针对IEEE802.11e Medium Access Control层的QoS机制高负载时存在远端节点冲突和低优先级业务资源被耗尽的问题,提出在牺牲较小带宽的基础上增加一条忙音信道,取代CTS帧在数据信道上的广播,减少远端节点的冲突.仿真结果表明,该方案具有...针对IEEE802.11e Medium Access Control层的QoS机制高负载时存在远端节点冲突和低优先级业务资源被耗尽的问题,提出在牺牲较小带宽的基础上增加一条忙音信道,取代CTS帧在数据信道上的广播,减少远端节点的冲突.仿真结果表明,该方案具有较小的冲突概率,有效地减少了远端节点冲突.同时提出一个解决公平性问题的新思路:在避退时间发送忙音抢占信道,以期提高低优先级业务的接入概率.展开更多
Using computer-aided design three-dimensional （3D） simulation technology, the recovery mechanism of single event upset and the effects of spacing and hit angle on the recovery are studied. It is found that the multi...Using computer-aided design three-dimensional （3D） simulation technology, the recovery mechanism of single event upset and the effects of spacing and hit angle on the recovery are studied. It is found that the multi-node charge collection plays a key role in recovery and shielding the charge sharing by adding guard rings. It cannot exhibit the recovery effect. It is also indicated that the upset linear energy transfer （LET） threshold is kept constant while the recovery LET threshold increases as the spacing increases. Additionally, the effect of incident angle on recovery is analysed and it is shown that a larger angle can bring about a stronger charge sharing effect, thus strengthening the recovery ability.展开更多
Hadoop technology is followed by some security issues. At its beginnings, developers paid attention to the development of basic functionalities mostly, and proposal of security components was not of prime interest. Be...Hadoop technology is followed by some security issues. At its beginnings, developers paid attention to the development of basic functionalities mostly, and proposal of security components was not of prime interest. Because of that, the technology remained vulnerable to malicious activities of unauthorized users whose purpose is to endanger system functionalities or to compromise private user data. Researchers and developers are continuously trying to solve these issues by upgrading Hadoop’s security mechanisms and preventing undesirable malicious activities. In this paper, the most common HDFS security problems and a review of unauthorized access issues are presented. First, Hadoop mechanism and its main components are described as the introduction part of the leading research problem. Then, HDFS architecture is given, and all including components and functionalities are introduced. Further, all possible types of users are listed with an accent on unauthorized users, which are of great importance for the paper. One part of the research is dedicated to the consideration of Hadoop security levels, environment and user assessments. The review also includes an explanation of Log Monitoring and Audit features, and detail consideration of authorization and authentication issues. Possible consequences of unauthorized access to a system are covered, and a few recommendations for solving problems of unauthorized access are offered. Honeypot nodes, security mechanisms for collecting valuable information about malicious parties, are presented in the last part of the paper. Finally, the idea for developing a new type of Intrusion Detector, which will be based on using an artificial neural network, is presented. The detector will be an integral part of a new kind of virtual honeypot mechanism and represents the initial base for future scientific work of authors.展开更多
With reference to sensor node architectures, we consider the problem of supporting forms of memory protection through a hardware/compiler approach that takes advantage of a low-cost protection circuitry inside the mic...With reference to sensor node architectures, we consider the problem of supporting forms of memory protection through a hardware/compiler approach that takes advantage of a low-cost protection circuitry inside the microcontroller, interposed between the processor and the storage devices. Our design effort complies with the stringent limitations existing in these architectures in terms of hardware complexity, available storage and energy consumption. Rather that precluding deliberately harmful programs from producing their effects, our solution is aimed at limiting the spread of programming errors outside the memory scope of the running program. The discussion evaluates the resulting protection environment from a number of salient viewpoints that include the implementation of common protection paradigms, efficiency in the distribution and revocation of access privileges, and the lack of a privileged (kernel) mode.展开更多
针对水下声信号的低传播速度导致的时空不确定性问题,能够高效的利用水下声信道的长传播时延的信道预约技术,常被水下传感器网络的媒体接入控制协议的设计所采用,为了探索设计水下传感器网络的高性能媒体接入控制协议,以信道预约技术为...针对水下声信号的低传播速度导致的时空不确定性问题,能够高效的利用水下声信道的长传播时延的信道预约技术,常被水下传感器网络的媒体接入控制协议的设计所采用,为了探索设计水下传感器网络的高性能媒体接入控制协议,以信道预约技术为基础,提出了一种新型的适用于移动水下传感器网络的,基于接收端同步的并发媒体接入控制协议,即CMACRS(concurrent medium access control based on receiver synchronization),新协议采用信道预约方法,实现了多个发送节点的并发传输。广泛的仿真结果显示,在吞吐量等性能方面,新协议优于非时隙级并发传输的水下媒体接入控制协议。展开更多
文摘针对IEEE802.11e Medium Access Control层的QoS机制高负载时存在远端节点冲突和低优先级业务资源被耗尽的问题,提出在牺牲较小带宽的基础上增加一条忙音信道,取代CTS帧在数据信道上的广播,减少远端节点的冲突.仿真结果表明,该方案具有较小的冲突概率,有效地减少了远端节点冲突.同时提出一个解决公平性问题的新思路:在避退时间发送忙音抢占信道,以期提高低优先级业务的接入概率.
基金supported by the State Key Program of the National Natural Science Foundation of China (Grant No.60836004)the National Natural Science Foundation of China (Grant Nos.61076025 and 61006070)
文摘Using computer-aided design three-dimensional （3D） simulation technology, the recovery mechanism of single event upset and the effects of spacing and hit angle on the recovery are studied. It is found that the multi-node charge collection plays a key role in recovery and shielding the charge sharing by adding guard rings. It cannot exhibit the recovery effect. It is also indicated that the upset linear energy transfer （LET） threshold is kept constant while the recovery LET threshold increases as the spacing increases. Additionally, the effect of incident angle on recovery is analysed and it is shown that a larger angle can bring about a stronger charge sharing effect, thus strengthening the recovery ability.
文摘Hadoop technology is followed by some security issues. At its beginnings, developers paid attention to the development of basic functionalities mostly, and proposal of security components was not of prime interest. Because of that, the technology remained vulnerable to malicious activities of unauthorized users whose purpose is to endanger system functionalities or to compromise private user data. Researchers and developers are continuously trying to solve these issues by upgrading Hadoop’s security mechanisms and preventing undesirable malicious activities. In this paper, the most common HDFS security problems and a review of unauthorized access issues are presented. First, Hadoop mechanism and its main components are described as the introduction part of the leading research problem. Then, HDFS architecture is given, and all including components and functionalities are introduced. Further, all possible types of users are listed with an accent on unauthorized users, which are of great importance for the paper. One part of the research is dedicated to the consideration of Hadoop security levels, environment and user assessments. The review also includes an explanation of Log Monitoring and Audit features, and detail consideration of authorization and authentication issues. Possible consequences of unauthorized access to a system are covered, and a few recommendations for solving problems of unauthorized access are offered. Honeypot nodes, security mechanisms for collecting valuable information about malicious parties, are presented in the last part of the paper. Finally, the idea for developing a new type of Intrusion Detector, which will be based on using an artificial neural network, is presented. The detector will be an integral part of a new kind of virtual honeypot mechanism and represents the initial base for future scientific work of authors.
文摘With reference to sensor node architectures, we consider the problem of supporting forms of memory protection through a hardware/compiler approach that takes advantage of a low-cost protection circuitry inside the microcontroller, interposed between the processor and the storage devices. Our design effort complies with the stringent limitations existing in these architectures in terms of hardware complexity, available storage and energy consumption. Rather that precluding deliberately harmful programs from producing their effects, our solution is aimed at limiting the spread of programming errors outside the memory scope of the running program. The discussion evaluates the resulting protection environment from a number of salient viewpoints that include the implementation of common protection paradigms, efficiency in the distribution and revocation of access privileges, and the lack of a privileged (kernel) mode.
文摘针对水下声信号的低传播速度导致的时空不确定性问题,能够高效的利用水下声信道的长传播时延的信道预约技术,常被水下传感器网络的媒体接入控制协议的设计所采用,为了探索设计水下传感器网络的高性能媒体接入控制协议,以信道预约技术为基础,提出了一种新型的适用于移动水下传感器网络的,基于接收端同步的并发媒体接入控制协议,即CMACRS(concurrent medium access control based on receiver synchronization),新协议采用信道预约方法,实现了多个发送节点的并发传输。广泛的仿真结果显示,在吞吐量等性能方面,新协议优于非时隙级并发传输的水下媒体接入控制协议。
