14,706 research outputs found
Teleoperators for remote operations in space
The primary objective of the remote nuclear teleoperator study program was to define in detail a program plan which would provide a qualified operational space teleoperator system by about 1980. The concept and philosophy presented provides a product considered to be an advanced teleoperator when compared to today's state-of-the-art. The teleoperator concept is formulated to meet NERVA requirements
Characterization of ASEC BSR 2 ohm-cm silicon solar cells with dielectric wraparound contacts as a function of temperature and intensity
Twenty high performance BSR 2 ohm-cm silicon solar cells manufactured by ASEC were evaluated at 1 AU conditions and at low temperature and low intensities representative of deep space. These cells showed evidence of series resistance of 1 AU conditions and approximately 50% had reduced power outputs under deep space conditions. Average efficiency of these cells was 12.4% of 1 AU conditions of 1 SC/+25 C
Scoping a public health impact assessment of aquaculture with particular reference to tilapia in the UK
Background. The paper explores shaping public health impact assessment tools for tilapia, a novel emergent aquaculture sector in the UK. This Research Council’s UK Rural Economy and Land Use project embraces technical, public health, and marketing perspectives scoping tools to assess possible impacts of the activity. Globally, aquaculture produced over 65 million tonnes of food in 2008 and will grow significantly requiring apposite global public health impact assessment tools.<p></p>
Methods. Quantitative and qualitative methods incorporated data from a tridisciplinary literature. Holistic tools scoped tilapia farming impact assessments. Laboratory-based tilapia production generated data on impacts in UK and Thailand along with 11 UK focus groups involving 90 consumers, 30 interviews and site visits, 9 visits to UK tilapia growers and 2 in The Netherlands.<p></p>
Results. The feasibility, challenges, strengths, and weaknesses of creating a tilapia Public Health Impact Assessment are analysed. Occupational and environmental health benefits and risks attached to tilapia production were identified.<p></p>
Conclusions. Scoping public health impacts of tilapia production is possible at different levels and forms for producers, retailers, consumers, civil society and governmental bodies that may contribute to complex and interrelated public health assessments of aquaculture projects. Our assessment framework constitutes an innovatory perspective in the field
Gravitational Instability in Collisionless Cosmological Pancakes
The gravitational instability of cosmological pancakes composed of
collisionless dark matter in an Einstein-de Sitter universe is investigated
numerically to demonstrate that pancakes are unstable with respect to
fragmentation and the formation of filaments. A ``pancake'' is defined here as
the nonlinear outcome of the growth of a 1D, sinusoidal, plane-wave, adiabatic
density perturbation. We have used high resolution, 2D, N-body simulations by
the Particle-Mesh (PM) method to study the response of pancakes to perturbation
by either symmetric (density) or antisymmetric (bending or rippling) modes,
with corresponding wavevectors k_s and k_a transverse to the wavevector k_p of
the unperturbed pancake plane-wave. We consider dark matter which is initially
``cold'' (i.e. with no random thermal velocity in the initial conditions). We
also investigate the effect of a finite, random, isotropic, initial velocity
dispersion (i.e. initial thermal velocity) on the fate of pancake collapse and
instability. Pancakes are shown to be gravitationally unstable with respect to
all perturbations of wavelength l<l_p (where l_p= 2pi/k_p). These results are
in contradiction with the expectations of an approximate, thin-sheet energy
argument.Comment: To appear in the Astrophysical Journal (1997), accepted for
publication 10/10/96, single postscript file, 61 pages, 19 figure
Effective 3D Geometry Extraction and Reverse CAD Modeling
The goal of this work is to develop and implement a technology capability for providing cost-effective and rapid geometry evaluation of parts and processes. We were motivated by the new availability of fully three dimensional nondestructive CT scanning for a variety of manufactured parts and assemblies on a rapid and cost-effective basis, with resolutions commensurate with the tolerances required for a variety of manufacturing processes. High-speed, high-quality three dimensional scanning can be accomplished on a overnight service basis for a variety of objects, for costs ranging from a few hundreds to a few thousands of dollars. The resulting images contain quantitative information relating the local x-ray density of scanned objects at every voxel in a three dimensional raster space. There have been significant advances in methods for quantitative volumetric processing and information extraction from these images. However, for many manufacturing process verification applications, the resulting three dimensional images contain more information than can be effectively handled by many end users, particularly when the size of the 3D image data files (often larger than 1 Gbyte) is considered
A Test of the Particle Paradigm in N-Body Simulations
We present results of tests of the evolution of small ``fluid elements'' in
cosmological N--body simulations, to examine the validity of their treatment as
particles. We find that even very small elements typically collapse along one
axis while expanding along another, often to twice or more their initial
comoving diameter. This represents a possible problem for high--resolution uses
of such simulations.Comment: Uses aasms4.sty; accepted for publication in ApJ Letters. Files
available also at ftp://kusmos.phsx.ukans.edu/preprints/ates
With a little help from my goals : integrating intergoal facilitation with the theory of planned behaviour to predict physical activity
Reproduced with permission from British Journal of Health Psychology © The British Psychological Society 2010.Peer reviewedPostprin
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