Geographic location of nodes is very useful in a sensor network. Previous localization algorithms assume that there exist some anchor nodes in this kind of network, and then other nodes are estimated to create their c...Geographic location of nodes is very useful in a sensor network. Previous localization algorithms assume that there exist some anchor nodes in this kind of network, and then other nodes are estimated to create their coordinates. Once there are not anchors to be deployed, those localization algorithms will be invalidated. Many papers in this field focus on anchor-based solutions. The use of anchors introduces many limitations, since anchors require external equipments such as global position system, cause additional power consumption. A novel positioning algorithm is proposed to use a virtual coordinate system based on a new concept--virtual anchor. It is executed in a distributed fashion according to the connectivity of a node and the measured distances to its neighbors. Both the adjacent member information and the ranging distance result are combined to generate the estimated position of a network, one of which is independently adopted for localization previously. At the position refinement stage the intermediate estimation of a node begins to be evaluated on its reliability for position mutation; thus the positioning optimization process of the whole network is avoided falling into a local optimal solution. Simulation results prove that the algorithm can resolve the distributed localization problem for anchor-free sensor networks, and is superior to previous methods in terms of its positioning capability under a variety of circumstances.展开更多
To predict the tensile capacity of adhesive anchors, a multilayered feed-forward neural network trained with the back-propagation algorithm is constructed. The ANN model have 5 inputs, including the compressive streng...To predict the tensile capacity of adhesive anchors, a multilayered feed-forward neural network trained with the back-propagation algorithm is constructed. The ANN model have 5 inputs, including the compressive strength of concrete, tensile strength of concrete, anchor diameter, hole diameter, embedment of anchors, and ultimate load. The predictions obtained from the trained ANN show a good agreement with the experiments. Meanwhile, the predicted ultimate tensile capacity of anchors is close to the one calculated from the strength formula of the combined cone-bond failure model.展开更多
为了解决仅依靠星间链路的自主运行导航星座缺乏时空基准的问题,北斗卫星导航系统引入地面锚固站,与空间卫星共同构成可自主运行的星地/星间一体化网络。在星间链路体制、可见性、载荷数量约束下,建立北斗系统星地/星间链路网络一体化...为了解决仅依靠星间链路的自主运行导航星座缺乏时空基准的问题,北斗卫星导航系统引入地面锚固站,与空间卫星共同构成可自主运行的星地/星间一体化网络。在星间链路体制、可见性、载荷数量约束下,建立北斗系统星地/星间链路网络一体化规划模型,提出基于网络分层的层间链路规划算法,以及基于模拟退火算法的测距链路位置精度衰减因子(position dilution of precision, PDOP)和网络连通度多目标优化算法。根据规划仿真结果,锚固站可以最少链路跳数实现向空间卫星的信息分发;卫星测距链路PDOP均小于1.4,且接近其参考下限;星地/星间一体化网络连通度优于3。结果表明,一体化规划算法能够满足锚固站向卫星的信息快速分发、网络空间基准维持的测距以及网络稳健性等性能需求。展开更多
基金the National Natural Science Foundation of China (60673054, 60773129)theExcellent Youth Science and Technology Foundation of Anhui Province of China.
文摘Geographic location of nodes is very useful in a sensor network. Previous localization algorithms assume that there exist some anchor nodes in this kind of network, and then other nodes are estimated to create their coordinates. Once there are not anchors to be deployed, those localization algorithms will be invalidated. Many papers in this field focus on anchor-based solutions. The use of anchors introduces many limitations, since anchors require external equipments such as global position system, cause additional power consumption. A novel positioning algorithm is proposed to use a virtual coordinate system based on a new concept--virtual anchor. It is executed in a distributed fashion according to the connectivity of a node and the measured distances to its neighbors. Both the adjacent member information and the ranging distance result are combined to generate the estimated position of a network, one of which is independently adopted for localization previously. At the position refinement stage the intermediate estimation of a node begins to be evaluated on its reliability for position mutation; thus the positioning optimization process of the whole network is avoided falling into a local optimal solution. Simulation results prove that the algorithm can resolve the distributed localization problem for anchor-free sensor networks, and is superior to previous methods in terms of its positioning capability under a variety of circumstances.
基金The National Natural Science Foundationof China (No50578025)
文摘To predict the tensile capacity of adhesive anchors, a multilayered feed-forward neural network trained with the back-propagation algorithm is constructed. The ANN model have 5 inputs, including the compressive strength of concrete, tensile strength of concrete, anchor diameter, hole diameter, embedment of anchors, and ultimate load. The predictions obtained from the trained ANN show a good agreement with the experiments. Meanwhile, the predicted ultimate tensile capacity of anchors is close to the one calculated from the strength formula of the combined cone-bond failure model.
文摘为了解决仅依靠星间链路的自主运行导航星座缺乏时空基准的问题,北斗卫星导航系统引入地面锚固站,与空间卫星共同构成可自主运行的星地/星间一体化网络。在星间链路体制、可见性、载荷数量约束下,建立北斗系统星地/星间链路网络一体化规划模型,提出基于网络分层的层间链路规划算法,以及基于模拟退火算法的测距链路位置精度衰减因子(position dilution of precision, PDOP)和网络连通度多目标优化算法。根据规划仿真结果,锚固站可以最少链路跳数实现向空间卫星的信息分发;卫星测距链路PDOP均小于1.4,且接近其参考下限;星地/星间一体化网络连通度优于3。结果表明,一体化规划算法能够满足锚固站向卫星的信息快速分发、网络空间基准维持的测距以及网络稳健性等性能需求。
