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  • Jänis, A., et al. (författare)
  • Microwave absorbing properties of structural nanocomposites with surface treated Co ferrite nanoparticles as filler
  • 2010
  • Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - 0277-786X. - 978-081948059-0 ; 7644
  • Konferensbidrag (övrigt vetenskapligt)abstract
    • An analysis of the microwave absorbing properties of several polymer-(epoxy) based nanocomposites is presented. The nanoparticles of interest for this study were cobalt ferrite nanoparticles. For better dispersion of the nanoparticles in the polymer matrix surface treatment of the nanoparticles with silane compounds was performed. The nanoparticles were surface-treated with 3-glycidoxypropyl- (GPTMS), aminopropyl- (APTMS) or methyl-silsesquioxane (MTMS). The nanoparticles with GPTMS-coating dispersed well in epoxy without sedimentation while the other nanoparticles formed agglomerates in epoxy. The GPTMS-based composites showed higher fracture toughness than the MTMS-based composites. The microwave properties, permittivity and permeability, of GPTMS-based composites were measured in the frequency range between 3.95 GHz and 18 GHz and showed no influence of surface treatment on permeability.
  • Ringaby, Erik, et al. (författare)
  • Co-aligning Aerial Hyperspectral Push-broom Strips for Change Detection
  • 2010
  • Ingår i: Electro-Optical Remote Sensing, Photonic Technologies, and Applications IV. - 978-0-8194-8353-9
  • Konferensbidrag (refereegranskat)abstract
    • We have performed a field trial with an airborne push-broom hyperspectral sensor, making several flights over the same area and with known changes (e.g., moved vehicles) between the flights. Each flight results in a sequence of scan lines forming an image strip, and in order to detect changes between two flights, the two resulting image strips must be geometrically aligned and radiometrically corrected. The focus of this paper is the geometrical alignment, and we propose an image- and gyro-based method for geometric co-alignment (registration) of two image strips. The method is particularly useful when the sensor is not stabilized, thus reducing the need for expensive mechanical stabilization. The method works in several steps, including gyro-based rectification, global alignment using SIFT matching, and a local alignment using KLT tracking. Experimental results are shown but not quantified, as ground truth is, by the nature of the trial, lacking.
  • Willander, Magnus, et al. (författare)
  • UV detectors and LEDs in different metal oxide nanostructures
  • 2014
  • Konferensbidrag (refereegranskat)abstract
    • Different composite nanostructures based pn-junctions have been synthesized using the low temperature hydrothermal chemical growth. The composite nanostructures based pn junctions demonstrated here include p-NiO/n-ZnO, p-CuO/n-ZnO, and p-NiO/n-TiO2. Structural characterization of these composite nanostructures based pn-junctions was performed by different complementary tools and the results indicated that reasonable device quality crystals have been achieved. His act was also confirmed by the rectifying electrical behavior observed from these junctions. Further, the different composite nanostructures based junctions were used to demonstrate UV detectors and visible light emitting diodes (LEDs) operating with acceptable performance.
  • Xu, Tianhua, et al. (författare)
  • Phase noise mitigation in coherent transmission system using a pilot carrier
  • 2011
  • Ingår i: Optical Transmission Systems, Subsystems, and Technologies IX. - SPIE - International Society for Optical Engineering. - 9780819489579
  • Konferensbidrag (refereegranskat)abstract
    • In this paper, we investigate the phase noise elimination employing an optical pilot carrier in the high speed coherent transmission system considering the equalization enhanced phase noise (EEPN). The numerical simulations are performed in a 28-Gsymbol/s quadrature phase shift keying (QPSK) coherent system with a polarization multiplexed pilot carrier. The carrier phase estimation is implemented by the one-tap normalized least mean square (NLMS) filter and the differential phase detection, respectively. Simulation results demonstrate that the application of the optical pilot carrier is very effective for the intrinsic laser phase noise cancellation, while is less efficient for the EEPN mitigation.
  • Absil, Olivier, et al. (författare)
  • The VORTEX project : first results and perspectives
  • 2014
  • Ingår i: Adaptive Optics Systems IV. - 978-0-8194-9616-4
  • Konferensbidrag (refereegranskat)abstract
    • Vortex coronagraphs are among the most promising solutions to perform high contrast imaging at small angular separations from bright stars. They feature a very small inner working angle (down to the diffraction limit of the telescope), a clear 360 degree discovery space, have demonstrated very high contrast capabilities, are easy to implement on high-contrast imaging instruments, and have already been extensively tested on the sky. Since 2005, we have been designing, developing and testing an implementation of the charge-2 vector vortex phase mask based on concentric sub-wavelength gratings, referred to as the Annular Groove Phase Mask (AGPM). Science-grade mid-infrared AGPMs were produced in 2012 for the first time, using plasma etching on synthetic diamond substrates. They have been validated on a coronagraphic test bench, showing broadband peak rejection up to 500: 1 in the L band, which translates into a raw contrast of about 6 x 10(-5) at 2 lambda/D. Three of them have now been installed on world-leading diffraction-limited infrared cameras, namely VLT/NACO, VLT/VISIR and LBT/LMIRCam. During the science verification observations with our L-band AGPM on NACO, we observed the beta Pictoris system and obtained unprecedented sensitivity limits to planetary companions down to the diffraction limit (0 : 1 0 0). More recently, we obtained new images of the HR 8799 system at L band during the AGPM first light on LMIRCam. After reviewing these first results obtained with mid-infrared AGPMs, we will discuss the short-and mid-term goals of the on-going VORTEX project, which aims to improve the performance of our vortex phase masks for future applications on second-generation high-contrast imager and on future extremely large telescopes (ELTs). In particular, we will briefly describe our current efforts to improve the manufacturing of mid-infrared AGPMs, to push their operation to shorter wavelengths, and to provide deeper starlight extinction by creating new designs for higher topological charge vortices. Within the VORTEX project, we also plan to develop new image processing techniques tailored to coronagraphic images, and to study some pre- and post-coronagraphic concepts adapted to the vortex coronagraph in order to reduce scattered starlight in the final images.
  • Ahmad, Naeem, et al. (författare)
  • Cost Optimization of a Sky Surveillance Visual Sensor Network
  • 2012
  • Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - Belgium : SPIE - International Society for Optical Engineering. - 978-0-8194-9129-9 ; s. Art. no. 84370U
  • Konferensbidrag (refereegranskat)abstract
    • A Visual Sensor Network (VSN) is a network of spatially distributed cameras. The primary difference between VSN and other type of sensor network is the nature and volume of information. A VSN generally consists of cameras, communication, storage and central computer, where image data from multiple cameras is processed and fused. In this paper, we use optimization techniques to reduce the cost as derived by a model of a VSN to track large birds, such as Golden Eagle, in the sky. The core idea is to divide a given monitoring range of altitudes into a number of sub-ranges of altitudes. The sub-ranges of altitudes are monitored by individual VSNs, VSN1 monitors lower range, VSN2 monitors next higher and so on, such that a minimum cost is used to monitor a given area. The VSNs may use similar or different types of cameras but different optical components, thus, forming a heterogeneous network.  We have calculated the cost required to cover a given area by considering an altitudes range as single element and also by dividing it into sub-ranges. To cover a given area with given altitudes range, with a single VSN requires 694 camera nodes in comparison to dividing this range into sub-ranges of altitudes, which requires only 96 nodes, which is 86% reduction in the cost.
  • Ahmad, Naeem, et al. (författare)
  • Solution space exploration of volumetric surveillance using a general taxonomy
  • 2013
  • Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - 978-081949504-4 ; s. Art. no. 871317
  • Konferensbidrag (refereegranskat)abstract
    • Visual surveillance systems provide real time monitoring of the events or the environment. The availability of low cost sensors and processors has increased the number of possible applications of these kinds of systems. However, designing an optimized visual surveillance system for a given application is a challenging task, which often becomes a unique design task for each system. Moreover, the choice of components for a given surveillance application out of a wide spectrum of available alternatives is not an easy job. In this paper, we propose to use a general surveillance taxonomy as a base to structure the analysis and development of surveillance systems. We demonstrate the proposed taxonomy for designing a volumetric surveillance system for monitoring the movement of eagles in wind parks aiming to avoid their collision with wind mills. The analysis of the problem is performed based on taxonomy and behavioral and implementation models are identified to formulate the solution space for the problem. Moreover, we show that there is a need for generalized volumetric optimization methods for camera deployment.
  • Anders, Åström, et al. (författare)
  • A High Speed 2D Time-to-Impact Algorithm Targeted for Smart Image Sensors
  • 2014
  • Ingår i: Proc. SPIE 9022, Image Sensors and Imaging Systems 2014. - International Society for Optical Engineering; 1999.
  • Konferensbidrag (refereegranskat)abstract
    • In this paper we present a 2D extension of a previously described 1D method for a time-to-impact sensor [5][6]. As in the earlier paper, the approach is based on measuring time instead of the apparent motion of points in the image plane to obtain data similar to the optical flow. The specific properties of the motion field in the time-to-impact application are used, such as using simple feature points which are tracked from frame to frame. Compared to the 1D case, the features will be proportionally fewer which will affect the quality of the estimation. We give a proposal on how to solve this problem. Results obtained are as promising as those obtained from the 1D sensor.
  • Anderson, Sterling J., et al. (författare)
  • Constraint-based semi-autonomy for unmanned ground vehicles using local sensing
  • 2012
  • Ingår i: UNMANNED SYSTEMS TECHNOLOGY XIV. - Bellingham, WA : SPIE - International Society for Optical Engineering. - 978-0-8194-9065-0 ; s. Article no. 83870K
  • Konferensbidrag (refereegranskat)abstract
    • Teleoperated vehicles are playing an increasingly important role in a variety of military functions. While advantageous in many respects over their manned counterparts, these vehicles also pose unique challenges when it comes to safely avoiding obstacles. Not only must operators cope with difficulties inherent to the manned driving task, but they must also perform many of the same functions with a restricted field of view, limited depth perception, potentially disorienting camera viewpoints, and significant time delays. In this work, a constraint-based method for enhancing operator performance by seamlessly coordinating human and controller commands is presented. This method uses onboard LIDAR sensing to identify environmental hazards, designs a collision-free path homotopy traversing that environment, and coordinates the control commands of a driver and an onboard controller to ensure that the vehicle trajectory remains within a safe homotopy. This system's performance is demonstrated via off-road teleoperation of a Kawasaki Mule in an open field among obstacles. In these tests, the system safely avoids collisions and maintains vehicle stability even in the presence of "routine" operator error, loss of operator attention, and complete loss of communications.
  • Andler, Sten F, et al. (författare)
  • SMARTracIn : a concept for spoof resistant tracking of vessels and detection of adverse intentions
  • 2009
  • Ingår i: Sensors, and Command, Control, Communications, and Intelligence (C3I) Technologies for Homeland Security and Homeland Defense VIII. - SPIE - International Society for Optical Engineering. - 9780819475718 ; s. 73050G-1-73050G-9
  • Konferensbidrag (refereegranskat)abstract
    • The aim of maritime surveillance systems is to detect threats earlyenough to take appropriate actions. We present the results ofa study on maritime domain awareness performed during the fallof 2008. We analyze an identified capability gap of worldwidesurveillance in the maritime domain, and report from a userworkshop addressing the identified gap. We describe a SMARTracIn conceptsystem that integrates information from surveillance systems with background knowledgeon normal conditions to help users detect and visualize anomaliesin vessel traffic. Land-based systems that cover the coastal watersas well as airborne, space-borne and ships covering open seaare considered. Sensor data are combined with intelligence information fromship reporting systems and databases. We describe how information fusion,anomaly detection and semantic technology can be used to helpusers achieve more detailed maritime domain awareness. Human operators area vital part of this system and should be activecomponents in the fusion process. We focus on the problemof detecting anomalous behavior in ocean-going traffic, and a roomand door segmentation concept to achieve this. This requires theability to identify vessels that enter into areas covered bysensors as well as the use of information management systemsthat allow us to quickly find all relevant information.
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