Helium nano-bubble bursting near the nickel surface

We have investigated the expansion and bursting of a helium nano-bubble near the surface of a nickel matrix using a molecular dynamics simulation. The helium atoms erupt from the bubble in an instantaneous and volcano-like process,which leads to surface deformation consisting of cavity formation on the surface, along with modification and atomic rearrangement at the periphery of the cavity. During the kinetic releasing process, the channel may undergo the "open" and"close" states more than once due to the variation of the stress inside the nano-bubble. The ratio between the number of helium atoms and one of vacancies can directly reflect the releasing rate under different temperatures and crystallographic orientation conditions, respectively. Moreover, a special relationship between the stress and He-to-vacancy ratio is also determined. This model is tested to compare with the experimental result from Hastelloy N alloys implanted by helium ions and satisfactory agreement is obtained.     

强动载荷下钢筋混凝土结构计算模型简评

针对侵彻、爆炸等强动载作用下混凝土类结构计算中涉及的状态方程、变形破坏弹塑性本构关系与强度准则等关键问题,根据混凝土多组分特征,简述考虑介质中孔隙压缩的状态模型及弹塑性变形破坏中动态损伤演化模型,并在计算实验方法的基础上,给出需要进一步研究的建议。     

分数阶Willis环脑迟发性动脉瘤时滞系统混沌分析

在脑血动脉瘤的临床研究中,Willis环脑动脉血管瘤系统(Willis aneurysm system,WAS)起着重要作用,分数阶WAS尽管能进一步加深该系统的机理刻画,但是不能描述原因不明的迟发性动脉瘤.鉴于此,本文提出分数阶Willis环脑迟发性动脉瘤时滞系统(fractional Willis aneurysm system with time-delay,FWASTD)并验证了其有效性;利用时间序列图、相图、Poincaré截面等证实了FWASTD的混沌特性;研究时滞对于系统的重要生理参量的影响,发现了血流阻力系数在时滞状态下对系统稳定的重要性;根据分数阶时滞系统的稳定性理论,设计相应线性控制器,对FWASTD进行了有效控制,同时也探讨了时滞系统的自同步控制.本文完善了脑动脉瘤系统的理论基础.     

射频感应耦合Ar-N2等离子体物理特性的Langmuir探针测量及理论研究

分别通过Langmuir探针测量和动力学模型模拟方法研究了射频感应耦合Ar-N₂等离子体中电子能量分布、电子温度、电子密度等物理量随N₂含量的变化规律.实验研究结果表明：电子能量分布呈现出非Maxwell型分布,并由双温分布向三温分布过渡;电子温度在不同的气压下随N₂含量的增加呈现出不同的变化规律.在放电气压小于1.3 Pa时,电子温度随N₂含量的增加而下降;当气压大于1.3 Pa时,电子温度随N₂关键词： 感应耦合等离子体 2混合气体放电')" href="#">Ar-N₂混合气体放电 电子能量分布 Langmuir探针     

光束品质因子M2对非同轴激光雷达探测性能的影响

光束品质因子M2直接影响高斯光束传播特性,光纤口径主要约束激光雷达接收系统的视场角.几何重叠因子是影响激光雷达探测性能的重要参量,其主要受激光束的发射特性、接收系统的结构等影响.通过探讨光束品质因子M2及耦合光纤口径对几何重叠因子的影响,为设计激光雷达发射接收系统,改善激光雷达的探测性能提供了优化方案.数值计算及初步实验表明,光纤的耦合效率与光纤的放置位置及光纤口径有很大的关系;几何重叠因子小于1的探测距离受到M2因子的较大影响且随着M2因子的增大而增大.     

位错规范场对于位错芯区的应用

本文用位错连续分布方法分析了位错所产生的应变和应力场,用位错规范场表出了位错芯区的位错分布,并在一定规范条件下求解了位错规范场。得到了螺位错芯区内、外的应力场。在螺位错芯区外,其应力场与Volterra位错的应力场完全一样,而在芯区内,当ρ趋于零时,螺位错的应力场是有解的。最后计算了螺位错的能量。 关键词：     

Analysis of the special hollow-core photonic crystal fibre by finite element method

Two kinds of fabricated hollow-core photonic crystal fibres （HC-PCFs） arc studied using finite element method （FEM） because the structures of the fibres are special, Normalized transmission spectra and transverse intensity distribution of the modes are calculated and measured. And the dispersion characteristics of these two kinds of HC- PCFs were analysed from 400 nm to 800 nm. Simulated and measured results show that the special structure could affect the properties of HC-PCFs, By comparing the simulated values with the measured results, it can be clarified that FEM is feasible and accurate for analysing photonic crystal fibres whose structures are irregular and complex.     

Parameters estimation online for Lorenz system by a novel quantum-behaved particle swarm optimization

This paper proposes a novel quantum-behaved particle swarm optimization （NQPSO） for the estimation of chaos＇ unknown parameters by transforming them into nonlinear functions＇ optimization. By means of the techniques in the following three aspects： contracting the searching space self-adaptively; boundaries restriction strategy; substituting the particles＇ convex combination for their centre of mass, this paper achieves a quite effective search mechanism with fine equilibrium between exploitation and exploration. Details of applying the proposed method and other methods into Lorenz systems are given, and experiments done show that NQPSO has better adaptability, dependability and robustness. It is a successful approach in unknown parameter estimation online especially in the cases with white noises.     

小动物正电子断层成像仪性能测试

设计了一系列实验对Concorde MicroPET Rodent R4小动物正电子断层成像系统(该系统是Concorde Microsystems公司开发的小动物专用PET扫描仪，该扫描仪具有32层探测器环，动物入口孔径为120mm，横向视野为100mm，轴向深度为78mm，标称的视野中央处的空间分辨率可达1.8mm以下)的空间分辨率、灵敏度、散射率等性能参数进行了测试，测试结果显示该扫描仪视野中心的横向空间分辨率为1.9mm, 轴向空间分辨率为1.88mm, 在能窗设定为250—750keV时系统的绝对灵敏度为39.88 cps/kBq, 同样能窗下二维重建散射分数为50.6%,三维重建散射分数为32.3%. 关键词： 正电子断层成像仪 性能测试     

成果导向教育理念下的涂料配方设计课程教学改革和实践*

为了实现“涂料配方设计”课程的教学目标,将成果导向教育(Outcome-based education, OBE)理念引入涂料配方设计课程教学改革实践中,遵循以预期学习成果为中心来设计、组织、实施和评价教学的结构模式。首先根据本校涂料人才培养定位制定课程的预期学习成果;然后在预期学习成果的基础上优化教学过程,如对教学内容进行选择,同时在教学实施中强化学生的主体地位,并且通过教学方法的改革促进预期学习成果的达成;最后构建合理的预期学习成果评价体系。尽管将OBE理念引入涂料配方设计课程教学中取得了一些成效,但该体系的建设还有待于进一步改进和完善。