无标度生物神经元网络的相干共振分析

本文以神经元二维映射模型为节点,构造了一个具有无标度连接特性的生物神经元网络.用高斯白噪声模拟生物神经系统中的环境噪声,通过数字仿真研究了噪声对神经网络动力学行为的影响.噪声可以提高神经元的兴奋性,诱导神经元产生峰电位,当噪声强度为某一适当值时,峰电位序列的有序度可以达到最佳,从而产生相干共振现象.另外,研究表明无标度...     

异质性和时滞作用下神经元网络的共振动力学

利用参数互异的Fitzhugh-Nagumo神经元构建了含耦合时滞的无标度神经元网络模型,通过数值模拟的方法,提出研究参数异质性和耦合时滞影响下神经元网络的共振动力学.结果发现,当耦合项中不含时滞时,适中的参数异质性能够使得神经元网络对外界弱周期信号的响应达到最优,即适中的参数异质性能够诱导神经元网络的共振响应,而且异质性诱导共振对耦合强度具有鲁棒性.更重要的是,耦合时滞对参数异质性作用下神经元网络的共振特性也有着显著性影响.当时滞约为信号周期的整数倍时,神经元网络能够周期性地出现共振现象,即适当的耦合时滞能够诱导神经元网络的多重共振,而且这种现象在异质性参数的适当范围内都能明显出现.     

神经元网络模型的弱信号随机共振检测研究

基于FitzHugh-Nagumo可兴奋细胞耦合后形成的神经元网络模型,对生物神经系统的弱周期信号随机共振检测机制进行研究。以加和网络的双层FHN神经元模型为例,对周期随机共振现象分别进行研究,并应用信噪比、互信息率对比评价方法,结合输出神经元动作电位的发放频率和幅值,从多个角度进行了定量和定性的描述和比较。实验结果表明,双层FHN神经元网络的随机共振响应优于单神经元的FHN模型,且具有更好的稳定性,可以在一定的噪声强度范围内对输入信号进行有效地检测。     

高斯白噪声对神经元映射模型动力学的影响*

研究了噪声引发的神经元相干共振现象。基于神经元二维映射模型,用高斯白噪声模拟生物神经系统中的环境噪声,通过数字仿真研究了噪声对神经元动力学特性的影响。研究发现,噪声可以提高静态神经元的可兴奋性,诱导其产生动作电位,当噪声达到某一适中强度时,动作电位的有序性可以达到最佳,产生相干共振现象。研究了系统参数的选取对神经元共振特性的影响,发现控制参数越接近分岔点,相干共振性越好。结果表明合适强度的噪声可以促进神经元的信息传递。     

噪声诱使模块化神经元网络产生随机多共振现象

首先,研究了噪声在多模块神经元网络中诱导的随机多共振现象.随机多共振现象是指存在不同的噪声强度,系统在这些噪声强度下对阈下信号的响应达到局部最优.其次,以FitzHugh-Nagumo神经元构成的模块化神经元网络为研究对象,通过数值模拟发现,神经元网络的系统响应随着噪声强度的增加多次达到局部最优,即产生随机多共振现象.同时,通过分析神经元网络平均膜电位的时序图,发现噪声通过诱导神经元网络在一个周期内产生多次发放进而诱导多次共振.最后,我们分析了两个子网络中加入不同强度的噪声时,噪声诱导神经元网络中的随机多共振现象.结果显示,当两个子网络加入不同强度的噪声时,随机多共振现象也会产生.     

随机信号在神经元网络中诱发的双空间相干共振

对确定性行为为静息的神经元网络施加随机信号进行控制,随着信号强度的增加,网络行为由无序到有序的空间行为一螺旋波再到无序,螺旋波的结构由复杂到简单再到复杂到简单的交替,由网络行为的空间结构函数计算出的信噪比会两次达到极大值,即发生了两次空间相干共振,结果不仅展示了该随机信号控制下的网络的动力学行为,还为通过施加控制因素诱导产生空间共振来提高神经系统的信息处理能力提供了可能的方法．     

网络噪声和振子数量对同步化行为的影响

选取了三个反映同步化程度的指标平均向量场、同步因子和放电概率,数值模拟研究了网络噪声和振子数量对同步化行为的影响.随着噪声强度的增大,三个指标都出现了先增加再降低的现象,即发生了相干共振.在不同的耦合强度和噪声强度下,三个同步化指标随着振子数量的增加都呈现出了降低的趋势,表明了网络同步化行为的减弱.研究结果对如何利用噪...     

Courbage神经元映射模型的随机共振研究

采用神经元二维映射模型,通过数字仿真研究了高斯白噪声对神经元非线性动力学特性的影响.研究发现,噪声可以诱导具有次阈值输入信号的神经元产生动作电位和随机共振.随机共振现象的产生与否和噪声强度的大小以及输入信号的频率具有密切的关系.另外,还研究了系统的控制参数对随机共振现象的影响.     

Genesio体系中的内信号随机共振

采用数值模拟的方法,研究了不同耦合方式下Genesio体系中振子的动力学行为,分别讨论了当体系处于周期-1振荡态时,单个振子、双边耦合和单边耦合情况下体系对噪声及耦合的响应情况。发现噪声强度、耦合方式及耦合强度都会对体系的内信号传递产生不同的影响。在合适的噪声水平和耦合强度及方式下,体系内信号能够被传递和放大,产生内信号随机共振现象。同时发现双边耦合比单边耦合更有利于信号的传递。本文的模拟结果将对内信号随机共振现象的试验研究有一定的意义。     

噪声在慢变系统中的随机Chay神经元模型的自共振

研究了白噪声在慢变系统中的Chay神经元模型的共振．被加到慢变量中的白噪声相当于钙离子的波动,这是更具有生理意义的．随着噪声强度的增加,发现在某一优化噪声水平处,信噪比经过极大值,这意味自共振的发生．同时,也证实了钙离子的波动可以引起信号的探察和转换．     

Fuzzy coherence measures

Coherence measures are a tool to compare those fuzzy sets that are sensitive to their own similarity as well as to their fuzzy nature. Within this article we can find three generalizations made about the definition of coherence measures: a first one for any fuzzy set, a second one for any definition about strong negation, and a final one for an extension in those coherence measures that, as a result, do not cause a value in the unit interval, but a fuzzy set in that interval. Tools and properties are offered to create coherence measures. © 2005 Wiley Periodicals, Inc. Int J Int Syst 20: 1–11, 2005.     

In-network cache coherence

We propose implementing cache coherence protocols within the network, demonstrating how an in-network implementation of the MSI directory-based protocol allows for in-transit optimizations of read and write delay. Our results show 15% and 24% savings on average in memory access latency for SPLASH-2 parallel benchmarks running on a 4/spl times/4 and a 16/spl times/16 multiprocessor respectively.     

Image-space hierarchical coherence buffer

Indirect illumination plays an important role in global illumination. However, computing indirect illumination is a time-consuming process and needs to be approximated to achieve interactive performance. Indirect illumination varies rather slowly across the surface. This leads to the idea of computing indirect illumination sparsely in the scene and interpolating the result. This paper presents a hierarchical structure, which enables efficient sampling. The hierarchy is constructed in the image space by exploiting coherences among the screen-space pixels. From the hierarchy, samples are chosen, each of which represents a group of coherent pixels. This paper presents two methods of utilizing the samples for indirect lighting computation. The methods produce plausible lighting results and show high performances. The proposed algorithms run entirely in the image space and are easy to implement in contemporary graphic hardware.     

An adaptive coherence filter

This paper derives an adaptive coherence filter for canceling interference from a signal of interest whose power spectral density is symmetric. A basic property of the Fourier transform of real signals is that their spectra are Hermitian symmetric. This property is exploited to determine which part of a spectrum is interference and which part is the signal of interest. An unconstrained Wiener filter is derived that exploits the frequency domain symmetry of the signal of interest. While the adaptive coherence filter is based on the Fourier transform property of real signals, an extension of the algorithm is provided so the filter can be used on any signal that displays spectral symmetry. A practical method for implementing the filter is provided. The filter has application in the area of telecommunications, but is applicable in wireless communication applications where a signal, that displays spectral symmetry, is corrupted by interfering signals within the signal of interest's bandwidth.     

Synchronization coherence: A transparent hardware mechanism for cache coherence and fine-grained synchronization

The quest to improve performance forces designers to explore finer-grained multiprocessor machines. Ever increasing chip densities based on CMOS improvements fuel research in highly parallel chip multiprocessors with 100s of processing elements. With such increasing levels of parallelism, synchronization is set to become a major performance bottleneck and efficient support for synchronization an important design criterion. Previous research has shown that integrating support for fine-grained synchronization can have significant performance benefits compared to traditional coarse-grained synchronization. Not much progress has been made in supporting fine-grained synchronization transparently to processor nodes: a key reason perhaps why wide adoption has not followed.     

Ordering states with coherence measures

The quantification of quantum coherence has attracted a growing attention, and based on various physical contexts, several coherence measures have been put forward. An interesting question is whether these coherence measures give the same ordering when they are used to quantify the coherence of quantum states. In this paper, we consider the two well-known coherence measures, the \(l_1\) norm of coherence and the relative entropy of coherence, to show that there are the states for which the two measures give a different ordering. Our analysis can be extended to other coherence measures, and as an illustration of the extension we further consider the formation of coherence to show that the \(l_1\) norm of coherence and the formation of coherence, as well as the relative entropy of coherence and the coherence of formation, do not give the same ordering too.     

Quantum correlation via quantum coherence

Quantum correlation includes quantum entanglement and quantum discord. Both entanglement and discord have a common necessary condition—quantum coherence or quantum superposition. In this paper, we attempt to give an alternative understanding of how quantum correlation is related to quantum coherence. We divide the coherence of a quantum state into several classes and find the complete coincidence between geometric (symmetric and asymmetric) quantum discords and some particular classes of quantum coherence. We propose a revised measure for total coherence and find that this measure can lead to a symmetric version of geometric quantum correlation, which is analytic for two qubits. In particular, this measure can also arrive at a monogamy equality on the distribution of quantum coherence. Finally, we also quantify a remaining type of quantum coherence and find that for two qubits, it is directly connected with quantum nonlocality.     

Classifying software-based cache coherence solutions

The authors propose a classification for software solutions to cache coherence in shared memory multiprocessors and show how it can be applied to more completely understand existing approaches and explore possible alternatives