51,542 research outputs found
Closed-loop Habitation Air Revitalization Model for Regenerative Life Support Systems
The primary function of any life support system is to keep the crew alive by providing breathable air, potable water, edible food, and for disposal of waste. In a well-balanced or regenerative life support system, the various components are each using what is available and producing what is needed by other components so that there will always be enough chemicals in the form in which they are needed. Humans are not just users, but also one of the participating parts of the system. If a system could continuously recycle the original chemicals, this would make it virtually a Closed-loop Habitation (CH). Some difficulties in trying to create a miniature version of a CH are briefly discussed. In a miniature CH, a minimal structure must be provided and the difference must be made up by artificial parts such as physicochemical systems that perform the conversions that the Earth can achieve naturally. To study the interactions of these parts, a computer model was designed that simulates a miniature CH with emphasis on the air revitalization part. It is called the Closed-loop Habitation Air Revitalization Model (CHARM)
Analog FM/FM versus digital color TV transmission aboard space station
Langley Research Center is developing an integrated fault tolerant network to support data, voice, and video communications aboard Space Station. The question of transmitting the video data via dedicated analog channels or converting it to the digital domain for consistancy with the test of the data is addressed. The recommendations in this paper are based on a comparison in the signal-to-noise ratio (SNR), the type of video processing required aboard Space Station, the applicability to Space Station, and how they integrate into the network
An image compression survey and algorithm switching based on scene activity
Data compression techniques are presented. A description of these techniques is provided along with a performance evaluation. The complexity of the hardware resulting from their implementation is also addressed. The compression effect on channel distortion and the applicability of these algorithms to real-time processing are presented. Also included is a proposed new direction for an adaptive compression technique for real-time processing
The topological susceptibility in `full' (UK)QCD
We report first calculations of the topological susceptibility measured using
the field theoretic method on SU(3) gauge configurations produced by the UKQCD
collaboration with two flavours of dynamical, improved, Wilson fermions. Using
three ensembles with matched lattice spacing but differing sea quark mass we
find that hybrid Monte Carlo simulation appears to explore the topological
sectors efficiently, and a topological susceptibility consistent with
increasing linearly with the quark mass.Comment: LaTeX. 4 PostScript figures. Contribution to LATTICE99(topology
Magnetic monopole clusters, and monopole dominance after smoothing in the maximally Abelian gauge of SU(2)
In the maximally Abelian gauge of SU(2), the clusters of monopole current are
found to divide into two distinct classes. The largest cluster permeates the
lattice, has a density that scales and produces the string tension. The
remaining clusters possess an approximate 1/l^3 number density distribution (l
is the cluster length), their radii vary as \sqrt l and their total current
density does not scale. Their contribution to the string tension is compatible
with being exactly zero. Their number density can be thought of as arising from
an underlying scale invariant distribution. This suggests that they are not
related to instantons. We also observe that when we locally smoothen the SU(2)
fields by cooling, the string tension due to monopoles becomes much smaller
than the SU(2) string tension. This dramatic loss of Abelian/monopole dominance
occurs even after just one cooling step.Comment: Talk presented at LATTICE97(topology). LaTeX, with 4 PS figure
Instantons and Monopoles in the Maximally Abelian Gauge
We study the Abelian projection of SU(2) instantons in the Maximally Abelian
gauge. We find that in this gauge an isolated instanton produces a closed
monopole loop within its core and the size of this loop increases with the core
size. We show that this result is robust against the introduction of small
quantum fluctuations. We investigate the effects of neighbouring
(anti)instantons upon each other and show how overlapping (anti)instantons can
generate larger monopole loops. We find, however, that in fields that are
typical of the fully quantised vacuum only some of the large monopole loops
that are important for confinement have a topological origin. We comment on
what this may imply for the role of instantons in confinement and chiral
symmetry breaking.Comment: 14 pages LaTeX plus 5 PostScript figures. Uses epsf.sty.
Self-unpacking, uuencoded tar-compressed fil
A mid-Archaean ophiolite complex, Barberton Mountain land
New field observations and structurally restored geologic sections through the southern part of 3.5-3.6 Ga Barberton greenstone belt show that its mafic to ultramafic rocks form a pseudostratigraphy comparable to that of Phanerozoic ophiolites; this ancient ophiolite is referred to as the Jamestown ophiolite complex. It consists of an intrusive-extrusive mafic-ultramafic section, underlain by a high-temperature tectono-metamorphic residual peridotitic base, and is capped by a chert-shale sequence which it locally intrudes. Geochemical data support an ophiolitic comparison. Fraction of high temperature melting PGE's 2500 C in the residual rocks suggest a lower mantle origin for the precursors of this crust. An oceanic rather than arc-related crustal section can be inferred from the absence of contemporaneous andesites. The entire simatic section has also been chemically altered during its formation by hyrothermal interaction with the Archean hydrosphere. The most primitive parent liquids, from which the extrusive sequence evolved, may have been picritic in character. Rocks with a komatiitic chemistry may have been derived during crystal accumulation from picrite-crystal mushes (predominantly olivine-clinopyroxene) and/or by metasomatism during one or more subsequent episodes of hydration-dehydration. The Jamestown ophiolite complex provides the oldest record with evidence for the formation of oceanic lithosphere at constructive tectonic boundaries
An Air Revitalization Model (ARM) for Regenerative Life Support Systems (RLSS)
The primary objective of the air revitalization model (ARM) is to determine the minimum buffer capacities that would be necessary for long duration space missions. Several observations are supported by the current configuration sizes: the baseline values for each gas and the day to day or month to month fluctuations that are allowed. The baseline values depend on the minimum safety tolerances and the quantities of life support consumables necessary to survive the worst case scenarios within those tolerances. Most, it not all, of these quantities can easily be determined by ARM once these tolerances are set. The day to day fluctuations also require a command decision. It is already apparent from the current configuration of ARM that the tighter these fluctuations are controlled, the more energy used, the more nonregenerable hydrazine consumed, and the larger the required capacities for the various gas generators. All of these relationships could clearly be quantified by one operational ARM
Making the Invisible, Visible: RtI and Reading Comprehension
For the better part of a century the educational community has had increased focus on the importance of reading. The publication of Why Johnny Can\u27t Read and What You Can Do About It (Flesch, 1955) began the surge of effort to better understand the cognitive process of reading to further examine how educators can help children become better readers. Since this 1950\u27s publication, reading research grew and philosophies developed and subsequently changed. However, one thing remained the same: understanding what we read is critically important to becoming a critical thinker. Thus, reading comprehension research continued to boom and the educational community continues to seek ways in which reading comprehension instruction can be improved. (excerpt
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