The utilization of waste concrete as a raw material for recycled concrete in the domain of prefabricated components is garnering greater interest.This paper delineates and examines the concept,categorization,methodolo...The utilization of waste concrete as a raw material for recycled concrete in the domain of prefabricated components is garnering greater interest.This paper delineates and examines the concept,categorization,methodologies of preparation,applicable sectors,and evaluative metrics of recycled concrete technology,highlighting its prospective benefits.Nonetheless,for the successful integration of recycled concrete technology into prefabricated component applications,it is imperative to systematically enhance its physical,mechanical,and attributes,as well as its environmental efficacy.Moreover,to foster the continued advancement of recycled concrete technology,innovative initiatives,standardization,educational programs,demonstration projects,and collaborative efforts are crucial to promote broader adoption and realize improved outcomes within the realm of prefabricated components.In conclusion,recycled concrete technology is poised to play a pivotal role in prefabricated construction,offering robust support for propelling the construction industry towards a sustainable future.展开更多
We previously found that monocyte locomotion inhibitory factor has a neuroprotective effect on ischemic brain injury during the acute phase of stro ke.Therefore,we modified the structure of an anti-inflammato ry monoc...We previously found that monocyte locomotion inhibitory factor has a neuroprotective effect on ischemic brain injury during the acute phase of stro ke.Therefore,we modified the structure of an anti-inflammato ry monocyte locomotion inhibitory factor peptide to construct an active cyclic peptide—Cyclo(MQCNS)(LZ-3)—and investigated its effects on ischemic stroke.In this study,we established a rat model of ischemic stroke by occluding the middle cerebral artery and then administered LZ-3(2 or 4 mg/kg) via the tail vein for 7 consecutive days.Our res ults showed that LZ-3(2 or 4 mg/kg) substantially decreased infarct volu m e,reduced co rtical ne rve cell death,improved neurological function,reduced cortical and hippocampal injury,and decreased the levels of inflammatory factors in the blood and brain tissues.In a well-diffe rentiated,oxygen-glucose deprivation/reoxygenation-induced BV2 cell model of poststroke,LZ-3(100 μM) inhibited the JAK1-STAT6 signaling pathway.LZ-3 regulated microglia/macrophage polarization from the M1 to the M2 type and inhibited microglia/macrophage phagocytosis and migration via the JAK1/STAT6 signaling pathway.To conclude,LZ-3 regulates microglial activation by inhibiting the JAK1/STAT6 sign aling pathway and improves functional recovery post-stroke.展开更多
The enhancement of near-field radiative heat transfer(NFRHT)has now become one of the research hotspots in the fieldsof thermal management and imaging due to its ability to improve the performance of near-field thermo...The enhancement of near-field radiative heat transfer(NFRHT)has now become one of the research hotspots in the fieldsof thermal management and imaging due to its ability to improve the performance of near-field thermoelectric devices and near-field imaging systems.In this paper,we design three structures(multilayer structure,nanoporous structure,and nanorod structure)based on high-entropy alloys to realize the enhancement of NFRHT.By combining stochastic electrodynamicsand Maxwell-Garnett's description of the effective medium,we calculate the radiative heat transfer under different parametersand find that the nanoporousstructure has the largest enhancement effect on NFRHT.The near-field heat transfer factor(q)of this structure(q=1.40×10^(9)W/(m^(2)·K))is three times higher than that of the planestructure(q=4.6×10^(8)W/(m^(2)·K)),and about two orders of magnitude higher than that of the SiO2plate.Thisresult providesa freshidea for the enhancement of NFRHT and will promote the application of high-entropy alloy materials in near-field heat radiation.展开更多
Meandering rivers of various scales are found globally and exhibit a high degree of regularity in their evolutionary processes. This study utilized remote sensing interpretation techniques to extract and analyze the p...Meandering rivers of various scales are found globally and exhibit a high degree of regularity in their evolutionary processes. This study utilized remote sensing interpretation techniques to extract and analyze the planform migration characteristics of meandering rivers. Specifically, remote sensing images of three meandering rivers—the Black and White Rivers in the Tibetan Plateau and the Itui River in the Amazon Basin—were selected for this analysis. By comparing these observations with existing research data, this study quantitatively revealed the lag response patterns in the planform migration processes of meandering rivers. The findings of the study revealed several key insights.(1) The average migration rates for the three rivers were determined to be 1.74, 3.84, and 2.34 m/a, respectively. The critical values of the relative curvature radius for the river channels ranged from 1.5 to 2.0, 1.7 to 2.2, and 2.5 to 3.0, where local migration rate peaks were observed. These findings align with previous research that reported critical values between 2.0 and 4.0.(2) A significant lag is observed in the migration rate relative to curvature in spatial variation, with lag distances for the Black, White, and Itui Rivers measuring 227, 281, and 324 m,corresponding to 2.02, 2.39, and 3.15 times the river width, respectively.(3) A comparison with other meandering rivers indicates that, despite significant variations in climatic and hydrological conditions and river discharges differing by over 1,000times, the ratio of lag distance to river width(relative lag distance) for meandering rivers consistently falls within the range of 2.0to 4.0. This study suggests that the establishment of critical values for the relative curvature radius and the concentration of the relative lag distance reflects distinct quantitative relationships that emerge during the evolutionary processes of meandering rivers, aiming to minimize energy expenditure. These relationships appear to be applicable to various types of alluvial rivers.展开更多
Evaluating environmental flow(EF)is pivotal for conserving and restoring riverine ecosystems.Yet,prevalent EF evaluations presume that a river reach's hydraulic conditions are exclusively governed by inflow discha...Evaluating environmental flow(EF)is pivotal for conserving and restoring riverine ecosystems.Yet,prevalent EF evaluations presume that a river reach's hydraulic conditions are exclusively governed by inflow discharge,presupposing a state of equilibrium in the river channel.This presumption narrows the scope of EF evaluations in expansive alluvial rivers like the Middle Yangtze River(MYR),characterized by marked channel alterations.Here we show the profound channel erosion process and its impact on EF requirements for riparian habitats within the MYR.Our research unveils that:(i)pronounced erosion has led to a mean reduction of 1.0-2.7 m in the riverbed across four sub-reaches of the MYR;(ii)notwithstanding a 37-107%increase in minimal discharges post the Three Gorges Project,the lowest river stages at some hydrometric stations diminished owing to bed erosion,signifying a notable transformation in MYR's hydraulic dynamics;(iii)a discernible rightward shift in the correlation curve between the weighted useable area and discharge from 2002 to 2020 in a specific sub-reach of the MYR,instigated by alterations in hydraulic conditions,necessitated an increase of 1500e2600 m^(3)s^(-1)in the required EF for the sub-reach;(iv)it is deduced that macroinvertebrate biomass rapidly decreases as the flow entrains the riverbed substrate,with the maximum survivable velocity for macroinvertebrates being contingent on their entrainment threshold.These findings highlight the importance of incorporating channel morphological changes in devising conservation strategies for the MYR ecosystem.展开更多
Anticancer drugs (ADs) have been detected in the environment and represent a risk to aquatic organisms, necessitating AD removal in drinking water and wastewater treatment. In this study, ozonation of the most commonl...Anticancer drugs (ADs) have been detected in the environment and represent a risk to aquatic organisms, necessitating AD removal in drinking water and wastewater treatment. In this study, ozonation of the most commonly used antimetabolite ADs, namely 5-fluorouracil (5-FU) and its prodrug capecitabine (CAP), was investigated to determine reaction kinetics, oxidation mechanisms, and residual toxicity. The specific second-order rate constants between aqueous ozone and 5-FU, 5-FU^-, 5-FU^2-, CAP, and CAP^- were determined to be 7.07(±0.11)×10^4 M^-1·s^-1,1.36(±0.06)×10^6 M^-1·s^-1,2.62(±0.17)×10^7M^-1·s^-1,9.69(±0.08)×10^3M^-1·s^-1,and 4.28(±0.07)×10^5M^-1·s^-1, respectively;furthermore, the second-order rate constants for *OH reaction with 5-FU and CAP at pH 7 were determined to be 1.85(±0.20)×10^9 M^-1·s^-1 and 9.95(±0.26)×10^9M^-1·s^-1, respectively. Density functional theory was used to predict the main ozone reaction sites of 5-FU (olefin) and CAP (olefin and deprotonated secondary amine), and these mechanisms were supported by the identified transformation products. Carboxylic acids constituted a majority of the residual organic matter for 5-FU ozonation;however, carboxylic acids and aldehydes were important components of the residual organic matter generated by CAP. Ozone removed the toxicity of 5-FU to Vibriofischeri, but the residual toxicity of ozonated CAP solutions exhibited an initial increase before subsequent removal. Ultimately, these results suggest that ozone is a suitable technology for treatment of 5-FU and CAP, although the residual toxicity of transformation products must be carefully considered.展开更多
Previous studies on the relationship between polar motion and water mass change have mainly concentrated on the excitation of polar motion via global terrestrial water storage changes(TWSC). In view of the uneven dist...Previous studies on the relationship between polar motion and water mass change have mainly concentrated on the excitation of polar motion via global terrestrial water storage changes(TWSC). In view of the uneven distribution of global terrestrial water storage, the relationship between regional water mass change and polar motion needs to be further explored owing to the lack of documented results. In addition, given the uncertainty in the estimation of TWSC, it is required to develop appropriate indices to describe water mass change from different perspectives. The Amazon River basin(referred to Amazon hereafter), containing the world's largest river, located at around the 90°W longitude, is selected as the study area. Water vapor flux, precipitation, runoff and TWSC are selected as the indices of water mass changes to reveal the relationship between polar motion and water mass change in this giant basin. The Mann-Kendall(M-K) method, the accumulated anomaly analysis method and the curvature method are used to identify the abrupt change points; the least squares method is used to estimate the trends,and the Fast Fourier Transform(FFT) and the Ensemble Empirical Mode Decomposition(EEMD) are used to perform a periodic analysis, for all the above indices. It is shown that, of all the indices from 1948 to 2011, water vapor flux is the most closely related index to polar motion. In detail, precipitation and water vapor flux contain beat periods of polar motion; water vapor flux,precipitation and polar motion have a common M-K test abrupt change point(occurring in ca. 1968) at the 0.05 significance level; water vapor flux has a similar accumulated anomaly curve with that of polar motion; and water vapor flux is more highly correlated with polar motion than most other indexes. It is found, just like global TWSC, the χ2 component of the excitation via water vapor flux and water storage change in the Amazon follows that of observed polar motion; χ1 does not follow. However, the pattern in the Amazon that the χ2 component of the excitation by water follows that of observed polar motion is at a more significant level than in global. Finally, the new index termed Location of Vapor-based Inter Tropical Convergence Zone(LVITCZ) we proposed to describe the annual mean latitudinal location of water mass change shows a more close and visual relationship between water mass change and polar motion than other chosen indices do.展开更多
The Yellow River Estuary(YRE)alternatively experienced channel aggradation and degradation during the period 1990-2016.To study the variation in flood discharge capacity during the process of river bed evolution,bankf...The Yellow River Estuary(YRE)alternatively experienced channel aggradation and degradation during the period 1990-2016.To study the variation in flood discharge capacity during the process of river bed evolution,bankfull characteristic parameters were investigated on the basis of measured hydrological data and surveyed cross-sectional profiles,which was crucial for comprehending the processes and the key factors to cause these rapid changes.A reach-averaged method was presented in this study in order to calculate the characteristic bankfull parameters in the YRE,and this method integrated the geometric mean using the logarithmic transformation with a weighted mean based on the distance between the two successive sections.The reach-averaged bankfull parameters in the tail reach of the Yellow River Estuary(the Lijin-Xihekou reach)during the period 1990-2016 were then calculated.Calculated results indicated that the adoption of a concept of reach-averaged bankfull discharge was much more representative than the cross-sectional bankfull discharge,and the results also indicated that bankfull discharges decreased during the process of channel aggradation,and increased during the process of channel degradation.Finally,an empirical formula and a delayed response function were established between the reach-averaged bankfull discharge and the previous 4-year average fluvial erosion intensity during flood seasons,and both of them were adopted to reproduce the reach-averaged bankfull discharges,and calculated results showed high correlations(R^(2)>0.8)of these two methods.展开更多
Changes in the elements of the Earth system are closely related.Finding the key factors linked with hydrological changes is significant for in-depth analysis of hydrological changes.This study chooses polar motion,whi...Changes in the elements of the Earth system are closely related.Finding the key factors linked with hydrological changes is significant for in-depth analysis of hydrological changes.This study chooses polar motion,which is the movement of the Earth’s rotational axis relative to its crust,as a key factor in the investigation of the physical processes of its interaction with several hydrological elements.First,the statistical relationships between polar motion and multi-hydrological elements(i.e.,precipitation,evaporation,runoff,and terrestrial water storage)are investigated,using trend analysis,mutation analysis,cycle analysis,and correlation analysis methods,from basinal to global and from intra-annual to inter-annual scales.Second,their interactions are explored.The study quantifies the effect of hydrological changes on polar motion using the excitation function.It explores the effect of polar motion on hydrological changes based on the theory of equilibrium tides and atmospheric dynamics.The results show that they are significantly correlated and abruptly changed at a similar time.First,regional to global hydrological changes can significantly excite polar motion.From April 2002 to June 2020,the global terrestrial water storage decreased significantly(by approximately−4.68 mm yr^(−1)),which significantly drove polar motion towards the direction of the Greenwich Meridian(by approximately 4.32 mas yr^(−1)).Changes in regional terrestrial water storage also contributed significantly to directional changes in polar motion around 2005 and 2012.Second,polar motion can perturb the Earth’s centrifugal force system and generate equilibrium tides,and thus further cause changes in sea-level pressure,wind,and water vapor transport.Results show that polar motion-induced water vapor flux divergences correlate significantly with actual precipitation and terrestrial water storage changes in the Yangtze River and the Pearl River basins.Their correlations are also significant when trends are removed,and the polar motion-induced changes are 4 to 14 months earlier.This study further demonstrates the relationship between polar motion and hydrological changes and helps to understand the related factors of hydrological changes in other Earth systems.展开更多
基金Supported by the Science and Technology Research Program of Chongqing Municipal Education Commission(Grant No.KJQN202204305,and No.KJQN202305501).
文摘The utilization of waste concrete as a raw material for recycled concrete in the domain of prefabricated components is garnering greater interest.This paper delineates and examines the concept,categorization,methodologies of preparation,applicable sectors,and evaluative metrics of recycled concrete technology,highlighting its prospective benefits.Nonetheless,for the successful integration of recycled concrete technology into prefabricated component applications,it is imperative to systematically enhance its physical,mechanical,and attributes,as well as its environmental efficacy.Moreover,to foster the continued advancement of recycled concrete technology,innovative initiatives,standardization,educational programs,demonstration projects,and collaborative efforts are crucial to promote broader adoption and realize improved outcomes within the realm of prefabricated components.In conclusion,recycled concrete technology is poised to play a pivotal role in prefabricated construction,offering robust support for propelling the construction industry towards a sustainable future.
文摘We previously found that monocyte locomotion inhibitory factor has a neuroprotective effect on ischemic brain injury during the acute phase of stro ke.Therefore,we modified the structure of an anti-inflammato ry monocyte locomotion inhibitory factor peptide to construct an active cyclic peptide—Cyclo(MQCNS)(LZ-3)—and investigated its effects on ischemic stroke.In this study,we established a rat model of ischemic stroke by occluding the middle cerebral artery and then administered LZ-3(2 or 4 mg/kg) via the tail vein for 7 consecutive days.Our res ults showed that LZ-3(2 or 4 mg/kg) substantially decreased infarct volu m e,reduced co rtical ne rve cell death,improved neurological function,reduced cortical and hippocampal injury,and decreased the levels of inflammatory factors in the blood and brain tissues.In a well-diffe rentiated,oxygen-glucose deprivation/reoxygenation-induced BV2 cell model of poststroke,LZ-3(100 μM) inhibited the JAK1-STAT6 signaling pathway.LZ-3 regulated microglia/macrophage polarization from the M1 to the M2 type and inhibited microglia/macrophage phagocytosis and migration via the JAK1/STAT6 signaling pathway.To conclude,LZ-3 regulates microglial activation by inhibiting the JAK1/STAT6 sign aling pathway and improves functional recovery post-stroke.
基金This work is supported by the National Natural Science Foundation of China(Grant Nos.52101233,51931007,and 52071279)the Hebei Natural Science Foundation(No.E2022203010)the Innovation Capability Improvement Project of Hebei Province(No.22567605H).
文摘The enhancement of near-field radiative heat transfer(NFRHT)has now become one of the research hotspots in the fieldsof thermal management and imaging due to its ability to improve the performance of near-field thermoelectric devices and near-field imaging systems.In this paper,we design three structures(multilayer structure,nanoporous structure,and nanorod structure)based on high-entropy alloys to realize the enhancement of NFRHT.By combining stochastic electrodynamicsand Maxwell-Garnett's description of the effective medium,we calculate the radiative heat transfer under different parametersand find that the nanoporousstructure has the largest enhancement effect on NFRHT.The near-field heat transfer factor(q)of this structure(q=1.40×10^(9)W/(m^(2)·K))is three times higher than that of the planestructure(q=4.6×10^(8)W/(m^(2)·K)),and about two orders of magnitude higher than that of the SiO2plate.Thisresult providesa freshidea for the enhancement of NFRHT and will promote the application of high-entropy alloy materials in near-field heat radiation.
基金supported by the National Natural Science Foundation of China (Grant Nos. U2040215 & 52379079)。
文摘Meandering rivers of various scales are found globally and exhibit a high degree of regularity in their evolutionary processes. This study utilized remote sensing interpretation techniques to extract and analyze the planform migration characteristics of meandering rivers. Specifically, remote sensing images of three meandering rivers—the Black and White Rivers in the Tibetan Plateau and the Itui River in the Amazon Basin—were selected for this analysis. By comparing these observations with existing research data, this study quantitatively revealed the lag response patterns in the planform migration processes of meandering rivers. The findings of the study revealed several key insights.(1) The average migration rates for the three rivers were determined to be 1.74, 3.84, and 2.34 m/a, respectively. The critical values of the relative curvature radius for the river channels ranged from 1.5 to 2.0, 1.7 to 2.2, and 2.5 to 3.0, where local migration rate peaks were observed. These findings align with previous research that reported critical values between 2.0 and 4.0.(2) A significant lag is observed in the migration rate relative to curvature in spatial variation, with lag distances for the Black, White, and Itui Rivers measuring 227, 281, and 324 m,corresponding to 2.02, 2.39, and 3.15 times the river width, respectively.(3) A comparison with other meandering rivers indicates that, despite significant variations in climatic and hydrological conditions and river discharges differing by over 1,000times, the ratio of lag distance to river width(relative lag distance) for meandering rivers consistently falls within the range of 2.0to 4.0. This study suggests that the establishment of critical values for the relative curvature radius and the concentration of the relative lag distance reflects distinct quantitative relationships that emerge during the evolutionary processes of meandering rivers, aiming to minimize energy expenditure. These relationships appear to be applicable to various types of alluvial rivers.
基金supported by the National Natural Science Foundation of China(Grant Nos.U2040215,51725902,U2240206,52379079)was partly supported by the Natural Science Foundation of Hubei Province(2021CFA029)+1 种基金the Special Project on Knowledge Innovation of Wuhan Science and Technology Bureau(2022020801020132)the Fundamental Research Funds for the Central Universities(2042023kf0160).
文摘Evaluating environmental flow(EF)is pivotal for conserving and restoring riverine ecosystems.Yet,prevalent EF evaluations presume that a river reach's hydraulic conditions are exclusively governed by inflow discharge,presupposing a state of equilibrium in the river channel.This presumption narrows the scope of EF evaluations in expansive alluvial rivers like the Middle Yangtze River(MYR),characterized by marked channel alterations.Here we show the profound channel erosion process and its impact on EF requirements for riparian habitats within the MYR.Our research unveils that:(i)pronounced erosion has led to a mean reduction of 1.0-2.7 m in the riverbed across four sub-reaches of the MYR;(ii)notwithstanding a 37-107%increase in minimal discharges post the Three Gorges Project,the lowest river stages at some hydrometric stations diminished owing to bed erosion,signifying a notable transformation in MYR's hydraulic dynamics;(iii)a discernible rightward shift in the correlation curve between the weighted useable area and discharge from 2002 to 2020 in a specific sub-reach of the MYR,instigated by alterations in hydraulic conditions,necessitated an increase of 1500e2600 m^(3)s^(-1)in the required EF for the sub-reach;(iv)it is deduced that macroinvertebrate biomass rapidly decreases as the flow entrains the riverbed substrate,with the maximum survivable velocity for macroinvertebrates being contingent on their entrainment threshold.These findings highlight the importance of incorporating channel morphological changes in devising conservation strategies for the MYR ecosystem.
文摘Anticancer drugs (ADs) have been detected in the environment and represent a risk to aquatic organisms, necessitating AD removal in drinking water and wastewater treatment. In this study, ozonation of the most commonly used antimetabolite ADs, namely 5-fluorouracil (5-FU) and its prodrug capecitabine (CAP), was investigated to determine reaction kinetics, oxidation mechanisms, and residual toxicity. The specific second-order rate constants between aqueous ozone and 5-FU, 5-FU^-, 5-FU^2-, CAP, and CAP^- were determined to be 7.07(±0.11)×10^4 M^-1·s^-1,1.36(±0.06)×10^6 M^-1·s^-1,2.62(±0.17)×10^7M^-1·s^-1,9.69(±0.08)×10^3M^-1·s^-1,and 4.28(±0.07)×10^5M^-1·s^-1, respectively;furthermore, the second-order rate constants for *OH reaction with 5-FU and CAP at pH 7 were determined to be 1.85(±0.20)×10^9 M^-1·s^-1 and 9.95(±0.26)×10^9M^-1·s^-1, respectively. Density functional theory was used to predict the main ozone reaction sites of 5-FU (olefin) and CAP (olefin and deprotonated secondary amine), and these mechanisms were supported by the identified transformation products. Carboxylic acids constituted a majority of the residual organic matter for 5-FU ozonation;however, carboxylic acids and aldehydes were important components of the residual organic matter generated by CAP. Ozone removed the toxicity of 5-FU to Vibriofischeri, but the residual toxicity of ozonated CAP solutions exhibited an initial increase before subsequent removal. Ultimately, these results suggest that ozone is a suitable technology for treatment of 5-FU and CAP, although the residual toxicity of transformation products must be carefully considered.
基金supported by the National Program on Key Basic Research Project (Grant No. 2012CB957802)National Key Research and Development Program of China project (Grant No. 2017YFA0603702)
文摘Previous studies on the relationship between polar motion and water mass change have mainly concentrated on the excitation of polar motion via global terrestrial water storage changes(TWSC). In view of the uneven distribution of global terrestrial water storage, the relationship between regional water mass change and polar motion needs to be further explored owing to the lack of documented results. In addition, given the uncertainty in the estimation of TWSC, it is required to develop appropriate indices to describe water mass change from different perspectives. The Amazon River basin(referred to Amazon hereafter), containing the world's largest river, located at around the 90°W longitude, is selected as the study area. Water vapor flux, precipitation, runoff and TWSC are selected as the indices of water mass changes to reveal the relationship between polar motion and water mass change in this giant basin. The Mann-Kendall(M-K) method, the accumulated anomaly analysis method and the curvature method are used to identify the abrupt change points; the least squares method is used to estimate the trends,and the Fast Fourier Transform(FFT) and the Ensemble Empirical Mode Decomposition(EEMD) are used to perform a periodic analysis, for all the above indices. It is shown that, of all the indices from 1948 to 2011, water vapor flux is the most closely related index to polar motion. In detail, precipitation and water vapor flux contain beat periods of polar motion; water vapor flux,precipitation and polar motion have a common M-K test abrupt change point(occurring in ca. 1968) at the 0.05 significance level; water vapor flux has a similar accumulated anomaly curve with that of polar motion; and water vapor flux is more highly correlated with polar motion than most other indexes. It is found, just like global TWSC, the χ2 component of the excitation via water vapor flux and water storage change in the Amazon follows that of observed polar motion; χ1 does not follow. However, the pattern in the Amazon that the χ2 component of the excitation by water follows that of observed polar motion is at a more significant level than in global. Finally, the new index termed Location of Vapor-based Inter Tropical Convergence Zone(LVITCZ) we proposed to describe the annual mean latitudinal location of water mass change shows a more close and visual relationship between water mass change and polar motion than other chosen indices do.
基金supported by the Program of the National Key Research and Development Plan(No.2017YFC0405501)supported partly by the National Natural Science Foundation of China(Grant Nos.51725902,51579186,51809196).
文摘The Yellow River Estuary(YRE)alternatively experienced channel aggradation and degradation during the period 1990-2016.To study the variation in flood discharge capacity during the process of river bed evolution,bankfull characteristic parameters were investigated on the basis of measured hydrological data and surveyed cross-sectional profiles,which was crucial for comprehending the processes and the key factors to cause these rapid changes.A reach-averaged method was presented in this study in order to calculate the characteristic bankfull parameters in the YRE,and this method integrated the geometric mean using the logarithmic transformation with a weighted mean based on the distance between the two successive sections.The reach-averaged bankfull parameters in the tail reach of the Yellow River Estuary(the Lijin-Xihekou reach)during the period 1990-2016 were then calculated.Calculated results indicated that the adoption of a concept of reach-averaged bankfull discharge was much more representative than the cross-sectional bankfull discharge,and the results also indicated that bankfull discharges decreased during the process of channel aggradation,and increased during the process of channel degradation.Finally,an empirical formula and a delayed response function were established between the reach-averaged bankfull discharge and the previous 4-year average fluvial erosion intensity during flood seasons,and both of them were adopted to reproduce the reach-averaged bankfull discharges,and calculated results showed high correlations(R^(2)>0.8)of these two methods.
基金supported by the National Key Research and Development Program of China (Grant No. 2018YFE0106500 & 2017YFA0603702)the National Program on Key Basic Research Project of China (Grant No. 2012CB957802)+1 种基金the Danida Fellowship Centre EOFor China project (Grant No. 18-M01-DTU)the China Water Sense project (Grant No. 8087-00002B)
文摘Changes in the elements of the Earth system are closely related.Finding the key factors linked with hydrological changes is significant for in-depth analysis of hydrological changes.This study chooses polar motion,which is the movement of the Earth’s rotational axis relative to its crust,as a key factor in the investigation of the physical processes of its interaction with several hydrological elements.First,the statistical relationships between polar motion and multi-hydrological elements(i.e.,precipitation,evaporation,runoff,and terrestrial water storage)are investigated,using trend analysis,mutation analysis,cycle analysis,and correlation analysis methods,from basinal to global and from intra-annual to inter-annual scales.Second,their interactions are explored.The study quantifies the effect of hydrological changes on polar motion using the excitation function.It explores the effect of polar motion on hydrological changes based on the theory of equilibrium tides and atmospheric dynamics.The results show that they are significantly correlated and abruptly changed at a similar time.First,regional to global hydrological changes can significantly excite polar motion.From April 2002 to June 2020,the global terrestrial water storage decreased significantly(by approximately−4.68 mm yr^(−1)),which significantly drove polar motion towards the direction of the Greenwich Meridian(by approximately 4.32 mas yr^(−1)).Changes in regional terrestrial water storage also contributed significantly to directional changes in polar motion around 2005 and 2012.Second,polar motion can perturb the Earth’s centrifugal force system and generate equilibrium tides,and thus further cause changes in sea-level pressure,wind,and water vapor transport.Results show that polar motion-induced water vapor flux divergences correlate significantly with actual precipitation and terrestrial water storage changes in the Yangtze River and the Pearl River basins.Their correlations are also significant when trends are removed,and the polar motion-induced changes are 4 to 14 months earlier.This study further demonstrates the relationship between polar motion and hydrological changes and helps to understand the related factors of hydrological changes in other Earth systems.
