有扰对称信道平均信息量的计算

照相手机让诺基亚抢了风头，这真是亚洲人的失策。在日本和韩国，内置摄像头的手机早就不是什么值得炫耀的东西了。不过日本人的动作还是很快的，GD88和N8一副后来居上的架势，让人不敢小瞧。     

Enhancing cognitive radio systems with robust reasoning

Cognitive radio systems dynamically reconfigure the algorithms and parameters they use, in order to adapt to the changing environment conditions. However, reaching proper reconfiguration decisions presupposes a way of knowing, with high enough assurance, the capabilities of the alternate configurations, especially in terms of achievable transmission capacity and coverage. The present paper addresses this problem, firstly, by specifying a complete process for extracting estimations of the capabilities of candidate configurations, in terms of transmission capacity and coverage, and, secondly, by enhancing these estimations with the employment of a machine learning technique. The technique is based on the use of Bayesian Networks, in conjunction with an effective learning and adaptation strategy, and aims at extracting and exploiting knowledge and experience, in order to reach robust (i.e. stable and reliable) estimations of the configurations' capabilities. Comprehensive results of the proposed method are presented, in order to validate its functionality. Copyright © 2007 John Wiley & Sons, Ltd.     

CDMA干扰对GSM系统的影响及消除方式

本文主要研究CDMA系统对GSM系统的上行干扰,通过实验以及理论计算分析CDMA干扰对GSM系统的影响,并结合天线隔离度分析两系统之间的安全距离.     

普光气田邻井干扰压降研究

根据普光气田现场资料,分析普光气田关井压降恢复时间和稳定生产时间的关系。建立邻井干扰计算模型,评价邻井干扰压降值及邻井干扰,并对邻井干扰规律进行敏感性分析。     

Joint relay selection and power allocation for amplify-and-forward two-path relaying networks

This paper presents a joint relay selection and power allocation scheme for amplify-and-forward two-path relaying networks,in which diferent relay nodes forward information symbols alternatively in adjacent time slots.Our approach is based on the maximization of the received signal-to-noise ratio under total power consumption by the transmission of the symbol.We show that in spite of inter-relay interferences,the maximization problem has a closed-form solution.Simulation results explicitly indicate that the performance of proposed approach outmatches the existing methods including equal power allocation and one-path relaying.     

蓝牙和IEEE802.11无线局域网共存问题探析

使用WiFi(Wireless Fidelity)IEEE 802.11b/g协议的无线局域网(WLAN)技术已经成为PC和笔记本电脑的标准而正在快速扩散到PDA(Personal Digital Assistant)和其它便携式设备。与此同时,蓝牙作为耳机,麦克风连到各种个样的无线设备的串口线的替代品已经越来越普遍。这两种无线协议都工作于2.40至2.48GHzISM(工业,科学和医疗)射频带。WiFi使用12个带宽为22MHz重叠的频道其中一个,而蓝在带宽为79MHz范围跳频[3]。因此,无论WiFi正在使用哪个频道两个系统间会存在互相干扰和共存的问题导致数据吞吐量的降低。实现IEEE802.11 WLAN协议的设使用FEC(Foward Error Correction)纠错技术来减轻于其它无线网的干扰。在该文中,我们将对RS(Reed Solomon)编码与BS(Binary Convolutional)编码使用于解决WLAN于BT共存问题的相对有效性进行一个调查并作出结论。     

Compact,ultra-low vibration,closed-cycle helium recycler for uninterrupted operation of MEG with SQUID magnetometers

A closed-cycle helium recycler was developed for continuous uninterrupted operation for magnetometer-based whole-head magnetoencephalography (MEG) systems. The recycler consists of a two stage 4 K pulse-tube cryocooler and is mounted on the roof of a magnetically shielded room (MSR). A flexible liquid helium (LHe) return line on the recycler is inserted into the fill port of the MEG system in the MSR through a slotted opening in the ceiling. The helium vapor is captured through a line that returns the gas to the top of the recycler assembly. A high-purity helium gas cylinder connected to the recycler assembly supplies the gas, which, after it is liquefied, increases the level of LHe in the MEG system during the start-up phase. No storage tank for evaporated helium gas nor a helium gas purifier is used. The recycler is capable of liquefying helium with a rate of ∼17 L/d after precooling the MEG system. It has provided a fully maintenance-free operation under computer control for 7 months without refill of helium. Although the recycler is used for single-orientation operation at this initial testing site, it is designed to operate at ±20° orientations, allowing the MEG system to be tilted for supine and reclining positions. Vibration of the recycler is dampened to an ultra-low level by using several vibration isolation methods, which enables uninterrupted operation during MEG measurements. Recyclers similar to this system may be quite useful even for MEG systems with 100% magnetometers.     

Preparation of Porous Silver Nanowires-Melamine Formaldehyde Hybrid Composite Materials and Their Electromagnetic Shielding and Flame-Retardant Properties

Along with the booming development of communication technology and electronic equipment, higher requirements of flame-retardant and EMI shielding performances for electromagnetic interference (EMI) shielding materials are put forward. Herein, the ultralight and porous silver nanowires (AgNWs)-melamine formaldehyde (MF) hybrid composite with unique micro-/nanostructure is developed by a facile dip-coating method, which uses the AgNWs as 1D conductive coating and MF foam (MF foam) as 3D skeleton template. Benefiting from the unique porous micro-/nanostructure, the resultant hybrid composite displays low density, excellent EMI shielding performances, and superior flame-retardant property. The EMI shielding effectiveness (SE) and specific EMI SE (SSEt) of the hybrid composite in X-band (8.2–12.4 GHz) can be up to 77 dB and 26971.4 dB cm⁻² g⁻¹, respectively. At the same time, the hybrid composite also passes the vertical burning test and shows an increased LOI value of 40.6%. The combination of flame-retardant and EMI shielding performances for EMI shielding materials makes the AgNWs-MF hybrid composite great application potential in civil and military fields. This work provides a new guide for the design of multifunctional high-performance EMI shielding materials.     

常规火焰原子吸收光谱法测定水中的痕量砷

利用砷、镉在 2 2 8.8nm波长处重叠谱线的光谱干扰效应 ,研究了砷、镉共存体系的干扰特点 ,采用均匀设计 ,数学方法和计算机技术进行数据处理 ,实现了用常规火焰原子吸收光谱法同时测定痕量砷和镉 ,其中测定砷的灵敏度可达 10ng/ml,利用该方法分析了水中的痕量砷 ,其结果令人满意。