Quickest Change Detection of a Markov Process Across a Sensor Array

Recent attention in quickest change detection in the multi-sensor setting has been on the case where the densities of the observations change at the same instant at all the sensors due to the disruption. In this work, a more general scenario is considered where the change propagates across the sensors, and its propagation can be modeled as a Markov process. A centralized, Bayesian version of this problem, with a fusion center that has perfect information about the observations and a priori knowledge of the statistics of the change process, is considered. The problem of minimizing the average detection delay subject to false alarm constraints is formulated as a partially observable Markov decision process (POMDP). Insights into the structure of the optimal stopping rule are presented. In the limiting case of rare disruptions, we show that the structure of the optimal test reduces to thresholding the a posteriori probability of the hypothesis that no change has happened. We establish the asymptotic optimality (in the vanishing false alarm probability regime) of this threshold test under a certain condition on the Kullback-Leibler (K-L) divergence between the post- and the pre-change densities. In the special case of near-instantaneous change propagation across the sensors, this condition reduces to the mild condition that the K-L divergence be positive. Numerical studies show that this low complexity threshold test results in a substantial improvement in performance over naive tests such as a single-sensor test or a test that wrongly assumes that the change propagates instantaneously.Comment: 40 pages, 5 figures, Submitted to IEEE Trans. Inform. Theor

Equivariant Giambelli and determinantal restriction formulas for the Grassmannian

The main result of the paper is a determinantal formula for the restriction to a torus fixed point of the equivariant class of a Schubert subvariety in the torus equivariant integral cohomology ring of the Grassmannian. As a corollary, we obtain an equivariant version of the Giambelli formula.Comment: 16 pages, 3 figures, LaTex, uses epsfig and psfrag; for the revised version: title changed; Proof of Theorem 3 changed; 3 references added and 1 deleted; other minor change

Semi-supervised and Active-learning Scenarios: Efficient Acoustic Model Refinement for a Low Resource Indian Language

We address the problem of efficient acoustic-model refinement (continuous retraining) using semi-supervised and active learning for a low resource Indian language, wherein the low resource constraints are having i) a small labeled corpus from which to train a baseline `seed' acoustic model and ii) a large training corpus without orthographic labeling or from which to perform a data selection for manual labeling at low costs. The proposed semi-supervised learning decodes the unlabeled large training corpus using the seed model and through various protocols, selects the decoded utterances with high reliability using confidence levels (that correlate to the WER of the decoded utterances) and iterative bootstrapping. The proposed active learning protocol uses confidence level based metric to select the decoded utterances from the large unlabeled corpus for further labeling. The semi-supervised learning protocols can offer a WER reduction, from a poorly trained seed model, by as much as 50% of the best WER-reduction realizable from the seed model's WER, if the large corpus were labeled and used for acoustic-model training. The active learning protocols allow that only 60% of the entire training corpus be manually labeled, to reach the same performance as the entire data

Evolving Role of Women in Terror Groups: Progression or Regression?

Historically, women have been victims to a much greater degree than perpetrators of violence. However, the 1970s witnessed the emergence of women as important protagonists in the conflicts across the world. Recent years have witnessed suicide attacks perpetrated by women suicide bombers. This growing trend of women bombers has the general public and counterterrorism specialists concerned because of its implication that women will be key players in future terrorist attacks. Women’s role in terrorist organisations have also transformed since 1970s.Women across the ideological spectrum played different roles at different times. The use of women for “soft tasks” like logistics and recruitment gradually started to change in the mid-1980s when they started playing a much more visible frontline role. A woman taking up a suicide bombing role diverges significantly and is far more dangerous than their traditional activity of playing logisticians, recruiters or even a frontline role. This paper scrutinizes this change. There are multi causal issues which drive women to join terrorism and more so as suicide bombers. Psychological, economic, political, religious and sociological factors can act as contributors to understanding the causes that drive women towards terrorism. This paper attempts to highlight the role played by women in various terrorist organisations around the world. It also tries to bring out the factors which influence women to participate in terrorist acts. It aims to bring out the above facts by analysing various groups which have women cadre. Previous studies in the same realm have focused on a particular group or a conflict whereas this paper attempts to examine female participation across multiple conflicts in different groups driven by different ideology, which provides a clear insight into the multi causal factors which are responsible for this trend. The methodology followed is a descriptive one wherein the analysis is conducted on information derived from published secondary data