Wireless Sensor Networks (WSNs) are mainly deployed for data acquisition, thus, the network performance can be passively measured by exploiting whether application data from various sensor nodes reach the sink. In thi...Wireless Sensor Networks (WSNs) are mainly deployed for data acquisition, thus, the network performance can be passively measured by exploiting whether application data from various sensor nodes reach the sink. In this paper, therefore, we take into account the unique data aggregation communication paradigm of WSNs and model the problem of link loss rates inference as a Maximum-Likelihood Estimation problem. And we propose an inference algorithm based on the standard Expectation-Maximization (EM) techniques. Our algorithm is applicable not only to periodic data collection scenarios but to event detection scenarios. Finally, we validate the algorithm through simulations and it exhibits good performance and scalability.展开更多
The phenomenon of EME and charge accumulation were included during the load-bearing failure processing of the rock.The mechanism and signal law of the two kinds of phenomenon through the experiment,as well as the mutu...The phenomenon of EME and charge accumulation were included during the load-bearing failure processing of the rock.The mechanism and signal law of the two kinds of phenomenon through the experiment,as well as the mutual relation of the two kinds of phenomenon,were contribute to monitor the regulation of the mine rock and pre- vent the dynamic disasters of the mine.There were two charge sensors,one electromag- netic radiated sensors and one pressure sensor in the experiment to detect the EME sig- nal and the charge intensity signal during the load-bearing failure processing of the rock. The results show that the charge intensity signal is prior to the EME signal through the date processing and numerical analysis.The two signals change obviously before the rock crush.The two kinds of phenomenon are homogenous and have obvious master-slave characteristic.With the appeared of the EME signal,the charge intensity signal decreased, the power is released.展开更多
Steel structures are widely used in railway infrastructures.Their stress state is the most important determinant of the safety of these structures.The elasto-magnetic (EM) sensor is the most promising for stress monit...Steel structures are widely used in railway infrastructures.Their stress state is the most important determinant of the safety of these structures.The elasto-magnetic (EM) sensor is the most promising for stress monitoring of in-service steel structures.Nevertheless,the necessity of magnetic excitation to saturation due to the use of a secondary coil for signal detection,keeps from its engineering application.In this paper,a smart elasto-magneto-electric (EME) sensor using magneto-electric (ME) sensing units to take the place of the secondary coil has been exploited for the first time.The ME sensing unit is made of ME laminated composites,which has an ultrahigh ME voltage coefficient and can measure the magnetic induction simply and precisely.Theoretical analysis and characterization experiments firstly conducted on the ME laminated composites showed that the ME sensing units can be applied in the EM sensor for improved performance in stress monitoring.A tension test of a steel bar was carried out to characterize our smart EME sensor and the results showed high accuracy and sensitivity.The present smart EME sensor is a promising tool for stress monitoring of steel structures in railway and other civil infrastructures.展开更多
In planning and executing marine controlled-source electromagnetic methods, seafloor electromagnetic receivers must overcome the problems of noise, clock drift, and power consumption. To design a receiver that perform...In planning and executing marine controlled-source electromagnetic methods, seafloor electromagnetic receivers must overcome the problems of noise, clock drift, and power consumption. To design a receiver that performs well and overcomes the abovementioned problems, we performed forward modeling of the E-field abnormal response and established the receiver＇s characteristics. We describe the design optimization and the properties of each component, that is, low-noise induction coil sensor, low-noise Ag/AgCI electrode, low-noise chopper amplifier, digital temperature-compensated crystal oscillator module, acoustic telemetry modem, and burn wire system. Finally, we discuss the results of onshore and offshore field tests to show the effectiveness of the developed seafloor electromagnetic receiver and its performance： typical E-field noise of 0.12 nV/m/rt（Hz） at 0.5 Hz, dynamic range higher than 120 dB, clock drift lower than 1 ms/day, and continuous operation of at least 21 days.展开更多
文摘Wireless Sensor Networks (WSNs) are mainly deployed for data acquisition, thus, the network performance can be passively measured by exploiting whether application data from various sensor nodes reach the sink. In this paper, therefore, we take into account the unique data aggregation communication paradigm of WSNs and model the problem of link loss rates inference as a Maximum-Likelihood Estimation problem. And we propose an inference algorithm based on the standard Expectation-Maximization (EM) techniques. Our algorithm is applicable not only to periodic data collection scenarios but to event detection scenarios. Finally, we validate the algorithm through simulations and it exhibits good performance and scalability.
基金the National Natural Science Foundation of China(50490275)Education Office of Liaoning Province(20082123)
文摘The phenomenon of EME and charge accumulation were included during the load-bearing failure processing of the rock.The mechanism and signal law of the two kinds of phenomenon through the experiment,as well as the mutual relation of the two kinds of phenomenon,were contribute to monitor the regulation of the mine rock and pre- vent the dynamic disasters of the mine.There were two charge sensors,one electromag- netic radiated sensors and one pressure sensor in the experiment to detect the EME sig- nal and the charge intensity signal during the load-bearing failure processing of the rock. The results show that the charge intensity signal is prior to the EME signal through the date processing and numerical analysis.The two signals change obviously before the rock crush.The two kinds of phenomenon are homogenous and have obvious master-slave characteristic.With the appeared of the EME signal,the charge intensity signal decreased, the power is released.
基金Project supported by the National Natural Science Foundation of China(Nos.50908202,51178426,90915008,and 60801011)the Zhejiang Provincial Natural Science Foundation,China(No.Y1090382)+1 种基金the Fok Ying-Tong Education Foundation for Young Teachers in the Higher Education Institutions of China(No.122012)the Key Science and Technology Innovation Team Program of Zhejiang Province,China(No.2010R50034)
文摘Steel structures are widely used in railway infrastructures.Their stress state is the most important determinant of the safety of these structures.The elasto-magnetic (EM) sensor is the most promising for stress monitoring of in-service steel structures.Nevertheless,the necessity of magnetic excitation to saturation due to the use of a secondary coil for signal detection,keeps from its engineering application.In this paper,a smart elasto-magneto-electric (EME) sensor using magneto-electric (ME) sensing units to take the place of the secondary coil has been exploited for the first time.The ME sensing unit is made of ME laminated composites,which has an ultrahigh ME voltage coefficient and can measure the magnetic induction simply and precisely.Theoretical analysis and characterization experiments firstly conducted on the ME laminated composites showed that the ME sensing units can be applied in the EM sensor for improved performance in stress monitoring.A tension test of a steel bar was carried out to characterize our smart EME sensor and the results showed high accuracy and sensitivity.The present smart EME sensor is a promising tool for stress monitoring of steel structures in railway and other civil infrastructures.
基金sponsored by the 863 Program(No.2009AA09A2012012AA09A201)+1 种基金China Geological Survey Project(No.201100307)the Fundamental Research Funds of the Ministry of Education for the Central Universities(No.2652011249)
文摘In planning and executing marine controlled-source electromagnetic methods, seafloor electromagnetic receivers must overcome the problems of noise, clock drift, and power consumption. To design a receiver that performs well and overcomes the abovementioned problems, we performed forward modeling of the E-field abnormal response and established the receiver＇s characteristics. We describe the design optimization and the properties of each component, that is, low-noise induction coil sensor, low-noise Ag/AgCI electrode, low-noise chopper amplifier, digital temperature-compensated crystal oscillator module, acoustic telemetry modem, and burn wire system. Finally, we discuss the results of onshore and offshore field tests to show the effectiveness of the developed seafloor electromagnetic receiver and its performance： typical E-field noise of 0.12 nV/m/rt（Hz） at 0.5 Hz, dynamic range higher than 120 dB, clock drift lower than 1 ms/day, and continuous operation of at least 21 days.
