Community detection in directed acyclic graphs

Some temporal networks, most notably citation networks, are naturally represented as directed acyclic graphs (DAGs). To detect communities in DAGs, we propose a modularity for DAGs by defining an appropriate null model (i.e., randomized network) respecting the order of nodes. We implement a spectral method to approximately maximize the proposed modularity measure and test the method on citation networks and other DAGs. We find that the attained values of the modularity for DAGs are similar for partitions that we obtain by maximizing the proposed modularity (designed for DAGs), the modularity for undirected networks and that for general directed networks. In other words, if we neglect the order imposed on nodes (and the direction of links) in a given DAG and maximize the conventional modularity measure, the obtained partition is close to the optimal one in the sense of the modularity for DAGs.Comment: 2 figures, 7 table

Feature-Aware Verification

A software product line is a set of software products that are distinguished in terms of features (i.e., end-user--visible units of behavior). Feature interactions ---situations in which the combination of features leads to emergent and possibly critical behavior--- are a major source of failures in software product lines. We explore how feature-aware verification can improve the automatic detection of feature interactions in software product lines. Feature-aware verification uses product-line verification techniques and supports the specification of feature properties along with the features in separate and composable units. It integrates the technique of variability encoding to verify a product line without generating and checking a possibly exponential number of feature combinations. We developed the tool suite SPLverifier for feature-aware verification, which is based on standard model-checking technology. We applied it to an e-mail system that incorporates domain knowledge of AT&T. We found that feature interactions can be detected automatically based on specifications that have only feature-local knowledge, and that variability encoding significantly improves the verification performance when proving the absence of interactions.Comment: 12 pages, 9 figures, 1 tabl

Steady state and mean recurrence time for random walks on stochastic temporal networks

Random walks are basic diffusion processes on networks and have applications in, for example, searching, navigation, ranking, and community detection. Recent recognition of the importance of temporal aspects on networks spurred studies of random walks on temporal networks. Here we theoretically study two types of event-driven random walks on a stochastic temporal network model that produces arbitrary distributions of interevent-times. In the so-called active random walk, the interevent-time is reinitialized on all links upon each movement of the walker. In the so-called passive random walk, the interevent-time is only reinitialized on the link that has been used last time, and it is a type of correlated random walk. We find that the steady state is always the uniform density for the passive random walk. In contrast, for the active random walk, it increases or decreases with the node's degree depending on the distribution of interevent-times. The mean recurrence time of a node is inversely proportional to the degree for both active and passive random walks. Furthermore, the mean recurrence time does or does not depend on the distribution of interevent-times for the active and passive random walks, respectively.Comment: 5 figure

"Scenes of Marvellous Variety" : the work-in-progress screenplays of Maurice

This article examines the work-in-progress screenplays of Maurice by Ivory (1987), which was adapted from E. M. Forster’s novel, published posthumously in 1971. The article examines the creative processes revealed in the writers’ treatment, and three manuscripts of the screenplay, held at King’s College, Cambridge, all of which differ from the film as it has subsequently been released in cinemas and on DVD. Writers James Ivory and Kit Hesketh-Harvey restructured the narrative order of the story in several different ways, before the film was eventually edited to follow (almost) the chronology of the novel. The screenplay was also significantly shaped through the collaborative assistance of Ruth Prawer Jhabvala, who is not credited as a writer for the film. This article charts these hitherto hidden creative and authorial processes, and argues that the narrative’s journey from page to screen was not a straight trajectory, but instead constituted a move away from mainstream narrative genres, such as the Bildungsroman and the love story, and then a recommitment to them in the film’s ‘final’ cut. The multiple versions of the screenplay add to the palimpsetuous inscriptions of this already multi-layered, in-flux narrative, which was revised repeatedly by E. M. Forster over a 45-year period, and has also been reworked through new book editions, a re-release of the DVD that includes deleted scenes as ‘extras’, and fan activity on the Internet

Temporal interactions facilitate endemicity in the susceptible-infected-susceptible epidemic model

Data of physical contacts and face-to-face communications suggest temporally varying networks as the media on which infections take place among humans and animals. Epidemic processes on temporal networks are complicated by complexity of both network structure and temporal dimensions. Theoretical approaches are much needed for identifying key factors that affect dynamics of epidemics. In particular, what factors make some temporal networks stronger media of infection than other temporal networks is under debate. We develop a theory to understand the susceptible-infected-susceptible epidemic model on arbitrary temporal networks, where each contact is used for a finite duration. We show that temporality of networks lessens the epidemic threshold such that infections persist more easily in temporal networks than in their static counterparts. We further show that the Lie commutator bracket of the adjacency matrices at different times is a key determinant of the epidemic threshold in temporal networks. The effect of temporality on the epidemic threshold, which depends on a data set, is approximately predicted by the magnitude of a commutator norm.Comment: 8 figures, 1 tabl

Using EMG Signals to Control an Arduino Prosthetic Arm

A prosthetic serves as an artificial limb to improve the lifestyle of a person with limb loss. Myoelectric technology allows for advancements in prosthetics to look and function like body parts before amputation by using electrical signals from surrounding muscles to power motors controlling the prosthetic. With newer designs of prosthetics being myoelectric, this technology has the potential to be more accessible to those that uses prosthetics. This research looks to incorporate myoelectric technology into a 3D-printed prosthetic arm prototype through the use of electromyography (EMG) sensors and an Arduino microcontroller board