Role of intermetallic phases in localized corrosion of AA5083

The presence of intermetallic inclusions very often plays a crucial role for the susceptibility of different aluminium alloys to localized corrosion attack. The intimate details of localized corrosion of 5083 aluminium alloy have been studied in the present work. Local techniques such as scanning Kelvin probe force microscopy, in situ atomic force microscopy, scanning electron microscopy coupled with energy dispersive spectroscopy were used to investigate the mechanisms and the kinetics of localized corrosion attack. The importance of iron-rich and Mg₂Si intermetallic phases in the initiation of corrosion processes is demonstrated in the paper.The Mg₂Si phase has a potential lower relatively to the matrix. Moreover, the high reactivity of magnesium leads to the dissolution and consequently to the fast dealloying of these intermetallics. However, hydroxide (Mg(OH)₂ and SiO₂·nH₂O) deposits formed during corrosion act as an additional diffusion barrier hindering the deep propagation of pits.The iron containing intermetallics have the potential higher with respect to the aluminum matrix playing the role of effective cathodic centers for oxygen reduction causing anodic polarization and pitting in the surrounding alloy matrix. Dealloying of such intermetallics with subsequent iron enrichment was also revealed. Pitting initiation seems to be statistical and independent of the composition of Fe-rich intermetallics. However, the active growth of the pits prevents initiation of localized corrosion attack in nearby sites. A new pit can start to grow only when a neighbor one becomes passivated.     

Non-contact electrostatic flow probes for measuring the flow rate and charge in the two-phase gas-solids flows

The paper presents mathematical models of a measuring system for real-time monitoring the net electric charge, the mass flow rate or concentration of charged particles, and the mean flow velocity of the particles in a pipe. The main problem lies in proper defining and establishing the unambiguous relationships between the electric parameters of a measuring system, which uses a probe, sensor or transducer based on electrostatic induction. Such devices are non-contact, non-obstructive ones and are intended for the two-phase flow metering of charged solids in pipelines. The probe's output potential (voltage) is derived as a function of an equivalent point charge representing the net charge of a charged particle column within the probe's sensing zone and flowing in a real pipe as well as a function of the net charge of this column and its dynamic space density. The relationships are established for the above three forms of charge travelling rectilinearly along or parallel to the probe's geometrical axis in a laminar or fully developed turbulent flow. The models presented here show a useful, helpful approach to the modelling of non-contact, non-intrusive measuring systems based on electrostatic induction. The substantial role the capacitance of the electrostatic flow probe itself and the whole measuring system plays in the physical process of electrostatic induction of charge and in the mathematical modelling of the probe and system is interpreted. The capacitance influence on the system bandwidth is also discussed.     

Acidity of sulfated zirconia as studied by FTIR spectroscopy of adsorbed CO and NH3 as probe molecules

The acid properties of pure and sulfated zirconias were studied by FTIR spectroscopy of adsorbed CO and NH₃ as probe molecules. Whereas pure monoclinic zirconia shows only Lewis acidity, sulfation of tetragonal and monoclinic zirconia creates new bridging OH groups. Two types of Brønsted-acidic centers and two types of Lewis-acidic centers with enhanced acid strength were identified. A communication between the different types of Lewis-acidic sites and the related adsorbed sulfate molecules could be shown. The coordination of basic molecules such as CO onto Lewis-acid sites induces a decrease of the intrinsic Brønsted-acidity of the bridging OH groups. These effects are discussed on the basis of a model of the acidic centers that was previously proposed.On leave from Department of Chemistry, Faculty of Science, Minia University, El-Minia, Egypt.     

基于固定型检测器和浮动车的路段行程时间获取技术

在深入分析交通流诱导系统信息需求的基础上,提出了一种新的路段行程时间获取技术。首先分别利用固定型检测器和浮动车计算路段平均行程时间,进而应用自适应指数平滑法进行短时预测,最后开发了不同可靠度下基于固定型检测器和浮动车的路段行程时间快速融合算法。试验结果表明,该技术能够准确、高效地获取路段行程时间,为交通流诱导系统提供高质量的输入数据,满足出行者的信息需求。     

基于traceroute的层析成像方法*

针对传统的网络拓扑识别方法（如traceroute）无法完成包含不协作节点的拓扑识别以及基于网络层析成像技术的拓扑识别方法的复杂性和不确定性问题,提出一种基于traceroute的层析成像技术的拓扑识别方法。该方法可通过提出的最小相似度聚类算法和匿名节点构造归并算法,将网络层析成像获得的拓扑信息与trace-route探测结果融合,构成最终的拓扑结构。NS2的仿真表明,该方法不仅可识别包含不协作节点的网络拓扑,且所使用的探测包的数量也大大减少。     

支持多故障定位的探测站点部署方法

基于矩阵向量扩张的性质,研究了主动探测的故障定位方法. 提出一种支持多故障定位的探
测站点部署方法. 通过该方法在网络中部署探测站点对网络进行主动探测,能以较小的代
价尽早定位网络中的故障. 实验证明,该方法可以有效减少探测站点的数目,并且从探测站
点发出的最优探测集合可以对多故障进行定位.     

刚果红与鲱鱼精DNA相互作用的光谱法和电化学研究

在生理pH下,采用光谱法、电化学、化学热力学和粘度法等方法,利用中性红作分子探针,研究了刚果红与鲱鱼精DNA之间的作用方式,获得了结合比、结合常数和热力学函数值.结果表明,刚果红与DNA之间以嵌插方式发生作用.刚果红与DNA之间的结合比为n(CR):n(DNA)=1:1,结合常数为K25℃θ4.50×103L/mol.25 ℃时,△rHmθ7.04×104J/mol,△rSmθ305.88 J/(mol·K),△rGmθ-2.08×104J/mol.刚果红与DNA之间的作用为熵驱动.     

新型路由器辅助的多播网络层析方法

提出了一种新型的路由器辅助的多播网络层析方法来估计网络性能的时空分布. 在MINC方法的基础上,利用路由器合作测量的背景数据流的统计结果,来提高低探测速率时多播探测的准确性. 同时,将最大似然估计方法和背景流量的辅助测量相结合,降低了推测误差,避免了增加探测速率对背景数据流的不利影响. 仿真结果证实了该方法的有效性.     

真核表达Hsa-miR-1基因及其检测方法的建立

获得Hsa-miR-1的方法主要由人工合成,需耗费很高的成本与时间。文章通过将Hsa-miR-1前体部分连接至pcDNA3.0,可实现Hsa-miR-1基因的高表达。构建含有Hsa-miR-1基因表达前体的表达载体pcDNA-Hsa-miR-1和含有与Hsa-miR-1基因完全互补序列的检测载体pEGFP-C1-CM1。通过共转染pcDNA-Hsa-miR-1和pEGFP-C1-CM1检测Hsa-miR-1基因的表达,并采用Taqman探针法定量检测Hsa-miR-1基因表达水平,成功构建了可高效表达Hsa-miR-1基因的真核生物质粒pcDNA-Hsa-miR-1,并首次建立起Hsa-miR-1基因的检测系统pEGFP-C1-CM1,该检测系统的建立将为今后Hsa-miR-1在肿瘤细胞中的研究提供准确、快捷的检测方法。