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大量实际工程问题需要用同时包含连续和离散变量的Markov跳变系统来描述.本文介绍了一类随机激励的单自由度(强)非线性Markov跳变系统的稳态响应的研究方法.首先,基于随机平均法导出具有Markov跳变参数的平均It随机微分方程,原系统方程的维数得到降低.接着,根据跳变过程原理,建立Fokker-Planck-Kolmogorov(FPK)方程组,方程组中的方程与系统的结构状态一一对应且互相耦合.求解该FPK方程组,得到Markov跳变系统的稳态随机响应及其统计量.最后,以一个高斯白噪声激励的Markov跳变Duffing振子为例,计算得到不同跳变规律下系统的稳态响应.研究结果表明,Markov跳变系统的稳态响应可以看作是各结构状态子系统稳态响应的加权和,加权值由跳变规律决定. 相似文献
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大多数MEMS器件(如梁、膜等)的动态特性方程为偏微分方程,因此建立对应组件的可重用参数化行为模型是一个难题.本文通过有限差分法把偏微分方程转化为常微分方程组,然后采用混合信号硬件描述语言进行描述,解决了该问题.针对电容式微型压力传感器,专门考虑膜片的空间连续行为以及结构、静电力的耦合作用,建立了包含接口电路在内的系统模型,据此进行了动态行为仿真.通过结果对比,验证了方法的实用性.相对于通用的参数化组件模型,当前MEMS商业化软件多采用逐个器件进行宏模型抽取的方式实现系统级建模和仿真. 相似文献
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提出一种考虑弥散时Streeter—Phelps一维稳态河流水质模型Chebyshev正交多项式的近似解法.通过对稳态河流水质模型的非线性高阶微分方程式分析,采用Chebyshev正交多项式对各阶微分和弥散系数D进行近似描述,得到稳态河流水质模型的近似表达式.针对近似模型给出了误差指标,并采用最小二乘对近似式中的未知参数进行估计;同时,对算法的总精度进行了讨论.仿真结果表明,该方法的精度高于多种微分方程数值计算方法(如龙格一库塔),不仅可以提高生化需氧量的计算精度,而且能够大大提高溶解氧浓度计算结果的准确性. 相似文献
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基于谐振式硅微结构压力传感器幅、相频率特性的分析,利用北京航空航天大学微传感器实验室研制的谐振式硅微结构传感器开环测试系统的测试实验结果和Matlab实验数据处理与拟和分析计算,建立了微传感器的二阶模型.该模型排除了未知相位延迟的影响,从幅值和相位混合的测试数据中精确计算出谐振频率、品质因数以及相位特性,为闭环测试系统的研制提供了依据. 相似文献
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李睿 《电脑编程技巧与维护》2017,(4)
传统的二阶中值曲率扩散模型(MCM)在去噪时虽然能有效地保持图像的边缘,但是在平滑区域却产生阶梯效应,以及过度扩散的现象.四阶偏微分方程模型(LLT)在去噪的同时虽能有效地抑制二阶偏微分方程产生的阶梯效应,能很好地保持图像的纹理信息,但却过多地损失了边缘信息.为了避免以上去噪过程中存在的问题,利用归一化的45N度旋转梯度等模算子作为权重,提出了传统的二阶中值曲率扩散模型(MCM)和四阶偏微分方程去噪模型(LLT)自适应的混合模型,使得它们在有效去除图像中噪声的同时,也能很好地保持图像的边缘和纹理细节信息.实验结果证实了所提出的模型的有效性. 相似文献
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一个流体欧拉网格格式 总被引:2,自引:0,他引:2
徐国荣 《数值计算与计算机应用》1990,(2)
1.在欧拉流体力学方程组数值解法的研究中存在两种建立计算格式的途径:一种是直接对欧拉流体力学方程组构造格式,例如[1,2]。另一种是分两步来完成,首先建立逼近忽略输运项的方程组的格式,然后将第一步的结果回映到原来的欧拉网格上,这种方法起源质点网格法[8],后来相继有[4-7]。我们称其为流体欧拉网格方法。这种方法对处理多种流体系统的计算是非常有用的。[4]和[5]的格式是按第二途径建立的二阶格式,其结果有较清楚的分辨率,他们的第一步格式属于Godunov型。计算量较大。 相似文献
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为揭示异质传感网恶意程序传播规律,提出一种基于扩展传染病理论的异质传感网恶意程序传播建模与分析方法。依据异质传感器节点状态的分析,扩展传统SIR(Susceptible-Infected-Removed)传染病模型,得到异质传感器节点状态转换关系模型。以一个异质传感器节点与其通信的节点数反映其异质特性,使用微分方程形式建立能反映异质传感网恶意程序传播过程中具有不同度的异质传感器节点状态动态变化的HSIORD(Heterogeneous Susceptible-Infected-isOlated-Removed-Deceased)模型。依据稳定点的数学特性,计算该模型的稳定点。采用下一代矩阵法计算该模型的基本再生数,并证明该模型稳定点的稳定性。通过实验仿真,验证了异质传感网恶意程序消亡的理论依据,为管理员有效抑制异质传感网恶意程序传播提供理论指导。 相似文献
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研究含有单向离合器、两滑轮及附件的轮-带驱动系统稳定稳态周期响应.通过单向离合器连接从动轮与附属系统,并计入传送带的横向振动的影响,导出了由偏微分-积分方程与分段常微分方程组成的连续-离散型非线性耦合方程组.利用Galerkin方法将连续非线性方程组截断为一组非线性常微分方程组,再运用谐波平衡法得到轮-带驱动系统耦合非线性振动的稳态响应.通过比较有无单向离合器装置的系统稳定稳态幅频响应曲线,研究了单向离合器对驱动系统以及轮-带系统非线性动态特性的影响.并首次研究了高频激励下轮-带系统的稳态响应.最后,运用Runge-Kutta方法对比验证了基于谐波平衡法得到的稳态响应. 相似文献
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基于二氧化锆纳米粒子固定乙酰胆碱酯酶的甲基对硫磷传感器 总被引:3,自引:0,他引:3
先在金电极表面电沉积二氧化锆纳米粒子并固定乙酰胆碱酯酶(AChE),将此电极浸入含有不同浓度的有机磷溶液中,根据电极在底物氯化乙酰巯基胆碱中电化学信号强度的大小来实现溶液中有机磷的定量检测.以甲基对硫磷为分析目标物,研究了传感器的主要响应特性、选择性及再生性能,考察了底物浓度、工作电位及溶液pH值对分析性能的影响.结果表明,该有机磷传感器在5.0×10-7~5.0×10-4 g/L浓度范围内对目标分析物有线性响应,检出限为1.0×10-7 g/L.该传感器灵敏度高,非特异性吸附小,再生性好,所用的二氧化锆纳米粒子层制备简单、操作方便,具有较大的应用潜力. 相似文献
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《Sensors and actuators. B, Chemical》2000,62(2):148-153
An amperometric biosensor for sulfite has been developed. The enzyme sulfite oxidase (SOD) and electron acceptor cytochrome c are mixed into the carbon ink that is deposited onto the working electrode of a screen-printed strip. A silver–silver chloride electrode is printed alongside the working electrode and serves as reference/counter electrode. The electrochemical behaviour of the biosensor surface in plain buffer has been investigated by cyclic voltammetry. In the voltage range −0.5 to +0.5 V, a well-defined anodic peak appeared at −0.15 V and a less well-defined anodic peak at about +0.2 V. In the presence of SO32−, the cyclic voltammogram obtained with the biosensor exhibited an increase in magnitude of the more positive peak; this was considered to result from the electrocatalytic oxidation of SO32− involving SOD and the heme (Fe2+/Fe3+) centre of cytochrome c. Amperometry in stirred solution was used to construct a hydrodynamic voltammogram for SO32− using the biosensor; this exhibited a single wave with a plateau beginning at +0.3 V. This wave corresponds to the electrocatalytic response observed by cyclic voltammetry. The pH and concentration of buffer components have been optimised for the determination of SO32− by amperometry in stirred solution. Using these conditions, a detection limit of 4 ppm was obtained. The stability of the biosensors was examined after storage in 0.05 M phosphate buffer pH 7.4 at 4°C; it was found that the initial response was retained for at least 45 days. The proposed biosensors were evaluated on samples of unspiked and spiked estuarine, river and tap waters. The recovery and precision data indicated that the devices could be expected to give reliable data in these waters. 相似文献
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基于纳米金修饰丝网印刷电极的乙醇生物传感器 总被引:1,自引:1,他引:0
在丝网印刷电极上利用吸附法固定乙醇脱氢酶,并用纳米金进行修饰,以铁氰化钾为介体制作了用于酒精检测的一次性乙醇脱氢酶电极试纸.纳米金颗粒修饰酶电极,极大地改善了电极电流响应,提高了传感器的灵敏度.此乙醇传感器的响应时间仅为25 s,灵敏度为0.06 μA(mmol/L)~(-1),线性浓度测量范围为1.0 mmol/L至10 mmol/L. 相似文献
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Enzyme-modified electrodes were fabricated by the immobilization of glycerol dehyrogenase into the polyaniline film and were used as glycerol biosensors. Two different electrodes were prepared by forming monolayer and bilayer electroactive films on the electrode surface and were compared. Potassium ferrocyanide was used as mediator of the biosensing reaction. The biosensors exhibit amperometric response to the glycerol in the range 5×10−6 to 2×10−3 M with detection limit of 1×10−6 M. The Michaelis–Menten constants, Km′, of the electrodes were calculated, their values indicates that the enzyme has not chemically modified with the electrode materials and has its original enzymatic activity. The electrode has a good stability and selectivity due to the enhanced stability of the deposited polyaniline film on Al substrate. 相似文献
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A potentiometric biosensor based on bovine serum albumin (BSA) embedded surface modified polypyrrole has been developed for the quantitative estimation of urea in aqueous solution. The enzyme, urease (Urs), was covalently linked to free amino groups present over the BSA embedded modified surface of the conducting polypyrrole film electrochemically deposited onto an indium–tin-oxide (ITO) coated glass plate. The biosensor has been characterized by UV–visible, infrared spectroscopy and SEM. Potentiometric and spectrophotometric response of the enzyme electrode (Urs/BSA-PPy/ITO) were measured as a function of urea concentration in Tris–HCl buffer (pH 7.0). It has been found that the electrode responds to low urea concentration with wider range of detection. The electrode showed a linear response range of 6.6 × 10−6 to 7.5 × 10−4 M urea. The response time is about 70–90 s reaching to a 95% steady-state potential value and 75% of the enzyme activity is retained for about 2 months. These results indicate an efficient covalent linkage of enzyme to free amino groups of the BSA molecules over the surface of polypyrrole film, which leads to high enzyme loading, an increased lifetime stability of the electrode and an improved wide range of detection of low urea concentration in aqueous solution. 相似文献