As a critical component of the oil drilling control system,blowout preventers(BOPs)shear failure accidents can occur in case of blowout incidents.Existing methods based on simulation and empirical formula do not perfo...As a critical component of the oil drilling control system,blowout preventers(BOPs)shear failure accidents can occur in case of blowout incidents.Existing methods based on simulation and empirical formula do not perform well in systematically evaluating the shear capacity of ram BOPs,and relevant research and testing are conducted under static ideal conditions,leading to a lack of effective guidance in field operations.Aiming at the above problems,this paper proposes a shear capability evaluation method of ram BOPs based on digital twin.The shear mechanism of ram BOPs is analyzed and the digital twin model of a ram BOP driven by real-time drilling data is constructed through joint simulation and model reduction.Finally,the shear capacity of ram BOP is evaluated multi-dimensionally in real-time by using the built digital twin model.The model can also simulate shearing process offline under different preset conditions.The results provide a theoretical basis for field operation and performance evaluations of the shear capability of ram BOPs.展开更多
This study presents an interdisciplinary framework to enhance the radar cross-section(RCS)reduction of next-generation long-range cruise missiles by integrating Mn Zn ferrite/epoxy-based radar-absorbing materials(RAM)...This study presents an interdisciplinary framework to enhance the radar cross-section(RCS)reduction of next-generation long-range cruise missiles by integrating Mn Zn ferrite/epoxy-based radar-absorbing materials(RAM),electromagnetic simulation,and multipath-aware flight profiles.The best-performing RAM exhibited a reflection loss of-23 d B at 9.8 GHz with a 3.4 GHz effective absorption bandwidth,supported by complex permittivity/permeability analysis and Lorentz-based dispersion modeling.When applied to realistic missile geometries,simulations showed RCS reductions exceeding 25 d B.Furthermore,integrating this material into a dynamic radar detection algorithm shows how sea-surface multipath effects can increase the generation of null channels,reducing reaction time by up to 94 s under simulated conditions.Results underscore the effectiveness of integrating RAM with adaptive trajectory profiles to develop new doctrines for future radio-frequency(RF)low-observable,long-range cruise missiles.展开更多
Magnetic tunnel junction(MTJ) based spin transfer torque magnetic random access memory(STT-MRAM) has been gaining tremendous momentum in high performance microcontroller(MCU) applications. As e Flash-replacement type ...Magnetic tunnel junction(MTJ) based spin transfer torque magnetic random access memory(STT-MRAM) has been gaining tremendous momentum in high performance microcontroller(MCU) applications. As e Flash-replacement type MRAM approaches mass production, there is an increasing demand for non-volatile RAM(nv RAM) technologies that offer fast write speed and high endurance. In this work, we demonstrate highly reliable 4 Mb nv RAM type MRAM suitable for industry and auto grade-1 applications. This nv RAM features retention over 10 years at 125 ℃, endurance of 1 × 1012cycles with 20 ns write speed, making it ideal for applications requiring both high speed and broad temperature ranges. By employing innovative MTJ materials, process engineering, and a co-optimization of process and design, reliable read and write performance across the full temperature range between -40 to 125 ℃, and array yield that meets sub-1 ppm error rate was significantly improved from 0 to above 95%, a concrete step toward applications.展开更多
The Hydrodynamic Ram(HRAM)effect occurs when a high kinetic energy projectile penetrates a fluid filled area,e.g.,a liquid filled tank.The projectile transfers its momentum and kinetic energy to the fluid,what causes ...The Hydrodynamic Ram(HRAM)effect occurs when a high kinetic energy projectile penetrates a fluid filled area,e.g.,a liquid filled tank.The projectile transfers its momentum and kinetic energy to the fluid,what causes a sudden,local pressure rise,further expanding as primary shock wave in the fluid and developing a cavity.It is possible that the entire tank ruptures due to the loads transferred through the fluid to its surrounding structure.In the past decades,additionally to experimental investigations,HRAM has been studied using various computational approaches particularly focusing on the description of the Fluid-Structure Interaction(FSI).This article reviews the published experimental,analytical and numerical results and delivers a chronological overview since the end of World War II.Furthermore,HRAM mitigation measures are highlighted,which have been developed with the experimental,analytical and numerical toolboxes matured over the past 80 years.展开更多
基金financially supported by the National Key Research and Development Program of China(Grant No.2024YFC3014001)National Natural Science Foundation of China(Grant No.52474274)。
摘要As a critical component of the oil drilling control system,blowout preventers(BOPs)shear failure accidents can occur in case of blowout incidents.Existing methods based on simulation and empirical formula do not perform well in systematically evaluating the shear capacity of ram BOPs,and relevant research and testing are conducted under static ideal conditions,leading to a lack of effective guidance in field operations.Aiming at the above problems,this paper proposes a shear capability evaluation method of ram BOPs based on digital twin.The shear mechanism of ram BOPs is analyzed and the digital twin model of a ram BOP driven by real-time drilling data is constructed through joint simulation and model reduction.Finally,the shear capacity of ram BOP is evaluated multi-dimensionally in real-time by using the built digital twin model.The model can also simulate shearing process offline under different preset conditions.The results provide a theoretical basis for field operation and performance evaluations of the shear capability of ram BOPs.
摘要This study presents an interdisciplinary framework to enhance the radar cross-section(RCS)reduction of next-generation long-range cruise missiles by integrating Mn Zn ferrite/epoxy-based radar-absorbing materials(RAM),electromagnetic simulation,and multipath-aware flight profiles.The best-performing RAM exhibited a reflection loss of-23 d B at 9.8 GHz with a 3.4 GHz effective absorption bandwidth,supported by complex permittivity/permeability analysis and Lorentz-based dispersion modeling.When applied to realistic missile geometries,simulations showed RCS reductions exceeding 25 d B.Furthermore,integrating this material into a dynamic radar detection algorithm shows how sea-surface multipath effects can increase the generation of null channels,reducing reaction time by up to 94 s under simulated conditions.Results underscore the effectiveness of integrating RAM with adaptive trajectory profiles to develop new doctrines for future radio-frequency(RF)low-observable,long-range cruise missiles.
基金supported by National Science and Technology Major Project (2020AAA0109003)the support from Hangzhou Innovation Team Program (TD2022018)。
摘要Magnetic tunnel junction(MTJ) based spin transfer torque magnetic random access memory(STT-MRAM) has been gaining tremendous momentum in high performance microcontroller(MCU) applications. As e Flash-replacement type MRAM approaches mass production, there is an increasing demand for non-volatile RAM(nv RAM) technologies that offer fast write speed and high endurance. In this work, we demonstrate highly reliable 4 Mb nv RAM type MRAM suitable for industry and auto grade-1 applications. This nv RAM features retention over 10 years at 125 ℃, endurance of 1 × 1012cycles with 20 ns write speed, making it ideal for applications requiring both high speed and broad temperature ranges. By employing innovative MTJ materials, process engineering, and a co-optimization of process and design, reliable read and write performance across the full temperature range between -40 to 125 ℃, and array yield that meets sub-1 ppm error rate was significantly improved from 0 to above 95%, a concrete step toward applications.
摘要The Hydrodynamic Ram(HRAM)effect occurs when a high kinetic energy projectile penetrates a fluid filled area,e.g.,a liquid filled tank.The projectile transfers its momentum and kinetic energy to the fluid,what causes a sudden,local pressure rise,further expanding as primary shock wave in the fluid and developing a cavity.It is possible that the entire tank ruptures due to the loads transferred through the fluid to its surrounding structure.In the past decades,additionally to experimental investigations,HRAM has been studied using various computational approaches particularly focusing on the description of the Fluid-Structure Interaction(FSI).This article reviews the published experimental,analytical and numerical results and delivers a chronological overview since the end of World War II.Furthermore,HRAM mitigation measures are highlighted,which have been developed with the experimental,analytical and numerical toolboxes matured over the past 80 years.