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.

Angular Distributions of Solar Energetic Particles

Abstract: We report observations, using data from the Wind spacecraft, of temporal variations in the angular distributions of H, He, O, and Fe ions at MeV energies during solar energetic particle (SEP) events under a variety of conditions. Detailed time-dependent angular distributions of O and Fe during SEP events are reported for the first time. Extended periods of particle streaming in small gradual events are consistent with continued acceleration that is expected at shock waves driven from the Sun by coronal mass ejections (CMEs). Particles accelerated from SEP events of moderate size show especially strong streaming along the magnetic fields inside an old CME. For the largest events, however, streaming rapidly diminishes, showing behavior that is qualitatively consistent with the theory of Ng et al. In very intense events, that theory predicts rapid growth of proton-generated Alfven waves, even near and beyond 1 AU, that soon scatter and isotropize the particles. We show, for the first time, cases where SEP streaming is organized by the value of the plasma beta βp, the ratio of the proton thermal energy to magnetic energy. Higher initial turbulence in the high-βp plasma may require less additional wave growth to reach significant levels of scattering in the largest SEP events.

Systematic Study on Thermo-Mechanical Durability of Pb-Free Assemblies: Experiments and FE Analysis

Abstract: As the ban of the Pb use in electronics products is approaching due to the waste electrical and electronic equipment (WEEE) and restriction of hazardous substances (ROHS) directives, electronics companies start to deliver the products using the Pb-free solders. There are extensive databases of mechanical properties, durability properties (for both mechanical and thermal cycling), and micromechanical characteristics for Sn-Pb solders. But similar databases are not readily yet available for Pb-free solders to predict its mechanical behavior under environmental stresses. In this study, the thermo-mechanical durability of the Pb-free Sn3.8Ag0.7Cu solder is investigated by a systematic approach combining comprehensive thermal cycling tests and finite element modeling. A circuit card assembly (CCA) test vehicle was designed to analyze several design and assembly process variables when subjected to environmental extremes. The effects of mixed solder systems, device types, and underfill are addressed in the thermal cycling tests. The thermal cycle profile consisted of temperature extremes from −55to+125° Celsius with a 15min dwell at hot, a 10min dwell at cold, and a 5–10° Celsius per minute ramp. Thermal cycling results show that Sn3.8Ag0.7Cu marginally outperforms SnPb for four different components under the studied test condition. In addition, the extensive detailed three-dimensional viscoplastic finite element stress and damage analysis is conducted for five different thermal cycling tests of both Sn3.8Ag0.7Cu and Sn37Pb solders. Power law thermo-mechanical durability models of both Sn3.8Ag0.7Cu and Sn37Pb are obtained from thermal cycling test data and stress and damage analysis. The results of this study provide an important basis of understanding the thermo-mechanical durability behavior of Pb-free electronics under thermal cycling loading and environmental stresses.

MMIC airbridge balun transformer

Abstract: A balun transformer and inductor are proposed having geometries that provide several windings of conductors in small areas. In one embodiment, the windings of the balun transformer and inductor have octagonal shapes with a lower and upper layer of wound conductors. The upper layer lies on supporting posts that stand on pedestals. The lower layer of conductors shadow the upper layer while curving to avoid the pedestals.

Infrared pyroelectric sensor for detection of vehicular traffic using digital signal processing techniques

Abstract: An experimental passive infrared system was designed and developed to detect and monitor vehicular road traffic. The system uses infrared pyroelectric sensors to sense vehicles passing through its field of view. In conjunction with computerized signal processing and correlation techniques the sensor information can then be used to count the number of vehicles passing and compute their speed and length. Laboratory and field tests results indicate that this technology should be cost effective, weather resistant and have the potential for a variety of sophisticated traffic monitoring applications. >

A second-order method for assembly tolerance analysis

Abstract: Linear analysis and Monte Carlo simulation are two wellestablished methods for statistical tolerance analysis of mechanical assemblies. Both methods have advantages and disadvantages. The Linearized Method, a form of linear analysis, provides fast analysis, tolerance allocation, and the capability to solve closed loop constraints. However, the Linearized Method does not accurately approximate nonlinear geometric effects or allow for non-normally distributed input or output distributions. Monte Carlo simulation, on the other hand, does accurately model nonlinear effects and allow for nonnormally distributed input and output distributions. Of course, Monte Carlo simulation can be computationally expensive and must be re-run when any input variable is modified. The second-order tolerance analysis (SOTA) method attempts to combine the advantages of the Linearized Method with the advantages of Monte Carlo simulation. The SOTA method applies the Method of System Moments to implicit variables of a system of nonlinear equations. The SOTA method achieves the benefits of speed, tolerance allocation, closed-loop constraints, non-linear geometric effects and non-normal input and output distributions. The SOTA method offers significant benefits as a nonlinear analysis tool suitable for use in design iteration. A comparison was performed between the Linearized Method, Monte Carlo simulation, and the SOTA method. The SOTA method provided a comparable nonlinear analysis to Monte Carlo simulation with 10 6 samples. The analysis time of the SOTA method was comparable to the Linearized Method.