A second-moment closure for the near-wall turbulence is proposed. The limiting behaviour of this closure near a wall is consistent with that of the exact Reynolds-stress transport equations, and it converts asymptotic...A second-moment closure for the near-wall turbulence is proposed. The limiting behaviour of this closure near a wall is consistent with that of the exact Reynolds-stress transport equations, and it converts asymptotically into a high- Reynolds-number closure remote from the wall. The closure is applied to a pressure- driven 3D transient channel flow. The predicted results are in fair agreement with the DNS data.展开更多
目的:通过3D/4D超声鼻唇表面成像,观察胎儿鼻唇部表面形态结构,排除鼻唇部表面异常。方法:使用VOLUSON GE 730及VOLUSON GE E8容积探头,通过对2063例孕22-25周胎儿进行3D/4D鼻唇部表面成像,要求清晰显示鼻尖、鼻柱、鼻翼、双鼻孔、鼻唇...目的:通过3D/4D超声鼻唇表面成像,观察胎儿鼻唇部表面形态结构,排除鼻唇部表面异常。方法:使用VOLUSON GE 730及VOLUSON GE E8容积探头,通过对2063例孕22-25周胎儿进行3D/4D鼻唇部表面成像,要求清晰显示鼻尖、鼻柱、鼻翼、双鼻孔、鼻唇沟、上下唇、下颌,观察胎儿鼻部形状、大小、结构、唇部完整性和连续性。结果:2063例孕22~25周胎儿中,获得清晰完整鼻唇3D/4D表面成像1689例,显示率为81.87%;获取部分鼻唇表面成像306例,显示率为14.83%;模糊或不能成像68例,占3.3%。结论:孕中期大部分胎儿3D/4D超声能获取鼻唇完整清晰表面成像,形象、逼真、直观显示鼻唇表面形态结构正常与否;掌握必要的检查方法、注意事项及技巧能提高鼻唇部清晰完整表面成像显示率。展开更多
基金The project supported by the National Natural Science Foundation of China
文摘A second-moment closure for the near-wall turbulence is proposed. The limiting behaviour of this closure near a wall is consistent with that of the exact Reynolds-stress transport equations, and it converts asymptotically into a high- Reynolds-number closure remote from the wall. The closure is applied to a pressure- driven 3D transient channel flow. The predicted results are in fair agreement with the DNS data.
文摘目的:通过3D/4D超声鼻唇表面成像,观察胎儿鼻唇部表面形态结构,排除鼻唇部表面异常。方法:使用VOLUSON GE 730及VOLUSON GE E8容积探头,通过对2063例孕22-25周胎儿进行3D/4D鼻唇部表面成像,要求清晰显示鼻尖、鼻柱、鼻翼、双鼻孔、鼻唇沟、上下唇、下颌,观察胎儿鼻部形状、大小、结构、唇部完整性和连续性。结果:2063例孕22~25周胎儿中,获得清晰完整鼻唇3D/4D表面成像1689例,显示率为81.87%;获取部分鼻唇表面成像306例,显示率为14.83%;模糊或不能成像68例,占3.3%。结论:孕中期大部分胎儿3D/4D超声能获取鼻唇完整清晰表面成像,形象、逼真、直观显示鼻唇表面形态结构正常与否;掌握必要的检查方法、注意事项及技巧能提高鼻唇部清晰完整表面成像显示率。
