燃料电池不锈钢双极板CrN/CrC薄膜表面改性研究

采用离子镀技术在质子交换膜燃料电池不锈钢双极板表面制备了CrN/CrC多层薄膜。测试结果表明,与未镀膜的不锈钢基体相比,镀膜不锈钢的接触电阻(120N/cm2压紧力)降低2个数量级,并且耐蚀性能显著改善,腐蚀电流密度降低0.5~1个数量级。同时,镀膜不锈钢的耐久性亦大幅提升,改性薄膜可以有效保护不锈钢基体免受腐蚀损害。     

Antimicrobial resistance in thermotolerant Campylobacter isolated from different stages of the poultry meat supply chain in Argentina

The objective of this study was to investigate the antimicrobial resistance in thermotolerant Campylobacter spp. isolated from different stages of the poultry meat supply chain in Argentina. Six poultry meat chains were studied from the reproductive farm to the chicken at the retail. Chickens sampled along each food chain were from the same batch. Samples collected were: a) cloacal samples from hens and chickens on the farm, b) chicken carcasses from the slaughterhouse and retail market. Samples obtained were examined for Campylobacter spp. Antimicrobial resistance was evaluated using the disk diffusion method. Almost all isolates were resistant to nalidixic acid (91.2%) and ciprofloxacin (88.2%). A large proportion of thermotolerant Campylobacter isolated from hens and broilers <1 wk showed resistance to erythromycin in comparison with the rest of the stages of the poultry meat supply chain (P = 0.031). Campylobacter isolated from broilers (both <1 wk and >5 wk) and carcasses at slaughterhouse and at retail showed a proportion of resistance to ciprofloxacin and enrofloxacin higher than isolates from hens (P = 0.015 and P = 0.031, respectively). One strain was resistant to all the antibiotics analyzed, and 46.1% of the isolates were resistant to three or more drug classes. Almost 50% of the isolates were resistant to all quinolones tested (ciprofloxacin, nalidixic acid, and enrofloxacin), and 13.2% were resistant to all quinolones and erythromycin. Campylobacter strains isolated from carcasses at retail showed higher resistance to all quinolones than strains isolated from hens (P = 0.016). These results reflect an alarming situation with potential serious consequences to the public health.     

单元式幕墙设计原理判断优劣

随着行业交流地扩大及设计师地流动,幕墙设计的相似度越来越高,既相互影响又相互借鉴。尽管所用之体系均归类于横滑式单元系统,但因不同厂家对单元式幕墙的理解不同,因此所设计出的产品也迴异。本文对市场上比较流行的两类作法进行剖析比对,从单元式幕墙的设计原理、加工特性着手,比较两种作法的优劣,使设计师能够有选择性地使用水密、气密性能更高的产品。     

A novel summation impedance protection adaptive to high‐resistance earth fault detection

While the high‐resistance earth fault frequently occurs on extra high voltage (EHV) transmission lines, existing protection schemes show great limitation for coping with this kind of fault scenario when the fault resistance is very high. In this paper, a novel protection methodology combining the measured impedance of the two ends is introduced, and a so‐called summation impedance protection, making use of this critical information, is thus put forward and assessed. Emphasis is placed on the principle of the summation impedance protection and its adaptive thresholds. A simulation model based on EMTDC/PSCAD, by which the performance of the summation impedance protection is evaluated, is then established. As confirmed by quantitative theoretical and experimental studies, the results indicate that the proposed protection scheme works well even when the fault resistance is extremely high under the internal fault condition, and it keeps itself from maloperation as an effect of its adaptive thresholds wherever an external fault occurs. These results highlight the necessity to work in conjunction with the existing main protections of transmission lines, by which means an enhanced ability to cope with the high‐resistance single‐phase earth fault can be achieved. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Biochemical factors responsible for susceptibility or resistance of various plants against the scarlet mite,brevipalpus phoenicis: i. amino acids analysis

Free amino acids show considerable variations among various species of plants that exhibit different degrees of susceptibility or resistance to various pests infestation. Some of the free amino acids, directly or indirectly, contribute to defense mechanism of the plants. Recently, 31 plant species were screened for susceptibility or resistance against the attack of the scarlet mite, Brevipalpus phoenicis (Geij.). Thin layer chromatography showed that all resistant species contain tryptophan, tyrosine and hydroxyproline, while all susceptible hosts had amino acids like α‐aminocaprylic acid and dihydroxyphenylalanine. The plants species lacking dihydroxyphenylalanine could not support the development of the scarlet mite.     

武汉二七长江大桥防雷与接地设计

介绍武汉二七长江大桥的直击雷防护、侧击雷防护措施和电涌保护器的设置．以及接地设计、接地电阻的检测、施工要求等。重点介绍大桥利用基础桩基内外边缘的结构钢筋（包括钢护筒）作为接地板的做法。     

全再生快速修补混凝土的制备及性能

根据修补区混凝土可开放交通的要求,优选出全再生快速修补混凝土最优配合比,并与常用的再生粗骨料快速修补混凝土进行比较.结果表明,全再生快速修补混凝土的抗压强度和粘结强度较易满足要求;其最优化配合比参数为:胶凝材料总量为500 kg/m3,再生细骨料在细骨料中掺量为30％,而其砂率为35％;其干燥收缩略大于常用的再生粗骨料快速修补混凝土,但显著提高了其抗氯离子渗透性能.     

断层破碎带上深基础施工分析

在工程建设中遇到断层破碎带时,由于断层破碎带主体及两侧岩土体强度的差异,往往需要特殊处理。该文针对具体的工程实例,通过有限元计算分析,主要研究讨论采取何种最合适的基础型式,并对该类场区施工应注意的问题提出建议。     

考虑结构和热力学参数的钢梁抗火性能预测

给出预测标准火灾条件下钢梁耐火时间的公式。首先,根据热力学特性找出影响钢梁抗火性能的关键参数,然后将其划分为结构参数或热力学参数。通过完全耦合热力学数值分析方法,研究发生大变形前各参数对耐火性能的影响。在进行广泛的参数分析前,利用试验结果验证了数值模拟的准确性。通过多元线性回归分析,得到各种设计条件下钢梁抗火时间的预测公式。统计分析表明,所提出的公式是有效的。详细说明了该公式在实际消防设计中的应用,也介绍了该公式的优点。