The active reflector of FAST ( five-hundred-meter aperture spherical radio telescope) is suppor- ted by a ring beam and a cable-net structure, in which nodes are actively controlled to form series of real-time parab...The active reflector of FAST ( five-hundred-meter aperture spherical radio telescope) is suppor- ted by a ring beam and a cable-net structure, in which nodes are actively controlled to form series of real-time paraboloids. To ensure the security and stability of the supporting structure, tension must be monitored for some typical cables. Considering the stringent requirements in accuracy and long- term stability, magnetic flux sensor, vibrating wire strain gauge and fiber bragg grating strain gauge are screened for the cable tension monitoring of the supporting cable-net. Specifically, receivers of radio telescopes have strict restriction on electro magnetic interference (EMI) or radio frequency in- terference (RFI). These three types of sensors are evaluated from the view of EMIfRFI. Firstly, these fundamentals are theoretically analyzed. Secondly, typical sensor signals are collected in the time and analyzed in the frequency domain, which shows the characteristic in the frequency domain. Finally, typical sensors are tested in an anechoic chamber to get the EMI levels. Theoretical analysis shows that Fiber Bragg Grating strain gauge itself will not lead to EMI/RFI. According to GJB151 A, frequency domain analysis and test results show that for the vibrating wire strain gauge and magnetic flux sensor themselves, testable EMIfRF1 levels are typically below the background noise of the ane- choic chamber. FAST finally choses these three sensors as the monitoring sensors of its cable ten- sion. The proposed study is also a reference to the monitoring equipment selection of other radio tele- scopes and large structures.展开更多
The Global Navigation Satellite System Reflectometry(GNSS-R) has been proven to be a powerful technique for retrieving geophysical parameters of ocean and land. Airborne GNSS-R is an important experimental platform, b...The Global Navigation Satellite System Reflectometry(GNSS-R) has been proven to be a powerful technique for retrieving geophysical parameters of ocean and land. Airborne GNSS-R is an important experimental platform, because it is not only needed as validation for spaceborne application, but also possesses the advantages to be capable of remote sensing of small and medium scale targets, such as rivers and lakes. This paper presents an overview of China's airborne GNSS-R campaign conducted on May 30, 2014, in Henan. The campaign has two objectives, i.e.:(1) to examine the capability of a GNSS-R payload developed by National Space Science Center,Chinese Academy of Sciences(NSSC, CAS) for airborneobservations and(2) to study the algorithms for soil moisture and river remote sensing, including altimetry and flow velocity measurement. A previous paper has presented results of soil moisture retrieval as part I, and in this paper,initial results of the Yellow River remote sensing are presented as part II. This paper presents the river altimetry results and explores a new potential application of GNSS-R technology, which is used to detect the flow velocity of the river. The river surface height results observed by code delay altimetry method were consistent with the height results of GPS dual-frequency differential positioning altimetry. The GNSS-R altimetry results showed that decimeter level heights were achieved in 1-min sliding average. Comparing with in situ measurements, the GNSSR flow velocity result was reasonable; the error was about0.027 m/s, which indicated the validity and feasibility of using GNSS-R technique to detect river flow velocity.展开更多
Objective:The rapid expansion of knowledge regarding the functional anatomy of hand and wrist,increasing functional demands of senior citizens and improved methodologies of achieving and maintaining anatomic restorat...Objective:The rapid expansion of knowledge regarding the functional anatomy of hand and wrist,increasing functional demands of senior citizens and improved methodologies of achieving and maintaining anatomic restoration of distal radius fractures has generated a renewed interest in addressing these fractures in a more precise manner.The purpose of our study was to evaluate the difference in patients function among those treated by 1) closed reduction and Plaster of Paris cast,2) distractor application,or 3) open reduction and internal fixation with a volar plate,and to assess the treatment choice for each particular fracture type.Methods:A prospective study was carried out on 60 patients with fractures of the distal end radius.Fractures were classified according to the AO classification into type A (extra-articular),type B (partial articular) and type C (complete articular).After initial evaluation patients were taken up for either conservative or operative treatment and were followed up for two years.Results:Anatomical results were evaluated according to the Sarmiento's modification of Lindstrom Criteria,which showed that excellent results were more frequent with open reduction and internal fixation using the plating technique.Clinical and functional results were evaluated according to the demerit point system of Gartland and Werley with Sarmiento modification,which was revealed to relate with the type of treatment techniques.Conclusion:There is no customized solution for all the fractures of the distal radius.The choice of treatment should be based on the fracture type,the patient's characteristics,the patient's demands and the treating surgeon's experience and preference.展开更多
基金Supported by the National Natural Science Foundation of China(No.11173035,11273036,11303059)
文摘The active reflector of FAST ( five-hundred-meter aperture spherical radio telescope) is suppor- ted by a ring beam and a cable-net structure, in which nodes are actively controlled to form series of real-time paraboloids. To ensure the security and stability of the supporting structure, tension must be monitored for some typical cables. Considering the stringent requirements in accuracy and long- term stability, magnetic flux sensor, vibrating wire strain gauge and fiber bragg grating strain gauge are screened for the cable tension monitoring of the supporting cable-net. Specifically, receivers of radio telescopes have strict restriction on electro magnetic interference (EMI) or radio frequency in- terference (RFI). These three types of sensors are evaluated from the view of EMIfRFI. Firstly, these fundamentals are theoretically analyzed. Secondly, typical sensor signals are collected in the time and analyzed in the frequency domain, which shows the characteristic in the frequency domain. Finally, typical sensors are tested in an anechoic chamber to get the EMI levels. Theoretical analysis shows that Fiber Bragg Grating strain gauge itself will not lead to EMI/RFI. According to GJB151 A, frequency domain analysis and test results show that for the vibrating wire strain gauge and magnetic flux sensor themselves, testable EMIfRF1 levels are typically below the background noise of the ane- choic chamber. FAST finally choses these three sensors as the monitoring sensors of its cable ten- sion. The proposed study is also a reference to the monitoring equipment selection of other radio tele- scopes and large structures.
基金supported by the National Youth Natural Science Foundations of China(41405040 and 41405039)the Scientific Research and Equipment Development Project of Chinese Academy of Sciences(YZ201129)the 12th Five-Year Plan of Civil Aerospace Technology Advanced Research Projects(Y1K0030044)
文摘The Global Navigation Satellite System Reflectometry(GNSS-R) has been proven to be a powerful technique for retrieving geophysical parameters of ocean and land. Airborne GNSS-R is an important experimental platform, because it is not only needed as validation for spaceborne application, but also possesses the advantages to be capable of remote sensing of small and medium scale targets, such as rivers and lakes. This paper presents an overview of China's airborne GNSS-R campaign conducted on May 30, 2014, in Henan. The campaign has two objectives, i.e.:(1) to examine the capability of a GNSS-R payload developed by National Space Science Center,Chinese Academy of Sciences(NSSC, CAS) for airborneobservations and(2) to study the algorithms for soil moisture and river remote sensing, including altimetry and flow velocity measurement. A previous paper has presented results of soil moisture retrieval as part I, and in this paper,initial results of the Yellow River remote sensing are presented as part II. This paper presents the river altimetry results and explores a new potential application of GNSS-R technology, which is used to detect the flow velocity of the river. The river surface height results observed by code delay altimetry method were consistent with the height results of GPS dual-frequency differential positioning altimetry. The GNSS-R altimetry results showed that decimeter level heights were achieved in 1-min sliding average. Comparing with in situ measurements, the GNSSR flow velocity result was reasonable; the error was about0.027 m/s, which indicated the validity and feasibility of using GNSS-R technique to detect river flow velocity.
文摘Objective:The rapid expansion of knowledge regarding the functional anatomy of hand and wrist,increasing functional demands of senior citizens and improved methodologies of achieving and maintaining anatomic restoration of distal radius fractures has generated a renewed interest in addressing these fractures in a more precise manner.The purpose of our study was to evaluate the difference in patients function among those treated by 1) closed reduction and Plaster of Paris cast,2) distractor application,or 3) open reduction and internal fixation with a volar plate,and to assess the treatment choice for each particular fracture type.Methods:A prospective study was carried out on 60 patients with fractures of the distal end radius.Fractures were classified according to the AO classification into type A (extra-articular),type B (partial articular) and type C (complete articular).After initial evaluation patients were taken up for either conservative or operative treatment and were followed up for two years.Results:Anatomical results were evaluated according to the Sarmiento's modification of Lindstrom Criteria,which showed that excellent results were more frequent with open reduction and internal fixation using the plating technique.Clinical and functional results were evaluated according to the demerit point system of Gartland and Werley with Sarmiento modification,which was revealed to relate with the type of treatment techniques.Conclusion:There is no customized solution for all the fractures of the distal radius.The choice of treatment should be based on the fracture type,the patient's characteristics,the patient's demands and the treating surgeon's experience and preference.