电沉积纳米晶Ni-Co-Fe-P合金镀层的组织结构与摩擦磨损性能

用脉冲电沉积方法制备了纳米晶N i-Co-Fe-P合金镀层.采用X射线衍射（XRD）,透射电镜（TEM）,扫描电镜（SEM）,能谱分析（EDS）等方法研究了合金镀层的微观组织结构和成份.采用显微硬度计和摩擦磨损试验机测试合金镀层的显微硬度和摩擦磨损性能.结果表明：纳米晶N i-40.41%Co-6.16%Fe-1.63%P合金镀层的晶粒尺寸为8.3 nm,显微硬度和耐磨性明显高于不含P的N i-Co-Fe镀层;适当温度退火可以提高镀层的硬度及耐磨性;镀层的耐磨性与其硬度成正相关,且随着硬度的提高,镀层的磨损机理由磨粒磨损和黏着磨损共同作用转变为磨粒磨损主导.     

Analysis of convergence for initial condition estimation of coupled map lattices based on symbolic dynamics

A novel approach to the inverse problem of diffusively coupled map lattices is systematically investigated by utilizing the symbolic vector dynamics.The relationship between the performance of initial condition estimation and the structural feature of dynamical system is proved theoretically.It is found that any point in a spatiotemporal coupled system is not necessary to converge to its initial value with respect to sufficient backward iteration,which is directly relevant to the coupling strength and local mapping function.When the convergence is met,the error bound in estimating the initial condition is proposed in a noiseless environment,which is determined by the dimension of attractors and metric entropy of the system.Simulation results further confirm the theoretic analysis,and prove that the presented method provides the important theory and experimental results for better analysing and characterizing the spatiotemporal complex behaviours in an actual system.     

基于符号动力学的耦合映像格子系统的初值估计

在符号动力学的基础上,深入探讨了基于动力学符号序列的局部耦合映像格子系统求逆问题.在理论上系统地分析耦合映像系统初值估计的性能与耦合系数及映射函数之间的数学关系,证明相空间I^M上的任意取值通过基于符号向量序列的逆迭代过程并不一定收敛至初值,其敛散性与耦合强度和映射函数的选择有直接关系.同时证明了混沌或其拓扑共轭的逆不一定为压缩映射,其总体的敛散性与整个逆迭代过程中的收敛与发散的强度对比有关.理论分析与数值实验结果完全一致,说明本文提出的耦合映像格子系统初值估计问题的分析 关键词： 耦合映像格子 符号动力学 初值估计     

一种小型液冷系统的设计研究

设计了一种用于冷却实验室设备的小型液冷系统,采用了压缩制冷和空气冷却复合的形式。该系统通过电磁阀的通断切换压缩制冷和强迫风冷模式,并运用各种传感器对温度、压力、流量进行调节和控制。该系统具有节能、可靠性高、结构紧凑、维护方便、换热效率高等优点。     

A method of recovering the initial vectors of globally coupled map lattices based on symbolic dynamics

Based on symbolic dynamics, a novel computationally efficient algorithm is proposed to estimate the unknown initial vectors of globally coupled map lattices (CMLs). It is proved that not all inverse chaotic mapping functions are satisfied for contraction mapping. It is found that the values in phase space do not always converge on their initial values with respect to sufficient backward iteration of the symbolic vectors in terms of global convergence or divergence (CD). Both CD property and the coupling strength are directly related to the mapping function of the existing CML. Furthermore, the CD properties of Logistic, Bernoulli, and Tent chaotic mapping functions are investigated and compared. Various simulation results and the performances of the initial vector estimation with different signal-to-noise ratios (SNRs) are also provided to confirm the proposed algorithm. Finally, based on the spatiotemporal chaotic characteristics of the CML, the conditions of estimating the initial vectors using symbolic dynamics are discussed. The presented method provides both theoretical and experimental results for better understanding and characterizing the behaviours of spatiotemporal chaotic systems.     

射频反应磁控溅射法退火生长Na-N共掺杂p-ZnO薄膜

采用射频反应磁控溅射法退火生长得到了Na-N共掺杂p-ZnO薄膜。XRD测试结果表明,退火前后均得到c轴择优取向的ZnO薄膜。Hall测试结果表明:退火后薄膜的电学性能明显改善,得到了p-ZnO薄膜,退火温度为450℃时取得最佳电学性能:室温电阻率为139.2Ω.cm,迁移率为0.2cm2.V-1.s-1,空穴浓度为2.5×1017cm-3。XPS分析表明:Na掺入ZnO中作为受主NaZn而存在,N主要以N—H键的形式存在,其受主NO的作用不明显,但是否存在NaZn-NO受主复合体,还需进一步的研究。     

利用拉曼光谱技术研究低剂量X射线辐射对人神经母细胞瘤细胞的影响

低剂量电离辐射引发的生物效应复杂而多样,其研究往往又受到辐射标志物和检测技术手段的限制。将拉曼光谱技术应用于低剂量辐射生物效应研究,利用10 mW,532 nm共聚焦拉曼光谱对经过100,200和500 mGy三种辐射剂量的X射线辐照之后的人神经母细胞瘤细胞进行检测,发现细胞嘌呤核苷酸（722～728和1 572～1 581 cm-1等等）、嘧啶核苷酸（770～785 cm-1等等）等DNA相关的拉曼特征峰受到电离辐射影响而发生变化,说明低剂量X射线辐照造成细胞DNA水平改变。采用流式细胞术对同样条件辐照后培养6 h的人神经母细胞瘤细胞进行细胞周期分析发现,三种剂量的X射线电离辐射均造成细胞在G2期阻滞,同样提示电离辐射引起DNA水平升高。通过划痕实验分析辐照后20 h的细胞迁移能力,结果显示,相较于未接受X射线照射的对照细胞,受到三种剂量电离辐射的人神经母细胞瘤细胞均出现迁移水平下降。研究结果表明,通过拉曼光谱分析发现低剂量X射线电离辐射引起人神经母细胞瘤细胞DNA水平变化,其结果与细胞周期分析和迁移分析的结果相一致,但检测时间大大提前,利用拉曼光谱技术可以实现低剂量辐射损伤等细胞生物学效应的早期发现与监测。     

A method of estimating initial conditions of coupled maplattices based on time-varying symbolic dynamics

A novel computationally efficient algorithm in terms of the time-varying symbolic dynamic method is proposed to estimate the unknown initial conditions of coupled map lattices (CMLs). The presented method combines symbolic dynamics with time-varying control parameters to develop a time-varying scheme for estimating the initial condition of multi-dimensional spatiotemporal chaotic signals. The performances of the presented time-varying estimator in both noiseless and noisy environments are analysed and compared with the common time-invariant estimator. Simulations are carried out and the obtained results show that the proposed method provides an efficient estimation of the initial condition of each lattice in the coupled system. The algorithm cannot yield an asymptotically unbiased estimation due to the effect of the coupling term, but the estimation with the time-varying algorithm is closer to the Cramer--Rao lower bound (CRLB) than that with the time-invariant estimation method, especially at high signal-to-noise ratios (SNRs).