盲恒模多用户检测算法的实现和性能优化

介绍了盲恒模多用户检测算法的实现方法,并针对恒模算法代价函数的特性对该算法进行了优化,在检测之前加入了预白化处理,使接收信号呈现高斯信号的特性,改善了收敛条件。仿真实验表明,与非白化处理的效果相比,预白化处理后的盲算法具有更好的性能,抗远近效应问题效果更明显,收敛速度也明显增加,更适合于实际应用。     

基于PICC编译环境编写PIC单片机程序

Microchip公司生产的PIC系列单片机具有实用、低价、简单易学、低功耗、高速度、体积小、功能强等特点。体现了单片机发展的一种新趋势，而PICC具有许多特殊的性质。并且进行了C语言的扩展，从而可以更轻松地完成编程任务。本文简单介绍了PIC系列单片机在国内的发展情况，以Hi-Tech Software公司的Hi-Tech PICC编译器为例介绍了PICC和标准C的异同及Hi-Tech PICC语言的特点，详细介绍了PICC中的变量、指针、函数以及C与汇编混合编程的一些相关知识。并列举了许多例子以便读者理解。此外还着重介绍了用PICC开发PIC系列单片机时应注意的一些问题。     

土石坝中测斜管接头处预留沉降量的探讨

预留沉降量的确定是土石坝中安装测斜管常见的问题，国内目前尚无定量的技术标准。文章结合小浪底土石坝中测斜管接头处安装预留沉降量的确认过程，提出了具有一定参考意义的量化指标。     

Design of an EEG Preamplifier for Brain-Computer Interface

As a non-invasive neurophysiologieal index for brain-computer interface （BCI）, electroencephalogram （EEG） attracts much attention at present. In order to have a portable BCI, a simple and efficient pre-amplifier is crucial in practice. In this work, a preamplifier based on the characteristics of EEG signals is designed, which consists of a highly symmetrical input stage, low-pass filter, 50 Hz notch filter and a post amplifier. A prototype of this EEG module is fabricated and EEG data are obtained through an actual experiment. The results demonstrate that the EEG preamplifier will be a promising unit for BCI in the future.     

Research on industrial control system intrusion detection method based on simulation modelling

At present,intrusion detection system over fieldbus network layer was a basic protection method in industrial control system.However,it has some weakness,such as poor generality,high false-positive rate,and unable to detect unknown anomaly.An industrial control system intrusion detection method based on fieldbus network equipment simulation was proposed.The method prevented control program from being tampered or destroyed based on controller simulation modelling.Controlled object simulation modelling was designed for ensuring that the system input was credible.Thus the intrusion detection of industrial control network was realized.At last,the results indicate that the proposed intrusion detecting method is available.     

μC/OS-Ⅱ在OMAP5910上的移植

简要分析了μ C/OS-Ⅱ的特点和内核结构,并通过对TI公司推出的DSP芯片OMAP5910体系结构的研究,分别介绍了移植的要点:与处理器相关的代码、与应用相关的代码和系统时钟,着重介绍了在CCS编译器下移植μ C/OS-Ⅱ和ADS编译器下移植μ C/OS-Ⅱ的区别,并且给出了部分移植函数的代码。将μ C/OS-Ⅱ成功移植到TI的OMAP5910的ARM核上,对于充分利用芯片的资源,减少开发周期和提高稳定性等方面有着重要的作用。     

被动调Q固体激光器的稳定性及增益预泵浦技术

研究了造成被动调 Q激光脉冲不稳定的原因 ,针对泵浦功率的起伏和饱和吸收体响应时间的影响 ,进行了深入的分析。提出了采用增益预泵浦方式提高被动调 Q激光器稳定性的方法 ,并就这种激光器进行了分析。结果表明 ,采用增益预泵浦 ,可提高被动调 Q激光器脉冲输出能量和工作效率。     

一种高效的完全值编号算法

值编号是一种重要的静态分析技术,广泛应用于优化编译器和程序验证工具。实际应用中的各种值编号算法在检测等值关系上都存在各种局限性。功能更加强大的能够检测全部 Herbrand 等值关系的完全值编号算法工作效率都十分低下而无法实用。我们发现采用静态单赋值形式能够大幅提高完全值编号算法的性能。本文基于 Herbrand 等值关系给出了静态单赋值形式的程序中值编号的一般定义,建立了值编号和 Herbrand 等值关系的对应关系。基于该定义,判断两个表达式之间的 Herbrand 等值关系等价于判断该两个表达式的值编号是否相同。之后给出了用于计算这种值编号的新的完全值编号算法。我们在 GCC 中实现了该算法并利用别名信息使其能够检测访存语句间的等值关系。基于新算法的部分冗余优化比 GCC 中原有算法消除了更多的动态冗余计算。     

Disruption tolerant networking by Smart Caching

Future mobile radio networks will aim at achieving ‘broadband access for all’, anywhere. The performance of a radio network vitally depends on the characteristics of the transmission path between the user terminal and the access point and the degree of network coverage. In urban areas, full broadband radio coverage is difficult to provide, causing a high variation in the link quality and making broadband services hard to realize. In rural regions, massive deployment costs prevent a full broadband coverage. Most of the time users have to settle for UMTS‐like wide area networks. For mobile users accessing services, such as video streaming, which require continuous broadband connectivity, it virtually results in intermittent network connectivity. The frequent disruption of the broadband link and its replacement with no or only low‐performance connections is a problem that should be addressed. This article introduces a new technique called Smart Caching (SC), which is able to mitigate variations in the network performance so that non‐real‐time and non‐interactive services' quality is substantially improved. SC supports pre‐fetching from a server and buffering data at the edge of the core network, in the so‐called Smart Cache. It transmits data with extremely high speed to be buffered in the mobile terminal when it is in the service range of an access point. This allows for the provisioning of data‐intensive services even in the case of patchy wireless broadband network coverage and intermittent connectivity. The performance of the SC service is evaluated with two different sophisticated queuing models, both based on the Markov arrival process. The benefit of the new technique is discussed and dimensioning issues are outlined. Furthermore, a comparison with legacy network setups is given. Copyright © 2009 John Wiley & Sons, Ltd.     

Symbol error rate calculation and data pre‐distortion for 16‐QAM transmission over nonlinear memoryless satellite channels

This paper presents a simplified mathematical approach to evaluate the performance of any given circular constellation of 16‐level quadrature amplitude modulation (16‐QAM) in terms of symbol error rate (SER). Following this approach, with the aim to work with memoryless nonlinear satellite channels, a model is derived as a generalized form for both linear and nonlinear channels in the presence of down link additive white Gaussian noise (AWGN). The analysis provides means to calculate the optimal ring ratio (RR) and phase difference (PD) for several possible candidates of 16‐QAM circular constellations. The effects of RR and PD on the SER performance are investigated in the analysis. To overcome the nonlinear distortion, data pre‐distortion is taken into account in the study. The paper gives a general procedure for data pre‐distortion implementation for all circular 16‐QAM constellations. The analytical formulation has been extended for total degradation (TD) performance measure as a function of input back‐off (IBO) of the nonlinear amplifier. A SER performance‐comparison between different constellations for 16‐QAM systems has also been presented in this paper. The analytical results are validated by simulation. Copyright © 2006 John Wiley & Sons, Ltd.