Entity

Time filter

Source Type

Fairfax, VA, United States

Samad O.E.,National Council for Scientific Research | Baydoun R.,National Council for Scientific Research | Nsouli B.,National Council for Scientific Research | Darwish T.,Center for Remote Sensing, Inc.
Journal of Environmental Radioactivity | Year: 2013

The concentrations of natural and artificial radionuclides at 57 sampling locations along the North Province of Lebanon are reported. The samples were collected from uncultivated areas in a region not previously reported. The samples were analyzed by gamma spectrometers with High Purity Germanium detectors of 30% and 40% relative efficiency. The activity concentrations of primordial naturally occurring radionuclides of 238U, 232Th, and 40K varied between 4-73Bqkg-1, 5-50Bqkg-1, and 57-554Bqkg-1 respectively. The surface activity concentrations due to the presence of these radionuclides were calculated and Kriging-geostatistical method was used to plot the obtained data on the Lebanese radioactive map. The results for 238U, 232Th, and 40K ranged from 0.2kBqm-2 to 9kBqm-2, from 0.2kBqm-2 to 3kBqm-2, and from 3kBqm-2 to 29kBqm-2 respectively. For the anthropogenic radionuclides, the activity concentrations of 137Cs founded in soil ranged from 2Bqkg-1 to 113Bqkg-1, and the surface activity concentration from 0.1kBqm-2 to 5kBqm-2. The total absorbed gamma dose rates in air from natural and artificial radionuclides in these locations were calculated. The minimum value was 6nGyh-1 and the highest one was 135nGyh-1 with an average of 55nGyh-1 in which the natural terrestrial radiation contributes in 99% and the artificial radionuclides mainly 137Cs contributes only in 1%. The total effective dose calculated varied in the range of 7μSvy-1 and 166μSvy-1 while the average value was 69μSvy-1 which is below the permissible limit 1000μSvy-1. © 2013 Elsevier Ltd. Source


Awad M.M.,Center for Remote Sensing, Inc.
International Journal of Remote Sensing | Year: 2012

Image segmentation is a central process in image processing. There are many segmentation methods such as region growing, edge detection, split and merge and artificial neural networks (ANNs). However, the most important and popular are clustering methods. Normally, clustering methods select cluster centres randomly to segment an image into disjoint and homogeneous regions. The use of random cluster centres without a priori knowledge leads to degradation in the accuracy of the obtained results. However, combined with edge detection, shape representation can help in improving the clustering methods. The improvement is obtained by knowing the optimal location of the cluster centres at the beginning of the image segmentation process. In this article, a new geometric model for high-resolution satellite image segmentation is implemented that can overcome the problem encountered in random clustering processes. The proposed model uses Canny-Deriche edge detection and the modified non-uniform rational B-spline (NURBS) methods to generate the control points of the edges. These points are used to identify cluster centres that are necessary to create the population of the hybrid dynamic genetic algorithm (HDGA). The new geometric model is compared with the self-organizing maps (SOMs) method, which is an efficient unsupervised ANN method. Two experiments are conducted using high-resolution satellite images, and the results prove the high accuracy and reliability of the new evolutionary geometric model. © 2012 Copyright Taylor and Francis Group, LLC. Source


Lar U.A.,University of Jos | Agene J.I.,Center for Remote Sensing, Inc. | Umar A.I.,Federal Ministry of Mines and Steel Development
Environmental Geochemistry and Health | Year: 2015

Geophagy is a common practice among certain cultural groups especially women in some rural communities in Nigeria. The safety of eating such clays in terms of their heavy metal composition has not been ascertained, neither is the link between them and disease conditions established in geophagists. The analysis of field survey data reveals that the majority (about 90 %) of the women did not go beyond secondary school education. The geology of an area has a direct influence on the chemical composition of the soils. Therefore, this research was carried out to determine the mineralogical and the heavy metal content of some geophagic clay materials from Nigeria. All the geophagic clay materials are hydrated silicates of either Al, (Na and Ca), (Al and Mg), or/and (Mg and Fe). The concentration levels of Na, Al, Ca, Fe, Mg, Cu, and Zn are tolerable and apparently could serve as a veritable source of mineral nutrients deficient in the human body. An assessment of the level of contamination of heavy metals on the basis of the index of geo-accumulation (Igeo) shows that Cr, Cu, Zn, Co, and Ni (all with Igeo < 1) did not contaminate the clay materials. On the contrary, they are extremely contaminated by As, Cd and Se (Igeo = >5), and are moderately to strongly contaminated by Pb and Sb (Igeo = 2–3). In terms of health risk assessment, the presence of heavy metals such as As, Cd, Pb, Se, and Sb with a health risk index (HRI) >1, renders the geophagic clays unsafe for human consumption. Similarly, Al, Fe, and Na are in excess in the clay (HRI ⋙ 1) posing serious human health risks. Thus, the ingestion of geophagic clay materials by pregnant women and children when it contains heavy metals like Pb, As, Cd, Se, and Sb poses the risk of some medical disorders and should therefore be considered a public health problem. Since geophagic practice will persist despite civilization, we advocate finding ways of reducing heavy metal pollutants in geophagic clays through suitable remediation technology. © 2014, Springer Science+Business Media Dordrecht. Source


Grant
Agency: Department of Defense | Branch: Missile Defense Agency | Program: SBIR | Phase: Phase I | Award Amount: 99.79K | Year: 2011

With the rapid strides in various avionics-related technologies, the need for advanced simulators will increase. Anti-jam receiver development and future improvements in PNT are critically dependent on the availability of advanced simulators. The needs include: flexible, accurate, adaptable, programmable, user-friendly, hardware in the loop operation, precise wavefront simulation, high dynamics, environment and jamming simulation, etc. The simulator for the 21st century will have to precisely accurately represent various environments ranging from urban canyons, nuclear and plasma effects for the complete wavefront. Large update rates and significant processing power are required. A navigation simulator with these features and capable of generating all current and future signals (CA, P, M, L2C, L5, Jammer waveforms,GNSS, etc.) is proposed. CRS has developed a modern wavefront simulator for all GNSS signals.This proposal details adapting the simulator to meet MDA objectives and optimize the system for cost/performance ratio. This system will be capable of multi-satellite, multi-interferer real-time RF output for multiple antennas. It will be capable of integration with a variety of other hardware simulation tools and GPS receivers. The proposed approach will leverage CRS"s current capabilities and expertise and will result, at the end of Phase II, in a fully functioning working system


Schmidt M.,Center for Remote Sensing, Inc. | Schmidt M.,University of Queensland | Lucas R.,University of New South Wales | Bunting P.,Aberystwyth University | And 3 more authors.
Remote Sensing of Environment | Year: 2015

High spatio-temporal resolution optical remote sensing data provide unprecedented opportunities to monitor and detect forest disturbance and loss. To demonstrate this potential, a 12-year time series (2000 to 2011) with an 8-day interval of a 30m spatial resolution data was generated by the use of the Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM) with Landsat sensor observations and Moderate Resolution Imaging Spectroradiometer (MODIS) data as input. The time series showed a close relationship over homogeneous forested and grassland sites, with r2 values of 0.99 between Landsat and the closest STARFM simulated data; and values of 0.84 and 0.94 between MODIS and STARFM. The time and magnitude of clearing and re-clearing events were estimated through a phenological breakpoint analysis, with 96.2% of the estimated breakpoints of the clearing event and 83.6% of the re-clearing event being within 40days of the true clearing. The study highlights the benefits of using these moderate resolution data for quantifying and understanding land cover change in open forest environments. © 2014 Elsevier Inc. Source

Discover hidden collaborations