Reciprocity, or the tendency of individuals to mirror behavior, is a key measure that describes information exchange in a social network. Users in social networks tend to engage in different levels of reciprocal behavior. Differences in such behavior may indicate the existence of communities that reciprocate links at varying rates. In this paper, we develop methodology to model the diverse reciprocal behavior in growing social networks. In particular, we present a preferential attachment model with heterogeneous reciprocity that imitates the attraction users have for popular users, plus the heterogeneous nature by which they reciprocate links. We compare Bayesian and frequentist model fitting techniques for large networks, as well as computationally efficient variational alternatives. Cases where the number of communities is known and unknown are both considered. We apply the presented methods to the analysis of Facebook and Reddit networks where users have non-uniform reciprocal behavior patterns. The fitted model captures the heavy-tailed nature of the empirical degree distributions in the datasets and identifies multiple groups of users that differ in their tendency to reply to and receive responses to wallposts and comments.

In indoor UWB TDoA localization systems, anchor clock drifts, RF and ADCs front end delay and their long term variation are main performance limiting factors. Anchor synchronization using reference tags instead of wired lines are promising for ease of deployment In this work, an error analysis on UWB TDoA localization system with reference tag is performed, focusing on propagation and clock drifts. A 500 MHz experimental UWB localization system with reference tag was built. Using single carrier UWB signal with a 127 chip PN code, the smallest TDoA measurement error is 21.7 cm and the worst error is 45.3 cm, as was shown by the test results.

Long-term ECG monitoring is desirable in many daily healthcare situations where a wearable device that can continuously record ECG signals is needed. In this work, we proposed a wearable heart rate belt for ambulant ECG monitoring which can be comfortably worn on the chest or the waist. Active textile electrodes were designed for ECG recording. And a battery powered circuit board was developed consisting of ECG signal conditioning circuits, a 3-axis accelerator for body motion detection, a 12-bit AD converter, a DSP for signal processing and a SD card for data storage. The system also includes a wireless communication module that can transmit heart rate data to a sport watch for displaying. Experiments were carried out which shows that the proposed system is unobtrusive and can be comfortably worn by the user during daily activities. When wearing on the waist, ECG signals with reasonably good quality were acquired in rest and walking situations. The proposed system shows promise for long-term ambulant ECG monitoring.