3,225 research outputs found
Infinitary Combinatory Reduction Systems: Normalising Reduction Strategies
We study normalising reduction strategies for infinitary Combinatory
Reduction Systems (iCRSs). We prove that all fair, outermost-fair, and
needed-fair strategies are normalising for orthogonal, fully-extended iCRSs.
These facts properly generalise a number of results on normalising strategies
in first-order infinitary rewriting and provide the first examples of
normalising strategies for infinitary lambda calculus
Job Developer Types, Placement Practices and Outcomes Technical Report
Despite numerous employment initiatives, people with disabilities are significantly more likely to experience unemployment and consequently, reduced economic and social well-being and a dminished quality of life than their non disabled peers. In a recent national survey of employers, less than 14% of companies indicated that they actively recruit jobseekers with disabilities. Thus, the role of the job development professional is pivotal to helping job seekers with disabilities to find, secure and maintain employment. This research report examined the attitudes and beliefs of job development processionals articulated in a previous technical report by TransCen, Inc. and looked to further explore the relationship between the types, other personal characteristics and placement outcomes of the various job developer types
Distinguishing fractional and white noise in one and two dimensions
We discuss the link between uncorrelated noise and Hurst exponent for one and
two-dimensional interfaces. We show that long range correlations cannot be
observed using one-dimensional cuts through two-dimensional self-affine
surfaces whose height distributions are characterized by a Hurst exponent lower
than -1/2. In this domain, fractional and white noise are not distinguishable.
A method analysing the correlations in two dimensions is necessary. For Hurst
exponents larger than -1/2, a crossover regime leads to a systematic over
estimate of the Hurst exponent.Comment: 3 pages RevTeX, 4 Postscript figure
The Properties of The Wood-Polystyrene Interphase Determined by Inverse Gas Chromatography
The properties of the interphase in wood-polymer composites are important determinants of the properties of the final composite. This study used inverse gas chromatography (IGC) to measure interphasal properties of composites of polystyrene and two types of wood fiber fillers and an inorganic substrate (CW) with varying amounts of surface coverage of polystyrene. Glass transition temperatures, thermodynamic parameters, and the London component of the surface free energy (YsL) were deter mined. Values for YsL became constant at higher coverages, allowing the thickness of the interphase to be estimated
Spatio-temporal distribution of euphausiids: an important component to understanding ecosystem processes in the Gulf of Alaska and eastern Bering Sea
Abstract
Euphausiids (principally Thysanoessa spp.) are found in high abundance in both the eastern Bering Sea (EBS) and the Gulf of Alaska (GOA). They are an important part of these cold-water coastal and pelagic ecosystems as a key prey item for many species, including marine mammals, seabirds, and fish, forming an ecological link between primary production and higher trophic levels. Acoustic-trawl (AT) survey methods provide a means of monitoring euphausiid abundance and distribution over a large spatial scale. Four years of AT and bottom-trawl survey data (2003, 2005, 2011, and 2013) were available from consistently sampled areas around Kodiak Island, including Shelikof Strait, Barnabas Trough, and Chiniak Trough. We identified euphausiid backscatter using relative frequency response and targeted trawling, and created an annual index of abundance for euphausiids. This index has broad application, including use in the stock assessments for GOA walleye pollock (Gadus chalcogrammus) and other species, as an ecosystem indicator, and to inform ecological research. We then used generalized additive models (GAMs) to examine the relationship between relative euphausiid abundance and potential predictors, including pollock abundance, temperature, bottom depth, and primary production. Model results were compared with an updated GAM of euphausiid abundance from the EBS to determine if the factors driving abundance and distribution were consistent between both systems. Temperature was not a strong predictor of euphausiid abundance in the GOA as in the EBS; warmer temperatures and lack of seasonal ice cover in the GOA may be a key difference between these ecosystems. Pollock abundance was significant in both the GOA and the EBS models, but was not a strongly negative predictor of euphausiid abundance in either system, a result not consistent with top-down control of euphausiid abundance
The Case for an Accelerating Universe from Supernovae
The unexpected faintness of high-redshift Type Ia supernovae (SNe Ia), as
measured by two teams, has been interpreted as evidence that the expansion of
the Universe is accelerating. We review the current challenges to this
interpretation and seek to answer whether the cosmological implications are
compelling. We discuss future observations of SNe Ia which could offer
extraordinary evidence to test acceleration.Comment: To appear as an Invited Review for PASP 20 pages, 13 figure
The Scattering of Electromagnetic Waves from Two-Dimensional Randomly Rough Penetrable Surfaces
An accurate and efficient numerical simulation approach to electromagnetic
wave scattering from two-dimensional, randomly rough, penetrable surfaces is
presented. The use of the M\"uller equations and an impedance boundary
condition for a two-dimensional rough surface yields a pair of coupled
two-dimensional integral equations for the sources on the surface in terms of
which the scattered field is expressed through the Franz formulas. By this
approach, we calculate the full angular intensity distribution of the scattered
field that is due to a finite incident beam of -polarized light. We
specifically check the energy conservation (unitarity) of our simulations (for
the non-absorbing case). Only after a detailed numerical treatment of {\em
both} diagonal and close-to-diagonal matrix elements is the unitarity condition
found to be well-satisfied for the non-absorbing case (), a
result that testifies to the accuracy of our approach.Comment: Revtex, 4 pages, 2 figure
Wavelet and R/S analysis of the X-ray flickering of cataclysmic variables
Recently, wavelets and R/S analysis have been used as statistical tools to
characterize the optical flickering of cataclysmic variables. Here we present
the first comprehensive study of the statistical properties of X-ray flickering
of cataclysmic variables in order to link them with physical parameters. We
analyzed a sample of 97 X-ray light curves of 75 objects of all classes
observed with the XMM-Newton space telescope. By using the wavelets analysis,
each light curve has been characterized by two parameters, alpha and Sigma,
that describe the energy distribution of flickering on different timescales and
the strength at a given timescale, respectively. We also used the R/S analysis
to determine the Hurst exponent of each light curve and define their degree of
stochastic memory in time. The X-ray flickering is typically composed of long
time scale events (1.5 < alpha < 3), with very similar strengths in all the
subtypes of cataclysmic variables (-3 < Sigma < -1.5). The X-ray data are
distributed in a much smaller area of the alpha-Sigma parameter space with
respect to those obtained with optical light curves. The tendency of the
optical flickering in magnetic systems to show higher Sigma values than the
non-magnetic systems is not encountered in the X-rays. The Hurst exponents
estimated for all light curves of the sample are larger than those found in the
visible, with a peak at 0.82. In particular, we do not obtain values lower than
0.5. The X-ray flickering presents a persistent memory in time, which seems to
be stronger in objects containing magnetic white dwarf primaries. The
similarity of the X-ray flickering in objects of different classes together
with the predominance of a persistent stochastic behavior can be explained it
terms of magnetically-driven accretion processes acting in a considerable
fraction of the analyzed objects.Comment: 10 pages, 3 figures, 2 tables. Language revision. Accepted for
publication in A&
Level Crossing Analysis of the Stock Markets
We investigate the average frequency of positive slope ,
crossing for the returns of market prices.
The method is based on stochastic processes which no scaling feature is
explicitly required. Using this method we define new quantity to quantify stage
of development and activity of stocks exchange. We compare the Tehran and
western stock markets and show that some stocks such as Tehran (TEPIX) and New
Zealand (NZX) stocks exchange are emerge, and also TEPIX is a non-active market
and financially motivated to absorb capital.Comment: 6 pages and 4 figure
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