For the purpose of improving the mechanical performance indices of uncertain structures with interval parameters and ensure their robustness when fluctuating under interval parameters, a constrained interval robust op...For the purpose of improving the mechanical performance indices of uncertain structures with interval parameters and ensure their robustness when fluctuating under interval parameters, a constrained interval robust optimization model is constructed with both the center and halfwidth of the most important mechanical performance index described as objective functions and the other requirements on the mechanical performance indices described as constraint functions. To locate the optimal solution of objective and feasibility robustness, a new concept of interval violation vector and its calculation formulae corresponding to different constraint functions are proposed. The math?ematical formulae for calculating the feasibility and objective robustness indices and the robustness?based preferential guidelines are proposed for directly ranking various design vectors, which is realized by an algorithm integrating Kriging and nested genetic algorithm. The validity of the proposed method and its superiority to present interval optimization approaches are demonstrated by a numerical example. The robust optimization of the upper beam in a high?speed press with interval material properties demonstrated the applicability and effectiveness of the proposed method in engineering.展开更多
Introduction:Ground-nesting birds experience high levels of nest predation.However,birds can make selection decisions related to nest site location and characteristics that may result in physical,visual,and olfactory ...Introduction:Ground-nesting birds experience high levels of nest predation.However,birds can make selection decisions related to nest site location and characteristics that may result in physical,visual,and olfactory impediments to predators.Methods:We studied daily survival rate[DSR]of greater sage-grouse(Centrocercus urophasianus)from 2008 to 2010 in an area in Wyoming experiencing large-scale alterations to the landscape.We used generalized linear mixed models to model fixed and random effects,and a correlation within nesting attempts,individual birds,and years.Results:Predation of the nest was the most common source of nest failure(84.7%)followed by direct predation of the female(13.6%).Generally,landscape variables at the nest site(≤30 m)were more influential on DSR of nests than features at larger spatial scales.Percentage of shrub canopy cover at the nest site(15-m scale)and distances to natural gas wells and mesic areas had a positive relationship with DSR of nests,whereas distance to roads had a negative relationship with DSR of nests.When added to the vegetation model,maximum wind speed on the day of nest failure and a 1-day lag in precipitation(i.e.,precipitation the day before failure)improved model fit whereby both variables negatively influenced DSR of nests.Conclusions:Nest site characteristics that reduce visibility(i.e.,shrub canopy cover)have the potential to reduce depredation,whereas anthropogenic(i.e.,distance to wells)and mesic landscape features appear to facilitate depredation.Last,predators may be more efficient at locating nests under certain weather conditions(i.e.,high winds and moisture).展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.51775491,51475417,U1608256,51405433)
文摘For the purpose of improving the mechanical performance indices of uncertain structures with interval parameters and ensure their robustness when fluctuating under interval parameters, a constrained interval robust optimization model is constructed with both the center and halfwidth of the most important mechanical performance index described as objective functions and the other requirements on the mechanical performance indices described as constraint functions. To locate the optimal solution of objective and feasibility robustness, a new concept of interval violation vector and its calculation formulae corresponding to different constraint functions are proposed. The math?ematical formulae for calculating the feasibility and objective robustness indices and the robustness?based preferential guidelines are proposed for directly ranking various design vectors, which is realized by an algorithm integrating Kriging and nested genetic algorithm. The validity of the proposed method and its superiority to present interval optimization approaches are demonstrated by a numerical example. The robust optimization of the upper beam in a high?speed press with interval material properties demonstrated the applicability and effectiveness of the proposed method in engineering.
文摘Introduction:Ground-nesting birds experience high levels of nest predation.However,birds can make selection decisions related to nest site location and characteristics that may result in physical,visual,and olfactory impediments to predators.Methods:We studied daily survival rate[DSR]of greater sage-grouse(Centrocercus urophasianus)from 2008 to 2010 in an area in Wyoming experiencing large-scale alterations to the landscape.We used generalized linear mixed models to model fixed and random effects,and a correlation within nesting attempts,individual birds,and years.Results:Predation of the nest was the most common source of nest failure(84.7%)followed by direct predation of the female(13.6%).Generally,landscape variables at the nest site(≤30 m)were more influential on DSR of nests than features at larger spatial scales.Percentage of shrub canopy cover at the nest site(15-m scale)and distances to natural gas wells and mesic areas had a positive relationship with DSR of nests,whereas distance to roads had a negative relationship with DSR of nests.When added to the vegetation model,maximum wind speed on the day of nest failure and a 1-day lag in precipitation(i.e.,precipitation the day before failure)improved model fit whereby both variables negatively influenced DSR of nests.Conclusions:Nest site characteristics that reduce visibility(i.e.,shrub canopy cover)have the potential to reduce depredation,whereas anthropogenic(i.e.,distance to wells)and mesic landscape features appear to facilitate depredation.Last,predators may be more efficient at locating nests under certain weather conditions(i.e.,high winds and moisture).
