Nonmonotonic effects of perpendicular magnetic anisotropy on current-driven vortex wall motions in magnetic nanostripes

In a magnetic nanostripe, the effects of perpendicular magnetic anisotropy（PMA） on the current-driven horizontal motion of vortex wall along the stripe and the vertical motion of the vortex core are studied by micromagnetic simulations.The results show that the horizontal and vertical motion can generally be monotonously enhanced by PMA. However, when the current is small, a nonmonotonic phenomenon for the horizontal motion is found. Namely, the velocity of the horizontal motion firstly decreases and then increases with the increase of the PMA. We find that the reason for this is that the PMA can firstly increase and then decrease the confining force induced by the confining potential energy. In addition, the PMA always enhances the driving force induced by the current.

Single-territory incomplete surgical revascularization improves regional wall motion of remote ventricular areas： results from a propensity-matched study

Objective Basic science studies demonstrated a general intramyocardial angiogenetic response potentially responsible for the creation of a microvascular neocapillaries network assisting myocardial function. We hypothesized that the benefit provided by the reperfusion of left anterior descending （LAD） territories and the biological angiogenetic drive triggered by the revascularization could translate in a global improvement in ventricular contractility, not restricted to the grafted area. Methods High-risk patients with multivessel coronary artery disease and preoperative wall motion abnormalities were retrospectively analyzed to compare outcomes and regional ventricular function of those who received optimal medical therapy （OMT） versus those who underwent off-pump coronary artery bypass grafting （OPCABG） and received an incomplete myocardial revascularization using left internal mammary artery （LIMA） on LAD （OPCABG group）. From January 2007 to December 2014, 206 patients （OMT, n = 136, OPCABG, n = 70） were propensity-score matched to have 70 matched pairs. Variables included in propensity score analyses were ejection fraction （EF）, left ventricular end diastolic volume （LVEDVi）, EuroSCORE II. Primary endpoint was the variation in the global wall motion score index （AWMSI） as evaluated by transthoracic echocardiography. Follow up was completed at 3 years from surgery or hospital discharge. Results Regional analysis of ventricular function revealed a regional WMSI improvement in the OPCABG group not only for LAD territories but also for non-LAD regions, associated with a reduction in the negative left ventricular ischemic remodeling, compared to patients discharged in optimal medical therapy. Global AWMSI was negative in OPCABG group （-3.4 ± 2.8%） and positive in the OMT group （5.9 ± 3.1%）, indicating a better wall motion score for OPCAB patients. Surprisingly, regional WMSI improved also in non-grafted territories in the off-pump CABG group with a delta value of -3.7 ± 5.3% for left circumflex artery （LCX） area and -3.5 ± 5.4% for right coronary artery （RCA） area. Conclusions In patients with multivessel coronary artery disease, LIMA-to-LAD grafting is associated with an improvement in the WMSI involving also the surrounding non-LAD ungrafted segments and with the attenuation of negative global and regional ischemic ventricular remodeling.

Current-Driven Domain Wall Motion: Velocity, Current and Phase Transition

The relation between domain wall motion and intensity of driven current is examined in a phenomenological theory where the kinetic energy is expanded as a series of polynomial function of current density just as the Landau phase transition theory. The dependency of velocity on current density is square root which degenerates into linear if the current is much higher than the critical value. The theory result is consistent with several previous experiments and also can explain the change of critical current in the presence of temperature. The role of temperature playing in the dynamics of domain wall motion is also discussed. The phase transition theory in terms of current density is employed to explain the critical behavior of domain wall motion.

A cellular scale numerical study of the effect of mechanical properties of erythrocytes on the near-wall motion of platelets

The effect of mechanical properties of erythrocytes on the near-wall motion of platelets was numerically studied with the immersed boundary method. Cells were modeled as viscous-fluid-filled capsules surrounded by hyper-elastic membranes with negligible thickness. The numerical results show that with the increase of hematocrit, the near-wall approaching of platelets is enhanced, with which platelets exhibit larger deformation and orientation angle of its near-wall tank-treading motion, and the lateral force pushing platelets to the wall is increased with larger fluctuation amplitude. Meanwhile the near-wall approaching is reduced by increasing the stiffness of erythrocytes.

Effect of puerarin on myocardial perfusion and ventricular wall motion in patients with acute coronary syndrome

Objective To investigate the effects of puerarin (Pur) on myocardial perfusion and ventricular wall motion in patients with acute coronary syndrome (ACS).Methods Thirty-seven patients with ACS were randomly divided into two groups:conventional treatment group (n= 17,11 males,range of age:32-80 years,average age:60.9±4.9 years) and Pur treatment group (n=20,12 males,range of age:40-76 years,average age:62.7±3.5 years).Patients in the conventional treatment group received standard treatment according to the current guidelines,while patients in the Pur treatment group received intravenous administration of Pur (500 mg/day) for 10 days plus conventional treatment.Real-time myocardial contrast echocardiography (RT-MCE) was performed to evaluate the change in myocardial perfusion index (MPI) and ventricular wall motion index (VWMI) at admission and 10 days after treatment.Results At 10 days after treatment,MPI was significantly higher (P【0.01) and VWMI significantly lower (P【0.01) in the Pur group comparing with those in the conventional group.Conclusions Puerarin might improve myocardial microcirculation perfusion and ventricular wall motion in patients with ACS.

Chaos Appearance during Domain Wall Motion under Electronic Transfer in Nanomagnets

In this paper, we study the likelihood of chaos appearance during domain wall motion induced by electronic transfer. Considering a time-varying current density theory, we proceed to a numerical investigation of the dynamics. Using the dissipation parameter, amplitude and frequency of current density as control parameters;we show how periodic regime as well as chaotic regime can be exhibited in nanomagnetic systems. Numerical results allow setting up the periodicity and quasi-periodicity of system and chaotic phenomena occurring during magnetization switching process in nanomagnet through electronic transfer.

Wall Effect of Underwater Explosion Load Based on Wave Motion Theories

Owing to the existence of the flow field boundary, the shock wave load near the boundary is different from the freefield shock wave load. In the present paper, the hull plate load subjected to underwater shock wave is investigated based onwave motion theories; in addition, the experimental study of the hull plate load is carried out. According to the theoreticalanalysis of the hull plate pressure, we find that the hull plate pressure oscillates repeatedly and decays rapidly with timepassing, the maximum hull plate pressure is 2/（1＋n） times the maximum free field pressure, where n is the ratio ofimpedance, and the impulse is much smaller than the free field impulse. Compared with the experimental study, thetheoretical results agree well with the experimental data.

MOTION AND DEFORMATION OF VISCOUS DROP IN STOKES FLOW NEAR RIGID WALL

A boundary integral method was developed for simulating the motion and deformation of a viscous drop in an axisymmetric ambient Stokes flow near a rigid wall and for direct calculating the stress on the wall. Numerical experiments by the method were performed for different initial stand-off distances of the drop to the wall, viscosity ratios, combined surface tension and buoyancy parameters and ambient flow parameters. Numerical results show that due to the action of ambient flow and buoyancy the drop is compressed and stretched respectively in axial and radial directions when time goes. When the ambient flow action is weaker than that of the buoyancy the drop raises and bends upward and the stress on the wall induced by drop motion decreases when time advances. When the ambient flow action is stronger than that of the buoyancy the drop descends and becomes flatter and flatter as time goes. In this case when the initial stand-off distance is large the stress on the wall increases as the drop evolutes but when the stand-off distance is small the stress on the wall decreases as a result of combined effects of ambient flow, buoyancy and the stronger wall action to the flow. The action of the stress on the wall induced by drop motion is restricted in an area near the symmetric axis, which increases when the initial stand-off distance increases. When the initial stand-off distance increases the stress induced by drop motion decreases substantially. The surface tension effects resist the deformation and smooth the profile of the drop surfaces. The drop viscosity will reduce the deformation and migration of the drop.

Rupture directivity and hanging wall effect in near field strong ground motion simulation

A random synthesis procedure based on finite fault model is adopted for near field strong ground motion simulation in this paper. The fault plane of the source is divided into a number of sub-sources, the whole moment magnitude is also divided into more sub-events. The Fourier spectrum of ground motion caused by a sub-event in given sub-source, then can be derived by means of taking the point source spectrum, attenuation with distance, energy dissipation, and near surface effect, into account. A time history is synthesized from this amplitude spectrum and a random phase spectrum, and being combined with an envelope function. The ground motion is worked out by superposition of all time histories from each sub-event in each sub-source, with time lags determining by the differences between the triggering times of sub-events and distances of the sub-sources. From the example of simulations at 21 near field points in a scenario earthquake with 4 dip angles of the fault plane, it is illustrated that the procedure can describe the rupture directivity and hanging wall effect very well. To validate the procedure, the response spectra and time histories recorded at three near fault stations MCN, LV3 and PCD during the Northridge earthquake in 1994, are compared with the simulated ones.

THE COUPLE MOTION BETWEEN VESSEL WALL AN DBLOOD IN THE ENTRANCE REGION OF A TAPERED VESSEL

A problem of couple motion between vessel wall and blood in the entrance regionof a tapered vessel is considered in this paper A mathematical model of co-coupleaction is formed for both motion of vessel wall and blood flow in the entrance regance regionof elastic vessel with tapered angle. Under the situation that the relative boundary conditions are satisfied a.set of velocity distribution formula. pressure distributionformula for the blood flow in a tapered elastic vessel are derived. Some importantconclusions are obtained.

基于非梗死区心肌全壁运动指数建立主要不良心血管事件发生风险评估模型

目的研究基于非梗死区心肌全壁运动指数(GWMI)建立急性心肌梗死经皮冠状动脉介入治疗(PCI)术后远期主要不良心血管事件(MACE)发生风险评估模型。方法选取2019年5月至2021年5月金华市中心医院心血管内科二区收治的急性心肌梗死行PCI患者350例,根据随访结果分为MACE组82例和非MACE组268例。采用logistic回归分析远期危险因素,并构建危险因素的回归方程模型,采用ROC曲线分析风险评估模型、全球急性冠状动脉事件注册(GRACE)评分对远期MACE的预测效能。结果MACE组GRACE评分、B型钠尿肽、GWMI明显高于非MACE组,淋巴细胞、血红蛋白及血运重建比例明显低于非MACE组,差异有统计学意义(P<0.05,P<0.01)。ROC曲线分析显示,GWMI预测MACE的截断值为1.04,曲线下面积为0.747(95%CI:0.678~0.815)。多因素logistic回归分析显示,B型钠尿肽、GWMI为MACE发生的危险因素,淋巴细胞、血红蛋白、血运重建为MACE发生的保护因素(P<0.05,P<0.01)。建立风险评估模型的回归方程,结果显示,风险评估模型、GRACE评分预测MACE的曲线下面积分别为0.903(95%CI:0.862~0.952)、0.757(95%CI:0.692~0.822)。结论非梗死区GWMI是急性心肌梗死PCI术后远期MACE的影响因素,基于非梗死区GWMI建立的风险评估模型可有效预测远期MACE发生风险。

自动功能成像对无室壁运动异常患者冠状动脉狭窄的预测价值

目的探讨自动功能成像(AFI)预测无室壁运动异常患者冠状动脉狭窄的价值。方法选择2018年7月至2019年9月新乡市中心医院收治的二维超声心动图检查无室壁运动异常且冠状动脉造影(CAG)证实冠状动脉狭窄≥70%的冠状动脉性心脏病患者40例为研究对象,比较AFI与CAG对冠状动脉狭窄≥70%的检出率;以CAG为金标准,评估AFI对冠状动脉狭窄≥70%的预测价值。结果AFI和CAG对冠状动脉狭窄≥70%的检出率比较差异无统计学意义(χ^(2)=1.667,P>0.05)。AFI预测左冠状动脉前降支狭窄≥70%的敏感度为100.0%、特异度为63.6%、阳性预测值为69.2%、阴性预测值为100.0%、准确度为80.0%;预测左冠状动脉回旋支狭窄≥70%的敏感度为56.2%、特异度为91.6%、阳性预测值为81.8%、阴性预测值为75.8%、准确度为77.5%;预测右冠状动脉狭窄≥70%的敏感度为95.6%、特异度为47.0%、阳性预测值为70.9%、阴性预测值为88.0%、准确度为75.0%;预测冠状动脉狭窄≥70%的总体敏感度为85.9%、特异度为69.8%、阳性预测值为72.0%、阴性预测值为84.6%、准确度为77.5%。结论AFI可以为临床早期预测无室壁运动异常患者冠状动脉狭窄≥70%提供一个灵敏、客观、无创、廉价的检查方法。

基于双混联机器人协同运动控制的薄壁件镜像铣削研究

为提高薄壁件镜像铣削过程中的加工质量,本文提出一种针对双混联机器人镜像铣削的协同运动控制策略。首先,结合机器人运动控制特点,研发出一种双CPU主从控制架构的开放式数控系统,以实现人机交互和运动控制;然后,为实现双机协同运动并提高薄壁件加工质量,在数控系统中集成了4大关键技术,分别是双机器人的镜像路径生成、同步速度规划、协同运动学和运动误差实时补偿;最后,基于自主开发的集成式镜像铣削数控系统,开展了单点和多点支撑、双机协同与非协同加工的平面薄壁件槽铣削试验,多点支撑的平面铣削试验,大曲率路径高速协同运动试验与曲面薄壁件槽铣削加工试验。试验结果表明,提出的协同运动控制策略能够保证双机器人具有较高的同步位置精度。此外,多点支撑方式在保证薄壁件铣削壁厚的同时,还可提高工件铣削的颤振稳定性。

超声识别冠心病患者下壁室壁运动异常假阳性的探索性研究

目的探讨基层医院利用常规超声识别冠心病患者下壁局限性室壁运动异常(RWMA)假阳性情况。方法选取2020年1—12月北京市昌平区医院超声疑似诊断下壁RWMA的45例冠心病患者作为研究对象。分析超声诊断结果,比较诊断真阳性与诊断假阳性患者合并症情况、超声参数及二尖瓣反流情况。结果45例超声疑似诊断左心室下壁RWMA患者中,诊断真阳性34例,诊断假阳性11例,诊断假阳性率为24.44%。诊断真阳性患者合并下侧壁RWMA比例高于诊断假阳性患者,差异有统计学意义(P<0.05);诊断真阳性与诊断假阳性患者合并前侧壁RWMA、存在二尖瓣反流比例比较差异无统计学意义。诊断真阳性与诊断假阳性患者室间隔、左心室后壁、左心室舒张末容积(LVEDV)、左心室收缩末容积(LVESV)、左心室射血分数(LVEF)比较差异无统计学意义;诊断真阳性患者右心室前后径、右心房左右径均大于诊断假阳性患者,差异有统计学意义(P<0.05)。结论超声诊断下壁RWMA可能存在诊断假阳性的情况,结合一些超声影像特点可能会减少误诊。

超声多模态成像对心肌梗死患者缺血节段识别及左心功能评估的作用

目的探讨联合应用经胸超声心动图(TTE)、二维斑点追踪成像技术(2D-STI)及肺超声对不同类型心肌梗死(MI)缺血节段识别、左心功能评估的临床应用价值。方法随机选取福建省泉州市第一医院心内科MI患者93例,其中非ST抬高型心梗(NSTEMI)45例、ST抬高型心梗(STEMI)48例。所有患者均在冠脉造影前24 h内行TTE、2D-STI及肺超声检查;TTE观察是否有节段性室壁运动异常(RWMA),并测量左室射血分数(LVEF)、左房容积指数(LAVI)、肺动脉收缩压(PASP)、二尖瓣血流E峰、二尖瓣环e'峰并计算E/e';2D-STI分析左室壁各节段心肌纵向峰值应变(LPS)、整体纵向峰值应变(GLPS);肺超声观察并计算肺B线积分;入院时急查B型钠肽(BNP)。比较TTE、2D-STI判断为缺血节段与冠脉造影结果的符合率;分析两组患者TTE参数、GLPS、肺B线积分及BNP间的相关性。结果NSTEMI组2D-STI缺血节段符合率较TTE升高(P<0.05);在NSTEMI组,LVEF与GLPS、肺B线积分、BNP呈弱相关性,而在STEMI组均呈较强的相关性;在两组患者中,GLPS、肺B线积分均与BNP呈较强的正相关关系,肺B线积分与E/e'、LAVI、PASP相关性较强。结论TTE联合2D-STI能提高NSTEMI患者缺血节段的识别率;联合肺超声能为MI患者左心功能及肺淤血程度的评估提供客观的影像学依据;对MI患者进行超声多模态成像具有一定的临床意义。

横向振动立管上升流中球形单颗粒运动特征

深海采矿过程中,输送矿石颗粒的立管在复杂海洋环境作用下会产生运动响应,这会对管道中矿石颗粒的运动行为产生重要影响,从而影响矿石提升效率,甚至可能危及整个采矿系统的安全.结合颗粒运动方程和软球碰撞模型,对横向振动立管中的球形单颗粒运动特征进行研究,主要分析了立管振动参数、颗粒与流体密度比以及颗粒与立管直径比对立管中单颗粒运动的影响.研究表明,随振动频率和幅度、颗粒与流体密度比以及颗粒与立管直径比的增加,颗粒垂向平均速度减小.颗粒与管壁之间无碰撞发生时,颗粒与立管之间横向相对速度幅值、颗粒运动与立管之间横向速度的相位差以及颗粒垂向速度波动幅值,与立管振动的频率和振幅、颗粒与流体密度比以及颗粒与立管直径比呈正相关.然而,当颗粒与立管之间有碰撞发生时,颗粒与立管间的横向速度的相位差减小,而颗粒垂向速度波动幅值显著增大.另外,随着密度比和直径比的增大,颗粒与管壁之间更容易发生碰撞,而碰撞会减弱密度比和直径比对颗粒横向速度和垂向速度的影响.

适应多种立面的磁吸附爬壁机器人设计与越障分析

针对现有的磁吸附爬壁机器人无法满足在多种立面作业的问题,提出了一种带有柔性关节履带结构,能自主适应多种立面的爬壁机器人。机器人每个柔性关节履带都具有前后俯仰自由度及左右翻转自由度,在平直立面或凹凸立面发生运动形态的变化时,自主与立面贴合。首先,建立机器人运动形态变化模型,分析机器人在曲率半径为(0.5~3)m的凹凸立面上运动时横摆角度与纵摆角度的变化规律。通过Adams虚拟样机,对机器人在壁面上的越障性能进行仿真,计算结果和仿真分析表明:机器人可以平稳越过39mm的障碍,具有一定的越障能力。

结合霍夫变换找墙体直线的沿墙导航算法

针对移动机器人沿墙导航过程中存在沿曲线墙体导航效果不佳、路径不够平滑等问题,提出了结合霍夫变换找墙体直线的沿墙导航算法。该算法由霍夫变换提取出当前位置障碍物中的直线,找到离机器人最近的直线作为沿墙参考直线,采集上一周期历史墙体直线状态和当前墙体直线状态决定机器人当前的运动方向,并根据当前墙体直线提取出沿墙导航预设路径进行导航,如此循环直至完成指定的沿墙导航任务。实验证明该算法可以在不同环境中较好地完成沿墙导航任务。

不同超声评估方法在左前降支狭窄中的临床价值

目的探讨不同超声评估方法在左前降支(left anterior descending,LAD)狭窄中的临床价值。方法回顾性分析我院2023年04月至2024年04月经冠状动脉造影(coronary angiography,CAG)确诊,且行室壁运动分析、速度向量成像(velocity vector imaging,VVI)、冠状动脉血流成像(coronary flow imaging,CFI)3种不同超声评估方法的240例患者的超声资料。按照LAD狭窄程度分为试验组(狭窄≥50%)120例、对照组(狭窄<50%)120例,总结两组室壁运动分析、VVI、CFI超声特征,并以CAG为金标准,分析3种不同超声评估方法的诊断效能。结果室壁运动分析显示试验组室壁运动异常比例高于对照组;VVI显示试验组前间隔和前壁收缩期纵向应变低于对照组;CFI显示试验组LAD的舒张期峰值速度快于对照组,差异均有统计学意义(P<0.05)。以CAG结果为金标准,室壁运动分析诊断LAD狭窄≥50%敏感度为0.467、特异度为0.717、准确度为0.591、阳性预测值为0.622、阴性预测值为0.573;VVI诊断LAD狭窄≥50%敏感度为0.800、特异度为0.817、准确度为0.808、阳性预测值为0.813、阴性预测值为0.803;CFI诊断LAD狭窄≥50%敏感度为0.850、特异度为0.783、准确度为0.817、阳性预测值为0.796、阴性预测值为0.839。一致性检验结果显示,室壁运动分析与CAG一致性一般,Kappa值为0.183,VVI、CFI与CAG一致性较高,Kappa值分别为0.617、0.633。受试者工作特征曲线分析显示室壁运动分析、VVI、CFI的曲线下面积分别为0.592、0.808、0.817。结论前间隔及前壁运动异常、前间隔及前壁收缩期纵向应变减低、LAD的舒张期峰值速度加速是LAD狭窄时室壁运动分析、VVI、CFI的超声特征,均可作为诊断依据,但前者的诊断效能明显低于后两者,VVI和CFI诊断LAD狭窄具有较高的诊断效能,且与CAG一致性较好,值得临床应用与推广。

心脏超声检查在冠心病节段性室壁运动异常中的应用

目的探讨冠心病节段性室壁运动异常诊断中心脏超声检查的应用价值,旨在为后续诊断及治疗工作提供参考价值。方法选取2021年10月—2023年10月漳州正兴医院超声科100例疑似冠心病节段性室壁运动异常者相关数据进行分析。以心脏冠状动脉造影为诊断“金标准”,所有入组者均实施心脏超声检查,对心脏超声检查的诊断价值进行分析,记录冠心病节段性室壁运动异常检出率、不良反应发生情况。结果不同诊断方法下冠心病节段性室壁运动异常检出率比较,差异无统计学意义(P>0.05);心脏超声检查的阳性预测值、特异度、阴性预测值、敏感度、准确度分别为98.82%(84/85)、90.90%(10/11)、66.67%(10/15)、94.38%(84/89)、94.00%(94/100),心脏超声检查的诊断价值较高;心脏超声检查下不良反应总发生率低于心脏冠状动脉造影检查,差异有统计学意义(P<0.05)。结论心脏超声检查的检出率较高,不良反应发生率低,具有较高的特异度、阳性预测值、准确度、阴性预测值、敏感度,对后续针对性治疗具有积极意义。