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Absorption spectrum of phytoplankton pigments derived from hyperspectral remote-sensing reflectance

REMOTE SENSING OF ENVIRONMENT 2004年第3期89卷 361-368页

作者： Lee, ZP Carder, KL USN Res Lab Stennis Space Ctr MS 39529 USA Univ S Florida Coll Marine Sci St Petersburg FL 33701 USA

For a data set collected around Baja California with chlorophyll-a concentration ((chl-a)) ranging from 0.16 to 11.3 mg/m(3), hyperspectral absorption spectra of phytoplankton pigments were independently inverted from hyperspectral remote-sensing reflectance using a newly developed ocean-color algorithm. The derived spectra were then compared with those measured from water samples using the filter-pad technique, and an average difference of 21.4% was obtained. These results demonstrate that the inversion algorithm worked quite well for the coastal waters observed and suggest a potential of using hyperspectral remote sensing to retrieve both chlorophyll-a and other accessory pigments. (C) 2003 Elsevier Inc. All rights reserved.

关键词： absorption spectrum of phytoplankton pigments inversion algorithms

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Spatio-temporal directional filtering for improved inversion of MR elastography images

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MEDICAL IMAGE ANALYSIS 2003年第4期7卷 465-473页

作者： Manduca, A Lake, DS Kruse, SA Ehman, RL Mayo Clin & Mayo Fdn Rochester MN 55901 USA

Dynamic magnetic resonance elastography can visualize and measure propagating shear waves in tissue-like materials subjected to harmonic mechanical excitation. This allows the calculation of local values of material parameters such as shear modulus and attenuation. Various inversion algorithms to perform such calculations have been proposed, but they are sensitive to areas of low displacement amplitude (and hence low SNR) that result from interference patterns due to reflection and refraction. A spatio-temporal directional filter applied as a pre-processing step can separate interfering waves so they can be processed separately. Weighted combinations of inversions from such directionally separated data sets can significantly improve reconstructions of shear modulus and attenuation. (C) 2003 Elsevier B.V. All rights reserved.

关键词： elasticity elastography inversion algorithms shear modulus tissue characterization

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Improved inversion of MR elastography images by spatio-temporal directional filtering

Improved inversion of MR elastography images by spatio-tempo...

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Medical Imaging 2003 Conference

作者： Manduca, A Lake, DS Ehman, RL Mayo Clin & Mayo Fdn Dept Physiol & Biophys & Biomath Resource Rochester MN 55905 USA

ISBN: (纸本)0819448338

MR e0lastography can visualize and measure propagating shear waves in tissue-like materials subjected to harmonic mechanical excitation. This allows the calculation of local values of material parameters such as shear modulus and attenuation. Various inversion algorithms to perform such calculations have been proposed, but they are sensitive to areas of low displacement amplitude (and hence low SNR) that result from interference patterns due to reflection and refraction. A spatio-temporal directional filter applied as a pre-processing step can separate interfering waves so they can be processed separately. Weighted combinations of inversions from such directionally separated data sets can significantly improve reconstructions of shear modulus and attenuation.

关键词： elasticity elastography shear modulus tissue characterization inversion algorithms digital filters wave propagation shear wave

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Water properties derived from water color versus measured from water sample: application of a new color-inversion algorithm

Water properties derived from water color versus measured fr...

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Conference on Ocean Remote Sensing and Applications

作者： Lee, ZP Carder, KL Patch, J Barnard, A Otis, D Trees, CC USN Res Lab Stennis Space Ctr MS 39529 USA

ISBN: (纸本)0819446785

Apply a newly developed ocean-color inversion algorithm to measurements made in the west Florida Shelf and off the California coast, we derived the particle backscattering coefficient and the total absorption coefficient. From the derived total absorption coefficient, we calculated the absorption coefficients of the phytoplankton pigments and that of the gelbstoff (Colored Dissolved Organic Matter). From the derived pigment absorption coefficients, we further calculated the chlorophyll-a concentrations. These derived values were compared with those measured from water samples. It is found that the derived values are very consistent with those measured ones, suggesting that the inversion methods work very well for these coastal waters, and can be applied to satellite data for wide observations.

关键词： optical properties inversion algorithms chlorophyll-a concentrations

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A modification of the Dewilde-van der Veen method for inversion of finite structured matrices

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LINEAR ALGEBRA AND ITS APPLICATIONS 2002年 343卷 419-450页

作者： Eidelman, Y Gohberg, I Tel Aviv Univ Raymond & Beverly Sackler Fac Exact Sci Sch Math Sci IL-69978 Tel Aviv Israel

We study a class of block structured matrices R = {R-ij}(i,j=1)(N) with a property that the solution of the corresponding system Rx = y of linear algebraic equations may be performed for O(N) arithmetic operations. In this paper for finite invertible matrices we analyze in detail factorization and inversion algorithms. These algorithms are related to those suggested by P.M. Dewilde and A.J. van der Veen (Time-varying Systems and Computations, Kluwer Academic Publishers, New York, 1998) for a class of finite and infinite matrices with a small Hankel rank. The algorithms presented here are more transparent and are a modification of the algorithms from the above reference, The approach and the proofs are essentially different from those in the above-mentioned reference. The paper contains also analysis of complexity and results of numerical experiments. (C) 2002 Elsevier Science Inc. All rights reserved.

关键词： structured matrices linear complexity algorithms inversion algorithms factorization algorithms solution of linear equations

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Data reduction methods for space lidar observation of clouds and aerosols

Data reduction methods for space lidar observation of clouds...

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Conference on Lidar Remote Sensing for Industry and Environment Monitoring

作者： Liu, ZY Voelger, P Sugimoto, N Natl Inst Environm Studies Tsukuba Ibaraki 3050053 Japan

ISBN: (纸本)0819438065

We studied data reduction algorithms for the retrievals of optical properties of cloud and aerosols for a two-wavelength (1053 nm and 527 nm) spaceborne lidar which has been developed in the frame of the Japanese spaceborne lidar project. We simulated cloud and aerosol observations with this lidar for prelaunch characterizations and investigation of the retrieval of cloud and aerosol optical properties. In the simulations, first, lidar return signals were generated for a two-dimensional artificial model atmosphere taking into account all possible noise sources as detector, background radiation, etc. and simulated realistically both the digitized data sampling process and the saturation behavior of the photon counting system. Then, the developed data reduction algorithms were tested with these simulated two-wavelength lidar signals to retrieve cloud and aerosol optical scattering parameters. The results showed that this lidar will provide not only qualitative information of cloud and aerosol distributions but also allows for the quantitative retrieval of optical properties of some aerosol layers and optically thin clouds. Recently, we applied the data reduction methods to the analysis of the data observed by the Lidar In-space Technology Experiment (LITE) in September 1994. The applicability of these methods to retrievals of optical properties of aerosols and optically thin clouds such as cirrus have been demonstrated. Moreover, comparisons of the simulated results for ELISE with the LITE observation were conducted to verify the developed simulation method. In this paper after a brief review of the data reduction algorithms, we present a three-component solution of the lidar equation for data analysis of high level thin clouds with volcanic aerosols and apply it to the LITE data of orbit 125.

关键词： space lidar lidar data reduction inversion algorithms cloud and aerosol observations

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A comparative study of processing simulated and experimental data in elastic laser light scattering

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MATHEMATICAL BIOSCIENCES 1999年第1-2期157卷 321-344页

作者： Popovici, MA Mincu, N Popovici, A Politehn Univ Bucharest Dept Phys Bucharest 77206 Romania Natl Inst Res & Dev Optoelect Bucharest 76900 Romania Romanian Acad Ctr Math Stat Bucharest 76100 Romania

The intensity of the laser light scattered by a suspension of biological particles undergoing Brownian motion contains information about their size distribution function and optical properties. We used several methods (implemented in MathCAD programs), including a new one, to invert the Fredholm integral equation of the first kind, which represents the angular dependence of the elastic scattering of light. The algorithms were first tested on different sets of simulated data. Experimental data were obtained using biological samples and an experimental arrangement which are briefly described. We study the stability of the inversion procedures relative to the noise levels, and compute the first two moments of the retrieved size distribution function. A comparison of the results corresponding to simulated and experimental data is done, to select the best processing algorithm. (C) 1999 Elsevier Science Inc. All rights reserved.

关键词： elastic light scattering biological particles particle size distribution function inversion algorithms

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Unique temperature profiles for the atmosphere below an observer from sunset images

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APPLIED OPTICS 1997年第27期36卷 6957-6961页

作者： Bruton, WD Kattawar, GW TEXAS A&M UNIV DEPT PHYSCTR THEORET PHYSCOLLEGE STNTX 77843

We were able to transform the usual refraction equations for an observer within a spherically symmetric atmosphere into an Abel integral equation that has a unique inverse. It is now possible to extract accurate temperature profiles of the atmosphere below an observer over the marine boundary layer with use of simple edge-finding software on solar images at sunset. Several examples are presented demonstrating the efficiency of the method. (C) 1997 Optical Society of America.

关键词： refraction temperature profiles inversion algorithms ocean optics

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SENSITIVITY OF inversion algorithms FOR RECOVERING ELASTIC-CONSTANTS OF ANISOTROPIC SOLIDS FROM LONGITUDINAL WAVESPEED DATA

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ULTRASONICS 1992年第1期30卷 43-48页

作者： EVERY, AG SACHSE, W CORNELL UNIV DEPT THEORET & APPL MECHITHACANY 14853

This paper discusses the sensitivity of inversion algorithms for recovering the elastic constants of moderately anisotropic solids using only ultrasonic longitudinal wavespeed data measured for various directions in a medium. This investigation is motivated, in part, by experience with the recently developed point source/point receiver technique, in which longitudinal wave arrivals are clearer and easier to measure accurately than the later transverse wave arrivals. A perturbation method is presented which shows that for a medium of triclinic symmetry, the longitudinal wavespeeds are most sensitive to the partial set of elastic constants C-11, C22, C33, (C-12 + 2C66), (C23 + 2C44) and (C-13 + 2C55), and it is these constants which can therefore be most accurately recovered from longitudinal wavespeed data. A number of illustrative numerical examples are presented which demonstrate the lack of sensitivity to certain constants and illustrate the recovery of elastic constants from simulated longitudinal mode data. These show that there is good convergence for the partial set of elastic constants, whereas the remaining elastic constants are much less accurately recovered.

关键词： inversion algorithms ELASTIC CONSTANTS LONGITUDINAL WAVESPEEDS

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MEASUREMENT OF WATER-VAPOR AND CLOUD LIQUID WATER-CONTENT BY A DUAL-CHANNEL GROUND-BASED MICROWAVE RADIOMETER

MEASUREMENT OF WATER-VAPOR AND CLOUD LIQUID WATER-CONTENT BY...

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1991 INTERNATIONAL GEOSCIENCE AND REMOTE SENSING SYMP - REMOTE SENSING : GLOBAL MONITORING FOR EARTH MANAGEMENT ( IGARSS 91 )

作者： ZHAO, CL CAI, HQ SONG, YD LIN, B

ISBN: (纸本)0879426756

The design principle and structural features of a new type of dual-channel ground-based microwave radiometer for measurement of water vapor and cloud liquid water content in the troposphere are discussed. A method independent of radiosonde data is used for system absolute calibrations. A statistical method for retrieving the total water vapor and cloud liquid water content and a nonlinear iterative algorithm for retrieving the water vapor profiles in the troposphere are discussed. A comparison is conducted between the measurement of the integrated amounts of water vapor and the tropospheric vapor profiles by the radiometer and the radiosonde data.

关键词： DIGITAL INSTRUMENT CALIBRATION inversion algorithms

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