Abstract-Optical and electrical properties of Er-doped Sinanocrystal (Si-NC) fiber amplifier are studied. Presence of Si-NC near Er 3+ ions in silica matrix induces strong coupling mechanism and improves the efficiency of Er 3+ excitation but in this process the size of Si-NC is important. We investigate effect of radius variation of Si-NC in the range of 2-6 nm by studying the steady state and time resolved luminescence signals at 1.54 µm. We conclude that by limiting the range of Si-NC sizes the amplifier gain is improved. On the other hand Si-NCs may introduce optical loss mechanism, such as confined carrier absorption loss that affects the possibility of obtaining positive net gain. But this detrimental event can be affected by change in the radius of Si-NC as reported in this article.
Abstract. User-generated contents are developing rapidly through VGI and contributors create the tags through the Web applications in a free mechanism. Semantic Knowledge in VGI like other user-generated contents needs to be combined with other authoritative data sources. One of the main challenges of integration is the semantic heterogeneity of user-generated contents which are describing the geographical objects as POIs. Geographical objects can be described in different semantic levels such as purpose or function. Significance of semantic levels defines the importance of related attributes. Analysis of significance for semantic levels of different POIs can be considered as a base to enhance the semantic quality of VGI. This paper proposes an approach based on the notions of rough set theory to measure the significance of semantic levels of tags which are applied to describe the buildings in OpenStreetMap. The proposed approach is implemented for tags which are applied to describe buildings in OpenStreetMap. Results show the high significance for tags which describing the semantic levels of geographic information constructs and purpose/ function for buildings.
Volunteered geographic information (VGI) provides geometric and descriptive sources of geospatial data. VGI exchange, reuse, and integration are serious challenges due to the subjective contribution process, lack of organization, and redundancy. This study aims to enhance the quality of VGI semantic data by presenting a new approach to integrating and formalizing the VGI semantic knowledge using formal concept analysis. The proposed approach is assessed using the building tags in OpenStreetMap (OSM) and CityGML.The alignment process discovers the conceptual overlap between the categories of Amenity (Others), Office, and Man-Made in Map Features (OSM) and Business and Trade, Recreation, Sport, and Industry in AbstractBuilding (CityGML). The k-means clustering of the results illustrated that class, usage/function, address, wheelchair, and website/wikidata/wikipedia are significant attributes to describe building categories. Moreover, results showed that the analysis of frequent itemsets and cluster characteristics provides significant information about custom tags in OSM's editing tools.
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