Geographic variation in body size is common within many animal species.The causes of this pattern,however,remain largely unexplored in most vertebrate groups.Bats are widely distributed globally owing to their ability...Geographic variation in body size is common within many animal species.The causes of this pattern,however,remain largely unexplored in most vertebrate groups.Bats are widely distributed globally owing to their ability of powered flight.Most bat species encounter a variety of climatic conditions across their distribution range,making them an ideal taxon for the study of ecogeographic patterns in body size.Here,we used adult least horseshoe bats,Rhinolophus pusillus,to test whether geographic variation in body size was determined by heat conservation,heat dissipation,climatic seasonality,or primary productivity.We measured body mass and head-body length for 246 adult bats from 12 allopatric colonies in China.We quantified the ecological conditions inhabited by each colony,including mean maximum temperature of the warmest month,mean minimum temperature of the coldest month,temperature seasonality,precipitation seasonality,and annual net primary productivity(ANPP).Body mass and head-body length,2 of the most reliable indicators of body size,exhibited marked differences between colonies.After controlling for spatial autocorrelation,the mean minimum temperature of the coldest month explained most of the variation in body size among colonies,regardless of sex.The mean maximum temperature,climatic seasonality,and ANPP had limited power in predicting body size of males or females in comparison with mean minimum temperature.These results support the heat conservation hypothesis and suggest adaptive responses of body size to cold climates in cave-dwelling bats.展开更多
Steam pipelines applied in power units operate at high pressures and temperatures.In addition,to stress from the pipeline pressure also arise high thermal stresses in transient states such as start-up,shutdown or a lo...Steam pipelines applied in power units operate at high pressures and temperatures.In addition,to stress from the pipeline pressure also arise high thermal stresses in transient states such as start-up,shutdown or a load change of the power unit.Time-varying stresses are often the cause of the occurrence of fatigue cracks since the plastic deformations appear at the stress concentration regions.To determine the transient temperature of the steam along the steam flow path and axisymmetric temperature distribution in the pipeline wall,a numerical model of pipeline heating was proposed.To determine the transient temperature of the steam and pipeline wall the finite volume method(FVM) was used Writing the energy conservation equations for control areas around all the nodes gives a system of ordinary differential equations with respect to time.The system of ordinary differential equations of the first order was solved by the Runge-Kutta method of the fourth order to give the time-temperature changes at the nodes lying in the area of the wall and steam.The steam pressure distribution along pipeline was determined from the solution of the momentum conservation equation.Based on the calculated temperature distribution,thermal stresses were determined.The friction factor was calculated using the correlations of Churchill and Haaland,which were proposed for pipes with a rough inner surface.To assess the accuracy of the proposed model,numerical calculations were also performed for the thin-walled pipe,and the results were compared to the exact analytical solution.Comparison of the results shows that the accuracy of the proposed model of pipeline heating is very satisfactory.The paper presents examples of the determination of the transient temperature of the steam and the wall.展开更多
基金We are grateful to Guanjun Lu,Rong Xu,Zhen Wang,and Xiaobin Huang for their assistance with the field work.We acknowledge the anonymous reviewers for valuable advices and comments on the manuscript.
文摘Geographic variation in body size is common within many animal species.The causes of this pattern,however,remain largely unexplored in most vertebrate groups.Bats are widely distributed globally owing to their ability of powered flight.Most bat species encounter a variety of climatic conditions across their distribution range,making them an ideal taxon for the study of ecogeographic patterns in body size.Here,we used adult least horseshoe bats,Rhinolophus pusillus,to test whether geographic variation in body size was determined by heat conservation,heat dissipation,climatic seasonality,or primary productivity.We measured body mass and head-body length for 246 adult bats from 12 allopatric colonies in China.We quantified the ecological conditions inhabited by each colony,including mean maximum temperature of the warmest month,mean minimum temperature of the coldest month,temperature seasonality,precipitation seasonality,and annual net primary productivity(ANPP).Body mass and head-body length,2 of the most reliable indicators of body size,exhibited marked differences between colonies.After controlling for spatial autocorrelation,the mean minimum temperature of the coldest month explained most of the variation in body size among colonies,regardless of sex.The mean maximum temperature,climatic seasonality,and ANPP had limited power in predicting body size of males or females in comparison with mean minimum temperature.These results support the heat conservation hypothesis and suggest adaptive responses of body size to cold climates in cave-dwelling bats.
文摘Steam pipelines applied in power units operate at high pressures and temperatures.In addition,to stress from the pipeline pressure also arise high thermal stresses in transient states such as start-up,shutdown or a load change of the power unit.Time-varying stresses are often the cause of the occurrence of fatigue cracks since the plastic deformations appear at the stress concentration regions.To determine the transient temperature of the steam along the steam flow path and axisymmetric temperature distribution in the pipeline wall,a numerical model of pipeline heating was proposed.To determine the transient temperature of the steam and pipeline wall the finite volume method(FVM) was used Writing the energy conservation equations for control areas around all the nodes gives a system of ordinary differential equations with respect to time.The system of ordinary differential equations of the first order was solved by the Runge-Kutta method of the fourth order to give the time-temperature changes at the nodes lying in the area of the wall and steam.The steam pressure distribution along pipeline was determined from the solution of the momentum conservation equation.Based on the calculated temperature distribution,thermal stresses were determined.The friction factor was calculated using the correlations of Churchill and Haaland,which were proposed for pipes with a rough inner surface.To assess the accuracy of the proposed model,numerical calculations were also performed for the thin-walled pipe,and the results were compared to the exact analytical solution.Comparison of the results shows that the accuracy of the proposed model of pipeline heating is very satisfactory.The paper presents examples of the determination of the transient temperature of the steam and the wall.
