The existing research results show that a fixed single station must conduct three consecutive frequency shift measurements and obtain the target’s moving speed by constructing two frequency difference equations. This...The existing research results show that a fixed single station must conduct three consecutive frequency shift measurements and obtain the target’s moving speed by constructing two frequency difference equations. This article proposes a new method that requires only two consecutive measurements. While using the azimuth measurement to obtain the angular difference between two radial distances, it also conducts two consecutive Doppler frequency shift measurements at the same target azimuth. On the basis of this measurement, a frequency difference equation is first constructed and solved jointly with the Doppler frequency shift equation. By eliminating the velocity variable and using the measured angular difference to obtain the target’s lead angle, the target’s velocity can be solved by using the Doppler frequency shift equation again. The new method avoids the condition that the target must move equidistantly, which not only provides an achievable method for engineering applications but also lays a good foundation for further exploring the use of steady-state signals to achieve passive positioning.展开更多
An applicable method to control regenerative cutting chatter automatically based on the optimal regulation of spindle speed is introduced. The optimal value of the phase shift angle of the regenerative chatter signal ...An applicable method to control regenerative cutting chatter automatically based on the optimal regulation of spindle speed is introduced. The optimal value of the phase shift angle of the regenerative chatter signal between the two successive cuts is 270°. The cutting process can be adjusted from the unstable region to stable one whenever regenerative chatter occurs if the phase shift angle is kept 270° by the optimal regulation of spindle speed. The theoretical analysis and the experimental results prove that the optimal regulation of spindle speed can effectively control regenerative cutting chatter. In addition, a reliablelly optimal control system of reliable spindle speed is presented. There is no need for system identification of the machine tool, and it is easy to put this regenerative chatter control method into practice, so the method has excellent application prospect.展开更多
There exist many methods to measure blood speed, all of which have some serious shortcomings. As fiber is characterized by tiny diameter, and low lost ratio of power and flexibility, it is suitable for measuring blood...There exist many methods to measure blood speed, all of which have some serious shortcomings. As fiber is characterized by tiny diameter, and low lost ratio of power and flexibility, it is suitable for measuring blood speed. It is proved that the speedometer has high space resolving power,high time resolving power, and outstanding capability of approaching target, etc.展开更多
This paper addresses the clustering problem for mobile ad hoc networks. In the proposed scheme, Doppler shift associated with received signals is used to estimate the relative speed between aelnster head and its membe...This paper addresses the clustering problem for mobile ad hoc networks. In the proposed scheme, Doppler shift associated with received signals is used to estimate the relative speed between aelnster head and its members. With the estimated speed, a node can predict its stay time in every nearby cluster. In the initial clustering stage, a node joins a duster that can provide it with the longest stay time in order to reduce the number of re-affiliations. In the cluster maintaining stage, strategies are designed to help node cope with connection break caused by channel fading and node mobility. Simulation results show that the proposed clustering scheme can reduce the number of re-affiliations and the average disconnection time compared with previous schemes.展开更多
EA公司的极品飞车系列游戏（英文名称：《Need For Speed》）在国内有着众多拥趸，其第13代作品《变速（Shift）》前段时间刚刚发布，各位飞车迷们恐怕早已按捺不住，相信手快的朋友们已经玩穿了第一遍。对于这样一款赛车佳作而言，我...EA公司的极品飞车系列游戏（英文名称：《Need For Speed》）在国内有着众多拥趸，其第13代作品《变速（Shift）》前段时间刚刚发布，各位飞车迷们恐怕早已按捺不住，相信手快的朋友们已经玩穿了第一遍。对于这样一款赛车佳作而言，我们想说的是——“不用方向盘去玩，实在浪费了!”展开更多
文摘The existing research results show that a fixed single station must conduct three consecutive frequency shift measurements and obtain the target’s moving speed by constructing two frequency difference equations. This article proposes a new method that requires only two consecutive measurements. While using the azimuth measurement to obtain the angular difference between two radial distances, it also conducts two consecutive Doppler frequency shift measurements at the same target azimuth. On the basis of this measurement, a frequency difference equation is first constructed and solved jointly with the Doppler frequency shift equation. By eliminating the velocity variable and using the measured angular difference to obtain the target’s lead angle, the target’s velocity can be solved by using the Doppler frequency shift equation again. The new method avoids the condition that the target must move equidistantly, which not only provides an achievable method for engineering applications but also lays a good foundation for further exploring the use of steady-state signals to achieve passive positioning.
文摘An applicable method to control regenerative cutting chatter automatically based on the optimal regulation of spindle speed is introduced. The optimal value of the phase shift angle of the regenerative chatter signal between the two successive cuts is 270°. The cutting process can be adjusted from the unstable region to stable one whenever regenerative chatter occurs if the phase shift angle is kept 270° by the optimal regulation of spindle speed. The theoretical analysis and the experimental results prove that the optimal regulation of spindle speed can effectively control regenerative cutting chatter. In addition, a reliablelly optimal control system of reliable spindle speed is presented. There is no need for system identification of the machine tool, and it is easy to put this regenerative chatter control method into practice, so the method has excellent application prospect.
文摘There exist many methods to measure blood speed, all of which have some serious shortcomings. As fiber is characterized by tiny diameter, and low lost ratio of power and flexibility, it is suitable for measuring blood speed. It is proved that the speedometer has high space resolving power,high time resolving power, and outstanding capability of approaching target, etc.
基金Supported by the National Science Foundation of China （No. 60830001）, the Program for Changjiang Scholars and Innovative Research Team in University （No. IRT0949） and the State key Laboratory of Rail traffic Con~ol and Safety （No. RCS2010ZT012）
文摘This paper addresses the clustering problem for mobile ad hoc networks. In the proposed scheme, Doppler shift associated with received signals is used to estimate the relative speed between aelnster head and its members. With the estimated speed, a node can predict its stay time in every nearby cluster. In the initial clustering stage, a node joins a duster that can provide it with the longest stay time in order to reduce the number of re-affiliations. In the cluster maintaining stage, strategies are designed to help node cope with connection break caused by channel fading and node mobility. Simulation results show that the proposed clustering scheme can reduce the number of re-affiliations and the average disconnection time compared with previous schemes.
