1,721,080 research outputs found
A Rule-Based Cognitive Radar Design for Target Detection and Imaging
No full textThis article handles the topic of cognitive radar (CR) architecture design in the framework of multifunction radar operating in a resource-constrained and spectrum-constrained environment. Despite the advances in this field of research and its relative technologies, the way humans and echolocation mammals are able to interact with the external environment goes beyond the capability of any available man-made system. A CR can be thought as a system in which the transmitter, receiver, and software parameters can be changed over time in response to the observed scene with the aim to optimize radar performances given limited resources and environment constraints. The radar, therefore, has to reason about what is being observed and has to take decisions about how to use its limited resources to improve its performance. Rules may represent the way the system reasons, while performance encodes the information contained into the received echoes, and can be used to control next actions and system memory. A rule-based cognitive architecture is proposed in this article as a way to design a CR that has to manage its resources dynamically while handling several tasks, such as target detection, imaging, and recognition in a complex and changing scenario
Major thoracic trauma - sternal trauma
No full textFrom 1999 to 2003, 101 patients (M/F = 83/18, mean age = 46 ± 18 y) with thoracic trauma have been admitted to the (.enter for Thoracic Surgery in Varese. Over 50% of pts. with major thoracic trauma were treated by chest tube drainage; however, surgery was necessary just in 16/101 pts.; 29 pts. were admitted to ICU; deaths were 3/101. The Authors recorded 23/101 sternal fractures. Routine blood test, chest radiography and FKC were performed in all patients; in case of abnormal FKCi, echocardiography was performed; in case of widened mediastinum, chest CT was mandatory. 13/23 pts. showed associated injuries, 12 pts. a non-aligned sterna! fracture, 7 pts. mediastinal hematoma. Simple observation in hospital was indicated in 15/23 pts. with sternal fractures; chest tubes were positioned in J pts. (hemopneumothorax) and one patient was surgically treated because of painful sternal pseudoarthrosis (2 months after trauma). Admission in ICU was necessary in 3 pts. with non-aligned sternal fracture, mediastinal hematoma and associated injuries. No patient with sternal fracture died. Copyright © 2005 Edizioni Luigi Pozzi
Electronic countermeasure for OFDM-based imaging passive radars
No full textPassive radars are notoriously robust to jamming because the receiver location cannot be detected. Moreover, the use of Orthogonal Frequency Division Multiplexing (OFDM)-based reference signals further improves the robustness against jammers. Nevertheless, deception/spoofing-type of jamming may still be possible. This article aims at proposing an electronic countermeasure (ECM) for OFDM-based passive radars with radar-imaging capabilities. Here, a target-on-board deception jammer is proposed that aims at protecting the target itself from being identified when passive radar imaging is used. A design of the architecture of the proposed target-borne jamming system is provided, which includes COmmercial of The Shelf (COTS) devices that are able to sample a broadband signal, modulate it in amplitude and phase, and retransmit it with a very short time delay. Theoretical and simulation results are also given proving that imaging and precise location of non-cooperative targets can be both affected by the presence of false and/or altered phase-modulated target echoes
Fractal behavior of sea SAR ERS-1 images
No full textFractal dimension of the sea surface is strictly related to its roughness, and may thus be helpful in determining the sea state, or where motion-damping oil spills are located. A possible way to determine the fractal dimension of the sea surface is that of performing a fractal analysis of remote sensing images, in particular satellite images, which have the advantage of observing a large area at one time. This paper aims to show the utility of fractal analysis of ERS-1 SAR images, and presents the results obtained by three different algorithms. The considered data was sensed by ERS-1 in the Mediterranean Sea at times and locations suitable for comparison with data coming from the Italian "Sistema Ondametrico Nazionale," an environmental measurement system including a number of buoys carrying accelerometers and communications instruments. The experimental results show some accordance between the buoy data and the ERS-1 fractal analysis outcome, but more data are required to provide statistical support to the conclusions
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