Synchronization and bursting transition of the coupled Hindmarsh-Rose systems with asymmetrical time-delays

The study of synchronization and bursting transition is very important and valuable in cognitive activities and action control of brain as well as enhancement for the reliability of the cortex synapses. However, we wonder how the synaptic strength and synaptic delay, especially the asymmetrical time-delays between different neurons can collectively influence their synchronous firing behaviors. In this paper, based on the Hindmarsh-Rose neuronal systems with asymmetrical time-delays, we investigate the collective effects of various delays and coupling strengths on the synchronization and bursting transition. It is shown that the interplay between delay and coupling strength can not only enhance or destroy the synchronizations but also can induce the regular transitions of bursting firing patterns. Specifically, as the coupling strength or time-delay increasing, the firing patterns of the time-delayed coupling neuronal systems consistently present a regular transition, that is, the periods of spikes during the bursting firings increase firstly and then decrease slowly. In particular, in contrast to the case of symmetrical time-delays, asymmetrical time-delays can lead to the paroxysmal synchronizations of coupling neuronal systems, as well as the concentration level of synchronization for the non-identically coupled system is superior to the one of identical coupling. These results more comprehensively reveal the rich nonlinear dynamical behaviors of neuronal systems and may be helpful for us to have a better understanding of the neural coding.     

The conditions for onset of beta oscillations in an extended subthalamic nucleus-globus pallidus network

The persistence of beta oscillations generated in the basal ganglia is typical pathological characteristic of Parkin-son's disease.In this paper,we construct a new network model,which is mainly composed of the subthalamic nu-cleus and the globus pallidus.Based on theory analysis,we obtained the beta shock conditions in the proposed model.It is shown that numerical simulations are in good agreement with analytical results.At last,the effects of cortex and striatum inputs on the generation of oscillations are also discussed.We hope that the obtained results may find applications to treatment of Parkinson’s disease and study of neural oscillations produced in other parts of the brain neural network.     

某机中央翼下壁板疲劳裂纹扩展寿命估算

为评估某型飞机中央翼下壁板萌生疲劳裂纹后的使用安全性,进行结构模拟件疲劳试验,并利用AFGROW软件对其疲劳裂纹的扩展寿命进行估算,与试验结果进行对比,初步确定出该部位裂纹扩展速率,为裂纹故障部位的修理提供参考依据.     

汽车碰撞时吸能螺纹剪切分析的网格优化

对螺纹剪切式吸能装置在汽车碰撞过程中的研究主要采用有限元法,为确定吸能螺纹合适的网格尺寸,以VPG(virtual proving ground)和LS-DYNA3D(livemore software-dyna)为平台,采用二分法逐渐细化网格尺寸,对单圈螺纹的剪切过程进行仿真分析。获得满足收敛性条件的合适的网格尺寸,即截面网格尺寸为0.2 mm×0.2 mm,螺纹螺旋方向的每段轴向增量亦为0.2 mm。结果显示,当剪切过程分析的网格尺寸取上述尺寸时,得到的加速度总趋势及各能量的变化与理论相符,剪切力与理论计算值的偏差很小,表明该网格尺寸能用于汽车碰撞时的仿真分析,对其他同类仿真计算的网格划分也有参考价值。     

High-resolution TEM observations of isolated rhombohedral crystallites in graphite blocks

Graphite blocks produced from natural graphite flake have been studied by high-resolution transmission electron microscopy (HRTEM). Previously, the rhombohedral structure was widely considered as a mosaic distribution in a hexagonal host and was probably produced only by mechanical shear or milling. In present investigation, isolated rhombohedral crystallites have been detected in graphite blocks, in addition to the hexagonal host with mosaic distributions of the rhombohedral phase. This was confirmed not only by the inclined angle of about 12° between {10–11} planes and the [0 0 0 1] direction, but also the rhombohedral ABC… stacking of graphite basal planes based on the HRTEM image.     

Bifurcation analysis for Hindmarsh-Rose neuronal model with time-delayed feedback control and application to chaos control

This paper is concerned with bifurcations and chaos control of the Hindmarsh-Rose(HR)neuronal model with the time-delayed feedback control.By stability and bifurcation analysis,we find that the excitable neuron can emit spikes via the subcritical Hopf bifurcation,and exhibits periodic or chaotic spiking/bursting behaviors with the increase of external current.For the purpose of control of chaos,we adopt the time-delayed feedback control,and convert chaos control to the Hopf bifurcation of the delayed feedback system.Then the analytical conditions under which the Hopf bifurcation occurs are given with an explicit formula.Based on this,we show the Hopf bifurcation curves in the two-parameter plane.Finally,some numerical simulations are carried out to support the theoretical results.It is shown that by appropriate choice of feedback gain and time delay,the chaotic orbit can be controlled to be stable.The adopted method in this paper is general and can be applied to other neuronal models.It may help us better understand the bifurcation mechanisms of neural behaviors.     

An actor-critic based learning method for decision-making and planning of autonomous vehicles

In order to improve the agility and applicability of trajectory planning algorithm for autonomous vehicles, this paper proposes a novel actor-critic based learning method for decision-making and planning in multi-vehicle complex traffic. It is the coupling planning of vehicle's path and speed thus to make the trajectory more flexible. First, generations from the decided action to the planned trajectory are described by the end-point of the trajectory. Then, the actor-critic based learning method is built to learn an optimal policy for the decision process. It can update the policy by the gradient of the current policy's advantage. In this process,features of the real traffic are carefully extracted by time headway(TH) and speed distribution. Reward function is built by the safety, efficiency and driving comfort. Furthermore, to make the policy network have better convergency, the policy network is modularized in two parts: the lane-changing network and the lane-keeping network, which decide the optimal end-point of the path and speed candidates respectively. Finally, the curved overtaking scenario and the interaction process with human driver are conducted to illustrate the feasibility and superiority. The results show that the proposed method has better real-time performance and can make the planned coupling trajectory more continuous and smoother than the existing rule-based method.     

合金熔体热物性参数集成测试系统的数据采集与处理

本文利用PC-5319D光电隔离模入接口卡,构建了合金熔体热物性参数集成测试系统的数据采集与处理单元,并在delphi 7.0环境下编制了相应的软件程序.该数据采集与处理单元配合集成测试系统多工位测试机构和新型传感器,实现了熔体表面张力、密度、电导率和粘度等热物性参数的快速集成测试.本文介绍了热物性参数测试的基本原理、数据采集与处理单元硬件构成和软件设计方法.     

Dynamical analysis of bursting oscillations in the Chay-Keizer model with three time scales

Based on the Chay-Keizer model with three time scales, we investigate the role of the slowest variable in generating bursting oscillations in pancreaticcells. It is shown that both of the two slow processes can interact to drive fast, medium and slow bursting oscillations typically observed in pancreaticcells. Moreover, diverse patterns of electrical bursting are presented, including the fold/fold bursting, fold/homoclinic bursting, fold/Hopf bursting via fold/fold hysteresis loop, and the fold/fold burstin...     

入侵检测系统中分布式Mobile Agent模型

通过在入侵检测系统中应用分布式移动代理技术,提出分布式入侵检测系统的框架结构,较全面地分析系统构成和工作方式.该模型充分利用移动代理独有特点,从而避免传统网络入侵检测系统得不足,提高入侵检测系统的效能.