Image transmission is one of the biggest challenges in wireless sensor networks because of the limited resource on sensor nodes. We proposed two image transmission schemes driven by reliability and real time considerations in order to transfer JPEG images over Zigbee-based sensor networks. By adding two bytes counter in the header of data packet, we can easily solve the repeated data reception problem caused by retransmission mechanism in traditional Zigbees network layer. We proposed an efficient retransmission and acknowledgment mechanism in Zigbees application layer. By classifying different data reception response events, we can provide data packets with differential responses and ensure that image packets can be transferred quickly even with large maximum number of retransmission. Practical results show the effectiveness of our solutions to make image transmission over Zigbee-based sensor networks efficient.

为提高实验教学示范中心设备管理水平,借鉴实验室认可管理体系的方法和内容,探索完善高校实验室设备管理模式.分析了实验室认可管理体系文件的构成,结合土木工程实验设备的功能特点,着重考虑了设备管理的责任范围、设备的安全及环境问题和设备的使用维护工作,确定了管理目标、制定了管理办法、编写了大型设备的操作规程和配套的记录表格格式.该管理模式有力地促进了设备管理办法的落实,有助于实验室设备管理工作的系统化及科学化.实践证明,制定科学系统的设备管理办法,建立相应的管理监督机制,编制与之相配套的科学实用的记录表格是将实验室认可管理体系在实验室设备管理工作中应用的合理途径.

Wireless image sensor networks acquire and transmit image data through self-organized method. Considering processing ability, energy consumption and cost, this paper implements a practical image sensor node with low-power sleeping mechanism in order to achieve image data's gathering, processing and transmission. To ensure transmission reliability of image data in wireless channel, this paper improves the weakness of retransmission mechanism in traditional Zigbee protocol, and proposes an efficient Zigbee-based retransmission and acknowledgment mechanism. Experimental results show the relationships among the total retransmission time, packet loss rate and the maximum number of retransmission.

Based on Cypress' s PSoC devices,a fan controller with temperature compensation is designd by the configuration of the programmable analog and digital modules,and IP multiplexing technique.The design is devided into four parts,which is control module,measurement module,input module,and feedback module.The implementation of PWM-driven fan,the speed measurement of fan using timer module,and the process of utilizing external temperature and feedback to stabilize the speed of fan are introduced.Finally,the effectiveness of solution is proved via a series of experimental results.Compared with the traditional microcontroller,PSoC has flexible hardware structure and easy software programming.