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Cardiovascular diseases and myocardium infarction are main causes of death worldwide. After acute myocardium infarction, remodeling occurs within weeks resulting from a loss of cardiomyocytes in the damaged myocardium, and subsequent changes with regional tissue organization. Imaging methods able to render the local tissue directivity would be useful to detect the lesion and evaluate its extent. In this field, diffusion MRI is the reference. However, because of its long acquisition time, it is not simple to make an image of the moving heart in vivo . For this reason, faster methods using ultrasound were developed. The purpose of this work is to study the spatial coherence method with an ultrasound plane wave ultrafast imaging approach. Simulations have been performed with CREANUIS software on a medium constituted by many angled fibers in order to mimic the orientation changes that appear in the myocardium. Experimental data were also acquired on a wires phantom. The wires of the phantom were set in parallel planes with changing orientation between [−45° and 45°] at a depth between [20 and 40 mm]. Results obtained with the method have permitted to evaluate properly the orientation with RMSE of 11.2° and 16.5° for simulation and experiments, respectively. [ABSTRACT FROM AUTHOR]

Inter-annual variability (IAV) of forest Net Primary Productivity (NPP) is a function of both extrinsic (e.g., climate) and intrinsic (e.g., stand dynamics) drivers. As estimates of NPP in forests are scaled from trees to stands to the landscape, an understanding of the relative effects of these factors on spatial and temporal behavior of NPP is important. Although a high degree of spatial coherence (i.e., the degree of spatial synchrony over time) is often assumed, this inherent behavior is rarely examined. Quantifying this term may improve future predictions as site-level estimates are scaled up spatially. We quantified the spatial coherence of bole biomass production (BBP) within and between trees, and bole-related NPP (NPP B ) between sites of varying age, elevation, moisture, and species composition across a forested landscape in the western Cascade Range of Oregon. Within sites, individual trees with lower than average BBP were the most coherent. IAV of BBP increased as average tree BBP increased and spatial coherence was reduced. Among sites, NPP B was the most spatially coherent ( r = 0.92) between young sites, while older sites and comparisons between age classes revealed a much larger range in spatial coherence ( r = −0.18 to 0.85). Our findings indicate climate variability may be of greater importance for spatial coherence between young sites, and that intrinsic factors could be decreasing spatial coherence between older sites or sites not in close proximity. The wide range in spatial coherence between sites found in this study, coupled with the complex land use history patterns across forested landscapes, has significant implications for modeling and scaling of NPP. [ABSTRACT FROM AUTHOR]

A phase delay spectrum model towards the representation of spatial coherence of stochastic wind fields is proposed. Different from the classical coherence functions used in the spectral representation methods, the model is derived from the comprehensive description of coherence of fluctuating wind speeds and from the thorough analysis of physical accounts of random factors affecting phase delay, building up a consistent mapping between the simulated fluctuating wind speeds and the basic random variables. It thus includes complete probabilistic information of spatial stochastic wind fields. This treatment prompts a ready and succinct scheme for the simulation of fluctuating wind speeds, and provides a new perspective to the accurate assessment of dynamic reliability of wind-induced structures. Numerical investigations and comparative studies indicate that the developed model is of rationality and of applicability which matches well with the measured data at spatial points of wind fields, whereby the phase spectra at defined datum mark and objective point are feasibly obtained using the numerical scheme associated with the starting-time of phase evolution. In conjunction with the stochastic Fourier amplitude spectrum that we developed previously, the time history of fluctuating wind speeds at any spatial points of wind fields can be readily simulated. [ABSTRACT FROM AUTHOR]

A lot of issues have to be taken into account when designing a reliable free space optical communication link. Among these are e.g., beam wander, fluctuation of optical intensity and loss of spatial coherence that are caused by atmospheric turbulence. This paper presents experimental measurements of spatial coherence of a laser beam. The experimental setup is based on Young's double pinhole experiment. Fringe patterns under atmospheric turbulence for four different pinhole separations are presented. From these fringe patterns, visibility is determined and the coherence radius is estimated. [ABSTRACT FROM AUTHOR]

A singnificant amount of acoustic spatial variability is characteristics of direct field acoustic testing using a single random signal to drive the loudspeaker sources. This has raised concerns about the potential for under-and over-testing of hardware, particularly becuase of the consequntial high sensitivty of the test environment upon the configuration of the test equipment and test hardware.Meanwhile,little is known about the specific spatial charectristics of the test acoustic filed. A recent demonstration single-drive direct filed acoustic test afforded the opportunity to map various planes of the acoustic filed with a 36 michrophone gird,offering unprecedented physical insihgt into the filed charectristics.Analysis of the data reveals that the filed is predominatly charactrized by wave interference patterns at any given frequency.These data correlate well with 3-dimensional numerical models. The presence of wave interference pattern created by the fully correlated array of sources also explain the occurrence of frequency bands where the acoustic levels were significantly overdrive as a consequence of the control michrophone location coinciding with acoustic nodes associated with the corresponding drive frequencies. For compression,the same mapping was performed in a conventional reverberant chamber the two test methods. This paper presents the highlights of this study and discusses ramifications for the use of this methodology. [ABSTRACT FROM AUTHOR]

Seismic response of underground pipelines is usually calculated by wave propagation theory, in which spatially full coherence of seismic ground motions is assumed. The analysis of data recorded at dense instrument arrays has confirmed the partial coherence of seismic ground motions at different stations. The effect of the partial coherence of seismic ground motions on underground continuous pipeline is not very clear. In this paper, seismic responses of underground continuous pipeline in both longitudinal and lateral directions in uniform medium are studied by the pseudo-excitation method in random vibration theory, and then the impacts of locality effect and coherence effect on underground continuous pipeline are analyzed respectively. The results show that it may be unsafe without consideration of the partial coherence of seismic ground motions, and different coherence models lead to different results. It is suggested that the partial coherence of seismic ground motions should be considered, and the coherence models should be chosen cautiously. [ABSTRACT FROM AUTHOR]

Abstract: We address the problem of segmenting an image sequence into rigidly moving 3D objects. An elegant solution to this problem in the case of orthographic projection is the multibody factorization approach in which the measurement matrix is factored into lower rank matrices. Despite progress in factorization algorithms, their performance is still far from satisfactory and in scenes with missing data and noise, most existing algorithms fail. In this paper we propose a method for incorporating 2D non-motion cues (such as spatial coherence) into multibody factorization. We show the similarity of the problem to constrained factor analysis and use the EM algorithm to find the segmentation. We show that adding these cues improves performance in real and synthetic sequences. [Copyright &y& Elsevier]

Abstract: Maps are vital tools for most government agencies and consumers. However, their manual generation and updating is tedious, time consuming, and expensive. To address these concerns, we are developing automated techniques. In this paper, we restrict our attention to residential regions. These regions provide a challenge, testing the current limits of automated image analysis. Such regions are also typically areas of rapid growth and development and, therefore, are of interest from the applications perspective. In previous studies, we introduced statistical measures to extract these kinds of regions from satellite images [in: Proceedings of the International Conference on Pattern Recognition, vol. 1, 2002, p. 127, IEEE Trans. GeoRS (2003), IEEE Trans. PAMI]. As the next step toward automatic map generation, here we introduce a novel system to detect houses and street networks in IKONOS multispectral images. These images have one meter panchromatic resolution with 4m resolution in the spectral bands. Our system consists of four major components: multispectral analysis to detect cultural activity, segmentation of regions of possible human activity (based on the surface material), decomposition of the segmented images, and graph theoretical algorithms over the decompositions to extract the street network and to detect houses. We tested our system on a large and diverse data set. Our results indicate the usefulness of our system in detecting houses and street networks, hence generating automated maps. [Copyright &y& Elsevier]

Delay-multiply-and-sum (DMAS) imaging is capable of suppressing clutter interference by introducing spatial coherence of received channel data into the beamforming process. Recently, double-stage DMAS beamforming (DS-DMAS) has been proposed by firstly calculating the column sum of auto-covariance matrix and then applying DMAS in the second stage to further highlight the channel coherence. In contrast, p -DMAS beamforming emphasizes the spatial coherence by adopting a single-stage p -th-root magnitude scaling of the channel signal and p -th-power restoration after channel sum. Though their implementation differs, DS-DMAS and p -DMAS produce visually similar image quality. In this study, the relation between DS-DMAS and p -DMAS is analytically demonstrated and verified using simulations and experiments. Results indicate that DS-DMAS beamforming is virtually equivalent to p -DMAS with p = 3 particularly when high coherent target such as wire reflectors are being imaged. Reconstructed B-mode image and corresponding quantitative metrics also suggest high similarity between DS-DMAS and p -DMAS for speckle-generating object. For numerical B-mode image, their absolute difference is below −43.5 dB for wire reflectors and −42.6 dB for pure speckle phantom. Due to their virtually equivalent performance, p -DMAS beamforming is a better alternative than DS-DMAS in terms of computational complexity. [ABSTRACT FROM AUTHOR]