Coal is the principal form of energy used in China. Hence, coal price variations are expected to have some influence on merchandise prices. Monthly data from January, 2002, to October, 2010, were used to construct a v...Coal is the principal form of energy used in China. Hence, coal price variations are expected to have some influence on merchandise prices. Monthly data from January, 2002, to October, 2010, were used to construct a varying-parameter state space model, and an error correction model, to estimate the influence of coat prices on Chinese merchandise prices. The time lag and the dynamic relationship were determined from the data. A long term equilibrium relationship between coal price and the PPI, and the CPI, can be observed. The long term influence of coal price fluctuations on the PPI is 0.263%. The corresponding value for the CPI is 0.157%. The PPI shows an influence from coal price change in the first period of observation： by eight periods the influence is obvious, after which it diminishes. The effect of coal price change on the CPI is rather weak and has no long term memory. Analysis of variance shows a similar situation. The elas- ticity coefficient of coal prices on the CPI, or the PPI, fluctuates over the 2002-2004 period. From 2002 to 2007 the influence elasticity on the CPI declined and subsequently levelled off after 2009.展开更多
The present work consists of dynamic detection of damages in reinforced concrete bridges by using a MMUM （mathematical model updating method） from incomplete test data. A well suited finite element model of a repair...The present work consists of dynamic detection of damages in reinforced concrete bridges by using a MMUM （mathematical model updating method） from incomplete test data. A well suited finite element model of a repaired bridge is carried out. The diagnosis enables us to locate and detect the damage in a reinforced concrete bridge. Thus, developments of analytical predictions have been checked by modal testing techniques. Besides, the FTCS （finite time centered space） scheme is developed to solve the set of equations which can easily handle finite element matrices of a bridge model. It is shown in this study that the method is applied to detect damages as well as existing cracks in real time of a repaired bridge. To check the efficiency of the method, the repaired bridge of OuedOumazer in Algeria has been selected. It is proven that identification methods have been able to detect the exact location of damage areas to be corrected avoiding the inaccuracy from the finite element model for the mass, stiffness and loading.展开更多
It is significant to consider the effect of uncertainty of the measured modal parameters on the updated finite element(FE) model,especially for updating the FE model of practical bridges,since the uncertainty of the m...It is significant to consider the effect of uncertainty of the measured modal parameters on the updated finite element(FE) model,especially for updating the FE model of practical bridges,since the uncertainty of the measured modal parameters cannot be ignored owing to the application of output-only identification method and the existence of the measured noise.A reasonable method is to define the objective of the FE model updating as the statistical property of the measured modal parameters obtained by conducting couples of identical modal tests,however,it is usually impossible to implement repeated modal test due to the limit of practical situation and economic reason.In this study,a method based on fuzzy finite element(FFM) was proposed in order to consider the effect of the uncertainty of the measured modal parameters on the updated FE model by using the results of a single modal test.The updating parameters of bridges were deemed as fuzzy variables,and then the fuzzification of objective of the FE model updating was proposed to consider the uncertainty of the measured modal parameters.Finally,the effectiveness of the proposed method was verified by updating the FE model of a practical bridge with the measured modal parameters.展开更多
This paper presents an effective approach for updating finite element dynamic model from incomplete modal data identified from ambient vibration measurements.The proposed method is based on the relationship between th...This paper presents an effective approach for updating finite element dynamic model from incomplete modal data identified from ambient vibration measurements.The proposed method is based on the relationship between the perturbation of structural parameters such as stiffness and mass changes and the modal data measurements of the tested structure such as measured mode shape readings.Structural updating parameters including both stiffness and mass parameters are employed to represent the differences in structural parameters between the finite element model and the associated tested structure.These updating parameters are then evaluated by an iterative solution procedure,giving optimised solutions in the least squares sense without requiring an optimisation technique.In order to reduce the influence of modal measurement uncertainty,the truncated singular value decomposition regularization method incorporating the quasi-optimality criterion is employed to produce reliable solutions for the structural updating parameters.Finally,the numerical investigations of a space frame structure and the practical applications to the Canton Tower benchmark problem demonstrate that the proposed method can correctly update the given finite element model using the incomplete modal data identified from the recorded ambient vibration measurements.展开更多
Inner Mongolia is the important ecological barrier zone in northern China,which plays an important role in the prevention and control of wind in the regional ecosystem.Based on the Revised Wind Erosion Equation(RWEQ)m...Inner Mongolia is the important ecological barrier zone in northern China,which plays an important role in the prevention and control of wind in the regional ecosystem.Based on the Revised Wind Erosion Equation(RWEQ)model and the cost-recovery method,this study simulated the wind erosion prevention service(WEPS)in Inner Mongolia in 2010 and 2015,investigated the spatial pattern of material and monetary value of WEPS,and analyzed the differences among various cities and various ecosystems.The results indicated that the total WEPS of Inner Mongolia was estimated to be 73.87×10^(8) t in 2015,which was 4.61×10^(8) t less than in 2010,while the monetary value of WEPS was calculated to be 738.66×10^(8) yuan in 2015,which was 46.16×10^(8) yuan less than in 2010.Among all the leagues and cities,Xilin Gol League supported the highest WEPS,reaching 18.65×10^(8) t in 2015,while Wuhai provided the lowest.The WEPS of Hulunbeier increased the most,by 4.37×10^(8) t from 2010 to 2015.The WEPS in the grassland ecosystem was the highest among the different ecosystems,accounting for more than55%of the total WEPS in Inner Mongolia,but it was reduced by 1.05×10^(8) t during the same period.The WEPS in the forest ecosystem increased the most,reaching 0.19×10^(8) t.This study found that the implementation of projects such as returning farmland to forests and grasses and sand control effectively increased the WEPS by increasing the forest area.However,unsuitable land use increased the desertification of ecosystems which resulted in a reduction of WEPS in Inner Mongolia.展开更多
基金support for this work, provided by the National Natural Science Foundation of China (No. 71003097)Jiangsu Province Social Science Foundation (No. 10EYD025)2008 China University of Mining and Technology Youth Foundation Program (No.2008W04)
文摘Coal is the principal form of energy used in China. Hence, coal price variations are expected to have some influence on merchandise prices. Monthly data from January, 2002, to October, 2010, were used to construct a varying-parameter state space model, and an error correction model, to estimate the influence of coat prices on Chinese merchandise prices. The time lag and the dynamic relationship were determined from the data. A long term equilibrium relationship between coal price and the PPI, and the CPI, can be observed. The long term influence of coal price fluctuations on the PPI is 0.263%. The corresponding value for the CPI is 0.157%. The PPI shows an influence from coal price change in the first period of observation： by eight periods the influence is obvious, after which it diminishes. The effect of coal price change on the CPI is rather weak and has no long term memory. Analysis of variance shows a similar situation. The elas- ticity coefficient of coal prices on the CPI, or the PPI, fluctuates over the 2002-2004 period. From 2002 to 2007 the influence elasticity on the CPI declined and subsequently levelled off after 2009.
文摘The present work consists of dynamic detection of damages in reinforced concrete bridges by using a MMUM （mathematical model updating method） from incomplete test data. A well suited finite element model of a repaired bridge is carried out. The diagnosis enables us to locate and detect the damage in a reinforced concrete bridge. Thus, developments of analytical predictions have been checked by modal testing techniques. Besides, the FTCS （finite time centered space） scheme is developed to solve the set of equations which can easily handle finite element matrices of a bridge model. It is shown in this study that the method is applied to detect damages as well as existing cracks in real time of a repaired bridge. To check the efficiency of the method, the repaired bridge of OuedOumazer in Algeria has been selected. It is proven that identification methods have been able to detect the exact location of damage areas to be corrected avoiding the inaccuracy from the finite element model for the mass, stiffness and loading.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51008097 and 11172078)the National Key Technology R&D Program (Grant No. 2011BAK02B02)
文摘It is significant to consider the effect of uncertainty of the measured modal parameters on the updated finite element(FE) model,especially for updating the FE model of practical bridges,since the uncertainty of the measured modal parameters cannot be ignored owing to the application of output-only identification method and the existence of the measured noise.A reasonable method is to define the objective of the FE model updating as the statistical property of the measured modal parameters obtained by conducting couples of identical modal tests,however,it is usually impossible to implement repeated modal test due to the limit of practical situation and economic reason.In this study,a method based on fuzzy finite element(FFM) was proposed in order to consider the effect of the uncertainty of the measured modal parameters on the updated FE model by using the results of a single modal test.The updating parameters of bridges were deemed as fuzzy variables,and then the fuzzification of objective of the FE model updating was proposed to consider the uncertainty of the measured modal parameters.Finally,the effectiveness of the proposed method was verified by updating the FE model of a practical bridge with the measured modal parameters.
文摘This paper presents an effective approach for updating finite element dynamic model from incomplete modal data identified from ambient vibration measurements.The proposed method is based on the relationship between the perturbation of structural parameters such as stiffness and mass changes and the modal data measurements of the tested structure such as measured mode shape readings.Structural updating parameters including both stiffness and mass parameters are employed to represent the differences in structural parameters between the finite element model and the associated tested structure.These updating parameters are then evaluated by an iterative solution procedure,giving optimised solutions in the least squares sense without requiring an optimisation technique.In order to reduce the influence of modal measurement uncertainty,the truncated singular value decomposition regularization method incorporating the quasi-optimality criterion is employed to produce reliable solutions for the structural updating parameters.Finally,the numerical investigations of a space frame structure and the practical applications to the Canton Tower benchmark problem demonstrate that the proposed method can correctly update the given finite element model using the incomplete modal data identified from the recorded ambient vibration measurements.
基金The Strategic Priority Research Program of Chinese Academy of Sciences(XDA20020402)The National Natural Science Foundation of China(41971272)。
文摘Inner Mongolia is the important ecological barrier zone in northern China,which plays an important role in the prevention and control of wind in the regional ecosystem.Based on the Revised Wind Erosion Equation(RWEQ)model and the cost-recovery method,this study simulated the wind erosion prevention service(WEPS)in Inner Mongolia in 2010 and 2015,investigated the spatial pattern of material and monetary value of WEPS,and analyzed the differences among various cities and various ecosystems.The results indicated that the total WEPS of Inner Mongolia was estimated to be 73.87×10^(8) t in 2015,which was 4.61×10^(8) t less than in 2010,while the monetary value of WEPS was calculated to be 738.66×10^(8) yuan in 2015,which was 46.16×10^(8) yuan less than in 2010.Among all the leagues and cities,Xilin Gol League supported the highest WEPS,reaching 18.65×10^(8) t in 2015,while Wuhai provided the lowest.The WEPS of Hulunbeier increased the most,by 4.37×10^(8) t from 2010 to 2015.The WEPS in the grassland ecosystem was the highest among the different ecosystems,accounting for more than55%of the total WEPS in Inner Mongolia,but it was reduced by 1.05×10^(8) t during the same period.The WEPS in the forest ecosystem increased the most,reaching 0.19×10^(8) t.This study found that the implementation of projects such as returning farmland to forests and grasses and sand control effectively increased the WEPS by increasing the forest area.However,unsuitable land use increased the desertification of ecosystems which resulted in a reduction of WEPS in Inner Mongolia.
