Monsoon gyres have been identified as one of the important large-scale circulation patterns associated with tropical cyclone （TC） formation in the western North Pacific.A recent observational analysis indicated that...Monsoon gyres have been identified as one of the important large-scale circulation patterns associated with tropical cyclone （TC） formation in the western North Pacific.A recent observational analysis indicated that most TCs form near the center of monsoon gyres or at the northeast end of the enhanced low-level southwesterly flows on the southeast-east periphery of monsoon gyres.In the present reported study,idealized numerical experiments were conducted to examine the tropical cyclogenesis associated with Rossby wave energy dispersion with an initial idealized monsoon gyre.The numerical simulations showed that the development of the low-level enhanced southwesterly flows on the southeasteast periphery of monsoon gyres can be induced by Rossby wave energy dispersion.Mesoscale convective systems emerged from the northeast end of the enhanced southwesterly flows with mid-level maximum relative vorticity.The simulated TC formed in the northeast of the monsoon gyre and moved westward towards the center of the monsoon gyre.The numerical experiment with a relatively smaller sized initial monsoon gyre showed the TC forming near the center of the initial monsoon gyre.The results of the present study suggest that Rossby wave energy dispersion can play an important role in TC formation in the presence of monsoon gyres.展开更多
A very fast simulated annealing（VFSA） global optimization is used to interpret residual gravity anomaly.Since,VFSA optimization yields a large number of best-fitted models in a vast model space;the nature of uncerta...A very fast simulated annealing（VFSA） global optimization is used to interpret residual gravity anomaly.Since,VFSA optimization yields a large number of best-fitted models in a vast model space;the nature of uncertainty in the interpretation is also examined simultaneously in the present study.The results of VFSA optimization reveal that various parameters show a number of equivalent solutions when shape of the target body is not known and shape factor ＇q＇ is also optimized together with other model parameters.The study reveals that amplitude coefficient k is strongly dependent on shape factor.This shows that there is a multi-model type uncertainty between these two model parameters derived from the analysis of cross-plots.However,the appraised values of shape factor from various VFSA runs clearly indicate whether the subsurface structure is sphere,horizontal or vertical cylinder type structure.Accordingly,the exact shape factor（1.5 for sphere,1.0 for horizontal cylinder and 0.5 for vertical cylinder）is fixed and optimization process is repeated.After fixing the shape factor,analysis of uncertainty and cross-plots shows a well-defined uni-model characteristic.The mean model computed after fixing the shape factor gives the utmost consistent results.Inversion of noise-free and noisy synthetic data as well as field data demonstrates the efficacy of the approach.展开更多
This paper presents a numerical investigation on the strain localization of an idealized sand in biaxial compression tests using the distinct element method(DEM).In addition to the dilatancy and material frictional an...This paper presents a numerical investigation on the strain localization of an idealized sand in biaxial compression tests using the distinct element method(DEM).In addition to the dilatancy and material frictional angle,the principal stress field,and distributions of void ratio,particle velocity,and the averaged pure rotation rate(APR)in the DEM specimen are examined to illustrate the link between microscopic and macroscopic variables in the case of strain localization.The study shows that strain localization of the granular material in the tests proceeds with localizations of void ratio,strain and APR,and distortions of stress field and force chains.In addition,both thickness and inclination of the shear band change with the increasing of axial swain,with the former valued around 10-14 times of mean grain diameter and the later overall described by the Mohr-Coulomb theory.展开更多
The selection of refracturing candidate is one of the most important jobs faced by oilfield engineers. However, due to the complicated multi-parameter relationships and their comprehensive influence, the selection of ...The selection of refracturing candidate is one of the most important jobs faced by oilfield engineers. However, due to the complicated multi-parameter relationships and their comprehensive influence, the selection of refracturing candidate is often very difficult. In this paper, a novel approach combining data analysis techniques and fuzzy clustering was proposed to select refracturing candidate. First, the analysis techniques were used to quantitatively calculate the weight coefficient and determine the key factors. Then, the idealized refracturing well was established by considering the main factors. Fuzzy clustering was applied to evaluate refracturing potential. Finally, reservoirs numerical simulation was used to further evaluate reservoirs energy and material basis of the optimum refracturing candidates. The hybrid method has been successfully applied to a tight oil reservoir in China. The average steady production was 15.8 t/d after refracturing treatment, increasing significantly compared with previous status. The research results can guide the development of tight oil and gas reservoirs effectively.展开更多
We verify the accuracy of the curvature-based potential.By means of the idealized numerical experiment,we show that the curvature-based potential is in good agreement with the numerical experiment,and the errors are w...We verify the accuracy of the curvature-based potential.By means of the idealized numerical experiment,we show that the curvature-based potential is in good agreement with the numerical experiment,and the errors are within a reasonable range.Based on the curvature-based potential,the equipotential surfaces of particles are derived,and the intrinsic relations between the equipotential surfaces and Weingarten helicoids are shown.展开更多
Recent observational and numerical studies have revealed the dependence of the intensification rate on the inner-core size of tropical cyclones(TCs). In this study, with the initial inner-core size(i.e., the radius of...Recent observational and numerical studies have revealed the dependence of the intensification rate on the inner-core size of tropical cyclones(TCs). In this study, with the initial inner-core size(i.e., the radius of maximum wind—RMW)varied from 20–180 km in idealized simulations using two different numerical models, we found a nonmonotonic dependence of the lifetime maximum intensification rate(LMIR) on the inner-core size. Namely, there is an optimal innercore size for the LMIR of a TC. Tangential wind budget analysis shows that, compared to large TCs, small TCs have large inward flux of absolute vorticity due to large absolute vorticity inside the RMW. However, small TCs also suffer from strong lateral diffusion across the eyewall, which partly offsets the positive contribution from large inward flux of absolute vorticity. These two competing processes ultimately lead to the TC with an intermediate initial inner-core size having the largest LMIR. Results from sensitivity experiments show that the optimal size varies in the range of 40–120 km and increases with higher sea surface temperature, lower latitude, larger horizontal mixing length, and weaker initial TC intensity. The 40–120 km RMW corresponds to the inner-core size most commonly found for intensifying TCs in observations, suggesting the natural selection of initial TC size for intensification. This study highlights the importance of accurate representation of TC inner-core size to TC intensity forecasts by numerical weather prediction models.展开更多
The aim of this study is to examine the difference in tropical cyclone （TC） formation in different cyclonic circulation locations using a mesoscale model on a beta plane. A weak initial vortex is imposed at differen...The aim of this study is to examine the difference in tropical cyclone （TC） formation in different cyclonic circulation locations using a mesoscale model on a beta plane. A weak initial vortex is imposed at different positions in a cyclonic circulation. Numerical experiments indicate that the tropical disturbances located in the center and northeastern parts of the cyclonic circulation are favorable to TC formation, while those located in the south of the cyclonic circulation are unfavorable. Since the asymmetric circulation induced by the beta effect peaks in the northeastern quadrant of the vortex, when the initial vortex is placed in the southern part of the cyclonic circulation, the vortex begins to develop in the south due to the effect of the westerly wind of the cyclonic circulation. The westerly wind of the cyclonic circulation gradually decreases and the vortex is contributed mainly by the beta effect afterwards. Thus, establishment of the convection circulation-moisture positive feedback is delayed, unfavorable to TC rapid development. On the contrary, when the initial vortex is placed in the northern part of the cyclonic circulation, the superposition of the beta gyres and easterly wind of the cyclonic circulation induces stronger wavenumber-1 wind in the northeastern part of the vortex. The greater asymmetric wind is closely associated with the symmetric wind through energy conversion, thus accelerating a positive feedback and facilitating vortex development into a stronger TC. Meanwhile, when the initial vortex is placed in the center and eastern parts of the cyclonic circulation, the vortex develops a little slower than when it is placed in the northern part, but stronger than when placed in the southern part.展开更多
My paper aims to investigate why and what lead to the love tragedy of Anna Karenina.Based on the understanding and analysis,the paper sums up the three major factors:social tragedy,religious ethics and psychological c...My paper aims to investigate why and what lead to the love tragedy of Anna Karenina.Based on the understanding and analysis,the paper sums up the three major factors:social tragedy,religious ethics and psychological character tragedy,and idealized love tragedy.展开更多
The newly developed nonhydrostatic(NH)global spectral dynamical core is evaluated by using three-dimensional(3D)benchmark tests with/without moisture.This new dynamical core differs from the original Aladin-NH like on...The newly developed nonhydrostatic(NH)global spectral dynamical core is evaluated by using three-dimensional(3D)benchmark tests with/without moisture.This new dynamical core differs from the original Aladin-NH like one in the combined use of a dry-mass vertical coordinate and a new temperature variable,and thus,it inherently conserves the dry air mass and includes the mass sink effect associated with precipitation flux.Some 3D dry benchmark tests are first conducted,including steady state,dry baroclinic waves,mountain waves in non-sheared and sheared background flows,and a dry Held–Suarez test.The results from these test cases demonstrate that the present dynamical core is accurate and robust in applications on the sphere,especially for addressing the nonhydrostatic effects.Then,three additional moist test cases are conducted to further explore the improvement of the new dynamical core.Importantly,in contrast to the original Aladin-NH like one,the new dynamical core prefers to obtain simulated tropical cyclone with lower pressure,stronger wind speeds,and faster northward movement,which is much closer to the results from the Model for Prediction Across Scales(MPAS),and it also enhances the updrafts and provides enhanced precipitation rate in the tropics,which partially compensates the inefficient vertical transport due to the absence of the deep convection parameterization in the moist Held–Suarez test,thus demonstrating its potential value for full-physics global NH numerical weather prediction application.展开更多
To investigate the influence of asymmetric tidal mixing(ATM) on sediment dynamics in tidal estuaries, we developed a vertically one-dimensional idealized analytical model, in which the M_2 tidal flow, residual flow an...To investigate the influence of asymmetric tidal mixing(ATM) on sediment dynamics in tidal estuaries, we developed a vertically one-dimensional idealized analytical model, in which the M_2 tidal flow, residual flow and suspended sediment concentration(SSC) are described. Model solutions are obtained in terms of tidallyaveraged, and tidally-varying components(M_2 and M_4) of both hydrodynamics and sediment dynamics. The effect of ATM was considered with a time-varying eddy viscosity and time-varying eddy diffusivity of SSC. For the first time, an analytical solution for SSC variation driven by varying diffusivity could be derived. The model was applied to York River Estuary, where higher(or lower) eddy diffusivity was observed during flood(or ebb) in a previous study. The model results agreed well with the observation in both hydrodynamics and sediment dynamics. The vertical sediment distribution under the influence of ATM was analyzed in terms of the phase lag of the M_2 component of SSC relative to tidal flow. The phase lag increases significantly in estuaries with typical ATM(higher diffusivity during flood and lower diffusivity during ebb) for the case of seaward-directed net bottom shear stress(e.g., strong river discharge). In contrary, the phase lag is reduced by ATM, if the tidally-averaged bottom shear stress is landward(e.g., strong horizontal density gradient). The dynamics of sediment transport was analyzed as a function of ATM phase lag to identify the time of highest sediment diffusivity, as well as a function of the residual flow, to evaluate the relative importance of seaward and landward residual flows. In estuaries with relative strong fresh water discharge or weak tidal forcing(in case of flood season or neap tide), the near bottom SSC could be higher during ebb than during flood, since the bottom shear stress is higher during ebb due to seaward residual flow. However, landward net sediment transport can be expected in these estuaries in case of a typical ATM, because higher diffusivity causes h展开更多
ICM （Idealized Cognitive Model） theory put forward by Lakoff has a guiding function in the analysis of discourse coherence without the coherent devices, based on which WANG Yin mentioned cognitive world. The cogniti...ICM （Idealized Cognitive Model） theory put forward by Lakoff has a guiding function in the analysis of discourse coherence without the coherent devices, based on which WANG Yin mentioned cognitive world. The cognitive world is of two kinds： ICM and background knowledge. The process of understanding discourse is the process of activating the human＇s ICM and background knowledge so that coherence is realized.展开更多
A 2D axisymmetric bin model is used to conduct idealized numerical experiments of cloud seeding.The simulations are performed for two clouds that differ in their initial wind shear.Results show that,although cloud see...A 2D axisymmetric bin model is used to conduct idealized numerical experiments of cloud seeding.The simulations are performed for two clouds that differ in their initial wind shear.Results show that,although cloud seeding with an ice concentration of 1000 Lin a regime that has relatively high supercooled liquid water can obtain a positive effect,the rainfall enhancement seems more pronounced when the cloud develops in a wind shear environment.In no-shear environment,the change in the microphysical thermodynamic field after seeding shows that,although more graupel is produced via riming and this can increase the surface rainfall intensity,the larger drag force and cooling of melting graupel is unfavorable for the development of cloud.On the contrary,when the cloud develops in a wind shear environment,since the main downdraft is behind the direction of movement of the cloud,its negative effect on precipitation is much weaker.展开更多
D’ansite is a rare mineral in solt deposits. R. Gorgey described its existence briefly in Hal solt deposit in 1909. But he did not name it nor give its mineralogical data. H. Autenrieth and G. Braune got the crystal ...D’ansite is a rare mineral in solt deposits. R. Gorgey described its existence briefly in Hal solt deposit in 1909. But he did not name it nor give its mineralogical data. H. Autenrieth and G. Braune got the crystal of d’ansite by synthesis in 1958 and its physical properties were determined. He named this mineral 'd’ansite'. Its existence in nature was confirmed when the mineral was discovered in a drill core of the Tertiary strata in the Jianghan Plain and was first investigated by Zheng Jinping in 1972. Later Qu Yihua et al. reported the results of their study on d’ansite.展开更多
If there is no imagination, there is no music appreciation. It should create imaginary world for students in the music classroom teaching practice, and it should foster the students＇ musical imagination. Thus, collea...If there is no imagination, there is no music appreciation. It should create imaginary world for students in the music classroom teaching practice, and it should foster the students＇ musical imagination. Thus, colleagues can make discussion about strategies proposed including pilot background, context led, screen hygiene conditions and others. We use Cognitive Linguistic Theories to introduce idealized cognitive model and its theoretical basis and the intensified impact on student musical imagination.展开更多
The main source of the noise of an axial flow fan is the fluctuating pressure field on blade surfaces caused by the shedding of vortices at the trailing edge of blades.An analytical model to predict the vortex sheddin...The main source of the noise of an axial flow fan is the fluctuating pressure field on blade surfaces caused by the shedding of vortices at the trailing edge of blades.An analytical model to predict the vortex shedding noise generated at the trailing edge of blades of axial flow fans was proposed by Lee in 1993.In this model,for mathematical convenience,an idealized vortex street is considered.However,the agreement between the analytical results and the experimental data needs to be improved because of the simplification about the Karman vortex street in the wake of blade.In the present study,a modified model is proposed based on the prediction model by Lee.The boundary layer theory is used to analyze and calculate the boundary layer development on both the pressure and the suction sides of blades.Considering the effect of boundary layer separation on the location of noise source,the predicted overall sound pressure level compares favorably with the experimental data of an axial fan.In the calculation of A-weighted sound pressure level(La),considering the effect of static pressure on radiate energy,the predicted broadband noise with the modified model compares favorably with the experimental data of a multiblade centrifugal fan.展开更多
基金supported by the typhoon research project (Grant No. 2009CB421503) of the National Basic Research Program of Chinathe National Natural Science Foundation of China (Grant No. 41275093)+2 种基金the social commonwealth research program of the Ministry of ScienceTechnology of the People’s Republic of China (Grant No. GYHY200806009)the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘Monsoon gyres have been identified as one of the important large-scale circulation patterns associated with tropical cyclone （TC） formation in the western North Pacific.A recent observational analysis indicated that most TCs form near the center of monsoon gyres or at the northeast end of the enhanced low-level southwesterly flows on the southeast-east periphery of monsoon gyres.In the present reported study,idealized numerical experiments were conducted to examine the tropical cyclogenesis associated with Rossby wave energy dispersion with an initial idealized monsoon gyre.The numerical simulations showed that the development of the low-level enhanced southwesterly flows on the southeasteast periphery of monsoon gyres can be induced by Rossby wave energy dispersion.Mesoscale convective systems emerged from the northeast end of the enhanced southwesterly flows with mid-level maximum relative vorticity.The simulated TC formed in the northeast of the monsoon gyre and moved westward towards the center of the monsoon gyre.The numerical experiment with a relatively smaller sized initial monsoon gyre showed the TC forming near the center of the initial monsoon gyre.The results of the present study suggest that Rossby wave energy dispersion can play an important role in TC formation in the presence of monsoon gyres.
文摘A very fast simulated annealing（VFSA） global optimization is used to interpret residual gravity anomaly.Since,VFSA optimization yields a large number of best-fitted models in a vast model space;the nature of uncertainty in the interpretation is also examined simultaneously in the present study.The results of VFSA optimization reveal that various parameters show a number of equivalent solutions when shape of the target body is not known and shape factor ＇q＇ is also optimized together with other model parameters.The study reveals that amplitude coefficient k is strongly dependent on shape factor.This shows that there is a multi-model type uncertainty between these two model parameters derived from the analysis of cross-plots.However,the appraised values of shape factor from various VFSA runs clearly indicate whether the subsurface structure is sphere,horizontal or vertical cylinder type structure.Accordingly,the exact shape factor（1.5 for sphere,1.0 for horizontal cylinder and 0.5 for vertical cylinder）is fixed and optimization process is repeated.After fixing the shape factor,analysis of uncertainty and cross-plots shows a well-defined uni-model characteristic.The mean model computed after fixing the shape factor gives the utmost consistent results.Inversion of noise-free and noisy synthetic data as well as field data demonstrates the efficacy of the approach.
基金This research was financially supported by the National Natural Science Foundation of China(Grant Nos.50679057 and 10972158).
文摘This paper presents a numerical investigation on the strain localization of an idealized sand in biaxial compression tests using the distinct element method(DEM).In addition to the dilatancy and material frictional angle,the principal stress field,and distributions of void ratio,particle velocity,and the averaged pure rotation rate(APR)in the DEM specimen are examined to illustrate the link between microscopic and macroscopic variables in the case of strain localization.The study shows that strain localization of the granular material in the tests proceeds with localizations of void ratio,strain and APR,and distortions of stress field and force chains.In addition,both thickness and inclination of the shear band change with the increasing of axial swain,with the former valued around 10-14 times of mean grain diameter and the later overall described by the Mohr-Coulomb theory.
基金Projects(51204054,51504203)supported by the National Natural Science Foundation of ChinaProject(2016ZX05023-001)supported by the National Science and Technology Major Project of China
文摘The selection of refracturing candidate is one of the most important jobs faced by oilfield engineers. However, due to the complicated multi-parameter relationships and their comprehensive influence, the selection of refracturing candidate is often very difficult. In this paper, a novel approach combining data analysis techniques and fuzzy clustering was proposed to select refracturing candidate. First, the analysis techniques were used to quantitatively calculate the weight coefficient and determine the key factors. Then, the idealized refracturing well was established by considering the main factors. Fuzzy clustering was applied to evaluate refracturing potential. Finally, reservoirs numerical simulation was used to further evaluate reservoirs energy and material basis of the optimum refracturing candidates. The hybrid method has been successfully applied to a tight oil reservoir in China. The average steady production was 15.8 t/d after refracturing treatment, increasing significantly compared with previous status. The research results can guide the development of tight oil and gas reservoirs effectively.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11072125 and 10872114)the Natural Science Foundation of Jiangsu Province (Grant No. SBK201140044)
文摘We verify the accuracy of the curvature-based potential.By means of the idealized numerical experiment,we show that the curvature-based potential is in good agreement with the numerical experiment,and the errors are within a reasonable range.Based on the curvature-based potential,the equipotential surfaces of particles are derived,and the intrinsic relations between the equipotential surfaces and Weingarten helicoids are shown.
基金supported by the National Natural Science Foundation of China (Grant No.41730960)Wuxi University Research Start-up Fund for Introduced Talents (2024r037)Yuqing WANG was supported by the NSF (Grant No. AGS-1834300)。
文摘Recent observational and numerical studies have revealed the dependence of the intensification rate on the inner-core size of tropical cyclones(TCs). In this study, with the initial inner-core size(i.e., the radius of maximum wind—RMW)varied from 20–180 km in idealized simulations using two different numerical models, we found a nonmonotonic dependence of the lifetime maximum intensification rate(LMIR) on the inner-core size. Namely, there is an optimal innercore size for the LMIR of a TC. Tangential wind budget analysis shows that, compared to large TCs, small TCs have large inward flux of absolute vorticity due to large absolute vorticity inside the RMW. However, small TCs also suffer from strong lateral diffusion across the eyewall, which partly offsets the positive contribution from large inward flux of absolute vorticity. These two competing processes ultimately lead to the TC with an intermediate initial inner-core size having the largest LMIR. Results from sensitivity experiments show that the optimal size varies in the range of 40–120 km and increases with higher sea surface temperature, lower latitude, larger horizontal mixing length, and weaker initial TC intensity. The 40–120 km RMW corresponds to the inner-core size most commonly found for intensifying TCs in observations, suggesting the natural selection of initial TC size for intensification. This study highlights the importance of accurate representation of TC inner-core size to TC intensity forecasts by numerical weather prediction models.
基金Supported by the National Basic ResearchDevelopment(973)Program of China(2014CB953902)+1 种基金National Natural Science Foundation of China(41505048,41461164005,41275001,and 41475074)LASW State Key Laboratory Special Fund(2015LASW-B04)
文摘The aim of this study is to examine the difference in tropical cyclone （TC） formation in different cyclonic circulation locations using a mesoscale model on a beta plane. A weak initial vortex is imposed at different positions in a cyclonic circulation. Numerical experiments indicate that the tropical disturbances located in the center and northeastern parts of the cyclonic circulation are favorable to TC formation, while those located in the south of the cyclonic circulation are unfavorable. Since the asymmetric circulation induced by the beta effect peaks in the northeastern quadrant of the vortex, when the initial vortex is placed in the southern part of the cyclonic circulation, the vortex begins to develop in the south due to the effect of the westerly wind of the cyclonic circulation. The westerly wind of the cyclonic circulation gradually decreases and the vortex is contributed mainly by the beta effect afterwards. Thus, establishment of the convection circulation-moisture positive feedback is delayed, unfavorable to TC rapid development. On the contrary, when the initial vortex is placed in the northern part of the cyclonic circulation, the superposition of the beta gyres and easterly wind of the cyclonic circulation induces stronger wavenumber-1 wind in the northeastern part of the vortex. The greater asymmetric wind is closely associated with the symmetric wind through energy conversion, thus accelerating a positive feedback and facilitating vortex development into a stronger TC. Meanwhile, when the initial vortex is placed in the center and eastern parts of the cyclonic circulation, the vortex develops a little slower than when it is placed in the northern part, but stronger than when placed in the southern part.
文摘My paper aims to investigate why and what lead to the love tragedy of Anna Karenina.Based on the understanding and analysis,the paper sums up the three major factors:social tragedy,religious ethics and psychological character tragedy,and idealized love tragedy.
基金Supported by the National Natural Science Foundation of China(42275062,41875121,and 41975066).
文摘The newly developed nonhydrostatic(NH)global spectral dynamical core is evaluated by using three-dimensional(3D)benchmark tests with/without moisture.This new dynamical core differs from the original Aladin-NH like one in the combined use of a dry-mass vertical coordinate and a new temperature variable,and thus,it inherently conserves the dry air mass and includes the mass sink effect associated with precipitation flux.Some 3D dry benchmark tests are first conducted,including steady state,dry baroclinic waves,mountain waves in non-sheared and sheared background flows,and a dry Held–Suarez test.The results from these test cases demonstrate that the present dynamical core is accurate and robust in applications on the sphere,especially for addressing the nonhydrostatic effects.Then,three additional moist test cases are conducted to further explore the improvement of the new dynamical core.Importantly,in contrast to the original Aladin-NH like one,the new dynamical core prefers to obtain simulated tropical cyclone with lower pressure,stronger wind speeds,and faster northward movement,which is much closer to the results from the Model for Prediction Across Scales(MPAS),and it also enhances the updrafts and provides enhanced precipitation rate in the tropics,which partially compensates the inefficient vertical transport due to the absence of the deep convection parameterization in the moist Held–Suarez test,thus demonstrating its potential value for full-physics global NH numerical weather prediction application.
基金The National Natural Science Foundation of China under contract Nos U2040220, 52079069, 52009066, 52379069,52009079, 42006156 and U2240220the CRSRI Open Research Program under contract No. CKWV20221003/KY+2 种基金the Open Research Program of Hubei Key Laboratory of Intelligent Yangtze and Hydroelectric Science under contract No. ZH2102000109the Outstanding Young and Middle-aged Scientific and Technological Innovation Team in Universities of Hubei Province under contract No. T2021003the Hubei Province Chutian Scholar Program (granted to Andreas Lorke)。
文摘To investigate the influence of asymmetric tidal mixing(ATM) on sediment dynamics in tidal estuaries, we developed a vertically one-dimensional idealized analytical model, in which the M_2 tidal flow, residual flow and suspended sediment concentration(SSC) are described. Model solutions are obtained in terms of tidallyaveraged, and tidally-varying components(M_2 and M_4) of both hydrodynamics and sediment dynamics. The effect of ATM was considered with a time-varying eddy viscosity and time-varying eddy diffusivity of SSC. For the first time, an analytical solution for SSC variation driven by varying diffusivity could be derived. The model was applied to York River Estuary, where higher(or lower) eddy diffusivity was observed during flood(or ebb) in a previous study. The model results agreed well with the observation in both hydrodynamics and sediment dynamics. The vertical sediment distribution under the influence of ATM was analyzed in terms of the phase lag of the M_2 component of SSC relative to tidal flow. The phase lag increases significantly in estuaries with typical ATM(higher diffusivity during flood and lower diffusivity during ebb) for the case of seaward-directed net bottom shear stress(e.g., strong river discharge). In contrary, the phase lag is reduced by ATM, if the tidally-averaged bottom shear stress is landward(e.g., strong horizontal density gradient). The dynamics of sediment transport was analyzed as a function of ATM phase lag to identify the time of highest sediment diffusivity, as well as a function of the residual flow, to evaluate the relative importance of seaward and landward residual flows. In estuaries with relative strong fresh water discharge or weak tidal forcing(in case of flood season or neap tide), the near bottom SSC could be higher during ebb than during flood, since the bottom shear stress is higher during ebb due to seaward residual flow. However, landward net sediment transport can be expected in these estuaries in case of a typical ATM, because higher diffusivity causes h
文摘ICM （Idealized Cognitive Model） theory put forward by Lakoff has a guiding function in the analysis of discourse coherence without the coherent devices, based on which WANG Yin mentioned cognitive world. The cognitive world is of two kinds： ICM and background knowledge. The process of understanding discourse is the process of activating the human＇s ICM and background knowledge so that coherence is realized.
基金This study was jointly supported by the National Key Research and Development Program of China[grant number 2018YFC1507900]the National Natural Science Foundation of China[grant numbers 41875172 and 42075192].
文摘A 2D axisymmetric bin model is used to conduct idealized numerical experiments of cloud seeding.The simulations are performed for two clouds that differ in their initial wind shear.Results show that,although cloud seeding with an ice concentration of 1000 Lin a regime that has relatively high supercooled liquid water can obtain a positive effect,the rainfall enhancement seems more pronounced when the cloud develops in a wind shear environment.In no-shear environment,the change in the microphysical thermodynamic field after seeding shows that,although more graupel is produced via riming and this can increase the surface rainfall intensity,the larger drag force and cooling of melting graupel is unfavorable for the development of cloud.On the contrary,when the cloud develops in a wind shear environment,since the main downdraft is behind the direction of movement of the cloud,its negative effect on precipitation is much weaker.
文摘D’ansite is a rare mineral in solt deposits. R. Gorgey described its existence briefly in Hal solt deposit in 1909. But he did not name it nor give its mineralogical data. H. Autenrieth and G. Braune got the crystal of d’ansite by synthesis in 1958 and its physical properties were determined. He named this mineral 'd’ansite'. Its existence in nature was confirmed when the mineral was discovered in a drill core of the Tertiary strata in the Jianghan Plain and was first investigated by Zheng Jinping in 1972. Later Qu Yihua et al. reported the results of their study on d’ansite.
文摘If there is no imagination, there is no music appreciation. It should create imaginary world for students in the music classroom teaching practice, and it should foster the students＇ musical imagination. Thus, colleagues can make discussion about strategies proposed including pilot background, context led, screen hygiene conditions and others. We use Cognitive Linguistic Theories to introduce idealized cognitive model and its theoretical basis and the intensified impact on student musical imagination.
基金supported by National Natural Science Foundation of China(51206149,51376055)Zhejiang Province Science and Technology Innovation Team Project(2013TD18)
文摘The main source of the noise of an axial flow fan is the fluctuating pressure field on blade surfaces caused by the shedding of vortices at the trailing edge of blades.An analytical model to predict the vortex shedding noise generated at the trailing edge of blades of axial flow fans was proposed by Lee in 1993.In this model,for mathematical convenience,an idealized vortex street is considered.However,the agreement between the analytical results and the experimental data needs to be improved because of the simplification about the Karman vortex street in the wake of blade.In the present study,a modified model is proposed based on the prediction model by Lee.The boundary layer theory is used to analyze and calculate the boundary layer development on both the pressure and the suction sides of blades.Considering the effect of boundary layer separation on the location of noise source,the predicted overall sound pressure level compares favorably with the experimental data of an axial fan.In the calculation of A-weighted sound pressure level(La),considering the effect of static pressure on radiate energy,the predicted broadband noise with the modified model compares favorably with the experimental data of a multiblade centrifugal fan.
