考虑空间效应的多支撑管线随机地震响应分析

提出了一种能考虑地震动空间变化效应的多支撑管线随机地震响应分析的解析方法.证明了多点地震作用下结构的平稳随机响应分析可转化为求解支座简谐运动时的确定性响应,直接给出了含有待定系数的简谐响应的形式,并通过边界条件和连续性条件建立待定系数的求解方程.与拟静位移分解法相比,该方法不用计算结构的振型以及拟静位移分量,完全是基于解析推导,因此在计算效率方面优势明显.数值算例中,采用该方法和拟静位移分解法计算了一个6跨管线在空间多点地震作用下的随机响应,对比验证了方法的正确性和高效性.     

激光共聚焦近红外荧光扫描系统光学设计

为了实现对近红外荧光的高分辨率扫描,设计了工作在近红外光谱区的激光共聚焦光学系统。采用结构简单的凹凸双透镜物镜实现了照明光路和发射光路的设计,并采用Zemax软件进行了光学设计和仿真。实验表明:照明光路的聚焦弥散斑小于1 m,照明针孔处的聚焦光斑小于40 m,满足照明针孔的尺寸要求;发射针孔处的聚焦光斑小于10 m,满足探测针孔尺寸要求;同时照明光路和发射光路的MTF曲线的截止频率都分别满足其衍射极限分辨率的要求,照明光路在全视场空间分辨率420 lp/mm处MTF0.08,发射光路在全视场空间频率400 lp/mm处MTF0.07。     

结构光数字栅线法对物体三维形貌的高精度测量

为了对物体的微观三维形貌进行高精度测量,开发了基于结构光的数字栅线三维纹理测量系统,该系统利用解位相的方法进行物体三维高度信息的计算。首先对相位主值的计算,采用了4步等步长相移法采集16幅等步长的相移图像,分成4组分别计算相位主值,再求其平均值作为最终的相位主值。为了滤除噪声及投影仪、CCD相机畸变等各种影响,对采集的条纹图像采用了自适应维纳滤波和小波多阈值方法进行预处理;其次对于位相展开,提出了基于多频的梯度导向相位展开算法,能够有效避开相位间断点,具有稳定的展开结果。实验结果表明,此系统所使用的方法在条纹图的P₀=22.7 mm-1时,获取的三维信息分辨率为2.75 μm,高度信息精度优于0.5 μm,同时具有测量快速,操作简单,无接触等特点,能够满足高精度的微观三维形貌测量的要求。     

基础设施BOT(build-operate-transter)项目特许权期决策的Bargaining博弈模型

特许权期是基础设施BOT项目融资建设中的一个重要决策变量,但目前缺乏计算特许权期的理论方法.SHEN等建立了特许权期的决策模型(BOTCc M),得出了特许权期的可行区间,但BOTCc M模型未能提供在该区间内选择具体的特许权期时间点的方法.这是该模型在应用中的一个重要缺陷,需要进一步改进和完善.应用博弈论原理,建立了特许权期决策的Bargaining博弈模型,克服了BOTCc M模型的缺陷,求出了特许权期决策的具体时间.最后,通过算例演示了特许权期决策的Bargaining博弈模型.研究结果表明,Bargaining博弈模型能为政府和企业进行特许权期决策提供有效的计算方法.     

耦合腔阵列与Λ-型三能级原子非局域耦合系统中单光子的传输特性研究

讨论了理想和非理想情况下耦合腔阵列中两个最邻近的腔与Λ-型三能级原子非局域耦合系统中单光子的传输特性.运用准玻色子方法,精确地解出了开放系统中单光子的透射率.Λ-型三能级原子与耦合腔阵列非局域耦合系统具有更多的优点,如:该系统比其他系统调控光子传输特性的可调控参数更多;单光子在该系统中传输的透射谱有三个透射峰.此外,该系统还具有自身的特点,当拉比频率?取值给定之后,改变原子与其中一个腔的耦合强度时,光子的透射谱有一个透射率始终为1的定点,该点对应的光子频率为ω_c-?.在非理想情况下,系统耗散对光子的透射谱有着很大的影响.当只考虑原子耗散时,耗散使得光子透射谱的谷值增大,而峰值不变;当只考虑腔场耗散时,光子透射谱的峰值减小,而谷值不变.另外,随着腔场耗散率和腔的个数的增多,光子透射谱的峰值逐渐减小,但谷值始终不变.对比原子耗散和腔场耗散的情况可以发现,原子耗散使得光子不能被完全反射,而腔场耗散使得光子不能被完全透射.当同时考虑原子和腔场耗散时,光子透射谱谷值的大小不但会受原子耗散率大小的影响,也受腔场耗散率大小的影响,随着腔场耗散率的增大,谷值反而减小;而光子透射谱的峰值始终只受腔场耗散率大小和腔的个数的影响,与原子耗散率取值的大小无关.     

可见近红外波段无人机载成像光谱仪设计

为了满足地物成像光谱分析的需要,设计了同轴安装、体积小、重量轻的适用于无人机载的棱镜-光栅-棱镜型可见近红外成像光谱仪.通过角放大率选择、光焦度分配、相对孔径计算设计了视场较大的前置物镜;通过光栅方程求解、体相位全息光栅布拉格条件约束、棱镜折射定律设计了光谱系统的初始结构;通过工作光谱上下限出射角与探测器光谱维宽度的关系确定了成像物镜的焦距;通过出射光角度明确了出射光谱的非线性.设计的无人机载成像光谱仪工作光谱范围为400~1 000nm,视场角为40°,全工作波段在空间截止频率20.8lp/mm处的传递函数值均大于0.67,光谱分辨率小于3nm.装调了无人机载成像光谱仪对室外绿化树木进行光谱推扫成像实验,实现了树叶的多光谱成像.该成像光谱仪能够有效实现光谱成像,性能良好.     

Dynamics of Symmetric Conserved Mass Aggregation Model on Complex Networks

We investigate the dynamical behaviour of the aggregation process in the symmetric conserved mass aggregation model under three different topological structures. The dispersion a（t, L） = （∑i（mi - ρo ） ^2 / L ）1/2 is defined to describe the dynamical behaviour where Po is the density of particle and mi is the particle number on a site. It is found numerically that for a regular lattice and a scale-free network, σ（t, L） follows a power-law scaling σ（ t, L） ~ t^δ1 and σ（ t, L） ~ t^δ4 from a random initial condition to the stationary states, respectively. However, for a small-world network, there are two power-law scaling regimes, σ（t, L） ~ t^δ2 when t 〈 T and 〈（t, L） ~ t^δ3 when t 〉 T. Moreover, it is found numerically that 62 is near to 61 for small rewiring probability q, and 63 hardly changes with varying q and it is almost the same as 64. We speculate that the aggregation of the connection degree accelerates the mass aggregation in the initial relaxation stage and the existence of the long-distance interactions in the complex networks results in the acceleration of the mass aggregation when t 〉 T for the small-world networks. We also show that the relaxation time r follows a power-law scaling τ ~ L^z and σ（t, L） in the stationary state follows a power-law Gs（L） - L^α for three different structures.     

Formation of Vegetation Patterns and Hysteresis Phenomena in Arid and Semiarid Zones

Considering the spatial effect of the complicated interactions between plant and resource （soil water） and the stochastic character of the complicated ecological processes in an ecosystem, we introduce a lattice gas model to investigate the vegetation pattern formation in the arid and the semiarid ecosystems with Monte Carlo sim- ulations. With consistency of some previous mean-field models, the model reproduces a wide range of patterns observed in the arid and the semiarid regions. The sequences of vegetation states are also investigated with scanning three parameters, i.e., the precipitation and the plant growth rate, and then the parameter ranges are identified where a hysteresis loop appears and two different stable states coexist. The simulation results denote that the complex structures occur only when the precipitation parameter decreases. Moreover, based on the model, it is found that an increase of the competition of the plant for the resource along the slope direction results in the regular stripes parallel to the hill＇s contours. The model provides an interesting mechanism to understand the formation of the other regular vegetation stripe in a limited resource condition.     

Kinetic Phase Transition in A2 ＋ B2 → 2AB Reaction System with Particle Diffusion

A lattice gas model for the A2 ＋ B2→2AB reaction system was studied by Monte Carlo simulation in a two- dimensional triangular lattice surface [Phys. Rev. E 69 （2004）046114]. In the model, a reactive window appears and the system exhibits a continuous phase transition to an ＇A＋vaoancy＇ covered state with infinitely many absorbing states. The critical behaviour was shown to belong to the robust directed percolation （DP） universality class. In this study, we find that as the particle A diffusion is considered, the infinitely many absorbing states for the continuous phase transition change into only two： one is that in which all sites are occupied by particle A and the other is that in which there is only one vacant site and other sites are occupied by particle A. Fhrthermore, a parity conserving character appears in the system when the particle A diffusion is included. It is found that the critical behaviour of the continuous phase transition changes from the DP class into the pair contact process with diffusion model （PCPD） class and the parity conserving character has no influence on the critical behaviour in the model.     

离子束表面改性及其在摩擦学中的应用

本文对离子束表面改性的各种方法和技术水平及其在摩擦学中的应用进行了综述,讨论了为使这种技术更加广泛地应用于实际摩擦学体系还必须研究的一些问题。大量文献资料表明,离子注入是改善材料摩擦学性能的一种有效方法。离子束辅助涂层是新近发展起来的一种离子束表面改性技术,包括离子束增强沉积或离子束辅助沉积、离子束混合和离子束反冲注入。利用它可以制得0.05到几个微米厚的涂层。由于界面的相互扩散混合,离子束辅助涂层能更强地与底材结合,并且常比物理或化学气相沉积的涂层更密实。作者认为,离子束技术今后将在两个相关领域中发展,即直接的离子注入和离子辅助涂层,并且指出离子补助涂层技术将拓宽离子束技术在摩擦学中的应用范围。