Fast synchrotron X-ray tomography study of the packing structures of rods with different aspect ratios

We present a fast synchrotron X-ray tomography study of the packing structures of rods with different aspect ratios. Utilizing the high flux of the X-rays generated from the third-generation synchrotron source, we can complete a high- resolution tomography scan within a short period of time, after which the three-dimensional （3D） packing structure can be obtained for the subsequent structural analysis. The image phase-retrieval procedure has been implemented to enhance the image contrast. We systematically investigated the effects of particle shape and aspect ratio on the structural properties including packing density and contact number. It turns out that large aspect ratio rod packings will have wider distributions of free volume fraction and larger mean contact numbers.     

光电反馈混沌系统脉冲同步特性研究

提出光电反馈混沌状态下的混沌脉冲同步.首先, 对激光器的混沌动力学方程进行了数值分析, 通过改变反馈系数和脉冲系数来观测混沌状态的变化, 实现了对混沌激光器的控制;然后, 对脉冲同步方程进行数值分析, 给出了同步的模拟图.实验结果表明此方法能实现混沌同步.     

Nonsingular terminal sliding mode approach applied to synchronize chaotic parameters and systems with unknown nonlinear inputs

This paper deals with the design of a novel nonsingular terminal sliding mode controller for finite-time synchro-nization of two different chaotic systems with fully unknown parameters and nonlinear inputs. We propose a novel nonsingular terminal sliding surface and prove its finite-time convergence to zero. We assume that both the master＇s and the slave＇s system parameters are unknown in advance. Proper adaptation laws are derived to tackle the unknown parameters. An adaptive sliding mode control law is designed to ensure the existence of the sliding mode in finite time. We prove that both reaching and sliding mode phases are stable in finite time. An estimation of convergence time is given. Two illustrative examples show the effectiveness and usefulness of the proposed technique. It is worthwhile noticing that the introduced nonsingular terminal sliding mode can be applied to a wide variety of nonlinear control problems.     

同步导数荧光光谱法测定食品中3种芳香族氨基酸

提出了同步导数荧光光谱法同时测定食品中色氨酸、酪氨酸和苯丙氨酸的方法。试验表明:为排除干扰,色氨酸、酪氨酸和苯丙氨酸的特征同步导数荧光波长宜选定279,224,256 nm,波长差Δλ为55,70,25 nm条件下进行同步扫描。3种芳香族氨基酸的浓度分别在一定范围内与其导数荧光强度呈线性关系,检出限（3s/k）分别为6.3×10^-9,1.6×10^-8,4.0×10^-7mol·L^-1。方法用于蜂蜜、羊奶粉和啤酒样品中3种芳香族氨基酸的测定,回收率在92.3%～103%之间。     

光折变晶体多重全息存储衍射效率均匀性的研究

推导出了全息多重存储时间递减曝光法各幅图象写入时间的解析表达式,研究了时间递减法和循环曝光法单次曝光时间、总曝光时间以及循环次数随存储图象的幅数之间的变化关系,结果表明时间递减法不但对记录系统的要求较低,而且也可获得相当均匀的衍射效率.     

基于光学储备池计算的高速混沌保密通信的研究

利用一个带有光反馈和光注入的光泵浦自旋垂直腔表面发射激光器的两个混沌偏振分量形成两个并行储备池计算机.这些储备池用来学习另外一个光泵浦自旋垂直腔表面发射激光器(发射激光器)混沌动力学行为.训练基于自旋垂直腔表面发射激光器的储备池获得一个发射的偏振分量和它相应的训练储备池之间的高质量混沌同步.在这种高质量同步条件以及确保...     

Dynamics of erbium-doped fibre laser with optical delay feedback and chaotic synchronization

The dynamical behaviour of the erbium-doped fibre single-ring laser with an optical delay feedback is discussed. Simulation shows that as the delay rate increases, the lasing light displays period-doubling which leads to chaos and via reverse period-doubling route returns from chaos to periodic. At a particular delay rate the intermittently chaotic route to chaos is also observed. The identical synchronization based on chaos in this ring laser is demonstrated by numerical simulation.     

同步荧光光谱比率法检测过氧亚硝酸根及其清除剂的研究

利用同步荧光光谱建立了一种新的荧光比率法检测过氧亚硝酸根(ONOO－)及评价其清除剂的方法。酪氨酸自身有荧光,在pH 8.5的磷酸缓冲溶液中,酪氨酸与CO₂和ONOO－反应生成强 荧光的酪氨酸二聚体,利用同步荧光光谱技术, 在荧光发射光谱中能同时获得酪氨酸单体(λ_em=364 nm)与二聚体的荧光峰(λ_em=406 nm),且两峰的荧光强度的比值与ONOO－的浓度呈计量相 关。结果表明荧光强度的比值不受实验参数改变的影响,与传统的荧光法相比,有利于扩大检测的线性范围,提高灵敏度。荧光强度的比值与ONOO－的浓度在1.60×10－7 mol·L-1～6.00× 10－6 mol·L-1范围内呈线性关系,线性相关系数为0.999,检测限为1.84×10－8 mol·L-1。对浓度为1.00×10－6 mol·L-1 ONOO－ 平行测定8次,其相对标准偏差为2.4％。利用该法测得抗癌药米托蒽醌的IC₅₀为0.065 μg·mL-1。方法简便易行,试剂廉价易得,体系稳定,可作为一种检测ONOO-及筛选其清除剂的方法。     

CSNS/RCS中的阻抗和束流不稳定性

中国散裂中子源（CSNS）的快循环同步加速器（RCS）是一台强流质子加速器,其束流平均功率达到100 kW。在此强流加速器中,真空部件的阻抗是引起束流不稳定的主要原因,它严重限制了束流强度及品质。对CSNS/RCS设计中的各种真空部件阻抗进行了详细计算,并以计算结果为出发点,理论分析了各种不稳定性强弱,确定了各种不稳定性发生的阻抗阈值,为真空部件结构设计提供了参考。对比较严重的电阻壁阻抗,采用阻抗壁尾场模型进行跟踪模拟,得到不稳定性增长率与理论计算值符合较好。自然色品有助于束流稳定,加入自然色品后模拟,电阻壁不稳定性消失。     

CSNS/RCS交流二极磁铁研制关键技术

针对交流二极磁铁的磁场特性和涡流问题,利用电磁场分析软件对磁铁进行了优化设计和温度场计算,确定了交流二极磁铁关键技术的方案。对交流二极磁铁极头端面采用了罗高斯基曲线和谐波削斜的方法来提高磁铁磁场质量;对铁芯端部和端板进行开槽优化设计,有效切断磁铁端部主要的涡流回路,降低了磁铁温升;磁铁线圈采用铝绞线导线进行绕制,以减少磁铁线圈内的涡流损耗。最后,通过对样机磁铁的测试,磁场均满足物理要求,磁铁温度也控制在安全范围内。