基于钛相变边缘传感器的超导单光子探测器特性

研究了基于钛TES的超导单光子探测器的特性,器件尺寸范围为5 μm×5 μm到20 μm×20 μm,集成光学腔体后在1 550 nm波长实测的系统探测效率最高达到72%,最佳能量分辨率为0.26 eV。在此基础上,采用二流体模型提取了基于钛TES的超导单光子探测器的特性参数（包括温度灵敏度、电流灵敏度、热容等）,并模拟计算了基于钛TES的超导单光子探测器的响应时间和能量分辨率,与实验结果完全吻合。结果表明优化探测器尺寸和临界温度,可以同时达到高探测效率和高能量分辨率,实现光子数可分辨的高性能单光子探测器。     

插拔式单晶LaB6阴极制备与应用

插拔式单晶LaB₆阴极是我国电子束类高端仪器及设备必需的关键元件和发展的主要瓶颈。本文围绕插拔式单晶LaB₆,开展了单晶精密加工、高效加热、机械夹持等制备工艺研究,并对阴极的发射性能、静态寿命等进行了测试,还开展了阴极在多个领域的应用研究。研究结果表明,所制备的阴极在电子发射性能及工作寿命方面均达到与进口阴极相当的水平,可应用于增材制造、扫描电镜、高分辨率CT等领域。     

增量式块主成分分析的焊缝图像特征提取算法北大核心CSCD

针对焊缝图像特征提取的实时性问题,该文提出一种增量式块主成分分析(incremental block principal component analysis,IBlockPCA)算法,用于焊缝特征主成分的提取。该算法先将焊缝表面图像分割成子图像块并对其进行重构,然后利用提出的IBlockPCA算法对局部块图像进行增量式特征提取,并采用KNN算法对提取的特征主成分进行分类识别;最后在焊缝数据集上进行了算法的性能对比。实验结果表明,该算法在收敛率、分类率及复杂度等方面均优于其他主成分分析(principal component analysis,PCA)算法,其分类识别率为97.5%,其平均处理速度可达50 frame/s,能够满足焊缝表面图像的实时性处理需求。     

一种加载铁氧体磁环的高功率宽带巴伦

针对高功率天线的差分馈电和阻抗匹配问题,文中提出了一种基于同轴线结构加载铁氧体磁环的宽 带巴伦模型。双同轴线具有阻抗变换功能和较好的功率承载能力,铁氧体磁环改善了巴伦在低频时的输入匹配和 两个输出端口不平衡度。仿真和实测表明,此巴伦在0. 05~1. 24 GHz 内回波损耗低于-10 dB,去除3. 0 dB 系统插损 后单端插入损耗在1. 5 dB 以内,两端输出的相位不平衡度在5°以内,幅度不平衡度在2%以内。通过分析巴伦的电 磁热损耗场、温度场和应力形变场,验证了巴伦在高功率馈电下的工作性能,结果表明此巴伦在工作频带内能够承 受500 W 的功率。     

面向注塑工艺过程中的注射速度最优操纵混合优化控制方法

在注塑工艺过程中,注射速度控制是其重要环节之一,实现注射速度的快速可靠优化控制对于注塑产品的高效生产具有重要意义。该文针对一类典型的注塑装备中的伺服电机驱动恒泵液压系统,研究了注塑机工作过程中的注射速度最优跟踪控制问题,提出一种高效的基于控制参数化与粒子群优化相结合的混合智能优化控制方法,分别设计实现了开环最优控制器和状态反馈最优控制器,将控制器设计问题转化为一序列最优参数选择问题,实现了在给定时间内对所期望的注射速度跟踪控制的高效求解。最后通过实验仿真结果验证了所提出的混合优化控制算法对于求解注塑工艺过程中注射速度的动态优化问题的可行性和有效性。     

Distribution of δD in 25-cm Surface Snow Along Trans-Antarctic Route (Ⅱ)——The “1990 International Trans-Antarctic Expedition” Glaciological Research

On the way of the "1990 International Trans-Antarctic Expedition", the first author of this paper, the Chinese member of the expedition, collected 104 snow samples in 25-cm surface snow along a 5986-km route on Antarctic ice sheet from west to east. The geographical distribution of δD across the Antarctica by the longest route is obtained from stable isotope analysis for the first time. After discussing regional differences of physical geographic conditions, maritime-continental influence, altitudes and latitudes at sampling sites, the distribution of δD is considered to have a close relation to latitudes, but the topographic effect is prominent in some particular regions. The mean annual temperature at sampling site and its relationship with δD in surface snow covering Antarctica from west to east are discussed also. The δD-temperature gradient from the south end of Antarctic Peninsula to Vostok obtained in this paper is very close to that in Terre Adelie Land obtained by predecessors. The snow-dri     

Electrooxidation Mechanism of Methanol at Pt-Ru Catalyst Modified GC Electrode in Electrolytes with Different pH Using Electrochemical and SERS Techniques

The electrochemical and in-situ surface-enhanced Raman spectroscopy （SERS） techniques were used to investigate the electrooxidation behavior of methanol in acidic, neutral and alkaline media at a Pt-Ru nanoparticle modified glassy carbon （Pt-Ru/GC） electrode. The results showed that methanol could be dissociated spontaneously at the Pt-Ru/GC electrode to produce a strongly adsorbed intermediate, CO. It was found that CO could be oxidized more easily in the alkaline medium than in the acidic and neutral media. The peak potential of methanol oxidation was shifted from 0.663 and 0.708 V in the acidic and neutral media to -0.030 V in the alkaline medium, which is due to that the adsorption strength of CO on the Pt surface in the alkaline medium is weaker than that in the acidic and neutral media. The final product of the methanol oxidation is CO2. However, in the alkaline medium, CO2 produced would form CO3^2- and HCO3^- resulting in the decrease in the alkaline concentration and then in the decrease in the performance of DMFC. Therefore, the performance of the alkaline DMFC is not Stable.     

正庚烷在超稳Y沸石(USY)负载超强酸催化剂上加氢异构化

The Pt-bearing SO₄^2-/ZrO₂ superacid catalysts supported on ultra stable Y (USY) zeolite were prepared by impregnation and characterized by X-ray diffraction, nitrogen adsorption and Hammett indicators. Their catalytic activities were evaluated in the hydroisomerization of n-heptane with an atmospheric fixed-bed reactor. The catalysts possessed a high surface area, superacidity and well maintained pore structure of USY support. The supported catalysts with a suitable SO₄^2-/ZrO₂ loading exhibited a higher catalytic activity and selectivity than the unsupported SO₄^2-/ZrO₂ catalyst or the Pt supported on USY catalyst without superacid. At the reaction temperature of 220 ℃, over the catalyst with a Pt loading of 0.8wt% and ZrO₂ loading of 10wt%, the conversion of n-heptane could be as high as 35.2% with a selectivity of 87.9% for isomerization products.