59,085 research outputs found
Verifying termination and error-freedom of logic programs with block declarations
We present verification methods for logic programs with delay declarations. The verified properties are termination and freedom from errors related to built-ins. Concerning termination, we present two approaches. The first approach tries to eliminate the well-known problem of speculative output bindings. The second approach is based on identifying the predicates for which the textual position of an atom using this predicate is irrelevant with respect to termination.
Three features are distinctive of this work: it allows for predicates to be used in several modes; it shows that block declarations, which are a very simple delay construct, are sufficient to ensure the desired properties; it takes the selection rule into account, assuming it to be as in most Prolog implementations. The methods can be used to verify existing programs and assist in writing new programs
New multiplicativity results for qubit maps
Let be a trace-preserving, positivity-preserving (but not necessarily
completely positive) linear map on the algebra of complex
matrices, and let be any finite-dimensional completely positive map.
For and , we prove that the maximal -norm of the product map
\Phi \ot \Omega is the product of the maximal -norms of and
. Restricting to the class of completely positive maps, this
settles the multiplicativity question for all qubit channels in the range of
values .Comment: 14 pages; original proof simplified by using Gorini and Sudarshan's
classification of extreme affine maps on R^
Energetic solar proton versus terrestrially trapped proton fluxes for the active years 1977 - 1983
Ratios of solar to trapped proton fluences were computed for circular-orbit, geocentric space missions to be flown during the active phase of the next solar cycle (1977-1983). The ratios are presented as functions of orbit altitude and inclination, mission duration, proton energy threshold, and the chance the mission planner is willing to take that the actually encountered solar proton fluence will exceed the design fluence provided by the statistical solar proton model. It is shown that the ratio is most sensitively dependent on orbit altitude and inclination, with trapped protons dominant for low inclination, low and mid altitude orbits and for high inclination, mid altitude orbits. Conversely, solar protons are dominant for high inclination, low altitude orbits, and for low and high inclination, high altitude orbits
Time-Separable Preference and Intertemporal-Substitution Models of Business Cycles
Time-separability of utility means that past work and consumption do not influence current and future tastes. This form of preferences does not restrict the size of intertemporal-substitution effects--notably, we can still have a strong response of labor supply to temporary changes in wages. However, there are important constraints on the relative responses of leisure and consumption to changes in relative-price and in permanent income. When the usual aggregation is permissible, time-separability has some important implications for equilibrium theories of the business cycle. Neglecting investment, we, find that changes in perceptions about the future -- which night appear currently as income effects -- have no influence on current equilibrium output. With investment included, no combination of income effects and shifts to the perceived profitability of investment will yield positive co-movements of output, employment, investment and consumption. Therefore, misperceived monetary disturbances or other sources of changed beliefs about the future cannot be used to generate empirically recognizable business cycles. Some richer specifications of intertemporal production opportunities may eventually yield more satisfactory answers. Because of the positive correlation between cyclical movements of consumption and work, equilibrium theories with time-separable preferences inevitably predict a procyclical behavior for the real wage rate, arising from shifts to labor's marginal product. Empirically, we regard the cyclical behavior of real wages as an open question. Aside from analyzing autonomous real shocks to productivity, we suggest that such shifts may occur as firms vary their capital utilization in response to intertemporal relative prices. However, we still lack some parts of a complete theory.
Skull Flexure from Blast Waves: A Mechanism for Brain Injury with Implications for Helmet Design
Traumatic brain injury [TBI] has become a signature injury of current
military conflicts, with debilitating, costly, and long-lasting effects.
Although mechanisms by which head impacts cause TBI have been well-researched,
the mechanisms by which blasts cause TBI are not understood. From numerical
hydrodynamic simulations, we have discovered that non-lethal blasts can induce
sufficient skull flexure to generate potentially damaging loads in the brain,
even without a head impact. The possibility that this mechanism may contribute
to TBI has implications for injury diagnosis and armor design.Comment: version in press, Physical Review Letters; 17 pages, 5 figures
(includes supplementary material
Improving CMB non-Gaussianity estimators using tracers of local structure
Local non-Gaussianity causes correlations between large scale perturbation
modes and the small scale power. The large-scale CMB signal has contributions
from the integrated Sachs Wolfe (ISW) effect, which does not correlate with the
small scale power. If this ISW contribution can be removed, the sensitivity to
local non-Gaussianity is improved. Gravitational lensing and galaxy counts can
be used to trace the ISW contribution; in particular we show that the CMB
lensing potential is highly correlated with the ISW signal. We construct a
nearly-optimal estimator for the local non-Gaussianity parameter \fnl and
investigate to what extent we can use this to decrease the variance on
{\fnl}. We show that the variance can be decreased by up to at Planck
sensitivity using galaxy counts. CMB lensing is a good bias-independent ISW
tracer for future more sensitive observations, though the fractional decrease
in variance is small if good polarization data is also available.Comment: 8 pages, 3 figures. Comments welcom
LRG-BEASTS III: Ground-based transmission spectrum of the gas giant orbiting the cool dwarf WASP-80
We have performed ground-based transmission spectroscopy of the hot Jupiter
orbiting the cool dwarf WASP-80 using the ACAM instrument on the William
Herschel Telescope (WHT) as part of the LRG-BEASTS programme. This is the third
paper of a ground-based transmission spectroscopy survey of hot Jupiters using
low-resolution grism spectrographs. We observed two transits of the planet and
have constructed transmission spectra spanning a wavelength range of
4640-8840A. Our transmission spectrum is inconsistent with a previously claimed
detection of potassium in WASP-80b's atmosphere, and is instead most consistent
with a haze. We also do not see evidence for sodium absorption at a resolution
of 100A.Comment: 11 pages, 9 figures. Accepted for publication in MNRA
Molecular Beams
Contains a report on a research project.Lincoln Laboratory (Purchase Order B-00306)United States ArmyUnited States NavyUnited States Air Force (Contract AF19(604)-5200
Electron Optics
Contains research objectives and summary of research.Joint Services Electronics Program (Contract DAAB07 -71 -C-0300
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