Effects of internal noise on the spiking regularity of a clustered Hodgkin-Huxley neuronal network

Spiking regularity in a clustered Hodgkin–Huxley (HH) neuronal network has been studied in this letter. A stochastic HH neuronal model with channel blocks has been applied as local neuronal model. Effects of the internal channel noise on the spiking regularity are discussed by changing the membrane patch size. We find that when there is no channel blocks in potassium channels, there exist some intermediate membrane patch sizes at which the spiking regularity could reach to a higher level. Spiking regularity increases with the membrane patch size when sodium channels are not blocked. Namely, depending on different channel blocking states, internal channel noise tuned by membrane patch size could have different influence on the spiking regularity of neuronal networks.     

Chaotic burst synchronization in heterogeneous small-world neuronal network with noise

Chaotic bursting is a fundamental behavior of neurons. In this paper, global and local burst synchronization is studied in a heterogeneous small-world neuronal network of non-identical Hindmarsh-Rose (HR) neurons with noise. It is found that the network can achieve global burst synchronization much more easily than phase synchronization and nearly complete synchronization. Moreover, local burst synchronized clusters have already formed before global burst synchronization happens. We study the effect of the shortcut-adding probability and the heterogeneity coefficient on local and global burst synchronization of the network and find that the introduction of shortcuts facilitates burst synchronization while the heterogeneity has little effect. Moreover, we study the spatiotemporal pattern of the network and find that there is an optimal coupling strength range in which the periodicity of the network is very apparent.     

Effects of information transmission delay and channel blocking on synchronization in scale-free Hodgkin-Huxley neuronal networks

In this paper,we investigate the evolution of spatiotemporal patterns and synchronization transitions in dependence on the information transmission delay and ion channel blocking in scale-free neuronal networks.As the underlying model of neuronal dynamics,we use the Hodgkin-Huxley equations incorporating channel blocking and intrinsic noise.It is shown that delays play a significant yet subtle role in shaping the dynamics of neuronal networks.In particular,regions of irregular and regular propagating excitatory fronts related to the synchronization transitions appear intermittently as the delay increases.Moreover,the fraction of working sodium and potassium ion channels can also have a significant impact on the spatiotemporal dynamics of neuronal networks.As the fraction of blocked sodium channels increases,the frequency of excitatory events decreases,which in turn manifests as an increase in the neuronal synchrony that,however,is dysfunctional due to the virtual absence of large-amplitude excitations.Expectedly,we also show that larger coupling strengths improve synchronization irrespective of the information transmission delay and channel blocking.The presented results are also robust against the variation of the network size,thus providing insights that could facilitate understanding of the joint impact of ion channel blocking and information transmission delay on the spatiotemporal dynamics of neuronal networks.     

Cluster synchronization and rhythm dynamics in a complex neuronal network with chemical synapses

Cluster synchronization and rhythm dynamics are studied for a complex neuronal network with the small world structure connected by chemical synapses. Cluster synchronization is considered as that in-phase burst synchronization occurs inside each group of the network but diversity may take place among different groups. It is found that both one-cluster and multi-cluster synchronization may exist for chemically excitatory coupled neuronal networks, however, only multi-cluster synchronization can be achieved for chemically inhibitory coupled neuronal networks. The rhythm dynamics of bursting neurons can be described by a quantitative characteristic, the width factor. We also study the effects of coupling schemes, the intrinsic property of neurons and the network topology on the rhythm dynamics of the small world neuronal network. It is shown that the short bursting type is robust with respect to the coupling strength and the coupling scheme. As for the network topology, more links can only change the type of long bursting neurons, and short bursting neurons are also robust to the link numbers.     

高温对砂岩宏细观损伤及BP神经网络单轴强度预测研究

为了研究高温后砂岩的力学特性和宏细观损伤变化,对高温作用后的砂岩进行单轴压缩试验、声波损伤检测、X射线衍射试验、扫描电镜试验,分析应力-应变曲线、峰值应力、峰值应变、弹性模量、质量损失率、X射线衍射成像和电镜扫描图像,得到砂岩的细观损伤变化对其单轴抗压强度的影响.利用BP神经网络模型对不同物理量进行训练,预测不同高温作...     

冲击地压时列建模的进化神经网络方法

考虑到冲击地压时序的特点,采用基于免疫进化规划的进化神经网络进行了冲击地压非线性系统的建模研究。并采用一个矿山实测得到的震级数列进行了进化神经网络方法的实用性验证,结果表明,进化神经网络不但模型拟合精度高,而且预测性能也较好。     

Strength differential effect and influence of strength criterion on burst pressure of thin-walled pipelines

In the framework of the finite deformation theory, the plastic collapse analysis of thin-walled pipes subjected to the internal pressure is conducted on the basis of the unified strength criterion (USC). An analytical solution of the burst pressure for pipes with capped ends is derived, which includes the strength differential effect and takes the influence of strength criterion on the burst pressure into account. In addition, a USC-based analytical solution of the burst pressure for end-opened pipes under the internal pressure is obtained. By discussion, it is found that for the end-capped pipes, the influence of different yield criteria and the strength differential effect on the burst pressure are significant, while for the end-opened pipes, the burst pressure is independent of the specific form of the strength criterion and strength difference in tension and compression.     

Effects of microstructure on uniaxial strength asymmetry of open-cell foams

Based on the elongated Kelvin model, the effect of microstructure on the uniaxial strength asymmetry of open-cell foams is investigated. The results indicate that this asymmetry depends on the relative density, the solid material, the cell morphology, and the strut geometry of open-cell foams. Even though the solid material has the same tensile and compressive strength, the tensile and compressive strength of open-cell foams with asymmetrical sectional struts are still different. In addition, with the increasing degree of anisotropy, the uniaxial strength as well as the strength asymmetry increases in the rise direction but reduces in the transverse direction. Moreover, the plastic collapse ratio between two directions is verified to depend mainly on the cell morphology. The predicted results are compared with Gibson and Ashby''s theoretical results as well as the experimental data reported in the literature, which validates that the elongated Kelvin model is accurate in explaining the strength asymmetry presented in realistic open-cell foams.     

破膜压力对氢气-甲烷-空气泄爆的影响

选取了300 mm×300 mm×1000 mm、顶部设有250 mm×250 mm泄爆口的管道,用不同厚度的铝箔密封泄爆口,注入氢气-甲烷-空气混合气体,进行泄爆实验,研究了0~44 kPa的爆破压力($ {p}_{\mathrm{v}} $)对火焰演化和管道内外压力变化的影响。结果表明,$ {p}_{\mathrm{v}} $会显著影响管道中火传焰播过程以及压力-时间变化曲线;所有实验中均观察到了内部压力的亥姆霍兹振荡,振荡频率随着${p}_{{\rm{v}}}$的增加而增大;当$ {p}_{\mathrm{v}} $≥12 kPa时会出现频率约为1200 Hz的声学振荡。对于某一确定的$ {p}_{\mathrm{v}} $,管道内最大内部超压随至泄爆口距离增加而增大;靠近泄爆口处和管道中心的最大内部超压几乎随着$ {p}_{\mathrm{v}} $呈线性增加,但是靠近底部处的最大压力与$ {p}_{\mathrm{v}} $呈非线性递增关系,外部爆炸所产生的压力峰值随$ {p}_{\mathrm{v}} $的增加而增大。     

Effect of the coupling matrix with a weight parameter on synchronization pattern in a globally coupled network

In this paper, effect of the coupling matrix with a weight parameter on synchronization pattern in a globally coupled network is investigated. On the basis of matrix theory, the threshold values of the coupling strength and the weight parameter for cluster synchronization have been obtained by utilizing the attractiveness criteria of the invariant synchronization manifold. It shows that cluster synchronization bifurcation comes forth, which concept is first put forward. That is to say, via changing the weight parameter and the coupling strength, the purpose of controlling the number of clusters is achieved, which provides a new idea for control the number of clusters in a network. Numerical simulations are given to demonstrate the theoretical results. In addition, the theoretical results and the numerical simulations also show that full synchronization may not be realized even if the network is globally coupled when there are some negative couplings.     

平头锥型回转体高速入水结构强度数值分析

为探究回转体在高速入水过程中的结构强度,基于非线性有限元LS-DYNA软件中流固耦合任意拉格朗日-欧拉(arbitrary Lagrangian-Eulerian, ALE)方法,分析了不同壁厚的回转体以100 m/s的初速度入水过程中的冲击力特性和结构强度。结果表明：数值计算得到的入水冲击压强峰值和速度衰减曲线与相应的理论值吻合较好,从而验证了数值方法的有效性;入水冲击载荷峰值出现在结构入水瞬间,结构入水后冲击载荷急剧变小且微小震荡;回转体的结构形式对其在高速入水过程中的结构强度有重要影响,尤其回转体头部厚度影响回转体结构强度,当回转体头部厚度为8 mm、后体壁厚大于2.5 mm时,可以保证回转体强度要求。

     

预应力对LY12铝层裂强度的影响

通过过盈配合的热装配方法和机械夹紧方法对LY12铝合金平面样品施加了径向预应变,采用平面飞片撞击方法获得了预应力对层裂特性的影响。结果表明:当飞片以500 m/s的速度撞击样品,预应变为0（无预应变）、25110-6、1 10810-6、1 88610-6时,层裂强度分别为1.130、0.935、0.755、0.643 GPa,初始预应力（变）明显降低了LY12铝层裂强度,证实了材料的层裂强度与初始应力状态密切相关,可为以后的非一维平面应变下的层裂研究提供参考。     

Stability of a class of neural network models with delay

ＩｎｔｒｏｄｕｃｔｉｏｎＲｅｃｅｎｔｌｙ,ｔｈｅｏｒｅｔｉｃａｌａｎｄａｐｌｉｅｄｓｔｕｄｉｅｓｏｆｎｅｕｒａｌｎｅｔｗｏｒｋｍｏｄｅｌｈａｖｅｂｅｎｔｈｅｎｅｗｆｏｃｕｓｏｆｓｔｕｄｉｅｓｉｎｔｈｅｗｏｒｌｄ．Ｉｔｉｓｗｅｌ＿ｋｎｏｗｎｔｈａｔｑｕ...     

Sensitivity analysis of freestream turbulence parameters on stagnation region heat transfer using a neural network

A neural network has been used to predict stagnation region heat transfer in the presence of freestream turbulence. The neural network was trained using data from an experimental study to investigate the influence of freestream turbulence on stagnation region heat transfer. The integral length scale, Reynolds number, all three components of velocity fluctuations and the vorticity field were used to characterize the freestream turbulence. The neural network is able to predict 50% of the test data within ±1%, while the maximum error of any data point is under 3%. A sensitivity analysis of the freestream turbulence parameters on stagnation region heat transfer was performed using the trained neural network. The integral length scale is found to have the least influence on the stagnation line heat transfer, while the normal and spanwise turbulence intensities have the highest influence.     

Modeling the effect of diffusion of the ambient medium on the long-term strength of a hollow cylinder under uniaxial tension

The problem of the long-term strength of an extended thick-walled tube containing a corrosive medium in the internal cavity is solved. The diffusion of this medium into the tube material is analyzed. The diffusion equation is solved approximately by introducing the diffusion front, and the error of the solution is estimated. The dependence of the time of fracture of the tube on the variable tensile stress and the concentration of the medium filling the cavity is obtained. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 4, pp. 88–93, July–August, 2007.     

动高压加载下锆基金属玻璃强度测量

为了研究Zr₅₁Ti₅Ni₁₀Cu₂₅Al₉金属玻璃的高压强度特性,进行了平靶冲击实验。采用反向碰撞方式,运用DISAR技术测量金属玻璃样品/LiF窗口界面粒子速度剖面,分析粒子速度剖面获得了37~66GPa压力范围锆基金属玻璃的屈服强度和剪切模量。实验结果表明,在上述压力范围金属玻璃的屈服强度和剪切模量均显示出一定程度的压力硬化效应,分析表明金属玻璃冲击加载波阵面剪应力衰减并非由损伤/破坏或温度软化等因素导致。

     

Simulation of capillary pressure curves using bond correlated site percolation on a simple cubic network

A stochastic approach to network modelling has been used to simulate quasi-static immiscible displacement in porous media. Both number-based and volume-based network saturation results were obtained. Number-based results include: number-based saturation curves for primary drainage, secondary imbibition and secondary drainage, fluid distribution data, and cluster trapping history. Using pore structure data of porous media, it is possible to convert the number-based curves to capillary pressure — saturation relationships. Pore size distribution functions and pore shapes which are thought to closely represent Berea sandstone samples were used to predict the capillary curves. The physical basis of these calculations is a one-to-one correspondence between the cumulative node and bond index fractions in the network analysis, and the cumulative number-based distributions of pore body and pore throat diameters, respectively. The oil-water capillary pressure curve simulated for primary drainage closely resembles those measured experimentally. The agreement between the simulated and the measured secondary imbition and secondary drainage curves is less satisfactory.     

The effect of spatially correlated blocking-up of some bonds or nodes of a network on the percolation threshold

This paper deals with percolation thresholds in networks in which the capacities of the bonds or sites to conduct are spatially correlated.The differential operator and the turning band methods have been used to simulate homogeneous random fields. Their values, calculated at the nodes or at the bond centers of the networks, define an order for the blocking-up of these bonds or nodes. The networks are square site networks, cubic bond and site networks and tetrahedral bond networks. Preliminary tests have been done to define the minimum dimensions of the grids and, simultaneously, the upper limit of the correlation lengths, and to verify the indifference of the choice of one of the two homogeneous random field simulators. The increase in the correlation length from 0 modifies the percolation threshold from a value, greatly dependent on the network features, to a limiting value which is, as a first approximation, independent of these features and of the correlation mode (exponential, spherical, or gaussian). This value equals 0.5 for two-dimensional networks and is comprised of between 0.1 and 0.2 for three-dimensional networks. We interpret these results by introducing the idea of blob percolation for highly correlated networks.     

结构系统静强度与断裂的综合可靠性分析

基于疲劳载荷作用下裂纹扩展的随机性,建立了结构系统综合考虑静强度和断裂的可靠性分析方法,该方法给出了元件静强度失效时所对应的当量寿命,并建立了元件综合失效判别准则,分析了元件静强度失效和断裂失效之间的相关性.算例表明,随使用年限的增加,元件静强度失效和断裂失效之间的相关性也在增加;在不同的使用年限内,结构系统主要失效路径是不同的,并且在结构系统主要失效路径中既有元件静强度失效又有元件断裂失效;若只考虑静强度或断裂的结构可靠性分析,分析结果偏于危险.     

基于突变特征的边坡双强度折减系数量化研究

边坡失稳是一个由渐变演化至突变破坏的过程,过程中土体的强度参数c和φ发挥作用的路径和衰减程度不同。目前,双强度折减策略DRM在边坡稳定性评估中已逐渐形成共识,但双强度参数间的真实折减关系或折减关系的求解方法难以准确定义。以坡体抵抗外部环境能力最大值原理为依据,引入非线性分析突变理论,以坡体的极限承载力为考察量,建立其与双强度折减比的突变模型函数来考察边坡整体稳定性,进而量化折减过程中c和φ的折减比。结合算例,通过与已有方法的计算结果进行对比,验证了方法的合理性,并探究了c和φ以及坡度与折减比间的演化规律及机理。研究的执行思路可为双强度折减技术的探讨提供有益参考。