2,544 research outputs found

    Contrasting Behavior of Carbon Nucleation in the Initial Stages of Graphene Epitaxial Growth on Stepped Metal Surfaces

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    Using first-principles calculations within density functional theory, we study the energetics and kinetics of carbon nucleation in the early stages of epitaxial graphene growth on three representative stepped metal surfaces: Ir(111), Ru(0001), and Cu(111). We find that on the flat surfaces of Ir(111) and Ru(0001), two carbon atoms repel each other, while they prefer to form a dimer on Cu(111). Moreover, the step edges on Ir and Ru surfaces cannot serve as effective trapping centers for single carbon adatoms, but can readily facilitate the formation of carbon dimers. These contrasting behaviors are attributed to the delicate competition between C-C bonding and C-metal bonding, and a simple generic principle is proposed to predict the nucleation sites of C adatoms on many other metal substrates with the C-metal bond strengths as the minimal inputs.Comment: 4 figures, submitted versio

    Efficient Querying from Weighted Binary Codes

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    Binary codes are widely used to represent the data due to their small storage and efficient computation. However, there exists an ambiguity problem that lots of binary codes share the same Hamming distance to a query. To alleviate the ambiguity problem, weighted binary codes assign different weights to each bit of binary codes and compare the binary codes by the weighted Hamming distance. Till now, performing the querying from the weighted binary codes efficiently is still an open issue. In this paper, we propose a new method to rank the weighted binary codes and return the nearest weighted binary codes of the query efficiently. In our method, based on the multi-index hash tables, two algorithms, the table bucket finding algorithm and the table merging algorithm, are proposed to select the nearest weighted binary codes of the query in a non-exhaustive and accurate way. The proposed algorithms are justified by proving their theoretic properties. The experiments on three large-scale datasets validate both the search efficiency and the search accuracy of our method. Especially for the number of weighted binary codes up to one billion, our method shows a great improvement of more than 1000 times faster than the linear scan.Comment: 13 pages, accepted by AAAI202


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    Characteristics of organic substance of the sediments of the West Lake are discussed in detail, including humic substance components and IR characteristics. The results showed that humus in the sediments of the West Lake is a typical lake sediment humus, and its humification level is high. Analysis on components of humus in the West Lake showed humin (59-71%) > humic acid (11-19%) > fulvic acid (8-15%) > lipid (3-12%). The Qianjiang River diversion project along with the planting of a lotus have both changed the organic composition of the sediment and will likely have an impact on the carbon cycling and eutrophication status in the West Lake.Article信州大学理学部附属諏訪臨湖実験所報告 11: 79-82(1999)departmental bulletin pape