609 research outputs found
Sampling errors of correlograms with and without sample mean removal for higher-order complex white noise with arbitrary mean
We derive the bias, variance, covariance, and mean square error of the
standard lag windowed correlogram estimator both with and without sample mean
removal for complex white noise with an arbitrary mean. We find that the
arbitrary mean introduces lag dependent covariance between different lags of
the correlogram estimates in spite of the lack of covariance in white noise for
non-zeros lags. We provide a heuristic rule for when the sample mean should be,
and when it should not be, removed if the true mean is not known. The sampling
properties derived here are useful is assesing the general statistical
performance of autocovariance and autocorrelation estimators in different
parameter regimes. Alternatively, the sampling properties could be used as
bounds on the detection of a weak signal in general white noise.Comment: 11 pages, 2 figures, To be published in Journal of Time Series
Analysi
Deriving the sampling errors of correlograms for general white noise
We derive the second-order sampling properties of certain autocovariance and
autocorrelation estimators for sequences of independent and identically
distributed samples. Specifically, the estimators we consider are the classic
lag windowed correlogram, the correlogram with subtracted sample mean, and the
fixed-length summation correlogram. For each correlogram we derive explicit
formulas for the bias, covariance, mean square error and consistency for
generalised higher-order white noise sequences. In particular, this class of
sequences may have non-zero means, be complexed valued and also includes
non-analytical noise signals. We find that these commonly used correlograms
exhibit lag dependent covariance despite the fact that these processes are
white and hence by definition do not depend on lag.Comment: Submitted to Biometrik
Role of spatial coherence in polarization tomography
We analyze an experimental setup in which a quasi-monochromatic spatially
coherent beam of light is used to probe a paraxial optical scatterer. We
discuss the effect of the spatial coherence of the probe beam on the Mueller
matrix representing the scatterer. We show that according to the degree of
spatial coherence of the beam, the \emph{same} scattering system can be
represented by \emph{different} Mueller matrices. This result should serve as a
warning for experimentalists.Comment: 3 pages, 1 figur
On the economic impacts of mortgage credit expansion policies: evidence from Help to Buy
Mortgage credit expansion policies – such as UK’s Help to Buy (HtB) – aim to increase access to and affordability of owner-occupied housing and are widespread around the world. We take advantage of spatial discontinuities in the HtB equity loan scheme, introduced in 2013, to explore the causal economic impacts and the effectiveness of this type of policies. Employing a Difference-in-Discontinuities design, we find that HtB increased house prices by more than the expected present value of the implied interest rate subsidy and had no discernible effect on construction volumes in the Greater London Authority (GLA), where housing supply is subject to severe long-run constraints and housing is already extremely unaffordable. HtB did increase construction numbers without affecting prices near the English/Welsh border, an area with less binding supply constraints and comparably affordable housing. HtB also led to bunching of newly built units below the price threshold, building of smaller new units and an improvement in the financial performance of developers. We conclude that credit expansion policies such as HtB may be ineffective in tightly supply constrained and already unaffordable areas
On the similarity of Information Energy to Dark Energy
Information energy is shown here to have properties similar to those of dark
energy. The energy associated with each information bit of the universe is
found to be defined identically to the characteristic energy of a cosmological
constant. Two independent methods are used to estimate the universe information
content of ~10^91 bits, a value that provides an information energy total
comparable to that of the dark energy. Information energy is also found to have
a significantly negative equation of state parameter, w < -0.4, and thus exerts
a negative pressure, similar to dark energy.Comment: 5 pages, no figures, no table
Instantaneous local wave vector estimation from multi-spacecraft measurements using few spatial points
Baade's red sheet resolved into stars with HST in the Blue Compact Dwarf Galaxy VII Zw 403
HST WFPC2 observations of the nearby Blue Compact Dwarf Galaxy VII~Zw~403 (=
UGC 6456) resolve single stars down to M-2.5, deep enough to
identify red giants. This population has a more uniform spatial distribution
than the young main-sequence stars and supergiants, forming the structure known
as "Baade's red sheet". We conclude that VII~Zw~403 is not a primeval galaxy.Comment: submitted to: ApJ Letter
O conselho escolar e a implementação no município de Cascavel-PR
This paper is aimed to present a summary of the production carried out in Master’s Degree dissertation entitled “Organization and School Management: an analysis of the School Council implemented in the city of Cascavel”. That research has had as its main goal to present an analysis of the School Council’s implementation process in the city of Cascavel, in 2012. The School Council, is part of the National Programme of School Councils Strengthening (PNFCE) which was created in 2004 during the first Luiz Inácio Lula da Silva’s government. This programme proclaims to promote the democratic management through the school community participation, for this, the programme offers education courses for the role performed by counsellor. Understanding that it is a programme guided by public policies and it’s not a movement which emerged from society, this study tries to reflect about the limit and the possibilities of the school community participation in a democratic management through an instrument which is the School Council. Hence, to develop this job, it was made a bibliographical research, a documental analysis and a field research through interviews and questionnaires with public municipal schools’ principals, and with others School Council’s members. In order to understand the research object, it was made some observations in Seminaries, education courses for counsellors and School Councils meetings. Our solicitude is to rescue the research questions and to put forward the limit and the possibilities of a School Council inside of a public school of the research field, recovering essential aspects of the community participation.Este trabalho tem por objetivo apresentar uma síntese da produção realizada na dissertação de mestrado intitulada ”Organização e Gestão Escolar: uma análise do Conselho Escolar na rede pública municipal de Cascavel”3. A pesquisa teve por objetivo principal apresentar uma análise do processo de implementação do Conselho Escolar no município de Cascavel no ano de 2012. O Conselho Escolar faz parte do Programa Nacional de Fortalecimento dos Conselhos Escolares (PNFCE), criado em 2004 na primeira gestão do então presidente Luiz Inácio Lula da Silva. Esse programa proclama fomentar a gestão democrática por meio da participação da comunidade escolar e, para isso, oferta cursos de formação para o desempenho do papel de conselheiro. Entendendo que é um programa direcionado por meio de políticas públicas e não por um movimento que emergiu da sociedade, o estudo buscou refletir sobre os limites e as possibilidades da participação da comunidade escolar na gestão da escola pública a partir de um instrumento que é o Conselho Escolar. Assim, para o desenvolvimento do trabalho realizou-se uma pesquisa bibliográfica, com análise de documentos e com pesquisa de campo realizada por meio de entrevistas e de questionários com diretores das escolas municipais, com demais membros do Conselho Escolar, para entendimento do objeto de pesquisa participamos ainda de observações em Seminários, cursos de formação para conselheiros e reunião do Conselho Escolar. Nossa preocupação é resgatar as questões da pesquisa e apontar os limites e possibilidades de um Conselho Escolar dentro de uma gestão na escola pública do campo de pesquisa, recuperando aspectos fundamentais da participação da comunidade
Evaluation of total and bioavailable heavy metals and other soilrelated variables in a rice paddy after the application of defecation lime
A two-year experiment was carried out in a paddy field to investigate the effects of the use of defecation lime derived from treated sewage sludge on soil total and soil phytoavailable heavy metals concentration. Heavy metals concentration was determined also in raw rice. Four treatments were arranged in a completely randomized block design: not fertilised (T0), organic fertilisation + chemical fertilisers (T1), defecation lime + chemical fertilisers (T2), defecation lime at pre-sowing (T3). For T3, the pH value increased significantly at the end of the second year, increasing from 5.8 to 6.11. T3 resulted in the highest soil organic carbon content (9.4 g kg-1), suggesting the potential of defecation lime both as soil corrective material and soil amendment. The application of defecation lime in the paddy field did not result in an increased phytoavailable amount of heavy metals in soil
The nitrification inhibitor Vizura® reduces N₂O emissions when added to digestate before injection under irrigated maize in the Po Valley (Northern Italy)
The agricultural area in the Po Valley is prone to high nitrous oxide (N\u2082O) emissions as it is characterized by irrigated maize-based cropping systems, high amounts of nitrogen supplied, and elevated air temperature in summer. Here, two monitoring campaigns were carried out in maize fertilized with raw digestate in a randomized block design in 2016 and 2017 to test the effectiveness of the 3, 4 DMPP inhibitor Vizura\uae on reducing N2O-N emissions. Digestate was injected into 0.15 m soil depth at side-dressing (2016) and before sowing (2017). Non-steady state chambers were used to collect N\u2082O-N air samples under zero N fertilization (N0), digestate (D), and digestate + Vizura\uae (V). Overall, emissions were significantly higher in the D treatment than in the V treatment in both 2016 and 2017. The emission factor (EF, %) of V was two and four times lower than the EF in D in 2016 and 2017, respectively. Peaks of NO\u2083-N generally resulted in N\u2082O-N emissions peaks, especially during rainfall or irrigation events. The water-filled pore space (WFPS, %) did not differ between treatments and was generally below 60%, suggesting that N\u2082O-N emissions were mainly due to nitrification rather than denitrification
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