Non-selective hunting of waterbirds poses a significant challenge in biodiversity-rich areas such as Important Bird Areas (IBAs), where protected and game species congregate. Here, we present evidence from three conse...Non-selective hunting of waterbirds poses a significant challenge in biodiversity-rich areas such as Important Bird Areas (IBAs), where protected and game species congregate. Here, we present evidence from three consecutive hunting seasons spanning autumn 2021 to spring 2024 at a Natura 2000 site in western Poland, based on analyses of hunting bag photographs, local hunting records, and standardized bird monitoring data. We recorded 1331 hunted individuals from 14 species, 43% of which are protected under national or EU legislation. Among these was the Vulnerable Common Pochard (Aythya ferina), listed on the IUCN Red List. For nearly all species, harvest rates exceeded the sustainable thresholds defined by BirdLife International. Statistical comparisons between species' environmental abundance and their representation in hunting bags indicated no selectivity in shooting, pointing to indiscriminate hunting practices. Simultaneous waterbird monitoring (2018–2024) revealed steep declines in the local waterbird community and a marked decrease in Common Crane (Grus grus) numbers, with average autumn roost counts dropping from over 2000 individuals prior to hunting to 320 during hunting seasons. Although causality cannot be directly confirmed, these patterns suggest substantial disturbance effects. Our findings demonstrate the impracticality of selective hunting in species-rich wetland refuges and highlight the systematic killing of protected species. We recommend banning waterbird hunting in IBAs and implementing mandatory bird identification training and certification for hunters to reduce unintended impacts on vulnerable species.展开更多
Purpose–High-speed turnouts are more complex in structure and thus may cause abnormal vibration of highspeed train car body,affecting driving safety and passenger riding experience.Therefore,it is necessary to analyz...Purpose–High-speed turnouts are more complex in structure and thus may cause abnormal vibration of highspeed train car body,affecting driving safety and passenger riding experience.Therefore,it is necessary to analyze the data characteristics of continuous hunting of high-speed trains passing through turnouts and propose a diagnostic method for engineering applications.Design/methodology/approach–First,Complete Ensemble Empirical Mode Decomposition with Adaptive Noise(CEEMDAN)is performed to determine the first characteristic component of the car body’s lateral acceleration.Then,the Short-Time Fourier Transform(STFT)is performed to calculate the marginal spectra.Finally,the presence of a continuous hunting problem is determined based on the results of the comparison calculations and diagnostic thresholds.To improve computational efficiency,permutation entropy(PE)is used as a fast indicator to identify turnouts with potential problems.Findings–Under continuous hunting conditions,the PE is less than 0.90;the ratio of the maximum peak value of the signal component to the original signal peak value exceeded 0.7,and there is an energy band in the STFT time-frequency map,which corresponds to a frequency distribution range of 1–2 Hz.Originality/value–The research results have revealed the lateral vibration characteristics of the high-speed train’s car body during continuous hunting when passing through turnouts.On this basis,an effective diagnostic method has been proposed.With a focus on practical engineering applications,a rapid screening index for identifying potential issues has been proposed,significantly enhancing the efficiency of diagnostic processes.展开更多
This work proposes an online collaborative hunting strategy for multi-robot systems based on obstacle-avoiding Voronoi cells in a complex dynamic environment. This involves firstly designing the construction method us...This work proposes an online collaborative hunting strategy for multi-robot systems based on obstacle-avoiding Voronoi cells in a complex dynamic environment. This involves firstly designing the construction method using a support vector machine(SVM) based on the definition of buffered Voronoi cells(BVCs). Based on the safe collision-free region of the robots, the boundary weights between the robots and the obstacles are dynamically updated such that the robots are tangent to the buffered Voronoi safety areas without intersecting with the obstacles. Then, the robots are controlled to move within their own buffered Voronoi safety area to achieve collision-avoidance with other robots and obstacles. The next step involves proposing a hunting method that optimizes collaboration between the pursuers and evaders. Some hunting points are generated and distributed evenly around a circle. Next, the pursuers are assigned to match the optimal points based on the Hungarian algorithm.Then, a hunting controller is designed to improve the containment capability and minimize containment time based on collision risk. Finally, simulation results have demonstrated that the proposed cooperative hunting method is more competitive in terms of time and travel distance.展开更多
Hunting stability is an important performance criterion in railway vehicles.This study proposes an incorporation of a bio-inspired limb-like structure(LLS)-based nonlinear damping into the motor suspension system for ...Hunting stability is an important performance criterion in railway vehicles.This study proposes an incorporation of a bio-inspired limb-like structure(LLS)-based nonlinear damping into the motor suspension system for traction units to improve the nonlinear critical speed and hunting stability of high-speed trains(HSTs).Initially,a vibration transmission analysis is conducted on a HST vehicle and a metro vehicle that suffered from hunting motion to explore the effect of different motor suspension systems from on-track tests.Subsequently,a simplified lateral dynamics model of an HST bogie is established to investigate the influence of the motor suspension on the bogie hunting behavior.The bifurcation analysis is applied to optimize the motor suspension parameters for high critical speed.Then,the nonlinear damping of the bio-inspired LLS,which has a positive correlation with the relative displacement,can further improve the modal damping of hunting motion and nonlinear critical speed compared with the linear motor suspension system.Furthermore,a comprehensive numerical model of a high-speed train,considering all nonlinearities,is established to investigate the influence of different types of motor suspension.The simulation results are well consistent with the theoretical analysis.The benefits of employing nonlinear damping of the bio-inspired LLS into the motor suspension of HSTs to enhance bogie hunting stability are thoroughly validated.展开更多
Human activities affect bird behavior both directly and indirectly.Birds constantly regulate their behavior in response to human disturbance.Gun hunting,a major directional disturbance,puts enormous selection pressure...Human activities affect bird behavior both directly and indirectly.Birds constantly regulate their behavior in response to human disturbance.Gun hunting,a major directional disturbance,puts enormous selection pressure on birds.In China,gun bans have been in place for nearly 30 years,and little hunting using guns occurs in modern cities.However,little attention has been paid to whether a history of hunting still affects the behavioral adaptations of urban birds.In this study,we compared the flight initiation distance(FiD)of the Eurasian tree sparrow Passer montanus,Azure-winged magpie Cyanopica cyanus,Common hoopoe Upupa epops and Eurasian magpie Pica pica in the presence of observers with or without popguns.The Eurasian tree sparrow,Azure-winged magpie,and Eurasian magpie effectively recognized the difference between the observers,and perceived the armed observer as a greater threat,exhibiting earlier escape behavior,but this phenomenon was not found in the Common hoopoe.The different expressions in FID of experimental bird species in China cities may be affected by the different levels of recognition of huntingpressuredue todifferent hunting histories.展开更多
The trophy hunting industry in Tanzania plays a significant role in wildlife conservation as well as economic and community development. Trophy hunting has been conducted in Rungwa Game Reserve (RGR) for several decad...The trophy hunting industry in Tanzania plays a significant role in wildlife conservation as well as economic and community development. Trophy hunting has been conducted in Rungwa Game Reserve (RGR) for several decades;however, the trophy hunting opinions from the local communities living adjacent to the reserve are not well documented. This study aimed to assess the awareness and attitudes of local communities living adjacent to Rungwa Game Reserves toward trophy hunting. Furthermore, the study assessed factors that influenced the opinions of participants by using structural equation modeling. We used semi-structured interviews and key informant interviews in the three villages adjacent to RGR. The local communities are aware of existing hunting operations around the game reserves. The study found positive attitudes among local communities toward trophy hunting, only if local people accrue benefits from hunting operations. The community’s attitudes towards trophy hunting varied across household size and occupation. Education and household position had an indirect influence on the community’s attitude. Our findings suggest that socio-demographic variables are important to consider when assessing awareness and attitudes toward trophy hunting. Local communities are willing to support trophy hunting operations if the benefits obtained from hunting are significant and it can improve wildlife conservation and their livelihood. In conclusion, trophy hunting is important to local communities living adjacent to protected areas, and banning them may have a significant impact on their livelihood and wildlife conservation. Therefore, it is recommended that conservation policies and interventions consider the dual significance of trophy hunting, fostering strategies that balance socio-economic benefits for communities and wildlife conservation.展开更多
Cooperative search-attack is an important application of unmanned aerial vehicle(UAV)swarm in military field.The coupling between path planning and task allocation,the heterogeneity of UAVs,and the dynamic nature of t...Cooperative search-attack is an important application of unmanned aerial vehicle(UAV)swarm in military field.The coupling between path planning and task allocation,the heterogeneity of UAVs,and the dynamic nature of task environment greatly increase the complexity and difficulty of the UAV swarm cooperative search-attack mission planning problem.Inspired by the collaborative hunting behavior of wolf pack,a distributed selforganizing method for UAV swarm search-attack mission planning is proposed.First,to solve the multi-target search problem in unknown environments,a wolf scouting behavior-inspired cooperative search algorithm for UAV swarm is designed.Second,a distributed self-organizing task allocation algorithm for UAV swarm cooperative attacking of targets is proposed by analyzing the flexible labor division behavior of wolves.By abstracting the UAV as a simple artificial wolf agent,the flexible motion planning and group task coordinating for UAV swarm can be realized by self-organizing.The effectiveness of the proposed method is verified by a set of simulation experiments,the stability and scalability are evaluated,and the integrated solution for the coupled path planning and task allocation problems for the UAV swarm cooperative search-attack task can be well performed.展开更多
While introducing foreign advanced technology and cooperating with Chinese famous research institutes,the high-speed vehicles are designed and take the major task of passenger transport in China.In high-speed vehicle,...While introducing foreign advanced technology and cooperating with Chinese famous research institutes,the high-speed vehicles are designed and take the major task of passenger transport in China.In high-speed vehicle,the characteristic of shock absorber is an important parameter which determines overall behavior of the vehicle.The most existing researches neglect the influence of the series stiffness of the shock absorber on the vehicle dynamic behavior and have one-sided views on the equivalent conicity of wheel tread.In this paper,a high speed passenger vehicle in China is modeled to investigate the effect of the parameters taking series hydraulic shock absorber stiffness into consideration on Ruzicka model.Using the vehicle dynamic model,the effect of main suspension parameters on critical speed is studied.In order to verify the reasonableness of shock absorber parameter settings,vibration isolation characteristics are calculated and the relationship between suspension parameters and the vehicle critical hunting speed is studied.To study the influence of equivalent conicity on vehicle dynamic behavior,a series of wheel treads with different conicities are set and the vehicle critical hunting speeds with different wheel treads are calculated.The discipline between the equivalent conicity of wheel tread and critical speed are obtained in vehicle nonlinear system.The research results show that the critical speed of vehicle much depends on wheelset positioning stiffness and anti-hunting motion damper,and the series stiffness produces notable effect on the vehicle dynamic behavior.The critical speed has a peak value with the equivalent conicity increasing,which is different from the traditional opinion in which the critical speed will decrease with the conicity increasing.The relationship between critical speed and conicity of wheel tread is effected by the suspension parameters of the vehicle.The study results obtained offer a method and useful data to designing the parameters of the high speed vehicle and simulation study.展开更多
The influences of steady aerodynamic loads on hunting stability of high-speed railway vehicles were investigated in this study.A mechanism is suggested to explain the change of hunting behavior due to actions of aerod...The influences of steady aerodynamic loads on hunting stability of high-speed railway vehicles were investigated in this study.A mechanism is suggested to explain the change of hunting behavior due to actions of aerodynamic loads：the aerodynamic loads can change the position of vehicle system（consequently the contact relations）,the wheel/rail normal contact forces,the gravitational restoring forces/moments and the creep forces/moments.A mathematical model for hunting stability incorporating such influences was developed.A computer program capable of incorporating the effects of aerodynamic loads based on the model was written,and the critical speeds were calculated using this program.The dependences of linear and nonlinear critical speeds on suspension parameters considering aerodynamic loads were analyzed by using the orthogonal test method,the results were also compared with the situations without aerodynamic loads.It is shown that the most dominant factors a ff ecting linear and nonlinear critical speeds are different whether the aerodynamic loads considered or not.The damping of yaw damper is the most dominant influencing factor for linear critical speeds,while the damping of lateral damper is most dominant for nonlinear ones.When the influences of aerodynamic loads are considered,the linear critical speeds decrease with the rise of cross wind velocity,whereas it is not the case for the nonlinear critical speeds.The variation trends of critical speeds with suspension parameters can be significantly changed by aerodynamic loads.Combined actions of aerodynamic loads and suspension parameters also a ff ect the critical speeds.The effects of such joint action are more obvious for nonlinear critical speeds.展开更多
Aim of this research is to explore the relation of hunting with aggressiveness. For this purpose, two samples of prison inmates (who were students of the prison secondary school) were collected (class A = 23, class B ...Aim of this research is to explore the relation of hunting with aggressiveness. For this purpose, two samples of prison inmates (who were students of the prison secondary school) were collected (class A = 23, class B = 12). The network indicators for superficial, idiosyncratic and strategic behavior (particularly, aggressiveness), applied in Bekiari and Hasanagas (2016), which were based on the primary network variables (outdegree, indegree, Katz status, pagerank, authority) were used. Non-network variables were also used for the criminal profile of the inmates. The data were sampled with questionnaire. Spearman test was conducted for detecting correlation between aggressiveness and hunting and Principal Component Analysis was used for formulating a typology. The following results were produced: The criminal profile seems hardly to be related with hunting experience or attitude. The relation of hunting experience and attitude with the superficial, idiosyncratic and strategic aggressiveness was examined. These three occasions of aggressiveness are expected to describe the incidental reaction, impulsive and adaptive reaction, respectively. The hunting is quite irrelevant to the incidental reaction. The impulsiveness seems to be more strongly correlated with hunting. In case of adaptiveness, there are many similarities with impulsiveness. The typology which is based on the existence (or not) of hunting experience seems to be more insightful, as it reveals a gradual involvement of aggressiveness dimensions, from incidentality to impulsiveness and further to adaptiveness. The following behavioral patterns of gradually enhanced aggressiveness appear: incidentally just provoking, impulsively being aggressive but without harming, and adaptively being aggressive and harming.展开更多
Vibration behaviors of bogie hunting motion contain key information that dominates the dynamic performance of rail vehicles,in which the eigenvalue of each mode reflects the damping ratio and the natural frequency.Thi...Vibration behaviors of bogie hunting motion contain key information that dominates the dynamic performance of rail vehicles,in which the eigenvalue of each mode reflects the damping ratio and the natural frequency.This paper focuses on the root loci curves of bogie hunting motion,starting from a rigid bogie,then to a bogie with flexible primary suspension.With regard to the rigid bogie,analytical formulas for the eigenvalues,the critical speed as well as the corresponding hunting frequency are derived and verified.While for the flexible bogie,the root loci curves are calculated numerically.The study shows that both free rigid bogie and free wheelset are dynamically unstable at any speed.The critical speed increases with diminished wheel-rail conicity,track gauge,and wheelset and bogie inertia,and with increased wheelbase and wheel radius.The dominating factors such as the stiffness of the primary suspension and the wheel-rail conicity should be optimized for a practical design.The influences of the damping coefficients and the variations of creep coefficients are negligible.The motor suspension affects the root loci curves and the critical speed significantly.Both inappropriate motor suspension design and rigidly suspended motor reduce the critical speed.The increase of critical speed by a motor suspension can only be achieved when the lower natural frequency of the motor-bogie frame-wheelsets system coincides with or is close to the hunting frequency.Special care should be taken for the design of motor suspension,the first is to avoid the decreased damping ratio in a certain speed range below the critical speed and the second is that the variations of parameters should not induce the rapid reduction of the critical speed.The main feature of the present study is that the root loci curves,which are derived as analytical formulas or calculated numerically,are used to study the vibrational behaviors of bogie hunting motion.Both the influencing laws of the dominating parameters and the principles regarding the motor suspension are significant for the stability design of modem railway vehicles which may use innovative structures/materials as well as modem control and monitoring technologies.展开更多
To solve the problem of multi-target hunting by an unmanned surface vehicle(USV)fleet,a hunting algorithm based on multi-agent reinforcement learning is proposed.Firstly,the hunting environment and kinematic model wit...To solve the problem of multi-target hunting by an unmanned surface vehicle(USV)fleet,a hunting algorithm based on multi-agent reinforcement learning is proposed.Firstly,the hunting environment and kinematic model without boundary constraints are built,and the criteria for successful target capture are given.Then,the cooperative hunting problem of a USV fleet is modeled as a decentralized partially observable Markov decision process(Dec-POMDP),and a distributed partially observable multitarget hunting Proximal Policy Optimization(DPOMH-PPO)algorithm applicable to USVs is proposed.In addition,an observation model,a reward function and the action space applicable to multi-target hunting tasks are designed.To deal with the dynamic change of observational feature dimension input by partially observable systems,a feature embedding block is proposed.By combining the two feature compression methods of column-wise max pooling(CMP)and column-wise average-pooling(CAP),observational feature encoding is established.Finally,the centralized training and decentralized execution framework is adopted to complete the training of hunting strategy.Each USV in the fleet shares the same policy and perform actions independently.Simulation experiments have verified the effectiveness of the DPOMH-PPO algorithm in the test scenarios with different numbers of USVs.Moreover,the advantages of the proposed model are comprehensively analyzed from the aspects of algorithm performance,migration effect in task scenarios and self-organization capability after being damaged,the potential deployment and application of DPOMH-PPO in the real environment is verified.展开更多
data is gathered to describe the relative location and relative motion state of the robots, which in turn forms the beginning stage of the fuzzy rule. The artificial immune algorithm optimizes and generates the rule d...data is gathered to describe the relative location and relative motion state of the robots, which in turn forms the beginning stage of the fuzzy rule. The artificial immune algorithm optimizes and generates the rule data base and adaptive design considers factors in measuring the hunting efficiency. The optimized rules are applied to the hunting task and the results show that the algorithm can effectively actualize hunting of multiple mobile robots.展开更多
A stochastic wheelset model with a nonlinear wheel-rail contact relationship is established to investigate the stochastic stability and stochastic bifurcation of the wheelset system with the consideration of the stoch...A stochastic wheelset model with a nonlinear wheel-rail contact relationship is established to investigate the stochastic stability and stochastic bifurcation of the wheelset system with the consideration of the stochastic parametric excitations of equivalent conicity and suspension stiffness.The wheelset is systematized into a onedimensional(1D)diffusion process by using the stochastic average method,the behavior of the singular boundary is analyzed to determine the hunting stability condition of the wheelset system,and the critical speed of stochastic bifurcation is obtained.The stationary probability density and joint probability density are derived theoretically.Based on the topological structure change of the probability density function,the stochastic Hopf bifurcation form and bifurcation condition of the wheelset system are determined.The effects of stochastic factors on the hunting stability and bifurcation characteristics are analyzed,and the simulation results verify the correctness of the theoretical analysis.The results reveal that the boundary behavior of the diffusion process determines the hunting stability of the stochastic wheelset system,and the left boundary characteristic value cL=1 is the critical state of hunting stability.Besides,stochastic D-bifurcation and P-bifurcation will appear in the wheelset system,and the critical speeds of the two kinds of stochastic bifurcation decrease with the increase in the stochastic parametric excitation intensity.展开更多
The purpose of this paper is to explore the promise of utilizing some relatively new feedback control techniques in ecosystem management. First, we set forth a basic ecological-economic model of a predator-prey-huntin...The purpose of this paper is to explore the promise of utilizing some relatively new feedback control techniques in ecosystem management. First, we set forth a basic ecological-economic model of a predator-prey-hunting system in which both the predator and prey have use(flow) and non-use(stock) value and when the predator can inflict transboundary damages. We then use new data from the US Mountain West to show how a particular feedback approach—linear parameter-varying(LPV) control—can be utilized in this context. Our LPV model is able to quantify the cost of managing disturbances that inevitably arise as a manager tries to keep the actual path of the system "close" to its optimum. The results suggest management strategies in mountain ecosystems that feature large, mammalian carnivores.展开更多
Bearing-based hunting protocols commonly adopt a leaderless consensus method,which requests an entire state of the target for each agent and ignores the necessity of collision avoidance.We investigate a hunting proble...Bearing-based hunting protocols commonly adopt a leaderless consensus method,which requests an entire state of the target for each agent and ignores the necessity of collision avoidance.We investigate a hunting problem of multi-quadrotor systems with hybrid bearing protocols,where the quadrotor systems are divided into master and slave groups for reducing the onboard loads and collision avoidance.The masters obtain the entire state of the target,whose hybrid protocols are based on the displacement and bearing constraints to maintain formation and to avoid the collision in the hunting process.However,the slaves’protocols merely depend on the part state of the masters to reduce loads of data transmission.We also investigate the feasibility of receiving the bearing state from machine vision.The simulation results are given to illustrate the effectiveness of the proposed hybrid bearing protocols.展开更多
Wetland means the surface of the earth that is permanently or seasonally or partially covered with water. Wetlands are most productive areas for biodiversity and local livelihood support. Nepal ratified Ramsar convent...Wetland means the surface of the earth that is permanently or seasonally or partially covered with water. Wetlands are most productive areas for biodiversity and local livelihood support. Nepal ratified Ramsar convention in 1987 and started to include the wetland in Ramsar site and till now nine wetland sites are included in Ramsar site. There are still lacking systematic research and conservation approach for these wetlands;therefore, our study attempted to assess the status of wetlands in the Dhorpatan Hunting Reserve, Nepal;and explored threats and conservation challenges. We prepared list of streams and lakes and collected detail information regarding area, district, block, elevation and cultural as well as ecological importance of lakes. We recorded total 11 lakes with total 304477 m2 areas. The Sundaha lake is largest lake of the reserve having significant religious importance. We also recorded 7 streams in the reserve. Wetlands of the reserve were facing problem of sedimentation, pollution, and change in climate has also effects on these wetland ecosystem and their importance.展开更多
The Crna River is a river in the Republic of Macedonia, right tributary to Vardar. Its source is in the mountains of Western Macedonia, west of Krusevo. It flows through the village of Sopotnica, and southwards throug...The Crna River is a river in the Republic of Macedonia, right tributary to Vardar. Its source is in the mountains of Western Macedonia, west of Krusevo. It flows through the village of Sopotnica, and southwards through the plains east of Bitola. The name means ＂black river＂ in Macedonian, which is translation for its former Thracian name. The purpose of this paper is to show the hunting and hunting areas for big and small Game （food）, the structure of the areas of certain hunting, fishing, fishing water objects, fish species, fishponds up to 20 years shown by municipalities and individual farms with ponds in the basin of Black River. It had used statistical data for the hunting grounds by areas, fishing ponds. Fish is very diverse in this river. Hunting in the Black River basin is of great importance for the economy of Republic of Macedonia. It is also a necessary factor for development of other economic activities.展开更多
文摘Non-selective hunting of waterbirds poses a significant challenge in biodiversity-rich areas such as Important Bird Areas (IBAs), where protected and game species congregate. Here, we present evidence from three consecutive hunting seasons spanning autumn 2021 to spring 2024 at a Natura 2000 site in western Poland, based on analyses of hunting bag photographs, local hunting records, and standardized bird monitoring data. We recorded 1331 hunted individuals from 14 species, 43% of which are protected under national or EU legislation. Among these was the Vulnerable Common Pochard (Aythya ferina), listed on the IUCN Red List. For nearly all species, harvest rates exceeded the sustainable thresholds defined by BirdLife International. Statistical comparisons between species' environmental abundance and their representation in hunting bags indicated no selectivity in shooting, pointing to indiscriminate hunting practices. Simultaneous waterbird monitoring (2018–2024) revealed steep declines in the local waterbird community and a marked decrease in Common Crane (Grus grus) numbers, with average autumn roost counts dropping from over 2000 individuals prior to hunting to 320 during hunting seasons. Although causality cannot be directly confirmed, these patterns suggest substantial disturbance effects. Our findings demonstrate the impracticality of selective hunting in species-rich wetland refuges and highlight the systematic killing of protected species. We recommend banning waterbird hunting in IBAs and implementing mandatory bird identification training and certification for hunters to reduce unintended impacts on vulnerable species.
基金support from the funds of National Natural Science Foundation of China(52308473)China Academy of Railway Science Corporation Limited(2022YJ192)are gratefully acknowledged。
文摘Purpose–High-speed turnouts are more complex in structure and thus may cause abnormal vibration of highspeed train car body,affecting driving safety and passenger riding experience.Therefore,it is necessary to analyze the data characteristics of continuous hunting of high-speed trains passing through turnouts and propose a diagnostic method for engineering applications.Design/methodology/approach–First,Complete Ensemble Empirical Mode Decomposition with Adaptive Noise(CEEMDAN)is performed to determine the first characteristic component of the car body’s lateral acceleration.Then,the Short-Time Fourier Transform(STFT)is performed to calculate the marginal spectra.Finally,the presence of a continuous hunting problem is determined based on the results of the comparison calculations and diagnostic thresholds.To improve computational efficiency,permutation entropy(PE)is used as a fast indicator to identify turnouts with potential problems.Findings–Under continuous hunting conditions,the PE is less than 0.90;the ratio of the maximum peak value of the signal component to the original signal peak value exceeded 0.7,and there is an energy band in the STFT time-frequency map,which corresponds to a frequency distribution range of 1–2 Hz.Originality/value–The research results have revealed the lateral vibration characteristics of the high-speed train’s car body during continuous hunting when passing through turnouts.On this basis,an effective diagnostic method has been proposed.With a focus on practical engineering applications,a rapid screening index for identifying potential issues has been proposed,significantly enhancing the efficiency of diagnostic processes.
基金supported by the National Natural Science Foundation of China (62273007,61973023)Project of Cultivation for Young Top-motch Talents of Beijing Municipal Institutions (BPHR202203032)。
文摘This work proposes an online collaborative hunting strategy for multi-robot systems based on obstacle-avoiding Voronoi cells in a complex dynamic environment. This involves firstly designing the construction method using a support vector machine(SVM) based on the definition of buffered Voronoi cells(BVCs). Based on the safe collision-free region of the robots, the boundary weights between the robots and the obstacles are dynamically updated such that the robots are tangent to the buffered Voronoi safety areas without intersecting with the obstacles. Then, the robots are controlled to move within their own buffered Voronoi safety area to achieve collision-avoidance with other robots and obstacles. The next step involves proposing a hunting method that optimizes collaboration between the pursuers and evaders. Some hunting points are generated and distributed evenly around a circle. Next, the pursuers are assigned to match the optimal points based on the Hungarian algorithm.Then, a hunting controller is designed to improve the containment capability and minimize containment time based on collision risk. Finally, simulation results have demonstrated that the proposed cooperative hunting method is more competitive in terms of time and travel distance.
基金the National Natural Science Foundation of China (Nos. 52388102, 52072317 and U2268210)the State Key Laboratory of Rail Transit Vehicle System (No. 2024RVL-T12)
文摘Hunting stability is an important performance criterion in railway vehicles.This study proposes an incorporation of a bio-inspired limb-like structure(LLS)-based nonlinear damping into the motor suspension system for traction units to improve the nonlinear critical speed and hunting stability of high-speed trains(HSTs).Initially,a vibration transmission analysis is conducted on a HST vehicle and a metro vehicle that suffered from hunting motion to explore the effect of different motor suspension systems from on-track tests.Subsequently,a simplified lateral dynamics model of an HST bogie is established to investigate the influence of the motor suspension on the bogie hunting behavior.The bifurcation analysis is applied to optimize the motor suspension parameters for high critical speed.Then,the nonlinear damping of the bio-inspired LLS,which has a positive correlation with the relative displacement,can further improve the modal damping of hunting motion and nonlinear critical speed compared with the linear motor suspension system.Furthermore,a comprehensive numerical model of a high-speed train,considering all nonlinearities,is established to investigate the influence of different types of motor suspension.The simulation results are well consistent with the theoretical analysis.The benefits of employing nonlinear damping of the bio-inspired LLS into the motor suspension of HSTs to enhance bogie hunting stability are thoroughly validated.
基金supported the National Natural Science Foundation of China(Nos.32160242 to JL and 32270526 to WL)the specifc research fund of The Innovation Platform for Academicians of Hainan ProvinceSY was supported by the Hainan Province Postdoctoral Research Project.
文摘Human activities affect bird behavior both directly and indirectly.Birds constantly regulate their behavior in response to human disturbance.Gun hunting,a major directional disturbance,puts enormous selection pressure on birds.In China,gun bans have been in place for nearly 30 years,and little hunting using guns occurs in modern cities.However,little attention has been paid to whether a history of hunting still affects the behavioral adaptations of urban birds.In this study,we compared the flight initiation distance(FiD)of the Eurasian tree sparrow Passer montanus,Azure-winged magpie Cyanopica cyanus,Common hoopoe Upupa epops and Eurasian magpie Pica pica in the presence of observers with or without popguns.The Eurasian tree sparrow,Azure-winged magpie,and Eurasian magpie effectively recognized the difference between the observers,and perceived the armed observer as a greater threat,exhibiting earlier escape behavior,but this phenomenon was not found in the Common hoopoe.The different expressions in FID of experimental bird species in China cities may be affected by the different levels of recognition of huntingpressuredue todifferent hunting histories.
文摘The trophy hunting industry in Tanzania plays a significant role in wildlife conservation as well as economic and community development. Trophy hunting has been conducted in Rungwa Game Reserve (RGR) for several decades;however, the trophy hunting opinions from the local communities living adjacent to the reserve are not well documented. This study aimed to assess the awareness and attitudes of local communities living adjacent to Rungwa Game Reserves toward trophy hunting. Furthermore, the study assessed factors that influenced the opinions of participants by using structural equation modeling. We used semi-structured interviews and key informant interviews in the three villages adjacent to RGR. The local communities are aware of existing hunting operations around the game reserves. The study found positive attitudes among local communities toward trophy hunting, only if local people accrue benefits from hunting operations. The community’s attitudes towards trophy hunting varied across household size and occupation. Education and household position had an indirect influence on the community’s attitude. Our findings suggest that socio-demographic variables are important to consider when assessing awareness and attitudes toward trophy hunting. Local communities are willing to support trophy hunting operations if the benefits obtained from hunting are significant and it can improve wildlife conservation and their livelihood. In conclusion, trophy hunting is important to local communities living adjacent to protected areas, and banning them may have a significant impact on their livelihood and wildlife conservation. Therefore, it is recommended that conservation policies and interventions consider the dual significance of trophy hunting, fostering strategies that balance socio-economic benefits for communities and wildlife conservation.
基金supported by the National Natural Science Foundation of China(61502534)the Shaanxi Provincial Natural Science Foundation(2020JQ-493)+2 种基金the Integrative Equipment Research Project of Armed Police Force(WJ20211A030018)the Military Science Project of the National Social Science Fund(WJ2019-SKJJ-C-092)the Theoretical Research Foundation of Armed Police Engineering University(WJY202148)。
文摘Cooperative search-attack is an important application of unmanned aerial vehicle(UAV)swarm in military field.The coupling between path planning and task allocation,the heterogeneity of UAVs,and the dynamic nature of task environment greatly increase the complexity and difficulty of the UAV swarm cooperative search-attack mission planning problem.Inspired by the collaborative hunting behavior of wolf pack,a distributed selforganizing method for UAV swarm search-attack mission planning is proposed.First,to solve the multi-target search problem in unknown environments,a wolf scouting behavior-inspired cooperative search algorithm for UAV swarm is designed.Second,a distributed self-organizing task allocation algorithm for UAV swarm cooperative attacking of targets is proposed by analyzing the flexible labor division behavior of wolves.By abstracting the UAV as a simple artificial wolf agent,the flexible motion planning and group task coordinating for UAV swarm can be realized by self-organizing.The effectiveness of the proposed method is verified by a set of simulation experiments,the stability and scalability are evaluated,and the integrated solution for the coupled path planning and task allocation problems for the UAV swarm cooperative search-attack task can be well performed.
基金supported by Doctoral Discipline Foundation of Ministry of Education of China (Grant No. 20090184110023)Unite Project of Basic Research Program on High-speed Railway of Railway Ministry of China (Grant No. U1134202)Independent Research Project of Traction Power State Key Laboratory of Southwest Jiaotong University,China (Grant No. 2009TPL-T06)
文摘While introducing foreign advanced technology and cooperating with Chinese famous research institutes,the high-speed vehicles are designed and take the major task of passenger transport in China.In high-speed vehicle,the characteristic of shock absorber is an important parameter which determines overall behavior of the vehicle.The most existing researches neglect the influence of the series stiffness of the shock absorber on the vehicle dynamic behavior and have one-sided views on the equivalent conicity of wheel tread.In this paper,a high speed passenger vehicle in China is modeled to investigate the effect of the parameters taking series hydraulic shock absorber stiffness into consideration on Ruzicka model.Using the vehicle dynamic model,the effect of main suspension parameters on critical speed is studied.In order to verify the reasonableness of shock absorber parameter settings,vibration isolation characteristics are calculated and the relationship between suspension parameters and the vehicle critical hunting speed is studied.To study the influence of equivalent conicity on vehicle dynamic behavior,a series of wheel treads with different conicities are set and the vehicle critical hunting speeds with different wheel treads are calculated.The discipline between the equivalent conicity of wheel tread and critical speed are obtained in vehicle nonlinear system.The research results show that the critical speed of vehicle much depends on wheelset positioning stiffness and anti-hunting motion damper,and the series stiffness produces notable effect on the vehicle dynamic behavior.The critical speed has a peak value with the equivalent conicity increasing,which is different from the traditional opinion in which the critical speed will decrease with the conicity increasing.The relationship between critical speed and conicity of wheel tread is effected by the suspension parameters of the vehicle.The study results obtained offer a method and useful data to designing the parameters of the high speed vehicle and simulation study.
基金supported by the National Basic Research Program(973 Program)of China(2011CB711100 and 2014CB046801)the National Natural Science Foundation of China(11072246 and51490673)the Knowledge Innovation Program of Chinese Academy of Sciences(KJCX2-EW-L01)
文摘The influences of steady aerodynamic loads on hunting stability of high-speed railway vehicles were investigated in this study.A mechanism is suggested to explain the change of hunting behavior due to actions of aerodynamic loads：the aerodynamic loads can change the position of vehicle system（consequently the contact relations）,the wheel/rail normal contact forces,the gravitational restoring forces/moments and the creep forces/moments.A mathematical model for hunting stability incorporating such influences was developed.A computer program capable of incorporating the effects of aerodynamic loads based on the model was written,and the critical speeds were calculated using this program.The dependences of linear and nonlinear critical speeds on suspension parameters considering aerodynamic loads were analyzed by using the orthogonal test method,the results were also compared with the situations without aerodynamic loads.It is shown that the most dominant factors a ff ecting linear and nonlinear critical speeds are different whether the aerodynamic loads considered or not.The damping of yaw damper is the most dominant influencing factor for linear critical speeds,while the damping of lateral damper is most dominant for nonlinear ones.When the influences of aerodynamic loads are considered,the linear critical speeds decrease with the rise of cross wind velocity,whereas it is not the case for the nonlinear critical speeds.The variation trends of critical speeds with suspension parameters can be significantly changed by aerodynamic loads.Combined actions of aerodynamic loads and suspension parameters also a ff ect the critical speeds.The effects of such joint action are more obvious for nonlinear critical speeds.
文摘Aim of this research is to explore the relation of hunting with aggressiveness. For this purpose, two samples of prison inmates (who were students of the prison secondary school) were collected (class A = 23, class B = 12). The network indicators for superficial, idiosyncratic and strategic behavior (particularly, aggressiveness), applied in Bekiari and Hasanagas (2016), which were based on the primary network variables (outdegree, indegree, Katz status, pagerank, authority) were used. Non-network variables were also used for the criminal profile of the inmates. The data were sampled with questionnaire. Spearman test was conducted for detecting correlation between aggressiveness and hunting and Principal Component Analysis was used for formulating a typology. The following results were produced: The criminal profile seems hardly to be related with hunting experience or attitude. The relation of hunting experience and attitude with the superficial, idiosyncratic and strategic aggressiveness was examined. These three occasions of aggressiveness are expected to describe the incidental reaction, impulsive and adaptive reaction, respectively. The hunting is quite irrelevant to the incidental reaction. The impulsiveness seems to be more strongly correlated with hunting. In case of adaptiveness, there are many similarities with impulsiveness. The typology which is based on the existence (or not) of hunting experience seems to be more insightful, as it reveals a gradual involvement of aggressiveness dimensions, from incidentality to impulsiveness and further to adaptiveness. The following behavioral patterns of gradually enhanced aggressiveness appear: incidentally just provoking, impulsively being aggressive but without harming, and adaptively being aggressive and harming.
基金supported by the National Natural Science Foundation of China(Grant Nos.51805452,and 51935002)the Independent Research Project of State Key Laboratory of Traction Power(Grant No.2020TPL-T02).
文摘Vibration behaviors of bogie hunting motion contain key information that dominates the dynamic performance of rail vehicles,in which the eigenvalue of each mode reflects the damping ratio and the natural frequency.This paper focuses on the root loci curves of bogie hunting motion,starting from a rigid bogie,then to a bogie with flexible primary suspension.With regard to the rigid bogie,analytical formulas for the eigenvalues,the critical speed as well as the corresponding hunting frequency are derived and verified.While for the flexible bogie,the root loci curves are calculated numerically.The study shows that both free rigid bogie and free wheelset are dynamically unstable at any speed.The critical speed increases with diminished wheel-rail conicity,track gauge,and wheelset and bogie inertia,and with increased wheelbase and wheel radius.The dominating factors such as the stiffness of the primary suspension and the wheel-rail conicity should be optimized for a practical design.The influences of the damping coefficients and the variations of creep coefficients are negligible.The motor suspension affects the root loci curves and the critical speed significantly.Both inappropriate motor suspension design and rigidly suspended motor reduce the critical speed.The increase of critical speed by a motor suspension can only be achieved when the lower natural frequency of the motor-bogie frame-wheelsets system coincides with or is close to the hunting frequency.Special care should be taken for the design of motor suspension,the first is to avoid the decreased damping ratio in a certain speed range below the critical speed and the second is that the variations of parameters should not induce the rapid reduction of the critical speed.The main feature of the present study is that the root loci curves,which are derived as analytical formulas or calculated numerically,are used to study the vibrational behaviors of bogie hunting motion.Both the influencing laws of the dominating parameters and the principles regarding the motor suspension are significant for the stability design of modem railway vehicles which may use innovative structures/materials as well as modem control and monitoring technologies.
基金financial support from National Natural Science Foundation of China(Grant No.61601491)Natural Science Foundation of Hubei Province,China(Grant No.2018CFC865)Military Research Project of China(-Grant No.YJ2020B117)。
文摘To solve the problem of multi-target hunting by an unmanned surface vehicle(USV)fleet,a hunting algorithm based on multi-agent reinforcement learning is proposed.Firstly,the hunting environment and kinematic model without boundary constraints are built,and the criteria for successful target capture are given.Then,the cooperative hunting problem of a USV fleet is modeled as a decentralized partially observable Markov decision process(Dec-POMDP),and a distributed partially observable multitarget hunting Proximal Policy Optimization(DPOMH-PPO)algorithm applicable to USVs is proposed.In addition,an observation model,a reward function and the action space applicable to multi-target hunting tasks are designed.To deal with the dynamic change of observational feature dimension input by partially observable systems,a feature embedding block is proposed.By combining the two feature compression methods of column-wise max pooling(CMP)and column-wise average-pooling(CAP),observational feature encoding is established.Finally,the centralized training and decentralized execution framework is adopted to complete the training of hunting strategy.Each USV in the fleet shares the same policy and perform actions independently.Simulation experiments have verified the effectiveness of the DPOMH-PPO algorithm in the test scenarios with different numbers of USVs.Moreover,the advantages of the proposed model are comprehensively analyzed from the aspects of algorithm performance,migration effect in task scenarios and self-organization capability after being damaged,the potential deployment and application of DPOMH-PPO in the real environment is verified.
基金Supported by the Liaoning Excellent Talents in University(No.LR2015045)Liaoning Province Natural Science Foundation(No.2015020010)
文摘data is gathered to describe the relative location and relative motion state of the robots, which in turn forms the beginning stage of the fuzzy rule. The artificial immune algorithm optimizes and generates the rule data base and adaptive design considers factors in measuring the hunting efficiency. The optimized rules are applied to the hunting task and the results show that the algorithm can effectively actualize hunting of multiple mobile robots.
基金Project supported by the National Natural Science Foundation of China(Nos.11790282,12172235,12072208,and 52072249)the Opening Foundation of State Key Laboratory of Shijiazhuang Tiedao University of China(No.ZZ2021-13)。
文摘A stochastic wheelset model with a nonlinear wheel-rail contact relationship is established to investigate the stochastic stability and stochastic bifurcation of the wheelset system with the consideration of the stochastic parametric excitations of equivalent conicity and suspension stiffness.The wheelset is systematized into a onedimensional(1D)diffusion process by using the stochastic average method,the behavior of the singular boundary is analyzed to determine the hunting stability condition of the wheelset system,and the critical speed of stochastic bifurcation is obtained.The stationary probability density and joint probability density are derived theoretically.Based on the topological structure change of the probability density function,the stochastic Hopf bifurcation form and bifurcation condition of the wheelset system are determined.The effects of stochastic factors on the hunting stability and bifurcation characteristics are analyzed,and the simulation results verify the correctness of the theoretical analysis.The results reveal that the boundary behavior of the diffusion process determines the hunting stability of the stochastic wheelset system,and the left boundary characteristic value cL=1 is the critical state of hunting stability.Besides,stochastic D-bifurcation and P-bifurcation will appear in the wheelset system,and the critical speeds of the two kinds of stochastic bifurcation decrease with the increase in the stochastic parametric excitation intensity.
基金the RIT College of Liberal Arts Faculty Research Fund for supplemental funding that enabled presentation of the preliminary results at the above mentioned AERE Conference in Asheville, NC
文摘The purpose of this paper is to explore the promise of utilizing some relatively new feedback control techniques in ecosystem management. First, we set forth a basic ecological-economic model of a predator-prey-hunting system in which both the predator and prey have use(flow) and non-use(stock) value and when the predator can inflict transboundary damages. We then use new data from the US Mountain West to show how a particular feedback approach—linear parameter-varying(LPV) control—can be utilized in this context. Our LPV model is able to quantify the cost of managing disturbances that inevitably arise as a manager tries to keep the actual path of the system "close" to its optimum. The results suggest management strategies in mountain ecosystems that feature large, mammalian carnivores.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61673217 and 61673214)the National Defense Basic Scientific Research Program of China(Grant No.JCKY2019606D001)the China Scholarship Council.
文摘Bearing-based hunting protocols commonly adopt a leaderless consensus method,which requests an entire state of the target for each agent and ignores the necessity of collision avoidance.We investigate a hunting problem of multi-quadrotor systems with hybrid bearing protocols,where the quadrotor systems are divided into master and slave groups for reducing the onboard loads and collision avoidance.The masters obtain the entire state of the target,whose hybrid protocols are based on the displacement and bearing constraints to maintain formation and to avoid the collision in the hunting process.However,the slaves’protocols merely depend on the part state of the masters to reduce loads of data transmission.We also investigate the feasibility of receiving the bearing state from machine vision.The simulation results are given to illustrate the effectiveness of the proposed hybrid bearing protocols.
文摘Wetland means the surface of the earth that is permanently or seasonally or partially covered with water. Wetlands are most productive areas for biodiversity and local livelihood support. Nepal ratified Ramsar convention in 1987 and started to include the wetland in Ramsar site and till now nine wetland sites are included in Ramsar site. There are still lacking systematic research and conservation approach for these wetlands;therefore, our study attempted to assess the status of wetlands in the Dhorpatan Hunting Reserve, Nepal;and explored threats and conservation challenges. We prepared list of streams and lakes and collected detail information regarding area, district, block, elevation and cultural as well as ecological importance of lakes. We recorded total 11 lakes with total 304477 m2 areas. The Sundaha lake is largest lake of the reserve having significant religious importance. We also recorded 7 streams in the reserve. Wetlands of the reserve were facing problem of sedimentation, pollution, and change in climate has also effects on these wetland ecosystem and their importance.
文摘The Crna River is a river in the Republic of Macedonia, right tributary to Vardar. Its source is in the mountains of Western Macedonia, west of Krusevo. It flows through the village of Sopotnica, and southwards through the plains east of Bitola. The name means ＂black river＂ in Macedonian, which is translation for its former Thracian name. The purpose of this paper is to show the hunting and hunting areas for big and small Game （food）, the structure of the areas of certain hunting, fishing, fishing water objects, fish species, fishponds up to 20 years shown by municipalities and individual farms with ponds in the basin of Black River. It had used statistical data for the hunting grounds by areas, fishing ponds. Fish is very diverse in this river. Hunting in the Black River basin is of great importance for the economy of Republic of Macedonia. It is also a necessary factor for development of other economic activities.
