Based on the overall analysis of the floating population among big and medium-sized cities in China,this paper, by means of statistics and questionnaires, makes a systematical study on the migratory features of the fl...Based on the overall analysis of the floating population among big and medium-sized cities in China,this paper, by means of statistics and questionnaires, makes a systematical study on the migratory features of the floating population in Mianyang, its employment structure, migrating causes and channels. According to the findings, the author finds a fact that with the strategy of Western Development, and with the construction of science and technology city of Mianyang, the migrating in Mianyang conforms to the general patterns of the migration, which has happened in those big and medium-sized cities in China.In addition,the city has a new but unique feature — economic factor, as the driving force of population migration, is quite distinct from that of those citiesin eastern areas of China.展开更多
In a fine adjustment mechanism of the second crystal in a double-crystal monochromator, a compression spring is usually used as a return force element, but it often produces permanent deform after some time. A novel f...In a fine adjustment mechanism of the second crystal in a double-crystal monochromator, a compression spring is usually used as a return force element, but it often produces permanent deform after some time. A novel fine adjust- ment mechanism is put forward, which utilizes permanent-magnet as the return force element instead of a compres- sion spring. Its principle and advantages of adjusting the pitch angle and the roll angle are analyzed, and the structure parameters of the permanent-magnet, which is the key part of the fine adjustment mechanism, are optimized. The magnetically adsorbed fine adjustment mechanism has been testified and applied successfully in the double-crystal monochromator of 4W1B beam line in Beijing Synchrotron Radiation Facility (BSRF).展开更多
In the light of the increasingly serious I/O bottleneck problem, the paper puts forward a method named RAID-M (RAID Matrix) to build high performance mass storage from cheap PC components based on the idea of multi-ch...In the light of the increasingly serious I/O bottleneck problem, the paper puts forward a method named RAID-M (RAID Matrix) to build high performance mass storage from cheap PC components based on the idea of multi-channel I/O and parallel access. Theoretical analyses prove that different RAID-M configurations vary their performance, space utilization and reliability, meeting various application goals. Experiments show that both the sequential read performance and sequential write performance of a RAID-M prototype machine have broken through the limitation of 32 bit/33 MHz PCI bus.展开更多
文摘Based on the overall analysis of the floating population among big and medium-sized cities in China,this paper, by means of statistics and questionnaires, makes a systematical study on the migratory features of the floating population in Mianyang, its employment structure, migrating causes and channels. According to the findings, the author finds a fact that with the strategy of Western Development, and with the construction of science and technology city of Mianyang, the migrating in Mianyang conforms to the general patterns of the migration, which has happened in those big and medium-sized cities in China.In addition,the city has a new but unique feature — economic factor, as the driving force of population migration, is quite distinct from that of those citiesin eastern areas of China.
文摘In a fine adjustment mechanism of the second crystal in a double-crystal monochromator, a compression spring is usually used as a return force element, but it often produces permanent deform after some time. A novel fine adjust- ment mechanism is put forward, which utilizes permanent-magnet as the return force element instead of a compres- sion spring. Its principle and advantages of adjusting the pitch angle and the roll angle are analyzed, and the structure parameters of the permanent-magnet, which is the key part of the fine adjustment mechanism, are optimized. The magnetically adsorbed fine adjustment mechanism has been testified and applied successfully in the double-crystal monochromator of 4W1B beam line in Beijing Synchrotron Radiation Facility (BSRF).
基金the National Natural Science Foundation of China(Grant No.60403043) the Doctorate Foundation of Tsinghua University.
文摘In the light of the increasingly serious I/O bottleneck problem, the paper puts forward a method named RAID-M (RAID Matrix) to build high performance mass storage from cheap PC components based on the idea of multi-channel I/O and parallel access. Theoretical analyses prove that different RAID-M configurations vary their performance, space utilization and reliability, meeting various application goals. Experiments show that both the sequential read performance and sequential write performance of a RAID-M prototype machine have broken through the limitation of 32 bit/33 MHz PCI bus.
