Multiscale Edge Detection in the Corona     

C. Alex Young  Peter T. Gallagher 《Solar physics》2008,248(2):457-469

Coronal Mass Ejections (CMEs) are challenging objects to detect using automated techniques, due to their high velocity and diffuse, irregular morphology. A necessary step to automating the detection process is to first remove the subjectivity introduced by the observer used in the current, standard, CME detection and tracking method. Here we describe and demonstrate a multiscale edge detection technique that addresses this step and could serve as one part of an automated CME detection system. This method provides a way to objectively define a CME front with associated error estimates. These fronts can then be used to extract CME morphology and kinematics. We apply this technique to a CME observed on 18 April 2000 by the Large Angle Solar COronagraph experiment (LASCO) C2/C3 and a CME observed on 21 April 2002 by LASCO C2/C3 and the Transition Region and Coronal Explorer (TRACE). For the two examples in this work, the heights determined by the standard manual method are larger than those determined with the multiscale method by ≈10% using LASCO data and ≈20% using TRACE data.  相似文献   

A multidimensional scaling approach to enforce reproduction of transition probabilities in truncated plurigaussian simulation   总被引：2，自引：1，他引：1  

Jared L. Deutsch  Clayton V. Deutsch 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(3):707-716

Truncated plurigaussian (TPG) simulation is a flexible method for simulating rock types in deposits with complicated ordering structures. The truncation of a multivariate Gaussian distribution controls the proportions and ordering of rock types in the simulation while the variogram for each Gaussian variable controls rock type continuity. The determination of a truncation procedure for complicated geological environments is not trivial. A method for determining the truncation and fitting variograms applicable to any number of rock types and multivariate Gaussian distribution is developed here to address this problem. Multidimensional scaling is applied to place dissimilar categories far apart and similar categories close together. The multivariate space is then mapped using a Voronoi decomposition and rotated to optimize variogram reproduction. A case study simulating geologic layers at a large mineral deposit demonstrates the potential of this method and compares the results with sequential indicator simulation (SIS). Input proportion and transition probability reproduction with TPG is demonstrated to be better than SIS. Variogram reproduction is comparable for both techniques.  相似文献   

Multivariate grid-free geostatistical simulation with point or block scale secondary data   总被引：1，自引：1，他引：0  

Yevgeniy Zagayevskiy  Clayton V. Deutsch 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(6):1613-1633

A novel grid-free geostatistical simulation method (GFS) allows representing coregionalized variables as an analytical function of the coordinates of the simulation locations. Simulation on unstructured grids, regridding and refinement of available realizations of natural phenomena including, but not limited to, environmental systems are possible with GFS in a consistent manner. The unconditional realizations are generated by utilizing the linear model of coregionalization and Fourier series-based decomposition of the covariance function. The conditioning to data is performed by kriging. The data can be measured at scattered point-scale locations or sampled at a block scale. Secondary data are usually used in conjunction with primary data for the improved modeling. Satellite imaging is an example of exhaustively sampled secondary data. Improvements and recommendations are made to the implementation of GFS to properly assimilate secondary exhaustive data sets in a grid-free manner. Intrinsic cokriging (ICK) is utilized to reduce computational time and preserve the overall quality of the simulation. To further reduce the computational cost of ICK, a block matrix inversion is implemented in the calculation of the kriging weights. A projection approach to ICK is proposed to avoid artifacts in the realizations around the edges of the exhaustive data region when the data do not cover the entire modeling domain. The point-scale block value representation of the block-scale data is developed as an alternative to block cokriging to integrate block-scale data into realizations within the GFS framework. Several case studies support the proposed enhancements.  相似文献   

Abrupt transition from fractional crystallization to magma mixing at Gorely volcano (Kamchatka) after caldera collapse     

Maxim Gavrilenko  Alexey Ozerov  Philip R. Kyle  Michael J. Carr  Alex Nikulin  Christopher Vidito  Leonid Danyushevsky 《Bulletin of Volcanology》2016,78(7):47

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Corrigendum to ‘‘Seismic damage evaluation in urban areas using a capacity spectrum based method: Application to Barcelona’’ [Soil Dynamics and Earthquake Engineering 28 (10–11) (2008) 851–865]     

Alex H Barbat  Luis G. Pujades  Nieves Lantada  Rosangel Moreno 《Soil Dynamics and Earthquake Engineering》2010

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The COPAS’08 expedition to the Patagonian Shelf: Physical and environmental conditions during the 2008 coccolithophore bloom     

Stuart C. Painter  Alex J. Poulton  John T. Allen  Rosalind Pidcock  William M. Balch 《Continental Shelf Research》2010

Here we present observations of the hydrography of the Patagonian Shelf, shelf break and offshore waters, with reference to the environmental conditions present during the period of peak coccolithophore abundance. Analysis of a hydrographic dataset collected in December 2008 (austral spring/summer), as part of the Coccolithophores of the Patagonian Shelf (COPAS) research cruise, identified 5 distinct surface water masses in the region between 37°S and 55°S. These water masses, identified through salinity gradients, displayed varying mixed layer depths, macronutrient inventories and chlorophyll-a fluorescence. Subantarctic Shelf Water (SSW), located to the north of the Falkland Islands and extending north along the shelf break, was also host to a large coccolithophore bloom. The similarities between the distribution of calcite, as seen in remote sensing data, and SSW indicate that the coccolithophore bloom encountered conditions conducive to bloom development within this water mass. Analysis of chemical and environmental data also collected during the COPAS cruise revealed that many of the commonly cited conditions for coccolithophore bloom development were present within SSW (e.g. low N:P ratio, high N:Si ratio, shallow mixed layer depth). In the other water masses present on the Patagonian Shelf greater variability in these same parameters may explain the more diffuse concentration of calcite, and the smaller size of possible coccolithophore blooms. The distribution of SSW is strongly influenced by the latitudinal variation in shelf break frontal width, which varies from 20 to 200 km, and consequently strong hydrographic controls underlie the position of the coccolithophore bloom during austral summer.  相似文献   

Interpreting and testing compositional data     

Alex Woronow  Karen M. Love  John C. Butler 《Mathematical Geology》1989,21(1):61-63

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A predictive model for space-based X-ray ccd degradation     

Alex Antunes  David N. Burrows  Gordon P. Garmire  David H. Lumb  John A. Nousek 《Experimental Astronomy》1993,4(2):159-175

The first generation of X-ray telescopes to use Charge-Coupled Devices (CCDs) is being launched this decade. With a read noise of a few electrons, CCDs provide Fano-limited spectral resolution across the soft X-ray band (0.1 – 10 keV). However, degradation of resolution due to charge transfer losses becomes noticeable as Charge Transfer Inefficiency (CTI) increases to 10^–5. In this paper, we present a model which calculates the effects of radiation damage in low Earth orbit in order to predict CCD lifetimes over which good charge transfer is maintained. The model presented here considers damage mechanisms within the CCD, environmental conditions in which the CCD operates, and experiment shielding. We find that the predicted CTI approaches 10^–5 after a one to two year mission for the flight instruments considered here.  相似文献   

The Interaction Physics of the Fast Ignitor Concept     

C. Deutsch  H. Furukawa  K. Mima  M. Murakami  K. Nishihara 《Astrophysics and Space Science》1997,256(1-2):161-168

The interaction of relativistic electrons produced by ultrafast lasers focussing them on strongly precompressed thermonuclearfuel is analytically modelled. Energy loss to target electrons is treated through binary collisions and Langmuir wave excitation. The overall penetration depth is determined by quasielastic and multiple scattering on target ions. It thus appears possible to ignite efficient hot spots in a target with density larger than 300 g/cc.  相似文献   

A perturbation method and some applications     

Alex Konopliv 《Celestial Mechanics and Dynamical Astronomy》1989,47(4):305-320

For differential equations with one fast variable, a perturbation method is introduced that transforms a solution valid over only a short time interval to a new solution composed of averaged variables plus a periodic function of the averaged variables. The averaged variables are governed by a set of differential equations where the fast variable has been removed and thus can be numerically integrated quickly or solved directly. This method is applied to a perturbed harmonic oscillator with a cubic perturbation, van der Pol's equation, coorbital motion in the restricted three-body problem, and to nearly circular motion of a particle near one of the primaries in the restricted three-body problem.  相似文献