The gas-water distribution and production heterogeneity of tight gas reservoirs have been summarized from experimental and geological observations, but the charging and accumulation mechanisms have not been examined q...The gas-water distribution and production heterogeneity of tight gas reservoirs have been summarized from experimental and geological observations, but the charging and accumulation mechanisms have not been examined quantitatively by mathematical model. The tight gas charging and accumulation mechanisms were revealed from a combination of physical simulation of nuclear magnetic resonance coupling displacement, numerical simulation considering material and mechanical equilibria, as well as actual geological observation. The results show that gas migrates into tight rocks to preferentially form a gas saturation stabilization zone near the source-reservoir interface. When the gas source is insufficient, gas saturation reduction zone and uncharged zone are formed in sequence from the source-reservoir interface. The better the source rock conditions with more gas expulsion volume and higher overpressure, the thicker the gas saturation stabilization and reduction zones, and the higher the overall gas saturation. When the source rock conditions are limited, the better the tight reservoir conditions with higher porosity and permeability as well as larger pore throat, the thinner the gas saturation stabilization and reduction zones, but the gas saturation is high. The sweet spot of tight gas is developed in the high-quality reservoir near the source rock, which often corresponds to the gas saturation stabilization zone. The numerical simulation results by mathematical model agree well with the physical simulation results by nuclear magnetic resonance coupling displacement, and reasonably explain the gas-water distribution and production pattern of deep reservoirs in the Xujiaweizi fault depression of the Songliao Basin and tight gas reservoirs in the Linxing-Huangfu area of the Ordos Basin.展开更多
Objective The natural gas exploration of the Sinian reservoirs in the central Sichuan Basin has made a significant breakthrough in recent years, and has thus attracted much attention among geologists. The Sichuan Bas...Objective The natural gas exploration of the Sinian reservoirs in the central Sichuan Basin has made a significant breakthrough in recent years, and has thus attracted much attention among geologists. The Sichuan Basin is known to have complicated geological settings, which has experienced multiple stages of tectonic evolution, fluid charging and hydrocarbon accumulation. This research aims to determine the geochemical characteristics of each stage of fluids, the features and time interval of fluid activity in different geologic periods, and further to restore the critical period and geological age of the hydrocarbon accumulation.展开更多
The Bozhong19-6(BZ19-6)condensate gas reservoirs,located in the southwestern Bozhong sub-basin,Bohai Bay Basin,China,were paleo-oil reservoirs in the geological past and have undergone at least three successive hydroc...The Bozhong19-6(BZ19-6)condensate gas reservoirs,located in the southwestern Bozhong sub-basin,Bohai Bay Basin,China,were paleo-oil reservoirs in the geological past and have undergone at least three successive hydrocarbon charging events.The hydrocarbon migration and accumulation process of“early oil and late gas”has occurred in the current reservoirs.At the end of the sedimentation of the Guantao Formation(N_(1)g,∼12 Ma),the reservoirs began to fill with first stage low-moderate mature crude oil.At the late stage of the Lower Minghuazhen Formation(N_(1)ml)(∼6.7 Ma),the reservoirs were largely charged with second stage high mature crude oil.Since the deposition of the upper Minghuazhen Formation(N_(2)m^(u),∼5.1 Ma),the paleo-oil reservoirs were transformed into shallow Neogene reservoirs due to the reactivation of basement faults.From the late stage of the N_(2)m^(u)to the present day(∼2.8–0 Ma),the reservoirs were rapidly filled by natural gas within a short period.In addition,analysis of the formation of the reservoir bitumen and the conspicuous loss of the lower molecular weight n-alkanes in the crude oil reveal that the injection of a large amount of gas in the late stage caused gas flushing of the early charged oil.展开更多
It is the purpose of the present paper to convert hydraulic energy to electric energy and saves both the pressure and electrical energy for re - use during the next system upstroke using two secondary units coupled to...It is the purpose of the present paper to convert hydraulic energy to electric energy and saves both the pressure and electrical energy for re - use during the next system upstroke using two secondary units coupled to induction motor to drive cylinder loads. During upstroke operation, the variable pump/motor （P/M） driven by both electric motor and the second （P/M） works as hydraulic pump and output flow to the cylinders which drive the load. During load deceleration, the cylinders work as pump while the operation of the two secondary units are reversed, the variable （P/M） works as a motor generating a torque with the electric motor to drive the other （P/M） which transforms mechanical energy to hydraulic energy that is saved in the accumulator. When the energy storage capacity of the accumulator is attained as the operation continues, energy storage to the accumulator is thermostatically stopped while the induction motor begins to work as a generator and generates electricity that is stored in the power distribution unit. Simulations were performed using a limited PT2 Block, i.e. 2nd-order transfer function with limitation of slope and signal output to determine suitable velocity of the cylinder which will match high performance and system stability. A mathematical model suited to the simulation of the hydraulic accumulator both in an open-or close-loop system is presented. The quest for improvement of lower energy capacity storage, saving and re-utilization of the conventional accumulator resulting in the short cycle time usage of hydraulic accumulators both in domestic and industrial purposes necessitates this research. The outcome of the research appears to be very efficient for generating fluctuation free electricity, power quality and reliability, energy saving/reutilization and system noise reduction.展开更多
The phenomenon of EME and charge accumulation were included during the load-bearing failure processing of the rock.The mechanism and signal law of the two kinds of phenomenon through the experiment,as well as the mutu...The phenomenon of EME and charge accumulation were included during the load-bearing failure processing of the rock.The mechanism and signal law of the two kinds of phenomenon through the experiment,as well as the mutual relation of the two kinds of phenomenon,were contribute to monitor the regulation of the mine rock and pre- vent the dynamic disasters of the mine.There were two charge sensors,one electromag- netic radiated sensors and one pressure sensor in the experiment to detect the EME sig- nal and the charge intensity signal during the load-bearing failure processing of the rock. The results show that the charge intensity signal is prior to the EME signal through the date processing and numerical analysis.The two signals change obviously before the rock crush.The two kinds of phenomenon are homogenous and have obvious master-slave characteristic.With the appeared of the EME signal,the charge intensity signal decreased, the power is released.展开更多
In an insulating system including solid and gas dielectrics, discharge type has a strong impact on charge accumulation at the interface between two dielectrics, and hence charge decay. In order to clarify the influenc...In an insulating system including solid and gas dielectrics, discharge type has a strong impact on charge accumulation at the interface between two dielectrics, and hence charge decay. In order to clarify the influence, a surface charge measurement system was constructed, and three types of discharge, i.e. surface discharge, and low intensity and high intensity coronas, were introduced to cause surface charge accumulation. The decay behavior of surface charges after different types of discharge was obtained at various temperatures. It was found that total surface charges monotonically decreased with time, and the decay rate became larger as temperature increased. However, after a surface discharge or a high intensity corona, surface charge density in the local area appeared to fluctuate during the decay process. Compared with this, the fluctuation of surface charge density was not observed after a low intensity corona. The mechanisms of surface charge accumulation and decay were analysed. Moreover, a microscopic physical model involving charge production, accumulation, and decay was proposed so that the experimental results could be explained.展开更多
Surface charge accumulation is considered to be a critical factor in flashover failure of three-post insulators.However,surface charge accumulation characteristics on threepost insulators with complex structures and u...Surface charge accumulation is considered to be a critical factor in flashover failure of three-post insulators.However,surface charge accumulation characteristics on threepost insulators with complex structures and uneven electric fields are still unclear.Furthermore,the temperature gradient field makes charge accumulation more complicated.In this presentation,surface charge profiles of DC three-post insulators under electro-thermal coupling stress are studied by establishing a multi-degree-of-freedom movement measurement system.The abdominal area of the three-post insulator accumulaftes charges of identical polarity as the DC voltage,while the leg area accumulates heteropolar charges.Charge density from the bottom of the leg to the center of the abdomen presents a trimodal distribution pattern,including two homopolar charge peaks and one heteropolar charge peak.Asymmetrical surface conductance distribution arising from the temperature gradient leads to a significant increase in amplitude and distribution range of the homopolar charge peak at the legs of insulator.Increase of the temperature gradient will further magnify the homopolar charge peak at the legs.When DC voltage is 100 kV and conductive pole temperature is 70℃,surface charge density of the three-post insulator can reach 100μC/m^(2).Therefore,surface conductance regulation of the leg region is the key to charge regulation and insulation optimization design of DC three-post insulators.展开更多
Polydimethylsiloxane (PDMS) is inactive to electric fields, but when combined with ferroelectric cyanoethyl sucrose (CR-U), it becomes an electrically active actuator material. The PDMS/CR-U composites were prepared b...Polydimethylsiloxane (PDMS) is inactive to electric fields, but when combined with ferroelectric cyanoethyl sucrose (CR-U), it becomes an electrically active actuator material. The PDMS/CR-U composites were prepared by casting method using tetrahydrofuran (THF) and acetone (ACT) as solvents. The effect of a mixed solvent composition was investigated. The viscosity of the PDMS/CR-U/solvent solution decreased as the THF composition increased. The composite film obtained by evaporation of the solvent and cross-linkage of PDMS showed a phase-separated structure. Spherical CR-U dispersed in the PDMS matrix with a skin layer on one surface side. Electrical resistance, dielectric constant, space-charge distribution, and electrically induced bending deformation behavior were investigated for these composite films. The composite films prepared from a THF-rich solvent exhibited lower surface resistivity than those prepared from a THF-poor solvent. Applying an electric field to the composite film resulted in an asymmetric space-charge distribution with charge accumulation in the skin layer. THF content decreased the viscosity of the solution, meaning the decrease of the apparent size of PDMS chain aggregates. It allows the dispersion of CR-U in the PDMS matrix and also results in the decline of resistivity, the increase of permittivity, and the increase of charge injection. The results explained the structure formation of the composite film and the electric field response as an actuator. A casting solvent of THF content of 87.5 wt% or more is essential for the function of the PDMS/CR-U composite.展开更多
A recurring challenge of a DC SF_(6)/N_(2)-filled GIS/GIL apparatus is the charge accumulation at DC stress.The conventional design rules and knowledge of AC spacers may not be applicable for this new type of apparatu...A recurring challenge of a DC SF_(6)/N_(2)-filled GIS/GIL apparatus is the charge accumulation at DC stress.The conventional design rules and knowledge of AC spacers may not be applicable for this new type of apparatus.A novel design rule is proposed considering the effect of accumulated charge on the threshold of electric field strength being resistant to the superposed voltage.A surface charge accumulation simulation model is introduced,and the key parameters in the simulation model are measured.In addition,an experimental platform for a 100 kV spacer flashover test is established.Spacer flashover tests under superimposed voltage with opposing polarities are carried out,and the withstanding voltage of the spacer is obtained.Finally,based on the proposed model,the threshold of the surface electric field strength(tangential component)on the DC spacer in SF_(6)/N_(2) mixed gases is discussed.For a reliable insulation design of a DC GIS/GIL apparatus filled with 0.7 MPa SF_(6)/N_(2),the threshold of surface electric field strength on the DC spacer is 12 kV/mm.The insulation design rule can be referenced in the design of a high-voltage DC SF_(6)/N_(2)-filled GIS/GIL apparatus.展开更多
Surface flashover of spacers is a key factor limiting the application of HVDC GIS/GIL,while the charge accumula-tion on the surface of the spacer could have a potential adverse effect on the surface flashover voltage....Surface flashover of spacers is a key factor limiting the application of HVDC GIS/GIL,while the charge accumula-tion on the surface of the spacer could have a potential adverse effect on the surface flashover voltage.This paper discusses the laws regarding distribution patterns of surface charges and the related mechanisms.The field-dependent property is discussed in detail to comprehensively illustrate the charge transport mecha-nism and explain the research differences regarding different surface charge patterns obtained by previous researchers.In addition,the main surface charge control methods for epoxy resin are summarized and discussed.The potential research directions of charge control methods and key points in manufacturing of spacers used in HVDC GIS/GIL are also explored.展开更多
Charge accumulation on the spacer surface in gas insulated equipment is very severe in the DC field,leading to easy flashover,which restricts the application of DC GIS/GIL.Therefore,knowledge about the charge accumula...Charge accumulation on the spacer surface in gas insulated equipment is very severe in the DC field,leading to easy flashover,which restricts the application of DC GIS/GIL.Therefore,knowledge about the charge accumulation characteristics of gas insulated equipment at DC stress is essential.In this paper,we reviewed the research methods and the characteristics of charge accumulation on spacers.A summary of charge measurement methods and setups are presented.And the surface charge inversion algorithms are introduced.Then the simulation model for charge accumulation in the DC field is reviewed.Subsequently,the charge accumulation mechanisms and phenomenon,the influence factor of surface charge accumulation and the influence of accumulated charge on spacer insulation characteristics are summarized.In addition,some suppression methods of surface charge accumulation are discussed.Finally,based on the understanding of charge accumulation on spacers,some suggestions on further studies are presented to aid in the design of a better spacer free from surface charges.展开更多
A novel silicon-on-insulator（SOI） super-junction（SJ） LDMOS with an ultra-strong charge accumulation effect is proposed. It has two key features： an assisted-accumulation trench-type extending gate（TEG） with a h...A novel silicon-on-insulator（SOI） super-junction（SJ） LDMOS with an ultra-strong charge accumulation effect is proposed. It has two key features： an assisted-accumulation trench-type extending gate（TEG） with a high-k（HK） dielectric and a step-dopedN pillar（TEG-SD SJ LDMOS）. In the on-state, electrons accumulate at the sidewall of the HK dielectric from the source to the drain by the TEG. Furthermore, the high permittivity of the HK dielectric leads to an ultra-strong charge accumulation effect. As a result, an ultra-low resistance current path is formed. The specific on-resistance（Ron;sp/ is thus greatly reduced and is independent of the drift doping concentration. In the off-state, the step-dopedN pillar effectively suppresses the substrate-assisted depletion effect by charge compensation. Moreover, the reshape effect of the HK dielectric and the new electric field（E-field） peak introduced by the step-dopedN pillar enhance the drift region E-field. Hence, the BV is improved. Simulation indicates that the TEG-SD SJ LDMOS achieves an extremely low Ron;sp of 1.06 m cm^2 and a BV of 217 V. Compared with the conventional SJ LDMOS, the TEG-SD SJ LDMOS decreases the Ron;sp by 77.5% and increases the BV by 33%,exhibiting a high figure of merits（FOM=BV^2/Ron;sp/ of 44 MW/cm^2.展开更多
Experiments with the limited space-charge accumulation（LSA） mode of oscillation in a large gap semiinsulating （SI） GaAs photoconductive semiconductor switch（PCSS） are discussed.It has been observed that growth a...Experiments with the limited space-charge accumulation（LSA） mode of oscillation in a large gap semiinsulating （SI） GaAs photoconductive semiconductor switch（PCSS） are discussed.It has been observed that growth and drift of a photo-activated charge domain（PACD） are quenched only when the bias voltage is more than twice the threshold voltage.The original negative resistance characteristics are directly utilized in the LSA mode;during LSA operation the spatial average of the electric field varies over a large portion of the negative differential mobility region of the velocity-electric field characteristic.The work efficiency of an SI GaAs PCSS is remarkably enhanced by electric field excursions into the positive resistance region when the total electric field is only below the threshold part of the time.The LSA mode can only operate in the certain conditions that satisfy the quenching of the accumulation layer and the smaller initial domain voltage.展开更多
The accumulation process of trapped charges in a TANOS cell during P/E cycling is investigated via numerical simulation. The recombination process between trapped charges is an important issue on the retention of char...The accumulation process of trapped charges in a TANOS cell during P/E cycling is investigated via numerical simulation. The recombination process between trapped charges is an important issue on the retention of charge trapping memory. Our results show that accumulated trapped holes during P/E cycling can have an influence on retention, and the recombination mechanism between trapped charges should be taken into account when evaluating the retention capability of TANOS.展开更多
As the main tracking detector of BESIII, the drift chamber provides accurate measurements of the position and the momentum of the charged particles produced in e＋e- collisions at BEPCII. After six years of operation,...As the main tracking detector of BESIII, the drift chamber provides accurate measurements of the position and the momentum of the charged particles produced in e＋e- collisions at BEPCII. After six years of operation, the drift chamber is suffering from aging problems due to huge beam-related background. The gains of the cells in the first ten layers show an obvious decrease, reaching a maximum decrease of about 29% for the first layer cells. Two calculation methods for the gain change （Bhabha events and accumulated charges with 0.3% aging ratio for inner chamber cells） give almost the same results. For the Malter effect encountered by the inner drift chamber in January 2012, about 0.2% water vapor was added to the MDC gas mixture to solve this cathode aging problem. These results provide an important reference for MDC operating high voltage settings and the upgrade of the inner drift chamber.展开更多
基金Supported by the National Natural Science Foundation of China(42302183,42272156,41922015)Sanya City Science and Technology Innovation Project(2022KJCX51).
文摘The gas-water distribution and production heterogeneity of tight gas reservoirs have been summarized from experimental and geological observations, but the charging and accumulation mechanisms have not been examined quantitatively by mathematical model. The tight gas charging and accumulation mechanisms were revealed from a combination of physical simulation of nuclear magnetic resonance coupling displacement, numerical simulation considering material and mechanical equilibria, as well as actual geological observation. The results show that gas migrates into tight rocks to preferentially form a gas saturation stabilization zone near the source-reservoir interface. When the gas source is insufficient, gas saturation reduction zone and uncharged zone are formed in sequence from the source-reservoir interface. The better the source rock conditions with more gas expulsion volume and higher overpressure, the thicker the gas saturation stabilization and reduction zones, and the higher the overall gas saturation. When the source rock conditions are limited, the better the tight reservoir conditions with higher porosity and permeability as well as larger pore throat, the thinner the gas saturation stabilization and reduction zones, but the gas saturation is high. The sweet spot of tight gas is developed in the high-quality reservoir near the source rock, which often corresponds to the gas saturation stabilization zone. The numerical simulation results by mathematical model agree well with the physical simulation results by nuclear magnetic resonance coupling displacement, and reasonably explain the gas-water distribution and production pattern of deep reservoirs in the Xujiaweizi fault depression of the Songliao Basin and tight gas reservoirs in the Linxing-Huangfu area of the Ordos Basin.
基金supported by the Natural Science Foundation of China(grant No.41372141)
文摘Objective The natural gas exploration of the Sinian reservoirs in the central Sichuan Basin has made a significant breakthrough in recent years, and has thus attracted much attention among geologists. The Sichuan Basin is known to have complicated geological settings, which has experienced multiple stages of tectonic evolution, fluid charging and hydrocarbon accumulation. This research aims to determine the geochemical characteristics of each stage of fluids, the features and time interval of fluid activity in different geologic periods, and further to restore the critical period and geological age of the hydrocarbon accumulation.
基金supported by the National Science&Technology Specific Project,China(No.2016ZX05024-003-008).
文摘The Bozhong19-6(BZ19-6)condensate gas reservoirs,located in the southwestern Bozhong sub-basin,Bohai Bay Basin,China,were paleo-oil reservoirs in the geological past and have undergone at least three successive hydrocarbon charging events.The hydrocarbon migration and accumulation process of“early oil and late gas”has occurred in the current reservoirs.At the end of the sedimentation of the Guantao Formation(N_(1)g,∼12 Ma),the reservoirs began to fill with first stage low-moderate mature crude oil.At the late stage of the Lower Minghuazhen Formation(N_(1)ml)(∼6.7 Ma),the reservoirs were largely charged with second stage high mature crude oil.Since the deposition of the upper Minghuazhen Formation(N_(2)m^(u),∼5.1 Ma),the paleo-oil reservoirs were transformed into shallow Neogene reservoirs due to the reactivation of basement faults.From the late stage of the N_(2)m^(u)to the present day(∼2.8–0 Ma),the reservoirs were rapidly filled by natural gas within a short period.In addition,analysis of the formation of the reservoir bitumen and the conspicuous loss of the lower molecular weight n-alkanes in the crude oil reveal that the injection of a large amount of gas in the late stage caused gas flushing of the early charged oil.
文摘It is the purpose of the present paper to convert hydraulic energy to electric energy and saves both the pressure and electrical energy for re - use during the next system upstroke using two secondary units coupled to induction motor to drive cylinder loads. During upstroke operation, the variable pump/motor （P/M） driven by both electric motor and the second （P/M） works as hydraulic pump and output flow to the cylinders which drive the load. During load deceleration, the cylinders work as pump while the operation of the two secondary units are reversed, the variable （P/M） works as a motor generating a torque with the electric motor to drive the other （P/M） which transforms mechanical energy to hydraulic energy that is saved in the accumulator. When the energy storage capacity of the accumulator is attained as the operation continues, energy storage to the accumulator is thermostatically stopped while the induction motor begins to work as a generator and generates electricity that is stored in the power distribution unit. Simulations were performed using a limited PT2 Block, i.e. 2nd-order transfer function with limitation of slope and signal output to determine suitable velocity of the cylinder which will match high performance and system stability. A mathematical model suited to the simulation of the hydraulic accumulator both in an open-or close-loop system is presented. The quest for improvement of lower energy capacity storage, saving and re-utilization of the conventional accumulator resulting in the short cycle time usage of hydraulic accumulators both in domestic and industrial purposes necessitates this research. The outcome of the research appears to be very efficient for generating fluctuation free electricity, power quality and reliability, energy saving/reutilization and system noise reduction.
基金the National Natural Science Foundation of China(50490275)Education Office of Liaoning Province(20082123)
文摘The phenomenon of EME and charge accumulation were included during the load-bearing failure processing of the rock.The mechanism and signal law of the two kinds of phenomenon through the experiment,as well as the mutual relation of the two kinds of phenomenon,were contribute to monitor the regulation of the mine rock and pre- vent the dynamic disasters of the mine.There were two charge sensors,one electromag- netic radiated sensors and one pressure sensor in the experiment to detect the EME sig- nal and the charge intensity signal during the load-bearing failure processing of the rock. The results show that the charge intensity signal is prior to the EME signal through the date processing and numerical analysis.The two signals change obviously before the rock crush.The two kinds of phenomenon are homogenous and have obvious master-slave characteristic.With the appeared of the EME signal,the charge intensity signal decreased, the power is released.
基金the financial support from National Natural Science Foundation of China (No. 51607128)Natural Science Foundation of Hubei Province (No. 2016CFB111)China Postdoctoral Science Foundation (No. 2016M602353)
文摘In an insulating system including solid and gas dielectrics, discharge type has a strong impact on charge accumulation at the interface between two dielectrics, and hence charge decay. In order to clarify the influence, a surface charge measurement system was constructed, and three types of discharge, i.e. surface discharge, and low intensity and high intensity coronas, were introduced to cause surface charge accumulation. The decay behavior of surface charges after different types of discharge was obtained at various temperatures. It was found that total surface charges monotonically decreased with time, and the decay rate became larger as temperature increased. However, after a surface discharge or a high intensity corona, surface charge density in the local area appeared to fluctuate during the decay process. Compared with this, the fluctuation of surface charge density was not observed after a low intensity corona. The mechanisms of surface charge accumulation and decay were analysed. Moreover, a microscopic physical model involving charge production, accumulation, and decay was proposed so that the experimental results could be explained.
基金supported by the National Natural Science Foundation of China(51737005,52127812,51929701).
文摘Surface charge accumulation is considered to be a critical factor in flashover failure of three-post insulators.However,surface charge accumulation characteristics on threepost insulators with complex structures and uneven electric fields are still unclear.Furthermore,the temperature gradient field makes charge accumulation more complicated.In this presentation,surface charge profiles of DC three-post insulators under electro-thermal coupling stress are studied by establishing a multi-degree-of-freedom movement measurement system.The abdominal area of the three-post insulator accumulaftes charges of identical polarity as the DC voltage,while the leg area accumulates heteropolar charges.Charge density from the bottom of the leg to the center of the abdomen presents a trimodal distribution pattern,including two homopolar charge peaks and one heteropolar charge peak.Asymmetrical surface conductance distribution arising from the temperature gradient leads to a significant increase in amplitude and distribution range of the homopolar charge peak at the legs of insulator.Increase of the temperature gradient will further magnify the homopolar charge peak at the legs.When DC voltage is 100 kV and conductive pole temperature is 70℃,surface charge density of the three-post insulator can reach 100μC/m^(2).Therefore,surface conductance regulation of the leg region is the key to charge regulation and insulation optimization design of DC three-post insulators.
文摘Polydimethylsiloxane (PDMS) is inactive to electric fields, but when combined with ferroelectric cyanoethyl sucrose (CR-U), it becomes an electrically active actuator material. The PDMS/CR-U composites were prepared by casting method using tetrahydrofuran (THF) and acetone (ACT) as solvents. The effect of a mixed solvent composition was investigated. The viscosity of the PDMS/CR-U/solvent solution decreased as the THF composition increased. The composite film obtained by evaporation of the solvent and cross-linkage of PDMS showed a phase-separated structure. Spherical CR-U dispersed in the PDMS matrix with a skin layer on one surface side. Electrical resistance, dielectric constant, space-charge distribution, and electrically induced bending deformation behavior were investigated for these composite films. The composite films prepared from a THF-rich solvent exhibited lower surface resistivity than those prepared from a THF-poor solvent. Applying an electric field to the composite film resulted in an asymmetric space-charge distribution with charge accumulation in the skin layer. THF content decreased the viscosity of the solution, meaning the decrease of the apparent size of PDMS chain aggregates. It allows the dispersion of CR-U in the PDMS matrix and also results in the decline of resistivity, the increase of permittivity, and the increase of charge injection. The results explained the structure formation of the composite film and the electric field response as an actuator. A casting solvent of THF content of 87.5 wt% or more is essential for the function of the PDMS/CR-U composite.
基金supported in part by the National Basic Research Program of China(973 Program)(2014CB239500)Young Elite Scientists Sponsorship Program by CAST YESS20160004the Fundamental Research Funds for the Central Universities(2019MS006).
文摘A recurring challenge of a DC SF_(6)/N_(2)-filled GIS/GIL apparatus is the charge accumulation at DC stress.The conventional design rules and knowledge of AC spacers may not be applicable for this new type of apparatus.A novel design rule is proposed considering the effect of accumulated charge on the threshold of electric field strength being resistant to the superposed voltage.A surface charge accumulation simulation model is introduced,and the key parameters in the simulation model are measured.In addition,an experimental platform for a 100 kV spacer flashover test is established.Spacer flashover tests under superimposed voltage with opposing polarities are carried out,and the withstanding voltage of the spacer is obtained.Finally,based on the proposed model,the threshold of the surface electric field strength(tangential component)on the DC spacer in SF_(6)/N_(2) mixed gases is discussed.For a reliable insulation design of a DC GIS/GIL apparatus filled with 0.7 MPa SF_(6)/N_(2),the threshold of surface electric field strength on the DC spacer is 12 kV/mm.The insulation design rule can be referenced in the design of a high-voltage DC SF_(6)/N_(2)-filled GIS/GIL apparatus.
基金This study is financially supported by the National Basic Research Program(2017YFB0903800)and the Electric Power Research Institute,Yunnan Electric Power Grid Co.Ltd,Kunming,Yunnan 650217,China(YNKJXM20160146).
文摘Surface flashover of spacers is a key factor limiting the application of HVDC GIS/GIL,while the charge accumula-tion on the surface of the spacer could have a potential adverse effect on the surface flashover voltage.This paper discusses the laws regarding distribution patterns of surface charges and the related mechanisms.The field-dependent property is discussed in detail to comprehensively illustrate the charge transport mecha-nism and explain the research differences regarding different surface charge patterns obtained by previous researchers.In addition,the main surface charge control methods for epoxy resin are summarized and discussed.The potential research directions of charge control methods and key points in manufacturing of spacers used in HVDC GIS/GIL are also explored.
基金This work was supported in part by the National Basic Research Program of China(973 Program)(2014CB239500)Young Elite Scientists Sponsorship Program by CAST YESS20160004+2 种基金Fok Ying-Tong Education Foundation for Young Teachers in the Higher Education Institutions of China(Grant No.161053)project of China Scholarship Council(CSC)the Fundamental Research Funds for the Central Universities(2019MS006).
文摘Charge accumulation on the spacer surface in gas insulated equipment is very severe in the DC field,leading to easy flashover,which restricts the application of DC GIS/GIL.Therefore,knowledge about the charge accumulation characteristics of gas insulated equipment at DC stress is essential.In this paper,we reviewed the research methods and the characteristics of charge accumulation on spacers.A summary of charge measurement methods and setups are presented.And the surface charge inversion algorithms are introduced.Then the simulation model for charge accumulation in the DC field is reviewed.Subsequently,the charge accumulation mechanisms and phenomenon,the influence factor of surface charge accumulation and the influence of accumulated charge on spacer insulation characteristics are summarized.In addition,some suppression methods of surface charge accumulation are discussed.Finally,based on the understanding of charge accumulation on spacers,some suggestions on further studies are presented to aid in the design of a better spacer free from surface charges.
基金Project supported by the National Natural Science Foundation of China(Nos.61176069,61376079)the Program for New Century Excellent Talents in University of Ministry of Education of China(No.NCET-11-0062)
文摘A novel silicon-on-insulator（SOI） super-junction（SJ） LDMOS with an ultra-strong charge accumulation effect is proposed. It has two key features： an assisted-accumulation trench-type extending gate（TEG） with a high-k（HK） dielectric and a step-dopedN pillar（TEG-SD SJ LDMOS）. In the on-state, electrons accumulate at the sidewall of the HK dielectric from the source to the drain by the TEG. Furthermore, the high permittivity of the HK dielectric leads to an ultra-strong charge accumulation effect. As a result, an ultra-low resistance current path is formed. The specific on-resistance（Ron;sp/ is thus greatly reduced and is independent of the drift doping concentration. In the off-state, the step-dopedN pillar effectively suppresses the substrate-assisted depletion effect by charge compensation. Moreover, the reshape effect of the HK dielectric and the new electric field（E-field） peak introduced by the step-dopedN pillar enhance the drift region E-field. Hence, the BV is improved. Simulation indicates that the TEG-SD SJ LDMOS achieves an extremely low Ron;sp of 1.06 m cm^2 and a BV of 217 V. Compared with the conventional SJ LDMOS, the TEG-SD SJ LDMOS decreases the Ron;sp by 77.5% and increases the BV by 33%,exhibiting a high figure of merits（FOM=BV^2/Ron;sp/ of 44 MW/cm^2.
基金Project supported by the National Natural Science Foundation of China(Nos.50837005,11204264)the Research Fund for Doctors of Xinjiang Normal University(No.XJNUBS 1220)the Research Fund for the Outstanding Young Teacher of Xinjiang Normal University (No.XJNU1214)
文摘Experiments with the limited space-charge accumulation（LSA） mode of oscillation in a large gap semiinsulating （SI） GaAs photoconductive semiconductor switch（PCSS） are discussed.It has been observed that growth and drift of a photo-activated charge domain（PACD） are quenched only when the bias voltage is more than twice the threshold voltage.The original negative resistance characteristics are directly utilized in the LSA mode;during LSA operation the spatial average of the electric field varies over a large portion of the negative differential mobility region of the velocity-electric field characteristic.The work efficiency of an SI GaAs PCSS is remarkably enhanced by electric field excursions into the positive resistance region when the total electric field is only below the threshold part of the time.The LSA mode can only operate in the certain conditions that satisfy the quenching of the accumulation layer and the smaller initial domain voltage.
基金Project supported by Samsung Electronics Co.Ltd.(Nos.20060001050,2006CB302705)
文摘The accumulation process of trapped charges in a TANOS cell during P/E cycling is investigated via numerical simulation. The recombination process between trapped charges is an important issue on the retention of charge trapping memory. Our results show that accumulated trapped holes during P/E cycling can have an influence on retention, and the recombination mechanism between trapped charges should be taken into account when evaluating the retention capability of TANOS.
基金Supported by the CAS Center for Excellence in Particle Physics(CCEPP)
文摘As the main tracking detector of BESIII, the drift chamber provides accurate measurements of the position and the momentum of the charged particles produced in e＋e- collisions at BEPCII. After six years of operation, the drift chamber is suffering from aging problems due to huge beam-related background. The gains of the cells in the first ten layers show an obvious decrease, reaching a maximum decrease of about 29% for the first layer cells. Two calculation methods for the gain change （Bhabha events and accumulated charges with 0.3% aging ratio for inner chamber cells） give almost the same results. For the Malter effect encountered by the inner drift chamber in January 2012, about 0.2% water vapor was added to the MDC gas mixture to solve this cathode aging problem. These results provide an important reference for MDC operating high voltage settings and the upgrade of the inner drift chamber.
