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对Pecora和Carroll的混沌自同步方案的延迟同步误差进行了研究.在计算机上对Lorenz混沌系统伪装的延迟同步误差进行了模拟:给定系统参数,对应不同延迟时间,得出了均方误差与采样步长的关系曲线;给定系统参数和延迟时间,对应不同采样步长,得到了混沌时间序列的误差曲线;给定采样步长,对应不同的系统参数,获得了混沌时间序列的尺度效应和均方误差与采样步长的关系曲线.提出了减小延迟同步误差的一些方法,得到一些对混沌同步和混沌控制应用有意义的结果.
关键词:
混沌同步
时间同步
误差分析 相似文献
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提出三种求解多模光纤非线性传输方程的误差估计准则—max,sum,ave准则,将多模误差向量转换为误差标量,基于对称分步傅里叶的局部误差法实现多模传输自适应步长统一变化.通过仿真高斯脉冲在渐变折射率多模光纤中的传输,验证了定变步长方法在不同准则下局部误差与全局误差的性能.实验结果表明三种准则的变步长算法都具有收敛性,且利用sum准则计算局部误差控制步长变化,在相同计算量的情况下能得到更高的数值精度,相同全局误差的情况下计算量相对更少,对进一步提高多模非线性传输方程的计算效率有参考意义. 相似文献
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在等离子体粒子模拟中,TA模型和NanBu模型被广泛用于处理库仑碰撞,这两种模型要求每个时间步长内全部粒子参与计算。为了降低参与碰撞的粒子数,提高库仑碰撞的计算效率,提出了一种基于截面的库仑碰撞模拟方法,并给出了库仑碰撞概率的计算公式。采用该方法对不同温度不同密度电子气的弛豫过程进行模拟,分别对比了电子速度分布函数、电子温度以及电子x、y方向上的温度与电子温度之比的模拟值与理论值,验证了该方法的准确性。在相同的小时间步长上,该方法相比TA模型计算效率提升可达40%以上。对于较大的时间步长,该方法仍能得到与理论解近似的模拟结果,相比Nanbu模型,在相同的精度下可取更大的时间步长,计算效率也有所提升。研究表明,该方法同样适用于电子-离子碰撞。因此在提高库仑碰撞计算效率上,该方法具有碰撞粒子数少以及适用于大时间步长的优势。 相似文献
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《光学学报》2015,(10)
基于独立成分分析法(ICA)能够实现偏振复用相干光正交频分复用(PDM-CO-OFDM)系统的盲信道均衡,与基于导频的信道均衡方法相比,能极大提高系统的频谱利用率。然而这种固定步长的ICA算法对每个子载波采用迭代算法来计算信道频率响应分离矩阵,需要经过几十次迭代才能收敛。为有效降低该算法的计算复杂度,提出一种基于自适应步长ICA的盲信道均衡算法,采用自适应分离步长提高迭代算法的收敛速度。基于100 Gb/s 16进制正交振幅调制(16 QAM)PDM-CO-OFDM系统,仿真实验表明该自适应算法的系统误码率性能优于固定步长ICA算法的结果,且收敛速度提高5倍以上,能够用于未来高速PDM-CO-OFDM系统接收端进行高效信道均衡。 相似文献
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根据 HL-2M 装置烘烤系统管路设计,建立烘烤系统的管道应力计算模型。对烘烤系统管路作初始
支架设计,并采用系统内的最高温度分布,对烘烤系统进行热应力计算,分析管道应力及设备管口载荷。以热应
力计算结果为依据,对管路布置进行优化,并改善支架的设计,对烘烤系统进行应力校核计算,完成烘烤系统可
靠性验证计算,完成了管口位移量计算。 相似文献
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Steel monopiles are nowadays widely used as foundations for a large number of offshore structures. The installation procedure commonly involves a pile driving process which can last up to several hours depending upon pile dimensions, soil conditions and input energy of the hydraulic hammer. In impact pile driving, a hydraulic hammer delivers a series of hammer blows at the head of the pile that drive the pile into the sediment. Each hammer strike results in pile vibrations that emit strong impulsive sounds into the water column which can be harmful for the marine ecosystem. With today's increasing concern regarding the environmental impact of such operations, engineering tools which will be able to provide reliable predictions of the underwater noise levels are required. In this study, a linear semi-analytical formulation of the coupled vibroacoustics of a complete pile–water–soil interaction model is addressed. The pile is described by a high order thin shell theory whereas both water and soil are modelled as three-dimensional continua. Results obtained with the developed model indicate that the near-field response in the water column consists mainly of pressure conical waves generated by the supersonic compressional waves in the pile excited by the impact hammer. The soil response is dominated by shear waves with almost vertical polarization. The Scholte waves are also generated at the water–seabed interface which can produce pressure fluctuations in the water column that are particularly significant close to the sea floor. The effects of soil elasticity and pile size are thoroughly investigated and their influence on the generated pressure levels is highlighted. The results are also compared with those ones of a similar model in which the soil is treated as an equivalent acoustic fluid. It is shown that the latter approximation can yield inaccurate results at low frequencies especially for harder soil sediments. 相似文献
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Stephanie A. Coronel Jean-Christophe Veilleux Joseph E. Shepherd 《Proceedings of the Combustion Institute》2021,38(3):3537-3545
The potential of water hammer events for igniting hydrogen-oxygen mixtures was examined in an experimental study. Compression waves simulating water-hammer events were created by projectile impact on a piston in a water-filled pipe terminated by a test section filled with gas. Triangular wave forms with peak pressures up to 50 MPa propagated through the piping system and compressed the gas in the test section. Experiments were carried out with both air and hydrogen-oxygen gas mixtures using high-speed video of the transparent test section, dynamic pressure and spectroscopic measurements to examine the motion of the water-gas interface and determine ignition thresholds. The impulsive acceleration of the water-gas interface and deceleration created by the compression of the gas resulted in Richtmyer-Meshkov and Rayleigh-Taylor instabilities that grew to create large distortions of the initially planar and horizontal water-gas interface. The gas layer was compressed in volume by up to a factor of 50 and the gas pressures increased to as high as 20 MPa within 2 to 4 ms. The distortion of the water surface during compression resulted in a significant increase in interfacial area and ultimately, creation of a two-phase mixture of water and compressed gas. Some ignition events were observed, but the dispersion and mixing of water with the gas almost completely suppressed the pressure rise during the ignition transient. Only by eliminating the instability of the water interface with a solid disk between the water and gas were we able to observe consistent ignition with significant pressure rises associated with the combustion. 相似文献
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We have studied the force characteristics of a collection of piano hammers, through studies of the acceleration of the hammer head, the force due to the compression of the hammer felt, Fh, and the associated bending of the hammer shank which occurs when a hammer strikes a rigid object. By integration of the acceleration one can estimate the compression of the felt, and thus obtain a force-compression Fh(z) relationship; our results for this function are compared with previous experiments and theoretical models. Close examination of our findings suggests that bending of the hammer shank, and also the time required for the force to be transmitted from the outer edge of the hammer to its core, play significant roles in the hammer dynamics. The data are used to estimate the quantitative impact of these effects on the derived Fh(z) relation. The implications for physical modeling of a piano tone are briefly discussed. 相似文献
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Noise levels and hearing thresholds in the drop forging industry 总被引:1,自引:0,他引:1
W Taylor B Lempert P Pelmear I Hemstock J Kershaw 《The Journal of the Acoustical Society of America》1984,76(3):807-819
A-weighted equivalent continuous noise levels for hammer and press operations in a drop-forging industry were determined using both tape recordings of the noise and personal noise dosimeters. The results indicated average A-weighted Leq values of 108 dB for hammer operators and 99 dB for press operators. Comparison of hearing level statistics for 716 hammer and press operators and 293 control subjects indicated the severe hazard to hearing of impact noise exposures. For mean exposure times of less than 10 years, hearing levels for the press (99 dB) and hammer (108 dB) operator age groups are nearly identical, and in the latter case are less than those predicted for exposure to equivalent continuous noise. For long-term exposures of 10 years or more, the results of this study indicate that hearing losses resulting from impact noise in the drop-forging industry are as great or greater than those resulting from continuous noise. 相似文献
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Complex pipelines may have various structural supports and boundary conditions, as well as branches. To analyse the vibrational characteristics of piping systems, frequency modelling and solution methods considering complex constraints are developed here. A fourteen-equation model and Transfer Matrix Method (TMM) are employed to describe Fluid–Structure Interaction (FSI) in liquid-filled pipes. A general solution for the multi-branch pipe is proposed in this paper, offering a methodology to predict frequency responses of the complex piping system. Some branched pipe systems are built for the purpose of validation, indicating good agreement with calculated results. 相似文献
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Arris S. Tijsseling Martin F. Lambert Angus R. Simpson Mark L. Stephens John P. Vítkovský 《Journal of sound and vibration》2008,310(3):718-728
Half a century ago Richard Skalak [see T.C. Skalak, A dedication in memoriam of Dr. Richard Skalak, Annual Review of Biomedical Engineering 1 (1999) 1-18] published a paper with the title “An extension of the theory of water hammer” [R. Skalak, An Extension of the Theory of Water Hammer, PhD Thesis, Faculty of Pure Science, Columbia University, New York, USA, 1954; R. Skalak, An extension of the theory of water hammer, Water Power 7/8 (1955/1956) 458-462/17-22; R. Skalak, An extension of the theory of water hammer, Transactions of the ASME 78 (1956) 105-116], which has been the basis of much subsequent work on hydraulic transients with fluid-structure interaction (FSI). The paper considers the propagation of pressure waves in liquid-filled pipes and the coupled radial/axial response of the pipe walls. In a tribute to Skalak's work, his paper is revisited and some of his less-known results are used to assess the dispersion of pressure waves in long-distance pipelines. Skalak's theory predicts that the spreading of wave fronts due to FSI is small, at most of the order of 10 pipe diameters. 相似文献