Generally speaking, "an economic circle" refers to a group of countriesand regions whose economic relations override the universally accepted in-ternational practice or norms and they have formulated new eco...Generally speaking, "an economic circle" refers to a group of countriesand regions whose economic relations override the universally accepted in-ternational practice or norms and they have formulated new economic ruleswhich are applicable only to countries and regions inside the circle.展开更多
According to the urban and rural income levels and the national poverty line,peasant households are classified into poor households,middle-income households and wealthy households.Based on the investigation data of 25...According to the urban and rural income levels and the national poverty line,peasant households are classified into poor households,middle-income households and wealthy households.Based on the investigation data of 259 peasant households in three villages of Hebei Province,the features of family structure,economy,ideology and communication of peasant households with different income levels in current status are analyzed.The result shows that there are great differences in family structure,ideology,economy and communication of peasant households with different income levels.The low-income households are featured by unreasonable family structure,heavy burden,conservative behavior and blocking information.While the middle and high income households are good at communicating and willing to take risk and armed with high skills.Based on this,relevant suggestions are put forward to promote the development of peasant households,such as optimizing family structure,cultivating the capacity of the core numbers of the family,guiding households to choose a suitable development path,encouraging farmers to work out,ensuring the legitimate rights and interests of migrant workers,flourishing rural culture,and setting up good platform for the communication of households.展开更多
Although the parallel mechanisms have the advantages of high accuracy, velocity, stiffness, and payload capacity, the shortcomings of the space utilization and workspace limit the applications in the confined space. A...Although the parallel mechanisms have the advantages of high accuracy, velocity, stiffness, and payload capacity, the shortcomings of the space utilization and workspace limit the applications in the confined space. A novel 3 degrees of freedom spatial parallel manipulator 3-PSR-O（prismatic-spherical-revolute） is proposed, which possesses a compact architecture and extended workspace while maintaining the inherent advantages of the parallel mechanisms. The direct-inverse position, singularity and workspace are investigated. The mapping method is adopted in the position analysis, and the closed form solution is derived in the form of a six order equation. The singularity analysis of the mechanism is also carried out based on the geometrical constraints, including six singularity boundaries. A feature boundary, which is independent of the prismatic joints＇ stroke limit, is obtained by integrating the six singularity boundaries. According to the formation of the reachable workspace, a concept of basic workspace is also introduced and presented in the analytical way. By demarcating the basic workspace along the central height with the feature boundary, the reachable workspace can be derived and analyzed more efficiently. Finally, a comparative study on the space utilization between the 3-PSP parallel mechanism and the new mechanism is also presented. The area of feature boundary of the new mechanism is about 140% of the 3-PSP parallel mechanism, while its installation radius is only 1/2 of the 3-PSP parallel mechanism. The proposed parallel mechanism shows great space utilization, and is ideally suited for applications in confined space occasions such as immersion lithography, nano-imprint etc.展开更多
On December 26,China Economic Information Agency of Xinhua News Agency and Baotou Rare Earth Product Exchange jointly released China Rare Earth Price Index(CREPI).This index is China’s first rare earth price index su...On December 26,China Economic Information Agency of Xinhua News Agency and Baotou Rare Earth Product Exchange jointly released China Rare Earth Price Index(CREPI).This index is China’s first rare earth price index supported by online trading data.Jia Yinsong,展开更多
文摘Generally speaking, "an economic circle" refers to a group of countriesand regions whose economic relations override the universally accepted in-ternational practice or norms and they have formulated new economic ruleswhich are applicable only to countries and regions inside the circle.
文摘According to the urban and rural income levels and the national poverty line,peasant households are classified into poor households,middle-income households and wealthy households.Based on the investigation data of 259 peasant households in three villages of Hebei Province,the features of family structure,economy,ideology and communication of peasant households with different income levels in current status are analyzed.The result shows that there are great differences in family structure,ideology,economy and communication of peasant households with different income levels.The low-income households are featured by unreasonable family structure,heavy burden,conservative behavior and blocking information.While the middle and high income households are good at communicating and willing to take risk and armed with high skills.Based on this,relevant suggestions are put forward to promote the development of peasant households,such as optimizing family structure,cultivating the capacity of the core numbers of the family,guiding households to choose a suitable development path,encouraging farmers to work out,ensuring the legitimate rights and interests of migrant workers,flourishing rural culture,and setting up good platform for the communication of households.
基金Supported by National Natural Science Foundation of China(Grant No.51221004)National Hi-tech Research and Development Program of China(863 Program,Grant No.2012AA040605)
文摘Although the parallel mechanisms have the advantages of high accuracy, velocity, stiffness, and payload capacity, the shortcomings of the space utilization and workspace limit the applications in the confined space. A novel 3 degrees of freedom spatial parallel manipulator 3-PSR-O（prismatic-spherical-revolute） is proposed, which possesses a compact architecture and extended workspace while maintaining the inherent advantages of the parallel mechanisms. The direct-inverse position, singularity and workspace are investigated. The mapping method is adopted in the position analysis, and the closed form solution is derived in the form of a six order equation. The singularity analysis of the mechanism is also carried out based on the geometrical constraints, including six singularity boundaries. A feature boundary, which is independent of the prismatic joints＇ stroke limit, is obtained by integrating the six singularity boundaries. According to the formation of the reachable workspace, a concept of basic workspace is also introduced and presented in the analytical way. By demarcating the basic workspace along the central height with the feature boundary, the reachable workspace can be derived and analyzed more efficiently. Finally, a comparative study on the space utilization between the 3-PSP parallel mechanism and the new mechanism is also presented. The area of feature boundary of the new mechanism is about 140% of the 3-PSP parallel mechanism, while its installation radius is only 1/2 of the 3-PSP parallel mechanism. The proposed parallel mechanism shows great space utilization, and is ideally suited for applications in confined space occasions such as immersion lithography, nano-imprint etc.
文摘On December 26,China Economic Information Agency of Xinhua News Agency and Baotou Rare Earth Product Exchange jointly released China Rare Earth Price Index(CREPI).This index is China’s first rare earth price index supported by online trading data.Jia Yinsong,
