In Vitro hydrodynamic evaluation of prosthetic polymer heart valves in steady flow

Hydrodynamic comparison of two polymer valves with two mechanical valves is presented. The valves were perfused in a steady flow system, and comparisons between the valves were made on the transvalvular pressure distribution and drop, opening area, and leakage volume. Particular emphasis was placed on a slit-type bileaflet polymer valve which was newly designed and fabricated in our research group. The results showed that the functional characteristics of a slit-type bileaflet polymer valve compared favorably with that of mechanical valves. This valve may be a viable and inexpensive alternative, especially for short-term use in TAH or VAD systems.     

佩戴防尘口罩对吸入气溶胶粒度影响的实验研究

本文介绍了应用级联撞击器和佩戴口罩的人头模型在天然铀燃料元件加工现场测定吸入气溶胶粒度的方法。结果表明,佩戴口罩使得吸入气溶胶的活度中值空气动力学直径(AMAD)变小,并且吸入气溶胶的 AMAD 值与场所气溶胶的 AMAD 值有一定关系,粒径分布类型也发生改变。文中还报告了口罩的漏过率有随微尘粒径减小而增大的趋势。实验结果对内照射剂量估算以及评价口罩的防尘能力有一定的参考价值。     

CAN总线在汽车轮胎监测系统中的应用设计

针对当前独立的汽车轮胎监测系统存在的弊端提出一种新的实现方案,动态监测汽车各轮胎的参数,并把动态参数通过CAN总线传输到汽车驾驶室仪表上,实现汽车轮胎故障预警功能.该方案增加了系统的可靠性、灵活性,扩展了汽车轮胎压力监测系统的使用场合,在大型车辆的安全系统中有很高的实用价值.     

对制冰池蒸发器的改造及分析

本文介绍了在某单位制冰池制冷系统改造项目中,蒸发器所出现的一些问题、解决方案以及一些细节问题.     

制氢工艺改造的节能效果

介绍甲醇裂解制氢工艺特性,比较电解制氢和甲醇裂解制氢不同生产工艺电能消耗,分析节电机理,计算削峰能力,评价经济效果,为制氢生产企业提供典例。     

压力容器的模糊可靠度计算

根据模糊数学原理和可靠性设计原理,介绍了模糊可靠度原理,并举例说明了压力容器的模糊可靠度计算。     

逻辑阀概述

对逻辑阀的特性、参数进行了总结,介绍了逻辑阀的使用方法和注意事项.     

体积补偿式正压漏孔校准方法改进分析

针对被校漏孔接头种类繁多,接头漏气难以避免且其值测量不方便的问题。采用两种方式进行修正:一方面利用进退活塞得到两个修正的体积系数,推导出接头漏气和漏孔漏率引起的差压变化之比的测试方法,用以修正接头漏气的影响;另一方面通过粘滞流公式推导出微小压力差下气体漏率与压力差近似成正比。通过调整校准室的压力,利用差分的原理减少漏气对校准结果的影响。两种修正方式的采取,解决了常规漏孔接头漏气难以原位测量或减小到可以忽略的问题,降低了对被校漏孔接头的要求,提升了体积补偿法的测量准确度和工作效率,同时将校准下限延伸到10^-7Pa·m³/s。     

变压器铁芯接地电流在线监测系统设计及其带电检测不确定度评定

摘要：在保持变压器铁芯接地电流在线监测系统硬件设施保持不变的前提下,研究一种该系统的算法升级策略。使用30个周期数据形成的多测点多列交叉神经网络支持的机器学习系统对该系统的接地电流进行测量,同时研究一种基于6倍标准误差率的检测不确定度标识方法,研究该系统算法升级策略的同时,分析不确定度的标识方法。技术革新后的变压器铁芯接地电流监测误差,小于±0.395%,可以基本满足对变压器铁芯接地电流的测量需求。且该算法可以排除实际测量中因为变压器内部、外部复合故障导致的接地电流产生机理差异性影响。同时,重点研究了对铁芯接地电流误差测量中的扩展不确定度测量方法确认问题,认为6倍标准偏差率作为扩展不确定度测量标度,可以满足该系统的测量误差标定需求。     

A practical procedure to assess critical defects in pressure vessels subjected to fatigue loads

PSA pressure vessels are equipments used in refining industries for cleaning the hydrogen upcoming from the reforming or hydrogen generation unities. In one regular inspection, some embedded cracks were found in the entrance nozzle-head weld. Then, instead of advance its decommissioning and waste much time until the refinery purchase a new vessel, a structural stress analysis using the finite element method was performed in order to obtain the stress field at the site of the crack, considering the real loading cycle. Despite the acting load is only the internal pressure, the nozzle-head weld is a region where a complex stress state is present (bending and axial stresses). ASME VIII Division 2, Appendix 5 addresses this issue by applying a rule for multiaxial fatigue life estimation for non-proportional loading. With ASME estimated fatigue life results, it was applied the British Standard 7910 procedure to decide if the equipment can operate safely. The calculation also assesses the crack growing by using a modified bi-linear Paris law. Finally, it was computed how long the cracks would take to get to their critical size and then retire definitively the equipment.