Chinese rescuers rush to assist disaster-stricken countries Avideo clip on Liu Xiangyang’s computer displays a moment he is very proud of. The clip shows an Iranian boy running after some vehicles, holding China’s n...Chinese rescuers rush to assist disaster-stricken countries Avideo clip on Liu Xiangyang’s computer displays a moment he is very proud of. The clip shows an Iranian boy running after some vehicles, holding China’s national flag in his hands and chanting "China, China..."展开更多
在当下种类繁多的少儿科普刊物中鲜见专门定位给学龄前儿童的幼儿科普刊物，新刊《幼儿大科学》是该领域内的一次突围。美国的同类型期刊Ranger Rick Jr．与之存在共性，但二者从封面设计、栏目设置、具体编排思路等方面营建起了各自的...在当下种类繁多的少儿科普刊物中鲜见专门定位给学龄前儿童的幼儿科普刊物，新刊《幼儿大科学》是该领域内的一次突围。美国的同类型期刊Ranger Rick Jr．与之存在共性，但二者从封面设计、栏目设置、具体编排思路等方面营建起了各自的独特风格。幼儿科普期刊文图并重，既需有效传达科学知识信息，又要潜在培养其审美品性，这要求文字简洁、活泼中不失准确性，并要巧妙转换具体表述；图片需要细节充分、选材独特，并具备图像美感；要努力实现期刊与读者的充分互动，以促使读者有效获取期刊内容，同时让期刊的内容效益最大化。展开更多
Forest rangers in Saihanba Forest Farm in north China＇s Hebei Province recently scooped a prestigious UN environment award for their outstanding contribution to restoration of degraded landscapes, amid the national e...Forest rangers in Saihanba Forest Farm in north China＇s Hebei Province recently scooped a prestigious UN environment award for their outstanding contribution to restoration of degraded landscapes, amid the national efforts to advance ecological civilization.展开更多
Due to the intense vibration durirLg launching and rigorous orbital temperature environment, the kinematic parameters of space robot may be largely deviated from their nominal parameters. The disparity will cause the ...Due to the intense vibration durirLg launching and rigorous orbital temperature environment, the kinematic parameters of space robot may be largely deviated from their nominal parameters. The disparity will cause the real pose （including position and orientation） of the end effector not to match the desired one, and further hinder the space robot from performing the scheduled mission. To improve pose accuracy of space robot, a new self-calibration method using the distance measurement provided by a laser-ranger fixed on the end-effector is proposed. A distance-measurement model of the space robot is built according to the distance from the starting point of the laser beam to the intersection point at the declining plane. Based on the model, the cost function about the pose error is derived. The kinematic calibration is transferred to a non-linear system optimization problem, which is solved by the improved differential evolution （DE） algoritlun. A six-degree of freedom （6-DOF） robot is used as a practical simulation example, and the simulation results show： 1） A significant improvement of pose accuracy of space robot can be obtained by distance measurement only; 2） Search efficiency is increased by improved DE; 3） More calibration configurations may make calibration results better.展开更多
文摘Chinese rescuers rush to assist disaster-stricken countries Avideo clip on Liu Xiangyang’s computer displays a moment he is very proud of. The clip shows an Iranian boy running after some vehicles, holding China’s national flag in his hands and chanting "China, China..."
文摘在当下种类繁多的少儿科普刊物中鲜见专门定位给学龄前儿童的幼儿科普刊物，新刊《幼儿大科学》是该领域内的一次突围。美国的同类型期刊Ranger Rick Jr．与之存在共性，但二者从封面设计、栏目设置、具体编排思路等方面营建起了各自的独特风格。幼儿科普期刊文图并重，既需有效传达科学知识信息，又要潜在培养其审美品性，这要求文字简洁、活泼中不失准确性，并要巧妙转换具体表述；图片需要细节充分、选材独特，并具备图像美感；要努力实现期刊与读者的充分互动，以促使读者有效获取期刊内容，同时让期刊的内容效益最大化。
文摘Forest rangers in Saihanba Forest Farm in north China＇s Hebei Province recently scooped a prestigious UN environment award for their outstanding contribution to restoration of degraded landscapes, amid the national efforts to advance ecological civilization.
基金Projects(60775049,60805033) supported by National Natural Science Foundation of ChinaProject(2007AA704317) supported by the National High Technology Research and Development Program of China
文摘Due to the intense vibration durirLg launching and rigorous orbital temperature environment, the kinematic parameters of space robot may be largely deviated from their nominal parameters. The disparity will cause the real pose （including position and orientation） of the end effector not to match the desired one, and further hinder the space robot from performing the scheduled mission. To improve pose accuracy of space robot, a new self-calibration method using the distance measurement provided by a laser-ranger fixed on the end-effector is proposed. A distance-measurement model of the space robot is built according to the distance from the starting point of the laser beam to the intersection point at the declining plane. Based on the model, the cost function about the pose error is derived. The kinematic calibration is transferred to a non-linear system optimization problem, which is solved by the improved differential evolution （DE） algoritlun. A six-degree of freedom （6-DOF） robot is used as a practical simulation example, and the simulation results show： 1） A significant improvement of pose accuracy of space robot can be obtained by distance measurement only; 2） Search efficiency is increased by improved DE; 3） More calibration configurations may make calibration results better.
