170 research outputs found
Background Subtraction Methods in Video Streams: A Review
Background subtraction is one of the most important parts in image and video processing field. There are some unnecessary parts during the image or video processing, and should be removed, because they lead to more execution time or required memory. Several subtraction methods have been presented for the time being, but find the best-suited method is an issue, which this study is going to address. Furthermore, each process needs to the specific subtraction technique, and knowing this issue helps researchers to achieve faster and higher performance in their research. This paper presents a comparative study of several existing background subtraction methods which have been investigated from simple background subtraction to more complex statistical techniques. The goal of this study is to provide a view of the strengths and drawbacks of the widely used methods. The methods are compared based on their memory requirement, the computational time and their robustness of different videos. Finally, a comparison between the existing methods has been employed with some factors like computational time or memory requirements. It is also hoped that this analysis helps researchers to address the difficulty of selecting the most convenient method for background subtraction
Are transnational tobacco companies' market access strategies linked to economic development models? A case study of South Korea.
Transnational tobacco companies (TTCs) have used varied strategies to access previously closed markets. Using TTCs' efforts to enter the South Korean market from the late 1980s as a case study, this article asks whether there are common patterns in these strategies that relate to the broader economic development models adopted by targeted countries. An analytical review of the existing literature on TTCs' efforts to access emerging markets was conducted to develop hypotheses relating TTCs' strategies to countries' economic development models. A case study of Korea was then undertaken based on analysis of internal tobacco industry documents. Findings were consistent with the hypothesis that TTCs' strategies in Korea were linked to Korea's export-oriented economic development model and its hostile attitude towards foreign investment. A fuller understanding of TTCs' strategies for expansion globally can be derived by locating them within the economic development models of specific countries or regions. Of foremost importance is the need for governments to carefully balance economic and public health policies when considering liberalisation
KiDS-1000: cosmic shear with enhanced redshift calibration
We present a cosmic shear analysis with an improved redshift calibration for
the fourth data release of the Kilo-Degree Survey (KiDS-1000) using
self-organising maps (SOMs). Compared to the previous analysis of the KiDS-1000
data, we expand the redshift calibration sample to more than twice its size,
now consisting of data of 17 spectroscopic redshift campaigns, and
significantly extending the fraction of KiDS galaxies we are able to calibrate
with our SOM redshift methodology. We then enhance the calibration sample with
precision photometric redshifts from COSMOS2015 and the Physics of the
Accelerated Universe Survey (PAUS), allowing us to fill gaps in the
spectroscopic coverage of the KiDS data. Finally we perform a Complete
Orthogonal Sets of E/B-Integrals (COSEBIs) cosmic shear analysis of the newly
calibrated KiDS sample. We find , which is in
good agreement with previous KiDS studies and increases the tension with
measurements of the cosmic microwave background to 3.4{\sigma}. We repeat the
redshift calibration with different subsets of the full calibration sample and
obtain, in all cases, agreement within at most 0.5{\sigma} in compared to
our fiducial analysis. Including additional photometric redshifts allows us to
calibrate an additional 6 % of the source galaxy sample. Even though further
systematic testing with simulated data is necessary to quantify the impact of
redshift outliers, precision photometric redshifts can be beneficial at high
redshifts and to mitigate selection effects commonly found in spectroscopically
selected calibration samples.Comment: 18 pages, 15 figures, 6 table
Dark Energy and Neutrino Masses from Future Measurements of the Expansion History and Growth of Structure
We forecast the expected cosmological constraints from a combination of
probes of both the universal expansion rate and matter perturbation growth, in
the form of weak lensing tomography, galaxy tomography, supernovae, and the
cosmic microwave background incorporating all cross-correlations between the
observables for an extensive cosmological parameter set. We allow for non-zero
curvature and parameterize our ignorance of the early universe by allowing for
a non-negligible fraction of dark energy (DE) at high redshifts. We find that
early DE density can be constrained to 0.2% of the critical density of the
universe with Planck combined with a ground-based LSST-like survey, while
curvature can be constrained to 0.06%. However, these additional degrees of
freedom degrade our ability to measure late-time dark energy and the sum of
neutrino masses. We find that the combination of cosmological probes can break
degeneracies and constrain the sum of neutrino masses to 0.04 eV, present DE
density also to 0.2% of the critical density, and the equation of state to 0.01
- roughly a factor of two degradation in the constraints overall compared to
the case without allowing for early DE. The constraints for a space-based
mission are similar. Even a modest 1% dark energy fraction of the critical
density at high redshift, if not accounted for in future analyses, biases the
cosmological parameters by up to 2 sigma. Our analysis suggests that throwing
out nonlinear scales (multipoles > 1000) may not result in significant
degradation in future parameter measurements when multiple cosmological probes
are combined. We find that including cross-correlations between the different
probes can result in improved constraints by up to a factor of 2 for the sum of
neutrino masses and early dark energy density.Comment: 25 pages, 12 figures. Added new figure, discussion of intrinsic
alignments, and references. Matches version accepted for publication in PR
KiDS-i-800: Comparing weak gravitational lensing measurements in same-sky surveys
We present a weak gravitational lensing analysis of 815 square degree of
-band imaging from the Kilo-Degree Survey (KiDS--800). In contrast to the
deep -band observations, which take priority during excellent seeing
conditions and form the primary KiDS dataset (KiDS--450), the complementary
yet shallower KiDS--800 spans a wide range of observing conditions. The
overlapping KiDS--800 and KiDS--450 imaging therefore provides a unique
opportunity to assess the robustness of weak lensing measurements. In our
analysis, we introduce two new `null' tests. The `nulled' two-point shear
correlation function uses a matched catalogue to show that the calibrated
KiDS--800 and KiDS--450 shear measurements agree at the level of \%. We use five galaxy lens samples to determine a `nulled' galaxy-galaxy
lensing signal from the full KiDS--800 and KiDS--450 surveys and find
that the measurements agree to \% when the KiDS--800 source
redshift distribution is calibrated using either spectroscopic redshifts, or
the 30-band photometric redshifts from the COSMOS survey.Comment: 24 pages, 20 figures. Submitted to MNRAS. Comments welcom
A scoping review of public hospitals autonomy in Iran: from budgetary hospitals to corporate hospitals
Background: Organizational reforms of hospitals in Iran are mainly aimed at improving efficiency, reducing government spending on health care, and improving the quality of services. These reforms began with hospital autonomization and have continued with other initiatives such as formation of board of trustees, independent and corporatized hospitals. Objective: The purpose of this scoping review was to summarize and compare the results of studies conducted on organizational reform of hospitals in Iran to paint a more clear picture of the status quo by identifying knowledge gaps, inform policymakers, and guide future studies and policies. Method: This review�s methodology was inspired by Arksey and O�Malley�s methodological framework to examine the extent, range, and nature of research activity about organizational hospital reforms in Iran. A literature search was performed using PubMed, Scopus, Web of Science, and Google Scholar for English papers as well as SID, IranDoc, Magiran, and the Social Security Research Institute Database for Persian papers from 1991 to April 2020. Results: Twenty studies were included in the review. Studies were grouped by the types of organizational reform, study�s objective, setting, methodology, data collection and analysis techniques, and key findings. Thematic construction was used based on the types of organizational reform to present a narrative account of existing literature. Conclusions: The autonomy granted to the hospitals was unbalanced and paradoxical in terms of key effective dimensions. Poor governance and regulatory arrangements, low commitment to corporate governance, Inappropriate board composition, weak internal controls, unsustainable financing and inefficient payment mechanisms, poor interaction with stakeholders and ignoring contextual factors have been cited as the main reasons for the failure of organizational reforms in Iran. The limited use of evidence and research was obvious at different stages of policymaking, especially in the policy formulation phase and evaluation of its results. © 2021, The Author(s)
Cosmology from large-scale structure. Constraining LambdaCDM with BOSS
We reanalyse the anisotropic galaxy clustering measurement from the Baryon Oscillation Spectroscopic Survey (BOSS), demonstrating that using the full shape information provides cosmological constraints that are comparable to other low-redshift probes. We find Ωm = 0.317+0.015−0.019, σ8 = 0.710±0.049, and h = 0.704 ± 0.024 for flat ΛCDM cosmologies using uninformative priors on Ωch2, 100θMC, ln1010As, and ns, and a prior on Ωbh2 that is much wider than current constraints. We quantify the agreement between the Planck 2018 constraints from the cosmic microwave background and BOSS, finding the two data sets to be consistent within a flat ΛCDM cosmology using the Bayes factor as well as the prior-insensitive suspiciousness statistic. Combining two low-redshift probes, we jointly analyse the clustering of BOSS galaxies with weak lensing measurements from the Kilo-Degree Survey (KV450). The combination of BOSS and KV450 improves the measurement by up to 45%, constraining σ8 = 0.702 ± 0.029 and S8 = σ8 Ωm/0.3 = 0.728 ± 0.026. Over the full 5D parameter space, the odds in favour of a single cosmology describing galaxy clustering, lensing, and the cosmic microwave background are 7 ± 2. The suspiciousness statistic signals a 2.1 ± 0.3σ tension between the combined low-redshift probes and measurements from the cosmic microwave background
Precision calculations of the cosmic shear power spectrum projection
We compute the spherical-sky weak-lensing power spectrum of the shear and convergence. We discuss various approximations, such as flat-sky, and first- and second-order Limber equations for the projection. We find that the impact of adopting these approximations is negligible when constraining cosmological parameters from current weak-lensing surveys. This is demonstrated using data from the Canada–France–Hawaii Telescope Lensing Survey. We find that the reported tension with Planck cosmic microwave background temperature anisotropy results cannot be alleviated. For future large-scale surveys with unprecedented precision, we show that the spherical second-order Limber approximation will provide sufficient accuracy. In this case, the cosmic-shear power spectrum is shown to be in agreement with the full projection at the sub-percent level for ℓ > 3, with the corresponding errors an order of magnitude below cosmic variance for all ℓ. When computing the two-point shear correlation function, we show that the flat-sky fast Hankel transformation results in errors below two percent compared to the full spherical transformation. In the spirit of reproducible research, our numerical implementation of all approximations and the full projection are publicly available within the package NICAEA at http://www.cosmostat.org/software/nicaea
CFHTLenS revisited: assessing concordance with Planck including astrophysical systematics
We investigate the impact of astrophysical systematics on cosmic shear cosmological parameter constraints from the Canada–France–Hawaii Telescope Lensing Survey (CFHTLenS) and the concordance with cosmic microwave background measurements by Planck. We present updated CFHTLenS cosmic shear tomography measurements extended to degree scales using a covariance calibrated by a new suite of N-body simulations. We analyse these measurements with a new model fitting pipeline, accounting for key systematic uncertainties arising from intrinsic galaxy alignments, baryonic effects in the non-linear matter power spectrum, and photometric redshift uncertainties. We examine the impact of the systematic degrees of freedom on the cosmological parameter constraints, both independently and jointly. When the systematic uncertainties are considered independently, the intrinsic alignment amplitude is the only degree of freedom that is substantially preferred by the data. When the systematic uncertainties are considered jointly, there is no consistently strong preference in favour of the more complex models. We quantify the level of concordance between the CFHTLenS and Planck data sets by employing two distinct data concordance tests, grounded in Bayesian evidence and information theory. We find that the two data concordance tests largely agree with one another and that the level of concordance between the CFHTLenS and Planck data sets is sensitive to the exact details of the systematic uncertainties included in our analysis, ranging from decisive discordance to substantial concordance as the treatment of the systematic uncertainties becomes more conservative. The least conservative scenario is the one most favoured by the cosmic shear data, but it is also the one that shows the greatest degree of discordance with Planck. The data and analysis code are publicly available at https://github.com/sjoudaki/cfhtlens_revisited
RCSLenS: testing gravitational physics through the cross-correlation of weak lensing and large-scale structure
The unknown nature of ‘dark energy’ motivates continued cosmological tests of large-scale gravitational physics. We present a new consistency check based on the relative amplitude of non-relativistic galaxy peculiar motions, measured via redshift-space distortion, and the relativistic deflection of light by those same galaxies traced by galaxy–galaxy lensing. We take advantage of the latest generation of deep, overlapping imaging and spectroscopic data sets, combining the Red Cluster Sequence Lensing Survey, the Canada–France–Hawaii Telescope Lensing Survey, the WiggleZ Dark Energy Survey and the Baryon Oscillation Spectroscopic Survey. We quantify the results using the ‘gravitational slip’ statistic EG, which we estimate as 0.48 ± 0.10 at z = 0.32 and 0.30 ± 0.07 at z = 0.57, the latter constituting the highest redshift at which this quantity has been determined. These measurements are consistent with the predictions of General Relativity, for a perturbed Friedmann–Robertson–Walker metric in a Universe dominated by a cosmological constant, which are EG = 0.41 and 0.36 at these respective redshifts. The combination of redshift-space distortion and gravitational lensing data from current and future galaxy surveys will offer increasingly stringent tests of fundamental cosmology
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