北京航空航天大学 电子信息工程学院 电磁兼容技术研究所,北京 100191
现有的反射面电磁成像系统体积庞大,无法满足机载、车载、无人机等应用平台要求。针对此类问题,研究了龙伯透镜的结构特性和成像特性,设计了大视场龙伯透镜电磁成像系统,利用空不变成像特性进行超分辨图像处理,实现了快速、大视场、宽频带、高分辨电磁辐射源分布成像。计算了口径300 mm带球核分层龙伯透镜参数,仿真了4~18 GHz龙伯透镜焦弧面场强分布,验证了龙伯透镜空不变的成像特性及其超分辨算法的有效性。实验对比了抛物反射面电磁成像系统和本文龙伯透镜电磁成像系统的体积、成像范围、源数目和分辨率,结果证明了本文系统的优越性,同样分辨率下,达到了方位角及俯仰角均为40°的大视场范围。
大视场电磁成像 龙伯透镜 空不变 图像超分辨 large field of view Luneburg lens space invariant super-resolution 强激光与粒子束
2024, 36(4): 043017
光学 精密工程
2023, 31(23): 3482
长春师范大学 计算机科学与技术学院,吉林长春130032
为了解决编码器-解码器网络结构在目标提取中抑制无关语义、跨越语义鸿沟等问题,以获取更高精度,采用U-Net作为提取特征的主干网络;为了减轻浅层特征与深层特征语义的差异,设计一种融合注意力感知的多尺度语义池化模块(Channel-Spatial-Pyramid, CSP),替代早期层中的跳跃链接。CSP模块从空间与通道两个层面强调更有意义的语义信息,通过4个不同池化核的并行分支提取不同尺度特征,聚合所有分支结果与后期层特征拼接。实验结果表明,CSP-Net在彩色眼底图像视盘分割中的Dice指数可达99.6%,视杯分割结果的Dice指数为92.1%,相比现有算法均有提高。所提出的CSP-Net对于眼底图像中的微小目标提取的有效性及抗干扰性较高,可为青光眼筛查与诊断临床提借鉴。
多尺度语义 注意力感知 目标提取 U-Net multi scale semantics attention perception target extraction U-Net 光学 精密工程
2023, 31(21): 3203
Author Affiliations
Abstract
1 State Key Laboratory of Nuclear Physics and Technology, and Key Laboratory of HEDP of the Ministry of Education, CAPT, Peking University, Beijing, China
2 Beijing Laser Acceleration Innovation Center, Beijing, China
3 Institute of Guangdong Laser Plasma Technology, Guangzhou, China
The discharged capillary plasma channel has been extensively studied as a high-gradient particle acceleration and transmission medium. A novel measurement method of plasma channel density profiles has been employed, where the role of plasma channels guiding the advantages of lasers has shown strong appeal. Here, we have studied the high-order transverse plasma density profile distribution using a channel-guided laser, and made detailed measurements of its evolution under various parameters. The paraxial wave equation in a plasma channel with high-order density profile components is analyzed, and the approximate propagation process based on the Gaussian profile laser is obtained on this basis, which agrees well with the simulation under phase conditions. In the experiments, by measuring the integrated transverse laser intensities at the outlet of the channels, the radial quartic density profiles of the plasma channels have been obtained. By precisely synchronizing the detection laser pulses and the plasma channels at various moments, the reconstructed density profile shows an evolution from the radial quartic profile to the quasi-parabolic profile, and the high-order component is indicated as an exponential decline tendency over time. Factors affecting the evolution rate were investigated by varying the incentive source and capillary parameters. It can be found that the discharge voltages and currents are positive factors quickening the evolution, while the electron-ion heating, capillary radii and pressures are negative ones. One plausible explanation is that quartic profile contributions may be linked to plasma heating. This work helps one to understand the mechanisms of the formation, the evolutions of the guiding channel electron-density profiles and their dependences on the external controllable parameters. It provides support and reflection for physical research on discharged capillary plasma and optimizing plasma channels in various applications.
channel-guided laser discharge capillary plasma density profile High Power Laser Science and Engineering
2023, 11(6): 06000e85
1 中国矿业大学(北京)化学与环境工程学院, 北京 100083
2 华电电力科学研究院有限公司, 杭州 310012
煤气化渣与粉煤灰均为煤炭资源利用过程中产生的固体废弃物, 可以应用在碱激发领域。从煤气化粗渣的性质入手, 采用粉煤灰对煤气化粗渣进行改性, 利用碱激发技术制备了煤气化粗渣-粉煤灰基地质聚合物, 并对所制备产物的性能进行研究。结果表明, 在体系中掺入粉煤灰可以明显改善其力学性能, 当粉煤灰掺入量为30%(质量分数)时, 样品的28 d抗压强度最高, 达到44.5 MPa。此外, 通过对样品进行物相分析与微观形貌表征发现, 样品的无定形产物主要为N(C)-A-S-H凝胶, 它能够结成相互连接的空间网状结构, 具有较强的黏结能力, 这是样品材料具有较高强度的主要原因。
煤气化粗渣 碱激发 粉煤灰 地质聚合物 N(C)-A-S-H凝胶 力学性能 coal gasification coarse slag alkali-activation fly ash geopolymer N(C)-A-S-H gel mechanical property