4,888 research outputs found
Analytical study of tunneling times in flat histogram Monte Carlo
We present a model for the dynamics in energy space of multicanonical
simulation methods that lends itself to a rather complete analytic
characterization. The dynamics is completely determined by the density of
states. In the \pm J 2D spin glass the transitions between the ground state
level and the first excited one control the long time dynamics. We are able to
calculate the distribution of tunneling times and relate it to the
equilibration time of a starting probability distribution. In this model, and
possibly in any model in which entering and exiting regions with low density of
states are the slowest processes in the simulations, tunneling time can be much
larger (by a factor of O(N)) than the equilibration time of the probability
distribution. We find that these features also hold for the energy projection
of single spin flip dynamics.Comment: 7 pages, 4 figures, published in Europhysics Letters (2005
Process transparency on construction sites : examples from construction companies in Brazil
Process transparency is the core concept in Visual Management (VM), which is one of the founding blocks of the Toyota Production System. This paper presents the
preliminary results of a collaborative research conducted between Brazil and the UK, as part of a research effort focused on the application of Visual Management in
construction. How process transparency is realized on construction sites is the main research question of the paper. The use of this concept and the implementation of the
transparency theory were investigated through multiple case studies, carried out in nine different construction companies. The findings are explained through six theoretical transparency increasing approaches. The affecting parameters in the application of, the management’s perception of and several methods in process
transparency in construction were identified. Further work, especially exploring the functions of process transparency on construction sites and reflecting the worker perception of the issue, is necessary to elaborate the process transparency concept
Early Enrichment of the Intergalactic Medium and its Feedback on Galaxy Formation
Supernova-driven outflows from early galaxies may have had a large impact on
the kinetic and chemical structure of the intergalactic medium (IGM). We use
three-dimensional Monte Carlo cosmological realizations of a simple linear
peaks model to track the time evolution of such metal-enriched outflows and
their feedback on galaxy formation. We find that at most 30% of the IGM by
volume is enriched to values above 10^-3 solar in models that only include
objects that cool by atomic transitions. The majority of enrichment occurs
relatively early (5 < z < 12) and resulting in a mass-averaged cosmological
metallicity between 10^-3 and 10^-1.5 solar. The inclusion of Population III
objects that cool through H2 line emission has only a minor impact on these
results: increasing the mean metallicity and filling factor by at most a factor
of 1.4, and moving the dawn of the enrichment epoch to a redshift of
approximately 14 at the earliest. Thus enrichment by outflowing galaxies is
likely to have been incomplete and inhomogeneous, biased to the areas near the
starbursting galaxies themselves. Models with a 10% star formation efficiency
can satisfactorily reproduce the nearly constant (2 < z < 5, Z approximately
3.5 x 10^-4 solar) metallicity of the low column density Ly-alpha forest
derived by Songaila (2001), an effect of the decreasing efficiency of metal
loss from larger galaxies. Finally, we show that IGM enrichment is intimately
tied to the ram-pressure stripping of baryons from neighboring perturbations.
This results in the suppression of at least 20% of the dwarf galaxies in the
mass range 10^8.5 to 10^9.5 solar, in all models with filling factors greater
than 2%, and an overall suppression of approximately 50% of dwarf galaxies in
the most observationally-favored model.Comment: 8 pages, 5 figures, accepted to Ap
Earnings management of brazilian firms in the IFRS era: The role of economic and institutional factors
This study investigates whether accounting quality – more specifically regarding the level of earnings management by accruals – is associated with a country’s economic and institutional factors that change over time in IFRS era. Based on a sample of 1,387 Brazilian firm-year observations and data regarding 2011 to 2018, econometric models are estimated considering the absolute amount of discretionary accruals as proxy for earnings management and different aspects related to economic and institutional factors of preeminent importance to an emerging economy. We show that in general, high inflation, stock market volatility, and policy uncertainty rates, as well as lower regulatory quality, on average, are associated with a higher level of earnings management in Brazil. This study contributes to the accounting literature in emerging economies discussing the role of economic and institutional factors on accounting quality in the IFRS era in one of the largest developing country in the world. Compared to developed countries or even to other developing economies, Brazil stands out as an emerging economy of considerable economic and political instability, making it a valuable setting for this analysisinfo:eu-repo/semantics/publishedVersio
Does national ethical judgment matter for earnings management?
This study analyses the effect of ethical judgment at country-level on earnings management. While previous literature document the role of ethical issues at personal- and organizational-level on earnings management practices, usually theoretically and through qualitative ways, we investigate that association in a large sample at international level taken a sample of 81,408 firm-year observations regarding 10,306 firms from 39 countries. Based on data from an international questionnaire developed by the World Values Survey, we construct a comprehensive index of ethical judgment of each country. Our empirical findings suggest that the level of ethical judgment of the countries are negative associated with accruals-based earnings management, suggesting that the manipulation of accounting amounts is lower in countries where ethically suspect behaviours are less acceptable. Additionally, we also provide empirical evidences that this phenomenon is verified both in developed and emerging countries, and that ethical judgment at country-level seem to moderate the association between IFRS adoption and earnings management practices.info:eu-repo/semantics/acceptedVersio
Capoeira : práticas culturais do recôncavo baiano e o processo pedagógico criativo inclusivo
Este tema enquadra-se no âmbito de um projeto de doutoramento, desenvolvido através do Centro de
Formação de Professores da UFRB/Brasil, enquadrado na área temática - Educação, Desenvolvimento e
Expressões ArtĂsticas. Propõe atividades vinculadas ao estudo da Cultura corporal, a partir das práticas
culturais do recôncavo baiano, na formação de pessoas com deficiência/doença mental e/ou em situação
de risco social e pessoal, com intuito de responder às dificuldades e perspetivas da ação pedagógica,
considerando o impacto educativo da musicalidade, movimento corporal e a dinamica das relações
interpessoais. Explora uma educação inclusiva a partir da reflexão sobre alternativas no trato com a
capoeira, samba, maculele, entre outras, para melhoria de questões que variam desde a cognição até de
auto-estima e identitárias, consignadas numa proposta de implementação de uma atividade de
enriquecimento curricular, em articulação com o currĂculo formal. Com este interesse foi traçada uma
metodologia centrada numa perspectiva qualitativa, a partir de um estudo de caso, considerando a
realidade de uma escola municipal. Assim, além de se observar significativos impactos na perspetiva de
inclusão destas pessoas, promovem-se práticas culturais e articula-se pesquisa, ensino e extensão,
garantindo o papel formativo e social da UFRB junto da comunidade da cidade de Amargosa e a
possibilidade de experimentar uma intervenção pedagógica criativa inclusiva com estudantes de Educação.Fundação para a Ciência e a Tecnologia (FCT
White light tunable emissions from ZnS: Eu3+ nanophosphors over 330–465nm excitation range for white LED applications
(ZnS: Eu3+ -CMC) nanophosphors of cubic (zinc blende) structure were synthesized using a
precipitation technique with doping concentrations of Eu3+ ions 1 mol% and 5 mol%. The crystal
sizes were 2.56 nmand 2.91 nmrespectively. Annealing at 300 °Cin a sulfur-rich atmosphere altered
the crystal size to 4.35 nmand 3.65 nmrespectively and the band gap from 4.2 eV to 3.76 eV and
3.81 eV respectively. The as-synthesized samples gave pure orange-red emission when excited at
wavelengths of 394 nmand 465 nm. After thermal annealing of the samples, a broad emission band in
the blue-green region assigned to defect related states emerged or were enhanced. Also enhanced were
the emission lines of Eu3+ ions in the orange-red region. A combination of these two transitions gave
white light of different shades (recorded on the CIE 1931 chromaticity diagram) from cool white
through day-light to warm white light, depending on Eu3+ concentration and the excitation
wavelengths (UV-330 to blue 465 nm), thus showing great potential of these nano-phosphors in the
generation of high quality white light
Towards absolute calibration of optical tweezers
Aiming at absolute force calibration of optical tweezers, following a
critical review of proposed theoretical models, we present and test the results
of MDSA (Mie-Debye-Spherical Aberration) theory, an extension of a previous
(MD) model, taking account of spherical aberration at the glass/water
interface. This first-principles theory is formulated entirely in terms of
experimentally accessible parameters (none adjustable). Careful experimental
tests of the MDSA theory, undertaken at two laboratories, with very different
setups, are described. A detailed description is given of the procedures
employed to measure laser beam waist, local beam power at the transparent
microspheres trapped by the tweezers, microsphere radius and the trap
transverse stiffness, as a function of radius and height in the (inverted
microscope) sample chamber. We find generally very good agreement with MDSA
theory predictions, for a wide size range, from the Rayleigh domain to large
radii, including the values most often employed in practice, and at different
chamber heights, both with objective overfilling and underfilling. The results
asymptotically approach geometrical optics in the mean over size intervals, as
they should, and this already happens for size parameters not much larger than
unity. MDSA predictions for the trapping threshold, position of stiffness peak,
stiffness variation with height, multiple equilibrium points and `hopping'
effects among them are verified. Remaining discrepancies are ascribed to focus
degradation, possibly arising from objective aberrations in the infrared, not
yet included in MDSA theory.Comment: 15 pages, 20 figure
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