Wireless sensor networks (WSN) face several challenges in field deployments due to strict limitations in nodes hardware capabilities and battery capacities. In addition, several environmental factors should be considered while designing or testing a WSN. Energy-efficient operation is one of the prominent challenges for successful deployment of WSN's. In this paper, we consider energy-efficient operation of WSN nodes implementation based on the Contiki real-time operating system. We inspect the effect of applying spatial configuration for the radio duty-cycle (RDC) frequencies of WSN nodes running ContikiMAC. We also propose two temporal update mechanisms namely: a distributed mechanism in which a WSN sink node collects network-wide statistics and broadcasts a threshold value to the nodes to adjust their duty cycles and an autonomous mechanism in which each node individually updates its dutycycle based on its battery capacity level. Our simulation results show significant gains in network life time while maintaining network delivery ratio at the same level compared with static schemes.

Energy-efficient operation is one of the prominent challenges for successful deployment of Wireless Sensor Networks (WSNs) along with maintaining certain quality of service (QoS) requirements. In this paper, we tackle the energy-efficient operation of WSN nodes implementation based on the Contiki real-time operating system (RTOS). We review the effect of applying spatial configuration for the radio duty-cycle (RDC) frequencies of WSN nodes running ContikiMAC. We propose an approach for enhancing the ContikiMAC duty cycling protocol, using adaptive radio duty cycling. Such approach would enhance multiple performance metrics of WSN's such as lifetime and sensory packets delivery ratio. Our proposal is based on two temporal duty cycles update mechanisms namely: a distributed mechanism in which a WSN sink node collects network-wide statistics and broadcasts a threshold value to sensory nodes for duty cycles adjustment, and an autonomous mechanism in which each node individually updates its duty-cycle based on local measured statistics. Such proposed framework should help achieving optimal balance between network lifetime and QoS requirements. Our simulation results for Contiki-AMAC show significant gains in network lifetime while maintaining network sensory packets delivery ratio at the same level, compared to static schemes of ContikiMAC.

On operating new trucks in one of the areas of the Egyptian western desert, unexpected fast engine failure occured. Although the technical maintenance to these trucks, was regularly done, the engine failure took place after covering 26000 Km only. In the meantime, no similar failures of trucks operating in other zones have been reported. Therefore, the main reason that led to the engine failure was attributed to the environmental conditions characterised by high dust concentration and relatively high temperature.After reviewing the air and cil filteration systems of the damaged engine and making the necessary inspection and measurements it could be said that the failure occured mainly due to inefficient oil filteration. SUMMARY-Upon uitilization of new trucks, in dusty zones, ofEgypt, unexpected failure of some engines occured after covering a relatively short distance. In the mean time, no failures in simillar engines operating in other zones have been recorded The main reason of the failure was attributed to the environmental field conditions characterized by high dust concentration and relatively high temperature. The engine failure was manifested by a high drop in the oil pressure and a noizy engine run. After reviewing the air and oil filteration systems of a one damaged engine, and making the necessary inspection, it could be said that the failure reason is the inefficient oil filteration. A new oil filter had to be designed by the engine manufacturer. The old and the new filters have been tested on a special testing rig designed and conducted by the author. The test rig enabled to evaluate the oil filter performance under simulated local environmental conditions. To determine the actual performance of the new filter, a similar engine provided with the new filter has been tested. The test results showed no drop in the oil pressure, and no excessive engine noize. This results proved the efficiency of the new filter under dusty conditions of Egypt. 101)-2312;7] SECOND A .m. E CONFERENCE 6 -8 May 1986 , Cairo r . . .