This paper aims to study the oscillation of a sparkgenerated submerged bubble located near or inside a circular aperture made in a flat plate using high-speed visualization technique. In the case of a bubble oscillati...This paper aims to study the oscillation of a sparkgenerated submerged bubble located near or inside a circular aperture made in a flat plate using high-speed visualization technique. In the case of a bubble oscillating near an aperture the initial free surface of the water was set at the bottom surface of the plate. The effects of aperture size and bubblefree surface distance on the bubble behavior as well as on the ensuing droplet dynamics are investigated. It was found that the direction of the bubble reentrant jet was towards the aperture or away from it respectively when the normalized aperture size was smaller or greater than a certain critical value. In addition, a toroidal vortex ring was observed to form, which rotated inwards as it moved away from the aperture. It was also found that if the bubble was incepted at a distance sufficiently away from a supercritical size aperture a single droplet could be produced. In the case of a bub- ble initiated in the middle of a circular aperture submerged just beneath the water free surface, the bubble was found to take the shape of an ellipsoid during its expansion. Then a reentrant jet was initiated and pierced the bubble from its top side.展开更多
Structural integrity of the flywheel of reactor coolant pump is important for safe operation of a nuclear power plant. A shrink-fit multi-ring flywheel is designed with a fall-off function, i.e., it will separate from...Structural integrity of the flywheel of reactor coolant pump is important for safe operation of a nuclear power plant. A shrink-fit multi-ring flywheel is designed with a fall-off function, i.e., it will separate from the shaft at a designed fall-off rotation speed, which is determined by the assembly process and the gravity. However, the two factors are ignored in the analytical method based on the Lame's equation. In this work, we conducted fall-off experiments to analyze the two factors and used the experimental data to verify the validity of the analytical method and the finite element method(FEM). The results show that FEM performs better than the analytical method in designing the falloff function of the flywheel, though FEM cannot successfully predict the strain variation with the rotational speed.展开更多
高速铁路信号系统安全数据网承载着我国高速铁路列控系统核心业务,对网络和设备的可靠性和实时性具有极高要求,目前的网络安全防护技术手段尚不能很好地适用于信号系统安全数据网。采用软件定义网络架构,从网络统一管控的角度出发进行...高速铁路信号系统安全数据网承载着我国高速铁路列控系统核心业务,对网络和设备的可靠性和实时性具有极高要求,目前的网络安全防护技术手段尚不能很好地适用于信号系统安全数据网。采用软件定义网络架构,从网络统一管控的角度出发进行探索性研究,提出并设计实现了针对我国高速铁路信号系统安全数据网的安全防护方案SD-SSDN(Software-defined Signal Safety Data Network)。实验结果表明:该防护方案可以有效阻断黑客攻击,提高信号安全数据网的安全性;同时,为了保障高实时性和可靠性,还提出基于SDN多级流表的冗余流表映射技术和自适应链路聚合技术;在10个交换机组成的环网中,链路失效恢复时间约为8ms,可以满足列控系统业务需求。展开更多
文摘This paper aims to study the oscillation of a sparkgenerated submerged bubble located near or inside a circular aperture made in a flat plate using high-speed visualization technique. In the case of a bubble oscillating near an aperture the initial free surface of the water was set at the bottom surface of the plate. The effects of aperture size and bubblefree surface distance on the bubble behavior as well as on the ensuing droplet dynamics are investigated. It was found that the direction of the bubble reentrant jet was towards the aperture or away from it respectively when the normalized aperture size was smaller or greater than a certain critical value. In addition, a toroidal vortex ring was observed to form, which rotated inwards as it moved away from the aperture. It was also found that if the bubble was incepted at a distance sufficiently away from a supercritical size aperture a single droplet could be produced. In the case of a bub- ble initiated in the middle of a circular aperture submerged just beneath the water free surface, the bubble was found to take the shape of an ellipsoid during its expansion. Then a reentrant jet was initiated and pierced the bubble from its top side.
基金supported by the National Natural Science Foundation of China(No.51576125)
文摘Structural integrity of the flywheel of reactor coolant pump is important for safe operation of a nuclear power plant. A shrink-fit multi-ring flywheel is designed with a fall-off function, i.e., it will separate from the shaft at a designed fall-off rotation speed, which is determined by the assembly process and the gravity. However, the two factors are ignored in the analytical method based on the Lame's equation. In this work, we conducted fall-off experiments to analyze the two factors and used the experimental data to verify the validity of the analytical method and the finite element method(FEM). The results show that FEM performs better than the analytical method in designing the falloff function of the flywheel, though FEM cannot successfully predict the strain variation with the rotational speed.
文摘高速铁路信号系统安全数据网承载着我国高速铁路列控系统核心业务,对网络和设备的可靠性和实时性具有极高要求,目前的网络安全防护技术手段尚不能很好地适用于信号系统安全数据网。采用软件定义网络架构,从网络统一管控的角度出发进行探索性研究,提出并设计实现了针对我国高速铁路信号系统安全数据网的安全防护方案SD-SSDN(Software-defined Signal Safety Data Network)。实验结果表明:该防护方案可以有效阻断黑客攻击,提高信号安全数据网的安全性;同时,为了保障高实时性和可靠性,还提出基于SDN多级流表的冗余流表映射技术和自适应链路聚合技术;在10个交换机组成的环网中,链路失效恢复时间约为8ms,可以满足列控系统业务需求。
