Measurement of field effects on dielectronic recombination of Si11+ ions

Cross sections for dielectronic recombination can be influenced by the presence of external electric fields in the electron--ion collision region. In most of the previous experiments with multiply charged ions such fields were present but unknown. Therefore, comparisons of experimental results with theoretical calculations were ambiguous: for obtaining best possible agreement, theory could use the field strength as a free parameter to adjust the calculated cross sections to the experiment. In recent measurements with 10 MeV/u Si¹¹⁺ ions stored in CRYRING, controlled external motional electric fields up to 183 V/cm were introduced in the electron cooler. Significant cross section enhancements were found for Rydberg states n > 20. This revised version was published online in August 2006 with corrections to the Cover Date.     

Theoretical and experimental investigations on microstrip active array antennas and power combiners

In this paper, microstrip active array antennas and power combiners are investigated. The mutual impedance of a rectangular microstrip patch array is analyzed based on the Richmond's reaction integral equation and Galerkin technique in spectral-domain. The computer-aided analysis and design of the active array are then carried out by coupling the mutual impedances to the large-signal characteristics of Gunn diodes with a harmonic balance technique. Based on the theoretical study, microstrip active patch array antennas are investigated experimentally.     

紫花地丁中汞的原子荧光法测定

利用还原气化的非色散型装置，以湿法消解的方式，建立了原子荧光测定紫花地丁中痕量汞的测定方法，同时比较了不同玻璃仪器的洗涤方法和不同的定量方法，试验回收率在86．9％－110．8％之间，误差＜8．5％，通过对实际样品的测定，得到了满意的结果。     

激光空泡刚性半球面内运动

采用甚高速照相技术与建立激光空泡在刚性半球壁面内的运动模型相结合的方法,确定了激光空泡在刚性半球面壁内的运动特性与无量纲距离的关系,提出了最佳无量纲距离概念。结果表明:半球反射面的半径与激光空泡最大半径之比小于1.1时,激光空泡在第1次膨胀时就会产生严重的变形并弹出半球面,并产生空化泡和空蚀,它们均会严重影响激光声的传播。该比值在1.1~3.3时,激光空泡将在第3次收缩之前接触半球面,容易对壁面造成空蚀。在该比值大于3.3的情况下,激光空泡在第3次收缩之前不会接触半球面,对激光声的传播和反射特性影响较小。如果考虑把空泡第1次溃灭时产生的激光声的声学中心控制在击穿点时,需要把该比值控制在5以上。     

湍流内尺度对光波起伏频谱的影响

在不同湍流内尺度情况下,对大气湍流引起的光波光强闪烁和到达角起伏的时间频谱特征进行了实验研究。由于实际大气湍流的复杂性和不可控性,利用大气湍流模拟箱来生成具有不同内尺度的大气湍流实验环境。利用位置敏感探测器对光波的光强闪烁和到达角起伏进行了同时测量,并反演得到了光传输路径上的湍流内尺度。实验结果显示:湍流内尺度为2.7~5.0 mm,对应同一湍流内尺度,闪烁频谱和到达角起伏频谱在高频段以相同的幂指数关系下降,幂指数的绝对值与湍流内尺度的大小呈线性关系,随着内尺度的增大,频谱指数变化区间逐渐向低频方向移动。     

Tuning exchange coupling by replacing CoFe with amorphous CoFeB in the CoFe/Ru/CoFe synthetic antiferromagnetic structure

We studied exchange coupling in the CoFe/Ru/CoFe synthetic antiferromagnetic structure with systematical replacement of the crystalline CoFe with amorphous CoFeB. Antiferromagnetic exchange coupling intensity decreases with an increase in the replacement in the bottom magnetic layer, which indicates that exchange coupling intensity could be tuned by the replacement. The origin of weakening antiferromagnetic exchange coupling is attributed to the amorphous CoFeB replacement inducing incomplete crystallization and disordered orientation in the Ru layer.     

Supercritical branching Brownian motion with catalytic branching at the origin

We consider a catalytic branching Brownian motion with general branching which takes place only when particles are at the origin at a rate β>0 on the local time scale. We first establish a spine decomposition for the case wherein the particles have a positive probability of having no children. Then using this tool, we obtain results regarding the asymptotic behavior of the number of particles above λt at time t for λ>0. Under an L log L condition, we prove a strong law of large numbers for this catalytic branching Brownian motion.     

A quantitative program for Hadwiger’s covering conjecture

In 1957,Hadwiger made a conjecture that every n-dimensional convex body can be covered by 2n translates of its interior.Up to now,this conjecture is still open for all n 3.In 1933,Borsuk made a conjecture that every n-dimensional bounded set can be divided into n + 1 subsets of smaller diameters.Up to now,this conjecture is open for 4 n 297.In this article we encode the two conjectures into continuous functions defined on the spaces of convex bodies,propose a four-step program to attack them,and obtain some partial results.     

非下采样小波变换红外光谱数据去噪

为了降低噪声对实测红外光谱信号的影响,引入了一种非下采样小波变换的红外光谱数据去噪方法。采用非下采样小波变换对原始光谱信号进行多尺度分解,提取信号的多尺度细节特征;根据光谱信号和噪声在不同尺度上的差异,通过应用变分偏微分方程方法调整分解后的各子带系数;重构各子带就可以将原始光谱信号中真实信号和噪声分离,从而达到剔除噪声的目的。通过两组实验对比传统小波和该方法针对红外光谱数据的消噪效果,实验结果表明:非下采样小波变换在红外光谱数据去噪方面具有明显的优势,不仅能够有效地去除噪声,很好地保持信号的形状,并且均方误差较小;在实际的红外光谱数据处理中能够获得较好的去噪效果。     

基于多重散射强度和偏振特征的舰船尾流气泡激光探测方法

研究多重散射效应对舰船尾流气泡群光散射强度和偏振特征的影响是舰船光尾流探测以及新型光自导鱼雷研究的基础. 基于矢量Monte Carlo方法建立了舰船尾流气泡群激光后向探测仿真模型, 重点研究了尾流气泡群的多重散射机理,分析了多重散射效应、尾流气泡群密度对回波信号强度和偏振特征的影响规律. 基于粒子碰撞重要性抽样的基本思想, 在传统能量接收方法的基础上, 提出了回波光子偏振贡献接收方法和回波信号偏振信息统计方法, 解决了小视场系统光子返回概率低无法形成回波能量的难题. 构建了模拟尾流气泡群激光散射强度和偏振探测实验平台, 从实验的角度验证了模拟结果的准确性. 实验和模拟结果的一致性表明, 利用回波强度、偏振信息可表征气泡群距离、密度信息, 从而可对舰船尾流特别是低密度尾流进行高精度的探测和辨识. 关键词： Monte Carlo 偏振 多重散射 气泡