Dongsheng Wu

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Let B = { B(t), t ∈ R+ } be an (N, d)-fractional Brownian sheet with Hurst index H = (H1, . . . , HN ) ∈ (0, 1) . The objective of the present paper is to characterize the anisotropic nature of B in terms of H. We prove the following results: (1) B is sectorially locally nondeterministic. (2) By introducing a notion of “dimension” for Borel measures and(More)
By definition, HSC (HyperSpectral Camera) images are much richer in spectral data than, say, a COTS (Commercial-Off-The-Shelf) color camera. But data are not information. If we do the task right, useful information can be derived from the data in HSC images. Nature faced essentially the identical problem. The incident light is so complex spectrally that(More)
Noninvasive imaging of cardiac electric activity is of importance for better understanding the underlying mechanisms and for aiding clinical diagnosis and intervention of cardiac abnormalities. We propose to image the three-dimensional (3-D) cardiac bioelectric source distribution from body-surface electrocardiograms. Cardiac electrical sources were modeled(More)
We have developed a method for estimating the three-dimensional distribution of equivalent current sources inside the brain from scalp potentials. Laplacian weighted minimum norm algorithm has been used in the present study to estimate the inverse solutions. A three-concentric-sphere inhomogeneous head model was used to represent the head volume conductor.(More)
Body surface Laplacian electrocardiogram (ECG) mapping using a set of disk electrodes is explored by both computer simulation and human experiments in 12 healthy subjects. The Laplacian ECG was estimated from body surface potentials using finite difference estimation algorithms. The performance of the finite difference Laplacian estimators was evaluated by(More)
We prove the following results about the images and multiple points of an N -parameter, d-dimensional Brownian sheet B: (1) If dimH F ≤ d/2, then B(F ) is almost surely a Salem set. (2) If N ≤ d/2, then with probability one dimB(F ) = 2 dimF for all Borel sets F ⊂ R+ , where “dim” could be everywhere replaced by the “Hausdorff,” “packing,” “upper(More)
where Ẇ (x, t) is an R-valued space-time white noise. Mueller and Tribe (2002) have proved necessary and sufficient conditions for the R-valued process {ut(x) : t ≥ 0, x ∈ R} to hit points and to have double points. In this paper, we continue their research by determining the Hausdorff and packing dimensions of the level sets and the sets of double times of(More)
We derive a decoupling formula for the Brownian sheet which has the following ready consequence: An N -parameter Brownian sheet in R has double points if and only if 2(d − 2N) < d. In particular, in the critical case where 2(d − 2N) = d, Brownian sheet does not have double points. This answers an old problem in the folklore of the subject. We also discuss(More)