Tetragonal tungsten bronze structure potassium lithium niobate (KLN) crystals pr omise as a potentially useful material for nonlinear optical applications,especi ally,for blue laser radiation by second harmonic genera...Tetragonal tungsten bronze structure potassium lithium niobate (KLN) crystals pr omise as a potentially useful material for nonlinear optical applications,especi ally,for blue laser radiation by second harmonic generation (SHG).We have grown KLN single crystals by TSSG method using different melt compositions and studied the properties of second harmonic generation (SHG).The crystals have the conten ts of Nb 2O 5 in the range of 51 54% and Li 2O in the range of 17.5 20% and a non critical SHG phase matching wavelength being a wide range from 843 and 9 67 nm. The dependence of temperature and SHG phase match wavelength and the temp erature acceptance were measured by a cw Ti∶Al 2O 3 laser(Spectra Physics M odel 3900S).The results show a linear relationship between phase match wavelengt h and temperature and a about 4℃ temperature acceptance.The homogeneity on a KL N crystal sample of 4×5×8mm was characterized where the SHG phase match wavele ngth changed within 887.8 and 887.5nm . With comparing the wavelength accepta nce being 0.5nm,the result suggests that the homogeneity is good. The dependence bet ween crystal composition,crystal lattice constants and SHG properties will be di scussed.展开更多
Wireless sensor networks consist of many small nodes with distributing devices to monitor conditions at different locations. Usually wireless sensor nodes are sprinkled in a sensor field grouping limited areas. This p...Wireless sensor networks consist of many small nodes with distributing devices to monitor conditions at different locations. Usually wireless sensor nodes are sprinkled in a sensor field grouping limited areas. This paper highlights the Enhanced Cluster Based Key management (ECBK) protocol to achieve secure data delivery based on clustering mechanism. This protocol gives more importance to Cluster Coordinator node, which is used to coordinate the members and provide protective communication among the sensor nodes to enhance reliability. In Enhanced Cluster Based Key management two types of nodes are deployed. The high power nodes form clusters with surrounding nodes to enable the routing process without interference. This paper introduces ECBK protocol that balances the load among the clusters, achieves high throughput, end to end delay will be reduced, routing overhead also reduced and also it prolongs the network lifetime. Simulation results show that the presence of high transmission nodes reduces the delay, load balance, routing overhead, and enhances the throughput increased by 45% compared to other similar methods.展开更多
In cellular networks, cooperative relaying is an economic and promising way to enlarge the network capacity and coverage. In the case that multiple users and multiple relays are taken into account, efficient resource ...In cellular networks, cooperative relaying is an economic and promising way to enlarge the network capacity and coverage. In the case that multiple users and multiple relays are taken into account, efficient resource allocation is important in such networks. In this paper, we consider the joint relay power control with amplify-and-forward(AF) strategy and dynamic pricing for uplink cellular networks in order to maximize the network administrator's system revenue. The system revenue is associated with pricing strategies and mobile users' random data request, which is supported by the relay assisted transmission. To deal with the problem of the coupling in pricing and relay resource allocation, we utilize Lyapunov optimization techniques to design online pricing and relay power control without any statistic information of random events in networks. Theoretical analysis shows that the proposed algorithm can achieve a near-optimal performance and simulation results also validate its effectiveness and robustness.展开更多
文摘Tetragonal tungsten bronze structure potassium lithium niobate (KLN) crystals pr omise as a potentially useful material for nonlinear optical applications,especi ally,for blue laser radiation by second harmonic generation (SHG).We have grown KLN single crystals by TSSG method using different melt compositions and studied the properties of second harmonic generation (SHG).The crystals have the conten ts of Nb 2O 5 in the range of 51 54% and Li 2O in the range of 17.5 20% and a non critical SHG phase matching wavelength being a wide range from 843 and 9 67 nm. The dependence of temperature and SHG phase match wavelength and the temp erature acceptance were measured by a cw Ti∶Al 2O 3 laser(Spectra Physics M odel 3900S).The results show a linear relationship between phase match wavelengt h and temperature and a about 4℃ temperature acceptance.The homogeneity on a KL N crystal sample of 4×5×8mm was characterized where the SHG phase match wavele ngth changed within 887.8 and 887.5nm . With comparing the wavelength accepta nce being 0.5nm,the result suggests that the homogeneity is good. The dependence bet ween crystal composition,crystal lattice constants and SHG properties will be di scussed.
文摘Wireless sensor networks consist of many small nodes with distributing devices to monitor conditions at different locations. Usually wireless sensor nodes are sprinkled in a sensor field grouping limited areas. This paper highlights the Enhanced Cluster Based Key management (ECBK) protocol to achieve secure data delivery based on clustering mechanism. This protocol gives more importance to Cluster Coordinator node, which is used to coordinate the members and provide protective communication among the sensor nodes to enhance reliability. In Enhanced Cluster Based Key management two types of nodes are deployed. The high power nodes form clusters with surrounding nodes to enable the routing process without interference. This paper introduces ECBK protocol that balances the load among the clusters, achieves high throughput, end to end delay will be reduced, routing overhead also reduced and also it prolongs the network lifetime. Simulation results show that the presence of high transmission nodes reduces the delay, load balance, routing overhead, and enhances the throughput increased by 45% compared to other similar methods.
文摘In cellular networks, cooperative relaying is an economic and promising way to enlarge the network capacity and coverage. In the case that multiple users and multiple relays are taken into account, efficient resource allocation is important in such networks. In this paper, we consider the joint relay power control with amplify-and-forward(AF) strategy and dynamic pricing for uplink cellular networks in order to maximize the network administrator's system revenue. The system revenue is associated with pricing strategies and mobile users' random data request, which is supported by the relay assisted transmission. To deal with the problem of the coupling in pricing and relay resource allocation, we utilize Lyapunov optimization techniques to design online pricing and relay power control without any statistic information of random events in networks. Theoretical analysis shows that the proposed algorithm can achieve a near-optimal performance and simulation results also validate its effectiveness and robustness.
