4,999 research outputs found
Analysis of rocket engine injection combustion processes
Mixing methodology improvement for the JANNAF DER and CICM injection/combustion analysis computer programs was accomplished. ZOM plane prediction model development was improved for installation into the new standardized DER computer program. An intra-element mixing model developing approach was recommended for gas/liquid coaxial injection elements for possible future incorporation into the CICM computer program
Analysis of rocket engine injection combustion processes
A critique is given of the JANNAF sub-critical propellant injection/combustion process analysis computer models and application of the models to correlation of well documented hot fire engine data bases. These programs are the distributed energy release (DER) model for conventional liquid propellants injectors and the coaxial injection combustion model (CICM) for gaseous annulus/liquid core coaxial injectors. The critique identifies model inconsistencies while the computer analyses provide quantitative data on predictive accuracy. The program is comprised of three tasks: (1) computer program review and operations; (2) analysis and data correlations; and (3) documentation
Surface compositional mapping by spectral ratioing of ERTS-1 MSS data in the Wind River Basin and Range, Wyoming
The author has identified the following significant results. ERTS data collected in August and October 1972 were processed on digital and special purpose analog recognition computers using ratio enhancement and pattern recognition. Ratios of band-averaged laboratory reflectances of some minerals and rock types known to be in the scene compared favorably with ratios derived from the data by ratio normalization procedures. A single ratio display and density slice of the visible channels of ERTS MSS data, Channel 5/Channel 4 (R5,4), separated the Triassic Chugwater formation (redbeds) from other formations present and may have enhanced iron oxide minerals present at the surface in abundance. Comparison of data sets collected over the same area at two different times of the year by digital processing indicated that spectral variation due to environmental factors was reduced by ratio processing
The PLATO End-to-End CCD Simulator -- Modelling space-based ultra-high precision CCD photometry for the assessment study of the PLATO Mission
The PLATO satellite mission project is a next generation ESA Cosmic Vision
satellite project dedicated to the detection of exo-planets and to
asteroseismology of their host-stars using ultra-high precision photometry. The
main goal of the PLATO mission is to provide a full statistical analysis of
exo-planetary systems around stars that are bright and close enough for
detailed follow-up studies. Many aspects concerning the design trade-off of a
space-based instrument and its performance can best be tackled through
realistic simulations of the expected observations. The complex interplay of
various noise sources in the course of the observations made such simulations
an indispensable part of the assessment study of the PLATO Payload Consortium.
We created an end-to-end CCD simulation software-tool, dubbed PLATOSim, which
simulates photometric time-series of CCD images by including realistic models
of the CCD and its electronics, the telescope optics, the stellar field, the
pointing uncertainty of the satellite (or Attitude Control System [ACS]
jitter), and all important natural noise sources. The main questions that were
addressed with this simulator were the noise properties of different
photometric algorithms, the selection of the optical design, the allowable
jitter amplitude, and the expected noise budget of light-curves as a function
of the stellar magnitude for different parameter conditions. The results of our
simulations showed that the proposed multi-telescope concept of PLATO can
fulfil the defined scientific goal of measuring more than 20000 cool dwarfs
brighter than mV =11 with a precision better than 27 ppm/h which is essential
for the study of earth-like exo-planetary systems using the transit method.Comment: 5 pages, submitted for the Proceedings of the 4th HELAS International
Conference: Seismological Challenges for Stellar Structur
Velocity profiles in shear-banding wormlike micelles
Using Dynamic Light Scattering in heterodyne mode, we measure velocity
profiles in a much studied system of wormlike micelles (CPCl/NaSal) known to
exhibit both shear-banding and stress plateau behavior. Our data provide
evidence for the simplest shear-banding scenario, according to which the
effective viscosity drop in the system is due to the nucleation and growth of a
highly sheared band in the gap, whose thickness linearly increases with the
imposed shear rate. We discuss various details of the velocity profiles in all
the regions of the flow curve and emphasize on the complex, non-Newtonian
nature of the flow in the highly sheared band.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Let
Evaluation of Damage by Vertebrate Pests in California Vineyards and Control of Wild Turkeys by Bioacoustics
Complaints of agricultural damage by wild turkeys (Meleagris gallopavo), particularly from wine grape growers, have increased in California. We assessed damage by vertebrate pests in vineyards and tested a bioacoustic-aversion technique for turkeys as an alternative to other control techniques (e.g., reflective tape, trapping, bird netting). We selected 12 vineyards in the Napa Valley and Sierra Foothills American Viticultural Areas of California. We conducted damage surveys to assess percentages of missing or damaged grapes (i.e., grapes that had been stripped, pecked, and plucked) for every grape cluster on 20 randomly-selected vines before harvest in 2007 and on 40 vines in 2008. We assumed that all observed damage was caused by vertebrate pests and that most of this damage was caused by birds. Grape damage caused by wild turkeys was identified by contiguous sections of berries plucked from a cluster, which we referred to as stripped damage. We attributed pecked and plucked damage to passerines. In 2008, we randomly selected 3 vineyards in each area for treatment with broadcast calls (wild turkey alarm, domestic turkey alarm, crow distress). We used motion-activated video cameras to document evidence of damage caused by turkeys and other animals. Damage in the vineyard perimeter was greater than in the interior for all damage types in 2008, but only for plucked damage in 2007. In 2008, stripped, pecked, and plucked damage means for treated vineyards were 1.3%, 1.4%, and 1.5%, respectively; stripped, pecked, and plucked damage means for untreated vineyards were 1.3%, 0.7%, and 0.2%, respectively. There was no difference in mean stripped damage between treated and untreated vineyards in 2008, indicating that broadcast calls had no effect. Comparison between treated sites in 2008 with the same untreated sites in 2007 yielded similar results. Turkeys caused damage in several of the study vineyards, but the problem varied among vineyards and was inconsistent between years. Motion-activated video recordings suggested that raccoons (Procyon lotor), gray foxes (Urocyon cinereoargenteus), and other vertebrate pests were to blame for some of the stripped damage
Shear-banding in a lyotropic lamellar phase, Part 1: Time-averaged velocity profiles
Using velocity profile measurements based on dynamic light scattering and
coupled to structural and rheological measurements in a Couette cell, we
present evidences for a shear-banding scenario in the shear flow of the onion
texture of a lyotropic lamellar phase. Time-averaged measurements clearly show
the presence of structural shear-banding in the vicinity of a shear-induced
transition, associated to the nucleation and growth of a highly sheared band in
the flow. Our experiments also reveal the presence of slip at the walls of the
Couette cell. Using a simple mechanical approach, we demonstrate that our data
confirms the classical assumption of the shear-banding picture, in which the
interface between bands lies at a given stress . We also outline
the presence of large temporal fluctuations of the flow field, which are the
subject of the second part of this paper [Salmon {\it et al.}, submitted to
Phys. Rev. E]
Developing an On-Line Interactive Health Psychology Module.
On-line teaching material in health psychology was developed which ensured a range of students could access appropriate material for their course and level of study. This material has been developed around the concept of smaller 'content chunks' which can be combined into whole units of learning (topics), and ultimately, a module. On the basis of the underlying philosophy that the medium is part of the message, we considered interactivity to be a key element in engaging the student with the material. Consequently, the key aim of this development was to stimulate and engage students, promoting better involvement with the academic material, and hence better learning. It was hoped that this was achieved through the development of material including linked programmes and supporting material, small Java Scripts and basic email, forms and HTML additions. This material is outlined as are some of the interactive activities introduced, and the preliminary student and tutor experience described
Structural characteristics of positionally-disordered lattices: relation to the first sharp diffraction peak in glasses
Positional disorder has been introduced into the atomic structure of certain
crystalline lattices, and the orientationally-averaged structure factor S(k)
and pair-correlation function g(r) of these disordered lattices have been
studied. Analytical expressions for S(k) and g(r) for Gaussian positional
disorder in 2D and 3D are confirmed with precise numerical simulations. These
analytic results also have a bearing on the unsolved Gauss circle problem in
mathematics. As the positional disorder increases, high-k peaks in S(k) are
destroyed first, eventually leaving a single peak, that with the lowest-k
value. The pair-correlation function for lattices with such high levels of
positional disorder exhibits damped oscillations, with a period equal to the
separation between the furthest-separated (lowest-k) lattice planes. The last
surviving peak in S(k) is, for example for silicon and silica, at a wavevector
nearly identical to that of the experimentally-observed first sharp diffraction
peak (FSDP) in the amorphous phases of those materials. Thus, for these
amorphous materials at least, the FSDP can be regarded as arising from
scattering from atomic configurations equivalent to the single family of
positionally-disordered local Bragg planes having the furthest separation.Comment: v2: changes in response to referees' comments: Figure 2 made more
readable, improved discussion of height of peaks in S(k), other minor changes
4 pages, 3 figures, submitted to Physical Review
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