Plasma disruption is often an unavoidable aspect of tokamak operations. It may cause severe damage to in-vessel components such as the vacuum vessel conductors, the first wall and the divertor target plates. Two types...Plasma disruption is often an unavoidable aspect of tokamak operations. It may cause severe damage to in-vessel components such as the vacuum vessel conductors, the first wall and the divertor target plates. Two types of disruption, the hot-plasma vertical displacement event and the major disruption with a cold-plasma vertical displacement event, are simulated by the DINA code for HL-2M. The time evolutions of the plasma current, the halo current, the magnetic axis, the minor radius, the elongation as well as the electromagnetic force and eddy currents on the vacuum vessel during the thermal quench and the current quench are investigated. By comparing the electromagnetic forces before and after the disruption, we find that the disruption causes great damage to the vacuum vessel conductors. In addition, the hot-plasma vertical displacement event is more dangerous than the major disruption with the cold-plasma vertical displacement event.展开更多
Microbially induced calcium carbonate precipitation(MICP)technology can induce calcium carbonate crystals with cementation and stable performance in the process of microbial metabolism or enzymization through the regu...Microbially induced calcium carbonate precipitation(MICP)technology can induce calcium carbonate crystals with cementation and stable performance in the process of microbial metabolism or enzymization through the regulation of environmental factors MICP can be used as a cementing agent to cement cohesionless sand particles to form the materials with the characteristics of higher strength,better durability and environmental friendli-ness,as well as a good engineering application prospect.In this paper,the shear strength of sand column was tested by triaxial compression tests,and the strength index was obtained.In order to further study the micro-strength mechanism and the failure process,based on the discrete element method,a numerical model of MICP cemented sand column was established considering the factors of matrix soil particle gradation,particle mor-phology,content ratio of induced calcium carbonate,pore distribution characteristics,inter-particle cementation and so on.The failure process of MICP cemented sand column under load was analysed by numerical simulation,and the reliability of the numerical model was tested by combining with the stress intensity curve of samples under test conditions.The results indicate that compared with the actual triaxial tests of MICP cemented sand column,although there are deviations in stress and strain,cohesion and internal friction angle,the numerical simulation shows similar development law and intensity amplitude,and the same failure trend.The work in this paper verifies the reliability of the numerical model and provides a theoretical basis for the subsequent analysis of the factors influencing the geotechnical mechanical properties of biomineralized materials.展开更多
A predictive study on the plasma current and position control was carried out by applying TSC to the EAST experiments with a plasma control system （PCS）. Good agreement was achieved between predicted and experimenta...A predictive study on the plasma current and position control was carried out by applying TSC to the EAST experiments with a plasma control system （PCS）. Good agreement was achieved between predicted and experimental results in the plasma current, major radius, minor radius, elongation and plasma electron density, etc., which indicates that TSC has high predictability and reliability.展开更多
Punch shear tests have been widely used to determine rock shear mechanical properties but without a standard sample geometric dimension suggestion.To investigate the impacts of sample geometric dimensions on shear beh...Punch shear tests have been widely used to determine rock shear mechanical properties but without a standard sample geometric dimension suggestion.To investigate the impacts of sample geometric dimensions on shear behaviors in a punch shear test,simulations using Particle Flow Code were carried out.The effects of three geometric dimensions(i.e.,disk diameter,ratio of shear surface diameter to disk diameter,and ratio of disk height to shear surface diameter)were discussed.Variations of shear strength,shear stiffness,and shear dilatancy angles were studied,and the fracture processes and patterns of samples were investigated.Then,normal stress on the shear surface during test was analyzed and a suggested disk geometric dimension was given.Simulation results show that when the ratio of the shear surface diameter to the disk diameter and the ratio of disk height to the shear surface diameter is small enough,the shear strength,shear stiffness,and shear dilatancy angles are extremely sensitive to the three geometric parameters.If the ratio of surface diameter to disk diameter is too large or the ratio of disk height to surface diameter is too small,a part of the sample within the shear surface will fail due to macro tensile cracks,which is characterized by break off.Samples with a greater ratio of disk height to shear surface diameter,namely when the sample is relatively thick,crack from one end to the other while others crack from both ends towards the middle.During test,the actual normal stress on the shear surface is greater than the target value because of the extra compressive stress from the part of sample outside shear surface.展开更多
基金Supported by the China ITER Plan Project Foundation under Grant Nos 2013GB113001 and 2014GB110004
文摘Plasma disruption is often an unavoidable aspect of tokamak operations. It may cause severe damage to in-vessel components such as the vacuum vessel conductors, the first wall and the divertor target plates. Two types of disruption, the hot-plasma vertical displacement event and the major disruption with a cold-plasma vertical displacement event, are simulated by the DINA code for HL-2M. The time evolutions of the plasma current, the halo current, the magnetic axis, the minor radius, the elongation as well as the electromagnetic force and eddy currents on the vacuum vessel during the thermal quench and the current quench are investigated. By comparing the electromagnetic forces before and after the disruption, we find that the disruption causes great damage to the vacuum vessel conductors. In addition, the hot-plasma vertical displacement event is more dangerous than the major disruption with the cold-plasma vertical displacement event.
基金sponsored by the National Natural Science Foundation of China(Grant No.12002173,12262027)Research start-up project of Inner Mongolia University of Technology(No.2200000924)key Lab.of University of Geological Hazards and Geotechnical Engineering Defense in Sandy and Drought Regions,Inner Mongolia Autonomous.
文摘Microbially induced calcium carbonate precipitation(MICP)technology can induce calcium carbonate crystals with cementation and stable performance in the process of microbial metabolism or enzymization through the regulation of environmental factors MICP can be used as a cementing agent to cement cohesionless sand particles to form the materials with the characteristics of higher strength,better durability and environmental friendli-ness,as well as a good engineering application prospect.In this paper,the shear strength of sand column was tested by triaxial compression tests,and the strength index was obtained.In order to further study the micro-strength mechanism and the failure process,based on the discrete element method,a numerical model of MICP cemented sand column was established considering the factors of matrix soil particle gradation,particle mor-phology,content ratio of induced calcium carbonate,pore distribution characteristics,inter-particle cementation and so on.The failure process of MICP cemented sand column under load was analysed by numerical simulation,and the reliability of the numerical model was tested by combining with the stress intensity curve of samples under test conditions.The results indicate that compared with the actual triaxial tests of MICP cemented sand column,although there are deviations in stress and strain,cohesion and internal friction angle,the numerical simulation shows similar development law and intensity amplitude,and the same failure trend.The work in this paper verifies the reliability of the numerical model and provides a theoretical basis for the subsequent analysis of the factors influencing the geotechnical mechanical properties of biomineralized materials.
基金supported by National Natural Science Foundation of China (Nos.10835009, 10975160)the Knowledge Innovation Program of the Chinese Academy of Sciences (No.KJCX3.SYW.N4)
文摘A predictive study on the plasma current and position control was carried out by applying TSC to the EAST experiments with a plasma control system （PCS）. Good agreement was achieved between predicted and experimental results in the plasma current, major radius, minor radius, elongation and plasma electron density, etc., which indicates that TSC has high predictability and reliability.
基金supported by the Fundamental Research Funds for the Central Universities,CHD(Nos.300102210307,300102210308)the National Natural Science Foundation of China(Nos.51708040,41831286,51678063,51978065).
文摘Punch shear tests have been widely used to determine rock shear mechanical properties but without a standard sample geometric dimension suggestion.To investigate the impacts of sample geometric dimensions on shear behaviors in a punch shear test,simulations using Particle Flow Code were carried out.The effects of three geometric dimensions(i.e.,disk diameter,ratio of shear surface diameter to disk diameter,and ratio of disk height to shear surface diameter)were discussed.Variations of shear strength,shear stiffness,and shear dilatancy angles were studied,and the fracture processes and patterns of samples were investigated.Then,normal stress on the shear surface during test was analyzed and a suggested disk geometric dimension was given.Simulation results show that when the ratio of the shear surface diameter to the disk diameter and the ratio of disk height to the shear surface diameter is small enough,the shear strength,shear stiffness,and shear dilatancy angles are extremely sensitive to the three geometric parameters.If the ratio of surface diameter to disk diameter is too large or the ratio of disk height to surface diameter is too small,a part of the sample within the shear surface will fail due to macro tensile cracks,which is characterized by break off.Samples with a greater ratio of disk height to shear surface diameter,namely when the sample is relatively thick,crack from one end to the other while others crack from both ends towards the middle.During test,the actual normal stress on the shear surface is greater than the target value because of the extra compressive stress from the part of sample outside shear surface.
