Froude similitude and friction similitude are the two crucial similarity conditions that are often used in physical-scale modeling of rivers.However,models often deviate from Froude similitude when dealing with real-w...Froude similitude and friction similitude are the two crucial similarity conditions that are often used in physical-scale modeling of rivers.However,models often deviate from Froude similitude when dealing with real-world situations.This study developed several fixed-bed river models with various curvatures to determine the effect of Froude similitude deviation on curved channel modeling.Models were constructed according to the characteristics of the Middle Yangtze River.Differences in longitudinal slope,transverse slope,and main stream line location were measured by varying Froude similitude deviation.The deviations of longitudinal slope and velocity were negligible because friction similitude was accounted for.The transverse slope varied significantly with the Froude similitude deviation,and the main stream line varied with the curvature and Froude similitude deviation.Formulae were derived to estimate the slope deviation.These analyses helped to clarify the feasibility of the method of Froude similitude deviation for curved channels.展开更多
DEAR EDITOR,Since the epoch-making observations of circadian rhythm in Mimosaceae plants,sleep has been investigated for centuries(de Mairan,1729;Du Monceau,1758).As a natural and reversible state,sleep is marked by r...DEAR EDITOR,Since the epoch-making observations of circadian rhythm in Mimosaceae plants,sleep has been investigated for centuries(de Mairan,1729;Du Monceau,1758).As a natural and reversible state,sleep is marked by reduced responsiveness to external stimuli,relative inactivity,and loss of consciousness.Although reduced responsiveness could potentially introduce significant danger to survival,nearly all animals in nature sleep.展开更多
The ratio ofγtransition-intensities from the initial capture state to low-lying states may represent the model-independentγ-strength function,which reflects the effects of different neutron-capture reaction mechanis...The ratio ofγtransition-intensities from the initial capture state to low-lying states may represent the model-independentγ-strength function,which reflects the effects of different neutron-capture reaction mechanisms.The extraordinary quenching of theγ0 transition from the p-wave neutron radiative capture in 57Fe is observed,for the first time,from the pronounced enhancement of theγ-strength function ratios fγ1/fγ0 and fγ2/fγ0.The 2p-1h doorway excitation leads to suppression of theγ0 transition to the ground state and the enhancement of theγ1 andγ2 transitions to the first and second excited states,respectively.The fp sub-shells supply the exact number of spaces required for the 2p-1h configuration,which features the neutron capture mechanism in the vicinity of A=55.展开更多
基金supported by the Project of Subsequent Work of the Three Gorges Project(Grant No.SXHXGZ-2020-3).
文摘Froude similitude and friction similitude are the two crucial similarity conditions that are often used in physical-scale modeling of rivers.However,models often deviate from Froude similitude when dealing with real-world situations.This study developed several fixed-bed river models with various curvatures to determine the effect of Froude similitude deviation on curved channel modeling.Models were constructed according to the characteristics of the Middle Yangtze River.Differences in longitudinal slope,transverse slope,and main stream line location were measured by varying Froude similitude deviation.The deviations of longitudinal slope and velocity were negligible because friction similitude was accounted for.The transverse slope varied significantly with the Froude similitude deviation,and the main stream line varied with the curvature and Froude similitude deviation.Formulae were derived to estimate the slope deviation.These analyses helped to clarify the feasibility of the method of Froude similitude deviation for curved channels.
基金This study was supported by the National Natural Science Foundation of China(31700897,31960178)Yunnan Provincial Natural Science Foundation of China(2018FB053,2019FA007)+1 种基金China Postdoctoral Science Foundation(2018M631105)Post-Doctoral Training Program in Yunnan Province,and Key Realm R&D Program of Guangdong Province(2019B030335001)。
文摘DEAR EDITOR,Since the epoch-making observations of circadian rhythm in Mimosaceae plants,sleep has been investigated for centuries(de Mairan,1729;Du Monceau,1758).As a natural and reversible state,sleep is marked by reduced responsiveness to external stimuli,relative inactivity,and loss of consciousness.Although reduced responsiveness could potentially introduce significant danger to survival,nearly all animals in nature sleep.
基金Supported by the National Natural Science Foundation of China(10175091,11305007)the National Research Foundation of Korea(2018R1A6A06024970)。
文摘The ratio ofγtransition-intensities from the initial capture state to low-lying states may represent the model-independentγ-strength function,which reflects the effects of different neutron-capture reaction mechanisms.The extraordinary quenching of theγ0 transition from the p-wave neutron radiative capture in 57Fe is observed,for the first time,from the pronounced enhancement of theγ-strength function ratios fγ1/fγ0 and fγ2/fγ0.The 2p-1h doorway excitation leads to suppression of theγ0 transition to the ground state and the enhancement of theγ1 andγ2 transitions to the first and second excited states,respectively.The fp sub-shells supply the exact number of spaces required for the 2p-1h configuration,which features the neutron capture mechanism in the vicinity of A=55.
