Toward Open-Set Face Recognition

Much research has been conducted on both face identification and face verification, with greater focus on the latter. Research on face identification has mostly focused on using closed-set protocols, which assume that all probe images used in evaluation contain identities of subjects that are enrolled in the gallery. Real systems, however, where only a fraction of probe sample identities are enrolled in the gallery, cannot make this closed-set assumption. Instead, they must assume an open set of probe samples and be able to reject/ignore those that correspond to unknown identities. In this paper, we address the widespread misconception that thresholding verification-like scores is a good way to solve the open-set face identification problem, by formulating an open-set face identification protocol and evaluating different strategies for assessing similarity. Our open-set identification protocol is based on the canonical labeled faces in the wild (LFW) dataset. Additionally to the known identities, we introduce the concepts of known unknowns (known, but uninteresting persons) and unknown unknowns (people never seen before) to the biometric community. We compare three algorithms for assessing similarity in a deep feature space under an open-set protocol: thresholded verification-like scores, linear discriminant analysis (LDA) scores, and an extreme value machine (EVM) probabilities. Our findings suggest that thresholding EVM probabilities, which are open-set by design, outperforms thresholding verification-like scores.Comment: Accepted for Publication in CVPR 2017 Biometrics Worksho

A Cosmic Microwave Background feature consistent with a cosmic texture

The Cosmic Microwave Background provides our most ancient image of the Universe and our best tool for studying its early evolution. Theories of high energy physics predict the formation of various types of topological defects in the very early universe, including cosmic texture which would generate hot and cold spots in the Cosmic Microwave Background. We show through a Bayesian statistical analysis that the most prominent, 5 degree radius cold spot observed in all-sky images, which is otherwise hard to explain, is compatible with having being caused by a texture. From this model, we constrain the fundamental symmetry breaking energy scale to be phi_0 ~ 8.7 x 10^(15) GeV. If confirmed, this detection of a cosmic defect will probe physics at energies exceeding any conceivable terrestrial experiment.Comment: Accepted by Science. Published electronically via Science Express on 25 October 2007, http://www.sciencemag.org/cgi/content/abstract/114869

Competing interactions in two dimensional Coulomb systems: Surface charge heterogeneities in co-assembled cationic-anionic incompatible mixtures

A binary mixture of oppositely charged components confined to a plane such as cationic and anionic lipid bilayers may exhibit local segregation. The relative strength of the net short range interactions, which favors macroscopic segregation, and the long range electrostatic interactions, which favors mixing, determines the length scale of the finite size or microphase segregation. The free energy of the system can be examined analytically in two separate regimes, when considering small density fluctuations at high temperatures, and when considering the periodic ordering of the system at low temperatures (F. J. Solis and M. Olvera de la Cruz, J. Chem. Phys. 122, 054905 (2000)). A simple Molecular Dynamics simulation of oppositely charged monomers, interacting with a short range Lennard Jones potential and confined to a two dimensional plane, is examined at different strengths of short and long range interactions. The system exhibits well-defined domains that can be characterized by their periodic length-scale as well as the orientational ordering of their interfaces. By adding salt, the ordering of the domains disappears and the mixture macroscopically phase segregates in agreement with analytical predictions.Comment: 8 pages, 5 figures, accepted for publication in J. Chem. Phys, Figure 1 include

Study of the spatial variation of the biodegradation rate of the herbicide bentazone with soil depth using contrasting incubation methods

Vertical and horizontal spatial variability in the biodegradation of the herbicide bentazone was compared in sandy-loam soil from an agricultural field using sieved soil and intact soil cores. An initial experiment compared degradation at five depths between 0 and 80 cm using sieved soil. Degradation was shown to follow the first-order kinetics, and time to 50% degradation (DT50), declined progressively with soil depth from 56 d at 0–10 cm to 520 d at 70–80 cm. DT50 was significantly correlated with organic matter, pH and dehydrogenase activity. In a subsequent experiment, degradation rate was compared after 127 d in sieved soil and intact cores from 0 to 10 and 50 to 60 cm depth from 10 locations across a 160 × 90 m portion of the field. Method of incubation significantly affected mean dissipation rate, although there were relatively small differences in the amount of pesticide remaining in intact cores and sieved soil, accounting for between 4.6% and 10.6% of that added. Spatial variability in degradation rate was higher in soil from 0 to 10 cm depth relative to that from 50 and 60 cm depth in both sieved soil and intact core assessments. Patterns of spatial variability measured using cores and sieved soil were similar at 50–60 cm, but not at 0–10 cm depth. This could reflect loss of environmental context following processing of sieved soil. In particular, moisture content, which was controlled in sieved soil, was found to be variable in cores, and was significantly correlated with degradation rate in intact topsoil cores from 0 to 10 cm depth