude, Drian van der; Pajer, Enrico
2016-01-01
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
An approximate fractional Gaussian noise model with computational cost
Sø rbye, Sigrunn H.; Myrvoll-Nilsen, Eirik; Rue, Haavard
2017-01-01
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
Large non-Gaussianity from two-component hybrid inflation
International Nuclear Information System (INIS)
Byrnes, Christian T.; Choi, Ki-Young; Hall, Lisa M.H.
2009-01-01
We study the generation of non-Gaussianity in models of hybrid inflation with two inflaton fields, (2-brid inflation). We analyse the region in the parameter and the initial condition space where a large non-Gaussianity may be generated during slow-roll inflation which is generally characterised by a large f NL , τ NL and a small g NL . For certain parameter values we can satisfy τ NL >> f NL 2 . The bispectrum is of the local type but may have a significant scale dependence. We show that the loop corrections to the power spectrum and bispectrum are suppressed during inflation, if one assume that the fields follow a classical background trajectory. We also include the effect of the waterfall field, which can lead to a significant change in the observables after the waterfall field is destabilised, depending on the couplings between the waterfall and inflaton fields
Perturbative corrections for approximate inference in gaussian latent variable models
DEFF Research Database (Denmark)
Opper, Manfred; Paquet, Ulrich; Winther, Ole
2013-01-01
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....
Polarization coupling of vector Bessel–Gaussian beams
International Nuclear Information System (INIS)
Takeuchi, Ryushi; Kozawa, Yuichi; Sato, Shunichi
2013-01-01
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)
Gaussian-state entanglement in a quantum beat laser
International Nuclear Information System (INIS)
Tahira, Rabia; Ikram, Manzoor; Nha, Hyunchul; Zubairy, M. Suhail
2011-01-01
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.
Yao, X. F.; Xiong, T. C.; Xu, H. M.; Wan, J. P.; Long, G. R.
2008-11-01
The residual stresses of the PMMA (polymethyl methacrylate) specimens after being drilled, reamed and polished respectively are investigated using the digital speckle correlation experimental method,. According to the displacement fields around the correlated calculated region, the polynomial curve fitting method is used to obtain the continuous displacement fields, and the strain fields can be obtained from the derivative of the displacement fields. Considering the constitutive equation of the material, the expression of the residual stress can be presented. During the data processing, according to the fitting effect of the data, the calculation region of the correlated speckles and the degree of the polynomial fitting curve is decided. These results show that the maximum stress is at the hole-wall of the drilling hole specimen and with the increasing of the diameter of the drilled hole, the residual stress resulting from the hole drilling increases, whereas the process of reaming and polishing hole can reduce the residual stress. The relative large discrete degree of the residual stress is due to the chip removal ability of the drill bit, the cutting feed of the drill and other various reasons.
General Galilei Covariant Gaussian Maps
Gasbarri, Giulio; Toroš, Marko; Bassi, Angelo
2017-09-01
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)].
Gaussian Embeddings for Collaborative Filtering
Dos Santos , Ludovic; Piwowarski , Benjamin; Gallinari , Patrick
2017-01-01
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...
Real-time monitoring of corks' water absorption using laser speckle temporal correlation
Nassif, Rana; Abou Nader, Christelle; Pellen, Fabrice; Le Jeune, Bernard; Le Brun, Guy; Abboud, Marie
2015-08-01
Physical and mechanical properties of cork allow it solving many types of problems and make it suitable for a wide range of applications. Our objective consists into studying cork's water absorption by analyzing the dynamic speckle field using the temporal correlation method. Experimental results show that the medium was inert at first with the absence of activity, and as the cap cork was more and more immersed into water, the presence of the activity becomes more significant. This temporal parameter revealed the sensibility of biospeckle method to monitor the amount of absorbed water by cork caps.
Speckle-based off-axis holographic detection for non-contact photoacoustic tomography
Directory of Open Access Journals (Sweden)
Buj C.
2015-09-01
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.
Non-Gaussian Methods for Causal Structure Learning.
Shimizu, Shohei
2018-05-22
Causal structure learning is one of the most exciting new topics in the fields of machine learning and statistics. In many empirical sciences including prevention science, the causal mechanisms underlying various phenomena need to be studied. Nevertheless, in many cases, classical methods for causal structure learning are not capable of estimating the causal structure of variables. This is because it explicitly or implicitly assumes Gaussianity of data and typically utilizes only the covariance structure. In many applications, however, non-Gaussian data are often obtained, which means that more information may be contained in the data distribution than the covariance matrix is capable of containing. Thus, many new methods have recently been proposed for using the non-Gaussian structure of data and inferring the causal structure of variables. This paper introduces prevention scientists to such causal structure learning methods, particularly those based on the linear, non-Gaussian, acyclic model known as LiNGAM. These non-Gaussian data analysis tools can fully estimate the underlying causal structures of variables under assumptions even in the presence of unobserved common causes. This feature is in contrast to other approaches. A simulated example is also provided.
Continuous-variable quantum teleportation with non-Gaussian resources
International Nuclear Information System (INIS)
Dell'Anno, F.; De Siena, S.; Albano, L.; Illuminati, F.
2007-01-01
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
Primordial non-Gaussian features from DBI Galileon inflation
International Nuclear Information System (INIS)
Choudhury, Sayantan; Pal, Supratik
2015-01-01
We have studied primordial non-Gaussian features of a model of potential-driven single field DBI Galileon inflation. We have computed the bispectrum from the three-point correlation function considering all possible cross correlations between the scalar and tensor modes of the proposed setup. Further, we have computed the trispectrum from a four-point correlation function considering the contribution from contact interaction, and scalar and graviton exchange diagrams in the in-in picture. Finally we have obtained the non-Gaussian consistency conditions from the four-point correlator, which results in partial violation of the Suyama-Yamaguchi four-point consistency relation. This further leads to the conclusion that sufficient primordial non-Gaussianities can be obtained from DBI Galileon inflation. (orig.)
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
1992-01-01
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
Non-Gaussian signatures arising from warm inflation driven by geometric tachyon
International Nuclear Information System (INIS)
Bhattacharjee, Anindita; Deshamukhya, Atri
2014-01-01
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
Speckle Interferometry at SOAR in 2014
Tokovinin, Andrei; Mason, Brian D.; Hartkopf, William I.; Mendez, Rene A.; Horch, Elliott P.
2015-08-01
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).
Speckle Interferometry of Red Dwarf Stars
Mason, Brian D.; Hartkopf, William I.; Miles, Korie N.; Subasavage, John P.; Raghavan, Deepak; Henry, Todd J.
2018-05-01
We report high-resolution optical speckle observations of 336 M dwarfs, which results in 113 measurements of the relative position of 80 systems and 256 other stars with no indications of duplicity. These are the first measurements for two of the systems. We also present the earliest measurements of relative position for 17 others. We include orbits for six of the systems, two revised and four reported for the first time. For one of the systems with a new orbit, G 161-7, we determine masses of 0.156 ± 0.011 and 0.1175+/- 0.0079 {{ \\mathcal M }}ȯ for the A and B components, respectively. All six of these new calculated orbits have short periods (between five and 38 years) and hold the promise of deriving accurate masses in the near future. For many other pairs we can establish their nature as physical or chance alignment, depending on their relative motion. Of the 80 systems, 32 have calculated orbits, 25 others are physical pairs, four are optical pairs, and 19 are currently unknown.
Laser speckle decorrelation for fingerprint acquisition
International Nuclear Information System (INIS)
Schirripa Spagnolo, Giuseppe; Cozzella, Lorenzo
2012-01-01
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)
X-ray pulse wavefront metrology using speckle tracking
International Nuclear Information System (INIS)
Berujon, Sebastien; Ziegler, Eric; Cloetens, Peter
2015-01-01
The theoretical description and experimental implementation of a speckle-tracking-based instrument which permits the characterisation of X-ray pulse wavefronts. An instrument allowing the quantitative analysis of X-ray pulsed wavefronts is presented and its processing method explained. The system relies on the X-ray speckle tracking principle to accurately measure the phase gradient of the X-ray beam from which beam optical aberrations can be deduced. The key component of this instrument, a semi-transparent scintillator emitting visible light while transmitting X-rays, allows simultaneous recording of two speckle images at two different propagation distances from the X-ray source. The speckle tracking procedure for a reference-less metrology mode is described with a detailed account on the advanced processing schemes used. A method to characterize and compensate for the imaging detector distortion, whose principle is also based on speckle, is included. The presented instrument is expected to find interest at synchrotrons and at the new X-ray free-electron laser sources under development worldwide where successful exploitation of beams relies on the availability of an accurate wavefront metrology
Speckle reduction methods in laser-based picture projectors
Akram, M. Nadeem; Chen, Xuyuan
2016-02-01
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.
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: ttani@sci.kumamoto-u.ac.jp [Department of Biological Sciences, Graduate School of Science and Technology, Kumamoto University, Chuo-ku, Kumamoto 860-8555 (Japan)
2014-03-28
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.
DEFF Research Database (Denmark)
Ma, Ning; Zhao, Juan; Hanson, Steen Grüner
2016-01-01
and applications of its intensity distribution. Recently, statistical properties of random electric vector fields referred to as Polarization Speckle have come to attract new interest because of their importance in a variety of areas with practical applications such as biomedical optics and optical metrology...
A statistical theory on the turbulent diffusion of Gaussian puffs
International Nuclear Information System (INIS)
Mikkelsen, T.; Larsen, S.E.; Pecseli, H.L.
1982-12-01
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.)
Simulation of speckle patterns with pre-defined correlation distributions
Song, Lipei; Zhou, Zhen; Wang, Xueyan; Zhao, Xing; Elson, Daniel S.
2016-01-01
We put forward a method to easily generate a single or a sequence of fully developed speckle patterns with pre-defined correlation distribution by utilizing the principle of coherent imaging. The few-to-one mapping between the input correlation matrix and the correlation distribution between simulated speckle patterns is realized and there is a simple square relationship between the values of these two correlation coefficient sets. This method is demonstrated both theoretically and experimentally. The square relationship enables easy conversion from any desired correlation distribution. Since the input correlation distribution can be defined by a digital matrix or a gray-scale image acquired experimentally, this method provides a convenient way to simulate real speckle-related experiments and to evaluate data processing techniques. PMID:27231589
Speckle Interferometry with the OCA Kuhn 22" Telescope
Wasson, Rick
2018-04-01
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.
Detection of fungi colony growth on bones by dynamic speckle
Vincitorio, F. M.; Budini, N.; Mulone, C.; Spector, M.; Freyre, C.; López Díaz, A. J.; Ramil, A.
2013-11-01
In this work we have studied the dynamic speckle patterns of mucor fungi colonies, which were inoculated on different samples. We were interested in analyzing the development of fungi colonies in bones, since during the last two years, a series of infections by mucor fungi have been reported on patients from different hospitals in Argentina. Coincidentally, all of these infections appeared on patients that were subjected to a surgical intervention for implantation of a titanium prosthesis. Apparently, the reason of the infection was a deficient sterilization process in conjunction with an accidental contamination. We observed that fungi growth, activity and death can be distinguished by means of the dynamic speckle technique.
Spatially resolved speckle-correlometry of sol-gel transition
Isaeva, A. A.; Isaeva, E. A.; Pantyukov, A. V.; Zimnyakov, D. A.
2018-04-01
Sol-gel transition was studied using the speckle correlometry method with a localized light source and spatial filtering of backscattered radiation. Water solutions of technical or food gelatin with added TiO2 nanoparticles were used as studied objects. Structural transformation of "sol-gel" system was studied at various temperatures from 25°C to 50°C using analysis of the correlation and structure functions of speckle intensity fluctuations. The characteristic temperatures of "sol - gel" transition were evaluated for studied systems. Obtained results can be used for various applications in biomedicine and food industry.
Feature Matching for SAR and Optical Images Based on Gaussian-Gamma-shaped Edge Strength Map
Directory of Open Access Journals (Sweden)
CHEN Min
2016-03-01
Full Text Available A matching method for SAR and optical images, robust to pixel noise and nonlinear grayscale differences, is presented. Firstly, a rough correction to eliminate rotation and scale change between images is performed. Secondly, features robust to speckle noise of SAR image are detected by improving the original phase congruency based method. Then, feature descriptors are constructed on the Gaussian-Gamma-shaped edge strength map according to the histogram of oriented gradient pattern. Finally, descriptor similarity and geometrical relationship are combined to constrain the matching processing.The experimental results demonstrate that the proposed method provides significant improvement in correct matches number and image registration accuracy compared with other traditional methods.
Detecting periodicities with Gaussian processes
Directory of Open Access Journals (Sweden)
Nicolas Durrande
2016-04-01
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.
Monogamy inequality for distributed gaussian entanglement.
Hiroshima, Tohya; Adesso, Gerardo; Illuminati, Fabrizio
2007-02-02
We show that for all n-mode Gaussian states of continuous variable systems, the entanglement shared among n parties exhibits the fundamental monogamy property. The monogamy inequality is proven by introducing the Gaussian tangle, an entanglement monotone under Gaussian local operations and classical communication, which is defined in terms of the squared negativity in complete analogy with the case of n-qubit systems. Our results elucidate the structure of quantum correlations in many-body harmonic lattice systems.
Breaking Gaussian incompatibility on continuous variable quantum systems
Energy Technology Data Exchange (ETDEWEB)
Heinosaari, Teiko, E-mail: teiko.heinosaari@utu.fi [Turku Centre for Quantum Physics, Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Kiukas, Jukka, E-mail: jukka.kiukas@aber.ac.uk [Department of Mathematics, Aberystwyth University, Penglais, Aberystwyth, SY23 3BZ (United Kingdom); Schultz, Jussi, E-mail: jussi.schultz@gmail.com [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)
2015-08-15
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.
Coherence of the vortex Bessel-Gaussian beam in turbulent atmosphere
Lukin, Igor P.
2017-11-01
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.
The POKEMON Speckle Survey of Nearby M-Dwarfs
van Belle, Gerard; von Braun, Kaspar; Horch, Elliott; Clark, Catherine; DSSI Speckle Team
2018-01-01
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!
Ultrasound speckle reduction based on fractional order differentiation.
Shao, Dangguo; Zhou, Ting; Liu, Fan; Yi, Sanli; Xiang, Yan; Ma, Lei; Xiong, Xin; He, Jianfeng
2017-07-01
Ultrasound images show a granular pattern of noise known as speckle that diminishes their quality and results in difficulties in diagnosis. To preserve edges and features, this paper proposes a fractional differentiation-based image operator to reduce speckle in ultrasound. An image de-noising model based on fractional partial differential equations with balance relation between k (gradient modulus threshold that controls the conduction) and v (the order of fractional differentiation) was constructed by the effective combination of fractional calculus theory and a partial differential equation, and the numerical algorithm of it was achieved using a fractional differential mask operator. The proposed algorithm has better speckle reduction and structure preservation than the three existing methods [P-M model, the speckle reducing anisotropic diffusion (SRAD) technique, and the detail preserving anisotropic diffusion (DPAD) technique]. And it is significantly faster than bilateral filtering (BF) in producing virtually the same experimental results. Ultrasound phantom testing and in vivo imaging show that the proposed method can improve the quality of an ultrasound image in terms of tissue SNR, CNR, and FOM values.
3-color photometry of a sunspot using speckle masking techniques
Wiehr, E.; Sütterlin, P.
1998-01-01
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
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 ...
Review of speckle observations of Supernova 1987A
International Nuclear Information System (INIS)
Meikle, W.P.S.
1988-01-01
SN 1987A is sufficiently close to allow a unique examination of the morphology of a supernova, using speckle interferometry. Several groups [Center for Astrophysics (CfA); Imperial College (IC); Mount Stromlo and Siding Spring Observatories/Anglo-Australian Observatory (M/A)] have reported optical speckle observations. At Hα, both CfA and M/A have determined the angular extent of the emission, and reasonable agreement is obtained. The speckle-derived values are consistent with those obtained from line profiles. IC has also succeeded in resolving the supernova at Hα. At wavelengths other than Hα, at early epochs, angular diameters obtained by CfA are larger than those derived from photometric and spectroscopic measurements, possibly due to scattering effects. At later epochs, the diameters exhibit little variation between the wavelengths examined. CfA reports significant asymmetry in the late epoch data. Several attempts have been made to re-observe (at optical wavelengths) the companion object, but none have succeeded. The nature of this phenomenon is still controversial, but the evidence indicates that the companion was real, with emission from dust apparently being the least problematic explanation. Support for this may lie in IR speckle observations (Haute Provence/Lyon) which, on about day 115, indicated the presence of one or more resolved components at an angular displacement comparable to that of the optical companion. 39 refs., 1 fig., 1 tab
Application of speckle decorrelation method for small translation measurements
Czech Academy of Sciences Publication Activity Database
Horváth, Pavel; Hrabovský, Miroslav; Šmíd, Petr
2004-01-01
Roč. 34, č. 2 (2004), s. 203-218 ISSN 0078-5466 R&D Projects: GA MŠk LN00A015 Institutional research plan: CEZ:AV0Z1010921 Keywords : speckle * decorrelation * in-plane and normal translation Subject RIV: BH - Optics, Masers, Lasers Impact factor: 0.308, year: 2004
Granulometry use for the study of dynamics speckles patterns
International Nuclear Information System (INIS)
Mavilioa, Adriana; Fernandez, Margarita; Trivi, Marcelo; Rabal, Hector; Arizaga, Ricardo
2009-01-01
Dynamic speckle patterns are generated by laser light scattering on surfaces that exhibit some kind of activity, due to physical or biological processes that take place in the illuminated object. The characterization of this dynamic process is carried out by studying the texture changes of auxiliary images: temporal history of the speckle pattern (THSP) obtained from this speckles patterns. The drying process of water borne paint is studied through a method based on mathematical morphology applied to the THSP image processing. It is based on obtaining the granulometry of these images and their characteristic granulometric spectrum. From the granulometric size distribution of each THSP image four parameters are obtained: mean length, standard deviation, asymmetry and kurtosis. These parameters are found to be suitable as texture features. The Mahalanobis distance is calculated between the texture features of the THSP images representative of the temporary stages of the drying process and the features of the final stage or pattern texture. The behavior of the distance function describes satisfactorily the drying process of the water borne paint. Finally, these results are compared with the obtained by other methods. Compared with others, the granulometric method reported in this work distinguished by its simplicity and easy implementation and can be used to characterize the evolution of any process recorded through dynamic speckles. (Author)
Impact of transducer frequency setting on speckle tracking measures
DEFF Research Database (Denmark)
Olsen, Flemming Javier; Svendsen, Jesper Hastrup; Køber, Lars
2018-01-01
.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...
Estudio de técnicas speckle opto-digitales
Henao Henao, Rodrigo de Jesús
1997-01-01
El presente Trabajo de Tesis se dirigió a la investigación, creación, desarrollo e implementación de técnicas que hacen uso del speckle y de su correlación digital, siendo su representante mas exitoso el DPSI. Doctor en Física(Facultad de Ciencias Exactas)
Laser speckle imaging: a novel method for detecting dental erosion.
Directory of Open Access Journals (Sweden)
Nelson H Koshoji
Full Text Available Erosion is a highly prevalent condition known as a non-carious lesion that causes progressive tooth wear due to chemical processes that do not involve the action of bacteria. Speckle images proved sensitive to even minimal mineral loss from the enamel. The aim of the present study was to investigate the use of laser speckle imaging analysis in the spatial domain to quantify shifts in the microstructure of the tooth surface in an erosion model. 32 fragments of the vestibular surface of bovine incisors were divided in for groups (10 min, 20 min. 30 min and 40 min of acid etching immersed in a cola-based beverage (pH approximately 2.5 twice a day during 7 days to create an artificial erosion. By analyzing the laser speckle contrast map (LASCA in the eroded region compared to the sound it was observed that the LASCA map shifts, proportionally to the acid each duration, by: 18%; 23%; 39% and 44% for the 10 min; 20 min; 30 min and 40 min groups, respectively. To the best of our knowledge, this is the first study to demonstrate the correlation between speckle patterns and erosion progression.
International Nuclear Information System (INIS)
Lock, James A.
2013-01-01
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
International Nuclear Information System (INIS)
McHugh, Derek; Buzek, Vladimir; Ziman, Mario
2006-01-01
We present a class of non-Gaussian two-mode continuous-variable states for which the separability criterion for Gaussian states can be employed to detect whether they are separable or not. These states reduce to the two-mode Gaussian states as a special case
Applying laser speckle images to skin science: skin lesion differentiation by polarization
Lee, Tim K.; Tchvialeva, Lioudmila; Dhadwal, Gurbir; Sotoodian, Bahman; Kalai, Sunil; Zeng, Haishan; Lui, Harvey; McLean, David I.
2012-01-01
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.
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)
2014-08-31
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)
Laser speckle contrast imaging of skin blood perfusion responses induced by laser coagulation
Ogami, M.; Kulkarni, R.; Wang, H.; Reif, R.; Wang, R. K.
2014-08-01
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.
Limit theorems for functionals of Gaussian vectors
Institute of Scientific and Technical Information of China (English)
Hongshuai DAI; Guangjun SHEN; Lingtao KONG
2017-01-01
Operator self-similar processes,as an extension of self-similar processes,have been studied extensively.In this work,we study limit theorems for functionals of Gaussian vectors.Under some conditions,we determine that the limit of partial sums of functionals of a stationary Gaussian sequence of random vectors is an operator self-similar process.
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...
On the dependence structure of Gaussian queues
Es-Saghouani, A.; Mandjes, M.R.H.
2009-01-01
In this article we study Gaussian queues (that is, queues fed by Gaussian processes, such as fractional Brownian motion (fBm) and the integrated Ornstein-Uhlenbeck (iOU) process), with a focus on the dependence structure of the workload process. The main question is to what extent does the workload
Shedding new light on Gaussian harmonic analysis
Teuwen, J.J.B.
2016-01-01
This dissertation consists out of two rather disjoint parts. One part concerns some results on Gaussian harmonic analysis and the other on an optimization problem in optics. In the first part we study the Ornstein–Uhlenbeck process with respect to the Gaussian measure. We focus on two areas. One is
Understanding the exposure-time effect on speckle contrast measurements for laser displays
Suzuki, Koji; Kubota, Shigeo
2018-02-01
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.
Entanglement in Gaussian matrix-product states
International Nuclear Information System (INIS)
Adesso, Gerardo; Ericsson, Marie
2006-01-01
Gaussian matrix-product states are obtained as the outputs of projection operations from an ancillary space of M infinitely entangled bonds connecting neighboring sites, applied at each of N sites of a harmonic chain. Replacing the projections by associated Gaussian states, the building blocks, we show that the entanglement range in translationally invariant Gaussian matrix-product states depends on how entangled the building blocks are. In particular, infinite entanglement in the building blocks produces fully symmetric Gaussian states with maximum entanglement range. From their peculiar properties of entanglement sharing, a basic difference with spin chains is revealed: Gaussian matrix-product states can possess unlimited, long-range entanglement even with minimum number of ancillary bonds (M=1). Finally we discuss how these states can be experimentally engineered from N copies of a three-mode building block and N two-mode finitely squeezed states
Gaussian vs non-Gaussian turbulence: impact on wind turbine loads
DEFF Research Database (Denmark)
Berg, Jacob; Natarajan, Anand; Mann, Jakob
2016-01-01
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...
Productive interactions: heavy particles and non-Gaussianity
International Nuclear Information System (INIS)
Flauger, Raphael; Mirbabayi, Mehrdad; Senatore, Leonardo; Silverstein, Eva
2017-01-01
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.
Productive interactions: heavy particles and non-Gaussianity
Energy Technology Data Exchange (ETDEWEB)
Flauger, Raphael [Department of Physics, The University of Texas at Austin, Austin, TX, 78712 (United States); Mirbabayi, Mehrdad [Institute for Advanced Study, Princeton, NJ 08540 (United States); Senatore, Leonardo; Silverstein, Eva, E-mail: flauger@physics.ucsd.edu, E-mail: mehrdadm@ias.edu, E-mail: senatore@stanford.edu, E-mail: evas@slac.stanford.edu [Stanford Institute for Theoretical Physics, Stanford University, Stanford, CA 94305 (United States)
2017-10-01
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{sup 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.
International Nuclear Information System (INIS)
Parra-Michel, Jorge; Martínez, Amalia; Rayas, J A; Anguiano-Morales, Marcelino
2010-01-01
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
The properties of the dark matter halo distribution in non-Gaussian scenarios
International Nuclear Information System (INIS)
Carbone, C.; Branchini, E.; Dolag, K.; Grossi, M.; Iannuzzi, F.; Matarrese, S.; Moscardini, L.; Verde, L.
2009-01-01
The description of halo abundance and clustering for non-Gaussian initial conditions has recently received renewed interest, motivated by the forthcoming large galaxy and cluster surveys, which can potentially detect primordial non-Gaussianity of the local form with a non-Gaussianity parameter |f NL | of order unity. This is particularly exciting because, while the simplest single-field slow-roll models of inflation predict a primordial |f NL | NL of large-scale structures that are expected to be above the predicted detection threshold [C. Carbone, L. Verde, and S. Matarrese, ApJL 684 (2008) L1]. We present tests on N-body simulations of analytical formulae describing the halo abundance and clustering for non-Gaussian initial conditions. In particular, when we calibrate the analytic non-Gaussian mass function of [S. Matarrese, L. Verde, L. and R. Jimenez, ApJL 541 (2000) 10] and [M. LoVerde, A. Miller, S. Shandera and L. Verde, JCAP 04 (2008) 014] and the analytic description of halo clustering for non-Gaussian initial conditions on N-body simulations, we find excellent agreement between the simulations and the analytic predictions if we make the substitutions δ c →δ c x√(q) and δ c →δ c xq where q≅0.75, in the density threshold for gravitational collapse and in the non-Gaussian fractional correction to the halo bias, respectively. We discuss the implications of these corrections on present and forecasted primordial non-Gaussianity constraints. We confirm that the non-Gaussian halo bias offers a robust and highly competitive test of primordial non-Gaussianity.
Increasing Entanglement between Gaussian States by Coherent Photon Subtraction
DEFF Research Database (Denmark)
Ourjoumtsev, Alexei; Dantan, Aurelien Romain; Tualle Brouri, Rosa
2007-01-01
We experimentally demonstrate that the entanglement between Gaussian entangled states can be increased by non-Gaussian operations. Coherent subtraction of single photons from Gaussian quadrature-entangled light pulses, created by a nondegenerate parametric amplifier, produces delocalized states...
Representation of Gaussian semimartingales with applications to the covariance function
DEFF Research Database (Denmark)
Basse-O'Connor, Andreas
2010-01-01
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...
Statistical spatial properties of speckle patterns generated by multiple laser beams
International Nuclear Information System (INIS)
Le Cain, A.; Sajer, J. M.; Riazuelo, G.
2011-01-01
This paper investigates hot spot characteristics generated by the superposition of multiple laser beams. First, properties of speckle statistics are studied in the context of only one laser beam by computing the autocorrelation function. The case of multiple laser beams is then considered. In certain conditions, it is shown that speckles have an ellipsoidal shape. Analytical expressions of hot spot radii generated by multiple laser beams are derived and compared to numerical estimates made from the autocorrelation function. They are also compared to numerical simulations performed within the paraxial approximation. Excellent agreement is found for the speckle width as well as for the speckle length. Application to the speckle patterns generated in the Laser MegaJoule configuration in the zone where all the beams overlap is presented. Influence of polarization on the size of the speckles as well as on their abundance is studied.
Speckle-modulating optical coherence tomography in living mice and humans
Liba, Orly; Lew, Matthew D.; Sorelle, Elliott D.; Dutta, Rebecca; Sen, Debasish; Moshfeghi, Darius M.; Chu, Steven; de La Zerda, Adam
2017-06-01
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.
Zhang, Xuming; Li, Liu; Zhu, Fei; Hou, Wenguang; Chen, Xinjian
2014-06-01
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.
Nicolas, F; Coëtmellec, S; Brunel, M; Allano, D; Lebrun, D; Janssen, A J E M
2005-11-01
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.
Operation of a quasi-optical gyrotron with a gaussian output coupler
Energy Technology Data Exchange (ETDEWEB)
Hogge, J.P.; Tran, T.M.; Paris, P.J.; Tran, M.Q. [Ecole Polytechnique Federale, Lausanne (Switzerland). Centre de Recherche en Physique des Plasma (CRPP)
1996-03-01
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.
2015-03-26
the number of speckle samples obtained, laser power and coherence length, spot size, target reflectance, speckle size, and pixels per speckle width...gated imaging systems,” Proc. SPIE, 6542: 654218, April 2007. 90 St. Pierre, Randall J. and others. “Active Tracker Laser (ATLAS),” IEEE J. Sel...numerical model developed here and existing theory developed by Hu. A 671 nm diode laser source with coherence length of 259 +/- 7 µm is reflected
Some continual integrals from gaussian forms
International Nuclear Information System (INIS)
Mazmanishvili, A.S.
1985-01-01
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
Loop corrections to primordial non-Gaussianity
Boran, Sibel; Kahya, E. O.
2018-02-01
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.
Gaussian Mixture Model of Heart Rate Variability
Costa, Tommaso; Boccignone, Giuseppe; Ferraro, Mario
2012-01-01
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. PMID:22666386
Non-Gaussianity from isocurvature perturbations
Energy Technology Data Exchange (ETDEWEB)
Kawasaki, Masahiro; Nakayama, Kazunori; Sekiguchi, Toyokazu; Suyama, Teruaki [Institute for Cosmic Ray Research, University of Tokyo, Kashiwa 277-8582 (Japan); Takahashi, Fuminobu, E-mail: kawasaki@icrr.u-tokyo.ac.jp, E-mail: nakayama@icrr.u-tokyo.ac.jp, E-mail: sekiguti@icrr.u-tokyo.ac.jp, E-mail: suyama@icrr.u-tokyo.ac.jp, E-mail: fuminobu.takahashi@ipmu.jp [Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwa 277-8568 (Japan)
2008-11-15
We develop a formalism for studying non-Gaussianity in both curvature and isocurvature perturbations. It is shown that non-Gaussianity in the isocurvature perturbation between dark matter and photons leaves distinct signatures in the cosmic microwave background temperature fluctuations, which may be confirmed in future experiments, or possibly even in the currently available observational data. As an explicit example, we consider the quantum chromodynamics axion and show that it can actually induce sizable non-Gaussianity for the inflationary scale, H{sub inf} = O(10{sup 9}-10{sup 11}) GeV.
Multipoint propagators for non-Gaussian initial conditions
International Nuclear Information System (INIS)
Bernardeau, Francis; Sefusatti, Emiliano; Crocce, Martin
2010-01-01
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.
Gaussian measures of entanglement versus negativities: Ordering of two-mode Gaussian states
International Nuclear Information System (INIS)
Adesso, Gerardo; Illuminati, Fabrizio
2005-01-01
We study the entanglement of general (pure or mixed) two-mode Gaussian states of continuous-variable systems by comparing the two available classes of computable measures of entanglement: entropy-inspired Gaussian convex-roof measures and positive partial transposition-inspired measures (negativity and logarithmic negativity). We first review the formalism of Gaussian measures of entanglement, adopting the framework introduced in M. M. Wolf et al., Phys. Rev. A 69, 052320 (2004), where the Gaussian entanglement of formation was defined. We compute explicitly Gaussian measures of entanglement for two important families of nonsymmetric two-mode Gaussian state: namely, the states of extremal (maximal and minimal) negativities at fixed global and local purities, introduced in G. Adesso et al., Phys. Rev. Lett. 92, 087901 (2004). This analysis allows us to compare the different orderings induced on the set of entangled two-mode Gaussian states by the negativities and by the Gaussian measures of entanglement. We find that in a certain range of values of the global and local purities (characterizing the covariance matrix of the corresponding extremal states), states of minimum negativity can have more Gaussian entanglement of formation than states of maximum negativity. Consequently, Gaussian measures and negativities are definitely inequivalent measures of entanglement on nonsymmetric two-mode Gaussian states, even when restricted to a class of extremal states. On the other hand, the two families of entanglement measures are completely equivalent on symmetric states, for which the Gaussian entanglement of formation coincides with the true entanglement of formation. Finally, we show that the inequivalence between the two families of continuous-variable entanglement measures is somehow limited. Namely, we rigorously prove that, at fixed negativities, the Gaussian measures of entanglement are bounded from below. Moreover, we provide some strong evidence suggesting that they
Sensitivity evaluation of dynamic speckle activity measurements using clustering methods
International Nuclear Information System (INIS)
Etchepareborda, Pablo; Federico, Alejandro; Kaufmann, Guillermo H.
2010-01-01
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.
Optical design of the comet Shoemaker-Levy speckle camera
Energy Technology Data Exchange (ETDEWEB)
Bissinger, H. [Lawrence Livermore National Lab., CA (United States)
1994-11-15
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.
Analysis of error functions in speckle shearing interferometry
International Nuclear Information System (INIS)
Wan Saffiey Wan Abdullah
2001-01-01
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
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
2012-01-01
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......, a rotational symmetric spatial filter is designed. The spatial filter converts the speckle dynamics into a photocurrent with a quasi-sinusoidal response to the out-of-plane motion. The spatial filter is here emulated with a CCD camera, and is tested on speckles arising from a real application. The analysis...
Analysis of the speckle properties in a laser projection system based on a human eye model.
Cui, Zhe; Wang, Anting; Ma, Qianli; Ming, Hai
2014-03-01
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.
Speckle imaging with the PAPA detector. [Precision Analog Photon Address
Papaliolios, C.; Nisenson, P.; Ebstein, S.
1985-01-01
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.
Speckle contrast diffuse correlation tomography of complex turbid medium flow
Energy Technology Data Exchange (ETDEWEB)
Huang, Chong; Irwin, Daniel; Lin, Yu; Shang, Yu; He, Lian; Kong, Weikai; Yu, Guoqiang [Department of Biomedical Engineering, University of Kentucky, Lexington, Kentucky 40506 (United States); Luo, Jia [Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, Kentucky 40506 (United States)
2015-07-15
Purpose: Developed herein is a three-dimensional (3D) flow contrast imaging system leveraging advancements in the extension of laser speckle contrast imaging theories to deep tissues along with our recently developed finite-element diffuse correlation tomography (DCT) reconstruction scheme. This technique, termed speckle contrast diffuse correlation tomography (scDCT), enables incorporation of complex optical property heterogeneities and sample boundaries. When combined with a reflectance-based design, this system facilitates a rapid segue into flow contrast imaging of larger, in vivo applications such as humans. Methods: A highly sensitive CCD camera was integrated into a reflectance-based optical system. Four long-coherence laser source positions were coupled to an optical switch for sequencing of tomographic data acquisition providing multiple projections through the sample. This system was investigated through incorporation of liquid and solid tissue-like phantoms exhibiting optical properties and flow characteristics typical of human tissues. Computer simulations were also performed for comparisons. A uniquely encountered smear correction algorithm was employed to correct point-source illumination contributions during image capture with the frame-transfer CCD and reflectance setup. Results: Measurements with scDCT on a homogeneous liquid phantom showed that speckle contrast-based deep flow indices were within 12% of those from standard DCT. Inclusion of a solid phantom submerged below the liquid phantom surface allowed for heterogeneity detection and validation. The heterogeneity was identified successfully by reconstructed 3D flow contrast tomography with scDCT. The heterogeneity center and dimensions and averaged relative flow (within 3%) and localization were in agreement with actuality and computer simulations, respectively. Conclusions: A custom cost-effective CCD-based reflectance 3D flow imaging system demonstrated rapid acquisition of dense boundary
Granger Causality and Transfer Entropy Are Equivalent for Gaussian Variables
Barnett, Lionel; Barrett, Adam B.; Seth, Anil K.
2009-12-01
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.
Suen, Ricky Wai
The work described in this thesis covers the conversion of HiLo image processing into MATLAB architecture and the use of speckle-illumination HiLo microscopy for use of ex-vivo and in-vivo imaging of thick tissue models. HiLo microscopy is a wide-field fluorescence imaging technique and has been demonstrated to produce optically sectioned images comparable to confocal in thin samples. The imaging technique was developed by Jerome Mertz and the Boston University Biomicroscopy Lab and has been implemented in our lab as a stand-alone optical setup and a modification to a conventional fluorescence microscope. Speckle-illumination HiLo microscopy combines two images taken under speckle-illumination and standard uniform-illumination to generate an optically sectioned image that reject out-of-focus fluorescence. The evaluated speckle contrast in the images is used as a weighting function where elements that move out-of-focus have a speckle contrast that decays to zero. The experiments shown here demonstrate the capability of our HiLo microscopes to produce optically-sectioned images of the microvasculature of ex-vivo and in-vivo thick tissue models. The HiLo microscope were used to image the microvasculature of ex-vivo mouse heart sections prepared for optical histology and the microvasculature of in-vivo rodent dorsal window chamber models. Studies in label-free surface profiling with HiLo microscopy is also presented.
Optimal unitary dilation for bosonic Gaussian channels
International Nuclear Information System (INIS)
Caruso, Filippo; Eisert, Jens; Giovannetti, Vittorio; Holevo, Alexander S.
2011-01-01
A general quantum channel can be represented in terms of a unitary interaction between the information-carrying system and a noisy environment. In this paper the minimal number of quantum Gaussian environmental modes required to provide a unitary dilation of a multimode bosonic Gaussian channel is analyzed for both pure and mixed environments. We compute this quantity in the case of pure environment corresponding to the Stinespring representation and give an improved estimate in the case of mixed environment. The computations rely, on one hand, on the properties of the generalized Choi-Jamiolkowski state and, on the other hand, on an explicit construction of the minimal dilation for arbitrary bosonic Gaussian channel. These results introduce a new quantity reflecting ''noisiness'' of bosonic Gaussian channels and can be applied to address some issues concerning transmission of information in continuous variables systems.
Optimal cloning of mixed Gaussian states
International Nuclear Information System (INIS)
Guta, Madalin; Matsumoto, Keiji
2006-01-01
We construct the optimal one to two cloning transformation for the family of displaced thermal equilibrium states of a harmonic oscillator, with a fixed and known temperature. The transformation is Gaussian and it is optimal with respect to the figure of merit based on the joint output state and norm distance. The proof of the result is based on the equivalence between the optimal cloning problem and that of optimal amplification of Gaussian states which is then reduced to an optimization problem for diagonal states of a quantum oscillator. A key concept in finding the optimum is that of stochastic ordering which plays a similar role in the purely classical problem of Gaussian cloning. The result is then extended to the case of n to m cloning of mixed Gaussian states
Encoding information using laguerre gaussian modes
CSIR Research Space (South Africa)
Trichili, A
2015-08-01
Full Text Available The authors experimentally demonstrate an information encoding protocol using the two degrees of freedom of Laguerre Gaussian modes having different radial and azimuthal components. A novel method, based on digital holography, for information...
Interweave Cognitive Radio with Improper Gaussian Signaling
Hedhly, Wafa; Amin, Osama; Alouini, Mohamed-Slim
2018-01-01
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
Statistically tuned Gaussian background subtraction technique for ...
Indian Academy of Sciences (India)
temporal median method and mixture of Gaussian model and performance evaluation ... to process the videos captured by unmanned aerial vehicle (UAV). ..... The output is obtained by simulation using MATLAB 2010 in a standalone PC with ...
A non-Gaussian multivariate distribution with all lower-dimensional Gaussians and related families
Dutta, Subhajit
2014-07-28
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.
A non-Gaussian multivariate distribution with all lower-dimensional Gaussians and related families
Dutta, Subhajit; Genton, Marc G.
2014-01-01
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.
One-and two-dimensional topological charge distributions in stochastic optical fields
CSIR Research Space (South Africa)
Roux, FS
2011-06-01
Full Text Available The presentation on topological charge distributions in stochastic optical fields concludes that by using a combination of speckle fields one can produce inhomogeneous vortex distributions that allow both analytical calculations and numerical...
International Nuclear Information System (INIS)
Jiao Yangxiu; Shan Huanyuan; Fan Zuhui
2011-01-01
Taking into account the noise from intrinsic ellipticities of source galaxies, we study the efficiency and completeness of halo detections from weak lensing convergence maps. Particularly, with numerical simulations, we compare the Gaussian filter with the so called MRLens treatment based on the modification of the Maximum Entropy Method. For a pure noise field without lensing signals, a Gaussian smoothing results in a residual noise field that is approximately Gaussian in terms of statistics if a large enough number of galaxies are included in the smoothing window. On the other hand, the noise field after the MRLens treatment is significantly non-Gaussian, resulting in complications in characterizing the noise effects. Considering weak-lensing cluster detections, although the MRLens treatment effectively deletes false peaks arising from noise, it removes the real peaks heavily due to its inability to distinguish real signals with relatively low amplitudes from noise in its restoration process. The higher the noise level is, the larger the removal effects are for the real peaks. For a survey with a source density n g ∼ 30 arcmin -2 , the number of peaks found in an area of 3 x 3 deg 2 after MRLens filtering is only ∼ 50 for the detection threshold κ = 0.02, while the number of halos with M > 5 x 10 13 M circleddot and with redshift z ≤ 2 in the same area is expected to be ∼ 530. For the Gaussian smoothing treatment, the number of detections is ∼ 260, much larger than that of the MRLens. The Gaussianity of the noise statistics in the Gaussian smoothing case adds further advantages for this method to circumvent the problem of the relatively low efficiency in weak-lensing cluster detections. Therefore, in studies aiming to construct large cluster samples from weak-lensing surveys, the Gaussian smoothing method performs significantly better than the MRLens treatment.
Gaussian sum rules for optical functions
International Nuclear Information System (INIS)
Kimel, I.
1981-12-01
A new (Gaussian) type of sum rules (GSR) for several optical functions, is presented. The functions considered are: dielectric permeability, refractive index, energy loss function, rotatory power and ellipticity (circular dichroism). While reducing to the usual type of sum rules in a certain limit, the GSR contain in general, a Gaussian factor that serves to improve convergence. GSR might be useful in analysing experimental data. (Author) [pt
Gaussian maximally multipartite-entangled states
Facchi, Paolo; Florio, Giuseppe; Lupo, Cosmo; Mancini, Stefano; Pascazio, Saverio
2009-12-01
We study maximally multipartite-entangled states in the context of Gaussian continuous variable quantum systems. By considering multimode Gaussian states with constrained energy, we show that perfect maximally multipartite-entangled states, which exhibit the maximum amount of bipartite entanglement for all bipartitions, only exist for systems containing n=2 or 3 modes. We further numerically investigate the structure of these states and their frustration for n≤7 .
Gaussian maximally multipartite-entangled states
International Nuclear Information System (INIS)
Facchi, Paolo; Florio, Giuseppe; Pascazio, Saverio; Lupo, Cosmo; Mancini, Stefano
2009-01-01
We study maximally multipartite-entangled states in the context of Gaussian continuous variable quantum systems. By considering multimode Gaussian states with constrained energy, we show that perfect maximally multipartite-entangled states, which exhibit the maximum amount of bipartite entanglement for all bipartitions, only exist for systems containing n=2 or 3 modes. We further numerically investigate the structure of these states and their frustration for n≤7.
International Nuclear Information System (INIS)
Prentice, H. J.; Proud, W. G.
2006-01-01
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
International Nuclear Information System (INIS)
Sivia, D.S.; Hamilton, W.A.; Smith, G.S.
1991-01-01
The analysis of neutron reflectivity data to obtain nuclear scattering length density profiles is akin to the notorious phaseless Fourier problem, well known in many fields such as crystallography. Current methods of analysis culminate in the refinement of a few parameters of a functional model, and are often preceded by a long and laborious process of trial and error. We start by discussing the use of maximum entropy for obtained 'free-form' solutions of the density profile, as an alternative to the trial and error phase when a functional model is not available. Next we consider a Bayesian spectral analysis approach, which is appropriate for optimising the parameters of a simple (but adequate) type of model when the number of parameters is not known. Finally, we suggest a novel experimental procedure, the analogue of astronomical speckle holography, designed to alleviate the ambiguity problems inherent in traditional reflectivity measurements. (orig.)
International Nuclear Information System (INIS)
Guelorget, Bruno; Francois, Manuel; Vial-Edwards, Cristian; Montay, Guillaume; Daniel, Laurent; Lu, Jian
2006-01-01
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 (ε t ≅ 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
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: bruno.guelorget@utt.fr; 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)
2006-01-15
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.
Non-Gaussian halo assembly bias
International Nuclear Information System (INIS)
Reid, Beth A.; Verde, Licia; Dolag, Klaus; Matarrese, Sabino; Moscardini, Lauro
2010-01-01
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
Adaptive Laguerre-Gaussian variant of the Gaussian beam expansion method.
Cagniot, Emmanuel; Fromager, Michael; Ait-Ameur, Kamel
2009-11-01
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.
Partial summations of stationary sequences of non-Gaussian random variables
DEFF Research Database (Denmark)
Mohr, Gunnar; Ditlevsen, Ove Dalager
1996-01-01
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)....... lognormal variables or polynomials of standard Gaussian variables. The dependency structure is induced by specifying the autocorrelation structure of the sequence of standard Gaussian variables. Particularly useful polynomials are the Winterstein approximations that distributionally fit with non...
Simulation of ultrasonic surface waves with multi-Gaussian and point source beam models
International Nuclear Information System (INIS)
Zhao, Xinyu; Schmerr, Lester W. Jr.; Li, Xiongbing; Sedov, Alexander
2014-01-01
In the past decade, multi-Gaussian beam models have been developed to solve many complicated bulk wave propagation problems. However, to date those models have not been extended to simulate the generation of Rayleigh waves. Here we will combine Gaussian beams with an explicit high frequency expression for the Rayleigh wave Green function to produce a three-dimensional multi-Gaussian beam model for the fields radiated from an angle beam transducer mounted on a solid wedge. Simulation results obtained with this model are compared to those of a point source model. It is shown that the multi-Gaussian surface wave beam model agrees well with the point source model while being computationally much more efficient
Multi-variate joint PDF for non-Gaussianities: exact formulation and generic approximations
Verde, Licia; Heavens, Alan F; Jimenez, Raul; Matarrese, Sabino
2013-01-01
We provide an exact expression for the multi-variate joint probability distribution function of non-Gaussian fields primordially arising from local transformations of a Gaussian field. This kind of non-Gaussianity is generated in many models of inflation. We apply our expression to the non- Gaussianity estimation from Cosmic Microwave Background maps and the halo mass function where we obtain analytical expressions. We also provide analytic approximations and their range of validity. For the Cosmic Microwave Background we give a fast way to compute the PDF which is valid up to 7{\\sigma} for fNL values (both true and sampled) not ruled out by current observations, which consists of expressing the PDF as a combination of bispectrum and trispectrum of the temperature maps. The resulting expression is valid for any kind of non-Gaussianity and is not limited to the local type. The above results may serve as the basis for a fully Bayesian analysis of the non-Gaussianity parameter.
Generation of correlated finite alphabet waveforms using gaussian random variables
Jardak, Seifallah
2014-09-01
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.
Modeling Non-Gaussian Time Series with Nonparametric Bayesian Model.
Xu, Zhiguang; MacEachern, Steven; Xu, Xinyi
2015-02-01
We present a class of Bayesian copula models whose major components are the marginal (limiting) distribution of a stationary time series and the internal dynamics of the series. We argue that these are the two features with which an analyst is typically most familiar, and hence that these are natural components with which to work. For the marginal distribution, we use a nonparametric Bayesian prior distribution along with a cdf-inverse cdf transformation to obtain large support. For the internal dynamics, we rely on the traditionally successful techniques of normal-theory time series. Coupling the two components gives us a family of (Gaussian) copula transformed autoregressive models. The models provide coherent adjustments of time scales and are compatible with many extensions, including changes in volatility of the series. We describe basic properties of the models, show their ability to recover non-Gaussian marginal distributions, and use a GARCH modification of the basic model to analyze stock index return series. The models are found to provide better fit and improved short-range and long-range predictions than Gaussian competitors. The models are extensible to a large variety of fields, including continuous time models, spatial models, models for multiple series, models driven by external covariate streams, and non-stationary models.
Galaxy bispectrum, primordial non-Gaussianity and redshift space distortions
Energy Technology Data Exchange (ETDEWEB)
Tellarini, Matteo; Ross, Ashley J.; Wands, David [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Portsmouth, PO1 3FX (United Kingdom); Tasinato, Gianmassimo, E-mail: matteo.tellarini@port.ac.uk, E-mail: ross.1333@osu.edu, E-mail: g.tasinato@swansea.ac.uk, E-mail: david.wands@port.ac.uk [Department of Physics, Swansea University, Singleton Park, Swansea, SA2 8PP (United Kingdom)
2016-06-01
Measurements of the non-Gaussianity of the primordial density field have the power to considerably improve our understanding of the physics of inflation. Indeed, if we can increase the precision of current measurements by an order of magnitude, a null-detection would rule out many classes of scenarios for generating primordial fluctuations. Large-scale galaxy redshift surveys represent experiments that hold the promise to realise this goal. Thus, we model the galaxy bispectrum and forecast the accuracy with which it will probe the parameter f {sub NL}, which represents the degree of primordial local-type non Gaussianity. Specifically, we address the problem of modelling redshift space distortions (RSD) in the tree-level galaxy bispectrum including f {sub NL}. We find novel contributions associated with RSD, with the characteristic large scale amplification induced by local-type non-Gaussianity. These RSD effects must be properly accounted for in order to obtain un-biased measurements of f {sub NL} from the galaxy bispectrum. We propose an analytic template for the monopole which can be used to fit against data on large scales, extending models used in the recent measurements. Finally, we perform idealised forecasts on σ {sub f} {sub N{sub L}}—the accuracy of the determination of local non-linear parameter f {sub NL}—from measurements of the galaxy bispectrum. Our findings suggest that current surveys can in principle provide f {sub NL} constraints competitive with Planck , and future surveys could improve them further.
Galaxy bispectrum, primordial non-Gaussianity and redshift space distortions
International Nuclear Information System (INIS)
Tellarini, Matteo; Ross, Ashley J.; Wands, David; Tasinato, Gianmassimo
2016-01-01
Measurements of the non-Gaussianity of the primordial density field have the power to considerably improve our understanding of the physics of inflation. Indeed, if we can increase the precision of current measurements by an order of magnitude, a null-detection would rule out many classes of scenarios for generating primordial fluctuations. Large-scale galaxy redshift surveys represent experiments that hold the promise to realise this goal. Thus, we model the galaxy bispectrum and forecast the accuracy with which it will probe the parameter f NL , which represents the degree of primordial local-type non Gaussianity. Specifically, we address the problem of modelling redshift space distortions (RSD) in the tree-level galaxy bispectrum including f NL . We find novel contributions associated with RSD, with the characteristic large scale amplification induced by local-type non-Gaussianity. These RSD effects must be properly accounted for in order to obtain un-biased measurements of f NL from the galaxy bispectrum. We propose an analytic template for the monopole which can be used to fit against data on large scales, extending models used in the recent measurements. Finally, we perform idealised forecasts on σ f NL —the accuracy of the determination of local non-linear parameter f NL —from measurements of the galaxy bispectrum. Our findings suggest that current surveys can in principle provide f NL constraints competitive with Planck , and future surveys could improve them further.
An approximate fractional Gaussian noise model with computational cost
Sørbye, Sigrunn H.
2017-09-18
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.
Evaluation of digital image correlation techniques using realistic ground truth speckle images
International Nuclear Information System (INIS)
Cofaru, C; Philips, W; Van Paepegem, W
2010-01-01
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
New gaussian points for the solution of first order ordinary ...
African Journals Online (AJOL)
Numerical experiments carried out using the new Gaussian points revealed there efficiency on stiff differential equations. The results also reveal that methods using the new Gaussian points are more accurate than those using the standard Gaussian points on non-stiff initial value problems. Keywords: Gaussian points ...
Coherence and polarization speckle generated by a rough-surfaced retardation plate depolarizer
DEFF Research Database (Denmark)
Ma, Ning; Hanson, Steen Grüner; Takeda, Mitsuo
2015-01-01
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...
Denisova, Yu. L.; Bazylev, N. B.; Rubnikovich, S. P.; Fomin, N. A.
2013-07-01
We have investigated the formation and dynamics of speckle biofi elds formed by hard biotissues of the oral cavity irradiated with low-intensity radiation. We present experimental methods for diagnosing the stressed-strained state of the maxillodental system and orthodontic and orthopedic structures based on speckle technologies and crosscorrelation analysis of speckle biofi elds.
Tandem-pulsed acousto-optics: an analytical framework of modulated high-contrast speckle patterns
Resink, Steffen; Steenbergen, Wiendelt
2015-01-01
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
Speckle Interferometry with the McMath-Pierce East Auxiliary Telescope
Harshaw, Richard; Ray, Jimmy; Douglass, David; Prause, Lori; Genet, Russell
2015-09-01
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.
Vermeltfoort, A.T.; Martens, D.R.W; Zijl, van G.P.A.G.
2007-01-01
The brick–mortar interaction is important in the mechanical behaviour of masonry. It affects the load transfer considerably, as shown by detailed deformation measurements taken using electronic speckle pattern interferometry (ESPI), a laser speckle interference technique. A companion paper [Canadian
Shift-Invariant Image Reconstruction of Speckle-Degraded Images Using Bispectrum Estimation
1990-05-01
process with the requisite negative exponential pelf. I call this model the Negative Exponential Model ( NENI ). The NENI flowchart is seen in Figure 6...Figure ]3d-g. Statistical Histograms and Phase for the RPj NG EXP FDF MULT METHOD FILuteC 14a. Truth Object Speckled Via the NENI HISTOGRAM OF SPECKLE
From synchrotron radiation to lab source: advanced speckle-based X-ray imaging using abrasive paper
Wang, Hongchang; Kashyap, Yogesh; Sawhney, Kawal
2016-02-01
X-ray phase and dark-field imaging techniques provide complementary and inaccessible information compared to conventional X-ray absorption or visible light imaging. However, such methods typically require sophisticated experimental apparatus or X-ray beams with specific properties. Recently, an X-ray speckle-based technique has shown great potential for X-ray phase and dark-field imaging using a simple experimental arrangement. However, it still suffers from either poor resolution or the time consuming process of collecting a large number of images. To overcome these limitations, in this report we demonstrate that absorption, dark-field, phase contrast, and two orthogonal differential phase contrast images can simultaneously be generated by scanning a piece of abrasive paper in only one direction. We propose a novel theoretical approach to quantitatively extract the above five images by utilising the remarkable properties of speckles. Importantly, the technique has been extended from a synchrotron light source to utilise a lab-based microfocus X-ray source and flat panel detector. Removing the need to raster the optics in two directions significantly reduces the acquisition time and absorbed dose, which can be of vital importance for many biological samples. This new imaging method could potentially provide a breakthrough for numerous practical imaging applications in biomedical research and materials science.
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...
Fractional statistics in 2+1 dimensions through the Gaussian model
International Nuclear Information System (INIS)
Murthy, G.
1986-01-01
The free massless field in 2+1 dimensions is written as an ''integral'' over free massless fields in 1+1 dimensions. Taking the operators with fractional dimension in the Gaussian model as a springboard we construct operators with fractional statistics in the former theory
The transition of a Gaussian chain end-grafted at a penetrable surface
Skvortsov, A.M.; Klusken, L.I.; Male, van J.; Leermakers, F.A.M.
2000-01-01
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
Sasaki, Misao; Wands, David
2010-06-01
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.
Zhao, Yuchen; Zemmamouche, Redouane; Vandenrijt, Jean-François; Georges, Marc P.
2018-05-01
A combination of digital holographic interferometry (DHI) and digital speckle photography (DSP) allows in-plane and out-of-plane displacement measurement between two states of an object. The former can be determined by correlating the two speckle patterns whereas the latter is given by the phase difference obtained from DHI. We show that the amplitude of numerically reconstructed object wavefront obtained from Fresnel in-line digital holography (DH), in combination with phase shifting techniques, can be used as speckle patterns in DSP. The accuracy of in-plane measurement is improved after correcting the phase errors induced by reference wave during reconstruction process. Furthermore, unlike conventional imaging system, Fresnel DH offers the possibility to resize the pixel size of speckle patterns situated on the reconstruction plane under the same optical configuration simply by zero-padding the hologram. The flexibility of speckle size adjustment in Fresnel DH ensures the accuracy of estimation result using DSP.
Graphical calculus for Gaussian pure states
International Nuclear Information System (INIS)
Menicucci, Nicolas C.; Flammia, Steven T.; Loock, Peter van
2011-01-01
We provide a unified graphical calculus for all Gaussian pure states, including graph transformation rules for all local and semilocal Gaussian unitary operations, as well as local quadrature measurements. We then use this graphical calculus to analyze continuous-variable (CV) cluster states, the essential resource for one-way quantum computing with CV systems. Current graphical approaches to CV cluster states are only valid in the unphysical limit of infinite squeezing, and the associated graph transformation rules only apply when the initial and final states are of this form. Our formalism applies to all Gaussian pure states and subsumes these rules in a natural way. In addition, the term 'CV graph state' currently has several inequivalent definitions in use. Using this formalism we provide a single unifying definition that encompasses all of them. We provide many examples of how the formalism may be used in the context of CV cluster states: defining the 'closest' CV cluster state to a given Gaussian pure state and quantifying the error in the approximation due to finite squeezing; analyzing the optimality of certain methods of generating CV cluster states; drawing connections between this graphical formalism and bosonic Hamiltonians with Gaussian ground states, including those useful for CV one-way quantum computing; and deriving a graphical measure of bipartite entanglement for certain classes of CV cluster states. We mention other possible applications of this formalism and conclude with a brief note on fault tolerance in CV one-way quantum computing.
Variational Gaussian approximation for Poisson data
Arridge, Simon R.; Ito, Kazufumi; Jin, Bangti; Zhang, Chen
2018-02-01
The Poisson model is frequently employed to describe count data, but in a Bayesian context it leads to an analytically intractable posterior probability distribution. In this work, we analyze a variational Gaussian approximation to the posterior distribution arising from the Poisson model with a Gaussian prior. This is achieved by seeking an optimal Gaussian distribution minimizing the Kullback-Leibler divergence from the posterior distribution to the approximation, or equivalently maximizing the lower bound for the model evidence. We derive an explicit expression for the lower bound, and show the existence and uniqueness of the optimal Gaussian approximation. The lower bound functional can be viewed as a variant of classical Tikhonov regularization that penalizes also the covariance. Then we develop an efficient alternating direction maximization algorithm for solving the optimization problem, and analyze its convergence. We discuss strategies for reducing the computational complexity via low rank structure of the forward operator and the sparsity of the covariance. Further, as an application of the lower bound, we discuss hierarchical Bayesian modeling for selecting the hyperparameter in the prior distribution, and propose a monotonically convergent algorithm for determining the hyperparameter. We present extensive numerical experiments to illustrate the Gaussian approximation and the algorithms.
Mode entanglement of Gaussian fermionic states
Spee, C.; Schwaiger, K.; Giedke, G.; Kraus, B.
2018-04-01
We investigate the entanglement of n -mode n -partite Gaussian fermionic states (GFS). First, we identify a reasonable definition of separability for GFS and derive a standard form for mixed states, to which any state can be mapped via Gaussian local unitaries (GLU). As the standard form is unique, two GFS are equivalent under GLU if and only if their standard forms coincide. Then, we investigate the important class of local operations assisted by classical communication (LOCC). These are central in entanglement theory as they allow one to partially order the entanglement contained in states. We show, however, that there are no nontrivial Gaussian LOCC (GLOCC) among pure n -partite (fully entangled) states. That is, any such GLOCC transformation can also be accomplished via GLU. To obtain further insight into the entanglement properties of such GFS, we investigate the richer class of Gaussian stochastic local operations assisted by classical communication (SLOCC). We characterize Gaussian SLOCC classes of pure n -mode n -partite states and derive them explicitly for few-mode states. Furthermore, we consider certain fermionic LOCC and show how to identify the maximally entangled set of pure n -mode n -partite GFS, i.e., the minimal set of states having the property that any other state can be obtained from one state inside this set via fermionic LOCC. We generalize these findings also to the pure m -mode n -partite (for m >n ) case.
Non-Gaussian probability distributions of solar wind fluctuations
Directory of Open Access Journals (Sweden)
E. Marsch
Full Text Available The probability distributions of field differences ∆x(τ=x(t+τ-x(t, where the variable x(t may denote any solar wind scalar field or vector field component at time t, have been calculated from time series of Helios data obtained in 1976 at heliocentric distances near 0.3 AU. It is found that for comparatively long time lag τ, ranging from a few hours to 1 day, the differences are normally distributed according to a Gaussian. For shorter time lags, of less than ten minutes, significant changes in shape are observed. The distributions are often spikier and narrower than the equivalent Gaussian distribution with the same standard deviation, and they are enhanced for large, reduced for intermediate and enhanced for very small values of ∆x. This result is in accordance with fluid observations and numerical simulations. Hence statistical properties are dominated at small scale τ by large fluctuation amplitudes that are sparsely distributed, which is direct evidence for spatial intermittency of the fluctuations. This is in agreement with results from earlier analyses of the structure functions of ∆x. The non-Gaussian features are differently developed for the various types of fluctuations. The relevance of these observations to the interpretation and understanding of the nature of solar wind magnetohydrodynamic (MHD turbulence is pointed out, and contact is made with existing theoretical concepts of intermittency in fluid turbulence.
Gaussian free turbulence: structures and relaxation in plasma models
International Nuclear Information System (INIS)
Gruzinov, A.V.
1993-01-01
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)
Rat retinal vasomotion assessed by laser speckle imaging
DEFF Research Database (Denmark)
Neganova, Anastasiia Y; Postnov, Dmitry D; Sosnovtseva, Olga
2017-01-01
Vasomotion is spontaneous or induced rhythmic changes in vascular tone or vessel diameter that lead to rhythmic changes in flow. While the vascular research community debates the physiological and pathophysiological consequence of vasomotion, there is a great need for experimental techniques...... 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...
Digital speckle correlation for nondestructive testing of corrosion
Paiva, Raul D., Jr.; Soga, Diogo; Muramatsu, Mikiya; Hogert, Elsa N.; Landau, Monica R.; Ruiz Gale, Maria F.; Gaggioli, Nestor G.
1999-07-01
This paper describes the use of optical correlation speckle patterns to detect and analyze the metallic corrosion phenomena, and shows the experimental set-up used. We present some new results in the characterization of the corrosion process using a model based in electroerosion phenomena. We also provide valuable information about surface microrelief changes, which is also useful in numerous engineering applications. The results obtained are good enough for showing that our technique is very useful for giving new possibilities to the analysis of the corrosion and oxidation process, particularly in real time.
Speckle tracking echocardiography in mature Irish Wolfhound dogs
DEFF Research Database (Denmark)
Westrup, Ulrik; McEvoy, Fintan
2013-01-01
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....
Lensless Photoluminescence Hyperspectral Camera Employing Random Speckle Patterns.
Czech Academy of Sciences Publication Activity Database
Žídek, Karel; Denk, Ondřej; Hlubuček, Jiří
2017-01-01
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 https://www.nature.com/articles/s41598-017-14443-4
Effect of low-frequency vibrations on speckle interferometry fringes
International Nuclear Information System (INIS)
Vikram, C.S.; Pechersky, M.J.
1998-01-01
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
Optoelectronic imaging of speckle using image processing method
Wang, Jinjiang; Wang, Pengfei
2018-01-01
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.
Body size evolution in insular speckled rattlesnakes (Viperidae: Crotalus mitchellii.
Directory of Open Access Journals (Sweden)
Jesse M Meik
2010-03-01
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
SPECKLE INTERFEROMETRY OF SECONDARY COMPONENTS IN NEARBY VISUAL BINARIES
International Nuclear Information System (INIS)
Tokovinin, Andrei; Horch, Elliott P.
2016-01-01
Statistical characterization of secondary subsystems in binaries helps to distinguish between various scenarios of multiple-star formation. The Differential Speckle Survey Instrument was used at the Gemini-N telescope for several hours in 2015 July to probe the binarity of 25 secondary components in nearby solar-type binaries. Six new subsystems were resolved, with meaningful detection limits for the remaining targets. The large incidence of secondary subsystems agrees with other similar studies. The newly resolved subsystem HIP 115417 Ba,Bb causes deviations in the observed motion of the outer binary from which an astrometric orbit of Ba,Bb with a period of 117 years is deduced.
Non-Gaussianity in island cosmology
International Nuclear Information System (INIS)
Piao Yunsong
2009-01-01
In this paper we fully calculate the non-Gaussianity of primordial curvature perturbation of the island universe by using the second order perturbation equation. We find that for the spectral index n s ≅0.96, which is favored by current observations, the non-Gaussianity level f NL seen in an island will generally lie between 30 and 60, which may be tested by the coming observations. In the landscape, the island universe is one of anthropically acceptable cosmological histories. Thus the results obtained in some sense mean the coming observations, especially the measurement of non-Gaussianity, will be significant to clarify how our position in the landscape is populated.
Entanglement negativity bounds for fermionic Gaussian states
Eisert, Jens; Eisler, Viktor; Zimborás, Zoltán
2018-04-01
The entanglement negativity is a versatile measure of entanglement that has numerous applications in quantum information and in condensed matter theory. It can not only efficiently be computed in the Hilbert space dimension, but for noninteracting bosonic systems, one can compute the negativity efficiently in the number of modes. However, such an efficient computation does not carry over to the fermionic realm, the ultimate reason for this being that the partial transpose of a fermionic Gaussian state is no longer Gaussian. To provide a remedy for this state of affairs, in this work, we introduce efficiently computable and rigorous upper and lower bounds to the negativity, making use of techniques of semidefinite programming, building upon the Lagrangian formulation of fermionic linear optics, and exploiting suitable products of Gaussian operators. We discuss examples in quantum many-body theory and hint at applications in the study of topological properties at finite temperature.
Kota, V K B; Chavda, N D; Sahu, R
2006-04-01
Interacting many-particle systems with a mean-field one-body part plus a chaos generating random two-body interaction having strength lambda exhibit Poisson to Gaussian orthogonal ensemble and Breit-Wigner (BW) to Gaussian transitions in level fluctuations and strength functions with transition points marked by lambda = lambda c and lambda = lambda F, respectively; lambda F > lambda c. For these systems a theory for the matrix elements of one-body transition operators is available, as valid in the Gaussian domain, with lambda > lambda F, in terms of orbital occupation numbers, level densities, and an integral involving a bivariate Gaussian in the initial and final energies. Here we show that, using a bivariate-t distribution, the theory extends below from the Gaussian regime to the BW regime up to lambda = lambda c. This is well tested in numerical calculations for 6 spinless fermions in 12 single-particle states.
Integral momenta of vortex Bessel-Gaussian beams in turbulent atmosphere.
Lukin, Igor P
2016-04-20
The orbital angular momentum of vortex Bessel-Gaussian beams propagating in turbulent atmosphere is studied theoretically. The field of an optical beam is determined through the solution of the paraxial wave equation for a randomly inhomogeneous medium with fluctuations of the refraction index of the turbulent atmosphere. Peculiarities in the behavior of the total power of the vortex Bessel-Gaussian beam at the receiver (or transmitter) are examined. The dependence of the total power of the vortex Bessel-Gaussian beam on optical beam parameters, namely, the transverse wave number of optical radiation, amplitude factor radius, and, especially, topological charge of the optical beam, is analyzed in detail. It turns out that the mean value of the orbital angular momentum of the vortex Bessel-Gaussian beam remains constant during propagation in the turbulent atmosphere. It is shown that the variance of fluctuations of the orbital angular momentum of the vortex Bessel-Gaussian beam propagating in turbulent atmosphere calculated with the "mean-intensity" approximation is equal to zero identically. Thus, it is possible to declare confidently that the variance of fluctuations of the orbital angular momentum of the vortex Bessel-Gaussian beam in turbulent atmosphere is not very large.
From plane waves to local Gaussians for the simulation of correlated periodic systems
International Nuclear Information System (INIS)
Booth, George H.; Tsatsoulis, Theodoros; Grüneis, Andreas; Chan, Garnet Kin-Lic
2016-01-01
We present a simple, robust, and black-box approach to the implementation and use of local, periodic, atom-centered Gaussian basis functions within a plane wave code, in a computationally efficient manner. The procedure outlined is based on the representation of the Gaussians within a finite bandwidth by their underlying plane wave coefficients. The core region is handled within the projected augment wave framework, by pseudizing the Gaussian functions within a cutoff radius around each nucleus, smoothing the functions so that they are faithfully represented by a plane wave basis with only moderate kinetic energy cutoff. To mitigate the effects of the basis set superposition error and incompleteness at the mean-field level introduced by the Gaussian basis, we also propose a hybrid approach, whereby the complete occupied space is first converged within a large plane wave basis, and the Gaussian basis used to construct a complementary virtual space for the application of correlated methods. We demonstrate that these pseudized Gaussians yield compact and systematically improvable spaces with an accuracy comparable to their non-pseudized Gaussian counterparts. A key advantage of the described method is its ability to efficiently capture and describe electronic correlation effects of weakly bound and low-dimensional systems, where plane waves are not sufficiently compact or able to be truncated without unphysical artifacts. We investigate the accuracy of the pseudized Gaussians for the water dimer interaction, neon solid, and water adsorption on a LiH surface, at the level of second-order Møller–Plesset perturbation theory.
From plane waves to local Gaussians for the simulation of correlated periodic systems
Energy Technology Data Exchange (ETDEWEB)
Booth, George H., E-mail: george.booth@kcl.ac.uk [Department of Physics, King’s College London, Strand, London WC2R 2LS (United Kingdom); Tsatsoulis, Theodoros; Grüneis, Andreas, E-mail: a.grueneis@fkf.mpg.de [Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart (Germany); Chan, Garnet Kin-Lic [Frick Laboratory, Department of Chemistry, Princeton University, Princeton, New Jersey 08544 (United States)
2016-08-28
We present a simple, robust, and black-box approach to the implementation and use of local, periodic, atom-centered Gaussian basis functions within a plane wave code, in a computationally efficient manner. The procedure outlined is based on the representation of the Gaussians within a finite bandwidth by their underlying plane wave coefficients. The core region is handled within the projected augment wave framework, by pseudizing the Gaussian functions within a cutoff radius around each nucleus, smoothing the functions so that they are faithfully represented by a plane wave basis with only moderate kinetic energy cutoff. To mitigate the effects of the basis set superposition error and incompleteness at the mean-field level introduced by the Gaussian basis, we also propose a hybrid approach, whereby the complete occupied space is first converged within a large plane wave basis, and the Gaussian basis used to construct a complementary virtual space for the application of correlated methods. We demonstrate that these pseudized Gaussians yield compact and systematically improvable spaces with an accuracy comparable to their non-pseudized Gaussian counterparts. A key advantage of the described method is its ability to efficiently capture and describe electronic correlation effects of weakly bound and low-dimensional systems, where plane waves are not sufficiently compact or able to be truncated without unphysical artifacts. We investigate the accuracy of the pseudized Gaussians for the water dimer interaction, neon solid, and water adsorption on a LiH surface, at the level of second-order Møller–Plesset perturbation theory.
Multi-brid inflation and non-gaussianity
International Nuclear Information System (INIS)
Sasaki, Misao
2008-01-01
We consider a class of multi-component hybrid inflation models whose evolution may be analytically solved under the slow-roll approximation. We call it multi-brid inflation (or n-brid inflation where n stands for the number of inflaton fields). As an explicit example, we consider a two-brid inflation model, in which the inflaton potentials are of exponential type and a waterfall field that terminates inflation has the standard quartic potential with two minima. Using the δN formalism, we derive an expression for the curvature perturbation valid to full nonlinear order. Then we give an explicit expression for the curvature perturbation to second order in the inflaton perturbation. We find that the final from of the curvature perturbation depends crucially on how the inflation ends. Using this expression, we present closed analytical expressions for the spectrum of the curvature perturbation Ps(k), the spectral index n s , the tensor to scalar ratio r, and the non-Gaussian parameter f NL local , in terms of the model parameters. We find that a wide range of the parameter space (n s , r, f NL local ) can be covered by varying the model parameters within a physically reasonable range. In particular, for plausible values of the model parameters, we may have a large non-Gaussianity f NL local ∼10-100. This is in sharp contrast to the case of single-field hybrid inflation in which these parameters are tightly constrained. (author)
Gaussian and 1/N approximations in semiclassical cosmology
International Nuclear Information System (INIS)
Mazzitelli, F.D.; Paz, J.P.
1989-01-01
We study the λphi 4 theory and the interacting O(N) model in a curved background using the Gaussian approximation for the former and the large-N approximation for the latter. We obtain the renormalized version of the semiclassical Einstein equations having in mind a future application of these models to investigate the physics of the very early Universe. We show that, while the Gaussian approximation has two different phases, in the large-N limit only one is present. The different features of the two phases are analyzed at the level of the effective field equations. We discuss the initial-value problem and find the initial conditions that make the theory renormalizable. As an example, we study the de Sitter self-consistent solutions of the semiclassical Einstein equations. Finally, for an identically zero mean value of the field we find the evolution equations for the classical field Ω(x) = (λ 2 >)/sup 1/2/ and the spacetime metric. They are very similar to the ones obtained by replacing the classical potential by the one-loop effective potential in the classical equations but do not have the drawbacks of the one-loop approximation
Invariant measures on multimode quantum Gaussian states
Lupo, C.; Mancini, S.; De Pasquale, A.; Facchi, P.; Florio, G.; Pascazio, S.
2012-12-01
We derive the invariant measure on the manifold of multimode quantum Gaussian states, induced by the Haar measure on the group of Gaussian unitary transformations. To this end, by introducing a bipartition of the system in two disjoint subsystems, we use a parameterization highlighting the role of nonlocal degrees of freedom—the symplectic eigenvalues—which characterize quantum entanglement across the given bipartition. A finite measure is then obtained by imposing a physically motivated energy constraint. By averaging over the local degrees of freedom we finally derive the invariant distribution of the symplectic eigenvalues in some cases of particular interest for applications in quantum optics and quantum information.
Invariant measures on multimode quantum Gaussian states
International Nuclear Information System (INIS)
Lupo, C.; Mancini, S.; De Pasquale, A.; Facchi, P.; Florio, G.; Pascazio, S.
2012-01-01
We derive the invariant measure on the manifold of multimode quantum Gaussian states, induced by the Haar measure on the group of Gaussian unitary transformations. To this end, by introducing a bipartition of the system in two disjoint subsystems, we use a parameterization highlighting the role of nonlocal degrees of freedom—the symplectic eigenvalues—which characterize quantum entanglement across the given bipartition. A finite measure is then obtained by imposing a physically motivated energy constraint. By averaging over the local degrees of freedom we finally derive the invariant distribution of the symplectic eigenvalues in some cases of particular interest for applications in quantum optics and quantum information.
Invariant measures on multimode quantum Gaussian states
Energy Technology Data Exchange (ETDEWEB)
Lupo, C. [School of Science and Technology, Universita di Camerino, I-62032 Camerino (Italy); Mancini, S. [School of Science and Technology, Universita di Camerino, I-62032 Camerino (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); De Pasquale, A. [NEST, Scuola Normale Superiore and Istituto Nanoscienze-CNR, I-56126 Pisa (Italy); Facchi, P. [Dipartimento di Matematica and MECENAS, Universita di Bari, I-70125 Bari (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Bari, I-70126 Bari (Italy); Florio, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Bari, I-70126 Bari (Italy); Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Piazza del Viminale 1, I-00184 Roma (Italy); Dipartimento di Fisica and MECENAS, Universita di Bari, I-70126 Bari (Italy); Pascazio, S. [Istituto Nazionale di Fisica Nucleare, Sezione di Bari, I-70126 Bari (Italy); Dipartimento di Fisica and MECENAS, Universita di Bari, I-70126 Bari (Italy)
2012-12-15
We derive the invariant measure on the manifold of multimode quantum Gaussian states, induced by the Haar measure on the group of Gaussian unitary transformations. To this end, by introducing a bipartition of the system in two disjoint subsystems, we use a parameterization highlighting the role of nonlocal degrees of freedom-the symplectic eigenvalues-which characterize quantum entanglement across the given bipartition. A finite measure is then obtained by imposing a physically motivated energy constraint. By averaging over the local degrees of freedom we finally derive the invariant distribution of the symplectic eigenvalues in some cases of particular interest for applications in quantum optics and quantum information.
Construction of Capacity Achieving Lattice Gaussian Codes
Alghamdi, Wael
2016-04-01
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].
Quantum information theory with Gaussian systems
Energy Technology Data Exchange (ETDEWEB)
Krueger, O.
2006-04-06
This thesis applies ideas and concepts from quantum information theory to systems of continuous-variables such as the quantum harmonic oscillator. The focus is on three topics: the cloning of coherent states, Gaussian quantum cellular automata and Gaussian private channels. Cloning was investigated both for finite-dimensional and for continuous-variable systems. We construct a private quantum channel for the sequential encryption of coherent states with a classical key, where the key elements have finite precision. For the case of independent one-mode input states, we explicitly estimate this precision, i.e. the number of key bits needed per input state, in terms of these parameters. (orig.)
Quantum information theory with Gaussian systems
International Nuclear Information System (INIS)
Krueger, O.
2006-01-01
This thesis applies ideas and concepts from quantum information theory to systems of continuous-variables such as the quantum harmonic oscillator. The focus is on three topics: the cloning of coherent states, Gaussian quantum cellular automata and Gaussian private channels. Cloning was investigated both for finite-dimensional and for continuous-variable systems. We construct a private quantum channel for the sequential encryption of coherent states with a classical key, where the key elements have finite precision. For the case of independent one-mode input states, we explicitly estimate this precision, i.e. the number of key bits needed per input state, in terms of these parameters. (orig.)
Model selection for Gaussian kernel PCA denoising
DEFF Research Database (Denmark)
Jørgensen, Kasper Winther; Hansen, Lars Kai
2012-01-01
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...
International Nuclear Information System (INIS)
Ji, Se-Wan; Nha, Hyunchul; Kim, M S
2015-01-01
It is a topic of fundamental and practical importance how a quantum correlated state can be reliably distributed through a noisy channel for quantum information processing. The concept of quantum steering recently defined in a rigorous manner is relevant to study it under certain circumstances and here we address quantum steerability of Gaussian states to this aim. In particular, we attempt to reformulate the criterion for Gaussian steering in terms of local and global purities and show that it is sufficient and necessary for the case of steering a 1-mode system by an N-mode system. It subsequently enables us to reinforce a strong monogamy relation under which only one party can steer a local system of 1-mode. Moreover, we show that only a negative partial-transpose state can manifest quantum steerability by Gaussian measurements in relation to the Peres conjecture. We also discuss our formulation for the case of distributing a two-mode squeezed state via one-way quantum channels making dissipation and amplification effects, respectively. Finally, we extend our approach to include non-Gaussian measurements, more precisely, all orders of higher-order squeezing measurements, and find that this broad set of non-Gaussian measurements is not useful to demonstrate steering for Gaussian states beyond Gaussian measurements. (paper)
Optical characterization of display screens by speckle patterns
Pozo, Antonio M.; Castro, José J.; Rubiño, Manuel
2013-10-01
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.
Accelerated speckle imaging with the ATST visible broadband imager
Wöger, Friedrich; Ferayorni, Andrew
2012-09-01
The Advanced Technology Solar Telescope (ATST), a 4 meter class telescope for observations of the solar atmosphere currently in construction phase, will generate data at rates of the order of 10 TB/day with its state of the art instrumentation. The high-priority ATST Visible Broadband Imager (VBI) instrument alone will create two data streams with a bandwidth of 960 MB/s each. Because of the related data handling issues, these data will be post-processed with speckle interferometry algorithms in near-real time at the telescope using the cost-effective Graphics Processing Unit (GPU) technology that is supported by the ATST Data Handling System. In this contribution, we lay out the VBI-specific approach to its image processing pipeline, put this into the context of the underlying ATST Data Handling System infrastructure, and finally describe the details of how the algorithms were redesigned to exploit data parallelism in the speckle image reconstruction algorithms. An algorithm re-design is often required to efficiently speed up an application using GPU technology; we have chosen NVIDIA's CUDA language as basis for our implementation. We present our preliminary results of the algorithm performance using our test facilities, and base a conservative estimate on the requirements of a full system that could achieve near real-time performance at ATST on these results.
Real time speckle monitoring to control retinal photocoagulation
Bliedtner, Katharina; Seifert, Eric; Brinkmann, Ralf
2017-07-01
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.
Developments In Electronic Speckle Pattern Interferometry For Automotive Vibration Analysis.
Davies, Jeremy C.; Buckberry, Clive H.; Jones, Julian D. C.; Pannell, Chris N.
1989-01-01
The incorporation of monomode fibre optics into an argon ion powered Electronic Speckle Pattern Interferometer (ESPI) is reported. The system, consisting of an optics assembly linked to the laser and a CCD camera transceiver, flexibly connected by 40m of monomode fibre optic cable to the optics, has been used to analyse the modal behaviour of structures up to 5m X 3m X 2m in size. Phase modulation of the reference beam in order to operate in a heterodyne mode has been implemented using a piezo-electric crystal operating on the monomode fibre. A new mode of operation - sequential time-average subtraction - and the results of a new processing algorithm are also reported. Their implementation enables speckle free, time-average vibration maps to be generated in real-time on large, unstable structures. Example results for a four cylinder power unit, a vehicle body shell component and an engine oil pan are included. In all cases the analysis was conducted in a general workshop environment without the need for vibration isolation facilities.
Speckle interferometry. Data acquisition and control for the SPID instrument.
Altarac, S.; Tallon, M.; Thiebaut, E.; Foy, R.
1998-08-01
SPID (SPeckle Imaging by Deconvolution) is a new speckle camera currently under construction at CRAL-Observatoire de Lyon. Its high spectral resolution and high image restoration capabilities open new astrophysical programs. The instrument SPID is composed of four main optical modules which are fully automated and computer controlled by a software written in Tcl/Tk/Tix and C. This software provides an intelligent assistance to the user by choosing observational parameters as a function of atmospheric parameters, computed in real time, and the desired restored image quality. Data acquisition is made by a photon-counting detector (CP40). A VME-based computer under OS9 controls the detector and stocks the data. The intelligent system runs under Linux on a PC. A slave PC under DOS commands the motors. These 3 computers communicate through an Ethernet network. SPID can be considered as a precursor for VLT's (Very Large Telescope, four 8-meter telescopes currently built in Chile by European Southern Observatory) very high spatial resolution camera.
Measurement of elasto-plastic deformations by speckle interferometry
Bova, Marco; Bruno, Luigi; Poggialini, Andrea
2010-09-01
In the paper the authors present an experimental equipment for elasto-plastic characterization of engineering materials by tensile tests. The stress state is imposed to a dog bone shaped specimen by a testing machine fixed on the optical table and designed for optimizing the performance of a speckle interferometer. All three displacement components are measured by a portable speckle interferometer fed by three laser diodes of 50 mW, by which the deformations of a surface of about 6×8 mm2 can be fully analyzed in details. All the equipment is driven by control electronics designed and realized on purpose, by which it is possible to accurately modify the intensity of the illumination sources, the position of a PZT actuator necessary for applying phase-shifting procedure, and the overall displacement applied to the specimen. The experiments were carried out in National Instrument LabVIEW environment, while the processing of the experimental data in Wolfram Mathematica environment. The paper reports the results of the elasto-plastic characterization of a high strength steel specimen.
Speckle reduction for a laser light sectioning sensor
Directory of Open Access Journals (Sweden)
Tutsch Rainer
2015-01-01
Full Text Available Automated optical inspection is an important test procedure in electronic circuits assembly. Frequently 3d information is required and laser light sectioning sensors are often applied. However, some effects complicate the reliable automatic detection of the shape of such assemblies and their components. The packages of electronic components often are made of black plastics or ceramics so that the intensity available for the optical detection is quite low, especially in comparison to the surface of the PCBs where the components are mounted on. In addition due to rough surfaces of the components and the coherence length of the laser light speckle structures arise. In the work presented here a piezo actuator is used to oscillate the illuminating laser lines along the direction of the lines. The aim is to reduce the visibility of the speckle structures by averaging while maintaining the geometrical shape of the lines. In addition, image processing methods like segmentation and skeletonization are used to allow the detection of the shape of components and assemblies also if materials with distinct differences in the reflectivity are involved. Investigations include the influence of the parameters amplitude and frequency of the piezo actuator.
Crawford, D C; Bell, D S; Bamber, J C
1993-01-01
A systematic method to compensate for nonlinear amplification of individual ultrasound B-scanners has been investigated in order to optimise performance of an adaptive speckle reduction (ASR) filter for a wide range of clinical ultrasonic imaging equipment. Three potential methods have been investigated: (1) a method involving an appropriate selection of the speckle recognition feature was successful when the scanner signal processing executes simple logarithmic compressions; (2) an inverse transform (decompression) of the B-mode image was effective in correcting for the measured characteristics of image data compression when the algorithm was implemented in full floating point arithmetic; (3) characterising the behaviour of the statistical speckle recognition feature under conditions of speckle noise was found to be the method of choice for implementation of the adaptive speckle reduction algorithm in limited precision integer arithmetic. In this example, the statistical features of variance and mean were investigated. The third method may be implemented on commercially available fast image processing hardware and is also better suited for transfer into dedicated hardware to facilitate real-time adaptive speckle reduction. A systematic method is described for obtaining ASR calibration data from B-mode images of a speckle producing phantom.
Remarks on non-Gaussian fluctuations of the inflaton and constancy of ζ outside the horizon
International Nuclear Information System (INIS)
Mahajan, N; Rangarajan, R
2014-01-01
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
The Wehrl entropy has Gaussian optimizers
DEFF Research Database (Denmark)
De Palma, Giacomo
2018-01-01
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...
Gaussian shaping filter for nuclear spectrometry
International Nuclear Information System (INIS)
Menezes, A.S.C. de.
1980-01-01
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
Asymptotic expansions for the Gaussian unitary ensemble
DEFF Research Database (Denmark)
Haagerup, Uffe; Thorbjørnsen, Steen
2012-01-01
Let g : R ¿ C be a C8-function with all derivatives bounded and let trn denote the normalized trace on the n × n matrices. In Ref. 3 Ercolani and McLaughlin established asymptotic expansions of the mean value ¿{trn(g(Xn))} for a rather general class of random matrices Xn, including the Gaussian U...
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,.
Additivity properties of a Gaussian channel
International Nuclear Information System (INIS)
Giovannetti, Vittorio; Lloyd, Seth
2004-01-01
The Amosov-Holevo-Werner conjecture implies the additivity of the minimum Renyi entropies at the output of a channel. The conjecture is proven true for all Renyi entropies of integer order greater than two in a class of Gaussian bosonic channel where the input signal is randomly displaced or where it is coupled linearly to an external environment
Modeling text with generalizable Gaussian mixtures
DEFF Research Database (Denmark)
Hansen, Lars Kai; Sigurdsson, Sigurdur; Kolenda, Thomas
2000-01-01
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...
Open problems in Gaussian fluid queueing theory
Dȩbicki, K.; Mandjes, M.
2011-01-01
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
Oracle Wiener filtering of a Gaussian signal
Babenko, A.; Belitser, E.
2011-01-01
We study the problem of filtering a Gaussian process whose trajectories, in some sense, have an unknown smoothness ß0 from the white noise of small intensity e. If we knew the parameter ß0, we would use the Wiener filter which has the meaning of oracle. Our goal is now to mimic the oracle, i.e.,
Oracle Wiener filtering of a Gaussian signal
Babenko, A.; Belitser, E.N.
2011-01-01
We study the problem of filtering a Gaussian process whose trajectories, in some sense, have an unknown smoothness β0 from the white noise of small intensity . If we knew the parameter β0, we would use the Wiener filter which has the meaning of oracle. Our goal is now to mimic the oracle, i.e.,
Perfusion Quantification Using Gaussian Process Deconvolution
DEFF Research Database (Denmark)
Andersen, Irene Klærke; Have, Anna Szynkowiak; Rasmussen, Carl Edward
2002-01-01
The quantification of perfusion using dynamic susceptibility contrast MRI (DSC-MRI) requires deconvolution to obtain the residual impulse response function (IRF). In this work, a method using the Gaussian process for deconvolution (GPD) is proposed. The fact that the IRF is smooth is incorporated...
A Gaussian graphical model approach to climate networks
Energy Technology Data Exchange (ETDEWEB)
Zerenner, Tanja, E-mail: tanjaz@uni-bonn.de [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)
2014-06-15
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.
A Gaussian graphical model approach to climate networks
International Nuclear Information System (INIS)
Zerenner, Tanja; Friederichs, Petra; Hense, Andreas; Lehnertz, Klaus
2014-01-01
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
Biasing and the search for primordial non-Gaussianity beyond the local type
Energy Technology Data Exchange (ETDEWEB)
Gleyzes, Jérôme; De Putter, Roland; Doré, Olivier [California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125 (United States); Green, Daniel, E-mail: jerome.l.gleyzes@jpl.nasa.gov, E-mail: rdputter@caltech.edu, E-mail: drgreen@cita.utoronto.ca, E-mail: olivier.p.dore@jpl.nasa.gov [Department of Physics, University of California, 366 LeConte hall, Berkeley, CA 94720 (United States)
2017-04-01
Primordial non-Gaussianity encodes valuable information about the physics of inflation, including the spectrum of particles and interactions. Significant improvements in our understanding of non-Gaussanity beyond Planck require information from large-scale structure. The most promising approach to utilize this information comes from the scale-dependent bias of halos. For local non-Gaussanity, the improvements available are well studied but the potential for non-Gaussianity beyond the local type, including equilateral and quasi-single field inflation, is much less well understood. In this paper, we forecast the capabilities of large-scale structure surveys to detect general non-Gaussianity through galaxy/halo power spectra. We study how non-Gaussanity can be distinguished from a general biasing model and where the information is encoded. For quasi-single field inflation, significant improvements over Planck are possible in some regions of parameter space. We also show that the multi-tracer technique can significantly improve the sensitivity for all non-Gaussianity types, providing up to an order of magnitude improvement for equilateral non-Gaussianity over the single-tracer measurement.
Investigation of Portevin-Le Chatelier band with temporal phase analysis of speckle interferometry
Jiang, Zhenyu; Zhang, Qingchuan; Wu, Xiaoping
2003-04-01
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.
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.
1995-01-01
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)
Pérez Suárez, Santiago T.; Travieso González, Carlos M.; Alonso Hernández, Jesús B.
2013-01-01
This article presents a design methodology for designing an artificial neural network as an equalizer for a binary signal. Firstly, the system is modelled in floating point format using Matlab. Afterward, the design is described for a Field Programmable Gate Array (FPGA) using fixed point format. The FPGA design is based on the System Generator from Xilinx, which is a design tool over Simulink of Matlab. System Generator allows one to design in a fast and flexible way. It uses low level details of the circuits and the functionality of the system can be fully tested. System Generator can be used to check the architecture and to analyse the effect of the number of bits on the system performance. Finally the System Generator design is compiled for the Xilinx Integrated System Environment (ISE) and the system is described using a hardware description language. In ISE the circuits are managed with high level details and physical performances are obtained. In the Conclusions section, some modifications are proposed to improve the methodology and to ensure portability across FPGA manufacturers.
Directory of Open Access Journals (Sweden)
Santiago T. Pérez Suárez
2013-12-01
Full Text Available This article presents a design methodology for designing an artificial neural network as an equalizer for a binary signal. Firstly, the system is modelled in floating point format using Matlab. Afterward, the design is described for a Field Programmable Gate Array (FPGA using fixed point format. The FPGA design is based on the System Generator from Xilinx, which is a design tool over Simulink of Matlab. System Generator allows one to design in a fast and flexible way. It uses low level details of the circuits and the functionality of the system can be fully tested. System Generator can be used to check the architecture and to analyse the effect of the number of bits on the system performance. Finally the System Generator design is compiled for the Xilinx Integrated System Environment (ISE and the system is described using a hardware description language. In ISE the circuits are managed with high level details and physical performances are obtained. In the Conclusions section, some modifications are proposed to improve the methodology and to ensure portability across FPGA manufacturers.
Learning non-Gaussian Time Series using the Box-Cox Gaussian Process
Rios, Gonzalo; Tobar, Felipe
2018-01-01
Gaussian processes (GPs) are Bayesian nonparametric generative models that provide interpretability of hyperparameters, admit closed-form expressions for training and inference, and are able to accurately represent uncertainty. To model general non-Gaussian data with complex correlation structure, GPs can be paired with an expressive covariance kernel and then fed into a nonlinear transformation (or warping). However, overparametrising the kernel and the warping is known to, respectively, hin...
International Nuclear Information System (INIS)
Zeng Lihui; Wang Nanping; Tian Gui
2012-01-01
In order to extract the information of peaks in different energy from the data of overlapping peaks in environmental gamma spectrometer, a spectrum data Gaussian decomposition software was designed based on least-square Gaussian fitting method. The interface of this software is friendly, it can complete the decomposition of overlapping peaks in gamma spectrometer quickly by the way of man-machines interactive. The result of field measured data decomposed by this software indicates that the Gaussian decomposition software can efficiently extract 137 Cs spectra from over lapping peaks, which has significance to estimate the human nuclide contamination in the environment. (authors)
International Nuclear Information System (INIS)
Zeng Lihui; Wang Nanping Tian Gui
2011-01-01
In order to extract the information of peaks in different energy from the data of overlapping peaks in environmental gamma spectrometer, a spectrum data Gaussian decomposition soft is designed based on least- square Gaussian fitting method. The interface of this software is friendly, it can complete the decomposition of overlapping peaks in gamma spectrometer quickly by the way of man-machines interactive. The result that applied gamma spectrometry to data analysis in the field measurement indicates that the Gaussian decomposition soft can efficiently extract 137 Cs from overlapping peaks which has significance to assess the human nuclide contamination of environment. (authors)
Directory of Open Access Journals (Sweden)
Alexandrov D.A.
2014-12-01
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.
MCEM algorithm for the log-Gaussian Cox process
Delmas, Celine; Dubois-Peyrard, Nathalie; Sabbadin, Regis
2014-01-01
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 ...
Spatial pattern formation induced by Gaussian white noise.
Scarsoglio, Stefania; Laio, Francesco; D'Odorico, Paolo; Ridolfi, Luca
2011-02-01
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.
Laser-driven acceleration with Bessel and Gaussian beams
International Nuclear Information System (INIS)
Hafizi, B.; Esarey, E.; Sprangle, P.
1997-01-01
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
Large non-Gaussianity in non-minimal inflation
Gong, Jinn-Ouk
2011-01-01
We consider a simple inflation model with a complex scalar field coupled to gravity non-minimally. Both the modulus and the angular directions of the complex scalar are slowly rolling, leading to two-field inflation. The modulus direction becomes flat due to the non-minimal coupling, and the angular direction becomes a pseudo-Goldstone boson from a small breaking of the global U(1) symmetry. We show that large non-Gaussianity can be produced during slow-roll inflation under a reasonable assumption on the initial condition of the angular direction. This scenario may be realized in particle physics models such as the Standard Model with two Higgs doublets.
Phase space structure of generalized Gaussian cat states
International Nuclear Information System (INIS)
Nicacio, Fernando; Maia, Raphael N.P.; Toscano, Fabricio; Vallejos, Raul O.
2010-01-01
We analyze generalized Gaussian cat states obtained by superposing arbitrary Gaussian states. The structure of the interference term of the Wigner function is always hyperbolic, surviving the action of a thermal reservoir. We also consider certain superpositions of mixed Gaussian states. An application to semiclassical dynamics is discussed.
Linking network usage patterns to traffic Gaussianity fit
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,
Zaroubi, S; Branchini, E
2005-01-01
We introduce a simple linear equation relating the line-of-sight peculiar-velocity and density contrast correlation functions. The relation, which we call the Gaussian cell two-point 'energy-like' equation, is valid at the distant-observer limit and requires Gaussian smoothed fields. In the variance
Nicolas, F.; Coëtmellec, S.; Brunel, M.; Allano, D.; Lebrun, D.; Janssen, A.J.E.M.
2005-01-01
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
The finite-temperature Gaussian effective potential from a variational principle
International Nuclear Information System (INIS)
Haugerud, H.; Ravndal, F.
1990-08-01
Writing the partition function for a scalar quantum field theory as a functional integral, it follows that the finite-temperature Gaussian effective potential is an upper limit to the free energy of the system. Explicit results are given for the anharmonic oscillator at finite temperature. 5 refs., 2 figs
Law, Yuen C.; Tenbrinck, Daniel; Jiang, Xiaoyi; Kuhlen, Torsten
2014-03-01
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.
M2 FILTER FOR SPECKLE NOISE SUPPRESSION IN BREAST ULTRASOUND IMAGES
Directory of Open Access Journals (Sweden)
E.S. Samundeeswari
2016-11-01
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.
SPECKLE OBSERVATIONS OF BINARY STARS WITH THE WIYN TELESCOPE. VII. MEASURES DURING 2008-2009
International Nuclear Information System (INIS)
Horch, Elliott P.; Bahi, Lizzie Anne P.; Gaulin, Joseph R.; Howell, Steve B.; Sherry, William H.; Baena Gallé, Roberto; Van Altena, William F.
2012-01-01
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).
Fabrication of nanoscale speckle using broad ion beam milling on polymers for deformation analysis
Directory of Open Access Journals (Sweden)
Qinghua Wang
2016-07-01
Full Text Available We first report a fabrication technique of nanoscale speckle patterns on polymers using broad ion beam milling. The proposed technique is simple and low-cost to produce speckles ranging from dozens of nanometers to less than three micrometers in a large area of several millimeters. Random patterns were successfully produced with an argon (Ar ion beam on the surfaces of four kinds of polymers: the epoxy matrix of carbon fiber reinforced plastic, polyester, polyvinyl formal-acetal, and polyimide. The speckle morphologies slightly vary with different polymers. The fabricated speckle patterns have good time stability and are promising to be used to measure the nanoscale deformations of polymers using the digital image correlation method.
Investigation of Rock Failure Pattern in Creep by Digital Speckle Correlation Method
Directory of Open Access Journals (Sweden)
Yunliang Tan
2013-01-01
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.
Optically sectioned in vivo imaging with speckle illumination HiLo microscopy
Lim, Daryl; Ford, Tim N.; Chu, Kengyeh K.; Mertz, Jerome
2011-01-01
We present a simple wide-field imaging technique, called HiLo microscopy, that is capable of producing optically sectioned images in real time, comparable in quality to confocal laser scanning microscopy. The technique is based on the fusion of two raw images, one acquired with speckle illumination and another with standard uniform illumination. The fusion can be numerically adjusted, using a single parameter, to produce optically sectioned images of varying thicknesses with the same raw data. Direct comparison between our HiLo microscope and a commercial confocal laser scanning microscope is made on the basis of sectioning strength and imaging performance. Specifically, we show that HiLo and confocal 3-D imaging of a GFP-labeled mouse brain hippocampus are comparable in quality. Moreover, HiLo microscopy is capable of faster, near video rate imaging over larger fields of view than attainable with standard confocal microscopes. The goal of this paper is to advertise the simplicity, robustness, and versatility of HiLo microscopy, which we highlight with in vivo imaging of common model organisms including planaria, C. elegans, and zebrafish.
Angular diameters of Magellanic Cloud plantary nebulae. I. Speckle interferometry
International Nuclear Information System (INIS)
Wood, P.R.; Bessell, M.S.; Dopita, M.A.
1986-01-01
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
Speckle interferometry application for erosion measurements in fusion devices
Energy Technology Data Exchange (ETDEWEB)
Gauthier, E.; Roupillard, R. [Association Euratom-CEA Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee
2003-07-01
In order to measure erosion/redeposition in fusion devices, a new diagnostic based on speckle interferometry is investigated. First experiments performed on carbon fibre composite (CFC) materials have shown that this technique is able to measure a modification of the surface in the range of 1 {mu}m. Further experiments have been performed on different materials using a second wavelength in order to carry out 3-dimensional measurements of the surface and to increase the dynamic range of the depth measurement. A diagnostic, based on two-wavelength TV-holography to measure in situ erosion/redeposition during long duration discharges on the CIEL limiter in Tore Supra, is under development at CEA Cadarache. (authors)
Dynamic-speckle profilometer for online measurements of coating thickness
Energy Technology Data Exchange (ETDEWEB)
Kamshilin, A A [Laboratory of Optical Sensor Technology, Department of Physics, University of Kuopio, PO Box 1627, FIN-70211 Kuopio (Finland); Semenov, D V [Laboratory of Optical Sensor Technology, Department of Physics, University of Kuopio, PO Box 1627, FIN-70211 Kuopio (Finland); Nippolainen, E [Laboratory of Optical Sensor Technology, Department of Physics, University of Kuopio, PO Box 1627, FIN-70211 Kuopio (Finland); Miridonov, S [Optics Department, CICESE, Carr. Tijuana-Ensenada km 107, C.P. 22860, A.P. 360, Ensenada, B.C. (Mexico)
2007-10-15
Online control of thickness of as-deposited coatings is of great importance because it directly affects the quality of protective coatings. We present a novel approach that enables online, real-time and non-contact measurements thickness of thermally sprayed coatings. The proposed technique uses dynamic speckles generated by rapidly deflecting laser beam. Within 10 ms the system can scan 500 times a small area of the deposited layer thus resulting in measurement accuracy of 5 microns irrespectively of the layer roughness. In comparison with traditional optical triangulation technique of distance measurements, our system has following advantages: (i) much simpler optical scheme that includes conventional photodiode to measure the scattered light, (ii) much simpler electronics for real-time data processing, (iii) much higher speed of measurements.
Dynamic-speckle profilometer for online measurements of coating thickness
International Nuclear Information System (INIS)
Kamshilin, A A; Semenov, D V; Nippolainen, E; Miridonov, S
2007-01-01
Online control of thickness of as-deposited coatings is of great importance because it directly affects the quality of protective coatings. We present a novel approach that enables online, real-time and non-contact measurements thickness of thermally sprayed coatings. The proposed technique uses dynamic speckles generated by rapidly deflecting laser beam. Within 10 ms the system can scan 500 times a small area of the deposited layer thus resulting in measurement accuracy of 5 microns irrespectively of the layer roughness. In comparison with traditional optical triangulation technique of distance measurements, our system has following advantages: (i) much simpler optical scheme that includes conventional photodiode to measure the scattered light, (ii) much simpler electronics for real-time data processing, (iii) much higher speed of measurements
Thermal strain measurements in graphite using electronic speckle pattern interferometry
International Nuclear Information System (INIS)
Tamulevicius, S.; Augulis, L.; Augulis, R.; Zabarskas, V.; Levinskas, R.; Poskas, P.
2001-01-01
Two 1500 MW(e) RBMK Units are operated at Ignalina NPP in Lithuania. Due to recent decision of the Parliament on the earlier closure of Unit 1, preparatory work for decommissioning have been initiated. Preferred decommissioning strategy is based on delayed dismantling after rather long safe enclosure period. Since graphite is one of the basic and probably the most voluminous components of the reactor internals, a sufficient information on status and behaviour of graphite moderator and reflector during long time safe enclosure period is of special significance. In this context, thermal strain in graphite is one of the parameters requiring particular interest. Electronic speckle pattern interferometry has been proposed and successfully tested to control this parameter using the real samples of graphite from Ignalina NPP Units. (author)