异步电机T形等效电路的数学推导方法

本文研究了一种易于学生理解的异步电机T形等效电路的推导方法。该方法根据异步电机的几个最基本的公式,采用简单的数学运算逐步推导出异步电机T形等效电路．它涉及的公式和推导方法都是最基本的,学生自学即可很容易理解、接受。     

直流电机复合定位控制系统的研究

特性及伯德图分析显示,比例、积分、微分控制器(PID)与压电陶瓷微位移定位系统(PZT)在直流电机定位控制过程中表现出较强的互补性.利用这一互补性,可构建直流电机复合定位控制系统(CPCS).运用Matlab软件对系统进行建模和仿真,动态响应曲线表明,对阶跃及连续参照位移信号,该系统可根据定位位移大小和定位精度要求,进行PID控制与PZT控制之间的自动切换,完成对目标定位物体的动态跟踪,实现快速精确定位,效果优于单一定位控制器.     

铝合金薄壁圆柱壳切削稳定性研究

对于圆柱壳的加工,由工件材料的性能和结构特点,可知其相对刚度较低,加工工艺性差,易变形,在加工中易产生振动。再生型切削颤振是机床切削振动的主要原因。在现有文献的基础上研究了圆柱壳再生型切削颤振系统极限切削宽度随机床主轴转速变化的规律,并通过动态测试实验、模态实验和动态切削力实验,对切削系统的动力学参数进行识别,最终得到了圆柱壳切削系统稳定性极限图,并在传统稳定性的基础上提出严格稳定区的概念。     

Experimental study of interband and intraband crosstalk in WDM networks

The impacts of interband and intraband erosstalk are studied and compared experimentally. Results show that interband crosstalk can be removed with narrow-band filters and has no influence on signal. Intraband crosstalk will result in signal eye diagram close and BER increasing. When the polarization states of signal and crosstalk align, intraband crosstalk seriously decreases signal quality. But when they misalign, it has little influence. Coherent and incoherent crosstalk are studied experimentally. Results show that coherent crosstalk is less harmful to system performance than incoherent crosstalk.     

Cognitive Radio Dynamic Access Techniques

The ever growing demand for wireless services has placed enormous burden on valuable resources such as spectral bandwidth. This has resulted in a major rethinking in resource allocation policies culminating in an explosion of research activity in the field of Cognitive Radio (CR) towards optimum resource usage. In this tutorial paper the physical layer design and transmission techniques for CR in the context of efficient spectrum utilization are discussed. Spectrum sensing as the key element of CR awareness is described. Orthogonal frequency division multiplexing (OFDM) as a spectrally efficient modulation scheme is discussed and the rationale for its use in the CR system is explained. Spectrum pooling for efficient use of spectrum is studied and the role of adaptive OFDM techniques in this method is highlighted. Wavelet basis function as a replacement of Fourier transform in OFDM is evaluated. MIMO system as an added value to the CR performance is described. Adaptive Waveform and beamforming as alternative techniques in CR are reviewed.

机载电子设备间高速数据传输研究

随着航空电子系统架构向综合化、模块化发展,对机舱内电子设备之间数据传输速率的要求也越来越高。这里介绍了LVDS(低电压差分信号)的工作原理及技术特点,提出采用LVDS技术解决机舱内电子设备之间高速数据传输问题的方案,测试结果显示传输距离超过5 m,表明这种方案是可行的。     

声卡音质软件测试系统

论文给出了测定声卡音质的好坏问题的一套解决方案.测试的方法不同于专用的检测仪器的测量,而是采用音频测试软件的方法.文中详细介绍了音频测试软件的设计和软件部分的算法,并用该软件对声卡的音质进行了实际测定.     

石英光纤中受激喇曼散射光谱形成及其能量转换

将泵浦光产生的受激喇曼散射（ Ｓ Ｒ Ｓ） 光谱看作新的独立的单色光源,在光纤内传播的过程中,每个光源按喇曼增益曲线各自独立地激发新的斯托克光谱, 因此 Ｓ Ｒ Ｓ 光谱曲线是光谱内无数个单色光源之间相互吸收相互放大的结果。据此,建立耦合波方程,利用 Ｒｕｎｇｅ － － Ｋｕｔｔａ方法可以计算 Ｓ Ｒ Ｓ 光谱。文中讨论了一阶斯托克光谱的形成,同阶斯托克光谱内的能量红移现象,高阶斯托克光之间以频移４４０ ｃｍ － １ 传递能量以及频带展宽等问题     

A MULTI-RESOLUTION SPECTRUM SENSING （MRSS） SCHEME UNDER MEASUREMENT-BASED CHANNEL MODELS IN COGNITIVE RADIO

Spectrum sensing is one of the key technologies in Cognitive Radios (CRs). Previous works are accomplished under simple channel models, which may lead to unreliable results when it applied to the over-the-air systems. In this paper, we investigate the performance of a Multi-Resolution Spectrum Sensing (MRSS) algorithm under measurement-based channel models in China. MRSS is a wavelet based algorithm which is suitable for non-stationary, wideband signal analysis. Using statistical modeling, measurement-based channel models are presented under typical urban and suburban scenarios in Shanghai, China. Then, the performance of the MRSS algorithm is evaluated under the measurement-based channel models. Simulation results show that, using MRSS, the performance is always better in the scenarios where Line-Of-Sight (LOS) path exist; also, in LOS scenarios, rich scattering effect helps to increase the performance.     

ZigBee同频攻击检测抑制模型研究

针对ZigBee通信中易遭受同频攻击导致数据阻塞和失真问题,该文提出一种同频攻击检测模型。该模型利用信号频谱的高斯分布规律和同频攻击对变换域幅值的影响进行同频攻击检测。在此基础上,通过嵌入空闲频带信道跳变机制和基于可变退避周期及接入概率的自适应退避算法,给出了同频攻击检测抑制方案。实验结果表明,该文模型和方案可以有效抵御同频攻击。