具有感觉记忆的忆阻器模型

人类记忆的形成包括感觉记忆、短期记忆、长期记忆三个阶段,类似的记忆形成过程在不同材料忆阻器的实验研究中有过多次报道.这类忆阻器的记忆形成过程存在有、无感觉记忆的两种情况,已报道的这类忆阻器的数学模型仅能够描述无感觉记忆的忆阻器.本文在已有模型的基础上,根据有感觉记忆的忆阻器的研究文献中所报道的实验现象,设计了具有感觉记忆的忆阻器模型.对所设计模型的仿真分析验证了该模型对于存在感觉记忆的这类忆阻器特性的描述能力:对忆阻器施加连续脉冲激励,在初始若干脉冲作用时忆阻器无明显的记忆形成,此时忆阻器处于感觉记忆阶段,后续的脉冲作用下忆阻器将逐渐形成短期、长期记忆,并且所施加脉冲的幅值越大、宽度越大、间隔越小,则感觉记忆阶段所经历的脉冲数量越少.模型状态变量的物理意义可用连通两电极的导电通道在外加电压作用下的形成与消失来给出解释.     

忆阻器、忆容器和忆感器的Simulink建模及其特性分析

忆阻器、忆容器和忆感器均是具有记忆特性的新型非线性电路元件,也被称为记忆元件.以三种电路元件的通用数学模型为依据,从数学分析的角度,对忆阻器、忆容器和忆感器的Simulink模型进行了建立.在Simulink模型中体现了记忆元件对历史状态和系统状态变量的依赖性,正确表现出其独特的记忆特性.通过一系列仿真分析,得到了忆阻器、忆容器和忆感器的元件特性,验证了模型的有效性.此外,通过对三者在不同参数、不同激励下的电路特性分析,得到了三种记忆元件等效模型随频率和幅值变化的规律,为以后忆阻器、忆容器和忆感器基于Simulink的仿真研究和应用研究奠定基础.     

传输线的电容和电阻特性及其应用

讨论了横向电磁传输线的另一个重要特性——电容和电阻特性,即单位长度的电容与电阻之积等于电容率与电阻率之积．并对一些典型的传输线进行了应用．     

忆阻器及其阻变机理研究进展

忆阻器是除电阻、电容、电感之外的第四种电路元件,在信息存储、逻辑运算和神经网络等研究领域具有重要的应用前景.本文综述了忆阻器以及忆阻器材料的研究进展,主要介绍了忆阻器的内涵与特征、阻变机理、材料类型以及应用前景,指出了目前忆阻器研究中需要关注的主要问题,并对以后的发展趋势进行了展望.     

用电容器的电阻和电容特性公式计算非平行板电容器的电容

讨论了电容器的电阻和电容特性公式,计算了非平行板电容器的电阻和电容.     

一个分数阶忆阻器模型及其简单串联电路的特性

忆阻器是具有时间记忆特性的非线性电阻. 经典HP TiO₂忆阻器模型的忆阻值为此前通过忆阻器电流的时间积分, 即记忆没有损失. 而最近研究证实HP TiO₂ 线性忆阻器掺杂层厚度不能等于零或者器件整体厚度, 导致器件的记忆有损失. 基于此发现, 本文首先提出了一个阶数介于0 与1间的分数阶HP TiO₂ 线性忆阻器模型, 研究了当受到周期外激励时, 分数阶导数的阶数对其忆阻值动态范围和输出电压动态幅值的影响规律, 推导出了磁滞旁瓣面积的计算公式. 结果表明, 分数阶导数阶数对磁滞回线的形状及所围成区域面积有重要影响. 特别地, 在外激频率大于1时, 分数阶忆阻器的记忆强度达到最大. 然后讨论了此分数阶忆阻器与电容或电感串联组成的单口网络的伏安特性. 结果表明, 在周期激励驱动时, 随着分数阶导数阶数的变化, 此分数阶忆阻器与电容的串联电路呈现出纯电容电路与忆阻电路的转换, 而它与电感的串联电路则呈现出纯电感电路与忆阻电路的转换.     

基于六角氮化硼二维薄膜的忆阻器

报道了一种基于多层六角氮化硼(h-BN)二维薄膜的忆阻器件.该器件不需要电预处理过程,且具有自限流的双极性阻变行为;具有较好的抗疲劳性和较长的数据保持时间.该器件在脉冲编程条件下具有模拟转变特性,即在连续的电压脉冲下器件的电阻态能被连续地调控,使得该器件能够模仿神经网络系统中的神经突触权重变化行为.综上所述,基于多层h-BN的忆阻器具有应用在非易失性存储和神经计算中的潜力.     

基于串并联磁控忆阻器的耦合行为研究

忆阻器是纳米级器件, 其功耗低, 集成度高, 有着巨大的应用潜能. 单个器件具有丰富的电学性质, 其串并联电路更展现了丰富的动力学行为. 然而, 忆阻器在高密度集成的环境下, 其耦合效应不可忽视. 因此, 本文首先基于磁控忆阻器推导了耦合忆阻器的数学模型. 其次, 在考虑不同极性连接和耦合强度的前提下, 讨论两个磁控忆阻器串并联的耦合情况, 进行了详细的理论分析, 并通过数值仿真探索了耦合效应对忆阻系统的影响. 同时, 设计了基于Matlab的图形用户界面, 直观地展示了不同参数下的耦合特性曲线. 进一步, 本文展示了有无耦合情况下, 初始阻值对忆阻器正常工作范围的影响. 最后, 构建耦合忆阻器的Pspice仿真器, 从电路的角度再次验证了忆阻器间的耦合效应. 实验结果表明: 同极性耦合增强了阻值的改变, 相反极性的耦合减缓了阻值的改变. 这些动力学特性可以很好地应用于忆阻网络中, 也为全面考虑忆阻系统电路的设计提供了强大的理论基础.     

具有经验学习特性的忆阻器模型分析

类似人类记忆的短期、长期记忆现象在不同材料忆阻器的实验研究中有过多次报道.在多篇这类忆阻器的研究文献中还报道了经验学习特性:学习-遗忘-再学习实验中,短期记忆遗忘后再次学习,记忆恢复的速度明显比初次学习的记忆形成速度更快.本文对这类忆阻器已有数学模型在学习-遗忘-再学习实验中的特性给出进一步分析.仅考虑短期、长期记忆现象的忆阻模型在该实验中表现为较快速再次学习特性,再次学习的记忆恢复速度较快主要是由于脉冲间隔期间的遗忘速度比初次学习时更慢.考虑经验学习特性的忆阻模型在再学习阶段的记忆恢复速度更快主要是因为脉冲作用时的记忆增速更快,同时仍然存在脉冲间隔期间的遗忘速度减慢.与经验学习特性相关的状态变量的物理意义可利用连通两电极的导电通道的周围区域在不同外加电压作用下的变化来给出解释.     

N型局部有源忆阻器的神经形态行为

局部有源忆阻器(locally-active memristor,LAM)凭借其高集成度、低功耗和局部有源特性等优点,在神经形态计算领域显示出巨大的潜力.本文提出了一种简单的N型LAM数学模型,通过揭示其非线性动力特性,设计了N型LAM神经元电路.采用Hopf分岔、数值分析等方法定量研究了该电路的动力学行为,成功模拟了多种神经形态行为,包括全或无行为、尖峰、簇发、周期振荡等.并利用该神经元电路结构模拟了生物触觉神经元的频率特性.仿真结果表明:当输入信号幅值低于阈值时,神经元电路输出信号的振荡频率与输入信号强度呈正相关(即兴奋状态),并在阈值处达到最大值.随后,继续增大激励强度,振荡频率则逐渐降低(即保护性抑制状态).最后,设计了N型LAM硬件仿真器,并完成了人工神经元电路的硬件实现,实验结果与仿真结果、理论分析相一致,验证了该N型LAM具备的神经形态行为.     

Effect of displacement on resistance and capacitance of polyaniline film

This paper investigates the properties of displacement sensors based on polyaniline (PANI) films. About 1 wt% of PANI micropowder is mixed and stirred in a solution of 90 wt% water and 10 wt% alcohol at room temperature. The films of PANI are deposited from solution by drop-casting on Ag electrodes,which are preliminary deposited on glass substrates. The thicknesses of the PANI films are in the range of 20 μm-80 μm. A displacement sensor with polyaniline film as an active material is designed and fabricated. The investigations showed that,on average,the AC resistance of the sensor decreases by 2 times and the capacitance accordingly increases by 1.6 times as the displacement changes in the range of 0 mm-0.5 mm. The polyaniline is the only active material of the displacement sensor. The resistance and capacitance of the PANI changes under the pressure of spring and elastic rubber,and this pressure is created by the downward movement of the micrometer.     

Multilevel resistive switching and synaptic behaviors in MnO-based memristor

Exploring new synaptic electronic devices that combine computing and memory is a promising strategy that fundamentally approaches intelligent machines. In this study, the multilevel resistive switching and synaptic behaviors of a MnO-based device is studied. The device is composed of Al/MnO/Ni sandwich structure, has stable resistance switching characteristics, has continuous nonvolatile memory state, can be used as electrically programmable and erasable analog memory. The gradual conductance modulation is realized by changing the compliance current and the maximum scanning voltage. The Al/MnO/Ni devices successfully mimic the basic functions of synapses, including the paired-pulse facilitation, spike-rate-dependent plasticity, excitatory postsynaptic current, short-term plasticity, long-term plasticity, and sike-timing-dependent plasticity.     

Investigation of dispersion characteristic in MI- and MII-type single mode optical fibers

Dispersion characteristic of MI and MII type single mode optical fibers is analytically investigated. For this purpose modal analysis of these fibers to obtain possible wave vectors for given system parameters are done. Then using numerical evaluation of the presented analytical relations, chromatic and waveguide dispersions are calculated. The effects of geometrical and optical parameters of the fibers on dispersion characteristics are investigated. In this analysis, we show that with increase of Δ (optical parameter) for MI structure the slope of dispersion curve is decreased and the case is reversed for MII structure. Also, with rising of Q (geometric parameter) for MI structure the slope of dispersion curve is decreased and the situation is reversed for MII structure. Finally, we show that with boosting of R₂ for MII structure the slope of dispersion is increased. As a final result, our simulations show that small values for optical parameters are better in MII structure for multi-channel optical communications. In MI structure to obtain small dispersion slope, Q can be increased that is easy for fabrication in practice. Finally, Q and R₂ are suitable parameters for control of dispersion in the proposed structures.     

Multi-polar resistance switching and memory effect in copper phthalocyanine junctions

Copper phthalocyanine junctions, fabricated by magnetron sputtering and evaporating methods, show multi-polar （unipolar and bipolar） resistance switching and the memory effect. The multi-polar resistance switching has not been observed simultaneously in one organic material before. With both electrodes being cobalt, the unipolar resistance switching is universal. The high resistance state is switched to the low resistance state when the bias reaches the set voltage. Generally, the set voltage increases with the thickness of copper phthalocyanine and decreases with increasing dwell time of bias. Moreover, the low resistance state could be switched to the high resistance state by absorbing the phonon energy. The stability of the low resistance state could be tuned by different electrodes. In Au/copper phthalocyanine/Co system, the low resistance state is far more stable, and the bipolar resistance switching is found. Temperature dependence of electrical transport measurements demonstrates that there are no obvious differences in the electrical transport mechanism before and after the resistance switching. They fit quite well with Mott variable range hopping theory. The effect of A1203 on the resistance switching is excluded by control experiments. The holes trapping and detrapping in copper phthalocyanine layer are responsible for the resistance switching, and the interfacial effect between electrodes and copper phthalocyanine layer affects the memory effect.     

不同运动状态下的飞机目标雷达散射截面积统计特性分析

目标的运动状态对其动态雷达散射截面积(RCS)起伏特性具有十分重要的影响,同一目标在不同运动状态下,可能具有不同的RCS起伏模型。结合实测数据,对在平稳直线飞行和曲线机动飞行两种状态下的飞机动态RCS进行统计分析。分析结果表明：在平稳直线飞行状态下,飞机目标的动态RCS起伏模型与观测视角内的静态RCS起伏模型近似;在曲线机动飞行状态下,飞机目标的动态RCS起伏更显著、更随机,当观测时间足够长、目标的运动随机性更大时,其起伏模型更接近于指数分布。     

Quantum capacitance in monolayers of silicene and related buckled materials

Silicene and related buckled materials are distinct from both the conventional two dimensional electron gas and the famous graphene due to strong spin orbit coupling and the buckled structure. These materials have potential to overcome limitations encountered for graphene, in particular the zero band gap and weak spin orbit coupling. We present a theoretical realization of quantum capacitance which has advantages over the scattering problems of traditional transport measurements. We derive and discuss quantum capacitance as a function of the Fermi energy and temperature taking into account electron–hole puddles through a Gaussian broadening distribution. Our predicted results are very exciting and pave the way for future spintronic and valleytronic devices.     

Tunable quantum capacitance and magnetic oscillation in bilayer graphene device

We address the quantum capacitance of a bilayer graphene device in the presence of Rashba spin–orbit interaction (SOI) by applying external magnetic fields and interlayer biases. Quantum capacitance reflects the mixing of the spin-up and spin-down states of Landau levels and can be effectively modulated by the interlayer bias. The interplay between interlayer bias and Rashba SOI strongly affects magnetic oscillations. The typical beating pattern changes tuned by Rashba SOI strength, interlayer bias energy, and temperature are examined as well.     

新型PTC热敏电阻的特性测量及其应用

简述了新型有机材料ＰＴＣ热敏电阻的特性、测量方法、实验结果及应用前景并与陶瓷ＰＴＣ热敏电阻进行了比较。     

Gate-induced drain leakage (GIDL) in MFMIS and MFIS negative capacitance FinFETs

The gate induced drain leakage (GIDL) effect in negative capacitance (NC) FinFET is investigated. A Landau–Ginzburg–Devonshire equation (which considers the polarization gradient in ferroelectric material) is used to estimate the characteristics of the NC FinFET. Specifically, metal-ferroelectric-metal-insulator-semiconductor (MFMIS) and metal-ferroelectric-insulator-semiconductor (MFIS) NC FinFETs are compared, in order to figure out the effect of the internal metal layer on the GIDL effect. To analyze the impact of the polarization gradient on the GIDL effect in NC FinFET, a polarization gradient coefficient is varied. For MFMIS, the polarization gradient doesn't significantly affect the device performance. The subthreshold swing improves but the GIDL effect deteriorates because of the “uniform” NC effect in channel region. For MFIS, the device performance is explicitly affected by the polarization gradient. Smaller polarization gradients result in non-uniform NC effect in channel region, resulting in severe GIDL effects. On the other hand, higher polarization gradients alleviate GIDL effects.     

LR串联电路稳态特性实验的教与学

通过实验测量结果及理论计算2组曲线的比较,研究了LR串联电路的稳态特性.发现理论值与实际值之间存在非正常误差范围的结果.本文通过多组(R取不同值)实验结果来分析电感元件中存在内阻时所带来的影响,探讨做好本实验的规律.