Ranking Spaces for Predicting Human Movement in an Urban Environment

A city can be topologically represented as a connectivity graph, consisting of nodes representing individual spaces and links if the corresponding spaces are intersected. It turns out in the space syntax literature that some defined topological metrics can capture human movement rates in individual spaces. In other words, the topological metrics are significantly correlated to human movement rates, and individual spaces can be ranked by the metrics for predicting human movement. However, this correlation has never been well justified. In this paper, we study the same issue by applying the weighted PageRank algorithm to the connectivity graph or space-space topology for ranking the individual spaces, and find surprisingly that (1) the PageRank scores are better correlated to human movement rates than the space syntax metrics, and (2) the underlying space-space topology demonstrates small world and scale free properties. The findings provide a novel justification as to why space syntax, or topological analysis in general, can be used to predict human movement. We further conjecture that this kind of analysis is no more than predicting a drunkard's walking on a small world and scale free network. Keywords: Space syntax, topological analysis of networks, small world, scale free, human movement, and PageRankComment: 11 pages, 5 figures, and 2 tables, English corrections from version 1 to version 2, major changes in the section of introduction from version 2 to

Quasi-stationary distributions as centrality measures of reducible graphs

Random walk can be used as a centrality measure of a directed graph. However, if the graph is reducible the random walk will be absorbed in some subset of nodes and will never visit the rest of the graph. In Google PageRank the problem was solved by introduction of uniform random jumps with some probability. Up to the present, there is no clear criterion for the choice this parameter. We propose to use parameter-free centrality measure which is based on the notion of quasi-stationary distribution. Specifically we suggest four quasi-stationary based centrality measures, analyze them and conclude that they produce approximately the same ranking. The new centrality measures can be applied in spam detection to detect ``link farms'' and in image search to find photo albums

Weighted citation: An indicator of an article's prestige

We propose using the technique of weighted citation to measure an article's prestige. The technique allocates a different weight to each reference by taking into account the impact of citing journals and citation time intervals. Weighted citation captures prestige, whereas citation counts capture popularity. We compare the value variances for popularity and prestige for articles published in the Journal of the American Society for Information Science and Technology from 1998 to 2007, and find that the majority have comparable status.Comment: 17 pages, 6 figure

Graph-theoretic characterization of cyber-threat infrastructures

In this paper, we investigate cyber-threats and the underlying infrastructures. More precisely, we detect and analyze cyber-threat infrastructures for the purpose of unveiling key players (owners, domains, IPs, organizations, malware families, etc.) and the relationships between these players. To this end, we propose metrics to measure the badness of different infrastructure elements using graph theoretic concepts such as centrality concepts and Google PageRank. In addition, we quantify the sharing of infrastructure elements among different malware samples and families to unveil potential groups that are behind specific attacks. Moreover, we study the evolution of cyber-threat infrastructures over time to infer patterns of cyber-criminal activities. The proposed study provides the capability to derive insights and intelligence about cyber-threat infrastructures. Using one year dataset, we generate notable results regarding emerging threats and campaigns, important players behind threats, linkages between cyber-threat infrastructure elements, patterns of cyber-crimes, etc