Ever since the first report of the discovery of an unknown novel coronavirus that had caused pneumonia in Wuhan,China,had filed to WHO by China,on December 31,2019,the government had instituted drastic measures to con...Ever since the first report of the discovery of an unknown novel coronavirus that had caused pneumonia in Wuhan,China,had filed to WHO by China,on December 31,2019,the government had instituted drastic measures to contain the outbreak of the epidemic.To keep transparency,the China's National Health Commission reports confirmed,suspected,recovered and death case numbers daily,yet the epidemiological community is still calling for more information.Specifically,they want to have the critical"Basic Reproduction,Number"Ro.According to Jones[1]and van den Driessche and Watmough[2],Ro,is defined as the expected number of secondary cases produced by a single(typical)infection in a completely susceptible population.展开更多
An analytical study of the flow and pressure fields inside a small-diameter dense-media cyclone is presented.The simulations were done with the help of the CFD software FLUENT.The following conclusions were reached:th...An analytical study of the flow and pressure fields inside a small-diameter dense-media cyclone is presented.The simulations were done with the help of the CFD software FLUENT.The following conclusions were reached:the tangential velocity tends to increase when moving from the center toward the exterior.The velocity then begins to decrease when the maximum velocity point is reached.The velocity field divides into two different sections;an inner swirling zone and an outer swirling zone.The axial velocity points down at the wall and gradually decreases toward the bottom.Continuing toward the bottom,the axial velocity passes through zero and then gradually increases in the opposite direction.In the cyclone's central zone,the pressure is negative and the suction of air allows an air column to be formed therein.At the center of the radial negative zone the pressure drops to its lowest value—phenomenon that has been verified by theoretical analysis.Some discrepancies between the observed data and the simulated data are noted when an analysis in made on a cyclone operating with either fresh water only or with water with added heavy particles.展开更多
The rotating circular plate is widely used in mechanical engineering, meanwhile the plates are often in the electromagnetic field in modern industry with complex loads. In order to study the resonance of a rotating ci...The rotating circular plate is widely used in mechanical engineering, meanwhile the plates are often in the electromagnetic field in modern industry with complex loads. In order to study the resonance of a rotating circular plate under static loads in magnetic field, the nonlinear vibration equation about the spinning circular plate is derived according to Hamilton principle. The algebraic expression of the initial deflection and the magneto elastic forced disturbance differential equation are obtained through the application of Galerkin integral method. By mean of modified Multiple scale method, the strongly nonlinear amplitude-frequency response equation in steady state is established. The amplitude frequency characteristic curve and the relationship curve of amplitude changing with the static loads and the excitation force of the plate are obtained according to the numerical calculation. The influence of magnetic induction intensity, the speed of rotation and the static loads on the amplitude and the nonlinear characteristics of the spinning plate are analyzed. The proposed research provides the theory reference for the research of nonlinear resonance of rotating plates in engineering.展开更多
Numerical simulation of fluid migration during the ore-forming process of the Carboniferous exhalation- sedimentary (Sedex) massive sulfide deposits in the Tongling district shows that fluid and thermal activities in ...Numerical simulation of fluid migration during the ore-forming process of the Carboniferous exhalation- sedimentary (Sedex) massive sulfide deposits in the Tongling district shows that fluid and thermal activities in lying-wall rocks were limited to a small area around the main draining passage, which led to weak mineralization and alteration in the lying-wall rock. Temperature and fluid fields indicate that mineralization and alteration in the lying-wall rock of the Sedex-type deposits are usually weaker than those of volcano-hosted massive sulfide deposits. Fluid migration involves the following processes: seawater penetrating and leaching the lying-wall rocks, then mixing with ascending hydrothermal fluids in the main draining passage, and finally jetting into seafloor. Although fluid activity-influenced area is rather small, the content of metals leached out from the lying-wall rocks is high enough to form large-scale ore deposits. Tensional contemporaneous faults accompanied with strong heat flows controlled the formation and distribution of Sedex deposits. The tensional tectonic regime on the northern margin of the Yangtze block during the Hercynian provided Sedex deposits with a prerequisite geodynamic condition.展开更多
Electro-bioremediation is an innovative method to remedy organic-polluted soil. However, the principle of electrokinetic technology enhancing the function of microbes, especially the relationship of electric intensity...Electro-bioremediation is an innovative method to remedy organic-polluted soil. However, the principle of electrokinetic technology enhancing the function of microbes, especially the relationship of electric intensity and biodegradation efficiency, is poorly investigated. Petroleum was employed as a target organic pollutant at a level of 50 g/kg （mass of petroleum/mass of dry soil）. A direct current power supply was used for tests with a constant direct current electric voltage （1.0 V/cm）. The petroleum concentrations Were measured at 3275-3285 nm after extraction using hexane, the group composition of crude oil was analyzed by column chromatography. The water content of soil was kept 25% （m/m）. The results indicated the degradation process was divided into two periods： from day 1 to day 40, from day 41 to day 100. The treatment of soil with an appropriate electric field led the bacteria to have a persistent effect in the whole period of 100 days. The highest biodegradation efficiency of 45.5% was obtained after treatment with electric current and bacteria. The electric-bioremediation had a positive effect on alkane degradation. The degradation rate of alkane was 1.6 times higher in the soil exposed to electric current than that treated with bacteria for 100 days. A proper direct current could stimulate the microbial activities and accelerate the biodegradation of petroleum. There was a positive correlation between the electric intensities and the petroleum bioremediation efficiencies with a coefficient of 0.9599.展开更多
Coastal structures may be built on natural sedimentary intermediate grounds, which mainly consist of silty soils and fine sandy soils. In this study, extensive field and laboratory tests were performed on the natural ...Coastal structures may be built on natural sedimentary intermediate grounds, which mainly consist of silty soils and fine sandy soils. In this study, extensive field and laboratory tests were performed on the natural marine intermediate deposits to demonstrate the difference in behavior between natural marine clayey soils and natural marine intermediate deposits. The natural intermediate deposits have almost the same ratios of natural water content to liquid limit as those of the soft natural marine clays, but the former have much higher in-situ strength and sensitivity than the latter. The research results indicate that grain size distributions of soils affect significantly tip resistance obtained in field cone penetration tests. The mechanical parameters of natural marine intermediate deposits are also significantly affected by sample disturbance due to their high sensitivity and relatively large permeability. Unconfined compression shear tests largely underestimate the strength of natural marine intermediate soils. The triaxial consolidated compression shear tests with simulated in-situ confined pressure give results much better than those of uncomfined compression shear tests.展开更多
As of October 2021,Communist Party of China(CPC)disciplinary authorities had filed 4.078 million corruption cases involving 4.379 million officials since the 18th National Congress in 2012.Among them,484 were investig...As of October 2021,Communist Party of China(CPC)disciplinary authorities had filed 4.078 million corruption cases involving 4.379 million officials since the 18th National Congress in 2012.Among them,484 were investigated,resulting in disciplinary and administrative punishments for 3.998 million individuals.In 2023,a record 54 high-ranking officials were detained,the highest number since 2012,according to data from the CPC Central Commission for Discipline Inspection(CCDI)。展开更多
To address the hazardous by-product of zinc smelting and resource utilization of jarosite residue,this study applies an electric field-assisted hot acid treatment to completely recycle iron(Fe).This innovative approac...To address the hazardous by-product of zinc smelting and resource utilization of jarosite residue,this study applies an electric field-assisted hot acid treatment to completely recycle iron(Fe).This innovative approach aims to enhance the leaching efficiency of Fe from jarosite residue.The introduction of an electric field changes the charge distribution on the surface of the particles to enhance ions and electrons exchange and promotes the collision between particles to strengthen reaction kinetics.Based on the above,the leaching efficiency of Fe in jarosite under sulfuric acid attack has improved observably.The result shows that Fe leaching efficiency reaches 98.83%,which is increased by 28%under the optimal experimental conditions:current density of 30 mA·cm^(-2),H_(2)SO_(4) concentration of 1.5 mol·L^(-1),solid-liquid ratio of 70 g·L^(-1),temperature of 80℃ and time of 12 h.Leaching kinetics calculations show that the apparent activation energy is 16.97 kJ·mol^(-1) and the leaching of jarosite residue is controlled by a mixture of chemical reaction and diffusion,as well as the temperature and concentration of the leaching solution have an influence on leaching.This work provides a feasible idea for the efficient leaching of Fe from jarosite residue.展开更多
0n May 29,a court in Shanghai dismissed a case filed by a local consumer,who attempted to force U.S.tech company Apple Inc.to cease charging its 30-percent commission on purchases in its App Store.Jin Xin,the consumer...0n May 29,a court in Shanghai dismissed a case filed by a local consumer,who attempted to force U.S.tech company Apple Inc.to cease charging its 30-percent commission on purchases in its App Store.Jin Xin,the consumer,brought the suit against Apple China in 2021.In addition to calling on the company to cease charging commissions,Jin insisted that consumers be allowed to use other payment systems besides Apple Pay when purchasing apps or services on Apple products,and asked for 100,000 yuan($13,800)in compensation for commissions he'd previously paid.展开更多
When a maintenance and operations ship is berthing,there is a chance the ship may collide into the wind turbine.When these ships collide into wind turbine structures,this can result in significant changes to the found...When a maintenance and operations ship is berthing,there is a chance the ship may collide into the wind turbine.When these ships collide into wind turbine structures,this can result in significant changes to the foundation and structure of the wind turbine.In this paper,the structural load of a 4 MW offshore wind turbine was analyzed during a collision with an operations and maintenance ship.The variations in the wind speeds on hub height,waves,and the sea currents were measured.The dynamic simulation of the wind turbine was carried out using the test data as the input parameters.As a result,the load condition of the turbine without a collision was obtained.Finally,the measured turbine load was compared with the simulation results.This study shows that the collision of the operation and the maintenance ship increases the bending moments at the tower’s bottom and the blade’s roots.展开更多
The study on the deformation distribution and crack propagation of concrete under axial compression was conducted by the digital image correlation (DIC) method. The main parameter in this test is the water-cement (fT/...The study on the deformation distribution and crack propagation of concrete under axial compression was conducted by the digital image correlation (DIC) method. The main parameter in this test is the water-cement (fT/C) ratio. The novel analysis process and numerical program for DIC method were established. The displacements and strains of coarse aggregate, and cement mortar and interface transition zone (ITZ) were obtained and verified by experimental results. It was found that the axial displacement distributed non-uniformly during the loading stage, and the axial displacements of ITZs and cement mortar were larger than that of coarse aggregates before the occurrence of macrocracks. The effect of W/C on the horizontal displacement was not obvious. Test results also showed that the transverse and shear deformation concentration areas (DCAs) were formed when stress reached 30%-40% of the peak stress. The transverse and shear DCAs crossed the cement mortar, and ITZs and coarse aggregates. However, the axial DCA mainly surrounded the coarse aggregate. Generally, the higher W/C was, the more size and number of DCAs were. The crack propagations of specimens varied with the variation of W/C. The micro-crack of concrete mainly initiated in the ITZs, irrespective of the W/C. The number and distribution range of cracks in concrete with high W/C were larger than those of cracks in specimen adopting low W/C. However, the value and width of eraeks in high W/C specimen were relatively small. The W/C had an obvious effect on the characteristics of concrete deterioration. Finally, the characteristics of crack was also evaluated by comparing the calculated results.展开更多
Based on outcrop,seismic and drilling data,the main regional unconformities in the Sichuan Basin and their controls on hydrocarbon accumulation were systematically studied.Three findings are obtained.First,six regiona...Based on outcrop,seismic and drilling data,the main regional unconformities in the Sichuan Basin and their controls on hydrocarbon accumulation were systematically studied.Three findings are obtained.First,six regional stratigraphic unconformities are mainly developed in the Sichuan Basin,from the bottom up which are between pre-Sinian and Sinian,between Sinian and Cambrian,between pre-Permian and Permian,between middle and upper Permian,between middle and upper Triassic,and between Triassic and Jurassic.Especially,16 of 21l conventional(and tight)gas fields discovered are believed to have formed in relation to regional unconformities.Second,regional unconformity mainly controls hydrocarbon accumulation from five aspects:(1)The porosity and permeability of reservoirs under the unconformity are improved through weathering crust karstification to form large-scale karst reservoirs;(2)Good source-reservoir-caprock assemblage can form near the unconformity,which provides a basis for forming large gas field;(3)Regional unconformity may lead to stratigraphic pinch-out and rugged ancient landform,giving rise to a large area of stratigraphic and lithologic trap groups;(4)Regional unconformity provides a dominant channel for lateral migration of oil and gas;and(5)Regional unconformity is conducive to large-scale accumulation of oil and gas.Third,the areas related to regional unconformities are the exploration focus of large gas fields in the Sichuan Basin.The pre-Sinian is found with source rocks,reservoir rocks and other favorable conditions for the formation of large gas fields,and presents a large exploration potential.Thus,it is expected to be an important strategic replacement.展开更多
This paper investigates a Luenberger flux observer with speed adaptation for a direct field oriented control of an induction motor. An improved method of speed estimation that operates on the principle of speed adapti...This paper investigates a Luenberger flux observer with speed adaptation for a direct field oriented control of an induction motor. An improved method of speed estimation that operates on the principle of speed adaptive flux and current observer has been proposed. An observer is basically an estimator that uses a plant model and a feedback loop with measured stator voltage and current. Simulation results show that the proposed direct field oriented control with the proposed observer provides good performance dynamic characteristics. The induction motor is fed by an indirect power electronics converter. This indirect converter is controlled by a sliding mode technique that enables minimization of harmonics introduced by the line converter, as well as the control of the power factor and DC-link voltage. The robustness of the overall system is studied using simulation for different operating modes and varied parameters.展开更多
Numerical simulation models of compact spinning with perforated drum, punched apron and lattice apron were established and computerized with computational fluid dynamics(CFD) software. Characteristics of airflow in co...Numerical simulation models of compact spinning with perforated drum, punched apron and lattice apron were established and computerized with computational fluid dynamics(CFD) software. Characteristics of airflow in condensing zone were achieved. Velocity vectors of the flow on different systems were contrasted and discussed. Then, trajectories of fibers in condensing zone were simulated by a specially designed MATLAB program routine. The result of the simulation clarified the compact mechanism of the compact spinning systems. Also, it applied a guideline for reasonable utilization of the airflow in condensing zone.展开更多
基金supported by the National Natural Science Foundation of China (41821004)。
文摘Ever since the first report of the discovery of an unknown novel coronavirus that had caused pneumonia in Wuhan,China,had filed to WHO by China,on December 31,2019,the government had instituted drastic measures to contain the outbreak of the epidemic.To keep transparency,the China's National Health Commission reports confirmed,suspected,recovered and death case numbers daily,yet the epidemiological community is still calling for more information.Specifically,they want to have the critical"Basic Reproduction,Number"Ro.According to Jones[1]and van den Driessche and Watmough[2],Ro,is defined as the expected number of secondary cases produced by a single(typical)infection in a completely susceptible population.
基金Projects 2007AA05Z339 supported by the Hi-tech Research and Development Program of ChinaCPEUKF08-10 by the Key Laboratory Opening Fund of Coal Processing & Efficient Utilization,Ministry of Education of China
文摘An analytical study of the flow and pressure fields inside a small-diameter dense-media cyclone is presented.The simulations were done with the help of the CFD software FLUENT.The following conclusions were reached:the tangential velocity tends to increase when moving from the center toward the exterior.The velocity then begins to decrease when the maximum velocity point is reached.The velocity field divides into two different sections;an inner swirling zone and an outer swirling zone.The axial velocity points down at the wall and gradually decreases toward the bottom.Continuing toward the bottom,the axial velocity passes through zero and then gradually increases in the opposite direction.In the cyclone's central zone,the pressure is negative and the suction of air allows an air column to be formed therein.At the center of the radial negative zone the pressure drops to its lowest value—phenomenon that has been verified by theoretical analysis.Some discrepancies between the observed data and the simulated data are noted when an analysis in made on a cyclone operating with either fresh water only or with water with added heavy particles.
基金Supported by National Natural Science Foundation of China(Grant No11472239)Hebei Provincial Natural Science Foundation of China(Grant No.A2015203023)Key Project of Science and Technology Research of Higher Education of Hebei Province of China(Grant No.ZD20131055)
文摘The rotating circular plate is widely used in mechanical engineering, meanwhile the plates are often in the electromagnetic field in modern industry with complex loads. In order to study the resonance of a rotating circular plate under static loads in magnetic field, the nonlinear vibration equation about the spinning circular plate is derived according to Hamilton principle. The algebraic expression of the initial deflection and the magneto elastic forced disturbance differential equation are obtained through the application of Galerkin integral method. By mean of modified Multiple scale method, the strongly nonlinear amplitude-frequency response equation in steady state is established. The amplitude frequency characteristic curve and the relationship curve of amplitude changing with the static loads and the excitation force of the plate are obtained according to the numerical calculation. The influence of magnetic induction intensity, the speed of rotation and the static loads on the amplitude and the nonlinear characteristics of the spinning plate are analyzed. The proposed research provides the theory reference for the research of nonlinear resonance of rotating plates in engineering.
基金the National NaturalScience Foundation of China(Project No.40303008 , Key Project No.40234051)the Special Research Project of the Ministry of Land and Resources of China(No.200101030) the 973 Research Project ofthe Ministry of Science and Technology of China(No.2002CB412605).
文摘Numerical simulation of fluid migration during the ore-forming process of the Carboniferous exhalation- sedimentary (Sedex) massive sulfide deposits in the Tongling district shows that fluid and thermal activities in lying-wall rocks were limited to a small area around the main draining passage, which led to weak mineralization and alteration in the lying-wall rock. Temperature and fluid fields indicate that mineralization and alteration in the lying-wall rock of the Sedex-type deposits are usually weaker than those of volcano-hosted massive sulfide deposits. Fluid migration involves the following processes: seawater penetrating and leaching the lying-wall rocks, then mixing with ascending hydrothermal fluids in the main draining passage, and finally jetting into seafloor. Although fluid activity-influenced area is rather small, the content of metals leached out from the lying-wall rocks is high enough to form large-scale ore deposits. Tensional contemporaneous faults accompanied with strong heat flows controlled the formation and distribution of Sedex deposits. The tensional tectonic regime on the northern margin of the Yangtze block during the Hercynian provided Sedex deposits with a prerequisite geodynamic condition.
基金supported by the Water Pollution Control and Management Key Project of Science and Technology of China (No. 2008ZX07208-800)
文摘Electro-bioremediation is an innovative method to remedy organic-polluted soil. However, the principle of electrokinetic technology enhancing the function of microbes, especially the relationship of electric intensity and biodegradation efficiency, is poorly investigated. Petroleum was employed as a target organic pollutant at a level of 50 g/kg （mass of petroleum/mass of dry soil）. A direct current power supply was used for tests with a constant direct current electric voltage （1.0 V/cm）. The petroleum concentrations Were measured at 3275-3285 nm after extraction using hexane, the group composition of crude oil was analyzed by column chromatography. The water content of soil was kept 25% （m/m）. The results indicated the degradation process was divided into two periods： from day 1 to day 40, from day 41 to day 100. The treatment of soil with an appropriate electric field led the bacteria to have a persistent effect in the whole period of 100 days. The highest biodegradation efficiency of 45.5% was obtained after treatment with electric current and bacteria. The electric-bioremediation had a positive effect on alkane degradation. The degradation rate of alkane was 1.6 times higher in the soil exposed to electric current than that treated with bacteria for 100 days. A proper direct current could stimulate the microbial activities and accelerate the biodegradation of petroleum. There was a positive correlation between the electric intensities and the petroleum bioremediation efficiencies with a coefficient of 0.9599.
基金This research project is financially supported by Jiangsu Transportation Scientific Funds (Grant No. 02Y015)
文摘Coastal structures may be built on natural sedimentary intermediate grounds, which mainly consist of silty soils and fine sandy soils. In this study, extensive field and laboratory tests were performed on the natural marine intermediate deposits to demonstrate the difference in behavior between natural marine clayey soils and natural marine intermediate deposits. The natural intermediate deposits have almost the same ratios of natural water content to liquid limit as those of the soft natural marine clays, but the former have much higher in-situ strength and sensitivity than the latter. The research results indicate that grain size distributions of soils affect significantly tip resistance obtained in field cone penetration tests. The mechanical parameters of natural marine intermediate deposits are also significantly affected by sample disturbance due to their high sensitivity and relatively large permeability. Unconfined compression shear tests largely underestimate the strength of natural marine intermediate soils. The triaxial consolidated compression shear tests with simulated in-situ confined pressure give results much better than those of uncomfined compression shear tests.
文摘As of October 2021,Communist Party of China(CPC)disciplinary authorities had filed 4.078 million corruption cases involving 4.379 million officials since the 18th National Congress in 2012.Among them,484 were investigated,resulting in disciplinary and administrative punishments for 3.998 million individuals.In 2023,a record 54 high-ranking officials were detained,the highest number since 2012,according to data from the CPC Central Commission for Discipline Inspection(CCDI)。
基金The National Natural Science Foundation of China(22276153,51974262)funded this work。
文摘To address the hazardous by-product of zinc smelting and resource utilization of jarosite residue,this study applies an electric field-assisted hot acid treatment to completely recycle iron(Fe).This innovative approach aims to enhance the leaching efficiency of Fe from jarosite residue.The introduction of an electric field changes the charge distribution on the surface of the particles to enhance ions and electrons exchange and promotes the collision between particles to strengthen reaction kinetics.Based on the above,the leaching efficiency of Fe in jarosite under sulfuric acid attack has improved observably.The result shows that Fe leaching efficiency reaches 98.83%,which is increased by 28%under the optimal experimental conditions:current density of 30 mA·cm^(-2),H_(2)SO_(4) concentration of 1.5 mol·L^(-1),solid-liquid ratio of 70 g·L^(-1),temperature of 80℃ and time of 12 h.Leaching kinetics calculations show that the apparent activation energy is 16.97 kJ·mol^(-1) and the leaching of jarosite residue is controlled by a mixture of chemical reaction and diffusion,as well as the temperature and concentration of the leaching solution have an influence on leaching.This work provides a feasible idea for the efficient leaching of Fe from jarosite residue.
文摘0n May 29,a court in Shanghai dismissed a case filed by a local consumer,who attempted to force U.S.tech company Apple Inc.to cease charging its 30-percent commission on purchases in its App Store.Jin Xin,the consumer,brought the suit against Apple China in 2021.In addition to calling on the company to cease charging commissions,Jin insisted that consumers be allowed to use other payment systems besides Apple Pay when purchasing apps or services on Apple products,and asked for 100,000 yuan($13,800)in compensation for commissions he'd previously paid.
基金supported by the National Key Research and Development Program of China(2018YFB0904005)。
文摘When a maintenance and operations ship is berthing,there is a chance the ship may collide into the wind turbine.When these ships collide into wind turbine structures,this can result in significant changes to the foundation and structure of the wind turbine.In this paper,the structural load of a 4 MW offshore wind turbine was analyzed during a collision with an operations and maintenance ship.The variations in the wind speeds on hub height,waves,and the sea currents were measured.The dynamic simulation of the wind turbine was carried out using the test data as the input parameters.As a result,the load condition of the turbine without a collision was obtained.Finally,the measured turbine load was compared with the simulation results.This study shows that the collision of the operation and the maintenance ship increases the bending moments at the tower’s bottom and the blade’s roots.
基金The authors gratefully acknowledge the support by the National Natural Science Foundation of China (Grant No. 51408346)the Taishan Scholarship Project of Shandong Province (No. tshw20130956)the China Postdoctoral Science Foundation Funded Project (Nos. 2015M572584, 2016T0914).
文摘The study on the deformation distribution and crack propagation of concrete under axial compression was conducted by the digital image correlation (DIC) method. The main parameter in this test is the water-cement (fT/C) ratio. The novel analysis process and numerical program for DIC method were established. The displacements and strains of coarse aggregate, and cement mortar and interface transition zone (ITZ) were obtained and verified by experimental results. It was found that the axial displacement distributed non-uniformly during the loading stage, and the axial displacements of ITZs and cement mortar were larger than that of coarse aggregates before the occurrence of macrocracks. The effect of W/C on the horizontal displacement was not obvious. Test results also showed that the transverse and shear deformation concentration areas (DCAs) were formed when stress reached 30%-40% of the peak stress. The transverse and shear DCAs crossed the cement mortar, and ITZs and coarse aggregates. However, the axial DCA mainly surrounded the coarse aggregate. Generally, the higher W/C was, the more size and number of DCAs were. The crack propagations of specimens varied with the variation of W/C. The micro-crack of concrete mainly initiated in the ITZs, irrespective of the W/C. The number and distribution range of cracks in concrete with high W/C were larger than those of cracks in specimen adopting low W/C. However, the value and width of eraeks in high W/C specimen were relatively small. The W/C had an obvious effect on the characteristics of concrete deterioration. Finally, the characteristics of crack was also evaluated by comparing the calculated results.
基金Supported by the National Natural Science Foundation Project of China(U22B6002)Prospective Basic Technology Research Project of PetroChina(2021DJ0605).
文摘Based on outcrop,seismic and drilling data,the main regional unconformities in the Sichuan Basin and their controls on hydrocarbon accumulation were systematically studied.Three findings are obtained.First,six regional stratigraphic unconformities are mainly developed in the Sichuan Basin,from the bottom up which are between pre-Sinian and Sinian,between Sinian and Cambrian,between pre-Permian and Permian,between middle and upper Permian,between middle and upper Triassic,and between Triassic and Jurassic.Especially,16 of 21l conventional(and tight)gas fields discovered are believed to have formed in relation to regional unconformities.Second,regional unconformity mainly controls hydrocarbon accumulation from five aspects:(1)The porosity and permeability of reservoirs under the unconformity are improved through weathering crust karstification to form large-scale karst reservoirs;(2)Good source-reservoir-caprock assemblage can form near the unconformity,which provides a basis for forming large gas field;(3)Regional unconformity may lead to stratigraphic pinch-out and rugged ancient landform,giving rise to a large area of stratigraphic and lithologic trap groups;(4)Regional unconformity provides a dominant channel for lateral migration of oil and gas;and(5)Regional unconformity is conducive to large-scale accumulation of oil and gas.Third,the areas related to regional unconformities are the exploration focus of large gas fields in the Sichuan Basin.The pre-Sinian is found with source rocks,reservoir rocks and other favorable conditions for the formation of large gas fields,and presents a large exploration potential.Thus,it is expected to be an important strategic replacement.
文摘This paper investigates a Luenberger flux observer with speed adaptation for a direct field oriented control of an induction motor. An improved method of speed estimation that operates on the principle of speed adaptive flux and current observer has been proposed. An observer is basically an estimator that uses a plant model and a feedback loop with measured stator voltage and current. Simulation results show that the proposed direct field oriented control with the proposed observer provides good performance dynamic characteristics. The induction motor is fed by an indirect power electronics converter. This indirect converter is controlled by a sliding mode technique that enables minimization of harmonics introduced by the line converter, as well as the control of the power factor and DC-link voltage. The robustness of the overall system is studied using simulation for different operating modes and varied parameters.
基金Fundamental Research Funds for the Central Universities,China(No.10D10101)
文摘Numerical simulation models of compact spinning with perforated drum, punched apron and lattice apron were established and computerized with computational fluid dynamics(CFD) software. Characteristics of airflow in condensing zone were achieved. Velocity vectors of the flow on different systems were contrasted and discussed. Then, trajectories of fibers in condensing zone were simulated by a specially designed MATLAB program routine. The result of the simulation clarified the compact mechanism of the compact spinning systems. Also, it applied a guideline for reasonable utilization of the airflow in condensing zone.
