5,242 research outputs found
Rational's experience using Ada for very large systems
The experience using the Rational Environment has confirmed the advantages forseen when the project was started. Interactive syntatic and semantic information makes a tremendous difference in the ease of constructing programs and making changes to them. The ability to follow semantic references makes it easier to understand exisiting programs and the impact of changes. The integrated debugger makes it much easier to find bugs and test fixes quickly. Taken together, these facilites have helped greatly in reducing the impact of ongoing maintenance of the ability to produce a new code. Similar improvements are anticipated as the same level of integration and interactivity are achieved for configuration management and version control. The environment has also proven useful in introducing personnel to the project and existing personnel to new parts of the system. Personnel benefit from the assistance with syntax and semantics; everyone benefits from the ability to traverse and understand the structure of unfamiliar software. It is often possible for someone completely unfamiliar with a body of code to use these facilities, to understand it well enough to successfully with a body of code to use these facilities to understand it well enough to successfully diagnose and fix bugs in a matter of minutes
Intrinsic point defects and volume swelling in ZrSiO4 under irradiation
The effects of high concentration of point defects in crystalline ZrSiO4 as
originated by exposure to radiation, have been simulated using first principles
density functional calculations. Structural relaxation and vibrational studies
were performed for a catalogue of intrinsic point defects, with different
charge states and concentrations. The experimental evidence of a large
anisotropic volume swelling in natural and artificially irradiated samples is
used to select the subset of defects that give similar lattice swelling for the
concentrations studied, namely interstitials of O and Si, and the anti-site
Zr(Si), Calculated vibrational spectra for the interstitials show additional
evidence for the presence of high concentrations of some of these defects in
irradiated zircon.Comment: 9 pages, 7 (color) figure
Truthful Multi-unit Procurements with Budgets
We study procurement games where each seller supplies multiple units of his
item, with a cost per unit known only to him. The buyer can purchase any number
of units from each seller, values different combinations of the items
differently, and has a budget for his total payment.
For a special class of procurement games, the {\em bounded knapsack} problem,
we show that no universally truthful budget-feasible mechanism can approximate
the optimal value of the buyer within , where is the total number of
units of all items available. We then construct a polynomial-time mechanism
that gives a -approximation for procurement games with {\em concave
additive valuations}, which include bounded knapsack as a special case. Our
mechanism is thus optimal up to a constant factor. Moreover, for the bounded
knapsack problem, given the well-known FPTAS, our results imply there is a
provable gap between the optimization domain and the mechanism design domain.
Finally, for procurement games with {\em sub-additive valuations}, we
construct a universally truthful budget-feasible mechanism that gives an
-approximation in polynomial time with a
demand oracle.Comment: To appear at WINE 201
Dynamical density functional theory for dense atomic liquids
Starting from Newton's equations of motion, we derive a dynamical density
functional theory (DDFT) applicable to atomic liquids. The theory has the
feature that it requires as input the Helmholtz free energy functional from
equilibrium density functional theory. This means that, given a reliable
equilibrium free energy functional, the correct equilibrium fluid density
profile is guaranteed. We show that when the isothermal compressibility is
small, the DDFT generates the correct value for the speed of sound in a dense
liquid. We also interpret the theory as a dynamical equation for a coarse
grained fluid density and show that the theory can be used (making further
approximations) to derive the standard mode coupling theory that is used to
describe the glass transition. The present theory should provide a useful
starting point for describing the dynamics of inhomogeneous atomic fluids.Comment: 14 pages, accepted for publication in J. Phys.: Condens. Matte
Florida’s Recycled Water Footprint: A Geospatial Analysis of Distribution (2009 and 2015)
Water shortages resulting from increased demand or reduced supply may be addressed, in part, by redirecting recycled water for irrigation, industrial reuse, groundwater recharge, and as effluent discharge returned to streams. Recycled water is an essential component of integrated water management and broader adoption of recycled water will increase water conservation in water-stressed coastal communities. This study examined spatial patterns of recycled water use in Florida in 2009 and 2015 to detect gaps in distribution, quantify temporal change, and identify potential areas for expansion. Databases of recycled water products and distribution centers for Florida in 2009 and 2015 were developed by combining the 2008 and 2012 Clean Water Needs Survey databases with Florida’s 2009 and 2015 Reuse Inventory databases, respectively. Florida increased recycled water production from 674.85 mgd in 2009 to 738.15 mgd in 2015, an increase of 63.30 mgd. The increase was primarily allocated to use in public access areas, groundwater recharge, and industrial reuse, all within the South Florida Water Management District (WMD). In particular, Miami was identified in 2009 as an area of opportunity for recycled water development, and by 2015 it had increased production and reduced the production gap. Overall, South Florida WMD had the largest increase in production of 44.38 mgd (69%), while Southwest Florida WMD decreased production of recycled water by 1.68 mgd, or 3%. Overall increase in use of recycled water may be related to higher demand due to increased population coupled with public programs and policy changes that promote recycled water use at both the municipal and individual level
Identifying Untapped Potential: A Geospatial Analysis of Florida and California’s 2009 Recycled Water Production
Increased water demand attributed to population expansion and reduced freshwater availability caused by saltwater intrusion and drought, may lead to water shortages. These may be addressed, in part, by use of recycled water. Spatial patterns of recycled water use in Florida and California during 2009 were analyzed to detect gaps in distribution and identify potential areas for expansion. Databases of recycled water products and distribution centers for both states were developed by combining the 2008 Clean Water Needs Survey database with Florida’s 2009 Reuse Inventory and California’s 2009 Recycling Survey, respectively. Florida had over twice the number of distribution centers (n 1/4 426) than California (n 1/4 228) and produced a larger volume of recycled water (674.85 vs. 597.48 mgd (3.78 mL/d1/4 1 mgd), respectively). Kernel Density Estimation shows the majority of distribution in central Florida (Orlando and Tampa), California’s Central Valley region (Fresno and Bakersfield), and around major cities in California. Areas for growth were identified in the panhandle and southern regions of Florida, and northern, southwestern, and coastal California. Recycled water is an essential component of integrated water management and broader adoption of recycled water will increase water conservation in water-stressed coastal communities by allocating the recycled water for purposes that once used potable freshwater
Australia's first fossil marsupial mole (Notoryctemorphia) resolves controversies about their evolution and palaeoenvironmental origins
Fossils of a marsupial mole (Marsupialia, Notoryctemorphia, Notoryctidae) are described from early Miocene deposits in the Riversleigh World Heritage Area, northwestern Queensland, Australia. These represent the first unequivocal fossil record of the order Notoryctemorphia, the two living species of which are among the world's most specialized and bizarre mammals, but which are also convergent on certain fossorial placental mammals (most notably chrysochlorid golden moles). The fossil remains are genuinely ‘transitional', documenting an intermediate stage in the acquisition of a number of specializations and showing that one of these—the dental morphology known as zalambdodonty—was acquired via a different evolutionary pathway than in placentals. They, thus, document a clear case of evolutionary convergence (rather than parallelism) between only distantly related and geographically isolated mammalian lineages—marsupial moles on the island continent of Australia and placental moles on most other, at least intermittently connected continents. In contrast to earlier presumptions about a relationship between the highly specialized body form of the blind, earless, burrowing marsupial moles and desert habitats, it is now clear that archaic burrowing marsupial moles were adapted to and probably originated in wet forest palaeoenvironments, preadapting them to movement through drier soils in the xeric environments of Australia that developed during the Neogene
Exchange interactions and magnetic phases of transition metal oxides: benchmarking advanced ab initio methods
The magnetic properties of the transition metal monoxides MnO and NiO are
investigated at equilibrium and under pressure via several advanced
first-principles methods coupled with Heisenberg Hamiltonian MonteCarlo. The
comparative first-principles analysis involves two promising beyond-local
density functionals approaches, namely the hybrid density functional theory and
the recently developed variational pseudo-self-interaction correction method,
implemented with both plane-wave and atomic-orbital basis sets. The advanced
functionals deliver a very satisfying rendition, curing the main drawbacks of
the local functionals and improving over many other previous theoretical
predictions. Furthermore, and most importantly, they convincingly demonstrate a
degree of internal consistency, despite differences emerging due to
methodological details (e.g. plane waves vs. atomic orbitals
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Editorial: Special issue – Austere relations: the changing relationship between the third sector, the state and the market in an era of austerity
The relationship between the third sector, the state and the market is in a state of flux. The Coalition, and subsequently the Conservative, administrations’ emphasis on austerity continues to play its part in shaping this relationship. As state funding for welfare services is cut and staffing levels are reduced in the name of deficit reduction, third sector organisations (TSOs), including community groups, and voluntary, charitable and other not-for-profit organisation, are increasingly being called upon to fill gaps in welfare provision and meet community needs. Their role and response to this call is shaped by a political ideology that seeks to blend free markets with communitarianism and volunteerism
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