一、风险投资项目评估的步骤
模糊理论指的是模糊逻辑学说,是多值逻辑的一个新的研究领域.在现实中有许多问题的界限是不清晰的,甚至是很模糊的,如'高个子的男人',多高才算高个子,并没有一个确切的数字.人们为了实际的目的,需...一、风险投资项目评估的步骤
模糊理论指的是模糊逻辑学说,是多值逻辑的一个新的研究领域.在现实中有许多问题的界限是不清晰的,甚至是很模糊的,如'高个子的男人',多高才算高个子,并没有一个确切的数字.人们为了实际的目的,需研究这些不清晰的、模糊的问题,使其清晰化,以获得有用的结果.这一研究中使用的逻辑称为模糊逻辑.20世纪20年代,人们开始研究多值逻辑,即三值逻辑、四值逻辑,甚至N0值逻辑(n为任何一自然数)和连续值逻辑.1965年美国数学家查德(Lotfi Asker Zadeh)在多值逻辑的基础上研究了模糊集合,由此发展了模糊逻辑,形成了模糊理论.展开更多
The pneumatic probe is widely used for contact measurements in turbomachinery flow field research.However,it inevitably interferes with the original flow field,leading to additional errors,particularly in wake flow fi...The pneumatic probe is widely used for contact measurements in turbomachinery flow field research.However,it inevitably interferes with the original flow field,leading to additional errors,particularly in wake flow fields or transonic regions with significant pressure gradients.This study employed Reynolds-Averaged Navier-Stokes delete and high-fidelity numerical simulation to investigate the impact of an inserted pneumatic probe on the wake flow field of a transonic turbine blade and compared it to the baseline flow field.Results indicate that the probe causes the shock waves premature occurrence in the high subsonic wake region near the turbine blade trailing edge.These shock waves affect vortex shedding by thickening the boundary layer near the trailing edge and changing the shedding pattern from high-frequency-low-energy to low-frequencyhigh-energy.In addition,the extra flow loss is incurred,and the blade's heat transfer characteristic is changed.This research provides a reference for testing experiments in complex transonic flow fields,guiding experimental researchers to minimize instrument interference with the original flow field.展开更多
文摘一、风险投资项目评估的步骤
模糊理论指的是模糊逻辑学说,是多值逻辑的一个新的研究领域.在现实中有许多问题的界限是不清晰的,甚至是很模糊的,如'高个子的男人',多高才算高个子,并没有一个确切的数字.人们为了实际的目的,需研究这些不清晰的、模糊的问题,使其清晰化,以获得有用的结果.这一研究中使用的逻辑称为模糊逻辑.20世纪20年代,人们开始研究多值逻辑,即三值逻辑、四值逻辑,甚至N0值逻辑(n为任何一自然数)和连续值逻辑.1965年美国数学家查德(Lotfi Asker Zadeh)在多值逻辑的基础上研究了模糊集合,由此发展了模糊逻辑,形成了模糊理论.
基金supported by the National Science and Technology Major Project(Grant Nos.2017-V-0016-0068,and J2019-V-0017-0112)the National Natural Science Foundation of China(Grant No.51776011).
文摘The pneumatic probe is widely used for contact measurements in turbomachinery flow field research.However,it inevitably interferes with the original flow field,leading to additional errors,particularly in wake flow fields or transonic regions with significant pressure gradients.This study employed Reynolds-Averaged Navier-Stokes delete and high-fidelity numerical simulation to investigate the impact of an inserted pneumatic probe on the wake flow field of a transonic turbine blade and compared it to the baseline flow field.Results indicate that the probe causes the shock waves premature occurrence in the high subsonic wake region near the turbine blade trailing edge.These shock waves affect vortex shedding by thickening the boundary layer near the trailing edge and changing the shedding pattern from high-frequency-low-energy to low-frequencyhigh-energy.In addition,the extra flow loss is incurred,and the blade's heat transfer characteristic is changed.This research provides a reference for testing experiments in complex transonic flow fields,guiding experimental researchers to minimize instrument interference with the original flow field.
