In this study, the dependence of dust budgets on dust emission schemes is investigated through the simulation of dust storm events, which occurred during 14–25 March 2002, over East Asia, by the Weather Research and ...In this study, the dependence of dust budgets on dust emission schemes is investigated through the simulation of dust storm events, which occurred during 14–25 March 2002, over East Asia, by the Weather Research and Forecasting with Chemistry(WRF/Chem) model coupled with six dust emission schemes. Generally, this model can reasonably reproduce the spatial distribution of surface dust concentration; however, the simulated total dust budget differs significantly with different emission schemes. Moreover, uncertainties in the simulated dust budget vary among regions. It is suggested that the dust emission scheme affects the regional dust budget directly through its impact on the total emitted dust amount; however, the inflow and outflow of dust aerosols simulated by different schemes within a region also depend on the geographical location of the dust emission region. Furthermore, the size distribution of dust particles for a specific dust emission scheme has proven to be important for dust budget calculation due to the dependence of dust deposition amount on dust size distribution.展开更多
The study on greenhouse gas inventory in urban China lags far behind the global level. The important factor that curbs the carbon inventory of cities of China is inventory methodology and scope. Given the insufficienc...The study on greenhouse gas inventory in urban China lags far behind the global level. The important factor that curbs the carbon inventory of cities of China is inventory methodology and scope. Given the insufficiency of Chinese cities carbon inventory, a system and accounting model （scopel＋ scope2） as well as principles and boundaries were proposed for China. The carbon emissions in scopel and scopel＋ scope2 were calculated in Chinese prefecture-level cities. The EDGAR dataset was used for the calculation of scopel carbon emissions in cities in China and the level of uncertainty was analyzed as well. The results showed that the direct carbon emission of cities in China was about 31.65% of China total emissions. The scopel＋ scope2 carbon emissions in cities of China were calculated based on the GIS and RS model. The results showed that the sum of direct （scopel） and indirect （scope2） carbon emissions of cities in China accounted for 38.80% of total China carbon emissions.展开更多
A probabilistic seismic hazard analysis was performed to generate seismic hazard maps for Jamaica. The analysis was then conducted using a standard logic-tree approach that allowed systematically taking into account t...A probabilistic seismic hazard analysis was performed to generate seismic hazard maps for Jamaica. The analysis was then conducted using a standard logic-tree approach that allowed systematically taking into account the model-based （i.e., epistemic） uncertainty and its influence on the computed ground motion parameters. Hazard computations have been performed using a grid of sites with a space of 0.05 degrees. Two different computation methodologies have been adopted： the standard approach based on the definition of appropriate seismogenic sources and the zone-free approach, which overcomes the ambiguities related with the definition of the seismic sources solely reflecting the characteristics of the earthquake catalogue. A comprehensive and updated earthquake catalogue for Jamaica has been compiled for the years 1551-2010 and new empirical relationships amongst magnitudes Mze-Ms and Mw-mb have been developed for the region. Uniform hazard spectra and their uncertainty have been calculated for the horizontal component of ground motion for rock site conditions and five return periods （95, 475, 975, 2,475 and 4,975 years） and spectral accelerations for 34 structural periods ranging from 0 to 3 s, and 5% of critical damping. The spectral accelerations have been calculated to allow the definition of seismic hazard in Jamaica according to the International Building Code 2012. The disaggregation analysis for Kingston Metropolitan Area suggests that the magnitude-distance pair that contributes most to the hazard corresponds to events with M 7.8 and M 7.0 in the Enriquillo Plantain Garden Fault and the Jamaican Faults at a distance of 28 km and 18 km for short and long period structures respectively corresponding to 2,475 years return period. However, for long period structures, a substantial contribution is found for a M 8.2 at a distance of 198 km in the Oriente Fault Zone.展开更多
A terminal sliding mode fuzzy control based on multiple sliding surfaces was proposed for ship course tracking steering, which takes account of rudder characteristics and parameter uncertainty. In order to solve the p...A terminal sliding mode fuzzy control based on multiple sliding surfaces was proposed for ship course tracking steering, which takes account of rudder characteristics and parameter uncertainty. In order to solve the problem, the controller was designed by employing the universal approximation property of fuzzy logic system, the advantage of Nussbaum function, and using multiple sliding mode control algorithm based on the recursive technique. In the last step of designing, a nonsingular terminal sliding mode was utilized to drive the last state of the system to converge in a finite period of time, and high-order sliding mode control law was designed to eliminate the chattering and make the system robust. The simulation results showed that the controller designed here could track a desired course fast and accurately. It also exhibited strong robustness peculiarly to system, and had better adaptive ability than traditional PID control algorithms.展开更多
A novel numerical procedure, which realizes the stochastic analysis with dimensional reduction integration （DRI）, C-type Gram-Charlier （CGC） series, and finite element （FE） model, is proposed to assess the proba...A novel numerical procedure, which realizes the stochastic analysis with dimensional reduction integration （DRI）, C-type Gram-Charlier （CGC） series, and finite element （FE） model, is proposed to assess the probability distribution of structural per- formance. From the relationship between the weighting function of orthogonal polynomial and probability density function （PDF） of random variable, the numerical integration formulas are derived for moment computation. Then, distribution of structural uncertainty response can be approximated by the CGC series with the calculated moments. Three engineering appli- cations for the distribution of, the maximum displacement of a ten-bar planer truss, natural frequency of an auto frame, and Von-Mises stress of a bending pipe, are employed to illustrate the computational efficiency and accuracy of the proposed methodology. As compared with plain Monte Carlo simulation （MCS）, the method can obtain the accurate distribution of structural performance. Especially at the tail region of cumulative distribution function （CDF）, results have shown the satisfy- ing estimators for small probabilities, say, Pc [104, 10-3]. That implies the method could be trusted for structural failure prob- ability prediction. As the computational efficiency is concerned, the procedure could save more than two orders of computational resources as compared with the direct numerical integration （NI） and MCS. Furthermore, realization of the procedure does not require computing the performance gradient or Hessian matrix with respect to random variables, or reshaping the finite element matrix as other stochastic finite element （SFE） codes. Therefore, it should be an efficient and reliable routine for uncertainty structural analysis.展开更多
基金jointly supported by the Strategic Priority Research Program of Chinese Academy of Sciences(XDA05110200)the International Science and Technology Cooperation Program of China(2011DFG23450)
文摘In this study, the dependence of dust budgets on dust emission schemes is investigated through the simulation of dust storm events, which occurred during 14–25 March 2002, over East Asia, by the Weather Research and Forecasting with Chemistry(WRF/Chem) model coupled with six dust emission schemes. Generally, this model can reasonably reproduce the spatial distribution of surface dust concentration; however, the simulated total dust budget differs significantly with different emission schemes. Moreover, uncertainties in the simulated dust budget vary among regions. It is suggested that the dust emission scheme affects the regional dust budget directly through its impact on the total emitted dust amount; however, the inflow and outflow of dust aerosols simulated by different schemes within a region also depend on the geographical location of the dust emission region. Furthermore, the size distribution of dust particles for a specific dust emission scheme has proven to be important for dust budget calculation due to the dependence of dust deposition amount on dust size distribution.
文摘The study on greenhouse gas inventory in urban China lags far behind the global level. The important factor that curbs the carbon inventory of cities of China is inventory methodology and scope. Given the insufficiency of Chinese cities carbon inventory, a system and accounting model （scopel＋ scope2） as well as principles and boundaries were proposed for China. The carbon emissions in scopel and scopel＋ scope2 were calculated in Chinese prefecture-level cities. The EDGAR dataset was used for the calculation of scopel carbon emissions in cities in China and the level of uncertainty was analyzed as well. The results showed that the direct carbon emission of cities in China was about 31.65% of China total emissions. The scopel＋ scope2 carbon emissions in cities of China were calculated based on the GIS and RS model. The results showed that the sum of direct （scopel） and indirect （scope2） carbon emissions of cities in China accounted for 38.80% of total China carbon emissions.
文摘A probabilistic seismic hazard analysis was performed to generate seismic hazard maps for Jamaica. The analysis was then conducted using a standard logic-tree approach that allowed systematically taking into account the model-based （i.e., epistemic） uncertainty and its influence on the computed ground motion parameters. Hazard computations have been performed using a grid of sites with a space of 0.05 degrees. Two different computation methodologies have been adopted： the standard approach based on the definition of appropriate seismogenic sources and the zone-free approach, which overcomes the ambiguities related with the definition of the seismic sources solely reflecting the characteristics of the earthquake catalogue. A comprehensive and updated earthquake catalogue for Jamaica has been compiled for the years 1551-2010 and new empirical relationships amongst magnitudes Mze-Ms and Mw-mb have been developed for the region. Uniform hazard spectra and their uncertainty have been calculated for the horizontal component of ground motion for rock site conditions and five return periods （95, 475, 975, 2,475 and 4,975 years） and spectral accelerations for 34 structural periods ranging from 0 to 3 s, and 5% of critical damping. The spectral accelerations have been calculated to allow the definition of seismic hazard in Jamaica according to the International Building Code 2012. The disaggregation analysis for Kingston Metropolitan Area suggests that the magnitude-distance pair that contributes most to the hazard corresponds to events with M 7.8 and M 7.0 in the Enriquillo Plantain Garden Fault and the Jamaican Faults at a distance of 28 km and 18 km for short and long period structures respectively corresponding to 2,475 years return period. However, for long period structures, a substantial contribution is found for a M 8.2 at a distance of 198 km in the Oriente Fault Zone.
基金the National Natural Science Foundation ofChina (60974136)
文摘A terminal sliding mode fuzzy control based on multiple sliding surfaces was proposed for ship course tracking steering, which takes account of rudder characteristics and parameter uncertainty. In order to solve the problem, the controller was designed by employing the universal approximation property of fuzzy logic system, the advantage of Nussbaum function, and using multiple sliding mode control algorithm based on the recursive technique. In the last step of designing, a nonsingular terminal sliding mode was utilized to drive the last state of the system to converge in a finite period of time, and high-order sliding mode control law was designed to eliminate the chattering and make the system robust. The simulation results showed that the controller designed here could track a desired course fast and accurately. It also exhibited strong robustness peculiarly to system, and had better adaptive ability than traditional PID control algorithms.
基金supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) and the University Network of Excellence in Nuclear Engineering (UNENE) through an Industrial Research Chair program,"Risk-Based Life Cycle Management of Engineering Systems",at the University of Waterloo
文摘A novel numerical procedure, which realizes the stochastic analysis with dimensional reduction integration （DRI）, C-type Gram-Charlier （CGC） series, and finite element （FE） model, is proposed to assess the probability distribution of structural per- formance. From the relationship between the weighting function of orthogonal polynomial and probability density function （PDF） of random variable, the numerical integration formulas are derived for moment computation. Then, distribution of structural uncertainty response can be approximated by the CGC series with the calculated moments. Three engineering appli- cations for the distribution of, the maximum displacement of a ten-bar planer truss, natural frequency of an auto frame, and Von-Mises stress of a bending pipe, are employed to illustrate the computational efficiency and accuracy of the proposed methodology. As compared with plain Monte Carlo simulation （MCS）, the method can obtain the accurate distribution of structural performance. Especially at the tail region of cumulative distribution function （CDF）, results have shown the satisfy- ing estimators for small probabilities, say, Pc [104, 10-3]. That implies the method could be trusted for structural failure prob- ability prediction. As the computational efficiency is concerned, the procedure could save more than two orders of computational resources as compared with the direct numerical integration （NI） and MCS. Furthermore, realization of the procedure does not require computing the performance gradient or Hessian matrix with respect to random variables, or reshaping the finite element matrix as other stochastic finite element （SFE） codes. Therefore, it should be an efficient and reliable routine for uncertainty structural analysis.
