基于无线传感器网络的智能灌溉系统研究

针对我国水资源紧缺以及农田节水灌溉的需求,根据现有的农田灌溉装备条件,应用领域作物、土壤、水源布点等情况,分析了目前实现精确农业亟待解决的关键技术问题,提出一套采用无线传感器网络技术、适合大面积农田智能灌溉控制方法。分析结果表明,该系统通过无线传感技术完成智能化灌溉,可很好地实现节水。且该系统工作稳定,具有一定的推广应用价值。     

PZT压电薄膜无阀微泵的制备工艺及实验研究

介绍了一种基于PZT薄膜的无阀压电微泵。该微泵利用聚二甲基硅氧烷(PDMS)作为泵膜,自制的压电圆型薄膜片作为驱动部件,采用收缩管/扩张管结构,压电圆型致动片和PDMS泵膜的组合可产生较大的泵腔体积改变。在对微泵制备工艺研究的基础上,对其性能进行了实验研究,结果表明:电压和频率对流速均有显著影响。在7.5 V1、80 Hz的正弦电压驱动下,该压电微泵的最大输出流速为2.05μL/min。该文制作的微泵具有流量稳定,驱动电压较低,性能稳定可靠和易控制等优点,可满足微流体系统的使用要求。     

花状ZnO纳米棒的合成及丙酮敏感特性的研究

利用水热法合成花状的ZnO纳米棒,并对其进行X射线衍射（X-ray diffraction, XRD)与扫描电子显微镜（scanning electron microscope, SEM) 表征.以该ZnO为敏感材料制成了旁热式结构气体传感器,测试了样品在不同温度下对丙酮气体的灵敏度.结果表明样品在290℃下对于丙酮气体具有高的灵敏度、快的响应恢复速度等特点.测试了传感器对于常见干扰气体的灵敏度,表明器件具有良好的选择性.     

1.5 V Sub‐mW CMOS Interface Circuit for Capacitive Sensor Applications in Ubiquitous Sensor Networks

In this paper, a low‐power CMOS interface circuit is designed and demonstrated for capacitive sensor applications, which is implemented using a standard 0.35‐μm CMOS logic technology. To achieve low‐power performance, the low‐voltage capacitance‐to‐pulse‐width converter based on a self‐reset operation at a supply voltage of 1.5 V is designed and incorporated into a new interface circuit. Moreover, the external pulse signal for the reset operation is made unnecessary by the employment of the self‐reset operation. At a low supply voltage of 1.5 V, the new circuit requires a total power consumption of 0.47 mW with ultra‐low power dissipation of 157 μW of the interface‐circuit core. These results demonstrate that the new interface circuit with self‐reset operation successfully reduces power consumption. In addition, a prototype wireless sensor‐module with the proposed circuit is successfully implemented for practical applications. Consequently, the new CMOS interface circuit can be used for the sensor applications in ubiquitous sensor networks, where low‐power performance is essential.     

基于无线传感器网络的农业环境监测系统

针对当前农业环境在线监测的需要,提出了一种利用具有自组织特性的无线传感器网络(wireless sensor networks,WSN)对温度、土地湿度和土壤的PH值等环境变量进行在线监测的方法.该方法采用了对等式网络体系结构、低功耗微小网络节点、基于拓扑树的网络初始化配置算法.实验测试表明节点能够有效地采集和处理数据,并可以在节点间成功地进行通信.     

热激励谐振型压力传感器激励电压的影响与分析

针对热激励谐振型压力传感器在不同激励电压下会产生不同的热梯度场,进而影响传感器的谐振频率这一现象,采用开环测试系统进行试验,得到热激励谐振型压力传感器的热激励幅度与谐振频率的变化规律;并对实验结果进行了进一步的分析,为合理优化设计传感器的相关参数提供了一定的理论依据.     

Ka波段Si基微机械宽带垂直过渡

介绍了一种适用于三维毫米波集成电路的Si基微机械垂直过渡,该垂直过渡是两层0.1mm厚的共面波导传输线通过0.3mm厚中间层,在中间层采用了同轴结构,该同轴结构通过金属化通孔来实现。这一设计原理简单,结构简洁,便于优化设计,具有很宽的带宽和平坦的幅度响应。运用三维电磁场仿真软件对该垂直过渡结构进行了建模,并作了优化设计与仿真计算,运用微机械金属化通孔工艺和多层键合工艺研制了样品。在片测试结果表明该样品性能良好,在26.5～34.0GHz该过渡插入损耗小于3.5dB,带内起伏小于2dB。     

Demonstration of a 4-Sensor Folded Sangac Sensor Array with Active Phase Biasing Scheme

A 4-sensor folded Sagnac sensor array with an active phase biasing scheme is presented. The overlapping of the signal and noise pulse is avoided through a time division multiplexing scheme and the noise pulses is eliminated almost completely. The scheme can address 16 sensors when the repeat frequency of input pulse is at 68.3 kHz. The alternative phase bias technique is demonstrated, which can provide sensors with stable phase bias. The future benefit of this technique is that the 1/f noise in the circuit can be suppressed.     

一种机载天文导航星图模拟的实现方法

星图模拟是研究机载天文导航的关键技术之一.通过分析近些年国内外天文导航技术研究方面的资料,结合机载条件下的实际运行环境、天文导航基本原理和成像的主要影响因素,改进了CCD星敏感器的光轴指向、视场范围和观测星的确定方法,对星体成像位置和灰度的确定方法及背景光和曝光时间对成像效果的影响进行了优化,并建立了相应的模型.最后运用Matlab编程生成了所需星图,为进一步研究机载天文导航技术打下了基础.     

Performance evaluation of an IEEE 802.15.4 sensor network with a star topology

One class of applications envisaged for the IEEE 802.15.4 LR-WPAN (low data rate—wireless personal area network) standard is wireless sensor networks for monitoring and control applications. In this paper we provide an analytical performance model for a network in which the sensors are at the tips of a star topology, and the sensors need to transmit their measurements to the hub node so that certain objectives for packet delay and packet discard are met. We first carry out a saturation throughput analysis of the system; i.e., it is assumed that each sensor has an infinite backlog of packets and the throughput of the system is sought. After a careful analysis of the CSMA/CA MAC that is employed in the standard, and after making a certain decoupling approximation, we identify an embedded Markov renewal process, whose analysis yields a fixed point equation, from whose solution the saturation throughput can be calculated. We validate our model against ns2 simulations (using an IEEE 802.15.4 module developed by Zheng [14]). We find that with the default back-off parameters the saturation throughput decreases sharply with increasing number of nodes. We use our analytical model to study the problem and we propose alternative back-off parameters that prevent the drop in throughput. We then show how the saturation analysis can be used to obtain an analytical model for the finite arrival rate case. This finite load model captures very well the qualitative behavior of the system, and also provides a good approximation to the packet discard probability, and the throughput. For the default parameters, the finite load throughput is found to first increase and then decrease with increasing load. We find that for typical performance objectives (mean delay and packet discard) the packet discard probability would constrain the system capacity. Finally, we show how to derive a node lifetime analysis using various rates and probabilities obtained from our performance analysis model.