应用Simulink模拟耦合神经元的同步活动

癫痫是一组由神经元异常放电所引起的短暂中枢神经系统功能异常为特征的慢性脑部疾病。其发病的原因正是由于神经元集体的异常同步放电行为所致。以FitzHugh-Nagumo神经元为例,使用simulink对耦合神经元的同步活动进行模拟,供相关研究人员进行研究。     

The fractional Fourier transform and quadratic field magnetic resonance imaging

The fractional Fourier transform (FrFT) is revisited in the framework of strongly continuous periodic semigroups to restate known results and to explore new properties of the FrFT. We then show how the FrFT can be used to reconstruct Magnetic Resonance (MR) images acquired under the presence of quadratic field inhomogeneity. Particularly, we prove that the order of the FrFT is a measure of the distortion in the reconstructed signal. Moreover, we give a dynamic interpretation to the order as time evolution of a function. We also introduce the notion of ρ-α space as an extension of the Fourier or k-space in MR, and we use it to study the distortions introduced in two common MR acquisition strategies. We formulate the reconstruction problem in the context of the FrFT and show how the semigroup theory allows us to find new reconstruction formulas for discrete sampled signals. Finally, the results are supplemented with numerical examples that show how it performs in a standard 1D MR signal reconstruction.     

ADRC Law of Spacecraft Rendezvous and Docking in Final Approach Phase

This article addresses the high-precision coordinated control problem of spacecraft autonomous rendezvous and docking, which couple the relative position and attitude in the final approach phase. The coupled dynamics equations of the tracking-target spacecrafts is derived by using dual quaternions. Then, a cascade Active Disturbance Rejection Controller is proposed, by which the extended state observer and nonlinear error feedback law is designed, the virtual value on which the actual control volume tracking is calculated to ensure the finite time convergence of the relative position and attitude tracking errors in spite of parametric uncertainties and external disturbances. Finally, numerical simulations are performed to demonstrate that the proposed approaches, which can avoid the coupling effect and restrain the interference, can track the target spacecraft in a relatively short period of time, and the control precision can satisfy the requirements of docking.     

Robust adaptive DSC of directly input‐coupled nonlinear systems with input unmodeled dynamics and time‐varying output constraints

In this paper, an adaptive robust dynamic surface control is proposed for a class of uncertain nonlinear interconnected systems with time‐varying output constraints and dynamic input and output coupling. The directly coupled inputs and control inputs are both of nonlinear input unmodeled dynamics. To counteract the instable impact of the nonlinear input unmodeled dynamics, normalization signals are designed on the basis of the convergence rates of their Lyapunov functions. With new state variables and control variables being defined, the real control inputs are obtained through solving the equations of intermediate control laws. The time‐varying constraints on output signals are implemented by introducing asymmetric barrier Lyapunov functions. In addition, dynamic signals and decentralized K‐filters are used to deal with the state unmodeled dynamics and to estimate the unmeasurable states, respectively. By the theoretical analysis, the signals in the closed‐loop system are proved to be semi‐globally uniformly ultimately bounded, and the output constraints are guaranteed simultaneously. A numerical example is provided to show the effectiveness of the proposed approach. Copyright © 2017 John Wiley & Sons, Ltd.     

Development of broadband forward‐wave directional couplers loaded by periodic patterned ground structure

In this paper two wideband Forward‐Wave Directional Couplers (FWDCs) with 0 dB and 3 dB coupling level are proposed. Using periodic patterned ground structure in a microstrip coupled lines by a new unit cell; even‐ and odd‐mode characteristic impedances of the couplers are equal over a wide frequency range. Moreover, it provides a constant phase difference between even and odd‐modes. The proposed cell is modeled using the equivalent circuit model and a design procedure is introduced for designing FWDCs for an arbitrary value of coupling level. The introduced couplers are numerically investigated and a prototype of both couplers is made. It is shown that for 0 dB coupling level, the measured coupling is 0.85 dB with 1 dB flatness over fractional bandwidth of 96% bandwidth. In case of 3 dB coupling, the measured coupling level is 3.5 dB at 7.42 GHz with 1 dB flatness over fractional bandwidth of 67.1%.     

Distributed filtering and synchronization of diffusively state‐coupled heterogeneous systems

This paper studies distributed filtering‐based ssynchronization of diffusively state‐coupled heterogeneous systems. For given heterogeneous subsystems and a network topology, sufficient conditions for the filtering‐based synchronization are developed with a guaranteed performance. The estimation and synchronization error dynamics are obtained in a decoupled form, and it is shown that the filter and the controller can be designed separately by LMIs. The feasibility of the proposed design method using LMIs is discussed, and the main results are validated through examples with various setup. Copyright © 2016 John Wiley & Sons, Ltd.     

一种基于PCNN的指纹特征提取算法

具有生物背景的脉冲耦合神经网络具有自适应提取指纹特征的特性,基于此,首次提出了一种指纹图像特征提取的新方法一一自适应耦合神经网络点火统计图的,此图不仅包含了指纹图像的灰度特征,还包含相邻像素之间的几何位置信息。此方法具有运算速度快及对旋转、平移、尺度不变性,是许多指纹特征提取算法不具备的优点。最后给出了部分实验的结果,以验证该方法的有效性．     

剪力墙结构力学性能探讨

分析了由短肢剪力墙组成的多种结构形式的内力、位移等力学特征,提出一种合理的结构形式,该结构既满足了墙肢截面弯矩不至过大,又保证了连梁截面高度不至过高的特点,且具有较好的力学性能。     

辨识方法的计算效率(1):递推算法

算法的计算量可用其乘法运算次数和加法运算次数表示(除法作为乘法对待,减法作为加法对待).一次乘法运算或一次加法运算称为一个flop,即一次浮点运算.作为"辨识方法的计算效率"系列3篇连载论文的第1篇,主要了讨论递推辨识算法的计算量,包括向量和矩阵基本运算的flop数,以及线性回归系统、多元线性回归系统、多变量系统的随机梯度辨识算法、最小二乘辨识算法、递推最小二乘辨识算法的最经济计算量,即实现算法的最少flop数.     

Multi-symplectic integration of coupled non-linear Schrödinger system with soliton solutions

Systems of coupled non-linear Schrödinger equations with soliton solutions are integrated using the six-point scheme which is equivalent to the multi-symplectic Preissman scheme. The numerical dispersion relations are studied for the linearized equation. Numerical results for elastic and inelastic soliton collisions are presented. Numerical experiments confirm the excellent conservation of energy, momentum and norm in long-term computations and their relations to the qualitative behaviour of the soliton solutions.