初论环境信息污染及预防

从SARS所引发的社会现象分析,首次从环境角度对信息污染进行探讨,提出了环境信息污染的含义及特征。并针对环境信息污染的潜在危害性,论述治理环境信息污染应以预防为主。建议政府和个人逐步通过建立“信息墙”,使信息更加有序、有条理,以此来预防和减少环境信息污染。     

气流导柱对集尘滤筒脉冲清灰性能的影响

常规滤筒集尘器在反吹清灰时,存在滤筒下部清灰能量过盛而上部清灰能量不足的现象,导致滤筒上部清灰不彻底而下部易破损.提出了在滤筒内部设置气流导柱,引导反吹气流,改善滤筒内部流场的方案.采用数值模拟与试验测试相结合的方法,对滤筒反吹清灰性能进行了分析.结果表明:内置气流导柱的新型滤筒反吹压力分布更加均匀,滤筒中下部冲击压强下降至原型滤筒的65％,解决了过喷吹问题,滤筒上部形成冲击压强尖峰解决了欠喷吹问题.同等工况下,内置气流导柱的新型滤筒相比原型滤筒拥有更长的使用寿命,预估使用寿命可达到普通滤筒的8倍.     

Amniotic fluid fibrinolytic system in fetal neural tube defects

Second trimester amniotic fluid fibrinolytic system was examined in normal pregnancies and those complicated by anencephaly, spina bifida and fetal chromosome abnormalities. No significant difference was demonstrated between the fibrinolytic systems from normal pregnancies and those complicated by fetal chromosome abnormalities. In pregnancies complicated with anencephaly and spina bifida no significant difference was demonstrated for alpha-1-antitrypsin, alpha-1-antichymotrypsin and urokinase. Plasminogen was significantly lower (p < 0.02) and plasmin significantly higher (p < 0.001) than levels from normal amniotic fluid. Alpha-2-macroglobulin, fibrinogen, FDP-D and FDP-E were detected only in pregnancies complicated with anencephaly and spina bifida.     

MATERNAL SERUM ALPHA-FETOPROTEIN SCREENING FOR OPEN NEURAL TUBE DEFECTS IN TWIN PREGNANCIES

Data on maternal serum alpha-fetoprotein (AFP) levels at 13–24 weeks' gestation in 46 twin pregnancies with open neural tube defects (22 with anencephaly, 24 with open spina bifida) and 169 unaffected twins were used to estimate the detection and false-positive rates associated with different cut-off levels. Using the conventional cut-off level of 2·5 multiples of the median (MoM) for unaffected singleton pregnancies of the same gestation and laboratory, the detection rate in twins was 99 per cent for anencephaly and 89 per cent for open spina bifida, with a false-positive rate of 30 per cent. Using a 5·0 MoM cut-off level to maintain a similar false-positive rate to that found among singleton pregnancies at 16–18 weeks' gestation (about 3 per cent), the detection rate was 83 per cent for anencephaly and 39 per cent for open spina bifida. Estimates are provided of the odds of having an affected twin pregnancy given a positive AFP result as well as the odds for individual women with a raised AFP level.     

Diagnosis of cardiac defects: where we've been,where we are and where we're going

There has been tremendous development in the field of prenatal diagnosis of cardiac disease in the last 30 years. Early work centered on the technical aspects of providing an accurate assessment of cardiac structure and function. Techniques of fetal cardiac screening have been developed and utilized throughout the world. More recently, investigators have begun to explore the ramifications of fetal cardiac diagnosis by assessing measures of outcome. In this article, the field of fetal echocardiography, as a screening tool for identifying congenital heart disease, and its impact on disease outcome is reviewed. Copyright © 2002 John Wiley & Sons, Ltd.     

珠光体耐热钢膜式水冷壁制造工艺优化

本文简要介绍了膜式水冷壁管屏制作工艺过程和珠光体耐热钢水冷壁管屏制造过程中易产生的缺陷分析,通过改进优化成排弯曲模具,焊前清理、预热,避免外侧管椭圆度、焊接气孔、咬边等缺陷。结合工艺试验分析了珠光体耐热钢管屏热矫正后不恰当的冷却方式引起延迟裂纹的原因,从而总结出珠光体耐热钢水冷管屏焊后热矫正时需特别注意的加热方法、加热温度及冷却方式,确保产品质量。     

综放工作面沿空留巷支护阻力研究

为了计算综放工作面沿空留巷支护阻力,以结构力学理论为基础,分析综放工作面沿空留巷支护阻力计算模型,建立沿空留巷围岩和支护体的结构力学模型,应用超静定结构和静定结构分析支护体与沿空留巷围岩相互作用机制,推导出巷旁支护阻力的计算公式.结果表明,进行沿空留巷支护阻力力学分析时,要考虑顶板极限断裂前和断裂后两种状态下的受力情况,支护阻力与岩层厚度、容重、煤体极限平衡区宽度、跨距、支护体宽度和巷道宽度等因素密切相关.工业性试验表明,该技术的应用是成功而有效的.因此,综放巷内沿空留巷围岩结构力学模型和支护阻力计算公式是合理的,可在类似条件的综放工作面中应用.