叶顶间隙对轴流风机气动噪声影响的数值研究

通过求解轴流风机全流场内三维非定常湍流的控制方程组,模拟了轴流风机叶顶间隙内的流场分布,捕捉到了叶顶间隙内泄漏涡的存在。在风机全流场数值模拟的基础上,对叶顶间隙内的气动噪声分布特性进行了数值预测:利用宽频声源模型模拟得到了叶片表面的声功率分布;利用大涡模拟(LES)、FW-H声学模型并结合快速傅里叶变换(FFT)技术,预测了叶顶间隙内各监测点不同频率下的气动噪声声压级的大小,并分析了叶顶间隙对气动噪声的影响。     

Assessment of particle retention and clearance in the intrapulmonary conducting airways of hamster lungs with the fractionator1

A modified version of the fractionator was used to estimate the total number of polystyrene microspheres retained in the airways of hamster lungs at two different time points after inhalation. A systematic three-stage subsampling procedure with known sampling fractions was adopted. First, each lung was cut into slices, from which primary disectors were sampled systematically with a known sampling fraction. From each primary disector, smaller sub-disectors were subsampled, and the corresponding sampling fraction was estimated by point counting. Finally, a few particles were counted at the microscopic level in the sub-disectors, and the final estimate of total particle number (which is unbiased irrespective of any tissue deformations) was easily computed as a product of the counted number times the reciprocal of the successive sampling fractions. The error variance of each estimate was assessed from the data using a new estimator. An average of 6% of the deposited particles were retained on the epithelial surface of the intrapulmonary conducting airways shortly after the inhalation, from which at least one-third was already phagocytosed by macrophages. After 24 h, an average of 87% of the particles retained shortly after the inhalation had been cleared. The proportion of particles ingested by macrophages had increased to at least 87%, in three out of four animals studied.     

离心空压机气封轴向间隙的探讨

指出了离心空压机气封轴向间隙存在的问题及造成的危害。根据实例分析了轴向间隙的影响因素，提出了解决轴向间隙不合理的方法。     

浇铅法修复电动机的滑动轴承

一般要求电动机的滑动轴承精度高、振动小 ,若滑动轴承间隙过大 ,不能继续使用 ,应尽量修复 ,本文介绍了用浇铅法修理滑动轴承的一般步骤。     

海拔2000m以上的低气压条件对电子产品安全性能的影响

讨论了高海拔低气压环境对电子产品绝缘性能和温升的影响,给出了不同气压下击穿电压的修正值以及不同气压条件下电气间隙的修正值。通过对显示器和适配器在不同温度不同气压条件下的比较试验说明了气压对样品温升的影响。     

冲槽机冲槽错位原因分析与改善

文章通过介绍冲槽机冲孔原理和分析冲槽模具间隙对冲孔断面的影响,针对对位错品质报废率上升的原因分析采取冲槽模具设备改造措施,完成品质改善,为公司制作高难度板内层对位缺陷改善和控制起到了关键作用;同时,设备改造技术推广直接产生巨额经济节余。     

蒸发时间对两级凝胶法制备的聚醚砜膜结构和性能的影响

主要探讨了蒸发时间对用两级凝胶法(dual—bath coagulation method)所制得的聚醚砜(PES)超滤膜的性能和结构的影响．结果表明,随着蒸发时间的延长,水通量先减小后增大;肌肝和尿素去除率均是先升高而后降低,然后再升高的趋势;膜的孔隙率上升,平均孔径下降．在蒸发时间为10s时,肌肝和尿素去除率最高,且水通量适中,是血液净化用聚醚砜膜的最佳成形条件．     

复合材料层合板连接件力学性能影响因素分析

在位移载荷作用下,基于二维有限元模型,通过编写材料失效准则和刚度退化规则的ABAQUS用户子程序USFLD,并考虑剪切非线性效应,分析了一般铺层下配合间隙、挤压面切向摩擦系数和开孔形状对复合材料层合板单钉螺栓连接力学性能的影响。结果表明:小的配合间隙、大的挤压面切向摩擦系数和开孔形状采用圆孔时均有利于提高连接强度。     

CCL中铜屑产生原因的分析和处理

通过分析CCL中铜屑产生的原因,阐明了CCL中铜屑的预防和发生铜屑的处理。     

邮政国际速递邮件EDI电子报关方案浅谈

简要介绍了我国海关EDI电子报关的情况及邮政国际速递报关现状，提出了两个邮政国际速递EDI电子报关方案并加以分析、比较。