Beauty of roundness" (yuan mei) is one of the important categories in classical Chinese aesthetics. Essentially, the philosophical meaning of “roundness" refers to orbicularity, ripeness and thoroughness, w...Beauty of roundness" (yuan mei) is one of the important categories in classical Chinese aesthetics. Essentially, the philosophical meaning of “roundness" refers to orbicularity, ripeness and thoroughness, with its endlessly comprehensive and diversified characteristics. In its aesthetic and poetic senses, the category of “beauty of roundness" (yuan mei) is more extensive and complicated. “Beauty of roundness" (yuan mei) possesses abundant connotations and is able to form its own system of aesthetic thoughts. The basic connotations of “beauty of roundness" (yuan mei) includes: obicularity, perfectness and naturalness; maturity, speeding-up and super-naturalness; fluxion, vividness and agility.展开更多
Casing treatment is one possible way of regaining axial compressor operating range. However, most of casing treatments extend the operating range with the cost of efficiency penalty. A new form of multiple cylindrical...Casing treatment is one possible way of regaining axial compressor operating range. However, most of casing treatments extend the operating range with the cost of efficiency penalty. A new form of multiple cylindrical holes casing treatment(MHCT) with pre-swirl blowing for the NASA Rotor-37 has been designed based on profound understanding of the stall inception. Unsteady numerical simulations have been performed for Rotor-37 with and without MHCT. Parametric studies of the total extraction holes area and their axial locations show that the compressor performance deteriorates as the area ratio increases but the stall margin is extended and there is an optimum extraction holes axial location for stall margin extending. The better configuration of MHCT could extend the stall margin by 6.2% with only 0.23% peak efficiency reduction. Detailed analysis of the physical mechanism behind the stall margin improvement shows that the casing treatment could eliminate the passage blockage by suppressing breakup of tip leakage vortex and decrease the blade load in tip region, which both contribute to improve stall margin of transonic axial compressors.展开更多
Aims In the Oregon of USA,the control of western juniper(Juniperus occidentalis)is an accepted rangeland management practice to restore sagebrush steppe habitats of importance to wildlife and livestock.The effects of ...Aims In the Oregon of USA,the control of western juniper(Juniperus occidentalis)is an accepted rangeland management practice to restore sagebrush steppe habitats of importance to wildlife and livestock.The effects of juniper cutting on ecosystem nitrogen,however,have not been well addressed although woody plant control has important implications for local watershed management and regional nitrogen pools.Methods We quantified ecosystem nitrogen stocks in two adjacent watersheds,comprised of a treated watershed(most juniper removed)and an untreated watershed(juniper not removed).Thirteen years after juniper removal,we measured aboveground nitrogen stocks for juniper trees,shrubs,grasses and litter in both watersheds.We also measured belowground nitrogen stocks(roots and soil)in both watersheds at two soil depths(0–25 and 25–50 cm).Important Findings Aboveground nitrogen stocks were 6.9 times greater in the untreated than in the treated watershed considering the much larger aboveground biomass.However,root nitrogen stocks were 3.1 times greater in the treated one due to the gain of understory root biomass associated with juniper cutting.Soil nitrogen stocks at both 0–25 and 25–50 cm depths were not affected by juniper removal.Overall,total ecosystem nitrogen stocks did not differ between the treated(9536 kg N ha−1)and untreated(9456 kg N ha−1)watersheds.The greatest ecosystem nitrogen accumulation(at least 95%total ecosystem nitrogen)resided belowground(soil 0–50 cm and roots)in both watersheds.This study provides evidence that the benefits of juniper removal can be attained without significantly affecting the capacity of ecosystem nitrogen storage.展开更多
文摘Beauty of roundness" (yuan mei) is one of the important categories in classical Chinese aesthetics. Essentially, the philosophical meaning of “roundness" refers to orbicularity, ripeness and thoroughness, with its endlessly comprehensive and diversified characteristics. In its aesthetic and poetic senses, the category of “beauty of roundness" (yuan mei) is more extensive and complicated. “Beauty of roundness" (yuan mei) possesses abundant connotations and is able to form its own system of aesthetic thoughts. The basic connotations of “beauty of roundness" (yuan mei) includes: obicularity, perfectness and naturalness; maturity, speeding-up and super-naturalness; fluxion, vividness and agility.
基金Financial support from the National Natural Science Foundation of China(Project No.51176187 and 51206163)International special cooperation projects(Project No.2014DFR70080)
文摘Casing treatment is one possible way of regaining axial compressor operating range. However, most of casing treatments extend the operating range with the cost of efficiency penalty. A new form of multiple cylindrical holes casing treatment(MHCT) with pre-swirl blowing for the NASA Rotor-37 has been designed based on profound understanding of the stall inception. Unsteady numerical simulations have been performed for Rotor-37 with and without MHCT. Parametric studies of the total extraction holes area and their axial locations show that the compressor performance deteriorates as the area ratio increases but the stall margin is extended and there is an optimum extraction holes axial location for stall margin extending. The better configuration of MHCT could extend the stall margin by 6.2% with only 0.23% peak efficiency reduction. Detailed analysis of the physical mechanism behind the stall margin improvement shows that the casing treatment could eliminate the passage blockage by suppressing breakup of tip leakage vortex and decrease the blade load in tip region, which both contribute to improve stall margin of transonic axial compressors.
基金This research was supported by Oregon State University and the Oregon Agricultural Experiment Station。
文摘Aims In the Oregon of USA,the control of western juniper(Juniperus occidentalis)is an accepted rangeland management practice to restore sagebrush steppe habitats of importance to wildlife and livestock.The effects of juniper cutting on ecosystem nitrogen,however,have not been well addressed although woody plant control has important implications for local watershed management and regional nitrogen pools.Methods We quantified ecosystem nitrogen stocks in two adjacent watersheds,comprised of a treated watershed(most juniper removed)and an untreated watershed(juniper not removed).Thirteen years after juniper removal,we measured aboveground nitrogen stocks for juniper trees,shrubs,grasses and litter in both watersheds.We also measured belowground nitrogen stocks(roots and soil)in both watersheds at two soil depths(0–25 and 25–50 cm).Important Findings Aboveground nitrogen stocks were 6.9 times greater in the untreated than in the treated watershed considering the much larger aboveground biomass.However,root nitrogen stocks were 3.1 times greater in the treated one due to the gain of understory root biomass associated with juniper cutting.Soil nitrogen stocks at both 0–25 and 25–50 cm depths were not affected by juniper removal.Overall,total ecosystem nitrogen stocks did not differ between the treated(9536 kg N ha−1)and untreated(9456 kg N ha−1)watersheds.The greatest ecosystem nitrogen accumulation(at least 95%total ecosystem nitrogen)resided belowground(soil 0–50 cm and roots)in both watersheds.This study provides evidence that the benefits of juniper removal can be attained without significantly affecting the capacity of ecosystem nitrogen storage.
