基于状态反馈控制的无线网络拥塞控制流体流模型的Hopf分岔

针对控制无线网络拥塞控制系统中流体流模型的Hopf分岔的问题,提出一种状态反馈控制器.通过选择通信时延作为分岔参数,验证模型在加入状态反馈控制器后,①增加了分岔参数的临界值,扩大了稳定性区域,使系统的Hopf分岔延迟;②通过选择合适的参数,可以容易地改变分岔周期解的稳定性及其分岔方向.理论分析和数据仿真验证了该方法能够有效地控制系统的Hopf分岔.     

时滞惯性神经网络的稳定性和分岔控制

针对一类二阶时滞惯性神经网络模型,提出一种基于时滞反馈的分岔控制方法.利用时滞微分方程动力学理论,给出反馈控制系统的稳定性以及发生Hopf分岔的判别条件.数值仿真显示所设计的控制器不仅能有效延迟网络分岔的发生,还能扩大稳定域并改善网络的收敛速度.     

一类非自治时滞反馈系统的分岔控制

对含有两个时滞参数、受简谐激励作用下的van der Pol-Duffing方程进行了研究，着重研究了时滞参数对该类参数激励系统的主共振的分岔响应控制.首先采用摄动法从理论上推导出时滞动力系统的分岔响应方程，用奇异性理论得到了退化余维一分岔和余维二分岔的条件，以及Hopf分岔的存在性及发生该分岔的条件，最后用数值模拟的方法研究了时滞参数对系统分岔响应的影响.研究结果表明，适当选取时滞参数，不仅可以改变分岔响应曲线的拓扑形态， 还可以改变分岔点的位置. 关键词： 摄动法 分岔控制 时滞动力系统     

厄尔尼诺-南方波涛动时滞海气振子耦合模型的分岔分析

本文研究了一类具有时滞的厄尔尼诺一南方波涛动模型．得到了该模型在平衡点稳定的充分条件．通过选择时滞η为分岔参数,得到了当时滞η通过一系列的临界值时,Hopf分岔产生,然后,应用中心流形和规范型理论,得到了确定Hopf分岔特性（例如Hopf分岔方向和分岔周期解的稳定性以及Hopf分岔周期解的周期等）的计算公式．最后进行数值模拟验证了所得结果的正确性．     

时滞与噪声影响 Notch信号通路动力学的模型化研究

本文基于Hill动力学与Michaelis-Menten方程,建立理论模型研究时滞与噪声影响Notch信号通路动力学.研究发现,her1、her7基因转录的时滞性在很大程度上调控着Notch信号通路的动力学行为.由于时滞性的调控,Notch系统动力学经历Hopf分岔,由稳态转变为周期演化特性.通过考察Notch信号通路的噪声效应,我们发现,由于噪声的扰动,Notch系统周期振荡动力学改变.在较小噪声幅值条件下,Notch信号通路中改变的周期节律性可以通过时滞得以平衡恢复,由此表明了her1、her7转录的时滞性促进了Notch信号通路的周期振荡.对于较强噪声环境,时滞效应很难改变Notch信号的巨大突变,其信号通路动力学行为被噪声影响.理论结果符合实验,并揭示了时滞与噪声对Notch信号通路动力学的一种调控机制,可为设计阻止Notch功能异常导致的多种疾病和癌症的通路治疗方案提供理论依据.     

基于辟谣机制的时滞谣言传播模型的动力学分析

在社交网络谣言传播模型中,考虑到辟谣机制和时滞效应对网络谣言传播的影响,建立基于辟谣机制和时滞效应的SIR谣言传播模型.利用再生矩阵谱半径方法得到R0;根据二次函数图像特征给出谣言盛行平衡点存在的条件;通过特征值理论和Routh-Hurwitz判据确定无谣言平衡点和谣言盛行平衡点的局部稳定性以及发生Hopf分支的条件;数值仿真结果表明政府和媒体发布的辟谣信息会加快谣言收敛的速度和降低谣言传播者的最大密度.     

基于局部路由策略的复杂网络拥塞控制

提出一种复杂网络上的局部路由策略,算法采用节点收缩法评估节点的重要度,发送节点根据邻居节点的重要度及网络的状态自适应地调整向邻居节点转发数据包的概率.在网络处于自由流通状态时充分发挥关键节点的优势,保证数据包快速到达目的地;在网络处于即将拥塞时分散业务,根据节点重要度准确识别网络中的关键节点,通过有效分流予以保护.仿真结果表明:在网络处于自由流通状态时,该局部路由策略能充分发挥网络中关键节点的枢纽作用,保持较低的传输时延;在网络部分关键节点出现拥塞时,该局部路由策略能有效避开拥挤严重的节点,将数据包均匀地分布在各个节点上,有效抑制网络拥塞,提高网络的容量.     

一类时滞非线性相对转动系统的Hopf分岔与周期解的稳定性

讨论了一类时滞非线性相对转动系统的Hopf分岔现象,给出了系统产生Hopf分岔的临界时滞条件,利用多尺度法研究了系统在主共振情况下时滞参数对分岔方向和周期解稳定性的影响,最后,用数值模拟对所得结论进行验证.     

logistic模型的倍周期分岔控制

研究了logistic模型的倍周期分岔的控制问题，设计了各种线性控制器，得到了系统在控制前和控制后的分岔图，改变了动力系统的分岔特性.根据实际的应用目的可以设计不同的控制器，使倍周期分岔延迟或提前出现，甚至消失.适当选择控制器增益可以使分岔控制的效果更好. 关键词： logistic模型 倍周期分岔 分岔控制 控制器     

时标正弦动力学方程稳定性与分岔分析

本文研究时标上正弦动力学方程的平衡点稳定性和分岔现象. 研究表明随时标参数的变化,正弦动力学方程展现出完全不同的解, 会产生n倍周期分岔和平衡点分裂等特有现象.同时,不增加系统参数, 仅改变时标的复杂性就能扩展动力学方程处于混沌状态的参数空间, 这为时标上动力学方程在混沌加密和雷达波形设计等领域的应用提供了潜在的优势.     

Hybrid control of bifurcation and chaos in stroboscopic model of Internet congestion control system

Interaction between transmission control protocol (TCP) and random early detection (RED) gateway in the Internet congestion control system has been modelled as a discrete-time dynamic system which exhibits complex bifurcating and chaotic behaviours. In this paper, a hybrid control strategy using both state feedback and parameter perturbation is employed to control the bifurcation and stabilize the chaotic orbits embedded in this discrete-time dynamic system of TCP/RED. Theoretical analysis and numerical simulations show that the bifurcation is delayed and the chaotic orbits are stabilized to a fixed point, which reliably achieves a stable average queue size in an extended range of parameters and even completely eliminates the chaotic behaviour in a particular range of parameters. Therefore it is possible to decrease the sensitivity of RED to parameters. By using the hybrid strategy, we may improve the stability and performance of TCP/RED congestion control system significantly.     

Hybrid control of bifurcation and chaos in stroboscopic model of Internet congestion control system

Interaction between transmission control protocol （TCP） and random early detection （RED） gateway in the Internet congestion control system has been modelled as a discrete-time dynamic system which exhibits complex bifurcating and chaotic behaviours. In this paper, a hybrid control strategy using both state feedback and parameter perturbation is employed to control the bifurcation and stabilize the chaotic orbits embedded in this discrete-time dynamic system of TCP/RED. Theoretical analysis and numerical simulations show that the bifurcation is delayed and the chaotic orbits are stabilized to a fixed point, which reliably achieves a stable average queue size in an extended range of parameters and even completely eliminates the chaotic behaviour in a particular range of parameters. Therefore it is possible to decrease the sensitivity of RED to parameters. By using the hybrid strategy, we may improve the stability and performance of TCP/RED congestion control system significantly.     

Bifurcation and stability of an improved time-delayed fluid flow model in internet congestion control

Based on the fluid flow time-delayed model proposed by Misra et al in internet congestion control, one modified time-delayed model is presented, where the influence of the communication delay on the router queue length is investigated in detail. The main advantage of the new model is that its stability domain is larger even without an extra controller. By linear stability analysis and numerical simulation, the effectiveness and feasibility of the novel model in internet congestion control are verified.     

烘丝过程中的组合积分控制器与双重控制研究

在烟草行业的烘丝过程中,烟丝的出口水分作为被控对象常常具有大滞后与强非线性的特性,且在工艺流程中通常存在干扰因素;当前,这一过程中大多仍采用传统PID控制器,存在响应稳态误差大、响应时间长等问题,进而影响烟丝的最终品质;针对这一情况,引入组合积分控制器替代传统PID控制器在烘丝过程中的作用;同时引入双重控制,并与组合积分控制器相结合;针对控制对象进行的仿真实验结果表明,这一新型控制策略在烘丝过程出口水分的控制效果上明显优于传统PID控制器,稳态误差较小且响应迅速,证明了组合积分控制器运用在双重控制系统中时具有优异的动态性能与鲁棒性;最后,这一新型双重控制算法已成功应用到烟草行业烘丝过程的水分控制上。     

Improved Canonical Quantization Method of Self Dual Field

In this paper,the improved canonical quantization method of the self dual field is given in order to overcome linear combination problem about the second class constraint and the first class constraint number maximization problem in the Dirac method.In the improved canonical quantization method,there are no artificial linear combination and the first class constraint number maximization problems,at the same time,the stability of the system is considered.Therefore,the improved canonical quantization method is more natural and easier accepted by people than the usual Dirac method.We use the improved canonical quantization method to realize the canonical quantization of the self dual field,which has relation with string theory successfully and the results are equal to the results by using the Dirac method.     

Time-delayed phase-control for suppression of the flow-induced noise from an open cavity

A flow over an open cavity causes a cavity resonance, which is a feedback mechanism between the acoustic waves and the pressure fluctuation of the cavity flow. Previous research on the reduction of the cavity resonance has focused on suppressing the flow disturbance. This paper presents a time-delayed phase-control method to reduce the global noise of the cavity. Acoustic feedback of the cavity noise, which amplifies the flow disturbance, can be generally reduced by this control method, regardless of the flow physics. The positions of the sensors and the actuator are determined to increase the control efficiency. Experiments show that this control method reduces the peak of the flow oscillation by suppressing the acoustic feedback.     

基于单片机的双燃料汽化器微机控制系统设计

汽油发动机双燃料汽化器采用乙醇和汽油分开放置的燃料储存方式,避免了乙醇汽油存在的诸多弊端,在此,设计了以AT89S52单片机为核心的双燃料汽化器的微机控制系统,该控制系统实现了双燃料汽化器的按键显示、缺液检测及报警、发动机转速测量及计算、乙醇泵堵转检测及保护、乙醇量喷射控制、液压缸液压杆限位检测及保护等功能,同时,能实时采集汽车发动机的转速信号,通过预置的软件对发动机转速进行分析,精确计算出乙醇单次喷射时间和喷射频率,从而准确控制乙醇与空气、汽油的按配比混合掺烧,提高了汽油的燃烧效率,降低了油耗,减少了有害物质的排放,达到了节能减排的目的。实际应用中,该控制系统运行稳定,抗干扰性能良好,控制准确,具有一定的实际应用价值。     

Control of Codimension-2 Bautin Bifurcation in Chaotic Lu System

In this paper, we design a feedback controller, and analytically determine a control criterion so as to control the codimension-2 Bautin bifurcation in the chaotic Lfi system. According to the control criterion, we determine a potential Bautin bifurcation region （denoted by P） of the controlled system. This region contains the Bautin bifurcation region （denoted by Q） of the uncontrolled system as its proper subregion. The controlled system can exhibit Bautin bifurcation in P or its proper subregion provided the control gains are properly chosen. Particularly, we can control the appearance of Bautin bifurcation at any appointed point in the region P. Due to the relationship between Bantin bifurcation and Hopf bifurcation, the control scheme thereby is also viable for controlling the creation and stability of the Hopf bifurcation. In the controller, there are two terms： a linear term and a nonlinear cubic term. We show that the former determines the location of the Hopf bifurcation while the latter regulates its criticality. We also carry out numerical studies, and the simulation results confirm our analyticai predictions.     

电压型双频率控制开关变换器的动力学建模与多周期行为分析

在断续导电模式下, 建立了电压型双频率控制开关变换器的动力学模型, 并推导了相应的特征值方程. 根据动力学模型, 采用分岔图研究了电路参数变化时变换器存在的边界碰撞分岔行为和周期2, 周期3,周期4等多周期行为, 结果表明: 变换器经历了周期1态、多周期态、周期1态的分岔路由; 周期态的转变均是由边界碰撞分岔引起的. 根据特征值方程, 采用Lyapunov指数研究了变换器的稳定性, 结果表明: 随着电路参数的变化, Lyapunov指数始终小于零, 变换器一直工作于稳定的周期态, 验证了电压型双频率控制开关变换器的周期3行为并不意味着变换器会必然发生混沌. 通过电路仿真, 分析了负载变化时变换器的时域波形、相轨图和频谱图, 验证了动力学模型的可行性和理论分析的正确性. 实验结果验证了文中的仿真结果. 关键词： 开关变换器 双频率控制 边界碰撞分岔 多周期行为