Institution
Raytheon
Company•Waltham, Massachusetts, United States•
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.
Topics: Signal, Antenna (radio), Radar, Turbine, Amplifier
Papers published on a yearly basis
Papers
More filters
••
TL;DR: In this paper, the authors obtained deep images of the highly isolated (d = 1 Mpc) Aquarius dwarf irregular galaxy (DDO 210) with the Hubble Space Telescope Advanced Camera for Surveys.
Abstract: We have obtained deep images of the highly isolated (d = 1 Mpc) Aquarius dwarf irregular galaxy (DDO 210) with the Hubble Space Telescope Advanced Camera for Surveys. The resulting color-magnitude diagram (CMD) reaches more than a magnitude below the oldest main-sequence turnoff, allowing us to derive the star formation history (SFH) over the entire lifetime of the galaxy with a timing precision of ≈10% of the lookback time. Using a maximum likelihood fit to the CMD we find that only ≈10% of all star formation in Aquarius took place more than 10 Gyr ago (lookback time equivalent to redshift z ≈ 2). The star formation rate increased dramatically ≈6-8 Gyr ago (z ≈ 0.7-1.1) and then declined until the present time. The only known galaxy with a more extreme confirmed delay in star formation is Leo A, a galaxy of similar M H I /M , dynamical mass, mean metallicity, and degree of isolation. The delayed stellar mass growth in these galaxies does not track the mean dark matter accretion rate from CDM simulations. The similarities between Leo A and Aquarius suggest that if gas is not removed from dwarf galaxies by interactions or feedback, it can linger for several gigayears without cooling in sufficient quantity to form stars efficiently. We discuss possible causes for the delay in star formation including suppression by reionization and late-time mergers. We find reasonable agreement between our measured SFHs and select cosmological simulations of isolated dwarfs. Because star formation and merger processes are both stochastic in nature, delayed star formation in various degrees is predicted to be a characteristic (but not a universal) feature of isolated small galaxies.
56 citations
•
28 Jun 2001TL;DR: In this paper, a phase shifter circuit includes first and second RF ports (104, 106), and a switch circuit comprising a plurality of micro-electro-mechanical switches (50A-50D) responsive to control signals.
Abstract: An RF phase shifter circuit includes first and second RF ports (104, 106), and a switch circuit comprising a plurality of micro-electro-mechanical ('MEM') switches (50A-50D) responsive to control signals. The switch circuit is arranged to select one of a plurality of discrete phase shift values introduced by the phase shifter circuit to RF signals passed between the first and second RF ports. The circuits can be connected to provide a single-pole-multiple-throw (SPMT) or multiple-pole-multiple-throw (MPMT) switch function. The SPMT and MPMT switch circuits can be employed in other applications, including switchable attenuators, switchable filter banks, switchable time delay lines, switch matrices and transmit/receive RF switches.
56 citations
•
26 Aug 2004TL;DR: In this paper, a real-time holographic medium is used to record the amplitude and phase information collected from a m oving platform at the aperture p lane of a side-looking optical sensor over the collection time.
Abstract: This invention uses a real-time holographic medium to record the amplitude and phase information collected from a m oving platform at t he aperture p lane of a side-looking optical sensor over the collection time. A back-scan mirror is used to compensate platform motion during the synthetic aperture integration time. Phase errors caused by a nonlinear platform motion are compensated by controlling the phase offset between the illumination beam and the reference beam used to write the hologram based on inertial measurements of the flight path and the sensor line-of-sight pointing angles. In the illustrative embodiment, a synthetic aperture ladar (SAL) imaging system is mounted on a mobile platform. The system is adapted to receive a beam of electromagnetic energy; record the intensity and phase pattern carried by the beam; and store the pattern to compensate for motion of the platform relative to an external reference. In the illustrative embodiment, the image is stored as a holographic image. The system includes a back-scan mirror, which compensates the stored holographic pattern for motion of the platform. The medium and back-scan mirror may be replaced with a digital camera and one-dimensional and two-dimensional arrays may be used. In a specific embodiment, a two-dimensional array is used with a time delay and integration (TDI) scheme, which compensates for motion of the platform in the storage of the optical signals. In an alternative embodiment, a back-scanning mirror is used to compensate for motion of the platform. Consequently, the interference pattern between a relayed image of the aperture plane and a reference beam is continuously stored. In this embodiment, the instantaneous location of the received beam on the recording medium is controlled to compensate for motion of the platform.
56 citations
•
14 Jul 2011TL;DR: In this paper, a host computer hosts a 3D model of a scene and dynamically captures and transmits a windowed portion of the visual representation over a wireless network to the mobile operators' handheld devices.
Abstract: eSAT pushes 3D scene awareness and targeting to forward positioned mobile operators and their handheld devices in environments such as found in military theaters of operation, border control and enforcement, police operations, search & rescue and large commercial industrial operations. A host computer hosts a 3D model of a scene and dynamically captures and transmits a windowed portion of the visual representation of that 3D model over a wireless network to the mobile operators' handheld devices. The windowed portion of the visual representation is streamed directly to the operators' handheld device displays. The mobile operators may interact with and control the 3D model via the wireless network. The host computer may synthesize the visual representation of the 3D model with live feeds from one or more of the handheld devices or other assets to improve situational awareness. Either the mobile operators or host operator can make point selections on the visual representation to extract geo-coordinates from the 3D model as a set of target coordinates.
56 citations
•
14 Nov 2011TL;DR: In this article, a cover is removed from the main case and a first gear set is set at least partially within the cover along a first accessory axis transverse to the accessory gearbox axis.
Abstract: An accessory system for a gas turbine engine includes a main case which defines an accessory gearbox axis. A cover is removably mountable to the main case and a first gear set at least partially within the cover along a first accessory axis transverse to the accessory gearbox axis.
56 citations
Authors
Showing all 15293 results
Name | H-index | Papers | Citations |
---|---|---|---|
Peter J. Kahrilas | 109 | 586 | 46064 |
Edward J. Wollack | 104 | 732 | 102070 |
Duong Nguyen | 98 | 674 | 47332 |
Miroslav Krstic | 95 | 955 | 42886 |
Steven L. Suib | 89 | 862 | 34189 |
Gabriel M. Rebeiz | 87 | 806 | 32443 |
Charles W. Engelbracht | 83 | 210 | 28137 |
Paul A. Grayburn | 77 | 397 | 26880 |
Eric J. Huang | 72 | 201 | 22172 |
Thomas F. Eck | 72 | 150 | 32965 |
David M. Margolis | 70 | 227 | 17314 |
David W. T. Griffith | 65 | 288 | 14232 |
Gerhard Klimeck | 65 | 685 | 18447 |
Nickolay A. Krotkov | 63 | 219 | 11250 |
Olaf Stüve | 63 | 290 | 14268 |