624 research outputs found
Combining Static and Dynamic Contract Checking for Curry
Static type systems are usually not sufficient to express all requirements on
function calls. Hence, contracts with pre- and postconditions can be used to
express more complex constraints on operations. Contracts can be checked at run
time to ensure that operations are only invoked with reasonable arguments and
return intended results. Although such dynamic contract checking provides more
reliable program execution, it requires execution time and could lead to
program crashes that might be detected with more advanced methods at compile
time. To improve this situation for declarative languages, we present an
approach to combine static and dynamic contract checking for the functional
logic language Curry. Based on a formal model of contract checking for
functional logic programming, we propose an automatic method to verify
contracts at compile time. If a contract is successfully verified, dynamic
checking of it can be omitted. This method decreases execution time without
degrading reliable program execution. In the best case, when all contracts are
statically verified, it provides trust in the software since crashes due to
contract violations cannot occur during program execution.Comment: Pre-proceedings paper presented at the 27th International Symposium
on Logic-Based Program Synthesis and Transformation (LOPSTR 2017), Namur,
Belgium, 10-12 October 2017 (arXiv:1708.07854
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Modeling light competition in the forests of western Oregon
A plant's immediate neighborhood reflects its realized level of competitive stress, since competition and natural selection act at the individual level. In stands with continuous canopies competition for light is the dominant spatial interaction. Over 100 spatially explicit indices have been used to characterize the local competitive environment in models of individual tree growth. These indices can be divided into those that indirectly characterize the light environment and those that directly characterize the light environment. The three classes of indirect measures are: size-distance, competitive influence zones, growing space and the two classes of direct measures are open sky views and light-interception methods. Studies that have compared the ability of the indirect indices of the light environment have failed to identify a universally superior measure of competition. However, the two direct measures of the light environment have not been included in the comparisons. An examination of the comparative studies showed that most of them identify indices characterizing competition from larger neighbors as superior. This finding leads to the conclusion that competition for light is the dominant spatial interaction in the stands examined. Thus, spatial indices that directly quantify light should explain more variation than those that quantify both above and below ground competition. Light intensity is modeled with the radiation transport equations. SEALS is a program for calculating light intensity in forest stands. It uses the radiation transport equations to model seasonal quantum light flux (SAL). It uses simulated hemispherical photographs to model direct beam light intensity (PCSHS). SAL and PCSHS were compared to three indirect measures of light competition in a planted western hemlock understory and 11 managed Douglas-fir plots. It was found that SAL reduced the residual variation in height growth of understory western hemlock by 48% over a model including only a power of tree height and PCSHS reduced the residual variation by 40%. SAL also reduced residual variation by 48% for overstory Douglas-fir and 18% for understory Douglas-fir while PCSHS reduced the residual variation by 15% and 14% respectively. These reductions were significantly better than those from the indirect classes of spatially explicit index
On the selective deposition of tin and tin oxide on various glasses using a high power diode laser
The deposition of SnO2 using a 120 W high power diode laser (HPDL) on both fused silica and soda-lime-silica glass has been successfully demonstrated. Deposition on both glass substrates was carried out with laser power densities of 650-1600 W cm-2 and at rates of 420-1550 mm min-1. The thickness of the deposited layers was typically around 250 m. The maximum theoretical coverage rate that it may be possible to achieve using the HPDL was calculated as being 3.72 m2 h-1. Owing to the wettability characteristics of Sn, it proved impossible to deposit the metal on either glass substrate. Evidence of solidified microstructures was observed, with the microstructures differing considerably across the same deposited track. These differences were attributed to variations in the solidification rate, R, and the thermal gradient, G. Adhesion of the SnO2 with the soda-lime-silica glass was found to be due to mechanical bonding. The adhesion of the SnO2 with the fused silica was seen to the result of a chemical bond arising from an interface region between the SnO2 and the fused silica glass substrate. This interface region was found to be comprised of mainly Si and rich with Sn3O4
Near-Earth asteroid (3200) Phaethon. Characterization of its orbit, spin state, and thermophysical parameters
The near-Earth asteroid (3200) Phaethon is an intriguing object: its
perihelion is at only 0.14 au and is associated with the Geminid meteor stream.
We aim to use all available disk-integrated optical data to derive a reliable
convex shape model of Phaethon. By interpreting the available space- and
ground-based thermal infrared data and Spitzer spectra using a thermophysical
model, we also aim to further constrain its size, thermal inertia, and visible
geometric albedo. We applied the convex inversion method to the new optical
data obtained by six instruments and to previous observations. The convex shape
model was then used as input for the thermophysical modeling. We also studied
the long-term stability of Phaethon's orbit and spin axis with a numerical
orbital and rotation-state integrator. We present a new convex shape model and
rotational state of Phaethon: a sidereal rotation period of 3.603958(2) h and
ecliptic coordinates of the preferred pole orientation of (319,
39) with a 5 uncertainty. Moreover, we derive its size
(=5.10.2 km), thermal inertia (=600200 J m
s K), geometric visible albedo
(=0.1220.008), and estimate the macroscopic surface
roughness. We also find that the Sun illumination at the perihelion passage
during the past several thousand years is not connected to a specific area on
the surface, which implies non-preferential heating.Comment: Astronomy and Astrophysics. In pres
ISOCAM OBSERVATIONS OF M31
Abstract We present ISOCAM images of the Andromeda galaxy center. They display an elliptical stellar bulge and a more complexe dust distribution. The spatial dust distribution follows a mini-spiral structure identical to the distribution of absorption in optical wavelengths. A discussion on the nature of the dust from CVF observations is also presented. The central part and the molecular ring of M31 are excellent targets for FIRST
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Height-diameter equations for six species in the coastal regions of the Pacific Northwest
Three equations for predicting tree height as a function of diameter (outside
bark) at breast height are presented for six species found in coastal regions of
the Pacific Northwest. Foresters can use these “height–diameter” equations
to avoid the time-consuming task of measuring heights of all individual trees
in an inventory, a stand exam, or a timber cruise. Equation coefficients were
estimated with weighted nonlinear regression techniques. Because the relationship
between a tree’s height and diameter depends on the tree’s competitive
position within the stand, alternative equations, including the average
height and average diameter of the 40 largest-diameter trees/ac, are also
presented. These equations are used in the Stand Management Cooperative
version of ORGANON
Parallel Dislocation Networks and Cottrell Atmospheres Reduce Thermal Conductivity of PbTe Thermoelectrics
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Pervasive remagnetization of detrital zircon host rocks in the Jack Hills, Western Australia and implications for records of the early geodynamo
It currently is unknown when Earth's dynamo magnetic field originated. Paleomagnetic studies indicate that a field with an intensity similar to that of the present day existed 3.5 billion years ago (Ga). Detrital zircon crystals found in the Jack Hills of Western Australia are some of the very few samples known to substantially predate this time. With crystallization ages ranging from 3.0–4.38 Ga, these zircons might preserve a record of the missing first billion years of Earth's magnetic field history. However, a key unknown is the age and origin of magnetization in the Jack Hills zircons. The identification of >3.9 Ga (i.e., Hadean) field records requires first establishing that the zircons have avoided remagnetization since being deposited in quartz-rich conglomerates at 2.65–3.05 Ga. To address this issue, we have conducted paleomagnetic conglomerate, baked contact, and fold tests in combination with U–Pb geochronology to establish the timing of the metamorphic and alteration events and the peak temperatures experienced by the zircon host rocks. These tests include the first conglomerate test directly on the Hadean-zircon bearing conglomerate at Erawandoo Hill. Although we observed little evidence for remagnetization by recent lightning strikes, we found that the Hadean zircon-bearing rocks and surrounding region have been pervasively remagnetized, with the final major overprinting likely due to thermal and/or aqueous effects from the emplacement of the Warakurna large igneous province at ∼1070 million years ago (Ma). Although localized regions of the Jack Hills might have escaped complete remagnetization, there currently is no robust evidence for pre-depositional (>3.0 Ga) magnetization in the Jack Hills detrital zircons
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Enhanced mortality equations for trees in the mixed conifer zone of Southwest Oregon
Equations for predicting the probability of a tree's dying in the
next 5 years are presented for eight conifer and eight hardwood
tree species from southwest Oregon. A logistic equation form was
used to characterize the probability of mortality. The parameters
of the equation were estimated using weighted, maximum likelihood
procedures. These equations are being incorporated into the
new southwest Oregon version of ORGANON, a model for predicting
stand development. In particular, the equations extend the previous model to older stands and and stands with a heavier component of hardwood tree species
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