Sample records for abel inversion technique

  1. Abel inversion using fast Fourier transforms.

    PubMed

    Kalal, M; Nugent, K A

    1988-05-15

    A fast Fourier transform based Abel inversion technique is proposed. The method is faster than previously used techniques, potentially very accurate (even for a relatively small number of points), and capable of handling large data sets. The technique is discussed in the context of its use with 2-D digital interferogram analysis algorithms. Several examples are given.

  2. Improved Abel transform inversion: First application to COSMIC/FORMOSAT-3

    NASA Astrophysics Data System (ADS)

    Aragon-Angel, A.; Hernandez-Pajares, M.; Juan, J.; Sanz, J.

    2007-05-01

    In this paper the first results of Ionospheric Tomographic inversion are presented, using the Improved Abel Transform on the COSMIC/FORMOSAT-3 constellation of 6 LEO satellites, carrying on-board GPS receivers.[- 4mm] The Abel transform inversion is a wide used technique which in the ionospheric context makes it possible to retrieve electron densities as a function of height based of STEC (Slant Total Electron Content) data gathered from GPS receivers on board of LEO (Low Earth Orbit) satellites. Within this precise use, the classical approach of the Abel inversion is based on the assumption of spherical symmetry of the electron density in the vicinity of an occultation, meaning that the electron content varies in height but not horizontally. In particular, one implication of this assumption is that the VTEC (Vertical Total Electron Content) is a constant value for the occultation region. This assumption may not always be valid since horizontal ionospheric gradients (a very frequent feature in some ionosphere problematic areas such as the Equatorial region) could significantly affect the electron profiles. [- 4mm] In order to overcome this limitation/problem of the classical Abel inversion, a studied improvement of this technique can be obtained by assuming separability in the electron density (see Hernández-Pajares et al. 2000). This means that the electron density can be expressed by the multiplication of VTEC data and a shape function which assumes all the height dependency in it while the VTEC data keeps the horizontal dependency. Actually, it is more realistic to assume that this shape fuction depends only on the height and to use VTEC information to take into account the horizontal variation rather than considering spherical symmetry in the electron density function as it has been carried out in the classical approach of the Abel inversion.[-4mm] Since the above mentioned improved Abel inversion technique has already been tested and proven to be a useful

  3. Bayesian Abel Inversion in Quantitative X-Ray Radiography

    DOE PAGES

    Howard, Marylesa; Fowler, Michael; Luttman, Aaron; ...

    2016-05-19

    A common image formation process in high-energy X-ray radiography is to have a pulsed power source that emits X-rays through a scene, a scintillator that absorbs X-rays and uoresces in the visible spectrum in response to the absorbed photons, and a CCD camera that images the visible light emitted from the scintillator. The intensity image is related to areal density, and, for an object that is radially symmetric about a central axis, the Abel transform then gives the object's volumetric density. Two of the primary drawbacks to classical variational methods for Abel inversion are their sensitivity to the type andmore » scale of regularization chosen and the lack of natural methods for quantifying the uncertainties associated with the reconstructions. In this work we cast the Abel inversion problem within a statistical framework in order to compute volumetric object densities from X-ray radiographs and to quantify uncertainties in the reconstruction. A hierarchical Bayesian model is developed with a likelihood based on a Gaussian noise model and with priors placed on the unknown density pro le, the data precision matrix, and two scale parameters. This allows the data to drive the localization of features in the reconstruction and results in a joint posterior distribution for the unknown density pro le, the prior parameters, and the spatial structure of the precision matrix. Results of the density reconstructions and pointwise uncertainty estimates are presented for both synthetic signals and real data from a U.S. Department of Energy X-ray imaging facility.« less

  4. Inverting ion images without Abel inversion: maximum entropy reconstruction of velocity maps.

    PubMed

    Dick, Bernhard

    2014-01-14

    A new method for the reconstruction of velocity maps from ion images is presented, which is based on the maximum entropy concept. In contrast to other methods used for Abel inversion the new method never applies an inversion or smoothing to the data. Instead, it iteratively finds the map which is the most likely cause for the observed data, using the correct likelihood criterion for data sampled from a Poissonian distribution. The entropy criterion minimizes the information content in this map, which hence contains no information for which there is no evidence in the data. Two implementations are proposed, and their performance is demonstrated with simulated and experimental data: Maximum Entropy Velocity Image Reconstruction (MEVIR) obtains a two-dimensional slice through the velocity distribution and can be compared directly to Abel inversion. Maximum Entropy Velocity Legendre Reconstruction (MEVELER) finds one-dimensional distribution functions Q(l)(v) in an expansion of the velocity distribution in Legendre polynomials P((cos θ) for the angular dependence. Both MEVIR and MEVELER can be used for the analysis of ion images with intensities as low as 0.01 counts per pixel, with MEVELER performing significantly better than MEVIR for images with low intensity. Both methods perform better than pBASEX, in particular for images with less than one average count per pixel.

  5. Serre duality, Abel's theorem, and Jacobi inversion for supercurves over a thick superpoint

    NASA Astrophysics Data System (ADS)

    Rothstein, Mitchell J.; Rabin, Jeffrey M.

    2015-04-01

    The principal aim of this paper is to extend Abel's theorem to the setting of complex supermanifolds of dimension 1 | q over a finite-dimensional local supercommutative C-algebra. The theorem is proved by establishing a compatibility of Serre duality for the supercurve with Poincaré duality on the reduced curve. We include an elementary algebraic proof of the requisite form of Serre duality, closely based on the account of the reduced case given by Serre in Algebraic groups and class fields, combined with an invariance result for the topology on the dual of the space of répartitions. Our Abel map, taking Cartier divisors of degree zero to the dual of the space of sections of the Berezinian sheaf, modulo periods, is defined via Penkov's characterization of the Berezinian sheaf as the cohomology of the de Rham complex of the sheaf D of differential operators. We discuss the Jacobi inversion problem for the Abel map and give an example demonstrating that if n is an integer sufficiently large that the generic divisor of degree n is linearly equivalent to an effective divisor, this need not be the case for all divisors of degree n.

  6. An ionospheric occultation inversion technique based on epoch difference

    NASA Astrophysics Data System (ADS)

    Lin, Jian; Xiong, Jing; Zhu, Fuying; Yang, Jian; Qiao, Xuejun

    2013-09-01

    Of the ionospheric radio occultation (IRO) electron density profile (EDP) retrievals, the Abel based calibrated TEC inversion (CTI) is the most widely used technique. In order to eliminate the contribution from the altitude above the RO satellite, it is necessary to utilize the calibrated TEC to retrieve the EDP, which introduces the error due to the coplanar assumption. In this paper, a new technique based on the epoch difference inversion (EDI) is firstly proposed to eliminate this error. The comparisons between CTI and EDI have been done, taking advantage of the simulated and real COSMIC data. The following conclusions can be drawn: the EDI technique can successfully retrieve the EDPs without non-occultation side measurements and shows better performance than the CTI method, especially for lower orbit mission; no matter which technique is used, the inversion results at the higher altitudes are better than those at the lower altitudes, which could be explained theoretically.

  7. Evaluation of Inversion Methods Applied to Ionospheric ro Observations

    NASA Astrophysics Data System (ADS)

    Rios Caceres, Arq. Estela Alejandra; Rios, Victor Hugo; Guyot, Elia

    The new technique of radio-occultation can be used to study the Earth's ionosphere. The retrieval processes of ionospheric profiling from radio occultation observations usually assume spherical symmetry of electron density distribution at the locality of occultation and use the Abel integral transform to invert the measured total electron content (TEC) values. This pa-per presents a set of ionospheric profiles obtained from SAC-C satellite with the Abel inversion technique. The effects of the ionosphere on the GPS signal during occultation, such as bending and scintillation, are examined. Electron density profiles are obtained using the Abel inversion technique. Ionospheric radio occultations are validated using vertical profiles of electron con-centration from inverted ionograms , obtained from ionosonde sounding in the vicinity of the occultation. Results indicate that the Abel transform works well in the mid-latitudes during the daytime, but is less accurate during the night-time.

  8. Spatially-resolved velocities of thermally-produced spray droplets using a velocity-divided Abel inversion of photographed streaks

    NASA Astrophysics Data System (ADS)

    Kawaguchi, Y.; Kobayashi, N.; Yamagata, Y.; Miyazaki, F.; Yamasaki, M.; Muraoka, K.

    2017-10-01

    Droplet velocities of thermal spray are known to have profound effects on important coating qualities, such as adhesive strength, porosity, and hardness, for various applications. For obtaining the droplet velocities, therefore, the TOF (time-of-flight) technique has been widely used, which relies on observations of emitted radiation from the droplets, where all droplets along the line-of-sight contribute to signals. Because droplets at and near the flow axis mostly contribute coating layers, it has been hoped to get spatially resolved velocities. For this purpose, a velocity-divided Abel inversion was devised from CMOS photographic data. From this result, it has turned out that the central velocity is about 25% higher than that obtained from the TOF technique for the case studied (at the position 150 mm downstream of the plasma spray gun, where substrates for spray coatings are usually placed). Further implications of the obtained results are discussed.

  9. A variational regularization of Abel transform for GPS radio occultation

    NASA Astrophysics Data System (ADS)

    Wee, Tae-Kwon

    2018-04-01

    In the Global Positioning System (GPS) radio occultation (RO) technique, the inverse Abel transform of measured bending angle (Abel inversion, hereafter AI) is the standard means of deriving the refractivity. While concise and straightforward to apply, the AI accumulates and propagates the measurement error downward. The measurement error propagation is detrimental to the refractivity in lower altitudes. In particular, it builds up negative refractivity bias in the tropical lower troposphere. An alternative to AI is the numerical inversion of the forward Abel transform, which does not incur the integration of error-possessing measurement and thus precludes the error propagation. The variational regularization (VR) proposed in this study approximates the inversion of the forward Abel transform by an optimization problem in which the regularized solution describes the measurement as closely as possible within the measurement's considered accuracy. The optimization problem is then solved iteratively by means of the adjoint technique. VR is formulated with error covariance matrices, which permit a rigorous incorporation of prior information on measurement error characteristics and the solution's desired behavior into the regularization. VR holds the control variable in the measurement space to take advantage of the posterior height determination and to negate the measurement error due to the mismodeling of the refractional radius. The advantages of having the solution and the measurement in the same space are elaborated using a purposely corrupted synthetic sounding with a known true solution. The competency of VR relative to AI is validated with a large number of actual RO soundings. The comparison to nearby radiosonde observations shows that VR attains considerably smaller random and systematic errors compared to AI. A noteworthy finding is that in the heights and areas that the measurement bias is supposedly small, VR follows AI very closely in the mean refractivity

  10. A comparison of techniques for inversion of radio-ray phase data in presence of ray bending

    NASA Technical Reports Server (NTRS)

    Wallio, H. A.; Grossi, M. D.

    1972-01-01

    Derivations are presented of the straight-line Abel transform and the seismological Herglotz-Wiechert transform (which takes ray bending into account) that are used in the reconstruction of refractivity profiles from radio-wave phase data. Profile inversion utilizing these approaches, performed in computer-simulated experiments, are compared for cases of positive, zero, and negative ray bending. For thin atmospheres and ionospheres, such as the Martian atmosphere and ionosphere, radio wave signals are shown to be inverted accurately with both methods. For dense media, such as the solar corona or the lower Venus atmosphere, the refractive recovered by the seismological Herglotz-Wiechert transform provide a significant improvement compared with the straight-line Abel transform.

  11. Chandra and XMM-Newton Observations of the Abell 3395/Abell 3391 Intercluster Filament

    NASA Astrophysics Data System (ADS)

    Alvarez, Gabriella E.; Randall, Scott W.; Bourdin, Hervé; Jones, Christine; Holley-Bockelmann, Kelly

    2018-05-01

    We present Chandra and XMM-Newton X-ray observations of the Abell 3391/Abell 3395 intercluster filament. It has been suggested that the galaxy clusters Abell 3395, Abell 3391, and the galaxy group ESO-161 -IG 006 located between the two clusters, are in alignment along a large-scale intercluster filament. We find that the filament is aligned close to the plane of the sky, in contrast to previous results. We find a global projected filament temperature kT = {4.45}-0.55+0.89 keV, electron density {n}e={1.08}-0.05+0.06× {10}-4 cm‑3, and {M}gas}={2.7}-0.1+0.2 × {10}13 M ⊙. The thermodynamic properties of the filament are consistent with that of the intracluster medium (ICM) of Abell 3395 and Abell 3391, suggesting that the filament emission is dominated by ICM gas that has been tidally disrupted during an early stage merger between these two clusters. We present temperature, density, entropy, and abundance profiles across the filament. We find that the galaxy group ESO-161 may be undergoing ram-pressure-stripping in the low-density environment at or near the virial radius of both clusters, due to its rapid motion through the filament.

  12. Hubble Frontier Field Abell 2744

    NASA Image and Video Library

    2014-01-07

    This long-exposure image from NASA Hubble Space Telescope of massive galaxy cluster Abell 2744 is the deepest ever made of any cluster of galaxies. Shown in the foreground is Abell 2744, located in the constellation Sculptor.

  13. Rapid Inversion of Angular Deflection Data for Certain Axisymmetric Refractive Index Distributions

    NASA Technical Reports Server (NTRS)

    Rubinstein, R.; Greenberg, P. S.

    1994-01-01

    Certain functions useful for representing axisymmetric refractive-index distributions are shown to have exact solutions for Abel transformation of the resulting angular deflection data. An advantage of this procedure over direct numerical Abel inversion is that least-squares curve fitting is a smoothing process that reduces the noise sensitivity of the computation

  14. Abel's theorem in the noncommutative case

    NASA Astrophysics Data System (ADS)

    Leitenberger, Frank

    2004-03-01

    We define noncommutative binary forms. Using the typical representation of Hermite we prove the fundamental theorem of algebra and we derive a noncommutative Cardano formula for cubic forms. We define quantized elliptic and hyperelliptic differentials of the first kind. Following Abel we prove Abel's theorem.

  15. Tomography and the Herglotz-Wiechert inverse formulation

    NASA Astrophysics Data System (ADS)

    Nowack, Robert L.

    1990-04-01

    In this paper, linearized tomography and the Herglotz-Wiechert inverse formulation are compared. Tomographic inversions for 2-D or 3-D velocity structure use line integrals along rays and can be written in terms of Radon transforms. For radially concentric structures, Radon transforms are shown to reduce to Abel transforms. Therefore, for straight ray paths, the Abel transform of travel-time is a tomographic algorithm specialized to a one-dimensional radially concentric medium. The Herglotz-Wiechert formulation uses seismic travel-time data to invert for one-dimensional earth structure and is derived using exact ray trajectories by applying an Abel transform. This is of historical interest since it would imply that a specialized tomographic-like algorithm has been used in seismology since the early part of the century (see Herglotz, 1907; Wiechert, 1910). Numerical examples are performed comparing the Herglotz-Wiechert algorithm and linearized tomography along straight rays. Since the Herglotz-Wiechert algorithm is applicable under specific conditions, (the absence of low velocity zones) to non-straight ray paths, the association with tomography may prove to be useful in assessing the uniqueness of tomographic results generalized to curved ray geometries.

  16. Point-source inversion techniques

    NASA Astrophysics Data System (ADS)

    Langston, Charles A.; Barker, Jeffrey S.; Pavlin, Gregory B.

    1982-11-01

    A variety of approaches for obtaining source parameters from waveform data using moment-tensor or dislocation point source models have been investigated and applied to long-period body and surface waves from several earthquakes. Generalized inversion techniques have been applied to data for long-period teleseismic body waves to obtain the orientation, time function and depth of the 1978 Thessaloniki, Greece, event, of the 1971 San Fernando event, and of several events associated with the 1963 induced seismicity sequence at Kariba, Africa. The generalized inversion technique and a systematic grid testing technique have also been used to place meaningful constraints on mechanisms determined from very sparse data sets; a single station with high-quality three-component waveform data is often sufficient to discriminate faulting type (e.g., strike-slip, etc.). Sparse data sets for several recent California earthquakes, for a small regional event associated with the Koyna, India, reservoir, and for several events at the Kariba reservoir have been investigated in this way. Although linearized inversion techniques using the moment-tensor model are often robust, even for sparse data sets, there are instances where the simplifying assumption of a single point source is inadequate to model the data successfully. Numerical experiments utilizing synthetic data and actual data for the 1971 San Fernando earthquake graphically demonstrate that severe problems may be encountered if source finiteness effects are ignored. These techniques are generally applicable to on-line processing of high-quality digital data, but source complexity and inadequacy of the assumed Green's functions are major problems which are yet to be fully addressed.

  17. ROSAT HRI images of Abell 85 and Abell 496: Evidence for inhomogeneities in cooling flows

    NASA Technical Reports Server (NTRS)

    Prestwich, Andrea H.; Guimond, Stephen J.; Luginbuhl, Christian; Joy, Marshall

    1994-01-01

    We present ROSAT HRI images of two clusters of galaxies with cooling flows, Abell 496 and Abell 85. In these clusters, x-ray emission on small scales above the general cluster emission is significant at the 3 sigma level. There is no evidence for optical counterparts. The enhancements may be associated with lumps of gas at a lower temperature and higher density than the ambient medium, or hotter, denser gas perhaps compressed by magnetic fields. These observations can be used to test models of how thermal instabilities form and evolve in cooling flows.

  18. An efficient and flexible Abel-inversion method for noisy data

    NASA Astrophysics Data System (ADS)

    Antokhin, Igor I.

    2016-12-01

    We propose an efficient and flexible method for solving the Abel integral equation of the first kind, frequently appearing in many fields of astrophysics, physics, chemistry, and applied sciences. This equation represents an ill-posed problem, thus solving it requires some kind of regularization. Our method is based on solving the equation on a so-called compact set of functions and/or using Tikhonov's regularization. A priori constraints on the unknown function, defining a compact set, are very loose and can be set using simple physical considerations. Tikhonov's regularization in itself does not require any explicit a priori constraints on the unknown function and can be used independently of such constraints or in combination with them. Various target degrees of smoothness of the unknown function may be set, as required by the problem at hand. The advantage of the method, apart from its flexibility, is that it gives uniform convergence of the approximate solution to the exact solution, as the errors of input data tend to zero. The method is illustrated on several simulated models with known solutions. An example of astrophysical application of the method is also given.

  19. The Filtered Abel Transform and Its Application in Combustion Diagnostics

    NASA Technical Reports Server (NTRS)

    Simons, Stephen N. (Technical Monitor); Yuan, Zeng-Guang

    2003-01-01

    Many non-intrusive combustion diagnosis methods generate line-of-sight projections of a flame field. To reconstruct the spatial field of the measured properties, these projections need to be deconvoluted. When the spatial field is axisymmetric, commonly used deconvolution method include the Abel transforms, the onion peeling method and the two-dimensional Fourier transform method and its derivatives such as the filtered back projection methods. This paper proposes a new approach for performing the Abel transform method is developed, which possesses the exactness of the Abel transform and the flexibility of incorporating various filters in the reconstruction process. The Abel transform is an exact method and the simplest among these commonly used methods. It is evinced in this paper that all the exact reconstruction methods for axisymmetric distributions must be equivalent to the Abel transform because of its uniqueness and exactness. Detailed proof is presented to show that the two dimensional Fourier methods when applied to axisymmetric cases is identical to the Abel transform. Discrepancies among various reconstruction method stem from the different approximations made to perform numerical calculations. An equation relating the spectrum of a set of projection date to that of the corresponding spatial distribution is obtained, which shows that the spectrum of the projection is equal to the Abel transform of the spectrum of the corresponding spatial distribution. From the equation, if either the projection or the distribution is bandwidth limited, the other is also bandwidth limited, and both have the same bandwidth. If the two are not bandwidth limited, the Abel transform has a bias against low wave number components in most practical cases. This explains why the Abel transform and all exact deconvolution methods are sensitive to high wave number noises. The filtered Abel transform is based on the fact that the Abel transform of filtered projection data is equal

  20. ROSAT HRI images of Abell 85 and Abell 496: Evidence for inhomogeneities in cooling flows

    NASA Technical Reports Server (NTRS)

    Prestwich, Andrea H.; Guimond, Stephen J.; Luginbuhl, Christian B.; Joy, Marshall

    1995-01-01

    We present ROSAT high-resolution images of two clusters of galaxies with cooling flows, Abell 496 and Abell 85. In these clusters, X-ray emission on small scales above the general cluster emission is significant at the 3 sigma level. There is no evidence for optical counterparts. If real, the enhancements may be associated with clumps of gas at a lower temperature and higher density than the ambient medium, or hotter, denser gas perhaps compressed by magnetic fields. These observations can be used to test models of how thermal instabilities form and evolve in cooling flows.

  1. The X-ray cluster Abell 744

    NASA Technical Reports Server (NTRS)

    Kurtz, M. J.; Huchra, J. P.; Beers, T. C.; Geller, M. J.; Gioia, I. M.

    1985-01-01

    X-ray and optical observations of the cluster of galaxies Abell 744 are presented. The X-ray flux (assuming H(0) = 100 km/s per Mpc) is about 9 x 10 to the 42nd erg/s. The X-ray source is extended, but shows no other structure. Photographic photometry (in Kron-Cousins R), calibrated by deep CCD frames, is presented for all galaxies brighter than 19th magnitude within 0.75 Mpc of the cluster center. The luminosity function is normal, and the isopleths show little evidence of substructure near the cluster center. The cluster has a dominant central galaxy, which is classified as a normal brightest-cluster elliptical on the basis of its luminosity profile. New redshifts were obtained for 26 galaxies in the vicinity of the cluster center; 20 appear to be cluster members. The spatial distribution of redshifts is peculiar; the dispersion within the 150 kpc core radius is much greater than outside. Abell 744 is similar to the nearby cluster Abell 1060.

  2. Smoothing Technique and Variance Propagation for Abel Inversion of Scattered Data

    DTIC Science & Technology

    1977-04-01

    42 42 44 44 46 46 26 27 29 32 33 35 36 37 39 4 AE DC-TR-76 -163 10, Input Data Defining a Curve with a Sudden...1.000000 E-02 -1.00O000 E-02 35 A E D C - T R - 7 6 - 1 6 3 As a further examination of the technique, the 31 ordinates generated from the function of...TI h -Ol 7. 889482 E-02 5. C~0000 K - 0 ) 7. ?15975 E - 0 I 5.531891 E-90 4 .59 .~ 35 E-C1 5.24~1~0 ~ -02 G. OO0000 E - 0 ) G. 78:933 E-OI -2

  3. A Strong Merger Shock in Abell 665

    NASA Technical Reports Server (NTRS)

    Dasadia, S.; Sun, M.; Sarazin, C.; Morandi, A.; Markevitch, M.; Wik, D.; Feretti, L.; Giovannini, G.; Govoni, F.

    2016-01-01

    Deep (103 ks) Chandra observations of Abell 665 have revealed rich structures in this merging galaxy cluster, including a strong shock and two cold fronts. The newly discovered shock has a Mach number of M =?3.0 +/- 0.6, propagating in front of a cold disrupted cloud. This makes Abell 665 the second cluster, after the Bullet cluster, where a strong merger shock of M is approximately 3 has been detected. The shock velocity from jump conditions is consistent with (2.7 +/- 0.7) × 10(exp 3) km s(exp -1). The new data also reveal a prominent southern cold front with potentially heated gas ahead of it. Abell 665 also hosts a giant radio halo. There is a hint of diffuse radio emission extending to the shock at the north, which needs to be examined with better radio data. This new strong shock provides a great opportunity to study the reacceleration model with the X-ray and radio data combined.

  4. Profile inversion in presence of ray bending

    NASA Technical Reports Server (NTRS)

    Wallio, H. A.; Grossi, M. D.

    1972-01-01

    Inversion of radio occultation data for planetary atmospheres and ionospheres has been performed using the seismological Herglotz-Wiechert method, as adapted by Phinney and Anderson to the radio-occultation case. Profile reconstruction performed in computer simulated experiments with this approach have been compared with the ones obtained with the straight-ray Abel transform. For a thin atmosphere and ionosphere, like the ones encountered on Mars, microwave occultation data can be inverted accurately with both methods. For a dense ionosphere like the sun's corona, ray bending of microwaves is severe, and recovered refractivity by the Herglotz-Wiechert method provides significant improvement over the straight-ray Abel transform: the error reduces from more than 60% to less than 20% at a height of 60,000 km above the base of the corona.

  5. A model-assisted radio occultation data inversion method based on data ingestion into NeQuick

    NASA Astrophysics Data System (ADS)

    Shaikh, M. M.; Nava, B.; Kashcheyev, A.

    2017-01-01

    Inverse Abel transform is the most common method to invert radio occultation (RO) data in the ionosphere and it is based on the assumption of the spherical symmetry for the electron density distribution in the vicinity of an occultation event. It is understood that this 'spherical symmetry hypothesis' could fail, above all, in the presence of strong horizontal electron density gradients. As a consequence, in some cases wrong electron density profiles could be obtained. In this work, in order to incorporate the knowledge of horizontal gradients, we have suggested an inversion technique based on the adaption of the empirical ionospheric model, NeQuick2, to RO-derived TEC. The method relies on the minimization of a cost function involving experimental and model-derived TEC data to determine NeQuick2 input parameters (effective local ionization parameters) at specific locations and times. These parameters are then used to obtain the electron density profile along the tangent point (TP) positions associated with the relevant RO event using NeQuick2. The main focus of our research has been laid on the mitigation of spherical symmetry effects from RO data inversion without using external data such as data from global ionospheric maps (GIM). By using RO data from Constellation Observing System for Meteorology Ionosphere and Climate (FORMOSAT-3/COSMIC) mission and manually scaled peak density data from a network of ionosondes along Asian and American longitudinal sectors, we have obtained a global improvement of 5% with 7% in Asian longitudinal sector (considering the data used in this work), in the retrieval of peak electron density (NmF2) with model-assisted inversion as compared to the Abel inversion. Mean errors of NmF2 in Asian longitudinal sector are calculated to be much higher compared to American sector.

  6. Tauberian theorems for Abel summability of sequences of fuzzy numbers

    NASA Astrophysics Data System (ADS)

    Yavuz, Enes; ćoşkun, Hüsamettin

    2015-09-01

    We give some conditions under which Abel summable sequences of fuzzy numbers are convergent. As corollaries we obtain the results given in [E. Yavuz, Ö. Talo, Abel summability of sequences of fuzzy numbers, Soft computing 2014, doi: 10.1007/s00500-014-1563-7].

  7. Oil core microcapsules by inverse gelation technique.

    PubMed

    Martins, Evandro; Renard, Denis; Davy, Joëlle; Marquis, Mélanie; Poncelet, Denis

    2015-01-01

    A promising technique for oil encapsulation in Ca-alginate capsules by inverse gelation was proposed by Abang et al. This method consists of emulsifying calcium chloride solution in oil and then adding it dropwise in an alginate solution to produce Ca-alginate capsules. Spherical capsules with diameters around 3 mm were produced by this technique, however the production of smaller capsules was not demonstrated. The objective of this study is to propose a new method of oil encapsulation in a Ca-alginate membrane by inverse gelation. The optimisation of the method leads to microcapsules with diameters around 500 μm. In a search of microcapsules with improved diffusion characteristics, the size reduction is an essential factor to broaden the applications in food, cosmetics and pharmaceuticals areas. This work contributes to a better understanding of the inverse gelation technique and allows the production of microcapsules with a well-defined shell-core structure.

  8. The wonderful apparatus of John Jacob Abel called the "artificial kidney".

    PubMed

    Eknoyan, Garabed

    2009-01-01

    Hemodialysis, which now provides life-saving therapy to millions of individuals, began as an exploratory attempt to sustain the lives of selected patients in the 1950s. That was a century after the formulation of the concept and determination of the laws governing dialysis. The first step in the translation of the laboratory principles of dialysis to living animals was the "vividiffusion" apparatus developed by John Jacob Abel (1859-1938), dubbed the "artificial kidney" in the August 11, 1913 issue of The Times of London reporting the demonstration of vividiffusion by Abel at University College. The detailed article in the January 18, 1914 of the New York Times, reproduced here, is based on the subsequent medical reports published by Abel et al. Tentative attempts of human dialysis in the decade that followed based on the vividiffusion apparatus of Abel and his materials (collodion, hirudin, and glass) met with failure and had to be abandoned. Practical dialysis became possible in the 1940s and thereafter after cellophane, heparin, and teflon became available. Abel worked in an age of great progress and experimental work in the basic sciences that laid the foundations of science-driven medicine. It was a "Heroic Age of Medicine," when medical discoveries and communicating them to the public were assuming increasing importance. This article provides the cultural, social, scientific, and medical background in which Abel worked, developed and reported his wonderful apparatus called the "artificial kidney."

  9. Anti-inflammatory and antioxidative effects of Camellia oleifera Abel components.

    PubMed

    Xiao, Xiaomei; He, Liangmei; Chen, Yayun; Wu, Longhuo; Wang, Lin; Liu, Zhiping

    2017-11-01

    Camellia oleifera Abel is a member of Camellia, and its seeds are used to extract Camellia oil, which is generally used as cooking oil in the south of China. Camellia oil consists of unsaturated fatty acids, tea polyphenol, squalene, saponin, carrot element and vitamins, etc. The seed remains after oil extraction of C. oleifera Abel are by-products of oil production, named as Camellia oil cake. Its extracts contain bioactive compounds including sasanquasaponin, flavonoid and tannin. Major components from Camellia oil and its cake have been shown to have anti-inflammatory, antioxidative, antimicrobial and antitumor activities. In this review, we will summarize the latest advance in the studies on anti-inflammatory or antioxidative effects of C. oleifera products, thus providing valuable reference for the future research and development of C. oleifera Abel.

  10. ParallABEL: an R library for generalized parallelization of genome-wide association studies.

    PubMed

    Sangket, Unitsa; Mahasirimongkol, Surakameth; Chantratita, Wasun; Tandayya, Pichaya; Aulchenko, Yurii S

    2010-04-29

    Genome-Wide Association (GWA) analysis is a powerful method for identifying loci associated with complex traits and drug response. Parts of GWA analyses, especially those involving thousands of individuals and consuming hours to months, will benefit from parallel computation. It is arduous acquiring the necessary programming skills to correctly partition and distribute data, control and monitor tasks on clustered computers, and merge output files. Most components of GWA analysis can be divided into four groups based on the types of input data and statistical outputs. The first group contains statistics computed for a particular Single Nucleotide Polymorphism (SNP), or trait, such as SNP characterization statistics or association test statistics. The input data of this group includes the SNPs/traits. The second group concerns statistics characterizing an individual in a study, for example, the summary statistics of genotype quality for each sample. The input data of this group includes individuals. The third group consists of pair-wise statistics derived from analyses between each pair of individuals in the study, for example genome-wide identity-by-state or genomic kinship analyses. The input data of this group includes pairs of SNPs/traits. The final group concerns pair-wise statistics derived for pairs of SNPs, such as the linkage disequilibrium characterisation. The input data of this group includes pairs of individuals. We developed the ParallABEL library, which utilizes the Rmpi library, to parallelize these four types of computations. ParallABEL library is not only aimed at GenABEL, but may also be employed to parallelize various GWA packages in R. The data set from the North American Rheumatoid Arthritis Consortium (NARAC) includes 2,062 individuals with 545,080, SNPs' genotyping, was used to measure ParallABEL performance. Almost perfect speed-up was achieved for many types of analyses. For example, the computing time for the identity-by-state matrix was

  11. ParallABEL: an R library for generalized parallelization of genome-wide association studies

    PubMed Central

    2010-01-01

    Background Genome-Wide Association (GWA) analysis is a powerful method for identifying loci associated with complex traits and drug response. Parts of GWA analyses, especially those involving thousands of individuals and consuming hours to months, will benefit from parallel computation. It is arduous acquiring the necessary programming skills to correctly partition and distribute data, control and monitor tasks on clustered computers, and merge output files. Results Most components of GWA analysis can be divided into four groups based on the types of input data and statistical outputs. The first group contains statistics computed for a particular Single Nucleotide Polymorphism (SNP), or trait, such as SNP characterization statistics or association test statistics. The input data of this group includes the SNPs/traits. The second group concerns statistics characterizing an individual in a study, for example, the summary statistics of genotype quality for each sample. The input data of this group includes individuals. The third group consists of pair-wise statistics derived from analyses between each pair of individuals in the study, for example genome-wide identity-by-state or genomic kinship analyses. The input data of this group includes pairs of SNPs/traits. The final group concerns pair-wise statistics derived for pairs of SNPs, such as the linkage disequilibrium characterisation. The input data of this group includes pairs of individuals. We developed the ParallABEL library, which utilizes the Rmpi library, to parallelize these four types of computations. ParallABEL library is not only aimed at GenABEL, but may also be employed to parallelize various GWA packages in R. The data set from the North American Rheumatoid Arthritis Consortium (NARAC) includes 2,062 individuals with 545,080, SNPs' genotyping, was used to measure ParallABEL performance. Almost perfect speed-up was achieved for many types of analyses. For example, the computing time for the identity

  12. Redshifts in the Southern Abell Redshift Survey Clusters. I. The Data

    NASA Astrophysics Data System (ADS)

    Way, M. J.; Quintana, H.; Infante, L.; Lambas, D. G.; Muriel, H.

    2005-11-01

    The Southern Abell Redshift Survey (SARS) contains 39 clusters of galaxies with redshifts in the range 0.021h (while avoiding the LMC and SMC), with |b|>40°. Cluster locations were chosen from the Abell and Abell-Corwin-Olowin catalogs, while galaxy positions were selected from the Automatic Plate Measuring Facility galaxy catalog with extinction-corrected magnitudes in the range 15<=bJ<19. SARS used the Las Campanas 2.5 m du Pont telescope, observing either 65 or 128 objects concurrently over a 1.5 deg2 field. New redshifts for 3440 galaxies are reported in the fields of these 39 clusters of galaxies.

  13. Abel's Theorem Simplifies Reduction of Order

    ERIC Educational Resources Information Center

    Green, William R.

    2011-01-01

    We give an alternative to the standard method of reduction or order, in which one uses one solution of a homogeneous, linear, second order differential equation to find a second, linearly independent solution. Our method, based on Abel's Theorem, is shorter, less complex and extends to higher order equations.

  14. The GenABEL Project for statistical genomics.

    PubMed

    Karssen, Lennart C; van Duijn, Cornelia M; Aulchenko, Yurii S

    2016-01-01

    Development of free/libre open source software is usually done by a community of people with an interest in the tool. For scientific software, however, this is less often the case. Most scientific software is written by only a few authors, often a student working on a thesis. Once the paper describing the tool has been published, the tool is no longer developed further and is left to its own device. Here we describe the broad, multidisciplinary community we formed around a set of tools for statistical genomics. The GenABEL project for statistical omics actively promotes open interdisciplinary development of statistical methodology and its implementation in efficient and user-friendly software under an open source licence. The software tools developed withing the project collectively make up the GenABEL suite, which currently consists of eleven tools. The open framework of the project actively encourages involvement of the community in all stages, from formulation of methodological ideas to application of software to specific data sets. A web forum is used to channel user questions and discussions, further promoting the use of the GenABEL suite. Developer discussions take place on a dedicated mailing list, and development is further supported by robust development practices including use of public version control, code review and continuous integration. Use of this open science model attracts contributions from users and developers outside the "core team", facilitating agile statistical omics methodology development and fast dissemination.

  15. The GenABEL Project for statistical genomics

    PubMed Central

    Karssen, Lennart C.; van Duijn, Cornelia M.; Aulchenko, Yurii S.

    2016-01-01

    Development of free/libre open source software is usually done by a community of people with an interest in the tool. For scientific software, however, this is less often the case. Most scientific software is written by only a few authors, often a student working on a thesis. Once the paper describing the tool has been published, the tool is no longer developed further and is left to its own device. Here we describe the broad, multidisciplinary community we formed around a set of tools for statistical genomics. The GenABEL project for statistical omics actively promotes open interdisciplinary development of statistical methodology and its implementation in efficient and user-friendly software under an open source licence. The software tools developed withing the project collectively make up the GenABEL suite, which currently consists of eleven tools. The open framework of the project actively encourages involvement of the community in all stages, from formulation of methodological ideas to application of software to specific data sets. A web forum is used to channel user questions and discussions, further promoting the use of the GenABEL suite. Developer discussions take place on a dedicated mailing list, and development is further supported by robust development practices including use of public version control, code review and continuous integration. Use of this open science model attracts contributions from users and developers outside the “core team”, facilitating agile statistical omics methodology development and fast dissemination. PMID:27347381

  16. A 1400-MHz survey of 1478 Abell clusters of galaxies

    NASA Technical Reports Server (NTRS)

    Owen, F. N.; White, R. A.; Hilldrup, K. C.; Hanisch, R. J.

    1982-01-01

    Observations of 1478 Abell clusters of galaxies with the NRAO 91-m telescope at 1400 MHz are reported. The measured beam shape was deconvolved from the measured source Gaussian fits in order to estimate the source size and position angle. All detected sources within 0.5 corrected Abell cluster radii are listed, including the cluster number, richness class, distance class, magnitude of the tenth brightest galaxy, redshift estimate, corrected cluster radius in arcmin, right ascension and error, declination and error, total flux density and error, and angular structure for each source.

  17. Tomographic inversion techniques incorporating physical constraints for line integrated spectroscopy in stellarators and tokamaks

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pablant, N. A.; Bell, R. E.; Bitter, M.

    2014-11-15

    Accurate tomographic inversion is important for diagnostic systems on stellarators and tokamaks which rely on measurements of line integrated emission spectra. A tomographic inversion technique based on spline optimization with enforcement of constraints is described that can produce unique and physically relevant inversions even in situations with noisy or incomplete input data. This inversion technique is routinely used in the analysis of data from the x-ray imaging crystal spectrometer (XICS) installed at the Large Helical Device. The XICS diagnostic records a 1D image of line integrated emission spectra from impurities in the plasma. Through the use of Doppler spectroscopy andmore » tomographic inversion, XICS can provide profile measurements of the local emissivity, temperature, and plasma flow. Tomographic inversion requires the assumption that these measured quantities are flux surface functions, and that a known plasma equilibrium reconstruction is available. In the case of low signal levels or partial spatial coverage of the plasma cross-section, standard inversion techniques utilizing matrix inversion and linear-regularization often cannot produce unique and physically relevant solutions. The addition of physical constraints, such as parameter ranges, derivative directions, and boundary conditions, allow for unique solutions to be reliably found. The constrained inversion technique described here utilizes a modified Levenberg-Marquardt optimization scheme, which introduces a condition avoidance mechanism by selective reduction of search directions. The constrained inversion technique also allows for the addition of more complicated parameter dependencies, for example, geometrical dependence of the emissivity due to asymmetries in the plasma density arising from fast rotation. The accuracy of this constrained inversion technique is discussed, with an emphasis on its applicability to systems with limited plasma coverage.« less

  18. Tomographic inversion techniques incorporating physical constraints for line integrated spectroscopy in stellarators and tokamaksa)

    DOE PAGES

    Pablant, N. A.; Bell, R. E.; Bitter, M.; ...

    2014-08-08

    Accurate tomographic inversion is important for diagnostic systems on stellarators and tokamaks which rely on measurements of line integrated emission spectra. A tomographic inversion technique based on spline optimization with enforcement of constraints is described that can produce unique and physically relevant inversions even in situations with noisy or incomplete input data. This inversion technique is routinely used in the analysis of data from the x-ray imaging crystal spectrometer (XICS) installed at LHD. The XICS diagnostic records a 1D image of line integrated emission spectra from impurities in the plasma. Through the use of Doppler spectroscopy and tomographic inversion, XICSmore » can provide pro file measurements of the local emissivity, temperature and plasma flow. Tomographic inversion requires the assumption that these measured quantities are flux surface functions, and that a known plasma equilibrium reconstruction is available. In the case of low signal levels or partial spatial coverage of the plasma cross-section, standard inversion techniques utilizing matrix inversion and linear-regularization often cannot produce unique and physically relevant solutions. The addition of physical constraints, such as parameter ranges, derivative directions, and boundary conditions, allow for unique solutions to be reliably found. The constrained inversion technique described here utilizes a modifi ed Levenberg-Marquardt optimization scheme, which introduces a condition avoidance mechanism by selective reduction of search directions. The constrained inversion technique also allows for the addition of more complicated parameter dependencies, for example geometrical dependence of the emissivity due to asymmetries in the plasma density arising from fast rotation. The accuracy of this constrained inversion technique is discussed, with an emphasis on its applicability to systems with limited plasma coverage.« less

  19. Magnetic resonance separation imaging using a divided inversion recovery technique (DIRT).

    PubMed

    Goldfarb, James W

    2010-04-01

    The divided inversion recovery technique is an MRI separation method based on tissue T(1) relaxation differences. When tissue T(1) relaxation times are longer than the time between inversion pulses in a segmented inversion recovery pulse sequence, longitudinal magnetization does not pass through the null point. Prior to additional inversion pulses, longitudinal magnetization may have an opposite polarity. Spatial displacement of tissues in inversion recovery balanced steady-state free-precession imaging has been shown to be due to this magnetization phase change resulting from incomplete magnetization recovery. In this paper, it is shown how this phase change can be used to provide image separation. A pulse sequence parameter, the time between inversion pulses (T180), can be adjusted to provide water-fat or fluid separation. Example water-fat and fluid separation images of the head, heart, and abdomen are presented. The water-fat separation performance was investigated by comparing image intensities in short-axis divided inversion recovery technique images of the heart. Fat, blood, and fluid signal was suppressed to the background noise level. Additionally, the separation performance was not affected by main magnetic field inhomogeneities.

  20. RADIO AND DEEP CHANDRA OBSERVATIONS OF THE DISTURBED COOL CORE CLUSTER ABELL 133

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Randall, S. W.; Nulsen, P. E. J.; Forman, W. R.

    2010-10-10

    We present results based on new Chandra and multi-frequency radio observations of the disturbed cool core cluster Abell 133. The diffuse gas has a complex bird-like morphology, with a plume of emission extending from two symmetric wing-like features. The plume is capped with a filamentary radio structure that has been previously classified as a radio relic. X-ray spectral fits in the region of the relic indicate the presence of either high-temperature gas or non-thermal emission, although the measured photon index is flatter than would be expected if the non-thermal emission is from inverse Compton scattering of the cosmic microwave backgroundmore » by the radio-emitting particles. We find evidence for a weak elliptical X-ray surface brightness edge surrounding the core, which we show is consistent with a sloshing cold front. The plume is consistent with having formed due to uplift by a buoyantly rising radio bubble, now seen as the radio relic, and has properties consistent with buoyantly lifted plumes seen in other systems (e.g., M87). Alternatively, the plume may be a gas sloshing spiral viewed edge-on. Results from spectral analysis of the wing-like features are inconsistent with the previous suggestion that the wings formed due to the passage of a weak shock through the cool core. We instead conclude that the wings are due to X-ray cavities formed by displacement of X-ray gas by the radio relic. The central cD galaxy contains two small-scale cold gas clumps that are slightly offset from their optical and UV counterparts, suggestive of a galaxy-galaxy merger event. On larger scales, there is evidence for cluster substructure in both optical observations and the X-ray temperature map. We suggest that the Abell 133 cluster has recently undergone a merger event with an interloping subgroup, initialing gas sloshing in the core. The torus of sloshed gas is seen close to edge-on, leading to the somewhat ragged appearance of the elliptical surface brightness edge

  1. Inversion technique for IR heterodyne sounding of stratospheric constituents from space platforms

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Shapiro, G. L.; Alvarez, J. M.

    1981-01-01

    The techniques which have been employed for inversion of IR heterodyne measurements for remote sounding of stratospheric trace constituents usually rely on either geometric effects based on limb-scan observations (i.e., onion peel techniques) or spectral effects by using weighting functions corresponding to different frequencies of an IR spectral line. An experimental approach and inversion technique are discussed which optimize the retrieval of concentration profiles by combining the geometric and the spectral effects in an IR heterodyne receiver. The results of inversions of some synthetic CIO spectral lines corresponding to solar occultation limb scans of the stratosphere are presented, indicating considerable improvement in the accuracy of the retrieved profiles. The effects of noise on the accuracy of retrievals are discussed for realistic situations.

  2. Inversion technique for IR heterodyne sounding of stratospheric constituents from space platforms.

    PubMed

    Abbas, M M; Shapiro, G L; Alvarez, J M

    1981-11-01

    The techniques which have been employed for inversion of IR heterodyne measurements for remote sounding of stratospheric trace constituents usually rely on either geometric effects based on limb-scan observations (i.e., onion peel techniques) or spectral effects by using weighting functions corresponding to different frequencies of an IR spectral line. An experimental approach and inversion technique are discussed which optimize the retrieval of concentration profiles by combining the geometric and the spectral effects in an IR heterodyne receiver. The results of inversions of some synthetic ClO spectral lines corresponding to solar occultation limb scans of the stratosphere are presented, indicating considerable improvement in the accuracy of the retrieved profiles. The effects of noise on the accuracy of retrievals are discussed for realistic situations.

  3. VizieR Online Data Catalog: Abell 315 spectroscopic dataset (Biviano+, 2017)

    NASA Astrophysics Data System (ADS)

    Biviano, A.; Popesso, P.; Dietrich, J. P.; Zhang, Y.-Y.; Erfanianfar, G.; Romaniello, M.; Sartoris, B.

    2017-03-01

    Abell 315 was observed at the European Southern Observatory (ESO) Very Large Telescope (VLT) with the VIsible MultiObject Spectrograph (VIMOS). The VIMOS data were acquired using 8 separate pointings, plus 2 additional pointings required to provide the needed redundancy within the central region and to cover the gaps between the VIMOS quadrants. Catalog of galaxies with redshifts in the region of the cluster Abell 315, with flags indicating whether these galaxies are members of the cluster, members of substructures within the cluster, and with probabilities for the cluster members to belong to the main cluster structure. (1 data file).

  4. A Geophysical Inversion Model Enhancement Technique Based on the Blind Deconvolution

    NASA Astrophysics Data System (ADS)

    Zuo, B.; Hu, X.; Li, H.

    2011-12-01

    A model-enhancement technique is proposed to enhance the geophysical inversion model edges and details without introducing any additional information. Firstly, the theoretic correctness of the proposed geophysical inversion model-enhancement technique is discussed. An inversion MRM (model resolution matrix) convolution approximating PSF (Point Spread Function) method is designed to demonstrate the correctness of the deconvolution model enhancement method. Then, a total-variation regularization blind deconvolution geophysical inversion model-enhancement algorithm is proposed. In previous research, Oldenburg et al. demonstrate the connection between the PSF and the geophysical inverse solution. Alumbaugh et al. propose that more information could be provided by the PSF if we return to the idea of it behaving as an averaging or low pass filter. We consider the PSF as a low pass filter to enhance the inversion model basis on the theory of the PSF convolution approximation. Both the 1D linear and the 2D magnetotelluric inversion examples are used to analyze the validity of the theory and the algorithm. To prove the proposed PSF convolution approximation theory, the 1D linear inversion problem is considered. It shows the ratio of convolution approximation error is only 0.15%. The 2D synthetic model enhancement experiment is presented. After the deconvolution enhancement, the edges of the conductive prism and the resistive host become sharper, and the enhancement result is closer to the actual model than the original inversion model according the numerical statistic analysis. Moreover, the artifacts in the inversion model are suppressed. The overall precision of model increases 75%. All of the experiments show that the structure details and the numerical precision of inversion model are significantly improved, especially in the anomalous region. The correlation coefficient between the enhanced inversion model and the actual model are shown in Fig. 1. The figure

  5. Flexion in Abell 2744

    NASA Astrophysics Data System (ADS)

    Bird, J. P.; Goldberg, D. M.

    2018-05-01

    We present the first flexion-focused gravitational lensing analysis of the Hubble Frontier Field observations of Abell 2744 (z = 0.308). We apply a modified Analytic Image Model technique to measure source galaxy flexion and shear values at a final number density of 82 arcmin-2. By using flexion data alone, we are able to identify the primary mass structure aligned along the heart of the cluster in addition to two major substructure peaks, including an NE component that corresponds to previous lensing work and a new peak detection offset 1.43 arcmin from the cluster core towards the east. We generate two types of non-parametric reconstructions: flexion aperture mass maps, which identify central core, E, and NE substructure peaks with mass signal-to-noise contours peaking at 3.5σ, 2.7σ, and 2.3σ, respectively; and convergence maps derived directly from the smoothed flexion field. For the primary peak, we find a mass of (1.62 ± 0.12) × 1014 h-1 M⊙ within a 33 arcsec (105 h-1 kpc) aperture, a mass of (2.92 ± 0.26) × 1013 h-1 M⊙ within a 16 arcsec (50 h-1 kpc) aperture for the north-eastern substructure, and (8.81 ± 0.52) × 1013 h-1 M⊙ within a 25 arcsec (80 h-1 kpc) aperture for the novel eastern substructure.

  6. Spectral line inversion for sounding of stratospheric minor constituents by infrared heterodyne technique from balloon altitudes

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Shapiro, G. L.; Allario, F.; Alvarez, J. M.

    1981-01-01

    A combination of two different techniques for the inversion of infrared laser heterodyne measurements of tenuous gases in the stratosphere by solar occulation is presented which incorporates the advantages of each technique. An experimental approach and inversion technique are developed which optimize the retrieval of concentration profiles by incorporating the onion peel collection scheme into the spectral inversion technique. A description of an infrared heterodyne spectrometer and the mode of observations for solar occulation measurement is presented, and the results of inversions of some synthetic ClO spectral lines corresponding to solar occulation limb-scans of the stratosphere are examined. A comparison between the new techniques and one of the current techniques indicates that considerable improvement in the accuracy of the retrieved profiles can be achieved. It is found that noise affects the accuracy of both techniques but not in a straightforward manner since there is interaction between the noise level, noise propagation through inversion, and the number of scans leading to an optimum retrieval.

  7. Study of the technique of stellar occultation

    NASA Technical Reports Server (NTRS)

    Hays, P. B.; Graves, M. E.; Roble, R. G.; Shah, A. N.

    1973-01-01

    The results are reported of a study of the stellar occultation technique for measuring the composition of the atmosphere. The intensity of starlight was monitored during the occultation using the Wisconsin stellar ultraviolet photometers aboard the Orbiting Astronomical Observatory (OAO-A2). A schematic diagram of an occultation is shown where the change in intensity at a given wavelength is illustrated. The vertical projection of the attenuation region is typically 60 km deep for molecular oxygen and 30 km deep for ozone. Intensity profiles obtained during various occultations were analyzed by first determining the tangential columm density of the absorbing gases, and then Abel inverting the column densities to obtain the number density profile. Errors are associated with each step in the inversion scheme and have been considered as an integral part of this study.

  8. U(1)-invariant membranes: The geometric formulation, Abel, and pendulum differential equations

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zheltukhin, A. A.; Fysikum, AlbaNova, Stockholm University, 106 91 Stockholm; NORDITA, Roslagstullsbacken 23, 106 91 Stockholm

    The geometric approach to study the dynamics of U(1)-invariant membranes is developed. The approach reveals an important role of the Abel nonlinear differential equation of the first type with variable coefficients depending on time and one of the membrane extendedness parameters. The general solution of the Abel equation is constructed. Exact solutions of the whole system of membrane equations in the D=5 Minkowski space-time are found and classified. It is shown that if the radial component of the membrane world vector is only time dependent, then the dynamics is described by the pendulum equation.

  9. Galaxy Cluster Abell 1689

    NASA Image and Video Library

    2017-12-08

    Release Date: March 10, 2010 - Distant galaxy clusters mysteriously stream at a million miles per hour along a path roughly centered on the southern constellations Centaurus and Hydra. A new study led by Alexander Kashlinsky at NASA's Goddard Space Flight Center in Greenbelt, Md., tracks this collective motion -- dubbed the "dark flow" -- to twice the distance originally reported, out to more than 2.5 billion light-years. Abell 1689, redshift 0.181. Credit: NASA/Goddard Space Flight Center/Scientific Visualization Studio/ESA/L. Bradley/JHU To learn more go to: www.nasa.gov/centers/goddard/news/releases/2010/10-023.html To see other visualizations related to this story go to: svs.gsfc.nasa.gov/goto?10580

  10. Non-thermal pressure in the outskirts of Abell 2142

    NASA Astrophysics Data System (ADS)

    Fusco-Femiano, Roberto; Lapi, Andrea

    2018-03-01

    Clumping and turbulence are expected to affect the matter accreted on to the outskirts of galaxy clusters. To determine their impact on the thermodynamic properties of Abell 2142, we perform an analysis of the X-ray temperature data from XMM-Newton via our SuperModel, a state-of-the-art tool for investigating the astrophysics of the intracluster medium already tested on many individual clusters (since Cavaliere, Lapi & Fusco-Femiano 2009). Using the gas density profile corrected for clumpiness derived by Tchernin et al. (2016), we find evidence for the presence of a non-thermal pressure component required to sustain gravity in the cluster outskirts of Abell 2142, that amounts to about 30 per cent of the total pressure at the virial radius. The presence of the non-thermal component implies the gas fraction to be consistent with the universal value at the virial radius and the electron thermal pressure profile to be in good agreement with that inferred from the SZ data. Our results indicate that the presence of gas clumping and of a non-thermal pressure component are both necessary to recover the observed physical properties in the cluster outskirts. Moreover, we stress that an alternative method often exploited in the literature (included Abell 2142) to determine the temperature profile kBT = Pe/ne basing on a combination of the Sunyaev-Zel'dovich (SZ) pressure Pe and of the X-ray electron density ne does not allow us to highlight the presence of non-thermal pressure support in the cluster outskirts.

  11. Abyssal BEnthic Laboratory (ABEL): a novel approach for long-term investigation at abyssal depths

    NASA Astrophysics Data System (ADS)

    Berta, M.; Gasparoni, F.; Capobianco, M.

    1995-03-01

    This study assesses the feasibility of a configuration for a benthic underwater system, called ABEL (Abyssal BEnthic Laboratory), capable of operating both under controlled and autonomous modes for periods of several months to over one year at abyssal depths up to 6000 m. A network of stations, capable of different configurations, has been identified as satisfying the widest range of scientific expectations, and at the same time to address the technological challenge to increase the feasibility of scientific investigations, even when the need is not yet well specified. The overall system consists of a central Benthic Investigation Laboratory, devoted to the execution of the most complex scientific activities, with fixed Satellite Stations acting as nodes of a measuring network and a Mobile Station extending ABEL capabilities with the possibility to carry out surveys over the investigation area and interventions on the fixed stations. ABEL architecture also includes a dedicated deployment and recovery module, as well as sea-surface and land-based facilities. Such an installation constitutes the sea-floor equivalent of a meteorological or geophysical laboratory. Attention has been paid to selecting investigation tools supporting the ABEL system to carry out its mission with high operativity and minimal risk and environmental impact. This demands technologies to enable presence and operation at abyssal depths for the required period of time. Presence can be guaranteed by proper choice of power supply and communication systems. Operations require visual and manipulative capabilities, as well as deployment and retrieval capabilities. Advanced control system architectures must be considered, along with knowledge based approaches, to comply with the requirements for autonomous control. The results of this investigation demonstrate the feasibility of the ABEL concept and the pre-dimensioning of its main components.

  12. Comparison of weighting techniques for acoustic full waveform inversion

    NASA Astrophysics Data System (ADS)

    Jeong, Gangwon; Hwang, Jongha; Min, Dong-Joo

    2017-12-01

    To reconstruct long-wavelength structures in full waveform inversion (FWI), the wavefield-damping and weighting techniques have been used to synthesize and emphasize low-frequency data components in frequency-domain FWI. However, these methods have some weak points. The application of wavefield-damping method on filtered data fails to synthesize reliable low-frequency data; the optimization formula obtained introducing the weighting technique is not theoretically complete, because it is not directly derived from the objective function. In this study, we address these weak points and present how to overcome them. We demonstrate that the source estimation in FWI using damped wavefields fails when the data used in the FWI process does not satisfy the causality condition. This phenomenon occurs when a non-causal filter is applied to data. We overcome this limitation by designing a causal filter. Also we modify the conventional weighting technique so that its optimization formula is directly derived from the objective function, retaining its original characteristic of emphasizing the low-frequency data components. Numerical results show that the newly designed causal filter enables to recover long-wavelength structures using low-frequency data components synthesized by damping wavefields in frequency-domain FWI, and the proposed weighting technique enhances the inversion results.

  13. X-ray emission from a complete sample of Abell clusters of galaxies

    NASA Astrophysics Data System (ADS)

    Briel, Ulrich G.; Henry, J. Patrick

    1993-11-01

    The ROSAT All-Sky Survey (RASS) is used to investigate the X-ray properties of a complete sample of Abell clusters with measured redshifts and accurate positions. The sample comprises the 145 clusters within a 561 square degree region at high galactic latitude. The mean redshift is 0.17. This sample is especially well suited to be studied within the RASS since the mean exposure time is higher than average and the mean galactic column density is very low. These together produce a flux limit of about 4.2 x 10-13 erg/sq cm/s in the 0.5 to 2.5 keV energy band. Sixty-six (46%) individual clusters are detected at a significance level higher than 99.7% of which 7 could be chance coincidences of background or foreground sources. At redshifts greater than 0.3 six clusters out of seven (86%) are detected at the same significance level. The detected objects show a clear X-ray luminosity -- galaxy count relation with a dispersion consistent with other external estimates of the error in the counts. By analyzing the excess of positive fluctuations of the X-ray flux at the cluster positions, compared with the fluctuations of randomly drawn background fields, it is possible to extend these results below the nominal flux limit. We find 80% of richness R greater than or = 0 and 86% of R greater than or = 1 clusters are X-ray emitters with fluxes above 1 x 10-13 erg/sq cm/s. Nearly 90% of the clusters meeting the requirements to be in Abell's statistical sample emit above the same level. We therefore conclude that almost all Abell clusters are real clusters and the Abell catalog is not strongly contaminated by projection effects. We use the Kaplan-Meier product limit estimator to calculate the cumulative X-ray luminosity function. We show that the shape of the luminosity functions are similiar for different richness classes, but the characteristic luminosities of richness 2 clusters are about twice those of richness 1 clusters which are in turn about twice those of richness 0

  14. PredictABEL: an R package for the assessment of risk prediction models.

    PubMed

    Kundu, Suman; Aulchenko, Yurii S; van Duijn, Cornelia M; Janssens, A Cecile J W

    2011-04-01

    The rapid identification of genetic markers for multifactorial diseases from genome-wide association studies is fuelling interest in investigating the predictive ability and health care utility of genetic risk models. Various measures are available for the assessment of risk prediction models, each addressing a different aspect of performance and utility. We developed PredictABEL, a package in R that covers descriptive tables, measures and figures that are used in the analysis of risk prediction studies such as measures of model fit, predictive ability and clinical utility, and risk distributions, calibration plot and the receiver operating characteristic plot. Tables and figures are saved as separate files in a user-specified format, which include publication-quality EPS and TIFF formats. All figures are available in a ready-made layout, but they can be customized to the preferences of the user. The package has been developed for the analysis of genetic risk prediction studies, but can also be used for studies that only include non-genetic risk factors. PredictABEL is freely available at the websites of GenABEL ( http://www.genabel.org ) and CRAN ( http://cran.r-project.org/).

  15. Abell 48 - a rare WN-type central star of a planetary nebula

    NASA Astrophysics Data System (ADS)

    Todt, H.; Kniazev, A. Y.; Gvaramadze, V. V.; Hamann, W.-R.; Buckley, D.; Crause, L.; Crawford, S. M.; Gulbis, A. A. S.; Hettlage, C.; Hooper, E.; Husser, T.-O.; Kotze, P.; Loaring, N.; Nordsieck, K. H.; O'Donoghue, D.; Pickering, T.; Potter, S.; Romero-Colmenero, E.; Vaisanen, P.; Williams, T.; Wolf, M.

    2013-04-01

    A considerable fraction of the central stars of planetary nebulae (CSPNe) are hydrogen-deficient. Almost all of these H-deficient central stars (CSs) display spectra with strong carbon and helium lines. Most of them exhibit emission-line spectra resembling those of massive WC stars. Therefore these stars are classed as CSPNe of spectral type [WC]. Recently, quantitative spectral analysis of two emission-line CSs, PB 8 and IC 4663, revealed that these stars do not belong to the [WC] class. Instead PB 8 has been classified as [WN/WC] type and IC 4663 as [WN] type. In this work we report the spectroscopic identification of another rare [WN] star, the CS of Abell 48. We performed a spectral analysis of Abell 48 with the Potsdam Wolf-Rayet (PoWR) models for expanding atmospheres. We find that the expanding atmosphere of Abell 48 is mainly composed of helium (85 per cent by mass), hydrogen (10 per cent) and nitrogen (5 per cent). The residual hydrogen and the enhanced nitrogen abundance make this object different from the other [WN] star IC 4663. We discuss the possible origin of this atmospheric composition.

  16. Evidence for an extensive intracluster medium from radio observations of distant Abell clusters

    NASA Technical Reports Server (NTRS)

    Hanisch, R. J.; Ulmer, M. P.

    1985-01-01

    Observations have been made of 18 distance class 5 and 6 Abell clusters of galaxies using the VLA in its 'C' configuration at a frequency of 1460 MHz. Half of the clusters in the sample are confirmed or probable sources of X-ray emission. All the detected radio sources with flux densities above 10 mJy are reported, and information is provided concerning the angular extent of the sources, as well as the most likely optical identification. The existence of an extensive intracluster medium is inferred by identifying extended/distorted radio sources with galaxies whose apparent magnitudes are consistent with their being cluster members and that are at projected distances of 3-4 Abell radii (6-8 Mpc) from the nearest cluster center. By requiring that the radio sources are confined by the ambient medium, the ambient density is calculated and the total cluster mass is estimated. As a sample calculation, a wide-angle-tail radio source some 5 Mpc from the center of Abell 348 is used to estimate these quantities.

  17. High-Performance Mixed Models Based Genome-Wide Association Analysis with omicABEL software

    PubMed Central

    Fabregat-Traver, Diego; Sharapov, Sodbo Zh.; Hayward, Caroline; Rudan, Igor; Campbell, Harry; Aulchenko, Yurii; Bientinesi, Paolo

    2014-01-01

    To raise the power of genome-wide association studies (GWAS) and avoid false-positive results in structured populations, one can rely on mixed model based tests. When large samples are used, and when multiple traits are to be studied in the ’omics’ context, this approach becomes computationally challenging. Here we consider the problem of mixed-model based GWAS for arbitrary number of traits, and demonstrate that for the analysis of single-trait and multiple-trait scenarios different computational algorithms are optimal. We implement these optimal algorithms in a high-performance computing framework that uses state-of-the-art linear algebra kernels, incorporates optimizations, and avoids redundant computations, increasing throughput while reducing memory usage and energy consumption. We show that, compared to existing libraries, our algorithms and software achieve considerable speed-ups. The OmicABEL software described in this manuscript is available under the GNU GPL v. 3 license as part of the GenABEL project for statistical genomics at http: //www.genabel.org/packages/OmicABEL. PMID:25717363

  18. High-Performance Mixed Models Based Genome-Wide Association Analysis with omicABEL software.

    PubMed

    Fabregat-Traver, Diego; Sharapov, Sodbo Zh; Hayward, Caroline; Rudan, Igor; Campbell, Harry; Aulchenko, Yurii; Bientinesi, Paolo

    2014-01-01

    To raise the power of genome-wide association studies (GWAS) and avoid false-positive results in structured populations, one can rely on mixed model based tests. When large samples are used, and when multiple traits are to be studied in the 'omics' context, this approach becomes computationally challenging. Here we consider the problem of mixed-model based GWAS for arbitrary number of traits, and demonstrate that for the analysis of single-trait and multiple-trait scenarios different computational algorithms are optimal. We implement these optimal algorithms in a high-performance computing framework that uses state-of-the-art linear algebra kernels, incorporates optimizations, and avoids redundant computations, increasing throughput while reducing memory usage and energy consumption. We show that, compared to existing libraries, our algorithms and software achieve considerable speed-ups. The OmicABEL software described in this manuscript is available under the GNU GPL v. 3 license as part of the GenABEL project for statistical genomics at http: //www.genabel.org/packages/OmicABEL.

  19. The application of the least squares finite element method to Abel's integral equation. [with application to glow discharge problem

    NASA Technical Reports Server (NTRS)

    Balasubramanian, R.; Norrie, D. H.; De Vries, G.

    1979-01-01

    Abel's integral equation is the governing equation for certain problems in physics and engineering, such as radiation from distributed sources. The finite element method for the solution of this non-linear equation is presented for problems with cylindrical symmetry and the extension to more general integral equations is indicated. The technique was applied to an axisymmetric glow discharge problem and the results show excellent agreement with previously obtained solutions

  20. Wavelength Modulation Spectroscopy for Temperature and Species Concentration in the Plume of a Supersonic Nozzle (Conference Paper with Briefing Charts)

    DTIC Science & Technology

    2017-07-12

    Aλ(y)) from Figure 5 to be converted into integrated absorbance as a function of radius (A’λ(r)), by the use of an inverse Abel transform (Equation...harsh environments,” Appl. Opt., vol. 48, no. 29, p. 5546, Oct. 2009. (8) Figure 8: Radial temperature distribution from inverse Abel transform...Results – Data processing – Absorbance area – Temperature measurements o Path averaged o Abel inversion – Species Concentration 5) Conclusions and

  1. Comparison of four stable numerical methods for Abel's integral equation

    NASA Technical Reports Server (NTRS)

    Murio, Diego A.; Mejia, Carlos E.

    1991-01-01

    The 3-D image reconstruction from cone-beam projections in computerized tomography leads naturally, in the case of radial symmetry, to the study of Abel-type integral equations. If the experimental information is obtained from measured data, on a discrete set of points, special methods are needed in order to restore continuity with respect to the data. A new combined Regularized-Adjoint-Conjugate Gradient algorithm, together with two different implementations of the Mollification Method (one based on a data filtering technique and the other on the mollification of the kernal function) and a regularization by truncation method (initially proposed for 2-D ray sample schemes and more recently extended to 3-D cone-beam image reconstruction) are extensively tested and compared for accuracy and numerical stability as functions of the level of noise in the data.

  2. Abell 1763: A Giant Gas Sloshing Spiral But No Cool Core

    NASA Astrophysics Data System (ADS)

    Douglass, Edmund

    2017-09-01

    We propose a 76 ksec observation of the z=0.23 galaxy cluster Abell 1763. Previous Chandra data reveals the system as host to a large 950 kpc gas sloshing spiral. Atypical of spiral-hosting clusters, an intact cool core is not detected. Its absence suggests the interaction has led to significant disruption since the onset of core sloshing. The primary cluster is accompanied by two X-ray emitting subsystems. Given the orientation of the spiral, both systems are strong candidates for being the perturber responsible for its formation. Abell 1763 provides us with the rare opportunity to examine an infall event (primary + perturber) resulting in sloshing to the point of core disintegration. Detailed analysis will be performed on the disrupted core, the spiral, and the perturber candidates.

  3. Retrieval Performance and Indexing Differences in ABELL and MLAIB

    ERIC Educational Resources Information Center

    Graziano, Vince

    2012-01-01

    Searches for 117 British authors are compared in the Annual Bibliography of English Language and Literature (ABELL) and the Modern Language Association International Bibliography (MLAIB). Authors are organized by period and genre within the early modern era. The number of records for each author was subdivided by format, language of publication,…

  4. The cluster Abell 780: an optical view

    NASA Astrophysics Data System (ADS)

    Durret, F.; Slezak, E.; Adami, C.

    2009-11-01

    Context: The Abell 780 cluster, better known as the Hydra A cluster, has been thouroughly analyzed in X-rays. However, little is known about its optical properties. Aims: We propose to derive the galaxy luminosity function (GLF) in this apparently relaxed cluster and to search for possible environmental effects by comparing the GLFs in various regions and by looking at the galaxy distribution at large scale around Abell 780. Methods: Our study is based on optical images obtained with the ESO 2.2m telescope and WFI camera in the B and R bands, covering a total region of 67.22 × 32.94 arcmin^2, or 4.235 × 2.075 Mpc2 for a cluster redshift of 0.0539. Results: In a region of 500 kpc radius around the cluster center, the GLF in the R band shows a double structure, with a broad and flat bright part and a flat faint end that can be fit by a power law with an index α ~ - 0.85 ± 0.12 in the 20.25 ≤ R ≤ 21.75 interval. If we divide this 500 kpc radius region in north+south or east+west halves, we find no clear difference between the GLFs in these smaller regions. No obvious large-scale structure is apparent within 5 Mpc from the cluster, based on galaxy redshifts and magnitudes collected from the NED database in a much larger region than that covered by our data, suggesting that there is no major infall of material in any preferential direction. However, the Serna-Gerbal method reveals a gravitationally bound structure of 27 galaxies, which includes the cD, and of a more strongly gravitationally bound structure of 14 galaxies. Conclusions: These optical results agree with the overall relaxed structure of Abell 780 previously derived from X-ray analyses. Based on observations obtained at the European Southern Observatory, program ESO 68.A-0084(A), P. I. E. Slezak. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics

  5. Deep Chandra Observations of Abell 586: A Remarkably Relaxed Non-Cool-Core Cluster

    NASA Astrophysics Data System (ADS)

    Richstein, Hannah; Su, Yuanyuan

    2018-01-01

    The dichotomy between cool-core and non-cool-core clusters has been a lasting perplexity in extragalactic astronomy. Nascent cores in non-cool-core clusters may have been disrupted by major mergers, yet the dichotomy cannot be reproduced in cosmology simulations. We present deep Chandra observations of the massive galaxy cluster Abell 586, which resides at z=0.17, thus allowing its gas properties to be measured out to its virial radius. Abell 586 appears remarkably relaxed with a nearly spherical X-ray surface brightness distribution and without any offset between its X-ray and optical centroids. We measure that its temperature profile does not decrease towards the cluster center and its central entropy stays above 100 keV cm2. A non-cool-core emerges in Abell 586 in the absence of any disruptions on the large scale. Our study demonstrates that non-cool-core clusters can be formed without major mergers. The origins of some non-cool-core clusters may be related to conduction, AGN feedback, or preheating.The SAO REU program is funded by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant AST-1659473, and by the Smithsonian Institution.

  6. Resolution of the apparent discrepancy between the number of massive subhaloes in Abell 2744 and ΛCDM

    NASA Astrophysics Data System (ADS)

    Mao, Tian-Xiang; Wang, Jie; Frenk, Carlos S.; Gao, Liang; Li, Ran; Wang, Qiao; Cao, Xiaoyue; Li, Ming

    2018-07-01

    Schwinn et al. have recently compared the abundance and distribution of massive substructures identified in a gravitational lensing analysis of Abell 2744 by Jauzac et al. and N-body simulation, and found no cluster in Lambda cold dark matter (ΛCDM) simulation that is similar to Abell 2744. Schwinn et al. identified the measured projected aperture masses with the actual masses associated with subhaloes in the Millenium XXL N-body simulation. We have used the high-resolution Phoenix cluster simulations to show that such an identification is incorrect: the aperture mass is dominated by mass in the body of the cluster that happens to be projected along the line of sight to the subhalo. This enhancement varies from factors of a few to factors of more than 100, particularly for subhaloes projected near the centre of the cluster. We calculate aperture masses for subhaloes in our simulation and compare them to the measurements for Abell 2744. We find that the data for Abell 2744 are in excellent agreement with the matched predictions from ΛCDM. We provide further predictions for aperture mass functions of subhaloes in idealized surveys with varying mass detection thresholds.

  7. VizieR Online Data Catalog: Halpha measurements in Abell 2465 (Wegner+, 2015)

    NASA Astrophysics Data System (ADS)

    Wegner, G. A.; Chu, D. S.; Hwang, H. S.

    2015-07-01

    The wavelength of the Hα line at the redshift of Abell 2465 is near 817nm in a clear spectral region between the many telluric emission lines. A custom narrow-band filter for observing Hα was obtained from the Andover Corp. It has a peak transmission at 817.7nm (m817) and a full width at half-maximum (FWHM) of 8.77nm. The wide filter was a Gunn i (ig) filter with nearly the same central wavelength of 820nm and a FWHM of 185nm, and was manufactured by Custom Scientific. Hα observations of Abell 2465 were obtained 2012 September 19-23 using the 2.4m Hiltner telescope at the MDM Observatory on Kitt Peak. The 'Nellie' CCD was used. (1 data file).

  8. Topology in two dimensions. II - The Abell and ACO cluster catalogues

    NASA Astrophysics Data System (ADS)

    Plionis, Manolis; Valdarnini, Riccardo; Coles, Peter

    1992-09-01

    We apply a method for quantifying the topology of projected galaxy clustering to the Abell and ACO catalogues of rich clusters. We use numerical simulations to quantify the statistical bias involved in using high peaks to define the large-scale structure, and we use the results obtained to correct our observational determinations for this known selection effect and also for possible errors introduced by boundary effects. We find that the Abell cluster sample is consistent with clusters being identified with high peaks of a Gaussian random field, but that the ACO shows a slight meatball shift away from the Gaussian behavior over and above that expected purely from the high-peak selection. The most conservative explanation of this effect is that it is caused by some artefact of the procedure used to select the clusters in the two samples.

  9. Hierarchical Velocity Structure in the Core of Abell 2597

    NASA Technical Reports Server (NTRS)

    Still, Martin; Mushotzky, Richard

    2004-01-01

    We present XMM-Newton RGS and EPIC data of the putative cooling flow cluster Abell 2597. Velocities of the low-ionization emission lines in the spectrum are blue shifted with respect to the high-ionization lines by 1320 (sup +660) (sub -210) kilometers per second, which is consistent with the difference in the two peaks of the galaxy velocity distribution and may be the signature of bulk turbulence, infall, rotation or damped oscillation in the cluster. A hierarchical velocity structure such as this could be the direct result of galaxy mergers in the cluster core, or the injection of power into the cluster gas from a central engine. The uniform X-ray morphology of the cluster, the absence of fine scale temperature structure and the random distribution of the the galaxy positions, independent of velocity, suggests that our line of sight is close to the direction of motion. These results have strong implications for cooling flow models of the cluster Abell 2597. They give impetus to those models which account for the observed temperature structure of some clusters using mergers instead of cooling flows.

  10. Anti-Brownian ELectrokinetic (ABEL) Trapping of Single High Density Lipoprotein (HDL) Particles

    NASA Astrophysics Data System (ADS)

    Bockenhauer, Samuel; Furstenberg, Alexandre; Wang, Quan; Devree, Brian; Jie Yao, Xiao; Bokoch, Michael; Kobilka, Brian; Sunahara, Roger; Moerner, W. E.

    2010-03-01

    The ABEL trap is a novel device for trapping single biomolecules in solution for extended observation. The trap estimates the position of a fluorescently-labeled object as small as ˜10 nm in solution and then applies a feedback electrokinetic drift every 20 us to trap the object by canceling its Brownian motion. We use the ABEL trap to study HDL particles at the single-copy level. HDL particles, essential in regulation of ``good'' cholesterol in humans, comprise a small (˜10 nm) lipid bilayer disc bounded by a belt of apolipoproteins. By engineering HDL particles with single fluorescent donor/acceptor probes and varying lipid compositions, we are working to study lipid diffusion on small length scales. We also use HDL particles as hosts for single transmembrane receptors, which should enable study of receptor conformational dynamics on long timescales.

  11. Three-Dimensional Inverse Transport Solver Based on Compressive Sensing Technique

    NASA Astrophysics Data System (ADS)

    Cheng, Yuxiong; Wu, Hongchun; Cao, Liangzhi; Zheng, Youqi

    2013-09-01

    According to the direct exposure measurements from flash radiographic image, a compressive sensing-based method for three-dimensional inverse transport problem is presented. The linear absorption coefficients and interface locations of objects are reconstructed directly at the same time. It is always very expensive to obtain enough measurements. With limited measurements, compressive sensing sparse reconstruction technique orthogonal matching pursuit is applied to obtain the sparse coefficients by solving an optimization problem. A three-dimensional inverse transport solver is developed based on a compressive sensing-based technique. There are three features in this solver: (1) AutoCAD is employed as a geometry preprocessor due to its powerful capacity in graphic. (2) The forward projection matrix rather than Gauss matrix is constructed by the visualization tool generator. (3) Fourier transform and Daubechies wavelet transform are adopted to convert an underdetermined system to a well-posed system in the algorithm. Simulations are performed and numerical results in pseudo-sine absorption problem, two-cube problem and two-cylinder problem when using compressive sensing-based solver agree well with the reference value.

  12. Generalized Uncertainty Quantification for Linear Inverse Problems in X-ray Imaging

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fowler, Michael James

    2014-04-25

    In industrial and engineering applications, X-ray radiography has attained wide use as a data collection protocol for the assessment of material properties in cases where direct observation is not possible. The direct measurement of nuclear materials, particularly when they are under explosive or implosive loading, is not feasible, and radiography can serve as a useful tool for obtaining indirect measurements. In such experiments, high energy X-rays are pulsed through a scene containing material of interest, and a detector records a radiograph by measuring the radiation that is not attenuated in the scene. One approach to the analysis of these radiographsmore » is to model the imaging system as an operator that acts upon the object being imaged to produce a radiograph. In this model, the goal is to solve an inverse problem to reconstruct the values of interest in the object, which are typically material properties such as density or areal density. The primary objective in this work is to provide quantitative solutions with uncertainty estimates for three separate applications in X-ray radiography: deconvolution, Abel inversion, and radiation spot shape reconstruction. For each problem, we introduce a new hierarchical Bayesian model for determining a posterior distribution on the unknowns and develop efficient Markov chain Monte Carlo (MCMC) methods for sampling from the posterior. A Poisson likelihood, based on a noise model for photon counts at the detector, is combined with a prior tailored to each application: an edge-localizing prior for deconvolution; a smoothing prior with non-negativity constraints for spot reconstruction; and a full covariance sampling prior based on a Wishart hyperprior for Abel inversion. After developing our methods in a general setting, we demonstrate each model on both synthetically generated datasets, including those from a well known radiation transport code, and real high energy radiographs taken at two U. S. Department of Energy

  13. Review of inversion techniques using analysis of different tests

    NASA Astrophysics Data System (ADS)

    Smaglichenko, T. A.

    2012-04-01

    Tomographic techniques are tools, which estimate the Earth's deep interior by inverting seismic data. Reliability of visualization provides adequate understanding of geodynamic processes for prediction of natural hazard and protection of environment. This presentation focuses on two interrelated factors, which affect on the reliability namely: particularities of geophysical medium and strategy for choice of inversion method. Three main techniques are under review. First, the standard LSQR algorithm is derived directly by the Lanczos algebraic application. The Double Difference tomography widely incorporates this algorithm and its expansion. Next, the CSSA technique, or method of subtraction has been introduced into seismology by Nikolaev et al. in 1985. This method got farther development in 2003 (Smaglichenko et al.) as the coordinate method of possible directions, which has been already known in the theory of numerical methods. And finally, the new Differentiated Approach (DA) tomography that has been recently developed by the author for seismology and introduced into applied mathematics as the modification of Gaussian elimination. Different test models are presented by detecting various properties of the medium and having a value for the mining sector as well for prediction of seismic activity. They are: 1) checker-board resolution test; 2) the single anomalous block surrounded by an uniform zone; 3) the large-size structure; 4) the most complicated case, when the model consist of contrast layers and the observation response is equal zero value. The geometry of experiment for all models is given in the note of Leveque et al., 1993. It was assumed that errors in experimental data are in limits of pre-assigned accuracy. The testing showed that LSQR is effective, when the small-size structure (1) is retrieved, while CSSA works faster under reconstruction of the separated anomaly (2). The large-size structure (3) can be reconstructed applying DA, which uses both

  14. Reconstructing source terms from atmospheric concentration measurements: Optimality analysis of an inversion technique

    NASA Astrophysics Data System (ADS)

    Turbelin, Grégory; Singh, Sarvesh Kumar; Issartel, Jean-Pierre

    2014-12-01

    In the event of an accidental or intentional contaminant release in the atmosphere, it is imperative, for managing emergency response, to diagnose the release parameters of the source from measured data. Reconstruction of the source information exploiting measured data is called an inverse problem. To solve such a problem, several techniques are currently being developed. The first part of this paper provides a detailed description of one of them, known as the renormalization method. This technique, proposed by Issartel (2005), has been derived using an approach different from that of standard inversion methods and gives a linear solution to the continuous Source Term Estimation (STE) problem. In the second part of this paper, the discrete counterpart of this method is presented. By using matrix notation, common in data assimilation and suitable for numerical computing, it is shown that the discrete renormalized solution belongs to a family of well-known inverse solutions (minimum weighted norm solutions), which can be computed by using the concept of generalized inverse operator. It is shown that, when the weight matrix satisfies the renormalization condition, this operator satisfies the criteria used in geophysics to define good inverses. Notably, by means of the Model Resolution Matrix (MRM) formalism, we demonstrate that the renormalized solution fulfils optimal properties for the localization of single point sources. Throughout the article, the main concepts are illustrated with data from a wind tunnel experiment conducted at the Environmental Flow Research Centre at the University of Surrey, UK.

  15. Suzaku observations of the outskirts of the galaxy cluster Abell 3395, including a filament toward Abell 3391

    NASA Astrophysics Data System (ADS)

    Sugawara, Yuuki; Takizawa, Motokazu; Itahana, Madoka; Akamatsu, Hiroki; Fujita, Yutaka; Ohashi, Takaya; Ishisaki, Yoshitaka

    2017-12-01

    The results of Suzaku observations of the outskirts of Abell 3395, including a large-scale structure filament toward Abell 3391, are presented. We measured temperature and abundance distributions from the southern outskirt of A 3395 to the north at the virial radius, where a filament structure has been found in the former X-ray and Sunyaev-Zel'dovich (SZ) effect observations between A 3391 and A 3395. The overall temperature structure is consistent with the universal profile proposed by Okabe, N., et al. 2014, PASJ, 66, 99 for relaxed clusters, except for the filament region. A hint of intracluster medium heating is found between the two clusters, which might be due to their interaction in the early phase of a cluster merger. Although we obtained a relatively low metal abundance of Z=0.169^{+0.164+0.009+0.018}_{-0.150-0.004-0.015} solar, where the first, second, and third errors are statistical, cosmic X-ray background systematic, and non-X-ray background systematic, respectively, at the virial radius in the filament, our results are still consistent with previous results for other clusters (Z ˜ 0.3 solar) within errors. Therefore, our results are also consistent with the early enrichment scenario. We estimated Compton y parameters only from X-ray results in the region between A 3391 and A 3395 assuming a simple geometry. They are smaller than the previous SZ results with the Planck satellite. The difference could be attributed to a more elaborate geometry such as a filament inclined to the line-of-sight direction, or underestimation of the X-ray temperature because of the unresolved multi-temperature structures or undetected hot X-ray emission of the shock-heated gas.

  16. A Modified Normalization Technique for Frequency-Domain Full Waveform Inversion

    NASA Astrophysics Data System (ADS)

    Hwang, J.; Jeong, G.; Min, D. J.; KIM, S.; Heo, J. Y.

    2016-12-01

    Full waveform inversion (FWI) is a technique to estimate subsurface material properties minimizing the misfit function built with residuals between field and modeled data. To achieve computational efficiency, FWI has been performed in the frequency domain by carrying out modeling in the frequency domain, whereas observed data (time-series data) are Fourier-transformed.One of the main drawbacks of seismic FWI is that it easily gets stuck in local minima because of lacking of low-frequency data. To compensate for this limitation, damped wavefields are used, as in the Laplace-domain waveform inversion. Using damped wavefield in FWI plays a role in generating low-frequency components and help recover long-wavelength structures. With these newly generated low-frequency components, we propose a modified frequency-normalization technique, which has an effect of boosting contribution of low-frequency components to model parameter update.In this study, we introduce the modified frequency-normalization technique which effectively amplifies low-frequency components of damped wavefields. Our method is demonstrated for synthetic data for the SEG/EAGE salt model. AcknowledgementsThis work was supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP) and the Ministry of Trade, Industry & Energy(MOTIE) of the Republic of Korea (No. 20168510030830) and by the Dual Use Technology Program, granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea.

  17. Determining the metallicity of the solar envelope using seismic inversion techniques

    NASA Astrophysics Data System (ADS)

    Buldgen, G.; Salmon, S. J. A. J.; Noels, A.; Scuflaire, R.; Dupret, M. A.; Reese, D. R.

    2017-11-01

    The solar metallicity issue is a long-lasting problem of astrophysics, impacting multiple fields and still subject to debate and uncertainties. While spectroscopy has mostly been used to determine the solar heavy elements abundance, helioseismologists attempted providing a seismic determination of the metallicity in the solar convective envelope. However, the puzzle remains since two independent groups provided two radically different values for this crucial astrophysical parameter. We aim at providing an independent seismic measurement of the solar metallicity in the convective envelope. Our main goal is to help provide new information to break the current stalemate amongst seismic determinations of the solar heavy element abundance. We start by presenting the kernels, the inversion technique and the target function of the inversion we have developed. We then test our approach in multiple hare-and-hounds exercises to assess its reliability and accuracy. We then apply our technique to solar data using calibrated solar models and determine an interval of seismic measurements for the solar metallicity. We show that our inversion can indeed be used to estimate the solar metallicity thanks to our hare-and-hounds exercises. However, we also show that further dependencies in the physical ingredients of solar models lead to a low accuracy. Nevertheless, using various physical ingredients for our solar models, we determine metallicity values between 0.008 and 0.014.

  18. Basis set expansion for inverse problems in plasma diagnostic analysis

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jones, B.; Ruiz, C. L.

    A basis set expansion method [V. Dribinski, A. Ossadtchi, V. A. Mandelshtam, and H. Reisler, Rev. Sci. Instrum. 73, 2634 (2002)] is applied to recover physical information about plasma radiation sources from instrument data, which has been forward transformed due to the nature of the measurement technique. This method provides a general approach for inverse problems, and we discuss two specific examples relevant to diagnosing fast z pinches on the 20–25 MA Z machine [M. E. Savage, L. F. Bennett, D. E. Bliss, W. T. Clark, R. S. Coats, J. M. Elizondo, K. R. LeChien, H. C. Harjes, J. M.more » Lehr, J. E. Maenchen, D. H. McDaniel, M. F. Pasik, T. D. Pointon, A. C. Owen, D. B. Seidel, D. L. Smith, B. S. Stoltzfus, K. W. Struve, W. A. Stygar, L. K. Warne, J. R. Woodworth, C. W. Mendel, K. R. Prestwich, R. W. Shoup, D. L. Johnson, J. P. Corley, K. C. Hodge, T. C. Wagoner, and P. E. Wakeland, in Proceedings of the Pulsed Power Plasma Sciences Conference (IEEE, 2007), p. 979]. First, Abel inversion of time-gated, self-emission x-ray images from a wire array implosion is studied. Second, we present an approach for unfolding neutron time-of-flight measurements from a deuterium gas puff z pinch to recover information about emission time history and energy distribution. Through these examples, we discuss how noise in the measured data limits the practical resolution of the inversion, and how the method handles discontinuities in the source function and artifacts in the projected image. We add to the method a propagation of errors calculation for estimating uncertainties in the inverted solution.« less

  19. Basis set expansion for inverse problems in plasma diagnostic analysis

    NASA Astrophysics Data System (ADS)

    Jones, B.; Ruiz, C. L.

    2013-07-01

    A basis set expansion method [V. Dribinski, A. Ossadtchi, V. A. Mandelshtam, and H. Reisler, Rev. Sci. Instrum. 73, 2634 (2002)], 10.1063/1.1482156 is applied to recover physical information about plasma radiation sources from instrument data, which has been forward transformed due to the nature of the measurement technique. This method provides a general approach for inverse problems, and we discuss two specific examples relevant to diagnosing fast z pinches on the 20-25 MA Z machine [M. E. Savage, L. F. Bennett, D. E. Bliss, W. T. Clark, R. S. Coats, J. M. Elizondo, K. R. LeChien, H. C. Harjes, J. M. Lehr, J. E. Maenchen, D. H. McDaniel, M. F. Pasik, T. D. Pointon, A. C. Owen, D. B. Seidel, D. L. Smith, B. S. Stoltzfus, K. W. Struve, W. A. Stygar, L. K. Warne, J. R. Woodworth, C. W. Mendel, K. R. Prestwich, R. W. Shoup, D. L. Johnson, J. P. Corley, K. C. Hodge, T. C. Wagoner, and P. E. Wakeland, in Proceedings of the Pulsed Power Plasma Sciences Conference (IEEE, 2007), p. 979]. First, Abel inversion of time-gated, self-emission x-ray images from a wire array implosion is studied. Second, we present an approach for unfolding neutron time-of-flight measurements from a deuterium gas puff z pinch to recover information about emission time history and energy distribution. Through these examples, we discuss how noise in the measured data limits the practical resolution of the inversion, and how the method handles discontinuities in the source function and artifacts in the projected image. We add to the method a propagation of errors calculation for estimating uncertainties in the inverted solution.

  20. A robust spatial filtering technique for multisource localization and geoacoustic inversion.

    PubMed

    Stotts, S A

    2005-07-01

    Geoacoustic inversion and source localization using beamformed data from a ship of opportunity has been demonstrated with a bottom-mounted array. An alternative approach, which lies within a class referred to as spatial filtering, transforms element level data into beam data, applies a bearing filter, and transforms back to element level data prior to performing inversions. Automation of this filtering approach is facilitated for broadband applications by restricting the inverse transform to the degrees of freedom of the array, i.e., the effective number of elements, for frequencies near or below the design frequency. A procedure is described for nonuniformly spaced elements that guarantees filter stability well above the design frequency. Monitoring energy conservation with respect to filter output confirms filter stability. Filter performance with both uniformly spaced and nonuniformly spaced array elements is discussed. Vertical (range and depth) and horizontal (range and bearing) ambiguity surfaces are constructed to examine filter performance. Examples that demonstrate this filtering technique with both synthetic data and real data are presented along with comparisons to inversion results using beamformed data. Examinations of cost functions calculated within a simulated annealing algorithm reveal the efficacy of the approach.

  1. Revisiting the monster: the mass profile of the galaxy cluster Abell 3827 using dynamical and strong lensing constrains

    NASA Astrophysics Data System (ADS)

    Rodrigo Carrasco Damele, Eleazar; Verdugo, Tomas

    2018-01-01

    The galaxy cluster Abell 3827 is one of the most massive clusters know at z ≦ 0.1 (Richness class 2, BM typeI, X-ray LX = 2.4 x 1044 erg s-1). The Brightest Cluster Galaxy (BCG) in Abell 3827 is perhaps the most extreme example of ongoing galaxy cannibalism. The multi-component BCG hosts the stellar remnants nuclei of at least four bright elliptical galaxies embedded in a common assymetric halo extended up to 15 kpc. The most notorious characteristic of the BCG is the existence of a unique strong gravitational lens system located within the inner 15 kpc region. A mass estimation of the galaxy based on strong lensing model was presented in Carrasco et al (2010, ApJL, 715, 160). Moreover, the exceptional strong lensing lens system in Abell 3827 and the location of the four bright galaxies has been used to measure for the first time small physical separations between dark and ordinary matter (Williams et al. 2011, MNRAS, 415, 448, Massey et al. 2015, MNRAS, 449, 3393). In this contribution, we present a detailed strong lensing and dynamical analysis of the cluster Abell 3827 based on spectroscopic redshift of the lensed features and from ~70 spectroscopically confirmed member galaxies inside 0.5 x 0.5 Mpc from the cluster center.

  2. Embedded spiral patterns in the massive galaxy cluster Abell 1835

    NASA Astrophysics Data System (ADS)

    Ueda, S.; Kitayama, T.; Dotani, T.

    2017-10-01

    We report on the properties of the intracluster medium (ICM) in the central region of the massive galaxy cluster, Abell 1835, obtained with the data from the Chandra X-ray Observatory. We find distinctive spiral patterns in the cool core in the residual image of the X-ray surface brightness after its nominal profile is subtracted. The spiral patterns consist of two arms. One of them appears as positive, and the other appears as negative excesses in the residual image. Their sizes are ˜ 70 kpc and their morphologies are consistent with each other. We find that the spiral patterns extend from the cool core out to the hotter surrounding ICM. We analyze the X-ray spectra extracted from both regions. We obtain that the ICM properties are similar to those expected by gas sloshing. We also find that the ICM in the two regions of spiral patterns is near or is in pressure equilibrium. Abell 1835 may now be experiencing gas sloshing induced by an off-axis minor merger. These results have been already published (Ueda, Kitayama, & Dotani 2017, ApJ, 837, 34).

  3. The Noble-Abel Stiffened-Gas equation of state

    NASA Astrophysics Data System (ADS)

    Le Métayer, Olivier; Saurel, Richard

    2016-04-01

    Hyperbolic two-phase flow models have shown excellent ability for the resolution of a wide range of applications ranging from interfacial flows to fluid mixtures with several velocities. These models account for waves propagation (acoustic and convective) and consist in hyperbolic systems of partial differential equations. In this context, each phase is compressible and needs an appropriate convex equation of state (EOS). The EOS must be simple enough for intensive computations as well as boundary conditions treatment. It must also be accurate, this being challenging with respect to simplicity. In the present approach, each fluid is governed by a novel EOS named "Noble Abel stiffened gas," this formulation being a significant improvement of the popular "Stiffened Gas (SG)" EOS. It is a combination of the so-called "Noble-Abel" and "stiffened gas" equations of state that adds repulsive effects to the SG formulation. The determination of the various thermodynamic functions and associated coefficients is the aim of this article. We first use thermodynamic considerations to determine the different state functions such as the specific internal energy, enthalpy, and entropy. Then we propose to determine the associated coefficients for a liquid in the presence of its vapor. The EOS parameters are determined from experimental saturation curves. Some examples of liquid-vapor fluids are examined and associated parameters are computed with the help of the present method. Comparisons between analytical and experimental saturation curves show very good agreement for wide ranges of temperature for both liquid and vapor.

  4. Trimming and procrastination as inversion techniques

    NASA Astrophysics Data System (ADS)

    Backus, George E.

    1996-12-01

    By examining the processes of truncating and approximating the model space (trimming it), and by committing to neither the objectivist nor the subjectivist interpretation of probability (procrastinating), we construct a formal scheme for solving linear and non-linear geophysical inverse problems. The necessary prior information about the correct model xE can be either a collection of inequalities or a probability measure describing where xE was likely to be in the model space X before the data vector y0 was measured. The results of the inversion are (1) a vector z0 that estimates some numerical properties zE of xE; (2) an estimate of the error δz = z0 - zE. As y0 is finite dimensional, so is z0, and hence in principle inversion cannot describe all of xE. The error δz is studied under successively more specialized assumptions about the inverse problem, culminating in a complete analysis of the linear inverse problem with a prior quadratic bound on xE. Our formalism appears to encompass and provide error estimates for many of the inversion schemes current in geomagnetism, and would be equally applicable in geodesy and seismology if adequate prior information were available there. As an idealized example we study the magnetic field at the core-mantle boundary, using satellite measurements of field elements at sites assumed to be almost uniformly distributed on a single spherical surface. Magnetospheric currents are neglected and the crustal field is idealized as a random process with rotationally invariant statistics. We find that an appropriate data compression diagonalizes the variance matrix of the crustal signal and permits an analytic trimming of the idealized problem.

  5. Filtering techniques for efficient inversion of two-dimensional Nuclear Magnetic Resonance data

    NASA Astrophysics Data System (ADS)

    Bortolotti, V.; Brizi, L.; Fantazzini, P.; Landi, G.; Zama, F.

    2017-10-01

    The inversion of two-dimensional Nuclear Magnetic Resonance (NMR) data requires the solution of a first kind Fredholm integral equation with a two-dimensional tensor product kernel and lower bound constraints. For the solution of this ill-posed inverse problem, the recently presented 2DUPEN algorithm [V. Bortolotti et al., Inverse Problems, 33(1), 2016] uses multiparameter Tikhonov regularization with automatic choice of the regularization parameters. In this work, I2DUPEN, an improved version of 2DUPEN that implements Mean Windowing and Singular Value Decomposition filters, is deeply tested. The reconstruction problem with filtered data is formulated as a compressed weighted least squares problem with multi-parameter Tikhonov regularization. Results on synthetic and real 2D NMR data are presented with the main purpose to deeper analyze the separate and combined effects of these filtering techniques on the reconstructed 2D distribution.

  6. A comparative study of surface waves inversion techniques at strong motion recording sites in Greece

    USGS Publications Warehouse

    Panagiotis C. Pelekis,; Savvaidis, Alexandros; Kayen, Robert E.; Vlachakis, Vasileios S.; Athanasopoulos, George A.

    2015-01-01

    Surface wave method was used for the estimation of Vs vs depth profile at 10 strong motion stations in Greece. The dispersion data were obtained by SASW method, utilizing a pair of electromechanical harmonic-wave source (shakers) or a random source (drop weight). In this study, three inversion techniques were used a) a recently proposed Simplified Inversion Method (SIM), b) an inversion technique based on a neighborhood algorithm (NA) which allows the incorporation of a priori information regarding the subsurface structure parameters, and c) Occam's inversion algorithm. For each site constant value of Poisson's ratio was assumed (ν=0.4) since the objective of the current study is the comparison of the three inversion schemes regardless the uncertainties resulting due to the lack of geotechnical data. A penalty function was introduced to quantify the deviations of the derived Vs profiles. The Vs models are compared as of Vs(z), Vs30 and EC8 soil category, in order to show the insignificance of the existing variations. The comparison results showed that the average variation of SIM profiles is 9% and 4.9% comparing with NA and Occam's profiles respectively whilst the average difference of Vs30 values obtained from SIM is 7.4% and 5.0% compared with NA and Occam's.

  7. An approximate inverse scattering technique for reconstructing blockage profiles in water pipelines using acoustic transients.

    PubMed

    Jing, Liwen; Li, Zhao; Wang, Wenjie; Dubey, Amartansh; Lee, Pedro; Meniconi, Silvia; Brunone, Bruno; Murch, Ross D

    2018-05-01

    An approximate inverse scattering technique is proposed for reconstructing cross-sectional area variation along water pipelines to deduce the size and position of blockages. The technique allows the reconstructed blockage profile to be written explicitly in terms of the measured acoustic reflectivity. It is based upon the Born approximation and provides good accuracy, low computational complexity, and insight into the reconstruction process. Numerical simulations and experimental results are provided for long pipelines with mild and severe blockages of different lengths. Good agreement is found between the inverse result and the actual pipe condition for mild blockages.

  8. The nature of the driving mechanism in the pulsating hybrid PG 1159 star Abell 43

    NASA Astrophysics Data System (ADS)

    Quirion, P.-O.; Fontaine, G.; Brassard, P.

    2005-10-01

    We extend our previous pulsational stability analyses of PG 1159 stars by modeling the hybrid PG 1159 type star Abell 43. We show that the standard κ-mechanism due to the ionization of C and O in the envelope of this H-rich PG 1159 star is perfectly able to drive g-mode pulsations. Thus, contrary to a recent suggestion, there is no need to invoke any new or exotic mechanism to explain the pulsational instabilities observed in this particular star. Our expected instability band for l=1 modes extends in period from ~2604 s to ~5529 s, which is consistent with the available photometric observations of Abell 43. We also suggest that efforts to detect luminosity variations in its sibling NGC 7094 be pursued.

  9. Simulation studies of phase inversion in agitated vessels using a Monte Carlo technique.

    PubMed

    Yeo, Leslie Y; Matar, Omar K; Perez de Ortiz, E Susana; Hewitt, Geoffrey F

    2002-04-15

    A speculative study on the conditions under which phase inversion occurs in agitated liquid-liquid dispersions is conducted using a Monte Carlo technique. The simulation is based on a stochastic model, which accounts for fundamental physical processes such as drop deformation, breakup, and coalescence, and utilizes the minimization of interfacial energy as a criterion for phase inversion. Profiles of the interfacial energy indicate that a steady-state equilibrium is reached after a sufficiently large number of random moves and that predictions are insensitive to initial drop conditions. The calculated phase inversion holdup is observed to increase with increasing density and viscosity ratio, and to decrease with increasing agitation speed for a fixed viscosity ratio. It is also observed that, for a fixed viscosity ratio, the phase inversion holdup remains constant for large enough agitation speeds. The proposed model is therefore capable of achieving reasonable qualitative agreement with general experimental trends and of reproducing key features observed experimentally. The results of this investigation indicate that this simple stochastic method could be the basis upon which more advanced models for predicting phase inversion behavior can be developed.

  10. The genus curve of the Abell clusters

    NASA Technical Reports Server (NTRS)

    Rhoads, James E.; Gott, J. Richard, III; Postman, Marc

    1994-01-01

    We study the topology of large-scale structure through a genus curve measurement of the recent Abell catalog redshift survey of Postman, Huchra, and Geller (1992). The structure is found to be spongelike near median density and to exhibit isolated superclusters and voids at high and low densities, respectively. The genus curve shows a slight shift toward 'meatball' topology, but remains consistent with the hypothesis of Gaussian random phase initial conditions. The amplitude of the genus curve corresponds to a power-law spectrum with index n = 0.21(sub -0.47 sup +0.43) on scales of 48/h Mpc or to a cold dark matter power spectrum with omega h = 0.36(sub -0.17 sup +0.46).

  11. The genus curve of the Abell clusters

    NASA Astrophysics Data System (ADS)

    Rhoads, James E.; Gott, J. Richard, III; Postman, Marc

    1994-01-01

    We study the topology of large-scale structure through a genus curve measurement of the recent Abell catalog redshift survey of Postman, Huchra, and Geller (1992). The structure is found to be spongelike near median density and to exhibit isolated superclusters and voids at high and low densities, respectively. The genus curve shows a slight shift toward 'meatball' topology, but remains consistent with the hypothesis of Gaussian random phase initial conditions. The amplitude of the genus curve corresponds to a power-law spectrum with index n = 0.21-0.47+0.43 on scales of 48/h Mpc or to a cold dark matter power spectrum with omega h = 0.36-0.17+0.46.

  12. Weak Gravitational Lensing by the Nearby Cluster Abell 3667.

    PubMed

    Joffre; Fischer; Frieman; McKay; Mohr; Nichol; Johnston; Sheldon; Bernstein

    2000-05-10

    We present two weak lensing reconstructions of the nearby (zcl=0.055) merging cluster Abell 3667, based on observations taken approximately 1 yr apart under different seeing conditions. This is the lowest redshift cluster with a weak lensing mass reconstruction to date. The reproducibility of features in the two mass maps demonstrates that weak lensing studies of low-redshift clusters are feasible. These data constitute the first results from an X-ray luminosity-selected weak lensing survey of 19 low-redshift (z<0.1) southern clusters.

  13. ABEL model: Evaluates corporations` claims of inability to afford penalties and compliance costs (version 3.0.16). Model-simulation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    NONE

    1998-11-01

    The easy-to-use ABEL software evaluates for-profit company claims of inability to afford penalties, clean-up costs, or compliance costs. Violators raise the issue of inability to pay in most of EPA`s enforcement actions regardless of whether there is any hard evidence supporting those claims. The program enables Federal, State and local enforcement professionals to quickly determine if there was any validity to those claims. ABEL is a tool that promotes quick settlements by performing screening analyses of defendants and potentially responsible parties (PRP`s) to determine their financial capacity. After analyzing some basic financial ratios that reflect a company`s solvency, ABEL assessesmore » the firm`s ability to pay by focusing on projected cash flows. The model explicitly calculates the value of projected, internally generated cash flows from historical tax information, and compares these cash flows to the proposed environmental expenditure(s). The software is extremely easy to use. Version 3.0.16 updates the standard values for inflation and discount rate.« less

  14. Environmental Effects on Galaxy Evolution. II. Quantifying the Tidal Features in NIR Images of the Cluster Abell 85

    NASA Astrophysics Data System (ADS)

    Venkatapathy, Y.; Bravo-Alfaro, H.; Mayya, Y. D.; Lobo, C.; Durret, F.; Gamez, V.; Valerdi, M.; Granados-Contreras, A. P.; Navarro-Poupard, F.

    2017-12-01

    This work is part of a series of papers devoted to investigating the evolution of cluster galaxies during their infall. In the present article, we image in NIR a selected sample of galaxies throughout the massive cluster Abell 85 (z = 0.055). We obtain (JHK‧) photometry for 68 objects, reaching ˜1 mag arcsec-2 deeper than 2MASS. We use these images to unveil asymmetries in the outskirts of a sample of bright galaxies and develop a new asymmetry index, {α }{An}, which allows us to quantify the degree of disruption by the relative area occupied by the tidal features on the plane of the sky. We measure the asymmetries for a subsample of 41 large-area objects, finding clear asymmetries in 10 galaxies; most of these are in groups and pairs projected at different clustercentric distances, and some of them are located beyond R 500. Combining information on the H I gas content of blue galaxies and the distribution of substructures across Abell 85 with the present NIR asymmetry analysis, we obtain a very powerful tool to confirm that tidal mechanisms are indeed present and are currently affecting a fraction of galaxies in Abell 85. However, when comparing our deep NIR images with UV blue images of two very disrupted (jellyfish) galaxies in this cluster, we discard the presence of tidal interactions down to our detection limit. Our results suggest that ram-pressure stripping is at the origin of such spectacular disruptions. We conclude that across a complex cluster like Abell 85, environmental mechanisms, both gravitational and hydrodynamical, are playing an active role in driving galaxy evolution.

  15. Anti-Brownian ELectrokinetic (ABEL) trapping of single β2-adrenergic receptors in the absence and presence of agonist

    NASA Astrophysics Data System (ADS)

    Bockenhauer, Samuel; Fuerstenberg, Alexandre; Yao, Xiao Jie; Kobilka, Brian K.; Moerner, W. E.

    2012-02-01

    The ABEL trap allows trapping of single biomolecules in solution for extended observation without immobilization. The essential idea combines fluorescence-based position estimation with fast electrokinetic feedback in a microfluidic geometry to counter the Brownian motion of a single nanoscale object, hence maintaining its position in the field of view for hundreds of milliseconds to seconds. Such prolonged observation of single proteins allows access to slow dynamics, as probed by any available photophysical observables. We have used the ABEL trap to study conformational dynamics of the β2-adrenergic receptor, a key G-protein coupled receptor and drug target, in the absence and presence of agonist. A single environment-sensitive dye reports on the receptor microenvironment, providing a real-time readout of conformational change for each trapped receptor. The focus of this paper will be a quantitative comparison of the ligandfree and agonist-bound receptor data from our ABEL trap experiments. We observe a small but clearly detectable shift in conformational equilibria and a lengthening of fluctuation timescales upon binding of agonist. In order to quantify the shift in state distributions and timescales, we apply nonparametric statistical tests to place error bounds on the resulting single-molecule distributions.

  16. Analysis of the optical emission of the young precataclysmic variables HS 1857+5144 and ABELL 65

    NASA Astrophysics Data System (ADS)

    Shimansky, V. V.; Pozdnyakova, S. A.; Borisov, N. V.; Bikmaev, I. F.; Vlasyuk, V. V.; Spiridonova, O. I.; Galeev, A. I.; Mel'Nikov, S. S.

    2009-10-01

    We analyze the physical state and the properties of the close binary systems HS 1857+5144 and Abell 65. We took the spectra of both systems over a wide range of orbital phases with the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS) and obtained their multicolor light curves with the RTT150 and Zeiss-1000 telescopes of the SAO RAS. We demonstrate that both Abell 65 and HS 1857+5144 are young precataclysmic variables (PV) with orbital periods of P orb = 1. d 003729 and P orb = 0. d 26633331, respectively. The observed brightness and spectral variations during the orbital period are due to the radiation of the cold component, which absorbs the short-wave radiation of the hot component and reemits it in the visual part of the spectrum. A joint analysis of the brightness and radial velocity curves allowed us to find the possible and optimum sets of their fundamental parameters. We found the luminosity excesses of the secondary components of HS 1857+5144 and Abell 65 with respect to the corresponding Main Sequence stars to be typical for such objects. The excess luminosities of the secondary components of all young PVs are indicative of their faster relaxation rate towards the quiescent state compared to the rates estimated in earlier studies.

  17. A redshift survey of the strong-lensing cluster ABELL 383

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Geller, Margaret J.; Hwang, Ho Seong; Kurtz, Michael J.

    2014-03-01

    Abell 383 is a famous rich cluster (z = 0.1887) imaged extensively as a basis for intensive strong- and weak-lensing studies. Nonetheless, there are few spectroscopic observations. We enable dynamical analyses by measuring 2360 new redshifts for galaxies with r {sub Petro} ≤ 20.5 and within 50' of the Brightest Cluster Galaxy (BCG; R.A.{sub 2000} = 42.°014125, decl.{sub 2000} = –03.°529228). We apply the caustic technique to identify 275 cluster members within 7 h {sup –1} Mpc of the hierarchical cluster center. The BCG lies within –11 ± 110 km s{sup –1} and 21 ± 56 h {sup –1} kpcmore » of the hierarchical cluster center; the velocity dispersion profile of the BCG appears to be an extension of the velocity dispersion profile based on cluster members. The distribution of cluster members on the sky corresponds impressively with the weak-lensing contours of Okabe et al. especially when the impact of foreground and background structure is included. The values of R {sub 200} = 1.22 ± 0.01 h {sup –1} Mpc and M {sub 200} = (5.07 ± 0.09) × 10{sup 14} h {sup –1} M {sub ☉} obtained by application of the caustic technique agree well with recent completely independent lensing measures. The caustic estimate extends direct measurement of the cluster mass profile to a radius of ∼5 h {sup –1} Mpc.« less

  18. Comparative interpretations of renormalization inversion technique for reconstructing unknown emissions from measured atmospheric concentrations

    NASA Astrophysics Data System (ADS)

    Singh, Sarvesh Kumar; Kumar, Pramod; Rani, Raj; Turbelin, Grégory

    2017-04-01

    The study highlights a theoretical comparison and various interpretations of a recent inversion technique, called renormalization, developed for the reconstruction of unknown tracer emissions from their measured concentrations. The comparative interpretations are presented in relation to the other inversion techniques based on principle of regularization, Bayesian, minimum norm, maximum entropy on mean, and model resolution optimization. It is shown that the renormalization technique can be interpreted in a similar manner to other techniques, with a practical choice of a priori information and error statistics, while eliminating the need of additional constraints. The study shows that the proposed weight matrix and weighted Gram matrix offer a suitable deterministic choice to the background error and measurement covariance matrices, respectively, in the absence of statistical knowledge about background and measurement errors. The technique is advantageous since it (i) utilizes weights representing a priori information apparent to the monitoring network, (ii) avoids dependence on background source estimates, (iii) improves on alternative choices for the error statistics, (iv) overcomes the colocalization problem in a natural manner, and (v) provides an optimally resolved source reconstruction. A comparative illustration of source retrieval is made by using the real measurements from a continuous point release conducted in Fusion Field Trials, Dugway Proving Ground, Utah.

  19. Astrometry With the Hubble Space Telescope: Trigonometric Parallaxes of Planetary Nebula Nuclei NGC 6853, NGC 7293, ABELL 31, and DeHt 5

    DTIC Science & Technology

    2009-12-01

    reserved. Printed in the U.S.A. ASTROMETRY WITH THE HUBBLE SPACE TELESCOPE: TRIGONOMETRIC PARALLAXES OF PLANETARY NEBULA NUCLEI NGC 6853, NGC 7293, ABELL 31...present absolute parallaxes and relative proper motions for the central stars of the planetary nebulae NGC 6853 (The Dumbbell), NGC 7293 (The Helix...Abell 31, and DeHt 5. This paper details our reduction and analysis using DeHt 5 as an example. We obtain these planetary nebula nuclei (PNNi

  20. Suzaku observations of low surface brightness cluster Abell 1631

    NASA Astrophysics Data System (ADS)

    Babazaki, Yasunori; Mitsuishi, Ikuyuki; Ota, Naomi; Sasaki, Shin; Böhringer, Hans; Chon, Gayoung; Pratt, Gabriel W.; Matsumoto, Hironori

    2018-04-01

    We present analysis results for a nearby galaxy cluster Abell 1631 at z = 0.046 using the X-ray observatory Suzaku. This cluster is categorized as a low X-ray surface brightness cluster. To study the dynamical state of the cluster, we conduct four-pointed Suzaku observations and investigate physical properties of the Mpc-scale hot gas associated with the A 1631 cluster for the first time. Unlike relaxed clusters, the X-ray image shows no strong peak at the center and an irregular morphology. We perform spectral analysis and investigate the radial profiles of the gas temperature, density, and entropy out to approximately 1.5 Mpc in the east, north, west, and south directions by combining with the XMM-Newton data archive. The measured gas density in the central region is relatively low (a few ×10-4 cm-3) at the given temperature (˜2.9 keV) compared with X-ray-selected clusters. The entropy profile and value within the central region (r < 0.1 r200) are found to be flatter and higher (≳400 keV cm2). The observed bolometric luminosity is approximately three times lower than that expected from the luminosity-temperature relation in previous studies of relaxed clusters. These features are also observed in another low surface brightness cluster, Abell 76. The spatial distributions of galaxies and the hot gas appear to be different. The X-ray luminosity is relatively lower than that expected from the velocity dispersion. A post-merger scenario may explain the observed results.

  1. Suzaku observations of low surface brightness cluster Abell 1631

    NASA Astrophysics Data System (ADS)

    Babazaki, Yasunori; Mitsuishi, Ikuyuki; Ota, Naomi; Sasaki, Shin; Böhringer, Hans; Chon, Gayoung; Pratt, Gabriel W.; Matsumoto, Hironori

    2018-06-01

    We present analysis results for a nearby galaxy cluster Abell 1631 at z = 0.046 using the X-ray observatory Suzaku. This cluster is categorized as a low X-ray surface brightness cluster. To study the dynamical state of the cluster, we conduct four-pointed Suzaku observations and investigate physical properties of the Mpc-scale hot gas associated with the A 1631 cluster for the first time. Unlike relaxed clusters, the X-ray image shows no strong peak at the center and an irregular morphology. We perform spectral analysis and investigate the radial profiles of the gas temperature, density, and entropy out to approximately 1.5 Mpc in the east, north, west, and south directions by combining with the XMM-Newton data archive. The measured gas density in the central region is relatively low (a few ×10-4 cm-3) at the given temperature (˜2.9 keV) compared with X-ray-selected clusters. The entropy profile and value within the central region (r < 0.1 r200) are found to be flatter and higher (≳400 keV cm2). The observed bolometric luminosity is approximately three times lower than that expected from the luminosity-temperature relation in previous studies of relaxed clusters. These features are also observed in another low surface brightness cluster, Abell 76. The spatial distributions of galaxies and the hot gas appear to be different. The X-ray luminosity is relatively lower than that expected from the velocity dispersion. A post-merger scenario may explain the observed results.

  2. Pixel Color–Magnitude Diagram Analysis of the Brightest Cluster Galaxies in Dynamically Young and Old Clusters Abell 1139 and Abell 2589

    NASA Astrophysics Data System (ADS)

    Lee, Joon Hyeop; Oh, Sree; Jeong, Hyunjin; Yi, Sukyoung K.; Kyeong, Jaemann; Park, Byeong-Gon

    2017-07-01

    As a case study to understand the coevolution of Brightest Cluster Galaxies (BCGs) and their host clusters, we investigate the BCGs in dynamically young and old clusters Abell 1139 (A1139) and Abell 2589 (A2589). We analyze the pixel color–magnitude diagrams (pCMDs) using deep g- and r-band images, obtained from the Canada–France–Hawaii Telescope observations. After masking foreground/background objects and smoothing pixels in consideration of the observational seeing size, detailed pCMD features are compared between the two BCGs. (1) Although the overall shapes of the pCMDs are similar to those of typical early-type galaxies, the A2589-BCG tends to have redder mean pixel color and smaller pixel color deviation at given surface brightness than the A1139-BCG. (2) The mean pixel color distribution as a function of pixel surface brightness (pCMD backbone) indicates that the A2589-BCG formed a larger central body (∼2.0 kpc in radius) via major dry mergers at an early epoch than the A1139-BCG (a central body ∼1.3 kpc in radius), whereas they have grown commonly in subsequent minor mergers. (3) The spatial distributions of the pCMD outliers reveal that the A1139-BCG experienced considerable tidal events more recently than the A2589-BCG, whereas the A2589-BCG has an asymmetric compact core, possibly resulting from a major dry merger at an early epoch. (4) The A2589-BCG shows a very large faint-to-bright pixel number ratio, compared to early-type non-BCGs, whereas the ratio for the A1139-BCG is not distinctively large. These results are consistent with the idea that the BCG in the dynamically older cluster (A2589) formed earlier and is better relaxed.

  3. The merging cluster Abell 1758: an optical and dynamical view

    NASA Astrophysics Data System (ADS)

    Monteiro-Oliveira, Rogerio; Serra Cypriano, Eduardo; Machado, Rubens; Lima Neto, Gastao B.

    2015-08-01

    The galaxy cluster Abell 1758-North (z=0.28) is a binary system composed by the sub-structures NW and NE. This is supposed to be a post-merging cluster due to observed detachment between the NE BCG and the respective X-ray emitting hot gas clump in a scenario very close to the famous Bullet Cluster. On the other hand, the projected position of the NW BCG coincides with the local hot gas peak. This system was been targeted previously by several studies, using multiple wavelengths and techniques, but there is still no clear picture of the scenario that could have caused this unusual configuration. To help solving this complex puzzle we added some pieces: firstly, we have used deep B, RC and z' Subaru images to perform both weak lensing shear and magnification analysis of A1758 (including here the South component that is not in interaction with A1758-North) modeling each sub-clump as an NFW profile in order to constrain masses and its center positions through MCMC methods; the second piece is the dynamical analysis using radial velocities available in the literature (143) plus new Gemini-GMOS/N measurements (68 new redshifts).From weak lensing we found that independent shear and magnification mass determinations are in excellent agreement between them and combining both we could reduce mass error bar by ~30% compared to shear alone. By combining this two weak-lensing probes we found that the position of both Northern BCGs are consistent with the masses centers within 2σ and and the NE hot gas peak to be offseted of the respective mass peak (M200=5.5 X 1014 M⊙) with very high significance. The most massive structure is NW (M200=7.95 X 1014 M⊙ ) where we observed no detachment between gas, DM and BCG.We have calculated a low line-of-sight velocity difference (<300 km/s) between A1758 NW and NE. We have combined it with the projected velocity of 1600 km/s which was estimated by previous X-ray analysis (David & Kempner 2004) and we have obtained a small angle between

  4. Zero-order bows in radially inhomogeneous spheres: direct and inverse problems.

    PubMed

    Adam, John A

    2011-10-01

    Zero-order ray paths are examined in radially inhomogeneous spheres with differentiable refractive index profiles. It is demonstrated that zero-order and sometimes twin zero-order bows can exist when the gradient of refractive index is sufficiently negative. Abel inversion is used to "recover" the refractive index profiles; it is therefore possible in principle to specify the nature and type of bows and determine the refractive index profile that induces them. This may be of interest in the field of rainbow refractometry and optical fiber studies. This ray-theoretic analysis has direct similarities with the phenomenon of "orbiting" and other phenomena in scattering theory and also in seismological, surface gravity wave, and gravitational "lensing" studies. For completeness these topics are briefly discussed in the appendixes; they may also be of pedagogic interest.

  5. Uncertainty estimates of a GRACE inversion modelling technique over Greenland using a simulation

    NASA Astrophysics Data System (ADS)

    Bonin, Jennifer; Chambers, Don

    2013-07-01

    The low spatial resolution of GRACE causes leakage, where signals in one location spread out into nearby regions. Because of this leakage, using simple techniques such as basin averages may result in an incorrect estimate of the true mass change in a region. A fairly simple least squares inversion technique can be used to more specifically localize mass changes into a pre-determined set of basins of uniform internal mass distribution. However, the accuracy of these higher resolution basin mass amplitudes has not been determined, nor is it known how the distribution of the chosen basins affects the results. We use a simple `truth' model over Greenland as an example case, to estimate the uncertainties of this inversion method and expose those design parameters which may result in an incorrect high-resolution mass distribution. We determine that an appropriate level of smoothing (300-400 km) and process noise (0.30 cm2 of water) gets the best results. The trends of the Greenland internal basins and Iceland can be reasonably estimated with this method, with average systematic errors of 3.5 cm yr-1 per basin. The largest mass losses found from GRACE RL04 occur in the coastal northwest (-19.9 and -33.0 cm yr-1) and southeast (-24.2 and -27.9 cm yr-1), with small mass gains (+1.4 to +7.7 cm yr-1) found across the northern interior. Acceleration of mass change is measurable at the 95 per cent confidence level in four northwestern basins, but not elsewhere in Greenland. Due to an insufficiently detailed distribution of basins across internal Canada, the trend estimates of Baffin and Ellesmere Islands are expected to be incorrect due to systematic errors caused by the inversion technique.

  6. UV Observations of the Galaxy Cluster Abell 1795 with the Optical Monitor on XMM-Newton

    NASA Technical Reports Server (NTRS)

    Mittaz, J. P. D.; Kaastra, J. S.; Tamura, T.; Fabian, A. C.; Mushotzky, F.; Peterson, J. R.; Ikebe, Y.; Lumb, D. H.; Paerels, F.; Stewart, G.

    2000-01-01

    We present the results of an analysis of broad band UV observations of the central regions of Abell 1795 observed with the optical monitor on XMM-Newton. As have been found with other UV observations of the central regions of clusters of galaxies, we find evidence for star formation. However, we also find evidence for absorption in the cD galaxy on a more extended scale than has been seen with optical imaging. We also report the first UV observation of part of the filamentary structure seen in H-alpha, X-rays and very deep U band imaging. The part of the filament we see is very blue with UV colours consistent with a very early (O/B) stellar population. This is the first direct evidence of a dominant population of early type stars at the centre of Abell 1795 and implies very recent star formation. The relationship of this emission to emission at other wavebands is discussed.

  7. Eversion-Inversion Labral Repair and Reconstruction Technique for Optimal Suction Seal.

    PubMed

    Moreira, Brett; Pascual-Garrido, Cecilia; Chadayamurri, Vivek; Mei-Dan, Omer

    2015-12-01

    Labral tears are a significant cause of hip pain and are currently the most common indication for hip arthroscopy. Compared with labral debridement, labral repair has significantly better outcomes in terms of both daily activities and athletic pursuits in the setting of femoral acetabular impingement. The classic techniques described in the literature for labral repair all use loop or pass-through intrasubstance labral sutures to achieve a functional hip seal. This hip seal is important for hip stability and optimal joint biomechanics, as well as in the prevention of long-term osteoarthritis. We describe a novel eversion-inversion intrasubstance suturing technique for labral repair and reconstruction that can assist in restoration of the native labrum position by re-creating an optimal seal around the femoral head.

  8. Mystery solved: discovery of extended radio emission in the merging galaxy cluster Abell 2146

    NASA Astrophysics Data System (ADS)

    Hlavacek-Larrondo, J.; Gendron-Marsolais, M.-L.; Fecteau-Beaucage, D.; van Weeren, R. J.; Russell, H. R.; Edge, A.; Olamaie, M.; Rumsey, C.; King, L.; Fabian, A. C.; McNamara, B.; Hogan, M.; Mezcua, M.; Taylor, G.

    2018-04-01

    Abell 2146 (z = 0.232) is a massive galaxy cluster currently undergoing a spectacular merger in the plane of the sky with a bullet-like morphology. It was the first system in which both the bow and upstream shock fronts were detected at X-ray wavelengths (Mach ˜2), yet deep Giant MetreWave Telescope 325 MHz observations failed to detect extended radio emission associated with the cluster as is typically seen in such systems. We present new, multiconfiguration 1-2 GHz Karl G. Jansky Very Large Array (VLA) observations of Abell 2146 totalling 16 h of observations. These data reveal for the first time the presence of an extended (≈850 kpc), faint radio structure associated with Abell 2146. The structure appears to harbour multiple components, one associated with the upstream shock that we classify as a radio relic and one associated with the subcluster core that is consisted as being a radio halo bounded by the bow shock. The newly detected structures have some of the lowest radio powers detected thus far in any cluster (P1.4 GHz, halo = 2.4 ± 0.2 × 1023 W Hz-1 and P1.4 GHz, relic = 2.2 ± 0.2 × 1023 W Hz-1). The flux measurement of the halo, as well as its morphology, also suggests that the halo was recently created (≈0.3 Gyr after core passage), consistent with the dynamical state of the cluster. These observations demonstrate the capacity of the upgraded VLA to detect extremely faint and extended radio structures. Based on these observations, we predict that many more radio relics and radio haloes in merging clusters should be detected by future radio facilities such as the Square Kilometre Array.

  9. Revisiting Abell 2744: a powerful synergy of GLASS spectroscopy and HFF photometry

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Wang

    We present new emission line identifications and improve the lensing reconstruction of the mass distribution of galaxy cluster Abell 2744 using the Grism Lens-Amplified Survey from Space (GLASS) spectroscopy and the Hubble Frontier Fields (HFF) imaging. We performed blind and targeted searches for faint line emitters on all objects, including the arc sample, within the field of view (FoV) of GLASS prime pointings. We report 55 high quality spectroscopic redshifts, 5 of which are for arc images. We also present an extensive analysis based on the HFF photometry, measuring the colors and photometric redshifts of all objects within the FoV, and comparing the spectroscopic and photometric redshift estimates. In order to improve the lens model of Abell 2744, we develop a rigorous algorithm to screen arc images, based on their colors and morphology, and selecting the most reliable ones to use. As a result, 25 systems (corresponding to 72 images) pass the screening process and are used to reconstruct the gravitational potential of the cluster pixellated on an adaptive mesh. The resulting total mass distribution is compared with a stellar mass map obtained from the Spitzer Frontier Fields data in order to study the relative distribution of stars and dark matter in the cluster.

  10. Inverse Function: Pre-Service Teachers' Techniques and Meanings

    ERIC Educational Resources Information Center

    Paoletti, Teo; Stevens, Irma E.; Hobson, Natalie L. F.; Moore, Kevin C.; LaForest, Kevin R.

    2018-01-01

    Researchers have argued teachers and students are not developing connected meanings for function inverse, thus calling for a closer examination of teachers' and students' inverse function meanings. Responding to this call, we characterize 25 pre-service teachers' inverse function meanings as inferred from our analysis of clinical interviews. After…

  11. Dark matter dynamics in Abell 3827: new data consistent with standard cold dark matter

    NASA Astrophysics Data System (ADS)

    Massey, Richard; Harvey, David; Liesenborgs, Jori; Richard, Johan; Stach, Stuart; Swinbank, Mark; Taylor, Peter; Williams, Liliya; Clowe, Douglas; Courbin, Frédéric; Edge, Alastair; Israel, Holger; Jauzac, Mathilde; Joseph, Rémy; Jullo, Eric; Kitching, Thomas D.; Leonard, Adrienne; Merten, Julian; Nagai, Daisuke; Nightingale, James; Robertson, Andrew; Romualdez, Luis Javier; Saha, Prasenjit; Smit, Renske; Tam, Sut-Ieng; Tittley, Eric

    2018-06-01

    We present integral field spectroscopy of galaxy cluster Abell 3827, using Atacama Large Millimetre Array (ALMA) and Very Large Telescope/Multi-Unit Spectroscopic Explorer. It reveals an unusual configuration of strong gravitational lensing in the cluster core, with at least seven lensed images of a single background spiral galaxy. Lens modelling based on Hubble Space Telescope imaging had suggested that the dark matter associated with one of the cluster's central galaxies may be offset. The new spectroscopic data enable better subtraction of foreground light, and better identification of multiple background images. The inferred distribution of dark matter is consistent with being centred on the galaxies, as expected by Λ cold dark matter. Each galaxy's dark matter also appears to be symmetric. Whilst, we do not find an offset between mass and light (suggestive of self-interacting dark matter) as previously reported, the numerical simulations that have been performed to calibrate Abell 3827 indicate that offsets and asymmetry are still worth looking for in collisions with particular geometries. Meanwhile, ALMA proves exceptionally useful for strong lens image identifications.

  12. The X-ray luminosity functions of Abell clusters from the Einstein Cluster Survey

    NASA Technical Reports Server (NTRS)

    Burg, R.; Giacconi, R.; Forman, W.; Jones, C.

    1994-01-01

    We have derived the present epoch X-ray luminosity function of northern Abell clusters using luminosities from the Einstein Cluster Survey. The sample is sufficiently large that we can determine the luminosity function for each richness class separately with sufficient precision to study and compare the different luminosity functions. We find that, within each richness class, the range of X-ray luminosity is quite large and spans nearly a factor of 25. Characterizing the luminosity function for each richness class with a Schechter function, we find that the characteristic X-ray luminosity, L(sub *), scales with richness class as (L(sub *) varies as N(sub*)(exp gamma), where N(sub *) is the corrected, mean number of galaxies in a richness class, and the best-fitting exponent is gamma = 1.3 +/- 0.4. Finally, our analysis suggests that there is a lower limit to the X-ray luminosity of clusters which is determined by the integrated emission of the cluster member galaxies, and this also scales with richness class. The present sample forms a baseline for testing cosmological evolution of Abell-like clusters when an appropriate high-redshift cluster sample becomes available.

  13. Inverse imaging of the breast with a material classification technique.

    PubMed

    Manry, C W; Broschat, S L

    1998-03-01

    In recent publications [Chew et al., IEEE Trans. Blomed. Eng. BME-9, 218-225 (1990); Borup et al., Ultrason. Imaging 14, 69-85 (1992)] the inverse imaging problem has been solved by means of a two-step iterative method. In this paper, a third step is introduced for ultrasound imaging of the breast. In this step, which is based on statistical pattern recognition, classification of tissue types and a priori knowledge of the anatomy of the breast are integrated into the iterative method. Use of this material classification technique results in more rapid convergence to the inverse solution--approximately 40% fewer iterations are required--as well as greater accuracy. In addition, tumors are detected early in the reconstruction process. Results for reconstructions of a simple two-dimensional model of the human breast are presented. These reconstructions are extremely accurate when system noise and variations in tissue parameters are not too great. However, for the algorithm used, degradation of the reconstructions and divergence from the correct solution occur when system noise and variations in parameters exceed threshold values. Even in this case, however, tumors are still identified within a few iterations.

  14. Oleiferoside W from the roots of Camellia oleifera C. Abel, inducing cell cycle arrest and apoptosis in A549 cells.

    PubMed

    Wu, Jiang-Ping; Kang, Nai-Xin; Zhang, Mi-Ya; Gao, Hong-Wei; Li, Xiao-Ran; Liu, Yan-Li; Xu, Qiong-Ming; Yang, Shi-Lin

    2017-07-06

    Camellia oleifera C. Abel has been widely cultivated in China, and a group of bioactive constituents such as triterpeniod saponin have been isolated from C. oleifera C. Abel. In the current study, a new triterpeniod saponin was isolated from the EtOH extract of the roots of C. oleifera C. Abel, named as oleiferoside W, and the cytotoxic properties of oleiferoside W were evaluated in non-small cell lung cancer A549 cells. At the same time the inducing apoptosis, the depolarization of mitochondrial membrane potential (Δψ), the up-regulation of related pro-apoptotic proteins, such as cleaved-PARP, cleaved-caspase-3, and the down-regulation of anti-apoptotic marker Bcl-2/Bax were measured on oleiferoside W. Furthermore, the function, inducing the generation of reactive oxygen species (ROS) and apoptosis, of oleiferoside W could be reversed by N-acetylcysteine (NAC). In conclusion, our findings showed that oleiferoside W induced apoptosis involving mitochondrial pathway and increasing intracellular ROS production in the A549 cells, suggesting that oleiferoside W may have the possibility to be a useful anticancer agent for therapy in lung cancer.

  15. Advanced Multivariate Inversion Techniques for High Resolution 3D Geophysical Modeling (Invited)

    NASA Astrophysics Data System (ADS)

    Maceira, M.; Zhang, H.; Rowe, C. A.

    2009-12-01

    We focus on the development and application of advanced multivariate inversion techniques to generate a realistic, comprehensive, and high-resolution 3D model of the seismic structure of the crust and upper mantle that satisfies several independent geophysical datasets. Building on previous efforts of joint invesion using surface wave dispersion measurements, gravity data, and receiver functions, we have added a fourth dataset, seismic body wave P and S travel times, to the simultaneous joint inversion method. We present a 3D seismic velocity model of the crust and upper mantle of northwest China resulting from the simultaneous, joint inversion of these four data types. Surface wave dispersion measurements are primarily sensitive to seismic shear-wave velocities, but at shallow depths it is difficult to obtain high-resolution velocities and to constrain the structure due to the depth-averaging of the more easily-modeled, longer-period surface waves. Gravity inversions have the greatest resolving power at shallow depths, and they provide constraints on rock density variations. Moreover, while surface wave dispersion measurements are primarily sensitive to vertical shear-wave velocity averages, body wave receiver functions are sensitive to shear-wave velocity contrasts and vertical travel-times. Addition of the fourth dataset, consisting of seismic travel-time data, helps to constrain the shear wave velocities both vertically and horizontally in the model cells crossed by the ray paths. Incorporation of both P and S body wave travel times allows us to invert for both P and S velocity structure, capitalizing on empirical relationships between both wave types’ seismic velocities with rock densities, thus eliminating the need for ad hoc assumptions regarding the Poisson ratios. Our new tomography algorithm is a modification of the Maceira and Ammon joint inversion code, in combination with the Zhang and Thurber TomoDD (double-difference tomography) program.

  16. RELICS Discovery of a Probable Lens-magnified SN behind Galaxy Cluster Abell 1763

    NASA Astrophysics Data System (ADS)

    Rodney, S.; Coe, D.; Bradley, L.; Strolger, L.; Brammer, G.; Avila, R.; Ryan, R.; Ogaz, S.; Riess, A.; Sharon, K.; Johnson, T.; Paterno-Mahler, R.; Molino, A.; Graham, M.; Kelly, P.; Filippenko, A.; Frye, B.; Foley, R.; Schmidt, K.; Umetsu, K.; Czakon, N.; Weiner, B.; Stark, D.; Mainali, R.; Zitrin, A.; Sendra, I.; Graur, O.; Grillo, C.; Hjorth, J.; Selsing, J.; Christensen, L.; Rosati, P.; Nonino, M.; Balestra, I.; Vulcani, B.; McCully, C.; Dawson, W.; Bouwens, R.; Lam, D.; Trenti, M.; Nunez, D. Carrasco; Matheson, T.; Merten, J.; Jha, S.; Jones, C.; Andrade-Santos, F.; Salmon, B.; Bradac, M.; Hoag, A.; Huang, K.; Wang, X.; Oesch, P.

    2016-07-01

    We report the discovery of a likely supernova (SN) in the background field of the galaxy cluster Abell 1763 (a.k.a. RXC J1335.3+4059, ZwCl 1333.7+4117). The SN candidate was detected in Hubble Space Telescope (HST) observations collected on June 17, 2016 as part of the Reionization Lensing Cluster Survey (RELICS, HST program ID: 14096, PI: D.Coe).

  17. Abell 2069 - An X-ray cluster of galaxies with multiple subcondensations

    NASA Technical Reports Server (NTRS)

    Gioia, I. M.; Maccacaro, T.; Geller, M. J.; Huchra, J. P.; Stocke, J.; Steiner, J. E.

    1982-01-01

    X-ray and optical observations of the cluster Abell 2069 are presented. The cluster is at a mean redshift of 0.116. The cluster shows multiple condensations in both the X-ray emission and in the galaxy surface density and, thus, does not appear to be relaxed. There is a close correspondence between the gas and galaxy distributions which indicates that the galaxies in this system do map the mass distribution, contrary to what might be expected if low-mass neutrinos dominate the cluster mass.

  18. Mass Mapping Abell 2261 with Kinematic Weak Lensing: A Pilot Study for NASAs WFIRST mission

    NASA Astrophysics Data System (ADS)

    Eifler, Tim

    2015-02-01

    We propose to investigate a new method to extract cosmological information from weak gravitational lensing in the context of the mission design and requirements of NASAs Wide-Field Infrared Survey Telescope (WFIRST). In a recent paper (Huff, Krause, Eifler, George, Schlegel 2013) we describe a new method for reducing the shape noise in weak lensing measurements by an order of magnitude. Our method relies on spectroscopic measurements of disk galaxy rotation and makes use of the well-established Tully-Fisher (TF) relation in order to control for the intrinsic orientations of galaxy disks. Whereas shape noise is one of the major limitations for current weak lensing experiments it ceases to be an important source of statistical error in our new proposed technique. Specifically, we propose a pilot study that maps the projected mass distribution in the massive cluster Abell 2261 (z=0.225) to infer whether this promising technique faces systematics that prohibit its application to WFIRST. In addition to the cosmological weak lensing prospects, these measurements will also allow us to test kinematic lensing in the context of cluster mass reconstruction with a drastically improved signal-to-noise (S/N) per galaxy.

  19. An off-axis galaxy cluster merger: Abell 0141

    NASA Astrophysics Data System (ADS)

    Caglar, Turgay

    2018-04-01

    We present structural analysis results of Abell 0141 (z = 0.23) based on X-ray data. The X-ray luminosity map demonstrates that Abell 0141 (A0141) is a bimodal galaxy cluster, which is separated on the sky by ˜0.65 Mpc with an elongation along the north-south direction. The optical galaxy density map also demonstrates this bimodality. We estimate sub-cluster ICM temperatures of 5.17^{+0.20}_{-0.19} keV for A0141N and 5.23^{+0.24}_{-0.23} keV for A0141S. We obtain X-ray morphological parameters w = 0.034 ± 0.004, c = 0.113 ± 0.004, and w = 0.039 ± 0.004, c = 0.104 ± 0.005 for A0141N and A0141S, respectively. The resulting X-ray morphological parameters indicate that both sub-clusters are moderately disturbed non-cool core structures. We find a slight brightness jump in the bridge region, and yet, there is still an absence of strong X-ray emitting gas between sub-clusters. We discover a significantly hotspot (˜10 keV) between sub-clusters, and a Mach number M = 1.69^{+0.40}_{-0.37} is obtained by using the temperature jump condition. However, we did not find direct evidence for shock-heating between sub-clusters. We estimate the sub-clusters' central entropies as K0 > 100 keV cm2, which indicates that the sub-clusters are not cool cores. We find some evidence that the system undergoes an off-axis collision; however, the cores of each sub-clusters have not yet been destroyed. Due to the orientation of X-ray tails of sub-clusters, we suggest that the northern sub-cluster moves through the south-west direction, and the southern cluster moves through the north-east direction. In conclusion, we are witnessing an earlier phase of close core passage between sub-clusters.

  20. The cD galaxy in Abell cluster 1775

    NASA Technical Reports Server (NTRS)

    Hayes, J. J. E.; Bhattacharya, B.

    1990-01-01

    Over the last 20 years, a number of workers have studied the multiple nuclei cD galaxy in the rich Abell cluster 1775, trying to discover its nature. In all the cases though, very little has been published concerning its morphology. The majority of arguments about the nature of this object have been based on the relative radial velocities of the 2 components with each other and with the other galaxies in the cluster, or its radio morphology. Very little work has been done on the optical morphology. To rectify that lack of data, the authors have obtained charge coupled device (CCD) images of the cD. The authors find from the CCD data that the cD is unlikely to be a bound object and that there is strong evidence for a collision.

  1. Cool Core Disruption in Abell 1763

    NASA Astrophysics Data System (ADS)

    Douglass, Edmund; Blanton, Elizabeth L.; Clarke, Tracy E.; Randall, Scott W.; Edwards, Louise O. V.; Sabry, Ziad

    2017-01-01

    We present the analysis of a 20 ksec Chandra archival observation of the massive galaxy cluster Abell 1763. A model-subtracted image highlighting excess cluster emission reveals a large spiral structure winding outward from the core to a radius of ~950 kpc. We measure the gas of the inner spiral to have significantly lower entropy than non-spiral regions at the same radius. This is consistent with the structure resulting from merger-induced motion of the cluster’s cool core, a phenomenon seen in many systems. Atypical of spiral-hosting clusters, an intact cool core is not detected. Its absence suggests the system has experienced significant disruption since the initial dynamical encounter that set the sloshing core in motion. Along the major axis of the elongated ICM distribution we detect thermal features consistent with the merger event most likely responsible for cool core disruption. The merger-induced transition towards non-cool core status will be discussed. The interaction between the powerful (P1.4 ~ 1026 W Hz-1) cluster-center WAT radio source and its ICM environment will also be discussed.

  2. A technique for increasing the accuracy of the numerical inversion of the Laplace transform with applications

    NASA Technical Reports Server (NTRS)

    Berger, B. S.; Duangudom, S.

    1973-01-01

    A technique is introduced which extends the range of useful approximation of numerical inversion techniques to many cycles of an oscillatory function without requiring either the evaluation of the image function for many values of s or the computation of higher-order terms. The technique consists in reducing a given initial value problem defined over some interval into a sequence of initial value problems defined over a set of subintervals. Several numerical examples demonstrate the utility of the method.

  3. Chandra Observation of the WAT Radio Source/ICM Interaction in Abell 623

    NASA Astrophysics Data System (ADS)

    Anand, Gagandeep; Blanton, Elizabeth L.; Randall, Scott W.; Paterno-Mahler, Rachel; Douglass, Edmund

    2017-01-01

    Galaxy clusters are important objects for studying the physics of the intracluster medium (ICM), galaxy formation and evolution, and cosmological parameters. Clusters containing wide-angle tail (WAT) radio sources are particularly valuable for studies of the interaction between these sources and the surrounding ICM. These sources are thought to form when the ram pressure from the ICM caused by the relative motion between the host radio galaxy and the cluster bends the radio lobes into a distinct wide-angle morphology. We present our results from the analysis of a Chandra observation of the nearby WAT hosting galaxy cluster Abell 623. A clear decrement in X-ray emission is coincident with the southern radio lobe, consistent with being a cavity carved out by the radio source. We present profiles of surface brightness, temperature, density, and pressure and find evidence for a possible shock. Based on the X-ray pressure in the vicinity of the radio lobes and assumptions about the content of the lobes, we estimate the relative ICM velocity required to bend the lobes into the observed angle. We also present spectral model fits to the overall diffuse cluster emission and see no strong signature for a cool core. The sum of the evidence indicates that Abell 623 may be undergoing a large scale cluster-cluster merger.

  4. DISENTANGLING THE ICL WITH THE CHEFs: ABELL 2744 AS A CASE STUDY

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jiménez-Teja, Y.; Dupke, R., E-mail: yojite@iaa.es

    Measurements of the intracluster light (ICL) are still prone to methodological ambiguities, and there are multiple techniques in the literature to address them, mostly based on the binding energy, the local density distribution, or the surface brightness. A common issue with these methods is the a priori assumption of a number of hypotheses on either the ICL morphology, its surface brightness level, or some properties of the brightest cluster galaxy (BCG). The discrepancy in the results is high, and numerical simulations just place a boundary on the ICL fraction in present-day galaxy clusters in the range 10%–50%. We developed amore » new algorithm based on the Chebyshev–Fourier functions to estimate the ICL fraction without relying on any a priori assumption about the physical or geometrical characteristics of the ICL. We are able to not only disentangle the ICL from the galactic luminosity but mark out the limits of the BCG from the ICL in a natural way. We test our technique with the recently released data of the cluster Abell 2744, observed by the Frontier Fields program. The complexity of this multiple merging cluster system and the formidable depth of these images make it a challenging test case to prove the efficiency of our algorithm. We found a final ICL fraction of 19.17 ± 2.87%, which is very consistent with numerical simulations.« less

  5. Galaxy Cluster Abell 1689

    NASA Image and Video Library

    2017-12-08

    Image release August 19, 2010 An international team of astronomers using gravitational lensing observations from the NASA/ESA Hubble Space Telescope has taken an important step forward in the quest to solve the riddle of dark energy, a phenomenon which mysteriously appears to power the Universe's accelerating expansion. Their results appear in the 20 August 2010 issue of the journal Science. This image shows the galaxy cluster Abell 1689, with the mass distribution of the dark matter in the gravitational lens overlaid (in purple). The mass in this lens is made up partly of normal (baryonic) matter and partly of dark matter. Distorted galaxies are clearly visible around the edges of the gravitational lens. The appearance of these distorted galaxies depends on the distribution of matter in the lens and on the relative geometry of the lens and the distant galaxies, as well as on the effect of dark energy on the geometry of the Universe. Credit: NASA, ESA, E. Jullo (JPL/LAM), P. Natarajan (Yale) and J-P. Kneib (LAM). To view a video of this image go to: www.flickr.com/photos/gsfc/4909967467 NASA Goddard Space Flight Center is home to the nation's largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe. Follow us on Twitter Join us on Facebook To read more go to: www.spacetelescope.org/news/heic1014/?utm_source=feedburn...

  6. A gEUD-based inverse planning technique for HDR prostate brachytherapy: Feasibility study

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Giantsoudi, D.; Department of Radiation Oncology, Francis H. Burr Proton Therapy Center, Boston, Massachusetts 02114; Baltas, D.

    2013-04-15

    Purpose: The purpose of this work was to study the feasibility of a new inverse planning technique based on the generalized equivalent uniform dose for image-guided high dose rate (HDR) prostate cancer brachytherapy in comparison to conventional dose-volume based optimization. Methods: The quality of 12 clinical HDR brachytherapy implants for prostate utilizing HIPO (Hybrid Inverse Planning Optimization) is compared with alternative plans, which were produced through inverse planning using the generalized equivalent uniform dose (gEUD). All the common dose-volume indices for the prostate and the organs at risk were considered together with radiobiological measures. The clinical effectiveness of the differentmore » dose distributions was investigated by comparing dose volume histogram and gEUD evaluators. Results: Our results demonstrate the feasibility of gEUD-based inverse planning in HDR brachytherapy implants for prostate. A statistically significant decrease in D{sub 10} or/and final gEUD values for the organs at risk (urethra, bladder, and rectum) was found while improving dose homogeneity or dose conformity of the target volume. Conclusions: Following the promising results of gEUD-based optimization in intensity modulated radiation therapy treatment optimization, as reported in the literature, the implementation of a similar model in HDR brachytherapy treatment plan optimization is suggested by this study. The potential of improved sparing of organs at risk was shown for various gEUD-based optimization parameter protocols, which indicates the ability of this method to adapt to the user's preferences.« less

  7. The Sunyaev-Zeldovich Effect in Abell 370

    NASA Technical Reports Server (NTRS)

    Grego, Laura; Carlstrom, John E.; Joy, Marshall K.; Reese, Erik D.; Holder, Gilbert P.; Patel, Sandeep; Cooray, Asantha R.; Holzappel, William L.

    2000-01-01

    We present interferometric measurements of the Sunyaev-Zeldovich (SZ) effect toward the galaxy cluster Abell 370. These measurements, which directly probe the pressure of the cluster's gas, show the gas distribution to be strongly aspherical, as do the X-ray and gravitational lensing observations. We calculate the cluster's gas mass fraction in two ways. We first compare the gas mass derived from the SZ measurements to the lensing-derived gravitational mass near the critical lensing radius. We also calculate the gas mass fraction from the SZ data by deprojecting the three-dimensional gas density distribution and deriving the total mass under the assumption that the gas is in hydrostatic equilibrium (HSE). We test the assumptions in the HSE method by comparing the total cluster mass implied by the two methods and find that they agree within the errors of the measurement. We discuss the possible system- atic errors in the gas mass fraction measurement and the constraints it places on the matter density parameter, Omega(sub M).

  8. Monte Carlo uncertainty analyses of a bLS inverse-dispersion technique for measuring gas emissions from livestock operations

    USDA-ARS?s Scientific Manuscript database

    The backward Lagrangian stochastic (bLS) inverse-dispersion technique has been used to measure fugitive gas emissions from livestock operations. The accuracy of the bLS technique, as indicated by the percentages of gas recovery in various tracer-release experiments, has generally been within ± 10% o...

  9. A forward model and conjugate gradient inversion technique for low-frequency ultrasonic imaging.

    PubMed

    van Dongen, Koen W A; Wright, William M D

    2006-10-01

    Emerging methods of hyperthermia cancer treatment require noninvasive temperature monitoring, and ultrasonic techniques show promise in this regard. Various tomographic algorithms are available that reconstruct sound speed or contrast profiles, which can be related to temperature distribution. The requirement of a high enough frequency for adequate spatial resolution and a low enough frequency for adequate tissue penetration is a difficult compromise. In this study, the feasibility of using low frequency ultrasound for imaging and temperature monitoring was investigated. The transient probing wave field had a bandwidth spanning the frequency range 2.5-320.5 kHz. The results from a forward model which computed the propagation and scattering of low-frequency acoustic pressure and velocity wave fields were used to compare three imaging methods formulated within the Born approximation, representing two main types of reconstruction. The first uses Fourier techniques to reconstruct sound-speed profiles from projection or Radon data based on optical ray theory, seen as an asymptotical limit for comparison. The second uses backpropagation and conjugate gradient inversion methods based on acoustical wave theory. The results show that the accuracy in localization was 2.5 mm or better when using low frequencies and the conjugate gradient inversion scheme, which could be used for temperature monitoring.

  10. UV spectroscopy including ISM line absorption: of the exciting star of Abell 35

    NASA Astrophysics Data System (ADS)

    Ziegler, M.; Rauch, T.; Werner, K.; Kruk, J. W.

    Reliable spectral analysis that is based on high-resolution UV observations requires an adequate, simultaneous modeling of the interstellar line absorption and reddening. In the case of the central star of the planetary nebula Abell 35, BD-22 3467, we demonstrate our current standard spectral-analysis method that is based on the Tübingen NLTE Model-Atmosphere Package (TMAP). We present an on- going spectral analysis of FUSE and HST/STIS observations of BD-22 3467.

  11. Shocking Tails in the Major Merger Abell 2744

    NASA Astrophysics Data System (ADS)

    Owers, Matt S.; Couch, Warrick J.; Nulsen, Paul E. J.; Randall, Scott W.

    2012-05-01

    We identify four rare "jellyfish" galaxies in Hubble Space Telescope imagery of the major merger cluster Abell 2744. These galaxies harbor trails of star-forming knots and filaments which have formed in situ in gas tails stripped from the parent galaxies, indicating they are in the process of being transformed by the environment. Further evidence for rapid transformation in these galaxies comes from their optical spectra, which reveal starburst, poststarburst, and active galactic nucleus features. Most intriguingly, three of the jellyfish galaxies lie near intracluster medium features associated with a merging "Bullet-like" subcluster and its shock front detected in Chandra X-ray images. We suggest that the high-pressure merger environment may be responsible for the star formation in the gaseous tails. This provides observational evidence for the rapid transformation of galaxies during the violent core passage phase of a major cluster merger.

  12. SHOCKING TAILS IN THE MAJOR MERGER ABELL 2744

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Owers, Matt S.; Couch, Warrick J.; Nulsen, Paul E. J.

    We identify four rare 'jellyfish' galaxies in Hubble Space Telescope imagery of the major merger cluster Abell 2744. These galaxies harbor trails of star-forming knots and filaments which have formed in situ in gas tails stripped from the parent galaxies, indicating they are in the process of being transformed by the environment. Further evidence for rapid transformation in these galaxies comes from their optical spectra, which reveal starburst, poststarburst, and active galactic nucleus features. Most intriguingly, three of the jellyfish galaxies lie near intracluster medium features associated with a merging 'Bullet-like' subcluster and its shock front detected in Chandra X-raymore » images. We suggest that the high-pressure merger environment may be responsible for the star formation in the gaseous tails. This provides observational evidence for the rapid transformation of galaxies during the violent core passage phase of a major cluster merger.« less

  13. Verification of the helioseismology travel-time measurement technique and the inversion procedure for sound speed using artificial data

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Parchevsky, K. V.; Zhao, J.; Hartlep, T.

    We performed three-dimensional numerical simulations of the solar surface acoustic wave field for the quiet Sun and for three models with different localized sound-speed perturbations in the interior with deep, shallow, and two-layer structures. We used the simulated data generated by two solar acoustics codes that employ the same standard solar model as a background model, but utilize different integration techniques and different models of stochastic wave excitation. Acoustic travel times were measured using a time-distance helioseismology technique, and compared with predictions from ray theory frequently used for helioseismic travel-time inversions. It is found that the measured travel-time shifts agreemore » well with the helioseismic theory for sound-speed perturbations, and for the measurement procedure with and without phase-speed filtering of the oscillation signals. This testing verifies the whole measuring-filtering-inversion procedure for static sound-speed anomalies with small amplitude inside the Sun outside regions of strong magnetic field. It is shown that the phase-speed filtering, frequently used to extract specific wave packets and improve the signal-to-noise ratio, does not introduce significant systematic errors. Results of the sound-speed inversion procedure show good agreement with the perturbation models in all cases. Due to its smoothing nature, the inversion procedure may overestimate sound-speed variations in regions with sharp gradients of the sound-speed profile.« less

  14. Color Dispersion as an Indicator of Stellar Population Complexity: Insights from the Pixel Color–Magnitude Diagrams of 32 Bright Galaxies in Abell 1139 and Abell 2589

    NASA Astrophysics Data System (ADS)

    Lee, Joon Hyeop; Pak, Mina; Lee, Hye-Ran; Oh, Sree

    2018-04-01

    We investigate the properties of bright galaxies of various morphological types in Abell 1139 and Abell 2589, using pixel color–magnitude diagram (pCMD) analysis. The sample contains 32 galaxies brighter than M r = ‑21.3 mag with spectroscopic redshifts, which are deeply imaged in the g and r bands using the MegaCam mounted on the Canada–France–Hawaii Telescope. After masking contaminants with two-step procedures, we examine how the detailed properties in the pCMDs depend on galaxy morphology and infrared color. The mean g ‑ r color as a function of surface brightness (μ r ) in the pCMD of a galaxy shows good performance in distinguishing between early- and late-type galaxies, but it is not perfect because of the similarity between elliptical galaxies and bulge-dominated spiral galaxies. On the other hand, the g ‑ r color dispersion as a function of μ r works better. We find that the best set of parameters for galaxy classification is a combination of the minimum color dispersion at μ r ≤ 21.2 mag arcsec‑2 and the maximum color dispersion at 20.0 ≤ μ r ≤ 21.0 mag arcsec‑2 the latter reflects the complexity of stellar populations at the disk component in a typical spiral galaxy. Finally, the color dispersion measurements of an elliptical galaxy appear to be correlated with the Wide-field Infrared Survey Explorer infrared color ([4.6]–[12]). This indicates that the complexity of stellar populations in an elliptical galaxy is related to its recent star formation activities. From this observational evidence, we infer that gas-rich minor mergers or gas interactions may have usually occurred during the recent growth of massive elliptical galaxies.

  15. Electron beam dispersion measurements in nitrogen using two-dimensional imaging of N2(+) fluorescence

    NASA Technical Reports Server (NTRS)

    Clapp, L. H.; Twiss, R. G.; Cattolica, R. J.

    1991-01-01

    Experimental results are presented related to the radial spread of fluorescence excited by 10 and 20 KeV electron beams passing through nonflowing rarefied nitrogen at 293 K. An imaging technique for obtaining species distributions from measured beam-excited fluorescence is described, based on a signal inversion scheme mathematically equivalent to the inversion of the Abel integral equation. From fluorescence image data, measurements of beam radius, integrated signal intensity, and spatially resolved distributions of N2(+) first-negative-band fluorescence-emitting species have been made. Data are compared with earlier measurements and with an heuristic beam spread model.

  16. Statistical analysis of catalogs of extragalactic objects. II - The Abell catalog of rich clusters

    NASA Technical Reports Server (NTRS)

    Hauser, M. G.; Peebles, P. J. E.

    1973-01-01

    The results of a power-spectrum analysis are presented for the distribution of clusters in the Abell catalog. Clear and direct evidence is found for superclusters with small angular scale, in agreement with the recent study of Bogart and Wagoner (1973). It is also found that the degree and angular scale of the apparent superclustering varies with distance in the manner expected if the clustering is intrinsic to the spatial distribution rather than a consequence of patchy local obscuration.

  17. A Statistical Study of Multiply Imaged Systems in the Lensing Cluster Abell 68

    NASA Astrophysics Data System (ADS)

    Richard, Johan; Kneib, Jean-Paul; Jullo, Eric; Covone, Giovanni; Limousin, Marceau; Ellis, Richard; Stark, Daniel; Bundy, Kevin; Czoske, Oliver; Ebeling, Harald; Soucail, Geneviève

    2007-06-01

    We have carried out an extensive spectroscopic survey with the Keck and VLT telescopes, targeting lensed galaxies in the background of the massive cluster Abell 68. Spectroscopic measurements are obtained for 26 lensed images, including a distant galaxy at z=5.4. Redshifts have been determined for 5 out of 7 multiple-image systems. Through a careful modeling of the mass distribution in the strongly lensed regime, we derive a mass estimate of 5.3×1014 Msolar within 500 kpc. Our mass model is then used to constrain the redshift distribution of the remaining multiply imaged and singly imaged sources. This enables us to examine the physical properties for a subsample of 7 Lyα emitters at 1.7<~z<~5.5, whose unlensed luminosities of ~=1041 ergs s-1 are fainter than similar objects found in blank fields. Of particular interest is an extended Lyα emission region surrounding a highly magnified source at z=2.6, detected in VIMOS integral field spectroscopy data. The physical scale of the most distant lensed source at z=5.4 is very small (<300 pc), similar to the lensed z~5.6 emitter reported by Ellis et al. in Abell 2218. New photometric data available for Abell 2218 allow for a direct comparison between these two unique objects. Our survey illustrates the practicality of using lensing clusters to probe the faint end of the z~2-5 Lyα luminosity function in a manner that is complementary to blank-field narrowband surveys. Data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Also based on observations collected at the Very Large Telescope (Antu/UT1 and Melipal/UT3), European Southern Observatory, Paranal, Chile (ESO programs 070.A-0643 and 073.A-0774), the NASA/ESA Hubble Space Telescope

  18. Electromagnetic modelling, inversion and data-processing techniques for GPR: ongoing activities in Working Group 3 of COST Action TU1208

    NASA Astrophysics Data System (ADS)

    Pajewski, Lara; Giannopoulos, Antonis; van der Kruk, Jan

    2015-04-01

    This work aims at presenting the ongoing research activities carried out in Working Group 3 (WG3) 'EM methods for near-field scattering problems by buried structures; data processing techniques' of the COST (European COoperation in Science and Technology) Action TU1208 'Civil Engineering Applications of Ground Penetrating Radar' (www.GPRadar.eu). The principal goal of the COST Action TU1208 is to exchange and increase scientific-technical knowledge and experience of GPR techniques in civil engineering, simultaneously promoting throughout Europe the effective use of this safe and non-destructive technique in the monitoring of infrastructures and structures. WG3 is structured in four Projects. Project 3.1 deals with 'Electromagnetic modelling for GPR applications.' Project 3.2 is concerned with 'Inversion and imaging techniques for GPR applications.' The topic of Project 3.3 is the 'Development of intrinsic models for describing near-field antenna effects, including antenna-medium coupling, for improved radar data processing using full-wave inversion.' Project 3.4 focuses on 'Advanced GPR data-processing algorithms.' Electromagnetic modeling tools that are being developed and improved include the Finite-Difference Time-Domain (FDTD) technique and the spectral domain Cylindrical-Wave Approach (CWA). One of the well-known freeware and versatile FDTD simulators is GprMax that enables an improved realistic representation of the soil/material hosting the sought structures and of the GPR antennas. Here, input/output tools are being developed to ease the definition of scenarios and the visualisation of numerical results. The CWA expresses the field scattered by subsurface two-dimensional targets with arbitrary cross-section as a sum of cylindrical waves. In this way, the interaction is taken into account of multiple scattered fields within the medium hosting the sought targets. Recently, the method has been extended to deal with through-the-wall scenarios. One of the

  19. Error analysis applied to several inversion techniques used for the retrieval of middle atmospheric constituents from limb-scanning MM-wave spectroscopic measurements

    NASA Technical Reports Server (NTRS)

    Puliafito, E.; Bevilacqua, R.; Olivero, J.; Degenhardt, W.

    1992-01-01

    The formal retrieval error analysis of Rodgers (1990) allows the quantitative determination of such retrieval properties as measurement error sensitivity, resolution, and inversion bias. This technique was applied to five numerical inversion techniques and two nonlinear iterative techniques used for the retrieval of middle atmospheric constituent concentrations from limb-scanning millimeter-wave spectroscopic measurements. It is found that the iterative methods have better vertical resolution, but are slightly more sensitive to measurement error than constrained matrix methods. The iterative methods converge to the exact solution, whereas two of the matrix methods under consideration have an explicit constraint, the sensitivity of the solution to the a priori profile. Tradeoffs of these retrieval characteristics are presented.

  20. Evolution of the UV upturn in cluster galaxies: Abell 1689

    NASA Astrophysics Data System (ADS)

    Ali, S. S.; Bremer, M. N.; Phillipps, S.; De Propris, R.

    2018-05-01

    We have measured the strength of the UV upturn for red sequence galaxies in the Abell 1689 cluster at z = 0.18, reaching to or below the L* level and therefore probing the general evolution of the upturn phenomenon. We find that the range of UV upturn strengths in the population as a whole has not declined over the past 2.2 Gyrs. This is consistent with a model where hot horizontal branch stars, produced by a Helium-enriched population, provide the required UV flux. Based on local counterparts, this interpretation of the result implies Helium abundances of at least 1.5 times the primordial value for this HB population, along with high formation and assembly redshifts for the galaxies and at least a subset of their stellar populations.

  1. Sodium ion conducting polymer electrolyte membrane prepared by phase inversion technique

    NASA Astrophysics Data System (ADS)

    Harshlata, Mishra, Kuldeep; Rai, D. K.

    2018-04-01

    A mechanically stable porous polymer membrane of Poly(vinylidene fluoride-hexafluoropropylene) has been prepared by phase inversion technique using steam as a non-solvent. The membrane possesses semicrystalline network with enhanced amorphicity as observed by X-ray diffraction. The membrane has been soaked in an electrolyte solution of 0.5M NaPF6 in Ethylene Carbonate/Propylene Carbonate (1:1) to obtain the gel polymer electrolyte. The porosity and electrolyte uptake of the membrane have been found to be 67% and 220% respectively. The room temperature ionic conductivity of the membrane has been obtained as ˜ 0.3 mS cm-1. The conductivity follows Arrhenius behavior with temperature and gives activation energy as 0.8 eV. The membrane has been found to possess significantly large electrochemical stability window of 5.0 V.

  2. A photometric analysis of Abell 1689: two-dimensional multistructure decomposition, morphological classification and the Fundamental Plane

    NASA Astrophysics Data System (ADS)

    Dalla Bontà, E.; Davies, R. L.; Houghton, R. C. W.; D'Eugenio, F.; Méndez-Abreu, J.

    2018-02-01

    We present a photometric analysis of 65 galaxies in the rich cluster Abell 1689 at z = 0.183, using the Hubble Space Telescope Advanced Camera for Surveys archive images in the rest-frame V band. We perform two-dimensional multicomponent photometric decomposition of each galaxy adopting different models of the surface-brightness distribution. We present an accurate morphological classification for each of the sample galaxies. For 50 early-type galaxies, we fit both a de Vaucouleurs law and a Sérsic law; S0s are modelled by also including a disc component described by an exponential law. Bars of SB0s are described by the profile of a Ferrers ellipsoid. For the 15 spirals, we model a Sérsic bulge, exponential disc and, when required, a Ferrers bar component. We derive the Fundamental Plane (FP) by fitting 40 early-type galaxies in the sample, using different surface-brightness distributions. We find that the tightest plane is that derived by Sérsic bulges. We find that bulges of spirals lie on the same relation. The FP is better defined by the bulges alone rather than the entire galaxies. Comparison with local samples shows both an offset and rotation in the FP of Abell 1689.

  3. An Innovations-Based Noise Cancelling Technique on Inverse Kepstrum Whitening Filter and Adaptive FIR Filter in Beamforming Structure

    PubMed Central

    Jeong, Jinsoo

    2011-01-01

    This paper presents an acoustic noise cancelling technique using an inverse kepstrum system as an innovations-based whitening application for an adaptive finite impulse response (FIR) filter in beamforming structure. The inverse kepstrum method uses an innovations-whitened form from one acoustic path transfer function between a reference microphone sensor and a noise source so that the rear-end reference signal will then be a whitened sequence to a cascaded adaptive FIR filter in the beamforming structure. By using an inverse kepstrum filter as a whitening filter with the use of a delay filter, the cascaded adaptive FIR filter estimates only the numerator of the polynomial part from the ratio of overall combined transfer functions. The test results have shown that the adaptive FIR filter is more effective in beamforming structure than an adaptive noise cancelling (ANC) structure in terms of signal distortion in the desired signal and noise reduction in noise with nonminimum phase components. In addition, the inverse kepstrum method shows almost the same convergence level in estimate of noise statistics with the use of a smaller amount of adaptive FIR filter weights than the kepstrum method, hence it could provide better computational simplicity in processing. Furthermore, the rear-end inverse kepstrum method in beamforming structure has shown less signal distortion in the desired signal than the front-end kepstrum method and the front-end inverse kepstrum method in beamforming structure. PMID:22163987

  4. A series of shocks and edges in Abell 2219

    DOE PAGES

    Canning, R. E. A.; Allen, S. W.; Applegate, D. E.; ...

    2016-09-22

    Here, we present deep, 170 ks, Chandra X-ray observations of Abell 2219 (z = 0.23), one of the hottest and most X-ray luminous clusters known, and which is experiencing a major merger event. We discover a ‘horseshoe’ of high-temperature gas surrounding the ram-pressure-stripped, bright, hot, X-ray cores. We confirm an X-ray shock front located north-west of the X-ray centroid and along the projected merger axis. We also find a second shock front to the south-east of the X-ray centroid making this only the second cluster where both the shock and reverse shock are confirmed with X-ray temperature measurements. We alsomore » present evidence for a possible sloshing cold front in the ‘remnant tail’ of one of the sub-cluster cores. The cold front and north-west shock front geometrically bound the radio halo and appear to be directly influencing the radio properties of the cluster.« less

  5. Research and application of spectral inversion technique in frequency domain to improve resolution of converted PS-wave

    NASA Astrophysics Data System (ADS)

    Zhang, Hua; He, Zhen-Hua; Li, Ya-Lin; Li, Rui; He, Guamg-Ming; Li, Zhong

    2017-06-01

    Multi-wave exploration is an effective means for improving precision in the exploration and development of complex oil and gas reservoirs that are dense and have low permeability. However, converted wave data is characterized by a low signal-to-noise ratio and low resolution, because the conventional deconvolution technology is easily affected by the frequency range limits, and there is limited scope for improving its resolution. The spectral inversion techniques is used to identify λ/8 thin layers and its breakthrough regarding band range limits has greatly improved the seismic resolution. The difficulty associated with this technology is how to use the stable inversion algorithm to obtain a high-precision reflection coefficient, and then to use this reflection coefficient to reconstruct broadband data for processing. In this paper, we focus on how to improve the vertical resolution of the converted PS-wave for multi-wave data processing. Based on previous research, we propose a least squares inversion algorithm with a total variation constraint, in which we uses the total variance as a priori information to solve under-determined problems, thereby improving the accuracy and stability of the inversion. Here, we simulate the Gaussian fitting amplitude spectrum to obtain broadband wavelet data, which we then process to obtain a higher resolution converted wave. We successfully apply the proposed inversion technology in the processing of high-resolution data from the Penglai region to obtain higher resolution converted wave data, which we then verify in a theoretical test. Improving the resolution of converted PS-wave data will provide more accurate data for subsequent velocity inversion and the extraction of reservoir reflection information.

  6. Application of a XMM-Newton EPIC Monte Carlo to Analysis And Interpretation of Data for Abell 1689, RXJ0658-55 And the Centaurus Clusters of Galaxies

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Andersson, Karl E.; /Stockholm U. /SLAC; Peterson, J.R.

    2007-04-17

    We propose a new Monte Carlo method to study extended X-ray sources with the European Photon Imaging Camera (EPIC) aboard XMM Newton. The Smoothed Particle Inference (SPI) technique, described in a companion paper, is applied here to the EPIC data for the clusters of galaxies Abell 1689, Centaurus and RXJ 0658-55 (the ''bullet cluster''). We aim to show the advantages of this method of simultaneous spectral-spatial modeling over traditional X-ray spectral analysis. In Abell 1689 we confirm our earlier findings about structure in temperature distribution and produce a high resolution temperature map. We also confirm our findings about velocity structuremore » within the gas. In the bullet cluster, RXJ 0658-55, we produce the highest resolution temperature map ever to be published of this cluster allowing us to trace what looks like the motion of the bullet in the cluster. We even detect a south to north temperature gradient within the bullet itself. In the Centaurus cluster we detect, by dividing up the luminosity of the cluster in bands of gas temperatures, a striking feature to the north-east of the cluster core. We hypothesize that this feature is caused by a subcluster left over from a substantial merger that slightly displaced the core. We conclude that our method is very powerful in determining the spatial distributions of plasma temperatures and very useful for systematic studies in cluster structure.« less

  7. Tomographic inversion of satellite photometry

    NASA Technical Reports Server (NTRS)

    Solomon, S. C.; Hays, P. B.; Abreu, V. J.

    1984-01-01

    An inversion algorithm capable of reconstructing the volume emission rate of thermospheric airglow features from satellite photometry has been developed. The accuracy and resolution of this technique are investigated using simulated data, and the inversions of several sets of observations taken by the Visible Airglow Experiment are presented.

  8. Vitamins and Violence: Can Micronutrients Make Students Behave, Schools Safer and Test Scores Better? The Abell Report. Volume 23, No.6

    ERIC Educational Resources Information Center

    Rodgers, Joann Ellison

    2010-01-01

    The notion that vitamins, minerals, and other "supplemental" nutrients profoundly change behavior, mood, and intellect has origins as old as recorded history. Research has indeed suggested connections between nutrient deficiencies and behavior problems, but correlations are not the same as causality. This "Abell Report" is an…

  9. Inversion group (IG) fitting: A new T1 mapping method for modified look-locker inversion recovery (MOLLI) that allows arbitrary inversion groupings and rest periods (including no rest period).

    PubMed

    Sussman, Marshall S; Yang, Issac Y; Fok, Kai-Ho; Wintersperger, Bernd J

    2016-06-01

    The Modified Look-Locker Inversion Recovery (MOLLI) technique is used for T1 mapping in the heart. However, a drawback of this technique is that it requires lengthy rest periods in between inversion groupings to allow for complete magnetization recovery. In this work, a new MOLLI fitting algorithm (inversion group [IG] fitting) is presented that allows for arbitrary combinations of inversion groupings and rest periods (including no rest period). Conventional MOLLI algorithms use a three parameter fitting model. In IG fitting, the number of parameters is two plus the number of inversion groupings. This increased number of parameters permits any inversion grouping/rest period combination. Validation was performed through simulation, phantom, and in vivo experiments. IG fitting provided T1 values with less than 1% discrepancy across a range of inversion grouping/rest period combinations. By comparison, conventional three parameter fits exhibited up to 30% discrepancy for some combinations. The one drawback with IG fitting was a loss of precision-approximately 30% worse than the three parameter fits. IG fitting permits arbitrary inversion grouping/rest period combinations (including no rest period). The cost of the algorithm is a loss of precision relative to conventional three parameter fits. Magn Reson Med 75:2332-2340, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

  10. Revisiting Abell 2744: a powerful synergy of the GLASS spectroscopy and the HFF photometry.

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Borello Schmidt, Kasper; Treu, Tommaso

    2015-08-01

    We present new emission line identifications and improve the strong lensing reconstruction of the massive cluster Abell 2744 using the Grism Lens-Amplified Survey from Space (GLASS) observations and the full depth of the Hubble Frontier Fields (HFF) imaging. We performed a blind and targeted search for emission lines in objects within the full field of view (FoV) of the GLASS prime pointings, including all the previously known multiple arc images. We report over 50 high quality spectroscopic redshifts, 4 of which are for the arc images. We also present an extensive analysis based on the HFF photometry, measuring the colors and photometric redshifts of all objects within the FoV, and comparing the spectroscopic and photometric results of the same ensemble of sources. In order to improve the lens model of Abell 2744, we develop a rigorous alogorithm to screen arc images, based on their colors and morphology, and selecting the most reliable ones to use. As a result, 21 systems (corresponding to 59 images) pass the screening process and are used to reconstruct the gravitational potential of the cluster pixellated on an adaptive mesh. The resulting total mass distribution is compared with a stellar mass map obtained from the deep Spitzer Frontier Fields data in a fashion very similar to the reduction of the Spitzer UltRa Faint SUrvey Program (SURFS UP) clusters, in order to study the relative distribution of stars and dark matter in the cluster. The maps of convergence, shear, and magnification are made publicly available in the standard HFF format.

  11. The investigation of advanced remote sensing, radiative transfer and inversion techniques for the measurement of atmospheric constituents

    NASA Technical Reports Server (NTRS)

    Deepak, Adarsh; Wang, Pi-Huan

    1985-01-01

    The research program is documented for developing space and ground-based remote sensing techniques performed during the period from December 15, 1977 to March 15, 1985. The program involved the application of sophisticated radiative transfer codes and inversion methods to various advanced remote sensing concepts for determining atmospheric constituents, particularly aerosols. It covers detailed discussions of the solar aureole technique for monitoring columnar aerosol size distribution, and the multispectral limb scattered radiance and limb attenuated radiance (solar occultation) techniques, as well as the upwelling scattered solar radiance method for determining the aerosol and gaseous characteristics. In addition, analytical models of aerosol size distribution and simulation studies of the limb solar aureole radiance technique and the variability of ozone at high altitudes during satellite sunrise/sunset events are also described in detail.

  12. Optimal Inversion Parameters for Full Waveform Inversion using OBS Data Set

    NASA Astrophysics Data System (ADS)

    Kim, S.; Chung, W.; Shin, S.; Kim, D.; Lee, D.

    2017-12-01

    In recent years, full Waveform Inversion (FWI) has been the most researched technique in seismic data processing. It uses the residuals between observed and modeled data as an objective function; thereafter, the final subsurface velocity model is generated through a series of iterations meant to minimize the residuals.Research on FWI has expanded from acoustic media to elastic media. In acoustic media, the subsurface property is defined by P-velocity; however, in elastic media, properties are defined by multiple parameters, such as P-velocity, S-velocity, and density. Further, the elastic media can also be defined by Lamé constants, density or impedance PI, SI; consequently, research is being carried out to ascertain the optimal parameters.From results of advanced exploration equipment and Ocean Bottom Seismic (OBS) survey, it is now possible to obtain multi-component seismic data. However, to perform FWI on these data and generate an accurate subsurface model, it is important to determine optimal inversion parameters among (Vp, Vs, ρ), (λ, μ, ρ), and (PI, SI) in elastic media. In this study, staggered grid finite difference method was applied to simulate OBS survey. As in inversion, l2-norm was set as objective function. Further, the accurate computation of gradient direction was performed using the back-propagation technique and its scaling was done using the Pseudo-hessian matrix.In acoustic media, only Vp is used as the inversion parameter. In contrast, various sets of parameters, such as (Vp, Vs, ρ) and (λ, μ, ρ) can be used to define inversion in elastic media. Therefore, it is important to ascertain the parameter that gives the most accurate result for inversion with OBS data set.In this study, we generated Vp and Vs subsurface models by using (λ, μ, ρ) and (Vp, Vs, ρ) as inversion parameters in every iteration, and compared the final two FWI results.This research was supported by the Basic Research Project(17-3312) of the Korea Institute of

  13. Time-reversal and Bayesian inversion

    NASA Astrophysics Data System (ADS)

    Debski, Wojciech

    2017-04-01

    Probabilistic inversion technique is superior to the classical optimization-based approach in all but one aspects. It requires quite exhaustive computations which prohibit its use in huge size inverse problems like global seismic tomography or waveform inversion to name a few. The advantages of the approach are, however, so appealing that there is an ongoing continuous afford to make the large inverse task as mentioned above manageable with the probabilistic inverse approach. One of the perspective possibility to achieve this goal relays on exploring the internal symmetry of the seismological modeling problems in hand - a time reversal and reciprocity invariance. This two basic properties of the elastic wave equation when incorporating into the probabilistic inversion schemata open a new horizons for Bayesian inversion. In this presentation we discuss the time reversal symmetry property, its mathematical aspects and propose how to combine it with the probabilistic inverse theory into a compact, fast inversion algorithm. We illustrate the proposed idea with the newly developed location algorithm TRMLOC and discuss its efficiency when applied to mining induced seismic data.

  14. Mass dependent galaxy transformation mechanisms in the complex environment of SuperGroup Abell 1882

    NASA Astrophysics Data System (ADS)

    Sengupta, Aparajita

    We present our data and results from panchromatic photometry and optical spectrometry of the nearest (extremely rich) filamentary large scale structure, SuperGroup Abell 1882. It is a precursor of a cluster and is an inevitable part of the narrative in the study of galaxy transformations. There has been strong empirical evidence over the past three decades that galaxy environment affects galaxy properties. Blue disky galaxies transform into red bulge-like galaxies as they traverse into the deeper recesses of a cluster. However, we have little insight into the story of galaxy evolution in the early stages of cluster formation. Besides, in relaxed clusters that have been studied extensively, several evolutionary mechanisms take effect on similar spatial and temporal scales, making it almost impossible to disentangle different local and global mechanisms. A SuperGroup on the other hand, has a shallower dark-matter potential. Here, the accreting galaxies are subjected to evolutionary mechanisms over larger time and spatial scales. This separates processes that are otherwise superimposed in rich cluster-filament interfaces. As has been found from cluster studies, galaxy color and morphology tie very strongly with local galaxy density even in a complex and nascent structure like Abell 1882. Our major results indicate that there is a strong dependence of galaxy transformations on the galaxy masses themselves. Mass- dependent evolutionary mechanisms affect galaxies at different spatial scales. The galaxy color also varies with radial projected distance from the assumed center of the structure for a constant local galaxy density, indicating the underlying large scale structure as a second order evolutionary driver. We have looked for clues to the types of mechanisms that might cause the transformations at various mass regimes. We have found the thoroughly quenched low mass galaxies confined to the groups, whereas there are evidences of intermediate-mass quenched galaxies

  15. In-depth study of 16CygB using inversion techniques

    NASA Astrophysics Data System (ADS)

    Buldgen, G.; Salmon, S. J. A. J.; Reese, D. R.; Dupret, M. A.

    2016-12-01

    Context. The 16Cyg binary system hosts the solar-like Kepler targets with the most stringent observational constraints. Indeed, we benefit from very high quality oscillation spectra, as well as spectroscopic and interferometric observations. Moreover, this system is particularly interesting since both stars are very similar in mass but the A component is orbited by a red dwarf, whereas the B component is orbited by a Jovian planet and thus could have formed a more complex planetary system. In our previous study, we showed that seismic inversions of integrated quantities could be used to constrain microscopic diffusion in the A component. In this study, we analyse the B component in the light of a more regularised inversion. Aims: We wish to analyse independently the B component of the 16Cyg binary system using the inversion of an indicator dedicated to analyse core conditions, denoted tu. Using this independent determination, we wish to analyse any differences between both stars due to the potential influence of planetary formation on stellar structure and/or their respective evolution. Methods: First, we recall the observational constraints for 16CygB and the method we used to generate reference stellar models of this star. We then describe how we improved the inversion and how this approach could be used for future targets with a sufficient number of observed frequencies. The inversion results were then used to analyse the differences between the A and B components. Results: The inversion of the tu indicator for 16CygB shows a disagreement with models including microscopic diffusion and sharing the chemical composition previously derived for 16CygA. We show that small changes in chemical composition are insufficient to solve the problem but that extra mixing can account for the differences seen between both stars. We use a parametric approach to analyse the impact of extra mixing in the form of turbulent diffusion on the behaviour of the tu values. We conclude on

  16. Eigenproblem solution by a combined Sturm sequence and inverse iteration technique.

    NASA Technical Reports Server (NTRS)

    Gupta, K. K.

    1973-01-01

    Description of an efficient and numerically stable algorithm, along with a complete listing of the associated computer program, developed for the accurate computation of specified roots and associated vectors of the eigenvalue problem Aq = lambda Bq with band symmetric A and B, B being also positive-definite. The desired roots are first isolated by the Sturm sequence procedure; then a special variant of the inverse iteration technique is applied for the individual determination of each root along with its vector. The algorithm fully exploits the banded form of relevant matrices, and the associated program written in FORTRAN V for the JPL UNIVAC 1108 computer proves to be most significantly economical in comparison to similar existing procedures. The program may be conveniently utilized for the efficient solution of practical engineering problems, involving free vibration and buckling analysis of structures. Results of such analyses are presented for representative structures.

  17. Shocks and Bubbles in a Deep Chandra Observation of the Cooling Flow Cluster Abell 2052

    DTIC Science & Technology

    2009-01-01

    the bubble rims related to radio source outbursts have been found in a few clusters including M87/ Virgo (Forman et al. 2005), Hydra A (Nulsen et al...Printed in the U.S.A. SHOCKS AND BUBBLES IN A DEEP CHANDRA OBSERVATION OF THE COOLING FLOW CLUSTER ABELL 2052 E. L. Blanton1, S. W. Randall2, E. M...Douglass1, C. L. Sarazin3, T. E. Clarke4,5, and B. R. McNamara2,6,7 1 Institute for Astrophysical Research , Boston University, 725 Commonwealth Avenue

  18. Tomographic reconstruction of tokamak plasma light emission from single image using wavelet-vaguelette decomposition

    NASA Astrophysics Data System (ADS)

    Nguyen van yen, R.; Fedorczak, N.; Brochard, F.; Bonhomme, G.; Schneider, K.; Farge, M.; Monier-Garbet, P.

    2012-01-01

    Images acquired by cameras installed in tokamaks are difficult to interpret because the three-dimensional structure of the plasma is flattened in a non-trivial way. Nevertheless, taking advantage of the slow variation of the fluctuations along magnetic field lines, the optical transformation may be approximated by a generalized Abel transform, for which we propose an inversion technique based on the wavelet-vaguelette decomposition. After validation of the new method using an academic test case and numerical data obtained with the Tokam 2D code, we present an application to an experimental movie obtained in the tokamak Tore Supra. A comparison with a classical regularization technique for ill-posed inverse problems, the singular value decomposition, allows us to assess the efficiency. The superiority of the wavelet-vaguelette technique is reflected in preserving local features, such as blobs and fronts, in the denoised emissivity map.

  19. Inversion of particle-size distribution from angular light-scattering data with genetic algorithms.

    PubMed

    Ye, M; Wang, S; Lu, Y; Hu, T; Zhu, Z; Xu, Y

    1999-04-20

    A stochastic inverse technique based on a genetic algorithm (GA) to invert particle-size distribution from angular light-scattering data is developed. This inverse technique is independent of any given a priori information of particle-size distribution. Numerical tests show that this technique can be successfully applied to inverse problems with high stability in the presence of random noise and low susceptibility to the shape of distributions. It has also been shown that the GA-based inverse technique is more efficient in use of computing time than the inverse Monte Carlo method recently developed by Ligon et al. [Appl. Opt. 35, 4297 (1996)].

  20. The Sunyaev-Zel'dovich Effect Spectrum of Abell 2163

    NASA Technical Reports Server (NTRS)

    LaRoque, S. J.; Carlstrom, J. E.; Reese, E. D.; Holder, G. P.; Holzapfel, W. L.; Joy, M.; Grego, L.; Six, N. Frank (Technical Monitor)

    2002-01-01

    We present an interferometric measurement of the Sunyaev-Zel'dovich effect (SZE) at 1 cm for the galaxy cluster Abell 2163. We combine this data point with previous measurements at 1.1, 1.4, and 2.1 mm from the SuZIE experiment to construct the most complete SZE spectrum to date. The intensity in four wavelength bands is fit to determine the Compton y-parameter (y(sub 0)) and the peculiar velocity (v(sub p)) for this cluster. Our results are y(sub 0) = 3.56((sup +0.41+0.27)(sub -0.41-0.19)) X 10(exp -4) and v(sub p) = 410((sup +1030+460) (sub -850-440)) km s(exp -1) where we list statistical and systematic uncertainties, respectively, at 68% confidence. These results include corrections for contamination by Galactic dust emission. We find less contamination by dust emission than previously reported. The dust emission is distributed over much larger angular scales than the cluster signal and contributes little to the measured signal when the details of the SZE observing strategy are taken into account.

  1. Tackling missing radiographic progression data: multiple imputation technique compared with inverse probability weights and complete case analysis.

    PubMed

    Descalzo, Miguel Á; Garcia, Virginia Villaverde; González-Alvaro, Isidoro; Carbonell, Jordi; Balsa, Alejandro; Sanmartí, Raimon; Lisbona, Pilar; Hernandez-Barrera, Valentín; Jiménez-Garcia, Rodrigo; Carmona, Loreto

    2013-02-01

    To describe the results of different statistical ways of addressing radiographic outcome affected by missing data--multiple imputation technique, inverse probability weights and complete case analysis--using data from an observational study. A random sample of 96 RA patients was selected for a follow-up study in which radiographs of hands and feet were scored. Radiographic progression was tested by comparing the change in the total Sharp-van der Heijde radiographic score (TSS) and the joint erosion score (JES) from baseline to the end of the second year of follow-up. MI technique, inverse probability weights in weighted estimating equation (WEE) and CC analysis were used to fit a negative binomial regression. Major predictors of radiographic progression were JES and joint space narrowing (JSN) at baseline, together with baseline disease activity measured by DAS28 for TSS and MTX use for JES. Results from CC analysis show larger coefficients and s.e.s compared with MI and weighted techniques. The results from the WEE model were quite in line with those of MI. If it seems plausible that CC or MI analysis may be valid, then MI should be preferred because of its greater efficiency. CC analysis resulted in inefficient estimates or, translated into non-statistical terminology, could guide us into inaccurate results and unwise conclusions. The methods discussed here will contribute to the use of alternative approaches for tackling missing data in observational studies.

  2. The Mass Function of Abell Clusters

    NASA Astrophysics Data System (ADS)

    Chen, J.; Huchra, J. P.; McNamara, B. R.; Mader, J.

    1998-12-01

    The velocity dispersion and mass functions for rich clusters of galaxies provide important constraints on models of the formation of Large-Scale Structure (e.g., Frenk et al. 1990). However, prior estimates of the velocity dispersion or mass function for galaxy clusters have been based on either very small samples of clusters (Bahcall and Cen 1993; Zabludoff et al. 1994) or large but incomplete samples (e.g., the Girardi et al. (1998) determination from a sample of clusters with more than 30 measured galaxy redshifts). In contrast, we approach the problem by constructing a volume-limited sample of Abell clusters. We collected individual galaxy redshifts for our sample from two major galaxy velocity databases, the NASA Extragalactic Database, NED, maintained at IPAC, and ZCAT, maintained at SAO. We assembled a database with velocity information for possible cluster members and then selected cluster members based on both spatial and velocity data. Cluster velocity dispersions and masses were calculated following the procedures of Danese, De Zotti, and di Tullio (1980) and Heisler, Tremaine, and Bahcall (1985), respectively. The final velocity dispersion and mass functions were analyzed in order to constrain cosmological parameters by comparison to the results of N-body simulations. Our data for the cluster sample as a whole and for the individual clusters (spatial maps and velocity histograms) in our sample is available on-line at http://cfa-www.harvard.edu/ huchra/clusters. This website will be updated as more data becomes available in the master redshift compilations, and will be expanded to include more clusters and large groups of galaxies.

  3. Oil encapsulation in core-shell alginate capsules by inverse gelation II: comparison between dripping techniques using W/O or O/W emulsions.

    PubMed

    Martins, Evandro; Poncelet, Denis; Rodrigues, Ramila Cristiane; Renard, Denis

    2017-09-01

    In the first part of this article, it was described an innovative method of oil encapsulation from dripping-inverse gelation using water-in-oil (W/O) emulsions. It was noticed that the method of oil encapsulation was quite different depending on the emulsion type (W/O or oil-in-water (O/W)) used and that the emulsion structure (W/O or O/W) had a high impact on the dripping technique and the capsules characteristics. The objective of this article was to elucidate the differences between the dripping techniques using both emulsions and compare the capsule properties (mechanical resistance and release of actives). The oil encapsulation using O/W emulsions was easier to perform and did not require the use of emulsion destabilisers. However, capsules produced from W/O emulsions were more resistant to compression and showed the slower release of actives over time. The findings detailed here widened the knowledge of the inverse gelation and gave opportunities to develop new techniques of oil encapsulation.

  4. The near-infrared Tully-Fisher relation - A preliminary study of the Coma and Abell 400 clusters

    NASA Technical Reports Server (NTRS)

    Guhathakurta, Puragra; Bernstein, Gary; Raychaudhury, Somak; Haynes, Martha; Giovanelli, Riccardo; Herter, Terry; Vogt, Nicole

    1993-01-01

    We have started a large project to study the NIR Tully-Fisher (TF) relation using H- and I-band surface photometry of spiral galaxies. A preliminary study of 20 spirals in the Coma and Abell 400 clusters is presented. The NIR images have been used to derive accurate inclinations and total magnitudes, and rotational linewidths are measured from high-quality 21-cm Arecibo data. The scatter in the Coma TF plot is found to be 0.19 mag in the H band and 0.20 mag in the I band for a set of 13 galaxies, if we assume that they are all at the same distance. The deviation of the Coma galaxies from the best-fit Tully-Fisher relation is correlated with their redshift, indicating that some of the galaxies are not bound to the cluster. Indeed, if we treat all the galaxies in the Coma sample as undergoing free Hubble expansion, the TF scatter drops to 0.12 and 0.13 mag for the H- and I-band datasets, respectively. The Abell 400 sample is best fit by a common distance model, yielding a scatter of 0.12 mag for seven galaxies in H using a fixed TF slope. We are in the process of studying cluster and field spirals out to about 10,000 km/s in order to calibrate the NIR TF relation and will apply it to more nearby galaxies to measure the peculiar velocity field in the local universe.

  5. Inversion of calcite twin data for paleostress (1) : improved Etchecopar technique tested on numerically-generated and natural data

    NASA Astrophysics Data System (ADS)

    Parlangeau, Camille; Lacombe, Olivier; Daniel, Jean-Marc; Schueller, Sylvie

    2015-04-01

    Inversion of calcite twin data are known to be a powerful tool to reconstruct the past-state of stress in carbonate rocks of the crust, especially in fold-and-thrust belts and sedimentary basins. This is of key importance to constrain results of geomechanical modelling. Without proposing a new inversion scheme, this contribution reports some recent improvements of the most efficient stress inversion technique to date (Etchecopar, 1984) that allows to reconstruct the 5 parameters of the deviatoric paleostress tensors (principal stress orientations and differential stress magnitudes) from monophase and polyphase twin data sets. The improvements consist in the search of the possible tensors that account for the twin data (twinned and untwinned planes) and the aid to the user to define the best stress tensor solution, among others. We perform a systematic exploration of an hypersphere in 4 dimensions by varying different parameters, Euler's angles and the stress ratio. We first record all tensors with a minimum penalization function accounting for 20% of the twinned planes. We then define clusters of tensors following a dissimilarity criterion based on the stress distance between the 4 parameters of the reduced stress tensors and a degree of disjunction of the related sets of twinned planes. The percentage of twinned data to be explained by each tensor is then progressively increased and tested using the standard Etchecopar procedure until the best solution that explains the maximum number of twinned planes and the whole set of untwinned planes is reached. This new inversion procedure is tested on monophase and polyphase numerically-generated as well as natural calcite twin data in order to more accurately define the ability of the technique to separate more or less similar deviatoric stress tensors applied in sequence on the samples, to test the impact of strain hardening through the change of the critical resolved shear stress for twinning as well as to evaluate the

  6. Mathematical Inversion of Lightning Data: Techniques and Applications

    NASA Technical Reports Server (NTRS)

    Koshak, William

    2003-01-01

    A survey of some interesting mathematical inversion studies dealing with radio, optical, and electrostatic measurements of lightning are presented. A discussion of why NASA is interested in lightning, what specific physical properties of lightning are retrieved, and what mathematical techniques are used to perform the retrievals are discussed. In particular, a relatively new multi-station VHF time-of-arrival (TOA) antenna network is now on-line in Northern Alabama and will be discussed. The network, called the Lightning Mapping Array (LMA), employs GPS timing and detects VHF radiation from discrete segments (effectively point emitters) that comprise the channel of lightning strokes within cloud and ground flashes. The LMA supports on-going ground-validation activities of the low Earth orbiting Lightning Imaging Sensor (LIS) satellite developed at NASA Marshall Space Flight Center (MSFC) in Huntsville, Alabama. The LMA also provides detailed studies of the distribution and evolution of thunderstorms and lightning in the Tennessee Valley, and offers interesting comparisons with other meteorological/geophysical datasets. In order to take full advantage of these benefits, it is essential that the LMA channel mapping accuracy (in both space and time) be fully characterized and optimized. A new channel mapping retrieval algorithm is introduced for this purpose. To characterize the spatial distribution of retrieval errors, the algorithm has been applied to analyze literally tens of millions of computer-simulated lightning VHF point sources that have been placed at various ranges, azimuths, and altitudes relative to the LMA network. Statistical results are conveniently summarized in high-resolution, color-coded, error maps.

  7. Favorable toxicity and biochemical control using real-time inverse optimization technique for prostate brachytherapy.

    PubMed

    Raben, Adam; Rusthoven, Kyle E; Sarkar, Abrihup; Glick, Andrew; Benge, Bruce; Jacobs, Dayee; Raben, David

    2009-01-01

    Favorable dosimetric results have been reported using intraoperative inverse optimization (IO) for permanent prostate brachytherapy. The clinical implications of these improvements in dosimetry are unclear. We review toxicity and early biochemical outcomes for patients implanted using IO technique. Between 2001 and 2007, 165 patients received permanent prostate implants using real-time IO and had >/=3 months of followup. Dose constraints for inverse planning were: the prostate volume receiving 100% of the prescription dose [prostate V(100)] was >95%; the dose received by 90% of the gland [prostate D(90)] was within the 140-180 by dose range; the volume of urethra receiving 150% of the prescription dose [urethra V(150)] was <30%; and the volume of rectal wall receiving 110% of the prescription dose [rectal V(110)] was <1.0 cc. Toxicity was prospectively scored using the Radiation Therapy Oncology Group toxicity scale and the International Prostate Symptom Score questionnaire. Biochemical control was determined using the nadir + 2 ng/mL definition. Mean followup was 30 months (range, 6-63 months). Risk classification was low risk in 89% and intermediate risk in 11%. Iodine-125 sources were used for 161 implants and palladium-103 sources for four implants. The median number of seeds and total activity implanted were 61 and 999 MBq, respectively, for a median prostate volume of 33.6 cc. Late GU and GI morbidity was uncommon. Among patients with at least 24 months followup, 16% had persistent Grade 2-3 urinary morbidity. Grade 2 rectal bleeding occurred in 1 patient (0.6%). Biochemical failure has occurred in only 4 patients at last followup. IO technique for prostate brachytherapy is associated with low rates of late morbidity and excellent early biochemical control. Additionally, the number of seeds and total implanted activity required to achieve a high-quality implant are lower compared with historical controls.

  8. Tomographic reconstruction of tokamak plasma light emission using wavelet-vaguelette decomposition

    NASA Astrophysics Data System (ADS)

    Schneider, Kai; Nguyen van Yen, Romain; Fedorczak, Nicolas; Brochard, Frederic; Bonhomme, Gerard; Farge, Marie; Monier-Garbet, Pascale

    2012-10-01

    Images acquired by cameras installed in tokamaks are difficult to interpret because the three-dimensional structure of the plasma is flattened in a non-trivial way. Nevertheless, taking advantage of the slow variation of the fluctuations along magnetic field lines, the optical transformation may be approximated by a generalized Abel transform, for which we proposed in Nguyen van yen et al., Nucl. Fus., 52 (2012) 013005, an inversion technique based on the wavelet-vaguelette decomposition. After validation of the new method using an academic test case and numerical data obtained with the Tokam 2D code, we present an application to an experimental movie obtained in the tokamak Tore Supra. A comparison with a classical regularization technique for ill-posed inverse problems, the singular value decomposition, allows us to assess the efficiency. The superiority of the wavelet-vaguelette technique is reflected in preserving local features, such as blobs and fronts, in the denoised emissivity map.

  9. Abell 1033: birth of a radio phoenix

    DOE PAGES

    de Gasperin, F.; Ogrean, G. A.; van Weeren, R. J.; ...

    2015-02-26

    We report that extended steep-spectrum radio emission in a galaxy cluster is usually associated with a recent merger. However, given the complex scenario of galaxy cluster mergers, many of the discovered sources hardly fit into the strict boundaries of a precise taxonomy. This is especially true for radio phoenixes that do not have very well defined observational criteria. Radio phoenixes are aged radio galaxy lobes whose emission is reactivated by compression or other mechanisms. Here in this paper, we present the detection of a radio phoenix close to the moment of its formation. The source is located in Abell 1033,more » a peculiar galaxy cluster which underwent a recent merger. To support our claim, we present unpublished Westerbork Synthesis Radio Telescope and Chandra observations together with archival data from the Very Large Array and the Sloan Digital Sky Survey. We discover the presence of two subclusters displaced along the N–S direction. The two subclusters probably underwent a recent merger which is the cause of a moderately perturbed X-ray brightness distribution. A steep-spectrum extended radio source very close to an active galactic nucleus (AGN) is proposed to be a newly born radio phoenix: the AGN lobes have been displaced/compressed by shocks formed during the merger event. This scenario explains the source location, morphology, spectral index, and brightness. Finally, we show evidence of a density discontinuity close to the radio phoenix and discuss the consequences of its presence.« less

  10. The inverse electroencephalography pipeline

    NASA Astrophysics Data System (ADS)

    Weinstein, David Michael

    The inverse electroencephalography (EEG) problem is defined as determining which regions of the brain are active based on remote measurements recorded with scalp EEG electrodes. An accurate solution to this problem would benefit both fundamental neuroscience research and clinical neuroscience applications. However, constructing accurate patient-specific inverse EEG solutions requires complex modeling, simulation, and visualization algorithms, and to date only a few systems have been developed that provide such capabilities. In this dissertation, a computational system for generating and investigating patient-specific inverse EEG solutions is introduced, and the requirements for each stage of this Inverse EEG Pipeline are defined and discussed. While the requirements of many of the stages are satisfied with existing algorithms, others have motivated research into novel modeling and simulation methods. The principal technical results of this work include novel surface-based volume modeling techniques, an efficient construction for the EEG lead field, and the Open Source release of the Inverse EEG Pipeline software for use by the bioelectric field research community. In this work, the Inverse EEG Pipeline is applied to three research problems in neurology: comparing focal and distributed source imaging algorithms; separating measurements into independent activation components for multifocal epilepsy; and localizing the cortical activity that produces the P300 effect in schizophrenia.

  11. A Joint Method of Envelope Inversion Combined with Hybrid-domain Full Waveform Inversion

    NASA Astrophysics Data System (ADS)

    CUI, C.; Hou, W.

    2017-12-01

    Full waveform inversion (FWI) aims to construct high-precision subsurface models by fully using the information in seismic records, including amplitude, travel time, phase and so on. However, high non-linearity and the absence of low frequency information in seismic data lead to the well-known cycle skipping problem and make inversion easily fall into local minima. In addition, those 3D inversion methods that are based on acoustic approximation ignore the elastic effects in real seismic field, and make inversion harder. As a result, the accuracy of final inversion results highly relies on the quality of initial model. In order to improve stability and quality of inversion results, multi-scale inversion that reconstructs subsurface model from low to high frequency are applied. But, the absence of very low frequencies (< 3Hz) in field data is still bottleneck in the FWI. By extracting ultra low-frequency data from field data, envelope inversion is able to recover low wavenumber model with a demodulation operator (envelope operator), though the low frequency data does not really exist in field data. To improve the efficiency and viability of the inversion, in this study, we proposed a joint method of envelope inversion combined with hybrid-domain FWI. First, we developed 3D elastic envelope inversion, and the misfit function and the corresponding gradient operator were derived. Then we performed hybrid-domain FWI with envelope inversion result as initial model which provides low wavenumber component of model. Here, forward modeling is implemented in the time domain and inversion in the frequency domain. To accelerate the inversion, we adopt CPU/GPU heterogeneous computing techniques. There were two levels of parallelism. In the first level, the inversion tasks are decomposed and assigned to each computation node by shot number. In the second level, GPU multithreaded programming is used for the computation tasks in each node, including forward modeling, envelope

  12. Electromagnetic inverse scattering

    NASA Technical Reports Server (NTRS)

    Bojarski, N. N.

    1972-01-01

    A three-dimensional electromagnetic inverse scattering identity, based on the physical optics approximation, is developed for the monostatic scattered far field cross section of perfect conductors. Uniqueness of this inverse identity is proven. This identity requires complete scattering information for all frequencies and aspect angles. A nonsingular integral equation is developed for the arbitrary case of incomplete frequence and/or aspect angle scattering information. A general closed-form solution to this integral equation is developed, which yields the shape of the scatterer from such incomplete information. A specific practical radar solution is presented. The resolution of this solution is developed, yielding short-pulse target resolution radar system parameter equations. The special cases of two- and one-dimensional inverse scattering and the special case of a priori knowledge of scatterer symmetry are treated in some detail. The merits of this solution over the conventional radar imaging technique are discussed.

  13. Illuminating a Dark Lens : A Type Ia Supernova Magnified by the Frontier Fields Galaxy Cluster Abell 2744

    NASA Astrophysics Data System (ADS)

    Rodney, Steven A.; Patel, Brandon; Scolnic, Daniel; Foley, Ryan J.; Molino, Alberto; Brammer, Gabriel; Jauzac, Mathilde; Bradač, Maruša; Broadhurst, Tom; Coe, Dan; Diego, Jose M.; Graur, Or; Hjorth, Jens; Hoag, Austin; Jha, Saurabh W.; Johnson, Traci L.; Kelly, Patrick; Lam, Daniel; McCully, Curtis; Medezinski, Elinor; Meneghetti, Massimo; Merten, Julian; Richard, Johan; Riess, Adam; Sharon, Keren; Strolger, Louis-Gregory; Treu, Tommaso; Wang, Xin; Williams, Liliya L. R.; Zitrin, Adi

    2015-09-01

    SN HFF14Tom is a Type Ia SN discovered at z=1.3457+/- 0.0001 behind the galaxy cluster Abell 2744 (z = 0.308). In a cosmology-independent analysis, we find that HFF14Tom is 0.77 ± 0.15 mag brighter than unlensed Type Ia SNe at similar redshift, implying a lensing magnification of {μ }{obs}=2.03+/- 0.29. This observed magnification provides a rare opportunity for a direct empirical test of galaxy cluster lens models. Here we test 17 lens models, 13 of which were generated before the SN magnification was known, qualifying as pure “blind tests.” The models are collectively fairly accurate: 8 of the models deliver median magnifications that are consistent with the measured μ to within 1σ. However, there is a subtle systematic bias: the significant disagreements all involve models overpredicting the magnification. We evaluate possible causes for this mild bias, and find no single physical or methodological explanation to account for it. We do find that model accuracy can be improved to some extent with stringent quality cuts on multiply imaged systems, such as requiring that a large fraction have spectroscopic redshifts. In addition to testing model accuracies as we have done here, Type Ia SN magnifications could also be used as inputs for future lens models of Abell 2744 and other clusters, providing valuable constraints in regions where traditional strong- and weak-lensing information is unavailable.

  14. Inverse boundary-layer theory and comparison with experiment

    NASA Technical Reports Server (NTRS)

    Carter, J. E.

    1978-01-01

    Inverse boundary layer computational procedures, which permit nonsingular solutions at separation and reattachment, are presented. In the first technique, which is for incompressible flow, the displacement thickness is prescribed; in the second technique, for compressible flow, a perturbation mass flow is the prescribed condition. The pressure is deduced implicitly along with the solution in each of these techniques. Laminar and turbulent computations, which are typical of separated flow, are presented and comparisons are made with experimental data. In both inverse procedures, finite difference techniques are used along with Newton iteration. The resulting procedure is no more complicated than conventional boundary layer computations. These separated boundary layer techniques appear to be well suited for complete viscous-inviscid interaction computations.

  15. Real Variable Inversion of Laplace Transforms: An Application in Plasma Physics.

    ERIC Educational Resources Information Center

    Bohn, C. L.; Flynn, R. W.

    1978-01-01

    Discusses the nature of Laplace transform techniques and explains an alternative to them: the Widder's real inversion. To illustrate the power of this new technique, it is applied to a difficult inversion: the problem of Landau damping. (GA)

  16. Bayesian inversion of refraction seismic traveltime data

    NASA Astrophysics Data System (ADS)

    Ryberg, T.; Haberland, Ch

    2018-03-01

    We apply a Bayesian Markov chain Monte Carlo (McMC) formalism to the inversion of refraction seismic, traveltime data sets to derive 2-D velocity models below linear arrays (i.e. profiles) of sources and seismic receivers. Typical refraction data sets, especially when using the far-offset observations, are known as having experimental geometries which are very poor, highly ill-posed and far from being ideal. As a consequence, the structural resolution quickly degrades with depth. Conventional inversion techniques, based on regularization, potentially suffer from the choice of appropriate inversion parameters (i.e. number and distribution of cells, starting velocity models, damping and smoothing constraints, data noise level, etc.) and only local model space exploration. McMC techniques are used for exhaustive sampling of the model space without the need of prior knowledge (or assumptions) of inversion parameters, resulting in a large number of models fitting the observations. Statistical analysis of these models allows to derive an average (reference) solution and its standard deviation, thus providing uncertainty estimates of the inversion result. The highly non-linear character of the inversion problem, mainly caused by the experiment geometry, does not allow to derive a reference solution and error map by a simply averaging procedure. We present a modified averaging technique, which excludes parts of the prior distribution in the posterior values due to poor ray coverage, thus providing reliable estimates of inversion model properties even in those parts of the models. The model is discretized by a set of Voronoi polygons (with constant slowness cells) or a triangulated mesh (with interpolation within the triangles). Forward traveltime calculations are performed by a fast, finite-difference-based eikonal solver. The method is applied to a data set from a refraction seismic survey from Northern Namibia and compared to conventional tomography. An inversion test

  17. VizieR Online Data Catalog: Magellan/M2FS spectroscopy of Abell 267 (Tucker+, 2017)

    NASA Astrophysics Data System (ADS)

    Tucker, E.; Walker, M. G.; Mateo, M.; Olszewski, E. W.; Bailey, J. I.; Crane, J. D.; Shectman, S. A.

    2018-02-01

    We select targets for Michigan/Magellan Fiber System (M2FS) observations by identifying galaxies detected in SDSS images (Data Release 12; Alam et al.2015, Cat. V/147) that are projected along the line of sight to Abell 267 and are likely to be quiescent cluster members. We observed 223 individual galaxy spectra on 2013 November 30 on the Clay Magellan Telescope using M2FS. We used the low-resolution grating on M2FS and chose a coverage range of 4600-6400Å with a resolution of R~2000. The detector used with M2FS consists of two 4096*4112 pixel CCDs. (1 data file).

  18. A compilation of redshifts and velocity dispersions for Abell clusters (Struble and Rood 1987): Documentation for the machine-readable version

    NASA Technical Reports Server (NTRS)

    Warren, Wayne H., Jr.

    1989-01-01

    The machine readable version of the compilation, as it is currently being distributed from the Astronomical Data Center, is described. The catalog contains redshifts and velocity dispersions for all Abell clusters for which these data had been published up to 1986 July. Also included are 1950 equatorial coordinates for the centers of the listed clusters, numbers of observations used to determine the redshifts, and bibliographical references citing the data sources.

  19. A Census of Star Formation and Active Galactic Nuclei Populations in Abell 1689

    NASA Astrophysics Data System (ADS)

    Jones, Logan H.; Atlee, David Wesley

    2016-01-01

    A recent survey of low-z galaxy clusters observed a disjunction between X-ray and mid-infrared selected populations of active galactic nuclei (X-ray and IR AGNs) (Atlee+ 2011, ApJ 729, 22.). Here we present an analysis of near-infrared spectroscopic data of star-forming galaxies in cluster Abell 1689 in order to confirm the identity of some of their IR AGN and to provide a check on their reported star formation rates. Our sample consists of 24 objects in Abell 1689. H and K band spectroscopic observations of target objects and standard stars were obtained by David Atlee between 2010 May 17 and 2011 June 6 using the Large Binocular Telescope's LUCI instrument. After undergoing initial reductions, standard stars were corrected for telluric absorption using TelFit (Gullikson+ 2014, AJ, 158, 53). Raw detector counts were converted to physical units using the wavelength-dependent response of the grating and the star's reported H and K band magnitudes to produce conversion factors that fully correct for instrumental effects. Target spectra were flux-calibrated using the airmass-corrected transmission profiles produced by TelFit and the associated H band conversion factor (or the average of the two factors, for nights with two standard stars). Star formation rates were calculated using the SFR-L(Ha) relation reported in Kennicutt (1998), with the measured luminosity of the Pa-a emission line at the luminosity distance of the cluster used as a proxy for L(Ha) (Kennicutt 1998, ARA&A 36, 189; Hummer & Stoney 1987, MNRAS 346, 1055). The line ratios H2 2.121 mm/Brg and [FeII]/Pab were used to classify targets as starburst galaxies, AGNs, or LINERs (Rodriguez-Ardila+ 2005, MNRAS, 364, 1041). Jones was supported by the NOAO/KPNO Research Experience for Undergraduates (REU) Program, which is funded by the National Science Foundation Research Experiences for Undergraduates Program (AST-1262829).

  20. Large-scale inverse model analyses employing fast randomized data reduction

    NASA Astrophysics Data System (ADS)

    Lin, Youzuo; Le, Ellen B.; O'Malley, Daniel; Vesselinov, Velimir V.; Bui-Thanh, Tan

    2017-08-01

    When the number of observations is large, it is computationally challenging to apply classical inverse modeling techniques. We have developed a new computationally efficient technique for solving inverse problems with a large number of observations (e.g., on the order of 107 or greater). Our method, which we call the randomized geostatistical approach (RGA), is built upon the principal component geostatistical approach (PCGA). We employ a data reduction technique combined with the PCGA to improve the computational efficiency and reduce the memory usage. Specifically, we employ a randomized numerical linear algebra technique based on a so-called "sketching" matrix to effectively reduce the dimension of the observations without losing the information content needed for the inverse analysis. In this way, the computational and memory costs for RGA scale with the information content rather than the size of the calibration data. Our algorithm is coded in Julia and implemented in the MADS open-source high-performance computational framework (http://mads.lanl.gov). We apply our new inverse modeling method to invert for a synthetic transmissivity field. Compared to a standard geostatistical approach (GA), our method is more efficient when the number of observations is large. Most importantly, our method is capable of solving larger inverse problems than the standard GA and PCGA approaches. Therefore, our new model inversion method is a powerful tool for solving large-scale inverse problems. The method can be applied in any field and is not limited to hydrogeological applications such as the characterization of aquifer heterogeneity.

  1. Television documentary, history and memory. An analysis of Sergio Zavoli's The Gardens of Abel.

    PubMed

    Foot, John

    2014-10-20

    This article examines a celebrated documentary made for Italian state TV in 1968 and transmitted in 1969 to an audience of millions. The programme - The Gardens of Abel - looked at changes introduced by the radical psychiatrist Franco Basaglia in an asylum in the north-east of Italy (Gorizia). The article examines the content of this programme for the first time, questions some of the claims that have been made for it, and outlines the sources used by the director, Sergio Zavoli. The article argues that the film was as much an expression of Zavoli's vision and ideas as it was linked to those of Franco Basaglia himself. Finally, the article highlights the way that this programme has become part of historical discourse and popular memory.

  2. Inhibition of α-glucosidase by polysaccharides from the fruit hull of Camellia oleifera Abel.

    PubMed

    Zhang, Sheng; Li, Xiang-Zhou

    2015-01-22

    We isolated and purified polysaccharides from the Camellia oleifera Abel. fruit hull and studied its hypoglycemic potential. Our results revealed six polysaccharides (CFPA-1-5 & CFPB) from the aqueous extract from the defatted C. oleifera fruit hull. Purified polysaccharides (purity >90%) were investigated for the inhibition of α-glucosidase activity in vitro. Two polysaccharides, CFPB and CFPA-3 were present in high concentration in the fruit hull and showed a dose-dependent inhibition of α-glucosidase activity, with IC50 concentrations of 11.80 and 10.95 μg/mL, respectively. This result suggests that polysaccharides (CFP) extracted from the fruit hull of C. oleifera may have potential as functional foods with featuring a hypoglycemic effect. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. On the merging cluster Abell 578 and its central radio galaxy 4C+67.13

    DOE PAGES

    Hagino, K.; Stawarz, Ł.; Siemiginowska, A.; ...

    2015-05-26

    Here we analyze radio, optical, and X-ray data for the peculiar cluster Abell 578. This cluster is not fully relaxed and consists of two merging sub-systems. The brightest cluster galaxy (BCG), CGPG 0719.8+6704, is a pair of interacting ellipticals with projected separation ~10 kpc, the brighter of which hosts the radio source 4C+67.13. The Fanaroff–Riley type-II radio morphology of 4C+67.13 is unusual for central radio galaxies in local Abell clusters. Our new optical spectroscopy revealed that both nuclei of the CGPG 0719.8+6704 pair are active, albeit at low accretion rates corresponding to the Eddington ratiomore » $$\\sim {{10}^{-4}}$$ (for the estimated black hole masses of $$\\sim 3\\times {{10}^{8}}\\;{{M}_{\\odot }}$$ and $$\\sim {{10}^{9}}\\;{{M}_{\\odot }}$$). The gathered X-ray (Chandra) data allowed us to confirm and to quantify robustly the previously noted elongation of the gaseous atmosphere in the dominant sub-cluster, as well as a large spatial offset (~60 kpc projected) between the position of the BCG and the cluster center inferred from the modeling of the X-ray surface brightness distribution. Detailed analysis of the brightness profiles and temperature revealed also that the cluster gas in the vicinity of 4C+67.13 is compressed (by a factor of about ~1.4) and heated (from $$\\simeq 2.0$$ keV up to 2.7 keV), consistent with the presence of a weak shock (Mach number ~1.3) driven by the expanding jet cocoon. As a result, this would then require the jet kinetic power of the order of $$\\sim {{10}^{45}}$$ erg s –1, implying either a very high efficiency of the jet production for the current accretion rate, or a highly modulated jet/accretion activity in the system.« less

  4. Frequency-domain elastic full waveform inversion using encoded simultaneous sources

    NASA Astrophysics Data System (ADS)

    Jeong, W.; Son, W.; Pyun, S.; Min, D.

    2011-12-01

    Currently, numerous studies have endeavored to develop robust full waveform inversion and migration algorithms. These processes require enormous computational costs, because of the number of sources in the survey. To avoid this problem, the phase encoding technique for prestack migration was proposed by Romero (2000) and Krebs et al. (2009) proposed the encoded simultaneous-source inversion technique in the time domain. On the other hand, Ben-Hadj-Ali et al. (2011) demonstrated the robustness of the frequency-domain full waveform inversion with simultaneous sources for noisy data changing the source assembling. Although several studies on simultaneous-source inversion tried to estimate P- wave velocity based on the acoustic wave equation, seismic migration and waveform inversion based on the elastic wave equations are required to obtain more reliable subsurface information. In this study, we propose a 2-D frequency-domain elastic full waveform inversion technique using phase encoding methods. In our algorithm, the random phase encoding method is employed to calculate the gradients of the elastic parameters, source signature estimation and the diagonal entries of approximate Hessian matrix. The crosstalk for the estimated source signature and the diagonal entries of approximate Hessian matrix are suppressed with iteration as for the gradients. Our 2-D frequency-domain elastic waveform inversion algorithm is composed using the back-propagation technique and the conjugate-gradient method. Source signature is estimated using the full Newton method. We compare the simultaneous-source inversion with the conventional waveform inversion for synthetic data sets of the Marmousi-2 model. The inverted results obtained by simultaneous sources are comparable to those obtained by individual sources, and source signature is successfully estimated in simultaneous source technique. Comparing the inverted results using the pseudo Hessian matrix with previous inversion results

  5. Inversion layer MOS solar cells

    NASA Technical Reports Server (NTRS)

    Ho, Fat Duen

    1986-01-01

    Inversion layer (IL) Metal Oxide Semiconductor (MOS) solar cells were fabricated. The fabrication technique and problems are discussed. A plan for modeling IL cells is presented. Future work in this area is addressed.

  6. Understanding Methane Emission from Natural Gas Activities Using Inverse Modeling Techniques

    NASA Astrophysics Data System (ADS)

    Abdioskouei, M.; Carmichael, G. R.

    2015-12-01

    Natural gas (NG) has been promoted as a bridge fuel that can smooth the transition from fossil fuels to zero carbon energy sources by having lower carbon dioxide emission and lower global warming impacts in comparison to other fossil fuels. However, the uncertainty around the estimations of methane emissions from NG systems can lead to underestimation of climate and environmental impacts of using NG as a replacement for coal. Accurate estimates of methane emissions from NG operations is crucial for evaluation of environmental impacts of NG extraction and at larger scale, adoption of NG as transitional fuel. However there is a great inconsistency within the current estimates. Forward simulation of methane from oil and gas operation sites for the US is carried out based on NEI-2011 using the WRF-Chem model. Simulated values are compared against measurements of observations from different platforms such as airborne (FRAPPÉ field campaign) and ground-based measurements (NOAA Earth System Research Laboratory). A novel inverse modeling technique is used in this work to improve the model fit to the observation values and to constrain methane emission from oil and gas extraction sites.

  7. Dynamic model inversion techniques for breath-by-breath measurement of carbon dioxide from low bandwidth sensors.

    PubMed

    Sivaramakrishnan, Shyam; Rajamani, Rajesh; Johnson, Bruce D

    2009-01-01

    Respiratory CO(2) measurement (capnography) is an important diagnosis tool that lacks inexpensive and wearable sensors. This paper develops techniques to enable use of inexpensive but slow CO(2) sensors for breath-by-breath tracking of CO(2) concentration. This is achieved by mathematically modeling the dynamic response and using model-inversion techniques to predict input CO(2) concentration from the slow-varying output. Experiments are designed to identify model-dynamics and extract relevant model-parameters for a solidstate room monitoring CO(2) sensor. A second-order model that accounts for flow through the sensor's filter and casing is found to be accurate in describing the sensor's slow response. The resulting estimate is compared with a standard-of-care respiratory CO(2) analyzer and shown to effectively track variation in breath-by-breath CO(2) concentration. This methodology is potentially useful for measuring fast-varying inputs to any slow sensor.

  8. Approximated Stable Inversion for Nonlinear Systems with Nonhyperbolic Internal Dynamics. Revised

    NASA Technical Reports Server (NTRS)

    Devasia, Santosh

    1999-01-01

    A technique to achieve output tracking for nonminimum phase nonlinear systems with non- hyperbolic internal dynamics is presented. The present paper integrates stable inversion techniques (that achieve exact-tracking) with approximation techniques (that modify the internal dynamics) to circumvent the nonhyperbolicity of the internal dynamics - this nonhyperbolicity is an obstruction to applying presently available stable inversion techniques. The theory is developed for nonlinear systems and the method is applied to a two-cart with inverted-pendulum example.

  9. Preview-Based Stable-Inversion for Output Tracking

    NASA Technical Reports Server (NTRS)

    Zou, Qing-Ze; Devasia, Santosh

    1999-01-01

    Stable Inversion techniques can be used to achieve high-accuracy output tracking. However, for nonminimum phase systems, the inverse is non-causal - hence the inverse has to be pre-computed using a pre-specified desired-output trajectory. This requirement for pre-specification of the desired output restricts the use of inversion-based approaches to trajectory planning problems (for nonminimum phase systems). In the present article, it is shown that preview information of the desired output can be used to achieve online inversion-based output tracking of linear systems. The amount of preview-time needed is quantified in terms of the tracking error and the internal dynamics of the system (zeros of the system). The methodology is applied to the online output tracking of a flexible structure and experimental results are presented.

  10. Normal-inverse bimodule operation Hadamard transform ion mobility spectrometry.

    PubMed

    Hong, Yan; Huang, Chaoqun; Liu, Sheng; Xia, Lei; Shen, Chengyin; Chu, Yannan

    2018-10-31

    In order to suppress or eliminate the spurious peaks and improve signal-to-noise ratio (SNR) of Hadamard transform ion mobility spectrometry (HT-IMS), a normal-inverse bimodule operation Hadamard transform - ion mobility spectrometry (NIBOHT-IMS) technique was developed. In this novel technique, a normal and inverse pseudo random binary sequence (PRBS) was produced in sequential order by an ion gate controller and utilized to control the ion gate of IMS, and then the normal HT-IMS mobility spectrum and the inverse HT-IMS mobility spectrum were obtained. A NIBOHT-IMS mobility spectrum was gained by subtracting the inverse HT-IMS mobility spectrum from normal HT-IMS mobility spectrum. Experimental results demonstrate that the NIBOHT-IMS technique can significantly suppress or eliminate the spurious peaks, and enhance the SNR by measuring the reactant ions. Furthermore, the gas CHCl 3 and CH 2 Br 2 were measured for evaluating the capability of detecting real sample. The results show that the NIBOHT-IMS technique is able to eliminate the spurious peaks and improve the SNR notably not only for the detection of larger ion signals but also for the detection of small ion signals. Copyright © 2018 Elsevier B.V. All rights reserved.

  11. EDITORIAL: Inverse Problems in Engineering

    NASA Astrophysics Data System (ADS)

    West, Robert M.; Lesnic, Daniel

    2007-01-01

    Presented here are 11 noteworthy papers selected from the Fifth International Conference on Inverse Problems in Engineering: Theory and Practice held in Cambridge, UK during 11-15 July 2005. The papers have been peer-reviewed to the usual high standards of this journal and the contributions of reviewers are much appreciated. The conference featured a good balance of the fundamental mathematical concepts of inverse problems with a diverse range of important and interesting applications, which are represented here by the selected papers. Aspects of finite-element modelling and the performance of inverse algorithms are investigated by Autrique et al and Leduc et al. Statistical aspects are considered by Emery et al and Watzenig et al with regard to Bayesian parameter estimation and inversion using particle filters. Electrostatic applications are demonstrated by van Berkel and Lionheart and also Nakatani et al. Contributions to the applications of electrical techniques and specifically electrical tomographies are provided by Wakatsuki and Kagawa, Kim et al and Kortschak et al. Aspects of inversion in optical tomography are investigated by Wright et al and Douiri et al. The authors are representative of the worldwide interest in inverse problems relating to engineering applications and their efforts in producing these excellent papers will be appreciated by many readers of this journal.

  12. Abell 1142 and the Missing Central Galaxy – A Cluster in Transition?

    NASA Astrophysics Data System (ADS)

    Jones, Alexander; Su, Yuanyuan; Buote, David; Forman, William; van Weeren, Reinout; Jones, Christine; Gastaldello, Fabio; Kraft, Ralph; Randall, Scott

    2018-01-01

    Two types of galaxy clusters exist: cool core (CC) clusters which exhibit centrally-peaked metallicity and X-ray emission and non-cool core (NCC) clusters, possessing comparably homogeneous metallicity and X-ray emission distributions. However, the origin of this dichotomy is still unknown. The current prevailing theories state that either there is a primordial entropy limit, above which a CC is unable to form, or that clusters can change type through major mergers and radiative cooling. Abell 1142 is a galaxy cluster that can provide a unique probe of the root of this cluster-type division. It is formed of two merging sub-clusters, each with its own brightest cluster galaxies (BCG). Its enriched X-ray centroid (possible CC remnant) lies between these two BCGs. We present the thermal and chemical distributions of this system using deep (180ks) XMM-Newton observations to shed light on the role of mergers in the evolution of galaxy clusters.

  13. Digital holographic interferometry employing Fresnel transform reconstruction for the study of flow shear stabilized Z-pinch plasmas.

    PubMed

    Ross, M P; Shumlak, U

    2016-10-01

    The ZaP-HD flow Z-pinch project provides a platform to explore how shear flow stabilized Z-pinches could scale to high-energy-density plasma (plasma with pressures exceeding 1 Mbar) and fusion reactor conditions. The Z-pinch is a linear plasma confinement geometry in which the plasma carries axial electric current and is confined by its self-induced magnetic field. ZaP-HD generates shear stabilized, axisymmetric Z-pinches with stable lifetimes approaching 60 μs. The goal of the project is to increase the plasma density and temperature compared to the previous ZaP project by compressing the plasma to smaller radii (≈1 mm). Radial and axial plasma electron density structure is measured using digital holographic interferometry (DHI), which provides the necessary fine spatial resolution. ZaP-HD's DHI system uses a 2 ns Nd:YAG laser pulse with a second harmonic generator (λ = 532 nm) to produce holograms recorded by a Nikon D3200 digital camera. The holograms are numerically reconstructed with the Fresnel transform reconstruction method to obtain the phase shift caused by the interaction of the laser beam with the plasma. This provides a two-dimensional map of line-integrated electron density, which can be Abel inverted to determine the local number density. The DHI resolves line-integrated densities down to 3 × 10 20 m -2 with spatial resolution near 10 μm. This paper presents the first application of Fresnel transform reconstruction as an analysis technique for a plasma diagnostic, and it analyzes the method's accuracy through study of synthetic data. It then presents an Abel inversion procedure that utilizes data on both sides of a Z-pinch local number density profile to maximize profile symmetry. Error estimation and Abel inversion are applied to the measured data.

  14. Television documentary, history and memory. An analysis of Sergio Zavoli's The Gardens of Abel

    PubMed Central

    Foot, John

    2014-01-01

    This article examines a celebrated documentary made for Italian state TV in 1968 and transmitted in 1969 to an audience of millions. The programme – The Gardens of Abel – looked at changes introduced by the radical psychiatrist Franco Basaglia in an asylum in the north-east of Italy (Gorizia). The article examines the content of this programme for the first time, questions some of the claims that have been made for it, and outlines the sources used by the director, Sergio Zavoli. The article argues that the film was as much an expression of Zavoli's vision and ideas as it was linked to those of Franco Basaglia himself. Finally, the article highlights the way that this programme has become part of historical discourse and popular memory. PMID:25937804

  15. Top-down estimates of methane and nitrogen oxide emissions from shale gas production regions using aircraft measurements and a mesoscale Bayesian inversion system together with a flux ratio inversion technique

    NASA Astrophysics Data System (ADS)

    Cui, Y.; Brioude, J. F.; Angevine, W. M.; McKeen, S. A.; Henze, D. K.; Bousserez, N.; Liu, Z.; McDonald, B.; Peischl, J.; Ryerson, T. B.; Frost, G. J.; Trainer, M.

    2016-12-01

    Production of unconventional natural gas grew rapidly during the past ten years in the US which led to an increase in emissions of methane (CH4) and, depending on the shale region, nitrogen oxides (NOx). In terms of radiative forcing, CH4 is the second most important greenhouse gas after CO2. NOx is a precursor of ozone (O3) in the troposphere and nitrate particles, both of which are regulated by the US Clean Air Act. Emission estimates of CH4 and NOx from the shale regions are still highly uncertain. We present top-down estimates of CH4 and NOx surface fluxes from the Haynesville and Fayetteville shale production regions using aircraft data collected during the Southeast Nexus of Climate Change and Air Quality (SENEX) field campaign (June-July, 2013) and the Shale Oil and Natural Gas Nexus (SONGNEX) field campaign (March-May, 2015) within a mesoscale inversion framework. The inversion method is based on a mesoscale Bayesian inversion system using multiple transport models. EPA's 2011 National CH4 and NOx Emission Inventories are used as prior information to optimize CH4 and NOx emissions. Furthermore, the posterior CH4 emission estimates are used to constrain NOx emission estimates using a flux ratio inversion technique. Sensitivity of the posterior estimates to the use of off-diagonal terms in the error covariance matrices, the transport models, and prior estimates is discussed. Compared to the ground-based in-situ observations, the optimized CH4 and NOx inventories improve ground level CH4 and O3 concentrations calculated by the Weather Research and Forecasting mesoscale model coupled with chemistry (WRF-Chem).

  16. [The reconstruction of welding arc 3D electron density distribution based on Stark broadening].

    PubMed

    Zhang, Wang; Hua, Xue-Ming; Pan, Cheng-Gang; Li, Fang; Wang, Min

    2012-10-01

    The three-dimensional electron density is very important for welding arc quality control. In the present paper, Side-on characteristic line profile was collected by a spectrometer, and the lateral experimental data were approximated by a polynomial fitting. By applying an Abel inversion technique, the authors obtained the radial intensity distribution at each wavelength and thus constructed a profile for the radial positions. The Fourier transform was used to separate the Lorentz linear from the spectrum reconstructed, thus got the accurate Stark width. And we calculated the electronic density three-dimensional distribution of the TIG welding are plasma.

  17. A complete and partial integrability technique of the Lorenz system

    NASA Astrophysics Data System (ADS)

    Bougoffa, Lazhar; Al-Awfi, Saud; Bougouffa, Smail

    2018-06-01

    In this paper we deal with the well-known nonlinear Lorenz system that describes the deterministic chaos phenomenon. We consider an interesting problem with time-varying phenomena in quantum optics. Then we establish from the motion equations the passage to the Lorenz system. Furthermore, we show that the reduction to the third order non linear equation can be performed. Therefore, the obtained differential equation can be analytically solved in some special cases and transformed to Abel, Dufing, Painlevé and generalized Emden-Fowler equations. So, a motivating technique that permitted a complete and partial integrability of the Lorenz system is presented.

  18. Inversion of calcite twin data for paleostress orientations and magnitudes: A new technique tested and calibrated on numerically-generated and natural data

    NASA Astrophysics Data System (ADS)

    Parlangeau, Camille; Lacombe, Olivier; Schueller, Sylvie; Daniel, Jean-Marc

    2018-01-01

    The inversion of calcite twin data is a powerful tool to reconstruct paleostresses sustained by carbonate rocks during their geological history. Following Etchecopar's (1984) pioneering work, this study presents a new technique for the inversion of calcite twin data that reconstructs the 5 parameters of the deviatoric stress tensors from both monophase and polyphase twin datasets. The uncertainties in the parameters of the stress tensors reconstructed by this new technique are evaluated on numerically-generated datasets. The technique not only reliably defines the 5 parameters of the deviatoric stress tensor, but also reliably separates very close superimposed stress tensors (30° of difference in maximum principal stress orientation or switch between σ3 and σ2 axes). The technique is further shown to be robust to sampling bias and to slight variability in the critical resolved shear stress. Due to our still incomplete knowledge of the evolution of the critical resolved shear stress with grain size, our results show that it is recommended to analyze twin data subsets of homogeneous grain size to minimize possible errors, mainly those concerning differential stress values. The methodological uncertainty in principal stress orientations is about ± 10°; it is about ± 0.1 for the stress ratio. For differential stresses, the uncertainty is lower than ± 30%. Applying the technique to vein samples within Mesozoic limestones from the Monte Nero anticline (northern Apennines, Italy) demonstrates its ability to reliably detect and separate tectonically significant paleostress orientations and magnitudes from naturally deformed polyphase samples, hence to fingerprint the regional paleostresses of interest in tectonic studies.

  19. LOFAR discovery of an ultra-steep radio halo and giant head-tail radio galaxy in Abell 1132

    NASA Astrophysics Data System (ADS)

    Wilber, A.; Brüggen, M.; Bonafede, A.; Savini, F.; Shimwell, T.; van Weeren, R. J.; Rafferty, D.; Mechev, A. P.; Intema, H.; Andrade-Santos, F.; Clarke, A. O.; Mahony, E. K.; Morganti, R.; Prandoni, I.; Brunetti, G.; Röttgering, H.; Mandal, S.; de Gasperin, F.; Hoeft, M.

    2018-01-01

    Low-Frequency Array (LOFAR) observations at 144 MHz have revealed large-scale radio sources in the unrelaxed galaxy cluster Abell 1132. The cluster hosts diffuse radio emission on scales of ∼650 kpc near the cluster centre and a head-tail (HT) radio galaxy, extending up to 1 Mpc, south of the cluster centre. The central diffuse radio emission is not seen in NRAO VLA FIRST Survey, Westerbork Northern Sky Survey, nor in C & D array VLA observations at 1.4 GHz, but is detected in our follow-up Giant Meterwave Radio Telescope (GMRT) observations at 325 MHz. Using LOFAR and GMRT data, we determine the spectral index of the central diffuse emission to be α = -1.75 ± 0.19 (S ∝ να). We classify this emission as an ultra-steep spectrum radio halo and discuss the possible implications for the physical origin of radio haloes. The HT radio galaxy shows narrow, collimated emission extending up to 1 Mpc and another 300 kpc of more diffuse, disturbed emission, giving a full projected linear size of 1.3 Mpc - classifying it as a giant radio galaxy (GRG) and making it the longest HT found to date. The head of the GRG coincides with an elliptical galaxy (SDSS J105851.01+564308.5) belonging to Abell 1132. In our LOFAR image, there appears to be a connection between the radio halo and the GRG. The turbulence that may have produced the halo may have also affected the tail of the GRG. In turn, the GRG may have provided seed electrons for the radio halo.

  20. Objective quantification of perturbations produced with a piecewise PV inversion technique

    NASA Astrophysics Data System (ADS)

    Fita, L.; Romero, R.; Ramis, C.

    2007-11-01

    PV inversion techniques have been widely used in numerical studies of severe weather cases. These techniques can be applied as a way to study the sensitivity of the responsible meteorological system to changes in the initial conditions of the simulations. Dynamical effects of a collection of atmospheric features involved in the evolution of the system can be isolated. However, aspects, such as the definition of the atmospheric features or the amount of change in the initial conditions, are largely case-dependent and/or subjectively defined. An objective way to calculate the modification of the initial fields is proposed to alleviate this problem. The perturbations are quantified as the mean absolute variations of the total energy between the original and modified fields, and an unique energy variation value is fixed for all the perturbations derived from different PV anomalies. Thus, PV features of different dimensions and characteristics introduce the same net modification of the initial conditions from an energetic point of view. The devised quantification method is applied to study the high impact weather case of 9-11 November 2001 in the Western Mediterranean basin, when a deep and strong cyclone was formed. On the Balearic Islands 4 people died, and sustained winds of 30 ms-1 and precipitation higher than 200 mm/24 h were recorded. Moreover, 700 people died in Algiers during the first phase of the event. The sensitivities to perturbations in the initial conditions of a deep upper level trough, the anticyclonic system related to the North Atlantic high and the surface thermal anomaly related to the baroclinicity of the environment are determined. Results reveal a high influence of the upper level trough and the surface thermal anomaly and a minor role of the North Atlantic high during the genesis of the cyclone.

  1. Full-Physics Inverse Learning Machine for Satellite Remote Sensing Retrievals

    NASA Astrophysics Data System (ADS)

    Loyola, D. G.

    2017-12-01

    The satellite remote sensing retrievals are usually ill-posed inverse problems that are typically solved by finding a state vector that minimizes the residual between simulated data and real measurements. The classical inversion methods are very time-consuming as they require iterative calls to complex radiative-transfer forward models to simulate radiances and Jacobians, and subsequent inversion of relatively large matrices. In this work we present a novel and extremely fast algorithm for solving inverse problems called full-physics inverse learning machine (FP-ILM). The FP-ILM algorithm consists of a training phase in which machine learning techniques are used to derive an inversion operator based on synthetic data generated using a radiative transfer model (which expresses the "full-physics" component) and the smart sampling technique, and an operational phase in which the inversion operator is applied to real measurements. FP-ILM has been successfully applied to the retrieval of the SO2 plume height during volcanic eruptions and to the retrieval of ozone profile shapes from UV/VIS satellite sensors. Furthermore, FP-ILM will be used for the near-real-time processing of the upcoming generation of European Sentinel sensors with their unprecedented spectral and spatial resolution and associated large increases in the amount of data.

  2. Convergence of Chahine's nonlinear relaxation inversion method used for limb viewing remote sensing

    NASA Technical Reports Server (NTRS)

    Chu, W. P.

    1985-01-01

    The application of Chahine's (1970) inversion technique to remote sensing problems utilizing the limb viewing geometry is discussed. The problem considered here involves occultation-type measurements and limb radiance-type measurements from either spacecraft or balloon platforms. The kernel matrix of the inversion problem is either an upper or lower triangular matrix. It is demonstrated that the Chahine inversion technique always converges, provided the diagonal elements of the kernel matrix are nonzero.

  3. X-ray constraints on the shape of the dark matter in five Abell clusters

    NASA Technical Reports Server (NTRS)

    Buote, David A.; Canizares, Claude R.

    1992-01-01

    X-ray observations obtained with the Einstein Observatory are used to constrain the shape of the dark matter in the inner regions of Abell clusters A401, A426, A1656, A2029, and A2199, each of which exhibits highly flattened optical isopleths. The dark matter is modeled as an ellipsoid with a mass density of about r exp -2. The possible shapes of the dark matter is constrained by comparing these model isophotes to the image isophotes. The X-ray isophotes, and therefore the gravitational potentials, have ellipticities of about 0.1-0.2. The dark matter within the central 1 Mpc is found to be substantially rounder for all the clusters. It is concluded that the shape of the galaxy distributions in these clusters traces neither the gravitational potential nor the gravitating matter.

  4. The Noble-Abel Stiffened-Gas equation of state

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Le Métayer, Olivier, E-mail: olivier.lemetayer@univ-amu.fr; Saurel, Richard, E-mail: richard.saurel@univ-amu.fr; RS2N, 371 Chemin de Gaumin, 83640 Saint-Zacharie

    2016-04-15

    Hyperbolic two-phase flow models have shown excellent ability for the resolution of a wide range of applications ranging from interfacial flows to fluid mixtures with several velocities. These models account for waves propagation (acoustic and convective) and consist in hyperbolic systems of partial differential equations. In this context, each phase is compressible and needs an appropriate convex equation of state (EOS). The EOS must be simple enough for intensive computations as well as boundary conditions treatment. It must also be accurate, this being challenging with respect to simplicity. In the present approach, each fluid is governed by a novel EOSmore » named “Noble Abel stiffened gas,” this formulation being a significant improvement of the popular “Stiffened Gas (SG)” EOS. It is a combination of the so-called “Noble-Abel” and “stiffened gas” equations of state that adds repulsive effects to the SG formulation. The determination of the various thermodynamic functions and associated coefficients is the aim of this article. We first use thermodynamic considerations to determine the different state functions such as the specific internal energy, enthalpy, and entropy. Then we propose to determine the associated coefficients for a liquid in the presence of its vapor. The EOS parameters are determined from experimental saturation curves. Some examples of liquid-vapor fluids are examined and associated parameters are computed with the help of the present method. Comparisons between analytical and experimental saturation curves show very good agreement for wide ranges of temperature for both liquid and vapor.« less

  5. Dynamical history of a binary cluster: Abell 3653

    NASA Astrophysics Data System (ADS)

    Caglar, Turgay; Hudaverdi, Murat

    2017-12-01

    We study the dynamical structure of a bimodal galaxy cluster Abell 3653 at z = 0.1089 using optical and X-ray data. Observations include archival data from the Anglo-Australian Telescope, X-ray observatories XMM-Newton and Chandra. We draw a global picture for A3653 using galaxy density, X-ray luminosity and temperature maps. The galaxy distribution has a regular morphological shape at the 3 Mpc size. The galaxy density map shows an elongation in the east-west direction, which perfectly aligns with the extended diffuse X-ray emission. We detect two dominant groups around the two brightest cluster galaxies (BCGs). BCG1 (z = 0.1099) can be associated with the main cluster A3653E, and a foreground subcluster A3653W is concentrated at BCG2 (z = 0.1075). Both X-ray peaks are dislocated from the BCGs by ∼35 kpc, which suggest an ongoing merger process. We measure the subcluster gas temperatures of 4.67 and 3.66 keV, respectively. Two-body dynamical analysis shows that A3653E and A3653W are very likely gravitationally bound (93.5 per cent probability). The highly favoured scenario suggests that the two subclusters have a mass ratio of 1.4 and are colliding close to the plane of sky (α = 17.61°) at 2400 km s-1, and will undergo core passage in 380 Myr. The temperature map also significantly shows a shock-heated gas (6.16 keV) between the subclusters, which confirms the supersonic infalling scenario.

  6. On the Merging Cluster Abell 578 and Its Central Radio Galaxy 4C+67.13

    NASA Astrophysics Data System (ADS)

    Hagino, K.; Stawarz, Ł.; Siemiginowska, A.; Cheung, C. C.; Kozieł-Wierzbowska, D.; Szostek, A.; Madejski, G.; Harris, D. E.; Simionescu, A.; Takahashi, T.

    2015-06-01

    Here we analyze radio, optical, and X-ray data for the peculiar cluster Abell 578. This cluster is not fully relaxed and consists of two merging sub-systems. The brightest cluster galaxy (BCG), CGPG 0719.8+6704, is a pair of interacting ellipticals with projected separation ˜10 kpc, the brighter of which hosts the radio source 4C+67.13. The Fanaroff-Riley type-II radio morphology of 4C+67.13 is unusual for central radio galaxies in local Abell clusters. Our new optical spectroscopy revealed that both nuclei of the CGPG 0719.8+6704 pair are active, albeit at low accretion rates corresponding to the Eddington ratio ˜ {{10}-4} (for the estimated black hole masses of ˜ 3× {{10}8} {{M}⊙ } and ˜ {{10}9} {{M}⊙ }). The gathered X-ray (Chandra) data allowed us to confirm and to quantify robustly the previously noted elongation of the gaseous atmosphere in the dominant sub-cluster, as well as a large spatial offset (˜60 kpc projected) between the position of the BCG and the cluster center inferred from the modeling of the X-ray surface brightness distribution. Detailed analysis of the brightness profiles and temperature revealed also that the cluster gas in the vicinity of 4C+67.13 is compressed (by a factor of about ˜1.4) and heated (from ≃ 2.0 keV up to 2.7 keV), consistent with the presence of a weak shock (Mach number ˜1.3) driven by the expanding jet cocoon. This would then require the jet kinetic power of the order of ˜ {{10}45} erg s-1, implying either a very high efficiency of the jet production for the current accretion rate, or a highly modulated jet/accretion activity in the system. Based on service observations made with the WHT operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

  7. X-Ray Spectroscopy of the Cluster of Galaxies Abell 1795 with XMM-Newton

    NASA Technical Reports Server (NTRS)

    Tamura, T.; Kaastra, J. S.; Peterson, J. R.; Paerels, F.; Mittaz, J. P. D.; Trudolyubov, S. P.; Stewart, G.; Fabian, A. C.; Mushotzky, R. F.; Lumb, D. H.

    2000-01-01

    The initial results from XMM-Newton observations of the rich cluster of galaxies Abell 1795 are presented. The spatially-resolved X-ray spectra taken by the European Photon Imaging Cameras (EPIC) show a temperature drop at a radius of - 200 kpc from the cluster center, indicating that the ICM is cooling. Both the EPIC and the Reflection Grating Spectrometers (RGS) spectra extracted from the cluster center can be described by an isothermal model with a temperature of approx. 4 keV. The volume emission measure of any cool component (less than 1 keV) is less than a few % of the hot component at the cluster center. A strong O VIII Lyman alpha line was detected with the RGS from the cluster core. The O abundance of the ICM is 0.2-0.5 times the solar value. The O to Fe ratio at the cluster center is 0.5 - 1.5 times the solar ratio.

  8. On the X-ray spectrum of the volume emissivity arising from Abell clusters

    NASA Technical Reports Server (NTRS)

    Stottlemyer, A. R.; Boldt, E. A.

    1984-01-01

    HEAO 1 A-2 X-ray spectra (2-15 keV) for an optically selected sample of Abell clusters of galaxies with z less than 0.1 have been analyzed to determine the energy dependence of the cosmological X-ray volume emissivity arising from such clusters. This spectrum is well fitted by an isothermal-bremsstrahlung model with kT = 7.4 + or - 1.5 KeV. This result is a test of the isothermal-volume-emissivity spectrum to be inferred from the conjecture that all contributing clusters may be characterized by kT = 7 keV, as assumed by McKee et al. (1980) in estimating the underlying luminosity function for the same sample. Although satisfied at the statistical level indicated, the analysis of a low-luminosity subsample suggests that this assumption of identical isothermal spectra would lead to a systematic error for a more statistically precise determination of the luminosity function's form.

  9. Anisotropic three-dimensional inversion of CSEM data using finite-element techniques on unstructured grids

    NASA Astrophysics Data System (ADS)

    Wang, Feiyan; Morten, Jan Petter; Spitzer, Klaus

    2018-05-01

    In this paper, we present a recently developed anisotropic 3-D inversion framework for interpreting controlled-source electromagnetic (CSEM) data in the frequency domain. The framework integrates a high-order finite-element forward operator and a Gauss-Newton inversion algorithm. Conductivity constraints are applied using a parameter transformation. We discretize the continuous forward and inverse problems on unstructured grids for a flexible treatment of arbitrarily complex geometries. Moreover, an unstructured mesh is more desirable in comparison to a single rectilinear mesh for multisource problems because local grid refinement will not significantly influence the mesh density outside the region of interest. The non-uniform spatial discretization facilitates parametrization of the inversion domain at a suitable scale. For a rapid simulation of multisource EM data, we opt to use a parallel direct solver. We further accelerate the inversion process by decomposing the entire data set into subsets with respect to frequencies (and transmitters if memory requirement is affordable). The computational tasks associated with each data subset are distributed to different processes and run in parallel. We validate the scheme using a synthetic marine CSEM model with rough bathymetry, and finally, apply it to an industrial-size 3-D data set from the Troll field oil province in the North Sea acquired in 2008 to examine its robustness and practical applicability.

  10. A Forward Glimpse into Inverse Problems through a Geology Example

    ERIC Educational Resources Information Center

    Winkel, Brian J.

    2012-01-01

    This paper describes a forward approach to an inverse problem related to detecting the nature of geological substrata which makes use of optimization techniques in a multivariable calculus setting. The true nature of the related inverse problem is highlighted. (Contains 2 figures.)

  11. Diffuse radio emission in the complex merging galaxy cluster Abell2069

    NASA Astrophysics Data System (ADS)

    Drabent, A.; Hoeft, M.; Pizzo, R. F.; Bonafede, A.; van Weeren, R. J.; Klein, U.

    2015-03-01

    Context. Galaxy clusters with signs of a recent merger in many cases show extended diffuse radio features. This emission originates from relativistic electrons that suffer synchrotron losses due to the intracluster magnetic field. The mechanisms of particle acceleration and the properties of the magnetic field are still poorly understood. Aims: We search for diffuse radio emission in galaxy clusters. Here, we study the complex galaxy cluster Abell 2069, for which X-ray observations indicate a recent merger. Methods: We investigate the cluster's radio continuum emission by deep Westerbork Synthesis Radio Telescope (WSRT) observations at 346 MHz and Giant Metrewave Radio Telescope (GMRT) observations at 322 MHz. Results: We find an extended diffuse radio feature roughly coinciding with the main component of the cluster. We classify this emission as a radio halo and estimate its lower limit flux density at 25 ± 9 mJy. Moreover, we find a second extended diffuse source located at the cluster's companion and estimate its flux density at 15 ± 2 mJy. We speculate that this is a small halo or a mini-halo. If true, this cluster is the first example of a double-halo in a single galaxy cluster.

  12. Emissions of organic compounds from produced water ponds II: Evaluation of flux chamber measurements with inverse-modeling techniques.

    PubMed

    Tran, Huy N Q; Lyman, Seth N; Mansfield, Marc L; O'Neil, Trevor; Bowers, Richard L; Smith, Ann P; Keslar, Cara

    2018-07-01

    In this study, the authors apply two different dispersion models to evaluate flux chamber measurements of emissions of 58 organic compounds, including C2-C11 hydrocarbons and methanol, ethanol, and isopropanol from oil- and gas-produced water ponds in the Uintah Basin. Field measurement campaigns using the flux chamber technique were performed at a limited number of produced water ponds in the basin throughout 2013-2016. Inverse-modeling results showed significantly higher emissions than were measured by the flux chamber. Discrepancies between the two methods vary across hydrocarbon compounds and are largest in alcohols due to their physical chemistries. This finding, in combination with findings in a related study using the WATER9 wastewater emission model, suggests that the flux chamber technique may underestimate organic compound emissions, especially alcohols, due to its limited coverage of the pond area and alteration of environmental conditions, especially wind speed. Comparisons of inverse-model estimations with flux chamber measurements varied significantly with the complexity of pond facilities and geometries. Both model results and flux chamber measurements suggest significant contributions from produced water ponds to total organic compound emission from oil and gas productions in the basin. This research is a component of an extensive study that showed significant amount of hydrocarbon emissions from produced water ponds in the Uintah Basin, Utah. Such findings have important meanings to air quality management agencies in developing control strategies for air pollution in oil and gas fields, especially for the Uintah Basin in which ozone pollutions frequently occurred in winter seasons.

  13. Multiple scattering and the density distribution of a Cs MOT.

    PubMed

    Overstreet, K; Zabawa, P; Tallant, J; Schwettmann, A; Shaffer, J

    2005-11-28

    Multiple scattering is studied in a Cs magneto-optical trap (MOT). We use two Abel inversion algorithms to recover density distributions of the MOT from fluorescence images. Deviations of the density distribution from a Gaussian are attributed to multiple scattering.

  14. Statistical atmospheric inversion of local gas emissions by coupling the tracer release technique and local-scale transport modelling: a test case with controlled methane emissions

    NASA Astrophysics Data System (ADS)

    Ars, Sébastien; Broquet, Grégoire; Yver Kwok, Camille; Roustan, Yelva; Wu, Lin; Arzoumanian, Emmanuel; Bousquet, Philippe

    2017-12-01

    This study presents a new concept for estimating the pollutant emission rates of a site and its main facilities using a series of atmospheric measurements across the pollutant plumes. This concept combines the tracer release method, local-scale atmospheric transport modelling and a statistical atmospheric inversion approach. The conversion between the controlled emission and the measured atmospheric concentrations of the released tracer across the plume places valuable constraints on the atmospheric transport. This is used to optimise the configuration of the transport model parameters and the model uncertainty statistics in the inversion system. The emission rates of all sources are then inverted to optimise the match between the concentrations simulated with the transport model and the pollutants' measured atmospheric concentrations, accounting for the transport model uncertainty. In principle, by using atmospheric transport modelling, this concept does not strongly rely on the good colocation between the tracer and pollutant sources and can be used to monitor multiple sources within a single site, unlike the classical tracer release technique. The statistical inversion framework and the use of the tracer data for the configuration of the transport and inversion modelling systems should ensure that the transport modelling errors are correctly handled in the source estimation. The potential of this new concept is evaluated with a relatively simple practical implementation based on a Gaussian plume model and a series of inversions of controlled methane point sources using acetylene as a tracer gas. The experimental conditions are chosen so that they are suitable for the use of a Gaussian plume model to simulate the atmospheric transport. In these experiments, different configurations of methane and acetylene point source locations are tested to assess the efficiency of the method in comparison to the classic tracer release technique in coping with the distances

  15. A direct-inverse method for transonic and separated flows about airfoils

    NASA Technical Reports Server (NTRS)

    Carlson, K. D.

    1985-01-01

    A direct-inverse technique and computer program called TAMSEP that can be sued for the analysis of the flow about airfoils at subsonic and low transonic freestream velocities is presented. The method is based upon a direct-inverse nonconservative full potential inviscid method, a Thwaites laminar boundary layer technique, and the Barnwell turbulent momentum integral scheme; and it is formulated using Cartesian coordinates. Since the method utilizes inverse boundary conditions in regions of separated flow, it is suitable for predicing the flowfield about airfoils having trailing edge separated flow under high lift conditions. Comparisons with experimental data indicate that the method should be a useful tool for applied aerodynamic analyses.

  16. A direct-inverse method for transonic and separated flows about airfoils

    NASA Technical Reports Server (NTRS)

    Carlson, Leland A.

    1990-01-01

    A direct-inverse technique and computer program called TAMSEP that can be used for the analysis of the flow about airfoils at subsonic and low transonic freestream velocities is presented. The method is based upon a direct-inverse nonconservative full potential inviscid method, a Thwaites laminar boundary layer technique, and the Barnwell turbulent momentum integral scheme; and it is formulated using Cartesian coordinates. Since the method utilizes inverse boundary conditions in regions of separated flow, it is suitable for predicting the flow field about airfoils having trailing edge separated flow under high lift conditions. Comparisons with experimental data indicate that the method should be a useful tool for applied aerodynamic analyses.

  17. Efficient 3D inversions using the Richards equation

    NASA Astrophysics Data System (ADS)

    Cockett, Rowan; Heagy, Lindsey J.; Haber, Eldad

    2018-07-01

    Fluid flow in the vadose zone is governed by the Richards equation; it is parameterized by hydraulic conductivity, which is a nonlinear function of pressure head. Investigations in the vadose zone typically require characterizing distributed hydraulic properties. Water content or pressure head data may include direct measurements made from boreholes. Increasingly, proxy measurements from hydrogeophysics are being used to supply more spatially and temporally dense data sets. Inferring hydraulic parameters from such datasets requires the ability to efficiently solve and optimize the nonlinear time domain Richards equation. This is particularly important as the number of parameters to be estimated in a vadose zone inversion continues to grow. In this paper, we describe an efficient technique to invert for distributed hydraulic properties in 1D, 2D, and 3D. Our technique does not store the Jacobian matrix, but rather computes its product with a vector. Existing literature for the Richards equation inversion explicitly calculates the sensitivity matrix using finite difference or automatic differentiation, however, for large scale problems these methods are constrained by computation and/or memory. Using an implicit sensitivity algorithm enables large scale inversion problems for any distributed hydraulic parameters in the Richards equation to become tractable on modest computational resources. We provide an open source implementation of our technique based on the SimPEG framework, and show it in practice for a 3D inversion of saturated hydraulic conductivity using water content data through time.

  18. Experimental investigation of an inversion technique for the determination of broadband duct mode amplitudes by the use of near-field sensor arrays.

    PubMed

    Castres, Fabrice O; Joseph, Phillip F

    2007-08-01

    This paper is an experimental investigation of an inverse technique for deducing the amplitudes of the modes radiated from a turbofan engine, including schemes for stablizing the solution. The detection of broadband modes generated by a laboratory-scaled fan inlet is performed using a near-field array of microphones arranged in a geodesic geometry. This array geometry is shown to allow a robust and accurate modal inversion. The sound power radiated from the fan inlet and the coherence function between different modal amplitudes are also presented. The knowledge of such modal content is useful in helping to characterize the source mechanisms of fan broadband noise generation, for determining the most appropriate mode distribution model for duct liner predictions, and for making sound power measurements of the radiated sound field.

  19. Magnetotelluric inversion via reverse time migration algorithm of seismic data

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ha, Taeyoung; Shin, Changsoo

    2007-07-01

    We propose a new algorithm for two-dimensional magnetotelluric (MT) inversion. Our algorithm is an MT inversion based on the steepest descent method, borrowed from the backpropagation technique of seismic inversion or reverse time migration, introduced in the middle 1980s by Lailly and Tarantola. The steepest descent direction can be calculated efficiently by using the symmetry of numerical Green's function derived from a mixed finite element method proposed by Nedelec for Maxwell's equation, without calculating the Jacobian matrix explicitly. We construct three different objective functions by taking the logarithm of the complex apparent resistivity as introduced in the recent waveform inversionmore » algorithm by Shin and Min. These objective functions can be naturally separated into amplitude inversion, phase inversion and simultaneous inversion. We demonstrate our algorithm by showing three inversion results for synthetic data.« less

  20. Inverse kinematic-based robot control

    NASA Technical Reports Server (NTRS)

    Wolovich, W. A.; Flueckiger, K. F.

    1987-01-01

    A fundamental problem which must be resolved in virtually all non-trivial robotic operations is the well-known inverse kinematic question. More specifically, most of the tasks which robots are called upon to perform are specified in Cartesian (x,y,z) space, such as simple tracking along one or more straight line paths or following a specified surfacer with compliant force sensors and/or visual feedback. In all cases, control is actually implemented through coordinated motion of the various links which comprise the manipulator; i.e., in link space. As a consequence, the control computer of every sophisticated anthropomorphic robot must contain provisions for solving the inverse kinematic problem which, in the case of simple, non-redundant position control, involves the determination of the first three link angles, theta sub 1, theta sub 2, and theta sub 3, which produce a desired wrist origin position P sub xw, P sub yw, and P sub zw at the end of link 3 relative to some fixed base frame. Researchers outline a new inverse kinematic solution and demonstrate its potential via some recent computer simulations. They also compare it to current inverse kinematic methods and outline some of the remaining problems which will be addressed in order to render it fully operational. Also discussed are a number of practical consequences of this technique beyond its obvious use in solving the inverse kinematic question.

  1. The Sunyaev-Zel'dovich Effect in Abell 370

    NASA Technical Reports Server (NTRS)

    Grego, Laura; Carlstrom, John E.; Joy, Marshall K.; Reese, Erik D.; Holder, Gilbert P.; Patel, Sandeep; Holzapfel, William L.; Cooray, Asantha K.

    1999-01-01

    We present interferometric measurements of the Sunyaev-Zel'dovich (SZ) effect towards the galaxy cluster Abell 370. These measurements, which directly probe the pressure of the cluster's gas, show the gas is strongly aspherical, on agreement with the morphology revealed by x-ray and gravitational lensing observations. We calculate the cluster's gas mass fraction by comparing the gas mass derived from the SZ measurements to the lensing-derived gravitational mass near the critical lensing radius. We also calculate the gas mass fraction from the SZ data by deriving the total mass under the assumption that the gas is in hydrostatic equilibrium (HSE). We test the assumptions in the HSE method by comparing the total cluster mass implied by the two methods. The Hubble constant derived for this cluster, when the known systematic uncertainties are included, has a very wide range of values and therefore does not provide additional constraints on the validity of the assumptions. We examine carefully the possible systematic errors in the gas fraction measurement. The gas fraction is a lower limit to the cluster's baryon fraction and so we compare the gas mass fraction, calibrated by numerical simulations to approximately the virial radius, to measurements of the global mass fraction of baryonic matter, OMEGA(sub B)/OMEGA(sub matter). Our lower limit to the cluster baryon fraction is f(sub B) = (0.043 +/- 0.014)/h (sub 100). From this, we derive an upper limit to the universal matter density, OMEGA(sub matter) <= 0.72/h(sub 100), and a likely value of OMEGA(sub matter) <= (0.44(sup 0.15, sub -0.12)/h(sub 100).

  2. Atmospheric inverse modeling via sparse reconstruction

    NASA Astrophysics Data System (ADS)

    Hase, Nils; Miller, Scot M.; Maaß, Peter; Notholt, Justus; Palm, Mathias; Warneke, Thorsten

    2017-10-01

    Many applications in atmospheric science involve ill-posed inverse problems. A crucial component of many inverse problems is the proper formulation of a priori knowledge about the unknown parameters. In most cases, this knowledge is expressed as a Gaussian prior. This formulation often performs well at capturing smoothed, large-scale processes but is often ill equipped to capture localized structures like large point sources or localized hot spots. Over the last decade, scientists from a diverse array of applied mathematics and engineering fields have developed sparse reconstruction techniques to identify localized structures. In this study, we present a new regularization approach for ill-posed inverse problems in atmospheric science. It is based on Tikhonov regularization with sparsity constraint and allows bounds on the parameters. We enforce sparsity using a dictionary representation system. We analyze its performance in an atmospheric inverse modeling scenario by estimating anthropogenic US methane (CH4) emissions from simulated atmospheric measurements. Different measures indicate that our sparse reconstruction approach is better able to capture large point sources or localized hot spots than other methods commonly used in atmospheric inversions. It captures the overall signal equally well but adds details on the grid scale. This feature can be of value for any inverse problem with point or spatially discrete sources. We show an example for source estimation of synthetic methane emissions from the Barnett shale formation.

  3. Computational inverse methods of heat source in fatigue damage problems

    NASA Astrophysics Data System (ADS)

    Chen, Aizhou; Li, Yuan; Yan, Bo

    2018-04-01

    Fatigue dissipation energy is the research focus in field of fatigue damage at present. It is a new idea to solve the problem of calculating fatigue dissipation energy by introducing inverse method of heat source into parameter identification of fatigue dissipation energy model. This paper introduces the research advances on computational inverse method of heat source and regularization technique to solve inverse problem, as well as the existing heat source solution method in fatigue process, prospects inverse method of heat source applying in fatigue damage field, lays the foundation for further improving the effectiveness of fatigue dissipation energy rapid prediction.

  4. Synthesis of nanostructured materials in inverse miniemulsions and their applications.

    PubMed

    Cao, Zhihai; Ziener, Ulrich

    2013-11-07

    Polymeric nanogels, inorganic nanoparticles, and organic-inorganic hybrid nanoparticles can be prepared via the inverse miniemulsion technique. Hydrophilic functional cargos, such as proteins, DNA, and macromolecular fluoresceins, may be conveniently encapsulated in these nanostructured materials. In this review, the progress of inverse miniemulsions since 2000 is summarized on the basis of the types of reactions carried out in inverse miniemulsions, including conventional free radical polymerization, controlled/living radical polymerization, polycondensation, polyaddition, anionic polymerization, catalytic oxidation reaction, sol-gel process, and precipitation reaction of inorganic precursors. In addition, the applications of the nanostructured materials synthesized in inverse miniemulsions are also reviewed.

  5. Joint inversion of regional and teleseismic earthquake waveforms

    NASA Astrophysics Data System (ADS)

    Baker, Mark R.; Doser, Diane I.

    1988-03-01

    A least squares joint inversion technique for regional and teleseismic waveforms is presented. The mean square error between seismograms and synthetics is minimized using true amplitudes. Matching true amplitudes in modeling requires meaningful estimates of modeling uncertainties and of seismogram signal-to-noise ratios. This also permits calculating linearized uncertainties on the solution based on accuracy and resolution. We use a priori estimates of earthquake parameters to stabilize unresolved parameters, and for comparison with a posteriori uncertainties. We verify the technique on synthetic data, and on the 1983 Borah Peak, Idaho (M = 7.3), earthquake. We demonstrate the inversion on the August 1954 Rainbow Mountain, Nevada (M = 6.8), earthquake and find parameters consistent with previous studies.

  6. Non-recursive augmented Lagrangian algorithms for the forward and inverse dynamics of constrained flexible multibodies

    NASA Technical Reports Server (NTRS)

    Bayo, Eduardo; Ledesma, Ragnar

    1993-01-01

    A technique is presented for solving the inverse dynamics of flexible planar multibody systems. This technique yields the non-causal joint efforts (inverse dynamics) as well as the internal states (inverse kinematics) that produce a prescribed nominal trajectory of the end effector. A non-recursive global Lagrangian approach is used in formulating the equations for motion as well as in solving the inverse dynamics equations. Contrary to the recursive method previously presented, the proposed method solves the inverse problem in a systematic and direct manner for both open-chain as well as closed-chain configurations. Numerical simulation shows that the proposed procedure provides an excellent tracking of the desired end effector trajectory.

  7. An evolutive real-time source inversion based on a linear inverse formulation

    NASA Astrophysics Data System (ADS)

    Sanchez Reyes, H. S.; Tago, J.; Cruz-Atienza, V. M.; Metivier, L.; Contreras Zazueta, M. A.; Virieux, J.

    2016-12-01

    Finite source inversion is a steppingstone to unveil earthquake rupture. It is used on ground motion predictions and its results shed light on seismic cycle for better tectonic understanding. It is not yet used for quasi-real-time analysis. Nowadays, significant progress has been made on approaches regarding earthquake imaging, thanks to new data acquisition and methodological advances. However, most of these techniques are posterior procedures once seismograms are available. Incorporating source parameters estimation into early warning systems would require to update the source build-up while recording data. In order to go toward this dynamic estimation, we developed a kinematic source inversion formulated in the time-domain, for which seismograms are linearly related to the slip distribution on the fault through convolutions with Green's functions previously estimated and stored (Perton et al., 2016). These convolutions are performed in the time-domain as we progressively increase the time window of records at each station specifically. Selected unknowns are the spatio-temporal slip-rate distribution to keep the linearity of the forward problem with respect to unknowns, as promoted by Fan and Shearer (2014). Through the spatial extension of the expected rupture zone, we progressively build-up the slip-rate when adding new data by assuming rupture causality. This formulation is based on the adjoint-state method for efficiency (Plessix, 2006). The inverse problem is non-unique and, in most cases, underdetermined. While standard regularization terms are used for stabilizing the inversion, we avoid strategies based on parameter reduction leading to an unwanted non-linear relationship between parameters and seismograms for our progressive build-up. Rise time, rupture velocity and other quantities can be extracted later on as attributs from the slip-rate inversion we perform. Satisfactory results are obtained on a synthetic example (FIgure 1) proposed by the Source

  8. Inverse halftoning via robust nonlinear filtering

    NASA Astrophysics Data System (ADS)

    Shen, Mei-Yin; Kuo, C.-C. Jay

    1999-10-01

    A new blind inverse halftoning algorithm based on a nonlinear filtering technique of low computational complexity and low memory requirement is proposed in this research. It is called blind since we do not require the knowledge of the halftone kernel. The proposed scheme performs nonlinear filtering in conjunction with edge enhancement to improve the quality of an inverse halftoned image. Distinct features of the proposed approach include: efficiently smoothing halftone patterns in large homogeneous areas, additional edge enhancement capability to recover the edge quality and an excellent PSNR performance with only local integer operations and a small memory buffer.

  9. Diffuse X-ray emission from Abell clusters 401 and 399 - A gravitationally bound system

    NASA Technical Reports Server (NTRS)

    Ulmer, M. P.; Kinzer, R.; Cruddace, R. G.; Wood, K.; Evans, W.; Byram, E. T.; Chubb, T. A.; Friedman, H.

    1979-01-01

    The X-ray emission from the Abell 401-399 region has been studied using data obtained by the A-1 proportional counter aboard HEAO 1 in two different ways. The first involved routine scanning of the region during the all-sky survey, and the second was an observation in which the instrument was pointed at A401 during a lunar occultation. The emission is shown to be unusually extended and to be centered on a point lying between A401 and A399. The best fit of a uniform disk model to the data yielded a radius of 25.5 + or -4.4 arcmin for the lunar occultation and 42 + or - 17 arcmin for the scans. A possible explanation of the results is that A401 and A399 are both diffuse cluster X-ray sources. Alternatively, the emission may come from a large gas cloud of at least 10 to the 15th solar masses enveloping both clusters.

  10. GalWeight: A New and Effective Weighting Technique for Determining Galaxy Cluster and Group Membership

    NASA Astrophysics Data System (ADS)

    Abdullah, Mohamed H.; Wilson, Gillian; Klypin, Anatoly

    2018-07-01

    We introduce GalWeight, a new technique for assigning galaxy cluster membership. This technique is specifically designed to simultaneously maximize the number of bona fide cluster members while minimizing the number of contaminating interlopers. The GalWeight technique can be applied to both massive galaxy clusters and poor galaxy groups. Moreover, it is effective in identifying members in both the virial and infall regions with high efficiency. We apply the GalWeight technique to MDPL2 and Bolshoi N-body simulations, and find that it is >98% accurate in correctly assigning cluster membership. We show that GalWeight compares very favorably against four well-known existing cluster membership techniques (shifting gapper, den Hartog, caustic, SIM). We also apply the GalWeight technique to a sample of 12 Abell clusters (including the Coma cluster) using observations from the Sloan Digital Sky Survey. We conclude by discussing GalWeight’s potential for other astrophysical applications.

  11. Anatomy of a Merger: A Deep Chandra Observation of Abell 115

    NASA Astrophysics Data System (ADS)

    Forman, William R.

    2017-08-01

    A deep Chandra observation of Abell 115 provides a unique probe of the anatomy of cluster mergers. The X-ray image shows two prominent subclusters, A115N (north) and A115S (south) with a projected separation of almost 1 Mpc. The X-ray subclusters each have ram-pressure stripped tails that unambiguously indicate the directions of motion. The central BCG of A115N hosts the radio source 3C28 which shows a pair of jets, almost perpendicular to the direction of the sucluster's motion. The jets terminate in lobes each of which has a "tail" pointing IN the direction of motion of the subcluster. The Chandra analysis provides details of the merger including the velocities of the subclusters both through analysis of the cold front and a weak shock. The motion of A115N through the cluster generates counter-rotating vortices in the subcluster gas that form the two radio tails. Hydrodynamic modeling yields circulation velocities within the A115N sub cluster. Thus, the radio emitting plasma acts as a dye tracing the motions of the X-ray emitting plasma. A115S shows two "cores", one coincident with the BCG and a second appears as a ram pressure stripped tail.

  12. Diffuse light and building history of the galaxy cluster Abell 2667

    NASA Astrophysics Data System (ADS)

    Covone, G.; Adami, C.; Durret, F.; Kneib, J.-P.; Lima Neto, G. B.; Slezak, E.

    2006-12-01

    Aims.We searched for diffuse intracluster light in the galaxy cluster Abell 2667 (z=0.233) from HST images in three broad band-filters. Methods: .We applied an iterative multi-scale wavelet analysis and reconstruction technique to these images, which allows to subtract stars and galaxies from the original images. Results: .We detect a zone of diffuse emission southwest of the cluster center (DS1) and a second faint object (ComDif) within DS1. Another diffuse source (DS2) may be detected at lower confidence level northeast of the center. These sources of diffuse light contribute to 10-15% of the total visible light in the cluster. Whether they are independent entities or part of the very elliptical external envelope of the central galaxy remains unclear. Deep VLT VIMOS integral field spectroscopy reveals a faint continuum at the positions of DS1 and ComDif but do not allow a redshift to be computed, so we conclude if these sources are part of the central galaxy or not. A hierarchical substructure detection method reveals the presence of several galaxy pairs and groups defining a similar direction to the one drawn by the DS1 - central galaxy - DS2 axis. The analysis of archive XMM-Newton and Chandra observations shows X-ray emission elongated in the same direction. The X-ray temperature map shows the presence of a cool core, a broad cool zone stretching from north to south, and hotter regions towards the northeast, southwest, and northwest. This might suggest shock fronts along these directions produced by infalling material, even if uncertainties remain quite large on the temperature determination far from the center. Conclusions: .These various data are consistent with a picture in which diffuse sources are concentrations of tidal debris and harassed matter expelled from infalling galaxies by tidal stripping and undergoing an accretion process onto the central cluster galaxy; as such, they are expected to be found along the main infall directions. Note, however

  13. Neural network explanation using inversion.

    PubMed

    Saad, Emad W; Wunsch, Donald C

    2007-01-01

    An important drawback of many artificial neural networks (ANN) is their lack of explanation capability [Andrews, R., Diederich, J., & Tickle, A. B. (1996). A survey and critique of techniques for extracting rules from trained artificial neural networks. Knowledge-Based Systems, 8, 373-389]. This paper starts with a survey of algorithms which attempt to explain the ANN output. We then present HYPINV, a new explanation algorithm which relies on network inversion; i.e. calculating the ANN input which produces a desired output. HYPINV is a pedagogical algorithm, that extracts rules, in the form of hyperplanes. It is able to generate rules with arbitrarily desired fidelity, maintaining a fidelity-complexity tradeoff. To our knowledge, HYPINV is the only pedagogical rule extraction method, which extracts hyperplane rules from continuous or binary attribute neural networks. Different network inversion techniques, involving gradient descent as well as an evolutionary algorithm, are presented. An information theoretic treatment of rule extraction is presented. HYPINV is applied to example synthetic problems, to a real aerospace problem, and compared with similar algorithms using benchmark problems.

  14. STRONG GRAVITATIONAL LENSING BY THE SUPER-MASSIVE cD GALAXY IN ABELL 3827

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Carrasco, E. R.; Gomez, P. L.; Lee, H.

    2010-06-01

    We have discovered strong gravitational lensing features in the core of the nearby cluster Abell 3827 by analyzing Gemini South GMOS images. The most prominent strong lensing feature is a highly magnified, ring-shaped configuration of four images around the central cD galaxy. GMOS spectroscopic analysis puts this source at z {approx} 0.2. Located {approx}20'' away from the central galaxy is a secondary tangential arc feature which has been identified as a background galaxy with z {approx} 0.4. We have modeled the gravitational potential of the cluster core, taking into account the mass from the cluster, the brightest cluster galaxy (BCG),more » and other galaxies. We derive a total mass of (2.7 {+-} 0.4) x 10{sup 13} M {sub sun} within 37 h {sup -1} kpc. This mass is an order of magnitude larger than that derived from X-ray observations. The total mass derived from lensing data suggests that the BCG in this cluster is perhaps the most massive galaxy in the nearby universe.« less

  15. Canibalismo Extremo y Lente Gravitacional Intensa en el Cúmulo de Galaxias Abell 3827

    NASA Astrophysics Data System (ADS)

    Díaz, R. J.; West, M.; Bergmann, M.; Carrasco, E. R.; Gomez, P.; Lee, H.; Miller, B.; Turner, J.

    Abell 3827 is one of the most massive known clusters and at its center we observe an extreme example of galactic canibalism: a super giant elliptical galaxy in its formation process, devoring five massive galaxies at the same time. Using high spatial resolution Gemini+GMOS imagery and multi-object spectroscopy, we derived the redshift (z=0.099) and the radial velocity dispersion of the 55 brightest galaxies in the cluster central region (1134 +- 125 km/s). The estimated virial mass is ~ 1E14 M(sun) inside a radius of 300 kpc of the cluster center. We have also found features corresponding to a strong gravitational lense, four anular features arranged in an Einstein Ring from a galaxy (z=0.2) at double redshift than the cluster, and a fifth arclet feature corresponding to the lensed light of a farther galaxy (z=0.4). The possible Einstein Ring is of small angular size and the gravitational lense morphology would confirm that the cluster is indeed very massive and dense. FULL TEXT IN SPANISH.

  16. Joint inversion of geophysical data using petrophysical clustering and facies deformation wth the level set technique

    NASA Astrophysics Data System (ADS)

    Revil, A.

    2015-12-01

    Geological expertise and petrophysical relationships can be brought together to provide prior information while inverting multiple geophysical datasets. The merging of such information can result in more realistic solution in the distribution of the model parameters, reducing ipse facto the non-uniqueness of the inverse problem. We consider two level of heterogeneities: facies, described by facies boundaries and heteroegenities inside each facies determined by a correlogram. In this presentation, we pose the geophysical inverse problem in terms of Gaussian random fields with mean functions controlled by petrophysical relationships and covariance functions controlled by a prior geological cross-section, including the definition of spatial boundaries for the geological facies. The petrophysical relationship problem is formulated as a regression problem upon each facies. The inversion of the geophysical data is performed in a Bayesian framework. We demonstrate the usefulness of this strategy using a first synthetic case for which we perform a joint inversion of gravity and galvanometric resistivity data with the stations located at the ground surface. The joint inversion is used to recover the density and resistivity distributions of the subsurface. In a second step, we consider the possibility that the facies boundaries are deformable and their shapes are inverted as well. We use the level set approach to perform such deformation preserving prior topological properties of the facies throughout the inversion. With the help of prior facies petrophysical relationships and topological characteristic of each facies, we make posterior inference about multiple geophysical tomograms based on their corresponding geophysical data misfits. The method is applied to a second synthetic case showing that we can recover the heterogeneities inside the facies, the mean values for the petrophysical properties, and, to some extent, the facies boundaries using the 2D joint inversion of

  17. Nonlinear adaptive inverse control via the unified model neural network

    NASA Astrophysics Data System (ADS)

    Jeng, Jin-Tsong; Lee, Tsu-Tian

    1999-03-01

    In this paper, we propose a new nonlinear adaptive inverse control via a unified model neural network. In order to overcome nonsystematic design and long training time in nonlinear adaptive inverse control, we propose the approximate transformable technique to obtain a Chebyshev Polynomials Based Unified Model (CPBUM) neural network for the feedforward/recurrent neural networks. It turns out that the proposed method can use less training time to get an inverse model. Finally, we apply this proposed method to control magnetic bearing system. The experimental results show that the proposed nonlinear adaptive inverse control architecture provides a greater flexibility and better performance in controlling magnetic bearing systems.

  18. Limit on graviton mass from galaxy cluster Abell 1689

    NASA Astrophysics Data System (ADS)

    Desai, Shantanu

    2018-02-01

    To date, the only limit on graviton mass using galaxy clusters was obtained by Goldhaber and Nieto in 1974, using the fact that the orbits of galaxy clusters are bound and closed, and extend up to 580 kpc. From positing that only a Newtonian potential gives rise to such stable bound orbits, a limit on the graviton mass m_g<10^{-29} eV was obtained (PRD 9,1119, 1974). Recently, it has been shown that one can obtain closed bound orbits for Yukawa potential (arXiv:1705.02444), thus invalidating the main ansatz used in Goldhaber and Nieto to obtain the graviton mass bound. In order to obtain a revised estimate using galaxy clusters, we use dynamical mass models of the Abell 1689 (A1689) galaxy cluster to check their compatibility with a Yukawa gravitational potential. We assume mass models for the gas, dark matter, and galaxies for A1689 from arXiv:1703.10219 and arXiv:1610.01543, who used this cluster to test various alternate gravity theories, which dispense with the need for dark matter. We quantify the deviations in the acceleration profile using these mass models assuming a Yukawa potential and that obtained assuming a Newtonian potential by calculating the χ^2 residuals between the two profiles. Our estimated bound on the graviton mass (m_g) is thereby given by, m_g < 1.37 × 10^{-29} eV or in terms of the graviton Compton wavelength of, λ_g>9.1 × 10^{19} km at 90% confidence level.

  19. The solar occultation technique for remote sensing of particulates in the earth's atmosphere. I - The inversion of horizon radiances from space

    NASA Technical Reports Server (NTRS)

    Schuerman, D. W.; Giovane, F.; Greenberg, J. M.

    1976-01-01

    The aerosol scattering coefficient as a function of height can be recovered from a direct inversion of the single-scattering horizon radiance provided the sun is above the horizon and an independent measurement of extinction as a function of height is made. Aerosol detection is effected by means of spacecraft measurements of the horizon radiance made during periods of spacecraft twilight. A solar occultation technique which allows the twilight measurements to be made when the sun is still above the horizon greatly reduces the complexity of the inversion problem. The second part of the paper reports on the use of a coronograph aboard Skylab to photograph the horizon just before spacecraft twilight in order to monitor the aerosol component above the tropopause. The coronograph picture, centered on 26.5 degrees E longitude and 63.0 degrees S latitude, shows that the aerosol layer peaks at a height of 48 plus or minus 1 km.

  20. A Computationally Efficient Parallel Levenberg-Marquardt Algorithm for Large-Scale Big-Data Inversion

    NASA Astrophysics Data System (ADS)

    Lin, Y.; O'Malley, D.; Vesselinov, V. V.

    2015-12-01

    Inverse modeling seeks model parameters given a set of observed state variables. However, for many practical problems due to the facts that the observed data sets are often large and model parameters are often numerous, conventional methods for solving the inverse modeling can be computationally expensive. We have developed a new, computationally-efficient Levenberg-Marquardt method for solving large-scale inverse modeling. Levenberg-Marquardt methods require the solution of a dense linear system of equations which can be prohibitively expensive to compute for large-scale inverse problems. Our novel method projects the original large-scale linear problem down to a Krylov subspace, such that the dimensionality of the measurements can be significantly reduced. Furthermore, instead of solving the linear system for every Levenberg-Marquardt damping parameter, we store the Krylov subspace computed when solving the first damping parameter and recycle it for all the following damping parameters. The efficiency of our new inverse modeling algorithm is significantly improved by using these computational techniques. We apply this new inverse modeling method to invert for a random transitivity field. Our algorithm is fast enough to solve for the distributed model parameters (transitivity) at each computational node in the model domain. The inversion is also aided by the use regularization techniques. The algorithm is coded in Julia and implemented in the MADS computational framework (http://mads.lanl.gov). Julia is an advanced high-level scientific programing language that allows for efficient memory management and utilization of high-performance computational resources. By comparing with a Levenberg-Marquardt method using standard linear inversion techniques, our Levenberg-Marquardt method yields speed-up ratio of 15 in a multi-core computational environment and a speed-up ratio of 45 in a single-core computational environment. Therefore, our new inverse modeling method is a

  1. Aerosol properties from spectral extinction and backscatter estimated by an inverse Monte Carlo method.

    PubMed

    Ligon, D A; Gillespie, J B; Pellegrino, P

    2000-08-20

    The feasibility of using a generalized stochastic inversion methodology to estimate aerosol size distributions accurately by use of spectral extinction, backscatter data, or both is examined. The stochastic method used, inverse Monte Carlo (IMC), is verified with both simulated and experimental data from aerosols composed of spherical dielectrics with a known refractive index. Various levels of noise are superimposed on the data such that the effect of noise on the stability and results of inversion can be determined. Computational results show that the application of the IMC technique to inversion of spectral extinction or backscatter data or both can produce good estimates of aerosol size distributions. Specifically, for inversions for which both spectral extinction and backscatter data are used, the IMC technique was extremely accurate in determining particle size distributions well outside the wavelength range. Also, the IMC inversion results proved to be stable and accurate even when the data had significant noise, with a signal-to-noise ratio of 3.

  2. Nonlinear Stimulated Raman Exact Passage by Resonance-Locked Inverse Engineering

    NASA Astrophysics Data System (ADS)

    Dorier, V.; Gevorgyan, M.; Ishkhanyan, A.; Leroy, C.; Jauslin, H. R.; Guérin, S.

    2017-12-01

    We derive an exact and robust stimulated Raman process for nonlinear quantum systems driven by pulsed external fields. The external fields are designed with closed-form expressions from the inverse engineering of a given efficient and stable dynamics. This technique allows one to induce a controlled population inversion which surpasses the usual nonlinear stimulated Raman adiabatic passage efficiency.

  3. Aerosol physical properties from satellite horizon inversion

    NASA Technical Reports Server (NTRS)

    Gray, C. R.; Malchow, H. L.; Merritt, D. C.; Var, R. E.; Whitney, C. K.

    1973-01-01

    The feasibility is investigated of determining the physical properties of aerosols globally in the altitude region of 10 to 100 km from a satellite horizon scanning experiment. The investigation utilizes a horizon inversion technique previously developed and extended. Aerosol physical properties such as number density, size distribution, and the real and imaginary components of the index of refraction are demonstrated to be invertible in the aerosol size ranges (0.01-0.1 microns), (0.1-1.0 microns), (1.0-10 microns). Extensions of previously developed radiative transfer models and recursive inversion algorithms are displayed.

  4. Molecular inversion probe assay.

    PubMed

    Absalan, Farnaz; Ronaghi, Mostafa

    2007-01-01

    We have described molecular inversion probe technologies for large-scale genetic analyses. This technique provides a comprehensive and powerful tool for the analysis of genetic variation and enables affordable, large-scale studies that will help uncover the genetic basis of complex disease and explain the individual variation in response to therapeutics. Major applications of the molecular inversion probes (MIP) technologies include targeted genotyping from focused regions to whole-genome studies, and allele quantification of genomic rearrangements. The MIP technology (used in the HapMap project) provides an efficient, scalable, and affordable way to score polymorphisms in case/control populations for genetic studies. The MIP technology provides the highest commercially available multiplexing levels and assay conversion rates for targeted genotyping. This enables more informative, genome-wide studies with either the functional (direct detection) approach or the indirect detection approach.

  5. Efficient sampling of parsimonious inversion histories with application to genome rearrangement in Yersinia.

    PubMed

    Miklós, István; Darling, Aaron E

    2009-06-22

    Inversions are among the most common mutations acting on the order and orientation of genes in a genome, and polynomial-time algorithms exist to obtain a minimal length series of inversions that transform one genome arrangement to another. However, the minimum length series of inversions (the optimal sorting path) is often not unique as many such optimal sorting paths exist. If we assume that all optimal sorting paths are equally likely, then statistical inference on genome arrangement history must account for all such sorting paths and not just a single estimate. No deterministic polynomial algorithm is known to count the number of optimal sorting paths nor sample from the uniform distribution of optimal sorting paths. Here, we propose a stochastic method that uniformly samples the set of all optimal sorting paths. Our method uses a novel formulation of parallel Markov chain Monte Carlo. In practice, our method can quickly estimate the total number of optimal sorting paths. We introduce a variant of our approach in which short inversions are modeled to be more likely, and we show how the method can be used to estimate the distribution of inversion lengths and breakpoint usage in pathogenic Yersinia pestis. The proposed method has been implemented in a program called "MC4Inversion." We draw comparison of MC4Inversion to the sampler implemented in BADGER and a previously described importance sampling (IS) technique. We find that on high-divergence data sets, MC4Inversion finds more optimal sorting paths per second than BADGER and the IS technique and simultaneously avoids bias inherent in the IS technique.

  6. Efficient Sampling of Parsimonious Inversion Histories with Application to Genome Rearrangement in Yersinia

    PubMed Central

    Darling, Aaron E.

    2009-01-01

    Inversions are among the most common mutations acting on the order and orientation of genes in a genome, and polynomial-time algorithms exist to obtain a minimal length series of inversions that transform one genome arrangement to another. However, the minimum length series of inversions (the optimal sorting path) is often not unique as many such optimal sorting paths exist. If we assume that all optimal sorting paths are equally likely, then statistical inference on genome arrangement history must account for all such sorting paths and not just a single estimate. No deterministic polynomial algorithm is known to count the number of optimal sorting paths nor sample from the uniform distribution of optimal sorting paths. Here, we propose a stochastic method that uniformly samples the set of all optimal sorting paths. Our method uses a novel formulation of parallel Markov chain Monte Carlo. In practice, our method can quickly estimate the total number of optimal sorting paths. We introduce a variant of our approach in which short inversions are modeled to be more likely, and we show how the method can be used to estimate the distribution of inversion lengths and breakpoint usage in pathogenic Yersinia pestis. The proposed method has been implemented in a program called “MC4Inversion.” We draw comparison of MC4Inversion to the sampler implemented in BADGER and a previously described importance sampling (IS) technique. We find that on high-divergence data sets, MC4Inversion finds more optimal sorting paths per second than BADGER and the IS technique and simultaneously avoids bias inherent in the IS technique. PMID:20333186

  7. Recursive partitioned inversion of large (1500 x 1500) symmetric matrices

    NASA Technical Reports Server (NTRS)

    Putney, B. H.; Brownd, J. E.; Gomez, R. A.

    1976-01-01

    A recursive algorithm was designed to invert large, dense, symmetric, positive definite matrices using small amounts of computer core, i.e., a small fraction of the core needed to store the complete matrix. The described algorithm is a generalized Gaussian elimination technique. Other algorithms are also discussed for the Cholesky decomposition and step inversion techniques. The purpose of the inversion algorithm is to solve large linear systems of normal equations generated by working geodetic problems. The algorithm was incorporated into a computer program called SOLVE. In the past the SOLVE program has been used in obtaining solutions published as the Goddard earth models.

  8. Application of Carbonate Reservoir using waveform inversion and reverse-time migration methods

    NASA Astrophysics Data System (ADS)

    Kim, W.; Kim, H.; Min, D.; Keehm, Y.

    2011-12-01

    Recent exploration targets of oil and gas resources are deeper and more complicated subsurface structures, and carbonate reservoirs have become one of the attractive and challenging targets in seismic exploration. To increase the rate of success in oil and gas exploration, it is required to delineate detailed subsurface structures. Accordingly, migration method is more important factor in seismic data processing for the delineation. Seismic migration method has a long history, and there have been developed lots of migration techniques. Among them, reverse-time migration is promising, because it can provide reliable images for the complicated model even in the case of significant velocity contrasts in the model. The reliability of seismic migration images is dependent on the subsurface velocity models, which can be extracted in several ways. These days, geophysicists try to obtain velocity models through seismic full waveform inversion. Since Lailly (1983) and Tarantola (1984) proposed that the adjoint state of wave equations can be used in waveform inversion, the back-propagation techniques used in reverse-time migration have been used in waveform inversion, which accelerated the development of waveform inversion. In this study, we applied acoustic waveform inversion and reverse-time migration methods to carbonate reservoir models with various reservoir thicknesses to examine the feasibility of the methods in delineating carbonate reservoir models. We first extracted subsurface material properties from acoustic waveform inversion, and then applied reverse-time migration using the inverted velocities as a background model. The waveform inversion in this study used back-propagation technique, and conjugate gradient method was used in optimization. The inversion was performed using the frequency-selection strategy. Finally waveform inversion results showed that carbonate reservoir models are clearly inverted by waveform inversion and migration images based on the

  9. On the Duality of Forward and Inverse Light Transport.

    PubMed

    Chandraker, Manmohan; Bai, Jiamin; Ng, Tian-Tsong; Ramamoorthi, Ravi

    2011-10-01

    Inverse light transport seeks to undo global illumination effects, such as interreflections, that pervade images of most scenes. This paper presents the theoretical and computational foundations for inverse light transport as a dual of forward rendering. Mathematically, this duality is established through the existence of underlying Neumann series expansions. Physically, it can be shown that each term of our inverse series cancels an interreflection bounce, just as the forward series adds them. While the convergence properties of the forward series are well known, we show that the oscillatory convergence of the inverse series leads to more interesting conditions on material reflectance. Conceptually, the inverse problem requires the inversion of a large light transport matrix, which is impractical for realistic resolutions using standard techniques. A natural consequence of our theoretical framework is a suite of fast computational algorithms for light transport inversion--analogous to finite element radiosity, Monte Carlo and wavelet-based methods in forward rendering--that rely at most on matrix-vector multiplications. We demonstrate two practical applications, namely, separation of individual bounces of the light transport and fast projector radiometric compensation, to display images free of global illumination artifacts in real-world environments.

  10. Eruption mass estimation using infrasound waveform inversion and ash and gas measurements: Evaluation at Sakurajima Volcano, Japan [Comparison of eruption masses at Sakurajima Volcano, Japan calculated by infrasound waveform inversion and ground-based sampling

    DOE PAGES

    Fee, David; Izbekov, Pavel; Kim, Keehoon; ...

    2017-10-09

    Eruption mass and mass flow rate are critical parameters for determining the aerial extent and hazard of volcanic emissions. Infrasound waveform inversion is a promising technique to quantify volcanic emissions. Although topography may substantially alter the infrasound waveform as it propagates, advances in wave propagation modeling and station coverage permit robust inversion of infrasound data from volcanic explosions. The inversion can estimate eruption mass flow rate and total eruption mass if the flow density is known. However, infrasound-based eruption flow rates and mass estimates have yet to be validated against independent measurements, and numerical modeling has only recently been appliedmore » to the inversion technique. Furthermore we present a robust full-waveform acoustic inversion method, and use it to calculate eruption flow rates and masses from 49 explosions from Sakurajima Volcano, Japan.« less

  11. Eruption mass estimation using infrasound waveform inversion and ash and gas measurements: Evaluation at Sakurajima Volcano, Japan [Comparison of eruption masses at Sakurajima Volcano, Japan calculated by infrasound waveform inversion and ground-based sampling

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fee, David; Izbekov, Pavel; Kim, Keehoon

    Eruption mass and mass flow rate are critical parameters for determining the aerial extent and hazard of volcanic emissions. Infrasound waveform inversion is a promising technique to quantify volcanic emissions. Although topography may substantially alter the infrasound waveform as it propagates, advances in wave propagation modeling and station coverage permit robust inversion of infrasound data from volcanic explosions. The inversion can estimate eruption mass flow rate and total eruption mass if the flow density is known. However, infrasound-based eruption flow rates and mass estimates have yet to be validated against independent measurements, and numerical modeling has only recently been appliedmore » to the inversion technique. Furthermore we present a robust full-waveform acoustic inversion method, and use it to calculate eruption flow rates and masses from 49 explosions from Sakurajima Volcano, Japan.« less

  12. XMM-Newton Observations of the Southeastern Radio Relic in Abell 3667

    NASA Astrophysics Data System (ADS)

    Storm, Emma; Vink, Jacco; Zandanel, Fabio; Akamatsu, Hiroki

    2018-06-01

    Radio relics, elongated, non-thermal, structures located at the edges of galaxy clusters, are the result of synchrotron radiation from cosmic-ray electrons accelerated by merger-driven shocks at the cluster outskirts. However, X-ray observations of such shocks in some clusters suggest that they are too weak to efficiently accelerate electrons via diffusive shock acceleration to energies required to produce the observed radio power. We examine this issue in the merging galaxy cluster Abell 3667 (A3667), which hosts a pair of radio relics. While the Northwest relic in A3667 has been well studied in the radio and X-ray by multiple instruments, the Southeast relic region has only been observed so far by Suzaku, which detected a temperature jump across the relic, suggesting the presence of a weak shock. We present observations of the Southeastern region of A3667 with XMM-Newton centered on the radio relic. We confirm the existence of an X-ray shock with Mach number of about 1.8 from a clear detection of temperature jump and a tentative detection of a density jump, consistent with previous measurements by Suzaku. We discuss the implications of this measurement for diffusive shock acceleration as the main mechanism for explaining the origin of radio relics. We then speculate on the plausibility of alternative scenarios, including re-acceleration and variations in the Mach number along shock fronts.

  13. Cardiovascular magnetic resonance of myocardial edema using a short inversion time inversion recovery (STIR) black-blood technique: Diagnostic accuracy of visual and semi-quantitative assessment

    PubMed Central

    2012-01-01

    Background The short inversion time inversion recovery (STIR) black-blood technique has been used to visualize myocardial edema, and thus to differentiate acute from chronic myocardial lesions. However, some cardiovascular magnetic resonance (CMR) groups have reported variable image quality, and hence the diagnostic value of STIR in routine clinical practice has been put into question. The aim of our study was to analyze image quality and diagnostic performance of STIR using a set of pulse sequence parameters dedicated to edema detection, and to discuss possible factors that influence image quality. We hypothesized that STIR imaging is an accurate and robust way of detecting myocardial edema in non-selected patients with acute myocardial infarction. Methods Forty-six consecutive patients with acute myocardial infarction underwent CMR (day 4.5, +/- 1.6) including STIR for the assessment of myocardial edema and late gadolinium enhancement (LGE) for quantification of myocardial necrosis. Thirty of these patients underwent a follow-up CMR at approximately six months (195 +/- 39 days). Both STIR and LGE images were evaluated separately on a segmental basis for image quality as well as for presence and extent of myocardial hyper-intensity, with both visual and semi-quantitative (threshold-based) analysis. LGE was used as a reference standard for localization and extent of myocardial necrosis (acute) or scar (chronic). Results Image quality of STIR images was rated as diagnostic in 99.5% of cases. At the acute stage, the sensitivity and specificity of STIR to detect infarcted segments on visual assessment was 95% and 78% respectively, and on semi-quantitative assessment was 99% and 83%, respectively. STIR differentiated acutely from chronically infarcted segments with a sensitivity of 95% by both methods and with a specificity of 99% by visual assessment and 97% by semi-quantitative assessment. The extent of hyper-intense areas on acute STIR images was 85% larger than

  14. Lens models under the microscope: comparison of Hubble Frontier Field cluster magnification maps

    NASA Astrophysics Data System (ADS)

    Priewe, Jett; Williams, Liliya L. R.; Liesenborgs, Jori; Coe, Dan; Rodney, Steven A.

    2017-02-01

    Using the power of gravitational lensing magnification by massive galaxy clusters, the Hubble Frontier Fields provide deep views of six patches of the high-redshift Universe. The combination of deep Hubble imaging and exceptional lensing strength has revealed the greatest numbers of multiply-imaged galaxies available to constrain models of cluster mass distributions. However, even with O(100) images per cluster, the uncertainties associated with the reconstructions are not negligible. The goal of this paper is to show the diversity of model magnification predictions. We examine seven and nine mass models of Abell 2744 and MACS J0416, respectively, submitted to the Mikulski Archive for Space Telescopes for public distribution in 2015 September. The dispersion between model predictions increases from 30 per cent at common low magnifications (μ ˜ 2) to 70 per cent at rare high magnifications (μ ˜ 40). MACS J0416 exhibits smaller dispersions than Abell 2744 for 2 < μ < 10. We show that magnification maps based on different lens inversion techniques typically differ from each other by more than their quoted statistical errors. This suggests that some models underestimate the true uncertainties, which are primarily due to various lensing degeneracies. Though the exact mass sheet degeneracy is broken, its generalized counterpart is not broken at least in Abell 2744. Other local degeneracies are also present in both clusters. Our comparison of models is complementary to the comparison of reconstructions of known synthetic mass distributions. By focusing on observed clusters, we can identify those that are best constrained, and therefore provide the clearest view of the distant Universe.

  15. Program manual for the Eppler airfoil inversion program

    NASA Technical Reports Server (NTRS)

    Thomson, W. G.

    1975-01-01

    A computer program is described for calculating the profile of an airfoil as well as the boundary layer momentum thickness and energy form parameter. The theory underlying the airfoil inversion technique developed by Eppler is discussed.

  16. Fat suppression with short inversion time inversion-recovery and chemical-shift selective saturation: a dual STIR-CHESS combination prepulse for turbo spin echo pulse sequences.

    PubMed

    Tanabe, Koji; Nishikawa, Keiichi; Sano, Tsukasa; Sakai, Osamu; Jara, Hernán

    2010-05-01

    To test a newly developed fat suppression magnetic resonance imaging (MRI) prepulse that synergistically uses the principles of fat suppression via inversion recovery (STIR) and spectral fat saturation (CHESS), relative to pure CHESS and STIR. This new technique is termed dual fat suppression (Dual-FS). To determine if Dual-FS could be chemically specific for fat, the phantom consisted of the fat-mimicking NiCl(2) aqueous solution, porcine fat, porcine muscle, and water was imaged with the three fat-suppression techniques. For Dual-FS and STIR, several inversion times were used. Signal intensities of each image obtained with each technique were compared. To determine if Dual-FS could be robust to magnetic field inhomogeneities, the phantom consisting of different NiCl(2) aqueous solutions, porcine fat, porcine muscle, and water was imaged with Dual-FS and CHESS at the several off-resonance frequencies. To compare fat suppression efficiency in vivo, 10 volunteer subjects were also imaged with the three fat-suppression techniques. Dual-FS could suppress fat sufficiently within the inversion time of 110-140 msec, thus enabling differentiation between fat and fat-mimicking aqueous structures. Dual-FS was as robust to magnetic field inhomogeneities as STIR and less vulnerable than CHESS. The same results for fat suppression were obtained in volunteers. The Dual-FS-STIR-CHESS is an alternative and promising fat suppression technique for turbo spin echo MRI. Copyright 2010 Wiley-Liss, Inc.

  17. Probabilistic Magnetotelluric Inversion with Adaptive Regularisation Using the No-U-Turns Sampler

    NASA Astrophysics Data System (ADS)

    Conway, Dennis; Simpson, Janelle; Didana, Yohannes; Rugari, Joseph; Heinson, Graham

    2018-04-01

    We present the first inversion of magnetotelluric (MT) data using a Hamiltonian Monte Carlo algorithm. The inversion of MT data is an underdetermined problem which leads to an ensemble of feasible models for a given dataset. A standard approach in MT inversion is to perform a deterministic search for the single solution which is maximally smooth for a given data-fit threshold. An alternative approach is to use Markov Chain Monte Carlo (MCMC) methods, which have been used in MT inversion to explore the entire solution space and produce a suite of likely models. This approach has the advantage of assigning confidence to resistivity models, leading to better geological interpretations. Recent advances in MCMC techniques include the No-U-Turns Sampler (NUTS), an efficient and rapidly converging method which is based on Hamiltonian Monte Carlo. We have implemented a 1D MT inversion which uses the NUTS algorithm. Our model includes a fixed number of layers of variable thickness and resistivity, as well as probabilistic smoothing constraints which allow sharp and smooth transitions. We present the results of a synthetic study and show the accuracy of the technique, as well as the fast convergence, independence of starting models, and sampling efficiency. Finally, we test our technique on MT data collected from a site in Boulia, Queensland, Australia to show its utility in geological interpretation and ability to provide probabilistic estimates of features such as depth to basement.

  18. Sensitivity analyses of acoustic impedance inversion with full-waveform inversion

    NASA Astrophysics Data System (ADS)

    Yao, Gang; da Silva, Nuno V.; Wu, Di

    2018-04-01

    Acoustic impedance estimation has a significant importance to seismic exploration. In this paper, we use full-waveform inversion to recover the impedance from seismic data, and analyze the sensitivity of the acoustic impedance with respect to the source-receiver offset of seismic data and to the initial velocity model. We parameterize the acoustic wave equation with velocity and impedance, and demonstrate three key aspects of acoustic impedance inversion. First, short-offset data are most suitable for acoustic impedance inversion. Second, acoustic impedance inversion is more compatible with the data generated by density contrasts than velocity contrasts. Finally, acoustic impedance inversion requires the starting velocity model to be very accurate for achieving a high-quality inversion. Based upon these observations, we propose a workflow for acoustic impedance inversion as: (1) building a background velocity model with travel-time tomography or reflection waveform inversion; (2) recovering the intermediate wavelength components of the velocity model with full-waveform inversion constrained by Gardner’s relation; (3) inverting the high-resolution acoustic impedance model with short-offset data through full-waveform inversion. We verify this workflow by the synthetic tests based on the Marmousi model.

  19. Control of a high beta maneuvering reentry vehicle using dynamic inversion.

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Watts, Alfred Chapman

    2005-05-01

    The design of flight control systems for high performance maneuvering reentry vehicles presents a significant challenge to the control systems designer. These vehicles typically have a much higher ballistic coefficient than crewed vehicles like as the Space Shuttle or proposed crew return vehicles such as the X-38. Moreover, the missions of high performance vehicles usually require a steeper reentry flight path angle, followed by a pull-out into level flight. These vehicles then must transit the entire atmosphere and robustly perform the maneuvers required for the mission. The vehicles must also be flown with small static margins in order to performmore » the required maneuvers, which can result in highly nonlinear aerodynamic characteristics that frequently transition from being aerodynamically stable to unstable as angle of attack increases. The control system design technique of dynamic inversion has been applied successfully to both high performance aircraft and low beta reentry vehicles. The objective of this study was to explore the application of this technique to high performance maneuvering reentry vehicles, including the basic derivation of the dynamic inversion technique, followed by the extension of that technique to the use of tabular trim aerodynamic models in the controller. The dynamic inversion equations are developed for high performance vehicles and augmented to allow the selection of a desired response for the control system. A six degree of freedom simulation is used to evaluate the performance of the dynamic inversion approach, and results for both nominal and off nominal aerodynamic characteristics are presented.« less

  20. Discovery of Ram-pressure Stripped Gas around an Elliptical Galaxy in Abell 2670

    NASA Astrophysics Data System (ADS)

    Sheen, Yun-Kyeong; Smith, Rory; Jaffé, Yara; Kim, Minjin; Yi, Sukyoung K.; Duc, Pierre-Alain; Nantais, Julie; Candlish, Graeme; Demarco, Ricardo; Treister, Ezequiel

    2017-05-01

    Studies of cluster galaxies are increasingly finding galaxies with spectacular one-sided tails of gas and young stars, suggestive of intense ram-pressure stripping. These so-called “jellyfish” galaxies typically have late-type morphology. In this paper, we present Multi Unit Spectroscopic Explorer (MUSE) observations of an elliptical galaxy in Abell 2670 with long tails of material visible in the optical spectra, as well as blobs with tadpole-like morphology. The spectra in the central part of the galaxy reveal a stellar component as well as ionized gas. The stellar component does not have significant rotation, while the ionized gas defines a clear star-forming gas disk. We argue, based on deep optical images of the galaxy, that the gas was most likely acquired during a past wet merger. It is possible that the star-forming blobs are also remnants of the merger. In addition, the direction and kinematics of the one-sided ionized tails, combined with the tadpole morphology of the star-forming blobs, strongly suggests that the system is undergoing ram pressure from the intracluster medium. In summary, this paper presents the discovery of a post-merger elliptical galaxy undergoing ram-pressure stripping.

  1. Unlocking the spatial inversion of large scanning magnetic microscopy datasets

    NASA Astrophysics Data System (ADS)

    Myre, J. M.; Lascu, I.; Andrade Lima, E.; Feinberg, J. M.; Saar, M. O.; Weiss, B. P.

    2013-12-01

    Modern scanning magnetic microscopy provides the ability to perform high-resolution, ultra-high sensitivity moment magnetometry, with spatial resolutions better than 10^-4 m and magnetic moments as weak as 10^-16 Am^2. These microscopy capabilities have enhanced numerous magnetic studies, including investigations of the paleointensity of the Earth's magnetic field, shock magnetization and demagnetization of impacts, magnetostratigraphy, the magnetic record in speleothems, and the records of ancient core dynamos of planetary bodies. A common component among many studies utilizing scanning magnetic microscopy is solving an inverse problem to determine the non-negative magnitude of the magnetic moments that produce the measured component of the magnetic field. The two most frequently used methods to solve this inverse problem are classic fast Fourier techniques in the frequency domain and non-negative least squares (NNLS) methods in the spatial domain. Although Fourier techniques are extremely fast, they typically violate non-negativity and it is difficult to implement constraints associated with the space domain. NNLS methods do not violate non-negativity, but have typically been computation time prohibitive for samples of practical size or resolution. Existing NNLS methods use multiple techniques to attain tractable computation. To reduce computation time in the past, typically sample size or scan resolution would have to be reduced. Similarly, multiple inversions of smaller sample subdivisions can be performed, although this frequently results in undesirable artifacts at subdivision boundaries. Dipole interactions can also be filtered to only compute interactions above a threshold which enables the use of sparse methods through artificial sparsity. To improve upon existing spatial domain techniques, we present the application of the TNT algorithm, named TNT as it is a "dynamite" non-negative least squares algorithm which enhances the performance and accuracy of

  2. Shear Wave Splitting Inversion in a Complex Crust

    NASA Astrophysics Data System (ADS)

    Lucas, A.

    2015-12-01

    Shear wave splitting (SWS) inversion presents a method whereby the upper crust can be interrogated for fracture density. It is caused when a shear wave traverses an area of anisotropy, splits in two, with each wave experiencing a different velocity resulting in an observable separation in arrival times. A SWS observation consists of the first arrival polarization direction and the time delay. Given the large amount of data common in SWS studies, manual inspection for polarization and time delay is considered prohibitively time intensive. All automated techniques used can produce high amounts of observations falsely interpreted as SWS. Thus introducing error into the interpretation. The technique often used for removing these false observations is to manually inspect all SWS observations defined as high quality by the automated routine, and remove false identifications. We investigate the nature of events falsely identified compared to those correctly identified. Once this identification is complete we conduct a inversion for crack density from SWS time delay. The current body of work on linear SWS inversion utilizes an equation that defines the time delay between arriving shear waves with respect to fracture density. This equation makes the assumption that no fluid flow occurs as a result of the passing shear wave, a situation called squirt flow. We show that the assumption is not applicable in all geological situations. When it is not true, its use in an inversion produces a result which is negatively affected by the assumptions. This is shown to be the case at the test case of 6894 SWS observations gathered in a small area at Puna geothermal field, Hawaii. To rectify this situation, a series of new time delay formulae, applicable to linear inversion, are derived from velocity equations presented in literature. The new formula use a 'fluid influence parameter' which indicates the degree to which squirt flow is influencing the SWS. It is found that accounting for

  3. The determination of solubility and diffusion coefficient for solids in liquids by an inverse measurement technique using cylinders of amorphous glucose as a model compound

    NASA Astrophysics Data System (ADS)

    Hu, Chengyao; Huang, Pei

    2011-05-01

    The importance of sugar and sugar-containing materials is well recognized nowadays, owing to their application in industrial processes, particularly in the food, pharmaceutical and cosmetic industries. Because of the large numbers of those compounds involved and the relatively small number of solubility and/or diffusion coefficient data for each compound available, it is highly desirable to measure the solubility and/or diffusion coefficient as efficiently as possible and to be able to improve the accuracy of the methods used. In this work, a new technique was developed for the measurement of the diffusion coefficient of a stationary solid solute in a stagnant solvent which simultaneously measures solubility based on an inverse measurement problem algorithm with the real-time dissolved amount profile as a function of time. This study differs from established techniques in both the experimental method and the data analysis. The experimental method was developed in which the dissolved amount of solid solute in quiescent solvent was investigated using a continuous weighing technique. In the data analysis, the hybrid genetic algorithm is used to minimize an objective function containing a calculated and a measured dissolved amount with time. This is measured on a cylindrical sample of amorphous glucose in methanol or ethanol. The calculated dissolved amount, that is a function of the unknown physical properties of the solid solute in the solvent, is calculated by the solution of the two-dimensional nonlinear inverse natural convection problem. The estimated values of the solubility of amorphous glucose in methanol and ethanol at 293 K were respectively 32.1 g/100 g methanol and 1.48 g/100 g ethanol, in agreement with the literature values, and support the validity of the simultaneously measured diffusion coefficient. These results show the efficiency and the stability of the developed technique to simultaneously estimate the solubility and diffusion coefficient. Also

  4. Damped regional-scale stress inversions: Methodology and examples for southern California and the Coalinga aftershock sequence

    USGS Publications Warehouse

    Hardebeck, J.L.; Michael, A.J.

    2006-01-01

    We present a new focal mechanism stress inversion technique to produce regional-scale models of stress orientation containing the minimum complexity necessary to fit the data. Current practice is to divide a region into small subareas and to independently fit a stress tensor to the focal mechanisms of each subarea. This procedure may lead to apparent spatial variability that is actually an artifact of overfitting noisy data or nonuniquely fitting data that does not completely constrain the stress tensor. To remove these artifacts while retaining any stress variations that are strongly required by the data, we devise a damped inversion method to simultaneously invert for stress in all subareas while minimizing the difference in stress between adjacent subareas. This method is conceptually similar to other geophysical inverse techniques that incorporate damping, such as seismic tomography. In checkerboard tests, the damped inversion removes the stress rotation artifacts exhibited by an undamped inversion, while resolving sharper true stress rotations than a simple smoothed model or a moving-window inversion. We show an example of a spatially damped stress field for southern California. The methodology can also be used to study temporal stress changes, and an example for the Coalinga, California, aftershock sequence is shown. We recommend use of the damped inversion technique for any study examining spatial or temporal variations in the stress field.

  5. Advanced Multivariate Inversion Techniques for High Resolution 3D Geophysical Modeling

    DTIC Science & Technology

    2011-09-01

    of seismic ambient noise – has been used to image crustal Vs variation with a lateral resolution upward of 100 km either on regional or on sub...to East Africa, we solve for velocity structure in an area with less lateral heterogeneity but great tectonic complexity. To increase the...demonstrate correlation with crustal geology. Figure 1 shows the 3D S-wave velocity model obtained from the joint inversion. The low-velocity anomaly

  6. Estimating surface acoustic impedance with the inverse method.

    PubMed

    Piechowicz, Janusz

    2011-01-01

    Sound field parameters are predicted with numerical methods in sound control systems, in acoustic designs of building and in sound field simulations. Those methods define the acoustic properties of surfaces, such as sound absorption coefficients or acoustic impedance, to determine boundary conditions. Several in situ measurement techniques were developed; one of them uses 2 microphones to measure direct and reflected sound over a planar test surface. Another approach is used in the inverse boundary elements method, in which estimating acoustic impedance of a surface is expressed as an inverse boundary problem. The boundary values can be found from multipoint sound pressure measurements in the interior of a room. This method can be applied to arbitrarily-shaped surfaces. This investigation is part of a research programme on using inverse methods in industrial room acoustics.

  7. Inverse Regional Modeling with Adjoint-Free Technique

    NASA Astrophysics Data System (ADS)

    Yaremchuk, M.; Martin, P.; Panteleev, G.; Beattie, C.

    2016-02-01

    The ongoing parallelization trend in computer technologies facilitates the use ensemble methods in geophysical data assimilation. Of particular interest are ensemble techniques which do not require the development of tangent linear numerical models and their adjoints for optimization. These ``adjoint-free'' methods minimize the cost function within the sequence of subspaces spanned by a carefully chosen sets perturbations of the control variables. In this presentation, an adjoint-free variational technique (a4dVar) is demonstrated in an application estimating initial conditions of two numerical models: the Navy Coastal Ocean Model (NCOM), and the surface wave model (WAM). With the NCOM, performance of both adjoint and adjoint-free 4dVar data assimilation techniques is compared in application to the hydrographic surveys and velocity observations collected in the Adriatic Sea in 2006. Numerical experiments have shown that a4dVar is capable of providing forecast skill similar to that of conventional 4dVar at comparable computational expense while being less susceptible to excitation of ageostrophic modes that are not supported by observations. Adjoint-free technique constrained by the WAM model is tested in a series of data assimilation experiments with synthetic observations in the southern Chukchi Sea. The types of considered observations are directional spectra estimated from point measurements by stationary buoys, significant wave height (SWH) observations by coastal high-frequency radars and along-track SWH observations by satellite altimeters. The a4dVar forecast skill is shown to be 30-40% better than the skill of the sequential assimilaiton method based on optimal interpolation which is currently used in operations. Prospects of further development of the a4dVar methods in regional applications are discussed.

  8. Influence of Gridded Standoff Measurement Resolution on Numerical Bathymetric Inversion

    NASA Astrophysics Data System (ADS)

    Hesser, T.; Farthing, M. W.; Brodie, K.

    2016-02-01

    The bathymetry from the surfzone to the shoreline incurs frequent, active movement due to wave energy interacting with the seafloor. Methodologies to measure bathymetry range from point-source in-situ instruments, vessel-mounted single-beam or multi-beam sonar surveys, airborne bathymetric lidar, as well as inversion techniques from standoff measurements of wave processes from video or radar imagery. Each type of measurement has unique sources of error and spatial and temporal resolution and availability. Numerical bathymetry estimation frameworks can use these disparate data types in combination with model-based inversion techniques to produce a "best-estimate of bathymetry" at a given time. Understanding how the sources of error and varying spatial or temporal resolution of each data type affect the end result is critical for determining best practices and in turn increase the accuracy of bathymetry estimation techniques. In this work, we consider an initial step in the development of a complete framework for estimating bathymetry in the nearshore by focusing on gridded standoff measurements and in-situ point observations in model-based inversion at the U.S. Army Corps of Engineers Field Research Facility in Duck, NC. The standoff measurement methods return wave parameters computed using linear wave theory from the direct measurements. These gridded datasets can range in temporal and spatial resolution that do not match the desired model parameters and therefore could lead to a reduction in the accuracy of these methods. Specifically, we investigate the affect of numerical resolution on the accuracy of an Ensemble Kalman Filter bathymetric inversion technique in relation to the spatial and temporal resolution of the gridded standoff measurements. The accuracies of the bathymetric estimates are compared with both high-resolution Real Time Kinematic (RTK) single-beam surveys as well as alternative direct in-situ measurements using sonic altimeters.

  9. Improving 130nm node patterning using inverse lithography techniques for an analog process

    NASA Astrophysics Data System (ADS)

    Duan, Can; Jessen, Scott; Ziger, David; Watanabe, Mizuki; Prins, Steve; Ho, Chi-Chien; Shu, Jing

    2018-03-01

    Developing a new lithographic process routinely involves usage of lithographic toolsets and much engineering time to perform data analysis. Process transfers between fabs occur quite often. One of the key assumptions made is that lithographic settings are equivalent from one fab to another and that the transfer is fluid. In some cases, that is far from the truth. Differences in tools can change the proximity effect seen in low k1 imaging processes. If you use model based optical proximity correction (MBOPC), then a model built in one fab will not work under the same conditions at another fab. This results in many wafers being patterned to try and match a baseline response. Even if matching is achieved, there is no guarantee that optimal lithographic responses are met. In this paper, we discuss the approach used to transfer and develop new lithographic processes and define MBOPC builds for the new lithographic process in Fab B which was transferred from a similar lithographic process in Fab A. By using PROLITHTM simulations to match OPC models for each level, minimal downtime in wafer processing was observed. Source Mask Optimization (SMO) was also used to optimize lithographic processes using novel inverse lithography techniques (ILT) to simultaneously optimize mask bias, depth of focus (DOF), exposure latitude (EL) and mask error enhancement factor (MEEF) for critical designs for each level.

  10. Mesoporous CeO2 nanoparticles synthesized by an inverse miniemulsion technique and their catalytic properties in methane oxidation

    NASA Astrophysics Data System (ADS)

    Nabih, Nermeen; Schiller, Renate; Lieberwirth, Ingo; Kockrick, Emanuel; Frind, Robert; Kaskel, Stefan; Weiss, Clemens K.; Landfester, Katharina

    2011-04-01

    Cerium(IV) oxide nanoparticles were synthesized using an inverse miniemulsion technique with cerium nitrate hexahydrate as precursor. The resulting nanocrystallites are as small as 5 nm with a specific surface area of 158 m2 g - 1 after calcination at 400 °C. With the addition of cetyltrimethylammonium bromide (CTAB) or (poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide)) triblock copolymers (PEO-PPO-PEO) as template in the miniemulsion droplets, the specific surface area can be increased up to 255 m2 g - 1. The miniemulsions were characterized by dynamic light scattering (DLS) and the obtained oxides were examined by x-ray diffraction (XRD), nitrogen sorption (BET and BJH), and transmission electron microscopy (TEM). The catalytic activity of the resulting ceria was investigated for the temperature-programmed oxidation (TPO) of methane.

  11. Effects of process variables on the encapsulation of oil in ca-alginate capsules using an inverse gelation technique.

    PubMed

    Abang, Sariah; Chan, Eng-Seng; Poncelet, Denis

    2012-01-01

    The objective of this study was to investigate the effects of process variables on the encapsulation of oil in a calcium alginate membrane using an inverse gelation technique. A dispersion of calcium chloride solution in sunflower oil (water-in-oil emulsion) was added dropwise to the alginate solution. The migration of calcium ions to the alginate solution initiates the formation of a ca-alginate membrane around the emulsion droplets. The membrane thickness of wet capsules and the elastic modulus of dry capsules increased following first-order kinetics with an increasing curing time. An increase in the calcium chloride concentration increased the membrane thickness of wet capsules and the elastic modulus of dry capsules. An increase in the alginate concentration decreased the mean diameter of wet capsules but increased the elastic modulus of dry capsules.

  12. Inverse analysis of aerodynamic loads from strain information using structural models and neural networks

    NASA Astrophysics Data System (ADS)

    Wada, Daichi; Sugimoto, Yohei

    2017-04-01

    Aerodynamic loads on aircraft wings are one of the key parameters to be monitored for reliable and effective aircraft operations and management. Flight data of the aerodynamic loads would be used onboard to control the aircraft and accumulated data would be used for the condition-based maintenance and the feedback for the fatigue and critical load modeling. The effective sensing techniques such as fiber optic distributed sensing have been developed and demonstrated promising capability of monitoring structural responses, i.e., strains on the surface of the aircraft wings. By using the developed techniques, load identification methods for structural health monitoring are expected to be established. The typical inverse analysis for load identification using strains calculates the loads in a discrete form of concentrated forces, however, the distributed form of the loads is essential for the accurate and reliable estimation of the critical stress at structural parts. In this study, we demonstrate an inverse analysis to identify the distributed loads from measured strain information. The introduced inverse analysis technique calculates aerodynamic loads not in a discrete but in a distributed manner based on a finite element model. In order to verify the technique through numerical simulations, we apply static aerodynamic loads on a flat panel model, and conduct the inverse identification of the load distributions. We take two approaches to build the inverse system between loads and strains. The first one uses structural models and the second one uses neural networks. We compare the performance of the two approaches, and discuss the effect of the amount of the strain sensing information.

  13. Applications for edge detection techniques using Chandra and XMM-Newton data: galaxy clusters and beyond

    NASA Astrophysics Data System (ADS)

    Walker, S. A.; Sanders, J. S.; Fabian, A. C.

    2016-09-01

    The unrivalled spatial resolution of the Chandra X-ray observatory has allowed many breakthroughs to be made in high-energy astrophysics. Here we explore applications of Gaussian gradient magnitude (GGM) filtering to X-ray data, which dramatically improves the clarity of surface brightness edges in X-ray observations, and maps gradients in X-ray surface brightness over a range of spatial scales. In galaxy clusters, we find that this method is able to reveal remarkable substructure behind the cold fronts in Abell 2142 and Abell 496, possibly the result of Kelvin-Helmholtz instabilities. In Abell 2319 and Abell 3667, we demonstrate that the GGM filter can provide a straightforward way of mapping variations in the widths and jump ratios along the lengths of cold fronts. We present results from our ongoing programme of analysing the Chandra and XMM-Newton archives with the GGM filter. In the Perseus cluster, we identify a previously unseen edge around 850 kpc from the core to the east, lying outside a known large-scale cold front, which is possibly a bow shock. In MKW 3s we find an unusual `V' shape surface brightness enhancement starting at the cluster core, which may be linked to the AGN jet. In the Crab nebula a new, moving feature in the outer part of the torus is identified which moves across the plane of the sky at a speed of ˜0.1c, and lies much further from the central pulsar than the previous motions seen by Chandra.

  14. Angle-domain inverse scattering migration/inversion in isotropic media

    NASA Astrophysics Data System (ADS)

    Li, Wuqun; Mao, Weijian; Li, Xuelei; Ouyang, Wei; Liang, Quan

    2018-07-01

    The classical seismic asymptotic inversion can be transformed into a problem of inversion of generalized Radon transform (GRT). In such methods, the combined parameters are linearly attached to the scattered wave-field by Born approximation and recovered by applying an inverse GRT operator to the scattered wave-field data. Typical GRT-style true-amplitude inversion procedure contains an amplitude compensation process after the weighted migration via dividing an illumination associated matrix whose elements are integrals of scattering angles. It is intuitional to some extent that performs the generalized linear inversion and the inversion of GRT together by this process for direct inversion. However, it is imprecise to carry out such operation when the illumination at the image point is limited, which easily leads to the inaccuracy and instability of the matrix. This paper formulates the GRT true-amplitude inversion framework in an angle-domain version, which naturally degrades the external integral term related to the illumination in the conventional case. We solve the linearized integral equation for combined parameters of different fixed scattering angle values. With this step, we obtain high-quality angle-domain common-image gathers (CIGs) in the migration loop which provide correct amplitude-versus-angle (AVA) behavior and reasonable illumination range for subsurface image points. Then we deal with the over-determined problem to solve each parameter in the combination by a standard optimization operation. The angle-domain GRT inversion method keeps away from calculating the inaccurate and unstable illumination matrix. Compared with the conventional method, the angle-domain method can obtain more accurate amplitude information and wider amplitude-preserved range. Several model tests demonstrate the effectiveness and practicability.

  15. Source encoding in multi-parameter full waveform inversion

    NASA Astrophysics Data System (ADS)

    Matharu, Gian; Sacchi, Mauricio D.

    2018-04-01

    Source encoding techniques alleviate the computational burden of sequential-source full waveform inversion (FWI) by considering multiple sources simultaneously rather than independently. The reduced data volume requires fewer forward/adjoint simulations per non-linear iteration. Applications of source-encoded full waveform inversion (SEFWI) have thus far focused on monoparameter acoustic inversion. We extend SEFWI to the multi-parameter case with applications presented for elastic isotropic inversion. Estimating multiple parameters can be challenging as perturbations in different parameters can prompt similar responses in the data. We investigate the relationship between source encoding and parameter trade-off by examining the multi-parameter source-encoded Hessian. Probing of the Hessian demonstrates the convergence of the expected source-encoded Hessian, to that of conventional FWI. The convergence implies that the parameter trade-off in SEFWI is comparable to that observed in FWI. A series of synthetic inversions are conducted to establish the feasibility of source-encoded multi-parameter FWI. We demonstrate that SEFWI requires fewer overall simulations than FWI to achieve a target model error for a range of first-order optimization methods. An inversion for spatially inconsistent P - (α) and S-wave (β) velocity models, corroborates the expectation of comparable parameter trade-off in SEFWI and FWI. The final example demonstrates a shortcoming of SEFWI when confronted with time-windowing in data-driven inversion schemes. The limitation is a consequence of the implicit fixed-spread acquisition assumption in SEFWI. Alternative objective functions, namely the normalized cross-correlation and L1 waveform misfit, do not enable SEFWI to overcome this limitation.

  16. Selected inversion as key to a stable Langevin evolution across the QCD phase boundary

    NASA Astrophysics Data System (ADS)

    Bloch, Jacques; Schenk, Olaf

    2018-03-01

    We present new results of full QCD at nonzero chemical potential. In PRD 92, 094516 (2015) the complex Langevin method was shown to break down when the inverse coupling decreases and enters the transition region from the deconfined to the confined phase. We found that the stochastic technique used to estimate the drift term can be very unstable for indefinite matrices. This may be avoided by using the full inverse of the Dirac operator, which is, however, too costly for four-dimensional lattices. The major breakthrough in this work was achieved by realizing that the inverse elements necessary for the drift term can be computed efficiently using the selected inversion technique provided by the parallel sparse direct solver package PARDISO. In our new study we show that no breakdown of the complex Langevin method is encountered and that simulations can be performed across the phase boundary.

  17. Recovering Long-wavelength Velocity Models using Spectrogram Inversion with Single- and Multi-frequency Components

    NASA Astrophysics Data System (ADS)

    Ha, J.; Chung, W.; Shin, S.

    2015-12-01

    Many waveform inversion algorithms have been proposed in order to construct subsurface velocity structures from seismic data sets. These algorithms have suffered from computational burden, local minima problems, and the lack of low-frequency components. Computational efficiency can be improved by the application of back-propagation techniques and advances in computing hardware. In addition, waveform inversion algorithms, for obtaining long-wavelength velocity models, could avoid both the local minima problem and the effect of the lack of low-frequency components in seismic data. In this study, we proposed spectrogram inversion as a technique for recovering long-wavelength velocity models. In spectrogram inversion, decomposed frequency components from spectrograms of traces, in the observed and calculated data, are utilized to generate traces with reproduced low-frequency components. Moreover, since each decomposed component can reveal the different characteristics of a subsurface structure, several frequency components were utilized to analyze the velocity features in the subsurface. We performed the spectrogram inversion using a modified SEG/SEGE salt A-A' line. Numerical results demonstrate that spectrogram inversion could also recover the long-wavelength velocity features. However, inversion results varied according to the frequency components utilized. Based on the results of inversion using a decomposed single-frequency component, we noticed that robust inversion results are obtained when a dominant frequency component of the spectrogram was utilized. In addition, detailed information on recovered long-wavelength velocity models was obtained using a multi-frequency component combined with single-frequency components. Numerical examples indicate that various detailed analyses of long-wavelength velocity models can be carried out utilizing several frequency components.

  18. Targeted next generation sequencing for the detection of ciprofloxacin resistance markers using molecular inversion probes

    DTIC Science & Technology

    2016-07-06

    1 Targeted next-generation sequencing for the detection of ciprofloxacin resistance markers using molecular inversion probes Christopher P...development and evaluation of a panel of 44 single-stranded molecular inversion probes (MIPs) coupled to next-generation sequencing (NGS) for the...padlock and molecular inversion probes as upfront enrichment steps for use with NGS showed the specificity and multiplexability of these techniques

  19. Spatial operator factorization and inversion of the manipulator mass matrix

    NASA Technical Reports Server (NTRS)

    Rodriguez, Guillermo; Kreutz-Delgado, Kenneth

    1992-01-01

    This paper advances two linear operator factorizations of the manipulator mass matrix. Embedded in the factorizations are many of the techniques that are regarded as very efficient computational solutions to inverse and forward dynamics problems. The operator factorizations provide a high-level architectural understanding of the mass matrix and its inverse, which is not visible in the detailed algorithms. They also lead to a new approach to the development of computer programs or organize complexity in robot dynamics.

  20. Mapping the Dark Matter Distribution of the Merging Galaxy Cluster Abell 115

    NASA Astrophysics Data System (ADS)

    Kim, Mincheol; Jee, Myungkook James; Forman, William; Golovich, Nathan; van Weeren, Reinout

    2018-01-01

    The colliding galaxy cluster Abell 115 shows a number of clear merging features including radio relics, double X-ray peaks, and offsets between the cluster member galaxies and the X-ray distributions. In order to constrain the merging scenario of this complex system, it is critical to know where the dark matter is. We present a high-fidelity weak-lensing analysis of the system using a state-of-the-art method that robustly models the detailed PSF variations. Our mass reconstruction reveals two distinct mass peaks. Through a careful bootstrapping analysis, we demonstrate that the positions of these two mass peaks are highly consistent with those of the cluster galaxies, although the comparison with the X-ray emission shows that the mass peaks lead the X-ray peaks. We obtain the first weak-lensing mass of each subcluster by simultaneously fitting two NFW profiles, as well as the total mass of the system. Interestingly, the total mass is a few factors lower than the published dynamical mass based on velocity dispersion. This large mass discrepancy may be attributed to a significant disruption of the cluster galaxy orbits due to the violent merger. Our preliminary analysis indicates that the two subclusters might have experienced a first off-axis collision a few Gyrs ago and might be now returning for a second collision.

  1. Chemical Enrichment History Of Abell 3112 Galaxy Cluster Out To The Virial Radius

    NASA Astrophysics Data System (ADS)

    Ezer, C.; Bulbul, E.; Ercan, E.; Smith, R.; Bautz, M.; Loewenstein, M.; McDonald, M.; Miller, E.

    2017-10-01

    The deep potential well of the galaxy clusters confines all metals produced via supernova explosions within the intra-cluster medium (ICM). The radial distributions of these metals along the ICM are direct records of the metal enrichment history. In this work, we investigate the chemical enrichment history of Abell 3112 galaxy cluster from cluster's core to out to radius R_{200} (˜ 1470 kpc) by analyzing a deep 1.2 Ms Suzaku observations with overlapping 72 ks Chandra observations. The fraction of supernova explosions enriching the ICM is obtained by fitting the X-ray spectra with a robust snapec model implemented in XSPEC. The ratio of supernova type Ia explosions to the core collapse supernova explosions is found in the range 0.12 - 0.16 and uniformly distributed out to R_{200}. The uniform spatial distribution of supernova enrichment indicates an early metal enrichment between the epoch of z ˜ 2 - 3. We also observe that W7, CDD, and WDD SN Ia models equally better explain the highest signal-to-noise region compared to 2D delayed detonation model CDDT. We further report the first time temperature (3.37 ± 0.77 keV) and metallicity (0.22 ± 0.08 Z_{⊙}) measurements of this archetypal cluster at its virial radius.

  2. Discovery of Ram-pressure Stripped Gas around an Elliptical Galaxy in Abell 2670

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sheen, Yun-Kyeong; Kim, Minjin; Smith, Rory

    Studies of cluster galaxies are increasingly finding galaxies with spectacular one-sided tails of gas and young stars, suggestive of intense ram-pressure stripping. These so-called “jellyfish” galaxies typically have late-type morphology. In this paper, we present Multi Unit Spectroscopic Explorer (MUSE) observations of an elliptical galaxy in Abell 2670 with long tails of material visible in the optical spectra, as well as blobs with tadpole-like morphology. The spectra in the central part of the galaxy reveal a stellar component as well as ionized gas. The stellar component does not have significant rotation, while the ionized gas defines a clear star-forming gasmore » disk. We argue, based on deep optical images of the galaxy, that the gas was most likely acquired during a past wet merger. It is possible that the star-forming blobs are also remnants of the merger. In addition, the direction and kinematics of the one-sided ionized tails, combined with the tadpole morphology of the star-forming blobs, strongly suggests that the system is undergoing ram pressure from the intracluster medium. In summary, this paper presents the discovery of a post-merger elliptical galaxy undergoing ram-pressure stripping.« less

  3. PREFACE: First International Congress of the International Association of Inverse Problems (IPIA): Applied Inverse Problems 2007: Theoretical and Computational Aspects

    NASA Astrophysics Data System (ADS)

    Uhlmann, Gunther

    2008-07-01

    This volume represents the proceedings of the fourth Applied Inverse Problems (AIP) international conference and the first congress of the Inverse Problems International Association (IPIA) which was held in Vancouver, Canada, June 25 29, 2007. The organizing committee was formed by Uri Ascher, University of British Columbia, Richard Froese, University of British Columbia, Gary Margrave, University of Calgary, and Gunther Uhlmann, University of Washington, chair. The conference was part of the activities of the Pacific Institute of Mathematical Sciences (PIMS) Collaborative Research Group on inverse problems (http://www.pims.math.ca/scientific/collaborative-research-groups/past-crgs). This event was also supported by grants from NSF and MITACS. Inverse Problems (IP) are problems where causes for a desired or an observed effect are to be determined. They lie at the heart of scientific inquiry and technological development. The enormous increase in computing power and the development of powerful algorithms have made it possible to apply the techniques of IP to real-world problems of growing complexity. Applications include a number of medical as well as other imaging techniques, location of oil and mineral deposits in the earth's substructure, creation of astrophysical images from telescope data, finding cracks and interfaces within materials, shape optimization, model identification in growth processes and, more recently, modelling in the life sciences. The series of Applied Inverse Problems (AIP) Conferences aims to provide a primary international forum for academic and industrial researchers working on all aspects of inverse problems, such as mathematical modelling, functional analytic methods, computational approaches, numerical algorithms etc. The steering committee of the AIP conferences consists of Heinz Engl (Johannes Kepler Universität, Austria), Joyce McLaughlin (RPI, USA), William Rundell (Texas A&M, USA), Erkki Somersalo (Helsinki University of Technology

  4. Decomposing Large Inverse Problems with an Augmented Lagrangian Approach: Application to Joint Inversion of Body-Wave Travel Times and Surface-Wave Dispersion Measurements

    NASA Astrophysics Data System (ADS)

    Reiter, D. T.; Rodi, W. L.

    2015-12-01

    Constructing 3D Earth models through the joint inversion of large geophysical data sets presents numerous theoretical and practical challenges, especially when diverse types of data and model parameters are involved. Among the challenges are the computational complexity associated with large data and model vectors and the need to unify differing model parameterizations, forward modeling methods and regularization schemes within a common inversion framework. The challenges can be addressed in part by decomposing the inverse problem into smaller, simpler inverse problems that can be solved separately, providing one knows how to merge the separate inversion results into an optimal solution of the full problem. We have formulated an approach to the decomposition of large inverse problems based on the augmented Lagrangian technique from optimization theory. As commonly done, we define a solution to the full inverse problem as the Earth model minimizing an objective function motivated, for example, by a Bayesian inference formulation. Our decomposition approach recasts the minimization problem equivalently as the minimization of component objective functions, corresponding to specified data subsets, subject to the constraints that the minimizing models be equal. A standard optimization algorithm solves the resulting constrained minimization problems by alternating between the separate solution of the component problems and the updating of Lagrange multipliers that serve to steer the individual solution models toward a common model solving the full problem. We are applying our inversion method to the reconstruction of the·crust and upper-mantle seismic velocity structure across Eurasia.· Data for the inversion comprise a large set of P and S body-wave travel times·and fundamental and first-higher mode Rayleigh-wave group velocities.

  5. Transdimensional, hierarchical, Bayesian inversion of ambient seismic noise: Australia

    NASA Astrophysics Data System (ADS)

    Crowder, E.; Rawlinson, N.; Cornwell, D. G.

    2017-12-01

    We present models of crustal velocity structure in southeastern Australia using a novel, transdimensional and hierarchical, Bayesian inversion approach. The inversion is applied to long-time ambient noise cross-correlations. The study area of SE Australia is thought to represent the eastern margin of Gondwana. Conflicting tectonic models have been proposed to explain the formation of eastern Gondwana and the enigmatic geological relationships in Bass Strait, which separates Tasmania and the mainland. A geologically complex area of crustal accretion, Bass Strait may contain part of an exotic continental block entrained in colliding crusts. Ambient noise data recorded by an array of 24 seismometers is used to produce a high resolution, 3D shear wave velocity model of Bass Strait. Phase velocity maps in the period range 2-30 s are produced and subsequently inverted for 3D shear wave velocity structure. The transdimensional, hierarchical Bayesian, inversion technique is used. This technique proves far superior to linearised inversion. The inversion model is dynamically parameterised during the process, implicitly controlled by the data, and noise is treated as an inversion unknown. The resulting shear wave velocity model shows three sedimentary basins in Bass Strait constrained by slow shear velocities (2.4-2.9 km/s) at 2-10 km depth. These failed rift basins from the breakup of Australia-Antartica appear to be overlying thinned crust, where typical mantle velocities of 3.8-4.0 km/s occur at depths greater than 20 km. High shear wave velocities ( 3.7-3.8 km/s) in our new model also match well with regions of high magnetic and gravity anomalies. Furthermore, we use both Rayleigh and Love wave phase data to to construct Vsv and Vsh maps. These are used to estimate crustal radial anisotropy in the Bass Strait. We interpret that structures delineated by our velocity models support the presence and extent of the exotic Precambrian micro-continent (the Selwyn Block) that was

  6. A study of the Ionospheric electron density profile with FORMOSAT-3/COSMIC observation data

    NASA Astrophysics Data System (ADS)

    Chou, Min-Yang; Tsai, Ho-Fang; Lin, Chi-Yen; Lee, I.-Te; Lin, Charles; Liu, Jann-Yenq

    2015-04-01

    The GPS Occultation Experiment payload onboard FORMOSAT-3/COSMIC microsatellite constellation is capable of scanning the ionospheric structure by the radio occultation (RO) technique to retrieve precise electron density profiles since 2006. Due to the success of FORMOSAT-3/COSMIC, the follow-on mission, FORMOSAT-7/COSMIC-2, is to launch 12 microsatellites in 2016 and 2018, respectively, with the Global Navigation Satellite Systems (GNSS) RO instrument onboard for tracking GPS, Galileo and/or GLONASS satellite signals and to provide more than 8,000 RO soundings per day globally. An overview of the validation of the FORMOSAT-3/COSMIC ionospheric profiling is given by means of the traditional Abel transform through bending angle and total electron content (TEC), while the ionospheric data assimilation is also applied, based on the Gauss-Markov Kalman filter with the International Reference Ionosphere model (IRI-2007) and global ionosphere map (GIM) as background model, to assimilate TEC observations from FORMOSAT-3/COSMIC. The results shows comparison of electron density profiles from Abel inversion and data assimilation. Furthermore, an observing system simulation experiment is also applied to determine the impact of FORMOSAT-7/COSMIC-2 on ionospheric weather monitoring, which reveals an opportunity on advanced study of small spatial and temporal variations in the ionosphere.

  7. Using machine learning to accelerate sampling-based inversion

    NASA Astrophysics Data System (ADS)

    Valentine, A. P.; Sambridge, M.

    2017-12-01

    In most cases, a complete solution to a geophysical inverse problem (including robust understanding of the uncertainties associated with the result) requires a sampling-based approach. However, the computational burden is high, and proves intractable for many problems of interest. There is therefore considerable value in developing techniques that can accelerate sampling procedures.The main computational cost lies in evaluation of the forward operator (e.g. calculation of synthetic seismograms) for each candidate model. Modern machine learning techniques-such as Gaussian Processes-offer a route for constructing a computationally-cheap approximation to this calculation, which can replace the accurate solution during sampling. Importantly, the accuracy of the approximation can be refined as inversion proceeds, to ensure high-quality results.In this presentation, we describe and demonstrate this approach-which can be seen as an extension of popular current methods, such as the Neighbourhood Algorithm, and bridges the gap between prior- and posterior-sampling frameworks.

  8. 3D Acoustic Full Waveform Inversion for Engineering Purpose

    NASA Astrophysics Data System (ADS)

    Lim, Y.; Shin, S.; Kim, D.; Kim, S.; Chung, W.

    2017-12-01

    Seismic waveform inversion is the most researched data processing technique. In recent years, with an increase in marine development projects, seismic surveys are commonly conducted for engineering purposes; however, researches for application of waveform inversion are insufficient. The waveform inversion updates the subsurface physical property by minimizing the difference between modeled and observed data. Furthermore, it can be used to generate an accurate subsurface image; however, this technique consumes substantial computational resources. Its most compute-intensive step is the calculation of the gradient and hessian values. This aspect gains higher significance in 3D as compared to 2D. This paper introduces a new method for calculating gradient and hessian values, in an effort to reduce computational overburden. In the conventional waveform inversion, the calculation area covers all sources and receivers. In seismic surveys for engineering purposes, the number of receivers is limited. Therefore, it is inefficient to construct the hessian and gradient for the entire region (Figure 1). In order to tackle this problem, we calculate the gradient and the hessian for a single shot within the range of the relevant source and receiver. This is followed by summing up of these positions for the entire shot (Figure 2). In this paper, we demonstrate that reducing the area of calculation of the hessian and gradient for one shot reduces the overall amount of computation and therefore, the computation time. Furthermore, it is proved that the waveform inversion can be suitably applied for engineering purposes. In future research, we propose to ascertain an effective calculation range. This research was supported by the Basic Research Project(17-3314) of the Korea Institute of Geoscience and Mineral Resources(KIGAM) funded by the Ministry of Science, ICT and Future Planning of Korea.

  9. Efficient Monte Carlo sampling of inverse problems using a neural network-based forward—applied to GPR crosshole traveltime inversion

    NASA Astrophysics Data System (ADS)

    Hansen, T. M.; Cordua, K. S.

    2017-12-01

    Probabilistically formulated inverse problems can be solved using Monte Carlo-based sampling methods. In principle, both advanced prior information, based on for example, complex geostatistical models and non-linear forward models can be considered using such methods. However, Monte Carlo methods may be associated with huge computational costs that, in practice, limit their application. This is not least due to the computational requirements related to solving the forward problem, where the physical forward response of some earth model has to be evaluated. Here, it is suggested to replace a numerical complex evaluation of the forward problem, with a trained neural network that can be evaluated very fast. This will introduce a modeling error that is quantified probabilistically such that it can be accounted for during inversion. This allows a very fast and efficient Monte Carlo sampling of the solution to an inverse problem. We demonstrate the methodology for first arrival traveltime inversion of crosshole ground penetrating radar data. An accurate forward model, based on 2-D full-waveform modeling followed by automatic traveltime picking, is replaced by a fast neural network. This provides a sampling algorithm three orders of magnitude faster than using the accurate and computationally expensive forward model, and also considerably faster and more accurate (i.e. with better resolution), than commonly used approximate forward models. The methodology has the potential to dramatically change the complexity of non-linear and non-Gaussian inverse problems that have to be solved using Monte Carlo sampling techniques.

  10. 3D motion picture of transparent gas flow by parallel phase-shifting digital holography

    NASA Astrophysics Data System (ADS)

    Awatsuji, Yasuhiro; Fukuda, Takahito; Wang, Yexin; Xia, Peng; Kakue, Takashi; Nishio, Kenzo; Matoba, Osamu

    2018-03-01

    Parallel phase-shifting digital holography is a technique capable of recording three-dimensional (3D) motion picture of dynamic object, quantitatively. This technique can record single hologram of an object with an image sensor having a phase-shift array device and reconstructs the instantaneous 3D image of the object with a computer. In this technique, a single hologram in which the multiple holograms required for phase-shifting digital holography are multiplexed by using space-division multiplexing technique pixel by pixel. We demonstrate 3D motion picture of dynamic and transparent gas flow recorded and reconstructed by the technique. A compressed air duster was used to generate the gas flow. A motion picture of the hologram of the gas flow was recorded at 180,000 frames/s by parallel phase-shifting digital holography. The phase motion picture of the gas flow was reconstructed from the motion picture of the hologram. The Abel inversion was applied to the phase motion picture and then the 3D motion picture of the gas flow was obtained.

  11. Phase-sensitive dual-inversion recovery for accelerated carotid vessel wall imaging.

    PubMed

    Bonanno, Gabriele; Brotman, David; Stuber, Matthias

    2015-03-01

    Dual-inversion recovery (DIR) is widely used for magnetic resonance vessel wall imaging. However, optimal contrast may be difficult to obtain and is subject to RR variability. Furthermore, DIR imaging is time-inefficient and multislice acquisitions may lead to prolonged scanning times. Therefore, an extension of phase-sensitive (PS) DIR is proposed for carotid vessel wall imaging. The statistical distribution of the phase signal after DIR is probed to segment carotid lumens and suppress their residual blood signal. The proposed PS-DIR technique was characterized over a broad range of inversion times. Multislice imaging was then implemented by interleaving the acquisition of 3 slices after DIR. Quantitative evaluation was then performed in healthy adult subjects and compared with conventional DIR imaging. Single-slice PS-DIR provided effective blood-signal suppression over a wide range of inversion times, enhancing wall-lumen contrast and vessel wall conspicuity for carotid arteries. Multislice PS-DIR imaging with effective blood-signal suppression is enabled. A variant of the PS-DIR method has successfully been implemented and tested for carotid vessel wall imaging. This technique removes timing constraints related to inversion recovery, enhances wall-lumen contrast, and enables a 3-fold increase in volumetric coverage at no extra cost in scanning time.

  12. Concentration Measurements in Self-Excited Momentum Dominated Low-Density Gas Jets

    NASA Technical Reports Server (NTRS)

    Yildirim, B. S.; Pasumarthi, K. S.; Agrawal, A. K.

    2004-01-01

    Flow structure of self-excited, laminar, axisymmetric, momentum-dominated helium jets discharged vertically into ambient air was investigated using high-speed rainbow schlieren deflectometry technique. Measurements were obtained at temporal resolution of 1 ms and spatial resolution of 0.19 mm for two test cases with Richardson number of 0.034 and 0.018. Power spectra revealed that the oscillation frequency was independent of spatial coordinates, suggesting global oscillations in the flow. Abel inversion algorithm was used to reconstruct the concentration field of helium. Instantaneous concentration contours revealed changes in the flow field and evolution of vortical structures during an oscillation cycle. Temporal evolution plots of helium concentration at different axial locations provided detailed information about the instability in the flow field.

  13. The Inverse-Square Law with Data Loggers

    ERIC Educational Resources Information Center

    Bates, Alan

    2013-01-01

    The inverse-square law for the intensity of light received at a distance from a light source has been verified using various experimental techniques. Typical measurements involve a manual variation of the distance between a light source and a light sensor, usually by sliding the sensor or source along a bench, measuring the source-sensor distance…

  14. Application of a stochastic inverse to the geophysical inverse problem

    NASA Technical Reports Server (NTRS)

    Jordan, T. H.; Minster, J. B.

    1972-01-01

    The inverse problem for gross earth data can be reduced to an undertermined linear system of integral equations of the first kind. A theory is discussed for computing particular solutions to this linear system based on the stochastic inverse theory presented by Franklin. The stochastic inverse is derived and related to the generalized inverse of Penrose and Moore. A Backus-Gilbert type tradeoff curve is constructed for the problem of estimating the solution to the linear system in the presence of noise. It is shown that the stochastic inverse represents an optimal point on this tradeoff curve. A useful form of the solution autocorrelation operator as a member of a one-parameter family of smoothing operators is derived.

  15. Investigation of Dynamic Properties of Water-Saturated Sand by the Results of the Inverse Experiment Technique

    NASA Astrophysics Data System (ADS)

    Bragov, A. M.; Balandin, Vl. V.; Kotov, V. L.; Balandin, Vl. Vl.

    2018-04-01

    We present new experimental results on the investigation of the dynamic properties of sand soil on the basis of the inverse experiment technique using a measuring rod with a flat front-end face. A limited applicability has been shown of the method using the procedure for correcting the shape of the deformation pulse due to dispersion during its propagation in the measuring rod. Estimates of the pulse maximum have been obtained and the results of comparison of numerical calculations with experimental data are given. The sufficient accuracy in determining the drag force during the quasi-stationary stage of penetration has been established. The parameters of dynamic compressibility and resistance to shear of water-saturated sand have been determined in the course of the experimental-theoretical analysis of the maximum values of the drag force and its values at the quasi-stationary stage of penetration. It has been shown that with almost complete water saturation of sand its shear properties are reduced but remain significant in the practically important range of penetration rates.

  16. The Effect of Flow Velocity on Waveform Inversion

    NASA Astrophysics Data System (ADS)

    Lee, D.; Shin, S.; Chung, W.; Ha, J.; Lim, Y.; Kim, S.

    2017-12-01

    The waveform inversion is a velocity modeling technique that reconstructs accurate subsurface physical properties. Therefore, using the model in its final, updated version, we generated data identical to modeled data. Flow velocity, like several other factors, affects observed data in seismic exploration. Despite this, there is insufficient research on its relationship with waveform inversion. In this study, the generated synthetic data considering flow velocity was factored in waveform inversion and the influence of flow velocity in waveform inversion was analyzed. Measuring the flow velocity generally requires additional equipment. However, for situations where only seismic data was available, flow velocity was calculated by fixed-point iteration method using direct wave in observed data. Further, a new waveform inversion was proposed, which can be applied to the calculated flow velocity. We used a wave equation, which can work with the flow velocities used in the study by Käser and Dumbser. Further, we enhanced the efficiency of computation by applying the back-propagation method. To verify the proposed algorithm, six different data sets were generated using the Marmousi2 model; each of these data sets used different flow velocities in the range 0-50, i.e., 0, 2, 5, 10, 25, and 50. Thereafter, the inversion results from these data sets along with the results without the use of flow velocity were compared and analyzed. In this study, we analyzed the results of waveform inversion after flow velocity has been factored in. It was demonstrated that the waveform inversion is not affected significantly when the flow velocity is of smaller value. However, when the flow velocity has a large value, factoring it in the waveform inversion produces superior results. This research was supported by the Basic Research Project(17-3312, 17-3313) of the Korea Institute of Geoscience and Mineral Resources(KIGAM) funded by the Ministry of Science, ICT and Future Planning of Korea.

  17. Structural Anomaly Detection Using Fiber Optic Sensors and Inverse Finite Element Method

    NASA Technical Reports Server (NTRS)

    Quach, Cuong C.; Vazquez, Sixto L.; Tessler, Alex; Moore, Jason P.; Cooper, Eric G.; Spangler, Jan. L.

    2005-01-01

    NASA Langley Research Center is investigating a variety of techniques for mitigating aircraft accidents due to structural component failure. One technique under consideration combines distributed fiber optic strain sensing with an inverse finite element method for detecting and characterizing structural anomalies anomalies that may provide early indication of airframe structure degradation. The technique identifies structural anomalies that result in observable changes in localized strain but do not impact the overall surface shape. Surface shape information is provided by an Inverse Finite Element Method that computes full-field displacements and internal loads using strain data from in-situ fiberoptic sensors. This paper describes a prototype of such a system and reports results from a series of laboratory tests conducted on a test coupon subjected to increasing levels of damage.

  18. Inversion of Zeeman polarization for solar magnetic field diagnostics

    NASA Astrophysics Data System (ADS)

    Derouich, M.

    2017-05-01

    The topic of magnetic field diagnostics with the Zeeman effect is currently vividly discussed. There are some testable inversion codes available to the spectropolarimetry community and their application allowed for a better understanding of the magnetism of the solar atmosphere. In this context, we propose an inversion technique associated with a new numerical code. The inversion procedure is promising and particularly successful for interpreting the Stokes profiles in quick and sufficiently precise way. In our inversion, we fit a part of each Stokes profile around a target wavelength, and then determine the magnetic field as a function of the wavelength which is equivalent to get the magnetic field as a function of the height of line formation. To test the performance of the new numerical code, we employed "hare and hound" approach by comparing an exact solution (called input) with the solution obtained by the code (called output). The precision of the code is also checked by comparing our results to the ones obtained with the HAO MERLIN code. The inversion code has been applied to synthetic Stokes profiles of the Na D1 line available in the literature. We investigated the limitations in recovering the input field in case of noisy data. As an application, we applied our inversion code to the polarization profiles of the Fe Iλ 6302.5 Å observed at IRSOL in Locarno.

  19. Aircraft automatic-flight-control system with inversion of the model in the feed-forward path using a Newton-Raphson technique for the inversion

    NASA Technical Reports Server (NTRS)

    Smith, G. A.; Meyer, G.; Nordstrom, M.

    1986-01-01

    A new automatic flight control system concept suitable for aircraft with highly nonlinear aerodynamic and propulsion characteristics and which must operate over a wide flight envelope was investigated. This exact model follower inverts a complete nonlinear model of the aircraft as part of the feed-forward path. The inversion is accomplished by a Newton-Raphson trim of the model at each digital computer cycle time of 0.05 seconds. The combination of the inverse model and the actual aircraft in the feed-forward path alloys the translational and rotational regulators in the feedback path to be easily designed by linear methods. An explanation of the model inversion procedure is presented. An extensive set of simulation data for essentially the full flight envelope for a vertical attitude takeoff and landing aircraft (VATOL) is presented. These data demonstrate the successful, smooth, and precise control that can be achieved with this concept. The trajectory includes conventional flight from 200 to 900 ft/sec with path accelerations and decelerations, altitude changes of over 6000 ft and 2g and 3g turns. Vertical attitude maneuvering as a tail sitter along all axes is demonstrated. A transition trajectory from 200 ft/sec in conventional flight to stationary hover in the vertical attitude includes satisfactory operation through lift-cure slope reversal as attitude goes from horizontal to vertical at constant altitude. A vertical attitude takeoff from stationary hover to conventional flight is also demonstrated.

  20. Inversions

    ERIC Educational Resources Information Center

    Brown, Malcolm

    2009-01-01

    Inversions are fascinating phenomena. They are reversals of the normal or expected order. They occur across a wide variety of contexts. What do inversions have to do with learning spaces? The author suggests that they are a useful metaphor for the process that is unfolding in higher education with respect to education. On the basis of…

  1. Multidimensional NMR inversion without Kronecker products: Multilinear inversion

    NASA Astrophysics Data System (ADS)

    Medellín, David; Ravi, Vivek R.; Torres-Verdín, Carlos

    2016-08-01

    Multidimensional NMR inversion using Kronecker products poses several challenges. First, kernel compression is only possible when the kernel matrices are separable, and in recent years, there has been an increasing interest in NMR sequences with non-separable kernels. Second, in three or more dimensions, the singular value decomposition is not unique; therefore kernel compression is not well-defined for higher dimensions. Without kernel compression, the Kronecker product yields matrices that require large amounts of memory, making the inversion intractable for personal computers. Finally, incorporating arbitrary regularization terms is not possible using the Lawson-Hanson (LH) or the Butler-Reeds-Dawson (BRD) algorithms. We develop a minimization-based inversion method that circumvents the above problems by using multilinear forms to perform multidimensional NMR inversion without using kernel compression or Kronecker products. The new method is memory efficient, requiring less than 0.1% of the memory required by the LH or BRD methods. It can also be extended to arbitrary dimensions and adapted to include non-separable kernels, linear constraints, and arbitrary regularization terms. Additionally, it is easy to implement because only a cost function and its first derivative are required to perform the inversion.

  2. Can standard cosmological models explain the observed Abell cluster bulk flow?

    NASA Technical Reports Server (NTRS)

    Strauss, Michael A.; Cen, Renyue; Ostriker, Jeremiah P.; Laure, Tod R.; Postman, Marc

    1995-01-01

    Lauer and Postman (LP) observed that all Abell clusters with redshifts less than 15,000 km/s appear to be participating in a bulk flow of 689 km/s with respect to the cosmic microwave background. We find this result difficult to reconcile with all popular models for large-scale structure formation that assume Gaussian initial conditions. This conclusion is based on Monte Carlo realizations of the LP data, drawn from large particle-mesh N-body simulations for six different models of the initial power spectrum (standard, tilted, and Omega(sub 0) = 0.3 cold dark matter, and two variants of the primordial baryon isocurvature model). We have taken special care to treat properly the longest-wavelength components of the power spectra. The simulations are sampled, 'observed,' and analyzed as identically as possible to the LP cluster sample. Large-scale bulk flows as measured from clusters in the simulations are in excellent agreement with those measured from the grid: the clusters do not exhibit any strong velocity bias on large scales. Bulk flows with amplitude as large as that reported by LP are not uncommon in the Monte Carlo data stes; the distribution of measured bulk flows before error bias subtraction is rougly Maxwellian, with a peak around 400 km/s. However the chi squared of the observed bulk flow, taking into account the anisotropy of the error ellipsoid, is much more difficult to match in the simulations. The models examined are ruled out at confidence levels between 94% and 98%.

  3. Clinical knowledge-based inverse treatment planning

    NASA Astrophysics Data System (ADS)

    Yang, Yong; Xing, Lei

    2004-11-01

    Clinical IMRT treatment plans are currently made using dose-based optimization algorithms, which do not consider the nonlinear dose-volume effects for tumours and normal structures. The choice of structure specific importance factors represents an additional degree of freedom of the system and makes rigorous optimization intractable. The purpose of this work is to circumvent the two problems by developing a biologically more sensible yet clinically practical inverse planning framework. To implement this, the dose-volume status of a structure was characterized by using the effective volume in the voxel domain. A new objective function was constructed with the incorporation of the volumetric information of the system so that the figure of merit of a given IMRT plan depends not only on the dose deviation from the desired distribution but also the dose-volume status of the involved organs. The conventional importance factor of an organ was written into a product of two components: (i) a generic importance that parametrizes the relative importance of the organs in the ideal situation when the goals for all the organs are met; (ii) a dose-dependent factor that quantifies our level of clinical/dosimetric satisfaction for a given plan. The generic importance can be determined a priori, and in most circumstances, does not need adjustment, whereas the second one, which is responsible for the intractable behaviour of the trade-off seen in conventional inverse planning, was determined automatically. An inverse planning module based on the proposed formalism was implemented and applied to a prostate case and a head-neck case. A comparison with the conventional inverse planning technique indicated that, for the same target dose coverage, the critical structure sparing was substantially improved for both cases. The incorporation of clinical knowledge allows us to obtain better IMRT plans and makes it possible to auto-select the importance factors, greatly facilitating the inverse

  4. Gemini Frontier Fields: Wide-field Adaptive Optics Ks-band Imaging of the Galaxy Clusters MACS J0416.1-2403 and Abell 2744

    NASA Astrophysics Data System (ADS)

    Schirmer, M.; Carrasco, E. R.; Pessev, P.; Garrel, V.; Winge, C.; Neichel, B.; Vidal, F.

    2015-04-01

    We have observed two of the six Frontier Fields galaxy clusters, MACS J0416.1-2403 and Abell 2744, using the Gemini Multi-Conjugate Adaptive Optics System (GeMS) and the Gemini South Adaptive Optics Imager (GSAOI). With 0.″ 08-0.″ 10 FWHM our data are nearly diffraction-limited over a 100\\prime\\prime × 100\\prime\\prime wide area. GeMS/GSAOI complements the Hubble Space Telescope (HST) redwards of 1.6 μm with twice the angular resolution. We reach a 5σ depth of {{K}s}˜ 25.6 mag (AB) for compact sources. In this paper, we describe the observations, data processing, and initial public data release. We provide fully calibrated, co-added images matching the native GSAOI pixel scale as well as the larger plate scales of the HST release, adding to the legacy value of the Frontier Fields. Our work demonstrates that even for fields at high galactic latitude where natural guide stars are rare, current multi-conjugated adaptive optics technology at 8 m telescopes has opened a new window on the distant universe. Observations of a third Frontier Field, Abell 370, are planned. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina). Based on observations made with ESO Telescopes at the La Silla and Paranal Observatories, Chile.

  5. Joint inversion of multiple geophysical and petrophysical data using generalized fuzzy clustering algorithms

    NASA Astrophysics Data System (ADS)

    Sun, Jiajia; Li, Yaoguo

    2017-02-01

    Joint inversion that simultaneously inverts multiple geophysical data sets to recover a common Earth model is increasingly being applied to exploration problems. Petrophysical data can serve as an effective constraint to link different physical property models in such inversions. There are two challenges, among others, associated with the petrophysical approach to joint inversion. One is related to the multimodality of petrophysical data because there often exist more than one relationship between different physical properties in a region of study. The other challenge arises from the fact that petrophysical relationships have different characteristics and can exhibit point, linear, quadratic, or exponential forms in a crossplot. The fuzzy c-means (FCM) clustering technique is effective in tackling the first challenge and has been applied successfully. We focus on the second challenge in this paper and develop a joint inversion method based on variations of the FCM clustering technique. To account for the specific shapes of petrophysical relationships, we introduce several different fuzzy clustering algorithms that are capable of handling different shapes of petrophysical relationships. We present two synthetic and one field data examples and demonstrate that, by choosing appropriate distance measures for the clustering component in the joint inversion algorithm, the proposed joint inversion method provides an effective means of handling common petrophysical situations we encounter in practice. The jointly inverted models have both enhanced structural similarity and increased petrophysical correlation, and better represent the subsurface in the spatial domain and the parameter domain of physical properties.

  6. Wavelet transform analysis of the small-scale X-ray structure of the cluster Abell 1367

    NASA Technical Reports Server (NTRS)

    Grebeney, S. A.; Forman, W.; Jones, C.; Murray, S.

    1995-01-01

    We have developed a new technique based on a wavelet transform analysis to quantify the small-scale (less than a few arcminutes) X-ray structure of clusters of galaxies. We apply this technique to the ROSAT position sensitive proportional counter (PSPC) and Einstein high-resolution imager (HRI) images of the central region of the cluster Abell 1367 to detect sources embedded within the diffuse intracluster medium. In addition to detecting sources and determining their fluxes and positions, we show that the wavelet analysis allows a characterization of the sources extents. In particular, the wavelet scale at which a given source achieves a maximum signal-to-noise ratio in the wavelet images provides an estimate of the angular extent of the source. To account for the widely varying point response of the ROSAT PSPC as a function of off-axis angle requires a quantitative measurement of the source size and a comparison to a calibration derived from the analysis of a Deep Survey image. Therefore, we assume that each source could be described as an isotropic two-dimensional Gaussian and used the wavelet amplitudes, at different scales, to determine the equivalent Gaussian Full Width Half-Maximum (FWHM) (and its uncertainty) appropriate for each source. In our analysis of the ROSAT PSPC image, we detect 31 X-ray sources above the diffuse cluster emission (within a radius of 24 min), 16 of which are apparently associated with cluster galaxies and two with serendipitous, background quasars. We find that the angular extents of 11 sources exceed the nominal width of the PSPC point-spread function. Four of these extended sources were previously detected by Bechtold et al. (1983) as 1 sec scale features using the Einstein HRI. The same wavelet analysis technique was applied to the Einstein HRI image. We detect 28 sources in the HRI image, of which nine are extended. Eight of the extended sources correspond to sources previously detected by Bechtold et al. Overall, using both the

  7. An improved pulse sequence and inversion algorithm of T2 spectrum

    NASA Astrophysics Data System (ADS)

    Ge, Xinmin; Chen, Hua; Fan, Yiren; Liu, Juntao; Cai, Jianchao; Liu, Jianyu

    2017-03-01

    The nuclear magnetic resonance transversal relaxation time is widely applied in geological prospecting, both in laboratory and downhole environments. However, current methods used for data acquisition and inversion should be reformed to characterize geological samples with complicated relaxation components and pore size distributions, such as samples of tight oil, gas shale, and carbonate. We present an improved pulse sequence to collect transversal relaxation signals based on the CPMG (Carr, Purcell, Meiboom, and Gill) pulse sequence. The echo spacing is not constant but varies in different windows, depending on prior knowledge or customer requirements. We use the entropy based truncated singular value decomposition (TSVD) to compress the ill-posed matrix and discard small singular values which cause the inversion instability. A hybrid algorithm combining the iterative TSVD and a simultaneous iterative reconstruction technique is implemented to reach the global convergence and stability of the inversion. Numerical simulations indicate that the improved pulse sequence leads to the same result as CPMG, but with lower echo numbers and computational time. The proposed method is a promising technique for geophysical prospecting and other related fields in future.

  8. Inverse dynamics of a 3 degree of freedom spatial flexible manipulator

    NASA Technical Reports Server (NTRS)

    Bayo, Eduardo; Serna, M.

    1989-01-01

    A technique is presented for solving the inverse dynamics and kinematics of 3 degree of freedom spatial flexible manipulator. The proposed method finds the joint torques necessary to produce a specified end effector motion. Since the inverse dynamic problem in elastic manipulators is closely coupled to the inverse kinematic problem, the solution of the first also renders the displacements and rotations at any point of the manipulator, including the joints. Furthermore the formulation is complete in the sense that it includes all the nonlinear terms due to the large rotation of the links. The Timoshenko beam theory is used to model the elastic characteristics, and the resulting equations of motion are discretized using the finite element method. An iterative solution scheme is proposed that relies on local linearization of the problem. The solution of each linearization is carried out in the frequency domain. The performance and capabilities of this technique are tested through simulation analysis. Results show the potential use of this method for the smooth motion control of space telerobots.

  9. RNA inverse folding using Monte Carlo tree search.

    PubMed

    Yang, Xiufeng; Yoshizoe, Kazuki; Taneda, Akito; Tsuda, Koji

    2017-11-06

    Artificially synthesized RNA molecules provide important ways for creating a variety of novel functional molecules. State-of-the-art RNA inverse folding algorithms can design simple and short RNA sequences of specific GC content, that fold into the target RNA structure. However, their performance is not satisfactory in complicated cases. We present a new inverse folding algorithm called MCTS-RNA, which uses Monte Carlo tree search (MCTS), a technique that has shown exceptional performance in Computer Go recently, to represent and discover the essential part of the sequence space. To obtain high accuracy, initial sequences generated by MCTS are further improved by a series of local updates. Our algorithm has an ability to control the GC content precisely and can deal with pseudoknot structures. Using common benchmark datasets for evaluation, MCTS-RNA showed a lot of promise as a standard method of RNA inverse folding. MCTS-RNA is available at https://github.com/tsudalab/MCTS-RNA .

  10. Inversion for the driving forces of plate tectonics

    NASA Technical Reports Server (NTRS)

    Richardson, R. M.

    1983-01-01

    Inverse modeling techniques have been applied to the problem of determining the roles of various forces that may drive and resist plate tectonic motions. Separate linear inverse problems have been solved to find the best fitting pole of rotation for finite element grid point velocities and to find the best combination of force models to fit the observed relative plate velocities for the earth's twelve major plates using the generalized inverse operator. Variance-covariance data on plate motion have also been included. Results emphasize the relative importance of ridge push forces in the driving mechanism. Convergent margin forces are smaller by at least a factor of two, and perhaps by as much as a factor of twenty. Slab pull, apparently, is poorly transmitted to the surface plate as a driving force. Drag forces at the base of the plate are smaller than ridge push forces, although the sign of the force remains in question.

  11. Joint inversion of fundamental and higher mode Rayleigh waves

    USGS Publications Warehouse

    Luo, Y.-H.; Xia, J.-H.; Liu, J.-P.; Liu, Q.-S.

    2008-01-01

    In this paper, we analyze the characteristics of the phase velocity of fundamental and higher mode Rayleigh waves in a six-layer earth model. The results show that fundamental mode is more sensitive to the shear velocities of shallow layers (< 7 m) and concentrated in a very narrow band (around 18 Hz) while higher modes are more sensitive to the parameters of relatively deeper layers and distributed over a wider frequency band. These properties provide a foundation of using a multi-mode joint inversion to define S-wave velocity. Inversion results of both synthetic data and a real-world example demonstrate that joint inversion with the damped least squares method and the SVD (Singular Value Decomposition) technique to invert Rayleigh waves of fundamental and higher modes can effectively reduce the ambiguity and improve the accuracy of inverted S-wave velocities.

  12. Frequency and time domain three-dimensional inversion of electromagnetic data for a grounded-wire source

    NASA Astrophysics Data System (ADS)

    Sasaki, Yutaka; Yi, Myeong-Jong; Choi, Jihyang; Son, Jeong-Sul

    2015-01-01

    We present frequency- and time-domain three-dimensional (3-D) inversion approaches that can be applied to transient electromagnetic (TEM) data from a grounded-wire source using a PC. In the direct time-domain approach, the forward solution and sensitivity were obtained in the frequency domain using a finite-difference technique, and the frequency response was then Fourier-transformed using a digital filter technique. In the frequency-domain approach, TEM data were Fourier-transformed using a smooth-spectrum inversion method, and the recovered frequency response was then inverted. The synthetic examples show that for the time derivative of magnetic field, frequency-domain inversion of TEM data performs almost as well as time-domain inversion, with a significant reduction in computational time. In our synthetic studies, we also compared the resolution capabilities of the ground and airborne TEM and controlled-source audio-frequency magnetotelluric (CSAMT) data resulting from a common grounded wire. An airborne TEM survey at 200-m elevation achieved a resolution for buried conductors almost comparable to that of the ground TEM method. It is also shown that the inversion of CSAMT data was able to detect a 3-D resistivity structure better than the TEM inversion, suggesting an advantage of electric-field measurements over magnetic-field-only measurements.

  13. An inverse dynamics approach to trajectory optimization for an aerospace plane

    NASA Technical Reports Server (NTRS)

    Lu, Ping

    1992-01-01

    An inverse dynamics approach for trajectory optimization is proposed. This technique can be useful in many difficult trajectory optimization and control problems. The application of the approach is exemplified by ascent trajectory optimization for an aerospace plane. Both minimum-fuel and minimax types of performance indices are considered. When rocket augmentation is available for ascent, it is shown that accurate orbital insertion can be achieved through the inverse control of the rocket in the presence of disturbances.

  14. Full-wave Nonlinear Inverse Scattering for Acoustic and Electromagnetic Breast Imaging

    NASA Astrophysics Data System (ADS)

    Haynes, Mark Spencer

    Acoustic and electromagnetic full-wave nonlinear inverse scattering techniques are explored in both theory and experiment with the ultimate aim of noninvasively mapping the material properties of the breast. There is evidence that benign and malignant breast tissue have different acoustic and electrical properties and imaging these properties directly could provide higher quality images with better diagnostic certainty. In this dissertation, acoustic and electromagnetic inverse scattering algorithms are first developed and validated in simulation. The forward solvers and optimization cost functions are modified from traditional forms in order to handle the large or lossy imaging scenes present in ultrasonic and microwave breast imaging. An antenna model is then presented, modified, and experimentally validated for microwave S-parameter measurements. Using the antenna model, a new electromagnetic volume integral equation is derived in order to link the material properties of the inverse scattering algorithms to microwave S-parameters measurements allowing direct comparison of model predictions and measurements in the imaging algorithms. This volume integral equation is validated with several experiments and used as the basis of a free-space inverse scattering experiment, where images of the dielectric properties of plastic objects are formed without the use of calibration targets. These efforts are used as the foundation of a solution and formulation for the numerical characterization of a microwave near-field cavity-based breast imaging system. The system is constructed and imaging results of simple targets are given. Finally, the same techniques are used to explore a new self-characterization method for commercial ultrasound probes. The method is used to calibrate an ultrasound inverse scattering experiment and imaging results of simple targets are presented. This work has demonstrated the feasibility of quantitative microwave inverse scattering by way of a self

  15. A cut-&-paste strategy for the 3-D inversion of helicopter-borne electromagnetic data - I. 3-D inversion using the explicit Jacobian and a tensor-based formulation

    NASA Astrophysics Data System (ADS)

    Scheunert, M.; Ullmann, A.; Afanasjew, M.; Börner, R.-U.; Siemon, B.; Spitzer, K.

    2016-06-01

    We present an inversion concept for helicopter-borne frequency-domain electromagnetic (HEM) data capable of reconstructing 3-D conductivity structures in the subsurface. Standard interpretation procedures often involve laterally constrained stitched 1-D inversion techniques to create pseudo-3-D models that are largely representative for smoothly varying conductivity distributions in the subsurface. Pronounced lateral conductivity changes may, however, produce significant artifacts that can lead to serious misinterpretation. Still, 3-D inversions of entire survey data sets are numerically very expensive. Our approach is therefore based on a cut-&-paste strategy whereupon the full 3-D inversion needs to be applied only to those parts of the survey where the 1-D inversion actually fails. The introduced 3-D Gauss-Newton inversion scheme exploits information given by a state-of-the-art (laterally constrained) 1-D inversion. For a typical HEM measurement, an explicit representation of the Jacobian matrix is inevitable which is caused by the unique transmitter-receiver relation. We introduce tensor quantities which facilitate the matrix assembly of the forward operator as well as the efficient calculation of the Jacobian. The finite difference forward operator incorporates the displacement currents because they may seriously affect the electromagnetic response at frequencies above 100. Finally, we deliver the proof of concept for the inversion using a synthetic data set with a noise level of up to 5%.

  16. Radio observations of the double-relic galaxy cluster Abell 1240

    NASA Astrophysics Data System (ADS)

    Hoang, D. N.; Shimwell, T. W.; van Weeren, R. J.; Intema, H. T.; Röttgering, H. J. A.; Andrade-Santos, F.; Akamatsu, H.; Bonafede, A.; Brunetti, G.; Dawson, W. A.; Golovich, N.; Best, P. N.; Botteon, A.; Brüggen, M.; Cassano, R.; de Gasperin, F.; Hoeft, M.; Stroe, A.; White, G. J.

    2018-05-01

    We present LOFAR 120 - 168 MHz images of the merging galaxy cluster Abell 1240 that hosts double radio relics. In combination with the GMRT 595 - 629 MHz and VLA 2 - 4 GHz data, we characterised the spectral and polarimetric properties of the radio emission. The spectral indices for the relics steepen from their outer edges towards the cluster centre and the electric field vectors are approximately perpendicular to the major axes of the relics. The results are consistent with the picture that these relics trace large-scale shocks propagating outwards during the merger. Assuming diffusive shock acceleration (DSA), we obtain shock Mach numbers of M=2.4 and 2.3 for the northern and southern shocks, respectively. For M≲ 3 shocks, a pre-existing population of mildly relativistic electrons is required to explain the brightness of the relics due to the high (>10 per cent) particle acceleration efficiency required. However, for M≳ 4 shocks the required efficiency is ≳ 1% and ≳ 0.5%, respectively, which is low enough for shock acceleration directly from the thermal pool. We used the fractional polarization to constrain the viewing angle to ≥53 ± 3° and ≥39 ± 5° for the northern and southern shocks, respectively. We found no evidence for diffuse emission in the cluster central region. If the halo spans the entire region between the relics (˜1.8 Mpc) our upper limit on the power is P1.4GHz = (1.4 ± 0.6) × 1023 W Hz-1 which is approximately equal to the anticipated flux from a cluster of this mass. However, if the halo is smaller than this, our constraints on the power imply that the halo is underluminous.

  17. Deep Chandra observations of the stripped galaxy group falling into Abell 2142

    NASA Astrophysics Data System (ADS)

    Eckert, D.; Gaspari, M.; Owers, M. S.; Roediger, E.; Molendi, S.; Gastaldello, F.; Paltani, S.; Ettori, S.; Venturi, T.; Rossetti, M.; Rudnick, L.

    2017-09-01

    In the local Universe, the growth of massive galaxy clusters mainly operates through the continuous accretion of group-scale systems. The infalling group in Abell 2142 is the poster child of such an accreting group, and as such, it is an ideal target to study the astrophysical processes induced by structure formation. We present the results of a deep (200 ks) observation of this structure with Chandra that highlights the complexity of this system in exquisite detail. In the core of the group, the spatial resolution of Chandra reveals a leading edge and complex AGN-induced activity. The morphology of the stripped gas tail appears straight in the innermost 250 kpc, suggesting that magnetic draping efficiently shields the gas from its surroundings. However, beyond 300 kpc from the core, the tail flares and the morphology becomes strongly irregular, which could be explained by a breaking of the drape, for example, caused by turbulent motions. The power spectrum of surface-brightness fluctuations is relatively flat (P2D ∝ k-2.3), which indicates that thermal conduction is strongly inhibited even beyond the region where magnetic draping is effective. The amplitude of density fluctuations in the tail is consistent with a mild level of turbulence with a Mach number M3D 0.1 - 0.25. Overall, our results show that the processes leading to the thermalization and mixing of the infalling gas are slow and relatively inefficient.

  18. A computationally efficient parallel Levenberg-Marquardt algorithm for highly parameterized inverse model analyses

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lin, Youzuo; O'Malley, Daniel; Vesselinov, Velimir V.

    Inverse modeling seeks model parameters given a set of observations. However, for practical problems because the number of measurements is often large and the model parameters are also numerous, conventional methods for inverse modeling can be computationally expensive. We have developed a new, computationally-efficient parallel Levenberg-Marquardt method for solving inverse modeling problems with a highly parameterized model space. Levenberg-Marquardt methods require the solution of a linear system of equations which can be prohibitively expensive to compute for moderate to large-scale problems. Our novel method projects the original linear problem down to a Krylov subspace, such that the dimensionality of themore » problem can be significantly reduced. Furthermore, we store the Krylov subspace computed when using the first damping parameter and recycle the subspace for the subsequent damping parameters. The efficiency of our new inverse modeling algorithm is significantly improved using these computational techniques. We apply this new inverse modeling method to invert for random transmissivity fields in 2D and a random hydraulic conductivity field in 3D. Our algorithm is fast enough to solve for the distributed model parameters (transmissivity) in the model domain. The algorithm is coded in Julia and implemented in the MADS computational framework (http://mads.lanl.gov). By comparing with Levenberg-Marquardt methods using standard linear inversion techniques such as QR or SVD methods, our Levenberg-Marquardt method yields a speed-up ratio on the order of ~10 1 to ~10 2 in a multi-core computational environment. Furthermore, our new inverse modeling method is a powerful tool for characterizing subsurface heterogeneity for moderate- to large-scale problems.« less

  19. A computationally efficient parallel Levenberg-Marquardt algorithm for highly parameterized inverse model analyses

    NASA Astrophysics Data System (ADS)

    Lin, Youzuo; O'Malley, Daniel; Vesselinov, Velimir V.

    2016-09-01

    Inverse modeling seeks model parameters given a set of observations. However, for practical problems because the number of measurements is often large and the model parameters are also numerous, conventional methods for inverse modeling can be computationally expensive. We have developed a new, computationally efficient parallel Levenberg-Marquardt method for solving inverse modeling problems with a highly parameterized model space. Levenberg-Marquardt methods require the solution of a linear system of equations which can be prohibitively expensive to compute for moderate to large-scale problems. Our novel method projects the original linear problem down to a Krylov subspace such that the dimensionality of the problem can be significantly reduced. Furthermore, we store the Krylov subspace computed when using the first damping parameter and recycle the subspace for the subsequent damping parameters. The efficiency of our new inverse modeling algorithm is significantly improved using these computational techniques. We apply this new inverse modeling method to invert for random transmissivity fields in 2-D and a random hydraulic conductivity field in 3-D. Our algorithm is fast enough to solve for the distributed model parameters (transmissivity) in the model domain. The algorithm is coded in Julia and implemented in the MADS computational framework (http://mads.lanl.gov). By comparing with Levenberg-Marquardt methods using standard linear inversion techniques such as QR or SVD methods, our Levenberg-Marquardt method yields a speed-up ratio on the order of ˜101 to ˜102 in a multicore computational environment. Therefore, our new inverse modeling method is a powerful tool for characterizing subsurface heterogeneity for moderate to large-scale problems.

  20. A computationally efficient parallel Levenberg-Marquardt algorithm for highly parameterized inverse model analyses

    DOE PAGES

    Lin, Youzuo; O'Malley, Daniel; Vesselinov, Velimir V.

    2016-09-01

    Inverse modeling seeks model parameters given a set of observations. However, for practical problems because the number of measurements is often large and the model parameters are also numerous, conventional methods for inverse modeling can be computationally expensive. We have developed a new, computationally-efficient parallel Levenberg-Marquardt method for solving inverse modeling problems with a highly parameterized model space. Levenberg-Marquardt methods require the solution of a linear system of equations which can be prohibitively expensive to compute for moderate to large-scale problems. Our novel method projects the original linear problem down to a Krylov subspace, such that the dimensionality of themore » problem can be significantly reduced. Furthermore, we store the Krylov subspace computed when using the first damping parameter and recycle the subspace for the subsequent damping parameters. The efficiency of our new inverse modeling algorithm is significantly improved using these computational techniques. We apply this new inverse modeling method to invert for random transmissivity fields in 2D and a random hydraulic conductivity field in 3D. Our algorithm is fast enough to solve for the distributed model parameters (transmissivity) in the model domain. The algorithm is coded in Julia and implemented in the MADS computational framework (http://mads.lanl.gov). By comparing with Levenberg-Marquardt methods using standard linear inversion techniques such as QR or SVD methods, our Levenberg-Marquardt method yields a speed-up ratio on the order of ~10 1 to ~10 2 in a multi-core computational environment. Furthermore, our new inverse modeling method is a powerful tool for characterizing subsurface heterogeneity for moderate- to large-scale problems.« less

  1. Metallicity Gradients in the Intracluster Gas of Abell 496

    NASA Astrophysics Data System (ADS)

    Dupke, Renato A.; White, Raymond E., III

    2000-07-01

    Analysis of spatially resolved ASCA spectra of the intracluster gas in Abell 496 confirms there are mild metal abundance enhancements near the center, as previously found in a joint analysis of spectra from Ginga Large Area Counter and Einstein solid state spectrometer. Simultaneous analysis of spectra from all ASCA instruments (SIS+GIS) shows that the iron abundance is 0.36+/-0.03 solar 3'-12' from the center of the cluster and rises ~50% to 0.53+/-0.04 solar within the central 2'. The F-test shows that this abundance gradient is significant at the more than 99.99% level. Nickel and sulfur abundances are also centrally enhanced. We use a variety of elemental abundance ratios to assess the relative contribution of Type Ia supernovae (SNe Ia) and Type II supernovae (SNe II) to the metal enrichment of the intracluster gas. We find spatial gradients in several abundance ratios, indicating that the fraction of iron from SNe Ia increases toward the cluster center, with SNe Ia accounting for ~50% of the iron mass 3'-12' from the center and ~70% within 2'. The increased proportion of SN Ia ejecta at the center is such that the central iron abundance enhancement can be attributed wholly to SNe Ia; we find no significant gradient in SN II ejecta. These spatial gradients in the proportion of SN Ia/II ejecta imply that the dominant metal enrichment mechanism near the center is different than in the outer parts of the cluster. We show that the central abundance enhancement is unlikely to be due to ram pressure stripping of gas from cluster galaxies or to secularly accumulated stellar mass loss within the central cD. We suggest that the additional SN Ia ejecta near the center is the vestige of a secondary SN Ia-driven wind from the cD (following a more energetic protogalactic SN II-driven wind phase), which was partially smothered in the cD due to its location at the cluster center.

  2. Time-lapse joint inversion of geophysical data with automatic joint constraints and dynamic attributes

    NASA Astrophysics Data System (ADS)

    Rittgers, J. B.; Revil, A.; Mooney, M. A.; Karaoulis, M.; Wodajo, L.; Hickey, C. J.

    2016-12-01

    Joint inversion and time-lapse inversion techniques of geophysical data are often implemented in an attempt to improve imaging of complex subsurface structures and dynamic processes by minimizing negative effects of random and uncorrelated spatial and temporal noise in the data. We focus on the structural cross-gradient (SCG) approach (enforcing recovered models to exhibit similar spatial structures) in combination with time-lapse inversion constraints applied to surface-based electrical resistivity and seismic traveltime refraction data. The combination of both techniques is justified by the underlying petrophysical models. We investigate the benefits and trade-offs of SCG and time-lapse constraints. Using a synthetic case study, we show that a combined joint time-lapse inversion approach provides an overall improvement in final recovered models. Additionally, we introduce a new approach to reweighting SCG constraints based on an iteratively updated normalized ratio of model sensitivity distributions at each time-step. We refer to the new technique as the Automatic Joint Constraints (AJC) approach. The relevance of the new joint time-lapse inversion process is demonstrated on the synthetic example. Then, these approaches are applied to real time-lapse monitoring field data collected during a quarter-scale earthen embankment induced-piping failure test. The use of time-lapse joint inversion is justified by the fact that a change of porosity drives concomitant changes in seismic velocities (through its effect on the bulk and shear moduli) and resistivities (through its influence upon the formation factor). Combined with the definition of attributes (i.e. specific characteristics) of the evolving target associated with piping, our approach allows localizing the position of the preferential flow path associated with internal erosion. This is not the case using other approaches.

  3. Deconvolving regional and fault-driven uplift in Calabria using drainage inversion techniques and field observations

    NASA Astrophysics Data System (ADS)

    Quye-Sawyer, Jennifer; Whittaker, Alexander; Roberts, Gareth; Rood, Dylan

    2017-04-01

    A key challenge in the Earth Sciences is to understand the timing and extent of the coupling between geodynamics, tectonics, and surface processes. In principle, the landscape adjusts to surface uplift or tectonic events, and present-day topography records a convolution of these processes. The inverse problem, the ability to find the 'best fit' theoretical scenario to match present day observations, is particularly desirable as it makes use of real data, encompasses the complexity of natural systems and quantifies model uncertainty through misfit. The region of Calabria, Italy, is known to have experienced geologically rapid uplift ( 1 mm/yr) since the Early Pleistocene, inferred from widespread marine terraces (ca. 1 Myr old) at elevations greater than 1 km. In addition, this is a tectonically active area of normal faulting with several highly destructive earthquakes in recent centuries. Since there has been some debate about the relative magnitudes of the uplift caused by regional processes or by faulting, the ability to model these effects on a regional scale may help resolve this problem. Therefore, Calabria is both a suitable and important site to model large magnitude recent geomorphic change. 1368 river longitudinal profiles have been generated from satellite digital elevation models (DEMs). These longitudinal profiles were compared to aerial photography to confirm the accuracy of this automated process. The longitudinal profiles contain numerous non-lithologically controlled knickpoints. Field observations support the presence of knickpoints extracted from the DEM and measurements of pebble imbrication from fluvial terraces suggest the planform stability of the drainage network in the last 1 Myr. By assuming fluvial erosion obeys stream power laws with an exponent of upstream area of 0.5 ± 0.1, the evolution of the landscape is computed using a linearized joint inversion of the longitudinal profiles. This has produced a spatially and temporally continuous

  4. Porosity Estimation By Artificial Neural Networks Inversion . Application to Algerian South Field

    NASA Astrophysics Data System (ADS)

    Eladj, Said; Aliouane, Leila; Ouadfeul, Sid-Ali

    2017-04-01

    One of the main geophysicist's current challenge is the discovery and the study of stratigraphic traps, this last is a difficult task and requires a very fine analysis of the seismic data. The seismic data inversion allows obtaining lithological and stratigraphic information for the reservoir characterization . However, when solving the inverse problem we encounter difficult problems such as: Non-existence and non-uniqueness of the solution add to this the instability of the processing algorithm. Therefore, uncertainties in the data and the non-linearity of the relationship between the data and the parameters must be taken seriously. In this case, the artificial intelligence techniques such as Artificial Neural Networks(ANN) is used to resolve this ambiguity, this can be done by integrating different physical properties data which requires a supervised learning methods. In this work, we invert the acoustic impedance 3D seismic cube using the colored inversion method, then, the introduction of the acoustic impedance volume resulting from the first step as an input of based model inversion method allows to calculate the Porosity volume using the Multilayer Perceptron Artificial Neural Network. Application to an Algerian South hydrocarbon field clearly demonstrate the power of the proposed processing technique to predict the porosity for seismic data, obtained results can be used for reserves estimation, permeability prediction, recovery factor and reservoir monitoring. Keywords: Artificial Neural Networks, inversion, non-uniqueness , nonlinear, 3D porosity volume, reservoir characterization .

  5. [Study of inversion and classification of particle size distribution under dependent model algorithm].

    PubMed

    Sun, Xiao-Gang; Tang, Hong; Yuan, Gui-Bin

    2008-05-01

    For the total light scattering particle sizing technique, an inversion and classification method was proposed with the dependent model algorithm. The measured particle system was inversed simultaneously by different particle distribution functions whose mathematic model was known in advance, and then classified according to the inversion errors. The simulation experiments illustrated that it is feasible to use the inversion errors to determine the particle size distribution. The particle size distribution function was obtained accurately at only three wavelengths in the visible light range with the genetic algorithm, and the inversion results were steady and reliable, which decreased the number of multi wavelengths to the greatest extent and increased the selectivity of light source. The single peak distribution inversion error was less than 5% and the bimodal distribution inversion error was less than 10% when 5% stochastic noise was put in the transmission extinction measurement values at two wavelengths. The running time of this method was less than 2 s. The method has advantages of simplicity, rapidity, and suitability for on-line particle size measurement.

  6. Photonic band gap in (Pb,La)(Zr,Ti)O3 inverse opals

    NASA Astrophysics Data System (ADS)

    Li, Bo; Zhou, Ji; Hao, Lifeng; Hu, Wei; Zong, Ruilong; Cai, Minmin; Fu, Min; Gui, Zhilun; Li, Longtu; Li, Qi

    2003-05-01

    (Pb,La)(Zr,Ti)O3 (PLZT) inverse opal photonic crystals were synthesized by a process of self-assembly in combination with a sol-gel technique. In this process, PLZT precursors were infiltrated into the interstices of the opal template assembled by monodisperse submicron polystyrene spheres, and then gelled in a humid environment. Polystyrene template was removed by calcining the specimen at a final temperature of 700 °C accompanied with the crystallization of perovskite phase in PLZT inverse opal network. Scanning electron microscope images show that the inverse opals possess a fcc structure with a lattice constant of 250 nm. A wide photonic band gap in the visible range is observed from transmission spectra of the sample. Such PLZT inverse opals as photonic crystals should be of importance in device applications.

  7. Fast Component Pursuit for Large-Scale Inverse Covariance Estimation.

    PubMed

    Han, Lei; Zhang, Yu; Zhang, Tong

    2016-08-01

    The maximum likelihood estimation (MLE) for the Gaussian graphical model, which is also known as the inverse covariance estimation problem, has gained increasing interest recently. Most existing works assume that inverse covariance estimators contain sparse structure and then construct models with the ℓ 1 regularization. In this paper, different from existing works, we study the inverse covariance estimation problem from another perspective by efficiently modeling the low-rank structure in the inverse covariance, which is assumed to be a combination of a low-rank part and a diagonal matrix. One motivation for this assumption is that the low-rank structure is common in many applications including the climate and financial analysis, and another one is that such assumption can reduce the computational complexity when computing its inverse. Specifically, we propose an efficient COmponent Pursuit (COP) method to obtain the low-rank part, where each component can be sparse. For optimization, the COP method greedily learns a rank-one component in each iteration by maximizing the log-likelihood. Moreover, the COP algorithm enjoys several appealing properties including the existence of an efficient solution in each iteration and the theoretical guarantee on the convergence of this greedy approach. Experiments on large-scale synthetic and real-world datasets including thousands of millions variables show that the COP method is faster than the state-of-the-art techniques for the inverse covariance estimation problem when achieving comparable log-likelihood on test data.

  8. Adaptive Inverse Control for Rotorcraft Vibration Reduction

    NASA Technical Reports Server (NTRS)

    Jacklin, Stephen A.

    1985-01-01

    convergence with increased possibility of unstable identification. In the simulation studies, the LMS adaptive inverse control algorithm is shown to be capable of adapting the inverse (controller) matrix to track changes in the flight conditions. The algorithm converges quickly for moderate disturbances, while taking longer for larger disturbances. Perfect knowledge of the inverse matrix is not required for good control of the N/Rev vibration. However it is shown that measurement noise will prevent the LMS adaptive inverse control technique from controlling the vibration, unless the signal averaging method presented is incorporated into the algorithm.

  9. Anisotropy effects on 3D waveform inversion

    NASA Astrophysics Data System (ADS)

    Stekl, I.; Warner, M.; Umpleby, A.

    2010-12-01

    In the recent years 3D waveform inversion has become achievable procedure for seismic data processing. A number of datasets has been inverted and presented (Warner el al 2008, Ben Hadj at all, Sirgue et all 2010) using isotropic 3D waveform inversion. However the question arises will the results be affected by isotropic assumption. Full-wavefield inversion techniques seek to match field data, wiggle-for-wiggle, to synthetic data generated by a high-resolution model of the sub-surface. In this endeavour, correctly matching the travel times of the principal arrivals is a necessary minimal requirement. In many, perhaps most, long-offset and wide-azimuth datasets, it is necessary to introduce some form of p-wave velocity anisotropy to match the travel times successfully. If this anisotropy is not also incorporated into the wavefield inversion, then results from the inversion will necessarily be compromised. We have incorporated anisotropy into our 3D wavefield tomography codes, characterised as spatially varying transverse isotropy with a tilted axis of symmetry - TTI anisotropy. This enhancement approximately doubles both the run time and the memory requirements of the code. We show that neglect of anisotropy can lead to significant artefacts in the recovered velocity models. We will present inversion results of inverting anisotropic 3D dataset by assuming isotropic earth and compare them with anisotropic inversion result. As a test case Marmousi model extended to 3D with no velocity variation in third direction and with added spatially varying anisotropy is used. Acquisition geometry is assumed as OBC with sources and receivers everywhere at the surface. We attempted inversion using both 2D and full 3D acquisition for this dataset. Results show that if no anisotropy is taken into account although image looks plausible most features are miss positioned in depth and space, even for relatively low anisotropy, which leads to incorrect result. This may lead to

  10. Waveform inversion of acoustic waves for explosion yield estimation

    DOE PAGES

    Kim, K.; Rodgers, A. J.

    2016-07-08

    We present a new waveform inversion technique to estimate the energy of near-surface explosions using atmospheric acoustic waves. Conventional methods often employ air blast models based on a homogeneous atmosphere, where the acoustic wave propagation effects (e.g., refraction and diffraction) are not taken into account, and therefore, their accuracy decreases with increasing source-receiver distance. In this study, three-dimensional acoustic simulations are performed with a finite difference method in realistic atmospheres and topography, and the modeled acoustic Green's functions are incorporated into the waveform inversion for the acoustic source time functions. The strength of the acoustic source is related to explosionmore » yield based on a standard air blast model. The technique was applied to local explosions (<10 km) and provided reasonable yield estimates (<~30% error) in the presence of realistic topography and atmospheric structure. In conclusion, the presented method can be extended to explosions recorded at far distance provided proper meteorological specifications.« less

  11. Waveform inversion of acoustic waves for explosion yield estimation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kim, K.; Rodgers, A. J.

    We present a new waveform inversion technique to estimate the energy of near-surface explosions using atmospheric acoustic waves. Conventional methods often employ air blast models based on a homogeneous atmosphere, where the acoustic wave propagation effects (e.g., refraction and diffraction) are not taken into account, and therefore, their accuracy decreases with increasing source-receiver distance. In this study, three-dimensional acoustic simulations are performed with a finite difference method in realistic atmospheres and topography, and the modeled acoustic Green's functions are incorporated into the waveform inversion for the acoustic source time functions. The strength of the acoustic source is related to explosionmore » yield based on a standard air blast model. The technique was applied to local explosions (<10 km) and provided reasonable yield estimates (<~30% error) in the presence of realistic topography and atmospheric structure. In conclusion, the presented method can be extended to explosions recorded at far distance provided proper meteorological specifications.« less

  12. Testing joint inversion techniques of gravity data and cosmic ray muon flux at a well-characterized site for use in the detection of subsurface density structures beneath volcanoes.

    NASA Astrophysics Data System (ADS)

    Cosburn, K.; Roy, M.; Rowe, C. A.; Guardincerri, E.

    2017-12-01

    Obtaining accurate static and time-dependent shallow subsurface density structure beneath volcanic, hydrogeologic, and tectonic targets can help illuminate active processes of fluid flow and magma transport. A limitation of using surface gravity measurements for such imaging is that these observations are vastly underdetermined and non-unique. In order to hone in on a more accurate solution, other data sets are needed to provide constraints, typically seismic or borehole observations. The spatial resolution of these techniques, however, is relatively poor, and a novel solution to this problem in recent years has been to use attenuation of the cosmic ray muon flux, which provides an independent constraint on density. In this study we present a joint inversion of gravity and cosmic ray muon flux observations to infer the density structure of a target rock volume at a well-characterized site near Los Alamos, New Mexico, USA. We investigate the shallow structure of a mesa formed by the Quaternary ash-flow tuffs on the Pajarito Plateau, flanking the Jemez volcano in New Mexico. Gravity measurements were made using a Lacoste and Romberg D meter on the surface of the mesa and inside a tunnel beneath the mesa. Muon flux measurements were also made at the mesa surface and at various points within the same tunnel using a muon detector having an acceptance region of 45 degrees from the vertical and a track resolution of several milliradians. We expect the combination of muon and gravity data to provide us with enhanced resolution as well as the ability to sense deeper structures in our region of interest. We use Bayesian joint inversion techniques on the gravity-muon dataset to test these ideas, building upon previous work using gravity inversion alone to resolve density structure in our study area. Both the regional geology and geometry of our study area is well-known and we assess the inferred density structure from our gravity-muon joint inversion within this known

  13. Structure and Formation of cD Galaxies: NGC 6166 in ABELL 2199

    NASA Astrophysics Data System (ADS)

    Bender, Ralf; Kormendy, John; Cornell, Mark E.; Fisher, David B.

    2015-07-01

     Hobby-Eberly Telescope (HET) spectroscopy is used to measure the velocity dispersion profile of the nearest prototypical cD galaxy, NGC 6166 in the cluster Abell 2199. We also present composite surface photometry from many telescopes. We confirm the defining feature of a cD galaxy; i.e., (we suggest), a halo of stars that fills the cluster center and that is controlled dynamically by cluster gravity, not by the central galaxy. Our HET spectroscopy shows that the velocity dispersion of NGC 6166 rises from σ ≃ 300 km s-1 in the inner r˜ 10\\prime\\prime to σ =865+/- 58 km s-1 at r ˜ 100″ in the cD halo. This extends published observations of an outward σ increase and shows for the first time that σ rises all the way to the cluster velocity dispersion of 819 ± 32 km s-1. We also observe that the main body of NGC 6166 moves at +206 ± 39 km s-1 with respect to the cluster mean velocity, but the velocity of the inner cD halo is ˜70 km s-1 closer to the cluster velocity. These results support our picture that cD halos consist of stars that were stripped from individual cluster galaxies by fast tidal encounters.  However, our photometry does not confirm the widespread view that cD halos are identifiable as an extra, low-surface-brightness component that is photometrically distinct from the inner, steep-Sérsic-function main body of an otherwise-normal giant elliptical galaxy. Instead, all of the brightness profile of NGC 6166 outside its core is described to ±0.037 V mag arcsec-2 by a single Sérsic function with index n≃ 8.3. The cD halo is not recognizable from photometry alone. This blurs the distinction between cluster-dominated cD halos and the similarly-large-Sérsic-index halos of giant, core-boxy-nonrotating ellipticals. These halos are believed to be accreted onto compact, high-redshift progenitors (“red nuggets”) by large numbers of minor mergers. They belong dynamically to their central galaxies. Still, cDs and core-boxy-nonrotating Es

  14. Optimization of the Inverse Algorithm for Estimating the Optical Properties of Biological Materials Using Spatially-resolved Diffuse Reflectance Technique

    USDA-ARS?s Scientific Manuscript database

    Determination of the optical properties from intact biological materials based on diffusion approximation theory is a complicated inverse problem, and it requires proper implementation of inverse algorithm, instrumentation, and experiment. This work was aimed at optimizing the procedure of estimatin...

  15. Full-waveform inversion of GPR data for civil engineering applications

    NASA Astrophysics Data System (ADS)

    van der Kruk, Jan; Kalogeropoulos, Alexis; Hugenschmidt, Johannes; Klotzsche, Anja; Busch, Sebastian; Vereecken, Harry

    2014-05-01

    Conventional GPR ray-based techniques are often limited in their capability to image complex structures due to the pertaining approximations. Due to the increased computational power, it is becoming more easy to use modeling and inversion tools that explicitly take into account the detailed electromagnetic wave propagation characteristics. In this way, new civil engineering application avenues are opening up that enable an improved high resolution imaging of quantitative medium properties. In this contribution, we show recent developments that enable the full-waveform inversion of off-ground, on-ground and crosshole GPR data. For a successful inversion, a proper start model must be used that generates synthetic data that overlaps the measured data with at least half a wavelength. In addition, the GPR system must be calibrated such that an effective wavelet is obtained that encompasses the complexity of the GPR source and receiver antennas. Simple geometries such as horizontal layers can be described with a limited number of model parameters, which enable the use of a combined global and local search using the Simplex search algorithm. This approach has been implemented for the full-waveform inversion of off-ground and on-ground GPR data measured over horizontally layered media. In this way, an accurate 3D frequency domain forward model of Maxwell's equation can be used where the integral representation of the electric field is numerically evaluated. The full-waveform inversion (FWI) for a large number of unknowns uses gradient-based optimization methods where a 3D to 2D conversion is used to apply this method to experimental data. Off-ground GPR data, measured over homogeneous concrete specimens, were inverted using the full-waveform inversion. In contrast to traditional ray-based techniques we were able to obtain quantitative values for the permittivity and conductivity and in this way distinguish between moisture and chloride effects. For increasing chloride

  16. The Distance and Mass of the Galaxy Cluster Abell 1995 Derived from Sunyaev-Zeldovich Effect and X-Ray Measurements

    NASA Technical Reports Server (NTRS)

    Patel, Sandeep K.; Joy, Marshall; Carlstrom, John E.; Holder, Gilbert P.; Reese, Erik D.; Gomez, Percy L.; Hughes, John P.; Grego, Laura; Holzapfel, William L.

    2000-01-01

    We present multiwavelength observations of the Abell 1995 galaxy cluster. From an analysis of X-ray spectroscopy and imaging data, we derive the electron temperature, cluster core radius, and central electron number density. Using optical spectroscopy of 15 cluster members, we derive an accurate cluster redshift and velocity dispersion. Finally, the interferometric imaging of the Sunyaev-Zeldovich effect toward Abell 1995 at 28.5 GHz provides a measure of the integrated pressure through the cluster. The X-ray and Sunyaev-Zeldovich effect observations are combined to determine the angular diameter distance to the cluster of D(sub A) = 1294(sup +294 +438, sub -283 -458) Mpc (Statistical followed by systematic uncertainty), implying a Hubble constant of H(sub 0) = 52.2(sup +11.4 +18.5, sub -11.9 -17.7) km/s.Mpc for Omega(sub M) = 0.3 and Omega(sub lambda) = 0.7. We find a best-fit H(sub 0) of 46 km/s.Mpc for the Omega(sub M) = 1 and Omega(sub lambda) = 0 cosmology, and 48 km/s.Mpc for Omega(sub M) = 0.3 and Omega(sub lambda) = 0.0. The X-ray data are also used to derive a total cluster mass of M(sup HSE, sub tot)(r(sub 500)) = 5.18(sup +0.62, sub -0.48) x 10(exp 14)/h solar mass; the optical velocity dispersion yields an independent and consistent estimate of M(sup virial, sub tot)(r(sub 500)) = 6.35(sup +1.51, sub -1.19) X 10(exp 14) /h solar mass. Both of the total mass estimates are evaluated at a fiducial radius, r(sub 500) = 830 /h kpc, where the overdensity is 500 times the critical density. The total cluster mass is then combined with gas mass measurements to determine a cluster gas mass fraction of F(sub g) = 0.056(sup +0.010, sub -0.013) /h(sup 3/2) in combination with recent baryon density constraints, the measured gas mass fraction yields an upper limit on the mass density parameter of Omega(sub M) h(sup 1/2) <= 0.34(sup +/0.06, sub 0.05.

  17. Inverse estimation of parameters for an estuarine eutrophication model

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shen, J.; Kuo, A.Y.

    1996-11-01

    An inverse model of an estuarine eutrophication model with eight state variables is developed. It provides a framework to estimate parameter values of the eutrophication model by assimilation of concentration data of these state variables. The inverse model using the variational technique in conjunction with a vertical two-dimensional eutrophication model is general enough to be applicable to aid model calibration. The formulation is illustrated by conducting a series of numerical experiments for the tidal Rappahannock River, a western shore tributary of the Chesapeake Bay. The numerical experiments of short-period model simulations with different hypothetical data sets and long-period model simulationsmore » with limited hypothetical data sets demonstrated that the inverse model can be satisfactorily used to estimate parameter values of the eutrophication model. The experiments also showed that the inverse model is useful to address some important questions, such as uniqueness of the parameter estimation and data requirements for model calibration. Because of the complexity of the eutrophication system, degrading of speed of convergence may occur. Two major factors which cause degradation of speed of convergence are cross effects among parameters and the multiple scales involved in the parameter system.« less

  18. Inverse Opal Scaffolds and Their Biomedical Applications.

    PubMed

    Zhang, Yu Shrike; Zhu, Chunlei; Xia, Younan

    2017-09-01

    Three-dimensional porous scaffolds play a pivotal role in tissue engineering and regenerative medicine by functioning as biomimetic substrates to manipulate cellular behaviors. While many techniques have been developed to fabricate porous scaffolds, most of them rely on stochastic processes that typically result in scaffolds with pores uncontrolled in terms of size, structure, and interconnectivity, greatly limiting their use in tissue regeneration. Inverse opal scaffolds, in contrast, possess uniform pores inheriting from the template comprised of a closely packed lattice of monodispersed microspheres. The key parameters of such scaffolds, including architecture, pore structure, porosity, and interconnectivity, can all be made uniform across the same sample and among different samples. In conjunction with a tight control over pore sizes, inverse opal scaffolds have found widespread use in biomedical applications. In this review, we provide a detailed discussion on this new class of advanced materials. After a brief introduction to their history and fabrication, we highlight the unique advantages of inverse opal scaffolds over their non-uniform counterparts. We then showcase their broad applications in tissue engineering and regenerative medicine, followed by a summary and perspective on future directions. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Role of various DNA repair pathways in chromosomal inversion formation in CHO mutants.

    PubMed

    Cartwright, Ian M; Kato, Takamitsu A

    2015-01-01

    In an effort to better understand the formation of chromosomal inversions, we investigated the role of various DNA repair pathways, including the non-homologous end joining (NHEJ), homologous recombination (HR), and Fanconi Anemia (FA) repair pathways for the formation of radiation induced chromosomal inversions. CHO10B2 wild type, CHO DNA repair-deficient, and CHO DNA repair-deficient corrected mutant cells were synchronized into G1 phase and exposed to gamma-rays. First post-irradiation metaphase cells were analyzed for chromosomal inversions by a differential chromatid staining technique involving a single cycle pre-irradiation ethynyl-uridine treatment and statistic calculations. It was observed that inhibition of the NHEJ pathway resulted in an overall decrease in the number of radiation-induced inversions, roughly a 50% decrease when compared to the CHO wild type. Interestingly, inhibition of the FA pathway resulted in an increase in both the number of spontaneous inversions and the number of radiation-induced inversions observed after exposure to 2 Gy of ionizing radiation. It was observed that FA-deficient cells contained roughly 330% (1.24 inversions per cell) more spontaneous inversions and 20% (0.4 inversions per cell) more radiation-induced inversions than the wild-type CHO cell lines. The HR mutants, defective in Rad51 foci, showed similar number of spontaneous and radiation-induced inversion as the wild-type cells. Gene complementation resulted in both spontaneous and radiation-induced inversions resembling the CHO wild-type cells. We have concluded that the NHEJ repair pathway contributes to the formation of radiation-induced inversions. Additionally, through an unknown molecular mechanism it appears that the FA signal pathway prevents the formation of both spontaneous and radiation induced inversions.

  20. BOOK REVIEW: Inverse Problems. Activities for Undergraduates

    NASA Astrophysics Data System (ADS)

    Yamamoto, Masahiro

    2003-06-01

    into the nature of inverse problems and the appropriate mode of thought, chapter 1 offers historical vignettes, most of which have played an essential role in the development of natural science. These vignettes cover the first successful application of `non-destructive testing' by Archimedes (page 4) via Newton's laws of motion up to literary tomography, and readers will be able to enjoy a wide overview of inverse problems. Therefore, as the author asks, the reader should not skip this chapter. This may not be hard to do, since the headings of the sections are quite intriguing (`Archimedes' Bath', `Another World', `Got the Time?', `Head Games', etc). The author embarks on the technical approach to inverse problems in chapter 2. He has elegantly designed each section with a guide specifying course level, objective, mathematical and scientifical background and appropriate technology (e.g. types of calculators required). The guides are designed such that teachers may be able to construct effective and attractive courses by themselves. The book is not intended to offer one rigidly determined course, but should be used flexibly and independently according to the situation. Moreover, every section closes with activities which can be chosen according to the students' interests and levels of ability. Some of these exercises do not have ready solutions, but require long-term study, so readers are not required to solve all of them. After chapter 5, which contains discrete inverse problems such as the algebraic reconstruction technique and the Backus - Gilbert method, there are answers and commentaries to the activities. Finally, scripts in MATLAB are attached, although they can also be downloaded from the author's web page (http://math.uc.edu/~groetsch/). This book is aimed at students but it will be very valuable to researchers wishing to retain a wide overview of inverse problems in the midst of busy research activities. A Japanese version was published in 2002.

  1. Inverse transport calculations in optical imaging with subspace optimization algorithms

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ding, Tian, E-mail: tding@math.utexas.edu; Ren, Kui, E-mail: ren@math.utexas.edu

    2014-09-15

    Inverse boundary value problems for the radiative transport equation play an important role in optics-based medical imaging techniques such as diffuse optical tomography (DOT) and fluorescence optical tomography (FOT). Despite the rapid progress in the mathematical theory and numerical computation of these inverse problems in recent years, developing robust and efficient reconstruction algorithms remains a challenging task and an active research topic. We propose here a robust reconstruction method that is based on subspace minimization techniques. The method splits the unknown transport solution (or a functional of it) into low-frequency and high-frequency components, and uses singular value decomposition to analyticallymore » recover part of low-frequency information. Minimization is then applied to recover part of the high-frequency components of the unknowns. We present some numerical simulations with synthetic data to demonstrate the performance of the proposed algorithm.« less

  2. 128Xe Lifetime Measurement Using the Coulex-Plunger Technique in Inverse Kinematics

    NASA Astrophysics Data System (ADS)

    Konstantinopoulos, T.; Lagoyannis, A.; Harissopulos, S.; Dewald, A.; Rother, W.; Ilie, G.; Jones, P.; Rakhila, P.; Greenlees, P.; Grahn, T.; Julin, R.; Balabanski, D. L.

    2008-05-01

    The lifetimes of the lowest collective yrast and non-yrast states in 128Xe were measured in a Coulomb excitation experiment using the recoil distance method (RDM) in inverse kinematics. Hereby, the Cologne plunger apparatus was employed together with the JUROGAM spectrometer. Excited states in 128Xe were populated using a 128Xe beam impinging on a natFe target with E(128Xe)~525 MeV. Recoils were detected by means of an array of solar cells placed at forward angles. Recoil-gated γ-spectra were measured at different plunger distances.

  3. Cooperative inversion of magnetotelluric and seismic data sets

    NASA Astrophysics Data System (ADS)

    Markovic, M.; Santos, F.

    2012-04-01

    Cooperative inversion of magnetotelluric and seismic data sets Milenko Markovic,Fernando Monteiro Santos IDL, Faculdade de Ciências da Universidade de Lisboa 1749-016 Lisboa Inversion of single geophysical data has well-known limitations due to the non-linearity of the fields and non-uniqueness of the model. There is growing need, both in academy and industry to use two or more different data sets and thus obtain subsurface property distribution. In our case ,we are dealing with magnetotelluric and seismic data sets. In our approach,we are developing algorithm based on fuzzy-c means clustering technique, for pattern recognition of geophysical data. Separate inversion is performed on every step, information exchanged for model integration. Interrelationships between parameters from different models is not required in analytical form. We are investigating how different number of clusters, affects zonation and spatial distribution of parameters. In our study optimization in fuzzy c-means clustering (for magnetotelluric and seismic data) is compared for two cases, firstly alternating optimization and then hybrid method (alternating optimization+ Quasi-Newton method). Acknowledgment: This work is supported by FCT Portugal

  4. Gravity inversion of a fault by Particle swarm optimization (PSO).

    PubMed

    Toushmalani, Reza

    2013-01-01

    Particle swarm optimization is a heuristic global optimization method and also an optimization algorithm, which is based on swarm intelligence. It comes from the research on the bird and fish flock movement behavior. In this paper we introduce and use this method in gravity inverse problem. We discuss the solution for the inverse problem of determining the shape of a fault whose gravity anomaly is known. Application of the proposed algorithm to this problem has proven its capability to deal with difficult optimization problems. The technique proved to work efficiently when tested to a number of models.

  5. Quantum Effects in Inverse Opal Structures

    NASA Astrophysics Data System (ADS)

    Bleiweiss, Michael; Datta, Timir; Lungu, Anca; Yin, Ming; Iqbal, Zafar; Palm, Eric; Brandt, Bruce

    2002-03-01

    Properties of bismuth inverse opals and carbon opal replicas were studied. The bismuth nanostructures were fabricated by pressure infiltration into porous artificial opal, while the carbon opal replicas were created via CVD. These structures form a regular three-dimensional network in which the bismuth and carbon regions percolate in all directions between the close packed spheres of SiO_2. The sizes of the conducting regions are of the order of tens of nanometers. Static susceptibility of the bismuth inverse opal showed clear deHaas-vanAlphen oscillations. Transport measurements, including Hall, were done using standard ac four and six probe techniques in fields up to 17 T* and temperatures between 4.2 and 200 K. Observations of Shubnikov-deHaas oscillations in magnetoresistance, one-dimensional weak localization, quantum Hall and other effects will be discussed. *Performed at the National High Magnetic Field Lab (NHMFL) FSU, Tallahassee, FL. This work was partially supported by grants from DARPA-nanothermoelectrics, NASA-EPSCOR and the USC nanocenter.

  6. Three-Dimensional Anisotropic Acoustic and Elastic Full-Waveform Seismic Inversion

    NASA Astrophysics Data System (ADS)

    Warner, M.; Morgan, J. V.

    2013-12-01

    Three-dimensional full-waveform inversion is a high-resolution, high-fidelity, quantitative, seismic imaging technique that has advanced rapidly within the oil and gas industry. The method involves the iterative improvement of a starting model using a series of local linearized updates to solve the full non-linear inversion problem. During the inversion, forward modeling employs the full two-way three-dimensional heterogeneous anisotropic acoustic or elastic wave equation to predict the observed raw field data, wiggle-for-wiggle, trace-by-trace. The method is computationally demanding; it is highly parallelized, and runs on large multi-core multi-node clusters. Here, we demonstrate what can be achieved by applying this newly practical technique to several high-density 3D seismic datasets that were acquired to image four contrasting sedimentary targets: a gas cloud above an oil reservoir, a radially faulted dome, buried fluvial channels, and collapse structures overlying an evaporate sequence. We show that the resulting anisotropic p-wave velocity models match in situ measurements in deep boreholes, reproduce detailed structure observed independently on high-resolution seismic reflection sections, accurately predict the raw seismic data, simplify and sharpen reverse-time-migrated reflection images of deeper horizons, and flatten Kirchhoff-migrated common-image gathers. We also show that full-elastic 3D full-waveform inversion of pure pressure data can generate a reasonable shear-wave velocity model for one of these datasets. For two of the four datasets, the inclusion of significant transversely isotropic anisotropy with a vertical axis of symmetry was necessary in order to fit the kinematics of the field data properly. For the faulted dome, the full-waveform-inversion p-wave velocity model recovers the detailed structure of every fault that can be seen on coincident seismic reflection data. Some of the individual faults represent high-velocity zones, some represent

  7. IMPROVED SEARCH OF PRINCIPAL COMPONENT ANALYSIS DATABASES FOR SPECTRO-POLARIMETRIC INVERSION

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Casini, R.; Lites, B. W.; Ramos, A. Asensio

    2013-08-20

    We describe a simple technique for the acceleration of spectro-polarimetric inversions based on principal component analysis (PCA) of Stokes profiles. This technique involves the indexing of the database models based on the sign of the projections (PCA coefficients) of the first few relevant orders of principal components of the four Stokes parameters. In this way, each model in the database can be attributed a distinctive binary number of 2{sup 4n} bits, where n is the number of PCA orders used for the indexing. Each of these binary numbers (indices) identifies a group of ''compatible'' models for the inversion of amore » given set of observed Stokes profiles sharing the same index. The complete set of the binary numbers so constructed evidently determines a partition of the database. The search of the database for the PCA inversion of spectro-polarimetric data can profit greatly from this indexing. In practical cases it becomes possible to approach the ideal acceleration factor of 2{sup 4n} as compared to the systematic search of a non-indexed database for a traditional PCA inversion. This indexing method relies on the existence of a physical meaning in the sign of the PCA coefficients of a model. For this reason, the presence of model ambiguities and of spectro-polarimetric noise in the observations limits in practice the number n of relevant PCA orders that can be used for the indexing.« less

  8. Coupled Hydrogeophysical Inversion and Hydrogeological Data Fusion

    NASA Astrophysics Data System (ADS)

    Cirpka, O. A.; Schwede, R. L.; Li, W.

    2012-12-01

    Tomographic geophysical monitoring methods give the opportunity to observe hydrogeological tests at higher spatial resolution than is possible with classical hydraulic monitoring tools. This has been demonstrated in a substantial number of studies in which electrical resistivity tomography (ERT) has been used to monitor salt-tracer experiments. It is now accepted that inversion of such data sets requires a fully coupled framework, explicitly accounting for the hydraulic processes (groundwater flow and solute transport), the relationship between solute and geophysical properties (petrophysical relationship such as Archie's law), and the governing equations of the geophysical surveying techniques (e.g., the Poisson equation) as consistent coupled system. These data sets can be amended with data from other - more direct - hydrogeological tests to infer the distribution of hydraulic aquifer parameters. In the inversion framework, meaningful condensation of data does not only contribute to inversion efficiency but also increases the stability of the inversion. In particular, transient concentration data themselves only weakly depend on hydraulic conductivity, and model improvement using gradient-based methods is only possible when a substantial agreement between measurements and model output already exists. The latter also holds when concentrations are monitored by ERT. Tracer arrival times, by contrast, show high sensitivity and a more monotonic dependence on hydraulic conductivity than concentrations themselves. Thus, even without using temporal-moment generating equations, inverting travel times rather than concentrations or related geoelectrical signals themselves is advantageous. We have applied this approach to concentrations measured directly or via ERT, and to heat-tracer data. We present a consistent inversion framework including temporal moments of concentrations, geoelectrical signals obtained during salt-tracer tests, drawdown data from hydraulic tomography

  9. Improved preconditioned conjugate gradient algorithm and application in 3D inversion of gravity-gradiometry data

    NASA Astrophysics Data System (ADS)

    Wang, Tai-Han; Huang, Da-Nian; Ma, Guo-Qing; Meng, Zhao-Hai; Li, Ye

    2017-06-01

    With the continuous development of full tensor gradiometer (FTG) measurement techniques, three-dimensional (3D) inversion of FTG data is becoming increasingly used in oil and gas exploration. In the fast processing and interpretation of large-scale high-precision data, the use of the graphics processing unit process unit (GPU) and preconditioning methods are very important in the data inversion. In this paper, an improved preconditioned conjugate gradient algorithm is proposed by combining the symmetric successive over-relaxation (SSOR) technique and the incomplete Choleksy decomposition conjugate gradient algorithm (ICCG). Since preparing the preconditioner requires extra time, a parallel implement based on GPU is proposed. The improved method is then applied in the inversion of noisecontaminated synthetic data to prove its adaptability in the inversion of 3D FTG data. Results show that the parallel SSOR-ICCG algorithm based on NVIDIA Tesla C2050 GPU achieves a speedup of approximately 25 times that of a serial program using a 2.0 GHz Central Processing Unit (CPU). Real airborne gravity-gradiometry data from Vinton salt dome (southwest Louisiana, USA) are also considered. Good results are obtained, which verifies the efficiency and feasibility of the proposed parallel method in fast inversion of 3D FTG data.

  10. Reducing uncertainties in the velocities determined by inversion of phase velocity dispersion curves using synthetic seismograms

    NASA Astrophysics Data System (ADS)

    Hosseini, Seyed Mehrdad

    Characterizing the near-surface shear-wave velocity structure using Rayleigh-wave phase velocity dispersion curves is widespread in the context of reservoir characterization, exploration seismology, earthquake engineering, and geotechnical engineering. This surface seismic approach provides a feasible and low-cost alternative to the borehole measurements. Phase velocity dispersion curves from Rayleigh surface waves are inverted to yield the vertical shear-wave velocity profile. A significant problem with the surface wave inversion is its intrinsic non-uniqueness, and although this problem is widely recognized, there have not been systematic efforts to develop approaches to reduce the pervasive uncertainty that affects the velocity profiles determined by the inversion. Non-uniqueness cannot be easily studied in a nonlinear inverse problem such as Rayleigh-wave inversion and the only way to understand its nature is by numerical investigation which can get computationally expensive and inevitably time consuming. Regarding the variety of the parameters affecting the surface wave inversion and possible non-uniqueness induced by them, a technique should be established which is not controlled by the non-uniqueness that is already affecting the surface wave inversion. An efficient and repeatable technique is proposed and tested to overcome the non-uniqueness problem; multiple inverted shear-wave velocity profiles are used in a wavenumber integration technique to generate synthetic time series resembling the geophone recordings. The similarity between synthetic and observed time series is used as an additional tool along with the similarity between the theoretical and experimental dispersion curves. The proposed method is proven to be effective through synthetic and real world examples. In these examples, the nature of the non-uniqueness is discussed and its existence is shown. Using the proposed technique, inverted velocity profiles are estimated and effectiveness of this

  11. Towards Full-Waveform Ambient Noise Inversion

    NASA Astrophysics Data System (ADS)

    Sager, Korbinian; Ermert, Laura; Afanasiev, Michael; Boehm, Christian; Fichtner, Andreas

    2017-04-01

    Noise tomography usually works under the assumption that the inter-station ambient noise correlation is equal to a scaled version of the Green function between the two receivers. This assumption, however, is only met under specific conditions, e.g. wavefield diffusivity and equipartitioning, or the isotropic distribution of both mono- and dipolar uncorrelated noise sources. These assumptions are typically not satisfied in the Earth. This inconsistency inhibits the exploitation of the full waveform information contained in noise correlations in order to constrain Earth structure and noise generation. To overcome this limitation, we attempt to develop a method that consistently accounts for the distribution of noise sources, 3D heterogeneous Earth structure and the full seismic wave propagation physics. This is intended to improve the resolution of tomographic images, to refine noise source distribution, and thereby to contribute to a better understanding of both Earth structure and noise generation. First, we develop an inversion strategy based on a 2D finite-difference code using adjoint techniques. To enable a joint inversion for noise sources and Earth structure, we investigate the following aspects: i) the capability of different misfit functionals to image wave speed anomalies and source distribution and ii) possible source-structure trade-offs, especially to what extent unresolvable structure can be mapped into the inverted noise source distribution and vice versa. In anticipation of real-data applications, we present an extension of the open-source waveform modelling and inversion package Salvus (http://salvus.io). It allows us to compute correlation functions in 3D media with heterogeneous noise sources at the surface and the corresponding sensitivity kernels for the distribution of noise sources and Earth structure. By studying the effect of noise sources on correlation functions in 3D, we validate the aforementioned inversion strategy and prepare the

  12. 2D Inversion of Transient Electromagnetic Method (TEM)

    NASA Astrophysics Data System (ADS)

    Bortolozo, Cassiano Antonio; Luís Porsani, Jorge; Acácio Monteiro dos Santos, Fernando

    2017-04-01

    A new methodology was developed for 2D inversion of Transient Electromagnetic Method (TEM). The methodology consists in the elaboration of a set of routines in Matlab code for modeling and inversion of TEM data and the determination of the most efficient field array for the problem. In this research, the 2D TEM modeling uses the finite differences discretization. To solve the inversion problem, were applied an algorithm based on Marquardt technique, also known as Ridge Regression. The algorithm is stable and efficient and it is widely used in geoelectrical inversion problems. The main advantage of 1D survey is the rapid data acquisition in a large area, but in regions with two-dimensional structures or that need more details, is essential to use two-dimensional interpretation methodologies. For an efficient field acquisition we used in an innovative form the fixed-loop array, with a square transmitter loop (200m x 200m) and 25m spacing between the sounding points. The TEM surveys were conducted only inside the transmitter loop, in order to not deal with negative apparent resistivity values. Although it is possible to model the negative values, it makes the inversion convergence more difficult. Therefore the methodology described above has been developed in order to achieve maximum optimization of data acquisition. Since it is necessary only one transmitter loop disposition in the surface for each series of soundings inside the loop. The algorithms were tested with synthetic data and the results were essential to the interpretation of the results with real data and will be useful in future situations. With the inversion of the real data acquired over the Paraná Sedimentary Basin (PSB) was successful realized a 2D TEM inversion. The results indicate a robust geoelectrical characterization for the sedimentary and crystalline aquifers in the PSB. Therefore, using a new and relevant approach for 2D TEM inversion, this research effectively contributed to map the most

  13. Inverse-dispersion technique for assessing lagoon gas emissions

    USDA-ARS?s Scientific Manuscript database

    Measuring gas emissions from treatment lagoons and storage ponds poses challenging conditions for existing micrometeorological techniques because of non-ideal wind conditions, such as those induced by trees and crops surrounding the lagoons, and lagoons with dimensions too small to establish equilib...

  14. Inverse dynamic substructuring using the direct hybrid assembly in the frequency domain

    NASA Astrophysics Data System (ADS)

    D'Ambrogio, Walter; Fregolent, Annalisa

    2014-04-01

    The paper deals with the identification of the dynamic behaviour of a structural subsystem, starting from the known dynamic behaviour of both the coupled system and the remaining part of the structural system (residual subsystem). This topic is also known as decoupling problem, subsystem subtraction or inverse dynamic substructuring. Whenever it is necessary to combine numerical models (e.g. FEM) and test models (e.g. FRFs), one speaks of experimental dynamic substructuring. Substructure decoupling techniques can be classified as inverse coupling or direct decoupling techniques. In inverse coupling, the equations describing the coupling problem are rearranged to isolate the unknown substructure instead of the coupled structure. On the contrary, direct decoupling consists in adding to the coupled system a fictitious subsystem that is the negative of the residual subsystem. Starting from a reduced version of the 3-field formulation (dynamic equilibrium using FRFs, compatibility and equilibrium of interface forces), a direct hybrid assembly is developed by requiring that both compatibility and equilibrium conditions are satisfied exactly, either at coupling DoFs only, or at additional internal DoFs of the residual subsystem. Equilibrium and compatibility DoFs might not be the same: this generates the so-called non-collocated approach. The technique is applied using experimental data from an assembled system made by a plate and a rigid mass.

  15. Estimation of near-surface shear-wave velocity by inversion of Rayleigh waves

    USGS Publications Warehouse

    Xia, J.; Miller, R.D.; Park, C.B.

    1999-01-01

    The shear-wave (S-wave) velocity of near-surface materials (soil, rocks, pavement) and its effect on seismic-wave propagation are of fundamental interest in many groundwater, engineering, and environmental studies. Rayleigh-wave phase velocity of a layered-earth model is a function of frequency and four groups of earth properties: P-wave velocity, S-wave velocity, density, and thickness of layers. Analysis of the Jacobian matrix provides a measure of dispersion-curve sensitivity to earth properties. S-wave velocities are the dominant influence on a dispersion curve in a high-frequency range (>5 Hz) followed by layer thickness. An iterative solution technique to the weighted equation proved very effective in the high-frequency range when using the Levenberg-Marquardt and singular-value decomposition techniques. Convergence of the weighted solution is guaranteed through selection of the damping factor using the Levenberg-Marquardt method. Synthetic examples demonstrated calculation efficiency and stability of inverse procedures. We verify our method using borehole S-wave velocity measurements.Iterative solutions to the weighted equation by the Levenberg-Marquardt and singular-value decomposition techniques are derived to estimate near-surface shear-wave velocity. Synthetic and real examples demonstrate the calculation efficiency and stability of the inverse procedure. The inverse results of the real example are verified by borehole S-wave velocity measurements.

  16. Solution of some types of differential equations: operational calculus and inverse differential operators.

    PubMed

    Zhukovsky, K

    2014-01-01

    We present a general method of operational nature to analyze and obtain solutions for a variety of equations of mathematical physics and related mathematical problems. We construct inverse differential operators and produce operational identities, involving inverse derivatives and families of generalised orthogonal polynomials, such as Hermite and Laguerre polynomial families. We develop the methodology of inverse and exponential operators, employing them for the study of partial differential equations. Advantages of the operational technique, combined with the use of integral transforms, generating functions with exponentials and their integrals, for solving a wide class of partial derivative equations, related to heat, wave, and transport problems, are demonstrated.

  17. Inverse-collimated proton radiography for imaging thin materials

    NASA Astrophysics Data System (ADS)

    Freeman, Matthew S.; Allison, Jason; Andrews, Malcolm; Ferm, Eric; Goett, John J.; Kwiatkowski, Kris; Lopez, Julian; Mariam, Fesseha; Marr-Lyon, Mark; Martinez, Michael; Medina, Jason; Medina, Patrick; Merrill, Frank E.; Morris, Chris L.; Murray, Matthew M.; Nedrow, Paul; Neukirch, Levi P.; Prestridge, Katherine; Rigg, Paolo; Saunders, Alexander; Schurman, Tamsen; Tainter, Amy; Trouw, Frans; Tupa, Dale; Tybo, Josh; Vogan-McNeil, Wendy; Wilde, Carl

    2017-01-01

    Relativistic, magnetically focused proton radiography was invented at Los Alamos National Laboratory using the 800 MeV LANSCE beam and is inherently well-suited to imaging dense objects, at areal densities >20 g cm-2. However, if the unscattered portion of the transmitted beam is removed at the Fourier plane through inverse-collimation, this system becomes highly sensitive to very thin media, of areal densities <100 mg cm-2. Here, this inverse-collimation scheme is described in detail and demonstrated by imaging Xe gas with a shockwave generated by an aluminum plate compressing the gas at Mach 8.8. With a 5-mrad inverse collimator, an areal density change of just 49 mg cm-2 across the shock front is discernible with a contrast-to-noise ratio of 3. Geant4 modeling of idealized and realistic proton transports can guide the design of inverse-collimators optimized for specific experimental conditions and show that this technique performs better for thin targets with reduced incident proton beam emittance. This work increases the range of areal densities to which the system is sensitive to span from ˜25 mg cm-2 to 100 g cm-2, exceeding three orders of magnitude. This enables the simultaneous imaging of a dense system as well as thin jets and ejecta material that are otherwise difficult to characterize with high-energy proton radiography.

  18. Inverse-collimated proton radiography for imaging thin materials.

    PubMed

    Freeman, Matthew S; Allison, Jason; Andrews, Malcolm; Ferm, Eric; Goett, John J; Kwiatkowski, Kris; Lopez, Julian; Mariam, Fesseha; Marr-Lyon, Mark; Martinez, Michael; Medina, Jason; Medina, Patrick; Merrill, Frank E; Morris, Chris L; Murray, Matthew M; Nedrow, Paul; Neukirch, Levi P; Prestridge, Katherine; Rigg, Paolo; Saunders, Alexander; Schurman, Tamsen; Tainter, Amy; Trouw, Frans; Tupa, Dale; Tybo, Josh; Vogan-McNeil, Wendy; Wilde, Carl

    2017-01-01

    Relativistic, magnetically focused proton radiography was invented at Los Alamos National Laboratory using the 800 MeV LANSCE beam and is inherently well-suited to imaging dense objects, at areal densities >20 g cm -2 . However, if the unscattered portion of the transmitted beam is removed at the Fourier plane through inverse-collimation, this system becomes highly sensitive to very thin media, of areal densities <100 mg cm -2 . Here, this inverse-collimation scheme is described in detail and demonstrated by imaging Xe gas with a shockwave generated by an aluminum plate compressing the gas at Mach 8.8. With a 5-mrad inverse collimator, an areal density change of just 49 mg cm -2 across the shock front is discernible with a contrast-to-noise ratio of 3. Geant4 modeling of idealized and realistic proton transports can guide the design of inverse-collimators optimized for specific experimental conditions and show that this technique performs better for thin targets with reduced incident proton beam emittance. This work increases the range of areal densities to which the system is sensitive to span from ∼25 mg cm -2 to 100 g cm -2 , exceeding three orders of magnitude. This enables the simultaneous imaging of a dense system as well as thin jets and ejecta material that are otherwise difficult to characterize with high-energy proton radiography.

  19. An experimental investigation of gas fuel injection with X-ray radiography

    DOE PAGES

    Swantek, Andrew B.; Duke, D. J.; Kastengren, A. L.; ...

    2017-04-21

    In this paper, an outward-opening compressed natural gas, direct injection fuel injector has been studied with single-shot x-ray radiography. Three dimensional simulations have also been performed to compliment the x-ray data. Argon was used as a surrogate gas for experimental and safety reasons. This technique allows the acquisition of a quantitative mapping of the ensemble-average and standard deviation of the projected density throughout the injection event. Two dimensional, ensemble average and standard deviation data are presented to investigate the quasi-steady-state behavior of the jet. Upstream of the stagnation zone, minimal shot-to-shot variation is observed. Downstream of the stagnation zone, bulkmore » mixing is observed as the jet transitions to a subsonic turbulent jet. From the time averaged data, individual slices at all downstream locations are extracted and an Abel inversion was performed to compute the radial density distribution, which was interpolated to create three dimensional visualizations. The Abel reconstructions reveal that upstream of the stagnation zone, the gas forms an annulus with high argon density and large density gradients. Inside this annulus, a recirculation region with low argon density exists. Downstream, the jet transitions to a fully turbulent jet with Gaussian argon density distributions. This experimental data is intended to serve as a quantitative benchmark for simulations.« less

  20. An experimental investigation of gas fuel injection with X-ray radiography

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Swantek, Andrew B.; Duke, D. J.; Kastengren, A. L.

    In this paper, an outward-opening compressed natural gas, direct injection fuel injector has been studied with single-shot x-ray radiography. Three dimensional simulations have also been performed to compliment the x-ray data. Argon was used as a surrogate gas for experimental and safety reasons. This technique allows the acquisition of a quantitative mapping of the ensemble-average and standard deviation of the projected density throughout the injection event. Two dimensional, ensemble average and standard deviation data are presented to investigate the quasi-steady-state behavior of the jet. Upstream of the stagnation zone, minimal shot-to-shot variation is observed. Downstream of the stagnation zone, bulkmore » mixing is observed as the jet transitions to a subsonic turbulent jet. From the time averaged data, individual slices at all downstream locations are extracted and an Abel inversion was performed to compute the radial density distribution, which was interpolated to create three dimensional visualizations. The Abel reconstructions reveal that upstream of the stagnation zone, the gas forms an annulus with high argon density and large density gradients. Inside this annulus, a recirculation region with low argon density exists. Downstream, the jet transitions to a fully turbulent jet with Gaussian argon density distributions. This experimental data is intended to serve as a quantitative benchmark for simulations.« less

  1. 23RD International Conference on Phenomena in Ionized Gases, Volume 3

    DTIC Science & Technology

    1998-12-01

    discharges, and high pressure glows; arcs; high frequency discharges; ionospheric magnetospheric, and astrophysical plasmas; plasma diagnostic methods ...kf) in pulse reflectometry. Second, it different frequencies , and an Abel inversion is gives a quantitative model of the behaviour of the wave... design V method in the case of narrow mutual pitch of surface electrodes for high concentration ozone generation. 2. Experimental setup 20 The electrode

  2. Indium oxide inverse opal films synthesized by structure replication method

    NASA Astrophysics Data System (ADS)

    Amrehn, Sabrina; Berghoff, Daniel; Nikitin, Andreas; Reichelt, Matthias; Wu, Xia; Meier, Torsten; Wagner, Thorsten

    2016-04-01

    We present the synthesis of indium oxide (In2O3) inverse opal films with photonic stop bands in the visible range by a structure replication method. Artificial opal films made of poly(methyl methacrylate) (PMMA) spheres are utilized as template. The opal films are deposited via sedimentation facilitated by ultrasonication, and then impregnated by indium nitrate solution, which is thermally converted to In2O3 after drying. The quality of the resulting inverse opal film depends on many parameters; in this study the water content of the indium nitrate/PMMA composite after drying is investigated. Comparison of the reflectance spectra recorded by vis-spectroscopy with simulated data shows a good agreement between the peak position and calculated stop band positions for the inverse opals. This synthesis is less complex and highly efficient compared to most other techniques and is suitable for use in many applications.

  3. A regional high-resolution carbon flux inversion of North America for 2004

    NASA Astrophysics Data System (ADS)

    Schuh, A. E.; Denning, A. S.; Corbin, K. D.; Baker, I. T.; Uliasz, M.; Parazoo, N.; Andrews, A. E.; Worthy, D. E. J.

    2010-05-01

    Resolving the discrepancies between NEE estimates based upon (1) ground studies and (2) atmospheric inversion results, demands increasingly sophisticated techniques. In this paper we present a high-resolution inversion based upon a regional meteorology model (RAMS) and an underlying biosphere (SiB3) model, both running on an identical 40 km grid over most of North America. Current operational systems like CarbonTracker as well as many previous global inversions including the Transcom suite of inversions have utilized inversion regions formed by collapsing biome-similar grid cells into larger aggregated regions. An extreme example of this might be where corrections to NEE imposed on forested regions on the east coast of the United States might be the same as that imposed on forests on the west coast of the United States while, in reality, there likely exist subtle differences in the two areas, both natural and anthropogenic. Our current inversion framework utilizes a combination of previously employed inversion techniques while allowing carbon flux corrections to be biome independent. Temporally and spatially high-resolution results utilizing biome-independent corrections provide insight into carbon dynamics in North America. In particular, we analyze hourly CO2 mixing ratio data from a sparse network of eight towers in North America for 2004. A prior estimate of carbon fluxes due to Gross Primary Productivity (GPP) and Ecosystem Respiration (ER) is constructed from the SiB3 biosphere model on a 40 km grid. A combination of transport from the RAMS and the Parameterized Chemical Transport Model (PCTM) models is used to forge a connection between upwind biosphere fluxes and downwind observed CO2 mixing ratio data. A Kalman filter procedure is used to estimate weekly corrections to biosphere fluxes based upon observed CO2. RMSE-weighted annual NEE estimates, over an ensemble of potential inversion parameter sets, show a mean estimate 0.57 Pg/yr sink in North America

  4. Towards a Full Waveform Ambient Noise Inversion

    NASA Astrophysics Data System (ADS)

    Sager, K.; Ermert, L. A.; Boehm, C.; Fichtner, A.

    2015-12-01

    Noise tomography usually works under the assumption that the inter-station ambient noise correlation is equal to a scaled version of the Green's function between the two receivers. This assumption, however, is only met under specific conditions, for instance, wavefield diffusivity and equipartitioning, zero attenuation, etc., that are typically not satisfied in the Earth. This inconsistency inhibits the exploitation of the full waveform information contained in noise correlations regarding Earth structure and noise generation. To overcome this limitation we attempt to develop a method that consistently accounts for noise distribution, 3D heterogeneous Earth structure and the full seismic wave propagation physics in order to improve the current resolution of tomographic images of the Earth. As an initial step towards a full waveform ambient noise inversion we develop a preliminary inversion scheme based on a 2D finite-difference code simulating correlation functions and on adjoint techniques. With respect to our final goal, a simultaneous inversion for noise distribution and Earth structure, we address the following two aspects: (1) the capabilities of different misfit functionals to image wave speed anomalies and source distribution and (2) possible source-structure trade-offs, especially to what extent unresolvable structure could be mapped into the inverted noise source distribution and vice versa.

  5. Gone with the Wind: Watching Galaxy Transformation in Abell 2125

    NASA Astrophysics Data System (ADS)

    Keel, W.; Owen, F.; Ledlow, M.; Wang, D.

    2003-12-01

    Dense environments clearly foster the transformation of galaxies, but it has proven difficult to untangle the roles of various processes in cluster environments. We have found a uniquely strong case for ongoing stripping of gas from the galaxy C153 in Abell 2125. The cluster, at z=0.25, includes merging subsystems with a relative line-of-sight velocity near 2000 km/s. C153, identified using the VLA as a strong radio source powered by star formation, is the brightest cluster member with activity of this kind, and part of the less populous blueshifted grouping. Several lines of evidence indicate that it is being swept by a stripping event. (1) A tail of ionized gas is seen in [O II] emission, which extends at least 70 kpc toward the cluster core, coinciding with a soft X-ray feature seen in the Chandra observations reported by Wang et al. (2) HST WFPC2 images reveal disturbed and clumpy morphology, including luminous star-forming complexes and chaotic dust features. (3) The spectral energy distribution and Gemini GMOS absorption-line spectrum indicate a massive burst of star formation ≈ 108 years ago superimposed on an older and much fainter population. (4) The stellar and gas kinematics are decoupled, with multiple gas velocity systems including counter-rotating components. The large velocity difference between the galaxy and (most of the) intracluster medium may contribute to the signatures being more prominent than hitherto seen. The starburst age is consistent with estimates of the time since the closest encounter of the major subsystems during the cluster-level merger. We continue to explore whether a starburst outflow or tidal damage has added to the role of stripping by the ICM, and how star formation has proceeded in the gas after leaving the galaxy disk. This work was supported by NASA through HST grant GO-07279.01-96A, and by the NSF through facilities at NRAO, Kitt Peak, and Gemini-North.

  6. Crazy heart: kinematics of the "star pile" in Abell 545

    NASA Astrophysics Data System (ADS)

    Salinas, R.; Richtler, T.; West, M. J.; Romanowsky, A. J.; Lloyd-Davies, E.; Schuberth, Y.

    2011-04-01

    We study the structure and internal kinematics of the "star pile" in Abell 545 - a low surface brightness structure lying in the center of the cluster. We have obtained deep long-slit spectroscopy of the star pile using VLT/FORS2 and Gemini/GMOS, which is analyzed in conjunction with deep multiband CFHT/MEGACAM imaging. As presented in a previous study the star pile has a flat luminosity profile and its color is consistent with the outer parts of elliptical galaxies. Its velocity map is irregular, with parts being seemingly associated with an embedded nucleus, and others which have significant velocity offsets to the cluster systemic velocity with no clear kinematical connection to any of the surrounding galaxies. This would make the star pile a dynamically defined stellar intra-cluster component. The complicated pattern in velocity and velocity dispersions casts doubts on the adequacy of using the whole star pile as a dynamical test for the innermost dark matter profile of the cluster. This status is fulfilled only by the nucleus and its nearest surroundings which lie at the center of the cluster velocity distribution. Based on observations taken at the European Southern Observatory, Cerro Paranal, Chile, under programme ID 080.B-0529. Also based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil) and SECYT (Argentina); and on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National

  7. Multi-scale signed envelope inversion

    NASA Astrophysics Data System (ADS)

    Chen, Guo-Xin; Wu, Ru-Shan; Wang, Yu-Qing; Chen, Sheng-Chang

    2018-06-01

    Envelope inversion based on modulation signal mode was proposed to reconstruct large-scale structures of underground media. In order to solve the shortcomings of conventional envelope inversion, multi-scale envelope inversion was proposed using new envelope Fréchet derivative and multi-scale inversion strategy to invert strong contrast models. In multi-scale envelope inversion, amplitude demodulation was used to extract the low frequency information from envelope data. However, only to use amplitude demodulation method will cause the loss of wavefield polarity information, thus increasing the possibility of inversion to obtain multiple solutions. In this paper we proposed a new demodulation method which can contain both the amplitude and polarity information of the envelope data. Then we introduced this demodulation method into multi-scale envelope inversion, and proposed a new misfit functional: multi-scale signed envelope inversion. In the numerical tests, we applied the new inversion method to the salt layer model and SEG/EAGE 2-D Salt model using low-cut source (frequency components below 4 Hz were truncated). The results of numerical test demonstrated the effectiveness of this method.

  8. Research on Inversion Models for Forest Height Estimation Using Polarimetric SAR Interferometry

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Duan, B.; Zou, B.

    2017-09-01

    The forest height is an important forest resource information parameter and usually used in biomass estimation. Forest height extraction with PolInSAR is a hot research field of imaging SAR remote sensing. SAR interferometry is a well-established SAR technique to estimate the vertical location of the effective scattering center in each resolution cell through the phase difference in images acquired from spatially separated antennas. The manipulation of PolInSAR has applications ranging from climate monitoring to disaster detection especially when used in forest area, is of particular interest because it is quite sensitive to the location and vertical distribution of vegetation structure components. However, some of the existing methods can't estimate forest height accurately. Here we introduce several available inversion models and compare the precision of some classical inversion approaches using simulated data. By comparing the advantages and disadvantages of these inversion methods, researchers can find better solutions conveniently based on these inversion methods.

  9. Inversion of solar extinction data from the Apollo-Soyuz Test Project Stratospheric Aerosol Measurement (ASTP/SAM) experiment

    NASA Technical Reports Server (NTRS)

    Pepin, T. J.

    1977-01-01

    The inversion methods are reported that have been used to determine the vertical profile of the extinction coefficient due to the stratospheric aerosols from data measured during the ASTP/SAM solar occultation experiment. Inversion methods include the onion skin peel technique and methods of solving the Fredholm equation for the problem subject to smoothing constraints. The latter of these approaches involves a double inversion scheme. Comparisons are made between the inverted results from the SAM experiment and near simultaneous measurements made by lidar and balloon born dustsonde. The results are used to demonstrate the assumptions required to perform the inversions for aerosols.

  10. Intraatrial baffle repair of isolated ventricular inversion with left atrial isomerism.

    PubMed

    McElhinney, D B; Reddy, V M; Silverman, N H; Hanley, F L

    1996-11-01

    Isolated ventricular inversion with left atrial isomerism, partial anomalous pulmonary venous connection, and interruption of the inferior vena cava with azygos continuation to a right superior vena cava was diagnosed by echocardiography in a neonate. At 48 days of age, the patient underwent successful anatomic correction with redirection of flow from the superior vena cava and hepatic veins to the left-sided tricuspid valve, and flow from the pulmonary veins to the right-sided mitral valve. In the present report, the surgical techniques of this case are described, along with a survey of the surgical literature covering anatomic repair of isolated ventricular inversion.

  11. The Earthquake Source Inversion Validation (SIV) - Project: Summary, Status, Outlook

    NASA Astrophysics Data System (ADS)

    Mai, P. M.

    2017-12-01

    Finite-fault earthquake source inversions infer the (time-dependent) displacement on the rupture surface from geophysical data. The resulting earthquake source models document the complexity of the rupture process. However, this kinematic source inversion is ill-posed and returns non-unique solutions, as seen for instance in multiple source models for the same earthquake, obtained by different research teams, that often exhibit remarkable dissimilarities. To address the uncertainties in earthquake-source inversions and to understand strengths and weaknesses of various methods, the Source Inversion Validation (SIV) project developed a set of forward-modeling exercises and inversion benchmarks. Several research teams then use these validation exercises to test their codes and methods, but also to develop and benchmark new approaches. In this presentation I will summarize the SIV strategy, the existing benchmark exercises and corresponding results. Using various waveform-misfit criteria and newly developed statistical comparison tools to quantify source-model (dis)similarities, the SIV platforms is able to rank solutions and identify particularly promising source inversion approaches. Existing SIV exercises (with related data and descriptions) and all computational tools remain available via the open online collaboration platform; additional exercises and benchmark tests will be uploaded once they are fully developed. I encourage source modelers to use the SIV benchmarks for developing and testing new methods. The SIV efforts have already led to several promising new techniques for tackling the earthquake-source imaging problem. I expect that future SIV benchmarks will provide further innovations and insights into earthquake source kinematics that will ultimately help to better understand the dynamics of the rupture process.

  12. Part-to-itself model inversion in process compensated resonance testing

    NASA Astrophysics Data System (ADS)

    Mayes, Alexander; Jauriqui, Leanne; Biedermann, Eric; Heffernan, Julieanne; Livings, Richard; Aldrin, John C.; Goodlet, Brent; Mazdiyasni, Siamack

    2018-04-01

    Process Compensated Resonance Testing (PCRT) is a non-destructive evaluation (NDE) method involving the collection and analysis of a part's resonance spectrum to characterize its material or damage state. Prior work used the finite element method (FEM) to develop forward modeling and model inversion techniques. In many cases, the inversion problem can become confounded by multiple parameters having similar effects on a part's resonance frequencies. To reduce the influence of confounding parameters and isolate the change in a part (e.g., creep), a part-to-itself (PTI) approach can be taken. A PTI approach involves inverting only the change in resonance frequencies from the before and after states of a part. This approach reduces the possible inversion parameters to only those that change in response to in-service loads and damage mechanisms. To evaluate the effectiveness of using a PTI inversion approach, creep strain and material properties were estimated in virtual and real samples using FEM inversion. Virtual and real dog bone samples composed of nickel-based superalloy Mar-M-247 were examined. Virtual samples were modeled with typically observed variations in material properties and dimensions. Creep modeling was verified with the collected resonance spectra from an incrementally crept physical sample. All samples were inverted against a model space that allowed for change in the creep damage state and the material properties but was blind to initial part dimensions. Results quantified the capabilities of PTI inversion in evaluating creep strain and material properties, as well as its sensitivity to confounding initial dimensions.

  13. Velocity structure of a bottom simulating reflector offshore Peru: Results from full waveform inversion

    USGS Publications Warehouse

    Pecher, I.A.; Minshull, T.A.; Singh, S.C.; von Huene, Roland E.

    1996-01-01

    Much of our knowledge of the worldwide distribution of submarine gas hydrates comes from seismic observations of Bottom Simulating Reflectors (BSRs). Full waveform inversion has proven to be a reliable technique for studying the fine structure of BSRs using the compressional wave velocity. We applied a non-linear full waveform inversion technique to a BSR at a location offshore Peru. We first determined the large-scale features of seismic velocity variations using a statistical inversion technique to maximise coherent energy along travel-time curves. These velocities were used for a starting velocity model for the full waveform inversion, which yielded a detailed velocity/depth model in the vicinity of the BSR. We found that the data are best fit by a model in which the BSR consists of a thin, low-velocity layer. The compressional wave velocity drops from 2.15 km/s down to an average of 1.70 km/s in an 18m thick interval, with a minimum velocity of 1.62 km/s in a 6 m interval. The resulting compressional wave velocity was used to estimate gas content in the sediments. Our results suggest that the low velocity layer is a 6-18 m thick zone containing a few percent of free gas in the pore space. The presence of the BSR coincides with a region of vertical uplift. Therefore, we suggest that gas at this BSR is formed by a dissociation of hydrates at the base of the hydrate stability zone due to uplift and subsequently a decrease in pressure.

  14. On the inversion of geodetic integrals defined over the sphere using 1-D FFT

    NASA Astrophysics Data System (ADS)

    García, R. V.; Alejo, C. A.

    2005-08-01

    An iterative method is presented which performs inversion of integrals defined over the sphere. The method is based on one-dimensional fast Fourier transform (1-D FFT) inversion and is implemented with the projected Landweber technique, which is used to solve constrained least-squares problems reducing the associated 1-D cyclic-convolution error. The results obtained are as precise as the direct matrix inversion approach, but with better computational efficiency. A case study uses the inversion of Hotine’s integral to obtain gravity disturbances from geoid undulations. Numerical convergence is also analyzed and comparisons with respect to the direct matrix inversion method using conjugate gradient (CG) iteration are presented. Like the CG method, the number of iterations needed to get the optimum (i.e., small) error decreases as the measurement noise increases. Nevertheless, for discrete data given over a whole parallel band, the method can be applied directly without implementing the projected Landweber method, since no cyclic convolution error exists.

  15. Twin radio relics in the nearby low-mass galaxy cluster Abell 168

    NASA Astrophysics Data System (ADS)

    Dwarakanath, K. S.; Parekh, V.; Kale, R.; George, L. T.

    2018-06-01

    We report the discovery of twin radio relics in the outskirts of the low-mass merging galaxy cluster Abell 168 (redshift=0.045). One of the relics is elongated with a linear extent ˜800 kpc and projected width of ˜80 kpc and is located ˜900 kpc towards the north of the cluster centre, oriented roughly perpendicular to the major axis of the X-ray emission. The second relic is ring-shaped with a size ˜220 kpc and is located near the inner edge of the elongated relic at a distance of ˜600 kpc from the cluster centre. These radio sources were imaged at 323 and 608 MHz with the Giant Meterwave Radio Telescope and at 1520 MHz with the Karl G. Jansky Very Large Array (VLA). The elongated relic was detected at all frequencies, with a radio power of 1.38 ± 0.14 × 1023 W Hz-1 at 1.4 GHz and a power law in the frequency range 70-1500 MHz (S ∝ να, α = -1.1 ± 0.04). This radio power is in good agreement with that expected from the known empirical relation between the radio powers of relics and host cluster masses. This is the lowest mass (M500 = 1.24 × 1014 M⊙) cluster in which relics due to merger shocks are detected. The ring-shaped relic has a steeper spectral index (α) of -1.74 ± 0.29 in the frequency range 100-600 MHz. We propose this relic to be an old plasma, revived due to adiabatic compression by the outgoing shock that produced the elongated relic.

  16. Detection of a pair of prominent X-ray cavities in Abell 3847

    NASA Astrophysics Data System (ADS)

    Vagshette, Nilkanth D.; Naik, Sachindra; Patil, Madhav. K.; Sonkamble, Satish S.

    2017-04-01

    We present the results obtained from a detailed analysis of a deep Chandra observation of the bright FRII radio galaxy 3C 444 in Abell 3847 cluster. A pair of huge X-ray cavities are detected along the north and south directions from the centre of 3C 444. X-ray and radio images of the cluster reveal peculiar positioning of the cavities and radio bubbles. The radio lobes and X-ray cavities are apparently not spatially coincident and exhibit offsets by ˜61 and 77 kpc from each other along the north and south directions, respectively. Radial temperature and density profiles reveal the presence of a cool core in the cluster. Imaging and spectral studies showed the removal of substantial amount of matter from the core of the cluster by the radio jets. A detailed analysis of the temperature and density profiles showed the presence of a rarely detected elliptical shock in the cluster. Detection of inflating cavities at an average distance of ˜55 kpc from the centre implies that the central engine feeds a remarkable amount of radio power (˜6.3 × 1044 erg s-1) into the intra-cluster medium over ˜108 yr, the estimated age of cavity. The cooling luminosity of the cluster was estimated to be ˜8.30 × 1043 erg s-1 , which confirms that the AGN power is sufficient to quench the cooling. Ratios of mass accretion rate to Eddington and Bondi rates were estimated to be ˜0.08 and 3.5 × 104, respectively. This indicates that the black hole in the core of the cluster accretes matter through chaotic cold accretion.

  17. Multivariate Formation Pressure Prediction with Seismic-derived Petrophysical Properties from Prestack AVO inversion and Poststack Seismic Motion Inversion

    NASA Astrophysics Data System (ADS)

    Yu, H.; Gu, H.

    2017-12-01

    A novel multivariate seismic formation pressure prediction methodology is presented, which incorporates high-resolution seismic velocity data from prestack AVO inversion, and petrophysical data (porosity and shale volume) derived from poststack seismic motion inversion. In contrast to traditional seismic formation prediction methods, the proposed methodology is based on a multivariate pressure prediction model and utilizes a trace-by-trace multivariate regression analysis on seismic-derived petrophysical properties to calibrate model parameters in order to make accurate predictions with higher resolution in both vertical and lateral directions. With prestack time migration velocity as initial velocity model, an AVO inversion was first applied to prestack dataset to obtain high-resolution seismic velocity with higher frequency that is to be used as the velocity input for seismic pressure prediction, and the density dataset to calculate accurate Overburden Pressure (OBP). Seismic Motion Inversion (SMI) is an inversion technique based on Markov Chain Monte Carlo simulation. Both structural variability and similarity of seismic waveform are used to incorporate well log data to characterize the variability of the property to be obtained. In this research, porosity and shale volume are first interpreted on well logs, and then combined with poststack seismic data using SMI to build porosity and shale volume datasets for seismic pressure prediction. A multivariate effective stress model is used to convert velocity, porosity and shale volume datasets to effective stress. After a thorough study of the regional stratigraphic and sedimentary characteristics, a regional normally compacted interval model is built, and then the coefficients in the multivariate prediction model are determined in a trace-by-trace multivariate regression analysis on the petrophysical data. The coefficients are used to convert velocity, porosity and shale volume datasets to effective stress and then

  18. Inverse Tomo-Lithography for Making Microscopic 3D Parts

    NASA Technical Reports Server (NTRS)

    White, Victor; Wiberg, Dean

    2003-01-01

    According to a proposal, basic x-ray lithography would be extended to incorporate a technique, called inverse tomography, that would enable the fabrication of microscopic three-dimensional (3D) objects. The proposed inverse tomo-lithographic process would make it possible to produce complex shaped, submillimeter-sized parts that would be difficult or impossible to make in any other way. Examples of such shapes or parts include tapered helices, paraboloids with axes of different lengths, and even Archimedean screws that could serve as rotors in microturbines. The proposed inverse tomo-lithographic process would be based partly on a prior microfabrication process known by the German acronym LIGA (lithographie, galvanoformung, abformung, which means lithography, electroforming, molding). In LIGA, one generates a precise, high-aspect ratio pattern by exposing a thick, x-ray-sensitive resist material to an x-ray beam through a mask that contains the pattern. One can electrodeposit metal into the developed resist pattern to form a precise metal part, then dissolve the resist to free the metal. Aspect ratios of 100:1 and patterns into resist thicknesses of several millimeters are possible.

  19. Efficient Stochastic Inversion Using Adjoint Models and Kernel-PCA

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Thimmisetty, Charanraj A.; Zhao, Wenju; Chen, Xiao

    2017-10-18

    Performing stochastic inversion on a computationally expensive forward simulation model with a high-dimensional uncertain parameter space (e.g. a spatial random field) is computationally prohibitive even when gradient information can be computed efficiently. Moreover, the ‘nonlinear’ mapping from parameters to observables generally gives rise to non-Gaussian posteriors even with Gaussian priors, thus hampering the use of efficient inversion algorithms designed for models with Gaussian assumptions. In this paper, we propose a novel Bayesian stochastic inversion methodology, which is characterized by a tight coupling between the gradient-based Langevin Markov Chain Monte Carlo (LMCMC) method and a kernel principal component analysis (KPCA). Thismore » approach addresses the ‘curse-of-dimensionality’ via KPCA to identify a low-dimensional feature space within the high-dimensional and nonlinearly correlated parameter space. In addition, non-Gaussian posterior distributions are estimated via an efficient LMCMC method on the projected low-dimensional feature space. We will demonstrate this computational framework by integrating and adapting our recent data-driven statistics-on-manifolds constructions and reduction-through-projection techniques to a linear elasticity model.« less

  20. Plasma inverse transition acceleration

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Xie, Ming

    It can be proved fundamentally from the reciprocity theorem with which the electromagnetism is endowed that corresponding to each spontaneous process of radiation by a charged particle there is an inverse process which defines a unique acceleration mechanism, from Cherenkov radiation to inverse Cherenkov acceleration (ICA) [1], from Smith-Purcell radiation to inverse Smith-Purcell acceleration (ISPA) [2], and from undulator radiation to inverse undulator acceleration (IUA) [3]. There is no exception. Yet, for nearly 30 years after each of the aforementioned inverse processes has been clarified for laser acceleration, inverse transition acceleration (ITA), despite speculation [4], has remained the least understood,more » and above all, no practical implementation of ITA has been found, until now. Unlike all its counterparts in which phase synchronism is established one way or the other such that a particle can continuously gain energy from an acceleration wave, the ITA to be discussed here, termed plasma inverse transition acceleration (PITA), operates under fundamentally different principle. As a result, the discovery of PITA has been delayed for decades, waiting for a conceptual breakthrough in accelerator physics: the principle of alternating gradient acceleration [5, 6, 7, 8, 9, 10]. In fact, PITA was invented [7, 8] as one of several realizations of the new principle.« less

  1. Inverse problems biomechanical imaging (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Oberai, Assad A.

    2016-03-01

    It is now well recognized that a host of imaging modalities (a list that includes Ultrasound, MRI, Optical Coherence Tomography, and optical microscopy) can be used to "watch" tissue as it deforms in response to an internal or external excitation. The result is a detailed map of the deformation field in the interior of the tissue. This deformation field can be used in conjunction with a material mechanical response to determine the spatial distribution of material properties of the tissue by solving an inverse problem. Images of material properties thus obtained can be used to quantify the health of the tissue. Recently, they have been used to detect, diagnose and monitor cancerous lesions, detect vulnerable plaque in arteries, diagnose liver cirrhosis, and possibly detect the onset of Alzheimer's disease. In this talk I will describe the mathematical and computational aspects of solving this class of inverse problems, and their applications in biology and medicine. In particular, I will discuss the well-posedness of these problems and quantify the amount of displacement data necessary to obtain a unique property distribution. I will describe an efficient algorithm for solving the resulting inverse problem. I will also describe some recent developments based on Bayesian inference in estimating the variance in the estimates of material properties. I will conclude with the applications of these techniques in diagnosing breast cancer and in characterizing the mechanical properties of cells with sub-cellular resolution.

  2. COST Action TU1208 - Working Group 3 - Electromagnetic modelling, inversion, imaging and data-processing techniques for Ground Penetrating Radar

    NASA Astrophysics Data System (ADS)

    Pajewski, Lara; Giannopoulos, Antonios; Sesnic, Silvestar; Randazzo, Andrea; Lambot, Sébastien; Benedetto, Francesco; Economou, Nikos

    2017-04-01

    opportunity of testing and validating, against reliable data, their electromagnetic-modelling, inversion, imaging and processing algorithms. One of the most interesting dataset comes from the IFSTTAR Geophysical Test Site, in Nantes (France): this is an open-air laboratory including a large and deep area, filled with various materials arranged in horizontal compacted slices, separated by vertical interfaces and water-tighted in surface; several objects as pipes, polystyrene hollows, boulders and masonry are embedded in the field. Data were collected by using nine different GPR systems and at different frequencies ranging from 200 MHz to 1 GHz. Moreover, some sections of this test site were modelled by using gprMax and the commercial software CST Microwave Studio. Hence, both experimental and synthetic data are available. Further interesting datasets were collected on roads, bridges, concrete cells, columns - and more. (v) WG3 contributed to the TU1208 Education Pack, an open educational package conceived to teach GPR in University courses. (vi) WG3 was very active in offering training activities. The following courses were successfully organised: Training School (TS) "Microwave Imaging and Diagnostics" (in cooperation with the European School of Antennas; 1st edition: Madonna di Campiglio, Italy, March 2014, 2nd edition: Taormina, Italy, October 2016); TS "Numerical modelling of Ground Penetrating Radar using gprMax" (Thessaloniki, Greece, November 2015); TS "Electromagnetic Modelling Techniques for Ground Penetrating Radar" (Split, Croatia, November 2016). Moreover, WG3 organized a workshop on "Electromagnetic modelling with the Finite-Difference Time-Domain technique" (Nantes, France, February 2014) and a workshop on "Electromagnetic modelling and inversion techniques for GPR" (Davos, Switzerland, April 2016) within the 2016 European Conference on Antennas and Propagation (EuCAP). Acknowledgement: The Authors are deeply grateful to COST (European COoperation in Science and

  3. 2D Inviscid and Viscous Inverse Design Using Continuous Adjoint and Lax-Wendroff Formulation

    NASA Astrophysics Data System (ADS)

    Proctor, Camron Lisle

    The continuous adjoint (CA) technique for optimization and/or inverse-design of aerodynamic components has seen nearly 30 years of documented success in academia. The benefits of using CA versus a direct sensitivity analysis are shown repeatedly in the literature. However, the use of CA in industry is relatively unheard-of. The sparseness of industry contributions to the field may be attributed to the tediousness of the derivation and/or to the difficulties in implementation due to the lack of well-documented adjoint numerical methods. The focus of this work has been to thoroughly document the techniques required to build a two-dimensional CA inverse-design tool. To this end, this work begins with a short background on computational fluid dynamics (CFD) and the use of optimization tools in conjunction with CFD tools to solve aerodynamic optimization problems. A thorough derivation of the continuous adjoint equations and the accompanying gradient calculations for inviscid and viscous constraining equations follows the introduction. Next, the numerical techniques used for solving the partial differential equations (PDEs) governing the flow equations and the adjoint equations are described. Numerical techniques for the supplementary equations are discussed briefly. Subsequently, a verification of the efficacy of the inverse design tool, for the inviscid adjoint equations as well as possible numerical implementation pitfalls are discussed. The NACA0012 airfoil is used as an initial airfoil and surface pressure distribution and the NACA16009 is used as the desired pressure and vice versa. Using a Savitsky-Golay gradient filter, convergence (defined as a cost function<1E-5) is reached in approximately 220 design iteration using 121 design variables. The inverse-design using inviscid adjoint equations results are followed by the discussion of the viscous inverse design results and techniques used to further the convergence of the optimizer. The relationship between

  4. ASCA observations of distant clusters of galaxies.

    NASA Astrophysics Data System (ADS)

    Tsuru, T.; Koyama, K.; Hughes, J. P.; Arimoto, N.; Kii, T.; Hattori, M.

    It is important not only in studies of clusters of galaxies but also in cosmological aspects to investigate the evolution of X-ray properties of clusters of galaxies. ASCA enables detailed spectral studies on distant clusters and the evolution of temperature for the first time. The authors present here "preliminary" results of ASCA observation of 17 distant (z = 0.14 - 0.55) clusters of galaxies. The sample includes: Cl0016+16 Abell 370, Abell 1995, Abell 959, ACGG 118, Zw 3136, EMSS 1305.4+2941, Abell 1851, Abell 963, Abell 2163, EMSS 0839.8+2938, Abell 665, Abell 1689, Abell 2218, Abell 586, Abell 1413, Abell 1895. The cosmological constants of H0 = 50 km/s/Mpc and q0 = 0.5 are adopted in this paper.

  5. Real-time inverse planning for Gamma Knife radiosurgery.

    PubMed

    Wu, Q Jackie; Chankong, Vira; Jitprapaikulsarn, Suradet; Wessels, Barry W; Einstein, Douglas B; Mathayomchan, Boonyanit; Kinsella, Timothy J

    2003-11-01

    The challenges of real-time Gamma Knife inverse planning are the large number of variables involved and the unknown search space a priori. With limited collimator sizes, shots have to be heavily overlapped to form a smooth prescription isodose line that conforms to the irregular target shape. Such overlaps greatly influence the total number of shots per plan, making pre-determination of the total number of shots impractical. However, this total number of shots usually defines the search space, a pre-requisite for most of the optimization methods. Since each shot only covers part of the target, a collection of shots in different locations and various collimator sizes selected makes up the global dose distribution that conforms to the target. Hence, planning or placing these shots is a combinatorial optimization process that is computationally expensive by nature. We have previously developed a theory of shot placement and optimization based on skeletonization. The real-time inverse planning process, reported in this paper, is an expansion and the clinical implementation of this theory. The complete planning process consists of two steps. The first step is to determine an optimal number of shots including locations and sizes and to assign initial collimator size to each of the shots. The second step is to fine-tune the weights using a linear-programming technique. The objective function is to minimize the total dose to the target boundary (i.e., maximize the dose conformity). Results of an ellipsoid test target and ten clinical cases are presented. The clinical cases are also compared with physician's manual plans. The target coverage is more than 99% for manual plans and 97% for all the inverse plans. The RTOG PITV conformity indices for the manual plans are between 1.16 and 3.46, compared to 1.36 to 2.4 for the inverse plans. All the inverse plans are generated in less than 2 min, making real-time inverse planning a reality.

  6. Joint inversion of apparent resistivity and seismic surface and body wave data

    NASA Astrophysics Data System (ADS)

    Garofalo, Flora; Sauvin, Guillaume; Valentina Socco, Laura; Lecomte, Isabelle

    2013-04-01

    A novel inversion algorithm has been implemented to jointly invert apparent resistivity curves from vertical electric soundings, surface wave dispersion curves, and P-wave travel times. The algorithm works in the case of laterally varying layered sites. Surface wave dispersion curves and P-wave travel times can be extracted from the same seismic dataset and apparent resistivity curves can be obtained from continuous vertical electric sounding acquisition. The inversion scheme is based on a series of local 1D layered models whose unknown parameters are thickness h, S-wave velocity Vs, P-wave velocity Vp, and Resistivity R of each layer. 1D models are linked to surface-wave dispersion curves and apparent resistivity curves through classical 1D forward modelling, while a 2D model is created by interpolating the 1D models and is linked to refracted P-wave hodograms. A priori information can be included in the inversion and a spatial regularization is introduced as a set of constraints between model parameters of adjacent models and layers. Both a priori information and regularization are weighted by covariance matrixes. We show the comparison of individual inversions and joint inversion for a synthetic dataset that presents smooth lateral variations. Performing individual inversions, the poor sensitivity to some model parameters leads to estimation errors up to 62.5 %, whereas for joint inversion the cooperation of different techniques reduces most of the model estimation errors below 5% with few exceptions up to 39 %, with an overall improvement. Even though the final model retrieved by joint inversion is internally consistent and more reliable, the analysis of the results evidences unacceptable values of Vp/Vs ratio for some layers, thus providing negative Poisson's ratio values. To further improve the inversion performances, an additional constraint is added imposing Poisson's ratio in the range 0-0.5. The final results are globally improved by the introduction of

  7. Non-cavitating propeller noise modeling and inversion

    NASA Astrophysics Data System (ADS)

    Kim, Dongho; Lee, Keunhwa; Seong, Woojae

    2014-12-01

    Marine propeller is the dominant exciter of the hull surface above it causing high level of noise and vibration in the ship structure. Recent successful developments have led to non-cavitating propeller designs and thus present focus is the non-cavitating characteristics of propeller such as hydrodynamic noise and its induced hull excitation. In this paper, analytic source model of propeller non-cavitating noise, described by longitudinal quadrupoles and dipoles, is suggested based on the propeller hydrodynamics. To find the source unknown parameters, the multi-parameter inversion technique is adopted using the pressure data obtained from the model scale experiment and pressure field replicas calculated by boundary element method. The inversion results show that the proposed source model is appropriate in modeling non-cavitating propeller noise. The result of this study can be utilized in the prediction of propeller non-cavitating noise and hull excitation at various stages in design and analysis.

  8. Developing a Near Real-time System for Earthquake Slip Distribution Inversion

    NASA Astrophysics Data System (ADS)

    Zhao, Li; Hsieh, Ming-Che; Luo, Yan; Ji, Chen

    2016-04-01

    Advances in observational and computational seismology in the past two decades have enabled completely automatic and real-time determinations of the focal mechanisms of earthquake point sources. However, seismic radiations from moderate and large earthquakes often exhibit strong finite-source directivity effect, which is critically important for accurate ground motion estimations and earthquake damage assessments. Therefore, an effective procedure to determine earthquake rupture processes in near real-time is in high demand for hazard mitigation and risk assessment purposes. In this study, we develop an efficient waveform inversion approach for the purpose of solving for finite-fault models in 3D structure. Full slip distribution inversions are carried out based on the identified fault planes in the point-source solutions. To ensure efficiency in calculating 3D synthetics during slip distribution inversions, a database of strain Green tensors (SGT) is established for 3D structural model with realistic surface topography. The SGT database enables rapid calculations of accurate synthetic seismograms for waveform inversion on a regular desktop or even a laptop PC. We demonstrate our source inversion approach using two moderate earthquakes (Mw~6.0) in Taiwan and in mainland China. Our results show that 3D velocity model provides better waveform fitting with more spatially concentrated slip distributions. Our source inversion technique based on the SGT database is effective for semi-automatic, near real-time determinations of finite-source solutions for seismic hazard mitigation purposes.

  9. ANNIT - An Efficient Inversion Algorithm based on Prediction Principles

    NASA Astrophysics Data System (ADS)

    Růžek, B.; Kolář, P.

    2009-04-01

    Solution of inverse problems represents meaningful job in geophysics. The amount of data is continuously increasing, methods of modeling are being improved and the computer facilities are also advancing great technical progress. Therefore the development of new and efficient algorithms and computer codes for both forward and inverse modeling is still up to date. ANNIT is contributing to this stream since it is a tool for efficient solution of a set of non-linear equations. Typical geophysical problems are based on parametric approach. The system is characterized by a vector of parameters p, the response of the system is characterized by a vector of data d. The forward problem is usually represented by unique mapping F(p)=d. The inverse problem is much more complex and the inverse mapping p=G(d) is available in an analytical or closed form only exceptionally and generally it may not exist at all. Technically, both forward and inverse mapping F and G are sets of non-linear equations. ANNIT solves such situation as follows: (i) joint subspaces {pD, pM} of original data and model spaces D, M, resp. are searched for, within which the forward mapping F is sufficiently smooth that the inverse mapping G does exist, (ii) numerical approximation of G in subspaces {pD, pM} is found, (iii) candidate solution is predicted by using this numerical approximation. ANNIT is working in an iterative way in cycles. The subspaces {pD, pM} are searched for by generating suitable populations of individuals (models) covering data and model spaces. The approximation of the inverse mapping is made by using three methods: (a) linear regression, (b) Radial Basis Function Network technique, (c) linear prediction (also known as "Kriging"). The ANNIT algorithm has built in also an archive of already evaluated models. Archive models are re-used in a suitable way and thus the number of forward evaluations is minimized. ANNIT is now implemented both in MATLAB and SCILAB. Numerical tests show good

  10. Dynamics of cD clusters of galaxies. II: Analysis of seven Abell clusters

    NASA Technical Reports Server (NTRS)

    Oegerle, William R.; Hill, John M.

    1994-01-01

    We have investigated the dynamics of the seven Abell clusters A193, A399, A401, A1795, A1809, A2063, and A2124, based on redshift data reported previously by us (Hill & Oegerle, (1993)). These papers present the initial results of a survey of cD cluster kinematics, with an emphasis on studying the nature of peculiar velocity cD galaxies and their parent clusters. In the current sample, we find no evidence for significant peculiar cD velocities, with respect to the global velocity distribution. However, the cD in A2063 has a significant (3 sigma) peculiar velocity with respect to galaxies in the inner 1.5 Mpc/h, which is likely due to the merger of a subcluster with A2063. We also find significant evidence for subclustering in A1795, and a marginally peculiar cD velocity with respect to galaxies within approximately 200 kpc/h of the cD. The available x-ray, optical, and galaxy redshift data strongly suggest that a subcluster has merged with A1795. We propose that the subclusters which merged with A1795 and A2063 were relatively small, with shallow potential wells, so that the cooling flows in these clusters were not disrupted. Two-body gravitational models of the A399/401 and A2063/MKW3S systems indicate that A399/401 is a bound pair with a total virial mass of approximately 4 x 10(exp 15) solar mass/h, while A2063 and MKW3S are very unlikely to be bound.

  11. Galaxy evolution in the cluster Abell 85: new insights from the dwarf population

    NASA Astrophysics Data System (ADS)

    Habas, Rebecca; Fadda, Dario; Marleau, Francine R.; Biviano, Andrea; Durret, Florence

    2018-04-01

    We present the first results of a new spectroscopic survey of the cluster Abell 85 targeting 1466 candidate cluster members within the central ˜1 deg2 of the cluster and having magnitudes mr < 20.5 using the VIsible MultiObject Spectrograph on the VLT and the Hydra spectrograh on WIYN. A total of 520 galaxies are confirmed as either relaxed cluster members or part of an infalling population. A significant fraction are low mass; the median stellar mass of the sample is 109.6 M⊙, and 25 per cent have stellar masses below 109 M⊙ (i.e. 133 dwarf galaxies). We also identify seven active galactic nuclei (AGN), four of which reside in dwarf host galaxies. We probe the evolution of star formation rates, based on Hα emission and continuum modelling, as a function of both mass and environment. We find that more star-forming galaxies are observed at larger clustercentric distances, while infalling galaxies show evidence for recently enhanced star-forming activity. Main-sequence galaxies, defined by their continuum star formation rates, show different evolutionary behaviour based on their mass. At the low-mass end, the galaxies have had their star formation recently quenched, while more massive galaxies show no significant change. The time-scales probed here favour fast quenching mechanisms, such as ram-pressure stripping. Galaxies within the green valley, defined similarly, do not show evidence of quenching. Instead, the low-mass galaxies maintain their levels of star-forming activity, while the more massive galaxies have experienced a recent burst.

  12. Inverse scattering theory: Inverse scattering series method for one dimensional non-compact support potential

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yao, Jie, E-mail: yjie2@uh.edu; Lesage, Anne-Cécile; Hussain, Fazle

    2014-12-15

    The reversion of the Born-Neumann series of the Lippmann-Schwinger equation is one of the standard ways to solve the inverse acoustic scattering problem. One limitation of the current inversion methods based on the reversion of the Born-Neumann series is that the velocity potential should have compact support. However, this assumption cannot be satisfied in certain cases, especially in seismic inversion. Based on the idea of distorted wave scattering, we explore an inverse scattering method for velocity potentials without compact support. The strategy is to decompose the actual medium as a known single interface reference medium, which has the same asymptoticmore » form as the actual medium and a perturbative scattering potential with compact support. After introducing the method to calculate the Green’s function for the known reference potential, the inverse scattering series and Volterra inverse scattering series are derived for the perturbative potential. Analytical and numerical examples demonstrate the feasibility and effectiveness of this method. Besides, to ensure stability of the numerical computation, the Lanczos averaging method is employed as a filter to reduce the Gibbs oscillations for the truncated discrete inverse Fourier transform of each order. Our method provides a rigorous mathematical framework for inverse acoustic scattering with a non-compact support velocity potential.« less

  13. Inverse problems in the modeling of vibrations of flexible beams

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Powers, R. K.; Rosen, I. G.

    1987-01-01

    The formulation and solution of inverse problems for the estimation of parameters which describe damping and other dynamic properties in distributed models for the vibration of flexible structures is considered. Motivated by a slewing beam experiment, the identification of a nonlinear velocity dependent term which models air drag damping in the Euler-Bernoulli equation is investigated. Galerkin techniques are used to generate finite dimensional approximations. Convergence estimates and numerical results are given. The modeling of, and related inverse problems for the dynamics of a high pressure hose line feeding a gas thruster actuator at the tip of a cantilevered beam are then considered. Approximation and convergence are discussed and numerical results involving experimental data are presented.

  14. Eruption mass estimation using infrasound waveform inversion and ash and gas measurements: Evaluation at Sakurajima Volcano, Japan

    NASA Astrophysics Data System (ADS)

    Fee, David; Izbekov, Pavel; Kim, Keehoon; Yokoo, Akihiko; Lopez, Taryn; Prata, Fred; Kazahaya, Ryunosuke; Nakamichi, Haruhisa; Iguchi, Masato

    2017-12-01

    Eruption mass and mass flow rate are critical parameters for determining the aerial extent and hazard of volcanic emissions. Infrasound waveform inversion is a promising technique to quantify volcanic emissions. Although topography may substantially alter the infrasound waveform as it propagates, advances in wave propagation modeling and station coverage permit robust inversion of infrasound data from volcanic explosions. The inversion can estimate eruption mass flow rate and total eruption mass if the flow density is known. However, infrasound-based eruption flow rates and mass estimates have yet to be validated against independent measurements, and numerical modeling has only recently been applied to the inversion technique. Here we present a robust full-waveform acoustic inversion method, and use it to calculate eruption flow rates and masses from 49 explosions from Sakurajima Volcano, Japan. Six infrasound stations deployed from 12-20 February 2015 recorded the explosions. We compute numerical Green's functions using 3-D Finite Difference Time Domain modeling and a high-resolution digital elevation model. The inversion, assuming a simple acoustic monopole source, provides realistic eruption masses and excellent fit to the data for the majority of the explosions. The inversion results are compared to independent eruption masses derived from ground-based ash collection and volcanic gas measurements. Assuming realistic flow densities, our infrasound-derived eruption masses for ash-rich eruptions compare favorably to the ground-based estimates, with agreement ranging from within a factor of two to one order of magnitude. Uncertainties in the time-dependent flow density and acoustic propagation likely contribute to the mismatch between the methods. Our results suggest that realistic and accurate infrasound-based eruption mass and mass flow rate estimates can be computed using the method employed here. If accurate volcanic flow parameters are known, application of

  15. Joint two dimensional inversion of gravity and magnetotelluric data using correspondence maps

    NASA Astrophysics Data System (ADS)

    Carrillo Lopez, J.; Gallardo, L. A.

    2016-12-01

    Inverse problems in Earth sciences are inherently non-unique. To improve models and reduce the number of solutions we need to provide extra information. In geological context, this information could be a priori information, for example, geological information, well log data, smoothness, or actually, information of measures of different kind of data. Joint inversion provides an approach to improve the solution and reduce the errors due to suppositions of each method. To do that, we need a link between two or more models. Some approaches have been explored successfully in recent years. For example, Gallardo and Meju (2003), Gallardo and Meju (2004, 2011), and Gallardo et. al. (2012) used the directions of properties to measure the similarity between models minimizing their cross gradients. In this work, we proposed a joint iterative inversion method that use spatial distribution of properties as a link. Correspondence maps could be better characterizing specific Earth systems due they consider the relation between properties. We implemented a code in Fortran to do a two dimensional inversion of magnetotelluric and gravity data, which are two of the standard methods in geophysical exploration. Synthetic tests show the advantages of joint inversion using correspondence maps against separate inversion. Finally, we applied this technique to magnetotelluric and gravity data in the geothermal zone located in Cerro Prieto, México.

  16. RF Tomography for Tunnel Detection: Principles and Inversion Schemes

    NASA Astrophysics Data System (ADS)

    Lo Monte, L.; Erricolo, D.; Inan, U. S.; Wicks, M. C.

    2008-12-01

    We propose a novel way to detect underground tunnels based on classical seismic tomography, Ground Penetrating Radar (GPR), inverse scattering principles, and the deployment of distributed sensors, which we call "Distributed RF Tomography". Tunnel detection has been a critical problem that cannot be considered fully solved. Presently, tunnel detection is performed by methods that include seismic sensors, electrical impedance, microgravity, boreholes, and GPR. All of these methods have drawbacks that make them not applicable for use in unfriendly environments, such as battlefields. Specifically, they do not cover wide surface areas, they are generally shallow, they are limited to vertical prospecting, and require the user to be in situ, which may jeopardize one's safety. Additional application of the proposed distributed RF tomography include monitoring sensitive areas, (e.g. banks, power plants, military bases, prisons, national borders) and civil applications (e.g. environmental engineering, mine safety, search and rescue, speleology, archaeology and geophysics). The novelty of a Distributed RF tomography system consists of the following. 1) Sensors are scattered randomly above the ground, thus saving time and money compared to the use of boreholes. 2) The use of lower operating frequency (around HF), which allows for deeper penetration. 3) The use of CW diffraction tomography, which increases the resolution to sub-wavelength values, independently from the sensor displacement, and increases the SNR. 4) Use of linear inversion schemes that are suited for tunnel detection. 5) The use of modulation schemes and signal processing algorithms to mitigate interferences and noise. This presentation will cover: 1. Current physical limits of existing techniques for tunnel detection. 2. Concept of Distributed RF Tomography. 3. Inversion theories and strategies a. Proper forward model for voids buried into an homogeneous medium b. Extended matched filtering inversion c. Near

  17. Near-infrared optical properties of ex vivo human uterus determined by the Monte Carlo inversion technique

    NASA Astrophysics Data System (ADS)

    Ripley, P. M.; Laufer, J. G.; Gordon, A. D.; Connell, R. J.; Bown, S. G.

    1999-10-01

    The optical properties, absorption (µa) and reduced scattering coefficient (µs´), of ex vivo human myometrium and leiomyoma (fibroid) have been determined by the Monte Carlo inversion technique over the wavelength range 600 - 1000 nm. This region is currently of interest for new, minimal-access, surgical laser procedures such as photodynamic therapy (PDT) for abnormalities of the uterus, and interstitial laser photocoagulation (ILP) for the thermal ablation of fibroids. In the region 630 - 675 nm (corresponding to PDT), the optical coefficients of myometrium are µa = 0.041±0.012 mm-1 and µs´ = 1.37±0.19 mm-1. For the wavelength range 800-1000 nm (associated with infrared lasers for ILP), the optical coefficients of fibroid were found to be µa = 0.020±0.003 mm-1 and µs´ = 0.56±0.03 mm-1. Overall, the optical properties of fibroid were found to be lower than myometrium, and this was attributed to the differences in both anatomy and vascularity. The results show that PDT for ablation of the uterine endometrium is most unlikely to affect any tissues beyond the myometrium, and that the region around 800 nm is the most effective for ablation of fibroids using ILP as the penetration depth of light is greatest at this wavelength.

  18. Discovery of large-scale diffuse radio emission in low-mass galaxy cluster Abell 1931

    NASA Astrophysics Data System (ADS)

    Brüggen, M.; Rafferty, D.; Bonafede, A.; van Weeren, R. J.; Shimwell, T.; Intema, H.; Röttgering, H.; Brunetti, G.; Di Gennaro, G.; Savini, F.; Wilber, A.; O'Sullivan, S.; Ensslin, T. A.; De Gasperin, F.; Hoeft, M.

    2018-07-01

    Extended, steep-spectrum radio synchrotron sources are pre-dominantly found in massive galaxy clusters as opposed to groups. LOFAR Two-Metre Sky Survey images have revealed a diffuse, ultra-steep-spectrum radio source in the low-mass cluster Abell 1931. The source has a fairly irregular morphology with the largest linear size of about 550 kpc. The source is only seen in LOFAR observations at 143 MHz and Giant Metre Radio Telescope observations at 325 MHz. The spectral index of the total source between 143 and 325 MHz is α _{143}^{325} = -2.86 ± 0.36. The source remains invisible in Very Large Array (1-2 GHz) observations as expected given the spectral index. Chandra X-ray observations of the cluster revealed a bolometric luminosity of LX = (1.65 ± 0.39) × 1043 erg s-1 and a temperature of 2.92_{-0.87}^{+1.89} keV which implies a mass of around ˜1014 M⊙. We conclude that the source is a remnant radio galaxy that has shut off around 200 Myr ago. The brightest cluster galaxy, a radio-loud elliptical galaxy, could be the source for this extinct source. Unlike remnant sources studied in the literature, our source has a steep spectrum at low radio frequencies. Studying such remnant radio galaxies at low radio frequencies is important for understanding the scarcity of such sources and their role in feedback processes.

  19. Discovery of large-scale diffuse radio emission in low-mass galaxy cluster Abell 1931

    NASA Astrophysics Data System (ADS)

    Brüggen, M.; Rafferty, D.; Bonafede, A.; van Weeren, R. J.; Shimwell, T.; Intema, H.; Röttgering, H.; Brunetti, G.; Di Gennaro, G.; Savini, F.; Wilber, A.; O'Sullivan, S.; Ensslin, T. A.; De Gasperin, F.; Hoeft, M.

    2018-04-01

    Extended, steep-spectrum radio synchrotron sources are pre-dominantly found in massive galaxy clusters as opposed to groups. LOFAR Two-Metre Sky Survey images have revealed a diffuse, ultra-steep spectrum radio source in the low-mass cluster Abell 1931. The source has a fairly irregular morphology with a largest linear size of about 550 kpc. The source is only seen in LOFAR observations at 143 MHz and GMRT observations at 325 MHz. The spectral index of the total source between 143 MHz and 325 MHz is α _{143}^{325} = -2.86 ± 0.36. The source remains invisible in Very Large Array (1-2 GHz) observations as expected given the spectral index. Chandra X-ray observations of the cluster revealed a bolometric luminosity of LX = (1.65 ± 0.39) × 1043 erg s-1 and a temperature of 2.92_{-0.87}^{+1.89} keV which implies a mass of around ˜1014M⊙. We conclude that the source is a remnant radio galaxy that has shut off around 200 Myr ago. The brightest cluster galaxy, a radio-loud elliptical galaxy, could be the source for this extinct source. Unlike remnant sources studied in the literature, our source has a steep spectrum at low radio frequencies. Studying such remnant radio galaxies at low radio frequencies is important for understanding the scarcity of such sources and their role in feedback processes.

  20. Total-variation based velocity inversion with Bregmanized operator splitting algorithm

    NASA Astrophysics Data System (ADS)

    Zand, Toktam; Gholami, Ali

    2018-04-01

    Many problems in applied geophysics can be formulated as a linear inverse problem. The associated problems, however, are large-scale and ill-conditioned. Therefore, regularization techniques are needed to be employed for solving them and generating a stable and acceptable solution. We consider numerical methods for solving such problems in this paper. In order to tackle the ill-conditioning of the problem we use blockiness as a prior information of the subsurface parameters and formulate the problem as a constrained total variation (TV) regularization. The Bregmanized operator splitting (BOS) algorithm as a combination of the Bregman iteration and the proximal forward backward operator splitting method is developed to solve the arranged problem. Two main advantages of this new algorithm are that no matrix inversion is required and that a discrepancy stopping criterion is used to stop the iterations, which allow efficient solution of large-scale problems. The high performance of the proposed TV regularization method is demonstrated using two different experiments: 1) velocity inversion from (synthetic) seismic data which is based on Born approximation, 2) computing interval velocities from RMS velocities via Dix formula. Numerical examples are presented to verify the feasibility of the proposed method for high-resolution velocity inversion.

  1. 3-D acoustic waveform simulation and inversion at Yasur Volcano, Vanuatu

    NASA Astrophysics Data System (ADS)

    Iezzi, A. M.; Fee, D.; Matoza, R. S.; Austin, A.; Jolly, A. D.; Kim, K.; Christenson, B. W.; Johnson, R.; Kilgour, G.; Garaebiti, E.; Kennedy, B.; Fitzgerald, R.; Key, N.

    2016-12-01

    Acoustic waveform inversion shows promise for improved eruption characterization that may inform volcano monitoring. Well-constrained inversion can provide robust estimates of volume and mass flux, increasing our ability to monitor volcanic emissions (potentially in real-time). Previous studies have made assumptions about the multipole source mechanism, which can be thought of as the combination of pressure fluctuations from a volume change, directionality, and turbulence. This infrasound source could not be well constrained up to this time due to infrasound sensors only being deployed on Earth's surface, so the assumption of no vertical dipole component has been made. In this study we deploy a high-density seismo-acoustic network, including multiple acoustic sensors along a tethered balloon around Yasur Volcano, Vanuatu. Yasur has frequent strombolian eruptions from any one of its three active vents within a 400 m diameter crater. The third dimension (vertical) of pressure sensor coverage allows us to begin to constrain the acoustic source components in a profound way, primarily the horizontal and vertical components and their previously uncharted contributions to volcano infrasound. The deployment also has a geochemical and visual component, including FLIR, FTIR, two scanning FLYSPECs, and a variety of visual imagery. Our analysis employs Finite-Difference Time-Domain (FDTD) modeling to obtain the full 3D Green's functions for each propagation path. This method, following Kim et al. (2015), takes into account realistic topographic scattering based on a digital elevation model created using structure-from-motion techniques. We then invert for the source location and source-time function, constraining the contribution of the vertical sound radiation to the source. The final outcome of this inversion is an infrasound-derived volume flux as a function of time, which we then compare to those derived independently from geochemical techniques as well as the inversion of

  2. Improving rotorcraft survivability to RPG attack using inverse methods

    NASA Astrophysics Data System (ADS)

    Anderson, D.; Thomson, D. G.

    2009-09-01

    This paper presents the results of a preliminary investigation of optimal threat evasion strategies for improving the survivability of rotorcraft under attack by rocket propelled grenades (RPGs). The basis of this approach is the application of inverse simulation techniques pioneered for simulation of aggressive helicopter manoeuvres to the RPG engagement problem. In this research, improvements in survivability are achieved by computing effective evasive manoeuvres. The first step in this process uses the missile approach warning system camera (MAWS) on the aircraft to provide angular information of the threat. Estimates of the RPG trajectory and impact point are then estimated. For the current flight state an appropriate evasion response is selected then realised via inverse simulation of the platform dynamics. Results are presented for several representative engagements showing the efficacy of the approach.

  3. A Generalization of the Spherical Inversion

    ERIC Educational Resources Information Center

    Ramírez, José L.; Rubiano, Gustavo N.

    2017-01-01

    In the present article, we introduce a generalization of the spherical inversion. In particular, we define an inversion with respect to an ellipsoid, and prove several properties of this new transformation. The inversion in an ellipsoid is the generalization of the elliptic inversion to the three-dimensional space. We also study the inverse images…

  4. Deformation measurement for a rotating deformable lap based on inverse fringe projection

    NASA Astrophysics Data System (ADS)

    Liao, Min; Zhang, Qican

    2015-03-01

    The active deformable lap (also namely stressed lap) is an efficient polishing tool in optical manufacturing. To measure the dynamic deformation caused by outside force on a deformable lap is important and helpful to the opticians to ensure the performance of a deformable lap as expected. In this paper, a manual deformable lap was designed to simulate the dynamic deformation of an active stressed lap, and a measurement system was developed based on inverse projected fringe technique to restore the 3D shape. A redesigned inverse fringe has been projected onto the surface of the measured lap, and the deformations of the tested lap become much obvious and can be easily and quickly evaluated by Fourier fringe analysis. Compared with the conventional projection, this technique is more obvious, and it should be a promising one in the deformation measurement of the active stressed lap in optical manufacturing.

  5. Joint inversion of high-frequency surface waves with fundamental and higher modes

    USGS Publications Warehouse

    Luo, Y.; Xia, J.; Liu, J.; Liu, Q.; Xu, S.

    2007-01-01

    Joint inversion of multimode surface waves for estimating the shear (S)-wave velocity has received much attention in recent years. In this paper, we first analyze sensitivity of phase velocities of multimodes of surface waves for a six-layer earth model, and then we invert surface-wave dispersion curves of the theoretical model and a real-world example. Sensitivity analysis shows that fundamental mode data are more sensitive to the S-wave velocities of shallow layers and are concentrated on a very narrow frequency band, while higher mode data are more sensitive to the parameters of relatively deeper layers and are distributed over a wider frequency band. These properties provide a foundation of using a multimode joint inversion to define S-wave velocities. Inversion results of both synthetic data and a real-world example demonstrate that joint inversion with the damped least-square method and the singular-value decomposition technique to invert high-frequency surface waves with fundamental and higher mode data simultaneously can effectively reduce the ambiguity and improve the accuracy of S-wave velocities. ?? 2007.

  6. Male infertility associated with de novo pericentric inversion of chromosome 1.

    PubMed

    Balasar, Özgür; Zamani, Ayşe Gül; Balasar, Mehmet; Acar, Hasan

    2017-12-01

    Inversion occurs after two breaks in a chromosome have happened and the segment rotates 180° before reinserting. Inversion carriers have produced abnormal gametes if there is an odd number crossing- over between the inverted and the normal homologous chromosomes causing a duplication or deletion. Reproductive risks such as infertility, abortion, stillbirth and birth of malformed child would be expected in that case. A 54-year- old male patient was consulted to our clinic for primary infertility. The routine chromosome study were applied using peripheral blood lymphocyte cultures and analyzed by giemsa-trypsin-giemsa (GTG) banding, and centromer banding (C-banding) stains. Y chromosome microdeletions in the azoospermia factor (AZF) regions were analyzed with polymerase chain reaction. Additional test such as fluorescence in situ hybridization (FISH) was used to detect the sex-determining region of the Y chromosome (SRY). Semen analysis showed azoospermia. A large pericentric inversion of chromosome 1 46,XY, inv(1) (p22q32) was found in routine chromosome analysis. No microdeletions were seen in AZF regions. In our patient the presence of SRY region was observed by using FISH technique with SRY-specific probe. Men who have pericentric inversion of chromosome 1, appear to be at risk for infertility brought about by spermatogenic breakdown. The etiopathogenic relationship between azoospermia and pericentric inversion of chromosome 1 is discussed.

  7. Uncertainties in the cluster-cluster correlation function

    NASA Astrophysics Data System (ADS)

    Ling, E. N.; Frenk, C. S.; Barrow, J. D.

    1986-12-01

    The bootstrap resampling technique is applied to estimate sampling errors and significance levels of the two-point correlation functions determined for a subset of the CfA redshift survey of galaxies and a redshift sample of 104 Abell clusters. The angular correlation function for a sample of 1664 Abell clusters is also calculated. The standard errors in xi(r) for the Abell data are found to be considerably larger than quoted 'Poisson errors'. The best estimate for the ratio of the correlation length of Abell clusters (richness class R greater than or equal to 1, distance class D less than or equal to 4) to that of CfA galaxies is 4.2 + 1.4 or - 1.0 (68 percentile error). The enhancement of cluster clustering over galaxy clustering is statistically significant in the presence of resampling errors. The uncertainties found do not include the effects of possible systematic biases in the galaxy and cluster catalogs and could be regarded as lower bounds on the true uncertainty range.

  8. Inverse estimation of the spheroidal particle size distribution using Ant Colony Optimization algorithms in multispectral extinction technique

    NASA Astrophysics Data System (ADS)

    He, Zhenzong; Qi, Hong; Wang, Yuqing; Ruan, Liming

    2014-10-01

    Four improved Ant Colony Optimization (ACO) algorithms, i.e. the probability density function based ACO (PDF-ACO) algorithm, the Region ACO (RACO) algorithm, Stochastic ACO (SACO) algorithm and Homogeneous ACO (HACO) algorithm, are employed to estimate the particle size distribution (PSD) of the spheroidal particles. The direct problems are solved by the extended Anomalous Diffraction Approximation (ADA) and the Lambert-Beer law. Three commonly used monomodal distribution functions i.e. the Rosin-Rammer (R-R) distribution function, the normal (N-N) distribution function, and the logarithmic normal (L-N) distribution function are estimated under dependent model. The influence of random measurement errors on the inverse results is also investigated. All the results reveal that the PDF-ACO algorithm is more accurate than the other three ACO algorithms and can be used as an effective technique to investigate the PSD of the spheroidal particles. Furthermore, the Johnson's SB (J-SB) function and the modified beta (M-β) function are employed as the general distribution functions to retrieve the PSD of spheroidal particles using PDF-ACO algorithm. The investigation shows a reasonable agreement between the original distribution function and the general distribution function when only considering the variety of the length of the rotational semi-axis.

  9. Forced-flow bioreactor for sucrose inversion using ceramic membrane activated by silanization.

    PubMed

    Nakajima, M; Watanabe, A; Jimbo, N; Nishizawa, K; Nakao, S

    1989-02-20

    A forced-flow enzyme membrane reactor system for sucrose inversion was investigated using three ceramic membranes having different pore sizes. Invertase was immobilized chemically to the inner surface of a ceramic membrane activated by a silane-glutaraldehyde technique. With the cross-flow filtration of sucrose solution, the reaction rate was a function of the permeate flux, easily controlled by pressure. Using 0.5 microm support pore size of membrane, the volumetric productivity obtained was 10 times higher than that in a reported immobilized enzyme column reactor, with a short residence time of 5 s and 100% conversion of the sucrose inversion.

  10. Radiative-conductive inverse problem for lumped parameter systems

    NASA Astrophysics Data System (ADS)

    Alifanov, O. M.; Nenarokomov, A. V.; Gonzalez, V. M.

    2008-11-01

    The purpose of this paper is to introduce a iterative regularization method in the research of radiative and thermal properties of materials with applications in the design of Thermal Control Systems (TCS) of spacecrafts. In this paper the radiative and thermal properties (emissivity and thermal conductance) of a multilayered thermal-insulating blanket (MLI), which is a screen-vacuum thermal insulation as a part of the (TCS) for perspective spacecrafts, are estimated. Properties of the materials under study are determined in the result of temperature and heat flux measurement data processing based on the solution of the Inverse Heat Transfer Problem (IHTP) technique. Given are physical and mathematical models of heat transfer processes in a specimen of the multilayered thermal-insulating blanket located in the experimental facility. A mathematical formulation of the inverse heat conduction problem is presented too. The practical testing were performed for specimen of the real MLI.

  11. A simulation based method to assess inversion algorithms for transverse relaxation data

    NASA Astrophysics Data System (ADS)

    Ghosh, Supriyo; Keener, Kevin M.; Pan, Yong

    2008-04-01

    NMR relaxometry is a very useful tool for understanding various chemical and physical phenomena in complex multiphase systems. A Carr-Purcell-Meiboom-Gill (CPMG) [P.T. Callaghan, Principles of Nuclear Magnetic Resonance Microscopy, Clarendon Press, Oxford, 1991] experiment is an easy and quick way to obtain transverse relaxation constant (T2) in low field. Most of the samples usually have a distribution of T2 values. Extraction of this distribution of T2s from the noisy decay data is essentially an ill-posed inverse problem. Various inversion approaches have been used to solve this problem, to date. A major issue in using an inversion algorithm is determining how accurate the computed distribution is. A systematic analysis of an inversion algorithm, UPEN [G.C. Borgia, R.J.S. Brown, P. Fantazzini, Uniform-penalty inversion of multiexponential decay data, Journal of Magnetic Resonance 132 (1998) 65-77; G.C. Borgia, R.J.S. Brown, P. Fantazzini, Uniform-penalty inversion of multiexponential decay data II. Data spacing, T2 data, systematic data errors, and diagnostics, Journal of Magnetic Resonance 147 (2000) 273-285] was performed by means of simulated CPMG data generation. Through our simulation technique and statistical analyses, the effects of various experimental parameters on the computed distribution were evaluated. We converged to the true distribution by matching up the inversion results from a series of true decay data and a noisy simulated data. In addition to simulation studies, the same approach was also applied on real experimental data to support the simulation results.

  12. Microscopy and Chemical Inversing Techniques to Determine the Photonic Crystal Structure of Iridescent Beetle Scales in the Cerambycidae Family

    NASA Astrophysics Data System (ADS)

    Richey, Lauren; Gardner, John; Standing, Michael; Jorgensen, Matthew; Bartl, Michael

    2010-10-01

    Photonic crystals (PCs) are periodic structures that manipulate electromagnetic waves by defining allowed and forbidden frequency bands known as photonic band gaps. Despite production of PC structures operating at infrared wavelengths, visible counterparts are difficult to fabricate because periodicities must satisfy the diffraction criteria. As part of an ongoing search for naturally occurring PCs [1], a three-dimensional array of nanoscopic spheres in the iridescent scales of the Cerambycidae insects A. elegans and G. celestis has been found. Such arrays are similar to opal gemstones and self-assembled colloidal spheres which can be chemically inverted to create a lattice-like PC. Through a chemical replication process [2], scanning electron microscopy analysis, sequential focused ion beam slicing and three-dimensional modeling, we analyzed the structural arrangement of the nanoscopic spheres. The study of naturally occurring structures and their inversing techniques into PCs allows for diversity in optical PC fabrication. [1] J.W. Galusha et al., Phys. Rev. E 77 (2008) 050904. [2] J.W. Galusha et al., J. Mater. Chem. 20 (2010) 1277.

  13. Solving inversion problems with neural networks

    NASA Technical Reports Server (NTRS)

    Kamgar-Parsi, Behzad; Gualtieri, J. A.

    1990-01-01

    A class of inverse problems in remote sensing can be characterized by Q = F(x), where F is a nonlinear and noninvertible (or hard to invert) operator, and the objective is to infer the unknowns, x, from the observed quantities, Q. Since the number of observations is usually greater than the number of unknowns, these problems are formulated as optimization problems, which can be solved by a variety of techniques. The feasibility of neural networks for solving such problems is presently investigated. As an example, the problem of finding the atmospheric ozone profile from measured ultraviolet radiances is studied.

  14. Steven J. Ostro: Pioneer in Asteroid Lightcurve Inversion

    NASA Astrophysics Data System (ADS)

    Harris, Alan W.

    2009-09-01

    In 1906, Henry Norris Russell wrote a landmark paper (Astrophys. J. 24, 1-18, 1906) that set the field of lightcurve inversion back by more than three quarters of a century, until Steve Ostro and Robert Connolly published a paper on "convex profile inversion” (Icarus 57, 443-463, 1984). Russell's stifling contribution was innocent enough, and entirely correct: he showed that with "two cans of paint", one can decorate any arbitrarily shaped body in an infinite number of ways to yield any particular lightcurve, even, for example, a cigar shape that is brightest viewed end-on. This sufficed to discourage serious mathematical attack on the problem until Ostro & Connolly's landmark paper of 1984. They showed that if you have only "one can of paint", that is, in the absence of albedo variegation, the problem is tractable and one can make remarkable progress in lightcurve inversion to obtain shapes, or at least the "convex profile” of the real shape. As we now know, nature appears to have only one can of paint (per asteroid), that is, asteroids seem to paint themselves grey so that the uniform reflectivity assumption is quite excellent. Both radar and optical lightcurve inversion techniques are now quite mature, thanks to Steve's pioneering insights.

  15. Wake Vortex Inverse Model User's Guide

    NASA Technical Reports Server (NTRS)

    Lai, David; Delisi, Donald

    2008-01-01

    NorthWest Research Associates (NWRA) has developed an inverse model for inverting landing aircraft vortex data. The data used for the inversion are the time evolution of the lateral transport position and vertical position of both the port and starboard vortices. The inverse model performs iterative forward model runs using various estimates of vortex parameters, vertical crosswind profiles, and vortex circulation as a function of wake age. Forward model predictions of lateral transport and altitude are then compared with the observed data. Differences between the data and model predictions guide the choice of vortex parameter values, crosswind profile and circulation evolution in the next iteration. Iterations are performed until a user-defined criterion is satisfied. Currently, the inverse model is set to stop when the improvement in the rms deviation between the data and model predictions is less than 1 percent for two consecutive iterations. The forward model used in this inverse model is a modified version of the Shear-APA model. A detailed description of this forward model, the inverse model, and its validation are presented in a different report (Lai, Mellman, Robins, and Delisi, 2007). This document is a User's Guide for the Wake Vortex Inverse Model. Section 2 presents an overview of the inverse model program. Execution of the inverse model is described in Section 3. When executing the inverse model, a user is requested to provide the name of an input file which contains the inverse model parameters, the various datasets, and directories needed for the inversion. A detailed description of the list of parameters in the inversion input file is presented in Section 4. A user has an option to save the inversion results of each lidar track in a mat-file (a condensed data file in Matlab format). These saved mat-files can be used for post-inversion analysis. A description of the contents of the saved files is given in Section 5. An example of an inversion input

  16. Comparison of Compressed Sensing Algorithms for Inversion of 3-D Electrical Resistivity Tomography.

    NASA Astrophysics Data System (ADS)

    Peddinti, S. R.; Ranjan, S.; Kbvn, D. P.

    2016-12-01

    Image reconstruction algorithms derived from electrical resistivity tomography (ERT) are highly non-linear, sparse, and ill-posed. The inverse problem is much severe, when dealing with 3-D datasets that result in large sized matrices. Conventional gradient based techniques using L2 norm minimization with some sort of regularization can impose smoothness constraint on the solution. Compressed sensing (CS) is relatively new technique that takes the advantage of inherent sparsity in parameter space in one or the other form. If favorable conditions are met, CS was proven to be an efficient image reconstruction technique that uses limited observations without losing edge sharpness. This paper deals with the development of an open source 3-D resistivity inversion tool using CS framework. The forward model was adopted from RESINVM3D (Pidlisecky et al., 2007) with CS as the inverse code. Discrete cosine transformation (DCT) function was used to induce model sparsity in orthogonal form. Two CS based algorithms viz., interior point method and two-step IST were evaluated on a synthetic layered model with surface electrode observations. The algorithms were tested (in terms of quality and convergence) under varying degrees of parameter heterogeneity, model refinement, and reduced observation data space. In comparison to conventional gradient algorithms, CS was proven to effectively reconstruct the sub-surface image with less computational cost. This was observed by a general increase in NRMSE from 0.5 in 10 iterations using gradient algorithm to 0.8 in 5 iterations using CS algorithms.

  17. Contribution of 3D inversion of Electrical Resistivity Tomography data applied to volcanic structures

    NASA Astrophysics Data System (ADS)

    Portal, Angélie; Fargier, Yannick; Lénat, Jean-François; Labazuy, Philippe

    2016-04-01

    The electrical resistivity tomography (ERT) method, initially developed for environmental and engineering exploration, is now commonly used for geological structures imaging. Such structures can present complex characteristics that conventional 2D inversion processes cannot perfectly integrate. Here we present a new 3D inversion algorithm named EResI, firstly developed for levee investigation, and presently applied to the study of a complex lava dome (the Puy de Dôme volcano, France). EResI algorithm is based on a conventional regularized Gauss-Newton inversion scheme and a 3D non-structured discretization of the model (double grid method based on tetrahedrons). This discretization allows to accurately model the topography of investigated structure (without a mesh deformation procedure) and also permits a precise location of the electrodes. Moreover, we demonstrate that a complete 3D unstructured discretization limits the number of inversion cells and is better adapted to the resolution capacity of tomography than a structured discretization. This study shows that a 3D inversion with a non-structured parametrization has some advantages compared to classical 2D inversions. The first advantage comes from the fact that a 2D inversion leads to artefacts due to 3D effects (3D topography, 3D internal resistivity). The second advantage comes from the fact that the capacity to experimentally align electrodes along an axis (for 2D surveys) depends on the constrains on the field (topography...). In this case, a 2D assumption induced by 2.5D inversion software prevents its capacity to model electrodes outside this axis leading to artefacts in the inversion result. The last limitation comes from the use of mesh deformation techniques used to accurately model the topography in 2D softwares. This technique used for structured discretization (Res2dinv) is prohibed for strong topography (>60 %) and leads to a small computational errors. A wide geophysical survey was carried out

  18. Imaging of the native inversion layer in Silicon-On-Insulator wafers via Scanning Surface Photovoltage: Implications for RF device performance

    NASA Astrophysics Data System (ADS)

    Dahanayaka, Daminda; Wong, Andrew; Kaszuba, Philip; Moszkowicz, Leon; Slinkman, James; IBM SPV Lab Team

    2014-03-01

    Silicon-On-Insulator (SOI) technology has proved beneficial for RF cell phone technologies, which have equivalent performance to GaAs technologies. However, there is evident parasitic inversion layer under the Buried Oxide (BOX) at the interface with the high resistivity Si substrate. The latter is inferred from capacitance-voltage measurements on MOSCAPs. The inversion layer has adverse effects on RF device performance. We present data which, for the first time, show the extent of the inversion layer in the underlying substrate. This knowledge has driven processing techniques to suppress the inversion.

  19. Mini-batch optimized full waveform inversion with geological constrained gradient filtering

    NASA Astrophysics Data System (ADS)

    Yang, Hui; Jia, Junxiong; Wu, Bangyu; Gao, Jinghuai

    2018-05-01

    High computation cost and generating solutions without geological sense have hindered the wide application of Full Waveform Inversion (FWI). Source encoding technique is a way to dramatically reduce the cost of FWI but subject to fix-spread acquisition setup requirement and slow convergence for the suppression of cross-talk. Traditionally, gradient regularization or preconditioning is applied to mitigate the ill-posedness. An isotropic smoothing filter applied on gradients generally gives non-geological inversion results, and could also introduce artifacts. In this work, we propose to address both the efficiency and ill-posedness of FWI by a geological constrained mini-batch gradient optimization method. The mini-batch gradient descent optimization is adopted to reduce the computation time by choosing a subset of entire shots for each iteration. By jointly applying the structure-oriented smoothing to the mini-batch gradient, the inversion converges faster and gives results with more geological meaning. Stylized Marmousi model is used to show the performance of the proposed method on realistic synthetic model.

  20. Estimating rainfall time series and model parameter distributions using model data reduction and inversion techniques

    NASA Astrophysics Data System (ADS)

    Wright, Ashley J.; Walker, Jeffrey P.; Pauwels, Valentijn R. N.

    2017-08-01

    Floods are devastating natural hazards. To provide accurate, precise, and timely flood forecasts, there is a need to understand the uncertainties associated within an entire rainfall time series, even when rainfall was not observed. The estimation of an entire rainfall time series and model parameter distributions from streamflow observations in complex dynamic catchments adds skill to current areal rainfall estimation methods, allows for the uncertainty of entire rainfall input time series to be considered when estimating model parameters, and provides the ability to improve rainfall estimates from poorly gauged catchments. Current methods to estimate entire rainfall time series from streamflow records are unable to adequately invert complex nonlinear hydrologic systems. This study aims to explore the use of wavelets in the estimation of rainfall time series from streamflow records. Using the Discrete Wavelet Transform (DWT) to reduce rainfall dimensionality for the catchment of Warwick, Queensland, Australia, it is shown that model parameter distributions and an entire rainfall time series can be estimated. Including rainfall in the estimation process improves streamflow simulations by a factor of up to 1.78. This is achieved while estimating an entire rainfall time series, inclusive of days when none was observed. It is shown that the choice of wavelet can have a considerable impact on the robustness of the inversion. Combining the use of a likelihood function that considers rainfall and streamflow errors with the use of the DWT as a model data reduction technique allows the joint inference of hydrologic model parameters along with rainfall.

  1. Astrometry With the Hubble Space Telescope: Trigonometric Parallaxes of Planetary Nebula Nuclei NGC 6853, NGC 7293, ABELL 31, and DeHt 5

    NASA Technical Reports Server (NTRS)

    Benedict, G. F.; McArthur, Barbara E.; Napiwotzki, Ralf; Harrison, Thomas E.; Harris, Hugh C.; Nelan, Edmund; Bond, Howard E; Patterson, Richard J.; Ciardullo, Robin

    2009-01-01

    We present absolute parallaxes and relative proper motions for the central stars of the planetary nebulae NGC 6853 (The Dumbbell), NGC 7293 (The Helix), Abell 31, and DeHt 5. This paper details our reduction and analysis using DeHt 5 as an example. We obtain these planetary nebula nuclei (PNNi) parallaxes with astrometric data from Fine Guidance Sensors FGS 1r and FGS 3, white-light interferometers on the Hubble Space Telescope. Proper motions, spectral classifications and VJHKT2M and DDO51 photometry of the stars comprising the astrometric reference frames provide spectrophotometric estimates of reference star absolute parallaxes. Introducing these into our model as observations with error, we determine absolute parallaxes for each PNN. Weighted averaging with previous independent parallax measurements yields an average parallax precision, sigma (sub pi)/ pi = 5%. Derived distances are: d(sub NGC6853) = 405(exp +28 sub -25) pc, d(sub NGC7293) = 216(exp +14 sub -12) pc, d(sub Abell31) = 621(exp +91 sub -70) pc, and d(sub DeHt5) = 345(exp +19 sub -17) pc. These PNNi distances are all smaller than previously derived from spectroscopic analyses of the central stars. To obtain absolute magnitudes from these distances requires estimates of interstellar extinction. We average extinction measurements culled from the literature, from reddening based on PNNi intrinsic colors derived from model SEDs, and an assumption that each PNN experiences the same rate of extinction as a function of distance as do the reference stars nearest (in angular separation) to each central star. We also apply Lutz-Kelker bias corrections. The absolute magnitudes and effective temperatures permit estimates of PNNi radii through both the Stefan-Boltzmann relation and Eddington fluxes. Comparing absolute magnitudes with post-AGB models provides mass estimates. Masses cluster around 0.57 solar Mass, close to the peak of the white dwarf mass distribution. Adding a few more PNNi with well

  2. Super-resolution Time-Lapse Seismic Waveform Inversion

    NASA Astrophysics Data System (ADS)

    Ovcharenko, O.; Kazei, V.; Peter, D. B.; Alkhalifah, T.

    2017-12-01

    Time-lapse seismic waveform inversion is a technique, which allows tracking changes in the reservoirs over time. Such monitoring is relatively computationally extensive and therefore it is barely feasible to perform it on-the-fly. Most of the expenses are related to numerous FWI iterations at high temporal frequencies, which is inevitable since the low-frequency components can not resolve fine scale features of a velocity model. Inverted velocity changes are also blurred when there is noise in the data, so the problem of low-resolution images is widely known. One of the problems intensively tackled by computer vision research community is the recovering of high-resolution images having their low-resolution versions. Usage of artificial neural networks to reach super-resolution from a single downsampled image is one of the leading solutions for this problem. Each pixel of the upscaled image is affected by all the pixels of its low-resolution version, which enables the workflow to recover features that are likely to occur in the corresponding environment. In the present work, we adopt machine learning image enhancement technique to improve the resolution of time-lapse full-waveform inversion. We first invert the baseline model with conventional FWI. Then we run a few iterations of FWI on a set of the monitoring data to find desired model changes. These changes are blurred and we enhance their resolution by using a deep neural network. The network is trained to map low-resolution model updates predicted by FWI into the real perturbations of the baseline model. For supervised training of the network we generate a set of random perturbations in the baseline model and perform FWI on the noisy data from the perturbed models. We test the approach on a realistic perturbation of Marmousi II model and demonstrate that it outperforms conventional convolution-based deblurring techniques.

  3. New Inversion and Interpretation of Public-Domain Electromagnetic Survey Data from Selected Areas in Alaska

    NASA Astrophysics Data System (ADS)

    Smith, B. D.; Kass, A.; Saltus, R. W.; Minsley, B. J.; Deszcz-Pan, M.; Bloss, B. R.; Burns, L. E.

    2013-12-01

    Public-domain airborne geophysical surveys (combined electromagnetics and magnetics), mostly collected for and released by the State of Alaska, Division of Geological and Geophysical Surveys (DGGS), are a unique and valuable resource for both geologic interpretation and geophysical methods development. A new joint effort by the US Geological Survey (USGS) and the DGGS aims to add value to these data through the application of novel advanced inversion methods and through innovative and intuitive display of data: maps, profiles, voxel-based models, and displays of estimated inversion quality and confidence. Our goal is to make these data even more valuable for interpretation of geologic frameworks, geotechnical studies, and cryosphere studies, by producing robust estimates of subsurface resistivity that can be used by non-geophysicists. The available datasets, which are available in the public domain, include 39 frequency-domain electromagnetic datasets collected since 1993, and continue to grow with 5 more data releases pending in 2013. The majority of these datasets were flown for mineral resource purposes, with one survey designed for infrastructure analysis. In addition, several USGS datasets are included in this study. The USGS has recently developed new inversion methodologies for airborne EM data and have begun to apply these and other new techniques to the available datasets. These include a trans-dimensional Markov Chain Monte Carlo technique, laterally-constrained regularized inversions, and deterministic inversions which include calibration factors as a free parameter. Incorporation of the magnetic data as an additional constraining dataset has also improved the inversion results. Processing has been completed in several areas, including Fortymile and the Alaska Highway surveys, and continues in others such as the Styx River and Nome surveys. Utilizing these new techniques, we provide models beyond the apparent resistivity maps supplied by the original

  4. Inverse Calibration Free fs-LIBS of Copper-Based Alloys

    NASA Astrophysics Data System (ADS)

    Smaldone, Antonella; De Bonis, Angela; Galasso, Agostino; Guarnaccio, Ambra; Santagata, Antonio; Teghil, Roberto

    2016-09-01

    In this work the analysis by Laser Induced Breakdown Spectroscopy (LIBS) technique of copper-based alloys having different composition and performed with fs laser pulses is presented. A Nd:Glass laser (Twinkle Light Conversion, λ = 527 nm at 250 fs) and a set of bronze and brass certified standards were used. The inverse Calibration-Free method (inverse CF-LIBS) was applied for estimating the temperature of the fs laser induced plasma in order to achieve quantitative elemental analysis of such materials. This approach strengthens the hypothesis that, through the assessment of the plasma temperature occurring in fs-LIBS, straightforward and reliable analytical data can be provided. With this aim the capability of the here adopted inverse CF-LIBS method, which is based on the fulfilment of the Local Thermodynamic Equilibrium (LTE) condition, for an indirect determination of the species excitation temperature, is shown. It is reported that the estimated temperatures occurring during the process provide a good figure of merit between the certified and the experimentally determined composition of the bronze and brass materials, here employed, although further correction procedure, like the use of calibration curves, can be demanded. The reported results demonstrate that the inverse CF-LIBS method can be applied when fs laser pulses are used even though the plasma properties could be affected by the matrix effects restricting its full employment to unknown samples provided that a certified standard having similar composition is available.

  5. Chromosome Inversion Polymorphisms in DROSOPHILA MELANOGASTER. I. Latitudinal Clines and Associations between Inversions in Australasian Populations

    PubMed Central

    Knibb, W. R.; Oakeshott, J. G.; Gibson, J. B.

    1981-01-01

    Nineteen Australasian populations of Drosophila melanogaster have been screened for chromosome inversion polymorphisms. All 15 of the inversion types found are paracentric and autosomal, but only four of these, one on each of the major autosome arms, are common and cosmopolitan. North-south clines occur, with the frequencies of all four of the common cosmopolitan inversions increasing toward the equator. These clines in the Southern Hemisphere mirror north-south clines in the Northern Hemisphere, where the frequencies of all four of the common cosmopolitan inversions again increase towards the equator.—While few of the Australasian populations show significant disequilibrium between linked common cosmopolitan inversions, those that do invariably have excesses of coupling gametes, which is consistent with other reports. We also find nonrandom associations between the two major autosomes, with the northern populations in Australasia (those with high inversion frequencies) tending to be deficient in gametes with common cosmopolitan inversions on both major autosomes, while the southern populations in Australasia (low inversion frequencies) tend to have an excess of this class of gametes.—The clines and the nonrandom associations between the two major autosomes are best interpreted in terms of selection operating to maintain the common cosmopolitan inversion polymorphisms in natural populations of D. melanogaster. PMID:17249108

  6. Surface Wave Mode Conversion due to Lateral Heterogeneity and its Impact on Waveform Inversions

    NASA Astrophysics Data System (ADS)

    Datta, A.; Priestley, K. F.; Chapman, C. H.; Roecker, S. W.

    2016-12-01

    Surface wave tomography based on great circle ray theory has certain limitations which become increasingly significant with increasing frequency. One such limitation is the assumption of different surface wave modes propagating independently from source to receiver, valid only in case of smoothly varying media. In the real Earth, strong lateral gradients can cause significant interconversion among modes, thus potentially wreaking havoc with ray theory based tomographic inversions that make use of multimode information. The issue of mode coupling (with either normal modes or surface wave modes) for accurate modelling and inversion of body wave data has received significant attention in the seismological literature, but its impact on inversion of surface waveforms themselves remains much less understood.We present an empirical study with synthetic data, to investigate this problem with a two-fold approach. In the first part, 2D forward modelling using a new finite difference method that allows modelling a single mode at a time, is used to build a general picture of energy transfer among modes as a function of size, strength and sharpness of lateral heterogeneities. In the second part, we use the example of a multimode waveform inversion technique based on the Cara and Leveque (1987) approach of secondary observables, to invert our synthetic data and assess how mode conversion can affect the process of imaging the Earth. We pay special attention to ensuring that any biases or artefacts in the resulting inversions can be unambiguously attributed to mode conversion effects. This study helps pave the way towards the next generation of (non-numerical) surface wave tomography techniques geared to exploit higher frequencies and mode numbers than are typically used today.

  7. Approaches to highly parameterized inversion-A guide to using PEST for groundwater-model calibration

    USGS Publications Warehouse

    Doherty, John E.; Hunt, Randall J.

    2010-01-01

    Highly parameterized groundwater models can create calibration difficulties. Regularized inversion-the combined use of large numbers of parameters with mathematical approaches for stable parameter estimation-is becoming a common approach to address these difficulties and enhance the transfer of information contained in field measurements to parameters used to model that system. Though commonly used in other industries, regularized inversion is somewhat imperfectly understood in the groundwater field. There is concern that this unfamiliarity can lead to underuse, and misuse, of the methodology. This document is constructed to facilitate the appropriate use of regularized inversion for calibrating highly parameterized groundwater models. The presentation is directed at an intermediate- to advanced-level modeler, and it focuses on the PEST software suite-a frequently used tool for highly parameterized model calibration and one that is widely supported by commercial graphical user interfaces. A brief overview of the regularized inversion approach is provided, and techniques for mathematical regularization offered by PEST are outlined, including Tikhonov, subspace, and hybrid schemes. Guidelines for applying regularized inversion techniques are presented after a logical progression of steps for building suitable PEST input. The discussion starts with use of pilot points as a parameterization device and processing/grouping observations to form multicomponent objective functions. A description of potential parameter solution methodologies and resources available through the PEST software and its supporting utility programs follows. Directing the parameter-estimation process through PEST control variables is then discussed, including guidance for monitoring and optimizing the performance of PEST. Comprehensive listings of PEST control variables, and of the roles performed by PEST utility support programs, are presented in the appendixes.

  8. Convergence acceleration in scattering series and seismic waveform inversion using nonlinear Shanks transformation

    NASA Astrophysics Data System (ADS)

    Eftekhar, Roya; Hu, Hao; Zheng, Yingcai

    2018-06-01

    Iterative solution process is fundamental in seismic inversions, such as in full-waveform inversions and some inverse scattering methods. However, the convergence could be slow or even divergent depending on the initial model used in the iteration. We propose to apply Shanks transformation (ST for short) to accelerate the convergence of the iterative solution. ST is a local nonlinear transformation, which transforms a series locally into another series with an improved convergence property. ST works by separating the series into a smooth background trend called the secular term versus an oscillatory transient term. ST then accelerates the convergence of the secular term. Since the transformation is local, we do not need to know all the terms in the original series which is very important in the numerical implementation. The ST performance was tested numerically for both the forward Born series and the inverse scattering series (ISS). The ST has been shown to accelerate the convergence in several examples, including three examples of forward modeling using the Born series and two examples of velocity inversion based on a particular type of the ISS. We observe that ST is effective in accelerating the convergence and it can also achieve convergence even for a weakly divergent scattering series. As such, it provides a useful technique to invert for a large-contrast medium perturbation in seismic inversion.

  9. Chemically Patterned Inverse Opal Created by a Selective Photolysis Modification Process.

    PubMed

    Tian, Tian; Gao, Ning; Gu, Chen; Li, Jian; Wang, Hui; Lan, Yue; Yin, Xianpeng; Li, Guangtao

    2015-09-02

    Anisotropic photonic crystal materials have long been pursued for their broad applications. A novel method for creating chemically patterned inverse opals is proposed here. The patterning technique is based on selective photolysis of a photolabile polymer together with postmodification on released amine groups. The patterning method allows regioselective modification within an inverse opal structure, taking advantage of selective chemical reaction. Moreover, combined with the unique signal self-reporting feature of the photonic crystal, the fabricated structure is capable of various applications, including gradient photonic bandgap and dynamic chemical patterns. The proposed method provides the ability to extend the structural and chemical complexity of the photonic crystal, as well as its potential applications.

  10. GUEST EDITORS' INTRODUCTION: Testing inversion algorithms against experimental data: inhomogeneous targets

    NASA Astrophysics Data System (ADS)

    Belkebir, Kamal; Saillard, Marc

    2005-12-01

    Habashy, Application of the multiplicative regularized contrast source inversion method TM- and TE-polarized experimental Fresnel data, present results of profile inversions obtained using the contrast source inversion (CSI) method, in which a multiplicative regularization is plugged in. The authors successfully inverted both TM- and TE-polarized fields. Note that this paper is one of only two contributions which address the inversion of TE-polarized data. A Baussard, Inversion of multi-frequency experimental data using an adaptive multiscale approach, reports results of reconstructions using the modified gradient method (MGM). It suggests that a coarse-to-fine iterative strategy based on spline pyramids. In this iterative technique, the number of degrees of freedom is reduced, which improves robustness. The introduction, during the iterative process, of finer scales inside areas of interest leads to an accurate representation of the object under test. The efficiency of this technique is shown via comparisons between the results obtained with the standard MGM and those from an adaptive approach. L Crocco, M D'Urso and T Isernia, Testing the contrast source extended Born inversion method against real data: the case of TM data, assume that the main contribution in the domain integral formulation comes from the singularity of Green's function, even though the media involved are lossless. A Fourier Bessel analysis of the incident and scattered measured fields is used to derive a model of the incident field and an estimate of the location and size of the target. The iterative procedure lies on a conjugate gradient method associated with Tikhonov regularization, and the multi-frequency data are dealt with using a frequency-hopping approach. In many cases, it is difficult to reconstruct accurately both real and imaginary parts of the permittivity if no prior information is included. M Donelli, D Franceschini, A Massa, M Pastorino and A Zanetti, Multi-resolution iterative

  11. Interplay of Nitrogen-Atom Inversion and Conformational Inversion in Enantiomerization of 1H-1-Benzazepines.

    PubMed

    Ramig, Keith; Subramaniam, Gopal; Karimi, Sasan; Szalda, David J; Ko, Allen; Lam, Aaron; Li, Jeffrey; Coaderaj, Ani; Cavdar, Leyla; Bogdan, Lukasz; Kwon, Kitae; Greer, Edyta M

    2016-04-15

    A series of 2,4-disubstituted 1H-1-benzazepines, 2a-d, 4, and 6, were studied, varying both the substituents at C2 and C4 and at the nitrogen atom. The conformational inversion (ring-flip) and nitrogen-atom inversion (N-inversion) energetics were studied by variable-temperature NMR spectroscopy and computations. The steric bulk of the nitrogen-atom substituent was found to affect both the conformation of the azepine ring and the geometry around the nitrogen atom. Also affected were the Gibbs free energy barriers for the ring-flip and the N-inversion. When the nitrogen-atom substituent was alkyl, as in 2a-c, the geometry of the nitrogen atom was nearly planar and the azepine ring was highly puckered; the result was a relatively high-energy barrier to ring-flip and a low barrier to N-inversion. Conversely, when the nitrogen-atom substituent was a hydrogen atom, as in 2d, 4, and 6, the nitrogen atom was significantly pyramidalized and the azepine ring was less puckered; the result here was a relatively high energy barrier to N-inversion and a low barrier to ring-flip. In these N-unsubstituted compounds, it was found computationally that the lowest-energy stereodynamic process was ring-flip coupled with N-inversion, as N-inversion alone had a much higher energy barrier.

  12. An Inverse Modeling Plugin for HydroDesktop using the Method of Anchored Distributions (MAD)

    NASA Astrophysics Data System (ADS)

    Ames, D. P.; Osorio, C.; Over, M. W.; Rubin, Y.

    2011-12-01

    The CUAHSI Hydrologic Information System (HIS) software stack is based on an open and extensible architecture that facilitates the addition of new functions and capabilities at both the server side (using HydroServer) and the client side (using HydroDesktop). The HydroDesktop client plugin architecture is used here to expose a new scripting based plugin that makes use of the R statistics software as a means for conducting inverse modeling using the Method of Anchored Distributions (MAD). MAD is a Bayesian inversion technique for conditioning computational model parameters on relevant field observations yielding probabilistic distributions of the model parameters, related to the spatial random variable of interest, by assimilating multi-type and multi-scale data. The implementation of a desktop software tool for using the MAD technique is expected to significantly lower the barrier to use of inverse modeling in education, research, and resource management. The HydroDesktop MAD plugin is being developed following a community-based, open-source approach that will help both its adoption and long term sustainability as a user tool. This presentation will briefly introduce MAD, HydroDesktop, and the MAD plugin and software development effort.

  13. GePb Alloy Growth Using Layer Inversion Method

    NASA Astrophysics Data System (ADS)

    Alahmad, Hakimah; Mosleh, Aboozar; Alher, Murtadha; Banihashemian, Seyedeh Fahimeh; Ghetmiri, Seyed Amir; Al-Kabi, Sattar; Du, Wei; Li, Bauhoa; Yu, Shui-Qing; Naseem, Hameed A.

    2018-04-01

    Germanium-lead films have been investigated as a new direct-bandgap group IV alloy. GePb films were deposited on Si via thermal evaporation of Ge and Pb solid sources using the layer inversion metal-induced crystallization method for comparison with the current laser-induced recrystallization method. Material characterization of the films using x-ray diffraction analysis revealed highly oriented crystallinity and Pb incorporation as high as 13.5% before and 5.2% after annealing. Transmission electron microscopy, scanning electron microscopy, and energy-dispersive x-ray mapping of the samples revealed uniform incorporation of elements and complete layer inversion. Optical characterization of the GePb films by Raman spectroscopy and photoluminescence techniques showed that annealing the samples resulted in higher crystalline quality as well as bandgap reduction. The bandgap reduction from 0.67 eV to 0.547 eV observed for the highest-quality material confirms the achievement of a direct-bandgap material.

  14. GePb Alloy Growth Using Layer Inversion Method

    NASA Astrophysics Data System (ADS)

    Alahmad, Hakimah; Mosleh, Aboozar; Alher, Murtadha; Banihashemian, Seyedeh Fahimeh; Ghetmiri, Seyed Amir; Al-Kabi, Sattar; Du, Wei; Li, Bauhoa; Yu, Shui-Qing; Naseem, Hameed A.

    2018-07-01

    Germanium-lead films have been investigated as a new direct-bandgap group IV alloy. GePb films were deposited on Si via thermal evaporation of Ge and Pb solid sources using the layer inversion metal-induced crystallization method for comparison with the current laser-induced recrystallization method. Material characterization of the films using x-ray diffraction analysis revealed highly oriented crystallinity and Pb incorporation as high as 13.5% before and 5.2% after annealing. Transmission electron microscopy, scanning electron microscopy, and energy-dispersive x-ray mapping of the samples revealed uniform incorporation of elements and complete layer inversion. Optical characterization of the GePb films by Raman spectroscopy and photoluminescence techniques showed that annealing the samples resulted in higher crystalline quality as well as bandgap reduction. The bandgap reduction from 0.67 eV to 0.547 eV observed for the highest-quality material confirms the achievement of a direct-bandgap material.

  15. Human inversions and their functional consequences

    PubMed Central

    Puig, Marta; Casillas, Sònia; Villatoro, Sergi

    2015-01-01

    Polymorphic inversions are a type of structural variants that are difficult to analyze owing to their balanced nature and the location of breakpoints within complex repeated regions. So far, only a handful of inversions have been studied in detail in humans and current knowledge about their possible functional effects is still limited. However, inversions have been related to phenotypic changes and adaptation in multiple species. In this review, we summarize the evidences of the functional impact of inversions in the human genome. First, given that inversions have been shown to inhibit recombination in heterokaryotes, chromosomes displaying different orientation are expected to evolve independently and this may lead to distinct gene-expression patterns. Second, inversions have a role as disease-causing mutations both by directly affecting gene structure or regulation in different ways, and by predisposing to other secondary arrangements in the offspring of inversion carriers. Finally, several inversions show signals of being selected during human evolution. These findings illustrate the potential of inversions to have phenotypic consequences also in humans and emphasize the importance of their inclusion in genome-wide association studies. PMID:25998059

  16. On the inversion-indel distance

    PubMed Central

    2013-01-01

    Background The inversion distance, that is the distance between two unichromosomal genomes with the same content allowing only inversions of DNA segments, can be computed thanks to a pioneering approach of Hannenhalli and Pevzner in 1995. In 2000, El-Mabrouk extended the inversion model to allow the comparison of unichromosomal genomes with unequal contents, thus insertions and deletions of DNA segments besides inversions. However, an exact algorithm was presented only for the case in which we have insertions alone and no deletion (or vice versa), while a heuristic was provided for the symmetric case, that allows both insertions and deletions and is called the inversion-indel distance. In 2005, Yancopoulos, Attie and Friedberg started a new branch of research by introducing the generic double cut and join (DCJ) operation, that can represent several genome rearrangements (including inversions). Among others, the DCJ model gave rise to two important results. First, it has been shown that the inversion distance can be computed in a simpler way with the help of the DCJ operation. Second, the DCJ operation originated the DCJ-indel distance, that allows the comparison of genomes with unequal contents, considering DCJ, insertions and deletions, and can be computed in linear time. Results In the present work we put these two results together to solve an open problem, showing that, when the graph that represents the relation between the two compared genomes has no bad components, the inversion-indel distance is equal to the DCJ-indel distance. We also give a lower and an upper bound for the inversion-indel distance in the presence of bad components. PMID:24564182

  17. Some Phenomena on Negative Inversion Constructions

    ERIC Educational Resources Information Center

    Sung, Tae-Soo

    2013-01-01

    We examine the characteristics of NDI (negative degree inversion) and its relation with other inversion phenomena such as SVI (subject-verb inversion) and SAI (subject-auxiliary inversion). The negative element in the NDI construction may be" not," a negative adverbial, or a negative verb. In this respect, NDI has similar licensing…

  18. A general approach to regularizing inverse problems with regional data using Slepian wavelets

    NASA Astrophysics Data System (ADS)

    Michel, Volker; Simons, Frederik J.

    2017-12-01

    Slepian functions are orthogonal function systems that live on subdomains (for example, geographical regions on the Earth’s surface, or bandlimited portions of the entire spectrum). They have been firmly established as a useful tool for the synthesis and analysis of localized (concentrated or confined) signals, and for the modeling and inversion of noise-contaminated data that are only regionally available or only of regional interest. In this paper, we consider a general abstract setup for inverse problems represented by a linear and compact operator between Hilbert spaces with a known singular-value decomposition (svd). In practice, such an svd is often only given for the case of a global expansion of the data (e.g. on the whole sphere) but not for regional data distributions. We show that, in either case, Slepian functions (associated to an arbitrarily prescribed region and the given compact operator) can be determined and applied to construct a regularization for the ill-posed regional inverse problem. Moreover, we describe an algorithm for constructing the Slepian basis via an algebraic eigenvalue problem. The obtained Slepian functions can be used to derive an svd for the combination of the regionalizing projection and the compact operator. As a result, standard regularization techniques relying on a known svd become applicable also to those inverse problems where the data are regionally given only. In particular, wavelet-based multiscale techniques can be used. An example for the latter case is elaborated theoretically and tested on two synthetic numerical examples.

  19. Adjoint Sensitivity Method to Determine Optimal Set of Stations for Tsunami Source Inversion

    NASA Astrophysics Data System (ADS)

    Gusman, A. R.; Hossen, M. J.; Cummins, P. R.; Satake, K.

    2017-12-01

    We applied the adjoint sensitivity technique in tsunami science for the first time to determine an optimal set of stations for a tsunami source inversion. The adjoint sensitivity (AS) method has been used in numerical weather prediction to find optimal locations for adaptive observations. We implemented this technique to Green's Function based Time Reverse Imaging (GFTRI), which is recently used in tsunami source inversion in order to reconstruct the initial sea surface displacement, known as tsunami source model. This method has the same source representation as the traditional least square (LSQ) source inversion method where a tsunami source is represented by dividing the source region into a regular grid of "point" sources. For each of these, Green's function (GF) is computed using a basis function for initial sea surface displacement whose amplitude is concentrated near the grid point. We applied the AS method to the 2009 Samoa earthquake tsunami that occurred on 29 September 2009 in the southwest Pacific, near the Tonga trench. Many studies show that this earthquake is a doublet associated with both normal faulting in the outer-rise region and thrust faulting in the subduction interface. To estimate the tsunami source model for this complex event, we initially considered 11 observations consisting of 5 tide gauges and 6 DART bouys. After implementing AS method, we found the optimal set of observations consisting with 8 stations. Inversion with this optimal set provides better result in terms of waveform fitting and source model that shows both sub-events associated with normal and thrust faulting.

  20. An inverse problem for a semilinear parabolic equation arising from cardiac electrophysiology

    NASA Astrophysics Data System (ADS)

    Beretta, Elena; Cavaterra, Cecilia; Cerutti, M. Cristina; Manzoni, Andrea; Ratti, Luca

    2017-10-01

    In this paper we develop theoretical analysis and numerical reconstruction techniques for the solution of an inverse boundary value problem dealing with the nonlinear, time-dependent monodomain equation, which models the evolution of the electric potential in the myocardial tissue. The goal is the detection of an inhomogeneity \

  1. Spin model for nontrivial types of magnetic order in inverse-perovskite antiferromagnets

    NASA Astrophysics Data System (ADS)

    Mochizuki, Masahito; Kobayashi, Masaya; Okabe, Reoya; Yamamoto, Daisuke

    2018-02-01

    Nontrivial magnetic orders in the inverse-perovskite manganese nitrides are theoretically studied by constructing a classical spin model describing the magnetic anisotropy and frustrated exchange interactions inherent in specific crystal and electronic structures of these materials. With a replica-exchange Monte Carlo technique, a theoretical analysis of this model reproduces the experimentally observed triangular Γ5 g and Γ4 g spin-ordered patterns and the systematic evolution of magnetic orders. Our Rapid Communication solves a 40-year-old problem of nontrivial magnetism for the inverse-perovskite manganese nitrides and provides a firm basis for clarifying the magnetism-driven negative thermal expansion phenomenon discovered in this class of materials.

  2. Recursive inverse factorization.

    PubMed

    Rubensson, Emanuel H; Bock, Nicolas; Holmström, Erik; Niklasson, Anders M N

    2008-03-14

    A recursive algorithm for the inverse factorization S(-1)=ZZ(*) of Hermitian positive definite matrices S is proposed. The inverse factorization is based on iterative refinement [A.M.N. Niklasson, Phys. Rev. B 70, 193102 (2004)] combined with a recursive decomposition of S. As the computational kernel is matrix-matrix multiplication, the algorithm can be parallelized and the computational effort increases linearly with system size for systems with sufficiently sparse matrices. Recent advances in network theory are used to find appropriate recursive decompositions. We show that optimization of the so-called network modularity results in an improved partitioning compared to other approaches. In particular, when the recursive inverse factorization is applied to overlap matrices of irregularly structured three-dimensional molecules.

  3. Exploring the origin of a large cavity in Abell 1795 using deep Chandra observations

    NASA Astrophysics Data System (ADS)

    Walker, S. A.; Fabian, A. C.; Kosec, P.

    2014-12-01

    We examine deep stacked Chandra observations of the galaxy cluster Abell 1795 (over 700 ks) to study in depth a large (34 kpc radius) cavity in the X-ray emission. Curiously, despite the large energy required to form this cavity (4PV = 4 × 1060 erg), there is no obvious counterpart to the cavity on the opposite side of the cluster, which would be expected if it has formed due to jets from the central active galactic nucleus (AGN) inflating bubbles. There is also no radio emission associated with the cavity, and no metal enhancement or filaments between it and the brightest cluster galaxy, which are normally found for bubbles inflated by AGN which have risen from the core. One possibility is that this is an old ghost cavity, and that gas sloshing has dominated the distribution of metals around the core. Projection effects, particularly the long X-ray bright filament to the south-east, may prevent us from seeing the companion bubble on the opposite side of the cluster core. We calculate that such a companion bubble would easily have been able to uplift the gas in the southern filament from the core. Interestingly, it has recently been found that inside the cavity is a highly variable X-ray point source coincident with a small dwarf galaxy. Given the remarkable spatial correlation of this point source and the X-ray cavity, we explore the possibility that an outburst from this dwarf galaxy in the past could have led to the formation of the cavity, but find this to be an unlikely scenario.

  4. Automatic 3D Moment tensor inversions for southern California earthquakes

    NASA Astrophysics Data System (ADS)

    Liu, Q.; Tape, C.; Friberg, P.; Tromp, J.

    2008-12-01

    We present a new source mechanism (moment-tensor and depth) catalog for about 150 recent southern California earthquakes with Mw ≥ 3.5. We carefully select the initial solutions from a few available earthquake catalogs as well as our own preliminary 3D moment tensor inversion results. We pick useful data windows by assessing the quality of fits between the data and synthetics using an automatic windowing package FLEXWIN (Maggi et al 2008). We compute the source Fréchet derivatives of moment-tensor elements and depth for a recent 3D southern California velocity model inverted based upon finite-frequency event kernels calculated by the adjoint methods and a nonlinear conjugate gradient technique with subspace preconditioning (Tape et al 2008). We then invert for the source mechanisms and event depths based upon the techniques introduced by Liu et al 2005. We assess the quality of this new catalog, as well as the other existing ones, by computing the 3D synthetics for the updated 3D southern California model. We also plan to implement the moment-tensor inversion methods to automatically determine the source mechanisms for earthquakes with Mw ≥ 3.5 in southern California.

  5. Bayesian Inversion of 2D Models from Airborne Transient EM Data

    NASA Astrophysics Data System (ADS)

    Blatter, D. B.; Key, K.; Ray, A.

    2016-12-01

    The inherent non-uniqueness in most geophysical inverse problems leads to an infinite number of Earth models that fit observed data to within an adequate tolerance. To resolve this ambiguity, traditional inversion methods based on optimization techniques such as the Gauss-Newton and conjugate gradient methods rely on an additional regularization constraint on the properties that an acceptable model can possess, such as having minimal roughness. While allowing such an inversion scheme to converge on a solution, regularization makes it difficult to estimate the uncertainty associated with the model parameters. This is because regularization biases the inversion process toward certain models that satisfy the regularization constraint and away from others that don't, even when both may suitably fit the data. By contrast, a Bayesian inversion framework aims to produce not a single `most acceptable' model but an estimate of the posterior likelihood of the model parameters, given the observed data. In this work, we develop a 2D Bayesian framework for the inversion of transient electromagnetic (TEM) data. Our method relies on a reversible-jump Markov Chain Monte Carlo (RJ-MCMC) Bayesian inverse method with parallel tempering. Previous gradient-based inversion work in this area used a spatially constrained scheme wherein individual (1D) soundings were inverted together and non-uniqueness was tackled by using lateral and vertical smoothness constraints. By contrast, our work uses a 2D model space of Voronoi cells whose parameterization (including number of cells) is fully data-driven. To make the problem work practically, we approximate the forward solution for each TEM sounding using a local 1D approximation where the model is obtained from the 2D model by retrieving a vertical profile through the Voronoi cells. The implicit parsimony of the Bayesian inversion process leads to the simplest models that adequately explain the data, obviating the need for explicit smoothness

  6. Obtaining valid geologic models from 3-D resistivity inversion of magnetotelluric data at Pahute Mesa, Nevada

    USGS Publications Warehouse

    Rodriguez, Brian D.; Sweetkind, Donald S.

    2015-01-01

    The 3-D inversion was generally able to reproduce the gross resistivity structure of the “known” model, but the simulated conductive volcanic composite unit horizons were often too shallow when compared to the “known” model. Additionally, the chosen computation parameters such as station spacing appear to have resulted in computational artifacts that are difficult to interpret but could potentially be removed with further refinements of the 3-D resistivity inversion modeling technique.

  7. The Inverse Problem for Confined Aquifer Flow: Identification and Estimation With Extensions

    NASA Astrophysics Data System (ADS)

    Loaiciga, Hugo A.; MariñO, Miguel A.

    1987-01-01

    The contributions of this work are twofold. First, a methodology for estimating the elements of parameter matrices in the governing equation of flow in a confined aquifer is developed. The estimation techniques for the distributed-parameter inverse problem pertain to linear least squares and generalized least squares methods. The linear relationship among the known heads and unknown parameters of the flow equation provides the background for developing criteria for determining the identifiability status of unknown parameters. Under conditions of exact or overidentification it is possible to develop statistically consistent parameter estimators and their asymptotic distributions. The estimation techniques, namely, two-stage least squares and three stage least squares, are applied to a specific groundwater inverse problem and compared between themselves and with an ordinary least squares estimator. The three-stage estimator provides the closer approximation to the actual parameter values, but it also shows relatively large standard errors as compared to the ordinary and two-stage estimators. The estimation techniques provide the parameter matrices required to simulate the unsteady groundwater flow equation. Second, a nonlinear maximum likelihood estimation approach to the inverse problem is presented. The statistical properties of maximum likelihood estimators are derived, and a procedure to construct confidence intervals and do hypothesis testing is given. The relative merits of the linear and maximum likelihood estimators are analyzed. Other topics relevant to the identification and estimation methodologies, i.e., a continuous-time solution to the flow equation, coping with noise-corrupted head measurements, and extension of the developed theory to nonlinear cases are also discussed. A simulation study is used to evaluate the methods developed in this study.

  8. A pericentric inversion of chromosome X disrupting F8 and resulting in haemophilia A.

    PubMed

    Xin, Yu; Zhou, Jingyi; Ding, Qiulan; Chen, Changming; Wu, Xi; Wang, Xuefeng; Wang, Hongli; Jiang, Xiaofeng

    2017-08-01

    The frequency of X chromosome pericentric inversion is much less than that of autosome chromosome. We hereby characterise a pericentric inversion of X chromosome associated with severe factor VIII (FVIII) deficiency in a sporadic haemophilia A (HA) pedigree. PCR primer walking and genome walking strategies were adopted to identify the exact breakpoints of the inversion. Copy number variations (CNVs) of the F8 and the whole chromosomes were detected by AccuCopy and Affymetrix CytoScan High Definition (HD) assays, respectively. A karyotype analysis was performed by cytogenetic G banding technique. We identified a previously undescribed type of pericentric inversion of the X chromosome [inv(X)(p11.21q28)] in the proband with FVIII:C <1%. One breakpoint was located in the intron 7 of the F 8, which disrupted the transcription of the F8, and the other located in the upstream of the PFKFB1 of the X chromosome. The inversion segment was approximately 64.4% of the total chromosomal length. The karyotype analysis of the X chromosome confirmed the pericentric inversion of the X chromosome in the proband and his mother. A haplotype analysis traced the inversion to his maternal grandfather, who was not a somatic mosaic of the inversion. This finding indicated that the causative mutation may originate from his germ cells or a rare possibility of germ-cell mosaicism. The characterisation of pericentric inversion involving F8 extended the molecular mechanisms causing HA. The pericentric inversion rearrangement involves F8 by non-homologous end joining is responsible for pathogensis of severe HA. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

  9. Uniform Contribution of Supernova Explosions to the Chemical Enrichment of Abell 3112 out to R{sub 200}

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ezer, Cemile; Ercan, E. Nihal; Bulbul, Esra

    2017-02-10

    The spatial distribution of the metals residing in the intra-cluster medium (ICM) of galaxy clusters records all the information on a cluster’s nucleosynthesis and chemical enrichment history. We present measurements from a total of 1.2 Ms Suzaku XIS and 72 ks Chandra observations of the cool-core galaxy cluster Abell 3112 out to its virial radius (∼1470 kpc). We find that the ratio of the observed supernova type Ia explosions to the total supernova explosions has a uniform distribution at a level of 12%–16% out to the cluster’s virial radius. The observed fraction of type Ia supernova explosions is in agreementmore » with the corresponding fraction found in our Galaxy and the chemical enrichment of our Galaxy. The non-varying supernova enrichment suggests that the ICM in cluster outskirts was enriched by metals at an early stage before the cluster itself was formed during a period of intense star formation activity. Additionally, we find that the 2D delayed detonation model CDDT produce significantly worse fits to the X-ray spectra compared to simple 1D W7 models. This is due to the relative overestimate of Si, and the underestimate of Mg in these models with respect to the measured abundances.« less

  10. Time domain localization technique with sparsity constraint for imaging acoustic sources

    NASA Astrophysics Data System (ADS)

    Padois, Thomas; Doutres, Olivier; Sgard, Franck; Berry, Alain

    2017-09-01

    This paper addresses source localization technique in time domain for broadband acoustic sources. The objective is to accurately and quickly detect the position and amplitude of noise sources in workplaces in order to propose adequate noise control options and prevent workers hearing loss or safety risk. First, the generalized cross correlation associated with a spherical microphone array is used to generate an initial noise source map. Then a linear inverse problem is defined to improve this initial map. Commonly, the linear inverse problem is solved with an l2 -regularization. In this study, two sparsity constraints are used to solve the inverse problem, the orthogonal matching pursuit and the truncated Newton interior-point method. Synthetic data are used to highlight the performances of the technique. High resolution imaging is achieved for various acoustic sources configurations. Moreover, the amplitudes of the acoustic sources are correctly estimated. A comparison of computation times shows that the technique is compatible with quasi real-time generation of noise source maps. Finally, the technique is tested with real data.

  11. On the dosimetric effect and reduction of inverse consistency and transitivity errors in deformable image registration for dose accumulation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bender, Edward T.; Hardcastle, Nicholas; Tome, Wolfgang A.

    2012-01-15

    Purpose: Deformable image registration (DIR) is necessary for accurate dose accumulation between multiple radiotherapy image sets. DIR algorithms can suffer from inverse and transitivity inconsistencies. When using deformation vector fields (DVFs) that exhibit inverse-inconsistency and are nontransitive, dose accumulation on a given image set via different image pathways will lead to different accumulated doses. The purpose of this study was to investigate the dosimetric effect of and propose a postprocessing solution to reduce inverse consistency and transitivity errors. Methods: Four MVCT images and four phases of a lung 4DCT, each with an associated calculated dose, were selected for analysis. DVFsmore » between all four images in each data set were created using the Fast Symmetric Demons algorithm. Dose was accumulated on the fourth image in each set using DIR via two different image pathways. The two accumulated doses on the fourth image were compared. The inverse consistency and transitivity errors in the DVFs were then reduced. The dose accumulation was repeated using the processed DVFs, the results of which were compared with the accumulated dose from the original DVFs. To evaluate the influence of the postprocessing technique on DVF accuracy, the original and processed DVF accuracy was evaluated on the lung 4DCT data on which anatomical landmarks had been identified by an expert. Results: Dose accumulation to the same image via different image pathways resulted in two different accumulated dose results. After the inverse consistency errors were reduced, the difference between the accumulated doses diminished. The difference was further reduced after reducing the transitivity errors. The postprocessing technique had minimal effect on the accuracy of the DVF for the lung 4DCT images. Conclusions: This study shows that inverse consistency and transitivity errors in DIR have a significant dosimetric effect in dose accumulation; Depending on the image pathway

  12. Identification of polymorphic inversions from genotypes

    PubMed Central

    2012-01-01

    Background Polymorphic inversions are a source of genetic variability with a direct impact on recombination frequencies. Given the difficulty of their experimental study, computational methods have been developed to infer their existence in a large number of individuals using genome-wide data of nucleotide variation. Methods based on haplotype tagging of known inversions attempt to classify individuals as having a normal or inverted allele. Other methods that measure differences between linkage disequilibrium attempt to identify regions with inversions but unable to classify subjects accurately, an essential requirement for association studies. Results We present a novel method to both identify polymorphic inversions from genome-wide genotype data and classify individuals as containing a normal or inverted allele. Our method, a generalization of a published method for haplotype data [1], utilizes linkage between groups of SNPs to partition a set of individuals into normal and inverted subpopulations. We employ a sliding window scan to identify regions likely to have an inversion, and accumulation of evidence from neighboring SNPs is used to accurately determine the inversion status of each subject. Further, our approach detects inversions directly from genotype data, thus increasing its usability to current genome-wide association studies (GWAS). Conclusions We demonstrate the accuracy of our method to detect inversions and classify individuals on principled-simulated genotypes, produced by the evolution of an inversion event within a coalescent model [2]. We applied our method to real genotype data from HapMap Phase III to characterize the inversion status of two known inversions within the regions 17q21 and 8p23 across 1184 individuals. Finally, we scan the full genomes of the European Origin (CEU) and Yoruba (YRI) HapMap samples. We find population-based evidence for 9 out of 15 well-established autosomic inversions, and for 52 regions previously predicted by

  13. Inverse-collimated proton radiography for imaging thin materials

    DOE PAGES

    Freeman, Matthew S.; Allison, Jason; Andrews, Malcolm; ...

    2017-01-01

    Relativistic, magnetically-focused proton radiography was invented at Los Alamos National Laboratory using the 800 MeV LANSCE beam, and is inherently well-suited to imaging dense objects, at areal densities >20 g cm -2. However, if the unscattered portion of the transmitted beam is removed at the Fourier plane through inverse-collimation, this system becomes highly sensitive to very thin media, of areal densities <100 mg cm -2. Here, this inversecollimation scheme is described in detail and demonstrated by imaging Xe gas with a shockwave generated by an aluminum plate compressing the gas at Mach 8.8. With a 5-mrad inverse collimator, an arealmore » density change of just 49 mg cm-2 across the shock front is discernible with a contrast-to-noise ratio of 3. Geant4 modeling of idealized and realistic proton transports can guide the design of inverse-collimators optimized for specific experimental conditions and show that this technique performs better for thin targets with reduced incident proton beam emittance. This work increases the range of areal densities to which the system is sensitive to span from ~25 mg cm -2 to 100 g cm -2, exceeding three orders of magnitude. This enables the simultaneous imaging of a dense system, as well as thin jets and ejecta material that are otherwise difficult to characterize with high-energy proton radiography.« less

  14. Genotyping the factor VIII intron 22 inversion locus using fluorescent in situ hybridization.

    PubMed

    Sheen, Campbell R; McDonald, Margaret A; George, Peter M; Smith, Mark P; Morris, Christine M

    2011-02-15

    The factor VIII intron 22 inversion is the most common cause of hemophilia A, accounting for approximately 40% of all severe cases of the disease. Southern hybridization and multiplex long distance PCR are the most commonly used techniques to detect the inversion in a diagnostic setting, although both have significant limitations. Here we describe our experience establishing a multicolor fluorescent in situ hybridization (FISH) based assay as an alternative to existing methods for genetic diagnosis of the inversion. Our assay was designed to apply three differentially labelled BAC DNA probes that when hybridized to interphase nuclei would exhibit signal patterns that are consistent with the normal or the inversion locus. When the FISH assay was applied to five normal and five inversion male samples, the correct genotype was assignable with p<0.001 for all samples. When applied to carrier female samples the assay could not assign a genotype to all female samples, probably due to a lower proportion of informative nuclei in female samples caused by the added complexity of a second X chromosome. Despite this complication, these pilot findings show that the assay performs favourably compared to the commonly used methods. Copyright © 2010 Elsevier Inc. All rights reserved.

  15. Double point source W-phase inversion: Real-time implementation and automated model selection

    USGS Publications Warehouse

    Nealy, Jennifer; Hayes, Gavin

    2015-01-01

    Rapid and accurate characterization of an earthquake source is an extremely important and ever evolving field of research. Within this field, source inversion of the W-phase has recently been shown to be an effective technique, which can be efficiently implemented in real-time. An extension to the W-phase source inversion is presented in which two point sources are derived to better characterize complex earthquakes. A single source inversion followed by a double point source inversion with centroid locations fixed at the single source solution location can be efficiently run as part of earthquake monitoring network operational procedures. In order to determine the most appropriate solution, i.e., whether an earthquake is most appropriately described by a single source or a double source, an Akaike information criterion (AIC) test is performed. Analyses of all earthquakes of magnitude 7.5 and greater occurring since January 2000 were performed with extended analyses of the September 29, 2009 magnitude 8.1 Samoa earthquake and the April 19, 2014 magnitude 7.5 Papua New Guinea earthquake. The AIC test is shown to be able to accurately select the most appropriate model and the selected W-phase inversion is shown to yield reliable solutions that match published analyses of the same events.

  16. Chemical Source Inversion using Assimilated Constituent Observations in an Idealized Two-dimensional System

    NASA Technical Reports Server (NTRS)

    Tangborn, Andrew; Cooper, Robert; Pawson, Steven; Sun, Zhibin

    2009-01-01

    We present a source inversion technique for chemical constituents that uses assimilated constituent observations rather than directly using the observations. The method is tested with a simple model problem, which is a two-dimensional Fourier-Galerkin transport model combined with a Kalman filter for data assimilation. Inversion is carried out using a Green's function method and observations are simulated from a true state with added Gaussian noise. The forecast state uses the same spectral spectral model, but differs by an unbiased Gaussian model error, and emissions models with constant errors. The numerical experiments employ both simulated in situ and satellite observation networks. Source inversion was carried out by either direct use of synthetically generated observations with added noise, or by first assimilating the observations and using the analyses to extract observations. We have conducted 20 identical twin experiments for each set of source and observation configurations, and find that in the limiting cases of a very few localized observations, or an extremely large observation network there is little advantage to carrying out assimilation first. However, in intermediate observation densities, there decreases in source inversion error standard deviation using the Kalman filter algorithm followed by Green's function inversion by 50% to 95%.

  17. Recombination rate predicts inversion size in Diptera.

    PubMed Central

    Cáceres, M; Barbadilla, A; Ruiz, A

    1999-01-01

    Most species of the Drosophila genus and other Diptera are polymorphic for paracentric inversions. A common observation is that successful inversions are of intermediate size. We test here the hypothesis that the selected property is the recombination length of inversions, not their physical length. If so, physical length of successful inversions should be negatively correlated with recombination rate across species. This prediction was tested by a comprehensive statistical analysis of inversion size and recombination map length in 12 Diptera species for which appropriate data are available. We found that (1) there is a wide variation in recombination map length among species; (2) physical length of successful inversions varies greatly among species and is inversely correlated with the species recombination map length; and (3) neither the among-species variation in inversion length nor the correlation are observed in unsuccessful inversions. The clear differences between successful and unsuccessful inversions point to natural selection as the most likely explanation for our results. Presumably the selective advantage of an inversion increases with its length, but so does its detrimental effect on fertility due to double crossovers. Our analysis provides the strongest and most extensive evidence in favor of the notion that the adaptive value of inversions stems from their effect on recombination. PMID:10471710

  18. A Strassen-Newton algorithm for high-speed parallelizable matrix inversion

    NASA Technical Reports Server (NTRS)

    Bailey, David H.; Ferguson, Helaman R. P.

    1988-01-01

    Techniques are described for computing matrix inverses by algorithms that are highly suited to massively parallel computation. The techniques are based on an algorithm suggested by Strassen (1969). Variations of this scheme use matrix Newton iterations and other methods to improve the numerical stability while at the same time preserving a very high level of parallelism. One-processor Cray-2 implementations of these schemes range from one that is up to 55 percent faster than a conventional library routine to one that is slower than a library routine but achieves excellent numerical stability. The problem of computing the solution to a single set of linear equations is discussed, and it is shown that this problem can also be solved efficiently using these techniques.

  19. A fast new algorithm for a robot neurocontroller using inverse QR decomposition

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Morris, A.S.; Khemaissia, S.

    2000-01-01

    A new adaptive neural network controller for robots is presented. The controller is based on direct adaptive techniques. Unlike many neural network controllers in the literature, inverse dynamical model evaluation is not required. A numerically robust, computationally efficient processing scheme for neutral network weight estimation is described, namely, the inverse QR decomposition (INVQR). The inverse QR decomposition and a weighted recursive least-squares (WRLS) method for neural network weight estimation is derived using Cholesky factorization of the data matrix. The algorithm that performs the efficient INVQR of the underlying space-time data matrix may be implemented in parallel on a triangular array.more » Furthermore, its systolic architecture is well suited for VLSI implementation. Another important benefit is well suited for VLSI implementation. Another important benefit of the INVQR decomposition is that it solves directly for the time-recursive least-squares filter vector, while avoiding the sequential back-substitution step required by the QR decomposition approaches.« less

  20. Using emulsion inversion in industrial processes.

    PubMed

    Salager, Jean-Louis; Forgiarini, Ana; Márquez, Laura; Peña, Alejandro; Pizzino, Aldo; Rodriguez, María P; Rondón-González, Marianna

    2004-05-20

    Emulsion inversion is a complex phenomenon, often perceived as an instability that is essentially uncontrollable, although many industrial processes make use of it. A research effort that started 2 decades ago has provided the two-dimensional and three-dimensional description, the categorization and the theoretical interpretation of the different kinds of emulsion inversion. A clear-cut phenomenological approach is currently available for understanding its characteristics, the factors that influence it and control it, the importance of fine-tuning the emulsification protocol, and the crucial occurrence of organized structures such as liquid crystals or multiple emulsions. The current know-how is used to analyze some industrial processes involving emulsion inversion, e.g. the attainment of a fine nutrient or cosmetic emulsion by temperature or formulation-induced transitional inversion, the preparation of a silicone oil emulsion by catastrophic phase inversion, the manufacture of a viscous polymer latex by combined inversion and the spontaneous but enigmatic inversion of emulsions used in metal working operations such as lathing or lamination.

  1. Tomography of a simply magnetized toroidal plasma

    NASA Astrophysics Data System (ADS)

    Ruggero, BARNI; Stefano, CALDIROLA; Luca, FATTORINI; Claudia, RICCARDI

    2018-02-01

    Optical emission spectroscopy is a passive diagnostic technique, which does not perturb the plasma state. In particular, in a hydrogen plasma, Balmer-alpha (H α ) emission can be easily measured in the visible range along a line of sight from outside the plasma vessel. Other emission lines in the visible spectral range from hydrogen atoms and molecules can be exploited too, in order to gather complementary pieces of information on the plasma state. Tomography allows us to capture bi-dimensional structures. We propose to adopt an emission spectroscopy tomography for studying the transverse profiles of magnetized plasmas when Abel inversion is not exploitable. An experimental campaign was carried out at the Thorello device, a simple magnetized torus. The characteristics of the profile extraction method, which we implemented for this purpose are discussed, together with a few results concerning the plasma profiles in a simply magnetized torus configuration.

  2. Study of multilayer thermal insulation by inverse problems method

    NASA Astrophysics Data System (ADS)

    Alifanov, O. M.; Nenarokomov, A. V.; Gonzalez, V. M.

    2009-11-01

    The purpose of this paper is to introduce a new method in the research of radiative and thermal properties of materials with further applications in the design of thermal control systems (TCS) of spacecrafts. In this paper the radiative and thermal properties (emissivity and thermal conductance) of a multilayered thermal-insulating blanket (MLI), which is a screen-vacuum thermal insulation as a part of the TCS for perspective spacecrafts, are estimated. Properties of the materials under study are determined in the result of temperature and heat flux measurement data processing based on the solution of the inverse heat transfer problem (IHTP) technique. Given are physical and mathematical models of heat transfer processes in a specimen of the multilayered thermal-insulating blanket located in the experimental facility. A mathematical formulation of the inverse heat conduction problem is presented as well. The practical approves were made for specimen of the real MLI.

  3. Magnetic topology of Co-based inverse opal-like structures

    NASA Astrophysics Data System (ADS)

    Grigoryeva, N. A.; Mistonov, A. A.; Napolskii, K. S.; Sapoletova, N. A.; Eliseev, A. A.; Bouwman, W.; Byelov, D. V.; Petukhov, A. V.; Chernyshov, D. Yu.; Eckerlebe, H.; Vasilieva, A. V.; Grigoriev, S. V.

    2011-08-01

    The magnetic and structural properties of a cobalt inverse opal-like crystal have been studied by a combination of complementary techniques ranging from polarized neutron scattering and superconducting quantum interference device (SQUID) magnetometry to x-ray diffraction. Microradian small-angle x-ray diffraction shows that the inverse opal-like structure (OLS) synthesized by the electrochemical method fully duplicates the three-dimensional net of voids of the template artificial opal. The inverse OLS has a face-centered cubic (fcc) structure with a lattice constant of 640±10 nm and with a clear tendency to a random hexagonal close-packed structure along the [111] axes. Wide-angle x-ray powder diffraction shows that the atomic cobalt structure is described by coexistence of 95% hexagonal close-packed and 5% fcc phases. The SQUID measurements demonstrate that the inverse OLS film possesses easy-plane magnetization geometry with a coercive field of 14.0 ± 0.5 mT at room temperature. The detailed picture of the transformation of the magnetic structure under an in-plane applied field was detected with the help of small-angle diffraction of polarized neutrons. In the demagnetized state the magnetic system consists of randomly oriented magnetic domains. A complex magnetic structure appears upon application of the magnetic field, with nonhomogeneous distribution of magnetization density within the unit element of the OLS. This distribution is determined by the combined effect of the easy-plane geometry of the film and the crystallographic geometry of the opal-like structure with respect to the applied field direction.

  4. Inversion of Airborne Electromagnetic Data: Application to Oil Sands Exploration

    NASA Astrophysics Data System (ADS)

    Cristall, J.; Farquharson, C. G.; Oldenburg, D. W.

    2004-05-01

    In general, three-dimensional inversion of airborne electromagnetic data for models of the conductivity variation in the Earth is currently impractical because of the large amount of computation time that it requires. At the other extreme, one-dimensional imaging techniques based on transforming the observed data as a function of measurement time or frequency at each location to values of conductivity as a function of depth are very fast. Such techniques can provide an image that, in many circumstances, is a fair, qualitative representation of the subsurface. However, this is not the same as a model that is known to reproduce the observations to a level considered appropriate for the noise in the data. This makes it hard to assess the quality and reliability of the images produced by the transform techniques until other information such as bore-hole logs is obtained. A compromise between these two interpretation strategies is to retain the approximation of a one-dimensional variation of conductivity beneath each observation location, but to invert the corresponding data as functions of time or frequency, taking advantage of all available aspects of inversion methodology. For example, using an automatic method such as the GCV or L-curve criteria for determining how well to fit a set of data when the actual amount of noise is not known, even when there are clear multi-dimensional effects in the data; using something other than a sum-of-squares measure for the misfit, for example the Huber M-measure, which affords a robust fit to data that contain non-Gaussian noise; and using an l1-norm or similar measure of model structure that enables piecewise constant, blocky models to be constructed. These features, as well as the basic concepts of minimum-structure inversion, result in a flexible and powerful interpretation procedure that, because of the one-dimensional approximation, is sufficiently rapid to be a viable alternative to the imaging techniques presently in use

  5. Validation of ionospheric electron density profiles inferred from GPS occultation observations of the GPS/MET experiment

    NASA Astrophysics Data System (ADS)

    Kawakami, Todd Mori

    In April of 1995, the launch of the GPS Meteorology Experiment (GPS/MET) onboard the Orbview-1 satellite, formerly known as Microlab-1, provided the first technology demonstration of active limb sounding of the Earth's atmosphere with a low Earth orbiting spacecraft utilizing the signals transmitted by the satellites of the Global Positioning System (GPS). Though the experiment's primary mission was to probe the troposphere and stratosphere, GPS/MET was also capable of making radio occultation observations of the ionosphere. The application of the GPS occultation technique to the upper atmosphere created a unique opportunity to conduct ionospheric research with an unprecedented global distribution of observations. For operational support requirements, the Abel transform could be employed to invert the horizontal TEC profiles computed from the L1 and L2 phase measurements observed by GPS/MET into electron density profiles versus altitude in near real time. The usefulness of the method depends on how effectively the TEC limb profiles can be transformed into vertical electron density profiles. An assessment of GPS/MET's ability to determine electron density profiles needs to be examined to validate the significance of the GPS occultation method as a new and complementary ionospheric research tool to enhance the observational databases and improve space weather modeling and forecasting. To that end, simulations of the occultation observations and their inversions have been conducted to test the Abel transform algorithm and to provide qualitative information about the type and range of errors that might be experienced during the processing of real data. Comparisons of the electron density profiles inferred from real GPS/MET observations are then compared with coincident in situ measurements from the satellites of Defense Meteorological Satellite Program (DMSP) and ground-based remote sensing from digisonde and incoherent scatter radar facilities. The principal focus of

  6. A trade-off solution between model resolution and covariance in surface-wave inversion

    USGS Publications Warehouse

    Xia, J.; Xu, Y.; Miller, R.D.; Zeng, C.

    2010-01-01

    Regularization is necessary for inversion of ill-posed geophysical problems. Appraisal of inverse models is essential for meaningful interpretation of these models. Because uncertainties are associated with regularization parameters, extra conditions are usually required to determine proper parameters for assessing inverse models. Commonly used techniques for assessment of a geophysical inverse model derived (generally iteratively) from a linear system are based on calculating the model resolution and the model covariance matrices. Because the model resolution and the model covariance matrices of the regularized solutions are controlled by the regularization parameter, direct assessment of inverse models using only the covariance matrix may provide incorrect results. To assess an inverted model, we use the concept of a trade-off between model resolution and covariance to find a proper regularization parameter with singular values calculated in the last iteration. We plot the singular values from large to small to form a singular value plot. A proper regularization parameter is normally the first singular value that approaches zero in the plot. With this regularization parameter, we obtain a trade-off solution between model resolution and model covariance in the vicinity of a regularized solution. The unit covariance matrix can then be used to calculate error bars of the inverse model at a resolution level determined by the regularization parameter. We demonstrate this approach with both synthetic and real surface-wave data. ?? 2010 Birkh??user / Springer Basel AG.

  7. Invariant-Based Inverse Engineering of Crane Control Parameters

    NASA Astrophysics Data System (ADS)

    González-Resines, S.; Guéry-Odelin, D.; Tobalina, A.; Lizuain, I.; Torrontegui, E.; Muga, J. G.

    2017-11-01

    By applying invariant-based inverse engineering in the small-oscillation regime, we design the time dependence of the control parameters of an overhead crane (trolley displacement and rope length) to transport a load between two positions at different heights with minimal final-energy excitation for a microcanonical ensemble of initial conditions. The analogy between ion transport in multisegmented traps or neutral-atom transport in moving optical lattices and load manipulation by cranes opens a route for a useful transfer of techniques among very different fields.

  8. MATLAB Simulation of Gradient-Based Neural Network for Online Matrix Inversion

    NASA Astrophysics Data System (ADS)

    Zhang, Yunong; Chen, Ke; Ma, Weimu; Li, Xiao-Dong

    This paper investigates the simulation of a gradient-based recurrent neural network for online solution of the matrix-inverse problem. Several important techniques are employed as follows to simulate such a neural system. 1) Kronecker product of matrices is introduced to transform a matrix-differential-equation (MDE) to a vector-differential-equation (VDE); i.e., finally, a standard ordinary-differential-equation (ODE) is obtained. 2) MATLAB routine "ode45" is introduced to solve the transformed initial-value ODE problem. 3) In addition to various implementation errors, different kinds of activation functions are simulated to show the characteristics of such a neural network. Simulation results substantiate the theoretical analysis and efficacy of the gradient-based neural network for online constant matrix inversion.

  9. pyGIMLi: An open-source library for modelling and inversion in geophysics

    NASA Astrophysics Data System (ADS)

    Rücker, Carsten; Günther, Thomas; Wagner, Florian M.

    2017-12-01

    Many tasks in applied geosciences cannot be solved by single measurements, but require the integration of geophysical, geotechnical and hydrological methods. Numerical simulation techniques are essential both for planning and interpretation, as well as for the process understanding of modern geophysical methods. These trends encourage open, simple, and modern software architectures aiming at a uniform interface for interdisciplinary and flexible modelling and inversion approaches. We present pyGIMLi (Python Library for Inversion and Modelling in Geophysics), an open-source framework that provides tools for modelling and inversion of various geophysical but also hydrological methods. The modelling component supplies discretization management and the numerical basis for finite-element and finite-volume solvers in 1D, 2D and 3D on arbitrarily structured meshes. The generalized inversion framework solves the minimization problem with a Gauss-Newton algorithm for any physical forward operator and provides opportunities for uncertainty and resolution analyses. More general requirements, such as flexible regularization strategies, time-lapse processing and different sorts of coupling individual methods are provided independently of the actual methods used. The usage of pyGIMLi is first demonstrated by solving the steady-state heat equation, followed by a demonstration of more complex capabilities for the combination of different geophysical data sets. A fully coupled hydrogeophysical inversion of electrical resistivity tomography (ERT) data of a simulated tracer experiment is presented that allows to directly reconstruct the underlying hydraulic conductivity distribution of the aquifer. Another example demonstrates the improvement of jointly inverting ERT and ultrasonic data with respect to saturation by a new approach that incorporates petrophysical relations in the inversion. Potential applications of the presented framework are manifold and include time

  10. Effects of crustal layering on source parameter inversion from coseismic geodetic data

    NASA Astrophysics Data System (ADS)

    Amoruso, A.; Crescentini, L.; Fidani, C.

    2004-10-01

    We study the effect of a superficial layer overlying a half-space on the surface displacements caused by uniform slipping of a dip-slip normal rectangular fault. We compute static coseismic displacements using a 3-D analytical code for different characteristics of the layered medium, different fault geometries and different configurations of bench marks to simulate different kinds of geodetic data (GPS, Synthetic Aperture Radar, and levellings). We perform both joint and separate inversions of the three components of synthetic displacement without constraining fault parameters, apart from strike and rake, and using a non-linear global inversion technique under the assumption of homogeneous half-space. Differences between synthetic displacements computed in the presence of the superficial soft layer and in a homogeneous half-space do not show a simple regular behaviour, even if a few features can be identified. Consequently, also retrieved parameters of the homogeneous equivalent fault obtained by unconstrained inversion of surface displacements do not show a simple regular behaviour. We point out that the presence of a superficial layer may lead to misestimating several fault parameters both using joint and separate inversions of the three components of synthetic displacement and that the effects of the presence of the superficial layer can change whether all fault parameters are left free in the inversions or not. In the inversion of any kind of coseismic geodetic data, fault size and slip can be largely misestimated, but the product (fault length) × (fault width) × slip, which is proportional to the seismic moment for a given rigidity modulus, is often well determined (within a few per cent). Because inversion of coseismic geodetic data assuming a layered medium is impracticable, we suggest that only a case-to-case study involving some kind of recursive determination of fault parameters through data correction seems to give the proper approach when layering is

  11. From analytic inversion to contemporary IMRT optimization: Radiation therapy planning revisited from a mathematical perspective

    PubMed Central

    Censor, Yair; Unkelbach, Jan

    2011-01-01

    In this paper we look at the development of radiation therapy treatment planning from a mathematical point of view. Historically, planning for Intensity-Modulated Radiation Therapy (IMRT) has been considered as an inverse problem. We discuss first the two fundamental approaches that have been investigated to solve this inverse problem: Continuous analytic inversion techniques on one hand, and fully-discretized algebraic methods on the other hand. In the second part of the paper, we review another fundamental question which has been subject to debate from the beginning of IMRT until the present day: The rotation therapy approach versus fixed angle IMRT. This builds a bridge from historic work on IMRT planning to contemporary research in the context of Intensity-Modulated Arc Therapy (IMAT). PMID:21616694

  12. Inversion climatology at San Jose, California

    NASA Technical Reports Server (NTRS)

    Morgan, T.; Bornstein, R. D.

    1977-01-01

    Month-to-month variations in the early morning surface-based and near-noon elevated inversions at San Jose, Calif., were determined from slow rise radiosondes launched during a four-year period. A high frequency of shallow, radiative, surface-based inversions were found in winter during the early morning hours, while during the same period in summer, a low frequency of deeper based inversions arose from a combination of radiative and subsidence processes. The frequency of elevated inversions in the hours near noon was lowest during fall and spring, while inversion bases were highest and thicknesses least during these periods.

  13. Accommodating Chromosome Inversions in Linkage Analysis

    PubMed Central

    Chen, Gary K.; Slaten, Erin; Ophoff, Roel A.; Lange, Kenneth

    2006-01-01

    This work develops a population-genetics model for polymorphic chromosome inversions. The model precisely describes how an inversion changes the nature of and approach to linkage equilibrium. The work also describes algorithms and software for allele-frequency estimation and linkage analysis in the presence of an inversion. The linkage algorithms implemented in the software package Mendel estimate recombination parameters and calculate the posterior probability that each pedigree member carries the inversion. Application of Mendel to eight Centre d'Étude du Polymorphisme Humain pedigrees in a region containing a common inversion on 8p23 illustrates its potential for providing more-precise estimates of the location of an unmapped marker or trait gene. Our expanded cytogenetic analysis of these families further identifies inversion carriers and increases the evidence of linkage. PMID:16826515

  14. Spatially constrained Bayesian inversion of frequency- and time-domain electromagnetic data from the Tellus projects

    NASA Astrophysics Data System (ADS)

    Kiyan, Duygu; Rath, Volker; Delhaye, Robert

    2017-04-01

    The frequency- and time-domain airborne electromagnetic (AEM) data collected under the Tellus projects of the Geological Survey of Ireland (GSI) which represent a wealth of information on the multi-dimensional electrical structure of Ireland's near-surface. Our project, which was funded by GSI under the framework of their Short Call Research Programme, aims to develop and implement inverse techniques based on various Bayesian methods for these densely sampled data. We have developed a highly flexible toolbox using Python language for the one-dimensional inversion of AEM data along the flight lines. The computational core is based on an adapted frequency- and time-domain forward modelling core derived from the well-tested open-source code AirBeo, which was developed by the CSIRO (Australia) and the AMIRA consortium. Three different inversion methods have been implemented: (i) Tikhonov-type inversion including optimal regularisation methods (Aster el al., 2012; Zhdanov, 2015), (ii) Bayesian MAP inversion in parameter and data space (e.g. Tarantola, 2005), and (iii) Full Bayesian inversion with Markov Chain Monte Carlo (Sambridge and Mosegaard, 2002; Mosegaard and Sambridge, 2002), all including different forms of spatial constraints. The methods have been tested on synthetic and field data. This contribution will introduce the toolbox and present case studies on the AEM data from the Tellus projects.

  15. Regional W-Phase Source Inversion for Moderate to Large Earthquakes in China and Neighboring Areas

    NASA Astrophysics Data System (ADS)

    Zhao, Xu; Duputel, Zacharie; Yao, Zhenxing

    2017-12-01

    Earthquake source characterization has been significantly speeded up in the last decade with the development of rapid inversion techniques in seismology. Among these techniques, the W-phase source inversion method quickly provides point source parameters of large earthquakes using very long period seismic waves recorded at teleseismic distances. Although the W-phase method was initially developed to work at global scale (within 20 to 30 min after the origin time), faster results can be obtained when seismological data are available at regional distances (i.e., Δ ≤ 12°). In this study, we assess the use and reliability of regional W-phase source estimates in China and neighboring areas. Our implementation uses broadband records from the Chinese network supplemented by global seismological stations installed in the region. Using this data set and minor modifications to the W-phase algorithm, we show that reliable solutions can be retrieved automatically within 4 to 7 min after the earthquake origin time. Moreover, the method yields stable results down to Mw = 5.0 events, which is well below the size of earthquakes that are rapidly characterized using W-phase inversions at teleseismic distances.

  16. Development of a coupled FLEXPART-TM5 CO2 inverse modeling system

    NASA Astrophysics Data System (ADS)

    Monteil, Guillaume; Scholze, Marko

    2017-04-01

    Inverse modeling techniques are used to derive information on surface CO2 fluxes from measurements of atmospheric CO2 concentrations. The principle is to use an atmospheric transport model to compute the CO2 concentrations corresponding to a prior estimate of the surface CO2 fluxes. From the mismatches between observed and modeled concentrations, a correction of the flux estimate is computed, that represents the best statistical compromise between the prior knowledge and the new information brought in by the observations. Such "top-down" CO2 flux estimates are useful for a number of applications, such as the verification of CO2 emission inventories reported by countries in the framework of international greenhouse gas emission reduction treaties (Paris agreement), or for the validation and improvement of the bottom-up models used in future climate predictions. Inverse modeling CO2 flux estimates are limited in resolution (spatial and temporal) by the lack of observational constraints and by the very heavy computational cost of high-resolution inversions. The observational limitation is however being lifted, with the expansion of regional surface networks such as ICOS in Europe, and with the launch of new satellite instruments to measure tropospheric CO2 concentrations. To make an efficient use of these new observations, it is necessary to step up the resolution of atmospheric inversions. We have developed an inverse modeling system, based on a coupling between the TM5 and the FLEXPART transport models. The coupling follows the approach described in Rodenbeck et al., 2009: a first global, coarse resolution, inversion is performed using TM5-4DVAR, and is used to provide background constraints to a second, regional, fine resolution inversion, using FLEXPART as a transport model. The inversion algorithm is adapted from the 4DVAR algorithm used by TM5, but has been developed to be model-agnostic: it would be straightforward to replace TM5 and/or FLEXPART by other

  17. Inverse sampling regression for pooled data.

    PubMed

    Montesinos-López, Osval A; Montesinos-López, Abelardo; Eskridge, Kent; Crossa, José

    2017-06-01

    Because pools are tested instead of individuals in group testing, this technique is helpful for estimating prevalence in a population or for classifying a large number of individuals into two groups at a low cost. For this reason, group testing is a well-known means of saving costs and producing precise estimates. In this paper, we developed a mixed-effect group testing regression that is useful when the data-collecting process is performed using inverse sampling. This model allows including covariate information at the individual level to incorporate heterogeneity among individuals and identify which covariates are associated with positive individuals. We present an approach to fit this model using maximum likelihood and we performed a simulation study to evaluate the quality of the estimates. Based on the simulation study, we found that the proposed regression method for inverse sampling with group testing produces parameter estimates with low bias when the pre-specified number of positive pools (r) to stop the sampling process is at least 10 and the number of clusters in the sample is also at least 10. We performed an application with real data and we provide an NLMIXED code that researchers can use to implement this method.

  18. On the Structural Plasticity of the Human Genome: Chromosomal Inversions Revisited

    PubMed Central

    Alves, Joao M; Lopes, Alexandra M; Chikhi, Lounès; Amorim, António

    2012-01-01

    With the aid of novel and powerful molecular biology techniques, recent years have witnessed a dramatic increase in the number of studies reporting the involvement of complex structural variants in several genomic disorders. In fact, with the discovery of Copy Number Variants (CNVs) and other forms of unbalanced structural variation, much attention has been directed to the detection and characterization of such rearrangements, as well as the identification of the mechanisms involved in their formation. However, it has long been appreciated that chromosomes can undergo other forms of structural changes - balanced rearrangements - that do not involve quantitative variation of genetic material. Indeed, a particular subtype of balanced rearrangement – inversions – was recently found to be far more common than had been predicted from traditional cytogenetics. Chromosomal inversions alter the orientation of a specific genomic sequence and, unless involving breaks in coding or regulatory regions (and, disregarding complex trans effects, in their close vicinity), appear to be phenotypically silent. Such a surprising finding, which is difficult to reconcile with the classical interpretation of inversions as a mechanism causing subfertility (and ultimately reproductive isolation), motivated a new series of theoretical and empirical studies dedicated to understand their role in human genome evolution and to explore their possible association to complex genetic disorders. With this review, we attempt to describe the latest methodological improvements to inversions detection at a genome wide level, while exploring some of the possible implications of inversion rearrangements on the evolution of the human genome. PMID:23730202

  19. Inferior olive mirrors joint dynamics to implement an inverse controller.

    PubMed

    Alvarez-Icaza, Rodrigo; Boahen, Kwabena

    2012-10-01

    To produce smooth and coordinated motion, our nervous systems need to generate precisely timed muscle activation patterns that, due to axonal conduction delay, must be generated in a predictive and feedforward manner. Kawato proposed that the cerebellum accomplishes this by acting as an inverse controller that modulates descending motor commands to predictively drive the spinal cord such that the musculoskeletal dynamics are canceled out. This and other cerebellar theories do not, however, account for the rich biophysical properties expressed by the olivocerebellar complex's various cell types, making these theories difficult to verify experimentally. Here we propose that a multizonal microcomplex's (MZMC) inferior olivary neurons use their subthreshold oscillations to mirror a musculoskeletal joint's underdamped dynamics, thereby achieving inverse control. We used control theory to map a joint's inverse model onto an MZMC's biophysics, and we used biophysical modeling to confirm that inferior olivary neurons can express the dynamics required to mirror biomechanical joints. We then combined both techniques to predict how experimentally injecting current into the inferior olive would affect overall motor output performance. We found that this experimental manipulation unmasked a joint's natural dynamics, as observed by motor output ringing at the joint's natural frequency, with amplitude proportional to the amount of current. These results support the proposal that the cerebellum-in particular an MZMC-is an inverse controller; the results also provide a biophysical implementation for this controller and allow one to make an experimentally testable prediction.

  20. Simultaneous estimation of aquifer thickness, conductivity, and BC using borehole and hydrodynamic data with geostatistical inverse direct method

    NASA Astrophysics Data System (ADS)

    Gao, F.; Zhang, Y.

    2017-12-01

    A new inverse method is developed to simultaneously estimate aquifer thickness and boundary conditions using borehole and hydrodynamic measurements from a homogeneous confined aquifer under steady-state ambient flow. This method extends a previous groundwater inversion technique which had assumed known aquifer geometry and thickness. In this research, thickness inversion was successfully demonstrated when hydrodynamic data were supplemented with measured thicknesses from boreholes. Based on a set of hybrid formulations which describe approximate solutions to the groundwater flow equation, the new inversion technique can incorporate noisy observed data (i.e., thicknesses, hydraulic heads, Darcy fluxes or flow rates) at measurement locations as a set of conditioning constraints. Given sufficient quantity and quality of the measurements, the inverse method yields a single well-posed system of equations that can be solved efficiently with nonlinear optimization. The method is successfully tested on two-dimensional synthetic aquifer problems with regular geometries. The solution is stable when measurement errors are increased, with error magnitude reaching up to +/- 10% of the range of the respective measurement. When error-free observed data are used to condition the inversion, the estimated thickness is within a +/- 5% error envelope surrounding the true value; when data contain increasing errors, the estimated thickness become less accurate, as expected. Different combinations of measurement types are then investigated to evaluate data worth. Thickness can be inverted with the combination of observed heads and at least one of the other types of observations such as thickness, Darcy fluxes, or flow rates. Data requirement of the new inversion method is thus not much different from that of interpreting classic well tests. Future work will improve upon this research by developing an estimation strategy for heterogeneous aquifers while drawdown data from hydraulic tests

  1. Development of the (d,n) Proton-transfer Reaction in Inverse Kinematics for Structure Studies

    NASA Astrophysics Data System (ADS)

    Jones, K. L.; Thornsberry, C.; Allen, J.; Atencio, A.; Bardayan, D. W.; Blankstein, D.; Burcher, S.; Carter, A. B.; Chipps, K. A.; Cizewski, J. A.; Cox, I.; Elledge, Z.; Febbraro, M.; Fijałkowska, A.; Grzywacz, R.; Hall, M. R.; King, T. T.; Lepailleur, A.; Madurga, M.; Marley, S. T.; O'Malley, P. D.; Paulauskas, S. V.; Pain, S. D.; Peters, W. A.; Reingold, C.; Smith, K.; Taylor, S.; Tan, W.; Vostinar, M.; Walter, D.

    Transfer reactions have provided exciting opportunities to study the structure of exotic nuclei and are often used to inform studies relating to nucleosynthesis and applications. In order to benefit from these reactions and their application to rare ion beams (RIBs) it is necessary to develop the tools and techniques to perform and analyze the data from reactions performed in inverse kinematics, that is with targets of light nuclei and heavier beams. We are continuing to expand the transfer reaction toolbox in preparation for the next generation of facilities, such as the Facility for Rare Ion Beams (FRIB), which is scheduled for completion in 2022. An important step in this process is to perform the (d,n) reaction in inverse kinematics, with analyses that include Q-value spectra and differential cross sections. In this way, proton-transfer reactions can be placed on the same level as the more commonly used neutron-transfer reactions, such as (d,p), (9Be,8Be), and (13C,12C). Here we present an overview of the techniques used in (d,p) and (d,n), and some recent data from (d,n) reactions in inverse kinematics using stable beams of 12C and 16O.

  2. Comparing inversion techniques for constraining CO2 fluxes in the Brazilian Amazon Basin with aircraft observations

    NASA Astrophysics Data System (ADS)

    Chow, V. Y.; Gerbig, C.; Longo, M.; Koch, F.; Nehrkorn, T.; Eluszkiewicz, J.; Ceballos, J. C.; Longo, K.; Wofsy, S. C.

    2012-12-01

    The Balanço Atmosférico Regional de Carbono na Amazônia (BARCA) aircraft program spanned the dry to wet and wet to dry transition seasons in November 2008 & May 2009 respectively. It resulted in ~150 vertical profiles covering the Brazilian Amazon Basin (BAB). With the data we attempt to estimate a carbon budget for the BAB, to determine if regional aircraft experiments can provide strong constraints for a budget, and to compare inversion frameworks when optimizing flux estimates. We use a LPDM to integrate satellite-, aircraft-, & surface-data with mesoscale meteorological fields to link bottom-up and top-down models to provide constraints and error bounds for regional fluxes. The Stochastic Time-Inverted Lagrangian Transport (STILT) model driven by meteorological fields from BRAMS, ECMWF, and WRF are coupled to a biosphere model, the Vegetation Photosynthesis Respiration Model (VPRM), to determine regional CO2 fluxes for the BAB. The VPRM is a prognostic biosphere model driven by MODIS 8-day EVI and LSWI indices along with shortwave radiation and temperature from tower measurements and mesoscale meteorological data. VPRM parameters are tuned using eddy flux tower data from the Large-Scale Biosphere Atmosphere experiment. VPRM computes hourly CO2 fluxes by calculating Gross Ecosystem Exchange (GEE) and Respiration (R) for 8 different vegetation types. The VPRM fluxes are scaled up to the BAB by using time-averaged drivers (shortwave radiation & temperature) from high-temporal resolution runs of BRAMS, ECMWF, and WRF and vegetation maps from SYNMAP and IGBP2007. Shortwave radiation from each mesoscale model is validated using surface data and output from GL 1.2, a global radiation model based on GOES 8 visible imagery. The vegetation maps are updated to 2008 and 2009 using landuse scenarios modeled by Sim Amazonia 2 and Sim Brazil. A priori fluxes modeled by STILT-VPRM are optimized using data from BARCA, eddy covariance sites, and flask measurements. The

  3. Using the dGEMRIC technique to evaluate cartilage health in the presence of surgical hardware at 3T: comparison of inversion recovery and saturation recovery approaches.

    PubMed

    d'Entremont, Agnes G; Kolind, Shannon H; Mädler, Burkhard; Wilson, David R; MacKay, Alexander L

    2014-03-01

    To evaluate the effect of metal artifact reduction techniques on dGEMRIC T(1) calculation with surgical hardware present. We examined the effect of stainless-steel and titanium hardware on dGEMRIC T(1) maps. We tested two strategies to reduce metal artifact in dGEMRIC: (1) saturation recovery (SR) instead of inversion recovery (IR) and (2) applying the metal artifact reduction sequence (MARS), in a gadolinium-doped agarose gel phantom and in vivo with titanium hardware. T(1) maps were obtained using custom curve-fitting software and phantom ROIs were defined to compare conditions (metal, MARS, IR, SR). A large area of artifact appeared in phantom IR images with metal when T(I) ≤ 700 ms. IR maps with metal had additional artifact both in vivo and in the phantom (shifted null points, increased mean T(1) (+151 % IR ROI(artifact)) and decreased mean inversion efficiency (f; 0.45 ROI(artifact), versus 2 for perfect inversion)) compared to the SR maps (ROI(artifact): +13 % T(1) SR, 0.95 versus 1 for perfect excitation), however, SR produced noisier T(1) maps than IR (phantom SNR: 118 SR, 212 IR). MARS subtly reduced the extent of artifact in the phantom (IR and SR). dGEMRIC measurement in the presence of surgical hardware at 3T is possible with appropriately applied strategies. Measurements may work best in the presence of titanium and are severely limited with stainless steel. For regions near hardware where IR produces large artifacts making dGEMRIC analysis impossible, SR-MARS may allow dGEMRIC measurements. The position and size of the IR artifact is variable, and must be assessed for each implant/imaging set-up.

  4. FOREWORD: 5th International Workshop on New Computational Methods for Inverse Problems

    NASA Astrophysics Data System (ADS)

    Vourc'h, Eric; Rodet, Thomas

    2015-11-01

    This volume of Journal of Physics: Conference Series is dedicated to the scientific research presented during the 5th International Workshop on New Computational Methods for Inverse Problems, NCMIP 2015 (http://complement.farman.ens-cachan.fr/NCMIP_2015.html). This workshop took place at Ecole Normale Supérieure de Cachan, on May 29, 2015. The prior editions of NCMIP also took place in Cachan, France, firstly within the scope of ValueTools Conference, in May 2011, and secondly at the initiative of Institut Farman, in May 2012, May 2013 and May 2014. The New Computational Methods for Inverse Problems (NCMIP) workshop focused on recent advances in the resolution of inverse problems. Indeed, inverse problems appear in numerous scientific areas such as geophysics, biological and medical imaging, material and structure characterization, electrical, mechanical and civil engineering, and finances. The resolution of inverse problems consists of estimating the parameters of the observed system or structure from data collected by an instrumental sensing or imaging device. Its success firstly requires the collection of relevant observation data. It also requires accurate models describing the physical interactions between the instrumental device and the observed system, as well as the intrinsic properties of the solution itself. Finally, it requires the design of robust, accurate and efficient inversion algorithms. Advanced sensor arrays and imaging devices provide high rate and high volume data; in this context, the efficient resolution of the inverse problem requires the joint development of new models and inversion methods, taking computational and implementation aspects into account. During this one-day workshop, researchers had the opportunity to bring to light and share new techniques and results in the field of inverse problems. The topics of the workshop were: algorithms and computational aspects of inversion, Bayesian estimation, Kernel methods, learning methods

  5. Physics for clinicians: Fluid-attenuated inversion recovery (FLAIR) and double inversion recovery (DIR) Imaging.

    PubMed

    Saranathan, Manojkumar; Worters, Pauline W; Rettmann, Dan W; Winegar, Blair; Becker, Jennifer

    2017-12-01

    A pedagogical review of fluid-attenuated inversion recovery (FLAIR) and double inversion recovery (DIR) imaging is conducted in this article. The basics of the two pulse sequences are first described, including the details of the inversion preparation and imaging sequences with accompanying mathematical formulae for choosing the inversion time in a variety of scenarios for use on clinical MRI scanners. Magnetization preparation (or T2prep), a strategy for improving image signal-to-noise ratio and contrast and reducing T 1 weighting at high field strengths, is also described. Lastly, image artifacts commonly associated with FLAIR and DIR are described with clinical examples, to help avoid misdiagnosis. 5 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017;46:1590-1600. © 2017 International Society for Magnetic Resonance in Medicine.

  6. A remarkably large depleted core in the Abell 2029 BCG IC 1101

    NASA Astrophysics Data System (ADS)

    Dullo, Bililign T.; Graham, Alister W.; Knapen, Johan H.

    2017-10-01

    We report the discovery of an extremely large (Rb ˜2.77 arcsec ≈ 4.2 kpc) core in the brightest cluster galaxy, IC 1101, of the rich galaxy cluster Abell 2029. Luminous core-Sérsic galaxies contain depleted cores - with sizes (Rb) typically 20-500 pc - that are thought to be formed by coalescing black hole binaries. We fit a (double nucleus) + (spheroid) + (intermediate-scale component) + (stellar halo) model to the Hubble Space Telescope surface brightness profile of IC 1101, finding the largest core size measured in any galaxy to date. This core is an order of magnitude larger than those typically measured for core-Sérsic galaxies. We find that the spheroid's V-band absolute magnitude (MV) of -23.8 mag (˜25 per cent of the total galaxy light, I.e. including the stellar halo) is faint for the large Rb, such that the observed core is 1.02 dex ≈ 3.4σs (rms scatter) larger than that estimated from the Rb-MV relation. The suspected scouring process has produced a large stellar mass deficit (Mdef) ˜4.9 × 1011 M⊙, I.e. a luminosity deficit ≈28 per cent of the spheroid's luminosity prior to the depletion. Using IC 1101's black hole mass (MBH) estimated from the MBH-σ, MBH-L and MBH-M* relations, we measure an excessive and unrealistically high number of 'dry' major mergers for IC 1101 (I.e. N ≳ 76) as traced by the large Mdef/MBH ratios of 38-101. The large core, high mass deficit and oversized Mdef/MBH ratio of IC 1101 suggest that the depleted core was scoured by overmassive SMBH binaries with a final coalesced mass MBH ˜ (4-10) × 1010 M⊙, I.e. ˜ (1.7-3.2) × σs larger than the black hole masses estimated using the spheroid's σ, L and M*. The large core might be partly due to oscillatory core passages by a gravitational radiation-recoiled black hole.

  7. CSAMT Data Processing with Source Effect and Static Corrections, Application of Occam's Inversion, and Its Application in Geothermal System

    NASA Astrophysics Data System (ADS)

    Hamdi, H.; Qausar, A. M.; Srigutomo, W.

    2016-08-01

    Controlled source audio-frequency magnetotellurics (CSAMT) is a frequency-domain electromagnetic sounding technique which uses a fixed grounded dipole as an artificial signal source. Measurement of CSAMT with finite distance between transmitter and receiver caused a complex wave. The shifted of the electric field due to the static effect caused elevated resistivity curve up or down and affects the result of measurement. The objective of this study was to obtain data that have been corrected for source and static effects as to have the same characteristic as MT data which are assumed to exhibit plane wave properties. Corrected CSAMT data were inverted to reveal subsurface resistivity model. Source effect correction method was applied to eliminate the effect of the signal source and static effect was corrected by using spatial filtering technique. Inversion method that used in this study is the Occam's 2D Inversion. The results of inversion produces smooth models with a small misfit value, it means the model can describe subsurface conditions well. Based on the result of inversion was predicted measurement area is rock that has high permeability values with rich hot fluid.

  8. Synergism and foaming properties in binary mixtures of a biosurfactant derived from Camellia oleifera Abel and synthetic surfactants.

    PubMed

    Jian, Hong-lei; Liao, Xiao-xia; Zhu, Li-wei; Zhang, Wei-ming; Jiang, Jian-xin

    2011-07-15

    A biosurfactant, named tea saponin (TS), was isolated and purified from the defatted seed of Camellia oleifera Abel. The characterization of TS including molecular weight, glycosyl composition, and thermal behavior as well as the surface and foaming properties was conducted. The synergistic interactions of binary systems of CTAB-TS, SDS-TS, and Brij35-TS were investigated. The results show that TS had a weight-average molecular weight of 809.12 g mol(-1) and contained four aglycones of L-rhamnose, D-galactose, D-glucose, and D-glucuronic acid. The critical micelle concentration (cmc) of 2.242 mmol L(-1) and the minimum surface tension (γ(cmc)) of 43.5 mN m(-1) were determined for TS. Synergisms in surface tension reduction efficiency, in mixed micelle formation, and in surface tension reduction effectiveness were observed in CTAB-TS and SDS-TS systems, whereas that was not shown in Brij35-TS mixtures. The mixtures of TS with CTAB and SDS showed synergism in foaming efficiency, but this synergism did not exist in Brij35-TS system with respect to the surface properties. Nevertheless, there appears to be no significant correlation between foam stability and the surface properties. Copyright © 2011 Elsevier Inc. All rights reserved.

  9. Parana Basin Structure from Multi-Objective Inversion of Surface Wave and Receiver Function by Competent Genetic Algorithm

    NASA Astrophysics Data System (ADS)

    An, M.; Assumpcao, M.

    2003-12-01

    The joint inversion of receiver function and surface wave is an effective way to diminish the influences of the strong tradeoff among parameters and the different sensitivity to the model parameters in their respective inversions, but the inversion problem becomes more complex. Multi-objective problems can be much more complicated than single-objective inversion in the model selection and optimization. If objectives are involved and conflicting, models can be ordered only partially. In this case, Pareto-optimal preference should be used to select solutions. On the other hand, the inversion to get only a few optimal solutions can not deal properly with the strong tradeoff between parameters, the uncertainties in the observation, the geophysical complexities and even the incompetency of the inversion technique. The effective way is to retrieve the geophysical information statistically from many acceptable solutions, which requires more competent global algorithms. Competent genetic algorithms recently proposed are far superior to the conventional genetic algorithm and can solve hard problems quickly, reliably and accurately. In this work we used one of competent genetic algorithms, Bayesian Optimization Algorithm as the main inverse procedure. This algorithm uses Bayesian networks to draw out inherited information and can use Pareto-optimal preference in the inversion. With this algorithm, the lithospheric structure of Paran"› basin is inverted to fit both the observations of inter-station surface wave dispersion and receiver function.

  10. Improved resistivity imaging of groundwater solute plumes using POD-based inversion

    NASA Astrophysics Data System (ADS)

    Oware, E. K.; Moysey, S. M.; Khan, T.

    2012-12-01

    vectors (100) contained enough a priori information to constrain the inversion. Increasing the amount of data or number of selected basis images did not translate into significant improvement in imaging results. For synthetic #2, the RMSE and error in total mass were lowest for the POD inversion. However, the peak concentration was significantly overestimated by the POD approach. Regardless, the POD-based inversion was the only technique that could capture the bimodality of the plume in the reconstructed image, thus providing critical information that could be used to reconceptualize the transport problem. We also found that, in the case of synthetic #2, increasing the number of resistivity measurements and the number of selected basis vectors allowed for significant improvements in the reconstructed images.

  11. Bayesian inversion of data from effusive volcanic eruptions using physics-based models: Application to Mount St. Helens 2004--2008

    USGS Publications Warehouse

    Anderson, Kyle; Segall, Paul

    2013-01-01

    Physics-based models of volcanic eruptions can directly link magmatic processes with diverse, time-varying geophysical observations, and when used in an inverse procedure make it possible to bring all available information to bear on estimating properties of the volcanic system. We develop a technique for inverting geodetic, extrusive flux, and other types of data using a physics-based model of an effusive silicic volcanic eruption to estimate the geometry, pressure, depth, and volatile content of a magma chamber, and properties of the conduit linking the chamber to the surface. A Bayesian inverse formulation makes it possible to easily incorporate independent information into the inversion, such as petrologic estimates of melt water content, and yields probabilistic estimates for model parameters and other properties of the volcano. Probability distributions are sampled using a Markov-Chain Monte Carlo algorithm. We apply the technique using GPS and extrusion data from the 2004–2008 eruption of Mount St. Helens. In contrast to more traditional inversions such as those involving geodetic data alone in combination with kinematic forward models, this technique is able to provide constraint on properties of the magma, including its volatile content, and on the absolute volume and pressure of the magma chamber. Results suggest a large chamber of >40 km3 with a centroid depth of 11–18 km and a dissolved water content at the top of the chamber of 2.6–4.9 wt%.

  12. A ''Voice Inversion Effect?''

    ERIC Educational Resources Information Center

    Bedard, Catherine; Belin, Pascal

    2004-01-01

    Voice is the carrier of speech but is also an ''auditory face'' rich in information on the speaker's identity and affective state. Three experiments explored the possibility of a ''voice inversion effect,'' by analogy to the classical ''face inversion effect,'' which could support the hypothesis of a voice-specific module. Experiment 1 consisted…

  13. From inverse problems to learning: a Statistical Mechanics approach

    NASA Astrophysics Data System (ADS)

    Baldassi, Carlo; Gerace, Federica; Saglietti, Luca; Zecchina, Riccardo

    2018-01-01

    We present a brief introduction to the statistical mechanics approaches for the study of inverse problems in data science. We then provide concrete new results on inferring couplings from sampled configurations in systems characterized by an extensive number of stable attractors in the low temperature regime. We also show how these result are connected to the problem of learning with realistic weak signals in computational neuroscience. Our techniques and algorithms rely on advanced mean-field methods developed in the context of disordered systems.

  14. On the calibration process of film dosimetry: OLS inverse regression versus WLS inverse prediction.

    PubMed

    Crop, F; Van Rompaye, B; Paelinck, L; Vakaet, L; Thierens, H; De Wagter, C

    2008-07-21

    The purpose of this study was both putting forward a statistically correct model for film calibration and the optimization of this process. A reliable calibration is needed in order to perform accurate reference dosimetry with radiographic (Gafchromic) film. Sometimes, an ordinary least squares simple linear (in the parameters) regression is applied to the dose-optical-density (OD) curve with the dose as a function of OD (inverse regression) or sometimes OD as a function of dose (inverse prediction). The application of a simple linear regression fit is an invalid method because heteroscedasticity of the data is not taken into account. This could lead to erroneous results originating from the calibration process itself and thus to a lower accuracy. In this work, we compare the ordinary least squares (OLS) inverse regression method with the correct weighted least squares (WLS) inverse prediction method to create calibration curves. We found that the OLS inverse regression method could lead to a prediction bias of up to 7.3 cGy at 300 cGy and total prediction errors of 3% or more for Gafchromic EBT film. Application of the WLS inverse prediction method resulted in a maximum prediction bias of 1.4 cGy and total prediction errors below 2% in a 0-400 cGy range. We developed a Monte-Carlo-based process to optimize calibrations, depending on the needs of the experiment. This type of thorough analysis can lead to a higher accuracy for film dosimetry.

  15. Strategies for efficient resolution analysis in full-waveform inversion

    NASA Astrophysics Data System (ADS)

    Fichtner, A.; van Leeuwen, T.; Trampert, J.

    2016-12-01

    Full-waveform inversion is developing into a standard method in the seismological toolbox. It combines numerical wave propagation for heterogeneous media with adjoint techniques in order to improve tomographic resolution. However, resolution becomes increasingly difficult to quantify because of the enormous computational requirements. Here we present two families of methods that can be used for efficient resolution analysis in full-waveform inversion. They are based on the targeted extraction of resolution proxies from the Hessian matrix, which is too large to store and to compute explicitly. Fourier methods rest on the application of the Hessian to Earth models with harmonic oscillations. This yields the Fourier spectrum of the Hessian for few selected wave numbers, from which we can extract properties of the tomographic point-spread function for any point in space. Random probing methods use uncorrelated, random test models instead of harmonic oscillations. Auto-correlating the Hessian-model applications for sufficiently many test models also characterises the point-spread function. Both Fourier and random probing methods provide a rich collection of resolution proxies. These include position- and direction-dependent resolution lengths, and the volume of point-spread functions as indicator of amplitude recovery and inter-parameter trade-offs. The computational requirements of these methods are equivalent to approximately 7 conjugate-gradient iterations in full-waveform inversion. This is significantly less than the optimisation itself, which may require tens to hundreds of iterations to reach convergence. In addition to the theoretical foundations of the Fourier and random probing methods, we show various illustrative examples from real-data full-waveform inversion for crustal and mantle structure.

  16. Donor states in inverse opals

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mahan, G. D.

    We calculate the binding energy of an electron bound to a donor in a semiconductor inverse opal. Inverse opals have two kinds of cavities, which we call octahedral and tetrahedral, according to their group symmetry. We put the donor in the center of each of these two cavities and obtain the binding energy. The binding energies become very large when the inverse opal is made from templates with small spheres. For spheres less than 50 nm in diameter, the donor binding can increase to several times its unconfined value. Then electrons become tightly bound to the donor and are unlikelymore » to be thermally activated to the semiconductor conduction band. This conclusion suggests that inverse opals will be poor conductors.« less

  17. EDITORIAL: Introduction to the special issue on electromagnetic inverse problems: emerging methods and novel applications Introduction to the special issue on electromagnetic inverse problems: emerging methods and novel applications

    NASA Astrophysics Data System (ADS)

    Dorn, O.; Lesselier, D.

    2010-07-01

    Inverse problems in electromagnetics have a long history and have stimulated exciting research over many decades. New applications and solution methods are still emerging, providing a rich source of challenging topics for further investigation. The purpose of this special issue is to combine descriptions of several such developments that are expected to have the potential to fundamentally fuel new research, and to provide an overview of novel methods and applications for electromagnetic inverse problems. There have been several special sections published in Inverse Problems over the last decade addressing fully, or partly, electromagnetic inverse problems. Examples are: Electromagnetic imaging and inversion of the Earth's subsurface (Guest Editors: D Lesselier and T Habashy) October 2000 Testing inversion algorithms against experimental data (Guest Editors: K Belkebir and M Saillard) December 2001 Electromagnetic and ultrasonic nondestructive evaluation (Guest Editors: D Lesselier and J Bowler) December 2002 Electromagnetic characterization of buried obstacles (Guest Editors: D Lesselier and W C Chew) December 2004 Testing inversion algorithms against experimental data: inhomogeneous targets (Guest Editors: K Belkebir and M Saillard) December 2005 Testing inversion algorithms against experimental data: 3D targets (Guest Editors: A Litman and L Crocco) February 2009 In a certain sense, the current issue can be understood as a continuation of this series of special sections on electromagnetic inverse problems. On the other hand, its focus is intended to be more general than previous ones. Instead of trying to cover a well-defined, somewhat specialized research topic as completely as possible, this issue aims to show the broad range of techniques and applications that are relevant to electromagnetic imaging nowadays, which may serve as a source of inspiration and encouragement for all those entering this active and rapidly developing research area. Also, the

  18. Modelisations et inversions tri-dimensionnelles en prospections gravimetrique et electrique

    NASA Astrophysics Data System (ADS)

    Boulanger, Olivier

    The aim of this thesis is the application of gravity and resistivity methods for mining prospecting. The objectives of the present study are: (1) to build a fast gravity inversion method to interpret surface data; (2) to develop a tool for modelling the electrical potential acquired at surface and in boreholes when the resistivity distribution is heterogeneous; and (3) to define and implement a stochastic inversion scheme allowing the estimation of the subsurface resistivity from electrical data. The first technique concerns the elaboration of a three dimensional (3D) inversion program allowing the interpretation of gravity data using a selection of constraints such as the minimum distance, the flatness, the smoothness and the compactness. These constraints are integrated in a Lagrangian formulation. A multi-grid technique is also implemented to resolve separately large and short gravity wavelengths. The subsurface in the survey area is divided into juxtaposed rectangular prismatic blocks. The problem is solved by calculating the model parameters, i.e. the densities of each block. Weights are given to each block depending on depth, a priori information on density, and density range allowed for the region under investigation. The present code is tested on synthetic data. Advantages and behaviour of each method are compared in the 3D reconstruction. Recovery of geometry (depth, size) and density distribution of the original model is dependent on the set of constraints used. The best combination of constraints experimented for multiple bodies seems to be flatness and minimum volume for multiple bodies. The inversion method is tested on real gravity data. The second tool developed in this thesis is a three-dimensional electrical resistivity modelling code to interpret surface and subsurface data. Based on the integral equation, it calculates the charge density caused by conductivity gradients at each interface of the mesh allowing an exact estimation of the potential

  19. ENDOR with band-selective shaped inversion pulses

    NASA Astrophysics Data System (ADS)

    Tait, Claudia E.; Stoll, Stefan

    2017-04-01

    Electron Nuclear DOuble Resonance (ENDOR) is based on the measurement of nuclear transition frequencies through detection of changes in the polarization of electron transitions. In Davies ENDOR, the initial polarization is generated by a selective microwave inversion pulse. The rectangular inversion pulses typically used are characterized by a relatively low selectivity, with full inversion achieved only for a limited number of spin packets with small resonance offsets. With the introduction of pulse shaping to EPR, the rectangular inversion pulses can be replaced with shaped pulses with increased selectivity. Band-selective inversion pulses are characterized by almost rectangular inversion profiles, leading to full inversion for spin packets with resonance offsets within the pulse excitation bandwidth and leaving spin packets outside the excitation bandwidth largely unaffected. Here, we explore the consequences of using different band-selective amplitude-modulated pulses designed for NMR as the inversion pulse in ENDOR. We find an increased sensitivity for small hyperfine couplings compared to rectangular pulses of the same bandwidth. In echo-detected Davies-type ENDOR, finite Fourier series inversion pulses combine the advantages of increased absolute ENDOR sensitivity of short rectangular inversion pulses and increased sensitivity for small hyperfine couplings of long rectangular inversion pulses. The use of pulses with an almost rectangular frequency-domain profile also allows for increased control of the hyperfine contrast selectivity. At X-band, acquisition of echo transients as a function of radiofrequency and appropriate selection of integration windows during data processing allows efficient separation of contributions from weakly and strongly coupled nuclei in overlapping ENDOR spectra within a single experiment.

  20. The 2-D magnetotelluric inverse problem solved with optimization

    NASA Astrophysics Data System (ADS)

    van Beusekom, Ashley E.; Parker, Robert L.; Bank, Randolph E.; Gill, Philip E.; Constable, Steven

    2011-02-01

    The practical 2-D magnetotelluric inverse problem seeks to determine the shallow-Earth conductivity structure using finite and uncertain data collected on the ground surface. We present an approach based on using PLTMG (Piecewise Linear Triangular MultiGrid), a special-purpose code for optimization with second-order partial differential equation (PDE) constraints. At each frequency, the electromagnetic field and conductivity are treated as unknowns in an optimization problem in which the data misfit is minimized subject to constraints that include Maxwell's equations and the boundary conditions. Within this framework it is straightforward to accommodate upper and lower bounds or other conditions on the conductivity. In addition, as the underlying inverse problem is ill-posed, constraints may be used to apply various kinds of regularization. We discuss some of the advantages and difficulties associated with using PDE-constrained optimization as the basis for solving large-scale nonlinear geophysical inverse problems. Combined transverse electric and transverse magnetic complex admittances from the COPROD2 data are inverted. First, we invert penalizing size and roughness giving solutions that are similar to those found previously. In a second example, conventional regularization is replaced by a technique that imposes upper and lower bounds on the model. In both examples the data misfit is better than that obtained previously, without any increase in model complexity.