构建基于患者个体化的Stanford B型主动脉夹层计算流体力学数值模拟分析模型

目的:探索简便、高效、精确的构建基于真实人体解剖形态结构的Stanford B型主动脉夹层计算流体力学数值模拟分析模型的方法.方法:利用Siemens Sensation Cardiac 64层螺旋CT薄层扫描技术,基于1mm层厚获取6例Stanford B型主动脉夹层连续断层DICOM格式图像,导入Materialise MIMICS v12.11软件,界定目标区域后生成三维动脉模型,经网格优化处理去除低质量及相交面网格,保存结果输出,导入TGrid 5.0软件,对主动脉面网格模型进行几何修复,使面网格扭曲率<0.75,采用自由分网方式生成Stanford B型主动脉夹层计算流体力学分析体网格模型,并对所构建模型进行血流属性、流场边界等界定,初步验证模型的有效性.结果:通过初步计算求解,确定所构建的6例Stanford B型主动脉夹层计算流体力学分析模型分别包含1857030,1820501,1844181,1849651,1858246及1814914个四面体单元.结论:利用64层螺旋CT薄层扫描技术获取DICOM格式连续断层CT图像可快速、准确地构建Stanford B型主动脉夹层计算流体力学数值模拟分析模型,为进一步的计算流体力学分析奠定了良好的基础.     

Comparison of Aerodynamic Forces and Moments Calculated by Three-dimensional Unsteady Blade Element Theory and Computational Fluid Dynamics

In previous work,we modified blade element theory by implementing three-dimensional wing kinematics and modeled the unsteady aerodynamic effects by adding the added mass and rotational forces.This method is referred to as Unsteady Blade Element Theory (UBET).A comparison between UBET and Computational Fluid Dynamics (CFD) for flapping wings with high flapping frequencies (＞30 Hz) could not be found in literature survey.In this paper,UBET that considers the movement of pressure center in pitching-moment estimation was validated using the CFD method.We investigated three three-dimensional (3D) wing kinematics that produce negative,zero,and positive aerodynamic pitching moments.For all cases,the instantaneous aerodynamic forces and pitching moments estimated via UBET and CFD showed similar trends.The differences in average vertical forces and pitching moments about the center of gravity were about 10％ and 12％,respectively.Therefore,UBET is proven to reasonably estimate the aerodynamic forces and pitching moment for flight dynamic study of FW-MAV.However,the differences in average wing drags and pitching moments about the feather axis were more than 20％.Since study of aerodynamic power requires reasonable estimation of wing drag and pitching moment about the feather axis,UBET needs further improvement for higher accuracy.     

A study of wall shear stress in 12 aneurysms with respect to different viscosity models and flow conditions

Recent computational fluid dynamics (CFD) studies relate abnormal blood flow to rupture of cerebral aneurysms. However, it is still debated how to model blood flow with sufficient accuracy. Common assumptions made include Newtonian behaviour of blood, traction free outlet boundary conditions and inlet boundary conditions based on available literature. These assumptions are often required since the available patient specific data is usually restricted to the geometry of the aneurysm and the surrounding vasculature. However, the consequences of these assumptions have so far been inadequately addressed.     

Computational fluid dynamics modeling of mass transfer behavior in a bioreactor for hairy root culture. I. Model development and experimental validation

A two-dimensional axisymmetric computational fluid dynamics (CFD) model based on a porous media model and a discrete population balance model was established to investigate the hydrodynamics and mass transfer behavior in an airlift bioreactor for hairy root culture.During the hairy root culture of Echinacea purpurea, liquid and gas velocity, gas holdup, mass transfer rate, as well as oxygen concentration distribution in the airlift bioreactor were simulated by this CFD model. Simulative results indicated that liquid flow and turbulence played a dominant role in oxygen mass transfer in the growth domain of the hairy root culture. The dissolved oxygen concentration in the hairy root clump increased from the bottom to the top of the bioreactor cultured with the hairy roots, which was verified by the experimental detection of dissolved oxygen concentration in the hairy root clump. This methodology provided insight understanding on the complex system of hairy root culture and will help to eventually guide the bioreactor design and process intensification of large-scale hairy root culture.     

对比增强高分辨率MRI评价大脑中动脉斑块的时程变化与脑脊液炎性因子水平的相关性

摘要 目的：探究对比增强高分辨率MRI评价大脑中动脉斑块的时程变化与脑脊液炎性因子水平的相关性。方法：采用高脂饮食联合两次球囊内皮剥脱术,在45只新西兰白兔的主动脉中诱导动脉粥样硬化斑块。27只兔子继续相同的饮食,而18只兔子除了饮食外还接受了吡格列酮（10 mg/kg口服）。36只动物接受了¹⁸F-FDG-PET/CT,45只动物在基线、治疗开始后1个月和3个月接受了 DCE-MRI。同时,监测脑脊液代谢参数。成像完成后进行主动脉组织学分析和相关性分析。结果：¹⁸F-FDG-PET/CT检测到对照组平均标准化摄取值（SUV）升高（P<0.05）,而治疗组SUV值稳定。DCE-MRI 检测到吡格列酮组的曲线下面积（AUC）降低（P<0.05）。与对照组相比,治疗组的脑脊液IL-6和TNF-α含量、载脂蛋白B密度以及氧化磷脂密度均显著降低,差异有统计学意义（P<0.05）,而平滑肌肌动蛋白密度差异无统计学意义（P＞0.05）。检测到SUV和IL-6以及AUC和TNF-α之间存在强正相关（分别为 r²=0.86,P<0.05和 r²=0.66,P=0.004）。结论：18F-FDG-PET/CT和DCE-MRI无创地证明了吡格列酮对粥样斑块的抗炎作用,并可分析大脑中动脉斑块的时程变化与脑脊液炎性因子水平的相关性,两种成像方式均可监测动脉粥样硬化的炎症变化,具有较高应用价值。