基于开窗结构和寄生单元的双陷波超宽带天线

设计了一种具有双陷波特性的平面超宽带天线。超宽带基础天线的馈电采用渐变式阶梯阻抗匹配结构作,使得天线具有了宽阻抗匹配能力。通过在椭形辐射器内进行开窗,以及在地面添加矩形寄生单元,实现了天线的双陷波特性。测试结果表明,该天线的工作带宽(VSWR<2）为3.1~10 GHz,工作在超宽带(UWB)频率范围,两个陷波分别在3.3~4.0 GHz和5.0~5.85 GHz,可以应用于WiMAX和WLAN频段的信号抑制。仿真与实测结果表明,该天线结构简单、实现了良好的陷波功能,能够较好地应用于超宽带通信系统中。     

基于问题学习的“光学”课程教学改革

本文阐述了基于问题学习的含义,并根据"光学"课程的教学内容和我校当前该课程的实际教学状况,将PBL教学模式与传统讲授教学模式相结合。我们采用"问题引导模式"、"问题研讨模式"和"问题主导模式"对"光学"课程教学进行改革,取得了良好的教学效果。     

一种小型UHF RFID抗金属标签天线的设计

针对射频识别标签天线小型化、抗金属环境的实际需求,提出了一种可应用于金属环境的超高频射频识别标签天线.通过在矩形贴片上开槽来实现小型化,天线总尺寸为56 mm×50 mm×1.6 mm.通过改变槽的尺寸调节标签天线的输入阻抗,结合等效电路图分析抗金属标签天线的设计过程,从而方便地实现与标签芯片的共轭匹配.实验结果表明,实测和仿真结果比较吻合,标签阻抗匹配良好,实测最大读取距离达3.1m.与其他标签天线相比,该天线具有结构简单、成本低、易于实现和读取距离远等优势.     

Magnetostriction, composition and microstructure of Tb0.29（Dy1–xPrx）0.71Fe1.97 alloys with heat treatment

Tb_0.29(Dy_1-xPr_x)_0.71Fe_1.97 (x=0, 0.1, 0.2 and 0.3) alloys prepared by the directional solidification method were treated at 1073, 1123, 1173, 1223 and 1273 K for 4 h for homogenization, respectively. The magnetostriction, micro-morphology and composition distribution were studied by the standard resistance strain gauge technique, optical microscopy and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). The results indicated that heat treatment could make the microstructure of alloys homogeneous effectively and improve the magnetostriction significantly. The optimum temperature was 1223 K. Compared to the as-cast ones, the increase amplitudes of magnetostriction of the corresponding samples were 39.5%, 64.9%, 95.3% and 50.8% when x=0, 0.1, 0.2 and 0.3, respectively at the compressive stress of 2 MPa and a magnetic field of 80 kA/m. The compressive stress could also improve the magnetostriction. However, further Pr element addition and over high heat treatment temperature would lead to the excessive decomposition of PrFe₂ and destroy the homogeneity, resulting in the decline of magnetostriction of alloys.     

厦门世茂海峡大厦项目核心筒全液压爬模施工技术

我国自行研制的全液压爬模施工技术,采用爬升一次,浇筑一次竖向结构的施工工艺,已成功的在中国第一双子塔厦门世茂海峡大厦项目全面应用。全液压自爬升模板具有整体刚度大、操作方便、爬升速度快等特性,能够保证核心筒结构的快速施工     

双裁切近端策略优化算法

近端策略优化(proximal policy optimization, PPO)是一种稳定的深度强化学习算法,该算法的关键点之一是使用裁切后的代理目标限制更新步长.实验发现当使用经验最优的裁切系数时, KL散度(Kullback-Leibler divergence)无法被确立上界,这有悖于置信域优化理论.本文提出一种改进的双裁切近端策略优化算法(proximal policy optimization with double clipping boundaries, PPO-DC).该算法通过基于概率的两段裁切边界调整KL散度,将参数限制在置信域内,以保证样本数据得到充分利用.在多个连续控制任务中, PPO-DC算法取得了好于其他算法的性能.