20,014 research outputs found
Application of thermal radiation data to fishery oceanography
Work on Project Little Window-1 and -2, DRIR data conversion, improvements on the APT receiver, equatorial upwelling, and the topic of thermal fronts is discussed
Study of extraterrestrial disposal of radioactive wastes. Part 1: Space transportation and destination considerations for extraterrestrial disposal of radioactive wastes
A feasibility study of extraterrestrial disposal of radioactive waste is reported. This report covers the initial work done on only one part of the NASA study, that evaluates and compares possible space destinations and space transportation systems. The currently planned space shuttle was found to be more cost effective than current expendable launch vehicles by about a factor of 2. The space shuttle requires a third stage to perform the waste disposal missions. Depending on the particular mission, this third stage could be either a reusable space tug or an expendable stage such as a Centaur
Crucial Dependence of ``Precarious'' and ``Autonomous'' phi^4s Upon the Normal-ordering Mass
Using the Gaussian wave-functional approach with the normal-ordering
renormalization prescription, we show that for the (3+1)-dimensional massive
lambda phi^4 theory, ``precarious'' and ``autonomous'' phi^4s can exist if and
only if the normal-ordering mass is equal to the classical masses at the
symmetrc and asymmetric vacua, respectively.Comment: 6 pages, no figures, Revtex file, accepted for publication in Mod.
Phys. Lett.
NEOWISE observations of comet C/2013 A1 (Siding Spring) as it approaches Mars
The Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) mission
observed comet C/2013 A1 (Siding Spring) three times at 3.4 {\mu}m and 4.6
{\mu}m as the comet approached Mars in 2014. The comet is an extremely
interesting target since its close approach to Mars in late 2014 will be
observed by various spacecraft in-situ. The observations were taken in 2014
Jan., Jul. and Sep. when the comet was at heliocentric distances of 3.82 AU,
1.88 AU, and 1.48 AU. The level of activity increased significantly between the
Jan. and Jul. visits but then decreased by the time of the observations in
Sep., approximately 4 weeks prior to its close approach to Mars. In this work
we calculate Af\r{ho} values, and CO/CO2 production rates.Comment: 9 pages, 3 figures, accepted by Astrophysical Journal Letter
Influence of convective transport on tropospheric ozone and its precursors in a chemistry-climate model
The impact of convection on tropospheric O<sub>3</sub> and its precursors has been examined in a coupled chemistry-climate model. There are two ways that convection affects O<sub>3</sub>. First, convection affects O<sub>3</sub> by vertical mixing of O<sub>3</sub> itself. Convection lifts lower tropospheric air to regions where the O<sub>3</sub> lifetime is longer, whilst mass-balance subsidence mixes O<sub>3</sub>-rich upper tropospheric (UT) air downwards to regions where the O<sub>3</sub> lifetime is shorter. This tends to decrease UT O<sub>3</sub> and the overall tropospheric column of O<sub>3</sub>. Secondly, convection affects O<sub>3</sub> by vertical mixing of O<sub>3</sub> precursors. This affects O<sub>3</sub> chemical production and destruction. Convection transports isoprene and its degradation products to the UT where they interact with lightning NO<sub>x</sub> to produce PAN, at the expense of NO<sub>x</sub>. In our model, we find that convection reduces UT NO<sub>x</sub> through this mechanism; convective down-mixing also flattens our imposed profile of lightning emissions, further reducing UT NO<sub>x</sub>. Over tropical land, which has large lightning NO<sub>x</sub> emissions in the UT, we find convective lofting of NO<sub>x</sub> from surface sources appears relatively unimportant. Despite UT NO<sub>x</sub> decreases, UT O<sub>3</sub> production increases as a result of UT HO<sub>x</sub> increases driven by isoprene oxidation chemistry. However, UT O<sub>3</sub> tends to decrease, as the effect of convective overturning of O<sub>3</sub> itself dominates over changes in O<sub>3</sub> chemistry. Convective transport also reduces UT O<sub>3</sub> in the mid-latitudes resulting in a 13% decrease in the global tropospheric O<sub>3</sub> burden. These results contrast with an earlier study that uses a model of similar chemical complexity. Differences in convection schemes as well as chemistry schemes – in particular isoprene-driven changes are the most likely causes of such discrepancies. Further modelling studies are needed to constrain this uncertainty range
Mind The Gap
We discuss an optimisation criterion for the exact renormalisation group
based on the inverse effective propagator, which displays a gap. We show that a
simple extremisation of the gap stabilises the flow, leading to better
convergence of approximate solutions towards the physical theory. This improves
the reliability of truncations, most relevant for any high precision
computation. These ideas are closely linked to the removal of a spurious scheme
dependence and a minimum sensitivity condition. The issue of predictive power
and a link to the Polchinski RG are discussed as well. We illustrate our
findings by computing critical exponents for the Ising universality class.Comment: 6 pages, Talk presented at 2nd Conference on Exact Renormalization
Group (ERG2000), Rome, Italy, 18-22 Sep 200
Study of noise reduction characteristics of double-wall panels
The noise reduction characteristics of general aviation type, flat, double-wall structures were investigated. The experimental study was carried out on 20-by-20 inch panels with an exposed area of 18 by 18 inches. A frequency range from 20 to 5000 Hz was covered. The experimental results, in general, follow the expected trends. At low frequencies the double-wall structures are no better than the single-wall structures. However, for depths normally used in the general aviation industry, the double-wall panels are very attractive. The graphite-spoxy skin panels have higher noise reduction at very low frequencies ( 100 Hz) than the Kevlar skin panels. But the aluminum panels have higher noise reduction in the high frequency region, due to their greater mass. Use of fiberglass insulation is not effective in the low frequency region, and at times it is even negative. But the insulation is effective in the high-frequency region. The theoretical model for predicting the transmission loss of these multilayered panels is also discussed
Challenging the orthodoxy: union learning representatives as organic intellectuals
Teacher education and continuing professional development have become a key areas of controversy in England since the period of school sector restructuring following the 1988 Education Reform Act. More recently teacher training and professional development have often been used to promote and reinforce a narrow focus on the governmentâs âstandards agendaâ. However, the emerging discourse of ânew professionalismâ has raised the profile of professional development in schools, and together with union learning representatives, there are opportunities to secure real improvements in teachersâ access to continuing professional development. This paper argues however that union learning representatives must go beyond advocating for better access to professional development and should raise more fundamental questions about the nature of professional development and the education system it serves. Drawing on Gramsciâs notion of the âorganic intellectualâ, the paper argues that union learning representatives have a key role as organisers of ideas â creating spaces in which the ideological dominance of current policy orthodoxy might be challenged
Asteroid family identification using the Hierarchical Clustering Method and WISE/NEOWISE physical properties
Using albedos from WISE/NEOWISE to separate distinct albedo groups within the
Main Belt asteroids, we apply the Hierarchical Clustering Method to these
subpopulations and identify dynamically associated clusters of asteroids. While
this survey is limited to the ~35% of known Main Belt asteroids that were
detected by NEOWISE, we present the families linked from these objects as
higher confidence associations than can be obtained from dynamical linking
alone. We find that over one-third of the observed population of the Main Belt
is represented in the high-confidence cores of dynamical families. The albedo
distribution of family members differs significantly from the albedo
distribution of background objects in the same region of the Main Belt, however
interpretation of this effect is complicated by the incomplete identification
of lower-confidence family members. In total we link 38,298 asteroids into 76
distinct families. This work represents a critical step necessary to debias the
albedo and size distributions of asteroids in the Main Belt and understand the
formation and history of small bodies in our Solar system.Comment: Accepted to ApJ. Full version of Table 3 to be published
electronically in Ap
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