2,297 research outputs found
Traffic congestion in shop collection systems
A computer simulation model is developed which will aid in predicting the data traffic congestion for shop data collection systems. Two data traffic input distributions, Poisson and Bernoulli, gamma distributed service times; and random or order of arrival queue discipline
Characterization of preclones by matrix collections
Preclones are described as the closed classes of the Galois connection
induced by a preservation relation between operations and matrix collections.
The Galois closed classes of matrix collections are also described by explicit
closure conditions.Comment: 11 page
Gyrotropic impact upon negatively refracting surfaces
Surface wave propagation at the interface between different types of gyrotropic materials and an isotropic negatively refracting medium, in which the relative permittivity and relative permeability are, simultaneously, negative is investigated. A general approach is taken that embraces both gyroelectric and gyromagnetic materials, permitting the possibility of operating in either the low GHz, THz or the optical frequency regimes. The classical transverse Voigt configuration is adopted and a complete analysis of non-reciprocal surface wave dispersion is presented. The impact of the surface polariton modes upon the reflection of both plane waves and beams is discussed in terms of resonances and an example of the influence upon the Goos–Hänchen shift is given
Permutative categories, multicategories, and algebraic K-theory
We show that the -theory construction of arXiv:math/0403403, which
preserves multiplicative structure, extends to a symmetric monoidal closed
bicomplete source category, with the multiplicative structure still preserved.
The source category of arXiv:math/0403403, whose objects are permutative
categories, maps fully and faithfully to the new source category, whose objects
are (based) multicategories
Cognition in Context: Pathways and Compound Risk in a Sample of US Non-Hispanic Whites
The population of individuals with cognitive impairment and dementia is growing rapidly, necessitating etiological investigation. It is clear that individual differences in cognition later in life have both genetic and multi-level environmental correlates. Despite significant recent progress in cellular and molecular research, the exact mechanisms linking genes, brains, and cognition remain elusive. In relation to cognition, it is unlikely that genetic and environmental risk factors function in a vacuum, but rather interact and cluster together. The purpose of the present study was to examine whether aspects of individual socioeconomic status (SES) explain the cognitive genotype-phenotype association, and whether neighborhood SES modifies the effects of genes and individual SES on cognitive ability. Using data from non-Hispanic White participants in the 2016 wave of the Health and Retirement Study, a national sample of United States adults, we examined links between a polygenic score for general cognition and performance-based cognitive functioning. In a series of weighted linear regressions and formal tests of mediation, we observed a significant genotype-phenotype association that was partially attenuated after including individual education to the baseline model, although little reductions were observed for household wealth or census tract-level percent poverty. These findings suggest that genetic risk for poor cognition is partially explained by education, and this pathway is not modified by poverty-level of the neighborhood
Monitoring and assessing land degradation: new approaches
This chapter examines land degradation in southern Africa. The focus is on the major issue of erosion by water at scales ranging from a few square metres to assessments that aim to cover the whole region. Approaches to measure and reconstruct both current and historical erosion rates are considered, focusing on the period since the arrival of Europeans who brought many of their farming and management practices with them. In most parts of the country, the impact of humans on the landscape has been clear for the last 200 years. This is referred to as ’accelerated erosion’, i.e., erosion at rates that are above the natural geological norm for the current climatic conditions. The chapter considers a range of techniques including direct measurement, remote sensing, fingerprinting and modelling as approaches to the monitoring and assess land degradation
Nonlinear surface waves in left-handed materials
We study both linear and nonlinear surface waves localized at the interface
separating a left-handed medium (i.e. the medium with both negative dielectric
permittivity and negative magnetic permeability) and a conventional (or
right-handed) dielectric medium. We demonstrate that the interface can support
both TE- and TM-polarized surface waves - surface polaritons, and we study
their properties. We describe the intensity-dependent properties of nonlinear
surface waves in three different cases, i.e. when both the LH and RH media are
nonlinear and when either of the media is nonlinear. In the case when both
media are nonlinear, we find two types of nonlinear surface waves, one with the
maximum amplitude at the interface, and the other one with two humps. In the
case when one medium is nonlinear, only one type of surface wave exists, which
has the maximum electric field at the interface, unlike waves in right-handed
materials where the surface-wave maximum is usually shifted into a
self-focussing nonlinear medium. We discus the possibility of tuning the wave
group velocity in both the linear and nonlinear cases, and show that
group-velocity dispersion, which leads to pulse broadening, can be balanced by
the nonlinearity of the media, so resulting in soliton propagation.Comment: 9 pages, 10 figure
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