Synchronization of two coupled exciters in a vibrating system of spatial motion

The paper proposes an analytical approach to investigate the synchronization of the two coupled exciters in a vibrating system of spatial motion. Introducing the distur- bance parameters for average angular velocity of two excit- ers, we deduce the non-dimensional coupling equations of angular velocities of two exciters, in which the inertia cou- pling matrix is symmetric and the stiffness coupling matrix is antisymmetric in a non-resonant vibrating system. The analysis of the coupling dynamic characteristic shows that the coupled cosine effect of the phase angles will cause the torque acting on two motors to limit the increase of phase difference between two exciters as well as sustain its sym- metry of two exciters during the running process. It physi- cally explains the peculiarity of self-synchronization of two exciters. The cosine effect of phase angles of the vibrations excited by each exciter will decrease its moment of inertia. The residual moment of inertia of each exciter represents its relative moment of inertia. The stability condition of synchro- nization of two exciters is that the relative non-dimensional moments of inertia of two exciters are all greater than zero and four times their product is greater than the square of their coefficient of coupled cosine effect of phase angles, which is equivalent to that the inertia coupling matrix is positive definite and all its elements are positive. The numeric results show that the structure of the vibrating system can ensure the stability condition of synchronous operation.     

A NEW SYNCHRONIZATION SCHEME USING PERFECT PUNCTURED BINARY SEQUENCE PAIRS IN DS-UWB SYSTEM

Ultra WideBand （UWB） radio is a new wireless technology that transmits extremely short duration radio impulses. In this paper, a new synchronization scheme is proposed in Direct Sequence （DS） UWB system using Perfect Punctured Binary Sequence Pairs （PPBSP） as the preamble. It can acquire both Pseudo- Noise （PN） sequence and frame synchronization at the same time. The properties and the combinatorial admissibility conditions of PPBSP are presented. The simulation results show that PPBSP is good for synchronization by their good cross-correlation properties both under Additive White Gaussian Noise （AWGN） channel and modified Saleh-Valenzuela channel.     

μCos-II在嵌入式通信信号源中的应用

嵌入式通信信号源采用MCU控制DDS芯片的结构,产生FSK、LFM(线性调频)和MSK等多种信号模式。运行实时操作系统μCos-II,将应用程序按功能划分为几个核心任务,由实时内核进行调度,实现了多任务的并行执行,提高了嵌入式系统开发的效率、实时性和可靠性。通过以实时嵌入式操作系统μCos-II为软件平台的嵌入式通信信号源的系统设计,介绍了μCos-II的系统开销、移植和配置、多任务编程以及任务间同步、通信的实现方法。     

Individual bit island reversal and switching field distribution in perpendicular magnetic bit patterned media

The switching of single bit magnetic islands in bit patterned media (BPM) for two cases with 10 times difference in coercivity, as well as the switching field distribution (SFD) of the islands, has been studied using magnetic force microscopy (MFM) measurements. The intrinsic SFD is measured to be ∼9-11% of the remanence coercivity (H_cr), which contributes only ∼20-50% of the total SFD broadening (∼23-41% of H_cr). High resolution MFM observations clearly showed the influence of surrounding islands on the switching behaviour and switching fields of individual bit islands, resulting in significant contributions in SFD broadening due to non-intrinsic dipolar interactions. It was further observed that single magnetic islands could be switched within a very narrow switching field range as small as 4 Oe, which indicates very sharp and uniform switching for each individual island of BPM.     

R-D optimized tree-structured compression algorithms with discrete directional wavelet transform

A new image coding method based on discrete directional wavelet transform (S-WT) and quad-tree decomposition is proposed here. The S-WT is a kind of transform proposed in [V. Velisavljevic, B. Beferull-Lozano, M. Vetterli, P.L. Dragotti, Directionlets: anisotropic multidirectional representation with separable filtering, IEEE Trans. Image Process. 15(7) (2006)], which is based on lattice theory, and with the difference with the standard wavelet transform is that the former allows more transform directions. Because the directional property in a small region is more regular than in a big block generally, in order to sufficiently make use of the multidirectionality and directional vanishing moment (DVM) of S-WT, the input image is divided into many small regions by means of the popular quad-tree segmentation, and the splitting criterion is on the rate-distortion sense. After the optimal quad-tree is obtained, by means of the embedded property of SPECK, a resource bit allocation algorithm is fast implemented utilizing the model proposed in [M. Rajpoot, Model based optimal bit allocation, in: IEEE Data Compression Conference, 2004, Proceedings, DCC 2004.19]. Experiment results indicate that our algorithms perform better compared to some state-of-the-art image coders.     

Reducing Host Interference from Spread Spectrum Watermarking

Spread spectrum watermarking (SSW) is one of the most promising watermarking techniques. While SSW is very robust against additive noise, it suffers from an inherent noise. The noise results from host interference on detection of the embedded hidden information. The host interference is one of the main reasons for the relatively low embedding rate in SSW and its reduction is important. In this paper, a new method for use in an SSW detector is proposed to reduce the host interference. The proposed method is based on the law of large numbers and symbol detection of embedded information, instead of bit detection. Since the method is based on the detection of symbols longer than one bit, the detector can employ PN sequences with a larger length, resulting in decrease of the interference. The symbol error rate using this algorithm is calculated employing the maximum a posteriori criterion. Comparison of bit error rates between the modified SSW algorithm and conventional bit detection shows that the modified algorithm is much more robust against the host interference.     

Partial synchronization in linearly and symmetrically coupled ordinary differential systems

In this paper, we discuss partial synchronization of linearly and symmetrically coupled ordinary differential equations (LSCODEs). The synchronization phenomena are investigated via invariant synchronization manifolds. On the basis of geometrical analysis of the synchronization manifold, several criteria for the global attractivity of the invariant synchronization manifold are obtained. Combining these criteria with some numerical examples, we investigate how topological structure affects partial synchronization, and give a valuable discussion about the possibility of partial synchronization with increasing coupling strength.     

多路复用设备的应用

介绍了采用多路复用的形式传送电话计费信息和网管数据信息的必要性及多路复用的方法和特点，介绍了NOKIA的DM2基群复用设备及使用基群复用设备应当注意的问题。     

基于MPEG_2视频码流的错误分析

由于可变字长码（ ＶＬＣ） 在视频信号的高度压缩中会产生负面影响，因此全面分析了视频码流的结构和ＤＣ、ＡＣ 系数码字的单比特错误及可能给图像质量造成的影响， 这对于采取必要的手段来提高图像的质量有着十分重要的意义。     

频率选择性衰落信道GMSK误码性能分析

通过对数字移动信道脉冲响应时延展宽包络 ( PDSP)波形的研究 ,分析了GMSK调制下的脉冲时延展宽包络与误码率之间的变化关系 ,建立了两者之间关系的理论模型和计算机仿真模型 ,同时给出了在四种较为典型的 PDSP作用下 ,GMSK误码率特性的计算机仿真结果。