Random lasers are a type of lasers that lack typical resonator structures,offering benefits such as easy integration,low cost,and low spatial coherence.These features make them popular for speckle-free imaging and ran...Random lasers are a type of lasers that lack typical resonator structures,offering benefits such as easy integration,low cost,and low spatial coherence.These features make them popular for speckle-free imaging and random number generation.However,due to their high threshold and phase instability,the production of picosecond random lasers has still been a challenge.In this work,we have developed three dyes incorporating polymer optical fibers doped with various scattering nanoparticles to produce short-pulsed random fiber lasers.Notably,stable picosecond random laser emission lasting600 ps is observed at a low pump energy of 50μJ,indicating the gain-switching mechanism.Population inversion and gain undergo an abrupt surge as the intensity of the continuously pumped light nears the threshold level.When the intensity of the continuously pumped light reaches a specific value,the number of inversion populations in the“scattering cavity”surpasses the threshold rapidly.Simulation results based on a model that considers power-dependent gain saturation confirmed the above phenomenon.This research helps expand the understanding of the dynamics behind random medium-stimulated emission in random lasers and opens up possibilities for mode locking in these systems.展开更多
There are two recognized classes of strategic-form symmetric games,both of which can be conveniently defined through the corresponding player symmetry groups.We investigate the basic properties of these groups and sev...There are two recognized classes of strategic-form symmetric games,both of which can be conveniently defined through the corresponding player symmetry groups.We investigate the basic properties of these groups and several related concepts.We generalize the notion of coveringness and adapt their results to characterize these player symmetry groups.We study the relationships between the coveringnesses of various symmetry groups.Our results demonstrate that these symmetry groups have rich mathematical structures that are of game theoretical and economic interests.展开更多
Sediment in rivers plays an essential role in the river and watershed ecosystem.Recently,Dethier et al.[1]used an empirical model,which was developed using the data in America and Taiwan Province in China,to estimate ...Sediment in rivers plays an essential role in the river and watershed ecosystem.Recently,Dethier et al.[1]used an empirical model,which was developed using the data in America and Taiwan Province in China,to estimate suspended sediment concentration(SSC)and generate a long-term record of SSC and sediment fluxes in 414 major rivers worldwide since 1984.The authors concluded that the widespread decreases in river sediment fluxes in the North Hemisphere(NH)resulted from the dams,while the increases in river sediment fluxes in the South Hemisphere were possibly related to changes in land use.Regardless of the discussion on whether such an empirical model could be extrapolated to the global rivers for accurately retrieving SSC from Landsat imagery,the elucidation of the continuous declines in SSC in the NH rivers since1980s was incomplete.As Dethier et al.[1]demonstrated,the spatial and temporal variations in river sediment were regulated by climate change and human activities[2],including precipitation,land cover and land use,damming,and dredging activities[3-6].展开更多
In order to isolate mitochondrial genes easily, we have developed a new method to construct S-type CMS maize mitochondrial gene library by means of embedding mitochondria and enzymatic digesting mitochondria in situ, ...In order to isolate mitochondrial genes easily, we have developed a new method to construct S-type CMS maize mitochondrial gene library by means of embedding mitochondria and enzymatic digesting mitochondria in situ, preparing mtDNA by electrophoresis, digesting LMP agarose with β-agarase, using BAC vector and electroporation. About 2 500 white clones of Mo17 CMS-J mitochondrial gene library were obtained with the average size of 18.24 kb, ranging from 5 to 40 kb, 63.6% inserts came from mitochondrial genome and represented 48 × mitochondrial genome equivalents. All the probes had detected the positive clones in the gene library. It is helpful to elucidating the maize mitochondrial genome structure and mechanism of S-type CMS, and may give some valuable reference to the construction of other plant mitochondrial genome library.展开更多
In this paper,we consider throughput maximization in cognitive radio systems with proper power control.In particular,we incorporate location-awareness into the power control design and maximize the average throughput ...In this paper,we consider throughput maximization in cognitive radio systems with proper power control.In particular,we incorporate location-awareness into the power control design and maximize the average throughput of the cognitive system.As we shall show,the proposed approach effectively utilizes the“spatial opportunity”to maximize the system throughput,which clearly outperforms traditional power control methods.Further,the proposed approach still exhibits significant throughput gain even considering imperfect position information,with appropriate robust design modifications.展开更多
The conflict between scarcity of spectrum resources and low spectrum utilization motivates the concept of cognitive radio,which allows secondary unlicensed users to borrow temporally unused spectrum bands from primary...The conflict between scarcity of spectrum resources and low spectrum utilization motivates the concept of cognitive radio,which allows secondary unlicensed users to borrow temporally unused spectrum bands from primary licensed users.Spectrum sensing is one of the key functionalities that enable spectrum hole discovery and interference avoidance.As single user spectrum sensing may experience performance degradation in harsh wireless environment due to fading and shadowing,user cooperation is introduced to exploit spatial diversity for better sensing performance.However,local sensing results must be transmitted via a control channel.The advantage of cooperative sensing can be compromised by bandwidth limitation of the control channel.To overcome this,a benching cooperative sensing scheme is proposed in this paper.This scheme can reduce time overhead of sensing information exchange under a communication constraint.Analytical results of periodic sensing efficiency are then deduced while sensing parameters are optimized.Based on these,a recursive sensing algorithm exploiting prior channel state information is developed.Numerical results are presented to demonstrate the potential of our scheme.展开更多
基金supported by the National Natural Science Foundation of China(Nos.12174002,11874012,11874126,and 51771186)the Excellent Scientific Research and Innovation Team of Anhui Province(No.2022AH010003)+3 种基金the Key Research and Development Plan of Anhui Province(No.202104a05020059)the Innovation Project for the ReturnedOverseasScholarsofAnhuiProvince(No.2021LCX011)the University Synergy Innovation Program of Anhui Province(No.GXXT-2020-052)the Anhui Young Wanjiang Scholars Talent Project(No.Z010118167)。
文摘Random lasers are a type of lasers that lack typical resonator structures,offering benefits such as easy integration,low cost,and low spatial coherence.These features make them popular for speckle-free imaging and random number generation.However,due to their high threshold and phase instability,the production of picosecond random lasers has still been a challenge.In this work,we have developed three dyes incorporating polymer optical fibers doped with various scattering nanoparticles to produce short-pulsed random fiber lasers.Notably,stable picosecond random laser emission lasting600 ps is observed at a low pump energy of 50μJ,indicating the gain-switching mechanism.Population inversion and gain undergo an abrupt surge as the intensity of the continuously pumped light nears the threshold level.When the intensity of the continuously pumped light reaches a specific value,the number of inversion populations in the“scattering cavity”surpasses the threshold rapidly.Simulation results based on a model that considers power-dependent gain saturation confirmed the above phenomenon.This research helps expand the understanding of the dynamics behind random medium-stimulated emission in random lasers and opens up possibilities for mode locking in these systems.
基金supported by National Natural Science Foundation of China(72192804)and National Key Research Program(2018AAA0101000)+1 种基金supported by Natural Natural Science Foundation of China(72271016)Beijing Natural Science Foundation(Z220001)。
文摘There are two recognized classes of strategic-form symmetric games,both of which can be conveniently defined through the corresponding player symmetry groups.We investigate the basic properties of these groups and several related concepts.We generalize the notion of coveringness and adapt their results to characterize these player symmetry groups.We study the relationships between the coveringnesses of various symmetry groups.Our results demonstrate that these symmetry groups have rich mathematical structures that are of game theoretical and economic interests.
基金supported by the National Natural Science Foundation of China(U2243205 and 42101378)the Natural Science Foundation of Jiangsu Province(BK20210989)。
文摘Sediment in rivers plays an essential role in the river and watershed ecosystem.Recently,Dethier et al.[1]used an empirical model,which was developed using the data in America and Taiwan Province in China,to estimate suspended sediment concentration(SSC)and generate a long-term record of SSC and sediment fluxes in 414 major rivers worldwide since 1984.The authors concluded that the widespread decreases in river sediment fluxes in the North Hemisphere(NH)resulted from the dams,while the increases in river sediment fluxes in the South Hemisphere were possibly related to changes in land use.Regardless of the discussion on whether such an empirical model could be extrapolated to the global rivers for accurately retrieving SSC from Landsat imagery,the elucidation of the continuous declines in SSC in the NH rivers since1980s was incomplete.As Dethier et al.[1]demonstrated,the spatial and temporal variations in river sediment were regulated by climate change and human activities[2],including precipitation,land cover and land use,damming,and dredging activities[3-6].
文摘In order to isolate mitochondrial genes easily, we have developed a new method to construct S-type CMS maize mitochondrial gene library by means of embedding mitochondria and enzymatic digesting mitochondria in situ, preparing mtDNA by electrophoresis, digesting LMP agarose with β-agarase, using BAC vector and electroporation. About 2 500 white clones of Mo17 CMS-J mitochondrial gene library were obtained with the average size of 18.24 kb, ranging from 5 to 40 kb, 63.6% inserts came from mitochondrial genome and represented 48 × mitochondrial genome equivalents. All the probes had detected the positive clones in the gene library. It is helpful to elucidating the maize mitochondrial genome structure and mechanism of S-type CMS, and may give some valuable reference to the construction of other plant mitochondrial genome library.
基金The research is supported by National Natural Science Fundation of China under Grant NO. 10671108 and Province Natural Science Foundation of Shandong under Grant NO. Y2005A04.
基金This work was supported by the National Natural Science Foundation of China(Grant No.60832008)National Natural Science Foundation of China/Research Grants Council of Hong Kong(No.N-HKUST622/06).
文摘In this paper,we consider throughput maximization in cognitive radio systems with proper power control.In particular,we incorporate location-awareness into the power control design and maximize the average throughput of the cognitive system.As we shall show,the proposed approach effectively utilizes the“spatial opportunity”to maximize the system throughput,which clearly outperforms traditional power control methods.Further,the proposed approach still exhibits significant throughput gain even considering imperfect position information,with appropriate robust design modifications.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.60832008 and 60902001).
文摘The conflict between scarcity of spectrum resources and low spectrum utilization motivates the concept of cognitive radio,which allows secondary unlicensed users to borrow temporally unused spectrum bands from primary licensed users.Spectrum sensing is one of the key functionalities that enable spectrum hole discovery and interference avoidance.As single user spectrum sensing may experience performance degradation in harsh wireless environment due to fading and shadowing,user cooperation is introduced to exploit spatial diversity for better sensing performance.However,local sensing results must be transmitted via a control channel.The advantage of cooperative sensing can be compromised by bandwidth limitation of the control channel.To overcome this,a benching cooperative sensing scheme is proposed in this paper.This scheme can reduce time overhead of sensing information exchange under a communication constraint.Analytical results of periodic sensing efficiency are then deduced while sensing parameters are optimized.Based on these,a recursive sensing algorithm exploiting prior channel state information is developed.Numerical results are presented to demonstrate the potential of our scheme.
