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91.
在文献[1-2]的基础上,研究了非线性差分方程xn+1=a-bxpn-k/A-x2n的全局稳定性和正解的周期性,其中a,A为非负实数,b为正实数,k,p∈{1,2,…},p≥2.证明了该方程的一个正平衡点是一个全局吸引子,并给出了相应的吸引域. 相似文献
92.
A variable nozzle turbocharger (VNT) was applied to a 2.2-liter L4 natural gas engine,and a VNT control system was designed to operate it.Based on VNT matching test results,a VNT control strategy was studied,in which VNT adjustment is carried out through pre-calibrated VNT handling rod position,combined with a closed-loop target boost pressure feedback using proportional-integral-derivative(PID) algorithm.Experimental results showed that the VNT control system presented in this thesis can lead to optimized ... 相似文献
93.
Given that fretting wear causes failure in steel wires, we carried out tangential fretting wear tests of steel wires on a self-made fretting wear test rig under contact loads of 9 and 29 N and fretting amplitudes ranging from 5 to 180 μm. We observed morphologies of fretted steel wire surfaces on an S-3000N scanning electron microscope in order to analyze fretting wear mecha-nisms. The results show that the fretting regime of steel wires transforms from partial slip regime into mixed fretting regime and gross slip regime with an increase in fretting amplitudes under a given contact load. In partial slip regime, the friction coefficient has a relatively low value. Four stages can be defined in mixed fretting and gross slip regimes. The fretting wear of steel wires in-creases obviously with increases in fretting amplitudes. Fretting scars present a typical morphology of annularity, showing slight damage in partial slip regime. However, wear clearly increases in mixed fretting regime where wear mechanism is a combination of plastic deformation, abrasive wear and oxidative wear. In gross slip regime, more severe degradation is present than in the other regimes. The main fretting wear mechanisms of steel wires are abrasive wear, surface fatigue and friction oxidation. 相似文献
94.
脉冲清灰是袋式除尘器的过滤再生循环过程,相关的流场分布特性直接影响其清灰性能。针对清灰过程喷吹时间短、速度变化快的特点,建立相应的质量通量方程及非稳态流场模型。通过改变喷嘴结构及喷吹控制参数,采用数值模拟方法获得各种条件下的压力、速度分布云图。实际应用表明:基于数值模拟探讨影响清灰效果的因素及其规律,可为袋式除尘器喷吹清灰的优化设计提供重要参考。 相似文献
95.
To eliminate the perturbation of interceptor detection induced by aerodynamic heating,the head pursuit (HP) guidance law for three-dimensional interception was presented. The guidance law positioned the interceptor ahead of the target on its flight trajectory,and the speed of interceptor was required to be lower than that of the target. On the basis of a novel head pursuit three-dimensional guidance model,a nonlinear guidance law was developed based on smooth sliding mode control theory. At the same time,a special observer was designed to estimate the target acceleration,and a numerical example on maneuvering ballistic target interception verified the effectiveness of the presented guidance law. 相似文献
96.
A new preamble structure is designed for wireless LAN based on MIMO OFDM systems, which can be used for both synchronization and channel estimation. Modulatable orthogonal polyphase sequence is utilized in training symbol design regarding its correlation properties. The time synchronization and channel estimation are achieved by measuring the correlation between the received training sequence and the locally generated training sequence. Repeated training symbols are used to get carrier frequency offset (CFO) estimation. It is shown from the analysis that the accuracy of frequency synchronization is close to the Cramér-Rao lower bound. The training sequences are optimal for channel estimation based on the minimum mean square error (MMSE). 相似文献
97.
98.
该文将部分最小二乘算法与径向基函数神经网络相结合,给出了一种非线性部分最小二乘建模方法,可以更加有效地处理过程非线性和数据共线性等复杂特性,提高模型的精度和推广能力。该方法在确定径向基函数神经网络的隐节点时,采用了一种改进型的k-均值聚类算法来自动确定最优的聚类区数。对煤气化炉合成气组分浓度软测量建模的应用结果表明,采用该方法建立的软测量模型在模型精度和推广能力等方面明显优于二次型多项式部分最小二乘方法建立的模型,并且计算精度满足工业生产的实际要求。 相似文献
99.
In order to reduce oxides of nitrogen (NOx) emanated from a diesel eng ine, a comprehensive urea selective catalyst reduction (SCR) DeNOx catalys t was modeled in which numerical simulations were used as a complementary tool f or the experimental investigations to make the design decisions, and hence short en the development process. In this approach, relevant conversion reactions were studied in 1D model, and the parameters obtained in this way were transferred t o 3D simulations. According to the results ... 相似文献
100.
提出了一种基于图像分割和模板匹配的短波跳频信号盲检测算法。该算法将实际跳频信号的STFT(Short Time Fourier Transform)时频谱图当做一幅图像,利用图像分割手段分离背景噪声,并通过模板匹配来实现跳频信号的检测。实验结果表明该算法能够有效克服实际短波信道中复杂的背景噪声,计算复杂度低,易于工程实现。 相似文献