无线传感器网络体系结构和关键技术研究

文章介绍了无线传感器网络的体系结构,提出了一种基于跨层设计的管理控制机制;在对无线传感器网络的关键技术,如媒体接入控制(MAC)技术和无线路由协议,分别进行阐述和比较的基础上,提出了一种把简单的IEEE 802 MAC协议应用于无线传感器网络的思想;为了提高系统容量,提出了多信道策略,可以用来有效减少系统碰撞阻塞率,减少接入时延;认为虽然无线传感器网络的应用前景非常广阔,但是仍存在很多问题,除了要尽量减少功耗外,必须提高系统容量,减少碰撞阻塞率,以加快无线传感器网络实用化的进程.     

Regulating the Water Molecular in the Solvation Structure for Stable Zinc Metal Batteries

Rechargeable aqueous zinc batteries are promising energy storage devices because of their low cost, high safety, and high energy density. However, their performance is plagued by the unsatisfied cyclability due to the dendrite growth and hydrogen evolution reaction (HER) at the Zn anode. Herein, it is demonstrated that the concentrated hybrid aqueous/non-aqueous ZnCl₂ electrolytes constitute a peculiar chemical environment for not only the Zn-ions but also water molecules. The high concentration of chloride ions substitutes the H₂O molecular in the solvation structure of Zn²⁺, while the acetonitrile further interacts with H₂O to decrease its activity. The hybrid electrolytes both inhibit the dendrite formation and HER, enabling an ultrahigh average Coulombic efficiency of 99.9% in the Zn||Cu half-cell and a highly reversible Zn plating/stripping with a low overpotential of 21 mV. Using this hybrid electrolyte, the Zn||polytriphenylamine (PTPAn) full cell deliveres a high discharge capacity of 110 mAh g⁻¹, a high power density of 9200 W kg⁻¹ at 100 °C and maintains 85% of the capacity for over 6000 cycles at 10 °C. This study provides a deep understanding between the solvation structure and columbic efficiency of Zn anode, thus inspiring the development for stable Zn batteries.     

A Review of FPGA-Based Custom Computing Architecture for Convolutional Neural Network Inference

Convolutional neural network (CNN) has been widely adopted in many tasks. Its inference process is usually applied on edge devices where the computing resources and power consumption are limited. At present, the performance of general processors cannot meet the requirement for CNN models with high computation complexity and large number of pa-rameters. Field-programmable gate array (FPGA)-based custom computing architecture is a promising solution to further enhance the CNN inference performance. The software/hardware co-design can effectively reduce the computing overhead, and improve the inference performance while ensuring accuracy. In this paper, the mainstream methods of CNN structure design, hardware-oriented model compression and FPGA-based custom architecture design are summarized, and the improvement of CNN inference performance is demonstrated through an example. Challenges and possible research directions in the future are concluded to foster research efforts in this domain.     

LTE系统中软件跟踪调试技术的研究与实现

论述了在LTE系统中基于ARM11内核的嵌入式跟踪调试技术.为了满足LTE系统中高速数据业务的需求,方便产品开发期间ARM子系统的运行流程控制和异常情况的定位分析,提出了一种可靠性高、性能强的实时跟踪调试技术方案.该方案的难点在于跟踪信息片内缓存的管理和嵌入式操作系统中高低优先级任务切换时跟踪信息的缓存处理方法,保证LTE系统的高速率运行和跟踪信息的时序性.     

室内多载波CDMA系统在深度衰落环境下的能量受控均衡策略

多载波CDMA(MC-CDMA)是将多载波调制OFDM与DS-CDMA结合起来的多址访问技术。如何从接收到的信号恢复出发送信号，涉及到频率分集接收和均衡。本文提出的能量受控均衡技术，在多用户的环境下能较好地恢复扩频码的正交性且避免信道深度衰落的影响，而且，实验表明该方法对于不同的信道状况均能很好适应。     

防空兵指挥控制网络可视化问题研究

文中在传统防空作战防空兵指挥控制网络的基础上,运用WS小世界网络模型理论构建了网络化防空作战防空兵指挥控制模型。使用Matlab语言对模型进行了仿真,并且使用了稀疏矩阵的方法,解决了大型网络仿真分析消耗内存巨大、难以进行仿真的问题。对网络化防空作战的组织和实施有一定的参考价值。     

单路反馈射频功放预失真线性化方法

该文基于记忆多项式模型,提出一种采用单路反馈的射频功放预失真线性化新方法,只需用正交解调后的IQ信号中的一路,就可完成对预失真器模型参数的获取。该方法可消除使用正交解调器所带来的增益和相位不平衡问题,且节省了一路反馈采样电路,在降低成本、简化设计的同时还能提高预失真线性化的性能。仿真和物理实验结果表明,该文提出的方法是正确的,能达到比较好的线性化效果。     

纳秒激光加工石英微通道的实验与理论研究

利用调Q Nd…YAG激光器输出的1064nm纳秒脉冲激光聚焦在石英上,分别采用激光热加工法和激光诱导等离子体法加工微通道。热加工的通道长度可控,通道周围产生热裂纹;诱导等离子体加工的微通道内壁光滑,通道深度可达4mm。研究了激光热加工微通道时的温度场和热应力分布,分析了激光诱导等离子体加工微通道的过程。研究表明,激光热加工时温度场的存在导致热应力的产生,热应力超过石英断裂阈值使石英发生炸裂,导致微通道的形成及热裂纹的产生;激光诱导等离子体法由于等离子体屏蔽效应产生的高温等离子体烧蚀石英形成微通道,避免了热裂纹的产生。     

A MAC-Layer QoS Provisioning Protocol for Cognitive Radio Networks

Due to the proliferation of diverse network devices with multimedia capabilities, there is an increasing need for Quality of Service (QoS) provisioning in wireless networks. The MAC layer protocol with enhanced distributed channel access (EDCA) in the IEEE 802.11-2007 is able to provide differentiated QoS for different traffic types in wireless networks through varying the Arbitration Inter-Frame Spaces (AIFS) and contention window sizes. However, the performance of high priority traffic can be seriously degraded in the presence of strong noise over the wireless channels. Schemes utilizing adaptive modulation and coding (AMC) technique have also been proposed for the provisioning of QoS. They can provide limited protection in the presence of noise but are ineffective in a high noise scenario. Although multiple non-overlapped channels exist in the 2.4 and 5?GHz spectrum, most IEEE 802.11-based multi-hop ad hoc networks today use only a single channel at anytime. As a result, these networks cannot fully exploit the aggregate bandwidth available in the radio spectrum provisioned by the standards. By identifying vacant channels through the use of cognitive radios technique, the noise problem can be mitigated by distributing network traffic across multiple vacant channels to reduce the node density per transmission channel. In this paper, we propose the MAC-Layer QoS Provisioning Protocol (MQPP) for 802.11-based cognitive radio networks (CRNs) which combines adaptive modulation and coding with dynamic spectrum access. Simulation results demonstrate that MQPP can achieve better performance in terms of lower delay and higher throughput.     

存在参数微扰的非自治超混沌系统的同步

本文对四维非自治的超混沌光学模型的同步问题进行了讨论。结合误差反馈同步方法和参数自适应同步方法,使参数不同的两个系统达到同步,数值计算结果也表明同步效果很好。同时对控制函数的参数与同步建立的时间两者之间的关系进行了仿真,结果表明,存在最佳参数使得同步建立的时间最短。