4,470 research outputs found
Flight investigation of various control inputs intended for parameter estimation
An experiment assessing the stability and control derivatives resulting from various control inputs was undertaken using the F-8 digital fly by wire aircraft. Improved control inputs have been proposed as a means of making stability and contol derivative estimation more efficient, thus reducing the cost of flight testing and data analysis. The subject inputs were either generated by the pilot or preprogrammed in a remote ground computer and telemetered to the aircraft. Nine preprogrammed inputs and three pilot generated inputs were assessed at subsonic and supersonic flight conditions, and both unaugmented and highly augmented flight control systems were used. Effects of input amplitude were also assessed. The inputs were divided into two general types - sinusoidal or with corners (a rapid and distinct change in slope). The inputs with corners, performed in the unaugmented mode, produced the best sets of stability and control derivatives. The simplest of these inputs, the pilot generated doublet, produced sets of derivatives as good as those produced by the more complex inputs. Small inputs produced worse derivatives than the unaugmented mode, and sinusoidal inputs produced worse derivatives than corner containing inputs
Subsonic stability and control derivatives for an unpowered, remotely piloted 3/8-scale F-15 airplane model obtained from flight test
In response to the interest in airplane configuration characteristics at high angles of attack, an unpowered remotely piloted 3/8-scale F-15 airplane model was flight tested. The subsonic stability and control characteristics of this airplane model over an angle of attack range of -20 to 53 deg are documented. The remotely piloted technique for obtaining flight test data was found to provide adequate stability and control derivatives. The remotely piloted technique provided an opportunity to test the aircraft mathematical model in an angle of attack regime not previously examined in flight test. The variation of most of the derivative estimates with angle of attack was found to be consistent, particularly when the data were supplemented by uncertainty levels
Stability and control derivatives of the T-37B airplane
Subsonic stability and control derivatives were determined by a modified maximum likelihood estimator from flight data for the longitudinal and lateral-directional modes of the T-37B airplane. Data from two flights, in which 166 stability and control maneuvers were performed, were used in the determination. The configurations investigated were: zero flaps, gear up; half flaps, gear up; full flaps, gear up; and zero flaps, gear down
Goddard X-ray astronomy contributions to the IAU/COSPAR (1982)
The relation of X-ray flux to both the continuum flux in the optical and radio bands, and to the line emission properties of these objects were studied. The Einstein Observatory, because of increased sensitivity and improved angular resolution, increased substantially the number of known X-ray emitting active galactic nuclei. The Einstein imaging instruments detected morphology in AGN X-ray emission, in particular from jetlike structures in Cen-A, M87, and 3C273. The improved energy resolution and sensitivity of the spectrometers onboard the Observatory provide information on the geometry and ionization structure of the region responsible for the broad optical emission lines in a few AGN's. This information, combined with theoretical modeling and IUE and optical observations, allows the construction of a moderately detailed picture of the broad line region in these objects
Flight Evaluation of an Aircraft with Side and Center Stick Controllers and Rate-Limited Ailerons
As part of an ongoing government and industry effort to study the flying qualities of aircraft with rate-limited control surface actuators, two studies were previously flown to examine an algorithm developed to reduce the tendency for pilot-induced oscillation when rate limiting occurs. This algorithm, when working properly, greatly improved the performance of the aircraft in the first study. In the second study, however, the algorithm did not initially offer as much improvement. The differences between the two studies caused concern. The study detailed in this paper was performed to determine whether the performance of the algorithm was affected by the characteristics of the cockpit controllers. Time delay and flight control system noise were also briefly evaluated. An in-flight simulator, the Calspan Learjet 25, was programmed with a low roll actuator rate limit, and the algorithm was programmed into the flight control system. Side- and center-stick controllers, force and position command signals, a rate-limited feel system, a low-frequency feel system, and a feel system damper were evaluated. The flight program consisted of four flights and 38 evaluations of test configurations. Performance of the algorithm was determined to be unaffected by using side- or center-stick controllers or force or position command signals. The rate-limited feel system performed as well as the rate-limiting algorithm but was disliked by the pilots. The low-frequency feel system and the feel system damper were ineffective. Time delay and noise were determined to degrade the performance of the algorithm
Comparison of the COBE FIRAS and DIRBE Calibrations
We compare the independent FIRAS and DIRBE observations from the COBE in the
wavelength range 100-300 microns. This cross calibration provides checks of
both data sets. The results show that the data sets are consistent within the
estimated gain and offset uncertainties of the two instruments. They show the
possibility of improving the gain and offset determination of DIRBE at 140 and
240 microns.Comment: Accepted for publication in the Astrophysical Journal 11 pages, plus
3 figures in separate postscript files. Figure 3 has three part
Nurses\u27 Alumnae Association Bulletin - Volume 7 Number 11
Anna M. Shafer
Barton Memorial Division
Births
Changes in the Ophthalmology Division
Change of Address
Clara Melville Fund
Continental Tour
Deceased
Digest of Meetings
Inter-County Hospitalization Plan
Katherine Childs\u27 Letter
Lost Members
Marriages
Miscellaneous
Nursing Home Committee\u27s Report
Physical Advantages
President James L. Kauffman\u27s Letter
President\u27s Greeting
Private Duty Section
Prizes
Relief Fund
School Nursing
Silhouette of a Public Health Nurse
Rooming-in of Infant with Mother
Staff Activities
The Student
White Haven Divisio
The calibrated population resistance tool: standardized genotypic estimation of transmitted HIV-1 drug resistance
Summary: The calibrated population resistance (CPR) tool is a web-accessible program for performing standardized genotypic estimation of transmitted HIV-1 drug resistance. The program is linked to the Stanford HIV drug resistance database and can additionally perform viral genotyping and algorithmic estimation of resistance to specific antiretroviral drugs
New procedures for testing whether stock price processes are martingales
We propose procedures for testing whether stock price processes are
martingales based on limit order type betting strategies. We first show that
the null hypothesis of martingale property of a stock price process can be
tested based on the capital process of a betting strategy. In particular with
high frequency Markov type strategies we find that martingale null hypotheses
are rejected for many stock price processes
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