With the help of digital image processing technology, an automatic measurement method for the three-phase contact angles in the pore throats of the microfluidic model was established using the microfluidic water flood...With the help of digital image processing technology, an automatic measurement method for the three-phase contact angles in the pore throats of the microfluidic model was established using the microfluidic water flooding experiment videos as the data source. The results of the new method were verified through comparing with the manual measurement data.On this basis, the dynamic changes of the three-phase contact angles under flow conditions were clarified by the contact angles probability density curve and mean value change curve. The results show that, for water-wetting rocks, the mean value of the contact angles is acute angle during the early stage of the water flooding process, and it increases with the displacement time and becomes obtuse angle in the middle-late stage of displacement as the dominant force of oil phase gradually changes from viscous force to capillary force. The droplet flow in the remaining oil occurs in the central part of the pore throats, without three-phase contact angle. The contact angles for the porous flow and the columnar flow change slightly during the displacement and present as obtuse angles in view of mean values, which makes the remaining oil poorly movable and thus hard to be recovered. The mean value of the contact angle for the cluster flow tends to increase in the flooding process, which makes the remaining oil more difficult to be recovered. The contact angles for the membrane flow are mainly obtuse angles and reach the highest mean value in the late stage of displacement, which makes the remaining oil most difficult to be recovered. After displacement, the remaining oils under different flow regimes are just subjected to capillary force, with obtuse contact angles, and the wettability of the pore throat walls in the microfluidic model tends to be oil-wet under the action of crude oil.展开更多
A three-phase confocal elliptical cylinder model is proposed to analyze micromechanics of one-dimensional hexagonal piezoelectric quasicrystal （PQC） compos- ites. Exact solutions of the phonon, phason, and electric ...A three-phase confocal elliptical cylinder model is proposed to analyze micromechanics of one-dimensional hexagonal piezoelectric quasicrystal （PQC） compos- ites. Exact solutions of the phonon, phason, and electric fields are obtained by using the conformal mapping combined with the Laurent expansion technique when the model is subject to far-field anti-plane mechanical and in-plane electric loadings. The effective elec- troelastic constants of several different composites made up of PQC, quasicrystal （QC）, and piezoelectric （PE） materials are predicted by the generalized self-consistent method. Numerical examples are conducted to show the effects of the volume fraction and the cross-sectional shape of inclusion （or fiber） on the effective electroelastic constants of these composites. Compared with other micromechanical methods, the generalized self- consistent and Mori-Tanaka methods can predict the effective electroelastic constants of the composites consistently.展开更多
Based on the conductance fluctuation signals measured from vertical upward oil-gas-water three-phase flow experiment, time frequency representation and surrogate data method were used to investigate dynamical characte...Based on the conductance fluctuation signals measured from vertical upward oil-gas-water three-phase flow experiment, time frequency representation and surrogate data method were used to investigate dynamical characteristics of oil-in-water type bubble and slug flows. The results indicate that oil-in-water type bubble flow will turn to deterministic motion with the increase of oil phase fraction f o and superficial gas velocity U sg under fixed flowrate of oil-water mixture Q mix . The dynamics of oil-in-water type slug flow becomes more complex with the increase of U sg under fixed flowrate of oil-water mixture. The change of f o leads to irregular influence on the dynamics of slug flow. These interesting findings suggest that the surrogate data method can be a faithful tool for characterizing dynamic characteristics of oil-in-water type bubble and slug flows.展开更多
This paper presents a TOPF （three-phase optimal power flow） model that represents photovoltaic systems. The PV plant is modeled in the TOPF as active and reactive power source. Reactive power can be generated or abs...This paper presents a TOPF （three-phase optimal power flow） model that represents photovoltaic systems. The PV plant is modeled in the TOPF as active and reactive power source. Reactive power can be generated or absorbed using the available capacity and the adjustable power factor of the inverter. The reduction of unbalance voltage and losses in the distribution systems is obtained by actions of reactive power control of the inverter. The TOPF is formulated by current balance equations and the PV systems are modeled via an equivalent circuit. The primal-dual interior point method is used to obtain the optimal operating points for the systems for different scenarios of solar irradiance and temperature, thus providing a detailed view of the impact of photovoltaic distributed generation.展开更多
Transformers are normally designed and built for use at rated frequency and sinusoidal load current. A non-linear load on a transformer leads to harmonic power losses which cause increased operational costs and additi...Transformers are normally designed and built for use at rated frequency and sinusoidal load current. A non-linear load on a transformer leads to harmonic power losses which cause increased operational costs and additional heating in transformer parts. It leads to higher losses, early fatigue of insulation, premature failure and reduction of the useful life of the transformer. To prevent these problems, the rated capacity of transformer which supplies harmonic loads must be reduced. In this work, a typical 50 kVA three-phase distribution transformer with real practical parameters is taken under non-linear loads generated due to domestic loads. The core losses is evaluated using the three dimensional model of the transformer developed in FEM （finite element method） program based on valid model of transformer under high harmonic conditions. And finally a relation associated with core losses and amplitude of high harmonic order are reviewed ＆ analyzed and then a comparison is being carried out on the results obtained by different excitation current in transformer windings.展开更多
The train plan of urban rail transit under multi-routing mode can be divided into three parts： train formation, train operation periods and corresponding train counts of each routing in each period. Based on the anal...The train plan of urban rail transit under multi-routing mode can be divided into three parts： train formation, train operation periods and corresponding train counts of each routing in each period. Based on the analysis of passen- ger＇s general travel expenses and operator＇s benefits, the constraints and objective functions are defined and the multiobjective optimization model for the train plan of urban rail transit is presented. Factors considered in the multi- objective optimization model include transport capacity, the requirements of traffic organization, corporation benefits, passenger demands, and passenger choice behavior under multi-train-routing mode. According to the characteristics of this model and practical planning experience, a three-phase solution was designed to gradually optimize the train formarion, train counts as well as operation periods. The instance of Changsha Metro Line 2 validates the feasibility and efficiency of this approach.展开更多
Ecological degradation is a global problem, and ecological restoration technologies have played and will continue to play an important role in its mitigation. However, the lack of systematic research and evaluations o...Ecological degradation is a global problem, and ecological restoration technologies have played and will continue to play an important role in its mitigation. However, the lack of systematic research and evaluations of ecological technologies has thus far affected their effective application in vulnerable ecological regions. This study therefore provides an overview of the main technologies for remediating soil and water erosion, desertification, and rock desertification in China and throughout the world. It addresses key issues and recommends approaches for evaluating ecological restoration technologies. Restoration technology emerged as early as 1800. Over the years such technology has changed from single objective applications to multi-purpose, multi-objective applications employing strategies that take into account ecosystem rehabilitation and integrated ecological and socioeconomic development. Along with this technological evolution, different countries have taken pertinent actions as part of their restoration initiatives. However, key issues remain, including the lack of location-specific restoration technologies and a methodological strategy to assess and prioritize existing technologies. This study proposes a four-level analytical hierarchical framework in conjunction with an indicator system that highlights the establishment and adaptation of associative indicators, while also recommending a three-phase evaluation method（The Mert）, targeting The Mert to qualitative（quick and extensive） and quantitative（detailed） evaluations in order to select the most appropriate restoration technologies available. This study can also be used as a basis for understanding the evaluation and prioritization of restoration technologies, while increasing the awareness of decision makers and the public on the role of technology in restoring degraded ecosystems.展开更多
A three-phase composite cylinder model is utilized to study the interaction of a wedge disclination dipole with a coated cylindrical inhomogeneity. The explicit expression of the force acting on the wedge disclination...A three-phase composite cylinder model is utilized to study the interaction of a wedge disclination dipole with a coated cylindrical inhomogeneity. The explicit expression of the force acting on the wedge disclination dipole is calculated. The motilities and the equilibrium po- sitions of the disclination dipole near the coated inhomogeneity are discussed for various material combinations, relative thicknesses of the coating layer and the features of the disclination dipole. The results show that the material properties of the coating layer have a major part to play in alteringi the strengthening effect or toughening effect produced by the coated inhomogeneity.展开更多
The problem of determining the effective moduli of a ceramic matrix piezocomposite with respect to multiscale porosity was considered.To solve the homogenization problem,the method of effective moduli in the standard ...The problem of determining the effective moduli of a ceramic matrix piezocomposite with respect to multiscale porosity was considered.To solve the homogenization problem,the method of effective moduli in the standard formulation,the finite element method and the ANSYS computational package were used.Various models of two-phase and three-phase composites consisting of a piezoceramic matrix,elastic inclusions of corundum and pores of various sizes have been investigated.Finite element models of representative volumes of 3–0 and 3–0–0 connectivities were developed.The results of computational experiments showed that effective moduli depend quite significantly not only on the volume fractions of inclusions and pores,but also on the structure and size of pores in comparison with the characteristic sizes of inclusions.展开更多
基金Supported by National Science and Technology Major Project of China (51674271)Major Technical Field Test of PetroChina (2019F-33)。
文摘With the help of digital image processing technology, an automatic measurement method for the three-phase contact angles in the pore throats of the microfluidic model was established using the microfluidic water flooding experiment videos as the data source. The results of the new method were verified through comparing with the manual measurement data.On this basis, the dynamic changes of the three-phase contact angles under flow conditions were clarified by the contact angles probability density curve and mean value change curve. The results show that, for water-wetting rocks, the mean value of the contact angles is acute angle during the early stage of the water flooding process, and it increases with the displacement time and becomes obtuse angle in the middle-late stage of displacement as the dominant force of oil phase gradually changes from viscous force to capillary force. The droplet flow in the remaining oil occurs in the central part of the pore throats, without three-phase contact angle. The contact angles for the porous flow and the columnar flow change slightly during the displacement and present as obtuse angles in view of mean values, which makes the remaining oil poorly movable and thus hard to be recovered. The mean value of the contact angle for the cluster flow tends to increase in the flooding process, which makes the remaining oil more difficult to be recovered. The contact angles for the membrane flow are mainly obtuse angles and reach the highest mean value in the late stage of displacement, which makes the remaining oil most difficult to be recovered. After displacement, the remaining oils under different flow regimes are just subjected to capillary force, with obtuse contact angles, and the wettability of the pore throat walls in the microfluidic model tends to be oil-wet under the action of crude oil.
基金Projected supported by the National Natural Science Foundation of China(Nos.11502123 and11262012)the Natural Science Foundation of Inner Mongolia Autonomous Region of China(No.2015JQ01)
文摘A three-phase confocal elliptical cylinder model is proposed to analyze micromechanics of one-dimensional hexagonal piezoelectric quasicrystal （PQC） compos- ites. Exact solutions of the phonon, phason, and electric fields are obtained by using the conformal mapping combined with the Laurent expansion technique when the model is subject to far-field anti-plane mechanical and in-plane electric loadings. The effective elec- troelastic constants of several different composites made up of PQC, quasicrystal （QC）, and piezoelectric （PE） materials are predicted by the generalized self-consistent method. Numerical examples are conducted to show the effects of the volume fraction and the cross-sectional shape of inclusion （or fiber） on the effective electroelastic constants of these composites. Compared with other micromechanical methods, the generalized self- consistent and Mori-Tanaka methods can predict the effective electroelastic constants of the composites consistently.
基金Supported by the National Natural Science Foundation of China (50974095, 41174109)Gao Zhongke (高忠科) was also supported by the National Natural Science Foundation of China (61104148)+2 种基金the National Science and Technology Major Projects (2011ZX05020-006)Specialized Research Fund for the Doctoral Program of Higher Education of China(20110032120088)the Independent Innovation Foundation of Tianjin University
文摘Based on the conductance fluctuation signals measured from vertical upward oil-gas-water three-phase flow experiment, time frequency representation and surrogate data method were used to investigate dynamical characteristics of oil-in-water type bubble and slug flows. The results indicate that oil-in-water type bubble flow will turn to deterministic motion with the increase of oil phase fraction f o and superficial gas velocity U sg under fixed flowrate of oil-water mixture Q mix . The dynamics of oil-in-water type slug flow becomes more complex with the increase of U sg under fixed flowrate of oil-water mixture. The change of f o leads to irregular influence on the dynamics of slug flow. These interesting findings suggest that the surrogate data method can be a faithful tool for characterizing dynamic characteristics of oil-in-water type bubble and slug flows.
文摘This paper presents a TOPF （three-phase optimal power flow） model that represents photovoltaic systems. The PV plant is modeled in the TOPF as active and reactive power source. Reactive power can be generated or absorbed using the available capacity and the adjustable power factor of the inverter. The reduction of unbalance voltage and losses in the distribution systems is obtained by actions of reactive power control of the inverter. The TOPF is formulated by current balance equations and the PV systems are modeled via an equivalent circuit. The primal-dual interior point method is used to obtain the optimal operating points for the systems for different scenarios of solar irradiance and temperature, thus providing a detailed view of the impact of photovoltaic distributed generation.
文摘Transformers are normally designed and built for use at rated frequency and sinusoidal load current. A non-linear load on a transformer leads to harmonic power losses which cause increased operational costs and additional heating in transformer parts. It leads to higher losses, early fatigue of insulation, premature failure and reduction of the useful life of the transformer. To prevent these problems, the rated capacity of transformer which supplies harmonic loads must be reduced. In this work, a typical 50 kVA three-phase distribution transformer with real practical parameters is taken under non-linear loads generated due to domestic loads. The core losses is evaluated using the three dimensional model of the transformer developed in FEM （finite element method） program based on valid model of transformer under high harmonic conditions. And finally a relation associated with core losses and amplitude of high harmonic order are reviewed ＆ analyzed and then a comparison is being carried out on the results obtained by different excitation current in transformer windings.
基金supported by the National Natural Science Foundation of China (No. 70901076)Research Fund for the Doctoral Program of Higher Education of China (No. 20090162120021)Natural Science Foundation of Hunan Province (No. 10JJ4046)
文摘The train plan of urban rail transit under multi-routing mode can be divided into three parts： train formation, train operation periods and corresponding train counts of each routing in each period. Based on the analysis of passen- ger＇s general travel expenses and operator＇s benefits, the constraints and objective functions are defined and the multiobjective optimization model for the train plan of urban rail transit is presented. Factors considered in the multi- objective optimization model include transport capacity, the requirements of traffic organization, corporation benefits, passenger demands, and passenger choice behavior under multi-train-routing mode. According to the characteristics of this model and practical planning experience, a three-phase solution was designed to gradually optimize the train formarion, train counts as well as operation periods. The instance of Changsha Metro Line 2 validates the feasibility and efficiency of this approach.
基金National Key Research and Development Program of China(2016YFC0503700)
文摘Ecological degradation is a global problem, and ecological restoration technologies have played and will continue to play an important role in its mitigation. However, the lack of systematic research and evaluations of ecological technologies has thus far affected their effective application in vulnerable ecological regions. This study therefore provides an overview of the main technologies for remediating soil and water erosion, desertification, and rock desertification in China and throughout the world. It addresses key issues and recommends approaches for evaluating ecological restoration technologies. Restoration technology emerged as early as 1800. Over the years such technology has changed from single objective applications to multi-purpose, multi-objective applications employing strategies that take into account ecosystem rehabilitation and integrated ecological and socioeconomic development. Along with this technological evolution, different countries have taken pertinent actions as part of their restoration initiatives. However, key issues remain, including the lack of location-specific restoration technologies and a methodological strategy to assess and prioritize existing technologies. This study proposes a four-level analytical hierarchical framework in conjunction with an indicator system that highlights the establishment and adaptation of associative indicators, while also recommending a three-phase evaluation method（The Mert）, targeting The Mert to qualitative（quick and extensive） and quantitative（detailed） evaluations in order to select the most appropriate restoration technologies available. This study can also be used as a basis for understanding the evaluation and prioritization of restoration technologies, while increasing the awareness of decision makers and the public on the role of technology in restoring degraded ecosystems.
基金Project supported by the National Natural Science Foundation of China(Nos.11172094 and 11172095)the New Century Excellent Talents in University(NCET-11-0122)Hunan Provincial Natural Science Foundation for Creative Research Groups of China(No.12JJ7001)
文摘A three-phase composite cylinder model is utilized to study the interaction of a wedge disclination dipole with a coated cylindrical inhomogeneity. The explicit expression of the force acting on the wedge disclination dipole is calculated. The motilities and the equilibrium po- sitions of the disclination dipole near the coated inhomogeneity are discussed for various material combinations, relative thicknesses of the coating layer and the features of the disclination dipole. The results show that the material properties of the coating layer have a major part to play in alteringi the strengthening effect or toughening effect produced by the coated inhomogeneity.
基金Project No.9.1001.2017/4.6 of the competitive part of the state task of the Ministry of Science and Higher Education of Russia.
文摘The problem of determining the effective moduli of a ceramic matrix piezocomposite with respect to multiscale porosity was considered.To solve the homogenization problem,the method of effective moduli in the standard formulation,the finite element method and the ANSYS computational package were used.Various models of two-phase and three-phase composites consisting of a piezoceramic matrix,elastic inclusions of corundum and pores of various sizes have been investigated.Finite element models of representative volumes of 3–0 and 3–0–0 connectivities were developed.The results of computational experiments showed that effective moduli depend quite significantly not only on the volume fractions of inclusions and pores,but also on the structure and size of pores in comparison with the characteristic sizes of inclusions.
