The hydrophobicity of the lotus leaf is mainly due to its surface micro-nano composite structure. In order to mimic the lotus structure, ZnO micro-nano composite hydrophobic films were prepared via the three-step meth...The hydrophobicity of the lotus leaf is mainly due to its surface micro-nano composite structure. In order to mimic the lotus structure, ZnO micro-nano composite hydrophobic films were prepared via the three-step method. On thin buffer films of SiO2, which were first fabricated on glass substrates by the so,gel dip-coating method, a ZnO seed layer was deposited via RF magnetron sputtering. Then two different ZnO films, micro-nano and micro-only flowerlike structures, were grown by the hydrothermal method. The prepared films have different hydrophobic properties after surface modification. The structures of the obtained ZnO films were characterized using x-ray diffraction and field-emission scanning electron microscopy. A conclusion that a micro-nano composite structure is more beneficial to hydrophobicity than a micro-only structure was obtained through research into the effect of structure on hydrophobic properties.展开更多
A two-dimensional numerical model based on the Navier-Stokes equations and computational Lagrangian-Eulerian advection remap-volume of fluid （CLEAR-VOF） method was developed to simulate wave and flow problems. The N...A two-dimensional numerical model based on the Navier-Stokes equations and computational Lagrangian-Eulerian advection remap-volume of fluid （CLEAR-VOF） method was developed to simulate wave and flow problems. The Navier-Stokes equations were discretized with a three-step finite element method that has a third-order accuracy. In the CLEAR-VOF method, the VOF function F was calculated in the Lagrangian manner and allowed the complicated free surface to be accurately captured. The propagation of regular waves and solitary waves over a flat bottom, and shoaling and breaking of solitary waves on two different slopes were simulated with this model, and the numerical results agreed with experimental data and theoretical solutions. A benchmark test of dam-collapse flow was also simulated with an unstructured mesh, and the capability of the present model for wave and flow simulations with unstructured meshes, was verified. The results show that the model is effective for numerical simulation of wave and flow problems with both structured and unstructured meshes.展开更多
A stable finite element method for the time dependent Navier-Stokes equations was used for studying the wind flow and pollutant dispersion within street canyons. A three-step fractional method was used to solve the ve...A stable finite element method for the time dependent Navier-Stokes equations was used for studying the wind flow and pollutant dispersion within street canyons. A three-step fractional method was used to solve the velocity field and the pressure field separately from the governing equations. The Streamline Upwind Petrov-Galerkin(SUPG) method was used to get stable numerical results. Numerical oscillation was minimized and satisfactory results can be obtained for flows at high Reynolds numbers. Simulating the flow over a square cylinder within a wide range of Reynolds numbers validates the wind field model. The Strouhal numbers obtained from the numerical simulation had a good agreement with those obtained from experiment. The wind field model developed in the present study is applied to simulate more complex flow phenomena in street canyons with two different building configurations. The results indicated that the flow at rooftop of buildings might not be assumed parallel to the ground as some numerical modelers did. A counter-clockwise rotating vortex may be found in street canyons with an inflow from the left to right. In addition, increasing building height can increase velocity fluctuations in the street canyon under certain circumstances, which facilitate pollutant dispersion. At high Reynolds numbers, the flow regimes in street canyons do not change with inflow velocity.展开更多
目的探讨“三步教学法”联合以案例为基础的教学模式(case-based learning,CBL)在研究生介入专业选修课教学实践中的应用效果。方法选取2019年1月至2022年12月于首都医科大学附属北京佑安医院选修肿瘤微创介入治疗基础与进展课程的52名...目的探讨“三步教学法”联合以案例为基础的教学模式(case-based learning,CBL)在研究生介入专业选修课教学实践中的应用效果。方法选取2019年1月至2022年12月于首都医科大学附属北京佑安医院选修肿瘤微创介入治疗基础与进展课程的52名研究生作为研究对象,采用随机数字表法分为研究组与对照组,每组26名。研究组接受“三步教学法”联合CBL教学模式,对照组接受传统讲授式教学方法(lecture based learning,LBL)。比较两组培训前后考试成绩及学员对教学模式的满意度。结果培训前,两组考试成绩比较差异无统计学意义;培训后,两组考试成绩均高于培训前,且研究组高于对照组,差异有统计学意义(P<0.05)。研究组在影像学检查综合分析能力、临床思维能力、文献阅读水平、团队合作能力、学习兴趣、教学方法方面的满意度均高于对照组,差异有统计学意义(P<0.05)。结论“三步教学法”联合CBL在研究生介入专业选修课教学培训中成效显著,且学员满意度较高。展开更多
基金supported by the Science Fund of Anhui Province,China(Grant No 070414187)the National Fund for Fostering Talents in Basic Science of China(Grant No J0630319/J0103)
文摘The hydrophobicity of the lotus leaf is mainly due to its surface micro-nano composite structure. In order to mimic the lotus structure, ZnO micro-nano composite hydrophobic films were prepared via the three-step method. On thin buffer films of SiO2, which were first fabricated on glass substrates by the so,gel dip-coating method, a ZnO seed layer was deposited via RF magnetron sputtering. Then two different ZnO films, micro-nano and micro-only flowerlike structures, were grown by the hydrothermal method. The prepared films have different hydrophobic properties after surface modification. The structures of the obtained ZnO films were characterized using x-ray diffraction and field-emission scanning electron microscopy. A conclusion that a micro-nano composite structure is more beneficial to hydrophobicity than a micro-only structure was obtained through research into the effect of structure on hydrophobic properties.
基金supported by the National Natural Science Foundation of China (Grant No. 50679008)
文摘A two-dimensional numerical model based on the Navier-Stokes equations and computational Lagrangian-Eulerian advection remap-volume of fluid （CLEAR-VOF） method was developed to simulate wave and flow problems. The Navier-Stokes equations were discretized with a three-step finite element method that has a third-order accuracy. In the CLEAR-VOF method, the VOF function F was calculated in the Lagrangian manner and allowed the complicated free surface to be accurately captured. The propagation of regular waves and solitary waves over a flat bottom, and shoaling and breaking of solitary waves on two different slopes were simulated with this model, and the numerical results agreed with experimental data and theoretical solutions. A benchmark test of dam-collapse flow was also simulated with an unstructured mesh, and the capability of the present model for wave and flow simulations with unstructured meshes, was verified. The results show that the model is effective for numerical simulation of wave and flow problems with both structured and unstructured meshes.
文摘A stable finite element method for the time dependent Navier-Stokes equations was used for studying the wind flow and pollutant dispersion within street canyons. A three-step fractional method was used to solve the velocity field and the pressure field separately from the governing equations. The Streamline Upwind Petrov-Galerkin(SUPG) method was used to get stable numerical results. Numerical oscillation was minimized and satisfactory results can be obtained for flows at high Reynolds numbers. Simulating the flow over a square cylinder within a wide range of Reynolds numbers validates the wind field model. The Strouhal numbers obtained from the numerical simulation had a good agreement with those obtained from experiment. The wind field model developed in the present study is applied to simulate more complex flow phenomena in street canyons with two different building configurations. The results indicated that the flow at rooftop of buildings might not be assumed parallel to the ground as some numerical modelers did. A counter-clockwise rotating vortex may be found in street canyons with an inflow from the left to right. In addition, increasing building height can increase velocity fluctuations in the street canyon under certain circumstances, which facilitate pollutant dispersion. At high Reynolds numbers, the flow regimes in street canyons do not change with inflow velocity.
文摘目的探讨“三步教学法”联合以案例为基础的教学模式(case-based learning,CBL)在研究生介入专业选修课教学实践中的应用效果。方法选取2019年1月至2022年12月于首都医科大学附属北京佑安医院选修肿瘤微创介入治疗基础与进展课程的52名研究生作为研究对象,采用随机数字表法分为研究组与对照组,每组26名。研究组接受“三步教学法”联合CBL教学模式,对照组接受传统讲授式教学方法(lecture based learning,LBL)。比较两组培训前后考试成绩及学员对教学模式的满意度。结果培训前,两组考试成绩比较差异无统计学意义;培训后,两组考试成绩均高于培训前,且研究组高于对照组,差异有统计学意义(P<0.05)。研究组在影像学检查综合分析能力、临床思维能力、文献阅读水平、团队合作能力、学习兴趣、教学方法方面的满意度均高于对照组,差异有统计学意义(P<0.05)。结论“三步教学法”联合CBL在研究生介入专业选修课教学培训中成效显著,且学员满意度较高。
