Nowadays, there are many larger and taller engineering structures than in the past. These structures are commonly designed to be more flexible. Thus, they are sensitive to severe wind gust and earthquake tremor. For t...Nowadays, there are many larger and taller engineering structures than in the past. These structures are commonly designed to be more flexible. Thus, they are sensitive to severe wind gust and earthquake tremor. For the dynamic response prediction, finite element (FE) modal updating and structural health monitoring, the dynamic characteristics of a structure are becoming increasingly important. The aim of this paper is to show an emerging tool-the real time kinematic (RTK) global positioning system (GPS), which is used to measure and monitor the low-frequency vibration of Dalian BeiDa Bridge, a medium span suspension bridge. The modal analysis is firstly performed on the developed three-dimensional FE model according to the original blue prints of the bridge to provide the analytical frequencies and mode shapes. The field ambient vibration tests using the accelerometers on the bridge deck are conducted just prior to the use of the GPS system in order to validate the FE model. And then, the calibration test is done to assess the dynamic displacement measurement accuracy of the GPS in three orthogonal directions. The GPS signal properties, such as the amplitude, standard deviations (STD), power spectral density (PSD), and probability density functions (PDF), are studied in details. After that, a structural health monitoring system based on the GPS is devised and installed on the bridge to provide real-time measurement of deck movement. The output-only modal parameter identification is carried out by using the Periodogram method to investigate the responses of the bridge. The result shows that the spectral densities of the displacements measured by the GPS correspond well with the results by the FEM analysis and the accelerometer vibration test. It is concluded that the GPS method is reliable and useful to clarify the ambient vibration response behaviors of the flexible structures. The integration of the GPS and accelerometer methods results in a hybrid arrangement that can help to eliminate some disadvantages of th展开更多
在室内环境下,全球定位系统(GPS)以及其他定位技术受许多不可抗拒的因素影响无法对用户进行精准定位。然而,从移动互联到物联网,位置是一个基础的不可或缺的信息,对于精细化的行业应用需求来说,越精准的定位信息越能带来更高的价值。所...在室内环境下,全球定位系统(GPS)以及其他定位技术受许多不可抗拒的因素影响无法对用户进行精准定位。然而,从移动互联到物联网,位置是一个基础的不可或缺的信息,对于精细化的行业应用需求来说,越精准的定位信息越能带来更高的价值。所以,为向群众提供无所不在的位置服务,对UWB(Ultra Wide Band)技术与TOA(Time of Arrival)的定位算法进行了研究,并设计出了一款基于UWB技术的高精度室内定位系统。最后,通过试验验证了系统的精准度能达到厘米级,且实时性较好。展开更多
Traditional agriculture is facing several challenges worldwide such as increased population growth,rapid forestry and urbanization,resource scarcity,climate change,environmental pollution,competition among different m...Traditional agriculture is facing several challenges worldwide such as increased population growth,rapid forestry and urbanization,resource scarcity,climate change,environmental pollution,competition among different markets.Hence,farmers need to improve productivity in order to maintain the output level.This study attempted to evaluate the benefits of using Real-Time Kinematic(RTK)positioning in precision agriculture through a series of real measurements carried out when farming cereals.All farming management actions involved in the cereal crop process(raise fallow,plow,sow,fertilize,mow,and harvest)have been done using an automatic guidance system that has reduced costs.A reduction of 20%has been quantified in the fuel,the amount of fertilizer,the labor costs and the hours of work.Consequently,the environmental impact has been also reduced.An inexpensive system consisting of a reference base station near the field and a mobile unit mounted on the test vehicle has been installed in order to increase the benefits in cereal crops.Global Navigation Satellite System(GNSS)systems including Global Positioning System(GPS),GLONASS,Galileo and Beidou have been used in the analysis.This research serves as a practical guide to implementing a low-cost guidance system to achieve best management practice.展开更多
基金supported by the 111 Project (Grant No. B08014)the Na-tional Natural Science Foundation of China (Grant No. 50708013)+3 种基金the Key Project of Foreign Teacher Recruit Held by the Chinese Ministry of Educationthe Research Fund for the Doctoral Program of Higher Educa-tion (Grant No. 20070141036)the General and Special Program of China Postdoctoral Science Foundation (Grant No. 20070420113)the Open Fund of State Key Laboratory of Coastal and Offshore Engineering (LP0905)
文摘Nowadays, there are many larger and taller engineering structures than in the past. These structures are commonly designed to be more flexible. Thus, they are sensitive to severe wind gust and earthquake tremor. For the dynamic response prediction, finite element (FE) modal updating and structural health monitoring, the dynamic characteristics of a structure are becoming increasingly important. The aim of this paper is to show an emerging tool-the real time kinematic (RTK) global positioning system (GPS), which is used to measure and monitor the low-frequency vibration of Dalian BeiDa Bridge, a medium span suspension bridge. The modal analysis is firstly performed on the developed three-dimensional FE model according to the original blue prints of the bridge to provide the analytical frequencies and mode shapes. The field ambient vibration tests using the accelerometers on the bridge deck are conducted just prior to the use of the GPS system in order to validate the FE model. And then, the calibration test is done to assess the dynamic displacement measurement accuracy of the GPS in three orthogonal directions. The GPS signal properties, such as the amplitude, standard deviations (STD), power spectral density (PSD), and probability density functions (PDF), are studied in details. After that, a structural health monitoring system based on the GPS is devised and installed on the bridge to provide real-time measurement of deck movement. The output-only modal parameter identification is carried out by using the Periodogram method to investigate the responses of the bridge. The result shows that the spectral densities of the displacements measured by the GPS correspond well with the results by the FEM analysis and the accelerometer vibration test. It is concluded that the GPS method is reliable and useful to clarify the ambient vibration response behaviors of the flexible structures. The integration of the GPS and accelerometer methods results in a hybrid arrangement that can help to eliminate some disadvantages of th
文摘在室内环境下,全球定位系统(GPS)以及其他定位技术受许多不可抗拒的因素影响无法对用户进行精准定位。然而,从移动互联到物联网,位置是一个基础的不可或缺的信息,对于精细化的行业应用需求来说,越精准的定位信息越能带来更高的价值。所以,为向群众提供无所不在的位置服务,对UWB(Ultra Wide Band)技术与TOA(Time of Arrival)的定位算法进行了研究,并设计出了一款基于UWB技术的高精度室内定位系统。最后,通过试验验证了系统的精准度能达到厘米级,且实时性较好。
基金This work was supported by the Project of University of Alcalá(Grant No.CCG2016/EXP-055).
文摘Traditional agriculture is facing several challenges worldwide such as increased population growth,rapid forestry and urbanization,resource scarcity,climate change,environmental pollution,competition among different markets.Hence,farmers need to improve productivity in order to maintain the output level.This study attempted to evaluate the benefits of using Real-Time Kinematic(RTK)positioning in precision agriculture through a series of real measurements carried out when farming cereals.All farming management actions involved in the cereal crop process(raise fallow,plow,sow,fertilize,mow,and harvest)have been done using an automatic guidance system that has reduced costs.A reduction of 20%has been quantified in the fuel,the amount of fertilizer,the labor costs and the hours of work.Consequently,the environmental impact has been also reduced.An inexpensive system consisting of a reference base station near the field and a mobile unit mounted on the test vehicle has been installed in order to increase the benefits in cereal crops.Global Navigation Satellite System(GNSS)systems including Global Positioning System(GPS),GLONASS,Galileo and Beidou have been used in the analysis.This research serves as a practical guide to implementing a low-cost guidance system to achieve best management practice.
