U71Mn钢表面激光熔覆Ni60-25％WC涂层工艺参数优化的研究

目的研究U71Mn钢表面激光熔覆Ni60-25%WC涂层的最佳工艺参数。方法首先通过单道单因素试验初步选取激光功率、送粉量、扫描速度和光斑直径4个工艺参数,然后进行4因素3水平的单道正交试验,以熔覆层的宽度、高度和稀释率作为判断熔覆层质量的指标,做极差分析,最后得到最优工艺参数并分析了熔覆层的显微硬度及显微组织。结果单道单因素试验及单道正交试验得到的工艺参数均为:激光功率1500 W,送粉量4 g/min,扫描速度6 mm/s,光斑直径2.2 mm。通过单道正交试验极差表分析发现,工艺参数对质量指标的影响程度不同,对熔覆层宽度的影响为扫描速度送粉量激光功率光斑直径,对熔覆层高度的影响为送粉量扫描速度光斑直径激光功率,对熔覆层稀释率的影响为送粉量光斑直径扫描速度激光功率,对比发现送粉量是熔覆层的最大影响因子。熔覆层的显微硬度最高可达到1170HV,是基体的3.7倍。结论在U71Mn钢表面激光熔覆Ni60-25%WC涂层,可以制备出光滑且紧密结合的熔覆层,且表面硬度明显提高。     

开封农村地区婴幼儿中肠道病毒71型和柯萨奇病毒A组16型中和抗体水平及流行趋势

目的了解开封农村地区婴幼儿中肠道病毒71型(EV71)和柯萨奇病毒A组16型(CA16)中和抗体水平及流行趋势。方法应用微量细胞病变法,对2004年开封农村地区采集的349名7～30月龄婴幼儿血清进行EV71和CA16中和抗体检测。结果7～30月龄婴幼儿EV71和CA16中和抗体阳性率分别为36.7%(128/349)和36.5%(123/337),但二者流行趋势不同。EV71抗体阳性率由10～12月龄组的18.2%上升至25～30月龄组的81.3%,上升约4.5倍,抗体几何平均滴度(GMTs)也缓慢上升;CA16抗体阳性率由13～15月龄组的23.0%上升至22～24月龄组的47.6%,上升约2.1倍,GMTs在125～338之间波动;不同月龄婴幼儿中存在EV71和CA16混合感染的情况,19～24和25～30月龄组的EV71和CA16混合感染率显著高于7～12和13～18月龄组。结论开封农村地区婴幼儿中EV71和CA16中和抗体阳性率高,但二者上升的趋势不同,18月龄后的婴幼儿中EV71和CA16混合感染的比例显著升高。     

起重机轨道闪光焊焊接技术

由于起重机轨道通常采用高碳中锰的U71Mn钢轧制而成,手工焊接性能较差,焊缝接头容易产生裂纹、夹渣等缺陷,故对轨道传统手工焊接工艺改革非常必要.文中引进高铁常用的轨道焊接技术闪光焊,其特点是焊接速度快,接头质量稳定,是一种成熟的轨道焊接形式.研究闪光焊运用于起重机轨道焊接,并通过多条轨道焊接试验,形成详细的闪光焊轨道焊...     

基于71M6521的数字单相多功能电能表的设计

介绍了单相多功能电能计量芯片71M6521的基本功能和特点.在此基础上,设计了计最精度高、工作稳定、成本相对较低的数字单相多功能电能表,以实现对三相电流、电压,有功、无功功率,电能脉冲的输出等的计量.该数字单相多功能表可用于电力系统、工矿企业、智能大厦的电力临控.     

一种三相电能表的温度补偿新方法

针对电能表在不同的温度范围使用时,温差使各元器件产生了温度漂移造成的系统累积误差的问题,介绍了基于 TDK71M6513H 设计的三相电能表的两种温度补偿方法,以提高计量精度。一种是针对TDK71 M6513 H芯片本身的温度补偿,通过增益控制进行温度补偿使系统达到恒定;另一种是针对时钟的温度补偿,采用软件程序根据相应的修正值对时钟自动补偿,用以克服温度造成的晶振的频率漂移。     

基于热泵的大豆低温干燥储存系统设计

目的 针对环境温湿度变化以及大豆种子呼吸作用在储存室内引起的结顶、结块现象,造成储存过程中出现霉变或发芽等问题,基于热泵系统为大豆育种样本设计一套低温干燥储存系统。方法 通过数学模型计算各部件负荷,利用CFD模拟仿真技术选择合适的气流组织形式,然后对设计的系统送风温湿度稳定性、储存室内送风均匀性以及温度均匀性进行试验分析。结果 基于单侧送风+对侧回风气流组织设计的系统,在工作过程中,送风温度波动范围为±1 ℃,相对湿度波动范围为±4%,室内最大温度偏差为1.8 ℃,室内送风速度小于2 m/s。结论 基于合理的选型设计计算以及送风组织布置,结合育种样本长期储存的环境需求,设计了能够提供理想环境的控制系统,均匀的温度场以及气流分布在确保了样本储存质量的同时,有效降低了人工倒仓成本。这一设计能够为育种研究提供可靠的技术支持,对推动农业发展产生积极影响。     

The Bottlenecks of Preparing Virus Particles by Size Exclusion for Antibody Generation

Enterovirus 71 (EV71) is the major etiological agent contributing to the development of hand-foot-mouth disease (HFMD). There are not any global available vaccines or antibody drugs against EV71 released yet. In this study, we perform the virus immunization in a cost-effective and convenient approach by preparing virus particles from size exclusion and immunization of chicken. Polyclonal yolk-immunoglobulin (IgY) was simply purified from egg yolk and monoclonal single-chain variable fragments (scFv) were selected via phage display technology with two scFv libraries containing 6.0 × 10⁶ and 1.3 × 10⁷ transformants. Specific clones were enriched after 5 rounds of bio-panning and four identical genes were classified after the sequence analysis. Moreover, the higher mutation rates were revealed in the CDR regions, especially in the CDR3. IgY showed specific binding activities to both EV71-infected and Coxsackievirus 16-infected cell lysates and high infectivity inhibitory activity of EV71. However, while IgY detected a 37 kDa protein, the selected scFv seemingly detected higher size proteins which could be cell protein instead of EV71 proteins. Despite the highly effective chicken antibody generation, the purity of virus particles prepared by size exclusion is the limitation of this study, and further characterization should be carried out rigorously.     

Photography in 1848: Five Case Studies from Central Europe

This article examines the role of photography in the Year of Revolution and the place this topic holds in historiography. Unlike many historical disciplines which perceive 1848 as a turning point in the nineteenth century, the history of photography gives the impression that photographic production was not really affected by the upheavals which otherwise had a great impact on the whole of continental Europe. Collections and archives, however, contain large amounts of visual and written material that indicate the very opposite – that the involvement of photography in the events of 1848 was not rare. Using five examples from Central Europe, three portraits and two cityscapes, this article provides an insight into the cultural and historical backgrounds of photographic production in that year. The article demonstrates the ways in which photographs were involved in the social, political, and cultural events of the time, and how they helped shape ideas about them.     

Inhibitory of EV-A71 virus-induced apoptosis by ZVAD through ROS mediated signaling pathways

Emerging evidence that Enterovirus A 71 (EV-A71) infection closely related to apoptosis. The ZVAD is a caspase inhibitor that can prevent apoptosis. The aims of this project were to evaluate the mechanism of the ZVAD inhibited EV-A71 virus and to provide experiment basis for finding new antiviral drugs. In this study, after treated with ZVAD in EV-A71 infected Vero cells, the viral replication was reduced, and the cell viability was higher than EV-A71 group. Additionally, ZVAD decreased the cell apoptosis and the level of inflammatory cytokines induced by EV-A71 in the infected Vero cells. ZVAD inhibited cell apoptosis by regulating ROS mediated signaling pathway and inflammation cytokines to achieve antiviral.