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Computational Fluid Dynamics Model Analysis of the Blood Flow in the Right Coronary Artery on the Beating Heart 心脏右冠状动脉血流的计算流体动力学模型分析
Pub Date : 2001-11-11 DOI: 10.1115/imece2001/bed-23003
H. Hayashi, T. Ohashi, D. Mori, T. Yamaguchi
It is very important to elucidate the specific mechanism for the formation, growth, and breakdown of coronary plaque, in order to diagnose and prevent ischemic heart disease, such as myocardial infarction. Coronary atherosclerotic plaque has some characteristic background conditions from a mechanical viewpoint. Of these, the beating motion of the heart wall on which the major coronary arteries are fixed is very interesting, due to its possible mechanical influence on the flow inside the artery, and hence on atherogenesis. This study conducted a computational flow dynamics (CFD) simulation using a simplified model of the right coronary artery, which deforms with contraction of the heart. The right coronary artery was modeled using an ordinary helix, whose torsion and curvature changed in time with the contraction and dilatation of the heart. The results are discussed with respect to local hemodynamics’ characteristics, particularly the wall shear stress distribution.
阐明冠状动脉斑块形成、生长和分解的具体机制,对诊断和预防缺血性心脏病(如心肌梗死)具有重要意义。从力学角度看,冠状动脉粥样硬化斑块具有一些特征性的背景条件。其中,固定主要冠状动脉的心壁的跳动运动非常有趣,因为它可能对动脉内的流动产生机械影响,从而对动脉粥样硬化产生影响。本研究采用简化的右冠状动脉模型进行了计算流动力学(CFD)模拟,右冠状动脉随心脏收缩而变形。右冠状动脉模型采用普通螺旋结构,其扭转度和曲率随心脏的收缩和扩张而随时间变化。讨论了局部血流动力学特性,特别是壁面剪切应力分布。
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引用次数: 0
Effects of Wall Shear Stress on the Expression of Occludin in Human Umbilical Vein Endothelial Cells 壁面剪切应力对人脐静脉内皮细胞Occludin表达的影响
Pub Date : 2001-11-11 DOI: 10.1115/imece2001/bed-23010
D. M. Brey, Xu Yang, R. Keynton, Thomas J. Rousse, W. Ehringer, J. Alexander
The most common cause for chronic term (> 30 days) failure of vascular bypass grafts is the rapid growth of underlying tissues within arteries called intimal hyperplasia (EH) [1]. IH has been found to primarily exist in low wall shear stress regions within distal anastomoses [2]; however, the exact mechanism by which shear stress induces IH has not been ascertained. We hypothesize that endothelial lining permeability is induced by wall shear stress during tissue reorganization such as occurs within vascular bypass constructs. Occludin is an adhesion protein that is actively involved in endothelial cell (EC) tight junctions, and thus, may effect EC layer permeability. To date, no studies have been conducted to determine the effect of wall shear stress on this adhesion protein. Therefore, the purpose of this study is to evaluate the role of wall shear stress upon the expression of occludin within cultured endothelial cells.
血管旁路移植术长期(> 30天)失败的最常见原因是动脉内下层组织的快速生长,称为内膜增生(内膜增生)[1]。IH主要存在于远端吻合口的低壁剪切应力区[2];然而,剪切应力诱发IH的确切机制尚未确定。我们假设内皮细胞的通透性是由组织重组过程中的壁剪切应力引起的,比如在血管旁路结构中。Occludin是一种积极参与内皮细胞(EC)紧密连接的粘附蛋白,因此可能影响EC层的通透性。到目前为止,还没有研究确定壁面剪切应力对这种粘附蛋白的影响。因此,本研究的目的是评估壁剪切应力对培养内皮细胞内occludin表达的作用。
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引用次数: 0
Simulation of the Central Airways for Identifying Airway Partial Obstruction 识别气道部分阻塞的中央气道模拟
Pub Date : 2001-11-11 DOI: 10.1115/imece2001/bed-23105
A. Al-Jumaily, Y. Du
The frequency spectrum of the input impedance determined at the throat is analysed to identify partial occlusion in the branched central bronchi. The airways are modelled starting from the trachea to the second generation and the result demonstrates that the input impedance resonant frequencies can map the location, severity and degree of an obstruction in any of the considered branches.
在喉部确定的输入阻抗频谱进行分析,以识别分支的中央支气管的部分闭塞。从第一代气管到第二代气管的气道建模结果表明,输入阻抗谐振频率可以映射任何考虑分支的阻塞位置,严重程度和程度。
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引用次数: 0
A Spring-Loaded Constant Force Exercise Device 一种弹簧加载恒力运动装置
Pub Date : 2001-11-11 DOI: 10.1115/imece2001/bed-23006
Matthew J. Chatham, B. A. Todd, J. Parker, Audrey S. House, Jenny L. Taylor
Bone mineral density loss has been observed in astronauts who have spent a significant amount of time in a micro-gravity environment [1]. The lack of mechanical stress placed on the bones while in this environment is a major factor in the decrease in bone mineral density. To counteract these effects, resistive exercise has been the focus of many studies. Weighted plates have been used to provide a constant force resistance in ground-based bed rest studies. Bed rest has been established as one of the best ways to simulate the long-term effects of micro-gravity on earth [2]. In weightlessness, however, an alternate source of resistive force is required Some exercise devices provide resistance with elastic bands. Unfortunately, these elastic bands tend to lose their mechanical stiffness with use, requiring many spare elastic bands to be available for long duration missions in space. A more robust system that requires less maintenance would be preferable. Metallic helical springs meet this requirement The mechanical properties of helical springs are predictable, and these springs have a long life, making them well suited for long duration missions. However, helical springs exhibit linear behavior. That is, the resistive force provided by the spring is directly proportional to the amount of deflection. Therefore, a mechanism was designed to interact with the linear springs to provide a constant output force over a given length of travel.
在微重力环境中度过大量时间的宇航员中观察到骨密度损失[1]。在这种环境下,骨骼缺乏机械应力是骨密度下降的主要因素。为了抵消这些影响,阻力运动一直是许多研究的重点。在地面卧床休息研究中,加重板已被用来提供恒定的力阻力。卧床休息已被认为是模拟地球上微重力长期影响的最佳方法之一[2]。然而,在失重状态下,需要一种替代的阻力来源。一些运动装置用松紧带提供阻力。不幸的是,这些松紧带往往会随着使用而失去其机械刚度,因此需要许多备用松紧带用于长时间的太空任务。一个需要更少维护的更强大的系统将是可取的。金属螺旋弹簧满足这一要求。螺旋弹簧的机械性能是可预测的,这些弹簧有很长的寿命,使它们非常适合长时间的任务。然而,螺旋弹簧表现为线性行为。也就是说,弹簧提供的阻力与挠度成正比。因此,设计了一种与线性弹簧相互作用的机构,以在给定的行程长度上提供恒定的输出力。
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引用次数: 0
A Total Knee Replacement Model for Evaluation of Joint Mechanics 全膝关节置换术关节力学评估模型
Pub Date : 2001-11-11 DOI: 10.1115/imece2001/bed-23087
Jason P. Halloran, P. Rullkoetter
The success of current total knee replacement (TKR) devices is contingent on the kinematics and contact mechanics during in vivo physiological activity. A great deal of research has gone into determining parameters important to proper long-term joint function. Indicators of potential wear performance in ultra-high molecular weight polyethylene (UHMWPE) total joint replacement components include contact stress and area due to articulations, and tibio-femoral and patello-femoral kinematics. All have been used to compare implant designs and serve as a basis for differentiation of systems.
目前全膝关节置换术(TKR)装置的成功取决于体内生理活动中的运动学和接触力学。大量的研究都是为了确定对关节长期正常功能有重要意义的参数。超高分子量聚乙烯(UHMWPE)全关节置换部件的潜在磨损性能指标包括关节接触应力和面积,胫骨-股骨和髌骨-股骨运动学。所有这些都被用来比较植入物的设计,并作为区分系统的基础。
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引用次数: 0
Hybrid Adaptive Kalman Filter: Calibrating a Hemodynamic Model for Continuous Arterial Pressure Monitoring
Pub Date : 2001-11-11 DOI: 10.1115/imece2001/bed-23015
Yi Zhang, H. Asada
A Hybrid Adaptive Kalman Filter (HAKF), consisting of a continuous Standard Kalman Filter (SKF) and an intermittent Least Squares Parameter Estimator (LSPE), is proposed to calibrate the hemodynamic model for continuous arterial pressure monitoring. Simulations of the HAKF using a classic Windkessel model are carried out to prove the principle of the proposal.
提出了一种由连续标准卡尔曼滤波器(SKF)和间歇最小二乘参数估计器(LSPE)组成的混合自适应卡尔曼滤波器(HAKF),用于校准连续动脉压力监测的血流动力学模型。利用经典的Windkessel模型对haf进行了仿真,验证了该方法的原理。
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引用次数: 0
Development of a Rate-Dependent Material Model for UHMWPE Joint Replacement Components 超高分子量聚乙烯关节置换部件速率相关材料模型的建立
Pub Date : 2001-11-11 DOI: 10.1115/imece2001/bed-23050
W. Houchaime, A. Petrella, T. Dietz, J. Halloran, P. Rullkoetter
Polyethylene wear has been implicated in osteolysis and can lead eventually to implant loosening. Abrasive/adhesive wear and delamination or pitting damage in ultra-high molecular weight polyethylene (UHMWPE) joint replacement components has been in part attributed to high joint contact stresses. The propensity of total joint replacement systems for these types of wear is often assessed by evaluating the joint contact stresses and contact areas and these often serve as a basis for differentiation of systems. The rate-dependency of polyethylene can have a significant effect on these contact characteristics of joint replacement components. Previously, researchers have used experimental and analytical methods to determine joint contact characteristics. Most of the analytical studies, however, have not included the important time-dependent behavior of UHWMPE.
聚乙烯磨损与骨溶解有关,最终可导致植入物松动。超高分子量聚乙烯(UHMWPE)关节置换部件的磨料/粘合剂磨损和分层或点蚀损伤部分归因于高关节接触应力。对于这些类型的磨损,通常通过评估关节接触应力和接触面积来评估全关节置换系统的倾向性,这些通常作为区分系统的基础。聚乙烯的速率依赖性可以对关节置换部件的这些接触特性产生显著影响。以前,研究人员使用实验和分析方法来确定关节接触特性。然而,大多数分析研究都没有包括UHWMPE重要的时间依赖行为。
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引用次数: 0
A Method for the Rapid Prototyping of Custom Contoured Cushions 一种定制轮廓垫的快速成型方法
Pub Date : 2001-11-11 DOI: 10.1115/imece2001/bed-23097
M. Parkinson, Jane Huggins
Decubitous ulcers (“pressure sores”) are a significant concern for people using wheelchairs. In fact, results published by the University of Kansas [1] indicate that over half of those using wheelchairs will develop a pressure sore at some point. This susceptibility is due to the conditions under which these ulcers develop: shear stress and pressure work together to cut off the blood supply to the surface tissue, which subsequently dies. Heat and moisture can increase the likelihood of this necrosis and the rate at which it occurs. Although sores can develop quickly (onset can occur in as few as fifteen minutes), they may take months to heal. Appropriate seat cushion selection helps to mitigate the causative factors [2]. In particular, custom-contoured cushions (CCC) can offer dramatic improvements. Research has shown that CCC’s offer the best distribution of pressure and reduction of shear stress, reducing these factors by as much as 80% [3]. CCC’s are not commonly used, however, because the cost and time involved in design, manufacture, and delivery are prohibitive. The obstacles of cost, time, and inconvenience, can be overcome by applying mass-customization and rapid-prototyping principles to the process used to create CCC’s. This involves automating the basic steps of the process: creating an electronic representation of the seating surface and machining that surface using a computer-controlled (CNC) mill. Similar systems have been put in place to automate a variety of processes, from the creation of custom orthotics for footwear to the design and creation of impeller wheels [4]. Such a system would be capable of producing a suitable custom-contoured cushion in minutes or hours rather than weeks or months.
褥疮(“压疮”)是使用轮椅的人非常关心的问题。事实上,堪萨斯大学(University of Kansas)发表的研究结果[1]表明,超过一半使用轮椅的人会在某个时候出现压疮。这种易感性是由于这些溃疡形成的条件:剪切应力和压力共同作用,切断了表面组织的血液供应,随后死亡。高温和潮湿会增加这种坏死的可能性和发生的速度。尽管溃疡发展迅速(15分钟内就会发作),但可能需要数月才能愈合。选择合适的坐垫有助于减轻致病因素[2]。特别地,定制形状的坐垫(CCC)可以提供显著的改善。研究表明,CCC提供了最佳的压力分布和剪切应力降低,将这些因素降低了80%[3]。然而,CCC并不常用,因为设计、制造和交付所涉及的成本和时间令人望而却步。成本,时间和不便的障碍,可以通过大规模定制和快速原型设计原则,用于创建CCC的过程中克服。这包括自动化加工过程的基本步骤:创建座位表面的电子表示,并使用计算机控制(CNC)铣床加工该表面。类似的系统已经到位,以实现各种流程的自动化,从鞋类定制矫形器的创建到叶轮轮的设计和创建[4]。这样的系统将能够在几分钟或几小时内而不是几周或几个月内生产出合适的定制形状的垫子。
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引用次数: 2
Indentation of Articular Cartilage: Effects of Specimen Radius on Determined Properties 关节软骨的压痕:试样半径对确定性能的影响
Pub Date : 2001-11-11 DOI: 10.1115/imece2001/bed-23058
C. Spoon, J. Wayne
The indentation test is a commonly used experimental setup to determine properties of articular cartilage, both in the laboratory and as a clinical tool, as it is a test that can be performed in situ. Behavior of normal cartilage and tissue generated in reparative studies have been thus obtained [1, 2, 3]. It has been shown from a finite element study [4] that the behavior of cartilage in indentation stress relaxation can be affected by the tissue width relative to the radius of the indenter. Another finite element study of the indentation of osteochondral defects showed that this ratio also affected specifications of boundary conditions [5]. This investigation sought to evaluate the effect of changing geometric parameters (e.g. tissue width and indenter radius) on the properties determined from creep indentation experiments.
压痕测试是一种常用的实验装置,用于确定关节软骨的特性,无论是在实验室还是作为临床工具,因为它是一种可以在原位进行的测试。因此,修复研究中产生的正常软骨和组织的行为已经得到[1,2,3]。一项有限元研究[4]表明,软骨在压痕应力松弛中的行为会受到相对于压痕半径的组织宽度的影响。另一项骨软骨缺陷压痕的有限元研究表明,该比值也会影响边界条件的规格[5]。本研究旨在评估改变几何参数(如组织宽度和压头半径)对蠕变压痕实验确定的性能的影响。
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引用次数: 0
Active Learning in Mechanics Courses in Biomedical Engineering 生物医学工程力学课程的主动学习
Pub Date : 2001-11-11 DOI: 10.1115/imece2001/bed-23019
G. Livesay, K. Dee, E. Nauman, R. T. Hart
In the Fall of 1999, the Department of Biomedical Engineering at Tulane University significantly revised the undergraduate curriculum to both increase the biomedical engineering content and move this BMEN content earlier in the students’ BMEN career. A major component of this revision was the introduction of bridge courses designed to ‘bridge’ from traditional engineering topics to biomedical engineering topics in the major sub-disciplines within biomedical engineering -Bioelectronics, Bioelectricity, Cell & Tissue Engineering, Biomaterials, and Biomechanics.
1999年秋季,杜兰大学生物医学工程系对本科课程进行了重大修订,既增加了生物医学工程的内容,又将生物医学工程的内容提前到学生的生物医学工程职业生涯中。此次修订的一个主要组成部分是引入桥梁课程,旨在将生物医学工程中的主要子学科——生物电子学、生物电学、细胞与组织工程、生物材料和生物力学——从传统工程主题“连接”到生物医学工程主题。
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引用次数: 0
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Advances in Bioengineering
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