Weifeng Zhou

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PURPOSE This work develops a compressive sensing approach for diffusion-weighted (DW) MRI. THEORY AND METHODS A phase-constrained low-rank (PCLR) approach was developed using the image coherence across the DW directions for efficient compressive DW MRI, while accounting for drastic phase changes across the DW directions, possibly as a result of eddy(More)
A new model for the simulation of bipolar organic semiconductor devices by a three-dimensional master equation is proposed. A single-layer diode with a cubic lattice is investigated. Generation and recombination of electrons and holes are included consistently, where a single parameter, the lifetime, controls the rates. Current-voltage characteristics,(More)
This paper is concerned with the controllability and observability for a class of fractional linear systems with two different orders. The sufficient and necessary conditions for state controllability and state observability of such systems are established. The results obtained extend some existing results of controllability and observability for fractional(More)
Sparse approximation has shown to be a significant tool in improving image restoration quality, assuming that the targeted images can be approximately sparse under some transform operators. However, it is impossible for a fixed system to be always optimal for all the images. In this paper, we present an adaptive wavelet tight frame technology for sparse(More)
Noise analysis in bipolar organic semiconductor devices is performed via the Langevin approach for a three-dimensional master equation under the sinusoidal steady-state condition. A single-layer diode with a cubic lattice is investigated. Hopping, generation and recombination of charge carriers are all treated as Poisson processes. Calculations of the power(More)