The hot compressive deformation behaviors of ZHMn34-2-2-1 manganese brass are investigated on Thermecmastor-Z thermal simulator over wide processing domain of temperatures （923–1073 K） and strain rates （0.01–10 s...The hot compressive deformation behaviors of ZHMn34-2-2-1 manganese brass are investigated on Thermecmastor-Z thermal simulator over wide processing domain of temperatures （923–1073 K） and strain rates （0.01–10 s^–1）. The true stress–strain curves exhibit a single peak stress, after which the stress monotonously decreases until a steady state stress occurs, indicating a typical dynamic recrystallization. The analysis of deviation between strain-dependent Arrhenius type constitutive and experimental data revealed that the material parameters （n, A, and Q） for the ZHMn34-2-2-1 manganese brass are not constants but varies as functions of the deformation conditions. A revised strain-independent sine hyperbolic constitutive was proposed, which considered the coupled effects of strain rate temperature and strain on material parameters. The correlation coefficient and the average absolute relative error are used to evaluate the accuracy of the established constitutive model. The quantitative results indicate that the proposed constitutive model can precisely characterize the hot deformation behavior of ZHMn34-2-2-1 manganese brass.展开更多
Spatial and temporal variation of fish assemblages were investigated seasonally from May 2007 to February 2008 across 11 study sites in a subtropical small stream, the Puxi Stream, of the Huangshan Mountain. Along the...Spatial and temporal variation of fish assemblages were investigated seasonally from May 2007 to February 2008 across 11 study sites in a subtropical small stream, the Puxi Stream, of the Huangshan Mountain. Along the longitudinal gradient from headwater to downstream, fish species richness and abundance increased gradually, but then decreased significantly at the lower reaches. The highest species richness and abundance were observed in August and the lowest in February. Based on analysis of similarities （ANOSIM）, fish assemblages were significantly different in spatial variation but not in temporal variation. Although differences were observed both among sites and among stream orders, the lower R value in order-variation suggested stream order was not the optimal factor explaining the spatial variation of fish assemblages. In addition, dam construction did not significantly alter fish assemblages in the sites adjacent to and immediately downstream to dams. Using cluster analysis and non-metric Multi Dimensional Scaling analysis （NMS）, assemblages were separated into three groups at a Bray-Curtis similarity value of 42%： the upper, middle and lower groups. Following analysis of similarity percentages of species contributions （SIM- PER）, shifts in occurrence or abundance of S. curriculus, Z. platypus, R. bitterling and A. fasciatus contributed most to the differences amongst the three groups. Standard Deviation Redundancy Analysis （RDA） suggested that habitat structure （such as elevation, substrate, and flow velocity） contributed to the spatial and temporal pattem of fish assemblages in the Puxi Stream. In conclusion, the fish assemblages in Puxi Stream presented significant spatial but not temporal variation. Human disturbance has perhaps induced the decrease in species diversity in the lower reaches. However, no significant change was observed for fish assemblages in sites far from and immediately downstream from low-head dams [Current Zoology 56 （6）： 670-677, 2010].展开更多
In this paper, the authors used the Princeton Ocean Model (POM) to simulate the seasonal evolu- tions of circulation and thermal structure in the Yellow Sea. The simulated circulation showed that the Yellow Sea Warm C...In this paper, the authors used the Princeton Ocean Model (POM) to simulate the seasonal evolu- tions of circulation and thermal structure in the Yellow Sea. The simulated circulation showed that the Yellow Sea Warm Current (YSWC) was a compensation current of monsoon-driven current, and that in winter, the YSWC became stronger with depth, and could flow across the Bohai Strait in the north. Sensitivity and control- ling tests led to the following conclusions. In winter, the direction of the Yellow Sea Coastal Current in the sur- face layer was controlled partly by tide instead of wind. In summer, a cyclonic horizontal gyre existed in the middle and eastern parts of the Yellow Sea below 10 m. The downwelling in upper layer and upwelling in lower layer were somehow similar to Hu et al. (1991) conceptual model. The calculated thermal structure showed an obvious northward extending YSWC tongue in winter, its position and coverage of the Yellow Sea Cold Water Mass in summer.展开更多
基金Project(2012ZX04010-081) supported by the National Science and Technology Major Project of the Ministry of Science and Technology of China
文摘The hot compressive deformation behaviors of ZHMn34-2-2-1 manganese brass are investigated on Thermecmastor-Z thermal simulator over wide processing domain of temperatures （923–1073 K） and strain rates （0.01–10 s^–1）. The true stress–strain curves exhibit a single peak stress, after which the stress monotonously decreases until a steady state stress occurs, indicating a typical dynamic recrystallization. The analysis of deviation between strain-dependent Arrhenius type constitutive and experimental data revealed that the material parameters （n, A, and Q） for the ZHMn34-2-2-1 manganese brass are not constants but varies as functions of the deformation conditions. A revised strain-independent sine hyperbolic constitutive was proposed, which considered the coupled effects of strain rate temperature and strain on material parameters. The correlation coefficient and the average absolute relative error are used to evaluate the accuracy of the established constitutive model. The quantitative results indicate that the proposed constitutive model can precisely characterize the hot deformation behavior of ZHMn34-2-2-1 manganese brass.
基金supported by the National Basic Research Program of China (2009CB119200)Anhui Provincial Natural Science Foundation (090413080)Natural Science Foundation of Anhui Education Bureau (KJ2008B211,KJ2009A110)
文摘Spatial and temporal variation of fish assemblages were investigated seasonally from May 2007 to February 2008 across 11 study sites in a subtropical small stream, the Puxi Stream, of the Huangshan Mountain. Along the longitudinal gradient from headwater to downstream, fish species richness and abundance increased gradually, but then decreased significantly at the lower reaches. The highest species richness and abundance were observed in August and the lowest in February. Based on analysis of similarities （ANOSIM）, fish assemblages were significantly different in spatial variation but not in temporal variation. Although differences were observed both among sites and among stream orders, the lower R value in order-variation suggested stream order was not the optimal factor explaining the spatial variation of fish assemblages. In addition, dam construction did not significantly alter fish assemblages in the sites adjacent to and immediately downstream to dams. Using cluster analysis and non-metric Multi Dimensional Scaling analysis （NMS）, assemblages were separated into three groups at a Bray-Curtis similarity value of 42%： the upper, middle and lower groups. Following analysis of similarity percentages of species contributions （SIM- PER）, shifts in occurrence or abundance of S. curriculus, Z. platypus, R. bitterling and A. fasciatus contributed most to the differences amongst the three groups. Standard Deviation Redundancy Analysis （RDA） suggested that habitat structure （such as elevation, substrate, and flow velocity） contributed to the spatial and temporal pattem of fish assemblages in the Puxi Stream. In conclusion, the fish assemblages in Puxi Stream presented significant spatial but not temporal variation. Human disturbance has perhaps induced the decrease in species diversity in the lower reaches. However, no significant change was observed for fish assemblages in sites far from and immediately downstream from low-head dams [Current Zoology 56 （6）： 670-677, 2010].
基金Contribution No. 4616 from Institute of Oceanology, CAS. Project No.40406025 supported by NSFC.
文摘In this paper, the authors used the Princeton Ocean Model (POM) to simulate the seasonal evolu- tions of circulation and thermal structure in the Yellow Sea. The simulated circulation showed that the Yellow Sea Warm Current (YSWC) was a compensation current of monsoon-driven current, and that in winter, the YSWC became stronger with depth, and could flow across the Bohai Strait in the north. Sensitivity and control- ling tests led to the following conclusions. In winter, the direction of the Yellow Sea Coastal Current in the sur- face layer was controlled partly by tide instead of wind. In summer, a cyclonic horizontal gyre existed in the middle and eastern parts of the Yellow Sea below 10 m. The downwelling in upper layer and upwelling in lower layer were somehow similar to Hu et al. (1991) conceptual model. The calculated thermal structure showed an obvious northward extending YSWC tongue in winter, its position and coverage of the Yellow Sea Cold Water Mass in summer.
