946 research outputs found
Beyond the lognormal approximation: a general simulation scheme
No full textWe present a public code to generate random fields with an arbitrary probability distribution function (PDF) and an arbitrary correlation function. The algorithm is cosmology independent and applicable to any stationary stochastic process over a three-dimensional grid. We implement it in the case of the matter density field, showing its benefits over the lognormal approximation, which is often used in cosmology for the generation of mock catalogues. We find that the covariance of the power spectrum from the new fast realizations is more accurate than that from a lognormal model. As a proof of concept, we also apply the new simulation scheme to the divergence of the Lagrangian displacement field. We find that information from the correlation function and the PDF of the displacement-divergence provides modest improvement over other standard analytical techniques to describe the particle field in the simulation. This suggests that further progress in this direction should come from multiscale or non-local properties of the initial matter distribution
Augmenting photometric redshift estimates using spectroscopic nearest neighbours
No full textAs a consequence of galaxy clustering, close galaxies observed on the plane
of the sky should be spatially correlated with a probability that is inversely
proportional to their angular separation. In principle, this information can be
used to improve photometric redshift estimates when spectroscopic redshifts are
available for some of the neighbouring objects. Depending on the depth of the
survey, however, this angular correlation is reduced by chance projections. In
this work, we implement a deep-learning model to distinguish between apparent
and real angular neighbours by solving a classification task. We adopted a
graph neural network architecture to tie together photometry, spectroscopy, and
the spatial information between neighbouring galaxies. We trained and validated
the algorithm on the data of the VIPERS galaxy survey, for which photometric
redshifts based on spectral energy distribution are also available. The model
yields a confidence level for a pair of galaxies to be real angular neighbours,
enabling us to disentangle chance superpositions in a probabilistic way. When
objects for which no physical companion can be identified are excluded, all
photometric redshift quality metrics improve significantly, confirming that
their estimates were of lower quality. For our typical test configuration, the
algorithm identifies a subset containing ~75% high-quality photometric
redshifts, for which the dispersion is reduced by as much as 50% (from 0.08 to
0.04), while the fraction of outliers reduces from 3% to 0.8%. Moreover, we
show that the spectroscopic redshift of the angular neighbour with the highest
detection probability provides an excellent estimate of the redshift of the
target galaxy, comparable to or even better than the corresponding
template-fitting estimate.Comment: 9 pages, 12 figures, matching the accepted version. NezNet is
available at https://github.com/tos-1/NezNe
Muscle-ups : improved approximations of the matter field with the extended Press–Schechter formalism and Lagrangian perturbation theory
No full textLagrangian algorithms to simulate the evolution of cold dark matter (CDM) are invaluable tools to generate large suites of mock halo catalogues. In this paper, we first show that the main limitation of current semi-analytical schemes to simulate the displacement of CDM is their inability to model the evolution of overdensities in the initial density field, a limit that can be circumvented by detecting halo particles in the initial conditions. We thus propose 'MUltiscale Spherical Collapse Lagrangian Evolution Using Press-Schechter' (MUSCLE-UPS), a new scheme that reproduces the results from Lagrangian perturbation theory on large scales, while improving the modelling of overdensities on small scales. In muscle-ups, we adapt the extended Press and Schechter formalism to Lagrangian algorithms of the displacement field. For regions exceeding a collapse threshold in the density smoothed at a radius R, we consider all particles within a radius R collapsed. Exploiting a multiscale smoothing of the initial density, we build a halo catalogue on the fly by optimizing the selection of halo candidates. This allows us to generate a density field with a halo mass function that matches one measured in N-body simulations. We further explicitly gather particles in each halo together in a profile, providing a numerical, Lagrangian-based implementation of the halo model. Compared to previous semi-analytical Lagrangian methods, we find that muscle-ups improves the recovery of the statistics of the density field at the level of the probability density function, the power spectrum, and the cross-correlation with the N-body result
MANOVA modelling of a chiropractic longitudinal study using multiple imputation
No full textThe purpose of this report is to present the detailed statistical analysis of a randomised, placebo-controlled trial comparing two different treatment modalities to an intervention of no known benefit for people with acute or subacute thoracic spine pain.
The therapy arms consist of Spinal Manipulative Therapy (SMT) and Graston Technique (GT) and the placebo is a non-functional ultrasound. A placebo group was utilised because at present there are no proven treatments for non-specific thoracic pain. This trial is registered with the Australia and New Zealand Clinical Trials Registry. Ethics approval has been granted by Murdoch University Human Research and Ethics Committee, number 2007/274.
The aim of this three arm trial was to test the efficacy of SMT and GT as independent modalities compared to detuned ultrasound for the outcomes of pain and disability. The latter were measured using the Visual Analogue Scale (VAS) and a modified Oswestry Back Pain Disability Index. The study was conducted at the Murdoch University Chiropractic student clinic in Perth, Australia, and the protocol published in Crothers et al (2008).
In this report, Section 2 provides an initial exploratory analysis of the data, Section 3 outlines the statistical models used in the final analysis, Section 4 defines these models in mathematical terms, Section 5 discusses the management of missing values via multiple imputation and Section 6 presents the results of the statistical modelling and hypothesis tests. The clinical study will be published in full elsewhere
Constraints on massive neutrinos from the CFHTLS angular power spectrum
No full textWe use the galaxy angular power spectrum at z ∼ 0.5-1.2 from the Canada-France-Hawaii-Telescope Legacy Survey Wide fields (CFHTLS-Wide) to constrain separately the total neutrino mass ∑m ν and the effective number of neutrino species N eff. This survey has recently benefited from an accurate calibration of the redshift distribution, allowing new measurements of the (non-linear) matter power spectrum in a unique range of scales and redshifts sensitive to neutrino free streaming. Our analysis makes use of a recent model for the effect of neutrinos on the weakly non-linear matter power spectrum derived from accurate N-body simulations. We show that CFHTLS, combined with WMAP7 and a prior on the Hubble constant provides an upper limit of ∑m ν<0.29 eV and N eff=4.17 +1.62 -1.26 (2σ confidence levels). If we omit smaller scales which may be affected by non-linearities, these constraints become ∑m ν<0.41 eV and N eff=3.98 +2.02 -1.20 (2σ confidence levels). Finally we show that the addition of other large scale structures probes can further improve these constraints, demonstrating that high redshift large volumes surveys such as CFHTLS are complementary to other cosmological probes of the neutrino mass
Experimental characterisation of self-healing in reconstituted Boom Clay
No full textGreen Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Geo-engineerin
The Methodological Reflection about the Criticism to Hu Hong in The Doubt of Zhi Yan by Zhu Hsi
No full text本文討論《知言疑義》中朱熹對胡宏的批評意見，企圖澄清兩造思路的差異，從而各自呈現兩家思維的特色與要點。《知言疑義》中胡宏的文句多半是本體工夫論合構的發言，因此語多跳躍，致引朱熹之批評。朱熹即由性善論的本體論立場批評胡宏有「性無善惡」之說，及由存有論思路的「心統性情說」批評胡宏的心性相關語句之不佳，以及由「未發涵養已發察識」的工夫次第思路批評胡宏並未重視平日涵養一節。本文將藉由作者所提之「實踐哲學的解釋架構」，以及「存有論哲學」的問題意識分析，以澄清兩造哲學問題意識的不同，因而並未形成真正的衝突，從而亦藉此說明朱熹與胡宏各自論學之重點意旨。The discussion in this article is about the criticism to Hu Hong in The doubt of Zhi yan Proposed by Zhu Hsi. The author is aiming to clear the dissimilar way of thinking between the two philosophers to the effect that both their significant theory could be appeared. Hu Hong’s philosophical announcement always integrates the ontological and practical theory, which results to the ambiguity and give rise to the criticism from Zhu Hsi. Zhu Hsi possessed the position of the goodness of nature to query Hu Hong about his no good and no evil opinion toward the theory of the human nature. In the definition of the mind and nature, master Zhu Hsi proposed the mind comprise the nature and the felling and argued with Hu Hong’s different opining. Concerning about the practical procedure theory, Zhu Hsi insist the cultivation should be built on daily life, and critic Hu Hong’s philosophy being short of this understanding. In this article the author will use the interpretational structure of the practical theory and the theory of being to analyze the different consciousness in these two systems and suggest that there exist no real conflict between them so as to explain both their philosophical thinking
St. Scholastica's interactive timeline exhibition
No full textCurrently, the information on the history of the Benedictine Sisters and St. Scholastica's College is scattered around in various PowerPoint presentations, websites, and off course books and other analog media. For the Museum Archives, a more structured exhibition is aimed for, allowing visitors to browse the history of the Philippines, the Benedictine sisters and St. Scholastica's College in the past 100 years. This interactive exhibit will be the center piece of the Museum Archives of the Missionary Benedictine Sisters in the Philippines. We are to design such a system, and start to implement it. Also, we should ensure continuity of the project by making the staff familiar with the system. This way they can take it along after we are gone, maintaining it as its database growsElectrical Engineering, Mathematics and Computer Scienc
www.website4free.co.nz
No full textReport on the planning, design, development and testing of the 'content management' management website 'website4free.co.nz'. The goal of this project was to develop a system that will allow the users to register and build their own website base on a chosen template.Computer ScienceElectrical Engineering, Mathematics and Computer Scienc
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