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
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
Agency: Department of Defense | Branch: Army | Program: SBIR | Phase: Phase II | Award Amount: 749.96K | Year: 2006
Fast acquisition and tracking of GPS signals are necessary in various military and civilian sectors. These are essential for operations under high dynamics as well as degraded conditions such as jamming and obscuration. Direct P/Y code acquisition under degraded condition involves external aiding in terms of precise time, ephemeris or other relevant data in order to facilitate the search process and also for long integration needed with data wipe-off. We have designed an architecture which allows these diverse conditions to be accommodated. Using block processing implemented in modern DPSs and FPGAs cost-effective receiver with flexible architecture is designed. Block processing is inherently suitable for P(Y) code as well as for several other new codes, particularly under high dynamics. CRS has developed novel software based development tools that allow rapid design, test, validation and prototyping of GPS systems using a single platform. We used this toolset for the simulation and design of Network Assisted GPS Receiver with direct P(Y) acquisition capability. During Phase II, we propose to develop a fully functional hardware prototype receiver and demonstrate its capabilities using simulated and live signals. We have demonstrated the feasibility of such implementation using commercial COTS components and using our software radio technology. The approach will provide means for future upgrades for different navigational signals and will allow easy implementation of advanced techniques for specialized applications.
Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 99.57K | Year: 2007
High fidelity robust testing of modern receivers demands highly accurate signal generation that is commensurate with complex environmental conditions. Demands of the modern digital receivers can only be met with a flexible signal generation scheme that will faithfully reproduce subtle features of the signal wavefront. CRS has demonstrated software based complex signal simulators and receivers for navigation, communication and radar applications. We propose to extend the software based real time signal simulation capabilities for the design and development of advanced simulators for various applications in navigation, radar, communication, EW, etc. The simulator will be able to generate live RF signals for different bands and will provide faithful reproduction of all aspects of signal generation (waveform, code, carrier, antenna, power, source motions, orientation, etc.), propagation (attenuation, dispersion, scattering through atmosphere, plasma, troposphere terrain, foliage, etc.) and receiver configuration (antennas, receiver dynamics etc.). A variety of signal waveforms (radar, communication, jammer, navigation, etc.) will be built in and additional waveforms can be added as needed. High fidelity and precision will be maintained throughout the system (accuracy of 1 mm is achieved) and special care in terms of analog portions particularly in those involving code and phase relationships will be maintained. During Phase I we shall perform requirements analysis, design the system architecture, and provide end-to-end simulation of the entire system that would allow us to obtain the performance metrics and help engineering design during Phase II. A hardware demonstration (using available hardware) will also be provided during Phase I to demonstrate the feasibility of software based implementation approach.