机械系统动力刚化机理分析

采用计及变形约束的非线性运动学分析方法及传统分析方法建立简单柔性机械臂线性化的动力学方程。笔者认为：运动的柔性机械构件春变形运动的耦合产生动力刚化，传统分析方法失去了刚体运动与弹性振耦合的动力刚化项；如果在建立运动学方程时，计及运动学的非线性项，至少要计及振动坐标的二阶小量，将非线性保留到适当阶段，再线性化，熊猫是到一致化性化的动力学方程，这种方法适合于机械系统件的小变形问题，对动力刚化的研究实际     

复合盘压电超声换能器的径向振动频率方程

提出并研究一种复合盘压电超声换能器的径向振动特性。依据机电类比原理,建立复合系统的径向振动等效电路,并推导出其径向振动频率方程。数值计算表明,当换能器半径比一定时,对给定材料换能器径向共振频率与压电晶片直径的积为常数。此外,径向复合换能器不满足传统的“半波长”级联规律,必须进行整体设计。作为算例,给出常用材料钢、铝和钛与PZT-4复合压电超声换能器的径向共振频率常数与其半径比的拟合关系曲线。试验加工两个径向复合压电超声换能器,并测定其共振基频。结果表明,换能器谐振频率误差小于3%,能够满足工程应用需要。     

超声波轴承用挤压式压电换能器的共振频率

设计了一种超声悬浮轴承用新型径向挤压式压电换能器,用于验证超声波轴承径向共振频率理论计算的正确性。基于弹性理论、压电方程和机电类比原理,建立压电换能器机电等效电路图,理论推导出了压电换能器径向振动的共振频率方程;然后,应用Matlab软件计算出了压电换能器的共振频率。采用有限元软件对已知结构尺寸的换能器进行模态分析,计算出压电换能器所需振型及该振型下的共振频率,数值仿真分析了换能器结构尺寸对换能器共振频率和径向振幅的影响。最后,设计了 一台样机,从理论、仿真及实验三方面对其共振频率进行验证。实验结果显示：换能器径向振动共振频率的理论值与实验结果相对误差为5.89%,仿真值与实验结果误差为3.53%。实验结果证明了理论计算方法的正确性,为压电挤压换能器的设计提供了理论依据。     

The cardiovascular functions of salusin‐β mediated by muscarinic receptors,glutamate receptors or L‐type calcium channels within the rostral ventrolateral medulla of rats

Salusin‐α and salusin‐β are newly identified bioactive peptides of 28 and 20 amino acids, respectively, that were initially predicted using in silico analyses and are widely distributed in the endocrine system, hematopoietic system, and central nervous system. The goal of our study was to investigate the cardiovascular effect of salusin‐β microinjections into the rostral ventrolateral medulla (RVLM) in anesthetized rats and study their mechanism of action. Microinjection of the artificial cerebrospinal fluid (aCSF) into the RVLM did not affect the blood pressure (BP) or heart rate (HR) in anesthetized rats. Topical application of salusin‐β into the RVLM produced a dose‐dependently increase of BP in anesthetized rats. Microinjection of higher dose salusin‐β produced significant tachycardia. Prior application of the L‐NAME into the RVLM of rats did not alter the hypertension and tachycardia induced by intra‐RVLM salusin‐β. Notable, the cardiovascular functions elicited by intra‐RVLM salusin‐β were significantly decreased by pretreatment with Nic, KYN and atropine. In conclusion, the present study shows that the hypertension and tachycardia induced by intra‐RVLM salusin‐β might be partly mediated, at least in our opinion, by muscarinic receptors, glutamate receptors or L‐type calcium channels.     

复合管功率超声压电换能器的径向振动特性

在纵向复合压电超声换能器基础上,提出并研究带预应力外壳的径向复合管压电超声换能器的径向振动特性。换能器由径向极化薄壁压电陶瓷圆管与预应力金属圆管外壳径向复合而成。依据机电类比原理,建立起复合系统的径向振动等效电路,并给出其径向振动共振频率方程。结合数值计算例,探讨换能器的共振和反共振频率以及有效机电耦合系数与预应力圆管半径比之间的关系。设计制作4个径向复合管压电超声换能器样品,通过试验测量换能器径向振动共振和反共振频率。结果表明,换能器径向共振频率的理论值与测量结果符合较好,误差小于5%。     

Immunocytochemical analysis of connexin expression in the healthy and diseased cardiovascular system

Gap junctions play essential roles in the normal function of the heart and arteries, mediating the spread of the electrical impulse that stimulates synchronized contraction of the cardiac chambers, and contributing to co-ordination of activities between cells of the arterial wall. In common with other multicellular systems, cardiovascular tissues express multiple connexin isotypes that confer distinctive channel properties. This review highlights how state-of-the-art immunocytochemical and cellular imaging techniques, as part of a multidisciplinary approach in gap junction research, have advanced our understanding of connexin diversity in cardiovascular cell function in health and disease. In the heart, spatially defined patterns of expression of three connexin isotypes-connexin43, connexin40, and connexin45-underlie the precisely orchestrated patterns of current flow governing the normal cardiac rhythm. Derangement of gap junction organization and/or reduced expression of connexin43 are associated with arrhythmic tendency in the diseased human ventricle, and high levels of connexin40 in the atrium are associated with increased risk of developing atrial fibrillation after coronary by-pass surgery. In the major arteries, endothelial gap junctions may simultaneously express three connexin isotypes, connexin40, connexin37, and connexin43; underlying medial smooth muscle, by contrast, predominantly expresses connexin43, with connexin45 additionally expressed at restricted sites. In normal arterial smooth muscle, the abundance of connexin43 gap junctions varies according to vascular site, and shows an inverse relationship with desmin expression and positive correlation with the quantity of extracellular matrix. Increased connexin43 expression between smooth muscle cells is closely linked to phenotypic transformation in early human coronary atherosclerosis and in the response of the arterial wall to injury. Current evidence thus suggests that gap junctions in both their guises, as pathways for cell-to-cell signaling in the vessel wall and as pathways for impulse conduction in the heart, contribute to the initial pathogenesis and eventual clinical manifestation of human cardiovascular disease.     

Vibration-assisted filling capability in thin wall investment casting

Understanding the mechanism of the vibration needed to fill thin section and clarifying the dominant control parameters of the vibration in thin wall investment casting are the keys to producing sound casting. The filling capability in thin wall investment casting method can be assessed by the metal head. It was found that the effect of the vibration on the metal head is markedly dependent on acceleration of applied vibration. Two potential mechanisms were observed from the experimental results during the filling process in thin wall casting: discontinuous propagation flow in vibration conditions and continuous propagation flow without vibration. These mechanisms can modify the contact angles between liquid metal and a wall of the mold. Experiments also showed that two features of the transition can be observed from the front of the morphology: coherent liquid metal front, this occurs in thin wall investment casting when the acceleration due to vibration is less than (1?g) and jetting at the free surface, this occurs in thin wall investment casting when the acceleration due to vibration exceeds 1?g.     

差动变压器式位移传感器及其在磁悬浮轴承中的应用

针对差动变压器式位移传感器的性能及其在磁悬浮轴承中的应用,理论分析传感器与磁悬浮轴承转子之间加入不同隔层时对传感器输出的影响;对传感器进行静态和动态标定,并将其应用于2自由度和5自由度磁悬浮轴承试验台进行静态和动态悬浮。研究结果表明：该传感器测试范围在–0.5～＋0.5 mm时,线性度可达±1.38%,灵敏度为20.18 mV/μm,截止频率在800 Hz左右;理论分析加入非导磁隔层不影响传感器性能,但实际中涡流、漏磁等多方面原因将影响传感器的静动态性能;在2自由度试验台上实现磁悬浮转子2自由度的静态悬浮,不加入隔层时转子的静态位移振动峰峰值小于5 μm,加入隔层时转子的静态位移振动峰峰值小于10 μm;在5自由度试验台上实现了磁悬浮转子的高速旋转,转速为30 kr/min,不加隔层时转子两端的径向振动峰峰值为25 μm,加入隔层时转子两端的径向振动峰峰值为25 μm,但波形没有不加隔层时规则。研究结果为差动变压器式位移传感器的设计,并将其应用于磁悬浮轴承系统中提供一定的理论和试验基础。     

基于BP神经网络的立铣加工振动快速预估

结合研制的立铣加工过程虚拟仿真系统和实验测量铣削力信号,训练并建立BP神经网络模型,快速实现铣削过程刀具-工件系统振动状态的预估.预估的振动结果与实验测量数据较为吻合,表明铣削虚拟仿真系统与神经网络技术的结合能够高效低耗地用于不同铣削加工条件下铣削振动状态的快速预估和加工过程监测.     

高阶统计量与RBF网络结合用于齿轮故障分类

提出一种基于高阶统计量特征提取的径向基函数网络齿轮故障分类方法,以齿轮箱振动信号的高阶统计量估计值作为齿轮故障特征,以径向基函数神经网络作为分类器,成功地对齿轮故障进行了分类。研究表明,高阶统计量和径向基函数神经网络相结合的齿轮故障分类方法是有效的。     

新型高压清洗机自动调速系统的理论与实验研究

介绍新研制的一种新型清洗机所采用的调压溢流阀和转速调节阀结构、原理及工作过程。结合调压溢流阀和转速调节阀的结构和工作原理,运用弹性水击理论、阀和泵动作的边界条件,对两阀内部和两阀之间的管道流场建立相应的数学模型,得出管道系统的压力变化规律。在两阀内部,利用计算出来的解析解对阀内部结构尺寸参数和弹簧弹性系数进行优化设置,最后通过实验,检验了计算结果的正确性。     

电动汽车的开关磁阻电动机驱动及其系统激振仿真

将新型开关磁阻电动机（switched reluctance motor,SRM）作为驱动源,应用于电动汽车。同时,根据开关磁阻电机的振动特性,以电机为激振源,导出了电机径向力和切向力随时间变化的解析表达式,用解析方法分析了它们对车辆振动系统的激振程度。仿真计算结果显示,开关磁阻电机的径向力是振源的主要激振力,是系统振动的主要因素。研究结果为电动汽车驱动系统的开发及其运行稳定性研究提供了理论依据。     

探讨高血压合并冠心病患者动态血压与心电图的相关性

目的探讨高血压合并冠心病患者的血压波动与ST-T改变及心律失常发生的相关性。方法对88例高血压和/或冠心病患者进行分组研究,其中高血压合并冠心痛组25例,高血压无并发症组28例.冠心病组35例,所有患者均同步监测24h动态血压(ABPM)和动态心电图(DCG),观察不同组血压波动与ST-T改变和心律失常发生的相关性并进行对照分析。结果 ABPM与DCG同步检出高血压合并冠心痛组血压变化与ST-T改变和心律失常发生率为88%,明显高于高血压无并发症组42.9%和冠心病组65.7%,表明高血压合并冠心痛患者血压变化与ST-T改变及心律失常有关联。结论 ABPM与DCG同步检测有助于鉴别血压变化与心脏的关系,对预防心血管事件的发生具有积极的临床意义。     

Dynamic characteristics of the rotor in a magnetically suspended control moment gyroscope with active magnetic bearing and passive magnetic bearing

For a magnetically suspended control moment gyroscope, stiffness and damping of magnetic bearing will influence modal frequency of a rotor. In this paper the relationship between modal frequency and stiffness and damping has been investigated. The mathematic calculation model of axial passive magnetic bearing (PMB) stiffness is developed. And PID control based on internal model control is introduced into control of radial active magnetic bearing (AMB), considering the radial coupling of axial PMB, a mathematic calculation model of stiffness and damping of radial AMB is established. According to modal analysis, the relationship between modal frequency and modal shapes is achieved. Radial vibration frequency is mainly influenced by stiffness of radial AMB; however, when stiffness increases, radial vibration will disappear and a high frequency bending modal will appear. Stiffness of axial PMB mainly affects the axial vibration mode, which will turn into high-order bending modal. Axial PMB causes bigger influence on torsion modal of the rotor.     

镶拼式复合压电超声换能器的径向振动特性

对一种镶拼式复合压电超声换能器的径向振动特性进行分析。该镶拼式复合压电超声换能器由弹性内芯、矩形压电陶瓷晶堆环组及金属预应力管径向复合而成。采用压电陶瓷晶堆,可大幅提高换能器的功率容量及有效机电耦合系数。依据机电类比原理,得出换能器的机电等效电路和共振频率方程;探讨换能器的第1、2阶共振和反共振频率及机电耦合系数与其几何尺寸之间的关系,并进行有限元仿真分析和试验测试。研究表明,换能器第1阶径向共振及反共振频率随其内芯内径及预应力管外径增大而降低;第2阶共振频率随内芯内径增大存在极小值,但随预应力管外径增大而下降,并且第2阶共振模式的有效机电耦合系数较高。对换能器共振频率的测试和仿真表明,理论与试验及仿真结果相符合。     

Frequency correspondence between membranes and functionally graded spherical shallow shells of polygonal planform

The present work presents further development of the linking relationships between vibration frequencies predicted by different theories, and they are extended from a flat plate to a spherical shallow shell. In analogy with the membrane vibration problem, exact correspondences are found for vibration frequencies of a functionally graded spherical shallow shell using the classical theory and the first-order and third-order shear deformation theories. Only the predominantly stretching and thickness-shear vibration of dilatational type and predominantly flexural vibration are considered in this work. They are decoupled from the predominantly stretching and thickness-shear vibration of rotational type. These results apply to a simply supported functionally graded spherical shallow shell of polygonal planform with arbitrarily varying material properties in the thickness direction. A Winkler–Pasternak elastic foundation and rotary inertias are incorporated. It is proved that the mathematical analogy warrants positive free vibration frequencies for the shallow shell. Mori–Tanaka's scheme is used to estimate the material properties in the numerical results.     

滚珠丝杠进给系统滚动结合部径向动态特性参数辨识

针对滚珠丝杠进给系统滚动结合部径向动态特性参数难以确定的问题,提出了一种进给系统在整机状态下滚动结合部径向动态特性参数辨识方法。该方法将丝杠简化为欧拉-伯努利梁,以建立在简谐激振力作用下丝杠轴向上各截面的径向振动方程;设计实验以测量丝杠上测量点的径向振动位移,结合丝杠径向振动方程所计算的理论值建立优化目标函数,基于人工鱼群算法优化识别出滚动结合部的径向刚度及径向阻尼参数。以自行研制的滚珠丝杠进给实验台为研究对象,采用该方法对其导轨副、两端轴承组及滚珠丝杠副滚动结合部的径向刚度与径向阻尼参数进行识别。实验结果表明：以该方法辨识的结合部的参数所计算的丝杠上测量点的径向振动位移与实验测试值之间的误差在3.0%以内,验证了该方法的正确性和有效性。     

计及动力刚化的柔体动力学

提出两种计及动力刚化影响的动力学建模方法；有限段方法和一致线性化动力学方法。分析了这两种动力不主动力刚化的机理，有限段方法将柔体动力学问题转化为带有柔性的多刚体体系统动力学问题，计及了几何非线性的影响，适合于解决梁式结构的动力学问题；一致线性化动力学方法将变形场描述成为变形广义坐标的非线性形式，在适当的阶段线性化，可得到一致线性化动力学方程，自然计及了动力刚化项，适合于柔体的小变形问题。     

杆状弯曲行波超声电机定子和转子的优化设计

采用有限元模态分析和谐响应分析方法，分析了杆状弯曲行波型超声电机定了上开槽尺寸与其一介弯曲固有频率的关系以及开槽尺寸与定子上与转子接触部位振幅的关系。对电机转子的两种设计方案进行运动分析和有限元接触分析，并得出两者结论是一致的。     

用于高速转轴径向振动检测的光纤传感技术

采用光纤测量技术实现航空叶轮泵高速转轴径向振动的检测,对检测系统的工作原理做了详细介绍。设计了新型的光纤测头,提出相应的补偿方案,并对补偿机理进行了详细的分析。对测试系统的特性进行了研究,得出位移特性调制函数表达式,给出了仿真曲线。理论计算和仿真分析表明, 该测试系统能有效地消除因光源光强波动、光纤弯曲损耗、表面反射率等因素对输出特性的影响,可以在叶轮泵内部电磁干扰严重和高温等恶劣环境下实现对高速转轴径向振动的检测。实验测试结果表明,随着转轴转速由1 000 r/min提高到10 000 r/min,径向振动幅值单调增加,这与实际情况相符合。