149 research outputs found
Role of terms of trade in Indian agricultural growth: a national and state level analysis
Using time series data, this paper analyses the relative contributions of terms of trade and non-price variables in explaining agricultural growth in recent decades in India. Agricultural growth is largely explained by expansion of irrigation, (which in the model is also a proxy for HYVs and other capital investments), and, until the 1970s, by increases in the net cultivated area. Agricultural output is inelastic, and is becoming increasingly more so over time. The terms of trade was not an important factor in explaining past growth. Even during the late 1960s and early 1970s when the terms of trade improved by 18 percent for agriculture, they only accounted for 15 percent of the growth in output. Increases in agricultural output are also found to worsen the terms of trade for agriculture, despite government attempts to control prices. The results highlight the importance of further investments in agricultural research, extension, irrigation and other supply-enhancing inputs if the ongoing policy reforms in India are to translate into more rapid and sustained agricultural growth.Agricultural productivity India., Terms of trade India., Investment of public funds India.,
Agricultural growth linkages in Sub-Saharan Africa:
How much extra net income growth can be had in rural areas of Africa by increasing the spending power of local households? The answer depends on how rural households spend increments to income, whether the items desired can be imported to the local area in response to increased demand, and, if not, whether increased demand will lead to new local production or simply to price rises. For every dollar in new farm income earned, at least one additional dollar could be realized from growth multipliers, according to Agricultural Growth Linkages in Sub-Saharan Africa.Income Rural areas Africa., Agricultural development Africa., Agricultural policy Economic aspects., Households Zimbabwe., Social accounting., Africa sub-Saharan,
Probing hot gas around luminous red galaxies through the Sunyaev-Zel'dovich effect
We construct the mean thermal Sunyaev-Zel'dovich (tSZ) Comptonization y profile around Luminous Red Galaxies (LRGs) in the redshift range 0.16 < z < 0.47 from the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) using the Planck y map. The mean central tSZ signal for the full sample is y ~ 1.8 * 10^(-7) and we detect tSZ emission out to ~30 arcmin, which is well beyond the 10 arcmin angular resolution of the y map and well beyond the virial radii of the LRGs. We compare the measured profile with predictions from the cosmo-OWLS suite of cosmological hydrodynamical simulations. This comparison agrees well for models that include feedback from active galactic nuclei (AGN), but not with hydrodynamic models without this energetic feedback mechanism. This suggests that an additional heating mechanism is required over SNe feedback and star formation to explain the y data profile. We also compare our results with predictions based on the halo model with a universal pressure profile (UPP) giving the y signal. The predicted profile is consistent with the data, but only if we account for the clustering of haloes via a two-halo term and if halo masses are estimated using the mean stellar-to-halo mass (SHM) relation of Coupon et al. (2015) or Wang et al.(2016) estimated from gravitational lensing measurements. We also discuss the importance of scatter in the SHM relation on the model predictions
RCSLenS: The Red Cluster Sequence Lensing Survey
We present the Red Cluster Sequence Lensing Survey (RCSLenS), an application of the methods developed for the Canada–France–Hawaii Telescope Lensing Survey (CFHTLenS) to the ∼785 deg2, multi-band imaging data of the Red-sequence Cluster Survey 2. This project represents the largest public, sub-arcsecond seeing, multi-band survey to date that is suited for weak gravitational lensing measurements. With a careful assessment of systematic errors in shape measurements and photometric redshifts, we extend the use of this data set to allow cross-correlation analyses between weak lensing observables and other data sets. We describe the imaging data, the data reduction, masking, multi-colour photometry, photometric redshifts, shape measurements, tests for systematic errors, and a blinding scheme to allow for more objective measurements. In total, we analyse 761 pointings with r-band coverage, which constitutes our lensing sample. Residual large-scale B-mode systematics prevent the use of this shear catalogue for cosmic shear science. The effective number density of lensing sources over an unmasked area of 571.7 deg2 and down to a magnitude limit of r ∼ 24.5 is 8.1 galaxies per arcmin2 (weighted: 5.5 arcmin−2) distributed over 14 patches on the sky. Photometric redshifts based on four-band griz data are available for 513 pointings covering an unmasked area of 383.5 deg2. We present weak lensing mass reconstructions of some example clusters as well as the full survey representing the largest areas that have been mapped in this way. All our data products are publicly available through Canadian Astronomy Data Centre at http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/en/community/rcslens/query.html in a format very similar to the CFHTLenS data release
RCSLenS: The Red Cluster Sequence Lensing Survey
We present the Red Cluster Sequence Lensing Survey (RCSLenS), an application of the methods developed for the Canada–France–Hawaii Telescope Lensing Survey (CFHTLenS) to the ∼785 deg2, multi-band imaging data of the Red-sequence Cluster Survey 2. This project represents the largest public, sub-arcsecond seeing, multi-band survey to date that is suited for weak gravitational lensing measurements. With a careful assessment of systematic errors in shape measurements and photometric redshifts, we extend the use of this data set to allow cross-correlation analyses between weak lensing observables and other data sets. We describe the imaging data, the data reduction, masking, multi-colour photometry, photometric redshifts, shape measurements, tests for systematic errors, and a blinding scheme to allow for more objective measurements. In total, we analyse 761 pointings with r-band coverage, which constitutes our lensing sample. Residual large-scale B-mode systematics prevent the use of this shear catalogue for cosmic shear science. The effective number density of lensing sources over an unmasked area of 571.7 deg2 and down to a magnitude limit of r ∼ 24.5 is 8.1 galaxies per arcmin2 (weighted: 5.5 arcmin−2) distributed over 14 patches on the sky. Photometric redshifts based on four-band griz data are available for 513 pointings covering an unmasked area of 383.5 deg2. We present weak lensing mass reconstructions of some example clusters as well as the full survey representing the largest areas that have been mapped in this way. All our data products are publicly available through Canadian Astronomy Data Centre at http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/en/community/rcslens/query.html in a format very similar to the CFHTLenS data release
Gauge Issues in Extended Gravity and f(R) Cosmology
We consider issues related to the conformal mapping between the Einstein and
Jordan frames in f(R) cosmology. We consider the impact of the conformal
transformation on the gauge of a perturbed system and show that unless the
system is written in a restricted set of gauges the mapping could produce an
inconsistent result in the target frame. Newtonian gauge lies within the
restricted group but synchronous gauge does not. If this is not treated
carefully it could in principle contaminate numerical calculations.Comment: 12 pages, REVTeX4. Replaced with version accepted by JCAP. Citations
added and some clarification
The 6dF Galaxy Survey: z \approx 0 measurement of the growth rate and sigma_8
We present a detailed analysis of redshift-space distortions in the two-point
correlation function of the 6dF Galaxy Survey (6dFGS). The K-band selected
sub-sample which we employ in this study contains 81971 galaxies distributed
over 17000deg^2 with an effective redshift z = 0.067. By modelling the 2D
galaxy correlation function, xi(r_p,pi), we measure the parameter combination
f(z)sigma_8(z) = 0.423 +/- 0.055. Alternatively, by assuming standard gravity
we can break the degeneracy between sigma_8 and the galaxy bias parameter, b.
Combining our data with the Hubble constant prior from Riess et al (2011), we
measure sigma_8 = 0.76 +/- 0.11 and Omega_m = 0.250 +/- 0.022, consistent with
constraints from other galaxy surveys and the Cosmic Microwave Background data
from WMAP7. Combining our measurement of fsigma_8 with WMAP7 allows us to test
the relationship between matter and gravity on cosmic scales by constraining
the growth index of density fluctuations, gamma. Using only 6dFGS and WMAP7
data we find gamma = 0.547 +/- 0.088, consistent with the prediction of General
Relativity. We note that because of the low effective redshift of 6dFGS our
measurement of the growth rate is independent of the fiducial cosmological
model (Alcock-Paczynski effect). We also show that our conclusions are not
sensitive to the model adopted for non-linear redshift-space distortions. Using
a Fisher matrix analysis we report predictions for constraints on fsigma_8 for
the WALLABY survey and the proposed TAIPAN survey. The WALLABY survey will be
able to measure fsigma_8 with a precision of 4-10%, depending on the modelling
of non-linear structure formation. This is comparable to the predicted
precision for the best redshift bins of the Baryon Oscillation Spectroscopic
Survey (BOSS), demonstrating that low-redshift surveys have a significant role
to play in future tests of dark energy and modified gravity.Comment: 17 pages, 13 figures, 1 tabl
A census of baryons in the Universe from localized fast radio bursts
More than three quarters of the baryonic content of the Universe resides in a
highly diffuse state that is difficult to observe, with only a small fraction
directly observed in galaxies and galaxy clusters. Censuses of the nearby
Universe have used absorption line spectroscopy to observe these invisible
baryons, but these measurements rely on large and uncertain corrections and are
insensitive to the majority of the volume, and likely mass. Specifically,
quasar spectroscopy is sensitive either to only the very trace amounts of
Hydrogen that exists in the atomic state, or highly ionized and enriched gas in
denser regions near galaxies. Sunyaev-Zel'dovich analyses provide evidence of
some of the gas in filamentary structures and studies of X-ray emission are
most sensitive to gas near galaxy clusters. Here we report the direct
measurement of the baryon content of the Universe using the dispersion of a
sample of localized fast radio bursts (FRBs), thus utilizing an effect that
measures the electron column density along each sight line and accounts for
every ionised baryon. We augment the sample of published arcsecond-localized
FRBs with a further four new localizations to host galaxies which have measured
redshifts of 0.291, 0.118, 0.378 and 0.522, completing a sample sufficiently
large to account for dispersion variations along the line of sight and in the
host galaxy environment to derive a cosmic baryon density of (95% confidence). This independent
measurement is consistent with Cosmic Microwave Background and Big Bang
Nucleosynthesis values.Comment: Published online in Nature 27 May, 202
Tooling design and microwave curing technologies for the manufacturing of fiber-reinforced polymer composites in aerospace applications
The increasing demand for high-performance and quality polymer composite materials has led to international research effort on pursuing advanced tooling design and new processing technologies to satisfy the highly specialized requirements of composite components used in the aerospace industry. This paper reports the problems in the fabrication of advanced composite materials identified through literature survey, and an investigation carried out by the authors about the composite manufacturing status in China’s aerospace industry. Current tooling design technologies use tooling materials which cannot match the thermal expansion coefficient of composite parts, and hardly consider the calibration of tooling surface. Current autoclave curing technologies cannot ensure high accuracy of large composite materials because of the wide range of temperature gradients and long curing cycles. It has been identified that microwave curing has the potential to solve those problems. The proposed technologies for the manufacturing of fiber-reinforced polymer composite materials include the design of tooling using anisotropy composite materials with characteristics for compensating part deformation during forming process, and vacuum-pressure microwave curing technology. Those technologies are mainly for ensuring the high accuracy of anisotropic composite parts in aerospace applications with large size (both in length and thickness) and complex shapes. Experiments have been carried out in this on-going research project and the results have been verified with engineering applications in one of the project collaborating companies
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