超声粒子图像测速技术及应用

心血管疾病的产生与动脉血流的流动状况密切相关。然而,目前普遍应用的超声多普勒成像技术不能精确测量复杂血流流场信息。本文提出了一种基于超声造影微泡的超声全流场粒子图像测速技术,能够获得多维流速速度信息,且不依赖于声束与速度向量之间的夹角。本文首先着重阐述了超声全流场粒子测速技术的基本原理以及系统组成,并对直管流和旋转流场流体动力学特性进行了实验测试研究,实验结果表明本技术能够测量全流场速度,并可作为表征复杂血流流场的有力手段。      

Fast and exact flow measurements with the fast Fourier flow technique

The fast Fourier flow technique offers a convenient way for extremely exact flow measurements. In combination with ECG gating, arterial flow can be studied. The total acquisition time for a single measurement is about 10 s, an ECG-gated cine sequence can be acquired in about 4 min. Fast Fourier flow can, therefore, be easily combined with a conventional imaging examination.     

Optical coherence Doppler tomography quantifies laser speckle contrast imaging for blood flow imaging in the rat cerebral cortex

A dual-imaging modality is demonstrated for high-resolution quantitative imaging of local cerebral blood flow in the rat cortex by combining simultaneous spectral-domain Doppler optical coherence tomography (SDOCT) and full-field laser speckle contrast imaging (LSCI). Preliminary studies in tissue flow phantom and cocaine-induced cerebral blood flow changes indicated that by correlating coregistered cortical arterial blood flow, the relative measurement of flow changes by LSCI could be accurately calibrated by the absolute flow imaging provided by SDOCT (least square fit, r(2) approximately 0.96). Quantitative LSCI of cerebral blood flow is crucial to the quantitative analyses of the spatiotemporal hemodynamics of functional brain activations and thus improved understanding of neural process.     

Carotid blood flow measurement accelerated by compressed sensing: Validation in healthy volunteers

Measurement of blood flow by cine phase-contrast MRI is a valuable technique in the study of arterial disease but is time consuming, especially for multi-slice (4D) studies. Compressed sensing is a modern signal processing technique that exploits sparse signal representations to enable sampling at lower than the conventional Nyquist rate. It is emerging as a powerful technique for the acceleration of MRI acquisition. In this study we evaluated the accuracy of phase-contrast carotid blood flow measurement in healthy volunteers using threefold undersampling of kt-space and compressed sensing reconstruction.     

Robust estimation of the cerebral blood flow in arterial spin labelling

The introduction of arterial spin labelling (ASL) techniques in magnetic resonance imaging (MRI) has made feasible a non-invasive measurement of the cerebral blood flow (CBF). However, to date, the low signal-to-noise ratio of ASL gives us no option but to repeat the acquisition to accumulate enough data in order to get a reliable signal. The perfusion signal is then usually extracted by averaging across the repetitions. But the sample mean is very sensitive to outliers. A single incorrect observation can therefore be the source of strong detrimental effects on the perfusion-weighted image estimated with the sample mean.     

Echo particle image velocimetry technique and its applications

Developments of many cardiovascular problems have been shown to have a close relationship with arterial flow conditions.However,current ultrasound/Doppler imaging techniques cannot resolve the complex nature of arterial blood flow.We have recently developed a novel contrast-based echo particle imaging technique(Echo PIV) without angel dependence for non-invasively measuring multi-component flow vectors.This study introduces the Echo PIV principles,system characterization and utility examination to characterize hemodynamics in pipe laminar flow and rotating flow.Echo PIV measurement results show its capability to resolve the complex hemodynamics including proximal flow velocity vectors,and velocity mapping. The Echo PIV method provides an easy,direct and accurate means of quantitatively yet non-invasively characterizing the complex vascular hemodynamics.     

Noninvasive optical method of measuring tissue and arterial saturation: an application to absolute pulse oximetry of the brain

We present a frequency-domain optical method for real-time noninvasive measurement of absolute tissue and arterial saturation. This method is based on quantitative measurement of the tissue absorption spectrum (for tissue saturation) and of the amplitude of the arterial-pulsation-induced absorption oscillations (for arterial saturation) at eight wavelengths in the range 633-841 nm. We report results obtained from readings taken from the forehead of a healthy volunteer, showing baseline saturation values of 74.7+/-0.2% (tissue) and 96.9+/-0.5% (arterial). These values dropped to minimum values of 71.6+/-0.2% and 90.0+/-0.2% , respectively, after 1 min of reduced inspired oxygen concentration [10% (by volume) O(2) from a baseline value of 21% O(2) ].     

主干道交通流的路口效应

基于Nagel-Schreckenberg交通流模型的演化规则,建立了路口等距分布的主干道交通流模型,在开放性边界及路口以同步红绿灯控制的条件下对交通流进行了数值模拟.分析结果发现：主干道的通行能力由路口的通行能力决定;低密度时,流量与路口数目无关,利用平均场方法,可算出平均速度随绿灯周期变化的极值位置;高密度时,流量与路口数目有关,通过调整交通灯周期,可使主干道处于最佳交通状态. 关键词： 元胞自动机 交通流 数值模拟 平均场理论     

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.     

Measurement of vibrational energy flow in a plate with high energy flow boundary crossing using electronic speckle pattern interferometry

The measurement of vibrational energy flow is an important tool in understanding the vibrational behaviour of structures. In the past, because of transducer constraints, the measurement of vibrational energy flow was mostly restricted to single point measurements. However, recent developments in advanced laser measurement techniques, such as electronic speckle pattern interferometry (ESPI), have gained interest in applying two-dimensional, multi-point measurement techniques to the estimation of vibrational energy flow. This paper addresses the measurement of vibrational energy flow in a plate by using an ESPI based vibrational energy flow measurement technique. A radially symmetric bending wave plate vibration model is introduced and theoretical expressions for energy-based quantities are derived. To assess the accuracy of the measurement method, these theoretical quantities are compared to synthetic results derived from the ESPI energy flow measurement technique. The ESPI measurement technique is also applied to an experimental ‘infinite’ plate. Thus, a specially designed experimental apparatus was constructed so as to minimise undesired wave reflections in the plate and, thus, achieve a high energy flow boundary crossing at the edges of the plate. To reduce the effect of optical noise contamination on the ESPI measured out-of-plane plate displacement data, optimal filters were applied prior to the vibrational energy flow computation. To appraise the accuracy of the experimental method, measured vibrational power on the plate is compared with measured vibrational input power. A difference of less than 1 dB between both quantities indicates that vibrational energy flow within a rectangular plate that contains radially symmetric wave propagation can be measured to a good degree of accuracy if appropriate filtering is applied.     

测量组织局部血液灌注率的表面热干扰法

1日u云去正常的血液灌注是机体组织重要的生理要素之一，组织所需的氧、营养和药物靠灌注的血液来运输供应。心肌缺血（即冠心病）是当前困扰人们的发病率高的严重疾病之一。脑对血液的供应则更是敏感，脑血管的局部栓塞将导致局部脑组织缺血甚至坏死。因此，组织灌注状况的检测不仅对于生理和病理研究是重要的，对临床医学也是十分重要的。事实上，某些非缺血性疾病的治疗（例如癌瘤的热疗）过程也直接或间接地涉及到组织的灌注率。寻求一种测量组织灌注率的方法一直是人们孜孜以求的。近年来，各种测量方法的研究已有相当的发展山，其中热…     

基于非接触电导的气液两相流参数检测系统

研究了电容耦合式非接触电导检测技术(C~4D)应用于气液两相流测量的可行性,建立了一套基于非接触电导的毫米级气液两相流参数检测系统。利用所建立的系统,在内径为5 mm,9 mm的水平管上进行了气液两相流实验,获得了不同流型下的电导测量信号,并对段塞流、波状流、泡状流和环状流四种典型流型下的电导信号进行了分析与比较。研究结果表明,所建立的基于非接触电导的气液两相流参数检测系统是有效的,C~4D技术应用于气液两相流参数测量是可行的。不同流型下所获的电导信号特征均表现出明显差异,有望用于流型辨识。     

差压法测量两相流相含率的研究

本文通过差压式测量方法,对气液两相流中含气率及油水两相流中含水率的测量进行了深入的试验研究。通过水平及垂直上升段的结构组合,测量气液两相流中的含气率值,在对流型测量与分析的基础上,建立了不同流型下垂直上升段与水平段摩擦压降间的修正关系式,减小了测量误差;通过采用一缓流的垂直下降段,测量油水两相流中的含水率值,获得了好的结果。     

光纤深井水温梯度传感器

深井水温梯度精确地反映了地表热流量的大小。本文先简述了地表热流量与地震预报的关系,然后介绍了地表热流测量技术的现状,最后详细报告了精度达10^-5到10^-6℃、一次可测得10^-5个热流值的光纤深井水温梯度传感器的理论和实验研究结果。     

电阻层析成像技术在两相流测量中的应用

过程层析成像技术能实时提供封闭管道、容器等过程设备内物场运动状态的二／三维测量信息,它为解决两相流参数的检测问题提供一种新的途径。本文以基于电学敏感原理的电阻层析成像技术为测量手段,实现在多相流实验装置上对气／水、油／水两相流二维／三维时空分布信息的实际测量;介绍了基于测量数据特性分析的在线流型识别技术和相含率的估计方法,应用现代数据处理和模式识别技术进行数据融合与提取,实现两相管流流型识别和分相含率的估计;通过开展相关测量的研究,初步实现两相流中离散相流量的测量。     

在线超声波流量监测系统设计及其应用

为解决地源热泵系统中的进出水流量测量,设计研究基于超声波时差法原理的非接触式在线流量监测装置。系统以STM32F407 ZE为主控制器,定时采集流量、完成数据封包、加密和远端服务器交互任务;以MSP430F2618为流量测量控制器,采用时差法以TDC-GP22精准测量超声波在介质中传播时间,实现管道流体流速、流量实时监测。系统测试结果实现流量数据测量及上传存储到远端服务器,满足地源热泵系统流量监测需求。     

Non-intrusive flow measurement based on a distributed feedback fiber laser

We propose a new non-intrusive flow measurement method using the distributed feedback fiber laser(DFB-FL)as a sensor to monitor flow in the pipe.The relationship between the wavelength of the DFB-FL and the liquid flow rate in the pipeline is derived.Under the guidance of this theory,the design and test of the flow sensor is completed.The response curve is relatively flat in the frequency range of 10 Hz to 500 Hz,and the response of the flow sensor has high linearity.The flow from 0.6 m^3/h to 25.5 m^3/h is accurately measured under the energy analysis method in different frequency intervals.A minimum flow rate of 0.046 m/s is achieved.The experimental results demonstrate the feasibility of the new non-intrusive flow measurement method based on the DFB-FL and accurate measurement of small flow rates.     

Blood flow and arterial endothelial dysfunction: Mechanisms and implications

The arterial endothelium exquisitely regulates vascular function, and endothelial dysfunction plays a critical role in the development of atherosclerosis. Atherosclerotic lesions develop preferentially at arterial branches and bifurcations where the blood flow is disturbed. Understanding the basis for this observation requires elucidating the effects of blood flow on the endothelial cell (EC) function. The goal of this review is: (1) to describe our current understanding of the relationships between arterial blood flow and atherosclerosis, (2) to present the wide array of flow-induced biological responses in ECs, and (3) to discuss the mechanisms by which ECs sense, transmit, and transduce flow-derived mechanical forces. We conclude by presenting some future perspectives in the highly interdisciplinary field of EC mechanotransduction.     

基于扩散相关光谱的血流检测方法研究

组织血流信息在临床诊断和治疗中具有重要的作用,无创血流检测是医患双方的期望。研究采用了近红外扩散相关光谱方法对生物组织血流进行无创检测,理论分析了散射光斑强度的变化和被测组织中血细胞运动状态的函数关系,建立了检测组织血流的理论模型及检测系统。该系统通过求解组织表面散射光斑电场强度的时间自相关函数来推断组织中血细胞的运动状态,进行组织血流的定量分析。采用健康人体前臂袖带加压实验模型对该系统进行了验证,实验结果验证了该系统进行组织无创血流检测的可行性,同时也表明该系统可以提供从浅层到深层的组织血流变化信息。     

基于齿轮传动与红外遥感技术测量流速实验的设计与实现

流体流速是流体力学研究中最重要的参数之一,是判断流动稳定性与力学计算的基础,流速测量是实验研究中最必要的环节.本文主要对齿轮的各项物理特性及红外遥感技术进行深入的研究,设计了一组可以同时测出水流的平均速度与当前时刻水流瞬时速度的实验装置,以解决目前实验室测水流速课程中测量数据单一,实验仪器繁多等问题.设计的实验内容包括齿轮传动比的测量、基于单片机和齿轮组的路程时间测量,以及红外测速仪的瞬时速度读取,实验环节环环相扣,可以更好地锻炼学生的独立研究能力及培养学生的思维缜密性.通过上述实验,可以较为准确地测量出流体的平均流速以及在当前时刻的瞬时流速,并通过灵敏度的计算判断出各个参数对流速的影响比例.