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In this paper, an improved variational level set method for the Chan-Vese model is proposed to drive level set function to become fast and stably close to signed distance function. A restriction item that is a nonlinear heat equation with balanced diffusion rate is added to the traditional Chan-Vese model, and therefore the costly re-initialization(More)
Sensitivity matrix generation in electromagnetic tomography was an important step to reconstruct images. Threshold sensitivity matrix calculation method based on electrical field centre lines was applied to speed up generation of a sensitivity matrix, and improve reconstructed images quality. Firstly, the necessity and complexity about sensitivity matrix(More)
Image reconstruction in electrical capacitance tomography is an ill-posed inverse problem, and regularization techniques are usually used to solve the problem for suppressing noise. An anisotropic regional regularization algorithm for electrical capacitance tomography is constructed using a novel approach called spectral transformation. Its function is(More)
Methods and development of electromagnetic tomography (EMT) are introduced. Based on conjugate gradient algorithm, modified conjugate gradient algorithm for EMT is proposed, which improves quality of reconstructed image and convergence speed efficiently. The convergence is analyzed. The Conclusions is that the modified conjugate gradient algorithm is(More)
An electron injection regime in laser wake-field acceleration, namely electron bow-wave injection, is investigated by two- and three-dimensional particle-in-cell simulation as well as analytical model. In this regime electrons in the intense electron bow wave behind the first bubble catch up with the bubble tail and are trapped by the bubble finally,(More)
An analytical model for energy absorption during the interaction of an ultrashort, ultraintense laser with an overdense plasma is proposed. Both the compression effect of the electron density profile and the oscillation of the electron plasma surface are self-consistently included, which exhibit significant influences on the laser energy absorption. Based(More)
The development of transverse instability in the radiation-pressure-acceleration dominant laser-foil interaction is numerically examined by two-dimensional particle-in-cell simulations. When a plane laser impinges on a foil with modulated surface, the transverse instability is incited, and periodic perturbations of the proton density develop. The growth(More)
Simultaneous generation of monoenergetic tunable protons and carbon ions from intense laser multi-component nanofoil interaction is demonstrated by using particle-in-cell simulations. It is shown that, the protons with the largest charge-to-mass ratio are instantly separated from other ion species and are efficiently accelerated in the "phase stable" way.(More)
Efficient energy boost of the laser-accelerated ions is critical for their applications in biomedical and hadron research. Achiev-able energies continue to rise, with currently highest energies, allowing access to medical therapy energy windows. Here, a new regime of simultaneous acceleration of ~100 MeV protons and multi-100 MeV carbon-ions from plasma(More)
This paper presents an improved variational formulation for active contours model that forces level set function to be fast and stably close to signed distance function. The improvement can completely eliminates the need of the costly Re-initialization procedure. A restriction item that is nonlinear heat equation with balanced diffusion rate is added to the(More)