UWB signal digitization depends, to a large extent, on the accuracy of sampling time. A highaccuracy programmable timer is therefore the key to implementing UWB signal data acquisition. A high-accuracy programmable ti...UWB signal digitization depends, to a large extent, on the accuracy of sampling time. A highaccuracy programmable timer is therefore the key to implementing UWB signal data acquisition. A high-accuracy programmable timer based on the principle of ramp generators is described in this paper. The counting range of the timer is up to 16 bits, the timing precision is 8 ps, and the equivalent sampling rate is up to 50G Hz. No other identical product has been reported so far. This timer was successfully used in the data acquisition system for geological radar signals developed by us.展开更多
The general construction procedure of the steel middle pylon is briefly introduced. The alignment control of the pylon is carried out during the whole process of the construction. The control concept is extended to th...The general construction procedure of the steel middle pylon is briefly introduced. The alignment control of the pylon is carried out during the whole process of the construction. The control concept is extended to the manufacture stage. The manufacturing alignment error is strictly controlled in the segments precast process in factory, and the error is recognized and predicted precisely during the installation stage. The adjusting joints are employed to amend the accumulated error, which ensure that the steel pylon alignment could satisfy the precision requirements after installation.展开更多
In this work,a focused ion beam(FIB)-scanning electron microscopy(SEM) dual beam system was successfully built by integrating a FIB column and a graphics generator onto a SEM.Real-time observation can be realized by S...In this work,a focused ion beam(FIB)-scanning electron microscopy(SEM) dual beam system was successfully built by integrating a FIB column and a graphics generator onto a SEM.Real-time observation can be realized by SEM during the process of FIB milling.All kinds of graphics at nanoscale regime,such as lines,characters,and pictures,were achieved under the control of graphics generator.Moreover,the FIB milling line width can be reduced nearly 27% by the introduction of simultaneous electron beam,and a line width as small as 10 nm was achieved.The numerical analysis indicates that the significant improvement on line width is induced by the Coulomb interaction between the electrons and ions.展开更多
基金This research is sponsored by National Natural Science Foundation of China,Special Fund of Scientific Instruments:The studyand development of flameproof ground penetrating radar (50127402).
文摘UWB signal digitization depends, to a large extent, on the accuracy of sampling time. A highaccuracy programmable timer is therefore the key to implementing UWB signal data acquisition. A high-accuracy programmable timer based on the principle of ramp generators is described in this paper. The counting range of the timer is up to 16 bits, the timing precision is 8 ps, and the equivalent sampling rate is up to 50G Hz. No other identical product has been reported so far. This timer was successfully used in the data acquisition system for geological radar signals developed by us.
基金National Science and Technology Support Program of China ( No. 2009BAG15B02) Key Pro-grams for Science and Technology Development of Chinese Transportation Industry( No. 2008-353-332-180)
文摘The general construction procedure of the steel middle pylon is briefly introduced. The alignment control of the pylon is carried out during the whole process of the construction. The control concept is extended to the manufacture stage. The manufacturing alignment error is strictly controlled in the segments precast process in factory, and the error is recognized and predicted precisely during the installation stage. The adjusting joints are employed to amend the accumulated error, which ensure that the steel pylon alignment could satisfy the precision requirements after installation.
基金supported by the National Natural Science Foundation of China (Grant No. 50971011)Beijing Natural Science Foundation (Grant No. 1102025)+1 种基金Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20091102110038)the Fundamental Research Funds for the Central Universities (Grant No. 11174023)
文摘In this work,a focused ion beam(FIB)-scanning electron microscopy(SEM) dual beam system was successfully built by integrating a FIB column and a graphics generator onto a SEM.Real-time observation can be realized by SEM during the process of FIB milling.All kinds of graphics at nanoscale regime,such as lines,characters,and pictures,were achieved under the control of graphics generator.Moreover,the FIB milling line width can be reduced nearly 27% by the introduction of simultaneous electron beam,and a line width as small as 10 nm was achieved.The numerical analysis indicates that the significant improvement on line width is induced by the Coulomb interaction between the electrons and ions.
