A nonlinear seismic analysis method for complex frame structures subjected to sta- tionary random ground excitations is proposed.The nonlinear elasto-plastic behaviors may take place only on a small part of the struct...A nonlinear seismic analysis method for complex frame structures subjected to sta- tionary random ground excitations is proposed.The nonlinear elasto-plastic behaviors may take place only on a small part of the structure.The Bouc-Wen differential equation model is used to model the hysteretic characteristics of the nonlinear components.The Pseudo Excitation Method (PEM)is used in solving the linearized random differential equations to replace the solution of the less efficient Lyapunov equation.Numerical results of a real bridge show that the method proposed is effective for practical engineering analysis.展开更多
This study measured stable carbon and nitro- gen isotope ratios in phytoplankton, zooplankton, five inver- tebrates species, eight fishes species and three seabirds spe- cies collected in Bohai Bay. δ 13C ranged from...This study measured stable carbon and nitro- gen isotope ratios in phytoplankton, zooplankton, five inver- tebrates species, eight fishes species and three seabirds spe- cies collected in Bohai Bay. δ 13C ranged from ?25.38‰ to ?11.08‰ showing a relative low enrichment in the food web from Bohai Bay. The mean δ 13C of mullet is higher than that of other organisms, and this might be due to that mullet is migration fish and feeds mainly on inshore sources. δ 15N ranged from 4.08‰ to 13.98‰, and showed a step-wise en- richment with trophic level of 3.8‰. The δ 15N enrichment factor was used to construct an isotopic food web model to establish trophic relationships within this marine food web. According to this model, exact trophic levels of all organisms were estimated as 1.46?2.10, 1.91?3.32, 2.55?4.23 and 2.98?4.28 for plankton, invertebrates, fishes, and seabirds.展开更多
基金Project supported by the National Natural Science Foundation of China(No.10072015)the National Key Base Research Special Foundation(No.G1999032805).
文摘A nonlinear seismic analysis method for complex frame structures subjected to sta- tionary random ground excitations is proposed.The nonlinear elasto-plastic behaviors may take place only on a small part of the structure.The Bouc-Wen differential equation model is used to model the hysteretic characteristics of the nonlinear components.The Pseudo Excitation Method (PEM)is used in solving the linearized random differential equations to replace the solution of the less efficient Lyapunov equation.Numerical results of a real bridge show that the method proposed is effective for practical engineering analysis.
基金This work was supported by the National Basic Research Program of China(Grant No.2003CB415004)the National Natural Science Foundation of China(Grant No.40021101)the Japanese Intermational Cooperation Agency.
文摘This study measured stable carbon and nitro- gen isotope ratios in phytoplankton, zooplankton, five inver- tebrates species, eight fishes species and three seabirds spe- cies collected in Bohai Bay. δ 13C ranged from ?25.38‰ to ?11.08‰ showing a relative low enrichment in the food web from Bohai Bay. The mean δ 13C of mullet is higher than that of other organisms, and this might be due to that mullet is migration fish and feeds mainly on inshore sources. δ 15N ranged from 4.08‰ to 13.98‰, and showed a step-wise en- richment with trophic level of 3.8‰. The δ 15N enrichment factor was used to construct an isotopic food web model to establish trophic relationships within this marine food web. According to this model, exact trophic levels of all organisms were estimated as 1.46?2.10, 1.91?3.32, 2.55?4.23 and 2.98?4.28 for plankton, invertebrates, fishes, and seabirds.
