An electrochemical method for the Pt nanoparticles deposition on porous and high surface carbon substrates (carbon black and carbon nanotubes), as an alternative way to prepare gas diffusion electrodes for polymer electrolyte fuel cells (PEFCs), is herein described. Pt nanoparticles well distributed and localized on the electrode surface were obtained by using an electric field. The electro-catalysts were prepared by single and multiple pulse galvanostatic polarizations in 1 M sulphuric acid + 5 mM exachloroplatinic acid solution. Chemical analysis, cyclic voltammetry and field emission gun scanning electron microscopy were used to determine the electrochemical features of Pt deposits and the influence of electro-deposition method on their nano-morphology. Electro-catalytic performances were studied by investigating the methanol oxidation reaction and the results are presented in form of surface specific activity and mass specific activity to take into account the electrochemical real surface and Pt loading. A comparison with commercial E-TEK Pt/C catalysts, prepared by traditional chemical reduction and heat treatment in hydrogen, shows that the electrodeposited catalyst presents higher activity at lower Pt loading. 相似文献
An improvement of open addressing resolution schemes for hash-based files on secondary storage is defined in this paper. Linked hashing exploits the increase in compressibility of a hash file when buckets are larger, given a fixed file allocation. Both average access times and the number of records stored can significantly improve, for large files where the ratio between the key length and the record length is much less than 1. 相似文献
A reliable and fast sensor for in vitro evaluation of solar protection factors (SPFs) of cosmetic products, based on the photobleaching kinetics of a nanocrystalline TiO2/dye UV-dosimeter, has been devised. The accuracy, robustness and suitability of the new device was demonstrated by the excellent matching of the predicted and the in vivo results up to SPF 70, for four standard samples analyzed in blind. These results strongly suggest that our device can be useful for routine SPF evaluation in laboratories devoted to the development or production of cosmetic formulations, since the conventional in vitro methods tend to exhibit unacceptably high errors above SPF ∼30 and the conventional in vivo methods tend to be expensive and exceedingly time consuming. 相似文献
Multiresolution Hierarchies (MH) and Directed Acyclic Graphs (DAG) are two recent approaches for the compression of high‐resolution shadow information. In this paper, we introduce Merged Multiresolution Hierarchies (MMH), a novel data structure that unifies both concepts. An MMH leverages both hierarchical homogeneity exploited in MHs, as well as topological similarities exploited in DAG representations. We propose an efficient hash‐based technique to quickly identify and remove redundant subtree instances in a modified relative MH representation. Our solution remains lossless and significantly improves the compression rate compared to both preceding shadow map compression algorithms, while retaining the full run‐time performance of traditional MH representations. 相似文献
Pattern Analysis and Applications - There are different types of lesions that can be investigated with the hematoxylin–eosin staining protocol. Lymphoma is a type of malignant disease which... 相似文献
Nutrient Cycling in Agroecosystems - Organic phosphorus (Po) plays an important role in tropical forest nutrition on strongly-weathered soils. However, of its role in Eucalyptus nutrition little is... 相似文献
Journal of Applied Electrochemistry - The addition of silver in hypoeutectic Al-Si alloys have been demonstrated to have promising mechanical and electrical properties. However, the relationships... 相似文献
C-Mantec neural network constructive algorithm Ortega (C-Mantec neural network algorithm implementation on MATLAB. https://github.com/IvanGGomez/CmantecPaco, 2015) creates very compact architectures with generalization capabilities similar to feed-forward networks trained by the well-known back-propagation algorithm. Nevertheless, constructive algorithms suffer much from the problem of overfitting, and thus, in this work the learning procedure is first analyzed for networks created by this algorithm with the aim of trying to understand the training dynamics that will permit optimization possibilities. Secondly, several optimization strategies are analyzed for the position of class separating hyperplanes, and the results analyzed on a set of public domain benchmark data sets. The results indicate that with these modifications a small increase in prediction accuracy of C-Mantec can be obtained but in general this was not better when compared to a standard support vector machine, except in some cases when a mixed strategy is used.
In the Andeans, it is common to find homemade containers, chairs, structures made with Schoenoplectus californicus sub. californicus, commonly known as totora. Popularly is known that the homemade products possess resistance and durability due to the incorporation of this fiber, although nowadays the mechanic properties of this material are unknown. This research begins with the study of the variety of the totora which is present in the Province of Imbabura, Ecuador. Considering the geometrical variation of the stem, it is divided in three parts. Based on standard ASTM D4761-02a totora is characterized under tension. Finally, the mechanic characteristics under tension of Schoenoplectus californicus are presented from the stress-strain curve and its comparative analysis among the groups of transversal sections. It is determined that its behavior corresponds to a fragile material with an average of maximum stress up to 88.501 6.92 MPa, and an average of a maximum strain of 0.05132 0.00610 mm/mm. 相似文献