Independent Base Vector Representation to Address Endmember Variability in Hyperspectral Unmixing

The normal compositional model (NCM) is a well-known and powerful model in hyperspectral unmixing which represents endmembers as independent Gaussian vectors to capture endmember variability. However, the assumption of independent endmembers diminishes the model accuracy because the high degree of correlation between endmembers of a scene and identical sources of variability demonstrate that the endmembers are dependent. This paper proposes a new hyperspectral unmixing algorithm which represents endmembers using dependent Gaussian vectors to estimate abundance fractions. To overcome the higher complexity caused by dependence assumption, this algorithm introduces new independent Gaussian vectors named Base Vectors to represent different endmembers by a weighted linear combination. Also, the proposed unmixing algorithm uses maximum likelihood method to estimate weight coefficients of Base Vectors which are used to represent mixed pixel. Finally, abundance estimation can be done using the new representation for endmembers and mixed pixel. The proposed algorithm is evaluated and compared with other state-of-the-art unmixing algorithms using simulated and real hyperspectral images. Experimental results demonstrate that the proposed unmixing algorithm can unmix pixels composed of correlated endmembers in hyperspectral images in the presence of spectral variability more accurately than previous methods.     

Asymmetrical turbid surface-plume deposition near ice-outlets of the Pleistocene Laurentide ice sheet in the Labrador Sea

 Ice-sheet drainage of glacial detritus into the sea involves size fractionation by ice-margin winnowing on a giant scale caused by the lower density of meltwater entering cold seawater. Despite its load of suspended sediment, the fresh water rises to or stays at the sea surface forming turbid surface plumes, whereas the coarse-grained sediment forms bed load. On the Labrador Slope south of the Hudson Strait turbid plumes were supplied by meltwater from the Pleistocene ice sheet (LIS). Sediments with the seismic characteristics of plume deposits occur in a 200-km-long slope sector up to 130 km seawards from the strait. The widespread distribution of these deposits is attributed to entrainment of the surface plumes by the south-flowing Labrador Current and suppressed flocculation due to the high detrital carbonate-content of the suspended sediment. Deposits with typical characteristics of surface plume deposits have been recovered within 20 km from former ice margin south of or in front of outlets, but not north of outlets. They consist of 1 to 2-cm-thick alternations of fine sandy silt/coarse silt layers with finer-grained clayey silt/silty clay, and for brevity are called plumites. Received: 6 August 1996/Revision received: 21 January 1997     

Spatiotemporal shoreline change in Boushehr Province coasts,Iran

Journal of Oceanology and Limnology - Since coastal areas have highly dynamic nature and are one of the most beneficial regions of civilizations, it is of great significance to understand their...     

Mercury in soil from the area of Dayton,Ohio

Mercury concentrations in “A-zone” soil from seventeen urban, suburban, and rural town locations in the area of Dayton, Ohio range from 0.24 to 1.50 ppm. A positive correlation is indicated between the mercury concentrations and the amount of fallout of settleable particulate matter from the air at these sites. Airborne pollution may be an important source of the element in Dayton area soils.     

Endmember orthonormal mapping in hyperspectral mixture analysis to address endmember variability

Spectral unmixing estimates the abundance of each endmember at every pixel of a hyperspectral image. Each material in traditional unmixing algorithms is represented through a constant spectral signature. However, endmember variability always exists due to environmental, atmospheric, and temporal conditions, which leads to poor accuracy of the estimated abundances. This paper proposes a new unmixing algorithm based on a new linear transformation called endmember orthonormal mapping (EOM) to overcome the aforementioned problem. The EOM transformation maps original spectral space to a new EOM space to reduce endmember variability. In the original spectral space, each material is represented by a set of spectra (endmember set) which is extracted using the automated endmember bundles (AEB) method. The EOM transforms each endmember set to a vector in the EOM space so that these vectors are orthonormal. On account of orthonormalized endmembers, the condition number of the mixing matrix in the EOM space reduces. Furthermore, we consider the noise term as an additional virtual endmember set mapped to a vector that is orthogonal to other endmembers. As a result, a promising unmixing accuracy is obtained through applying the least squares abundance estimation in the subspace orthogonal to noise. Experimental results of both synthetic and real hyperspectral images demonstrate that the proposed algorithms provide much enhanced performance compared with the state-of-the-art algorithms.     

An investigation into the effects of block size distribution function on the strength of bimrocks based on large-scale laboratory tests

Considering the geomechanical characteristics of rocks which are a mixture of rock blocks embedded in fine grain matrix can be challenging due to their complex structure and difficulty in preparing representative in situ or laboratory samples. In the literature, this group of rocks is called block in matrix Rocks (bimrocks). In this paper, the effects of volumetric block proportion (VBP), maximum block size, and distribution function on the compressive strength and failure patterns of these rocks were considered by executing the unconfined compressive test on large-scale synthetic samples. The compressive strength of bimrocks was found to have a direct relation with VBP and maximum block size and an indirect one with fractal dimension in accordance with multivariable regression analysis. The fracture patterns of remolded samples were changed from an inter-granular facture to a matrix and between-granular one by the reducing the VBP and increasing the fractal dimension. In addition, the failure mechanism was spalling for the low values of VBP and the high values of fractal dimension and it was changed to shear failure by increasing VBP and decreasing fractal dimension.