7 research outputs found
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A mobile assisted coverage hole patching scheme based on particle swarm optimization for WSNs
Wireless sensor networks (WSNs) have drawn much research attention in recent years due to the superior performance in multiple applications, such as military and industrial monitoring, smart home, disaster restoration etc. In such applications, massive sensor nodes are randomly deployed and they remain static after the deployment, to fully cover the target sensing area. This will usually cause coverage redundancy or coverage hole problem. In order to effectively deploy sensors to cover whole area, we present a novel node deployment algorithm based on mobile sensors. First, sensor nodes are randomly deployed in target area, and they remain static or switch to the sleep mode after deployment. Second, we partition the network into grids and calculate the coverage rate of each grid. We select grids with lower coverage rate as candidate grids. Finally, we awake mobile sensors from sleep mode to fix coverage hole, particle swarm optimization (PSO) algorithm is used to calculate moving position of mobile sensors. Simulation results show that our algorithm can effectively improve the coverage rate of WSNs
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A PSO based coverage hole patching scheme for WSNs
In this paper, a mobile assist node deployment algorithm is proposed to patch coverage holes in wireless sensor network (WSNs). In initial phase, sensor nodes are randomly deployed in target area, they remain static or switch to sleep mode after deployment. Then, we partition the network into girds and calculate the coverage rate of each gird. Finally, we wake mobile sensors from sleep mode to fix coverage hole, and we utilize particle swarm optimization (PSO) algorithm to calculate the moving position of mobile sensors. Simulation results show that our algorithm can effectively improve the coverage rate of WSNs
Hot Carrier Transfer in graphene/PtSe2 Heterostructure Tuned by Built-in Electric Field
Van der Waals
heterojunction involving graphene (Gr) with transition metal dichalcogenides
(TMDs) is regard as a promising structure for their outstanding performance in
optical and optoelectronic response. The
electron-hole thermalization has been deemed to be the main reason for the
sub-bandgap-excitation charge transfer from Gr to TMDs. However, the role of
the intricate interlayer interaction of the Gr and the TMDs still require
intensive investigation. Here, we have investigated the photocarrier dynamics
in 5-layer PtSe2/Gr heterojunction by using time-resolved optical pump
and terahertz probe spectroscopy. Interestingly, after photoexcitation,
electron transfer from PtSe2 to Gr in PtSe2/Gr/substrate
heterojunction has been demonstrated successfully, by contrast, no observable
charge transfer occurs in the Gr/PtSe2/substrate heterostructure.
The prominent difference for the different stacking sequence between Gr and
PtSe2 can be ascribed to the effective built-in field introduced by fused
silica substrate. A physical picture accounting for built-in electric field
introduced by substrate has been proposed to interpret the charge transfer
process in the TMD/Gr heterostructure–the substrate built-in electric field
plays a dominated role for controlling the charge transfer pathway in the
TMDs/Gr heterojunction. This study not only shed the light to the substrate
engineering but also provide a new insight into the dynamic in Gr/TMDs
heterojunction, which provides a new method to optimize the performance of
photodetection. </p
Recommended from our members
A mobile assisted coverage hole patching scheme based on particle swarm optimization for WSNs
Wireless sensor networks (WSNs) have drawn much research attention in recent years due to the superior performance in multiple applications, such as military and industrial monitoring, smart home, disaster restoration etc. In such applications, massive sensor nodes are randomly deployed and they remain static after the deployment, to fully cover the target sensing area. This will usually cause coverage redundancy or coverage hole problem. In order to effectively deploy sensors to cover whole area, we present a novel node deployment algorithm based on mobile sensors. First, sensor nodes are randomly deployed in target area, and they remain static or switch to the sleep mode after deployment. Second, we partition the network into grids and calculate the coverage rate of each grid. We select grids with lower coverage rate as candidate grids. Finally, we awake mobile sensors from sleep mode to fix coverage hole, particle swarm optimization (PSO) algorithm is used to calculate moving position of mobile sensors. Simulation results show that our algorithm can effectively improve the coverage rate of WSNs