2,292 research outputs found
A Vernacular for Coherent Logic
We propose a simple, yet expressive proof representation from which proofs
for different proof assistants can easily be generated. The representation uses
only a few inference rules and is based on a frag- ment of first-order logic
called coherent logic. Coherent logic has been recognized by a number of
researchers as a suitable logic for many ev- eryday mathematical developments.
The proposed proof representation is accompanied by a corresponding XML format
and by a suite of XSL transformations for generating formal proofs for
Isabelle/Isar and Coq, as well as proofs expressed in a natural language form
(formatted in LATEX or in HTML). Also, our automated theorem prover for
coherent logic exports proofs in the proposed XML format. All tools are
publicly available, along with a set of sample theorems.Comment: CICM 2014 - Conferences on Intelligent Computer Mathematics (2014
Extension to order of the high-temperature expansions for the spin-1/2 Ising model on the simple-cubic and the body-centered-cubic lattices
Using a renormalized linked-cluster-expansion method, we have extended to
order the high-temperature series for the susceptibility
and the second-moment correlation length of the spin-1/2 Ising models on
the sc and the bcc lattices. A study of these expansions yields updated direct
estimates of universal parameters, such as exponents and amplitude ratios,
which characterize the critical behavior of and . Our best
estimates for the inverse critical temperatures are
and . For the
susceptibility exponent we get and for the correlation
length exponent we get .
The ratio of the critical amplitudes of above and below the critical
temperature is estimated to be . The analogous ratio for
is estimated to be . For the correction-to-scaling
amplitude ratio we obtain .Comment: Misprints corrected, 8 pages, latex, no figure
Surface and capillary transitions in an associating binary mixture model
We investigate the phase diagram of a two-component associating fluid mixture
in the presence of selectively adsorbing substrates. The mixture is
characterized by a bulk phase diagram which displays peculiar features such as
closed loops of immiscibility. The presence of the substrates may interfere the
physical mechanism involved in the appearance of these phase diagrams, leading
to an enhanced tendency to phase separate below the lower critical solution
point. Three different cases are considered: a planar solid surface in contact
with a bulk fluid, while the other two represent two models of porous systems,
namely a slit and an array on infinitely long parallel cylinders. We confirm
that surface transitions, as well as capillary transitions for a large
area/volume ratio, are stabilized in the one-phase region. Applicability of our
results to experiments reported in the literature is discussed.Comment: 12 two-column pages, 12 figures, accepted for publication in Physical
Review E; corrected versio
Diurnal shifts in nutritive value of alfalfa harvested as hay and evaluated by animal intake and digestion
Forages accumulate nonstructural carbohydrates
during the day, with animals showing
preference and improved daily responses from
afternoon compared with morning cut hays. This
study evaluated alfalfa (Medicago sativa L.) hay
harvested at 0700, 1000, 1300, 1600, and 1900
h to determine how nutritive value changes during
the day and to assess the impact of these
changes on animal preference using cattle (Bos
taurus L.), sheep (Ovis aries L.), and goat (Capra
hircus L.) responses. Total nonstructural carbohydrates
were altered by time of cut (cubic contrast,
P < 0.01) ranging from 85 g kg?1 at 0700 h
to 83 g kg?1 at 1000 h, then increasing to 97 g
kg?1 by 1600 h with little change at 1900 h (96 g
kg?1). Fiber fractions also varied diurnally, with a
quadratic decrease from 418 g kg?1 at 0700 h to
387 g kg?1 by 1900 h in neutral detergent fiber. A
combined analysis of three animal trials showed
a linear increase in dry matter intake (DMI) with
later hay harvest, a cubic response for dry matter
digestion (DMD), and a linear increase in
digestible DMI. Mean DMI increased from 27.5
g kg?1 body weight at 0700 h to a maximum
of 30.8 g kg?1 body weight at 1600 h, whereas
DMD decreased from 658 g kg?1 at 0700 to 647
g kg?1 at 1300 h and peaked at 664 g kg?1 at
1600 h. Digestible DMI increased from 18.1 g
kg?1 body weight at 0700 h to a maximum of
20.5 g kg?1 body weight at 1600 h. No additional
advantages in animal responses were noted by
cutting after 1600 h
Preference by sheep and goats among hay of eight tall fescue cultivars
Grazing ruminants use both visual cues
and taste in selecting their diet. Preference during grazing
may not be the same when forage is dried for hay
and cut into lengths prior to feeding in confinement.
Eight cultivars of tall fescue (Festuca arundinacea
Schreb.), previously evaluated for preference while
grazed, were harvested three times over a period of 2
yr. The hays were air-dried, baled, and passed through
a hydraulic bale processor prior to feeding. Five experiments
were conducted. All three harvests were evaluated
with sheep and the last two also with goats, using
six animals each time. During an adaptation phase,
hays were offered alone as meals. In the experimental
phase, every possible pair of hays (28 pairs) was presented
for a meal. Data were analyzed by multidimensional
scaling and by traditional analyses. Preference
was significant among cultivars in all experiments.
Multidimensional scaling showed that selection was
based on two criteria with two dimensions being significant.
Sheep preferred KENHY followed by KENTUCKY
31 and STARGRAZER but preferenced against
BARCEL. HIMAG, MO-96, and C1 were intermediate
and MOZARK was variable. Goats were similar to
sheep in preferring KENHY followed by STARGRAZER
and selected against MOZARK and BARCEL. KENTUCKY
31, HIMAG, MO-96, and Cl were intermediate.
In all five experiments, the general association was
positive for available carbohydrate fractions and negative
for fiber fractions that contribute to cell wall rigidity
Ruminant selection among switchgrass hays cut at either sundown or sunup
As a result of photosynthesis, plants typically have greater concentrations of nonstructural carbohydrates at the end of the photoperiod. The preference of ruminants for hays harvested within the same 24-h period can be greater for plants harvested late in the photoperiod with increased soluble carbohydrate. To test for variation in ruminant preference for afternoon versus morning harvested hays in a C4 grass harvested in the humid east, established fields of 'Kanlow' and 'Alamo' switchgrass (Panicum virgatum L.) were used to produce hays in 1998, 1999, and 2000 near Raleigh, NC. Harvests were paired so that each cutting in the evening (PM) was followed by a cutting the next morning (AM). We harvested in this manner three times in 1998 to produce six Kanlow hays; twice with Kanlow and once with Alamo at two levels of nitrogen fertility in 1999 to produce eight hays; and three times in 2000 to produce six Alamo hays. The hays were field-dried, baled, and passed through a hydraulic bale processor. Hays from each year were tested with cattle (Bos taurus L.), goats (Capra hircus L.), and sheep (Ovis aries L.). During an adaptation phase, hays were offered individually. In the experimental phase, all possible pairs of hays were presented. Data were analyzed by multidimensional scaling and by traditional analyses. Multidimensional scaling indicated that selection was based on multiple criteria. The suite of improvements associated with PM-harvested hays in fiber content, digestibility, and nonstructural carbohydrate observed for alfalfa and fescue hays in the western USA was difficult to reproduce with switchgrass hay in the southeastern USA. This difficulty is likely related to the less favorable environment for haymaking as well as the physiology, anatomy, and morphology of this C4 grass
Investment in Electricity Networks with Transmission Switching
We consider the application of Dantzig-Wolfe decomposition to stochastic integer programming problems arising in the capacity planning of electricity trans-mission networks that have some switchable transmission elements. The decomposition enables a column-generation algorithm to be applied, which allows the solution of large problem instances. The methodology is illustrated by its application to a problem of determining the optimal investment in switching equipment and transmission capacity for an existing network. Computational tests on IEEE test networks with 73 nodes and 118 nodes confirm the efficiency of the approach
Ring exchange, the Bose metal, and bosonization in two dimensions
Motivated by the high-T_c cuprates, we consider a model of bosonic Cooper
pairs moving on a square lattice via ring exchange. We show that this model
offers a natural middle ground between a conventional antiferromagnetic Mott
insulator and the fully deconfined fractionalized phase which underlies the
spin-charge separation scenario for high-T_c superconductivity. We show that
such ring models sustain a stable critical phase in two dimensions, the *Bose
metal*. The Bose metal is a compressible state, with gapless but uncondensed
boson and ``vortex'' excitations, power-law superconducting and charge-ordering
correlations, and broad spectral functions. We characterize the Bose metal with
the aid of an exact plaquette duality transformation, which motivates a
universal low energy description of the Bose metal. This description is in
terms of a pair of dual bosonic phase fields, and is a direct analog of the
well-known one-dimensional bosonization approach. We verify the validity of the
low energy description by numerical simulations of the ring model in its exact
dual form. The relevance to the high-T_c superconductors and a variety of
extensions to other systems are discussed, including the bosonization of a two
dimensional fermionic ring model
A simple two-module problem to exemplify building-block assembly under crossover
Theoretically and empirically it is clear that a genetic algorithm with crossover will outperform a genetic algorithm without crossover in some fitness landscapes, and vice versa in other landscapes. Despite an extensive literature on the subject, and recent proofs of a principled distinction in the abilities of crossover and non-crossover algorithms for a particular theoretical landscape, building general intuitions about when and why crossover performs well when it does is a different matter. In particular, the proposal that crossover might enable the assembly of good building-blocks has been difficult to verify despite many attempts at idealized building-block landscapes. Here we show the first example of a two-module problem that shows a principled advantage for cross-over. This allows us to understand building-block assembly under crossover quite straightforwardly and build intuition about more general landscape classes favoring crossover or disfavoring it
Crossover from 2-dimensional to 1-dimensional collective pinning in NbSe3
We have fabricated NbSe structures with widths comparable to the
Fukuyama-Lee-Rice phase-coherence length. For samples already in the
2-dimensional pinning limit, we observe a crossover from 2-dimensional to
1-dimensional collective pinning when the crystal width is less than 1.6
m, corresponding to the phase-coherence length in this direction. Our
results show that surface pinning is negligible in our samples, and provide a
means to probe the dynamics of single domains giving access to a new regime in
charge-density wave physics.Comment: 4 pages, 2 figures, and 1 table. Accepted for publication in Physical
Review
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