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.

Radial and Transverse Velocities of Nearby Galaxies

Abstract: Analysis of the peculiar velocities of the galaxies should take account of the uncertainties in both redshifts and distances. We show how this can be done by a numerical application of the action principle. The method is applied to an improved catalog of the galaxies and tight systems of galaxies within 4h Mpc, supplemented with a coarser sample of the major concentrations at 4h Mpc to 20h Mpc distance. Inclusion of this outer zone improves the fit of the mass tracers in the inner zone to their measured redshifts and distances, yielding best fits with reduced χ2 in redshift and distance in the range 1.5-2. These solutions are based on the assumption that the galaxies in and near the Local Group trace the mass, and a powerful test would be provided by observations of proper motions of the nearby galaxies. Predicted transverse galactocentric velocities of some of the nearby galaxies are confined to rather narrow ranges of values, and are on the order of 100 km s-1, large enough to be detected and tested by the proposed SIM and GAIA satellite missions.

Method for manufacturing fiber-reinforced parts utilizing stereolithography tooling

Abstract: A method of manufacturing a three-dimensional fiber-reinforced part utilizing the single-tool method of stereolithography. The tool is fabricated by designing the tool on a computer-aided design system and curing successive layers of a fluid medium via a computer-controlled irradiation source to form the three-dimensional tool. The desired part is generated by applying layers of resin-wetted fabric to the tool, curing the fabric on the tool, removing the tool from the designed part and cleaning, trimming and inspecting the designed part.

Nonlinearity and microwave losses in cubic strontium-titanate

Abstract: The complex dielectric constant of single-crystal strontium-titanate has been measured from 90\ifmmode^\circ\else\textdegree\fi{} to 230\ifmmode^\circ\else\textdegree\fi{}K at microwave frequencies. The real part of the dielectric constant consists of a large field-independent contribution which obeys a Curie-Weiss law over the entire range of measurement plus a smaller anisotropic field-dependent contribution. These results are shown to be in qualitative agreement with the theory of ferroelectricity in perovskite structures as proposed by Slater. The observed loss tangent consists of a contribution which is quadratic in an applied biasing field plus a field-independent contribution. The field-independent loss tangent goes through a minimum at about 170\ifmmode^\circ\else\textdegree\fi{} with a much steeper slope on the low-temperature side of the minimum than on the high-temperature side. The origin of the behavior of the field-independent loss tangent is discussed.

MBE growth of HgCdTe on silicon substrates for large-area infrared focal plane arrays: a review of recent progress

Abstract: We review the rapid progress that has been made during the past three years in the heteroepitaxial growth of HgCdTe infrared detector device structures on Si substrates by molecular-beam epitaxy. The evolution of this technology has enabled the fabrication of high performance, large-area HgCdTe infrared focal-plane arrays on Si substrates. A key element of this heteroepitaxial approach has been development of high quality CdTe buffer layers deposited on Si(112) substrates. We review the solutions developed by several groups to address the difficulties associated with the CdTe/Si(112) heteroepitaxial system, including control of crystallographic orientation and minimization of defects such as twins and threading dislocations. The material quality of HgCdTe/Si and the performance of HgCdTe detector structures grown on CdTe/Si(112) composite substrates is reviewed. Finally, we discuss some of the challenges related to composition uniformity and defect generation encountered with scaling the MBE growth process for HgCdTe to large-area Si substrates.

Upper limits on gravitational wave bursts in LIGO's second science run

Abstract: We perform a search for gravitational wave bursts using data from the second science run of the LIGO detectors, using a method based on a wavelet time-frequency decomposition. This search is sensitive to bursts of duration much less than a second and with frequency content in the 100–1100 Hz range. It features significant improvements in the instrument sensitivity and in the analysis pipeline with respect to the burst search previously reported by LIGO. Improvements in the search method allow exploring weaker signals, relative to the detector noise floor, while maintaining a low false alarm rate, O(0.1) μHz. The sensitivity in terms of the root-sum-square (rss) strain amplitude lies in the range of hrss∼10-20-10-19 Hz-1/2. No gravitational wave signals were detected in 9.98 days of analyzed data. We interpret the search result in terms of a frequentist upper limit on the rate of detectable gravitational wave bursts at the level of 0.26 events per day at 90% confidence level. We combine this limit with measurements of the detection efficiency for selected waveform morphologies in order to yield rate versus strength exclusion curves as well as to establish order-of-magnitude distance sensitivity to certain modeled astrophysical sources. Both the rate upper limit and its applicability to signal strengths improve our previously reported limits and reflect the most sensitive broad-band search for untriggered and unmodeled gravitational wave bursts to date.