Raytheon

About: Raytheon is a company organization based out in Waltham, Massachusetts, United States. It is known for research contribution in the topics: Signal & Antenna (radio). The organization has 15290 authors who have published 18973 publications receiving 300052 citations.

Robust EEG emotion classification using segment level decision fusion

Abstract: In this paper we address single-trial binary classification of emotion dimensions (arousal, valence, dominance and liking) using electroencephalogram (EEG) signals that represent responses to audio-visual stimuli. We propose an innovative three step solution to this problem: (1) in contrast to the typical feature extraction on the response-level, we represent the EEG signal as a sequence of overlapping segments and extract feature vectors on the segment level; (2) transform segment level features to the response level features using projections based on a novel non-parametric nearest neighbor model; and (3) perform classification on the obtained response-level features. We demonstrate the efficacy of our approach by performing binary classification of emotion dimensions on DEAP (Dataset for Emotion Analysis using electroencephalogram, Physiological and Video Signals) and report state-of-the-art classification accuracies for all emotional dimensions.

An economical method for calculating the discrete Fourier transform

Abstract: With the advent of digital computers it became possible to compute the Discrete Fourier Transform for a large number of input points in relatively reasonable times. However, for certain uses a demand developed to compute the Discrete Fourier Transform in a very short time or even in real time. Also, a demand developed for computing the Fourier Transform for a very large number of input points. These demands resulted in a requirement for computing the Fourier Transform in the fastest time possible. A very economical way for computing the Fourier Transform was developed a few years ago and is known as the Cooley-Tukey Algorithm. This article describes another algorithm for computing the Discrete Fourier Transform where the required number of additions and subtractions is the same as in the Cooley-Tukey Algorithm; but the required number of multiplications is only one half of that in the Cooley-Tukey Algorithm.

Delving Deeper into the Tumultuous Lives of Galactic Dwarfs: Modeling Star Formation Histories

Abstract: The paucity of observed dwarf galaxies in the Local Group relative to the abundance of predicted dark matter halos remains one of the greatest puzzles of the ΛCDM paradigm. Solving this puzzle now requires not only matching the numbers of objects but also understanding the details of their star formation histories. We present a summary of such histories derived from the HST data using the color-magnitude diagram fitting method. To reduce observational uncertainties, we condense the data into five cumulative parameters: the fractions of stellar mass formed in the last 1, 2, 5, and 10 Gyr, and the mean stellar age. We interpret the new data with a phenomenological model based on the mass assembly histories of dark matter halos and the Schmidt law of star formation. The model correctly predicts the radial distribution of the dwarfs and the fractions of stars formed in the last 5 and 10 Gyr. However, in order to be consistent with the observations, the model requires a significant amount of recent star formation in the last 2 Gyr. Within the framework of our model, this prolonged star formation can be achieved by adding a stochastic variation in the density threshold of the star formation law. The model results are not sensitive to late gas accretion, the slope of the Schmidt law, or the details of cosmic reionization. A few discrepancies still remain: our model typically predicts too large stellar masses, only a modest population of ultrafaint dwarfs, and a small number of dwarfs with anomalously young stellar populations. Nevertheless, the observed star formation histories of Local Group dwarfs are generally consistent the expected star formation in cold dark matter halos.

Comparing the ancient star formation histories of the Magellanic Clouds

Abstract: We present preliminary results from a new Hubble Space Telescope ( HST ) archival program aimed at tightly constraining the ancient (>4 Gyr ago) star formation histories (SFHs) of the field populations of the Small Magellanic Cloud (SMC) and Large Magellanic Cloud (LMC). We demonstrate the quality of the archival data by constructing HST /Wide Field Planetary Camera 2-based colour–magnitude diagrams (CMDs; M F 555 W ∼ +8) for seven spatially diverse fields in the SMC and eight fields in the LMC. The HST -based CMDs are > mag deeper than any from ground-based observations, and are particularly superior in high surface brightness regions, e.g. the LMC bar, which contain a significant fraction of star formation and are crowding limited from ground-based observations. To minimize systematic uncertainties, we derive the SFH of each field using an identical maximum likelihood CMD fitting technique. We then compute an approximate mass weighted average SFH for each galaxy. From the average SFHs, we find that both galaxies lack a dominant burst of early star formation, which suggests either a suppression or an underfuelling of ancient star formation in the Magellanic Clouds (MCs). From 10 to 12 Gyr ago, we find that the LMC experienced a period of enhanced stellar mass growth relative to the SMC. Similar to some previous studies, we find two notable peaks in the SFH of the SMC at ∼4.5 and 9 Gyr ago, which could be due to repeated close passages with the LMC, implying an interaction history that has persisted for at least 9 Gyr. We find little evidence for strong periodic behaviour in the lifetime SFHs of both MCs, suggesting that repeated encounters with the Milky Way are unlikely. Beginning ∼3.5 Gyr ago, both galaxies show sharp increases in their SFHs, in agreement with previous studies. Subsequently, the SFHs track either remarkably well. Spatial variations in the SFH of the SMC are consistent with a picture where gas was driven into the centre of the SMC ∼3.5 Gyr ago, which simultaneously shut down star formation in the outer regions while dramatically increasing the star formation rate in the centre. In contrast, the LMC shows little spatial variation in its ancient SFH. The planned additional analysis of HST pointings at larger galactocentric radii will allow us to make more confident statements about spatial variations in the SFHs of the SMC and LMC.