This paper presents a novel parametric Ultrawideband (UWB) channel model to characterize frequency dependency of small scale fading. The model is based on electromagnetic diffraction mechanism, which is a major factor of frequency dependent fading in UWB systems, geometric theory of diffraction, and scattering center analysis. The statistical distribution of model parameters can be easily estim...

Abstract: In this paper, four kinds of block diffraction models were proposed on the basis of the uniform geometrical theory of diffraction, and these models were validated by experiments with 45 GHz millimeter wave in the laboratory. The results are in agreement with the theoretical analysis. Some errors exist in the measurement results because of the unsatisfactory experimental environment. S...

We describe improvements to our 2008 system that result in a top-performing summarization system. The motivating ideas are (1) improve sentence boundary detection to avoid damaging errors in preprocessing; (2) prune sentences that are unlikely to work well in a summary; (3) leverage sentence position to improve update summarization; (4) focus on high-precision sentence compression to improve re...

A deterministic model for spherical wave propagation in microcellular urban environment is presented. This methodis based on ray tracing and uniform theory of diffraction. The various ray contributions includes the diffraction from corner of obstacle, reflection from ground and direct wave. According to the height of transmitting station, different ray paths will be presented in the received si...

While the study of terrorism has expanded dramatically since the 1970s, most analyses are limited to qualitative case studies or quantitative analyses of international incidents only—which comprise a very small proportion of all terrorist events. Until now, empirical data on both domestic and international terrorist events have not existed. We have compiled information from more than 69,000 ter...

We show how to apply the techniques of microlocal analysis to the Potter-Moses attributed scattering center model, which is based on the Geometrical Theory of Diffraction (GTD). The microlocal methods enable us to determine how scattering centers will appear in the radar data. We show also how to extend the model to some multiple-scattering events, and we apply the microlocal techniques to the ...

SpaceEval (SemEval 2015 Task 8), which concerns spatial information extraction, builds on the spatial role identification tasks introduced in SemEval 2012 and used in SemEval 2013. Among the host of subtasks presented in SpaceEval, we participated in subtask 3a, which focuses solely on spatial relation extraction. To address the complexity of a MOVELINK, we decompose it into smaller relations s...

In this paper we present our approach for assigning degrees of relational similarity to pairs of words in the SemEval-2012 Task 2. To measure relational similarity we employed lexical patterns that can match against word pairs within a large corpus of 12 million documents. Patterns are weighted by obtaining statistically estimated lower bounds on their precision for extracting word pairs from a...