Dynamics about Neural Array with Simple Lateral Inhibitory Connections

Lateral inhibitory effect is a well-known feature of information processing in neural systems. This paper presents a neural array model with simple lateral inhibitory connections. After detailed examining into the dynamics of this kind of neural array, the author gives the sufficient conditions under which the outputs of the network will tend to a special stable pattern called spatial sparse pattern in which if the output of a neuron is 1, then the outputs of the neurons in its neighborhood are 0. This ability called spatial sparse coding plays an important role in self-coding, self-organization and associative memory for patterns and pattern sequences. The main conclusions about the dynamics of this kind of neural array which is related to spatial sparse coding are introduced.     

动态MTF的数值计算与分析

受振动的影响,在积分时间内,光学系统成像是一个动态过程.对于动态成像,常采用动态调制传递函数(MTF)作为评价振动对像质影响的工具.针对动态MTF,提出一种适用于任意运动形式的数值计算方法,该方法还可以扩展到计算二维运动时的动态MTF.该方法可用于预估和评价动态成像系统的成像质量,计算的结果还可用于运动模糊图像的仿真与...     

Bulk viscosity of low-temperature strongly interacting matter

We study the bulk viscosity of a pion gas in unitarized Chiral Perturbation Theory at low and moderate temperatures, below any phase transition to a quark-gluon plasma phase.We argue that inelastic processes are irrelevant and exponentially suppressed at low temperatures. Since the system falls out of chemical equilibrium upon expansion, a pion chemical potential must be introduced, so we extend the existing theories that include it. We control the zero modes of the collision operator and Landau?s conditions of fit when solving the Boltzmann equation with the elastic collision kernel.The dependence of the bulk viscosity with temperature is reminiscent of the findings of Fernández-Fraile and Gómez Nicola (2009) [1], while the numerical value is closer to that of Davesne (1996) [2]. In the zero-temperature limit we correctly recover the vanishing viscosity associated to a non-relativistic monoatomic gas.     

幅度调制原子力显微镜仿真平台

基于欧拉-伯努利模型,对幅度调制原子力显微镜( AM-AFM)进行建模,采用P]D控制器进行反馈控制,建立了一套幅度调制原子力显微镜仿真平台.仿真结果表明,该平台准确地模拟了AM-AFM探针接近样品和扫描样品的过程中探针的运动状态及AM-AFM的工作系统,可作为大学生做原子力显微镜实验的辅助工具,使学生对AM-AFM的...     

Sensitivity and amplitude calibration of a Fourier transform 3D quadrupole ion trap mass spectrometer

With a three-dimensional (3D) quadrupole ion trap running in a Fourier transform operating mode, the detected signal is an image of the collective motion of the confined ions. Consequently, it is assumed that the image signal is the sum of the axial trajectories of the simultaneously confined ions. The resulting frequency spectrum after Fourier transformation comprises frequency peaks at the axial secular frequencies of the confined species according to their mass/charge ratio. With a singly confined species, the maximal amplitude of the image signal is proportional to the amplitude of the secular axial frequency peak. The matrix method is employed to express the axial trajectory sampled at the confinement field period. In that case, the expression of the image signal, as well as its maximal amplitude, is calculated as a function of the trap operating conditions and initial axial positions and axial velocities of the ions. The initial position and velocity distributions are connected to the injection mode. With the steady ion flow injection mode (SIFIM) and an initial phase of the confinement field equal to kπ, the maximal amplitude of the image signal is proportional to either the sum of the initial axial positions or the number of confined ions and the mean value of the initial axial positions. By simulation, amplitude fluctuation of the frequency peak is then calculated for a number of ions ranging between some tens to some thousands of ions injected by SIFIM. The peak amplitude fluctuations induced by the fluctuations of the number of ions are seven times greater than those induced by the fluctuations of the distribution of the initial axial positions.     

The pseudoscalar meson and baryon octet interaction with strangeness S= −2 in the unitary coupled-channel approximation

The interaction of the pseudoscalar meson and the baryon octet with strangeness $S=-2$ and isospin $I=1/2$ is investigated by solving the Bethe–Salpeter equation in the infinite and finite volume respectively. It is found that there is a resonance state generated dynamically, which owns a mass of about 1550 MeV and a large decay width of 120–200 MeV. This resonance state couples strongly to the π${\rm{\Xi }}$ channel. Therefore, it might not correspond to the ${\rm{\Xi }}(1620)$ particle announced by Belle collaboration. At the same time, this problem is studied in the finite volume, and an energy level at 1570 MeV is obtained, which is between the ${\pi }{\rm{\Xi }}$ and $\bar{K}{\rm{\Lambda }}$ thresholds and independent of the cubic box size.     

Large-amplitude dust acoustic solitons in an opposite polarity dusty plasma with generalized polarization force

Linear and nonlinear dust acoustic(DA)waves have been investigated in an opposite polarity dusty plasma comprising negatively and positively charged dust grains,Maxwellian electrons and ions,including the generalized polarization force effect.The properties of linear DA waves have been significantly altered by the dual dust polarity and polarization force.Large amplitude DA solitons have been discussed in the framework of the Sagdeev potential technique.Our results show that both rarefactive and compressive solitons can exist in such a dusty plasma.The basic features of the Sagdeev potential have been examined under the effect of the polarization force parameter R,the ratio of the charge number of the positive dust to that of the negative dust Z,and the Mach number M.The results show that these parameters play a significant role in determining the region of existence of large amplitude DA solitons.     

High-fidelity resonant tunneling passage in three-waveguide system

An N-stage three-waveguide system is proposed to improve the robustness and the fidelity of the resonant tunneling passage.The analytic solutions to the tunneling dynamics at the output are derived.When the number of subsystems increases,tunneling efficiency approaches to 100%in a large range and resonant tunneling is robust against variations in the phase mismatch and peak tunneling rate.     

基于循环自相关/平均幅度差函数的弹道目标微动周期估计

雷达微多普勒(m-D)是弹道目标的突出特征,为弹头识别提供了重要手段.然而,当弹道目标的微动伴随平动时,时频分布不再表现为正弦调制曲线,此时基于时频分布正弦假设的微多普勒特征提取方法可能失效.针对这一问题,提出了一种循环自相关函数(CACF)和循环平均幅度差函数(CAMDF)相结合的估计算法,来获取时频分布的循环系数矩阵和该矩阵的平均循环系数,从而估计出弹道目标的微动周期.该算法以时频分布的循环周期性代替正弦调制的周期性,不需要假设目标平动已被准确补偿,有效克服了传统微动周期估计方法的不足.理论推导论证了该算法的可行性,仿真实验验证了该算法的有效性和抗噪性.     

SVPWM调制策略下永磁同步发电机损耗分析

永磁同步发电系统中,发电机与PWM变流器直接相连,使永磁同步发电机谐波损耗增大,甚至会导致永磁材料不可逆去磁.针对该问题,本文利用AnSoft联合仿真研究了基于矢量控制的SVPWM调制策略下,设置不同调制比与载波频率对永磁同步发电机铜耗、铁耗及转子损耗的影响,并深入分析了损耗随调制比与载波频率变化的规律.仿真结果表明:SVPWM调制策略下的PMSG-PWM系统中,载波频率一定时,随着调制比的增大,永磁同步发电机铜耗、铁耗及转子损耗逐渐减小,且调制比每增加0.1对发电机铜耗的影响最大;调制比一定时,永磁同步发电机的铜耗、铁耗及转子损耗也逐渐减小,但载波频率每增加1kHz,对发电机铁耗及转子损耗的影响最大.研究结果为SVPWM调制策略下设定合理的调制比与载波频率以保障永磁同步发电机的安全运行提供了参考.