Influence of different carbon nanostructures on the electrocatalytic activity and stability of Pt supported electrocatalysts

Commercially available graphitized carbon nanofibers and multi-walled carbon nanotubes, two carbon materials with very different structure, have been functionalized in a nitric–sulfuric acid mixture. Further on, the materials have been platinized by a microwave assisted polyol method. The relative degree of graphitization has been estimated by means of Raman spectroscopy and X-ray diffraction while the relative concentration of oxygen containing groups has been estimated by X-ray photoelectron spectroscopy, which resulted in a graphitic character trend: Pt/GNF > Pt/F-GNF ? Pt/MWCNT > Pt/F-MWCNT. Transmission electron microscopy showed that the Pt particle size is around 3 nm for all samples, which was similar to the crystallite size obtained by X-ray diffraction. The activity towards electrochemical reduction of oxygen has been quantified using the thin-film rotating disk electrode, which has shown that all the samples have a better activity than the commercially available electrocatalysts. The trend obtained for the graphitic character maintained for the electrochemical activity, while the reverse trend has been obtained for the accelerated ageing test. Long-term potential cycling has demonstrated that the functionalization improves the stability for multi-walled carbon nanotubes, at the cost of decreased activity.     

Multivariate methods using mixtures: Correspondence analysis,scaling and pattern-detection

Matrices of binary or count data are modelled under a unified statistical framework using finite mixtures to group the rows and/or columns. These likelihood-based one-mode and two-mode fuzzy clusterings provide maximum likelihood estimation of parameters and the options of using likelihood ratio tests or information criteria for model comparison. Geometric developments focused on pattern detection give likelihood-based analogues of various techniques in multivariate analysis, including multidimensional scaling, association analysis, ordination, correspondence analysis, and the construction of biplots. Illustrative examples demonstrate the effectiveness of these visualisations for identifying patterns of ecological significance (e.g. abrupt versus slow species turnover).     

SnO2 nanocrystallines decorated g-C3N4 composites with enhanced visible-light photocatalytic activity

Abstract

A series of SnO₂ nanocrystallines decorated g-C₃N₄ architectures were synthesized using a facile solvothermal method. The structural, morphological, and optical properties of the as-prepared nanocomposites were characterized in detail, indicating that SnO₂ nanocrystallines with diameter ～ 4?nm were well-dispersed on the surface of g-C₃N_4. The photocatalytic activity of the composites was investigated by degrading rhodamine B (RhB) under visible light irradiation. The CNS2 heterostructure exhibits enhanced photocatalytic activity than bare SnO₂ and g-C₃N₄. Kinetic study revealed a promising degradation rate constant of 0.0593?min^?1 for the CNS2, which is 118 and 7 times higher than that of pure SnO₂ and g-C₃N₄, respectively. What’s more, the CNS2 still retained the photocatalytic activity after three cycle measurements. The enhanced photocatalytic performances of the nanocomposite may be due to its large surface area (116.2 m²/g), appropriate ratio of SnO₂/g-C₃N₄ and the compact structure of the junction between the SnO₂ nanocrystallines and the g-C₃N₄, which inhibits the recombination of photogenerated electrons and holes.     

Kinetic study on the metallothermic reduction of chromite ore using magnesium scrap

A study on the metallothermic reduction of chromite ore is presented and discussed, using magnesium scrap as reducing agent. Microstructural analysis corroborated the distribution of phases inside the particles, where Fe and Cr were located at the centre surrounded by layers of reaction products, mainly MgO. The maximum conversion efficiency of Fe and Cr was 38% at 1050°C, after a reaction time of 3 hours, using 75% excess of magnesium scrap. A kinetic study was performed fitting the experimental data to available kinetic models, where the data adjusted to the chemical reaction model, especially at the beginning of reaction. A second reaction stage was confirmed once the experimental data was adjusted to the Jander diffusion model. For the chemical reaction model, the constant rate and the activation energy were 0.32?h^?1 and 60.12?kJ?mol^?1, respectively. For the diffusion model, the rate constant was 0.20?h^?1 and the activation energy 47.04?kJ?mol^?1.     

金属渗透梯度层陶瓷基片在LED散热中的应用

在LED散热领域,铝基板居很大市场份额.介绍了金属渗透梯度层陶瓷基片,这种陶瓷基片由陶瓷与金属材料相互扩散形成的,导热性、绝缘性、抗剥离强度及抗震动性好,可解决大功率LED的散热问题.这种基板已用于制作大功率LED灯,并取得了明显的社会经济效益.     

Color smoothing for RGB-D data using entropy information

RGB-D sensors are capable of providing 3D points (depth) together with color information associated with each point. These sensors suffer from different sources of noise. With some kinds of RGB-D sensors, it is possible to pre-process the color image before assigning the color information to the 3D data. However, with other kinds of sensors that is not possible: RGB-D data must be processed directly. In this paper, we compare different approaches for noise and artifacts reduction: Gaussian, mean and bilateral filter. These methods are time consuming when managing 3D data, which can be a problem with several real time applications. We propose new methods to accelerate the whole process and improve the quality of the color information using entropy information. Entropy provides a framework for speeding up the involved methods allowing certain data not to be processed if the entropy value of that data is over or under a given threshold. The experimental results provide a way to balance the quality and the acceleration of these methods. The current results show that our methods improve both the image quality and processing time, as compared to the original methods.     

Particle breakdown dynamics of heterogeneous foods during mastication: Peanuts embedded inside different food matrices

Heterogeneous foods are widely consumed but little is known about the dynamics of their breakdown during mastication. To investigate these dynamics the particle size and bolus mass at regular stages of the chewing sequence were investigated using a single subject, who was carefully selected according to strict mastication and dental criteria. A standardized volume of both a gelatine gel and chocolate matrix containing roasted peanuts was chewed and expectorated after a specified number of chews or at the point of swallowing. The mass of various components of the bolus was determined along with peanut particle parameters (d₅₀, broadness (b), and specific surface area) at each interval.Results showed that for this subject the type of matrix influenced the pathway that the peanut particles (embedded inside each matrix) were broken down. The d₅₀ of peanut particles within the bolus of the gelatine gel were greater than within the bolus of the chocolate throughout the chewing sequence until the point of swallowing. At the point of swallowing, the d₅₀ of peanut particles inside the bolus of the gelatine gel and chocolate were the same. The broadness value (b) and specific surface area of the peanut particles in the bolus of the chocolate were greater than those in the bolus of the gelatine gel throughout the chewing sequence. The matrices also induced different dynamic trends in the mass of bolus components during the chewing sequence.     

强化管理制度 降低电能消耗

通过重新修订各项制度、明确各单位的责任、强化用电管理;通过修订和严格执行大型用电设备启停机制度;通过杜绝空负荷运转、合理避开波峰时段用电;通过采取制度约束与新技术应用并举等有效减少了电能消耗.     

印度东部钛磁铁矿的氧化行为和相分析

钛磁铁矿是一种复杂的共生矿石,含有钛铁矿、磁铁矿、铁铝尖晶石和镁铁铝尖晶石等矿物。对从印度东部采集到的钛磁铁矿石进行XRD、WDXRF、SEM和M？ssbauer谱分析。在氧气气氛下,通过TG-DTA分析对矿石的氧化行为进行研究。随后,在氧气和空气气氛下,将样品在不同温度下（873-1473 K）保温不同时间,进行等温氧化实验。观察到在较低的温度下钛铁矿相转变为赤铁矿、氧化钛,而在较高的温度下转变为钛酸亚铁相。将氧化后的矿样与焦炭混合压制成圆柱形球团,在1473 K下进行直接还原,成功地实现了将磁铁矿铁转变为氧化铁和二氧化钛的相变。