This work presents an algorithm to perform radiowave coverage predictions in urban environments using the Uniform Theory of Diffraction (UTD). The ray-tracing algorithm is based on the image theory for a quasi-3D environment. Multiple reflections and diffractions are considered through the separation of multipath components into four different classes, used to determine the scattered field. The...

or Introduction Details of a planning study for USAF computer security requirements are presented. An Advanced development and Engineering program to obtain an open-use, multilevel secure computing capability is described. Plans are also presented for the related developments of communications security products and the interim solution to present secure computing problems. Finally a Exploratory...

Private information retrieval (PIR) schemes enable a user to access one or more servers that hold copies of a database and privately retrieve parts of the n bits of data stored in the database. This means that the queries give each individual database no partial information (in the information theoretic or computational sense) on the identity of the item retrieved by the user. All known PIR sch...

Keyword advertising, or “sponsored links” that appear alongside online search results or other online content, has grown into a multibillion-dollar market. Providers of keyword advertising, such as Google and Yahoo, profit by auctioning keywords to advertisers. An issue of increasing importance for advertising providers is the “share structure” problem—that is, of the total available resources ...

In this paper we introduce a minimalist hypothesis for keywords extraction: keywords can be extracted from text documents by considering concepts underlying document terms. Furthermore, central concepts are individuated as the concepts that are more related to title concepts. Namely, we propose five metrics, that are diverse in essence, to compute the centrality of concepts in the document body...

•Extending our previous work on visual keywords, we use the concept of template-based visual keywords using MPEG-7 color descriptors. MPEG-7, also called the Multimedia Content Description Interface, has been a standard for many years. These color descriptors have the ability to characterize perceptual color similarity and need relatively low complexity operations to extract them, besides being...

Keyword-based web query languages suffer from a lack of precision when searching for a precise kind of documents. Indeed, some documents cannot be simply characterized by a list of keywords. For example, searching for on-line pictures dealing with formula one using only simple keywords with general-purpose search-engines gives imprecise answers. This imprecision is due to the method that consid...

In this paper, we present characterizations of pairs of graphs whose join graphs are 2-minimally nonouterplanar. In addition, we present a characterization of pairs of graphs whose join graphs are 2-minimally nonouterplanar in terms of forbidden subgraphs.

For the family of graphs with xed-size vertex cover k, we present all of the forbidden minors (obstructions), for k up to ve. We derive some results, including a practical nite-state recognition algorithm, needed to compute these obstructions.