Failure and hydrodynamic function testing of explanted pericardial and porcine bioprosthetic valves

The long-term durability and function of cardiac bioprostheses can be affected by both calcification and mechanical failure of the tissue. The mechanisms of failure and hydrodynamic function of 66 explanted bioprostheses have been studied. The majority of porcine valves were heavily calcified with leaflet tears adjacent to the calcification at the commissures. These tears caused prolapsed leaflets and regurgitation of between 30 and 70 per cent. Only three porcine valves had tissue failure in the absence of calcification. The majority of pericardial valves failed due to leaflet tears at the edge of the frame in the absence of macroscopic calcification. These tears also produced prolapsed leaflets and large regurgitation in hydrodynamic tests. Three pericardial valves were heavily calcified and stenotic without leaflet tears. Leaflet dynamics in the pericardial valves were affected by host tissue ingrowth which produced increased pressure drops across the valves, an asymmetrical open position and leaflet flutter. In the absence of calcification and leaflet tears, there was little change in the function of explanted porcine valves.     

Continuous-wave Doppler for the noninvasive evaluation of aortic blood velocity and rate of change of velocity: evaluation in dogs

A new continuous-wave Doppler device is described, which has the capability of measuring peak aortic blood velocity and acceleration noninvasively in the ascending aorta of patients. To test the accuracy of the device, blood velocity and acceleration in the ascending aorta were compared with measurements obtained using an electromagnetic flowmeter in 16 open-chest anesthetized dogs. The Doppler probe was hand held directly on the aorta. Aortic flow was measured with a cuff electromagnetic flow transducer placed at the root of the aorta. Isoproterenol and propranolol, sometimes in combination with lidocaine, were administered intravenously to augment or reduce left ventricular contractile performance. Values of peak velocity, measured with the Doppler, corresponded closely to values measured with the electromagnetic flowmeter (r = 0.95). Values of peak acceleration also corresponded closely with the electromagnetic flow measurements (r = 0.96). The results indicate that valid measurements of blood acceleration in the ascending aorta, as well as blood velocity, can be obtained with continuous-wave Doppler.     

Two-component laser Doppler anemometer for measurement of velocity and turbulent shear stress near prosthetic heart valves

The velocity and turbulent shear stress measured in the immediate vicinity of prosthetic heart valves play a vital role in the design and evaluation of these devices. In the past hot wire/film and one-component laser Doppler anemometer (LDA) systems were used extensively to obtain these measurements. Hot wire/film anemometers, however, have some serious disadvantages, including the inability to measure the direction of the flow, the disturbance of the flow field caused by the probe, and the need for frequent calibration. One-component LDA systems do not have these problems, but they cannot measure turbulent shear stresses directly. Since these measurements are essential and are not available in the open literature, a two-component LDA system for measuring velocity and turbulent shear stress fields under pulsatile flow conditions was assembled under an FDA contract. The experimental methods used to create an in vitro data base of velocity and turbulent shear stress fields in the immediate vicinity of prosthetic heart valves of various designs in current clinical use are also discussed.     

Theoretical calculations and experimental verification for the pumping effect caused by the dynamic micro-tapered angle

The atomizer with micro cone apertures has advantages of ultra-fine atomized droplets, low power consumption and low temperature rise. The current research of this kind of atomizer mainly focuses on the performance and its application while there is less research of the principle of the atomization. Under the analysis of the dispenser and its micro-tapered aperture’s deformation, the volume changes during the deformation and vibration of the micro-tapered aperture on the dispenser are calculated by coordinate transformation. Based on the characters of the flow resistance in a cone aperture, it is found that the dynamic cone angle results from periodical changes of the volume of the micro-tapered aperture of the atomizer and this change drives one-way flows. Besides, an experimental atomization platform is established to measure the atomization rates with different resonance frequencies of the cone aperture atomizer. The atomization performances of cone aperture and straight aperture atomizers are also measured. The experimental results show the existence of the pumping effect of the dynamic tapered angle. This effect is usually observed in industries that require low dispersion and micro- and nanoscale grain sizes, such as during production of high-pressure nozzles and inhalation therapy. Strategies to minimize the pumping effect of the dynamic cone angle or improve future designs are important concerns. This research proposes that dynamic micro-tapered angle is an important cause of atomization of the atomizer with micro cone apertures.     

差速搅拌捏合机的螺棱设计及其螺旋角优化

针对煤质活性炭制备过程中煤粉物料的混合均匀度问题,根据物料特性,对现有差速搅拌捏合机进行了螺棱的重新设计,使其更能满足特定物料的混合。由于螺棱螺旋角对搅拌质量、搅拌效果有很大影响,对影响螺棱螺旋角的两个因素(物料与螺棱摩擦角、物料内部剪切角)进行了分析,得出一个螺旋角的合理取值范围。对其在合理取值范围之内的螺旋角,通过ANSYS进行了不同螺旋中径螺旋角下螺棱危险节点的应力最大值的分析,归纳出了螺旋角对应力最大值的影响规律。研究结果表明,在满足合理定义域、物料内部剪切力的条件下,螺棱危险节点的应力最大值在螺棱螺旋角取范围为70°β75°时最小;当螺棱螺旋角位于这个取值范围内时,螺棱对物料的搅拌质量较高,且螺棱使用寿命更长,工作更为可靠。     

Mathematical model for determination of strand twist angle and diameter in stranded-wire helical springs

The twist angle of strands has a significant effect on the performance of stranded-wire helical springs. This paper proposes two models (a precise mathematical model and an approximate mathematical model) for calculation of the twist angle and the diameter of strands formed of an arbitrary number of wires. These two parameters can be derived from the screw pitch of strands and the diameter and number of their wires, regardless of the model used. In comparative and analytical studies, it was determined that for strands with the same number of wires, the larger the ratio of the screw pitch to the diameter of the wires is, the smaller the relative errors of the two models are. Only when the foresaid ratio is two times larger than the number of wires, the results of the approximate mathematical model can be acceptable. In other cases, the approximate mathematical model cannot be used. Finally, application software was developed for direct precise-mathematical-model calculation of the twist angle and diameter of strands formed of arbitrary wires.     

Comparison of statistical methods for single component velocity determination in a bubble flow

The separate determination of single component velocities in two-phase flow systems by statistical methods requires signals, which are proportional to the individual flow patterns. Suitable values can be measured by optical transmission techniques with simultaneous absorption and scattering of visible or infrared radiation. Under turbulent flow conditions there is usually only low correlation of measured quantities, especially for a greater sensor distance in flow direction. Therefore, the efficiencies of different statistical methods for transit time determination with respect to single component velocities are compared in this investigation, utilising an extended diffusion model for the transport process. An application to bubble flow is discussed.     

平面低副四杆机构极位夹角及行程速比系数分析

通过对平面低副四杆机构极位夹角传统定义的分析,根据机构中各杆长的变化,对极位夹角的定义进行了扩展,在此基础上对行程速比系数的取值范围进行了合理的选择。     

Improved instrumentation for blood flow velocity measurements in the microcirculation of small animals

Microcirculation is the generic name of vessels with internal diameter less than 100 microm of the circulatory system, whose main functions are tissue nutrition and oxygen supply. In microcirculatory studies, it is important to know the amount of oxyhemoglobin present in the blood and how fast it is moving. The present work describes improvements introduced in a classical hardware-based instrument that has usually been used to monitor blood flow velocity in the microcirculation of small animals. It consists of a virtual instrument that can be easily incorporated into existing hardware-based systems, contributing to reduce operator related biases and allowing digital processing and storage. The design and calibration of the modified instrument are described as well as in vitro and in vivo results obtained with electrical models and small animals, respectively. Results obtained in in vivo studies showed that this new system is able to detect a small reduction in blood flow velocity comparing arteries and arterioles (p <0.002) and a further reduction in capillaries (p<0.0001). A significant increase in velocity comparing capillaries and venules (p <0.001) and venules and veins (p <0.001) was also observed. These results are in close agreement with biophysical principles. Moreover, the improvements introduced in the device allowed us to clearly observe changes in blood flow introduced by a pharmacological intervention, suggesting that the system has enough temporal resolution to track these microcirculatory events. These results were also in close conformity to physiology, confirming the high scientific potential of the modified system and indicating that this instrument can also be useful for pharmacological evaluations.     

血液中铅镉分析方法的研究

在人体中,铅和镉都属于有害元素。随着工业的发展,铅、镉的世界排量及排入环境汇总的量逐年增加,排入环境中的铅和镉通过空气、水、食物、烟草、饮料等途径进入人体,对人体健康构成潜在危害。本文利用石墨炉原子吸收光谱法,采用直接稀释方式处理血液,并用中国疾病预防控制中心的标准样品进行对比。结果表明,利用血液铅镉分析仪作为分析仪器,直接测定血液中铅、镉含量,结果可靠。     

Note: Reflection-type micro multipoint laser Doppler velocimeter for measuring velocity distributions in blood vessels

We have developed a laser Doppler velocimeter (LDV) for measuring velocity distributions in blood vessels. We converted a transmission-based LDV into a reflection-based LDV to make it suitable for clinical applications. The velocity distribution image of a serpentine flow channel obtained could be qualitatively explained by the numerical results. Finally, we evaluated the system by using it to measure injection of blood into a glass tube by a syringe pump. The results obtained demonstrate that erythrocytes can be used as seeding particles for the reflection-type micro multipoint LDV. The results obtained are useful as basic data for clinical applications.     

核电站用核级阀门开发及准入条件

一、核电发展背景 从20世纪90年代初我国建成第一座自行设计、建造和运行的核电机组，至今已运行15年，创造了良好的业绩。至21世纪初近30年历程，通过自主开发或国外引进相继建成了11座核电机组（秦山一期300MW、秦山二期2×600MW、大亚湾2×900MW、岭澳一期2×900MW、田湾2×1000MW、秦山三期2×1000MW），总装机容量达到了8700MW。[第一段]     

A venous pulse Doppler catheter-tip flowmeter for measuring arterial blood velocity, flow, and diameter in deep arteries.

Numerous schemes have been used for measuring hemodynamic properties of deeply lying arteries; however, all have their limitations. This paper describes a new relatively nontraumatic intravenous approach that uses a catheter in connection with a pulsed ultrasonic Doppler velocity meter (PUDVM) and an echo track. The catheter was initially tested in a hydraulic model system for calibration of velocity and flow parameters. Lately, the catheter has permittted measurements of local instantaneous blood velocity, flow, and wall motion characteristics in adult Beagle dogs in the abdominal aorta and iliac artery. Evaluation studies have been conducted to compare the catheter-tip recordings with an independent method for measuring blood flow and wall motion. Coupling of this catheter-tip device with the PUDVM and echo track provides chronic measurements of hemodynamic parameters in these deep vessels which were virtually impossible to obtain previously. This technique may prove useful in monitoring vessel pathology longitudinally as well as in basic experimental situations requiring flow and arterial wall mechanical properties.     

通用阀门焊接评定ASME和EN标准的应用

分析了阀门行业在进行ISO9000和CE认证过程中，在焊接工艺评定和焊工评定方面所使用的ASMEⅨ与EN287和EN288标准的不同之处。指出了焊接评定过程中应特别注意的问题。     

百万吨乙烯主要装备国产化浅析之泵阀篇

泵是石化生产装置中用量最大的转动设备,主要用于输送各种液体介质,如原油、成品油、化工原料、中间产品和成品等。据统计,一个1000万t／a的炼油厂需要各种泵1000多台;一个100万t／a的乙烯厂需要各种泵达3000多台（见表1）。预计“十一五”期间,国内新建炼油和石化项目对石化用泵的需求量达N30000～40000台。     

城市天然气输配系统阀门的选型

介绍了我国燃气系统用阀门的现状 ,分析了城镇天然气输配用阀门的使用工况、阀门结构性能要求及其合理的选型条件 ,给出了地下管网中燃气阀门的发展方向和选用方法     

Subsurface hardening in erosion-damaged copper as inferred from the dislocation cell structure,and its dependence on particle velocity and angle of impact

Previously published measurements of the cell diameters d of dislocation cells underneath copper surfaces exposed to particle erosion were evaluated in terms of the subsurface stresses τ to which they correspond. These were compared with the elastic stresses expected underneath spherical indenters impacting on the surface with different speeds. The inferred stresses differ markedly from theoretical predictions, not only in regard to the dependence on speed and angle of impact but even in regard to their decay along the z axis, the direction normal to the surface. Instead of τ decreasing as z^?n with n continuously rising from 0 at a shallow depth to 2 at large depths, as predicted from elastic theory, the stresses follow a z^?1 dependence throughout the measured range. All data are satisfactorily explained by the relationship $\text{1/d = (7/z)v}{}^{\mathrm{<mtext>2</mtext><mtext>5</mtext>}}\text{sin α ≈ τ/100}$ (using MKS units), where v stands for the velocity of the impacting particles, namely rather irregularly shaped alumina particles 50 μm in diameter, and α is the angle of impact. No theoretical explanation has so far been found to account for this result. It is noted, however, that previously a z^?1 decay of stress had already given excellent results in a theoretical interpretation of the subsurface shear strain underneath a surface subject to sliding wear. Further, sin α is the direction cosine for the normal force component, whereas a velocity dependence of $\text{v}{}^{\mathrm{<mtext>2</mtext><mtext>5</mtext>}}$ is found from elastic theory for the depth scaling of the elastic stress due to a spherical indenter. Suggestions are made for further experiments.     

核电厂闸阀锅炉效应的危害与防治

论述了核电站用阀门锅炉效应的危害及其产生的机理。结合阀门的功能结构、核电厂的运行以及事故工况、概率安全分析和利益代价比分析等因素,给出待改进阀门的判断方法。针对阀门的不同情况,提出了相应的改进方案。以大亚湾核电厂和岭澳核电厂为实例,介绍了防治阀门锅炉效应的良好实践。     

核电泵阀国产化工作取得重要进展

国家积极发展核电战略和自主发展核电的方针，为装备制造业带来了前所未有的发展机遇，也使装备制造业面，临着巨大压力。近两年国产化工作取得了重要进展。自2007年7月大连核电装备国产化会议以来，国产化工作取得了重要进展。在建的二代改进型百万千瓦核电站综合国产化率达到75％～80％，新近核准项目综合国产化率可达80％以上。实践证明在核电建设中，坚持四个自主的方针是完全正确的，装备国产化大大降低了工程造价和运行费用，为大力发展核电创造了条件；与此同时装备制造业的设计制造水平、装备能力和企业管理水平都有了全面提升。     

阀门流量流阻测试装置测量不确定度的研究

分析了影响阀门流量流阻测试装置测量不确定度的主要因素,以及流量系数与流阻系数测量不确定度的求解方法,并通过A类不确定度方法举例计算。