关于极小曲面度量特征的一个证明

通过构造某个乘积流形中的一个子流形Q及Q上外微分式环中某个理想的一组生成元,利用[4]的主要工作,在这里证明了理想是d-封闭的。从而确定了一个3维积分子流形S.并由此给出了空间形式中一类极小曲面的度量特征的一个独特的构造性的证明。其中关于丛映射的证明对一般情形也适用,     

拉压循环载荷下正交异性钢桥面板肋-面板焊缝裂纹扩展分析

采用四步法计算了考虑循环载荷中压应力影响的正交异性钢桥面板的肋-面板焊缝表面裂纹扩展。第一步是基于正交异性钢桥面板的疲劳分析模型,计算肋-面板焊缝处的应力,第二步是通过肋-面板焊缝的三维局部模型,用Schwartz-Neumann交替法计算焊缝表面裂纹的应力强度因子分布,第三步是用二维断裂力学模型和增量塑性损伤模型,计算循环载荷中的压应力对裂纹扩展的影响,第四步是用第二步中的三维裂纹分析结果和第三步中的二维断裂力学模型得到的裂纹扩展公式,计算钢桥面板的肋-面板焊缝表面裂纹扩展。计算结果表明,对应于正交异性钢桥面板肋-面板焊缝处的循环应力,本文所用模型的裂纹尖端反向塑性区导致裂纹扩展率增加50%以上。研究结果为正交异性钢桥面板肋-面板焊缝裂纹的疲劳寿命分析提供了研究基础。     

In- and Anti-transition of Firing Patterns Induced by Random Long-range Connections in Coupled Hindmarsh-Rose Neurons System

The effects of random long-range connections (shortcuts) on the transitions of neural firing patterns in coupled Hindmarsh-Rose neurons are investigated, where each neuron is subjected to an external current. It is found that, on one hand, the system can achieve the transition of neural firing patterns from the fewer-period state to the multi-period one, when the number of the added shortcuts in the neural network is greater than a threshold value, indicating the occurrence of in-transition of neural firing patterns. On the other hand, for a stronger coupling strength, we can also find the similar but reverse results by adding some proper random connections. In addition, the influences of system size and coupling strength on such transition behavior, as well as the internality between the transition degree of firing patterns and its critical characteristics for different external stimulation current, are also discussed.     

Topological probability and connection strength induced activity in complex neural networks

Recent experimental evidence suggests that some brain activities can be assigned to small-world networks. In this work, we investigate how the topological probability p and connection strength C affect the activities of discrete neural networks with small-world (SW) connections. Network elements are described by two-dimensional map neurons (2DMNs) with the values of parameters at which no activity occurs. It is found that when the value of p is smaller or larger, there are no active neurons in the network, no matter what the value of connection strength is; for a given appropriate connection strength, there is an intermediate range of topological probability where the activity of 2DMN network is induced and enhanced. On the other hand, for a given intermediate topological probability level, there exists an optimal value of connection strength such that the frequency of activity reaches its maximum. The possible mechanism behind the action of topological probability and connection strength is addressed based on the bifurcation method. Furthermore, the effects of noise and transmission delay on the activity of neural network are also studied.     

一种双MCP选通型30~40 ps软X射线分幅相机

研制了一种双微通道板（Microchannel Plate,MCP）双选通型软X射线分幅相机.该相机采用两块厚度为0.5 mm的MCP,近贴放置成“V”形结构,用两列高压脉冲依次选通两块级联的MCP,通过控制两列脉冲之间的延迟时间,利用微通道板的电子渡越时间效应和非线性增益的相互作用,以损失一部分电子为代价获得比单MCP（60 ps）选通相机更短的曝光时间,并且可以降低直穿X射线造成的背景光噪音.     

火灾后钢筋套筒灌浆连接混凝土柱抗震性能研究

目前套筒灌浆连接在装配式结构中运用越来越广泛, 为了研究火灾后钢筋套筒灌浆连接混凝土柱的抗震性能, 通过有限元软件Abaqus与Python程序结合对预制混凝土柱火灾后的抗震性能进行模拟, 并经试验其结果得到验证. 在此基础上分析了混凝土柱的滞回特性、骨架曲线, 研究了剪跨比、轴压比、受火时间等因素对火灾后钢筋套筒灌浆连接混凝土柱耗能能力、延性系数、承载力等抗震性能指标的影响. 结果表明: 受火时间越长, 试件的滞回曲线捏拢现象越明显, 峰值荷载明显降低, 受火60、90、120min后, 峰值荷载分别降低26.2%~34.4%、31.8%~43.2%、39.9%~50.3%. 火灾损伤会影响预制试件的延性, 受火60、90、120min后预制试件的延性系数分别减小4.2%~28.4%、13.9%~35.8%、25.4%~33.5%. 火灾后, 预制柱的耗散能系数降低, 降低趋势与现浇试件相似; 初始刚度随着火灾时间的增长明显降低. 通过参数分析, 建立了火灾后套筒灌浆连接预制柱的承载力公式, 为火灾后同类构件承载力评估提供参考依据.     

基于代理模型的箭体连接结构极值响应分析与优化

螺栓法兰连接结构在航空航天等工程领域中广泛应用,其力学性能在不同工况和装配情况下十分复杂。由于拉压刚度差异,含连接结构的箭体动力学响应呈现明显的非线性特征。因此,考虑不同连接参数及工况下的连接非线性动力学响应,对结构优化设计有着重要意义。本文针对以双线性弹簧表征螺栓法兰连接非线性的箭体等效动力学模型,基于径向基函数(RBF)神经网络和响应面法分别建立其连接面处的极值响应代理模型,对比发现RBF神经网络模型在较高精度上可以实现对动响应极值的预测及分析;同时分析了不同载荷参数及刚度变化对连接结构动响应极值的影响;最后,利用RBF神经网络代理模型,开展了连接面加速度极值响应与螺栓弹簧力最小化为目标的连接结构参数优化。     

考虑刚度折减的多棱锥型套接钢管杆挠度及附加弯矩研究

多棱锥型钢管杆广泛应用于城市周边输电线路,管与管之间通常采用法兰连接,套接连接应用不大。鉴于目前对于多棱锥型套接钢管杆挠度的计算方法研究相对较少,本文根据梁的挠曲线微分方程理论,结合套接节点刚度折减,推导出在常见荷载(弯矩M、水平力P和均布力q)作用下多棱锥型套接钢管杆挠度和附加弯矩的计算方法。最后,选取典型套接钢管杆进行对比分析,得出了一些重要结论。本文对套接钢管杆挠度计算进行细致的研究,可作为输电线路钢管杆套接连接设计的参考     

Exponential Families with External Parameters

In this paper we introduce a class of statistical models consisting of exponential families depending on additional parameters, called external parameters. The main source for these statistical models resides in the Maximum Entropy framework where we have thermal parameters, corresponding to the natural parameters of an exponential family, and mechanical parameters, here called external parameters. In the first part we we study the geometry of these models introducing a fibration of parameter space over external parameters. In the second part we investigate a class of evolution problems driven by a Fokker-Planck equation whose stationary distribution is an exponential family with external parameters. We discuss applications of these statistical models to thermodynamic length and isentropic evolution of thermodynamic systems and to a problem in the dynamic of quantitative traits in genetics.     

半刚性连接平面钢框架整体稳定分析的单元刚度矩阵

经数学推导首先得出仅考虑几何缺陷及二阶效应的梁单元转角位移方程(有3种形式,分别为轴力大于零、等于零及小于零).在此基础上对转角位移方程进行修改,并将3种情况下的转角位移方程统一为1种形式,进而得出综合考虑几何缺陷、二阶效应和半刚性连接特性的平面梁单元刚度矩阵.所得结果可用于具有任意分布几何缺陷的半刚性连接钢框架结构的整体稳定分析.