Browsing by Subject "Novelty detection"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
Item Open Access Novelty detection for topic tracking(John Wiley & Sons, Inc., 2012) Aksoy, C.; Can, F.; Kocberber, S.Multisource web news portals provide various advantages such as richness in news content and an opportunity to follow developments from different perspectives. However, in such environments, news variety and quantity can have an overwhelming effect. New-event detection and topic-tracking studies address this problem. They examine news streams and organize stories according to their events; however, several tracking stories of an event/topic may contain no new information (i.e., no novelty). We study the novelty detection (ND) problem on the tracking news of a particular topic. For this purpose, we build a Turkish ND test collection called BilNov-2005 and propose the usage of three ND methods: a cosine-similarity (CS)-based method, a language-model (LM)-based method, and a cover-coefficient (CC)-based method. For the LM-based ND method, we show that a simpler smoothing approach, Dirichlet smoothing, can have similar performance to a more complex smoothing approach, Shrinkage smoothing. We introduce a baseline that shows the performance of a system with random novelty decisions. In addition, a category-based threshold learning method is used for the first time in ND literature. The experimental results show that the LM-based ND method significantly outperforms the CS- and CC-based methods, and categorybased threshold learning achieves promising results when compared to general threshold learning. © 2011 ASIS&T.Item Open Access Novelty detection using soft partitioning and hierarchical models(IEEE, 2017) Ergen, Tolga; Gökçesu, Kaan; Şimşek, Mustafa; Kozat, Süleyman SerdarIn this paper, we study novelty detection problem and introduce an online algorithm. The algorithm sequentially receives an observation, generates a decision and then updates its parameters. In the first step, to model the underlying distribution, algorithm constructs a score function. In the second step, this score function is used to make the final decision for the observed data. After thresholding procedure is applied, the final decision is made. We obtain the score using versatile and adaptive nested decision tree. We employ nested soft decision trees to partition the observation space in an hierarchical manner. Based on the sequential performance, we optimize all the components of the tree structure in an adaptive manner. Although this in time adaptation provides powerful modeling abilities, it might suffer from overfitting. To circumvent overfitting problem, we employ the intermediate nodes of tree in order to generate subtrees and we then combine them in an adaptive manner. The experiments illustrate that the introduced algorithm significantly outperforms the state of the art methods.Item Open Access Unseen face presentation attack detection using sparse multiple kernel fisher null-space(IEEE, 2020) Arashloo, Shervin RahimzadehWe address the face presentation attack detection problem in the challenging conditions of an unseen attack scenario where the system is exposed to novel presentation attacks that were not available in the training stage. To this aim, we pose the unseen face presentation attack detection (PAD) problem as the one-class kernel Fisher null-space regression and present a new face PAD approach that only uses bona fide (genuine) samples for training. Drawing on the proposed kernel Fisher null-space face PAD method and motivated by the availability of multiple information sources, next, we propose a multiple kernel fusion anomaly detection approach to combine the complementary information provided by different views of the problem for improved detection performance. And the last but not the least, we introduce a sparse variant of our multiple kernel Fisher null-space face PAD approach to improve inference speed at the operational phase without compromising much on the detection performance. The results of an experimental evaluation on the OULU-NPU, Replay-Mobile, Replay-Attack and MSU-MFSD datasets illustrate that the proposed method outperforms other methods operating in an unseen attack detection scenario while achieving very competitive performance to multi-class methods (that benefit from presentation attack data for training) despite using only bona fide samples in the training stage.