The problem of blind separation of signals in post nonlinear mixture is addressed in this paper. The post nonlinear mixture is formed by a component wise nonlinear distortion after the linear mixture. Hence a nonlin...The problem of blind separation of signals in post nonlinear mixture is addressed in this paper. The post nonlinear mixture is formed by a component wise nonlinear distortion after the linear mixture. Hence a nonlinear adjusting part placed in front of the linear separation structure is needed to compensate for the distortion in separating such signals. The learning rules for the post nonlinear separation structure are derived by a maximum likelihood approach. An algorithm for blind separation of post nonlinearly mixed sub and super Gaussian signals is proposed based on some previous work. Multilayer perceptrons are used in this algorithm to model the nonlinear part of the separation structure. The algorithm switches between sub and super Gaussian probability models during learning according to a stability condition and operates in a block adaptive manner. The effectiveness of the algorithm is verified by experiments on simulated and real world signals.展开更多
Under the condition of combined effects of group--velocitydispersion and self- phase modulation, the step Fourier method isused to simulate the propagation of initial chirped super-Gaussianpulses inside fiber. The ini...Under the condition of combined effects of group--velocitydispersion and self- phase modulation, the step Fourier method isused to simulate the propagation of initial chirped super-Gaussianpulses inside fiber. The initial chirp influences the shapes of superGaussian pulses in propagation process, and positive and negativechirps have different effects. For the existing of initial chirp, thesplits of pulses and the spreading speed move ahead and increase.When the amplitude of super-Gaussian pulses increases by 1.4 times,in the range of │C│<1.5, pulses can keep good shapes along theirpropagation distance.展开更多
In this paper,an iterative regularized super resolution (SR) algorithm considering non-Gaussian noise is proposed.Based on the assumption of a generalized Gaussian distribution for the contaminating noise,an lp norm i...In this paper,an iterative regularized super resolution (SR) algorithm considering non-Gaussian noise is proposed.Based on the assumption of a generalized Gaussian distribution for the contaminating noise,an lp norm is adopted to measure the data fidelity term in the cost function.In the meantime,a regularization functional defined in terms of the desired high resolution (HR) image is employed,which allows for the simultaneous determination of its value and the partly reconstructed image at each iteration step.The convergence is thoroughly studied.Simulation results show the effectiveness of the proposed algorithm as well as its superiority to conventional SR methods.展开更多
The molecular orientation created by laser fields is important for steering chemical reactions. In this paper, we propose a theoretical scheme to manipulate field-free molecular orientation by using an intense super-G...The molecular orientation created by laser fields is important for steering chemical reactions. In this paper, we propose a theoretical scheme to manipulate field-free molecular orientation by using an intense super-Gaussian laser pulse and a time-delayed terahertz half-cycle pulse(THz HCP). It is shown that the degree of field-free orientation can be doubled by the combined pulse with respect to the super-Gaussian pulse or THz HCP alone. Moreover, different laser intensities, carrier envelop phases, shape parameters, and time delays have great influence on the positive and negative orientations, with other conditions unchanged. Furthermore, it is indicated that the maximum degree and direction of molecular orientation can be precisely controlled by half of the duration of the super-Gaussian pulse. Finally, by adjusting the laser parameters of the super-Gaussian laser pulse and THz HCP, the optimal results of negative orientation and corresponding rotational populations are obtained at different temperatures of the molecular system.展开更多
The intensity distribution in the focal region of a high-NA lens for the incident azimuthally polarized multi Gaussian beam transmitted through a multi belt spiral phase hologram is studied on the basis of the vector ...The intensity distribution in the focal region of a high-NA lens for the incident azimuthally polarized multi Gaussian beam transmitted through a multi belt spiral phase hologram is studied on the basis of the vector diffraction theory. Here we report a new method used to generate a needle of transversely polarized light beam with sub diffraction beam size of 0.366A that propagates without divergence over a long distance of about 22A in free space. We also expect that such a light needle of transversely polarized beam may find its applications in utilizing optical materials or instruments responsive to the transversal field only.展开更多
【目的】高光谱图像因其丰富的光谱信息而备受关注,然而,由于成像硬件条件的限制,通常很难直接获得高空间分辨率的高光谱图像。为了提高分辨率,将高光谱图像与从同一场景采集的高空间分辨率的多光谱图像融合是一种经济有效的方法。然而...【目的】高光谱图像因其丰富的光谱信息而备受关注,然而,由于成像硬件条件的限制,通常很难直接获得高空间分辨率的高光谱图像。为了提高分辨率,将高光谱图像与从同一场景采集的高空间分辨率的多光谱图像融合是一种经济有效的方法。然而,现有的大多数基于深度学习的方法未充分挖掘图像间空间和光谱相关性,导致融合性能受限。【方法】本文提出了一种结合图像去噪、光谱特征与空间特征增强的高光谱图像超分辨率融合方法。首先,通过使用不同标准差的高斯模糊核对高光谱与多光谱图像进行高斯模糊处理,有效减少这2种模态图像中包含的噪声。其次,为了提高融合图像的精确度,在利用不同模态图像间光谱和空间相关性重建高分辨率图像时,分别引入通道注意力和空间注意力,利用增强图像关键信息的方式获得不同模态间更好的空间和光谱相关性。最后,利用增强的空间和光谱相关性,将映射得到的高分辨率图像特征聚合起来,重建出高空间分辨率的高光谱图像。【结果】在ZY-m和Chikusei数据集上融合结果的PSNR分别为53.586和53.738,在ZY-m数据集上较次优方法空谱解耦互引导网络(Spatial-Spectral Unfolding Network with Mutual Guidance,SMGU-Net)提高2.8%,在Chikusei数据集上较次优方法带有双条件调制模块的扩散模型(Diffusion Model with two Conditional Modulation Modules,DDIF)提高1.70%;SAM值达到0.006和0.018,在ZY-m数据集上较次优方法 SMGU-Net降低14.28%,在Chikusei数据集上较次优方法 DDIF降低5.26%。【结论】本文方法具有良好的光谱保真度和空间细节增强能力,为高光谱图像的超分辨率提供了一种有效技术方案,展示了其在国土资源勘查、环境监测等领域的良好应用潜力。展开更多
In multi-slice magnetic resonance imaging (MRI), the resolution in the slice direction is usually reduced to allow faster acquisition times and to reduce the amount of noise in each 2D slice. To address this issue, a ...In multi-slice magnetic resonance imaging (MRI), the resolution in the slice direction is usually reduced to allow faster acquisition times and to reduce the amount of noise in each 2D slice. To address this issue, a number of super resolution (SR) methods have been proposed to improve the resolution of 3D MRI volumes. Most of the methods involve the use of prior models of the MRI data as regularization terms in an ill-conditioned inverse problem. The use of user-defined parameters produces better results for these approaches but an inappropriate choice may reduce the overall performance of the algorithm. In this paper, we present a wavelet domain SR method which uses a Gaussian scale mixture (GSM) model in a sparseness constraint to regularize the ill-posed SR inverse problem. The proposed approach also makes use of an extension of the Dual Tree Complex Wavelet Transform to provide the ability to analyze the wavelet coefficients with sub-level precision. Our results show that the 3D MRI volumes reconstructed using this approach have quality superior to volumes produced by the best previously proposed approaches.展开更多
Inverse bremsstrahlung absorption in laser-heated plasmas is studied using the Fokker–Planck equation in the low-field limit.Compared with the commonly used fitting formulas of Langdon and Matte et al.,our work emplo...Inverse bremsstrahlung absorption in laser-heated plasmas is studied using the Fokker–Planck equation in the low-field limit.Compared with the commonly used fitting formulas of Langdon and Matte et al.,our work employs fewer approximations and provides more accurate predictions for the super-Gaussian orderβand the heating rate.Simulation results show that the super-Gaussian order is generally lower than the fitting results of Matte et al.,which leads to an increase in absorption.However,we find two other factors that reduce absorption:the high-order term of the collision frequency and the effects caused by high laser intensity.Therefore,the final simulated absorption can either be higher or lower,depending on the conditions.These phenomena are theoretically analyzed using the Fokker–Planck equation.Fitting formulas are proposed for the super-Gaussian order and the heating rate,showing a discrepancy within∼10%of the simulation results.We also compare the simulation results with the experimental results from several recent papers.展开更多
文摘The problem of blind separation of signals in post nonlinear mixture is addressed in this paper. The post nonlinear mixture is formed by a component wise nonlinear distortion after the linear mixture. Hence a nonlinear adjusting part placed in front of the linear separation structure is needed to compensate for the distortion in separating such signals. The learning rules for the post nonlinear separation structure are derived by a maximum likelihood approach. An algorithm for blind separation of post nonlinearly mixed sub and super Gaussian signals is proposed based on some previous work. Multilayer perceptrons are used in this algorithm to model the nonlinear part of the separation structure. The algorithm switches between sub and super Gaussian probability models during learning according to a stability condition and operates in a block adaptive manner. The effectiveness of the algorithm is verified by experiments on simulated and real world signals.
文摘Under the condition of combined effects of group--velocitydispersion and self- phase modulation, the step Fourier method isused to simulate the propagation of initial chirped super-Gaussianpulses inside fiber. The initial chirp influences the shapes of superGaussian pulses in propagation process, and positive and negativechirps have different effects. For the existing of initial chirp, thesplits of pulses and the spreading speed move ahead and increase.When the amplitude of super-Gaussian pulses increases by 1.4 times,in the range of │C│<1.5, pulses can keep good shapes along theirpropagation distance.
基金National Natural Science Foundations of China(No.60705012,No.60802025)
文摘In this paper,an iterative regularized super resolution (SR) algorithm considering non-Gaussian noise is proposed.Based on the assumption of a generalized Gaussian distribution for the contaminating noise,an lp norm is adopted to measure the data fidelity term in the cost function.In the meantime,a regularization functional defined in terms of the desired high resolution (HR) image is employed,which allows for the simultaneous determination of its value and the partly reconstructed image at each iteration step.The convergence is thoroughly studied.Simulation results show the effectiveness of the proposed algorithm as well as its superiority to conventional SR methods.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11674198 and 11874241)the Taishan Scholar Project of Shandong Province,China
文摘The molecular orientation created by laser fields is important for steering chemical reactions. In this paper, we propose a theoretical scheme to manipulate field-free molecular orientation by using an intense super-Gaussian laser pulse and a time-delayed terahertz half-cycle pulse(THz HCP). It is shown that the degree of field-free orientation can be doubled by the combined pulse with respect to the super-Gaussian pulse or THz HCP alone. Moreover, different laser intensities, carrier envelop phases, shape parameters, and time delays have great influence on the positive and negative orientations, with other conditions unchanged. Furthermore, it is indicated that the maximum degree and direction of molecular orientation can be precisely controlled by half of the duration of the super-Gaussian pulse. Finally, by adjusting the laser parameters of the super-Gaussian laser pulse and THz HCP, the optimal results of negative orientation and corresponding rotational populations are obtained at different temperatures of the molecular system.
文摘The intensity distribution in the focal region of a high-NA lens for the incident azimuthally polarized multi Gaussian beam transmitted through a multi belt spiral phase hologram is studied on the basis of the vector diffraction theory. Here we report a new method used to generate a needle of transversely polarized light beam with sub diffraction beam size of 0.366A that propagates without divergence over a long distance of about 22A in free space. We also expect that such a light needle of transversely polarized beam may find its applications in utilizing optical materials or instruments responsive to the transversal field only.
文摘【目的】高光谱图像因其丰富的光谱信息而备受关注,然而,由于成像硬件条件的限制,通常很难直接获得高空间分辨率的高光谱图像。为了提高分辨率,将高光谱图像与从同一场景采集的高空间分辨率的多光谱图像融合是一种经济有效的方法。然而,现有的大多数基于深度学习的方法未充分挖掘图像间空间和光谱相关性,导致融合性能受限。【方法】本文提出了一种结合图像去噪、光谱特征与空间特征增强的高光谱图像超分辨率融合方法。首先,通过使用不同标准差的高斯模糊核对高光谱与多光谱图像进行高斯模糊处理,有效减少这2种模态图像中包含的噪声。其次,为了提高融合图像的精确度,在利用不同模态图像间光谱和空间相关性重建高分辨率图像时,分别引入通道注意力和空间注意力,利用增强图像关键信息的方式获得不同模态间更好的空间和光谱相关性。最后,利用增强的空间和光谱相关性,将映射得到的高分辨率图像特征聚合起来,重建出高空间分辨率的高光谱图像。【结果】在ZY-m和Chikusei数据集上融合结果的PSNR分别为53.586和53.738,在ZY-m数据集上较次优方法空谱解耦互引导网络(Spatial-Spectral Unfolding Network with Mutual Guidance,SMGU-Net)提高2.8%,在Chikusei数据集上较次优方法带有双条件调制模块的扩散模型(Diffusion Model with two Conditional Modulation Modules,DDIF)提高1.70%;SAM值达到0.006和0.018,在ZY-m数据集上较次优方法 SMGU-Net降低14.28%,在Chikusei数据集上较次优方法 DDIF降低5.26%。【结论】本文方法具有良好的光谱保真度和空间细节增强能力,为高光谱图像的超分辨率提供了一种有效技术方案,展示了其在国土资源勘查、环境监测等领域的良好应用潜力。
文摘In multi-slice magnetic resonance imaging (MRI), the resolution in the slice direction is usually reduced to allow faster acquisition times and to reduce the amount of noise in each 2D slice. To address this issue, a number of super resolution (SR) methods have been proposed to improve the resolution of 3D MRI volumes. Most of the methods involve the use of prior models of the MRI data as regularization terms in an ill-conditioned inverse problem. The use of user-defined parameters produces better results for these approaches but an inappropriate choice may reduce the overall performance of the algorithm. In this paper, we present a wavelet domain SR method which uses a Gaussian scale mixture (GSM) model in a sparseness constraint to regularize the ill-posed SR inverse problem. The proposed approach also makes use of an extension of the Dual Tree Complex Wavelet Transform to provide the ability to analyze the wavelet coefficients with sub-level precision. Our results show that the 3D MRI volumes reconstructed using this approach have quality superior to volumes produced by the best previously proposed approaches.
基金supported by the Natural Science Foundation of China(Grant Nos.12035002,12405235,and U2430207)the China Postdoctoral Science Foundation(Grant No.2023M740336)the CAEP foundation(Grant No.YZJJZQ2023020).
文摘Inverse bremsstrahlung absorption in laser-heated plasmas is studied using the Fokker–Planck equation in the low-field limit.Compared with the commonly used fitting formulas of Langdon and Matte et al.,our work employs fewer approximations and provides more accurate predictions for the super-Gaussian orderβand the heating rate.Simulation results show that the super-Gaussian order is generally lower than the fitting results of Matte et al.,which leads to an increase in absorption.However,we find two other factors that reduce absorption:the high-order term of the collision frequency and the effects caused by high laser intensity.Therefore,the final simulated absorption can either be higher or lower,depending on the conditions.These phenomena are theoretically analyzed using the Fokker–Planck equation.Fitting formulas are proposed for the super-Gaussian order and the heating rate,showing a discrepancy within∼10%of the simulation results.We also compare the simulation results with the experimental results from several recent papers.
