The satellite orbital pursuit game focuses on studying spacecraft maneuvering strategies in space.Traditional numerical methods often face real-time inadequacies and adaptability limitations when dealing with highly n...The satellite orbital pursuit game focuses on studying spacecraft maneuvering strategies in space.Traditional numerical methods often face real-time inadequacies and adaptability limitations when dealing with highly nonlinear problems.With the advancement of Deep Reinforcement Learning(DRL)technology,continuous-time orbital control capabilities have significantly improved.Despite this,the existing DRL technologies still need adjustments in action delay and discretization structure to better adapt to practical application scenarios.Combining continuous learning and model planning demonstrates the adaptability of these methods in continuous-time decision problems.Additionally,to more effectively handle action delay issues,a new scheduled action execution technique has been developed.This technique optimizes action execution timing through real-time policy adjustments,thus adapting to the dynamic changes in the orbital environment.A Hierarchical Reinforcement Learning(HRL)strategy was also adopted to simplify the decision-making process for long-distance pursuit tasks by setting phased subgoals to gradually approach the target.The effectiveness of the proposed strategy in practical satellite pursuit scenarios has been verified through simulations of two different tasks.展开更多
Immunotherapy has brought unprecedented breakthroughs to advanced malignant tumors,yet the immune microenvironment shaped by the tumor stroma has often been underestimated in the traditional focus on the“immune check...Immunotherapy has brought unprecedented breakthroughs to advanced malignant tumors,yet the immune microenvironment shaped by the tumor stroma has often been underestimated in the traditional focus on the“immune checkpoint-T cell”axis.Collagen not only constitutes a mechanical barrier that distinguishes between the periphery and core of solid tumors but also systematically remodels the orientation of metabolism,vasculature,and immune cell phenotypic plasticity through its spatial density,fiber arrangement,and crosslinking patterns(F igure 1)[1,2].Abundant evidence suggests that over-accumulated types I and III collagen drive CD8+T cell exhaustion,NK cell functional inhibition,and tumor-associated macrophage polarization through ligand-receptor networks involving LAIR-1,DDR2,andβ1/β3 integrins[3-6].Mechanistically,collagen engagement of LAIR-1 delivers inhibitory signals in effector lymphocytes,promoting dysfunctional or exhausted states[7-9].In parallel,collagen-β1/β3 integrin signaling activates mechanotransduction pathways(e.g.,FAK/SRC),reducing T-cell motility and immune-tumor contact,while DDR2 activation supports matrix-remodeling programs that limit lymphocyte trafficking.展开更多
A sensitive label-free fluorescent aptasensing strategy for the detection of adenosine triphosphate（ATP）has been developed with a metallocyclodextrin, tris（bipyridine）ruthenium（Ⅱ） complex containing six cyclode...A sensitive label-free fluorescent aptasensing strategy for the detection of adenosine triphosphate（ATP）has been developed with a metallocyclodextrin, tris（bipyridine）ruthenium（Ⅱ） complex containing six cyclodextrin units（6CD-Ru）, which exhibited much stronger emission signal compared to the parent compound Ru（bpy）_3Cl_2. Furthermore, the emission spectrum showed that the ATP-aptamer（ss DNA）could increase the fluorescence intensity of 6CD-Ru dramatically, attributed to the interaction between aptamer and cyclodextrin, which could provide protection to the ruthenium core from the quenching of emission by oxygen in the solution. With the addition of ATP, the interaction between aptamer and cyclodextrins on 6CD-Ru was diminished, since the ATP/aptamer complex had the priority to be formed,leading to the corresponding reduction of fluorescence intensity, which could be utilized to detect ATP quantitatively. A linear relationship was displayed between the fluorescence and the logarithm of ATP concentrations in the range from 1 nmol/L to 1μmmol/L with the detection limit of 0.5 nmol/L（S/N = 3）.The proposed fluorescent aptasensing strategy exhibited high sensitivity and specificity, without any labeling or amplification procedures, and it could also be applied for the detection of many other aptamer-specific targets.展开更多
How to represent a human face pattern?While it is presented in a continuous way in human visual system,computers often store and process it in a discrete manner with 2D arrays of pixels.The authors attempt to learn a ...How to represent a human face pattern?While it is presented in a continuous way in human visual system,computers often store and process it in a discrete manner with 2D arrays of pixels.The authors attempt to learn a continuous surface representation for face image with explicit function.First,an explicit model(EmFace)for human face representation is pro-posed in the form of a finite sum of mathematical terms,where each term is an analytic function element.Further,to estimate the unknown parameters of EmFace,a novel neural network,EmNet,is designed with an encoder-decoder structure and trained from massive face images,where the encoder is defined by a deep convolutional neural network and the decoder is an explicit mathematical expression of EmFace.The authors demonstrate that our EmFace represents face image more accurate than the comparison method,with an average mean square error of 0.000888,0.000936,0.000953 on LFW,IARPA Janus Benchmark-B,and IJB-C datasets.Visualisation results show that,EmFace has a higher representation performance on faces with various expressions,postures,and other factors.Furthermore,EmFace achieves reasonable performance on several face image processing tasks,including face image restoration,denoising,and transformation.展开更多
The problem of collision avoidance for non-cooperative targets has received significant attention from researchers in recent years.Non-cooperative targets exhibit uncertain states and unpredictable behaviors,making co...The problem of collision avoidance for non-cooperative targets has received significant attention from researchers in recent years.Non-cooperative targets exhibit uncertain states and unpredictable behaviors,making collision avoidance significantly more challenging than that for space debris.Much existing research focuses on the continuous thrust model,whereas the impulsive maneuver model is more appropriate for long-duration and long-distance avoidance missions.Additionally,it is important to minimize the impact on the original mission while avoiding noncooperative targets.On the other hand,the existing avoidance algorithms are computationally complex and time-consuming especially with the limited computing capability of the on-board computer,posing challenges for practical engineering applications.To conquer these difficulties,this paper makes the following key contributions:(A)a turn-based(sequential decision-making)limited-area impulsive collision avoidance model considering the time delay of precision orbit determination is established for the first time;(B)a novel Selection Probability Learning Adaptive Search-depth Search Tree(SPL-ASST)algorithm is proposed for non-cooperative target avoidance,which improves the decision-making efficiency by introducing an adaptive-search-depth mechanism and a neural network into the traditional Monte Carlo Tree Search(MCTS).Numerical simulations confirm the effectiveness and efficiency of the proposed method.展开更多
A security issue with multi-sensor unmanned aerial vehicle(UAV)cyber physical systems(CPS)from the viewpoint of a false data injection(FDI)attacker is investigated in this paper.The FDI attacker can employ attacks on ...A security issue with multi-sensor unmanned aerial vehicle(UAV)cyber physical systems(CPS)from the viewpoint of a false data injection(FDI)attacker is investigated in this paper.The FDI attacker can employ attacks on feedback and feed-forward channels simultaneously with limited resource.The attacker aims at degrading the UAV CPS's estimation performance to the max while keeping stealthiness characterized by the Kullback-Leibler(K-L)divergence.The attacker is resource limited which can only attack part of sensors,and the attacked sensor as well as specific forms of attack signals at each instant should be considered by the attacker.Also,the sensor selection principle is investigated with respect to time invariant attack covariances.Additionally,the optimal switching attack strategies in regard to time variant attack covariances are modeled as a multi-agent Markov decision process(MDP)with hybrid discrete-continuous action space.Then,the multi-agent MDP is solved by utilizing the deep Multi-agent parameterized Q-networks(MAPQN)method.Ultimately,a quadrotor near hover system is used to validate the effectiveness of the results in the simulation section.展开更多
In recent years,the availability of space orbital resources has been declining,and the increasing frequency of spacecraft close approach events has heightened the urgency for enhanced space security measures.This pape...In recent years,the availability of space orbital resources has been declining,and the increasing frequency of spacecraft close approach events has heightened the urgency for enhanced space security measures.This paper establishes a comprehensive framework for intelligent orbital game technology in space,encompassing four core technologies:threat perception of noncooperative targets,intent recognition,situation assessment,and intelligent orbital game countermeasures.The concepts of multi-turn,multi-round and multi-match in space orbital games are defined,clarifying the core technological requirements for intelligent space orbital games and establishing a cohesive technological framework.Subsequently,the current status of research on these four core technologies is investigated.The challenges faced in the existing research are analyzed,and potential solutions for future studies are proposed.This paper aims to provide readers with a thorough understanding of the latest advancements in space intelligent orbital game technology.along with insights into the future directions and challenges in this field.展开更多
Understanding the ecological adaptation of tree species can not only reveal the evolutionary potential but also benefit biodiversity conservation under global climate change.Quercus is a keystone genus in Northern Hem...Understanding the ecological adaptation of tree species can not only reveal the evolutionary potential but also benefit biodiversity conservation under global climate change.Quercus is a keystone genus in Northern Hemisphere forests,and its wide distribution in diverse ecosystems and long evolutionary history make it an ideal model for studying the genomic basis of ecological adaptations.Here we used a newly sequenced genome of Quercus gilva,an evergreen oak species from East Asia,with 18 published Fagales genomes to determine how Fagaceae genomes have evolved,identify genomic footprints of ecological adaptability in oaks in general,as well as between evergreen and deciduous oaks.We found that oak species exhibited a higher degree of genomic conservation and stability,as indicated by the absence of large-scale chromosomal structural variations or additional whole-genome duplication events.In addition,we identified expansion and tandem repetitions within gene families that contribute to plant physical and chemical defense(e.g.,cuticle biosynthesis and oxidosqualene cyclase genes),which may represent the foundation for the ecological adaptation of oak species.Circadian rhythm and hormone-related genes may regulate the habits of evergreen and deciduous oaks.This study provides a comprehensive perspective on the ecological adaptations of tree species based on phylogenetic,genome evolutionary,and functional genomic analyses.展开更多
Defect engineering and interface engineering exhibit remarkable potential in the quest for efficient and stable bifunctional catalysts for the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).Herein,...Defect engineering and interface engineering exhibit remarkable potential in the quest for efficient and stable bifunctional catalysts for the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).Herein,we innovatively designed a Ni-MoO_(2)/NiMoO_(4-x) heterojunction electrocatalyst enriched with lattice defects using a novel thermal reduction strategy.For this catalyst,the strain effect induced by the lattice defects optimizes the electronic structure,while the heterogeneous interface significantly accelerates the electron transport efficiency,thereby substantially enhancing catalytic activity and pro-moting reaction kinetics.Using advanced spherical aberration-corrected transmission electron microscopy(AC-TEM)combined with geometric phase analysis(GPA)simulations,we directly visualized and con-firmed the presence of strain effects and heterostructures,which are pivotal factors in improving catalytic performance.In an alkaline seawater environment,the Ni-MoO_(2)/NiMoO_(4-x) catalyst exhibited exceptional performance with the HER overpotential as low as 27 mV and the OER overpotential of 216 mV at a cur-rent density of 10 mA cm^(-2).Furthermore,in a membrane electrode assembly(MEA)electrolyzer,the het-erojunction catalyst can drive a current density of 147 mA cm^(-2) at a voltage of only 1.82 V,and maintain stable operation for over 100 h without degradation.In-depth theoretical simulations and experimen-tal analyses revealed that the enriched Ni defect sites optimized the adsorption energy of hydrogen and oxygen intermediates,thereby boosting the catalytic efficiency for both HER and OER.This study not only pioneers a new approach to optimizing the performance of transition metal oxide catalysts but also pro-vides robust theoretical support and experimental foundations for the practical application of hydrogen production technology through electrolytic water splitting in the future.展开更多
This paper presents a tunable and polarization-insensitive wideband metamaterial absorber based on single-layer graphene.By comparing the simulated experimental data with theoretical derivations,it was found that the ...This paper presents a tunable and polarization-insensitive wideband metamaterial absorber based on single-layer graphene.By comparing the simulated experimental data with theoretical derivations,it was found that the absorbance of the material can be sustained above 90%in the frequency range of 2.78 to 7.14(4.36)THz,of which the absorption rate exceeds 99%in the frequency range of 4.1–4.54(0.44)THz,and remarkably,perfect absorption is achieved at4.32 THz.In the range of 2.78–7.14 THz,the average absorption rate is 96.1%,by adjusting the physical size of the graphene layer pattern,we can modify the working band gap of the absorber.By applying a voltage to modulate the Fermi level of graphene,we can increase the absorption bandwidth.When the chemical potential is 1.0 e V,at the bandwidth of 4.36 THz,its absorption rate exceeds 90%.The working principle of absorbing materials was deeply explored using the principles of electromagnetic field distribution and impedance adaptation.Through detailed analysis of different polarization states and incident angles,we found that the absorber is not sensitive to polarization due to its symmetrical structure,and found that it exhibits low sensitivity at incidence angles.In addition,after comparative analysis,significant differences were observed in the absorption efficiency of the absorber under various relaxation time conditions,and the obtained data were elaborated in detail using the carrier mechanism of plasma vibration.We found that in addition to obtaining an almost perfect absorber with wide band by adjusting the parameters,it is also feasible to obtain an approximately narrow band absorber by changing the relaxation time without having to remanufacture the structure.The absorber offers several advantages,including tunability,a wide absorption band,a high absorption rate,polarization insensitivity,and a simple structure.Therefore,this absorber exhibits great potential for absorption,monitoring,and sensing in the terahertz band.展开更多
基金supported by the National Natural Science Foundation of China(No.12202281)the Shanghai Natural Science Foundation,China(No.23ZR1461800)the Research Initiation Fund of Northwestern Polytechnical University,China(No.G2024KY05103)。
文摘The satellite orbital pursuit game focuses on studying spacecraft maneuvering strategies in space.Traditional numerical methods often face real-time inadequacies and adaptability limitations when dealing with highly nonlinear problems.With the advancement of Deep Reinforcement Learning(DRL)technology,continuous-time orbital control capabilities have significantly improved.Despite this,the existing DRL technologies still need adjustments in action delay and discretization structure to better adapt to practical application scenarios.Combining continuous learning and model planning demonstrates the adaptability of these methods in continuous-time decision problems.Additionally,to more effectively handle action delay issues,a new scheduled action execution technique has been developed.This technique optimizes action execution timing through real-time policy adjustments,thus adapting to the dynamic changes in the orbital environment.A Hierarchical Reinforcement Learning(HRL)strategy was also adopted to simplify the decision-making process for long-distance pursuit tasks by setting phased subgoals to gradually approach the target.The effectiveness of the proposed strategy in practical satellite pursuit scenarios has been verified through simulations of two different tasks.
基金supported by the National Natural Science Foundation of China(82472842 and 82473350)and Wuxi Double-Hundred Talent Fund Project(BJ2023075).
文摘Immunotherapy has brought unprecedented breakthroughs to advanced malignant tumors,yet the immune microenvironment shaped by the tumor stroma has often been underestimated in the traditional focus on the“immune checkpoint-T cell”axis.Collagen not only constitutes a mechanical barrier that distinguishes between the periphery and core of solid tumors but also systematically remodels the orientation of metabolism,vasculature,and immune cell phenotypic plasticity through its spatial density,fiber arrangement,and crosslinking patterns(F igure 1)[1,2].Abundant evidence suggests that over-accumulated types I and III collagen drive CD8+T cell exhaustion,NK cell functional inhibition,and tumor-associated macrophage polarization through ligand-receptor networks involving LAIR-1,DDR2,andβ1/β3 integrins[3-6].Mechanistically,collagen engagement of LAIR-1 delivers inhibitory signals in effector lymphocytes,promoting dysfunctional or exhausted states[7-9].In parallel,collagen-β1/β3 integrin signaling activates mechanotransduction pathways(e.g.,FAK/SRC),reducing T-cell motility and immune-tumor contact,while DDR2 activation supports matrix-remodeling programs that limit lymphocyte trafficking.
基金financially supported by the National Natural Science Foundation of China(Nos.21275054,21405049,31300819)
文摘A sensitive label-free fluorescent aptasensing strategy for the detection of adenosine triphosphate（ATP）has been developed with a metallocyclodextrin, tris（bipyridine）ruthenium（Ⅱ） complex containing six cyclodextrin units（6CD-Ru）, which exhibited much stronger emission signal compared to the parent compound Ru（bpy）_3Cl_2. Furthermore, the emission spectrum showed that the ATP-aptamer（ss DNA）could increase the fluorescence intensity of 6CD-Ru dramatically, attributed to the interaction between aptamer and cyclodextrin, which could provide protection to the ruthenium core from the quenching of emission by oxygen in the solution. With the addition of ATP, the interaction between aptamer and cyclodextrins on 6CD-Ru was diminished, since the ATP/aptamer complex had the priority to be formed,leading to the corresponding reduction of fluorescence intensity, which could be utilized to detect ATP quantitatively. A linear relationship was displayed between the fluorescence and the logarithm of ATP concentrations in the range from 1 nmol/L to 1μmmol/L with the detection limit of 0.5 nmol/L（S/N = 3）.The proposed fluorescent aptasensing strategy exhibited high sensitivity and specificity, without any labeling or amplification procedures, and it could also be applied for the detection of many other aptamer-specific targets.
基金National Natural Science Foundation of China,Grant/Award Number:92370117。
文摘How to represent a human face pattern?While it is presented in a continuous way in human visual system,computers often store and process it in a discrete manner with 2D arrays of pixels.The authors attempt to learn a continuous surface representation for face image with explicit function.First,an explicit model(EmFace)for human face representation is pro-posed in the form of a finite sum of mathematical terms,where each term is an analytic function element.Further,to estimate the unknown parameters of EmFace,a novel neural network,EmNet,is designed with an encoder-decoder structure and trained from massive face images,where the encoder is defined by a deep convolutional neural network and the decoder is an explicit mathematical expression of EmFace.The authors demonstrate that our EmFace represents face image more accurate than the comparison method,with an average mean square error of 0.000888,0.000936,0.000953 on LFW,IARPA Janus Benchmark-B,and IJB-C datasets.Visualisation results show that,EmFace has a higher representation performance on faces with various expressions,postures,and other factors.Furthermore,EmFace achieves reasonable performance on several face image processing tasks,including face image restoration,denoising,and transformation.
基金co-supported by the Foundation of Shanghai Astronautics Science and Technology Innovation,China(No.SAST2022-114)the National Natural Science Foundation of China(No.62303378),the National Natural Science Foundation of China(Nos.124B2031,12202281)the Foundation of China National Key Laboratory of Science and Technology on Test Physics&Numerical Mathematics,China(No.08-YY-2023-R11)。
文摘The problem of collision avoidance for non-cooperative targets has received significant attention from researchers in recent years.Non-cooperative targets exhibit uncertain states and unpredictable behaviors,making collision avoidance significantly more challenging than that for space debris.Much existing research focuses on the continuous thrust model,whereas the impulsive maneuver model is more appropriate for long-duration and long-distance avoidance missions.Additionally,it is important to minimize the impact on the original mission while avoiding noncooperative targets.On the other hand,the existing avoidance algorithms are computationally complex and time-consuming especially with the limited computing capability of the on-board computer,posing challenges for practical engineering applications.To conquer these difficulties,this paper makes the following key contributions:(A)a turn-based(sequential decision-making)limited-area impulsive collision avoidance model considering the time delay of precision orbit determination is established for the first time;(B)a novel Selection Probability Learning Adaptive Search-depth Search Tree(SPL-ASST)algorithm is proposed for non-cooperative target avoidance,which improves the decision-making efficiency by introducing an adaptive-search-depth mechanism and a neural network into the traditional Monte Carlo Tree Search(MCTS).Numerical simulations confirm the effectiveness and efficiency of the proposed method.
文摘A security issue with multi-sensor unmanned aerial vehicle(UAV)cyber physical systems(CPS)from the viewpoint of a false data injection(FDI)attacker is investigated in this paper.The FDI attacker can employ attacks on feedback and feed-forward channels simultaneously with limited resource.The attacker aims at degrading the UAV CPS's estimation performance to the max while keeping stealthiness characterized by the Kullback-Leibler(K-L)divergence.The attacker is resource limited which can only attack part of sensors,and the attacked sensor as well as specific forms of attack signals at each instant should be considered by the attacker.Also,the sensor selection principle is investigated with respect to time invariant attack covariances.Additionally,the optimal switching attack strategies in regard to time variant attack covariances are modeled as a multi-agent Markov decision process(MDP)with hybrid discrete-continuous action space.Then,the multi-agent MDP is solved by utilizing the deep Multi-agent parameterized Q-networks(MAPQN)method.Ultimately,a quadrotor near hover system is used to validate the effectiveness of the results in the simulation section.
基金co-supported by the National Natural Science Foundation of China(Nos.124B2031,12202281)the Shanghai Natural Science Foundation,China(No.23ZR1461800)the Northwestern Polytechnical University Scientific Research Initiation Foundation,China(No.G2024KY05103).
文摘In recent years,the availability of space orbital resources has been declining,and the increasing frequency of spacecraft close approach events has heightened the urgency for enhanced space security measures.This paper establishes a comprehensive framework for intelligent orbital game technology in space,encompassing four core technologies:threat perception of noncooperative targets,intent recognition,situation assessment,and intelligent orbital game countermeasures.The concepts of multi-turn,multi-round and multi-match in space orbital games are defined,clarifying the core technological requirements for intelligent space orbital games and establishing a cohesive technological framework.Subsequently,the current status of research on these four core technologies is investigated.The challenges faced in the existing research are analyzed,and potential solutions for future studies are proposed.This paper aims to provide readers with a thorough understanding of the latest advancements in space intelligent orbital game technology.along with insights into the future directions and challenges in this field.
基金supported by the National Natural Science Foundation of China(No.31901217)the Special Fund for Scientific Research of Shanghai Landscaping and City Appearance Administrative Bureau(grant numbers G192422,G242414,and G242416).
文摘Understanding the ecological adaptation of tree species can not only reveal the evolutionary potential but also benefit biodiversity conservation under global climate change.Quercus is a keystone genus in Northern Hemisphere forests,and its wide distribution in diverse ecosystems and long evolutionary history make it an ideal model for studying the genomic basis of ecological adaptations.Here we used a newly sequenced genome of Quercus gilva,an evergreen oak species from East Asia,with 18 published Fagales genomes to determine how Fagaceae genomes have evolved,identify genomic footprints of ecological adaptability in oaks in general,as well as between evergreen and deciduous oaks.We found that oak species exhibited a higher degree of genomic conservation and stability,as indicated by the absence of large-scale chromosomal structural variations or additional whole-genome duplication events.In addition,we identified expansion and tandem repetitions within gene families that contribute to plant physical and chemical defense(e.g.,cuticle biosynthesis and oxidosqualene cyclase genes),which may represent the foundation for the ecological adaptation of oak species.Circadian rhythm and hormone-related genes may regulate the habits of evergreen and deciduous oaks.This study provides a comprehensive perspective on the ecological adaptations of tree species based on phylogenetic,genome evolutionary,and functional genomic analyses.
基金supported by the National Natural Science Foundation of China(Nos.22103045 and 52273077)the State Key Laboratory of Bio-Fibers and Eco-Textiles,Qingdao University(Nos.ZDKT202108,RZ2000003334,and G2RC202022).
文摘Defect engineering and interface engineering exhibit remarkable potential in the quest for efficient and stable bifunctional catalysts for the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).Herein,we innovatively designed a Ni-MoO_(2)/NiMoO_(4-x) heterojunction electrocatalyst enriched with lattice defects using a novel thermal reduction strategy.For this catalyst,the strain effect induced by the lattice defects optimizes the electronic structure,while the heterogeneous interface significantly accelerates the electron transport efficiency,thereby substantially enhancing catalytic activity and pro-moting reaction kinetics.Using advanced spherical aberration-corrected transmission electron microscopy(AC-TEM)combined with geometric phase analysis(GPA)simulations,we directly visualized and con-firmed the presence of strain effects and heterostructures,which are pivotal factors in improving catalytic performance.In an alkaline seawater environment,the Ni-MoO_(2)/NiMoO_(4-x) catalyst exhibited exceptional performance with the HER overpotential as low as 27 mV and the OER overpotential of 216 mV at a cur-rent density of 10 mA cm^(-2).Furthermore,in a membrane electrode assembly(MEA)electrolyzer,the het-erojunction catalyst can drive a current density of 147 mA cm^(-2) at a voltage of only 1.82 V,and maintain stable operation for over 100 h without degradation.In-depth theoretical simulations and experimen-tal analyses revealed that the enriched Ni defect sites optimized the adsorption energy of hydrogen and oxygen intermediates,thereby boosting the catalytic efficiency for both HER and OER.This study not only pioneers a new approach to optimizing the performance of transition metal oxide catalysts but also pro-vides robust theoretical support and experimental foundations for the practical application of hydrogen production technology through electrolytic water splitting in the future.
基金the support form the National Natural Science Foundation of China(Grant Nos.51606158,11604311,12074151)the Funded by the Guangxi Science and Technology Base and Talent Special Project(Grant No.AD21075009)+3 种基金the funded by the Sichuan Science and Technology Program(Grant No.2021JDRC0022)the Open Fund of the Key Laboratory for Metallurgical Equipment and Control Technology of Ministry of Education in Wuhan University of Science and Technology,China(Grant Nos.MECOF2022B01MECOF2023B04)the Project supported by Guangxi Key Laboratory of Precision Navigation Technology and Application,Guilin University of Electronic Technology(Grant No.DH202321)。
文摘This paper presents a tunable and polarization-insensitive wideband metamaterial absorber based on single-layer graphene.By comparing the simulated experimental data with theoretical derivations,it was found that the absorbance of the material can be sustained above 90%in the frequency range of 2.78 to 7.14(4.36)THz,of which the absorption rate exceeds 99%in the frequency range of 4.1–4.54(0.44)THz,and remarkably,perfect absorption is achieved at4.32 THz.In the range of 2.78–7.14 THz,the average absorption rate is 96.1%,by adjusting the physical size of the graphene layer pattern,we can modify the working band gap of the absorber.By applying a voltage to modulate the Fermi level of graphene,we can increase the absorption bandwidth.When the chemical potential is 1.0 e V,at the bandwidth of 4.36 THz,its absorption rate exceeds 90%.The working principle of absorbing materials was deeply explored using the principles of electromagnetic field distribution and impedance adaptation.Through detailed analysis of different polarization states and incident angles,we found that the absorber is not sensitive to polarization due to its symmetrical structure,and found that it exhibits low sensitivity at incidence angles.In addition,after comparative analysis,significant differences were observed in the absorption efficiency of the absorber under various relaxation time conditions,and the obtained data were elaborated in detail using the carrier mechanism of plasma vibration.We found that in addition to obtaining an almost perfect absorber with wide band by adjusting the parameters,it is also feasible to obtain an approximately narrow band absorber by changing the relaxation time without having to remanufacture the structure.The absorber offers several advantages,including tunability,a wide absorption band,a high absorption rate,polarization insensitivity,and a simple structure.Therefore,this absorber exhibits great potential for absorption,monitoring,and sensing in the terahertz band.
文摘路由与波长分配是下一代光网络的需要解决的核心问题之一。本文采用智能蚁群算法,研究了卫星光网络的路由与波长分配问题,为通信请求寻找最优的数据传输光路径。基于请求区域受限策略(Restricted Request Area,RRA)和链路波长负载平衡策略,建立了考虑传输延迟和波长连续性约束的双主星分布式星群节点结构光网络系统模型。利用智能蚁群路由和波长分配(Smart Ant Colony Routing And Wavelength Assignment,SAC-RWA)算法求解系统模型,以找到具有稀疏波长转换的卫星光网络中最小成本波长路径。所提出的算法允许单个蚂蚁同时完成路由和波长分配,仿真结果表明,RRA能够明显改进卫星光网络的性能,以略微增加拥塞率的代价显著降低了计算复杂度。
