The study aims to explore the damage characteristics and protection technologies of liquid-filled structures under high-speed projectile impact.A series of penetration impact experiments were conducted by focusing on ...The study aims to explore the damage characteristics and protection technologies of liquid-filled structures under high-speed projectile impact.A series of penetration impact experiments were conducted by focusing on different air layer configurations.By using high-speed camera and dynamic measurement systems,the effects of air layers on the projectile penetration,pressure wave propagation,cavitation evolution,and structural dynamic responses were analyzed.The results showed that the rarefaction wave reflected from the air-liquid interface significantly reduced the peak and specific impulse of the initial pressure wave,thereby diminishing the impact load on the structure.Additionally,the compressibility of air layers also attenuated the cavitation extrusion load.Both front and rear plates exhibited superimposed deformation modes,i.e.,local deformation or petal fracture with global deformation.Air layers effectively mitigated global deformation.However,when the air layer was positioned on the projectile's trajectory,it split the water-entry process and velocity attenuation of the projectile into two relatively independent phases.And the secondary water entry pressure wave caused more severe local deformation and petal fractures on the rear plate.展开更多
Controlled,guided munitions can reduce dispersion in the shot,while providing the capability of engaging both stationary and maneuvering targets.The Netherlands Organisation for Applied Scientific Research has develop...Controlled,guided munitions can reduce dispersion in the shot,while providing the capability of engaging both stationary and maneuvering targets.The Netherlands Organisation for Applied Scientific Research has developed a fin-less control technology called Stagnation Pressure Reaction Control(SPRC)that takes stagnation pressure air and directs it sideways to control non-spinning projectiles.In a previous study,this technology was demonstrated at Mach 2 wind-tunnel conditions to achieve up to 1.5°controllable angle of incidence for a non-spinning,aerodynamically unstable projectile-like test object.In an operational scenario,the decelerating projectile will experience a decline in control force while the simultaneous forward shift of the center of pressure increases the need for control force.Furthermore,angles of incidence exceeding 1.5°will be experienced under realistic flight conditions,especially against maneuvering targets.This work addresses these challenges and presents an operational feasibility study for a practical application of SPRC in a non-spinning mid-caliber gun-launched projectile,using experiment data on control latency and force of the earlier study.It illustrates the combined effect of the control-and stability dynamics and underlines the potential of an SPRC projectile as a precisionoperation ammunition.This research revealed that SPRC technology can stabilize and control the hypothesized projectile in a direct fire scenario against stationary and maneuvering targets.展开更多
The rheological properties of two kinds of oil-based drilling fluids with typically composition were studied at pressures up to 138 MPa and temperatures up to 204 ℃ using the RheoChan 7400 Rheometer.The experimental ...The rheological properties of two kinds of oil-based drilling fluids with typically composition were studied at pressures up to 138 MPa and temperatures up to 204 ℃ using the RheoChan 7400 Rheometer.The experimental results show that the apparent viscosity,plastic viscosity and yield point decrease with the increase of temperature,and increase with the increase of pressure.The effect of pressure on the apparent viscosity,plastic viscosity and yield point is considerable at ambient temperature.However,this effect gradually reduces with the increase of temperature.The major factor influencing the rheological properties of oil-based drilling fluids is temperature instead of pressure in the deep sections of oil wells.On the basis of numerous experiments,the model for predict the apparent viscosity,plastic viscosity and yield point of oil-based drilling fluids at high temperature and pressure was established using the method of regressive analysis.It is confirmed that the calculated data are in good agreement with the measured data,and the correlation coefficients are more than 0.98.The model is convenient for use and suitable for the application in drilling operations.展开更多
This paper presents a computational study of the air flow past a triangular boattailed projectile.The study shows that there is a single normal shock wave impinges the projectile at transonic speeds.At supersonic spee...This paper presents a computational study of the air flow past a triangular boattailed projectile.The study shows that there is a single normal shock wave impinges the projectile at transonic speeds.At supersonic speeds,the formed shock waves are smeared compared to a conical boattailed projectile.Also,there is a reduction of the wake region behind the triangular base and the rear stagnation point is nearer to the projectile base resulting in base drag reduction.Moreover,there is an improvement of the stability of the triangular boattailed projectile since a lower overturning moment is incurred.展开更多
目的:总结重症监护室(ICU)经口气管插管病人口腔黏膜压力性损伤预防的最佳证据,并探讨基于此证据制订的实践方案的应用效果。方法:检索UpToDate、BMJ Best Practice、Joanna Briggs Institute(JBI)循证卫生保健中心数据库等国内外数据...目的:总结重症监护室(ICU)经口气管插管病人口腔黏膜压力性损伤预防的最佳证据,并探讨基于此证据制订的实践方案的应用效果。方法:检索UpToDate、BMJ Best Practice、Joanna Briggs Institute(JBI)循证卫生保健中心数据库等国内外数据库及相关专业组织网站中ICU经口气管插管病人口腔黏膜压力性损伤预防的相关文献,检索时限为建库至2023年5月31日。由2名经过循证培训的研究者独立进行文献质量评价和提取数据。随后,基于证据制订相应的实践方案并在某三级甲等医院综合ICU开展循证实践,评价实践效果。结果:共纳入12篇文献,从风险评估、插管管理、口腔护理等方面总结出12项预防策略。第2轮实践后,高危病人识别率从62.1%提高至91.7%,气管插管固定规范率从60.50%升至100.00%,口腔护理规范率从42.70%升至100.00%,口腔黏膜压力性损伤发生率从35.2%降至10.0%,2期及以上损伤比例从14.8%降至0;医护人员相关知识得分从(12.5±2.3)分提高至(18.6±1.1)分。结论:总结的ICU经口气管插管病人口腔黏膜压力性损伤预防策略可有效提高口腔黏膜压力性损伤的预防效果、高危病人识别率及护理规范化水平,降低口腔黏膜压力性损伤发生率,提升医护人员相关知识。展开更多
基金the financial support provided by National Natural Science Foundation of China(Grant Nos.52271338,52371342 and 51979277).
文摘The study aims to explore the damage characteristics and protection technologies of liquid-filled structures under high-speed projectile impact.A series of penetration impact experiments were conducted by focusing on different air layer configurations.By using high-speed camera and dynamic measurement systems,the effects of air layers on the projectile penetration,pressure wave propagation,cavitation evolution,and structural dynamic responses were analyzed.The results showed that the rarefaction wave reflected from the air-liquid interface significantly reduced the peak and specific impulse of the initial pressure wave,thereby diminishing the impact load on the structure.Additionally,the compressibility of air layers also attenuated the cavitation extrusion load.Both front and rear plates exhibited superimposed deformation modes,i.e.,local deformation or petal fracture with global deformation.Air layers effectively mitigated global deformation.However,when the air layer was positioned on the projectile's trajectory,it split the water-entry process and velocity attenuation of the projectile into two relatively independent phases.And the secondary water entry pressure wave caused more severe local deformation and petal fractures on the rear plate.
文摘Controlled,guided munitions can reduce dispersion in the shot,while providing the capability of engaging both stationary and maneuvering targets.The Netherlands Organisation for Applied Scientific Research has developed a fin-less control technology called Stagnation Pressure Reaction Control(SPRC)that takes stagnation pressure air and directs it sideways to control non-spinning projectiles.In a previous study,this technology was demonstrated at Mach 2 wind-tunnel conditions to achieve up to 1.5°controllable angle of incidence for a non-spinning,aerodynamically unstable projectile-like test object.In an operational scenario,the decelerating projectile will experience a decline in control force while the simultaneous forward shift of the center of pressure increases the need for control force.Furthermore,angles of incidence exceeding 1.5°will be experienced under realistic flight conditions,especially against maneuvering targets.This work addresses these challenges and presents an operational feasibility study for a practical application of SPRC in a non-spinning mid-caliber gun-launched projectile,using experiment data on control latency and force of the earlier study.It illustrates the combined effect of the control-and stability dynamics and underlines the potential of an SPRC projectile as a precisionoperation ammunition.This research revealed that SPRC technology can stabilize and control the hypothesized projectile in a direct fire scenario against stationary and maneuvering targets.
基金Project(50574061) supported by the National Natural Science Foundation of ChinaProject(IRT0411) supported by the Changjiang Scholars and Innovative Research Team,Ministry of Education
文摘The rheological properties of two kinds of oil-based drilling fluids with typically composition were studied at pressures up to 138 MPa and temperatures up to 204 ℃ using the RheoChan 7400 Rheometer.The experimental results show that the apparent viscosity,plastic viscosity and yield point decrease with the increase of temperature,and increase with the increase of pressure.The effect of pressure on the apparent viscosity,plastic viscosity and yield point is considerable at ambient temperature.However,this effect gradually reduces with the increase of temperature.The major factor influencing the rheological properties of oil-based drilling fluids is temperature instead of pressure in the deep sections of oil wells.On the basis of numerous experiments,the model for predict the apparent viscosity,plastic viscosity and yield point of oil-based drilling fluids at high temperature and pressure was established using the method of regressive analysis.It is confirmed that the calculated data are in good agreement with the measured data,and the correlation coefficients are more than 0.98.The model is convenient for use and suitable for the application in drilling operations.
文摘This paper presents a computational study of the air flow past a triangular boattailed projectile.The study shows that there is a single normal shock wave impinges the projectile at transonic speeds.At supersonic speeds,the formed shock waves are smeared compared to a conical boattailed projectile.Also,there is a reduction of the wake region behind the triangular base and the rear stagnation point is nearer to the projectile base resulting in base drag reduction.Moreover,there is an improvement of the stability of the triangular boattailed projectile since a lower overturning moment is incurred.
文摘目的:总结重症监护室(ICU)经口气管插管病人口腔黏膜压力性损伤预防的最佳证据,并探讨基于此证据制订的实践方案的应用效果。方法:检索UpToDate、BMJ Best Practice、Joanna Briggs Institute(JBI)循证卫生保健中心数据库等国内外数据库及相关专业组织网站中ICU经口气管插管病人口腔黏膜压力性损伤预防的相关文献,检索时限为建库至2023年5月31日。由2名经过循证培训的研究者独立进行文献质量评价和提取数据。随后,基于证据制订相应的实践方案并在某三级甲等医院综合ICU开展循证实践,评价实践效果。结果:共纳入12篇文献,从风险评估、插管管理、口腔护理等方面总结出12项预防策略。第2轮实践后,高危病人识别率从62.1%提高至91.7%,气管插管固定规范率从60.50%升至100.00%,口腔护理规范率从42.70%升至100.00%,口腔黏膜压力性损伤发生率从35.2%降至10.0%,2期及以上损伤比例从14.8%降至0;医护人员相关知识得分从(12.5±2.3)分提高至(18.6±1.1)分。结论:总结的ICU经口气管插管病人口腔黏膜压力性损伤预防策略可有效提高口腔黏膜压力性损伤的预防效果、高危病人识别率及护理规范化水平,降低口腔黏膜压力性损伤发生率,提升医护人员相关知识。
