目的:研究胚胎移植时气液滴距子宫基底距离和妊娠率之间的关系。方法:回顾性研究南方医院妇产科生殖医学中心2005.01-2006.09间超声引导下取卵周期胚胎移植者610例。通过腹部B超测量移植内管尖距宫底距离及移植时推出气液滴距宫底距离,...目的:研究胚胎移植时气液滴距子宫基底距离和妊娠率之间的关系。方法:回顾性研究南方医院妇产科生殖医学中心2005.01-2006.09间超声引导下取卵周期胚胎移植者610例。通过腹部B超测量移植内管尖距宫底距离及移植时推出气液滴距宫底距离,分析各组间妊娠率的关系及与异常妊娠的关系。结果:不同胚胎移植内管尖距宫腔基底距离(transfer distance from the fundus,TDF)之间的妊娠率无显著差异,>2cm组妊娠率最高,<1cm组最低,但2cm组早期自然流产率较高。不同气液滴到宫底距离与妊娠率无关。其中2cm组妊娠率最高(61.1%),<1cm组妊娠率最低(42.9%),而0距离组自然流产率最高(20%)。气液滴-移植内管尖距离3组妊娠率无显著差异。结论:气液滴及移植内管尖位置与妊娠率没有显著性差异。展开更多
Modelling and simulations are conducted on velocity slip and interfacial momentum transfer for supersonic two-pha.se (gas-droplet) flow in the transient section inside and outside a Laval jet(LJ). The initial velocity...Modelling and simulations are conducted on velocity slip and interfacial momentum transfer for supersonic two-pha.se (gas-droplet) flow in the transient section inside and outside a Laval jet(LJ). The initial velocity slip between gas and droplets causes an interfacial momentum transfer flux as high as (2.0-5.0) x 104 Pa. The relaxation time corresponding to this transient process is in the range of 0.015-0.090ms for the two-phase flow formed inside the LJ and less than 0.5ms outside the LJ. It demonstrates the unique performance of this system for application to fast chemical reactions using electrically active media with a lifetime in the order of 1 ms. Through the simulations of the transient processes with initial Mach number Mg from 2.783 to 4.194 at different axial positions inside the LJ, it is found that Mg has the strongest effect on the process. The momentum flux increases as the Mach number decreases. Due to compression by the shock wave at the end of the LJ, the flow pattern becomes two dimensional and viscous outside the LJ. Laser Doppler velocirneter (LDV) measurements of droplet velocities outside the LJ are in reasonably good agreement with the results of the simulation.展开更多
Absorption of gaseous species into stationary droplets is a fundamental interest of mass transfer between liquid droplets and ambient gas, which plays a key role in atmospheric environment control and many industrial ...Absorption of gaseous species into stationary droplets is a fundamental interest of mass transfer between liquid droplets and ambient gas, which plays a key role in atmospheric environment control and many industrial applications. In this paper, two different considerations including equilibrium and non-equilibrium relations at the interface are used to analyze and predict the absorption time for a physical absorption at a relatively low solubility of gas. For the equilibrium pattern, in the beginning period of absorption, the mass transfer rate is considerably rapid and afterward becomes slower and slower and finally comes to almost zero as the droplet concentration closes to the saturated value. Differently, when the non-equilibrium model is adopted, the interfacial concentration increases gradually with the bulk concentration of liquid droplet, and the absorption rate mildly decelerates with the increase of bulk one throughout the process, which leads to a longer absorption time. Based on the diffusion equation of species, the concentration distribution within the droplet at different times is computed. A solution for CO2 absorption into a small water droplet is given.展开更多
In this article, a theoretical model for predicting the equilibrium morphology of gas–liquid Janus droplets was built. Based on this model, the effects of bubble radius and volume ratio on morphology change was syste...In this article, a theoretical model for predicting the equilibrium morphology of gas–liquid Janus droplets was built. Based on this model, the effects of bubble radius and volume ratio on morphology change was systematically studied. The increase of bubble radius causes the two parts(bubble and oil drop) in Janus droplets tend to merge while the impact of volume ratio is complicated. When volume ratio increases, these two parts firstly tend to merge, then gradually separate. The accuracy of this model was verified by experimental results.展开更多
This paper analyzes the entropy generation rate of simple pure droplet combustion in a tempera-ture-elevated air convective environment based on the solutions of flow, and heat and mass transfer between the two phases...This paper analyzes the entropy generation rate of simple pure droplet combustion in a tempera-ture-elevated air convective environment based on the solutions of flow, and heat and mass transfer between the two phases. The flow-field calculations are carried out by solving the respective conservation equations for each phase, accounting for the droplet deformation with the axisymmetric model. The effects of the temperature, velocity and oxygen fraction of the free stream air on the total entropy generation rate in the process of the droplet combustion are investigated. Special attention is given to analyze the quantitative effects of droplet deformation. The results re-veal that the entropy generation rate due to chemical reaction occupies a large fraction of the total entropy generated, as a result of the large areas covered by the flame. Although, the magnitude of the entropy generation rate per volume due to heat transfer and combined mass and heat transfer has a magnitude of one order greater than that due to chemical reaction, they cover a very limited area, leading to a small fraction of the total entropy generated. The en-tropy generation rate due to mass transfer is negligible. High temperature and high velocity of the free stream are advantageous to increase the exergy efficiency in the range of small Reynolds number (<1) from the viewpoint of the second-law analysis over the droplet lifetime. The effect of droplet deformation on the total entropy generation is the modest.展开更多
文摘目的:研究胚胎移植时气液滴距子宫基底距离和妊娠率之间的关系。方法:回顾性研究南方医院妇产科生殖医学中心2005.01-2006.09间超声引导下取卵周期胚胎移植者610例。通过腹部B超测量移植内管尖距宫底距离及移植时推出气液滴距宫底距离,分析各组间妊娠率的关系及与异常妊娠的关系。结果:不同胚胎移植内管尖距宫腔基底距离(transfer distance from the fundus,TDF)之间的妊娠率无显著差异,>2cm组妊娠率最高,<1cm组最低,但2cm组早期自然流产率较高。不同气液滴到宫底距离与妊娠率无关。其中2cm组妊娠率最高(61.1%),<1cm组妊娠率最低(42.9%),而0距离组自然流产率最高(20%)。气液滴-移植内管尖距离3组妊娠率无显著差异。结论:气液滴及移植内管尖位置与妊娠率没有显著性差异。
基金Supported by the National Natural Science Foundation of China (No. 29876022) and Grant of State Key Laboratory of High Speed Hydrodynamics (No. 2007).
文摘Modelling and simulations are conducted on velocity slip and interfacial momentum transfer for supersonic two-pha.se (gas-droplet) flow in the transient section inside and outside a Laval jet(LJ). The initial velocity slip between gas and droplets causes an interfacial momentum transfer flux as high as (2.0-5.0) x 104 Pa. The relaxation time corresponding to this transient process is in the range of 0.015-0.090ms for the two-phase flow formed inside the LJ and less than 0.5ms outside the LJ. It demonstrates the unique performance of this system for application to fast chemical reactions using electrically active media with a lifetime in the order of 1 ms. Through the simulations of the transient processes with initial Mach number Mg from 2.783 to 4.194 at different axial positions inside the LJ, it is found that Mg has the strongest effect on the process. The momentum flux increases as the Mach number decreases. Due to compression by the shock wave at the end of the LJ, the flow pattern becomes two dimensional and viscous outside the LJ. Laser Doppler velocirneter (LDV) measurements of droplet velocities outside the LJ are in reasonably good agreement with the results of the simulation.
基金Supported by the National Natural Science Foundation of China (No. 20176036).
文摘Absorption of gaseous species into stationary droplets is a fundamental interest of mass transfer between liquid droplets and ambient gas, which plays a key role in atmospheric environment control and many industrial applications. In this paper, two different considerations including equilibrium and non-equilibrium relations at the interface are used to analyze and predict the absorption time for a physical absorption at a relatively low solubility of gas. For the equilibrium pattern, in the beginning period of absorption, the mass transfer rate is considerably rapid and afterward becomes slower and slower and finally comes to almost zero as the droplet concentration closes to the saturated value. Differently, when the non-equilibrium model is adopted, the interfacial concentration increases gradually with the bulk concentration of liquid droplet, and the absorption rate mildly decelerates with the increase of bulk one throughout the process, which leads to a longer absorption time. Based on the diffusion equation of species, the concentration distribution within the droplet at different times is computed. A solution for CO2 absorption into a small water droplet is given.
基金Supported by the National Natural Science Foundation of China(21476121,21322604)Beijing Natural Science Foundation(2162020)a Foundation for Tsinghua Independent Research Projects(2014z21026)
文摘In this article, a theoretical model for predicting the equilibrium morphology of gas–liquid Janus droplets was built. Based on this model, the effects of bubble radius and volume ratio on morphology change was systematically studied. The increase of bubble radius causes the two parts(bubble and oil drop) in Janus droplets tend to merge while the impact of volume ratio is complicated. When volume ratio increases, these two parts firstly tend to merge, then gradually separate. The accuracy of this model was verified by experimental results.
基金Supported by the National Natural Science Foundation of China （51276157） and the Natural Science Foundation of Zhejiang Province （LY 12E060026）.
文摘This paper analyzes the entropy generation rate of simple pure droplet combustion in a tempera-ture-elevated air convective environment based on the solutions of flow, and heat and mass transfer between the two phases. The flow-field calculations are carried out by solving the respective conservation equations for each phase, accounting for the droplet deformation with the axisymmetric model. The effects of the temperature, velocity and oxygen fraction of the free stream air on the total entropy generation rate in the process of the droplet combustion are investigated. Special attention is given to analyze the quantitative effects of droplet deformation. The results re-veal that the entropy generation rate due to chemical reaction occupies a large fraction of the total entropy generated, as a result of the large areas covered by the flame. Although, the magnitude of the entropy generation rate per volume due to heat transfer and combined mass and heat transfer has a magnitude of one order greater than that due to chemical reaction, they cover a very limited area, leading to a small fraction of the total entropy generated. The en-tropy generation rate due to mass transfer is negligible. High temperature and high velocity of the free stream are advantageous to increase the exergy efficiency in the range of small Reynolds number (<1) from the viewpoint of the second-law analysis over the droplet lifetime. The effect of droplet deformation on the total entropy generation is the modest.
