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111.
跳频技术具有较强的抗干扰、抗噪声,抗频率选择性衰减的能力和较低的误码率。通过建立跳频通信的仿真模型,实现跳频通信在噪声干扰下的性能分析,用Matlab/Simulink选取不同仿真参数来仿真,对比得出比较好的最佳仿真效果。通过分析跳频通信技术难点,给出相应的最佳方案。 相似文献
112.
In this paper, Zr, Cr and V were selected as the partial substitution elements for Ti to form Mg35Ti5M5Ni55 quaternary alloys prepared by means of mechanical alloying on the basis of the ternary Mg35Ti10Ni55 electrode alloy previously studied by the authors. It is found that all the three quaternary alloys possess an amorphous main phase and exhibit improved cycling stability than the original ternary Mg35Ti10Ni55. The Zr-substituted alloy has also a higher discharge capacity. X-ray photoelectron spectroscopy (XPS) surface analysis reveals that on the surface of each alloy a multi-component oxide composite film is formed, which is more compact and corrosion resistant than the Mg(OH)2 film and the (TiO2)x(NiO)y(Mg(OH)2)z composite films reported previously. Auger electron spectroscopy (AES) analysis shows that the substituting elements tend to reduce the thickness of the passivation films. The thickness of composite oxide film on the alloys is in the following order: Mg35Ti10Ni55>Mg35Ti5V5Ni55>Mg35Ti5Zr5Ni55>Mg35Ti5Cr5Ni55. The result agrees well with that of the polarization resistances (RP) values obtained from the electrochemical impedance spectroscopy (EIS) Nyquist diagrams. It demonstrates that the thicker the passivation film is, the higher the RP is and the more difficultly the charge transfer reaction proceeds. Anodic polarization curves indicate that the addition of Cr and Zr decreases effectively the corrosion current. However, the corrosion of the electrode alloys in the electrolyte is still high and proceeds constantly as the corrosion current remains almost constant during further cycles. 相似文献
113.
Xishu Wang Lina Zhang Yanping Zeng Xishan Xie 《北京科技大学学报(英文版)》2006,13(3):244-249
The low-cycle fatigue behavior of powder metallurgy Rene95 alloy containing surface inclusions was investigated by in-situ observation with scanning electron microscopy (SEM). The process of fatigue crack initiation and early stage of propagation behavior indicates that fatigue crack mainly occurs at the interface between the inclusion and the matrix. The effect of inclusion on the fatigue crack initiation and the early stage of crack growth was very obvious. The fatigue crack growth path in the matrix is similar to the shape of inclusion made on the basis of fatigue fracture image analysis. The empiric relation between the surface and inside crack growth length, near a surface inclusion, can be expressed. Therefore, the fatigue crack growth rate or life of P/M Rene95 alloy including the inclusions can be evaluated on the basis of the measurable surface crack length parameter. In addition, the effect of two inclusions on the fatigue crack initiation behavior was investigated by the in-situ observation with SEM. 相似文献
114.
鉴于通信系统是实现配电自动化系统的重要组成部分,采用一种新型的网络设备成功组建配网通信模式算是我们在这方面的一次大胆探索。目前比较先进的配电主干通信网多采用光纤加光纤收发器或光端机构成的光纤环网,在此采用一种由工业以太网设备服务器或交换机(EtherDeviceServer,简称EDS)代替光纤收发器或光端机的新型通信方案。从多层次对它们进行了比较,并对这种新型通信方式的特点、先进性及可推广性做了重点说明。嵌入该新型通信方式的配电自动化系统产品已投入现场运行。实践证明,其性能优越,技术先进,值得推广。 相似文献
115.
116.
实现了一个基于高斯混合模型(GMM)的说话人辨识系统。GMM是用多个高斯分布的概率密度函数的组合来描述特征矢量在概率空间的分布状况,不同的说话人对应了不同的GMM。模型的训练采取了极大似然估计(ML)的EM方法。并在不同的数据集上实验,得到了好的结果。 相似文献
117.
118.
ChunmingWang XingfangWu JieLiu Ning'anXu 《北京科技大学学报(英文版)》2005,12(1):43-47
The free structure of M/A islands in pipeline steel X70 has been studied by transmission electron microscope (TEM). It is shown that the M/A islands are about 1-2 μm in size and distribute at the grain boundary of irregular massive ferrite or acicular ferrite in the microstructure of the steel undergoing TMCP (thermo-mechanical controlled processing). The analysis of diffraction contrast shows that the M/A islands consist of retained austenite and some martensite lamellae different in size and orientation. The microtwinning and midrib exist in the lamella of lenticular martensite, which exhibit the typical character of high-carbon martensite. The influences of TMCP parameters on M/A islands have been studied carefully. With the increase of the cooling speed, the amount of M/A islands decrease slightly and the morphology of M/A islands changes to thin dispersive short bars from thick irregular long strips. 相似文献
119.
Jeong-Ha You 《Journal of Nuclear Materials》2005,336(1):97-109
Fibrous metal matrix composites possess advanced mechanical properties compared to conventional alloys. It is expected that the application of these composites to a divertor component will enhance the structural reliability. A possible design concept would be a system consisting of tungsten armour, copper composite interlayer and copper heat sink where the composite interlayer is locally inserted into the highly stressed domain near the bond interface. For assessment of the design feasibility of the composite divertor concept, a non-linear multi-scale finite element analysis was performed. To this end, a micro-mechanics algorithm was implemented into a finite element code. A reactor-relevant heat flux load was assumed. Focus was placed on the evolution of stress state, plastic deformation and ductile damage on both macro- and microscopic scales. The structural response of the component and the micro-scale stress evolution of the composite laminate were investigated. 相似文献
120.
转速信号是发动机测功系统十分重要的物理量,其检测方法与电路设计直接关系到测功系统的性能和测试控制精度。在详细分析M法、T法和M/T法等测速方法的基础上,本文设计了M/T法测速的硬件电路和自动量程切换的软件实现方法,利用磁电式转速传感器实现了发动机测功系统转速的高精度测量。测速系统实际运行表明,本文设计的非接触式转速测量系统结构简单、抗干扰能力强适用于交、直流全数字化调速系统的数字测速装置的工程设计实践中。 相似文献