The evolution of polarization singularities supported in a one-dimensional periodic plasmonic system is studied.The lateral inversion symmetry of the system,which breaks the in-plane inversion symmetry and up-down mir...The evolution of polarization singularities supported in a one-dimensional periodic plasmonic system is studied.The lateral inversion symmetry of the system,which breaks the in-plane inversion symmetry and up-down mirror symmetry simultaneously,yields abundant polarization states.A complete evolution process with geometry for the polarization states is traced.In the evolution,circularly polarized points(C points)can stem from 3 different processes.In addition to the previously reported processes occurring in an isolated band,a new type of C point appearing in two bands simultaneously due to the avoided band crossing,is observed.Unlike the dielectric system with a similar structure which only supports at-Γbound states in the continuum(BICs),accidental BICs off theΓpoint are realized in this plasmonic system.This work provides a new scheme of polarization manipulation for the plasmonic systems.展开更多
The metasurface possesses great potential in a 3D holographic display due to its powerful ability to manipulate optical fields,ultracompact structure,and extraordinary information capacity.However,the in-plane and int...The metasurface possesses great potential in a 3D holographic display due to its powerful ability to manipulate optical fields,ultracompact structure,and extraordinary information capacity.However,the in-plane and interplane crosstalk caused by the coupling between the meta-atoms of the current 3D holographic metasurface limits the quality of the reconstructed image,which has become a significant obstacle to high-performance 3D display applications.Additionally,the interleaved or multilayer design strategy of metasurfaces increases the complexity of structural design and manufacturing,facing challenges in meeting the requirements for miniaturization and low cost-effectiveness.Here,we propose a strategy for a free-space 3D multiplane color holographic multiplex display based on a single-cell metasurface.By utilizing a modified holographic optimization strategy,multiple holographic information is encoded into three mutually independent bases of incident photons and integrated into a metasurface,thereby creating high-quality 3D vectorial metaholography with minimal crosstalk across the visible spectrum.展开更多
The environment of low-altitude urban airspace is complex and variable due to numerous obstacles,non-cooperative aircraft,and birds.Unmanned Aerial Vehicles(UAVs)leveraging environmental information to achieve three-d...The environment of low-altitude urban airspace is complex and variable due to numerous obstacles,non-cooperative aircraft,and birds.Unmanned Aerial Vehicles(UAVs)leveraging environmental information to achieve three-dimension collision-free trajectory planning is the prerequisite to ensure airspace security.However,the timely information of surrounding situation is difficult to acquire by UAVs,which further brings security risks.As a mature technology leveraged in traditional civil aviation,the Automatic Dependent Surveillance-Broadcast(ADS-B)realizes continuous surveillance of the information of aircraft.Consequently,we leverage ADS-B for surveillance and information broadcasting,and divide the aerial airspace into multiple sub-airspaces to improve flight safety in UAV trajectory planning.In detail,we propose the secure Sub-airSpaces Planning(SSP)algorithm and Particle Swarm Optimization Rapidly-exploring Random Trees(PSO-RRT)algorithm for the UAV trajectory planning in law-altitude airspace.The performance of the proposed algorithm is verified by simulations and the results show that SSP reduces both the maximum number of UAVs in the sub-airspace and the length of the trajectory,and PSO-RRT reduces the cost of UAV trajectory in the sub-airspace.展开更多
Chirality is one of the important phenomena at the vicinity of exceptional point(EP). The conventional understanding is that the chirality is determined by asymmetrical scattering efficiency(?), which reaches to zero ...Chirality is one of the important phenomena at the vicinity of exceptional point(EP). The conventional understanding is that the chirality is determined by asymmetrical scattering efficiency(?), which reaches to zero only when the resonance approaches EP. Here we study the possibility to enhance the chirality in open systems with a more robust mechanism. By combining chirality with avoided resonance crossing, we show that the chirality and ? can be dramatically modified. Taking a spiral shaped annular cavity as an example, we show that the chirality of optical resonances can be significantly improved when two sets of chiral states approach each other. The imbalance between counterclockwise(CCW) components and clockwise(CW) components has been enhanced by more than an order of magnitude. Our research provides a new route to tailor and control the chirality in open systems.展开更多
mong the many forms of renewable energy generation, wind power is the most mature. However, the method used to assess the economic value of large grid connected wind farms still needs further study. At present the tra...mong the many forms of renewable energy generation, wind power is the most mature. However, the method used to assess the economic value of large grid connected wind farms still needs further study. At present the traditional method of project economic assessment as widely used in China isolates the wind farm from the whole power system and ignores the influence of reliability on the cost of wind generation; therefore, the evaluation results can not reflect the true economic value of wind power generation. After reviewing the many assessment methods used at home and abroad, this paper uses the Avoided Cost Method as theoretical basis to establish an economic evaluation model for large wind farms including the characteristics of other conventional forms of power generation like thermal power as well as the system load. The generating reliability is also combined into the economic evaluation. The model is used to evaluate China's largest wind farm, Dabancheng Wind Farm in Xinjiang.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
Aiming to address the Unmanned Aerial Vehicle(UAV) formation collision avoidance problem in Three-Dimensional(3-D) low-altitude environments where dense various obstacles exist, a fluid-based path planning framework n...Aiming to address the Unmanned Aerial Vehicle(UAV) formation collision avoidance problem in Three-Dimensional(3-D) low-altitude environments where dense various obstacles exist, a fluid-based path planning framework named the Formation Interfered Fluid Dynamical System(FIFDS) with Moderate Evasive Maneuver Strategy(MEMS) is proposed in this study.First, the UAV formation collision avoidance problem including quantifiable performance indexes is formulated. Second, inspired by the phenomenon of fluids continuously flowing while bypassing objects, the FIFDS for multiple UAVs is presented, which contains a Parallel Streamline Tracking(PST) method for formation keeping and the traditional IFDS for collision avoidance. Third, to rationally balance flight safety and collision avoidance cost, MEMS is proposed to generate moderate evasive maneuvers that match up with collision risks. Comprehensively containing the time and distance safety information, the 3-D dynamic collision regions are modeled for collision prediction. Then, the moderate evasive maneuver principle is refined, which provides criterions of the maneuver amplitude and direction. On this basis, an analytical parameter mapping mechanism is designed to online optimize IFDS parameters. Finally, the performance of the proposed method is validated by comparative simulation results and real flight experiments using fixed-wing UAVs.展开更多
Advertising avoidance is resistance to advertising intrusion.This issue has been the subject of much academic research in recent years.To guide scholars to better carry out relevant research and promote enterprises to...Advertising avoidance is resistance to advertising intrusion.This issue has been the subject of much academic research in recent years.To guide scholars to better carry out relevant research and promote enterprises to better implement advertising activities,this study intends to summarize the relevant research on advertising avoidance in recent years.The specific method is to use the core literature meta-analysis method to identify,filter,and screen relevant literature published in core journals from 1997 to 2020 with the keywords advertising avoidance and advertising resistance.We review the collected articles from the following perspectives:the definition and classification,external stimulating factors,internal perception factors,and moderating factors of advertising avoidance.On this basis,the SOMR model of advertising avoidance is constructed according to the SOR model.Finally,some prospects for future related research are presented.展开更多
This study aims to systematically review the various factors influencing corporate tax avoidance.Tax avoidance refers to legal strategies used to minimize tax liabilities and has become a critical issue in accounting ...This study aims to systematically review the various factors influencing corporate tax avoidance.Tax avoidance refers to legal strategies used to minimize tax liabilities and has become a critical issue in accounting and corporate governance.The study examines key determinants of tax avoidance,including firm characteristics(such as size,leverage,and multinational scale),managerial attributes,executive compensation,ownership structure,corporate social responsibility(CSR)performance,as well as the impact of regulations and legal reforms.The review findings highlight that the motivations behind tax avoidance are multifaceted,driven by the interaction of economic incentives,organizational ethics,external pressures,and public policies.Moreover,strict regulatory environments and strong CSR practices can mitigate tax avoidance behaviors,although their effectiveness is often contingent upon a firm’s cultural and political context.This study offers a comprehensive mapping of the current literature and recommends future research that integrates additional variables and broader time spans to enhance the understanding of tax avoidance behavior across different national contexts.展开更多
As the problem of surface garbage pollution becomes more serious,it is necessary to improve the efficiency of garbage inspection and picking rather than traditional manual methods.Due to lightness,Unmanned Aerial Vehi...As the problem of surface garbage pollution becomes more serious,it is necessary to improve the efficiency of garbage inspection and picking rather than traditional manual methods.Due to lightness,Unmanned Aerial Vehicles(UAVs)can traverse the entire water surface in a short time through their flight field of view.In addition,Unmanned Surface Vessels(USVs)can provide battery replacement and pick up garbage.In this paper,we innovatively establish a system framework for the collaboration between UAV and USVs,and develop an automatic water cleaning strategy.First,on the basis of the partition principle,we propose a collaborative coverage path algorithm based on UAV off-site takeoff and landing to achieve global inspection.Second,we design a task scheduling and assignment algorithm for USVs to balance the garbage loads based on the particle swarm optimization algorithm.Finally,based on the swarm intelligence algorithm,we also design an autonomous obstacle avoidance path planning algorithm for USVs to realize autonomous navigation and collaborative cleaning.The system can simultaneously perform inspection and clearance tasks under certain constraints.The simulation results show that the proposed algorithms have higher generality and flexibility while effectively improving computational efficiency and reducing actual cleaning costs compared with other schemes.展开更多
Multiple quadrotors target encirclement is widely used in the intelligent field,as it can effectively monitor and control target behavior.However,it faces the danger of collision,as well as difficulties in localizatio...Multiple quadrotors target encirclement is widely used in the intelligent field,as it can effectively monitor and control target behavior.However,it faces the danger of collision,as well as difficulties in localization and tracking.Therefore,we propose a complete target encirclement method.Firstly,based on Hooke's law,a collision avoidance controller is designed to maintain a safe flying distance among quadrotors.Then,based on the consensus theory,a formation tracking controller is designed to meet the requirements of formation transformation and encirclement tasks,and a stability proof based on Lyapunov was provided.Besides,the target detection is designed based on YOLOv5s,and the target location model is constructed based on the principle of pinhole projection and triangle similarity.Finally,we conducted experiments on the built platform,with 3 reconnaissance quadrotors detecting and localization 3 target vehicles and 7 hunter quadrotors tracking them.The results show that the minimum average error for localization targets with reconnaissance quadrotors can reach 0.1354 m,while the minimum average error for tracking with hunter quadrotors is only 0.2960 m.No quadrotors collision occurred in the whole formation transformation and tracking experiment.In addition,compared with the advanced methods,the proposed method has better performance.展开更多
A set of permutations is called sign-balanced if the set contains the same number of even permutations as odd permutations.Let S_(n)(σ_(1),σ_(2),...,σ_(r))denote the set of permutations in the symmetric group S_(n)...A set of permutations is called sign-balanced if the set contains the same number of even permutations as odd permutations.Let S_(n)(σ_(1),σ_(2),...,σ_(r))denote the set of permutations in the symmetric group S_(n)which avoid patternsσ_(1),σ_(2),...,σ_(r).The aim of this paper is to investigate when,for certain patternsσ_(1),σ_(2),...,σ_(r),S_(n)(σ_(1),σ_(2),...,σ_(r))is sign-balanced for every integer n>1.We prove that for any{σ_(1),σ_(2),...,σ_(r)}?S_3,if{σ_(1),σ_(2),...,σ_(r)}is sign-balanced except for{132,213,231,312},then S_(n)(σ_(1),σ_(2),...,σ_(r))is sign-balanced for every integer n>1.In addition,we give some results in the case of avoiding some patterns of length 4.展开更多
Global warming leads to snow cover loss in the alpine ecosystem,exposing seeds to extreme diurnal temperature fluctuations during the growing season.The risk of freezing increases as seeds have increased moisture cont...Global warming leads to snow cover loss in the alpine ecosystem,exposing seeds to extreme diurnal temperature fluctuations during the growing season.The risk of freezing increases as seeds have increased moisture content.Studying the survival mechanisms of seeds at low temperatures can help analyze changes in alpine meadow populations and target conservation efforts.Here,we used three species of Poaceae as a model to understand freezing stress.Fully imbibed Elymus dahuricus,Festuca elata,and Lolium multiflorum seeds were subjected to programmed cooling at fast and slow rates(-1.0/0.05℃/min)and then assessed for survival.Differential Scanning Calorimetry was used to analyze thermal transitions during cooling.HE-stained paraffin sections and a Transmission Electron Microscope were employed to observe internal morphology and ultrastructural changes.E.dahuricus seeds exhibited greater tolerance to low temperatures than those of the other two species,with an LT_(50)of approximately-20℃for both cooling rates and maintained relatively intact ultrastructure.The observed the low-temperature exotherm(LTE)correlated with seed survival,with viability decreasing extensively below LTE.Fast cooling caused fewer changes to seed morphology and ultrastructure than slow cooling,suggesting that the primary survival mechanism during fast cooling is freezing avoidance through supercooling.Seeds exhibited greater freeze tolerance under slow than fast cooling,primarily by migrating intracellular water to extracellular spaces where it froze,causing considerable damage to cell ultrastructure and forming apparent cavities in some seeds.展开更多
Emergency evacuation involves rapid transfer of individuals from hazardous areas,where limited time and space can lead to collisions.Although the collision behavior of evacuees has been studied previously,there is a l...Emergency evacuation involves rapid transfer of individuals from hazardous areas,where limited time and space can lead to collisions.Although the collision behavior of evacuees has been studied previously,there is a lack of systematic summaries.This study used the CiteSpace visualization software to analyze keywords in the evacuation collision literature.Based on the frequency of keyword occurrence,we determined the research trend;classified the keywords;and analyzed and summarized their influencing factors,behavioral characteristics,and research methods.Clearly,the evacuation environment and emergency guidance directly affect individual behavior and emotions,mainly affecting gait adjustment and decisionmaking processes,which in turn determine evacuation efficiency and collision risk.In the future,emphasis should be placed on post-collision psychological activities,coping strategies,and the application of virtual and mixed reality technologies to observe the interaction between individuals and the environment and to strengthen evacuation research.展开更多
The Titanic sunk 113 years ago on April 14-15,after hitting an iceberg,with human error likely causing the ship to wander into those dangerous waters.Today,autonomous systems built on AI can help ships avoid such acci...The Titanic sunk 113 years ago on April 14-15,after hitting an iceberg,with human error likely causing the ship to wander into those dangerous waters.Today,autonomous systems built on AI can help ships avoid such accidents.But could such a system explain to the captain why it was controlling the ship in a certain way?展开更多
Autonomous trucks have the potential to enhance both safety and convenience in intelligent transportation.However,their maximum speed and ability to navigate a variety of driving conditions,particularly uneven roads,a...Autonomous trucks have the potential to enhance both safety and convenience in intelligent transportation.However,their maximum speed and ability to navigate a variety of driving conditions,particularly uneven roads,are limited by a high center of gravity,which increases the risk of rollover.Road bulges,sinkholes,and unexpected debris all present additional challenges for autonomous trucks’operational design,which current perception and decisionmaking algorithms often overlook.To mitigate rollover risks and improve adaptability to damaged roads,this paper presents a novel Road Obstacle-Involved Trajectory Planner(ROITP).The planner categorizes road obstacles using a learning-based algorithm.A discrete optimization algorithm selects a multi-objective optimal trajectory while taking into account constraints and objective functions derived from truck dynamics.Validation across various scenarios on a hardware-in-loop platform demonstrates that the proposed planner is effective and feasible for real-time implementation.展开更多
This paper presents a quadcopter system for naviga-tion in outdoor urban environments.The main contributions include the hardware design,the establishment of global occu-pancy grid maps based on millimeter-wave radars...This paper presents a quadcopter system for naviga-tion in outdoor urban environments.The main contributions include the hardware design,the establishment of global occu-pancy grid maps based on millimeter-wave radars,the trajec-tory planning scheme based on optimal virtual tube methods,and the controller structure based on dynamics.The proposed system focuses on utilizing a compact and lightweight quadro-tor with sensors to achieve navigation that conforms to the direction of urban roads with high computational efficiency and safety.Our work is an application of millimeter-wave radars and virtual tube planning for obstacle avoidance in navigation.The validness and effectiveness of the proposed system are verified by experiments.展开更多
Objectives:Positive family functioning(FF)is critical for adolescent development,yet only a few studies have examined this developmental trajectory pathway.This study aimed to identify different types of FF developmen...Objectives:Positive family functioning(FF)is critical for adolescent development,yet only a few studies have examined this developmental trajectory pathway.This study aimed to identify different types of FF development trajectories during junior high school students,investigate their influence on social avoidance(SA),and further examine the mediating role of preference for solitude(PS)between them.Methods:A three-wave longitudinal study was used with six-month intervals.Questionnaire data were collected from 436 junior high school students in Jiangxi Province,China.Participants ranged in age from 11 to 14 years old(Mean=12.89 years,SD=1.08;50.2%male).Results:Four heterogeneous types of FF trajectories were identified:(1)a high and increasing group(14.7%);(2)a consistently high group(36.24%);(3)a consistently moderate group(45.86%);and(4)a rapid growth group(3.2%).The developmental trajectories of FF among junior high students significantly varied in their levels of SA(F(3,432)=32.03,p<0.001).Compared to the high and increasing groups,the consistently high,consistently medium,and rapid growth groups exhibited higher levels of SA.PS mediated the association between the developmental trajectory of FF and SA.Conclusion:There was a close relationship between the developmental trajectory of FF and SA.Interventions focusing on family system optimization and solitary preference management could effectively mitigate SA behaviors.These findings are important for promoting healthy socialization in adolescents.展开更多
Throughout the lifespan,an animal can encounter predators frequently,thus the ability to avoid attacks from predators is crucial for its survival.The chances of evading danger can be greatly improved if the animal can...Throughout the lifespan,an animal can encounter predators frequently,thus the ability to avoid attacks from predators is crucial for its survival.The chances of evading danger can be greatly improved if the animal can respond immediately to the threat.Therefore,when an animal detects a threat through its visual system,it must quickly direct its gaze and attention toward the source of danger,assess the threat level,and take appropriate action.展开更多
Advancements in artificial intelligence and big data technologies have led to the gradual emergence of intelligent ships,which are expected to dominate the future of maritime transportation.Supporting the navigation o...Advancements in artificial intelligence and big data technologies have led to the gradual emergence of intelligent ships,which are expected to dominate the future of maritime transportation.Supporting the navigation of intelligent ships,route planning technologies have developed many route planning algorithms that prioritize economy and safety.This paper conducts an in-depth study of algorithm efficiency for a route planning problem,proposing an intelligent ship route planning algorithm based on the adaptive step size Informed-RRT^(*).This algorithm can quickly plan a short route according to automatic obstacle avoidance and is suitable for planning the routes of intelligent ships.Results show that the adaptive step size Informed-RRT^(*) algorithm can shorten the optimal route length by approximately 13.05%while ensuring the running time of the planning algorithm and avoiding approximately 23.64%of redundant sampling nodes.The improved algorithm effectively circumvents unnecessary calculations and reduces a large amount of redundant sampling data,thus improving the efficiency of route planning.In a complex water environment,the unique adaptive step size mechanism enables this algorithm to prevent restricted search tree expansion,showing strong search ability and robustness,which is of practical significance for the development of intelligent ships.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos.12074049 and 12047564)the Fundamental Research Funds for the Central Universities,China (Grant Nos.2020CDJQY-Z006 and 2020CDJQYZ003)the Research Foundation of SWUST (Grant No.21zx7141)。
文摘The evolution of polarization singularities supported in a one-dimensional periodic plasmonic system is studied.The lateral inversion symmetry of the system,which breaks the in-plane inversion symmetry and up-down mirror symmetry simultaneously,yields abundant polarization states.A complete evolution process with geometry for the polarization states is traced.In the evolution,circularly polarized points(C points)can stem from 3 different processes.In addition to the previously reported processes occurring in an isolated band,a new type of C point appearing in two bands simultaneously due to the avoided band crossing,is observed.Unlike the dielectric system with a similar structure which only supports at-Γbound states in the continuum(BICs),accidental BICs off theΓpoint are realized in this plasmonic system.This work provides a new scheme of polarization manipulation for the plasmonic systems.
基金National Natural Science Foundation of China(61905167)National Key Research and Development Program of China(2020YFA0714001,2021YFC2202203)。
文摘The metasurface possesses great potential in a 3D holographic display due to its powerful ability to manipulate optical fields,ultracompact structure,and extraordinary information capacity.However,the in-plane and interplane crosstalk caused by the coupling between the meta-atoms of the current 3D holographic metasurface limits the quality of the reconstructed image,which has become a significant obstacle to high-performance 3D display applications.Additionally,the interleaved or multilayer design strategy of metasurfaces increases the complexity of structural design and manufacturing,facing challenges in meeting the requirements for miniaturization and low cost-effectiveness.Here,we propose a strategy for a free-space 3D multiplane color holographic multiplex display based on a single-cell metasurface.By utilizing a modified holographic optimization strategy,multiple holographic information is encoded into three mutually independent bases of incident photons and integrated into a metasurface,thereby creating high-quality 3D vectorial metaholography with minimal crosstalk across the visible spectrum.
基金supported by the National Key R&D Program of China(No.2022YFB3104502)the National Natural Science Foundation of China(No.62301251)+2 种基金the Natural Science Foundation of Jiangsu Province of China under Project(No.BK20220883)the open research fund of National Mobile Communications Research Laboratory,Southeast University,China(No.2024D04)the Young Elite Scientists Sponsorship Program by CAST(No.2023QNRC001).
文摘The environment of low-altitude urban airspace is complex and variable due to numerous obstacles,non-cooperative aircraft,and birds.Unmanned Aerial Vehicles(UAVs)leveraging environmental information to achieve three-dimension collision-free trajectory planning is the prerequisite to ensure airspace security.However,the timely information of surrounding situation is difficult to acquire by UAVs,which further brings security risks.As a mature technology leveraged in traditional civil aviation,the Automatic Dependent Surveillance-Broadcast(ADS-B)realizes continuous surveillance of the information of aircraft.Consequently,we leverage ADS-B for surveillance and information broadcasting,and divide the aerial airspace into multiple sub-airspaces to improve flight safety in UAV trajectory planning.In detail,we propose the secure Sub-airSpaces Planning(SSP)algorithm and Particle Swarm Optimization Rapidly-exploring Random Trees(PSO-RRT)algorithm for the UAV trajectory planning in law-altitude airspace.The performance of the proposed algorithm is verified by simulations and the results show that SSP reduces both the maximum number of UAVs in the sub-airspace and the length of the trajectory,and PSO-RRT reduces the cost of UAV trajectory in the sub-airspace.
基金supported by the National Natural Science Foundation of China(Grant Nos.11204055,61222507 and 11374078)the Program for New Century Excellent Talents in University(Grant No.NCET-11-0809)+1 种基金the Shenzhen Peacock Plan(Grant No.KQCX2012080709143322 and KQCX20130627094615410)Shenzhen Fundamental Researches(Grant Nos.JCYJ20130329155148184,JCYJ20140417172417110 and JCYJ20140417172417096)
文摘Chirality is one of the important phenomena at the vicinity of exceptional point(EP). The conventional understanding is that the chirality is determined by asymmetrical scattering efficiency(?), which reaches to zero only when the resonance approaches EP. Here we study the possibility to enhance the chirality in open systems with a more robust mechanism. By combining chirality with avoided resonance crossing, we show that the chirality and ? can be dramatically modified. Taking a spiral shaped annular cavity as an example, we show that the chirality of optical resonances can be significantly improved when two sets of chiral states approach each other. The imbalance between counterclockwise(CCW) components and clockwise(CW) components has been enhanced by more than an order of magnitude. Our research provides a new route to tailor and control the chirality in open systems.
文摘mong the many forms of renewable energy generation, wind power is the most mature. However, the method used to assess the economic value of large grid connected wind farms still needs further study. At present the traditional method of project economic assessment as widely used in China isolates the wind farm from the whole power system and ignores the influence of reliability on the cost of wind generation; therefore, the evaluation results can not reflect the true economic value of wind power generation. After reviewing the many assessment methods used at home and abroad, this paper uses the Avoided Cost Method as theoretical basis to establish an economic evaluation model for large wind farms including the characteristics of other conventional forms of power generation like thermal power as well as the system load. The generating reliability is also combined into the economic evaluation. The model is used to evaluate China's largest wind farm, Dabancheng Wind Farm in Xinjiang.
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.
基金supported in part by the National Natural Science Foundations of China(Nos.61175084,61673042 and 62203046)the China Postdoctoral Science Foundation(No.2022M713006).
文摘Aiming to address the Unmanned Aerial Vehicle(UAV) formation collision avoidance problem in Three-Dimensional(3-D) low-altitude environments where dense various obstacles exist, a fluid-based path planning framework named the Formation Interfered Fluid Dynamical System(FIFDS) with Moderate Evasive Maneuver Strategy(MEMS) is proposed in this study.First, the UAV formation collision avoidance problem including quantifiable performance indexes is formulated. Second, inspired by the phenomenon of fluids continuously flowing while bypassing objects, the FIFDS for multiple UAVs is presented, which contains a Parallel Streamline Tracking(PST) method for formation keeping and the traditional IFDS for collision avoidance. Third, to rationally balance flight safety and collision avoidance cost, MEMS is proposed to generate moderate evasive maneuvers that match up with collision risks. Comprehensively containing the time and distance safety information, the 3-D dynamic collision regions are modeled for collision prediction. Then, the moderate evasive maneuver principle is refined, which provides criterions of the maneuver amplitude and direction. On this basis, an analytical parameter mapping mechanism is designed to online optimize IFDS parameters. Finally, the performance of the proposed method is validated by comparative simulation results and real flight experiments using fixed-wing UAVs.
文摘Advertising avoidance is resistance to advertising intrusion.This issue has been the subject of much academic research in recent years.To guide scholars to better carry out relevant research and promote enterprises to better implement advertising activities,this study intends to summarize the relevant research on advertising avoidance in recent years.The specific method is to use the core literature meta-analysis method to identify,filter,and screen relevant literature published in core journals from 1997 to 2020 with the keywords advertising avoidance and advertising resistance.We review the collected articles from the following perspectives:the definition and classification,external stimulating factors,internal perception factors,and moderating factors of advertising avoidance.On this basis,the SOMR model of advertising avoidance is constructed according to the SOR model.Finally,some prospects for future related research are presented.
文摘This study aims to systematically review the various factors influencing corporate tax avoidance.Tax avoidance refers to legal strategies used to minimize tax liabilities and has become a critical issue in accounting and corporate governance.The study examines key determinants of tax avoidance,including firm characteristics(such as size,leverage,and multinational scale),managerial attributes,executive compensation,ownership structure,corporate social responsibility(CSR)performance,as well as the impact of regulations and legal reforms.The review findings highlight that the motivations behind tax avoidance are multifaceted,driven by the interaction of economic incentives,organizational ethics,external pressures,and public policies.Moreover,strict regulatory environments and strong CSR practices can mitigate tax avoidance behaviors,although their effectiveness is often contingent upon a firm’s cultural and political context.This study offers a comprehensive mapping of the current literature and recommends future research that integrates additional variables and broader time spans to enhance the understanding of tax avoidance behavior across different national contexts.
基金supported in part by the National Natural Science Foundation of China under Grants 62071189,62201220 and 62171189by the Key Research and Development Program of Hubei Province under Grant 2021BAA026 and 2020BAB120。
文摘As the problem of surface garbage pollution becomes more serious,it is necessary to improve the efficiency of garbage inspection and picking rather than traditional manual methods.Due to lightness,Unmanned Aerial Vehicles(UAVs)can traverse the entire water surface in a short time through their flight field of view.In addition,Unmanned Surface Vessels(USVs)can provide battery replacement and pick up garbage.In this paper,we innovatively establish a system framework for the collaboration between UAV and USVs,and develop an automatic water cleaning strategy.First,on the basis of the partition principle,we propose a collaborative coverage path algorithm based on UAV off-site takeoff and landing to achieve global inspection.Second,we design a task scheduling and assignment algorithm for USVs to balance the garbage loads based on the particle swarm optimization algorithm.Finally,based on the swarm intelligence algorithm,we also design an autonomous obstacle avoidance path planning algorithm for USVs to realize autonomous navigation and collaborative cleaning.The system can simultaneously perform inspection and clearance tasks under certain constraints.The simulation results show that the proposed algorithms have higher generality and flexibility while effectively improving computational efficiency and reducing actual cleaning costs compared with other schemes.
基金the National Natural Science Foundation of China(Grant Nos.62303348 and 62173242)the Aeronautical Science Foundation of China(Grant No.2024M071048002)the National Science Fund for Distinguished Young Scholars(Grant No.62225308)to provide fund for conducting experiments.
文摘Multiple quadrotors target encirclement is widely used in the intelligent field,as it can effectively monitor and control target behavior.However,it faces the danger of collision,as well as difficulties in localization and tracking.Therefore,we propose a complete target encirclement method.Firstly,based on Hooke's law,a collision avoidance controller is designed to maintain a safe flying distance among quadrotors.Then,based on the consensus theory,a formation tracking controller is designed to meet the requirements of formation transformation and encirclement tasks,and a stability proof based on Lyapunov was provided.Besides,the target detection is designed based on YOLOv5s,and the target location model is constructed based on the principle of pinhole projection and triangle similarity.Finally,we conducted experiments on the built platform,with 3 reconnaissance quadrotors detecting and localization 3 target vehicles and 7 hunter quadrotors tracking them.The results show that the minimum average error for localization targets with reconnaissance quadrotors can reach 0.1354 m,while the minimum average error for tracking with hunter quadrotors is only 0.2960 m.No quadrotors collision occurred in the whole formation transformation and tracking experiment.In addition,compared with the advanced methods,the proposed method has better performance.
基金Supported by the National Natural Science Foundation of China(Grant No.12061030)the Natural Science Foundation of Hainan Province(Grant No.122RC652)2023 Excellent Science and Technology Innovation Team of Jiangsu Province Universities(Real-Time Industrial Internet of Things).
文摘A set of permutations is called sign-balanced if the set contains the same number of even permutations as odd permutations.Let S_(n)(σ_(1),σ_(2),...,σ_(r))denote the set of permutations in the symmetric group S_(n)which avoid patternsσ_(1),σ_(2),...,σ_(r).The aim of this paper is to investigate when,for certain patternsσ_(1),σ_(2),...,σ_(r),S_(n)(σ_(1),σ_(2),...,σ_(r))is sign-balanced for every integer n>1.We prove that for any{σ_(1),σ_(2),...,σ_(r)}?S_3,if{σ_(1),σ_(2),...,σ_(r)}is sign-balanced except for{132,213,231,312},then S_(n)(σ_(1),σ_(2),...,σ_(r))is sign-balanced for every integer n>1.In addition,we give some results in the case of avoiding some patterns of length 4.
基金supported by National Science Foundation of China(NSFC)[No.32001119].
文摘Global warming leads to snow cover loss in the alpine ecosystem,exposing seeds to extreme diurnal temperature fluctuations during the growing season.The risk of freezing increases as seeds have increased moisture content.Studying the survival mechanisms of seeds at low temperatures can help analyze changes in alpine meadow populations and target conservation efforts.Here,we used three species of Poaceae as a model to understand freezing stress.Fully imbibed Elymus dahuricus,Festuca elata,and Lolium multiflorum seeds were subjected to programmed cooling at fast and slow rates(-1.0/0.05℃/min)and then assessed for survival.Differential Scanning Calorimetry was used to analyze thermal transitions during cooling.HE-stained paraffin sections and a Transmission Electron Microscope were employed to observe internal morphology and ultrastructural changes.E.dahuricus seeds exhibited greater tolerance to low temperatures than those of the other two species,with an LT_(50)of approximately-20℃for both cooling rates and maintained relatively intact ultrastructure.The observed the low-temperature exotherm(LTE)correlated with seed survival,with viability decreasing extensively below LTE.Fast cooling caused fewer changes to seed morphology and ultrastructure than slow cooling,suggesting that the primary survival mechanism during fast cooling is freezing avoidance through supercooling.Seeds exhibited greater freeze tolerance under slow than fast cooling,primarily by migrating intracellular water to extracellular spaces where it froze,causing considerable damage to cell ultrastructure and forming apparent cavities in some seeds.
基金Project supported by the National Natural Science Foundation of China(Grant No.52304273)Opening Fund of Key Laboratory of Civil Aviation Emergency Science&Technology(CAAC)(Grant No.NJ2022022)Fundamental Research Funds for the Central Universities(Grant No.2023XJAQ01).
文摘Emergency evacuation involves rapid transfer of individuals from hazardous areas,where limited time and space can lead to collisions.Although the collision behavior of evacuees has been studied previously,there is a lack of systematic summaries.This study used the CiteSpace visualization software to analyze keywords in the evacuation collision literature.Based on the frequency of keyword occurrence,we determined the research trend;classified the keywords;and analyzed and summarized their influencing factors,behavioral characteristics,and research methods.Clearly,the evacuation environment and emergency guidance directly affect individual behavior and emotions,mainly affecting gait adjustment and decisionmaking processes,which in turn determine evacuation efficiency and collision risk.In the future,emphasis should be placed on post-collision psychological activities,coping strategies,and the application of virtual and mixed reality technologies to observe the interaction between individuals and the environment and to strengthen evacuation research.
文摘The Titanic sunk 113 years ago on April 14-15,after hitting an iceberg,with human error likely causing the ship to wander into those dangerous waters.Today,autonomous systems built on AI can help ships avoid such accidents.But could such a system explain to the captain why it was controlling the ship in a certain way?
基金Supported by National Natural Science Foundation of China (Grant Nos. 52072215, 52221005, 52272386)Beijing Municipal Natrual Science Foundation (Grant No. L243025)+2 种基金National Key R&D Program of China (Grant No. 2022YFB2503003)State Key Laboratory of Intelligent Green Vehicle and Mobilityfundamental Research Funds for the Central Universities
文摘Autonomous trucks have the potential to enhance both safety and convenience in intelligent transportation.However,their maximum speed and ability to navigate a variety of driving conditions,particularly uneven roads,are limited by a high center of gravity,which increases the risk of rollover.Road bulges,sinkholes,and unexpected debris all present additional challenges for autonomous trucks’operational design,which current perception and decisionmaking algorithms often overlook.To mitigate rollover risks and improve adaptability to damaged roads,this paper presents a novel Road Obstacle-Involved Trajectory Planner(ROITP).The planner categorizes road obstacles using a learning-based algorithm.A discrete optimization algorithm selects a multi-objective optimal trajectory while taking into account constraints and objective functions derived from truck dynamics.Validation across various scenarios on a hardware-in-loop platform demonstrates that the proposed planner is effective and feasible for real-time implementation.
基金supported by the National Key Research and Development Program of China(2022YFA1004703)the National Natural Science Foundation of China(62088101).
文摘This paper presents a quadcopter system for naviga-tion in outdoor urban environments.The main contributions include the hardware design,the establishment of global occu-pancy grid maps based on millimeter-wave radars,the trajec-tory planning scheme based on optimal virtual tube methods,and the controller structure based on dynamics.The proposed system focuses on utilizing a compact and lightweight quadro-tor with sensors to achieve navigation that conforms to the direction of urban roads with high computational efficiency and safety.Our work is an application of millimeter-wave radars and virtual tube planning for obstacle avoidance in navigation.The validness and effectiveness of the proposed system are verified by experiments.
基金supported by the National Natural Science Foundation of China(72164018)National Social Science Fund Project(BFA200065)Jiangxi Social Science Foundation Project(21JY13).
文摘Objectives:Positive family functioning(FF)is critical for adolescent development,yet only a few studies have examined this developmental trajectory pathway.This study aimed to identify different types of FF development trajectories during junior high school students,investigate their influence on social avoidance(SA),and further examine the mediating role of preference for solitude(PS)between them.Methods:A three-wave longitudinal study was used with six-month intervals.Questionnaire data were collected from 436 junior high school students in Jiangxi Province,China.Participants ranged in age from 11 to 14 years old(Mean=12.89 years,SD=1.08;50.2%male).Results:Four heterogeneous types of FF trajectories were identified:(1)a high and increasing group(14.7%);(2)a consistently high group(36.24%);(3)a consistently moderate group(45.86%);and(4)a rapid growth group(3.2%).The developmental trajectories of FF among junior high students significantly varied in their levels of SA(F(3,432)=32.03,p<0.001).Compared to the high and increasing groups,the consistently high,consistently medium,and rapid growth groups exhibited higher levels of SA.PS mediated the association between the developmental trajectory of FF and SA.Conclusion:There was a close relationship between the developmental trajectory of FF and SA.Interventions focusing on family system optimization and solitary preference management could effectively mitigate SA behaviors.These findings are important for promoting healthy socialization in adolescents.
基金supported by the National Natural Science Foundation of China(32471055 and 82171090)Shanghai Municipal Science and Technology Major Project(2018SHZDZX01)ZJLab,Shanghai Center for Brain Science and Brain-Inspired Technology,the Lingang Laboratory(LG-QS-202203-12).
文摘Throughout the lifespan,an animal can encounter predators frequently,thus the ability to avoid attacks from predators is crucial for its survival.The chances of evading danger can be greatly improved if the animal can respond immediately to the threat.Therefore,when an animal detects a threat through its visual system,it must quickly direct its gaze and attention toward the source of danger,assess the threat level,and take appropriate action.
文摘Advancements in artificial intelligence and big data technologies have led to the gradual emergence of intelligent ships,which are expected to dominate the future of maritime transportation.Supporting the navigation of intelligent ships,route planning technologies have developed many route planning algorithms that prioritize economy and safety.This paper conducts an in-depth study of algorithm efficiency for a route planning problem,proposing an intelligent ship route planning algorithm based on the adaptive step size Informed-RRT^(*).This algorithm can quickly plan a short route according to automatic obstacle avoidance and is suitable for planning the routes of intelligent ships.Results show that the adaptive step size Informed-RRT^(*) algorithm can shorten the optimal route length by approximately 13.05%while ensuring the running time of the planning algorithm and avoiding approximately 23.64%of redundant sampling nodes.The improved algorithm effectively circumvents unnecessary calculations and reduces a large amount of redundant sampling data,thus improving the efficiency of route planning.In a complex water environment,the unique adaptive step size mechanism enables this algorithm to prevent restricted search tree expansion,showing strong search ability and robustness,which is of practical significance for the development of intelligent ships.
