57,798 research outputs found
Controlled ecological life support system - biological problems
The general processes and controls associated with two distinct experimental paradigms are examined. Specific areas for research related to biotic production (food production) and biotic decomposition (waste management) are explored. The workshop discussions were directed toward Elemental cycles and the biological factors that affect the transformations of nutrients into food, of food material into waste, and of waste into nutrients were discussed. To focus on biological issues, the discussion assumed that (1) food production would be by biological means (thus excluding chemical synthesis), (2) energy would not be a limiting factor, and (3) engineering capacity for composition and leak rate would be adequate
Service Performance Indicators for Infrastructure Investment
Infrastructure systems serving modern economies are highly complex, highly interconnected, and often highly
interactive. The result is increased complexity in investment decision-making, and increased challenges in prioritising
that investment. However, this prioritisation is vital to developing a long-term, sound, robust and achievable pipeline
of national infrastructure.
One key to effective, objective and prudent investment prioritisation is understanding the real performance of
infrastructure. Many metrics are employed to this end, and many are imposed by governments or regulators, but
often these metrics relate only to inputs or outputs in a production process. Whilst these metrics may be useful for
delivery agencies, they largely fail to address the real expectations or requirements of infrastructure users — quality of
service, safety, reliability, and resilience.
What is required is a set of metrics which address not outputs but outcomes — that is, how well does the
infrastructure network meet service needs? This paper reports on a study undertaken at a national level, to identify
service needs across a range of infrastructure sectors, to assess service performance metrics in use, and to show
how they or other suitable metrics can be used to prioritise investment decisions across sectors and jurisdictions
Tests on Full-scale Roofing Systems
This report details an experimental investigation on three full-scale, cold-formed steel roofing systems. The test programme included both uniformly and variably distributed loadings representative of drifting snow. Comparisons between the performance of each roof subject to these distributions are made and recommendations for the design of roofs loaded with variably distributed loads are presented. Finally observations on the tests to failure are discussed
Infall near clusters of galaxies: comparing gas and dark matter velocity profiles
We consider the dynamics in and near galaxy clusters. Gas, dark matter and
galaxies are presently falling into the clusters between approximately 1 and 5
virial radii. At very large distances, beyond 10 virial radii, all matter is
following the Hubble flow, and inside the virial radius the matter particles
have on average zero radial velocity. The cosmological parameters are imprinted
on the infall profile of the gas, however, no method exists, which allows a
measurement of it. We consider the results of two cosmological simulations
(using the numerical codes RAMSES and Gadget) and find that the gas and dark
matter radial velocities are very similar. We derive the relevant dynamical
equations, in particular the generalized hydrostatic equilibrium equation,
including both the expansion of the Universe and the cosmological background.
This generalized gas equation is the main new contribution of this paper. We
combine these generalized equations with the results of the numerical
simulations to estimate the contribution to the measured cluster masses from
the radial velocity: inside the virial radius it is negligible, and inside two
virial radii the effect is below 40%, in agreement the earlier analyses for DM.
We point out how the infall velocity in principle may be observable, by
measuring the gas properties to distance of about two virial radii, however,
this is practically not possible today.Comment: 7 pages, 3 figures, to appear in MNRA
Search For A Permanent Electric Dipole Moment Using Atomic Indium
We propose indium (In) as a possible candidate for observing the permanent
electric dipole moment (EDM) arising from the violations of parity (P) and
time-reversal (T) symmetries. This atom has been laser cooled and therefore the
measurement of its EDM has the potential of improving on the current best EDM
limit for a paramagnetic atom which comes from thallium. We report the results
of our calculations of the EDM enhancement factor due to the electron EDM and
the ratio of the atomic EDM to the electron-nucleus scalar-pseudoscalar (S-PS)
interaction coupling constant in In in the framework of the relativistic
coupled cluster theory. It might be possible to get new limits for the electron
EDM and the S-PS CP violating coupling constant by combining the results of our
calculations with the measured value of the EDM of In when it is available.
These limits could have important implications for the standard model (SM) of
particle physics.Comment: 5 pages, 1 fig, Rapid Communicatio
Geometric criticality between plaquette phases in integer-spin kagome XXZ antiferromagnets
The phase diagram of the uniaxially anisotropic antiferromagnet on the
kagom\'e lattice includes a critical line exactly described by the classical
three-color model. This line is distinct from the standard geometric classical
criticality that appears in the classical limit () of the 2D XY
model; the geometric T=0 critical line separates two unconventional
plaquette-ordered phases that survive to nonzero temperature. The
experimentally important correlations at finite temperature and the nature of
the transitions into these ordered phases are obtained using the mapping to the
three-color model and a combination of perturbation theory and a variational
ansatz for the ordered phases. The ordered phases show sixfold symmetry
breaking and are similar to phases proposed for the honeycomb lattice dimer
model and model. The same mapping and phase transition can be
realized also for integer spins but then require strong on-site
anisotropy in the Hamiltonian.Comment: 5 pages, 2 figure
Scaling treatment of the random field Ising model
Analytic phenomenological scaling is carried out for the random field Ising
model in general dimensions using a bar geometry. Domain wall configurations
and their decorated profiles and associated wandering and other exponents
are obtained by free energy minimization. Scaling
between different bar widths provides the renormalization group (RG)
transformation. Its consequences are (1) criticality at in
with correlation length diverging like for and
for , where is a decoration constant; (2) criticality in dimensions at , , where
, .
Finite temperature generalizations are outlined. Numerical transfer matrix
calculations and results from a ground state algorithm adapted for strips in
confirm the ingredients which provide the RG description.Comment: RevTex v3.0, 5 pages, plus 4 figures uuencode
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