符合HVS特性的相关系数SAR干扰效果评估方法

该文提出了一种符合人眼视觉系统特性的合成孔径雷达干扰效果评估方法。该方法根据人眼视觉系统的对比敏感度函数,以及小波变换与人类视觉系统的多通道特性相匹配的特点,求取被干扰图像与原始图像之间在各子频带内小波分解系数的相关系数,最后通过非线性合并获得总的评价量小波加权相关系数。实验结果表明,该评估指标不仅能正确反映出SAR图像降质与干扰能量之间的关系,而且比传统的评估指标能更好地保持与人的主观感受一致。     

面向对象的机载雷达探测及干扰仿真

在该仿真系统中,通过对被仿对象的行为,特征等进行数学建模和仿真建模,特别是在干扰评估的数学建模中,导出了简单实用的数学模型,从而为准确的仿真打下了良好的基础。仿真系统采用ＪＡＶＡ语言面向对象编程。通过仿真可得到雷达在不同参数下的有效探测距离及干扰前后探测区域的变化,并能自动生成评估的表格。     

BOC调制信号的抗干扰性能研究

BOC调制技术在扩频通信中的应用已日趋广泛.为此,本文在对BOC调制信号的功率谱和自相关特性进行深入研究,以及将其与BPSK调制相比存在的优势进行深入分析的基础上,以BOC(10,5),BPSK(10.23)为例,进行了基于FFT的同步捕获环路的设计与仿真,并重点就不同干信比条件下两者的捕获性能进行了分析.结果表明,在一定条件下BOC调制信号具有更好的抗干扰能力,为进一步抗干扰技术的研究提供了理论基础.     

Jamming in granular shear flows of frictional,polydisperse cylindrical particles

In this work, frictional, cylindrical particle shear flows with different size distributions (monodisperse, binary, Gaussian, uniform) are simulated using the Discrete Element Method (DEM). The influences of particle size distribution and interparticle friction coefficient on the solid phase stresses, bulk friction coefficient, and jamming transition are investigated. In frictional dense flows, shear stresses rise rapidly with the increasing solid volume fraction when jamming occurs. The results suggest that at the jamming volume fraction, stress fluctuation and granular temperature achieve the maximum values, and the rate of the stress increase with increasing solid volume fraction approaches the peak value. Meanwhile, the degree of cylindrical particle alignment approaches a valley value. In the polydisperse flows, the jamming volume fraction exhibits significant dependences on the fraction of the longer particles and the particle size distribution. Two models considering the effect of particle size distribution are discussed for predicting the jamming volume fractions of polydisperse flows with frictional, cylindrical particles.     

The flow rate of granular materials through an orifice

The flow rate of grains through large orifices is known to be dependent on its diameter to a 5/2 power law. This relationship has been checked for big outlet sizes, whereas an empirical fitting parameter is needed to reproduce the behavior for small openings. In this work, we provide experimental data and numerical simulations covering a wide span of outlet sizes, both in three- and two-dimensions. This allows us to show that the laws that are usually employed are satisfactory only if a small range of openings is considered. We propose a new law for the mass flow rate of grains that correctly reproduces the data for all the orifice sizes, including the behaviors for very large and very small outlet sizes.     

条件匹配滤波器与雷达抗寻呼信号干扰

在某些特定频率点的增益为零的条件下,使滤波器的输出信噪比最大,我们称其为条件匹配波波器.本文讨论了条件匹配滤波器的基本原理和性能,与最佳滤波器相比,条件匹配滤波器既不需要多个数据样本用于形成协方差矩阵,也不需要求逆运算来得到权系数矢量.仿真和实测数据验证了条件匹配滤波器用于抑制寻呼信号干扰的可行性.     

微型计算机实时控制系统的抗干扰问题

微机实时控制系统能得以广泛应用的关键是采取行之有效的抗干扰措施。本文主要论述了在微机实时控制系统中干扰源的产生机理和干扰的传播途径.同时,介绍了一些行之有效的干扰抑制方法.     

超临界汽轮机再热主汽阀门卡涩分析

汽轮机再热主汽阀是汽轮机组的重要辅机,在动态性能、密封性、可靠性方面都有特殊要求。该类汽轮机再热主汽阀是汽轮机组的重要辅机,在动态性能、密封性、可靠性方面都有特殊要求。该类型阀门机构在冷起动过程中经常发生卡涩,且随蒸汽参数升高,出现故障的概率增大且更加严重,严重影响机组的正常运行。针对机构故障现象与结构特点,对动态行为异常变动进行分析,研究表明冷起动过程中,不同零件物理性能差异导致零件间热量传递速度存在较大差异,引起动静配合要素位置和形状变化,并进一步导致径向间隙和轴向间隙变动,严重影响机构的动力学性能。有限元法用来定量分析机构在冷起动至稳态过程中动态配合要素之间的间隙变化,并分析间隙对阀门机构的动态行为影响,数值分析的结果与电厂中出现的问题是一致的,其实际处理方案则验证该方法的正确性。从改进公差设计和制造精度控制两个方面提出解决该类阀门卡涩的具体方案,对于解决该类工程问题具有重要理论价值和现实指导意义。     

Theoretical analysis and seismic investigation for TBM jamming in squeezing fissile slate

The S tunnel is a 4.2 km-long headrace tunnel. In the tunnelling project, the ground was assumed to be hard slate and suitable for TBM excavation based on the primary site investigation. However, TBM jamming frequently occurred with the increase of the tunnel cover, and the TBM excavation was cancelled. In order to investigate the TBM jamming, theoretical analyses and seismic investigations were conducted. It was found that analytical model proposed in this paper well explained the influence of the cover on the possibility of TBM jamming. It was also found that the depth of the loosened zone was expanded 6–8 m at the location where TBM jamming occurred.     

液压滑阀卡紧现象的原因及对策

从零件加工、系统工况等方面分析了发生液压滑阀卡死现象的原因,针对不同原因,提出了行之有效的解决方案.