Dynamic Effect of Rolling Massage on Blood Flow

The Chinese traditional medical massage has been used as a natural therapy to eliminate some diseases. Here, the effect of the rolling massage frequency to the blood flow in the blood vessels under the rolling massage manipulation is studied by the lattice Boltzmann simulation. The simulation results show that when the frequency is smaller than or comparable to the pulsatile frequency of the blood flow, the effect on the blood flux by the rolling massage is small. 011 the contrast, if the frequency is twice or more times of the pulsatile frequency of the blood flow, the blood flux is greatly enhanced and increases linearly with respect to the frequency. Similar behavior has also been observed on the shear stress on the blood vessel walls. The result is helpful for understanding that the rolling massage has the function of promoting the blood circulation and removing the blood stasis.     

Effect of Rolling Massage on Particle Moving Behaviour in Blood Vessels

The rolling massage manipulation is a classic Chinese massage, which is expected to eliminate many diseases. Here the effect of the rolling massage on the particle moving property in the blood vessels under the rolling massage manipulation is studied by the lattice Boltzmann simulation. The simulation results show that the particle moving behaviour depends on the rolling velocity, the distance between particle position and rolling position. The average values, including particle translational velocity and angular velocity, increase as the rolling velocity increases almost linearly. The result is helpful to understand the mechanism of the massage and develop the rolling techniques.     

Lattice Boltzmann simulation of behaviour of particles moving in blood vessels under the rolling massage

The rolling massage is one of the most important manipulations in Chinese massage, which is expected to eliminate many diseases. Here, the effect of the rolling massage on a pair of particles moving in blood vessels under rolling massage manipulation is studied by the lattice Boltzmann simulation. The simulated results show that the motion of each particle is considerably modified by the rolling massage, and it depends on the relative rolling velocity, the rolling depth, and the distance between particle position and rolling position. Both particles' translational average velocities increase almost linearly as the rolling velocity increases, and obey the same law. The increment of the average relative angular velocity for the leading particle is smaller than that of the trailing one. The result is helpful for understanding the mechanism of the massage and to further develop the rolling techniques.     

Lattice BGK Simulations of the Blood Flow in Elastic Vessels

The lattice Boltzmann method is applied to study the flow in elastic blood vessels. The volume-flow rate increases considerably when the compliance constant of the blood vessel is below a critical value. There is a region of the compliance constant in which the average volume-flow rate is dramatically enhanced. A harmonic perturbation of the pressure does not change the behaviour of the average volume-flow rate while the harmonic wave attenuates very quickly along the tube when the resonant period is close to that of the input wave. The model, together with the simulation results, is expected to be helpful to understand the mechanism of the blood volume-flow rate related to the compliance constant of the blood vessel, especially on the dependence of the flux of human blood vessel under weather changes, which has medical significance.     

光谱技术检测鲜红斑痣病变程度的MC模拟

在分析鲜红斑痣病理的基础上,根据病变程度改变真皮上层血液层的厚度,并建立相应的光学模型,确定其组织光学参数.通过Monte Carlo模拟,得出：鲜红斑痣皮肤反射光谱与荧光光谱均可反映鲜红斑痣皮肤病变程度,特别是血管直径的变化;当血管直径增大时,鲜红斑痣皮肤反射光谱反射率与荧光光谱强度均明显下降.研究表明反射光谱和荧光光谱可能应用于判断或分析鲜红斑痣皮肤的病变程度,从而为鲜红斑痣的临床治疗方案及治疗效果提供参考.     

一种从辐射噪声中提取调制谱的方法

在水下航行器的辐射噪声中,螺旋桨节拍对航行器的宽带辐射噪声存在着明显的振幅调制,调制频率与航行器螺旋桨的转速有关。该特征可用于估计航行器的速度及目标分类与识别。本文利用子波变换原理,从实测的航行器辐射噪声中提取了它的调制谱,并据此对螺旋桨转速进行了估计,计算机仿真结果与实测的螺旋桨的转速具有良好的一致性。     

基于光纤光栅传感器的体外血管模型应力测量北大核心CSCD

血管中的血液流动会对血管壁产生周向应力,周向应力与血管的结构及功能变化密切相关,测量体外血管模型的周向应力是生物力学研究中较重要的问题。提出了利用光纤光栅测量血管周向应力的方法,基于微流控技术利用钢针模具建立了集成光纤光栅的三维圆形血管模型,通过仿真研究了不同流动速度与应力的关系。仿真结果得到流速在8 mm/s~75 mm/s范围内,应力随速度的改变呈线性变化。利用光纤光栅传感器测量了流体流动时产生的周向应力,根据实验得到了光栅波长改变量与速度的关系,流速范围在8 mm/s~75 mm/s之间变化时,速度引起波长的变化为0.173 nm。结合仿真实验得到了应力与光栅波长改变量的关系,为血液流动时产生周向应力的体外测量提供了新思路。     

Dynamic modeling of submerged nanoparticle pushing based on atomic force microscopy in liquid medium

This article introduces a theoretical analysis of submerged nanoparticle manipulation in liquid medium using the atomic force microscopy, and gives a review of the major differences between dry and submerged manipulation processes. In this regard, the manipulation is modeled by adding the influences of the hydrodynamic forces surface forces to the manipulation model in dry air. Then, the pushing of a gold nanoparticle of 50-nm radius on a silicon substrate at a velocity of 100 nm/s is simulated, and the dynamic behaviors of the tip and nanoparticle are investigated. The results show that, in water (as compared to air), the required manipulation force and time for nanoparticle sliding and rolling increase by 3.5 and 6.5%, for sliding and 2 and 4.3% for rolling, respectively. Also, in liquids with different viscosities, the critical values related to sliding and rolling have a maximum variation of 17 and 32% for the manipulation time, and 6 and 22% for the manipulation force, respectively, as compared to the critical values related to particle manipulation in air. Moreover, for various submerged lengths of the cantilever in water, the critical values related to sliding and rolling show a maximum time variation of 9 and 10.5%, and 7 and 7.2% (for the manipulation force), respectively. Qualitative comparisons between the obtained results and those of the existing experimental investigations show the advantages of the liquid medium for the manipulation purposes.     

A Deep Neural Network Method for Arterial Blood Flow Profile Reconstruction

Arterial stenosis will reduce the blood flow to various organs or tissues, causing cardiovascular diseases. Although there are mature diagnostic techniques in clinical practice, they are not suitable for early cardiovascular disease prediction and monitoring due to their high cost and complex operation. In this paper, we studied the electromagnetic effect of arterial blood flow and proposed a method based on the deep neural network for arterial blood flow profile reconstruction. The potential difference and weight matrix are used as inputs to the method, and its output is an estimate of the internal blood flow velocity distribution for arterial blood flow profile reconstruction. Firstly, the weight matrix is input into the convolutional auto-encode (CAE) network to extract its features. Then, the weight matrix features and potential difference are combined to obtain the features of the blood velocity distribution. Finally, the velocity features are reconstructed into blood flow velocity distribution by a convolution neural network (CNN). All data sets are obtained from a model of the carotid artery with different rates of stenosis in a uniform magnetic field by COMSOL. The results show that the average root mean square error of the reconstruction results obtained by the proposed method is 0.0333, and the average correlation coefficient is 0.9721, which is better than the corresponding indicators of the Tikhonov, back propagation (BP) and CNN methods. The simulation results show that the proposed method can achieve high accuracy in blood flow profile reconstruction and is of great significance for the early diagnosis of arterial stenosis and other vessel diseases.     

Cine-MR Detection of Geometrical Size Anomalies in the Descending Chest Aorthic Artery for Some Heart Pathologies.

In this MRI work the Fast Gradient-Echo technique has been applied to the detection of the geometrical and elastic properties of the chest aorthic descending artery to check probable troubles in the blood flux which subtend several heart pathologies. The average diameter and the time variations of the aorthic vessel have been measured in the axial scanning plane to minimize the experimental errors. From the analysis of the vessel average diameter and the related root mean square deviation, a parameter named Contractility has been defined, in close relation with the elastic properties of the aorthic vessel. This parameter measured in patients affected from heavy cardiac pathologies such as aorthic arc aneurysm and right atrial mixoma shows remarkable variations when compared to the values obtained in healthy subjects. The use of the Contractility is suggested for a quick MRI determination of these cardiocircolatory pathologies.     

Deformation and Motion of a Red Blood Cell in a Shear Flow Simulated by a Lattice Boltzmann Model

A lattice Boltzmann model is presented to simulate the deformation and motions of a red blood cell (RBC) in a shear flow. The curvatures of the membrane of a static RBC with different chemical potential drops calculated by our model agree with those computed by a shooting method very well. Our simulation results show that in a shear flow, a biconcave RBC becomes highly flattened and undergoes tank-treading motion. With intrinsically parallel dynamics, this lattice Boltzmann method is expected to find wide applications to both single and multi-vesicles suspension as well as complex open membranes in various fluid flows for a wide range of Reynolds numbers.     

Asymmetry of the water flux induced by the deformation of a nanotube

The behavior of nano-confined water is expected to be fundamentally different from the behavior of bulk water.At the nanoscale,it is still unclear whether water flows more easily along the convergent direction or the divergent one,and whether a hourglass shape is more convenient than a funnel shape for water molecules to pass through a nanotube.Here,we present an approach to explore these questions by changing the deformation position of a carbon nanotube.The results of our molecular dynamics simulation indicate that the water flux through the nanotube changes significantly when the deformation position moves away from the middle region of the tube.Different from the macroscopic level,we find water flux asymmetry(water flows more easily along the convergent direction than along the divergent one),which plays a key role in a nano water pump driven by a ratchet-like mechanism.We explore the mechanism and calculate the water flux by means of the Fokker-Planck equation and find that our theoretical results are well consistent with the simulation results.Furthermore,the simulation results demonstrate that the effect of deformation location on the water flux will be reduced when the diameter of the nanochannel increases.These findings are helpful for devising water transporters or filters based on carbon nanotubes and understanding the molecular mechanism of biological channels.     

Blood vessel enhancement for DSA images based on adaptive multi-scale filtering

Digital subtraction angiography (DSA) plays a significant role in the diagnosis, treatment planning and assessment of diseases. However, because of the geometrical complexity and fine characteristics of blood vessel structures, accurate and robust detection of blood vessels still remains a problem. In this paper, a blood vessel enhancement algorithm is proposed. The main purpose of this work is to improve the visual quality of blood vessels in DSA images. The new blood vessel enhancement algorithm is based on the multi-scale space theory and Hessian matrix. Not only the eigenvalues of Hessian matrix but also the angles between eigenvectors are utilized for the blood vessel enhancement of DSA. The filter parameters and scale factors are decided adaptively. Eigenvalues of the Hessian matrix are also used for the noise elimination. Experimental results show that the proposed algorithm has a good performance in blood vessel enhancement of DSA images. The proposed algorithm filters image background and non-vascular structure effectively. The deformation of blood vessels occurred in the enhancement process is avoided and more small blood vessels are visible in DSA images.     

Flow correlated percolation during vascular remodeling in growing tumors

A theoretical model based on the molecular interactions between a growing tumor and a dynamically evolving blood vessel network describes the transformation of the regular vasculature in normal tissues into a highly inhomogeneous tumor specific capillary network. The emerging morphology, characterized by the compartmentalization of the tumor into several regions differing in vessel density, diameter, and necrosis, is in accordance with experimental data for human melanoma. Vessel collapse due to a combination of severely reduced blood flow and solid stress exerted by the tumor leads to a correlated percolation process that is driven towards criticality by the mechanism of hydrodynamic vessel stabilization.     

立式低温容器真空丧失热分层现象数值模拟研究

对立式低温容器在真空丧失条件下的内部热分层现象进行了分析,采用双流体模型结合CFD求解器计算了立式低温容器内的流动及传热过程,考察了侧壁及底部热通量对液体热分层现象的影响。结果表明:侧壁热通量较底部热通量更易使容器内部产生热分层;容器内部形成的环流及其成长是导致热分层及温度突跳的根本原因。     

圆柱形水下爆炸实验容器壁部强度设计研究

 基于薄壁壳理论和水下爆炸理论,对圆柱形水下爆炸实验容器在爆炸冲击波作用下弹性范围内的壁部应变进行了理论分析和实验研究。导出了圆柱形水下爆炸实验容器在爆炸冲击波作用下壁部弹性应变与容器直径、壁厚及内部爆炸药量之间的关系,并对计算结果进行了实验验证。实验表明公式求解结果与实验结果具有较好的一致性。     

脂肪颗粒在颈动脉中的运动及其对血液动力学的影响

很多研究表明, 动脉粥样硬化通常发生在具有复杂血液动力学的区域, 比如分叉动脉和弯曲动脉. 这些地方常伴随有低壁面剪切力或震荡壁面剪切力, 这是动脉粥样硬化形成的一大诱因. 使用计算流体力学软件对2D颈动脉分叉血管进行了模拟, 研究了脂肪颗粒在颈动脉中的运动及其对血液动力学的影响. 研究表明: 1)血管狭窄对于脂肪颗粒的运动有重要影响, 同时也影响栓塞的形成; 2)脂肪颗粒可能会黏附在血管壁面, 但由于血流的冲击作用, 脂肪颗粒会随后在壁面略微铺展; 3)颈动脉狭窄区域后方是下一个血栓的可能生长位点; 4)当栓塞形成时, 速度和壁面剪切力分布将变得复杂多变, 这对于血管是有害的.     

血液对流换热的数值计算

在血管壁施加第三类边界条件是计算血液与组织间对流换热的一种近似计算方法.为分析其可行性,用有限元数值模拟方法计算血管分支结构中血液与组织的对流换热,得到不同流速和半径下分支血管内血液的截面平均Nu数沿管长的变化曲线.结果表明,血管树中分支血管的Nu数变化幅度不大,且趋于稳定值的速度很快.以相同边界条件下包含简单血管系统的舌体为例,分别用近似方法和完全耦合计算方法,进行血液流场和舌体温度场模拟.通过比较计算结果,得出两种方法得到的温度场分布趋势基本相同;用完全耦合计算方法得到的舌体温度略高于用近似方法得到的舌体温度,两者差值小于0.2℃.     

船舶运动状态下风速风向测量补偿与数字仿真

为了研究船舶运动状态下的风速风向精确测量,设计了一种船舶风速风向动态测量及误差补偿的数字仿真系统。通过对船舶航行状态下的风速风向测量原理进行分析,建立了船舶平面运动的相对风速风向和真风风速风向的解算模型,并根据船舶空间运动的风速风向测量及其误差补偿算法,对船舶横摇、纵摇状态下的风速风向的动态测量和误差补偿进行了数字仿真。数字仿真结果表明,该方法能够消除船舶航行时的运动姿态对风速风向测量带来的影响,为船舶的操纵控制和航行安全提供了精确和可靠的风速风向数据信息。     

不同激光参数照射下血管中血栓的演变

目前,激光是治疗葡萄酒色斑(Port Wine Stain,PWS)最有效的疗法。然而,由于选择性光热效应机理研究的欠缺,PWS的临床彻底清除率依然很低(<20%)。本文利用鼠脊视窗模型研究了不同激光参数照射下血管中光凝块和血栓的演变规律,以期为开发新的治疗策略提供依据。实验结果表明,Nd:YAG激光(1064 nm)照射后血管中只出现光凝块。长脉宽532nm激光照射后血管中首先形成光凝块,随着光凝块的流走,血栓产生并粘着血管壁。血栓面积随时间先增大后减小,存在时间长达4 h以上。短脉宽532 nm激光照射后,则形成非粘着血管壁血栓并随血流流走。由于形成完全堵塞血管的血栓是清除血管的前提,长脉宽532 nm激光联合抗血栓药物治疗PWS有望改善激光治疗PWS疗效。