One of the water source areas of the South-to-North Water Diversion Project is the Danjiangkou Reservoir （DJKR）. To understand seasonal variation in phytoplankton composition, abundance and distribution in the DJKR ...One of the water source areas of the South-to-North Water Diversion Project is the Danjiangkou Reservoir （DJKR）. To understand seasonal variation in phytoplankton composition, abundance and distribution in the DJKR area before water diversion, as well as to estimate potential risks of water quality after water diversion, we conducted an investigation on phytoplankton in the DJKR from August 2008 to May 2009. The investigation included 10 sampling sites, each with four depths of 0.5, 5, 10, and 20 m. In this study, 117 taxa belonging to 76 genera were identified, consisting of diatoms （39 taxa）, green algae （47 taxa）, blue-green algae （19 taxa）, and others （12 taxa）. Annual average phytoplankton abundance was 2.01×10^6 ind./L, and the highest value was 14.72 ×10^6 ind/L （at site 3 in August 2008）. Phytoplankton abundance in front of the Danjiangkou Dam （DJKD） was higher than that of the Danjiang Reservoir Basin. Phytoplankton distribution showed a vertical declining trend from 0.5 m to 20 m at most sites in August 2008 （especially at sites of 1, 2, 4 and 10）, but no distinct pattern in other sampling months. In December 2008 and March 2009, Stephanodiseus sp. was the most abundant species, amounting to 55.23% and 72.34%, respectively. We propose that high abundance ofStephanodiscus sp. may have contributed greatly to the frequent occurrence of Stephanodiscus sp. blooms in middle-low reaches of the Hanjiang River during the early spring of 2009. In comparison with previous studies conducted from 1992 to 2006, annual average phytoplankton density, green algae and blue-green algae species, as well as major nutrient concentrations increased, while phytoplankton diversity indices declined. This indicates a gradual decline in water quality. More research should be conducted and countermeasures taken to prevent further deterioration of water quality in the DJKR.展开更多
This article deals with the design of energy efficient water utilization systems allowing operation split. Practical features such as operating flexibility and capital cost have made the number of sub operations an im...This article deals with the design of energy efficient water utilization systems allowing operation split. Practical features such as operating flexibility and capital cost have made the number of sub operations an important parameter of the problem. By treating the direct and indirect heat transfers separately, target freshwater and energy consumption as well as the operation split conditions are first obtained. Subsequently, a mixed integer non-linear programming （MINLP） model is established for the design of water network and the heat exchanger network （HEN）. The proposed systematic approach is limited to a single contaminant. Example from literature is used to illustrate the applicability of the approach.展开更多
In this work,we studied the electronic band structure of the halogen(F,Cl,and Br)functionalized graphdiynes(GDYs)by using hybrid density functional theory.The results revealed that the bandgap energies of modified GDY...In this work,we studied the electronic band structure of the halogen(F,Cl,and Br)functionalized graphdiynes(GDYs)by using hybrid density functional theory.The results revealed that the bandgap energies of modified GDYs increase as the number of halogen atoms increases.It is also found that the position of the valence band maximum(VBM)is influenced by the electronegativity of halogen atoms.The higher the electronegativity,the deeper the VBM of the GDYs modified by the same number of halogen atoms.Importantly,our results revealed that the bandgap of GDY could be effectively tuned by mixing types of halogen atoms.The new generated conduction band and valence band edges are properly aligned with the oxidation and reduction potentials of water.Further thermodynamic analysis confirms that some models with mixing types of halogen atoms exhibit higher performance of overall photocatalytic water splitting than non-mixing models.This work provides useful insights for designing efficient photocatalysts that can be used for overall water splitting.展开更多
The fluid flow and oil-water separation were simulated using a Reynolds stress transport equation model of turbulence in water flow and a stochastic model of oil droplet motion. Simulation results give the axial and t...The fluid flow and oil-water separation were simulated using a Reynolds stress transport equation model of turbulence in water flow and a stochastic model of oil droplet motion. Simulation results give the axial and tangential velocity components, the pressure and turbulence intensity distribution and droplet trajectories for a hydrocyclone of F type and a hydrocyclone proposed by the present authors. The flow field predictions are in qualitative agreement with the LDV measurements. The results show that the proposed hydrocyclone has better performance than the hydrocyclone of F type due to creating stronger centrifugal force and lower axial velocity.展开更多
The harmonic analysis method based on high and low water levels is discussed in this paper. In order to make full use of the information of high and low water observations (the time derivative of water level at the ob...The harmonic analysis method based on high and low water levels is discussed in this paper. In order to make full use of the information of high and low water observations (the time derivative of water level at the observation time is zero), the weight coefficient, w, is introduced to control the importance of the part related to this information in the error formula. The major diurnal constituents, O 1 and K 1, and semi diurnal constituents, N 2, M 2 and S 2 are selected directly from the monthly data analysis, and some other important constituents, P 1, ν 2 and K 2, are included as the inferred constituents. The obtained harmonic constants of the major constituents are very close to those obtained from the analysis of hourly data, and this shows that high and low water data can be used to extract tidal constants with high accuracy. The analysis result also shows that the inference and the weighting coefficient are important in the high and low water data analysis, and it is suggested that w ≥1 should be taken in monthly high and low water data analysis. This analysis method can be used directly to analyze altimetric data with w =0.展开更多
According to the measured data after impoundment and operation of the Three Gorges Reservoir,the reservoir sediment deposition and downstream river channel scouring are described briefly and compared with the research...According to the measured data after impoundment and operation of the Three Gorges Reservoir,the reservoir sediment deposition and downstream river channel scouring are described briefly and compared with the research results achieved in the demonstration stage.It is indicated through analysis that the reservoir sediment deposition and downstream river channel scouring during 8-year impoundment and operation are still within the original forecast,so the original forecasting results are feasible.The further observation and comparison should be conducted because the comparison between the observed data and the original forecast is not so sufficient in time and the prototype observation and related research work should be strengthened in the future.展开更多
Floods are both risks and resources. Floodwater utilization is an important part of flood management. Considering the rising shortage of water resources, serious water pollution, and undersupply of electric power, it...Floods are both risks and resources. Floodwater utilization is an important part of flood management. Considering the rising shortage of water resources, serious water pollution, and undersupply of electric power, it’s imperative to strengthen flood management. In light of the hydrological characteristics of the Three Gorges Project (TGP) on the Yangtze River in P. R. China, we investigated the necessity and feasibility of TGP floodwater utilization, proprosed dynamic control of limited water level during flood season of the reservoir and basin-wide integrated floodwater management as strategies, and identified problems that might occur in practice.展开更多
A homeowner reported extensive settlement damage approximately two weeks after the groundwater in the vicinity of the home was lowered at a nearby construction project. The infrastructure improvement project consisted...A homeowner reported extensive settlement damage approximately two weeks after the groundwater in the vicinity of the home was lowered at a nearby construction project. The infrastructure improvement project consisted of installing a 27-inch-diameter sanitary sewer main with an invert elevation about 19 ft below existing grade. Groundwater was lowered 12 ft during construction, down to a depth of 23 ft below existing grade. This paper addresses the following key questions regarding settlement and potential structural damage as a result of a temporary drop in groundwater caused by construction dewatering： （1） How could a decrease in groundwater elevation cause settlement？ （2） Is this a highly unusual or atypical phenomenon that cannot be explained or estimated using science and engineering techniques available to the engineering profession？ （3） Based on the standard of care at the time, should these problems have been anticipated, or at least examined, by the engineering firms engaged on this project？ Answers to these questions are addressed herein using results from geotechnical analyses and data obtained from laboratory and in-situ tests.展开更多
基金Supported by the National Basic Research Program of China (973 Program) (No. 2008CB418006)the Knowledge Innovation Program of Chinese Academy of Sciences (No. KZCX-YW-14-1)
文摘One of the water source areas of the South-to-North Water Diversion Project is the Danjiangkou Reservoir （DJKR）. To understand seasonal variation in phytoplankton composition, abundance and distribution in the DJKR area before water diversion, as well as to estimate potential risks of water quality after water diversion, we conducted an investigation on phytoplankton in the DJKR from August 2008 to May 2009. The investigation included 10 sampling sites, each with four depths of 0.5, 5, 10, and 20 m. In this study, 117 taxa belonging to 76 genera were identified, consisting of diatoms （39 taxa）, green algae （47 taxa）, blue-green algae （19 taxa）, and others （12 taxa）. Annual average phytoplankton abundance was 2.01×10^6 ind./L, and the highest value was 14.72 ×10^6 ind/L （at site 3 in August 2008）. Phytoplankton abundance in front of the Danjiangkou Dam （DJKD） was higher than that of the Danjiang Reservoir Basin. Phytoplankton distribution showed a vertical declining trend from 0.5 m to 20 m at most sites in August 2008 （especially at sites of 1, 2, 4 and 10）, but no distinct pattern in other sampling months. In December 2008 and March 2009, Stephanodiseus sp. was the most abundant species, amounting to 55.23% and 72.34%, respectively. We propose that high abundance ofStephanodiscus sp. may have contributed greatly to the frequent occurrence of Stephanodiscus sp. blooms in middle-low reaches of the Hanjiang River during the early spring of 2009. In comparison with previous studies conducted from 1992 to 2006, annual average phytoplankton density, green algae and blue-green algae species, as well as major nutrient concentrations increased, while phytoplankton diversity indices declined. This indicates a gradual decline in water quality. More research should be conducted and countermeasures taken to prevent further deterioration of water quality in the DJKR.
基金Supported by the Major Project of National Natural Science Foundation of China （No.20409205） and National High Technology Research and Development Program of China （No.G20070040）.
文摘This article deals with the design of energy efficient water utilization systems allowing operation split. Practical features such as operating flexibility and capital cost have made the number of sub operations an important parameter of the problem. By treating the direct and indirect heat transfers separately, target freshwater and energy consumption as well as the operation split conditions are first obtained. Subsequently, a mixed integer non-linear programming （MINLP） model is established for the design of water network and the heat exchanger network （HEN）. The proposed systematic approach is limited to a single contaminant. Example from literature is used to illustrate the applicability of the approach.
基金funded by the National Natural Science Foundation of China(No.21973013 and No.21673040)the Natural Science Foundation of Fujian Province of China(No.2020J02025)“Chuying Program”for the Top Young Talents of Fujian Province。
文摘In this work,we studied the electronic band structure of the halogen(F,Cl,and Br)functionalized graphdiynes(GDYs)by using hybrid density functional theory.The results revealed that the bandgap energies of modified GDYs increase as the number of halogen atoms increases.It is also found that the position of the valence band maximum(VBM)is influenced by the electronegativity of halogen atoms.The higher the electronegativity,the deeper the VBM of the GDYs modified by the same number of halogen atoms.Importantly,our results revealed that the bandgap of GDY could be effectively tuned by mixing types of halogen atoms.The new generated conduction band and valence band edges are properly aligned with the oxidation and reduction potentials of water.Further thermodynamic analysis confirms that some models with mixing types of halogen atoms exhibit higher performance of overall photocatalytic water splitting than non-mixing models.This work provides useful insights for designing efficient photocatalysts that can be used for overall water splitting.
基金Supported by the Special Funds for Major State Basic Research (No. 1999-0222-08).
文摘The fluid flow and oil-water separation were simulated using a Reynolds stress transport equation model of turbulence in water flow and a stochastic model of oil droplet motion. Simulation results give the axial and tangential velocity components, the pressure and turbulence intensity distribution and droplet trajectories for a hydrocyclone of F type and a hydrocyclone proposed by the present authors. The flow field predictions are in qualitative agreement with the LDV measurements. The results show that the proposed hydrocyclone has better performance than the hydrocyclone of F type due to creating stronger centrifugal force and lower axial velocity.
基金supported by the project of NSFC(No.49906001)the Excellent Young Teacher Award Foundation of State Education Ministry[2000](No.6).
文摘The harmonic analysis method based on high and low water levels is discussed in this paper. In order to make full use of the information of high and low water observations (the time derivative of water level at the observation time is zero), the weight coefficient, w, is introduced to control the importance of the part related to this information in the error formula. The major diurnal constituents, O 1 and K 1, and semi diurnal constituents, N 2, M 2 and S 2 are selected directly from the monthly data analysis, and some other important constituents, P 1, ν 2 and K 2, are included as the inferred constituents. The obtained harmonic constants of the major constituents are very close to those obtained from the analysis of hourly data, and this shows that high and low water data can be used to extract tidal constants with high accuracy. The analysis result also shows that the inference and the weighting coefficient are important in the high and low water data analysis, and it is suggested that w ≥1 should be taken in monthly high and low water data analysis. This analysis method can be used directly to analyze altimetric data with w =0.
基金support from the Technology Pillar Program during the"Eleventh Five-year Plan"Period (No.2006BAB05B02No.2006BAB05B03) are acknowledged
文摘According to the measured data after impoundment and operation of the Three Gorges Reservoir,the reservoir sediment deposition and downstream river channel scouring are described briefly and compared with the research results achieved in the demonstration stage.It is indicated through analysis that the reservoir sediment deposition and downstream river channel scouring during 8-year impoundment and operation are still within the original forecast,so the original forecasting results are feasible.The further observation and comparison should be conducted because the comparison between the observed data and the original forecast is not so sufficient in time and the prototype observation and related research work should be strengthened in the future.
基金Funded by National Key Technologies R&D Program (2008BAB29B09)Open Foundation of State Key Laboratory of Water Resources and Hydropower Engineering Science (2007C017)China Postdoctoral Science Foundation (20080440956)
文摘Floods are both risks and resources. Floodwater utilization is an important part of flood management. Considering the rising shortage of water resources, serious water pollution, and undersupply of electric power, it’s imperative to strengthen flood management. In light of the hydrological characteristics of the Three Gorges Project (TGP) on the Yangtze River in P. R. China, we investigated the necessity and feasibility of TGP floodwater utilization, proprosed dynamic control of limited water level during flood season of the reservoir and basin-wide integrated floodwater management as strategies, and identified problems that might occur in practice.
文摘A homeowner reported extensive settlement damage approximately two weeks after the groundwater in the vicinity of the home was lowered at a nearby construction project. The infrastructure improvement project consisted of installing a 27-inch-diameter sanitary sewer main with an invert elevation about 19 ft below existing grade. Groundwater was lowered 12 ft during construction, down to a depth of 23 ft below existing grade. This paper addresses the following key questions regarding settlement and potential structural damage as a result of a temporary drop in groundwater caused by construction dewatering： （1） How could a decrease in groundwater elevation cause settlement？ （2） Is this a highly unusual or atypical phenomenon that cannot be explained or estimated using science and engineering techniques available to the engineering profession？ （3） Based on the standard of care at the time, should these problems have been anticipated, or at least examined, by the engineering firms engaged on this project？ Answers to these questions are addressed herein using results from geotechnical analyses and data obtained from laboratory and in-situ tests.
