SAGE信道估计算法在部分相关STTC-MIMO系统中的应用

利用天线空间相关函数和方向特性将完全不相关的信道衰落矩阵映射为更符合实际的部分相关MIMO(multiple input multiple output)信道衰落矩阵,结合STTC(space-time trellis code)空时编码方式建立部分相关的STTC-MIMO系统,并将基于SAGE(space-alternating generalized expectation-maximization)的信道估计算法应用在这一系统中.结果显示,和ML(most-likelihood)估计相比,部分相关信道中使用SAGE估计算法可以使系统信噪比提高约1 dB.此外,空时编码(space-time codes)的纠错性能对MIMO系统的信噪比也有极大的影响.     

呼延调蓄工程进水线路结构设计

叙述了呼延调蓄工程的进水线路、输水箱涵结构、进水闸结构、进水线路跌水等的设计思路,指出该线路设计合理,结构设计可靠,其效果达到了设计要求,具有一定的实用价值。     

MATLAB环境下的数字图像处理实验入门

简述了数字图像处理、MATLAB软件及两者之间的关系，针对数字图像处理技术的特点及MATLAB语言的应用环境，选择二雏离散傅里叶变换线性性质的MATLAB实现和直方图均衡化的MATLAB实现作为数字图像处理课程的入门实验，实现了数字图像处理与MATLAB之间的有机结合。     

TVD scheme for computing open channel wave flows

For the shallow water equations in the first approximation (Saint-Venant equations), a TVD scheme is developed for shock-capturing computations of open channel flows with discontinuous waves. The scheme is based on a special nondivergence approximation of the total momentum equation that does not involve integrals related to the cross-section pressure force and the channel wall reaction. In standard divergence difference schemes, most of the CPU time is spent on the computation of these integrals. Test computations demonstrate that the discontinuity relations reproduced by the scheme are accurate enough for actual discontinuous wave propagation to be numerically simulated. All the qualitatively distinct solutions for a dam collapsing in a trapezoidal channel with a contraction in the tailwater area are constructed as an example.     

Numerical study of magnetohydrodynamic laminar flow separation in a channel with smooth expansion

The flow of an electrically conducting incompressible viscous fluid in a plane channel with smooth expansion in the presence of a uniform transverse magnetic field has been analysed. A solution technique for the governing magnetohydrodynamic equations in primitive variable formulation has been developed. A co‐ordinate transformation has been employed to map the infinite irregular domain into a finite regular computational domain. The governing equations are discretized using finite‐difference approximations in staggered grid. Pressure Poisson equation and pressure correction formulae are derived and solved numerically. It is found that with increase in the magnetic field, the size of the flow separation zone diminishes and for sufficiently large magnetic field, the separation zone disappears completely. The peak u‐velocity decreases with increase in the magnetic field. It is also found that the asymmetric flow in a symmetric geometry, which occurs at moderate Reynolds numbers, becomes symmetric with sufficient increase in the transverse magnetic field. Thus, a transverse magnetic field of suitable strength has a stabilizing effect in controlling flow separation, as also in delaying the transition to turbulence. Copyright © 2008 John Wiley & Sons, Ltd.     

检察院业务、办公计算机网络管理信息系统

介绍了检察院各部门工作的特点和工作流程.阐述了检察院工作管理和信息处理自动化的必要性,并且较详细的给出了系统的设计方案.     

PC IEEE—488接口与存贮示波器构成的智能测试系统

本文介绍IBMPC微型计算机通过符合IEEE-488标准的GPIB总线接口,与数字存贮示波器构成的测试及数据处理系统。重点叙述I-7210-C接口板和接口技术及常用指令,并通过具体的信号频率谱分析应用,说明实现数据采集及数据处理的方法。     

双连杆柔性机械臂的变结构轨迹控制

针对双连杆具有柔性前臂的机器人建立了非线性动力学模型，柔性臂所在的动坐标系采用相对坐标系，即悬臂梁坐标系，使得关节的实际转动角度与动坐标系的转动角一致，利于控制方案的实施。基于输入输出线性化，提出了一种关节轨迹变结构跟踪控制方案，该方案考虑了柔性臂弹性变形的稳定性和对参数的变化的鲁棒性。     

Multi-Class Cost-Constrained Random Coding for Correlated Sources over the Multiple-Access Channel

This paper studies a generalized version of multi-class cost-constrained random-coding ensemble with multiple auxiliary costs for the transmission of N correlated sources over an N-user multiple-access channel. For each user, the set of messages is partitioned into classes and codebooks are generated according to a distribution depending on the class index of the source message and under the constraint that the codewords satisfy a set of cost functions. Proper choices of the cost functions recover different coding schemes including message-dependent and message-independent versions of independent and identically distributed, independent conditionally distributed, constant-composition and conditional constant composition ensembles. The transmissibility region of the scheme is related to the Cover-El Gamal-Salehi region. A related family of correlated-source Gallager source exponent functions is also studied. The achievable exponents are compared for correlated and independent sources, both numerically and analytically.     

Secure Polar Coding for the Primitive Relay Wiretap Channel

With the emergence of wireless networks, cooperation for secrecy is recognized as an attractive way to establish secure communications. Departing from cryptographic techniques, secrecy can be provided by exploiting the wireless channel characteristics; that is, some error-correcting codes besides reliability have been shown to achieve information-theoretic security. In this paper, we propose a polar-coding-based technique for the primitive relay wiretap channel and show that this technique is suitable to provide information-theoretic security. Specifically, we integrate at the relay an additional functionality, which allows it to smartly decide whether it will cooperate or not based on the decoding detector result. In the case of cooperation, the relay operates in a decode-and-forward mode and assists the communication by transmitting a complementary message to the destination in order to correctly decode the initial source’s message. Otherwise, the communication is completed with direct transmission from source to the destination. Finally, we first prove that the proposed encoding scheme achieves weak secrecy, then, in order to overcome the obstacle of misaligned bits, we implement a double-chaining construction, which achieves strong secrecy.