How will we keep the motivation during the second language as long as we can,which confuses us,though what the L2 motivation is and how it is developed have been discussed by the psychologists,educators,etc.The aim of...How will we keep the motivation during the second language as long as we can,which confuses us,though what the L2 motivation is and how it is developed have been discussed by the psychologists,educators,etc.The aim of this passage is to clarify the basic content of motivation,including the definition,classification,importance,etc.how the current situation is in senior high students’English learning motivation,what should be done to keep such motivation.In the following part,it will be read that the introduction,the chapter stating the content and classification of(L2)motivation,the chapter analyzing the necessity and state of L2 motivation at senor high,the chapter offering approach to keep that motivation,and the conclusion.All of them use the comparison,explanation and cites.展开更多
Consensus is an emerging technique using neighbor-to-neighbor interaction to generate steering commands for cooperative control of multiple vehicles. A three-dimensional formation keeping strategy for multiple unmanne...Consensus is an emerging technique using neighbor-to-neighbor interaction to generate steering commands for cooperative control of multiple vehicles. A three-dimensional formation keeping strategy for multiple unmanned aerial vehicles(multi-UAV) is proposed based on consensus, aiming at maintaining a specified geometric configuration. A formation control algorithm with guidance and corresponding flight controllers is given, managing position and attitude, respectively. In order to follow a three-dimensional predefined flight path, by introducing the tracking orders as reference states into the consensus, the formation control algorithm is designed, following the predefined flight path and maintaining geometric configuration simultaneously. The flight controllers are constructed by nonlinear dynamic inverse, including attitude design and velocity design. With the whole system composed of a nonlinear six-degree-of-freedom UAV model, the formation control algorithm and the flight controllers, the formation keeping strategy is closed loop and with full states. In simulation, three-dimensional formation flight demonstrates the feasibility and effectiveness of the proposed strategy.展开更多
The stratosphere airship provides a unique and promising platform for earth observation. Researches on the project design and control scheme for earth observation platforms are still rarely documented. Nonlinear dynam...The stratosphere airship provides a unique and promising platform for earth observation. Researches on the project design and control scheme for earth observation platforms are still rarely documented. Nonlinear dynamics, model uncertainties, and external disturbances contribute to the difficulty in maneuvering the stratosphere airship. A key technical challenge for the earth observation platform is station keeping, or the ability to remain fixed over a geo-location. This paper investigates the conceptual design, modeling and station-keeping attitude control of the near-space earth observation platform. A conceptual design of the earth observation platform is presented. The dynamics model of the platform is derived from the Newton-Euler formulation, and the station-keeping control system of the platform is formulated. The station-keeping attitude control approach for the platform is proposed. The multi-input multi-output nonlinear control system is decoupled into three single-input single-output linear subsystems via feedback linearization, the attitude controller design is carried out on the new linear systems using terminal sliding mode control, and the global stability of the closed-loop system is proven by using the Lyapunov theorem. The performance of the designed control system is simulated by using the variable step Runge-Kutta integrator. Simulation results show that the control system tracks the commanded attitude with an error of zero, which verify the effectiveness and robustness of the designed control system in the presence of parametric uncertainties. The near-space earth observation platform has several advantages over satellites, such as high resolution, fast to deploy, and convenient to retrieve, and the proposed control scheme provides an effective approach for station-keeping attitude control of the earth observation platform.展开更多
Approaches to the study of formation keeping for multiple mobile robots are analyzed and a behavior-based robot model is built in this paper. And, a kind of coordination architecture is presented, which is similar to ...Approaches to the study of formation keeping for multiple mobile robots are analyzed and a behavior-based robot model is built in this paper. And, a kind of coordination architecture is presented, which is similar to the infantry squad organization and is used to realize multiple mobile robots to keep formations. Simulations verify the validity of the approach to keep formation, which combines the behavior-based method and formation feedback. The effects of formation feedback on the performance of the system are analyzed.展开更多
In this paper, we show that circular polarization-keeping reflection can be achieved using reflective metasurfaces. The underlying physical mechanism of the polarization-keeping reflection is analyzed using a reflecti...In this paper, we show that circular polarization-keeping reflection can be achieved using reflective metasurfaces. The underlying physical mechanism of the polarization-keeping reflection is analyzed using a reflection matrix. A wideband circular polarization-keeping reflector is demonstrated using N-shaped resonators. Both the simulation and experiment results show that the polarization-keeping reflection can be achieved with a high efficiency larger than 98% over the frequency range from 9.2 GHz to 17.7 GHz for both incident left- and right-handed circularly polarized waves. Under oblique incidence, the bandwidth increases as the incident angle varies from 0°to 80°. Moreover, the co-polarization reflection is independent of the incident azimuth angles.展开更多
This paper presents the design of hardware and software of the house keeping system for a certain micro satellite. The system uses micro electronic technique, large scale integrated circuits, processors and computers ...This paper presents the design of hardware and software of the house keeping system for a certain micro satellite. The system uses micro electronic technique, large scale integrated circuits, processors and computers which has the advantages of strong function, high flexibility and reliability, It satisfies the requirements for efficient performance,light weight, small volume,and low consumption of power for micro satellite.展开更多
Using sucrose, citric acid and vitamin C as the basic liquid, different concentrations of 6-BA and B9 preservatives were added, and the carnation variety ＇ Master＇ was treated. The results showed that the formula of...Using sucrose, citric acid and vitamin C as the basic liquid, different concentrations of 6-BA and B9 preservatives were added, and the carnation variety ＇ Master＇ was treated. The results showed that the formula of 3% sucrose ＋ 50 mg/L citric acid ＋ 600 mg/L vitamin C ＋ 20 mg/L 6-BA could effectively maintain the water balance of the cut flower, prolong the vase life of the cut flower to 16.4 d, and maximize the flower diameter and the crown height.展开更多
文摘How will we keep the motivation during the second language as long as we can,which confuses us,though what the L2 motivation is and how it is developed have been discussed by the psychologists,educators,etc.The aim of this passage is to clarify the basic content of motivation,including the definition,classification,importance,etc.how the current situation is in senior high students’English learning motivation,what should be done to keep such motivation.In the following part,it will be read that the introduction,the chapter stating the content and classification of(L2)motivation,the chapter analyzing the necessity and state of L2 motivation at senor high,the chapter offering approach to keep that motivation,and the conclusion.All of them use the comparison,explanation and cites.
基金Project(61473229)supported by the National Natural Science Foundation of ChinaProjects(310832163403,310832161012)supported by the Special Fund for Basic Scientific Research of Central Colleges,Chang'an University,ChinaProject(CXY1512-3)supported by the Xi'an Science and Technology Plan,China
文摘Consensus is an emerging technique using neighbor-to-neighbor interaction to generate steering commands for cooperative control of multiple vehicles. A three-dimensional formation keeping strategy for multiple unmanned aerial vehicles(multi-UAV) is proposed based on consensus, aiming at maintaining a specified geometric configuration. A formation control algorithm with guidance and corresponding flight controllers is given, managing position and attitude, respectively. In order to follow a three-dimensional predefined flight path, by introducing the tracking orders as reference states into the consensus, the formation control algorithm is designed, following the predefined flight path and maintaining geometric configuration simultaneously. The flight controllers are constructed by nonlinear dynamic inverse, including attitude design and velocity design. With the whole system composed of a nonlinear six-degree-of-freedom UAV model, the formation control algorithm and the flight controllers, the formation keeping strategy is closed loop and with full states. In simulation, three-dimensional formation flight demonstrates the feasibility and effectiveness of the proposed strategy.
基金supported by Hunan Provincial Innovation Foundation for Postgraduate(Grant No. CX2011B005)National University of Defense Technology Innovation Foundation for Postgraduate, China(GranNo. B110105)
文摘The stratosphere airship provides a unique and promising platform for earth observation. Researches on the project design and control scheme for earth observation platforms are still rarely documented. Nonlinear dynamics, model uncertainties, and external disturbances contribute to the difficulty in maneuvering the stratosphere airship. A key technical challenge for the earth observation platform is station keeping, or the ability to remain fixed over a geo-location. This paper investigates the conceptual design, modeling and station-keeping attitude control of the near-space earth observation platform. A conceptual design of the earth observation platform is presented. The dynamics model of the platform is derived from the Newton-Euler formulation, and the station-keeping control system of the platform is formulated. The station-keeping attitude control approach for the platform is proposed. The multi-input multi-output nonlinear control system is decoupled into three single-input single-output linear subsystems via feedback linearization, the attitude controller design is carried out on the new linear systems using terminal sliding mode control, and the global stability of the closed-loop system is proven by using the Lyapunov theorem. The performance of the designed control system is simulated by using the variable step Runge-Kutta integrator. Simulation results show that the control system tracks the commanded attitude with an error of zero, which verify the effectiveness and robustness of the designed control system in the presence of parametric uncertainties. The near-space earth observation platform has several advantages over satellites, such as high resolution, fast to deploy, and convenient to retrieve, and the proposed control scheme provides an effective approach for station-keeping attitude control of the earth observation platform.
文摘Approaches to the study of formation keeping for multiple mobile robots are analyzed and a behavior-based robot model is built in this paper. And, a kind of coordination architecture is presented, which is similar to the infantry squad organization and is used to realize multiple mobile robots to keep formations. Simulations verify the validity of the approach to keep formation, which combines the behavior-based method and formation feedback. The effects of formation feedback on the performance of the system are analyzed.
基金Project supported by the National Natural Science Foundation of China(Grants Nos.61331005,11204378,11274389,11304393,and 61302023)the National Natural Science Foundation of Shaanxi Province,China(Grant Nos.2011JQ8031 and 2013JM6005)
文摘In this paper, we show that circular polarization-keeping reflection can be achieved using reflective metasurfaces. The underlying physical mechanism of the polarization-keeping reflection is analyzed using a reflection matrix. A wideband circular polarization-keeping reflector is demonstrated using N-shaped resonators. Both the simulation and experiment results show that the polarization-keeping reflection can be achieved with a high efficiency larger than 98% over the frequency range from 9.2 GHz to 17.7 GHz for both incident left- and right-handed circularly polarized waves. Under oblique incidence, the bandwidth increases as the incident angle varies from 0°to 80°. Moreover, the co-polarization reflection is independent of the incident azimuth angles.
文摘This paper presents the design of hardware and software of the house keeping system for a certain micro satellite. The system uses micro electronic technique, large scale integrated circuits, processors and computers which has the advantages of strong function, high flexibility and reliability, It satisfies the requirements for efficient performance,light weight, small volume,and low consumption of power for micro satellite.
文摘Using sucrose, citric acid and vitamin C as the basic liquid, different concentrations of 6-BA and B9 preservatives were added, and the carnation variety ＇ Master＇ was treated. The results showed that the formula of 3% sucrose ＋ 50 mg/L citric acid ＋ 600 mg/L vitamin C ＋ 20 mg/L 6-BA could effectively maintain the water balance of the cut flower, prolong the vase life of the cut flower to 16.4 d, and maximize the flower diameter and the crown height.
