Two simplifled and stabilized mixed element formats for the Stokes problem are derived by bubble function, and their convergence, i.e., error analysis, are proved. These formats can save more freedom degrees than othe...Two simplifled and stabilized mixed element formats for the Stokes problem are derived by bubble function, and their convergence, i.e., error analysis, are proved. These formats can save more freedom degrees than other usual formats.展开更多
Large underground caverns are commonly used in variety of applications. In many cases, because of the geomechanical limitations of dimensions and requirement of high volume, several parallel caverns are used. Plastic ...Large underground caverns are commonly used in variety of applications. In many cases, because of the geomechanical limitations of dimensions and requirement of high volume, several parallel caverns are used. Plastic zone integration requires a larger rock pillar distance of theses adjacent caverns while eco- nomic and access reasons require smaller distance. In lran many underground projects are located in West and South West, Asmari formation covers a large part of these regions. The stability of underground spaces that are constructed or will be constructed in this formation has been investigated. A proper cross section based on plastic analysis and a stability criterion has been proposed for each region. Finally, in each case, allowable rock pillar between adjacent caverns with similar dimension was determined with two methods （numerical analysis and fire service law）. Results show that Fire Service Law uses a very con- servative safety factor and it was proposed to use a correction factor for allowable distance based on application of underground space.展开更多
With the increasing number of detected exoplanet samples, the statistical properties of planetary systems have become much clearer. In this review, we sum- marize the major statistical results that have been revealed ...With the increasing number of detected exoplanet samples, the statistical properties of planetary systems have become much clearer. In this review, we sum- marize the major statistical results that have been revealed mainly by radial velocity and transiting observations, and try to interpret them within the scope of the classical core-accretion scenario of planet formation, especially in the formation of different orbital architectures for planetary systems around main sequence stars. Based on the different possible formation routes for different planet systems, we tentatively classify them into three major catalogs： hot Jupiter systems, standard systems and distant giant planet systems. The standard systems can be further categorized into three sub-types under different circumstances： solar-like systems, hot Super-Earth systems, and sub- giant planet systems. We also review the theory of planet detection and formation in binary systems as well as planets in star clusters.展开更多
In order to produce natural gas hydrate safely and efficiently,it is quite crucial to research the stability of hydrate reservoir in the process of its exploitation.The coupled thermal-hydrodynamic-mechanical(THM)nume...In order to produce natural gas hydrate safely and efficiently,it is quite crucial to research the stability of hydrate reservoir in the process of its exploitation.The coupled thermal-hydrodynamic-mechanical(THM)numerical simulation can clearly present the mechanical response laws in the process of hydrate exploitation by horizontal well,but the model is often simplified as a profile vertical to the production well,so the evolution characteristics of real formation deformation space cannot be described sufficiently.To this end,this paper develops a coupled THM simulator applicable to the large-scale hydrate exploitation by horizontal well by introducing interactive interface to the FLAC mechanics program based on the hydrate exploitation program TOUGHþHYDRATE.Then,based on the field data of second hydrate production test in South China Sea,the gas and water production and formation deformation laws under the middle-and long-term development conditions of horizontal wells are studied by taking the actual gas production of horizontal well during the production test as the constraint of coupled THM model.And the following research results are obtained.First,when the production pressure is 7 MPa and the horizontal well length is 300 m,the gas production of horizontal well can reach 1190×10^(4)m^(3),the pressure drop has a larger influence range in the free gas layer,the produced gas mainly comes from the free gas layer and the hydrate layer and the hydrate dissociation range is not large.Second,it is predicted that the seafloor settlement is about 0.16 m after 60 days'production test and 0.52 m after osne year's production.In conclusion,hydrate exploitation by horizontal well can cause a large range of seafloor settlement.The seafloor surface settles linearly and continuously and the spatial settlement distribute is in the shape of ellipse.What's more,the greatest deformation(vertical displacement)occurs at the horizontal well and above it,where formation damage happens the easiest.It is recommended to study seafloor deformation and landslip risk under the conditions of middle and long-term production based on seafloor topography,valley distribution and nonuniform spatial thickness of mineral ores.展开更多
The stability constants of the binary complexes of type PbB, PbB_2, and the mixed ligand complexes of type PbAB have been studied by potentiometric pH titration technique at ionic strength I=0.10 (KNO_3) and at temper...The stability constants of the binary complexes of type PbB, PbB_2, and the mixed ligand complexes of type PbAB have been studied by potentiometric pH titration technique at ionic strength I=0.10 (KNO_3) and at temperature 15, 25, 35 and 45℃ respectively, where A=2,2'-bipyridyl (bipy) or 1, 10-phenanthroline (phen); B=malonate (mal), succinate (suc), or anthranilate (anth). The equalibrium constants logK,~1 G, H, and S of the reaction PbA+PbB=PbAB+Pb^2+ have been calculated. The results show that the discriminating effects^2 between the primary ligand (bipy or phen) and the secondary ligand (real, suc or anth) in those non-transition metal mixed ligand complexes are also evident, and as a measurement of this effect, H is more appropriate than logK. The possible reasons which lead to these results have been discussed.展开更多
A density functional theory （DFT） study has been carried out for [Zn-1AI（OH2）n＋6（OH）2n-2]^3＋ （n=3-6） and [Znn-1AI（OH2）2n-2（OH）2n-2]^3＋ （n = 7） clusters, which include the basic structural information ...A density functional theory （DFT） study has been carried out for [Zn-1AI（OH2）n＋6（OH）2n-2]^3＋ （n=3-6） and [Znn-1AI（OH2）2n-2（OH）2n-2]^3＋ （n = 7） clusters, which include the basic structural information of the brucite-like lattice structure of Zn/Al layered double hydroxides （LDHs） with Zn/AI molar ratio （R） in the range 2-6, in order to understand the effect of the Zn/Al ratio on the structure and stability of binary Zn/Al LDHs. Based on systematic calculations of the geometric parameters and formation energies of the cluster models, it was found that it is possible for Zn^2＋ and Al^3＋ cations to replace Mg^2＋ isomorphously in the brucite-like structure with different R values, resulting in differences in microstructure of the clusters and unit cell parameter a of the Zn/Al LDHs. Analysis of the geometry and bonding around the trivalent Al^3＋ or divalent Zn^2＋ cations reveals that Al^3＋ plays a more significant role than Zn^2＋ in determining the microstructure properties, formation and bonding stability of the corresponding ZnRAl clusters when R〈5, while the influence of Zn^2＋ becomes the dominant factor in the case of R〉 5. These findings are in good agreement with experiments. This work provides a detailed electronic-level understanding of how the composition of cations affects the microstructure and stability of Zn-containing binary LDH layers.展开更多
A dynamic two-zone model is proposed to address the formation of granulation and drying zones in fluidized bed layering granulation processes with internal product classification. The model assumes a constant volume f...A dynamic two-zone model is proposed to address the formation of granulation and drying zones in fluidized bed layering granulation processes with internal product classification. The model assumes a constant volume for the granulation zone, but a variable overall volume for the fluidized bed to account for classified product removal. The model is used to study the effect of various process parameters on dynamics and process stability. Stability is shown to depend on the separation diameter of product removal and the flow rate of the injected liquid. A lower and upper range of separation diameters with stable process behavior are found. In an intermediate range instability in the form of self-sustained oscillations is observed. The lower stability boundary is in qualitative agreement with recent experimental observations （Schmidt, Bück, ＆ Tsotsas, 2015）; the upper boundary was reported in a theoretical paper by Vreman, Van Lare, and Hounslow （2009） based on a single zone model.展开更多
文摘Two simplifled and stabilized mixed element formats for the Stokes problem are derived by bubble function, and their convergence, i.e., error analysis, are proved. These formats can save more freedom degrees than other usual formats.
文摘Large underground caverns are commonly used in variety of applications. In many cases, because of the geomechanical limitations of dimensions and requirement of high volume, several parallel caverns are used. Plastic zone integration requires a larger rock pillar distance of theses adjacent caverns while eco- nomic and access reasons require smaller distance. In lran many underground projects are located in West and South West, Asmari formation covers a large part of these regions. The stability of underground spaces that are constructed or will be constructed in this formation has been investigated. A proper cross section based on plastic analysis and a stability criterion has been proposed for each region. Finally, in each case, allowable rock pillar between adjacent caverns with similar dimension was determined with two methods （numerical analysis and fire service law）. Results show that Fire Service Law uses a very con- servative safety factor and it was proposed to use a correction factor for allowable distance based on application of underground space.
基金supported by the National Natural Science Foundation of China (Nos. 10833001, 10925313, 11078001 and 11003010)Fundamental Research Funds for the Central Universities (No. 1112020102)the Research Fund for the Doctoral Program of Higher Education of China (Nos. 20090091110002 and 20090091120025)
文摘With the increasing number of detected exoplanet samples, the statistical properties of planetary systems have become much clearer. In this review, we sum- marize the major statistical results that have been revealed mainly by radial velocity and transiting observations, and try to interpret them within the scope of the classical core-accretion scenario of planet formation, especially in the formation of different orbital architectures for planetary systems around main sequence stars. Based on the different possible formation routes for different planet systems, we tentatively classify them into three major catalogs： hot Jupiter systems, standard systems and distant giant planet systems. The standard systems can be further categorized into three sub-types under different circumstances： solar-like systems, hot Super-Earth systems, and sub- giant planet systems. We also review the theory of planet detection and formation in binary systems as well as planets in star clusters.
基金Basic Foresight Research Project of Oil and GasDevelopment from Sinopec Ministry of Science and Technology:“Key technologies of drilling and completion and development of coring equipment for natural gas hydrate”(No.P20040-3)Sinopec Shengli Oilfield Post-doctoral Research Project:“Sand Production Dynamic Prediction and Technical Policy Boundaries in Natural Gas Hydrate Reservoir”(No.YKB2107)Youth Science Fund Project of National Natural Science Foundation of China:“Study on Non-Darcy Flow Characteristics of and Its Impact on Productivity in Low PermeabilityMuddy Silt Hydrate Reservoirs in South China Sea”(No.42102302).
文摘In order to produce natural gas hydrate safely and efficiently,it is quite crucial to research the stability of hydrate reservoir in the process of its exploitation.The coupled thermal-hydrodynamic-mechanical(THM)numerical simulation can clearly present the mechanical response laws in the process of hydrate exploitation by horizontal well,but the model is often simplified as a profile vertical to the production well,so the evolution characteristics of real formation deformation space cannot be described sufficiently.To this end,this paper develops a coupled THM simulator applicable to the large-scale hydrate exploitation by horizontal well by introducing interactive interface to the FLAC mechanics program based on the hydrate exploitation program TOUGHþHYDRATE.Then,based on the field data of second hydrate production test in South China Sea,the gas and water production and formation deformation laws under the middle-and long-term development conditions of horizontal wells are studied by taking the actual gas production of horizontal well during the production test as the constraint of coupled THM model.And the following research results are obtained.First,when the production pressure is 7 MPa and the horizontal well length is 300 m,the gas production of horizontal well can reach 1190×10^(4)m^(3),the pressure drop has a larger influence range in the free gas layer,the produced gas mainly comes from the free gas layer and the hydrate layer and the hydrate dissociation range is not large.Second,it is predicted that the seafloor settlement is about 0.16 m after 60 days'production test and 0.52 m after osne year's production.In conclusion,hydrate exploitation by horizontal well can cause a large range of seafloor settlement.The seafloor surface settles linearly and continuously and the spatial settlement distribute is in the shape of ellipse.What's more,the greatest deformation(vertical displacement)occurs at the horizontal well and above it,where formation damage happens the easiest.It is recommended to study seafloor deformation and landslip risk under the conditions of middle and long-term production based on seafloor topography,valley distribution and nonuniform spatial thickness of mineral ores.
文摘The stability constants of the binary complexes of type PbB, PbB_2, and the mixed ligand complexes of type PbAB have been studied by potentiometric pH titration technique at ionic strength I=0.10 (KNO_3) and at temperature 15, 25, 35 and 45℃ respectively, where A=2,2'-bipyridyl (bipy) or 1, 10-phenanthroline (phen); B=malonate (mal), succinate (suc), or anthranilate (anth). The equalibrium constants logK,~1 G, H, and S of the reaction PbA+PbB=PbAB+Pb^2+ have been calculated. The results show that the discriminating effects^2 between the primary ligand (bipy or phen) and the secondary ligand (real, suc or anth) in those non-transition metal mixed ligand complexes are also evident, and as a measurement of this effect, H is more appropriate than logK. The possible reasons which lead to these results have been discussed.
基金supported by the National Natural Science Foundation of China and the Program for Changjiang Scholars and Innovative Research Teams in Universities (Grant No.IRT0406)
文摘A density functional theory （DFT） study has been carried out for [Zn-1AI（OH2）n＋6（OH）2n-2]^3＋ （n=3-6） and [Znn-1AI（OH2）2n-2（OH）2n-2]^3＋ （n = 7） clusters, which include the basic structural information of the brucite-like lattice structure of Zn/Al layered double hydroxides （LDHs） with Zn/AI molar ratio （R） in the range 2-6, in order to understand the effect of the Zn/Al ratio on the structure and stability of binary Zn/Al LDHs. Based on systematic calculations of the geometric parameters and formation energies of the cluster models, it was found that it is possible for Zn^2＋ and Al^3＋ cations to replace Mg^2＋ isomorphously in the brucite-like structure with different R values, resulting in differences in microstructure of the clusters and unit cell parameter a of the Zn/Al LDHs. Analysis of the geometry and bonding around the trivalent Al^3＋ or divalent Zn^2＋ cations reveals that Al^3＋ plays a more significant role than Zn^2＋ in determining the microstructure properties, formation and bonding stability of the corresponding ZnRAl clusters when R〈5, while the influence of Zn^2＋ becomes the dominant factor in the case of R〉 5. These findings are in good agreement with experiments. This work provides a detailed electronic-level understanding of how the composition of cations affects the microstructure and stability of Zn-containing binary LDH layers.
文摘A dynamic two-zone model is proposed to address the formation of granulation and drying zones in fluidized bed layering granulation processes with internal product classification. The model assumes a constant volume for the granulation zone, but a variable overall volume for the fluidized bed to account for classified product removal. The model is used to study the effect of various process parameters on dynamics and process stability. Stability is shown to depend on the separation diameter of product removal and the flow rate of the injected liquid. A lower and upper range of separation diameters with stable process behavior are found. In an intermediate range instability in the form of self-sustained oscillations is observed. The lower stability boundary is in qualitative agreement with recent experimental observations （Schmidt, Bück, ＆ Tsotsas, 2015）; the upper boundary was reported in a theoretical paper by Vreman, Van Lare, and Hounslow （2009） based on a single zone model.
