Stathopoulos A.,College of William and Mary |
McCombs J.R.,Cobham Inc.
ACM Transactions on Mathematical Software | Year: 2010
This article describes the PRIMME software package for solving large, sparse Hermitian standard eigenvalue problems. The difficulty and importance of these problems have increased over the years, necessitating the use of preconditioning and near optimally converging iterative methods. However, the complexity of tuning or even using such methods has kept them outside the reach of many users. Responding to this problem, we have developed PRIMME, a comprehensive package that brings state-of-the-art methods from bleeding edge to production, with the best possible robustness, efficiency, and a flexible, yet highly usable interface that requires minimal or no tuning. We describe (1) the PRIMME multimethod framework that implements a variety of algorithms, including the near optimal methods GD+k and JDQMR; (2) a host of algorithmic innovations and implementation techniques that endow the software with its robustness and efficiency; (3) a multilayer interface that captures our experience and addresses the needs of both expert and end users. © 2010 ACM.
Youmans D.G.,Cobham Inc.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010
Several multiple-hypothesis range-rate algorithms are investigated to determine initial target acquisition capabilities of a direct detection ladar operating under low photo-electron return conditions. During initial acquisition of an object, the location of the object is not known, therefore the ladar returns cannot be simply summed in order to improve detection statistics. Analogous to classical radar multiple hypothesis algorithm approaches a "shift and sum," a "shift and accumulate," and a "numerically shift and histogram" algorithm are investigated. The probability density function for the maximum of the multiple-hypothesis range-rate algorithm matrix output is developed so that a threshold crossing probability can be determined and a "detection" declared (receiver-operating-characteristic). This is expressed as a function of false alarm rate which is a function of the number of ladar returns processed in the acquisition process and the length of the acquisition window. © 2010 SPIE.
Chadwick M.,University of Reading |
Trewin H.,Cobham Inc. |
Gawthrop F.,Cobham Inc. |
Wagstaff C.,University of Reading
International Journal of Molecular Sciences | Year: 2013
Sesquiterpenoids, and specifically sesquiterpene lactones from Asteraceae, may play a highly significant role in human health, both as part of a balanced diet and as pharmaceutical agents, due to their potential for the treatment of cardiovascular disease and cancer. This review highlights the role of sesquiterpene lactones endogenously in the plants that produce them, and explores mechanisms by which they interact in animal and human consumers of these plants. Several mechanisms are proposed for the reduction of inflammation and tumorigenesis at potentially achievable levels in humans. Plants can be classified by their specific array of produced sesquiterpene lactones, showing high levels of translational control. Studies of folk medicines implicate sesquiterpene lactones as the active ingredient in many treatments for other ailments such as diarrhea, burns, influenza, and neurodegradation. In addition to the anti-inflammatory response, sesquiterpene lactones have been found to sensitize tumor cells to conventional drug treatments. This review explores the varied ecological roles of sesquiterpenes in the plant producer, depending upon the plant and the compound. These include allelopathy with other plants, insects, and microbes, thereby causing behavioural or developmental modification to these secondary organisms to the benefit of the sesquiterpenoid producer. Some sesquiterpenoid lactones are antimicrobial, disrupting the cell wall of fungi and invasive bacteria, whereas others protect the plant from environmental stresses that would otherwise cause oxidative damage. Many of the compounds are effective due to their bitter flavor, which has obvious implications for human consumers. The implications of sesquiterpenoid lactone qualities for future crop production are discussed. © 2013 by the authors; licensee MDPI, Basel, Switzerland.
Cobham Inc. | Date: 2014-01-04
A tracking antenna system for discrete radio frequency spectrums includes a reflector, a pedestal supporting the reflector, a radome assembly enclosing both, a first feed for gathering radio waves within a first of discrete RF spectrums that is removably disposed in front of the reflector at the focal point, a first RF module operably connected to the first feed for converting the first gathered radio waves to first electronic signals, a feed mount for removably supporting the first feed and configured to removably support a second feed for gathering radio waves within a second of discrete RF spectrums, and a module mount for removably supporting the first RF module and configured to removably support a second RF module for converting the second radio waves to second electronic signals. A method of using the tracking antenna system adaptable for discrete radio frequency spectrums is also disclosed.
Cobham Inc. | Date: 2015-03-04
A rotationally-stabilizing tracking antenna system includes a three-axis pedestal, a drive assembly rotating a vertical support assembly relative to a base assembly, a cross-level driver pivoting a cross-level frame assembly relative to the vertical support assembly, and an elevation driver pivoting an elevation frame assembly relative to the cross-level frame assembly, a motion platform assembly affixed to the elevation frame assembly, three orthogonally mounted angular rate sensors disposed on the motion platform assembly sensing motion about X, Y and Z axes, a three-axis gravity accelerometer mounted on the motion platform assembly to determine a true-gravity zero reference, and a control unit determining the actual position of elevation frame assembly based upon sensed motion about X, Y, and Z axes and the true-gravity zero reference, and controlling the azimuth, cross-level and elevation drivers to position the elevation frame assembly in a desired position.
Cobham Inc. | Date: 2016-06-27
A multiple-feed antenna system includes a primary reflector that directs signals along a primary RF signal path and a subreflector assembly movable between a first position and a second position. When the subreflector assembly is in the first position, the subreflector assembly redirects signals traveling along the primary RF signal path to a first RF signal path. When the subreflector assembly is in the second position, the subreflector assembly redirects signals traveling along the primary RF signal path to a second RF signal path. The multiple-feed antenna system further includes: a first feed that intersects the first RF signal path and that communicates signals within a first frequency range; a second feed that intersects the second RF signal path and that communicates signals within a second frequency range; and an actuator that moves the subreflector assembly to the first position and to the second position.
Cobham Inc. | Date: 2015-01-28
A tracking antenna system for use in a plurality of discrete radio frequency (RF) spectrums includes a stabilized antenna support configured to direct and maintain the antenna in alignment with a communications satellite; a reflector mounted on the stabilized antenna support, the reflector reflecting radio waves along a first RF path; a first feed for gathering radio waves within a first of the discrete RF spectrums traveling from the reflector; a sub-reflector movable between first and second positions, the first position outside the first RF path and the second position in the first RF path to redirect radio waves traveling from the reflector along the first RF path to a second RF path; a second feed for gathering radio waves within a second of the discrete RF spectrums redirected along the second RF path; and an actuator for moving the sub-reflector between the first and second positions.
Cobham Inc. | Date: 2013-11-07
Gunshot detection system for locating the position of a shooter, mountable to a fixed object, a vehicle, or wearable by an individual.
News Article | August 20, 2015
Pedro joined the Chelsea squad at Cobham for his first training session Thursday afternoon. The 28-year-old signed a four-year contract following his switch from Barcelona on Thursday and joins in with Jose Mourinho and the squad ahead of their trip to West Bromwich Albion on Sunday.