The 4H-SiC crystal is found to have great potential in terahertz generation via nonlinear optical frequency conversion due to its extremely high optical damage threshold, wide transparent range, etc. In this paper, optical rectification (OR) with tilted-pulse-front (TPF) setting based on the 4H-SiC crystal is proposed. The theory accounts for the optimization of incident pulse pre-chirping in the TPF OR process under high-intensity femtosecond laser pumping. Compared with the currently recognized LiNbO₃-based TPF OR, which generates a single-cycle terahertz pulse within 3 THz, 4H-SiC demonstrates a significant advantage in producing ultra-widely tunable (up to over 14 THz, TPF angle 31°–38°) terahertz waves with high efficiency (~10^–2) and strong field (~MV/cm). Besides, the spectrum characteristics, as well as the evolution from single- to multi-cycle terahertz pulses can be modulated flexibly by pre-chirping. The simulation results show that 4H-SiC enables terahertz frequency extending to an unprecedent range by OR, which has extremely important potential in strong-field terahertz applications.

量子色动力学（Quantum Chromodynamics，QCD）在有限温度有限密度平面内具有丰富的相结构，关于相边界曲线、临界终点（Critical Endpoint，CEP）的位置以及各相的热力学性质、状态方程等的研究是目前理论和实验上的重点问题，寻找QCD相变信号，特别是确定CEP的位置，成为了相对论性重离子对撞机当前和未来实验计划的主要目标。本文简要小结在QCD的戴森-施温格方程（Dyson-Schwinger equation，DSE）方法框架下，关于手征对称性恢复相变和退禁闭相变研究的进展和主要结果，着重介绍关于DSE的截断方案的探索和完善、QCD相变的手征磁化率判据和推广的施温格（Schwinger）函数判据、及由之确定的手征和禁闭两种相变的相图。DSE方法预言的手征相变的CEP位置大致位于（T，μ_B）（110，600）MeV，与泛函重整化群等方法预言的结果一致。这些结果对于重离子对撞实验搜寻CEP信号具有指导价值。

在红外图像中，传统直方图均衡图像时细节像素容易被大量的背景像素淹没，导致图像产生过亮、过暗等现象。基于这样的状况，提出一种自适应逆直方图均衡化细节增强算法。该算法通过逆向统计、自适应选取阈值以及分段映射来增强图像细节。相比于传统直方图均衡化算法，逆直方图均衡化算法明显改善了图像在不同灰度层分布的视觉效果，使图像的不同区域亮度得到不同程度的增强。而且该算法在能够达到更好的图像处理效果的前提下仍然能够通过优化计算方法保证实时性，高效性，并且适合在FPGA硬件移植中采用。

Visible light positioning (VLP) is an emerging candidate for indoor positioning, which can simultaneously meet the requirements for accuracy, cost, coverage area, and security. However, intercell interference caused by light intensity superposition limits the application of VLP. In this Letter, we propose a united block sequence mapping (UBSM)-based VLP that utilizes superposition to integrate the multidimensional information from dense small cells into 2D information. The experimental result shows that UBSM-based VLP can achieve an accuracy of 1.5 cm with a 0.4 m row spacing and 0.35 m column spacing of LED lights.