2,470 research outputs found
En route position and time control of aircraft using Kalman filtering of radio aid data
Fixed-time-of-arrival (FTA) guidance and navigation is investigated as a possible technique capable of operation within much more stringent en route separation standards and offering significant advantages in safety, higher traffic densities, and improved scheduling reliability, both en route and in the terminal areas. This study investigated the application of FTA guidance previously used in spacecraft guidance. These FTA guidance techniques have been modified and are employed to compute the velocity corrections necessary to return an aircraft to a specified great-circle reference path in order to exercise en route time and position control throughout the entire flight. The necessary position and velocity estimates to accomplish this task are provided by Kalman filtering of data from Loran-C, VORTAC/TACAN, Doppler radar, radio or barometric altitude,and altitude rate. The guidance and navigation system was evaluated using a digital simulation of the cruise phase of supersonic and subsonic flights between San Francisco and New York City, and between New York City and London
Evaluation of thermal insulation materials
Data was obtained on silicone-bonded fiberglass, isocyanurate foam, and two dozen other insulators. Materials were selected to withstand heat sterilization, outer space, and the Martian atmosphere. Significant environmental parameters were vibration, landing shock, and launch venting
A system for synthetic vision and augmented reality in future flight decks
Rockwell Science Center is investigating novel human-computer interaction techniques for enhancing the situational awareness in future flight decks. One aspect is to provide intuitive displays that provide the vital information and the spatial awareness by augmenting the real world with an overlay of relevant information registered to the real world. Such Augmented Reality (AR) techniques can be employed during bad weather scenarios to permit flying in Visual Flight Rules (VFR) in conditions which would normally require Instrumental Flight Rules (IFR). These systems could easily be implemented on heads-up displays (HUD). The advantage of AR systems vs. purely synthetic vision (SV) systems is that the pilot can relate the information overlay to real objects in the world, whereas SV systems provide a constant virtual view, where inconsistencies can hardly be detected. The development of components for such a system led to a demonstrator implemented on a PC. A camera grabs video images which are overlaid with registered information. Orientation of the camera is obtained from an inclinometer and a magnetometer; position is acquired from GPS. In a possible implementation in an airplane, the on-board attitude information can be used for obtaining correct registration. If visibility is sufficient, computer vision modules can be used to fine-tune the registration by matching visual cues with database features. This technology would be especially useful for landing approaches. The current demonstrator provides a frame-rate of 15 fps, using a live video feed as background with an overlay of avionics symbology in the foreground. In addition, terrain rendering from a 1 arc sec. digital elevation model database can be overlaid to provide synthetic vision in case of limited visibility. For true outdoor testing (on ground level), the system has been implemented on a wearable computer
Just picking it up? Young children learning with technology at home
We describe a two-year empirical investigation of three- and four-year-old children's uses of technology at home, based on a survey of 346 families and 24 case studies. Using a sociocultural approach, we discuss the range of technologies children encounter in the home, the different forms their learning takes, the roles of adults and other children, and how family practices support this learning. Many parents believed that they do not teach children how to use technology. We discuss parents' beliefs that their children 'pick up' their competences with technology and identify trial and error, copying and demonstration as typical modes of learning. Parents tend to consider that their children are mainly self-taught and underestimate their own role in supporting learning and the extent to which learning with technology is culturally transmitted within the family
The Effectiveness of a Geriatrics Curriculum
With support from the AAMC/John A. Hartford Foundation the University of Massachusetts Medical School developed a Geriatrics curriculum and faculty development that would be integrated across all four years. Beginning in Fall 2001, these were implemented over the next two academic years in both preclinical and clinical areas and are highlighted on the timeline above. Would implementation of this new Geriatrics curriculum and faculty development impact studentsâ ratings of instruction time in Geriatrics?
Presented at the AAMC (Association of American Colleges) Annual Meeting, RIME (Research in Medical Education) Program, November 2005
Structure of the Large Magellanic Cloud from 2MASS
We derive structural parameters and evidence for extended tidal debris from
star count and preliminary standard candle analyses of the Large Magellanic
Cloud based on Two Micron All Sky Survey (2MASS) data. The full-sky coverage
and low extinction in K_s presents an ideal sample for structural analysis of
the LMC.
The star count surface densities and deprojected inclination for both young
and older populations are consistent with previous work. We use the full areal
coverage and large LMC diameter to Galactrocentric distance ratio to infer the
same value for the disk inclination based on perspective.
A standard candle analysis based on a sample of carbon long-period variables
(LPV) in a narrow color range, 1.6<J-K_s<1.7 allows us to probe the
three-dimensional structure of the LMC along the line of sight. The intrinsic
brightness distribution of carbon LPVs in selected fields implies that
\sigma_M\simlt 0.2^m for this color cut. The sample provides a {\it direct}
determination of the LMC disk inclination: .
Distinct features in the photometric distribution suggest several distinct
populations. We interpret this as the presence of an extended stellar component
of the LMC, which may be as thick as 14 kpc, and intervening tidal debris at
roughly 15 kpc from the LMC.Comment: 24 pages, 9 figures. Submitted to Ap
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Aspects of the winter predator--prey relationship between sauger and threadfin shad in Watts Bar Reservoir, Tennessee
This study sought to determine the impact of cold-induced mortality and impingement of threadfin shad (Dorsoma petenense) on the food consumption and prey selection of sauger (Stizostedion canadense), and to estimate the ability of sauger to digest meals consumed at low temperatures in winter. Prey selection of sauger was monitored from November 1976 through April 1977. Stomach contents of 536 sauger indicated threadfin provided the entire forage base for sauger through January. Food consumption of sauger was reduced and prey selection shifted to other species after January due to the combined effects of predation, impingement, and natural mortality of cold-stressed threadfin. Threadfin shad of a size available to most sauger were virtually eliminated by February. From February through April some sauger utilized alternate prey species. Laboratory digestion rate studies of sauger indicated digestion of force-fed meals of 4 to 7 g fathead minnows (Pimephales promelas) could proceed to 90 percent completion in 54 h at 5 C, 47 hr at 10 C, and 25 hr at 15 C. Conclusions of this study are: (1) that threadfin shad were the most abundant and vulnerable prey species available to and utilized by sauger during the late fall and winter months; (2) extensive mortalities of threadfin due to cold-stress increased sauger predation on four alternate prey species; (3) sauger continued feeding and digesting meals at temperatures between 5 and 15 C every 1 to 3 days; (4) sauger stored excess energy available from threadfin early in the winter as visceral fat which was available later when food consumption was reduced
Comparison of high-latitude line-of-sight ozone column density with derived ozone fields and the effects of horizontal inhomogeneity
International audienceExtensive ozone measurements were made during the second SAGE III Ozone Loss and Validation Experiment (SOLVE II). We compare high-latitude line-of-sight (LOS) slant column ozone measurements from the NASA DC-8 to ozone simulated by forward integration of measurement-derived ozone fields constructed both with and without the assumption of horizontal homogeneity. The average bias and rms error of the simulations assuming homogeneity are relatively small (?6 and 10%, respectively) in comparison to the LOS measurements. The comparison improves significantly (?2% bias; 8% rms error) using forward integrations of three-dimensional proxy ozone fields reconstructed from potential vorticity-O3 correlations. The comparisons provide additional verification of the proxy fields and quantify the influence of large-scale ozone inhomogeneity. The spatial inhomogeneity of the atmosphere is a source of error in the retrieval of trace gas vertical profiles and column abundance from LOS measurements, as well as a complicating factor in intercomparisons that include LOS measurements at large solar zenith angles
Superbubble evolution including the star-forming clouds: Is it possible to reconcile LMC observations with model predictions?
Here we present a possible solution to the apparent discrepancy between the
observed properties of LMC bubbles and the standard, constant density bubble
model. A two-dimensional model of a wind-driven bubble expanding from a
flattened giant molecular cloud is examined. We conclude that the expansion
velocities derived from spherically symmetric models are not always applicable
to elongated young bubbles seen almost face-on due to the LMC orientation. In
addition, an observational test to differentiate between spherical and
elongated bubbles seen face-on is discussed.Comment: 25 pages, 7 figures, accepted to ApJ (September, 1999 issue
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