Early prediction of myocardial viability after acute myocardial infarction by two-dimensional speckle tracking imaging

Background Identifying the transmural extent of myocardial necrosis and the degree of myocardial viability in acute myocardial infarction （AMI） is important clinically. The aim of this study was to assess myocardial viability using two-dimensional speckle tracking imaging （2D-STI） in patients with AMI. Methods 2D-STI was performed at initial presentation, three days, and six months after primary percutaneous coronary intervention （PCI） in 30 patients with AMI, who had a left anterior descending coronary artery （LAD） culprit lesion. In addition, 20 patients who had minimal stenotic lesions （〈 30% stenosis） on coronary angiography were also included in the control group. At six months dobutamine echocardiography was performed for viability assessment in seven segments of the LAD territory. According to the recovery of wall motion abnormality, segments were classified as viable or non-viable. Results A total of 131 segments were viable, and 44 were nonviable. Multivariate analysis revealed significant differences between the viable and nonviable segments in the peak systolic strain, the peak systolic strain rate at initial presentation, and peak systolic strain rate three days after primary PCI. Among these, the initial peak systolic strain rate had the highest predictive value for myocardial viability （hazard ratio： 31.22, P 〈 0.01）. Conclusions 2D-STI is feasible for assessing myocardial viability, and the peak systolic strain rate might be the most reliable predictor of myocardial viability in patients with AMI.

Value of myocardial function in children with Kawasaki disease by two-dimensional and three-dimensional ultrasound speckle tracking

Objective:To investigate the value of two-dimensional ultrasound speckle tracking(2D-STI)and three-dimensional ultrasound speckle tracking(3D-STI)in evaluating myocardial function in children with Kawasaki disease.Methods 92 children with Kawasaki disease admitted to our hospital from February 2017 to February 2019 were retrospectively analyzed.50 children who underwent 3D-STI examination were taken as observation group and 42 children who underwent 2D-STI examination were taken as control group.The left ventricular systolic function index,storage time and analysis time of the image,the diameter of coronary artery,the strain difference of left ventricular basal segment,middle segment,apical segment and whole segment were observed.Results The levels of left ventricular end-diastolic volume(LVEDV),left ventricular end-systolic volume(LVESV),left ventricular myocardial mass(LVMI)in the observation group were higher than those in the control group(P<0.05),but there was no statistical difference in left ventricular ejection fraction(LVEF)between the two groups(P>0.05).The storage time and analysis time of the image in the observation group were significantly lower than those in the control group(P<0.05).The left coronary artery(LCA)and right coronary artery(RCA)in the observation group were higher than those in the control group(P<0.05).There was no statistical difference between left anterior descending(LAD)in the two groups(P>0.05).The longitudinal peak systolic strain(LS),circumferential peak systolic strain(CS)and radial peak systolic strain(RS)in the observation group were higher than those in the control group(P<0.05).The global longitudinal peak strain(GLS),global circumferential peak strain(GCS)and global radial peak strain(GRS)in the observation group were higher than those in the control group(P<0.05).LS and CS in the middle segment of the observation group were higher than those in the control group(P<0.05).Conclusions Compared with 2D-STI,3D-STI can objectively and accurately reflect the myocardial function of children with Kawasaki disease.

Evaluation of the Effect of Sigmoid-Shaped Interventricular Septum on Left Ventricular Systolic Function in Patients with Essential Hypertension by Two-Dimensional Speckle Tracking Echocardiography

Objective: To evaluate left ventricular regional and global systolic function by measuring left ventricular longitudinal strain (LS) in hypertensive patients with sigmoid-shaped interventricular septum (SIS) by two-dimensional speckle tracking (2D-STE);in order to explore whether the sigmoid-shaped interventricular septum affects the left ventricular systolic function in patients with hypertension. Methods: Routine echocardiographic parameters were measured in 30 hypertensive patients with SIS (SIS group) and 30 hypertensive patients without SIS (non-SIS group). The left ventricular segments and global LS were measured by 2D-STE, and the two sets of parameters were compared. Results: The value of the thickness of the basal segment of the interventricular septum (IVSBT), the thickness of the middle segment of the interventricular septum (IVSMT) and the ratio of the basal segment of the ventricular septum to the middle segment of the interventricular septum (IVSBT/IVSMT) in SIS group was higher than that in non-SIS group. However, the value of left ventricular outflow tract diameter (LVOTD) in SIS group was lower than that in non-SIS group. There was a significant difference between the two groups (all P Conclusion: SIS affects left ventricular regional systolic function of patients with hypertension. 2D-STE can early evaluate left ventricular longitudinal systolic function in hypertensive patients with SIS.

Value of two-dimensional speckle tracking imaging in quantitative assessment of left ventricular function in patients with OSAS

Objective: To research the clinical application of two-dimensional speckle tracking imaging (2D-STI) in quantitative assessment of left ventricular function in patients with obstructive sleep apnea-hypopnea syndrome (OSAS). Method: From July 2016 to December 2018, 86 patients with OSAS were selected as OSAS group. According to sleep apnea hypopnea index (AHI), they were divided into mild OSAS group (24 cases), moderate OSAS group (29 cases) and severe OSAS group (33 cases). Another 50 healthy volunteers who underwent physical examination in our hospital during the same period were selected as the control group. The left ventricular function of all patients was quantitatively assessed by 2D-STI. The left ventricular function of all patients was quantitatively assessed by 2D-STI. The results of routine echocardiography and left ventricular global strain parameters of the OSAS group, the control group and the OSAS patients with different severity were compared and analyzed. Result: There were no significant differences in the levels of left ventricular ejection fraction (LVEF), left ventricular end diastolic diameter (LVEDd), left ventricular end systolic diameter (LVESd) between the two groups and OSAS patients with different severity (P>0.05). The levels of IVST, LVPW and LVMI in the OSAS group were significantly higher than those in the control group, the levels of end-diastolic interventricular septal thickness (IVS), left ventricular posterior wall thickness (LVPW), left ventricular mass index (LVMI) in the severe OSAS group were significantly higher than those in the mild and moderate OSAS group, and the levels of IVST, LVPW and LVMI in the moderate OSAS group were significantly higher than those in the mild OSAS group, there were significant differences between groups (P<0.05). The levels of GLS, GRS and GCS in the OSAS group were significantly lower than those in the control group (P<0.05). GLS, GRS and GCS levels in the severe OSAS group were significantly lower than those in the mild OSAS group and the moderate OSAS group, while the levels of global longitudinal strain (GLS), global radial strain (GRS) and global circumferential strain (GCS) in the moderate OSAS group were significantly lower than those in the mild OSAS group (P<0.05). Conclusion: The left ventricular systolic function of OSAS patients is obviously impaired. Left ventricular function in OSAS patients can be assessed timely and accurately by two-dimensional speckle tracking imaging.

Adaptive hierarchical block tracking method in case of partial occlusions

In order to solve the tracking problem occurred during occlusions, an adaptive hierarchical block tracking method is proposed after analyzing the changes of the target characteristics under partial occlusions. Firstly, color histogram features are selected to describe the target. The similarity between the target model and the candidates is measured by the Bhattacharyya coefficient, which can also be used to evaluate the degree of occlusions. The object is divided into four blocks when it is occluded, and the mean shift procedure is used to track each block separately. Then, according to the value of the Bhattacharyya coefficient, the partially occluded block is found and divided into four sub-blocks, which are tracked by block matching algorithm separately. Finally, the information of all the blocks is used to determine the displacement vector of the target. Experimental results show that compared to the traditional mean shift tracking method, this method can make full use of the features of the unoccluded sub-blocks, improve the tracking accuracy and solve the target tracking problem in case of partial occlusions.

Interannual and Decadal Variability of the North Pacific Blocking and Its Relationship to SST, Teleconnection and Storm Tracks

Climalological features of mid-latitude blocking occurring over the North Pacific Ocean during 52 winters (December to February) of 1948/1949-1999/2000 are statistically analyzed based on NCEP/ NCAR reanalysis data. Significant interannual variation with a period of about 3-7 years as well as decadal variability is found by wavelet analysis and power spectrum analysis. A decreasing trend of the 2-7 year bandscale-averaged variance occurs throughout the 52 years and an abrupt shift from a higher state to a lower state during the 1970s is also found, which suggests an interdecadal variation of the North Pacific blocking. The possible relationship between the variability of blocking and sea surface temperature (SST), storm tracks and teleconnection are shown using composite analysis. In strong blocking anomaly winter (SBW), the geopotential height anomaly at 500 hPa exhibits a typical PNA (Pacific-North American)-like wave-train pattern in the North Pacific. The storm tracks, representing the activity of transient eddies, extend northeastward to the western coast of North America along the mid latitudes of about 40°-50°N, with the SST anomaly exhibiting a Pacific decadal oscillation (PDO) mode at mid-latitude and a La Ni&#241;a-like pattern along the equator. Contrasting features appear in weak blocking anomaly winter (WBW).

Remote Impact of Blocking Highs on the Sudden Track Reversal of Tropical Cyclones

Previous work showed that some tropical cyclones （TCs） in the western Pacific Ocean undergo sudden track reversal, and the onset, maintenance and decay of blocking highs （BHs） coexisted with 19 of the studied TCs with sudden track reversal. In these cases, the phase relations between the BH, the continental high （CH）, the subtropical high （SH） and the suddenly reversed TCs could be classified into types A, B, C and D. Types C and D were the focal point of this follow-up study, in which Typhoon Pabuk （2007） and Lupit （2009） were employed to conduct numerical simulations. The results showed that the reversed tracks of Pabuk （2007） and Lupit （2009） could have been affected by the BH, particularly in terms of the turning location and the trend of movement after turning. Specifically, the two main features for Pabuk （2007） in the BH perturbations were the deflection of its turning point and a distinct anticlockwise rotation. Lupit （2009） deviated to the southwest and finally made landfall in the Philippines, or experienced further eastward movement, in the perturbed BH. The impact mechanisms can be attributed to the change in the vorticity field transported from the BH, leading to an intensity variation of midlatitude systems. BHs may have a positive feedback effect on the strength of the westerly trough （TR）, as indicated by a weakened and strengthened TR corresponding to negative and positive BH perturbations, respectively.

Point Selection for Triangular 2-D Mesh Design Using Adaptive Forward Tracking Algorithm

Two-dimensional mesh-based motion tracking preserves neighboring relations (through connectivity of the mesh) and also allows warping transformations between pairs of frames;thus, it effectively eliminates blocking artifacts that are common in motion compensation by block matching. However, available uniform 2-D mesh model enforces connec-tivity everywhere within a frame, which is clearly not suitable across occlusion boundaries. To overcome this limitation, BTBC (background to be covered) detection and MF (model failure) detection algorithms are being used. In this algorithm, connectivity of the mesh elements (patches) across covered and uncovered region boundaries are broken. This is achieved by allowing no node points within the background to be covered and refining the mesh structure within the model failure region at each frame. We modify the occlusion-adaptive, content-based mesh design and forward tracking algorithm used by Yucel Altunbasak for selection of points for triangular 2-D mesh design. Then, we propose a new triangulation procedure for mesh structure and also a new algorithm to justify connectivity of mesh structure after motion vector estimation of the mesh points. The modified content-based mesh is adaptive which eliminates the necessity of transmission of all node locations at each frame.

Energy Saving for Automatic Train Control in Moving Block Signaling System

With rapid development of the railway traffic, the moving block signaling system （MBS） method has become more and more important for increasing the track capacity by allowing trains to run in a shorter time-headway while maintaining the required safety margins. In this framework, the tracking target point of the following train is moving forward with its leading train. This paper focuses on the energy saving tracking control of two successive trains in MBS. Nonlinear programming method is used to optimize the energy-saving speed trajectory of the following train. The real-time location of the leading train could be integrated into the optimization process. Due to simplicity, it can be used for online implementation. The feasibility and effectiveness are verified through simulation. The results show that the new method is efficient on energy saving even when disturbances present.

钢管混凝土双块式轨枕无砟轨道结构疲劳性能试验研究

新型钢管混凝土(CFT)双块式轨枕克服了桁架钢筋双块式轨枕存在的生产制造复杂、存放易锈蚀、运营阶段易开裂等问题,可广泛应用于高速铁路和城市轨道交通无砟轨道结构。为检验CFT双块式轨枕无砟轨道结构的疲劳性能,采用11根预制CFT双块式轨枕现浇制作足尺无砟轨道结构节段模型,开展橡胶隔振垫式减振轨道和现浇整体式轨道节段的疲劳试验,揭示其疲劳损伤特性,分析典型疲劳加载循环次数后静载作用下轨道结构应变和变形分布及其演化规律。研究结果表明:1.5倍静轴重的疲劳荷载累计作用500万次后,减振节段及整浇节段CFT双块式轨枕无砟轨道结构混凝土均未出现肉眼可见的裂缝,轨枕与现浇道床整体工作性能良好,疲劳性能满足规范要求;停机开展静载试验过程中轨道结构各测点混凝土横向应变值随荷载增大而近似线性增大,最大拉压应变值均远小于混凝土的极限应变值,工作状态良好;轨道整浇节段道床板中处于整体受拉的状态,可见设置层间连接钢筋实现了道床与底座的共同工作;疲劳试验过程中轨道结构测点竖向位移值总体随着静载的增大而逐渐增大,位移量级较小,满足规范要求,减振轨道节段竖向位移值及其变化率大于整浇轨道节段。研究结果可供类似研究及钢管混凝土双块式轨枕无砟轨道结构工程应用参考。

基于机器视觉的垃圾分类算法研究与应用

垃圾分类识别算法是目前研究的热点问题,本文通过引入色块追踪模块Lab颜色模型对YOLOv3算法进行优化,利用优化后的算法搭建训练模型。并针对目前垃圾类别利用网络爬虫爬取日常生活中常见的垃圾图像并进行分类,形成数据集。其次通过优化的YOLOv3算法对处理好的数据集进行模型训练,将训练后的模型进行模型检测。最后通过实际测试,优化后的YOLOv3算法识别的平均准确率达到了94.33%,与原始算法相比,优化后的算法在稳定性和准确度上都有了明显的改善。

钢管混凝土双块式轨枕道床复合受力性能试验

新型钢管混凝土(CFT)双块式轨枕采用钢管混凝土取代了桁架钢筋的连接构件作用,具有结构简单、安全耐久性好等优点。为研究钢管混凝土双块式轨枕与现浇混凝土道床所形成的轨道结构的复合受力性能,采用某实际工程的材料和工艺制作了一段足尺CFT轨枕减振道床和现浇整体道床,经疲劳试验验证后,用绳锯将其沿横向切割成单承轨台和双承轨台的CFT轨枕道床试件,分别开展试件的轨下截面加载试验和中间截面加载试验,分析道床试件中轨枕、现浇道床、底座板混凝土和钢筋的应力、变形及裂缝的开展演化规律。试验结果表明:CFT轨枕道床受力破坏过程均表现出整体工作、带裂缝工作和破坏的典型三阶段特征;中间截面加载试件破坏时受拉钢筋被拉断而受压区混凝土未被压碎,类似于低筋破坏,轨下截面加载试件因竖向裂缝和弯剪区段斜裂缝之间的混凝土被压碎剥落而失效,受拉纵筋未屈服,类似于斜压破坏;CFT轨枕整体道床试件抗裂能力、承载能力更高,整体道床试件开裂荷载约为减振道床试件相应值的4.7倍,其极限荷载约为减振道床的2.3倍,道床与底座板之间采用拉结钢筋连接后能大幅提升轨道结构刚度和承载能力。CFT轨枕与现浇道床界面黏结及整体工作性能良好,研究成果可供钢管混凝土双块式无砟轨道理论研究和工程应用参考。

平曲线上大调整量弹性支承块式轨道结构动力响应规律分析

基于车辆-轨道耦合动力学及有限元方法,采用ABAQUS®-MATLAB®联合仿真技术,建立车辆-钢轨-弹性支承块式无砟轨道耦合动力学模型,研究不同的车辆类型在多种平曲线线型条件下大调整量弹性支承块式无砟轨道的动力响应特性,分析并评估弹性支承块式无砟轨道用于小半径曲线线路条件的适用性和可行性。研究结果表明:轨下垫板高度的调整对各项指标的影响比支承块帽檐高度调整对各项指标的影响小,当调高从-60 mm增加到60 mm时,轨距扩大量增幅达到了235.00%,当且仅当在调低或调高轨下垫板高度时,轨距扩大量才会发生明显变化;随曲线半径减小,轨距扩大、行车安全性、稳定性等指标随之增大;小曲线半径对支承块的轨距保持能力具有较大影响,当半径减小到2 800 m时,轨距扩大量相比于半径5 000 m的增大了67.50%;与客车相比,当货车运行至小半径曲线路段时,轨距扩大量具有明显的增大趋势,在相同运行条件下,相比于客车的轨距扩大量,货车的轨距扩大量增幅达到110.45%。总体而言,在不同曲线半径、支承块调高情况下,列车运行各项安全性、稳定性及轨距扩大量等指标均在规范规定的安全限值以内,总体来看轨道几何保持能力良好;在实际工程中,当列车尤其是货车经过小曲线半径路段时,应尽量降低行驶速度,以避免困难路段所带来的影响行车安全性、稳定性等隐患。

新型钢管混凝土枕式无砟轨道动力响应试验研究

采用钢管混凝土构件连接轨枕块形成钢管混凝土轨枕,基于钢管混凝土轨枕设计城市轨道交通用钢管混凝土枕式无砟轨道结构。为掌握钢管混凝土枕式无砟轨道结构在城市轨道交通列车运行条件下的力学性能,验证结构设计的安全性、合理性,分别在减振地段、普通地段铺设钢管混凝土枕式无砟轨道,通过行车试验,测试分析不同列车行驶速度下无砟轨道钢轨、轨枕、道床结构的动力响应。研究结果表明:在列车车速为40、60和80 km/h运行条件下,轮轨垂向力最大值为86.18 kN,横向力最大值为13.99 kN,脱轨系数最大值为0.21,轮重减载率最大值为0.23,测试值均明显小于相应的安全限值,无砟轨道结构满足行车安全性要求;在列车动荷载作用下,钢管混凝土轨枕钢管压应力最大值为3.55 MPa,拉应力最大值为3.77 MPa;轨枕块压应力最大值为1.32 MPa;道床钢筋压应力最大值为2.30 MPa,拉应力最大值为3.54 MPa;道床底压应力最大值0.22 MPa。这些动力响应结果均满足材料的的限值,表明结构保持了良好的力学性能,结构设计合理可行。

基于眼动追踪的历史街区意象要素视觉显著性分析——以广州永庆坊为例

历史街区城市意象要素是城市空间感知的重要内容。在原有的认知地图问卷调查基础上,以永庆坊为例,以照片和视频为媒介,利用眼动追踪技术定量分析其意象要素视觉显著性的构成特征。首先总结永庆坊认知地图之中意象要素的视觉显著物。其次利用眼动仪展开实验,收集大样本被试的眼动数据,并进行数学统计分析,以静态照片探究单一场景意象要素视觉显著性的构成机制,以动态视频探究不同场景意象要素之间的视觉显著性差异。最终获得历史街区意象要素视觉显著性的构成规律,并为其实践应用提出相关建议。

桥上CRTSⅠ型双块式无砟轨道早期开裂行为研究

以桥上CRTSⅠ型双块式无砟轨道为研究对象,基于混凝土早期性能发展基本理论,利用Ansys建立三维温度场与应力场分析模型,考虑养护方法、拆模龄期、拆模温度与钢筋直径等参数影响,对双块式无砟轨道早期开裂行为进行数值模拟。结果表明:无砟道床不同位置处混凝土主拉应力整体呈循环上升趋势;拆模前后混凝土应力时程曲线波动程度差异较大,拆模后4 h内道床混凝土主拉应力时程曲线出现明显增长。合理选用养护方式可有效降低道床板早期开裂风险;伴随着拆模龄期的延长与拆模温度的升高,拆模后无砟道床4 h内温度改变量与道床混凝土开裂风险均呈降低趋势;相同配筋率下,减小钢筋直径可降低桥上CRTSⅠ型双块式无砟轨道早期开裂风险。

近40年中国冬季寒潮的气候特征及大气环流异常

利用1980—2023年高分辨率中国气象站观测数据,根据寒潮标准及强度指数,对中国寒潮事件的强度及影响区域进行客观分类,探讨全国性、区域性寒潮事件的时空变化特征和环流演变。结果表明:近40年我国冬季寒潮频次呈显著减少趋势,其影响范围扩大,而强寒潮的强度呈显著增加趋势,且年际变化幅度明显增大。中国寒潮冷空气主要来源于新地岛东南地区,路径因寒潮类型而异。分析全国型、东北华北型和西北华北型寒潮前期和同期大气环流异常特征发现:格陵兰岛的异常深厚暖高压是全国型寒潮的重要前兆,欧亚大陆对流层中高层纬向波列是其爆发的显著特征;东北华北型寒潮与冷涡在中低纬度异常高压系统阻挡下的东移有关;西北华北型寒潮与东欧平原上空暖性高压脊的发展及欧亚大陆两脊一槽的形势密切相关。所有类型寒潮爆发前均有乌拉尔阻塞高压的维持和西伯利亚地区冷空气的堆积。

双块式无砟轨道端梁区高温拱曲影响因素及控制技术

针对高速铁路双块式无砟轨道线路路基段两头端梁区附近道床板上拱问题,采用有限元方法,研究不同温度组合、路基段长度及端梁桩土约束刚度对道床板上拱的影响规律。结果表明:道床板的温度变形是引起上拱的主因,但支承层的变形扰动及其与道床板的温度变形组合效应不可忽视;随着路基段长度的增加,上拱幅值增加趋势明显;端梁的桩土约束对上拱的影响较为复杂,在中间某一特定约束刚度时上拱达到峰值,而当约束刚度无论变大或变小,上拱都呈现变小的趋势;断开支承层对控制高温上拱变形效果不显著,断开道床板则效果显著,但需协调考虑对应区段的钢轨受力。

高铁隧道内地下水作用下双块式无砟轨道道床板裂缝扩展研究

针对我国高速铁路隧道内CRTSⅠ型双块式无砟轨道施工阶段道床板开裂问题,运用有限元软件建立隧道-无砟轨道三维实体模型,研究地下水作用下隧道内无砟轨道各结构层位移隆起变化规律,并结合FRANC3D软件,在道床板结构受力最不利位置插入不同形状的预制三维裂缝,分析水压、裂缝长度对道床板裂缝扩展的影响。研究结果表明:(1)三角形荷载作用相较于均布荷载作用时,道床板位移隆起量虽有所减小,但地下水压的反复作用始终会影响轨道结构的平顺性,甚至导致道床板与仰拱填充间出现离缝;(2)裂缝长度是裂缝失稳扩展的控制因素,在排水系统完全堵塞时,建议将裂缝长度控制在200 mm以内;(3)水压为裂缝扩展的关键影响因素,同等条件下水压越大,道床板裂缝扩展越迅速,均布荷载下道床板裂缝尖端应力强度因子是对应三角形荷载下的1.2~1.4倍。

双块式无砟轨道轨枕与道床板界面脱空损伤识别

为准确识别双块式无砟轨道轨枕与道床板连接面脱空损伤,建立了双块式无砟轨道冲击回波有限元模型,分析界面损伤对弹性波传播规律的影响。在室内浇筑含有不同损伤位置和不同损伤程度的混凝土复合试件,采用冲击回波法进行损伤识别。研究结果表明:脱空损伤会显著影响弹性波在界面处的传播,基于回波信号分析可识别损伤;弹性波频率主要受激振锤大小的影响,应结合结构易损位置和理论计算选取合适的激振锤;混凝土复合试件的试验厚度值与理论厚度值相差仅为1 cm,测试结果合理,可用于判断脱空损伤程度,但不能确定损伤区域;利用平面成像技术可准确识别轨枕与道床板界面脱空范围,为双块式无砟轨道结构养护维修提供一定参考,试验结果验证了冲击回波法用于双块式轨道层间脱空识别的可行性和合理性。