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  • Abrahamsson, Christoffer, et al. (författare)
  • Scatter correction of transmission NIR spectra by photon migration data - Quantitative analysis of solids
  • 2005
  • Ingår i: Optical Methods in Drug Discovery and Development,Boston, MA, United States,2005-10-23 - 2005-10-24. - : International Society for Optical Engineering. ; 6009, s. 60090-60090
  • Konferensbidrag (refereegranskat)abstract
    • The scope of this presentation is a new methodology to correct conventional NIR data for scattering effects. The technique aims at measuring the absorption coefficient of the samples rather than the total attenuation, measured by conventional NIR spectroscopy. The main advantage of this is that the absorption coefficient is independent of the path length of the light inside the sample, and therefore independent of the scattering effects. The measurements in this work were made using a novel system for time-resolved measurements, based on short light continuum pulses generated in an index-guided crystal fibre and a spectrometer-equipped streak camera. The system enables spectral recordings in the wavelength range 500 - 1200 nm with a spectral resolution of 5 nm and a temporal resolution of 30 ps. The evaluation scheme is based on modeling of light transport by diffusion theory, that provides an independent measure of the scattering properties of the samples, that later is used to correct conventional NIR data. This yields a clear advantage over other pre-processing techniques, where scattering effects are estimated and corrected for by using the shape of the measured spectrum only. PLS calibration models shows that, by using the proposed evaluation scheme, the predictive ability is improved by 50% as compared to models based on conventional NIR data. The method also makes it possible to predict the concentration of active substance in samples with physical properties different from those of the samples included in the calibration model.
  • Afanasiev, Sergey V., et al. (författare)
  • Experimental apparatus to study crystal channeling in an external SPS beamline
  • 2007
  • Ingår i: Proceedings of SPIE, the International Society for Optical Engineering. - 0277-786X .- 1996-756X. ; 6634
  • Tidskriftsartikel (refereegranskat)abstract
    • For the new generation of high intensity hadronic machines as, for instance, LHC, halo collimation is a necessary issue for the accelerator to operate at the highest possible luminosity and to prevent the damage of superconductor magnets.1 We propose an experiment aimed to systematic study of the channeling phenomenology and of the newly observed "volume reflection" effect. This experiment will be performed for an external SPS beamline and will make use of a primary proton beam with 400 GeV/c momentum and very small (∼ 3 μrad) divergence. The advantage of a proposed experiment is precise tracking of particles that interacted with a crystal, so that to determine the single-pass efficiency for all the processes involved. For this purpose, a telescope equipped with high-resolution silicon microstrip detectors will be used. New generation silicon crystals and an extra-precise goniometer are mandatory issues. Main goal of the experiment is to get the precise information on channeling of relativistic particles and, ultimately, on the feasibility of such technique for halo collimation at LHC. In this contribution we review the status of the setting-up of experimental apparatus and its future development in sight of the planned run in September 2006.
  • Alexander, N., et al. (författare)
  • IMAGINE project - A low cost, high performance, monolithic passive mm-wave imager front-end
  • 2012
  • Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - 0277-786X .- 1996-756X. ; 8544
  • Konferensbidrag (refereegranskat)abstract
    • The FP7 Research for SME project IMAGINE - a low cost, high performance monolithic passive mm-wave imager front-end is described in this paper. The main innovation areas for the project are: i) the development of a 94 GHz radiometer chipset and matching circuits suitable for monolithic integration. The chipset consists of a W-band low noise amplifier, fabricated using the commercially available OMMIC D007IH GaAs mHEMT process, and a zero bias resonant interband tunneling diode, fabricated using a patented epi-layer structure that is lattice matched to the same D007IH process; ii) the development of a 94 GHz antenna adapted for low cost manufacturing methods with performance suitable for real-time imaging; iii) the development of a low cost liquid crystal polymer PCB build-up technology with performance suitable for the integration and assembly of a 94 GHz radiometer module; iv) the assembly of technology demonstrator modules. The results achieved in these areas are presented.
  • Alfredson, J. (författare)
  • Individual differences in visual behaviour in simulated flight
  • 2002
  • Ingår i: Proceedings of SPIE, the International Society for Optical Engineering. - 0277-786X .- 1996-756X. ; 4662, s. 494-502
  • Konferensbidrag (övrigt vetenskapligt)abstract
    • Flying an aircraft is highly visually demanding. It is very important to map pilot visual behaviour, both for the purpose of evaluating the cockpit interface and to effectively integrate it with future adaptive interfaces and decision support systems. Pilots' visual behaviour was studied in two experiments. In the first experiment commercial aviation pilots were flying a commercial aviation scenario and eye point of gaze, and eye blinks were collected. In the second experiment military pilots were flying an air-to-air combat scenario and the visual behaviour was video recorded. In both of the experiments the results show individual differences in the pilots' visual behaviour. In the second experiment two different categories of eye blinks were found that might help explain the individual differences in visual behaviour. One category can be related to the systematic eye blinks found to occur when the eye point of gaze was changed between head-up/head-down and head-down/head-up. The other category could be related to other reasons, such as, mental workload or visual demands.
  • Andersen, Torben, et al. (författare)
  • A new concept for large deformable mirrors for extremely large telescopes
  • 2006
  • Ingår i: Astronomical Telescopes and Instrumentation - Advances in Adaptive Optics II, 2006,Orlando, FL, United States,2006-05-24 - 2006-05-31. - : SPIE. ; 6272:1, s. 324-331
  • Konferensbidrag (refereegranskat)abstract
    • For extremely large telescopes, there is strong need for thin deformable mirrors in the 3-4 m class. So far, feasibility of such mirrors has not been demonstrated. Extrapolation from existing techniques suggests that the mirrors could be highly expensive. We give a progress report on a study of an approach for construction of large deformable mirrors with a moderate cost. We have developed low-cost actuators and deflection sensors that can absorb mounting tolerances in the millimeter range, and we have tested prototypes in the laboratory. Studies of control laws for mirrors with thousands of sensors and actuators are in good progress and simulations have been carried out. Manufacturing of thin, glass mirror blanks is being studied and first prototypes have been produced by a slumping technique. Development of polishing procedures for thin mirrors is in progress
  • Andersen, Torben, et al. (författare)
  • A parallel integrated model of the Euro50
  • 2004
  • Ingår i: Modeling and Systems Engineering for Astronomy,Glasgow, United Kingdom,2004-06-24 - 2004-06-25. - : SPIE. ; 5497:1, s. 251-265
  • Konferensbidrag (refereegranskat)abstract
    • The Euro50 is an astronomical extremely large telescope for optical and infrared wavelength with a 50 m primary mirror. The telescope will have an elaborate control system ("live optics") to correct for atmospheric and telescope aberrations. To study and predict performance of the complete telescope system, an integrated model combining the structural model of the telescope, optics models, the control systems, and the adaptive optics has been established. Wind is taken into account on the basis of wind tunnel measurements and computer fluid dynamics calculations. Atmospheric aberrations are included using a seven-layer atmosphere model. The integrated model is written in Matlab and is run on a cluster computer to achieve acceptable execution times. Dedicated ordinary differential equation solvers have been written and a special toolkit for communication between Matlab processes on different nodes of the cluster computer has been set up. Preliminary results from the complete integrated model, including adaptive optics, are shown
  • Andersen, Torben, et al. (författare)
  • An Integrated Model of the European Extremely Large Telescope
  • 2008
  • Ingår i: Conference on Modeling, Systems Engineering and Project Management for Astronomy III,2008-06-26 - 2008-06-28. - : SPIE. ; 7017, s. 216-227
  • Konferensbidrag (refereegranskat)abstract
    • Integrated models including optics, structures, control systems, and disturbances are important design tools for Extremely Large Telescopes (ELTs). An integrated model has keen formulated for the European ELT and it includes telescope structure, main servos, primary mirror segment control system, wind, optics, wavefront sensor, deformable mirror, and an AO reconstructor and controller. There are three model phases: Initialization, execution of a solver to determine time responses, and post-processing. In near future, the model will be applied for performance studies and design trade-offs for the European ELT.
  • Andersen, Torben, et al. (författare)
  • An integrated simulation model of the Euro50
  • 2002
  • Ingår i: Workshop On Integrated Modeling of Telescopes,Lund, Sweden,2002-02-05 - 2002-02-07. - : The International Society for Optical Engineering. ; 4757, s. 84-92
  • Konferensbidrag (refereegranskat)abstract
    • The Euro50 is a proposed optical telescope with an equivalent aperture of 50 m. It will have a segmented primary mirror and full adaptive optics. To study the interaction of the telescope structure, the control system and the optics, an integrated simulation model has been formulated. The mechanical model is a modal version of an Ansys finite element model. The optics model is based on ray tracing and physical optics. The segments model takes the alignment servos and the segment dynamics into account. Wind variation over the primary mirror is included. Segment control system modeling is in progress. First results clearly demonstrate that a good enclosure is needed to protect the telescope well against wind. The results also suggest that the segment alignment system must have a bandwidth well above the lowest eigenfrequencies of the telescope.
  • Andersen, Torben, et al. (författare)
  • Euro50
  • 2003
  • Ingår i: Second Bäckaskog Workshop on Extremely Large Telescopes, 2003,Bäckaskog Castle, Sweden,2003-09-09 - 2003-09-11. - : SPIE. ; 5382:1, s. 169-182
  • Konferensbidrag (refereegranskat)abstract
    • The Euro50 is a telescope for optical and infrared wavelengths. It has an aspherical primary mirror with a size of 50 meters and 618 segments. The optical configuration is of Gregorian type and the secondary mirror is deformable for adaptive optics. Observations can take place in prime focus, Gregorian foci, and Nasmyth foci using additional relay mirrors. The telescope provides seeing limited observations, partial adaptive optics with ground layer correction, single conjugate adaptive optics and dual-conjugate adaptive optics. For prime focus observations, a clam-shell corrector with a doublet lens is used. The primary mirror segments can be polished using the precessions polishing technique. "Live Optics" denotes the joint segment alignment system, secondary mirror control system, adaptive optics and main axes servos. An overview is given of the live optics architecture, including feedback from wavefront sensors for natural and laser guide stars, and from primary mirror segment edge sensors. A straw man concept of the laser guide star system using sum-frequency YAG lasers is presented together with a solution to the laser guide star perspective elongation problem. The structural design involves a large steel structure and a tripod of carbon fiber reinforced polymer to support the secondary mirror. Integrated models have been set up to simulate telescope performance. Results show that an enclosure is needed to protect the telescope against wind during observations. The enclosure is very large box-shaped steel structure
  • Andersen, Torben, et al. (författare)
  • Integrated modeling of the Euro50
  • 2003
  • Ingår i: Second Bäckaskog Workshop on Extremely Large Telescopes, 2003,Bäckaskog Castle, Sweden,2003-09-09 - 2003-09-11. - : SPIE. ; 5382:1, s. 366-378
  • Konferensbidrag (refereegranskat)abstract
    • The Euro50 is a proposed 50 m optical and infrared telescope. It will have thousands of control loops to keep the optics aligned under influence of wind, gravity and thermal loads. Cross-disciplinary integrated modeling is used to study the overall performance of the Euro50. A sub-model of the mechanical structure originates from finite element modeling. The optical performance is determined using ray tracing, both non-linear and linearized. The primary mirror segment alignment control system is modeled with the 618 segments taken as rigid bodies. Adaptive optics is included using a layered model of the atmosphere and sub-models of the wavefront sensor, reconstructor and controller. The deformable mirror is, so far, described by a simple influence function and a second order dynamical transfer function but more detailed work is in progress. The model has been implemented using Matlab/Simulink on individual computers but it will shortly be implemented on a Beowulf cluster within a trusted network. Communication routines between Matlab on the cluster processors have been written and are being benchmarked. Representative results from the simulations are shown
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