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.

Ultrawideband Hybrid EBG/Ferrite Ground Plane for Low-Profile Array Antennas

Abstract: The design and analysis of an ultrawideband and low-profile hybrid electromagnetic band-gap (EBG)/ferrite ground plane is presented for implementation with antenna systems in airborne foliage penetrating radar and EW applications. The hybrid EBG/ferrite ground plane consists of an EBG structure with a ferrite slab placed on top of the structure's perfect electric conductor (PEC) ground plane. Reflectivity and phase analyses show that the hybrid EBG/ferrite ground plane offers ultrawideband operation beginning in the 100s of MHz with one design version offering an operational bandwidth exceeding 22:1 starting at 170 MHz. Additionally, analysis of the hybrid ground plane implemented with dipole antennas verifies that the hybrid ground plane effectively produces uni-directional radiation for bi-directional radiating antennas. The designed hybrid ground plane is also simulated with Raytheon's long slot array antenna and the obtained results further verify its ultrawideband performance

Multilingual system having dynamic language selection

Abstract: A multilingual system provides dynamic flipping of a displayed form from one language to another. The forms include a plurality of fields each of which includes properties that allow the form to be displayed in accordance with the conventions of the selected language. When switching from one language to another, the form field properties are modified to properly display the form in the new language.

Wind variability of B supergiants. IV. A survey of IUE time-series data of 11 B0 to B3 stars

Abstract: We present the most suitable data sets available in the International Ultraviolet Explorer (IUE) archive for the study of time-dependent stellar winds in early B supergiants. The UV line prole variability in 11 B0 to B3 stars is analysed, compared and discussed, based on 16 separate data sets comprising over 600 homogeneously reduced high-resolution spectrograms. The targets include ormal" stars with moderate rotation rates and examples of rapid rotators. A gallery of grey-scale images (dynamic spectra) is presented, which demonstrates the richness and range of wind variability and highlights dierent structures in the winds of these stars. This work emphasises the suitability of B supergiants for wind studies, under-pinned by the fact that they exhibit unsaturated wind lines for a wide range of ionization. The wind activity of B supergiants is substantial and has highly varied characteristics. The variability evident in individual stars is classied and described in terms of discrete absorption components, spontaneous absorption, bowed structures, recurrence, and ionization variability and stratication. Similar structures can occur in stars of dierent fundamental parameters, but also dierent structures may occur in the same star at a given epoch. We discuss the physical phenomena that may be associated with the spectral signatures. The diversity of wind patterns evident likely reflects the role of stellar rotation and viewing angle in determining the observational characteristics of azimuthally extended structure rooted at the stellar surface. In addition, SEI line-synthesis modelling of the UV wind lines is used to provide further information about the state of the winds in our program stars. Typically the range, implied by the line prole variability, in the product of mass-loss rate and ion fraction ( _ Mq i) is a factor of 1.5, when integrated between 0.2 and 0.9 v1 ;i t can however be several times larger over localised velocity regions. At a given eective temperature the mean relative ion ratios can dier by a factor of 5. The general excess in predicted (forward-scattered) emission in the low velocity regime is discussed in terms of structured outflows. Mean ion fractions are estimated over the B0 to B1 spectral classes, and trends in the ionic ratios as a function of wind velocity are described. The low values obtained for the ion fractions of UV resonance lines may reflect the role of clumping in the wind.

Tribological fundamentals of polycrystalline diamond films

Abstract: A decade's worth of SEM-tribometric work on polycrystalline diamond films is reviewed Diamond-coated Si and SiC specimens have been tested under oscillatory sliding, at temperatures from room ambient to 1000 °C in (a) ∼133×10 −3 Pa (∼1×10 −5 Torr) vacuum, (b) 13–39 Pa (01–03 Torr) partial pressures of hydrogen and (c) 26 Pa (02 Torr) partial pressure of oxygen The temperature- and atmosphere-controlled tribological behavior of the films is interpreted by the environment-dependent values and trends of the average coefficient of friction Accurate interpretation of the results is assisted by similar friction and wear data on various silicon crystallinities, complemented by applicable thermal desorption, surface chemical and tribometric data taken from the literature