Thermal shock damage in deep shale hydraulic fracturing can impact fracture propagation behaviors,potentially leading to the formation of complex fractures and enhancing gas recovery.This study introduces a thermalhyd...Thermal shock damage in deep shale hydraulic fracturing can impact fracture propagation behaviors,potentially leading to the formation of complex fractures and enhancing gas recovery.This study introduces a thermalhydraulic-mechnical(THM)coupled fracture propagation model relying on the phase field method to simulate thermal shock-induced fracturing in the deep shale considering dynamic temperature conditions.The validity of this model is confirmed through comparison of experimental and numerical results concerning the THM-coupled stress field and thermal cracking.Special attention is paid to the interaction of thermal shock-induced fractures in deep shale that contains weak planes.The results indicate that thermal shock-induced stress significantly amplifies the tensile stress range and deteriorates rock strength,resulting in a multi-point failure pattern within a fracture.The thermal shock damage degree is closely related to the fracture cooling efficiency,suggesting that considering downhole temperature conditions in THM-coupled fracture stress field calculations is advisable.Thermal shock can activate pre-existing natural fractures and enhance the penetration ability of hydraulic fractures,thereby leading to a fracture network.展开更多
The event-based vision sensor(EVS),which can generate efficient spiking data streams by exclusively detecting motion,exemplifies neuromorphic vision methodologies.Generally,its inherent lack of texture features limits...The event-based vision sensor(EVS),which can generate efficient spiking data streams by exclusively detecting motion,exemplifies neuromorphic vision methodologies.Generally,its inherent lack of texture features limits effectiveness in complex vision processing tasks,necessitating supplementary visual information.However,to date,no event-based hybrid vision solution has been developed that preserves the characteristics of complete spike data streams to support synchronous computation architectures based on spiking neural network(SNN).In this paper,we present a novel spike-based sensor with digitized pixels,which integrates the event detection structure with the pulse frequency modulation(PFM)circuit.This design enables the simultaneous output of spiking data that encodes both temporal changes and texture information.Fabricated in 180 nm process,the proposed sensor achieves a resolution of 128×128,a maximum event rate of 960 Meps,a grayscale frame rate of 117.1 kfps,and a measured power consumption of 60.1 mW,which is suited for high-speed,low-latency,edge SNNbased vision computing systems.展开更多
提出一种可根据负载变化在脉冲宽度调制(pulse width modulation,PWM)和脉冲频率调制(pulse frequency modulation,PFM)两种工作模式间自动切换的降压DC-DC芯片的设计法,推导出临界切换状态下的负载电流值表达式,在此基础上设计了一种PW...提出一种可根据负载变化在脉冲宽度调制(pulse width modulation,PWM)和脉冲频率调制(pulse frequency modulation,PFM)两种工作模式间自动切换的降压DC-DC芯片的设计法,推导出临界切换状态下的负载电流值表达式,在此基础上设计了一种PWM/PFM自动切换的DC-DC芯片.该系统在较大的负载变化范围内均具有较高效率.展开更多
基金paper is funded by the CNOOC Science and Technology Project(KJGG2022-0701)the National Natural Science Foundation of China(51904258,51874250).
文摘Thermal shock damage in deep shale hydraulic fracturing can impact fracture propagation behaviors,potentially leading to the formation of complex fractures and enhancing gas recovery.This study introduces a thermalhydraulic-mechnical(THM)coupled fracture propagation model relying on the phase field method to simulate thermal shock-induced fracturing in the deep shale considering dynamic temperature conditions.The validity of this model is confirmed through comparison of experimental and numerical results concerning the THM-coupled stress field and thermal cracking.Special attention is paid to the interaction of thermal shock-induced fractures in deep shale that contains weak planes.The results indicate that thermal shock-induced stress significantly amplifies the tensile stress range and deteriorates rock strength,resulting in a multi-point failure pattern within a fracture.The thermal shock damage degree is closely related to the fracture cooling efficiency,suggesting that considering downhole temperature conditions in THM-coupled fracture stress field calculations is advisable.Thermal shock can activate pre-existing natural fractures and enhance the penetration ability of hydraulic fractures,thereby leading to a fracture network.
基金supported in part by the National Key Research and Development Program of China(Grant No.2022YFB2804401)the National Natural Science Foundation of China(Grant Nos.62334008,62134004,62404218)+1 种基金the Beijing Natural Science Foundation(Grant No.Z220005)Chinese Academy of Sciences(Grant No.ZDBS-LY-JSC008).
文摘The event-based vision sensor(EVS),which can generate efficient spiking data streams by exclusively detecting motion,exemplifies neuromorphic vision methodologies.Generally,its inherent lack of texture features limits effectiveness in complex vision processing tasks,necessitating supplementary visual information.However,to date,no event-based hybrid vision solution has been developed that preserves the characteristics of complete spike data streams to support synchronous computation architectures based on spiking neural network(SNN).In this paper,we present a novel spike-based sensor with digitized pixels,which integrates the event detection structure with the pulse frequency modulation(PFM)circuit.This design enables the simultaneous output of spiking data that encodes both temporal changes and texture information.Fabricated in 180 nm process,the proposed sensor achieves a resolution of 128×128,a maximum event rate of 960 Meps,a grayscale frame rate of 117.1 kfps,and a measured power consumption of 60.1 mW,which is suited for high-speed,low-latency,edge SNNbased vision computing systems.
文摘提出一种可根据负载变化在脉冲宽度调制(pulse width modulation,PWM)和脉冲频率调制(pulse frequency modulation,PFM)两种工作模式间自动切换的降压DC-DC芯片的设计法,推导出临界切换状态下的负载电流值表达式,在此基础上设计了一种PWM/PFM自动切换的DC-DC芯片.该系统在较大的负载变化范围内均具有较高效率.
