Directed diffusion is a data dissemination protocol for wireless sensor networks. In directed diffusion, flooding is used for dissemination of interest and exploratory data, which will bring broadcast storm resulting ...Directed diffusion is a data dissemination protocol for wireless sensor networks. In directed diffusion, flooding is used for dissemination of interest and exploratory data, which will bring broadcast storm resulting in substantial energy consumption of networks. A grid-based directed diffusion is presented to improve the energy efficiency of directed diffusion. Virtual geographic grid clusters are constructed by self-organization of nodes using geographic location information. The flooding of interest and exploratory data of original directed diffusion is limited in cluster head nodes. The simulation results and testbed experiments show that the method effectively reduces the network energy consumption. This gain is not achieved at the cost of either delivery ratio or the delay. Importantly, the decreased load also leads to a better delivery ratio and lower delay.展开更多
Routing is a challenging task in Wireless Sensor Networks (WSNs) due to the limitation in energy and hardware capabilities in WSN nodes. This challenge prompted researchers to develop routing protocols that satisfy WS...Routing is a challenging task in Wireless Sensor Networks (WSNs) due to the limitation in energy and hardware capabilities in WSN nodes. This challenge prompted researchers to develop routing protocols that satisfy WSNs needs. The main design objectives are reliable delivery, low energy consumption, and prolonging network lifetime. In WSNs, routing is based on local information among neighboring nodes. Routing decisions are made locally;each node will select the next hop without any clue about the other nodes on the path. Although a full knowledge about the network yields better routing, that is not feasible in WSNs due to memory limitation and to the high traffic needed to collect the needed data about all the nodes in the network. As an effort to try to overcome this disadvantage, we are proposing in this paper aware diffusion routing protocol. Aware diffusion follows a semi-holistic approach by collecting data about the available paths and uses these data to enforce healthier paths using machine learning. The data gathering is done by adding a new stage called data collection stage. In this stage, the protocol designer can determine which parameters to collect then use these parameters in enforcing the best path according to certain criteria. In our implementation of this paradigm, we are collecting total energy on the path, lowest energy level on the path, and hop count. Again, the data collected is designer and application specific. The collected data will be used to compare available paths using non-incremental learning, and the outcome will be preferring paths that meet the designer criteria. In our case, healthier and shorter paths are preferred, which will result in less power consumption, higher delivery rate, and longer network life since healthier and fewer nodes will be doing the work.展开更多
The implementation of energy balanced routing is an effective way to prolong the lifetime of wireless sensor networks （WSNs）. To balance energy consumption, fuzzy next-hop selecting strategy was designed： nodes of ...The implementation of energy balanced routing is an effective way to prolong the lifetime of wireless sensor networks （WSNs）. To balance energy consumption, fuzzy next-hop selecting strategy was designed： nodes of different gradients are fuzzily classified into relevant levels; each level has a chance to provide a node with maximum residual energy as the next-hop. Based on the above strategy and directed diffusion （DD）, fuzzy next-hop selection based energy balance （FNSEB） routing protocol was proposed. The simulation results showed that FNSEB utilized the limited energy more thoroughly and rationally, decreased the average energy consumption and prolonged the lifetime of WSNs.展开更多
Architecture of fibrous building blocks with ordered structure and high electroactivity that enables quick charge kinetic transport/intercalation is necessary for high-energy-density electrochemical supercapacitors.He...Architecture of fibrous building blocks with ordered structure and high electroactivity that enables quick charge kinetic transport/intercalation is necessary for high-energy-density electrochemical supercapacitors.Herein,we report a heterostruc-tured molybdenum disulfide@vertically aligned graphene fiber(MoS_(2)@VA-GF),wherein well-defined MoS_(2)nanosheets are decorated on vertical graphene fibers by C-O-Mo covalent bonds.Benefiting from uniform microfluidic self-assembly and confined reactions,it is realized that the unique characteristics of a vertical-aligned skeleton,large faradic activity,in situ interfacial connectivity and high-exposed surface/porosity remarkably create efficiently directional ionic pathways,interfa-cial electron mobility and pseudocapacitive accessibility for accelerating charge transport and intercalation/de-intercalation.Resultant MoS_(2)@VA-GF exhibits large gravimetric capacitance(564 F g^(-1))and reversible redox transitions in 1 M H_(2)SO_(4)electrolyte.Furthermore,the MoS_(2)@VA-GF-based solid-state supercapacitors deliver high energy density(45.57 Wh kg-1),good cycling stability(20,000 cycles)and deformable/temperature-tolerant capability.Beyond that,supercapacitors can realize actual applications of powering multicolored optical fiber lamps,wearable watch,electric fans and sunflower toys.展开更多
An accurate and operational bidirectional reflectance distribution function （BDRF） canopy model is the basis of quantitative vegetation remote sensing. The canopy reflectance should be approximated as the sum of the...An accurate and operational bidirectional reflectance distribution function （BDRF） canopy model is the basis of quantitative vegetation remote sensing. The canopy reflectance should be approximated as the sum of the single scattering reflectance arising from the sun, pl, and the multiple scattering reflectance arising from the canopy, fin, as their directional characteristics are dramatically different. Based on the existing BRDF model, we obtain a new analytical expression of ρ1 and ρm in this paper, which is suitable for different illumination conditions and different vegetation canopies. According to the geometrical optic model at the leaf scale, the anisotropy of ρ1 can be ascribed to the geometry of the object, sun and the sensor, multiple scale clumping, and the fraction of direct solar radiation and diffuse sky radiation. Then, we parameterize the area ratios of four components： the sunlit foliage, sunlit ground, shadow foliage and shadow ground based on a Poisson distribution, and develop a new approximate analytical single scattering reflectance model. Assuming G=0.5, a recollision probability theory based scattering model is developed which considers the effects of diffuse sky radiation, scattering inside the canopy and rebounds between the canopy and soil. Validation using ground measurements of maize and black spruce forest proves the reliability of the model.展开更多
A distortion correction method for the elemental images of integral imaging（Ⅱ） by utilizing the directional diffuser is demonstrated. In the traditional Ⅱ, the distortion originating from lens aberration wraps ele...A distortion correction method for the elemental images of integral imaging（Ⅱ） by utilizing the directional diffuser is demonstrated. In the traditional Ⅱ, the distortion originating from lens aberration wraps elemental images and degrades the image quality severely. According to the theoretical analysis and experiments, it can be proved that the farther the three-dimensional image is displayed from the lens array, the more serious the distortion is. To analyze the process of eliminating lens distortion, one lens and its corresponding elemental image are separated from the traditional Ⅱ. By introducing the directional diffuser, the aperture stop of the separated optical system changes from the eye＇s pupil to the lens. In terms of contrast experiments, the distortion of the improved display system is corrected effectively. In the experiment, when the distance between the reconstructed image and lens array is equal to 120 mm, the largest lens distortion is decreased from 46.6% to 3.3%.展开更多
基金the National High Technology Research and Development Programme of China(No.2002AA142020)the National Natural Science Foundation of China(No.60475012)
文摘Directed diffusion is a data dissemination protocol for wireless sensor networks. In directed diffusion, flooding is used for dissemination of interest and exploratory data, which will bring broadcast storm resulting in substantial energy consumption of networks. A grid-based directed diffusion is presented to improve the energy efficiency of directed diffusion. Virtual geographic grid clusters are constructed by self-organization of nodes using geographic location information. The flooding of interest and exploratory data of original directed diffusion is limited in cluster head nodes. The simulation results and testbed experiments show that the method effectively reduces the network energy consumption. This gain is not achieved at the cost of either delivery ratio or the delay. Importantly, the decreased load also leads to a better delivery ratio and lower delay.
文摘Routing is a challenging task in Wireless Sensor Networks (WSNs) due to the limitation in energy and hardware capabilities in WSN nodes. This challenge prompted researchers to develop routing protocols that satisfy WSNs needs. The main design objectives are reliable delivery, low energy consumption, and prolonging network lifetime. In WSNs, routing is based on local information among neighboring nodes. Routing decisions are made locally;each node will select the next hop without any clue about the other nodes on the path. Although a full knowledge about the network yields better routing, that is not feasible in WSNs due to memory limitation and to the high traffic needed to collect the needed data about all the nodes in the network. As an effort to try to overcome this disadvantage, we are proposing in this paper aware diffusion routing protocol. Aware diffusion follows a semi-holistic approach by collecting data about the available paths and uses these data to enforce healthier paths using machine learning. The data gathering is done by adding a new stage called data collection stage. In this stage, the protocol designer can determine which parameters to collect then use these parameters in enforcing the best path according to certain criteria. In our implementation of this paradigm, we are collecting total energy on the path, lowest energy level on the path, and hop count. Again, the data collected is designer and application specific. The collected data will be used to compare available paths using non-incremental learning, and the outcome will be preferring paths that meet the designer criteria. In our case, healthier and shorter paths are preferred, which will result in less power consumption, higher delivery rate, and longer network life since healthier and fewer nodes will be doing the work.
基金Supported by the Research Fund for the Doctoral Program of Higher Education (20040486049)the Key Project of National Natural Science Foundation of China (60132030)
文摘The implementation of energy balanced routing is an effective way to prolong the lifetime of wireless sensor networks （WSNs）. To balance energy consumption, fuzzy next-hop selecting strategy was designed： nodes of different gradients are fuzzily classified into relevant levels; each level has a chance to provide a node with maximum residual energy as the next-hop. Based on the above strategy and directed diffusion （DD）, fuzzy next-hop selection based energy balance （FNSEB） routing protocol was proposed. The simulation results showed that FNSEB utilized the limited energy more thoroughly and rationally, decreased the average energy consumption and prolonged the lifetime of WSNs.
基金support from the National Natural Science Foundation of China(22278378)Zhejiang Provincial Natural Science Foundation of China(LDQ24E030001)+1 种基金Natural Science Foundation of Jiangsu Province(BK20211592)Science Foundation of Zhejiang Sci-Tech University(22212011-Y).
文摘Architecture of fibrous building blocks with ordered structure and high electroactivity that enables quick charge kinetic transport/intercalation is necessary for high-energy-density electrochemical supercapacitors.Herein,we report a heterostruc-tured molybdenum disulfide@vertically aligned graphene fiber(MoS_(2)@VA-GF),wherein well-defined MoS_(2)nanosheets are decorated on vertical graphene fibers by C-O-Mo covalent bonds.Benefiting from uniform microfluidic self-assembly and confined reactions,it is realized that the unique characteristics of a vertical-aligned skeleton,large faradic activity,in situ interfacial connectivity and high-exposed surface/porosity remarkably create efficiently directional ionic pathways,interfa-cial electron mobility and pseudocapacitive accessibility for accelerating charge transport and intercalation/de-intercalation.Resultant MoS_(2)@VA-GF exhibits large gravimetric capacitance(564 F g^(-1))and reversible redox transitions in 1 M H_(2)SO_(4)electrolyte.Furthermore,the MoS_(2)@VA-GF-based solid-state supercapacitors deliver high energy density(45.57 Wh kg-1),good cycling stability(20,000 cycles)and deformable/temperature-tolerant capability.Beyond that,supercapacitors can realize actual applications of powering multicolored optical fiber lamps,wearable watch,electric fans and sunflower toys.
基金supported by the National Natural Science Foundation of China(Grant Nos.41271346,41571329&41230747)the Major State Basic Research Development Program of China(Grant No.2013CB733402)
文摘An accurate and operational bidirectional reflectance distribution function （BDRF） canopy model is the basis of quantitative vegetation remote sensing. The canopy reflectance should be approximated as the sum of the single scattering reflectance arising from the sun, pl, and the multiple scattering reflectance arising from the canopy, fin, as their directional characteristics are dramatically different. Based on the existing BRDF model, we obtain a new analytical expression of ρ1 and ρm in this paper, which is suitable for different illumination conditions and different vegetation canopies. According to the geometrical optic model at the leaf scale, the anisotropy of ρ1 can be ascribed to the geometry of the object, sun and the sensor, multiple scale clumping, and the fraction of direct solar radiation and diffuse sky radiation. Then, we parameterize the area ratios of four components： the sunlit foliage, sunlit ground, shadow foliage and shadow ground based on a Poisson distribution, and develop a new approximate analytical single scattering reflectance model. Assuming G=0.5, a recollision probability theory based scattering model is developed which considers the effects of diffuse sky radiation, scattering inside the canopy and rebounds between the canopy and soil. Validation using ground measurements of maize and black spruce forest proves the reliability of the model.
基金supported by the Natural National Science Foundation of China(NSFC)(No.61705014)the Fundamental Research Funds for the Central Universities(No.2016ZX01)+1 种基金the fund of the State Key Laboratory of Information Photonics and Optical CommunicationsThe "863" Program(No.2015AA015902)
文摘A distortion correction method for the elemental images of integral imaging（Ⅱ） by utilizing the directional diffuser is demonstrated. In the traditional Ⅱ, the distortion originating from lens aberration wraps elemental images and degrades the image quality severely. According to the theoretical analysis and experiments, it can be proved that the farther the three-dimensional image is displayed from the lens array, the more serious the distortion is. To analyze the process of eliminating lens distortion, one lens and its corresponding elemental image are separated from the traditional Ⅱ. By introducing the directional diffuser, the aperture stop of the separated optical system changes from the eye＇s pupil to the lens. In terms of contrast experiments, the distortion of the improved display system is corrected effectively. In the experiment, when the distance between the reconstructed image and lens array is equal to 120 mm, the largest lens distortion is decreased from 46.6% to 3.3%.
