Influence of switchable magnetic field on the modulation property of nanostructured magnetic fluids

Magnetic fluid is a kind of colloidal material with tunable microstructure and unique optical properties. The tunable magneto-optical modulation property of magnetic fluid under externally switchable magnetic field with various modulation periods is investigated theoretically and experimentally. The transitional modulation period (lower limit of the working frequency) between the square-like and oscillation-like modulation is achieved and found to be magnetic-field- and sample-concentration-dependent. The modulation mechanism is analyzed and ascribed to the dynamic microstructure of magnetic fluid under different modulation periods of external magnetic fields. The result of this work may be helpful for the pragmatic applications of magnetic fluid based on the square-like modulation.     

脉冲激光频域干涉技术在超快动力学物理中的应用

介绍了一种具有fs时间分辨力的超短脉冲激光频域干涉测试技术,详细论述了该技术的工作原理和系统构成,指出传输时间差和相位差是影响频域干涉条纹周期的主要因素。采用脉冲激光频域干涉仪测量了200 nm厚度铝膜在波长800 nm、单脉冲能量0.7 mJ、脉宽35 fs脉冲激光作用下的运动速度剖面。在单次飞秒脉冲激光作用下,铝膜自由面的运动速度峰值可达960 m/s,速度剖面的上升前沿小于5.77 ps,表明脉冲激光频域干涉技术可用于测量材料在超快脉冲激光作用下的冲击动力学参数。     

飞行器供配电系统地面通用测试接口设计

供配电地面测试负责为飞行器提供模拟供电、控制状态切换、采集并传输系统状态信息,配合完成全飞行器全周期的综合测试任务。本文首先简要介绍了供配电地面测试系统的基本功能和设备组成,然后对供电、控制、测量的接口设计进行分析,最后提出接口通用化设计方案。本文为电气系统地面通用化测试研究提供了有益尝试。     

近红外光谱分析中建模校正集的选择

将极大线性无关组的概念及方法引入近红外光谱分析,探讨了在建立定量分析模型时代表性样品,即校正集样品的选择问题。以2 652个烟末样品为实验材料,随机选取1 001个样品构成预测集,其余1 651个样品为代表性样品备选集。用Matlab软件求出代表性样品备选集光谱矩阵的极大线性无关组,以此作为代表性样品,构成建模的校正集。用PLS回归法建立了烟末样品总糖含量定量分析的预测模型,并将模型用于预测集中1 001个烟末样品总糖含量的预测分析。实验结果表明,当选择的校正集包含的样品数量大于32时,所建各模型对预测集样品预测的平均相对误差均小于4%,平均相关系数大于0.96。其中选择32个代表性样品和146个代表性样品所建模型定量分析预测集中各样品的总糖含量,两个结果经统计检验没有显著性差异(α=0.05),说明求极大线性无关组的方法用于校正集样品的选择,可实现“少而精”选择样品的目的。此外,我们用求极大线性无关组选择校正集样品和随机方法选择校正集样品两种方法,选择了同样数目28,32,41,76,146,163个样品建模进行预测效果的对比实验,结果显示,求极大线性无关组法选择校正集建模的预测效果优于随机选择校正集建模的预测效果。     

HL-2M偏滤器CFC/CuCrZr靶板的非晶钎焊工艺研究

在采用商用的STEMET-1101非晶钎料、温度为710~750°C的真空钎焊下,对CFC/OFC(氯氟烃/无氧铜)复合块与CuCrZr(铬锆铜)的钎焊进行了研究。首先,通过X-射线衍射(XRD)和差式扫描量热分析对钎料的结构和熔化行为进行了表征;然后,通过光学显微镜、电子探针微分析和拉伸试验等方法对焊缝的组织形貌、元素成分分布、相结构和力学性能进行了分析;最后,通过高热负荷装置对CFC/OFC/CuCrZr钎焊模块的热疲劳性能进行测试。结果表明,在710~750°C钎焊温度内焊缝由Cu固溶体、(Cu, Ni)3P和Ni(Cu ,Cr)2P金属间化合物组成,焊缝平整无裂纹;特别是在750°C/15min情况下,抑制了焊缝金属间化合物的连续分布,OFC/CuCrZr的焊接强度大于OFC的抗拉强度,CuCrZr/CuCrZr的结合强度为210MPa,并呈现部分韧性断裂。在750°C/15min情况下制备的CFC/Cu/CuCrZr模块可以承受1000次7MW·m^-2的循环热负荷。     

基于SRLG约束和资源共享的交迭段保护机制研究

通过对共享风险链路组约束机制和交迭段保护机制的分析,将两者相结合并根据工作和保护路径分别采用动态链路权重调整,提出了一种基于共享风险链路组不相关的交迭段共享保护算法.交迭段共享保护算法在共享风险链路组不相关的约束条件下,为整个工作路由提供了多个交迭的保护段,并给出了一种能够合理有效选择这些交迭保护段的方法.对交迭段共享保护算法的分析和仿真结果表明,与以往保护算法相比,交迭段共享保护算法不但大大提高了网络连接的可靠性,而且还通过不同交迭保护段间资源的合理共享,有效地提高了网络资源的利用率.     

Effect of fused silica subsurface defect site density on light intensification

The effect of defect density on the modulation of incident laser waves is investigated. First, based on the actual defect distribution in the subsurface of fused silica, a three-dimensional (3D) grid model of defect sites is constructed. The 3D finite-difference time-domain method is developed to solve the Maxwell equations. Then the electrical field intensity in the vicinity of the defect sites in the subsurface of fused silica is numerically calculated. The relationships between the maximal electrical field intensity in fused silica and the geometry of the defect sites are given. The simulated results reveal that the modulation becomes more remarkable with an increase of the defect density. In addition, the effect of the distribution mode of defects on modulation is discussed. Meanwhile, the underlying physical mechanism is analyzed in detail.     

A new graphical coding of DNA sequence and its similarity calculation

The DNA primary sequence is translated into “structure graph” based on classification of its four bases. Then the invariants, such as topological indices, are extracted from those graphic representations of DNA primary sequences, and used to calculate the similarities among the eleven species. From these similarities/dissimilarities the homologies can be revealed that they are in agreement with evolutionary relation satisfactorily.     

Terfenol-D/Pb(Zr,Ti)O3 Disk-Ring Multiferroic Heterostructures Coupled Through Normal Stresses

Disk-ring multiferroic heterostructures composed of Terfenol-D and Pb(Zr,Ti)O₃ (PZT) were prepared and characterized, for which the ferromagnetic and ferroelectric phases were coupled through normal stresses instead of the shear stresses that acted in most of the previous multiferroic heterostructures. High low-frequency magnetoelectric coefficients of 0.10–0.75 V cm⁻¹ Oe⁻¹ were attained for the disk-ring heterostructures, which indicated the strong magnetoelectric coupling. Moreover, a symmetrical resonant peak was observed for dE ₃/dH ₃ in the frequency range of 1–200 kHz, while another weak peak with asymmetrical shape also existed at a lower frequency for dE ₃/dH ₁, which was due to the combination of two vibration modes.     

Observation of β-Relaxation in Sub-Tg Isothermally Annealed Al-Based Metallic Glasses

Al85Ni5 Y8Ca2 and Al88Ni5 Y6Co2Fe2 metallic glasses are fabricated by melt spinning. A kink or a small exothermic peak is observed for both the samples isothermally annealed at sub-glass transition temperatures. Temperature modulated differential scanning calorimetry （TMDSC） data disapprove amorphous phase separation. The activation energies derived from Kissinger plots of the exothermic process on DSC curve around glass transition temperature are consistent with those of β-relaxation of metallic glasses.