Excitation of piezoelectric device through resonant helical coil antenna-like structure

A resonant helical coil antenna-like structure has been explored for wireless excitation of piezoelectric devices. The basic idea behind this wireless excitation of piezoelectric device is electromagnetic resonance along with piezoelectric resonance. The analytical studies reveal that the maximum excitation occurs in the piezoelectric device when the operating frequency of the system coincides with its mechanical resonant frequency. It has been seen that the intensity of piezoelectric stimulation depends on the frequency of operation, air gap, relative position, electric load, and the generated electric field strength by the helical coil antenna-like structure. The analytical results are verified with the measured experimental results, and are found to be in well agreement. By adopting this proposed wireless excitation system the free actuation of the piezoelectric devices can be enabled as opposed to the confined motion for various potential applications.     

改进21FS彩管会聚品位

本文运用6Sigma工具定量分析了由于21FS彩管QPF电子枪的受聚焦电压影响SP光点位置相对移动,从而导致产品在用户处静会聚一致性差的重要原因。并通过设计优化电子枪偏孔设计特点,从理论和试验实践上解决了聚焦电压对21”静会聚的影响。     

基于空频相关性的大规模MIMO-OFDM信道压缩反馈算法

大规模MIMO-OFDM系统中,信道常常存在较强的空间和频域相关性。针对多数信道压缩反馈算法仅考虑空间或频域相关性的问题,该文提出一种空频联合压缩反馈算法。首先,根据压缩感知理论进行了信道空频2维稀疏度分析;然后,推导了信道矩阵在空间和频域2维相关性下的联合稀疏基;最后,利用该联合稀疏基给出了空频联合压缩算法。仿真结果与分析表明,该算法在保证信道反馈精度的同时,可显著降低反馈量。     

Location and calculation-free node-scheduling schemes in large wireless sensor networks

In wireless sensor networks that consist of a large number of low-power, short-lived, unreliable sensors, one of the main design challenges is to obtain long system lifetime without sacrificing system original performance (sensing coverage and sensing reliability). To solve this problem, one of the potential approaches is to identify redundant nodes at the sensing interface and then assign them an off-duty operation mode that has lower energy consumption than the normal on-duty mode. In our previous work [J. Wireless Commun. Mobile Comput. 3 (2003) 271; Processing of ACM Wireless Sensor Network and Application Workshop 2002, September 2002], we proposed a node-scheduling scheme, which can provide a 100% sensing coverage preservation capability. This, however, requires each node to be aware of its own and its neighbors’ location information. Also, in that scheme, each node has to do accurate geometrical calculation to determine whether to take an off-duty status. In this paper, we propose and study several alternative node-scheduling schemes, which cannot completely preserve the original system coverage, but are nonetheless light-weighted and flexible compared with the previous one. Our simulation results compare these schemes with the previous one and demonstrate their effectiveness.     

Providing incentives in providerless networks

This paper explores the extension of a model for the operation of an ad hoc mobile network to more general providerless networks, such as peer-to-peer systems. The model incorporates incentives for users to act as transit nodes on multi-hop paths and to be rewarded with their own ability to send traffic. The paper explores some of the trust questions that arise in this problem space and conjectures that the very structure of a peer organisation may have some hidden benefits for trust re-enforcement, that have not been previously explored (to our knowledge).     

一种抗频偏的时间精同步方法及性能分析

该文导出了互相关时间精同步的性能随频率偏移和信噪比变化的表达式,并提出一种受频偏影响较小的精同步方法。该文对同步性能表达式进行分析,得到在某一频偏下同步序列长度的上限值。新方法将同步序列分段,每段和接收信号分别作互相关,将各段的相关值延时相加作为同步的度量。通过仿真将新方法和其它时间同步方法进行了对比。仿真结果表明,新方法可以大大提高系统抗频偏的能力。     

Cross‐Layer Resource Allocation Scheme for WLANs with Multipacket Reception

Tailored for wireless local area networks, the present paper proposes a cross‐layer resource allocation scheme for multiple‐input multiple‐output orthogonal frequency‐division multiplexing systems. Our cross‐layer resource allocation scheme consists of three stages. Firstly, the condition of sharing the subchannel by more than one user is studied. Secondly, the subchannel allocation policy which depends on the data packets’ lengths and the admissible combination of users per subchannel is proposed. Finally, the bits and corresponding power are allocated to users based on a greedy algorithm and the data packets’ lengths. The analysis and simulation results demonstrate that our proposed scheme not only achieves significant improvement in system throughput and average packet delay compared with conventional schemes but also has low computational complexity.     

基于Zigbee技术的顶板离层仪网络研究

针对目前煤矿使用的顶板离层仪类型,以及根据顶板离层的测量原理和实际中工作人员记录顶板离层数据的方式,文章创新性地提出了采用Zigbee技术进行数据的传输;利用分站和每个测量点处的顶板离层仪构成了无线传感网络,通过分站人机交互界面就可对矿井巷道顶板离层的状态进行实时监测,实现了顶板离层监测的自动化和网络化;采用了分段式数字电容传感器,提高了产品整体测量精度,降低了成本。     

A robust adaptive weighted constant modulus algorithm for blind equalization of wireless communications systems under impulsive noise environment

A robust adaptive weighted constant modulus algorithm is proposed for blind equalization of wireless communication systems under impulsive noise environment. The influence of the impulsive noise is analyzed based on numerical analysis method. Then an adaptive weighted constant modulus algorithm is constructed to adaptively suppress impulsive noise. Theoretical analysis is provided to illustrate that the proposed algorithm has a robust equalization performance since the impulsive noise is adaptively suppressed. Moreover, the proposed algorithm has stable and quick convergence due to avoidance of large misadjuntment and adoption of large step size. Simulation results are presented to show the robust equalization performance and the fast convergence speed of the proposed algorithm under both impulsive noise and Gaussian noise environments.