Modification of platinum surfaces by spontaneous deposition: Methanol oxidation electrocatalysis

The presence of a second metal on platinum surfaces affects the performance of methanol oxidation. However, most of the electrocatalytic reactions are studied by using electrochemically deposited platinum alloys, but in the case of spontaneous deposition the situation is not so clear since the surface distribution, stability and morphology are usually not well documented. The formation of surface decorated samples on mono- and poly-crystalline platinum is followed by electrochemical and spectroscopic techniques and analysis of their performance towards methanol adsorption and oxidation compared with that on pure platinum. Pt/Sn and Pt/Ru are of special interest because of their well-known performance in methanol fuel cells. Methanol oxidation on Pt(111)/Ru, Pt(111)/Sn and Pt(111) shows that ruthenium is the only one able to promote the reaction since the simultaneous dissolution of tin occurs and competes with the process of interest. The in situ infrared spectroscopy is used to compare methanol oxidation on Pt(111)/Ru and Pt(111) in acid media using p-polarized light. The formation of bridge bound carbon monoxide is inhibited in the presence of ruthenium ad-species, whereas on Pt(111) the three adsorption configurations are observed. Linear sweep polarization curves and Tafel slopes (calculated from steady state potentiostatic plots) for methanol oxidation are compared on polycrystalline surfaces modified by tin or ruthenium at different coverages. There is almost no change in the Tafel slopes due to the presence of the foreign metal except for Pt/Ru, where a 0.09 V decade⁻¹ slope was calculated below 0.55 V due to hydroxyl adsorbates on ruthenium islands. The anodic stripping of methanol residues on the three surfaces indicates a lower amount of carbon monoxide-type adsorbates on Pt/Ru, and the simultaneous tin dissolution process leading to residues oxidation on Pt/Sn electrodes.     

Preparation of clean coal by flotation following ultra fine liberation

This paper reports the results of current fundamental research at the Department of Process Engineering, University of Miskolc on the processing of clean coal from Mecsek bituminous coal, Southern Hungary. The theoretical possibility of the separation of different petrographic components was proven experimentally and their liberation degree was determined based on the petrographic composition, flotation kinetic study of isolated components (groups of components), scanning electron microscopy and microprobe analyses. The mill with stirred ball media was chosen for the ultra-fine liberation of the coal components. It was revealed that along with the liberation of coal components, their surface oxidation and spontaneous agglomeration, entrapping the mineral impurities take place in ultra-fine grinding. This paper discusses the interfacial phenomena occurring in the ultra-fine grinding process and their influence on the flotation. The concept for the advanced preparation of clean coal was developed, tested and proved. The main steps of this concept are the ultra-fine liberation in the stirred-media mill, the de-agglomeration of flocs spontaneously formed during the ultra-fine grinding and the induced (hydrophobic) flocculation with the following two-step flotation in a flotation column.     

硫化矿石氧化性的实验室综合评判

探讨了一种硫化矿石氧化性综合评判的新方法 ,并将该方法应用于矿山实际 ,得到了准确的评判结果。该项成果对于硫化矿石自燃防治理论与技术的研究具有很高的参考价值。     

MEMORY·童年·印象--合肥市政务文化新区儿童公园概念性方案

合肥市政务文化新区儿童乐园的概念性方案,充分考虑了儿童的心理和成长交流需要,以儿童的自发活动为特色,兼顾各类活动设施,创造丰富活动空间,构筑了一个富有感染力、空间变幻多彩的都市儿童乐园.     

Effect of mineral matter on coal self-heating rate

Adiabatic self-heating tests have been conducted on subbituminous coal cores from the same seam profile, which cover a mineral matter content range of 11.2-71.1%. In all cases the heat release rate does not conform to an Arrhenius kinetic model, but can best be described by a third order polynomial. Assessment of the theoretical heat sink effect of the mineral matter in each of the tests reveals that the coal is less reactive than predicted using a simple energy conservation equation. There is an additional effect of the mineral matter in these cases that cannot be explained by heat sink alone. The disseminated mineral matter in the coal is therefore inhibiting the oxidation reaction due to physicochemical effects.     

基于修正灰色马尔科夫模型的煤自燃预测

煤自燃系统是一个复杂的巨系统,具有规律性、非线性和随机波动性特点,因此在煤自燃预警系统中利用单一的灰色预测方法很难对其动态发展趋势做出准确的预测.针对上述问题,提出一种将灰色模型和马尔科夫模型相结合对煤自燃进行预测的方法.首先建立煤自燃的GM(1,1)模型,其次以GM(1,1)模型预测值为基础进行马尔科夫预测,然后用平均残差修正预测值.仿真结果表明,灰色马尔科夫模型比灰色模型预测精度明显提高,平均误差减少2.24％,为煤层优化检测提供了依据.     

Charge trapping in bilayers of conducting polymers under open circuit conditions: a protection of conducting polymer films from spontaneous charging/discharging

Spontaneous charging/discharging processes of polymers: polypyrrole and poly(N-methylpyrrole), doped with perchlorate (anion exchanging PPy and PMPy, respectively) and poly(4-styrenesulphonate) ions (cation exchanging PPy(PSS) and PMPy(PSS)) occurring in aqueous electrolyte solutions were studied using different electrochemical techniques. These reactions (oxidation of the polymer by dissolved oxygen and discharge of the polymer redox capacitance) are usually undesired processes leading to alteration of the charge accumulated in the polymer films. This paper points out that these processes can be significantly limited in polymer bilayers due to effect of charge trapping.     

论当代大学生的创业人格缺陷及其健全策略

创业不仅是智慧的竞争 ,更重要的是人格的较量。当代部分大学生中存在着创业信念空虚、创业意志薄弱、创业动机错误、团队精神涣散等创业人格缺陷 ,这是社会道德失范、家庭教育失真、学校教育失序和个人心理失衡的结果 ,必须端正培养目标、优化创业环境、强化社会实践、加强自我修养 ,这样才能形成大学生理想的创业人格。     

渭河流域降水时空变化与干旱特征分析

以渭河流域14个典型气象站降水资料为基础,应用Mann-Kendall趋势检验法、频率分析法、差积曲线法以及游程分析法对研究区的降水变化规律及少水概率特征进行了研究。结果显示:40多年来渭河流域降水量呈明显减少趋势,以春、秋两季最为明显,这增加了区域发生干旱的可能性;流域降水过程呈丰枯交替的周期性现象,连丰或连枯较易发生,且存在干旱与洪涝并发现象;连枯年的概率比连丰年概率大,且少水期常持续2~3a,引发的干旱强度较大;1991年以后渭河流域干旱事件的频率、强度和烈度均有增加趋势,未来渭河流域的农业发展与水安全将面临更大的威胁,必须予以高度关注。     

FM radio for indoor localization with spontaneous recalibration

The position of mobile users has become highly important information in pervasive computing environments. Indoor localization systems based on Wi–Fi signal strength fingerprinting techniques are widely used in office buildings with an existing Wi–Fi infrastructure. Our previous work has proposed a solution based on exploitation of a FM signal to deal with environments not covered with Wi–Fi signal or environments with only a single Wi–Fi access point. However, a general problem of indoor wireless positioning systems pertains to signal degradation due to the environmental factors affecting signal propagation. Therefore, in order to maintain a desirable level of localization accuracy, it becomes necessary to perform periodic calibrations of the system, which is either time consuming or requires dedicated equipment and expert knowledge. In this paper, we present a comparison of FM versus Wi–Fi positioning systems and a combination of both systems, exploiting their strengths for indoors positioning. We also address the problem of recalibration by introducing a novel concept of spontaneous recalibration and demonstrate it using the FM localization system. Finally, the results related to device orientation and localization accuracy are discussed.