Quantification and variability of Escherichia coli and Staphylococcus aureus cross-contamination during serving and consumption of cooked thick porridge in Lungwena rural households, Malawi

The study investigated bacterial transfer to cooked thick porridge via ladles and hands during serving in 29 households in Lungwena, rural Malawi. Household stored water used for hand and ladle washing, was contaminated with Escherichia coli and Staphylococcus. aureus from hands of members of the household or from contaminated ladles used in food preparation. The results showed that hands became contaminated with E. coli and S. aureus cells in the range 0.6–3.7 and 2.2–4.3 log₁₀ CFU/cm², respectively, following washing with the contaminated water. Ladles became contaminated with 0.9–3.2 log₁₀ CFU/cm² of E. coli cells whereas contamination with S. aureus on ladles ranged between 1.9 and 4.6 log₁₀ CFU/cm². Bacterial transfer from hands to food ranged from <1 to 3.6 log₁₀ CFU/g for E. coli and 2.1 to 4.2 log₁₀ CFU/g for S. aureus. Ladle surfaces transferred from 1.3 to 3.1 and from 1.2 to 4.3 log₁₀ CFU/g of E. coli and S. aureus, respectively, on to the food. Contamination of food by hands was significantly (p < 0.05) higher than that of ladles and transfer of S. aureus was significantly (p < 0.05) higher than that of E. coli. The amount of bacteria transferred to the recipient depended on the wash water type and bacteria type. The study has demonstrated that although the traditional cooking of thick porridge inactivates S. aureus and E. coli, the porridge can be contaminated with bacteria during consumption using hands and serving on to a plate with wooden ladles.     

南京钢厂3500mm 轧机大型机架的冶炼浇注

简要介绍了多包精炼在南京钢厂 3 5 0 0mm轧机机架生产上的应用。利用三包冶炼 ,成功地冶炼浇注了两片 3 5 0 0mm轧机的两片机架 ,是我公司迄今为止生产过的最大的铸件。     

炼钢炉火焰喷补工艺参数的试验研究与优化

模拟转炉及钢包内衬条件 ,利用实验室小型火焰喷补机进行喷补试验 ,测试了喷补料组成、氧气与燃气的流量比、混合气与喷补料的流量比、喷射距离及受补面温度 (炉温 )等因素对喷补附着率及喷补层与残衬粘结强度的影响规律。利用模式识别和人工神经网络技术对影响喷补效果的工艺参数进行了优化与预报。结果表明 ,适宜的喷补工艺参数为 :喷补料中结合剂含量 (包括转炉渣与外加剂 )为 11.4 3%;氧气与燃气的流量比为 4 .87;混合气与喷补料的流量比为 0 .91m3 ·kg- 1;喷射距离约 4 0cm ;炉温 15 6 9K。这为火焰喷补技术的发展与应用奠定了基础。     

80 t转炉-钢包吹氩-连铸冶炼过程对Q235A钢气体夹杂含量的影响

检测和分析了80 t顶底复吹转炉-钢包吹氩-连铸流程冶炼Q235A钢(0.14%～0.22%C、0.30%～0.65%Mn)在转炉终点、转炉出钢过程合金化后、钢包吹氩、中间包、钢水和铸坯中的氧、氮和夹杂物含量.结果表明,转炉终点氧含量为350×10-6,加脱氧剂和合金化后,氧含量降低42%,经钢包吹氩,钢中氧含量进一步降低,铸坯中平均氧含量25×10-6;钢中氮含量由转炉终点20×10-6增至铸坯40×10-6;钢包加脱氧剂、合金化后吹氩,钢中可去除约50%夹杂物,使铸坯中夹杂物含量≤45×10-6,一般夹杂尺寸≤10μm,最大尺寸为20μm.     

铸造起重机主梁疲劳破坏的分析及对策

对武钢第二炼钢厂炉前１２５ｔ铸造起重机的主梁断裂进行了分析,根据该类起重机主梁的结构特点与发生事故的原因,提出了预防措施。     

钢包渣线浇注料基质组成及其抗渣性

采用特级高铝矾土熟料和电熔镁砂为主要原料,研究了Al2O3-MgO系浇注料中MgO/Al2O3质量比对浇注料基本性能的影响,并分析对比了基质中添加适量工业氧化格、镁锆合成料及矾土尖晶石对浇注料抗渣性的影响及其规律。结果表明：恰当控制基质中MgO/Al2O3质量比及在基质中添加适量的工业氧化铬等组分,可明显提高浇注料的抗渣性。     

二次精炼渣钢反应及成渣热对钢液温度的影响

通过现场实验,分阶段定量分析了出钢至出ＶＤ过程,渣钢反应热及成渣热对钢液温度的影响。结果表明,这两种热对钢液降温的影响极小,完全可以忽略。     

几种钢包用含碳耐火材料对IF钢增碳的比较

通过感应炉试验分析了钢包渣线用3种碳含量不同的镁碳砖(C的质量分数分别为8.3%、15.5%和17.9%),钢包底用蜡石-碳化硅砖(C的质量分数为3.71%)以及实验室开发的MgO-Al2O3-SiC质钢包渣线浇注料(C的质量分数为4.07%)对IF钢增碳的影响,并对其增碳的机理进行了初步分析讨论。试验结果表明:渣线镁碳砖的碳含量越高,对IF钢造成的增碳量越大;包底蜡石-碳化硅砖对IF钢水的增碳量达到渣线镁碳砖的7.73倍;MgO-Al2O3-SiC质浇注料也对IF钢产生明显的增碳效果,不宜用作冶炼超低碳钢的钢包渣线材料。     

钢包回转台检修方案设计

为保证其它钢包回转台的正常工作,并减少检修时间,设计了两座提升臂之间加装H型钢、4只液压缸同步顶升钢包回转臂的方案对钢包回转台检修,更换回转推力轴承以及与基座的连接螺栓。按设计的检修方案建立三维接触模型,施加边界条件。计算结果表明,方案中钢包回转台各零件和H型钢强度以及H型钢的稳定性满足要求,并得到了现场检修实践的验证。     

钢包车焊接车架结构有限元分析与研究

利用三维机械设计软件SolidWorks,结合实际对钢包车进行设计,建立了有限元分析模型。根据钢包车工作状态模拟施加载荷和约束,采用有限元分析软件COSMOS／Works对焊接车架进行静态分析,最终得出钢包车的应力和应变云图,确定了危险点和危险截面。