Morphologies and microstructures of tree-like carbon produced at different reaction conditions in a CVD process

Centimeter-size multi-branched tree-like carbon structures have been generated by the catalytic chemical vapor deposition of toluene using ferrocene as the catalyst precursor and investigated by means of SEM, TEM, and EDX. It is found that a temperature of 1000-1200 °C and a carrier gas flow rate of 1000-2500 ml/min are necessary for the generation of the carbon trees. Their morphologies and microstructures change greatly with the changing reaction conditions. The fractal dimensions of the trees are calculated to quantitatively investigate the influence of different reaction temperatures on the morphologies.     

试析冷战后中日关系中安全困境的成因

安全困境是现实主义解释国际政治的一个基本概念。从安全困境在国际政治学中的一般定义着手,结合中日地缘政治利益、实力对比、历史积怨及美国的介入等问题分析了中日安全困境的成因。     

压缩感知算法在阵列测向中的相干信号分辨

现有算法在进行信号重建时,需要原始信号的稀疏信息来控制初始原子集的大小和算法迭代的最大次数,这削弱了重建精度,增加了计算复杂度,限制了其实际应用能力。为了克服这个问题,提出了基于正交匹配追踪算法的改进算法。该算法将阵元个数作为假设稀疏度,在稀疏度未知的初始阶段扩展初始原子集。最后通过对测量信号的幅度进行阈值过滤以实现信号的分辨和信源数的估计。为解决测向人员面对监测软件所指示的多个信号示向度中,无法分辨哪些指示方向是同一个信号源所产生的折反射信号的问题,首次提出了基于压缩感知算法的相干关系分析和相干信号分辨的模型。实测数据结果表明,该算法在不同环境下可以清晰分辨相干信号,并且能够适应多种实验平台。     

认知任务驱动的fMRI脑功能网络构建方法

针对脑功能网络的构建受到特定大脑图谱对兴趣点描述准确度及覆盖度的限制,提出了基于认知任务信息和神经影像数据的脑功能网络构建方法。首先计算fMRI体素对于认知任务的敏感度,然后在此基础上选取兼顾分布均衡和去中心化的大脑兴趣点,从而构建任务驱动的脑功能网络。实验通过在人脸情绪识别认知任务相关的梭状回构造任务驱动的脑功能网络,其度中心性、聚类系数、全局效率、局部效率这四个复杂网络指标均优于典型大脑图谱梭状回中兴趣点构成的网络。结果表明,计算得到的大脑兴趣点具有更强的整合性,更适合用于表征特定认知任务下的脑功能网络。     

Micro cam system driven by electrostatic comb-drive actuators based on SOI-MEMS technology

Microsystem Technologies - This paper reports a design and fabrication process of a micro cam system (MCS) with a flat-faced translating follower. The cam rim with cover diameter of 2.4 mm...     

基于单片机的晶闸管触发器的设计与实现

设计了一种集同步电压检测、移相延迟角定时环节、触发脉冲时序分配等功能于一身的单片机控制的晶闸管触发器。采用软件实现了定时/计数、触发脉冲分配、双窄脉冲形成等功能。采用AT89C2051单片机实现三相全控桥式电路晶闸管的移相触发控制,降低了对单片机资源的需求。提出了用一个同步电压信号,通过触发脉冲延迟角的调整算法,实现了对称三相触发脉冲输出。设计中采用定时器计时同步方式,消除了干扰信号的影响,保证了三相桥式全控整流系统可靠工作。     

Nonlinear entanglement witnesses based on continuous-variable local orthogonal observables for bipartite systems

In this paper, a nonlinear entanglement witness criterion based on continuous-variable local orthogonal observables for bipartite states is established, which is strictly stronger than the the linear entanglement witnesses criterion introduced by Zhang et al. (Phys. Rev. Lett. 111:190501, 2013). This criterion is particularly applied to two-mode Gaussian states yielding a criterion in terms of the covariance matrix. Comparison with CCNR criterion is discussed.     

On the Controllability of Nonlocal Second‐Order Impulsive Neutral Stochastic Integro‐Differential Equations with Infinite Delay

In this paper, we investigate the controllability for a class of nonlocal second‐order impulsive neutral stochastic integro‐differential equations with infinite delay in Hilbert spaces. More precisely, a set of sufficient conditions for the controllability results of nonlocal second‐order impulsive neutral stochastic integro‐differential equations with infinite delay are derived by means of the Banach fixed point theorem combined with theories of a strongly continuous cosine family of bounded linear operators. As an application, an example is provided to illustrate the obtained theory.     

一种智能寻迹与搬运机器人的控制系统设计

提出寻迹与搬运机器人的一种智能控制系统设计;该系统主要由单片机、传感器和执行舵机组成;通过分析直行、弯道与取物等工作模式,建立相应的舵机驱动控制;传感器将检测到的路线和工件信号传送给单片机进行处理;按照不同的优先级别,由单片机发出脉冲信号,控制舵机的速度与方向,完成抓取、转运工件的任务;实验结果表明:多路传感器的信息融合能有效识别寻迹路径,确定优先级别的控制;舵机的驱动控制能满足寻迹与搬运的要求;系统设计简单,实用可靠,具有良好的开放性与扩展性.