Dogs are used for centuries as people helpers. One of possible use is a sport and service. BSM （Belgian Shepherd Malinois） and GS （German shepherd） dogs are most used breeds like service dogs and also most represe...Dogs are used for centuries as people helpers. One of possible use is a sport and service. BSM （Belgian Shepherd Malinois） and GS （German shepherd） dogs are most used breeds like service dogs and also most represented at sports competitions. Our aim was to compare the results of these breeds in the World Cup of International tests of working dogs （in years 2003-2011）, which is the peak of competitions. The authors evaluated results of German shepherd dog performance test and Belgian shepherd Malinois performance in disciplines such as tracking, obedience and defense. Belgian Shepherds achieved in all disciplines higher score than German shepherds. It was found out that Belgian shepherd Malinois get significant higher score in all disciplines （tracking, obedience and defense） than German shepherd. However, both of breeds are used successfully as service dogs.展开更多
Shepherd＇s purse seeds were collected from winter wheat fields and road sides in Hebei Province,China.Their sensitivities to tribenuron-methyl were evaluated in a whole plant dose response assay in the greenhouse.Res...Shepherd＇s purse seeds were collected from winter wheat fields and road sides in Hebei Province,China.Their sensitivities to tribenuron-methyl were evaluated in a whole plant dose response assay in the greenhouse.Results revealed that HB-1,HB-2,HB-3,HB-4,HB-6,HB-7,HB-17,HB-18,HB-19,HB-20,HB-21,and HB-22 populations were susceptible to tribenuron-methyl characterised by very low GR50 values of about 0.10 g a.i.ha-1.On the other hand,populations HB-15 and HB-16 had moderate resistance to tribenuron-methyl with resistance indices （RI） ranging from 10-100 folds,whilst populations HB-5,HB-8,HB-9,HB-10,HB-11,HB-12,HB-13,and HB-14 expressed high level of resistance to tribenuron-methyl with resistance indices over 100.The proportion of moderate resistance level was about 9.09%,and that of high resistance was about 36.36%.展开更多
The removal of large space debris from a geostationary orbit to a disposal orbit via an ion beam shepherd spacecraft was considered in this study,with attention given to the electrostatic effect.The generation of an i...The removal of large space debris from a geostationary orbit to a disposal orbit via an ion beam shepherd spacecraft was considered in this study,with attention given to the electrostatic effect.The generation of an ion force,which provides contactless thrust,occurs because of the transfer of momentum from the ions of the engine plume of the spacecraft to the space debris.This process is accompanied by the transfer of a positive charge to the space debris.As a result,electrostatic interactions occur between the spacecraft and space debris.The goals of this study were to assess the influence of this effect on the dynamics of space debris during contactless ion beam-assisted removal and to develop hybrid contactless transportation schemes based on the use of an ion beam and electrostatic interactions.A mathematical model describing the motion of space debris and spacecraft under the influence of ionic and electrostatic forces and torques was developed.The concepts of electrostatic ion beam shepherd,electrostatic tractor with ion beam,and charged ion beam shepherd were proposed and compared.The results of numerical simulations revealed that the electrostatic ion beam shepherd scheme is preferable from the perspective of minimizing fuel costs when solving the problem of removing space debris from a geostationary orbit.A control law for the spacecraft charge needed for space-debris detumbling during ion-beam transportation is proposed.A numerical simulation of space debris removal was performed via a hybrid scheme.展开更多
Swarming behaviors play an eminent role in both biological and engineering research, and show great potential applications in many emerging fields. Traditional swarming models still lack integrity, uniformity, and sta...Swarming behaviors play an eminent role in both biological and engineering research, and show great potential applications in many emerging fields. Traditional swarming models still lack integrity, uniformity, and stability in swarm forming processes,resulting in fragmentation and void phenomena. Inspired by the shepherding behaviors observed in nature, we propose an integrated negotiation-control scheme for distributed swarm control of massive robots. The core idea of this scheme is that the robots at the boundary of the group herd the internal robots to form an equilibrium swarm. For this purpose, we introduce a concept of virtual group center towards which boundary robots herd internal robots. Then, a distributed negotiation mechanism is designed to allow each robot to negotiate the virtual group center only through local interactions with its neighbors. After that, we propose a shepherding-inspired swarm control law to drive a group of robots to form an integrated, uniform, and stable configuration from any initial states. Both numerical and flight simulations are presented to verify the effectiveness of our proposed swarm control scheme.展开更多
To explain the long-term existence of Uranian narrow rings, we study the dynamical evolution of Uranian epsilon ring under the influence of its two shepherding satellites: Cordelia and Ophelia. The model of planar-ell...To explain the long-term existence of Uranian narrow rings, we study the dynamical evolution of Uranian epsilon ring under the influence of its two shepherding satellites: Cordelia and Ophelia. The model of planar-elliptic restricted three-body problem is employed, in which the three bodies are Uranus, a satellite and a test particle. Dissipations due to interparticle collisions are also taken into consideration. A mapping system has been obtained based on the differential equation system. Numerical results show that only those particles originally lying in the libration region of the resonance can be shepherded. The size of the libration region depends mainly on the orbital eccentricity and mass of the shepherd satellite. For the outer shepherd Ophelia with larger orbital eccentricity, if its mass is a third of the nominal mass 2.5 × 1019 g, most of the orbits are regular and the outer edge of the ring can be shepherded, but more fuzzy than the inner edge. Thus we infer that Ophelia has a smaller mass.展开更多
文摘Dogs are used for centuries as people helpers. One of possible use is a sport and service. BSM （Belgian Shepherd Malinois） and GS （German shepherd） dogs are most used breeds like service dogs and also most represented at sports competitions. Our aim was to compare the results of these breeds in the World Cup of International tests of working dogs （in years 2003-2011）, which is the peak of competitions. The authors evaluated results of German shepherd dog performance test and Belgian shepherd Malinois performance in disciplines such as tracking, obedience and defense. Belgian Shepherds achieved in all disciplines higher score than German shepherds. It was found out that Belgian shepherd Malinois get significant higher score in all disciplines （tracking, obedience and defense） than German shepherd. However, both of breeds are used successfully as service dogs.
基金supported by the State Key Laboratory for Biology of Plant Diseases and Insect Pests,Institute of Plant Protection (IPP),Chinese Academy of Agricultural Sciences,China (SKL2010OP15)the National Natural Science Foundation of China (31000856)
文摘Shepherd＇s purse seeds were collected from winter wheat fields and road sides in Hebei Province,China.Their sensitivities to tribenuron-methyl were evaluated in a whole plant dose response assay in the greenhouse.Results revealed that HB-1,HB-2,HB-3,HB-4,HB-6,HB-7,HB-17,HB-18,HB-19,HB-20,HB-21,and HB-22 populations were susceptible to tribenuron-methyl characterised by very low GR50 values of about 0.10 g a.i.ha-1.On the other hand,populations HB-15 and HB-16 had moderate resistance to tribenuron-methyl with resistance indices （RI） ranging from 10-100 folds,whilst populations HB-5,HB-8,HB-9,HB-10,HB-11,HB-12,HB-13,and HB-14 expressed high level of resistance to tribenuron-methyl with resistance indices over 100.The proportion of moderate resistance level was about 9.09%,and that of high resistance was about 36.36%.
基金supported by the Russian Science Foundation(Project No.22-19-00160,https://rscf.ru/en/project/22-19-00160/).
文摘The removal of large space debris from a geostationary orbit to a disposal orbit via an ion beam shepherd spacecraft was considered in this study,with attention given to the electrostatic effect.The generation of an ion force,which provides contactless thrust,occurs because of the transfer of momentum from the ions of the engine plume of the spacecraft to the space debris.This process is accompanied by the transfer of a positive charge to the space debris.As a result,electrostatic interactions occur between the spacecraft and space debris.The goals of this study were to assess the influence of this effect on the dynamics of space debris during contactless ion beam-assisted removal and to develop hybrid contactless transportation schemes based on the use of an ion beam and electrostatic interactions.A mathematical model describing the motion of space debris and spacecraft under the influence of ionic and electrostatic forces and torques was developed.The concepts of electrostatic ion beam shepherd,electrostatic tractor with ion beam,and charged ion beam shepherd were proposed and compared.The results of numerical simulations revealed that the electrostatic ion beam shepherd scheme is preferable from the perspective of minimizing fuel costs when solving the problem of removing space debris from a geostationary orbit.A control law for the spacecraft charge needed for space-debris detumbling during ion-beam transportation is proposed.A numerical simulation of space debris removal was performed via a hybrid scheme.
基金supported by the National Key R&D Program of China (Grant No. 2022YFB3305600)the National Natural Science Foundation of China (Grant Nos. 62103015 and 62141604)+1 种基金the China Postdoctoral Science Foundation (Grant No. 2023M740185)the Postdoctoral Fellows of Beihang “Zhuoyue” Program。
文摘Swarming behaviors play an eminent role in both biological and engineering research, and show great potential applications in many emerging fields. Traditional swarming models still lack integrity, uniformity, and stability in swarm forming processes,resulting in fragmentation and void phenomena. Inspired by the shepherding behaviors observed in nature, we propose an integrated negotiation-control scheme for distributed swarm control of massive robots. The core idea of this scheme is that the robots at the boundary of the group herd the internal robots to form an equilibrium swarm. For this purpose, we introduce a concept of virtual group center towards which boundary robots herd internal robots. Then, a distributed negotiation mechanism is designed to allow each robot to negotiate the virtual group center only through local interactions with its neighbors. After that, we propose a shepherding-inspired swarm control law to drive a group of robots to form an integrated, uniform, and stable configuration from any initial states. Both numerical and flight simulations are presented to verify the effectiveness of our proposed swarm control scheme.
文摘To explain the long-term existence of Uranian narrow rings, we study the dynamical evolution of Uranian epsilon ring under the influence of its two shepherding satellites: Cordelia and Ophelia. The model of planar-elliptic restricted three-body problem is employed, in which the three bodies are Uranus, a satellite and a test particle. Dissipations due to interparticle collisions are also taken into consideration. A mapping system has been obtained based on the differential equation system. Numerical results show that only those particles originally lying in the libration region of the resonance can be shepherded. The size of the libration region depends mainly on the orbital eccentricity and mass of the shepherd satellite. For the outer shepherd Ophelia with larger orbital eccentricity, if its mass is a third of the nominal mass 2.5 × 1019 g, most of the orbits are regular and the outer edge of the ring can be shepherded, but more fuzzy than the inner edge. Thus we infer that Ophelia has a smaller mass.
