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The Impact of Soil Freezing/Thawing Processes on Water and Energy Balances
A frozen soil parameterization coupling of thermal and hydrological processes is used to investigate how frozen soil processes affect water and energy balances in seasonal frozen soil. Simulation results of soil liquid water content and temperature using soil model with and without the inclusion of freezing and thawing processes are evaluated against observations at the Rosemount field station. By comparing the simulated water and heat fluxes of the two cases, the role of phase change processes in the water and energy balances is analyzed. Soil freezing induces upward water flow towards the freezing front and increases soil water content in the upper soil layer. In particular. soil ice obviously prevents and delays the infiltration during rain at Rosemount. In addition, soil freezing/thawing processes alter the partitioning of surface energy fluxes and lead the soil to release more sensible heat into the atmosphere during freezing periods....
2020-07-08 21:52:19浏览：68
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Multi-Objective Optimization of A Semisubmersible for Ultra-Deep Water
Semisubmersible will work well when oil exploitation goes to ultra-deep water because of its variable load capacities, and good motion performance in extreme waves. It is considered to be a main type of platform while the water depth is more than 3000 meters. This paper establishes a multi-objective optimization model of semisubmersible for ultra-deep water, and it is solved by a multi-objective genetic algorithm-NSGA-II. The model is applied to a practical design, and Pareto results are obtained. The effectiveness of the method is verified by hydrodynamic analysis....
2020-07-08 21:52:19浏览：51
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Formation and transport of intermediate water masses in a model of the Pacific Ocean
A basin-wide ocean general circulation model of the Pacific Ocean was used to investigate how the interior restoration in the Okhotsk Sea and the isopycnal diffusion affect the circulation and intermediate water masses. Four numerical experiments were conducted, including a run with the same isopycnal and thick-ness diffusivity of 1.0×103 m2/s, a run employing the interior restoration of temperature and salinity in the Okhotsk Sea with a time scale of 3 months, a run that is the same as the first run except for the enhanced isopycnal mixing, and a final run with the combination of the restoration in the Okhotsk Sea and large iso-pycnal diffusivity. Simulated results show that the intermediate water masses reproduced in the first run are relatively weak. An increase in isopycnal diffusivity can improve the simulation of both Antarctic and North Pacific intermediate waters, mainly increasing the transport in the interior ocean, but inhibiting the outflow from the Okhotsk Sea. The interior restoration generates the reverse current from the observation in the Ok-hotsk Sea, whereas the simulation of the temperature and salinity is improved in the high latitude region of the Northern Hemisphere because of the reasonable source of the North Pacific Intermediate Water. A com-parison of vertical profiles of temperature and salinity along 50°N between the simulation and observations demonstrates that the vertical mixing in the source region of intermediate water masses is very important....
2020-07-08 21:52:19浏览：29
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Water and Energy Conservation of Rainwater Harvesting System in the Loess Plateau of China
Water is the source of all the creatures on the earth and energy is the main factor driving the world. With the increasing population and global change, water and energy conservation have become worldwide focal issues, particularly in the water-stressed and energy-limited regions. Rainwater harvesting, based on the collection and storage of rainfall runoff, has been widely used for domestic use and agricultural production in arid and semiarid regions. It has advantages of simple operation, high adaption, low cost and less energy consumption. This study reviewed rainwater harvesting systems adopted in the Loess Plateau of China and analyzed water use efficiency (WUE) for various rainwater harvesting techniques. Supplemental irrigation using harvested rainwater could increase crop yield by more than 30%, and WUE ranged from 0.7 to 5.7 kg m-3 for spring wheat, corn and flax, and 30-40 kg m-3 for vegetables. Moreover, energy consumption for rainwater harvesting based on single family was compared with traditional water supply in the city of the Loess Plateau using the life cycle assessment (LCA) method. Results showed that energy consumption yielded per unit harvested rainwater was 25.96 MJ m-3 yr-1 which was much less than 62.25 MJ m-3 yr-1 for main water supply in Baoji City, Shanxi Province, meaning that rainwater harvesting saved energy by 139.8%as compared to the main water supply system. This study highlights the importance and potential of rainwater harvesting for water and energy conservation in the near future....
2020-07-08 21:52:19浏览：54
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Integrity of Local Ecosystems and Storm Water Management in Residential Areas
The authors designed an ecological storm water system in a residential area to replace the conventional underground channels for the collection of storm water so as to reduce the nutrients and sediments discharged. This system contains natural sub-creeks as drainage channels discharging overflow to nearby creeks, an open green trench, a storage pond,and natural sub-creeks. The sub-creeks were designed to be integrated into community landscape, which not only increases the efficiency of water usage, but also improves the aesthetic qualities of the community residence area as required by Agenda 21. This research proved the feasibility of an open storm water collection and utilization system for the design of a community water system....
2020-07-08 21:52:19浏览：63
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Application of Element-Free Method to water quality analysis of Miyun reservoir
This paper presents a 3D mathematical model for transfer and transform of water contaminants in reservoir, describes the discrete methods and the compute process of using an element-free collocation method. By these models and methods, the water quality conditions of Miyun reservoir area, the quantified description of three dimensions concerning the distribution and change of diversified contaminants are obtained within the assigned time. The distributions of total nitrogen and total phosphorus of the reservoir area in 2003, 2004 and 2005 are simulated and forecasted by the boundary conditions in 2003, so the main development trend is shown. It is found through calculation that: The contribution of the bed mud with regard to total phosphorus is comparatively marked. On the whole, the influence factor of the bed mud in the reservoir area and other comprehensive factors to total phosphorus are quite great. The influence of the living things or other function in the surface water of the Chaohe River valley in the east of the reservoir on the total phosphorus is comparatively conspicuous. Within the reservoir area in spring, summer and autumn, the concentration distribution of total nitrogen is basically in the trend of a slow progressive decrease, but the concentration of total phosphorus increases progressively. It is just contrary in autumn, winter and spring, the concentration of total nitrogen increases and the concentration of total phosphorus decreases. On the whole of the year's development, the total nitrogen is basically in a steady state, and the total phosphorus is in the increasing trend with years, but the kind of the trend is not conspicuous....
2020-07-08 21:52:19浏览：47
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Mechanism analysis of landslide of a layered slope induced by drawdown of water level
The frequent drawdown of water level of Yangtze River will greatly influence the stability of the widely existing slopes in the Three Gorges reservoir zone, especially those layered ones. Apart from the fluctuating speed of water level, the different geological materials will also play important roles in the failure of slopes. Thus, it must be first to study the mechanism of such a landslide caused by drawdown of water level.A new experimental setup is designed to study the performance of a layered slope under the drawdown of water level. The pattern of landslide of a layered slope induced by drawdown of water level has been explored by means of simulating experiments. The influence of fluctuating speed of water level on the stability of the layered slope is probed,especially the whole process of deformation and development of landslide of the slope versus time. The experimental results show that the slope is stable during the water level rising, and the sliding body occurs in the upper layer of the slope under a certain drawdown speed of water level. In the process of slope failure, some new small sliding body will develop on the main sliding body, and the result is that they speed up the disassembly of the whole slope.Based on the simulating experiment on landslide of a layered slope induced by drawdown of water level, the stress and displacement field of the slope are calculated.The seepage velocity, the pore water pressure, and the gradient of pore water head are also calculated for the whole process of drawdown of water level. The computing results are in good agreement with the experimental results. Accordingly, the mechanism of deformation and landslide of the layered slope induced by drawdown of water level is analyzed. It may provide basis for treating this kind of layered slopes in practical engineering....
2020-07-08 21:52:19浏览：66
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Density Functional Theory Study of Water Diffusion and Clustering on Pd(111)
The internal structures as well as adsorption and hopping energies of monomers,dimers, trimers, tetramers, pentamers and hexamers of water on Pd(111) have been studied by density functional theory (DFT) plane-wave pseudopotential method which performs the firstprinciples quantum-mechanical calculations to explore the properties of crystals and surfaces in materials. Based on the calculations, we suppose that their absorption is via one water molecule for monomers, dimmers and trimers, but three water molecules for pentamers and hexamers. Moreover,there is one water molecule bonding with Pd atom by O atom in pentamers and hexamers, which explains why pentamers and hexamers are stable. The binding energies of polymers may be used to explain why the trimer comes close to two nearby monomers to form a stable pentamer instead of tetramer. And the difference of mobility of small water clusters is due to their different hopping energies....
2020-07-08 21:52:19浏览：51
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Cropping Pattern Modifications Change Water Resource Demands in the Beijing Metropolitan Area
Adequate freshwater supply has become an issue of increasing local and international concern.Reducing water use in agriculture,which is the largest water using sector of the economy,is both important and urgent.The aim of this paper was to quantify how recent cropping pattern changes have influenced water resources in the great Beijing metropolitan area,an expanding megacity which also includes rural counties.Crop production affects blue water use through water consumption and water pollution,the latter assessed here using a critical dilution method.From 1990 to 2010,the total blue water used by crop production declined due to a decrease in overall cropped area,initially in response to local government policies favouring urban development.However,the average blue water use per hectare increased from 2 112 m3 ha-1 yr-1 in 1990 to 2 764 m3 ha-1 yr-1 in 2003,largely as the result of a transition from cereal to vegetable crops,and in particular an increase in intensively managed plastic and glass covered vegetable production systems.Current policies aim to conserve agricultural land,in the interests of food security,and to stimulate cereal production systems with higher ecosystem services provision.As such,in 2010 the average blue water use was 2 425 m3 ha-1 yr-1.These results demonstrate that cropping pattern changes in peri-urban regions and rural communities surrounding the Beijing metropolitan area can have a substantial impact on water resources.They also highlight the tradeoffs between food production and urban and industrial water supply and the need for integrated policy development....
2020-07-08 21:52:19浏览：58
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Gas chromatographic thermodynamics on hydration processes of magnesium chloride with low water
The dehydration and hydration processes of magnesium chloride hydrates were studied by means of frontal chromatography analysis, calorimetry, thermogravimetry and chemical analysis. The mathematical imitation for the adsorption isotherms of MgCl2*4H2O and MgCl2*2H2O at different temperatures indicates that Boltzmann Function is the ideal equation to describe those adsorption isotherms. Its adsorption heat is -13.06kJ/mol and -16.11kJ/mol, respectively. The adsorption equilibrium constants are also given. From the data obtained, there is a thermodynamical possibility to use partial dehydrated magnesium chloride hydrates as an absorbance to clean water vapor contained in bischophite dehydration equipment and let the protection gas HCl recycle in the fluid bed reaction system....
2020-07-08 21:52:19浏览：64
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Decay of Solutions to a Linear Viscous Asymptotic Model for Water Waves
The authors discuss a linear viscous asymptotic model for water waves and the decay rate of solutions towards the equilibrium....
2020-07-08 21:52:19浏览：38
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Applications of Water Sensitivity In Situ Remediation at Saltwater-Freshwater Interface
Based on the laboratory experiments with the saltwater and freshwater replacing each other in the level sand column, taking the kaolin, illite, smectite, bivalent hydrargyrum ion (Hg2+) and phenol (C6H5OH) as exam-ples, this paper studies the applications of water sensitivity in situ remediation in saltwater-freshwater transition zone. In the water sensitivity process, the release and migration of clay minerals can make the hydraulic conductiv-ity (HC) decrease and pollutants remove. A new type of low penetrable or impenetrable purdah can be built by adding clay minerals into the sand media to replace the underground concrete impenetrable wall to prevent seawater intrusion, and a number of the heavy metals and organic pollutants in the sand media can be removed by in situ remediation. The results show that the content of kaolin and illite influences the water sensitivity process slightly, and HC of the sand columns descends from 0.011 cm/s to 0.001 4 cm/s and 0.001 2 cm/s respectively even if the content reaches 12% (weight ratio, sic passim). However, for smectite, HC descends sharply to about 1×10-8 cm/s when its content reaches 4%, and no water can flow through the sand columns beyond 5%. The particle release and migration processes can remove the Hg2+ and C6H5OH out of the sand columns efficiently, the removing rate of Hg2+ is 31.68% when the freshwater and saltwater are filtered through the sand columns polluted by Hg2+, while it is 67.55% when the water sensitivity occurs. With the same method, the removing rates of C6H5OH under the fluid flow and water sensitivity are 55.71% and 43.43% respectively....
2020-07-08 21:52:19浏览：35
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STUDY ON THE EROSION RATE OF POWDERED ACTIVATED CARBON IN RAW WATER AQUEDUCT
Growing interest in using Powdered Activated Carbon (PAC) in raw water aqueduct,as a method of polluted surface water treatment,raises the question of transport of PAC in the aqueduct,which is related to the potential PAC erosion along the aqueduct.By means of a recently developed re-circulating flume,erosion rates of PAC with the grain size of 230 meshes (less than 62 μm)depending on shear stress and bulk density were the discussed with real-time measurement of suspended PAC conccntration.Lateral cross sectional averaging shear stress was decided by the actual value in the raw water conveying aqueduct of upstream Huangpu River,Shanghai,China,smaller than 1.8 N·m 2.As for the bulk density,it was measured with compacting times varying from 1 d to 15 d,equivalent to 1 550 kg/m3-1 800 kg/m3.Experiments were conducted for the shear stress and bulk density separately,so as to isolate and quantify the effects of one of the parameters.The results demonstrate that,for a particular PAC particle,the erosion rate increases with shear stress and decreases with bulk density as a function of power form.A product of powers of the lateral cross sectional averaging shear stress and bulk density to estimate PAC erosion rate is presented by approximating experimental data sets....
2020-07-08 21:52:19浏览：41
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Removal of NO and SO2 in Corona Discharge Plasma Reactor with Water Film
In this paper, a novel type of a corona discharge plasma reactor was designed, which consists of needle-plate-combined electrodes, in which a series of needle electrodes are placed in a glass container filled with flue gas, and a plate electrode is immersed in the water. Based on this model, the removal of NO and SO2 was tested experimentally. In addition, the effect of streamer polarity on the reduction of SO2 and NO was investigated in detail. The experimental results show that the corona wind formed between the high-voltage needle electrode and the water by corona discharge enhances the cleaning efficiency of the flue gas because of the presence of water,and the cleaning efficiency will increase with the increase of applied dc voltage within a definite range. The removal efficiency of SO2 up to 98%, and about 85% of NOx removal under suitable conditions is obtained in our experiments....
2020-07-08 21:52:19浏览：56
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Logistic Regression for Prediction and Diagnosis of Bacterial Regrowth in Water Distribution System
This paper focuses on the quantitative expression of bacterial regrowth in water distribution system. Considering public health risks of bacterial regrowth, the experiment was performed on a distribution system of selected area. Physical, chemical, and microbiological parameters such as turbidity, temperature, residual chlorine and pH were measured over a three-month period and correlation analysis was carried out. Combined with principal components analysis(PCA), a logistic regression model is developed to predict and diagnose bacterial regrowth and locate the zones with high risks of microbiology in the distribution system. The model gives the probability of bacterial regrowth with the number of heterotrophic plate counts as the binary response variable and three new prin-cipal components variables as the explanatory variables. The veracity of the logistic regression model was 90%, which meets the precision requirement of the model....
2020-07-08 08:49:41浏览：62
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