Spartina alterniflora was introduced to Beihai, Guangxi (China), for ecological engineering purposes in 1979. However, the exceptional adaptability and reproductive ability of this species have led to its extensive dispersal into other habitats, where it has had a negative impact on native species and threatens the local mangrove and mudflat ecosystems. To obtain the distribution and spread of Spartina alterniflora, we collected HJ-1 CCD imagery from 2009 and 2011 and very high resolution (VHR) imagery from the unmanned aerial vehicle (UAV). The invasion area of Spartina alterniflora was 357.2 ha in 2011, which increased by 19.07% compared with the area in 2009. A field survey was conducted for verification and the total accuracy was 94.0%. The results of this paper show that VHR imagery can provide details on distribution, progress, and early detection of Spartina alterniflora invasion. OBIA, object based image analysis for remote sensing (RS) detection method, can enable control measures to be more effective, accurate, and less expensive than a field survey of the invasive population.

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In this work, we use observations of the Hubble parameter from the differential ages of passively evolving galaxies and the recent detection of the Baryon Acoustic Oscillations (BAO) at z1 = 0.35 to constrain the Dvali-Gabadadze-Porrati (DGP) universe. For the case with a curvature term, we set a prior h = 0.73 ± 0.03 and the best-fit values suggest a spatially closed Universe. For a flat Universe, we set h free and we get consistent results with other recent analyses.

The universe, with large-scale homogeneity, is locally inhomogeneous, clustering into stars, galaxies and larger structures. Such property is described by the smoothness parameter α which is defined as the proportion of matter in the form of intergalactic medium. If we take consideration of the inhomogeneities in small scale, there should be modifications of the cosmological distances compared to a homogenous model. Dyer and Roeder developed a second-order ordinary differential equation (D-R equation) that describes the angular diameter distance-redshift relation for inhomogeneous cosmological models. Furthermore, we may obtain the D-R equation for observational H(z) data (OHD). The density-parameter Ω M , the state of dark energy ω, and the smoothnessparameter α are constrained by a set of OHD in a spatially flat ΛCDM universe as well as a spatially flat XCDM universe. By using of χ 2 minimization method we get α = 0.81 +0.19 −0.20 and Ω M = 0.32 +0.12 −0.06 at 1σ confidence level. If we assume a Gaussian prior of Ω M = 0.26 ± 0.1, we get α = 0.93 +0.07 −0.19 and Ω M = 0.31 +0.06 −0.05 . For XCDM model, α is constrained to α ≥ 0.80 but ω is weakly constrained around -1, where ω describes the equation of the state of the dark energy (p X = ωρ X ). We conclude that OHD constrains the smoothness parameter more effectively than the data of SNe Ia and compact radio sources.

The spatially averaged inhomogeneous Universe includes a kinematical backreaction term Q D that is relate to the averaged spatial Ricci scalar R D in the framework of general relativity. Under the assumption that Q D and R D obey the scaling laws of the volume scale factor a D , a direct coupling between them with a scaling index n is remarkable. In order to explore the generic properties of a backreaction model for explaining the accelerated expansion of the Universe, we exploit two metrics to describe the late time Universe. Since the standard FLRW metric cannot precisely describe the late time Universe on small scales, the template metric with an evolving curvature parameter κ D (t) is employed. However, we doubt the validity of the prescription for κ D , which motivates us apply observational Hubble parameter data (OHD) to constrain parameters in dust cosmology. First, for FLRW metric, by getting best-fit constraints of Ω arXiv:1704.01774v5 [astro-ph.CO]

We use the Radial Baryon Acoustic Oscillation (RBAO) measurements, distant type Ia supernovae (SNe Ia), the observational H(z) data (OHD) and the Cosmic Microwave Background (CMB) shift parameter data to constrain cosmological parameters of ΛCDM and XCDM cosmologies and further examine the role of OHD and SNe Ia data in cosmological constraints. We marginalize the likelihood function over h by integrating the probability density P ∝ e −χ 2 /2 to obtain the best fitting results and the confidence regions in the Ωm − ΩΛ plane. With the combination analysis for both of the ΛCDM and XCDM models, we find that the confidence regions of 68.3%, 95.4% and 99.7% levels using OHD+RBAO+CMB data are in good agreement with that of SNe Ia+RBAO+CMB data which is consistent with the result of Lin et al's work. With more data of OHD, we can probably constrain the cosmological parameters using OHD data instead of SNe Ia data in the future.