Current Issue : January - March Volume : 2012 Issue Number : 1 Articles : 5 Articles
The cognitive radio (CR) systems usually arrange for the quiet period to detect the primary user (PU) effectively. Since all CR users do not transmit any data during quiet period, the interference caused by other CR users can be prevented in the channel sensing for PU detection. Even though the quiet period improves the PU detection performance, it degrades the channel utilization of CR system. To cope with this problem, we propose a channel sensing scheme without quiet period, which is based on the pilot cancellation, and analyze its performance. The numerical results show that the proposed scheme highly outperforms the existing PU detection schemes....
Monitoring of fatigue cracking in steel bridges is of high interest to many bridge owners and agencies. Due to the variety of deterioration sources and locations of bridge defects, there is currently no single method that can detect and address the potential sources globally. In this paper, we presented a dual mode sensing methodology integrating acoustic emission and ultrasonic wave inspection based on the use of low-profile piezoelectric wafer active sensors (PWAS). After introducing the research background and piezoelectric sensing principles, PWAS crack detection in passive acoustic emission mode is first presented. Their acoustic emission detection capability has been validated through both static and compact tension fatigue tests. With the use of coaxial cable wiring, PWAS AE signal quality has been improved. The active ultrasonic inspection is conducted by the damage index and wave imaging approach. The results in the paper show that such an integration of passive acoustic emission detection with active ultrasonic sensing is a technological leap forward from the current practice of periodic and subjective visual inspection and bridge management based primarily on history of past performance....
Wireless sensor networks (WSNs) consist of a large number of low-cost miniature sensors, which can be applied to battlefield surveillance, environmental monitoring, target tracking, and other applications related to the positions of sensors. The location information of sensors is of great importance for wireless sensor networks. In this paper, we propose a new localization algorithm for the wireless sensor network based on time difference of arrival (TDOA), which is a typical algorithm in the wireless localization field. In order to improve the localization accuracy of a sensor, a new strategy is proposed for a localized sensor being upgraded to an anchor node, which is used to localize the position of the next sensor. Performance analysis and simulation results show that the revised TODA localization algorithm has the higher localization accuracy when compared with the original TDOA location method....
The present paper proposes a novel cableless magnetic actuator with a new propulsion module that exhibits a very high thrusting force. This actuator contains an electrical inverter that directly transforms DC from button batteries into AC. The electrical DC-AC inverter incorporates a mass-spring system, a reed switch, and a curved permanent magnet that switches under an electromagnetic force. The actuator is moved by the inertial force of the mass-spring system due to mechanical resonance energy. The experimental results show that the actuator is able to move upward at a speed of 19.7?mm/s when using 10 button batteries when pulling a 20?g load mass. This cableless magnetic actuator has several possible applications, including narrow pipe inspection and maintenance....
In urban vehicular sensor networks, vehicles equipped with onboard sensors monitor some area, and the result can be shared to neighbor vehicles to correct their own sensing data. However, due to the frequent change of vehicle topology compared to the wireless sensor network, it is required for a vehicle to discover neighboring vehicles. Therefore, efficient neighbor discovery algorithm should be designed for vehicular sensor networks. In this paper, two efficient tree-based neighbor discovery algorithms in vehicular sensor networks are proposed and analyzed. After suggesting detailed scenario and its system model, we show that the expected value of neighbor discovery delay has different characteristics depending on neighbor discovery algorithms. An interesting observation of our result is that M-binary tree-based neighbor discovery shows better performance than M-ary tree-based neighbor discovery in the parking lot scenario, which is a counterintuitive result. We analyze why such result appears extensively....
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