The cumulative sum （CUSUM） algorithm is proposed to detect the selfish behavior of a node in a wireless ad hoc network. By tracing the statistics characteristic of the backoff time between successful transmissions, ...The cumulative sum （CUSUM） algorithm is proposed to detect the selfish behavior of a node in a wireless ad hoc network. By tracing the statistics characteristic of the backoff time between successful transmissions, a wireless node can distinguish if there is a selfish behavior in the wireless network. The detection efficiency is validated using a Qualnet simulator. An IEEE 802.11 wireless ad hoc network with 20 senders and 20 receivers spreading out randomly in a given area is evaluated. The well-behaved senders use minimum contention window size of 32 and maximum con- tention window size of I 024, and the selfish nodes are assumed not to use the binary exponential strategy for which the contention window sizes are both fixed as 16. The transmission radius of all nodes is 250 m. Two scenarios are investigated： a single-hop network with nodes spreading out in 100 m^100 m, and all the nodes are in the range of each other; and a multi-hop network with nodes spreading out in 1 000 m~ 1 000 m. The node can monitor the backoff time from all the other nodes and run the detection algorithms over those samples. It is noted that the threshold can significantly affect the detection time and the detection accuracy. For a given threshold of 0.3 s, the false alarm rates and the missed alarm rates are less than 5%. The detection delay is less than 1.0 s. The simulation results show that the algorithm has short detection time and high detection accuracy.展开更多
Because of permanent matter and energy accumulation in the sea marginal biotopes, communities of organisms adapted to these specific conditions are developed. Terms contour biotopes and contourobiont＇s communities we...Because of permanent matter and energy accumulation in the sea marginal biotopes, communities of organisms adapted to these specific conditions are developed. Terms contour biotopes and contourobiont＇s communities were proposed. These habitats are populated by a great variety of organisms with numerical superiority of early stages of development of hydrobionts. Therefore, contour biotopes are responsible for the reproduction of many species of plants and animals, including commercialiy ~rnportant species of invertebrate and fish. But as a result of natural physical and chemical processes, the same habitats accumulate many substances that are harmful to living organisms, especially for early ontogenetic stages. So here formed main hotspots, critical ecological zones in seas and oceans, which need to be monitored in the first place. Understanding of the key role of contour biotopes and communities in marine ecological processes development is an ecological imperative. Making of ecological diagnoses, prediction of possible departures from the ecological norm and prevention of serious negative events in the marine environment needs special consideration of contour biotopes and their inhabitants, which are underestimated in traditional marine biological and ecological investigations.展开更多
The persistence of malachite green (MG), and its metabolite leucomalachite green (LMG), in fish tissues is still unclear, leading to many trade disputes. In this research, we established and evaluated an HPLC method t...The persistence of malachite green (MG), and its metabolite leucomalachite green (LMG), in fish tissues is still unclear, leading to many trade disputes. In this research, we established and evaluated an HPLC method that could detect MG and LMG simultaneously, and then investigated the persistence of these two toxins in the tissues of juvenile perch (Lateolabrax japonicus) post sub-chronic MG exposure at 1.0 mg/L. Exposure lasted for 2 h everyday and was repeated six times. The perch were then placed in MG-free seawater for 100 d to eliminate the toxins. Results show that MG accumulated in the tissues, including the gills, liver, muscle, blood and viscera, and then was metabolized rapidly to LMG. The concentrations of these two toxins increased significantly with the accumulation process. In general, the highest concentrations of MG and LMG in all tissue exceeded 1 000 μg/kg, except for MG in the muscle. The order of accumulation levels (highest to lowest) of MG was gill>blood>liver>viscera>muscle, while that of LMG was liver>blood>gill>viscera>muscle. High levels of MG or LMG could persist for several hours but decreased rapidly during the elimination process. The concentration of LMG was much higher than that of MG during the experiment, especially in the gill, liver and blood. Therefore, the three tissues play important roles in toxin accumulation, biotransformation, and elimination. Although the MG and LMG concentrations in muscle were much lower than in other tissues, the content still exceeded the European minimum required performance limit (MRPL), even after 2 400 h (100 d) of elimination. This demonstrates that it is extremely difficult to eliminate MG and LMG from tissues of perch, and therefore use of these toxins is of concern to public health.展开更多
Two-way packet exchange synchronization scheme has been widely used in wireless sensor networks. However, due to the fact that its synchronization error accumulates rapidly over hop count, its applications are greatly...Two-way packet exchange synchronization scheme has been widely used in wireless sensor networks. However, due to the fact that its synchronization error accumulates rapidly over hop count, its applications are greatly restricted. In this paper, the factors that cause the accumulation of synchronization error over hop count are investigated. Theoretical analysis shows that two factors including the clock drift and the asymmetry of two-way packet exchange, have distinct influences on synchronization error between two adjacent nodes. Further, the clock frequency order along synchronization path is found to be vital to the accumulation of synchronization error. The above three factors jointly determine the accumulation of synchronization error over hop count in wireless network. Theoretic results are also verified by three fine-grained experiments on wireless sensor network testbed. The conclusions can be used to decrease synchronization error for large-scale wireless network by careful network deployment.展开更多
基金Supported by National Natural Science Foundation of China (No. 60702038)National High Technology Research and Development Program of China ("863"Program, No. 2007AA01Z220)Cultivation Fund of Innovation Project,Ministry of Education of China (No. 708024)
文摘The cumulative sum （CUSUM） algorithm is proposed to detect the selfish behavior of a node in a wireless ad hoc network. By tracing the statistics characteristic of the backoff time between successful transmissions, a wireless node can distinguish if there is a selfish behavior in the wireless network. The detection efficiency is validated using a Qualnet simulator. An IEEE 802.11 wireless ad hoc network with 20 senders and 20 receivers spreading out randomly in a given area is evaluated. The well-behaved senders use minimum contention window size of 32 and maximum con- tention window size of I 024, and the selfish nodes are assumed not to use the binary exponential strategy for which the contention window sizes are both fixed as 16. The transmission radius of all nodes is 250 m. Two scenarios are investigated： a single-hop network with nodes spreading out in 100 m^100 m, and all the nodes are in the range of each other; and a multi-hop network with nodes spreading out in 1 000 m~ 1 000 m. The node can monitor the backoff time from all the other nodes and run the detection algorithms over those samples. It is noted that the threshold can significantly affect the detection time and the detection accuracy. For a given threshold of 0.3 s, the false alarm rates and the missed alarm rates are less than 5%. The detection delay is less than 1.0 s. The simulation results show that the algorithm has short detection time and high detection accuracy.
文摘Because of permanent matter and energy accumulation in the sea marginal biotopes, communities of organisms adapted to these specific conditions are developed. Terms contour biotopes and contourobiont＇s communities were proposed. These habitats are populated by a great variety of organisms with numerical superiority of early stages of development of hydrobionts. Therefore, contour biotopes are responsible for the reproduction of many species of plants and animals, including commercialiy ~rnportant species of invertebrate and fish. But as a result of natural physical and chemical processes, the same habitats accumulate many substances that are harmful to living organisms, especially for early ontogenetic stages. So here formed main hotspots, critical ecological zones in seas and oceans, which need to be monitored in the first place. Understanding of the key role of contour biotopes and communities in marine ecological processes development is an ecological imperative. Making of ecological diagnoses, prediction of possible departures from the ecological norm and prevention of serious negative events in the marine environment needs special consideration of contour biotopes and their inhabitants, which are underestimated in traditional marine biological and ecological investigations.
基金Supported by the Special Fund of Chinese Government for Basic Scientific Research Operations in Commonweal Research Institute (Yellow Sea Fisheries Research Institute) (No. 2007-qn-12)the Strategic Research Grant of the Databases and Risk Analysis of POPs in Aquatic Products (No. 2005DIB4J049)the Standard System Research on Quality and Safety of Aquatic Products (No. 2004DEA70880)
文摘The persistence of malachite green (MG), and its metabolite leucomalachite green (LMG), in fish tissues is still unclear, leading to many trade disputes. In this research, we established and evaluated an HPLC method that could detect MG and LMG simultaneously, and then investigated the persistence of these two toxins in the tissues of juvenile perch (Lateolabrax japonicus) post sub-chronic MG exposure at 1.0 mg/L. Exposure lasted for 2 h everyday and was repeated six times. The perch were then placed in MG-free seawater for 100 d to eliminate the toxins. Results show that MG accumulated in the tissues, including the gills, liver, muscle, blood and viscera, and then was metabolized rapidly to LMG. The concentrations of these two toxins increased significantly with the accumulation process. In general, the highest concentrations of MG and LMG in all tissue exceeded 1 000 μg/kg, except for MG in the muscle. The order of accumulation levels (highest to lowest) of MG was gill>blood>liver>viscera>muscle, while that of LMG was liver>blood>gill>viscera>muscle. High levels of MG or LMG could persist for several hours but decreased rapidly during the elimination process. The concentration of LMG was much higher than that of MG during the experiment, especially in the gill, liver and blood. Therefore, the three tissues play important roles in toxin accumulation, biotransformation, and elimination. Although the MG and LMG concentrations in muscle were much lower than in other tissues, the content still exceeded the European minimum required performance limit (MRPL), even after 2 400 h (100 d) of elimination. This demonstrates that it is extremely difficult to eliminate MG and LMG from tissues of perch, and therefore use of these toxins is of concern to public health.
基金Supported by the National Natural Science Foundation of China （61003307, 61173132, 60803159）,the Basic Disciplines Research Foundation of China University of Petroleum, Beijing （JCXK-2010-01）, Key Laboratory of Computer System and Architecture, ICT,CAS（ICT-ARCH200901）, and the Open Laboratory for the Internet Fundamental Technology, China Intemet Network Information Center（2012-N03）
文摘Two-way packet exchange synchronization scheme has been widely used in wireless sensor networks. However, due to the fact that its synchronization error accumulates rapidly over hop count, its applications are greatly restricted. In this paper, the factors that cause the accumulation of synchronization error over hop count are investigated. Theoretical analysis shows that two factors including the clock drift and the asymmetry of two-way packet exchange, have distinct influences on synchronization error between two adjacent nodes. Further, the clock frequency order along synchronization path is found to be vital to the accumulation of synchronization error. The above three factors jointly determine the accumulation of synchronization error over hop count in wireless network. Theoretic results are also verified by three fine-grained experiments on wireless sensor network testbed. The conclusions can be used to decrease synchronization error for large-scale wireless network by careful network deployment.
