密集型WSN冲突避免的MAC协议

无线传感器网络媒体接触控制层存在2种冲突。提出基于概率的时隙选择算法,使不同节点在相同时隙发送概率不同,从而降低域内冲突。实验结果显示,该算法的有效能量和损失能量相比Sift协议节省了17.6%和43.9%,能量有效率提高了14.3%。提出染色预防算法,通过提前确定节点活动时序解决域间冲突问题。实验结果显示,该算法的节点平均睡眠时间在87%以上,空闲侦听导致的能量消耗仅占总能量的7%。     

无线传感器网络MAC协议的研究与分析

针对不同的传感器网络应用,研究人员从不同方面提出多个无线传感器网络介质访问控制（MAC）协议,其中包括S-MAC,PMAC,DEANA,EMACs,Z—MAC以及AIMRP等协议。通过分析各类MAC典型协议特点,归纳其设计原则和分类方法,比较各协议间的性能差异,结果证明无线传感器网络MAC协议呈现多样性的特点,设计MAC协议需要兼顾能量效能和网络性能2个方面。给出MAC协议的设计策略。     

FireFly: a cross-layer platform for real-time embedded wireless networks

We propose a cross-layer approach with tightly-coupled time synchronization for real-time support and predictable lifetime in battery-operated sensor networks. Our design spans a sensor hardware platform with hardware-based global time synchronization, a TDMA link layer protocol with collision-free multi-hop support and node scheduling algorithms for maximum concurrency and streaming. Our dual-radio sensor platform, FireFly, features an IEEE 802.15.4 transceiver and supports global time synchronization indoors by using an AM radio carrier-current method and an atomic clock receiver for outdoors. A TDMA-based link protocol, RT-Link, leverages the hardware for fixed and mobile nodes with a near-optimal and predictable node lifetime of over 2 years. It outperforms comparable sensor network link protocols such as B-MAC and S-MAC in terms of end-to-end latency and throughput and node lifetime across all duty cycle ratios. Operating over RT-Link is MAX, a scheduling framework which offers optimal transmission concurrency and bandwidth management for networks with regular structure. Through analysis and experiments we show that global time sync is a robust, economical and scalable alternative to in-band software-based techniques. To illustrate the capabilities and flexibility of our platform, we describe our experiences with two-way voice streaming over multiple hops. We have deployed a 42-node network with sub-100 μs synchronization accuracy in the NIOSH experimental coal mine for people-tracking and voice communication.

A new procedure for determining specific filter cake resistance from filtration data

A new procedure has been developed for the determination of specific filter cake resistance from experimental filtration data. Unlike the conventional procedure which treats constant-pressure filtration data through the t/V vs. V plot and yields a single value of the average specific cake resistance (α_av) from a given experiment, this new procedure allows the establishment of the relationship of α_av vs. the cake compressive stress (p_s) over a range of p_s values. Results from the new procedures were compared with those obtained from the procedure based on the t/V vs. V plot as well as those from compression-permeability (C-P) measurements. Discussions on the possible improvement of the new procedure are also presented.     

北京市"中水"回用系统分析与优化

利用系统论基本原理,通过对北京市中水回用系统的结构分析、要素考察,优化中水供给、输送和利用环节,完善系统体系结构,判明系统发展方向,从而加强中水管理,提高中水利用效率,进一步达到减少污水排放量和治理污染源,节约和保护有限水资源、挖掘水资源承载能力和保护生态环境的目的。     

中锰渣在生产锰硅合金中的应用

通过生产实践,探索并总结出以中锰渣为主要原料,在生产普通锰硅合金中的操作要点.     

液化流程中氧液化器的流程组织和相关参数确定

简介了中压循环液化和低压循环液化两种主要的液化流程,对两种流程进行了比较;分析了在中压循环液化流程中单独设置氧液化器的必要性;探讨了在低压氧液化和中压氧液化时不同的氧液化器流程组织形式;提出了低压氧液化时合理的流程组织方案和相关参数。     

空间域二维信号滤波方法的研究

空间域二维信号常代表图像信号，滤波是信号去噪最重要的方法。本文就空间域二维信号两种不同滤波方法——线性滤波和中值滤波进行了比较研究，将线性滤波与非线性滤波有机的结合，通过大量实验，得出应用混合型滤波的信号滤波方法。实验表明，混合型滤波器的滤波效果优于单型滤波器。     

有效压力对低渗透多孔介质渗透率的影响

以低渗透多孔介质为研究对象 ,通过实验得出渗透率随有效压力变化曲线。实验结果表明 ,流体在低渗透多孔介质中渗流时 ,受有效压力的影响明显。这是因为低渗透多孔介质的孔隙很小 ,微小的孔隙度变化也会对渗透率产生较大的影响。因此在低渗透油气藏的开采中 ,不宜采用降压开采。     

用混合像元线性模型提取中等植被覆盖区的粘土蚀变信息

基于混合像元线性分解模型,针对中等植被覆盖区提出了一种提取粘土蚀变信息的新方法。主要分3步实现:用混合像元线性分解模型提取植被覆盖丰度;对线性模型进行完善,并依此重构不含有植被信息的新的多波段图像;利用TM5/TM7增强粘土蚀变信息。经验证,提取的植被信息以及粘土类蚀变信息与实际吻合较好,与基于比值-主成分分析的方法相比有明显的优越性。