Dissipative particle dynamics simulation of wettability alternation phenomena in the chemical flooding process

Wettability alternation phenomena is considered one of the most important enhanced oil recovery (EOR) mechanisms in the chemical flooding process and induced by the adsorption of surfactant on the rock surface. These phenomena are studied by a mesoscopic method named as dissipative particle dynamics (DPD). Both the alteration phenomena of water-wet to oil-wet and that of oil-wet to water-wet are simulated based on reasonable definition of interaction parameters between beads. The wetting hysteresis phenomenon and the process of oil-drops detachment from rock surfaces with different wettability are simulated by adding long-range external forces on the fluid particles. The simulation results show that, the oil drop is liable to spread on the oil-wetting surface and move in the form of liquid film flow, whereas it is likely to move as a whole on the water-wetting surface. There are the same phenomena occuring in wettability-alternated cases. The results also show that DPD method provides a feasible approach to the problems of seepage flow with physicochemical phenomena and can be used to study the mechanism of EOR of chemical flooding.

Interaction of linear waves with an array of infinitely long horizontal circular cylinders in a two-layer fluid of infinite depth

The linear water wave scattering and radiation by an array of infinitely long horizontal circular cylinders in a two-layer fluid of infinite depth is investigated by use of the multipole expansion method. The diffracted and radiated potentials are expressed as a linear combination of infinite multipoles placed at the centre of each cylinder with unknown coefficients to be determined by the cylinder boundary conditions. Analytical expressions for wave forces, hydrodynamic coefficients, reflection and transmission coefficients and energies are derived. Comparisons are made between the present analytical results and those obtained by the boundary element method, and some examples are presented to illustrate the hydrodynamic behavior of multiple horizontal circular cylinders in a two-layer fluid. It is found that for two submerged circular cylinders the influence of the fluid density ratio on internal-mode wave forces is more appreciable than surface-mode wave forces, and the periodic oscillations of hydrodynamic results occur with the increase of the distance between two cylinders; for four submerged circular cylinders the influence of adding two cylinders on the wave forces of the former cylinders is small in low and high wave frequencies, but the influence is appreciable in intermediate wave frequencies.

Interaction of linear waves with infinitely long horizontal cylinders studied by boundary element method

The two-dimensional problems concerning the interaction of linear water waves with cylinders of arbitrary shape in two-layer deep water are investigated by use of the Boundary Integral Equation method (BIEM). Simpler new expressions for the Green functions are derived, and verified by comparison of results obtained by BIEM with these by an analytical method. Examined are the radiation and scattering of linear waves by two typical configurations of cylinders in two-layer deep water. Hydrodynamic behaviors including hydrodynamic coefficients, wave forces, reflection and transmission coefficients and energies are analyzed in detail, and some interesting physical phenomena are observed.

Study on Water Resources Regulation and Reservoir Operating Prediction for Suppression of Salt Water Intrusion in the Pearl River Estuary

Salt water intrusion occurred frequently during dry season in Modaomen waterway of the Pearl River Estuary. With the development of region's economy and urbanization, the salt tides affect the region's water supply more and more seriously in recent years. Regulation and allocation of freshwater resources of the upper rivers of the estuary to suppress the salt tides is becoming important measures for ensuring the water supply security of the region in dry season. The observation data analysis showed that the flow value at the Wuzhou hydrometric station on the upper Xijiang river had a good correlation with the salinity in Modaomen estuary. Thus the flow rate of Wuzhou has been used as a control variable for suppression of salt tides in Modaomen estuary. However, the runoff at Wuzhou mainly comes from the discharge of Longtan reservoir on the upper reaches of Xijiang river and the runoff in the interval open valley between Longtan and Wuzhou sections. As the long distance and many tributaries as well as the large non-controlled watershed between this two sections, the reservoir water scheduling has a need for reasonable considering of interaction between the reservoir regulating discharge and the runoff process of the interval open watershed while the deployment of suppression flow at Wuzhou requires longer lasting time and high precision for the salt tide cycles. For this purpose, this study established a runoff model for Longtan - Wuzhou interval drainage area and by model calculations and observation data analysis, helped to understand the response patterns of the flow rate at Wuzhou to the water discharge of Longtan under the interval water basin runoff participating conditions. On this basis, further discussions were taken on prediction methods of Longtan reservoir discharge scheduling scheme for saline intrusion suppression and provided scientific and typical implementation programs for effective suppression flow process at the Wuzhou section.

Emergy Assessment of a Wheat-Maize Rotation System with Different Water Assignments in the North China Plain

Sustainable water use is seriously compromised in the North China Plain (NCP) due to the huge water requirements of agriculture, the largest use of water resources. An integrated approach which combines the ecosystem model with emergy analysis is presented to determine the optimum quantity of irrigation for sustainable development in irrigated cropping systems. Since the traditional emergy method pays little attention to the dynamic interaction among components of the ecological system and dynamic emergy accounting is in its infancy, it is hard to evaluate the cropping system in hypothetical situations or in response to specific changes. In order to solve this problem, an ecosystem model (Vegetation Interface Processes (VIP) model) is introduced for emergy analysis to describe the production processes. Some raw data, collected by investigating or observing in conventional emergy analysis, may be calculated by the VIP model in the new approach. To demonstrate the advantage of this new approach, we use it to assess the wheat-maize rotation cropping system at different irrigation levels and derive the optimum quantity of irrigation according to the index of ecosystem sustainable development in NCP. The results show, the optimum quantity of irrigation in this region should be 240-330 mm per year in the wheat system and no irrigation in the maize system, because with this quantity of irrigation the rotation crop system reveals: best efficiency in energy transformation (transformity = 6.05E + 4 sej/J); highest sustainability (renewability = 25%); lowest environmental impact (environmental loading ratio = 3.5) and the greatest sustainability index (Emergy Sustainability Index = 0.47) compared with the system in other irrigation amounts. This study demonstrates that application of the new approach is broader than the conventional emergy analysis and the new approach is helpful in optimizing resources allocation, resource-savings and maintaining agricultural sustainability.

Spontaneous volume transition of polyampholyte nanocomposite hydrogels based on pure electrostatic interaction

A circular system is employed in this paper to investigate the swelling behaviors of polyampholyte hydrogels; this circular system can effectively eliminate the disturbance of various factors and keep the surrounding environment constant. It is found that there exists a spontaneous volume transition to the collapsed state of polyampholyte hydrogels, which is attributed to the overshooting effect, and the transition can occur repeatedly under certain conditions. C-13 NMR is employed to investigate the swelling behavior of polyampholyte hydrogels.

A Simple Method for Preparing Carbon Nanotubes/Clay Hybrids in Water

A simple novel method for preparing multiwalled carbon nanotubes/montmorillonite (MWNTs/MMT) hybrids has been established through mixing pristine MWNTs in MMT aqueous dispersion. The principle of this method is based on the formation of stable dispersion containing both MWNTs and MMT in water, which results from strong interaction between MWNTs and MMT platelets. Sedimentation experiments, measurements of potential, and Raman spectra have been used to confirm the presence of strong interaction between MWNTs and MMT sheets. The morphology observation for the dried MWNTs/MMT hybrids shows that the obtained hybrids are homogeneous, in which MWNTs exist as the state of single nanotubes that are absorbed on the surface and edge of MMT sheets.

Water-resistant conducting hybrids from electrostatic interactions

Conductive hybrids were prepared in a water/ethanol solution via the Solgel process from an inorganic sol containing carboxyl groups and water-borne conductive polyaniline (cPANI). The inorganic sol was prepared by the hydrolysis and condensation of methyltriethoxysilane with the condensed product of maleic anhydride and aminopropyltriethoxysilane as a catalyst, for which the carboxyl counterion along the cPANI backbone acted as an electrostatic-interaction moiety. The existence of this electrostatic interaction could improve the compatibility of the two components and contribute to the homogeneous dispersion of cPANI in the silica phase. The electrostaticinteraction hybrids displayed a conductivity percolation threshold as low as 1.1 wt % polyaniline in an emeraldine base, showing 2 orders of magnitude higher electrical conductivity than that without electrostatic interactions. The electrostatic-interaction hybrids also showed good water resistance; the electrical conductivity with a cPANI loading of 16 wt % underwent a slight change after 14 days of soaking in water.

Extending electrochemical activity of polyaniline to alkaline media via electrostatic interaction and sol-gel route

The electroactivity of polyaniline was extended to pH = 14 alkaline media by preparation of a novel electrostatic interaction conductive hybrid from water-borne conductive polyaniline and silica network containing carboxyl groups via sol-gel process. In addition, the obtained conductive polyaniline hybrid film displayed very low conductivity threshold percolation and demonstrated excellent stability upon cycling.

The structural transition of DNA-Tris(1,10-phenanthroline) cobalt(III) complexes in ethanol-water solution

The interaction of DNA with Tris(1,10-phenanthroline) cobalt(III) was studied by means of atomic force microscopy. Changes in the morphologies of DNA complex in the presence of ethanol may well indicate the crucial role of electrostatic force in causing DNA condensation. With the increase of the concentration of ethanol, electrostatic interaction is enhanced corresponding to a lower dielectric constant. Counterions condense along the sugar phosphate backbone of DNA when e is lowered and the phosphate charge density can thus be neutralized to the level of DNA condensation. Electroanalytical measurement of DNA condensed with Co(phen)(3)(3+) in ethanol solution indicated that intercalating reaction remains existing. According to both the microscopic and spectroscopic results, it can be found that no secondary structure transition occurs upon DNA condensing. B-A conformation transition takes place at more than 60% ethanol solution.

Gas and water vapor transport through a series of novel poly(aryl ether sulfone) membranes

The permeation behavior of water vapor, H-2, CO2, O-2, N-2, and CH4 gases in a series of novel poly(aryl ether sulfone)s has been examined over a temperature range of 30-100 degreesC. These polymers include four alkyl-substituted cardo poly(aryl ether sulfone)s and four intermolecular interaction enhanced poly(aryl ether sulfone)s. Their water vapor and gas transport properties were compared to the unmodified cardo poly(aryl ether sulfone) (PES-C). It was found that the bulky alkyl substituents on the phenylene rings were advantageous for gas permeability, while the intermolecular hydrogen bonds and ionic bonds resulted in a considerable increase in gas permselectivity. The causes of the trend were interpreted according to free volume, interchain distance, and glass transition temperature, together with the respective contribution of gas solubility and diffusivity to the overall permeability. Of interest was the observation that IMPES-L, which simultaneously bears bulky isopropyl substituent and pendant carboxylic groups, displayed 377% higher O-2 permeability and 5.3% higher O-2/N-2 permselectivity than PES-C. Furthermore, sodium salt form PES-Na+ and potassium salt form PES-K+ exhibited water vapor permeability twice as high as PES-C and H2O/N-2 selectivity in 10(5) order of magnitude.

Mixed-layer water oscillations in tropical Pacific for ENSO cycle

The main modes of interannal variabilities of thermocline and sea surface wind stress in the tropical Pacific and their interactions are investigated, which show the following results. (1) The thermocline anomalies in the tropical Pacific have a zonal dipole pattern with 160 W as its axis and a meridional seesaw pattern with 6-8 degrees N as its transverse axis. The meridional oscillation has a phase lag of about 90 to the zonal oscillation, both oscillations get together to form the El Nino/La Nina cycle, which behaves as a mixed layer water oscillates anticlockwise within the tropical Pacific basin between equator and 12 degrees N. (2) There are two main patterns of wind stress anomalies in the tropical Pacific, of which the first component caused by trade wind anomaly is characterized by the zonal wind stress anomalies and its corresponding divergences field in the equatorial Pacific, and the abnormal cross- equatorial flow wind stress and its corresponding divergence field, which has a sign opposite to that of the equatorial region, in the off-equator of the tropical North Pacific, and the second component represents the wind stress anomalies and corresponding divergences caused by the ITCZ anomaly. (3) The trade winds anomaly plays a decisive role in the strength and phase transition of the ENSO cycle, which results in the sea level tilting, provides an initial potential energy to the mixed layer water oscillation, and causes the opposite thermocline displacement between the west side and east side of the equator and also between the equator and 12 degrees N of the North Pacific basin, therefore determines the amplitude and route for ENSO cycle. The ITCZ anomaly has some effects on the phase transition. (4) The thermal anomaly of the tropical western Pacific causes the wind stress anomaly and extends eastward along the equator accompanied with the mixed layer water oscillation in the equatorial Pacific, which causes the trade winds anomaly and produces the anomalous wind stress and the corresponding divergence in favor to conduce the oscillation, which in turn intensifies the oscillation. The coupled system of ocean-atmosphere interactions and the inertia gravity of the mixed layer water oscillation provide together a phase-switching mechanism and interannual memory for the ENSO cycle. In conclusion, the ENSO cycle essentially is an inertial oscillation of the mixed layer water induced by both the trade winds anomaly and the coupled ocean-atmosphere interaction in the tropical Pacific basin between the equator and 12 degrees N. When the force produced by the coupled ocean-atmosphere interaction is larger than or equal to the resistance caused by the mixed layer water oscillation, the oscillation will be stronger or maintain as it is, while when the force is less than the resistance, the oscillation will be weaker, even break.

小湾电站坝基岩体卸荷工程地质力学研究

Dam is the key main works in the construction of water power. The success or failure of the construction of the dam mainly depends on the stability of the dam foundation. The double curvature arch dam-XiaoWan Dam is the highest one among the dams with the same type in the world, and the water thrust acted on it reaches ton, so the rock bearing capacity of dam foundation becomes more important. Because of the high and steep valley-side slope, the large scale of excavation and the complex body type of excavation, it is prominent that the problem of stress release of the rock mass in dam foundation. More great attentions should be paid for the stability and the degraded of rock properties of rock mass induced by the stress release. In this paper, the phenomena of stress release of rock mass in XiaoWan Dam foundation and its mechanisms were analyzed based on the collection of data, the detailed field engineering investigations, measurement of the rock mass and the 2D numerical calculations. The rock mass under the foundation is weak-weathered to intact, the quality of which is good. After excavation of the foundation, the rock mass near the slope surface occurred extend, stretch and stick-slip along original textures till the new fracture surface formed. Then platy structure of the rock mass takes on. The rock mass in the dam foundation occur resilience due to stress release towards free faces with the characteristics of time effect and localized deformation. In-situ measurements show that the rock mass near the surface are degraded. The stress release induced by excavation is a process of the interaction between engineering structures and geologic body. The stress release of rock mass in dam foundation is related to the changed degree of geometrical conditions. The rock near excavation surface failed nearly under uniaxial stresses. The bending-breaking mechanism of plate girder can interpret the failure model of the rock mass with platy structure in dam foundation slope. In essence, the stress release is the change of stress field including the change of directions and magnitudes of stress induced by excavation, which can induce the comedown of the safety margin. In this paper, the inducing conditions of stress release were calculated by numerical analyses. Moreover, from the point of view that the change of stress field, the coefficient of K, i.e. the variable load coefficient was proposed. Then the law of the change of it is interpreted. The distributional characteristics of fracture zone were expressed by the coefficient. The stress release of hard rock has the characteristic of localization. The measuring technique of sound wave can not reflect the small cracks in this kind of rock mass due to stress release. So, the spectral analysis method was proposed. At the same time, the application foreground in engineering of the Stockwell Time-Frequency- Spectrum method was discussed with a view to the limitation of it.

降雨条件下碎石土滑坡稳定性研究

Debris Landslide is one of the types of landslides with the widest distribution, largest quantity, and the closest relationship with engineering construction. It is also one of the most important types of landslides that can cause disaster. This kind of landslide often occurs in the loose slopes which are made up of loose congeries formed by earth filling, residual soil, slope wash, dilapidation, landslide or full weathered material of hard rock. Rainfall is always the chief inducing factor of debris Landslide. Therefore, to research stability of debris Landslide during rainfall not only has important theoretical significance for understanding developing law and deformation and failure mechanism of debris landslide, but also has important practical significance for investigating, appraising, forecasting, preventing and controlling debris landslides. This thesis systematically summarized the relationships between rainfall and landslide, the method to survey water table in the landslides, the deformation and failure mechanism of debris landslide, and the progress in the stability analysis of landslides based on the analyses of data collected widely at home and abroad. The problems in the study of the stability of debris landslide during rainfall was reviewed and discussed. Due to the complicated geological conditions and the random rainfall conditions, the research on the landslides' stability must be based on engineering geological qualitative analysis. Through the collection of the data about the Panxi region and the Three Gorges Reservoir region, the author systematically summarized the engineering geological conditions, hydro-geological condition, distribution characteristics of stress field in the slope, physical and mechanical properties and hydro-mechanical properties of debris. In the viewpoint of dynamics of soil water and hydromechanics, physical process of rainfall to supply groundwater of debris landslides can be divided into two phases, i.e. non-saturated steady infiltrating phase and saturated unsteady supplying phase. The former can be described by mathematical model of surface water infiltration while the latter can be described by equivalent continuous medium model of groundwater seepage. With regard to specific hydrological geology system, we can obtain the dynamic variation law of water content, water table, landslide stability of rock and soil mass, along with quantity and duration of rainfall after the boundary condition on hydrological geology has been ascertained. This is a new way to study the response law of groundwater in the landslides during rainfall. After wet face of rock and soil mass connects with ground water table, the raising of water table will occur due to the supply of rainfall. Then interaction between ground water and rock and soil mass will occur, such as the action of physics, water, chemistry and mechanics, which caused the decrease of shearing strength of sliding zone. According to the action of groundwater on rock and soil mass, a concise mechanical model of debris landslide’s deformation was established during rainfall. The static equilibrium condition of landslide mass system was achieved according to the concise mechanical model, and then the typical deformation and failure process and failure mode of debris landslide during rainfall were discussed. In this thesis, the former limiting equilibrium slice method was modified and improved based on shearing strength theory of , a stability analysis program of debris landslide was established and developed taking account of the saturated-unsaturated seepage, by introducing the shearing strength theory of unsaturated soil mass made by (1978). The program has reasonable data storage and simple interface and is easy to operate, and can be perfectly used to carry out sensitivity analysis of influencing factors of landslides' stability, integrated with the program of Office Excel. The design of drainage engineering are always bases on empirical methods and is short of effective quantitative analysis and appraise, therefore, the conception of critical water table of debris landslide was put forward. For debris landslides with different kinds of slide face in the engineering practice, a program to search the critical water table of debris landslide was developed based on native groundwater table. And groundwater table in the slope should be declined below the critical water table in the drainage works, so the program can be directly used to guide drainage works in the debris landslide. Taking the slope deformation body in the back of former factory building of Muli Shawan hydroelectric power station as an example, a systematic and detailed research on debris landslides' stability during rainfall was researched systematically, the relationship among quantity of rainfall, water table and stability of slope was established, the debris landslides' stability in process of rainfall from dynamic viewpoint was analyzed and researched.

内蒙古克什克腾旗小东沟斑岩型钼矿床的成矿作用

In this paper, the Xiaodonggou porphyry molybdenum deposit located in the Xarmoron molybdenum metallogenic belt is chose as the research area. We have analyzed the petrology of the Xiaodonggou pluton in detail and made chemical analysis of the major and trace elements, Rb-Sr and Sm-Nd isotope, common lead isotope and SHRIMP zircon U-Pb dating et al; in the other hand, we use the molybdenite to make common lead analysis and Re-Os isotopic dating. The Xiaodonggou pluton is rich in silicon, potass, zirconium, and low in REE. In addition, it has no minus Eu abnormity and show a isotopic composition high in εNd(t) and low in Sri, indicating its magma origining from the melting of juvenile thicken lower crust. In the meanwhile, it contained the features of high temperature, quick melting, quick segregation and quick emplacement. The common lead analysis of the pluton orthoclase and molybdenite show that the former transfer from orogen to mantle and the latter come from mantle, which is consistent to the molybdenite sulfur isotopic and quartz oxygen isotopic composition, demonstrating that the rock and ore-forming materials of deposit having different sources, magma from the lower crust mixing with mantle fluid. In plus, we use the physical experiments results of the water-magma reaction to explain the interaction of magma and mantle fluid. In the deep crust, these two systems uplifted in a immiscible state; when they reached low depth, the stream film between fluid-magma collapsed, and the magma was broken into small agglomerates by the fluid, then they mixed thoroughly. The SHRIMP zircon U-Pb dating gave a result of 142±2Ma and the molybdenite Re-Os dating result is 138.1±2.8Ma, corresponding to the big tectonic transition period of 140Ma, when the major stress field changing from south and north to west and east. At this time, the Da Hinggan ling ranges area was under an extensive background, underplating proceeded and mantle materials could add into the magmas forming in the lower crust. So, from the above analysis, we propose the following model for the Xiaodonggou porphyry molybdenum deposit: in the early Cretaceous period, the Da Hinggan ling ranges area was under a extensive background, the adding of mantle fluid containing ore materials into heated lower crust made it melting to produce magmas. Following more mantle fluid got into the magma room and urged the magma to segregate from the source quickly. The fluid and magma uplifted together, when they arrived at shallow depth, the fluid-magma became unstable and the latter was broken into many small agglomerates with fluid connecting them in the interspaces. Because of the H+, K+ and various elements existing in the fluid, it would reacted with the magma and the rock through alteration and ore minerals crystallized out, forming the Xiaodonggou porphyry deposit with disseminated mineralization phenomenon.