石墨纳米片的原位分散及对聚丙烯力学性能的影响

石墨纳米片(GNP)在聚合物基体中的分散状态和界面相互作用是决定GNP/聚合物复合材料力学性能的关键因素。文中采用与聚丙烯(PP)共球磨剥离石墨得到GNP均匀包覆PP的母粒,进一步与PP熔融共混制备了PP/GNP复合材料。结果表明,与纯石墨和石墨烯相比,GNP与PP基体之间的界面相互作用更强,扫描电镜分析显示GNP分散更均匀,添加0.7%GNP的复合材料经差示扫描量热分析后发现,其结晶温度(Tc)显著提高。PP/GNP复合材料的拉伸强度和冲击强度相对于纯PP分别提升了33.34%和33.47%。该分散方法在开发其他高性能多功能GNP/聚合物复合材料方面具有巨大潜力。

A robust tensor watermarking algorithm for diffusion-tensor images

Watermarking algorithms that use convolution neural networks have exhibited good robustness in studies of deep learning networks.However,after embedding watermark signals by convolution,the feature fusion eficiency of convolution is relatively low;this can easily lead to distortion in the embedded image.When distortion occurs in medical images,especially in diffusion tensor images(DTIs),the clinical value of the DTI is lost.To address this issue,a robust watermarking algorithm for DTIs implemented by fusing convolution with a Transformer is proposed to ensure the robustness of the watermark and the consistency of sampling distance,which enhances the quality of the reconstructed image of the watermarked DTIs after embedding the watermark signals.In the watermark-embedding network,Ti-weighted(Tlw)images are used as prior knowledge.The correlation between T1w images and the original DTI is proposed to calculate the most significant features from the T1w images by using the Transformer mechanism.The maximum of the correlation is used as the most significant feature weight to improve the quality of the reconstructed DTI.In the watermark extraction network,the most significant watermark features from the watermarked DTI are adequately learned by the Transformer to robustly extract the watermark signals from the watermark features.Experimental results show that the average peak signal-to-noise ratio of the watermarked DTI reaches 50.47 dB,the diffusion characteristics such as mean diffusivity and fractional anisotropy remain unchanged,and the main axis deflection angleαAc is close to 1.Our proposed algorithm can effectively protect the copyright of the DTI and barely affects the clinical diagnosis.

Decaying evolution dynamics of double-pulse mode-locking

Taking advantage of the dispersive Fourier transformation technique, the decaying evolution processes of doublepulse mode-locking in a single-walled carbon-nanotube-based Er-doped fiber laser are observed in detail for the first time to our knowledge. The decaying dynamics of the double-pulse mode-locking state is analyzed in the spectral and temporal domains. We reveal that the two pulses in one cluster disappear either simultaneously or one by one during the decaying processes of double-pulse mode-locking states. In addition, the spectral evolution patterns of the special double-pulse states(i.e., bound states) are extremely distinct at different decline rates of the pump power.

Generation of coexisting high-energy pulses in a mode-locked all-fiber laser with a nonlinear multimodal interference technique

We demonstrate a passively mode-locked all-fiber laser incorporating a piece of graded-index multimode fiber as a mode-locking modulator based on a nonlinear multimodal interference technique, which generates two types of coexisting high-energy ultrashort pulses [i.e., the conventional soliton(CS) and the stretched pulse(SP)]. The CS with pulse energy as high as 0.38 n J is obtained at the pump level of 130 mW. When the pump increases to175 mW, the high-energy SP occurs at a suitable nonlinear phase bias and its pulse energy can reach 4 n J at a 610 mW pump. The pulse durations of the generated CS and SP are 2.3 ps and 387 fs, respectively. The theory of nonlinear fiber optics, single-shot spectral measurement by the dispersive Fourier-transform technique, and simulation methods based on the Ginzburg–Landau equation are provided to characterize the laser physics and reveal the underlying principles of the generated CS and SP. A rogue wave, observed between the CS and SP regions, mirrors the laser physics behind the dynamics of generating a high-energy SP from a CS. The proposed all-fiber laser is versatile, cost-effective and easy to integrate, which provides a promising solution for high-energy pulse generation.

Traditional soliton erbium-doped fiber laser with InSe as saturable absorber

Indium selenide(InSe)is a typical layered metal-chalcogenide semiconductor that has potential for developing ultrafast optoelectronic devices.In this work,InSe-polyvinyl alcohol(InSe-PVA)film is employed as saturable absorber and prepared by mixing InSe nanosheets solution and polyvinyl alcohol solution.The nonlinear absorption properties of the InSe saturable absorber(InSe-SA)are investigated,showing that the nonsaturable absorption and modulation depth are 37.5%and 9.55%,respectively.Traditional soliton lasers are generated in erbium-doped fiber(EDF)laser-employed InSe as a mode-locker.The central wavelength and pulse duration of the traditional soliton pulse are 1568.73 nm and 2.06 ps,respectively,under a repetition rate of 1.731 MHz.The maximum average output power is 16.4 mW at the pump power of 413 mW.To the best of our knowledge,this is the first demonstration of a traditional soliton pulse with InSe as a mode-locker.The experimental results further demonstrate that InSe is an outstanding nonlinear absorption material in ultrafast fiber laser.