1,289 research outputs found
Applying the Gini Coefficient to measure inequality of water use in the Olifants River water management area, South Africa
River basin management / Water stress / Water use / Indicators / Households / Rural areas / Irrigation programs / South Africa / Olifants River
African Water Laws: Plural Legislative Frameworks For Rural Water Management in Africa: an international workshop, Johannesburg, South Africa, 26-28 January 2005
Water law / Water management / Water policy / Poverty / River basins / Irrigation systems / Institutions / Wetlands
Graphical workstation capability for reliability modeling
In addition to computational capabilities, software tools for estimating the reliability of fault-tolerant digital computer systems must also provide a means of interfacing with the user. Described here is the new graphical interface capability of the hybrid automated reliability predictor (HARP), a software package that implements advanced reliability modeling techniques. The graphics oriented (GO) module provides the user with a graphical language for modeling system failure modes through the selection of various fault-tree gates, including sequence-dependency gates, or by a Markov chain. By using this graphical input language, a fault tree becomes a convenient notation for describing a system. In accounting for any sequence dependencies, HARP converts the fault-tree notation to a complex stochastic process that is reduced to a Markov chain, which it can then solve for system reliability. The graphics capability is available for use on an IBM-compatible PC, a Sun, and a VAX workstation. The GO module is written in the C programming language and uses the graphical kernal system (GKS) standard for graphics implementation. The PC, VAX, and Sun versions of the HARP GO module are currently in beta-testing stages
Lessons learnt from the IWRM demonstration projects: innovations in local-level integrated water resource development in Malawi, Mozambique, Swaziland and Zambia
Water resource management / Guidelines / Project planning / Financing / Multiple use / Irrigation water / Domestic water / Participatory management / Community involvement / Empowerment / Local government / Poverty / Public health / Malawi / Mozambique / Swaziland / Zambia
Do equal land and water rights benefit the poor?: Targeted irrigation development: The case of the Andhi Khola Irrigation Scheme in Nepal
Irrigation programs / Water rights / Poverty / Households / Surveys / Water allocation / Water distribution / Water usersâ associations / Farmers / Landlessness / Land ownership
Redressing racial inequities through water law in South Africa: revisiting old contradictions? Draft
Water lawCatchment areasRiver basinsSocial aspectsPovertyInstitutional development
Ram Pressure Stripping Made Easy: An Analytical Approach
The removal of gas by ram pressure stripping of galaxies is treated by a
purely kinematic description. The solution has two asymptotic limits: if the
duration of the ram pressure pulse exceeds the period of vertical oscillations
perpendicular to the galactic plane, the commonly used quasi-static criterion
of Gunn & Gott is obtained which uses the maximum ram pressure that the galaxy
has experienced along its orbit. For shorter pulses the outcome depends on the
time-integrated ram pressure. This parameter pair fully describes the gas mass
fraction that is stripped from a given galaxy. This approach closely reproduces
results from SPH simulations. We show that typical galaxies follow a very tight
relation in this parameter space corresponding to a pressure pulse length of
about 300 Myr. Thus, the Gunn & Gott criterion provides a good description for
galaxies in larger clusters. Applying the analytic description to a sample of
232 Virgo galaxies from the GoldMine database, we show that the ICM provides
indeed the ram pressures needed to explain the deficiencies. We also can
distinguish current and past strippers, including objects whose stripping state
was unknown.Comment: Accepted for publication in MNRAS. Several interactive JavaScript
tools which evaluate the analytical considerations of this paper are
available at http://www.astrophysik.uni-kiel.de/~koeppen/JS/RPShome.htm
Quasar Evolution and the Baldwin Effect in the Large Bright Quasar Survey
From a large homogeneous sample of optical/UV emission line measurements for
993 quasars from the Large Bright Quasar Survey (LBQS), we study correlations
between emission line equivalent width and both restframe ultraviolet
luminosity (i.e., the Baldwin Effect) and redshift. Our semi-automated spectral
fitting accounts for absorption lines, fits blended iron emission, and provides
upper limits to weak emission lines. Use of a single large, well-defined sample
and consistent emission line measurements allows us to sensitively detect many
correlations, most of which have been previously noted. A new finding is a
significant Baldwin Effect in UV iron emission. Further analysis reveals that
the primary correlation of iron emission strength is probably with redshift,
implying an evolutionary rather than a luminosity effect. We show that for most
emission lines with a significant Baldwin Effect, and for some without,
evolution dominates over luminosity effects. This may reflect evolution in
abundances, in cloud covering factors, or overall cloud conditions such as
density and ionization. We find that in our sample, a putative correlation
between Baldwin Effect slope and the ionization potential is not significant.
Uniform measurements of other large quasar samples will extend the luminosity
and redshift range of such spectral studies and provide even stronger tests of
spectral evolution.Comment: 16 pages, Latex, emulateapj style, including 3 tables and 6 figures.
Accepted April 02, 2001 for publication in ApJ Main Journal. See also
http://hea-www.harvard.edu/~pgreen/Papers.htm
Initial Ionization of Compressible Turbulence
We study the effects of the initial conditions of turbulent molecular clouds
on the ionization structure in newly formed H_{ii} regions, using
three-dimensional, photon-conserving radiative transfer in a pre-computed
density field from three-dimensional compressible turbulence. Our results show
that the initial density structure of the gas cloud can play an important role
in the resulting structure of the H_{ii} region. The propagation of the
ionization fronts, the shape of the resulting H_{ii} region, and the total mass
ionized depend on the properties of the turbulent density field. Cuts through
the ionized regions generally show ``butterfly'' shapes rather than spherical
ones, while emission measure maps are more spherical if the turbulence is
driven on scales small compared to the size of the H_{ii} region. The
ionization structure can be described by an effective clumping factor , where is number density of the gas. The larger
the value of , the less mass is ionized, and the more irregular the
H_{ii} region shapes. Because we do not follow dynamics, our results apply only
to the early stage of ionization when the speed of the ionization fronts
remains much larger than the sound speed of the ionized gas, or Alfv\'en speed
in magnetized clouds if it is larger, so that the dynamical effects can be
negligible.Comment: 9 pages, 10 figures, version with high quality color images can be
found in http://research.amnh.org/~yuexing/astro-ph/0407249.pd
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