20,079 research outputs found
Engineering Guidelines for Clean Assembly and Sterilization of Spaceflight Hardware
Engineering specifications for clean assembly and sterilization of space flight hardware to prevent contamination of planetary environment
Space shuttle post-entry and landing analysis. Volume 2: Appendices
Four candidate navigation systems for the space shuttle orbiter approach and landing phase are evaluated in detail. These include three conventional navaid systems and a single-station one-way Doppler system. In each case, a Kalman filter is assumed to be mechanized in the onboard computer, blending the navaid data with IMU and altimeter data. Filter state dimensions ranging from 6 to 24 are involved in the candidate systems. Comprehensive truth models with state dimensions ranging from 63 to 82 are formulated and used to generate detailed error budgets and sensitivity curves illustrating the effect of variations in the size of individual error sources on touchdown accuracy. The projected overall performance of each system is shown in the form of time histories of position and velocity error components
Homoclinic snaking in bounded domains
Homoclinic snaking is a term used to describe the back and forth oscillation of a branch of time-independent spatially localized states in a bistable, spatially reversible system as the localized structure grows in length by repeatedly adding rolls on either side. On the real line this process continues forever. In finite domains snaking terminates once the domain is filled but the details of how this occurs depend critically on the choice of boundary conditions. With periodic boundary conditions the snaking branches terminate on a branch of spatially periodic states. However, with non-Neumann boundary conditions they turn continuously into a large amplitude filling state that replaces the periodic state. This behavior, shown here in detail for the Swift-Hohenberg equation, explains the phenomenon of “snaking without bistability”, recently observed in simulations of binary fluid convection by Mercader, Batiste, Alonso and Knobloch (preprint)
SMC SMP 24: A newly radio-detected planetary nebula in the small magellanic cloud
In this paper we report new radio-continuum detection of an extragalactic PN:
SMC SMP 24. We show the radio-continuum image of this PN and present the
measured radio data. The newly reduced radio observations are consistent with
the multi-wavelength data and derived parameters found in the literature. SMC
SMP 24 appear to be a young and compact PN, optically thick at frequencies
below 2 GHz.Comment: accepted for publication in Serbian Astronomical Journa
Radio Continuum Study of Supernova Remnants in the Large Magellanic Cloud - SNR J0519-6926
We present the results of new high resolution ATCA observations of SNR
J0519-6926. We found that this SNR exhibits a typical "horseshoe" appearance
with alpha = -0.55 +- 0.08 and D=28+-1 pc. No polarization (or magnetic fields)
are detected to a level of 1%. This is probably due to a relatively poor
sampling of the uv plane caused be observing in "snap-shot" mode.Comment: 6 pages 4 figures, to be published in Serbian Astronomical Journa
Radio-Continuum Observations Of Small, Radially Polarised Supernova Remnant J0519-6902 In The Large Magellanic Cloud
We report on new Australian Telescope Compact Array (ATCA) observations of
SNR J0519-6902. The Supernova Remnant (SNR) is small in size (~8 pc) and
exhibits a typical SNR spectrum of alpha = -0.53 +- 0.07, with steeper spectral
indices found towards the northern limb of the remnant. SNR J0519-6902 contains
a low level of radially orientated polarisation at wavelengths of 3 & 6 cm,
which is characteristic of younger SNRs. A fairly strong magnetic field was
estimated of ~171 microG. The remnant appears to be the result of a typical
Type Ia supernovae, sharing many properties as another small and young Type Ia
LMC SNR, J0509-6731.Comment: 10 pages 7 figures, submitted to Serbian Astronomical Journa
Multifrequency Observations of One of the Largest Supernova Remnants in the Local Group of Galaxies, LMC - SNR J0450-709
We present the results of new Australia Telescope Compact Array (ATCA)
observations of one of the largest supernova remnants, SNR J0450-709, in the
Local Group of galaxies. We found that this Large Magellanic Cloud (LMC) ob
ject exhibits a typical morphology of an old supernova remnant (SNR) with
diameter D=102x75+-1 pc and radio spectral index alpha=-0.43+-0.06. Regions of
high polarisation were detected with peak value of ~40%.Comment: 7 pages, 4 figures, accepted for publication in Serbian Astronomical
Journa
Full-coverage film cooling on flat, isothermal surfaces: Data and predictions
The heat transfer and fluid mechanics characteristics of full-coverage film cooling were investigated. The results for flat, isothermal plates for three injection geometries (normal, slant, and compound angle) are summarized and data concerning the spanwise distribution of the heat transfer coefficient within the blowing region are presented. Data are also presented for two different numbers of rows of holes (6 and 11). The experimental results summarized can be predicted with a two dimensional boundary layer code, STANCOOL, by providing descriptors of the injection parameters as inputs
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