A second-order divided difference filter (SDDF) is derived for integrating line of sight measurement from vision sensor with acceleration and angular rate measurements of the follower to estimate the precise relative ...A second-order divided difference filter (SDDF) is derived for integrating line of sight measurement from vision sensor with acceleration and angular rate measurements of the follower to estimate the precise relative position,velocity and attitude of two unmanned aerial vehicles (UAVs).The second-order divided difference filter which makes use of multidimensional interpolation formulations to approximate the nonlinear transformations could achieve more accurate estimation and faster convergence from inaccurate initial conditions than standard extended Kalman filter.The filter formulation is based on relative motion equations.The global attitude parameterization is given by quarternion,while a generalized three-dimensional attitude representation is used to define the local attitude error.Simulation results are shown to compare the performance of the second-order divided difference filter with a standard extended Kalman filter approach.展开更多
Since 1980's English has been established as the important objective in the field of English language teaching in the class,many teachers and experts have got considerable experience in the process of teaching. In...Since 1980's English has been established as the important objective in the field of English language teaching in the class,many teachers and experts have got considerable experience in the process of teaching. In English teaching,teachers pay attention to the proportion of students entering higher school and neglect students' affection. Krashen's theory of second language acquisition consists of five hypotheses; one of them is affective filter hypothesis,which contains three main factors-motivation self-confidence and anxiety. This research will analyze the influence of motivation self-confidence and anxiety and tent to find the better way to solve the influence of affective by the qualitative and quantitative perspectives. The result shows that affective filter hypothesis could have an influence on the students' achievements.展开更多
Lots of factors are affecting second language acquisition,of which age is a hotly debated one.Some researchers do believe that age has a central effect on the acquisition of both first and second languages and there i...Lots of factors are affecting second language acquisition,of which age is a hotly debated one.Some researchers do believe that age has a central effect on the acquisition of both first and second languages and there is a critical(Lenneberg,1967) or sensitive period in language acquisition,while others think that no adequate evidence of starting early contributes to the proficiency of the target language.Here I will list some of the hypotheses related to age and second language acquisition and find out whether it is true that children acquire more than adults in second language.展开更多
电力系统运行在非理想状态时,容易产生短暂的电压波动,此时并联有源电力滤波器(shunt active power filter,SAPF)采用无源控制策略无法高效、精确地调节电能质量,而常规滑模控制又容易引起抖振。针对上述情况,将无源控制和抗干扰能力更...电力系统运行在非理想状态时,容易产生短暂的电压波动,此时并联有源电力滤波器(shunt active power filter,SAPF)采用无源控制策略无法高效、精确地调节电能质量,而常规滑模控制又容易引起抖振。针对上述情况,将无源控制和抗干扰能力更强的超螺旋二阶滑模控制相结合,提出了一种无源超螺旋二阶滑模控制策略。首先,根据有源电力滤波器的数学模型建立基于正负序分离的欧拉−拉格朗日模型;其次,对系统的模型进行了无源性分析,且根据其无源性设计了无源控制器,同时采用超螺旋二阶滑模控制对无源控制器进一步优化,提高了系统整体的鲁棒性和抗干扰能力;最后,在理想状态和负载突变、负载不平衡、电网电压不平衡、单相电压突变4种非理想状态下,通过仿真实验验证了无源超螺旋二阶滑模控制策略的有效性和优越性。展开更多
A current-mode low input and high output impedances first-order allpass filter using two multiple output second-generation current conveyors (MOCCIIs), one grounded capacitor and one grounded resistor is presented. Th...A current-mode low input and high output impedances first-order allpass filter using two multiple output second-generation current conveyors (MOCCIIs), one grounded capacitor and one grounded resistor is presented. The suggested filter uses a canonical number of passive components without requiring any component matching condition. The frequency responses simulation results of the proposed filter confirm the theoretical analysis.展开更多
Stephen Krashen's affective filter hypothesis plays a vital role in second language acquisition and foreign language teaching.This paper analyzes the affective factors which influence the English pronunciation lea...Stephen Krashen's affective filter hypothesis plays a vital role in second language acquisition and foreign language teaching.This paper analyzes the affective factors which influence the English pronunciation learning of the students in higher vocational college and put forward some suggestions on how to improve English pronunciation teaching,based on this affective filter hypothesis.展开更多
基金Sponsored by the Aerospace Technology Innovation Funding(Grant No. CASC0209)
文摘A second-order divided difference filter (SDDF) is derived for integrating line of sight measurement from vision sensor with acceleration and angular rate measurements of the follower to estimate the precise relative position,velocity and attitude of two unmanned aerial vehicles (UAVs).The second-order divided difference filter which makes use of multidimensional interpolation formulations to approximate the nonlinear transformations could achieve more accurate estimation and faster convergence from inaccurate initial conditions than standard extended Kalman filter.The filter formulation is based on relative motion equations.The global attitude parameterization is given by quarternion,while a generalized three-dimensional attitude representation is used to define the local attitude error.Simulation results are shown to compare the performance of the second-order divided difference filter with a standard extended Kalman filter approach.
文摘Since 1980's English has been established as the important objective in the field of English language teaching in the class,many teachers and experts have got considerable experience in the process of teaching. In English teaching,teachers pay attention to the proportion of students entering higher school and neglect students' affection. Krashen's theory of second language acquisition consists of five hypotheses; one of them is affective filter hypothesis,which contains three main factors-motivation self-confidence and anxiety. This research will analyze the influence of motivation self-confidence and anxiety and tent to find the better way to solve the influence of affective by the qualitative and quantitative perspectives. The result shows that affective filter hypothesis could have an influence on the students' achievements.
文摘Lots of factors are affecting second language acquisition,of which age is a hotly debated one.Some researchers do believe that age has a central effect on the acquisition of both first and second languages and there is a critical(Lenneberg,1967) or sensitive period in language acquisition,while others think that no adequate evidence of starting early contributes to the proficiency of the target language.Here I will list some of the hypotheses related to age and second language acquisition and find out whether it is true that children acquire more than adults in second language.
文摘电力系统运行在非理想状态时,容易产生短暂的电压波动,此时并联有源电力滤波器(shunt active power filter,SAPF)采用无源控制策略无法高效、精确地调节电能质量,而常规滑模控制又容易引起抖振。针对上述情况,将无源控制和抗干扰能力更强的超螺旋二阶滑模控制相结合,提出了一种无源超螺旋二阶滑模控制策略。首先,根据有源电力滤波器的数学模型建立基于正负序分离的欧拉−拉格朗日模型;其次,对系统的模型进行了无源性分析,且根据其无源性设计了无源控制器,同时采用超螺旋二阶滑模控制对无源控制器进一步优化,提高了系统整体的鲁棒性和抗干扰能力;最后,在理想状态和负载突变、负载不平衡、电网电压不平衡、单相电压突变4种非理想状态下,通过仿真实验验证了无源超螺旋二阶滑模控制策略的有效性和优越性。
文摘A current-mode low input and high output impedances first-order allpass filter using two multiple output second-generation current conveyors (MOCCIIs), one grounded capacitor and one grounded resistor is presented. The suggested filter uses a canonical number of passive components without requiring any component matching condition. The frequency responses simulation results of the proposed filter confirm the theoretical analysis.
文摘Stephen Krashen's affective filter hypothesis plays a vital role in second language acquisition and foreign language teaching.This paper analyzes the affective factors which influence the English pronunciation learning of the students in higher vocational college and put forward some suggestions on how to improve English pronunciation teaching,based on this affective filter hypothesis.
