Showing papers by "Raytheon published in 2000"

Lipotoxic heart disease in obese rats: implications for human obesity.

Abstract: To determine the mechanism of the cardiac dilatation and reduced contractility of obese Zucker Diabetic Fatty rats, myocardial triacylglycerol (TG) was assayed chemically and morphologically. TG was high because of underexpression of fatty acid oxidative enzymes and their transcription factor, peroxisome proliferator-activated receptor-α. Levels of ceramide, a mediator of apoptosis, were 2–3 times those of controls and inducible nitric oxide synthase levels were 4 times greater than normal. Myocardial DNA laddering, an index of apoptosis, reached 20 times the normal level. Troglitazone therapy lowered myocardial TG and ceramide and completely prevented DNA laddering and loss of cardiac function. In this paper, we conclude that cardiac dysfunction in obesity is caused by lipoapoptosis and is prevented by reducing cardiac lipids.

Interplanetary acceleration of coronal mass ejections

Abstract: Using an observed relation between speeds of CMEs near the Sun and in the solar wind, we determine an “effective” acceleration acting on the CMEs. We found a linear relation between this effective acceleration and the initial speed of the CMEs. The acceleration is similar to that of the slow solar wind in magnitude. The average solar wind speed naturally divides CMEs into fast and slow ones. Based on the relation between the acceleration and initial speed, we derive an empirical model to predict the arrival of CMEs at 1 AU.

Performance characterization of video-shot-change detection methods

Abstract: A number of automated shot-change detection methods for indexing a video sequence to facilitate browsing and retrieval have been proposed. Many of these methods use color histograms or features computed from block motion or compression parameters to compute frame differences. It is important to evaluate and characterize their performance so as to deliver a single set of algorithms that may be used by other researchers for indexing video databases. We present the results of a performance evaluation and characterization of a number of shot-change detection methods that use color histograms, block motion matching, or MPEG compressed data.

A thermal emission spectral library of rock-forming minerals

Abstract: A library of thermal infrared spectra of silicate, carbonate, sulfate, phosphate, halide, and oxide minerals has been prepared for comparison to spectra obtained from planetary and Earth-orbiting spacecraft, airborne instruments, and laboratory measurements. The emphasis in developing this library has been to obtain pure samples of specific minerals. All samples were hand processed and analyzed for composition and purity. The majority are 710 -1000 mm particle size fractions, chosen to minimize particle size effects. Spectral acquisition follows a method described previously, and emissivity is determined to within 2% in most cases. Each mineral spectrum is accompanied by descriptive information in database form including compositional information, sample quality, and a comments field to describe special circumstances and unique conditions. More than 150 samples were selected to include the common rock-forming minerals with an emphasis on igneous and sedimentary minerals. This library is available in digital form and will be expanded as new, well-characterized samples are acquired.

Use of the Surface Reference Technique for Path Attenuation Estimates from the TRMM Precipitation Radar

Abstract: Estimates of rain rate from the precipitation radar (PR) aboard the Tropical Rainfall Measuring Mission (TRMM) satellite require a means by which the radar signal attenuation can be corrected. One of the methods available is the surface reference technique in which the radar surface return in rain-free areas is used as a reference against which the path-integrated attenuation is obtained. Despite the simplicity of the basic concept, an assessment of the reliability of the technique is difficult because the statistical properties of the surface return depend not only on surface type (land/ocean) and incidence angle, but on the detailed nature of the surface scattering. In this paper, a formulation of the technique and a description of several surface reference datasets that are used in the operational algorithm are presented. Applications of the method to measurements from the PR suggest that it performs relatively well over the ocean in moderate to heavy rains. An indication of the reliability of...

Space Telescope Imaging Spectrograph Coronagraphic Observations of β Pictoris

Abstract: We present new coronagraphic images of β Pictoris obtained with the Space Telescope Imaging Spectrograph (STIS) in 1997 September. The high-resolution images (01) clearly detect the circumstellar disk as close to the star as 075, corresponding to a projected radius of 15 AU. The images define the warp in the disk with greater precision and at closer radii to β Pic than do previous observations. They show that the warp can be modeled by the projection of two components: the main disk and a fainter component, which is inclined to the main component by 4°-5° and extends only as far as ≈4'' from the star. We interpret the main component as arising primarily in the outer disk and the tilted component as defining the inner region of the disk. The observed properties of the warped inner disk are inconsistent with a driving force from stellar radiation. However, warping induced by the gravitational potential of one or more planets is consistent with the data. Using models of planet-warped disks constructed by Larwood & Papaloizou, we derive possible masses of the perturbing object.

Shape memory and nanostructure in poly(norbornyl-POSS) copolymers

Abstract: The microstructure and shape-memory properties of norbornyl-POSS hybrid copolymers having either cyclohexyl corner groups (CyPOSS) or cyclopentyl corner groups (CpPOSS) were investigated by transmission electron microscopy and thermomechanical analysis. Here, POSS refers to the polyhedral oligomeric silsesquioxane macromer. Samples containing 50wt% of POSS macromer have been mechanically drawn at temperatures above their glass transition temperatures, followed by rapid quenching in LN2 . Shape-memory properties of such drawn samples were explored by measuring recovered strain while heating above the T g using thermomechanical analysis. Incorporation of POSS comonomers within PN is found to slightly reduce the percentage recovery, while improving thermal stability significantly. Interestingly, the types of corner groups in the POSS macromer affect the shape-memory behaviour, with the CyPOSS copolymer showing lower percentage recovery than the CpPOSS copolymer due to enhanced aggregation of CyPOSS macromers. # 2000 Society of Chemical Industry

The shape of 433 eros from the NEAR-shoemaker laser rangefinder

Abstract: Measurements from the Near Earth Asteroid Rendezvous (NEAR)–Shoemaker Laser Rangefinder (NLR) indicate that asteroid 433 Eros is a consolidated body with a complex shape dominated by collisions. The offset between the asteroid's center of mass and center of figure indicates a small deviation from a homogeneous internal structure that is most simply explained by variations in mechanical structure. Regional-scale relief and slope distributions show evidence for control of topography by a competent substrate. Impact crater morphology is influenced by both gravity and structural control. Small-scale topography reveals ridges and grooves that may be generated by impact-related fracturing.

Network protocol for wireless ad hoc networks

Abstract: A method for establishing and maintaining a wireless ad hoc network comprising backbone nodes which forward packets through the network and non-backbone nodes which are capable of using the network, but do not forward packets. Signaling packets containing one or more protocol support records are periodically generated and transmitted by each node to neighboring nodes and are forwarded through the network by backbone nodes. Non-network nodes are initially selected to become backbone members during a SELECTION process based on an assessment of the node's connectivity relative to its neighbors. Link quality between nodes is monitored and used during an EXPANSION process in which additional non-network nodes may become backbone members. Disconnected backbone segments are interconnected during a CONNECTION process and the network is maintained during a MAINTENANCE process by periodically assessing the value of a backbone node's membership in the backbone. Efficient multicast routing is supported over the backbone by dynamically establishing and maintaining multicast trees. Signaling packets are periodically and frequently generated, thereby facilitating rapid adaptation to network changes. Further, the signaling packets are efficiently forwarded only by backbone nodes, thereby reducing bandwidth associated with establishing and maintaining the network.

Vacuum package fabrication of microelectromechanical system devices with integrated circuit components

Abstract: A method for vacuum packaging MEMS devices is provided that comprises forming a plurality of MEMS devices (12) on a device wafer (10). A first sealing ring (16) is formed surrounding one of the MEMS devices (12) and any associated mating pads (70). A plurality of integrated circuit devices (80) is formed on a lid wafer (30) where each integrated circuit device (80) has one or more associated mating pads (82) and one or more associated bonding pads (86). A plurality of second sealing rings (32) is formed on the lid wafer (30) where each of the second sealing rings (32) surrounds one of the integrated circuit devices (80) and any associated bonding pads (82). The second sealing ring (32) is positioned between the perimeter of the integrated circuit device (80) and the associated bonding pads (86). A sealing layer is formed on either each first sealing ring (16) or each second sealing ring (32). The device wafer (10) is mated with the lid wafer (30) in a vacuum environment to form a plurality of vacuum packages where each vacuum package encloses one or more of the MEMS devices (12) and one or more of the integrated circuit devices (80).

Will aerosol measurements from Terra and Aqua Polar Orbiting satellites represent the daily aerosol abundance and properties

Abstract: The Terra and Aqua missions will help quantify aerosol radiative forcing of climate by providing innovative measurements of the aerosol daily spatial distribution and identifying dust, smoke and regional pollution. However, these measurements are acquired at specific times of the day. To what extent can such measurements represent the daily average aerosol forcing of climate? We answer this question using 7 years of data from the Aerosol Robotic Network (AERONET) of 50–70 global ground-based instruments. AERONET measures the aerosol spectral optical thickness and the total precipitable water vapor every 15 minutes throughout the day. With a data set of 1/2 million measurements, AERONET demonstrates that Terra and Aqua aerosol measurements can represent the annual average value within 2% error. This excellent Terra representation of the daily average optical thickness is independent of the particle size or range of the optical thickness. This finding should facilitate ingest of satellite aerosol measurements in models that calculate radiative forcing and predict climate change.

Comprehensive review of the psychiatric uses of valproate

Abstract: The therapeutic effects of valproate in psychiatric conditions are most substantially recognized in bipolar disorder. However, this well-tolerated medication may be beneficial in the treatment of other mental illnesses. In this article, the authors comprehensively review studies of valproate as trea

640/spl times/486 long-wavelength two-color GaAs/AlGaAs quantum well infrared photodetector (QWIP) focal plane array camera

Abstract: We have designed and fabricated an optimized long-wavelength/very-long wavelength two-color quantum well infrared photodetector (QWIP) device structure. The device structure was grown on a 3-in semi-insulating GaAs substrate by molecular beam epitaxy (MBE). The wafer was processed into several 640/spl times/486 format monolithically integrated 8-9 and 14-15 /spl mu/m two-color (or dual wavelength) QWIP focal plane arrays (FPAs). These FPAs were then hybridized to 640/spl times/486 silicon CMOS readout multiplexers. A thinned (i.e., substrate removed) FPA hybrid was integrated into a liquid helium cooled dewar for electrical and optical characterization and to demonstrate simultaneous two-color imagery. The 8-9 /spl mu/m detectors in the FPA have shown background limited performance (BLIP) at 70 K operating temperature for 300 K background with f/2 cold stop. The 14-15 /spl mu/m detectors of the FPA reaches BLIP at 40 K operating temperature under the same background conditions. In this paper we discuss the performance of this long-wavelength dualband QWIP FPA in terms of quantum efficiency, detectivity, noise equivalent temperature difference (NE/spl Delta/T), uniformity, and operability.

Software FMEA techniques

Abstract: Assessing the safety characteristics of software driven safety critical systems is problematic. The author has performed software FMEA on embedded automotive platforms for brakes, throttle, and steering with promising results. Use of software FMEA at a system and a detailed level has allowed visibility of software and hardware architectural approaches which assure safety of operation while minimizing the cost of safety critical embedded processor designs. Software FMEA has been referred to in the technical literature for more than fifteen years. Additionally, software FMEA has been recommended for evaluating critical systems in some standards, notably draft IEC 61508. Software FMEA is also provided for in the current drafts of SAE ARP 5580. However, techniques for applying software FMEA to systems during their design have been largely missing from the literature. Software FMEA has been applied to the assessment of safety critical real-time control systems embedded in military and automotive products. The paper is a follow on to and provides significant expansion to the software FMEA techniques originally described by the author in the 1993 RAMS paper "Validating The Safety Of Real-Time Control Systems Using FMEA".

Method and apparatus for modeling a smart antenna in a network planning tool

Abstract: A network planning tool (NPT) computer program is used to model characteristics of a wireless telephone network (10). The network contains a plurality of cells (12) which each include a plurality of sectors (16-18) disposed about a base station (13) that has a respective antenna for each sector. Techniques are provided for modeling smart antennas (131), including use of a switched-beam transmit and receive patterns with approximately random allocation among the beams of frequencies assigned to an associated sector. In the case of an adaptive beam-forming smart antenna, power levels for that antenna and a remote antenna operating at the same frequency are adjusted so as to increase a differential therebetween by an improvement value associated with the smart antenna. Potential uplink interference at a given base station is modeled by simulating operation of other base stations at an uplink frequency with a reduced power level. Potential interfering signals are discounted to the extent a smart antenna can intelligently reject a limited number of undesired signals.

Single event effects in circuit-hardened SiGe HBT logic at gigabit per second data rates

Abstract: This attempt at circuit level single event effects (SEE) hardening of SiGe HBT logic provides the first reported indication of the level of sensitivity in this important technology, Characterization over data rate up to 3 Gbps and over a broad range of heavy ion LETs provides important clues to upset mechanisms and implications for upset rate predictions. We augment ion test data with pulsed laser SEE testing to indicate the sensitive targets within the circuit and to provide insights into the upset mechanism(s),.

Methods of manufacturing separable structures

Abstract: Methods for manufacturing composite material structures having one or more separable or replaceable skin portions. In one embodiment, the methods may include positioning first and second material pieces adjacent each other within a mold cavity and with a separating film disposed therebetween, introducing a first resin into the mold cavity to contact and substantially impregnate the first material piece with the first resin, and allowing the first resin to cure within the mold cavity to form a first part of the composite structure; and in which the separating film is substantially impermeable to the first resin.

Spectral Comparison of Red Giants in the Second-Parameter Globular Cluster Pair NGC 288 and NGC 362

Abstract: Abundances for 13 giants in the blue horizontal branch cluster NGC 288 and 12 giants in the red horizontal branch cluster NGC 362 are presented. The overall metallicities are found to be [Fe/H] = -1.39 ± 0.01 and -1.33 ± 0.01 for NGC 288 and NGC 362, respectively. [α/Fe] ratios for the two clusters are found to be nearly identical, although NGC 362 is found to have a 0.1 dex smaller [Ca/Fe] abundance. Contrary to previous investigations, oxygen-poor giants are found in both clusters. Although Na-O, Al-O anticorrelations are found in both clusters, zero-point and slope differences in the anticorrelations are found. These differences are attributed to ab initio higher O, Na, and Al abundances in NGC 288. Although the "mixed" giants in NGC 362 have significantly lower [O/Fe] ratios than those found in NGC 288, the extent of mixing is nearly equal in the two clusters because of this ab initio abundance difference. No significant difference is found in the r-process element Eu between the two clusters; however, the average Ba abundance, an s-process element, is slightly higher in NGC 288 than in NGC 362. Mass-loss indicators Hα and Na core velocities show little difference from previous investigations of other globular clusters. Excessive mass loss and deep mixing induced surface He abundance differences are ruled out as sources of the difference in horizontal-branch morphology for these two clusters.

Relationship between column aerosol optical thickness and in situ ground based dust concentrations over Barbados

Abstract: Aerosol optical depth measurements over Barbados acquired through the AERONET network are analyzed. Optical depth shows a pronounced seasonal pattern, with a maximum observed during summer. The temporal trends of the sunphotometry data were similar to those of ground-based dust concentration measurements. A simple linear regression relationship has been established between mean monthly values of aerosol optical depth and dust concentrations (correlation coefficient r=0.93), which allows the estimation of optical depth for any specific time period when dust concentration measurements are available. The robustness of the regression was validated with an independent data set.

Adiabatic Survey of Subdwarf B Star Oscillations. I. Pulsation Properties of a Representative Evolutionary Model

Abstract: We present the first results of a large, systematic adiabatic survey of the pulsation properties of models of subdwarf B (sdB) stars. This survey is aimed at providing the most basic theoretical data with which to analyze the asteroseismological properties of the recently discovered class of pulsating sdB stars (the EC 14026 stars). Such a theoretical framework has been lacking up to now. In this paper, the first of a series of three, an adiabatic pulsation code is used to compute, in the 80-1500 s period window, the radial (l = 0) and nonradial (from l = 1 up to l = 3) oscillation modes for a representative evolutionary model of subdwarf B stars. Quantities such as the periods, kinetic energies, first-order rotational splitting coefficients, eigenfunctions, and weight functions are given by the code, providing a complete set of very useful diagnostic tools with which to study the mode properties. The main goal is to determine how these quantities relate to the internal structure of B subdwarfs, a crucial and necessary step if one wants to eventually apply the tools of asteroseismology to EC 14026 stars. All modes (p, f, and g) were considered in order to build the most complete picture we can have on pulsations in these stars. In that context, we show that g-modes are essentially deep interior modes oscillating mainly in the radiative helium-rich core (but not in the convective nucleus), while p-modes are shallower envelope modes. We demonstrate that g-modes respond to a trapping/confinement phenomenon induced mainly by the He/H chemical transition between the H-rich envelope and the He-rich core of subdwarf B stars. This phenomenon is very similar in nature to the g-mode trapping and confinement mechanisms observed in pulsating white dwarf models. We emphasize that p-modes may also experience distortions of their period distribution due to this He/H transition, although these are not as pronounced as in the g-mode case. These phenomena are of great interest as they can potentially provide powerful tools for probing the internal structure of these objects, in particular, with respect to constraining the mass of their H-rich envelope. The results given in this first paper form the minimal background on pulsation mode characteristics in sdB stars. Upcoming discussions on additional mode properties in subdwarf B star models (Paper II and Paper III of this series) will strongly rely on these basic results since they provide essential guidance in understanding mode period behaviors as functions of B subdwarf stellar parameters and/or evolution.

Microbolometer and method for forming

Abstract: A microbolometer is provided that includes an absorber element having material properties to change temperature in response to absorbing infrared radiation. An amorphous silicon detector is thermally coupled to the absorber element and is suspended above a silicon substrate at a height of one-quarter wavelength of the infrared radiation to be detected. The amorphous silicon detector changes electrical resistance in response to the absorber element changing temperature. The microbolometer also includes electrode arms coupled to the silicon substrate to provide structural support for the amorphous silicon detector above the surface of the silicon substrate. The electrode arms further provide electrical connectivity for the microbolometer.

The HALO network/sup TM/

Abstract: The High Altitude Long Operation Network/sup TM/ is a broadband wireless metropolitan area network, with a star topology, whose solitary hub is located in the atmosphere above the service area at an altitude higher than commercial airline traffic. The HALO/Proteus airplane is the central node of this network. It will fly at altitudes higher than 51,000 ft. The signal footprint of the network, its "Cone of Commerce", will have a diameter on the scale of 100 km. The initial capacity of the network will be on the scale of 10 Gb/s, with growth beyond 100 Gb/s. The network will serve the communications needs of each subscriber with bit rates in the multimegabit per second range. A variety of spectrum bands licensed by the FCC for commercial wireless services could provide the needed millimeter wavelength carrier bandwidth. An attractive choice for the subscriber links is the LMDS band. The airplane's fuselage can house switching circuitry and fast digital network functions. An MMW antenna array and its related components will be located in a pod suspended below the aircraft fuselage. The antenna array will produce many beams, typically more than 100. Adjacent beams will be separated in frequency. Electronic beamforming techniques can be used to stabilize the beams on the ground, as the airplane flies within its station keeping volume. For the alternative of aircraft-fixed beams, the beams will traverse over a user location, while the airplane maintains station overhead, and the virtual path will be changed to accomplish the beam-to-beam handoff. For each isolated city to be served, a fleet of three aircraft will be operated in shifts to achieve around-the-clock service. In deployments where multiple cities will be served from a common primary flight base, the fleet will be sized for allocating, on average, two aircraft per city to be served. Flight operational tactics will be steadily evolved and refined to achieve continuous presence of the node above each city. Many services will be provided, including but not limited to T1 access, ISDN access, Web browsing, high-resolution videoconferencing, large file transfers, and Ethernet LAN bridging.

Robust Detection of Ionospheric Irregularities

Abstract: The Wide Area Augmentation System (WAAS) will provide real-time differential GPS corrections and integrity information for aircraft navigation use. The most stringent application of this system will be precision approach, where the system guides the aircraft to within a few hundred feet of the ground. Precision approach operations require the use of differential ionospheric corrections. WAAS must incorporate information from reference stations to create a correction map of the ionosphere. More importantly, this map must contain confidence bounds describing the integrity of the corrections. The confidence bounds must be large enough to describe the error in the correction, but tight enough to allow the operation to proceed. The difficulty in generating these corrections is that the reference station measurements are not co-located with the aviation user measurements. For an undisturbed ionosphere over the Conterminous United States (CONUS), this is not a problem as the ionosphere is nominally well behaved. However, a concern is that irregularities in the ionosphere will decrease the correlation between the ionosphere observed by the reference stations and that seen by the user. Therefore, it is essential to detect when such irregularities may be present and adjust the confidence bounds accordingly. The approach outlined in this paper conservatively bounds the ionospheric errors even for the worst observed ionospheric conditions to date, using data sets taken from the operational receivers in the WAAS reference station network. As we progress through the current solar cycle and gather more data on the behavior of the ionosphere, many of our pessimistic assumptions will be relaxed. This will result in higher availability while maintaining full integrity.

Magnéli phases of anion-deficient rutile as lubricious oxides. Part I. Tribological behavior of single-crystal and polycrystalline rutile (Ti n O2n−1)

Abstract: In part I of this paper series, wide temperature range SEM-tribometric results generated in vacuum and various partial pressures of oxygen are combined with relevant literature data to examine a hypothesis correlating the oxygen stoichiometry of the Ti n O2n−1 Magneli phases of the rutile polymorph of titania with their tribological behavior. Single-crystal and polycrystalline rutile specimens of narrow stoichiometry ranges were sliding against α-SiC and themselves. The surface shear strength changes were determined as a function of the thermal–atmospheric test environment, and the shear strength values were estimated by the coefficients of friction, the real area of contact and the published yield strength of rutile. The data appear to be sufficient and sufficiently reliable to confirm the accuracy of the hypothesis. The tendency of the rutile stoichiometry (ergo the friction) to shift as a function of temperature and partial pressure of oxygen causes this material to be thermo-oxidatively unstable for tribological applications in extreme environments. In part II, a study is described to formulate oxidatively more stable Magneli phases by Cu-doping, and test the new materials by SEM tribometry using a procedure used for pure rutile here in part I. By employing this doping methodology similar to creating high-temperature superconductive oxides in part II, some feasibility of producing oxidatively stable, lubricious oxides with acceptably low wear rates is indicated.

Adaptive whitening of the electromyogram to improve amplitude estimation

Abstract: Previous research showed that whitening the surface electromyogram (EMG) can improve EMG amplitude estimation (where EMG amplitude is defined as the time-varying standard deviation of the EMG). However, conventional whitening via a linear filter seems to fail at low EMG amplitude levels, perhaps due to additive background noise in the measured EMG. This paper describes an adaptive whitening technique that overcomes this problem by cascading a nonadaptive whitening filter, an adaptive Wiener filter, and an adaptive gain correction. These stages can be calibrated from two, five second duration, constant-angle, constant-force contractions, one at a reference level [e.g., 50% maximum voluntary contraction (MVC)] and one at 0% MVC. In experimental studies, subjects used real-time EMG amplitude estimates to track a uniform-density, band-limited random target. With a 0.25-Hz bandwidth target, either adaptive whitening or multiple channel processing reduced the tracking error roughly half-way to the error achieved using the dynamometer signal as the feedback. At the 1.00-Hz bandwidth, all of the EMG processors had errors equivalent to that of the dynamometer signal, reflecting that errors in this task were dominated by subjects' inability to track targets at this bandwidth. Increases in the additive noise level, smoothing window length, and tracking bandwidth diminish the advantages of whitening.

Method and apparatus for an improved single pole double throw micro-electrical mechanical switch

Abstract: A single pole, double throw micro-electromechanical (MEM) switch. The inventive switch includes a first contact providing a first terminal of the switch. A second contact provides a second terminal of said switch. A cantilever beam provides a third terminal of the switch. The inventive switch includes a system for electrostatically pushing or pulling the beam to disengage the first contact and engage the second contact. In an illustrative implementation, the system for electrostatically operating the switch includes a first charge storage structure on the beam, a second charge storage structure on the switch, and an electrical supply for creating an electrical charge on the first and the second charge storage structures. The first and second charge storage structures are effective to create a force of repulsion therebetween on the application of an electrical charge thereto. The 'pull' electrostatic force closes the MEM switch. The 'push' force aids in opening the switch. The 'push' capability is the result of the use of like (same polarity) electrostatic charges on the control surfaces. The like charges provide an electrostatic repulsion force during the switch opening process.